Laser-induced copper superhydrophobicity to improve heat transfer and reduce limestone deposition in water heating systems

Abstract

The spectroscopic and electrochemical properties of copper (Cu) superhydrophobic surfaces produced from laser scribing operating in the nanosecond pulsing regime are reported herein. µ-Raman spectroscopy highlighted the synthesis of copper oxide films with the simultaneous sharp increase of the substrates’ specific surface area through one single laser processing step. Higher laser power densities resulted in cupric oxide (CuO) with higher crystallinity and more homogeneous surface chemistry, whereas cuprous oxide (Cu2O) dominates surfaces processed at lower laser power densities. Steady-state contact angles using water of 162° ± 9° were measured for the lowest laser power employed, representing a grounded and meaningful development for substrates of this kind using laser technology. The results show that the combination of surface roughness and the presence of Cu2O and hydrocarbon chains at the surface contributed to the superhydrophobicity of the copper foils. Additionally, variations in the thermal conductivity of the samples’ surface are influenced by changes in the chemical composition. The surfaces were exposed to limestone-rich water and the amount of deposited solute was quantified using atomic absorption spectrometry. A fivefold reduction in calcium carbonate (CaCO3) was observed, unequivocally demonstrating the impact of laser treatments in reducing CaCO3 nucleation rates in Cu for water heating applications.