Reaction rate and spinel formation in the system MgO-Cr2O3

The solid state reaction of mixture of polycrystalline MgO and Cr2O3 was investigated for the purpose of studying the rate of reaction, the activation energy and the mechanism of spinel formation. X-ray diffraction, content of free MgO, and microscope photographs of reacted pieces were observed. As the result of study 1) Cell dimensions of MgCr2O4 spinel decreased with increasing chromium-ion substitution. 2) The reaction proceeds following diffusion controlled reaction and Jandar equation. 3) The state of formation of MgCr2O4 from polycrystalline MgO and Cr2O3 can be described by the expression k = 6.29 x 10-7 sec-1 and activation energy was calculated to be 47.88 Kcal/mole. (author)