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. mu -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 degrees +/- 9 degrees 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.

keywords

SCANNING THERMAL MICROSCOPY; OXIDE THIN-FILMS; FACILE FABRICATION; SURFACE; CORROSION; WETTABILITY; SUBSTRATE; OXIDATION; EXCHANGER; ALUMINUM

subject category

Chemistry; Materials Science; Physics

authors

Gaspar, G; Salvador, MA; Pereira, MJ; Carvalho, AF; Amaral, VS; Tedim, J; Deuermeier, J; Fernandes, AJS; Silva, RF; Costa, FM

Groups

G2 - Photonic, Electronic and Magnetic Materials
G3 - Electrochemical Materials, Interfaces and Coatings
G4 - Renewable Materials and Circular Economy

Projects

SGH : Smart Green Homes (Smart Green Homes)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

Collaboratory for Emerging Technologies, CoLab (EMERGING TECHNOLOGIES)

acknowledgements

This work was developed within the scope of the projects: SMART GREEN HOMES, Project 7678 (POCI-01-0247-FEDER-007678) , supported by the European Regional Development Fund (FEDER) through Portugal 2020 and the Competitiveness and Internationalization Operational Program (COMPETE 2020) ; and i3N Projects (LA/P/0037/2020 & UIDB/50025/2020 & UIDP/50025/2020) and CICECO-Aveiro Institute of Materials (LA/P/0006/2020 & UIDB/50011/2020 & UIDP/50011/2020) , both financed by national funds through the Portuguese Fundacao para a Ciencia e a Tecnologia (FCT) /MCTES. G. Gaspar acknowledges funding by the Portuguese FCT I.P./MCTES through national funds (PIDDAC) - UIDB/50019/2020 --IDL and the research action 2021.02841.CEECIND/CP1654/CT0004 (https://doi. org/10.54499/2021.02841.CEECIND/CP1654/CT0004) . The authors also thank Dr. Filipe Oliveira (CICECO) for assisting with the 3D pro-filometry measurements.