界面层对SiC_f/SiC复合材料力学性能及氧化行为的影响

为研究界面层对SiC_f/SiC复合材料力学性能及氧化行为的影响,采用先驱体浸渍裂解工艺制备了3种不同界面层体系的SiC_f/SiC复合材料。3种界面层分别为热解碳(PyC)、PyC+BN-Ⅰ和PyC+BN-Ⅱ(其中BN-Ⅰ表示B质量分数大约2%,BN-Ⅱ表示B质量分数大约20%)。研究表明,具有PyC界面层的SiC_f/SiC复合材料常温力学性能最高,其常温弯曲强度达到380MPa,而双界面层体系中,SiC_f/SiC复合材料常温弯曲强度分别为282MPa(PyC+BN-Ⅰ)和259MPa(PyC+BN-Ⅱ)。1200℃氧化试验表明,具有PyC+BN-Ⅱ界面层的SiC_f/SiC复合材料弯曲强度保留率最高,为54%。3种不同界面层体系的SiC_f/SiC复合材料在氧化后均表现为脆性断裂。微观结构显示,界面和纤维被氧化是导致材料最终失效的原因;能谱分析表明,具有PyC+BN-Ⅰ和PyC+BN-Ⅱ界面层的SiC_f/SiC复合材料纤维内部未检测到O原子存在,证实BN有保护纤维的作用。

Effect of Interface on Mechanical Property and Oxidation Behavior of SiCf/SiC Composites

In order to investigate the influence of interfaces on the mechanical properties and oxidation behaviors of SiCf/SiC composites,SiCf/SiC composites with 3 different interfaces (PyC,PyC+BN-Ⅰ and PyC+BN-]Ⅱ) were prepared via precursor infiltration and pyrolysis (PIP) method.Results showed that SiCf/SiC composites with PyC interface exhibited the highest flexural strength of 380MPa.SiCf/SiC composites with PyC+BN-Ⅰ and PyC+BN-Ⅱ interfaces exhibited flexural strengths of 282MPa and 259MPa,respectively.The flexural strength retention rate of SiCf/SiC composites with PyC+BN-Ⅱ interface was 54％ after heat treatment at 1200℃ in air for 2h,and all SiCf/SiC composites with different interfaces exhibited brittle fracture after heat treatment.The microstructure of SiCf/SiC composites demonstrated that the oxidation of interfaces and fibers caused the failure of the composites.Energy dispersive spectrometer had not detected oxygen on SiC fibers of SiCf/SiC composites with PyC+BN-Ⅰ and PyC+BN-Ⅱ interfaces,which indicated that BN interface can effectively protect fibers from oxidation.