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1098 B Saruhan et al. /Composites: Part A 32(2001)1095-1103 Table 1 Mechanical data of the composites and the thickness of the layers before and after heat-treatment Fiber coating As-hot-pressed Heat-treated at Continuous heat- Cyclic heat- 200°Cfor2 h treated at1300° treated at1300° for 1000 h for1000×1h Fracture strength 160 MPa 42.4 GPa 84.6 GPa Carbon(fugitive)ZrO2 Thickness of C-laye Thickness of oxide-layer 800 400nm 150nm Fracture strength 230 MPa 200 MPa 140 MPa 106 GPa 81 GPa Carbon(fugitive )AlO Thickness of C-layer 180 50 Thickness of oxide-lay 79 MPa 170 MPa 170 MPa 200 MPa Young's modulus 75 GPa 74 5 GPa 91 GPa 92 GPa The carbon layer in carbon/Al2O3-composites after no change compared with that of the as-coated one hot-pressing was about 150 nm, being only slightly thin- (Fig. 2(c)) ner than the thickness of the as-coated layer. The thick Heat-treatment of composites at 1200"C for 2 h in air ness of the AlO3-layer was reduced to 150 nm (initially yielded a gap between fiber and oxide layer by oxidation 800 nm). The morphology of the Al2Oj-layer showed of the carbon layer (fugitive layer)(Fig 3(a)-(c)). This 1300.1000K Fig. 4. Scanning electron micrographs of the interphases after continuous exposure at 1300.C in air for 1000 h: (a)reference sample; (b) fugitive/ZrO2: and (c)fugitive/Al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