Microencapsulation of Zn-10 mass% Al alloy phase change material via dry synthesis method

Thermal energy storage (TES) via latent heat storage (LHS) using metal alloy phase change material (PCM) offers advantages in medium-to-high temperature operation around 400 degrees C and high heat storage capacity. Microencapsulation of alloys as PCMs can mitigate issues of reactivity and improve handling properties of PCM. This research presents the novel development of microencapsulated PCM (MEPCM) with a core of Zn-10 mass% Al that operates around 400 degrees C. The MEPCMs were synthesized using high-speed impact blending (HIB), where fine AlOOH particles mechanically coat the surface of Zn-10 mass% Al alloy microspheres, resulting in robust surface modification. Subsequent heat-oxidation treatment at 800 degrees C was performed to obtain stable oxide coating. The HIB treatment resulted in an AlOOH coating containing Zn nanoparticles, which the heat-oxidation process transformed into alpha-Al2O3 and ZnO nanoparticles. The MEPCMs exhibited heat storage densities, including latent and sensible heat (Delta T=200 degrees C), that were 1.9 times higher than the capacity of solar salt, which is commonly used as a sensible heat storage material. Furthermore, the MEPCMs maintained their shape and latent heat capacity after 300 and 1000 cyclic tests. These superior MEPCM characteristics hold the potential to significantly advance the development of LHS-based TES systems operating around 400 degrees C, with applications in energy generation and industrial processes.