We present a comparative study of different oxidation methods for Cu, focusing on their effects on surface wettability for potential heat transfer applications. Various Cu2O/CuO nanostructures are formed on copper substrates using thermal and chemical oxidation methods. The morphology and chemical composition of the oxide layers are investigated using atomic force microscopy, scanning electron microscopy, and X-ray diffraction measurements. To evaluate the surface wettability, static contact angles are measured before and after each oxidation process. In thermal oxidation, the contact angle can be tailored from ∼15° to ∼90° by varying heating time (10 min ∼ 4 hrs) and temperature (150–250 °C). Chemical oxidation processes using hot alkali solutions yield stable CuO nanostructures with high roughness factors and unique morphologies, which cause significant changes in wettability. Both superhydrophilic and superhydrophobic surfaces are demonstrated using the chemical oxidation methods.

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