Surface properties of the fluorinated La-incorporated Ti/Zr-based AB 2 laves phase alloys

Abstract

A new class of fluorinated Ti/Zr-based AB 2 laves phase alloys with an extremely high reactivity to hydrogen was demonstrated by incorporating a small amount of rare earth metals such as La. Great benefits on improving the activation characteristics both in gas–solid and liquid–solid reactions were demonstrated. This is known to contribute to the formation of the La-fluoride layer on those La-enriched secondary phases homogeneously distributed at the grain boundaries of the AB 2 matrix. This research is based on a fluorination procedure invented in our laboratory in 1991 by using an aqueous F −-ion containing solution (F-solution) to form a fluorinated layer on conventional hydriding alloy surfaces. The aim of this paper is to elucidate the fluorination effects of La-incorporated Ti/Zr-based AB 2 laves phase alloys on the surface properties regarding their activation characteristics in gas–solid and electrochemical reactions through ESCA, EPMA, XRD studies and microscope observation. The results are to be correlated with former studies on the fluorinated AB 5 alloys, i.e. LaNi 4.7Al 0.3. The roles of Ni on the surface of both the AB 2 phase and La-enriched second phase before and after the fluorination will be described in this paper.