Thermally Conductive Magnetic Composite Phase Change Materials for Anisotropic Photo/Magnetic-to-Thermal Energy Conversion.

The distinctive thermal energy storage properties of phase change materials (PCMs) are critical for solving energy issues. However, their inherently low thermal conductivity and limited energy conversion capability impede their applications in advanced thermal energy harvesting and storage systems. Herein, we developed magnetic composite PCMs with enhanced thermal conductivity for anisotropic photothermal and magnetic-to-thermal energy conversions. The hierarchically interconnected ferroferric oxide-coated boron nitride/poly(vinyl alcohol) (BN@Fe 3 O 4 /PVA) porous scaffolds were constructed by a unidirectional freeze-casting method to enhance the directional heat transfer capability of the composite PCMs with a through-plane thermal conductivity of 1.84 W m -1 K -1 at a BN@Fe 3 O 4 loading of 25.4 wt %. The superparamagnetic Fe 3 O 4 nanoparticles endow the composite PCMs with unique solar absorption and magnetic response properties, and the energy conversion efficiency can be regulated by controlling the orientation of the synthesized magnetic particles in the composite PCMs. As a consequence, the resulting composite PCMs exhibit superior photo/magnetic-to-thermal energy conversion efficiency along the direction of orientation of magnetic particles. These novel findings provide an instructive guide to yield composite PCMs for efficient energy conversion.