C/C复合材料不同碳基体的纳米压痕行为研究

目的研究碳基体微观结构对材料整体性能的影响。方法用酚醛浸渍-碳化、中温煤沥青浸渍-碳化、甲烷为碳源前驱体,经化学气相沉积制备得到不同碳基体C/C复合材料。采用偏光显微镜对C/C复合材料不同碳基体的显微结构进行观察分析,采用XRD和Raman光谱对C/C复合材料的树脂碳基体、沥青碳基体和热解碳基体的微晶尺寸进行表征,以玻璃碳作为参比样品,通过纳米压痕测试不同碳基体试样的弹性模量和硬度。结果碳基体为热解碳和沥青碳的石墨微晶缺陷少,完整度较好,石墨化程度高。玻璃碳和树脂碳基体中石墨微晶排列紊乱,有序度低,石墨化程度低。酚醛浸渍-碳化得到的树脂碳的微晶尺寸Lc最小,为1.69 nm,弹性模量和硬度最大,分别为(23.17±0.54) GPa和(3.26±0.10) GPa;光滑层热解碳和粗糙层热解碳的弹性模量和硬度次之;沥青碳的微晶尺寸最大,Lc为9.36nm,而弹性模量和硬度最小,分别为(12.53±2.29) GPa和(0.72±0.14) GPa。结论不同碳基体的C/C复合材料中,碳基体的石墨化度越高,微晶尺寸越大,各向异性越显著,材料的弹性模量和硬度越低。

Nanoindentation Behavior of C/C Composites with the Different Carbon Matrices

Objective To study the effect of carbon matrix microstructure on the overall properties of materials. Methods Different carbon matrix C/C composites were prepared by resin-derived, pitch-derived, rough laminar and smooth laminar pyrocarbon. The microstructure of C/C composites with the different carbon matrices was observed by polarized light microscopy; and the crystallite size of carbon matrices of resin-derived, pitch-derived, rough laminar and smooth laminar pyrocarbon was characterized by X-ray diffraction and Raman spectroscopy. With vitreous carbon for reference, the elasticity modulus and hardness of samples with different carbon matrices were tested through nanoindentation. Results Graphite crystallites of pyrocarbon and pitch-derived carbon had fewer defects, better integrity and higher degree of graphitization; graphite crystallites of resin-derived and glassy carbon were disorderly arranged with low order and low degree of graphitization. The crystallite size Lc of carbon matrix by resin-derived was 1.69 nm, which was the smallest; but the modulus and hardness of that was the largest, separately (23.17±0.54) GPa and (3.26±0.10) GPa. The modulus and hardness of rough laminar and smooth laminar pyrocarbon was a litter smaller than that of resin derived carbon. The crystallite size Lc of the C/C-pitch composite was 9.36 nm, which was the largest; but the modulus and hardness was the smallest, about (12.53±2.29) GPa and (0.72±0.14) GPa. Conclusion In C/C composites of different carbon matrices, the higher the degree of graphitization, the larger the crystallite size, the more significant the anisotropicy, and the smaller the modulus and the hardness.