Binary nitrate molten salt magnetic microcapsules modified with Fe3O4-functionalized carbon nanotubes for accelerating thermal energy storage

Molten salts are important media for heat transfer and thermal energy storage in concentrated solar power (CSP) system, but it has drawbacks such as poor thermal conductivity and corrosive properties. This study increases the thermal energy utilization rate and expand the range of applications for phase change materials by developing a multifunctional magnetic microcapsule phase change material composed of SiO2@Solar Salt microcapsule and Fe3O4-functionalized carbon nanotubes (CNTs-Fe3O4). The microcapsules have regular spherical core-shell structure and relatively small size, which improves the disadvantage of corrosiveness of molten salt and prolongs their working life. The microcapsule not only shows a good latent heat-storage capability with satisfactory phase-change enthalpies of over 88.6 J/g under an encapsulation efficiency of over 61.6 %, but also exhibits high temperature stability and cycling stability. The encapsulation of SiO2 and introduction of the CNTs-Fe3O4 high thermal conductivity enhancement phase increased the thermal conductivity of the microcapsules by approximately 53.4 % compared with pure nitrate. The microcapsules also possess superparamagnetic characteristics and photothermal conversion characteristics, both of which may be used as an additional method to improve the thermal storage efficiency. As a result, this novel material provides a promising solution for energy collecting, conversion, and storage.