Plateau voltage-temperature curves

Anodic oxide formation Lakhiani and Shreir have studied the anodic oxidation of niobium in various electrolytes, and have observed that temperature and current density have a marked effect on the anodising characteristics. The plateau on the voltage/time curve has been shown by electron microscopy to correspond with the crystallisation of the oxide and rupture of the previously formed oxide. It would appear that this is a further example of field recrystallisation —a phenomenon which has been observed previously during anodisation of tantalum" . No significant data on the galvanic behaviour of niobium are available however, its behaviour can be expected to be similar to tantalum. 

FIGURE 33.4 Typical effect of temperature on plateau voltage for high-rate silver-zinc battery (operated without heaters). Curve 1-10-h rate curve 2-1-h rate curve 3-20-min. rate curve 4-10-min. rate. 

Reaction Cell Characteristics—Gas Phase. The right angle reaction cell with an applied electric field is effectively an ionization chamber. Current-voltage curves for different electrode configurations are shown in Figure 4 for 2 torr isobutylene at room temperature. Good saturation currents are achieved with internal electrodes. When the bottom electrode was external to the reaction cell, no saturation current plateau was found. 

More detailed measurements of the dependences Uth f) in pure and doped MBBA at various temperatures (for sandwich cells) were performed [76, 109]. The results of these measurements are represented in Fig. 5.20. The threshold of the vortical motion was taken as the onset of the circular tion of the solid impurity particles in the electrode plane. The shape of the curves in Fig. 5.20 depends on the electrical conductivity. With a high electrical conductivity the curves have a plateau in the low-frequency region and a characteristic dependence I7th oc at frequencies above the critical frequency. At the transition point to the nematic phase the threshold voltage of the instability does not change. It is shown in [109] that the height of the low-frequency plateau is proportional to and at frequencies of u > 47r(j/e the threshold field does not depend on <7. Moreover, it does not depend on the thickness of the sample, i.e., on the separation between the electrodes. 

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