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Alumina coated SiC whiskers were prepared by homogeneous precipitation of aluminum sulfate. The Si3N4 composites reinforced with coated SiC whiskers were fabricated by hot-pressing at 1800℃ for 2 h under an N2 atmosphere of 0.1 MPa to examine the effects of coated whiskers on the mechanical properties of SiC whisker reinforced Si3N4 composite. By the addition of alumina coated SiC whiskers instead of as received ones, the fracture toughness of composite was about 6.7 MPam1/2 which was slightly lower than as received SiC whisker reinforced composite. This result seems to be caused by the fact that the crack deflection and whisker pull-out were decreased. Thus, alumina coated SiC whiskers were considered to form relatively strong interface bond with Si3N4 matrix.