Influence of gaseous inclusions on aluminum-tungsten coatings investigated by XPS

Abstract

Although international thermonuclear experimental reactor project employs the use of beryllium–tungsten system as plasma-facing material in nuclear fusion devices, the scientific fusion community still considers aluminum–tungsten configuration a promising candidate for fusion-related devices, aluminum aiming to be a beryllium replacement. This study provides in-depth x-ray photoelectron spectroscopy results on the interaction of aluminum and tungsten atoms in the surface layers prepared in various gaseous environments, important for the fusion community: vacuum, nitrogen, helium, and oxygen. A surprising outcome of the analysis is the suggested aluminum–tungsten surface alloying even at temperatures below 100 °C as well as the chemical interaction between aluminum and tungsten atoms, with the formation of aluminum tungstate, the two surface processes reinforcing the conclusion of surface mixing metals. Additionally, aluminum has a particular behavior by protecting and maintaining tungsten in an alloyed and unoxidized state for vacuum, nitrogen, and helium plasma environments, while in the presence of oxygen manages to preserve tungsten state of alloying.