Fabrication and Properties of Microencapsulated Paraffin@SiO₂ Phase Change Composite for Thermal Energy Storage

Abstract

In this work, a novel microencapsulated phase change composite of paraffin@SiO2 was prepared by in situ emulsion interfacial hydrolysis and polycondensation of tetraethyl orthosilicate (TEOS). The as-prepared paraffin@SiO2 composite was determined by Fourier transformation infrared spectroscope (FT-IR), X-ray diffractometer (XRD), scanning electronic microscope (SEM), and transmission electron microscopy (TEM), respectively. The results showed that the paraffin@SiO2 composite is composed of quasi-spherical particles with diameters of 200–500 nm. The paraffin is encapsulated in a SiO2 shell, and there is no chemical reaction between them. The DSC results indicate that the melting temperature and latent heat of the composite are 56.5 °C and 45.5 J/g, respectively. The encapsulation ratio of paraffin was calculated to be 31.7% from the results of the DSC measurements, slightly lower than the loading content (32.5%) of paraffin in the microencapsulated composite from the TGA measurements. The as-prepared paraffin@SiO2 composite could maintain its phase transition perfectly after 30 melting–freezing cycles, and no leakage of paraffin was observed at 70 °C for 20 min. Moreover, the high heat storage capability and good thermal stability of the composite enable it to be a potential material to store thermal energy in practical applications.