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

The effect of mechanical activation (MA) on the characteristics of Ti + C reaction mixtures, their combustion kinetics, and the microstructure of TiC ceramics synthesized via forced SHS compaction was studied. It was shown that increasing MA time enhances the Ti–C contact surface, which directly dictates a ten-fold rise in burning velocity and a 3.5-fold decrease in TiC grain size.

Gadolinium aluminate and barium-doped gadolinium aluminate were prepared by a cost-effective planetary ball milling technique, followed by calcination at 1300°C for 4 h. The doping of Ba into GdAlO₃ led to unique structural and surface properties of the samples. The structural, optical, and morphological characteristics of the synthesized materials were analyzed by powder X-ray diffraction (XRD), Fourier transform infrared spectrophotometer (FTIR), UV-vis spectroscopy, field emission scanning electron microscope (FE-SEM), and X-ray photoelectron spectroscopy (XPS). The structural phase of the calcinated materials was orthorhombic of the space group Pnma, confirmed by XRD analysis. Rietveld refinement method was used to identify the lattice parameters and R-factors. FTIR spectra showed the metal–oxygen bonds at 654 and 488 cm^–1. The optical band gap energy of the materials was calculated in the range from 3.47 to 3.63 eV, using the Tauc plots from UV-vis analysis. The surface morphology and elemental composition of the materials were analyzed using FE-SEM and energy-dispersive X-ray spectroscopy (EDS). The oxidation states of Gd³⁺, Ba²⁺, and Al³⁺ for the prepared materials were evaluated by XPS analysis. Ba-doped GdAlO₃ samples exhibited dose-dependent antioxidant activity, achieving highest scavenging potential of 34.1%. The enhanced activity was attributed to barium-induced structural modifications, including increased surface reactivity and oxygen vacancy formation.

Mathematical modeling methods were employed to analyze the combustion failure of cylindrical samples in a gas-free mode under conductive and radiant heat loss conditions. A method was proposed for estimating critical parameters, including critical cylinder diameter, as well as temperature and velocity at the combustion limit under non–adiabatic combustion conditions. It was shown that experimentally determined front velocities allow for the calculation of the dimensional critical cylinder radius. The influence of the multi-dimensional nature of a non-adiabatic front on critical combustion conditions was investigated.

Thermal explosion method was employed to create TiC-based cermet with medium-entropy NiCoCr binder. The process involved heating a mixture of mechanically alloyed NiCoCr powder, Ti, and C in argon. Pre-explosion analysis revealed solid-phase diffusion of Ti and C into NiCoCr lattice, leading to subsequent reaction. Microstructural comparisons were conducted between cermets derived from mixtures utilizing NiCoCr alloy binder and those employing starting metal mixture (Ni + Co + Cr).

In this study, the influence of key mechanical processing parameters in a planetary ball mill, including jar rotation speed, milling duration, and speed ratio between the jar and the planetary disk (parameter K), was investigated with respect to the formation of composite reactive particles for self-propagating high-temperature synthesis (SHS) involving powders of varying ductility (Ni–Al, Ti–Si, Si–C). Both low-energy and high-energy ball milling were found to induce significant changes in particle morphology, amorphization of the crystal structure, and mechanochemical transformations in the studied systems. The results highlighted the critical importance of processing parameter control for tailoring the properties of composite materials. The synthesis of layered, multicomponent composites based on Ta/Ti/Nb/Zr/Hf, intended as precursors for subsequent SHS of high-entropy compounds, was demonstrated. Additionally, methods for producing reactive spherical Ti/Al powders and for surface modification of spherical AlSi10Mg powders for additive manufacturing applications were developed. Adjustment of parameter K influences not only the structure and particle size of the milled powders, but also the initiation temperature of SHS reactions. Optimal values of K facilitate the achievement of minimal ignition thresholds, whereas deviations from these values lead to a decrease in the reactivity of the powder mixtures. These findings confirm that the careful selection of milling regime and K value allows effective control over grinding, mechanochemical activation, and mechanochemical synthesis, opening new opportunities for the fabrication of nanocomposite materials with tailored functional and structural characteristics. This capability is of significant relevance to the development of advanced materials across a range of applications, including additive manufacturing and synthesis of high‑entropy compounds.

The Ti–6Al–4V alloy was prepared by self-propagating high-temperature synthesis (SHS) through aluminothermic reduction of V₂O₅. Guided by thermodynamic analysis, the combustion behavior of 0.9TiH₂ + 0.019V₂O₅ + xAl + yKBrO₃ mixture was investigated at 0.5 MPa argon pressure. Aluminum served both to reduce vanadium oxide and to supply the required alloying component to Ti–6Al–4V alloy. A self-sustaining combustion reaction was achieved only with the addition of potassium bromate (KBrO₃) as an auxiliary oxidizer. Optimal conditions of Ti–6Al–4V alloy synthesis were established using the composition 0.9TiH₂ + 0.019V₂O₅ + 0.177Al + yKBrO₃, with y ranging from 0.04 to 0.05. Within this range, combustion temperatures reached 1250–1350°C. By-products (KBr, Al₂O₃) of the combustion were removed by basic leaching. The synthesized alloy was characterized by X-ray diffraction analysis, particle size analysis, and scanning electron microscopy.

The effect of the particle size of Ti powders from different batches of the same brand and the binder content up to 30% on the combustion pattern and phase composition of TiC–CoCrFeNiAl metal ceramics synthesized from bulk-density powder mixtures was studied. The different dependence of the combustion velocity of titanium-based mixtures on the total content of high-entropy binder components was explained using convective–conductive combustion model by different conditions of heating the titanium particles ahead of the combustion front. The inhibitory effect of the impurity gas on the combustion front velocity of powder mixtures was determined quantitatively. The analysis of the combustion products' phase composition revealed that using finely dispersed titanium in cermet production resulted in a product free of intermetallic side phases for all X below 30%. In contrast, using coarse titanium achieved this only at X = 30%.

In this study, Mn_xNi_1–xFe₂O₄ (x = 0 to 1) nanoparticles (MNPs) were prepared by a sol–gel auto-combustion route. The X-ray diffraction (XRD) analysis, Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM) measurements are used to investigate the effect of Mn substitution on the structure and magnetic properties of the samples. The XRD patterns confirmed that all the samples show a cubic spinel structure; further, the spinel structure of ferrite is validated by FTIR. As Mn²⁺ ion concentration increases, the peak of the Fe–O bond moves to a lower frequency at tetrahedral sites. Transmission electron microscopy (TEM) analysis depicted particle sizes ranging from 47.70 ± 2.6 to 56.74 ± 3.1 nm with increasing Mn²⁺ substitution. The saturation magnetization (M_s) increased from 26.21 to 34.95 emu/g, while the coercivity (H_c) remained negligible with increasing Mn²⁺ content. The self-heating characteristics of Mn_xNi_1–xFe₂O₄ (x = 0 to 1) MNPs in an AC magnetic field were evaluated by specific absorption rate (SAR) and intrinsic loss power, both of which were presented with varying MNPs composition and field amplitudes. The optimized Mn_0.2Ni_0.8Fe₂O₄ MNPs can be used as a promising candidate for hyperthermia applications.

Cast refractory high-entropy alloys based on Nb–Ta–Hf, alloyed with 3d transition metals (Zr, Cr, V, Ti) and lanthanides (Gd, La + Ce), were successfully synthesized using a combined centrifugal casting–SHS method from thermite-type green mixtures containing target metal oxides. XRD and SEM analysis revealed that the primary phase in the synthesized alloys is a bcc solid solution. Introduction of alloying elements resulted in the formation of new structural precipitates, exhibiting bcc, fcc, and hcp structures, thus yielding complex multiphase microstructures.