Voltage critical

FIG. 22-28 Regimes of operation of cross-flow-electrofiltration (a) voltage less than critical, (h) voltage equal to the critical voltage, (c) voltage greater than critical. 

Ionization The critical voltage at which gas molecules are separated into positive and negative ions in an electrostatic precipitator. 

As indicated above, when a positive direct current is impressed upon a piece of titanium immersed in an electrolyte, the consequent rise in potential induces the formation of a protective surface film, which is resistant to passage of any further appreciable quantity of current into the electrolyte. The upper potential limit that can be attained without breakdown of the surface film will depend upon the nature of the electrolyte. Thus, in strong sulphuric acid the metal/oxide system will sustain voltages of between 80 and 100 V before a spark-type dielectric rupture ensues, while in sodium chloride solutions or in sea water film rupture takes place when the voltage across the oxide film reaches a value of about 12 to 14 V. Above the critical voltage, anodic dissolution takes place at weak spots in the surface film and appreciable current passes into the electrolyte, presumably by an initial mechanism involving the formation of soluble titanium ions. 

It follows from Eqs. (73) and (74) that the only stabilizing force for a-modes at long X is the membrane tension, and critical voltage vanishes as cr 0. In experiments with black lipid membranes the surface tension a arises from the contact of the bilayer with the bulk phase contained in the surrounding rim and is typically < 0.002 N/m. Then choosing... 

In the next step the wave-length corresponding to each peak is determined from the critical voltage and the quantum equation... 

In Figure 50, the lower curve for E=3.9 v/cm shows a transition in slope. The flux decreases with decreasing Reynolds numbers until a point is reached where the convective transport of particles toward the membrane is just equal to the electrophoretic migration away from the membrane-i.e. the voltage is now the critical voltage. Further decreases in the Reynolds number will not decrease the flux as there is now no concentration polarization. 

In such models, the bonding is considered to be partially ionic with a charge transfer from A1 to the Ni 3d valence band. To explain the properties of /J NiAl at a more sophisticated level, Fox and Tabernor (1991) measured four low-angle structure factors by the HEED critical-voltage technique. The deformation density based on these four reflections shows a depletion of density around both the Ni and A1 atoms, and a buildup of about 0.13 eA-3 along the [111] direction halfway between Ni and A1 nearest neighbors. 

ZnO-electrodes (band gap 3.2 eV) have in this connection been studied in great detail 30,31,47,48,49). We give here a few typical examples of the experimental results. Fig. 13 shows the dependence of the photocurrent on electrode potential for the dye rhodamine adsorbed at a ZnO-electrode with illumination in the wave length range of the absorption maximum of the dye (A=570 nm). The photocurrent reaches a saturation above a critical voltage which is about 0.25—... 

For a fixed distance, sparking occurs at a critical voltage leading to smoke, flame, flash, crackling, decomposition, ignition or explosion. This critical voltage is a measure of electric spark or electrostatic discharge sensitivity of the explosive under test [71-73]. 

In (5.4.8) V is the direct voltage component, whereas A and u = 27r/ = (2n/T) are, respectively, the amplitude and the cyclic frequency of a harmonic modulation superimposed upon V, above some critical voltage VCT. 

The critical voltage gradient can be expressed for a particular droplet as... 

Ec = Critical voltage gradient K Dielectric constant for the system... 

Certain metals, such as aluminum, magnesium, and tantulum, when immersed in an electrolyte, possess the property of allowing electricity to flow in one direction and not in the other, provided a certain critical voltage is not exceeded. Two electrodes of this kind practically prevent all flow of electricity and constitute what is known as an electrolytic or chemical condenser. This phenomenon was d Vovered bv Wheatstone in 1855. 

The critical voltages for aluminum plates in electrolytes formed by 1 per cent, solutions of various chemicals, tested after 24-hour formation of the film, are as follows ... 

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