314 International Journal of Applied Ceramic Technolog-Liu, et al. Vol.8,No.2,2011 Sic matrix Pyc interphase debonding Fig. 7. The nages of py C interphase:(a) Untreate PyC interphase as received in sample A and B showing the poor crystalline degree (b) Heat-treated py C interphase in sample C showing the improvement in the crystalline degree. ferring load to the fiber, and hence the fexural strength of both samples A and C increased with the decrease of the open Fig. 6. Transmission electron microscopic images of the ryc porosity, as shown in Fig 3. However, the PyC inter showing the debonding in Sic noccmtetpa ec(a) sample A terphase morphologies of three kinds of compos Phase in C/PyC/SiC compos cannot be debonded B showing no debonding in Cr/By aSiC interphase zone; and (o under the loading, when the SiC matrix transferred the owing the debonding in Cr/lyc ASiC interphase a load to the interphase, and there was no debondingThe SiC matrix played a role in transferring the load to the fiber, and hence the flexural strength of both samples A and C increased with the decrease of the open porosity, as shown in Fig. 3. However, the PyC inter￾phase in C/PyC/SiC composite cannot be debonded under the loading, when the SiC matrix transferred the load to the interphase, and there was no debonding SiC fiber untreated PyC interphase a heat treated PyC interphase SiC matrix b Fig. 7. The HRTEM images of PyC interphase: (a) Untreated PyC interphase as received in sample A and B showing the poor crystalline degree; (b) Heat-treated PyC interphase in sample C showing the improvement in the crystalline degree. SiC fiber SiC matrix PyC interphase debonding a carbon fiber PyC interphase SiC matrix b c SiCmatrix carbon fiber PyC interphase debonding Fig. 6. Transmission electron microscopic images of the PyC interphase morphologies of three kinds of composites: (a) sample A showing the debonding in SiCf /PyC/SiC interphase zone; (b) sample B showing no debonding in Cf /PyC/SiC interphase zone; and (c) sample C showing the debonding in Cf /PyC HT/SiC interphase zone. 314 International Journal of Applied Ceramic Technology—Liu, et al. Vol. 8, No. 2, 2011