Macroencapsulation and in-situ formed Al-Cu-Si ternary alloy phase change materials for high-temperature heat storage

Aluminum alloys hold great promise for high - temperature thermal storage, thanks to their high latent heat density and thermal conductivity. However, leakage and corrosion issues act as significant constraints on their practical application. This study developed Al-Cu-Si@Al₂O₃ macrocapsules via in-situ powder alloying and direct encapsulation. Al, Cu and Si powders at certain proportion were mixed to create the ternary alloy phase change core sphere, which was then coated with Al₂O₃ ceramic shell layer containing MgO sintering additives. A two-step sintering formation process was used to prepare the Al-Cu-Si@Al₂O₃ macrocapsules with cavities between the shell and core. Thermal physical tests were conducted on PCMs with different Al-Cu-Si mass ratios. The results showed that the phase change temperature and latent heat capacity of 65Al-30Cu-5Si were 521.2 °C and 348.2 J/g, respectively. Isostatic compression (200 MPa) enhanced thermal storage density, achieving 308 J/g and 749 J/cm³ between 500 and 600 °C. Post 200 thermal cycles in air, the macrocapsules maintained structural integrity without performance degradation. This design combines high energy density, thermal stability, and corrosion resistance, demonstrating potential applications in industrial high-temperature thermal storage systems.