• Volume 43, All articles

      Continuous Article Publishing mode

    • Enhanced performance of Fe-doped manganese oxide films as supercapacitor electrodes

      AVTAR SINGH DAVINDER KUMAR ANUP THAKUR BALRAJ SINGH SAINI RAMINDER KAUR

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      This paper reports enhancement in the specific capacitance of iron-doped manganese oxide (MnO$_2$) films, potentiostatically deposited on stainless-steel substrates. The properties of deposited films were investigated through cyclicvoltammetry and galvanostatic charge/discharge characteristics. The specific capacitance, as determined through cyclic voltammetry and galvanostatic charge/discharge characteristics, respectively, was found to be 248.79 and 277.5 F g$^{−1}$ for undoped films, whereas it exhibited an increase with doping and was found to be 449.61 and 487.5 F g$^{−1}$, respectively, corresponding to a dopant concentration of 4 atomic percentage. The electrochemical impedance data were fitted with a modified Randles equivalent circuit to find series resistance, charge-transfer resistance, double-layer capacitance and iondiffusion. According to electrochemical impedance spectroscopy, the enhancement of ion diffusion was found to be the major cause for enhancement in capacitive performance of the films.

    • Role of Ba(O$_2$)$_{1-x}$O$_x$ species in improvement of selective oxidation activity of CoO$_x$/CeO$_{2-y}$

      R K MORE N R LAVANDE P M MORE

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      A series of Ba-doped CoO$_x$/CeO$_{2-y}$ catalysts was prepared by co-precipitation followed by the deposition–precipitation method. The catalysts were investigated for selective oxidation (selox) of benzyl alcohol (B-ol) using tertiarybutyl hydroperoxide (TBHP) without solvent and activity was compared with Co$_{0.5}$/Ce$_{0.5}$. The Ba loading has been optimized with time and temperature for selox reaction. The catalyst was characterized by various surface and bulk characterization techniques. The characterization study indicates that the synergistic interaction between Ba and CoCe could form more oxygen vacancies and peroxide species responsible for the activation of B-ol and TBHP. The formation of Ba(O$_2$)$_{1-x}$O$_x$ oxide (peroxide) was observed and could be responsible for the activation of B-ol. The optimum Ba doping enhances selectivity and yields benzaldehyde. However, the increase in Ba concentration on CoO$_x$/CeO$_{2-y}$ could lead to the over-oxidation of B-ol to by-products.

    • Studies on polyoxyethylene octyl phenyl ether supported thorium(IV) phosphates: a new cation exchange material

      AMITA SOMYA KALPANA MAHERIA

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      A new surfactant supported cation exchanger and adsorbent named, polyoxyethylene octyl phenyl ether supported thorium(IV) phosphate (TX-100ThP) has been reported along with its synthesis, physico-chemical characterization such as scanning electron microscopy, X-ray diffraction, thermogravimetric analysis–differential thermal analysis and Fourier transform infra-red study. Following the characterization, the formed product has been tested for its efficiency in ion exchange chemistry and in analytical chemistry. For the testing, adsorption of alkaline earths—Mg$^{2+}$, Ca$^{2+}$, Sr$^{2+}$ and Ba$^{2+}$ and transition metal ions such as Fe$^{3+}$, Mn$^{2+}$, Ni$^{2+}$, Cd$^{2+}$, Co$^{2+}$, Cu$^{2+}$, Hg$^{2+}$ and Pb$^{2+}$ have been explored in different acidic media and the results revealed the selectivity of synthesized material towards Hg$^{2+}$ ions. On that basis, the material has been used to treat the binary laboratory-made samples, exploring the environmental importance of the cation exchanger in material science.

    • Studies on thermal stability and life estimation of epoxy adhesive by thermogravimetric analysis for high-temperature applications

      TANU SRIVASTAVA NARESH KUMAR KATARI BALAJI RAO RAVURI JUHI KUSHWAHA S KRISHNA MOHAN SREEKANTHA B JONNALAGADDA

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      Structural epoxy adhesive was investigated for its thermal stability and degradation behaviour in a thermooxidative environment by thermogravimetry analysis (TGA). Non-isothermal TGA was performed at temperatures between30 and 600$^{\circ}$C utilizing different heating rates. The ageing characteristics of material were determined by an accelerated ageing study using isothermal TGA at different temperatures for 5% threshold conversion. The activation energies from both non-isothermal TGA and isothermal TGA were estimated and the activation energy values for 5% degradation from both the methods were in good agreement. The epoxy adhesive with titanium dioxide as filler showed a shelf life exceeding 13 years at ambient conditions (27$^{\circ}$C). Additionally, the lap shear strength of the adhesive joint was also tested after treating thesamples at 70$^{\circ}$C with 90% relative humidity to evaluate the hydrothermal effect on adhesive joint.

    • Rapid fabrication of Cu$_2$ZnSnS$_4$:CdS graded interfaces via spray coating

      M T BISHOP B BHATTACHARYA A DOLGANOV DI HU

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      Cu$_2$ZnSnS$_4$ (CZTS) is a non-toxic and cheap photovoltaic absorber material, however, many challenges still remain for the successful fabrication of these devices. In this study, CZTS was deposited with CdS, a commonlyused buffer layer, using different spray coating procedures (i.e., two-step, single-step and graded deposition techniques), to demonstrate a facile and rapid fabrication technique of creating CZTS:CdS photovoltaic devices. Scanning electron microscopy (SEM) was used to determine the morphology of the deposited films, showing that the two-step, single-step and the graded deposition with 2 s of overlap time produced clear and defined layers. However, when the overlap time exceeded 4 s the layer became less defined, thicker and less dense, resulting in failed photovoltaic devices. This was attributed to the additional source of air during the deposition period, resulting in air being trapped by the deposited precursor, which therefore forms more foam-like functional layers. X-ray diffraction (XRD) analysis reflected this change in morphology, with graded samples above 4 s displaying no obvious CZTS peaks, suggesting an ineffective decomposition route. Depositions using a two-step, single-step and the gradeddeposition technique with 2 s of overlap time were shown to form functional photovoltaic devices, with a 2 s graded overlap performing three times better than the ungraded samples, resulting in an improved power conversion efficiencyof 0.41%. It is important to highlight that the device prepared with a 2 s graded interface significantly increased the current peak performance of CZTS photovoltaic devices deposited using xanthate precursors.

    • A novel carbon/germanium conic structure: theoretical study using density functional theory

      MOUMENA ELKEBICH SIHEM ZAATER SORAYA ABTOUCHE MEZIANE BRAHIMI

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      Complete optimization without geometry constraints and calculation of electronic properties of novel conic molecules such as C$_n$H$_n$Ge$_n$H$_n$ and C$_n$Ge$_n$H$_n$, with $n = 3−8$, was carried out with density functional theory using B3LYP and PBE1PBE functionals with 6-31$+$G(d, p) and cc-pVTZ basis sets. Calculations of formation energy showed stable and peculiar geometric and electronic properties. All carbon and germanium atoms for C$_n$H$_n$Ge$_n$H$_n$ compounds, which are sp$^3$-hybridized, were located in the same plane. This finding contradicts the notions of hybridization known to date. For these new molecular compounds, quantum descriptors such as electrochemical potential ($\mu$), chemical hardness ($\eta$), electrophilicity index ($\omega$), dipole moment, energy gap and the shape of the molecular orbital have been calculated in additionto nucleus independent chemical shifts, polarizability and harmonic oscillator model of aromaticity which are important tools for determining the aromaticity of the studied compounds. Thus, the aim of the work is, on the one hand, to propose new stable molecular structures formed of carbon and germanium atoms, and on the other hand, to challenge our understanding of hybridization and aromaticity notion.

    • Modelling experimental parameters for fabrication of nanofibres using Taguchi optimization by an electrospinning machine

      FARHAD MADANI ROGHAIEH DIDEKHANI MAHMOUD REZA SOHRABI SHIRIN MOFAVVAZ

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      In this research study, a photo-electrospinning device was designed and manufactured to produce nanofibres (NFs) by using an optical polymerizationmethod. For this purpose, an electrospinning machine was designed and optimized. Various parameters such as voltage, speed of collector and distance were investigated on the uniformity and diameter ofpolycaprolactone fibres. Therefore, a Taguchi experimental design was used to optimize the diameter of the fibres. Nine experiments were conducted using scanning electron microscopy to study the surface morphology of the obtained fibres. The best conditions for producing NFs include: voltage$=$15 V, speed of collector$=$600 rpm and distance$=$20 cm.

    • Photoinduced synthesis of variable-sized magnetite nanoparticles and their photodegradation for orange II

      BO LIU NANNAN WANG JIAYING JIN HUI LIU RUFEN CHEN

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      Magnetite (Fe$_3$O$_4$) nanoparticles with different particle sizes (9.9–29.1 nm) were prepared by using the aerial oxidation method under light irradiation with various wavelengths at room temperature. The photocatalytic degradation of orange II using Fe$_3$O$_4$ nanoparticles as photocatalysts was evaluated. Experimental results showed that the particle sizes of Fe$_3$O$_4$ nanocrystals decreased gradually with the decreasing wavelengths of light irradiation. With the decrease in the size of the samples, the Fe$_3$O$_4$ nanoparticles exhibited a large surface area and high adsorption. Furthermore, the smallparticle-sized Fe$_3$O$_4$ sample could cause an appropriate red shift of the spectra and promote the decomposition of H$_2$O$_2$, and produce high-content ${}^{\bullet}$OH radicals, which lead to an improvement of photodegradation efficiency of orange II.

    • Colorimetric molecular receptors for the sensing of acetate, fluoride and mercury based on Schiff’s bases

      SOBHI DANIEL

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      The real-time monitoring of biologically relevant anions and mercuric ion concentration in aqueous and physiological media and its quantitative determination across a large concentration range are of vital importance inenvironmental, health-care issues, industrial and scientific fields. Anion-like fluoride and acetate play an important role in a wide range of chemical and biological systems. This study reports the synthesis of a series of new molecular receptors based on Schiff’s bases by adopting a green strategy. The adopted procedures were simple and less complicated. A new simple colorimetric receptor based on salicylaldehyde Schiff’s bases sharing $–$OH and C$=$N moieties as anion binding sites have been successfully synthesized through one-step synthesis, and the sensing studies revealed that the receptors synthesized were found to be an elegant solution to the colorimetric sensing of the anions, especially acetate and fluoride.

    • Landau mean-field model with the cubic term for the $\alpha–\beta$ transition in quartz

      S ATES H YURTSEVEN

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      Thermodynamic quantities are calculated as a function of temperature by using Landau mean-field model for the $\alpha–\beta$ transition in quartz. By expanding the Gibbs free energy in terms of the order parameter ($Q$) with the cubic term ($Q_3$), the temperature dependence of the relevant thermodynamic quantities are predicted using the heat capacity ($C_{\rm P}$), which is fitted to the experimental data from the literature for the $\alpha–\beta$ transition in quartz. Our results indicate that the Landau mean-field model is adequate to describe the first-order $\alpha–\beta$ transition in quartz.

    • Effect of annealing temperature on the structural, dielectric and electric properties of Ni$_{0.7}$Cd$_{0.3}$Fe$_2$O$_4$ ferrites

      M ARIFUZZAMAN M B HOSSEN M H RASHID M S AHMED M S ISLAM

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      A composition of Ni$_{0.7}$Cd$_{0.3}$Fe$_2$O$_4$ (NCF) ferrite nanoparticles was synthesized by a sol–gel auto-combustion technique. The particles in powder form were annealed at 550 and 700$^{\circ}$C to study the structural, dielectric and electric properties of NCF by using X-ray diffraction (XRD), field emission scanning electron microscopy, impedance and modulusspectroscopy. XRD patterns confirmed the single phase cubic spinel structure of the sample. The average crystallite size of NCF was found to be 17 nm at 550$^{\circ}$C and 31 nm at 700$^{\circ}$C, respectively. The variation in complex dielectric constant, loss tangent and impedance along with the modulus properties of NCF with frequencies was observed at room temperature becauseof their size and annealing temperature. Notably, dielectric dispersion of the materials was observed at low frequencies because of Maxwell–Wagner interfacial polarization. The impedance and modulus spectroscopy were used to investigate the electric properties of the materials, which revealed the increase in grain and grain boundary resistance with annealing temperature. A non-Debye type of relaxation in the materials was evidenced through the Cole–Cole study of impedance and modulus spectra.

    • Electroplated Co$_3$O$_4$ selective coatings for high-temperature solar thermal applications

      R R UDAWANT M G TAKWALE S V GHAISAS K C MOHITE

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      This communication presents the optical characterization of Co$_3$O$_4$ films electroplated on Cu- and Ni-coated Cu substrates. Co$_3$O$_4$ films were successfully deposited by using the electrochemical deposition method with cobalt acetate tetrahydrate as a cobalt precursor followed by annealing at 350$^{\circ}$C. The as-prepared films were characterized using X-raydiffraction, UV–visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy and stagnation temperature test.The characterization shows the presence of only the cubic spinal Co$_3$O$_4$ phase in all films. The morphological analysis revealed the generation of unique fish-shaped Co$_3$O$_4$ particles with uniform size distribution for the films obtained on the Ni-coated Cu substrate. The Cu substrate with and without nickel plating used for deposition has shown a profound effect on the optical characteristics of films. The solar absorbance as high as 0.96 and thermal emittance as low as 0.02 were obtained for the films deposited on the Ni-coated Cu substrate. The highest value of the figure of merit ($F_1$) of $\sim$0.34 and extrapolated stagnation temperature of $\sim$362$^{\circ}$C were realized for films having better optical characteristics. The results obtained indicate very good potential of the deposited films for solar thermal applications.

    • 3D interconnected graphene aerogels/carbon foam networks with balanced performance in specific surface area and electrical conductivity for supercapacitors

      J M ZHAO Y Y ZHU Y LIU R XIONG

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      To balance the performance in specific surface area and electrical conductivity, ordered sheets of graphene aerogels were induced into porous carbon foam for supercapacitors with enhanced specific capacitance. Systematic investigations into morphology, structure and electrochemical properties confirmed that the introduction of graphene aerogels can effectively make specific surface area to increase, however, the declined resistance is neither due to electrolyte diffusion nor charge transfer, which gave rise to the improvement of electrochemical performance by 55.3% with a great specific capacitance of 210.5 F g$^{−1}$ at the current density of 0.5 A g$^{−1}$ compared to that of carbon foam.

    • Local structure analysis of $B$O$_6$ ($B = {\rm Fe, Cu}$) octahedron correlated with the magnetic properties of Cu-doped Ba$_{0.5}$Sr$_{0.5}$FeO$_{3–\delta}$

      F FITRIANA M ZAINURI M A BAQIYA M KATO P KIDKHUNTHOD S SUASMORO

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      Perovskite-based Ba$_{0.5}$Sr$_{0.5}$Fe$_{1–x}$Cu$_x$O$_{3–\delta}$ (BSFCO-$x$, $x = 0–0.2$) was synthesized by sol–gel self-combustionmethod. The crystallinity was evaluated through X-ray diffraction, besides further local structure analysis, using X-ray absorption spectroscopy (XAS) showed a cubic symmetry for $x = 0.05$; 0.10, which was tetragonal at higher values, $x =0.15; 0.20$. XAS analysis predicted the oxidation state (OS) of Cu to be a mixture of 3$+$ and 2$+$, while Fe includes 3$+$ and 4$+$. Conversely, the OS of Fe and Cu in the octahedron site influence the number of an unpair electron that determine the magnetic properties of perovskite. In addition, the magnetization for Ba$_{0.5}$Sr$_{0.5}$FeO$_{3–\delta}$ is 0.172 emu g$^{-1}$, originating from the ferromagnetic ordering Fe$^{3+}$($t_{2g}^3 e_g^2$)–O(2p)–Fe$^{4+}$($t_{2g}^3 e_g^1$) interaction. This effect increase, due to the presence of oxygen vacancy in BSFCO-0.05, which weakens the $d–p$ interaction of Fe-O, while the generation of higher Cu doping to increase the amount of Fe$^{4+}$ leads to a decline in Cu$^{3+}$. Therefore, Cu doping is confirmed to play a role in the paramagnetic–ferromagnetic transition.

    • Efficient electrocatalytic activity for oxygen reduction reaction by phosphorus-doped graphene using supercritical fluid processing

      S SURESH BALAJI P ANANDHA GANESH MEGALA MOORTHY M SATHISH

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      Oxygen reduction reaction (ORR) plays a vital role in various fields, such as combustion, corrosion and fuel cell applications. Herein, we report the production of phosphorus-doped reduced graphene oxide (P-RGO) using triphenylphosphine as a phosphorus source and graphene oxide in supercritical fluid method. The ratio of phosphorus source and graphene oxide has been varied to obtain optimum P-doping. P-RGO materials are characterized through X-raydiffractometer, Raman, field emission scanning electron microscopy and X-ray photoelectron spectroscopy techniques. The electrocatalytic activity of P-RGO materials are studied using linear sweep voltammetry and their ORR performanceare evaluated using linear sweep voltammetry-rotating ring disk electrode studies in 0.1 M KOH electrolyte. Among the three different P-RGO materials, RGO with phosphorus doping (2:1) delivered the best ORR performance (0.75 A mg$^{-1}$) compared to commercial HiSPEC Pt/C (0.12 A mg$^{-1}$) catalyst. The enhanced ORR activity could be ascribed to the existence of surface-active phosphorous sites over the RGO sheet surface.

    • Effect of addition of a mixed filler of CoCl$_2$ and LiBr into PEMA and its morphological, thermal and electrical properties

      E M ABDELRAZEK G M ASNAG A H ORABY A M ABDELGHANY A M ALSHEHARI

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      Poly ethyl methacrylate (PEMA) films doped with various concentrations of a mixed filler (CoCl$_2$ and LiBr) were prepared by using the casting method and their morphological, thermal and electrical properties were investigated.Scanning electron microscopy showed partial compatibility between the PEMA and the mixed filler. Differential scanning calorimetry was shown to increase their thermal stability with an increase in the concentration of the mixed filler in thefilms. The electrical properties were investigated using DC electrical conductivity ($\rho$), which showed an improvement in electrical conductivity after addition of the mixed filler.

    • Effect of WO$_3$ nanoparticle doping on the physical properties of PVC polymer

      A M A HENAISH A S ABOUHASWA

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      Poly(vinyl chloride)/tungsten oxide (PVC/WO$_3$) nanocomposite films were synthesized with different ratio of WO$_3$ content (0, 0.05, 0.1, 0.2 and 0.3 wt%). The sol–gel method was used to prepare WO$_3$ nanoparticles (NPs). X-ray diffraction and scanning electron microscope techniques confirmed that the WO$_3$ NPs were successfully dispersed in a PVC matrix with a single-phase structure. Characteristic absorption bands were observed in infrared spectra for pure PVC and nanocomposites. The morphology of WO$_3$ was observed using transmission electron microscope. The optical energy band gaps ($E_{\rm opt}$; direct and indirect) were estimated by using Tauc’s formula. It was found that the direct band gap energies decreased from 5.15 to 4.53 eV and the indirect bands decreased from 4.8 to 4.1 eV as WO$_3$ doping increased, while the Urbach energy ($E_{\rm u}$) increased as WO$_3$ content increased. It was found that the steepness parameter decreased, which confirms the formation of localized states in the band gap and increasing disorder in PVC polymer samples. The dielectric constant ($\epsilon'$) of the PVC/WO$_3$ nanocomposite films decreased as frequency increased. At a low frequency region, the loss factor ($\epsilon''$) has a high value and then sharply decreased as frequency increased, reaching a frequency independent region at high frequency values. The obtained data are very useful for using the investigated samples (PVC/WO$_3$) as the cores of high frequency transformers with very low dielectric loss.

    • Microstructure and wear behaviour of graphene–Si$_3$N$_4$ binary particle-reinforced aluminium hybrid composites

      MAHMUT CAN SENEL MEVLÜT GÜRBÜZ

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      In this study, Si$_3$N$_4$ and graphene-reinforced aluminium matrix composites (AMCs) with various contents (Si$_3$N$_4$: 1, 3, 6, 9 wt%; graphene: 0.1, 0.3, 0.5 wt%) were produced by the powder metallurgy method. The phase and microstructure analyses of the composites were performed by X-ray diffractometry and scanning electron microscopy, respectively. To investigate the tribological behaviour of Al–Si$_3$N$_4$ and Al–Si$_3$N$_4$–graphene composites, pin-on-disc experiments were conducted with different loads ($F = 10$, 20 and 30 N) at a constant sliding speed (200 rpm). Thus, the effects of Si$_3$N$_4$ and graphene contents on microstructure, Vickers hardness, apparent density, porosity, wear rate and friction coefficient of AMCs were investigated. Test results reveal that the highest Vickers hardness ($66 \pm 1$ HV), the lowest porosity (5.6%), wear rate ($3.1 \times 10^{−5}$ mm$^3$ N$^{−1}$ m$^{−1}$) and friction coefficient (0.13) were obtained for Al–9Si$_3$N$_4$–0.1 graphene. After attaining 0.1% graphene content, agglomeration was detected from the microstructure images of Si$_3$N$_4$–graphene reinforced AMCs. It was concluded that Si$_3$N$_4$ had an outstanding wear resistance and graphene was a good solid lubricantfor AMCs.

    • Preparation and thermophysical properties of graphene oxide–silver hybrid nanofluids

      DAN LI YUXIANG WANG MENG GUO MINGJUN SONG YANG REN

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      Ethylene glycol (EG)-based hybrid nanofluids containing graphene oxide–silver nanosheets (GO–Ag) were simply prepared without using any surfactant. The graphene oxide–silver composites were characterized using X-raydiffraction analysis, transmission electron microscope, infrared and UV–visible spectroscopy. The stability of GO–Ag nanofluids was estimated by UV–visible spectroscopy. The GO–Ag/EG hybrid nanofluids has good stability withoutsignificant sedimentation for 60 days. A few thermophysical properties of GO–Ag/EG nanofluids with 0.1, 0.2 and 0.3 wt% nanosheets were analysed experimentally at different temperatures ranging from 20 to 50$^{\circ}$C.

    • Effect of reaction temperature on the structural and electronic properties of stannic oxide nanostructures

      NIRMALA RANI NEENA JAGGI

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      Different nanostructured materials are having important roles in optoelectronics, gas sensing and photocatalytic applications due to their high surface to volume ratio. In this study, stannic oxide (SnO$_2$) nanostructures are prepared by hydrothermal method under optimal conditions at different temperatures (160, 180 and 200$^{\circ}$C) using surfactant cetyltrimethyl ammonium bromide. X-ray diffraction studies reveal rutile tetragonal structures of SnO$_2$ nanostructures, showing that average crystallite size is less than 10 nm. Field emission scanning electron microscope imaging reveals the morphological analysis of SnO$_2$ nanostructures fabricated at different reaction temperatures (160, 180 and 200$^{\circ}$C). Energy dispersive X-ray spectroscopy confirmed the elemental analysis of SnO$_2$ nanostructures. FTIR spectrum is recorded to confirm the presence of various functional and vibrational groups in the prepared SnO2 nanostructures. Optical properties of these nanostructures are analysed by UV–vis absorption studies. Bandgap of prepared SnO$_2$ decreased with increasing reaction temperature. Two-probe setup along with Keithley source metre is used for analysis of electricalproperties of SnO$_2$ nanostructures.

    • Strategy for enhancing the hydrogen evolution reaction properties of MoS$_2$ by utilizing the ordered mesoporous carbon as support and modification with nickel

      P VIJI S BHARKAVI P VIJAYAN M SIVADHAYANIDHY C SURESH

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      Surface modification of electrocatalyst suitable for yielding reduced over potential with improved exchange current density at the interface is highly desired for hydrogen evolution reaction (HER). Herein, the present report demonstratesthe HER performance of ordered mesoporous carbon (OMC)-supported nickel-modified MoS$_2$ electrocatalysts [NiMoS($x$)–OMC] synthesized by hydrothermal route. Inherent activity of pristine MoS$_2$ was improved by two vital surface strategies utilizing OMC as the support matrix for the dispersed growth of active catalyst and surpassing the active sites formation via augmentation of various concentrations of nickel. Crystalline phase, heterostructure vibrations, morphological orientationand electrocatalytic property of the prepared catalysts are comprehensively studied using different spectroscopic methods. Linear sweep voltammetric analysis suggests that the HER from the pristine MoS2 could be amplified by introducing OMC as support matrix. Synergistic enrichment of Ni (3 and 5 wt%) on MoS$_2$–OMC matrix enables both the lowest onset potential (180 and 185 mV) and Tafel slope values (103 and 100 mV per decade), with retained stability promising for further optimization and scalability.

    • Adsorption of H$_2$, N$_2$, CO, H$_2$S, NH$_3$, SO$_2$ and CH$_4$ on Li-functionalized graphitic carbon nitride investigated by density functional theory

      MARISOL IBARRA-RODRIGUEZ MARIO SANCHEZ

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      The interaction of small gas molecules as H$_2$, N$_2$, CO, H$_2$S, NH$_3$, SO$_2$ and CH$_4$ on Li-functionalized graphitic carbon nitride was investigated by using the density functional theory, to explore their gas adsorption properties. The calculated $E_{\rm ads}$ values of all gas molecules on [Li g-C$_3$N$_4$]$^+$ show that these gas molecules present favourable interaction with the lithium atom coordinated on the sheet. NH$_3$ and SO$_2$ molecules present strong interactions, with $E_{\rm ads}$ values of $-$18.60 and $-$9.50 kcal mol$^{-1}$. The natural bond orbital analysis indicates that donor orbitals belong to the lone pairs of oxygen, nitrogen, sulphur and carbon atoms from SO$_2$, N$_2$, NH$_3$, H$_2$S, CO molecules, and acceptor orbitals (LP$^*$) from the lithium atom. Computational studies suggest that H$_2$, N$_2$, CO, H$_2$S, NH$_3$, SO$_2$ and CH$_4$ molecules on [Li g-C$_3$N$_4$]$^+$ present physisorption.

    • Modified high-density polyethylene films: preparation, composition and their physical properties

      WEI-LI WU YI-WEN WANG

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      To prepare high-density polyethylene (HDPE) films with excellent mechanical properties and lower haze, HDPE was modified by using linear low-density polyethylene (LLDPE) and polypropylene (PP), and their characterizationswere performed by melt index, light transmittance/haze, dart impact and elongation at break, infrared (IR) spectra, scanning electron microscopy image and IR image analyses. The results showed that the modifying effect of the 10% PP/30% LLDPE/60% HDPE composition was the best; the haze was reduced 6% and the translucency, dart impact strength, elongation at break and tensile strength were increased 1, 27.3, 29.4 and 1.0%, respectively. The blend of 10% PP/30% LLDPE/60% HDPE had good compatibility, and PP, LLDPE and HDPE were only the physical entanglement, and no chemical reaction, the modified HDPE films can partly replace polyvinyl chloride and LLDPE films.

    • Carbon nanotube-incorporated cellulose nanocomposite sheet for flexible technology

      URENA MOSTAFA MOHAMMAD JELLUR RAHMAN TETSU MIENO MD ABU HASHAN BHUIYAN

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      A flexible, electrically conductive and low-cost composite sheet has been prepared combining multi-walled carbon nanotubes (MWCNTs) and cellulose pulp using simple solution mixing method. The uniform attachment of MWCNTs on to the cellulose fibres of the composites lead to a gradual decline of the sheet resistance with an enhanced electrical conductivity. The crystallinity of the composites is also found to be increased. The composites remain thermallystable up to 550 K as well as demonstrate improved flame retardancy. The conducting CNT networks of the composites are not disrupted even after 600 bending cycles, indicating almost no loss of conductivity. This conducting and flexible composite sheet can be used in different energy storage devices.

    • Reversible hydration of the perchlorate-intercalated layered double hydroxides of Li and Al: structure models for the dehydrated phases

      LATHA PACHAYAPPAN P VISHNU KAMATH

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      Imbibition of lithium sulphate into aluminium hydroxide is known to result in a sulphate-intercalated layered double hydroxide (LDH) of Li and Al. The perchlorate ion has the same size and molecular symmetry as the sulphate ion,but only half its charge. Consequently, twice the number of ClO$^−_4$ ions is needed to balance LDHs the charge on the metal hydroxide layer, compared to the SO$^{2−}_4$ ions. In this work, the ClO$^−_4$-intercalated LDHs were obtained from both the bayerite and gibbsite precursors. Inclusion of the hydration sphere along with the ClO$^−_4$ anion, induced turbostratic disorder in the stacking of the metal hydroxide layers. Temperature-induced dehydration ($T \sim 100$–140$^{\circ}$C) brought about a partial ordering in the interlayer region and the ClO$^−_4$ ion oriented itself with one of its $C_2$-axes parallel to the metal hydroxide layer. The close packing of ClO$^−_4$ ions could be realized by the complete dehydration of LDH and the distribution of the ClO$^−_4$ ions in all the available interlayer sites. In contrast, within the crystal of the sulphate analogue, the sulphate ions occupy only half the number of interlayer sites. The other half is occupied by the residual water molecules, as the sulphate analogue does not fully dehydrate even at elevated temperatures. This difference in the behaviour of the two LDHs has its origin in the largedifference in the hydration enthalpies of the two anions.

    • Natural dyes in hybrid chalcogenide multi-layer thin films

      K MILONAKOU-KOUFOUDAKI C MITZITHRA S HAMILAKIS C KOLLIA Z LOIZOS

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      New highly photoconductive hybrid multi-layer semiconductors have been developed, comprising cathodically electrodeposited CdSe or Zn$_x$Cd$_{1−x}$Se thin films and natural photosynthetic pigments, isolated from spinach. A layer of the organic dye, Chlorophyll α or Carotenes, is either deposited by spin coating technique over an inorganic thin film (two-layer structures) or ‘sandwiched’ between two inorganic semiconductive films (three-layer structures). X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, diffused reflectance spectroscopy and photoelectrochemical studies are employed, in order to fully characterize the received products. In the case of the three-layer hybrids, a significantly enhanced photo-response is observed, leading up to 300% improved photoelectrochemical efficiency values, compared to that of the pure inorganic films. This amelioration, stemming from the synergetic action of hybrids’ components, is more prominent in the case of Zn$_x$Cd$_{1−x}$Se systems, where a significant amount of Cd has been substituted by Zn: therefore, Znare considered environmentally friendlier alternatives to pure CdSe-based semiconductors.

    • Metal–insulator transition and small-to-large polaron crossover in La$_2$NiO$_{4+\delta}$/BaTiO$_3$ composites

      L T ANH THU N N DINH N VIET TUYEN B T CONG

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      Structure and electrical resistivity of $(1 − x)$La$_2$NiO$_{4+\delta}$/$x$BaTiO$_3$ composites ($x = 0.05$, 0.1, 0.2, 0.3, 0.5) produced by combining the sol–gel and ceramic sintering methods have been investigated. Among the samples sintered at temperature 1300$^{\circ}$C for 16 h, the metal–insulator transition (MIT) temperature of $x = 0.1$ sample, which is $T_{\rm MI} = 700$ K, is lower than the MIT temperature (800 K) of the pristine La$_2$NiO$_{4+\delta}$ (LNO) perovskite. Reduction of resistivity of $x \leq 0.3$ composite is mainly due to decrease of the scattering of electrical carriers by composite large grain boundaries and the structural change of the LNO component. The temperature dependence of the resistivity of $(1 − x)$La$_2$NiO$_{4+\delta}$/$x$BaTiO$_3$ composites is well-explained by a two conducting component model consisting of small polarons (SP) and large polarons (LP). A crossover between SP and LP with increasing temperature is described by the probability volume fraction function $f$ for SP and $1 − f$ for LP, which are equal to $1/2$ at transition temperature $T_{\rm MI}$. The observed lowest resistivity $\rho =11$ m$\Omega$ cm for $x = 0.1$ sample corresponds to the lowest SP thermal activation energy $E_{\rm a}$, the contributions of residual and phonon resistivities at $T_{\rm MI}$. The MIT of these composites satisfies approximately the Mott criterion.

    • A first-principles investigation on electronic, optical and thermoelectric properties of La$_2$Pd$_2$O$_5$ compound

      SIKANDER AZAM MUHAMMAD IRFAN MUHAMMAD WAQAS IQBAL MUHAMMAD ARSHAD KAMRAN R KHENATA T SEDDIK BANAT GUL M SHOAIB M SOHAIL SALEEM AYAZ KHAN S H NAQIB T OUAHRANI XIAOTIAN WANG

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      A number of ternary-semiconductor oxides have shown promise for potential applications in catalysis, thermoelectricity, optoelectronics and electrochemistry. In this work, the thermoelectric and optoelectronic properties of La$_2$Pd$_2$O$_5$ compound are studied by the full-potential linearized augmented plane wave method based on density functional theory. The electronic band structure shows an indirect band gap of 1.342 eV for La$_2$Pd$_2$O$_5$. Partial and total density of states indicate strong hybridization among different electronic orbitals. The upper part of the valence band is dominated by the Pd-d and O-p states, while the lower conduction band originates mainly from the Pd-d state. Dielectric functions including the imaginary and real parts, along with other optical constants, such as absorption coefficient, energy loss function, reflectivity and refractive index, have been reported for the first time. Thermoelectric properties, including electrical and thermal conductivity, Seebeck coefficient and power factor with variation in temperature are also presented and discussed using semi-classical Boltzmann transport theory for the first time for La$_2$Pd$_2$O$_5$. It has been found that La$_2$Pd$_2$O$_5$ has attractive optoelectronic and thermal properties that can make it a suitable candidate for efficient thermoelectric and optoelectronic device applications.

    • C$_3$N$_4$ supported on chitosan for simple and easy recovery of visible light active efficient photocatalysts

      KAMATCHI THIYAGARAJAN STANLY SAMUEL P SENTHIL KUMAR SUNDARAM GANESH BABU

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      To investigate the photocatalytic activities of heterogeneous systems under visible light, graphitic carbon nitride (g-C$_3$N$_4$) and chitosan (CS) were chosen as a model system. By solution cast method, C$_3$N$_4$ were embedded into a CS biopolymer matrix in this study. The purpose is to degrade methyl orange (MO) using a novel C$_3$N$_4$/CS nanocomposite thin film. Using a visible light-equipped photoreactor with a tungsten incandescent lamp, photo-decolourization of dye was carried out. To catalyse the photodegradation of organic dye pollutant MO, a C$_3$N$_4$/CS nanocomposite film photocatalyst was found to be successful and a recovery of 100% of the photocatalyst is achieved by a simple new hand-picking technique.Usingscanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform-infrared spectroscopy and UV–visible diffuse reflectance spectroscopy, detailed characterization was carried out. C$_3$N$_4$/CS has high capacity and better photocatalytic activity compared to g-C$_3$N$_4$ and CS, because C$_3$N$_4$ possesses a larger surface area and CS has highabsorption efficiency which is indicated by the photocatalytic discolouration of MO under visible light irradiation. The C$_3$N$_4$/CS nanocomposite thin film photocatalyst is regarded as an excellent catalyst with 98% degradation efficiency and is prepared by the simple solution cast method. The total organic carbon value was measured to be 86%. These values evidencethat the mineralization of MO was carried out under these conditions.

    • Fabrication of crystalline Sb$_2$S$_3$ sheaf structure composed of nanorods by a hot-injection method

      LILI LI LIN YANG BOWEN FU ZHIQIANG LI

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      Herein,we demonstrate a hot-injection method towards the fabrication of Sb$_2$S$_3$. The evolution from amorphous Sb$_2$S$_3$ nanoparticles to a sheaf of Sb$_2$S$_3$ nanorods cross-linked together occurring with the increase of reaction temperature and time is studied. The structural, compositional and morphological features of Sb$_2$S$_3$ products indicate the formation of crystalline Sb$_2$S$_3$ with orthorhombic phase and high purity. As the reaction proceeds, it can be observed that the individual nanorod grows along the elongated direction ($c$-axis), and it is noteworthy that its round cross-section could develop into the rectangular cross-section subsequently. In this study we also propose a possible formation mechanism for the growthprocess of Sb$_2$S$_3$, and it reveals that the present hot-injection could provide an ideal growth environment for synthesizing the nanostructured materials by optimizing the experimental parameters.

    • Mechanical and biological properties of polycaprolactone/fibrin nanocomposite adhesive produced by electrospinning method

      BAHARE HUSHMAND SHAHRIFI MAJID MOHAMMADI MEHDI MANOOCHEHRI AMIR ATASHI

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      Biopolymer nanocomposites exhibit an important role in regulating cell function in tissue engineering applications. Rapid degradation and good biological activities of these nanocomposites make them suitable for use in orthopaedic and medical applications. In this study, a polycaprolactone (PCL) scaffold and fibrin gluewere used as a matrix and reinforcement,respectively. PCL/fibrin nanocomposites with different aspect ratios were synthesized and used as a bioactive adhesive. The tensile strength of PCL/fibrin was measured using a tensile machine-equipped polymer load cell. Microstructural analysis of PCL and PCL/fibrin nanocomposites was investigated by field emission scanning electron microscopy.Microstructure results showed suitable porosity with proper distribution and size in the PCL–fibrin nanocomposites with a 1/10 aspect ratio. The results of wettability showed that fibrin as reinforcement in PCL decreased the contact angle and improved hydrophilic properties. The adhesion properties of PCL and PCL/fibrin scaffolds were determined by the 4$^{\prime}$,6-diamidino-2-phenylindoletest. Mesenchymal stem cells were cultured on the PCL and PCL/fibrin scaffolds. The results showed more and better adhesion of cells on the PCL/fibrin adhesive. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide test was performed on the scaffolds to determine cell viability and biocompatibility. The statistical results confirmed that the cell growth is higher on the PCL/fibrin after 4 days.

    • Influence of incorporation of carbon on the transparent conducting properties of CdO thin films

      A A DAKHEL

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      Thin films of CdO incorporated with different amounts of carbon element have been deposited on glass substrates by using the vacuum thermal evaporation method aiming at improving their transparent conducting (TC) properties. Thestructural and opto-electrical properties of the host CdO films were systematically studied. X-ray diffraction and optical investigations confirmed the inclusion of C species in the CdO lattice. The obtained results were explained through theoccupation of interstitial positions and structural vacancies of the host CdO lattice by C species. It was observed that the inclusion of carbon into the CdO lattice blue-shifted the optical band gap by $\sim$5−7%, which was attributed to the Moss–Burstein (B–M) effect. The electrical studies showed that the carrier mobility increased steadily with the increase in the C% inclusion level, so that with 5 wt% it attained $\sim$7.5 times the carrier mobility in un-doped CdO. Therefore, the present study showed that the prepared host CdO–C films have controllable TC degenerate semiconducting properties, which could berequired in different optoelectronic applications.

    • Chemical vapour deposited graphene: substrate pre-treatment, growth and demonstration as a simple graphene-based SERS substrate

      S NALINI S THOMAS M K JAYARAJ C SUDARSANAKUMAR K R KUMAR

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      In chemical vapour deposition (CVD) of graphene, surface roughness and purity of the copper substrate are very crucial for obtaining uniform films. Even though electrochemical polishing is an effective technique for obtaininghomogeneous graphene films, most of the experiments adopt complex experimental parameters like electrolyte heating, stirring and use of additives for better results. These are not applicable to thin copper foils used in CVD of graphene. In the present study, a simple electrochemical procedure is developed for deposition of high-quality graphene films with good coverage. The depositions of graphene films on bare and polished copper foils for the same growth conditions are analysed using various microscopic techniques. The uniformly grown graphene on copper is then directly employed as a surface-enhanced Raman scattering (SERS) substrate along with plasmonic silver nanoparticles. A simple SERS substrate having a reasonable detection limit of 10$^{−10}$ M for R6G is achieved with uniform SERS signals over a large area. Thehomogeneity of SERS substrate can be attributed to the uniformity of the deposited graphene film. A simple and efficient SERS substrate using conventional methods is achieved through the incorporation of chemical vapour deposited graphene. The study covers the growth of CVD graphene film starting from substrate pre-treatment, various analyses of the film andfinally the application in SERS.

    • Shear thickening fluid based on silica with neodymium oxide nanoparticles

      LI SUN YINRU LV MINGHAI WEI HONG SUN JIE ZHU

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      The rheological performance of shear thickening fluid (STF) based on silica with neodymium oxide nanoparticles (Nd$_2$O$_3$/SiO$_2$-STF) was investigated in this study. Nd$_2$O$_3$/SiO$_2$-STF suspensions of varied concentrations (9–15 wt%) were prepared using an ultrasonic oscillator. The presence of Nd$_2$O$_3$ particle and its interaction with silica nanoparticlesin the Nd$_2$O$_3$/SiO$_2$-STF were analysed using scanning electron microscopy, X-ray diffractometry and energy dispersive spectroscopy. Nd$_2$O$_3$/SiO$_2$ interaction demonstrated that silica nanoparticle could be completely attached on the needle branches of the Nd$_2$O$_3$ particles, and formed a considerable clustering effect. The steady rheological testing results indicated that an appropriate amount of Nd$_2$O$_3$ particle resulted in a marked increase in the peak viscosity from 51.95 (SiO$_2$-STF) to218.94 Pa.s (Nd$_2$O$_3$/SiO$_2$-STF), and a concomitant decrease in the critical shear rate from 199.65 (SiO$_2$-STF) to 50.18 s$^{−1}$ (Nd$_2$O$_3$/SiO$_2$-STF). Moreover, although the peak viscosity declined with the rise in temperature, shear thickening was remarkable compared to those of SiO$_2$-STF and became highly remarkable with Nd$_2$O$_3$ particle mass fraction increase.

    • Development of nanocrystalline multilayer Ni–Fe alloy coatings: characterization and its corrosion behaviour at elevated temperature

      D RASHMI G P PAVITHRA B M PRAVEEN DEEPA DEVAPAL

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      The present work deals with the galvanostatic fabrication of Ni–Fe nanostructured composition-modulated multilayer alloy (CMMA) coatings on steel panel from the newly optimized acid-sulphate bath solution. The recurringcathode current density combination (RCCC) and the number of layers have been optimized for enhanced performance of the coatings against corrosion. Corrosion behaviour of the nanostructured multilayered coatings was evaluated by Tafel extrapolation and electrochemical impedance spectroscopy (EIS) methods in 3.5% NaCl solution. Under optimal conditions, the CMMA coatings developed were more corrosion-resistant than the monolithic alloy coatings obtained from the same bath. Least corrosion rate (CR) was witnessed at 300 layers, above which saturation of corrosion resistance at a high temperature was found, which is attributed to a shorter relaxation time for redistribution of metal ions during multilayer deposition. Hardness and roughness of the coatings were evaluated using Vickers hardness test and atomic force microscope,respectively. Phase structure of the coatings was discussed using X-ray diffraction technique. The cross-sectional view of the coatings was characterized by scanning electron microscope. CR analysis and the surface morphology of the optimized coatings exposed to high temperature revealed the better performance of CMMA coatings at the elevated temperatures compared to the monolithic coatings.

    • Development of polymer-based superhydrophobic coating on cloth

      SRIPARNA CHATTERJEE PRITAM DAS URMIBALA TRIPATHY BIMAL P SINGH LAXMIDHAR BESRA

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      Facile, one-step fabrication of durable, superhydrophobic (water contact angle $\sim$154$^{\circ}$) fluorine-free polymer coating on cotton cloth is presented. The microstructure of the coating is evaluated with electron microscopy and X-ray diffraction study. The detailed analysis reflects that the superhydrophobicity is rendered by intrinsic hydrophobic nature of thenon-polar polymer, isotactic polypropylene. The chemical and mechanical stability of the coating on cloth is evaluated and it shows that the coating is extremely resilient in nature without almost negligible sacrifice in water contact angle. Because of simplicity of fabrication technique and quality of coating, this study is expected to be worthy enough for commodity as well as high technology applications.

    • Effect of processing route on the properties of LSCF-based composite cathode for IT-SOFC

      AAKASH AHUJA MANOJ GAUTAM AMIT SINHA J SHARMA P K PATRO A VENKATASUBRAMANIAN

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      A novel processing technique was developed to produce an in-situ nano-composite powder based on La$_{0.6}$Sr$_{0.4}$Co$_{0.2}$Fe$_{0.8}$O$_{3-\delta}$ (LSCF6428) and Gd$_{0.1}$Ce$_{0.9}$O$_{1.95}$ (GDC10) for application as cathode material in intermediate temperature solid oxide fuel cells (IT-SOFC). The nano-composite powder was produced using glycine-nitrate solution combustion technique starting from nitrates of six metal ions. The synthesized powder was characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), particle size and BET surface area analyses. XRD analysis of as-produced nano-composite powder confirmed the formation of desired phases right after combustion synthesis. The structural parameters of different phases present in the powders were estimated through Rietveld refinement of XRD data. Tocompare the electrical properties of nano-composite cathode powder produced through the present method, nano-powders of GDC10 and LSCF6428 were individually produced through glycine nitrate process and subsequently mixed through solidstate technique and characterized for functional properties. Using this in-situ nano-composite material, lower polarization resistance was achieved as compared to the LSCF–GDC composite produced from mechanical mixtures of nano-powders of GDC10 and LSCF6428 when used as cathode in GDC10 electrolyte-based symmetrical cell. The effects of cathode layer thickness and electrode firing temperature on the cathodic polarization resistance were studied using in-situ nano-composite cathode powder.

    • Insight view of mechanical, electronic and thermodynamic properties of the novel intermetallic REPt$_4$In$_4$ (RE $=$ Eu, Gd, Tb, Dy, Ho) compounds via ab initio calculations

      M Z BOUAYED A YAKOUBI R AHMED H KHACHAI R KHENATA S H NAQIB M M OBEID H R JAPPOR S J EDREES S BIN OMRAN XIAOTIAN WANG

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      In this study, the full potential linearized augmented plane wave method with the GGA approximation was employed to study the structural, elastic, electronic and thermal properties of the novel intermetallic REPt$_4$In$_4$ (RE$=$Eu,Gd, Tb, Dy, Ho) compounds. Our findings demonstrate that the equilibrium lattice parameters are in good agreement with the available experimental measurements. The elastic constants ($C_{\rm ij}$) were also calculated to understand the mechanical properties and structural stability of the compounds. Furthermore, the density of states and the charge density distributionsof the compounds were calculated to understand the nature of the bonding in the material. Our analysis of the calculated values of the Poisson’s ratio and the $B/G$ ratio shows their ductile structure. Additionally, the temperature-dependent thermodynamic parameters are computed by the quasi-harmonic Debye model in the range of 0–600 K, where the primitive cell volume and thermal expansion coefficients have been obtained successfully. Consequently, this study on the structural, elastic, bonding and thermal properties of REPt$_4$In$_4$ intermetallic compounds demonstrate that these compounds can be used as potential candidates in the domain of energy storage and electronic devices.

    • A DFT investigation of performance of metal-doped nanotubes as acceptable catalysts to SiO oxidation

      WEI GAO LI YAN YINGFANG LI MEYSAM NAJAFI

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      The Fe-doped nanotubes can be considered as novel catalysts to SiO oxidation. The information of SiO oxidation on nano-catalysts is not clear. In this study, the SiO oxidation on Fe-carbon nanotube (CNT) and Fe-boron nitride nanotube (BNNT) is examined through Langmuir-Hinshelwood (LH) and Eley-Rideal (ER) paths. The SiO joins in the Fe atom of Fe-surface-O$_2$$^*$ and Fe-surface-O$^*$ to create important structures with minor barrier energy. Cis-Fe-surface-OSiOO$^*$ in the ER is more stable than structures in LH pathway. In the LH and ER mechanisms the one and two SiO$_2$ are released at normal temperature, respectively. The abilities of Fe-CNT and Fe-BNNT to oxidation of SiO is investigated, and Fe-CNT and Fe-BNNT as novel metal-doped catalysts are proposed.

    • Characterization and application of cured epoxy resin reinforced with montmorillonite

      MAGDY WADID SABAA MOHAB ABDELHAKIM SOLIMAN MEHAWED ABDELLATIF SOLIMAN

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      Epoxy/nanoclay composites based on diglycidyl ether of bisphenol-A was cured by isophoronediamine and different weight percents of organically modified montmorillonite (O-MMT) clay (3, 5 and 7 wt%). Epoxy/nanoclay compositeswere characterized by different techniques such as Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction. The compressive strength of the epoxy/nanoclay composite with a 3 wt% of O-MMT was higher than that of pure epoxy and other composites. Thermogravimetric analysis showed no change in the thermal behaviour of the cured epoxy after incorporation of O-MMT

    • Development of hydroxyl and carboxylic acid functionalized CNTs–polysulphone nanocomposite fouling-resistant ultrafiltration membranes for oil–water separation

      VUNDADI SANTOSH P VEERA BABU JONNALAGADDA GOPINATH N NAGA MALLESWARA RAO ANNADANAM V SESHA SAINATH A V R REDDY

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      Fouling-resistant composite ultrafiltration (UF) membranes of hydroxyl functionalized multi-walled carbon nanotubes (MCNTs) (${}_{\rm OH}$CNT)/polysulphone (PSF)/polyvinylpyrrolidone (PVP) and carboxylic acid functionalized MCNTs (${}_{\rm COOH}$CNT)/PSF/PVP in weight ratios of 0.7/86.1/13.2 and 1.3/85.5/13.2 were prepared by phase inversion process from dimethylformamide solution. These membranes were characterized by infrared, scanning electron microscopy, atomic force microscopy, differential scanning calorimetry and water contact angle measurements. The molecular weight cut off values of these membranes were measured by permeating aqueous solutions of different molecular weight PEGs and dextrans. Among the fabricated UF membranes, ${}_{\rm COOH}$C$_{1.3}$PS$_{85.5}$PV$_{13.2}$ composite membrane showed a lower average contact angle (62$^{\circ}$). The${}_{\rm COOH}$C$_{0.7}$PS$_{86.1}$PV$_{13.2}$ membrane exhibited higher flux (99 l m$^{−2}$ h$^{−1}$) than all the fabricated membranes (62–78 l m$^{−2}$ h$^{−1}$) at 2 bar pressure. The flux recovery ratio values for bovine serum albumin feed solution were in the range of 63–72% for${}_{\rm COOH}$CNTs containing membranes and 53–64% for ${}_{\rm OH}$CNTs membranes, whereas PSF/PVP blend membrane exhibited45% at 2 bar applied pressure. The membranes containing 0.7 and 1.3 wt% carboxylic acid functionalized MCNTs showed 100% oil rejection when tested with an oil–water emulsion containing 1000 ppm lube oil. Conversely, membranes containing hydroxyl functionalized MCNTs showed relatively lower oil rejection (86–90%), whereas the PSF/PVP membrane showed 86% oil rejection.

    • Composite materials for printed electronics in Internet of Things applications

      K JANECZEK

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      Printed electronics belongs to one of the most prominent electronics technologies allowing us to manufacture electronic components and devices on different kinds of substrate materials. This manufacturing technology reveals to have significant potential to be used in Internet of Things (IoT) applications. In this paper, composite materials which are suitable for the production of a variety of IoT devices are discussed. Particular attention was focused on metal- and carbon-based composite materials allowing us to form conductive parts of the IoT devices produced. Further, sensor and encapsulation materials were reviewed as well. These conductive and sensor materials comprised of micro- and nano-particles, such as silver, copper, graphene oxide and its reduced forms, carbon nanotubes, carbon black or graphene nanoplatelets. Based on the conducted analysis, it was stated that further investigations of curing methods, fillers materials and composition of composites are recommended to be carried out in order to study mechanical, thermal and electrical properties of compositematerials required for IoT applications.

    • Resistive switching behaviour of amorphous silicon carbide thin films fabricated by a single composite magnetron sputter deposition method

      POREDDY CHAITANYA AKSHARA NILANJAN BASU JAYEETA LAHIRI GURUSWAMY RAJARAM M GHANASHYAM KRISHNA

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      Amorphous silicon carbide (a-SiC) films of thickness 50–300 nm are deposited by a single composite target magnetron sputtering process. Metal–SiC–metal structures are fabricated to demonstrate resistive switching. The top metal electrode is Cu, Pt or Ag and the bottom electrode is fixed as Au. Reversible resistive switching from high to low resistance states is observed for SiC films at voltages between 1 and 5 V. The interface between metal electrode and a-SiC films plays a significant role in achieving optimal switching performance. Resistance OFF/ON ratios of 10$^8$, retention times >10$^4$ s and endurance of 50 cycles are achieved in the best devices. Cross-sectional scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy are employed to understand the mechanism of device operation. Raman spectroscopy indicates the formation of nanocrystalline graphite in these devices after a few cycles of operation.

    • Electronic, optical and magnetic properties of low concentration Ni-doped CdSe by first principle method

      MUHAMMAD YASEEN MUHAMMAD DILAWAR HINA AMBREEN SHAMSA BIBI SHAFIQ UR REHMAN UMAIR SHAHID MEHWISH KHALID BUTT ABDUL GHAFFAR ADIL MURTAZA

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      The electronic, magnetic and optical properties of Ni-doped CdSe diluted magnetic semiconductors have been explored by density functional theory-based FPLAPW method as incorporated in the Wien2k code. The band structure anddensity of states analysis for up spin channel and down spin channel illustrate half-metallic ferromagnetic behaviour. The calculated values of the band gap in an insulating channel (down spin channel) increases from 0.4 to 0.8 eV with increasing the doping concentration of Ni from 6.25 to 25%. The magnetic moment of Ni decreases and magnetic moment on nonmagnetic side increases, which shows the strong pd-hybridization. Furthermore, the optical properties are characterized in terms of dielectric constants, refractive index, extinction coefficient, absorption coefficient and optical loss factor. The static valuesof the dielectric constant and refractive index are consistent with each other.

    • Electroanalytical characteristic of a novel biosensor designed with graphene–polymer-based quaternary and mesoporous nanomaterials

      KAMRUN NAHAR FATEMA MD ROKON UD DOWLA BISWAS SEONG HO BANG KWANG YOUN CHO WON-CHUN OH

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      Here, we propose the novel fabrication of graphene–polymer (GP)-based quaternary nanocomposite and mesoporous (MS) nanomaterials sensor [NaLa(MoO$_4$)$_2$-GO-PPy (NLMG-PPy), CuZnSnSe-GO-PPy (CZSG-PPy) and In$_2$O$_3$-G-SiO$_2$ 20% (IGS20)] to address ignored challenges for Escherichia coli bacteria recognition in polluted samples.Synthesized samples were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), energydispersive X-ray spectrometry (EDX), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, nitrogen adsorption–desorption isotherms, X-ray photoelectron spectroscopy (XPS) and diffuse reflectance spectroscopy (DRS). The sensor could recognize an individual E. coli cell in 1$\mu$l sample volume within 50 s. Through a low identification point of an individual cell, the MS and GP sensor had an absolute scope of 1–100 CFU per μl volume of sample (i.e. 103–105 CFU ml$^{−1}$). The high thickness of negative charge on the surface of E. coli cells actively regulates the concentration of dominant part charge carriers in the mesoporous and G-polymer monolayer, permitting an ongoing check of E. coli concentration in a known sample. Our biosensor is simple and low-cost with great selectivity and fast identification was effectively shown for E. coli detection.

    • Effect of transition metal doping on Cr–Ru alloys using first principles approach

      B O MNISI E M BENECHA H R CHAUKE P E NGOEPE M M TIBANE

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      Ab-initio density functional theory calculations have been used to explore the effect of transition metal alloying on A15 Cr–Ru intermetallic alloys.We study the structural, electronic and mechanical properties of Ru3Cr and Cr$_3$Ru alloys doped with transition metals (M $=$ Mn,Mo, Pt, Pd, Fe, Co, Re and Zr). Their thermodynamic and mechanical behaviours were deduced from the heat of formation, ratio of bulk to shear modulus, density of states (DOS) as well as elastic constants predictions.We find that Mn doping in these alloys leads to thermodynamic stability. These compounds also show a valence–conduction band overlap around the Fermi energy as depicted by the DOS. Furthermore, the Pugh ratio (the ratio of bulk to shear modulus) indicates the ductility character of these compounds. Their mechanical stability was illustrated by the Bohr mechanical stability criteria with all the elastic constants having a value $>$0. These results demonstrate that these systems can potentially be used as coating materials in high temperature structural applications.

    • DNA-assisted synthesis of nanoceria, its size dependent structural and optical properties for optoelectronic applications

      P S PRABHA JYOTHI B ANITHA S SMITHA B V VIBITHA P G ANU KRISHNA NISHA J THARAYIL

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      Cerium oxide (CeO$_{2−x}$) nanoparticles or nanoceria were synthesized by the chemical co-precipitation method using cerium nitrate hexahydrate and ammonium carbonate as starting materials and deoxyribonucleic acid (DNA) as acapping agent. The structural and optical characterization of the prepared nanoparticles was studied in depth by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy, Raman spectroscopy, UV–visible absorption and diffuse reflectance spectroscopy. The average crystallite size and latticeparameters of the cerium oxide nanoparticles at different calcination temperatures were studied using XRD analysis. The average crystallite size was found to be 6 nm and the size increases with calcination temperature. The polycrystalline nature and the size of the particles obtained are in close agreement with HRTEM and Raman analysis. The optical band gaps ofall samples were measured by Tauc plot which showed a blue shift with a decrease in size due to the quantum confinement effect. The optical absorption spectrum of the synthesized nanoparticles showed the absorption of UVA, UVB and UVC light, and the variation in structural and optical properties with size makes them suitable for the optoelectronic application. To the best of our knowledge, this is the first report on using DNA in the synthesis of nanostructured ceria.

    • Deposition and distribution of gold nanoparticles in a coffee-stain ring on the HOPG terraces

      IMTIAZ AHMAD

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      Cetyltrimethylammonium bromide (CTAB)-stabilized low-aspect ratio gold nanorods have been synthesized using seed-mediated wet chemical approach. Freshly cleaved highly oriented pyrolytic graphite (HOPG) surface is used as asubstrate for the deposition of nanoparticles via the droplet drying technique. Owing to the presence of CTAB molecules in suspension, nanoparticles on the non-wetting HOPG surface get deposited in the form of a coffee-stain ring. Such deposits at various positions of the coffee-stain ring have been characterized by scanning helium ion microscopy (HIM) and atomic force microscopy (AFM). Besides the assembly of nanoparticles, AFM is specially employed to investigate the deposition of CTAB molecules. The deposition and distribution of nanoparticles are studied and quantified at various positions of thecoffee-stain ring. On flat HOPG terraces, HIM shows merely the deposits of the gold nanostructures whereas AFM reveals both nanoparticles and CTAB deposits over the surface. This research study primarily focused on the nanoparticle deposits within the coffee-stain ring formed over the non-wetting HOPG terraces.

    • Structural, optical, electrical and catalytic properties of precursor solution-aged spray deposited undoped, Zn-doped and Ag-doped CdO thin films

      N RAJA V S NAGARETHINAM N MANJULA C RAJASHREE M SUGANYA S BALAMURUGAN K USHARANI A R BALU

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      Photocatalytic performance of precursor solution-aged undoped, Zn-doped CdO (CdO:Zn) and Ag-doped CdO (CdO:Ag) thin films has been reported in this paper. Perfume atomizer is adopted to deposit the films. CdO, CdO:Zn andCdO:Ag thin films exhibit cubic crystal structure. The crystallite size values were 34, 31 and 27 nm, respectively, for the CdO, CdO:Zn and CdO:Ag thin films. In the EDX spectra of the CdO:Zn and CdO:Ag thin films, Zn and Ag were observedalong with Cd and O. The CdO:Zn and CdO:Ag thin films exhibit increased transparency and widened band gap values. PL spectra showed peaks related to oxygen vacancies for all the films. Reduced resistivity was evinced for the CdO:Zn and CdO:Ag thin films. The degradation efficiencies of the CdO, CdO:Zn and CdO:Ag thin films against methyl orange after 75 min light exposure were 76.4, 84.3 and 90.4%, respectively. The CdO:Zn and CdO:Ag catalysts exhibit satisfactory stability with better reusable nature and are suitable for the effective treatment of organic toxic dyes.

    • Electromagnetic simulations of polarization-insensitive and wide-angle multiband metamaterial absorber by incorporating double asterisk resonator

      YADGAR I ABDULKARIM LIANWEN DENG HENG LUO SHENGXIANG HUANG LONGHUI HE LI YUHAN FAHMI F MUHAMMADSHARIF OLCAY ALTINTAS CUMALI SABAH MUHARREM KARAASLAN

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      A novel multiband metamaterial absorber (MTMA) is proposed which is capable of well presenting a polarization-insensitive and wide incident angle stability in the microwave frequency range. The proposed MTMA comprisingtwo vertically stacked asterisk-based copper resonators separated by dielectric layer of flame retardant type four and backed with a thin copper film. High-frequency structure simulator was used to simulate the absorber and to depict surface current distribution. The results showed that the absorber is operated at three narrow bands with high absorptivity of about 92, 100 and 100% at frequencies of 2.75, 4.3 and 9.5 GHz, respectively. The position of the resonant peaks can be effectively tuned by adjusting the geometry parameters of the structure, thereby achieving a multiband, polarization-independent andwide-angle absorber. The designed structure is important for the application of sensors, thermal images and in constructing broad multiband signals for electromagnetic compatibility/interference.

    • Investigation of the effect of MAI and PbI$_2$ concentrations on the properties of perovskite solar cells

      ALI MEHDIKHANI ARMAN SEDGHI ROOZBEH SIAVASH MOAKHAR NASTARAN RIAHI-NOORI

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      Here, the effect of perovskites layer quality on the performance of compact-TiO$_2$/mesoporous-TiO$_2$/CH$_3$NH$_3$PbI$_3$/carbon solar cells was investigated. Different perovskite layers were prepared by varying concentrationsof PbI$_2$ and CH$_3$NH$_3$I, while reaction temperature and dipping time were fixed. The range of concentrations for PbI$_2$ and methylammonium iodide (MAI) were 1–1.4 M and 6–10 mg ml$^{−1}$, respectively. Fabricated perovskite layers were first coated by carbon electrodes (5-layer) and then, the champion one was coated by Spiro-OMeTAD (as a hole transport material) andAu-evaporated layer as a cathode (6-layer). Fabricated films were fully characterized by field emission scanning electron microscopy, X-ray diffraction analysis, UV–Vis spectroscopy and photoluminescence spectrum. Photovoltaic properties were measured under AM 1.5. Output currents of 5-layer cells were in the range of 228–476 $\mu$A, of which the highest one was obtained by using 1.2M PbI$_2$ and 8 mg ml$^{−1}$ MAI. Ultimately, the maximum power conversion efficiency of 9.1% was obtained with 6-layer cell.

    • Morphological features, dielectric and thermal properties of epoxy–copper cobaltite nanocomposites: preparation and characterization

      KRISHNA PRATAP SINGH AMIT SINGH NAND KUMAR D N TRIPATHI

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      Epoxy (LY-556/HY-951) system was cured at ambient temperature and its copper cobaltite nanocomposites with different percentage loadings of nanoparticles were prepared via powered shear mixing with HY-951 (triethylene-tetraamine, TETA) hardener. Characterizations of the nanocomposites were done by various methods like XRD, TEM, FTIR, TGA, DSC, SEM, VNA, DETA and XPS. XRD, XPS and TEM showed the successful preparation of copper cobaltitenanoparticles. Further, FTIR studies confirmed accomplishment of curing and consequently the formation of cross-linked network in the nanocomposites. The morphological analysis revealed that the nanoparticles of the copper cobaltite were uniformly distributed inside the epoxy matrix to 5% loading. The enhancement in impact properties of nanocomposites with increase in filler content was supported by fractured surface studies for even distribution of copper cobaltite nanoparticles. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analyses showed enhancement in thermalstability as well as positive shift in the glass transition temperature for epoxy with copper cobaltite filler in comparison to neat epoxy resin. The positive shift in the glass transition temperature of the nanocomposites indicated improved interaction between copper cobaltite and epoxy matrix. These nanocomposites were also evaluated for their electromagnetic properties using dielectric thermal analyzer (DETA) and vector network analyzer (VNA) for determination of their permittivity and permeability, respectively. The improved thermal, mechanical and electromagnetic properties of epoxy–copper cobaltite nanocomposites make them potential candidates for microwave applications in a wide range of areas.

    • Novel 1:1 stoichiometric rare-earth HoX (X $=$ Pd, Ag and Cd) intermetallic compounds: DFT-based study

      MUHAMMAD NASIR RASUL MUHAMMAD SHAHID ALINA MANZOOR MUHAMMAD AZHAR KHAN MUHAMMAD AMIR RAFIQUE SALMAN MEHMOOD ALTAF HUSSAIN

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      A systematic investigation on structural, electronic, elastic, mechanical and optical properties of novel 1:1 stoichiometric rare-earth HoX (X $=$ Pd, Ag and Cd) intermetallic compounds has been made via ab-initio density functional theory-based linearized augmented plane wave method as coded in wien2k. An outline of local density approximation andgeneralized gradient approximation have been employed. Structural optimization established the stable CsCl-type cubic structure of HoX (X $=$ Pd, Ag and Cd) compounds. The determined crystal structure stability, compressibility and fracture strength of compounds are enhanced with X in the order HoPd > HoAg > HoCd. The interlacing electron dispersion curves at Fermi-level in band structure and density of states substantiate the metallic nature of compounds. The splitting gap between the lower and upper valence bands monotonously becomes narrower with the substitution of heavier core-element(Pd $\to$ Ag $\to$ Cd). The mechanical constants i.e., bulk modulus ($B$), Young’s modulus ($E$), shear modulus ($G_H$), Pugh’s ratio ($B/G_H$), Poisson’s ratio ($v$) and anisotropic factor ($A$) have been calculated to corroborate the mechanical properties of compounds. The cationic nature of Ho-atoms and anionic nature of X-atoms has been evaluated through the effective charge ($Q^∗$) computations. The observed peaks in the low energy region of optical conductivity spectra attribute the intra-band, while the high energy structures are associated with inter-band transitions in HoX (X $=$ Pd, Ag and Cd) compounds. The bond order calculations demonstrate the highest strength of HoCd compound among the herein studied compounds.

    • De-stabilization of charge-order state through in-homogeneity in random ionic distribution in the particles of polycrystalline Eu$_{0.2}$La$_{0.3}$Sr$_{0.2}$Ca$_{0.3}$MnO$_3$ sample

      K DE P DHAK S DE P DUTTA K DEY S MUKHERJEE S CHATTERJEE S DAS

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      In this study the perovskite manganite Eu$_{0.2}$La$_{0.3}$Sr$_{0.2}$Ca$_{0.3}$MnO$_{3}$ batch integrated sample is studied, with special modification done to introduce localized structural strain without micro-level (grains) modification. This consequence successfully generates opposite nature of high orthorhombic strain along b-axis in these samples, although the general structure is same for both with $Pnma$ space group. The sharp magnetic transitions (both Curie temperature and charge-ordertransition) are reported to be mixed in presence of random ionic distribution in its structure. The diffused insulator-metal behaviour, de-stabilization of magnetic state and phase transitions associated with inherent anisotropic strain is discussed and is explained based on chemical disorder-induced structural strain in the present system.

    • Magnetotactic curcumin iButtonbots as efficient bactericidal agents

      TAMANNA BHUYAN AMIT KUMAR SINGH SIDDHARTHA SANKAR GHOSH DIPANKAR BANDYOPADHYAY

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      The microbial contamination of drinking water is one of the most major concerns of community health in the developing world. Numerous water-borne pathogens are rapidly evolving and becoming resistant to traditional antibiotics.To get an efficacious bactericidal response, an assembly of several antibiotics or increased dosage are being administered, which may produce adverse side effects after prolonged use. Here, we describe a proficient method for disinfecting waterborne coliform bacterial strains of Escherichia coli DH5$\alpha$ from contaminated water samples using magnetic microbotsdecorated with curcumin (CU) conjugates. These magnetic microbots, namely, iButtonbots were composed of soft Agaricus bisporus (button mushroom) microcapsules with inherit antimicrobial properties. The locomotives were coated with magnetite nanoparticles for their remote guidance towards cells and collection along with CU for more enhanced bactericidal response. CU, a major active constituent of the Indian dietary spice turmeric and edible button mushrooms are known to exhibit antimicrobial activity against a wide range of bacterial species. The synergic antibacterial effect of CU and mushroomconstituents, imparts a profound bactericidal property to these magnetic microbots.We have demonstrated that microbots are capable of efficiently killing majority of bacterial cells in contaminated water samples. After extermination of bacteria, magnetic properties of embedded magnetite nanoparticles in porous mushroom matrix, allows collection of microbots from water samples. The presented biocompatible microbots offer an innovative method for rapid decontamination of bacteria-laden drinking water samples.

    • Electrochemical sensor based on Na$^+$-doped g-C$_3$N$_4$ for detection of phenol

      HAO YONG YIN YI FAN ZHENG LING WANG

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      In this work, a novel and enhanced electrochemical sensor based on Na$^+$-doped g-C$_3$N$_4$ was constructed for the detection of phenol. First, the g-C$_3$N$_4$ was formed through polymerizing melamine under 520$^{\circ}$C. And then the Na$^+$-doped g-C$_3$N$_4$ was fabricated by a simple wet chemical method. The electrochemical sensor was constructed by modifying the carbon paper with the resulting Na$^+$-doped g-C$_3$N$_4$. The morphology, chemical compositions and structure of Na$^+$-dopedg-C$_3$N$_4$ were characterized by scanning electron microscopy, transmission electronic microscopy, energy-dispersive X-ray detector and X-ray diffraction. The Na$^+$-doped g-C$_3$N$_4$ electrode was used for the cyclic voltammetry and amperometric response detection of phenol in a 0.1 M phosphate buffer (pH 9.0). Under the optimal conditions, the prepared sensordisplayed good performance for the electrochemical detection of phenol with a wide linear range of 1–110 $\mu$M, as well as low detection limit of 0.23 $\mu$M.

    • Investigation of physicochemical and electrical properties of TiO$_2$ nanotubes/graphene oxide nanocomposite

      MARWA HAMANDI MOHAMED TRIKI JORDI LLORCA FETHI JOMNI NUHAD AALOMAIR HAFEDH KOCHKAR

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      Graphene oxide (GO)-based nanocomposites have received a great attention due to their emerging applications. Here, we thoroughly examined the structural, electronic and surface properties of GO/TiO$_2$ nanotubes nanocomposite. The nanocomposite is prepared by simple impregnation of TiO$_2$ nanotubes (HNT400) with GO dispersion. GO is elaborated byan improved Hummer’s method, while HNT400 is obtained using alkaline hydrothermal treatment of TiO$_2$ P25, followed by calcination at 400$^{\circ}$C. XRD and Raman analyses show that GO nanosheets do not change the structural properties of TiO$_2$ nanotubes. TEM analysis confirms the formation of GO nanosheets assembled to TiO$_2$ nanotubes. XPS and EPR results confirm the electron transfer between GO and TiO$_2$ nanotubes. PL analysis reveals that GO inhibits the recombination of photogenerated electron–hole pairs in the nanocomposite. The ac conductivity measurements suggest the presence of grain and grain boundary effects in GO/HNT400.

    • Wear and corrosion resistance of titanium carbo-nitride coated Al-7075 produced through PVD

      M K SRINATH M S GANESHA PRASAD

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      Titanium carbo-nitride coatings were deposited using plasma-assisted physical vapour deposition technique on Al-7075 aluminium alloy plates. Studies were conducted to understand the bonding between the coating and substrate, and to examine the wear- and corrosion-resistant properties under heat treatments. The nature of bonding was characterized using scanning electron microscope. The pin-on-disc wear test, according to G99 ASTM standard, displayed the frictional force, coefficient of friction and wear for the samples. Simultaneously, the corrosion tests, according to G5-14 ASTM standard,performed for a period of 48 h, using electrochemical impedance and potentiodynamic polarization tests displayed the Nyquist and Tafel plots for analysis. The wear and corrosion rates of samples heat-treated at 500$^{\circ}$C for 1 h were found tobe 0.066e-6 g s$^{−1}$ and 2.962e2 g mm$^{−2}$ s$^{−1}$, respectively. While that of samples heat-treated at 500$^{\circ}$C for 12 h were found to be 0.366e-6 g s$^{−1}$ and 4.177e2 g mm$^{−2}$ s$^{−1}$. Both the wear and the corrosion performance investigations were in goodagreement with each other. Thus, the tribo-corrosive deterioration of titanium carbo-nitride coated Al-7075 had escalated with an increase in durations of the heat treatment.

    • Heavy metal removal by $N$-acetylcysteine-functionalized cryogels

      SINEM EVLI ARIFE ALEV KARAGÖZLER GÜLSEN GÜVEN HANDE ORHAN MURAT UYGUN DENIZ AKTAS UYGUN

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      In the present work, $N$-acetylcysteine attached poly(acrylamide-co-methyl methacrylate) [poly(AAm-MMA)] cryogels were synthesized and used for removal of heavy metal ions (Zn(II), Cd(II) and Pb(II)). For this, poly(AAm-MMA)cryogels were synthesized by free radical cryopolymerization technique and then, modified by $N$-acetylcysteine. Synthesized cryogel was characterized by FTIR, SEM and EDX analyses. Removed amounts of heavy metal were demonstrated by stripping voltammetry and the heavy metal removal efficiency was found to be 98.33 for Zn(II), 90.74 for Cd(II) and 96.19% for Pb(II). Additionally, this newly synthesized cryogel was successfully used for removal of heavy metals fromenvironmental and biological media.

    • Influence of sodium pretreatments on the preparation of Ag-doped polycationic bentonite for antibacterial purposes

      J A ROSÁRIO M A P CECHINEL C M OLIVEIRA A DE NONI M PETERSON N C KUHNEN H G RIELLA

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      Sodium bentonites have excellent cation exchange capacity (CEC) giving them great power of silver adsorption, which enables their use as precursors of antimicrobial materials. Countries like Brazil, however, do not have natural sources of sodium bentonite, only calcium or polycationic clays that do not show the same adsorption and ion exchange potential. In this study, the adsorption of silver in a polycationic bentonite from Quatro Barras, Brazil, previously subjected to a sodium treatment is evaluated. Samples were first modified with Na$_2$CO$_3$ or NaOH and then, subjected to silver impregnation in abatch system under controlled ambient conditions. Antibacterial properties of silver-exchanged clays were evaluated by the disk susceptibility and the minimum inhibitory concentration tests on Escherichia coli and Staphylococcus aureus bacteria. Results show that the sodium treatment with Na$_2$CO$_3$ allowed higher concentrations within a shorter time, increasing the pH without compromising the montmorillonite structure, which resulted on greater CEC and swelling values. Such better performance of the samples previously treated with sodium carbonate also caused an enhanced silver adsorption, resultingon a material of greater antibacterial potential. Experimental adsorption data fitted well to Freundlich isotherm.

    • Growth of Ag$_2$O$_2$ micro-particles and Cu$_2$(OH)$_3$NO$_3$ nano-sheets by atmospheric pin-to-solution electrical discharge

      M REZVANI JALAL H HOJJATI J REZVANI JALAL S EBRAHIMI M R ZANGENE BIGHASHI

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      In this paper, interaction of the air plasma generated in an atmospheric pressure pin-to-solution electrical discharge with aqueous solutions of silver nitrate, copper nitrate and also their mixture is experimentally investigated inthe cathode-plasma electrolysis configuration. Experiments show that a black (green–blue) powder is obtained for pure solution of AgNO$_3$(Cu(NO$_3$)$_2$ ·3H$_2$O). Through X-ray diffraction (XRD) characterizations, the black (green–blue) powder is found to be Ag$_2$O$_2$(Cu$_2$(OH)$_3$NO$_3$). On the other hand, the electrolysis product for AgNO$_3$/Cu(NO$_3$)$_2$ · 3H$_2$O mixture solution is a black–brown powder. XRD and EDS analyses of the powder along with its FESEM images reveal that it is truly Cu$_2$(OH)$_3$NO$_3$ micro-plates covered sparsely with Ag$_7$NO$_{11}$ nanoparticles of diameter $\sim$30 nm.

    • Study on the improvement of p-type multi-crystalline silicon material for solar cells by the hydrogenation with electron injection

      SHAOMIN LI JIANBO SHAO XI XI GUILIN LIU RUOYING PENG RULONG CHEN LIPING CHEN YANFENG JIANG XIAOFENG GU

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      In this paper, we have found that the efficiency of p-type mono-crystalline silicon (mono-Si) passivated emitter and rear contact (PERC) solar cells can be increased by 0.12%abs. with the process of hydrogenation with electron injection(HEI). However, the same scheme was not suitable for p-type multi-crystalline silicon (mc-Si) solar cells. To promote power conversion efficiency (PCE) for the mc-Si solar cells, we have explored a developed HEI process for the mc-Si solar cells to improve the device performance. Meanwhile, we also analysed the mechanization inside the solar cells after applying the HEI process. Through the design of experiment (DOE), the correlation among injection current, temperature, injection time and efficiency improvement was analysed in detail. It was proved that mc-Si solar cells require higher current injection andtemperature to passivate the complex impurities in the bulk, when compared to mono-Si solar cells.With the optimal scheme explored by this paper, the open circuit voltage (Uoc), short circuit current density (Jsc) and fill factor (FF) of p-type mc-Si solar cells, respectively, increased by 1.2 mV, 0.11 mA cm$^{−2}$ and 0.05% abs., respectively. The efficiency was improved about $0.11\pm 0.005$% abs.. These results will provide a certain method and basis for further improving the efficiency of mc-Si PERC cells and overcoming the light-elevated temperature-induced degradation by HEI process.

    • Effect of carbon on structural and magnetic properties of Ge$_{1−x}$Mn$_x$ nanocolumns

      T G LE V LE THANH L MICHEZ

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      We have investigated the structural and magnetic properties of Ge$_{0.94}$Mn$_{0.06−\delta}$C_${\delta}$ films ($\delta = 0.005$, 0.01 and0.02) using reflexion high-energy electron diffraction (RHEED) technique, transmission electron microscopy (TEM) and superconducting quantum interference device magnetometer. All films have been prepared by co-depositing Ge, Mn and C by molecular beam epitaxy. RHEED pattern shows the increase in sample surface roughness when doping carbon into the GeMn films. TEM analyses indicate that adding carbon greatly reduces the surface diffusion of both Ge and Mn elements. Ferromagnetic ordering in samples containing carbon contents of 0.01 and 0.02, persists at temperatures >400 K. An increasein net magnetization is found for carbon-doped samples with increasing carbon content from 0.01 to 0.02. However, we found a decrease in the net magnetization and the Curie temperature of the samples after annealing at 450 and 650$^{\circ}$C. The Curie temperature reduces down to about 300 K, which is comparable to the value of the free-carbon sample showing a harmful effect of the post-annealing on the magnetic properties of carbon-doped GeMn nanocolumns.

    • Optical properties and defects of ZnO nanorods that are modified by treatment with H$_2$O$_2$ and used as conductive filaments for poly(methyl methacrylate)-based resistive switching applications

      NIAN-HAO YAN YOW-JON LIN TING-HONG SU HSING-CHENG CHANG

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      The optical and structural properties of ZnO nanorods that are modified using H$_2$O$_2$ and used as the conductive filament (CF) for poly(methyl methacrylate) (PMMA)-based resistive switching (Rs) applications are studied. ZnO nanorods are used as the CF for a PMMA-based Rs device, to determine their specific properties and to determine the effect of oxygen vacancies on the Rs performance in ZnO. The Rs performance for PMMA-based devices is affected by treatment with H$_2$O$_2$. An appropriate H$_2$O$_2$ treatment time produces a significant change in the Rs performance for a PMMA/ZnO nanorod array device, because there is a change in the number of oxygen vacancies in ZnO that is treated with H$_2$O$_2$ solution at 60$^{\circ}$C for60 s. This study demonstrates the operation of a PMMA-based Rs device that features a ZnO CF that undergoes treatment with H$_2$O$_2$.

    • Tensile strength and elongation of NBR/PVC/CuFe$_2$O$_4$ magnetic nanocomposites: a response surface methodology optimization

      S MIRSAFAI K TORABI M ASHRAFI M HAMADANIAN

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      This paper reports the development of nitrile butadiene rubber (NBR) nanocomposite toughened by the combination of polyvinyl chloride (PVC) and CuFe$_2$O$_4$ nanoparticles (NPs). CuFe$_2$O$_4$ NPs synthesized by sol–gel auto-combustion route. Response surface methodology was applied for optimization and modelling of the tensile strength and elongationof NBR/PVC/CuFe$_2$O$_4$ nanocomposite. By using XRD, SEM, EDX and VSM, we characterized CuFe$_2$O$_4$ NPs and the optimized NBR/PVC/CuFe$_2$O$_4$ nanocomposite, and investigated the mechanical properties of NBR/PVC/CuFe$_2$O$_4$ nanocomposite. Results showed that the surface cracking of NBR decreased as the PVC and CuFe$_2$O$_4$ content increased,which leads to better mechanical properties of NBR.

    • Electrochemical behaviour of bismuth in HCl solutions

      AWAD SADEK MOGODA

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      Measurements of open circuit potential and electrochemical impedance spectroscopy (EIS) at open circuit condition have been employed to characterize the behaviour of the mechanically polished bismuth surface in hydrochloricacid solution of various concentrations (0.01–1.0 M). The air-formed (pre-immersion) bismuth oxide grows on the surface in all the test solutions, but its thickness decreases as the HCl concentration increases. The impedance results showed that bismuth surface reactivity towards oxide thickening decreases as chloride ions concentration increases as a result of their aggressiveness nature. The equivalent circuit model for fitting the spectra of the EIS data of bismuth in HCl solution indicated that the mechanism of Bi corrosion is controlled by the charge-transfer and diffusion processes. The mechanically polished bismuth surface was examined by scanning electron microscopy before and after immersion in 0.023 M HCl solution. The scanning electron micrographs have shown that the flawed regions formed on the mechanically polished Bi surface were repaired after immersion in the acid solution due to thickening of the oxide film.

    • Effect of titanium oxide ceramic particles concentration on microstructure and corrosion behaviour of Ni–P–Al$_2$O$_3$–TiO$_2$ composite coating

      FARHAD MOHSENIFAR HADI EBRAHIMIFAR

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      Composite coatings are coatings that have been considered in terms of properties, such as corrosion resistance, oxidation resistance and excellent hardness. In this study, Ni–P–Al$_2$O$_3$–TiO$_2$ composite coating was made on AISI 316 steel using direct current deposition technique. The microstructure of the coating and its corrosion resistance were studied bychanging the amount of titanium oxide (1, 2, 3 and 4 g l$^{−1}$) in the bath. To investigate the morphology of the coating and the analysis of the coated material, a scanning electron microscope (SEM) and EDS microscopy were conducted, respectively. The results showed that in the bath containing 4 g l$^{−1}$ titanium oxide, the coating is perfectly uniform and continuous, while by reducing the amount of titanium oxide, it is not possible to form a suitable coating on the entire surface of the substrate. To investigate the corrosion resistance, the potentiodynamic polarization and electrochemical impedance spectroscopy testsin aqueous solution of 3.5% NaCl were carried out on coated and uncoated samples. The results of these tests were also correlated with microscopic images and showed that the coatings in a bath containing 4 g l$^{−1}$ titanium oxide has the highest corrosion resistance.

    • Improved thermal stability and oxidation resistance of electrodeposited NiCrP amorphous alloy coatings

      Y Q GUO J K YU H B YANG Q QIAO Q Y LI X C ZHAO

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      Amorphous NiP and NiCrP alloy coatings were prepared on copper substrates by electrodeposition. The thermal stability of the obtained coatings were evaluated by the onset temperature of phase transformation identified with differential scanning calorimetry measurements, and their high temperature oxidation resistances were characterized by the oxidation kinetics curve and the oxidation activation energy. The mechanism of the doping effect of Cr element on crystallization temperature and oxidation resistance of the alloy coatings were discussed based on X-ray diffraction analysis. The results show that the crystallization temperature of NiP amorphous alloy was 344$^{\circ}$C, and the oxidation activation energy was calculated to be 1.54 $\times$ 103 J mol$^{−1}$. As for NiCrP alloy coating with a Cr content of 1.8 wt%, the crystallization temperature increased to 403.8$^{\circ}$C and the calculated oxidation activation energy was 3.53 $\times$ 104 J mol$^{−1}$, 2.29 times higher than theNiP coating. The remarkably enhanced high-temperature oxidation resistance of NiCrP alloy coating can be attributed to the compact metal oxide film formed on the surface.

    • Bi$_2$O$_3$-doped SnO$_2$ varistors with low breakdown electric fields

      GUO-ZHONG ZANG RUI-QING CHU ZHI-JUN XU

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      This work presents Bi$_2$O$_3$-doped SnO$_2$ ceramic varistors prepared through conventional ceramic processing in the sintering temperature range of 1290–1320$^{\circ}$C. The sample sintered at 1300$^{\circ}$C exhibits a breakdown electric field as low as 11.6 V mm$^{−1}$. Scanning electron microscopy images reveal that all the samples have a compact structure, andenergy dispersive spectroscopy results for the sample sintered at 1300$^{\circ}$C indicate that Bi distributes homogeneously along the grain boundaries and aggregates inhomogeneously on the grain surfaces. With increasing sintering temperature, the grain boundary barrier height remains nearly constant at 0.80 eV. In both the dielectric loss and electric modulus spectra of the sample sintered at 1300$^{\circ}$C, obvious relaxations were observed and the activation energies obtained from the respectivespectra were 0.33 and 0.15 eV, which are expected to be related to oxygen vacancies and interstitial ions, respectively. Complex impedance spectra are employed to develop a non-typical equivalent circuit model for the Bi$_2$O$_3$-doped SnO$_2$ ceramic varistors at low voltage that yields an excellent fit to the data.

    • Electrochemical energy storage systems: India perspective

      BHARAT KALE SANDIP CHATTERJEE

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      Design and fabrication of energy storage systems (ESS) is of great importance to the sustainable development of human society. Great efforts have been made by India to build better energy storage systems. ESS, such as supercapacitors and batteries are the key elements for energy structure evolution. These devices have attracted enormous attention due to their potential applications in future electric vehicles, smart electric grids, etc. This paper first addresses the fundamental principles, structure and classification of supercapacitors and batteries, and then focus on the recent advances on thesedevices made by India especially from Centre for Materials for Electronics Technology (C-MET), a scientific society under the ministry of electronics and information technology, government of India. Also the current global market scenario and market in India are also discussed in detail to recognize the most appropriate energy systems for the emerging economy like India.

    • Impedance variation with different relative humidities of PAni/Mn nanofibres

      DIVYANSHI SRIVASTAVA R K SHUKLA

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      This paper presents the humidity sensing properties of surface-modified polyaniline (PAni). In this study, the impedance response and dielectric properties of pure- and doped-PAni have been investigated as a function of relativehumidity (RH%) and frequency. PAni and PAni/Mn composite samples are synthesized by one-step interfacial polymerization process. The structural properties and surface morphologies of the prepared materials have been characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), respectively. XRD confirms the formation of PAni and it shows semi-crystalline behaviour. FESEM shows granular, porous and well-distributed structure. It has been observed that the porosity and nanogranular structure increased with increasing doping percentage. Here, we observe thatporous and granular structure of Mn-doped PAni shows better response and recovery time ($\sim$28 s) and decreases in electrical impedance. Dielectric constants, dielectric loss and AC conductivity have also been discussed with variations in frequency and relative humidity.

    • Novel highly active Ni–Re super-alloy nanowire type catalysts for CO-free hydrogen generation from steam methane reforming

      LINSHENG WANG

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      Novel Ni–Re super-alloy nanowire type catalyst system is found for hydrogen generation from steam methane reforming. The novel nanowire type catalysts exhibit the super-high catalytic activity for hydrogen generation from steammethane reforming with CO-free in the product at lower reaction temperatures. The Ni–Re alloy nanowire type catalysts are active for converting methane and water to hydrogen and carbon dioxide at a low reaction temperature of about 623 K, which is about 200 K lower than that is needed for steam methane reforming on the conventional catalysts. The CO-free hydrogen is efficiently generated from steam methane reforming on the nanowire type catalysts at the lower reaction temperatures, in which water–gas shift reaction step is not needed for CO-free hydrogen production.

    • Silver nanoparticles biosynthesized by Anabaena flos-aquae enhance the apoptosis in breast cancer cell line

      Z EBRAHIMZADEH A SALEHZADEH A S NAEEMI A JALALI

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      Silver nanoparticles (AgNPs) are one of the new cancer treatment tools due to their unique properties that enhance potential therapeutic efficacy. In this study, we describe the extracellular biosynthesis and anticancer activity ofAgNPs using the Anabaena flos-aquae biomass extract as reducing agent. The formation of dark-brown AgNO$_3$/extract solution confirmed the reduction of silver ions into AgNPs. In addition, the ultraviolet–visible spectroscopy showed the surface plasmon peak at 425 nm as characteristic peak for AgNPs. Transmission electron microscopy and scanning electron microscopy showed highly stable and mostly spherical AgNPs with average size of 5–25 nm. Fourier transform infrared spectral analysis confirmed the presence of biomolecules in the extract involved in the reduction and stabilization of AgNPs. In vitro, study of anticancer and cytotoxic effect of AgNPs and extract against T47D cell lines by MTT assay and flowcytometry confirmed the anti-proliferation potential of AgNPs against breast cancer cells. In conclusion, our results revealed that Anabaena can be used as a good organism for biologically synthesis of AgNPs and confirmed the potent therapeutic value of these nanoparticles as anticancer drugs.

    • Study of physicochemical properties of nanohydroxyapatite–chitosan composites

      EVGENY BULANOV NADEZHDA SILINA MAXIM LELET ALEXANDER KNYAZEV LARISA SMIRNOVA DIANA ALEYNIK IRINA CHARYKOVA

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      Hydroxyapatite nanoparticles were synthesized using modified sol–gel approach. Its biocompatibility was proved by in vitro experiments with diploid fibroblasts. The experiment showed that the presence of hydroxyapatite in the environment of cells does not reduce their viability. The observed phase transition of hydroxyapatite was explained as order/disorder transition, saving the crystal structure symmetry. Organo–inorganic composites of chitosan and hydroxyapatite were obtained by preparing a joint solution and pouring onto a glass substrate. According to XRD and DTA data, addition ofhydroxyapatite reduces the softening and decomposition temperature of chitosan. This information is necessary to optimize the manufacturing processes of organo–inorganic scaffolds.

    • Effect of intercalated anions on the electrical and dielectric properties of NiAl-X layered double hydroxide (${\rm X} = {\rm CO}^{2−}_3$, NO$^−_3$ and H$_2$PO$^−_4$): investigation by impedance spectroscopy

      F Z BOURAGBA W ELHATIMI R LAHKALE E M MOUJAHID E SABBAR

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      This paper reports the effect of interlayer species on the electrical and dielectric behaviours of a lamellar structure. The successful intercalation of three oxyanions (CO$^{2−}_3$, NO$^−_3$ and H$_2$PO$^−_4) in the interlayer space of NiAl-layered double hydroxide (LDH) was confirmed by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysisand inductively coupled plasma. Using complex impedance spectroscopy measurements, equivalent circuit consisting of three serially connected R-CPE units was established for each sample. Each unit contains a resistance and a constant phase element representing contributions of grain, grain boundary and electrode interface, which allowed the determination of their electrical parameters. The adjustment of experimental data of conductivity by the double power law allowed the determination of $\sigma_{\rm dc}$ and other conductivity parameters, and therefore, the investigation of the effect of intercalated anions on NiAl LDH electrical behaviour. Indeed, dihydrogenophosphates intercalated sample was found to decrease $\sigma_{\rm ac}$ over the frequency range of measure, comparing to the other anions. The intercalation of this anion has also an effect on dielectric properties, it reduces the value of dielectric constant of NiAl LDH, and shifts the maximum of $\tan \delta$ towards medium frequencies with a decrease in the value of loss tangent above $10^5$ Hz. Carbonate and nitrate intercalated LDH showed a similarity in their effect on electrical and dielectric properties of NiAl LDH.

    • Tribological properties of compatabilizer and graphene oxide-filled polypropylene nanocomposites

      S H YETGIN

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      Effect of maleic-anhydride-grafted-polypropylene (PP-g-MA) and graphene oxide (GO) addition on the tribological properties of polypropylene (PP) nanocomposites were investigated in this study. Graphene oxides with differentlevels (0.05 and 0.15 wt%) were used as reinforcing filler for PP nanocomposites. Maleic-anhydride-grafted-polypropylene (3 wt%) was added as a compatibilizer agent to increase the interaction between the GO and PP matrix. GO-filled PPnanocomposites with and without PP-g-MA were produced by a twin-screw extruder followed by injection moulding.Wear tests were carried out under dry sliding conditions against AISI 1040 steel disc using a pin-on-disc device at 0.4–1.6 m s$^{−1}$ sliding speed and 10–40 N loads. The tribological test results showed that the coefficient of friction and wear rate of PP nanocomposites increased with applied loads and sliding speeds. The coefficient of friction decreased by 8.2, 14.2, 37.3 and 74.7% under 1.2 m s$^{−1}$ sliding speed and 40 N load with the addition of PP-g-MA and GO to the PP nanocomposites. Thewear rate of PP and its nanocomposites was 10$^{−13}$ m$^2$ N$^{−1}$. The minimum wear rate was obtained for 0.15 wt% GO and 3 wt% PP-g-MA-filled PP nanocomposites with a value of 5.7537E$^{−14}$ m$^2$ N$^{−1}$ at 0.4 m s$^{−1}$ sliding speed and 10 N load in this study.

    • Effect of thermal cycling on mechanical and thermal properties of basalt fibre-reinforced epoxy composites

      FARZIN AZIMPOUR-SHISHEVAN HAMIT AKBULUT M A MOHTADI-BONAB

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      Current study investigated the effect of thermal fatigue on mechanical and thermal properties of basalt fibrereinforced polymer (BFRP) composites. To this, basalt fibre textiles in $2/2$ twill pattern was used to fabricate BFRPcomposites. Thermal cycling experiment was carried out between $−$40 and $+$120$^{\circ}$C for 20, 40, 60, 80 and 120 cycles. Moreover, dynamic mechanical analyzer (DMA) was used to evaluate the effect of thermal cycling on thermal properties of BFRPs. Moreover, we compared the extracted viscoelastic characteristics, such as storage modulus, loss modulus and loss factor curves with original thermal-treated BFRP specimens. Based on the results, thermal cycling affected the characteristics of composites in the post-curing stage due to an increase in temperature. Finally, the effect of thermal cycling on waterabsorption properties of BFRP composites was examined by hydrophobicity test. The results showed that tensile strength, flexural modulus and ILSS values increased with the increase in the number of cycles up to 80 cycles. In other words, an increase in the number of cycles increased the hydrophobicity of BFRP composites by decreasing the contact angles. Finally, the mechanical properties of tested composites were significantly decreased when the number of cycles reached 120. This was due to the mismatch of thermal expansion coefficient and long crack formation in the structure of composite.

    • Effect of heat treatment on the optical properties of layered muscovite single crystal sheets

      M KIRUBANITHY N SIVANANTHAM N GOPALAKRISHNAN K BALAMURUGAN

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      Naturally, thin sheets of layered, dioctahedral muscovite single crystals are transparent to visible light. Upon heat treatments performed up to 900$^{\circ}$C, the single crystal sheets of thickness $\sim$200 $\mu$m exhibited changes in its optical transparent character. The muscovite sheets exhibited either translucent or nontransparent, dark-brown, gold or copper like luster, varying optical band gap (from $\sim$3.7 to 2.7 eV) and photoluminescence (PL) properties, which depend on the temperature of the heat treatment. A comprehensive investigation has been made using X-ray diffraction, thermal analyses, energy dispersive X-ray and Raman spectroscopies to understand how/why the optical properties of the muscovite sheets changed up on heat treatments. Besides, no phase changes were found in the layered, lamellar crystal structure, evidences for the known dehydroxylation of muscovite were clearly seen from the thermal analyses data. Further, the Raman spectrum of the muscovite sheet heat treated at 900$^{\circ}$C showed no evidence for the presence of hydroxyl group (OH$^−$), which confirmed the completion of the dehydroxylation. The dihydroxylation-induced changes in the structural-elements (for example, Al-(O,OH)$_6$ partly or fully changing to Al-O$_5$/O$_6$ and its effects on the lattice constants, and also the defect levels introduced by the heat treatments are responsible for the changes in the optical transparency, colour of appearance, band gap and PL of the muscovite natural single crystal sheets.

    • Step-edge guided growth of nanowires on three-fold symmetric vicinal Si(111) surfaces

      DEBOLINA DAS TIRTHANKAR CHOUDHURY

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      Clean vicinal surfaces exhibit a stepped pattern due to the presence of narrow terraces formed on a clean surface. Therefore, this provides a platform for the aligned growth of nanowires. Using this type of surface as a template, we have grown nanowires of iron di-silicide, which are preferentially directed along the length of the terraces and are following the step-edges. These nanowires do not follow underlying three-fold symmetry of the substrate. We have thus shown two-fold symmetric growth on a three-fold symmetric surface, where diffusion barrier energy plays an important role in determining the shape of the islands. The orientations of nanowires are governed primarily by the presence of step-edges. However, the crystallographic symmetry properties of the underlying substrate have also played its role in controlling the nanowire orientation. The system was grown by molecular beam epitaxy and analysed by scanning tunneling microscopy.

    • Synergistic effect of manganese and nitrogen codoping on photocatalytic properties of titania nanoparticles

      I BIRLIK D DAGDELEN

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      Titanium dioxide is an n-type semiconductor widely used in applications like catalysts, optoelectonic materials, ceramics, H$_2$ generation, self-cleaning, water purification and solar cells. Sol–gel method has been chosen for nanoparticle synthesis because of its easy stoichiometry control, cost effectiveness and low temperature synthesis. In this study, titanium dioxide nanoparticles doped with different amounts of manganese (Mn) and nitrogen (N) were synthesized with sol–gel method. Crystal structure of undoped, Mn-doped, and Mn–N-codoped nanoparticles were determined with X-ray diffraction (XRD) analysis. Fourier transform infrared spectroscopy (FTIR) analysis was performed to identify the functional groups of nanoparticles. Photocatalytic analysis was carried out by methylene blue degredation under UV light for 1 h. X-rayphotoelectron spectroscopy (XPS) analysis was conducted to identify the chemical state and composition of the nanoparticles. Compared to the undoped TiO$_2$, which had 79.37% efficiency, Mn-doped and Mn–N-codoped TiO$_2$ nanoparticles have shown greater photocatalytic efficiency with 86.25 and 99.11% efficiencies, respectively. The results confirm that doping ofmanganese and nitrogen has affirmative effect on photocatalytic properties of synthesized nanoparticles.

    • New age monolithic design-based visible light responsive and reusable photocatalyst material using iron oxide-modified mesoporous titania framework

      S NAVEEN KUMAR VIVEK JAMES VINEETH JAMES M AKHILA MAHESWARI N SIVARAMAN C V S BRAHMANANDA RAO D PRABHAKARAN

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      In this work, we report a facile route for the synthesis of worm-like mesoporous Fe$_2$O$_3$-doped TiO$_2$ monolithic composites through a direct template sol–gel method, for the photocatalytic degradation of textile dye (acid blue 113) pollutants. The monolith surface morphology and structural properties have been characterized using p-XRD, HR-SEM–EDAX, HR-TEM–SAED, TGA, UV–Vis–DRS, PLS, FTIR, XPS and BET analyses. The stoichiometric doping of Fe$_2$O$_3$ unleashes visible light photocatalytic activity through a red shift in the light absorption character of TiO$_2$, thereby narrowing the energy band gap, and an eventual increase in e$^−$$/$h$^+$ separation centres. The monolithic photocatalyst exhibits better properties in terms of surface area, pore volume and diameter. The physico-chemical parameters, such as solution pH, dopant stoichiometry, catalyst quantity, dye concentration, photo-sensitizers and light intensity have been optimized to enhance the photocatalysis efficiency. The photocatalyst exhibits complete dye mineralization within 0.5 h, and also reusable for five continuous cycles.

    • Synthesis and surface characterization of electrodeposited quaternary chalcogenide Cu$_2$Zn$_x$Sn$_y$S$_{1+x+2y}$ thin film as transparent contact electrode

      R A BUSARI B A TALEATU S A ADEWINBI O E ADEWUMI E OMOTOSO K O OYEDOTUN A Y FASASI

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      A low-cost technique, electrochemical deposition has been used to grow nanocrystalline quaternary Cu–Zn–Sn–S (CZTS) on indium tin oxide (ITO)-coated glass substrate. Effects of variations in deposition potentials and sulphurcontent on the chemical composition, optical, morphological, structural and electrical properties of the deposited films have been investigated. The morphologies showed and confirmed the results from XRD analysis that the films are of polycrystalline grains. Average interplanar spacing of the films is 3.376 $\AA$. The average film’s thickness as estimated from Rutherford back-scattered spectroscopy studies was 34 nm. The estimated stoichiometry was found to be that of Cu$_2$ZnSnS$_4$ tetragonal kesterite structure. Optical studies showed that the absorption characteristic of the deposited CZTS film across thewavelength region is significantly dependent on growth deposition potentials and electrolyte concentration. Estimated band gap is between 1.75 and 1.81 eV. The electrical studies showed that the deposited films exhibit ohmic characteristics. This study demonstrated successful deposition of tetragonal kesterite structures of CZTS using a two-electrode cell approach. It also revealed the novel route of growing CZTS thin film over the conventional three electrode cells.

    • BaZrO$_3$ doping in (Na, K)(Nb, Ta)O$_3$: investigating the phase transformation behaviour, piezoelectric, dielectric, ferroelectric properties and their stability

      BHUPENDER RAWAL PRASHANT DIXIT N N WATHORE B PRAVEENKUMAR H S PANDA

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      This study highlights the effect of BaZrO$_3$ doping on (Na$_{0.52}$K$_{0.48}$)(Nb$_{0.95}$Ta$_{0.05}$)O$_3$ lead-free composition. The doping, interestingly, reveals the formation of a new polymorphic phase boundary between rhombohedral and tetragonalphases, while eliminating the orthorhombic phase. Rietveld refinement of temperature dependent X-ray diffraction data, in conjunction with dielectric studies, was utilized to corroborate the findings. The study also addresses in detail the process optimization methodology, involving calcination, sintering and poling process, which is highly relevant to the research community. Two mol% BaZrO$_3$-doped samples exhibited better piezoelectric, ferroelectric and dielectric properties. The doping also substantially improved the stability of properties during ageing, under thermal and cyclic electrical loadings.

    • Study on thermodynamic, electronic and magnetic properties of RE$_2$Cu$_2$Cd (RE $=$ Dy $−$Tm) intermetallics: first-principle calculation

      NAVEEN KUMAR SACHIN KUMAR KAMNA YADAV ARVIND KUMAR PAWAN K SINGH NEELABH SRIVASTAVA RISHI P SINGH

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      RE$_2$Cu$_2$Cd (RE $=$ heavy rare earth elements: Dy, Ho, Er, Tm) intermetallics show the interesting physical, magnetic and chemical properties with reference to magnetocaloric effect. To explore the relevant complex performance of RE$_2$Cu$_2$Cd materials, which crystallizes in Mo$_2$B$_2$Fe-type structure with space group P4/$mbm$; electronic, magnetic and thermodynamic properties have been studied using first principle theory. Electronic properties, i.e. spin-polarized electron dispersion curves (band structure) and density of state calculations showthat (Dy/Ho/Er/Tm)$_2$Cu$_2$Cd compounds aremetallic with dominant character of Dy-f spin down channels. Whereas magnetic and electron spin-polarization calculations show that studied materials behave like metallic ferromagnet having nearly fully spin-polarized characteristics. The effect of temperature on bulk modulus, $B$, volume of unit cell, $V$, entropy, $S$ and specific heat, $C_{\rm v}$ has also been studied using quasi-harmonic Debye model.

    • Substitution tuned electronic absorption, charge transfer and non-linear optical properties of some D–A type 2,4,6-trisubstituted-1,3,5-triazines: a DFT study

      V M VIDYA CHETTI PRABHAKAR

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      We have investigated theoretically a series of donor–acceptor (D–A) type star-shaped triazine derivatives by employing density functional theory using 6-311G(d,p) basis set to understand the effect of variable substitution (on triazinecore with substituents having diverse electron releasing or withdrawing capabilities) on their linear and non-linear optical properties (first hyperpolarizabilities). The investigation of influence of various electron donors/acceptors on the charge transfer characteristics of triazine molecules under study was also conducted. Present computational study reveals that thesubstitution of strong electron donors and greater charge delocalization enhance the first hyperpolarizability of the molecules.

    • Fabrication of two-dimensional chemically reduced graphene oxide nanosheets for the electrochemical determination of epinephrine

      SUSAN IMMANUEL R SIVASUBRAMANIAN

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      A simple and selective electrochemical sensor for the determination of epinephrine (EP) was developed using chemically reduced graphene oxide nanosheets (CRGO). The CRGO nanosheets were prepared using modified Hummer’s method and the material was characterized using transmission electronmicroscope (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) and UV–visible spectroscopy, respectively. The CRGO modified glassy carbon electrode (GCE) was employed for the electrochemical studies on EP using cyclic voltammetry (CV). The modified electrode showed significant catalytic activity compared to GO/GCE and bare GCE. The electron transfer kinetics revealed a two electron transfer for all the electrodes with CRGO/GCE exhibiting a high heterogeneous rate constant (0.127 s$^{−1}$). The detectionwas carried out using differential pulse voltammetry (DPV) through reduction of epinephrine chrome to leucoepinephrine chrome. The detection through the electrochemical reduction avoids the interference of similar analytes and improves the selectivity of the sensor. The detection limit was found to be 1.6 $\mu$M with two different linear ranges viz. 10–300 and400–1300 $\mu$M. Further, the electrode was subjected to stability, reproducibility and interference studies. The reliability of the proposed sensor was tested in the presence of biological serum samples.

    • A study on defect annealing in GaAs nanostructures by ion beam irradiation

      ONKAR MANGLA SAVITA ROY S ANNAPOORNI K ASOKAN

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      In this study, annealing of deep level (EL2) defect in gallium arsenide (GaAs) nanostructures by argon ion beam irradiation has been reported. GaAs nanodots of diameter ranging from 15 to 22 nm were deposited on silicon substratesusing the ions of GaAs generated by hot, dense and extremely non-equilibrium argon plasma in a modified dense plasma focus device. GaAs nanodots thus obtained were irradiated by Ar$^{2+}$ ion beam of energy 200 keV with varying ion fluences from $1 \times 10^{13}$ to $5 \times 10^{15}$ ions cm$^{−2}$ in the low energy ion-beam facility. The ion-beam irradiation transformed the as deposited GaAs nanodots into uniform GaAs nanostructured films of thickness $\sim$30 nm. The obtained nanostructured films are polycrystalline with paucity of arsenic antisite (EL2) deep level defect. The excess arsenic present in the as-deposited GaAs nanodots is the main cause of EL2 defect. Raman and photoluminescence measurements of GaAs nanostructured films indicates removal of excess arsenic, which was present in as-deposited GaAs nanodots, thereby suggesting annealing of EL2 defect from the ion-irradiated GaAs nanostructured films. The change in conductivity type from n- to p-type obtainedfrom Hall measurement further confirms annealing of EL2 defects. The ion-irradiated GaAs nanostructured films have low leakage current due to removal of defects as obtained in current–voltage study, which corroborate the annealing of EL2 defect. The defect-free GaAs nanostructured films thus obtained have potential applications in fabrication of highly efficient optoelectronic and electronic devices.

    • AC impedance measurement for the enzyme kinetics of urea–urease system: a model for impedimetric biosensor

      MOHANARANGAN SUNDARARAM KUMAR JANAKIRAMAN ANNAMALAI SENTHIL KUMAR V LAKSHMINARAYANAN KRISHNAN SANKARAN

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      The measurement of time evolution of electrochemical impedance enables enzymatic kinetic studies in realtime, and obviates the need of using additional reagents as in many popular spectroscopic methods. This can eventually leadto the development of enzyme biosensors.We have used the urea–urease system as a model for this study. The usage of a free enzyme (without any immobilization steps) in this work makes the technique very simple and unique for electrochemical measurement on urease. The impedance vs. time measurement of urease exhibits Michaelis–Menten (MM) behaviour with the MM constant ($K_{\rm m}$) of 0.8 mM and maximum velocity ($V_{\rm max}$) of 5000 ohms min$^{−1}$. This $K_{\rm m}$ value closely matched the one, which is obtained from the conventional colorimetric method (values). The enzyme kinetics was performed in a standard three-electrode system and reproduced in a fabricated mini electrochemical cell in an Eppendorf tube, which couldpave the way for the development of impedimetric biosensors for a variety of enzyme systems, especially the ones for which spectrometric techniques cannot be readily applied.

    • Investigation of potentials of C$_{30}$ and Ge$_{30}$ as anode in metal-ion batteries

      ZENGCAI MI KAIJIN ZHU LIFENG DING MEYSAM NAJAFI

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      Performances of C$_{30}$ and Ge$_{30}$ nanocages for anode electrodes in metal-ion battery (MI-B) are studied. Abilities of halogens (F, Br and Cl) adsorption on C$_{30}$ and Ge$_{30}$ potential for anode electrodes of MI-Bs were investigated. Gibbs free energy, voltage of cell, adsorption energy and orbital energy values of studied complexes were calculated and werecompared. Results displayed the $V_{\rm cell}$ of K-Ge$_{30}$ was higher than Na- and Li-Ge$_{30}$ 0.15 and 0.29 V. $V_{\rm cell}$ of K, Na and Li onGe$_{30}$ were higher than C$_{30}$ 0.18, 0.17 and 0.15 V. The G$_{\rm ad}$ of halogens (F, Br and Cl) on Ge$_{30}$ were higher than C$_{30}$ 5.19,4.63 and 4.91 eV. $V_{\rm cell}$ of K-halogen-, Na-halogen- and Li-halogen-Ge$_{30}$ are higher than C$_{30}$ 0.39, 0.36 and 0.32 V. G$_{\rm ad}$ of2, 3 and 4 halogens (F, Br and Cl) on Ge$_{30}$ are higher than C$_{30}$ ca 5.12, 3.29 and 4.64 eV, respectively. Finally, the F-Ge$_{29}$ with high performance and $V_{\rm cell}$ was proposed as anode electrode of potassium ion battery.

    • Quasi-solid sodium ions electrolyte of Na$_2$O−B$_2$O$_3$−SiO$_2$−H$_2$O system hydrated glass

      YINGMING ZHAO FAN TONG CHENYAO FAN SIQI YU BING HAN JIAYANG GAO YUNCHAO LOU PENGLIN JIANG ZHIYU WANG

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      Na$_2$O−B$_2$O$_3$−SiO$_2$−H$_2$O system hydrated glass with $T_{\rm g}$ ranges from $−$10 to 150$^{\circ}$C is synthesized by aqueouschemical methods and is applied to symmetrical cells as quasi-solid electrolyte. At the temperature around $T_{\rm g}$, the solid state transforms to quasi-solid state, whose mechanical property keeps like gel electrolyte, but the conductivity leaps from $5.31 \times 10^{−6}$ S cm$^{−1}$ to $5.43 \times 10^{−3}$ S cm$^{−1}$, much higher than most of the glass–ceramic electrolytes. As most of the solvated water is evaporated, H$_2$O left in the system distributes in the intervals as hydroxyl, which is much benefit to the ions transportation, and more important is to increase the voltage window to 2.24 V and even higher. The cycle performance is also researched. After 1000 circulations, there is still 65% capacity retention and no obvious damage is discovered in the electrolyte, which means much better cycle property of the electrolyte than gel electrolyte. Other compositions in the quasi-solid system including different contents of B$_2$O$_3$, Na$_2$SO$_4$ and m in sodium silicate NaO$_2$·mSiO$_2$ are also studied. In general, quasi-solid Na$_2$O−B$_2$O$_3$−SiO$_2$−H$_2$O system owns better conductivity and cycle performance than mostglass–ceramic solid electrolyte, and it is environment-friendly, inexpensive and practical to be used as sodium ions quasi-solid electrolyte.

    • Quality evaluation of solvent-cast 3D printing of poly(lactic acid) films

      MARINA FERNANDES COSATE DE ANDRADE RENATO CARAJELESCOV NONATO RENATO BOTTINI ANA RITA MORALES

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      This study aims to analyse the process conditions in the production of poly(lactic acid) (PLA) films by solventcast 3D printing. The films were evaluated according to thickness, roughness and visual aspect. An experimental design22 was performed with centre point in triplicate to study solvent/PLA ratio and printing speed. The solvent/PLA ratio and printing speed had a significant negative effect on film thickness and positive effect on film roughness. The film that presented the best classification in the visual aspect was the one moulded with the highest printing speed and solvent/PLA ratio.

    • Synthesis of mesoporous manganese dioxide/expanded graphite composite and its lithium-storage performance

      YAN LIN XIE LIU XIAO-QIN LIU LIN-BING SUN FENG CHEN CHENGBAO LIU ZHENGYING WU ZHIGANG CHEN

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      A mesoporous manganese dioxide (MnO$_2$)/expanded graphite (EG) composite was successfully fabricated using mesoporous silica decorated EG (KIT-6/EG) as a hard template. Different amounts of EG were introduced to thesynthetic system to adjust the MnO$_2$:EG mass ratio of the composite. X-ray diffraction, transmission electron microscopy, scanning electron microscopy and nitrogen adsorption–desorption analyses were employed to characterize the structure and morphology of the composite. Results show that the distribution of MnO$_2$ nanoparticles grown on the EG layers decreases gradually with increasing EG content. Moreover, in the presence of excess EG, the specific surface area of the samples dramatically decreases. As the anode electrode of a Li-ion battery (LIB), the composite (MnO$_2$:EG $=$ 34% w/w) exhibitsa specific capacity of $\sim$250 mAh g$^{−1}$ at a current density of 200 mA g$^{−1}$ for up to 100 cycles, this capacity is much higher than that of pure MnO$_2$ ($\sim$10 mAh g$^{−1}$) due to its improved electrical conductivity. The composite also shows good rating performance when the current density is tuned. These results indicate that the composite has potential application as ananode material for next-generation LIBs.

    • Tuning the electronic and optical properties of [26] annulene by electron donor and acceptor groups (push–pull system)

      SEYYEDE MEHRANGIZ ATYABI HAMID REZA SHAMLOUEI GODARZ MOHSENI ROOZBAHANI ELHAM ASGARI

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      This study was aimed at investigating the effect of electron donor and acceptor groups on electrical and optical properties of pi-conjugated [26] annulene. The results of the study showed that almost all selected substitutions reduced the value of $E_{\rm g}$ compared with pristine annulene. Calculated dipole moments for the sandwiched forms of annulene are noticeably greater than those of its pristine form, of which the ED2–ANN–QB2 had the maximum value for dipole moment. It was found that the influence of electron donor and acceptor groups on annulene optical properties is very significant. Moreoptical activity improvement was seen in the case of using QB2 and QB3 in one side and other electron donor groups in opposite side of [26] annulene molecule. The higher optical activity of these sandwiched molecules corresponds to higherelectron transfer in them. The results of this research may be useful in designing new photosensitizers.

    • Influence of Bi$_2$O$_3$, Sb$_2$O$_3$ and Y$_2$O$_3$ on optical properties of Er$_2$O$_3$-doped CaO–P$_2$O$_5$–B$_2$O$_3$ glasses

      G RAVI KUMAR CH SRINIVASA RAO

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      The glasses of the composition 25CaO–10(M$_2$O$_3$)–14P$_2$O$_5$–50B$_2$O$_3$:1Er$_2$O$_3$ (where M$=$Bi/Sb/Y) are prepared. The prepared samples are characterized by XRD, thermoluminescence (TL),UVand photoluminescence (PL) techniques. TL reports suggest that the sample of 10 mol%Y2O3 concentration (EY) exhibiting good shape symmetry factor ($u = 0.484$) and low AEs ($E_{\tau} = 1.189$, $E_{\delta} = 1.218$ and $E_{\omega} = 1.210$) under $\gamma$-irradiation might be a good TL asset. The optical absorptions of present glasses are studied well through the Judd–Ofelt theory.The evaluations such as Judd–Ofelt parameters are additionallyprojected. They are found to be the best ($\Omega_2 = 1.62 \times 10^{−21}$ cm$^2$, $\Omega_4 = 1.56 \times 10^{−21}$ cm$^2$ and $\Omega_6 = 0.59 \times 10^{−21}$ cm$^2$) for the sample of 10 mol% Y$_2$O$_3$ concentration (E$_{\rm Y}$), which may be a good optical asset to develop a novel class of laser resources. The radiative evolutions corresponding to the emissive transition ${}^4$S$_{3/2}$ $\to$ ${}^4$I$_{15/2}$ are assessed by PL technique. The evaluations are found to be the best ($A_t = 7089$ s$^{−1}$, $\tau_{\rm rad} = 140$ $\mu$s and $\beta = 96.1$%) for the sample of 10 mol% Y$_2$O$_3$concentration (E$_{\rm Y}$), which may be a useful luminescent resource.

    • pH and secondary structure instructed aggregation to a thixotropic hydrogel by a peptide amphiphile

      PAYEL DOWARI BAPAN PRAMANIK DEBAPRATIM DAS

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      Peptide-amphiphile (PA)-based supramolecular thixotropic hydrogels are useful in medical sciences due to multiple advantageous features along with its biocompatibility and biodegradability. In this work, we have developed aself-assembled peptide-based hydrogel from a $\beta$-sheet forming short PA. Hydrogelation of the PA is controlled by pH and consequent changes in secondary structures attained by the PA. Under acidic conditions, the PA remains in random coil conformation. While increasing the pH to 9, a rapid transformation to anti-parallel β-sheet leads to a strong hydrogel. Interestingly, the disulphide-linked dimer of the PA failed to attain such aggregation pattern. The pH-induced sol–gel–sol transition can be achieved for several cycles without any change in aggregation pattern. The hydrogel was also found to show thixotropic rheological behaviour and thus, it can be utilized as an injectable hydrogel for biomedical applications.

    • Ion recognition and fluorescent imaging of conjugated polymer fluorescent probes for Fe(III)

      LEI ZHENG ZHAO CHENG HAO HE HAO XU FEI LIANG LONG PANG

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      Novel polymer fluorescent probes for Fe(III) were synthesized to achieve a steady combination of ferric ions. In the Schiff base reaction of probes’ synthetic process, $o$-, $m$- and $p$-phenylenediamine were respectively introduced toresult in a series of new conjugated polymer fluorescent probes. Analyses on optical properties of the probes and probe-Fe(III) characteristic recognition through FS showed an application of the conjugated probes in quantitative identification and detection of Fe(III) with quick responses. Fluorescent imaging of the probes and probe-Fe(III) in living cells in vitro revealedlow toxicity of the probes and predicted the probes’ further application for instant Fe$^{3+}$ detection in clinical diagnosis and dynamic tracing of Fe$^{3+}$ in biological systems.

    • Effect of thermal spray process on chemical composition, magnetic behaviour, structure and mechanical properties of coatings based on milled Fe, Co and Al$_2$O$_3$ powder

      A YOUNES N DILMI A BOUAMER

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      Coated steel substrate by FeCo/Al$_2$O$_3$ nanoparticle with various Co concentrations realized by a thermal spraying process, preliminary powder alloy was elaborated by mechanical alloying technique for 20 h of milling time. The aims of this work are to study the effect of thermal spraying process and mechanical alloying on chemical composition, magnetic behaviour, structure and mechanical properties of coating. After mechanical alloying, the crystallite sizes of the powder were decreased from 18 to 7 nm and the lattice strains increased from 0.36 to 0.56%. This is due to the phenomenon of diffusion of cobalt in the iron lattice and the milling effect. After thermal spraying, many different phases appeared in the coating, such as Al$_2$FeO$_4$, CoAl$_2$O$_4$, CoFe and CoFe$_2$O$_4$. Magnetic behaviour was influenced by this change in the chemical composition of coating. The maximum saturation magnetization was found in Fe$_{40}$Co$_{20}$(Al$_2$O$_3$)$_{40}$ sprayed powder, however, the minimum coercivity was found in Fe$_{50}$Co$_{10}$(Al$_2$O$_3$)$_{40}$ sprayed powder. Mechanical properties’ parameters such as microhardeness andYoung’s modulus were enhanced by the change in chemical composition during mechanical alloying and thermal spraying process.

    • Preparation and characterization of porous (Si$_{1−x}$Ti$_x$)O$_2$ ($x \leq 0.25$) prepared by sol–gel hydrothermal process

      ROBERTO MENDOZA-SERNA JOSÉ OCOTLÁN FLORES-FLORES MARINA CABALLERO-DÍAZ ATENEA JOSEFINA CHONG-SANTIAGO LUCILA VALDEZ-CASTRO ROBERTO YSACC SATO-BERRÚ

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      An experimental strategy was developed to obtain (Si$_{1−x}$Ti$_x$ )O$_2$ ($x \leq 0.25$) porous materials via the sol–gel hydrothermal process. The sol was prepared from Si(OEt)$_4$ (TEOS), Ti(OBu)$_4$ (OBu: OCH$_2$CH$_2$CH$_2$CH$_3$), anhydrous ethanol, deionized water and nitric acid. The reagents were mixed at room temperature (293 K) to obtain a homogeneous colourless liquid which was subjected to a hydrothermal process at 473 K using a stainless steel container. Finally, the material obtained was treated at 873 K in air. The surface area of the treated solids was determined by N$_2$ adsorption/desorption isotherms. The corresponding average pore diameter was evaluated using the Barret, Joiner and Halenda and Horváth-Kawazoe methods. Porous structures were obtained, in which the average pore diameter of the microporous ones was 1.4 nm. The characterization techniques employed were Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, Raman spectroscopy, scanning electron microscopy, thermal gravimetric analysis, differential scanning calorimetry and UV–Vis diffuse reflectance spectroscopy. The Si–O–Ti bonds were detected by FTIR.

    • Synthesis and characterization of Cu–Ni/Gr nanocomposite coatings by electro-co-deposition method: effect of current density

      AJAY D PINGALE SACHIN U BELGAMWAR JITENDRA S RATHORE

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      Cu–Ni alloys are widely used and implemented due to their remarkable mechanical and electrochemical properties in most of the engineering applications. The reinforcement of graphene nanoplatelets (Gr) in Cu–Ni alloy can be utilized to enhance the properties of Cu–Ni alloy. In the present work, Ni as an alloying element and graphene nanoplatelets as reinforcing element were co-deposited with Cu to prepare Cu–Ni/Gr composite coatings by electro-co-deposition method. The influence of various current densities on surface morphology, composition, microstructure, crystallite size, lattice strain,microhardness, coefficient of friction and corrosion resistance of the resulting composite coatings were investigated and were presented in detail. Based on the experimental results, the coatings prepared at 6 A dm$^{−2}$, exhibit a reduced grain size with enhanced mechanical properties and corrosion resistance.

    • Few-layer-graphene as intercalating agent for spray-pyrolysed fluorine-doped tin oxide transparent conducting electrode

      L GO L MACARAIG E ENRIQUEZ

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      In this work, the development of a robust method for the fabrication of a low-cost transparent conducting electrode (TCE) via the addition of graphene in the spray-pyrolysis of fluorine-doped tin oxide (FTO) is explained. Alcoholic suspensions of few-layer-graphene were produced via the liquid exfoliation of graphite in different alcoholic solutions as sonicating solvent. These mixtures were then mixed with ammonium fluoride and tin (II) chloride dihydrate precursors to fabricate graphene/FTO composite through spray pyrolysis. Graphene exfoliated with 50% aqueous ethanol proved to yield improved TCE properties with nearly two-fold enhancement in figure of merit (FOM) measured in terms of the ratio of optical transmittance and sheet resistance. Using optimized spraying conditions, graphene/FTO coatings still yielded slightly higher FOM compared to plain FTO. The increase in FOM is largely attributed to the decrease in sheet resistance with the incorporation of graphene flakes.

    • Monovalent (Li$^{+1}$) doping effect in multiferroic GdMnO$_3$

      RINKU SARKAR BIDYUT SARKAR SUDIPTA PAL

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      This paper reports the temperature- and field-dependent magnetic properties of monovalent-doped polycrystalline sample Gd$_{0.85}$Li$_{0.15}$MnO$_3$ (GLMO) prepared by conventional solid-state reaction route. Final sintering at 1673 K for 18 h yields in the formation of well-grown, impurity phase free, single-phased, orthorhombic structured (with Pbnm space group) crystal. The optical properties have been investigated by UV-absorption spectra. The room temperature UV-absorption spectrum using Tauc’s formula gives an optical band gap of $\sim$3.12 eV. The paramagnetic (PM) state to incommensurateantiferromagnetic (ICAFM) state transition temperature increases due to Li doping. Magnetic hysteresis curve at 5 K signifies the Gd spin ordering.

    • Effect of sintering pressure on electrical transport and thermoelectric properties of polycrystalline SnSe

      J Y CHO M SIYAR S H BAE J S MUN M Y KIM S H HONG C PARK

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      Tin selenide (SnSe), which has high thermoelectric (TE) performance due to its low thermal conductivity, is considered as a promising TE material. It is good that TE properties were reported in single crystal form because polycrystalline SnSe exhibits low electrical conductivity compared to that of single crystal SnSe. To improve the electrical conductivity of polycrystalline SnSe, the effects of the pressure applied during spark plasma sintering (SPS) on the electrical charge transport and the TE properties of the polycrystalline SnSe were investigated. Degree of texture was enhanced with increasing sintering pressure from 30 to 120 MPa during SPS, which lead to the increase in carrier mobility, which resultedin the increase in electrical conductivity. Increase in pressure led to a significant increase in thermal conductivity due to an increase in the lattice thermal conductivity, which can be attributed to the decrease in phonon scattering at the grain boundary. A ZT of $\sim$0.7 was obtained at 823 K from the polycrystalline SnSe sintered with a pressure of 60 MPa, which can result from large increase in electrical conductivity with very small increase in the thermal conductivity. This study shows that the TE properties of the polycrystalline SnSe can be enhanced by controlling the degree of texture which can be accomplished by changing the pressure applied during SPS.

    • Tailoring LaB$_6$ nanoparticle-based self-healing film for heat-shielding window

      QIAN LIU CHAOFAN ZHANG LIXIA YANG LIANGJIU BAI YING LIANG WENXIANG WANG HUAWEI YANG DONGLEI WEI HOU CHEN

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      Effective insulation of near-infrared (NIR) from solar energy via the use of transparent coating on the windows is one of the most essential issues in energy savings. In this work, a novel lanthanum hexaboride (LaB$_6$)/poly(methacrylate-2-ureido-4[1H]-pyrimidinone) functionalized poly($n$-butyl acrylate) (PnBA-$r$-PMAUPy) film was prepared via an in-situ radical polymerization method to achieve heat insulation and self-healing performance. LaB$_6$ nanoparticles synthesized bya low-temperature method were employed as a NIR shielding material, while PnBA-$r$-PMAUPy was utilized as a material to enhance the reliability of long-term service. Benefitting from hydrogen bonding interaction, the film showed a marked progress in self-healing property at ambient temperature. As displayed by optical absorption results, the increase of LaB$_6$ content can effectively enhance the NIR shielding ability. The NIR blocking ratio of the thermal barrier film with a thickness of 0.64 mm can reach 97.5%, and the self-healing rate is about 84% for 20 mg LaB$_6$, respectively. The self-healing film forheat-shielding window can be a promising candidate with long-term service.

    • Thin film chemiresistive gas sensor on single-walled carbon nanotubes-functionalized with polyethylenimine (PEI) for NO$_2$ gas sensing

      SUNIL KUMAR VLADIMIR PAVELYEV PRABHASH MISHRA NISHANT TRIPATHI

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      Chemical detection of toxic gases, such as greenhouse gases is still very important as a research topic. To design gas sensor detectors based on single-walled carbon nanotubes (SWCNTs) with high sensitivity and selectivity for the toxic environment is a continuous process. The aim is to detect NO$_2$ gas with better sensitivity. In the present work, the thin-film sensor is fabricated on SiO$_2$ substrate and it is functionalized with polyethylenimine (PEI). It has been established that PEI functionalized SWCNTs (F-SWCNTs) show high sensitivity towards strong electron-withdrawing particles. It was found that at room temperature, SWCNTs-PEI functionalized gas sensor exhibited a higher sensitivity of 37.00% as compared with bare SWCNTs gas sensor. The gas sensor has shown the repeatable response for the entire concentration range studied.The sensing properties and the PEI functionalization duration effects on the behaviour of SWCNTs-based gas sensors were demonstrated.

    • Effect of back electrode on trap energy and interfacial barrier height of crystal violet dye-based organic device

      SUDIPTA SEN N B MANIK

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      In this work, we have studied the effect of aluminium-coated mylar (Al–M) sheet-based back electrode and aluminium (Al)-coated back electrode on trap energy ($E_{\rm t}$) and barrier height ($\phi_{\rm b}$) of crystal violet (CV) dye-based organic device. Two devices have been prepared using two different back electrodes. In both the devices, ITO-coated glass is used as front electrode. Both the organic devices have been prepared by using spin-coating techniques. We have measured the steady state current–voltage ($I –V$) characteristics of these devices to estimate the trap energy ($E_{\rm t}$) and barrier height ($\phi_{\rm b}$) of the devices. Because of the insertion of a reflecting back electrode, the charge carriers are confined in the active layer, which reduces the $E_{\rm t}$ from 0.044 to 0.034 eV and $\phi_{\rm b}$ is reduced from 0.80 to 0.77 eV. The barrier height is also estimated by using another alternative method, which is known as Norde method. By using Norde method, $\phi_{\rm b}$ is estimated, which reduces from 0.83 to 0.79 eV in the presence of reflecting back electrode. Both the methods show good consistency with each other. The reductions of these parameters indicate the enhancement of charge injection through the metal-organic dye interface. With the use of polished back electrode in the CV dye-based organic device, it is possible to modify the barrier height and trap energy and thereby modifies the conductivity.

    • Structural, mechanical and optoelectronic properties of cubic Be$_x$Mg$_{1−x}$S, Be$_x$Mg$_{1−x}$Se and Be$_x$Mg$_{1−x}$Te semiconductor ternary alloys: a density functional study

      BIMAL DEBNATH MANISH DEBBARMA DEBANKITA GHOSH SAYANTIKA CHANDA RAHUL BHATTACHARJEE SURYA CHATTOPADHYAYA

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      Structural,mechanical and optoelectronic features of cubic Be$_x$Mg$_{1−x}$S, Be$_x$Mg$_{1−x}$Se and Be$_x$Mg$_{1−x}$Te alloyshave been explored by DFT-based FP-LAPW approach. Nonlinear reduction in lattice constant, but increment in bulk modulus and each of the elastic constants $C_{11}$, $C_{12}$ and $C_{44}$, occurs with increasing Be-concentration $x$ in each system. All the specimens exhibit elastic anisotropy. Specimens at $x = 0.0$, 0.25 and 0.50 show ductility, but remaining specimens at $x = 0.75$ and 1.0 show brittleness. Each ternary alloy is a direct ($\Gamma$−$\Gamma$) band gap ($E_{\rm g}$) semiconductor. Almost linear decrease in $E_{\rm g}$ with increase in $x$ is observed in each alloy system. Ionic bonding exists among the constituents of all specimens. The occupied valence chalcogen-p as initial and unoccupied conduction Be-3s, 2p and Mg-4s, 3p as final states play a keyrole in optical transitions. Nature of variation of zero-frequency limit in each of the $\epsilon_1(\omega)$, $n(\omega)$ and $R(\omega)$ spectra with $x$ isopposite to, while critical point in each of the $\epsilon_2(\omega)$, $k(\omega)$, $\sigma(\omega)$ and $\alpha(\omega)$ spectra with $x$ is similar to, the nature of variation of $E_{\rm g}$ with $x$.

    • Effect of barium sulphate on mechanical, DMA and thermal behaviour of woven aloevera/flax hybrid composites

      M ARULMURUGAN A S SELVAKUMAR KRISHNASAMY PRABU G RAJAMURUGAN

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      The natural fibre-reinforced polymeric composites attract themanufacturing industries due to their recyclability, cost-effectiveness and eco-friendly nature. The natural hybrid reinforced polymeric (HNRP) composite overcomes thelimitations in mechanical properties of the mono-natural fibre-reinforced composites. In this research work, the effect of barium sulphate (BaSO$_4$) on the mechanical characterization of HNRP (aloevera/flax/barium sulphate) composites was examined as per ASTM standard. BaSO$_4$ is preferred as a filler based on the absence of self-motion, high density and high melting point (1580◦C). The thermal stability of the HNRP composite was determined by thermogravimetric analysis (Model: TG/DTA 6200). The water absorption and dynamic mechanical properties of the HNRP composites were estimated.The fractography images were analysed to recognize the fractured surface morphology using a scanning electron microscope. The HNRP5 composite has the maximum tensile strength of 34.72 MPa, predominantly based on the interlocking of the flax fibre and plasticity of the composite improved by the influence of BaSO$_4$. The impact strength decreased noticeably with theaddition of barium sulphate in the composite. The weight reduction of around 7–9% was observed in the temperature range of 100–200$^{\circ}$C. The mono-composites (HNRP1&2) absorbed, respectively, 4.8 and 3.5% of moisture; with the addition of BaSO$_4$, the same combination absorbed 4.2 and 3.2% of water content, which was due to the low water absorption capability of BaSO$_4$. The storage modulus of the HNRP5 composite has maximum magnitude in the glassy region and minimum in the rubber region.

    • Green synthesis and structural characterization of gold nanoparticles from Achillea wilhelmsii leaf infusion and in vitro evaluation

      MARYAM ASARIHA AZAM CHAHARDOLI NADIA KARIMI MARYAM GHOLAMHOSSEINPOUR ALIREZA KHOSHROO HOUSHANG NEMATI YALDA SHOKOOHINIA ALI FATTAHI

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      The aim of this study is to green-synthesize gold nanoparticles (GNPs) by leaf infusion of Achillea wilhelmsii (AW) and to evaluate their biological effects. The synthesized AW-GNPs were characterized by UV–Vis spectroscopy, Fourier transform infrared, X-ray diffraction (XRD), transmission electron microscopy (TEM) and dynamic light scattering analyses. The antibacterial and cytotoxicity activities of AW infusion and AW-GNPs were evaluated. Antioxidant activity was evaluated by 1, 1-diphenyl-2-picrylhydrazyl test. Moreover, the electrochemical activity of AW-GNPs as a modifier ata glassy carbon electrode (GCE) was studied. The surface plasmon resonance absorption band at 540nm in the UV–Vis spectrum discloses the reduction of gold cations into GNPs. The XRD pattern of GNPs shows the crystal structure of AW-GNPs, and TEM image displays the spherical shape of GNPs with small size (2.7–38.7 nm). The AWinfusion and AW-GNPs demonstrated a maximum antioxidant activity of 68 and 58%, respectively. AW-GNPs showed antibacterial activity against gram-positive bacteria, without affecting gram-negative bacteria. Also, AW-GNPs exhibited the cytotoxicity effects against MDA-MB-468 cancer cell line, and the electrochemical study indicated a significant electrocatalytic activity of AW-GNPs. The results indicate the advantages of using AW leaf infusion for the production of GNPs with antibacterial, antioxidant, cytotoxic and electrocatalytic activities.

    • Pristine and modified-mesoporous alumina: molecular assistance-based drug loading and sustained release activity

      PRITAM SINGH P K MAITI KAMALIKA SEN

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      The present article reports on the synthesis of mesoporous alumina and its modification through $\beta$-cyclodextrin (BCD) incorporation for loading and release studies of amoxicillin. The drug loading in the mesoporous matrices was found to be activated upon providing molecular assistance by amino acids, L-methionine, L-proline and L-phenylalanine. The effect of molecular assistance has been attributed to intermolecular interactions between the drug and the individual amino acids which have been further confirmed by different spectroscopic studies. The drug-loaded material with BCD modification wasfound to exhibit a sustained release mechanism in physiological pH and is suggested as a proposed material for hip joint prosthesis.

    • Synthesis and characterization of Dy-doped Lu$_1$Gd$_2$Ga$_2$Al$_3$O$_{12}$ phosphor for LEDs

      U FAWAD IBRAHIM GUL H J KIM WAZIR MUHAMMAD MATIULLAH KHAN

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      The synthesis and characterization of Dy-doped Lu$_1$Gd$_2$Ga$_2$Al$_3$O$_{12}$ are reported in this article. Solid-statereaction method is used to synthesize the material. X-ray diffraction and scanning electron microscopy characterization techniques are used to study the phase and structure of the synthesized material. Luminescence, which is the main propertyof the phosphor material, is characterized by UV- and X-ray-induced luminescence spectroscopy. Lu$_1$Gd$_2$Ga$_2$Al$_3$O$_{12}$:Dy$^{3+}$phosphor shows its highest emission spectra in blue and yellow regions. A combination of yellow and blue gives us white light, displayed by chromaticity diagram for this phosphor. Hence, this phosphor may be used in white-light-emitting diodes. The absorption spectra of our material match well with spectral curve of LEDs. Therefore, it may be used in LEDs applications.

    • Temperature-dependence calculation of lattice thermal conductivity and related parameters for the zinc blende and wurtzite structures of InAs nanowires

      HAWBASH H KARIM M S OMAR

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      Theoretical calculations are performed on lattice thermal conductivity (LTC) and related parameters for the zinc blende and wurtzite structure of InAs nanowires (NWs) with diameters of 50, 63, 66, 100 and 148 nm through the Morelli–Callaway model. For the model to be efficiently applicable, the longitudinal and transverse modes are considered. The melting point of the various-sized NWs is considered to estimate the Debye and phonon group velocities. The impacts of Grüneisen parameter, dislocations and surface roughness are also successfully utilized to address the calculated and measured LTC of the semiconductor under investigation. Results show that the Grüneisen parameter increases with decreasing NW diameter and that phonon confinement leads to an observable deviation of the calculated LTC curve from that of the experimental one in the case of bulk InAs. We assume that NW boundaries, dislocations and imperfections are responsible for the scattering of phonons along with electrons and other phonons because of normal and Umklapp processes. Therefore, at a specified temperature, LTC depends on the size and crystal structure of the semiconductor. As such, the thermal and mechanicalparameters of InAs can be greatly modified by decreasing the size and dimension of the semiconductor as a result of the quantum-confinement effect.

    • Gold-nanoparticle- and nanostar-loaded paper-based SERS substrates for sensing nanogram-level Picric acid with a portable Raman spectrometer

      SREE SATYA BHARATI MORAM CHANDU BYRAM VENUGOPAL RAO SOMA

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      Nanoparticle (NP)-loaded filter paper (FP)-based surface-enhanced Raman scattering (SERS) substrates have been prepared using differently shaped gold (Au) NPs. The shape of Au NPs plays a significant role in the amplification ofSERS signal. Here, two differently shaped Au NPs were synthesized using two different techniques: (a) femtosecond (fs) laser ablation in liquid and (b) chemical method. Spherical shaped Au NPs were obtained using fs ablation of a bulk Autarget in distilled water and Au nanostars (NSs) were achieved through chemical process utilizing N-vinyl-2-pyrrolidone as a reducing/capping agent. The size and shapes of these synthesized NPs and NSs were investigated meticulously usingdifferent characterization techniques such as transmission electron microscopy, field emission scanning electron microscopy and X-ray diffraction. Both the NPs and NSs were subsequently loaded onto commercially available FP by simple drop casting method. To achieve higher number of hot spots, the aggregated spherical NPs were obtained by addition of NaCl. The non-aggregated spherical, aggregated spherical, and star Au NPs loaded on FP were used for the detection of a dye (Nile blue) and an explosive molecule (Picric acid).

    • Comparative analysis on optical and photocatalytic properties of chlorophyll/curumin-sensitized TiO$_2$ nanoparticles for phenol degradation

      AZADEH HAGHIGHATZADEH

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      In this work, natural-dye-sensitized photocatalysts (NDSPs) of TiO$_2$ were prepared by a simple wetness impregnation method, in which natural pigments of chlorophyll and curcumin were initially extracted from fresh parsley leaves andlong roots of dried turmeric, respectively. The as-prepared NDSPs were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) and UV–vis diffuse reflectance (DRS) spectroscopy. XRD and SEM studies verified intact structural and morphological properties for NDSPs of TiO$_2$ compared to non-sensitized nanostructures, while FT-IR and DRS analyses confirmed the presence of dye pigments on the surface of TiO$_2$ photocatalysts after the photosensitization process. A red-shift towards longer wavelengths was observed in band-gap energies ofdye-sensitized samples. These NDSPs indicated efficient photocatalytic performances towards decomposing phenol in visible light irradiation. Phenol degradation experiments are systematically conducted to optimize four key operating parameters, including irradiation time, initial pH of the reaction mixture, dye-sensitized TiO$_2$ dosage and initial phenol concentration. Dye-sensitization using chlorophyll pigments results in the highest phenol degradation rate (85%) compared with that of samples sensitized with curcumin pigments (75%), which is perfectly in agreement with the corresponding band-gap energies. Photodegradation processes were modelled by the Langmuir–Hinshelwood kinetics, while the adsorption equilibrium was investigated based on Langmuir and Freundlich isotherms. Lastly, possible mechanisms involved in the process of phenol photodecomposition were proposed.

    • Eu(III)-doped barium tellurooxyphosphate phosphor with orange-red emission

      K MOHANRAO HANSNATH TIWARI S ASIRI NAIDU U V VARADARAJU

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      Eu$^{3+}$ photoluminescence (PL) is studied in the tellurooxyphosphate, Ba$_2$TeO(PO$_4$)$_2$, host. A series of phosphor compositions with varying concentrations of Eu$^{3+}$ dopant in Ba$_2$TeO(PO$_4$)$_2$ are synthesized by high temperature solid-state reaction and the PL spectra are recorded. Under 395 nm wavelength excitation, the emission spectrum shows a single peak corresponding to the non-degenerate transition, ${}^5$D$_0$ $\to$ ${}^7$F$_0$ indicating that Eu$^{3+}$ preferentially occupies a singlecrystallographic site. The peak due to the degenerate hypersensitive ${}^5$D$_0$ $\to$ ${}^7$F$_2$ electric dipole transition of Eu$^{3+}$ in theemission spectrum indicates that the site occupied by Eu$^{3+}$ in the tellurooxyphosphate host lattice is non-centrosymmetric. The CIE coordinate values are $x = 0.61$ and $y = 0.34$ and are found to be close to the values of the reference phosphor Y$_2$O$_3$:Eu$^{3+}$.

    • An improved synthesis of iron phosphate as a precursor to synthesize lithium iron phosphate

      DANPING JIANG XIANGJUN ZHANG TING ZHAO BINGXUE LIU RONG YANG HONGKUN ZHANG TENGFEI FAN FAN WANG

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      Two different kinds of FePO$_4$: amorphous FePO$_4$ and crystalline FePO$_4$, were synthesized as a precursor to synthesize LiFePO$_4$/C. The crystalline FePO$_4$ was obtained by treating amorphous FePO$_4$ with phosphoric acid refluxing. Inductively coupled plasma-atomic emission spectrometry was used to evaluate the impurity content. The obtained materialswere characterized by chemical analysis, scanning electron microscopy and X-ray diffraction. The results showed that the performance of LiFePO$_4$/C synthesized by crystalline FePO$_4$ is significantly better than when LiFePO$_4$/C is synthesized from amorphous FePO$_4$. The capacity retention and capacity fade of LiFePO4/C synthesized from crystalline FePO$_4$ was 70.9% at $−$20$^{\circ}$C and 0.012% per cycle after 150 cycles at 1$C$, respectively. The better performance from using crystalline precursor resulted from a more uniform powder with fewer crystalline defects and impurities.

    • Theoretical examination of oxygen reduction reaction (ORR) on carbon nanocone (CNC) for fuel cells

      XIAOMIN SHANG MENG SUN MINGXIAO JIN XIAOQIU LIU MEYSAM NAJAFI

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      Recently, various studies were performed to propose and discover acceptable catalysts for oxygen reduction reaction (ORR) in various fuel cells. Here, performance of boron-doped carbon nanocone (CNC) as catalyst to ORR via theoretical methods is examined. The ORR paths through ER and LH mechanisms were studied. Results showed that onsetpotentialand over-potential on ORR of boron–CNC were 0.73 and 0.50 V, respectively. The calculated exchange current density and transfer coefficient of B–CNC were $ca.$ $6.5 \times 10^{−6}$ A cm$^{−2}$ and 0.52, respectively. Results demonstrate that boron-doped CNC is a high-potential catalyst to ORR.

    • Time-resolved fluorescence decay and Gaussian analysis of P3HT-derived Ho$^{3+}$- and Tm$^{3+}$-doped ZnO nanostructures

      G L KABONGO P SMBULE G H MHLONGO B M MOTHUDI M S DHLAMINI

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      The fluorescence vibrational features of as-synthesized P3HT–ZnO:Ho${}^{3+}$ and P3HT–ZnO:Tm${}^{3+} thin films were investigated using Gaussian analysis. Relative to P3HT–ZnO:Tm$^{3+}$ film, detailed Gaussian analysis of the fluorescence spectra revealed weaker intensity exhibited in P3HT–ZnO:Ho$^{3+}$ film due to better charge transfer. Moreover, we comparatively present the Huang–Rhys factor and relaxation energy of the samples, which are calculated using relations derived from the Franck–Condon theory. Furthermore, P3HT–ZnO:Ho$^{3+}$ film exhibits lower relaxation energy as compared with P3HT–ZnO:Tm$^{3+}$ film, which implies better conjugation length. Finally, the singlet exciton lifetime of P3HT–ZnO:Ho$^{3+}$ samplewas found to be shorter as compared with P3HT–ZnO:Tm$^{3+}$, while the calculated exciton diffusion length was 6.4 and 10.3 nm, respectively.

    • Titania-based porous nanocomposites for potential environmental applications

      S WADHWA A MATHUR R PENDURTHI U SINGHAL M KHANUJA S S ROY

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      Titania–zeolite Y composites were synthesized by a facile solid-state dispersion method. The synergistic effects of porous zeolite structure and novel photocatalysis properties of titania nanoparticles were exploited. The physical properties of the composites were characterized by scanning electron microscopy, energy-dispersive X-ray, X-ray diffraction, diffuse reflectance spectroscopy, fourier transform infra-red spectroscopy and photoluminescence spectroscopy. Porosity and surface area of the composites were determined from Brunauer–Emmett–Teller studies. The antibacterial effect and the photocatalysis properties of these composites were studied. Composites exhibited higher growth reduction of Escherichia coli and Staphylococcus aureus as compared with the pure forms ($P$25 titania and zeolite Y). Maximum growth reduction of both types of bacterial cells (gram-positive as well as gram-negative) was observed with 20% titania–zeolite composite. The composite demonstrated 40 and 30% enhancement in the growth reduction of E. coli and S. aureus, respectively, as compared with the pure forms; 10% composite exhibited 50% enhancement in the photocatalysis efficiency of methylene blue dye degradation as compared with $P$25 titania nanoparticles and led to a complete removal of the dye in the first 60 min of photocatalysis process. Mechanisms for both applications have been proposed in light of the observed results.

    • Synthesis, characterization and anticorrosion behaviour of a novel hydrazide derivative on mild steel in hydrochloric acid medium

      P PREETHI KUMARI PRAKASH SHETTY SUMA A RAO DHANYA SUNIL T VISHWANATH

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      A novel corrosion inhibitor, namely $N'$-[(4-methyl-1$H$-imidazole-5-yl)methylidene]-2-(naphthalen-2-yloxy) acetohydrazide (IMNH), has been synthesized and characterized by ${}^1$H NMR and FTIR spectroscopic techniques. The anticorrosion behaviour of IMNH on mild steel in 1M hydrochloric acid (HCl) medium was studied by potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques. The percentage inhibition efficiency of IMNH increased with increase in its concentration and temperature. The adsorption of IMNH followed chemisorption andobeyed Langmuir’s adsorption isotherm. PDP study revealed that IMNH functioned as a mixed type inhibitor. Theoretical study of the adsorption behaviour of this inhibitor was carried out by quantum chemical calculations using density functional theory (DFT). Scanning electron microscopy (SEM), atomic force microscopy (AFM) and energy-dispersive X-ray spectroscopy (EDX) studies confirmed the formation of a protective film of IMNH on the mild steel surface.

    • Synthesis, characterization and quantum chemical study of optoelectronic nature of ferrocene derivatives

      AHMAD IRFAN FIRAS KHALIL AL-ZEIDANEEN ISHTIAQ AHMED ABDULLAH G AL-SEHEMI MOHAMMED A ASSIRI SAMI ULLAH GHULAM ABBAS

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      Two new ferrocene derivatives N-(2-hydroxy-5-methylphenyl) ferrocylideneamine (Fe1) and N-(2-hydroxy-5-chlorophenyl) ferrocylideneamine (Fe2) have been synthesized to study the effect on electronic, optical and charge transfer properties while changing the electron donating group with electron withdrawing group. The synthesized compounds were characterized by different spectroscopic (FTIR, UV–Vis, ${}^1$H NMR, ${}^{13}$C NMR) and spectrometric (EI) techniques. Thegeometries for ground and excited states were optimized by density functional theory (DFT/B3lyp/6-31G$^{**}$, LANL2DZ) and time-dependent DFT (TD-B3lyp/6-31G$^{**}$, LANL2DZ) levels, respectively. The absorption, fluorescence and phosphorescence spectra were estimated using TD-B3LYP and TD-wB97XD functionals and 6-31G$^{**}$ basis set for C, H, N, O and LANL2DZ for Fe atoms in dichloromethane.

    • Atom probe analysis of Ni–Nb–Zr metallic glasses

      LEONARDO PRATAVIEIRA DEO STEFAN NIKODEMSKI

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      Atomic short arrangements of two Ni–Nb–Zr glassy alloys (doped and undoped) were examined through the 3D atomic reconstruction technique, atom probe tomography (APT). The chemical short configurations predicted accordingto two distinct theoretical models were compared with APT reconstructions, and inconsistencies were found. Additionally, diffraction experiments confirmed that the alloys under investigation were amorphous in nature.

    • Effect of amino-functionalization of MWCNTs on the mechanical and thermal properties of MWCNTs/epoxy composites

      ARISHA KASHYAP NAVJOT PAL SINGH SHALINI ARORA VASUNDHARA SINGH V K GUPTA

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      The study investigates the tensile, flexural and thermal properties of epoxy resin matrix reinforced with pristine as well as amino-functionalized multi-walled carbon nanotubes (MWCNTs, 0, 0.25 and 0.50 wt%). The combination ofultrasonication and magnetic stirring has been used for the fabrication of MWCNTs/epoxy composite samples. The epoxy composite reinforced with 0.50 wt% amino-functionalized MWCNTs exhibits superior mechanical and thermal properties. The tensile and flexural strengths of this composite are noticed to be higher by about 13.5 and 17%, respectively, as compared with the neat epoxy specimen. The improvement in properties offered by amino-functionalized MWCNTs/epoxy composites is attributed to uniform distribution of MWCNTs in epoxy matrix as well as better interfacial adhesion between MWCNTsreinforcement and epoxy matrix,when compared with those noticed for epoxy composite reinforced with pristine MWCNTs.

    • Synthesis and characterization of inherently radiopaque nanocomposites using biocompatible iodinated poly(methyl methacrylate-$co$-acrylamide) and graphene oxide

      SAEED SHIRALIZADEH HOSSEIN NASR-ISFAHANI AMIR HOSSEIN AMIN MOSTAFA AZIMZADEH RAMEZAN ALI TAHERI

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      New inherently radiopaque nanocomposites were prepared using iodine-containing poly(methyl methacrylateco-acrylamide) and graphene oxide. For this purpose, P(MMA-$co$-AA) was synthesized via copolymerization of methylmethacrylate and acrylic acid, and modified with 4-iodophenyl isocyanate and 3,4,5-triiodophenyl isocyanate to form poly[(methyl methacrylate-$co$-(N-4-iodophenyl)acrylamide)] (1I-P(MMA-$co$-AA)) and poly[(methyl methacrylate-$co$-(N-3,4,5-triiodophenyl)acrylamide)] (3I-P(MMA-$co$-AA)), respectively. For comparative evaluation, the non-iodinatedcopolymer (PIC-P(MMA-$co$-AA)) was prepared via reaction of the P(MMA-$co$-AA) with phenyl isocyanate to investigate the effect of iodinated substituents on the morphology and thermal characteristics of the nanocomposites. All the nanocomposites were characterized by X-ray diffraction analysis, scanning electron microscopy, X-radiography and thermogravimetricanalysis. The results proved that thermal properties of the nanocomposites improved by the introduction of different amounts of graphene oxide into the copolymers’matrix. Radiopacity measurements showed the excellent radiopacityof iodinated nanocomposites and proved that 3I-GO-5 had radiopacity equivalent to that of an aluminium wedge with 2-mm thickness.

    • Growth, spectral, mechanical, electrical and optical characterization of guanidinium hydrogen succinate single crystal

      K KRISHNARAJ N SIVAKUMAR P PRAVEEN KUMAR

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      Slow evaporation method was employed to grow an organic crystal: guanidinium hydrogen succinate (GHS). Monoclinic structure of GHS was confirmed by single-crystal X-ray diffraction study and its space group was determined to be $P2_1/c$. Different functional groups present in GHS were estimated qualitatively by Fourier transform infrared analysis. The crystalline quality of the grown GHS was ascertained by high-resolution X-ray diffraction study. The UV–Vis absorption spectrum reveals a lower cut-off wavelength of 235 nm. The minimum absorption shows the wide optical transparency in the entire visible region.Work hardening co-efficient value ($n = 1.7$) shows that the GHS crystal belongs to soft material category. Behaviour of dipoles in the crystal was examined through dielectric study. The third-order nonlinear optical analysis wascarried out on GHS crystal through Z-scan technique. The nonlinear refractive index ($n_2$), nonlinear absorption coefficient ($\beta$) and third-order nonlinear optical susceptibility ($\chi^{(3)}$) were estimated to be $−5.78\times 10^{−8}$ cm$^2$ W$^{−1}$, $0.72\times 10^{−4}$ cm W$^{−1}$ and $8.09 \times 10^{−6}$ esu, respectively.

    • Effect of tertiary butylpyridine in stability of methylammonium lead iodide perovskite thin films

      S C EZIKE A B ALABI A N OSSAI A O AINA

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      Perovskite material is a great visible light absorber in perovskite solar cells (PSCs). PSC has reported power conversion efficiency (PCE) of 22.1%. However, performance instability of the solar device base on this material hampersits commercialization. One of the factors responsible for performance instability in the cell is temperature. In this work, we carried out stability study of perovskite film treated with tertiary butylpyridine (tBP) as a surface modifier. Concentrationsof tBP added in perovskite material film were varied and the samples were subjected to temperature degradation test in a temperature-controlled chamber for 120 h. Ultraviolet–visible (UV–Vis) spectrophotometers, Fourier-transform infrared (FT-IR) spectrometers andX-ray diffractometers (XRD) were used to characterize the properties of the temperature-stabilitytested samples. The results show that the sample treated with 100 $\mu$l of tBP has the best resistance to temperature degradation after the duration of the test. The surface-modified perovskite films, with 100 $\mu$l of tBP, may reduce the degradation of PSCs.

    • Mesoporous $x$[Cu(II)O] nanoclusters dispersed and immobilized on $y$[SiO$_2$] matrix: structure and effective controlled biocidal activity against Pseudomonas aeruginosa and Bacillus subtilis

      DHIMAN BANIK S CHENNAKESAVULU MONIKA SINGH NIDHI PANDEY RAGINI TILAK ARAMATI BINDU MADHAVA REDDY PRADIP PAIK

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      Herein we report the synthesis of mesoporous nanostructures comprising copper (II) oxide {$x$[Cu(II)O]} immobilized on silica $y$[SiO$_2$] template for release of copper ions by precipitation via sol–gel technique. Three different specimens with increasing amount of Cu in the matrix with amount of Si being the same in all the samples, viz. ‘6Cu:5Si’, ‘4.5Cu:5Si’ and ‘3Cu:5Si’ where the numbers refer to the respective molar ratios of their respective domains, were prepared. Increase of crystallinity in the mesoporous material with increase in incorporation of copper domains consisting of CuO in SiO$_2$ matrix has been established. The average size of the CuO nanoparticle (NP) (domain) is 20–30 nm. The BET surface area has been found to be 276–390 m$^2$ g$^{−1}$ and Langmuir surface area has been found to be 422–605.9 m2 g−1 for the samples5Si:3Cu–5Si:6Cu, respectively, having pore size of 4–6.5 nm. The cytotoxicity data show that the NPs are less toxic below concentration of 125 $\mu$g ml$^{−1}$. A steady increase in percentage of bacterial-‘Escherichia coli’, ‘Pseudomonas aeruginosa’ and ‘Bacillus subtilis’ cell death (indicated by decrease in optical density) due to increase in concentrations of NPs after incubation for 14 h, showing sensitivity even at very low concentrations (5–20 $\mu$g), has been observed. A comparative antibacterial activity test among the three prepared specimens has been reported, which shows better antibacterial activity with the lowest copper concentration. Better antibacterial sensitivity when compared with equivalent amount of commercial CuO is established.

    • Thermal stability and flame-retardant characteristic of irradiated LDPE and composites

      MAZIYAR SABET HASSAN SOLEIMANI SEYEDNOOROLDIN HOSSEINI

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      Magnesium hydroxide (MH) and alumina trihydrate (ATH) are extensively consumed as fillers in polyolefins to fabricate naturally responsive cables. Halogen-free wires, and especially cross-linked or thermoplastic elastomers, arefurther prevalent in worldwide use. The limited oxygen index (LOI), cone calorimeter, smoke density and thermogravimetry (TGA) experiments explain the thermal decomposition, flame-retardant and physical characteristics of samples. Results from studies of TGA, smoke emission and LOI testers showed that the thermal strength and flame-retardant characteristics of the samples containing MH compared with corresponding specimens containing ATH have superior thermal stability. The flame-retardant and heat resistance characteristics of samples were improved due to irradiation and the development of cross-linking bonds in the polymer framework. The results of the smoke density experiment show that adding MH to low-density polyethylene (LDPE) results in the lowest smoke density associated with LDPE and LDPE/ATH compounds. This study proved that the inclusion of MH and irradiation of specimens caused a greater thermal strength and also a superior flame-retardant polymeric product compared with the inclusion of ATH to similar irradiated specimens. These successes are useful and appropriate specifically for cable companies to deliver halogen-free flame-retardant cable materials.

    • Design of Permalloy–ferrite–polymer soft magnetic composites doped by ferrite nanoparticles and visualization of magnetic domains

      M STRECKOVA J SZABO I BATKO M BATKOVA Z BIRCAKOVA J FUZER P KOLLAR A KOVALCIKOVA R BURES L MEDVECKY

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      Soft magnetic composite materials were prepared by powder metallurgy technology. The composition of the new family of the materials was based on Permalloy type of ferromagnetic particles covered by Ni$_{0.2}$Zn$_{0.8}$Fe$_2$O$_4$ nanoparticles. The spinel ferrite was prepared by electrospinning technology for achieving high-quality nanoparticles. A small amount of organic additives was included in final samples. The influence of magnetic ferrite dielectric coating on the magnetic properties of prepared composites was studied. The relatively high electrical resistivity leads to the real part of complex permeability up to 52 with stability up to high frequencies of about 1 MHz. SEM and TEM analyses were employed for composite characterization. The preparation of samples for magnetic force microscopic analysis is outlined in detail. The visualization of magnetic domain structure was done in order to understand the material behaviour of magnetic materials.

    • Crystallization and kinetics studies of Ti$_{20}$Zr$_{20}$Cu$_{60−x}$Ni$_x$ ($x = 10$, 20, 30 and 40) metallic glasses

      P RAMA RAO ANIL K BHATNAGAR BHASKAR MAJUMDAR

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      Synthesis and characterization of Ti$_{20}$Zr$_{20}Cu$_{60−x}$ Ni$_x$ ($x = 10$, 20, 30 and 40) metallic glasses are reported in this paper. Glassy ribbons are produced by rapid quenching using the standard copper wheel roller technique in argon atmosphere. Their structural characterization is carried out by X-ray diffraction (XRD) and thermal behaviour (crystallization) study by differential scanning calorimetry (DSC). Results of XRD on both sides of each ribbon sample confirmed that each sample was indeed amorphous/glassy as only a very broad peak in XRD pattern was observed. Metallic glass Ti$_{20}$Zr$_{20}$Cu$_{50}$Ni$_{10}$ shows three crystallization peaks in non-isothermal DSC scans while other three samples show only a single crystallization peak. The activation energy of crystallization for each sample has been calculated using three available models, namely, those of Kissinger, Augis–Bennett and Ozawa. All the three models gave nearly similar activation energies for a given sample within 10%.

    • Characterization of organic light-emitting diode using a rubrene interlayer between electrode and hole transport layer

      DHRUBAJYOTI SAIKIA RANJIT SARMA

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      In this paper, we report the characteristic properties of an organic light-emitting diode (OLED) using a rubrene buffer layer over the fluorine-doped tin oxide (FTO) surface. Our study includes both electrical and optical properties of the device. Here, we study the OLED devices at different thicknesses of the buffer layer, which varies from 3 to 11 nm. For device fabrication, we use a thermal evaporation unit. Finally, we report that device performance in a bilayer anode form is always higher than that of a single-FTO-based device. Maximum device efficiency is found to be 6.31 cd A$^{−1}$ around 8-nm thickness of rubrene layer over the FTO surface.We also study the stability of both the single-layer and double-layer anode OLED devices. Through this study, we found that both device efficiency and luminance intensity of the bilayer anode OLED remain more stable for more number of days compared with the single-FTO OLED device.

    • Microstructure and optical characterization of mechanosynthesized nanostructured TiSi$_x$N$_{(1−x)}$ cermets

      UJJWAL KUMAR BHASKAR S K PRADHAN

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      Nanocrystalline cubic titanium silicon nitrides (TiSi$_x$N$_{(1−x)}$) with different Si concentrations have been synthesized at room temperature by mechanical alloying the stoichiometric compositions of ingredient powders in a nitrogenatmosphere. Structure and microstructure characterizations of unmilled and all ball-milled powders are carried out byanalysing respective X-ray diffraction patterns employing the Rietveld structure and microstructure refinement method.The presence of titanium, silicon and nitrogen in TiSi$_x$N$_{(1−x)}$ has been confirmed by energy-dispersive X-ray transmission electron microscopy analysis. Transmission electron microscopy image reveals that the average size of the spherical particles of 9-h-milled powder is $\sim$5 nm and size distribution is almost monodispersed, which corroborates well with the result of the Rietveld analysis. Bandgap energies of these solid solutions are determined by analysing respective UV–Vis absorption spectrum and it is found that the addition of silicon to insulating nanocrystalline TiN results in a reduction of bandgap energy and all solid solutions become wide-bandgap semiconductors with the addition of Si in different proportions.

    • Effect of bismuth oxide nanoparticles on the physicochemical properties of porous silicon thin films

      S OUSSIDHOUM D HOCINE M O BENSIDHOUM D CHAUMONT E BOURENNANE S BOUDINAR A MOUSSI E LESNIEWSKA N GEOFFROY M S BELAKID

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      In this work, bismuth oxide nanoparticles were successfully deposited on porous silicon (PSi) in order to enhancethe light absorption and reduce the optical losses. The obtained bismuth oxide (Bi$_2$O$_3$)/PSi samples were characterizedby means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning electronmicroscopy (SEM) combined with energy-dispersive spectroscopy (EDS), atomic force microscopy (AFM), photoluminescence(PL), UV–visible absorption and reflection spectroscopy techniques. The XRD studies revealed the formation of themonoclinic $\alpha$-Bi$_2$O$_3$ phase. The XPS analysis demonstrates the formation of highly pure Bi$_2$O$_3$ nanoparticles in accordance with XRD results. The SEM and AFM analyses confirmed that the bismuth oxide nanoparticles are well incorporated and uniformly distributed over the surface of PSi without changes in the arrangement and shape of the pores, resulting in an optimized microstructure. The Bi$_2$O$_3$/PSi films showed better absorption than PSi layers as indicated by UV–Vis absorption technique. The reflection measurements confirmed a further reduction in reflectivity of PSi from 6.4 to 3.5% after the inclusion of Bi$_2$O$_3$ nanoparticles, which is of significant importance for solar cells application since it can enhance its conversion efficiency. The Bi$_2$O$_3$/PSi films have a great promise to be used as efficient antireflection coatings in innovative concepts of higher efficiency and cost-effective solar cells.

    • Investigation of optical properties and glass transition temperature of nano-epoxy matrix

      TAGREED M AL-SAADI BUSHRA H HUSSEIN SUAD H ALEABI

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      In this research work, nanocomposites were synthesized by addition of fractions (0.0, 0.02, 0.04 and 0.06) of multi-wall carbon nanotubes (MWCNTs) to epoxy resin to investigate the optical properties and glass transition temperature. Optical measurement shows that epoxy matrix films have high absorption at the different MWCNTs fractions (0.0, 0.02, 0.04 and 0.06). The optical energy gaps for allowed direct transition were evaluated and found to decrease with increasing film fractions, precisely, from 2.85 to 1.32 eV when fractions increased from 0.0 to 0.06 of the matrix weights that indicated strong shifts at 435–935 nm with increasing fraction. The values of the absorption coefficient and extinction coefficientincreased with fractions of MWCNTs while the refractive index and the real part of dielectric constant decreased with the fractions of MWCNTs. Also, the glass transition temperature was investigated and was found to increase with increasing fraction of carbon nanotube in the matrix.

    • Fabrication of micro–nano-roughened surface with superhydrophobic character on an aluminium alloy surface by a facile chemical etching process

      MOHAMMAD REZA ATTAR EHSAN KHAJAVIAN SAMAN HOSSEINPOUR ALI DAVOODI

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      In the present work, we have fabricated a superhydrophobic surface on aluminium alloy 2024 through a simpleimmersion chemical etching method in hydrochloric acid followed by a functionalization step in stearic acid solution. Theimpact of etching time on water contact angle was investigated and a contact angle of $\sim$167$^{\circ}$ was reached on the superhydrophobic surface, which was etched for 4 min. Morphology of the surface was evaluated by scanning electron microscopy and the surface chemical analysis was performed by energy-dispersive X-ray spectroscopy and Raman spectroscopy. We show that the fabricated superhydrophobic samples can besides water, also repel other liquids.We also demonstrate the selfcleaning properties of the fabricated samples using graphite particles as contaminants. Ultimately, we assessed the corrosionresistance properties of the fabricated surfaces by the potentiodynamic polarization method. The superhydrophobic surface exhibited increased corrosion potential and polarization resistance along with reduced corrosion current density, all of which are indicative of a significant improvement in corrosion performance of the superhydrophobic surface in comparison withtypical aluminium 2024. The cheap and facile superhydrophobic surface fabrication method presented in this study can beapplied to large scale samples with no need for electricity or expensive raw materials.

    • Influence of NH$_4$Br as an ionic source on the structural/electrical properties of dextran-based biopolymer electrolytes and EDLC application

      M H HAMSAN M F SHUKUR SHUJAHADEEN B AZIZ Y M YUSOF M F Z KADIR

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      Biopolymer electrolytes (BPEs), consisting of ammonium bromide (NH$_4$Br) as the ionic provider and dextran(Leuconostoc mesenteroides) as the polymer host, are prepared by the solution cast technique. Interactions of cations from the salt have been confirmed with hydroxyl (OH) and glycosidic linkage (C–O–C) groups of dextran via Fourier transforminfrared analysis. Electrolyte with 20 wt% NH4Br maximized the ionic conductivity up to $(1.67 \pm 0.36) \times 10^{−6}$ S cm$^{−1}$. The trend of conductivity has been verified by field emission scanning electron microscopy, where the electrolyte surface became rough as the concentration of NH4Br exceeded 20 wt%. The contribution of ions as the main charge carrier in theBPE is confirmed by transference number analysis as $t_{\rm ion} = 0.92$ and $t_e = 0.08$. From linear sweep voltammetry, it is found that the highest conducting BPE in this work is electrochemically stable from 0 to 1.62 V. The fabricated electrochemical double-layer capacitor (EDLC) has been tested for 100 charge–discharge cycles and verified by cyclic voltammetry.

    • Fabrication of MOF-177 for electrochemical detection of toxic Pb$^{2+}$ and Cd$^{2+} ions

      S SANGEETHA G KRISHNAMURTHY

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      We have studied the electrochemical behaviour of room-temperature synthesized MOF-177. The MOF-177sample was characterized by various techniques like Fourier transform infrared spectroscopy, scanning electron microscopy,energy dispersive X-ray, powder X-ray diffraction, nuclear magnetic resonance and CHNS elemental analysis. The MOF-177 electrode was prepared and electrochemical performance was carried out to explore the electrical activity of MOF-177.Cyclic voltammetry studies were performed in 0.05 M K$_4$Fe(CN)$_6$ solution and electrochemical sensing experiments were performed in 0.05MH$_2$SO$_4$ and pH 7 buffer solution. A significantly increased electron transfer property has been observed and it has been explored for the electrochemical detection of heavy metal ions. The MOF-177/cp electrode has shown excellent sensitivity towards toxic heavy metal ions such as Pb$^{2+}$ and Cd$^{2+}$ at the limit of detection of 0.004 and 0.03 $\mu$M, respectively.

    • Titanium-doped carbon and boron nitride nanocages (Ti–C$_{48}$ and Ti–B$_{24}$N$_{24}$) as catalysts for ClO $+$ 1/2O$_2$ $\to$ ClO$_2$ reaction: theoretical study

      CHAO SUI ZHIPING ZHANG XUE CAI QI ZHOU MEYSAM NAJAFI

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      The performances of Ti-doped carbon and boron nitride nanocages towards chloride monoxide (ClO) oxidation were examined. Details of mechanisms of oxidation of ClO on Ti-doped carbon and boron nitride nanocages were examined. Ti atoms of Ti–C$_{48}$ and Ti–B$_{24}$N$_{24}$ show catalytic activity towards ClO adsorption with low-barrier energies. Resultsdisplayed that the Ti-doped carbon and boron nitride nanocages oxidized ClO by the mechanisms of Eley–Rideal (ER) and Langmuir–Hinshelwood (LH). Catalytic activities in the LH path were limited by irremediable adsorption of chloridedioxide (ClO$_2$) on Ti–C$_{48}$ and Ti–B$_{24}$N$_{24}$.While, in the ER path, the first and second ClO$_2$ were separated, directly. Finally,the results proved that the Ti–C$_{48}$ and Ti–B$_{24}$N$_{24}$ show suitable catalytic abilities towards ClO oxidation via the ER path.

    • A kaolinite/TiO$_2$/ZnO-based novel ternary composite for photocatalytic degradation of anionic azo dyes

      A K M MAKSUDUL HASAN SHAIKAT CHANDRA DEY MUHAMMAD MOMINUR RAHMAN ABDULLAH MUHAMMAD ZAKARIA MITHUN SARKER MD ASHADUZZAMAN SAYED MD SHAMSUDDIN

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      Solar-assisted photocatalytic degradation of organic pollutants has emerged as efficient technology for the effective treatment of industrial wastewater. Here, we report a simple technique for the fabrication of a novel ternary photocatalystfrom kaolinite (K), TiO$_2$ (T) and ZnO (Z). The most efficient catalyst was prepared at a calcination temperature of 60$^{\circ}$C. The fabricated ternary composite was characterized using different analytical techniques including Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, field emission-scanning electronmicroscopy and energy dispersive X-ray spectroscopy. The photocatalytic degradation was performed at room temperature (25$^{\circ}$C) using Remazol Red (RR), an anionic azo dye, as the model compound. A maximum of 98% degradation of RR was found with the ternary catalyst K$_{0.50}$T$_{0.45}$Z$_{0.05}$, which was prepared from 50% kaolinite (w/w), 45% TiO$_2$ (w/w) and 5% ZnO (w/w). The catalyst was found to be suitable for long-term repeated applications. Mechanistic investigation through radical trapping experiments confirmed hydroxyl radicals as the potential contributor to the photocatalytic degradation of RR. It is highly expected that a novel photocatalyst design such as this will pave way towards further development ofmaterials capable of hazardous dye removal from industrial effluents.

    • A proof of concept for low-cost rechargeable aqueous aluminium-ion batteries

      SUNNY NANDI HOMEN LAHAN SHYAMAL K DAS

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      In an effort to develop Al$^{3+}$ ion-based rechargeable electrochemical cells, there is massive exploration of appropriate electrode materials in contemporary times. Aluminium is a natural choice due to its high abundance, low cost and easy processing. Herein, the working of rechargeable aqueous aluminium-ion batteries which comprise graphite from pencil sketch as the cathode, TiO$_2$ as the anode and an Al$^{3+}$ ion conducting aqueous electrolyte is demonstrated for the first time. The aluminium-ion cell delivers a discharge voltage of 1.5 V and stable specific capacities of 25 mAh g$^1{−1}$ over 1000 cycles. This proof of concept emphasizes on the possibility of achieving sustainable, easy to assemble and low-cost rechargeable batteries.

    • Synthesis and evaluation of antibacterial properties of magnesium oxide nanoparticles

      JOYSHREE MAJI SANJEEV PANDEY SOUMEN BASU

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      In this paper we studied the efficiency of magnesium oxide (MgO) nanoparticles with an average size of 27 nm synthesized by a simple soft chemical method, in killing both Gram negative and Gram positive pathogenic bacteria. The antibacterial activity was determined by a minimum inhibitory concentration technique, agar cup method and live count technique. These nanoparticles show the maximum antibacterial activity towards Bacillus sp. in comparison with Escherichia coli. Transmission electron microscopy analyses of the treated-bacterial strains showed a morphological deformation with increased cell wall disruption. From the analysis of the antibacterial activity of MgO nanoparticles it is revealed that6 $\mu$g ml$^{−1}$ of dose is sufficient for killing Bacillus sp. whereas it is 7.5 $\mu$g ml$^{−1}$ for E. coli. These doses may be used in medical application. MgO nanoparticles could be used as antibacterial agents after completion of successful in vivo trials.

    • Synthesis of cerium-oxide NPs and their surface morphology effect on biological activities

      MALATESH S PUJAR SHIRAJAHAMMAD M HUNAGUND DELICIA A BARRETTO VANI R DESAI SHIVAPRASADAGOUDA PATIL SHYAM KUMAR VOOTLA ASHOK H SIDARAI

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      Herein, reliable work has been carried out on the synthesis of cerium-oxide (CeO$_2$) nanoparticles (NPs) viahydrothermal and co-precipitation methods. We emphasize the highly adequate hydrothermal method for synthesizingCeO$_2$ NPs for biomedical applications. Absorption spectra showed peaks at 283 and 274 nm, which confirm the formationof CeO$_2$ NPs for hydrothermal (HYNPs) and co-precipitation (CONPs) methods, respectively. Functional group analysisfirmly showed the presence of organic and inorganic species, which revealed similar characteristics of both HYNPs andCONPs. The cubic structure and the average crystallite size of the synthesized NPs are determined using Scherrer’s andWilliamson–Hall methods. The obtained average particle size is compared by using high-resolution transmission electronmicroscopy, which is around 10 and 5 nm for HYNPs and CONPs, respectively. Further, we studied their antimicrobial activities and consequently, the synthesized CeO$_2$ NPs showed excellent antimicrobial activities. Moreover, HYNPs yieldedpromising antioxidant activity with the lowest IC$_{50}$ as compared with CONPs. Owing to the biological activity of CeO$_2$ NPs, HYNPs act as best therapeutic agents in biomedical applications as well as its vital role in antibiotics.

    • Constitutive modelling of Al7075 using the Johnson–Cook model

      SAJAD RASAEE A H MIRZAEI D ALMASI

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      In this paper, hot compression behaviour of Al7075 in the temperature range of 573–723 K and the strain rate range of 0.001–0.1 s$^{−1}$, based on standard requirements, was studied. The prediction of flow stress was performed using constitutive equations based on the basic and modified-Johnson–Cook model and the accuracy of the proposed models was estimated by comparing with the experimental results by the statistical error analysis method. Based on the experimental results, flow stress is changed significantly with changes in the strain rate and temperature. However, the basic model cannot predict the correlated effects of these parameters which decrease its accuracy of model, the flow stress of the materials especially at high temperatures. During the calculation of the constants based on the modified model, the effects of hardening and softening behaviour were included in addition to considering the correlated effects of the parameters. The accuracy of the modified model increased significantly when compared with experimental results.

    • First-principles computations of Y$_x$Ga$_{1−x}$As-ternary alloys: a study on structural, electronic, optical and elastic properties

      S TOUAM R BELGHIT R MAHDJOUBI Y MEGDOUD H MERADJI MUHAMMAD SHEHRYAR KHAN R AHMED R KHENATA S GHEMID D P RAI Y AL-DOURI

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      In this work, the first-principles computational study on the structural, elastic, electronic and optical propertiesof Y$_x$Ga$_{1−x}$As as a function of yttrium concentration ($x$) is presented. The computations are performed using the fullpotential linearized augmented plane wave plus local orbital method designed within density functional theory. Firstly,we performed our calculations on the most stable phases, NaCl and zinc blende, then their transition pressure for eachconcentration is determined and analysed. Our computed results for the zero yttrium concentration are found consistentwith the available experimental measurements as well as with theoretical predictions. Moreover, the dependencies of theseparameters upon yttrium concentration ($x$) were found to be non-linear.We also report computed results on electronic-bandstructure, electronic energy band gap results and density of states. A systematic study on optical properties to analyse itsoptoelectronic character and elastic properties is presented.

    • Cyclic oxidation of Ni–Fe$_2$O$_3$ composite coating electrodeposited on AISI 304 stainless steel

      MOHSEN ABAEI MORTEZA ZANDRAHIMI HADI EBRAHIMIFAR

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      Protective coatings can be applied to enhance the performance of interconnects in solid oxide fuel cells. In this study, AISI 304 steel was coated with a Ni–Fe$_2$O$_3$ composite to form a modified-Watt’s type electrolyte by the conventional electro co-deposition method. The characterization of the coatings before and after cyclic oxidation was performed by scanning electron microscopy and X-ray diffraction. In order to evaluate the oxidation behaviour, thermal cycling was carried out in a furnace at 850$^{\circ}$C. The results indicated that the coated steel had better oxidation resistance in comparison with the uncoated steel. After 60 cycles of oxidation, the Ni–Fe$_2$O$_3$ composite coating was converted to FeNi$_2$O$_4$, NiCrO$_4$, MnFe$_2$O$_4$ and Fe$_2$NiO$_4$. The Fe$_2$O$_3$/NiFe$_2$O$_4$ composite coating reduced the outward migration of chromium and the growth rate ofthe Cr$_2$O$_3$ layer.

    • The effect of shape and size of ZnO nanoparticles on their antimicrobial and photocatalytic activities: a green approach

      SAURABH SHARMA KULDEEP KUMAR NAVEEN THAKUR S CHAUHAN M S CHAUHAN

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      In this paper, ZnO nanoparticles (NPs) having potent photocatalytic and antimicrobial activities have been synthesized by using the aloe vera plant extract. The ZnO NPs have been synthesized using (Zn(CH$_3$COO)$_2$·2H$_2$O) (5, 10 and 50 mmol kg$^{−1}$), at temperature 70$^{\circ}$C and pH 11.5. The synthesized NPs were examined using UV–Visible, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and transmission electron microscopy(TEM) characterization techniques. TEM analysis confirms the synthesis of ZnO NPs with hexagonal, spherical, cylindrical and cuboidal shapes decorated under different concentrations of precursor metal salt. UV–Visible studies revealed thatZnO NPs have a wide energy band gap varying from 3.36 to 3.43 eV. The synthesized ZnO NPs were examined for the photocatalytic degradation of methyl orange dye which resulted in up to 95% degradation. ZnO NPs are also inspected for the antibacterial activity against Bacillus subtilis (MTCC 441), Staphylococcus aureus (MTCC 737) and Escherichia coli (MTCC 739) pathogenic bacteria.

    • Investigation of flow behaviour and lubrication capabilities of MoS$_2$

      P THAPLIYAL G D THAKRE

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      Flow behaviour of lubricants largely depends on their rheological properties which in turn strongly influence their lubrication capabilities and ultimately the machine life. Modern chemistry plays a great role in the synthesis of nano-additives that help in enhancing the rheological and tribological properties of the lubricants. In the present study, the rheological and tribological studies of MoS$_2$ nanofluids are presented in order to determine their flow behaviour and lubrication capabilities. For studying the effect of MoS$_2$ nanoparticles on the flow behaviour and lubrication capabilities of lubricants, two commercially available blended synthetic engine oils of SAE grades 5W-40 were selected. MoS$_2$ nanoparticles were synthesized by hydrothermal methods. Surface modification of the synthesized MoS$_2$ nanoparticles was performedbefore blending them with the base lubricants in 0.1, 0.15 and 0.2% concentrations. Standard ASTM and IS procedures were used to determine physicochemical properties and tribo-performance behaviour of oils, respectively. The rheological parameters of MoS$_2$ nanofluids were determined using a rheometer. The study reveals that tested MoS$_2$ nanofluids behavedas non-Newtonian lubricants with shear thinning behaviour at all tested temperatures and exhibited viscoelastic behaviour at small-shear rates. As a result of this anti-wear property showed a significant enhancement up to 20% for 0.2% MoS$_2$ indicating better anti-wear properties of MoS$_2$ nanofluids. However, a marginal reduction in friction for the tuning of 4% observed for 0.2 wt% of MoS$_2$ nanoparticles in the tested lubricants indicates that finished products have little scope to improve anti-friction properties under the influence of the already present additives.

    • Antibacterial activity of ZnO nanoflowers deposited on biodegradable acrylic acid hydrogel by chemical bath deposition

      SINAN TEMEL FATMA OZGE GOKMEN ELIF YAMAN

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      In the first part of this study, acrylic acid (AA) hydrogels were produced by a free radical reaction. Chemical and morphological structures of AA-hydrogels were specified by using Fourier transform infrared (FT-IR) spectroscopy andscanning electron microscopy (SEM) techniques. In the second part of the study, ZnO nanoflowers were synthesized on the AA-hydrogel by using a chemical bath deposition (CBD) technique for the first time in the literature. The AA-hydrogel acted as the substrate in the CBD process. The deposition time effect on the morphological properties of ZnO nanoflowers was determined by applying SEM. According to the SEM results, the deposition time in the production of ZnO nanoflowers has played a vital role in the surface morphology. Chemical, morphological and thermal properties of the ZnO nanoflowers were determined by applying FT-IR, scanning electron microscopy-energy dispersive X-ray spectroscopy and thermogravimetric analysis techniques. Elemental mapping of ZnO nanostructures was carried out using SEM. The antibacterial activity of theZnO nanoflower-deposited AA-hydrogel was determined against Gram-negative and Gram-positive bacteria. Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were used as test microorganisms. Gram-negative bacteria were moreresistant to hydrogels and ZnO nanoflowers compared to Gram-positive bacteria.

    • A remarkable enhancement between optical transparency and SHG efficiency on doped-KHP single crystals

      J AARTHI S GOWRI C S KAVIYA S A BHEETER

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      Potassium hydrogen phthalate (KHP) single crystals are non-linear optical materials and their transmittance window are remarkably enhanced by an organic dopant such as resorcinol. The present study was mainly focused on the growth and characterization of the single-crystal KHP doped with resorcinol which was synthesized by a slow evaporation solution technique and its dimension was found to be $8 \times 7 \times 2.75$ mm$^3$ at ambient temperature. Vibrationalassignments of the functional groups confirmed the presence of dopants. The optical behaviour of the grown crystal was explored by ultraviolet–visible–near-infrared studies which result in 99% of the transmittance with the cut-off wavelength of 250 nm. The mechanical property was analysed by the Vickers microhardness test. The apparent microhardness increases with increasing applied indentation load revealing the reverse indentation size effect behaviour. Organic impurity increases the second harmonic generation efficiency of KHP, suggesting that the molecular alignment in the presence of resorcinolresults in enhanced non-linearity.

    • Silicone rubber composites fabricated using KH550-modified poplar leaves graphene

      WEILI WU HE HUANG

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      Silicone rubber (SR) composites were fabricated using poplar leaves graphene (PG). PG was synthesized from poplar leaves and modified-poplar leaves graphene (MPG) was obtained by treating graphene with a silane coupling agent $\gamma$-aminopropyltriethoxysilane (KH550). The biosynthesized PG and MPG were characterized by using organic elemental analysis, X-ray photoelectron spectroscopy, atomic force microscopy and scanning electron microscopy (SEM). The PGmodified SR composites were studied by using their mechanical properties, Fourier transform infrared spectroscopy, SEM and thermogravimetric analysis. The results showed that the PG synthesized by poplar leaves had high-carbon content and purity. The MPG was more evenly dispersed into SR than the PG, the mechanical properties of the MPG/SR composites were better than those of the PG/SR when the MPG content was 0.1 phr (parts per hundred rubber), the tensile strength and elongation at break were increased by 36.2 and 19.4% respectively and the wear resistance was increased by 57.1%. The thermal stability of the MPG/SR was higher than that of the PG/SR and SR. This important discovery could not only solve the problem of the origin of graphene, but also broaden the application of SR composites.

    • Investigating the role of amides on the textural and optical properties of mesoporous-nanostructured $\theta$-Al$_2$O3

      SOURAV GHOSH SUKANYA KUNDU RITUPARNA DAS MILAN KANTI NASKAR

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      Mesoporous-nanostructured $\theta$-Al$_2$O$_3$ was synthesized by an autoclaving technique using different amidesi.e., formamide (F), dimethyl formamide (DMF) and diethyl formamide (DEF) at 150$^{\circ}$C/24 h followed by calcinationat 1000$^{\circ}$C. Crystallization and structural behaviour of the as-synthesized materials were characterized by X-raydiffraction and Fourier transform infrared spectroscopy. The porosity study was carried out by N2 adsorption–desorption(BET) technique. Microstructural features were measured by transmission electron microscopy (TEM). The amidebasedsolvents played a deliberate role in microstructural and textural features of $\theta$-Al$_2$O$_3$. The DMF-based solventshowed an enhanced surface area of 158 m$2^$ g$^{−1}$. The as-prepared $\theta$-Al$_2$O$_3$ rendered a nano-sheet, nano-rod and nano-flake like morphology for F, DMF and DEF derived products, respectively. From the UV–Vis spectroscopic measurement, the estimated band-gap of $\theta$-Al$_2$O$_3$ was found to be 5.16–5.40 eV. Photoluminescence investigation further revealed blue emission particularly for excitation at a wavelength of 252 nm. A DMF-derived sample rendered thelowest band gap due to its smaller crystallite size and higher surface area compared to that of F- and DEF-derivedsamples.

    • Comparative machinability characterization of wire electrical discharge machining on different specialized AISI steels

      B CHOUDHURI R SEN S K GHOSH S C SAHA

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      In this work, we have attempted to prepare a comparative machinability study of wire electrical discharge machining of different difficult-to-machine materials, viz., stainless steel (SS) 316, H21 hot work tool steel and M42 highspeedsteel (HSS). The key features, which are compared during the analysis, are mainly material removal rate, average surface roughness, kerf width, wire consumption rate (WCR), recast layer (RL), elemental diffusion, surface morphology and micro-hardness of the machined surface. They are found to be greatly influenced by pulse energy. The pulse energy is calculated in terms of ‘specific discharge energy’. Apart from the discharge energy, the thermal conductivity of the material also plays an important role in the formation of RL and inclusion of foreign elements such as carbon, oxygen, copper andzinc in RL. H21 steel has been found to be more prone to thermal defects due to its high-thermal conductivity and high tensile residual stresses, whereas more re-solidification of foreign materials is observed in SS316 and M42 HSS due to theirhigh adhesive properties and low-thermal conductivity. But, in low-energy cutting, more uniform surfaces are observed in H21 steel in comparison with other two types of steel.

    • Enhanced topical econazole antifungal efficacy by amine-functionalized silica nanoparticles

      M MONTAZERI M RAZZAGHI-ABYANEH S A NASROLLAHI H MAIBACH S NAFISI

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      The present study aims at developing efficient econazole (ECO) platforms as topical creams for the treatment offungal skin infections. The hexagonalmesoporous silica nanoparticle, known as MCM41,was synthesized and functionalized by aminopropyl groups (MCM41-NH$_2$). Various ECO concentrations were loaded into MCM41 and MCM41-NH$_2$ (MSNs); the optimized complexes with the highest entrapment efficiencies were characterized by X-ray powder diffraction, scanning electron microscopy (SEM) and gas-volumetric analysis (BET). SEM images showed a spherical shape of the parent nanoparticles—higher drug loading and incorporation into the nanoparticles were obtained by amino-functionalized MCM41. Cytotoxicity assays of MCM41 and MCM41-NH$_2$ and the ECO inclusion complexes elucidated no toxicity to human dermal fibroblast cell lines. Enhanced antifungal activity against Candida albicans was observed for ECO/MCM41-NH$_2$ compared with ECO/MCM41 and simple cream. No irritation was observed by the cream containing ECO/MSN application on white male rabbit skin after 72 h. MSNs were stable within 1 year storage. ECO-loaded silica nanoparticles can be considered for the development of reliable alternatives to ECO cream for the treatment of skin fungal infections.

    • Synthesis of ZrO$_2$ nanostructure for gas sensing application

      E HEMALATHA N GOPALAKRISHNAN

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      ZrO$_2$ nanopowder has been synthesized by the conventional precipitation method for gas-sensing application. The synthesized powder was dropcast and subsequently annealed at 100$^{\circ}$C. The drop-casted film has been subjected to X-ray diffraction analysis, scanning electron microscopy, ultraviolet–visible diffuse reflectance spectroscopy, photoluminescence study and $I –V$ measurement in order to observe its structural, morphological, optical and electrical properties. The gas sensing measurement has been performed for the thus prepared ZrO$_2$ film by an exposure to different reducing gases(ammonia, ethanol, formaldehyde, acetone and xylene) at different temperatures for various gas concentrations. It has been observed that the film shows a better response towards ammonia (about 18%) compared to all other gases due to faster diffusion. Also, a quick response and recovery time have been found as 70 and 70 s, respectively, for ammonia.

    • High-temperature corrosion of aluminized-AISI 1020 steel with NaCl and Na$_2$SO$_4$ deposits

      M BADARUDDIN SUGIYANTO D ASMI

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      High-temperature corrosion of aluminized-American Iron and Steel Institute (AISI) 1020 steel with sodium chloride (NaCl) and sodium sulphate (Na$_2$SO$_4$) deposits was studied using isothermal oxidization in a dry air environment at 700$^{\circ}$C for 49 h. NaCl and Na$_2$SO$_4$ deposits on the aluminide layer interfered with protective alumina/aluminium oxide(Al$_2$O$_3$) scale formation on the steel substrate. Chlorine and sulphur gases (Cl$_{2g}$ and S$_g$, respectively) released into the atmosphere corroded the protective Al$_2$O$_3$ layer. Corrosion of the Al$_2$O$_3$ layer was also due to local formation of iron oxide (Fe$_2$O$_3$). Fe$_2$O$_3$ growth is attributed to ferric chloride (FeCl$_3$) vaporization. S$_g$ diffusion into the Al$_2$O$_3$ scale via Al$^{3+}$ vacancy defects led to the formation of aluminium sulphide on the aluminide layer surface. Cl and S consequently induced hot corrosion of the aluminized steel, thereby increasing cyclic oxychloridation and sulphidation rates at high temperatures.

    • An in vitro comparative study of layered-double hydroxide nanoconjugate in the delivery of small interference and short-hairpin ribonucleic acid

      RITUPARNA ACHARYA MONISHA CHAKRABORTY JUI CHAKRABORTY

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      Alzheimer’s disease is a disease which cannot be cured completely. In this aspect ribonucleic acid interference(RNAi) therapy is a prospective therapeutic mechanism which can be used for identifying a future curative procedure. RNAitherapy comprises small interfering RNA (siRNA), short hairpin (shRNA) and micro-RNA therapeutics. Within these threemechanisms we have identified two of them as an effective method of combating this genetic incurable disease. siRNAs andshRNAs are very much effective in vitro that is already proved in many research work. In our study we have used a very potent, biocompatible nanoparticle-layered double hydroxide for delivering these macromolecules. However, the intercalation and cellular internalization of these macromolecules demonstrated significant differences. As siRNAs have low-molecular weight than shRNAs they demonstrated different characteristics in the case of internalization within layered-double hydroxide and while cellular internalization. At the end of this study it has been found that both of these macromolecules may be used as a therapeutic approach of Alzheimer’s disease after studying it in future in animal and human subjects.

    • Adsorption of benzene, aniline and benzoic acid in water by fullerene (C$_{60}$) and fullerene nanowhiskers

      HIDEO HASHIZUME CHIKA HIRATA KUN’ICHI MIYAZAWA

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      Most aromatic hydrocarbons and their derivatives are harmful organic molecules. Despite their low solubility, trace amounts of aromatic hydrocarbons can be present in water. If water is contaminated by aromatic hydrocarbons, it isvery difficult to remove these from water. Through contaminated water, these compounds can exert deleterious effects in plants and animals, as well as on human health. Fullerenes and their derivatives typically exhibit hydrophobic characteristics, and are therefore considered as good adsorbents for the removal of aromatic hydrocarbons. Herein, the removal of benzene,aniline and benzoic acid by fullerene and fullerene nanowhiskers was evaluated. While benzene was removed satisfactorily from water, aniline and benzoic acid were not, owing to the presence of ionized functional groups. However, adjustment of the solution pH to values where the functional groups of aniline or benzoic acid do not have any charge, resulted in an increase in their adsorption. High pH values were found to have a positive effect on the removal of aniline, while low pH values were beneficial for the adsorption of benzoic acid. Fullerenes and fullerene nanowhiskers were thus found to be promising adsorbents for the removal of aromatic hydrocarbons.

    • Study on the corrosion and wear characteristics of magnesium alloy AZ91D in simulated body fluids

      R VAIRA VIGNESH R PADMANABAN M GOVINDARAJU

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      Bioimplants made of metallic materials induce a stress-shielding effect and delayed osteoblast activity during in-vivo experiments. Bioimplants also suffer corrosion, wear and combined effect of corrosion–wear during their service time. Bioimplants made of magnesium alloys result in a negligible stress shielding effect, owing to their similarity with bone’s elastic modulus. However, the soft matrix of the magnesium alloy is susceptible to high-wear rates. In this study, magnesiumalloy AZ91D is subjected to the corrosion test (immersion and electrochemical), adhesive wear and simultaneous corrosion–wear test to test the significance of the body fluid in the corrosion–wear rate of the bioimplants. The surface morphology,elemental composition and phase composition of the specimens are characterized using field emission scanning electronmicroscopy, energy dispersive X-ray spectroscopy and X-ray diffraction analytic techniques. The results indicate that thesimulated-body fluid has a significant effect on the corrosion rate and corrosion–wear rate of the specimens.

    • Candle soot-coated egg carton material for oil water separation and detergent adsorption

      PUNEET AZAD SAMRIDDHI RAUT RAHUL VAISH

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      A hydrophobic and superoleophilic adsorbent was prepared by coating candle soot (CS) on the surface of a recycled egg carton material (ECM). This waste material has been explored as a cost-effective adsorbent to remove oiland detergent from water. The surface of the material was coated with CS solution prepared by mixing soot with acetone and characterized by scanning electron microscopy and contact angle measurements. The rate of fall of contact angle for water and oil was evident of water rejection and oil absorption capability of the coated-waste material. Further, the effect of temperature on the contact angle between water and surface was observed. The carbon-coated ECM demonstrates good absorption capacity with oils of different densities, without pre-treatments and surface modifications. It also shows its capability to absorb detergent from water with a pH value declining towards 7. Thus, a waste material can act as an effective alternative for filtering of oil and detergent water for households and industries.

    • Enhancement of impact strength of poly(lactic acid)/silicon carbide nanocomposites through surface modification with titanate-coupling agents

      JI-BO ZHANG HENG ZHANG FAN-LONG JIN SOO-JIN PARK

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      In this study, poly(lactic acid) (PLA)-based nanocomposites were fabricated from PLA and silicon carbide (SiC) using solution blending. The surfaces of SiC nanoparticles were treated with a titanate-coupling agent. The influence of the SiC content on thermal stability, flexural properties, impact strength and fracture morphology of the nanocomposites was investigated. The impact strength of the nanocomposites was increased by the introduction of SiC nanoparticles. The nanocomposites containing SiC nanoparticles treated with a titanate-coupling agent (termed T-SiC) exhibited higher impact strengths than the nanocomposites containing neat SiC nanoparticles under the same conditions. Scanning electron microscopy results showed good compatibility between the T-SiC nanoparticles and the PLA matrix.

    • Self-support wood-derived carbon/polyaniline composite for high-performance supercapacitor electrodes

      JIANGTAO SHI MUMUKSHU D PATEL LIPING CAI WONBONG CHOI SHELDON Q SHI

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      Wood-derived carbon is a neoteric self-supporter electrode material for supercapacitors or batteries. To improve the electrochemical characteristics, polyaniline (PANI) was deposited on wood carbon (WC) by an in-situ polymerization method. The sandwich-like symmetrical solid-state supercapacitor was developed by preparing WC/PANI composites andtheir electrochemical properties were examined. The device showed an excellent capacity retention and displayed the maximum specific capacitance of 22.5 mF cm$^{−2}$ at a scan rate of 10 mV s$^^{−1}$. It was also demonstrated an excellent electrical conductivity and an outstanding retention of $\sim$82%. It was suggested that the PANI accommodated into WC without any significant morphological change during the charge–discharge cycling of the hybrid WC-based composites. The microstructure and chemical structure of WC/PANI composites were also characterized by the Fourier-transform infrared, Ramanspectroscopy and X-ray diffraction techniques.

    • Synthesis and electrochemical properties of Co-doped ZnMn$_2$O$_4$ hollow nanospheres

      XUELIANG ZHU ZHIQIANG WEI LONG MA JIAHAO LIANG XUDONG ZHANG

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      Spinel structure Co-doped ZnMn$_2$O$_4$ nanocrystals were successfully synthesized by a hydrothermal method. The effects of Co-doping concentration on the structure and electrochemical properties of the samples were investigated.The experimental results manifest that all samples exhibit a single-phase with a tetragonal structure, and morphologies are regular hollow microspheres. Cyclic voltammetry curves for all samples are similar to a rectangular shape with symmetric nature and no obvious redox peak.Galvanostatic charge–discharge curves were triangular and symmetric. Impedance spectra revealed that Zn$_{1−x}$Co$_x$Mn$_2$O$_4$ possess low resistance. Better electrochemical properties of the ZnMn$_2$O$_4$ electrode could be obtained when the Co-doping ratio is 0.3. Zn$_{0.7}$Co$_{0.3}$Mn$_{2}$O$_4$ exhibits much higher specific capacitance (306 F g$^{−1}$) at a scan rate of 5 mV s$^{−1}$, and shows excellent cycling stability and retains 98.2% of its initial capacitance after 1000 cycles. The enhanced capacitive performance in this work can be attributed to the incorporation of Co ions doped into the ZnMn$_2$O$_4$ host lattice.

    • Removal of Cu(II), Co(II) and Cd(II) from water solutions by layered-double hydroxides with different [Mg(II)]/[Fe(III)] molar ratios

      L N PUZYRNAYA G N PSHINKO V YA ZUB O V ZUY

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      This work presents a study of sorption of heavy metals (HMs)—Cu(II), Co(II) and Cd(II)—from water media by carbonated and calcined forms of layered-double hydroxides (LDH) with various Mg(II)/Fe(III) molar ratios, whichare obtained by precipitation. It is ascertained that the maximum sorption (99.9%) of the HM ions stated is observed with the use of calcined forms of LDH at pH > 2.8 (pH after sorption $\geq$8.3). Such an increase in the pH of the aqueous suspension causes sorption of the HM ions by the mechanism of their precipitation in the form of hydroxides or hydroxocarbonates (for Cu(II)). Sufficiently high degrees of sorption of HMs, even at low pH of the aqueous medium, are apparently caused not only by the precipitation of their hydroxide forms, but also due to the complex formation with ferrinol groups of brucite sorbent layers. An increase in the Mg/Fe ratio from 2 to 4 and a corresponding decrease in the positive charge of the layers, which determines the size of the interlayer space in the LDH, have virtually no effect on the degree of extraction of HMs. The presented results suggest that the use of the studied-LDH in practice might be promising.

    • Effects of different polymers and solvents on crystallization of the NaYF$_4$:Yb/Er phase

      M VUKOVIC I DINIC M G NIKOLIC B A MARINKOVIC A M L M COSTA K RADULOVIC O MILOSEVIC L MANCIC

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      Up-converting NaYF$_4$:Yb,Er nanoparticles were obtained by polymer-assisted solvothermal synthesis using a common solution of hydrated RE nitrates in ethanol or ethylene glycol. It was shown that polymer choice (polyacrylic acid—PAA, polyvinylpyrrolidone—PVP and chitosan—CS) controls the size and shape of NaYF$_4$:Yb,Er nanoparticles, while the solvent type and pH value affect their crystallinity. Consequently, the spherical nanoparticles of a cubic ($\alpha$) phase, the average size of which ranged from 60 to 140 nm, were obtained either when PVP/ethanol or PVP/ethylene glycol were used solely during synthesis, whereas NaOH addition induced hexagonal ($\beta$) phase nucleation. The formation of the hierarchically organized spherical aggregates and nanofoils was observed when CS and PAA were used during synthesis, respectively. The average crystallite size, microstrain, doping level, lattice parameters, as well as, the presence of the certain ligands on the particle surface were determined and correlated with the intensity of visible-light emission observed under 980 nm laser-diode excitation.

    • Some aspects of new Cu(NbC) films

      CHON-HSIN LIN

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      In this study, new barrier-free Cu(NbC) alloy films with two different thicknesses, i.e., 8 and 300 nm, containing 0.3 at% C and 0.5 at% Nb, which are deposited via co-sputtering on three types of substrates, viz., Si, stainless steel and polyimide (PI), have been developed, annealed, measured and analysed. The resistivity value of the new 300-nm-thick films atop Si substrates is 3.07 $\mu\Omega$ cm after annealing at 450$^{\circ}$C for 200 h. The low resistivity and diffusion depth of the new films exhibit their good quality in anti-oxidation stability in a high-temperature environment. The films also display high-adhesive strength atop either stainless-steel or PI substrates, $\sim$7–8 times greater than that of their pure-Cu counterparts. In sharp contrast, the antibacterial ratio of the new films is $\sim$96% while that of their pure-Cu counterparts is 0%. In addition, the contact angles of Cu(NbC) films are greater than those of their pure-Cu counterparts, resulting in a far superior antibacterialefficacy for the new films to pure-Cu films against, for example, Staphylococcus aureus BCRC 10451.With these desirable merits, the new films seem to be a good candidate material for bacteria killing and prevention, reduction of legionella spread inside hospitals and/or large buildings, biological medical care systems and advanced surgical tools. The new films deposited on PI substrates also seem to be suitable for making supple electrically conductive parts or devices, such as flexible panels, keyboards, screens, smartphones embedded in smart textiles and so forth.

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