Preparation of Al<sub>2</sub>O<sub>3</sub>-Coated TiC Whiskers and Their Sintering Behavior

Al2O3-coated TiC whiskers, which were synthesized by the homogeneous precipitation technique using urea, were used as raw materials in the precipitation of TiC whisker-dispersed Al2O3 ceramics, and the effects of the coating and sintering conditions on the structure and mechanical strength of composite were investigated. Use of the Al2O3-coated TiC whiskers changed little the dispersion state of TiC whisker in the composite. On the other hand, the formation of titanium oxycarbide at the interface between the matrix and whisker was promoted. The increase in the bonding force at the Al2O3-TiC interface resulted in an increase in the mechanical strength of the composite. To improve the mechanical strength of the composite, however, precise control of reaction at the Al2O3-TiC interfaces by controlling the amount of the Al2O3 coating as well as the hot-pressing conditions was found to be important. As a result, the composite ceramics sintered at 1600°C for 30min using Al2O3 (25 vol%)-coated TiC whisker showed the bending strength of 560MPa (about 1.8 times higher than Al2O3 ceramics sintered under the same hot-pressing conditions) at room temperature.