高导热液态金属/相变材料设计与界面机制研究

The existing solid-solid phase change material has multiple advantages including non-corrosion, small volume change, high phase transition temperature, etc. However, it remains a challenge to improve the thermal conductivity. The traditional idea of adding a large amount of high thermal conductivity filler could not increase the thermal conductivity effectively. In addition, it will induce the embarrassing situation of declining thermal storage capacity. This project innovatively introduces liquid metal with phase-change capability and high thermal conductivity to improve the heat capacity and heat transfer performance simultaneously. The major thrusts are (i) to explore the regulatory mechanism between liquid metal and solid-solid phase change material interface heat transfer and (ii) to construct the continuous heat transfer channels via the phase transition material pore properties. We proposed to control the adhesion work of liquid metal on the solid-solid phase change material by adjusting surface properties (functional group modification, surface density) and topological structures (roughness, topography). The effects of surface properties and structures on the interface heat transfer mechanism between will be further investigated via scanning thermal microscopy. A model of a unit cell capable of accurately describing the microstructural characteristics of the material is established to obtain the intrinsic relationship among “interface”-“continuous nanoporous structure”-“heat transfer performance”. This model will guide the preparation of liquid metal / solid-solid phase transition composite material with high thermal conductivity. The implementation of the project will provide theoretical knowledge and technical support for solving the problem of low thermal conductivity of phase change materials in the fields of solar energy utilization and industrial waste heat recovery.

现有固-固相变材料具有无腐蚀、体积变化小、较高相变温度等优点，但存在导热系数低的难题。传统思路通过添加大量高导热填料来增加材料的导热系数，但收效甚微，同时也会带来储热能力下降的窘境。本项目创新性地引入具有相变能力和高导热的液态金属，实现储热能力和传热性能同时提高。开展液态金属与固-固相变材料界面处热量传递调控机制及相变孔道性质构建连续传热渠道的关键科学问题研究。拟通过相变材料表面化学性质(官能团种类，密度)和拓扑结构（粗糙度、形貌）调控液态金属在相变材料表面的粘着功，采用扫描热显微镜探索表面性质和结构对液态金属/固-固相变材料界面热量传递的影响。建立能够准确描述材料微结构特征的体胞单元模型，获得界面-连续纳微孔结构-传热性能之间的内在关系，并据此进一步制备高导热液态金属/固-固相变复合材料。项目的实施将为解决太阳能利用、工业余热回收等领域中相变材料低导热的难题提供理论参考和技术支撑。

针对复合材料界面热阻大等问题，本项目以液态金属为研究探针，通过外场强化、界面改性及增强粘附调控探针表面能，研究了液态金属复合材料界面传热机制和系列功能材料制备方法，制备出高导热、耐磨及传感复合材料。（1）通过材料的微观结构特征，建立体胞单元模型进行数值模拟，分析孔径大小、孔隙率等参数对多孔材料的影响，并对热场中体胞单元的传热机理进行数值模拟研究，揭示孔结构-传热性能之间的内在规律，为高导热液态金属/相变材料设计建立理论依据；（2）采用组分剥离的方法制备多孔材料，通过对多孔材料及液态金属进行表面改性，调整表面官能团种类，增强界面相互作用。通过外场强化调控液态金属的表面形貌及尺寸，并将其引入多孔材料中，成功构建液态金属连续导热渠道，复合材料的导热系数较原材料提升33倍，同时兼具良好的储热能力；（3）研究发现通过界面改性和液态金属粘度调节，进而可以调控涂层内部液态金属的尺寸和分散性，开发出十二硫醇表面改性的液态金属/聚酰亚胺耐磨涂层，提高复合涂层热稳定性，其磨损程度仅为原始涂层的1/10，为先进自润滑材料设计提供了新方向；（4）通过与无机填料复合，调控液态金属的流动性，构筑出“平面滚轮”结构，设计出自愈合度达90%的高灵敏液态金属基传感材料，灵敏度最高可达15.47（现有材料的灵敏度仅为0.1-5），且具备900%以上的断裂伸长率，该方法为工业应用中制备高灵敏传感材料提供理论依据。