高导热三维石墨烯作为相变储能材料载体的协同传热储热机理研究

Phase change materials (PCMs) for thermal energy storage (TES) have been used in a wide of application in thermal management of electronic device, like LED. It has been proved to be an effective way for thermal management due to its high storage capacity and small temperature variation from storage to retrieval. Nevertheless, most PCMs exhibit inherent low thermal conductivity and high coefficient of thermal expansion, which decreases the overall power of the thermal storage device. To increase the heat transfer ability of the PCM, a heat transfer intensifier is necessary for the TES system. In the present work, three-dimensional foam-like graphene (Graphene foam, GFs) macrostructures with high thermal conductivity, low density, low coefficient of thermal expansion and chemical inertness are under investigation as a thermal enhancer and a container in PCM (Wood's alloy and stearic acid). GFs would be prepared by template-directed chemical vapour deposition. GFs offer a large number of interconnected open pores and good compatibility with many surfaces, which can be filled with various materials. High thermal conductivity of the ligaments in GFs allow heat to transfer throughout the PCM rapidly. Good continuity at the interfaces and throughout the GF structure would supply a ''path'' for heat transferring. As an important factor of a TES system, thermal properties of the composite would be characterized. Effects of the structure and thermal performance of the three-dimensional graphene matrix on the composite would be discussed in detail.

相变储能材料可有效解决热能供求在时间和空间上不匹配的矛盾，广泛应用于大功率LED等电子器件的热管理。本项研究针对相变储能材料存在的热导率低和热膨胀系数大等问题，拟采用具有高导热、低密度、低热膨胀系数和耐腐蚀等优点的多孔三维石墨烯，分别作为相变储能材料硬脂酸和伍德合金的强化传热载体。研究内容包括：（1）多孔三维石墨烯的制备。以模板法CVD生长热导率高、热膨胀系数低、孔结构可调和机械性能良好的多孔三维石墨烯，作为相变储能材料的强化传热载体；（2）石墨烯相变储能复合材料的设计制备。考察复合材料组成和结构特征对体系热响应速率、储能密度、热膨胀行为和热循稳定性的影响机制，对复合材料进行优化设计；（3）强化传热机理研究。通过石墨烯复合材料对LED热管理的演示验证研究，揭示石墨烯作为相变储能材料载体的协同传热储热机理，建立描述此种非均质复合材料的热导率方程。

相变储能材料可有效解决热能供求在时间和空间上不匹配的矛盾，是实现热能利用和环境保护的重要手段之一。本项研究针对相变储能材料存在的热导率低和热膨胀系数大等问题，采用具有高导热、低密度、低热膨胀系数和耐腐蚀等优点的多孔三维石墨烯，作为相变储能材料硬脂酸的强化传热载体。主要开展了以下研究内容：（1）多孔三维石墨烯的制备。探索性地在绝缘非金属衬底上制备了高质量的石墨烯宏观体材料，研究石墨烯在二氧化硅衬底上的生长和成核机理。将石墨烯宏观体材料引入到相变储能材料中，作为相变储能材料的强化传热载体，大大提高了相变储能材料的热导率；（2）石墨烯相变储能复合材料的设计制备。采用真空法制得三维石墨烯/硬脂酸相变储能复合材料，其热导率约为2.635 W/mK，是硬脂酸的14倍。考察了复合材料组成和结构特征对体系热响应速率、储能密度、热膨胀行为和热循稳定性的影响机制，对复合材料进行了优化设计；（3）强化传热机理研究。采用红外热成像手段，在线监测了石墨烯相变储热复合材料的循环储热放热过程。三维多孔石墨烯宏观体高度连通的网络结构，是实现其对相变储能材料协同传热储热的结构基础；（4）将制备的石墨烯/碳管复合材料对作为相变储能材料支撑体，其大量的孔结构能吸附相变储能材料，实现增强导热的作用，同时，其与相变储热材料较好的相容性，为实现其相变潜热和热循环稳定性提供了重要保障。