A unique micro electrochemical machining (ECM) method based on a scanning micro electrochemical flow cell (SMEFC), in which the electrolyte is confined beneath the tool electrode instead of spreading ...on the workpiece surface, has been developed and its feasibility for fabricating mesoscale channels has been investigated. The effects of the surface conditions, the applied current, the feed rate, the concentration of the electrolyte and several geometrical parameters on the machining performance have been investigated through a series of experiments. The cross-sectional profile of the channels, the roughness of the channel bottom, the width and depth of the channel, the microstructures on the machined surface and the morphologies of the moving droplet have been analyzed and compared under different machining conditions. Furthermore, experiments with different overlaps of the electrolyte droplet traces have also been conducted, in which the SMEFC acts as a “milling tool”. The influences of the electrode offset distance (EOD), the current and the feed rate on the machining performance have also been examined through the comparison of the corresponding cross-sectional profiles and microstructures. The results indicate that, in addition to machining individual channels, the SMEFC system is also capable of generating shallow cavities with a suitable superimposed motion of the tool electrode.
This work extended the previous scanning micro electrochemical flow cell (SMEFC) with one electrode in the past work to the multi-electrode mode, aiming at enhancement of the machining efficiency. ...The design and fabrication of the test rig has been introduced in details, especially the considerations on the 3D-printed suction head and the electrode sealing scheme. The array of mesoscale cavities and channels have been fabricated by this test rig. The roundness of the cavities is evaluated and the elliptical shape of the cavities is explained through a qualitative simulation of the flow fluid in the inter-electrode gap. The consistency analysis for these structures is demonstrated. Based on these initial experimental results, the test rig shows the potential in fabrication of the array of mesoscale features.
A scanning micro electrochemical flow cell (SMEFC) has been developed to post-process the surface produced by micro-electrical discharge machining (EDM). The working principle of this compact SMEFC ...system built in-house is explained in details. Preliminary experiments show that a good handling and control of the electrolyte in a small region can be realized by this SMEFC, which avoids submerging the whole workpiece electrode in the electrolyte. In order to investigate the interrelation between the EDM traces and the finishing performance, experiments of line scanning with direct current and pulse current have been conducted on the micro-EDMed surfaces produced on a SARIX® SX-100 machine. The effects of the current density and feed rate on the finishing performance have also been analysed. Experiments have demonstrated that the recast layers and defects can be removed selectively, resulting in a better surface roughness. It is also proved that this finishing technique is feasible for post-processing discrete small regions of interest.
Focused microwaves in electrochemical processes Marken, Frank; Sur, Ujjal Kumar; Coles, Barry A. ...
Electrochimica acta,
02/2006, Letnik:
51, Številka:
11
Journal Article, Conference Proceeding
Recenzirano
The effects of high intensity microwave radiation in electrochemistry are summarized and discussed. In situ microwave activation of electrochemical processes has been introduced recently and is ...possible by placing a carefully designed electrochemical cell directly into a microwave cavity. Self-focusing of intense microwave radiation occurs into a region close to the electrode
|
solution (electrolyte) interface of a microelectrode placed into the electrochemical cell. The electrode diameter and the electrode material strongly affect the observed mass transport enhancement and temperature effects. Experiments have been conducted to determine the temperature at the electrode surface electrochemically and to quantify the rate of chemical processes which occur in the vicinity of the electrode under high intensity microwave conditions. The effects of microwaves in a wide range of solvent systems from aqueous solutions to organic solvents (DMSO, acetonitrile, DMF, formamide) and in an ionic liquid (BMIM
+PF
6
−) have been investigated. Considerable current and temperature enhancements are observed in all solvents and are explained based on the interaction of microwaves with the liquid (electrolyte) and the physical properties of the liquids or solutions.
A new flow-injection/anodic stripping voltammetry has been demonstrated to assess ultra-trace mercury(II) using track-etched microporous membrane electrodes. The electrodes were prepared by the ...sputtering of gold or platinum onto both sides of a membrane filter with a smooth flat surface and with cylindrical pores having uniform diameter. The deposition of mercury from a mercury(II) solution was performed while the sample solution flowed through the membrane electrodes. After the deposition step, an anodic stripping voltammogram was obtained by sweeping the potential from 0 to +0.8 V vs. Ag/AgCl. In this case, the sample solution flowed through the pores of the 10-μm-thick membrane filters. Efficient electrolysis occurred during passage of the sample solution through the electrode, of which the pore size was 0.4 μm. In this study, the voltammetry described above was demonstrated using an FIA system. The continuous-flow mode showed a detection limit of 0.04 μg L−1 when the experimental conditions of the flow rate and the deposition time were set at 0.5 mL min−1 and 180 s. In the sample-injection mode equipped with a 1-mL sample loop, a linear relation was found for 0.5 – 4.0 μg L−1 of a mercury(II) standard solution (r = 0.995). The detection limit was 0.05 μg L−1. This method was applied to the ultra-trace determination of mercury(II) in river-water samples.
A new anodic stripping voltammetry (ASV) using a microporous membrane electrode has been developed for the on-line monitoring of trace CuII in concentrated alkaline solutions. Microporous membrane ...electrodes were prepared by plating gold onto membrane filters made of polypropylene (PP). By SEM observations, it was confirmed that the membrane filter was modified by gold fine particles. The microporous membrane electrodes were set in a penetrated-type electrochemical flow-cell, and CuII was deposited while the sample solution passed through the electrode. The concentration of CuII was estimated with the anodic stripping peak currents. The calibration curve showed linearity within a range of 0 - 25 μg L-1 CuII in a 48% KOH solution. The proposed method will become a useful technique for an on-line monitoring system for trace CuII, which has been in urgent demand by the semiconductor manufacturing.
In situ microwave activation of electrochemical processes is possible by self-focusing of intense microwave radiation into a region close to the electrode|solution (electrolyte) interface of a ...microelectrode placed inside a microwave cavity. A systematic study of the microwave activation effects in electrochemical processes is reported for two redox systems,
Fe
(
CN
)
6
3
-
/
4
-
and
Ru
(
NH
3
)
6
3
+
/
2
+
, in aqueous KCl solution. Platinum microelectrodes of 100, 50, and 25 μm diameter are employed and at the 25 μm diameter electrode, extreme current enhancements of up to three orders of magnitude are detected. A typical Nernst diffusion layer thickness in aqueous solution of less than 100 nm can be achieved routinely and, consequently, high temperature steady state voltammetry is possible in the sub-millisecond time domain. Volatile reagents reduce the efficiency of this effect and therefore a steam bubble mechanism is proposed to explain the observations. Microwave effects on the rate of interfacial electron transfer are discussed.
We present a new coupled discretization approach for species transport in an incompressible fluid. The Navier–Stokes equations for the flow are discretized by the divergence-free Scott–Vogelius ...element on barycentrically refined meshes guaranteeing LBB stability. The convection–diffusion equation for species transport is discretized by the Voronoi finite volume method. In accordance to the continuous setting, due to the exact integration of the normal component of the flow through the Voronoi surfaces, the species concentration fulfills discrete global and local maximum principles. Besides of the numerical scheme itself, we present important aspects of its implementation. Further, for the case of homogeneous Dirichlet boundary conditions, we give a convergence proof for the coupled scheme. We report results of the application of the scheme to the interpretation of limiting current measurements in an electrochemical flow cell with cylindrical shape.
A new anodic stripping voltammetry (ASV) using a microporous membrane electrode has been developed for the on-line monitoring of trace CuII in concentrated alkaline solutions. Microporous membrane ...electrodes were prepared by plating gold onto membrane filters made of polypropylene (PP). By SEM observations, it was confirmed that the membrane filter was modified by gold fine particles. The microporous membrane electrodes were set in a penetrated-type electrochemical flow-cell, and CuII was deposited while the sample solution passed through the electrode. The concentration of CuII was estimated with the anodic stripping peak currents. The calibration curve showed linearity within a range of 0 – 25 μg L−1 CuII in a 48% KOH solution. The proposed method will become a useful technique for an on-line monitoring system for trace CuII, which has been in urgent demand by the semiconductor manufacturing.
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