A. I. Kharlamov

Influence of the mechanochemical treatment on the reactivity of V-containing oxide systems

Abstract Mechanical treatment of V 2 O 5 or V-P-O catalysts causes a substantial increase of both catalytic activity in n -butane oxidation and the selectivity to maleic anyhydride. Changes in specific surface area and anisotropic deformation take place. Mechanochemical treatment of the initial reagent impairs such properties that they remarkably influence the catalytic properties of the final catalyst.

New method for synthesis of fullerenes and fullerene hydrides from benzene

New and simple method for synthesis of C60 fullerene and fullerene (C60, C70, and C82) hydrides was developed. The substances synthesized were characterized by laser mass spectrometry, IR spectroscopy, temperature-programmed desorption mass spectrometry, and X-ray phase and chemical analyses.

New products of a new method for pyrolysis of pyridine

New method for pyrolysis of pyridine is suggested. One of yielded by the method is a new type of heteroatomic molecules in the form of exohedrally hydrogenated and hydroxylated azafullerenes (C35N5)H9, (C45N5) (OH)3H14, and (C49N11)(OH)5H18. C60 fullerene, its hydrides, and new carbon molecules, such as quasi-fullerene C48 and C3-C15, are detected for the first time in pyridine pyrolysis products by mass-spectral analysis. Hydrides of the carbon molecules are synthesized for the first time without using fullerene.

New low-temperature method for joint synthesis of C60 fullerene and new carbon molecules in the form of C3-C15 and quasi-fullerenes C48, C42, C40

Method for joint synthesis of C60 fullerene and new carbon molecules in the form of C3-C15 and quasifullerenes C48, C42, and C40, alternative to arc-discharge technique, was developed for the first time. The process of fullerenization of benzene molecules into carbon molecules is performed at comparatively low (∼1000°C) temperatures. It is shown that C3-C18 nanoclusters are generated as main components of a monoatomic carbon vapor under conditions that rule out sublimation of carbon. Crystalline substances containing exceedingly active small carbon molecules were synthesized for the first time. The products of benzene fullerenization were studied by methods of mass-spectrometric analysis, electron-probe X-ray microanalysis, and optical microscopy.

Preparation of onion-like carbon with high nitrogen content (∼15%) from pyridine

A new procedure of pyridine pyrolysis is suggested. It allows preparation of onion-like carbon with high nitrogen content (∼15%) as a promising material for producing lubricants, adsorbents, and catalysts. The distinctive features of the mechanisms leading to the formation of carbon onion structures with different nitrogen carbon contents are discussed. High-nitrogen carbon is formed from pyridine molecules via their polymerization and polycondensation in the reaction flow and is transported with this flow into low-temperature zone of the reaction space. Onion structures of large size with low nitrogen content (<3.0%) are formed and localized in the high-temperature zone of the reactor together with nanotubes and fibers.

Hollow Silicon Carbide Nanostructures

Hollow silicon carbide nanostructures with length up to 1 μm have been produced for the first time along with threadlike structures. The preparation of SiC nanostructures from silicon and carbon at 1000-1100 °C was carried out without prior gasification of these elements. The growth of SiC nanostructures involves a step featuring atomization of silicon and carbon at such low temperatures. The growth of SiC nanotubes upon the reduction of carbon by SiO2 in the initial period of the preparation proceeds with their predominant formation as bundles. Silicon carbide may correspond to the highly textured α-modification.

Effect of mechanochemical treatment on the structure and physicochemical properties of MoO3

Using X-ray phase analysis, IR spectroscopy, and derivatography we have shown that when molybdenum(IV) undergoes mechanochemical treatment in a planetary mill, along with an increase in the specific surface area changes also occur in the chemical composition and structure. The Mo−O−Mo bonds of the oxide lattice and the terminal Mo=O bonds are weakened and lengthened, evidence for which comes from IR spectroscopy data. Partial reduction of the molybdenum ions occurs with formation of the phase MoO2.8 in water, water-benzene, and water-alcohol medium. In the presence of ethanol, the Magnéli phase χ-Mo8O23 can be formed for a certain energy load according to a crystallographic shift mechanism. The presence of reduced phase and the increase in specific surface area promote an increase in the activity of the oxide in oxidation of benzene. Selective oxidation of benzene to maleic anhydride is favored by an increase in the relative content of the (020) crystallographic face.

Wetting of Hot-Pressed Aluminum Borides and Borocarbides by Molten Aluminum and Copper

The sessile drop method has been used to determine the temperature dependence of the wetting of boride and borocarbide phases by molten aluminum and copper. Hot-pressed substrates have been used made of aluminum boride and borocarbides, which are well wetted by aluminum above 1000°C. Aluminum borocarbide phases are not wetted by copper under these conditions. The temperature dependence is derived for the synthesis of finely divided aluminum boride and borocarbide powders from simple substances. Details are given of the nucleation and formation of an aluminum phase containing boron. The aluminum borides and borocarbides are formed not as a result of boration of the metal lattice (which occurs in the synthesis of transition-metal borides) but by metallation (alumination) of the boron lattice.

New method for synthesis of oxygen-doped graphite-like carbon nitride from pyridine

Simple method for single-stage synthesis of O-doped carbon nitride (O-C3N) with a C/N ratio of 3.46 and high content of oxygen (11.1 wt %) is suggested. Carbon nitride is formed in the reaction flow of pyridine pyrolysis products, carried by this flow away from the high-temperature (1050°C) reaction zone, and localized in the low-temperature (<70°C)zone of the reaction space. The mass spectra of the thermolysis products of the thus synthesized O-C3N show not only molecules (HCN, C2N2, and CO) and nitrogen-carbon fragments (CN+, C4N2+, and C2N+), but also carbon and nitrogen atoms. O-C3Nx was studied by the methods of X-ray diffraction and chemical analyses, temperature-programmed desorption/mass spectrometry, and IR and XPS spectroscopies.

Low-Temperature Reactions between Vaporizing Silicon and Carbon

A new model is proposed for reactions between solids assuming formation of product in the gas phase (pores) due to the reaction of vaporizing reagents. Experimental results are given for the first time, which convincingly show that the reaction between solid-phase silicon and carbon below 1050 °C to give thread-like silicon carbide occurs due to rapidly vaporizing silicon and carbon atoms.