Preparation and Properties of Stearic Acid–Acetanilide Eutectic Mixture/Expanded Graphite Composite Phase-Change Material for Thermal Energy Storage

In this study, a series of binary mixtures of stearic acid (SA) and acetanilide (AA) at various mass fractions was prepared. A binary mixture of SA and AA with a ratio of 81.0:19.0 mol % is a eutectic mixture with a melting temperature of (342.45±0.25) K and a melting latent heat of (220.04±10.02) J g −1 . To improve the thermal properties of the SA–AA eutectic mixture to obtain a composite phase-change material (CPCM) with a high thermal conductivity, large heat storage capacity, and good thermal stability and reliability for heat energy storage, expanded graphite (EG) at different mass fractions was added into the SA–AA eutectic mixture. The resulting material exhibited a remarkable energy storage capacity with a latent heat of 176.14 J g −1 . The thermal conductivity of the CPCM was enhanced by 14.5 times compared to that of the SA–AA eutectic mixture. The thermophysical properties of the SA–AA/EG CPCM after 100 accelerated thermal cycles were slightly decreased, which did not influence the heat storage. Thus, the prepared SA–AA/EG CPCM is a promising material for latent heat storage systems.