The wettability of metal-based composite foils with hierarchical structure prepared by ultrasonic-assisted composite electrodeposition.

To promote the development and application of ultra-thin heat dissipation devices, Cu/grapheme (GR) composite foils with hierarchical microscale structure were prepared by ultrasonic-assisted composite electrodeposition, and chemical etching and plasma oxidation treatment were applied to obtain superhydrophilic. The study found that the hierarchical multi-scale structure on the mold electrode surface can be replicated on the foil surface. Ultrasonic refines the grains and reduces the internal defects, while an increase in the GR content not only further refines the grains but also makes the microstructure multi-directional. The combined effect of ultrasonic and GR significantly improves the microhardness of the foils up to 125 HV0.01. Without any surface treatment, the contact angle (CA) of foil gradually increased with the introduction of ultrasonic and GR, the wettability developed towards hydrophobic, and the highest CA reached 98.43°. Chemical etching can change the submicron-scale structure of the foil surface, and then make the wettability towards to hydrophilic, but not enough to reach the superhydrophilic state. After plasma oxidation treatment, a large number of nanoscale CuO and Cu2O particles are generated on the surface of the chemical etching foils, which not only further enriches the multi-scale structure, but also improves the surface energy. As a result, the wettability of foil surface is further improved, showing a superhydrophilic state, and the CA is less than 5°. Moreover, with the introduction of ultrasonic and the increase of GR content, the hydrophily of the foil surface also tends to improve, and the minimum CA can reach 1.89°. [ABSTRACT FROM AUTHOR]