Effects of milling and subsequent heat treatment on preparation of mullite–zirconia nanocomposites

Mullite-zirconia composites were fabricated through reaction sintering of mechanically activated alumina and zircon powder mixtures. X-ray diffraction results showed that increasing milling time resulted in gradual weakening and broadening of alumina and zircon peaks. For the sample milled for 70 h in which there are no peaks present from zircon, heating at 1200°C resulted in the reappearance of the zircon peaks. Samples sintered at 1500°C achieved complete formation of mullite and zirconia. These samples exhibited the following physical and mechanical properties: density 3.87 g/cm³, open porosity 3.45%, hardness 11.44 ± 0.3 GPa and fracture toughness 4.7 Mpam^1/2.