各向同性煤沥青制备炭/石墨纤维的研究

以各向同性煤沥青为原料,采用熔融纺丝工艺制备了直径为55μm的沥青纤维,经预氧化、炭化和石墨化处理后得到炭纤维和石墨纤维,并采用偏光显微镜、XRD和SEM等对其形貌、结构和性能进行表征。结果表明,炭/石墨纤维具有与沥青原料相似的各向同性光学结构;随热处理温度升高,炭/石墨纤维截面逐渐变粗糙,且内部石墨微晶逐步发育并长大,3 000℃下石墨化纤维微晶增大较明显,其堆积高度和平面尺寸分别约为5nm和11nm;1 600℃炭化纤维的力学性能较好,其拉伸强度和杨氏模量分别达到0.57GPa和32.19GPa,进一步提高热处理温度,纤维拉伸强度逐步降低,但是其杨氏模量逐渐增加,3 000℃石墨化纤维的拉伸强度和杨氏模量分别为0.26GPa和40.57GPa;炭/石墨纤维室温轴向电阻率随热处理温度的升高而降低,1 000℃炭化纤维室温轴向电阻率为47.78μΩ.m,3 000℃石墨化纤维室温轴向电阻率降至21.98μΩ.m。

Preparation of carbon fibers from an isotropic coal tar pitch

Pitch fibers with a diameter of 55 μm were prepared by a melt-spinning method with an isotropic coal tar pitch as the raw material.Carbon fibers and graphite fibers were obtained by pre-oxidation,carbonization and graphitization treatments.The morphology,texture and performance of various fibers were characterized by polarized light microscope,scanning electron microscope,X-ray diffraction,monofilament tensile instrument and micro-ohmmeter,respectively.The results show that carbon fibers and graphite fibers possess a similar optical isotropic texture to their precursor pitch.With the increase in heat treatment temperature,the transverse section of fibers becomes rougher and the graphite microcrystal in fibers gradually grows up.The microcrystal parameters（Lc and La） in the fibers graphitized at 3 000 ℃ increase obviously to ~5 nm and ~11 nm,respectively.Carbon fibers treated at 1 600 ℃ possess better mechanical properties,and their tensile strength and Young＇s modulus reach 0.57 GPa and 32.19 GPa,respectively.With further increase in heat treatment temperature,the tensile strength of fibers decreases but Young＇s modulus increases.The tensile strength and Young＇s modulus of graphite fibers treated at 3 000 ℃ are 0.26 GPa and 40.57 GPa,respectively.The room temperature axial electrical resistivity of fibers gradually decreases with the increase of heat treatment temperature.The electrical resistivity of carbon fibers treated at 1 000 ℃ is 47.78 μΩ·m,which decreases to 21.98 μΩ·m after treatment at 3 000 ℃.