Using steel slag and fly ash solid wastes to fabricate ceramics-based phase change composites with excellent mechanical and thermal properties applied in thermal energy storage.

Developing low-cost phase change composites (PCCs) with high performance is of significant importance in thermal energy storage. Herein, four PCCs were prepared with steel slag-fly ash solid wastes and eutectic salt (NaNO 3 -KNO 3), i.e., pure fly ash based PCC (pFA), pure steel slag based PCC (pSS), steel slag-fly ash based PCC (DSWM), and steel slag-fly ash-kaolin based PCC (HPCP). First, the optimal ratios of raw materials were predicted using the Facility for the Analysis of Chemical Thermodynamics (FactSage) software. Then, the composite's mechanical, thermal, and cyclic properties were characterized. The results indicate that the HPCP composite presents superior mechanical properties, with compressive strength and Young's modulus of 43.84 and 10563.86 MPa, respectively. Its thermal conductivity is 1.203 ± 0.054 W m−1 K−1, and after 40 thermal cycles, the mass and thermal conductivity decrease by 1.7 % and 5.2 %, respectively. The excellent properties of HPCP were due to the formation of a high-purity anorthite ceramic crystalline phase in PCC, which could minimize the defects of the porous medium, and reduce the leakage of encapsulated molten salts, thus enhancing the mechanical properties and cyclic thermal stability of the HPCP. This study can provide important guidance in preparing low-cost PCCs with industrial solid wastes. [Display omitted] [ABSTRACT FROM AUTHOR]