O. P. Parenago

Formation and Properties of the Triboactive Nanoparticles of Molybdenum Sulfides

The methods of synthesizing molybdenum trisulfide nanoparticles soluble in lubricants and active antifriction and antiwear additives into oils are proposed. Bis(tetraalkylammonium)tetrathiomolybdates that are the precursors of the formation of molybdenum trisulfide nanoparticles are synthesized by the interaction between ammonium thiomolybdate and tetraalkylammonium halides involving alkyl groups of different nature. The methods of UV and IR spectroscopy along with thermogravimetry are used to study the properties of the obtained molybdenum compounds. Molybdenum trisulfide nanoparticles are produced by the thermolysis of bis(tetraalkylammonium)tetrathiomolybdates, and small angle X-ray scattering is applied to determine their sizes and size distribution. With the use of different types of tribometers, the antifriction and antiwear activities of both tetraalkylammonium derivatives of thiomolybdates and molybdenum trisulfide nanoparticles are shown.

Synthesis of tungsten sulfide nanoparticles and their tribological properties as additives for lubricating oils

Tetrathiotungstates with different alkyl groups have been synthesized by an exchange reaction between ammonium tetrathiotungstate and tetraalkylammonium halides. Synthesized samples are analyzed by elemental analysis and optical and thermal methods. Nano-WS3 particles that are stable and soluble in nonpolar hydrocarbons are prepared by thermolysis of alkyltetrathiotungstates. The average particle size of nano-WS3 is about 10–100 nm and depends on the nature of raw tetraalkylammonium halides. It is shown that nanoparticles of WS3 are soluble in Vaseline oil (1–2 wt %) and exhibit antiwear activity.

Comparison of antiwear properties of titanium-containing compounds

In search for environmentally friendly lubricant additives, titanium 2-ethylhexanoate and titanium oleate, which titanium compounds soluble in white oil, have been synthesized, as well as titanium dioxide nanoparticles modified with tetra-(2-ethylhexyl)thiuram disulfide and di(2-ethylhexyl)thiophosphonodisulfide. These titanium compounds have been characterized by elemental analysis, thermogravimetry, and IR spectroscopy. By means of the small-angle X-ray scattering technique, it has been found that the TiO2 nanoparticles have a size of 1–10 nm. Evaluation of antiwear properties of titanium compounds on a ChS-hMT-1 tribometer in a white oil solution shows that the decrease in wear scar diameter is 38–49% compared with the white oil. Analysis of the friction surfaces by atomic-force microscopy and X-ray microanalysis has shown a decrease in roughness of the friction surface caused by the presence of titanium atoms in the surface layers.

Comparative 13C NMR analysis of the composition of saturated petroleum and bitumenoid hydrocarbons: Potentialities and outlook

The informativity of 13C NMR spectroscopy as applied to solving the class of problems based on the data of comparative analysis of objects has been evaluated using a material from the southern part of the Anadyr oil-and-gas basin (saturated-hydrocarbon fractions of crude oils and bitumenoids). A set of 27 parameters measured from 13C NMR spectra has been proposed to characterize the composition of the samples with different degrees of detailing the structure of all components of the fractions. Methods for the determination of the degree of closeness of the sample composition have been considered, and it has been shown that not all of them satisfy the natural requirement of transitivity. A simple comparison procedure has been proposed for the case of multiparameter description of the fractions, with the values of the parameters lying in a wide range that has the property of transitivity on the material in question. It has been shown that 13C NMR radically extends the capabilities of the comparative analysis of the composition of crude oils relative to the conventional methods (GLC, GC-MS). In contrast to the results of study of the individual composition of saturated hydrocarbons (including the presumably most informative data on the composition of cyclic biomarkers), the 13C NMR data for the given material revealed a regular change of oils from the bottom up the section and to establish that the bitumenoids from its lowest part has nothing in common with the crude oils examined. The analytical parameters derived from the 13C NMR spectral data are not, in this case, too sensitive to inevitable variations in composition associated with sampling procedures or other insignificant factors. Thus, the generally accepted view on 13C NMR as a technique useless for tackling this class of problems can be regarded as refuted.

Synthesis and physicochemical properties of tetraalkylammonium thiomolybdates as precursors of triboactive molybdenum sulfides

Tetraalkylammonium thiomolybdates with different alkyl groups as ligands were synthesized. The composition and structure of the molybdenum complexes were studied by elemental analysis and UV and IR spectral techniques. The thermogravimetric characteristics of these compounds were determined. The tribological properties of the molybdenum complexes were assessed in terms of the coefficient of friction.

Carbon Nanotubes From Graphenes In The Pores Of Inorganic Membranes

The new technique of synthesis of new carbon nanostructures is proposed: the oriented carbon nanotubes with graphene walls (OCNTG). To synthesize these structures the consistent covering of surface of pores of ultrafiltration inorganic membranes with monolayers of graphenes was held. These monolayers were formed during pyrolysis of the definite quantity of methane. This resulted in formation of OCNTG inside the nano-size pores (Dav.< 50 nm). Formation of the monolayer of graphenes was identified with the help of X-ray photoelectron spectroscopy (XPS). The depth of covering with monolayer was controlled with scanning electron microscope investigation (SEM). It was shown that OCNTG which were formed inside the pores of membrane were able to sorb and desorb hydrogen in the same quantities as traditional carbon nanotubes do.

Sulfur-containing molybdenum compounds as high-performance lubricant additives (Review)

Published data on the use of sulfur-containing molybdenum compounds as additives for lubricants used in modern technology are reviewed. Various types of sulfur-containing molybdenum compounds as friction modifiers have been considered, and aspects of their activity and mechanism of action have been discussed. The role of these additives as inhibitors of oxidation of hydrocarbon materials has been shown. The environmental problems of using heavy metal compounds in lubricant additive formulations are discussed. The results of recent studies on the use of nanosized molybdenum sulfide particles as friction modifiers are presented.

Synthesis of novel promising materials via impregnation of crosslinked polymeric networks with metal complexes in supercritical carbon dioxide

Three types of polymers, phenol-formaldehyde copolymer and polypropyleneimine and polyamidoamine dendrimers, are synthesized using the polycondensation method. Mesoporous polymeric networks are formed by treating the above dendrimers with crosslinking agents. Impregnation of polymeric networks with rhodium acetylacetonate in supercritical carbon dioxide has been carried out for the first time and its optimal conditions have been determined. Using Raman spectroscopy, it has been shown that the metal content in polymer networks falls in the range 0.3–2.0 mass % depending on the type of the polymer and the crosslinking agent and on the crosslinking degree. Polymer samples including rhodium nanoparticles have been prepared by reducing immobilized rhodium acetylacetonate with molecular hydrogen. According to the preliminary data, the resulting samples possess extremely high activity as catalysts for hydrogenation of unsaturated compounds.

Features of reduction and chemisorption properties of nanosized iron(III) oxide

Nanosized iron(III) oxide with an average particle size of 8–10 nm has been synthesized by the thermolysis of iron(III) acetylacetonate using diphenyl ether as a dispersion medium. Reduction processes in a hydrogen atmosphere in the presence of nanosized iron oxide and natural mineral hematite (Fe2O3) have been studied by the temperature-programmed reduction method. The activation energies of the reduction processes have been determined by the Kissinger method; it has been shown that, in the case of nano-Fe2O3, the activation energies are several times higher than the respective values observed for hematite. The adsorption properties of nano-Fe2O3 and hematite have been studied; the isosteric heats of chemisorption of hydrogen and carbon monoxide on the surface of these samples have been determined.

Tribological Properties of Plastic Lubricants Infused with Molybdenum-Containing Additives

The wear and score resistance of different types of plastic lubricants infused with additives based on sulfur-containing molybdenum compounds are studied. It is shown that the tribological properties of all the studied lubricants are improved by infusion with 2-8 wt. % of molybdenum dithiocarbamate and that the additives are most active in the lubricants containing polyurea thickener.