LAUSR

Solar salt has great advantages in solar thermal power generation compared to other molten salts, but its thermal conductivity needs to be further improved. Multi-walled carbon nanotubes (MWCNTs) have excellent thermal properties that can improve the thermal conductivity of materials as additives. In this study, five kinds of solar salt/MWCNTs composites with different doping amounts were prepared by a high-temperature melting method. The results showed that doping with MWCNTs can indeed improve the thermal properties of solar salt. We studied their quantitative structure-activity relationship (QSAR) in order to explain these phenomena. According to the TG-DSC analysis, there was almost no change in the melting point and decomposition temperature; the XRD analysis revealed that the bulk of the material was still NaNO3 and KNO3, which did not change; and according to Archimedes' method, the density of the materials also changes little. The thermal conductivity of the material was measured by the laser flash method; the results showed that the thermal conductivity of the sample with 0.3% doping increased by 293%, reaching 1.65 W (m K)−1. XPS analysis showed that the MWCNTs were purified and the impurity groups were largely removed after high-temperature melting. From the laser Raman analysis, the V3 frequency peak of the sample with 0.3% doping was red-shifted, and for the other samples was blue-shifted. The SEM images showed that the sample with 0.3% doping was the most uniformly dispersed. When the doping amounts are appropriate, the improvement in thermal conductivity may be attributed to two reasons: (1) the MWCNTs can be uniformly dispersed, as the SEM shows; (2) tiny thermally conductive channels may be formed on the interface between the molten salt and the MWCNTs, thereby generating a boundary effect. This kind of composite material may help improve solar heat storage and heat transfer capacity, and thereby increase the efficiency of solar thermal power generation.