Preparation of tungsten powder by an unmixed carbon reduction method based on carbon diffusion

Abstract

In this study, a new unmixed carbon reduction method was proposed for the preparation of pure W powder. The effects of reduction temperature, reduction time, carbon distance and thickness of WO3 layer on the phase of the reduction products were investigated. Results show that pure tungsten powder with a carbon content of less than 150 ppm can be prepared at 950 °C with a WO3 layer thickness of 5 mm and a carbon distance of 2 mm. Increased carbon distance and thickness of WO3 layer will lead to a decrease in the reduction ratio. Additionally, particle size of the tungsten powder gradually increases from 1 μm to 8 μm due to sintering with the extended reduction time. Furthermore, a two-stage carbon reduction process with WO2 as an intermediate product is proposed, which avoids the sintering and growth of tungsten powder particles and the particle size of tungsten powder was successfully reduced to 2 μm. This unmixed carbon reduction reduces the carbon concentration and prevents the carbonization of tungsten powder. The experiment verifies the feasibility of carbon as a reducing agent in producing pure tungsten powder by reducing WO3.