In situ X-ray nanotomography of metal surfaces during electropolishing (original) (raw)
Related papers
Physical chemistry chemical physics : PCCP, 2015
Electropolishing of metals often leads to supersaturation conditions resulting in precipitation of complex compounds. The solubility diagrams and Gibbs adsorption isotherms of the electropolishing products are thus very important to understand the thermodynamic mechanism of precipitation of reaction products. Electropolishing of tungsten wires in aqueous solutions of potassium hydroxide is used as an example illustrating the different thermodynamic scenarios of electropolishing. Electropolishing products are able to form highly viscous films immiscible with the surrounding electrolyte or porous shells adhered to the wire surface. Using X-ray nanotomography, we discovered a gel-like phase formed at the tungsten surface during electropolishing. The results of these studies suggest that the electropolishing products can form a rich library of compounds. The surface tension of the electrolyte depends on the metal oxide ions and alkali-metal complexes.
Transport-limited electrochemical formation of long nanosharp probes from tungsten
Nanotechnology, 2013
We show that electrochemical formation of long probes with nanosharp tips can be controlled by choosing an appropriate thermodynamic pathway of metal to metal oxide and hydroxide transformation. Currently, convection-limited electropolishing (CLE) is extensively used. Nanosharp probes are produced by electrochemically etching a wire until it breaks into two pieces. This process is difficult to control because of the complexity of the associated hydrodynamic flows. We introduce transport-limited electropolishing (TLE), where the electrochemical reaction results in the formation of metal oxides and hydroxides which form a porous surface layer hindering the flow of electrolyte. The developed TLE method enables one to make long tapered needles. The taper can spread over more than 6 mm while the radius of tip curvature can be decreased down to 30 nm. These needles are strong and were successfully applied for piercing single smooth vascular muscle cells.
Electrospray from Nanostructured Tungsten Oxide Surfaces with Ultralow Sample Volume
Analytical Chemistry, 2005
This study demonstrated the feasibility of performing protein analysis with ultralow sample volume by combining a tungsten oxide nanowire (TON) fiber with a miniaturized electrospray ionization interface. An increase in wettability of the tugsten surface after growing randomly oriented TON on its surface allows strong adhesion of ∼50 nL of the methanol solution at its tip. Under the influence of a high electric field, electrospray from a Taylor cone on the adhered methanol solution was observed and the multiply charged ions of protein molecules predissolved in the solution were detected.
Preparation and characterization of ultrasharp tungsten wires
2008
We investigated the mechanism of mass transfer during DC electropolishing of a tungsten wire in 2M KOH electrolyte solution. It appears that a viscous layer formed by the products of electrochemical reaction on anode surface has distinguishable optical and physicochemical properties. The viscous fluid flow is initiated by formation and detaching of a small droplet at the wire tip. Therefore, according to Tate's law, effects of surface tension and gravitational forces exerted on the film are comparable. Using high speed flow imaging, we estimated the density of this layer as 3 / 1075 m kg and its interfacial tension as m N / 10 82. 5 6 .
Flow of Viscous Surface Layer during Electropolishing of Tungsten Wire
2008
We investigated the mechanism of mass transfer during DC electropolishing of a tungsten wire in 2M KOH electrolyte solution. It appears that a viscous layer formed by the products of electrochemical reaction on anode surface has distinguishable optical and physicochemical properties. The viscous fluid flow is initiated by formation and detaching of a small droplet at the wire tip. Therefore, according to Tate’s law, effects of surface tension and gravitational forces exerted on the film are comparable. Using high speed flow imaging, we estimated the density of this layer as 3 / 1075 m kg and its interfacial tension as m N / 10 82 . 5 6 .
Electrochemistry, 2015
In the electrochemical surface science during the past 20 years, in-situ electrochemical scanning tunneling microscopy (EC-STM) and atomic force microscopy (AFM) have made significant contribution to understand various electrochemical processes with atomic scale. For examples, the underpotential deposition of copper, silver, and other metal ions; the specific adsorption of anions such as iodine and sulfate/bisulfate ions; electrochemical etching processes of metals and semiconductors and the molecular assembly of many organic molecules, such as metalloporphyrins, and metallophthalocyanines. Furthermore, we have recently developed a high resolution laser confocal microscope, combined with a differential interference contrast microscope, which enables to follows fast dynamic electrochemical processes at atomic height resolution in relatively large areas. It has been shown for the first time that single atomic steps of metals can be successfully seen by the newly developed optical microscope. Surface imaging techniques provide local pictures of electrode processes on the atomic scale, not averaged information in large areas.
Eurasian Chemico-Technological Journal, 2020
The electrodeposition of binary and ternary coatings Fe-W and Fe-Co-W from mono ligand citrate electrolyte has been investigated. The Fe-Co-W coatings were formed from electrolytes, which composition differs in the ratio of the concentrations of the alloying components and the ligand content. The investigation results indicate a competitive reduction of iron, cobalt and tungsten, the nature of which depends both on the ratio of electrolyte components, and electrolysis parameters. The effect of both current density amplitude and pulse on off time on quality, composition and surface morphology of the galvanic alloys was determined. Coatings deposited on a direct current with a density of more than 6.5 A/dm2, crack and peel off from the substrate due to the inclusion of Fe (III) compounds containing hydroxide anions. The use of non-stationary electrolysis allows us to extend the working range of current density to 8.0 A/dm2 and form electrolytic coatings of sufficient quality with sign...
Electrochemistry, 2015
In the electrochemical surface science during the past 20 years, in-situ electrochemical scanning tunneling microscopy (EC-STM) and atomic force microscopy (AFM) have made significant contribution to understand various electrochemical processes with atomic scale. For examples, the underpotential deposition of copper, silver, and other metal ions; the specific adsorption of anions such as iodine and sulfate/bisulfate ions; electrochemical etching processes of metals and semiconductors and the molecular assembly of many organic molecules, such as metalloporphyrins, and metallophthalocyanines. Furthermore, we have recently developed a high resolution laser confocal microscope, combined with a differential interference contrast microscope, which enables to follows fast dynamic electrochemical processes at atomic height resolution in relatively large areas. It has been shown for the first time that single atomic steps of metals can be successfully seen by the newly developed optical microscope. Surface imaging techniques provide local pictures of electrode processes on the atomic scale, not averaged information in large areas.
Reproducible Electrochemical Etching of Tungsten Probe Tips
Nano Letters, 2002
An electrochemical procedure in KOH electrolyte has been developed to reproducibly produce ∼5 nm radius tungsten probe tips. It has been found that a spurious electrochemical etching process, driven by the natural potential difference between an Ir electrode and the W tip, causes rapid tip blunting at the end of the electrochemical etching period. By electrically reversing this potential difference within 500 ns following tip separation, the blunting process is eliminated yielding sharp tips with varying cone angles.