Tunable melting temperature of Sn encased by Cu nanoparticles for high temperature energy storage

Abstract

With respect to high temperature thermal storage systems, there is a critical need to develop advanced metallic phase change materials (PCM) for improving storage efficiencies. However, the melted metal is generally in a high temperature state, and exhibits a high chemical corrosion to iron and other shell materials. In this work, a new kind of nanocomposite with leakage prevention is probed, which is prepared by using excellent-adsorption-capacity nanoparticles to encircle the metallic PCM densely. By using Cu nanoparticle as additive and Sn material as the PCM, Sn/Cu nanocomposite is prepared by cold pressing methods and then sintering treatment. Cu nanoparticles can not only serve as thermal-conductivity enhancer, but also could greatly encircle Sn to prevent the leakage of molten Sn in the thermal storage process. Most importantly, the phase change temperature of Sn matrix can be effectively adjusted and the effective specific heat capacity of the whole system can be obviously enhanced, by regulating the weight fraction of Cu nanoparticles in the composite, because of the appearance of many Sn nanowires after sintering treatment. For the addition of 50 nm Cu nanoparticles, the melting temperature of Sn PCM can be reduced by 5 °C, and melting temperature can be further reduced by decreasing the size of Cu nanoparticles. When the weight fraction of Cu nanoparticles in the composite is 5 %, the specific heat capacity can be enlarged nearly 10 % than the normal composites without Sn nanowires forming. This work provides a new idea for the preparation of nanocomposite PCM, which can significantly reduce or even overcome the phenomenon of liquid leakage during the phase change process, obviously improve the specific heat capacity of the PCM, effectively adjust the melting temperature, and make PCM possess high strength but maintain lightweight.