Search Results (57)

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

To overcome the problem of Cr₂O₃ and Al₂O₃ inclusions in CuCr50 alloy prepared by aluminothermic reduction method, in this paper, a novel methodology for strengthening metal–slag separation through in situ slagging is proposed. CuCr50 alloys were prepared by metallothermic reduction using Al and Al-Mg as reducing agents, and the physical properties of the slag, such as viscosity, density, and surface tension, were adjusted by controlling the proportion of CaO in the slagging agent in the raw material to achieve good separation of the slag–metal. The results show that with the ratio of CaO increased, CaO and MgO were coupled to make slag, which combined with Cr₂O₃ and Al₂O₃ to form CaCr₂O₄, MgCr₂O₄, and CaAl₄O₇ in the slag, thus reducing the content of impurities in the alloy. When RCaO/(CaO + Al₂O₃ + MgO) = 20%, the Cr content ranged from 46.61% to 47.09%, the inclusions accounted for 1.60%, the Cr particle size was refined to 20 µm, the number of Cr spherical crystals accounted for 9.88%, the conductivity reached 14.96 MS/m, and the hardness reached 100.23 HB. After heat treatment, the Cr phase was refined in the alloy, the conductivity increased from 14.96 MS/m to 18.27 MS/m, and the hardness increased from 100.23 HB to 103.1 HB. This method is expected to provide an effective method for the preparation of CuCr50 contact materials. Full article

We investigated the reaction kinetics and initial chemical conditions in the production of silicon alloys, employing aluminum as the reductant for calcium silicate slag, to enhance process economics and scalability to industrial levels. The apparent kinetics and transient chemical conditions were studied by immersing solid aluminum into molten slag, allowing the reaction to proceed for varying durations without external agitation, before quenching the reaction for chemical and microscopic analyses of the resulting silicon alloy and slag. The majority of the conversion was observed within the first 15 s at 1650 °C, driven by significant chemical interactions and interfacial turbulence introduced upon aluminum immersion. For Al-SiO₂ stoichiometries ranging from 0.5 to 1.2, the slag phase reaction conformed to first-order kinetics during the initial two minutes, when it approached equilibrium. The mass transfer coefficients for Al₂O₃ were estimated at 1–2 × 10⁻⁴ m/s, comparable to those for SiO₂ and CaO. A constant mass transfer coefficient could not be established for stoichiometries of 1.6 and 2, as these deviated from the standard slag mass transfer relationship and did not adhere to established relationships. Despite near-complete reactions, alloy–slag mixing was extensive, decreasing with lower stoichiometry values. Full article

To achieve better process control of silicon (Si) alloy production using aluminum as a reductant of calcium silicate (CaO-SiO₂) slag, it is necessary to understand the reaction phenomena concerning the behavior of formed phases at the metal-slag interface during conversion. The interfacial interaction behavior of non-agitated melt was investigated using the sessile drop method for varying time and temperature, followed by EPMA phase analysis at the vicinity of the metal–slag interface. The most remarkable features of the reaction were the accumulation of solid calcium aluminate product layers at the Al alloy–slag interface and spontaneous emulsion of Si-alloy droplets in the slag phase. The reduction is strictly limited at 1550 °C due to the slow transfer of calcium aluminates away from the metal-slag interface into the partially liquid bulk slag. Reduction was significantly improved at 1600–1650 °C despite an interfacial layer being present, where the conversion rate is most intense in the first minutes of the liquid–liquid contact. A high mass transfer rate across the interface was shown related to the apparent interfacial tension depression of the wetting droplet along with a significant perturbed interface and emulsion due to Kelvin–Helmholtz instability driven by built-up interfacial charge at the interface. The increased reaction rate observed from 1550 °C to 1600–1650 °C for the non-agitated melt was attributed to the advantageous physical properties of the slag phase, which can be further regulated by the stoichiometry of metal–slag interactions and the composition of the slag. Full article

A novel high-efficiency industrialized clean production technology based on multi-stage gradient batching and smelting was proposed for the production of high-quality ferrovanadium. The thermodynamic mechanism of aluminothermic reduction equilibrium, alloy settlement and raw material impurity distribution were confirmed, and a multi-stage double-gradient aluminum addition pattern (DG-ADP), the highly efficient separation of molten slag and alloy, and typical impurity control standards of raw materials were achieved on the basis of a self-propagating high-temperature synthesis with an electric auxiliary heating (SHS-EAH) process. The reduction efficiency, separation efficiency and the comprehensive utilization rate of the secondary resources were significantly improved, as the whole total vanadium (T.V) content in the industrially produced residue slag reduced from 2.34 wt.% to 0.60 wt.%, while the corresponding smelting yield increased from 93.7 wt.% to 98.7 wt.% and the aluminum consumption decreased from 510 kg·t⁻¹ to 400 kg·t⁻¹. The multi-stage DG-ADP process enabled the internal circulation of vanadium-bearing materials in the ferrovanadium smelting system, as well as the external circulation of iron and residue slag in the same system, and finally achieved the zero discharge of solid and liquid waste from the ferrovanadium production line, which provides a brand-new perspective for the cleaner production of ferrovanadium alloy. Full article

Titanium oxide is a major component of bauxite residue (BR) with a high value, but it is often an unwanted element in common BR reuse options such as cement or iron production. Conventional carbothermic reduction smelting of BR produces a slag still containing a large amount of Ti. This study investigates an aluminothermic process for producing an FeTi alloy by combining BR, ilmenite ore, and fluxes. Based on thermodynamic calculations and batch experiments, the amounts of aluminum (reductant) and fluxes were investigated to achieve the optimum alloy production in parallel with a slag that could be further valorized in the cement industry. The mineralogical and chemical analysis of the metallic and slag phase agreed with the thermodynamic calculations. The results obtained by this study can lead to the development of a new process for the complete valorization of BR, paving the way for scaling up aluminothermic processes for producing ferroalloys from all iron-rich residues. Full article