Showing papers in "Bulletin of Materials Science in 2014"

Facile template-free hydrothermal synthesis and microstrain measurement of ZnO nanorods

Abstract: ZnO nanorods were synthesized at low temperature by hydrothermally heating 0·1 M solution of ZnCl2 for 5, 10 and 15 h at a pH of 10. No template, seeded substrate, catalyst and autoclave were employed for the synthesis of ZnO nanorods. The effect of heating durations on the morphology and crystal orientation of the structure were investigated by using scanning electron microscopy and X-ray diffraction, respectively. SEM images showed that the flower-like structures were formed in 5 h hydrothermally-heated sample, whereas the hexagonal zinc oxide nanorods were perfectly fabricated with the increase in growth time. XRD patterns showed that the preferred orientation in nanorods could be controlled by hydrothermal treatment time. The crystallite size and microstrain were analysed by Williamson–Hall and Halder–Wagner methods. These results revealed the presence of defects in ZnO nanorods. However, by increasing the hydrothermal treatment time, both defects in lattice and crystallite size are decreased.

Ciprofloxacin conjugated zinc oxide nanoparticle: A camouflage towards multidrug resistant bacteria

Abstract: Gradual development of antibiotic resistant bacteria is producing severe global threat. Newer strategies are now being employed in order to control the microbial infections and to reduce the mortality as well as infection rates. Herein we describe successful synthesis of ZnO nanoparticles (ZNP) under microwave assisted condition followed by functionalization with ciprofloxacin, an antibiotic, using EDC/NHS chemistry. Successful conjugation of ciprofloxacin was confirmed by FTIR spectra. Ciprofloxacin-conjugated ZnO nanoparticles (ZN-CIP) exhibited excellent antibacterial activity against clinically isolated multidrug resistant bacterial strains of Escherichia coli, Staphylococcus aureus and Klebsiella sp. ZNP were small in size with particle size distribution 18–20 nm as obtained from transmission electron microscope (TEM). Surface topology was obtained from atomic force microscopic (AFM) image and x-ray diffraction confirmed that ZNP possessed hexagonal crystal structure. A concentration of 10 µg/mL of ZN-CIP was a benchmark concentration. During evaluation of minimum inhibitory concentration (MIC) values, similar concentration of antibiotic was incapable of producing antibacterial activity.

Bioactive nanocrystalline wollastonite synthesized by sol–gel combustion method by using eggshell waste as calcium source

Abstract: The sol–gel combustion method was employed to synthesize the nanocrystalline wollastonite by taking the raw eggshell powder as a calcium source and TEOS as a source of silicate. Glycine was used as a reductant or fuel and nitrate ions present in metal nitrate acts as an oxidizer. The phase purity of the wollastonite was analysed by powder XRD and the product is found to contain single-phasic wollastonite. FT–IR spectrum shows the characteristic peaks of the functional groups present in the wollastonite. SEM images show that particles are agglomerated and the particle size is found to be in the nanoregime. The calcination temperature was optimized based on the thermal analysis of the precursor. The bioactivity of wollastonite was investigated by immersing the scaffold in a simulated body fluid for 15 days at 37 °C and intermediate analysis of the surface by XRD shows the deposition of hydroxyapatite layer after 5 days.

Effect of tempering after cryogenic treatment of tungsten carbide–cobalt bounded inserts

Abstract: Cryogenic treatment is a recent advancement in the field of machining to improve the properties of cutting tool materials. Tungsten carbide is the most commonly used cutting tool material in the industry and the technique can also be extended to it. Although the importance of tempering after cryogenic treatment has been discussed by many researchers, very little information is available in published literature about the effect of multi-tempering after cryogenic treatment. In this study, an attempt has been made to understand effect of the number of post-tempering cycles during cryogenic treatment on tungsten carbide–cobalt inserts. Metallurgical investigations have been performed to observe the effect of such post-tempering on the inserts by analysing microhardness and micro-structural changes. The crystal structure and morphology were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction analysis. Metallurgical investigations revealed a significant improvement in tungsten carbide inserts having three tempering cycles, after cryogenic treatment, with marginal differences for two cycles of tempered inserts, established by the study of wear behaviour in turning.

Structural, optical and electrical properties of ZnO thin films prepared by spray pyrolysis: Effect of precursor concentration

Abstract: ZnO thin films have been prepared using zinc acetate precursor by spray pyrolytic decomposition of zinc acetate on glass substrates at 450 °C. Effect of precursor concentration on structural and optical properties has been investigated. ZnO films are polycrystalline with (002) plane as preferential orientation. The optical transmission spectrum shows that transmission increases with decrease in the concentration and the maximum transmission in visible region is about 95% for ZnO films prepared with 0·1 M. The direct bandgap value decreases from 3·37 to 3·19 eV, when the precursor concentration increases from 0·1 to 0·4 M. Photoluminescence spectra at room temperature show an ultraviolet (UV) emission at 3·26 eV and two visible emissions at 2·82 and 2·38 eV. Lowest resistivity is obtained at 2·09 Ω cm for 0·3 M. The current– voltage characteristic of the ZnO thin films were measured in dark and under UV illumination. The values of photocurrent and photoresponsivity at 5 V are increased with increase in precursor concentration and reaches to maximum value of 1148 μA and 0·287 A/W, respectively which is correlated to structural properties of ZnO thin films.

Distinction between SnO2 nanoparticles synthesized using co-precipitation and solvothermal methods for the photovoltaic efficiency of dye-sensitized solar cells

Abstract: Nanocrystalline SnO2 powders prepared by solvothermal and co-precipitation pathways have been characterized using XRD, TEM, UV-Visible absorption, BET specific surface area (S BET) method, EIS and J-V measurements. The obtained powders have a surface area and size of 38.59 m2/g and 10.63 nm for the SnO2 powders synthesized solvothermally at a temperature of 200 °C for 24 h, while the values were 32.59 m2/g and 16.20 nm for the formed hydroxide precursor annealed at 1000 °C for 2 h by co-precipitation route. The microstructure of the formed powders appeared as tetragonal-like structure. Thus, the prepared SnO2 nanopowders using two pathways were applied as an electrode in dye-sensitized solar cell (DSSC). The photoelectrochemical measurements indicated that the cell presents short-circuit photocurrent (J sc), open circuit voltage (V oc) and fill factor (FF) were 7.017 mA/cm2, 0.690 V and 69.68%, respectively, for solvothermal route and they were 4.241 mA/cm2, 0.756 V and 66.74%, respectively, for co-precipitation method. The energy conversion efficiency of the solvothermal SnO2 powders was considerably higher than that formed by co-precipitation powders; ∼ 3.20% (solvothermal) and 2.01% (co-precipitation) with the N719 dye under 100 mW/cm2 of simulated sunlight, respectively. These results were in agreement with EIS study showing that the electrons were transferred rapidly to the surface of the solvothermal-modified SnO2 nanoparticles, compared with that of a co-precipitation-modified SnO2 nanoparticles.

Processing of water-based LiNi1/3Mn1/3Co1/3O2 pastes for manufacturing lithium ion battery cathodes

Abstract: In order to meet the demand for more ecological and economic fabrication of lithium ion (Li-ion) batteries, water is considered as an alternative solvent for electrode paste preparation. In this study, we report on the feasibility of water-based processing of LiNi 1/3 Mn 1/3 Co 1/3 O 2 -based pastes for manufacturing cathode electrodes. The influence of the total solid content, the amount of conductive agent and binder materials on paste rheology and the final electrode properties was investigated. Suitable paste formulations which enable favourable paste flow behaviour, appropriate electrode properties and good electrochemical performance have been found. Results show that a substitution of the conventional organic solvent-based manufacturing route for LiNi 1/3 Mn 1/3 Co 1/3 O 2 cathodes by water-based processing exhibits a promising way to realise Li-ion batteries with comparable electrochemical behaviour, while avoiding toxic processing aids and reducing overall manufacturing costs.

Study of electrical properties of polyvinylpyrrolidone/polyacrylamide blend thin films

Abstract: Electrical properties of polyvinylpyrrolidone, polyacrylamide and their blend thin films have been investigated as a function of temperature and frequency. The films were prepared using solution casting method and the measurements on films were carried out at different temperatures ranging from 305 to 345 K covering a frequency range from 102 to 105 Hz. The conductivity of film samples was found to increase upon increasing the temperature. Lowering of activation energy by increasing the polyvinylpyrrolidone percentage may be due to the predominance of ion conduction mechanism caused by polyvinylpyrrolidone in the blend. The permittivity (𝜖 r) and dielectric loss (𝜖 i) were found to decrease upon increasing frequency. Temperature and frequency dependence of impedance, relaxation time and electric modulus of thin film samples have also been studied. From electric modulus formalism, polarization and conduction relaxation behaviour in the film samples have been discussed.

A.c. conductivity and dielectric study of LiNiPO4 synthesized by solid-state method

Abstract: LiNiPO4 compound was prepared by the conventional solid-state reaction. The sample was characterized by X-ray powder diffraction, infrared, Raman analysis spectroscopy and electrical impedance spectroscopy. The compound crystallizes in the orthorhombic system, space group Pnma with a = 10·0252(7) A, b = 5·8569(5) A and c = 4·6758(4) A. Vibrational analysis was used to identify the presence of \( \mathrm{PO}_4^{3- } \) – group in this compound. The complex impedance has been measured in the temperature and frequency ranges 654–716 K and 242 Hz–5 MHz, respectively. The Z′ and Z″ vs frequency plots are well-fitted to an equivalent circuit consisting of series of combination of grains and grain boundary elements. Dielectric data were analysed using complex electrical modulus M* for the sample at various temperatures. The modulus plots are characterized by the presence of two peaks thermally activated. The frequency dependence of the conductivity is interpreted in terms of equation: \( {\sigma_{\mathrm{a}.\mathrm{c}.}}\left( \omega \right)=\left[ {{{{{\sigma_{\mathrm{g}}}}} \left/ {{\left( {1+{\tau^2}{\omega^2}} \right)}} \right.}+\left( {{{{{\sigma_{\infty }}{\tau^2}{\omega^2}}} \left/ {{1+{\tau^2}{\omega^2}}} \right.}} \right)+A{\omega^{\mathrm{n}}}} \right] \). The near values of activation energies obtained from the analysis of M″, conductivity data and equivalent circuit confirms that the transport is through ion hopping mechanism dominated by the motion of Li+ in the structure of the investigated material.

One-pot synthesis of hydroxyapatite–silica nanopowder composite for hardness enhancement of glass ionomer cement (GIC)

Abstract: Hydroxyapatite–silica nanopowder composite was prepared using one-pot sol–gel technique. The morphology of the powder consists of a mixture of spherical silica particles (∼30 nm) embedded within the elongated hydroxyapatite (∼103 nm). The synthesized nanoparticles were incorporated into commercial glass ionomer cement (GIC) and Vickers hardness was evaluated. Results shown that the addition of the nanopowder composite gave ∼73% increment in the hardness compared to the pure GIC. Higher content of hydroxyapatite–silica nanopowder resulted in dense cement and produced a stronger GIC and the application of this material with improved hardness property might lead to extend the clinical indications, especially in stress bearing areas.

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

Abstract: 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.

Growth, optical, thermal and mechanical characterization of an organic crystal: Brucinium 5-sulfosalicylate trihydrate

Abstract: Single crystals of Brucinium 5-sulfosalicylate trihydrate (B5ST) were grown from ethanol–water (1:1) mixed solvent by the slow solvent evaporation method. X-ray powder diffraction analysis reveals that the crystal belongs to orthorhombic system with space group P212121. The various reflections were indexed and the lattice parameters were calculated. Photoluminescence (PL) shows peaks corresponding to protonation of the amino group. The optical absorption spectrum shows that the crystal has 90% transmittance in the visible region with a lower cut-off wavelength of 312 nm. Thermal analysis performed on the grown crystal indicates the thermal stability of the crystal and various thermodynamical parameters were calculated from the thermogravimetry (TG) data. The mechanical properties like Vickers microhardness number (H v), stiffness constant (C 11) and yield strength (σ v) of the crystal were estimated by Vickers hardness test.

Characterization of composite materials based on Fe powder (core) and phenol–formaldehyde resin (shell) modified with nanometer-sized SiO2

Abstract: Soft magnetic composites based on Fe powder and phenol–formaldehyde resin (PFR) modified with tetraethylorthosilicate are investigated in detail. The chemical synthesis of PFR, its modification with nanometer-sized SiO2 particles created by sol–gel method and subsequent coating, enables a preparation of insulating PFR–SiO2 (PFRT) layer on the surface of Fe particles. Thermal degradation and FTIR analysis of PFR and PFRT with different amount of SiO2 was examined. Mechanical hardness and flexural strength of FePFRT composites was studied depending on the amount of nanosized-SiO2 in the coating. SEM serves in evidence of a defectless microstructure if the coating contains at least 2% of silica particles. The morphology of Fe particles implies uniform coating without any visible exfoliation. A presence of fine SiO2 particles was verified by TEM. The best magnetic properties were found in Fe–PFRT composite with 2% of SiO2 in the insulating layer on behalf of its uniform arrangement and homogeneity.

Synthesis of selenium nanorods with assistance of biomolecule

Abstract: Nanorods of one-dimensional (1D) trigonal selenium (t-Se) are synthesized using biomolecule substances for five different aging times (1 h, 2 h, 3 h, 1 day and 4 days) by precipitation method. XRD analysis indicates a shift of the (1 0 1) plane towards higher diffraction angle for 1 day aging time. It is observed that the crystallite size decreases with increase in aging time except for an aging period of 4 days. FTIR analysis confirmed that the presence of stretching and bending vibrations of Se–O in both synthesized and commercial selenium samples at 465, 668 and 1118 cm −1. The FESEM micrographs are evident for the changes of rod size as a function of aging time. It is observed that the optical band gap energy is increased with aging time up to 1 day, whereas it decreases in 4 days aging time.

Chemical bath deposition of CdS thin films doped with Zn and Cu

Abstract: Zn- and Cu-doped CdS thin films were deposited onto glass substrates by the chemical bath technique. ZnCl2 and CuCl2 were incorporated as dopant agents into the conventional CdS chemical bath in order to promote the CdS doping process. The effect of the deposition time and the doping concentration on the physical properties of CdS films were investigated. The morphology, thickness, bandgap energy, crystalline structure and elemental composition of Zn- and Cu-doped CdS films were investigated and compared to the undoped CdS films properties. Both Zn- and Cu-doped CdS films presented a cubic crystalline structure with (1 1 1) as the preferential orientation. Lower values of the bandgap energy were observed for the doped CdS films as compared to those of the undoped CdS films. Zn-doped CdS films presented higher thickness and roughness values than those of Cu-doped CdS films. From the photoluminescence results, it is suggested that the inclusion of Zn and Cu into CdS crystalline structure promotes the formation of acceptor levels above CdS valence band, resulting in lower bandgap energy values for the doped CdS films.

Effects of fibre orientation on mechanical properties of hybrid bamboo/glass fibre polymer composites

Abstract: The usage of natural fibre as reinforcement in polymer composites have widely increased because of its enhanced properties. The usage of plant fibre cannot alone satisfy all the needs of the composites. Hence, introduction of hybrid plays a vital role in enhancing the mechanical properties of the FRP composites. Fibre orientation contributes significant role in improving the mechanical properties of the FRP composites. In this proposal, hybrid bamboo/glass fibre woven in different orientations such as 0°/90° and ± 45° was used and its effect on mechanical properties were studied. Composites containing hybrid fibres found to possess better mechanical properties, when compared to pure bamboo. In order to justify this, the following mechanical properties such as tensile, flexural, impact and hardness were investigated. SEM analysis shows the bonding between the matrix and reinforcement. All the above test results indicate that the introduction of natural bamboo fibre in glass reduces the overall cost of the composites with no compromise in strength and also attracted several studies covering green technologies.

ALD TiO2 thin film as dielectric for Al/p-Si Schottky diode

Abstract: Electrical analysis of Al/p-Si Schottky diode with titanium dioxide (TiO2) thin film was performed at room temperature. The forward and reverse bias current–voltage (I–V) characteristics of diode were studied. Using thermionic emission (TE) theory, the main electrical parameters of the Al/TiO2/p-Si Schottky diode such as ideality factor (n), zero bias barrier height (ϕ Bo) and series resistance (R s) were estimated from forward bias I–V plots. At the same time, values of n, ϕ Bo and R s were obtained from Cheung’s method. It was shown that electrical parameters obtained from TE theory and Cheung’s method exhibit close agreement with each other. The reverse-bias leakage current mechanism of Al/TiO2/p-Si Schottky barrier diodes was investigated. The I–V curves in the reverse direction are taken and interpreted via both Schottky and Poole–Frenkel effects. Schottky effect was found to be dominant in the reverse direction. In addition, the capacitance–voltage (C–V) and conductance–voltage (G/w–V) characteristics of diode were investigated at different frequencies (50–500 kHz). The frequency dependence of interface states density was obtained from the Hill–Coleman method and the voltage dependence of interface states density was obtained from the high–low frequency capacitance method.

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

Abstract: 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.

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

Abstract: 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.

Porous graphitic materials obtained from carbonization of organic xerogels doped with transition metal salts

Abstract: Porous carbons with a well developed graphitic phase were obtained via the pyrolysis of FeCl3-, NiCl2-, and CoCl2-doped organic xerogels. Doping was realized through salt solubilization in a water/methanol solution of resorcinol and furfural. Carbon xerogels with tailored particles, porous morphology and various degrees of graphitization were obtained depending of the water/methanol ratio and the salt content and type in the starting solution of substrates. When obtained via pyrolysis, carbon xerogels retain the overall open-celled structure exhibiting depleted microporosity and a well-developed mesoporic region that expands into macropores. The removal of metal leads to carbon xerogels with specific surface areas between 170 and 585 m2/g and pore volume up to 0·76 cm3/g. The possibility of enhancing the porosity of xerogels via templating with colloidal silica was also investigated. It was assumed that from the three investigated salts, FeCl3 makes the best choice for graphitization catalyst precursor to obtain uniformly graphitized mesoporous carbon xerogels. The obtained carbon samples were characterized by means of SEM, TEM, X-ray diffraction, Raman spectroscopy, N2 physisorption and thermogravimetric analysis.

Rapid hydrothermal route to synthesize cubic-phase gadolinium oxide nanorods

Abstract: An inexpensive fabrication route and growth mechanism is being reported for obtaining quality gadolinium oxide (Gd2O3) nanoscale rods. The elongated nanoscale systems, as produced via a hydrothermal process, were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), optical absorption spectroscopy, photoluminescence (PL) spectroscopy, Raman spectroscopy and magnetic hysteresis measurements. XRD patterns of the nanorods, as-prepared from independent precursors of different pH, depict a cubic crystal phase and an average crystallite size of 5–6.5 nm. As revealed from HRTEM micrographs, diameter of the nanorods prepared at pH = 13.3 (∼ 7 nm) was much smaller than the rods prepared at pH = 10.8 (∼ 19 nm). However, the aspect ratio was more than double in the former case than the latter case. PL response was found to be dominated by defect mediated emissions, whereas Raman spectrum of a given specimen (pH = 10.8) has revealed characteristic F g + A g modes of cubic phase of Gd2O3 nanorods, apart from other independent modes. Furthermore, M ∼ H plot of the nanorod system (pH = 10.8) exhibited slight departure from the ideal superparamagnetic behaviour, with low remanence and coercive field values. The exploitation of one-dimensional Gd2O3 nanorods have immense potential in the production of advanced contrast agents, smart drives and also in making novel ferrofluids of technological relevance.

Pulse electrodeposition and corrosion properties of Ni-Si3N4 nanocomposite coatings

Abstract: The development of modern technology requires metallic materials with better surface properties. In the present investigation; Si3N4-reinforced nickel nanocomposite coatings were deposited on a mild steel substrate using pulse current electrodeposition process employing a nickel acetate bath. Surface morphology, composition, microstructure and crystal orientation of Ni and Ni–Si3N4 nanocomposite coatings were investigated by scanning electron microscope, energy dispersive X-ray spectroscopy and X-ray diffraction analysis, respectively. The effect of incorporation of Si3N4 particles in the Ni nanocomposite coating on the micro hardness, corrosion behaviour has been evaluated. Smooth composite deposits containing well-distributed silicon nitride particles were obtained and the crystal grains on the surface of Ni–Si3N4 composite coating are compact. The crystallite structure was face centred cubic (fcc) for electrodeposited nickel and Ni–Si3N4 nanocomposite coatings. The micro hardness of the composite coatings (720 HV) was higher than that of pure nickel (310 HV) due to dispersion-strengthening and matrix grain refining and increased with the increase of incorporated Si3N4 particle content. The corrosion potential (E corr) in the case of Ni–Si3N4 nanocomposite had shown a negative shift, confirming the cathodic protective nature of the coating.

Influence of annealing temperature on ZnO thin films grown by dual ion beam sputtering

Abstract: We have investigated the influence of in situ annealing on the optical, electrical, structural and morphological properties of ZnO thin films prepared on p-type Si(100) substrates by dual ion beam sputtering deposition (DIBSD) system. X-ray diffraction (XRD) measurements showed that all ZnO films have (002) preferred orientation. Full-width at half-maximum (FWHM) of XRD from the (002) crystal plane was observed to reach to a minimum value of 0.139° from ZnO film, annealed at 600 °C. Photoluminescence (PL) measurements demonstrated sharp near-band-edge emission (NBE) at ~ 380 nm along with broad deep level emissions (DLEs) at room temperature. Moreover, when the annealing temperature was increased from 400 to 600 °C, the ratio of NBE peak intensity to DLE peak intensity initially increased, however, it reduced at further increase in annealing temperature. In electrical characterization as well, when annealing temperature was increased from 400 to 600 °C, room temperature electron mobility enhanced from 6.534 to 13.326 cm2/V s, and then reduced with subsequent increase in temperature. Therefore, 600 °C annealing temperature produced good-quality ZnO film, suitable for optoelectronic devices fabrication. X-ray photoelectron spectroscopy (XPS) study revealed the presence of oxygen interstitials and vacancies point defects in ZnO film annealed at 400 °C.

Metal-polyaniline nanofibre composite for supercapacitor applications

Abstract: The aim of the present work is to increase the electrical conductivity and specific capacitance of the polyaniline (PANi) nanofibres by introducing the metallic nanostructures. Herein, metal nanoparticle-incorporated PANi nanofibres were prepared from interfacially synthesized PANi nanofibres as seeds. In the main step of aniline polymerization, the seeds were employed to produce a large amount of PANi nanofibres in the next steps. Also, metal-PANi nanofibres were chemically prepared by adding inorganic salts (nickel and copper salts) which incorporated PANi nanofibres via the self-assembly process. Increased conductivity and good electrochemical behaviour were observed for these metal-PANi nanofibres at room temperature compared with the single PANi nanofibres, which was previously reported. SEM, FT-IR and UV-Vis techniques were applied for characterization of the products. Finally, the potential application of the composites to use as electrode materials for supercapacitor was examined. Elevated specific capacitance in addition to good cycle stability was observed for the metal-PANi nanofibres. Also, electrochemical impedance spectroscopy and charge/discharge experiments show that these metal-PANi nanofibres possess the high conductivity and low charge transfer resistance, which make them suitable candidates for high-performance supercapacitors.

Preparation and characterization of PEG–Mg(CH 3 COO) 2 –CeO 2 composite polymer electrolytes for battery application

Abstract: Composite polymer electrolytes based on poly(ethylene glycol) (PEG), magnesium acetate [Mg(CH3COO)2], and x wt% of cerium oxide (CeO2) ceramic fillers (where x = 0, 5, 10, 15 and 20, respectively) have been prepared using solution casting technique. X-ray diffraction patterns of PEG–Mg(CH3COO)2 with CeO 2 ceramic filler indicated the decrease in the degree of crystallinity with increasing concentration of the filler. DSC measurements of PEG–Mg(CH3COO)2–CeO2 composite polymer electrolyte system showed that the melting temperature is shifted towards the lower temperature with increase of the filler concentration. The conductivity results indicate that the incorporation of ceramic filler up to a certain concentration (i.e. 15 wt%) increases the ionic conductivity and upon further addition the conductivity decreases. The transference number data indicated the dominance of ion-type charge transport in these specimens. Using this (PEG–Mg(CH3COO)2–CeO2) (85-15-15) electrolyte, solid-state electrochemical cell was fabricated and their discharge profiles were studied under a constant load of 100 kΩ.

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

Abstract: 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.

Synthesis and characterization of TiO 2 –SiO 2 nanoparticles as catalyst for dehydrogenation of 1,4-dihydropyridines

Abstract: Nanoparticles of binary TiO2–SiO2 mixed oxides was prepared via sol–gel method using tetraethylorthosilicate (TEOS) and titanium isopropoxide (TIPP) in different reaction conditions (solvent and pH) using ammonium hyhdroxide, acetic acid, sodium hydroxide, ethyleneglycol and polyethylene glycol followed by calcination at 850–970 °C. The morphologies, structures and chemical compositions were determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Fourier transmission infrared spectroscopy (FTIR) techniques. The catalytic activity of the obtained nanomaterials was explored for the dehydrogenation of 1,4-dihydropyridines (1,4-DHPs). Observation of 86–100% conversion and 100% selectivity towards the formation of desired products with prepared nanoparticles will be discussed here.

Electrodeposition and characterization of Ni-W/ZrO2 nanocomposite coatings

Abstract: Ni-W/ZrO2 nanocomposite coatings were prepared by electrodeposition in Ni-W plating bath containing ZrO2 nanoparticles. The influences of preparation parameter, such as ZrO2 nanoparticles concentration, current density and stirring rate, on weight percentage of codeposited ZrO2 nanoparticles in the nanocomposite coatings were investigated. The surface morphology of Ni-W/ZrO2 nanocomposite coating was characterized by scanning electron microscopy (SEM). The microhardness, wear resistance and corrosion resistance properties of Ni-W/ZrO2 nanocomposite coatings were studied. The results indicated that the addition of ZrO2 nanoparticles leads to an increase in microhardness and wear resistance of the nanocomposite coatings and a reduction in the wear weight loss. The corrosion behaviour of Ni-W/ZrO2 nanocomposite coatings was evaluated by the anodic polarization curves and weight loss measurements. The results revealed that Ni-W/ZrO2 nanocomposite coating has better corrosion resistance than the Ni-W alloy coating.

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

Abstract: 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.

Characterization, dielectric and electrical behaviour of BaTiO3 nanoparticles prepared via titanium(IV) triethanolaminato isopropoxide and hydrated barium hydroxide

Abstract: A new sol-precipitation technique for the preparation of nano BaTiO3 crystallite has been developed by reacting 0·2 M each of Ti(IV) triethanolaminato isopropoxide and hydrated barium hydroxide in methanol such that the molar ratio of Ba : Ti is 1·02 at 80 °C under stirring (1200 rpm) for one hour in alkaline media using tetra methyl ammonium hydroxide (TMAH). It was calcined at 100 °C for 12 h. Structural and compositional properties were investigated by XRD, SEM, EDX, TEM, SAED and DLS techniques. FT–IR and TG–DTA were used to characterize its purity and the thermal stability. The BaTiO3 particles prepared were found to be spherical, homogeneous and cubic in structure. The particle size was found to be 23–31 nm. The dielectric constant and dissipation factor after sintering at 400 °C were 5379 and 0·63, respectively at 100 Hz frequency. The a.c. conductivity (σ a.c.) was found to be 2 × 10–5 S-cm–1 at room temperature (30 °C). It increased with increasing temperature up to 50 °C and decreased with further increase in temperature. The impedance was 3·37 × 105 ohms at room temperature. It decreased with increasing frequency.