No 3 (2023)

The features of formation of surface morphology of polyethylene terephthalate under the influence of high-power ion beam of nanosecond duration have been investigated. It has been established that at a single exposure of such a beam to polyethylene terephthalate, as well as for the majority of other polymers, pores are formed in a near-surface layer, however their quantity is much less. Significant differences begin to appear when the polymer is repeatedly irradiated with a high-power ion beam. For most polymers this leads to an increase in surface porosity and partial local destruction of the near-surface layer. Under such irradiation conditions, various spatial structures are formed on the polyethylene terephthalate surface, the type and sizes of which depend on the number of irradiation pulses. X-ray microanalysis of the near-surface layer showed a significant (1.4 times) decrease of oxygen content after ion irradiation. Irradiation of polyethylene terephthalate by high-power ion beam does not result in the formation of a thin carbon layer on its surface. The possible reasons of formation of such surface morphology under the action of high-power ion beam on polyethylene terephthalate have been considered.

The patterns of structure formation, as well as the wettability, were investigated for thin films of aluminum and Al–2.1 at % Mn and Al–1.4 at % Ni alloys on glass substrates prepared by ion beam-assisted deposition. The application of scanning probe microscopy (SPM) and scanning electron microscopy allowed characterizing nano- and micrometer-sized topographic heterogeneities on the film surfaces and studying the nature of their wettability measured by sessile drop method. Within the framework of the profile and topographic approaches for the analytical analysis of SPM images, a set of discrete roughness parameters was used, supplemented by dimensionless parameters-complexes (ψ and k) and a parameter-function of probability density of the heights and valleys of the surface nanorelief. The proposed research hybrid parameter k characterizes the shape of the irregularities of the nanorelief profile, has visibility and relates to the amplitude and roughness step. The informativity of the system of nine selected parameters for estimating the roughness and irregularity of the local structure of the film surface in the cross-section and longitudinal section was shown, which allowed not only studying numerically structural-morphological changes during aluminum doping, but also determining the quantitative relationships between the microgeometry of film surface and the deposition conditions. The effect of the initial relief of the glass substrate on the parameters of the surface irregularities of the films, which, as obtained, have the form of submicron cones and local hillocks, was revealed. The Gaussian distribution of the film nanorelief of aluminum and its alloys over the surface area was obtained, and the coating surfaces could be considered as a realization of a random normal process. The frequency distributions of the microdroplet fraction by size were lognormal. The film roughness parameters were found to correlate with the size and density of droplet fraction microparticles. It was revealed that the deposition of Al-containing films reduced the surface hydrophilicity of the film/glass substrate system. When doping aluminum, the degree of morphological heterogeneity of the film surface, as well as their wettability, decreased. The homogeneous regime of film wetting with water and its dependence on the material, morphology, and chemical composition homogeneity of the surface are discussed.

In this work, the surface of the N18 alloy was modified with argon ions in a repetitively pulsed regime. In situ electron spectroscopy methods were used to study changes in the chemical composition and local atomic structure caused by ion action on the surface. The chemical composition was determined by Auger electron spectroscopy using argon ion profiling. The analysis of the local atomic structure was carried out by the method of spectroscopy of extended thin structures of electron energy losses. The excitation spectra of the iron M_2,3-edge and the K-edge of oxygen were obtained in the geometry of backscattering from the surface. The variation in the energy of the incident electron beam made it possible to obtain a signal from the excitation of oxygen and iron atoms from the same depth. The analysis of experimental data was carried out by the method of solving the inverse problem for finding pair correlation functions using regularization according to Tikhonov. The study of the local atomic structure was carried out at profiling depths of 5, 25, and 50 nm. It is shown that the ion-modified layer within the projective range of argon ions consists mainly of iron oxides. At a profiling depth of 50 nm, the parameters of the local environment of Fe atoms are close to those of unoxidized iron. Nickel as a result of surface diffusion is found at a depth of more than 50 nm.

The uniformly moving charged particle generates the transition radiation under the motion in the non-uniform medium (in particular, under crossing the interface between two media) and the transition radiation under the motion near the non-uniformities of the medium without crossing theid boundaries. Both diffraction and transition radiation can be used for detection of the charged particles and beam monitoring. While the methods based on the transition radiation from both relativistic and non-relativistic particles are widely used, the utilization of the diffraction radiation for that goals are still under study. The diffraction radiation generation is weakly perturbing for the particle’s motion that permits to develop the non-destructive methods of the beam diagnostics. The description of the diffraction radiation from the charged particle on the conducting sphere has been developed earlier using the method of images known from electrostatics. The method of finding the parameters of the particle’s flying by the sphere based on that approach using the single point detector sensitive to both intensity and polarization of diffraction radiation was proposed earlier. Here we propose the scheme with three detectors that solves the same problem without registration of the polarization.

In the first order of perturbation theory, it is shown that the potential energy of interaction between two atoms can be calculated by solving a system of nonlinear equations. The system of equations has been constructed both with and without regard to the Pauli principle, and the atomic form factor has been calculated using wave functions that approximate the solution of the Hartree–Fock equation for isolated nitrogen atoms. The graph of the potential energy of the interaction of two nitrogen atoms satisfactorily agrees with the known results when the Pauli principle is taken into account. It is shown that without taking into account the Pauli principle and collective oscillations of the electrons of atoms, it is not possible to obtain agreement with experiment. It is shown that the total energy of a diatomic molecule is a functional that depends on the electron density of isolated atoms.

The yield of reaction products depends on the interaction between processes on the catalyst surface: adsorption, activation, reaction, desorption, and others. These processes, in turn, depend on the magnitude of the flows of reaction mixtures, temperature, and pressure. Under stationary conditions, active sites on the surface can be poisoned by reaction by-products or blocked by an excess of adsorbed reactant molecules. Dynamic control of reaction parameters takes into account changes in surface properties and adjusts temperature, flow rates and other parameters accordingly. A reinforcement learning algorithm was applied to control the oxidation reaction of carbon monoxide CO on the surface of palladium nanoparticles. The algorithm was trained to maximize the rate of carbon dioxide production based on information about the magnitude of CO, O₂ and CO₂ fluxes at each time step. A gradient policy algorithm with a continuous action space was chosen, and observations of the flow rates were extended over several successive time steps, which made it possible to obtain a set of non-stationary solutions. The maximum yield of the product is achieved with a periodic change in gas flows, which ensures a balance between the available adsorption sites and the concentration of activated intermediates. This methodology opens up prospects for optimizing catalytic reactions under nonstationary conditions.

The visualization of microfluidic chips was considered to study morphology of microfluidic channel surface and estimate the quality of 3D printing technology based on digital light processing. The visualization was performed by X-ray microtomography using different iodine-based contrast agents and by scanning electron microscopy. It was shown that X-ray microtomography visualization made it possible to control the quality of device printing relative to geometrical parameters of the models specified at the prototyping stage, as well as to visualize a 3D model of microfluidic channels and surface morphology. The spatial resolution of scanning electron microscopy exceeds the print pixel size and makes it possible to clarify the presence of local defects caused by uneven solidification of the resin during sample washing.

For the first time, the influence of the aging temperature and the applied constant magnetic field on the aging of beryllium bronze BrB-2 has been studied by methods of microhardness, transmission electron microscopy and measurements of magnetic properties. Samples of beryllium bronze BrB-2 were kept for 0.33 h at a temperature of 800°С, then quenched by rapid immersion in water (20°С) and subjected to artificial aging at temperatures of 250–500°С for 1 h in a PMF with a strength of 557.2 kA/m and without him. A negative magnetoplastic effect was found, leading to an increase in microhardness up to ~30%. The presence of the strengthening phase α-CuBe, which plays a large role in the formation of the strength properties of the alloy, is established, and the imposition of the constant magnetic field leads to the activation of the aging process. When the constant magnetic field is applied, a tendency is observed for the transition of the alloy from the diamagnetic state to the superparamagnetic state.