Effect of alkaline pH on formation of lauric acid/SiO_2 nanocapsules via solgel process for solar energy storage

摘要

Nanoencapsulated phase change materials (NEPCMs) as typical energy storage materials can be promisingly applied in solar energy storage system. Specially, NEPCMs with small size as well as high thermal storage capacity are desired for the working fluid of solar thermal collectors. In this work, we prepared the lauric acid (LA)/silicon dioxide (SiO2) NEPCMs via the sol-gel method with the aim to obtain desired nanocapsules by optimizing the key synthetic conditions of pH. Eight samples were prepared by changing pH value from 8.9 to 12.4, and some characterization methods were used to test the performance of these samples. The results show that the nanocapsules prepared have the latent heat as high as 160.0 J/g with the particle size of 357 nm, which corresponds to the encapsulation ratio of 83.0%. Further analysis reveals that the pH range of 9.4-10.2 is suitable for the synthesis of nanocapsules with high latent heat and small particle size. Thus, pH can be identified as a vital factor which affects the preparation process as well as the performence of nanocapsules preparaed. By systemically analysing the effect of pH on the synthesis process, the role of pH in the synthetic process of NEPCMs was identified and the mechanism of synthesis for the nanocapsules was further proposed. The nanocapsules prepared in this work would have great potential for energy storage in solar thermal utilization, and the mechanism of synthesis proposed in this paper provides theoretical basis for the further improvement of nanocapsules.