Preparation and thermal properties of stearic acid/diatomite composites as form-stable phase change materials for thermal energy storage via direct impregnation method

Stearic acid/diatomite composite form-stable phase change materials (PCMs) have been prepared by using a direct impregnation method without vacuum treatment. The surface morphology, chemical compatibility, thermal properties and thermal stability were characterized by scanning electron microscopy, Fourier transform infrared spectrometer and X-ray diffraction (XRD), differential scanning calorimeter and thermogravimetric analysis (TG), respectively. The results show that there are only physical interactions between stearic acid and diatomite in composite PCM. XRD analysis reveals that crystal type is not affected by composite technology of SA/diatomite composite form-stable PCM with decrease in crystal size due to the limited pores in diatomite. The melting and freezing temperatures of stearic acid/diatomite composite, respectively, are 52.3 and 48.4 °C. The latent heat of SA/diatomite composite reaches 57.1 J g−1, potential to be used in a practical application. TG result indicates that the decomposition of SA/diatomite composite starts at 192 °C, implying that the SA/diatomite has a good thermal stability.