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

Solution combustion synthesis (SCS) is a widely used method to prepare nanomaterials tailored for specific applications, with a primary focus on understanding the influence of precursors on material properties and microstructure evolution. There is also a lack of systematic studies to understand the kinetics of SCS reactions. This work reports on the preparation of pure nickel by the combustion of Ni(NO₃)₂ + citric acid (C₆H₈O₇) solution and the investigation of SCS reaction mechanism by thermal analysis technique. The lower and upper combustion limits were determined depending on the citric acid to Ni(NO₃)₂ ratio. The optimal composition of the initial mixture was revealed to prepare nickel powder without using an additional post–synthesis reduction of metal oxides. Ozawa’s method was employed to calculate the effective activation energy (∼101 ± 5 kJ mol^–1) of the nickel formation reaction based on the TGA data. The magnetization of the nickel powder agglomerates with ∼80–200-nm nanoscale particles was measured to be 55.1 Am² kg^–1.

In our study, we aimed to synthesize the Cu₂Sb phase with a tetragonal structure. We achieved this by subjecting compacts (2Cu + Sb) to electrothermal explosion (ETE) with a high current density of 500 Å. To analyze the constituent phases of the alloy composite, we employed X-ray diffraction analysis with the MAUD program, which utilizes the Rietveld method, as well as scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques. Furthermore, we investigated the mechanical properties through Vickers indentation and compression techniques.

The Co_0.8–xMg_xZn_0.2Fe₂O₄ (x = 0.00 to 0.56) ferrites were prepared by solid state reaction route. The phase composition and morphology of the synthesized ferrites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. From the XRD results, single phase cubic spinal structure with space group Fd-3m was confirmed. The lattice constant (a), particle size (D), hopping lengths (L_A and L_B), bond lengths (A–O and B–O), ionic radii (r_A and r_B), microstrain (ε,) and dislocation density (ρ_D) were reported. The lattice constant increased as magnesium additive increased. The SEM image affirmed size and shape of particles. Crystallite size and microstrain were realized by W–H plot and SSP.

The study focuses on the synthesis and energy transfer mechanism between the cerium and neodymium co-doped YAG phosphors. YAG:Ce,Nd powders were synthesized using a mixed fuel combustion method. The effect of the synthesis procedure on the crystallinity and luminescence spectra were examined. The influence of Si⁴⁺ doping in YAG:Ce,Nd phosphors were also studied.

The combustion modes of granular mixtures (100 – X)(Ti + C) + XNiCr, X = 0–30%, were studied. The experimental setup provided filtration of impurity gases released during combustion, either in the direction of propagation of the combustion front, or through the side surface of the sample. The comparison of burning velocities in different gas filtration schemes indicates the influence of convective heat transfer on the combustion patterns of mixtures with X < 30%. A method was proposed for determining the composition of the mixture in which the transition to the convective combustion mode occurs. The content of impurity gases in mixtures of different compositions was estimated quantitively. The comparison of experimental data with calculations based on the theory of filtration combustion showed that there is a conductive combustion mode for all mixtures of 0.6-mm granules and a mixture of 1.7-mm granules with X = 30%. XRD analysis of the synthesis products revealed no intermetallic phases, regardless of the size of the granules.

The phase formation and macro/microstructure of a porous skeleton based on Ti₃SiC₂ MAX phase prepared by self-propagating high-temperature synthesis of green mixtures consisting of Ti powders differing in particle size, different carbon powder forms, and Si powder in a sand backfill in air. Comparative data on porosity, compressive strength, and quantitative phase composition of synthesized samples were presented. It was established that the fractional composition (particle size) of Ti and C powders, as well as the form of C (graphite, carbon black) influence markedly the macrostructure of porous SHS skeletons. The porous skeleton obtained using coarse Ti and medium colloidal graphite powders was found to have high content of Ti₃SiC₂ MAX phase (66%) and to possess high density and compressive strength (2.41 g/cm³ and 104 MPa, respectively).

Bi- and trimetallic catalysts based on multi-walled carbon nanotubes (MWCNT) and metal (Me) phthalocyanines (Pc) (MePc) (MWCNT–CoPc–NiPc, MWCNT–CuPc–NiPc, MWCNT–CoPc–CuPc, and MWCNT–CoPc–CuPc–Pd) for electrochemical oxygen reduction reaction (ORR) were synthesized by high-temperature synthesis at 1000°C in an inert atmosphere. The obtained materials were characterized by scanning electron microscopy (SEM), low-temperature nitrogen absorption–desorption, and Raman spectroscopy. The change in textural characteristics and morphology of electrocatalysts during high-temperature synthesis was studied. It was shown that the nature of the metal significantly changes the physicochemical characteristics of electrocatalysts based on carbon nanotubes. The electrochemical experiment was carried out in the linear voltammetry algorithm using a three-electrode chamber with a rotating disk electrode. The main characteristics of the process of electroreduction of oxygen from an alkaline electrolyte—limiting diffusion current, potential half-waves, and initial reaction potential—were determined. MWCNT–CoPc–CuPc–Pd catalyst was found to exhibit the highest activity in the reaction of electrochemical oxygen reduction in an alkaline liquid, reaching high efficiency and corrosiveness as with platinum catalysts, with a decrease in activity after 1000 cycles of less than 7%.

The combustion patterns of powder mixtures (100 – X)(Ti + C) + XNiCr, X = 0–20%, and phase composition of synthesis products were studied. The different nature of the dependence of the burning velocity on the nichrome content for blends containing titanium powders with particles of characteristic sizes of 60 and 120 μm was explained within the framework of the convective–conductive model by the retarding influence of impurity gases released ahead of the combustion front. The conditions for warming up Ti particles before the front were not met for mixtures of fine and coarse titanium powders. XRD spectra of combustion products showed the necessity of using fine titanium powder to obtain cermets without side phases of intermetallic compounds.

TiC-based composites with various initial compositions can be successfully synthesized by self-propagating high-temperature synthesis (SHS) from either mixtures containing thermite reactions or from pure elements. The effect of various experimental parameters on the combustion reaction kinetics and the relationship between structure, microstructure and mechanical behavior of products was identified. It was found that the matrix’s strengthening is one of the most important variables in boosting the composite’s strength, and adding alloy elements reduces the rate and size of cracks and pores in the cermet microstructure. The presence of TiC particles inhibits dislocation motion and has a significant effect on the composite’s mechanical behavior.

The catalytic properties of materials based on terbium-doped and nickel-modified mesoporous silica gels prepared by the high-temperature template method were studied. The surface morphology and textural characteristics of the obtained samples were studied by scanning electron microscopy, X-ray phase analysis, and inductively coupled plasma mass spectrometry. The catalytic activity of the obtained catalysts was studied in the hydrogenation reaction of benzene, m-, p-, and o-xylene in the temperature range of 80–170°C and at a hydrogen pressure of 3 atm. It was established that doping with terbium leads to an increase in the catalytic activity of the catalyst modified with nickel in the hydrogenation reaction of benzene derivatives. Therefore, it was shown that mesoporous silica gel doped with terbium and modified with nickel is an effective catalyst for the hydrogenation of benzene and xylenes.