高导热Diamond/SiC复合材料近终形成形的基础研究

Diamond particle-reinforced silicon carbide composite (Diamond/SiC) is deemed to be one of the most potential new generation packaging materials for high-performance electronic equipments due to its excellent properties of high thermal conductivity, lower coefficient of thermal expansion and lower density etc. However, Diamond/SiC composites are difficult to be synthesized and machined. In this study, a near-net-shape forming technology of powder injection molding - reactive infiltration of gaseous Si process is established to obtain high-performance Diamond/SiC composite parts. In order to explore the approach to enhancing the interfacial bonding，reducing the interfacial thermal resistance and inhibiting the graphitization of diamond, the interface behaviors of the composites and the graphitization mechanism of diamond particles at high temperature will be studied. By researching the flowing and mold-filling rules laws of diamond particles during the injection molding, the evolution rules of pores in the preforms during the debinding and pre-sintering, and the reactive infiltration of gaseous Si processes，the theoretical systems about the control of the microstructure and the dimensions of the diamond performs will be established and the densification mechanism of Diamond/SiC composites will be revealed, which will lay a theoretic and technologic foundation for developing the near-net-shape forming technology for high-performance Diamond/SiC composite parts. The achievements will exhibit a crucial significance in promoting the application of high-performance Diamond/SiC composites, which will satisfy the requirements of the development in advanced weapon equipments and modern electronic industry.

金刚石颗粒增强碳化硅复合材料（Diamond/SiC）因其具有高导热、高强度、低热膨胀系数和低密度等特点，是高性能电子装备用最有发展前景的新一代封装材料之一。本项目针对Diamond/SiC复合材料难复合和难加工成形等问题，以建立高性能Diamond/SiC复合材料零件的粉末注射成形－气相硅反应渗透近终形成形技术为目标。通过研究复合材料界面行为和高温下金刚石颗粒的石墨化机理，探索增强界面结合、降低界面热阻和抑制金刚石石墨化的途径；通过金刚石颗粒注射成形流动充模规律、预成形坯孔隙演化规律以及气相硅反应渗透过程的研究，建立金刚石预成形坯的组织与尺寸精确控制理论，揭示Diamond/SiC复合材料的致密化机理，为发展高性能Diamond/SiC复合材料零件的近终形成形技术奠定理论和技术基础。研究成果对于促进Diamond/SiC复合材料的应用，满足先进武器装备和现代电子工业发展需要具有重要意义。

Diamond/SiC复合材料具有热导率极高、热膨胀系数较低、密度低、稳定性高、工作温度高等优点，是最有潜力的新型高性能电子封装材料。本项目针对Diamond/SiC复合材料难复合和难加工成形等问题，以高性能Diamond/SiC复合材料零件的近终成形技术为目标，采用真空气相反应渗硅工艺在较低的温度和压力下制备了性能优异的Diamond/SiC复合材料。研究了多孔基体的制备及其孔隙特性，讨论了反应渗透过程以及渗透过程中的硅碳反应机理，分析了不同工艺条件下金刚石的石墨化现象，同时对复合材料的热物理性能及力学性能进行了研究，最后对复合材料的制备工艺，特别是近净成形工艺进行了讨论，主要结论如下：. 真空条件下当温度升高到 1600℃以上时，液态硅由平面蒸发转变为沸腾蒸发。大量的气态硅渗入多孔基体内部的连通孔道中并逐渐液化。随后液态硅在毛细管力的作用下向更细小的孔隙渗透并填充孔隙。合适的孔隙结构、 充足的硅源、良好的硅/碳润湿性、反应渗透过程中的放热以及体积膨胀效应保证了 1600℃下渗透 1 小时即可获得几乎全致密的复合材料。复合材料的热膨胀系数随着金刚石含量增加而降低。相同含量下，金刚石粒径越小，品级越高，复合材料的热膨胀系数越低。金刚石含量为 30~50vol.% 时，复合材料的热膨胀系数从2.14×10-6K-1降低到 1.81×10-6K-1。复合材料的热导率随着金刚石含量的增加而提高。相同含量下，金刚石粒径大，品级越高，复合材料的热导率越高。采用粒径110μm单晶金刚石制备的含量约51vol.%的复合材料的热导率可达 598W· m-1· K-1。复合材料的弯曲强度随着金刚石含量的增加而提高。相同含量时，金刚石粒径越小品级越低，复合材料的弯曲强度越高。含有约40vol.%粒径30μm 金刚石破碎料的复合材料的弯曲强度达到327 MPa。 . 本项目为发展高性能Diamond/SiC复合材料零件的近终成形技术奠定理论和技术基础。研究成果对于促进Diamond/SiC复合材料的应用，满足先进武器装备和现代电子工业发展需要具有重要意义。