The sintering behavior of mullite-alumina composites containing 68 to 90 wt% of Al2O3 synthesized by a sol-gel method was studied. Crystallization of mullite from amorphous starting materials occurred at above 1280°C. Solid solutions of mullite were formed over a range of compositions from 3Al2O3. 2SiO2 to 2Al2O3. SiO2 by heating at 1700°C. The time dependence of densification of the 3Al2O3. 2SiO3 ceramic followed a semilogarithmic relation between relative density and sintering time during the first stage, then relative density decreased a little accompanied with the development of rod-like particles. Relative density, Vickers microhardness, fracture toughness and Young's modulus of the sintered mullite-alumina bodies were fairly low at the mullite composition (3Al2O3. 2SiO2) but increased with increasing Al2O3 concentration.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Process Chemistry and Technology
- Surfaces, Coatings and Films
- Materials Chemistry