High-temperature Synthesis Method Research Articles

Simple synthesis of flower-like ZnO@Pt composites for dual-mode colorimetric detecting Hg2+ with smartphone and UV–vis

BackgroundMercury is one of the most toxic heavy metal contaminants that can be harmful to human health through the food chain. Recently, the colorimetric detection of heavy metals based on nanozyme catalytic activity has received extensive interest due to the simplicity, signal visibility and suitability for in situ detection. However, the majority of these nanozymes that can be utilized for detecting mercury with high synthesis temperature and complicated synthesis methods, which limited their practical application. ResultsIn this work, flower-like ZnO@Pt composites were simply synthesized at room temperature, the flower-like structure and the high electron mobility of ZnO endow ZnO@Pt with stronger peroxidase-like activity. Consequently, dual-mode (UV–vis and smartphone) colorimetric sensors were designed to detect Hg2+. In UV–vis mode, the Hg2+ concentration linear range was 10–400 nM, and the limit of detection (LOD) was 0.54 nM. In smartphone mode, the Hg2+ concentration linear range was 50–1250 nM, and the LOD was 29.8 nM. A parallel analysis in 3 real water samples was confirmed by ICP-MS, the results showed good correlations (R2 > 0.98), indicating the practical reliability of these sensors. SignificanceThe novel flower-like ZnO@Pt composites with high stability, catalytic activity and Hg2+ response were simply synthesized at room temperature, simplifying the synthesis steps and reducing costs. The sensitivity of the developed colorimetric sensor in UV–vis mode was 3–145 times higher than that of the similar methods. The colorimetric sensor in smartphone mode broadened the detection range and improved the portability of Hg2+ detection. Thus, the dual-mode (UV–vis and smartphone) colorimetric sensors providing new detection modes for rapid monitoring of Hg2+ in environmental water.

Highly Exothermic and Fast Mechanochemical Redox and Intercalation Reactions of V2O5 with Sodium Hydride.

Vanadium oxides exhibit promising characteristics for electrochemical energy storage, owing to their capability to switch between different oxidation states, in combination with the incorporation of alkali metals. Here, we report on a systematic investigation of the mechanochemical reduction of V2O5 with NaH. In contrast to conventional high-temperature synthesis methods, the mechanochemical reaction occurs already after a few minutes. We observed a mixture of different (sodium) vanadium oxides with vanadium oxidation states ranging from +III to +V. Remarkably, these highly exothermic self-propagating reactions occur even within a rudimentary pistil-mortar setup. Hereby, the hydride concentration has a greater effect on the final sample composition than the milling time. In general, higher percentages of sodium vanadates are formed instead of vanadium oxides, and the lower oxidation states of vanadium are accessible with increasing amounts of NaH. Theoretical calculations confirm these experimental observations and emphasize the central role of sodium vanadates, especially with vanadium in the +V oxidation state, in carrying out the observed exothermic reactions. This comprehensive study sheds light on the mechanochemical reduction of vanadium oxides and underlines their potential for further development of electrochemical energy storage systems.

Preparation of a hard AlTiVCr compositionally complex alloy by self-propagating high-temperature synthesis

In this study, an AlTiVCr compositionally complex alloy with a high hardness of 865 ± 34 HV was prepared by a one-step self-propagating high-temperature synthesis (SHS) method using TiO2, V2O5, Cr2O3, and Al as starting materials. Experimental results confirmed the formation of a two-phase alloy having BCC solid solution dendritic grains reinforced by a Ti-rich intermetallic phase. Elemental analysis results confirmed that the Ti at.% in the synthesized alloy was lower than other elements. The addition of extra TiO2 to the reactants, pre-milling of the TiO2-Al mixture, and using the Rutile polymorph of TiO2 instead of Anatase as the starting material increased the atomic percent of Ti. The composition of the proper synthesized alloy was formulated as Al27.3Ti17.2V28.7Cr26.8 which is close to the desired AlTiVCr alloy. To clarify the reaction sequence during the SHS, the binary mixtures were analyzed by thermal analysis. It was postulated that the melting of Al facilitated the reduction reaction of Cr2O3 and VxOy compounds, while TiO2 was the last oxide compound reduced by Al. This hindered the completion of the TiO2 reduction reaction and as a consequence, the unreacted TiO2 entered the slag which lowered the concentration of Ti in the composition of the final alloy.

Antibacterial activity and biocompatibility of titanium nickelide augments with the addition of silver nanoparticles for bone grafting: an experimental study

BACKGROUND: The relevance of this study was supported by the increasing number of infectious complications of bone augmentation in children and adults. Currently, porous titanium nickelide alloys are among the most preferred materials used in bone plasty. Despite the observable advantages of porous nickelide titanium alloys in terms of biochemical and biomechanical compatibility with the body, research on the antibacterial activity of alloys is ongoing to counter the development of infections at the implant–biological tissue border.
 AIM: To perform an experimental study of the biocompatible antibacterial surface in porous titanium nickelide alloys with the addition of silver nanoparticles.
 MATERIALS AND METHODS: Titanium nickelide alloys with 62% porosity were obtained using the self-propagating high-temperature synthesis method from nickel, titanium, and nanosilver powders at concentrations of 0.2 at.% Ag, 0.5 at.% Ag, and 1.0 at.% Ag, respectively. The experiment was conducted on nine sexually mature female white laboratory rats. They were divided into three groups, with three rats each. All animals were implanted with titanium nickelide along with porous granules of silver additives. The first group was the control, the second received 0.2 at.% silver, and the third received 0.5% silver. The standard method of incubating Staphylococcus epidermidis in liquid broth in the presence of the studied images was used to determine bactericidal activity, followed by seeding on solid media and counting colonies.
 RESULTS: The antibacterial effect of the samples on S. epidermidis gradually increased with increasing silver concentration. The significance of the differences between the experiment and control was confirmed by Student’s criterion p 0.005, whereas the sample without silver nanoparticles and the control do not differ significantly. Thus, these alloys may have bioactive properties because they contain silver nanoparticles. An alloy with a silver concentration of 0.5 at.% Ag showed the best antibacterial activity to S. epidermidis. In the clinical evaluation of the results of the experimental study, purulent inflammatory complications were not observed in all animals at all times. On day 75, the animals underwent computed tomography, which showed good occupancy of the bone defect and absence of a dystrophic effect on the area where the bone and soft tissue are in contact with the material.
 CONCLUSIONS: If the concentration of silver nanoparticles is increased up to 0.5 at%, the antibacterial activity and cytocompatibility of the implant also increase. Clinical experimental evaluation in all groups of animals showed that osteointegration of alloys with 0.5 at.% Ag begins immediately after implantation and is completed 2 weeks earlier than that in the remaining groups.

Self-propagating high-temperature synthesis of AlxCoCrFeNiMoy high-entropy alloys: thermochemical modelling, microstructural evaluation and high temperature oxidation behaviour

In this study, the feasibility of the synthesis of AlxCoCrFeNiMoy (0.5 < x < 3, y = 0.5,1) alloys via cost and energy efficient thermochemical modelling assisted (FactSage™) aluminothermic self-propagating high-temperature synthesis (SHS) method was investigated. In addition, selected SHS alloys were also suction-casted into a bar shape by using a vacuum arc melter and the microstructural changes and oxidation behaviour of selected alloys were investigated. The characterization results demonstrated that AlxCoCrFeNiMoy (0.5 < x < 3, y = 0.5,1) master alloys can be successfully synthesized via thermochemical modelling assisted SHS method with a substantial composition control. The microstructures of the SHS alloys were found to comprise of the FCC-A1, BCC (A2, B2) and σ phases with varying fractions depending on the composition. Increasing Al content was found to increase the hardness of the alloys from 278 HV to 829 HV for the AlxCoCrFeNiMo0.5 system. For AlxCoCrFeNiMo system, on the other hand, it had an increasing effect from Al0.5 to Al1.0 (from 659 HV to 903 HV) initially and then decreased the hardness to the levels of 773 HV with the further addition of Al. Suction-cast alloys exhibited rather similar microstructures with similar phase constituents and hardness values. As a general trend primer B2 phase fraction was increased due to higher cooling rate. Oxidation studies revealed that the Al3.0Mo0.5 alloy, which has higher B2 content (919 HV), exhibited better oxidation resistance after 100 h of exposure to air at 800 °C. Postulated scaling mechanisms, supported with the CALPHAD simulations and Raman analyses, revealed the formation of non-protective spinel oxides and sublimation of volatile MoOx oxides before the stabilization of a protective M2O3 (M = Al,Cr) layer, especially for the AlCoCrFeNiMo alloy.

Polyoxometallate Cluster Induced High-Entropy Oxide Sub-1 nm Nanosheets as Photoelectrocatalysts for Zn-Air Batteries.

The lack of highly efficient and inexpensive catalysts severely hinders the large-scale application of Zn-air batteries (ZABs). High-entropy oxides (HEOs) exhibit unique structures and attractive properties; thus, they are promising to be used in ZABs. However, conventional high-temperature synthesis methods tend to obtain microscale HEOs with a lower exposure rate of active sites. Here, we report a facile solvothermal strategy for preparing two-dimensional (2D) HEO sub-1 nm nanosheets (SNSs) induced by polyoxometalate (POM) clusters. Taking advantage of the special 2D sub-1 nm structure and precise element regulation, these 2D HEOs-POM SNSs exhibit enhanced bifunctional oxygen evolution and oxygen reduction reaction activity under light irradiation. Further applying these 2D HEOs-POM SNSs to ZABs as cathode catalysts, the CoFeNiMnCuZnOx-phosphomolybdic acid SNSs-based ZABs deliver a low charge/discharge voltage gap of 0.25 V at 2 mA cm-2 under light irradiation. Meanwhile, it could maintain an ultralong-term stability for 1600 h at 2 mA cm-2 and 930 h at 10 mA cm-2. The 2D sub-1 nm structure and fine element control in HEOs provide opportunities to solve the problems of low intrinsic activity, limited active sites, and instability of air cathodes in ZABs.

Preparation of High-Performance Mn-Doped SnTe Materials at High Pressure and High Temperature.

SnTe is an environmentally friendly medium-temperature thermoelectric material, but its inherent low power factor (PF) and high lattice thermal conductivity severely limit its application. In this study, based on the fact that Mn doping can induce band convergence, the high-pressure and high-temperature (HPHT) synthesis method was used to optimize the sample preparation and shorten the synthesis cycle to 30 min. The results show that the Sn0.93Mn0.10Te sample achieves the maximum PF value of 34.00 μW cm-1 K-2 at 775 K and PFave value of 21.36 μW cm-1 K-2 between 300-875 K. Microstructure analysis shows that the high-pressure synthesis method introduces abundant grain boundaries, various grain sizes, multiple defects, and pore structures into the sample. These microscopic crystal structures can effectively scatter phonons and lower the lattice thermal conductivity. The modification of these micromorphologies results in the Sn0.92Mn0.11Te sample attaining a minimum lattice thermal conductivity of 0.45 W m-1 K-1 at 625 K. The thermoelectric figure of merit (zT) of sample Sn0.92Mn0.11Te reaches a maximum value of 1.1 at 775 K, and the zTave reaches 0.63 in the range of 300-875 K. This study indicates that the synergistic effect of Mn element doping and microstructure modification can effectively optimize the thermoelectric transport performance of SnTe materials.

A sensor based on Fe/B/N codoped hierarchical porous carbon spheres that amplify the aggregation-induced electrochemiluminescence of calcein for florfenicol trace detection

Electrochemiluminescence (ECL) signal amplification is an important method for improving sensor sensitivity. In this study, an ECL sensor was developed for florfenicol detection based on the aggregation-induced electrochemiluminescence of calcein and Fe/B/N codoped hierarchical porous carbon spheres (B-N-Fe-HPCs). First, B-N-Fe-HPCs were prepared by a simple high-temperature synthesis method, attached to the gold electrode surface, and used as a signal amplification element. Then, a molecularly imprinted polymer (MIP) was prepared using florfenicol as a template molecule and phthalylenediamine as a functional monomer and doped with calcein on the B-N-Fe-HPC-modified electrode. After the elution of florfenicol, the sensor retains an imprinted site that specifically recognizes florfenicol can readsorb florfenicol in the sample. Because calcein aggregates in the MIP to generate an ECL signal, B-N-Fe-HPCs effectively amplifies this ECL signal. Thus, because the ECL signal of the sensor can be quenched, a new method for detecting florfenicol was established. The sensor used for florfenicol showed very high sensitivity and good selective performance, with a linear range of 1–8000 × 10−12 mol/L and a detection limit of 4.65 × 10−13 mol/L. The sensor was applied to detect actual samples, such as chicken, and the results were satisfactory, with the recovery rate of the spike from 91.2 % to 105.3 %.

Ba2Co2-xZnxFe12O22 Hexaferrites produced by the method of self-propagating high-temperature synthesis: Structure, properties, application

In this study, Y-type hexaferrites Ba2Co2-xZnxFe12O22 (Co2-xZnx-Y, x = 0.0, 0.5, 1.0, 1.5) powders were synthesized by the method of self-propagating high-temperature synthesis. Hexaferrite powders were obtained both with and without preliminary mechanical activation before synthesis. A comprehensive analysis of the microstructure, morphology, phase composition and magnetic properties has been carried out. The synthesis conditions for obtaining hexaferrite powder with the highest content of the target phase are determined. An increase in the content of the target phase was revealed when using preliminary mechanical activation before synthesis. The magnetocrystalline anisotropy fields and magnetomechanical ratios for Ba2Co2-xZnxFe12O22 powder hexaferrites have been determined for the first time by ferromagnetic resonance method. The study of the spectra of reflection loss and permeability of composites made on the basis of Co2-xZnx-Y hexaferrites synthesized with preliminary mechanical activation showed that these composites can serve as an effective absorber to reduce side electromagnetic radiation in the frequency range of 6–18 GHz.

Исследование структуры и свойств металл-интерметаллидного материала на основе (Ti – Al – Mg)/Ti, полученного методом самораспространяющегося высокотемпературного синтеза совмещенного с прессованием

The method of self-propagating high-temperature synthesis (SHS), combined with pressing, for the first time obtained a metal-intermetallic material based on gorenje products of the layered system (Ti – Al – Mg)/Ti. Exothermic synthesis from elementary powders was carried out at a pressure of 10 MPa, and pressing of the hot synthesis product at a pressure of 250 MPa. The paper demonstrates that as a result of SHS-pressing, an integral connection of the “intermetallic/metal” layers is formed. The main features of microstructure formation, phase composition and strength properties of transition zones at the boundary between reacting SHS compositions Ti – Al – Mg and Ti-substrate are investigated. The thickness of the transition zone between the layers was at least 15 µm. The results of energy dispersion analysis (EDA) showed that magnesium Mg in the synthesized alloy is mainly in the intergranular layers, in the form of a small amount of Ti – Al – Mg compound, which indicates incomplete reaction diffusion between Ti – Al and Al – Mg layers. The microhardness of Ti – Al grains in the synthesized alloy has an average value of 5820 MPa, and the matrix based on Al – Mg is 3980 MPa. The hydrostatic density is 3.3 g/cm3, with a porosity of less than 13 %. As a result, the method of SHS-pressing turned out to reduce the porosity of the resulting Ti – Al – Mg-based alloy by 3 times.

УЛЬТРАМАЛІ КВАНТОВІ ТОЧКИ: ОСОБЛИВОСТІ СИНТЕЗУ, ОПТИЧНІ ВЛАСТИВОСТІ ТА ПЕРСПЕКТИВИ ПРАКТИЧНОГО ВИКОРИСТАННЯ (ОГЛЯД)

In recent years, interest in ultra-small (on the order of 2 nm) quantum dots (QDs) has increased. This subset of CTs includes clusters of magic sizes corresponding to a certain, clearly defined number of atoms. Ultrasmall CTs are characterized by unique properties - sharp absorption of light and almost complete surface luminescence. They are promising for a variety of applications, ranging from dye-sensitized solar cells, white light LEDs, and biomedical sensing due to their controllable electronic structure and large specific surface area. In this review, modern methods of synthesis of ultrasmall quantum dots are considered: the method of high-temperature organic synthesis, the method of hot injection, sonochemical synthesis of QDs of magical sizes, etc. Ultra-small quantum dots are used in solar cells. Due to their large surface-to-volume ratio, compared to traditional materials, they have a higher absorption efficiency, meaning they can convert a higher percentage of incident light into electricity. In contrast to the traditional production of solar cells based on organic solutions, which require high-temperature processing or an inert atmosphere during sputtering, and also have low stability in the open air, a method of processing solar cells with a solution containing PbS/ZnO is proposed. of nanocrystals in open air and at room temperature. Ultrasmall quantum dots are used in medicine due to their unique properties. Overall, they have several advantages over traditional imaging and sensing tools, such as higher brightness, longer fluorescence lifetimes, and tunable emission spectra. Current research is focused on increasing the stability and biocompatibility of quantum dots and developing new methods for their inclusion in various biomedical applications.

Izuchenie vozmozhnosti pererabotki otsevov ferrovanadiya v rezhime goreniya

The possibility of recycling dispersed ferroalloys using the method of self-propagating high-temperature synthesis (SHS) is demonstrated using the example of the synthesis of composite ferrovanadium nitride in the processing of ferrovanadium screenings grades FeV50 and FeV80. It has been established that in order to obtain the maximum nitrogen content in the synthesis products, it is necessary to use unshaped samples with a charge porosity of more than 50%, and the nitriding process should be carried out at a reacting gas pressure of 6-8 MPa.

Review of progress in the materials development of Re, Os, and Ir-based double perovskite oxides

In this review, we examine the latest experimental advances in materials science, focusing primarily on 5d transition metal-based double perovskite oxides, particularly rhenium (Re), osmium (Os), and iridium (Ir). These materials have attracted considerable attention because of their unique properties compared to conventional perovskite oxides, including high-TC ferrimagnetism, half-metallicity, insulating ferromagnetism, polar ferroelectricity, and multipolar magnetism. We have shown through many experiments that the high-temperature and high-pressure synthesis method is effective for introducing 5d transition metals such as Re, Os, and Ir into the B site of perovskite oxides. Here, we mainly discuss the high-pressure synthesis of novel double perovskite oxides and their properties. This process leads to characteristic relativistic effects and properties not observed in conventional perovskites. The adaptable nature of the double perovskite structure allows for significant modification of both A- and B-site elements, resulting in a wide range of physical properties. In this review, we will organize our understanding of Re-, Os-, and Ir-based double perovskites, highlight the influence of crystal structure on various properties, and explore potential applications across multiple technical and scientific domains. The goal is to provide a comprehensive overview that will enhance understanding and facilitate advances in the field of double perovskite materials research.

Synthesis of micro- and nano-sized zinc sulfide crystallites by the method of self-propagating high-temperature synthesis

The paper presents the results that demonstrate how ZnS crystallites of different sizes can be obtained by the method of self-propagating high-temperature synthesis (SHS). The SHS is possible due to an exothermic reactions occurring in mixtures of Zn and S powders, due to a large amount of heat released (enthalpy of formation being 202 kJ/mol). Pressed powders of Zn and S are placed in a stoichiometric ratio into a reactor filled with Ar or N under a pressure of P&gt;0.5 MPa. After initiated by ignition, the chemical reaction propagates through the mixture to produce a sample in the form of an ingot. ZnS crystallites with a characteristic size of ~ 30 μm are obtained in the traditional solid-state reaction of the SHS. Аfter the passage of the combustion wave, the reaction of the components continues in parallel with crystallization processes, which causes the formation of an active medium where self-organization processes occur. Sometimes, abnormally large ("giant") crystallites with length ~ 1 mm, thickness 0.1-0.2 mm, and regularly-shaped spatial structures are observed. The size of synthesized zinc sulfide crystallites can be changed with a dispersant, NH4Cl. When 5 wt.% of the dispersant is introduced, the monolithic sample is polycrystalline ZnS with a characteristic grain size of ~ 40 μm, and when 7 wt.% is introduced, the grain size decreases to 20 μm. As the concentration of the dispersant is increased to 10 wt. %, the synthesized material becomes loose, the characteristic grain size decreasing to 5-10 μm. At concentrations greater than 10 wt. %, powder-like ZnS is formed. The SHS method makes it possible to obtain meso- and nano-sized ZnS, with grain sizes of order 50 – 100 nm and 2 – 50 nm, respectively, in two ways. The first one consists in the condensation of the substance’s vapor in a rarefied inert atmosphere. When, during the SPS, the pressure of the inert gas changes in the interval from 40 to 400 Pa, a part of the reactants in the form of steam escapes from the ampoule into the reactor bulk. When the steam particles collide with the inert gas atoms, they quickly lose their kinetic energy to form particles with sizes of 2 to 100 nm. To form particles of the required size, it is necessary to adjust the pressure of the inert gas in the reactor. The second method for obtaining nanoparticles by the SBC is based on the use of an inert diluent, which prevents the growth of the forming particles. The main requirement for the diluent material is its inertness to both the reagents in the charge and the synthesized material. The effect of changing the pressure of the inert gas on the size of the obtained nanoparticles manifests itself both directly and indirectly—through the size of the condensation zone. As the gas pressure increases, its density increases, heat removal increases, the rate of crystallization center formation in the gas phase decreases, but the rate of crystal growth increases. As a result, so does the size of the resulting particles. The shape of nanoparticles obtained by this method depends on their size. Nanoparticles of size &lt;20 nm have a shape close to spherical, which is a result changing the relative fraction of the surface energy in the total energy of a nanoparticle as its size decreases. Larger-size particles are faceted.

The effect of high temperature aging on fluorescence properties of Eu3+-doped La2(Zr0.7Ce0.3)2O7

Introduction of luminescent rare earth ions into thermal barrier coatings (TBCs) for the study of TBCs failure mechanism is a very effective non-destructive method. In this paper, Eu3+ ions were doped into La2(Zr0.7Ce0.3)2O7 (LZ7C3) to form LZ7C3:Eu fluorescent material using a high-temperature solid-phase synthesis method. By analyzing the physical structure, fluorescence properties and thermophysical properties of LZ7C3:Eu powders synthesized with different Eu3+ dopant concentrations at different temperatures, we determined that a synthesis temperature of 1400 °C, a dopant concentration of 1 mol% are the optimal synthesis conditions for LZ7C3:Eu. Independent LZ7C3:Eu coating was prepared by atmospheric plasma spraying technology, and high temperature aging test was carried out at 1400 °C. The influence of high temperature aging on the 5D0→7F2 energy level transition peak of Eu3+ in LZ7C3 powder and its coating was examined by microscopic emission spectroscopy. The results show that the peak of the 5D0→7F2 energy level transition is red-shifted, and the peak intensity and the full width at half maxima (FWHM) of the powder decrease gradually with the increase of high temperature aging time. The peak of the 5D0→7F2 energy level transition of the coating exhibits a constantly fluctuating tendency of red-shifting and then blue-shifting, and the peak intensity and the FWHM also continue to decrease. High temperature aging has a negative effect on the fluorescence properties of LZ7C3:Eu materials.

Bridging graphene sheets to ultra-high-performance graphene-based bulk materials via Si-C bonding and Y-type carbon structure

Graphene is the strongest material ever identified. However, the fabrication of graphene-based bulk materials from graphene powders presents a significant challenge. Here, a new strategy to fabricate high performance graphene based bulk materials by introducing silicon nanoparticle is proposed. Consequently, ultra-high compressive strength and high flexural strength are achieved, measuring as high as 1102 MPa and 455 MPa, respectively. The compressive strength at the microscale even reaches a remarkable 5.17 GPa. The superior strength of the bulk material is primarily attributed to the Y-type carbon structure and Si-C bonds. The Y-type carbon structures in graphene, produced by the self-propagating high-temperature synthesis (SHS) method, and the Si-C covalent bonds formed at the interface between graphene and SiC contribute to a tight linkage of graphene sheets, thereby preventing slippage of graphene sheets. In addition, the microstructure evolution process of Si-SHS-graphene bulk material is clarified. With the introduction of silicon nanoparticles, the oxidation resistance of graphene based bulk materials is substantially improved, the weight loss is around 6% after oxidized at 1000 °C. This study carries extensive implications for understanding the impact of Y-type carbon structures and the effect of Si-C bonds in graphene-based bulk materials.

IMPROVING THE THERMAL STABILITY OF CARBON-CARBON COMPOSITE MATERIALS USING SELF-PROPAGATINGHIGH-TEMPERATURE SYNTHESIS

Abstract.This research focuses on the development of effective protective coatings for carbon-carbon composite materials (CCСM), which are important components in high-temperature processes in aerospace engineering. The application of CCСM is limited by their sensitivity to oxidation, erosion and burnout in gas streams. In light of these limitations, our work is aimed at creating protective coatings using the method of self-propagating high-temperature synthesis, which provide increased performance and extend the service life of composites. The main task of the research is to identify the optimal compositions of powders for chromium-doped protective coatings through the SHS process. Various methods of obtaining protective coatings were analyzed, including chemical-thermal methods and methods of saturation from the liquid phase, revealing the peculiarities of the interaction of coatings with the CCСM matrix and changes in their mechanical characteristics. In addition to the classical methods of obtaining coatings, the method of surface saturation from the solid phase in an active gas environment as part of the SHS process was investigated. This method provides high-quality coating surfaces, reduction of processing time and the possibility of reaching high temperatures, depending on the composition of the SHS mixture. An important element of the research is the analysis of modern publications and research in the field of protective coatings. Special attention is paid to the problems associated with chemical interaction with the matrix of CCСM and uneven formation of carbide phases along the cross-section of the material. Experimental studies include a factorial experiment to identify the compositions of powder mixtures that provide high wear resistance. Various independent variables, such as chromium, silicon, titanium and aluminum content, are considered for their effect on the physical and mechanical properties of the coatings. The study focuses on the optimization of the parameters of thermal autoinitiation of SHS mixtures under process conditions. The regression equation for evaluating the dependences of the wear resistance of coatings on auto-initiation parameters and the content of alloying elements is given. The analysis of the research results includes the construction of three-dimensional graphic dependencies to optimize the wear resistance of coatings in the Cr-Al-Ti and Cr-Al-Si systems. Chromoalumosilicization of the coating showed better wear resistance, exceeding the wear resistance of untreated samples by 2.6-3.2 times, which allows the use of this technology for parts of aerospace equipment. It is interesting that the porous surface of coatings obtained by the SHS method prevents the penetration of oxygen into the material, contributing to the formation of oxide protective membranes, such as SiO2, TiO2, Cr2O3, Al2O3.

SELF-PROPAGATING HIGH-TEMPERATURE SYNTHESIS OF HIGH-ENTROPY CARBIDES IN THE REGIME OF A GASLESS THERMAL EXPLOSION

High-entropy carbides are a new class of inorganic compounds promising for a wide range of applications. The paper presents a new concept for the synthesis of powders of high-entropy carbides by the method of self-propagating high-temperature synthesis (SHS) in the gasless thermal explosion mode from previously mechanically synthesized and structured reaction mixtures. For the first time, high-entropy carbides TaTiNbVWC5 and TaNbVMoWC5 were obtained by this method, their crystal structure was determined, which was compared with similar compositions obtained by sintering.

Structural-Phase Composition and Hardness of Steel of the Fe–Cr–Mn–Mo–Al–Mg–N–C System Obtained by the Method of Self-Propagating High-Temperature Synthesis Under Nitrogen Pressure

Structural-Phase Composition and Hardness of Steel of the Fe–Cr–Mn–Mo–Al–Mg–N–C System Obtained by the Method of Self-Propagating High-Temperature Synthesis Under Nitrogen Pressure

Preparation and characterization of lithium-ion sieve with attapulgite

Extracting lithium from liquid lithium resources has emerged as a research hotspot. Attapulgite (ATP), a layered materials with unique pore structure, exhibits certain ion exchange properties, and is a suitable candidate for preparing lithium-ion sieves. In this study, high value lithium-ion sieve was prepared by high temperature synthesis method using inexpensive ATP. The prepared lithium-ion sieve H-ATP-3 calcined at 400 °C was achieved optimal adsorption efficiency, which was consistent with Langmuir and pseudo-second-order model and the maximum adsorption capacity reached 29.18 mg·g−1. After 5 cycles, the adsorption capacity only decreased to 26.46 mg·g−1, still reaching 90.68 %. In the simulated Mg2+ and Li+ ion solution, the adsorption capacity was 5.689 mg·g−1 and 28.66 mg·g−1, respectively. H-ATP-3 possessed excellent selective adsorption, stability and recycling properties. During adsorption, Li+ reacted with H-ATP-3, which formed Li4SiO4, Li2SiO3 and LiAlSi2O6, forming the Li+ memory pore. After Li+ adsorption, the specific surface area decreased from 185.50 to 15.14 m2/g, indicating Li+ entered ion sieve and filled the pore. Moreover, the -OH and interlayer water in H-ATP-3 exchanged with Li+. The synthesis method is relatively simple, and has high selectivity, effectively recovering Li+ and expanding the market application prospect of attapulgite resources.