无机盐高温相变微胶囊在高温环境下结构和热物性演化研究

The energy storage technologies can not only promote the development of clean energy, but also enhance the energy efficiency, being one of the significant fields of energy storage in future. High temperature phase change materials are one of the important thermal energy storage materials at high temperature and used for concentrating solar power technologies and industrial waste heat recovery. The energy storage efficiency of inorganic salt high-temperature phase change materials will be greatly enhanced when the inorganic salt high-temperature phase change materials are prepared into inorganic salt high-temperature phase change microcapsule (ISHPCM), and the ISHPCM can be used more conveniently and widely.. The present research focuses on the evolution of the structure and thermal properties of ISHPCM at high temperature. The proper shell structure design of ISHPCM will be done to resist volume expansion and corrosion of fused inorganic salts. The influence of different preparing methods, such as spray drying and solvent evaporation, on the structure and thermal properties of ISHPCM will be studied. The transformation mechanism of ISHPCM shell made of ceramic precursor resin from organic resin structure to inorganic ceramic structure will be investigated. The effects of volume expansion and corrosion of fused inorganic salts on the ISHPCM shell structure will be researched. The influence of phase change cycles on the structure and thermal properties of ISHPCM will be studied and the corresponding variation will be confirmed. The significance of the project lies in obtaining a new high-temperature phase change microcapsule with excellent performance and the evolution of the structure and thermal properties of ISHPCM at high temperature, which will provide significant application basics knowledge.

储能技术既可以推动清洁能源发展，又能提高能源利用效率，是未来能源技术发展的重要方向之一。无机盐高温相变材料是一种重要的高温热能储存材料，用于太阳能热发电和工业余热回收等领域。将无机盐高温相变材料制备成微胶囊可以极大地提高其储热效率，增加其使用便捷性，拓展其应用领域。本项目以获得无机盐高温相变微胶囊在高温下的结构和热物性演化规律为目标，设计结构合理的防膨胀耐腐蚀无机盐高温相变微胶囊壳体，探索喷雾干燥法、溶剂挥发法等不同制备方法对微胶囊结构和热物性影响，揭示陶瓷前驱体树脂制成的微胶囊壳体在高温下从有机树脂结构转化为无机陶瓷结构的转化机制，探究熔融无机盐的体积膨胀和腐蚀性对微胶囊壳体结构的影响，研究相变循环对微胶囊结构和热物性的影响，明确其变化规律。项目的意义在于获得一种新型的高性能高温相变微胶囊，并揭示其在高温下的结构和热物性演化规律，为促进储能技术发展提供重要的应用基础知识。

以无机盐高温相变材料NaNO3 为微胶囊芯材，以陶瓷前躯体树脂为壳体材料，采用溶剂萃取和超声分散相结合的方法制备出了无机盐高温相变微胶囊。采用扫描电子显微镜、差示扫描量热仪、光学显微镜、红外光谱等分析手段，表征了该微胶囊的结构和热物性。结果显示，该微胶囊相变温度为306℃，相变焓值约为159kJ/kg，该相变微胶囊壳体很薄，相变芯材占微胶囊的质量分数达到85%，NaNO3 相变微胶囊的熔点几乎不变，其凝固点比纯NaNO3 的凝固点低2.57 ℃。微胶囊中的硝酸钠的热稳定性提高，表现为分解温度提高了36℃。通过二次微胶囊化，提高了MCP-NaNO3的热稳定性。该微胶囊在250-350℃经过80次相变热循环后，热物性稳定，其相变焓值只有小幅下降，从136.1 降到125.3 J/g。在500℃以前，该微胶囊的热物性是较为稳定的，其相变焓值从136.1降到130.3J/g。为了制备相变点和相变焓值更高的相变微胶囊，选择LiCl作为微胶囊芯材，LiCl微胶囊的相变点为604.32 ℃，相变焓值为308.9 J/g。LiCl微胶囊的的过冷度为-1.20 ℃，这表明LiCl微胶囊在降温过程中能够及时地释放出其储存的热量。LiCl微胶囊在650 ℃加热后无相变材料泄露。此外，通过对80次热循环前后的二次微胶囊化的NaNO3微胶囊的截面结构进行元素线扫描和面扫描分析，更加直接地给出了微胶囊壳体和相变材料的分布，证明了相变循环前后PHPS树脂壳体严密地包裹在相变芯材表面。该研究为高温相变微胶囊的制备提供了一种简单有效的制备方法，适用于微胶囊的大批量制备，为高温相变材料在相变储能领域和相变热控领域的应用提供了重要技术支撑。