Search Results (62)

Based on the thermodynamic design of metallurgical reduction, this paper investigates the thermodynamic principles and reaction regulation mechanism of aluminothermic self-propagating reduction for the in situ synthesis of a Ti₄₅Al₈Nb (at%) titanium–aluminum–niobium alloy. The influence of the aluminum distribution coefficient (ADC) on the self-propagating reaction process was verified via high-temperature thermal state experiments. The results show that the thermodynamically predicted trends of phase composition and alloy composition are consistent with the experimental results, with only a ~20% lateral offset in the ADC. When the ADC is set to 0.8, the mass fractions of Ti, Al, Nb, O, and N in the alloy are 51.8%, 29.5%, 17.4%, 1.2%, and 0.0016%, respectively, with a homogeneous microstructure and inclusion size no larger than 8 µm. The alloy presents a typical coarse-grained structure, where 83.1% of the total grain boundary length is low-angle grain boundaries, and the <111> orientation is dominant. A low-energy coherent interface is formed between the Ti-enriched and Nb-enriched regions by TiAl, TiAl₃ and Al₃Nb phases, which enhances the structural stability of the alloy. Full article

Conventional titanium alloy production based on the Kroll process features high energy consumption and long procedures, making low-cost, short-process fabrication a research focus in titanium metallurgy. In this work, low-interstitial γ-TiAl alloys were prepared via a coupled self-propagating high-temperature synthesis (SHS)–slag washing refining–vacuum arc remelting (VAR) process using TiO₂ as the raw material. Slag washing refining was performed at 1750 °C with 150 g of CaO-Al₂O₃-SiO₂-CaF₂ mold flux and 1.5 wt.% Ca, followed by VAR under a vacuum of 10⁻²–10⁻³ Pa. γ-TiAl alloy with a composition of Ti 66.01 ± 0.5 wt.%, Al 33.8 ± 0.5 wt.%, O 0.054 ± 0.002 wt.%, N 0.046 ± 0.005 wt.%, and C 0.085 ± 0.008 wt.% was obtained, and the inclusion size was refined to 0–3 μm. This coupled approach provides a scalable, low-cost route for the industrial preparation of low-interstitial γ-TiAl alloys. Full article

Phase formation characteristics during the thermochemical reduction of metals from natural coltan using aluminum and calcium–aluminum alloy at 1400–1450 °C were investigated to develop methods for extracting niobium and tantalum from rare metal raw materials. The studied coltan sample consists of a columbite–tantalite solid solution with the composition (Mn,Fe)(Nb,Ta)₂O₆, cassiterite Sn_0.9O₂, tapiolite (Ta,Nb)₂(Mn,Fe)O₆, and calcioolivine Ca₂SiO₄. This study established that the choice of reducing agent determines the sequence of oxide phase transformations. During the aluminothermic process, orthorhombic columbite–tantalite is completely reduced, while tetragonal tapiolite persists even at 1400 °C. The use of a calcium–aluminum alloy containing 69.4 wt.% Ca results in a reversal of this trend: tapiolite is reduced at the early stages (800–1250 °C) through an intermediate (Ta,Nb)O₂ phase, whereas the columbite–tantalite solid solution remains up to 1250 °C. Calcium, having a high affinity for oxygen, forms intermediate perovskite-type oxide phases that act as diffusion barriers, limiting the access of the reducing agent to residual mineral inclusions (mainly Nb-Ta minerals of the orthorhombic crystal system). A temperature rise to 1450 °C initiates the redistribution of oxide components: the content of CaNbO₃ decreases, the Ca₂(Nb,Ta)AlO₆ phase disappears, and its components are involved in the formation of Ca(Nb,Ta)_0.25MnO_2.74 and Ca₄Nb₂O₉. Diffusion constraints are reduced, and the residual columbite–tantalite solid solution is reduced, as confirmed by its complete absence in the products at 1450 °C. In the metallic phase, solid solutions of tantalum and niobium, Ta-Nb-Sn intermetallic compounds (Ta,Nb)₃Sn, titanium aluminide, and ferroalloys with an increased (Ta,Nb)/(Fe,Mn) ratio are formed. The phase transformations elucidated during metallothermic reduction of coltan using different reducing agents, together with the formation of metallic and intermetallic phases, establish a scientific foundation for the development of advanced rare metal extraction processes. Full article

Vanadium (V), molybdenum (Mo), iron (Fe), and aluminum (Al) are crucial alloying elements in certain high-performance titanium alloys. Traditionally, these elements are added to titanium alloys in the form of binary master alloys such as V-Al, Mo-Al, and Ti-Fe. The preparation and use of multiple master alloys complicates titanium alloy production and increases cost. It is therefore desirable to introduce a single multi-component master alloy containing several alloying elements into the titanium alloy smelting process. This study proposes an aluminothermic co-reduction process for V₂O₅ and MoO₃ to form a V-Al-Mo-Fe alloy with Al and Fe. Thermodynamic analysis indicates that the reduction of MoO₃ by aluminum takes precedence over that of Fe₂O₃ and V₂O₅. Utilizing metallic iron as the iron source can effectively control the heat release of the system and reduce aluminum consumption. The formation of an Al-Fe alloy prior to the aluminothermic reactions decreases the reducibility of Al. Experiments confirmed that a specific Al/O ratio in the starting materials is necessary to complete the aluminothermic reduction of V₂O₅ and MoO₃. The results show that the recovery rates of V, Mo, and Fe are strongly influenced by the Al/O ratio. When the Al/O ratio exceeds 1.6, recovery rates over 99% can be achieved for all alloying elements, with complete reduction of vanadium oxide and clear slag–alloy separation. This research provides a fundamental basis for preparing V-Al-Mo-Fe multi-component master alloys, demonstrating significant potential for applying the aluminothermic process to the preparation of other alloys. Full article

This study investigates the reaction thermodynamics of the sodium oxide-fluxed aluminothermic reduction of pyrolusite-based manganese ore under self-propagating high-temperature synthesis (SHS) conditions, using Si, Cr, and Cu as collector metals. The experimental results are compared with thermochemical equilibrium calculations using FactSage 7.3 thermochemistry software. Experimental mixtures were prepared with controlled additions of aluminium, sodium silicate, calcium oxide, and collector metals and heated to the ignition temperature in a muffle furnace preheated to 1350 °C. The resulting alloys and slags were analysed for bulk composition. Collector metals significantly influence alloy carbon saturation and manganese recovery. The individual reaction’s Gibbs free energy values and the gas–slag–metal equilibrium were calculated. Discrepancies between the experimental and equilibrium-predicted results highlight the kinetic factors of SHS processes, particularly with respect to aluminium uptake and manganese volatilisation. The main difference is the alloy’s aluminium uptake. The difference between the calculated and experimental aluminium levels is, in part, due to the higher partial oxygen pressure predicted in the gas–slag–metal equilibrium calculations, compared with that of the likely Al–Al₂O₃ governing reaction equilibrium. Short-circuiting of aluminium to the alloy is also a possible contributing factor. The findings provide insights into optimising feed formulations and process parameters for improved manganese recovery. Full article

Aluminothermic reduction is gaining renewed interest as an alternative processing route for the circular economy. A unique Na₂O-fluxed MnO₂ ore formulation with a small quantity of carbon reductant was applied to ensure rapid pre-reduction to MnO. This approach negates the pre-roasting step. The Na₂O flux enables the formation of the water-soluble compound, NaAlO₂, which enables recycling of Al₂O₃ for aluminium production. The addition of copper as a collector metal improved the overall alloy yield from 43% to 57%, which includes a 6% increase in Mn recovery to the alloy. The product alloy is a medium-carbon Fe–Mn–Si–Al–Cu complex ferroalloy that can be used as a steelmaking ferroalloy additive. The ferroalloy consists of 54% Mn, 19% Fe, 2.1% Si, 2.6% Al, 21% Cu, and 1.2% C. This carbon content is modulated by low-carbon solubility copper, despite the use of a graphite crucible. The formulated slag exhibits high Al₂O₃ solubility, enabling effective alloy–slag separation from the high Al₂O₃ content slag of 52% Al₂O₃. Gas–slag–metal equilibrium calculations for 1650 °C–1950 °C overlap with the experimentally produced alloy chemistry in %C and %Si, but not the %Al, as the uptake of aluminium exceeds the equilibrium calculation at 0.03–0.17%. Full article

Ladle slag (LF slag) is a by-product of secondary steelmaking that presents unique valorization challenges compared to BOF or EAF slags due to its distinctive chemical composition (high Al₂O₃ and CaO content) and uncontrolled hydraulic activity. While other steelmaking slags can be reused as supplementary cementitious materials or aggregates, LF slag is predominantly landfilled, with over 2 million tons discarded annually in Europe alone. This study introduces a novel pyrometallurgical valorization strategy that, unlike conventional approaches focused solely on mineral recovery, simultaneously recovers both metallic and mineral value through aluminothermic reduction. This process utilizes end-of-waste aluminum scrap rather than virgin materials to reduce Fe and Si oxides, creating a circular economy solution that addresses two waste streams simultaneously. The process generates two valuable products with low liquidus temperatures: a ferrosilicon alloy (FeSi15-50 grade) and a residual oxide rich in calcium and magnesium aluminates suitable for cementitious or ceramic applications. Through the integration of FactSage thermodynamic simulations with experimental validation, it is possible to predict and control phase evolution during equilibrium cooling, an approach not previously applied to LF slag valorization. Experimental validation using industrial slags confirms the theoretical predictions and demonstrates the process operates in a near-energy-neutral, self-sustaining mode by recovering both chemical and sensible thermal energy (50–100 kWh per ton of slag). This represents approximately 90% lower energy consumption compared to conventional ferrosilicon production. The work provides a comprehensive and scalable approach to transform a problematic waste material into valuable products, supporting circular economy principles and low-carbon metallurgy objectives. Full article

Aluminum–chromium slag (ACS), a by-product of aluminothermic reduction, which is used to produce metallic chromium and its alloys, contains toxic, carcinogenic hexavalent chromium (Cr(VI)). Therefore, improper ACS utilization may severely harm human health and the environment. This study analyzed the Cr(VI) contents, leaching characteristics, and surface concentrations in ACS and four industrially utilized products derived from it (fused alumina for refractories, ferrochromium, aluminum–chromium bricks, and high-chromium bricks). A risk assessment framework was established to evaluate their human health and environmental risks. Results showed 111 mg/kg Cr(VI) in the ACS, with its leaching concentration (7.8 mg/L) exceeding China’s hazardous waste standard. The Cr(VI) contents in the products were low (from <2 mg/kg to 16 mg/kg), and their maximum leaching concentration was below the detection limit (<0.004 mg/L). Furthermore, the four products were found to have acceptable levels of human health risk (<10⁻⁵ carcinogenic risk and <1 noncarcinogenic hazard quotient) under two risk assessment methods (particle-contact- and surface-contact-based methods). Additionally, the predicted concentration of leached Cr(VI) in groundwater (0.008 mg/L) was below the drinking water standard (0.05 mg/L). Cr(VI) limit standards for the products were then proposed based on the risk assessment (≤31 mg/kg content, ≤0.189 mg/m² surface concentration, and ≤0.259 mg/L leaching concentration). Overall, these results may provide a reference for the safe utilization and risk management of ACS and other solid wastes. Full article

Aluminothermic reduction is gaining renewed interest as an alternative processing route for the circular economy. Aluminium is produced electrochemically in the Hall–Héroult process with minimal CO₂ emissions if electricity is sourced from non-fossil fuel energy sources. The Al₂O₃ product from the aluminothermic reduction process can be recycled via hydrometallurgy, with leaching as the first step. NaAlO₂ is a water-leachable compound that forms a pathway for recycling Al₂O₃ with hydrometallurgy. In this work, a suitable slag formulation is applied in the aluminothermic reduction of manganese ore to form a Na₂O-based slag of high Al₂O₃ solubility to effect good alloy–slag separation. The synergistic effect of added chromium metal as a collector metal is illustrated with an increased alloy yield at 68%, from 43% without added Cr. The addition of small amounts of carbon reductant to MnO₂-containing ore ensures rapid pre-reduction to MnO. This approach negates the need for a pre-roasting step. The alloy and slag chemical analyses are compared to the thermochemistry-predicted phase chemistry. The alloy consists of 57% Mn, 18% Cr, 18% Fe, 3.4% Si, 1.5% Al, and 2.2% C. The formulated slag exhibits high Al₂O₃ solubility, enabling effective alloy–slag separation, even at an Al₂O₃ content of 55%. Full article

This study presents the structural and compositional characterisation of a newly developed Ti55Al27Mo13 alloy synthesised via aluminothermic reaction. The alloy was designed to overcome the limitations of conventional processing routes for high–melting–point elements such as Ti and Mo, enabling the formation of a complex, multi–phase microstructure in a single high–temperature step. The aim was to develop and characterise a material with microstructural features expected to enhance wear resistance, oxidation behaviour, and thermal stability in future applications. The alloy is intended as a precursor for composite nanopowders and surface coatings applied to aluminium–, magnesium–, and iron–based substrates subjected to mechanical and thermal loading. Elemental analysis (XRF, EDS) confirmed the presence of Ti, Al, Mo, and minor elements such as Si, Fe, and C. Microstructural investigations using laser confocal and scanning electron microscopy revealed a heterogeneous structure comprising solid solutions, eutectic regions, and dispersed oxide and carbide phases. Notably, the alloy exhibits high hardness values, reaching >2400 HV in Al₂O₃ regions and ~1300 HV in Mo– and Si–enriched solid solutions. These results suggest the material’s substantial potential for protective surface engineering. Further tribological, thermal, and corrosion testing, conducted with meticulous attention to detail, will follow to validate its functional performance in target applications. Full article

Aluminothermic reduction is an alternative processing route for the circular economy because Al is produced electrochemically in the Hall–Héroult process with minimal CO₂ emissions if the electricity input is sourced from non-fossil fuel energy sources. This circular processing option attracts increased research attention in the aluminothermic production of manganese and silicon alloys. The Al₂O₃ product must be recycled through hydrometallurgical processing, with leaching as the first step. Recent work has shown that the NaAlO₂ compound is easily leached in water. In this work, a suitable slag formulation is applied in the aluminothermic reduction of manganese ore to form a Na₂O-based slag of high Al₂O₃ solubility to effect good alloy–slag separation. The synergistic effect of carbon and silicon reductants with aluminium is illustrated and compared to the test result with only carbon reductant. The addition of small amounts of carbon reductant to MnO₂-containing ore ensures rapid pre-reduction to MnO, facilitating aluminothermic reduction. At 1350 °C, a loosely sintered mass formed when carbon was added alone. The alloy and slag chemical analyses are compared to the thermochemistry predicted phase chemistry. The alloy consists of 66% Mn, 22–28% Fe, 2–9% Si, 0.4–1.4% Al, and 2.2–3.5% C. The higher %Si alloy is formed by adding Si metal. Although the product slag has a higher Al₂O₃ content (52–55% Al₂O₃) compared to the target slag (39% Al₂O₃), the fluidity of the slags appears sufficient for good alloy separation. Full article

Vanadium (V), molybdenum (Mo), and aluminum (Al) are important alloying elements in titanium alloys, typically introduced through master alloys such as V-Al and Mo-Al. Current preparation of these master alloys predominantly relies on the spontaneous reduction of V₂O₅ or MoO₃ by aluminum. However, separate production and addition of master alloys increase the cost of the titanium alloy. Insufficient understanding of the exothermic behavior and slag-forming process during the aluminothermic reaction often leads to low alloy yield and elevated impurity levels due to splashing and poor alloy–slag separation. This study focused on the controllable aluminothermic reaction of V₂O₅ and MoO₃ to produce high-quality and high-yield V/Al/Mo alloy. Thermodynamic calculations indicate that the reduction of MoO₃ to Mo by aluminum is more favorable than the reduction of V₂O₅ to V. Al% in the V-Al-Mo alloy is crucial for controlling reaction temperature. When the Al/O ratio in the raw materials exceeds 1.0, increasing aluminum reduces both the reaction exothermicity and theoretical reaction temperature. A combination of thermodynamic calculations and high-temperature experiments demonstrates that the heat generation and slag composition can be effectively controlled by Al/O ratio in raw materials. When the Al/O ratio in raw materials is 1.6–2.0, the yields of Mo and V exceed 99% and 95%, respectively. This study provides an effective approach to producing V/Al/Mo alloy under controllable conditions, which shows great potential for other aluminothermic reactions. Extensive solid solutions of V/Al/Mo also provide invaluable data for the optimization of the alloy database. Full article

SmF₃ cannot be reduced to metallic samarium by aluminum due to variable valence states of Sm. This study investigates the reduction products of SmF₃ via an aluminothermic reduction. The effect of molar ratios of Al/SmF₃ on the morphology, elemental distribution, crystal structure, and chemical valence of the samples were investigated by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The thermodynamic results show that it is feasible for SmF₃ reduction by Al to form SmF₂ in 933~1356 K. SmF_2.413, AlF₃, and Sm(AlF)₅ are obtained under the condition of the molar ratio of Al to SmF₃ at 1:3, 2:3, 3:3, 4:3, and 5:3. The samarium of the reduction products exhibits mixed valence states of Sm³⁺ and Sm²⁺, with the ratio δ of F to Sm determined by a(δ) = −0.1794δ + 5.819 (0 ≤ δ ≤ 0.4615). The presence of adsorbed oxygen in the products facilitates the oxidation process from Sm²⁺ to Sm³⁺. These findings may provide a theoretical basis on the development of valence states for other rare earth elements in aluminothermic reduction. Full article

This study focuses on the innovative application of HCI and XR technologies in behavioral skills training (BST) in the digital age, exploring their potential in education, especially experimental training. Despite the opportunities these technologies offer for immersive BST, traditional methods remain mainstream, with XR devices like HMDs causing user discomfort and current research lacking in evaluating user experience. To address these issues, we propose the spatial reality display (SRD) method, a new BST approach based on spatial reality display. This method uses autostereoscopic technology to avoid HMD discomfort, employs intuitive gesture interactions to reduce learning costs, and integrates BST content into serious games (SGs) to enhance user acceptance. Using the aluminothermic reaction in chemistry experiments as an example, we developed a Unity3D-based XR application allowing users to conduct experiments in a 3D virtual environment. Our study compared the SRD method with traditional BST through simulation, questionnaires, and interviews, revealing significant advantages of SRD in enhancing user skills and intrinsic motivation. Full article

Titanium is one of the most abundant metals with superior properties such as excellent mechanical properties, high strength-to-weight ratio, and oxidation and corrosion resistance. However, it is commercially expensive to produce; hence, its use is limited. Currently, the Kroll process remains the most commercially exploited to produce titanium. Therefore, this paper thoroughly reviews some other proposed and developing thermo-reduction methods using the two main precursors titanium dioxide (TiO₂) and titanium chloride (TiCl₄) together with the environmental impacts they cause. The exorbitant production cost and environmental issues have resulted in enormous research and development to innovate more sustainable methods of titanium production. The various processes were comprehensively analyzed to assess whether they have the potential to expand to be economically viable. From this review, it is apparent that most of the methods still require further research to scale them up to an industrial and commercial level. Recent developments including the Council for Scientific and Industrial Research-Ti (CSIR-Ti), Titanium Reduction Oxide (TiRO), Preform Reduction Process (PRP), and hydrogen-assisted magnesiothermic reduction (HAMR) processes are auspicious for producing high-purity titanium sustainably. Full article