Poverhnostʹ. Rentgenovskie, sinhrotronnye i nejtronnye issledovaniâ

Knowledge of the emissivity and thermal conductivity of thin metal films used in conjunction with multilayer mirrors for spectral selection of radiation in the extreme ultraviolet and soft X-ray wavelength ranges is necessary in order to correctly calculate the heating of film elements at high heat loads. Heating is associated with the absorption in the film of a significant fraction of the incident intensity, and the concept of a high heat load is somewhat arbitrary, since even at an absorbed intensity level of the order of 1 W/cm² a freestanding film can be heated in vacuum by several hundred degrees. In the first approximation, to estimate the thermal conductivity coefficient, one could use tabular values for massive samples of the corresponding metals or use the well-known Wiedemann–Franz law which links the thermal conductivity and the electrical resistivity of the sample – the latter is easier to be measured. However, an analysis of the literature data indicates significant errors that are possible when using any of these approaches. Therefore, in this work, we have measured the thermal conductivity directly by processing the temperature distribution obtained by IR pyrometry over a film sample mounted on a heated frame or heated by a flowing electric current. Thermophysical characteristics (thermal conductivity and emissivity) were determined for samples of film absorption filters based on Mo, Al, and Be of submicron thickness (from 100 nm), as well as for films of copper – a metal whose bulk samples have high thermal and electrical conductivity. As expected, significant differences were found between the thermal and electrical properties of the film materials and the properties of the same metals in monolithic samples.

To increase the average and peak power of modern laser systems, there is a need for new materials or the possibility of modifying existing ones to create composites based on them. Such composite materials using optical materials with high thermal conductivity can serve to remove heat from the active medium. Most often, this is achieved by planting materials on an optical contact. One of the promising materials for these purposes is single-crystal sapphire, since it has a sufficiently high thermal conductivity (~23–25 W/(m · K) at 323 K) and a low temperature coefficient of linear expansion (~10^–6 K^–1 at T = 323 K). The effect of the energy and angles of incidence of argon ions on the surface roughness of A-cut single-crystal sapphire was studied in this work. In the course of the work, the effect of smoothing the surface roughness by 30% relative to the initial value of roughness in the spatial frequency range 0.049–63 μm^–1 was demonstrated. The possibility of ion treatment of such surfaces is also shown, in particular, at angles of incidence of ions ± 40° on the sample surface, the value of effective roughness does not change much, which allows local correction of shape errors without leading to significant changes.

The X-ray optical and mechanical properties of dielectric multilayer mirrors based on pairs of C/Si and B₄C/Si materials are synthesized and studied. The mirrors are optimized for a wavelength of 13.5 nm. The parameters of the deposition process are found that simultaneously ensure the fulfillment of three conditions: relatively high reflection coefficients at the operating wavelength, near-zero mechanical stresses in the film, and the absence of electrical conductivity. At zero internal stresses, the reflection coefficient of C/Si multilayer mirrors deposited on superpolished silicon substrates at an operating wavelength of 13.5 nm is R = 11%, the spectral bandwidth is Δλ = 0.33 nm. The B₄C/Si mirror provides the following characteristics: R = 8.2%, spectral bandwidth Δλ = 0.3 nm. However, blistering has been found in B₄C/Si multilayer mirrors, i.e., the appearance of bubbles on the film due to the accumulation of hydrogen inside, which excludes their use for deposition on commercially available microelectromechanical system micromirrors. The deposition of a C/Si coating made it possible for the first time to obtain a workable system that reflects X-rays at an operating wavelength of 13.5 nm. The reflection coefficient is about R ~ 3%. The low value of the reflection coefficient is due to the high, about 1.5 nm, microroughness of the surface of the microelectromechanical system micromirrors. The study performed indicates the fundamental possibility of creating a matrix X-ray optical element for modulating the spatiotemporal characteristics of X-ray beams.

The interface features of the W–C system obtained by chemical vapor deposition and Ni–P–W layers of various compositions obtained by chemical-catalytic metallization are studied. Ni–P–W layers are used as support layers for coatings of the W–C system to improve the adhesive strength of the applied coatings to steels and resistance to loads directed along the normal to the surface. The methods of scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy have been used to study the morphology, phase and elemental composition of the obtained layers, as well as phase transformations occurring in the layers during heat treatment. Mechanical tests have shown that Ni–P layers with low phosphorus content, in terms of their characteristics, demonstrate the best support properties.

A characteristic feature of A^I–B^III–C^VI ternary chalcogenide compounds, which has a significant effect on the possibility of controlling the functional properties of materials based on them, is a strong tendency to stoichiometry deviation. The existence of ordered vacancy compounds in nanocrystals of the A^I–B^III–C^VI system was substantiated using the triangulation method (N.A. Goryunova’s method for predicting the composition of diamond-like semiconductors). Taking into account the assumption of the formation of electrically neutral defect complexes consisting of a vacancy in the position of the group I atom \(2[0]_{{\text{I}}}^{{ - 1}}\) and a doubly ionized antistructural defect \({\text{In}}_{{\text{I}}}^{{ + 2}}\) vacancies are presented as a pseudo-element of the “zero group”, while the system is considered from the point of view of the concentration tetrahedron so that the triangulation operations are transformed into tetrahedration operations. In the presence of such a “virtual” element, instead of a single stoichiometric composition in the A^I–B^III–C^VI system, a set of ternary compounds with an ordered content of vacancies known from the literature is determined, corresponding to semiconductors with four bonds per individual atom.

The effect of implantation of N⁺ ions on the chemical composition and atomic structure of the surface layers of titanium alloy VT6 is investigated. The accumulation of nitrogen in the surface layers up to concentrations of 30 at % and more and the formation of chemical compounds of titanium nitride TiN in the form of phase inclusions is shown. Presumably, this is due to processes of chemical nature, in particular, the chemical activity of titanium atoms, their tendency to interact with nitrogen atoms. In addition, despite the fact that in the conditions of ion bombardment, the integral oxygen concentration in the surface layers decreases due to sputtering, nevertheless, oxidation of the components of the titanium alloy VT6 is observed in deeper layers. Presumably, both oxygen from the natural oxide layer and from the residual atmosphere of the vacuum chamber, penetrating into deeper surface layers during irradiation, participate in the oxidation of titanium alloy components. The accumulation of nitrogen, the formation of titanium nitrides and the oxidation of the components of the titanium alloy VT6 indicate a significant role of chemical processes in the formation of the structural-phase state of the surface layers of titanium alloy VT6 under the conditions of implantation of N⁺ ions.

In this work, properties of fine grain graphite that will be used as a plasma-facing material in the T-15MD Tokamak are measured and studied. Density and porosity, thermal diffusivity and thermal conductivity, as well as the crystal grain size and impurity content of graphite are measured. The measurement results were compared to the corresponding parameters of MPG-6, MPG-7 and MPG-8 graphites. Characteristics of hydrogen and methane retention in graphite and conditions of their desorption depending on temperature of preliminary annealing, its duration, exposition of fully annealed samples in atmospheric gas at normal conditions. Influence of irradiation of the samples by deuterium ions with different energies on the characteristics of hydrogen trapping and desorption. In all cases, attention was paid to the possibility of influence of experimental conditions on trapping and desorption of hydrogen left in graphite after its production, as well as the one trapped from the atmosphere. Based on the data obtained and the expected conditions in the T-15MD’s plasma chamber, optimal modes for annealing of graphite received from producer and temperatures of the tokamak’s plasma-facing elements that assist in removal of hydrogen from graphite are determined.

Changes in the surface of micron-sized melamine-formaldehyde microparticles in dusty structures in a glow-discharge plasma in Ne and Kr were experimentally studied. Microparticles were placed in plasma-dust structures with subsequent extraction. Two effects depending on the exposure time in plasma were established in the experiment: a comprehensive decrease in the particle size and a change in the morphology of their surface. A model was considered, which makes it possible to estimate the contribution of various mechanisms of the interaction of charged plasma particles with the surface of melamine-formaldehyde. The estimates obtained are in good agreement with the experimental data.

Due to the development of the chemical industry, the need to obtain high-purity monodisperse nanoparticles is increasing. Therefore, it is necessary to choose the right method of obtaining. The paper demonstrates a unique method – induction flow levitation, which allows to obtain a large list of metal nanoparticles on one installation. In this work, magnesium nanoparticles were obtained using this method. The morphology was studied using scanning electron microscopy, where the resulting nanoparticles were clusters of primary particles. Energy dispersive analysis showed that the surface of magnesium nanoparticles after interaction with atmospheric air is completely covered with a small layer of oxide. Analysis of the phase composition showed that the powder consists of magnesium without traces of oxide. Mass spectrometry with inductively coupled plasma showed the purity of the obtained particles 99.99%. The characteristics of the porous structure were determined by low temperature porosimetry. The size of the obtained particles did not exceed 40 nm, and the average size was 23 nm. The used method of obtaining nanoparticles demonstrated high productivity (up to 50 g/h) and continuity of the process of obtaining nanoparticles (NP), the ability to control the size of the obtained nanoparticles (NP) in a wide range, non-contact heating, which leads to a high purity of the resulting product confirmed by mass spectrometry with inductive plasma bound.