Magnetic nanoparticle-embedded PCM nanocapsules based on paraffin core and polyurea shell

•Magnetic nanoparticle-embedded PCM nanocapsules were prepared.•Magnetic nanoparticle provided enhanced thermal conductivity of PCM capsules.•PCM capsules could possess additional magnetic functionality.•PCM nanocapsules also had capability of storing and releasing heat. We described the synthesis and characterization of magnetic Fe3O4 nanoparticle (NP)-embedded phase change material (PCM) nanocapsules (Mag-PCM) based on a paraffin core and polyurea shell (paraffin@polyurea). The Mag-PCM nanocapsules were synthesized via interfacial polycondensation between tolylene diisocyanate (TDI) and ethylene diamine (EDA) with various concentrations (0, 2.2, 3.7, and 4.6wt%) of Fe3O4 nanoparticles. FTIR and TGA analyses confirmed the successful preparation of Mag-PCM nanocapsules. TEM and SEM images revealed that most of the Fe3O4 NPs were localized in the polyurea shell layer due to the Pickering effect. Laser flash (LFA) and DSC analyses demonstrated that the embedment of Fe3O4 NPs could increase the thermal conductivity of PCM nanocapsules and reduce the supercooling of the paraffin between bulk and nano-size confinement conditions.