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

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.