Experimental research and molecular dynamics simulation on thermal properties of capric acid/ethylene-vinyl/graphene composite phase change materials

In this paper, a new series of phase change materials (PCMs) composed of capric acid/ethylene-vinyl acetate/graphene (CA/EVA/GR) were prepared and thermal properties were investigated using molecular dynamics simulation. The composite PCMs were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermal conductivity measurement. FT-IR, XRD and SEM results manifest that CA can be successfully wrapped by EVA and GR additives, and there is no chemical reaction between CA, EVA and GR. DSC results indicate that adding GR into CA/EVA can result in composite PCMs maintain the high latent heat, while too much GR will cause a significant reduction in latent heat. Thermal conductivity obtained from experimental tests reveal that GR can gradually enhance the thermal conductivity of CA/ EVA with increasing dosage of GR. The experimental results of thermal conductivity fall close to that of molecular dynamics (MD) simulation at GR dosages below 1.8 wt%, but the experimental results present a trend which is contrary to MD simulation at higher GR dosages. The mean square displacement (MSD) results manifest that composite PCMs containing 1.8 wt% GR has the highest diffusion coefficient, while higher GR dosage will reduce the diffusion coefficient gradually.

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