Systematic investigation on preparation and characterization of silica shell microencapsulated phase change materials based on sodium silicate precursor

A kind of paraffin@silica (Pn@SiO2) microencapsulated phase change materials (MEPCM) were prepared by sol-gel method using sodium silicate as silica precursor. The investigation of this synthesis technique demonstrates that pH value and core/shell ratio play key role in optimizing the morphology and microstructure of Pn@SiO2 microcapsules to achieve optimal thermal storage properties. Therefore, we systematically investigated the effects of pH value and core/shell ratio on the microstructure, crystallization behavior and phase transition properties of Pn@SiO2. It was determined that at pH 3 and Pn/SiO2 ratio of 5:1, the synthesized Pn@SiO2 exhibited well-defined core-shell structure and regularly spherical morphology. The encapsulation rate reached 74.14 % with latent heat of about 186.4 J/g due to the formation of perfect microstructure and morphology. In addition, Pn@SiO2 presents excellent heat storage capacity, high thermal stability and good shape stability, and shows reliable and durable phase-change performance. In summary, sodium silicate was used as the SiO2 precursor for the first synthesis of MEPCM with high encapsulation rate and regularly spherical morphology.