Shaped electrodes

Electromagnetic flow meters ate avadable with various liner and electrode materials. Liner and electrode selection is governed by the corrosion characteristics of the Hquid. Eor corrosive chemicals, fluoropolymer or ceramic liners and noble metal electrodes are commonly used polyurethane or mbber and stainless steel electrodes are often used for abrasive slurries. Some fluids tend to form an insulating coating on the electrodes introducing errors or loss of signal. To overcome this problem, specially shaped electrodes are avadable that extend into the flow stream and tend to self-clean. In another approach, the electrodes are periodically vibrated at ultrasonic frequencies. 

In order to pilot this process, SNPE has developed an annular ceU having a cone-shaped electrode section. The magnesium anode is placed into the conic section and fed like a pencil into a sharpener as it is consumed during electrolysis. The carbon dioxide is introduced into the electrolyte externally to the cell. 

When a droplet is deformed asymmetrically, the ratchet motions of the droplet can be induced as demonstrated on the vibrated gradient surface and on a saw-shaped electrode on which the wetting was changed by electrowetting [48]. 

Up until the mid-1940s, most physical electrochemistry was based around the dropping mercury electrode. However, in 1942, Levich showed that rotating a disc-shaped electrode in a liquid renders it uniformly accessible to diffusion, yet the hydrodynamics of the liquid flow are soluble and the kinetic equations relatively simple. In addition, in contrast to the case of a stationary planar electrode, the current at an RDE rapidly attains a steady-state value. 

The ion trap mass analyzer is similar to the quadrupole but with the important distinction that it can isolate and trap ions in an electrical field. Notably, the ion trap differs significantly from quadrupoles in design and operation in that triple quadrupoles perform tandem mass analysis on ions as they pass through an analyzer ion traps are capable of isolating and retaining specific ions for fragmentation upon collision with an inert gas in the same cell. An ion trap is about the size of a tennis ball and consists of a donut-shaped electrode and two perforated disk-like end-cap electrodes. 

In a recently developed process, the consumable rods used in REP are replaced by disk-shaped electrodes, since such electrodes are easier to fabricate than long round rods. During atomization, a rotating consumable disk is melted at its periphery. 

Fig. 1.6 Two different immersion cell designs optimized for special applications, (a) Set-up for fast removal and rinsing of a strip-shaped electrode by fast rotation of the shaft (solid arrow). This set-up is useful for measurements of transient electrode processes like...

Figure 50. (a) Primary potential distribution surrounding a disk-shaped electrode. (Reprinted with permission from ref 47. Copyright 2004 John Wiley Sons.) (b) Finite-element calculation of the 2D primary potential profile near an electrode with regular periodic contact to the electrolyte

contour plot are lines of constant potential vertical lines follow the current path. 

Some ISEs containing no inner reference solution, as well as tubular potentiometric sensors, has been used in conjunction with FI systems for the determination of vitamins B, and Bg in pharmaceutical preparations. The membranes used for this purpose were prepared from the vitamin tetra(2-chlorophenyl)borate dissolved in o-nitrophenyloctyl ether and immobilized in PVC. The intrinsic behaviour of the tubular electrodes was assessed by using a low-dispersion single-channel FI manifold and compared with those of conventionally-shaped electrodes using the same membrane the results provided by both were very similar [119]. 

Other Unusual Electrode Shapes. Various modifications of the rotating disk electrode are described in the literature. For example, the rotating disk electrode with ring sometimes suffers from bubbles that collect in the cotter and make it difficult to determine the fraction of the disk available for electrode reactions. One remedy is to use a cone-shaped electrode the ring is on the side of the cote and the disk at the tip. Bubbles don t like tips and skelter. 

Assume that a disk-shaped electrode (gold, platinum, carbon, etc.) has been coated with a Film of poly (vinyl ferrocene) (Table 13.2). This can be accomplished by dissolving the polymer in chloroform, applying a drop of the solution to the electrode surface, and allowing the solvent to evaporate. The electrochemistry of the resulting polymer film-coated electrode can be investigated using the same electrochemical cell and equipment as described in the previous example. 

An entirely new principle of the ion-trap mass spectrometers is the Orbitrap with a coaxial inner spindle-shaped electrode in an outer barrel-like electrode. The peripheral injected ions move due to their electrostatic attraction to the inner electrode on orbits around and swing simultaneously along the electrode. The frequency of these harmonic oscillations is inversely proportional to the square root of mJz. The detected signals are induced by the frequency of these swings and resulted... 

This mass separator is a new type, especially accommodated to be compatible with the 2V2-D geometries available in this fabrication process. The synchronous ion shield (SIS) analyzer selects the mass, for which the filter is transparent, by a traveling high frequency rectangular pulse stream (rise and fall time <1 ns) of a swept frequency (0-270 MHz), which is supplied to a comb shaped electrode arrangement. 

John Daniell (English physicist) developed the first modern storage cell based on Faraday s principles. This consists of a large glass jar with a copper star-shaped electrode in the bottom and a zinc "crow s foot" shaped electrode suspended near the top. The bottom of the jar was filled with a concentrated copper sulfate solution. On top of this was poured dilute sulfuric acid, whose lower density kept it on top. This was the first practical battery to find wide use to power telegraphs and railway signaling systems and home doorbells. 

Fig. 41. Calculated spatial variation of the double layer potential of a disk-shaped electrode in a hollow cylinder (cf. Fig. 3a) at different phases of an oscillation. (Reproduced from A. Karantonis and S. Naka-bayashi, Electrochimica Acta 46 (2000) 745-757 with permission from Elsevier Science.)... 

Figure 16. (A). The virgin curve and full AHE curve of a patterned Co/Pt multilayer with a dot size is 120 nm. The loop is measured form about 200 dots in the area of the Hall cross, (B) SEM image of a 60 nm FePt dot (bright spot) covered with a Pt cross-shaped electrode, (C) AHE loops for 10 and 300 K with an inset of the unpatterned FePt film at 300 K.

Voltammetry study made on platinum and gold needle-shaped electrodes have shown, that at low electrode polarization rates (< 0.1 V s"1) voltammograms exhibit two well-defined waves of carbon dioxide electroreduction with limiting currents and half-wave potentials - (A) E 1/2 = - 0,44 V (B) E m = - 0,78 V (Fig. 2). 

Rod-shaped electrodes — if used in a great number and connected to a oommon source of the current — have a drawback because great care must be taken to ensure good contact at each single electrode otherwise some would have an insufficient current load and some would be overloaded. Also the ourrent density is not uniformly distributed around them. Surface areas of the... 

Tube-shaped electrodes are usually not used in the electrolytic cells. Lead dioxide electrodes serve as a rare example these may be produced by an electrochemical deposition of lead dioxide on a graphite rod. When electrolysis is terminated the graphite core is removed by drilling so that the remaining tube consists only of lead dioxide. Sometimes, however, cylindrical electrodes are used which are made of a thin metal sheet rolled into a wide cylinder. In... 

The way of connecting the current conductors to electrodes which remain permanently dipped into the solution of electrolytes depends on the material of the electrode (whether noninetallic, such as graphite, or metallic.) One possible method of connecting a graphite rod to the current conductor is schematically represented in Fig. 41. the upper end of the electrode has a small recess it is encompassed by a two-piece copper terminal which is connected to the current conductor. A terminal for connection of a plate shaped electrode to the current conductor is illustrated in Fig. 42. At first the upper edge of plate A is fitted... 

The cathode is a wire-shaped electrode with relatively high electrical resistance, which emits electrons when heated electrically (6.3-V cathode heater circuit, which often is not shown). 

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