Showing papers by "Sampat Raj Vadera published in 2010"

Synthesis and studies on photochromic properties of vanadium doped TiO2 nanoparticles

Abstract: Pure and (0.5–3 at%) vanadium doped TiO 2 nanoparticles have been synthesized by wet chemical method. The as synthesized materials have been characterized by using XRD, atomic force microscope (AFM), Raman, EPR and UV–vis spectroscopy techniques. From XRD studies, both pure as well as vanadium doped TiO 2 have been found to show pure anatase phase. The value of lattice constant c is smaller in doped TiO 2 as compared to undoped and has been found to decrease with increase in vanadium concentration. AFM studies show formation of spherical particles with particle size ∼23 nm in all the samples. Photochromic behavior of these materials has been studied by making their films in alkyd resin. Vanadium doped TiO 2 films show reversible change in color from beige-yellow to brownish violet on exposure to UV light. The mechanism of coloration and bleaching process has been discussed.

Preparation of polybenzoxazine–Ni–Zn ferrite magnetic nanocomposite and its magnetic property

Abstract: The synthesis of a new type, high performance polybenzoxazine–ferrite nanocomposite has been reported. A simple aqueous solution based method was developed for preparation of several compositions of Ni1–xZnxFe2O4 (x=0.20–0.60) nanopowders using metal nitrates and EDTA. Benzoxazine monomer was prepared by employing a solvent less method using aniline, paraformaldehyde and bisphenol A as starting materials. Polybenzoxazine–ferrite nanocomposites were prepared by using a solvent casting method followed by thermal curing. The synthesised powders, monomer, polymer and the resultant composites were characterised by using thermogravimetric analysis and differential scanning calorimeter, surface area and pore size analyser, scanning electron microscope (SEM) and transmission electron microscope. X-ray diffraction spectra of the powders revealed the formation of single phase Ni–Zn ferrite, with average crystallite size of about 20–30 nm. Transmission electron microscopy micrographs confirmed the average f...

Development of a Novel Aqueous Solution Based Chemical Methodology for Synthesis of Ni(1-x)ZnxFe2O4 Nanopowders and their Electrical and Magnetic Property

Abstract: A simple aqueous solution-based chemical methodology has been developed for the preparation of single-phase Ni1-xZnxFe2O4 nanopowder, where x = 0.2, 0.35.0.5 and 0.6. The average particle size of the synthesized powders was in the range of 30–50 nm. Precursor powders were synthesized by reacting aqueous solutions of metal nitrates with polyvinyl alcohol and sucrose and then evaporating the resulting solution to dryness. The precursors were calcined in air for 2.30 h at different temperatures ranging from 650 to 950°C. The synthesized powders were characterized by using thermogravimetric analysis-differential scanning calorimetric analysis, X-ray diffraction, transmission electron microscopy, scanning electron microscopy. Change of DC electrical resistivity with change in sintering temperature and microstructure was measured by using the two-probe method. The as synthesized nanopowders possess a high room temperature resistivity of ∼106–107 Ωcm. They exhibit a good amount of magnetization in the range of 4...

Microstructure DC resistivity and magnetic property of Ni-Zn ferrite nano-powders synthesized by EDTA precursor based method

Abstract: Ni 1-x Zn x Fe 2 O 4 (0 ≤ x ≤1) nanopowders (average particle size ∼ 30 nm) have been synthesized by using a ethylenediamine tetraacetic acid precursor based method. The synthesized nanopowders were obtained by calcining the precursors in air at 450°C. Microstructures of the nanopowders and samples obtained on sintering have been studied by using Scanning Electron Microscopy. DC electrical resistivity was found to be ∼10 7 Ωcm for the as-synthesized nanopowders and ∼10 6 Ωcm for sintered samples. Room temperature magnetization has also been measured for all compositions and it exhibits a decrease with increasing Zn content in the samples.