Pb-Bi Alloys Research Articles

Electrosynthesis of Amino Acids from Biomass and Nitrate at Industrial Current Densities Using Porous PbBi Electrodes.

Electrosynthesis is a rising and attractive method for efficient amino acid production. However, industrial-grade electrosynthesis of high-value amino acids from simple carbon and nitrogen substrates is confronted with a great challenge. Herein, we design a dual-site PbBi alloy catalyst for various amino acids' electrosynthesis from keto acids and nitrate. An alanine Faradaic efficiency of 59.7% is delivered at -1.5 V vs SCE, reaching the industrial current density of 570 mA cm-2 with high catalytic durability of the porous Pb1Bi0.1 catalyst. In the tandem reaction process, nitrate is first converted to NH2OH via electrochemical reduction mainly over the Bi site. Then the obtained NH2OH integrates with the α-keto acid to form the oxime intermediate. Lastly, the Pb site facilitates the electroreduction of oxime to the final amino acids. More importantly, over 10 kinds of α-amino acids can be successfully synthesized in excellent FE and high yield at high current density, indicating the superior catalytic activity and wide universality of our strategy. In short, this work opens up a novel approach to realize the one-pot electrosynthesis of various amino acids from renewable biomass feedstocks and nitrate waste industrially.

Type-II superconductivity at 9K in Pb–Bi alloy

In the present work, we report the synthesis of Pb–Bi alloy with enhanced Tc of up to 9K, which is higher than that of Pb. The alloy is synthesized via a solid-state reaction route in the vacuum-encapsulated quartz tube at 700°C in an automated furnace. The synthesized sample is characterized by X-ray Diffraction(XRD) and Energy dispersive X-ray analysis(EDAX) for its phase purity and elemental composition. Rietveld refinement of XRD reveals that the end product is a majority hexagonal Pb7Bi3, with minor rhombohedral Bi. The electronic transport measurement shows metallic behavior with the Debye temperature of 108K and a superconductivity transition temperature (Tc) below 9K, which is the maximum to date for any reported Pb–Bi alloy, Pb or Bi at ambient pressure. Partial substitution of Bi at the Pb site may modify the free density of electronic states within the BCS model to attain the optimum Tc, which is higher by around 2K from the reported Tc of Pb. The superconductor phase diagram derived from magneto-transport measurements reveals that the synthesized alloy is a conventional superconductor with an upper critical field (Hc2) of 3.9 T, which lies well within the Pauli paramagnetic limit. The magnetization measurements carried out following ZFC(Zero Field Cool) protocols infer that the synthesized alloy is a bulk superconductor below 9K. The isothermal M-H(Magnetization vs. Field) measurements performed below Tc establish it as a type-II superconductor. The specific heat capacity measurements show that the Pb–Bi alloy is a strongly coupled bulk superconductor below around 9K with possibly two superconducting gaps.

Preparation and characterization of ion-exchanged Ni-Na-β”-Al2O3 and Fe-Na-β”-Al2O3 solid electrolytes for applications in liquid metals

Accurate determinations of the thermochemical properties for the steel alloying elements (Fe, Cr, Ni, Co and Mn) dissolved as corrosion product impurities in Pb and Pb–Bi alloy (LBE) are relevant for the development of Lead-Cooled Fast Nuclear Reactors (LFRs). Ion-selective solid electrolytes are suitable for an electrochemical characterization of the dissolved impurities. Among these, ion-exchanged Ni-β”-Al2O3 and Fe-β”-Al2O3 are promising solid electrolytes for the selective detection of Ni and Fe dissolved in HLMs. In the present works we proposed a preliminary test of liquid and vapor ion-exchanges on commercial polycrystalline Na-β”-Al2O3 tubes at different conditions of temperature and reaction time with NiCl2 and FeCl2 salts, characterizing the effects on the material microstructure. The resulting Ni-Na-β”-Al2O3 and Fe-Na-β”-Al2O3 samples were only partially replaced by nickel or iron, extremely porous, damaged by molten salt corrosion, and contaminated by residual chlorides. When tested as selective sensors in molten LBE, they failed in detecting dissolved nickel or iron. Thus, ion-exchange procedure on polycrystalline Na-β”-Al2O3 substrates still needs to be improved by properly combining the liquid and vapor ion-exchange with optimized reaction conditions in order to increase the sodium replacement yield. Alternatively, efforts may be focused on the preparation and application of other different nickel and iron solid electrolytes.

Vitrification of lead–bismuth alloy nuclear waste into a glass waste form

AbstractLead–bismuth eutectic (LBE), a promising coolant in advanced nuclear systems, can be activated by neutrons during nuclear reactor operations. The decommissioning of nuclear facilities would generate lead–bismuth (Pb–Bi) alloy‐contaminated nuclear waste. The current metallic nuclear waste treatment approach involves remelting followed by cementitious solidification. This increases the waste volume and the risk of radionuclide migration in groundwater. Therefore, this study developed a method for vitrification of Pb–Bi alloy waste. Different amounts of SiO2 were added at 750–1100°C in the air to turn the simulated LBE waste into glass waste form. The values of the normalized elemental leaching rates (Pb, Bi, Si, Te, and Ni) determined using the 28‐day static leaching test were less than .2 g m−2 d−1 and varied with SiO2 addition. Furthermore, a three‐stage evolution of the glass structure with SiO2 addition was proposed according to the structural analysis performed using Raman and X‐ray photoelectron spectroscopies. The evolution stages were as follows: (i) the stage of heavy metal transition from covalent to ionic heavy metals (7.5 wt% < SiO2 < 15 wt%), (ii) the stage of increase in bridging oxygen (15 wt% < SiO2 < 20 wt%), and (iii) the stage of domination of the Si–O network (20 wt% < SiO2 < 25 wt%). The evolution of the glass structure resulted in varying glass chemical durability. Finally, the glass‐forming region of (20–48)PbO–(35–70)Bi2O3–(7.5–25)SiO2 (wt%) and the temperature needed to melt those glasses were determined through the melting test, where radionuclides and toxic heavy metals showed undetectable volatilization during vitrification. Hence, turning LBE waste into glass waste form will be a potential approach for treating Pb–Bi alloy nuclear waste.

Negative effect of bismuth in lead on liquid metal embrittlement of a ferritic steel

Liquid metal embrittlement (LME) of a Fe-10Cr-4Al ferritic steel was studied at 375 °C in liquid Pb-Bi alloys. Slow strain rate testing (SSRT) in low oxygen conditions was used to evaluate the ductility as a function of Bi concentration. It was found that susceptibility to LME increased strongly with the Bi concentration. The steel showed a reduction in its total strain to failure, which started at 3–5 wt.% Bi. The alloying elements (Fe, Cr, and Al) have a higher solubility in Bi than pure lead (Pb), so they are expected to dissolve more readily when Bi is added to the Pb. This is believed to be part of the explanation for the observed increase of LME. Lead with up to 3 wt.% Bi induced no LME in the studied corrosion resistance FeCrAl alloy.

The influence of Y addition on oxide layers of 15-15Ti-Y steel exposed to static Pb-Bi alloys with containing oxygen

The corrosion behavior was investigated in a static environment of liquid Pb-Bi eutectic (LBE) saturated with 10−6 wt.% oxygen at 500°C and 600 °C. The investigation focused on 15-15Ti and 15-15Ti-Y austenitic stainless steel specimens, exposing them for up to 5000 h. Additionally, both steel types were analysed after exposure to liquid Pb40Bi60 alloy with 10−6 wt.% oxygen concentration at 600 °C for 2000 h. The main objective was to investigate the structure and composition of oxide layers formed during corrosion, with specific attention to the role of yttrium (Y) in influencing corrosion behavior. The addition of Y resulted in promoting denser spinel oxide layer formation, which exhibited enhanced properties in reducing outward cation diffusion, inward oxygen diffusion, and PbBi penetration into the steels.

Elucidating of the influence of tin and cadmium in the Bi–Pb alloy on its thermal and nuclear properties as a coolant in fast neutron reactors

The purpose of this research is to investigate the physical properties and shielding characteristics of prepared (Bi–Pb) and (Bi–Pb–Sn–Cd) alloys, to be used as a coolant in a liquid metal nuclear fast reactor. The physical properties density, kinetics and mechanism of melting applying the reverse Johnson–Mehl–-Avrami rule and reduced time plot were applied, showing that melting processes take place in two dimensions, enthalpy and heat capacity were measured on the other hand for the prepared alloys within the solid and liquid states, respectively. Moreover, the results indicated that the bulk density and melting temperature of (Bi–Pb–Sn–Cd) alloys are lower than (Bi–Pb) alloys. Likewise, the thermal properties of (Bi–Pb–Sn–Cd) alloys seemed more suitable applicants than that of (Bi–Pb) alloys. Additionally, eight different gamma-ray energy lines in the range 0.12178–1.40792 MeV were used to determine the mass attenuation for the alloy samples. Also, gamma radiation attenuation characteristics, the half-value layer and effective atomic number were determined using Phy-x/PSD software. Furthermore, three types of neutron energies (slow neutrons, total slow neutrons, as well as neutrons of energies greater than 0.4 eV) were used to determine the macroscopic neutron cross-sections for the prepared alloys. The calculated values of mass attenuation coefficients exhibited a very good agreement with the experimental values of those parameters. The values of neutron macroscopic cross sections at fast neutrons for (Bi–Pb) and (Bi–Pb–Sn–Cd) alloys are small, this means that there is no consequence on fast neutrons used in a nuclear breeder reactor. Finally, we may reach the conclusion that Bi–Pb–Sn–Cd alloys are a possible candidate to be used as a coolant in fast nuclear reactors, as well as it is most suitable as an outer cooling and shielding blanket vessel as well.

Study on continuous crystallization and purification of bismuth from Pb-Bi alloy

The crude bismuth obtained from the smelting of bismuth concentrate and bismuth-containing by-products contains 5%∼20% lead, which needs to be removed during the refining of crude bismuth. Due to the similar physical and chemical properties and metallurgical behavior of lead and bismuth, it is not easy to perform the separation by conventional methods. Although the conventional process of chlorinating crude bismuth to remove lead can meet the requirements of the refining process, the amount of chlorinated slag produced is large, and the safety of chlorine gas is difficult to control, making it difficult to achieve clean production. In this paper, single-factor experiments and semi-industrial experiments for the separation and purification of bismuth from Pb-Bi alloy were carried out by the continuous crystallization method, and the results showed that the bismuth content of Pb-Bi alloy increased from 90.24% to 98.98%, the direct yield of bismuth was 87.37%, the metal recovery rate was 99.84%, and the slag production rate was 0.62%. In comparison with existing processes and studies, the method is low-cost, clean, and efficient, has a wide treatment range, can be operated continuously, and can be easily industrialized and promoted. Theoretically, this method, combined with the process of vacuum distillation to treat Pb-Bi binary alloys with greater than 55.5% bismuth content, results in a 99.99% bismuth product.

Impact of Bi content on the accuracy of oxygen concentration measurements in liquid Pb–Bi alloys

Accurate measurements of the oxygen concentration in liquid lead-bismuth eutectic (LBE) alloys are essential for ensuring optimum cooling conditions in heavy liquid metal coolant fast reactors. However, while unavoidable variations in the Bi contents of these alloys can affect the accuracy of these measurements, this issue has not yet been rigorously evaluated. The present work addresses this issue by evaluating variations in oxygen concentration measurements obtained experimentally for oxygen-saturated liquid LBE alloys with different Bi contents at different temperatures using a solid electrolyte oxygen sensor. Theoretical relationships are established between sensor voltage, oxygen concentration, temperature, and Bi content under the applied experimental conditions, and excellent agreement is obtained between the experimental and theoretical results. The theoretical relationships establish that the voltage decreases by about 1 mV for every 1 wt% increase in Bi content at a temperature of 400 °C. At a fixed voltage, with the increase of T, the influence of the Bi content on the CO calculation results gradually increased. Finally, the impact of varying Bi contents on the accuracy of oxygen concentration measurements is evaluated under practical reactor operation conditions, and higher requirements for the control of dissolved oxygen in LBE-cooled fast reactors are proposed.

Improvement of the mechanical properties and LBE cavitation erosion resistance of laser cladded FeCrAlTiC coating by Y2O3 addition

• Y 2 O 3 addition causes the evolution of microstructure and distribution of TiC. • Y 2 O 3 addition increases hardness and adhesive strength of the coating. • Adding Y 2 O 3 inhibits the crack of coating in the LBE cavitation erosion condition. This work proves that Y 2 O 3 addition could significantly improve the mechanical properties of laser cladded FeCrAlTiC coatings. Due to the formation of Y 2 TiO 5 and Y 2 Ti 2 O 7 after adding Y 2 O 3 , the TiC particles in coating were refined and their morphologies changed from short bar to sphere. Comparing with the coatings without Y 2 O 3 , the microhardness of the coating increased by 9.88 %, and the adhesive strength of the coating increased by 53.7 %. Moreover, the coating adding Y 2 O 3 showed much better cavitation erosion resistance in high temperature liquid Pb-Bi alloys than the coatings without Y 2 O 3 .

Solvent-free, efficient synthesis of methyl phenyl carbonate over an SBA-15 loaded Pb–Bi bimetallic catalyst

Methyl phenyl carbonate (MPC) is one of the versatile carbonates; in particular, it is an important component in lithium-ion batteries. In recent years, the catalytic synthesis of MPC has become an important topic, but the development of highly active catalysts is still challenging. In this study, SBA-15-loaded nano-sized Pb–Bi catalysts with different Pb/Bi molar ratios were prepared by deposition–precipitation to improve the efficiency and selectivity. To investigate the relationship between the structure and performance of the catalysts, XRD, BET, SEM-EDS, HRTEM, H 2 -TPR, and XPS characterization, as well as catalytic activity and stability tests, were conducted. Results revealed that Pb–Bi/SBA-15 can efficiently catalyze the synthesis of MPC under solvent-free conditions, with the highest catalytic activity obtained over 6 Pb–1Bi/SBA-15. SBA-15 with a large pore size and a high specific surface area was suitable as catalyst carrier, and the average diameter of Pb–Bi oxide particles was ∼3.57 nm. The addition of Bi led to the improved dispersion of active components, which were highly and evenly dispersed on the SBA-15 surface. Furthermore, an appropriate proportion of Pb and Bi on SBA-15 was conducive to the considerable enhancement of the catalytic activity. Besides, Pb–Bi/SBA-15 also exhibited good durability and recyclability, making it a promising catalytic material for the synthesis of various carbonates. SBA-15-loaded nano-sized Pb–Bi catalysts were synthesized by a deposition-precipitation method, which can efficiently catalyze the synthesis of MPC without the use of a solvent. The 6 Pb–1Bi/SBA-15 catalyst exhibited the highest catalytic activity as well as superior stability and recyclability. • Efficient synthesis of methyl phenyl carbonate was performed using a Pb–Bi bimetallic catalyst. • Methyl phenyl carbonate was obtained in high yield and selectivity without solvent. • Formation of a highly dispersed Pb–Bi alloy on the catalyst surface was verified. • A facile catalytic approach for efficient synthesis of various organic carbonates was presented.

Binary and ternary phase diagrams of lead, bismuth, and lead oxide

The phase diagrams of binary and ternary mixtures of lead (Pb), bismuth (Bi), and lead oxide (PbO) are necessary for the application of Pb-Bi alloys as coolants in nuclear reactors. In this study, the solidus and liquidus temperatures of Pb-Bi, Pb-PbO, Bi-PbO binary mixtures and the liquidus temperature of Pb-Bi-PbO ternary mixture were measured via differential thermal analysis. The eutectic points of the three binary mixtures and the liquidus temperature of ternary mixture were experimentally determined and the effect of PbO on the phase diagram of the Pb-Bi mixture was analyzed. Furthermore, an optimized regular solution model, which showed much better prediction accuracy than the traditional model, was proposed for the phase diagrams of sub-binary and ternary Pb-Bi-PbO mixtures.

Revealing the Phase Segregation and Evolution Dynamics in Binary Nanoalloys via Electron Beam-Assisted Ultrafast Heating and Cooling.

Gas-phase synthesized binary nanoparticles (NPs) possess ultraclean surfaces, which benefit versatile uses in sensors and catalysts. However, precise control of their configuration and properties is still a big challenge because the growth mechanism and phase evolution dynamics in these NPs are very hard to unveil. Here, we report a strategy to investigate the phase evolution dynamics in binary NPs by using e-beam assisted ultrafast local heating and cooling inside a transmission electron microscope. With this strategy, the phase segregation and corresponding shape evolution of PbBi NPs are in situ revealed. It is found that the as-prepared PbBi alloy NPs will transform into heterostructures under e-beam stimulated structural relaxation, leading to the formation of featured Janus configurations with faceted Bi polyhedron parts and intermetallic hemisphere parts. During phase segregation, Pb1Bi1 and Pb7Bi3 phases are captured and identified, and a model of phase and shape evolution of PbBi nanoalloys is developed and contrasted with that of their bulk counterparts. These findings benefit the understanding of the phase dynamics of binary NPs and can provide in-depth information for engineering their structures for practical applications.

Pyroelectrometallurgical processing of bismuth-containing oxides

In this work, we substantiate and develop a general pyroelectrometallurgical technology for processing bismuth dross and oxides (the intermediate products of lead bullion refining by the Betterton-Kroll process) to obtain crude bismuth. The research focuses on bismuth dross (3–5% Bi; 80–85% Pb) remelted at 500–600°С in the presence of NaNO3 and NaOH, as well as the obtained alkaline melt (bismuth oxides, 1–5% Bi; 60–70% Pb). The conducted experiments allowed us to determine optimal parameters of the main steps of processing bismuth oxide, as well as the characteristics of obtained products. Reduction smelting of bismuth oxides at 1150°C (with the addition of sodium carbonate, quartz and fine coke in the amount of 66, 25 and 5% of bismuth oxides mass, respectively) is proposed, leading to bismuth lead formation. Its decoppering is carried out at 350–600°C with 2.0% sulfur (by its weight), added to the melt. We propose to carry out the alkaline treatment of the decoppered Pb-Bi alloy at 500oC in contact with sodium hydroxide, sodium nitrate and sodium chloride, taken in amounts up to 10.2, 8.3 and 1.4% by weight of bismuth lead, respectively. Subsequent electrolysis comprises electrolytic processing of purified Pb-Bi alloy ingots at 550oC. The electrolyte consists of a melt with the following composition, %: NaCl – 7, KCl – 35, PbCl2 – 18 and ZnCl2 – 40. As a result, two end products were obtained by the proposed bismuth oxide processing. The anodic product at the second stage of electrolysis, crude bismuth (yielded 1.1% by the weight of oxides) contains 93.62% Bi and 4.14% Pb, extraction from oxides amounts to 19.0% Bi and 0.1% Pb. About 1.2% Bi and 9.1% Pb of their initial content in the oxides are transferred to the cathodic product containing 0.033% Bi and 97.83% Pb (the yield equalled 5.1% of the oxides).

Structural and superconducting properties of low-temperature ultrathin PbBi<sub>3</sub> films

Bismuth (Bi), as a stable heaviest element in the periodic table of elements, has strong spin-orbit coupling, which has attracted a lot of attention as the parent material of various known topological insulators. Previous calculations predicted that Bi(111) with a thickness less than eight bilayers and the ultrathin black-phosphorus-like Bi(110) films are single-element two-dimensional (2D) topological insulators. However, it is generally believed that these crystalline bismuth phases are not superconducting or their transition temperature should be lower than 0.5 mK. Lead (Pb) is a good superconducting elementary material, and there is a relatively small difference in radius between the Bi atom and Pb atom. According to the Hume-Rothery rule, it is expected that Pb/Bi alloys in an arbitrary ratio should be superconducting. One may thus expect to form crystalline Bi based superconductors by Pb substitution, which might host intriguing topological superconductivity. While our previous work has demonstrated a low-temperature stable Pb<sub>1–<i>x</i></sub>Bi<sub><i>x</i></sub> (<i>x</i>~0.1) alloy phase in which Pb in the Pb(111) structure is partially replaced by Bi, the Bi crystalline structure-based phases of the superconducting alloys still lack in-depth research. Here, we report a new low-temperature phase of Pb-Bi alloy thin film, namely PbBi<sub>3</sub>, on the Si(111)-(7 × 7) substrate, by co-depositing Pb and Bi at a low temperature of about 100 K followed by an annealing treatment of 200 K for 2 h. Using low-temperature scanning tunneling microscopy and spectroscopy (STM/STS), we characterize <i>in situ</i> the surface structure and superconducting properties of the Pb-Bi alloy film with a nominal thickness of about 4.8 nm. Two spatially separated phases with quasi-tetragonal structure are observed in the surface of the Pb-Bi alloy film, which can be identified as the pure Bi(110) phase and the PbBi<sub>3</sub> phase, respectively, based on their distinct atomic structures, step heights and STS spectra. The PbBi<sub>3</sub> film has a base structure similar to Bi(110), where about 25% of the Bi atoms are replaced by Pb, and the surface shows a <inline-formula><tex-math id="M2">\begin{document}$\sqrt 2 \times \sqrt 2 R{45^ \circ }$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220050_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220050_M2.png"/></alternatives></inline-formula> reconstructed structure. The superconducting behavior of the PbBi<sub>3</sub> phase is characterized using variable-temperature STS spectra. We obtain that the superconducting transition temperature of PbBi<sub>3</sub> is about 6.13 K, and the <inline-formula><tex-math id="M3">\begin{document}$2\varDelta (0)/{k_{\text{B}}}{T_{\text{c}}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220050_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220050_M3.png"/></alternatives></inline-formula> ratio is about 4.62 using the fitting parameter of <inline-formula><tex-math id="M4">\begin{document}$\varDelta (0) = 1.22{\text{ meV}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220050_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220050_M4.png"/></alternatives></inline-formula> at 0 K. By measuring the magnetic field dependent superconducting coherence length, the critical field is estimated at larger than 0.92 T. We further investigate the superconducting proximity effect in the normal metal-superconductor (N-S) heterojunction consisting of the non-superconducting Bi(110) domain and the superconducting PbBi<sub>3</sub> domain. The N-S heterojunctions with both in-plane configuration and step-like configuration are measured, which suggest that the atomic connection and the area of the quasi-2D Josephson junctions and the external magnetic field can affect the lateral superconducting penetration length. We also observe the zero-bias conductance peaks (ZBCPs) in the superconducting gap of the PbBi<sub>3</sub> surface in some cases at zero magnetic field. By measuring d<i>I</i>/d<i>V</i> spectra at various temperatures and by adopting a superconducting Nb tip, we identify that the ZBCP originates from the superconductor-insulator-superconductor (S-I-S) junction formed between a superconducting tip and the sample. Nevertheless, the Bi(110)-based PbBi<sub>3</sub> phase may provide a possible platform to explore the intriguing topological superconducting behaviors at the vortexes under magnetic fields, or in the vicinity of the potentially topological superconducting Bi(110) islands by considering the proximity effect.

Electrolytic Processing of Pb-Bi Alloy

Metal bismuth is mainly produced as a by-product in the production of lead, tungsten, copper, silver, gold, tin and zinc. Approximately 90 % of all extracted bismuth is obtained from lead, copper and other concentrates. The main source of bismuth is lead concentrates obtained during the processing of lead, as well as lead-zinc and other polymetallic ores. During the processing of these concentrates, bismuth almost completely enters the rough lead, from which it is removed during its refining. The most common technologies for the recovery of bismuth from lead ingots are the Kroll-Betterton process and the Betts electrolytic process. During the electrolysis of the Bi-Pb alloy, the separation of three products has been established, they are anode and cathode alloys, as well as salt melt. The complexity of pyroelectrometallurgical processing of a bismuth-poor alloy with the production of rough bismuth in one stage is confirmed, which necessitates the use of two stages of electrolysis. At the first stage of electrolysis, the anode product‑1 (17.3–48.5 % of the initial Pb-Bi alloy) of the composition has been isolated,%: 16.6–48.4 Bi; 51.4–83.2 Pb; operational extraction,%: 92.2–96.6 Bi; 9.8–44.4 Pb; main phases Bi0,3Pb0,7 and Bi0,95Pb0,05. A six-fold bismuth enrichment is achieved in the anode product. At the second stage of electrolysis of the previously isolated anode product of the composition,%: 26.7 Bi; 73.1 Pb; 0.13 Cu; 0.08 Zn, the anode product‑2 (28.1 % of the enriched Pb-Bi alloy) of the composition has been separated,%: 93.6 Bi; 4.1 Pb; 0.086 Ag; 0.0066 As; 0.006 Sb; 0.0013 Cu; 0.001 Sn; 0.0014 Zn; stage extraction,%: 98.6 Bi; 1.6 Pb; main phase Bi0,95Pb0,05. As a result of pyroelectrometallurgical processing of a Pb-Bi alloy (~10 % Bi) with anode polarization in two stages, an anode product (8.7 % of the initial alloy) of the composition has been isolated,%: ≥ 93.6 Bi; 4.1 Pb; extraction from the initial alloy,%: 93.0 Bi; 0.4 Pb has been obtained. The following modes are recommended for pyroelectrometallurgical processing in two stages of Pb-Bi alloy: process temperature 550–600 °C; anode current density: 0.5 A/cm2 at the first stage; 0.2–0.3 A/cm2 at the second stage; cathode current density: 1.5 A/cm2 at the first stage; 1.0 A/cm2 at the second stage; operating voltage on the tub: at the first stage 8–12 V; at the second stage 5–8 V; the composition of the electrolyte at both stages,%: 7 NaCl; 35 KCl; 18 PbCl2; 40 ZnCl2; the amount of electrolyte output for processing: at the first stage – 10 % of the mass of the Pb-Bi alloy after alkaline treatment; at the second stage – 10 % of the mass of the anode product of the first stage

High-temperature-tolerable superconducting Nb-alloy and its application to Pb- and Cd-free superconducting joints between NbTi and Nb3Sn wires

For more than 30 years, Pb–Bi alloy and Wood's metal (50% Bi, 26.7% Pb, 13.3% Sn, and 10% Cd) have been used as representative superconducting solder intermedia to establish superconducting joints between NbTi and Nb3Sn wires in high-field nuclear magnetic resonance magnet systems. However, the use of Pb and Cd has been severely restricted by environmental regulations, such as the Restriction of Hazardous Substances Directive. Herein, a novel method of forming a superconducting joint between NbTi and Nb3Sn wires without Pb and Cd has been proposed. This approach is based on metallurgical bonding processes using a superconducting Nb-alloy intermedium, whose fine microstructure is maintained even after exposure to temperatures higher than 650 °C. Further, fine crystal defects become sources of magnetic flux pinning centers. Among transition elements close to Nb, Hf is considered the most suitable additive for realizing high-temperature-tolerable (HTT) superconducting Nb-alloy intermedia. Utilizing the HTT characteristic of Nb–Hf, a superconducting joint between Nb3Sn filaments and one end of the Nb–Hf alloy core was created by forming a superconducting Nb3Sn layer at the interface through a chemical reaction. The other end of the Nb–Hf alloy core was cold-pressed with NbTi filaments, to connect their active new surfaces to each other in order to create a superconducting joint. Ultimately, a superconducting joint between NbTi and Nb3Sn wires was realized with a high critical magnetic field (Bc2) of more than 1 T. The formation of the superconducting joint was confirmed by current decay measurements. This method of forming a superconducting joint is promising for application in environmentally friendly nuclear magnetic resonance magnet systems.Graphical abstract

Переработка висмутистых окислов

Introduction. The paper is devoted to the creation of an environmentally safe, technologically efficient and cost-effective high-performance integrated scheme for the recycling of lead-containing industrial products and waste, in particular, bismuth oxides and drosses formed during the melting of copper-electrolyte sludge, with the production of commodity monoelement products. To solve the problem, a combined technology is used, which is based on hydrometallurgical operations that allow separating chemical elements with similar properties with high extraction into finished products. The aim of the work is to study and develop fundamental approaches and rational integrated technologies for recycling bismuth drosses and oxides-industrial products of refining rough lead, using reducing melts of raw materials and bismuth-enriched sludge, electrolysis of bismuth lead to obtain rough bismuth containing ≥ 90 % Bi with its direct extraction of ≥ 70 %. Methods and approaches: melting at a temperature of 1,100…1,150 oC a charge of optimal composition containing bismuth oxides, sodium carbonate, silicon dioxide and carbon. Novelty: a decrease in the content of noble metals and accompanying chalcogenes in secondary copper-containing raw materials with an increase in the amount of impurity elements. Results and discussion: joint melting (1,100…1,150 °C) of bismuth oxides, sodium carbonate, silicon dioxide and carbon, taken in the mass ratio 100 : (15‒66) : (11‒25) : (5‒7), allows to transfer 89.0 – 93.6 % of bismuth and 99.5 ‒ 99.7 % of lead from the initial oxides to bismuth lead containing ~7 % Bi and ~80 % Pb. The main phase of the Pb-Bi alloy is elemental lead. The increased flux consumption leads to an increase in the amount of recycled silicate slags that are poor in target metals, into which it passes,%: 1.4 Bi; 2 Pb; 47 Zn; 23 Sb; 33 Sn. Main slag phases are following: Na2CaSiO4, Na4Mg2Si3O10, MgO, Pb, ZnS, PbS. The practical relevance is determined by the optimal mode of reducing melting of bismuth oxides (100 %) to obtain lead bismuth, %: 66 Na2CO3, 25 SiO2, 5 C; the process temperature is 1,150 ° C. The presence of impurities makes it necessary to introduce reagent treatment of lead bismuth into the technological scheme for recycling bismuth oxides. Decontamination and alkaline softening will make it possible to obtain a Pb-Bi alloy suitable for pyroelectrometallurgical recycling.

Phase segregating and complex forming Pb-based (=X-Pb) liquid alloys

ABSTRACT We have used a theoretical model based on the assumption of compound formation in binary alloys to study the thermodynamic, microscopic and surface properties of Bi-Pb and In-Pb liquid alloys. A review of the phase diagrams for these alloys shows that one of the stable complexes for Bi-Pb liquid alloy is BiPb3; also that In-Pb is a stable phase in liquid In-Pb alloys. Using the same interaction parameters that are fitted for free energy of mixing, we have been able to compute the bulk and thermodynamic properties of the alloys. From our observations, we are able to show that the Bi-Pb liquid alloy exhibits compound formation over the whole concentration range and the In-Pb alloys undergo phase separation. With regard to surface properties Pb segregates more to the surface in In-Pb alloys than in Bi-Pb alloys. The viscosity isotherms have positive deviation from ideality for both Bi-Pb and In-Pb alloys.

Characterization of structure and superconducting properties of low-temperature phase of Pb-Bi alloy films

Lead-bismuth (Pb-Bi) alloys, as a superconducting material, have been widely studied at their superconducting transition temperatures and the critical magnetic fields for different composition ratios. Most of experimental studies focused on the stable ε phase formed at high temperatures, but less on the Pb-Bi alloys grown at low temperatures. So far, the structural and superconducting properties of the low-temperature Pb-Bi phases are far from good understanding. Here, we report our investigation of structural and superconducting properties of a low-temperature phase of Pb-Bi alloy. The Pb-Bi alloy films with a nominal thickness of about 6 nm are prepared by co-depositing Bi and Pb on Bi(111)/Si(111)-(7 × 7) substrates at a low temperature of 100 K followed by annealing at a treatment of 200 K for 2 h. The structural and superconducting properties of the Pb-Bi alloy films are characterized in situ by using low-temperature scanning tunneling microscopy/spectroscopy (STM/STS). It is observed that the spatially separated phases of nearly pure Bi(111) domains and Pb<sub>1–<i>x</i></sub>Bi<i><sub>x</sub></i> alloy domains are formed in the films, where these phases can be identified by their distinct differences in the atomic structure and the distributions of step heights in the atomically resolved STM images, as well as by their distinguished STS spectra. The Pb<sub>1–<i>x</i></sub>Bi<i><sub>x</sub></i> alloy phase presents the structure of Pb(111), in which about <i>x</i> ≈ 0.1 Bi is substituted for Pb. The STS spectra show that the Pb<sub>1–<i>x</i></sub>Bi<i><sub>x</sub></i> alloy phase is superconducting, with a transition temperature <i>T</i><sub>c</sub> = 7.77 K derived from the variable-temperature measurements. This transition temperature is higher than that in pure Pb film (6.0–6.5 K), which can be well explained by the Mattias rules, with considering the fact that the average number of valance electrons increases after Bi atoms with five valance-electrons have been substituted for Pb atoms with four valance-electrons. The analysis shows that the ratio <inline-formula><tex-math id="M1">\begin{document}$ 2\Delta (0)/{k_{\rm{B}}}{T_{\rm{C}}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="17-20210482_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="17-20210482_M1.png"/></alternatives></inline-formula> is about 4.94 with the superconducting gap <inline-formula><tex-math id="M2">\begin{document}$ \varDelta (0) = 1.66$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="17-20210482_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="17-20210482_M2.png"/></alternatives></inline-formula> meV at 0 K, indicating that the Pb<sub>1–<i>x</i></sub>Bi<i><sub>x</sub></i> alloy is a strongly-coupled superconductor. The non-superconducting Bi(111) and the superconducting Pb<sub>1–<i>x</i></sub>Bi<i><sub>x</sub></i> alloy domains form an in-plane superconductor-normal metal-superconductor (S-N-S) Josephson junction. The proximity effect in the Bi(111) domains is measured at different N-S junctions, which suggests that the lateral superconducting penetration length in Bi(111) might be affected by the area of the quasi-two-dimensional interface. The superconducting gap in the Bi(111) region with a narrow width of 23 nm in an S-N-S Josephson junction is found to be greatly enhanced due to the existence of multiple Andreev reflections. Since Bi can host potential topological properties, the lateral Bi(111)-Pb<sub>1–<i>x</i></sub>Bi<i><sub>x</sub></i> heterostructures, because of the existing proximity effect, could have potential applications in exploring the novel topological and superconducting phenomena.