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In this study, tantalum network nanoparticles are prepared from a Ta 2 O 5 + k Mg system via a liquid magnesium-controlled combustion reaction. Super-stoichiometric amounts of magnesium are used in the preparation of a reaction mixture to produce a liquid magnesium pool capable of lowering the combustion temperature and leading to the formation of Ta network structures. The heat transfer kinetics from the hot reaction zone of 'cold' Mg particles is determined using heat transfer-coupled fluid dynamics simulation software. The formation of network structures is characterized through SEM, TEM, XRD, and BET analysis techniques. The mechanism of network formation is explained based on solid particle collisions in liquid media. Our method is able to produce Ta network structures in which the size of individual particles ranges between 50 and 700 nm. [ABSTRACT FROM AUTHOR]

Abstract The adiabatic temperatures and equilibrium phases in the FeTiO 3 - α Mg-C(B, Si)- k NaCl system (where α = 0.2–15, k = 0–3) were analyzed to predict the formation of fine powders of titanium compounds from natural ilmenite sand. From the parametric study, the critical variables were identified and optimized for the synthesis of FeTi, TiC, TiB 2 , and TiFeSi 2 under a combustion regime. The experimentally measured temperatures were in good agreement with those predicted from thermochemical calculations in the 900–1800 °C range. The purified products were characterized using X-ray diffraction, transmission electron microscopy, and Raman spectroscopy. The fine powders of titanium compounds were mainly single phase with a purity of at least 95 wt%. Considering the various stages of the synthetic process, a mechanism is proposed to explain how the process of ilmenite recovery occurred. Graphical abstract Image Highlights • Natural ilmenite was used as a precursor for synthesizing Ti compounds. • Combustion temperatures and phases were determined in FeTiO 3 -αMg-C(B, Si)- k NaCl system. • The effect of Mg and NaCl concentration on the combustion temperature was revealed. • The ilmenite was converted into FeTi, TiC, TiB 2, and FeTiSi 2 fine powders. • A reduction pathway in the synthesis of Ti compounds was proposed. [ABSTRACT FROM AUTHOR]

In this study, a combustion process for a TiO 2 + 0.12Al + (2.5 + 6 k )Mg + 0.021V 2 O 5 + k MgCl 2 ·6H 2 O mixture was studied to fabricate Ti-6Al-4V alloy spherical particles. From the temperature-time profiles, the average value of the synthesis temperature was estimated to be 1650 ± 20 °C. Based on FESEM observations, spherical shape particles were obtained when 0.05–0.1 mol MgCl 2 ·6H 2 O was added to the initial reaction mixture. Therefore, spherical alloy particles were achieved by consecutive processes of cooling and acid purification of the burned down sample. According to laser particle size analysis, the average diameter of the spheres was between 5 and 25 μm. A selective laser melting process was applied to build dense Ti-6Al-4V alloy samples. The tensile properties and the microhardness were evaluated and compared to those characteristics of a reference sample prepared from commercial Ti-6Al-4V alloy spherical powder. [ABSTRACT FROM AUTHOR]

This study deals with combustion behavior of B 2 O 3 /Mg/NH 4 Cl/C complex systems for the synthesis of amorphous boron (B), boron carbide (B 4 C), and boron nitride (BN) nanostructures. The raw mixtures used in the experiments were prepared on the base of a B 2 O 3 –Mg precursor mixture, which is sufficiently exothermic to maintain a self-propagating regime of the combustion reaction. Thermodynamic analysis of the combustion temperatures and experimental validation indicate that the 1000–1500 °C temperature range is very effective for synthesizing the nanostructures of B, B 4 C, and BN. It was found that B-containing functional nanostructures are mainly spherical nanoparticles (B) or nanosheets (B 4 C, BN). The phase composition and microstructural characteristics of the final products were evaluated based on the combustion temperature and solid/liquid phase changes. [ABSTRACT FROM AUTHOR]

The synthesis of AlN nanoparticles in non-isothermal high-temperature conditions was developed. The process involved Al 2 O 3 –Mg–NH 4 Cl mixtures preparation and combustion in nitrogen atmosphere. Temperature profiles in the combustion waves were recorded by thermocouples, and the values of combustion temperature and wave velocity were determined from the recorded profiles. The existence of two independed combustion regimes with maximum temperatures of about 850 °C and 1400–1600 °C were revealed based on concentrations of NH 4 Cl. AlN nanocrystals were obtained and investigated by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller surface area. AlN nanocrystals prepared under non-isothermal combustion process were comprised well distributed multi-faceted particles with an average size of 50–200 nm. The chemical reactions in the combustion wave were discussed and a possible thermochemical pathway for the synthesis of AlN nanoparticles was proposed. [ABSTRACT FROM AUTHOR]