Light scattering near phase transition points in solids

The present state of theoretical and experimental investigations of the light scattering near phase transition points in solids is reviewed. It is emphasized that the results available here may be understood on the ground of a simple but rather general phenomenological or semiphenomenological theory. From this point of view the anomaly of the total (integrated) light scattering intensity is considered with account taken of a coupling of the order parameter to other quantities including elastic strains and long-range electric fields. The temperature dependence of the scattered light spectral distribution is discussed in detail, the main attention being given to the so-called central peak problem. The influence of defects both on the total intensity and on the spectral distribution of the scattered light is also examined.     

Effect of anodic current on carbon dioxide reforming of methane on Pt electrode in a cell with solid oxide electrolyte

The carbon dioxide reforming of methane in a cell with a solid oxygen-conducting electrolyte:

Primitive Illumination Systems for Families of Convex Bodies in the Plane

Let F= {C₁,C₂,...,C} be a family of ndisjoint convex bodies in the plane. We say that a set Vof exterior light sources illuminates F, if for every boundary point of any member of Fthere is a point in Vsuch that is visible from ,i.e. the open line segment joining and is disjoint from F. An illumination system Vis called primitive if no proper subset of Villuminates F. Let p_max(F) denote the maximum number of points forming a primitive illumination system for F, and letp_max(n) denote the minimum of F) taken over all families Fconsisting of ndisjoint convex bodies in the plane. The aim of this paper is to investigate the quantities p_max(F) and p_max(n).     

Dissociative adsorption of oxygen and hydrogen, and the formation of hydroxyl groups on the surface of Cu, Ag, Ni, Pd and Pt

By the semi-empirical interacting bonds method, the heats of oxygen and hydrogen adsorption in a dissociative form on the (100) face of Cu, Ag, Ni, Pd and Pt have been calculated. It has been shown that most stable are the multiply bonded adsorption forms. For the different bonding states, the heat of hydroxyl group formation from O₂ and H₂ varies but slightly. The calculated values are compared with the experimental data.

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(100) Cu, Ag, Ni, Pd, Pt. , . - H₂ O₂. .

     

Decomposition of ammonia on rhenium I. Hydrogen adsorption on rhenium

Field emission microscopy and thermal desorption studies of hydrogen adosrption on a monocrystal tip and a polycrystalline rhenium wire indicate dissociative adsorption which proceeds with an initial sticking coefficient of S_o0.2 and an isosteric adsorption heat of about 138 kJ/mol.

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. , , S_o0.2 138 /.

     

Oxygen adsorption on silver-gold alloy

Oxygen adsorption on Ag/Au alloys has been studied by field-emission microscopy (FEM). A decrease in the silver concentration of alloy is accompanied by a drastic fall in its ability to absorb oxygen. Using the interacting bonds method (IBM), the adsorption heat of atomic oxygen on the (100) plane of the silver-gold alloy has been calculated.

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. , . (100) .

     

Studying the Interaction between Water Vapor and a γ-Al2O3 Surface by IR Spectroscopy

Russian Journal of Physical Chemistry A - The interaction between a γ-Al2O3 surface and vapors of H2O and D2O is studied via IR spectroscopy. It is shown that surface hydroxyl groups of...     

On the nature of non-faradaic catalysis on metal electrodes

Non-Faradaic change of the rate of catalytic oxidation on polarization of the catalyst electrode deposited on a solid oxygen-conducting electrolyte has been shown to result from a chain reaction mechanism involving electrochemically generated oxygen species.     

Acid and catalytic properties of MnOm?ZrO2 (M=Ca, Ba, Sm, Yb) compositions

The volume stages of ethylene glycol oxidation to glyoxal on silver have been studied by varying the catalyst grain size. Temperature oscillations have been detected in the catalyst layer. The nature of the oscillations and the range of their generation were investigated by varying the oxygen, ethylene glycol and water vapor contents in the reaction mixture. Glyoxal formation was shown to occur on the silver catalyst surface. The generation of oscillations is responsible for the CO to CO₂ oxidation in the volume between the catalyst grains.     

Adsorption of oxygen on copper and silver

Oxygen adsorption on silver has been studied using field-emission microscopy. It has been shown that adsorption is an activated process which proceeds on rough planes through the stage of formation of adsorption islands, O_ads. Using a semi-empirical interacting bonds method, the heat of oxygen adsorption has been estimated in a dissociative from on the (111), (100) and (201) planes of silver and on the (111) and (100) planes of copper.

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. , _. (111), (100), (201) (111), (100) .