Pulse Reverse Plating of Copper Micro-Structures in Magnetic Gradient Fields

Micro-structured copper layers are obtained from pulse-reverse electrodeposition on a planar gold electrode that is magnetically patterned by magnetized iron wires underneath. 3D numerical simulations of the electrodeposition based on an adapted reaction kinetics are able to nicely reproduce the micro-structure of the deposit layer, despite the height values still remain underestimated. It is shown that the structuring is enabled by the magnetic gradient force, which generates a local flow that supports deposition and hinders dissolution in the regions of high magnetic gradients. The Lorentz force originating from radial magnetic field components near the rim of the electrode causes a circumferential cell flow. The resulting secondary flow, however, is superseded by the local flow driven by the magnetic gradient force in the vicinity of the wires. Finally, the role of solutal buoyancy effects is discussed to better understand the limitations of structured growth in different modes of deposition and cell geometries

AL2O3-Me LAYERS OBTAINED BY THE ELECTROCHEMICAL METHOD

Fine membranes with controlled size of pores were produced by the two step anodizing process of the aluminium in oxalic acid solution. Highly ordered Co, Fe and CoFe nanowire arrays were prepared by two electrodeposition techniques: pulsed (PED) and potentiostatic electrodeposition (DC) into the anodic alumina membrane (AAM) templates. It has been observed that both experimental methods (PED, DC) enable the embedding of Co, Fe as well as CoFe alloy into the pores of the AAM with a high aspect ratio

Combining magnetic forces for contactless manipulation of fluids in microelectrode-microfluidic systems

A novel method to drive and manipulate fluid in a contactless way in a microelectrode-microfluidic system is demonstrated by combining the Lorentz and magnetic field gradient forces. The method is based on the redox-reaction [Fe(CN)6]3−/[Fe(CN)6]4− performed in a magnetic field oriented perpendicular to the ionic current that crosses the gap between two arrays of oppositely polarized microelectrodes, generating a magnetohydrodynamic flow. Additionally, a movable magnetized CoFe micro-strip is placed at different positions beneath the gap. In this region, the magnetic flux density is changed locally and a strong magnetic field gradient is formed. The redox-reaction changes the magnetic susceptibility of the electrolyte near the electrodes, and the resulting magnetic field gradient exerts a force on the fluid, which leads to a deflection of the Lorentz force-driven main flow. Particle Image Velocity measurements and numerical simulations demonstrate that by combining the two magnetic forces, the flow is not only redirected, but also a local change of concentration of paramagnetic species is realized

On the electrolyte convection around a hydrogen bubble evolving at a microelectrode under the influence of a magnetic field

Water electrolysis was carried out in a 1 M H2SO4 solution under different potentiostatic conditions in the presence of a magnetic field oriented normal to the horizontal microelectrode (100 μm in diameter). The imposed magnetohydrodynamic (MHD) electrolyte flow around the evolving hydrogen bubble was studied to clarify the effect on the detachment of the bubble from the electrode and the mass transfer toward the electrode. Different particle imaging and tracking techniques were applied to measure the three-dimensional flow in the bulk of the cell as well as in close vicinity of the evolving bubble. The periodic bubble growth cycle was analyzed by measurements of the current oscillations and microscopic high-speed imaging. In addition, a numerical study of the flow was conducted to support the experimental results. The results demonstrate that the MHD flow imposes only a small stabilizing force on the bubble. However, the observed secondary flow enhances the mass transfer toward the electrode and may reduce the local supersaturation of dissolved hydrogen

Electrodeposition of manganese layers from sustainable sulfate based electrolytes

Functional manganese-(Mn)-containing layers are becoming increasingly important in the fields of sacrificial corrosion protection, biodegradable medical devices or electrochemical energy conversion systems. Electrodeposition can be a low cost and time-efficient production route, but the very electronegative nature of Mn makes this reduction process quite challenging. In this paper, electrolytic potentiostatic deposition of metallic Mn layers from environmentally friendly aqueous manganese sulfate electrolytes with pH 3 is successfully demonstrated. A continuous electrolyte flow in the cathodic compartment of the electrochemical cell for controlling the pH value during deposition was found to be essential for achieving good layer qualities. Based on cyclic voltammetry analysis in combination with quartz crystal microbalance measurements a suitable deposition potential range was identified. The obtained electrodeposited layers were characterized by means of SEM, XRD, GD-OES and XPS. The shift of the deposition potential from − 2.4 VMSE to − 2.6 VMSE (deposition time 60 min) yields a thickness increase of the metallic α-Mn deposits from < 500 nm to ~ 2 μm. Only thin additional surface regions of Mn-oxides/-hydroxides were identified. The important role of (NH4)2SO4 as complex-forming electrolyte additive is discussed and an impact of the salt concentration on the deposit properties is revealed. This is a promising starting point for further Mn alloy deposition analysis

Directly Anodized Sulfur-Doped TiO2 Nanotubes as Improved Anodes for Li-ion Batteries

TiO2 represents one of the promising anode materials for lithium ion batteries due to its high thermal and chemical stability, relatively high theoretical specific capacity and low cost. However, the electrochemical performance, particularly for mesoporous TiO2, is limited and must be further developed. Elemental doping is a viable route to enhance rate capability and discharge capacity of TiO2 anodes in Li-ion batteries. Usually, elemental doping requires elevated temperatures, which represents a challenge, particularly for sulfur as a dopant. In this work, S-doped TiO2 nanotubes were successfully synthesized in situ during the electrochemical anodization of a titanium substrate at room temperature. The electrochemical anodization bath represented an ethylene glycol-based solution containing NH4F along with Na2S2O5 as the sulfur source. The S-doped TiO2 anodes demonstrated a higher areal discharge capacity of 95 µAh·cm−2 at a current rate of 100 µA·cm−2 after 100 cycles, as compared to the pure TiO2 nanotubes (60 µAh·cm−2). S-TiO2 also exhibited a significantly improved rate capability up to 2500 µA·cm−2 as compared to undoped TiO2. The improved electrochemical performance, as compared to pure TiO2 nanotubes, is attributed to a lower impedance in S-doped TiO2 nanotubes (STNTs). Thus, the direct S-doping during the anodization process is a promising and cost-effective route towards improved TiO2 anodes for Li-ion batteries

Electrodeposition of Sr-substituted hydroxyapatite on low modulus beta-type Ti-45Nb and effect on in vitro Sr release and cell response

Beta-type Ti-based alloys are promising new materials for bone implants owing to their excellent mechanical biofunctionality and biocompatibility. For treatment of fractures in case of systemic diseases like osteoporosis the generation of implant surfaces which actively support the problematic bone healing is a most important aspect. This work aimed at developing suitable approaches for electrodeposition of Sr-substituted hydroxyapatite (Srx-HAp) coatings onto Ti-45Nb. Potentiodynamic polarization measurements in electrolytes with 1.67 mmol/L Ca(NO3)2, which was substituted by 0, 10, 50 and 100% Sr(NO3)2, and 1 mmol/L NH4H2PO4 at 333 K revealed the basic reaction steps for OH– and PO4 3− formation needed for the chemical precipitation of Srx-HAp. Studies under potentiostatic control confirmed that partial or complete substitution of Ca2+- by Sr2+-ions in solution has a significant effect on the complex reaction process. High Sr2+-ion contents yield intermediate phases and a subsequent growth of more refined Srx-HAp coatings. Upon galvanostatic pulse-deposition higher reaction rates are controlled and in all electrolytes very fine needle-like crystalline coatings are obtained. With XRD the incorporation of Sr-species in the hexagonal HAp lattice is evidenced. Coatings formed in electrolytes with 10 and 50% Sr-nitrate were chemically analyzed with EDX mapping and GD-OES depth profiling. Only a fraction of the Sr-ions in solution is incorporated into the Srx-HAp coatings. Therein, the Sr-distribution is laterally homogeneous but non-homogeneous along the cross-section. Increasing Sr-content retards the coating thickness growth. Most promising coatings formed in the electrolyte with 10% Sr-nitrate were employed for Ca, P and Sr release analysis in Tris-Buffered Saline (150 mM NaCl, pH 7.6) at 310 K. At a sample surface: solution volume ratio of 1:200, after 24 h the amount of released Sr-ions was about 30–35% of that determined in the deposited Srx-HAp coating. In vitro studies with human bone marrow stromal cells (hBMSC) revealed that the released Sr-ions led to a significantly enhanced cell proliferation and osteogenic differentiation and that the Sr-HAp surface supported cell adhesion indicating its excellent cytocompatibility. © 2019 The Author

Anodization Treatment of Ti6Al4V in Electrolytes Containing HF

The Ti6Al4V alloy is already well-known likely material for implant applications. As well as pure titanium, Ti6Al4V alloy possess the ability to form spontaneously a thin passive oxide layer on the surface. This oxide layer provides an enhanced biocompatibility and may be optimum for the osseointegration if it is applied a tailoring of the surface topology and chemistry. The present paper addresses a study of Ti6Al4V surface modification by anodization as function of HF concentration in electrolyte and time, with the purpose to achieve an ordered porous titanium oxide layer. Prior to the anodization treatment the as-prepared surfaces were microstructurally characterized by SEM, EDX and XRD. The oxidized surfaces were subjected to SEM measurement in order to observe the achieved morphology

A comparative study of the influence of the deposition technique (electrodeposition versus sputtering) on the properties of nanostructured Fe70Pd30 films

Sputtering and electrodeposition are among the most widespread techniques for metallic thin film deposition. Since these techniques operate under different principles, the resulting films typically show different microstructures even when the chemical composition is kept fixed. In this work, films of Fe70Pd30 were produced in a thickness range between 30 and 600 nm, using both electrodeposition and sputtering. The electrodeposited films were deposited under potentiostatic regime from an ammonia sulfosalicylic acid-based aqueous solution. Meanwhile, the sputtered films were deposited from a composite target in radio frequency regime. Both approaches were proven to yield high quality and homogenous films. However, their crystallographic structure was different. Although all films were polycrystalline and Fe and Pd formed a solid solution with a body-centered cubic structure, a palladium hydride phase was additionally detected in the electrodeposited films. The occurrence of this phase induced internal stress in the films, thereby influencing their magnetic properties. In particular, the thickest electrodeposited Fe70Pd30 films showed out-of-plane magnetic anisotropy, whereas the magnetization easy axis lied in the film plane for all the sputtered films. The domain pattern of the electrodeposited films was investigated by magnetic force microscopy. Finally, nanoindentation studies highlighted the high quality of both the sputtered and electrodeposited films, the former exhibiting higher reduced Young’s modulus and Berkovich hardness values

Pulse Reverse Plating of Copper Micro-Structures in Magnetic Gradient Fields

Micro-structured copper layers are obtained from pulse-reverse electrodeposition on a planar gold electrode that is magnetically patterned by magnetized iron wires underneath. 3D numerical simulations of the electrodeposition based on an adapted reaction kinetics are able to nicely reproduce the micro-structure of the deposit layer, despite the height values still remain underestimated. It is shown that the structuring is enabled by the magnetic gradient force, which generates a local flow that supports deposition and hinders dissolution in the regions of high magnetic gradients. The Lorentz force originating from radial magnetic field components near the rim of the electrode causes a circumferential cell flow. The resulting secondary flow, however, is superseded by the local flow driven by the magnetic gradient force in the vicinity of the wires. Finally, the role of solutal buoyancy effects is discussed to better understand the limitations of structured growth in different modes of deposition and cell geometries