Flux, of hydrogen

The possible preparation of InAs by crystallization from the melt depends also on the liquidus shape (especially in the In-rich region). A summary of previous liquidus measurements was reported by De Winter and Pollack (1986) who employed a source dissolution method based on the equilibration, at a fixed temperature, of a known quantity of high-purity indium with single crystals of InAs, the weight loss of which was determined. The experiments were carried out under a flux of hydrogen purified via permeation through palladium. 

Environmental barrier coatings are a type of laminar composite. As with heat transfer, diffusion in laminar composites can be modeled as steady state diffnsion throngh a composite wall, as iUnstrated in Fignre 4.56. Here, hydrogen gas is in contact with solid material A at pressnre Pi and in contact with solid B at pressnre P2. At steady state, the molar flux of hydrogen throngh both walls mnst be the same (i.e., Jh ax = Bj) and Fick s Law [Eq. (4.4)] in the x direction becomes... 

Combine your information to calculate the flux of hydrogen (in kg/m s) through the composite wall if both metals have a thickness of 1 mm. 

The experiment was performed with a quench-and-look approach, whereby the model system was first heated to 673 K and exposed to low amounts of atomic hydrogen produced by dissociating H2 on a glowing tungsten filament. The flux of hydrogen was then terminated, and the clusters were exposed to thiophene at an elevated sample temperature of about 500 K. Subsequently, the model system was... 

The nitrogen cycle is closely connected with the fluxes of hydrogen, sulfur, and other chemicals (Smith et al., 1998 Dimitroulopoulou and Marsh, 1997 Chapin et al., 2002 Rhee et al., 2005 Stevenson and Cole, 1999). Nitrogen and hydrogen react under great pressure and temperature in the presence of a catalyst to make ammonia. The study of correlations between the cycles of these elements is necessary to improve... 

Of particular interest is the mechanism of impurity transport in the Tokamak plasma. Classical transport theory predicts an accumulation of heavy impurities in the plasma core with an adequate outward flux of hydrogen. However, various processes, such as plasma turbulence, can have an opposite effect and this problem is still a subject of theoretical investigation49. ... 

Thereafter, combining Equations 5.81 through 5.83 the flux of hydrogen can be written with the help of the ambipolar diffusion equation [45,69]... 

When supposing that hydrogen in the probe is contained in traps with different binding energies u,. and corresponding diffusion constant D , and hydrogen concentrations one can use the superposition principle, due to linearity of diffusion equation (5). Then the total flux of hydrogen from the probe q(t) can be expressed by the sum ... 

Data obtained at NETL for hydrogen flux through the ANL-1 dense ceramic membranes were correlated to yield a flux expression. The flux of hydrogen through these... 

If transport through a membrane involving both surface reaction (dissociation) and diffusion was limited by surface reactions, then n = 1. If transport was diffusion-limited, then n = 0.5. Intermediate values of n (0.5proton transport membranes was modeled with the same form of the equations used to model diffusion membranes, Eqns. 3 and 4. Values of k H2 and n were determined from Eqn. 3. The concentration of hydrogen on the permeate-side was insignificant relative to the concentration on the retentate-side. Therefore was equated to... 

An attempt was made to correlate the slope of the sensor response curve to the initial diffusible hydrogen concentration in the sample. The steady state portion of the curve could be assumed to be proportional to the flux of hydrogen from the weld metal. To investigate this possibility theoretical curves were generated using an equation derived from the error function erf(x). 

A pseudosteady state may be assumed to exist in the cataiyst bed, and the temperature of a catalyst particle may be thought to be constant. In such a case, all of the heat produced by the reaction must be transported from the catalyst surface to the surroundings by convection to the gas stream. In this way the feedback of heat is established from the reaction site to the gaseous reactant. Under the above conditions the molar flux of hydrogen (which we call reactant A) to the surface of the particle, multiplied by the heat liberated per molar unit of A converted (-A//r)A must be equal to the heat flux coming from the surface ... 

Charge balance requires that the outward flux of cations from the silicate be balanced by the inward flux of hydrogen ions. For example, the apparent sodium diffusion coefficient in equation 5 is therefore really the interdiffusion coefficient, +,... 

Measurement of palladium membrane permeability. The permeation rate of hydrogen gas through the palladium membrane, Q , was assumed to obey the half-power pressure law(20). The permeation flux of hydrogen through the membrane is proportional to the difference between the souare roots of the hydrogen partial pressure on the high and low pressure sides of membrane. 

Fig. 32. Computed fluxes of hydrogen atoms in flame of Fig. 25. (a) Convective flux, Afiun (see eqn. (64)) (b) ordinary diffusions flux, j (c) thermal diffusional flux,yjf (d) overall flux, MGyf.

The fluxes of hydrogen sulfide to the atmosphere have not been easy to establish with... 

To save the space, further development deals solely with stress assisted diffusion since its generalization for the case of stress-assisted diffusion is straightforward. According to previous studies [2], it is assumed that hydrogen diffusion through material proceeds toward the sites where the lowest concentration or the higher hydrostatic stresses occur. The combination of these factors results in an equation for the stress-assisted diffusion flux of hydrogen which is ... 

Fig. 9.25. Flux of hydrogen (O), helium (V), carbon dioxide (+) and sulphur hexafluoride A as a function of temperature at a feed pressure of 100 kPa. After Vroon et al. [72-74].

Note that D21 is zero regardless of the composition of the mixture. Hence, the flux of hydrogen (2) depends on its own composition gradient Vx2 only... 

The flux of hydrogen (component 1) is not too different from the flux estimated using the linearized equations in Example 5.3.1. However, the effective diffusivity method predicts a very small flux of nitrogen (component 2), a result quite different from the predictions of the linearized theory. This, of course, is because the effective diffusivity method ignores the contribution due to the driving forces of the other components. We will investigate the consequences of this prediction in Example 6.4.1. ... 

The iron is especially important. In freshwater ecosystems, fluxes of hydrogen sulfide are also relatively small owing to the lack of sufficient sulfate as a substrate for dissimilatory reduction and to the relatively greater incorporation of the available sulfur into biomass. However, the release of hydrogen sulfide is significant from wetlands. In addition, H2S emission from plant canopy occurs when S plant uptake is in excess of biosynthetic demands. The latter process may account for as much as 40% of total natural S emission. 

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