Two-Electrode Growth and Optimization of Copper Nanocone\nStructures for Immersion Phase-Change Liquid Cooling

Utilizing\nsuperwettability micro/nanostructures to enhance immersion\nphase-change liquid cooling (IPCLC) performance of metal heat sinks\nhas attracted great interest due to its academic and commercial values.\nHere, we demonstrate IPCLC performance maximization of copper nanocone\narray structures via two-electrode growth technique optimization.\nThrough regulating current density, reaction temperature, pH, concentration\nof electrolytes involving copper sulfate, poly(ethylene glycol), nickel\nsulfate, sodium hypophosphite, boric acid, and trisodium citrate,\nand reaction time, we realize the optimization of growth conditions\nand IPCLC performance of copper nanocone structure. As compared to\nthe flat copper surface, the optimal copper nanocone structure can\nexhibit maximally 13.4 °C decrease in the surface temperature\nof the simulated chip heat source. We found that each variable has\nproper values for creating the optimal IPCLC surface. Among others,\nthe reaction time is the most sensitive variable that can affect the\nIPCLC performance. Besides, in each group of orthogonal experiments,\nthe IPCLC performance optimization of nanocones has no rules with\nthe variation of their density, bottom radius, and height but is positively\nassociated with their total surface area. The larger the surface area,\nthe better the performance. Based on energy disperse spectroscopy,\nX-ray diffraction, and transmission electron microscope characterizations,\nthe optimal nanocones are demonstrated to be polycrystalline, consisting\nof face-centered cubic copper-doped with a tiny amount (3.7 wt %)\nof nickel. This work establishes a mass-producible two-electrode growth\nrecipe for low-cost and large-area fabrication of copper nanocones,\nwhich helps develop high-performance IPCLC devices for chip cooling\nas well as explore more technological applications.