Effects of Porosity and Ni/Al Molar Ratio in Ni–Al Oxide Precursors on Porous Intermetallic Nickel Aluminide Nanopowders Prepared by Chemical Route

Abstract

It is challenging to prepare intermetallic Ni–Al nanopowders via chemical processes due to the difficulty in reducing Al-based oxides. Previously, we successfully obtained the single phase porous nanopowders of Ni₃Al and NiAl from the low porosity oxide precursors in molten LiCl–CaH₂ at 600°C. In this study, we examined the effects of porosity and the Ni/Al molar ratio of the oxide precursors on the BET surface areas and phases of the final Ni–Al nanopowders. The results showed that the porosity was not reflected in the final products, but the Ni/Al molar ratio defined the crystal structures. The intermetallic Ni₅Al₃ phase was not obtained at all, possibly due to the low rate of formation, whereas pure intermetallic Ni₃Al and NiAl phases were obtained separately without any impurity phases.