高定向导热炭材料的研究进展

Research Progress on Carbon Materials with High-Oriented Thermal Conductivity

微电子及通讯技术领域的快速发展对热管理材料提出了更高要求,迫切需要设计和开发高定向导热炭材料。高定向炭材料因其较高的石墨微晶结晶度和石墨化度、有序规整堆叠的石墨烯层片,而具有典型的各向异性高导热特性。粉末状炭材料(如鳞片石墨、气相生长炭纤维、纳米碳管、石墨烯等)的热导率虽然很高,但作为导热填料制备的复合材料的整体导热效果不佳,因此其在大型高功率集成器件散热领域的应用会受到一定限制。控制炭材料内部石墨微晶大小、取向和取向连续性是实现炭材料高定向导热性的关键。通过选择合适的碳质前驱体、成型工艺和热处理条件,调控石墨烯层片连续取向得到的宏观尺寸炭材料(如柔性石墨、天然鳞片石墨模压块、高定向热解石墨、聚酰亚胺石墨膜/块体、中间相沥青基炭纤维连续长丝及其复合材料等),可使石墨晶体沿(002)晶面方向保持高导热特性,实现高定向、连续、多维度可调控热传导,因此在导热、散热、热防护等领域具有广阔的应用市场。

The rapid development in the fields of microelectronics and communication technologies has put forward higher requirements for thermal management materials,and there is an urgent need for designing and developing carbon materials with high-oriented thermal conductivity.High-oriented carbon materials possess typical anisotropic and high thermal conductivities,owing to their high crystallinity and graphitization degree as well as orderly stacking of graphene sheets.Although powdery carbon materials,such as flake graphite,vapor-grown carbon fiber,carbon nanotube,graphene,etc.have high thermal conductivities,the thermal conduction of composites using powdery carbon materials as thermal conductive fillers is not well-performed.Therefore,their application will be subject to certain restrictions in the field of thermal dissipation of large integrated devices with high power.It is critical to achieve high-oriented thermal conductive performance for carbon materials by controlling the size,orientation and orientation continuity of graphite microcrystal.Macro-sized carbon materials,such as flexible graphite,natural flake graphite-molded block,high-oriented pyrolytic graphite,polyimide graphite film/block,mesophase pitch-based continuous carbon filament and its composite,etc.can be obtained via choosing suitable carbonaceous precursors,forming processes and heat treatment conditions,as well as controlling the continuous orientation of graphene sheets.The graphite crystal of macro-sized carbon materials along the(002)crystalline direction maintains high thermal conductive performance,so that their high-oriented,continuous and multi-dimension-tunable thermal conduction will come true.Therefore,the macro-sized carbon materials have a broad application market in the field of thermal management,such as thermal conduction,thermal dissipation and thermal protection,etc.