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

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.

A new mode of combustion of granular mixtures Zr + 0.5C in a co-current argon flow with the formation of a finger-like front instability was discovered. The observed phenomena were explained under the assumption of a decrease in the permeability of synthesis products due to significant shrinkage of the sample in the longitudinal direction, which prevented the filtration of argon through the products. Redirection of the gas flow into the gap between the granules and the side surface of the cylindrical reactor contributed to the formation of a finger. It was shown that a decrease in the sample size in the longitudinal direction is provided by the pressure drop of argon, and a decrease in the cross-section occurs under the action of surface tension forces due to a transverse temperature gradient.

Alumina (Al₂O₃) is widely used in a variety of applications because it has superior physical and chemical properties which are high heat resistance, excellent electrical isolation, abrasion resistance, and high corrosion resistance. Generally, alumina is manufactured with a purity of 99.6–99.9% mainly by the Bayer process with bauxite as the starting material. It is used in refractory products, spark plugs, IC substrates, and so on. High-purity alumina (HPA), which has a purity of more than 99.99% and has a uniform fine particle, is widely used in translucent tubes for high-pressure sodium lamps, single crystal materials such as sapphires for watch covers, high-strength ceramic tools, abrasives for magnetic tape, and the like. In recent years, the demand for high-purity alumina has been expanding in fields that are expected to show a high growth rate e.g., display materials, energy, automobiles, semiconductors, and computers. There are several complicated processes reported in literature to produce single phase α-HPA, which consumes more energy, and power and are very costly. In this paper, we report the preparation of nano-α alumina powders with a purity of 3N (99.9%) by a simple, economical, and faster method i.e., one-step auto combustion method. To obtain single phase α-alumina, the calcination temperature required is 1200°C but, in our work, we achieved single phase α-alumina at 500°C temperature by one-step auto combustion method. The as-prepared HPA is characterized through XRD, BET surface area, SEM and ICP, TGA, and LIBS to test for purity and its application in LED fabrication.

Titanium carbide (TiC) powder was synthesized by the magnesiothermic combustion of the TiO₂-rich alteration product leucoxene and activated carbon (AC) in argon. Leucoxene and C were combined at a molar ratio of 1.0 : 1.5, and the effect of magnesium (Mg) fuel in the reaction system was studied at ratios of 1.0, 1.5, 2.0, 2.5, and 3.0. XRD analysis showed that the as-leached powder from a reactant mixture with a Mg molar ratio of 3.0 has fewer unwanted phases, and that leucoxene, C, Mg mixed at 1.0 : 1.5 : 3.0 produce TiC powder of a higher purity than the other reacted mixtures. The higher purity of the product was due to the more exothermic character of the combustion reaction, which had a higher enthalpy of reaction (ΔH) and adiabatic temperature (T_ad). SEM observation of the as-leached powder revealed agglomerated fine particles of sub-micrometer size. The TiC powder was successfully coated with nickel by an electroless plating process. SEM/EDX demonstrated that the Ni-coated TiC powder consists of Ni particles smaller than 500 nm, which are well distributed on TiC particles.