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

The stability of combustion of titanium + carbon black powder mixture to a local excess of the component was experimentally studied. The influence of the spreading of titanium melt or liquid reaction product on the stability of the combustion transition through transverse carbon powder barrier was considered. The direction of melt movement with respect to the front propagation direction was determined. It was shown that the stability of the combustion transition through the barrier is determined by thermal interaction between the combustion wave and the barrier and is not directly related to the convective heat transfer by the melt.

This paper presents an in-depth study on the combustion synthesis, solid-solution formation, processing, and characterization of NbB₂–HfB₂ ceramics, aiming to explore their potential applications, particularly in industries requiring high-performance materials. We conducted macrokinetic measurements and fitted regression models to predict combustion temperature and velocity for compositions ranging from 50 to 100% HfB₂. A combined method of ball milling and hot pressing was developed for processing the combustion products into dense ceramics. These methods resulted in samples with relative densities reaching 97%, hardness of up to 34 GPa, and Young’s modulus of up to 530 GPa, with NbB₂–50% HfB₂ solid solution exhibiting the best mechanical properties. The study revealed a linear increase in thermal properties and density with the rise in HfB₂ content. The thermal conductivity of the solid solutions in the Nb–Hf–B system ranged from 34 to 40 W/mK and was found to increase with temperature, making these ceramics suitable for ultra-high-temperature applications. The findings have significant implications for aerospace and high-performance engineering sectors and provide a solid foundation for further investigation of Nb–Hf–B ceramics under real-world operational conditions.

Co–Ni supported catalysts were prepared by low-temperature combustion of dried mixture of solutions of cobalt and nickel nitrates and urea after impregnation of silica fabric (>97% SiO₂) premodified with 5, 10, and 15 wt % Al₂O₃. Modification of support was carried out by low-temperature combustion of dried mixture of solutions of aluminum nitrate and urea. Prepared supports and related catalysts were characterized by XRD, SEM, EDS, and BET method. The unreduced catalysts were found to contain oxides and complex oxides of nickel and cobalt. Reduction of catalysts with hydrogen at 400°C for 1 h was shown to contribute to forming metallic phases of Co and Ni; however, the nickel phase was detected only in reduced catalyst on unmodified fabric. The catalytic activity of catalysts was determined in the temperature range of 150–400°С. It was found that the reduced catalyst on support modified with 5 wt % Al₂O₃ possesses the highest CO₂ conversion (61.8%) and methane yield (3.61 vol %) at 400°С.

: Forced SHS compaction, mechanical activation, titanium nickelide, combustion temperature, burning velocity, phase composition

The solution combustion synthesis (SСS) was used to prepare ZnO from mixtures of solutions of zinc nitrate (oxidizer) and citric acid (fuel) with different fuel-to-oxidizer ratio, as well as for doping ZnO with one of the elements Fe, Co, Cu, and Mg whose concentration was 0.1, 0.3, 1, 3, 10, and 15 wt % when adding corresponding doping element nitrate to the reagent mixture. Combustion characteristics (ignition delay time, combustion duration, coefficient of product mass conservation), composition, and structure of combustion products were studied. It was shown that the content of carbon impurities in the combustion product can be reduced from 8–30 to 1 wt % as a result of calcination for 1 h at 650°C. Calcinated and attrition-ground ZnO powder consisting of individual highly dispersed (<1 µm) nano-sized and submicron ZnO particles with an average crystallite size of 40 nm and sintered porous agglomerates ranging in size from 0.2 to 100 µm was found to exhibit high photocatalytic activity in the decomposition of phenol under ultraviolet irradiation. Doping ZnO with elements Fe, Co, and Cu decreased the photocatalytic activity, and only doping with 1 wt % Mg markedly increased it. However, both undoped and doped ZnO were not effective in photocatalytic decomposition of phenol under visible light.

combustion, self-propagating high-temperature synthesis (SHS), Mo-based cast ceramic, gravity forces

Light turquoise pigment was synthesized by solution combustion of a mixture containing Al(OH)₃, solutions of boric, citric, and phosphoric acids, and copper nitrate and subsequent annealing at temperatures up to 900°C. To increase the thermal stability of pigments, the synthesis was carried out using an aluminophosphate binder. The synthesized pigments were found to contain amorphous borates, boron phosphate, phosphates and pyrophosphates of aluminum and copper. The copper phosphide CuP₂ impurity formed during the synthesis process and subsequent annealing at 700°C gives the pigment a grayish tint but increases its anticorrosion properties.

Using scanning electron microscopy, X-ray phase analysis, and hardness measurement we investigated the structure, phase composition, and mechanical properties of Ni₃Al–TiC composite (TiC content varied in the interval from 0 to 30 vol %) fabricated by self-propagating high-temperature synthesis in the thermal explosion mode from a powder mixture of nickel, aluminum, and titanium carbide. It was found that the synthesis of Ni₃Al intermetallic compound occurred almost completely when TiC content in the green powder mixture was up to 15 vol %. TiC particles were arranged in clusters and individually. Each particle, including in the clusters, was surrounded with the matrix material. The hardness of the composite essentially increased with an increase in the TiC content in the green powder mixture up to 10 vol %. Then the hardness gain was slow. The matrix of the composite contained Ni₃Al and NiAl intermetallic phases as well as unreacted nickel when the fraction of TiC in the green powder mixture increased to 30 vol %. TiC particles were adjacent to each other in the clusters and there was a free volume between them. Thus, it was concluded that the synthesis of Ni₃Al–TiC composite under thermal explosion condition from the mixture of nickel, aluminum, and titanium carbide powders satisfactorily took place when the fraction of titanium carbide in the green powder mixture was 15 vol % and less.

MgAlON were prepared by self-propagation high temperature synthesis (SHS) using powder and granular mixtures of aluminum, aluminum oxide, magnesium oxide, and magnesium perchlorate. The influence of granulation of starting particles of Al + Al₂O₃ + MgO + Mg(ClO₄)₂ powder mixtures on the microstructure and phase composition of combustion products was studied. It was revealed that the granulation of mixtures reduces the combustion temperature and burning velocity. It was found that the combustion products derived from granular mixtures consists of up to four phases (MgAlON, aluminum oxide, aluminum nitride, and unreacted aluminum), while the products of powder mixtures are represented by single MgAlON phase.