Abstract

Phase Change Materials (PCMs) are materials with a high latent heat of fusion, so they are able to store and release high amounts of energy during the melting and solidification processes. Therefore, they can be of relevance for their use in a Thermal Energy Storage step for Concentrated Solar Power plants, in order to mitigate the intermittencies of sunlight, or to improve the performance of Heat Transfer Fluids. When used as the solid phase in a nanofluid, i.e. as the nanoparticles, PCMs need to have a core-shell structure, with a PCM nucleus and a high-melting point encapsulating material that prevents the particles from collapsing into each other while in liquid phase. Metallic nanoPCMs usually have a shell of metallic oxide naturally formed by passivation in contact with oxygen. However, this layer might not be enough as encapsulation and issues of further oxidation of the nuclei due to high temperatures, thermal cycling or interaction with the base fluid can be encountered. In this work, Atomic Layer Deposition has been used to create a second encapsulating layer of silica on Sn/SnO core-shell structured nanoparticles. The composition, structure and behaviour through thermal cycling of the multi-layered nanoparticles have been analysed, as well as their performance in a thermal oil based nanofluid regarding rheometry and stability.