Two sulfide phases of composition Nd1.5Y(Tb)1.5Ga1.67S7 were obtained from high-purity simple substances in evacuated quartz ampoules at a maximum synthesis temperature of 1100 degrees C. The synthesized alloys were homogenized by annealing at a temperature of 500 degrees C for one month. The crystal structure of the sulfides Nd1.5Y1.5Ga1.67S7 (a = 9.720(1) & Aring;, c = 6.103(1) & Aring;, RI = 0.0804, Rp = 0.2806) and Nd1.5Tb1.5Ga1.67S7 (a = 9.8866(7) & Aring;, c = 6.0877(6) & Aring;, RI = 0.0800, Rp = 0.2536) was studied by powder X-ray diffraction. Their structure belongs to the structural type La3CuSiS7 (space group P63; Pearson symbol hP24). In these structures, the rare-earth (R) atoms [Nd and Y(Tb)] are statistically distributed in the site 6c (x y z) and together with the S atoms form trigonal prisms with one additional atom [R S6+1]. The Ga1 site 2a is defective with an atomic packing factor APF = 66.7 %, and Ga2 site 2b with full atomic occupancy. The Ga1 and Ga2 atoms have octahedral and tetrahedral environments, respectively. Sulfur in the crystal lattice has three atomic positions: S1, S2 (site 6c) and S3 (site 2b). The primitive hexagonal unit cell contains two formula units Nd1.5Y(Tb)1.5Ga1.67S7. Trigonal prisms [R S6+1] are connected by edges and form "blocks" (three prisms each). Octahedrons [Ga1 S6] have common faces and form "columns" in the direction of the main axis. Trigonal prisms with octahedra form common faces. Tetrahedra [Ga2 S4] are isolated from each other. Using density functional theory within the framework of the Kohn-Shem formalism, the band-energy structure of synthesized sulfides was studied.
An industrial technology for thermal diffusion deposition of complex-alloyed protective coatings of the Ni-Al-Si-Cr-La system on heat-resistant nickel alloys ChS-70VM and EP-539LM has been developed and optimized. Saturation was carried out in powder mixtures based on ferroaluminum, ferrosilicon, and specially smelted Fe-Al-Si master alloys (20-30% Al, 15-25% Si) with the activator Na2SiF6 at 900-950 degrees C. The influence of temperature and time conditions of saturation and subsequent annealing on the coating growth kinetics, phase composition, and microstructure of the base was determined. It was shown that the optimal conditions (quenching at 1160 degrees C + aging at 1050 degrees C + saturation at 950 degrees C, 6-8 hours) provide a coating thickness of 40-60 & micro;m, a microhardness of 7500-9000 MPa, and the preservation of the structural stability of the gamma '-phase of the alloy. The coatings demonstrate twice the heat resistance and corrosion re-sistance in diesel fuel combustion products with the addition of sea salt compared to traditional aluminide coatings. Bench and engine tests (600 hours) confirmed the resource efficiency of the developed technology.
The study examines how partial substitution of strontium (Sr) for barium (Ba) in HgBa1.6-xSrxLa0.4Ca2Cu3O8+delta superconductors influences their structural and electrical proper-ties. Samples with Sr concentrations of x = 0, 0.1, and 0.2 were synthesized using the solid-state reaction method. X-ray diffraction (XRD) analysis confirmed that all samples maintained the tetragonal phase characteristic of the Hg-1223 structure. As Sr content increased, there were notable changes in lattice parameters and mass density. These changes were attributed to the smaller ionic radius of Sr compared to Ba, leading to a reduction in the c/a ratio. This structural modification positively influenced the superconducting properties, as indicated by the critical temperature (Tc) measurements obtained using the four-point probe method. The Tc onset increased from 127 K to 139 K, while the Tc offset rose from 118 K to 126 K as Sr content increased from 0 to 0.2. Microscopic analysis through scanning electron microscopy (SEM) revealed a re-duction in grain size as the Sr concentration increased. This reduction in grain size likely minimized insulating grain boundaries, potentially enhancing the superconducting behavior. Over-all, the findings suggest that Sr substitution improves superconducting properties by altering the material's microstructure and enhancing phase stability.
A glow discharge nitriding method has been developed, which includes preliminary hydrogenation of metal surfaces and promotes the intensification of diffusion processes during nitriding in a plasma chamber. Both hydrogenation and nitriding processes are carried out sequentially in the same discharge chamber and do not require any additional equipment. The combination of hydrogenation and subsequent glow discharge nitriding is expected to increase the number of phase structural components of the nitrided layer, particularly the epsilon- and gamma-phases, which will significantly improve its physicochemical and operational properties such as strength, ductil-ity, corrosion resistance, and fatigue strength. The increase in the thickness of the nitride layer reaches its maximum at an argon content of 20%. With a further increase in argon content, the thickness of the nitride layer decreases for all studied materials. This is presumably due to internal stresses exceeding the strength limits of the materials, resulting in relaxation through massive dislocation emission to the surface, micropore formation, and a decrease in hydrogen pressure in internal voids-referred to as collectors. Preliminary ion-plasma hydrogenation in an environment with 20% argon content followed by glow discharge nitriding made it possible to increase the thickness of the nitride layer in the studied materials by approximately 1.7 times. Additionally, corrosion-mechanical wear resistance in a buffer solution of citric acid with pH 6.5 increased by 1.45 to 1.62 times compared to conventional methods. Cavitation-erosion resistance in a 3% NaCl solution increased by 4.7, 5.3, and 8.9 times for steels 20, 45, and cast iron SCH 20, respectively.
The comprehensive study provides a reliable understanding of the trends in the joint behavior of structural components in water-salt systems of nitrate precursors of neodymium, cesium, strontium in the preparatory stages of technological regulations for both concentration and immobilization of liquid radioactive waste of the nuclear energy industrial complex( 137)Cs, Sr-90 and thermal activation. The stages of such transformations have been revealed; the patterns of complex and phase formation in the systems and the factors influencing them have been clarified. Various physicochemical properties of the resulting intermediate phases of neodymium coordination nitrates were studied: their composition, types of compounds, atomic crystal structure, shapes of Ln coordination polyhedra, types of ligand coordination, features and patterns of behavior in heat treatment processes. It has been established that under the conditions of the existence of solutions, the system CsNO3-Nd(NO3)(3)-H2O is characterized by the formation of 2 anionic complex compounds Ln(3+), the system Sr(NO3)(2)-Nd(NO3)(3)-H2O-is of the eutonic type. The ongoing competing reactions are a powerful technological factor that has a significant impact on changes in the activity of structural forms of Ln(3+). Systematized information enables to elucidate the mechanisms and kinetics of transformations of structural components in similar objects. Also, it enables to transfer the resulting system of knowledge to the promising technological solutions for the solidification of liquid radioactive wastes.
Organic field-effect transistors (OFETs) have emerged as promising components in flexible and low-cost electronic applications due to their mechanical flexibility, compatibility with solution processing, and the ability to tune electrical properties. A critical element in OFET performance is the gate dielectric, with polymeric dielectrics such as PMMA, PVP, and polystyrene offering notable advantages in terms of processability, dielectric strength, and interface engineering. This review presents a comprehensive analysis of OFETs utilizing polymeric gate dielectrics, with a focus on the deposition of organic semiconductors by spin-coating and thermal evaporation methods. The review discusses how the interaction between polymer dielectrics and semiconductors affects charge transport, interface traps, threshold voltage, and overall device stability. Key device architectures including bottom-gate and top-gate configurations are evaluated, highlighting performance trends and material selection strategies. Finally, new designs such as bilayer dielectrics, organic–inorganic hybrid systems, and low-voltage organic field-effect transistors are considered to address issues related to environmental sensitivity and lifetime. This review aims to guide future research in optimizing material combinations and fabrication techniques to advance the practical application of polymeric-gated OFETs in next-generation electronics.
A new method for creating elements of a heterogeneous detector for sampling-calorimeters of the "Shashlik" type using FDM 3D-printing technology is proposed. An experimental sample was manufactured using the proposed method. The scintillation layers were printed with a filament made of a material consisting of polystyrene with the addition of 2 wt% paraterphenyl (p-TP), 0.05 wt% 2,2-p-phenylene-bis(5-phenyloxazole) (POPOP) and 0.2 wt% dioctyl phthalate. The absorption layers were printed with a filament made of a eutectic alloy (52% Bi, 32% Pb, 16% Sn). The light reflection function is implemented without additional reflective layers due to specular reflection from the metallic surfaces of the absorber. It has been experimentally shown that the proposed method ensures the formation of scintillator-absorber blocks in a single technological cycle. The amplitude spectrum of the response of the printed detector element was investigated. The proposed 3D-printing method may be useful in the development of sampling-detectors with improved energy resolution.
This work presents a comprehensive, comparative study of two primary SiC polytypes, cubic (3C) and hexagonal (6H), using large-scale molecular dynamics simulations powered by a high-fidelity Machine Learning Interatomic Potential (MLIP) trained on a custom dataset of 5152 first-principles configurations. We present a complete set of thermo-mechanical properties, including the coefficient of thermal expansion (CTE) and the full elastic tensor (C-ij), from 0 K to 2000 K. A crucial finding from the analysis of the uniaxial Young's modulus is that the 6H poly-type undergoes thermal softening at a rate of approximately 49 MPa/K, which is almost twice as fast as the 3C polytype at 25 MPa/K. This pronounced single-crystal anisotropy contrasts with the behavior of the Voigt-Reuss-Hill averaged polycrystalline moduli, which show similar softening rates of similar to 33 MPa/K for both materials. The presented properties are validated against established experimental and theoretical data, providing a quantitative understanding of thermo-mechanical behavior behavior of SiC and delivering the essential property data needed to enhance the fidelity of engineering models for SiC components.
In this study, the efficiency of the improved super alloy on cobalt base (F-75) by modifying the surface components of the alloy using the diffusion coating method in aluminum with presence of the thermal barrier of titanium oxide (TiO2)at 1070 degrees C and in a vacuum atmosphere to avoid oxi-dation. The periodic oxidation process and a hot corrosion process was performed on the samples at a temperature of (1100 degrees C) with the presence of sodium sulfate (Na2SO4) and sodium chloride (NaCl), to determine their behavior on the one hand, and to study the structural composition of the samples through a set of technical tests, including optical microscopy,x-ray diffraction (XRD(, scanning electron microscope (SEM) as well as quantitative and qualitative examinations through the energy dispersive spectroscopy (EDS), specifications for the prepared alloys
A quantum-mechanical approach in the density functional theory is proposed for calculation of elastic modulus of composite materials. The modulus of elasticity is the ratio of the changes in the total energy and volume of the crystal lattice when the crystal is deformed in a certain crystallographic direction. The elastic moduli of Ni, Cu and composites based on them have been calculated in the [100] and [110] directions. The results are in good agreement with the experimental data obtained by bending the substrate and measuring the mechanical stress arising in the metal film deposited on the substrate.
By analogy with distillation refining of a flowing liquid, the possibility of refining by pulling a crystal from a melt stream is considered. The technological parameters of the named processes are (in addition to the effective separation coefficient) the evaporation rate or crystallization rate, respectively, and the evaporation surface area or crystal cross-section, respectively, and the flow of refined substance. The fundamental possibility of implementing continuous crystallization refining using a thin layer of melt to increase the purification efficiency is noted.
In this manuscript, a composite material was developed using unsaturated polyester resin as the base matrix and aluminum oxide as a reinforcing agent. The study focused on evaluating key mechanical properties, including hardness, compressive strength, and impact resistance. To investigate the effect of filler concentration, samples were prepared with varying Al2O3 weight fractions ranging from 1% to 10%. The results indicated that the optimal improvement in mechanical performance occurred at an Al2O3 content of 6%. The influence of processing temperature was examined by curing the composite samples at four different temperatures: 7 degrees C, 25 degrees C, 80 degrees C, and 150 degrees C. At 25 degrees C, the composites demonstrated notable enhancements in impact resistance, compressive strength, and hardness, accompanied by a reduction in Young's modulus. At other processing temperatures (7 degrees C, 80 degrees C, and 150 degrees C), the mechanical properties exhibited varying trends, with some increasing while others decreased. It was observed that thermal conductivity increases with increasing and decreasing temperature compared to room temperature. These findings suggest that both filler content and processing temperature significantly influence the mechanical and thermal behavior of Al2O3 reinforced unsaturated polyester composites.
The study investigates the efficiency of improving the fretting resistance of tribosystems by forming oil-retaining discretely textured surfaces (DTS) with regularly arranged microdimples. Phenomenologically, such surfaces were considered as having a discrete texture, and the microdimples acted as reservoirs providing continuous regeneration of boundary lubricant layers in the frictional contact zone. The DTSs in the form of a system of prismatic and spherical microdimples with specified texture parameters were created on the working surfaces of samples using an impact-plastic deformation method. Friction pairs with different hardness of contacting materials were studied. Pairs with DTS formed on samples with hardness higher than that of their counterbodies were usually called direct pairs. In contrast, pairs with lower DTS hardness compared to the counterbody were called inverse pairs. It has been established that under fretting conditions with lubricated polished surfaces, lubrication does not provide a significant increase in the fretting resistance of the studied materials, both in direct and in-verse pairs; this indicates insufficient stability of boundary lubricant layers on such surfaces. Under identical fretting wear and lubrication conditions, friction pairs with DTS demonstrated significantly increased resistance to fretting-corrosive wear. The most pronounced improvement in wear resistance was achieved in direct pairs with spherical dimple profiles. Compared to the baseline version, the wear of samples with pairs of spherical dimples was more than six times lower. At the same time, the wear of counterbodies and the total wear of the pair also decreased significantly. It was shown that for given DTS formation parameters and fretting conditions, the spherical profile ensured the higher lubrication efficiency of microdimples compared to the pris-matic profile. Based on the experimental results, statistical analysis was performed, and regres-sion models were developed to describe the dependence of wear on the technological parameters of surface texturing and fretting conditions.
Calcium phosphates modified with complexes of ions Na+,Mg2+,Cu2+,CO32-/ (BO33-BO2-) or Na+,Mg2+,Cu2+,Fe3+,CO32-/(BO33-,BO2-), as well as composites based on calcium phosphate containing Na+,Mg2+,CO32-/(BO33-,BO2-) and (10 or 25 wt%) CuFe2O4 have been obtained from the aqueous solution and further heated to 600 degrees C. It was found that borate-ions in the initial solutions allowed stabilization of the apatite-type phase, whereas in the case of a carbonate-con-taining system a biphasic calcium phosphate was obtained in composite with 25 wt% CuFe2O4. Systems containing carbonates produced larger particles (28-34 nm) than borate-containing systems (range 19-23 nm). The presence of different types of anions (PO43-, CO32-, BO33-, BO2, OH-) was confirmed by FTIR spectroscopy. Composites based on biphasic calcium phosphate with 25 wt% CuFe2O4 demonstrated higher activity with respect to partial dissolution in the model solution compared to modified calcium phosphates and composites based on them with CuFe2O4. The highest antibacterial properties against S. aureus or P. aeruginosa strains were found for borate-containing apatite. Obtained results can be important in the creation of materials with special bioactivity and antibacterial properties for medical application.
Graphene oxide is often used in cement-based materials due to its high strength, toughness and strong surface activity, which can not only improve mechanical properties but also enhance durability. Modified concrete with different graphene oxide dosings (0,0.04%, 0.08% and 0.12% (mass fraction)) was prepared by doping graphene oxide into concrete. The effects of graphene oxide dosage on the microstructure, crystal structure, mechanical properties, slump and porosity of the modified concrete were studied. The results show that an appropriate amount of graphene oxide doping accelerates the hydration reaction of the modified concrete, refines the pore structure and improves the density. With the increase of the doping amount of graphene oxide, the compressive strength and flexural strength of the modified concrete first increase and then decrease, while the slump and porosity first decrease and then increase. When the doping amount of graphene oxide is 0.08% (mass fraction), the compressive strength and flexural strength both reach the maximum values of 46.3MPa and 7.5 MPa respectively at 28 days. The slump and porosity reached the minimum values of 27.6 mm and 25.1% respectively. It should be noted that with a graphene oxide content of 0.08% (by mass fraction), the comprehensive performance of the modified concrete is the best.
In this study, we examine the impact of aluminum substitution on the structural, electronic, and magnetic properties of single-walled (6,0) silicon carbide nanotubes using spin-polarized density functional theory calculations. The introduction of Al into the nanotube lattice significantly alters its electronic structure, leading to a transition toward half-metallic behavior. Specifically, the spin-up channel retains a semiconducting nature, while the spin-down channel becomes metallic, indicating a clear spin-dependent conductivity. The partial density of states analysis reveals that the electronic states near the Fermi level are dominated by carbon p-orbitals, with additional contributions from the d-orbitals of the aluminum dopant. Spin-resolved charge density distributions further show the emergence of a net magnetic moment of approximately 1.0 mu B, which is mainly localized on the carbon atoms adjacent to the Al impurity. A comparison of total energies for ferromagnetic and antiferromagnetic configurations indicates that the antiferromagnetic state is energetically more stable and therefore represents the ground state of the system. Taken together, these findings suggest that Al@Si-doped (6,0) SiC nanotubes possess a combination of half-metallic characteristics and stable magnetic ordering, making them promising materials for spintronic applications such as spin filters and antiferromagnetic memory devices.
Environmental sustainability is a serious problem, which needs to be overcome for practical application. Therefore, our goal is to develop the butanolic extract of the plant Hyppomarathrum Libanotis (EBHL), belonging to the Apiaceae family, as an API 5L Gr-B carbon metal deterioration inhibitor in 1M HCl solution. To test the efficacy of inhibition, the effects of solution concentration, immersion time, and temperature on the deterioration processes of API 5L Gr-B metal in 1 M HCl medium in the presence of an inhibitor were studied. The study included mass loss analysis, electrochemical impedance spectroscopy, and potentiodynamic polarization. The obtained tests showed that increasing the concentration improves the output of EBHL inhibition and achieves a value of 82 % at 700 ppm. The temperature rise contributed to a major drop in the production of inhibitions. Potentiodynamic polarization tests indicate the role of the extract as a dual-action inhibitor. In the Langmuir isotherm model, the main influence is on the anodic region, and as a result, a retention process occurs. Based on the above results, thermodynamic and activation parameters were established. Furthermore, deep structural and chemical analysis was also performed. X-ray photoelectron spectrometry and scanning electron microscopy were utilized for the study. The results indicate the formation of a protective coating on the carbon steel sheet.
This review summarizes recent advances in the theoretical analysis of the stability of magnetized flows in a non-uniformly rotating layer of electrically conductive nanofluid, incorporating the effects of Brownian diffusion and thermophoresis. In the absence of temperature gradients, different forms of magnetorotational instability (MRI): standard (SMRI), azimuthal (AMRI), and helical (HMRI) are investigated for nanofluid layers subjected to axial, azimuthal, and helical magnetic fields. The corresponding growth rates and instability regions are analyzed in relation to the rotation profile (quantified by the Rossby number Ro) and the radial wave number k. When temperature gradients and nanoparticle concentration effects are present, stationary convective modes in both axial and helical magnetic fields are examined under conditions of non-uniform rotation. Analytical expressions for the critical Rayleigh number Rast are derived, and neutral stability curves are constructed as functions of the angular velocity profile, the azimuthal magnetic field inhomogeneity (magnetic Rossby number Rb, and the wave number k. The study identifies and discusses key mechanisms responsible for the stabilization or destabilization of stationary convection in axial and spiral magnetic field configurations, highlighting the role of nanoparticle-driven effects in modifying classical magnetoconvective behavior.
J-aggregates, highly ordered molecular assemblies, continue to attract significant attention in hybrid nanophotonic research owing to their strong absorption, efficient energy transfer, and pronounced fluorescence properties. When combined with nanostructured materials, their spectral properties – such as quantum yield, lifetime, and exciton dynamics – can be substantially modified. This review discusses various aspects of J-aggregates′ interactions with different nanostructured materials, focusing on their impact on the aggregates′ optical properties, particularly fluorescence. Strategies for enhancing the spectral response of J-aggregates in both liquid and solid media are highlighted.
The properties and structure of composites based on epoxy polymer and the synthetic antibiotic trimethoprim were investigated. It was found that the dispersed filler trimethoprim C14H18N4O3 exhibited an amorphous structure in the volume of the epoxy polymer, partially post-curing the polymer matrix. The introduction of trimethoprim into the epoxy matrix at a content of q = 10-15 wt.%. makes it possible to obtain new polymeric materials with improved mechanical properties, in particular: the flexural elastic modulus increases from E = 2.90 GPa to E = 3.67 GPa; the impact strength increases from W = 7.0 kJ/m2 to W = 12.8 kJ/m2; the flexural strength increases from 0b = 48.0 MPa to 0b = 87.7 MPa compared to the original epoxy composite. The change in the morphology of the epoxy polymer upon the introduction of an active filler was studied by optical microscopy. Based on the analysis of infrared spectra in the wavenumber range nu = 900-4000 cm-1, structural changes in the studied materials were determined, indicating the chemical interaction of the antibiotic with the epoxy polymer. X-ray diffraction analysis showed that the initial dispersed filler trimethoprim has a crystalline structure, and the epoxy polymer filled with trimethoprim has an amorphous structure. This may indicate the dissolution of the filler in the volume of the epoxy polymer.
