埃洛石纳米管表面微孔结构的构筑及其复合储热相变材料的制备

Phase change materials play an important role on the scientific, reasonable and efficient utilization of energy. In present work, we transform natural halloysite nanotubes into metal/porous nanotubes through surface etching and modification method. The structure of metal/porous nanotubes is highly suitable for encapsulating the organic phase change materials, which can overcome some unprecedented problems in the practical application, such as unfeasible encapsulation, poor thermal conductivity, high cost and so on. First, we use the alkalescent molten salt system with appropriate eutectic point to etch SiO2, Al2O3 selectively and fabricate porous structure controllably on the surface of halloysite nanotubes. The porous structure of nanotubes can improve encapsulation ability for the phase change materials. Secondly, the porous halloysite nanotubes are modified by silane coupling agents to absorb more metal cations onto the surface, and the metal cations are further chemically reduced into metal nanocrystallines loaded on the nanotube surface, which can improve their thermal performance. Finally, the phase change materials are encapsulated in the lumen of metal/porous halloysite nnaotubes in vacuum condition. The etching reaction mechanism of molten salt system is elucidated and extended to an applicable etching method to fabricate microporous materials for silicate materials. The adsorption and diffusion mechanism of organic phase change materials into lumen of halloysite nanotubes is invesgated to prepare a new kind of composite phase change material with high thermal storage density and thermal conductivity. The results of this study are hoped to provide some theoretical guidance for applications of halloysite nanotubes in the field of thermal storage.

相变储热材料研究对于能源的合理、高效利用有重要意义。课题以天然埃洛石纳米管为结构单元，对其表面进行刻蚀和修饰形成复合金属/多孔纳米管，用其封装相变材料，解决以往有机相变材料存在的封装难、导热性差、成本高等问题。首先，选择适当弱碱性的混合熔盐体系，对埃洛石纳米表面SiO2,Al2O3进行选择性刻蚀，在埃洛石纳米管表面形成可控的多孔结构，提高其对相变材料的封装能力；其次，通过对多孔埃洛石纳米管表面改性，使金属阳离子能够富集到其表面，然后用化学方法将金属阳离子还原成纳米晶负载到纳米管表面，提高其导热性能；最后，采用真空吸附法制备埃洛石复合相变材料。研究混合熔盐体系刻蚀埃洛石纳米管的反应机理，提供一种适用于硅酸盐材料表面微孔构筑的新方法；研究有机相变材料在金属/埃洛石纳米管内的扩散、吸附行为，形成一种高储热密度、高导热性能的新型相变复合材料，为埃洛石纳米管在储热领域应用提供理论依据。

相变储热材料的制备对于热能、太阳能的合理、高效利用非常重要。为了使相变材料和埃洛石纳米管的复合材料能够实际应用，需要解决其封装难、导热性差等问题。本研究中采取的办法如下：首先，选择适当弱碱性的混合熔盐体系，对埃洛石纳米表面SiO2,Al2O3进行选择性刻蚀，在埃洛石纳米管表面形成可控的多孔结构，提高其对相变材料的封装能力；其次，通过对多孔埃洛石纳米管表面改性，使金属阳离子能够富集到其表面，然后用化学方法将金属阳离子还原成纳米晶负载到纳米管表面，提高其导热性能；最后，采用真空吸附法制备埃洛石复合相变材料。 本研究提供了对硅酸盐材料表面微孔构筑的新方法，同时制备了高储热密度、高导热性能的新型相变复合材料， 为埃洛石纳米管在储热领域应用提了供新的思路。