Stearic acid hybridizing coal–series kaolin composite phase change material for thermal energy storage

This paper aimed at developing a novel form-stable composite phase change material (PCM) by using stearic acid (SA) to hybridize coal–series kaolinite (Kc) via vacuum impregnation method. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The thermal properties of the composite were characterized by using differential scanning calorimetry (DSC) and thermal cycling test analysis technique. Natural kaolin (K) was also used as the support to make further investigation on the thermal properties of the kaolinite-based composite PCM. The crystallinity of SA in SA/Kc (90.1%) was higher than that of SA/K (84.9%). The SA/Kc composite showed an enhanced thermal storage capacity compared with the SA/K composite. The latent heats of melting (66.30 J/g) and freezing (65.60 J/g) for SA/Kc were higher than those of SA/K sample (59.25 and 59.01 J/g, respectively). Furthermore, the SA/Kc composite PCM showed an excellent stability after up to 200 thermal cycling. The corresponding mechanism was discussed in detail.