• Volume 38, Issue 2

April 2015,   pages  283-582

• Enhanced thermo-mechanical performance and strain-induced band gap reduction of TiO2@PVC nanocomposite films

The present paper reports the fabrication of TiO2@PVC nanocomposites by incorporating TiO2 in polyvinyl chloride (PVC) followed by solution casting to prepare TiO2@PVC nanocomposite thin films. The asprepared TiO2@PVC nanocomposite films were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, high-resolution transmission electron microscopy, thermogravimetric analysis, optical spectroscopy and mechanical strength analyses. The TiO2@PVC nanocomposites were found to be thermally and mechanically more stable compared with pure PVC. The anatase TiO2 in the TiO2@PVC nanocomposite showed a lower indirect band gap compared with pure TiO2, which can be attributed to the strain within the nanocomposite, thereby affecting the band-structure of the nanocomposite. Significant enhancement in the mechanical properties of TiO2@PVC compared with pure PVC was observed with a 10 wt% TiO2 loading, such as a 50% increase in Young's modulus and almost 100% improvement in the tensile strength.

• Sol-gel synthesized mesoporous anatase titanium dioxide nanoparticles for dye sensitized solar cell (DSSC) applications

Hierarchically structured titanium dioxide nanoparticles were successfully synthesized by the sol-gel method. The synthesized nanoparticles were subjected to powder X-ray diffraction, UV-Vis DRS spectroscopy, Brunauer–Emmett–Teller method, Barrett–Joyner–Halenda analysis, field emission scanning electron microscopy, high-resolution transmission electron microscopy and energy-dispersive X-ray analysis. The powder X-ray diffraction pattern shows that the obtained particles are of anatase phase with good crystallite nature. The nitrogen adsorption and desorption isotherms show that the prepared material has surface area of 31.71 m2 g-1 and the pore size distribution analysis shows the average pore diameters of mesoporous TiO2 nanostructures to be 7.1 and 9.3 nm. The UV–Vis DRS spectrum shows that the TiO2 nanoparticles are having absorption in the ultraviolet region. The optical band gap of the nanoparticles is 3.2 eV. The morphological studies show the morphology of the particles as spherical in shape. The elemental compositions of TiO2 nanoparticles were confirmed by energy-dispersive X-ray spectrum analysis. The conversion efficiency of the solar cell was 3.415% with open-circuit voltage (𝑉oc), short-circuit current (𝐽sc) and fill factor (FF) of 0.607 V, 13.206 mA cm-2 and 42.56%, respectively.

• Synthesis, characterization, scale-up and catalytic behaviour of Co3O4 nanoparticles

Highly uniform cobalt oxide (Co3O4) nanoparticles were synthesized via thermal decomposition of cobalt hydroxy carbonates with particle size around 16 ± 1 nm. The process gives reproducible results in batches of 1–5 kg. The particles show good catalytic activity for the oxidation of oxalic acid and benzaldehyde under mild temperature conditions. The characterization was performed by X-ray diffractometry (XRD), Transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR) spectrum and Nuclear magnetic resonance (NMR). The XRD measurements show cubic spinel phase and Debye–Scherrer relation was used to measure average particle size. The convenience of the production of catalyst can be exploited for its large-scale production and use in laboratories, R&amp;Ds and industries.

• Photoelectrochemical studies on aqueous suspensions of some nanometal oxide/chalcogenide semiconductors for hydrogen production

Photoproduction of hydrogen was achieved by photolysis of aqueous suspensions of mixed TiO2/V2O5 or CdS/ZnS semiconductor (SC) nanoparticle in phosphate buffers containing [Fe(CN)6]4−. Manipulations of the band structure of the SC materials took place by either combining oxides/sulphides in binary mixtures or by modification of the SC surface with an organic semiconductor. Studies show that the bandgap of these mixed materials varied monotonically with the percent composition of the mixture. Furthermore, results show that maximum generation of hydrated electrons by [Fe(CN)6]4− occurred at pH 6. Mixtures of CdS/ZnS showed greater photoactivity than metal oxides TiO2/V2O5. On the other hand, surface-modified CdS or TiO2 gave much better photoreduction than the high percentage composite mixtures. The aqueous nanosystems used in these studies sustained their stability as indicated by the reproducibility of their photocatalytic activities.

• Effect of carbon nanofibre addition on the mechanical properties of different 𝑉f carbon-epoxy composites

Carbon-epoxy (C-epoxy) laminated composites having different fibre volume fractions (40, 50, 60 and 70) were fabricated with and without the addition of aminofunctionalized carbon nanofibres (A-CNF). Flexural strength, interlaminar shear strength (ILSS) and tensile strength of the composite laminates were determined. It was observed that, the ability of A-CNF to enhance the mechanical properties of C-epoxy diminished significantly as the fibre volume fraction (𝑉f) of the C-epoxy increased from 40 to 60. At 70𝑉f, the mechanical properties of the A-CNF reinforced C-epoxy were found to be lower compared to the C-epoxy composite made without the addition of A-CNF. In this paper suitable mechanisms for the observed trends are proposed on the basis of the fracture modes of the composite.

• Optical and morphological investigation of aluminium and nickel oxide composite films deposited by spray pyrolysis method as a basis of solar thermal absorber

Applications of alumina and nickel oxide in various fields specially in solar energy conversion technology encouraged us to study physical properties of such materials. Hence after the deposition of the thin films on glass substrate by spray pyrolysis, using X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–visible spectrophotometry, various physical properties were investigated. Different optical quantities such as optical band gap, refractive index, extinction coefficient, dielectric constants, volume and surface energy loss functions and optical conductivity were determined. Within this paper for different nickel to aluminium ratio (from 20/80 to 80/20 ratio) at specific substrate temperatures (300°C), decrease of optical transmittance with nickel content was notable. Using the transmittance data, other optical quantities were achieved by a numerical approximation method. We also observed an increase in the volume energy loss (VELF) more than the surface energy loss (SELF) and simultaneously a decrease trend prevailed according to nickel amount. On the basic of the XRD results, the amorphous phase changed by the presence of more nickel and according to SEM, more obvious nanosized spherical grains at higher nickel ratios can be observed.

• Poly(propylene carbonate)/exfoliated graphite nanocomposites: selective adsorbent for the extraction and detection of gold(III)

In this study, poly(propylene carbonate) (PPC) and exfoliated graphite (PPC–EG) composites were prepared by the solution blending method and their selective extraction and detection of gold(III) were investigated. Specifically, a new effective adsorbent was developed for a selective extraction and determination of gold(III) by use of inductively coupled plasma optical emission spectrometry. The selectivity of PPC (PPC–EG 0.5, PPC–EG 1, PPC–EG 2, PPC–EG 3 and PPC–EG 5) was investigated toward several metal ions, including Au(III), Cd(II), Co(II), Cu(II), Hg(II), Pb(II), Pd(II) and Zn(II). Based on selectivity and pH studies, Au(III) was the most quantitatively adsorbed on PPC–EG 0.5 phase at pH 2, indicating that PPC–EG 0.5 was the most selective toward Au(III) among other metal ions. The adsorption isotherm followed the Langmuir model with adsorption capacity of 157.61 mg g−1 of PPC–EG 0.5 for Au(III), which was in agreement with experimental data of adsorption isotherm study. The kinetic of adsorption for Au(III) was investigated by a pseudo-first- and second-order models. Results of kinetic models displayed that the adsorption of Au(III) on the PPC–EG 0.5 phase obeyed a pseudo-second-order kinetic model. In addition, results of thermodynamic investigation demonstrated that the adsorption mechanism of PPC–EG 0.5 toward Au(III) was a general spontaneous process and favourable.

• Effect of electro-co-deposition parameters on surface mechanical properties of Cu–TiO2 composite coating

The present work describes processing and properties of Cu–TiO2 electrodeposited coating on copper substrate with optimized current density and ultrafine ceramic TiO2 powder in the plating bath. Direct current electrodeposition process was employed to develop the composite coating with Cu matrix and ceramic oxide (TiO2) nanoparticles as reinforcement on copper substrate. The coatings were developed with 0 (unreinforced), 10 and 30gl−1 TiO2 powder in bath, at four different current densities (5, 8, 11 and 14 A dm−2) to study the effect of current density and particle concentration in bath on the structure and properties of the developed coatings. Phase, microstructure and compositional analysis of the coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), respectively. Hardness and wear resistance of the coatings were analysed by using microhardness tester and ball on plate wear tester and improvement in these properties was observed due to particle reinforcement and crystallographic texture.

• Preparation and investigations of thermal properties of copper oxide, aluminium oxide and graphite based on new organic phase change material for thermal energy storage

The effects of copper oxide, aluminium oxide and graphite on the thermal and structural properties of the organic phase change material (PCM) were investigated. Ethyl 2-(1H-benzotriazole-1-yl)acetate was selected as the pure PCM. Fourier transform infrared (FT-IR) spectroscopy, X-ray, energy dispersive X-ray (EDX) and scanning electron microscope (SEM) were used to determine the chemical structure, crystalloid phase, chemical composition and microstructure of the composites, respectively. The thermal properties were investigated by differential scanning calorimetry and thermogravimetric analyzer. The FT-IR analyses indicated that there was no chemical interaction between the pure PCM and the supporting materials such as copper oxide, aluminium oxide and graphite. The X-ray diffractograms of the samples were nearly the same, but the peak intensities changed according to the supporting materials. The SEM results showed that the C, N and O elements were well adsorbed into the porous network of the graphite, Al2O3 and CuO. According to the supporting materials, the graphite had the minimum porosity and the maximum crystallite size.

• Electrophoretic deposition and reaction-bond sintering of Al2O3/Ti composite coating: evaluation of microstructure, phase and wear resistance

In this study, Al2O3/Ti composite coating was deposited on TiAl6V4 substrate in various compositions using the electrophoretic deposition method. After the deposition, samples were dried at room temperature then the coated samples were sintered at 1050°C for 4 h. Scanning electron microscope and X-ray diffraction analysis were used to analyse the microstructure and morphology of coatings. The friction coefficient, wear (missing volume) and hardness of coatings have been studied in comparison with uncoated sample. The results demonstrate that the density of Al2O3/Ti composite coating increased considerably after heat treatment process. Moreover, wearing resistance of TiAl6V4 alloy escalated considerably, increasing its potential for application in orthopedic implants and artificial joints.

• Effect of organic modification on the thermal transformations of abentonite during sintering up to 1250°C

X-ray diffraction (XRD) and thermal analysis techniques were used to study the thermal transformations of raw (Maghnia bentonite) and modified bentonite (algae extract (ulvans) within clay). XRD data showed that the basal spacing (𝑑001) was gradually decreased from ∼12.80 Å (6.90°(2𝜃)) at room temperature to about 9.97 Å (8.86°(2𝜃)) and 10.08 Å (8.74°(2𝜃)) after calcination at 200, 400 and 600° C for raw and modified bentonites, respectively. Such behaviour was assigned to the loss of physisorbed water molecules (200° C) and to the occurrence of a distorted octahedral metal (complex for modified bentonite) in the clay. Calcinations above 800° C gaverisetoa complete distortion of this crystal lattice, leading to the disappearance of 𝑑001 XRD peak due to the dehydroxylation of bentonites. The occurrence of cordierite was enhanced at lower temperature (1100° C instead of 1250° C) in the modified bentonite.

• First-principle calculations of the structural, electronic, thermodynamic and thermal properties of ZnSxSe1−x ternary alloys

First-principle calculations were performed to study the structural, electronic, thermodynamic and thermal properties of ZnSxSe1−x ternary alloys using the full potential-linearized augmented plane wave method (FP-LAPW) within the density functional theory (DFT). In this approach the Wu–Cohen generalized gradient approximation (WC-GGA) and Perdew–Wang local density approximation (LDA) were used for the exchange–correlation potential. For band structure calculations, in addition to WC-GGA approximation, both Engel–Vosko (EV-GGA) generalized gradient approximation and recently proposed modified Becke–Johnson (mBJ) potential approximation have been used. Our investigation on the effect of composition on lattice constant, bulk modulus and band gap for ternary alloys shows a linear dependence on alloy composition with a small deviation. The microscopic origins of the gap bowing were explained using the approach of Zunger and co-workers. Besides, a regular-solution model was used to investigate the thermodynamic stability of the alloys which mainly indicates a phase miscibility gap. Finally, the quasi-harmonic Debye model was applied to see how the thermal properties vary with temperature at different pressures.

• Use of sodium salt electrolysis in the process of continuous modification of eutectic EN AC-AlSi12 alloy

This paper presents test results concerning the selection of sodium salt for the technology of continuous modification of the EN AC-AlSi12 alloy, which is based on electrolysis of sodium salts, occurring directly in a crucible with liquid alloy. Sodium ions formed as a result of the sodium salt dissociation and the electrolysis are 'transferred' through walls of the retort made of solid electrolyte. Upon contact with the liquid alloy, which functions as a cathode, sodium ions are transformed into the atomic state, modifying the alloy. As a measure of the alloy modification extent, the obtained increase of the tensile strength 𝑅m and change of metallographic structure are used, confirming obtained modification effect of the investigated alloy.

• Effect of nickel content on the anodic dissolution and passivation of zinc–nickel alloys in alkaline solutions by potentiodynamic and potentiostatic techniques

The effect of systematic increase of Ni on the anodic dissolution and passivation of Zn–Ni alloys in various concentrations of KOH solution (0.1–1 M) was investigated. The anodic dissolution and passivation behaviour for each pure Zn and Ni in the same studied solutions was also investigated, and the obtained data were compared. Potentiodynamic and potentiostatic methods were used, and the corrosion layer formed on each electrode surface was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results of the anodic potentiodynamic measurements exhibited that the polarization curves showed active/passive transition in the case of Ni and active/pseudopassive in the case of both Zn and its alloys. The results showed that the increase in Ni content increases the activation energy (𝐸a) and decreases the dissolution rate of the alloys in KOH solution, and the lowest dissolution rate was obtained at 10% Ni. The results of both potentiodynamic and potentiostatic measurements exhibit sudden increase in current density which is observed at certain positive potential (+0.42 V 𝑣𝑠.SCE) in the case of the investigated alloys. This indicates that the addition of Ni to Zn promotes the electrochemical reaction (in the passive region). However, the passivation potential shifted to more positive direction with the increase in Ni content in the alloy.

• Studies on Cr(VI) removal from aqueous solutions by nanotitania under visible light and dark conditions

The current study deals with Cr(VI) removal by nanotitania under fluorescent light and dark conditions. The equilibrium removal capacities, 85.85 and 59.4 mg of Cr(VI)g−1 of nanoparticle were noted for nanotitania interacted under light and dark conditions, respectively, at optimized conditions (pH: 7.0, contact time: 30 min, initial Cr(VI) concentration: 20 mg l−1, nanoparticle dosage: 0.1 g l−1). Under both the conditions, the equilibrium removal data fitted well with the Langmuir isotherm model. The nanotitania followed a second-order kinetics under light condition whereas a pseudo-second-order kinetics was observed under dark condition. The surface characterization of nanotitania was carried out by zeta potential measurement and transmission electron microscope (TEM). Fourier transform infrared (FT-IR) studies carried out under light and dark conditions indicate the interaction of surface functional groups to Cr(VI). Cr(VI) removal study carried out in the Cr(VI)–Cr(III) mixture showed a decrease in Cr(VI) removal capacity with increase in Cr(III) concentration. A 92% regeneration of nanoparticle was observed indicating efficient reusability of the system. The applicability of the nanotitania in Cr(VI) contaminated water was studied by spiking Cr(VI) in natural water matrices like ground water and lake water.

• HRTEM investigation of phase stability in alumina–zirconia multilayer thin films

Phase stability of nanostructured thin films can be significantly different from the stability of the same materials in bulk form because of the increased contribution from surface and interface effects. Zirconia (ZrO2), stabilized in tetragonal and cubic phases, is a technologically important material and is used for most high temperature applications. In literature, zirconia can be found to be stabilized in its high temperature phases down to room temperature via two routes, doping with divalent or trivalent cations and crystallite size controls. Apart from these, in the alumina/zirconia thin-film multilayer system, a constraining effect on the zirconia layers provides another route to stabilization of the tetragonal zirconia phase at room temperature. However, in such nanostructured geometries, at high temperatures, the small diffusion lengths involved can influence the phase stability. The present work deals with the high-resolution transmission electron microscope (HRTEM) studies of pulsed laser ablated alumina–zirconia thin-film multilayers in the as deposited state and annealed up to 1473 K at 2 × 10−5 mbar. Conventional techniques such as X-ray diffraction lack the ability to detect localized phase changes at nanometre length scales and also for the low volume fraction of newly formed phases. Cross-sectional HRTEM techniques have been successful in detecting and characterizing these interactions.

• Lightweight cordierite–mullite refractories with low coefficients of thermal conductivity and high mechanical properties

Lightweight cordierite–mullite refractories with low coefficients of thermal conductivity (CTCs), high strengths and high thermal-shock resistances were prepared using porous cordierite ceramics as aggregates. Phase compositions and microstructures of lightweight refractories were measured by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), etc. The effect of the relative mullite content of matrix (RMCM) on the microstructures and properties of lightweight refractories was investigated. It was found that the RMCM has a strong effect on the CTC and the mechanical properties. With an increase of RMCM, the compressive and flexural strengths of specimen increase. The thermal-shock resistance is the highest when the RMCM is 22 wt%, and also improved slightly when the RMCM is 46 wt% comparing with the specimen without mullite. When the RMCM is 46 wt%, the CTC reaches the minimum. Specimen with the RMCM of 46 wt% is the most appropriate mode, which has a moderate apparent porosity of 30%, a high compressive strength of 135.1 MPa, a high flexural strength of 20.5 MPa, a good thermal-shock resistance and a low CTC of 0.61 W mK−1.

• Effect of Zn(NO3)2 filler on the dielectric permittivity and electrical modulus of PMMA

Composite films consisting of polymethyl methacrylate (PMMA) and Zn(NO3)2 were developed in the laboratory through the sol casting technique. These films were characterized using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The morphological analysis was carried out by scanning electron microscopy (SEM). These analyses revealed the homogeneous and semi-crystalline behaviour of the films. The dielectric response measurement was conducted in the frequency range from 100 Hz to 5 MHz. The real and imaginary part of the dielectric permittivity decreased with the increase in frequency but increased with temperature. The electrical conductivity measurement showed a plateau-like behaviour in the low-frequency region and dispersion in the high-frequency region. The frequency-dependent electrical modulus obeyed Arrhenius law, and it showed an increase in the dipolar interaction with the temperature due to thermal activation. The activation energy of the film specimen was estimated to be about 0.448 eV. Thus the polymeric composite PMMA–Zn(NO3)2 is one of the appropriate candidate for numerous technical applications such as supercapacitors, high-speed computers and gate dielectric material for organic FETs.

• Structure stability and magnetic properties of Os𝑛B(𝑛 = 11–20) clusters

The structure and magnetic properties of Os𝑛B(𝑛 = 11–20) clusters have been systematically investigated by using density functional theory within the generalized gradient approximation (GGA). For each size, the average binding energy per atom, the second-order differences of total energies, the dissociation energies and the formation energies are calculated to analyse the stability of clusters. Os12B, Os15B, Os17B and Os19B clustersare found to be more stable than other clusters. The B atom has little influence on Os𝑛B cluster stability. d electrons exhibit locality compared to s and p electrons in most cases. Os14B cluster has the strongest magnetism among all the clusters, and the local magnetic moment of B atom does little effect to the total magnetic moment.

• Electrochemical preparation of nitrogen-doped graphene quantum dots and their size-dependent electrocatalytic activity for oxygen reduction

Here we report a remarkable transformation of nitrogen-doped multiwalled carbon nanotubes (MWCNTs) to size selective nitrogen-doped graphene quantum dots (N-GQDs) by a two-step electrochemical method. The sizes of the N-GQDs strongly depend on the applied anodic potential, moreover increasing potential resulted in a smaller size of N-GQDs. These N-GQDs display many unusual size-dependant optoelectronic (blue emission) and electrocatalytic (oxygen reduction) properties. The presence of N dopants in the carbon framework not only causes faster unzipping of MWCNTs but also provides more low activation energy site for enhancing the electrocatalytic activity for technologically daunting reactions like oxygen reduction. The smaller size of N-GQDs has shown better performance as compared to the large N-GQDs. Interestingly, N-GQDs-3 (size = 2.5 ± 0.3 nm, onset potential = 0.75 V) show a 30-mV higher positive onset potential shift compared to that of N-GQDs-2 (size = 4.7 ± 0.3 nm, onset potential = 0.72 V) and 70 mV than that of N-GQDs-1 (size = 7.2 ± 0.3, onset potential = 0.68 V) for oxygen reduction reaction (ORR) in a liquid phase. These result in the size-dependent electrocatalytic activity of N-GQDs for ORR as illustrated by the smaller sized N-GQDs (2.5 ± 0.3 nm) undoubtedly promising metal-free electrocatalysts for fuel cell applications.

• Co-TPP functionalized carbon nanotube composites for detection of nitrobenzene and chlorobenzene vapours

We report preparation of nanocomposites by non-covalent functionalization of carbon nanotubes (CNTs) with metal-tetraphenylporphyrins (M-TPP). Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM) results suggest formation of nanosized clusters of Co-TPP around the CNTs surface. X-ray diffraction studies indicate electronic charge re-distribution and strong interactions among CNTs and Co-TPP on functionalization. The films of the hybrid CNT–M-TPP nanocomposite exhibit change in conductivity on exposure to some chemical vapours. In the present work, the films prepared from the cobalt-TPP functionalized CNTs hybrid composites have been investigated for the detection of chlorobenzene (CB) and nitrobenzene (NB) vapours at room temperature. The films show response time of few seconds on exposure to both the NB and CB vapours while the recovery time for NB is significantly different compared to CB. A distinct and highly reproducible response pattern in the relative changes in resistance, recovery and response times on exposure to the vapours of NB, CB and few other chemicals at room temperature has been exploited to differentiate CB and NB vapours from one another.

• Insights into the effect of structure-directing agents on structural properties of mesoporous carbon for polymer electrolyte fuel cells

Synthesis of mesoporous carbon (MC) with well-defined morphologies and, wide range of surface area and pore size, is reported by organic–organic interaction between thermally decomposable surfactants (structure-directing agents) and the cost-effective carbon precursors, such as phloroglucinol and formaldehyde. Selected surfactants based on tri-block co-polymer, non-ionic and ionic, are used for synthesis of MCs with wide variation in their physical properties. The present method could be applied to large-scale production of porous carbon with desired surface area and pore morphology and would practically be relevant to many emerging technologies including electrochemical power sources such as super-capacitors and fuel cells. In the present study, we have successfully used MCs as gas-diffusion layers in fuel cell electrodes and established proper balance between air permeability and water management. The porous carbon contributes significantly to reduce mass transfer existing at high current density region resulting in improved performance of the polymer electrolyte fuel cells.

• Synthesis and spectroscopic characterization of palladium-doped titanium dioxide catalyst

In this work, we reported synthesis of palladium (Pd)-doped titanium dioxide (TiO2)(Pd-TiO2) nanoparticles by the sol–gel-assisted method. The synthesized Pd-doped TiO2 nanoparticles were characterized using X-ray diffraction, transmission electronic microscopy, energy-dispersive spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and voltammetry techniques. The analysis showed that particles are spherical in shape and pure anatase form with average size about 10 nm. To investigate the catalytic efficiency of Pd-TiO2 nanoparticles, the hydrogen evolution reaction using the deposited film of Pd-TiO2 nanoparticles on glassy carbon electrode (Pd-TiO2/GCE) was studied in 0.1 M H2SO4 solution using linear scanning voltammetry. This study demonstrates the feasibility of using gelatin for the synthesis of Pd-TiO2 catalyst.

• Novel D–𝜋–A dye sensitizers of polymeric metal complexes with triphenylamine derivatives as donor for dye-sensitized solar cells: synthesis, characterization and application

Because of being the key component of dye-sensitized solar cells and acting as an important role, dye sensitizer and its synthesis and application has been extensively researched. In this paper, four novel polymeric metal complexes with D–𝜋–A structure that use 4-(octyloxymethyl)-N, N-diphenylbenzenamine as donor group (D), C=N bondasa 𝜋-conjugation linkage (𝜋), and transition metal complexes as an acceptor (A), were functionally designed and synthesized. All the four polymeric metal complexes exhibited some photovoltaic performance, the highest photoelectric conversion efficiency of compound P4 reached 1.09% (𝐽sc = 2.55 mA cm−2, 𝑉oc = 0.61 V and FF = 70.14%) under simulate AM 1.5 G solar irradiation. A new path for the synthesis and study of the dye sensitizer was provided.

• Spectroscopic characterization of manganese-doped alkaline earth lead zinc phosphate glasses

Alkaline earth lead zinc phosphate glasses doped with Mn(II) are characterized by spectroscopic techniques like X-ray diffraction (XRD), UV–visible, differential scanning calorimetry (DSC), electron paramagnetic resonance (EPR), Fourier transform infrared (FTIR) and Raman. Optical absorption spectrum exhibits four bands which are characteristic of Mn(II) in distorted octahedral site symmetry. The crystal field parameter Dq and Racah interelectronic-repulsion parameters 𝐵 and 𝐶 have been evaluated. All investigated samples exhibit EPR signals which are characteristic to the Mn2+ ions. The shapes of spectra are also changed with varying alkaline earth ions content. FTIR spectra show specific vibrations of phosphate units. The characteristic Raman bands of these glasses due to stretching and bending vibrations were identified and analysed by varying alkaline earth content. The intensity and frequency variations for the characteristic phosphate group vibrations have been correlated with the changes of the structural units present in these glasses. Depolymerization of the phosphate chains in all the glasses is observed with replacement of alkaline earth content by spectroscopic studies. This leads to a strong decrease of the average chain length and a small decrease of the average P–O–P bridging angle with replacement of alkaline earth content.

• Spray deposited CeO2–TiO2 counter electrode for electrochromic devices

Optically passive thin films of CeO2–TiO2 mixed oxides with molar ratio of Ce/Ti of 0.05 were deposited by the spray pyrolysis technique (SPT) on a glass and fluorine-doped tin oxide (FTO)-coated glass substrates. Precursor solution containing cerium nitrate hexahydrate (Ce(NO3)2·6H2O) and titanium tetraiso-propoxide (Ti(OiPr)4) having different volumetric proportions (0–5 vol% of Ti) in methanol were used. These films were characterized for structural, morphological, molecular, optical, electrochromic and colourimetric analysis. CeO2–TiO2 films deposited at 400° C were found to be polycrystalline with cubic fluorite crystal structure. Transformation from polycrystalline to amorphous phase was observed with increasing TiO2 content. The band centred at 539 cm−1 is assigned to Ce–O stretching vibration and the two medium intensity bands assigned to (Ti–O) and (Ti–O–Ti) stretching modes at 798 and 451 cm−1, which confirms the mixed CeO2 and TiO2 phases. The band gap energy decreases (𝐸g) from 3.45 eV for pristine CeO2 to 2.98–3.09 eV for CeO2–TiO2 films. The ion storage capacity (ISC) of CeO2–TiO2 thin film with 3 vol% Ti (Ce–Ti3 sample) was found to be 26 mC cm−2 and electrochemical stability up to 30,000 cycles in 0.5 M LiClO4-PC electrolyte. The optically passive behaviour of CeO2–TiO2 thin film is confirmed by its negligible transmission modulation (𝛥 𝑇 ∼ 2.5%) upon Li+ ion insertion/extraction, irrespective of the extent of Li+ ion intercalation. The optical modulation of sputter deposited electrochromic WO3 thin film was found to be enhanced from 56 to 61% with rapid increase in colouration efficiency (CE) from 42 to 231 cm2 C−1 when CeO2–TiO2 is coupled as a counter electrode with WO3 in an electrochromic device (ECD). On reduction of WO3 thin film with CeO2–TiO2 as counter electrode, the CIELAB 1931 2° colour space coordinates show the transition from colourless to the deep blue state (𝐿* = 88.07, 𝑎* = −2.37, 𝑏* = 24.59 and 𝐿* = 40.32, 𝑎* = −1.16, 𝑏* = −5.65) with steady decrease in relative lightness. Yxy and 𝐿*𝑎*𝑏* coordinates signify CeO2–TiO2 films and it also exhibits the application as counter electrode in electrochromic smart windows in which they are able to retain their transparency under charge insertion/extraction.

• Room temperature synthesis of crystalline Sb2S3 for SnO2 photoanode-based solar cell application

The preparation of crystalline antimony sulphide (Sb2S3) by chemical route at room temperature was reported in this paper. The structural, morphological and optical properties of as-synthesized sample were system- atically investigated. X-ray diffraction (XRD) analysis confirms the orthorhombic crystal phase for prepared Sb2S3. Scanning electron microscope (SEM) images show uniform, dense spherical morphology having diameter around 200–220 nm. Energy band gap calculated from optical absorption spectra was observed around 2.17 eV. Contact angle measurement confirms the hydrophilic nature of the deposited film. The photoluminescence analysis shows low green luminescence as well as Stoke's shift for as-prepared Sb2S3. The nanostructured solar cell is fabricated for energy harvesting purpose with Sb2S3-sensitized SnO2 photoanode and polysulphide electrolyte. The solar cell with FTO/SnO2/Sb2S3 photoanode shows 𝑉OC ∼ 240 mV, 𝐽sc ∼ 0.640 mA cm−2 and FF ∼ 35%. The working mechanism and energy level diagram of Sb2S3/SnO2 system have been discussed.

• Experimental and quantum chemical studies on corrosion inhibition performance of fluconazole in hydrochloric acid solution

The corrosion inhibition effect of fluconazole (FLU) was investigated on steel in 1 M hydrochloric acid solution. Weight loss measurements and atomic force microscope analysis were utilized to investigate the corrosion inhibition properties and film formation behaviour of FLU. Quantum chemical approach was also used to calculate some electronic properties of the molecule in neutral and protonated form in order to find any correlation between the inhibition effect and molecular structure of FLU molecule. The results showed that FLU can act as a good corrosion inhibitor for steel in hydrochloric acid solution at different temperatures and it can inhibit steel corrosion up to 95%. The adsorption followed the Langmuir isotherm and the thermodynamic parameters were also determined and discussed. Quantum chemical studies showed that in adsorption process of FLU molecules, nitrogen and oxygen atoms and benzene ring act as active centres.

• Ion beam analysis of gas turbine blades: evaluation of refurbishment quality

Refurbishment of hot components of gas turbines damaged in the harsh working environments is necessary to increase their lifetime. Scanning proton microscopy was employed to evaluate the quality of refurbishment process of gas turbine blades. Distribution patterns of different elements were observed in the polished cross-sections of turbine blade samples by proton microbeam. In the cross-sections of refurbished and used samples, distinct regions were identified corresponding to the base superalloy, original protection layer and applied coating for refurbishment. The elemental composition of each of these regions was measured by Micro-PIXE analysis. Inhomogeneous and high content of Si as well as undesired light elements were observed in the cross-sections of refurbished samples, indicating imperfections in the refurbishment process.

• Nonisothermal crystallization behaviour of poly(ρ-dioxanone) and poly(L-lactic acid) blends

Blends of poly(ρ-dioxanone) (PPDO) and poly(L-lactic acid) (PLLA) in different proportions were prepared by solution co-precipitation. The nonisothermal crystallization behaviour of pure PPDO and PPDO/PLLA blends was investigated by differential scanning calorimetry. The Avrami, Ozawa and Mo models were used to analyse the nonisothermal kinetics. The addition of PLLA significantly increases the crystallization peak temperature and crystallinity of PPDO, but has little effect on crystallization half-time. The activation energies of crystallization were calculated using the Kissinger equation. The results suggest that PLLA plays two roles in the nonisothermal crystallization of PPDO; PLLA both promotes the crystallization of PPDO as a nucleating agent and meanwhile restricts the motion of PPDO chains.

• Phase stability of silver particles embedded calcium phosphate bioceramics

In this paper, we report the compositional variation-dependent phase stability of hydroxyapatite (Ca10(PO4)6(OH)2) on doping with silver. The transformation of hydroxyapatite to (𝛽/𝛼) tricalcium phosphate phases during sintering has been explored using Raman spectroscopy and X-ray diffraction techniques. The optical absorption spectroscopy analysis reveals the presence of Ag+ ions at low doping levels. As the doping increases, abundance of Ag particles is enhanced.

• Effect of cooling rate on the microstructure and mechanical properties of a C–Mn–Cr–B steel

The microstructure and mechanical properties of a low carbon steel containing 30 ppm boron have been investigated. The steel was subjected to various cooling conditions in a thermo-mechanical simulator to generate continuous cooling transformation (CCT) diagram. Similar cooling conditions were also applied to tensile samples in order to evaluate their mechanical properties. The results indicate profuse banding in the hot strip of thickness 2.5 mm. This effect is attributed to the presence of manganese. In addition, variation in cooling rate led to increase in strength but severely affected percentage elongation albeit in an acceptable limit of 6%. This effect is discussed in the light of degree of banding of strips and microstructural constituents generated during heat treatment of steel strips of different thicknesses.

• Microscopic properties of MPCVD diamond coatings studied by micro-Raman and micro-photoluminescence spectroscopy

Diamond coatings were deposited on silicon (100) substrate using the microwave plasma chemical vapour deposition (MPCVD) technique at different process conditions. Process parameters such as CH4–H2 gas mixture concentration, microwave power, chamber pressure and substrate temperature were varied. The diamond coatings were characterized by micro-Raman and micro-photoluminescence (PL) spectroscopy techniques. In this paper we report a comparison of the overall quality of MPCVD polycrystalline diamond coatings grown under different processing conditions in terms of stress distribution, thickness uniformity and surface roughness. Micro-Raman spectroscopy studies over various points on the deposited coating showed that the Raman line widths of diamond peak varied from 3.2 to 18.3 cm−1 with the variation of CH4 and H2 gas concentration. The micro-PL spectra suggested the presence of impurity concentration and defects within the diamond coating synthesized at different processing conditions. Transmission electron microscopy (TEM) images provide the direct evidence of the presence of crystal defects which corroborates the Raman and PL results. The coherence scanning interferometry (CSI) showed that surface roughness of diamond coating varied from 0.43 to 11 𝜇m with thickness at different positions of the three coating samples. It has been concluded that Raman line-width broadening and Raman-shift are due to the presence of crystal defects as well as non-uniform distribution of stresses present in the diamond crystals of the coating, due to the incorporation of Si as impurity element and non-uniform temperature distribution during growth. Defect density gets reduced at higher processing temperatures. It is also being proposed that better thickness uniformity and lower surface roughness can be achieved for coatings deposited at low methane concentration under optimized process conditions.

• Anorthite porcelain: synthesis, phase and microstructural evolution

In the present study, anorthite (CaAl2Si2O8) porcelain was fabricated using Ca(OH)2, Al(OH)3, quartz, aluminous cement and feldspar as raw materials. Two compositions were formulated (coded as CAQ and CFQ)and their physico-mechanical properties (%AP, BD, flexural strength) were studied and compared. CAQ (21.2 wt% Ca(OH)2, 44.5 wt% Al(OH)3 and 34.3 wt% quartz) shows very poor densification and strength even after heating at 1450° C, although anorthite formation is observed on heating it at various temperatures. On the other hand, CFQ (48.6 wt% aluminous cement, 29.37 wt% feldspar and 22.06 wt% quartz) achieved full densification and superior strength at 1450° C with more anorthite formation compared to CAQ. X-ray diffraction and scanning electron microscope studies were also carried out to analyse the phase and microstructure evolution. The coefficient of thermal expansion of the anorthite-based sample was found to be lower than quartz and mullite porcelain which suggests its application as cooking ware.

• Thermal and electrical properties of 60V2O5–5P2O5–(35−𝑥)B2O3–𝑥CeO2(1 ≤ 𝑥 ≤ 5) glasses

The samples of composition 60V2O5–5P2O5–(35−𝑥)B2O3–𝑥CeO2, 𝑥 = 1, 2, 3, 4 and 5 mol% were prepared by the melt-quench method. The prepared samples were characterized by X-ray diffraction, thermogravimetric-differential thermal analysis and impedance spectroscopy. The activation energies were evaluated using glass transition temperature (𝑇g) and peak temperature of crystallization (𝑇c). The dependence of activation energy on composition was discussed. AC conductivity of samples has been analysed. Electrical conductance and capacitance were measured over a frequency range of 20 Hz–1 MHz and a temperature range of 303–473 K. At room temperature, maximum value of electrical conductivity was observed to be 0.0024 S cm−1 for 𝑥 = 1.The samples show semiconducting features predominantly based on an ionic mechanism.

• An investigation of proton conductivity of binary matrices sulfonated polysulfone/polyvinyltriazole after doping with inorganic acids

As anhydrous proton conductive membranes, sulfonated polysulfone (SPSU) and polyvinyl triazole were studied as binary matrices. The sulfonation of polysulfone was performed with trimethylsilylchlorosulfonate and high degree of sulfonation (140%) was obtained. Ion exchange capacity of SPSU was determined as 3.05 mmol−1/g. The polymer electrolyte membranes were prepared by blending of sulfonated polysulfone with polyvinyl triazole and phosphoric acid. Fourier transform infrared spectroscopy confirmed the sulfonation of the polysulfone and the ionic interaction between sulfonic acid and triazole units. Thermogravimetric analysis showed that the polymer electrolyte membranes are thermally stable up to at least 150° C. Scanning electron microscopy analysis indicated the homogeneity of the ternary composites. The maximum proton conductivity has been measured as 3.63 × 10−4S cm−1 at 150° C.

• Electrochemical behaviour of superhydrophobic coating fabricated by spraying a carbon nanotube suspension

In this study, superhydrophobic films were prepared through a spraying process of carbon nanotube (CNT) suspension on aluminium alloy substrate and characterized by scanning electronic microscope (SEM) contact angles (CAs) and potentiodynamic polarization tests in 0.1 M NaCl solution. Results indicate the positive effect of superhydrophobic film on the CA ($\ge 160^\circ$) in comparison with the bare metal due to the high porosity density at the surface caused by the presence of CNTs. The electrochemical observations indicate the presence of a positive shift of 𝐸corr that confers a better corrosion resistance of the coated samples.

• # Bulletin of Materials Science

Volume 43, 2020
All articles
Continuous Article Publishing mode

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019