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In this paper, the tension-tension fatigue behavior of unidirectional SiC/Si 3 N 4 ceramic-matrix composite with strong and weak interface bonding at room temperature has been investigated using a micromechanical approach. The hysteresis loops models considering different interface slip cases have been developed to establish the relationships between fatigue hysteresis loops, hysteresis dissipated energy, hysteresis modulus, and the interface shear stress. The damage evolution process under tension-tension fatigue loading has been analyzed using hysteresis loops. By comparing experimental fatigue hysteresis dissipated energy with theoretical computational values, the interface shear stresses of SiC/Si 3 N 4 composite with weak and strong interface bonding were obtained for different cycle numbers. The fatigue life S‒N curves and broken fibers fraction versus cycle number curves corresponding to different fatigue peak stresses have been predicted. For SiC/Si 3 N 4 with strong interface bonding, the fatigue limit stress approaches to 75% tensile strength, which is much higher than that of composite with weak interface bonding, i.e., 58% tensile strength, due to the higher interface shear stress degradation rate for weak bonding interface. [ABSTRACT FROM AUTHOR]

The atomic structure of Si(110)/SiC(0001) heterojunctions prepared on 6H-SiC(0001) was characterized by transmission electron microscopy and X-ray diffraction. An FCC-on-HCP parallel epitaxy is achieved for the Si(110)/SiC(0001) heterostructure with a growth temperature of 1050 °C and the in-plane orientation relationship is Si[1-10]//6H-SiC[11-20]. The pure edge misfit dislocations with a Burgers vector of 1 3 <11-20> SiC parallel to the interface are observed to accommodate the extreme lattice mismatch. Along the in-plane orientation Si[1-10]SiC[11-20], the Si/6H-SiC interface has a 4:5 Si-to-SiC matching mode with a residual lattice-mismatch of 0.26%. The misfit dislocation density at the Si/SiC interface is calculated as 1.217×10 14 cm −2 . [ABSTRACT FROM AUTHOR]