Preparation and properties of Ag nanoparticle-filled expanded graphite paraffin-based composite phase change materials with high temperature response properties

Paraffin wax (PW), despite being an excellent energy storage material, suffers from limited applications due to its low thermal conductivity and propensity for liquid-phase leakage. In this study, PW is employed as the phase change material (PCM), expanded graphite (EG) serves as the support material, and silver nanoparticles function as additives to enhance thermal conductivity. Silver-modified expanded graphite (Ag@EG) is synthesized through a liquid-phase reduction process. Subsequently, composite PCMs of Ag@EG/PW with varying mass ratios, which exhibit high thermal conductivity and stability, are fabricated via a vacuum impregnation method. Characterization techniques, including SEM, FTIR, XPS, and SEM-EDX, confirm the existence of Ag in EG in the form of well-dispersed elemental silver. XRD analysis demonstrates the favorable chemical compatibility of the composite PCMs. The prepared composite PCMs all possess a latent heat exceeding 110 J/g. Specifically, the thermal conductivity of the 1wt%Ag@10wt%EG/PW composite PCMs reaches 0.989 W/(m·K), representing a 292.5 % enhancement compared to PW. Additionally, this composite material exhibits excellent thermal cycling stability, anti-leakage properties, and temperature responsiveness. In conclusion, this research is expected to pave the way for the application of Ag@EG/PW composite PCMs in fields where high temperature sensitivity is required.