Enhanced cold storage performance of Na2SO4·10H2O/expanded graphite composite phase change materials

Abstract Emerging phase change cold storage material named SBCKN tailored by sodium sulfate decahydrate (Na2SO4·10H2O, SSD), borax (B), carboxymethyl cellulose (CMC), potassium chloride (KCl), and ammonium chloride (NH4Cl), has successfully suppressed supercooling and phase separation, and its melting phase change temperature is 8.01 °C. Expanded graphite (EG) was added to improve the shape stability and thermal conduction properties of the SBCKN. The results indicated that the melting phase change temperature of SBCKN/EG5 added with 5% EG was 5.92 °C, whose melting and cooling latent heat of melt values were 99.35 J g−1 and 66.39 J g−1. Compared to SSD, the supercooling degree of SBCKN/EG5 was reduced by 18.93 °C. The thermal conductivity of SBCKN/EG5 was 0.43 W m−1 k−1, which was 1.75 times that of the SBCKN, as demonstrated in both the thermal storage and release experiment and transient temperature experiment. The crystal structure and chemical bonds of the tailored composites were further investigated, and the composites had good chemical stability, which possessed potential application in cold chain transportation. Moreover, the mechanism of the phase transition process of the SBCKN/EG composites was revealed.