In-situ growth of copper oxide nanowires for enhanced thermal performance in phase change material–metal foam systems

Phase change materials (PCMs) are widely used in thermal energy storage (TES) systems, but their inherently low thermal conductivity limits charging and discharging rates. Dispersing high-conductivity nanoparticles can improve thermal performance, but challenges such as agglomeration and sedimentation during thermal cycling remain. Embedding PCMs in metal foams offer a more stable enhancement, yet performance can be compromised by trapped air at the interface often caused by poor impregnation or weak adhesion between the PCM and foam ligaments. To address this, the present study introduces an in-situ surface modification technique that grows copper oxide (CuO) nanowires directly on copper substrates and foam ligaments, improving interfacial wettability and contact without altering the PCM's bulk properties. PCM melting test on flat surfaces showed that CuO-coated copper enhanced paraffin and PEG6000 melting, reducing melting time by up to 21.2 % and increasing final wetted area by over 250 %. The micro-computed tomography (μCT) imaging confirmed that CuO nanowires eliminated interfacial air gaps in solidified PCM, reducing air pocket coverage from up to 35 % to zero. Melting and solidification tests with PCM-infiltrated copper foam showed that CuO-coated foams reduced melting time by 9.1 % for paraffin and 16 % for PEG6000, and solidification time by 8.6 % and 4.5 %, respectively, compared to bare foam. These results are comparable to or better than those of metal foam–nanoparticle composites while avoiding dispersion issues. The approach offers a passive, scalable, and durable solution for improving interfacial heat transfer in PCM–metal foam systems.