高导热石墨膜制备及导热机理研究

In order to fulfill the requirement of heat dissipation material with high efficiency for electronic industry, two kind of graphite films with high thermal conductivity, polyimide (PI)-derived graphite and graphene, are designed and developed. PI-derived graphite film is fabricated using PI film precursor and treated by carbonization and graphitization process. Graphene is obtained by mechanical exfoliation process using PI-derived graphite film as raw material. The key scientific issues of this project are the fabrication of material、characterization of micro-structure、 evaluation of thermal performance and establishment of the thermal conduction mechanism model. Based on the design and control of micro-structure, the law of micro-structure transformation during fabrication is studied. The relationship between process, micro-structure and thermal properties is established. The innovation of this project included designing and preparing the materials, controlling the micro-structure. As results, optimizing preparation processes for the graphite films, including PI-derived graphite film and graphene, are obtained. Especially, the relationships with the preparation process, the micro-structure and the thermal properties of the materials are established. The thermal conduction mechanism of graphite films with micro/nano-scale is explained. Finally, the graphite films with optimize thermal properties are developed.

本项目基于电子工业对高效散热材料的需求，设计开发聚酰亚胺基（PI）导热石墨膜和石墨烯两种厚度分别在微米、纳米尺度的高导热石墨膜。利用PI薄膜作为前驱体，通过炭化-石墨化工艺，制备PI基高导热石墨膜，并以此为原料，使用机械剥离手段制备石墨烯材料。如何通过高导热石墨膜的制备研究明晰高导热石墨膜的导热机理，是项目需要解决的关键问题。借助微观结构设计与调控，通过试验与理论结合的方法重点研究材料制备过程中的结构转变规律；通过结构表征和性能测试，建立材料的热学性能与原材料组分结构及制备工艺参数的关联性。项目在制备工艺、结构设计与控制、热学性能表征等方面的研究具有创新性。通过研究，获得PI基高导热石墨膜及衍生石墨烯的优化制备工艺，揭示材料的制备工艺、微观结构与其热学性能的关系规律，阐明微纳米厚度尺度高导热石墨膜的导热机理，实现高导热石墨膜的制备及综合性能优化。

石墨烯由于独特的晶体结构，使其具有许多独特的性能，如良好的导电性和导热性、高力学强度、超大比表面积等，是电子、能源及新材料领域的研究和应用热点。目前，使用化学剥离法或机械剥离法能够低成本批量制备石墨烯，但存在缺陷较多、结构损伤严重的问题，优异性能难以获得充分发挥。本项目以聚酰亚胺薄膜为前驱体，通过合理的热处理制度，制备了高导热石墨膜材料，并以此为基础，通过机械剥离法和化学剥离法进行了石墨烯材料的制备研究，获得了损伤较小、分散较好的石墨烯材料。项目对石墨烯作为复合材料强韧相进行了相关的应用研究，所制备石墨烯强韧化陶瓷材料断裂韧性提升20%以上，石墨烯材料层间强化缠绕成型炭/炭复合材料有效避免了二维复合材料在制备过程中分层等缺陷的产生，初步实现了高性能炭/炭复合材料的高效制备（层间结合强度提高16%以上，制备周期缩短13%以上）。通过本项目的实施，一方面有利于明晰高导热材料的导热机制，为大尺寸块体高导热炭/炭复合材料研究和开发提供技术支撑；同时石墨烯界面强化缠绕成型炭/炭复合材料的相关基础研究，初步解决了困扰国内炭材料界多年的二维炭/炭复合材料层间强化问题，通过引入石墨烯这一新型增强材料，实现了纳米结构层间强化，为高性能炭/炭复合材料的高效制备研究打开了一扇新的大门。此外，通过石墨烯在炭/炭复合材料的应用研究，促进炭/炭复合材料向高性能、低成本、快速制备方向发展，有利于下游应用领域（如光伏、先进陶瓷、金属冶炼等行业）实现精细化、高效化生产，促进相关行业竞争力提高。