Tungsten Borides Prepared from Tungsten-Containing Concentrate via Exposure to Microwave Plasma

We have studied the structure of tungsten borides prepared from a tungsten-containing mineral concentrate using an experimental microwave arc plasma system. A configuration of such a system has been proposed which includes a microwave generator, indirect plasma source, and reaction chamber. We address some issues pertaining to the positioning of the plasma source on the waveguide chamber and the formation of a microwave plasma flow in the confusor zone, followed by the exit of the flow to the concentrator zone, and describe processes involved in the plasma synthesis of tungsten borides. A process is proposed for the preparation of a mixture based on a multicomponent mineral (scheelite) concentrate from the Russian Far East and results are presented on the physicochemical properties of tungsten borides prepared via local exposure to a high-energy plasma flow with a power density from 10 to 100 kW/cm(2). In our experiments, the WB, WB2, W2B, and W2B5 compounds have been obtained. We assess the potential of using plasma technologies for preparing boron- and tungsten-based refractory compounds from scheelite concentrate.