The synthesis of tungsten trioxide gel by dissolution of tungsten in hydrogen peroxide and its transformations during the heat treatment in oxidation and reduction atmospheres

Abstract

The structure and the thermal behavior of WO3 samples in air and in reduction atmosphere were studied. Sample 1 was prepared by the dissolution of fine metallic tungsten powder in hydrogen peroxide followed by solvent evaporation in the air at 60 °C. Sample 2 was obtained by draining a part of sample 1 at 60 °C and then heating it up to 430 °C. By means of X-ray diffractometry, scanning electron microscopy and thermal analysis, it was evidenced that sample 1 was an amorphous hydrated gel, with the WO3·1.5H2O composition, while the second one was the anhydrous monoclinic WO3 with the mean particle size of 100 nm. Additionally, using thermogravimetric and differential thermal analysis simultaneously in the reduction atmosphere, both samples types were examined. After reduction, the population of metal particles with respect to the particle diameter was examined using electron microscopy.