Effect of Sintering Additives on Microstructure and Performance of Csf/SiC-BN-ZrC-ZrB2 Multiphase Ceramic Matrix Composites
How to effectively promote the densification of Csf/SiC-BN-ZrC-ZrB2 while reducing the damage to carbon fibers has always been a challenge in the application of this composite.In the current work,sintering aids,such as B4C-Cg,Al2O3-Y2O3 and phenolic resin,were used to prepare Csf/SiC-BN-ZrC-ZrB2,by using hot pressing process.The influence of sintering aid types and contents on microstructure,mechanical property and carbon fiber structure of the composites was studied by using XRD,SEM,EDS and mechanical property testing.It is found that addition of 2 wt.％B4C-Cg reduced the damage of carbon fibers to a certain extent.The composite possessed a fracture toughness of 7.39 MPa·m1/2,with non-brittle fracture mode.When the content of B4C-Cg was increased to 4 wt.％,the effect of sintering aid on mechanical properties was leveled off,while erosion of carbon fibers cannot be further reduced.The addition of phenolic resin hindered the dispersion between fibers and the ceramic matrix,thus leading to serious fiber aggregation and property degradation.The addition of Al2O3-Y2O3 improved the bending strength of the composite(σbb=147.45 MPa).However,the YAG severely corroded the carbon fibers,resulting in short pulling-out length and rough surface for the fibers,while the fracture toughness was decreased to 6.94 MPa·m1/2.In conclusion,B4C-Cg is helpful to remove the oxide films and impurities on the surface of ceramic powders,which promoted the atomic diffusion and the densification of the composite and also reduced the erosion of the carbon fibers.
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