• Issue front cover thumbnail

      Volume 37, Issue 6

      October 2014,   pages  1191-1561

    • Photoluminescent properties of Sr2CeO4 : Eu3+ and Sr2CeO4 : Eu2+ phosphors suitable for near ultraviolet excitation

      K Suresh N V Poornachandra Rao K V R Murthy

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      Powder phosphors of 1 mol% Eu3+- and Eu2+-doped strontium cerium oxide (Sr2CeO4) were synthesized by standard solid-state reaction method. Eu3+- and Eu2+-doped Sr2CeO4 phosphors fired at 1100 °C for 2 h were analysed by X-ray diffraction (XRD) and photoluminescence (PL) techniques. The XRD patterns confirm that the obtained phosphors are a single phase of Sr2CeO4 composed of orthorhombic structure. Room temperature PL excitation spectrum of air-heated Sr2CeO4 : Eu phosphor has exhibited bands at 260, 280 and 350 nm. Whereas the excitation spectrum of Sr2CeO4 : Eu phosphor heated under reducing (carbon) atmosphere exhibited single broadband range from 260 to 390 nm. The (PL) emission peaks of both the phosphors at 467 (blue), 537 (green) and 616 nm (red) generate white light under 260, 280 and 350 nm excitation wavelengths. The Commission International de l’Eclairage (CIE) colour coordinates conforms that these phosphors emitting white light. The results reveal that these phosphors are multifunctional phosphors which emit white light under these excitations that they could be used as white components for display and lamp devices and as well as possible good light-conversion phosphor LEDs under near-ultraviolet (nUV) chip.

    • Influence of hydrogen on chemical vapour synthesis of different carbon nanostructures using propane as precursor and nickel as catalyst

      R K Sahoo H Mamgain C Jacob

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      The role of hydrogen in the catalytic chemical vapour deposition of carbon nanotubes using sputtered nickel thin film as a catalyst is explained in this work. The growth of different carbon nanostructures with the variation in the precursor gas content was studied by keeping all other process parameters constant and using sputtered Ni thin film as a catalyst. The catalyst granule size, its external morphology and the resulting products were analysed. Carbon nanotubes (CNTs), carbon nanofibres (CNFs) and carbon nanoribbons (CNRs) were observed under different growth conditions. The different conditions of growth leading to form tubes, fibres or ribbons were analysed by varying the flow ratio of propane and hydrogen gas during the high temperature growth. Scanning and transmission electron microscopies confirmed the above structures under different growth conditions. The role of hydrogen on the surface passivation behaviour of the Ni catalyst and its correlative effect on the growth of carbon nanostructures is analysed. This direct approach can, in principle, be used to synthesize different types of carbon nanostructures by tailoring the hydrogen concentration.

    • Synthesis, characterization, photoluminescence and thermally stimulated luminescence investigations of orange red-emitting Sm3+-doped ZnAl2O4 phosphor

      Mithlesh Kumar V Natarajan S V Godbole

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      Sm3+-doped ZnAl2O4 phosphor was synthesized by citrate sol–gel method and characterized using X-ray diffraction and scanning electron microscopy to identify the crystalline phase and determine the particle size. Photoluminescence (PL) studies on the sample showed emission peaks at 563, 601, 646 and 707 nm with 𝜆ex = 230 nm corresponding to the ${}^{4}G_{5/2} \rightarrow {}^{6}H_{5/2}, {}^{4}G_{5/2} \rightarrow {}^{6}H_{7/2}, {}^{4}G_{5/2} \rightarrow {}^{6}H_{9/2}$ and ${}^{4}G_{5/2} \rightarrow {}^{6}H_{11/2}$ transitions, respectively, due to Sm3+ ions. PL lifetime decay studies confirmed that Sm3+ ions partly entered into the lattice by replacing Al3+ ions and remaining located at the surface of ZnAl2O4 host matrix. Thermally stimulated luminescence (TSL) studies of 𝛾-irradiated Sm3+-doped ZnAl2O4 sample showed two glow peaks at 440 and 495 K, the former being most intense than the latter. The trap parameters were determined using different heating rate methods. Spectral characteristics of the TSL glow showed emission around 565, 599 and 641 nm, indicating the role of Sm3+ ion as the luminescent centre. A probable mechanism for the prominent TSL glow peak, observed at 440 K, was proposed. CIE chromaticity coordinates for the system was evaluated, which suggested that Sm3+-doped ZnAl2O4 could be employed as a potential orange red-emitting phosphor.

    • Improvement in the microwave dielectric properties of SrCa4Nb4TiO17 ceramics by Ba substitution

      Abdul Manan Yaseen Iqbal

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      Microwave dielectric ceramics in the Sr1–𝑥Ba𝑥Ca4Nb4TiO17 (0 ≤ 𝑥 ≤ 0.75) composition series were fabricated via a solid-state mixed oxide route. All the compositions formed single phase in Sr1–𝑥Ba𝑥Ca4Nb4TiO17 (0 ≤ 𝑥 ≤ 0.75) solid solutions within the detection limit of in-house X-ray diffraction (XRD). The sintered microstructure of these ceramics comprised densely packed elongated and plate-like grains. The dielectric properties varied linearly with 𝑥. Relative permittivity (𝜀r) increased from 47.2 to 54.5, unloaded quality factor multiplying the resonant frequency (𝑄u 𝑓o) decreased from 11,984 to 9345 GHz and temperature coefficient of resonant frequency (𝜏f) increased from –78.6 to 20 ppm/°C with an increase in x from 0 to 0.75. In the present study, 𝜀r ≈ 51.6, 𝑄u 𝑓o ≈ 10,160 GHz (5.37 GHz) and 𝜏f ≈ –13.5 ppm/°C were achieved for Sr0.5Ba0.5Ca4Nb4TiO17 (𝑥 = 0.5) ceramics.

    • Effect of mechanical activation on cordierite synthesis through solid-state sintering method

      S K Nath Sanjay Kumar Rakesh Kumar

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      Synthesis of cordierite (5SiO2.2MgO.2Al2O3) has attracted special attention from researchers for its special characteristics. Most common method of cordierite preparation is solid-state reaction using source of alumina, silica and magnesia, which requires temperature of 1350 °C or above. This study deals with the effect of mechanical activation on cordierite synthesis at lower temperature. Talc, kaolinite clay and alumina powder were taken as precursor materials and the batches were formulated on the basis of stoichometric cordierite formation. Particle size distribution (PSD) was measured to get the distribution pattern of milled powder. Pellets were prepared by compaction of dried milled powders and fired at 1200 °C temperature. X-ray diffraction (XRD) technique was used to characterize crystalline phases. Microstructural analysis was done under scanning electron microscope (SEM). It was observed that properties were improved with milling time. Dense and uniform microstructures were formed when samples were milled for 45 and 60 min.

    • Higher d.c. resistivity of Li–Zn–Cd ferrites prepared by microwave sintering compared with conventional sintering

      Mamata Maisnam Sumitra Phanjoubam

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      Cd2+-substituted Li–Zn ferrites having the general formula Li$^{+}_{0.4–x/2}$Zn$^{2+}_{0.2}$Cd$^{2+}_{x}$Fe$^{3+}_{2.4–x/2}$O$^{2-}_{4}$ where x = 0.02, 0.03 and 0.04 have been prepared by both microwave sintering and conventional sintering. In the former case, sintering was done at 1050 °C for 25 min, whereas in the latter case sintering was done at 1050 °C for 6 h. The various structural properties, microstructures and d.c. resistivity of the samples prepared by the two techniques were compared. The study showed higher d.c. resistivity and higher activation energies in the samples prepared by microwave sintering. The mechanisms pertaining to the results are discussed.

    • Relaxor behaviour in BaBi4Ti4O15 ceramics fabricated using the powders obtained by mechanochemically assisted synthesis route

      Sunil Kumar K B R Varma

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      Mechanochemically activated reactants were found to facilitate the synthesis of fine powders comprising 200–400 nm range crystallites of BaBi4Ti4O15 at a significantly lower temperature (700 °C) than that of solid-state reaction route. Reactants (CaCO3, Bi2O3 and TiO2) in stoichiometric ratio were ball milled for 48 h to obtain homogeneous mixture. The evolution of the BaBi4Ti4O15 phase was systematically followed using X-ray powder diffraction (XRD) technique. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to probe its structural and microstructural details. The electron diffraction studies established the presence of correlated octahedral rotations and associated long-range polar ordering. High-resolution TEM imaging nevertheless revealed structural inhomogeneities leading to intergrowth defects. Dense BaBi4Ti4O15 ceramics with an average grain size of 0.9 𝜇m were fabricated using mechanochemically assisted synthesized powders at relatively low temperature (1000 °C). The effect of grain size on the dielectric and relaxor behaviour of BaBi4Ti4O15 ceramics was investigated. Fine-grained ceramics (average grain size ∼ 0.9 𝜇m) showed higher diffusion in phase transition, lower temperature of phase transition, lower Vogel–Fulcher freezing temperature and higher activation energy for the polarization reversal than those for coarse-grained ceramics (average grain size ∼ 7 𝜇m) fabricated via the conventional solid-state reaction route.

    • Comparative study of highly dense aluminium- and gallium-doped zinc oxide transparent conducting sol–gel thin films

      Naji Al Dahoudi

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      Transparent conducting aluminium- and gallium-doped zinc oxide (AZO and GZO) layers have been deposited by spin coating on glass substrates. The coatings have been sintered in air at 450 °C for 30 min and then post-annealed at 350 °C in a reducing atmosphere for 30 min. The electrical, optical and morphological properties of both coatings have been studied and compared. The conventional sols lead to very thin coating, typically 24 nm for a single layer of AZO and 32 nm of GZO with electrical resistivity of 0.72 and 0.35 𝛺 cm, respectively. The value however, drastically decreases down to a minimum of 2.6 × 10-2 𝛺 cm for AZO and 1.76 × 10-2 𝛺 cm for GZO, when five multilayer coatings are made. The origin of these differences is due to the different morphology of the coatings showing different electron scattering process. The GZO sol leads to denser smoother structure (porosity of 5%) layers with an average roughness of 2.76 Å, while the AZO coating is formed by a more porous assembly (porosity of 20%) with an average roughness of 3.46 Å. Both coatings exhibit high transparency (𝑇 > 85%) in the visible spectrum range with a slight shift of the absorption energy gap.

    • Synthesis and photoluminescence property of silicon carbide nanowires thin film by HF-PECVD system

      Zhang Enlei Wang Guosheng Long Xiaozhu Wang Zhumin

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      A sample and scalable synthetic strategy was developed for the fabrication of nanocrystalline SiC (nc-SiC) thin film. Thin sheet of nanocrystalline diamond was deposited on Si substrate by hot filamentassisted plasma-enhanced chemical vapour deposition system (HF-PECVD). Further, the resulting carbonbased sheet was heated at 1200 °C to allow a solid state reaction between C and Si substrate to form the SiC thin films. The synthesized films mainly consist of 𝛽-SiC nanowires with diameters of about 50 nm and tens of micrometers long. The nanowires axes lie along the [1 1 1] direction and possess a high density of planar defects. The 𝛽-SiC nanowires thin films exhibit the strong photoluminescence (PL) peak at a wavelength of 400 nm, which is significantly shifted to the blue compared with the reported PL results of SiC materials. The blue shift may be ascribed to morphology, quantum size confinement effects of the nanomaterials and abundant structure defects that existed in the nanowires.

    • Effect of composition on optical properties of GeSe3–Sb2Se3–ZnSe thin films

      M R Balboul H M Hosni M A Soliman S A Fayek

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      Optical properties of the chalcogenides GeSe3, Sb2Se3, ZnSe, (GeSe3)80(Sb2Se3)20 and (GeSe3)70 (Sb2Se3)10(ZnSe)20 thin films are investigated. Incorporation of ZnSe into both GeSe3, Sb2Se3 results in amorphous (GeSe3)70(Sb2Se3)10(ZnSe)20 composition. The estimated optical energy gap, 𝐸g, is found to decrease from 3.06 eV for ZnSe to 1.81 eV for (GeSe3)70(Sb2Se3)10(ZnSe)20. While, the band tail width, 𝐸e, exhibits an opposite trend. The 𝐸g behaviour is believed to be associated with cohesive energy, CE, as the incorporation of ZnSe lowers its value. The calculated number of the excess of Se–Se homopolar bonds is found to affect mainly the 𝐸e values. The refractive index, 𝑛, is discussed in terms of Wemple–DiDomenico single oscillator dispersion model in the normal dispersion region. The oscillator energy, 𝐸o, and the dispersion energy, 𝐸d, are determined for films under investigation.

    • On the microstructure and interfacial properties of sputtered nickel thin film on Si (1 0 0)

      B Geetha Priyadarshini S Aich M Chakraborty

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      Ni films of thickness ranging from 150 to 250 nm were deposited by DC magnetron sputtering on to Si (100) substrates maintained at room temperature and followed by post-annealing at 300 and 500 °C for 30 min. Other set of Ni films were deposited on to Si (1 0 0) substrates held at annealing temperature of 300 and 500 °C for 30 min. Microstructural investigation by field emission scanning electron microscope (FE-SEM) and atomic force microscope (AFM) revealed columnar morphology with voided boundaries for films deposited at room temperature and was retained after post-deposition annealing at higher temperatures. Nickel silicide formation with isosceles triangle diffusion front was confirmed by cross-sectional highresolution transmission electron microscopy (X-HRTEM) for post-annealed Ni films. Thin film deposited at high substrate temperatures having near-equiaxed structure found to be the best route to fabricate thin films without silicide formation.

    • Optimization of AZO films prepared on flexible substrates

      C C Hu T W Lu C Y Chou J T Wang H H Huang C Y Hsu

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      Transparent conductive Al2O3-doped zinc oxide (in AZO, Al2O3 content is ∼ 2 wt%) thin films are deposited on flexible polyethylene terephthalate (PET) substrates, using radio frequency (rf) magnetron sputtering. The Taguchi method with an 𝐿9 (34) orthogonal array, a signal-to-noise ratio and analysis of variance (ANOVA) was used to determine the performance characteristics of the coating operations. Using grey relational analysis, the optimization of these deposition process parameters for AZO thin films with multiple characteristics was performed. The electrical resistivity of AZO/PET films is reduced from 2.6 × 10-2 to 5.5 × 10-3 𝛺-cm and the visible range transmittance is > 83%, using the grey relational analysis. ANOVA results for the grey relational grade indicate that rf power and working pressure are the two most influential factors. The effect of the rf power (in the range from 30 to 70 W) and the argon working pressure (in the range from 0.90 to 1.1 Pa) on the morphology and optoelectronic performance of AZO films are also investigated. An analysis of the influence of the dominant parameters in the optimal design region is helpful for adjustment of the coating parameters.

    • Influence of substrate on structural, morphological and optical properties of ZnO films grown by SILAR method

      F N Jiménez-García C L Londoño-Calderón D G Espinosa-Arbeláez A Del Real M E Rodríguez-García

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      ZnO films were obtained by successive ionic layer adsorption and reaction (SILAR) method from four different substrates: glass microslides, corning glass, quartz and silicon with and without oxide layer. For films deposition, a precursor solution of ZnSO4 was used, complexed with ammonium hydroxide. Prior to the film deposition, wettability of the substrates was analysed using a CCD camera. It was found that the Si without the oxide layer substrate shows hydrophobic behaviour, which makes the films less adherent and not uniform, while in the other substrates, the behaviour was optimal for the growing process. ZnO films grown on glass microslides, corning glass, quartz and Si with oxide layer were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–Vis techniques. According to the XRD patterns, the films were polycrystalline, with hexagonal wurtzite structure and the patterns mentioned showed significant differences in crystallite sizes, microstrain and texture coefficient with respect to the employed substrates. The morphology of the ZnO films constituted by rice-like and flower-like structures shows differences in form and size depending on the substrate. The UV–Vis spectroscopy results show that the substrate did not influence the band gap energy value obtained from films.

    • CeO2 thin film as a low-temperature formaldehyde sensor in mixed vapour environment

      R Pandeeswari B G Jeyaprakash

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      Nanostructured cerium oxide thin film was deposited onto the glass substrate under optimized condition using spray-pyrolysis technique. X-ray diffraction result indicates polycrystalline nature of the film with fluorite-type face-centered-cubic structure. The atomic force micrograph indicates the presence of nanocrystallites over the film surface. The vapour sensing characteristics of the annealed film were studied by chemiresistive method for various concentrations of formaldehyde vapour at room temperature (∼ 30 °C). For 0.5 ppm of formaldehyde vapour, the film shows a response and recovery time of 36 and 1 s, respectively. The vapour sensing properties of the cerium oxide film in mixed environment were studied and reported.

    • Optimization of process conditions for the production of TiO2–𝑥N𝑦 film by sol–gel process using response surface methodology

      Rui Liu Ching-Shieh Hsieh Wein-Duo Yang Hui-Yi Tsai

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      TiO2–𝑥N𝑦 film has been synthesized successfully through the sol–gel method. It is found that the anatase phase is formed at 400 °C and converted to rutile phase at 600 °C. The response surface methodology (RSM) and Box–Behnken design were employed to optimize the process conditions of sol–gel process. Based on the results in preliminary experiments, we selected molar ratio of surfactant to Ti, molar ratio of acetylacetone to Ti, molar ratio of water to Ti and calcination temperature as the key process factors affecting the roughness of TiO2–𝑥N𝑦 film. The adjusted determination coefficient ($R^{2}_{\text{Adj}}$) of the regression model was 0.9651, which indicated that the regression model is significant. By analysing the contour plots of response surface as well as solving the regression model, the optimized conditions were obtained as: 0.19 for molar ratio of surfactant to Ti, 2.01 for molar ratio of acetylacetone to Ti, 1.38 for molar ratio of water to Ti and 500 °C for calcination temperature. The predicted roughness of TiO2–𝑥N𝑦 film for the optimized condition was calculated to be 41 nm. Confirmation experiments using the optimized conditions were performed, and a value about 43 nm was obtained. The experimental results are in good agreement with the predicted results.

    • Heavy lithium-doped ZnO thin films prepared by spray pyrolysis method

      M Ardyanian N Sedigh

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      Lithium-doped ZnO thin films (ZnO : Li𝑥) were prepared by spray pyrolysis method on the glass substrates for 𝑥 (𝑥 = [Li]/[Zn]) value varied between 5 and 70%. Structural, electrical and optical properties of the samples were studied by X-ray diffraction (XRD), UV–Vis–NIR spectroscopy, scanning electron microscopy (SEM), Hall effect and sheet resistance measurements. XRD results show that for 𝑥 ≤ 50%, the structure of the films tends to be polycrystals of wurtzite structure with preferred direction along (0 0 2). The best crystalline order is found at 𝑥 = 20% and the crystal structure is stable until 𝑥 = 60%. The Hall effect results describe that Li doping leads to change in the conduction type from 𝑛- to 𝑝-type, again it changes to 𝑛-type at 𝑥 = 70% and is attributed to self-compensation effect. Moreover, the carrier density was calculated in the order of 1013 cm-3. The resistivity of Li-doped films decreases until 22 𝛺 cm at 𝑥 = 50%. Optical bandgap was reduced slightly, from 3.27 to 3.24 eV as a function of the grain size. Optical transmittance in the visible range reaches 𝑇 = 97%, by increasing of Li content until 𝑥 = 20%. Electrical and optical properties are coherent with structural results.

    • Optimization of compressive strength of zirconia based dental composites

      U V Hambire V K Tripathi

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      Dental composites are tooth-coloured restorative material used by dentists for various applications. Restoration of a lost tooth structure requires a material having mechanical as well as aesthetic properties similar to that of tooth. This poses challenges to engineers and the dentist alike. Dental composites consist of a matrix and a dispersed phase called filler, which are mainly responsible for its mechanical properties. Most commonly used matrix is bisphenol glycidyl methacrylate (Bis-GMA) and triethylene glycol dimethacrylate (TEGMA). Silica and glass are conventional fillers used in the past. Recently, zirconia is being used due to its improved mechanical properties. A study was conducted to evaluate the contribution of zirconia to the mechanical properties in general and compressive strength in particular. We have attempted to make an experimental dental composite with a conglomerate of nanofillers, namely, zirconia, glass and silica, and optimize this filler volume percentage and obtain an optimum compressive strength for the experimental dental composite.

    • Promising in vitro performances of nickel-free nitrogen containing stainless steels for orthopaedic applications

      Mohd Talha C K Behera O P Sinha

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      The aim of the present work was to study the in vitro corrosion resistance in Hank’s solution and biocompatibility of indigenized low-cost Ni-free nitrogen containing austenitic stainless steels (HNSs) and to compare with conventionally used 316L and 316LVM. The electrochemical behaviour was assessed using electrochemical impedance spectroscopy, potentiostatic polarization and scanning electron microscopy. The MTT assay [3-(4,5-dimethythiazol 2-yl)-2,5-diphenyltetrazolium bromide] was performed using Dalton’s lymphoma cell line for cytotoxicity evaluation and cell adhesion test. The resistance of surface film was raised by increasing nitrogen content in stainless steel (SS). The corrosion current density was decreased with increase in nitrogen content and corrosion potentials for HNS were observed to be more positive. Shallower and smaller pits were associated with HNS, indicating that nitrogen suppresses the pit formation. The HNS had higher cell proliferation and cell growth and it increases by increasing the nitrogen content. The surface wettability of the alloys was also investigated by water contact-angle measurements. The value of contact angles was found to decrease with increase in nitrogen content. This indicates that the hydrophilic character increases with increasing nitrogen content, which is further attributed to enhance the surface free energy that would be conducive to cell adhesion, which in turn increases the cell proliferation.

    • Study on osteopotential activity of Terminalia arjuna bark extract incorporated bone substitute

      G Krithiga T Hemalatha R Deepachitra Kausik Ghosh T P Sastry

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      Bark extract of Terminalia arjuna (TA) possesses potent medical properties and therefore, holds a reputed position in both Ayurvedic and Unani systems of medicine. Bone substitutes play an inevitable role in traumatic bone damages. Growth factors induce osteoinductivity, but suffer from limitations such as high cost and side effects. This study aims to evaluate the osteoinductive potential of bark extract of TA in bone substitutes. Bone substitutes prepared with TA bark extract were characterized for their physicochemical properties. In vitro biomineralization study was carried out using simulated body fluid. Cytotoxicity, alkaline phosphatase activity and mineralization potential were assessed using MG-63 cell lines. Scanning electron microscope revealed apatite formation on the surface after biomineralization. Thermogravimetric analysis showed 15% increase in residual weight by deposition of calcium and phosphate and their presence was identified by energy dispersive analysis. Increased alkaline phosphatase and calcium release was observed in bone substitutes prepared with TA extract compared with control. The functional groups of TA bark extract help in in vitro biomineralization. In MG-63 cells, it showed potential influence in cell differentiation. TA extract may be used as low-cost alternative for growth factors for treatment of fractured bones.

    • Structural properties of BeO at high pressure

      Umesh Kumar Sakalle Anita Singh Ekta Sharma

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      In the present paper, we have investigated the phase transition and elastic properties of BeO at high pressure using three-body potential model (TBPM). The present interaction potential consists of longrange coulomb and three-body interactions and short-range overlap repulsion effective up to second neighbour ions. We have studied the phase transition from wurtzite (𝐵4) to rock salt (𝐵1) for BeO. The phase transition pressure (𝑃t) obtained from this approach shows a respectably good agreement with experimental and other theoretical data. We have also computed the collapse of relative volume changes (𝛥 𝑉(𝑃t)/𝑉(0)). Three-body potential model has also been used to derive the correct expressions for third-order elastic constants and pressure derivatives of second-order elastic constants for BeO.

    • High-pressure structural stability of the ductile intermetallic compound, ErCu

      S Meenakshi

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      High-pressure angle dispersive X-ray diffraction measurements up to 23.6 GPa have been carried out on the ductile intermetallic compound, ErCu. Our measurements show that the ambient CsCl structure (𝑆𝐺: 𝑃𝑚-3𝑚) is stable up to the highest pressure of the present measurements. A second-order Birch–Murnaghan equation of state fit to the pressure, volume data yielded a bulk modulus of 67.6 GPa with the pressure derivative of bulk modulus fixed at 4.

    • Impurity binding energy for 𝛿-doped quantum well structures

      V Tulupenko C A Duque R Demediuk O Fomina V Akimov V Belykh T Dmitrichenko V Poroshin

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      The binding energy of an impurity delta layer situated either in the centre or at the edge of a quantum well (QW) is theoretically considered for the example of 𝑛-type Si0.8Ge0.2/Si/Si0.8Ge0.2 QW doped with phosphorus. Calculations are made for the case of not so big impurity concentrations, when impurity bands are not yet formed and it is still possible to treat impurity as isolated ones. It is shown on the base of self-consistent solution of Schrödinger, Poisson and electro-neutrality equations that impurity binding energy is dependent on the degree of impurity ionization and the most noticeably for the case of edge-doped QWs.

    • Nanoporous Ag template from partially sintered Ag–Zn compact by dezincification

      M Mandal A P Moon S Sangal K Mondal

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      A novel approach is followed to successfully fabricate nanoporous thin Ag template using partial sintering of elemental Ag and Zn (both have 99.9% purity) and subsequent dezincification. The starting materials for dezincification are partially sintered Ag–Zn aggregates (2.5, 5 and 10 wt% Zn). Partial sintering is done in order to achieve only interfacial bonding with the aim to maintain maximum potential difference between Ag and Zn particles during dezincification process in 1 N HCl and 3.5 wt% NaCl solutions. Two different dissolution methods, namely, simple immersion for 45 days and electrochemical way (holding the sample at critical potential), are employed. Electrochemical polarization tests are carried out to determine the critical potential for subsequent chrono-amperometry. X-ray diffraction, optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy are carried out to examine microstructural evolution, size, distribution and nature of pores in sintered aggregate as well as in template.

    • Non-enzymatic hydrogen peroxide sensor based on Co3O4 nanocubes

      Guang Sheng Cao Lei Wang Pengfei Yuan Chao Gao Xiaojuan Liu Tong Li Tianmin Li

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      The Co3O4 nanocubes were prepared by using hydrogen peroxide (H2O2) as oxidant, Co(NO3)2. 6H2O as a cobalt source. The products were characterized in detail by multiform techniques: scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The prepared Co3O4 nanocubes were applied to study the electrocatalytic reduction of hydrogen peroxide (H2O2) in 0.01 M pH 7.0 phosphate buffer medium. The Co3O4 nanocubes exhibit remarkable electrocatalytic activity for H2O2 reduction. Furthermore, the obtained Co3O4 nanocubes have been employed as electrode materials for electrochemical sensing H2O2.

    • Preparation and characterization of Fe–V/TiO2–SiO2 nanocatalyst modified by zinc

      Mostafa Feyzi Hamid Reza Rafiee Fataneh Jafari

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      The Fe–V/TiO2–SiO2 nanocatalyst promoted with zinc is prepared by combination of sol–gel and wetness impregnation methods. The effects of different weight percentages of iron, vanadium and zinc, titania to silica mole ratio, synthesis temperature and heating rate of calcination on the structure and morphology of nanocatalyst are investigated. Results showed that the modified nanocatalyst containing 40 wt% of Fe, 12 wt% of V and 2 wt% of zinc (all on weight percent) supported on TiO2–SiO2 with synthesis temperature of 45 °C has highest surface area, pore volume and pore diameter. Characterizations of catalysts were carried out using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectrometry, scanning electron microscopy (SEM), vibrating sample magnetometry (VSM) and N2 physisorption measurements. It was found that the nanocatalyst has a particle size about 56 nm and its saturation magnetization factor is equal to 10.173 emu/g. The catalyst can easily be separated from medium by a magnet.

    • Laser-induced transformation of GaS and GaSe nanosheets to onion structures with closed cages

      K Vasu

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      Experimental evidence for the transformation of nanosheets of GaS and GaSe into onion structures on UV excimer pulsed laser irradiation is presented. Few-layer GaS and GaSe on Si substrates were exposed to KrF pulsed laser with wavelength of 248 nm and the effect was studied as a function of number of laser pulses. Laser-induced dewetting of the layers results in the formation of spherical nanoparticles after 50 laser pulses. HREM images of these particles reveal the formation of onions with several concentric layers. The initial thickness of the layers controls the size of the onion cages. A mechanism of transformation of few layers to closed cage onions on UV pulsed laser irradiation is presented.

    • Synthesis of polyanthranilic acid–Au nanocomposites by emulsion polymerization: development of dopamine sensor

      Bhavana Gupta Ambrose Melvin Rajiv Prakash

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      Polyanthranilic acid (PANA) and polyanthranilic acid–gold (PANA–Au) nanocomposites have been synthesized through emulsion polymerization technique. Use of gold chloride as an oxidant for anthranilic acid not only provides a new route for chemical synthesis of PANA, but also explores a facile method for the formation of nanocomposites. Emulsion polymerization helps in slowing down kinetics of polymerization in comparison to one-phase polymerization and thereby induces formation of monodispersed, both pure and Au nanoparticles, embedded PANA sphere. Reaction progress of nanocomposite formation is studied by UV–Vis spectroscopy for 0–24 h. PANA–Au nanocomposites are characterized by SEM, equipped with EDS, TGA, FT–IR, XRD and electrochemical techniques. XRD of nanocomposites depicts the amorphous nature of polymer and crystalline nature of Au with crystallite size of ∼ 24 nm. Differential pulse voltammetry has shown the electro-active nature of PANA. The nanocomposites with improved thermal properties show good dispersion in common organic solvents, and it can be explored for application in interference-free dopamine sensors with sensitivity 12.5 𝜇A/mM. Acidic group (–COOH) on the polymer makes the sensor free from ascorbic acid interference.

    • Designed synthesis of tunable amorphous carbon nanotubes (a-CNTs) by a novel route and their oxidation resistance properties

      Longlong Xu Yifu Zhang Xiongzhi Zhang Yu Huang Xiaoyu Tan Chi Huang Xiao Mei Fei Niu Changgong Meng Gongzhen Cheng

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      Tunable amorphous carbon nanotubes (a-CNTs) were successfully synthesized using V3O7.H2O and glucose solution as the starting materials by a novel route for the first time. The as-obtained samples were separately characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), energy-dispersive spectrometer (EDS), elemental analysis (EA), Fourier transform infrared spectroscopy (FT–IR) and Raman spectrum. The results showed that the as-obtained a-CNTs had uniform diameters with outer diameter ranging from 140 to 250 nm and inner diameter about 28 nm on an average, and their length was up to several micrometres. No VO𝑥 residues remaining in a-CNTs showed the as-obtained a-CNTs with high purity. The as-prepared a-CNTs were a kind of hydrogenated a-CNTs containing both the 𝑠𝑝3- and 𝑠𝑝2-type carbons. Furthermore, the thermal stability of the as-obtained a-CNTs in the air atmosphere were investigated by thermo-gravimetric/differential thermal analyser (TG-DTA), revealing that the as-obtained a-CNTs had good thermal stability and oxidation resistance below 300 °C in air.

    • Conductivity study of PEO–LiClO4 polymer electrolyte doped with ZnO nanocomposite ceramic filler

      S U Patil S S Yawale S P Yawale

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      The preparation and characterization of composite polymer electrolytes comprising PEO and LiClO4 with different concentrations of ZnO nanoparticles are studied. Conductivity measurements were carried out and discussed. In order to ascertain the thermal stability of the polymer electrolyte with maximum conductivity, films were subjected to TG/DTA analysis in the range of 298–823 K. In the present work, FTIR spectroscopy is used to study polymer structure and interactions between PEO and LiClO4, which can make changes in the vibrational modes of the atoms or molecules in the material. FTIR spectra show the complexation of LiClO4 with PEO. The SEM photographs indicated that electrolytes are miscible and homogeneous.

    • Formation and surface characterization of nanostructured Al2O3–TiO2 coatings

      Vairamuthu Raj Mohamed Sirajudeen Mumjitha

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      One pot synthesis of Al2O3–TiO2 nanoceramic coatings from environment-friendly potassium titanium oxalate (PTO) electrolyte using facile electrochemical anodization has been reported for the first time. Systematic analysis of the anodization parameters such as applied current density and concentration of the PTO electrolyte influence on the morphology of the ceramic coatings was done. The textural properties of the coatings (thickness, growth rate, coating ratio) showed a linear regime with current density and electrolyte concentration decreases up to a certain level and then decreases. The growth process, distribution of chemical elements, phase constitutions and corrosion resistance of the coatings were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Tafel polarization technique and electrochemical impedance spectroscopy (EIS). The relation between the corrosion resistivity of the anodic coating and the aforementioned anodization parameters is investigated. The mechanisms that are involved in the formation of the ceramic coatings are also discussed. The coatings formed from 30 g/L concentration of PTO and 0.02 A/cm2 current density show good morphology, textural properties and optimum corrosion resistance.

    • Wash fastness improvement of malachite green-dyed cotton fabrics coated with nanosol composites of silica–titania

      I Kartini I Ilmi E S Kunarti Kamariah

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      Washing fastness of dyed cotton fabrics by malachite green (MG) blended with nanosols composite of SiO2–TiO2 has been significantly enhanced. The nanoparticulate inorganic sols were prepared by acidcatalyzed hydrolysis of titanium (IV) tetraisopropoxide (TTIP) and tetraethylortosilicate (TEOS) in ethanol at room temperature. The effect of silica on the characteristics of nanosols composite of TiO2–SiO2 was studied. Nanosols morphology was examined by transmission electron microscope (TEM). The nanosols silica–titania composite showed homogeneous morphology of interconnected spheres of about 20–25 nm. Enhanced dye absorption was observed at nanosols with silica content. The reflection spectra of the samples before and after leaching test using sodium dodecyl sulphate were recorded. The results showed that embedding TiO2–SiO2 and SiO2 sols into the MG dye can improve the wash fastness by 40–95%. The highest improvement was obtained by SiO2–MG-coated cotton fabrics as well as composites of SiO2–TiO2–MG-dyed cotton fabrics at highest silica content. The MG-nanosols composite silica–titania dyed cotton fabric has also shown remarkable antibacterial activity over Staphylococcus aureus and Escherichia coli.

    • Improvement in structural and electrical properties of cuprous oxide-coated multiwalled carbon nanotubes

      Shivani Dhall Neena Jaggi

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      In the present work, cuprous oxide (Cu2O) nanoparticles are coated on multi-walled carbon nanotubes (MWCNTs) using Fehling’s reaction. The coating of Cu2O nanoparticles on the nanotubes was confirmed by SEM and X-ray diffraction (XRD) spectra. The calculated 𝐼D/𝐼G ratio of Cu2O (using 3% CuSO4 by wt)-coated MWCNTs by Raman spectra is found to decrease to 0.94 as compared to 1.14 for pristine MWCNTs. It shows that the presence of Cu2O nanoparticles on nanotubes decreases the inherent defects present in the form of some pentagons/heptagons in the honeycomb hexagonal carbon atoms in the structure of graphene sheets of MWCNTs and increases the crystalline nature of MWCNTs, which is also confirmed by the XRD peaks. Whereas the value of 𝐼D/𝐼G ratio increases to 1.39 for sample 2 (using 5% CuSO4 by wt), which represents the structural deformation. Moreover, the electrical conductivity of MWCNTs was increased by 3 times after coating the nanotubes with Cu2O (using 3% CuSO4 by wt).

    • Silver nanoparticles prepared in presence of ascorbic acid and gelatin, and their electrocatalytic application

      Fereshteh Chekin Somayeh Ghasemi

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      In this paper, we reported a simple and low-cost procedure to synthesize silver nanoparticles (AgNPs) by using ascorbic acid as reducing agent and gelatin as stabilizer. The synthesized AgNPs were characterized by various means such as transmission electron microscope (TEM), powder X-ray diffraction (XRD) and energy-dispersive X-ray (EDX). TEM observations and XRD analysis demonstrated that the size of AgNPs is about 20 nm. Silver nanoparticles modified with carbon-paste electrode (AgNPs–CPE) displayed excellent electrochemical catalytic activities towards hydrogen peroxide (H2O2). The reduction overpotential of H2O2 was decreased significantly compared with those obtained at the bare CPE. The sensor responded linearly to hydrogen peroxide (H2O2) in the concentration of 10–350 𝜇M, with detection limit of 5.6 𝜇M at 3𝜎 using amperometry. The studied sensor exhibited good reproducibility and long-term stability.

    • Statistical analysis of thermal conductivity of nanofluid containing decorated multi-walled carbon nanotubes with TiO2 nanoparticles

      Sedigheh Abbasi Seyed Mojtaba Zebarjad Seyed Hossein Noie Baghban Abbas Youssefi

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      In this paper, we report for the first time the statistical analysis of thermal conductivity of nanofluids containing TiO2 nanoparticles, pristine MWCNTs and decorated MWCNTs with different amounts of TiO2 nanoparticles. The functionalized MWCNT and synthesized hybrid of MWCNT–TiO2 were characterized using transmission electron microscopy (TEM). TEM image confirmed that the ends of MWCNTs were opened during their oxidation of them in HNO3 and TiO2 nanoparticles successfully attach to the outer surface of oxidized MWCNTs. Thermal conductivity measurements of nanofluids were analysed via two-factor completely randomized design and comparison of data means is carried out with Duncan’s multiple-range test. Statistical analysis of experimental data show that temperature and weight fraction have a reasonable impact on the thermal conductivity of all tested nanofluids (𝛼 = 0.05). The results also show that increased temperature and weight fraction leads to the increased thermal conductivity.

    • Facile synthesis of monodisperse thermally immiscible Ag–Ni alloy nanoparticles at room temperature

      S Tabatabaei S K Sadrnezhaad

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      Ag and Ni are immiscible, mainly due to their large lattice mismatch. This paper reports on their nanoscale formation of solid solution at room temperature by simple reduction reactions which lead to the amorphous Ag–Ni alloy nanoparticles (ANPs) with mono-disperse distribution. Microscopic and spectroscopic studies confirmed dependence of the alloy composition on size of nanoparticles. In the presence of different ligands such as sodium citrate, polyvinyl alcohol and potassium carbonate a mixture of silver oxide and Ag–Ni ANPs was achieved. Stoichiometry of the Ag–Ni ANPs was also found to be strongly dependent on ligands of the reduction reaction and further study shows without any ligand 100% Ag–Ni ANPs was observed in the system. Using Tetrakis hydroxymethyl phosphonium chloride resulted in construction of near-uniform ANPs in the easily controllable conditions of the present alloying procedure. Nanoparticles having up to 65% Ni were observed for the first time in this research.

    • Effect of alloy content on microstructure and microchemistry of phases during short term thermal exposure of 9Cr–W–Ta–0.1C reduced activation ferritic/martensitic (RAFM) steels

      Ravikirana R Mythili S Raju S Saroja G Paneerselvam T Jayakumar E Rajendra Kumar

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      This paper presents the results of an experimental study on the microstructural evolution in 9Cr reduced activation ferritic/martensitic steels during short term thermal exposures. Since the microstructure is strongly influenced by the alloying additions, mainly W, Ta and C contents, the effect of varying W and Ta contents on the martensite structure that forms during normalizing treatment and the subsequent changes during tempering of the martensite in the temperature regime of 923–1033 K have been studied. Microstructural changes like subgrain formation and nature of precipitates have been evaluated and correlated to hardness variations. The systematic change in size distribution and microchemistry of M23C6 carbide is studied with variation in W content at different temperatures.

    • Growth and characterization of propyl-para-hydroxybenzoate single crystals

      N Karunagaran P Ramasamy R Perumal Ramasamy

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      Single crystals of propyl-𝑝-hydroxybenzoate have been grown by slow evaporation solution technique. The structure of the compound was confirmed by FT–IR, FT–Raman spectroscopy and single crystal X-ray diffraction studies. The crystalline perfection of the grown single crystals has been analysed by high resolution X-ray diffraction measurements. Optical properties of the grown single crystals were studied by UV–Vis NIR spectrum. The luminescence behaviour of the single crystal has been analysed by photoluminescence analysis and found maximum luminescence in the lower wavelength region. A simple interferometric technique was used for measuring birefringence of the crystal. The laser damage threshold of the crystal is 1.3 GW/cm2. The mechanical strength of the grown crystal is measured using Vickers microhardness tester. The dielectric properties have been investigated.

    • Electronic structure and first hyperpolarizability of poly(𝜇2-L-alanine-𝜇3-sodium nitrate (I)) crystals

      A Duarte Moller

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      Poly(𝜇2-L-alanine-𝜇3-sodium nitrate (I)), 𝑝-LASN, crystals have been grown by slow evaporation at room temperature. The nominal size of the crystals obtained by the method was of 500 nm. The UV–Vis spectrum shows a wide range, where absorption is lacking around 532 nm, which is required in order to have the second harmonic emission, when an incident radiation of 1064 nm strikes on the crystal. This guarantees the possible use of the crystal in visible light applications. The transparent nature of the crystal in the visible and infrared regions within the transmission spectrum confirms the nonlinear optical properties of the crystal. Additionally, Fourier transform infrared spectroscopy displays its functional groups which correspond to the poly(𝜇2-L-alanine-𝜇3-sodium nitrate (I)), where the presence of nitrates in the lattice generally can be identified by their characteristic signature within the 1660–1625, 1300–1255, 870–833 and 763–690 cm-1 range. Single crystal diffraction was carried out in order to determine atomic structure and lattice parameter. Structural parameters were 𝑎 = 5.388(9) Å, 𝑏 = 9.315(15) Å and 𝑐 = 13.63(2) Å. The structure of poly(𝜇2-Lalanine-𝜇3-sodium nitrate (I)) shown by single crystal diffraction shows an asymmetric unit consisting of one sodium and one nitrate ion and one L-alanine molecule. The coordination geometry around the sodium atom was trigonal bipyramidal, with three bidentate nitrate anions coordinating through their oxygen atoms and two L-alanine molecules, each coordinating through one carboxyl oxygen atom. Electronic structure was obtained by using the Becke–Lee–Yang–Part and Hartree–Fock approximations with hybrid exchangecorrelation three-parameter functional and G-311**G(𝑑𝑝) basis set. Theoretical and experimental results were compared and discussed as having an excellent agreement among them.

    • Boron-doped MnTe semiconductor-sensitized ZnO solar cells

      Auttasit Tubtimtae Suwanna Sheangliw Kritsada Hongsith Supab Choopun

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      We studied the photovoltaic performance of boron-doped MnTe semiconductor-sensitized solar cells (B-doped MnTe SSCs). The B-doped MnTe semiconductor was grown on ZnO using two stages of the successive ionic layer adsorption and reaction (SILAR) technique. The two phases of B-doped semiconductor nanoparticles (NPs), i.e. MnTe and MnTe2 were observed with a diameter range of approximately 15–30 nm. The result of the energy conversion efficiency of the sample with boron doping was superior compared to that of an undoped sample, due to the substantial change in the short-circuit current density and the open-circuit voltage. In addition, plots of (𝛼 ℎ 𝜈)2 vs ℎ 𝜈 with band gaps of 1.30 and 1.27 eV were determined for the undoped and B-doped MnTe NPs, respectively. It can be noted that the boron doping effects with the change in the band gap and lead to an improvement in the crystalline quality and also intimate contact between the larger sizes of MnTe NPs. Hence, a noticeably improved photovoltaic performance resulted. However, this kind of semiconductor sensitizer can be further extended by experiments on yielding a higher power conversion efficiency and greater stability of the device.

    • Preparation and characterization of hydrophobic platinum-doped carbon aerogel catalyst for hydrogen isotope separation

      M K Singh R Singh A Singh D K Kohli U Deshpande P K Gupta

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      We report preparation of hydrophobic platinum-doped carbon aerogel (PtCA) catalyst and its characterization for catalytic exchange reactions between hydrogen isotopes. The PtCA powder was synthesized by sol–gel polymerization method, mixed with colloidal PTFE solution, and coated on Dixon rings to obtain hydrophobic catalyst. The Pt cluster size in PtCA powder was observed to vary from 3 to 5 nm for a change in resorcinol to alkali molar ratio in synthesis solution from 20 to 200. Transmission electron microscopy of powder showed that the Pt clusters were uniformally dispersed and Pt0 metallic content estimated by X-ray photoelectron spectroscopy (XPS) was found to be of ∼ 70%. The catalytic activity was found to depend on Pt cluster size and was higher for smaller cluster size. For the smallest achieved Pt cluster size of 3 nm, catalytic activity of ∼ 0.8 m3 (STP) s-1 m-3 was obtained for hydrogen isotope exchange in atmospheric pressure conditions.

    • Enhanced efficiency and improved photocatalytic activity of 1 :1 composite mixture of TiO2 nanoparticles and nanotubes in dye-sensitized solar cell

      D Maheswari P Venkatachalam

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      TiO2-based nanotubes (NTs), nanoparticles (NPs) and composite structural film (50% NP + 50% NT film) were synthesized by sol–gel hydrothermal process. Synthetic indigo dye was used as a sensitizer with the unique combination of electrolyte (EMII + BMII + PMII) and with cobalt sulphide as counter electrode. The structure and morphology of the three films, namely, NP, NT and NPNT is studied through X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The absorption spectra and incident photon-to-current conversion efficiency (IPCE) of the three films were compared and found to be higher for NPNT film. The efficiency and photocatalytic activity of three films were evaluated. The composite structure showed improved efficiency (1.72%) than NP (1%) and NT films (0.78%). The photocatalytic activity of the three films were measured using organic dye, methylene blue under UV light radiation. The composite structure showed higher dye absorption and higher rate of reaction with time. This paper certainly proves that there are many rooms to focus on the photoanode configuration, which plays a key role to improve the efficiency of dye-sensitized solar cell (DSSC).

    • Thermally stimulated discharge conductivity study of zinc oxide thermoelectrets

      Vijaya S Sangawar Manisha C Golchha

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      The present work deals with transmission electron microscopy (TEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermally stimulated discharge current (TSDC) study of inorganic metal oxide (ZnO) nanoparticles and its thermoelectrets. The thermoelectrets were prepared by applying different electric polarizing field (𝐸P) at constant polarizing temperature (𝑇P), for constant polarization time (𝑡P). The TSDC study was carried out in the temperature region of 313–473 K. It was observed that the conductivity of ZnO samples increases with the increase in temperature and polarizing field. The dependence of TSDC data on polarizing agents, i.e. field and temperature shows Arrhenius type of behviour and is explained on the basis of variable range hopping mechanism.

    • A novel organic–inorganic hybrid based on Anderson-type polyoxometalate: H(C5N5H5)2(C5N5H6)2[Al(OH6)Mo6O18].10H2O

      Safa Thabet Brahim Ayed Amor Haddad

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      A new organic–inorganic hybrid compound, H(C5N5H5)2(C5N5H6)2[Al(OH6)Mo6O18].10H2O, has been synthesized and structurally characterized by single crystal X-ray diffraction, elemental analyses, IR, UV–Vis spectra and thermogravimetric analyses. This compound crystallized in the triclinic system, space group 𝑃-1, with 𝑎 = 8.033(5) Å, 𝑏 = 9.960(4) Å, 𝑐 = 16.797(7) Å, 𝛼 = 73.43(3)°, 𝛽 = 87.85(1)°, 𝛾 = 81.47(1)° and 𝑍 = 1. The crystal structure can be described by infinite polyanions [Al(OH)6Mo6O18]3- organized in layers parallel to the 𝑐-direction alternating with organic cations associated in ribbons spreading along the 𝑏-direction. Multiple hydrogen bonds originating from amine, hydroxyl groups and water molecules connect different components of the lattice.

    • Influence of Be doping on the characteristics of CdO/p-Si heterojunction for optoresponse applications

      A A Dakhel

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      In this work, the optoelectronic properties of Be-doped CdO films grown on p-Si forming CdO : Be/p-Si hetero-p–n junctions were investigated. The spotlight was on the influence of electronic properties of CdO : Be layers, which were controlled by Be-dopant content, on the optoelectronic properties of the constructed p–n heterojunction. The characterization of the transparent conducting oxide CdO : Be layer was performed with X-ray diffraction, scanning electron microscopy, electrical measurements and spectral photometry. It was found that Be doping greatly enhanced the optoresponse (𝑆*) of the p–n heterojunction, such that 𝑆* was boosted by ∼36 times for CdO : 0.10% Be/p-Si sample, compared with the undoped CdO/p-Si. This 𝑆*-enhancement was explained by the improvement of carrier mobility in host CdO with Be doping. Therefore, the utmost 𝑆* that was found with 0.10% Be-doped CdO sample was due to its highest carrier mobility among other samples of different Be content. The results of optoelectronic measurements in visible and NIR spectral range demonstrate the utility of the CdO : Be/p-Si heterojunction in photodetection applications.

    • Iron–carbon hybrid capacitor: A proof-of-concept study

      V R Chari S R Aravamuthan A K Shukla

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      In the present study, cost-intensive Ni electrode is replaced by high surface-area activated carbon (AC) cathode and the possibility of the Fe anode, used in Ni–Fe battery, to function as Fe–C hybrid capacitor has been examined. The electrochemical properties of Fe–C hybrid capacitor assembly are studied using cyclic voltammetry (CV) and galvanostatic charge–discharge cycles. Over 100 galvanostatic charge–discharge cycles for Fe–C hybrid capacitor are carried out and a maximum capacitance of 24 F g-1 is observed.

    • In vitro corrosion investigations of plasma-sprayed hydroxyapatite and hydroxyapatite–calcium phosphate coatings on 316L SS

      Gurpreet Singh Hazoor Singh Buta Singh Sidhu

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      The present paper discusses various issues associated with biological corrosion of uncoated and plasma-sprayed hydroxyapatite (HA)-coated 316L SS and studies the effect of contents of calcium phosphate (CaP) on corrosion behaviour of hydroxyapatite (HA) coatings in simulated body fluid (Ringer’s solution). Three types of coatings, i.e. HA + 20 wt% CaP (type 1), HA + 10 wt% CaP (type 2), HA (type 3), were laid on 316L SS using plasma-spraying technique. Structural characterization techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to investigate the crystallinity, microstructure and morphology of the coatings. Electrochemical potentiodynamic tests were performed to determine the corrosion resistance of uncoated and all the three coatings. After the electrochemical corrosion testing, the samples were examined by XRD, SEM and EDX. The electrochemical study showed a significant improvement in the corrosion resistance after HA coating and corrosion resistance of type 3 coating was found maximum.

    • A simple and efficient electrochemical reductive method for graphene oxide

      Yanyun Liu Dong Zhang Yu Shang Chao Guo

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      The electrochemical reduction of graphene oxide typically involves complicated procedures, such as modification of electrodes and preparation of electrolytes, which is often needed in previous reports. In this paper, a simple and efficient electrochemical process is described for the synthesis of high-quality reduced graphene oxide. The main procedures involve the electrophoretic deposition of graphene oxide onto positive electrode and the subsequent in situ electrochemical negative reduction when the electrode changes from positive to negative. This approach opens up a new, practical and green reducing method to prepare largescale graphene.

    • One-step electrodeposition process of CuInSe2: Deposition time effect

      O Meglali N Attaf A Bouraiou M S Aida S Lakehal

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      CuInSe2 thin films were prepared by one-step electrodeposition process using a simplified twoelectrodes system. The films were deposited, during 5, 10, 15 and 20 min, from the deionized water solution consisting of CuCl2, InCl3 and SeO2 onto ITO-coated glass substrates. As-deposited films have been annealed under vacuum at 300 °C during 30 min. The structural, optical band gap and electrical resistivity of elaborated films were studied, respectively, using X-ray diffraction (XRD), Raman spectroscopy, UV spectrophotometer and four-point probe method. The micro structural parameters like lattice constants, crystallite size, dislocation density and strain have been evaluated. The XRD investigation proved that the film deposited at 20 min present CuInSe2 single phase in its chalcopyrite structure and with preferred orientation along (1 1 2) direction, whereas the films deposited at 5, 10 and 15 min show the CuInSe2 chalcopyrite structure with the In2Se3 as secondary phase. We have found that the formation mechanism of CuInSe2 depends on the In2Se3 phase. The optical band gap of the films is found to decrease from 1.17 to 1.04 eV with increase in deposition time. All films show Raman spectra with a dominant A1 mode at 174 cm-1, confirming the chalcopyrite crystalline quality of these films. The films exhibited a range of resistivity varying from 2.3 × 10-3 to 4.4 × 10-1 𝛺 cm.

    • Electrical impedance spectroscopy measurements to estimate the uniaxial compressive strength of a fault breccia

      Sair Kahraman Michael Alber

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      Fault breccias are usually not suitable for preparing smooth specimens or else the preparation of such specimens is tedious, time consuming and expensive. To develop a predictive model for the uniaxial compressive strength (UCS) of a fault breccia from electrical resistivity values obtained from the electrical impedance spectroscopy measurements, twenty-four samples of a fault breccia were tested in the laboratory. The UCS values were correlated with corresponding resistivity values and a strong correlation between them could not be found. However, a strong correlation was found for the samples having volumetric block proportion (VBP) of 25–75%. In addition, it was seen that VBP strongly correlated with resistivity. It was concluded that the UCS of the tested breccia can be estimated from resistivity for the samples having VBP of 25–75%.

    • Microstructure and oxidation performance of a 𝛾–𝛾' Pt-aluminide bond coat on directionally solidified superalloy CM-247LC

      Md Zafir Alam N Hazari Dipak K Das

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      The microstructure of a Pt-modified 𝛾-𝛾' bond coat on CM-247LC Ni-base superalloy has been examined and its cyclic oxidation performance at 1100 °C in air is comparatively evaluated with that of a conventional 𝛽-(Ni, Pt)Al bond coat. The 𝛾-𝛾' bond coat was effective in imparting oxidation resistance to the CM-247LC alloy for about 100 h, whereas the 𝛽 coating imparted oxidation resistance for significantly longer duration of about 1000 h. The nature of surface damage that occurred to the 𝛾-𝛾' coating during oxidation has been compared with that reported in the case of 𝛽 coating.

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