Hydrogen capacitance

Such an equation can be applied for the determination of - pseudocapacitances (e.g., hydrogen capacitance of a platinum electrode) in the case of the so-called charging curve experiments. 

Eigure 3-5.4.1 was constructed from data in Table A-4-1.3. It shows that hydrogen s LMIE is found for small diameter spark electrodes using a circuit having a small capacitance and hence a small RC time constant. The same general trend is also found for methane and is primarily due to reduced... 

FIQURE 3-5.4.1 Effect of electrode diameter and circuit capacitance on MIE of hydrogen in... 

As the tank fills the capacitance increases while the leakage resistance decreases in proportion to the wetted area. The conservative case is to consider only the floor area. Assume that the charging current Iq < 10 pA and that the gas involved is hydrogen, whose LMIE W = 0.016 mJ. Eor lining thickness d = 2 mm, dielectric constant = 4, and floor area A = 10 m, the... 

Table A-4-1.3a, based on data in [62], shows how the MIE (mJ) of 28 vol% hydrogen and 8.5 vol% methane in air vary with circuit capacitance (pF) and electrode diameter (mm). Points refers to the use of steel gramophone needles. The table shows that MIE is decreased with decreased capacitance and electrode diameter however, as reflected in Figure 3-5.4.1 corona...

To apply these data and equations to the problem of ground resistance, the maximum anticipated current must first be estimated. For practical industrial situations, Iq varies in the range 0.01-100/rA. The upper value represents extreme cases such as microfiltration and the lower value to slow flow in pipe. Typical charging currents for tank tmck loading are of the order 1 /rA (5-3.1.1). As an example, consider a system such as a tank with a capacitance less than 1000 pF. First, consider the minimum ignition voltages in Table A-4-1.3b. From Eq. (2), f L = In the case of hydrogen the mini-... 

Transient measnrements (relaxation measurements) are made before transitory processes have ended, hence the current in the system consists of faradaic and non-faradaic components. Such measurements are made to determine the kinetic parameters of fast electrochemical reactions (by measuring the kinetic currents under conditions when the contribution of concentration polarization still is small) and also to determine the properties of electrode surfaces, in particular the EDL capacitance (by measuring the nonfaradaic current). In 1940, A. N. Frumkin, B. V. Ershler, and P. I. Dolin were the first to use a relaxation method for the study of fast kinetics when they used impedance measurements to study the kinetics of the hydrogen discharge on a platinum electrode. 

The plasma potential is about 25 V (Figure 63a). This value of the plasma potential is typical for the silane plasmas in the asymmetric capacitively coupled RF reactors as used in the ASTER deposition system, and is also commonly found in argon or hydrogen plasmas [170, 280, 327]. From the considerable decrease of the dc self-bias with increasing frequency (Figure 63a) it is inferred that the... 

Plasma processes have been successfully demonstrated for production of metals from their oxides and chlorides intermediates. Reducing agents are, of course, to be used. Thus, a plasma-based process involving reduction of tantalum chloride in hydrogenous atmosphere has been claimed to yield highly pure metal powder suitable for making of porous capacitor of high capacitance. 

This was averaged over the total distribution of ionic and dipolar spheres in the solution phase. Parameters in the calculations were chosen to simulate the Hg/DMSO and Ga/DMSO interfaces, since the mean-spherical approximation, used for the charge and dipole distributions in the solution, is not suited to describe hydrogen-bonded solvents. Some parameters still had to be chosen arbitrarily. It was found that the calculated capacitance depended crucially on d, the metal-solution distance. However, the capacitance was always greater for Ga than for Hg, partly because of the different electron densities on the two metals and partly because d depends on the crystallographic radius. The importance of d is specific to these models, because the solution is supposed (perhaps incorrectly see above) to begin at some distance away from the jellium edge. 

The decrease in free carriers (holes) after hydrogenation of p-type Si is also evidenced by the decrease in IR absorption at the longer wavelengths, where free-carrier absorption dominates, and by a decrease in the device capacitance of Schottky-barrier diodes, due to the increase in the depletion width (at a given reverse bias) as the effective acceptor concentration decreases. 

Fig. 3. Capacitance transient spectra from Au-diffused p-type Si showing passivation of the Au donor level (Ev + 0.35eV) after exposure to a hydrogen plasma.

Fig. 5. Capacitance and current transient spectra from -type, CZ grown Si annealed for 18h at 450°C to form the shallow, oxygen thermal donors. (Chantre et al., 1987). Hydrogenation at 200°C passivates the electrical activity of these thermal donors (Chantre et at, 1987).

Fig. 8. Capacitance transient spectra recorded under the same conditions for Ar+ sputter etched n-type Ge. (a) substrate temperature 25°C during sputtering, (b) substrate temperature 100°C during sputtering and (c) after sputter etching and hydrogenation at 180 C for 20 min. (Pearton et al., 1983).

Fig. 9. Capacitance transient spectra for (a) sputter-etched p-type Si and (b) after hydrogenation of the sputter-damaged Si at 180°C for 20 min.

Fig. 11. (a) Capacitance transient spectra from Co-60 - irradiated, n-type Si samples, one of which had been pretreated in an H plasma. Note the reduced defect state density in this sample, (b) Concentration profile of the O-V centers induced in these samples. There is a reduced defect concentration only in the region in which atomic hydrogen was incorporated. 

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