Bi Alloy Research Articles

Influence of Ag and Zn on the Microstructure and Properties of Sn-40 Bi Alloy for Improved Soldering Applications

Influence of Ag and Zn on the Microstructure and Properties of Sn-40 Bi Alloy for Improved Soldering Applications

The Effect of Bi Addition on the Electromigration Properties of Sn-3.0Ag-0.5Cu Lead-Free Solder

As electronic packaging technology advances towards miniaturization and integration, the issue of electromigration (EM) in lead-free solder joints has become a significant factor affecting solder joint reliability. In this study, a Sn-3.0Ag-0.5Cu (SAC305) alloy was used as the base, and different Bi content alloys, SAC305-xBi (x = 0, 0.5, 0.75, 1.0 wt.%), were prepared for tensile strength, hardness, and wetting tests. Copper wire was used to prepare EM test samples, which were subjected to EM tests at a current density of approximately 0.6 × 104 A/cm2 for varying durations. The interface microstructure of the SAC305-xBi alloys after the EM test was observed using an optical microscope. The results showed that the 0.5 wt.% Bi alloy exhibited the highest ultimate tensile strength and microhardness, improving by 33.3% and 11.8% compared to SAC305, respectively, with similar fracture strain. This alloy also displayed enhanced wettability. EM tests revealed the formation of Cu6Sn5 and Cu3Sn intermetallic compounds (IMCs) at both the cathode and anode interfaces of the solder alloy. The addition of Bi inhibited the diffusion rate of Sn in Cu6Sn5, resulting in similar total IMC thickness at the anode interface across different Bi contents under the same test conditions. However, the total IMC thickness at the cathode interface decreased and stabilized with increasing EM time, with the SAC305-0.75Bi alloy demonstrating the best resistance to EM.

Effects of Different Zinc Content on Solidification, Microstructure, and Mechanical Properties in Tin–Bismuth Alloy

The present aims to evaluate the effect of adding Zn (0.5% and 9.0% in wt%) on phase transformation temperatures, microstructure coarsening, solidification parameters (cooling rate‐L and growth rate‐VL), macrosegregation, and mechanical properties of directionally solidified Sn‐34wt%Bi‐xZn alloys. The samples have been characterized by optical microscopy, scanning electron microscopy, X‐ray fluorescence, and X‐ray diffraction, in addition to Vickers microhardness and tensile tests. The CALPHAD method has been used for thermodynamic computations via Thermo‐calc software, in order to obtain thermodynamic data. The microstructure of Sn–Bi–Zn alloys is mainly dendritic, composed of a Sn‐rich matrix (β‐Sn) with Bi precipitates inside and surrounded by a Sn+Bi eutectic mixture of phases, predominantly observed at the coarse scale. Coarse Zn needles are also observed in the Sn‐34wt%Bi‐9wt%Zn alloy due to the high Zn content. On the whole, Zn provoked a coarsening of the dendritic arrangement. Moreover, Zn additions cause inverse segregation of Bi, as compared to the rather constant macrosegregation profile observed in the binary Sn–Bi alloy. On the whole, both additions of Zn (0.5 and 9.0) promoted increase in Vickers microhardness, yield strength (σY), and ultimate tensile strength (σu), however, causing an overall reduction in elongation‐to‐fracture (δ).

Precise synthesis of In–Bi alloy nanodroplets through controlled surface reactions on a Si(111) surface at ambient temperature

The synthesis of alloy nanocatalysts with controllable sizes and shapes is a critical prerequisite for vapor–liquid–solid (VLS) growth of one-dimensional nanostructures. In this work, we comprehensively examined surface reactions between evaporated In atoms and a Bi thin film on a Si(111) surface at ambient temperature. InBi2 liquid nanodroplets nucleate and grow during initial vapor–solid (VS) reaction between the In vapor and surface Bi atoms, and the reaction proceeds until a saturation point is reached, following which InBi2 begins to catalyze subsequent VLS growth of various nanocrystals under persistent In-beam flux. The scaled size distribution of individual InBi2 nanodroplets could be explained adequately using the classical capillary nucleation theory, which suggests that the simultaneous homogeneous nucleation of InBi2 nanodroplets occurs during the vapor–solid (VS) reaction of In and Bi.

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.

Determination of the Complex Refractive Index of GaSb1−xBix by Variable‐Angle Spectroscopic Ellipsometry

Variable‐angle spectroscopic ellipsometry is used to determine the room temperature complex refractive index of molecular beam epitaxy grown GaSb1−xBix films with x ≤ 4.25% over a spectral range of 0.47–6.2 eV. By correlating to critical points in the extinction coefficient k, the energies of several interband transitions are extracted as functions of Bi content. The observed change in the fundamental bandgap energy (E0, −36.5 meV per %Bi) agrees well with previously published values; however, the samples examined here show a much more rapid increase in the spin‐orbit splitting energy (Δ0, +30.1 meV per Bi) than previous calculations have predicted. As in the related GaAsBi, the energy of transitions involving the top of the valence band are observed to have a much stronger dependence on Bi content than those that do not, suggesting the valence band maximum is most sensitive to Bi alloying. Finally, the effects of surface droplets on both the complex refractive index and the critical point energies are examined.

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.

In situ analysis of solute and flow fields in directional solidification of immiscible Al–Bi alloy

Segregation of the solidification structure of an immiscible alloy is related to the convection induced by the density differences of the components under gravity during solidification. Here, the solidification of the Al–Bi alloy in both opposing and parallel directions to the gravity force was investigated in situ using radiography and optical flow techniques. A quantitative analysis was performed on the flow, solute, and constitutional undercooling fields at the interface. During upward solidification, a flat solute-enriched layer was observed, with the melt flowing toward the center from both sides of the interface. During downward solidification, the solute-enriched layer was deformed, and solute plumes were observed, with the melt flowing toward the sides from the center of the interface. A high solute concentration gradient enhances the local flow and solute transport. The elongation of the plumes was attributed not only to the convective diffusion of the solute but also to the dispersion of droplet clusters. The forces acting on the droplets were calculated, and it was found that the resultant force on the droplets increased the area of the solute-enriched layer. Convection within the bulk melt and the motion of the droplets have synergistic effects on the flow pattern and solute distribution. Distinct microstructures were observed in opposite directions of solidification owing to the differences in constitutional undercooling and flow instability. This work offers insights into the quantitative measurement and understanding of the multi-physics fields during the solidification process.

The influence of Sn content on the electrochemical performance and discharge characteristics of Al-0.2Mg-0.02In-xSn-0.02Bi alloy anodes in aluminum-air batteries

The influence of Sn content on the electrochemical performance and discharge characteristics of Al-0.2Mg-0.02In-xSn-0.02Bi alloy anodes in aluminum-air batteries

Influence of non-stoichiometry and local atomic environments on carrier transport in GaAs1−x−yNxBiy alloys

We have investigated the influence of non-stoichiometry and local atomic environments on carrier transport in GaAs(N)Bi alloy films using local-electrode atom probe tomography (LEAP) in conjunction with time-resolved terahertz photoconductivity measurements. The local concentrations of N, Bi, and excess As, as well as Bi pair correlations, are quantified using LEAP. Using time-resolved THz photoconductivity measurements, we show that carrier transport is primarily limited by excess As, with the highest carrier mobilities for layers with yBi > 0.035.

Realizing high conversion efficiency in all-ZrCoSb-based half-Heusler thermoelectric power generators

ZrCoSb-based thermoelectric materials exhibit promising potential for power generation applications due to their high performance in both p- and n-type constituents. In this work, a newly developed all-ZrCoSb-based module achieves a maximum conversion efficiency of ∼9.3 % at a temperature difference of 668 K. This high conversion efficiency is enabled by the enhanced average thermoelectric properties for both types of ZrCoSb-based materials via Bi alloying and Sn/Ni doping. The hole and electron carrier concentrations were tuned to match the theoretically predicted optimized values, contributing to high weight mobility and power factor. Additionally, the increased mass and strain field fluctuations enhance point defect scattering, leading to a significant reduction in the lattice thermal conductivity of ZrCoSb. Consequently, peak zT values of ∼1.2 and ∼1.0 at 973 K were respectively obtained in p-type ZrCo(Sb0.5Bi0.5)0.85Sn0.15 and n-type ZrCo0.85Ni0.15Sb0.5Bi0.5, resulting in high average zT values of ∼0.75 and ∼0.51 in the temperature of 300 to 973 K. This work underscores the significant potential of all-ZrCoSb-based half-Heuslers in waste heat recovery.

EVOLUTION OF WEAR AND CORROSION RESISTANCE OF Bi ALLOY-LAMINATED Al/TiO2 COMPOSITE STRIPS FABRICATED VIA APB PROCESS

In this study, Bi alloy AA1100/TiO2/AA5083 composites were produced by accumulative press bonding (APB) for the first time. In the first step, two bars of aluminum alloys 1100 and 5083 with 5[Formula: see text]wt.% of uniformly scattered TiO2 particles were stacked together and pressed with a 50% reduction ratio. Then, this process was continued up to six steps. Corrosion properties of composites were studied by potential dynamic polarization and electrochemical impedance spectroscopy measurement in 3.5[Formula: see text]wt.% NaCl solution. So, in this investigation and as its novelty, a considerable improvement was revealed in the main electrochemical parameters as a result of enhancing the influence of APB steps and the inert character of the particles. Moreover, using the wear test, the wear resistance of these bi alloy composites has been studied vs the APB steps. Also, the wear and electrochemical experiments showed that corrosion and wear resistance of samples were improved by the APB steps by 70% and 34%, respectively.

Effect of Bi alloying and cold rolling on microstructure and mechanical properties of LA141 Mg[sbnd]Li alloy

LA141-xBi (x = 0, 1, 2, 3) alloys were prepared, and the effects of Bi alloying and cold rolling on the microstructure and mechanical properties were investigated. The results indicate that, with the addition of Bi, the grains were refined, and Mg3Bi2 phase is formed in the alloys. The as-cast LA141-2Bi possesses the tensile strength of 174 MPa, 21% higher than that of LA141 alloy. The cold rolled LA141-2Bi alloy exhibits a good balance between strength and plasticity, with a tensile strength of 237 MPa and an elongation of 30.5%. This improvement is primarily attributed to grain refinement, the dispersion of second-phase particles, high-density dislocations, and the presence of nano-twins.

Three-dimensional faveolate porous N-doped carbon skeleton embodied with nano Bi toward stable less-Na sodium metal batteries

Sodium metal batteries (SMBs) have been widely investigated recently due to the low price of Na metal, satisfactory energy density and similar chemical properties to lithium. However, SMBs also face challenges like low Na utilization, dendrite growth, dead sodium accumulation, unstable solid electrolyte interphase and massive bubble generation. To improve their safety and cycling stability, herein, we fabricate a porous hybrid framework, i.e., fine Bi nanoparticles anchored in porous N-doped carbon matrix (Bi@PNC), as a modified layer upon Cu collector toward stable SMBs. Upon electrochemical activation, the nanoscale Bi-derived Na–Bi alloy with high sodiophilicity reduces the nucleation overpotential of Na, inhibits the formation of Na dendrites, and decreases the loss of Na during cycling. Thanks to these striking merits, the half cells assembled with Na undergo 1600 cycles (3200 h) at 1 mA cm−2, 1 mAh cm−2 with the average Coulombic efficiency of 99.95%. The optimized Bi@PNC based symmetric cells still maintain the overpotential of ∼9.2 mV under 1 mA cm−2 and depth of discharge of 16.7% after cycling for 2420 h. Furthermore, the assembled less-Na full SMBs exhibit superb electrochemical properties. Our strategy here provides meaningful avenue to construct stable less-Na metallic anodes for advanced SMBs.

Effect of doping the PM6:Y7 active layer with MoS2 nanospheres in organic solar cells

Herein, MoS2 nanostructures were synthetized and characterized, as well as PM6:Y7 based organic solar cells (OSCs) were fabricated, tested, and modelled through SCAPS-1D software. Devices were assembled and tested under regular atmosphere conditions including the top electrode Field's Metal (FM), which is a eutectic alloy of Bi, In and Sn easily deposited by melting it at ∼ 95 °C. The modelled binary OSCs through SCAPS-1D achieved a PCE of 14.2%. The active layer was doped with MoS2 nanoparticles at two different concentrations, 1 and 2% v/v, the reached experimental average PCE values were 9.1%, 10.2% and 9.3% for control devices, and for the two doping concentrations, respectively; it means a PCE percentage enhancement of 11.2% when doping at 1% of MoS2. The enhanced experimental PCE value could be partially explained because of the light absorption into the active layer through the localized surface plasmonic resonance (LSPR) phenomenon induced by the nanostructures, among other optical phenomena such as light reflection and interference effects.

Thermophysical Properties of Cu-Based Subsystems of High-Entropy Alloys

According to the well-known concept of multicomponent high-entropy alloys, high entropy of mixing can stabilize the formation of solid solutions (simple bcc or fcc crystal structure) during solidification. Stabilization of the solid solution and prevention of the formation of intermetallic phases during solidification is provided by the high entropy of mixing in the solid and liquid states. High-entropy alloys have increased strength, high hardness, thermal stability in combination with good resistance to oxidation and corrosion. These properties allow to significantly expand the scope of these alloys. In this work, the electrical resistivity, thermoelectric power and surface tension of binary Cu–Sn, Cu–Ga and Cu–Bi alloys, which are the sub-system components of model low-temperature high-entropy Bi–Cu–Ga–Pb–Sn alloys, have been studied in a wide temperature range including solid and liquid states. The lack of the surface tension data of the above-mentioned alloys is compensated by the model predicted values.

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.

Intrinsic heterogeneity of grain boundary phase transitions in the Cu–Bi system: insights from grain boundary diffusion measurements

Abstract Diffusion of Bi and Ag in a series of polycrystalline Cu–Bi alloys is investigated using a radiotracer technique and applying the 207Bi and 110m Ag isotopes, respectively. Together with the previous measurements (Divinski S., Lohmann M., Herzig C., Straumal B., Baretzky B., Gust W. Grain-boundary Melting Phase Transition in the Cu−Bi System. Phys. Rev. B 2005, 71, 104104), a temperature–concentration interval of strong, by orders of magnitude, enhancements of Bi grain boundary diffusion rates is distinguished and the results are interpreted in terms of a grain boundary pre-wetting/wetting phase transition. Grain boundary diffusivity of Ag exhibits as well a step-wise increase with rising Bi content, mirroring the behaviour observed for the Bi tracer. However, contrary to the Bi tracer atoms for which grain boundary enhancement is observed at about 60 ppm of Bi in Cu–Bi alloys, this transition is revealed by the Ag tracer atoms at a significantly higher concentration, specifically between 90 and 100 ppm of Bi at 1080 K. The Ag diffusion rates in alloys with a moderate Bi content turn out to be not affected by the Bi-induced grain boundary phase transition and the measured grain boundary diffusion coefficients of Ag are nearly the same as those determined for pure polycrystalline Cu. This spectacular result suggests a strong heterogeneity of Bi segregation and Bi-induced phase transition for general high-angle grain boundaries in a given alloy. The behaviour is discussed in terms of the extrinsic grain boundary defects and their impact on mechano-chemical coupling which is accompanying the grain boundary phase transitions.

Silicon Oxycarbide-Coated Bismuth for Enhanced Anode Stability in Lithium-Ion Batteries

The current state-of-the-art lithium-ion batteries (LIBs) with graphite as an anode foresees shortcomings to demands in energy storage and supplies with high energy and power densities for large-scale applications such as electric vehicles. Metallic Bi alloy is among the promising alternative alloy candidates to replace the graphitic anode owing to its high volumetric capacity (3765 mAh cm−3), relatively small volume expansion (~215%), and unique layered crystalline structure with large interlayer spacing along the c-axis (d 003 = 3.95 Å). Nevertheless, inevitable volume expansion during repetitive Li+-ion insertion/extraction build-ups localized mechanical strain, causing particle pulverization, cracking, and isolations, eventually leading to cell failure. Herein, to achieve decent reversibility of alloys, we introduce a polymer-derived ceramic silicon oxycarbide (SiOC) coating onto Bi nanoparticles (NPs) via facile dispersion of bismuth hydroxide in silicone oil and consecutive heat treatment. The SiOC coating layer alone is an active conversion material with a higher specific capacity but lower volumetric capacity than Bi. To promote the fabrication of high volumetric capacity Bi-based composites using higher tap density materials with a well-balanced specific capacity, the content of the metal precursor and silicone oil were varied. The sturdy SiOC matrix embedded with the Bi NPs cushions the stress cultivated upon (de)lithiation reactions, achieving stable capacity (507 mAh g−1 at 0.05 A g−1 after 150 cycles), high volumetric capacity (872 mAh cm−3), superb cyclic stability (380 mAh g−1 at 0.5 A g−1 after 500 cycles), and adequate cell integrity when tested as an anode in a half cell. In a full cell configuration coupled with a LiNi0.5Co0.2Mn0.3O2 cathode, high gravimetric and volumetric energy densities of 343 Wh kg−1 and 607 Wh L−1 can be estimated, respectively. The conducted kinetic and postmortem analyses provide additional insights into the effectiveness of amorphous SiOC as a protective layer in preventing excess solid electrolyte interface passivation and preserving the electrically conductive network for continuous transport of ions and electrons. Figure 1

Advances in Electrochemical Energy Storage over Metallic Bismuth-Based Materials.

Bismuth (Bi) has been prompted many investigations into the development of next-generation energy storage systems on account of its unique physicochemical properties. Although there are still some challenges, the application of metallic Bi-based materials in the field of energy storage still has good prospects. Herein, we systematically review the application and development of metallic Bi-based anode in lithium ion batteries and beyond-lithium ion batteries. The reaction mechanism, modification methodologies and their relationship with electrochemical performance are discussed in detail. Additionally, owing to the unique physicochemical properties of Bi and Bi-based alloys, some innovative investigations of metallic Bi-based materials in alkali metal anode modification and sulfur cathodes are systematically summarized for the first time. Following the obtained insights, the main unsolved challenges and research directions are pointed out on the research trend and potential applications of the Bi-based materials in various energy storage fields in the future.