Separation of dope compounds from NS-tungsten-metal powder: About the origin of dope inclusions

Abstract

Dope compounds can be separated from WO 2 and from W by treatment in H 2O 2. The intermediate brown oxide of the reduction of K, Al, Si-doped blue oxide contains amoeba-like formations of a consolidated melt and of small spherical particles besides the tetragonal K-W-oxidebronze. The as-reduced NS metal-powder grains are covered by a consolidated melt, and this shell and also small spherical particles remain after the treatment in H 2O 2. After washing the metal powder in HF and treating the washed powder in H 2O 2, the residue does not contain any more fragments of the shells and includes only the small spherical particles. The dope particles in the intermediate brown oxide contain K, Si, and, at most, traces of Al. The residue of the metal powder contains in every case, in every particle, K, Al, and Si. The fragments of the shells contain more Si than the small spherical particles.