Numerical and Experimental Study of the Multichannel Nature of the Synthesis of Carbon Nanostructures in DC Plasma Jets

Plasma Chemistry and Plasma Processing - Wide spectrum of carbon nanostructures was synthesized by means of simple plasma chemistry using DC plasma torch: carbon nanotubes, nanowalls, graphene,...     

Optimization of Steel-Surface Hardening by Carbon Nanostructures Followed by Treatment with High-Intensity Energy Sources

The effect whereby a steel surface is modified by its covering with a nanocarbon material followed by fast electron- or laser-beam irradiation is studied. The initial material is low-carbon steel. Soot produced via the thermal sputtering of graphite electrodes in an electric arc with the subsequent extraction of fullerenes is used as the nanocarbon coating. Due to the fact that nanocarbon-coated samples are irradiated with a 60-keV electron beam, the material microhardness enhances considerably. The dependence between the microhardness and the irradiation energy is nonmonotonic and reaches its maximum (about 600 ± 20 HV) under the condition that the electron-irradiation energy is 460 J/cm² and the intensity is 1.53 kW/cm². This corresponds to a fourfold increase in the microhardness. Electron-beam irradiation of the treated surface is accompanied by a 1.5–2-fold decrease in the friction coefficient. Experimental results are compared with data obtained under laser irradiation of the nanocarbon-coated steel surface.     

Optical limiting in Pluronic F-127 hydrogel with nanocarbon inclusions

Characteristics of nonlinear optical limiting (limiting curves) of laser radiation in aqueous polymer systems with nanocarbon inclusions have been studied. Suspensions of nanotubes and soot stabilized by the amphiphilic polymer Pluronic F-127, the additives of which provide the system’s transition to a solid-like hydrogel aggregate state at room temperature, have been considered. The limiting materials after their optical breakdown by high-intensity radiation in the gel state have been regenerated using the thermoreversible hydrogel–isotropic solution phase transition. These systems are shown to be promising for self-healing optical materials.     

Kinetic anomalies of mixed crystal growth and their effect on the crystal isomorphic composition

Growth rate anomalies in aqueous solution growth of NaClO₃ and KClO₃ were first revealed by V. V. Sipyagin in 1967 and attributed to “kinetic anomalies”. These phenomena were confirmed in a series of other studies and for a variety of substances. Therefore, some universality of these anomalies was supposed that should be due to structural transformations in the liquid solutions. In this paper, we present for the first time results on growth rate oscillations found in mixed crystal growth and their impact on the isomorphic composition of solid solutions. Thick (100) Na(Cl,Br)O₃ layers were grown at fixed supercooling conditions onto NaClO₃ seeds in a microcrystallization cell equipped with an optical microscope. In the temperature range of 33 – 41 °C, four kinetic anomalies were found in solutions of a chlorate: bromate molar ratio of 20: 1 at supercoolings of 2.0 K and 3.0 K. Lattice parameter measurements of the grown Na(Cl,Br)O₃ layers revealed a linear dependence of lattice constant vs. growth rate. By measuring Vegard's law (lattice parameter vs. solid solution composition) we were able to determine the oscillations in mixed crystal composition that accompany the kinetic anomalies in solid solution systems. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Reconstruction of the spatial distribution of a turbulent medium from pulse scattering: “Space tomography” method

Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 33, No. 4, pp. 395–402, April, 1990.     

Integral intensities of absorption bands of silicon tetrafluoride in the gas phase and cryogenic solutions: Experiment and calculation

The spectral characteristics of the SiF₄ molecule in the range 3100–700 cm^?1, including the absorption range of the band ν₃, are studied in the gas phase at P = 0.4–7 bar and in solutions in liquefied Ar and Kr. In the cryogenic solutions, the relative intensities of the vibrational bands, including the bands of the isotopically substituted molecules, are determined. The absorption coefficients of the combination bands 2ν₃, ν₃ + ν₁, ν₃ + ν₄, and 3ν₄ are measured in the solution in Kr. In the gas phase of the one-component system at an elevated pressure of SiF₄, the integrated absorption coefficient of the absorption band ν₃ of the ²⁸SiF₄ molecule was measured to be A(ν₃) = 700 ± 30 km/mol. Within the limits of experimental error, this absorption coefficient is consistent with estimates obtained from independent measurements and virtually coincides with the coefficient A(ν₃) = 691 km/mol calculated in this study by the quantum-chemical method MP2(full) with the basis set cc-pVQZ.