Fabrication and Thermal Properties of a Gallium and Porous Foam Composite Phase Change Material

A thermal energy storage composite is fabricated by infiltrating liquid metal gallium (Tm = 30.76 ± 0.3 °C) into an open-cell porous nickel foam (dp ≈ 0.25 mm, porosity 95%). Sample preparation and process refinement lead to a reduction in material voiding to an observed 2.4 ± 0.84% volume fraction while remaining fabricable with common benchtop laboratory equipment. Comprehensive infiltration results in a measured thermal conductivity of 39.1 ± 2.9 W/m-K at 75 °C with the gallium fraction in liquid state, owing to the enhancement effect of the conductive nickel lattice. Gravimetric latent heat of melting is reduced in rough proportion to the mass fraction of nickel and measured at 72.56 ± 0.18 J/g. Taken together, these properties represent a best-in-class performance among near-room temperature phase change materials (Tm < 100 °C) according to power density figure of merit. Furthermore, retention in the high-surface area foam network through capillary effects precludes the need for elaborate liquid confinement during application insertion and mitigates the degree of supercooling upon solidification (observed in ∼100 mg composite samples as ΔTsub: 25–40 °C vs pure samples ΔTsub: 50–60 °C).