Effect of TiO2 on Sintering and Grain Growth Kinetics of MgO from MgCl2·6H2O

Abstract

The effect of TiO2 on the grain growth kinetics of MgO prepared from MgCl2·6H2O was studied by the tradition phenomenological rate equation. The results showed that the addition of TiO2 decreased the activation energy of MgO grain growth, accelerated the growth rate of MgO grain, and markedly promoted the sintering of MgO. Without TiO2 addition, the MgO grain growth exponent \( n \) was 3, the grain growth activation energy \( Q \) was 556.9 kJ·mol−1, and the process was considered as volume diffusion controlled. With 0.2 wt pct TiO2 addition, the MgO grain growth exponent \( n \) was 2, the grain growth activation energy \( Q \) was 272.8 kJ·mol−1, and the process was considered as interface diffusion controlled. The apparent and closed porosities of MgO-0.2 wt pct TiO2 sample were decreased significantly, and the bulk density increased to 3.49 g·cm−3 (relative density is 97.5 pct). The main mechanism of TiO2 promoting the sintering of MgO was that TiO2 solubilized in MgO to form unequivalence substitutional solid solutions and cation vacancies that were favorable to cation diffusion.