界面相对3D-C/SiC复合材料热膨胀性能的影响

Effects of Interphases on Thermal Expansion of 3D-C/SiC Composites

利用减压化学气相浸渗(LPCVI)技术制备了3D C/SiC复合材料,从热解碳(PyC)界面相厚度对界面结合强度和热应力的影响出发,研究了界面相对复合材料热膨胀性能的影响。结果表明:①界面相厚度对3D C/SiC复合材料热膨胀性能的影响主要归因于其对界面结合强度和脱黏面上的滑移阻力的影响。在一定厚度范围(约70～220nm)内,材料的热膨胀系数随热解碳厚度的增加而逐渐降低;②热处理可提高材料的热稳定性,并通过改变材料内部结构,使热应力重新分布,对复合材料的高温热膨胀产生显著影响,但是,并没有改变基体裂纹的愈合温度(900℃)。

3D-C/SiC composites with PyC interphase in different thickness were fabricated by low pressure chemical vapour infiltration (LPCVI), and the effect of PyC interphase thickness on thermal expansion of 3D-C/SiC composites is studied. It is shown that the effect of interphase thickness on thermal expansion of 3D-C/ SiC composites lies in its influence on interphase bonding strength and sliding resistance in the debonding layer. In a certain thickness range (about 70-220 nm), coefficient of thermal expansion (CTE) of the composites decreases gradually with increasing of PyC interphase thickness. Moreover, heat treatment improves the thermal stability of the composites, and influences the CTE by changing interfacial thermal stress and microstructure of the composites, and changes CTE of the composites intensively at high temperatures by changing inter-facial thermal stress and microstructure of materials. However, heat treatment does not change the matrix crack sealed temperature.