Preparation Process Of BN Interface Layer Of SiC_f/SiC Composite Material

SiC fiber reinforced Si C matrix?SiC_f/SiC?composites have important potential applications in the fields of aerospace and nuclear power generation.Without the interface layer,SiC fiber and SiC matrix are easy to form strong adhesion and reduce the performance of the composite.Therefore,it is important to prepare the proper interface layer to obtain a weak interface between fiber/matrix interface.At present,the PyC interface layer has a widely application in ceramic matrix composites.While,the PyC interface layer has poor oxidation resistance and the BN interface layer has better oxidation resistance than PyC,which can significantly improve the performance of the ceramic matrix composite.In this paper,the effects of different deposition temperatures and different heat treatment temperatures on the BN interface layer prepared by chemical vapor deposition?CVD?were studied.The effects of BN single interface layer and?BN/SiC?double interface layer on the properties of SiC_f/SiC composites were also studied.The main research content and results are as follows:1.The BN interface layer was prepared by CVD using BCl₃ and NH₃ as precursor gases.The effects of deposition temperature and heat treatment temperature on the properties of BN interface layer were investigated.The results show that the BN interface layer prepared at 650?without heat treatment is suitable.2.The microstructures and compositions of the CVD-BN interface layer were investigated.The crystallization degree of BN was improved with the increase of the heat treatment temperatures.The high temperature heat treatment can degrade the tensile strength of SiC fibers while the CVD process of BN interface layer has little effect on the tensile strength of SiC fibers.The experimental results show that the tensile strength of KD-S SiC fibers is degrade from 2.60 GPa to 1.72 GPa after the high temperature heat treatment at 1000?,while the tensile strength of SiC fibers is 2.66 GPa after the heat treatment at 650?.3.The?BN/SiC?double interface layer were successfully deposited on SiC fibers by CVD process.The mechanical property tests showed that?BN/SiC?double interface layer improves the performance of composites more obviously than the BN single interface layer.The flexural strength and fracture toughness of the?BN/SiC?double interface composites are 543.4 MPa and 20.4 MPa·m^1/2,respectively.While the flexural strength and fracture toughness of the BN single interface composites are 463.5 MPa and 17.2MPa·m^1/2,respectively.This is because the double interface layer deflects the crack better and increases the crack spread path before the material breaks.