Reaction Synthesis And Oxidation Behaviours Of SiC-BN-C Composites

SiC-BN-C composites were prepared by reaction hot-pressing to develop a new material. The influences of sintering temperature and volume fraction of in-situ formed SiC and BN in the composites on microstructure, room temperature mechanical properties, room temperature friction and wear properties, and high temperature oxidation behavior have been studied in detail by using modern analyzing methods. Mechanisms of strengthening, friction and wear, and oxidation behavior of the composites have also been investigated.The relative density of the composites increases with increasing sintering temperature, and there is a small increment at the sintering temperature higher than 2000℃. The relative density of sample C50, with 50vol% carbon content, is 60% at 1900℃, 84.94% at 2000℃and 86.09% at 2100℃.Microstructure analysis indicates that the sintering temperature and carbon content play an important role in the microstructure of the composites. With increasing carbon content and sintering temperature, there is a obvious increase in the quantity of plate-like morphology structure.The mechanical properties results show that the relative density, flexural strength, fracture toughness and Vickers hardness of the composite increase with the sintering temperature. The highest values of sample C50 are 89.06%, 133.7MPa, 2.0MPa·m^1/2 and 0.53GPa. The relative density, flexural strength, fracture toughness and Vickers hardness of the SiC-BN-C composite decrease with increasing carbon content.The oxidation behaviors of SiC-BN-C composites were studied in the different temperature. The oxidation mechanisms of the composites have systemically analyzed with the research of oxidation behaviors and microstructures. The weight losses of the composites when oxidized at 600℃, 800℃and 1000℃are obviously reduced compared with carbon materials. The weight losses of the composites increase at first, and then decrease with the increasing temperature. And at 800℃, the biggest weight loss of the composites has been got. When oxidized at 600℃and 1000℃, there is no oxide layer found on the surface of the composites. Because of...