多孔碳基定形相变复合体系的热性能与温控相变机理

Nowdays, the enhancement of the thermal properties of phase change materials to utilize the energy in more efficient way is of great importance in the energy field. Based on the purpose of better utilization of the solar energy and industrial waster heat, new phase change heat control systems are built in this project by introducing the porous carbon with special structures to the organic phase change materials. The efficiency of heat utilization is greatly improved on the basis of the enhancement of the heat storage and release property of solid-liquid phase change materials. The effect of different carbon materials types on the heat storage and release performance of the composite phase change systems are studied to select a more efficient one to improve the thermal stability, recycling, conductivity and latent heat of phase change etc. The influence of the porous structure and surface properties of the porous carbon matrices on phase equilibrium are studied to reveal the effect rules of the confined crystallization effect and small size effect within the pore channels on the heat storage and release performance, phase change rate and crystal structure of solid-liquid phase change heat control systems. And then the mechanism of temperature control phase change in this special environment is clarified. Based on above effect rules and phase change mechanism under the porous confinement for the shape-stabilized composite phase change systems, the application technology of the phase change heat control systems can be optimized solving the problems of easy leakage and low thermal conductivity of the organic solid-liquid phase change materials and broadening its applications in the temperature control and energy saving fields.

借助相变材料的控热性能提高能源使用效率是当前能源领域的重要研究方向；本项目中，以太阳能、工业余热和废热等能量利用为导向，将具有特殊结构的多孔碳材料引入到有机固-液相变材料中构筑新型相变控热体系，在提升固-液相变材料储-放热性能的基础上，实现对热能利用效率的大幅提高。通过研究不同类型的碳材料对复合相变控热体系储-放热性能的影响规律，筛选出最有效能的碳多孔材料，从而提升该控热体系的热稳定性、热循环性、热传导性、相变潜热等性质。研究多孔碳基质结构和表面性质对相平衡的影响规律，揭示孔道内的受限结晶效应、小尺寸效应对固-液相变控热体系储-放热性能、相变速率和晶体结构的影响规律，阐明此特殊环境下的温控相变机理。基于定形相变复合体系的储-放热性能的变化规律和多孔限域下的相变原理， 优化该定形相变控热体系的应用技术，解决有机固-液相变材料易泄漏、导热率低的技术瓶颈问题，拓宽其在体系控温和节能领域的应用。

借助相变材料的控热性能提高能源使用效率是当前能源领域的重要研究方向；本项目中，以太阳能、工业余热和废热等能量利用为导向，将具有特殊结构的多孔碳材料引入到有机固-液相变材料中构筑新型相变控热体系，在提升固-液相变材料储-放热性能的基础上，实现对热能利用效率的大幅提高。通过研究不同类型的碳材料对复合相变控热体系储-放热性能的影响规律，筛选出最有效能的碳多孔材料，从而提升该控热体系的热稳定性、热循环性、热传导性、相变潜热等性质。研究多孔碳基质结构和表面性质对相平衡的影响规律，揭示孔道内的受限结晶效应、小尺寸效应对固-液相变控热体系储-放热性能、相变速率和晶体结构的影响规律，阐明此特殊环境下的温控相变机理。基于定形相变复合体系的储-放热性能的变化规律和多孔限域下的相变原理， 优化该定形相变控热体系的应用技术，解决有机固-液相变材料易泄漏、导热率低的技术瓶颈问题，拓宽其在体系控温和节能领域的应用。研究发现，采用的11种多孔碳载体基质中，在复合相变材料保持定形时使PEG含量最高（90wt%）的基体有：膨胀石墨（EG）、有序介孔碳（CMK-5）、泡沫碳（CF）、含不同取代基（-NH2、-COOH、-OH）的多壁碳纳米管（MWNTs-x）和本征碳纳米管（MWNTs），相变焓相对较高的样品有90wt%PEG2000/CF（△Hm = 168.4 J•g-1，△Hc = 168.5 J•g-1）和90wt%PEG6000/EG（△Hm= 156.6 J•g-1，△Hc = 151 J•g-1），复合相变材料中PEG与多孔碳基质的相互作用涉及毛细力、表面张力和氢键作用，为PEG结晶度和相变行为的主要影响因素。