Growth of mullite whiskers in mechanochemically activated oxides doped with WO3

The effect of WO3 on mullite formation and mullite whisker morphology, in oxide mixtures activated by a high-energy ball milling process, was investigated. Differential thermal analysis (DTA) measurement indicated that WO3 enhanced the mullite phase formation, with mullitization temperature of 951 °C, 921 °C and 835 °C for the samples doped with 5, 10 and 20 mol% WO3, respectively. However, the presence of WO3 had an undesired effect on the whisker morphology. A decrease in the length of mullite whisker was observed with increasing WO3 content. The effect of WO3 on the mullite phase formation temperature, as well as the whisker morphology, was explained using a dissolution-precipitation mechanism.