Calcium Chloride Hexahydrate/Diatomite/Paraffin as Composite Shape-Stabilized Phase-Change Material for Thermal Energy Storage

摘要

In this work, the calcium chloride hexahydrate/diatomite/paraffin composite phase-change material (PCM) was fabricated by impregnating calcium chloride hexahydrate into diatomite and further coating with paraffin. Scanning electron microscope (SEM) results showed that the hydrated salt could be impregnated into a diatomite well and the paraffin could be coated on a diatomite surface. The Fourier transform infrared spectroscopy (FT-IR) demonstrated that no chemical interactions were found between calcium chloride hexahydrate and diatomite matrix except that of hydrogen bonds. The melting and crystallizing enthalpy of the coated composite PCM are 108.2 and 98.5 J/g, respectively. The supercooling of hydrated salts was weakened due to the nucleation positions on the huge surface of diatomite and the coating effect of the paraffin, and phase segregation was eliminated in 100 cycles by microvolume effect in the pores of the diatoniite. Additionally, coated composite PCM and composite PCM exhibited better thermal stability and reliability than hydrated salts due to the interactions of hydrated bonds, the capillary force and the surface tension as well as the coating of the paraffin. After the 100 cycles, the melting and crystallizing enthalpy of coated composite PCM declined to 106.2 and 93.8 J/g from 108.2 and 98.5 J/g, dropping by 1.8% and 4.8%, respectively. The coated composite PCM with well thermal properties, thermal reliability, and chemical stability was a promising PCM candidate for heat-energy storage applications.