Use of thin film of a Co<Subscript>15</Subscript>Ti<Subscript>40</Subscript>N<Subscript>35</Subscript> alloy for CVD catalytic growth of carbon nanotubes

It is shown that multiwalled carbon nanotubes can be grown on the catalytic surface of a Co–Ti–N alloy with low (~10 at %) cobalt content by the conventional method of chemical deposition from acetylene. Adding nitrogen to the composition of the Co–Ti contributes the formation of the TiN compound and extrusion of Co onto the surface where it makes a catalytic effect for CNT growth. It was found that the tubes begin growth at a temperature of 400°C. It is shown by studies using Raman spectroscopy that the quality of CNT improves with increasing temperature.     

Low-temperature process of the formation of tubular and graphene carbon structures

The formation of carbon nanostructures by chemical vapor deposition enhanced by glow-discharge plasma is considered. The studies are conducted in the temperature range 300 to 700°C. Dependences of the structure of the carbon deposit on the thickness of the Ni catalyst film and on the concentration of the carbon-containing component in the vapor phase are analyzed. The reproducible growth of arrays of homogeneous vertical nanotubes or graphene flakes is observed at a low temperature (∼350°C). The electrical properties of the structures are studied.     

Synthesis of functionalized liquid rubbers from polyisoprene

Noncatalytic transformation of cis‐1,4‐polyisoprene rubber (M_n = 320,000) into functionalized liquid rubbers containing various amounts of carbonyl groups was studied. The process is performed via selective carboxidation of the polymer C?C bonds by nitrous oxide (N₂O) in the temperature range of 180–230°C and under 3–6 MPa pressure. The carboxidation proceeds by the nonradical type mechanism involving the 1,3‐dipolar cycloaddition of N₂O to the C?C bond. The main route of the reaction (ca. 65%) proceeds without cleavage of the internal C?C bonds and leads to the formation of ketone groups in the polymer backbone. The second route (ca. 35%) includes the cleavage of C?C bonds, yielding the molecules of a smaller size. This route results in a manifold decrease of the molecular weight, which, depending on the carboxidation degree, may be more than two orders of magnitude less than that of the parent rubber. A series of functionalized liquid rubbers having M_n value from 1000 to 19,000, and the oxygen content from 0.3 to 3.9 wt % was obtained in the form of the liquid unsaturated polyketones. Similar polyketones can also be prepared by carboxidation of the natural rubber. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

New methods for the preparation of high-octane components from catalytic cracking olefins

A new method has been suggested for the preparation of high-octane components from the butane–butylene fraction (BBF) in two stages. At the first stage, the BBF olefins are oxidized with N₂O into carbonyl compounds with high selectivity without forming the products of deep oxidation and water. The process occurs in the gas phase in a flow reactor without using a catalyst at a temperature of 400°C and a pressure of 2 MPa with high conversion of both olefins and nitrous oxide. The blending octane number of the oxidation product is 118–133 (RON) and 99–104 (MON). At the second stage, the mixture of carbonyl compounds is hydrogenated with hydrogen in the presence of the Ni/Al₂O₃ catalyst. The hydrogenation occurs at 150–160°C in a flow reactor in the gas phase. The aldehydes are completely transformed into alcohols, while the ketones can remain in the product under certain conditions. The blending octane number of the hydrogenation product is 111–112 (RON) and 95–96 (MON), which is smaller than for the BBF oxidation product, but larger than for the alkylate obtained in the course of conventional butene alkylation with isobutane (RON is 95–97 and MON is 93–95). Synthesis of high-octane components by this procedure can be useful in practice, especially in productions with huge release of nitrous oxide.     

Modern approaches and principles for analyzing radiological consequences for projected and operating nuclear power plants with VVER

The fundamental principles and approaches used in the modern methodology of computational analysis of radiological consequences in validating radiological safety for projected and operating nuclear power plants with VVER are described. The application of this methodology, developed by specialists at the National Research Center Kurchatov Institute for validating the radiological safety of projected and operating nuclear power plants with VVER and VVER nuclear fuel in Russia and other countries, made it possible to raise the methodology to a level conforming to modern Russian and international requirements and standards. The development of this methodology was made possible largely due to the results obtained in computational and R&D work performed as part of the AES-2006 design work.     

Mechanisms of Iron Activation on Fe-Containing Zeolites and the Charge of α-Oxygen

According to previous Mössbauer data [1] -sites formation at the activation of Fe-containing zeolites is accompanied by irreversible self-reduction of the iron, proceeding without participation of an external reducing agent. Reduced Fe²⁺ ions are inert to O₂ but are reversibly oxidized to Fe³⁺ by N₂O, generating the -oxygen species, O, which provide selective oxidation of hydrocarbons.In this work, the mechanism of -sites formation was studied via quantitative measurement of the dioxygen amount desorbed into the gas phase at the step of self-reduction. A prominent role of the zeolite matrix chemical composition has been revealed. For example, with zeolites of Al–Si composition (FeZSM-5 and Fe-), heating to 900 °C in a closed vacuum space leads to irreversible evolution of O₂, which is accompanied by the immediate formation of -sites. Similar heating of B–Si and Ti–Si zeolites also leads to dioxygen evolution; however, this evolution is reversible and is not accompanied by formation of -sites. Activation of these zeolites occurs only in the presence of water vapor. Stoichiometric measurements showed that in terms of charge one regular O^2- ion, removed at the activation, is equivalent to two -oxygen atoms. So, -oxygen is identified as an ion-radical species O ^-., whose unique oxidation properties still distinguish it from the generally observed O^-. radicals.The mechanism of -sites formation is proposed, in which the process of strong chemical stabilization of reduced Fe²⁺ atoms in the zeolite structure is a key step, making impossible the reoxidation of the iron with O₂.