Pool-Boiling Performance of Hierarchical Micro/Nanoporous Carbon Nanotube–Copper Hybrid Surfaces Fabricated via Scalable Electrochemical Processing

Abstract Hierarchical surface engineering that integrates nanoscale capillarity with microscale vapor-release pathways offers a promising route for advancing pool-boiling heat-transfer performance. In this study, we develop a scalable, low-temperature electrochemical– electrophoretic fabrication strategy combining ethanol-based electrophoretic deposition (EPD) of carboxylated MWCNTs, pulsed copper backfilling to metallurgically bridge carbon nanotube (CNT) junctions, and brief oxygen-plasma activation. This process yields robust micro/nanoporous CNT–Cu hybrid coatings (MS-Cu-CNT#1–#3) without vacuum processing or chemically intensive steps, enabling environmentally friendly and industry-viable surface modification. Systematic variation arising from the fabrication sequence produces coatings with tunable roughness (Ra = 1.45–3.20 μm), hierarchical porosity (ε ≈ 0.25–0.52), and superhydrophilicity (contact angle 23 deg → 4 deg), collectively promoting capillary-driven liquid replenishment, microlayer stabilization, and enhanced thermal conduction. Nanoscale Cu nodules (≈30–150 nm) deposited between CNT bundles strengthen mechanical anchoring and reduce interfacial thermal resistance, overcoming durability limitations of conventional nanowire mats. Pool-boiling experiments demonstrate substantial performance gains: the MS-Cu-CNT#2 surface delivers a heat-transfer coefficient of ≈286 kW·m−2·K−1 (+440% versus bare Cu) and a critical heat flux (CHF) of ≈2226 kW·m−2 (+107%), with stable performance over 300 h of cyclic testing (<5% deviation). A durable and scalable micro/nanostructured CNT–Cu hybrid surface was developed, demonstrating significant enhancement in pool-boiling heat transfer. These surfaces show potential for high-flux thermal management in electronics, electric-vehicle battery systems, and compact energy devices.