Hydrogen recombination

It must be remembered that the interface of steel and enamel reacts very sensitively to hydrogen recombination, which causes cracks (fish scales) and spalling. 

The amount of the hydrogen that is liberated on or near a metal surface, which then enters the metal, varies according to the environment and condition of the metal. The main factor that promotes the entry of hydrogen into a metal is the presence on the metal of a surface poison such as sulfide or other species, which inhibit the hydrogen recombination reaction. 

Nickel compounds as catalysts, 191 Nickel-copper alloys, 252, 253 atomic hydrogen recombination, 273-279... 

The sudden expansion of the gases, as they are heated in the arc plasma, causes the formation of a high-speed arc jet so that the atomic hydrogen and the reactive carbon species are transported almost instantly to the deposition surface and the chances of hydrogen recombination and of vapor-phase reactions are minimized. 

Calculations carried out by Gottesfeld et al. [52], who borrowed from studies of thermal desorption of H2 from Cu [56, 57], indicate that H2 rather than H20 should be a product of formaldehyde oxidation at Cu at potentials up to ca. +0.4 V vs. RHE. This is provided conditions are such that the activation energy for hydrogen recombination and desorption does not exceed 10 kcal/mole. Obviously a relatively high activation energy (which appears never to be observed at Cu) favors eventual oxidation of adsorbed H atoms, before recombinative desorption can occur. Gottesfeld et al. s calculation is interesting, but perhaps not a definitive calculation since it is... 

Fig. 6. Computer simulation for hydrogen TDS from chemisorbed ethylene on Pt(lll) (a) First order process only, with activation energy - 15.0 Kcal/mole (dashed line) (b) same as (a) but including a hydrogen recombination step (solid line) (c) experimental data (crosses). See details in text.

We have measured the kinetics of ethylidyne formation from chemisorbed ethylene over Pt(lll) surfaces. The rates of reaction display a first order dependence on the ethylene coverage. There is an isotope effect, since the reaction for CjH is about twice as fast as for CjD. We obtain values for the activation energy of 15.0 and 16.7 Kcal/mole for the normal and deuterated ethylene, respectively. These values are lower than those obtained from TDS experiments, but the differences can be reconciled by taking into account the hydrogen recombination when analyzing the thermal desorption data. 

Note the discontinuous change of slope at log(t) = 5.7. This corresponds with the onset of hydrogen recombination in the photosphere (see text). 

Our direct determination of the distance to the supernova, unlike these determinations of the distance to the LMC, involves no distance ladder calibrations or selection effects. In addition, the assumptions involved in this method are independently tested by a) the match between the frequency dependence of the computed and observed spectra, b) the requirement that the ratio of the two time dependent quantities (R and 0) that determine the distance remains constant, and c) the predicted break in the (weaker) line profiles. It is especially important that we acquire accurate data for other dates so that we can invoke test (b). We believe that the distance to any Type II supernova is most reliably determined during that period of time when the photosphere lies within the hydrogen recombination shell, because this gives a long time base with which to more accurately determine R as well as a sharper photosphere to more accurately determine 0. 

Following hydrogen recombination the luminosity rises at a rate that is very sensitive to the explosion energy, the envelope mass, and to the opacity in the helium core. The ultimate source of the energy here is the decay of Co to 56Fe, a reaction that has powered the light curve since late March and especially through the peak and tail. Because the amount of 5 Ni synthesized is artificially constrained to be the same (0.07 Me V) in all our models, the peak... 

If the subsequent stage is at a lower temperature, carbon oxides and hydrogen recombine to methane, increasing the calorific value. Following C02 removal, very little enrichment is required lo achieve a product fully interchangeable with natural gas. 

Quint, W., Kaiser, R., Hall, D.S. and Gabrielse, G. (1993). (Anti)hydrogen recombination studies in a nested Penning trap. Hyperfine Interactions 76 181-188. 

Results. The presence of Pt reduces the corrosion rate of Ti by shifting the free corrosion potential to more noble values (Fig. 6) where the Ti dissolution rate is slower. This shift is produced by the catalytic effect of Pt on hydrogen recombination which alters the cathodic reactions at the alloy surface. At the corrosion potential, the cathodic and anodic currents are equal. Although the shift in corrosion potential reduces the anodic current, anodic dissolution of Ti still occurs. The long-term corrosion rate of a surface alloy depends upon what happens to the Pt as the Ti is being dissolved. If Pt is removed from the surface, the corrosion rate will increase as the implanted volume of the alloy is dissolved. If Pt builds up on the surface, the corrosion rate should remain low. 

The salient features of these reactions are the promotion of hydrogen recombination and the scavenging of oxygen radicals by molecular phosphorus. This in turn will reduce the number of effective flame propagating radical species below the level at which the flame can be sustained.26... 

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