金刚石连续构型与界面热阻对金刚石/铝复合材料导热性能的影响机理

Diamond/metal composites have gained great prevalence as new-generation electronic packaging materials .So far, great achievements have been achieved on the thermal conductivity of diamond particles reinforced composites by increasing the diamond connectivity and improving the interfacial bonding. However, in such diamond dispersed metal matrix composites, the highly thermally conductive diamond reinforcements are isolated from each other. The large number of diamond/metal interfaces bring large amount of thermal interface, which is difficult to achieve good synergistic effect between the diamond particles. As a result, it is hard for the highly thermally conductive diamond reinforcements to reach their full potential. Therefore, it is an effective strategy to improve the thermal conductivity of the composites by changing the architecture of the composite from the “isolated” to “continuous”. In this project, CVD process will be used to form continuous diamond channels and networks on the copper substrates. The key scientific problems that need to be solved in this project are the effects of the architectures of composite and the interfacial thermal resistance to the thermal conductive properties of the composites. By investigating the influence of different dimensions of the continuous diamond reinforcements and the interfacial microstructure on the thermal conductive properties of the composites, we are able to achieve the controllable preparation of different architectures of diamond reinforced Al-matrix composites and establish the relationship between the structure of the reinforcements and the performance of the composites. This research will provide theoretical and experimental basis for the design and fabrication of high-performance diamond/metal composites with low density, low thermal expansion 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，目前国内外通过提高金刚石颗粒的连通性和优化金刚石/金属的复合界面，均不同程度地提升了复合材料的导热性能。然而，金刚石颗粒的复合构型仍然为“离散构型”，存在大量的金刚石/金属界面，界面热阻高，金刚石颗粒难以产生有效的协同作用，使金刚石优异的导热性能难以充分发挥。解决问题的途径是将“离散构型”变为“连续构型”，即采用化学气相沉积技术，在铜衬底表面构建金刚石连续构型，在复合材料中构建快速导热通道。目前有待解决的科学问题是，金刚石连续构型与界面热阻对复合材料导热性能的影响。通过研究不同维度的金刚石连续构型及其界面结构对复合材料导热性能的影响，获得不同构型金刚石铝基复合材料及其界面的调控技术，探究金刚石铝基复合材料的“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新的思路和理论科学依据。

金刚石/铝复合材料是未来最具应用潜力的轻质金属基热管理材料。目前研究以颗粒构型增强体为主，重点在于两相界面改性降低界面热阻所涉及的关键科学问题。然而受界面认知水平和制备工艺的限制，改性层或厚度不均、或成分结构难控制、或本征热导率较低，使得孤立分布的金刚石颗粒之间难以产生高效的协同作用。本项目采用有限元分析软件研究金刚石连续构型的结构参数和界面状态对复合材料导热性能的影响，揭示了金刚石连续构型与界面热阻对金刚石/铝复合材料“构-效关系”的影响机理，为不同维度（零维/一维/二维/三维/不同维度耦合）金刚石增强体/金属基复合材料的设计奠定理论和实验基础。基于模拟分析结果，项目组采用化学气相沉积技术，在不同维度的铜衬底上构建高质量的金刚石连续构型（一维/二维/三维），再利用气压熔渗技术与铝基体复合，实现不同维度金刚石/铝基复合材料的可控制备，获得了具有高导热、高界面结合强度的多维度金刚石/铝基复合材料。实验结果表明，单一构型增强体中，三维连续构型导热效果最好，金刚石体量为9.5 vol.%时，复合材料热导率达到356.4 W/mK，在颗粒金刚石与三维连续金刚石混合比例为11:5，且金刚石总体积分数为30.4 vol.%的情况下，金属基复合材料热导率为569.9 W/mK。相较于泡沫金刚石/铝复合材料有显著提升，复合材料热导率而与体积分数超过50 vol.%的颗粒金刚石增强铝基复合材料的文献报道值相当，导热效率优势明显，表现出较为明显的竞争优势。此外，基于前期对金刚石/铝复合材料的研究经验，项目组将SiC颗粒与金刚石颗粒（三维连续金刚石）进行多比例调控，并制备出金刚石-碳化硅/铝基体复合材料，该材料在金刚石体量仅在5.2 %的情况下，复合材料热响应速度接近于铜，导热效率是颗粒增强复合材料的3.7倍。以上结果表明金刚石连续构型在复合材料中具有巨大的导热优势。这些结果最终为高导热、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新的思路和科学依据。