Effects of stannous ions on the electrochemical performance of the alkaline zinc electrode

The effect of stannous ions as an electrolyte additive on the electrodeposition characteristics of Zn was investigated by chronoamperometry, the potential-step method and cyclic voltammetry. The chronoamperometry measurements showed that the addition of stannous ions inhibited the dendritic growth of Zn deposits. SEM observation also revealed that the Zn deposit was in the form of compact cylinders with rounded tops that consist of many small crystallites, rather than the classical dendrites with side branches. The inhibition effect of Sn²⁺ on the very initial electrocrystallization of Zn was not a substrate effect. The 0.17 V difference in reduction potential between Zn and Sn resulted in the codeposition of Sn and Zn. An interruption effect was proposed to illuminate the inhibition effect of Sn²⁺ on the formation of Zn dendrites. Furthermore, Sn²⁺ additive was found to suppress the corrosion reaction of Zn by 87% in the Sn²⁺-containing zincate electrolyte, comparing to that in the blank zincate electrolyte.     

Optimization of Opto-Electrical and Photocatalytic Properties of SnO<Subscript>2</Subscript> Thin Films Using Zn<Superscript>2+</Superscript> and W<Superscript>6+</Superscript> Dopant Ions

Abstract  

A series of Zn²⁺ and W⁶⁺ doped tin oxide (SnO₂) thin films with various dopant concentrations were prepared by spray pyrolysis deposition, and were characterized by X-ray diffraction, atomic force microscopy, contact angle, absorbance, current density–voltage (J–V) and photocurrent measurements. The results showed that W⁶⁺ doping can prevent the growth of nanosized SnO₂ crystallites. When Zn²⁺ ions were used, the crystallite sizes were proved to be similar with the undoped sample due to the similar ionic radius between Zn²⁺ and Sn⁴⁺. Regardless of the dopant ions’ type or concentration, the surface energy has a predominant dispersive component. By using Zn²⁺ dopant ions it is possible to decrease the band gap value (3.35 eV) and to increase the electrical conductivity. Photocatalytic experiments with methylene blue demonstrated that with zinc doped SnO₂ films photodegradation efficiencies close to 30% can be reached.     

多功能硫酸盐镀锡添加剂的研制

硫酸盐光度锡工艺具有电流次效率高、沉积速度快、成本低及废水易处理等优点,在电镀生产中已广泛应用。为进一步提高镀锡层的性能,研制出一种多功能硫酸盐镀锡添加剂。通过赫尔槽试验优选出最佳镀液配方和工艺条件,并对镀液、镀层性能进行了测试。结果表明：采用自制的多功能添加剂能明显提高镀液的稳定性,所得镀层光亮、致密、均匀,无锡须,结合力强,可焊性和抗氧化性好。     

Structure and thermal properties of SrCe1-xSnxO3 (x=0.1 … 0.5) as a promising thermal barrier coating

Gas turbines efficiency growth is primarily associated with an increase in the operating temperature of the combustion chamber, which places new stringent requirements on the materials of thermal barrier coatings. Strontium cerate doped with tin SrCe_{1- x}Sn_xO₃ where x = 0.1 … 0.5, was proposed as a promising material. The research has shown that the lightly doped solid solution SrCe_1-xSn_xO₃ has an orthorhombic Pnma structure at x < 0.3, whereas at a high content of Sn⁴⁺ the monoclinic structure P2₁/m becomes more favorable. Thermogravimetric analysis (TGA) in reducing atmosphere (5%H₂ in Ar) shows no mass lost as a result of unchangeable charge of Ce⁴⁺ and Sn⁴⁺. An increase in the distortion of the crystal lattice, due to the large difference in the ionic radii of Ce⁴⁺ and Sn⁴⁺, leads to a deterioration in the symmetry of the crystal lattice, a reduction of thermal conductivity (from 1.9 to 1.4 W m⁻¹ K⁻¹ at 1000 °C) and at the same time, growth of hardness and porosity. The increase in porosity, along with an increase in the required temperature of solid-state synthesis, indicates an enhancement in the melting point of the obtained materials. For the compounds with an orthorhombic structure, the thermal expansion coefficient increases with a growth in the Sn content, achieving a highest point 12.47·10⁻⁶ K⁻¹ at 1100 °C for x = 0.3. The combination of the revealed properties and their comparison with advanced refractories makes the solid solution, primarily SrCe_0.5Sn_0.5O₃, a promising material for application as thermal barrier coatings.     

Bimetallic Pt–Sn/γ-alumina catalyst for highly selective liquid phase hydrogenation of diethyl succinate to γ-butyrolactone

Platinum–tin bimetallic catalyst on γ-alumina support was prepared by impregnation method and was reduced by sodium borohydride at room temperature. XRD and XPS characterization revealed that platinum was reduced to Pt⁰ while, tin was probably partially reduced to Sn²⁺ due to the low temperature reduction method and Sn⁰ was completely absent, avoiding the formation of Pt–Sn alloy. Pt–Sn/γ-alumina (Pt 1%, Sn 9%) thus prepared was found to give almost complete selectivity to γ-butyrolactone in liquid phase hydrogenation of diethyl succinate. A plausible reaction pathway is proposed involving Pt–O–Sn state and high selectivity to GBL is due to the Lewis acidity of Sn^2+/4+.     

Effect of low concentrations of Pb on Sn electrodeposition in methyl sulphonic acid solutions

The influence of Pb²⁺ on the initial stages of Sn electrodeposition onto copper from methyl sulphonic acid solutions in the absence of organic additives has been investigated. Particular attention is placed on the effect of Pb²⁺ at concentrations much lower than previously reported and where no lead is detected in the resulting deposit. Linear sweep scans and i-t transients show that Pb²⁺ catalyzes Sn plating at Pb²⁺:Sn²⁺ molar concentration ratios between about 1:1000 and 20:1000. This effect can be significant, with as much as a 30% increase in the amount of tin deposited over that obtained in the absence of Pb²⁺ when the concentration ratio is 2:1000 or 5:1000. At concentration ratios above 20:1000, the effect disappears and, in fact, Pb²⁺ has an inhibitory effect on Sn²⁺ reduction. Under conditions where Pb²⁺ enhances Sn electrodeposition, it also begins to affect electrocrystallization by promoting faster nucleation and a more 2-dimensional coating that more rapidly covers the substrate. This trend continues as the Pb²⁺ concentration is further increased and the catalytic effect disappears.     

SnO2‐supported palladium catalysts: activity in deNOx at low temperature

High surface area tin dioxide (174 m²/g) has been synthetised and characterised by XRD, TEM and UV‐visible DRS. DRS gives evidence for the formation of oxygen vacancies (donor levels) under reducing conditions. CO adsorption gives rise to terminal carbonyl species linked to Sn⁴⁺ and Sn²⁺. Palladium–tin oxide catalysts have been prepared from various precursors (Pd(acac)₂ and Pd(NO₃)₂) and by different preparation methods (grafting, photodeposition); they are active in deNOx reactions at low temperature (180 °C) in the presence of stoichiometric CO–NO–O₂ mixtures. A mechanism involving palladium and oxygen vacancies is proposed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal stability of tin charge states in the structure of the (As<Subscript>2</Subscript>Se<Subscript>3</Subscript>)<Subscript>0.4</Subscript>(SnSe)<Subscript>0.3</Subscript>(GeSe)<Subscript>0.3</Subscript> glass

Two valence states of tin atoms (namely, the doubly charged Sn²⁺ and quadruply charged Sn⁴⁺ states) in the structure of the (As₂Se₃)_0.4(SnSe)_0.3(GeSe)_0.3 glasses are identified by ¹¹⁹Sn Mössbauer spectroscopy. It is demonstrated that the concentration ratio of the doubly charged Sn²⁺ and quadruply charged Sn⁴⁺ states in the glass of this composition depends on the rate of quenching of the melt and on the initial temperature of the melt before quenching. The optical band gap and the activation energy for electrical conduction of the studied glass do not depend on the concentration ratio of the Sn²⁺ and Sn⁴⁺ ions. This behavior of the optical band gap and the activation energy is explained within the model according to which the structure of the glasses under investigation is built up of the structural units AsS_3/2, As_2/2Se_4/4, GeSe_4/2, SnSe_4/2, and SnSe_3/3, which correspond to the compounds AsSe₃, AsSe, GeSe₂, SnSe₂, and SnSe, respectively.     

Structural,magnetic, thermal and optical properties of Sn2+ cation doped magnetite nanoparticles

Tin doped nanomagnetites, Sn_xFe_3-xO₄, were synthesized with various concentrations of Sn²⁺ ion (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) by co-precipitation method. XRD, VSM, TG-DTA, SEM-EDX and UV–Vis were used to characterize and study the structural, magnetic, thermal, and optical properties of Sn_xFe_3-xO₄ nanoparticles. XRD confirmed the presence of cubic structure and spinel phase of tin doped magnetites. The d-spacing, lattice parameter, density, crystallite size and cation distribution were derived from the XRD analysis. The M − H curves exhibited changes in saturation magnetization (M_s), coercive field (H_c), remanent magnetization (M_r) and susceptibility (χ), with increasing concentration of non-magnetic Sn²⁺ ions. Differential thermal analysis was used to study the thermal stability of Sn_xFe_3-xO₄ nanoparticles. The SEM images revealed the surface morphology of the nanoparticles and the EDX spectra showed an increase in the Sn content and a corresponding decrease in the Fe content for the tin doped samples. The optical bandgap was found to be centered at 3.9 eV for the synthesized materials. This systematic study may be the first comprehensive report on synthesis and characterization of tin doped magnetites.     

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.     

The state of tin impurity atoms in vitreous germanium chalcogenides

Tin atoms formed after the radioactive decay of the ^119mmSn and ¹¹⁹Sb impurity atoms in the structure of Ge _x S_{1 ? x} and Ge _x Se_{1 ? x} glasses are stabilized in the form of Sn²⁺ and Sn⁴⁺ centers or in germanium nodes (after ^119mmSn decay), or in the nodes of structural units formed by ¹¹⁹Sb atoms. The Sn²⁺ and Sn⁴⁺ centers correspond to the ionized states of amphoteric two-electron tin center with negative correlation energy. ¹¹⁹Sn atoms formed after the radioactive decay of the ^119mTe atoms in the structure of Ge _x S_{1 ? x} and Ge _x Se_{1 ? x} glasses are stabilized in both chalcogen and germanium nodes.     

Corrosion of tin in aqueous solutions of mono-, Di- and trichloroacetic acids

The corrosion behaviour of tin in stagnant mono-, di- and trichloroacetic acids solutions in the pH range 1–6 and at concentrations 4.0 to 5 × 10^?4 M was investigated. The results indicate behaviour that is generally the same but there is some dependence on the acid concentration and the pH value. In 4.0 to 10^?2 M solutions, the corrosion rate (W) increased with increasing acid concentration and decreasing pH value from 1 to 4 as follows: log W=a+b log C, where b=0.70, 0.42 and 0.35 for tri-, di- and mono-chloroacetic acids respectively. At high concentrations 4.0 to 10^?2 M and in the pH range 1–6, the steady state corrosion potential shifted in the negative direction with increase of acid concentration accompanied by an increase in the corrosion rate, indicating that the corrosion process becomes anodically controlled by the complexing of Sn²⁺ ions with organic acid anions and that the order of aggressiveness is mono-<di-<trichloroacetic acids. In dilute solutions (10^?2 to 5.10^?4 M) in the pH range 1–6 the steady state potential shifted in the noble direction with increase of acid concentration (accompanied by a remarkable decrease in the corrosion rate). Corrosion inhibition in dilute solutions was attributed to film formation on the surface of tin which may result from the hydrolysis of tin species.     

Removal of tin from dilute solutions

The fluidised bed cell of inert glass beads is an electrolytic reactor which is designed to provide higher ion‐transfer conditions during electrolysis, thus enabling metals to be removed efficiently from dilute solutions. The effectiveness of the method as a means of removing metals from effluent to meet discharge consent levels is studied for the in situ removal of tin from dilute solution (concentration range 0.25–1.00 gdm⁻³). The results show that the combination of high mass transport conditions and a moderately high electrode surface area per unit electrode volume provides a system for continuous removal of metal from dilute solutions. The effects of acid concentration, tin concentration, current density, fluidised bed agitation, electrode spacing, type of electrode and lead impurities on the removal of tin are reported and expressed in terms of the percentage removal of tin (α_Sn), the efficiency of tin deposition (ϕ_Sn), and the energy consumption (W_Sn) for 1 kg of tin deposited. The results show that tin can, under optimised conditions, be removed from dilute solutions to a residual concentration of 0.001 gdm⁻³. © 2001 Society of Chemical Industry     

Electrochemical synthesis of Ni-Sn alloys in molten LiCl-KCl

The electrochemical formation of Ni-Sn was investigated in molten LiCl-KCl in the temperature range 380-580 °C. Before, an electrochemical study of the Ni²⁺/Ni⁰, Sn⁴⁺/Sn²⁺ and Sn²⁺/Sn⁰ redox couples was performed by cyclic voltametry and chronopotentiometry in a wide temperature range. It had been pointed out that in the case of the Sn⁴⁺/Sn²⁺ redox couple, an insoluble compound is probably formed for T < 460 °C. For higher temperature, this compound becomes soluble and then, the shape of the cyclic voltammogram is analogue to the one usually observed when a diffusion-controlled process is involved. The diffusion coefficient values of Ni²⁺ and Sn²⁺ ions were determined. For instance, D_Ni(II) and D_Sn(II) values deduced from chronopotentiometry were about 2.1 × 10⁻⁵ and 2.7 × 10⁻⁵ cm² s⁻¹ at 440 °C, respectively. Then, Ni-Sn alloys have been formed in potentiostatic mode. The electrochemical route proposed in this paper leads to the formation of crystallized alloys with a well-defined composition depending on the operating conditions.     

Effects of tin doping on physicochemical and electrochemical performances of LiFe1−xSnxPO4/C (0 ≤ x ≤ 0.07) composite cathode materials

Nanocrystalline LiFe_1−xSn_xPO₄ (0 ≤ x ≤ 0.07) samples are synthesized using SnCl₄·5H₂O as dopant via an inorganic-based sol–gel method. The dependency of the physicochemical and electrochemical properties on the doping amount of tin are systemically worked out and regular changes are revealed. In the whole concentration range, the chemical valence of Fe²⁺ is not basically changed whereas tin is found in two different oxidation states, namely +2 and +4. The replacement of Fe²⁺ by supervalent Sn⁴⁺ would lead to electron compensation. Under the synergetic effects between the charge compensation and the crystal distortion, the electrical conductivities for the bulk samples first increase and then decrease with the increasing amount of Sn doping. Upon the doping amount, the apparent lithium-ion diffusion coefficient and the electrochemical performance also display the similar trends. The doping is beneficial to refine the particle size and narrow down the size distribution, however optimizing the doping amount is necessary. Compared with other samples, the sample with a doping amount of about 3 mol% delivers the highest capacities at all C-rates and exhibits the excellent rate capability due to the high electrical conductivity and the fast lithium-ion diffusion velocity.     

Temperature dependent negative permittivity in solid solutions Sr2Mn1-xSnxO4 (x = 0, 0.3, 0.5)

A few compositions of the system Sr₂Mn_1-xSn_xO₄ (x = 0.0, 0.3, 0.5) were synthesized in the air by the solid-state ceramic route. A change in the sign (positive to negative) of the permittivity above a particular temperature (T_C) is observed at all the measured frequencies. The negative permittivity was analyzed by the Drude-Lorentz model. It was found that negative permittivity is caused by the plasma oscillations of thermally excited free charge carriers. Analysis of XPS spectra confirmed the presence of mixed-valence states of both Mn (Mn⁴⁺ and Mn³⁺) and Sn (Sn⁴⁺ and Sn²⁺) ions. The UV–vis.-IR spectroscopy results indicated generation of a large number of defect states in the forbidden bandgap region of Sr₂MnO₄ on the substitution of Sn at Mn site. Synthesized samples are promising metamaterials for radio frequency (10 Hz -2 MHz) region applications due to the high-temperature plasmonic behavior.     

Relationship between foaming properties and solution properties of protein/nonionic surfactant mixtures

The foaming properties of bovine serum albumin (BSA), in the absence and presence of Triton X-100 (TX-100), have been investigated using shaking tests. The results showed that increases in the TX-100 bulk concentration rapidly reduced both foam height and foam stability at TX-100 concentrations below about 0.25 mM, but increased foam height and foam stability at TX-100 concentration above 0.3 mM. The interaction between BSA and TX-100 has been studied using fluorescence spectroscopy. The surfactant appeared to bind to BSA with a low molar ratio (about one surfactant molecule per protein molecule) at concentrations below the critical micelle concentration (CMC); the binding became weaker at concentrations above the CMC. It was confirmed that protein-protein or protein-surfactant interactions had significant influence upon foaming properties of mixed protein/surfactant system.     

Mechanism of the reverse dissolution of zinc in the presence of nickel

Cyclic voltammetry and impedance measurements were used to investigate the influence of an additive, triethyl-benzyl-ammonium chloride, on the kinetics of zinc deposition in acidic sulphate electrolytes containing Niu²⁺ ions able to induce the reverse dissolution of zinc deposits. It is shown that the adsorbed additive inhibits both the nucleation and growth of zinc deposits. By competing with the formation of a nickel-containing surface compound responsible for a stimulation of hydrogen evolution, the additive adsorption also inhibits hydrogen evolution and thereby stabilizes the galvanostatic deposition of zinc.     

The origin of the electrical inactivity of iron and tin impurity atoms in crystalline and vitreous alloys A III B IV (A = Ga, In; B = Te, S)

Tin and iron impurity atoms in the structure of crystalline and vitreous alloys Ga_1?y Te_y (y = 0.6, 0.8) and In_1?y Te_y (y=0.6) are shown to be stabilized in their normal valence states. It is demonstrated that the electrical inactivity of tin and iron impurity ions is caused by the compensating effect of Ga⁺ and In⁺ ions, which are responsible for the fixed position of the Fermi level at the midpoint of the band gap. Tin impurity ions in the structure of the β-In₂S₃ crystal are analogs of two-electron centers (with a negative Hubbard energy) proposed for chalcogenide glasses. Within this model, Sn²⁺ ions are ionized acceptors and Sn⁴⁺ ions are ionized donors.     

Fast Separation of Tin(IV) from Tin(II) and from Numerous Metal Ions on Ion-Exchange Papers

Abstract

A fast method for the separation of Sn⁴⁺ and Sn²⁺ has been developed on titanic tungstate ion-exchange papers. Sn⁴⁺ can also be separated from 40 other cations on these papers in only 20 min.