Self-propagating High-temperature Synthesis Research Articles

Self-propagating high temperature synthesis (SHS) of ZrC-TiC nanocomposites: Comparison of Mg and Al reductant usage and process optimization

Self-propagating high temperature synthesis (SHS) of ZrC-TiC nanocomposites: Comparison of Mg and Al reductant usage and process optimization

Self-Propagating High Temperature Synthesis of Composite Material Based on Zirconium and Chromum Oxide

Ceramic composite materials based on stabilized zirconium oxide were obtained by self-propagating high-temperature synthesis. Yttrium oxide was used as a stabilizing additive. The work studied the effect of the content of yttrium oxide additive on the temperature and combustion rate of the materials studied. Also, based on the results of X-ray phase analysis and scanning electron microscopy, the effect of yttrium oxide on the phase composition and microstructure of the synthesized materials was studied.

Electron Microscopic Analysis of the Nb<sub>5</sub>Si<sub>3</sub>/NBC/NbSi<sub>2</sub> Composite Structure

The method of aluminothermic self-propagating high-temperature synthesis was used to obtain a composite material based on Nb-Si-C. The study of this system is of interest from the point of view of obtaining high-temperature materials of a new generation for gas turbine engine building, capable of replacing heat-resistant nickel alloys, as well as the potential possibility of forming MAX-phases (phases Mn + 1AXn where n = 1, 2, 3, ...; M is transitional d-metal, A – p-element, X – carbon). The resulting Nb-Si-C composite were studied by X-ray diffraction, scanning electron microscopy, and X-ray spectral microanalysis. It is shown that NbC carbide and silicides γ-Nb5Si3 and NbSi2 are formed in the sample. A detailed analysis of the morphological distribution of the constituent phases has been carried out.

Alumina-based ceramic coatings obtained by the SHS process for high temperature corrosion and wear protection of steel tubulars

Ceramic coatings have much potential for steel tubulars' protection against high temperature corrosion of gases and liquids, often containing abrasive solid particles, and to enhance their integrity in severe power generation, mineral and oil & gas production environments. Combining self-propagating high-temperature synthesis (SHS) with high-speed centrifugal process, alumina-based coatings were produced onto the inner surface of tubulars for these applications. According to the developed SHS batch formulation and the designed centrifugal device and process, well-consolidated composite ceramic layers with a thickness of 1.5–3 mm have been obtained. The developed SHS process does not create hazardous gases, and it takes ∼30 s for the ceramic phase formation. A high-level compaction due to centrifugal forces and a liquid phase sintering approach provided a dense gradient ceramic structure formed by oxide grains cemented by a glassy phase and bonded with a steel substrate through a thin iron layer. The coatings were successfully produced onto the inner surface of carbon and stainless steels’ tubes of up to 12 ft-lengths and standard dimensions from 2 to 3/8″ to 7.5” OD. The coatings were tested, for the first time, in wear and high-temperature corrosive environments, e.g., in steam–H2S–CO2 gases and molten salts, with encouraging results due to high contents of Al2O3 and some other oxides and consolidated ceramic structure. They can be recommended for applications in high-temperature (900 °C and greater) corrosive environments and erosive flows.

Magnesium-Thermal Self-Propagating High-Temperature Synthesis of Silicon Carbide Using Carbon Fibers as the Carbon Source

Magnesium-Thermal Self-Propagating High-Temperature Synthesis of Silicon Carbide Using Carbon Fibers as the Carbon Source

Synthesis of strontium hexaferrite (SrFe12O19) by self-propagating high-temperature synthesis (SHS) method and investigation of the effect of milling on morphology and magnetic properties

In this research, strontium hexaferrite (SrFe12O19) was synthesized using the self-propagating high-temperature synthesis (SHS) method, and its structural and magnetic properties were investigated. Raw materials such as strontium peroxide (SrO2), iron (Fe), and iron (III) oxide (Fe2O3) were used to prepare green compact. The current research investigated the effect of milling time and speed on the morphology and magnetic properties of strontium hexaferrite, and the optimum temperature for calcination was obtained. X-ray diffraction (XRD), vibrating magnetometer (VSM), field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) were used to study the mentioned parameters and choose the optimal conditions for the synthesis of strontium hexaferrite. Milling at speeds of 100, 200, and 300 rpm for 30 and 90 min was investigated. Also, calcination was performed at temperatures of 1000, 1100, 1200, and 1300 °C for 90 min to obtain the optimal temperature. According to the results of VSM analysis, the sample milled at 300 rpm for 90 min and calcined at 1200 °C for 90 min had the highest magnetic properties. Magnetic saturation (MS), magnetic remanence (Mr), and coercivity (HC), with values of 56.43 emu/g, 30.85 emu/g, and 5705.96 Oe, were obtained for this sample. Also, FE-SEM images showing the formation of hexagonal plates with an average particle size of 380 nm after calcination were obtained for the sample with optimal parameters. TEM and HRTEM images also showed the formed particles of strontium hexaferrite with hexagonal morphology.

Selection of heat treatment and its impact on the structure and properties of AK10M2N–10%TiC composite material obtained via SHS method in the melt

The composite materials based on the Al–Si system alloys, strengthened with a highly dispersed titanium carbide phase, possess improved characteristics and belong to the group of promising structural materials. Currently, self-propagating high-temperature synthesis (SHS) based on the exothermic interaction, wherein titanium and carbon precursors directly involve in the melt, is the most accessible and effective method to obtain them. This paper proves the feasibility and demonstrates the successful synthesis of a 10 wt.% titanium carbide phase in the melt of the AK10M2N alloy, resulting in the AK10M2H-10% TiC composite material. Samples of the matrix alloy and the composite material were subjected to heat treatment according to the T6 mode, with various temperature-time parameters for hardening and aging operations. Based on the results, optimal heat treatment modes were selected to ensure maximum hardness. We studied the macroand microstructure of the obtained samples and performed micro X-ray spectral and X-ray diffraction phase analyses. Different groups of properties underwent comparative tests. It was established that the density of AK10M2N–10%TiC samples before and after heat treatment, according to optimal modes, is close to the calculated value. We showed that the combination of reinforcement and heat treatment significantly increases hardness, microhardness, and compressive strength, with a slight decrease in ductility. Additionally, it maintains the values of the coefficient of thermal linear expansion, high-temperature strength, and resistance to carbon dioxide and hydrogen sulfide corrosion at the level of the original alloy. The greatest effect was observed during the investigation of tribological characteristics: heat treatment of the composite material according to the recommended mode significantly reduces the wear rate and friction coefficient, eliminates seizure and tearing, and prevents temperature rise due to friction heating.

Fabrication of high speed steel electrodes with MoSi2–MoB–HfB2 ceramic additives for electrospark deposition on die steel

The electrodes for electrospark deposition (ESD) were fabricated from hot-pressed blanks composed of a mechanically alloyed powder mixture of R6M5K5 high speed steel. This mixture was enriched with a 40 % addition of heat-resistant MoSi2–MoB–HfB2 ceramics, produces through the self-propagating high-temperature synthesis method (resulting in the R6M5K5-K electrode), as well as variant without any ceramic addition (resulting in the R6M5K5 electrode). We examined both the composition and structure of the electrode materials and the coatings derived from them, identifying the characteristics of mass transfer from hot-pressed electrodes to substrates of 5KhNM die steel under various frequencies and energy conditions during processing. The R6M5K5 electrode consists of an α-Fe-based matrix incorporating dissolved alloying elements and contains discrete particles of ferrovanadium, tungsten carbide, and molybdenum. The R6M5K5-K electrode, in addition to the α-Fe-based matrix, includes borides and carbides, as well as hafnium oxide. The use of the R6M5K5 electrode resulted in a consistent weight increase in the cathode throughout the entire 10-minute processing period. In contrast, the application of the ceramicenhanced electrode led to weight gain only during the initial 3 min of processing. Subsequently, ESD produced coatings of 22 and 50 μm thickness on the surface of 5KhNM steel using R6M5K5 and R6M5K5-K electrodes, respectively. The introduction of SHS ceramics escalated the roughness (Ra) of the surface layers from 6 to 13 μm and the hardness from 9.1 to 15.8 GPa. The coating from the R6M5K5 electrode was composed of austenite (γ-Fe) and exhibited high uniformity. Conversely, the coating from the R6M5K5-K electrode consisted of a diverse matrix with both crystalline and amorphous iron, an amorphous phase rooted in the Fe–B alloy, and scattered phases of HfO2, HfSiO4, Fe3Si, and Fe3B. High-temperature tribological testing at 500 °C in an air atmosphere showed that the coatings possess a friction coefficient of 0.55–0.57 when coupled with a counterbody of AISI 440C steel. The integration of heat-resistant ceramics notably enhanced the coating's wear resistance, increasing it by a factor of 13.5.

Sulfidation of Zinc oxide by interaction with Antimony sulfide

The mechanism of interaction between ZnO and Sb2S3 in the temperature range of 500-700°С was studied. The methods of differential thermal analysis, X-ray diffraction, diffuse reflectance spectroscopy and IR transmission spectroscopy, as well as thermodynamic calculations established the exchangeable acid-base reaction mechanism with the removal of the most volatile of the products – Sb2O3. The final and only product of interaction in the system is ZnS of cubic modification (sphalerite) without phase impurities. Condensate mainly contains Antimony oxides of various compositions. In the same way, it is possible to remove oxygen-containing impurities (mainly ZnO) from zinc sulfide obtained by the method of self-propagating high-temperature synthesis.

Intercalation based synthesis of Chevrel phase superconductors

This work focuses on the superconducting and magnetic properties of Chevrel phase (CP) compounds (Cu2Mo6S8 and Ni2Mo6S8) processed via a novel self-propagating high-temperature synthesis (SHS) method involving ternary cation intercalation in MoS2 high-temperature polymorphs. Green pellets of the precursor materials sealed under vacuum and exposed to 1050 °C or 1200 °C rapidly transformed from a powder mixture into submicron CPs within minutes. X-ray diffraction analysis confirmed the presence of Cu2Mo6S8 CP (67%), and Ni2Mo6S8 (93%). This group has illustrated the first time CP were formed at low energy cost and full stoichiometry. Magnetization versus temperature data obtained for the samples under different field conditions confirmed the superconducting behavior of the Cu–CP at a critical temperature of 8.3 K. The Ni–CP behaved as a superparamagnetic at low temperature (4.2 K). The results of this work suggest that the novel SHS process offers a viable scalable synthesis route for the Chevrel family of compounds and that it is worth exploring the functional applications of the new compounds of this material system.

Study of anisotropy in polydispersed 2D micro and nano-composites by Elbow and K-Means clustering methods

A new two-dimensional polydisperse model for testing multiphase composites is developed. The verification of the model is carried out based on the microstructure of two composites obtained in the ex-situ and in-situ techniques produced in the Friction Stir Processing (Al–Si–Cu/SiCp) and the Self-propagating High temperature Synthesis (Al/nano-TiCp). The examined microstructure is considered on macro-, meso- and micro- levels. Besides the reinforcement phase distribution concentration, an anisotropy coefficient κ is calculated for every meso-cell. It is the cumulative vector parameter that characterizes the spatial two-point correlation of inclusions. In particular, κ determines the principal axes of the effective conductivity tensor over a meso-cell. The anisotropy spatial distribution ϰ(x) is introduced as the discrete function of values κ calculated over meso-cells centered at the point x. This new distribution ϰ(x) accumulates the geometrical information of the considered microstructure. A computational experiment is designed and carried out in order to study the influence of the reinforcement phase redistribution on the anisotropy. Therefore, it adequately describes the anisotropy of fields in composites modeling thermal and electric conductivity, diffusion, and elastic antiplane deformation. The results of the computational experiments are analyzed using the Elbow and K-Means clustering machine learning algorithm. The detailed analysis is carried out to divide the data set into up to 5 clusters. A research hypothesis concerning the criterion of isotropy of the distribution of reinforcing phase particles in the composite structure is formulated

The influence of hydrogen on the synthesis of biocompatible alloy Ti-6Al-7 Nb by a new Hydride Cycle method

The Hydride Cycle (HC) method is proposed as a new approach for synthesis of biocompatible alloy Ti-6Al-7 Nb. In this approach, preliminary, (Ti-7 Nb)H3.81 hydride is synthesised by Self-propagating High-temperature Synthesis (SHS) method. The heating of a mixture of this hydride with aluminum, (Ti-7 Nb)H3.81+6Al, at 1000°C for 30 minutes in the HC device results in the synthesis of Ti-6Al-7 Nb alloy containing the α- and β-phases of Ti, 92 wt% and 8 wt%, respectively. The alloy interacted with hydrogen in the combustion mode (SHS) forming the hydride (Ti-6Al-7 Nb)H3.17 with hydrogen content 3.07 wt%. This amount of hydrogen ensures the brittleness of the hydride and its grinding for 30–40 minutes to the agglomerates down to submicron or nano sizes. The presence of hydrogen in the crystal lattice enhances the plasticity of the hydride facilitating its compaction. The compaction of the (Ti-6Al-7 Nb)H3.17 alloy hydride and dehydrogenation under T=1000°C results in the reaction-activated sintering and the formation of practically porous less Ti-6Al-7 Nb alloy. The HC synthesis of the biocompatible alloy Ti-6Al-7 Nb compiled with SHS mode of the hydride synthesis is provided with the several advantages over the traditional methods. It is a low temperature, short duration, waste less process, proceeding by solid-state mechanism without melting of components, being an energy-saving in total. The proposed HC approach for synthesis of Ti-6Al-7 Nb alloy in combination with the high-technology SHS process for the hydrides formation can be used in manufacturing the biocompatible alloys. The hydrogenation-sintering of the alloy hydride (Ti-6Al-7 Nb)H3.17 can be used for producing of items of any designed complex form, particularly of implants.

Methanol Reforming over Cu-Ce-Al Catalysts Prepared by Solution Combustion Synthesis Method

The demand for environmentally friendly types of energy is growing all over the world, which naturally increases the intensity of studies on fuel mixtures that have high contents of hydrogen. In this case, methanol steam reforming is a leading effective research area, as it is a process with low energy consumption. The results of the steam reforming of methanol on synthesized catalysts by the solution combustion synthesis (SCS), self-propagating high-temperature synthesis (SHS), and moisture impregnation capacity methods are presented. A study was conducted to evaluate the activity of Cu-Ce-Al catalysts with varying ratios of components for hydrogen production, comparing the SCS method with the other mentioned methods. The methanol conversion reached 99% and the selectivity of H2 was 88% at 500 °C. The study showed that the replacement of Al3+ ions with Cu2+ and Ce3+ cations leads to the formation of spinels, such as CuAl2O4 and CeAlO3. As a consequence, the CuAl2O4 and CeAlO3 lattice parameters increase because of the difference in the ionic radii of Al3+ (0.53 Å), Cu2+ (0.73 Å), and Ce3+ (1.07 Å). Advantages of SCS catalysts in the process of the steam reforming of methanol have been demonstrated. The goal of this research is to create a new catalyst for methanol’s conversion into hydrogen-containing fuel mixtures, the production of which, in the future, will be a huge step in the transition to more energy-efficient and environmentally friendly methods of their synthesis.

Analysis of Fragmentation Phenomenon of Composite Layers of Fe-TiC Type Obtained “in situ” in Steel Casting

A method for fabrication of a composite layer on the surface of a steel casting using coating containing TiC substrates was presented. The reaction of the synthesis of the ceramic phase was based on the SHS method (Self-propagating High-temperature Synthesis) and was triggered by the heat of molten steel. High hardness titanium carbide ceramic phases were obtained, which strengthened the base material improving its performance properties presented in this article. Microstructural examinations carried out by light microscopy (LM) on the in-situ produced composite layers showed that the layers were the products of reaction of the TiC synthesis – the phenomenon called “fragmentation” by the authors of study. The examinations carried out by scanning electron microscopy (SEM) have revealed the presence of spheroidal precipitated and free of impurities. The presence of titanium carbide was twofold increase in hardness in the area of the composite layer as compared to the base alloy which was carbon cast steel.

FORMATION OF CHROMATED COATINGS ON A PRESS TOOLING IN THE PRODUCTION OF RUBBER PRODUCTS FOR ROCKET AND SPACE TECHNOLOGY

This research analyzes the influence of residual stresses formed as a result of the process of self-propagating high-temperature synthesis on the mechanical properties and durability of structural materials and protective coatings. The main emphasis is placed on the analysis of the relationship between residual stresses and adhesive strength and durability of the obtained coatings. Rubber-based composites may prove to be competitive and eventually replace traditional materials in a number of applications, as there are many advantages to using these materials. For example, rubber-based composites often have a lower density than traditional materials such as metals. This leads to a reduction in the weight of products, which is important in a variety of industries where lightness is a key characteristic. Rubber composites are characterized by cushioning, flexibility, and elasticity, which makes them able to handle dynamic loads and adapt to various forms of deformation without losing structural properties. Research was carried out on parts of press tooling used for manufacturing of rubber-technical products in rocket-space engineering. It was found that residual stresses formed during the SHS process have a significant effect on the adhesion properties of protective coatings. Residual stresses appear after SHS treatment under conditions of thermal self-ignition of SHS charges. At the cooling stage of the SHS process, residual compressive stresses appear as a result of the elastic interaction of the alloyed titanium coating and the structural material, which have different sizes and coefficients of thermal expansion. The maximum values of adhesion strength of titanium coatings on steel 45 were 120-150 MPa when alloyed with aluminum and 180-210 MPa when alloyed with chromium. This research emphasizes the importance of residual stress control for improving the strength and durability of protective coatings obtained under SHS conditions and their possible role in extending the service life of structures and equipment. Additional research in this direction may contribute to process optimization and product quality improvement in the aerospace industry.

Insights into the effects of La on the grain refinement and mechanical properties of Al-Ti-C intermediate alloy and pure Al: A first-principle study and experimental investigation

This paper employs the self-propagating high-temperature synthesis (SHS) to prepare Al-Ti-C master alloys and explores the effects of integrating the rare earth element lanthanum to create Al-Ti-C-La composites. This research focuses on the microstructural changes in both the master alloy and pure aluminum, which aimed to elucidate the mechanisms that enhance grain refinement and resistance to grain refinement fading. The analysis reveals that when Al-Ti-C-La master alloys are incorporated into molten Al, the predominant structures formed include an Al matrix, rod-like Al3Ti phases, and TiC particles, alongside AlLa phases and substantial Al20Ti2La compounds. The grain refining capability of Al-Ti-C-La master alloys is significantly exceeds that of the Al-Ti-C master alloys. The addition of La markedly reduces the settling of TiC particles, thereby granting the Al-Ti-C-La master alloys excellent resistance to grain refinement fading. The newly formed Al20Ti2La phase plays a crucial role in refining the aluminum matrix, with metallic bond characteristics present on the side towards the Al matrix at the Al20Ti2La/Al interface and distinct covalent bond characteristics on the Al20Ti2La side. Moreover, the Al20Ti2La (110)/Al (110) interface exhibits the highest interfacial adhesion energy and stronger covalent bond features. Consequently, α-Al is prone to heterogeneously nucleate on the Al20Ti2La phase via the Al20Ti2La (110)/Al (110)-HCP orientation, which refines the grains of the aluminum matrix, ultimately enhancing the performance of aluminum-based alloys.

Wear and corrosion resistance of Al2O3 and TiC deposition on steel substrate using self- propagating high temperature synthesis method

In the present work, a low-carbon steel substrate was coated with Al2O3 and TiC using self-propagating high temperature synthesis. The synthesized coatings were annealed at 450 °C for 2–6 h. The characteristics of the substrate, coated, and annealed samples were examined, including microhardness, wear resistance, and corrosion resistance. A pin-on-disc tribometer was employed to conduct the wear test by varying the load, sliding velocity, and distance. The impact of these factors on the wear rate and worn surface morphology was then examined. Further, corrosion resistance was evaluated using electrochemical corrosion testing with 3.5 wt% NaCl as electrolyte. Results showed that Al2O3 and TiC specimens annealed at 450 °C for 5 h and 4 h improved the microhardness by 1.3 and 1.06 times than that of as-coated specimens respectively. The synthesized Al2O3 and TiC coatings showed an abrasive wear mechanism at higher loads and tribolayer formation was observed at higher sliding velocity and distances. The corrosion and wear resistances of the samples were found as follows: substrate< Al2O3 coated < TiC coated < Al2O3 annealed < TiC annealed. The Al2O3 and TiC ceramic coatings were found to improve wear and corrosion resistance having potential applications in cement, petrochemical, and marine industries.

Production of iron triad-based colored spinels by the self-propagating high-temperature synthesis

Blue, green, and khaki spinels were produced by self-propagating high-temperature synthesis (SHS) using Co3O4–ZnO–Mg(NO3)2·6H2O–Al(OH)3–Al, Ni2O3–ZnO–Cr2O3–Al(OH)3–Al, and Co2O3–Fe2O3–Al(OH)3–Al mixtures. The composition of the synthesis products was characterized by X-ray diffraction and IR spectroscopy. The oxides Co3O4, Co2O3, ZnO, Ni2O3, Cr2O3, Fe2O3, and aluminum hydroxide Al(OH)3 were used for the synthesis. Fuel was provided by aluminum powder (ASD-4). The spinel-type ceramic pigments were synthesized using layer-by-layer combustion, which involves two parallel exothermic reactions: aluminum oxidation and aluminothermic reactions. The fast self-propagating reactions and high synthesis temperatures rapidly destroy the structure of Al(OH)3 hydroxide in the starting mixture, producing gaseous reaction products that prevent the sintering of the spinels. The surface morphology of pigment powders and their composition was studied using a Quanta 3D 200i, FEI Co. scanning electron microscope and a Philips SEM 515 scanning electron microscope equipped with a local energy dispersive X-ray analysis (EDAX). The particle size of the synthesized spinels was approximately 1–5 μm. Colored spinels powders obtained by the SHS process can be used as ceramic pigments.

Liquid metal assistant self-propagating high-temperature synthesis of S-containing high-entropy MAX-phase materials

Due to their high-entropy effects, the high-entropy (HE) MAX-phase materials improve the comprehensive performance of MAX phases, opening up more possibilities for practical engineering applications. However, it is still challenging to obtain S-containing high-entropy MAX phases because of the high volatilization behavior of sulfur, suffering from issues such as high reaction temperature and long reaction time of traditional synthesis methods. This paper proposes a novel process named as liquid metal assistant self-propagating high-temperature synthesis (LMA-SHS) for efficient synthesis of high-purity S-containing high-entropy MAX-phase materials. Low-melting-point metal (Sn or In) has been introduced into the raw mixture and melted into a liquid phase during the early stage of the SHS reaction. By serving as a “binder” between transition metal atoms of the M-site due to the negative mixing enthalpy, this liquid phase can accelerate mass and heat transfer during the SHS process, ensuring a uniform solid solution of each element and realizing the synthesis of high-purity (TiNbVZr)2SC in an extremely short time. The synthesis method for high-entropy MAX-phase materials developed in this study, i.e., LMA-SHS, showing very short reaction time, low energy consumption, high yield, and low cost, has the promise to be a general energy- and resource-efficient route towards high-purity HE materials.

Effect of SHS powder processing on structure formation and optical transmittance of MgO–Y2O3 composite ceramic

Extending the transparency range of MgO–Y2O3 composite ceramic to wavelength less than 3 μm is highly desirable, as it broadens their potential applications in infrared (IR) optics. This study illustrates the effectiveness of deagglomerating a mixture of magnesium oxide and yttrium sesquioxide powders, derived from self-propagating high-temperature synthesis (SHS), in achieving this goal. The impact of powder deagglomeration on the microstructure and porosity defects of hot-pressed MgO–Y2O3 ceramic was analyzed using electron and IR microscopy. The results showed that the deagglomeration enhanced the homogeneity of the composite grain mixture, slowed down the grain growth, suppressed the formation of large grains, and significantly reduced the number of porosity microdefects in the material. The optical transmittance increased from 42 % to 77 % at a wavelength of 2 μm (for samples with a thickness of 1.2 mm) when deagglomerated powders were used, compared to non-deagglomerated ones.