Study on NiO excess in preparing NiAl2O4

When nickel aluminate spinel was prepared by solid-state reaction, an excess of NiO in products was observed, which was explained as the result of Al2O3 dissolving into spinel at high temperature. To reduce NiO and improve the formation of NiAl2O4, four factors were investigated in this study. The results showed that the milling time and starting materials had an important effect on the excess of NiO while the sintering temperature and sintering time had little effect on it.