Stearic acid/expanded graphite composite phase change material with high thermal conductivity for thermal energy storage
Ci Ao, Suying Yan, Sitong Zhao, Wenqi Hu, Long Zhao, Yuting Wu
Abstract
In this study, expanded graphite (EG) was added to melted stearic acid (SA) by the melt blending method to prepare SA/EG composite phase change material (PCM) with different ratios. EG with ultra-high porosity and large specific surface area can effectively adsorb melted SA through capillary force and van der Waals force. The results showed that when the loading amount of EG was 12 wt.%, almost no liquid leakage occurred and the composite showed excellent stability. In addition, the three-dimensional network structure of EG interconnection provides an efficient heat transfer path and reduces the thermal resistance of the interface. Therefore, the thermal conductivity of the composite was as high as 6.54 W m−1 K−1, which was 19.179 times higher than that of pure SA. Furthermore, the melting enthalpy and melting temperature of the composite were 163.35 J g−1 and 67.08 °C, respectively. X-ray diffraction and Fourier transform infrared spectroscopy shown that physical interaction instead of chemical reaction happened between EG and SA. When the mass fraction of EG is 12 wt.%, the composite PCM shows a relatively more balanced and uniform thermal image compared with SA, and the heat storage rate of the composite PCM was about 2.3 times of SA, and the heat release rate was 3.1 times of SA. In addition, the composite PCM showed excellent thermal stability, chemical stability, and cyclic stability, indicating that the working performance of the composite PCM was relatively stable within the temperature range of 100 °C.