Fabrication and Properties of a Thermal Conduction-Enhanced SiO2–Ag Double-Shell Nanoencapsulated Lauric Acid Phase Change Material

To significantly improve the thermal conductivity of nanocapsule shells, lauric acid (LA)/SiO₂–Ag composite shell phase change nanocapsules are synthesized via sol–gel and chemical reduction methods. Three types with varying Ag shell thicknesses are obtained, showing particle sizes of 946–982 nm, latent heat of 21.59–59.81 J g⁻¹, and volume encapsulation ratio ($R_V$) of 63.78–86.96%. After 1000 thermal cycles, the latent heat decay is only 1.87%, indicating good thermal reliability. Specifically, a detailed porosity correction is performed, and the corrected effective thermal conductivity of LA/SiO₂–Ag nanocapsules is 22.11–80.04 W (m K)⁻¹, indicating that the thermal conductivity of LA/SiO₂–Ag nanocapsules is significantly improved. Furthermore, a 1D unsteady-state thermal conduction device tested the heat transfer performance of stacked nanocapsules. The results demonstrate that LA/SiO₂–Ag nanocapsules exhibit a significantly faster heat transfer rate than LA/SiO₂ nanocapsules, reducing heat transfer time by 108.1%. The simulation results further reveal that the Ag shell facilitates interfacial heat transfer in stacked nanocapsules, allowing heat to propagate rapidly from the bottom to the top. Additionally, for single nanocapsules, the high thermal conductivity of the Ag shell promotes uniform inward heat transfer, expediting phase transition and enhancing thermal performance.