弹性相变复合材料的导热网络设计及机理研究

This Proposal bids for the goal-defined task 42 of “Fostering Project”: Research on the design of thermally conductive network and mechanism of elastic phase changing composite. The proposed research contents include the preparation of the elastic phase changing composite, relationship between thermally conductive property and microstructure, thermally conductive mechanism and performance-based design method. Now desensitizers are developed towards multifunctionality and composite required by energetic materials. Based on our research accumulation in phase changing materials and graphene, we will use methods of Pickering emulsion, hydrothermal process, vacuum freeze-drying and impregnation to combine graphene based phase changing microcapsules, three-dimensional graphene network and elastic polymer into elastic phase changing composite with multileveled microstructure and multifunction of elasticity, phase-changing, thermal and electric conductivities. The three-dimensional graphene network acts as framework of the composite and can build effectively thermally and electrically conductive network in the composite. Graphene based phase changing microcapsules adhered on the framework possess advantages of thin shell, high strength, good tightness, high core-shell ratio and thermal conductivity. Elastic polymer is filled in the remaining pore space. Therefore, the composite have excellent phase changing property, thermal conductivity and durability, and can satisfy the needs of energetic materials.

本申请针对“培育项目”的明确目标课题42：弹性相变复合材料的导热网络设计及机理研究，拟研究弹性相变复合材料制备方法、导热性能与微观结构关系、导热机理和性能设计方法等内容。目前含能材料要求钝感剂向多功能化和复合化方向发展。我们基于前期在相变材料和石墨烯方面研究积累，利用Pickering乳液、水热过程、真空冻干和浸渍等方法将石墨烯相变微胶囊、三维网状石墨烯和弹性聚合物等结构要素有机结合，形成具有多层次微观结构的弹性相变复合材料。该复合材料以三维网状石墨烯为骨架，在骨架上镶嵌以石墨烯为囊壁的相变材料微胶囊，在其余孔隙中填满弹性聚合物，是一种兼具弹性、相变、导热和导电多种功能的多功能复合材料。其中三维网状石墨烯在复合材料中形成有效导热/导电网络，石墨烯相变微胶囊具有厚度薄、强度高、密封性好、芯壳比高和导热性能好等优点，使得弹性相变复合材料具有优良的相变、导热和耐久性能，满足含能材料对钝感剂需求。

针对相变材料导热性能较差，不利于其吸收热点瞬间产生的大热量的问题，本项目利用具有较高导热性能的三维网状石墨烯等组分制备相变复合材料，具体研究内容包括复合材料的制备方法、导热性能与微观结构关系、导热机理和性能设计方法等。通过系列研究，取得如下研究结果。（1）三维网状石墨烯气凝胶及其相变复合材料的制备方法，包括石墨烯微胶囊的制备方法、三维网状石墨烯气凝胶的制备方法以及基于它们的相变复合材料的制备方法。尤其是建立了具有取向结构特征的三维网状石墨烯气凝胶和由石墨烯与膨胀石墨构成的混杂石墨烯气凝胶的制备方法，对于丰富石墨烯气凝胶和调控促进相变复合材料的导热性能具有重要价值。（2）三维网状石墨烯气凝胶相变复合材料渗流导热网络数值计算模型。利用有限元分析方法，建立了三维网状石墨烯气凝胶相变复合材料渗流导热网络机理模型。该模型可用于模拟和分析石墨烯导热渗流结构和取向排列结构。采用该模型研究了三维网状石墨烯气凝胶结构特征对渗流结构形成和复合材料导热性能的影响规律。（3）石墨烯相变复合材料界面耦合机理分子动力学模型。在实验研究基础上，建立了石墨烯相变复合材料界面耦合机理分子动力学模型。利用该模型对石墨烯与相变材料之间的界面热阻进行研究。分析了石墨烯官能团种类、数量和分布、石墨烯与相变材料之间的键合类型等因素对界面热阻以及复合材料的导热性能的影响规律。（4）渗流结构表征方法创新。采用近年来新发展的连续切片扫描电子显微镜（Serial block-face scanning electron microscopy，SBF-SEM）三维重构技术对三维网状石墨烯气凝胶的微观结构进行表征。SBF-SEM是一种利用计算机图像处理方法获得材料三维空间结构的表征手段。通过SBF-SEM技术重构了通过冰偏析诱导自组装法制备的各向异性石墨烯气凝胶的渗流网络结构。研究结果表明该气凝胶具有沿冰晶生长方向的取向结构，石墨烯片层间隙在50-150μm之间。所获三维透视表征结果对于建立更精确的三维网状石墨烯气凝胶相变复合材料渗流导热网络模型具有重要价值。