Magnetic Polyurethane Microcarriers from Nanoparticle-Stabilized Emulsions for Thermal Energy Storage
Olaia Álvarez‐Bermúdez, Inés Adam-Cervera, Adrián Aguado-Hernándiz, Katharina Landfester, Rafael Muñoz‐Espí
Abstract
Hydrated inorganic salts are phase change materials (PCMs) with promising thermal energy storage capacity. However, their application is commonly restricted because of problems of phase segregation, incongruent melting, cycling instability, or supercooling. This work presents an encapsulation method of hydrophilic PCMs that allows for the incorporation of additional functionalities within a protective shell occluding a storage core. Interfacial polymerization in nanoparticle-stabilized inverse emulsions (also called “Pickering emulsions”) is used as a synthetic platform to guarantee the stability and latent heat storage efficiency of sodium sulfate decahydrate, taken as a model case of a hydrated salt. Thus, functional polyurethane hybrid microcapsules with magnetic and/or catalytic species (e.g., CeO2, TiO2, Fe3O4) accessible on the surface were used for the encapsulation of an aqueous solution of sodium sulfate decahydrate salt. The hermeticity of the polyurethane shell combined with the thermal conductivity of magnetite nanoparticles and the nucleating ability of a second salt with a similar structure (e.g., sodium dihydrogen phosphate dihydrate) guaranteed the chemical stability, recyclability, and a minimization of the supercooling of the phase change material. Magnetically recoverable microcarriers, with high storage capacity and stability, are proposed for the controlled storage and release of thermal energy at living temperatures.