Synthesis of mullite whiskers using Na2SO4 flux

In order to study a synthesis of mullite whiskers using Na2SO4 flux, powder mixtures consisting of Al-2(SO4)(3), amorphous SiO2 and Na2SO4 were heated in alumina crucibles. After heating, the reaction product in the crucible was treated with hot hydrochloric acid to get mullite whiskers. Optimum conditions such as heating temperature, duration time and mixing ratio of the starting materials to get a large amount of mullite whiskers with high aspect ratio were established. When a powder mixture consisting of Al-2(SO4)(3) : amorphous SiO2 : Na2SO4 = 1 : 1 : 4 (molar ratio) was heated at 1000degreesC for 2 h, 10-25 mum length and 0.5-2 mum diameter (aspect ratio: 15-20) mullite whiskers were formed.