Narrow Results

Ordered arrays of Ni and Co nanowires and nanotubes, with diameters between 30 nm and 60 nm, were prepared by electrodeposition into nanoporous alumina templates. The study of the corresponding magnetization reversal processes was performed by analyzing the angular dependence of coercivity (H_c) and using a simple analytical model. The agreement between experimental and theoretical data shows that magnetization in nanowire arrays reverses by means of nucleation and propagation of a transverse domain wall, independently of the diameter. However, a critical diameter of ~ 50 nm was found in the case of nanotubes, above which a nonmonotonic angular dependent H_c was observed, evidencing a transition between vortex and transverse reversal modes.

Nanostructured thin-film electrode materials are proposed for supercapacitors due to their outstanding performance over bulk materials. In this work, we fabricated a TiO₂ nanotube film over a titanium foil using a top-down approach for supercapacitor electrodes. We noticed that the fabricated nanotubes are uniform and well aligned, confirmed by FESEM; the TiO₂ nanotube parameters were further simulated using COMSOL Multiphysics. Simulations show an areal capacitance of 1.19393 pF/cm² with oxidation and reduction peak currents of 6.18921 × 10⁻¹⁵ A and −6.0320 × 10⁻¹⁵ A, respectively, at 10 mV/s scan rate. The as-prepared nanotubes show a poor areal capacitance of 1.0193 F/cm², which is improved to 12.8764 F/cm² at a scan rate of 10 mV/s, that is approximately 12.63 times with oxidation and reduction peak currents of 0.129 mA/cm² and −0.105 mA/cm², respectively, by performing an electrochemical etching. Further, the surface roughness of both as-prepared and etched samples is studied to comment on their surface area changes. The effect of the etched sample is studied, compared and validated with simulation, which reveals that the etched TiO₂ nanotubes thin-film sample shows considerable similarity with the simulation results.