ABSTRACTCrack-healing of structural ceramics is a most valuable technique to overcome their weak point such as surface cracks. Crack-healing ability appeared by admixing SiC to ceramics, because this function is to use the oxidation of SiC. Endowment of crack-healing ability as well as improvement in fracture toughness was expected to be achieved by compositing SiC whiskers. For this purpose, alumina / 30 vol% SiC whiskers and alumina/ 20vol% SiC whiskers/ 10 vol% SiC particles multi-composites were developed. Crack-healing ability and fracture toughness of these composites were investigated. Alumina/ 20 vol% SiC whiskers/ 10 vol% SiC particles multi-composite and alumina/ 30vol% SiC whiskers composite were found to have 1.43 times and 1.65 times higher fracture toughness than monolithic alumina, respectively. From the results of the strength recovery by crack-healing, alumina/ 20 vol% SiC whiskers/ 10 vol% SiC particles multi-composite and alumina / 30vol% SiC whiskers composite were found to be able to heal the pre-crack below 0.250 μm and 0.200 μm in surface length, respectively. In spite of the same SiC content, SiC particles and SiC whiskers multi-compositing enlarged the limit crack size to be able to crack-heal. On the other hand, increasing SiC whiskers content enhanced strength recovery of the specimen with the large crack above limit crack-size.
Synthesis of high porosity, monolithic alumina aerogels
