Deposition of tungsten by reduction of its hexafluoride with hydrogen under the stoichiometric component ratio: An environmentally pure production process

Abstract

The reduction of WF6 with hydrogen on a heated surface under atmospheric pressure, temperatures of 500–600°C, and a stoichiometric ratio of components with the subsequent additional reduction of tungsten hexafluoride at t = 800°C and condensation of formed HF is described. The method of calculation of the completeness (α) of reduction of WF6 and productivity (M) of deposition of tungsten depending on the temperature, gas flow rate, and sizes of the reaction surface is developed based on the physicochemical mechanism of the process. The possibility of attaining M = 5.1 kg/h and α = 80% when fabricating crucibles 300 mm in diameter and 500 mm in height is shown. The additional reduction of WF6 provides the summary magnitude α > 99.9%. The almost complete condensation of HF initially at t = +1°C and then at t = −78°C makes it possible to decrease its concentration in exhaust gases below the maximum permissible concentration (MPC).