Self-propagating High-temperature Synthesis Research Articles

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

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.

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.

Nano- and Submicron-Sized TiB2 Particles in Al–TiB2 Composite Produced in Semi-Industrial Self-Propagating High-Temperature Synthesis Conditions

Nano- and Submicron-Sized TiB2 Particles in Al–TiB2 Composite Produced in Semi-Industrial Self-Propagating High-Temperature Synthesis Conditions

Enhanced oxidation resistance of ZrB2-MoSi2 coating through MoSi2-TaSi2 double-silicide alloying modifying

This study explored how MoSi2-TaSi2 ratios in silicide alloys influence the oxygen resistance of ZrB2-MoSi2-TaSi2 coatings, using self-propagating high-temperature synthesis and spark plasma sintering. The oxidative self-separation effect of TaSi2 and MoSi2 enhances nanoscale Zr and Ta oxide particle dispersion, forming a Zr-B-Ta-Si-O glass with optimal oxygen-blocking in the 50ZrB2-(MoSi2-10TaSi2) coating (ZMT10). Compared to ZrB2-MoSi2, ZMT10 showed 28.87 % and 48.21 % reductions in weight gain and oxygen penetration, increasing protection to 99.71 %. Excessive TaSi2 leads to Ta5+ dissolution, oxide aggregation, and a dendritic structure, facilitating oxygen diffusion and oxidation, raising the oxygen penetration in 50ZrB2-(MoSi2-30TaSi2) to 0.73 %, lowering protection to 99.18 %.

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.&#x0D; AIM: To perform an experimental study of the biocompatible antibacterial surface in porous titanium nickelide alloys with the addition of silver nanoparticles.&#x0D; 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.&#x0D; 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.&#x0D; 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.

A Review of the State of Art of Fabrication Technologies of Titanium Aluminide (Ti-Al) Based on US Patents

This article evaluates the fabrication technologies of titanium aluminide (Ti-Al) and its practical applications by comparing it with the well-known Ti-Al binary phase diagram and US patents. Meanwhile, by analyzing and discussing the various patented Ti-Al fabrication technologies and applications, this article discusses the applications of Ti-Al-based alloys, mainly in the aircraft field. The improved fabrication processes and new application technologies are under patent protection. These technologies are classified into six categories: basic research on Ti-Al-based alloys, powder metallurgy of Ti-Al-based alloys, casting and melting of Ti-Al-based alloys, PM and AM manufacturing methods for aircraft applications, other fabrication technologies by Ti-Al-based alloys, and self-propagating high-temperature synthesis (SHS) of Ti-Al-based alloys. By comparing the principles and characteristics of the above techniques, the advantages, disadvantages, and application fields of each are analyzed and their developments are discussed. Based on the characteristics of Ti-Al, new fabrication and application technologies can be developed, which can overcome the existing disadvantages and be used to form new aircraft components.

Sorption of Radium-226 on Few-Layer Graphene Synthesized under Conditions of Self-Propagating High-Temperature Synthesis

Sorption of Radium-226 on Few-Layer Graphene Synthesized under Conditions of Self-Propagating High-Temperature Synthesis

Structural characteristics and properties of heat-resistant nickel β-alloys produced via the centrifugal SHS-casting method

Employing centrifugal self-propagating high-temperature synthesis (SHS) metallurgy, complemented by advanced metallurgical processes such as vacuum induction melting (VIM) and vacuum arc remelting (VAR), yielded the alloy formulation denoted as base–2.5Mo–1.5Re–1.5Ta–0.2Ti. This study investigates the effects of various technological modes and additional metallurgical treatments on the alloy's impurity and non-metallic inclusion content, structural characteristics, mechanical behavior under compression, and its oxidation mechanisms and kinetics when exposed to temperatures of 1150 °C for 30 h. With increasing centrifugal acceleration, the proportion of non-metallic inclusions (number of points) drops from 5 to 1–2 points. The best combination mechanical properties, including σucs = 1640 ± 20 MPa, σys = 1518 ± 10 MPa, and residual deformation were observed in alloys processed under conditions of increased gravitational force (g = 50). Within a centrifugal force range of g = 20÷300, the composition of the synthesis products aligned with the theoretical expectations. The total content of impurities is 0.15 ± 0.02 %, with a decrease in gas impurities–oxygen and nitrogen levels reduced to 0.018 % and 0.0011 %, respectively. The structural analysis of the alloys revealed the presence of globular and streaked inclusions of a chromium-based solid solution embedded within the matrix. Inclusions with thickness of 2–8 μm are present in the intergranular space: (Cr)Ni,Mo,Co, (Cr)Mo,Re and (Cr)Re,Mo. The formation of the Ni(Al,Ti) phase at grain boundaries was identified, contributing to an enhancement in plastic resistance and overall strength of the alloy. Oxidation mechanisms varied across different processing modes, with the size of structural components significantly influencing oxidation kinetics. The weight gain observed in SHS samples was 70 ± 10 g/m2 with oxidation predominantly occurring along the NiAl interphase boundaries and penetrating into the depth of the sample. TEM facilitated the identification of phases enriched with Ti microadditions, reducing the levels of dissolved nitrogen and oxygen within the intermetallic phase to a combined weight percentage (ΣO,N) of 0.0223 wt.%.

Determination of nitrogen in titanium, aluminum, silicon, hafnium nitrides and compositions on their base using a Metavak-AK analyzer

Methods for determining nitrogen in the products of self-propagating high-temperature synthesis (SHS), i.e., titanium, aluminum, silicon, and hafnium nitrides using a Metavak-AK gas analyzer have been developed. The optimal modes of analysis have been selected: the time and temperature of degassing of the crucible with flux in the furnace, the time and temperature of purging the extraction chamber with the sample, the time of automatic dumping of the sample from the loading chamber into the crucible, the time and temperature of purging the chamber after loading, the time of removal of gaseous products of reduction melting and registration of nitrogen signals. Furnace operating programs were compiled to determine the nitrogen content in TiN, AlN, Si3N4, HfN. Reduction melting of the samples took place in a helium flow at a furnace temperature of 2700°C for TiN, AlN, HfN, and 2500°C for Si3N4. To speed up the process and complete nitrogen extraction, a metal bath was used: nickel grit in the case of titanium and hafnium nitrides, and combined Sn/Ni flux for aluminum and silicon nitrides. The nitrogen content in the studied samples was determined in the range from 0.12 up to 39.3 %wt., the relative standard deviation was 0.6 – 3.6%. The accuracy of the results obtained on a Metavak-AK gas analyzer is confirmed by the Kjeldahl and Dumas reference methods.

Using the Spark Plasma Sintering System for Fabrication of Advanced Semiconductor Materials.

The interest in the Spark Plasma Sintering (SPS) technique has continuously increased over the last few years. This article shows the possibility of the development of an SPS device used for material processing and synthesis in both scientific and industrial applications and aims to present manufacturing methods and the versatility of an SPS device, presenting examples of processing Arc-Melted- (half-Heusler, cobalt triantimonide) and Self-propagating High-temperature Synthesis (SHS)-synthesized semiconductor (bismuth telluride) materials. The SPS system functionality development is presented, the purpose of which was to broaden the knowledge of the nature of SPS processes. This approach enabled the precise design of material sintering processes and also contributed to increasing the repeatability and accuracy of sintering conditions.

Refinement of the Manufacturing Route and Evaluation of the Reinforcement Effect of MAX Phases in Al Alloy Matrix Composite Materials

Microwave Assisted Self-propagating High-temperature Synthesis (MASHS) was used to prepare open-porous MAX phase preforms in Ti-Al-C and Ti-Si-C systems, which were further used as reinforcements for Al-Si matrix composite materials. The pretreatment of substrates was investigated to obtain open-porous cellular structures. Squeeze casting infiltration was chosen to be implemented as a method of composites manufacturing. Process parameters were adjusted in order to avoid oxidation during infiltration and to ensure the proper filling. Obtained materials were reproducible, well saturated and dense, without significant residual porosity or undesired interactions between the constituents. Based on this and the previous work of the authors, the reinforcement effect was characterized and compared for both systems. For the Al-Si+Ti-Al-C composite, an approx. 4-fold increase in hardness and instrumental Young's modulus was observed in relation to the matrix material. Compared to the matrix, Al-Si+Ti-Si-C composite improved more than 5-fold in hardness and almost 6-fold in Young's modulus. Wear resistance (established for different loads: 0.1, 0.2 and 0.5 MPa) for Al-Si+Ti-Al-C was two times higher than for the sole matrix, while for Al-Si+Ti-Si-C the improvement was up to 32%. Both composite materials exhibited approximately two times lower thermal expansion coefficients than the matrix, resulting in enhanced dimensional stability.