Shell-Driven Localized Oxide Nanoparticles Determine the Thermal Stability of Microencapsulated Phase Change Material

Not all encapsulation techniques are universally apt for every type of phase change material (PCM), highlighting the imperative for methodological precision. This study addresses the challenges of microencapsulated PCM (MEPCM) arising from the immiscible pairing of α-Al 2 O 3 nanoparticles with Sn microparticles. The high-speed impact blending (HIB) dry synthesis technique is employed, facilitating large-volume production of Sn@α-Al 2 O 3 MEPCMs. The resulting MEPCMs not only seamlessly endure 100 cycles of melting–solidification but also, with the strategic incorporation of a glass frit, exhibit remarkable thermal durability, withstanding up to 1000 melting–solidification cycles. Even under ultrafast thermal fluctuations, the α-Al 2 O 3 shell remained resilient through 100 cycles. A marked reduction in supercooling is observed, which is attributed to the formation of SnO and SnO 2 nanoparticles within the α-Al 2 O 3 crystal lattice. The atomically resolved interface dynamics between SnO 2 and α-Al 2 O 3 play a pivotal role, lowering the energy barrier for Sn nuclei formation during solidification. This affects the accelerated Sn nucleation rate, effectively suppressing supercooling. Such insights offer a deeper understanding of the interplay between nanoscale crystal lattice imperfections and their implications for energy storage applications.