Gourav Singla

Evolution of structural and thermal properties of carbon-coated TaC nanopowder synthesized by single step reduction of Ta-ethoxide

Carbon-coated nano tantalum carbide (TaC) has been synthesized at 800 °C using tantalum-ethoxide precursor by the single step chemical reaction route without using any external carbon source. The XRD results of the synthesized samples indicate that formation of TaC starts immediately upon heating but the complete transformation is observed only after 10 h of holding at 800 °C. The 10h sample shows distinct decarburization and oxidation peaks in DSC/DTG. The surface weighted sizes obtained from double-Voigt method were confirmed by BET. The BET analysis shows that synthesized powders have large surface area and contain a mixture of micropores and mesopores. The morphology and particle size distribution analysis shows that the powders are of faceted to spherical shape with thin carbon coating having size variation primarily between 20–40 nm. DSC/TG, XRD and microstructure analysis results have been used to predict the mechanism for the formation of the carbon coated nano-TaC particles.

The role of carbon in structural evolution during single step synthesis of nano tantalum carbide

Cubic phase carbon-coated nano tantalum carbide (TaC) has been synthesized at 800 °C in a single step from tantalum oxide using the carbon and hydrogen produced in situ via decomposition of acetone in an autoclave. In the product phase(s) carbon exists: (a) inside the carbide, (b) on the surface of the carbide particles and (c) as free carbon (amorphous as well as graphitic). The effects of initial carbon concentration on the final carbon content inside as well as outside the TaC have been studied. The structural features of the final product have a complex dependency on the initial carbon concentration. The thermal behaviour of the final product clearly delineates the effects of internal and external carbon content. The soaking time studies show that the grain growth of TaC within the autoclave follows the simultaneous grain boundary migration and grain rotation model. The DSC/TG, XRD and microstructure analysis results along with thermal calculations have been used to predict the formation mechanism for the carbide particles. The reaction mechanism analysis brings forth the role of Mg in lowering the reaction temperature. In this process the carbon content of TaC, the size as well as the strain of the synthesized powders and the %free carbon content can be tailored as per the requirement for the given application.

Effect of TiO2 on the photocatalytic properties of bismuth oxide

Bi2−xTixO3+x/2 (x=0.05, 0.10 and 0.15) photocatalysts are prepared by solid-state technique. The band gap of the prepared sample was estimated from the onset of UV–Vis absorption spectra. The photocatalytic activities of as prepared samples are investigated under UV light irradiation for the decomposition of methyl orange (MO). It has been observed that the rate of decomposition of MO increased with increasing Ti4+ content in the present samples. Moreover, it shows better photocatalytic activity than undoped Bi2O3 and TiO2. The lowest band gap is observed for x=0.15 sample, i.e. 2.55 eV, which also showed the highest photocatalytic activity in the present sample.

Effect of Processing Variables on WC Nanoparticles Synthesized by Solvothermal Route

In this work, the effect of processing variables on the synthesis of WC nanoparticles by solvothermal route has been reported. Nanoparticles of tungsten carbide (WC) have been prepared by taking metallic magnesium (Mg), acetone (C3H6O), and tungsten trioxide (WO3) in an autoclave at 600°C. The XRD results showed that the optimization of the reaction time facilitates the reduction as well as carburization of the tungsten source. The Williamson-–Hall analysis was used to study the effect of synthesis time on the crystallite size and lattice strain of the sample. Differential thermal analysis/thermogravimetric analysis shows the stability of the synthesized product. It has been observed that the synthesis of WC nanoparticles is a multistep process and the complete carburization reaction occurs at particular carburization time.

Synthesis of nanocrystalline tungsten carbide (WC) powder

Nanocrystalline tungsten carbide (WC) has been obtained from bulk WO3 by in situ reduction and carbonization reactions at low temperature (∼ 600 °C) by taking Mg as reductant and acetone C3H6O as carbon source. It was aimed to elucidate carburization behavior of WO3 powder and to establish optimal conditions for the synthesis of nanocrystalline WC. The role of reaction time on the synthesis of WC has been investigated and discussed. The synthesized powders were characterized by X-ray powder diffraction, differential thermal analyzer (DTA), thermo gravimetric analysis (TGA).