金刚石/铝网络互穿结构及其界面对复合材料导热性能的影响

Diamond/metal composites have gained great prevalence as new-generation electronic packaging materials, whose core is how to improve their thermal conductivity. Nowadays, increasing the content of diamond particles and promoting the interface of these components are quite attractive, and some considerable results have also been obtained. But the high-thermal-conductivity diamond particles (1800~2200 W/mK) in these composites are just like isolated island connected by the metals with low thermal conductivity (240W/mK and 400W/mK for Al and Cu, respectively), which not only increases the number of interfaces, but also makes it hard to form synergy, impairing the extraordinary thermal conductivity of diamond. The innovation of this project is to establish continuous diamond network skeletons, turning the isolated islands into high heat conduction channels. The detailed research approach is described below. High quality diamond network skeleton will be firstly deposited on foamy copper by chemical vapor deposition, and subsequently composited with Al by pressure infiltration technique, forming interpenetrated network structures. Combining experimental data and theoretical analysis, the working mechanism of interpenetrated network structures and successive interface on thermal conductivity of composites will then be studied, establishing the relationship between materials structure and performance. Finally this research will provide theoretical and experimental basis for the design and fabrication of diamond/metal composites with low density, low thermal expansion coefficient and high thermal conductivity.

金刚石/金属基复合材料是新一代电子封装材料的研究热点，核心是如何提高材料的导热性能，目前国内外主要研究思路是增加金刚石颗粒含量和改善金刚石颗粒/金属的复合界面，均取得了较好的效果。然而，此种结构中的金刚石颗粒（热导率1800-2200W/mK）犹如一座座由金属（Al-237W/mK、Cu-398W/mK）连接的导热孤岛，既增加了两相界面数量，又难产生协同作用，使金刚石优异的导热性能难以充分发挥。本项目的创新思路是在复合材料中构建连续的金刚石网络骨架，变高导热孤岛为高导热通道。具体研究思路为：以泡沫铜为衬底，利用CVD技术制备高质量金刚石网络骨架，再利用压力熔渗技术与铝复合，使金刚石与铝形成网络互穿结构，结合实验测试和理论分析，研究金刚石/铝网络互穿结构及其界面对复合材料导热性能的作用机理，准确建立其构-效关系，为高导热、低热膨胀、低密度金刚石/金属基复合材料的设计与制备提供理论和实验依据。

传统的热管理材料由于热导率不足，已无法满足高功率电子元器件的散热要求。开发新一代高导热、低热膨胀和轻质的金属基复合材料成为决定相关产业发展的关键。本项目的创新思路是在复合材料中构建连续的金刚石网络骨架，变高导热孤岛为高导热通道。首先，我们利用有限元软件对实际应用中高功率电子器件局部高温区的热流传递情况进行了模拟仿真，得到了三种不同结构对应的热通量分布场，揭示了复合构型设计对热管理材料的整体导热性能的影响规律。然后，对比研究了衬底和中间层种类对泡沫金刚石热学性能的影响规律。采用热丝-蒸镀技术在金刚石表面沉积钨纳米层，优化了沉积参数调控，实现了钨纳米层厚度的可控调节，通过纳米尺度复合界面表征，确定了复合界面微观结构状态，建立了复合界面结合状态和厚度对界面热阻的影响规律。同时，优化了泡沫铜衬底的孔隙率、化学气相沉积参数，制备了高质量的泡沫金刚石网络骨架。最后，通过气体压力辅助熔渗技术成功制备了泡沫金刚石/铝复合材料，通过优化熔渗工艺，获得了高致密、良好界面结合、较低界面反应，且泡沫金刚石增强体保持完整的铝基复合材料，揭示了三维构型泡沫金刚石对复合材料的导热增强机理，计算了复合材料单位体积分数增强体对热导率提升的贡献值。此外，我们将泡沫金刚石骨架应用于石蜡相变复合材料。为了进一步提高泡沫金刚石宏观大孔内填充的复合材料的传热，受恒温动物“动脉-毛细血管”分级结构的启发，我们在泡沫金刚石骨架的基础上，设计并制备了超长碳纳米管次级导热网络骨架，即泡沫金刚石-碳纳米管分级导热骨架，其泡沫金刚石-碳纳米管/石蜡复合材料的热导率高达9.72W/(m•K)，为石蜡的92倍，为泡沫金刚石/石蜡的2.5倍。以上结果表明泡沫金刚石、泡沫金刚石-碳纳米管分级导热骨架在复合材料中具有巨大的导热增强优势。这些结果将为高导热、低热膨胀、低密度金刚石/金属基复合材料的设计与制备提供重要的理论和实验依据。