Preparation and characterization of steel slag-based low, medium, and high-temperature composite phase change energy storage materials

In this study, industrial solid waste steel slag was used as supporting material for the first time, and polyethylene glycol (PEG), sodium nitrate (NaNO3), and sodium sulfate (Na2SO4) were used as low, medium, and high-temperature phase change materials (PCMs). A series of shape-stable composite phase change materials (C-PCMs) were prepared by vacuum impregnation and mixing-sintering methods. The morphology, thermal properties, and thermal reliability of C-PCMs were characterized by scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FT-IR), and differential scanning calorimetry (DSC). The results show that the three PCMs are uniformly dispersed in the pores of steel slag, and the maximum loading is 35 %, 40 %, and 50 %, respectively, and they have good chemical compatibility with steel slag. Compared with their pure PCMs, the three prepared C-PCMs showed a reduction in subcooling of 2.64 °C, 4.53 °C and 0.79 °C, respectively, and an increase in thermal conductivity of 172 %, 54.9 % and 82.4 %, respectively, all with good phase change thermal storage properties. Even after 100 thermal cycles, the latent heat retention rate was more than 97 %, which had good thermal reliability. Therefore, it can be concluded that the three kinds of low, medium, and high-temperature C-PCMs have considerable application potential in different temperature areas, such as building latent heat storage, solar energy storage systems, and industrial waste heat recovery system.