Thermal Performance and Shape Stability Evaluation of Boron Nitride and Expanded Graphite Synergy in Beeswax-Based Composite Phase Change Material

Phase change materials (PCMs) are efficient thermal energy storage materials due to their high energy density and ability to maintain a constant temperature during phase transitions. Nonetheless, the low thermal conductivity and liquid phase leakage of PCMs constrain their efficient heat transfer and widespread adoption. The development of leakage-free composite PCMs with high thermal conductivity remained a challenge. This work presents the first synergistic enhancement of thermal conductivity and shape stability of beeswax PCM with a dual-scale filler system of h-BN nanoparticles and EG microparticles that has not been reported previously in the literature. The composite containing 3 wt.% of h-BN with 10 wt.% of EG exhibited no leakage at 80°C, with a 312% enhancement in thermal conductivity and a 68.5% decrease in light transmittance. Only a minor reduction of ~12% in latent heat was noted in comparison to the base PCM. Further, the composite exhibited comparable performance after 300 thermal cycles.