The calcium-hydride method is a promising approach for producing homogeneous ultrafine and nano TiC powder. Thermodynamic calculations of TiO2-Ca/CaH2-C/CaC2 systems were used to study the effect of the reducing agent excess and the form of the carbon-containing component on the isobaric-isothermal potential of TiC formation, the adiabatic heating temperature of the synthesis products, and the activity of carbon for its complete conversion to titanium carbide. It was determined that the sign and magnitude of the Gibbs free energy of the calcium-hydride reaction depend on the excess of CaH2. To ensure a smooth synthesis reaction, avoiding charge emissions or a sharp increase in hydrogen pressure, the excess reducing agent should be 50–100 wt% relative to the required amount for the complete reduction of TiO2. The presence of an excess reducing agent also suppresses the formation of impurity phases (Magneli phases and CaTiO3). The use of carbon black as a carbon source allows for the production of homogeneous TiC powder at low process temperatures (1273–1373 K). The optimal composition of the batch and the reduction temperature for the synthesis of TiC powder with at least 95 wt% of the target phase and an average particle size of ∼0.15 μm were determined.

High-entropy carbides (HECs) possess improved physical and mechanical properties due to severe lattice distortion; however, microstructure plays a pivotal role in polycrystalline materials. This study examines how the phase complexity of precursor powders impacts densification and microstructure of HECs prepared via spark plasma sintering. It is shown that heterodiffusion in the multi-phase powder hinders densification, thereby elevating sintering temperature by 200-350 degrees C compared to the single-phase powder. The sintering of the singlephase powder yields twice smaller grains (similar to 230 nm) related to the multi-phase powder (similar to 470 nm) with a relative density of 0.95. Thermal conductivity depends on the structure and decreases by 16-20 % per one-order grain size reduction (similar to 5.7 mu m to similar to 0.2 mu m), a decrease in relative density from 0.97 to 0.95, and an increase in lattice microstrain.

Molybdenum carbide (Mo2C) is a material with a combination of excellent functional characteristics, making it interesting for a practical application in variety of fields. In this study, the synthesis of Mo C was successfully conducted using a combined solution combustion synthesis (SCS) and controlled thermal annealing. Optimal synthesis conditions were identified through thermodynamic analysis, revealed that exothermic reactions occur with ammonium nitrate-to-ammonium molybdate ratios of 10-50 and fuel-to-oxidizer ratios (phi) of 1.5-5.0. The materials exhibited a highly porous structure, with single-phase Mo C achieved after annealing with glycine as a reducer. Mo C enhances thermocatalytic decomposition of synthetic aviation oil. Notably, Mo C reduces the activation energy by 25 % compared to homogeneous decomposition, achieving process efficiency improvements up to 639 %, at 250 degrees C. These findings highlight potential of application of combined SCS-thermal annealing method for the obtaining Mo C, while the synthesized materials have high potential for advanced catalytic applications in energy and aerospace.

CoCrFeNiTi high-entropy alloy (HEA) thin films were prepared on Si/SiO2 substrate by DC magnetron sputtering from one target of Co0.22Cr0.23Fe0.29Ni0.2Ti0.06 composition. The influence of sputtering time and power on the morphology, structure, chemical composition, resistivity, and temperature coefficient of resistance (TCR) has been studied. The thin films of the CoCrFeNiTi alloy exhibit a wide range of properties that can be tailored by adjusting the deposition parameters. The films demonstrate tunable TCR. The best TCR of 2.7 +/- 0.8 ppm/degrees C has been achieved. In addition, a head-to-head comparison with state-of-the-art thin-film resistor materials (NiCr, TaN, and HEA analogues) is presented for the first time. The study of the thermoelectric properties of the obtained films revealed a highest power factor (PF) value of similar to 0.015 mW/(m degrees C-2) and a linear behavior of PF increase in the range from -196 to 200 degrees C.

The study represents a low-cost, efficient, and rapid method to produce a high-entropy carbide-boride (HEC-HEB) ceramic through the self-propagating high-temperature synthesis and spark plasma sintering. Commercial metal, boron, and carbon reactants were successfully converted to ceramic powders possessing a heterogeneous structure. Spark plasma sintering at 1800 degrees C under 50 MPa yields a compact HEC-HEB sample with a high hardness of 22.0 GPa and improved toughness of 5.6 MPa & sdot;/m, which exceeds that for a simple multicomponent carbide (18.8 GPa, 4.2 MPa & sdot;/m) obtained by the same method. The heterogeneous structure of HEC-HEB also promotes compaction compared to simple HEB, where a dense structure was not achieved under identical sintering modes. In HEC-HEB, cracks propagate predominantly through the intergranular mechanism accompanied by crack deflection and grain pull-out effects; meanwhile, in simple HEC, the transgranular mechanism is most common. Our findings demonstrate that SPS enables the obtaining of improved ceramics with minimum efforts and can be considered a promising method for the fabrication of multicomponent carbide-boride composites with a heterogeneous structure.

The calciothermic synthesis of a LaNi5 powder is a complex process requiring careful control of synthesis temperature, holding time, excess of reducing agent, method of compacting a charge, and conditions of hydrometallurgical treatment. This study examines how these factors affect the phase composition and impurity content in LaNi5. It has been found that LaNi5 forms due to the diffusion saturation of solid Ni particles with La from La melt with no impurity phases from the Ca-Ni system. Optimization of synthesis parameters ensures the formation of single-phase LaNi5 at >= 1000 degrees C in >= 4 hours. It has been found that slaking duration considerably affects oxygen content. Contamination with Fe from crucible material occurs when the synthesis temperature exceeds a certain value. Overall, the study demonstrates that LaNi5 powder with low impurity content possessing high sorption properties can be obtained by providing optimal synthesis conditions and careful post-synthesis treatments such as leaching and slaking.

ABSTRACTA method has been developed for separating a mixture of calcium, magnesium and sodium sulfates obtained through the interaction of sulfuric acid and waste from the water purification process generated by using membrane filters. The primary goal of this method is to extract gypsum and produce gypsum‐based binders. Patterns were identified regarding how various types, ratio and quantities of additives: blast furnace slag, granite screenings, portland cement, electric steel smelting slag affect the water‐gypsum ratio, strength properties, and water resistance of high‐strength gypsum binders. It was found that adding a single‐component additive specifically to enhance water resistance does not significantly impact these properties. Complex additives have been developed based on Portland cement, granulated blast furnace slag, electric furnace slag, expanded clay dust, and granite screenings of various fractions. These additives are designed to maximize the water resistance of high‐strength gypsum binder based on synthetic calcium sulfate dihydrate. As a result, the water resistance coefficient increased from 0.45 to 0.52. Additionally, a technological block diagram of the process has been proposed.

The compressive creep properties of (Hf0.2Ta0.2Ti0.2Nb0.2Zr0.2)C high entropy ceramic (HEC), prepared by spark plasma sintering of the self-propagating high temperature synthesized powders, are investigated at 1400-1600 degrees C with stresses of 150 similar to 300 MPa. The as-received HEC was annealed at 2000 degrees C and 2100 degrees C for 1 h (HT2000 and HT2100) to eliminated the impurities. The phase composition, microstructure, and dislocation structures are characterized by an X-ray diffractometer, scan electron microscopy, and transmission electron microscopy, respectively. It is found that the steady creep rates of the HT2000 and HT2100 are similar at the same creep conditions, both being 10(-8)similar to 10(-9) s(-1). The creep resistance of both HECs is superior to those of the monolithic carbides. The creep damage includes the grains growth, formation of pores and cracks at the grain boundaries. The creep mechanisms of both HECs include atomic diffusion, grain boundary sliding and dislocation slip. At 1600 degrees C, Burgers vector of dislocation is a/2 <01( over bar)1>, and the main slip system is a/2 <01( over bar)1>{111}. The excellent creep resistance of the HECs is contributed by the slow atomic diffusion and restricted dislocation motion.

In this work, the influence of refractory Zr and Ti and their combination (Zr,Ti) on the oxidation behavior of the (Hf,Ta,Nb)(C,N) carbonitride under non-isothermal and isothermal conditions at 1200 degrees C was studied, the effect of nitrogen addition was demonstrated, and a possible oxidation mechanisms were identified. The best result was achieved for high-entropy carbonitride (Hf,Ta,Nb,Zr,Ti)(C,N). The introduction of nitrogen into the of highentropy carbide lattice contributed to a decrease in the specific weight gain by 12 %, and the addition of Ti, Zr, and (Zr,Ti) to the (Hf,Ta,Nb)(C,N) - a decrease of 47, 65, and 83 %, respectively.

In this work, Ti 25 Zr 25 Nb 25 Hf 25 and Ti 20 Zr 20 Nb 20 Hf 20 Ta 20 powders were obtained by the calciothermic reduction of oxide mixtures at 1200°C, and the structure and hydrogen properties were investigated. Tantalum has a negative effect, preventing the formation of a homogeneous structure, while the Ta-free alloy tends to form a single BCC phase. The TiZrHfNb powder, with its homogeneous structure, exhibits faster absorption kinetics up to 0.5 wt% H 2 and a higher hydrogen capacity of 1.93 wt% (H/M = 1.98). Our results indicate that homogeneous structure is crucial for enhanced sorption properties.

High-entropy alloys are currently considered as prospective hydrogen storage materials and getters, which can be utilized to create a high vacuum in specialized devices. To provide high sorption properties, it is crucial to use highly porous materials or powders that makes powder metallurgy an attractive and suitable method. In the current work, a powder high-entropy alloy TiZrHfNbTa was obtained by reducing transition metal oxides with calcium hydride. The mechanism and features of the calcium-hydride synthesis of the high-entropy alloy have been studied. Phase composition has shown to be dependent on holding time at a temperature of 1200 degrees C. The powder's structure comprises four BCC solutions based on Nb, Ta, TiZrHf, and TiZrHfNb, when holding time is up to two hours. Prolonged holding leads to more homogeneous structure, and the final product possesses two BCC phases: Ti0.21Zr0.24Hf0.24Nb0.25Ta0.06 (BCC-I: 75 wt%) and Ti0.15Zr0.05Hf0.08Nb0.10Ta0.62 (BCC-II: 25 wt%). The analysis of BCC-I formation kinetics with the aid of the Avrami equation has shown that a quite prolonged time of around 48 hours is necessary to achieve a single-phase structure of the powder due to the presence of tantalum, which impedes homogenization. Parameter n in the Avrami equation has been determined to be 0.361.

High-temperature shape memory alloys are suitable materials for substituting hydraulic elements in the aerospace industry due to light weight and high reactive stresses developing during thermoelastic martensitic transformation and acceptable recoverable strain. These properties may be improved by plastic deformation; however, the plastic deformation of NiTiHf alloys along with structure investigation has yet to be studied systematically. Here, the hot deformation behavior of a NiTiHf alloy with hafnium content >20 at.% has been investigated, and the processing map has been elaborated according to the dynamic material model (DMM) based on the Prasad instability criterion. The deformation heating effect has been shown to affect the flow curves and accounts for profound softening during deformation due to quasi-adiabatic deformation mode at high strain rates. NiTiHf alloys have a much higher activation energy of plastic flow, and the instability region of plastic flow is much larger compared to binary NiTi alloys. Microstructural observations have revealed that in the instability regions, oxide bands and crack nucleation occur, whereas outside this region, such defects are not observed. Electron backscatter diffraction has demonstrated that at high temperatures and slow strain rates, discontinuous dynamic recrystallization occurs resulting in the necklace-type structure, while at high strain rates, this phenomenon has not been observed. Based on the obtained results, the preferable deformation conditions are established to be 850-1000 degrees C and 0.003-0.05 s(-1).

This study assesses the effectiveness of empirical stability descriptors — the normalized geometric packing parameter, lattice size difference, electronegativities mismatch, and the convex hull analysis based on information on mutually dissolving components, and ab-initio calculated entropy forming ability (EFA) for high-throughput materials discovery in high-entropy ceramics. A sample containing 53,130 medium and high-entropy carbide combinations from the Materials Project database has been analyzed, comparing solid solutions selected based on empirical descriptors and EFA calculations. The suitability of various electronegativity scales is evaluated, while Automatic FLOW (AFLOW) partial occupation (AFLOW-POCC) and special quasirandom structures (SQS) calculations provide insights into enthalpies, bulk moduli, and lattice parameters. It is shown that local distortions play a role in determining the stability of high-entropy ceramics and estimated lattice parameters, Young’s modulus, fracture toughness, and Vickers hardness by computational and experimental approaches. Our analysis demonstrates the efficacy of density functional theory (DFT) approaches for high-throughput screening and highlights the need for the further exploration of the cocktail effect on high-entropy ceramics’ mechanical properties.

Metal carbides are widely used in various applications as catalysts, components of composite materials, cutting tools, and abrasive materials where the particle/grain size has a great impact on target properties. Here, we report a facile way to synthesize nano- and ultra-fine carbides of IVb-Vb groups, including high-entropy carbides, which are of interest nowadays due to their superior properties, by the combination of calcium-hydride reduction of metal oxides and the direct reaction of the reduced metals with carbon in one production step. By tailoring the synthesis parameters, it is possible to obtain the carbide powders of a size in the range of 50-1500 nm with high crystallinity. The average particle size is found to be dependent on the homologous synthesis temperature and follows a power law. We have also shown the possibility of obtaining ultrafine-grained bulk carbides (d = 0.24-0.9 mu m) via spark-plasma sintering at a temperature of 1500-1650 degrees C with a relative density >95 % without using additives. The HEC (Ti,Zr,Nb,Hf,Ta)C has a higher activation energy of grain growth (collective recrystallization) compared to binary TaCx (x = 0.8 and 1), which confirms the effect of lattice distortion on diffusion coefficients. The suggested fabrication route can be widely used for nano and ultrafine carbide powder preparation on the industrial scale.

ABSTRACT The article presents the results of experimental studies of the efficiency of purification of model and real wastewater from dyeing and finishing industries using pneumatic flotation using an ozone‐air mixture instead of air and a combination of ultrasonic treatment and ozonation. The influence of gas mixture consumption, dye concentration, and ozone concentration in the gas mixture on the cleaning efficiency was studied. The purification efficiency was assessed by optical density and COD. By using an ozone‐air mixture instead of air in the flotation process, an efficiency increase of up to 12 times was achieved. It has also been shown that wastewater treatment efficiency increases by up to 12% when combining ozone‐air flotation with ultrasonic treatment at 630 W and operating frequency 22% ± 10% kHz. This effect may be associated, first of all, with the dispersion of bubbles of the ozone‐air mixture, which leads to an increase in their total surface and, accordingly, to the rise in the kinetics of mass transfer—ozone dissolution.

A high-entropy alloy TiZrHfNbTa has been synthesized by a method of the mutual reduction of the higher oxides of corresponding metals with calcium hydride. The alloy structure was characterized and hydrogen absorption properties were studied. The alloy of overall equiatomic composition TiZrHfNbTa consists of two BCC phases with unit cell parameters of 3.419 and 3.328Å. The distribution of the elements was established as follows: Ti0.21Zr0.24Hf0.24Nb0.25Ta0.06 (BCC-I) and Ti0.15Zr0.05Hf0.10Nb0.08Ta0.62 (BCC-II). The hydrogenation behavior of the alloy under different conditions was thoroughly studied. It was shown that complete hydrogenation resulted in the formation of FCC-type (H/M → 2) and BCT-type hydrides (H/M → 1) from BCC-I and BCC-II, respectively. Under low hydrogen pressure (< 212.8Torr), BCC-I absorbed up to 0.33 at. H/M within a solid solution without changing the structural type. According the kinetic analysis, this process can be described as a second order reaction with activation energy of 102kJ/mol. The BCC-I-based solid solution is capable of retaining hydrogen in a deep vacuum at a temperature of 430 °C. The fast kinetics of hydrogen absorption and high thermal stability allow us to suggest the studied two-phase TiZrHfNbTa alloy as a promising getter for vacuum devices.

AbstractThe effects of severe plastic deformation on NiTi alloys’ structure and properties have been extensively studied over the past decades. However, there is a notable lack of systematic data regarding the impact of industrial hot deformation techniques on these alloys. This gap arises from challenges in manufacturing processes related to the unevenness of ingots produced by casting technologies. This study investigates the effects of hot rotary swaging, extrusion, and radial shear rolling on the martensitic transformation, shape memory effect, superelasticity, and damping capacity of NiTi Ni-rich alloys fabricated through powder metallurgy. The properties were investigated under torsional load on wires prepared by spark eroding from deformed rods. Our findings indicate that samples after rolling and extrusion exhibit a superelastic strain of 14 ± 0.5% attributed to a high yield stress of approximately 600–800 MPa and torsional testing providing the material to be fully involved in recovery process. Samples after rolling and swaging demonstrate a high level of reversible strain with a one-way shape memory effect ranging from 5 to 7%. Conversely, extrusion, due to the inhomogeneity of resulting workpieces, induces a complex, multi-stage martensitic transformation that undermines the shape memory effect. Furthermore, all deformation methods except extrusion contribute to increased alloy homogeneity, resulting in a narrower temperature range for martensitic transformations. Rotary swaging notably increases the height of an internal friction peak from 0.015 to 0.045 compared to the undeformed material, whereas rolling gives the lowest value of 0.012 among others. This study provides valuable insights into how hot thermomechanical processing influences the properties of NiTi alloys and shows that powder metallurgy combined with hot deformation can be considered an alternative approach for achieving high functional properties of these alloys.

Medical β-alloys of the Ti – Zr – Nb system are promising materials for creating bone implants that do not contain metals toxic to the human body. Powder metallurgy makes it possible to create porous structures based on this class of materials, thereby improving the osseointegration of bone tissues. However, the shape and size of the pores in an implant depend on the size and morphology of the initial powder. In light of this, the effect of the temperature and duration of calcium-hydride synthesis on the phase composition and morphology of the Ti – 18 Zr – 15 Nb (at. %) powder is studied in the current research. It has been established that with an increase in the duration and temperature of synthesis, the average size of powder particles increases, and the powder morphology and particle size distribution law change due to the formation of agglomerates. It has also been shown that during the formation of the β-solid solution, the synthesis process occurs in three stages. The first stage is governed by reduction reactions on the contact surface “oxide – liquid calcium”. The third stage is controlled by solid solution heterodiffusion. At the second stage, the synthesis process combines both mechanisms.

In the research, a one-step method for the rapid preparation of spherical nanostructured particles of Ca3Co4O9, involving the combustion of reactive aerosol drops containing calcium and cobalt nitrates as the metal precursors and hexamethylenetetramine as the fuel, is reported. The results of thermodynamic analysis and study of crystalline structure of obtained materials suggest that the reaction in the investigated system proceeds with heat release, which indicates its self-sustaining nature. Applying hexamethylenetetramine fuel at φ range of 0.4 – 0.6 and ambient temperature of 900 ℃ resulted in formation of Ca3Co4O9 powders with narrow particle size distribution of 0.2 – 1 µm. Microstructural studies revealed that the Ca3Co4O9 particles are hollow with nanometer-scale wall thicknesses and their surface consists of lamellar grains with sizes ranging from 14 to 100 nm.