Resumen de From macro- to nanoscale electrodeposited iron-copper (fe-cu) for energy-efficient and sustainable applications
This work is focused on the electrodeposition and study of Fe–Cu in the form of continuous and patterned thin films and coatings as well as the fabrication and characterization of submicron motifs, nano/microrods and tubes targeted towards a variety of environmental and energy-efficient applications.
Firstly, different electrolytes are developed for the electrochemical deposition of FexCu1−x coatings of several micrometers in thickness over a wide composition range (0≤x≤86). The effect of various complexing agents and plating conditions such as pH, temperature and magnetic stirring on the morphology, structure, elemental composition and magnetic behavior is investigated. It is shown that the coatings are partially alloyed, despite the low mutual solubility of Fe and Cu, and saturation magnetization can be easily tuned by an adjustment of the Fe content.
Next, the synthetic protocols for the continuous coatings are extrapolated to the fabrication of patterned thin films with a hierarchical porosity achieved by coupling electrodeposition with colloidal lithography. The wetting properties of these films and their potential towards water-oil separation in mixtures and emulsions is assessed as a proof of concept. The high surface-to-volume ratio of the films in conjunction with the high roughness achieved by the macroporous network and the nanosized features along the pore walls lead to a strong hydrophobic/oleophilic nature of the deposits and an impressive absorption capacity. Notably, contrary to the thick coatings, the continuous and patterned Fe75Cu25 and Fe85Cu15 thin films are demonstrated to be fully alloyed.
Furthermore, the high surface-to-volume ratio and the inherent nanoporosity of the narrow pore walls of the patterned films unveil their excellent potential towards voltage control of magnetization. Indeed, a coercivity reduction of up to 25% under application of a negative bias is achieved. This constitutes a promising way to curtail power consumption since magnetization reversal can then occur with lower applied magnetic fields (i.e., lower electric currents and minimized Joule heating power dissipation).
Next, given the current trend towards miniaturization, submicron structures of three geometries and sizes are produced through electrodeposition onto pre-lithographed substrates. These substrates were previously prepared using electron-beam lithography which ensured a high feature quality. While existing literature on lithographed submicron motifs is largely based on structures below 50 nm in height, the structures prepared here are approximately 200-300 nm in height depending on plating conditions. This gives rise to interesting phenomena such as a compositional gradient, and thus different structural properties along the thickness. The magnetic properties are also thoroughly investigated with magnetic force microscopy suggesting magnetic curling effects.
Finally, compositionally graded magnetic nano- and microrods and tubes of various diameters are fabricated in polycarbonate track-etched membranes through conventional as well as micelle-assisted electrodeposition methods. The ferromagnetic character of the material enables wireless magnetic steering while photocatalytically-driven directional propulsion of the microtubes is also confirmed.
