On the Role of Boric Acid in the Copper-Tin Alloy Bath

The role of boric acid in the copper tin alloy bath has been investigated by means of the cathodic polarization curves,cyclic voltammograms,rate of alloy electrodeposition and morphological analysis of deposits.The results indicate that the presence of boric acid in weak acidic solution for electrodeposition of Cu Sn alloy raises the overvoltage of hydrogen discharge and lowers the overvoltage of Cu,Sn and Cu Sn alloy deposition on the Pt,and accelerates the rate of depostion.Boric acid was adsorbed on the surface of cathode and inhibited reduction of hydrogen,then the adsorbed boric acid promoted electrodeposition of metals as a catalyzator.However,as the concentration of boric acid is more than 0.50 mol/L,the above effect was weakened due to the complexation reaction between the excessive boric acid and metallic ions.

Influence of Rare Earths on the Directional Solidification Microstructure of Tin-Lead Eutectic Alloy

The research on the influence of RE on the directional solidified microstructure of tin lead alloy reveals that the addition of RE can cause chopping and irregular lamellar and smaller lamellar spacing. When RE content increases, the microstructure changes to peritectic structure. Moreover, the eutectic point of Sn Pb alloy deviates because the affinity of RE for Sn, which results in the existence of primary Pb rich phases contained hypocutectic grown layers. Sn RE intermetallic compound has no effect on the solidification of Sn Pb alloy.

New Asymmetric Model for Predicting Ternary Thermodynamic Properties

The prediction of the thermodynamic properties of ternary systems from the properties of their sub-binary systems is of great importance to phase diagram calculations. In the present study, a new asymmetric model which has more clear physical significance has been developed for evaluating the ternary thermodynamic properties from its three binary components. The model is considered to be rigorous in the case where the pseudobinary systems of fixed X2/X3 are regular are regular solution. The application of new model to the prediction of ternary enthalpies of mixing for Bi-Ga-Sn, Au-Ag-Sn and NaCl-KCl-CaCl2 systems shows that the calculated results by new model are closer to experimental data than those by Toop's model.

First-principles calculations and experimental studies of Sn-Zn alloys as negative electrode materials for lithium-ion batteries

The physical characters and electrochemical properties of various phases in a Sn-Zn electrode, such as formation energy, plateau potential, specific capacity, as well as volume expansion, were calculated by the first-principles plane-wave pseudo-potential method based on the den- sity functional theory. Sn-Zn films were also deposited on copper foils by an electroless plating technique. The actual composition and chemical characters were explored by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, plasma atomic emission spectrometry （ICP）, and constant current charge/discharge measurements （CC）. The results show that separation phases with tin and zinc including a small quantity of Cu6Sn5 phase were obtained, the initial lithium insertion capacity of the Sn-Zn film was 661 mAh/g, and obvious potential pla- teaus of about 0.4 V and 0.7 V were displayed, which is in accordance with the results of theoretical calculations. The capacity of the Sn-Zn film decreased seriously with the increase of cycle number.

Effect of rolling technologies on the properties of Pb?0.06wt%Ca?1.2wt%Sn alloy anodes during copper electrowinning

The objective of this work was to study the effect of different rolling technologies on the properties of Pb-0.06wt%Ca-1.2wt%Sn anodes during copper electrowinning and to determine the relationship between the properties of the anodes and rolling techniques during copper electrowinning. The anode process was investigated via anodic polarization curves, cyclic voltammetry curves, electrochemical impedance spectra, and corrosion tests. The microscopic morphology and phase composition of the anodic oxide layers were observed by scanning electron microscopy and X-ray diffraction, respectively. Observable variations in the electrocatalytic activity and reaction kinetics of anodes during electrowinning indicated that the electrochemical behavior of the anodes was strongly affected by the rolling technology. An increase in the rolling number tended to decrease the oxygen evolution overpotential and the corrosion rate of the anodes. These trends are contrary to that of the apparent exchange current density. Furthermore, the intensities of diffraction peaks associated with PbO, PbOx, and α-PbO2 tended to increase with increasing rolling number. In addition, the rolled anodes exhibited a more uniform microstructure. Compared with one-way rolled anodes, the eight-time cross rolled anodes exhibited better electrocatalytic activity and improved corrosion resistance.

Selective growth of tin whiskers from its alloys on Ti_(2)SnC

The spontaneous growth of metal whiskers has been investigated for more than 70 years.However,there is still no agreement on its growth mechanism,and moreover,new characteristics of this whiskering phenomenon continue to emerge.In this study,Ti_(2)SnC is found to be capable of extracting Sn out of its alloys(Sn Bi,Sn Ag)by selectively growing Sn whiskers,and the Sn whiskers share the features of the traditional whiskers on platings and solders.Replacing the Ti_(2)SnC substrate with Ti C or Si C,under the same conditions,however,the selective growth of Sn whisker does not happen,which means Ti_(2)SnC plays a critical role in it.Based on the unique crystal structure of Ti_(2)SnC,active Sn atoms diffusing through the basal planes of Ti_(2)SnC is proposed to explain the selectivity.The driving force is suggested to be the high interfacial energy between Ti_(2)SnC and tin.This study is of importance to further understand the growth mechanism of metallic whiskers,and it may be also possible to be harnessed to develop paradigm-shifting technologies of metal purification and metallic whisker/nanowire preparation.