Ethylene Adsorption and Oxidation Kinetics in the Reactions with Pd(II)/SiO2 and Cr(VI)/SiO2: Consideration of Substrate Distribution between the Gas Phase,Silica Gel,and Reaction Centers

The kinetics of ethylene oxidation by PdCl₂ and CrO₃ complexes supported on silica gel (300 K, closed batch reactor) and the adsorption of C₂H₄ by silica gel and metal complex reaction centers (M ⁿ ) were studied. A new version of the kinetic distribution method was applied to determine the rate constants of ethylene reactions with metal complexes with consideration for the equilibrium distribution of C₂H₄ among the reactor gas phase, silica gel, and M ⁿ . The rate constant of a first-order reaction with respect to Cr(VI) (k _e) remained constant as [M ⁿ ] was increased up to 0.15 mol % with the absence of detectable ethylene adsorption by chromium(VI). In the case of Pd(II)/SiO₂, strong ethylene adsorption by palladium(II) was found, and k _e was an exponential function of [M ⁿ ]. This exponential function is indicative of an increase in the specific activity of Pd(II) with palladium concentration on SiO₂. Taking into account the adsorption of ethylene (physisorption on SiO₂ and chemisorption on Pd(II)), we found an analogy between the kinetic behaviors of Pd(II) in reactions with ethylene on silica gel and with ethylene and other hydrocarbons in solutions.     

Epitaxy of AlxGa1−xSb films from a molten metal.

Conclusions Crystallization from a solution of antimony in a gallium-aluminum melt has been used to produce epitaxial Al_xGa_1–xSb films with x=0 to 0.4; isothermal (T = 450, 500, 550°C) and isoconcentration (0; 1; 2.4 at. % Al) sections have been drawn for the liquidus surface on the composition plane. X-ray microspectral analysis has been used to examine the composition of the Al_xGa_1–xSb films in relation to aluminum content in the melt, as well as the distribution of Al and Ga over the epitaxial film. These films had a perfect structure. The results enable one to determine the solution composition needed to grow Al_xGa_1–xSb epitaxial films at 450–550°C on gallium antimonide substrates, and it is shown to be possible to make heterostructures in the Al_xGa_1–xSb-GaSb system.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 16, No. 9, pp. 146–148, September.We are indebted to Zh. I. Alferov and V. I. Shveikin for attention and support in this work.     

Structural chaos and a quasi-crystalline stochastic web in low dimensional nonlinear systems

The problem of equilibrium of one-dimensional, discrete nonlinear models of a solid is reduced to a 4-dimensional representation generated by a stochastic web whose symmetry depends on the model parameters. The Trade and Economics Institute of the Krasnoyarsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 42, No. 1, pp. 44–49, January, 1999.