• Issue front cover thumbnail

      Volume 37, Issue 3

      May 2014,   pages  371-741

    • Studies on interfacial interactions of TiO2 nanoparticles with bacterial cells under light and dark conditions

      Swayamprava Dalai Sunandan Pakrashi Sujay Chakravarty Shamima Hussain N Chandrasekaran Amitava Mukherjee

      More Details Abstract Fulltext PDF

      The probable underlying mechanism(s) of bacterial cell–TiO2 nanoparticles (TiO2 NPs) interaction in the absence of photo-irradiation has been less studied since most of the prior cytotoxicity studies focused on irradiated TiO2. The present study draws attention to the possible role of cell surface–TiO2 NP interactions under dark conditions, through an array of spectroscopic and microscopic investigations. A dominant freshwater bacterial isolate, Bacillus licheniformis, which interacted with environmentally relevant concentrations of TiO2 NPs (1 𝜇g/mL), was analysed and compared under both light and dark conditions. Aggregation of cells upon NP interaction and adsorption of NPs onto the cell membrane was evident from the scanning electron micrographs under both light and dark conditions. The FT–IR and FT–Raman spectra suggested stress response of bacterial cells by elevated protein and polysaccharide content in the cell–NP interaction. The X-ray photoelectron spectroscopic data substantiated the reduction of titanium from Ti(IV) to Ti(III) species which might have contributed to the redox interactions on the cell surface under light as well as dark conditions. The internalization of NPs in the cytoplasm were obvious from the transmission electron micrographs. The consequent cell death/damage was confirmed through fluorescence spectroscopy and microscopy. To conclude, the current study established the substantial role of interfacial interactions in cytotoxicity of the TiO2 NPs irrespective of the irradiation conditions.

    • Nanoscale grain growth behaviour of CoAl intermetallic synthesized by mechanical alloying

      S N Hosseini M H Enayati F Karimzadeh

      More Details Abstract Fulltext PDF

      Grain growth behaviour of the nanocrystalline CoAl intermetallic compound synthesized by mechanical alloying has been studied by isothermal annealing at different temperatures and durations. X-ray diffraction method was employed to investigate structural evolutions during mechanical alloying and annealing processes. The disordered CoAl phase with the grain size of about 6 nm was formed via a gradual reaction during mechanical alloying. The results of isothermal annealing showed that the grain growth behaviour can be explained by the parabolic grain growth law. The grains were at nanometric scale after isothermal annealing up to 0.7 𝑇m. The grain growth exponent remained constant above 873 K indicating that grain growth mechanism does not change at high temperatures. The calculated activation energy indicated that the grain growth mechanism in the disordered CoAl phase at high temperatures was diffusing Co and Al atoms in two separate sublattices. Furthermore, an equation has been suggested to describe the grain growth kinetics of nanocrystalline CoAl under isothermal annealing at temperatures above 873 K (𝑇/𝑇m ≥ 0.5).

    • Parametric characterizations in superparamagnetic latex

      Seda Beyaz Hakan Kockar Taner Tanrisever

      More Details Abstract Fulltext PDF

      The effect of synthesis parameters on the production of superparamagnetic latex, which are magnetite nanoparticles covered with a poly(methyl methacrylate) layer, were studied. The synthesis method was based on the developed route of emulsifier-free emulsion polymerization. Under this study, effects of the monomer and initiator concentrations, the amount of magnetic sol, the stirring rate and the adding rate of the magnetic sol on the properties of synthesized latexes were investigated. The characterizations were performed by a high resolution transmission electron microscopy, a dynamic light scattering, a vibrating sample magnetometer and a gel permeation chromatography. The results showed that the monomer concentration was found to be the most effective parameter on latex stability. As the initiator amount and the stirring rate increased, saturation magnetization and average molecular weight decreased due to the reactions occurring between surfaces of magnetite nanoparticles and initiator fragments. On increasing amount of magnetic sol, the saturation magnetization and polymer molecular weight increased but the size of nanospheres was unchanged because of the ions in magnetic sol. It was seen that the desired size and magnetic properties of the latex could be obtained since the parameters were found to have substantial impact on their properties.

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

      L Motevalizadeh Z Heidary M Ebrahimizadeh Abrishami

      More Details Abstract Fulltext PDF

      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.

    • Structural study of nanosized yttrium-doped CaMnO3 perovskites

      J Zagorac A Zarubica A Radosavljevic-Mihajlovic D Zagorac B Matovic

      More Details Abstract Fulltext PDF

      Nanostructured compounds with general formula Ca1-𝑥Y𝑥MnO3 (0 ≤ 𝑥 ≤ 1) were synthesized by modified glycine nitrate procedure. In the next step, we have investigated crystal structure and microstructure of the synthesized samples using X-ray methods and Rietveld analysis. Focus of this research was the structural stability of the yttrium-doped CaMnO3 perovskite phases, which crystallize in orthorhombic space group Pnma. We observed that the unit cell volumes of the investigated compounds increase proportionally with yttrium amount. Furthermore, we investigated the influence of yttrium amount on Mn–O bond angles and distances, tilting of MnO6 octahedra and deformation due to the presence of Jahn–Teller distortion around Mn3+ cation. In order to estimate effective coordination of 𝐴 and 𝐵 sites, bond valence calculations (BVC) were performed for 𝐴 and 𝐵 site cations. Finally, the photoelectron spectroscopy (XPS) method was applied in order to follow yttrium concentration in the perovskite phases.

    • Structural, optical and photoluminescence study of nanocrystalline SnO2 thin films deposited by spray pyrolysis

      Akhilesh Tripathi R K Shukla

      More Details Abstract Fulltext PDF

      Undoped SnO2 thin films prepared by spray pyrolysis method reveal polycrystalline nature with prominent peaks along (110), (101) and (211) planes. All the films are nanocrystalline with particle size lying in the range of 3.14–8.6 nm calculated by DS formula. Orientation along plane (200) decreases continuously as molar concentration of SnO2 increases. Dislocation density along plane (110) also decreases as molar concentration increases except 0.4 M SnO2 thin film. Scanning electron microscopy image of the films contain jelly structures along with agglomerated clusters of particles. SnO2 synthesized successfully, which confirms by Fourier transform infra-red spectroscopy. The optical transmittance spectra of 0.2 M SnO2 thin film shows transmittance about 50–60% transmission in visible and near infrared region with a sharp cut off in the ultraviolet region. The transmission decreases in visible and near infrared region as molar concentration increases. Broad UV emission at 398 nm is observed in photoluminescence spectra of the films along with a blue emission, when excited at 250 nm wavelength. Emission intensity randomly changed as SnO2 molar concentration increases. When excited at 320 nm, one UV and two visible peaks appeared at 385, 460 and 485 nm, respectively.

    • Nanocrystalline Pt-doped TiO2 thin films prepared by spray pyrolysis for hydrogen gas detection

      Lalchand A Patil Dinesh N Suryawanshi Idris G Pathan Dhanashri G Patil

      More Details Abstract Fulltext PDF

      Nanostructured pure and Pt-doped TiO2 thin films were prepared by chemical spray pyrolysis technique. Aqueous solution of TiCl3.6H2O (0.01 M) was chosen as the starting solution for the preparation of pure TiO2 thin film. Aqueous solutions of PtCl6.6H2O (0.01 M) and TiCl3.6H2O (0.01 M) were mixed in volume % of 1 : 99, 2.5 : 97.5 and 5 : 95 respectively to obtain Pt-doped TiO2 thin films. The solutions were sprayed onto quartz substrate heated at 350 °C temperature to obtain the films. These thin films were fired for one hour at 550 °C. The sensing performance of these films was tested for various gases such as LPG, H2, CO2, ethanol, NH3 and Cl2 (1000 ppm). The Pt-doped TiO2 (1 : 99) was observed to be most sensitive (572) to H2 at 400 °C with high selectivity against other gases. Its response time was short (10 s) and recovery was also fast (14 s). To understand the reasons behind the gas-sensing performance of the films, their structural and micro-structral properties were studied using X-ray diffraction and electron microscopy (FE–SEM and TEM), respectively. Thicknesses of all these samples were determined using Surface Profiler. The results are interpreted.

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

      F Zahedi R S Dariani S M Rozati

      More Details Abstract Fulltext PDF

      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 band-gap 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.

    • Synthesis and characterization of thermally oxidized ZnO films

      A P Rambu N Iftimie

      More Details Abstract Fulltext PDF

      Metallic zinc thin films were deposited onto glass substrates using vacuum thermal evaporation method. By thermal oxidation of as-deposited Zn films, in ambient conditions, at different temperatures (570, 670 and 770 K, respectively, for 1 h) zinc oxide thin films were obtained. The structural characteristics of the obtained films were investigated by X-ray diffraction technique and atomic force microscopy. Characteristic XRD patterns of oxidized films show small and narrow peaks superimposed on the large broad background of the amorphous component of the substrate. Optical transmittance spectra were recorded and it was observed that the transmittances of the studied films increased with increasing oxidation temperature. The values of the optical bandgap, 𝐸g, evaluated from Tauc plots, were found to be ranged between 3.22 and 3.27 eV. Electrical conductivity measurements were performed and it was observed that, after performing a heat treatment, the electrical conductivity of analysed samples decreased with one or two orders of magnitude. The gas sensitivity was investigated for some reducing gases such as acetone, methane and liquefied petroleum gas and it was observed that the films studied were selective to acetone.

    • Experiment and prediction on thermal conductivity of Al2O3/ZnO nano thin film interface structure

      Ping Yang Liqiang Zhang Haiying Yang Dongjing Liu Xialong Li

      More Details Abstract Fulltext PDF

      We predict that there is a critical value of Al2O3/ZnO nano thin interface thickness based on two assumptions according to an interesting phenomenon, which the thermal conductivity (TC) trend of Al2O3/ZnO nano thin interface is consistent with that of relevant single nano thin interface when the nano thin interface thickness is > 300 nm; however, TC of Al2O3/ZnO nano thin interface is higher than that of relevant single nano thin interface when the thin films thickness is < 10 nm. This prediction may build a basis for the understanding of interface between two different oxide materials. It implies an idea for new generation of semiconductor devices manufacturing.

    • Temperature influence and reset voltage study of bipolar resistive switching behaviour in ZrO2 thin films

      Ying Li Gaoyang Zhao Jian Su Erfeng Shen Yang Ren

      More Details Abstract Fulltext PDF

      We have fabricated ZrO2 thin films by sol–gel deposition and annealed them at 300, 500 and 700 °C. Reproducible 𝐼-𝑉 curves can be obtained for the device Cu/ZrO2/ATO which is measured at room temperature (300 K). During the RESET operation, 𝑅L and 𝑅H values can be controlled by the RESET voltage. Moreover, the Cu/ZrO2/ATO device which the ZrO2 thin film annealed at 300 °C can be measured as resistive switching sweeps at 200, 100 and 50 K. It was found that the ratio of 𝑅off/𝑅on reduced when the measured temperature decreased. When the 𝐼-𝑉 measurement temperature decreases, 𝑅on decreases obviously which is typical for electronic transportation in a Cu metal. It is indicated that the Cu metallic conduction filament has been formed in the ZrO2 films. Besides, the microstructure by high resolution transmission electrical microscopy (HRTEM) was also investigated.

    • A.c. and d.c. conduction processes in octakis[(4-tert-butylbenzylthio)-porphyrazinato]Cu(II) thin films with gold electrodes

      Bahadir Keskin Ahmet Altindal Ulvi Avciata Ahmet Gül

      More Details Abstract Fulltext PDF

      The d.c. and a.c. electrical transport properties of Au/Pz/Au devices with various thickness of Pz(octakis[(4-tert-butylbenzylthio)-porphyrazinato]Cu(II)) layer have been investigated. Measurements revealed that, in contrast to previously investigated Au/Pc/Au structures, low voltage d.c. behaviour of the films can be described by the field-lowering mechanisms with a $\log$(𝐽) ∝ 𝑉1/2 current density-voltage characteristics under forward and reverse bias. For high reverse voltages, the observed ln (𝐽/𝑉2) - 1/𝑉 characteristics indicated that the origin of conduction mechanism is Fowler–Nordheim tunnelling (FNT). On the other hand, the voltage dependence of current density at the higher forward-voltage region indicates that the mechanism of conduction in Au/Pz/Au devices is space charge limited conduction dominated by exponential trap distribution. A thickness independent barrier height was observed for tunnelling, while the total trap concentration show a general tendency to decrease with increasing film thickness. The a.c. conductivity showed two regions in the ln (𝜎a.c.) - ln(𝑓) plots having different slopes, leading to the conclusion that for low frequency region, the dominant conduction mechanism is a small polaron tunnelling at all temperatures, whereas for high frequency region, correlated barrier hopping model is the dominant mechanism in the investigated devices.

    • Zn incorporation in CuInSe2: Particle size and strain effects on microstructural and electrical properties

      M Benabdeslem A Bouasla N Benslim L Bechiri S Mehdaoui O Aissaoui A Djekoun M Fromm X Portier

      More Details Abstract Fulltext PDF

      Incorporation of the doping element Zn in the temperature range (550–700 °C) and the impact on structural and electrical properties of CuInSe2 material are investigated. X-ray diffraction patterns showed the chalcopyrite nature of the pure and doped CuInSe2 and revealed that diffusion temperature governs particle size as well as tensile strain. The calculated lattice parameters and cell volumes revealed that Zn diffuses in CuInSe2 by substitution on Cu sites. Electrical properties of the material have been investigated using a contact-less technique based on high frequency microwave (HF). It is found that Zn atoms influence the defect equilibrium resulting in the conversion of the conduction type. The conductivity of the samples has been found increasing as the diffusion temperature increases.

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

      M Ben Bechir A Ben Rhaiem K Guidara

      More Details Abstract Fulltext PDF

      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) Å, 𝑏 = 5.8569(5) Å and 𝑐 = 4.6758(4) Å. Vibrational analysis was used to identify the presence of PO$^{3-}_{4}$ 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: 𝜎_a.c.(𝜔) = [𝜎g/(1 + 𝜏2𝜔2) + (𝜎𝜏2𝜔2/1 + 𝜏2𝜔2) + A𝜔n]. 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.

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

      Ravindra H Upadhyay Anant P Argekar Rajendra R Deshmukh

      More Details Abstract Fulltext PDF

      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 (𝜎a.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.

    • Growth, characterization and dielectric property studies of gel grown barium succinate single crystals

      M P Binitha P P Pradyumnan

      More Details Abstract Fulltext PDF

      Single crystals of barium succinate (BaC4H4O4) were grown in silica gel medium using controlled chemical reaction method. Plate-like single crystals of size up to 3 × 2 × 0.2 mm3 was obtained. Single crystal X-ray diffraction (XRD) studies confirmed that structure of the title compound is tetragonal. Powder X-ray diffraction (PXRD) pattern of the grown crystal and the Fourier transform infrared (FT–IR) spectrum in the range 400–4000 cm-1 are recorded. The vibrational bands corresponding to different functional groups are assigned. Thermal stability of the grown crystals is confirmed by differential scanning calorimetry (DSC). Dielectric constant and dielectric loss have been calculated and discussed as a function of frequency at different temperatures.

    • Magnetodielectric effect in Ni0.5Zn0.5Fe2O4–BaTiO3 nanocomposites

      Shilpi Banerjee Partha Hajra Anindya Datta Asim Bhaumik Mykanth Reddy Mada Sri Bandyopadhyay Dipankar Chakravorty

      More Details Abstract Fulltext PDF

      Composites comprising of nanoparticles of Ni0.5Zn0.5Fe2O4 (NZF) and BaTiO3 (BT), respectively were synthesized by a chemical method. The particles had diameters in the range of 15–31 nm. NZF was prepared by a coprecipitation technique. This was soaked in a sol containing BT. Compositions synthesized were 𝑥NZF-(1 - 𝑥) BT, where 𝑥 = 0.7, 0.5 and 0.3, respectively. The composites showed ferromagnetic hysteresis loops due to NZF phase. The analysis of coercivity variation as a function of temperature gave blocking temperatures in the range of 306–384 K depending on the diameter of the ferrite nanoparticles. This implied that superparamagnetic interactions are above these temperatures. The nanocomposites also exhibited ferroelectric behaviour arising due to the presence of BT. The remanent polarization of the samples was small. This was adduced to the nanosize of BT. The specimens showed magneto-dielectric (MD) effect in the magnetic field range 0–0.7 Tesla. The MD parameter measured at the maximum magnetic field was around 2\%. This was one order of magnitude higher than that reported so far in similar composite systems. This was explained on the basis of a two-phase inhomogeneous medium model with an interface between them, the phases possessing drastically different electrical conductivities.

    • Dielectric and photo-dielectric properties of TlGaSeS crystals

      A F Qasrawi Samah F Abu-Zaid Salam A Ghanameh N M Gasanly

      More Details Abstract Fulltext PDF

      The room temperature, dark and photo-dielectric properties of the novel crystals TlGaSeS are investigated in the frequency, intensity and biasing voltage having ranges of ~ 1–120 MHz, 14–40 klux and 0–1 V, respectively. The crystals are observed to exhibit a dark high frequency effective dielectric constant value of ∼ 10.65 × 103 with a quality factor of ∼ 8.84 × 104 at ∼ 120 MHz. The dielectric spectra showed sharp resonance–antiresonance peaks in the frequency range of ∼ 25–250 kHz. When photoexcited, pronounced increase in the dielectric constant and in the quality factor values with increasing illumination intensity are observed. Signal amplification up to ∼ 33% with improved signal quality up to ∼ 29% is attainable via photoexcitation. On the other hand, the illuminated capacitance–voltage characteristics of the crystals reflected a downward shift in the voltage biasing and in the built-in voltage of the device that is associated with increase in the uncompensated carrier density. The increase in the dielectric constant with increasing illumination intensity is ascribed to the decrease in the crystal's resistance as a result of increased free carrier density. The light sensitivity of the crystals, the improved dielectric properties and the lower biasing voltage obtained via photoexcitation and the well-enhanced signal quality factor of the crystals make them promising candidates for optical communication systems.

    • Guest–host interaction in ferroelectric liquid crystal–nanoparticle composite system

      Dharmendra Pratap Singh Swadesh Kumar Gupta Satya Prakash Yadav P K Sharma A C Pandey Rajiv Manohar

      More Details Abstract Fulltext PDF

      The present paper deals with the characterization of a ferroelectric liquid crystal–nanoparticle (FLC–NP) composite system. The dielectric, electrical and polarization property of the FLC–NP composite system have been studied as a function of temperature and frequency. Ferroelectric Cu-doped ZnO (Cu–ZnO) nanoparticles have been added to the pure ferroelectric liquid crystal (FLC) Felix 17/100. The nanoparticles are bigger in size as compared to FLC molecules; therefore, they distort the existing geometry of FLC matrix and set up an antiparallel correlation with the dipole moments of the host FLC molecules. This antiparallel correlation of guest–host geometry reduces the net ferroelectricity of the composite system and modifies all the physical properties of the pure FLC. The change in properties has been analysed and explained in the light of guest–host interaction.

    • Microstructural and optical properties of transparent conductive ZnO : Al : Mo films deposited by template-assisted sol–gel method

      H-Y He J-F Huang Z He J Lu Q Shen

      More Details Abstract Fulltext PDF

      Transparent conductive ZnO : Al : Mo films with a molar ratio of Zn : Al : Mo = 99 : 0.99 : 0.01 were deposited on quartz glass substrate by a template-assisted sol-gel process and characterized by X-ray diffraction, atomic force microscopy, scanning electron microscopy, and UV–Vis and luminescent spectrophotometries. The four types of organic template have induced nanowire morphology with varying aspect ratio. Dip coating in one constant positive and reverse direction causes the parallel array of ZnO : Al : Mo nanowires on the quartz glass substrate. Long and parallel arrayed nanowire films show obviously blue shifts and enhanced transmittances in the UV-Vis light range. The PEG-1000 and PEG-2000 have optimal effects among four templates as constant weight content is used. The films show strong ultraviolet, violet and bluish violet emissions. The templates also lead to overall thicker film and more native defect and thereby remarkably enhancing photoluminescence of the films. Long chain organic template can be used to optimize the optical properties of the doped ZnO film.

    • Structural verification and optical characterization of SiO2–Au–Cu2O nanoparticles

      Hossein Rezvani Nikabadi Nasser Shahtahmasebi Mahmood Rezaee Rokn-Abadi Masoud Karimipour M M Bagheri Mohagheghi

      More Details Abstract Fulltext PDF

      In this paper, SiO2–Au–Cu2O core/shell/shell nanoparticles were synthesized by reducing gold chloride on 3-amino-propyl-triethoxysilane molecules attached silica nanoparticle cores for several stages. Cu2O nanoparticles were synthesized readily with the size of 4–5 nm using a simple route of sol–gel method. Then, they were clung to the surface of Au seeds. The morphology of the resultant particles was studied using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Transmission electron microscopy images demonstrate growth of monodispersed gold seeds and Cu2O nanoparticles in narrow size up to 10 nm and 5 nm, respectively. The presence of gold and Cu2O coating was confirmed by X-ray diffraction, Fourier transform infrared spectroscopy and UV–Vis spectroscopy. Absorption spectroscopy shows considerably 40 nm blue shift in absorption edge for SiO2–Au–Cu2O nanostructure rather than SiO2–Au core/shell nanoparticles.

    • Effect of oxidation and annealing temperature on optical and structural properties of SnO2

      M Zarrinkhameh A Zendehnam S M Hosseini N Robatmili M Arabzadegan

      More Details Abstract Fulltext PDF

      Tin oxide thin films were deposited on glass substrate with 100 nm thickness of Sn, which was coated by magnetron sputtering followed by thermal oxidation at different temperatures. The effect of oxidation temperature on the optical and structural properties of SnO2 films were investigated. Higher transmittance, lower absorption and lesser structural defects were obtained at higher temperatures. Optical bandgap increases with temperature, while the Urbach energy showed reduction. The X-ray diffraction studies showed that at lower temperatures (300, 350 °C), a combined phase of SnO and SnO2 was obtained, while at higher temperatures (400, 450 °C), a nearly polycrystalline SnO2 film with preferred orientation of (101) was produced. Annealing of the samples at 500–650 °C caused the transmittance and optical bandgap increased, while the absorption decreased. Reduction of the Urbach energy after annealing could be attributed to the reduction of the degree of thermal disorder. AFM studies showed that although the thin films were annealed under similar condition, their roughness was not similar because of different oxidation temperatures, which means that initial oxidation temperature played an important role on surface uniformity of SnO2 thin films.

    • Structural, optical and magnetic properties of cobalt-doped CdSe nanoparticles

      Jaspal Singh N K Verma

      More Details Abstract Fulltext PDF

      Pure and Co-doped CdSe nanoparticles have been synthesized by hydrothermal technique. The synthesized nanoparticles have been characterized using X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV–Visible), photoluminescence spectroscopy (PL), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and superconducting quantum interference device (SQUID), at room temperature. From XRD analysis, pure and cobalt-doped CdSe nanoparticles have been found to be polycrystalline in nature and possess zinc blende phase having cubic structure. In addition to this, some peaks related to secondary phase or impurities such as cobalt diselenide (CoSe2) have also been observed. The calculated average crystallite size of the nanoparticles lies in the range, 3–21 nm, which is consistent with the results obtained from TEM analysis. The decrease in average crystallite size and blue shift in the band gap has been observed with Co-doping into the host CdSe nanoparticles. The magnetic analysis shows the ferromagnetic behaviour up to 10% of Co-doping concentration. The increase of Co content beyond 10% doping concentration leads to antiferromagnetic interactions between the Co ions, which suppress the ferromagnetism.

    • High pressure phase transitions for CdSe

      Bo Kong Ti-Xian Zeng Zhu-Wen Zhou De-Liang Chen Xiao-Wei Sun

      More Details Abstract Fulltext PDF

      The structure and pressure-induced phase transitions for CdSe are investigated using first-principles calculations. The pressure-induced phase transition sequence WZ/ZB $\to$ Rs $\to$ 𝐶𝑚𝑐𝑚 $\to$ CsCl for CdSe is drawn reasonably for the fist time, the corresponding transition pressures are 3.8, 29 and 107 GPa, respectively and the intermediate states between the 𝐶𝑚𝑐𝑚 structure and the CsCl structure should exist.

    • Optical and electrical properties of nickel xanthate thin films

      İ A Kariper T Özpozan

      More Details Abstract Fulltext PDF

      Nickel xanthate thin films (NXTF) were successfully deposited by chemical bath deposition, on to amorphous glass substrates, as well as on 𝑝- and 𝑛-silicon, indium tin oxide and poly(methyl methacrylate). The structure of the films was analysed by X-ray diffraction (XRD), far-infrared spectrum (FIR), mid-infrared (MIR) spectrum, nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM). These films were investigated from their structural, optical and electrical properties point of view. Uniform distribution of grains was clearly observed from the photographs taken by scanning electron microscope (SEM). The higher transmittance was about 50–60% after optimizing the parameters of deposition time and temperature (4 h, 50 °C). The optical bandgap of the NXTF was graphically estimated as 3.90–3.96 eV. The resistivity of the films was calculated as 62.6–90.7 𝛺.cm on commercial glass depending on the film thickness and 62.2–74.5 𝛺.cm on the other substrates. The MIR and FIR spectra of the films conformed to the literature and their solid powder forms. The expected peaks of nickel xanthate were observed in NMR analysis on glass. The films were dipped into chloroform as organic solvent and were analysed by NMR.

    • High temperature magnetic properties of nanocrystalline Sn0.95Co0.05O2

      O Mounkachi E Salmani M Boujnah H Labrim H El Moussaoui M Hamedoun A Benyoussef A El Kenz H Ez-Zahraouy R Masrour E K Hlil

      More Details Abstract Fulltext PDF

      Structural and magnetic properties of Sn0.95Co0.05O2 nanocrystalline and diluted magnetic semiconductors have been investigated. This sample has been synthesized by co-precipitation route. Study of magnetization hysteresis loop measurements infer that the sample of Sn0.95Co0.05O2 nanoparticle shows a well-defined hysteresis loop at 300 K temperature, which reflects its ferromagnetic behaviour. We confirmed the room-temperature intrinsic ferromagnetic (FM) semiconductors by ab initio calculation, using the theory of the functional of density (DFT) by employing the method of Korringa–Kohn–Rostoker (KKR) as well as coherent potential approximation (CPA, explain the disorder effect) to systems. The ferromagnetic state energy was calculated and compared with the local-moment-disordered (LMD) state energy for local density approximation (LDA) and LDA–SIC approximation. Mechanism of hybridization and interaction between magnetic ions in Sn0.95Co0.05O2 is also investigated. To explain the origin of ferromagnetic behaviour, we give information about total and atoms projected density of state functions.

    • Optimization of process parameters for friction stir processing (FSP) of Al–TiC in situ composite

      Ranjit Bauri

      More Details Abstract Fulltext PDF

      Segregation of in situ formed particles at the grain boundaries is a major drawback of in situ composites. In this study, it has been demonstrated that friction stir processing (FSP) can be used as an effective tool to homogenize the particle distribution in Al based in situ composites and FSP processing parameters were optimized for this purpose. An Al-5 wt% TiC composite was processed in situ using K2TiF6 and graphite in Al melt and subjected to FSP. Processing parameters for FSP were optimized to get a defect free stir zone and homogenize the particle distribution. It was found that a rotation speed > 800 rpm is needed. A rotation speed of 1000 rpm and a traverse speed of 60 mm/min were found to be an optimum combination. The grain size was also refined in addition to homogenization of the as-cast microstructure. This resulted in significant improvement in the mechanical properties of the processed composite.

    • Low resistance polycrystalline diamond thin films deposited by hot filament chemical vapour deposition

      Mahtab Ullah Ejaz Ahmed Abdelbary Elhissi Waqar Ahmed

      More Details Abstract Fulltext PDF

      Polycrystalline diamond thin films with outgrowing diamond (OGD) grains were deposited onto silicon wafers using a hydrocarbon gas (CH4) highly diluted with H2 at low pressure in a hot filament chemical vapour deposition (HFCVD) reactor with a range of gas flow rates. X-ray diffraction (XRD) and SEM showed polycrystalline diamond structure with a random orientation. Polycrystalline diamond films with various textures were grown and (111) facets were dominant with sharp grain boundaries. Outgrowth was observed in flowerish character at high gas flow rates. Isolated single crystals with little openings appeared at various stages at low gas flow rates. Thus, changing gas flow rates had a beneficial influence on the grain size, growth rate and electrical resistivity. CVD diamond films gave an excellent performance for medium film thickness with relatively low electrical resistivity and making them potentially useful in many industrial applications.

    • Rapid mixing chemical oxidative polymerization: an easy route to prepare PANI coated small-diameter CNTs/PANI nanofibres composite thin film

      G Venkata Ramana Balaji Padya Vadali V S S Srikanth P K Jain

      More Details Abstract Fulltext PDF

      Composite thin film containing polyaniline (PANI) coated small diameter carbon nanotubes (SDCNTs)/PANI nanofibres (NFs) has been prepared using an easy in situ rapid mixing chemical oxidative polymerization method. SDCNTs thin film was obtained using thermal chemical vapour deposition method in a separate experiment, whilst PANI NFs are formed in situ during the synthesis of composite. In the composite, PANI coated SDCNTs are uniformly distributed among PANI NFs. The presence of SDCNTs during the composite synthesis does not influence the nucleation and growth of PANI NFs. Raman analysis shows a good interaction between PANI and SDCNTs. Room temperature d.c. electrical sheet resistance of SDCNTs/PANI NFs composite thin film surface is three orders lesser than that of PANI NFs thin film (PANI NFs have the same morphology as in the composite) synthesized using the same method but without the presence of SDCNTs.

    • One-step synthesis of mesoporous silica–graphene composites by simultaneous hydrothermal coupling and reduction of graphene oxide

      Juliet Q Dalagan Erwin P Enriquez

      More Details Abstract Fulltext PDF

      Silica–graphene oxide composites were synthesized by hydrothermal method with simultaneous functionalization and reduction of graphene oxide (GO) in the presence of mesoporous silica. Two types of silica were used in the study, mesoporous synthetic silica (MSU-F) synthesized by sol-gel method and mesoporous mineral silica (meso-celite) from pseudomorphic synthesis. The infrared spectra of the composites showed the disappearance of the carboxyl peak at 1735 cm-1 which could be due to the reduction of the –COOH group. The enhancement of the band at 1385 cm-1 is attributed to the vibration of the Si–O–C=O moiety formed by reaction of the –COOH group of GO and the silanol (Si–OH) of silica. The Raman spectra of the composites show a diminished intensity ratio of D to G band indicating that GO was reduced to graphene sheets. The TEM images demonstrate the coupling of silica to GO surface revealing dense loading of silica on GO in planar structure.

    • Processing, structure and flexural strength of CNT and carbon fibre reinforced, epoxy-matrix hybrid composite

      K Chandra Shekar M Sai Priya P K Subramanian Anil Kumar B Anjaneya Prasad N Eswara Prasad

      More Details Abstract Fulltext PDF

      Advanced materials such as continuous fibre-reinforced polymer matrix composites offer significant enhancements in variety of properties, as compared to their bulk, monolithic counterparts. These properties include primarily the tensile stress, flexural stress and fracture parameters. However, till date, there are hardly any scientific studies reported on carbon fibre (Cf) and carbon nanotube (CNT) reinforced hybrid epoxy matrix composites (unidirectional). The present work is an attempt to bring out the flexural strength properties along with a detailed investigation in the synthesis of reinforced hybrid composite. In this present study, the importance of alignment of fibre is comprehensively evaluated and reported. The results obtained are discussed in terms of material characteristics, microstructure and mode of failure under flexural (3-point bend) loading. The study reveals the material exhibiting exceptionally high strength values and declaring itself as a material with high strength to weight ratio when compared to other competing polymer matrix composites (PMCs); as a novel structural material for aeronautical and aerospace applications.

    • Characterization of gamma irradiated plasticized carboxymethyl cellulose (CMC)/gum arabic (GA) polymer blends as absorbents for dyestuffs

      Sayeda M Ibrahim Issa M Mousaa Mervat S Ibrahim

      More Details Abstract Fulltext PDF

      Polymer blends based on carboxymethylcellulose (CMC) and gum arabic (GA) were prepared by solution casting method. Glycerol was added to the polymer blend solution as a plasticizer with different ratios (2.5, 5, 10 and 20%). Then, the plasticized blends were exposed to gamma irradiation at different doses (5, 10 and 20 kGy). The physical properties of the plasticized polymer blends were investigated in terms of gel fraction (%) and swelling percent (%). Thermal properties were investigated by TGA. Also, the structure of the plasticized polymer blends was characterized by Fourier transform infrared spectroscopy. Scanning electron microscope was investigated in order to examine the compatibility between two polymers in the blend and also between polymer blend and plasticizer. The prepared plasticized polymer blends were used as an adsorbent for different dyestuffs. The sorption of dyestuffs by the plasticized polymer blend was determined by a method based on spectroscopic analysis. The results showed that the plasticized polymer blend has a high affinity for basic, acid, reactive and direct dyes. The obtained results showed that using glycerol as plasticizer improved the swellability of polymer blend and also the dye uptake (%).

    • Synthesis and characterization of mesoporous Si-MCM-41 materials and their application as solid acid catalysts in some esterification reactions

      Tarun F Parangi Rajesh M Patel Uma V Chudasama

      More Details Abstract Fulltext PDF

      Mesoporous MCM-41 has been synthesized by sol–gel method at room temperature possessing good thermal stability, high surface area as well as retention of surface area at high temperature. The MCM-41 neutral framework has been modified and put to practical use by incorporating Al3+ in the siliceous MCM-41 framework and supporting 12-TPA (12-tungstophosphoric acid) onto MCM-41 by process of anchoring and calcination to induce Brønsted acidity in MCM-41 to yield Al-MCM-41 and 12TPA-MCM-41, respectively. The synthesized materials have been characterized for elemental analysis by ICP-AES, XRD, SEM, TEM, EDX, FT–IR and TGA. Surface area has been determined by BET method and pore size and pore size distribution determined by BJH method. Surface acidity has been evaluated by NH3-TPD method. The potential use of Al-MCM-41 and 12TPA-MCM-41 as solid acid catalysts has been explored and compared by studying esterification as a model reaction wherein monoesters such as ethyl acetate (EA), propyl acetate (PA), butyl acetate (BA) and benzyl acetate (BzA) have been synthesized, optimizing several parameters such as catalyst amount, reaction time, reaction temperature and mole ratio of reagents.

    • Ionic liquid modified carbon paste electrode and investigation of its electrocatalytic activity to hydrogen peroxide

      Erhan Canbay Hayati Türkmen Erol Akyilmaz

      More Details Abstract Fulltext PDF

      This paper reports on the preparation and advantages of novel amperometric biosensors in the presence of hydrophobic ionic liquid (IL), 1-methyl-3-butylimidazolium bromide ([MBIB]). Carbon paste bio-sensor has been constructed by entrapping horseradish peroxidase in graphite and IL mixed with paraffin oil as a binder. The resulting IL/graphite material brings new capabilities for electrochemical devices by combining the advantages of ILs composite electrodes. Amounts of H2O2 were amperometrically detected by monitoring current values at reduction potential (–0.15 V) of K3Fe(CN)6. Decrease in biosensor responses were linearly related to H2O2 concentrations between 10 and 100 𝜇M with 2 s response time. Limit of detection of the biosensor were calculated to be 3.98 𝜇M for H2O2. In the optimization studies of the biosensor some parameters such as optimum pH, optimum temperature, enzyme amount, interference effects of some substances on the biosensor response, reproducibility and storage stability were carried out. The promising results are ascribed to the use of an ionic liquid, which forms an excellent charge-transfer bridge and wide electrochemical windows in the bulk of carbon paste electrode.

    • Manganese–Schiff base complex immobilized silica materials for electrocatalytic oxygen reduction

      Vellaichamy Ganesan Manas Pal Manoj Tiwari

      More Details Abstract Fulltext PDF

      Curtailment of platinum catalysts loading in fuel cell is a recent central issue. As substitutes, these days several organic metal chelate compounds having featured moieties of M–N4 or M–N2O2 (M = transition metal ion) are being used as cathode catalysts in fuel cells. Here, in this study, we report in detail the electrocatalytic activity of manganese–Schiff base complexes for oxygen reduction reaction in 0.05 M HClO4 at room temperature. Actually, [Mn(salen)]+: [N,N′-bis(salicylaldehyde) ethylenediimino manganese(III)]+ and [Mn(salophen)]+: [N,N′-bis(salicylaldehyde)-1,2-phenylenediimino manganese(III)]+ were introduced into/onto the MCM-41 type silica spheres and used for the electrocatalytic reduction of oxygen. Synthesized materials were characterized by UV–Vis, FT–IR and electrochemical techniques. Significant low overpotential for oxygen reduction in 0.05 M HClO4 on [Mn(salen)]+- and [Mn(salophen)]+-incorporated silica-modified glassy carbon electrodes was observed.

    • Influence of temperature and voltage on electrochemical reduction of graphene oxide

      Xiuqiang Li Dong Zhang Peiying Zhu Chao Yang

      More Details Abstract Fulltext PDF

      In this paper, the influence of temperature and voltage on direct electrochemical reduction were discussed in detail. Reduced graphene oxide is characterized with X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT–IR) and field emission scanning electron microscopy (FE–SEM). It is found that the reduction degree of graphene oxide (GO) decreases gradually with the increase of applied temperature. The optimal applied temperature found in our experiment is 20 °C; Meanwhile, as the applied voltage increases from 0.1 to 12.5 V, the reduction degree of graphene oxide increases gradually. However, above 2.5 V, increasing voltage has little effect on the reduction degree of graphene oxide.

    • New route for synthesis of electrocatalytic Ni(OH)2 modified electrodes—electrooxidation of borohydride as probe reaction

      A V Narendra Kumar S Harish James Joseph

      More Details Abstract Fulltext PDF

      Immobilization of redox species like Ni(OH)2 onto the electrode surface is important in the application areas such as super capacitor, electrochromic displays and electrocatalysis. Nickel hexacyanoferrate (NiHCF) modified glassy carbon could be further derivatized with Ni(OH)2 by electrochemical cycling in alkali. The electrodeposition of Ni(OH)2 was usually carried out onto the electrode surface from nickel salt at high interfacial pH. This paper reports the preparation of Ni(OH)2 from insoluble nickel tetracyanonickelate supported on carbon (NTN/C). This insoluble precursor complex was decomposed by two methods.

      1. By potential cycling of modified electrode with the above complex in alkali.

      2. By thermal decomposition of the precursor complex (NTN/C) to form metallic nickel followed by cycling in alkali. Ni(OH)2 modified electrodes formed using both methods were characterized by cyclic voltammetry and also by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy.

      Further, electrocatalytic properties of Ni(OH)2/C modified electrodes formed by the above two methods were studied and compared using borohydride oxidation as probe reaction.

    • Chemical shift of U L3 edges in different uranium compounds obtained by X-ray absorption spectroscopy with synchrotron radiation

      D Joseph C Nayak P Venu Babu S N Jha D Bhattacharyya

      More Details Abstract Fulltext PDF

      Uranium L3 X-ray absorption edge was measured in various compounds containing uranium in U4+, U5+ and U6+ oxidation states. The measurements have been carried out at the Energy Dispersive EXAFS beamline (BL-08) at INDUS-2 synchrotron radiation source at RRCAT, Indore. Energy shifts of ∼ 2–3 eV were observed for U L3 edge in the U-compounds compared to their value in elemental U. The different chemical shifts observed for the compounds having the same oxidation state of the cation but different anions or ligands show the effect of different chemical environments surrounding the cations in determining their X-ray absorption edges in the above compounds. The above chemical effect has been quantitatively described by determining the effective charges on U cation in the above compounds.

    • Effect of calcination methods on electrochemical performance of NiO used as electrode materials for supercapacitor

      L Wang X Y Qin

      More Details Abstract Fulltext PDF

      Ni(OH)2 precursors were prepared via the precipitation transformation method, which was originated from Na2C2O4, NiSO4.6H2O and urea. NiO samples were successfully obtained by calcining Ni(OH)2 precursor with different calcination methods. Some were calcination in a tube furnace under the nitrogen flow and others were calcination in a muffle furnace. The products were well-characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The influence of calcination methods on electrochemical performance of NiO samples were investigated. Moreover, the possible reason was proposed. The charge storage mechanism of NiO positive electrode in aqueous electrolyte was discussed. The electrochemical test showed that the as-prepared NiO prepared in a tube furnace can exhibit a good pseudocapacitance behaviour due to the higher utilization of active material.

    • Hydrogen absorption/desorption characteristics of room temperature ZrMn2-𝑥Ni𝑥 system (𝑥 = 1.25-1.50)

      Vinod Kumar D Pukazhselvan A K Tyagi S K Singh

      More Details Abstract Fulltext PDF

      The present communication deals with the hydrogen storage characteristics of C15 laves phase ZrMn2-𝑥Ni𝑥 system tailored within the x values of 1.25 to 1.50. Drastic variations in thermodynamics of the hydride phase is observed for any little changes of concentration x within this narrow range. The most promising room temperature hydrogen storage materials are found to be formed within the range of 1.35 to 1.45 where ∼ 2.5 to 2.9 H/F.U. can be reversibly stored under the ideal operating conditions. The heat of the reaction is found to be ∼ 17 kJ/mol, which means these are promising candidates for stationary and short range mobile applications. The phase structural features and the thermodynamic aspects of all the materials are discussed in detail.

    • Study of rigidity of semiconducting vanadate glasses and its importance in use of coatings

      Yasser B Saddeek M S Gaafar

      More Details Abstract Fulltext PDF

      The elastic moduli of some multicomponent vanadate based glasses were analysed in terms of the bond compression model by some physical parameters such as, the density, average stretching force constant and average atomic ring size. These parameters were calculated for all the glass series and for all the glass composition to estimate the rigidity of these glasses. The results showed that the average force constant and the elastic moduli of these glasses are sensitive to the decrease in PbO content. This behaviour was attributed to the increase in the molar volume and the role of different modifiers. These parameters along with the coordination number of the glasses affect the glass transition temperature. The correlation between the elastic moduli and thermal properties of these samples showed that 0.25MoO3–0.25PbO–0.5V2O5 glass is the most rigid and has an applicable glass transition temperature for coating.

    • Study of effect of chromium on titanium dioxide phase transformation

      A Bellifa L Pirault-Roy C Kappenstein A Choukchou-Braham

      More Details Abstract Fulltext PDF

      MTi𝑋 samples with different atomic chromium percentages were synthesized by sol–gel method and calcined at 400 °C under air. The effects of Cr and temperature on titanium dioxide phase transition were studied. In situ measurement showed the presence of anatase phase for all samples at temperature < 500 °C. Without Cr content, the anatase–rutile transition takes place at 600 °C and the rutile fraction increases with increase of temperature. In the presence of Cr content, rutile phase appeared at 700 °C. Cr2O3 phase was shown only in the case of CrTi20 content at 800 °C which indicates that the segregation remains modest. We have also studied the anatase–rutile transition kinetics by using in situ X-ray measurements. It was found that the anatase phase stability increases as the chromium content increases. Results confirm that the transformation of anatase–rutile is of first order.

    • Synthesis and microwave dielectric properties of Ca substituted SrLa4Ti4.93Zr0.07O17 ceramics

      Abdul Manan Ibrahim Qazi

      More Details Abstract Fulltext PDF

      Microwave dielectric ceramics in Sr1-𝑥Ca𝑥La4Ti4.93Zr0.07O17 (0 ≤ 𝑥 ≤ 0.5) composition series were processed via a solid-state sintering rout. X-ray diffraction revealed single phase ceramics. Ca substitutions for Sr tuned 𝜏f towards zero with increased 𝑄u𝑓o values. In the present study, 𝜖r∼ 55, 𝑄u𝑓o ∼ 11960 GHz and 𝜏𝑓∼ 5.2 ppm/°C were achieved for the composition with 𝑥 = 0.3.

    • Development of a new solid-state absorber material for dye-sensitized solar cell (DSSC)

      Swapna Lilly Cyriac B Deepika Bhaskaran Pillai S V Nair K R V Subramanian

      More Details Abstract Fulltext PDF

      In contrast to the conventional DSSC systems, where the dye molecules are used as light harvesting material, here a solid-state absorber was used as a sensitizer in conjunction with the dye. The materials like ZnO and Al2O3 : C, which will show optically stimulated luminescence (OSL) upon irradiation were used as extremely thin absorber layers. This novel architecture allows broader spectral absorption, an increase in photocurrent, and hence, an improved efficiency because of the mobility of the trapped electrons in the absorber material after irradiation, to the TiO2 conduction band. Nanocrystalline mesoporous TiO2 photoanodes were fabricated using these solid-state absorber materials and after irradiation, a few number of samples were co-sensitized with N719 dye. On comparing both the dye loaded photoanodes (ZnO/TiO2 and Al2O3 : C/TiO2), it can be concluded from the present studies that, the Al2O3 : C is superior to ZnO under photon irradiation. Al2O3 : C is more sensitive to photon irradiation than ZnO and hence there can be more trap centres produced in Al2O3 : C.

    • Processing and characterization of alumina/LAS bioceramics for dental applications

      M Guedes V Costa T Silva A Teles X Yang A C Ferro

      More Details Abstract Fulltext PDF

      Alumina allows to recreate the functionality and aesthetics of natural teeth. However, its low fracture toughness rises concern regarding use in dental restoration. Structural reliability is addressed here by formulating a material containing alumina and a glass–ceramic from LAS system. The presence of LAS in the mixtures result in formation of glass phase during sintering, promoting densification at lower temperature and enhanced surface finishing. A composite microstructure with increased toughness can thus be produced. Powder mixtures containing 0, 20, 50, 80 and 100 wt\%-LAS were prepared by planetary milling and uniaxial pressing and sintered. The compositions were investigated regarding their processability, mechanical performance and biological behaviour. Aesthetics was evaluated by comparison with a commercial dental matching guide. Variations on hardness and fracture toughness with starting LAS fraction were assessed by indentation. Interaction with biological medium was evaluated by immersion in a simulated body fluid. Resulting microstructures were characterised by FEG–SEM, EDS and XRD.

    • Structural, electrical and electrochemical behaviours of LiNi0.4M0.1Mn1.5O4 (𝑀 = Al, Bi) as cathode material for Li-ion batteries

      G P Nayaka J Manjanna K C Anjaneya P Manikandan P Periasamy V S Tripathi

      More Details Abstract Fulltext PDF

      In order to improve the cycling performance of LiMn2O4 based cathode materials, we have synthesized a new composition, LiNi0.4M0.1Mn1.5O4 (𝑀 = Al, Bi), by the sol–gel method. The formation of solid solutions is confirmed by structural characterization using TG/DTA, XRD, FT–IR, EPR, SEM and EPR. A.c.-impedance (Nyquist plot) showed a high frequency semicircle and a sloping line in the low-frequency region. The semicircle is ascribed to the Li-ion migration through the interface from the surface layer of the particles to the electrolyte. Cyclic voltammogram (between 3.5 and 4.9 V) for these materials using CR2032 coin-type cell shows two pairs of redox peaks corresponding to two-step reversible intercalation process, wherein Li-ions occupy two different tetragonal 8a sites in spinel Li𝑥Mn2O4 (𝑥 < 1) lattice. The galvanostatic charge/discharge curves for 𝑀 = Al (77 mAh g-1) showed reasonably good capacity retention than that of 𝑀 = Bi (11 mAh g-1) at the end of 17th cycle.

    • Corrosion behaviour of Ni–Co alloy coatings at Kish Island (marine) atmosphere

      Kourosh Sharifi Mohammad Ghorbani

      More Details Abstract Fulltext PDF

      In this study, the corrosion behaviour of Ni-Co alloys with low Co content, electroplated on steel substrate in sulphate bath, was investigated. The morphology of coatings was studied by optical and SEM microscopy. The corrosion products were analyzed using EDX. The results showed that Ni–1% Co coatings had a better corrosion resistance 0.30, 0.92 and 3.75 mpy for atmospheric, salt spray and polarization tests, respectively. These are 0.41, 1.20 and 5.40 mpy for pure nickel coatings that indicate the least corrosion resistance. Surface analysis revealed the presence of oxides, sulphides and chlorides in corrosion products.

    • Pulse electrodeposition and corrosion properties of Ni–Si3N4 nanocomposite coatings

      S Kasturibai G Paruthimal Kalaignan

      More Details Abstract Fulltext PDF

      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 (𝐸corr) in the case of Ni–Si3N4 nanocomposite had shown a negative shift, confirming the cathodic protective nature of the coating.

    • Influence of mineral phase in mineralization of a biocomposite containing chitosan, demineralized bone matrix and bone ash—in vitro study

      Krithiga Gunasekaran Santhosh Kumar Baskar Divya Sapphire Mohan Thotapalli P Sastry

      More Details Abstract Fulltext PDF

      A resorbable composite which acts as a active barrier in guided bone regeneration was fabricated using chitosan, demineralized bone matrix and bone ash. Its potential to form bone like apatite in simulated body fluid was assessed in this study. The mechanical strength of these composites was correlated with bone ash ratios and composites with better tensile strength were studied for their acellular bioactivity by incubating in simulated body fluid for 21 days. Composites without bone ash did not show acellular bioactivity which was confirmed by thermogravimetric analysis. In case of biocomposites with bone ash, there was an increase in residual weight indicating the mineralization of the composite. The composite containing bone ash has shown the peaks related to phosphate vibrations in its Fourier-transform infrared spectrum. Scanning micrographs revealed formation of apatite like crystals on its surface. Ca/P ratio was found to be 1.7 which is nearer to that of natural bone. Thus, prepared composites can be used as resorbable biocomposite in maxillofacial and oral defects.

    • Synthesis and characterization of bio-based polyurethane from benzoylated cashewnut husk tannins

      A J Sunija S Siva Ilango K P Vinod Kumar

      More Details Abstract Fulltext PDF

      Benzoylated tannin prepared by benzoylation of cashewnut husk tannin, was treated with hexame-thylenediisocyanate in the presence of 1,4-butanediol as an extender to prepare thermosetting polyurethane. The sample was characterized using FT–IR and 13C NMR spectra. Thermal, morphological, physico-chemical and electrical properties were also investigated. Polyurethane obtained was sensitive to moisture but had very good solvent resistance. Results show that 𝑇g of the sample is 260 °C and thermal decomposition begins at 280 °C. The dielectric constant varies randomly with temperature. The conductivity of the sample was found to increase with increase in temperature but shows random variation at 90 and 150 °C

  • Bulletin of Materials Science | News

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2017-2019 Indian Academy of Sciences, Bengaluru.