Thermal conductivity enhancement of diatomite-based composite phase change materials by interfacial reduction deposition of Cu nanoparticles

Phase change materials (PCMs) with high thermal storage density and constant working temperature suffer from low thermal conductivity, hindering their large-scale application. Herein, in situ reduction deposition of Cu, a relatively inexpensive and highly thermally conductive metal, on PCM carrier has been proposed to mitigate the low thermal conductivity issue of PCMs. Specifically, through the in-situ reduction method, the copper nanoparticles (Cu NPs) are firstly deposited on the surface and in the pore channels of the carrier (i.e., diatomite). Then the Cu-deposited diatomite was used to encapsulate paraffin as PCM to prepare composite phase change materials (CPCMs). The latent heat of the prepared CPCMs reached 78.6 J/g, and the associated thermal conductivity reached 0.561 W m(-1) K-1, which is 97.5 % and 48.9 % higher than that of paraffin and paraffin/diatomite, respectively. Compared with the traditional method of simply adding thermal conductive particles, the proposed in-situ deposition method is more effective owing to the reduced contact thermal resistance between the interfaces of different materials. The prepared CPCM was an ideal candidate for energy storage due to its high latent heat, good thermal conductivity, appropriate phase change temperature, good shape stability, thermal stability, and thermal reliability. As such, the study results provide a new, low-cost and effective method for the thermal conductivity enhancement of CPCMs.