X-ray photoelectron spectroscopic investigations of the activation of FeTi for hydrogen uptake

Abstract

Activation of FeTi alloy could either give rise to surface segrcgation and subsequent oxidation of titanium and the formation of iron clusters or the formation of mctastable TiFeO, suboxide. The wflidity of either of the postulates could be gauged by monitoring the nature and concentration of each of the oxidation states of iron and titanium by depth profile analysis by XPS. These studies showed that fresh samples contained multiple oxidation states of iron and titanium though the concentrations of lower valcnt oxides are usually small. Sputtering studies showed that this oxide layer is of considerable depth and during activation, iron oxides are easily reduced to the metallic state as compared to the oxides of titanium. The chemical rcaction induced, segregation may be the contributing factor for the enhanced concentration of titanium on the surface of these alloys.