Research on the interfacial structure and property improvement of the Cfiber/2Si-B-3C-N ceramic matrix composite

A mixture of the mechanically alloyed 2Si-B-3C-N powder and short carbon fiber was hot pressed at 1800 °C for 30 mins in nitrogen. Careful investigation to the prepared Cfiber/2Si-B-3C-N ceramic matrix composite revealed that the composite was very difficult to be densified. Heterogeneous nucleation, abnormal grain growth and severe interface reaction occurred on the fiber surface or between the fiber and the ceramic matrix, leading to a small density and weak mechanical properties of the composite. For the prepared composite without any additive, the relative density, flexural strength, elastic modulus and fracture toughness is 71.7%, 64.6 MPa, 14.7 GPa and 1.47 MPa·m1/2, respectively. The average size of the SiC grains close to and far away from the carbon fiber is 249.10 nm and 50.45 nm, respectively. However, with the addition of ZrO2 (7.5 mol%), the above mentioned phenomenons are changed noticeably, and those properties are significantly increased to 88.5%, 112.4 MPa, 111.1 GPa and 2.94 MPa·m1/2, respectively. At the same time, the SiC grains close to or far away from the carbon fiber almost have the same average size of about 448.21 nm, and almost no interface reaction occurs. It shows that the addition of ZrO2 not only facilitates the sintering and densification process, but also depresses the interface reaction, promotes the homogeneous nucleation and grain growth, and hence significantly improves the mechanical properties of the Cfiber/2Si-B-3C-N composite. This interesting finding is favorable for the preparation of carbon fiber reinforced ceramic matrix composite, which requires both a large relative density and well controlled interface reaction.