纳米胶囊智能可调相变材料的制备及蓄热特性基础研究

Energy storage plays an important role in reducing CO2 emissions and solving the energy shortage. Moreover, the efficiency of energy storage system is usually low due to the poor thermal conductivity of phase change material(PCM). Thus, the study on heat transfer performance of PCM is essential and crucial. Based on the previous work, the nano-encapsulated smart tunable composite were prepared to improve the thermal conductivity and heat transfer of PCM. We achieved the intercalation of different types of organic PCMs inside carbon nanotubes (CNTs) by means of self-sustained diffusion followed by a proper rinsing at normal temperature and pressure. The study includes the preparation technology, morphology, heat transfer performance, heat storage capacity, working stability and long term performance of nano-encapsulated composite. Meanwhile, the intercalation mechanism and the energy storage mechanism was discussed. Through the research, a novel nano-encapsulated composite phase change material is developed, which has a rapid thermal response, a tunable phase change temperature, a high heat storage density, a favorable reversible phase change and a long service life. It opens new opportunities for PCMs attracting attention in the field of energy saving and environmental protection, energy storage, temperature regulation, and so on.

强化相变材料传热性能以提高储能系统效率，对减少CO2排放和解决能源短缺具有重要的科学意义和实用价值。申请人在原有工作基础上，将有机烷烃相变材料（PCM）向碳纳米管（CNTs）管内填充，制备成智能可调的相变纳米胶囊，以强化PCM的导热和相变传热性能。深入研究常温常压下溶质连续自扩散嵌入碳纳米管的胶囊化技术，研究基于此技术制备的CNTs/PCM复合相变蓄热材料的制备工艺、形貌、相变传热性能、蓄热能力、工作稳定性和长期使用性能，并研究PCM向CNTs管内自扩散的填充机理，阐述该类材料的储能机制。在此基础上开发出热响应迅速、相变温度可调、储热密度高、相变可逆性好、使用寿命长的新一代纳米胶囊型复合相变蓄热材料，拓宽其在节能环保、能源储存、温度调控等相关领域中的应用。

本文采用真空渗透法，将相变材料石蜡和月桂酸进行碳纳米管（CNTs）的管内填充，制备了纳米胶囊相变蓄热材料，CNTs管内石蜡和月桂酸的质量百分比分别为16.24%和8.47%。由于纳米受限空间效应，石蜡和月桂酸进入CNTs管内后的相变温度均低于纯相变材料。与将空的碳纳米管添加到导热油中相比，添加石蜡纳米胶囊相变材料到导热油中作为热界面材料时，具有更好的控温能力。分子动力学研究结果说明，与自由状态下杂乱无章的形貌不同，正二十六烷烃分子在纳米尺度受限空间中呈现靠近碳纳米管的环状结构。当温度保持不断上升时，通过碳原子随机热运动，碳纳米管中的烷烃分子有序性下降，即相变材料的熔化过程为一有序度降低的过程。高有序性、 CNTs对烷烃分子的受限作用是导致纳米胶囊相变材料相变温度降低的重要原因，验证了实验数据。烷烃分子的填充度会影响烷烃分子在管内的分布、有序度和扩散性质，填充数目增加会在管内形成多层环状结构，但CNTs的手性对以上参数影响不大。本研究成果获得了纳米胶囊相变材料在纳米尺度受限空间条件下的热物理性质变化规律，对有机相变材料在微电子冷却领域作为热界面导热材料的应用进行了探索，为其实际应用提供了参考依据。