Vol 63, No 12 (2018)

Modification of a steel surface by coating with fullerenes C₆₀ and subsequent treatment by intense laser radiation has been investigated. The initial samples are made of low-carbon steel. The laser source is a commercial LTA4-1 laser with a wavelength of 1.064 µm, pulse energy up to 12 J, and pulse width of 2 ms. The obtained dependences of the surface microhardness on the specific laser energy are nonmonotonic with a maximum in the range of 100–150 J/cm². An eight-fold increase in the surface microhardness can be reached under optimal treatment conditions. There is an increasing dependence of the degree of surface strengthening on the fullerene-coating thickness. In addition, the laser irradiation of the treated surface is accompanied by a decrease in the friction coefficient by several tens of percent. The experimental results are compared with the data of similar measurements for nanocarbon soot used as the coating, which was obtained by the electric-arc sputtering of graphite with subsequent extraction of fullerenes.

The effect of Raman scattering (RLS) signal amplification by carbon nanotubes (CNTs) was studied. Single-layered nanotubes were synthesized by the chemical vapor deposition (CVD) method using methane as a carbon-containing gas. The object of study used was water, the Raman spectrum of which is rather well known. Amplification of the Raman scattering signal by several hundred percent was attained in our work. The maximum amplification of a Raman scattering signal was shown to be achieved at an optimal density of nanotubes on a substrate. This effect was due to the scattering and screening of plasmons excited in CNTs by neighboring nanotubes. The amplification mechanism and the possibilities of optimization for this effect were discussed on the basis of the theory of plasmon resonance in carbon nanotubes.

A general covariance variational model of reversible thermodynamics is developed in which the kinematic and force variables are the components of unified tensor objects in the space−time continuum, and the resolving equations of the dynamic thermoelasticity and heat-conduction of an ideal (defect-free) media are described by the 4D-vector equation. It is shown that the formulations of relations of the generalized Duhamel−Neumann representation and the Maxwell−Cattaneo law follow directly from the constitutive relations of the space−time-continuum model without additional hypotheses and assumptions. It is proved that the Maxwell−Cattaneo and Fourier generalized heat-conduction laws are unambiguously characterized by well-known thermomechanical parameters determined under isothermal and adiabatic conditions for reversible coupled deformation processes and heat-conduction despite the fact that one usually relates both the Fourier law and the relaxation time in the Maxwell−Cattaneo law with the dissipative processes.

In this paper, we determined the main regularities of suppression of combustion and thermal decomposition of typical forest combustible materials (leaves and needles as an example) when they are exposed to droplet aerosol with a variable specific water consumption. The conditions for suppressing the thermal decomposition in the material layer were controlled using low-inertia thermocouples. The size and concentration of water droplets in the aerosol were determined by using the cross-correlation complex and optical recording methods while the density of irrigation was calculated. The typical suppression times of combustion and thermal decomposition of the materials under study are determined. For the dependence of the suppression times on the specific water consumption, two typical ranges illustrating the necessary and sufficient conditions for effective combustion suppression are established. Based on an analysis of the experimental data, we formulated a hypothesis on the dominant heat and mass exchange in the suppression of combustion and the thermal decomposition of typical forest combustible materials with water.

The trinomial asymptotic expansions of potential flow kinetic energy in an ideal fluid are constructed for the motion of two spheres of variable radii in the vicinity of their contact. Based on these expansions, it is possible to study the process of two pulsating gas bubbles approaching up to their contact.

The existence of a symmetric mode in an elastic solid wedge for all allowable values of the Poisson ratio and arbitrary openings close to π has been proven. A radically new effect—the presence of a wave localized in a vicinity of the edge of a wedge with an opening larger than a flat angle—has been found.

This article presents a description and comparative analysis of an integrated natural gas utilization technology for concurrently producing electricity and synthetic liquid engine fuel and partially sequestering carbon dioxide. In the daytime, the installation produces electricity, heat, and methanol. In the night-time hours of minimum load, CO₂ is partially captured from flue gases and is converted in a plasmatron to obtain H₂ + CO by adding natural gas and steam. The produced synthesis gas is forwarded to a catalytic synthesis reactor for boosting the operation of the methanol producing installation. In comparison with state-of-the-art installations for separate production of electricity, heat, and methanol, the proposed installation makes it possible to save about 20% of natural gas and decrease the amount of CO₂ emissions into the atmosphere by as much as 30%.