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以硼酸和尿素为先驱体,采用浸渍-涂覆法在氮气气氛中在SiC纤维表面制备BN界面相。利用SEM/EDS、XRD和FT-IR对BN界面相的形貌和结构进行表征。采用化学气相渗透法(CVI)制备SiCf/SiC复合材料,并研究BN界面相对复合材料力学性能的影响。结果表明:光滑的BN界面相覆盖在SiC纤维表面,厚度约为0.4μm,为紊乱层状的t-BN物相。有无BN界面相的复合材料弯曲强度分别为180和95 MPa,并且有BN界面相的复合材料表现出明显的韧性断裂行为。微观结构分析表明,BN界面相在基体渗透过程中保护纤维免受化学腐蚀,减弱纤维和基体之间的界面结合强度方面发挥重要作用,这有助于大幅度提高复合材料的力学性能。
Using boric acid and urea as precursors, BN interface phase was prepared on the surface of SiC fiber by impregnation-coating method under a nitrogen atmosphere. The morphology and structure of the BN interface phase were characterized by SEM / EDS, XRD and FT-IR. SiCf / SiC composites were prepared by chemical vapor infiltration (CVI), and the effect of BN interface on the mechanical properties of composites was investigated. The results show that the smooth interface layer of BN is covered on the surface of SiC fiber and the thickness is about 0.4μm, which is a disordered t-BN phase. The flexural strength of composites with and without BN interface was 180 and 95 MPa, respectively, and the composites with BN interface phase showed obvious ductile fracture behavior. The microstructure analysis shows that the BN interface phase plays an important role in protecting the fiber from chemical attack and weakening the bonding strength between the fiber and the matrix during the matrix infiltration process, which helps to greatly improve the mechanical properties of the composite.