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

Finding new energy effective methods for the production of refractory multi-principal element alloys (MPEAs) is a challenge for rapidly developing MPEA materials science. Formation of equimolar TiZrHfVNb MPEA and evaluation of alloy potential for use as hydrogen storage material were investigated. In this study, we demonstrated, for the first time to the best of our knowledge, that MPEA can be produced using SHS hydrides as precursor materials by “Hydride Cycle” (HC) method. The hydrogenation of obtained alloy by self-propagating high-temperature synthesis (SHS) method was studied. Crystal structure, surface microstructure, chemical composition, and thermal stability of synthesized materials were studied. It was shown that two-phase (α + β) alloy was synthesized. As a result of the SHS hydrogenation process, TiZrHfVNb alloy absorbed 1.8 wt % of hydrogen.

In this paper, we presented structural, Fourier infrared spectroscopic, and dielectric analysis of cobalt chromate (Co²⁺({text{Cr}}_{2}^{{3 + }})O₄) with 2 mol % of gadolinium (Gd³⁺) rare earth metal additions under humidity and non-humidity circumstances. The Gd³⁺ doped Co²⁺({text{Cr}}_{2}^{{3 + }})O₄ samples were prepared by solution combustion method and sintered for 2 h at 650°C to get single phase. Doped and undoped samples were characterized by X-ray powder diffraction (XRD) analysis providing the detailed information of the Co²⁺({text{Cr}}_{2}^{{3 + }})O₄ phase and crystallinity. Furthermore, the average crystallite sizes were found to be in the range of 18 to 7 nm. The general nature of ferrite materials was revealed via FTIR analysis. The octahedral and tetrahedral stretching band in FTIR spectra were confirmed a ferrite structure without impurity. Scanning electron microscopic images exhibited that samples are highly porosity. We investigated the relevant conductivity of the samples, the reaction time of the capacitive sensor, and the humidity influence on the relative permittivity characteristics at a constant frequency of 1 kHz. Our findings indicate that Gd³⁺ doped Co²⁺({text{Cr}}_{2}^{{3 + }})O₄ could be exploited as an active material in humidity sensor applications.

(Ti–Al–Mn)/Ti metal–intermetallic layered material was prepared by SHS pressing. It was found that the combustion product obtained in Ti–Al–Mn layer consists of hexagonal Ti(Mn_0.755Al_1.246) and cubic Ti_0.25Al_0.67Mn_0.08 phases. The transition zone forming between the Ti–Al–Mn layer and the Ti foil was shown to have a thickness of 10–15 µm and to be represented by Ti_xAl phase with variable composition.

In the present work, CuEu_0.01Fe_1.99O₄ and CuEu_0.01Sc_0.01Fe_1.98O₄ nanoparticles were prepared by self-propagating high-temperature synthesis method for reporting the structural, microstructural, and magnetic properties of prepared samples. X-ray diffraction (XRD) patterns confirmed the spinel cubic structure with space group Fd3m. An average crystallite size was found in the range of 20–40 nm. Scanning electron microscopy (SEM) investigations indicated the porous nature and particles agglomeration. The elemental composition of samples was studied by using energy-dispersive X-ray spectroscopy (EDS). The magnetic hysteresis loop revealed the soft ferromagnetic nature. Magnetic parameters such as saturation magnetization, coercivity, and remanence magnetization decrease with an increase in Eu³⁺ and Sc³⁺ concentration.

Ultra-high-temperature TiC–ZrC composites with submicron structure were synthesized by electro-thermal explosion (ETE) under pressure. The precursors for synthesis were prepared from a mixture containing Ti, Zr, and carbon black powders by high energy ball milling in hexane. The influence of mechanical activation (MA) on the metal crystalline structure was studied. It was shown that the phase composition of the precursor depends on MA duration. The partial amorphization of metal particles occurred after 40 min of MA; while after 90 min, the amorphization was completed. In the last case, carbide phase crystallites with a cubic structure were formed. It was shown that the composite synthesized from precursor activated for 40 min contains Zr_0.50Ti_0.50C single-phase solid solution with a grain size of 3–5 μm, while the composite synthesized from precursor activated for 90 min consists of Zr_0.14Ti_0.86C and Zr_0.74Ti_0.26C phases with a grain size of about 0.2 μm. The Vickers hardness of composites with a residual porosity of no more than 10% was found to be in the range from 11.3 to 18.53 GPa.

Submicron-porous ceramic materials were prepared from mixtures consisting of coarse α-Al₂O₃ filler and ultrafine binders by combined use of SHS, compaction, and sintering. Variation in starting reagent size and filler/binders ratio made it possible to control the porosity, pore size, and permeability of synthesized materials. It was found that in materials with pore size between 0.4 to 1.3 µm, pore size has a dominating influence on their permeability rather than porosity.

B–N and B–N–xSiO₂ nitride ceramics were prepared by SHS method under high pressure of nitrogen gas. It was shown that BN–10 wt % SiO₂ and BN–25 wt % SiO₂ contain h-BN as a basis with additions of B₆O and Si. h-BN–xSiO₂ ceramics were found to represent a scaly layered structure whose grain size decreased as SiO₂ was added. High SiO₂ ceramics showed high dielectric characteristics: dielectric permittivity of 5.9–13.5 and dielectric loss tangent of 0.034.

Cobalt doped Mg–Zn ferrite (Mg_(0.56)Co_(0.14)Zn_(0.30)Fe₂O₄) was synthesized by the modified sol–gel auto combustion method (MSG) in which lemon extracts were used as the source of energy. X-ray diffraction (XRD) technique was employed to confirm the formation of cubic spinel ferrite phase. The lattice parameter was evaluated to be 8.39 Å with an average crystallite size ranging from 41–51 nm. Dislocation density, mechanical properties, and hopping length were determined. Crystallite size and strain were evaluated using W–H plot and size–strain plot.

The aim of this research is to synthesize Ni–Cr₃C₂ nanocomposite powder by mechanochemical method at low temperature from initial powder oxides of NiO and Cr₂O₃. In this study, magnesium was added for the reduction of the oxide material and graphite was used for carbidification. According to the calculation of the adiabatic temperature it was found that the synthesis of the Cr₃C₂ was self propagating. The mechanochemical process was done in a high energy planetary ball mill with a ball-to-powder weight ratio of 1 : 20. XRD analysis was used for phase determination. The results showed that the Ni–Cr₃C₂ composite was gradually synthesized after 3 h milling and the synthesized products obtained during the milling process were Cr₃C₂, Ni, and MgO. Furthermore, it was seen that the addition of 10% excess Mg to the powder mixture changed the reaction from gradual stage to combustion. The morphological studies using FESEM showed that the composite powder had a semi-spherical morphology. XRD patterns and elemental map images showed that after the acid leaching process, MgO was completely removed. The study on the particle size of the composite powder by TEM showed that the size of particles was around 55 nm.