Preparation of Nanosized Tungsten and Tungsten Oxide Powders

Resumo

Nanopowder tungsten oxide and metallic tungsten are obtained via pyrolysis of ammonium metatungstate. Two methods are used for the synthesis of tungsten oxide: the use of a fibrous matrix and pyrolysis of aerosol particles. Tungsten oxide particles are formed during the pyrolysis in air. Metallic tungsten nanoparticles are obtained via subsequent thermal reduction of tungsten oxide in hydrogen. The structure and morphology of the samples are studied with X-ray diffraction and scanning electron microscopy. Tungsten nanopowders with average sizes from 7 to 30 nm are obtained depending on synthesis temperature. The electrochemical characteristics of electrodes coated with tungsten nanoparticles are studied with cyclic voltammetry, impedance spectroscopy, and galvanostatic charge–discharge methods. An electrode with W nanoparticles exhibited a specific low-frequency capacitance of about 90 F/g due to thin tungsten oxide film on the surface of tungsten nanoparticles.