Electrolytic deformation

From the CV characteristics and excess response upon step voltage of electrolytic deformation, the dependence of strain and diffusion coefficient (D) on the ionic type can be obtained. The diffusion coefficient can be obtained from the time dependence of the applied electric charge at an early period upon application of a step voltage [102],... 

Rehbinder and co-workers were pioneers in the study of environmental effects on the strength of solids [144], As discussed by Frumkin and others [143-145], the measured hardness of a metal immersed in an electrolyte solution varies with applied potential in the manner of an electrocapillary curve (see Section V-7). A dramatic demonstration of this so-called Rehbinder effect is the easy deformation of single crystals of tin and of zinc if the surface is coated with an oleic acid monolayer [144]. 

Aperture impedance measurements of cell volume must take into account the osmolaUty and pH of the medium. A hypotonic medium causes cells to swell a hypertonic medium causes them to shrink. Some manufacturers of aperture impedance counters deHberately provide hypertonic electrolytic media for red blood cell measurements. The shmnken red cells not only become more nearly spherical and thus less affected by orientation, but also less deformable than cells in isotonic media and thus less affected by differences in hemoglobin content. 

Silver is often preferred as an undercoat for rhodium by reason of its high electrical conductivity. A further advantage of silver in the case of the thicker rhodium deposits (0-0025 mm) applied to electrical contacts for wear resistance is that the use of a relatively soft undercoat permits some stress relief of the rhodium deposit by plastic deformation of the under-layer, and hence reduces the tendency to cracking , with a corresponding improvement in protective value. Nickel, on the other hand, may be employed to provide a measure of mechanical support, and hence enhanced wear resistance, for a thin rhodium deposit. A nickel undercoating is so used on copper printed connectors, where the thickness of rhodium that may be applied from conventional electrolytes is limited by the tendency of the plating solution to attack the copper/laminate adhesive, and by the lifting effect of internal stress in the rhodium deposit. 

Beryllium is obtained by electrolytic reduction of molten beryllium chloride. The element s low density makes it useful for the construction of missiles and satellites. Beryllium is also used as windows for x-ray tubes because Be atoms have so few electrons, thin sheets of the metal are transparent to x-rays and allow the rays to escape. Beryllium is added in small amounts to copper the small Be atoms pin the Cu atoms together in an interstitial alloy that is more rigid than pure copper but still conducts electricity well. These hard, electrically conducting alloys are formed into nonsparking tools for use in oil refineries and grain elevators, where there is a risk of explosion. Beryllium-copper alloys are also used in the electronics industry to form tiny nonmagnetic parts and contacts that resist deformation and corrosion. 

A DEA is basically a compliant capacitor where an incompressible, yet highly deformable, dielectric elastomeric material is sandwiched between two complaint electrodes. The electrodes are designed to be able to comply with the deformations of the elastomer and are generally made of a conducting material such as a colloidal carbon in a polymer binder, graphite spray, thickened electrolyte solution, etc. Dielectric elastomer films can be fabricated by conventional... 

The working electrode, in the form of a rectangle of thin foil, c. 20 pm thick, is glued to a piezo-electric ceramic element of the same lateral dimensions. Both the piezo element and the edge of the working electrode arc then isolated from the electrolyte with inert epoxy cement. The essence of the piezo-electric effect is that if the ceramic element is deformed in any way, a... 

Radial thermal variance. When a potential difference is applied over an electrolyte solution, a current flow is generated between the electrodes in the solution. The current gives rise to Joule heating that leads to a parabolic zone deformation, owing to the formation of a radial... 

Electrical field perturbation variance. It is well established in HPLC that when the injected sample solution has a different eluting strength than that of the mobile phase, peak deformation is bound to occur. A similar effect is observed in CE. Instead of eluting strengths, it concerns here differences in conductivity between the sample zone and the bulk electrolyte in the capillary [9,32], The conductivity (y, Ohm 1 m ) of a solution is given by the cumulative effect of the contributions of different ions ... 

The major problems with Ni-based anodes and NiO cathodes are structural stability and NiO dissolution, respectively (9). Sintering and mechanical deformation of the porous Ni-based anode under compressive load lead to severe performance decay by redistribution of electrolyte in a MCFC stack. The dissolution of NiO in molten carbonate electrolyte became evident when thin electrolyte structures were used. Despite the low solubility of NiO in carbonate electrolytes ( 10 ppm), Ni ions diffuse in the electrolyte towards the anode, and metallic Ni can precipitate in regions where a H2 reducing environment is encountered. The precipitation of Ni provides a sink for Ni ions, and thus promotes the diffusion of dissolved Ni from the cathode. This phenomenon... 

A stabilising effect in the presence of salt was also noted by Aronson and Petko [90]. Addition of various electrolytes was shown to lower the interfacial tension of the system. Thus, there was increased adsorption of emulsifier at oil/water interface and an increased resistance to coalescence. Salt addition also increased HIPE stability during freeze-thaw cycles. Film rupture, due to expansion of the water droplets on freezing, did not occur when aqueous solutions of various electrolytes were used. The salt reduced the rate of ice formation and caused a small amount of aqueous solution to remain unfrozen. The dispersed phase droplets could therefore deform gradually, allowing expansion of the oil films to avoid rupture [114]. 

Figure 8.11—Effecl of diffusion on the efficiency obtained in HPLC and CE. Diffusion increases with the square of tube diameter. This is, thus, more important in HPLC. In CE. the electrolyte is repelled by the wall leading to an almost perfect plane-like flow contrary to the usual parabolic profile obtained under hydrodynamic flow. However, other factors that depend on the difference in conductivity between the electrolyte and solutes can lead to peak deformation.

This is the kinetic equation for a simple A/AX interface model and illustrates the general approach. The critical quantity which will be discussed later in more detail is the disorder relaxation time, rR. Generally, the A/AX interface behaves under steady state conditions similar to electrodes which are studied in electrochemistry. However, in contrast to fluid electrolytes, the reaction steps in solids comprise inhomogeneous distributions of point defects, which build up stresses at the boundary on a small scale. Plastic deformation or even cracking may result, which in turn will influence drastically the further course of any interface reaction. 

In addition to the occurrence of the residual stress, cells warp toward the cathode side because of the mismatch of the thermal expansion behavior between the electrolyte and anode. Thus, the deformations of cells at room temperature are also... 

Fig. 10.29 Calculated stress distribution at the electrolyte for the single-cell stack model. The stress is calculated from the data shown in Figure 10.15. To magnify the deformation of the electrolyte at the edge, the deformed shape of the electrolyte is illustrated at x 10 magnification.

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