The role of carbon and metal in self-assembly of the iron-carbon system at various component ratios

The problem of self-assembly in a metal-carbon system under dynamic conditions (equilibrium and nonequilibrium) is considered using the iron-carbon system as an example. It is proved theoretically and experimentally that the ratio of the components of the system affects the possibility of carbon self-assembly with the formation of fractal iron structures and of metal self-assembly with the participation of polyhapto derivatives of iron and the formation of fullerene-like carbon structures.     

Mössbauer study of the effect of preparation parameters in rapidly quenched Fe−Cr−P−C,Fe−Cr−B and Ni(57Fe)P amorphous alloys

Mössbauer spectroscopy was used to get information about the effect of preparation parameters (quenching rate, temperature and time of solution treatment of melt) on the structure of rapidly quenched Fe₇₀Cr₁₀C₇P₁₃, Fe₇₉Cr₁₅B₁₅ and Ni₈₀ ⁵⁷Fe₁P₁₉ amorphous alloys. We have found smaller but measurable thickness dependent changes in the average Mössbauer parameters and in the hyperfine field distribution of Fe₇₀Cr₁₀C₇P₁₃ samples than those observed in Fe₇₀Cr₁₀C₁₀P₁₀ amorphous alloys [3]. On the other hand, differences were found in the hyperfine field distribution of very rapidly quenched Fe₇₀Cr₁₀C₇P₁₃ alloys with increasing time of solution treatment of melt. Changes in the average parameters and in the quadrupole splitting distribution were also observed with variation of thickness as well as of temperature of melt in the Fe₇₀Cr₁₅B₁₅ and Ni₈₀(Fe)P₁₉ samples, respectively. The finding can be interpreted in terms of changes in the short range order due to different preparation conditions.     

Stoichiometric synthesis of fullerene compounds with lithium and sodium and analysis of their IR and EPR spectra

A modified method is proposed for preparing fullerene compounds with alkali metals in a solution. The compounds synthesized have the general formula Me _n C₆₀(THF)_x, where Me = Li or Na; n=1–4, 6, 8, or 12; and THF = tetrahydrofuran. The use of preliminarily synthesized additives MeC₁₀H₈ makes it possible to prepare fullerene compounds with an exact stoichiometric ratio between C ₆₀ ^n? and Me ⁺. The IR and EPR spectra of the compounds prepared are analyzed and compared with the spectra of their analogs available in the literature. The intramolecular modes T _u (1)-T _u (4) for the C ₆₀ ^n? anion are assigned. The splitting of the T _u (1) mode into a doublet at room temperature for Me _n C₆₀(THF)_x (n=1, 2, 4) compounds indicates that the fullerene anion has a distorted structure. An increase in the intensity of the T _u (2) mode, a noticeable shift of the T _u (4) mode toward the long-wavelength range, and an anomalous increase in the intensity of the latter mode for the Li₃C₆₀(THF)_x complex suggest that, in the fullerene anion, the coupling of vibrational modes occurs through the charge-phonon mechanism. The measured EPR spectra of lithium-and sodium-containing fullerene compounds are characteristic of C ₆₀ ^? anions. The g factors for these compounds are almost identical and do not depend on temperature. The g factor for the C ₆₀ ^n? anion depends on the nature of the metal and differs from the g factor for the C ₆₀ ^? anion.     

Formation,properties, and thermal decomposition of bisarene chromium(i) and molybdenum(i) fullerides

Fullerides [(⁶-Ph₂)₂Cr]⁺[C₆₀]^·–, [(⁶-C₁₀H₁₂)₂Cr]⁺[C₆₀]^·– (C₁₀H₁₂ is tetralin), and [(⁶-PhCH₃)₂Mo]⁺[C₆₀]^·– were synthesized. The molecular structure of [(⁶-Ph₂)₂Cr]⁺[C₆₀]^·– was established. In this compound at 100 K, radical anions C₆₀ ^–· are linked by an ordinary bond to form dimers, whereas at 293 K they are disordered and do not form dimers. The [(⁶-tetralin)₂Cr]⁺[C₆₀]^·– fulleride is stable in vacuo (10^–2 Torr) below 429 K, and [(⁶-toluene)₂Mo]⁺[C₆₀]^·– is stable below 581 K.Based on the materials presented at the International Conference Modern Trends in Organoelement and Polymer Chemistry (Moscow, May 30–June 4, 2004) dedicated to the 50th anniversary of the A. N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1973–1976, September, 2004.     

Adhesive strength, superhardness, and the phase and elemental compositions of nanostructured coatings based on Ti-Hf-Si-N

New superhard coatings based on Ti-Hf-Si-N with good physical and mechanical properties have been fabricated. A comparative analysis of the physical, mechanical, and tribomechanical characteristics of the coatings has been performed. The values of hardness, modulus of elasticity, elastic recovery, adhesive strength, friction coefficient, and wear rate of the coatings have been determined and calculated. The specific features of deformation and fracture of the coatings deposited on a steel substrate during the adhesion tests have been described. It has been shown that the parameters measured during scratching make it possible to distinguish the threshold values of the critical load, which lead to different (cohesive and adhesive) types of failure of the coatings during tribological tests. The stoichiometry for different series of samples with Ti-Hf-Si-N coatings has been determined using Rutherford backscattering, secondary ion mass spectrometry, and energy dispersive microanalysis.     

Surface tension at the boundaries of helium-argon and neon-argon solutions at 108–140 K

The capillary constant was measured and surface tension determined for helium-argon and neon-argon solutions by the differential version of the capillary rise method over the temperature range 108–140 K at pressures up to 4 MPa. The adsorption of helium and neon in interfacial solution layers was calculated.     

Synchrotron,X-Ray,and Electron Microscopic Studies of Catalyst Systems Based on Multiwalled Carbon Nanotubes Modified by Copper Nanoparticles

Physics of the Solid State - The results of the studies of a composite based on multiwalled carbon nanotubes (MWCNTs), onto the outer surface of which nanosized copper particles are deposited by...     

Structure of complexes of catalytic system for hydrosilylation of olefins

Conclusions It was specifically found that tricolorosilane reacts with Ni(acac)₂ to give nickel bis-3-(trichlorosilyl)acetylacetonate.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1620–1622, July, 1979.     

Hydroformylation of 1-octene in the presence of cobalt alkylidynecarbonyl clusters

The hydroformylation of 1-octene in the presence of Co₃(CO)₉(-CR) (R=H, Me, Ph, CO₂Me, CO₂Et, CO₂Prⁱ, CO₂Bu^t, Cl, Br, OMe) alkylidynecarbonyl clusters, as well as triphenylphosphine derivatives of these complexes and heteronuclear Co₂Ni compounds have been studied. The nature of the catalytically active species in hydroformylation, as well as the processes of their formation and transformation during the reaction, have been established by means of IR spectroscopy. The effects of the reaction conditions, the nature of the substituent at the apical carbon atom, the electron donating phosphine substituent, and the substituent in the metal cluster framework have been discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1388–1393, August, 1993.