Integrating Porous Copper for Supercooling Mitigation in Gallium-Based Phase Change Material Thermal Storage

Phase change materials (PCMs) undergo a transition from solid to liquid, absorbing a substantial amount of latent heat, making them suitable for systems that efficiently store and release heat as needed. Research on PCMs is actively pursued in various fields such as energy harvesting, air conditioning, and electronic device thermal management. Paraffin has been extensively utilized in PCM research primarily due to its high specific latent heat (~230 kJ/kg) and cost-effectiveness. Nevertheless, challenges arise when paraffin is applied to systems requiring rapid thermal response, such as electronic devices, due to its low thermal conductivity of approximately 0.2 W/mK.<br/><br/>To address these challenges, researchers have turned to gallium-based liquid metals with an appropriate specific latent heat (80 kJ/kg) and a comparatively high thermal conductivity of approximately 40 W/mK. While gallium may possess a lower specific latent heat per unit mass compared to paraffin-based PCMs, its density exceeds that of paraffin by more than six times. As a result, the specific latent heat per unit volume increases, enabling efficient heat absorption within confined volumes. Furthermore, gallium exhibits high thermal conductivity, enabling rapid system response under conditions of fluctuating thermal load. However, gallium faces a supercooling issue, where it remains in a liquid state after absorbing heat and fails to transition back to a solid state when the temperature drops below its freezing point. In this context, resolving the supercooling problem is imperative for the successful application of gallium in PCM systems.<br/><br/>This study suggests a gallium-porous copper composite to mitigate gallium's supercooling issue. Deoxidized gallium and porous copper were efficiently combined to create the composite material in a low-concentration hydrochloric acid environment. The porous structure increased the surface area, and the intermetallic compound CuGa2 that formed at the interface facilitated heterogeneous nucleation, reducing the supercooling of gallium. The quantitative performance of supercooling mitigation was verified through differential scanning calorimetry and multi-cycle heating and cooling experiments.