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10 pages, 2719 KiB

Open AccessArticle

Corrosion of Molybdenum-Based and Ni–Mo Alloys in Liquid Bismuth–Lithium Alloy

by Aleksander V. Abramov, Ruslan R. Alimgulov, Anastasia I. Trubcheninova, Arkadiy Yu. Zhilyakov, Sergey V. Belikov, Vladimir A. Volkovich and Ilya B. Polovov

Metals 2023, 13(2), 366; https://doi.org/10.3390/met13020366 - 11 Feb 2023

Cited by 1 | Viewed by 1286

Abstract

Bismuth–lithium alloys are considered primary candidates for the reductive extraction step in the on-line reprocessing of molten salt reactor fuel. The corrosion behavior of molybdenum-based alloys and Hastelloy^® B-3 alloy (taken for comparison) was examined here in a liquid Bi–Li (5 mol.%) [...] Read more.

Bismuth–lithium alloys are considered primary candidates for the reductive extraction step in the on-line reprocessing of molten salt reactor fuel. The corrosion behavior of molybdenum-based alloys and Hastelloy^® B-3 alloy (taken for comparison) was examined here in a liquid Bi–Li (5 mol.%) alloy at 650 °C. MoW10, MoW30, and TZM corrosion-resistant alloys were studied as prospective construction materials for holding liquid bismuth–lithium alloy. Rates of corrosion were determined by the gravimetric method as well as by chemical analysis of corrosion products formed in liquid-phase Bi–Li alloy. The microstructure and chemical composition of samples of the materials and Bi–Li alloys containing the corrosion products after the tests were determined using inductively coupled plasma–atomic emission spectroscopy, X-ray fluorescence analysis, scanning electron microscopy, and energy dispersive spectroscopy. TZM molybdenum-based alloy corrodes in the bismuth-lithium alloy due to the formation of a zirconium–bismuth intermetallic compound, which passes into the liquid phase. The corrosion rates of MoW10, MoW30, and TZM alloys at 650 °C were 16, 16, and 23 µm/year, respectively. Hastelloy^® B-3 alloy, despite its high molybdenum content, was subjected to severe corrosion in liquid Bi–Li alloys due to dissolution of nickel in liquid bismuth. The corrosion rate of this alloy was 14 mm/year. Full article

(This article belongs to the Special Issue Liquid Metals, Alloys, Salts, Oxides, and Their Coexistence and Interaction with Solid Phases)

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10 pages, 1934 KiB

Open AccessArticle

Self-Diffusion Coefficients of Components in Liquid Binary Alloys of Noble Metals

by Nikolay Dubinin and Roman Ryltsev

Metals 2022, 12(12), 2167; https://doi.org/10.3390/met12122167 - 16 Dec 2022

Cited by 1 | Viewed by 1319

Abstract

An accurate determination of transport coefficients in liquids, such as diffusivity, is crucial for studying fundamental chemical processes, for constructing and verifying model theories of liquid, and for the optimization of technological processes. However, a reliable experimental determination of the diffusivity is a [...] Read more.

An accurate determination of transport coefficients in liquids, such as diffusivity, is crucial for studying fundamental chemical processes, for constructing and verifying model theories of liquid, and for the optimization of technological processes. However, a reliable experimental determination of the diffusivity is a difficult and sometimes nearly impossible task. In this regard, the development of model theories that allow calculating characteristics of atomic transport is of special interest. Here, the concentration dependencies of the self-diffusion coefficients of the components in Cu-Ag, Cu-Au, and Ag-Au liquid alloys at T = 1423 K and T = 1573 K are calculated in the framework of the linear trajectory approximation in conjunction with the square-well model and the semi-analytical representation of the mean spherical approximation. We reveal that peculiarities in the behavior of the obtained dependencies are related to the peculiarities of the phase diagrams of the alloys under consideration. Additionally, we verify our calculation method on Al₈₀-Cu₂₀ and Al₈₀-Au₂₀ liquid alloys. The results obtained are in good agreement with available experimental and molecular-dynamic simulation data. In the cases when the experimental information is not available, the presented results can be considered as predictive to estimate the quantities under consideration approximately. Full article

(This article belongs to the Special Issue Liquid Metals, Alloys, Salts, Oxides, and Their Coexistence and Interaction with Solid Phases)

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13 pages, 3785 KiB

Open AccessArticle

Effect of Copper on the Formation of L1₂ Intermetallic Phases in Al–Cu–X (X = Ti, Zr, Hf) Alloys

by Elvira Popova, Pavel Kotenkov, Ivan Gilev, Stepan Pryanichnikov and Alexey Shubin

Metals 2022, 12(12), 2067; https://doi.org/10.3390/met12122067 - 30 Nov 2022

Viewed by 1237

Abstract

Transition metal trialuminides of the Al₃X type of groups 4 and 5 of the periodic system have reduced density, high melting points, and corrosion resistance. Aluminides with a cubic lattice of the Al₃Sc type can be used as a [...] Read more.

Transition metal trialuminides of the Al₃X type of groups 4 and 5 of the periodic system have reduced density, high melting points, and corrosion resistance. Aluminides with a cubic lattice of the Al₃Sc type can be used as a nucleating phase for aluminum alloys. However, low plasticity and a tetragonal lattice limit their application. In this work, we stabilized the metastable cubic lattice of Al₃X-type aluminides by replacing aluminum with copper. The conditions for the formation of L1₂ metastable aluminides in the Al–Cu–TM (TM: Ti, Zr, Hf) alloys were studied using a wide range of copper concentrations. A high concentration of copper (hypereutectic alloys) is the one of the necessary conditions for the formation of (Al_1−xCu_x)₃Ti, (Al_1−xCu_x)₃Zr, (Al_1−xCu_x)₃Hf aluminides. With an increase in the copper concentration, the number of metastable aluminides sharply increased. The process of their formation strongly depended on the sequence of dissolution of the corresponding components in the melts. The low volume fraction of precipitated titanium aluminides was the result of insufficient supersaturation of α-Al with titanium (at the peritectic temperature) compared to that for alloys with zirconium and hafnium. Under identical synthesis conditions in the crystal lattice of metastable aluminides formed in experimental Al–Cu–Ti, Al–Cu–Zr, Al–Cu–Hf alloys, copper was found to substitute up to 8, 10, and 13 at.% of aluminum, respectively. The crystallographic and dimensional similarities of the lattices in metastable transition metal aluminides and in α-Al suggest their usefulness as modifying additions in aluminum-based alloys. Full article

(This article belongs to the Special Issue Liquid Metals, Alloys, Salts, Oxides, and Their Coexistence and Interaction with Solid Phases)

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13 pages, 1947 KiB

Open AccessArticle

Enhanced Absorption Performance of Dye-Sensitized Solar Cell with Composite Materials and Bilayer Structure of Nanorods and Nanospheres

by Anees Ur Rehman, Najeeb Ullah, Muhammad Abid Saeed and Usman Khan Khalil

Metals 2022, 12(5), 852; https://doi.org/10.3390/met12050852 - 17 May 2022

Cited by 5 | Viewed by 1569

Abstract

The concept of localized surface plasmon resonance has been applied to increase the absorption efficiency of dye-sensitive solar cells (DSSCs) by using various photoanode structures. A three-dimensional model for a photoanode of the DSSC based on composite materials was developed using COMSOL Multiphysics. [...] Read more.

The concept of localized surface plasmon resonance has been applied to increase the absorption efficiency of dye-sensitive solar cells (DSSCs) by using various photoanode structures. A three-dimensional model for a photoanode of the DSSC based on composite materials was developed using COMSOL Multiphysics. Spherical-, rod- and triangular-shaped aluminum nanoparticles were employed in the core of SiO₂ to examine the influence of morphology on the performance of DSSCs in the 350–750 nm wavelength range. The UV-Vis absorption results indicated that aluminum nanoparticles with spherical, rod and triangle morphologies had 39.5%, 36.1% and 34.6% greater absorption capability than aluminum-free nanoparticles. In addition, we investigated the effect of plasmonic absorption in DSSCs for photoanodes made of TiO₂, SiO₂ and bilayer TiO₂/SiO₂ with and without covering aluminum nanoparticles. The TiO₂ and SiO₂ nanoparticles had fixed diameters of 90 nm each. The UV-Vis absorption and Tauc curves indicated that the TiO₂/SiO₂ bilayer structure (with and without aluminum nanoparticles) had greater absorption and lower bandgap energies than individual TiO₂ and SiO₂ nanoparticles. Furthermore, bilayer photoanode nanostructures were investigated based on nanospheres and nanorods for core–shell Al@SiO₂ nanoparticles. The results indicated that a photoanode with nanorod/nanosphere structure had a 12% better absorption capability than a nanosphere/nanorod configuration. This improvement in absorption is attributed to the high surface area, which boosts dye loading capacity and long-term light capture, resulting in greater interaction between the dye and the photon. Our study develops core–shell nanoparticles with optimized shape and materials for bilayer photoanode structures in photovoltaic technology. Full article

(This article belongs to the Special Issue Liquid Metals, Alloys, Salts, Oxides, and Their Coexistence and Interaction with Solid Phases)

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12 pages, 2372 KiB

Open AccessArticle

Aluminum Alloy Selection for In Situ Composite Production by Oxygen Blowing

by Arkady Finkelstein, Arseny Schaefer and Nikolay Dubinin

Metals 2021, 11(12), 1984; https://doi.org/10.3390/met11121984 - 9 Dec 2021

Cited by 3 | Viewed by 1956

Abstract

We considered the possibility of using AlMg10, AlCu5, AlCu5Cd, AlSi12, and AlSi7Zn9 as initial alloys for in situ composites production via oxygen blowing of hydrogen pre-saturated melts as an alternative to AlSi7Fe. The production process provides the destruction of the oxide film on [...] Read more.

We considered the possibility of using AlMg10, AlCu5, AlCu5Cd, AlSi12, and AlSi7Zn9 as initial alloys for in situ composites production via oxygen blowing of hydrogen pre-saturated melts as an alternative to AlSi7Fe. The production process provides the destruction of the oxide film on the melt surface. It was demonstrated that oxide film on AlMg10 alloy did not get destroyed due to the heavy thickness because of the porous structure that contributed to its kinetically based growth. Copper-bearing alloys AlCu5 and AlCu5Cd were characterized by the low-strength oxide film and got destroyed before floating, causing the oxide porosity. Silicon-bearing alloys AlSi12 and AlSi7Zn9 provide the dense structure, which makes it clear that to understand the Pilling–Bedworth ratio for basic alloying elements is required for a non-destructed oxide void floating and shall exceed the range of 1.64–1.77. However, the oxide film in silicon-bearing alloys under investigation did not get destroyed into fine particles. AlSi7Zn9 alloy had inclusions of smaller sizes as compared to AlSi12 alloy due to the ZnO that embrittled the film, but which were grouped to form oxide islands. Moreover, zinc was evaporated during blowing. The mechanical properties of the produced composites were based on the alloys under investigation which were in line with their structures. A higher value of the Pilling–Bedworth ratio of impurities was required for fine crushing: The conventionally used AlSi7Fe alloy met this requirement and was therefore considered to be the optimum version. Full article

(This article belongs to the Special Issue Liquid Metals, Alloys, Salts, Oxides, and Their Coexistence and Interaction with Solid Phases)

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17 pages, 4451 KiB

Open AccessArticle

Laves Phase Formation in High Entropy Alloys

by Roman Ryltsev, Vasiliy Gaviko, Svetlana Estemirova, Evgenii Sterkhov, Lubov Cherepanova, Denis Yagodin, Nikolay Chtchelkatchev, Nikolay Dubinin and Sergey Uporov

Metals 2021, 11(12), 1962; https://doi.org/10.3390/met11121962 - 6 Dec 2021

Cited by 6 | Viewed by 3144

Abstract

One of the intriguing recent results in the field of high-entropy alloys is the discovery of single-phase equiatomic multi-component Laves intermetallics. However, there is no clear understanding that a combination of chemical elements will form such high-entropy compounds. Here we contribute to understanding [...] Read more.

One of the intriguing recent results in the field of high-entropy alloys is the discovery of single-phase equiatomic multi-component Laves intermetallics. However, there is no clear understanding that a combination of chemical elements will form such high-entropy compounds. Here we contribute to understanding this issue by modifying the composition of duodenary TiZrHfNbVCrMoMnFeCoNiAl (12x) alloy in which we recently reported the fabrication of hexagonal C14 Laves phase. We consider three alloys based on 12x: 7x = 12x-VCrMoMnFe, 12x + Sc, 12x + Be and observe that all of them crystalize with the formation of C14 Laves phase as a dominant structure. We report that 12x + Be alloy reveals a single-phase C14 structure with a very high concentration of structural defects and ultra-fine dendritic microstructure with an almost homogenous distribution of the constituted elements over the alloy matrix. The analysis of electrical and magnetic properties reveals that the Laves phases are Curie-Weiss paramagnets, which demonstrate metallic conduction; 7x and 12x alloys also reveal a pronounced Kondo-like anomaly. Analysis of experimental data as well as ab initio calculations suggest that chemical complexity and compositional disorder cause strong s-d band scattering and thus the rather high density of d-states in the conduction band. Full article

(This article belongs to the Special Issue Liquid Metals, Alloys, Salts, Oxides, and Their Coexistence and Interaction with Solid Phases)

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15 pages, 9029 KiB

Open AccessArticle

Effective Pair Interactions and Structure in Liquid Noble Metals within Wills-Harrison and Bretonnet-Silbert Models

by Nikolay Dubinin and Roman Ryltsev

Metals 2021, 11(7), 1115; https://doi.org/10.3390/met11071115 - 12 Jul 2021

Cited by 3 | Viewed by 1481

Abstract

Recently, for calculating the effective pair interactions in liquid transition metals, we have developed an approach which includes the Wills-Harrison and Bretonnet-Silbert models as limit cases. Here, we apply this approach to noble liquid metals. The dependencies of pair potentials and corresponding MD-simulated [...] Read more.

Recently, for calculating the effective pair interactions in liquid transition metals, we have developed an approach which includes the Wills-Harrison and Bretonnet-Silbert models as limit cases. Here, we apply this approach to noble liquid metals. The dependencies of pair potentials and corresponding MD-simulated pair correlation functions in pure liquid Cu, Ag and Au on the portion of the non-diagonal (with respect to the magnet quantum number) d-d-electron couplings in the metal under consideration are studied. The model provides a good agreement with experimental and ab initio data for pair correlation functions, structure factors and velocity autocorrelation functions. Full article

(This article belongs to the Special Issue Liquid Metals, Alloys, Salts, Oxides, and Their Coexistence and Interaction with Solid Phases)

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13 pages, 62565 KiB

Open AccessArticle

Corrosion of Metals and Nickel-Based Alloys in Liquid Bismuth–Lithium Alloy

by Aleksandr V. Abramov, Ruslan R. Alimgulov, Anastasia I. Trubcheninova, Arkadiy Yu. Zhilyakov, Sergey V. Belikov, Vladimir A. Volkovich and Ilya B. Polovov

Metals 2021, 11(5), 791; https://doi.org/10.3390/met11050791 - 13 May 2021

Cited by 3 | Viewed by 2913

Abstract

Bismuth–lithium alloys are considered as primary candidates for the reductive extraction step of on-line reprocessing of a molten salt reactor fuel. The corrosion behavior of pure metals and nickel-based alloys was studied in a liquid Bi–Li (5 mol.%) alloy at 650 °C. The [...] Read more.

Bismuth–lithium alloys are considered as primary candidates for the reductive extraction step of on-line reprocessing of a molten salt reactor fuel. The corrosion behavior of pure metals and nickel-based alloys was studied in a liquid Bi–Li (5 mol.%) alloy at 650 °C. The tantalum, molybdenum, and corrosion-resistant alloys VDM^® Alloy C-4, Hastelloy^® G-35^®, KhN62M, VDM^® Alloy 59 were studied as prospective materials for this liquid metal media. The corrosion rates were determined by gravimetric method as well as chemical analysis of corrosion products in Bi–Li alloy. Microstructure and chemical composition of samples of the materials and Bi–Li alloys containing the corrosion products after the tests were evaluated using inductively coupled plasma–atomic emission spectroscopy, X-ray fluorescence analysis, scanning electron microscopy, and energy dispersive spectroscopy. Metallic tantalum and molybdenum do not chemically interact with liquid Bi–Li alloy; the corrosion rate of these metals is determined only by the solubility in this medium. The corrosion rates of Ta and Mo at 650 °C were 0.09 and 0.07 mm/year, respectively. Nickel alloys are subjected to severe corrosion in liquid Bi–Li alloys due to dissolution of nickel in liquid bismuth. Alloys of this type cannot be used in such an environment. Full article

(This article belongs to the Special Issue Liquid Metals, Alloys, Salts, Oxides, and Their Coexistence and Interaction with Solid Phases)

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9 pages, 2573 KiB

Open AccessFeature PaperArticle

Dehydrogenation of AlSi7Fe1 Melt during In Situ Composite Production by Oxygen Blowing

by Arkady Finkelstein, Arseny Schaefer and Nikolay Dubinin

Metals 2021, 11(4), 551; https://doi.org/10.3390/met11040551 - 28 Mar 2021

Cited by 1 | Viewed by 1696

Abstract

The technology of producing a composite material in situ envisages the pre-saturation of an AlSi7Fe1 melt with hydrogen; afterwards, the melt is blown with oxygen until the hydrogen dissolved in the melt is burned out. The hydrogen content was researched during the manufacturing [...] Read more.

The technology of producing a composite material in situ envisages the pre-saturation of an AlSi7Fe1 melt with hydrogen; afterwards, the melt is blown with oxygen until the hydrogen dissolved in the melt is burned out. The hydrogen content was researched during the manufacturing process of the composite material; before oxygen blowing, and at incomplete and complete burning out of the dissolved hydrogen. The interrelation between the absorbed hydrogen content and the aluminum oxide fraction was identified. A mathematical model was proposed which demonstrated that during the saturation process of the melt with oxide particles, hydrogen was absorbed on their surface as a layer close to monoatomic, which does not lead to the realization of the pores’ heterogeneous nucleation mechanism. Due to this, castings produced from the researched composite material are leakless. Incomplete burning out of hydrogen dissolved in the melt leads to the formation of significant hydrogen porosity. The proposed method of prevention of gas porosity in cast composites is an alternative to the conventional one and offers not only the purging of the melt from oxide inclusions but, on the contrary, a significant increase in their specific surface, which allows for the reduction in hydrogen content on the inclusion surface to the monoatomic level. Full article

(This article belongs to the Special Issue Liquid Metals, Alloys, Salts, Oxides, and Their Coexistence and Interaction with Solid Phases)

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11 pages, 1303 KiB

Open AccessFeature PaperArticle

Application of Low Melting Metals for Separation of Uranium and Zirconium in a “Fused Chloride—Liquid Alloy” System

by Vladimir A. Volkovich, Dmitry S. Maltsev, Mariya N. Soldatova, Aleksandr A. Ryzhov and Aleksandr B. Ivanov

Metals 2021, 11(4), 550; https://doi.org/10.3390/met11040550 - 28 Mar 2021

Cited by 4 | Viewed by 2037

Abstract

Closeness of electrochemical properties of uranium and zirconium makes separation of these metals in pyroelectrochemical reprocessing of spent nuclear fuels a challenging task. Varying electrode material can change metals’ deposition potentials. The study was aimed at assessing the effect of the cathode material [...] Read more.

Closeness of electrochemical properties of uranium and zirconium makes separation of these metals in pyroelectrochemical reprocessing of spent nuclear fuels a challenging task. Varying electrode material can change metals’ deposition potentials. The study was aimed at assessing the effect of the cathode material on deposition potentials of zirconium and uranium from 3LiCl–2KCl based melts. Solid (tungsten) and liquid (gallium, zinc, Ga–Zn, Ga–Sn and Ga–In alloy) working electrodes were tested at 532–637 °C. Galvanostatic cathodic polarization was employed and the applied cathodic current varied from 0.0001 to 1 A. Gallium–zinc eutectic alloy demonstrated the largest difference of zirconium and uranium deposition potentials. Zirconium/uranium separation factors were experimentally determined in a “molten salt—liquid metal” system for gallium and Ga–Zn eutectic based alloys. Full article

(This article belongs to the Special Issue Liquid Metals, Alloys, Salts, Oxides, and Their Coexistence and Interaction with Solid Phases)

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8 pages, 1150 KiB

Open AccessArticle

Self-Diffusion in Liquid Copper, Silver, and Gold

by Nikolay Dubinin

Metals 2020, 10(12), 1651; https://doi.org/10.3390/met10121651 - 7 Dec 2020

Cited by 6 | Viewed by 2547

Abstract

The recently developed by us semi-analytical representation of the mean spherical approximation in conjunction with the linear trajectory approximation is applied to the quantitative study of self-diffusivities in liquid Cu, Ag and Au at different temperatures. The square-well model is employed for the [...] Read more.

The recently developed by us semi-analytical representation of the mean spherical approximation in conjunction with the linear trajectory approximation is applied to the quantitative study of self-diffusivities in liquid Cu, Ag and Au at different temperatures. The square-well model is employed for the description of the interatomic pair interactions in metals under study. It is found that our theoretical results are in good agreement with available experimental and computer-simulation data and can be considered as a prediction when such data are absent. Full article

(This article belongs to the Special Issue Liquid Metals, Alloys, Salts, Oxides, and Their Coexistence and Interaction with Solid Phases)

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12 pages, 970 KiB

Open AccessArticle

Mechanism of Ion-Diffusion Solid-Phase Reduction of Iron Oxides of Technogenic Origin in the Presence of the Liquid Phase and without it

by Oleg Sheshukov, Mikhail Mikheenkov, Larisa Vedmid’, Iliya Nekrasov and Denis Egiazaryan

Metals 2020, 10(12), 1564; https://doi.org/10.3390/met10121564 - 24 Nov 2020

Cited by 9 | Viewed by 2112

Abstract

The processes of iron oxides’ reduction have a complex physicochemical mechanism, with the participation of solid, liquid, and gaseous substances. The article discusses the existing models for the reduction of iron oxides and provides data on the thermodynamic possibility of carrying out the [...] Read more.

The processes of iron oxides’ reduction have a complex physicochemical mechanism, with the participation of solid, liquid, and gaseous substances. The article discusses the existing models for the reduction of iron oxides and provides data on the thermodynamic possibility of carrying out the reactions of their reduction through the solid and gas phases. Experimental data on the reduction of iron from industrial scale, obtained by the DSC (differential scanning calorimetry) method, show the kinetic dependence of the rate and completeness of recovery on external factors: pressing pressure during sample preparation and the reagents’ composition. The pressing pressure, under conditions of iron ions’ solid-phase diffusion, has the significant effect by increasing the reagents’ contact area. Under conditions of iron ions’ comprehensive diffusion, the pressing pressure does not affect the reduction processes rate. The introduction of 10 mass.% flux into the raw mixture composition leads to a partially liquid-phase diffusion of iron ions and weakens the effect of the pressing pressure in this process. An ion diffusion-catalytic mechanism is proposed to describe the observed effects during the reduction of iron oxide of technogenic origin. Full article

(This article belongs to the Special Issue Liquid Metals, Alloys, Salts, Oxides, and Their Coexistence and Interaction with Solid Phases)

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