Formation of mullite from precursor powders: sintering, microstructure and mechanical properties

The effect of precursor powders using aluminium sulphate/boehmite and colloidal silica on the green compact, mullitization, densification, microstructure and mechanical properties was investigated. Mullite precursor powders prepared from aluminium sulphate contain more pores that lowered the density of the green compact and alternatively reduced the density of sintered samples. The average grain size of aluminum sulphate-derived mullite enlarged from 1400 to 1700 °C and some elongated grains appeared. The more pores and elongated grains caused the reduction of strength in aluminum sulphate-derived mullite, while these elongated grains lead the toughness values in the range of boehmite derived mullite.