Radar Absorbing NiCo Nanoparticles in Carbon Matrix of Nanocomposites in the Microwave Range

Russian Physics Journal - The paper focuses on the synthesis of NiCo/C nanocomposites comprising the Ni–Co alloy nanoparticles uniformly distributed and stabilized in a carbon matrix. The...     

Ethylene production by the oxidative condensation of methane in the presence of MnMW/SiO<Subscript>2</Subscript> catalysts (M = Na,K, and Rb)

The samples of MnMW/SiO₂ (M = Na, K, and Rb) were synthesized using various synthesis methods under varied heat treatment conditions and their physicochemical properties and activity in the reaction of the oxidative condensation of methane (OCM) were studied for the development of an effective catalyst for the resource-saving process of natural gas conversion into ethylene. It was found that the preparation method exerts an effect on the textural characteristics of the samples and the reducing properties of the cations of manganese and tungsten. It was determined that the composition of a W-containing phase depends on the alkali metal, and a ratio between the polymorphous modifications of SiO₂ is controlled by the method of synthesis and the conditions of catalyst heat treatment. It was established that the yield of C₂ hydrocarbons in the OCM reaction increased with the use of incipient wetness impregnation instead of the method of mixing with a suspension for catalyst preparation and with an increase in the catalyst heat treatment temperature from 700 to 1000°C. The optimum composition of the catalyst and the condition of its synthesis were found: 2Mn_0.8Na₃W/SiO₂ obtained by the impregnation method and calcined at 1000°C ensured the yield of target products of ~20% with a CH₄ conversion of ~35% at a reaction temperature of 850°C.     

The role of curvature of the crystal structure in the formation of micropores and crack development under fatigue fracture of commercial titanium

The multiscale mechanism of fatigue fracture of titanium with the surface layer hydrogenated under alternating bending at room temperature is studied. It is shown that the generation of the fatigue fracture occurs in the surface layer subjected to plastic deformation in conjunction with an elastically loaded substrate. The latter causes the appearance of a strong curvature of the material and the appearance of micropores in these areas along with any fatigue cracks. The emergence of the local curvature of the crystal structure plays a central role in the origin and the development of the fatigue fracture as the structural phase decomposition of the material under cyclic loading.     

Unsymmetrical fluorine-containing disulfides

Russian Chemical Bulletin -     

EPR spectra of branched fluorinated radicals,derivatives of 2-trifluoromethyl-2-hydroperfluoropentanethione-3

Conclusions EPR was used to study new stable branched fluorinated radicals, adducts of organic and heteroorganic radicals with 2-trifluoromethyl-2-hydroperfluoropentathione-3. Predominant conformations and transition barriers between the radicals have been established.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 317–321, February, 1988.     

Rearrangements of 3<Emphasis Type="Italic">H</Emphasis>-Pyrazoles—Adducts of Dimethyl Acetylenedicarboxylate with Diphenyldiazomethane and 9-Diazofluorene

Structurally related 3H-pyrazoles resulting from 1,3-dipolar cycloaddition of diphenyldiazomethane and 9-diazofluorene to dimethyl acetylenedicarboxylate undergo van Alphen–Hüttel rearrangement on heating in a polar solvent (methanol, ethanol, acetic acid). In the first case, the rearrangement involves strictly regioselective 1,5-phenyl migration toward the carbon atom with the formation of relatively stable 4H-pyrazole. Post-rearrangement of the product on heating at 180°C in toluene gives a mixture of methyl 1H-pyrazole-1-carboxylates via successive migrations of the CO₂Me group. In the second case, the aryl substituent concurrently migrates both to nitrogen atom with the formation of 1H-pyrazole structure (phenanthridine derivative) and to carbon atom with subsequent rearrangement of unstable 4H-pyrazole to 3H-pyrazole fused to phenanthrene fragment. Heating of dimethyl acetylenedicarboxylate adducts (3H-pyrazoles) in an aprotic solvent (benzene, toluene) leads to the corresponding denitrogenation products. This process is especially facile for the spirocyclic 3H-pyrazole derived from 9-diazofluorene, and it yields cyclopropene derivative. Some previous errors in the structure determination of the rearrangement products have been corrected.     

One-Step Reactions to the Synthesis of Fluorine-Containing 1,3-Tiazoles,Thiazines and Heterodienes

A preparatively simple access to partially fluorinated cyclic- and open-chain heterocompounds containing sulfur and nitrogen was developed by the reactions of easily available and perfectly stable perfluorinated α,β-unsaturated isothiocyanates and thiocyanates with N-nucleophiles.     

α,β-unsaturated sulfenyl chlorides

Conclusions A method has been developed for the preparation of perfluorinated,-unsaturated sulfenyl chlorides, and their reactions with basic reagents and Lewis Acids have been studied.For a previous communication, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1123–1130, May, 1982.