十水硫酸钠/膨胀蛭石薄膜复合相变材料的制备及性能分析

Preparation and performance analysis of sodium sulfate decahydrate/expanded vermiculite film phase change composite

利用膨胀蛭石(EV)丰富的孔隙结构,采取真空吸附法和薄膜真空封装技术制备了一种十水硫酸钠/膨胀蛭石薄膜复合相变材料(简称薄膜相变材料)。用扫描电子显微技术(SEM)、X射线衍射技术(XRD)、自制温度参比相变潜热测试箱等表征测试手段,分析了薄膜相变材料的过冷和相分离等问题。结果表明,十水硫酸钠中掺入50%EV时,EV内部孔隙负载力达到饱和;在EV和硼砂共同作用下,经步冷曲线测得薄膜相变材料的过冷度为0.5℃;经薄膜真空封装后,十水硫酸钠均匀负载于EV层状结构内部,50%EV掺量的薄膜相变材料相变潜热在105 J/g以上,经300次相变循环后材料相变潜热趋于稳定,在500次相变循环后材料相变潜热保持在90 J/g以上,潜热留存率83.45%,循环性能优于常压封装下同种材料。薄膜真空封装技术获得膨胀蛭石对十水硫酸钠的良好负载效果,相变材料能够有效抑制十水硫酸钠的过冷和相分离等问题,具有较高的相变循环寿命。

The vacuum absorption and film vacuum encapsulation was utilized using the abundant pore structure of expanded vermiculite,a type of sodium sulfate decahydrate/EV film phase change composite(film phase change material).The supercooling and phase separation of film composites were analyzed by scanning electron microscopy,X-ray diffraction,and self-made temperature reference phase transition latent heat test chamber.The result shows that when 50%EV is added to sodium sulfate decahydrate,the pore loading capacity of EV reaches saturation.Also under the combined cation of EV and borax,the supercooling degree of the film phase change composite measured by step cooling curve was 0.5℃.However,after the film vacuum encapsulation,the sodium sulfate decahydrate is uniformly loaded inside the EV-layered structure.The latent heat of the film phase change composite with 50%EV content is more than 105 J/g,and it should be stable after three hundred phase change cycles.Also,after five hundred phase change cycles,the latent heat remains above 90 J/g,and the latent heat retention rate is 83.45%.The cyclic performance is better than atmospheric pressure encapsulating,and the film vacuum encapsulation can obtain a better loading effect of expanded vermiculite on sodium sulfate decahydrate.The film phase change composite can effectively inhibit the supercooling,and phase separation of sodium sulfate decahydrate,which has a high phase change cycle life.