By in suit whisker formation, α-Si_3N_4(w)/RBSN, β-SiC(w)/RBSN, β-Si_3N_4(w)/Si_3N_4 and β-SiC(w)/Si_3N_4, composites were prepared. The microstructure of the different whiskers was observed and analysed by using TEM and SEM. It was shown that different whiskers have different crystallographic reactions of whisker growth and different type of crystal defeats. Phase composition of the whiskers and the composites were determiend by X-ray diffraction. The mechanical properities of β-Si_3N_4(w)/Si_3N_4, and β-SiC(w)/Si_3N_4 have been measured and its toughening mechanism was disscussed. In order to keep the stability of the whiskers, the kinetics and thermodynamics of in situ whisker formation was investigated. To produce the dense silicon nitride matrix, the nitriding mechenism have been discussed. The growth mechenisms and conditions of the whiskers were investigated. It was shown that the problems of nonhomogenous dispossion of whisker in matrix was solved effectively. The whiskers were kept away from mechanical damage during mixing and chemical corrsion. The simplified process technology of ceramic compsites may be a very useful method.
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