Abstract
The present paper is concerned with the effect of preparation temperature of NiMn 2O 4 spinel on the oxidation mechanism. For NiMn 2O 4 prepared at 430°C (25 m 2 g −1 specific surface area), the oxidation proceeds through two steps showing single-phase cation deficient spinel for the first step of oxidation at low temperature with a kinetic controlled by a diffusion. During the second step this metastable spinel phase decomposes into NiMnO 3 and α-Mn 2O 3 with sigmoidal kinetic curves. When NiMn 2O 4 is obtained by sintering at 1200°C and then ground (2 m 2g −1 specific surface area), the increase of particle size causes the spinel phase to decompose directly according to the nucleation-growth mechanism.
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