Effect of transition metal oxides on mullite whisker formation from mechanochemically activated powders

The effect of transition metal oxides, including FeO1.5, CoO and NiO, on the phase formation and morphology development of mullite (3Al2O3·2SiO2) whiskers from oxide mixtures activated by the high-energy ball milling process, were investigated. With the addition of FeO1.5, the mullite formation temperature was almost the same as that required for the system of Al2O3 and SiO2 without doping, while the presence of CoO and NiO inhibited the mullitization. The effect of the transition metal oxides on the mullite phase formation could be explained in terms of the mullitization mechanism. The size of the whiskers in the CoO-doped samples was larger than that in the samples doped with FeO1.5 and NiO. The present result showed that the dimension of the whiskers could be altered through addition transition metal oxides.