Search Results (41)

To enhance the molten salt corrosion resistance of Ni200 alloy plasma arc welds, the welds were subjected to tensile deformation followed by heat treatment. The grain boundary character distribution (GBCD) was analyzed using electron backscatter diffraction (EBSD) in conjunction with orientation imaging microscopy (OIM). A constant-temperature corrosion test at 900 °C was conducted to evaluate the impact of GBCD on the corrosion resistance of the welds. Results demonstrated that after processing with 6% tensile deformation, and annealing at 950 °C for 30 min, the fraction of low-ΣCSL grain boundaries increased from 1.2% in the as-welded condition to 57.3%, and large grain clusters exhibiting Σ3ⁿ orientation relationships were formed. During the heat treatment, an increased number of recrystallization nucleation sites led to a reduction in average grain size from 323.35 μm to 171.38 μm. When exposed to a high-temperature environment of 75% Na₂SO₄-25% NaCl mixed molten salt, the corrosion behavior was characterized by intergranular attack, with oxidation and sulfidation reactions resulting in the formation of NiO and Ni₃S₂. The corrosion resistance of Grain boundary engineering (GBE)-treated samples was significantly superior to that of Non-GBE samples, with respective corrosion rates of 0.3397 mg/cm²·h and 0.8484 mg/cm²·h. These findings indicate that grain boundary engineering can effectively modulate the grain boundary character distribution in Ni200 alloy welds, thereby enhancing their resistance to molten salt corrosion. Full article

Inconel 617 is a nickel-based superalloy that is a primary candidate for use in next-generation nuclear applications such as the Gen IV Molten Salt Reactor (MSR) and Very-High-Temperature Reactor (VHTR) due to its corrosion and oxidation resistance and high strength in elevated temperatures. However, Inconel 617 machinability is poor due to its hardness and tendency to work harden during manufacturing. While the machinability of its sister grade, Inconel 718, has been widely studied and understood due to its applications in aerospace, there is a lack of knowledge regarding the behaviour of Inconel 617 in machining. To address this gap, this paper investigates the influence of cutting parameters in the turning of Inconel 617 and compares the impact of Minimum Quantity Lubrication (MQL) turning against conventional coolant. This investigation was performed through three distinct studies: Study A compared the performance of commercial coatings, Study B investigated the influence of cutting parameters on the surface finish, and Study C compared the performance of MQL to flood coolant. This work demonstrated that AlTiN coatings performed the best and doubled the tool life of a standard tungsten carbide insert compared to its uncoated form. Additionally, the feed rate had the largest impact on the surface roughness, especially at high feeds, with the best surface quality found at the lowest feed rate of 0.075 mm/rev. The utilization of MQL had mixed results compared to a conventional flood coolant in the machining of Inconel 617. Surface finish was improved as high as 47% under MQL conditions compared to the flood coolant; however, work hardening at the surface was also shown to increase by 10–20%. Understanding this, it is possible that MQL can completely remove the need for a conventional coolant in the machining of Inconel 617 components for the manufacturing of next-generation reactors. Full article

With the large-scale application of lithium-ion batteries in the field of new energy, many retired lithium batteries not only cause environmental pollution problems but also lead to serious waste of resources. Repairing failed lithium batteries and regenerating new materials has become a crucial path to break through this dilemma. Based on the research on the failure mechanism of ternary cathode materials, this paper systematically combs through the multiple factors leading to their failure, extensively summarizes the influence of heat treatment process parameters on the performance of recycled materials, and explores the synergistic effect between heat treatment technology and other processes. Studies have shown that the failure of ternary cathode materials is mainly attributed to factors such as cation mixing disorder, the generation of microcracks, phase structure transformation, and the accumulation of by-products. Among them, cation mixing disorder damages the crystal structure of the material, microcracks accelerate the pulverization of the active substance, phase structure transformation leads to lattice distortion, and the generation of by-products will hinder ion transport. The revelation of these failure mechanisms lays a theoretical foundation for the efficient recycling of waste materials. In terms of recycling technology, this paper focuses on the application of heat treatment technology. On the one hand, through synergy with element doping and surface coating technologies, heat treatment can effectively improve the crystal structure and surface properties of the material. On the other hand, when combined with processes such as the molten salt method, coprecipitation method, and hydrothermal method, heat treatment can further optimize the microstructure and electrochemical properties of the material. Specifically, heat treatment plays multiple key roles in the recycling process of ternary cathode materials: repairing crystal structure defects, enhancing the electrochemical performance of the material, removing impurities, and promoting the uniform distribution of elements. It is a core link to achieving the efficient reuse of waste ternary cathode materials. Full article

Magnesium reduction of Ta₂O₅ (tantalum pentoxide) is a metallurgical process widely used to extract metallic tantalum powder from its oxide form using magnesium as a reducing agent in a molten salt medium. This study explores the mechanisms and patterns of phase transformation during the magnesium reduction of Ta₂O₅ in a molten salt medium, focusing on the influence of temperature and time on the physical and chemical properties of the resulting tantalum powder. The results reveal that under various reaction conditions in a molten salt medium, the magnesium reduction of Ta₂O₅ follows four distinct pathways: Ta₂O₅ → Ta, Ta₂O₅ → MgTa₂O₆ → Ta, Ta₂O₅ → MgTa₂O₆ → Mg₄Ta₂O₉ → Ta, and Ta₂O₅ → Mg₄Ta₂O₉ → Ta. Each pathway significantly affects the physical and chemical properties of the resulting tantalum powder. Using a uniform mixing method, the reaction proceeds directly from Ta₂O₅ to Ta powder in a single step. As the reaction temperature increases from 600 °C to 900 °C, the average particle size of the tantalum powder enlarges from 30 nm to 150 nm, with the product phase transitioning from a mixture of Ta and Ta₂O to a single Ta phase. Additionally, prolonged holding time improves the uniformity of the tantalum powder’s particle distribution. This study accomplishes directional control over the phase transformation and the properties of tantalum powder during the reduction process, thus offering valuable guidance for the preparation of high-performance tantalum powder. Full article

This work presents the synthesis, purification, and characterization of a molten salt fuel for the irradiation experiment SALIENT-03 (SALt Irradiation ExperimeNT), a collaborative effort between the Nuclear Research and Consultancy Group and the Joint Research Centre, European Commission. The primary objective of the project is to investigate the corrosion behavior of selected Ni-alloy based structural materials which are being considered for the construction of fluoride molten salt reactors. During the test, these materials will be exposed to selected liquid molten fuel salts under irradiation in the High Flux Reactor in Petten, the Netherlands. In addition, the properties and distribution of the fission products formed in the fuel salt during burn-up will be studied by various post irradiation examinations. In the SALIENT-03 fuel, U and Pu fluorides, as fissile material, are dissolved in a carrier melt based on a 78⁷LiF-22ThF₄ eutectic mixture to form fuel salts with four different compositions, containing PuF₃, UF₄, UF₃, and CrF₃. This article comprehensively describes all the steps of this fuel synthesis process: the synthesis of the required pure fluoride powders (⁷LiF, ThF₄, UF₄, UF₃, and PuF₃); the mixing, melting, and purification of the different fuel salt compositions; and the fabrication of solid ingots to be loaded into the irradiation capsules. The characterization of the intermediate and final products is also carried out, following a rigorous quality assurance protocol. The quality assurance is achieved using an analytical scheme consisting of mass balance-based conversion efficiency evaluation, X-ray diffraction, and differential scanning calorimetry analyses. All experimental goals were successfully achieved, highlighting promising prospects for advancing future research and development regarding fuel production methods for fluoride-based molten salt reactors. Full article

After the high-temperature pretreatment of α-spodumene to induce a phase transition to β-spodumene, a derivative of the silica polymorph keatite, often coexisting with metastable Li-stuffed β-quartz (γ-spodumene)_, the conventional approach to access lithium is through ion exchange with hydrogen using concentrated sulfuric acid, which presents drawbacks associated with the production of low-value leaching residues. As sodium and magnesium can produce more interesting aluminosilicate byproducts, this study investigates Na⁺ ↔ Li⁺ and Mg²⁺ ↔ 2 Li⁺ substitution efficiencies in β-spodumene and β-quartz. Thermal annealing at 850 °C of the LiAlSi₂O₆ silica derivatives mixed with an equimolar proportion of Na endmember glass of equivalent stoichiometry (NaAlSi₂O₆) indicates that sodium incorporation in β-quartz is limited, whereas the main constraint for not attaining complete growth to a Na_0.5Li_0.5AlSi₂O₆ β-spodumene solid solution is co-crystallization of minor nepheline. For similar experiments in the equimolar LiAlSi₂O₆-Mg_0.5AlSi₂O₆ system, the efficient substitution of Mg for Li is observed in both β-spodumene and β-quartz, consistent with the alkaline earth having an ionic radius closer to lithium than sodium. Ion exchange at lower temperatures was also evaluated by exposing coexisting β-spodumene and β-quartz to molten salts. In NaNO₃ at 320 °C, sodium for lithium exchange reaches ≈90% in β-spodumene but less than ≈2% in β-quartz, suggesting that to be an efficient lithium recovery route, the formation of β-quartz during the conversion of α-spodumene needs to be minimized. At 525 °C in a molten MgCl₂/KCl medium, although full LiAlSi₂O₆-Mg_0.5AlSi₂O₆ solid solution is observed in β-quartz, structural constraints restrict the incorporation of magnesium in β-spodumene to a Li_0.2Mg_0.4AlSi₂O₆ stoichiometry, limiting lithium recovery to 80%. Full article

This study proposes a new dense membrane for selectively separating CO₂ and O₂ at high temperatures and simultaneously producing syngas. The membrane consists of a cermet-type material infiltrated with a ternary carbonate phase. Initially, the co-doped ceria of composition Ce_0.9Zr_0.05Y_0.05O_2−δ (CZY) was synthesized by using the conventional solid-state reaction method. Then, the ceramic was mixed with commercial silver powders using a ball milling process and subsequently uniaxially pressed and sintered to form the disk-shaped cermet. The dense membrane was finally formed via the infiltration of molten salts into the porous cermet supports. At high temperatures (700–850 °C), the membranes exhibit CO₂/N₂ and O₂/N₂ permselectivity and a high permeation flux under different CO₂ concentrations in the feed and sweeping gas flow rates. The observed permeation properties make its use viable for CO₂ valorization via the oxy-CO₂ reforming of methane, wherein both CO₂ and O₂ permeated gases were effectively utilized to produce hydrogen-rich syngas (H₂ + CO) through a catalytic membrane reactor arrangement at different temperatures ranging from 700 to 850 °C. The effect of the ceramic filler in the cermet is discussed, and continuous permeation testing, up to 115 h, demonstrated the membrane’s superior chemical and thermal stability by confirming the absence of any chemical interaction between the material and the carbonates as well as the absence of significant sintering concerns with the pure silver. Full article

High temperature represents a critical constraint in the development of gas sensors. Therefore, investigating gas sensors operating at room temperature holds significant practical importance. In this study, coal-based porous carbon (C-700) and coal-based C/MoO₂ nanohybrid materials were synthesized using a simple one-step vapor deposition and sintering method, and their gas-sensing performance was investigated. The gas-sensing performance for several VOC gases (phenol, ethyl acetate, ethanol, acetone, triethylamine, and toluene) and a 95% RH high-humidity environment were tested. The results indicated that the C/MoO₂-450 sample sintered at 450 °C exhibited excellent specific selectivity towards acetone at room temperature, with a response value of 4153.09% and response/recovery times of 10.8 s and 2.9 s, respectively. Furthermore, the C/MoO₂-450 sample also demonstrated good repeatability and long-term stability. The sensing mechanism of the synthesized materials was also explored. The superior gas-sensing performance can be attributed to the synergistic effect between the porous carbon and MoO₂ nanoparticles. Given the importance of enhancing the high-tech and high-value-added utilization of coal, this study provides a viable approach for utilizing coal-based carbon materials in detecting volatile organic compounds at room temperature. Full article

Concentrated solar power (CSP) has gained traction for generating electricity at high capacity and meeting base-load energy demands in the energy mix market in a cost-effective manner. The linear Fresnel reflector (LFR) is valued for its cost-effectiveness, reduced capital and operational expenses, and limited land impact compared to alternatives such as the parabolic trough collector (PTC). To this end, the aim of this study is to optimize the operational parameters, such as the solar multiple (SM), thermal energy storage (TES), and fossil fuel (FF) backup system, in LFR power plants using molten salt as a heat transfer fluid (HTF). A 50 MW LFR power plant in Duba, Saudi Arabia, serves as a case study, with a Direct Normal Irradiance (DNI) above 2500 kWh/m². About 600 SM-TES configurations are analyzed with the aim of minimizing the levelized cost of electricity (LCOE). The analysis shows that a solar-only plant can achieve a low LCOE of 11.92 ¢/kWh with a capacity factor (CF) up to 36%, generating around 131 GWh/y. By utilizing a TES system, the SM of 3.5 and a 15 h duration TES provides the optimum integration by increasing the annual energy generation (AEG) to 337 GWh, lowering the LCOE to 9.24 ¢/kWh, and boosting the CF to 86%. The techno-economic optimization reveals the superiority of the LFR with substantial TES over solar-only systems, exhibiting a 300% increase in annual energy output and a 20% reduction in LCOE. Additionally, employing the FF backup system at 64% of the turbine’s rated capacity boosts AEG by 17%, accompanied by a 5% LCOE reduction. However, this enhancement comes with a trade-off, involving burning a substantial amount of natural gas (503,429 MMBtu), leading to greenhouse gas emissions totaling 14,185 tonnes CO₂ eq. This comprehensive analysis is a first-of-a-kind study and provides insights into the optimal designs of LFR power plants and addresses thermal, economic, and environmental considerations of utilizing molten salt with a large TES system as well as employing natural gas backup. The outcomes of the research address a wide audience including academics, operators, and policy makers. Full article

Silicon steel (electrical steel) has been used in electric motors that are important components in sustainable new energy Electrical Vehicles (EVs). The Ruhrstahl–Heraeus process is commonly used in the refining process of silicon steel. The refining effect inside the RH degasser is closely related to the flow and mixing of molten steel. In this study, a 260 t RH was used as the prototype, and the transport process of the passive scalar tracer (virtual tracer) and salt tracer (considering density effect) was studied using numerical simulation and water model research methods. The results indicate that the tracer transports from the up snorkel of the down snorkel to the bottom of the ladle, and then upwards from the bottom of the ladle to the top of the ladle. Density and gravity, respectively, play a promoting and hindering role in these two stages. In different areas of the ladle, density and gravity play a different degree of promotion and obstruction. Moreover, in different regions of the ladle, the different circulation strength leads to the different promotion degrees and obstruction degrees of the density. This results in the difference between the concentration growth rate of the salt tracer and the passive scalar in different regions of the ladle top. From the perspective of mixing time, density and gravity have no effect on the mixing time at the bottom of the ladle, and the difference between the passive scalar and NaCl solution tracer is within the range of 1–5%. For a larger dosage of tracer case, the difference range is reduced. However, at the top of the ladle, the average mixing time for the NaCl solution case is significantly longer than that of the passive scalar case, within the range of 3–14.7%. For a larger dosage of tracer case, the difference range is increased to 17.4–41.1%. It indicates that density and gravity delay the mixing of substances at the top area of the ladle, and this should be paid more attention when adding denser alloys in RH degasser. Full article

Metallic materials play a vital role in the economic life of modern societies; hence, research contributions are sought on fresh developments that enhance our understanding of the fundamental aspects of the relationships between processing, properties, and microstructures. Disciplines in the metallurgical field ranging from processing, mechanical behavior, phase transitions, microstructural evolution, and nanostructures, as well as unique metallic properties, inspire general and scholarly interest among the scientific community. Three of the most important elements are included in unit operations in non-ferrous extractive metallurgy: (1) hydrometallurgy (leaching under atmospheric and high-pressure conditions, mixing of a solution with a gas and mechanical parts, neutralization of a solution, precipitation and cementation of metals from a solution aiming at purification, and compound productions during crystallization), (2) pyrometallurgy (roasting, smelting, and refining), and (3) electrometallurgy (aqueous electrolysis and molten salt electrolysis). Advances in our understanding of unit operations in non-ferrous extractive metallurgy are required to develop new research strategies for the treatment of primary and secondary materials and their application in industry. Full article

The presence of calcium-containing molten salts in the electrolysis of oxides for metal production can lead to the formation of CaO and, subsequently, the generation of intermediate products, affecting the reduction of metals. To investigate the impact of CaO on the reduction process, experiments were conducted using a Fe₂O₃-CaO cathode and a graphite anode in a NaCl-CaCl₂ molten salt electrolyte at 800 °C. The electrochemical reduction kinetics of the intermediate product Ca₂Fe₂O₅ were studied using cyclic voltammetry and I-t curve analysis. The phase composition and morphology of the electrolysis products were analyzed using XRD, SEM-EDS, and XPS. The experimental results demonstrate that upon addition of CaO to the Fe₂O₃ cathode, Ca₂Fe₂O₅ is formed instantly in the molten salt upon the application of an electrical current. Research conducted at different voltages, combined with electrochemical analysis, indicates that the reduction steps of Ca₂Fe₂O₅ in the NaCl-CaCl₂ molten salt are as follows: Ca₂Fe₂O₅ ⟶ Fe₃O₄ ⟶ FeO ⟶ Fe. The presence of CaO accelerates the electrochemical reduction rate, promoting the formation of Fe. At 0.6 V and after 600 min of electrolysis, all of the Ca₂Fe₂O₅ is converted into Fe, coexisting with CaCO₃. With an increase in the electrolysis voltage, the electrolysis product Fe particles visibly grow larger, exhibiting pronounced agglomeration effects. Under the conditions of a 1 V voltage, a study was conducted to investigate the influence of time on the reduction process of Ca₂Fe₂O₅. Gradually, it resulted in the formation of CaFe₃O₅, CaFe₅O₇, FeO, and metallic Fe. With an increased driving force, one gram of Fe₂O₃-CaO mixed oxide can completely turn into metal Fe by electrolysis for 300 min. Full article

Transition metal oxide materials are promising oxygen catalysts that are alternatives to expensive and precious metal-containing catalysts. Integration of transition metal oxides with high activity for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is an important pathway for good bifunctionality. In contrast to the conventional physical mixing and hybridization strategies, perovskite-type oxide provides an ideal structure for the integration of the transition metal element atoms on an atomic scale. Herein, B-site ordered double-perovskite-type La_1.6Sr_0.4MnCoO₆ nanocrystallites with ultra-small cubic (20–50 nm) morphology and high specific surface areas (25 m² g⁻¹) were proposed. Rational designs were integrated to promote the ORR-OER catalysis, e.g., introducing oxygen vacancies via A-site cation substitution, further increasing surface oxygen vacancies via integration of a small amount of Pt/C and nanosizing of the material via a facile molten-salt method. The batteries with the La_1.6Sr_0.4MnCoO₆ nanocrystallites and an aqueous alkaline electrolyte demonstrate decent discharge−charge voltage gaps of 0.75 and 1.10 V at 1 and 30 mA cm⁻², respectively, and good cycling stability of 250 h (1500 cycles). A coin-type battery with a gel−polymer electrolyte also presents a good performance. Full article

To enhance the contact between the electrolyte (source of O²⁻) and the carbon fuel in solid oxide–direct carbon fuel cells (SO-DCFCs), molten metals and molten salts were used in the anode chamber. Oxygen ions can dissolve and be transported in the molten medium to the anode three-phase boundary to reach and oxidize the carbon particles. To improve the sluggish kinetics of the electrochemical oxidation of carbon, the same molten media can act as redox mediators. Moreover, using a liquid metal/salt anode, tolerant to fuel impurities, the negative effect of carbon contaminants on cell performance is mitigated. In this work, an overview of SO-DCFCs with liquid metals, liquid carbonates, and mixed liquid metals/liquid carbonates in the anode chamber is presented and their performance was compared to that of conventional SO-DCFCs. Full article

This study presents the design and computational fluid dynamics (CFD) analysis of a mini demonstrator for a dual fluid reactor (DFR). The DFR is a novel concept currently under investigation. The DFR is characterized by the implementation of two distinct liquid loops dedicated to fuel and coolant. It integrates the principles of molten salt reactors and liquid metal cooled reactors; thus, it operates in a high temperature and fast neutron spectrum, presenting a distinct approach in the field of advanced nuclear reactor design. The mini demonstrator serves as a scaled-down version of the actual reactor, primarily aimed at gaining insights into the CFD analysis intricacies of the reactor while minimizing computational costs. The CFD modeling of the MD intends to add valuable data for the purpose of modeling validation against experiments to be conducted on the MD. These experiments can be used for DFR licensing and design optimization. The coolant and fuel utilized in the mini demonstrator are of low Prandtl number (Pr = 0.01) liquid lead, operating at two distinct inlet temperatures, namely 873 K and 1473 K. The study showed a rapid increase in turbulence due to intense mixing and abrupt changes in flow areas and directions, despite the relatively low inlet velocities. Hot spots characterized by elevated temperatures were identified, analyzed, and justified based on their spatial distribution and flow conditions. Flow swirling within pipes was identified and a remedy approach was suggested. Inconsistent mass flow rates were observed among the fuel pipes, with higher rates observed in the lateral pipes. Although lower fuel temperatures were observed in the lateral pipes, they consistently exhibited higher heat exchange characteristics. The study concludes by giving physical insights into the heat transfer and flow behavior, and proposing design considerations for the dual fluid reactor to enhance structural safety and durability, based on the preliminary analysis conducted. Full article