铝/金刚石复合材料各向异性界面可控机制及对导热性能影响的研究

Diamond particles reinforced aluminum (Al/diamond) composites can obtain the excellent thermo-physical properties theoretically. It is the promising candidate for a new generation of thermal management materials. Currently, thermal conductivity of Al/diamond composites can be enhanced significantly by using the new preparation technology as gas pressure infiltration. However, it is found that the interfacial optimization at {111} interface is violent weak comparing with {100} interface, which means that the interface of composites behaves a distinct character of anisotropy. By means of the effective control of optimization process at {111} and {100} interfaces, thermal conductivity of Al/composites can be further improved. This proposal is focused on the problems of anisotropic interface. On this research, a series of composites will be fabricated by gas pressure infiltration. Moreover, the interface state of the composites will be controlled by regulating fabricating parameters. Based on the analysis of interfacial microstructure with methods of FIB & TEM, the control mechanism of anisotropic interface affected by fabricating parameters will be systematic investigated.Furthermore，detection of thermal conductivity distribution and measurement of interfacial thermal conductance can be done by SThM. And in view of the theory of acoustic heat transfer, the physical mechanism is explored to clarify the effect of interfacial microstructure on interfacial thermal conductance. Then, the theoretical model describing thermal conductivity of particles reinforced composites will be reasonable improved to accommodate the anisotropic interface. Finally, through comprehensive analysis, we try to initially establish the relationship between technique, microstructure and properties, which are the three elements of materials science and technology, for Al/diamond composites fabricated by gas pressure infiltration. The findings can provide the scientific basis for designing Al/diamond composites with higher thermal conductivity. Simultaneously, it has important signification to promote the application of Al/diamond composites and popularization of gas pressure infiltration technology.

金刚石颗粒增强铝基复合材料理论上可以获得优异的热物理性能，是理想的电子封装材料。目前，采用气体压力熔渗法可以使复合材料热导率得到显著提高，但发现{111}界面的优化程度明显弱于{100}界面，表现为界面各向异性。通过{111}和{100}界面优化进程的有效调控，有望进一步提高材料热导率。本项目即针对各向异性界面问题，通过改变气体压力熔渗工艺参数，获得具有不同界面状态的复合材料，结合界面显微结构的深入分析，系统研究成型工艺对各向异性界面的控制机制和影响规律；测定热导分布及界面热导，利用声子导热理论揭示界面显微结构决定界面热导的物理机制；完善适用于各向异性界面的复合材料导热模型。通过本项目工作，初步建立气体压力熔渗制备铝/金刚石复合材料中工艺、组织、性能的材料科学与工程三要素间基本关联，研究成果为高导热铝/金刚石复合材料的设计提供科学依据，同时对促进材料应用和气体压力熔渗技术推广具有重要意义。

本项目针对气体压力熔渗制备高导热Al/diamond复合材料中{111}和{100}界面各向异性问题开展研究工作。金属铝与金刚石的两相界面反应可以分为金刚石表面碳原子结构转变和反应产物Al4C3相形核长大两个过程，他们都受到{111}和{100}面不同结构和形貌影响而表现出明显差别。碳原子过程主要是sp3结构向石墨sp2结构的转变。在{111}面，由于具有扭曲的石墨六角结构，因此只需碳原子平整化即可快速实现结构重排；而在{100}面，则需要进行碳原子的大幅度移动，因此转变过程由{111}小面化进程和相应的碳原子重排协同完成。两相反应产物Al4C3相呈现为非均匀形核及长大过程。在{111}面，碳化物沿着垂直台阶的台阶边缘进行；而在{100}面，碳化物以小面化进程提供的大量{111}面作为核心进行，因此与原{100}面呈55°夹角。碳化物与金刚石间具有确定的晶体学取向关系：[1 0]Diamond // [2 0]Al4C3以及{111}Diamond // (0003)Al4C3。上述过程是{111}和{100}界面各向异性形成的根本机制，这对Al/diamond复合材料中两相界面反应形成了全新的认识，并明显区别与传统观点。保温时间、成形温度/压力以及反应时间等工艺参数正是通过对上述过程的不同影响实现对各向异性界面的调控。基于对两相界面结构和传热特性的分析，建立了考虑界面反应和界面各向异性两大问题的整体界面热导基本模型和计算方法，配合声子错配理论的Debye模型，可以完成对Al/diamond复合材料热导率的良好预测和分析评价。基于以项目研究成果指导的工艺优化，气体压力熔渗制备Al/diamond复合材料热导率进一步提高至大于760 W/mK。