Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques最新文献

The paper presents a new approach to optimizing the cyclic procedure of deep reactive ion etching (DRIE) of silicon. The etching parameters were adjusted based on direct measurements of the rates of deposition and etching processes in a cycle on the surface of oxidized silicon using a laser interferometer. A high-quality etching profile with minimal erosion of the SiO₂ mask (maximum process selectivity) was achieved by adapting the three-stage DRIE process according to the measured duration of polymer removal at the bottom of the grooves in silicon. It has been shown that the profile shape can be corrected by changing the DRIE parameters during the etching process. As a result of optimization, a recipe was obtained for etching grooves 30 µm wide to a depth of 350 µm with a wall angle of 0.36° at a process rate and selectivity of 3.4 µm/min and ~400, respectively. The adapted recipe was successfully applied in the manufacturing technology of the sensitive element of a micromechanical gyroscope.

Two series of Cr coatings were deposited on E110 zirconium alloy by magnetron sputtering using different modes of ion surface treatment. The crystal structure and microstructure of the Cr coating and its adhesion and corrosion resistance during high-temperature oxidation in air at a temperature of 1100°C with isothermal exposure for 20 and 60 min were studied. The short-term Ar⁺ irradiation of the Zr alloy with a current density of less than 1.6 mA/cm² caused a preferential growth of Cr crystallites in (200) plane, an increase in the size of columns in the “coating-alloy” zone, and a high uniformity of the columnar microstructure over the thickness. Without ion treatment, the Cr coating was less resistant to cracking and more vulnerable to high-temperature oxidation. Due to the high permeability of the Cr coating to oxygen and nitrogen, the oxidation of Zr alloy occurred with the formation of (ZrO₂ + ZrN) layer underneath the coating. The Cr coating with (200) texture was more resistant to cracking during scratch testing. Because of a lower permeability of oxygen and nitrogen through the Cr (200) coating, the extended dendritic structures α-Zr(O,N) were formed in the Zr alloy up to a depth of 250–270 μm during prolonged air oxidation.

A composite based on magnesium hydride and nanosized aluminum powder obtained by electric explosion of wires was synthesized. Mechanical synthesis was carried out in a planetary ball mill. The time and frequency of synthesis, the mass ratio of balls and composite, and the percentage of aluminum were constant, while the diameter of grinding balls was varied: 3, 6, and 10 mm. Scanning electron microscopy was used to determine the average particle size of the composite depending on the diameter of the grinding balls. It was found that with a decrease in diameter from 10 to 3 mm the average particle size decreased from 2.7 to 2.2 μm. Energy dispersion analysis showed that nanosized aluminum particles were distributed evenly over the surface of magnesium hydride. A “core–shell” structure was formed. X-ray phase analysis revealed β-magnesium hydride, magnesium, magnesium oxide, and aluminum in the composite. X-ray diffraction patterns of the samples made it possible to calculate the structural parameters of the obtained composites, including microstresses. The average microstress value varied in the range of 0.004–0.006. A hypothesis has been put forward about an inversely proportional relationship between microstress and desorption temperature.

Beam loss control is one of the critical tasks during the operation of high-intensity charged particle accelerators. The paper presents the concept of a nondestructive beam loss monitoring system based on beam current transformers for a linear resonance proton accelerator of the DARIA compact neutron source. Features of the practical implementation and operation of the proposed beam current transformers based on ferrite cores and the necessary preamplifier electronics using transimpedance amplifiers are considered. Particular attention is paid to the method of monitoring the difference of the measured beam currents between two successive detectors and the principles of generating an alarm signal for the implementation of a fast emergency protection system for the accelerator. Control of the current difference is implemented on the fast integration and mutual comparison of the beam pulses charge passing through the detectors which increases the accuracy of measurements, while it is possible to select several discrete values of the measured difference: for the nominal operating mode and the accelerator tuning procedure, when beam losses can increase significantly. The system works at any beam pulse repetition rate, and to prevent false block from possible interferences, the final alarm signal is generated as the sum of three consecutive signals of the comparison circuit at the beam pulse repetition rate.

The effect of annealing on the microstructure, defect structure, and mechanical properties of nanoscale metal systems consisting of alternating layers of Zr and Nb is considered. The effect of annealing was studied on coatings pre-irradiated with protons. Nanoscale Zr/Nb metal layers were prepared using the magnetron sputtering method, each layer was 50 nm thick, and the total thickness of coatings was about 1 μm. Using electron microscopy and glow discharge optical emission spectrometry, it was shown that the multilayer structure was preserved after both irradiation and annealing of irradiated Zr/Nb samples. After annealing at 300°C, a decrease in hydrogen luminescence intensity and proton redistribution were observed. Using X-ray phase analysis, it was shown that at an annealing temperature of 200°C, the interplanar distances for Zr and Nb decreased. At an annealing temperature of 300°C, a sharp increase in the interplanar distance in Zr layers and a slight decrease in the interplanar distance in Nb layers were detected. Layer-by-layer analysis of defects in nanoscale metal layers using variable-energy positron beam and Doppler broadening spectroscopy showed that increasing the annealing temperature stimulated the migration and annihilation of defects at interfaces. Regions of reduced electron density at the interfaces on the zirconium side remain the predominant positron capture centers.

In this work, the effect of the type of mechanical treatment of the surface of titanium alloy Ti–6Al–4V obtained by electron-beam melting before the magnetron deposition of a titanium nitride (TiN) coating on its resistance to hydrogenation at a test temperature of 560°C and a hydrogen pressure of 2 atm is studied. Sandblasting and mechanical grinding/polishing of Ti–6Al–4V alloy are used as surface-preparation procedures for experimental samples. It is found that a TiN coating (with a thickness of 1 μm) obtained using reactive magnetron sputtering can reduce hydrogenation of the titanium alloy by 18 times compared to the uncoated alloy when preliminary grinding/polishing of the sample surface to a roughness (R_a) of 0.05 μm is applied. For samples of polished Ti–6Al–4V alloy with a coating, after hydrogenation tests, a decrease in the coating hardness from 20.8 to 10.9 GPa and a noticeable decrease in the critical load, at which delamination of the coating occurs (from 28.4 to 19.2 N), are observed. When applying a TiN coating to the titanium-alloy surface after sandblasting, the β phase of titanium is stabilized, and titanium hydride TiH₂ is formed during Ti–6Al–4V-alloy hydrogenation.

The results of an experimental study of changes in the chemical composition and surface topography of two-component AlSi thin films with an initial Si concentration of 1% under low-energy ion-plasma sputtering are presented. Using scanning electron microscopy, scanning Auger electron spectroscopy, and secondary-ion mass spectrometry, it is established that when irradiated with argon ions with an energy from 40 to 200 eV, the concentration of Si in the surface layer of the film increases by more than an order of magnitude. Nanostructures in the form of hills with a diameter of 20–50 nm and a height of 15–30 nm are formed on the surface, which can be identified as silicon nanostructures. The reason for enrichment of the surface with Si and the formation of nanostructures may be differences in the sputtering coefficients and threshold values of the sputtering energy of the film components.

The paper presents the results of a study on the distribution of lithium in a solid-state thin-film lithium-ion battery using the Rutherford backscattering spectrometry (RBS) method. The analysis employs He⁺ ions with an energy of 1.8 MeV, scattered at an angle of 165° with normal incidence to the surface. Based on the energy loss of scattered ions, we determine the concentration of Li ions in the battery layers in both charged and discharged states. The study shows that the Li-concentration values obtained through the RBS method and the galvanostatic-measurement method coincide, provided that the specific stopping cross section for lithium ε_Li in the anode layer is half of that in the single-element substance.

The paper focuses on the description of the structural phase state and sorption characteristics of the Ti₃₃V₃₃Cr₃₃ alloy. This alloy was synthesized by two different methods: abnormal glow discharge plasma (AGDP) melting and arc melting (AM). X-ray diffraction analysis revealed the presence of the main TiVCr phase with a BCC lattice, as well as the α-Ti phase in the AGDP method. In the case of the AM method, the formation of TiCrV and Ti₃O phases is observed. The alloys synthesized by the AM method showed improved cyclic stability, while those obtained by the AGDP method demonstrated an increased maximum hydrogen capacity.

The study describes an original approach to the synthesis of composites based on the MAX-phase Ti₃SiC₂ by a combined powder metallurgy technique. The described approach includes a two-stage heat treatment and consolidation of powders by solid-phase vacuum sintering and spark plasma sintering technologies. Powder mixtures 3Ti/1.2Si/2C and Ti/1.2Si/2TiC were considered as feedstocks for the synthesis. The selected mixtures were presintered in a vacuum furnace at a temperature of 1400°C for 1 h. The obtained compacts were milled with the addition of pure silicon powder and spark plasma sintered at a temperature of 1300°C and a pressure of 50 MPa. The silicon overage in each of the sintering steps promoted the phase formation of Ti₃SiC₂. The influence of isothermal holding time at the additional synthesis stage in the range of 5–10 min on phase composition and surface microstructure of the obtained materials was studied. The maximum content of the Ti₃SiC₂ phase, 77.8 vol %, was reached for composites synthesized by the combined sintering of Ti/Si/C and Ti/Si/TiC mixtures at an additional sintering time of 10 and 5 min, respectively. It has been shown that the microstructure of the surfaces of the synthesized composites is represented by elongated grains of the MAX-phase Ti₃SiC₂ with length from 4 to 12 µm, agglomerates of titanium carbide, and precipitations of titanium disilicide.