Sn Phase Research Articles

Comments on: “Encapsulation in ceramic material of the metals Cr, Ni, and Cu contained in galvanic sludge via the solidification/stabilization method. J. Environ. Chem. Eng. 5 (2017) pp. 3834–3843

Simultaneous extraction of metallic Pd, Rh, Ru, Ag, Zn and nonmetallic Cs using liquid tin metal as the collecting metal from the highly simulated borosilicate glass containing high level radioactive waste was examined under reductive and oxidative heat treatment. High Sn recovery efficiency was obtained under reductive atmosphere compared to that under air. The noble metals were concentrated into Sn phase, meanwhile Cs was phase-separated on the contact surface of the glass phase. The highest extraction % of Pd, Ru, Rh, Ag and Zn in Sn aggregation were 94.5, 79.4, 95.6, 84.2, 100 and 54, respectively, from the highly simulated glass after reductive heat treatment. Cs on the glass surface was extracted by leaching with high extraction efficiency up to 80%. Liquid Sn extraction is evidenced to be effective for simultaneously extraction of the noble metals and other nonmetallic fission products from the highly simulated borosilicate glass.

Synthesis, crystal structures, phase width and electrochemical performances of γ-brass type phases in Cu–Zn–Sn system

Cu–Zn–Sn ternary phases were synthesized by high-temperature solid-state synthesis. Structural characterization was performed by means of X-ray diffraction and energy dispersive X-ray analysis. The ternary compounds were found to adopt γ-brass (Cu5Zn8) structure type. X-ray diffraction analyses show that γ-brass type phases in Cu–Zn–Sn system crystallize in P4¯3m space group (cP52, 215). Ternary Cu–Zn–Sn γ-brass type phases exist in an extended homogeneity range. The phase-pure ternary compounds are found to exist for compositions ranging between 48 and 70 atomic % Cu, between 15 and 46 atomic % Zn, and between 5 and 15 atomic % Sn. The phase width arises due to the statistical distribution of constituent elements, which is typical for intermetallic compounds. The Cu–Zn–Sn γ-brass structures consist of two compositionally different γ-clusters (consists of the four polyhedral shells: inner tetrahedron (IT), outer tetrahedron (OT), octahedron (OH), cuboctahedron (CO)) centered at high symmetric sites in a primitive cubic unit cell. The γ-brass cluster (A) at (0,0,0) site is Cu-rich, chemically more ordered than the cluster (B) present at (½,½,½). For A cluster, only IT site is mixed (Zn/Sn) and OT, OH, CO sites are exclusively occupied by Cu, throughout the entire homogeneity range. The B cluster is heavily disordered; only the OT site is exclusively occupied by Cu all over the phase region. For Zn rich region IT site is fully occupied by Zn, then mixed occupied between Cu and Zn at intermediate Zn-concentration, and completely occupied by Cu at Cu-rich side of the Cu–Zn–Sn phases. OH site is fully occupied by Zn at Zn rich side. The same site is mixed occupied between Cu, Zn and Sn for the composition at intermediate Zn-concentration and Cu/Sn at Zn poor side. CO site of B cluster is occupied by Zn and Sn. The electrochemical properties of four Cu–Zn–Sn based samples with different compositions were studied as an anode material for lithium and sodium-ion storage using galvanostatic charge-discharge cycles. Li-ion half-cells transpired excellent retention of charge capacity (>80%) with more than 99% Coulombic efficiency. The results further encourage the prospects of ternary Cu–Zn–Sn alloy anodes to utilize in real energy storage applications.

Effect of microstructure of Au80Sn20 solder on the thermal resistance TO56 packaged GaN-based laser diodes

Au80Sn20 alloy is a widely used solder for laser diode packaging. In this paper, the thermal resistance of GaN-based blue laser diodes packaged in TO56 cans were measured by the forward voltage method. The microstructures of Au80Sn20 solder were then investigated to understand the reason for the difference in thermal resistance. It was found that the microstructure with a higher content of Au-rich phase in the center of the solder and a lower content of (Au,Ni)Sn phase at the interface of the solder/heat sink resulted in lower thermal resistance. This is attributed to the lower thermal resistance of Au-rich phase and higher thermal resistance of (Au,Ni)Sn phase.

Deformed Microstructure Characteristics and Nano-Mechanical Properties of CuSn10P1 Alloy

Enclosed cooling slope channel was adopted to prepare CuSn10P1 semi-solid sample. Compared with as-cast sample by conventional liquid forming, the brittle phases among intergranular microstructure reduced, which prevented the risk of thermal cracks. During hot deformation process, the formation and movement of dislocations results in slipping bands. The β' -Cu13.7Sn phase balanced the Young's modulus in the microstructure and improved the ability of coordinated deformation among grains. These findings provide a theoretical guidance for semi-solid CuSn10P1 deformation process.

Diffusion reaction-induced microstructure and strength evolution of Cu joints bonded with Sn-based solder containing Ni-foam

Sn based composite solder, reinforced with low porosity Ni-foam, was used to fabricate high melting point Cu interconnects by soldering at 260 °C. The effects of soldering time on the microstructure and mechanical properties of the joints were investigated. The Sn matrix was rapidly consumed by the formation of (Cu,Ni)6Sn5 and (Ni,Cu)3Sn4 phases in under 10 min. With increasing soldering time, the (Cu,Ni)6Sn5 phase was largely transformed into the (Ni,Cu)3Sn4 phase, accompanied by the refinement in the size of the phases. The average shear strength of the joint soldered for 60 min was up to 76.9 MPa, which is significantly stronger than commonly reported for Cu joints soldered with Sn based alloys.

Crystal structure of incommensurate ηʺ-Cu1.235Sn intermetallic

Abstract The crystallographic parameters of the incommensurately ordered phase ηʺ of the composition Cu1.235Sn are reported. This phase belongs to the group of ordered Ni2In/NiAs-type phases, with a NiAs-type arrangement Cu(1)Sn and additional Cu(2) atoms partially occupying trigonal-bipyramidal interstices in an ordered fashion, leading to the formula Cu(1)Cu(2)0.235Sn = Cu1.235Sn. The structure model, afterward refined on the basis of powder X-ray diffraction data, has been derived on the basis of the slightly Cu-poorer commensurately ordered η′-Cu6Sn5 (=Cu1.2Sn) phase but also on previously reported commensurate structure models η8-Cu1.25Sn and η4+1-Cu1.243Sn derived from selected area electron diffraction data. In line with a recent work (Leineweber, Wieser & Hügel, Scr. Mater. 2020, 183, 66–70), the incommensurate ηʺ phase is regarded as a metastable phase formed upon partitionless ordering of the η high-temperature phase with absent long-range ordering of the Cu(2) atoms. The previously described η8 and η4+1 superstructure are actually of the same phase, and the corresponding superstructure models can be regarded as approximant structures of the ηʺ phase. The refined structure model is described in 3+1 dimensional superspace group symmetry C2/c(q 10-q 3)00 with a unit cell of the average structure with lattice parameters of a av = 4.21866(3) Å, b av = 7.31425(5) Å, c av = 5.11137(3) Å and b av = 90.2205(5)° and a unit cell volume V = 157.717(2) Å3. The modulation vector is with q 1 = 0.76390(4), q 3 = 1.51135(5), and governs the spatial modulation of the occupancy of the Cu(2) atoms described by a Crenel function. The occupational ordering is accompanied by displacive modulations of the atoms constituting the crystal structure, ensuring reasonable interatomic distances on a local level. In particular, the spatial requirements of pairs of edge-sharing Cu(2)Sn5 trigonal bipyramids (Cu(2)2Sn8) lead to a measurable splitting of some fundamental reflections in the powder diffraction data. This splitting is considerable smaller in η′-Cu1.20Sn, which lacks such pairs due to the lower Cu content.

Microstructural properties and peritectic reactions in a binary Co–Sn alloy by means of scanning electron microscopy and atom probe tomography

Recent studies of lithium-ion batteries suggest that the use of binary CoSn alloys as anodes should provide an improvement over currently used anode materials. However, the implementation of CoSn alloys is challenging due to uncertainties regarding the phase transformations within this system. In order to understand these, we evaluate the compositions of different intermetallic compounds produced via the peritectic reactions, nucleate and grow within the microstructure of binary Sn − 25 at.% Co by employing atom probe tomography (APT). The stoichiometric phase, which is produced upon the cooling of the melt, is not only found as part of the peritectic solidification sequence but also as clusters within the pure Sn phase. The phase was found as a nano sized layer and is attributed to the peritectic reaction between the phase and the pure Sn phase. The production of the compound was enhanced by the phase transformation of the phase. Furthermore, clusters had formed in the pure Sn phase. A limited solubility within the pure Sn phase was also determined to be (0.6 ± 0.1) at.% Co.

Selective hydrogenation of acetylene over Pd-Sn catalyst: Identification of Pd2Sn intermetallic alloy and crystal plane-dependent performance

In Pd catalyzed acetylene semi-hydrogenation, high selectivity always comes at the expense of activity while improving both selectivity and activity is challenging. In this work, the performance of Pd alloy catalysts was enhanced by inserting Sn phase to modify both surface Pd ensembles and electronic structures. Compared with Pd/C, the optimal Pd2Sn/C catalyst exhibits higher selectivity at the same acetylene conversion level, with its selectivity increased from 10 % to nearly 95 % at ca 100 % acetylene conversion. Both experimental and DFT calculation results reveal that the specific performance is attributed to the redispersion of surface Pd ensembles by Sn insertion and down-shift of d-band center of catalysts, thus changing the adsorption behavior of the reaction gases. This design principle provides an efficient method for tailoring and optimizing durable Pd-based catalysts with desirable reactivity and ethylene selectivity for selective hydrogenation of acetylene.

Microstructure and mechanical properties of Cu joints soldered with a Sn-based composite solder, reinforced by metal foam

In this study, Ni foam, Cu coated Ni foam and Cu-Ni alloy foams were used as strengthening phases for pure Sn solder. Cu-Cu joints were fabricated by soldering with these Sn-based composite solders at 260 °C for different times. The tensile strength of pure Sn solder was improved significantly by the addition of metal foams, and the Cu-Ni alloy/Sn composite solder exhibited the highest tensile strength of 50.32 MPa. The skeleton networks of the foams were gradually dissolved into the soldering seam with increasing soldering time, accompanied by the massive formation of (Cu,Ni)6Sn5 phase in the joint. The dissolution rates of Ni foam, Cu coated Ni foam and Cu-Ni alloy foams into the Sn matrix increased successively during soldering. An increased dissolution rate of the metal foam leads to an increase in the Ni content in the soldering seam, which was found to be beneficial in refining the (Cu,Ni)6Sn5 phase and inhibiting the formation of the Cu3Sn IMC layer on the Cu substrate surface. The average shear strength of the Cu joints was improved with increasing soldering time, and a shear strength of 61.2 MPa was obtained for Cu joints soldered with Cu-Ni alloy/Sn composite solder for 60 min.

Effects of the Ni(P) plating thickness on microstructure evolution of interfacial IMCs in Sn–58Bi/Ni(P)/Cu solder joints

Effects of the Ni(P) plating thickness on interfacial reaction in the Sn–58Bi/Ni(P)/Cu joint system were revealed. It was found that the interfacial reaction was significantly influenced by the thickness of Ni(P) plating, and 0.1 μm Ni(P) plating completely transformed into Ni2SnP layer after soldering. This Ni2SnP layer not only provided a large number of diffusion channels but also reduced the solder joint reliability, demonstrating that 0.1 μm Ni(P) plating was not efficient in inhibiting the diffusion process between solder and substrate. However, the Ni(P) plating with thickness more than 0.5 μm could effectively inhibit atomic diffusion, and the Sn–Ni interaction would dominate the interfacial reaction instead of Cu–Sn phases. Although the Ni(P) plating with thickness of 0.5 μm partly transformed into Ni2SnP layer, the growth rate of compound layer was suppressed. In addition, the Ni3Sn4 would transform into (Cu,Ni)6Sn5 since Ni2SnP layer provided channels for Cu diffusing toward the solder/Ni3Sn4 interface. The Ni(P) plating with thickness of 1.5 μm remained integrated even after aging for 240 h, nonetheless, the excessive thickness of this barrier was unnecessary. Thus, it could be concluded that the appropriate thickness of Ni(P) plating should be controlled at 0.5–1.5 μm.

Prediction of ternary alkaline-earth metal Sn(II) and Pb(II) chalcogenide semiconductors

Sn(II) and Pb(II) compounds, especially chalcogenides, are important functional materials. The complementary properties of these two families of compounds, with differences related to the differences in stability of the divalent state and relativistic effects on the band structures, provide tunability of properties and also can guide searches for new phases. In particular, it suggests the existence of previously unknown ternary Sn(II) and Pb(II) chalcogenide phases. Here, we predict the existence of stable compounds via first-principles global optimization structure searches on the alkaline-earth metal Sn(II) and Pb(II) chalcogenide systems. This leads to five new stoichiometries. These unreported phases, ${\mathrm{SrSnS}}_{2}$, ${\mathrm{SrSnSe}}_{2}$, ${\mathrm{SrPbSe}}_{2}$, ${\mathrm{BaSnSe}}_{2}$, and ${\mathrm{BaPbS}}_{2}$, are thermodynamically preferred by Sn-rich (or Pb-rich) conditions, which favor the divalent state. They are semiconducting with band gaps ranging from 0.80 to 1.85 eV, strong visible light absorption and relatively light hole and electron effective masses ($l1$ ${\mathrm{m}}_{0}$). The valence band maxima of these compounds have antibonding character involving metal $s$ and chalcogen $p$ character. This is a feature that is often associated with defect tolerant behavior. In addition the compounds show complex band structures of a type that is favorable for thermoelectric performance.

Electrochemical Separation and Recovery of Metallic Zr from KCl-LiCl-K2ZrF6-PrCl3 Molten Salt System

The electrochemical behavior of Zr(IV) and Pr(III) in LiCl-KCl melt on W and Sn electrodes was studied by various electrochemical methods. Electrochemical results indicated that the deposition potentials of Pr and Zr on Sn electrode shifted towards more positive value than that on W electrode due to forming different Sn-Zr and Sn-Pr intermetallic compounds. By means of cyclic voltammetry, square wave voltammetry, the deposited potentials of Pr and Zr on the Sn electrode were confirmed at -1.18 V and -0.8 V, respectively. Thus the selective potential range for separating Zr(IV) and Pr(III) was approximately -0.8 V to -1.1 V. The effects of applied potentials on separation were also studied and the optimal separation conditions were confirmed. The results of XRD and SEM-EDS indicated that the product consisted of Sn and Sn2Zr phases, and the separation of Zr and Pr could be achieved by potential electrolysis. Acknowledgement The work was financially supported by the National Natural Science foundation of China (11675044, 21790373, 21876034 and 11875116), and the International Exchange Program of Harbin Engineering University for Innovation−oriented Talents Cultivation.

Towards Ultra-Low Specific Contact Resistance on P-Type and N-Type Narrow Bandgap GeSn Semiconductors

GeSn alloys are group IV semiconductors that have attracted remarkable interest owing to their ability of strain and bandgap engineering by controlling the Sn content, their compatibility with the Si CMOS platform and their tunable and direct band gap. These material properties make GeSn a promising candidate for many electronic and optoelectronic applications including among others tunnel field effect transistors, infrared (IR) photodectors, and IR emitters. However, in order to produce high quality GeSn devices to enable these applications, it is of paramount importance to develop ohmic metal contacts with very low specific contact resistivity on both n-type and p-type doped GeSn layers used in these devices. This could be achieved by realizing high doping levels and attaining low intrinsic barrier heights between the metal and the contacted GeSn layer.The growth of metastable GeSn semiconductors is typically performed at temperatures well below 400 ºC to avoid Sn segregation and phase separation, which would compromise the opto-electronic properties of the material. [1] Therefore, major care is required when developing post-growth processes that are commonly required for device fabrication. For instance, ohmic contact formation using the conventional process of rapid thermal annealing of nickel contacts cannot be made and the GeSn cannot be cured after dopant implantation because of the very limited thermal budget. We investigated both the epitaxial growth of highly doped layers, as well as the passivation of undoped GeSn samples in order to circumvent these limitations and achieve the desired barrier heights for both p-type and n-type GeSn while varying the Sn content.First, epitaxially grown GeSn layers with p- and n-type doping are demonstrated. For GeSn doping, the CVD growth of in-situ doped GeSn layers is done using B2H6 for p-type, and AsH3 for n-type. We show high active doping levels in the orders of 1019 and 1020 cm-3 for both p-GeSn and n-GeSn, respectively. These results were obtained from the capacitance voltage measurements (CV) using metal oxide semiconductor (MOS) back-to-back devices. In addition, secondary ion mass spectroscopy (SIMS) and atom probe tomography (APT) data support the high and uniform doping levels.Secondly, since the strong Fermi level pinning (FLP) of Ge is a major problem in the development of n-type contacts due to the loss of metal work function modulation of the barrier height [2], it is expected that the GeSn materials system with low Sn levels exhibits the same behavior, thereby degrading the properties of direct metal/n-GeSn contacts. Therefore, we develop processes aiming to release the Fermi level pinning at metal/GeSn interface, thus restoring the metal work function control of the barrier height. Samples used in this study are CVD grown intrinsic GeSn relaxed samples with increasing Sn concentrations up to 11 at. %. These samples are unintentionally p-type with defect doping levels in the order of 1017 cm-3 as obtained by CV measurements on MOS devices. Our process starts by chemical passivation of these samples, then the deposition and patterning of four metals with different work functions close to the band gap is realized to obtain transfer length method (TLM) structures used for current-voltage (IV) measurements. We then extract the contact properties of these devices and estimate the change of the barrier height induced by the chemical passivation due to the depinning of the FL. This demonstrates the potential use of our process in the fabrication of future metal/n-GeSn contacts. Acknowledgements O.M. acknowledges support from NSERC Canada (Discovery, SPG, and CRD Grants), Canada Research Chairs, Canada Foundation for Innovation, Mitacs, PRIMA Québec, and Defence Canada (Innovation for Defence Excellence and Security, IDEaS).

Large-Scale Sonochemical Synthesis of Bi-Sn Eutectic Alloy Nanoparticles.

Lead-free Bi-Sn alloy is an alternative solder material with a low eutectic melting temperature and environmental compatibility. Although extensive research has been conducted on this Bi-Sn eutectic alloy, a lack of facile synthetic methods with scalability hinders the implementation of finepatterned interconnectors for emerging electronic applications. In this study, we employed a facile sonochemical synthetic method to synthesize Bi-Sn alloy nanoparticles in large quantities. Highenergy ultrasonication treatment of Bi-Sn bimetallic particles resulted in nanoparticle formation with repeated formation, growth, and collapse of induced gas bubbles. The size of the nanoparticles was controlled from 92 to 506 nm of the mean diameter with variations in ultrasonication power and irradiation time. The nanoparticles exhibited a stable eutectic melting point at 139.8 °C. Interestingly, the sonochemically synthesized nanoparticles exhibited coexistence of metastable Bi2Sn and stable Bi-Sn phases. Finally, we demonstrated that Bi-Sn eutectic nanoparticles could be synthesized at a gram scale of approximately 1.7 g for future mass production.

Bowlesite, PtSnS, a new platinum group mineral (PGM) from the Merensky Reef of the Bushveld Complex, South Africa

AbstractBowlesite is a new mineral discovered in the Merensky Reef of the Rustenburg Platinum Mine, Bushveld complex, South Africa. Bowlesite forms tiny grains (maximum dimension 20 μm). It is associated with sulfides including chalcopyrite, pyrrhotite and pentlandite, in contact with silicates including plagioclase, pyroxene- and minor serpentine-subgroup and amphibole-supergroup minerals. Bowlesite is brittle and has a metallic lustre. In plane-polarised light, bowlesite has a light bluish grey colour. It shows weak bireflectance, no pleochroism and has weak anisotropism. Internal reflections were not observed. Reflectance values of bowlesite in air (R1, R2 in %) are: 50.3–51.4 at 470 nm, 48.5–48.9 at 546 nm, 47.9–48.6 at 589 nm and 47.8–48.7 at 650 nm. Ten spot analyses of bowlesite give the average composition: Pt 56.85, Pd 0.02, Sn 34.03 and S 9.15, total 100.05 wt.%, corresponding to the empirical formula (Pt1.001Pd0.001)Σ1.002Sn0.997S1.001, based on 3 atoms per formula unit. The simplified formula is PtSnS. Due to the small size of bowlesite, the crystal structure was solved and refined from the powder X-ray-diffraction data of synthetic PtSnS. The calculated density is 10.06 g⋅cm–3. The mineral is orthorhombic, space group: Pca21 (#29) with a = 6.11511(10), b = 6.12383(10), c = 6.09667(11) Å, V = 228.31(1) Å3 and Z = 4. Bowlesite is isotypic with cobaltite, CoAsS. The origin of bowlesite is probably related to low-T exsolution of Pt–Sn phases from high-T sulfides crystallised from the sulfide melt. The mineral honours Dr. John Bowles (Manchester University, UK) for his contributions to ore mineralogy and mineral deposits related to mafic–ultramafic rocks.

Microstructure evolution and mechanical properties of the In–Sn–20Cu composite particles TLP bonding solder joints

In this study, the Cu/In–Sn–20Cu/Cu solder joints were fabricated under the bonding temperature of 260 °C, bonding stress of 3 MPa and bonding time of 0.5–60 min by transient liquid phase bonding. The influence of bonding time on the microstructure evolution and the shear strength of the solder joints was investigated. The results indicated that the intermetallic compound in the interface reaction zone was Cu3(In, Sn) phase, and its thickness was increased continuously with increasing bonding time. The scallop-type Cu6(In, Sn)5 phase was formed at the interface of Cu3(In, Sn)/In–Sn–20Cu composite solder and then gradually grew to connect the island-type Cu6(In, Sn)5 phase which formed in the in situ reaction zone. The transformation of Cu6(In, Sn)5 phase to Cu3(In, Sn) phase occurred in the in situ reaction zone after the bonding time reached 15 min. The shear strength of the Cu/In–Sn–20Cu/Cu solder joints was increased first and then decreased with increasing bonding time. The maximum shear strength was 26.54 MPa when the bonding time reached 15 min. The shear fracture mechanism of solder joints transited from brittle fracture to ductile–brittle mixed fracture with increasing bonding time.

Microstructural and shear strength properties of RHA-reinforced Sn–0.7Cu composite solder joints on bare Cu and ENIAg surface finish

In this study, the joint effect of rice husk ash (RHA) reinforcement as an alternative silica source and electroless nickel immersion silver (ENIAg) surface finish on the intermetallic compound (IMC) formation and shear strength of the Sn–0.7Cu solder system was investigated. A series of plain and composite lead-free solder systems (Sn–0.7Cu−xRHA; x = 0, 0.01, 0.05 and 0.1 wt%) was successfully developed and subjected to reflow soldering on bare Cu and ENIAg surface finish. After conducting a comprehensive microstructural study using the scanning electron microscopy and energy dispersive spectroscopy techniques, the Cu6Sn5 and Cu3Sn intermetallic compound (IMC) phases were observed at the interface of the Sn–0.7Cu−xRHA/Cu composite solder joints. On the other hand, the (Cu,Ni)6Sn5 and Ni3Sn4 IMC phases dominated the interface of the Sn–0.7Cu−xRHA/ENIAg counterparts. Given the promising potential of the ENIAg surface finish, the Sn–0.7Cu−xRHA/ENIAg exhibited IMC thickness values within a range of 3.81–4.74 µm as compared to the 6.13–9.3 µm range exhibited by the Sn–0.7Cu−xRHA/Cu counterpart. More so, the ENIAg surface finish was effective in improving the shear strength of the plain solder joint, with the Sn–0.7Cu/ENIAg exhibiting 13.44 MPa relative to the 11.5 MPa exhibited by the Sn–0.7Cu/Cu counterpart. Overall, the strengthening effect of the RHA reinforcement was well marked in the Sn–0.7Cu−xRHA/Cu composite solder joints with the composite having 0.1 wt% RHA exhibiting the highest shear strength (14.6 MPa) across the board.

Review of Emerging Potassium-Sulfur Batteries.

This is the first review on potassium-sulfur (K-S) batteries (KSBs), which are emerging metal battery (MB) systems. Since KSBs are quite new, there are fundamental questions regarding the electrochemistry of S-based cathode and of K metal anode, as well as the holistic aspects of full-cell performance. The manuscript begins with a critical discussion regarding the potassium-sulfur electrochemistry and on how it differs from the much better-known lithium-sulfur. Cathodes are discussed next, focusing on the role of sulfur structure, carbon host chemistry and porosity, and electrolytes in establishing the reversible potassium sulfide K2 Sn phase sequence, the parasitic polysulfide shuttle, pulverization-driven capacity fade, etc. Following is a discussion of solid-state electrolytes (SSEs), including of hybrid solid-liquid systems that show much promise. Potassium metal anodes are then critically reviewed, emphasizing electrolyte reactions to form stable versus unstable solid electrolyte interphase (SEI), covering the current understanding of potassium dendrites, and highlighting the deep-eutectic K-Na alloying approaches for room temperature liquid anodes. The manuscript concludes with K-S batteries, focusing on cell architectures and providing quantitative performance comparisons as master plots. Unanswered scientific/technological questions are identified, emerging research opportunities are discussed, and potential experimental and simulation-based studies that can unravel these unknowns are proposed.

Seismic Attenuation and Velocity Measurements of the Uppermost Mantle Beneath the Central and Eastern United States and Implications for the Temperature of the North American Lithosphere

AbstractWe constructed a detailed map of the uppermost mantle seismic structure beneath the Central and Eastern United States (CEUS) using the International Seismological Centre Bulletin and seismic waveforms from USArray. Identical Pn and Sn travel time data sets were inverted to tomographically image the uppermost mantle P wave (Pn) velocity, S wave (Sn) velocity, and the velocity ratio (VPn/VSn). Furthermore, we modified the two‐station method in order to limit the contributions of site response and estimate the effective attenuation of Sn phase (Q−1Sn).Lower Q values generally correspond with lower velocities in terms of both Pn and Sn wave speeds (e.g., New England and the Mississippi Embayment), but some regions, including southern Georgia, eastern South Carolina, and the New Madrid Seismic Zone, show high velocity and low QSn values. This can be explained by scattering attenuation of the Sn phase. To estimate the uppermost mantle temperature, a constrained grid‐search algorithm was conducted using the observed VSn, VPn, and QSn with the calculated velocities of specific compositional models. The uppermost mantle temperature result shows ~300–500 °C beneath the northern midcontinent and 1100 °C beneath New England. Although our temperature results appear to be well resolved, we found that VPn, VSn, and QSn are not enough to constrain the detailed uppermost mantle composition model. Our results highlight significant temperature heterogeneity in the uppermost mantle across the CEUS and is consistent with there not being any melt within the uppermost mantle beneath the CEUS.

Microstructure evolution and deformation behavior of Au–20Sn eutectic alloy during hot rolling process

Au–20Sn preforms such as microscale thin foils or wires can be widely used as lead-free solder in the high-power optoelectronics and hermetic sealing applications. However, as-cast Au–20Sn eutectic alloy with Au 5 Sn and AuSn phases is intrinsically brittle at room temperature due to limited slip systems associated with their complicated trigonal structure and hexagonal packed structure. In this study, we successfully made an Au–20Sn foil with thickness of 48 μm by multi-pass hot rolling on as-cast alloy with an initial thickness of 4 mm. The microstructure, texture and recrystallization evolutions of the Au–20Sn eutectic alloy during hot rolling process were investigated in detail. The results indicated that plastic instability occurs in the eutectic lamellar structure when the nanoscale layers were subjected to the rolling strain, and promoted the microstructural spheroidization. Besides, the spheroidizing behavior in AuSn phase was found more preferential compared with that in the Au 5 Sn phase. After dynamic recrystallization, <0001>∥TD deformation texture was introduced in the AuSn phase while <0001>∥ND deformation texture was formed in the Au 5 Sn phase. These phenomena were attributed to the difference in slip systems activated in the two phases associated with their different c/a ratios. A transition of dynamic recrystallization mechanism from the initial lamellar phase to the later equiaxed phase (in other words, from continuous dynamic recrystallization mechanism to discontinuous dynamic recrystallization) was observed, as evidenced by the evolutions of in-grain misorientation accumulation and grain boundary migration. Additionally, an interesting recrystallization phenomenon occurred that the AuSn grains could nucleate in the Au 5 Sn phase during hot rolling, which was considered as a strain induced phase decomposition behavior. The present studies can provide insight into understanding microstructural evolution of Au–20Sn eutectic alloy during hot rolling, which enables a further optimization of processing parameters to fabricate Au–20Sn alloy foils with desired microstructure and properties. • Au–20Sn foil with thickness of 48 μm is successfully made by hot rolling process. • Plastic instability occurs in the eutectic lamellar structure during hot rolling. • Different textures are introduced in the AuSn and Au 5 Sn eutectic phases. • Transition of recrystallization from CDRX to DDRX is found in the eutectic alloy. • AuSn phase can precipitate in Au 5 Sn grains which subjected to severe local strain.