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

The article presents the results of a study of the dynamics of structure formation in the ceramic–metal material TiC–CoCrFeNiCu with a high-entropy binder in the self-propagating high-temperature synthesis (SHS) mode. The studies were carried out in situ using dynamic X-ray and synchrotron radiation diffraction (“diffraction cinema”). It was shown that these two methods complement each other and allow one to obtain a fairly complete picture of the evolution of phase composition and crystal structure of multicomponent systems during SHS. The results obtained demonstrate new possibilities for direct experimental study of structure formation in high-entropy materials.

The regularities of filtration combustion of porous layer of titanium powder in adjacent inclined channels were studied. The influence of gravitational forces on combustion stability, change of gas filtration modes during combustion, and formation and propagation of cellular afterburning waves was analyzed.

In the present study, a series of pure and cobalt-doped zinc oxide nanoparticle samples with different concentrations (15, 25, 35, and 45%) of cobalt were successfully synthesized using sol–gel auto-combustion method followed by annealing at 800°C. The crystal structure was characterized using an X-ray diffractometer, revealing that all synthesized samples had hexagonal wurtzite structure. The lattice constants (a and c), crystallite sizes (D), unit cell volume (V), and microstrain (ε) were reported. The Williamson–Hall plot and size–strain plot were also employed to understand the structural and mechanical attributes of the synthesized samples.

The solution combustion synthesis method was used to prepare samples with stoichiometric La_0.7Ca_0.3Mn_1–xNi_xO₃ (x = 0 and 0.07) using glycine and tris(hydroxymethyl)aminomethane (TRIS) as fuels. X-ray diffraction showed that the samples crystallized into an orthorhombic structure of the Pnma space group with slight changes in the lattice parameters according to the type of fuel used, which can be attributed to their heat capacity. Likewise, using the transmission electron microscope technique, conglomerates of particles with relatively uniform morphology and crystallite sizes that varied in a range of 17–26 nm were observed. The electrical behavior exhibited a metal–semiconductor transition that displaced the temperature peak towards lower values, according to the Ni content. It was concluded that the properties of this type of complex inorganic oxide such as manganites can be varied with the use of different fuels in the synthesis process.

Selective laser melting (SLM) was first used to deposit products made of SHS-produced intermetallic alloy Ti₂₀Al₃Si₉ powder on the Ti substrate. It was shown that formed Ti₂₀Al₃Si₉ alloy/Ti substrate composites have a strong bond. The influence of SLM parameters for processing SHS-produced powder on microstructure and phase composition of clad samples was studies.

Porous ceramic materials were sintered from fine SiC filler powder produced via SHS with binders SiO₂ and MgO at temperatures of 800–1300°C. The effect of sintering temperature on the properties of the resulting ceramics such as pore size, open porosity, bending strength, and pure water permeability was investigated. SiC-based membrane rejected completely solid SiC particles with D₅₀ = 0.5 μm while maintaining stable permeability and physical and mechanical characteristics after repeated filtration/regeneration cycles.

MgAlON ceramics were prepared by combined use of self-propagating high-temperature synthesis of Al + Al₂O₃ + MgO + Mg(ClO₄)₂ mixtures doped with sintering agent LiF, CaCO₃ or La₂O₃ + Y₂O₃ + MgO and pressureless sintering. The effect of additives on the combustion process and phase formation of synthesized products, as well as their subsequent sintering was studied. Introduction of 10 wt % CaCO₃ was shown to lower the combustion temperature followed by stopping the combustion front. It was revealed that the density of sintered ceramic materials reaches 90% of the theoretical value. The sintered sample prepared by doping with 0.6 wt % CaCO₃ was found to possess the highest density (3.3 g/cm³) and light transmittance (16%).

Cast Mo–Nb–Ta–(Cr,V,Zr,Hf) refractory high-entropy alloys were first prepared via gravity-assisted SHS metallurgy. It was shown that the ingots crystallize from the liquid state, in which a homogeneous distribution of constituting elements is provided. The phase composition of synthesized RHEA ingots was revealed to be doped component dependent. Combined reduction of metals of V (Nb, Ta, V) and VI (Cr, Mo) groups formed single-phase alloys with a bcc crystal structure. MoNbTaCr alloys doped with Zr or Hf having hexagonal crystal structure were found to consist of fcc and hcp phases in addition to bcc solid solution.