Boriana Tzaneva

In recent years, Cu-Sb-based alloys have been considered promising materials for various green applications; for instance, they can serve as catalysts for CO2 reduction, anodic material for metal-ion batteries, and a light-absorbing layer in solar cell. Our research is focused on the electrodeposition of antimony-copper alloy layers with copper content between 18–30 wt.%. The layers were observed by scanning, atomic force and transmission electron spectroscopies. Their phase structure, roughness, and hardness were also determined. The electrochemical properties were investigated by using electrochemical impedance spectroscopy and potentiodynamic polarization tests in 0.5 M sulfuric acid. Decreasing the copper content leads to an increase in chemical and morphological heterogeneity and an increase in the roughness from 1.74 to 2.94 μm due to the separation of antimony crystal clusters protruding above the surface but does not significantly affect the hardness and electrochemical behavior of the layers. Copper is recorded only in the form of the Cu2Sb phase. The corrosion current density and potentials of the layers are close to those of pure antimony (about 20 µA cm−2 and about −30 mV vs. Ag/AgCl). The highly porous structure obtained after anodic polarization seems suitable for catalytic purposes.

A straightforward and inexpensive electrophoretic method for obtaining environment-friendly nanocrystalline piezo layers from Rochelle salt (RS) is presented here. The electrophoretic deposition process includes the formation of nanocrystals by precipitation of Rochelle salt/water solutions in ethanol (anti-solvent method) under the influence of a high electric field. A nanoporous anodic aluminum oxide membrane is used to separate the electrochemical cell into two chambers. The composition of the RS:H2O:EtOH mixture and the spatial separation of the process of precipitation from electrophoretic deposition allow control of the nanocrystal size and the uniformity of the layer. The reaction kinetics, the morphology, and the piezo response to the resulting layers are all investigated. The best samples were obtained at RS:H2O:EtOH ratio 1:22.5:37.5. Under these conditions, the nanocrystals are preferentially oriented on the aluminum substrate and form a dense and homogeneous layer. Although the obtained structure is polycrystalline, the resulting piezo effect is 1120 pC/N, which is comparable to inorganic monocrystals and piezoceramics. This allows the use of electrophoretically deposited polycrystalline piezo layers in applications such as energy harvesting.