甲烷吸附和碳原子热扩散规律对三维网状石墨烯生长均匀性及其热导率影响的研究

As one of new nano-materials, graphene has the potential to replace traditional materials and play a momentous role in the heat transport area. Preparing three-dimensional graphene networks (3DGNs) by chemical vapor deposition method has attracted more and more attention. However, some key scientific issues on the formation of the 3DGNs have not been will-researched. This project will focus on the mass transfer process during the growth of the 3DGNs from decomposition of methane on surface of foam nickel (FN) under high temperature. Reveals the competition mechanism of methane and hydrogen on the effective adsorption sites of the FN, and illuminates the law of the influence on this competition from temperature and composition of the reaction atmosphere. According to the above research, relationship between uniformity of the 3DGNGs and coverage of the methane molecular on the NF will be revealed, which is crucial to prepare the 3DGNGs with homogeneous thickness. Moreover, the mass transfer law of carbon atoms will be studied, and the influences on the thickness of the 3DGNs from reaction time and cooling rate of substrate will be promulgated. Homogeneous thermal diffusion of carbon atoms can be realized based on optimizing cooling rate of the substrate, which is benefit to achievement the growth of the 3DGNs with controlled number of layers. Scanning electron microscopy, Transmission electron microscopy, Atom forces microscopy and Raman spectra will be adopted to analyze the morphology, thickness and quality of the 3DGNs. Laser flash analysis and differential scanning calorimetry were used to measure and calculate the thermal conductivity of the 3DGNs, and this parameter will be employed as an important criterion to judge the quality of product. The findings of this project reveal the fundamental law of the 3DGNs growth, which can be used to guide the preparation of the 3DGNs with controlled thickness and high quality.

石墨烯有望取代传统材料在热输运领域发挥重要作用。采用化学气相沉积制备三维网状石墨烯已引起科学界的广泛关注,但其生长过程中的关键热科学问题没有得到系统研究。本课题将围绕高温条件下，泡沫镍表面甲烷吸附、裂解及后续碳原子扩散制备三维网状石墨烯的传质过程开展研究。探究甲烷和氢气对衬底表面有效吸附位的竞争规律；阐明反应温度和气氛比例对此竞争吸附的影响规律；揭示衬底表面甲烷覆盖率对三维网状石墨烯厚度均匀性及热导率的影响。进一步研究反应时间、衬底降温速率对碳原子传质的影响规律，实现碳原子扩散的均匀性及速率的合理性；揭示碳原子扩散对三维网状石墨烯层数的影响。采用扫描电子显微镜、透射电子显微镜和拉曼光谱等对产物进行均匀性和层数表征；采用激光热导仪和差示扫描量热仪测试计算产物的热导率。本课题将揭示三维网状石墨烯生长的基本传质规律，完善其生长动力学，指导厚度均匀、层数可控且具有高热导率的三维网状石墨烯的制备。

近年来微电子技术迅速发展，伴随着电子器件的性能和集成度不断提高，其发热量也急剧增大，严重影响了电子设备运行的稳定性和可靠性。为了提高器件的散热效率，常采用热界面材料填充器件各部分接触界面处的空隙。为了满足实际使用要求（1~5 Wm-1K-1），环氧树脂基材中填料的添加量往往高达60%（质量分数），但过高的填料比例会带来新的问题，导致复合物的密度过大且同时降低其机械强度。作为一种严格的二维材料，石墨烯是目前已知的导热性能最强的物质，其热导率高达5,000 Wm-1K-1，因此成为新一代导热填料的热门候选材料。但采用化学气相沉积法制备具有三维网状结构的石墨烯材料的制备依然存在瓶颈，其生长过程中的传热传质规律尚需进一步揭示。另外三维网状石墨烯修饰的复合热界面材料的热性能及相关的影响规律值得进一步研究。. 本课题围绕高温条件下，泡沫镍表面催化裂解甲烷制备三维网状石墨烯的传质过程开展了研究。探究甲烷和氢气对衬底表面有效吸附位的竞争规律；阐明反应温度和气氛比例对此竞争吸附的影响规律；揭示衬底表面甲烷覆盖率对三维网状石墨烯厚度均匀性的影响。进一步研究反应时间、衬底降温速率对碳原子传质的影响规律，实现碳原子扩散的均匀性及速率的合理性；揭示了石墨烯修饰的复合热界面材料的热输运机制以及石墨烯缺陷密度对复合物热性能影响的规律。揭示了石墨烯基复合热界面材料的热输运机理，石墨烯基复合热界面材料的热输运需要依赖石墨烯，环氧树脂以及它们的界面等三种区域。石墨烯表面缺陷密度对填料与基材在界面处的热接触具有显著影响。经过优化后将复合热界面材料的热导率提高至6 Wm-1K-1。. 本课题的研究结果具有一定科学意义和实际意义，完善了三维网状石墨烯的生长理论和石墨烯基复合热界面材料的热输运机制，同时为三维网状石墨烯及其修饰的复合热界面材料的大规模制备提供了理论支撑和实验数据。