Development of a novel Al-Si microcapsules with heat-resistant, high latent heat, and efficient solar heat absorption

Abstract

Aluminum-silicon (Al-Si) alloys are prominent in high-temperature thermal storage due to their high thermal storage density, thermal conductivity, and low cost. Despite their potential, the corrosivity and chemical activity from their liquid phase leakage limit broader applications. The hydrothermal method, often used for encapsulating Al-Si into microencapsulated phase change materials (MEPCMs), consumes the core material, reducing latent heat values. Additionally, the inability to modify the shell material fails to meet multifunctional demands. Addressing solar thermal application needs, we developed a novel heat-resistant, high-latent-heat Al-Si MEPCMs using a “double-layer coating, sacrificial inner layer” approach. This method, originally proposed by our research group and first extended to the microencapsulation of high-temperature phase change materials (PCM), uses Al-12Si as the core, PMMA as the sacrificial layer, and SiO2 as the outer shell.The MEPCMs demonstrated an encapsulation efficiency of 90.7 % and a latent heat value of 454.9 J/g. By adjusting the core–shell ratio, the size of the internal void was optimized to enhance thermal performance and cyclic stability, with MEPCM-S3 maintaining 98.6 % of its latent heat (439.5 J/g) after 10 thermal shocks and 300 thermal cycles. Furthermore, surface loading of carbon black (CB) enhanced the spectral absorption rate to 87.72 % in the 200–2500 nm range, marking an 11 % increase. These modifiable, high-latent heat, and cycle-resistant Al-Si MEPCMs hold broad prospects for applications in high-temperature thermal storage and as next-generation efficient solar energy storage media.