Fundamental’nye problemy sovremennogo materialovedenia / Basic Problems of Material Science

ADVANCED NON-VOLATILE MEMORY TECHNOLOGIES: FERROELECTRIC AND RESISTIVE STORAGE DEVICES

Yuri Gafner — 2025-09-30

The current limitations of traditional microelectronics in solving many complex technical problems are one of the reasons for the development of nanotechnology. Such problems include the need to improve the characteristics of long-term memory devices. If we consider the evolution of information storage systems, then electrical, magnetic, optical and phase-structural properties of materials used for data recording are of particular interest. We will consider two of the listed methods, namely, a method of storing information using systems whose operating principle is based on the polarization of the ferroelectric layer (FRAM) and control of the electrical resistance of the working layer using an electric field (RRAM). In FRAM, data is written by applying an electric field that changes the direction of the polarization vector that determines the state of the bit. Then the information can be repeatedly read without destroying the cell state, and also restored by reverse switching of the polarization state. RRAM operation assumes that the resistance of the material changes, thereby quickly writing and reading information. Both methods demonstrate significant advantages over traditional types of non-volatile memory devices, but further research is needed to reduce power consumption, improve reliability, and meet the technical challenges of today.

STRUCTURE AND PROPERTIES OF HIGH SPEED MOLYBDENUM STEEL SURFACING

Victor Gromov — 2025-09-30

Using methods of modern physical materials science (optical, scanning electron microscopy, micro-hardness measurement), the structural-phase states and properties of plasma surfacing with current-carrying flux-cored wire in a nitrogen environment of high-speed molybdenum steel type M10 on a substrate of medium-carbon steel 30 KhGSA were studied. The formed layer is ~10 mm thick. It has a polycrystalline dendritic structure. Map-ping methods revealed the localization of molybdenum, chromium, aluminum, and silicon in the structure of the sur-facing. Using the point-by-point X-ray spectral microanalysis method, it was shown that carbon, nitrogen and oxy-gen are present in areas of the material enriched with aluminum atoms. This leads to the formation of oxycarboni-trides of submicron size, randomly located. The relative content of all surfacing elements, excluding carbon, oxygen and manganese, decreases as one approaches the surfacing-substrate contact zone. The constructed microhardness profile revealed its significant dependence on the distance to the substrate. The surface layer with a thickness of ~1 mm has the maximum microhardness (average value 5.60 GPa). As one moves away from the surface, the micro-hardness decreases sharply, approaching the microhardness of the substrate. The average microhardness of the sur-facing is ~1.8 times higher than the microhardness of 30KhGSA steel (substrate).

EFFECT OF SURFACE TREATMENT WITH PULSED ELECTRON BEAM ON STRUCTURAL AND FUNCTIONAL PROPERTIES OF POLYTETRAFLUOROETHYLENE

Alena Korzhova — 2025-09-30

The article presents the results of studying the structural and functional properties of polytetrafluoroethylene (PTFE) after surface treatment with a pulsed electron beam. Electron beam modification was carried out at an exposure duration of 100 μs; beam current density of 0.25-1.23 A/cm², pressure of 5-7 Pa and accelerating voltage of 8-9 kV. The surface wettability and free surface energy of the samples, changes in strength, elongation and elastic modulus as a result of modification, material hardness and crystalline properties were studied. For modified PTFE, a decrease in the wetting angle to 64.5° and an increase in the free surface energy to 55.5 mN/m were noted. For most of the studied samples, an increase in tensile strength and a decrease in the relative elongation at break were observed. The elastic modulus of the samples significantly increased. The crystalline structure of PTFE after modification changes insignificantly, while the size of crystallites in the material decreases from 74 nm to 67-73 nm. Pulsed electron beam treatment of PTFE significantly increases the surface energy while maintaining mechanical properties. The data indicate that the method is promising for effective modification of the surface of polytetrafluoroethylene without reducing strength.

SUPERSONIC CROWDIN-FOCUSON TANDEMS IN 3D COMPUTER MODEL OF Cu CRYSTAL

Nikolay Medvedev — 2025-09-30

In this paper, using the method of molecular dynamics using a modified Morse potential, the prob-lem of excitation of n-crowdions in 3D models of FCC crystals is considered. The need to modify the Morse po-tential is due to the fact that when modeling the interaction of atoms at high speeds, it underestimates their diame-ters. A copper crystal model was used. The results of simultaneous triggering of several neighboring atoms located in a tightly packed row with the same kinetic energies by an order of magnitude and more exceeding the threshold energy of formation of a Frenkel pair were studied. Emerging supersonic crowdions and n-crowdions have been found to inevitably accompany a number of focusons. The number of focusons may be one less than or equal to the number of crowdions. The sum of the number of focusons and crowdions is always equal to the number of at-oms that were initially given an initial speed. With the help of a pair of atoms located several interatomic distances from each other and to which the initial kinetic energy was communicated above the threshold energy of formation of Frenkel pairs, the mechanism of transformation of crowdion into focuson was studied. The conditions are de-termined under which atoms that are given an initial kinetic energy much higher than the energy of formation of a Frenkel pair always form only crowdions.

ELECTRONIC STRUCTURE OF CRYSTALS LiMO2 (M = B, Al, Ga, In, Tl)

Ekaterina Duginova — 2025-09-30

Within the framework of density functional theory (DFT), the chalcopyrite structure of hypothetical LiMO₂ compounds (M = Al, Ga, In, Tl) was investigated for the first time, and equilibrium structural parameters were determined. Calculations of the energy band structure of LiMO₂ crystals were performed using CRYSTAL and Quantum Espresso software codes with LDA, GGA, PBE, and PBEsol functionals. The energy band structure and density of states of LiMO₂ crystals were calculated at high-symmetry points for chalcopyrites (T, Γ, N). All studied LiMO₂ crystals are wide-bandgap materials. The values of the bandgap Eg were estimated, and peculiarities of E_g variation and the total width of the valence band were established during cation substitution in the series B→Al→Ga→In→Tl. This affects the change in properties in the series of crystals from explicit dielectrics (the first three) to narrow-gap (LiTlO₂) semiconductors. Features of the conduction band edge formation were revealed depending on the chemical composition of LiMO₂ crystals. The conduction band minimum at the Γ point of LiMO₂ crystals has Γ_1C or Γ_3C symmetry, which results in the distinction between direct and pseudodirect bandgap crystals, respectively. It was revealed that the crystals exhibit properties of both semiconductors and dielectrics.

Study of the possibility of obtaining sialon powder in the mode of self-propagating high-temperature synthesis using SiO2 of different fractions

Ludmila Kondratieva — 2025-09-30

The article presents the results of studies of the possibility of obtaining sialon powder using the azide technology of self-propagating high-temperature synthesis. Sialon was obtained by burning a reaction mixture consisting of sodium azide NaN₃, aluminum fluoride AlF₃and silicon oxide SiO₂. Silicon oxide was used in the form of quartz sand of two fractions (0.8-1.2 mm and 0.1-0.3 mm) and aerosil. The use of quartz sand of the 0.1-0.3 mm fraction resulted in obtaining a product with the highest amount of the sialon phase (55%). In addition, sialon of the composition Si_1.96Al_0.04O_1.04N_1.96 was synthesized already at a temperature of 1200ºС, which is several hundred degrees lower than the temperature of obtaining sialons using other technologies. The microstructure of the target product, when using quartz sand with a particle size of 0.1-0.3 mm in the SiO₂-NaN₃-AlF₃ charge, consisted of equiaxed particles of sialon Si_1.96Al_0.04O_1.04N_1.96, sodium hexafluoroaluminate Na₃AlF₆ and silicon oxide SiO₂. The average particle size of sialon was in the range from 100 to 150 nm. In the product synthesized from the batch containing aerosil, sialon phases of a different composition were found: Si_1.6Al_0.4O_1.4N_1.6(8%) and SiAlON (12%). This indicates that different fractions of SiO₂ in the initial batch affect the phase composition of not only the entire final product, but also the composition of sialon.

OBTAINING POROUS MATERIALS FOR BONE TISSUE RESTORATION BASED ON SiO₂-CaO BIOGLASS

Daria Lytkina — 2025-09-30

Abstract. The World Health Organization notes a significant increase in the proportion of musculoskeletal diseases as a cause of loss of healthy life years, which emphasizes the need to develop effective strategies for bone tissue regeneration. The problem of osteoporosis, which ranks fourth among non-communicable diseases, is of particular relevance. Traditional methods of treatment, including autotransplantation, have significant limitations, such as a shortage of donor material and the risk of complications. In this regard, a promising direction is the creation of synthetic biomaterials capable of reproducing the structure and function of natural bone tissue. The key requirements for such materials are optimal porosity, mechanical strength and bioactivity. Of particular interest are composites based on bioactive glass (BS), demonstrating high osteogenic potential. Modification of BS with amino acids, in particular glycine, opens up new possibilities for controlling the morphology and functional properties of the material. However, the mechanisms of interaction of amino acids with the BS surface remain insufficiently studied, which limits the targeted design of such systems. The paper presents the synthesis and characterization of composite materials based on bioactive glass (BS) of the SiO₂-CaO (60/40 mol.%) system modified with glycine. A set of physicochemical methods was used to characterize the materials: scanning electron microscopy, X-ray phase analysis to determine the crystal structure, IR spectroscopy to identify functional groups, low-temperature nitrogen adsorption to assess the specific surface area and porosity. Cell viability was determined after 6 days of incubation with samples using the Alamar Blue fluorescent test. The results demonstrate the promise of the developed composite materials for use in regenerative medicine. It was found that the synthesis parameters and modification with glycine significantly affect the morphology, porous structure and biological activity of the materials. The purpose of this study is to develop composite materials based on the SiO₂-CaO system modified with amino acids and a comprehensive study of their physicochemical and biomedical characteristics.

PULSE CURRENT TREATMENT OF GRADE 5 TITANIUM PLATES AFTER BENDING TO REDUCE SPRINGBACK EFFECT

Alina Morkina — 2025-09-30

Springback in titanium alloys after bending remains a significant technological challenge in aero-space, medical and other industries. This study investigates the possibility of reducing springback in grade 5 titani-um alloy plates using post-deformation electropulsing treatment. Unlike conventional approaches requiring work-piece heating, the proposed technology involves applying pulsed current through tooling (die and punch), signifi-cantly simplifying the process. Experiments were conducted on samples with thicknesses of 0.77 and 2.1 mm and width of 4 mm at voltages on the capacitor battery of 100-180 V and pulse numbers ranging from 1 to 10. The re-sults demonstrated that for thin plates (0.77 mm), properly selected treatment parameters can completely eliminate springback, while for thicker samples the recovery angle decreases from 107-109.5° to 100°. SEM microstructural analysis revealed that springback reduction is associated with the α→β phase transformation in the plastic defor-mation zone, as well as surface layer enrichment with iron (up to 14-16 wt.%) due to steel punch erosion. The ob-tained results demonstrate the promise of electropulse treatment as a technological method for controlling geometric accuracy of titanium alloy products, combining springback suppression with surface layer chemical modification.

THE USE OF SUPERPLASTIC FILLINGS IN SOLID-PHASE WELDING TECHNOLOGY

Ramil Lutfullin — 2025-09-30

The highest efficiency of using superplasticity in solid-phase welding technology is determined by the possibility of its implementation in the welded zone. It is most rational that the superplastic deformation should not be subjected to the welded workpieces themselves, but what is more technologically advanced if it is limited in a narrow-connected zone. This possibility of controlling the locality of the superplastic deformation is possible if in-termediate superplastic interlayers are used between the workpieces to be connected. The results of experimental work on solid-phase welding of blanks made of industrial titanium alloy VT6 using fine-grained and ultrafine-grained interlayers made of titanium alloys of different names are considered. The use of fine-grained interlayers makes it possible to successfully weld coarse-grained blanks that are incapable of superplastic deformation in the traditional joint venture mode. When using nanostructured or ultrafine-grained interlayers, it becomes possible to successfully weld fine-grained and coarse-grained workpieces in temperature conditions of both traditional and low-temperature superplasticity. Solid-phase welding of heat-resistant nickel alloys through a superplastic interlayer seems promising. In this case, along with achieving high quality of the welded joint, the technologically complex problem of preparing an ultrafine-grained structure in large-sized workpieces is avoided.

REVIEW OF RECENT WORK ON ELECTRIC PULSE TREATMENT OF STEELS TO IMPROVE THEIR PROPERTIES

Ilya Sugonyako — 2025-09-30

Electric pulse treatment (EPT) of steels based on the electroplastic effect (EPE) has found wide application in various branches of industry. The EPE is most often explained by the combined effect of thermal ef-fects (non-uniform release of joule heat on structural defects), athermal effects (the effect of the electron wind, the skin effect, and the interaction of dislocations with local stoppers), and the effect of a magnetic field (the pinch ef-fect and the spin softening of the metal). EPT is usually applied for the purpose of healing defects (fatigue cracks or pores), improving microstructure (grain refinement, changing phase composition, performing phase transformations, dissolving precipitates), increasing mechanical properties (plasticity), increasing corrosion resistance and wear re-sistance, reducing residual stresses and increasing the efficiency of metal processing methods (drawing, rolling, etc.). The purpose of this review was to analyze the work and summarize the achievements in the EPT of steels over the past few years. The works on EPT of various steels for each of the above-mentioned purposes were reviewed. In addition, new achievements in the field of EPT include the use of this method to improve the microstructure of steels produced using additive manufacturing technologies. Computer simulations (such as finite element methods) and machine learning techniques are also being used in the study of EPT.

Investigation of the thermal properties of a system of high-entropy alloys based on CoCrFeMnNi by differential thermal analysis

Anna Shubert — 2025-09-30

The study focuses on the thermal properties of the high-entropy alloy CoCrFeMnNi, which is known for its exceptional plasticity at extreme temperatures and resistance to deformation and wear. The research justifies the choice of this alloy due to its long history of investigation, yet its thermal properties remain insufficiently explored. The subject of the study is the CoCrFeMnNi alloy system, where the composition of iron (Fe) and manganese (Mn) varies from 5% to 30%, while chromium (Cr), cobalt (Co), and nickel (Ni) remain constant at 20% each. The aim of the study is to analyze the thermal transitions and phase changes in the alloy using differential thermal analysis (DTA), a method that allows the detection of endothermic and exothermic reactions during heating and cooling. The methodology involves heating the samples at a controlled rate of 20°C per minute up to 1550°C in an argon atmosphere to prevent oxidation. The results highlight significant differences in thermal behavior depending on the Fe and Mn content, with variations in melting points, phase transitions, and energy distribution. The conclusions show that the chemical composition significantly impacts the alloy's thermal properties, making the findings relevant for further applications in industries requiring high thermal and structural stability.

STRUCTURE AND PHASE COMPOSITION OF A BIMETALLIC NI-TI ALLOY PRODUCED BY A WIRE-FEED ELECTRON-BEAM ADDITIVE MANUFACTURING

Andrey Luchin — 2025-09-30

The production of Ni-Ti-based alloys by additive manufacturing is one of the most topical technological tasks, the solution of which would help to reduce the cost and simplify the production of large-sized functional products of complex shape. In this work, a sample of a bimetallic Ni-Ti alloy was produced by the method of wire electron beam additive manufacturing (EBAM) by layered deposition of Ni layers in its lower part, and then Ti layers in the upper part. According to X-ray diffraction analysis and energy dispersive X-ray spectroscopy, the resulting multilayer bimetallic sample contains many phases, the presence and distribution of which depends on the ratio of Ni and Ti in each layer. These phases are pure Ni in the lower part of the sample, α–Ti with different concentrations of dissolved nickel in the upper part, and Ni₃Ti, NiTi, and NiTi₂ intermetallics in the central "transition" region between Ni and Ti. The microhardness in the "transition" region varies over a wide range of 3.5 – 5.5 GPa values. It is determined by the ratio and distribution of intermetallic phases formed due to different ratios of elements and the "thermal history" of each subsequent layer. The analysis of metallographic images and scanning electron microscopy images showed that there are no macroscopic or microscopic pores or cracks in the resulting material, and the material within each layer is continuous. These findings confirm the prospects of using the EBAM method for the production of functional intermetallic alloys based on Ni-Ti and bimetallic materials based on them.