超临界流体制备石墨烯、氧化钛纳米薄层的过程及热性能研究

发布时间：2018-03-13 05:21

  本文选题：超临界流体　切入点：石墨烯　出处：《上海交通大学》2015年博士论文　论文类型：学位论文

【摘要】：石墨烯、氧化钛纳米薄层具备许多优异的性能,如何实现大规模化制备仍然是一大挑战。探索新途径制备纳米薄层材料具有十分重要的实际意义。超临界流体具有独特的特性,如低表面张力、高扩散系数、低粘度系数、优异的表面湿润能力。因此,可以充分利用超临界流体的优点剥离层状材料制备纳米薄层材料。本文针对超临界流体制备过程中的关键技术问题、热性能方面展开深入研究。超临界流体操作参数、初始原料、再循环处理工艺极大地影响到石墨烯的产率,通过实验研究,得到最佳实验操作参数。天然石墨作为原料时,石墨烯的产率比较低,天然石墨经过硝酸预处理后,表面附着少量的极性官能团,通过双极性作用吸附大量的DMF分子,提高了石墨烯的产率,极性官能团在高温高压环境中会还原,因此,基本保留石墨烯的本征特性。利用超(亚)临界水还原氧化石墨烯制备还原石墨烯。并通过超(亚)临界水和DMF对比实验,澄清了超(亚)临界水中H~+对氧化石墨烯的高效催化还原作用。氧化石墨烯水相分散液在密闭反应器中进行热处理(200℃-400℃),该方法绿色、简单、快速、高效。同时,将氧化石墨分散在二甲基甲酰胺溶剂中进行同样的热处理(200℃-400℃),作为对比试验探索超(亚)临界水还原氧化石墨烯的过程。结果发现,水是一种典型的质子性溶剂,在200℃-400℃温度范围内,能够产生大量的H~+,并快速催化氧化石墨烯的脱水还原反应,得到还原石墨烯,大大提高了石墨烯的还原程度和还原速率。提出超临界流体法剥离层状钛酸制备氧化钛纳米薄层材料,如何选择溶剂是超临界流体制备技术中最重要的问题。通过合理设计实验探索其中规律,结果表明,以典型的非质子性溶剂如二甲基甲酰胺为超临界流体时,仅有剥离过程发生。而以典型的质子性溶剂如水为超临界流体时,水是一种典型的质子性溶剂,在这一温度范围内,能够产生大量H~+,在H~+存在的情况下,层状材料不但有剥离发生,同时还伴随晶型相变发生,并进一步探索相变过程。XRD和SEM结果证明层状钛酸通过溶解和再结晶过程相变成锐钛矿。电子工业向高集成化、大功率化方向迅猛发展,对高效热界面材料的需求突显得尤为重要。石墨烯具有高导热率、低皮卡尔热阻,是环氧树脂基复合材料最理想的填充材料。将超临界流体法以及水热还原法得到的石墨烯作为热界面材料中的纳米添加剂,所有的石墨烯都按体积分数(2%、4%、6%、8%、10%)填充制备石墨烯-环氧树脂复合物,研究热界面材料的热性能,发现导热率明显提高。同时,通过导热理论模型对复合物的热导率进行计算,并与实验结果对比,发现理论计算值与实验规律相一致。
[Abstract]:There are many excellent properties of graphene and titanium oxide nanocrystalline, how to achieve large-scale preparation is still a big challenge. It is of great practical significance to explore new ways to prepare nano-thin layer material. Supercritical fluid has unique properties. Such as low surface tension, high diffusion coefficient, low viscosity coefficient, excellent surface wetting ability. The advantages of supercritical fluid can be fully utilized to peel off layered materials to prepare nano-thin layer materials. In this paper, the thermal properties of supercritical fluids are studied in detail in view of the key technical problems in the preparation process. The operating parameters of supercritical fluids, The yield of graphene is greatly affected by the process of initial raw material and recycling treatment. The optimum operating parameters are obtained through experimental study. When natural graphite is used as raw material, the yield of graphene is relatively low, and the natural graphite is pretreated with nitric acid. A small amount of polar functional groups were attached to the surface, and a large number of DMF molecules were adsorbed by bipolar interaction, which increased the yield of graphene, and the polar functional groups would be reduced under high temperature and high pressure. The basic intrinsic properties of graphene were preserved. Reduction of graphene by supercritical water was used to prepare reduced graphene. The experiments of supercritical water and DMF were carried out. The catalytic reduction of graphene oxide by H ~ in supercritical water was clarified. The aqueous dispersion of graphene oxide was heat-treated in a closed reactor at 200 鈩，

本文编号：1604998