Mössbauer spectroscopy of activated FeTi II. Products of activation to 500° C

Abstract

Results are presented of a conversion electron Mossbauer spectroscopy (CEMS) investigation of FeTi ( 57 Fe isotopic abundance enriched to approximately 10%) which has been subjected to an activation for hydrogen absorption (AHA) process. This work is a continuation of an earlier study in which an “800°C prescription was used for the AHA process and which gave activated FeTi powder having CEM spectra corresponding only to the presence of Fe 2 Ti in the surface region of the powder grains. The CEMS measurements presented here, from an FeTi powder activated according to a “500°C prescription, show only the presence of peaks due to ferromagnetic iron in the vicinity of the powder grain surface. Both of these activation processes produce FeTi which readily absorbs hydrogen gas, from which it can be concluded that the presence of iron, to the level observable in our CEMS measurements, in the vicinity of the surface of an FeTi powder grain, is not a necessary requirement for the absorption of hydrogen in that grain, as has been suggested elsewhere. The CEMS peaks indicating the presence of iron were observed both with and without the use of hydrogen in the 500°C prescription, indicating that the presence of iron peaks was not linked specifically to the use of hydrogen in an AHA process, a connection which has also been suggested in the past. Some discussion is given of possible origins for the observed concentration of iron in the surface region of activated FeTi powder grains.