Effects of the hot shearing of mesophase pitch on the thermal conductivity of the resulting carbon
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摘要: 以中间相沥青为原料，在变径模具中通过热态高压流变剪切促进分子有序排列制备了中间相有序块体导热炭材料。采用XRD、SEM和偏光显微镜表征了流变收缩比（1∶1、2∶1、2.5∶1和3∶1）对中间相有序排列块体炭材料微观织构及导热性能的影响。结果表明：中间相沥青在高压流变剪切的作用下实现了中间相炭微球之间的融并和有序生长，最终形成了微观有序、类纤维结构特征的块体炭材料。流变收缩比的提高，促进了中间相炭微球之间的融并生长，从而有利于获得更为完美的石墨结构。流变剪切不仅促进了中间相炭微球之间的有序融并在轴向形成了类纤维组织结构，而且能够促进径向不同层面之间中间相炭微球有序融并所形成细棒状纤维结构，正是该结构的存在改善增加了样品的导热系数。当流变收缩比由1∶1增加到3∶1时，样品轴向导热系数由96.88W/(m · K)增大至131.02W/(m · K)，径向导热系数由140.85W/(m · K)增大至160.46W/(m · K)。流变收缩比的提高缩小了样品两维方向上导热特性的差异。Abstract: Monolithic carbons were prepared by hot extrusion shearing of mesophase pitch under high pressure in a mould with decreasing diameter, followed by carbonization and graphitization. The influence of the shrinkage ratio(1∶1, 2∶1, 2.5∶1 and 3∶1) of the mould on the microstructure and thermal conductivity of the carbon monoliths was investigated by X-ray diffraction, scanning electron microscopy and polarized light microscopy. Results showed that mesophase carbon microspheres melted and re-combined to form fibrous and orientated domains along the axial direction under the hot extrusion shearing. A favorable microstructure for improving thermal conductivity of the carbon monoliths was obtained by the increase of the shrinkage ratios. With the increase of the ratio from 1∶1 to 3∶1, the thermal conductivity of the monoliths increased from 96.88 to 131.02W/(m · K) and 140.85 to 160.46W/(m · K) in the axial and radial directions, respectively.
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Key words:
- Mesophase pitch /
- Hot extrusion shearing /
- Carbon monolithic /
- Thermal conductivity
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