The co-deposition of copper and zinc inclusion in electrodeposition of silver from silver cyanide bath

The co-deposition behavior of a trace of copper and zinc as an impurity in cyanide baths for silver plating was studied by means of a radioactive tracer. The authors selected ⁶⁴CuCN and ⁶⁵Zn(CN)₂ as a labelled compound and added it to the cyanide baths for silver plating.Each amount of copper and zinc co-deposited with silver increased with increasing copper and zinc concentration in silver plating baths and temperature. It was found that the co-deposition of copper and zinc depended on cathode potentials and was not diffusion-determining. The co-deposition of copper abruptly increased in the high current density range. In the potential range Cu co-deposition is observed with Cu reversible potential through limiting current of silver deposition, and evolution of hydrogen. At low current density, Cu and Zn co-deposition are saturated at about 6400 Å thickness of electrodeposited silver and occluded in the electrodeposits is not smooth and coarse structure is observed on it.     

Reaction between zinc oxide and chamotte refractories

Conclusions As a result of chemical reaction between chamotte and zinc oxide, zinc aluminate ZnAl₂O₄ and zinc silicate Zn₂SiO₄ are formed.The mullite is not chemically resistant under the action of zinc oxide. Even at 900°C mullite reacts with zinc oxide, forming ZnAl₂O₄ and SiO₂.In accordance with the quantity of melt formed in the refractory under the action of zinc oxide, high-alumina products should be more resistant to the action of vapors and oxides of zinc at elevated temperatures than chamotte and semiacid refractories.Translated from Ogneupory, No. 7, pp. 36–39, July, 1971.     

载银锌纳米二氧化硅抗菌剂的制备及应用

利用纳米二氧化硅的结构特性,将其作为抗菌剂载体,制成了一种载银锌双组分纳米二氧化硅抗菌剂,研究了提高抗菌剂分散性的方法。结果表明,使用振动磨加分散剂的方法进行分散,可以提高载银锌纳米二氧化硅抗菌剂在涤纶基体中的分散性;该抗菌剂对大肠杆菌及金黄色葡萄球菌的抗菌率达96％以上,且抗菌涤纶具有良好的力学性能。     

Interaction of zinc deposited from an alkaline solution with a polycrystalline silver substrate

The interaction of zinc electrodeposited from an alkaline solution with a polycrystalline silver substrate is studied with cyclic voltammetry, microprobe technique and ellipsometry. Zinc forms alloys with the substrate via diffusion. Two phases are identified: one as the ε-phase (AgZn₃) and the other as the ζ-phase (AgZn). A penetration coefficient (k) of 7 × 10^?4 cm² s^?1 is calculated. Transformations into phases with lower zinc content take place continuously, probably resulting in the formation of the α-phase.     

Scale-up effects in modelling a full-size zinc electrowinning cell

The scale-up of a mathematical model of a (10 dm³) pilot-plant zinc electrowinning cells is considered. All scale-up effects considered were relatively small in magnitude and their inclusion required only readily available full-size cell data. Excellent agreement was obtained between the model predictions and experimental results from an (instrumented) operational full-size cell.     

A zinc–air cell employing a porous zinc electrode fabricated from zinc–graphite-natural biodegradable polymer paste

Porous zinc anodes have been fabricated from a mixture of zinc and graphite powder using gelatinized agar solution as the binding agent. Agar is a biodegradable polysaccharide polymer extracted from marine algae. The graphite content and the agar solution concentration were varied to find the best electrode composition. Zinc–air cells were fabricated using the porous zinc anode, a commercially available air cathode sheet and KOH electrolyte in the form of elastic jelly granules. The electrode performance was evaluated from the zinc–air cell galvanostatic discharge capability. In the cell design, a thin agar layer was introduced between the electrode-gelled electrolyte interfaces, resulting in substantially improved cell discharge performance. The inclusion of particulate graphite into the electrode did not enhance the electrode performance due to the formation of a graphite-rich layer, which obscured the electrode porosity. A zinc–air cell employing the optimized porous zinc electrode demonstrated a capacity of 2066 mA h and specific energy density of 443 Wh kg^–1.     

Zinc-manganese dioxide galvanic cell using zinc sulphate as electrolyte. Rechargeability of the cell

The discharge capacity of the Zn|ZnSo₄(aq)|MnO₂ galvanic cell increases with increase in the concentration of ZnSO₄; use of a 2 M aqueous solution of ZnSO₄ gives 65% utilization of MnO₂. When the cell is charged after discharging, X-ray diffraction analysis of the positive electrode material indicates regeneration of -MnO₂ during the charging. Repeated charging and discharging under various modes reveals that the cell is rechargeable more than 30 times. When the cell is charged to 1.70V and discharged to 0.9V, the cell shows about 100% coulombic efficiency with an average discharging voltage of about 1.3V (energy efficiency=83%) and 57% utilization of MnO₂. The cell is rechargeable after discharging to 0V.     

Effect of silver nanoelectrode ensembles on the electrocatalytic reduction of NO2 by zinc phthalocyanine

Ag nanoparticles anchored on mesoporous silica materials with and without zinc phthalocyanine (ZnPc) were prepared (Ag-MPS and Ag-MPS-ZnPc respectively). The morphology, structure and composition of the materials were characterized by transmission electron microscopy, X-ray diffraction, UV/vis diffuse reflectance spectra, and X-ray photoelectron spectroscopy techniques. The new materials were used for electrode modification and the nanoelectrode ensemble (NEE) behavior of Ag-MPS and Ag-MPS-ZnPc materials was semi-quantitatively evaluated by cyclic voltammetry. Further, electrocatalytic reduction of nitrite is demonstrated at these NEE.     

Studies on the silver/silver oxide electrode

The electrochemical behaviour of silver/silver oxides electrodes in 1 N KOH or 1 N KOH + methanol have been studied by measuring current-potential and impedance-potential curves under the potential sweep in the cathodic direction starting from the AgO formation region.Two specific anodic current peaks A and X were observed in current-potential curves. It was concluded that X was due to the incomplete oxidation of Ag₂O to AgO under the anodic sweep or due to the partial decomposition of AgO layer, and A was due to the catalytic reaction of AgO with methanol followed by the electrochemical oxidation of Ag₂O to AgO.The values of the impedance tend to decrease in the vicinity of the peak A at the low frequency, which may be attributed to the reduction of AgO with methanol.     

A validated mathematical model for a zinc electrowinning cell

A set of (95) equations forming a dynamic, nonlinear model of an industrial pilot-plant scale zinc electrowinning cell fed with high purity electrolyte is presented. Only the solution of the steady-state model is considered in this paper. Values for unknown model parameters have either been obtained from the literature or else estimated using experimental data taken from the pilot-plant cell. Sensitivity studies showed that uncertainties in the temperature dependency of the zinc and hydrogen reaction exchange current densities and the exchange coefficient for the hydrogen reaction have a major effect on the model predictions. Excellent agreement between predicted and experimental results was obtained, provided that cathodic mass transfer effects were included in the model. Both parameter estimation and solution of the steady-state model were carried out using the SPEEDUP flowsheeting package.     

A new cell design for the determination of transport numbers in molten silver nitrate-rubidium nitrate system

A new design of a concentration cell with transference for the determination of transport numbers is described. Very small asymmetry potentials and steady emf's without fluctuation could be observed using the new cell in molten silver nitrate-rubidium nitrate system. The internal transport numbers of silver and rubidium ions relative to nitrate ion were determinedat 250, 300 and 350°C. A comparison is made among the internal mobilities of the cations in several molten silver nitrate-alkali metal nitrate systems.     

The mechanism of electrode process in the system silver/silver cyanide complexes

The electrode's surface inhomogeneity was taken into account studying the mechanism of process. The effect of CN⁻ adsorption and partial surface coverage was investigated by electrochemical fast Fourier transform (FFT) impedance spectroscopy (0.03-3900 Hz). The isopotential solutions (E₀=−0.350 V) as well as solutions containing constant silver cyanide complex concentration (0.05 M) and different free cyanide ion concentrations (from 0.01 to 1.0 M) were studied. The exchange current density, re-calculated for only active area, gives electrochemical reaction order (R_CN=1.8 for α=0.5, and R_CN=2 for α=0.6) which is independent from CN⁻ concentration and from the composition of complexes prevailing in the bulk of electrolyte. The value of R_CN close to 2, obtained in a series of isopotential solutions confirms that in all cases the complex ions Ag(CN)₂⁻ take direct part in the charge transfer step.     

The use of indoline dyes in a zinc oxide dye-sensitized solar cell

The effects of the position and the type of carboxyl anchor group in double rhodanine-type indoline dyes on the performance of a zinc oxide dye-sensitized solar cell were examined. The optimum position for the carboxymethyl group was on the inner rhodanine moiety; a carboxymethyl group gave optimum results among carboxymethyl, -ethyl, and -propyl derivatives.     

银镀层中银离子的迁移现象(二)

文章的第2部分论述了银镀层发生离子迁移的实验方法和检测方法.实验方法有环境实验法和溶液实验法;检测方法包括光学观察,绝缘电阻值测量,感应电特性,SEM观察,组成分析,放射化分析,软X射线观察,AFM观察和激光显微镜观察等.     

Comparative voltammetric behaviour of the silver/silver oxide electrode prepared on vitreous carbon and silver substrates

The voltammetric behaviour of vitreous carbon/chemically precipitated silver hydroxide layer and silver/electrochemically formed silver oxide layer electrodes are compared. As the former type of electrode is free from silver substrate contributions during the oxidation-reduction cycles (ORC) the voltammetric data indicate the occurrence of soluble Ag(I) species in the gel-like silver hydroxide matrix. Soluble species can be formed during the ORC as a consequence of AgOH formation at the early stages of the oxidation and reduction processes. Nucleation and growth of new phases produce a non-homogeneous layer structure and a decrease in the amount of active material participating in the ORC under preset conditions.     

The kinetics of silver bromide film formation on the silver anode

The anodic potentiodynamic formation of an AgBr film on an Ag rotating disc electrode was studied in aqueous bromide solutions. As the electron transfer step (1) is intrinsically fast,

and as the film remains porous throughout its growth, the rate of film growth is limited by physical parameters such as ionic diffusion and migration in the solution.The anodic E/I curves for AgBr film formation were calculated quantitatively by computer on the basis of the following model of film growth. Film formation occurs initially by the nucleation of islands of film to a critical thickness, and then these islands spread laterally until only small pores remain between them. As these pores become small, the resistance of the solution within them becomes rate limiting (at the anodic current peak). After the peak, the concentration of bromide ions at the pore base falls to zero and current is then controlled by the diffusion of bromide ions into the lengthening pores of the film.This lateral spreading mechanism and the subsequent retention of the porous film morphology has been substantiated by comprehensive Scanning Electron Microscope investigations.     

The kinetics of silver iodide film formation on the silver anode

The potentiodynamic formation of AgI films by reaction (1) on an Ag rotating disc electrode was studied and the results were compared to previous work regarding the formation of anodic AgBr and Ag₂S films,

In dilute iodide solutions, a very porous AgI film is formed at a rate controlled by the diffusion of I^? to the electrode surface. At higher iodide concentrations, and particularly in high conductivity supporting electrolytes, a porous AgI film forms at a rate initially limited by ionic migration in solution followed by diffusion of I^? in the pores of the AgI film.In 1 M NaI solutions, when AgI becomes rather soluble, thick granular AgI films form at a rate limited by the solid-state migration of ions in the bulk of the film. On the basis of the low-field model of film growth, the ionic conductivity of these AgI films has been determined to be 8.7 × 10^?5 Scm^?1