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Titanium suboxides with the general formula TinO2n−1 (n > 1.0), also referred to as Magneli phases, have been the subject of numerous studies due to their unique properties. Titanium low oxygen suboxides located at n = 1 (TiO) or below (Ti6O, Ti3O and Ti2O) are no less important; however, there is a lack of research on the synthesis of such materials. Therefore, in this article, the combustion process in a TiO2-KClO4-kAl-Flux exothermic system for 0.5 ≤ k ≤ 4.0 (k is moles of Al) is investigated experimentally and thermodynamically to synthesize TinO2n−1 ingots in the 0.5 to 1.0 range of n. The synthesis temperatures and equilibrium reaction phases are calculated with and without a KClO4 booster and several fluxes (CaF2, NaF, CaO and Na3AlF6), which are used to melt the reaction product and achieve the self-separation of the TinO2n−1 ingot from the Al2O3-containing slag. The formation TiO, Ti2O, Ti3O and Ti6O phases is confirmed via XRD analysis and the effectiveness of fluxes is highlighted.

Strontium lanthanum vanadate La1-xSrxVO3 (LSVO) is a promising anode material for electrochemical devices, especially for solid oxide fuel cells, thanks to its irregular electrical conductivity. However, the known synthesis methods are incapable of producing well-dispersed LSVO nanoparticles (NPs) with homogeneous size distribution, which partly impedes the applicability of the material. Thus, a new approach to synthesize LSVO NPs with such characteristics is of paramount importance. In the present work, we successfully prepare LSVO NPs with a high dispersion degree and homogeneous size distribution via a modified co-precipitation pathway, followed by hydrogen reduction at a temperature as low as 700 oC. The prepared LSVO NPs display uniform sizes in the range of 50 ~ 100 nm and do not contain any secondary phases, according to XRD analysis. The chemical mechanism of reactions that occur to form the LSVO is thoroughly highlighted. The work functions of NPs measured by the UPS analysis are in the 2.13 ~ 3.62 eV range, making the LSVO powders promising for use in thermionic devices. An explanation of the role of Sr substitution in work function values of LSVO is also proposed.

This study investigates two-dimensional REB6 nanostructures formation from a reaction mixture of RE2O3–B2O3–Mg–NaCl composition (RE is Ce, La, Nd, or Eu). The reaction mixture is sealed in a metal cup and is preliminarily heated in argon to reach the flash point. A combustion wave forms on the top surface of the pellet after self-ignition at ~650 °C. This wave quickly propagates through the sample and increases the sample temperature to 800–950 °C, converting the raw mixture into the final product. Processing of the final product leads to the formation of pure hexaboride phases of RE, the particles of which are in the form of nanosheets with a thickness of 50 nm (or less) and a BET surface of 23.8–50.8 m2/g. In addition, CeB6 nanosheets were tested as a catalyst in NaAlH4 dehydrogenation/hydrogenation processes. The results demonstrated that the catalytic activity of CeB6 nanosheets increases with higher portions of NaCl.

In this study, tantalum network nanoparticles are prepared from a Ta2O5+kMg 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.

This article presents a β-SiC nanopowder synthesis process based on the combustion of a Na2CO3–kSi solid system (k indicates the moles of Si) in an Ar atmosphere. The authors of this study monitored the combustion parameters (temperature and wave velocity), reaction phases, and morphological changes as the Si/Na2CO3 molar ratio was increased. The combustion reaction produced temperatures of 1235–1550°C and resulted in the formation of either carbon nanosheets (k = 1) or SiC nanopowder (k = 2–5) and sodium metasilicate (Na2SiO3) as by-product. The SiC nanopowder was tested for its suitability as an anode material for high-performance rechargeable Li-ion batteries. As a result, good battery performance was obtained, with 407 mAh g–1 at the 5th cycle and 400 mAh g–1 at the 60th cycle, at a capacity retention of approximately 98%.

This study describes the development of a one-pot strategy to produce spherical alloy microparticles for advanced near-net-shape manufacturing processes, including additive manufacturing and powder injection molding. The AlSi12 eutectic alloy (ca. 12 wt% Si) system was chosen as the model with which the main experiments were carried out. The proposed process synergistically integrates a few common, low-cost processing techniques including the mixing of Al micrometer size particles with silicon and sodium chloride, heat-treating the mixture at temperatures of 650–810 °C, and the dissolution of salt in water to produce spherical AlSi12 alloy particles without the need to rely on costly melting and atomizing techniques. This new process can use laow-cost source Al and Si powders as the raw materials to produce 10–200 μm-sized spherical particles of AlSi12. The Ansys-CFX computational fluid dynamics software was used to analyze the flow behavior of AlSi12 liquid droplets and particle size refinement in the narrow voids of the sample.

Recent developments have seen breakthroughs in zero-, one-, two-, and three-dimensional AlN micro- and nanostructures, such as nanoparticles, nanowires, nanotubes, thin films and 3D multifold symme...

Through a combinatorial approach involving theory and experiments, this study investigated the mechanism of the dendritic growth of AlN microcrystals during the combustion of Al + 0.1AlF3 + kAl2O3 powder mixtures under nitrogen-rich conditions. The experimentally observed morphology of the dendritic AlN crystals is characterized by the six-fold branches that developed outward within an equatorial plane and secondary dendrites that grew above and below the equatorial plane. The physical mechanisms that lead to the shape-controlled synthesis of AlN dendritic crystals were studied through experimental analysis and theoretical investigation including density functional theory (DFT) calculation and phase-field (PF) crystal growth modeling. Based on the DFT-calculated surface energy values, an energy minimization argument was used to construct the AlN nucleus. PF crystal growth modeling provides the details of the sequential crystallization process of the dendritic AlN crystals. The results of this study provid...

This study investigated the high-temperature stability of CSZ, YSZ, and MSZ specimens in a CaCl2-CaF2-CaO molten salt at 1200 °C for the application of the materials as oxygen-ion-conducting solid-oxide membrane anodes in the electroreduction process of metal oxides. YSZ exhibited the lowest degradation among the tested specimens in a high-temperature stability test, whereas CSZ showed the highest degradation. The weight loss was not severe with concentrations of CaO up to 10 wt%. CSZ showed peaks for m-ZrO2, YSZ showed peaks for t-ZrO2 and CaZrO3, and MSZ showed peaks for t-ZrO2 and m-ZrO2 in 0 wt% CaO. In the case of 5 wt% CaO, all specimens exhibited m-ZrO2 and CaZrO3 peaks, In the cases of 10 wt% and 20 wt% CaO, CSZ and MSZ showed peaks for CaZrO3, and YSZ showed peaks for m-ZrO2 and CaZrO3. While CSZ and MSZ became significantly looser as the CaO concentration was increased to 10 wt%, YSZ became significantly denser due to the formation of a protective layer and attack dependent on the solubility of CaO in the molten CaCl2. In terms of long-term operation, YSZ was demonstrated to possess superior high-temperature stability compared to CSZ and MSZ, and CaO concentrations from 5 wt% to 10 wt% were found to be significantly more stable than other concentrations.

The adiabatic temperatures and equilibrium phases in the FeTiO3-αMg-C(B, Si)-kNaCl 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, TiB2, and TiFeSi2 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.

This paper reports the preparation of Ti microparticles that are angular and spherical in shape through the combustion of a TiO2 + αCa (where α is moles of Ca) exothermic mixture in an inert atmosphere. The relationship between the combustion parameters and the properties of the resultant Ti particles is discussed with consideration of the effect of Ca concentration. Using excess amounts of Ca in the experiment was effective in modifying the shape of the particles from angular to spherical. The Ti powder was found to be well-dispersed and the diameter of individual particles ranged from 5 µm to 50 µm. Based on the combustion parameters, the activation energy for the redox reaction was calculated as ∼ 138 kJ/mol. This paper discusses the chemistry of the reduction process and highlights the effects of combustion temperature and the amount of liquid calcium on the characteristics of the Ti particles.

This paper demonstrates for the first time the fabrication of Zr-Cu alloy ingots from a Hf- free ZrO2 precursor in a molten CaCl2 medium to recover nuclear-grade Zr. The reduction of ZrO2 in the presence of CaO was accelerated by the formation of Ca metal in the intermediate stage of the process. Tests conducted with various amounts of ZrO2 indicate that the ZrO2 was reduced to the metallic form at low potentials applied at the cathode, and the main part of the zirconium was converted to a CuZr alloy with a different composition. The maximum oxygen content values in the CuZr alloy and Zr samples upon using liquid Cu were less than 300 and 891 ppm, respectively. However, Al contamination was observed in the CuZr during the electroreduction process. In order to solve the Al contamination problem, the fabrication process of CuZr was performed using the metallothermic reduction process, and the produced CuZr was used for electrorefining. The CuZr alloy was further purified by a molten salt electrorefining process to recover pure nuclear-grade Zr in a LiF-Ba2ZrF8-based molten salt, the latter of which was fabricated from a waste pickling acid of a Zr clad tube. After the electrorefining process, the recovered Zr metal was fabricated into nuclear-grade Zr buttons through arc melting following a salt distillation process. The results suggest that the removal of oxygen from the reduction product is a key reason for the use of a liquid CaCu reduction agent.

We developed an attractive combustion approach for synthesizing uniformly shaped AlN dendritic crystals by combustion of Al + 0.1AlF3+ kAl2O3 powder mixtures in a nitrogen atmosphere. The combustion temperature measured for various k values was between 1650 and 1750 °C and the micro-droplets of Al formed in the beginning stages of the process were enveloped by the solid layers of Al2O3, and the subsequent multipoint nucleation and crystallization produced morphologically and size uniform dendritic crystals. We proposed a theoretical model for calculating the thickness and the number of Al2O3 layers around of Al microdroplets at known concentration of Al2O3. Depending on the concentration of Al2O3, these structures were simple stars with six points and stellar dendrites with multiple petals.

With the assistance of alkali metal carbonate M2CO3 (M is Na and K) as a carbon source and silicon as a displacement agent, an exothermic and self-sustaining reaction to produce two-dimensional (2-D) hierarchically porous carbon nanosheets (denoted as HP-CNSs) was achieved. The combustion reaction developed a temperature in the range of 1100–1400 °C and resulted in a two-phase product consisting of HP-CNSs and alkali metal silicate (M2O⋅nSiO2). After dissolving the M2O⋅nSiO2 in distilled water, a black carbon powder was formed. Despite the simple synthesis process, the HP-CNSs had a BET surface area of about 178.6–860 m2g−1 and a pore diameter in the range 0.5–150 nm. HP-CNSs based capacitors showed a specific capacity of about 85–240 Fg−1 and good cyclic performance for over 1000 cycles.

The combustion phenomenon is characterized by rapid self-sustaining reactions, which can occur in the solid, liquid, or gas phase. Specific types of these reactions are used to produce valuable materials by different combustion synthesis (CS) routes. In this article, all three CS approaches, i.e. solid-phase, solution, and gas-phase flame, are reviewed to demonstrate their attractiveness for fabrication of zero-, one-, two-, and three-dimensional nanostructures of a large variety of inorganic compounds. The review involves five sections. First, a brief classification of combustion synthesis methods is given along with the scope of the article. Second, the state of art in the field of solid-phase combustion synthesis is described. Special attention is paid to the relationships between combustion parameters and structure/properties of the produced nanomaterials. The third and fourth sections describe details for controlling material structures through solution combustion synthesis and gas-phase flame synthesis, respectively. A variety of properties (e.g., thermal, electronic, electrochemical, and catalytic) associated with different types of CS nanoscale materials are discussed. The conclusion focuses on the most promising directions for future research in the field of advanced nanomaterial combustion synthesis.

In this study, a single-step combustion process for the synthesis 1-D, 2-D, and 3-D micro and nanostructures of AlN was developed. The structures were grown by combustion of Al+kAlF3 (or ZnF2)+mNH4Cl reaction mixture under 4.0 MPa nitrogen atmosphere. Based on experimental data, the growth conditions, morphology, and composition, optical, and thermal properties of AlN micro and nanostructures were determined. The formation of structures was associated with the combustion temperature, liquid and gas-phase reactions, and the type of additives used in the experiments. The new insight, we gleaned from this study may help in the selective growth of AlN micro and nanostructures of different morphology, enhancing their functionality.

In this study, we examined the effect of potassium perchlorate (KClO4) and magnesium hydroxide (Mg(OH)2) additives on the combustion behavior of a ZrO2 + 2Mg mixture to produce a fine powder of zirconium metal. The results of thermodynamic analysis and experiments imply that nearly 0.04 mol of KClO4 is needed to initiate a combustion reaction in the ZrO2 + 2Mg system. As the amount of KClO4 increases from 0.04 to 0.1 mol, the combustion temperature increases from 1250 to 1850 °C. This results in formation of fine zirconium powder with a typical particle size of less than 5 µm, and with 1.4–2.2 wt% residual oxygen. Subsequent reduction of particle size to 100–500 nm, and oxygen content to

In this paper we describe a progressive two-step process that allows zirconium fluoride (ZrF 4 ) contained in spent baths for etched zirconium alloys to be effectively recycled on a pilot scale and produce a high purity regenerated pickling acid. In the first step, a spent pickling liquor is treated by a BaF 2 suspension to produce water insoluble Ba 2 ZrF 8 . After filtration of Ba 2 ZrF 8 more than 99.9 wt % purity pickling acid is regenerated. The precipitation mechanism of Ba 2 ZrF 8 is discussed and the role of BaF 2 particles size on the precipitation process is demonstrated. In the second step the as-precipitated Ba 2 ZrF 8 is mixed with Mg and Cu metal powders and heat-treated at 1200 °C (or above) to produce CuZr alloy ingot. The characteristics of the ingot are discussed in regard to Cu concentration and the heating temperature.

The exothermic reduction of oxides mixture (MoO3+2SiO2) by magnesium in NaF melt enables the synthesis of nanocrystalline MoSi2 powders in near-quantitative yields. The combustion wave with temperature of about 1000–1200 °C was recorded in highly diluted by NaF starting mixtures. The by-products of combustion reaction (NaF and MgO) were subsequently removed by leaching with acid and washing with water. The as-prepared MoSi2 nanopowder composed of spherical and dendritic shape particles was consolidated using the spark plasma sintering method at 1200–1500 °C and 50 MPa for 10 min. The result was dense compacts (98.6% theoretical density) possessing submicron grains and exhibiting hardness of 8.74–12.92 GPa.

The nucleation and spontaneous pattern formation of AlN via the combustion of Al- kC-AlF3 mixtures (k is mol of C) in nitrogen is investigated. The formation of 2D AlN hexagonal facet micro- and nanoplates, dodecagon-type AlN crystals, and six-wing hexagons is highlighted. Phase-field simulation in 2D-space is applied to interpret and/or anticipate the growth mechanisms of such crystals in limited space.

The present study demonstrates the synthesis of fine hafnium (Hf) metal powders via a chemically activated combustion synthesis (CS) approach, which develops temperatures in the range of 1000–1600 °C. The current CS approach can be employed to obtain Hf powders with a single-crystalline hexagonal close-packed (hcp) structure in addition to high compositional uniformity and average particle sizes ranging from 0.05 to 2.0 μm. The mechanism of Hf particle formation can be understood by analyzing the process thermodynamics, including adiabatic temperatures and equilibrium reaction phases. In addition, analytical methods, including X-ray diffraction, SEM/TEM BET, FTIR, and oxygen analysis, were employed to characterize the synthesized Hf powders. Theoretical analysis was also conducted to predict the oxygen content according to Hf particle size. To the author's best knowledge, this work is the first known report demonstrating the preparation of hafnium micro- and nanopowders by the combustion synthesis method.

This paper reports a promising method to decrease the operating temperature during electrolysis of natural ilmenite to produce a porous and laminar flake-type intermetallic ferrotitanium (FexTi, x = 1, 2) with a thickness of less than 1 μm by choosing a LiCl-Li2O electrolyte with a lower operating temperature (625 °C) under an inert atmosphere. Results indicate that the Li2O content in the electrolyte has a key effect on the phase transformation of natural ilmenite occurring in the electrochemical reduction process. Full conversion of natural ilmenite into ferrotitanium products can be achieved when the Li2O amount in the electrolyte and the cell voltage are approximately 1 wt.% and −2.5 V, respectively. In addition, the electrochemical reduction mechanism of natural ilmenite is proposed and discussed based on our experimental results and thermodynamic analysis.

Tantalum is a key material that is used to produce small solid capacitors with high volumetric efficiency. To achieve higher capacitances in a given volume, Ta nanopowders (NPs) with a large surface area are required for anode preparation. In this study, we report the synthesis of porous tantalum network structures by the combustion method and its electrochemical performance as a capacitor. The network structures, which consist of Ta NPs, are formed via a high-temperature sintering process. The Ta NPs were produced with a minimum size of less than 50 nm and a BET surface area of 31.47 m2/g. Additionally, the formation of Ta porous network structures according to the Ta/Mg ratio was theoretically analysed using a phase field sintering model. According to an analysis of the electrical properties of a sintered Ta anode (k=20), a capacitance of ~190,000 μFV/g is achieved with Ta NPs having a BET surface area of 19.2 cm2/g. In the near future, we hope to achieve ~300,000 μFV/g capacitance with 31.47 m2/g BET surface area Ta NPs.

Combustion of inorganic powder mixtures is not only one of the chemical routes of fabrication of advanced inorganic materials but is also drawing attention as a high-temperature process to grow inorganic nanocrystals of various shapes and morphologies. Here, we demonstrate the formation of AlN 3-D structures with diverse morphologies: from 6-fold patterned crystals to multilayer hierarchical structures. We examined the possible chemical mechanisms governing the formation of AlN crystals and the growth behaviour based on FESEM and TEM observations.

Zirconium(Zr) nuclear fuel cladding tubes are made using a three-time pilgering and annealing process. In order to remove the oxidized layer and impurities on the surface of the tube, a pickling process is required. Zr is dissolved in HF and HNO3 mixed acid during the process and pickling waste acid, including dissolved Zr, is totally discarded after being neutralized. In this study, the waste acid was recycled by adding BaF2, which reacted with the Zr ion involved in the waste acid; Ba2ZrF8 was subsequently precipitated due to its low solubility in water. It is very difficult to extract zirconium from the as-recovered Ba2ZrF8 because its melting temperature is 1031 oC. Hence, we tried to recover Zr using an electrowinning process with a low temperature molten salt compound that was fabricated by adding ZrF4 to Ba2ZrF8 to decrease the melting point. Change of the Zr redox potential was observed using cyclic voltammetry; the voltage change of the cell was observed by polarization and chronopotentiometry. The structure of the electrodeposited Zr was analyzed and the electrodeposition characteristics were also evaluated.

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.

The present investigation studied the recycling of zinc from brass ash which is a secondary product produced during the brass smelting process. A retiring cycle was devised to produce high-purity ZnO nanopowders. Recovery of > 90 wt% of the total zinc available was achieved after the calcination of brass ash at 700 °C and a multistage hydrometallurgical treatment at room temperature. ZnO powder produced by the developed method was analyzed by X-ray diffraction, transmission electron scanning microscopy, ICP-AES and BET analysis. The ZnO nanopowder obtained from the brass ash was well dispersed and the size of the individual particles was in the range of 30–50 nm. The purity of the powder was 99.83 wt%, and the surface area was about 30.5 m 2 /g. A relative density level of about 98.1% was reached with ZnO pellets sintered at 1300 °C.

For the first time, we experimentally detected the formation of 6-fold symmetry patterned microcrystals of AlN (aluminum nitride), such as simple prisms, stellar and sectored plates, and stellar and fernlike stellar dendrites. These crystals were formed during combustion of a solid mixture of Al + kAlF3 (k = 0.05–0.1 mol) under a nitrogen atmosphere (PN2 = 2.5 MPa). The combustion temperature recorded with a thermocouple was in the 1700–1900 °C range. We examined the physical mechanisms governing the formation of AlN crystals, and we treated this problem as a case study of the dynamics of crystal growth from the liquid phase. Particular attention was given to the basic theoretical understanding of the subject, utilizing first-principles density functional theory calculations. The Wulff construction method was applied to identify equilibrium structures of nano- and microscale AlN crystals. Energy minimization arguments were used to show that certain crystal planes of AlN are more probable than others, givi...

Hollow carbon nanospheres as potential cathode materials for lithium-sulfur (Li-S) batteries were successfully synthesized using a metathesis reaction between sodium azide and halogen polymer. The reaction was driven by thermal heat from the exothermic recombination of Na+ and Cl− (or F−) ions into NaCl (or NaF) salts. The result was an increase of the overall system temperature up to 1320–1750 °C followed by the simultaneous formation of sodium halide-carbon core–shell nanoparticles. Therefore, hollow carbon nanospheres with diameter and shell thickness of ∼50–500 nm and ∼10–50 nm, respectively, were produced after water washing of the reaction product. The composite cathode materials for Li-S batteries were manufactured by infiltrating sulfur into the hollow core of nanospheres. The electrochemical cycling showed discharge capacity of ∼700 mAh g−1 (after 100 cycles) at 0.5 C current rate which is more than ∼2.4 times larger than that for the sulfur/carbon black composites prepared by the same technique. The enhancement of battery performance was attributed to the well-organized and unique 3D structure of hollow carbon, enabling better utilization of sulfur.

In this paper, the formation of β-Si3N4 3D self-assemblies via combustion of Si-(C2F4)n-KClO4 solid mixture in nitrogen atmosphere is demonstrated. The coupling of (C2F4)n and KClO4 additives with Si powder stimulates the combustion-nitridation process and leads to the formation and 3D self-assemblies composed of β-Si3N4 prismatic crystals. The self-assemblies are classified as sheet-type, circular-type, castle-type geometry objects, high symmetry multipods and ‘crystals bouquets’ having a central junction. The formation of 3D self-assemblies is based on prismatic crystals twining process and among twinned structures, penetration, contact and circular twins were distinguished. Based on SEM and TEM results a scheme showing the growth process of self-assemblies is proposed.

In this paper, we describe a progressive two-step process that allows titanium and zirconium fluorides (TiF4, ZrF4) contained in spent liquors of etched Ti and Zr alloys to be effectively recycled into CuTi and CuZr alloy compositions and a regenerated pickling acid of high purity. In the first step, spent pickling liquor is treated with a BaF2 suspension to produce water-insoluble BaTiF6 and Ba2ZrF8 fluoride salts. In the second step, the as-precipitated BaTiF6 and Ba2ZrF8 fluoride salts are mixed with Mg and Cu metals powder and heat-treated at 1300 °C to produce CuTi and CuZr alloy ingots. The microstructures of the ingots are discussed in regard to Cu concentration.

Silicone polymers, more accurately referred to as polysiloxanes (PSs), do not have carbon as part of the backbone structure and thus can serve as sustainable precursors for the fabrication of Si nanoparticles (Si NPs) for applications as anode materials for lithium ion batteries. First, PS is burnt in air and the combustion product is calcined at 800 °C to produce carbon free SiO2 nanoparticles (SiO2 NPs). Then SiO2 NPs are reduced by Mg under combustion regime, in the presence of NaCl. Si NPs between 5 and 100 nm is obtained by changing the concentration of NaCl. The Si NPs are tested as an anode material for Li-ion battery (LIB). The cycling performance and rate capability of LIB anodes are measured according to the size of the Si NPs. The results showed good cycling performance over 300 cycles with a low fading rate of 0.04% per cycle at 1 C and a high coulombic efficiency above 98%.

High-quality two-dimensional (2D) nanosheets of B4C were synthesized using a facile combustion reaction with a reaction mixture comprising boron oxide (B2O3), magnesium (Mg), and polyvinylchloride (C2H3Cl)n. The ability to tune the nanosheets of boron carbide was achieved by controlling the combustion temperature within a range of 1500–1700 °C and by using polyvinylchloride powder as the carbon source. FE-SEM and TEM images of the acid leached combustion products show sheet-like B4C particles with thicknesses of about 10–50 nm and edge lengths from 0.1 to several micrometers. The chemistry of the combustion process and the formation mechanism of B4C nanosheets are discussed based on the experimental findings.

The harsh atmosphere of the sulfur–iodine process used for producing hydrogen requires better corrosion resistance and mechanical properties than are possible to obtain with pure tantalum. Ta–W alloy is superior to pure tantalum but is difficult to alloy due to its high melting temperature. In this study, substrate samples were coated with Ta–W (Ta–7W, Ta–4W and Ta–1W) using the Multi-Anode Reactive alloy Coating (MARC) process in molten salt (LiF–NaF–K 2 TaF 7 ), with varying distances between cathode and anode. In the case of Ta–4W, a corrosion rate of less than 0.011 mm/year was attained in hydriodic acid at 160 °C, and thickness uniformity was 80.3 ± 2.15 μm. Also, the resulting coated films had hardnesses up to 12.9% stronger than pure tantalum coated film. The alloy coating films also contributed to significant enhancement of corrosion resistance.

Combustion based synthesis of AlN nanoparticles using the “solid nitrogen” promotion reaction was investigated in Al2O3 + 3Mg system in nitrogen atmosphere. A controlled amount of Mg + 0.5NH4Cl mixture as a solid source of nitrogen was blended with the Al2O3 + 3Mg starting system and the synthesis reaction of AlN nanoparticles was conducted using the exothermic heat of the entire reaction system. The resulting AlN nanoparticles were characterized by X-ray diffraction (XRD), Raman and Fourier transform infrared spectroscopy (FTIR), PL spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller surface area techniques. The analysis results confirmed that single phase and crystalline AlN nanoparticles with an average size of 50–500 nm were obtained from the developed approach. Photoluminescence spectra of AlN nanopowders under the excitation of 230–270 nm UV light revealed that AlN emits yellow-red light having a wavelength near to 590 nm. The chemistry of the combustion process is discussed and the basic reactions that led to the formation of AlN are presented.

A melt-assisted solid flame synthesis approach was applied to synthesize boron nanoparticles in argon gas and air atmospheres. For this purpose, we investigated the characteristics of a thermally induced combustion wave in B 2 O 3 + α Mg mixtures ( α = 1.0–1.5 mol) in argon and air atmospheres. Utilizing stoichiometrically insufficient amounts of magnesium ensured that a large portion of molten B 2 O 3 remained in the sample, which reduced the combustion parameters and favored the formation of boron nanoparticles. Under these conditions the combustion temperature and burning velocity were controlled in the range of 1300–1580 °C and 0.065–0.18 cm/s, respectively, and boron nanoparticles in a ∼20–200 nm size range were obtained. The characteristics of boron nanoparticles (morphology, purity, specific surface area, oxidation activity, etc.) were analyzed and a reaction pathway leading to boron nanoparticles synthesis was proposed.

The precipitation behaviors of intergranular carbides on various types of grain boundaries and their effect on tensile properties at room temperature were investigated systematically in Inconel 690 tubes. Precipitates of intergranular chromium carbide were identified as Cr-rich M23C6. It was observed that the M23C6 carbide behavior is obviously influenced by grain boundary character and interfacial energy. The intergranular M23C6 carbides were suppressed on low-angle boundaries and coincidence-site lattice boundaries. Plenty of M23C6 carbides precipitated at random high-angle boundaries with high interfacial energy. With increasing aging time, the precipitated carbides became coarse and grew into the matrix near grain boundaries. The ultimate tensile strength and elongation of the Inconel 690 tube solution annealed at 1373 K (1100 °C) for 15 minutes were 671.2 MPa and 47.2 pct, respectively. After aging treatment, the ultimate tensile strength and elongation drastically decreased with increasing aging time. The tensile test generated a number of cracks at the grain boundaries due to coarse intergranular M23C6 carbides near the fracture. Both the decrease of ultimate tensile strength and elongation of the aged Inconel 690 tube were mainly caused by breaking of the coarse M23C6 carbide and reduced chromium concentration in the matrix.

We have investigated a thermally induced combustion route for preparing 2D hexagonal BN nanoplates from B2O3+(3+0.5k)Mg+kNH4Cl solid system, for k=1–4 interval. Temperature–time profiles recorded by thermocouples indicated the existence of two sequential exothermic processes in the combustion wave leading to the BN nanoplates formation. The resulting BN nanoplates were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy, PL spectrometry, and Brunauer–Emmett–Teller surface area analysis. It was found that B2O3 was converted into BN completely (by XRD) at 1450–1930 °C within tens of seconds in a single-step synthesis process. The BN prepared at a k=1–4 interval comprised well-shaped nanoplates with an average edge length ranging from 50 nm to several micrometer and thickness from 5 to 100 nm. The specific surface area of BN nanoplates was 13.7 g/m2 for k=2 and 28.4 m2/g for k=4.

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.

We demonstrated a facile approach for synthesizing three-dimensional (3D), honeycomb-structured graphene scaffold in the solid flame of a (0.5+ k ) Zn+ k CuO+(CH 2 -CHCl)n reaction system. FESEM-based analyses of the acid purified porous graphene samples revealed that the synthesized graphene had a 3D, honeycomb-like structure with cell sizes of 20–100 nm and wall thicknesses of 1–3 nm. The specific surface area of the graphene sample prepared in the solid flame was about ~1043 m 2 /g).

In this study, we demonstrate the synthesis of few-atomic-layer hexagonal boron nitride (h-BN) sheets in a solid thermal wave implemented in a B2O3 + (3 + 0.5k)Mg + kNH4Cl exothermic mixture (here, k is the mole number of NH4Cl). The maximum synthesis temperature, developed using a thermal wave, was between 1030 and 1250 °C as k was changed from 5 to 7 moles. The phase content, morphology, and optical properties of the products were characterized. It is shown that BN sheets synthesized at the given k were 1.5–3 nm thick and had a hexagonal structure. The number of atomic layers in one sheet ranged from 5 to 10; the lateral dimension of individual sheets ranged from 50 to 1000 nm. The developed method allowed the synthesis of a large amount of uniform and high quality BN nanosheets (tens of grams in laboratory-scale experiments); this method will reduce the overall production cost.

Electroless deposition reaction (EDR) is a promising route for the synthesis of copper (Cu) and silver (Ag) dendritic structures with a controllable morphology. Here, we demonstrate the use of an electroless deposition reaction on the interface between an iron foil and aqueous solutions of either Cu or Ag salts to produce well-defined Cu and Ag dendritic nanostructures at room temperature. The dendritic structures and morphology were characterized based on the reaction time, Cu and Ag salt concentration, and diethylene glycol (DEG) content in the aqueous solution. We also demonstrate control over the dendrite sizes, morphologies and growth mechanisms. The electrical resistivity and improved sheet resistance were also evaluated in an anisotropic conductive film prepared from dendritic silver powder.

Amorphous boron nanoparticles were synthesized by heating a B 2 O 3 + 3 Mg + k NaCl ( k is the number of moles of NaCl) exothermic mixture in a laboratory oven at 800 °C under argon flow. NaCl was used as inert material to decrease the maximum combustion temperature of the reaction mixture when it was self-ignited after the melting of Mg at 650 °C. The size of the boron nanoparticles extracted from the final product by acid leaching ranged between 30 and 300 nm for k values ranging from 1 to 5. Moreover, increasing the value of k from 1 to 5 resulted in an increase in the specific surface area of the nanoparticles from 40 to 74 m 2 g −1 . However, at k = 10, a decrease in the specific surface area to 47.56 m 2 g −1 was recorded due to incomplete reduction of B 2 O 3 . The ignition point of boron nanoparticles in air as estimated using a thermocouple was approximately 300 °C. Digital camera recording of the combustion process of boron nanoparticles in air revealed that the burning speed of the nanoparticles increased significantly from 0.3 to 15 cm/s when k increased from 1 to 5.

A facile synthesis method has been developed to directly convert solid Na 2 SiO 3 hollow microspheres into non-aggregated hollow SiO 2 microspheres at ambient pressure and temperature. An initial dispersion of Na 2 SiO 3 microspheres (mean diameter: 10–50 μm) in ethanol was prepared, and subsequent hydrolysis of Na 2 SiO 3 was performed using a HCl solution. Other precipitants such as ammonium salts (NH 4 Cl, (NH 4 ) 2 SO 4 ) and boron oxide (B 2 O 3 ) were also tested. The characteristics of the synthesized hollow microspheres were investigated in detail by thermogravimetric analysis, field emission scanning electron microscopy, N 2 adsorption–desorption isotherms, and X-ray diffraction. The as-prepared SiO 2 microspheres were hollow with diameters between 10 and 50 μm. The surface area of these microspheres, determined by Brunauer–Emmett–Teller analysis, was in the range 193–288 m 2 g −1 . Using the proposed method, the size and shape of the obtained silica microspheres are largely determined by the size of low-cost and environmentally friendly precursor sodium silicate microspheres.

Herein, we present the low-temperature solid-phase combustion synthesis of tantalum carbide (TaC), TaC/tantalum silicide (TaSi2), and TaC/tantalum boride (TaB) nanoparticles by the silicothermic reduction of potassium fluorotantalate (K2TaF7) in the presence of carbon, boron, and polytetrafluoroethylene (PTFE, 1 (C2F4)n). The temperature–time profiles of the combustion wave were measured by thermocouples and used to calculate the combustion parameters: temperature and wave velocity. The flame temperature was found to increase with the concentration of PTFE. Using high resolution transmission electron microscopy, a homogeneous distribution of highly crystalline nanoparticles was observed. The thermal–kinetic activation energy, the heat released during each of the individual reactions, and the chemical mechanism of the overall combustion process are discussed with respect to the final products.

High-purity Nd metal was recovered from waste Nd–Fe–B magnet by the molten salt electrowinning process with chemical pretreatment. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), cyclic voltammetry (CV), chronopotentiometry (CP), and inductively coupled plasma-atomic emission spectrometer (ICP/AES) were used to characterize the deposit and electrochemical behaviors. The results show that NdF3 is effectively synthesized from the Nd–Fe–B magnet using HCl solution and NH4F. During the chemical treatment of the waste magnet, iron impurity is eliminated as a soluble [NH4]3[FeF6] complex. Electrowinning using NdF3 in LiF molten salt shows that Nd metal is deposited from the electrolyte on the cathode at the reduction potentials ranging from −1.48 to −1.35 V (vs. W) with the concentration change of NdF3. The final purity of Nd metal deposit is higher than 99.78 %.