高定向石墨块的控制制备及其导热性能影响因素研究

以廉价易得的高结晶度天然鳞片石墨(NG)和中间相沥青为原料, 采用中温热模压一次成型再高温炭化、石墨化处理可以制备高密度、高定向、高导热石墨块体材料。XRD、SEM和PLM分析表明该石墨块具有高度择优取向结构, 其内部石墨片垂直热压方向有序堆积排列。原料中鳞片石墨和沥青粘结剂的组成和配比以及制备工艺参数等对所制石墨材料的面向导热性能有显著影响。采用86wt%+32目鳞片石墨和14wt%AR中间相沥青在500℃、10 MPa下热模压成型的炭块经1000℃炭化、2800℃石墨化后样品的热物理综合性能较好, 其体积密度达到1.91 g/m³以上, 室温面向热导率为550 W/(m·K), 3000℃石墨化室温面向热导率高达620 W/(m·K)。

Controlled Preparation and Thermal Conductivity of Highly Oriented Graphite Blocks

Using cheap and available natural flake graphite with high crystallinity and mesophase pitch as raw materials, graphite block materials with high bulk density, highly preferred orientation and high thermal conductivity, were prepared by a hot-press molding at mild temperatures and subsequent carbonization and graphitization treatments at high temperatures. XRD, SEM and PLM analyses indicate that the prepared graphite block has a highly preferred structural orientation, the graphitic layers of the graphite flakes inside are clearly oriented perpendicular to the hot-pressing direction. The components of various sized flake graphite and different types of pitch binders, and the proportions of raw materials, as well as the preparation process parameters (including hot-pressing temperature and pressure, heat treatment temperature, etc.), have great influences on the room-temperature in-plane thermal conductivity of the resultant graphite blocks. Graphitized blocks prepared from 86wt% NG (+32 mesh) and 14wt% AR mesophase pitch through hot-pressed at 500℃ at a fixed pressure of 10 MPa for 5 h and subsequently underwent 1000℃ carbonization and 2800℃ graphitization, have a good comprehensive thermophysical property. Their bulk density reaches above 1.91 g/m³, and room-temperature in-plane thermal conductivity is measured as high as 550 W/(m·K), and improved to 620 W/(m·K) after 3000℃ graphitization treatment.