N P Bansal /Journal of the European Ceramic Sociery 29(2009)525-535 No Anneal 550°C 800°C 100um 100um 900°C 1000°c 1100°C 副-邮圆 100 Fig 9. SEM micrographs showing fracture surfaces of BNSiC-coated Hi-Nicalon fiber-reinforced celsian matrix composites annealed in air for 100 h at various 3.7. SEM of fracture surfaces toughening behavior for all the annealed CMC samples. Typical higher magnification SEM pictures showing fracture surfaces SEM micrographs of fracture surfaces of the composites, of the as-fabricated CMC and the one air-annealed at 1100C annealed for 100 h in air at various temperatures up to 1100C, are presented in Fig. 10. Debonding occurs primarily between fter the room temperature flexure test, are shown in Fig. 9. the fiber and the innermost coating in both specimens. In some Extensive long lengths of fiber pullout are observed indicating instances, the coating appears to stay with the fibers, particu Unannealed 1100° C Anneal 0 Fig. 10. SEM micrographs showing fracture surfaces of BN/SiC-coated Hi-Nicalon fiber-reinforced celsian matrix composites: as-fabricated and those annealed atN.P. Bansal / Journal of the European Ceramic Society 29 (2009) 525–535 531 Fig. 9. SEM micrographs showing fracture surfaces of BN/SiC-coated Hi-Nicalon fiber-reinforced celsian matrix composites annealed in air for 100 h at various temperatures. 3.7. SEM of fracture surfaces SEM micrographs of fracture surfaces of the composites, annealed for 100 h in air at various temperatures up to 1100 ◦C, after the room temperature flexure test, are shown in Fig. 9. Extensive long lengths of fiber pullout are observed indicating toughening behavior for all the annealed CMC samples. Typical higher magnification SEM pictures showing fracture surfaces of the as-fabricated CMC and the one air-annealed at 1100 ◦C are presented in Fig. 10. Debonding occurs primarily between the fiber and the innermost coating in both specimens. In some instances, the coating appears to stay with the fibers, particu￾Fig. 10. SEM micrographs showing fracture surfaces of BN/SiC-coated Hi-Nicalon fiber-reinforced celsian matrix composites: as-fabricated and those annealed at 1100 ◦C for 100 h in air