Core-Shell structural SiO2@C microspheres enhanced thermal properties and electromagenetic wave absorption performance of PU phase-change composites for thermal management

Composite structures featuring low density, high thermal conductivity, and high mechanical strength have been developed to address the liquid leakage problem in organic phase change materials (PCMs) and to improve their thermal conductivity, thereby broadening their applications in thermal regulation and energy conversion. In this work, core-shell structured SiO ₂ @C microspheres were synthesized via a sol-gel method and incorporated into polyurethane (PU) to form SiO ₂ @C composite PCMs, with polyethylene glycol (PEG) encapsulated within the cross-linked PU network. The resulting composite demonstrates excellent phase-change behaviors, with melting and freezing enthalpies of 167.56 J/g and 166.67 J/g, respectively. Additionally, it exhibits a photothermal conversion efficiency of 90.43%. In terms of electromagnetic wave absorption, the PU/SiO ₂ @C-2 composite achieves a minimum reflection loss of -20.06 dB at 16.64 GHz with a thickness of 7.76 mm, and an effective absorption bandwidth of 4.42 GHz. These results highlight its multifunctional integration of thermal energy storage and electromagnetic wave absorption properties. This design overcomes the single-function limitation of conventional PCMs, offering a multifunctional solution for compact electronic devices that combines efficient thermal management with broadband electromagnetic protection.