Volume 45, Nº 1 (2019)

The influence of initial conditions on specific features of the formation and development of a cathode-directed ionization wave between two flat electrodes in argon at atmospheric pressure was studied at nanosecond time resolution using a high-speed photoelectron monitor and numerical simulations based on the two-dimensional axisymmetric diffusion–drift model.

The photostimulated adsorption of glucose oxidase (GOx) on the surface of single-crystalline Si wafers with an amorphous silicon (a-Si) layer was examined. Estimation of the difference between the surface coverage by GOx molecules deposited under illumination and in the dark showed that this value increased for the structures with a-Si layer by a factor of 2.5 in the case of n-Si and by a factor of 1.5 in the case of p-Si. It is revealed that the n-Si/a-Si structures can be used for preliminary photostimulation of the GOx adsorption  process.

Composite materials based on AMg2 aluminum alloy reinforced by additions of 0.05 wt % multiwalled carbon nanotubes (MWCNTs) or Al/MWCNT hybrid nanostructures have been obtained by powder metallurgy techniques. The evolution of MWCNTs and Al/MWCNT hybrid nanostructures at various stages of powder composite material formation has been studied by Raman spectroscopy. It is established that Al/MWCNT hybrid filler is subjected to lower damage and less favors the formation of Al₄C₃ phase during isothermal consolidation stage as compared to the case of nonmodified MWNTs.

The spall strength and dynamic yield stress of polycrystalline hafnium have been measured in a series of plane-wave shock loading experiments using flat sample–transparent window composite targets, with the transparent windows representing polymethyl methacrylate or lithium fluoride plates arranged on the rear side of a hafnium sample. The front side of the target was subjected to shock impact of a copper striker, the rear surface velocity was measured, and the sample was recovered for subsequent metallographic examination. The results were also used for evaluation of the accuracy of spall strength measurements and the analysis of features of high-rate deformation of hafnium.

The temperature dependences of magnetization M(T) of thin ion-implanted Ge:Mn (4 at % Mn) films containing Ge₃Mn₅ clusters were measured on samples cooled in the absence of magnetic field (zero field cooled, ZFC) and in a magnetic field of 10 kOe (field-cooled, FC). It has been established that the shape of ZFC–FC differential M(T) curves is determined by lognormal distribution of the size-dependent magnetic anisotropy energy of Ge₃Mn₅ clusters. Analysis of the observed ZFC–FC magnetization curves allowed the magnetic anisotropy dispersion (variance) and magnetic anisotropy constant to be estimated.

The process of cavitation inception and development in turbulent flow of a hydrocarbon fuel in a square channel under the action of a large constant pressure difference has been studied. It is established that the flow in this system is substantially unsteady and, despite the fact that the channel possesses both vertical and horizontal symmetry, the structure of cavitating flow is significantly asymmetric. This circumstance plays an important role in analysis of the fundamental problem of cavitation inception and development in a wide range of practical problems. The mathematical modeling of turbulent cavitating flows was based on the Navier–Stokes equations supplemented by the equation of state of a barotropic medium. Simulations were performed using a modified algorithm of the open-source computational fluid dynamics toolbox OpenFOAM. Comparison of the results of test simulations to available experimental data showed the appropriateness and efficiency of the proposed algorithm.

New possibilities offered by the method of secondary ion mass spectrometry (SIMS) for analysis of the phase composition of carbon-containing materials are considered. Differences are established between the mass spectra of three carbon phases: diamond, diamond-like carbon (DLC), and graphite. A simple algorithm for the quantitative determination of different phases in two-phase systems diamond–graphite and DLC–graphite is proposed that is based on the measurement of relative intensities of secondary cluster ions such as C₈/C₅ and CsC₈/CsC₄. It is shown that nonuniform depth profiles of various carbon phases are formed in diamond structures upon laser cutting and in DLC structures upon thermal annealing.

The dynamics of a non-autonomous oscillator in which the phase of external force linearly depends on a dynamic variable has been investigated. This control of the external-drive phase leads to the formation of a hierarchy of various periodic and chaotic oscillations. The structure of the space of control parameters has been studied. It is established that dynamics of the system exhibits oscillatory regimes analogous to those of a non-autonomous oscillator with potential in the form of a periodic function.