Application of a geometric model to the hydrides of FeTi

Autor: D. G. Westlake
Rok vydání: 1984
Předmět:
Zdroj: Journal of Materials Science. 19:316-326
ISSN: 1573-4803
0022-2461
DOI: 10.1007/bf02403141
Popis: Criteria of hole size and hydrogen-hydrogen distance have been used to develop rationales for the observed stoichiometries and preferred hydrogen sites in theα-,β1-,β2- andγ-phases of the FeTi-H system. For these four phases of FeTiHn, the respective values ofn approximate 0, 1, 1.4 and 2. Structures and position vectors for the metal atoms were obtained from the literature for use in calculating the radii of the various interstices and the intersite distances in each phase. The model does not allow one to predict the nature of the structural transformations that occur in this system with increasing hydrogen concentrations, but knowing the metal atom positions in each phase does allow one to predict the preferred sites for hydrogen atoms. Most of the occupied interstices are octahedral sites coordinated by four titantium atoms and two iron atoms, but the reported occupation of a pseudo-octahedral site in FeTiD is explained within the framework of the model by allowing a deuterium atom to occupy a hexahedral interstice coordinated by three titanium atoms and two iron atoms. Forn −-2, i.e. for theγ phase, geometric considerations allow the correct prediction of some hydrogen atoms situated in octahedral interstices coordinated by four iron atoms and two titanium atoms. Occupation of such a site could not have been predicted by considering the relative affinities of the metals titanium and iron for hydrogen.
Databáze: OpenAIRE
Externí odkaz: