Surface Properties and Microstructure of Catalytically Active Ni₇₀Ga₃₀, Ni₇₀Sn₃₀ and Ni₇₀In₃₀ Melt Spun Intermetallics Subjected to Oxidation-Reduction Heat Treatment

Abstract

Melt spun Ni₇₀Ga₃₀, Ni₇₀Sn₃₀ and Ni₇₀In₃₀ show different oxidation behaviour following heat treatment at 900°C in air. The Ni₇₀Ga₃₀ ribbon develops a continuous layer of Ga₂O₃ oxide, which passivates the surface and prevents further oxidation of the Ni₃Ga bulk phase. On the contrary, the Ni₇₀Sn₃₀ and Ni₇₀In₃₀ ribbons undergo considerable segregation and decomposition and aside from the Ni and NiO and the primary Ni₃Sn and Ni₃In also comprise SnO₂ and In₂O₃ phases. Results are conformed from XRD, TEM and XPS analysis. The oxidation behaviour especially in the case of the Ni₇₀Sn₃₀ ribbon is promising with view for development of fine Ni particles on the Ni₃Sn support.