Abstract: Nanometric zinc oxide was prepared by sol-gel method using two different capping agents e.g., ethylene diamine (EDA) and citric acid (CAM) in different solvents. Nanorods of ZnO was prepared by sol-gel method using zinc nitrate hexahydrate (1M). The as-synthesized samples were characterized using XRD, FESEM-EDAX, TG/DTA techniques. FESEM micrographs suggest that the formation of nanorods of ZnO takes place for EDA and CAM in MeOH after calcination at 150 °C and 170 °C, respectively for 12h. The antibacterial activity tests (also known as plus-minus tests) were done by allowing bacteria to grow normally in laboratory conditions, and also by subjecting to ZnO nanoparticles in the powder form. On comparison of the above two Petri plates, the presence of a zone of inhibition indicates the antibacterial nature, which would have not existed if the bacteria did not experience any adverse effects by the presence of the ZnO nanorods. In the present study, the activity tested against Escherichia coli ATCC 25922 (gram-negative) Micrococcus leuteus and Bacillus subtilis (gram-positive) the results suggest the selective activity of the nanoparticles against these species.
Abstract: Different types of carbon nanostructure materials have been grown on nano-sized transition metal oxide based catalyst particles by catalytic chemical vapour deposition. The present investigation reveals an important role of melting or surface melting of oxide catalysts for the growth of carbon nanostructure materials. In the reducing environment prevailing during the growth of nanostructures, oxide catalysts are reduced to metals, which may act as a template for the growth of carbon nanostructure materials. Flow rate of acetylene gas is crucial in catalyzing the growth, as high flow rate of acetylene may cover the catalyst particles with a layer of decomposed carbon, rendering the particles incapable of playing the role of catalyst. The size of the catalyst and the extent of melting, determined primarily by the extent of doping, are important in deciding whether the conditions are favourable for the growth of multi walled carbon nanotube, nanofiber or other nanostructures. Smaller particle size and low doping level favour the growth of multi walled carbon nanotube while growth of nanofiber is commonly observed with larger particles and higher doping level. The size (i.e. diameter) of the nanostructures growing around the catalyst is proportional to the particle size of the catalyst.
Abstract: Nickel oxide based bimetallic mixed metal oxide nanoparticles are of considerable interest and they have been used as catalysts for NOx decomposition and as reactive adsorbents for ultra deep desulfurization. In the present study, nanoparticles of NiO-ZnO, NiO-CuO and NiO-MgO were synthesized by sol-gel method. The mixed metal oxide nanoparticles were characterized by X-ray diffraction, diffuse reflectance spectroscopy, field emission scanning electron microscopy and transmission electron microscopy. Pure NiO nanoparticles show a band gap of 4.24 eV and the band gap shows a blue shift or red shift in the case of mixed metal oxide nanoparticles.
Abstract: MgO based nanocomposites possess a wide range of applications in various catalytic reactions. Transition metal oxide based MgO nanocomposites are expected to be useful in spintronics. MgO has been chosen due to its less interaction with magnetic nanoparticles and also it provides stability to the magnetic nanoparticles. In the present study, MgO–Co3O4 and MgO–NiO nanocomposites have been synthesized by a simple precursor approach. Firstly, magnesium oxychloride precursors were prepared using aqueous solutions of magnesium chloride, cobalt chloride (or nickel chloride) and nanocrystalline MgO which on calcination at 500°C led to MgO–Co3O4 and MgO–NiO nanocomposites. The nanocomposites were characterized by XRD, FE-SEM, EDXA, TEM and magnetic measurements. The XRD results indicate the formation of Co3O4 and NiO along with MgO on calcination of the precursors. The SEM and TEM images indicate the presence of MgO particles along with transition metal oxide nanoparticles. Magnetic measurements of both the nanocomposites (M-H) indicate superparamagnetic behavior at 5 K.
Abstract: Abstract. LaF3 nanocrystals doped with lanthanides like Ce3+, Pr3+ and Nd3+ have been prepared using microwave technique. These synthesized crystals have been characterized by X-ray powder diffraction. Well dispersed, elongated, nanorods of hexagonal geometry (approximately 20nm in size) have been found in TEM analysis. The average particle size estimated from XRD analysis is about 20 nm and is in close agreement with the TEM results. Four characteristic peaks one at 3434 cm-1 (broad) and other at 2924, 2853, 1632 cm-1(sharp) have been observed in the FTIR spectra. Intense Blue colour (458 nm) emission has been recorded when crystals are excited with photons of wavelength 254 nm. Non Linear Optical (NLO) properties of the synthesized nanocrystals have been studied. It has been found that second harmonic generation (SHG) efficiency of the prepared samples containing rare earth elements is less than pure Potassium dihydrogen phosphate (KDP) crystals.
Abstract: In this work, an effective and economic way of transition metal doping in tin oxide nanoparticles is presented. The x-ray diffraction (XRD) measurements confirmed that the SnO2 nanoparticles are of single phase with rutile structure. Transmission electron microscopy (TEM) micrographs show that nanoparticles exhibit spherical shape with size of ~4 nm. To check the incorporation of cobalt and its chemical bonding with oxygen, systematic FTIR measurements were performed. The stretching-vibration mode (A2u) of Sn-O and deformation-vibration mode (Eu) of O-Sn-O were found to be broadened and shifted towards the higher wave numbers in case of cobalt doped samples. The Co-O/O-Co-O modes of the stable phase of cobalt oxide (Co2O3) were not detected in any doped samples. The results indicate that cobalt is present in the tin oxide lattice and do not form any metallic clusters or its oxide phases.
Abstract: In the present work, the effect of Li salt i.e. LiClO4 contained in composite plasticizer (PC+DEC) with three different concentrations on ionic transport and other electrochemical properties of PMMA based gel polymer electrolytes synthesized has been investigated. The electrolytes have been synthesized by solution casting technique by varying the wt (%) of salt and plasticizer. The formation of polymer-salt complexes and their structural characterization have been carried out by FTIR spectroscopic and XRD analyses. The room temperature ionic conductivity of the electrolyte composition 0.6PMMA-0.125(PC+DEC)-0.15LiClO4 (wt %) has been found to be maximum whose magnitude is 0.40×10-5 S/cm as determined by ac impedance analysis. The temperature dependent ionic conductivity of electrolyte sample0.6PMMA-0.125(PC+DEC)-0.15LiClO4 has further been investigated. Thermal analyses of electrolyte samples of all three compositions have also been done.
Abstract: Studies on the analysis of impedance spectroscopy of polycrystalline samples with compositions x ≤ 0.20 in the system Ba1-xBixTi1-xFexO3 are made. For this all the samples are prepared using solid state ceramic route. Preliminary X-ray diffraction patterns showed single phase formation of all compositions with tetragonal symmetry for x = 0.02 and cubic symmetry for compositions with x ≥ 0.10. For composition with x = 0.02, the dielectric anomaly at ~100 °C indicates paraelectric to ferroelectric transition. Impedance spectroscopic studies over the temperature range 25 °C to 180 °C have shown the presence of both bulk and grain boundary effects. The bulk conductivity has exhibited Arrehenius type thermally activated hopping process which is supported by ac conductivity behavior as a function of frequency.
Abstract: Glasses in the SrO-ZnO-B2O3-SiO2 (SZBS) system with different additives like V2O5, Cr2O3, TiO2, and Al2O3 have been prepared by melt-quench method. Glasses were subjected to controlled heat treatment for conversion into glass-ceramics. Investigated glasses and glass-ceramics have thermal expansion coefficients (TEC) in the range of 95-120 x 10-7/oC (30-600 oC) which closely match with TEC of other SOFC components. XRD indicates the crystallization of Sr2ZnSi2O7 solid-solution phase in glasses upon heat treatment. Structural studies revealed that mainly Q1 and Q2 silicate structural units are present in the glass network and B2O3 enters in the network as triangular borate (BO3) structural units. Only small fraction of B2O3 enters as tetragonal borate (BO4) structural units at higher concentration of B2O3. Glass network depolymerizes with the addition of additives and concentration of Q1 units increases at the expense of Q2 units. Small addition of V2O5 in SZBS glass is beneficial for increasing TEC and achieving better flowability at lower sealing temperature. Studied SZBS glasses also show good bonding with Crofer-22-APU. Elemental line scans indicate that interdiffusion of Fe, Cr, Sr and Si across interface is responsible for good bonding with Crofer-22-APU. To show suitability of material for high temperature sealing, seals have been prepared and tested for vacuum integrity at 850oC for 500h.
Abstract: Piezoelectric materials have wide applications in today’s advanced technologies. However, most commercially used piezoelectric material PZT (PbZr1-xTixO3) is now strictly restricted worldwide due to hazardous nature of Pb. Research for the development of new lead free materials with properties comparable to that of PZT is in progress in recent years. In the present work, an effort has been made to synthesize low amount of rare earth gadolinium modified (Bi1-xGdx)0.5Na0.5TiO3 (BGNT) with compositions (x) = 0, 0.02, 0.03 and 0.04 by a novel Semi–Wet Technique. The structural, microstructure, phase transition and dielectric properties have been investigated. The XRD patterns have shown single phase formation for all the samples with a rhombohedral symmetry at RT. Gd3+ doping has shown a significant effect on the grain growth. The dielectric measurement has been carried out over the temperature range from RT to 400 oC at 1, 10 and 100 kHz frequency. It has been observed from the εr vs T plots that two phase transitions (i) ferroelectric to anti-ferroelectric and (ii) anti ferroelectric to paraelectric occur in all the samples. The composition with x = 0.02 has shown significantly high value of dielectric constant (εr ~ 1567) and low value of dielectric loss (Tan δ ~ 0.043) at room temperature.