Papers by Keyword: Self-Propagating High-Temperature Synthesis (SHS)

Abstract: Conventional techniques for obtaining ligatures, ferroalloys, or modifiers are often associated with prolonged processing times, material losses, low energy efficiency, and environmental challenges. The self-propagating high-temperature synthesis (SHS) metallurgy method partially eliminates these drawbacks, allowing ligatures to be formed from hard- and soft-melting elements. The present work focuses on selecting a metallurgical technique for producing SHS complex ligatures in the Fe–Mn–B system, studying the structure and chemical composition of obtained ligatures, and evaluating their corrosion properties.

Abstract: Production of nanoscale catalytic materials is an urgent technological challenge. Catalysts have a wide range of applications, such as for neutralizing nuclear waste, decontaminating water polluted with mercury, purifying the atmosphere from various micro-particles, in molecular sieves, and in chemical synthesis, oil refining, etc. Another important application of nanostructured materials is in rechargeable batteries and fuel cells, where their high specific surface area is essential to ensure the speed and effectiveness of the interactions between different materials. Active nanostructured materials with a sufficiently high density of controlled surface defects meet these requirements well and, therefore, offer significant potential for optimizing the high energy consumption in batteries. Currently, the particle size of natural and industrially synthesized manganese oxide materials is typically in the micron range or larger. From perspectives, the most developed and promising methods for synthesizing manganese dioxide are ion exchange, hydrothermal, electrolytic, and chemical synthesis. In this work, a distinctive method for synthesizing nanostructured manganese dioxide is proposed, described, and analyzed. Experiments were conducted to determine the optimal synthesis routes using the Self-propagating High-temperature Synthesis (SHS) method, as a distinctive technological approach that uses manganese ore enrichment waste as raw material and ammonium chloride as a pretreatment chemical agent.

Abstract: The influence of mechanoactivated reagents cladding on the structural-phase state of the SHS-products was investigated. Titanium and aluminum powders were used as reagents. Mechanical activation was performed on the AGO-2 planetary ball mill. The coating on Ti+Al mechanocomposite was carried out using magnetron installation “VSE-PVD-Power”. At deposition time of 40 minutes, the reaction start temperature increases from 525 °C to 648 °C (compared to reagents without cladding). It can be assumed that an increase in the thickness of the deposited SiO₂ film serves as a barrier to the reaction start, thereby increasing ignition temperature. Apart from pretreatment, the phase composition of the final product contains intermetallic compounds TiAl, TiAl₃, Ti₃Al₅, as well as the small amount of residual Ti. The main phase is TiAl.

Abstract: The article is devoted to the study of the characteristics of shock-wave processing of powder mixtures capable of an exothermic reaction of the synthesis of metal-ceramic materials. Experiments on shock-wave initiation of synthesis in systems based on Ti-B and Ti-C with 10% and 20% Ni content were carried out. Explosive loading was carried out by oblique throwing of a steel drummer with speeds of 1000 m / s and 1500 m / s. X-ray phase analysis of synthesis products showed the presence of TiB₂ diboride and TiC carbide in the nickel bond. The significant role of the mechanical activation of powder mixtures in increasing the sensitivity of SHS-mixtures to shock-wave loading is shown.

Abstract: The article presents the study of factors affecting the ability to control the self-propagating high-temperature synthesis of nanomaterials. It is established that there are two steps in the combustion process nanomaterial: burning of surface layer and deep combustion area, which can be considered as the thermal explosion. It was found that the surface roughness and the thermal conductivity of the substrate do not affect the combustion front velocity. The presence of glass transition on the substrate surface also does not affect the velocity of the front. It was established that the parameters of the deep combustion area do not depend on the nature of the initiation of combustion, being the second stage of the development of combustion; in all cases this stage is characterized by the same parameters. When varying the type of ignition source, the length of the surface burning front can vary up to 33%. The time of induction of a thermal explosion increases when the bulk layer of powder ignites from above.

Abstract: The feasibility of creating conditions for control of high-temperature synthesis (SHS) of nanomaterials has been studied. Experiments were carried out to determine the velocity of the combustion wave propagation of aluminum nanopowder obtained by electric explosion. In the course of the study, the factors influencing formation of the induction time: the thermal diffusivity of the substrate, the method of initiation of the combustion wave (flame, spark, heated body), the induction time between the initiating front and the front of the thermal explosion were considered. The relation describing the time of induction of thermal explosion is established.

Abstract: ZrB₂-ZrC composite powders were synthesized from zircon sand by self-propagating high-temperature synthesis (SHS). The reactions were verified and the feasibility of obtaining the predicted products was calculated from the adiabatic temperature (T_ad) and the equilibrium composition using the HSC^® chemistry program. The results show that the SHS products consisted of ZrB₂, ZrC, ZrO₂, ZrSiO₄, MgO, and Mg₂SiO₄. Leaching the products with 0.5 M of HCl solution eliminated the by-product of MgO and the intermediate Mg₂SiO₄ phases. The phase composition of the products was characterized by X-ray diffraction (XRD) and the morphologies were characterized by scanning electron microscopy (SEM) coupled with energy-dispersive X-ray (EDX).

Abstract: Processes and products of combustion of systems of "sodium azide – aluminum and boron halides " are studied. Halide salts AlF₃, Na₃AlF₆, KBF₄ and NH₄BF₄ are used as precursors of Al and B elements. The measured combustion temperature is in the range from 900 to 1800°C. It is established that the end product of combustion synthesis consists of several phases, not only the target phases (AlN and BN), but also the by-products (Na₃AlF₆, К₂NaAlF₆, NaF, KF), part of which is removed by water washing. The composite powder of AlN-BN is formed only in the case of AlF₃ as precursor of Al; in doing so, it is formed with side, impurity product К₂NaAlF₆ or Na₃AlF₆. In the case of precursor Na₃AlF₆, the washed product of SHS may only be a by-product К₂NaAlF₆ or Na₃AlF₆ or along with the by-product, it may contain AlN or BN, but not their composition. That is explained by different combustion temperature.The structure formation of the composite powder is investigated. The obtained agglomerated nitride nano- and micropowders have an irregular and predominantly acicular shape with an average particle size of 50-170 nm in the agglomerates.

Abstract: One-stage technology of obtaining aluminum-ceramic skeleton composites by combining the processes of self-propagating high-temperature synthesis (SHS) of the porous skeleton and its infiltration under pressure with molten aluminum (method SHS-pressing) was considered. Experimental study of the effect of the pressure of infiltration on the distribution of the content of aluminum over the height and radius of the disk-shaped sample with SHS skeleton made of a cermet of TiC-Ni was performed. Mechanisms of the formation of structure and properties of the composite depending on the infiltration pressure were described.

Abstract: A review of the methods of obtaining and properties of aluminum matrix composites, discretely reinforced with ceramic particles and nanoparticles of aluminum nitride AlN, is given. The survey shows that at low weight, nanocomposites Al-AlN possess improved physical and mechanical properties, including at high temperatures up to 400-550°C, which makes them very attractive for applications in automotive, aerospace and semiconductor technology. However, due to the long duration and energy consumption, expensive and complicated equipment, low productivity of existing solid-phase methods of powder metallurgy and liquid-phase metallurgical processes of fabrication of nanocomposites of Al-AlN, there are not yet the mastered technologies of industrial production of these composites. Azide technology of self-propagating high-temperature synthesis (SHS-AZ) using sodium azide NaN₃ as a solid nitriding reagent allows you to get relatively inexpensive nanopowder of aluminum nitride in the form of nanofibers along with side salt of cryolite Na₃AlF₆, which can play the role of flux when working with molten aluminum. A new simple ex-situ method of introduction of AlN particles in the molten aluminum alloy in the form of a composite master alloy obtained by fusing together a flux carnallite KCl·MgCl₂ with AlN nanopowder mixed with cryolite Na₃AlF₆ was proposed. Results of experiments on the application of the proposed method for obtaining nanocomposite with matrix made of aluminum-magnesium alloy AlMg6 containing up to 1 % of the reinforcing phase AlN are presented.