Effect of TiO2 nanoparticles on the horizontal hardness properties of Sn-3.0Ag-0.5Cu-1.0TiO2 composite solder

The improvement in the hardness of Sn-3.0Ag-0.5Cu solder alloy reinforced with 1.0 wt % TiO₂ nanoparticles was evaluated by nanoindentation. A specific indentation array was performed on four different horizontal cross sections of the composite solder with different heights and diameters, in order to verify the mixing homogeneity of TiO₂ nanoparticles within the Sn-3.0Ag-0.5Cu solder paste during the ball milling process. The phase analysis indicated successful blending of the Sn-3.0Ag-0.5Cu with the TiO₂ nanoparticles. According the scanning electron microscopy micrographs, presence of the TiO₂ nanoparticles reduced the size of the Cu₆Sn₅ and Ag₃Sn intermetallic compound phases. Incorporation of the 1.0 wt % TiO₂ nanoparticles improved the hardness values up to 26.2% than that of pure SAC305. The hardness values increased gradually from the top cross sections towards adjacent to the solder/substrate interface. The mechanism of the hardness improvement attained by the TiO₂ nanoparticles addition were also investigated on the horizontal cross sections of the samples.     

Effect of triethanolamine and heliotropin on cathodic polarization of weakly acidic baths and properties of Sn-Ag-Cu alloy electrodeposits

The effect of triethanolamine (TEA) and heliotropin (HT) on the cathodic polarization of weakly acidic baths and the properties of Sn-Ag-Cu alloy electrodeposits were investigated. Lead-free Sn-Ag-Cu solder alloy were electrodeposited in weakly acidic baths (pH 5.5) containing Sn(CH₃SO₃)₂, AgI, Cu(CH₃SO₃)₂, K₄P₂O₇, KI, hydroquinone, TEA, HT and methylsulfonic acid (MSA). The cathodic polarization of baths and the properties of electrodeposits were evaluated by Liner sweep voltammetry (LSV), scanning electron microscopy (SEM), X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR) and X-ray photoelectron spectroscopy (XPS). The results indicate that HT is a main brightening agent that increases the cathodic polarization of baths and refines the grains of electrodeposits; TEA is a complexing agent for copper ions and a brightening promoter that decreases the cathodic polarization of baths and densifies the electrodeposits. The bright, compact, and smooth Sn-Ag-Cu alloy electrodeposits contain 88-95 wt% tin, 5-10 wt% silver and 0.5-2 wt% copper. Organic compounds used in the baths neither adsorb on the electrodeposits surfaces nor are included in the electrodeposits. It can be therefore concluded that the use of both TEA and HT is better than that of them either in the process of electroplating bright Sn-Ag-Cu alloy.     

Study of the electrochemical deposition of Sn-Ag-Cu alloy by cyclic voltammetry and chronoamperometry

The electrochemical deposition of Sn-Ag-Cu alloy from weakly acidic baths onto glassy carbon electrodes (GCE) was studied by cyclic voltammetry (CV) and chronoamperometry (CA). The properties of the electrodeposits were characterized by scanning electron microscopy (SEM), energy-dispersive spectrometery (EDS) and X-ray diffraction (XRD). Test results indicate that the two cathodic peaks in the CV curves, at −0.6 V and −0.85 V during the forward scan towards the negative potentials, correspond to the irreversible deposition of a solid solution of tin, silver and copper. The underpotential deposition (UPD) of Sn occurs at −0.6 V during the cathodic period and the amount of Ag and Cu in the Sn-Ag-Cu alloy decreases with increasingly negative cathodic potentials. During the forward scan, towards the positive potentials used in CV testing, cathodic peaks at −0.85 V appear in the CV curves for baths containing mixtures of tin salts and triethanolamine (TEA). This corresponds to a reduction of transient complex ions [Sn(TEA)_x]²⁺ on the surface of the cathode. Furthermore, the formation and reduction of [Sn(TEA)_x]²⁺ is a diffusion controlled process. On the surface of the GCE, the actual nucleus growth mechanism of the Sn-Ag-Cu alloy is represented by the progressive nucleation model.     

Formation of intermediate intermetallic layers on interaction of electrodeposited Sn,Ni-Fe,Ni-B coatings with different metallic substrata

The structure of layers and formation of intermetallic phases after thermal treatment in the system of thin electrodeposited Sn, Ni-Fe and sputtered Cu, Fe-Ni layers (thickness 0.1-2.0 μm) and thick electrodeposited Sn (thickness 6-10 μm) and Fe-Ni and Ni-B layers (thickness 2 μm) have been investigated by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and by metallographic and X-ray diffraction (XRD) techniques. The formation of intermetallic phases NiSn₃, Ni₃Sn₂, FeSn₂ and considerable reduction in the formation of brittle layers Ni₃Sn₄, Cu₆Sn₅, Cu₃Sn are determined by the structure and purity of electrodeposited tin [C (0.5-5) x 10-²; N (1-5) x 10-²; Fe, Cu, Bi, Pb (0.15-5.0) x 10^-2 wt%] in the system Sn/Fe-Ni/Cu. Electrodeposited Fe-Ni (80% Ni) as barrier layer in the system Sn/Fe-Ni/sputtered Cu completely prevents formation of Cu₆Sn₅, Cu₃Sn as a result of thermal treatment at 170°C up to 75 h. An amorphous Ni-B layer [B 4-8; C (3-7) x 10^-2 wt%] prevents formation of Ni₃Sn₄ and Cu₆Sn₅ in the system Sn/Ni-B/Cu (or Cu-Zn alloy) as a result of thermal treatment at 130°C (200 h) and 170°C (150 h).     

Cyclic durable high-capacity Sn/Cu6Sn5 composite thin film anodes for lithium ion batteries prepared by electron-beam evaporation deposition

Sn/Cu₆Sn₅ alloy composite thin films were directly prepared by electron-beam deposition for anodes of lithium ion batteries. The thin film was comprised of micro/sub-microcrystalline Sn and Cu₆Sn₅, where the polyhedral micro-sized Sn grains were uniformly dispersed in the loose Cu₆Sn₅ matrix. Lithiation reaction kinetics were confirmed to be controlled by a diffusion step and the diffusion coefficient of Li⁺ in the thin film anode was determined to be 1.91 × 10⁻⁷ cm²/s. The galvanostatic cycling behavior of Sn/Cu₆Sn₅ composite thin film anodes was studied under different conditions. Stable capacities of more than 370 mAh/g were obtained by discharging from 1.25 to 0.1 V. Structure changes and fading mechanism of the thin film electrodes was discussed based on SEM, XRD and EDX investigations. The present results demonstrated that the multi-phase composite structure can improve electrochemical performance of the Cu-Sn alloy thin film electrodes.     

One-step electrodeposition synthesis and electrochemical properties of Cu6Sn5 alloy anodes for lithium-ion batteries

Cu₆Sn₅ alloys were successfully electrodeposited on rough Cu foils and smooth Cu sheets using a facile one-step electrodepositing method, and their structural and electrochemical properties were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charging/discharging testing and electrochemical impedance spectroscopy (EIS). The influence of surface morphology of the current collectors on the cycleability and the interfacial performance of the Cu₆Sn₅ alloy electrode are both discussed. The results demonstrate that the Cu₆Sn₅ alloy electrode on the rough Cu foil presented better electrochemical performance than that on the smooth Cu sheet because its rough surface could buffer the volume changes to some extent. The first discharging (lithiation) and charging (delithiation) capacities were measured at 462 and 405 mAh g⁻¹ respectively with high initial coulomb efficiency of 88%, with charging capacity in the 50th cycle remaining 76% of that in the first cycle. The phase transformation during initial lithiation was detected by electrochemical impedance spectroscopy (EIS) and its trend versus electrode potential is also discussed.     

Beneficial effects of Mo on the electrochemical properties of tin as an anode material for lithium batteries

A simple, novel method for improving the electrochemical response of Sn in lithium cells is proposed that involves preparing Sn by a reduction procedure in the presence of Mo powders. Four different Mo_xSn_1 − x mixtures (0 < x < 0.26) were electrochemically tested and their structural and textural properties determined by using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties of the resulting composites in lithium cells were studied by galvanostatic, step potential electrochemical spectroscopy (SPES) and electrochemical impedance spectroscopy (EIS) measurements. The mixtures were found to consist of crystalline Sn and Mo; however, the presence of the latter element modified the Sn habit in two ways, namely, by significantly decreasing particle size and increasing the reactivity towards oxygen. Although Mo is inert towards lithium, it increased both the discharge capacity and the capacity retention of the electrode in relation to pure Sn. The improved interparticle connectivity, reduced electrolyte decomposition and decreased charge-transfer resistance observed in the Mo-containing samples appear to be beneficial effects of the addition of Mo.     

Crystallization Behavior and Corrosion Resistance of Cu<Subscript>50</Subscript>Zr<Subscript>40</Subscript>Ag<Subscript>10</Subscript> Amorphous Alloy

In this study, Cu₅₀Zr₄₀Ag₁₀ amorphous alloy ribbons were prepared by a single roller melt-spinning method. The crystallization behavior of the Cu₅₀Zr₄₀Ag₁₀ amorphous alloy has been investigated using X-ray diffraction (XRD), differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and high resolution TEM (HRTEM). Moreover, the polarization and passivation behaviors of the as-quenched and as-annealed amorphous alloy have been studied in 1 N H₂SO₄. The surfaces of corroded samples have been examined using scanning electron microscopy (SEM) and the element distribution across the pits has been analyzed using energy dispersive spectrometer (EDS). The results show that the Cu₅₀Zr₄₀Ag₁₀ amorphous alloy has a large supercooled region up to 36 K. The ω-(ZrCu), ZrO₂ and Cu₁₀Zr₇ phases can firstly precipitate from the amorphous matrix below glass transition temperature during annealing for 30 min. Moreover, the corrosion resistance of the as-quenched amorphous alloy is better than that of partial and full crystallization products. In addition, Zr plays a crucial role in enriching the passive film and enhancing corrosion resistance.     

Microstructure and performance of brazed diamonds with multilayer graphene-modified Cu–Sn–Ti solder alloys

This study aims to improve the hardness of solidified Cu–Sn–Ti solder alloys and reduce the erosion of diamonds caused by these solder alloys during brazing. To achieve this aim, a new type of multilayer graphene-modified Cu–Sn–Ti composite solder alloy was proposed for brazing diamonds. The brazed diamond specimens were subjected to morphological observation, characterization of the interfacial microstructures. The static compressive strength and impact toughness of brazed diamond grits were measured. The Vickers microhardness of the solidified solder alloy was quantified, and the microstructure of the solidified solder alloy was also analysed. The results show that brazed diamond specimens fabricated with the No. 2 composite alloy containing 1 wt% multilayer graphene exhibited the best morphology. Addition of excess multilayer graphene reduced the flow properties of the molten Cu–Sn–Ti composite solder alloy. The dominant phases in the solidified Cu–Sn–Ti solder alloys were α-(Cu), Sn₃Ti₅, and CuSn₃Ti₅. Cu, Sn, and Ti were adsorbed by the multilayer graphene, forming C-rich and TiC-dominant phases. Consequently, erosion of the diamonds was reduced during brazing, and TiC was formed in the solidified solder alloy. Thus, increasing the content of multilayer graphene enhanced the static compressive strength and impact toughness of the brazed diamond grits, and increased the hardness of the solidified Cu–Sn–Ti solder alloy.     

Design and Properties of New Lead-Free Solder Joints Using Sn-3.5Ag-Cu Solder

This article aims to reduce the melting temperature of lead-free solder alloy and promote its mechanical properties. Eutectic tin-silver lead-free solder has a high melting temperature 221 ^°C used for electronic component soldering. This melting temperature, higher than that of lead–tin conventional eutectic solder, is about 183 ^°C. The effect of the melt spinning process and copper additions into eutectic Sn-Ag solder enhances the crystallite size to about 47.92 nm which leads to a decrease in the melting point to about 214.70 ^°C, where the reflow process for low heat-resistant components on print circuit boards needs lower melting point solder. The results showed the presence of intermetallic compound Ag₃Sn formed in nano-scale at the Sn-3.5Ag alloy due to short time solidification. The presence of new intermetallic compound, IMC from Ag_0.8Sn_0.2 and Ag phase improves the mechanical properties, and then enhances the micro-creep resistance especially at Sn-3.5Ag-0.7Cu. The higher Young’s modulus of Sn-3.5Ag-0.5Cu alloy 55.356 GPa could be attributed to uniform distribution of eutectic phases. Disappearance of tin whiskers in most of the lead-free melt-spun alloys indicates reduction of the internal stresses. The stress exponent (n) values for all prepared alloys were from 4.6 to 5.9, this indicates to climb deformation mechanism. We recommend that the Sn_95.7-Ag_3.5-Cu_0.7 alloy has suitable mechanical properties, low internal friction 0.069, low pasty range 21.7 ^°C and low melting point 214.70 ^°C suitable for step soldering applications.     

Influence of microstructure and composition on the corrosion behaviour of Mg/Al alloys in chloride media

The influence of the microstructure and aluminium content of commercial AZ31, AZ80 and AZ91D magnesium alloys was evaluated in terms of their corrosion behaviour in an aerated 3.5 wt.% NaCl solution at 25 °C. The corrosion process was monitored by electrochemical impedance spectroscopy (EIS). The surface was characterized by scanning electron microscopy (SEM), scanning Kelvin probe force microscopy (SKPFM) and low-angle X-ray diffraction (XRD). The extent of corrosion damage was strongly dependent on the aluminium content and alloy microstructure. Two key factors were observed for the lowest corrosion rates, which occurred for the AZ80 and AZ91D two-phase alloys: the aluminium enrichment on the corroded surface for the AZ80 alloy, and the β-phase (Mg₁₇Al₁₂), which acted as a barrier for the corrosion progress for the AZ80 and AZ91D alloys. Surface potential maps suggested that, between the β-phase and the α-matrix, the galvanic coupling was not significant.     

Electrodeposition of Sn-Bi lead-free solders: Effects of complex agents on the composition, adhesion, and dendrite formation

The influences of complex agents, including citric acid, ethylenediaminetetraacetic acid (EDTA), and polyethylene glycol (PEG) on the electrochemical co-deposition of Sn-Bi alloys were systematically investigated through the linear sweeps voltammetric (LSV) analyses. The onset deposition potential of Bi ions is obviously shifted to a negative value, close to that of Sn ions by the simultaneous addition of the above three compounds into the plating solution. Based on the LSV results, deposits plated from the typical solutions with the Sn⁴⁺/Bi³⁺ ratio of 1, pH of 6.0, and various combinations of complex agents were characterized by scanning electron microscopic (SEM), energy-dispersive spectroscopic (EDS), and X-ray diffraction (XRD) analyses. The 30Sn-70Bi alloy (in wt%) is successfully plated from the typical plating bath containing 0.4 M citric acid, 1.0 M EDTA, and 0.2 M PEG, suggesting the possibility in plating the Sn-Bi alloys with their composition around the eutectic point (42Sn-58Bi). The adhesion of deposits and the formation of dendrites are respectively improved and inhibited by the synergistic effects of these three complex agents. Contrary to this combination, nearly pure Bi deposits are obtained from the typical plating solutions containing complex agents in the other combinations.     

Nanostructured Sn–Ti–C composite anodes for lithium ion batteries

Nanostructured Sn–Ti–C composites have been synthesized by a facile, inexpensive high energy mechanical milling process and investigated as an anode material for lithium-ion cells. Characterization data collected with X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) reveal an uniform dispersion of Sn nanoparticles within the conductive, amorphous (or poorly crystalline) TiC + C matrix. Among the three Sn–Ti–C compositions investigated, the Sn₁₁Ti₃₁C₅₈ composite exhibits the best electrochemical performance, with a capacity of ∼370 mAh/g and excellent capacity retention over 300 cycles studied. It also exhibits excellent cycle life with LiMn₂O₄ spinel cathode, suggesting a tolerance of the Sn–Ti–C anodes toward poisoning by the manganese leached out from the spinel cathode. The superior electrochemical performance of Sn₁₁Ti₃₁C₅₈ composite is attributed to a homogeneous distribution of the electrochemically active amorphous Sn, suppression of Sn grain growth, and the mechanical buffering effect provided by the conductive TiC + C matrix toward the volume expansion-contraction occurring during cycling.     

High-performance Sn–Ni alloy nanorod electrodes prepared by electrodeposition for lithium ion rechargeable batteries

To reduce irreversible capacity and improve cycle performance of tin used in lithium ion batteries, Sn–Ni alloy nanorod electrodes with different Sn/Ni ratios were prepared by an anodic aluminum oxide template-assisted electrodeposition method. The structural and electrochemical performance of the electrode were characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, cyclic voltammetry, and galvanostatic charge–discharge cycling measurement. The results showed that the copper substrate is covered with uniformly distributed Sn–Ni alloy nanorods with an average diameter of 250 nm. Different phases (Sn, Ni₃Sn₄ and metastable phases) of alloy nanorod formed in the electrodeposition baths with different compositions of Sn²⁺ and Ni²⁺ ions. Sn–Ni alloy nanorod electrode delivered excellent capacity retention and rate performance.     

Hot corrosion of glass coating on nickel base superalloy

Hot corrosion behaviour of BaO–MgO–SiO₂ based glass coating on nickel base superalloy was studied using 80 wt.% Na₂SO₄ + 20 wt.% NaCl salt mixture, which melts at about 700 °C. In one set of experiments the glass coated superalloy substrates were immersed in the molten salt wherein in the other samples were suspended in the salt vapour at 1000 °C. During the test, mass loss per unit surface area was observed to be higher for specimens suspended in the salt vapour. The phase composition and microstructure of the corroded coating were investigated by X-ray diffraction (XRD), optical microscopy and scanning electron microscopy (SEM) in association with energy dispersive X-ray (EDX) analysis.     

The colloidal synthesis of unsupported nickel‐tin bimetallic nanoparticles with tunable composition that have high activity for the reduction of nitroarenes

Ni‐Sn bimetallic nanoparticles with controllable size and composition were prepared by facile method in ambient air using inexpensive metal salts. Adjusting stoichiometric ratio of Ni and Sn precursors afforded nanoparticles with different compositions, such as Ni₁₀₀, Ni₇₄‐Sn₂₆, Ni₅₉‐Sn₄₁, and Ni₅₀‐Sn₅₀. The characterization of nanoparticles was performed by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM), and energy dispersive X-ray analysis (EDX). Ni₇₅‐Sn₂₅ and Ni₆₀‐Sn₄₀ nanoparticles showed enhanced catalytic activity towards 2-nitroaniline reduction as compared with Ni nanoparticles. Furthermore, Ni₇₅‐Sn₂₅ nanocatalyst exhibited excellent activity for the reduction of a number of nitro aromatic compounds under mild conditions along with high level of reusability.     

Chemical reduction of nano-scale Cu2Sb powders as anode materials for Li-ion batteries

A novel process was attempted to prepare nano-scale Cu₂Sb alloy powders as anode materials for Li-ion batteries. The preparation started with chemical reduction of Cu₂Sb in an aqueous solution with sodium citrate as a complexing agent and KBH₄ as a reducer. The analysis of scanning electron microscopy and X-ray diffraction showed that as-prepared nano-scale Cu₂Sb powders presented tetragonal structure with particle size of 50-70 nm. Cycling between 0 and 1.2 V, the nano-scale Cu₂Sb alloy showed good cyclability with a stable specific capacity of 200 mAh g⁻¹ within 25 cycles.     

Study on the preparation of Mg-Li-Zn alloys by electrochemical codeposition from LiCl-KCl-MgCl2-ZnCl2 melts

Electrochemical codeposition of Mg, Li, and Zn on a molybdenum electrode in LiCl-KCl-MgCl₂-ZnCl₂ melts at 943 K to form Mg-Li-Zn alloys was investigated. Cyclic voltammograms (CVs) showed that the potential of Li metal deposition, after the addition of MgCl₂ and ZnCl₂, is more positive than the one of Li metal deposition before the addition. Chronopotentiometry measurements indicated that the codeposition of Mg, Li, and Zn occurs at current densities lower than −0.78 A cm⁻² in LiCl-KCl-MgCl₂ (8 wt.%) melts containing 1 wt.% ZnCl₂. Chronoamperograms demonstrated that the onset potential for the codeposition of Mg, Li, and Zn is −2.000 V, and the codeposition of Mg, Li, and Zn is formed when the applied potentials are more negative than −2.000 V. X-ray diffraction (XRD) indicated that Mg-Li-Zn alloys with different phases were prepared via galvanostatic electrolysis. The microstructure of typical α + β phase of Mg-Li-Zn alloy was characterized by optical microscope (OM) and scanning electron microscopy (SEM). The analysis of energy dispersive spectrometry (EDS) showed that the elements of Mg and Zn distribute homogeneously in the Mg-Li-Zn alloy. The results of inductively coupled plasma analysis showed that the chemical compositions of Mg-Li-Zn alloys are consistent with the phase structures of the XRD patterns, and that the lithium and zincum contents of Mg-Li-Zn alloys depend on the concentrations of MgCl₂ and ZnCl₂.     

Preparation of micrometer-sized α-Al2O3 platelets by thermal decomposition of AACH

Micrometer-sized α-Al₂O₃ platelets with hexagonal shape were prepared by thermal decomposition of ammonium aluminum carbonate hydroxide (AACH) using AlF₃ as an additive. The precursor and the calcined product were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy and differential scanning calorimetry. The α-Al₂O₃ platelets with the size of 2-3 μm were obtained by calcining AACH at 1200 °C with 5 wt.% AlF₃. The morphology modification is attributed to the various growth rates along different crystal orientations due to the adsorption and uneven distribution of AlF₃. A step growth mode is responsible for the formation of the platelets.     

Enhanced activity of PtSn/C anodic electrocatalyst prepared by formic acid reduction for direct ethanol fuel cells

The Pt₃Sn/C catalyst with high electrochemical activity was synthesized under optimizing preparation conditions. The surface of carbon support pretreated by strong acid contains many O-H and CO groups, which will increase the active sites of PtSn/C catalysts. The catalyst structure was characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and temperature programmed reduction (TPR). The co-reduction of Pt⁴⁺ and Sn²⁺ ions causes Sn to enter Pt crystal lattice to form PtSn alloy whose surface, however, contains tin oxides with Sn⁴⁺ and Sn²⁺ valences, which can promote the ethanol oxidation. The crystallinity of PtSn decreases with the reduction of the atomic ratio of Pt:Sn. By prolonging the reaction time of formic acid, the forward anodic peak current of ethanol oxidation reaches 16.2 mA on the Pt₃Sn/C catalyst with 0.025 mg Pt loading.