Preparation Of SiCp/SiC Composite By Chemical Vapor Infiltration

SiC is an excellent kind of high temperature material, for its resistance to high-temperature, oxidation resistance, ablation resistance, and its low density, high specific strength, high specific modulus etc, but it's very brittle and its reliability of performance is poor. SiC ceramic matrix composite toughened by particle has many advantages, such as isotropy, easy control of particle size and distribution, stable performance, and its manufacture process is simple, its cost is low. But the toughening capability of particle is now very weak, so it's significant to explore structure of particle ceramic matrix composite and its preparation method, which could toughen the ceramic effectively.In this thesis, chemical vapor infiltration(CVl) was applied to prepare SiC particle toughened SiC ceramic matrix composite(SiCp/SiC). The microstructure of the composite was studied by SEM and TEM, its bending strength was tested by three points bending method, and the relationship between the process and the microstructure and properties were researches. The following are the main research contents and results:(1) The influence of process parameters on the preform was studied. It was found that the process parameters such as the concentration of resin/ethanol solution as binder agent, the dosage of the binder agent, the pre-pressure, the forming pressure etc, influence the structure of the preform very much.(2) The influence of the preparation process with chemical vapor infiltration on the properties of SiCp/SiC ceramic matrix composite was studied. Research results indicated that the structure of preform, the size of the conglomeration, the particle size had great influence on the properties of the composite.(3) The relationship between the composite structure and its mechanical properties was analyzed. The binder agent phenolic resin decomposed into carbon through thermal decomposition during the CVI process. One part of the carbonformed the weak interface layer distributing among the SiC particles uniformly, the other part of the carbon clustered among the particle, they both decreased the mechanical properties of the composite. In addition, the porous SiC matrix also decreased the mechanical properties.(4) The influence of the carbon-eliminating process on the properties of SiCp/SiC ceramic matrix composite was investigated. The results showed that the mechanical properties weren't increased when the carbon-eliminating process was used.