Preparation and Thermophysical Properties of High Thermal Conductive Solar Salt/MWCNTs Composite Materials

Abstract To improve the heat transfer performance of the photothermal molten salt (Solar salt), a composite material of Solar salt doped with MWCNTs (Multi‐walled carbon nanotubes) which has excellent thermal conductivity, was prepared and analyzed. XRD was used to analyze the composition of the composite, which remained as NaNO 3 and KNO 3 without change. XPS was used to analyze the C1s energy spectrum, the carbon nanotubes were purified and the impurity groups were greatly reduced after high temperature melting. Melting point, phase change enthalpy and specific heat of composite materials were measured by DSC; the decomposition temperature of composite material were measured by TGA; the density was measured by the Archimedes method; the thermal diffusivity was measured by the laser flash method. The thermal conductivity was calculated according to the thermal conductivity formula: k=Cp⋅ρ⋅α . When the Solar salt was doped with 0.4% MWCNTs, the thermal conductivity was greatly improved, increasing by 87% to 0.77 W/(m⋅k). And the influence of carbon nanotubes on the spatial structure of nitrate was analyzed by Raman spectroscopy. This composite material had superior thermal properties than Solar salt and was expected to be applied in solar thermal power generation to improve solar energy utilization efficiency.