Form-stable phase change materials enhanced photothermic conversion and thermal conductivity by Ag-expanded graphite

Phase change materials (PCMs), which exhibit significant capacity of latent heat absorption and release during the phase change process , have been promisingly used for solar energy conversion and storage. However, the application of organic PCMs for solar energy storage remains a great challenge owing to their low thermal conductivity and liquid leakage problem. In this work, a form-stable PCM with polyethylene glycol (PEG) and epoxy resin (EP) was prepared by melt blending (the mass ratio is 1:1). The experimental results indicated that the leakage problem of PEG was solved by the cross-linking of the molecular chains of PEG and EP. Meanwhile, in order to improve the solar energy conversion capability and thermal conductivity , an extremely low loading (4 wt%) of expanded graphite (EG) modified with Ag nanoparticle was added into the PEG/EP matrix. The results suggested that Ag nanoparticles were uniformly dispersed by electroless silver plating in the surface of EG, and the electroless modified EG was evenly distributed in the PEG/EP matrix. Moreover, the composite fillers exhibited prominent solar energy conversion capability (90.7 %) and higher thermal conductivity (121 %). Therefore, this novel composite has favorable potential in practical applications of solar energy storage.