Diffusion separation of chemical elements on a catalytic surface

Experimental and Theoretical Simulation of Heterogeneous Catalysis in Aerothermochemistry (a Review)

“…Heat flux q 0 = q/q f c at the stagnation point on a blunt body as a function of k w : 1 and 2 correspond to the nonequilibrium and frozen boundary layers, respectively. The continuous curves correspond to the calculations made using the asymptotic formulas [44][45][46] and the broken curves to the calculations in [106]. The bluntness radius R 0 = 0.5 m, T w = 700 K, T e = 6900 K, and p e = 0.216 atm ducibility of the heat fluxes on standard materials the oxide film must be stable and its catalytic properties should not vary during the thermochemical action.…”

“…In a multicomponent nonequilibrium boundary layer asymptotic formulas [44][45][46] can be used to determine k w (Fig. 1).…”

“…1). Using these formulas, the experimental data [9] on the recombination probabilities for the "Space Shuttle" heat shield coating were interpreted and the diffusion separation of the mixture elements associated with the selectivity of the catalytic action of the surface on atom recombination was detected and explained [45][46][47][48].…”

“…By virtue of the linear dependence of the system of stoichiometric equations of heterogeneous catalytic and homogeneous reactions, the rates R A can be expressed in terms of deviations of the independent homogeneous reactions v r from equilibrium in the form R s = W s ε −1 s v. The components of the matrices W s and ε s depend on the temperature, the partial pressures, the rate coefficients of the inverse processes of heterogeneous reaction, the adsorption-desorption equilibrium constants, and the independent homogeneous reaction equilibrium constants [45]. The published models of heterogeneous recombination on heat shield coatings follow from the above formulas for certain sets of parameters.…”

“…In [65,92] these reactions and the incomplete accommodation of the recombination energy on SiO 2 were taken into Curves 1-5 correspond to α 1 = ∞, 5, 1, 0.3, and 0, respectively [45] account within the framework of the shock and associative recombination mechanisms. For an N-N 2 binary mixture it was found that the quantities γ N and γ N differ strongly at low T w (β N 2 ≈ 0.2), when it is assumed that the shock recombination mechanism predominates, and are similar at high T w (β N 2 = 1), when the associative mechanism predominates (Fig.…”