Novel low-cost steel slag porous ceramic-based composite phase change material: An innovative strategy for comprehensive utilization of steel slag resources

This work creatively proposes a novel and low-cost steel slag porous ceramic (SSPC)-based NaNO3 salt composite phase change material (PCM) using industrial solid waste steel slag as the main raw material. In this study, the foaming-gel casting process prepares SSPC with high porosity (77–83%) and mechanical strength (0.36–1.13 MPa), which shows good adsorption of NaNO3 salts. The spontaneous infiltration method prepares and characterizes the NaNO3/SSPC composite PCM by performance properties. The results show that the NaNO3 salt is uniformly adsorbed in the pores of SSPC with good chemical compatibility, and the maximum filling rate reaches 86.26%. The porous media can effectively prevent the leakage of molten NaNO3 salt. The prepared composite PCMs have lower melting and freezing temperatures, lower subcooling by 5.47 °C, and higher thermal conductivity by 121.6% compared to pure NaNO3 salt. The latent heat retention of the composite after 50 thermal cycles is more than 96%, with good thermal reliability. Finally, a prospective process of using steel slag to prepare composite PCMs for collecting and storing waste heat from the steel industry is proposed. Reusing steel slag and storing waste heat from the steel industry are realized, both beneficial for sustainable development.