A brief strategy for designing self-encapsulated Al-Si base phase change materials with high thermal energy storage performance

This paper reports a brief strategy for self-encapsulated Al-Si base phase change materials with high thermal energy storage performance using the hydrogen generation products of Al-Bi-Si alloy composite powders. Firstly, Al-10Bi-4Si (wt%) alloy composite powders were prepared through high-pressure gas atomization processing. These composite powders were hydrolyzed in distilled water at 40 degrees C for producing hydrogen. Secondly, hy-drolysis products were calcined under high-temperature nitrogen to prepare Al-Si base phase change materials with an Al2O3 protective layer. The results show that hydrogen generation products still maintain good sphericity after the hydrolysis reaction, which is conducive to obtaining a large amount of Al-Si thermal energy storage medium. The prepared materials have a thermal energy storage density of 117.3 J/g-240 J/g. In the hydrolysis reaction, the powder surface can continuously react with water, forming an Al(OH)3 layer that tightly covers the unreacted part of the powder. After calcination, the formation of the Al2O3 layer realizes the self-encapsulation of phase change materials. During thermal cycles, the Al2O3 protective layer of the phase change materials has a strong ability to withstand thermal stress which is caused by volume expansion at high temperatures; this maintains good thermal energy storage performance under thermal cycles over hundreds of hours. This research is expected to provide a basis for the large-scale production of Al-Si base phase change materials and obtain hydrogen energy during this process.