New solution of the Landau kinetic equation for the energy loss of fast particles in crystals

A solution of the Landau kinetic equation for the energy loss of fast particles in crystals has been constructed in the form of a series, each term of which corresponds to the Gaussian distribution. The calculated results are compared with the experimental ones.     

Composites Based on Polytetrafluoroethylene and Detonation Nanodiamonds: Filler–Matrix Chemical Interaction and Its Effect on a Composite’s Properties

Specific properties of PTFE composites filled with ultradisperse detonation diamonds (UDDs) with different surface chemistries are studied. It is found for the first time that filler in the form of UDDs affects not only the rate of PTFE thermal decomposition in vacuum pyrolysis, but also the chemical composition of the products of degradation. The wear resistance of UDD/PTFE composites is shown to depend strongly on the UDD surface chemistry. The presence of UDDs in a PTFE composite is found to result in perfluorocarbon telomeres, released as a readily condensable fraction upon composite pyrolysis. The chemical interaction between PTFE and UDDs, characterized by an increase in the rate of gas evolution and a change in the desorbed gas’s composition, is found to occur at temperature as low as 380°C. It is shown that the intensity of this interaction depends on the concentration of oxygen-containing surface groups, the efficiency of UDDs in terms of the composite’s wear resistance being reduced due to the presence of these groups. Based on the experimental data, a conclusion is reached about the chemical interaction between UDDs and a PTFE matrix, its dependence on the nanodiamond surface chemistry, and its effect on a composite’s tribology.     

Cleaning of the Surface of Silver Crystals Used as Catalysts of Gas-Phase Oxidation of Ethylene Glycol to Glyoxal

The procedure for cleaning polycrystalline fibers of electrolytic silver used as a catalyst for gas phase oxidation of ethylene glycol to glyoxal was developed with the aid of X-ray photoelectron spectroscopy.     

State of palladium in palladium-aluminosilicate catalysts as studied by XPS and the catalytic activity of the catalysts in the deep oxidation of methane

Palladium catalysts based on Siralox and AS aluminosilicate supports for the deep oxidation of methane were studied. With the use of XRD analysis, it was found that they were heterophase systems consisting of an amorphous aluminosilicate and γ-Al₂O₃ stabilized against agglomeration. It was found that the catalytic activity of palladium-aluminosilicate catalysts in the deep oxidation of methane at 500°C depended on the support precalcination temperature. X-ray photoelectron spectroscopy (XPS) was used to study the states of the AS-30 aluminosilicate support calcined at 600, 800, or 1000°C and palladium supported on it. It was found that the action of an acid impregnation solution of palladium nitrate on the aluminosilicate calcined at 800°C resulted in a structural rearrangement of the aluminosilicate surface. This rearrangement resulted in the stabilization of both palladium oxide and palladium metal particles at surface defects and the incorporation of these particles into the aluminosilicate after catalyst calcination. As a result, an anomalous decrease in catalytic activity was observed in aluminosilicate samples calcined at 800°C. According to XPS data, palladium in the catalyst was stabilized in the following three phases: metal (E _b(Pd 3d _5/2) = 334.8 eV), oxide (E _b(Pd 3d _5/2) = 336.8 eV), and “interaction” (E _b(Pd 3d _5/2) = 335.8 eV) phases. The ratio between these phases depended on support and catalyst calcination temperatures. The interaction phase, which consisted of PdO_x clusters stabilized in the aluminosilicate structure, was responsible for the retention of activity after calcination at high temperatures (800°C). Based on an analysis of XPS data, it was hypothesized that palladium in the interaction phase occurred in a charged state with the formal charge on the Pd atom close to 1 + (δ+ phase).     

Role of phosphates in promotion of silver catalysts for partial oxidation: II. Formation of active sites in the structure of silver phosphate under the action of a reductive medium

The morphology and chemical composition of the surface of silver phosphate are studied. The qualitative and quantitative compositions of silver phosphate are quite the same as those of the surface of the phosphorus-promoted silver catalyst. Silver particles surrounded by silver phosphate form in the subsurface region upon treatment of the sample with hydrogen. As a result, a complex catalytic system is formed in which silver phosphate is both the precursor of the reactive component (metallic silver particles) and the stabilizing matrix for this component. The system obtained is stable toward high temperature and redox reaction media.Translated from Kinetika i Kataliz, Vol. 46, No. 1, 2005, pp. 161–166.Original Russian Text Copyright © 2005 by Knyazev, Magaev, Vodyankina, Titkov, Salanov, Koshcheev, Boronin.     

Connectedness and solar properties of sets in normed linear spaces

The connectedness of certain classes of suns is studied. In particular, it is proved that a compact sun is connected in a normed space. Every sun is connected in a uniformly non-square Banach space.Translated from Matematicheskii Zametki, Vol. 19, No. 2, pp. 267–278, February, 1976.     

The chemistry of the surface of modified detonation nanodiamonds of different types

The influence of standard chemical treatment used to extract interstellar nanodiamonds from meteorites on the chemical composition of the surface of synthetic nanodiamonds with substantially different properties was studied by thermal desorption mass spectrometry and IR spectroscopy. The chemistry of the surface of nanodiamonds after treatment was substantially different from that of initial particles. The suggestion was made that the chemical structure of the surface of diamond particles in the interstellar space could be reconstructed from the data on meteorite diamonds. Mass spectrometric studies also gave information about possible mechanisms of the release of noble gases from meteorite diamonds at various temperatures.     

Thermodesorption mass spectrometry in the light of solution of the problem of certification and unification of the surface properties of detonation nano-diamonds

The results of study of the surface chemistry of detonation nano-diamonds of various types by means of the temperature-programmed desorption mass spectrometry are presented. The efficiency of surface modifications by means of severe acidic treatment and thermal oxidation as a way to unification of functional surface layer of the detonation nano-diamonds is investigated.