Fabrication of shape-stable glycine water-based phase-change material using modified expanded graphite for cold energy storage

A shape-stable glycine water-based phase-change material (GPCM) was fabricated herein via natural adsorption using modified expanded graphite (MEG) as a porous carrier. Cetyltrimethylammonium bromide (CTAB) was introduced as a modifier on the surface of expanded graphite (EG) to synthesise MEG, which improved compatibility between EG and GPCM. Furthermore, the adsorption capacities of EG and MEG on GPCM were compared and analysed. The thermophysical properties of the as-prepared MEG/GPCM composite were evaluated using differential scanning calorimetry. Results revealed that MEG modified with 0.1 g of CTAB (MEG-0.1) had the best compatibility with GPCM and its adsorption capacity increased from 73.96% to 84.05% compared with that of unmodified EG. When the MEG content was 14%, the MEG/GPCM composite had a suitable melting temperature of −5.06 °C and high latent heat of 243.80 J/g. Moreover, the thermal conductivity was 1.836 W/(m⋅K), 216.33% higher than that of GPCM. After 100 thermal cycles, and the melting temperature and latent heat of the MEG/GPCM composite only decreased by 1.38% and 6.15% to −5.13 °C and 228.79 J/g, respectively. Thus, the prepared composites exhibited excellent thermal properties and showed great potential in the application of low-temperature cold energy storage and cold-chain transportation.