金刚石/铝高连通度复合构型调控及其导热机理研究

As the most promising candidate of thermal management materials, diamond/Al composites, with uniformly dispersed diamond particles, did not exhibit desirable thermal conductivity yet. The thermal conductivity of diamond/Al composites with improved particle connectivity structures will be enhanced through tailoring the path of heat conduction. In this project, the effect and strengthening mechanism of different diamond particle connectivity in diamond/Al composites, with the same volume fraction of diamond particles but different structures, on the thermal conductivity will be investigated to achieve desirable thermal property. Discrete Element Method (DEM) software will be used to simulate the stacking of composite powders, and then according to the simulation results, the composite structure with optimal particle connectivity will be obtained by altering aluminum-to-diamond particle size ratio (PSR). Effects of diamond particle connectivity on diamond/Al interfacial bonding and thermal conductivity of the composites will be studied in detail. In addition, Synchrotron Radiation Computed Tomography (SR-CT) will be applied for in-situ observing the distribution of diamond particles. Finally, the strengthening mechanism of thermal conductivity by diamond particle connectivity and diamond/Al interfacial bonding will be revealed, which would supply a theoretical basis and technical support for developing high thermal conductive metal matrix composites in the future.

高导热金刚石/铝复合材料是未来最具应用潜力的新型热管理材料，目前制备的金刚石/铝复合材料中的金刚石都呈均匀分布，材料导热性能仍未达到理想的复合效果。金刚石呈高连通度分布的非均匀复合构型，通过改变热流传导路径，改善金刚石与铝基体的载流配置，可望提高复合材料热导率。本项目从复合材料构效关系出发，以相同体积含量下最大限度发挥金刚石的导热增强效率为目标，采用离散元软件模拟分析复合粉末的空间堆垛规律，通过调控粉末粒径比，获得最佳金刚石连通度的复合构型，系统研究金刚石连通度对金刚石/铝界面结合状态与材料热导率的影响规律。同时，采用同步辐射光源位相衬度显微断层技术，原位无损观察金刚石的三维空间分布状态，揭示金刚石连通度与金刚石/铝界面结合对材料导热性能的耦合响应机理，为高导热金属基复合材料的研发提供理论依据和技术支撑。

高导热金刚石/铝基复合材料（Dia/Al）是未来最具应用潜力的新型轻量化热管理材料，但以往制备的均匀构型复合材料导热性能有待提高（一般为60-90%理论值）。针对金刚石/铝基复合材料高效热传导与复合构型化的科学问题，本项目首先采用离散元软件模拟分析了两种刚性球形粉末的空间堆垛规律，通过调控粉末粒径比（PSR）获得了最佳增强体连通度和最高热导率的复合构型，进而采用热压烧结技术实验验证了PSR对金刚石的空间分布状态与材料热导率的影响规律，并探讨了其变化原理与机制。.离散元模拟结果表明，随PSR从0.2增加到1，不同体积比例的球形颗粒堆垛后增强体连通度与计算的热导率均显著增大。实验结果与同步辐射成像分析表明，随PSR从PSR0.225增加到0.9，40-50vol.%Dia/Al复合材料致密度与界面结合状态基本相当，但金刚石连通度与复合材料热导率也逐渐增大。当PSR由0.225增加到0.9时，40vol.%Dia/Al热导率由389 W/mK增加到472 W/mK（达到近100%理论值），增幅达21%；50vol.%Dia/Al热导率由442W/mK增加到628W/mK（达到理论值的110%），增幅高达41%。因此，通过构筑非均匀复合构型，调控金刚石连通性，可达到甚至突破复合材料的理论热导率。金刚石连通度取决于其周围金属粉末的配位数，配位数越低金属粉末越粗大越少，就更难将金刚石分隔开而呈现高连通；高连通度金刚石提高复合材料热导率，则与金刚石声子自由程高、易于实现颗粒间声子传播、降低界面热阻有关。本项目通过金刚石连通度与非均匀构型复合化研究，为高导热金属基复合材料的研发提供理论依据和技术支撑。