Peculiarities of the behavior of the W–Al2O3 system in a controlled reducing atmosphere

Abstract

The W–Al₂O₃ system at T = 2400 K and standard pressure (controlled Ar + H₂ atmosphere) has been calculated by stochastic simulation. It is shown that the presence of hydrogen leads to the formation of aluminum hydrides, hydrogen oxides, and aluminum hydroxides; the compounds from the two latter groups (except for water) can interact directly with tungsten. The main chemical reactions occurring in the system are determined, based on which a conclusion about the cyclic character of the processes is drawn. Some recommendations on the composition and pressure of controlled atmosphere for growing sapphire crystals are given.