Improved Ablation Resistance of 3D-Cf/sibcn Composites with (pyc/sic)3 Multi-Layers As Interphase

Ablation behavior of 3D-Cf/SiBCN composites with (PyC/SiC)(3) multi-layers as interphase was investigated in plasma ablation flame at a heat flux of 4.02 MW m(-2). During ablation, amorphous SiBCN matrix is firstly oxidized and forms a borosilicate glass, in which B2O3 is volatilized as the ablation going on. At the ablation center with higher temperature, SiC and Si3N4 grains are precipitated from the amorphous SiBCN matrix. And then, these SiC and Si3N4 grains are oxidized, forming a certain viscous silica rich protective coating on the sample surface. Moreover, it is revealed that the SiC layers in (PyC/SiC)(3) multi-layers interphase can protect the carbon fibers from ablation damage effectively. Compared with the C-f/(PyC)SiBCN composites, much improved ablation resistance is achieved for the C-f/(PyC/SiC)3SiBCN composites. The linear and mass recession rates of the Cf/(PyC/SiC)3SiBCN composites are as low as 1.7 +/- 0.4 mu ms(-1) and 0.0427 +/- 0.0053 mg mm(-2)s(-1),which are -43 % and-21 % lower than those of Cf/(PyC)SiBCN.