Synthesis of precursor for fibrous mullite powder by alkoxide hydrolysis method

Precursor for fibrous mullite powder was synthesized by simple alkoxide hydrolysis method without special treatment, and the formation mechanism of fibrous mullite precursor was investigated. As-synthesized precursor was amorphous and consisted of nano-scaled particles, and Al2O3 and SiO2 components containing small amount of Si-O-Al components existed in the precursor. During heat-treatment, Al-Si spinel phase and amorphous SiO2 formed around 1000 °C, and the products after heat-treatment above 1200 °C consisted of single mullite phase as fibrous shape of mullite precursor was maintained. In the present synthesis process, fibrous precursor derived from aluminum isopropoxide acted as a template for fibrous mullite precursor. Specific surface area of as-synthesized mullite precursor was 380 m2/g, and it gradually decreased with increasing heat-treatment temperature. Specific surface area of the products significantly decreased around 1200 °C, that corresponded to crystallization temperature, and that of the product after heat-treatment at 1300 °C was 13 m2/g.