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The stages of chemical transformation in the combustion wave of an Fe2O3/Al/AlN exothermic mixture in nitrogen atmosphere is studied using an original method for stopping a combustion front. It is revealed that, in an Fe2O3/6Al stoichiometric mixture diluted with 35% (wt.) AlN, the combustion front is stopped following the combustion of a (30–40)-mm mixture column. The zones of a stopped combustion wave are investigated by the local analysis methods. It is shown that the alumothermal reduction of iron (III) oxide to iron aluminide proceeds in stages via the formation of a (FeAl) $$_{x}$$ O $$_{y}$$ double oxide of varying chemical composition. The final synthesis products include aluminum oxynitride, iron aluminide, and unreacted aluminum nitride.

We have studied the spontaneous comminution of cast materials consisting of a Mn-doped Cr2AlC MAX phase and chromium, manganese, and aluminum carbides and aluminides. The materials were prepared in the form of ingots by self-propagating high-temperature synthesis (SHS) in a 3-L reactor at an argon pressure p = 5 MPa. The starting mixtures consisted of manganese(IV) oxide, chromium(III) oxide, aluminum (ASD-1), and carbon. The presence of aluminum carbide (Al4C3) in a cast material has been shown to lead to spontaneous comminution of the cast material (without mechanical or chemical influences) into powders with a crystalline particle size under 100 μm. The particle size reduction has been shown to result from reaction between aluminum carbide and atmospheric moisture. The synthesized materials have been characterized by X-ray diffraction and X-ray microanalysis, and we have studied structural and phase states of particles of the desired products obtained as a result of self-comminution of a cast SHS material.

A lightweight intermetallic alloy containing the ternary phase Al18Ti2Mg3 has been prepared for the first time in the Ti–Al–Mg system by self-propagating high-temperature synthesis. In the binary system Ti–Al, synthesis has been carried out in the thermal explosion regime, whereas in the ternary system Ti–Al–Mg layer-by-layer combustion synthesis has been performed. The porosity of the synthesized materials is 43.3%, and its density is 2.4 g/cm3.

A material based on a (VCr)2AlC solid solution has been obtained for the first time by self-propagating high-temperature synthesis from a powder reaction mixture of vanadium(V) and chromium(III) oxides with aluminum and carbon (graphite). The synthesized material has been studied by X-ray diffraction and microstructural analyses. It has been shown that the product also contains vanadium and chromium carbides and intermetallics. The presence of these phases seems to be associated with the nonequilibrium character of the synthesis process due to a short “lifetime” of melt and its fast cooling and crystallization. The synthesized material is an electrical conductor, which demonstrates a metallic character of conductivity throughout the entire measured temperature range of 300–1300 K. The room-temperature specific resistance of the composite material based on a (Cr,V)2AlC solid solution is 1.14 µΩ m, which is higher than the specific resistance of the materials based on the Cr2AlC and V2AlC MAX phases. The microhardness of the synthesized material is 6.9 GPa.

High-temperature synthesis of cast composite materials in the Cr–Mn–Al–C system with various ratios between the Cr2AlC MAX phase and chromium and manganese aluminides and carbides was studied. Experiments were performed in a universal 3-L reactor under argon pressure Р = 5 MPa. Mixtures of powders of chromium(III) and manganese(II, IV) oxides and calcium peroxide with aluminum (ASD-I) and carbon were used as a charge. The synthesis features and the phase composition and microstructure of the target products are significantly influenced by the reactant ratio in the charge. At the stoichiometric ratio of the components corresponding to the Cr2AlC phase, a cast composite material consisting of the Cr2AlC MAX phase, chromium carbides Cr7C3 and Cr3C2, and chromium aluminide Cr5Al8 is formed. In the course of combustion of the charge with the component ratio corresponding to the Mn2AlC phase, a cast composite material consisting of manganese carbides (Mn3AlC, Mn0.545Al0.42C0.035) and aluminide (MnAl) is formed. When these compositions are combined in an 0.75 : 0.25 ratio, the final product is a composite material consisting of a solid solution based on the Cr2AlC MAX phase, manganese carbides (Mn3AlC), and chromium aluminides (Cr2Al). When these compositions are combined in an 0.5 : 0.5 ratio, the final product is a composite material consisting of the manganese-doped Cr2AlC MAX phase and of manganese (Mn14Al86, Mn22.5Al77.5) and chromium (Cr5Al8) aluminides. The final products were characterized by X-ray diffraction and local microstructural analysis.

An intermetallic alloy based on the Heusler phase—Cu2TiAl—has been obtained by self-propagating high-temperature synthesis (SHS) in the Cu–Ti–Al system for the first time. The modes of frontal combustion of the green mixtures and the processes of phase formation during synthesis have been studied. The resulting products have been studied by X-ray analysis (including high-temperature diffractometry with step heating up to 900 K), scanning electron microscopy, and differential thermal analysis (DTA), and some physical properties have been studied. Electrophysical and magnetic measurements are also carried out for the alloy. The results of X-ray analysis and scanning electron microscopy using energy-dispersive analysis (EDA) have shown that the content of the Heusler phase in the synthesized product is at least 82%. The product also contains copper (CunineAl4) and titanium (Ti3Al2) aluminides. The temperature dependence of the electrical resistivity of the synthesized product is measured for a wide temperature range of 90–1000 K. The resistivity at T = 300 K is 0.3 μm Ωm. The metallic type of conductivity for obtained samples and the anomalous behavior of the temperature curve of electrical resistance in the region of 770–790 K are revealed. Thermal analysis is used to measure the melting point of the synthesized product and reveal additional heat effects at 788, 848, and 1248 K associated with possible phase transitions in the Cu2TiAl intermetallic compound. One possible mechanism of these phase transitions is considered in accordance with the phase diagram of the Cu–Ti–Al system. Magnetic measurement results show that intermetallic samples of the compound obtained by the SHS method exhibit weak ferromagnetic properties with residual magnetization of 0.069 A m2/kg.

For the first time, an intermetallic alloy based on the Heusler phase – Cu2TiAl – was obtained by self-propagating high-temperature synthesis (SHS) in the Cu–Ti–Al reaction mixture. The frontal combustion modes of green mixture compositions and phase formation processes during synthesis were studied. The products obtained were studied by X-ray diffraction analysis including high-temperature diffractometry with stage heating up to 900 K, scanning electron microscopy, differential thermal analysis (DTA), and some physical properties were studied. Also, electrophysical and magnetic measurements were carried out for the obtained alloy. The results of X-ray analysis and SEM using energy-dispersive analysis (EDA) showed that the Heusler phase content in the synthesized product is at least 82 %. The product also contains copper (Cu9Al4) and titanium (Ti3Al2) aluminides. The temperature dependence of the synthesized product electrical resistivity was measured for a wide temperature range of 90–1000 K, which was 0.3 μmm at T = 300 K. The metallic type of the conductivity for the samples obtained and the abnormal behavior of the electrical resistance temperature curve in the region of Т = 770÷790 K were revealed. Thermal analysis was used to measure the melting point of the synthesized product and to reveal additional heat effects at Т = 788, 848 and 1248 К associated with possible phase transitions in the Cu2TiAl intermetallic compound. A possible mechanism of phase transitions is considered in accordance with the Cu–Ti–Al system phase diagram. Magnetic measurements results showed that intermetallic samples obtained by the SHS method feature by weak ferromagnetic properties with residual magnetization of 0.069 A·m2/kg.

We have examined for the first time the feasibility of producing cast Nb-, Si-, and B-doped Mo-based composite materials by a spin-casting self-propagating high-temperature synthesis metallurgy method and obtained new results regarding control over their composition and structure. In synthesis, we used combinations of a highly exothermic (MoO3/Nb2O5/Al/Si/B) and a low-exothermic (Mo/Nb/Si/B) composition. We have assessed the effect of the ratio of the ratio of the highly exothermic and low-exothermic compositions (α) and acceleration (a) on the composition and structure of the cast composite materials. The mixtures have been shown to be capable of combustion at up to 80% low-exothermic composition. The combustion products have cast form in the range 0 ≤ α ≤ 65%. At α in the range from 0 to 40% and accelerations from 40g to 400g, the combustion products have the form of a two-layer ingot: the lower layer (Mo–Nb–Si–B) consists of the required product and the upper layer (Al2O3) is a slag product. The optimal parameters for the preparation of cast Mo–Nb–Si–B materials are α = 20–30% and a > 100g.

An alloy based on the Heusler phase Fe2TiAl is obtained for the first time by self-propagating high-temperature synthesis (SHS). Experiments have shown that the alloy is synthesized in the thermal explosion mode. Features of the structure- and phase formation during combustion in the 2Fe–Ti–Al system are studied and their mechanisms are proposed. The electrophysical properties of the combustion product are studied.

This article investigates the microstructural features, phase composition, and electrophysical properties of Co2TiAl intermetallic alloy produced by self-propagating high-temperature synthesis (SHS) in combination with pressing. For the first time, a practically single-phase alloy based on the Co2TiAl Heusler compound with the weight content of at least 82% was produced using SHS; the synthesis products also contain TiCox intermetallic compounds of variable composition. The unit cell parameter of Co2TiAl was a = 5.8433 ± 0.0002 A. Metallographic analysis of the microstructure after SHS pressing demonstrated structure densification and decrease in porosity in comparison with samples produced by regular SHS without application of load to the combusted sample. The average microhardness of the synthesized alloy was Hμ = 5650 MPa, and the electrical resistance of the synthesized material at ambient temperature was 1.35 μΩ m. Variations of specific electrical resistance were studied in vacuum of 1.33 × 10–3 Pa in the temperature range of 77–1300 K. At temperatures above 600 K, the electrical resistance as a function of temperature ρ(T) in Co2TiAl alloy exhibits a decrease in slope; that is, for the given alloy, there exists the so-called effect of resistance saturation. The Curie point corresponding to transition from the magnetic to paramagnetic state was 133 K.

The paper experimentally demonstrates the possibility of synthesizing cast W–C–Ni composite materials (CMs) by SHS metallurgy from highly exothermic mixtures based on WO3 and NiO oxides and a complex reducing agent consisting of Al, Ca, and graphite at an elevated gas (nitrogen) pressure. It is shown that by varying the WO3 and NiO ratio, the initial mixtures of the contents of carbon, aluminum, and calcium retain the ability to burn in a wide range of values, and the combustion temperature exceeds the melting temperature of the composite and slag (oxide) combustion products. Under the action of gravity there is a separation of the melts of the CM and slag; and with subsequent cooling, the formation of their structure. This paper studies the laws of combustion of mixtures, gravitational separation of combustion products, and the formation of their composition and structure.

Combustion and the formation of structures and phases in a 2Co–Ti–Al system during self-propagating high-temperature synthesis in a thermal explosion are under study. It is determined that a single-phase product (a Co2TiAl Geissler compound) can be obtained in this system. Morphology, microstructure, and physical-magnetic properties of combustion products of the system are investigated.

TiC + xC composites comprising titanium carbide particles, unreacted carbon black particles, and a graphite nanofilm have been prepared by self-propagating high-temperature synthesis pressing. The fused titanium carbide particles form a robust skeleton, whose voids contain carbon black particles separated from the titanium carbide particles by the graphite nanofilm. We have examined the effect of composition and temperature on the resistivity of the TiC + xC composites. The resistivity of the composites has been shown to increase with increasing carbon content. In the temperature range 300–1300 K, the temperature coefficient of resistivity (TCR) of the TiC + 0.25C, TiC + 0.5C, and TiC + 0.75C composites is 8.9 × 10–4, 9.5 × 10–4, and 9.7 × 10–4 K–1, respectively. In the temperature range 1000–1010 K, the resistivity of the composites remains constant as a result of the ordering of the carbon sublattice in TiC.

It is known that materials based on MAX phases possess a large potential for use in aerospace, automobile, and industrial spheres because they have a unique combination of features of both metals and ceramics with high mechanical, chemical, thermal, and electrical properties. In this work, the experimental results of fabricating cast materials in the Cr–Al–C system with different ratios between the Cr2AlC MAX phase and chromium aluminides and carbides by SHS metallurgy are presented. The experiments were performed in an SHS reactor 3 L in volume at an initial inert gas (argon) pressure of 5 MPa. The synthesis was performed based on chemically coupled reactions: weakly exothermic (heat acceptor)—Cr2O3/3Al/C and strongly exothermic (heat donor)—3CaO2/2Al. The experimental results have good correlation with the preliminary thermodynamic calculations. It is shown that, when varying the composition of initial mixtures, it is possible to substantially affect the calculated and experimental synthesis parameters, as well as the phase composition and microstructure of final products. Optimal synthesis conditions of the material providing the maximal yield of the Cr2AlC phase in the ingot composition are established. The determining factor affecting the Cr2AlC content in the product is the occurrence time of the liquid phase under the synthesis conditions. It is shown that the maximal content of the Cr2AlC MAX phase and target product yield are attained at the 30% content of the strongly exothermic additive (3CaO2/2Al) in the initial charge.

Using the method of self-propagating high-temperature synthesis (SHS metallurgy), cast composite materials were produced in the Cr–Ti–B system. The experiments were carried out in universal SHS reactors with an initial argon pressure of Рin = 5 MPa. Mixtures of CaCrO4, TiO2, Al, and B powders were used as batch. It was shown that by varying the mass ratio α of CaCrO4/2Al/2B and 3TiO2/4Al/6B mixtures in a batch, it is possible to significantly affect the synthesis patterns, phase composition, and microstructure of the target products. The initial mixtures are capable of burning in the range of α 0–20%. The phase separation limit occurs at α = 15%. The introduction of a highly exothermic CaO2 + Al additive into the mixture made it possible to expand the phase separation limit to α = 20%. As α increases, the amount of titanium boride in the final product increases. The resulting composite material consists of titanium-chromium boride distributed in a matrix of chromium boride. The synthesized materials were characterized by X-ray and local microstructural analysis. The structural phase states of the target products produced under various conditions were studied.

Molybdenum is a refractory metal, with a melting point of 2900 K. Its alloys with B and Si, obtained via powder metallurgy, have high heat resistance and have potential use in aircraft engine building. In this paper, the authors examined the possibility of using centrifugal SHS-metallurgy for the production of Mo–Si–B. To synthesize Mo–Si–B, a combination of a highly exothermic mixture (MoO3/Al/Si/B) and a moderately exothermic mixture (Mo/Si/B) were used. In a wide range of ratios, the combustion temperature exceeds 3000°C, which makes it possible to obtain combustion products in a cast form. Studies have shown that variation in the composition of the mixture and the magnitude of the centrifugal effect allows the parameters of combustion to be controlled, along with the composition and structure of molybdenum silicoborides.

A cermet material based on the system Ni–Al–SiO2 with different SiO2 weight content (0 – 50%) in the mixture was obtained by means of self-propagating high-temperature synthesis (SHS) with preliminary mechanoactivation (MA). It is shown that preliminary mechanoactivation of the powder mixture strongly affects the morphology of the final product. Depending on the composition of the initial mixture, the phases NiAl, Al2O3, Ni2Si, and NiSi2 can form in the final product of synthesis.

Experimental data are presented on the high-temperature synthesis of cast composite materials in the Cr–Al–C system with different relative amounts of the MAX phase Cr2AlC and chromium carbides and aluminides. The experiments were carried out in multipurpose self-propagating high-temperature synthesis (SHS) reactors at an argon pressure p = 5 MPa. The starting mixtures consisted of calcium chromate (CaCrO4), aluminum (ASD-1), and carbon powders. It has been shown that varying the percentage of carbon in the starting mixture may have a significant effect on the synthesis process and the phase composition and microstructure of the final products. It has been found that, in the case of the stoichiometric starting mixture composition, the synthesis yields cast composite materials consisting predominantly of the MAX phase Cr2AlC and containing the lower chromium carbide Cr7C3 and the chromium aluminide Cr5Al8. The addition of excess (superstoichiometric) carbon to the starting mixture leads to an increase in the percentage of the MAX phase Cr2AlC in the synthesis product, disappearance of the chromium aluminide Cr5Al8, and the formation of the higher chromium carbide Cr3C2 instead of the lower carbide. The final synthesis products have been characterized by X-ray diffraction and local microstructural analysis. The structure and composition of the synthesis products obtained under various conditions have been determined.

The results of the study of intermetallic rods in a steel shell obtained by high-temperature gas extrusion for the first time used for reactive powder mixtures are presented. Tests were conducted on the basis of model system Ni-Al.

The results of studying steel cladded intermetallic rods manufactured by means of high-temperature gas extrusion applied for the first time for reactive powder mixtures are presented. The tests were performed on the Ni–Al model system.

The laws and mechanism of combustion of TiO2 based thermite systems with a complex reducing agent (Al and Ca) under the influence of overload are revealed. The thermite system includes a basic composition whose combustion products are target elements (Ti, Al, Nb, and Cr) and a high-energy additive (CaO2, Al, and Ca) for ensuring high-temperature combustion. With the introduction of an energy additive, the system acquires the ability to burn. With a sufficient content of this additive, the combustion products (TixAly and Al2O3 and CaO oxide solutions) can melt. As the fraction of Ca in the base mixture composition increases, the burning rate drops and the reduction completeness of the target oxides increases. With an optimal ratio of Ca and Al in the mixture, the yield of the target elements in the ingot is close to the calculated value.

Mechanically synthesized hybrid powders of the AMg2/graphite + Al2O3 system and coatings deposited by cold gas dynamic spraying from these powders are studied. The effect of Al2O3 concentration in the powder on surface morphology, structure and microhardness of the coatings formed is determined.

We have studied in detail the structuring of combustion products in the Ti–Al–C system at low carbon concentrations (96 wt % (Ti + Al) + 4 wt % graphite) prepared by self-propagating high-temperature synthesis and compared the results to those for carbon-free samples prepared by the same method. A thin (~500 nm) TiC carbide layer has been shown to be formed on the surface of unreacted graphite particles, followed by the growth of the Ti2AlC MAX phase, which has a laminate structure. The presence of the Ti2AlC phase in the synthesized samples has been confirmed by X-ray diffraction and energy dispersive analysis. TiC has not been detected by X-ray diffraction, presumably because it is present in a small amount.

TiAl-based composite materials have been produced by spin-casting self-propagating high-temperature synthesis metallurgy methods using thermite-type mixtures, general relationships in the formation of their composition and structure have been investigated, the synthesis conditions have been optimized, a method for obtaining large ingots has been proposed, and their composition and structure have been determined. We have obtained cast Nb- and Cr-doped TiAl-based composite materials using mixtures of Ti, Nb, Cr, and Ca oxides with a combined reducing agent (Al and Ca) under the effect of an overload above 200g. It has been shown that partial Ca substitution for Al in the starting mixture ensures complete reduction of the TiO2, and the resultant metallic phase contains calculated amounts of Ti and Al. Mixtures of optimized composition make it possible to produce a cast composite material similar in composition to alloy 4822.

In this paper, we studied the reaction mechanism of chemical transformations of the initial components in the combustion wave of MoO3/TiO2/Al/Si mixtures of the thermite type in the synthesis of molded molybdenum disilicide (MoSi2) and binary molybdenum titanium silicates ((MoTi)Si2). Syntheses were carried out in a high-temperature synthesis reactor at an initial argon pressure of P0 = 5 MPa. The effect of the ratio of initial reagents and geometric factors on the laws of synthesis of these materials was experimentally studied. The intervals of the component ratios, at which molybdenum and titanium silicides can be synthesized with specified compositions, are determined. We carried out experiments on stopping the combustion front. The chemical transformation of the components of the initial MoO3/TiO2/Al/Si mixtures in the combustion wave is shown to proceed in stages, and chemical reactions can be considered as chemically conjugated processes. The obtained results provide the scientific basis for the creation of promising molded silicide ceramics with high performance properties.

This paper reports the preparation of cast dimolybdenum pentaboride by a self-propagating high-temperature synthesis (SHS) metallurgy method. Experiments were carried out in SHS reactors at an initial excess gas (Ar) pressure p0 = 5 MPa. In the experiments, we used thermite-type starting mixtures consisting of molybdenum oxide, aluminum, boron oxide, and elemental boron powders. The combustion of such mixtures yields two types of final product: Mo2B5 and Al2O3. The combustion temperatures of the starting mixtures used in our experiments have been shown to exceed the melting points of the final products, which are thus formed in a liquid (cast) state. Under the effect of gravity, the heavier phase Mo2B5 settles down to form a lower ingot, whereas the lighter phase Al2O3 forms an upper ingot. The synthesis products have been characterized by X-ray diffraction and local microstructural analysis. The results demonstrate that the composition and amount of the starting mixture have a significant effect on the synthesis parameters and the composition and microstructure of the Mo2B5. We have optimized conditions for the preparation of single-phase cast dimolybdenum pentaboride.

The structure, phase composition, and electrical conductivity of TiB2–AlN–BN-based ceramics fabricated by self-propagating high-temperature synthesis (SHS) are investigated. The temperature dependence of the specific electrical conductivity was measured in range T = 300–1300 K in vacuum of 2 × 10–3 Pa according to the standard four-probe dc-current procedure. It is established that the TiN and BN contents in the synthesis products increase while those of TiB2 and Al decrease with an increase in the TiB2 content in the initial mixture from 60 to 80 wt % and a decrease in the Al concentration from 40 to 20 wt % because of the reaction of TiB2 with nitrogen. A decrease in the Al concentration in the initial mixture leads to a decrease in the AlN content in the synthesis products. The results showed the mismatch of electrical resistance curves ρ(T) during the heating–cooling cycle for all ceramics compositions, which is associated with the variation in the length of the contact zone of conducting phases in range T = 800–1200 K. Three characteristic temperature regions are found: (I) from 300 to 800 K, when ρ monotonically increases with an increase in temperature; herewith, heating and cooling ρ(T) curves coincide completely; (II) the behavior of electrical resistance varies at T = 800–1200 K—its values depend strongly on the heat treatment mode of the sample; and (III) heating–cooling curves coincide completely at T > 1200 K.

A review of publications on the structure, properties, fabrication methods, and application fields of materials based on the Cr2AlC MAX phase is given. It is noted that the most promising method of formation of such materials is self-propagating high-temperature synthesis (SHS), one of the directions of which is SHS metallurgy. A powder mixture of chromium III and chromium VI oxides of the analytical grade, aluminum of ASD-1 grade, and carbon is used as the base charge in investigations. The adiabatic combustion temperature and composition of final products is calculated using the THERMO special program. Experiments were performed in an SHS reactor with volume V = 3 dm3 under the initial pressure of inert gas (Ar) P0 = 5 MPa. The influence of the ratio of initial reagents on SHS parameters (the combustion rate, pressure increment, and yield of the target product), composition, and microstructure of target products is investigated experimentally. A scientific approach of the formation of cast materials in the Cr–Al–C system consisting of the Cr2AlC MAX phase and phases Cr3C2 and Cr5Al8 by the SHS metallurgy method is developed. The structural-phase states of target products are studied. It is established experimentally that, varying the content of initial reagents (aluminum and carbon) in the charge, it is possible to substantially affect the synthesis regularities, composition, and microstructure of final products. An increase in the content of the Cr2AlC MAX phase in the final product and a decrease in the Cr5Al8 content occur with an increase in the carbon content (above stoichiometric) in the initial mixture. An increase in the aluminum content (above stoichiometric) in the initial mixture leads to an increase in the content of the Cr2AlC MAX phase in the final product and a decrease in the content of the Cr3C2 phase.

A method for the conversion of a surface layer of monolithic polymetallic carriers into highly active catalytic phases with a high specific surface area, which contain nanosized formations, was developed. An intermetallide layer was formed in the course of the high-temperature aluminum coating of the carrier surface; this layer was transformed into an active form by leaching and stabilization. A method was proposed for the enrichment of the aluminized layer in alloy additives. The microstructure of the intermetallide layer and the distribution of elements in it were studied with the use of chrome-nickel stainless steel gauze as an example. The physicochemical characteristics of the active phase were examined using a BET method, scanning electron microscopy, and X-ray diffraction analysis. The catalytic properties of the samples were studied in the processes of the deep oxidation of CO and propane and the hydrogenation of CO2.

The possibility of combustion of a mixture of chromium peroxide with aluminum nitride is shown experimentally. The effect of initial pressure of nitrogen and ratio of reagents on an average linear burning rate, as well as on a relative mass loss in the combustion of a CrO3/AlN mixture is studied. The concentration limits of the burning rate of the test mixture are determined. The microstructure and phase and chemical compositions of the combustion products of the chromium–nitride-aluminum mixture are described.

High-speed micro video recording and electron and atomic force microscopy have been used to obtain new experimental data at the initial stage of the titanium melt spreading along a carbon material (oriented pyrolytic graphite) and the formation of a reaction product. It has been shown that the melt spreading at the initial stages takes place along a framework of flat submicron crystalline grains of TiC with an open porosity. The grains form an island structure at the reagent contact boundary with gaps of about 100 nm in width between them, and these gaps are connected to each other to give a continuous network of channels along which the melt spreads. Thus, at the initial stage of the interaction, despite the formation of a solid product, direct contact of the reagents is retained, which ensures a high process speed.

Composite materials (CMs) based on niobium with functional and alloying additives (Si, Hf, Ti, Al, etc.) have prospects for industrial approval in aviation propulsion engineering. The authors previously showed that such CMs can be synthesized in an autowave mode (combustion mode) using highly exothermic mixtures of Nb2O5 with Al, Si, Hf, and Ti. It was found that hafnium actively participates in the reduction of Nb2O5, which complicates its introduction into the CM. This study is directed at investigating the possibility to synthesize Nb-based composite materials with a high Hf content using methods of centrifugal SHS metallurgy. It is shown in experimental investigations using a centrifugal installation under the effect of acceleration of 40 g that the replacement of active Hf by its less active compounds Hf–Al or Hf–Ti–Si–Al in the composition of the Nb2O5/Al mixtures makes it possible to transfer the combustion of the mixture from the explosion-like mode into the steady-state combustion mode. The content of Hf in the CM increases with an increase in the size of Hf–Al granules from 0–40 to 160–300 μm from 1.3 to 3.8 wt %. The introduction of Hf–Ti–Si–Al granules with a particle size from 1 to 3 mm into the initial charge makes it possible to form cast CMs based on niobium silicides with a Hf content up to 8.1 wt %. The integral composition and distribution of base and impurity elements in structure components of cast CMs, as well as their phase composition, were determined using electron microscopy and X-ray phase analysis. CMs with the maximal Hf content (8.1 wt %) contain three structural components: (1) the base, which includes Nb, Si, and Ti; (2) intergrain boundaries containing Nb, Ti, and Al; and (3) inclusions based on hafnium oxide. Three phases are revealed in the X-ray diffraction pattern of the CM, notably, solid solutions based on Nb and Nb5Si3, as well as a minor amount of Nb3Si.

Steel clad NiAl rods were prepared by high-temperature gas extrusion (HTGE) of steel cartridges stuffed with reactive Ni–Al powder compacts upon variation in warmup temperature Tw (600–780 °C) and gas (Ar) pressure P (200–480 MPa). A largest amount of NiAl and Ni3Al intermetallics in rod core was obtained at Tw = 780°С and P = 200 MPa. For Tw

Experimental data are presented on the high-temperature synthesis of cast inorganic materials in the MgO–Al2O3 system. Experiments were carried out in multipurpose self-propagating high-temperature synthesis (SHS) reactors at an argon pressure p = 5 MPa. The starting mixtures used in the experiments consisted of molybdenum(VI) and magnesium(II) oxides and aluminum. It has been shown that, varying synthesis parameters, one can control the phase composition and microstructure of the final oxide products. We have optimized synthesis conditions for the preparation of single-phase magnesium aluminate spinel, MgAl2O4. The SHS products have been characterized by X-ray diffraction and local microstructural analysis.

The production of hafnium aluminides from mixtures of hafnium or its oxide with aluminum in the combustion mode is impossible because of a near-zero thermal effect. The present study is aimed at stimulating autowave chemical transformation with the help of energetic formulations and producing cast hafnium aluminides by means of combustion methods. The characteristics of the autowave synthesis and the conditions for producing cast hafnium aluminides are determined, and their composition and structure are investigated.

Composite materials based on Nb with functional (Si, C, B) and alloying dopants (Hf, Ti, Al, etc.) are promising materials for aircraft engine applications. Our previous studies have shown that such composites can be synthesized in the autowave mode (combustion mode) using highly exothermic mixtures of Nb2O5 with Al, Si, Hf, and Ti. It has been found that in the combustion wave, Hf actively participates in the reduction of Nb2O5, which complicates its introduction into the composite material and leads to an excess of Al in the alloy. In the present study, we investigated the possibility of replacing Hf in the starting mixture by less active HfAl3 and also determined the effect of the grain size of HfAl3 on the Hf content in the composite material.

SHS-Metallurgy methods were used to obtain samples in the form of aluminum oxynitride Al5O6N ingots (AlON) using mixtures of the thermit type. The experiments were performed in SHS reactors at initial nitrogen pressure 5 MPa. The optimal conditions for the synthesis of the most stable phase of aluminum oxynitride Al5O6N were determined. Regimes were developed for comminuting the synthesized ingots into powder with definite fractions. Spark plasma sintering (SPS) was used to obtain from them experimental samples with high density, hardness, and transparency.

A new method for the synthesis of catalysts on polymetallic supports via the formation of intermetallic (aluminide) layer on the support surface followed by leaching and stabilization of the layer has been proposed. The intermetallic layer structure and distribution of elements in the layer were studied by scanning electron microscope considering a nickel chromium stainless-steel grid as an example. The morphology and elemental composition of the active phase on the catalyst surface were studied. The complex structure of this phase was found to consist of two types of entities with different composition located on the continuous highly porous substrate. The catalyst sample was tested in deep oxidation of CO and propane and demonstrated high activity. The developed method can be used to obtain new high-performance polymetallic catalysts.

We investigated the peculiarities of the combustion wave propagation as well as the structure and phase formation in bi-layered metal powder compacts of (Ti − Al)/(Ni − Al), with a special emphasis on the use of infrared thermography to monitor the reaction front propagation. The location of the combustion wave front along the direction of propagation at different times was determined to calculate the front velocity. The data of SEM analysis demonstrated the welding of two layers during combustion with the formation of a transition layer with a thickness of about 200 μm and a sharp diffusion barrier for Ti in the Ni-Al layer.