Preparation and thermal properties of stearic acid-benzamide eutectic mixture/expanded graphite composites as phase change materials for thermal energy storage

A series of stearic acid (SA)/benzamide (BA) binary mixtures were prepared and demonstrated, and then the phase diagram and Tammann plot were established. The results showed that the molar fraction of SA in SA-BA eutectic mixture was 0.757. The eutectic mixture melted at 339.05 K with 200.15 J·g −1 latent heat. Expanded graphite (EG) was added to eutectic mixture to form composite phase change materials (PCMs) owing to the eutectic mixture has low thermal conductivity . It was found that the binary mixture and EG had good chemical compatibility, and the thermal conductivity of the composite with 12 wt% EG was significant increased by 12.30 times compared to eutectic mixture. Besides, the phase change properties of eutectic mixture/12 wt% EG composite phase change material (PCM) had a little change after 100 thermal cycles, and had negligible mass loss after leakage test. These results demonstrated that the composite PCM had good thermal reliability and stability. Based on the above results, the composite PCM has great potential in thermal energy storage application.