Sweep curves

The hemispherical electrode may be coupled with a ring [20] to form a rotating ring-hemisphere electrode (RRHSE) as shown as Fig. 9(d). The ability of this combination to detect intermediate reaction products is demonstrated in Fig. 10, where a series of cathodic sweep curves for the reduction of Cu2 + in acidic cupric chloride solution are... 

Fig. 5. In situ Mossbauer spectra of the same electrode as in a) Fig. 4 at -0.3 V, after a potential step (Curve a), and after a potential sweep (Curve b), from -1.1 V. Curve c was obtained at a potential of -1.2 V.

The most well known work that Conway and his colleagues completed in Ottawa was on the analysis of potential sweep curves. I had been critical of the application of potential sweep theory to reactions which involved intermediates on the electrode surface and, working particularly early with Gilaedi and then with Halina Kozlowska, and to some extent with Paul Stonehart, Conway developed an analysis of the effect of intermediate radicals on the shape and properties of potential sweep showing how interesting electrode kinetic parameters could be thereby obtained. 

Fig. 7.79. Current-voltage sweep curves on platinum single-crystal faces (100), (111), and (110) at 25 °C. Sweep range 50-1550 mV, sweep rate 0.1 V/s. (Reprinted from F. G. Will, J. Electrochem. Soc. 112(4) 451, 1965. Reproduced by permission of The Electrochemical Society, Inc.)...

Quantitative Calculation of Kinetic Parameters from Potential-Sweep Curves... 

Figure 9-25 Comparison of sweep rates on nmr absorption curves (a) 500-sec sweep, (b) 50-sec sweep, (c) 10-sec sweep. The ringing in the faster sweep curves is a transient effect that has a small effect on the position of the peak and none on the integral.

The one exception in which phase contrast is not due to the dissipation arises when the tip jumps between attraction phases (>90°) and repulsion phases (<90°). Since sine is a symmetric function about 90°, the phase changes symmetric even if there are no losses in the tip-sample interaction. The relative contribution of the repulsive and attractive forces can be estimated experimentally from the frequency-sweep curves in Fig. lib by measuring the effective quality factor as Qe=co0/Ao)1/2, where Ago1/2 is the half-width of the amplitude curve. The relative contribution of the attractive forces was shown to increase with increasing the set-point ratio rsp=As/Af. Eventually, this may lead to the inversion of the phase contrast when the overall force becomes attractive [110,112]. The effect of the attractive forces becomes especially prominent for dull tips due to the larger contact area [147]. 

Figure 9.1 (a) Cyclic voltammetric sweep curve for the Nafion/ZnO/Au electrode without... 

Fig. 6.17. Cyclic voltammograms of o-phenylenediamine (101 M) oxidation for W03 thermal-treated (350°C) anodic films (b) and smooth platinum electrode (c) first sweep (curves 1) and repeated sweep (curves 2) scan rate was 80 mV/cm2. The left picture shows a schematic representation of the morphology of thermal-treated anodic W03 film tungsten support, highly defective oxide (including the continuous donor clusters), moderately doped oxide (non-shaded region), poly-o-phenylenediamine deposits.

Fig. 8. Cyclic voltammograms, recorded in the dark at 50 mV s", in deaerated 0.1 M aqueous NaOH, illustrating cathodic reduction of the species photogenerated at the Ti02 electrode in open circuit. Time of exposure to UV illumination (X > 335 nm) 2 min 30 min and 14 h for, respectively, curves b, c, and d. Delay of 2 min between the light-off and starting of the cathodic sweep. Curve a is r resentative of the second and following sweeps ...

Moreover, rotational rheometers can be used in dynamic oscillatory mode, frequency sweep, to assess the elastic G module as well as the viscous G" module and the correlated phase angle 6, as a function of the frequency co. G and G" allow to study the viscoelastic behaviour of HA macromolecules. Fig. (15) shows the frequency sweep curves (G, G", and tg(5) vs. the frequency co) for an HA sample (Mw=1350 kDa, polydispersity index D=1.6, concentration c = 2%) at 20 °C. 

Fig. 11.10 Linear sweep semi-integral and semi-differential curves of 10 SM Cd(II) in 1M NaCI at a DME. Average of 25 scans, (a) Linear sweep curve, (b) Linear extrapolation of background current, (c) Background-corrected linear sweep curve, (d) Semi-integral curve, (e) Least-squares fitted semi-integral curve, (f) Semi-differential curve. (Reproduced from [39] with permission of the American Chemical Society).

Figure 5A SMART Pd technology sweep curve Efficiency %...

It is possible to evaluate U from direct analysis of the potential sweep curve/ Assuming reversibility of the hydrogen wave during the potential sweep, we may rewrite Eq. (5) as... 

Fig. 57. Convolutive and deconvolutive transformations of current transients for reversible systems. Solution of 1 x 10 M Cd in 0.11 M KCl 1 and 1 forward and backward linear sweep curves, 0.2Vs" 2 and 2 semiintegral curves (convolution vs. time) 3 and 3 semidifferential curves (deconvolution vs. potential). Dimensionless variable y results in particulate operations. Adapted according to [123].

When a crystal is. placed on an X-ray goniometer and rotated in the X-ray beam, the intensity of reflection rises to a maximum and then falls away. The more ideal the crystal the sharper is this sweep curve . Calculations have been made of the angular breadth of the sweep curve for an ideal crystal, which show that only a few seconds of arc will cover the whole breadth of the curve. Analogous calculations for a mosaic crystal indicated a much greater angular breadth of the sweep curve , which may amount in extreme cases to several degrees. In Table 78 (15) are illustrated the observed breadths of sweep curves at their points of half intensity and also values of the integrated reflection defined as... 

Although pure WC has no significant ORR catalytic activity, the addition of it to Pt could lead to an improvement [75, 76]. Figure 2.27 shows the linear sweep curves of ORR on W2C, Pt/C, and W2C-Pt/C catalysts. The best activity can be observed with a W2C-Pf/C catalyst. 

Figure 2.27. Linear sweep curves of oxygen reduction on different catalysts in 02-saturated 0.5 M H2SO4 solution at 25 °C curve 1, 80 pg W2C curve 2, 80 pg Pt/C curve 3, 40 pg Pt+80 pg W2C scan rate 2 mV/s [75]. (Reprinted with permission from J Phys Chem B 2005 109 22705-9. Copyright 2005 American Chemical Society.)...

Interpretation of IC-AFM images is complicated by the fact that the tip-sample force is a nonlinear function of tip-sample separation. The tip-surface interactions in IC-AI have been modeled extensively and have been recently reviewed [109, 143]. Two important conclusions have come from the modeling. First, the nonlinear interaction of the dynamic tip with the surface can lead to two stable oscillation states one that follows a net attractive path and the other that follows a net repulsive path [147, 148]. A hint of this is seen in the phase versus frequency plot (see Fig. 3.32) where the cantilever initially oscillates along an adhesive path and then abruptly transitions to the repulsive path. Simulated amplitude and phase (z-sweep) curves can reproduce those determined experimentally. These have been interpreted in terms of force based interaction models that include the effect of capillary forces and adhesive forces when they are known or can be estimated. The transition between the bistable states depends on a number of factors including the cantilever Q, Ao, and r p, and the drive frequency as well as the surface properties [149]. In general high Q cantilevers or small Ao favor the net attractive path. 

Figure 12.3 Strain-sweep curves of thickened emulsions containing 80% water and 0.3 wt% polymer (1) or 4.0 wt% fatty alcohol (2) at 25 C upper set of curves shows G, lower set G"...

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