基于负热膨胀的异质结构复合材料的设计制备与热性能研究

High-power LED as a new generation of green lighting has following advantages,as energy conservation, reduction of atmospheric pollutants and protect the environment.Huge dismatch of the thermal expansion coefficient between the heat sink material and the chip material for high power LED would cause serious degradation of the product reliability, this issue has become the bottleneck of the development of high power LED technology. This project conduct research for this difficult problem, proposing that using the negative thermal expansion (NTE) particles as well as high thermal conductivity of the graphene and the Cu matrix composites to solve the coordination and harmonization between heat sink material of low thermal expansion and high thermal conductivity. In order to realizing low thermal expansion using as low volume of NTE particles as possible to ensure the high thermal conductivity and thermal stability of purpose, this project proposed to study on the controlling morphologu of NTE particle, designing the thermal conductivity of graphene channel and adjusting composite structures control. By examining the influence of the ratio of raw materials, topography, synthetic methods on composition, structure and thermal properties of the composite materials to clarify the composition, structure-activity relationship between the structure and thermal properties. The aim of this project is understanding the working mechanism of thermal conductivity of graphene channel; and eventually fabricating NTE/graphene/Cu bulk composite materials with core-shell or sheet structure , realizing the ultra-thin LED heat sink material with low thermal expansion, high thermal conductivity and high thermal stability.

大功率发光二极管（LED）的热沉材料与芯片材料之间存在过大的热膨胀性能的不匹配，造成产品可靠性的严重退化，已成为大功率LED的技术瓶颈。本项目即针对此难点问题开展研究，以Cu基热沉材料为研究对象，提出通过采用具有负热膨胀(NTE)特性的粒子来调控材料的热膨胀，以高热导性的石墨烯为快速导热通道制备NTE/石墨烯/Cu三相复合材料以解决热沉材料低膨胀和高热导之间的协调与统一。为达到在较低填充体积下即可实现降低热膨胀，保证高热导和热稳定性的目的，拟从NTE颗粒的选择与形貌控制、石墨烯导热通道的设计和复合材料结构及界面控制三个方面进行研究。通过考察原料的配比、形貌、制备方法等对复合材料的组成、结构和热性能的影响，阐明组成、结构和热性能之间的构效关系;理解石墨烯导热通道工作机制与工作原理；并通过制备出包覆型或片层型NTE/石墨烯/Cu块体复合材料，实现热沉材料的超薄、低膨胀、高热导和高稳定性的目标。

本项目针对铜（Cu）基热沉与芯片材料之间存在过大的热膨胀系数不匹配的现象展开研究，提出以负热膨胀（NTE）材料为复合相，利用石墨烯高热导的特点，制备了NTE/石墨烯/Cu三相复合材料以解决热沉材料低膨胀和高热导之间的协调与统一。首先采用化学法合成了性能稳定热膨胀系数可控的ZrW2-xMoxO8（0.5<x<1.5）和Sc2W(Mo)3O12系列负热膨胀粉体，通过选择合适的制备条件及离子取代实现了热性能的调控。采用超声化学镀的方法成功制备出了不同ZrWMoO8百分含量的铜包覆ZrWMoO8的复合粉体，之后与纯Cu粉按一定比例机械球磨混合获得后制备ZrWMoO8/Cu复合材料，500℃/3h烧结后的ZrWMoO8/Cu复合材料无明显孔洞，且晶粒大小较均匀，其致密度随ZrWMoO8含量的升高而降低。50%包覆粉复合材料的热膨胀系数为3.3774×10-6 K-1，与硅锗芯片材料的热膨胀系数相一致。此外，利用单分散石墨烯片层为控制剂，采用水热法合成了一系列Sc2W3O12/GO复合粉体，石墨烯添加量会对产物的结晶度、形貌和颗粒尺寸造成影响，Sc2W3O12/GO复合块体在25～800℃区间内的热膨胀系数高达-19.58×10-6K-1。在此基础上，围绕负热膨胀材料及NTE/石墨烯/Cu三相复合材料，开展了制备方法及热性能的研究，发现：通过调节Sc2W3O12/GO的复合量，可以调节三相复合材料的热膨胀性能。在室温~300℃内，Sc2W3O12/GO/Cu复合材料的热膨胀系数皆线性一致，随着Sc2W3O12/GO的质量分数的改变，其热膨胀系数可以控制在4~14×10-6 K-1之间。