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.