ON CORRELATION BETWEEN SURFACE STRUCTURE AND CATALYTIC ACTIVITY OF AMORPHOUS ALLOYS

The present paper is a review summarizing our results gained in the field of catalysis over amorphous alloys. The route leading to the formation of the catalytically active phase is presented and the factors which may play a decisive role in this process is discussed. Following the surface characterization of amorphous alloys led to the constructions of a surface model its modifying effects are described. Their catalytic properties are further influenced by the structure and the morphology. These parameters are crucial to the formation of the active metal ensembles and to the behaviour of reactants over the surface. These factors are discussed in detail for the utilization of amorphous alloys, primarily as catalyst precursors

Relativistic diffusive motion in random electromagnetic fields

We show that the relativistic dynamics in a Gaussian random electromagnetic field can be approximated by the relativistic diffusion of Schay and Dudley. Lorentz invariant dynamics in the proper time leads to the diffusion in the proper time. The dynamics in the laboratory time gives the diffusive transport equation corresponding to the Juettner equilibrium at the inverse temperature \beta^{-1}=mc^{2}. The diffusion constant is expressed by the field strength correlation function (Kubo's formula).Comment: the version published in JP

Relativistic diffusion with friction on a pseudoriemannian manifold

We study a relativistic diffusion equation on the Riemannian phase space defined by Franchi and Le Jan. We discuss stochastic Ito (Langevin) differential equations (defining the diffusion) as a perturbation by noise of the geodesic equation. We show that the expectation value of the angular momentum and the energy grow exponentially fast. We discuss drifts leading to an equilibrium. It is shown that the diffusion process corresponding to the Juettner or quantum equilibrium distributions has a bounded expectation value of angular momentum and energy. The energy and the angular momentum tend exponentially fast to their equilibrium values. As examples we discuss a particle in a plane fronted gravitational wave and a particle in de Sitter universe. It is shown that the relativistic diffusion of momentum in de Sitter space is the same as the relativistic diffusion on the Minkowski mass-shell with the temperature proportional to the de Sitter radius.Comment: the version published in CQ

Relativistic diffusion of elementary particles with spin

We obtain a generalization of the relativistic diffusion of Schay and Dudley for particles with spin. The diffusion equation is a classical version of an equation for the Wigner function of an elementary particle. The elementary particle is described by a unitary irreducible representation of the Poincare group realized in the Hilbert space of wave functions in the momentum space. The arbitrariness of the Wigner rotation appears as a gauge freedom of the diffusion equation. The spin is described as a connection of a fiber bundle over the momentum hyperbolic space (the mass-shell). Motion in an electromagnetic field, transport equations and equilibrium states are discussed.Comment: 21 pages,minor changes,the version published in Journ.Phys.

Nanoscale bimetallic catalysts: are they really bimetallic?

The existence of bimetallic particles (and their reducibility and location on/or in the support) inRu–Co/NaYand Pt–Co/NaY samples has been studied by in situ X-ray adsorption spectroscopy (XAS). It is establishedthat in Ru–Co/NaY the monometallic clusters maintain their identity, whereas in Pt–Co/NaY the existenceof small bimetallic particles can be established. In both cases the results are supported by other techniques,such as XPS and temperature-programmed reduction

Oxidative conversion of isobutane to isobutene over V-Sb-Ni oxide catalysts

Insertion of proper amounts of nickel oxide into alumina-supported V-Sb oxide catalyst for the oxidative dehydrogenation of isobutane substantially increases isobutane conversion (from 36 to 42-44%) at selectivity to isobutene similar to70%. Fresh and used catalysts (including reference bulk V-Sb-O and V-Sb-Ni-O systems) were characterised by BET, XRD, XPS and H-2-TPR. Formation of new phase of nickel vanadate NiV2O6 at the expense of free VOx-phase leads to more reducible catalyst with increased amounts of mobile lattice oxygen. The facile redox cycle of vanadium species is considered to improve the catalyst activity. (C) 2003 Elsevier Science B.V. All rights reserved