热处理温度对聚酰亚胺基炭纤维结构性能影响

Effect of heat treatment temperature on the microstructure and properties of polyimide-based carbon fibers

以聚酰亚胺（PI）纤维为前驱体，经800—2800℃连续高温处理，制备出不同性能的聚酰亚胺基炭（石墨）纤维。采用元素分析、SEM、HR-TEM、Raman、纤维强力仪、电阻率仪等分析手段研究热处理温度对炭纤维（CF）元素含量、结构形貌、力学性能、传导性能等方面的影响。结果表明，随着热处理温度的升高，聚酰亚胺基炭纤维中碳含量从78．97％（800℃）提高到99．72％（2800℃），非碳原子含量降低；聚酰亚胺基炭纤维表面缺陷数目增加且尺寸增大。同时，纤维的微观结构也从二维乱层石墨结构向有序的三维层状结构发展，表现为石墨化程度的提高及石墨微晶尺寸的增大；炭纤维拉伸强度先增加后降低，最大拉伸强度924．4MPa，断裂伸长率降低，电阻率减小，热导率增加，2800℃石墨化处理后纤维热导率为228．4W·m^-1·K^-1，是800℃处理后的50．4倍。

Polyimide （PI） -based carbon fibers with different properties were prepared by carbonization of PI fibers at 800 ℃, fol- lowed by heat treatment from 800 to 2 800 ℃. The effect of heat treatment temperature （HTT） on elemental composition, surface morphology, mechanical properties, and the thermal and electrical conductivities of PI-based carbon fibers were investigated by ele- mental analysis, SEM, HRTEM, Raman spectroscopy, mechanical testing, and electrical and thermal conductivity measurements. Results showed that as a result of HTT the carbon content increased from 78.97% to 99.72%, the tensile strength exhibited a maxi- mum of 924.4 MPa, and the degree of graphitization and the size of graphite crystallites were both increased. Distinct reductions in strain-to-failure and electrical resistivity were observed with increasing HTT. The thermal conductivity can reach 228.4 W· m^-1· K^-1 after heat treatment at 2 800℃. PI fiber may be a good precursor for carbon fibers with a high thermal conductivity.