Microstructure development and phase evolution of alumina-mullite nanocomposite

In this work, alumina-mullite composites (5-15 vol.%) were prepared using sol-gel derived alumina composite nanopowders. The results revealed the formation of intragranular and intergranular mullites inside and between the alumina grains, respectively. Accordingly, the intragranular mullites (average grain size, 0.3 ?m) were smaller than the intergranular mullites (average grain size, 0.5 ?m). Moreover, the alumina grains (average grain size, 1.0 ?m) are larger than the mullites. Meanwhile, the mullites showed positive results in the prevention of the alumina grains growth and the retardation of densification. The relative density of alumina-15 vol.% mullite that was sintered at 1650?C for 2 h, was obtained as 98.7 %. After sintering at 1750?C for 2 h, the mullite was decomposed.