Hydrogen discharges

A container of hydrogen at 2 bar at 27 F is damaged causing a 1 cm" sharp-edged opening What is the rate of hydrogen discharge into the atmosphere ... 

Reider et al. (1965) describe the incident at Los Alamos Laboratory in Jackass Flats, Nevada. An experiment was conducted on January 9, 1964, to test a rocket nozzle, primarily to measure the acoustic sound levels in the test-cell area which occurred during the release of gaseous hydrogen at high flow rates. Hydrogen discharges were normally flared, but, in order to isolate the effect of combustion... 

Anodic or cathodic inhibitors This classification is based on whether the inhibitor causes increased polarisation of the anodic reaction (metal dissolution) or of the cathodic reaction, i.e. oxygen reduction (near-neutral solutions) or hydrogen discharge (acid solutions). 

In acid conditions oxide films are not usually present on the metal surface and the cathodic reaction is primarily that of hydrogen discharge rather than oxygen reduction. Thus, inhibitors are required that will adsorb or bond directly onto the bare metal surfaces and/or raise the overpotential for hydrogen ion discharge. Inhibitors are usually organic compounds... 

Fig. 15-1. The spectrum of light emitted by a hydrogen discharge tube.

Hydrogen discharge Tube emiTs 1 tghT crt special frequencies only... 

Fig. 15-2. Contrast between the continuous spectrum of a hot tungsten ribbon and the line spectrum of a hydrogen discharge tube.

High voltage hydrogen discharge lamps which give continuous radiation in the ultra-violet can be constructed quite simply and elaborate designs are unnecessary for many purposes. A very simple... 

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. 

In a silane-hydrogen discharge the feedstock gases SiHa and H2 take part in all the processes that occur. A large number of reactions have been proposed (see e.g. Kushner [190]). Nienhuis et al. [191] have performed a sensitivity analysis in their self-consistent fluid model, from which a minimum set of reactions have been extracted for a typical low-pressure RF discharge. Tables II and III list these reactions. They will be used in the plasma models described in subsequent sections. The review articles on silane chemistry by Perrin et al. [192] and on hydrogen by Phelps [193] and Tawara et al. [194] have been used. The electron collision data are compiled in Figure 13 [189]. 

The ID fluid discharge model has been applied to the ASTER deposition system (see Section 1.2.4). The deposition reactor has an inner volume of 10 1 and an inner diameter of 20 cm. The upper electrode is grounded (see Fig. 4a), and the powered electrode is located 2.7 cm lower. Other typical silane-hydrogen discharge parameters are summarized in Table IV. 

As a first attempt to modify the code to be able to run simulations on SiH4-H2 discharges, a hybrid PlC/MC-fluid code was developed [264, 265]. It turned out in the simulations of the silane-hydrogen discharge that the PIC/MC method is computationally too expensive to allow for extensive parameter scans. The hybrid code combines the PIC/MC method and the fluid method. The electrons in the discharge were handled by the fluid method, and the ions by the PIC/MC method. In this way a large gain in computational effort is achieved, whereas kinetic information of the ions is still obtained. 

The plasma potential determined from I-V data for argon increases linearly from about 24 to 27 V with increasing power at a pressure of 0.05 mbar. At the highest pressure of 0.35 mbar these values have shifted downwards by about 2 V only. For the hydrogen discharge similar behavior is observed, with an increase... 

FIG. 30. Electron (a) and ion (b) density as a function of power for different pressures in the case of a hydrogen discharge. 

Sheath Properties of an Argon-Silane and Two Silane-Hydrogen Discharges"... 

Finally, nickel is electrolytically produced from the purified nickel-bearing solution. In electrowinning of nickel, the hydrogen discharge reaction competes with nickel deposition at the cathode. This counterproductive effect is minimized by keeping the acidic anolyte solution separate from the catholyte by means of a diaphragm cloth. 

Franck and Hertz (1913) first demonstrated that an electron has to acquire a minimum energy before it can ionize. Thus, they provided an operational definition of the ionization potential and showed that it is an atomic or molecular property quite free from experimental artifacts. However, this kind of experiment does not tell anything about the nature of the positive ion for this, one needs a mass spectrometric analysis. Although Thompson had demonstrated the existence of H+, H2+, and H3+ in hydrogen discharge, it seems that Dempster (1916) was the first to make a systematic study of the positive ions. 

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