Bi Alloy Research Articles

Improvements in mechanical properties of Sn–Bi alloys with addition of Zn and In

In order to improve the mechanical properties after thermal aging of an Sn–45Bi–2.6Zn (SBZ) alloy, which we had proposed in a previous study, in this study, we prepared Sn–Bi–Zn–In alloys and investigated the effects of the addition of In and Zn on their microstructure and mechanical properties before and after thermal aging. We found that the addition of In suppressed the microstructural coarsening of SBZ during thermal aging and can potentially help reduce the brittleness of Sn–Bi alloys. Moreover, the addition of In had significant effect on the elongation of SBZ. We theorized that the segregation of Zn at the Sn/Bi phase boundary and the formation of a solid solution of In in the Sn phase are responsible for this result. Thus, the investigated alloys have potential for use as lead-free solder materials in the electronics industry. • The addition of Zn and In in a trace amount was effective in suppressing the microstructural coarsening of Sn–Bi alloys during thermal aging. Moreover, the addition of In had a significant effect on the elongation of the alloys. •The segregation of Zn at the Sn/Bi phase boundary and the formation of a solid solution of In in the Sn phase are responsible for the phenomenon of microstructural retention during thermal aging.

Effect of Bi content on microstructure and corrosion behaviour of Zn–8Al–(Bi) alloys

ABSTRACT Electrochemical techniques such as Polarisation and Galvanic tests as well as immersion test were used to analyse both the effects of different Bi contents and the length scale of dendritic spacings on Zn–8 wt-%Al–(1.5, 2.3 and 3 wt-%Bi) alloys on their corrosion behaviour. The results revealed that no significant differences in the corrosion kinetics were observed with the scale of the dendritic and lamellar spacings. Conversely, the corrosion behaviour was shown to be dependent on the alloy Bi content. Despite the cathodic character of Bi, its addition to the Zn–8%Al alloy was shown to reduce the corrosion rate as compared with that of the binary alloy.

Improved corrosion response of squeeze-cast AZ91 magnesium alloy with calcium and bismuth additions

The corrosion responses of the individual and combined Ca and Bi incorporated AZ91 alloy are investigated through the immersion, hydrogen evolution, and electrochemical tests. All the modified alloys exhibit better corrosion resistance than the base AZ91 alloy. The AZ91 + 1.0Ca (wt%) alloy unveils better corrosion resistance than the AZ91 + 0.5Bi (wt%) alloy owing to the Al2Ca phase formation. The combined Ca and Bi added AZ91 alloys acquire better corrosion resistance than the individual Ca or Bi added AZ91 alloys. The AZ91 + 2.0Ca + 0.5Bi (wt%) and AZ91 + 1.0Ca + 1.0Bi (wt%) alloys exhibit the lowest and the highest corrosion rates among the combined additions.

Microstructure, thermal behavior and joint strength of Sn-0.7Cu-1.5Bi/electroless nickel immersion gold (ENIG)

This paper details an investigation into the microstructure, thermal behaviors and joint strength of Sn-0.7Cu-1.5Bi solder alloy on electroless nickel immersion gold (ENIG) surface finish. Besides conventional techniques, the real-time synchrotron imaging was used to analyze the microstructure evolution in Sn-0.7Cu-1.5Bi/ENIG. This research investigated the growth behavior of the primary (Cu,Ni)6Sn5 intermetallic compounds (IMCs) in the solder joint with the Bi alloying. The elemental distribution analysis showed the Ni diffused from the ENIG surface finish and dissolved into the bulk solder during solidification and that the size of the primary (Cu,Ni)6Sn5 IMCs decreased due to the addition of 1.5 wt% Bi. The average kinetic growth rate of the primary (Cu,Ni)6Sn5 IMCs in Sn-0.7Cu-1.5Bi/ENIG was lower than that of the Sn-0.7Cu/ENIG. The thermal analysis revealed that the pasty range slightly increased and the undercooling degree decreased due to the addition of 1.5 wt% Bi for free-standing solder and soldering on ENIG surface finish. The shear strength of the Sn-0.7Cu-1.5Bi/ENIG was determined using a high-speed bond tester, and it increased by ~12% at bulk solder fracture of ~15% within the solder joint interfacial fracture due to the addition of 1.5 wt% Bi into the Sn-0.7Cu. These occurrences can be attributed to the solid solution strengthening effect at the bulk solder and the formation of finer interfacial (Cu,Ni)6Sn5 IMCs within the solder joints. The results indicated that the microstructural changes, especially the size reduction of IMCs, in Sn-0.7Cu-1.5Bi/ENIG impacted the joint strength.

Thermomechanical fatigue resistance of low temperature solder for multiwire interconnects in photovoltaic modules

Novel interconnect technologies leveraging low melting temperature solders, such as multiwire interconnects, are being deployed in photovoltaic (PV) modules for improved reliability through interconnect redundancy and lower thermal loads during interconnection and lamination. However, the equivalency of standardized accelerated testing to field conditions has not yet been established for these emerging technologies. In this study, the thermomechanical fatigue resistance of low temperature solder alloys is investigated and compared to that of conventional SnPb to assess the acceleration behavior of these alloys. While InSn is shown to have sufficient thermomechanical fatigue resistance on the order of that of SnPb, these results indicate Sn–Bi alloys may have poor thermomechanical fatigue resistance at field conditions. The results also show that Sn–Bi alloys have thermal cycling acceleration factors of less than one. This indicates that the standardized accelerated thermal cycling test, such as that in IEC 61215, will produce misleading results for Sn–Bi alloys and that unique testing is required for this PV module architecture. Though accelerated thermal cycling may be a meaningful qualification test for SnPb solder joints, these results suggest that mechanical loading may be a more appropriate test for Sn–Bi multiwire interconnects. This is due to the distinct processing and geometry of multiwire interconnects which may allow for mechanical, rather than strictly metallurgical interconnections.

Synthesis and Characterization of PtCo Alloy Nanoparticles Supported on a Reduced Graphene Oxide/g-C₃N₄ Composite for Efficient Methanol Electro-Oxidation.

In the development of direct methanol fuel cell (DMFC) the fabrication of an anode comprising of a Pt or Pt-based bi or tri-metallic alloys nanoparticles on a suitable support material having higher stability, higher surface area, electrical conductivity and strong interaction is very important. In the present work we have solved this problem by using a nanocomposite of reduced graphene oxide (rGO) and graphitic carbon nitride (g-C₃N₄) as the support material and deposited PtCo nanoparticles by in-situ chemical reduction. The electro-oxidation of methanol is carried out in an acidic medium. The electrochemical behaviour of as-synthesized PtCo/rGO-gC₃N₄ catalyst was found to be much superior to Pt/rGO-g-C₃N₄ catalysts towards electro-oxidation of methanol and is mainly due to the homogeneous dispersion of PtCo nanoparticles onto rGO-g-C₃N₄ nano composite, higher electrical conductivity and a strong interaction between metal nanoparticles and N group of the support material. By using the as-synthesized electro-catalyst the adsorption or poisoning of Pt due to CO is greatly reduced and more active Pt sites are created for the electro-oxidation of methanol. Thus, the as-synthesized electro-catalyst can be used as an efficient anode material in a direct methanol fuel cell.

Bi Nanoparticles Embedded in 2D Carbon Nanosheets as an Interfacial Layer for Advanced Sodium Metal Anodes.

Sodium metal is regarded as one of the most prospective next-generation anodes material owing to its high theoretical capacity, low redox potential, low cost, and natural abundance. Its most notable problem is the dendrite growth during Na plating/striping, which causes not only the safety concern but also the generation of inactive Na. Here, it is demonstrated that 2D carbon nanosheets embedded by bismuth nanoparticles (NPs) (denoted as Bi⊂CNs) serve as a robust nucleation buffer layer to endow the sodium metal anodes (SMAs) with high Coulombic efficiencies (CEs) and dendrite-free deposition during long-term cycling. The embedded Bi nanoparticles significantly reduce the nucleation barrier through the "sodiophilic" Na-Bi alloy. Meanwhile, the carbon frameworks effectively circumvent the gradual failure of those Na-Bi nucleation sites. As a result, the metallic Na on the Bi⊂CNs nucleation layer is repeatedly plated/stripped for nearly 7700 h (1287 cycles) at 3mA h cm-2 with an average CE of 99.92%. Moreover, the Na||Na symmetric cells with the Bi⊂CNs buffer layer are stably plated/stripped for 4000 h at 1mA cm-2 and 1mA h cm-2 . It is found that the cycling stability is closely related to the Na utilization of SMAs and current rate.

Au@Gqds@Ptxbi Nano-Dendrites Endows Alkaline Methanol Highly Electro-Catalytic Activity and Stability

In this work, we put forward a simple and green strategy to design and synthetic a highly efficient Au@GQDs@Pt3.5Bi nano-catalyst with a novel nanostructure composed of an Au@GQDs core and Pt3.5Bi alloy shell. This material showed outstanding catalytic capability for the oxidation of methanol (MOR) than that of the commercial Pt/C catalyst. The sequence of the mass activity was arranged to be commercial Pt/C (0.29 A mgPt−1) < Au@Pt3.5Bi (1.6 A mgPt−1) < Au@GQDs@Pt (1.81 A mgPt−1) < Au@GQDs@Pt3.5Bi (17.45 A mgPt−1). The outcomes ascribed to the unique core-shell structure with dendrites, interior electronic and synergistic effect with Bi and Pt. This work enlightens on the delicate proposal of novel core-shell nano-material for improving the electro-catalytic performance of MOR.

Thermodynamic properties of rare‐earth alloys by electrochemical emf measurements

Thermodynamic properties of Nd–Bi and Nd–Sn alloys were determined via electromotive force (emf) measurements at 725–1075 K. The emf measurements of an Nd–Bi alloy at mole fraction xNd = 0.20 were conducted using a solid CaF2–NdF3 electrolyte relative to pure Nd(s). The emf values from the CaF2–NdF3 electrolyte were verified in separate experiments in molten LiCl–KCl–NdCl3 where pure Nd(s) was electrodeposited. The Nd–Bi (xNd = 0.20) exhibited two‐phase behavior with a peritectic reaction (L + NdBi = NdBi2) at 926 K from differential scanning calorimetry. The two‐phase Nd–Bi (xNd = 0.20) was employed as a stable reference electrode in molten LiCl–KCl–NdCl3 for emf measurements of Nd–Bi (xNd = 0.15–0.40) and Nd–Sn (xNd = 0.10) alloys. The emf measurements of these alloys were reproducible during thermal cycles over 50 h and were used to calculate thermodynamic properties, including the partial molar Gibbs energy, entropy, and enthalpy.

Evaluating Microstructure, Wear Resistance and Tensile Properties of Al-Bi(-Cu, -Zn) Alloys for Lightweight Sliding Bearings

One of the most important routes for obtaining Al-Bi-x monotectic alloys is directional solidification. The control of the thermal solidification parameters under transient heat flow conditions can provide an optimized distribution of the Bismuth (Bi) soft minority phase embedded into an Al-rich matrix. In the present contribution, Al-Bi, Al-Bi-Zn, and Al-Bi-Cu alloys were manufactured through this route with their microstructures characterized and dimensioned based on the solidification cooling rates. The main purpose is to evaluate the influence of typical hardening elements in Al alloys (zinc and copper) in the microstructure, tensile properties, and wear of the monotectic Al-Bi alloy. These additions are welcome in the development of light and more resistant alloys due to the growing demands in new sliding bearing designs. It is demonstrated that the addition of 3.0 wt.% Cu promotes microstructural refining, doubles the wear resistance, and triples the tensile strength with some minor decrease in ductility in relation to the binary Al-3.2 wt.% Bi alloy. With the addition of 3.0 wt.% Zn, although there is some microstructural refining, little contribution can be seen in the application properties.

A compact Bi2WO6 microflowers anode for potassium-ion storage: Taming a sequential phase evolution toward stable electrochemical cycling

Potassium-ion batteries (KIBs) are considered an important alternative for lithium-ion batteries owing to the abundant potassium (K) resources and low-cost. To date, most reported anode materials for KIBs have been limited to carbonaceous materials which can well accommodate the large potassium ions (K + ) but show humble capacity performance. As compared, metal oxide-based anodes can potentially provide higher capacity yet cyclability is poor, which has been rarely researched. Herein, we report a sequential phase evolution mechanism for bimetallic oxide anode. Upon potassiation, the microflower-like Bi 2 WO 6 undergoes a multistep evolution process, which first combines with K + then converts into a highly reversible phase of Bi, then via a solid-solution reaction eventually it forms the K 3 Bi alloy. After repeated cycling process, such unique hierarchical and mesoporous morphology of Bi 2 WO 6 can be well maintained, leading to superior cyclability with a high specific potassium storage capacity (652 mAh g −1 at 100 mA g −1 ). Even at a large current density of 1 A g −1 , a reversible specific capacity of 216 mAh g −1 can still be delivered over 300 cycles. Such a novel working mechanism of bimetallic oxide anodes will promote the practical use of KIBs in diverse energy storage applications. • A novel sequential phase evolution mechanism for KIBs. • The unique highly reversible series transition reactions from Bi 2 WO 6 to Bi-K alloy. • Self-assembled interlaced microflower-like Bi 2 WO 6 anodes are prepared by hydrothermal method. • Structural evolution is analyzed by in-situ XRD and ex-situ TEM. • At a current density of 1 A g −1 , a reversible capacity of 216 mAh g −1 over 300 cycles is still delivered.

Mechanical alloying boosted SnTe thermoelectrics

The well converged transporting valence bands in SnTe-MnTe alloys ensures a superior electronic performance, while their thermal transport properties still need to be further optimized for higher thermoelectric performance. Herein, the mechanical alloying is utilized to fabricate the SnTe-15%MnTe-2%Bi alloys, leading to a remarkable reduction of grain size as well as the formation of dense dislocations. Unexpectedly, the solubility of MnTe is reduced to ∼6% by mechanical alloying at room temperature, inducing an enhanced phonon scattering from nanoprecipitates. These full-scale hierarchical microstructures effectively decrease the lattice thermal conductivity of SnTe-15%MnTe-2%Bi to ∼0.5 W m−1 K−1 at 850 K. In addition, the increased vacancy formation energy triggers a reduction in carrier concentration (∼3 × 1019 cm−3) due to the decreased MnTe content in matrix. Moreover, the energy filtering effect through precipitate-matrix interface enables an improvement in Seebeck coefficient. Accordingly, the figure of merit of SnTe-15%MnTe-2%Bi is dramatically increased to ∼1.5 at 850 K by mechanical alloying. This work clearly demonstrates that mechanical alloying changes the composition and microstructure of materials, which significantly affect the thermoelectric transport properties, enabling an obvious performance enhancement.

Visualizing the multifractal wave functions of a disordered two-dimensional electron gas

The wavefunctions of a disordered two-dimensional electron gas at the quantum-critical Anderson transition are predicted to exhibit multifractal scaling in their real space amplitude. We experimentally investigate the appearance of these characteristics in the spatially resolved local density of states of a two-dimensional mixed surface alloy Bi_xPb_{1-x}/Ag(111), by combining high-resolution scanning tunneling microscopy with spin and angle-resolved inverse-photoemission experiments. Our detailed knowledge of the surface alloy electronic band structure, the exact lattice structure and the atomically resolved local density of states enables us to construct a realistic Anderson tight binding model of the mixed surface alloy, and to directly compare the measured local density of states characteristics with those from our model calculations. The statistical analyses of these two-dimensional local density of states maps reveal their log-normal distributions and multifractal scaling characteristics of the underlying wavefunctions with a finite anomalous scaling exponent. Finally, our experimental results confirm theoretical predictions of an exact scaling symmetry for Anderson quantum phase transitions in the Wigner-Dyson classes.

Change of solidification behaviors in the superheating Sn-40wt.%Bi alloy from the viewpoint of the relaxation of properties

Change of solidification behaviors in the superheating Sn-40wt.%Bi alloy from the viewpoint of the relaxation of properties

The effects of different dopant on the optical parameters for selenium tellurium thin films

Glasses of (Se90Te10)95M5 (where M = Zn and Bi) were prepared using a melt–quench procedure. These incorporated elements were chosen as examples of transition metals and basic metal groups, respectively. Thin films of these glasses at a thickness of 100 nm were evaporated onto cleaned glass substrates. Structural investigations were studied using XRD, SEM, and DSC. The glass transition, Tg, and Onset crystallization behavior of glasses, Tc of (Se90Te10)95M5 (M = Zn and Bi) alloys were analyzed using DSC at a heating rate of 15 K min−1. XRD patterns confirmed the amorphous nature of the films. The absorption coefficient, α, and refractive index, n, were obtained for (Se90Te10)95M5 (M = Zn and Bi) films. The Eg values of Se90Te10 increase as dopant by Zn. Conversely, it decreases as dopant by Bi. Moreover, the optical constants of (Se90Te10)95M5 (M = Zn and Bi) films were estimated. The estimated results confirm the applicability of modifying samples to be used using in optoelectronics applications.

Nanoporous bismuth electrocatalyst with high performance for glucose oxidation application

Although direct glucose fuel cell (DGFC) is widely regarded as one of the most promising energy systems, the low catalytic activity and inferior instability of most anode catalysts during electro-oxidation of glucose has greatly hampered its potential applications. In this work, an efficient and durable anode catalyst of nanoporous bismuth (Bi) for the alkaline electro-oxidation of glucose was proposed just by a simple de-alloying method. The microstructure and catalytic performance of nanoporous bismuth could be finely tuning through actively controlling the composition of precursor Mg–Bi alloy. A three-dimension structure was formed after de-alloying Mg–Bi precursor, giving rise to an increased specific surface area and correspondingly resulting in an enhanced electro-catalytic performance. It has intimated that the optimal nanoporous Bi catalyst with an open, bi-continuous interpenetrating pore-to-ligament structure was constructed based on Mg65Bi35 alloy etching and exhibited an enhanced current density (as high as 8.04 mA/cm2) during alkaline electro-oxidation of glucose, together with the lowest poisoning rate of 5.6 × 10−3%. The remarkable electrochemical performance of the nanoporous Bi catalyst, coupling with facile dealloying strategy may facilitate design and development of renewable energy device.

Enhanced thermoelectric properties of n-type Cl doped PbS-based materials via Bi alloying

PbS-based thermoelectric (TE) materials in the intermediate temperature range have attracted extensive attentions for energy-conversion applications owing to their cost-effectiveness and earth-abundant constituent elements. However, the high TE properties are quite difficult to obtain due to the low carrier concentration and high lattice thermal conductivity (κlat). In this paper, the TE properties of n-type PbS-based materials are enhanced through synergistically optimizing the electrical conductivity (σ) and κlat by Cl doping and Bi alloying. It is found that the substitutions of Cl for S (ClS) and Bi for Pb (BiPb) in lattice remarkably increase the Hall carrier concentration and thus enhance σ, which brings about large power factors (S2σ) of ∼15 μWcm−1K−2 at 573 K and ∼12 μWcm−1K−2 at 823 K. Meanwhile, the introduced ClS and BiPb point defects and micro- or nano-scale precipitates (Bi and Pb) can effectively scatter heat-carrying phonons, resulting in a low κlat. As a consequence, a maxmium ZT value of ∼0.8 at 823 K is acquired for Pb0.99Bi0.01S-0.067%PbCl2, which is ∼1.78 times as high as that of undoped PbS.

Surface Properties of Indium, Tin, Bismuth, and Binary In–Bi and Sn–Bi Alloys

Surface Properties of Indium, Tin, Bismuth, and Binary In–Bi and Sn–Bi Alloys

Bi Alloying into Rare Earth Double Perovskites Enhances Synthesizability and Visible Light Absorption.

A high throughput combinatorial synthesis utilizing inkjet printing of precursor inks was used to rapidly evaluate Bi-alloying into double perovskite oxides for enhanced visible light absorption. The fast visual screening of photo image scans of the library plates identifies 4-metal oxide compositions displaying an increase in light absorption, which subsequent UV-vis spectroscopy indicates is due to bandgap reduction. Structural characterization by X-ray diffraction (XRD) and Raman spectroscopy demonstrates that the visually darker composition range contains Bi-alloyed Sm2MnNiO6 (double perovskite structure), of the form (Bi,Sm)2MnNiO6. Bi alloying not only increases the visible absorption but also facilitates crystallization of this structure at the relatively low annealing temperature of 615 °C. Investigation of additional seven combinations of a rare earth (RE) and a transition metal (TM) with Bi and Mn indicates that Bi-alloying on the RE site occurs with similar effect in the family of rare earth oxide double perovskites.

Anomalous Octahedron Distortion of Bi-Alloyed Cs2AgInCl6 Crystal via XRD, Raman, Huang-Rhys Factor, and Photoluminescence.

The refinement of XRD patterns only provides the average structure parameters for the alloying materials because of the symmetric protection. Raman vibrational modes can append the detailed information about the bond length and structure. The refinements of XRD patterns for Bi alloying Cs2AgInCl6 revealed the strong structure distortion with the enlarged octahedron of In(Bi)Cl6 and the contracted octahedron of AgCl6 with the increasing Bi. Raman spectra supported the expanded octahedron of InCl6 and the reduced octahedron of AgCl6 but identified the anomalous shortening bond length of Bi-Cl with the increasing Bi. These distorting octahedrons break parity forbidden transition, modify Huang-Rhys factor, and result in the maximum values at 30% Bi alloying and the same variation trend for both photoluminescence and Huang-Rhys factor with the increasing Bi alloying.