Fluoride microcapsules with high phase change temperature

Abstract

Microcapsules of high-temperature phase change materials (PCMs) with excellent heat storage capability have numerous applications. Fluoride has a higher phase change temperature and enthalpy value, confirming the significance of using fluoride as a phase change material in high-temperature applications. The authors created a novel fluoride microcapsule with a single carbon shell that can withstand volume expansion during the solid-liquid phase change at high temperatures. Initially, a phenolic resin shell was encapsulated onto the surface of the fluoride particles via a water-induced phase separation process. The phenolic resin shell was then cross-linked and carbonized to obtain the fluoride@carbon microcapsule. The structure and composition of the microcapsules were confirmed by SEM, FT-IR, EDS, TGA, and XRD results. DSC was used to evaluate the enthalpy of the microcapsules and PCMs. The magnesium fluoride@carbon (MgF2 @C) microcapsules had a high phase change temperature of 1262 ℃ and enthalpy of 718.4 kJ/kg, and the lithium fluoride@carbon (LiF@C) microcapsules had a high phase change temperature of 840 ℃ and enthalpy of 458.2 kJ/kg. The MgF2 @C microcapsules have the highest phase change temperature of any PCM microcapsule reported. The structure of the microcapsules was well preserved even after several heat-cool cycles, with no leakage detected, demonstrating excellent thermal stability. This technique can be used to create a variety of PCMs microcapsules, such as fluoride, alloy, metal, and more.