In situ synthesis of alumina-matrix oxide/oxide composites by reactive sintering

In situ processing is an attractive and cost-effective approach to fabricate ceramic matrix composites with high performances. In this paper, the in situ synthesis of alumina-matrix oxide/oxide composites reinforced with Ba-β-Al2O3 or Ba-β-Al2O3/ZrO2 phases through reactive sintering of Al2O3/BaCO3 or Al2O3/BaZrO3 powder mixtures is briefly reviewed. The in situ synthesized composites exhibited a microstructural feature of elongated Ba-β-Al2O3 and equiaxed ZrO2 particles, which were distributed in Al2O3 matrix homogeneously. The TEM observations suggest that the longitudinal interface between Ba-β-Al2O3 phase and Al2O3 matrix is parallel to the basal planes of the Ba-β-Al2O3 phase. The formation of the elongated Ba-β-Al2O3 particles is likely to be due to the preferred diffusion of Ba cations along (0001) basal planes. Furthermore, the diffusion of Ba cations dominates the in situ reaction processes. The presence of Ba-β-Al2O3 and ZrO2 phases resulted in crack deflection and crack bridging, thus improving the fracture toughness of the Al2O3 matrix composites.