材料期刊网

以丙烷为气源,采用等温等压化学气相渗透技术制备了炭/炭复合材料,利用X射线衍射、偏光显微镜、扫描电镜、纳米压痕仪、三点弯曲法研究了热处理温度对热解炭以及炭/炭复合材料微观结构和力学性能的影响.微观结构观察显示随着热处理温度的升高,热解炭层间距减小,同时石墨化度提高;由于发生了局部应力石墨化,热解炭出现同心微裂纹,并且随热处理温度的升高裂纹的数量和宽度增加.纳米压痕测试表明,热解炭的纳米压痕行为是完全的弹性形变,完全卸载后热解炭表面没有残余压痕,但加载和卸载曲线没有重合而是存在一定的能量耗散,随着热处理温度的升高,热解炭的弹性模量增大.热处理后纤维强度降低,并且纤维与基体炭界面脱离,导致炭/炭复合材料的弯曲强度和模量下降.

Carbon/carbon composites were infiltrated by isobaric, isothermal chemical vapor infiltration using propane as the carbon source. Effects of heat-treatment temperature up to 2500℃ on the microstructure and the mechanical properties of pyrocarbon and carbon/carbon composites were investigated by X-ray diffractom-etry, polarized light microscope, scanning electron microscope, nanoindentation, and three points bending tests. The microstructural investigations of samples reveal a pronounced decreased of the interlayer spacing with a simultaneous enhance of the graphitization degree, and polarized light microscope results exhibit dis-tinct concentric cracks due to local stress induced graphitization, the number and width of cracks increase with the increase of heat-treatment temperature. Nanoindentation carded out on the pyrocarbon shows the in-dentation behavior is purely elastic, but the curves of loading and unloading do not overlap with significant amount of energy dissipation, the elastic modulus of pyrocarbon increases with the increase of heat-treatment temperature. On the other hand, with the decrease of fiber strength and the debonding of fiber/matrix inter-face after heat-treatment, the flexural strength and modulus of the carbon/carbon composites decrease.