Steady state and dynamic characteristics of two-center mechanisms of catalytic reactions

Various model mechanisms of catalytic reactions proceeding over two active centers are described. The conditions for the multiplicity of setady states are analyzed. A possibility for the quasi-chaotic behaviour of these system is shown.

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On a diffusion model of a catalytic reaction

A model to describe a catalytic reaction with simultaneous diffusion is analyzed. The possibility of formation of periodic structures in space is shown.

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Crystal structures of lanthanide and zirconium phosphates with general formula Ln0.33Zr2(PO4)3, where Ln=Ce, Eu, Yb

Crystal structures of synthetic phosphates Ce_0.33Zr₂(PO₄)₃, Eu_0.33Zr₂(PO₄)₃ and Yb_0.33Zr₂(PO₄)₃ have been refined by Rietveld method using powder diffraction data. Unit cell parameters: a=8.7419 (4), c=23.128 (2) Å; a=8.7659 (1), c=22.822 (1) Å; a=8.8078 (4), c=22.485 (3) Å, respectively; Z=6. Values of final R-factors in isotropic approximation: R_wp=4.00, R_wp=3.33, R_wp=4.12%, respectively. New space group P3¯c has been established for the compounds with general formula Ln_0.33Zr₂(PO₄)₃, where Ln=Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y. It has been confirmed that the synthetic phosphates with general formula Ln_0.33Zr₂(PO₄)₃ belong to the NZP (sodium zirconium phosphate) structure type.     

Parametric analysis of eigenvalues of matrices corresponding to linear one-route catalytic reaction mechanism

The parametric analysis of accepted eigenvalues of matrices observed in chemical kinetics and corresponding to the linear n-stage one-route mechanisms with irreversible stages has been conducted. Relaxation times with varying one of the rate constants are given. The possibility of nonmonotonic change of relaxation times with growing rate constants is shown.

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Effective heterogeneous palladium catalysis of the reactions of organoboron compounds with aryl halides

Reactions of [Ph₄B]Na and ArB(OH)₂ with aryl halides are effectively catalyzed by heterogeneous palladium catalysts (PdCl₂C, Pd(0)/C, and palladium black) to give cross-coupling products in high yields. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1399–1401, July, 1997.     

Scanning tunnelling microscopic investigation of fullerene monolayers

C₆₀ fullerene monolayers have been investigated by scanning tunnelling microscopy/spectroscopy. Single C₆₀ molecules have been resolved and a regular surface lattice structure of fullerene – in – surfactant is observed. Tunnel electron spectroscopic measurements results in typical I(V) curves which are interpreted in terms of the two-junction Coulomb blockade effect.     

Variation in the EPR characteristics of nanosized zirconia particles under exposure to X-ray radiation and annealing in hydrogen

The effects of various external factors on the properties of nanosized zirconia particles are studied using electron paramagnetic resonance. It is shown that x-rays initiate radiation-stimulated oxidation of chromium impurity ions according to the scheme Cr³⁺ → Cr⁵⁺. Annealing of samples in hydrogen at temperatures in the range 250–650°C brings about a substantial decrease in the fraction of chromium ions in the Cr⁵⁺ charge state, but subsequent annealing of these samples in air leads to an increase in the Cr⁵⁺ fraction. Samples annealed in hydrogen generate a singlet EPR signal with the g factor of 2.0033 ± 0.0005 originating from electrically conducting regions which are formed on the surface of zirconia nanoparticles during their annealing in hydrogen.     

Gas formation upon γ-irradiation of cement material

The effect of ionizing radiation on cement material was studied over a dose range of up to 2 MGy. Hydrogen is the main gaseous product. Its initial yield is ～0.8 molecule/100 eV. Incorporation of nitrates into the cement compound leads to an almost complete suppression of hydrogen formation. Simulation results show that the cement is characterized by the process of transfer of ionizing-radiation energy between water and the solid components.