Fabrication and characterization of nano-additives modified microencapsulated phase change materials with high thermal conductivity for thermal energy storage

Microencapsulation technology solves the problems that phase change materials (PCM) are easy to leak, difficult to transport, and vulnerable to contamination. However, the shell materials are mostly organic materials with low thermal conductivity, which limits their specific application in the field of thermal energy storage. In this regard, in order to enhance the thermal conductivity, a novel type of microencapsulated phase change materials (MicroEPCM) based on an n-eicosane core and a phenol-formaldehyde resin shell modified by nano-BN and nano-SiC, respectively, were fabricated via in-situ polymerization method. The effect of the mass fractions (2, 4 and 6 wt%) of nano-additives on the performance of MicroEPCM-BN and MicroEPCM-SiC was systematically investigated. The morphology, chemical structure and thermal properties of modified MicroEPCM were characterized by SEM, FTIR, XRD and DSC, respectively, to determine the optimum incorporation of nano-additives. Conclusions are as follows: modified MicroEPCM still had a spherical morphology with an average particle size range of 2–8 μm. Furthermore, the addition of nano-additives significantly improved the thermal conductivity of MicroEPCM, and the thermal conductivity gradually increased with the progressive increase in nano-additives content. MicroEPCM-4%BN and MicroEPCM-6%SiC had the best overall performance with phase change enthalpies of 145.83J/g and 131.30J/g, respectively, and the thermal conductivity increased by 61 % and 97 %, respectively, compared to that of MicroEPCM without nano-additives. They also showed excellent thermal cycling and degradation stability. Consequently, MicroEPCM modified by nano-additives will have great potential for thermal energy storage applications.