International Journal of Self-Propagating High-Temperature Synthesis最新文献

This investigation aimed to synthesize Ti–5Al–5V–5Mo–3Cr–1Zr (Ti–55531) alloy by energy-efficient “hydride cycle” (HC) method. From X-ray powder diffraction it was found that the synthesized alloy consists of two phases: HCP α and BCC β. Scanning electron microscopy (SEM) unveiled discernible surface characteristics on the Ti–55531 alloy, delineating two predominant phases with distinct variations in light and dark shades. These observed phases corresponded to microstructural compositions attributed to the α and β phases. The interaction of obtained Ti–55531 alloy with hydrogen in self-propagating high-temperature synthesis (SHS) mode was studied. It was demonstrated that the compacted alloy without preliminary crushing or mechanical treatment could absorb 3.4 wt % of hydrogen during the SHS process. Additionally, it was determined that the synthesized hydride of multicomponent alloy consists of two phases: TiH₂ phase with FCC structure and β-phase with BCC structure. The thermal stability of synthesized hydride was analyzed using differential thermal analysis (DTA) method, revealing a hydrogen desorption process characterized by two endo-peaks at 334 and 574°C.

Cast Mo–Cr, W–Cr, and Cr–Al master alloys were prepared via centrifugal SHS metallurgy. The effect of variation in component fractions in green mixtures (100 – α)(Cr₂O₃ + Al) + α(MoO₃ + Al) and (100 – α)(Cr₂O₃ + Al) + α(WO₃ + Al) on the synthesis of Mo–Cr and W–Cr alloys, respectively, was thermodynamically analyzed. Thermodynamic calculation of Cr–Al master alloy production was presented and provided the necessity of using a complex oxidizing agent, chromium(III) oxide and chromium(VI) oxide in a certain ratio. Experiments for Mo–Cr, W–Cr, and Cr–Al systems proved the necessity of applying overloading at an acceleration of no less than 50 g to prolong the lifetime of the melt. Introduction of functional additives CaF₂ (fluorspar) and sodium hexafluoroaluminate Na₃[AlF₆] (cryolite) to the green mixture lowered the melting temperature of the slag phase (reduced its viscosity) and facilitated the phase separation. EDS and mass spectroscopy analyses showed that the chemical compositions of synthesized master alloys are close to their calculated and target values. XRD results revealed the existence of solid solutions based on target elements.

In the category of oxides, spinel oxides can be identified by their chemical formula. Spinel oxides have the structure AB₂O₄ and are distinguished by their amazing magnetic, electric, and multiferroic properties. Additionally, they exhibit a wide variety of functional responses. A description of the experimental, structural, and electrical properties of Co_1–xLa_xCr₂O₄ (where x = 0 and 0.05) was presented in this study for the very first time. During the course of the experimental characterization, data on AC conductivity and dielectric parameters, as well as XRD and SEM micrographs, were collected. It was demonstrated beyond a reasonable doubt that a spinel cubic structure is produced by the XRD characteristics of each sample. The scanning electron micrographs (SEM) showed that every single one of the samples is very porous. An overall increasing trend of the dielectric constant was seen in the La³⁺ doped CoCr₂O₄ sample as the concentration of La³⁺ increased. This is a result of the probable hopping of Cr²⁺ to Cr³⁺, as well as an increase in the average crystallite size with La doping. Koop’s phenomenological theory was utilized in order to provide an explanation for the AC conductivity, and the hopping process was utilized in order to characterize the electrical properties of each sample. All of the samples exhibited outstanding alternating current conductivity and a low dielectric loss tangent at higher frequency ranges throughout the whole spectrum.

ZnO is an earth abundant, safe, environmentally friendly, and relatively inexpensive resource for the application in the manufacturing of thermoelectric materials. In this work hollow spherical particles of Zn_0.995In_0.005O produced by the spray solution combustion synthesis (SSCS) with the stochiometric (φ₁) and excessive (φ₃) amount of glycine fuel were sintered at 900°C by the spark plasma sintering technique and thermoelectric properties of sintered Sφ₁ and Sφ₃ materials was measured. The best thermoelectric figure of merit zT ∼ 0.08 at 1050 K obtained for the materials produced at stoichiometric amount of fuel (φ₁). It was shown that lower amount of fuel (φ₁) used during the synthesis favors formation of porous and less textured structure which exhibits better thermoelectrical properties. The Lotgering factor (LF) calculated from the intensities of XRD (002) peaks was 0.65 for Sφ₃ sample, whereas for Sφ₁ sample LF (002) = 0.08. The average pore size of sintered Sφ₁ and Sφ₃ materials was around 200 nm. The total porosity was about 5–8% for Sφ₁ and 2–3% for Sφ₃ material.

Spatial modes of combustion of the donor–acceptor system were numerically modelled. The discrete character of the combustion wave was determined by the unit cell size. The burning velocity of the sample depending on the unit cubic cell size was calculated. It was shown that as unit cell size grows, the average burning velocity of the sample increases, which is explained by a decrease in the specific area of the cell contact boundaries. Single-hot point spin modes of combustion of the parallelepiped sample with a discrete structure were found.

Ferrites, known for their unique magnetic, structural, and electrical properties, have garnered significant attention across various scientific and industrial domains. This review provides a comprehensive analysis of the effects of zinc doping on three prominent ferrite materials: MnFe₂O₄, CuFe₂O₄, and CaFe₂O₄. Zinc doping, as a strategic method for tailoring these properties, has emerged as a promising avenue for enhancing their functionality and versatility. In the introduction part to the significance of ferrites, their wide-ranging applications are discussed. This review provides a basic overview of the many synthesis methods, such as co-precipitation, sol–gel, hydrothermal, solid-state etc., and a detailed investigating some nano ferrites. It then delves into the distinct characteristics of each ferrite, highlighting their magnetic behaviors, structural features, and electrical properties. The different methods to study the structural, magnetic, and dielectric properties are also discussed. The effects of zinc doping on MnFe₂O₄, CuFe₂O₄, and CaFe₂O₄ ferrites are discussed comprehensively. This study extensively concentrates on recent industrial applications like photoluminescence, biomedical, and sensors using spinel ferrites.

Matrix based on pyrochlore Y₂Ti₂O₇ for immobilization of high-level radioactive waste was prepared via SHS process. The phase composition and structure of the synthesized matrices were characterized. The influence of aluminum additive and composition/amount of gases emitted during combustion on the porosity of the matrices was studied.

MgAlON was prepared by self-propagating high-temperature synthesis using powder mixture of aluminum, aluminum oxide, magnesium oxide, magnesium, and magnesium perchlorate as an oxidizer. The effect of magnesium oxidation and aluminum nitriding reactions on the combustion parameters was studied. It was revealed that combustion temperature and burning velocity increase as Mg is added. It was found that the combustion products derived from mixtures containing magnesium powder have a fine-grained structure composed by only MgAlON.

High-entropy alloys were produced by centrifugal self-propagating high-temperature synthesis and used as precursors for preparation of catalysts for CO and propane deep oxidation and CO₂ hydrogenation. The precursors were converted into catalysts by aluminum leaching and stabilization with hydrogen peroxide solution. Prepared FeCoNiCu, FeCoNiCuMo, FeCoNiCuMn, and FeCoNiCuCr catalysts were characterized by XRD, SEM/EDS, and BET methods and tested in the processes of deep oxidation of CO and propane and methanation of CO₂. The highest CO₂ conversion, 50.6%, with methane selectivity of 77.5% was achieved on FeCoNiCu catalyst at 400°C. The best catalyst for the deep oxidation process was shown to be FeCoNiCuCr, on which the temperature of 100% CO conversion was 250°C and 100% conversion of propane was achieved at 450°C.

A new phenomenon was discovered: an oscillatory combustion mode of hydrogen releasing under the non-isothermal decomposition of titanium hydride in air.