Thermophysical properties investigation of phase change microcapsules with low supercooling and high energy storage capability: Potential for efficient solar energy thermal management

Abstract

Microencapsulation of phase change materials (MPCM) is an effective way to achieve solar energy management. However, the crystallization of phase change materials (PCMs) in microcapsules will produce supercooling, which will affect the energy storage efficiency of MPCM. The incorporation of TiO2 nanoparticles into MPCM can alleviate supercooling. In this work, octadecyltrimethoxysilane (ODTMS) was used to modify the solid nucleating agent TiO2 (m-TiO2) to improve its compatibility with n-Octadecane. Then, MPCM based on m-TiO2 nucleating agent, melamine-formaldehyde resin (MF) shell material, and n-Octadecane core material was prepared. Differential scanning calorimetry (DSC) results demonstrate that the supercooling degree (ΔT) of MPCM (MPCM-02) decreases to 0 °C with a tiny level of 0.25 wt% m-TiO2, while the MPCM with unmodified TiO2 is 6.1 °C and the MPCM without nucleating agent is 4.1 °C. Besides, the phase change enthalpy (ΔHm) and encapsulation efficiency (E) of MPCM-02 remain at 183.7 J/g and 95.3 %, respectively. Finally, phase change composite materials with photothermal conversion capabilities were constructed by MXenes, MPCM, and polyurethane acrylate (PUA). When 1 wt% MXenes and 30 wt% MPCM were incorporated into PUA matrix, the thermal conductivity and surface temperature after 1200s of infrared light irradiation were 48.8 % and 8.2 °C higher than pure PUA matrix. These results demonstrate the good solar energy storage capabilities of the MPCM, which possesses promising application potential in the field of solar energy thermal management and human thermal regulation.