Ultra-long Fe nanowires by pulsed electrodeposition with full filling of alumina templates

Abstract

With the increasing demand for high quality methods for the fast fabrication of extremely high aspect ratio nanoparticles, the research for efficient, low-cost and simple techniques has become fundamental. A promising approach on the synthesis of these materials is here addressed. Pulsed electrodeposition in porous anodic alumina templates was improved enabling, for the first time, a simple and cost effective fabrication method for vertically aligned nanomaterials with aspect ratios never reported with this method. Iron nanowires were electrodeposited and the effect of electrolyte molar concentration, temperature and stirring, pulse shape and barrier layer thickness on the deposition quality was investigated to potentially increase the template filling and the nanowires length. The electro-deposition temperature and current density were also found to be determinant parameters affecting NWs crystallography. A methodology of surface response design of experiment was conducted to retrieve the optimum values for the deposition parameters. With the determined optimized process, we were able to obtain filling ratios up to 93% and aspect ratios over 10 times higher than previous reports for an alternating current method. The high deposition homogeneity combined with the simplicity of the pulsed deposition method, can open new opportunities for the nanofabrication of nanowires.

Magnetic behavior of NiCu nanowire arrays: Compositional, geometry and temperature dependence

“…2,28 If their length is higher than 8 lm, both coercivity and squareness show a more pronounced decrease which can be attributed to enhanced magnetostatic interactions among wires 2,29 and to the averaging of inhomogeneities in morphology or in composition along the length of the nanowires due to the decrease of ions in the electrolyte during the electrodeposition. 28,30,31 Figure 5(b) shows the dependence of coercivity and squareness as function of the nanowire diameters for Ni 70 Cu 30 nanowires with length of 8 lm. The coercivity and squareness of nanowires decrease with their diameter.…”

Tailoring magnetic properties in arrays of pulse-electrodeposited Co nanowires: The role of Cu additive

“…The electroplating techniques in PAO templates, made by the conventional anodization process, have been categorized as the alternating current (ac), the direct current (dc), and the pulsed ac and dc electrodepositions [13,[22][23][24][25]. By controlling the parameters involved in the pulsed electrodeposition technique, such as the voltage, current density, shape of the pulse applied and the off-time between pulses, it is possible to tailor the composition, crystalline structure and magnetic properties [15,23,26,27].…”

“…By controlling the parameters involved in the pulsed electrodeposition technique, such as the voltage, current density, shape of the pulse applied and the off-time between pulses, it is possible to tailor the composition, crystalline structure and magnetic properties [15,23,26,27]. Due to the presence of alumina barrier layer, it is necessary to remove this insulator before performing the pulsed dc electrodeposition and consequently sputtering an electrical contact at the bottom of nanopores [24].…”

“…Due to the presence of alumina barrier layer, it is necessary to remove this insulator before performing the pulsed dc electrodeposition and consequently sputtering an electrical contact at the bottom of nanopores [24]. In contrast, using the pulsed ac technique, the electrodeposition of ions could be provided by only reducing the thickness of the alumina barrier layer through decreasing the final anodization voltage, thereby easing the fabrication process of NWs compared to the pulsed dc technique [23,25,28].…”

Double-walled iron oxide nanotubes via selective chemical etching and Kirkendall process

“…1a). Oxalic acid was used due to its high reproducibility rate and because it yields nanometric pore diameter necessary for high surface areas 22 . Other pore sizes are currently under study and not reported in this work.…”