Abstract: Al-Si alloy, a high temperature phase change material, has great potential in thermal management due to its advantages of high heat storage density and thermal conductivity. Microencapsulation of Al-Si alloy is one of the effective techniques to solve high temperature leakage and corrosion. In this paper, commercial Al-10Si alloy micro powders were encapsulated with flexible ceramic shells whose total thickness is below 1 µm by hydrothermal treatment and heat treatment in N₂ atmosphere. The compositions and microstructures were characterized by XRD, SEM and TEM. The shell was composed of AlN fibers network structure embedded with α-Al₂O₃/AlN which prevented the alloy from leaking and oxidizing, as well as had excellent thermal stability. The latent heat of microcapsules was 351.8 J g^-1 for absorption and 372.7 J g^-1 for exothermic. The microcapsules showed near zero thermal performance loss with latent heat storage (LHS)/ release (LHR) was 353.2/ 403.7 J g^-1 after 3000 cycles. Compared with the published Al-Si alloy microcapsules, both high heat storage density and super thermal cycle stability were achieved, showing promising development prospects in high temperature thermal management.

Key words: Al-Si alloy, Microcapsules, Ceramic shell, AlN fiber network, Thermal performance