高导热中间相沥青基炭纤维的微观结构分析

Microstructure analyses of mesophase pitch-based carbon fibers with high thermal conductivity

中间相沥青基炭纤维具有低电阻、高导热特性,是目前最具发展前景的功能型导热、散热材料,但是国内对其微观结构和性能的研究报道较少。对国外高导热中间相沥青基炭纤维的微观结构和形貌进行了分析,同时将实验室研发的不同截面形状中间相沥青基炭纤维进行比较。研究结果表明中间相沥青基炭纤维具有的高导热特性源于其内部三维有序堆积的类石墨层状结构和较为完整生长的石墨晶体。热处理温度越高,其类石墨晶体生长越完善,层片取向程度越高。与圆形截面辐射状结构中间相沥青炭纤维相比,带状截面炭纤维有效解决了劈裂问题,其石墨片层间距为0.337nm,层片堆积高度达到26.77nm,轴向热导率高于800W/(m.K)。

Mesophase pitch-based carbon fibers are most attractive candidates for thermally conductive materials and heat dissipation materials due to their low electrical resistivity and high thermal conductivity,but there are few research reports on their microstructrues and properties in our country.The microstructure and morphology of high conductive mesophase pith-based carbon fibers prepared by foreign country were analyzed in contrast with those of mesophase pitch-based carbon fibers with different transverse shapes fabricated in our laboratory.The results show that the high thermal conductivity of mesophase pitch-based carbon fibers is owing to their three-dimensional structure of graphite layers with oriented stacking and prefect graphite crystals.The higher heat-treated temperature,the more perfect growth of graphite crystals,and the more orientation of structure.In comparison to round-shaped mesophase pitch-based carbon fibers with radial structure in transverse section,the ribbon-shaped carbon fibers efficiently resolve the problem of splitting crack,which possess a interlayer spacing of 0.337nm,a crystallite thickness of 26.77nm,and a high thermal conductivity of 800W/（m·K） along axial direction at room temperature.