Zn Powder Research Articles

Study on Microstructure and Properties of Mechanically Deposited Zn-Sn Coating

A Zn-Sn coating of ~30 µm thickness was prepared on an iron substrate by mechanical deposition using zinc and tin powders as raw materials. The Zn-Sn coating consists of zinc powder particles physically stacked with tin powder particles and filled with reduced tin, and the tin content in the coating is 20%–30%. The resulting Zn-Sn coating was characterized and analyzed with scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), polarization curves (Tafel), electrochemical impedance (EIS), and energy dispersive X-ray spectrometry (EDS). The results showed that the Zn powder was co-deposited with the Sn powder in a portable manner and the Sn powder was deflected and deformed to a great extent. The spot-flocculated reduced Sn also covered the surface of the Zn powder to fill the interstices of the coating to make the coating more compact. Compared with the pure Zn coating, the Zn-Sn coating has a positive shift of 68 mV in the self-corrosion potential in the polarization test, and the corrosion current was only 20% of that of the pure Zn coating. The reduced Sn had a shielding effect on the Zn powder and at the same time, in combination with inert tin powder, the polarization resistance of the plated layer increased to 1118 Ω/cm2. Furthermore, compared to the pure zinc layer, the time of white rust and red rust increased by 24 and 240 h, respectively. In addition, the XPS results showed that the Zn-Sn plating layer was clearly passivated, which was mainly due to the formation of Zn(OH)2 and Sn(OH)2. The results also emphasized that the tin element in the Zn-Sn plated layer can maintain the morphology of zinc powder, compact the plating layer, and prevent the release of corrosion products, thus improving the corrosion resistance of the Zn-Sn coating.

Binder-Free Freestanding 3D Zn-Graphene Anode Induced from Commercial Zinc Powders and Graphene Oxide for Zinc Ion Battery with High Utilization Rate

Aqueous zinc-ion batteries (AZIBs) have received widespread attention owing to the increasing demand for safety and inexpensive batteries. However, a zinc metal anode suffers from dendrite growth during continuous cycling, and side reactions occurred on anode surface such as hydrogen evolution reaction (HER) and passivation. Moreover, the low utilization of Zn metal is also a neglected issue leading to a low energy density at the cell-level. Herein, a nondendrite Zn anode with high utilization was designed by spontaneous reaction of commercial Zn powders and graphene oxide (GO). The formed binder-free three-dimensional (3D) anode Zn_G achieves a cycling time over 550 h and extremely low voltage hysteresis of ∼20 mV with 7.4% DOD (130 h for Zn foil with 1.3% DOD and 80 h for Zn powders with 7.4% DOD) at a current density of 1 mA cm–2 in a symmetric cell. In Zn||MnO2 full batteries, Zn_G greatly enhances the gravimetric energy density on the cell level and achieved more than 1600 cycles much higher than Zn foil (Zn_F) with 700 cycles and Zn powders (Zn_P) with 500 cycles. The low N/P ratio of 3 also achieved high stability with 126 mAh g–1 and 74.5% retention after 1000 cycles.

A Semi‐Liquid Electrode toward Stable Zn Powder Anode

AbstractZn powder anode possesses great versatility compared to the Zn foil counterpart, but the rough surface with a high surface area aggravates the corrosion and dendrite growth. Herein, a dendrite‐free and anti‐corrosive semi‐liquid Zn anode (SLA) is successfully fabricated based on Zn powder and a thickening agent. Benefiting from the rheological property, the unique anode effectively releases the stress induced by Zn plating, especially under high‐current densities. Meanwhile, the dual‐conductive medium, i.e., ionic and electronic, homogenizes the ion flux and allows the stripping/plating to occur within the entire anode. In a symmetric cell, the SLA anode exhibits stable electrochemical behavior with a prolonged lifespan at the current density of 5 mA cm−2/10 mA cm−2under the capacity of 5 mAh cm−2/10 mAh cm−2. Improved durability of more than 5000 cycles is endowed when assembling an SLA anode with a vanadium‐based cathode. This study provides an electrode rheology‐based approach to overcome the stability challenge of powder anode for scale‐up manufacturing.

Direct 3D printing of stress-released Zn powder anodes toward flexible dendrite-free Zn batteries

The notorious dendrite growth and poor deformation endurance of Zn metal anode impede the on-going rapid development of flexible Zn-ion batteries (ZIBs). Herein, a direct 3D printing approach architecting a novel Ag-anchored hierarchical porous flexible Zn anode (3DP-ZA) is for the first time proposed for flexible dendrite-free ZIBs. The 3DP-ZA anode demonstrates excellent inherent mechanical flexibility and structural stability: (1) the interaction between the components in the formulated ink (CNT, graphene and cellulose) drives an assembly of a robust intertwined flexible network where Zn powder is homogeneously embedded; (2) the 3D-printing customized macro holes guarantee sufficient buffer space for stress relief to accommodate volume change and maintain structural integrity upon plating/striping. Moreover, the introduced zincophilic Ag source and hierarchical porous structure of the anode endow uniform electronic/ionic fluxes and homogeneous Zn growth. Consequently, the 3DP-ZA//3DP-ZA symmetrical cell delivers a superior lifespan of over 330 h at 1 mA cm−2 and 1 mAh cm−2 with a low voltage hysteresis of 35 mV. Furthermore, a flexible full cell adopting 3DP-ZA anode and PANI coated carbon cloth (PANI@CC) cathode exhibits stable electrochemical performance under continuous deformation. This work points to a new mindset that elaborate 3D structural electrode design for high-performance flexible Zn batteries could be readily realized by 3D printing, which caters to a broad range of flexible energy storage applications.

Chemical Treatment of Sn‐Containing Transparent Conducting Oxides for the Enhanced Adhesion and Thermal Stability of Electroplated Metals

AbstractA surface treatment process, named ReTreat, is presented, and is shown to enhance the adhesion of electroplated metals on Sn‐containing transparent conducting oxides (TCOs). The ReTreat process uses Zn powders, FeSO4 and glycine‐buffered aqueous solutions (pH 3 to 5) in order to regulate a controlled and uniform conversion of SnO2 surfaces to SnO, Sn metal, and FexSny alloys. These surface metallic and intermetallic layers selectively enrich the electroplating of metallic films (including Ni, Au, and Ag). Subsequently, the process has been used to fabricate thermally stable metal films on rigid FTO‐coated glass and flexible ITO‐coated PET substrates. Standardized testing confirms that the metallic coatings exhibit sufficient adhesion to the underlying TCO with high thermal stability and tolerance to flexural strain. A reaction mechanism for the heterogenous surface treatment is deduced from X‐ray diffraction, X‐ray photoelectron spectroscopy, and in situ transmittance measurements. These investigations show how the process parameters (e.g., Zn powders, FeSO4 concentration, pH, and TCO type) impact the reaction rate, morphology, and composition of the treated TCO surface. This report provides detailed insights necessary for the future implementation of this innovative surface treatment, which has the prospect to be a customary process for electroplating onto Sn‐containing TCOs.

(Digital Presentation) Corrosion Resistance of 55%Al-Zn Alloy Fabricated By Ball Milling and Spark Plasma Sintering

Hot-dip 55mass%Al-Zn coated steels show good corrosion resistance because the 55%Al-Zn alloy coating layer acts as a sacrificial anode and protects the steel substrate from atmospheric corrosion.1 The balance between sacrificial behavior and dissolution resistance is important for improving the corrosion protection ability of the Al-Zn coating. In this study, 55%Al-Zn alloy was fabricated by ball milling and spark plasma sintering, and the effect of microstructure on the dissolution behavior of the 55%Al-Zn alloy was investigated. The 55%Al-Zn alloy specimen was fabricated by ball milling of Al and Zn powders and subsequent spark plasma sintering. The coating layer on the hot-dip 55%Al-Zn coated steel was used to compare the dissolution behavior. The dissolution behavior of 55%Al-Zn alloys was analyzed by galvanic current measurements and polarization measurements in a diluted synthetic seawater. In the sintered 55%Al-Zn alloy, Zn-rich phases with diameter less than 500 nm were dispersed in the Al matrix. The galvanic current measurements between the sintered 55%Al-Zn alloy and the steel substrate showed that the sintered 55%Al-Zn alloy acted as a sacrificial anode. In the galvanostatic polarization measurements, the potential of the sintered 55%Al-Zn alloy remained lower than that of the hot-dip 55%Al-Zn coating layer.Reference: S. Tokuda, I. Muto, Y. Sugawara, M. Takahashi, M. Matsumoto, and N. Hara, Corros. Sci., 129, 126–135 (2017).

Effect of Process Parameters on Properties of Cold-Sprayed Zn-Al Composite Coatings.

Al–Zn composite coating can provide effective cathodic protection for E235 steel. This study aims to obtain the Al–Zn composite coating with the best anti-corrosion performance by optimizing the spraying temperature, spraying distance and powder-feeding motor speed. The Al and Zn powders were analyzed by scanning electron microscope (SEM), and the microstructure of the coatings prepared by different process parameters was observed by optical microscope. The mechanical and anticorrosive properties of the coating were evaluated using hardness, porosity, thickness and electrochemical tests. According to the experimental results, when the spraying temperature, spraying distance and powder-feeding motor speed were 500 °C, 27 mm and 1.5 r/min, respectively, the hardness of the coating was 67 HV, the porosity was 0.57% and the thickness was 0.588 mm. The EIS test results show that the coating has the maximum polarization resistance, and therefore the coating has good corrosion resistance at this parameter.

(Invited, Digital Presentation) Aqueous Zinc Battery for Safe Energy Storage

Development of energy storage system in the past year focus on improvement of energy density. While the progress is remarkable, safety problems of lithium-ion batteries (LIB) have been intensively exposed. On one hand, LIB is not intrinsically safe with very active anode, flammable electrolyte and oxygen-releasing cathode; on the other hand, many application scenarios actually don’t require very high energy density.We work on aqueous electrolyte batteries to achieve both high energy density and superior safety performance. We developed a few approaches to improve stability of Zn anode and figured out potential problems of the current Zn anode studies. We tackled the challenge of stability of Zn anode at high areal capacity and high current density by developing artificial SEI film, electrolyte regulation and organic anode development. In addition, we develop Zn powder based anode and improve their stability for more practical applications.In terms of cathode of cathode materials, we develop various Mn, PBA, organic materials and MXenes based materials, targeting on a stable and high-capacity ones. We also develop a few cathode materials based on conversion mechanism, providing extraordinary capacity and decent voltage output. We also developed a few approaches to regulate conventional cathode materials for better stability.Our research purpose is to develop aqueous Zn batteries for large scale energy storage with ultimate safety performance and integrate them with renewable energy systems. We hope our research can contribute to sustainable society development.

A Scalable Method for Improving Zn Crystallinity for Low-Gassing Alkaline Batteries

The corrosion of zinc particles in alkaline environments is an energetically parasitic process that produces hydrogen gas as a byproduct. This “gassing” phenomenon is thermodynamically favorable in standard zinc-alkaline battery chemistries. Building hydrogen pressure within these primary cells can eventually lead to cell rupture, leaking the high-pH electrolyte and slurry from the cell, often destroying the electronic device that the cell was meant to power. One of the particle-level variables that can control the gassing and corrosion rate is the particle crystallinity. As the crystallinity of the zinc particles is enhanced (larger grains and fewer grains per particle), a reduction in the rate of this undesirable gassing phenomenon is expected.In this study, we demonstrate a systematic method for enhancing zinc particle crystallinity by thermally growing zinc grains. Since thermally growing zinc grains requires temperature exposure above the melting point of metallic zinc, an oxide layer is first grown around the outside of the particle surface. Oxides tend to have significantly higher melting temperatures than their metallic counterparts and this is true in the zinc/zinc oxide case where the melting temperature of metallic zinc is 420 oC and the melting temperature of zinc oxide is 1975 oC. Forming a thin oxide layer around the particle allows the metallic zinc core to be recrystallized whilst simultaneously retaining the particle shape. Following the grain growth step, the oxide layer is easily washed away with a quick acetic acid treatment. Outlined in this work is a detailed study on the scalable three-step process for growing zinc grains and enhancing bulk zinc powder crystallinity by the following: 1) oxide layer formation, 2) grain growth, and 3) oxide layer removal. Following the treatment, both achievable capacity and the corrosion rate were tested. It will be shown that the higher crystallinity particles have superior performance and lower gassing than traditional Zn powders without the treatment.

Effect of pressure on electrical and optical properties of metal doped TiO2

A comparative study of electrical and optical properties of powder and its corresponding pellets has been done on 3d-doped TiO2. Ti1-xMxO2 (M = Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) powder and its corresponding pellet with doping concentration x = 0.05 has been prepared using solid state route. Optical and electrical measurements have been performed for all prepared samples and interestingly, it is observed that due to having external pressure (i.e. strain) both the properties change significantly. A rigorous theoretical calculation has been carried out to verify the experimental band gap obtained from optical absorption spectroscopy. In case of pellet sample band gap decreases as compared to the powder sample due to variation of pressure inside the structures. Role of doping has also been investigated both in pellet and powder forms and found that the band gap decreases as the atomic number of dopants increases. A cross-over behavior seen in pellet sample on doping with Ni, Cu and Zn (i.e. band gap increases with increase in atomic number of dopant). Electrical resistivity measurements have been carried out for both pellet and powder samples and it is found that in case of strain free samples the value of resistivity is smaller while in case of strained sample it is quite large. We believe that the present study suggests a novel approach for tuning the electrical and optical properties of semiconducting oxides either from doping or from applied pressure (or strain).

Effect of Sn concentration on the structural, morphological and thermoelectric transport properties of zinc Stannates thin films

This study aimed to set suitable Tin dopant concentration in ZnO based thin films to get optimal structural, morphological and thermoelectric properties. The samples under investigation were prepared by thermal evaporation technique using stoichiometric ratios of Zn and Sn powders. X-ray diffractograms showed that all grown samples are fully c-axis oriented but increasing Sn concentration caused a blue shift in XRD peak position. Raman spectrum of ZTO nanoparticles has confirmed the perfect wurtzite structure having an intense E2 mode. It was further showed that with increasing crystallite size, the frequency of E2 (highest peak) phonon mode decreases whereas its line width increases. The Seebeck coefficient has maximum value (800 μV/K) for un-doped sample while the value of electrical conductivity (5.2 S/cm) has maximum value for sample having Sn concentration 4%. This behavior of thermoelectric properties can be understood by the fact that Sn doping concentration increases the free carrier concentration in the host crystal of ZnO which resulted in the reduction of Seebeck coefficient and enhancement of electrical conductivity. This argument was further highlighted by the SEM measurements.

Upcycling spent alkaline batteries into rechargeable zinc metal batteries

Recycling/upcycling alkaline batteries are significant for the sustainable development. Here, for the first time, we upcycle spent alkaline batteries into rechargeable Zn metal batteries through a simple thermal treatment of electrode waste. The regenerated Zn powder anode shows super-zincophilicity and low overpotentials even under fast rates (8 mA cm−2) and high depth-of-discharge (50 %), which can be ascribed to coating of hydroxyl-rich organic layer with abundant nucleation sites as well as high orientation of favorable (002) plane and induced horizontal plating behavior. The regenerated cathode composed of MnO2 and MnOOH manifests enhanced capacity in comparison to pristine ones. Under a low negative-to-positive capacity ratio of 3.8 and high loading of ~10 mg cm−2, the regenerated electrodes are paired to fabricate zinc metal batteries which demonstrate high energy and power densities (94 Wh kg−1, 1349 W kg−1), holding potential for practical applications. Given the sustainable, low-cost, environmental-friendly, and value-added features, the strategy proposed here will open a new pathway toward battery recycling/upcycling.

Green Synthesis of Zinc Oxide Nanoparticles Using Red Seaweed for the Elimination of Organic Toxic Dye from an Aqueous Solution

This study aims to produce green zinc oxide nanoparticles (ZnO-NPs) derived from red seaweed (Pterocladia Capillacea) and evaluate their potential to absorb Ismate violet 2R (IV2R) ions from an aqueous solution. UV-vis spectrophotometry, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and a Brunauer–Emmett–Teller surface area analysis (BET) were used to analyze the structural, morphological, and optical features of the synthesized nanoparticles. The change in color of the chemical solution revealed the formation of zinc oxide nanoparticles. The FTIR examination confirmed the synthesis of both Zn and ZnO nanoparticle powder, with a BET surface area of 113.751 m2 g−1 and an average pore size of 2.527 nm for the synthesized adsorbent. Furthermore, the maximum removal effectiveness of IV2R was 99% when 0.08 g ZnO-NPs was applied at a pH of 6, a temperature of 55 °C, and a contact time of 120 min. The dye adsorption capacity of the ZnO-NPs was 72.24 mg g−1. The adsorption process was also controlled by the Freundlich adsorption model and pseudo-second-order reaction kinetics. The adsorption of IV2R ions onto the ZnO-NPs could be represented as a nonideal and reversible sorption process of a nonuniform surface, according to Freundlich adsorption isotherms. In addition, the constant values of the model parameters were determined using various nonlinear regression error functions. Moreover, thermodynamic parameters such as entropy change, enthalpy change, and free energy change were investigated; the adsorption process was spontaneous and endothermic. The high capacity of the ZnO-NPs synthesized by red seaweed promotes them as promising substances for applications in water treatment for the removal of IV2R dye from aqueous systems.

Synthesis and Electrochemical Performance of the Orthorhombic V2O5·nH2O Nanorods as Cathodes for Aqueous Zinc Batteries.

Aqueous zinc-ion batteries offer the greatest promise as an alternative technology for low-cost and high-safety energy storage. However, the development of high-performance cathode materials and their compatibility with aqueous electrolytes are major obstacles to their practical applications. Herein, we report the synthesis of orthorhombic V2O5·nH2O nanorods as cathodes for aqueous zinc batteries. As a result, the electrode delivers a reversible capacity as high as 320 mAh g−1 at 1.0 A g−1 and long-term cycling stability in a wide window of 0.2 to 1.8 V using a mild ZnSO4 aqueous electrolyte. The superior performance can be attributed to the improved stability of materials, inhibited electrolyte decomposition and facilitated charge transfer kinetics of such materials for aqueous zinc storage. Furthermore, a full cell using microsized Zn powder as an anode within capacity-balancing design exhibits high capacity and stable cycling performance, proving the feasibility of these materials for practical application.

Analysis of Chloramphenicol in Shrimp Using Standard Addition Method Based on Diazotization

This research aimed to determine the concentration of chloramphenicol in shrimp using the standard addition method based on the diazotization reaction using Zn powder as a reducing agent of chloramphenicol, followed by the use of N-(1-naphthyl) ethylenediamine dihydrochloride as a coupling agent and measured at 565 nm. Based on the test, the shrimp sample was found to contain 1964.91 mg/kg of chloramphenicol and it exceeded the requirements set by the European Commission which was 0,15 mg/kg. The limit of detection (LOD) value is 0.19 mg/mL and the limit of quantitation (LOQ) value is 0.64 mg/mL. The correlation coefficient (R2) was 0.9991 for the concentration range of 0-50 ppm. The analysis of the results showed that the %recovery in shrimp analysis using this method was 87.41%-107.73% with an average of 109.38%.

Investigation on Mechanical, Biocorrosion, and Biocompatibility Behavior of HAp-Assisted Sr-Based Mg Composites

Numerous biodegradable Mg-based biomaterials have been developed in recent years because of their outstanding biocompatibility, biodegradation, and mechanical properties. The Mg-based composite is an appropriate candidate for orthopedic implants, such as supporting the fractured bone due to its superb biocompatibility and biodegradation properties. In the present work, a Mg-based biomaterial is developed by incorporating low wt % of alloying elements such as Zn, Ca, Mn, and Sr and ceramic powders such as HAp to improve the biocompatibility and biodegradebility and strengthen the mechanical properties. In this study, the Mg-4Zn-3Ca-1HAp-0.5Mn and Mg-4Zn-2.9Ca-1HAp-0.5Mn-0.1Sr composites are prepared, and the mechanical, microstructure, and in vitro degradation behavior of these composites are studied. The Mg-4Zn-2.9Ca-1HAp-0.5Mn-0.1Sr composite has good mechanical properties and a low uniform in vitro degradation rate (0.587 mm/year). From the dynamic mechanical analysis, it is found that the composites have better damping characteristics than the pure Mg. The composites are chosen for further evaluation. All the composites show no cytotoxicity to MG63 cells. The composite having Sr with PVA/ZrO2 coating showed the highest cell viability. On the basis of the above observation, the viability of the Mg-4Zn-3Ca-1HAp-0.5Mn and Mg-4Zn-2.9Ca-1HAp-0.5Mn-0.1Sr composites is discussed systematically for the use as an orthopedic implant. This investigation delivers a new idea for the evolution of a high-performance Sr-based Mg composite having excellent mechanical and corrosion properties while successfully reducing the cytotoxicity effect.

The annealing microstructural evolution of Al-10Zn alloy prepared by continuous extrusion of mixed heterogeneous elemental powders

Al and Zn powders in the ratio of 9:1 (wt%) were alloyed into rods with a dense structure by using the continuous extrusion technique. To promote metallurgical bonding of heterogeneous elements, the microstructures of these rods with different holding times (1, 3, and 5 min) at the same annealing temperature were investigated. With the increase of annealing time, the microstructure consisted mainly of (α-Al) and (α + η) phases and an (α +η)-rich phase. The solid solubility of Zn into Al also gradually increased. The calculated x-ray diffraction (XRD) data showed that the lattice parameter of Al decreased to 4.04793 Å after 5 min of annealing, which was decreased by 0.062% compared to the lattice parameter of Al in the powder state. The microscopic stress and dislocation density of Al were increased by 0.27% and 12.52 × 1014 m−2 respectively after extrusion, and the microscopic deformation and dislocation density were decreased to 0.2% and 8.71 × 1014 m−2 respectively after being annealed for 5 min. The dislocation density and lattice distortion after annealing gradually decreased with increasing annealing time, and the scanning electron microscopy (SEM) results indicated that the mass percentage of Zn increased with increasing annealing time.

Nanoporous Vesicular Membranes of Amphiphilic Polymers Containing Trans / Cis Isomers

Nanoporous Vesicular Membranes of Amphiphilic Polymers Containing <i>Trans</i> / <i>Cis</i> Isomers

Low-Temperature Reactive Sintered Porous Mg-Al-Zn Alloy Foams

By using carbamide granules as the space holder, Mg alloy foams with interconnected pore structures were synthesized by reactive sintering of a mixture of Mg, Al and Zn powders. The effect of Zn/Al on the microstructural evolution and compressive strength of porous Mg-9Al-xZn (x = 1, 5) alloy foams was investigated. The phase diagram simulation approach was used to determine the sintering temperature. The analysis results show that the formation of binary secondary phases or intermetallic compounds is a crucial factor in achieving bonding strength for the porous Mg alloy foams. The intermetallic compounds were formed by solid-state diffusion between the metal powder elements. Mg17Al12 intermetallics was the most stable compound formed in the cell walls of porous Mg alloy foams. The addition of Zn influences the solubility and stability of the intermetallic compound. Thermodynamic calculations show that Mg17Al12 was preferentially formed in the cell walls owing to its high negative enthalpy energy. Moreover, various metastable transition phases may exist in the microstructures, especially in the porous Mg-9Al-5Zn alloy foam. The intermetallic phases act as reinforcing phases, combined with grain refinement, significantly increasing the strength of the foam. At the given relative density of 0.42, the porous Mg-9Al-5Zn alloy foam exhibits the highest yield strength of 9.0 MPa, which is 23% higher than the strength of the porous Mg-9Al-1Zn alloy foam.

Interfacial Microstructure and Bonding Area of Sn-based Alloy-GG25 Gray Iron Bimetallic Material Using Flux, Sn, and Sn-Zn Interlayer Compound Casting

A bimetallic casting consisting of GG25 gray iron substrate and Sn-based alloy using the liquid-solid technique has been studied in this paper. Three different pretreatment processes of gray iron surface substrates including flux only, flux and Sn powder, and flux and Sn-8.8% Zn powder eutectic alloy surface treatment were adopted for the aim of improving the quality of tinning, the interfacial structure, and the bonding area of the Sn-based alloy/gray iron bimetallic composite in order to promote the bonding quality of bimetallic castings. Microstructure characterization on the bonding interface was conducted. The novel tinning material for gray cast iron substrate comprising of Sn-8.8% Zn eutectic alloy powder in combination with flux interlayer improved the bonding area, the interfacial bimetal structure, and the shear stress. This improvement is due to the higher interface reaction of Zn with Fe that leads to the formation of a very thin layer of Fe-Zn and Fe-Sn intermetallic phases.