Current Efficiency Measurements Research Articles

クエン酸を用いた電気ニッケルめっき浴

A new nickel electroplating bath called a “Nickel citrate bath” uses citric acid in place of boric acid. In order to clarify its properties, a Hull cell test and measurements of current efficiency and pH titration curves were performed. The results were compared with those obtained from a Watts bath. The citric acid in a Nickel citrate bath consists of various ratios of citrate ion and nickel-citrate complexes forming complex equilibrium at various pH levels. A Nickel citrate bath with a concentration of citric acid above 0.06M has a good appearance, current efficiency, and pH buffering action for the bath. The results were almost the same as those obtained with a Watts bath under the same conditions. This result is attributed to interaction of nickel-citrate complexes at the electrode surface in the Nickel citrate bath.

Sulphurous acid as anodic depolarizer in copper electrowinning. Part II

The growing interest in the electrowinning of copper has lead to several modifications including anodic reactions proposed to reduce the high energy requirement. The addition of sulphurous acid to a copper sulphate electrolyte has been studied to avoid oxygen evolution at the anode which requires a potential in excess of 2 V. In particular, the effect of different anode materials, concentration of sulphurous acid, current density, copper and sulphuric acid concentrations in the electrolyte have been investigated. Measurements of anode potential, cell voltage, current efficiency and energy consumption during the electrowinning of copper have been made using a diaphragm cell. It was found that graphite and lead coated with Ir–O2 are better electrode materials than lead and DSA anodes and sulphurous acid can be used as anodic depolarizer.

Radiation damage studies of multi-guard ring p-type bulk diodes

Abstract Several diodes with different multi-guard ring structures were fabricated from 10 kΩ cm p-type bulk material. Studies on the performance of such devices are presented here. They include the measurement of the leakage current, breakdown voltage and charge collection efficiency before and after 2×10 14 p/cm 2 irradiation with 63.3 MeV kinetic protons.

Confocal Laser Scanning Microscopy, Electrochemistry, and Quartz Crystal Microbalance Studies of Leveling Effects of Thiourea on Copper Deposition

Three techniques were used to evaluate and study the effect of additives in the electrodeposition process. The evolution of surface profiles on model copper surface topography was monitored by confocal laser scanning microscopy (CLSM) in the presence of different concentrations of thiourea in copper sulfate solutions. The model surfaces were fabricated by photolithography. Along with the CLSM, concurrent measurements of electrochemistry and quartz crystal microbalance (QCM) were made. It was found that thiourea acted as a mediator in the electrochemical reactions that occurred at the electrode surface as revealed by current efficiency measurements. The cathodic consumption of thiourea was found to be negligible and it was strongly adsorbed on the surface. From the CLSM and QCM, it was found that thiourea acted as a brightening agent and did not exhibit any leveling ability.

Characterization of thin film ZnO/ZnCdS/CuGaSe2 heterojunctions

Polycrystalline thin film solar cells with structure ZnO/ZnCdS/CuGaSe2 were fabricated. The absorber layers of CuGaSe2 were prepared by laser assisted evaporation. A multilayer window consisting of reactively evaporated ZnO and sprayed ZnCdS was deposited onto CuGaSe2 to complete the cell; ZnO improves the light coupling and window sheet resistance, and ZnCdS serves as a buffer layer. The electrical and optical properties of the individual layers were studied. The junction behaviour was evaluated using current density-voltage, capacitance-voltage and quantum efficiency measurements, showing that the junction transport is controlled by tunnelling at low temperatures and recombination above room temperature. A conversion efficiency of 5.8% was obtained on an area of 1 cm2 with cell parameters Voc = 700 mV, Jsc = 12.5 mA cm−2 and FF = 0.56 without antireflection coating. The results obtained are presented and the requirements for optimizing the device efficiency are discussed.

In‐situ measurement of interfacial pH using a rotating ring‐disk electrode

AbstractA nonintrusive technique for the in‐situ measurement of interfacial pH and current efficiency has been developed. A ring electrode, operated potentiometrically at opencircuit, is used to measure the pH change at a rotating disk electrode. The technique takes advantage of the well‐characterized hydrodynamics at the rotating disk electrode and has the added advantage that the pH probe, the ring electrode, is not interfering with the flow field and the current distribution on the disk. To determine the pH at the disk electrode by measuring the potential of the ring, the radial transport of hydronium ions across the insulating gap and on the ring is analyzed taking into account the effect of homogeneous dissociation reactions of water and metal‐hydroxide ion complexes. Shifts in the ring potential caused by hydrogen super‐saturation and ohmic drop are also evaluated. A platinized ring electrode in a hydrogensaturated electrolyte is shown to provide a stable and reproducible hydrogen ion sensor with a Nernstian response to the changes in the bulk pH. Performance of the ring is evaluated by generating hydrogen at the disk electrode from a dilute acid solution, in the absence of other electrochemical reactions. The technique is then applied to determine the interfacial pH of nickel, iron and nickel‐iron alloy electrodeposition with concurrent hydrogen evolution. This method was also used to measure the current efficiency of nickel electrodeposition in a fast, nonintrusive and in‐situ manner.

On the Electrodeposition of Black Nickel

SUMMARYElectrodeposition of black nickel has been investigated from sulphate baths, to which phenyl thiourea and sodium potassium tartrate had been added as additives. The baths consist of: 0·15-0·60 mol l−1 NiSO4 6H2 O, 0·05-0·23 mol l−1 (NH4)2SO4, 0·20 mol l−1 Na2SO4.10 H2O, 0·40 mol l−1 H3BO3 3·30-16·50 mol l−1 phenyl thiourea and 0·125-0·600 mol l−1 sodium potassium tartrate. Polarization curves, cathodic current efficiency and electrocapillary measurements were the main electrochemical measurements carried out. Spectrophotometric measurements as well as elemental analysis were also applied. Moreover, surface morphology studies were made on the as-deposited nickel. From these studies, the role played by phenyl thiourea is ascribed to its ability to act as a surface active substance and to partially block the cathode surface. Addition of sodium potassium tartrate resulted in better quality deposits. The black deposit is not purely metallic nickel and is contaminated with some other components.

Differential gain in bulk and quantum well diode lasers

Differential gain (g/sup '/) of bulk and single-quantum-well (SQW) lasers was determined from threshold current density and differential quantum efficiency measurements. The threshold measurement technique was used to show that g/sup '/ is a function of cavity length (L) in SQW lasers and independent of L in bulk lasers. It was found that g/sup '/ of long SQW lasers (1000 mu m) is about 7*10/sup -16/ cm/sup 2/, approximately two times that of bulk lasers. At short cavity lengths (250 mu m), g/sup '/ is about the same for both laser types. >

Electrochemical determination of current efficiency for aluminium deposition on solid substrates from cryolitic melts

A potentiostatic double pulse method has been developed for the measurement of current efficiency of aluminium deposition from cryolitic melts on solid substrates. The method is based on the measurement of the ratio of anodic to cathodic charge. Its application is at present limited to laboratory cells. The method described is useful for the study of the influence of different parameters such as electrolyte composition, temperature or convection conditions on current efficiency for aluminium deposition.

The role of ion bridging in controlling competitive electrodeposition processes

It was shown by the following three different types of measurements that the effect of thiocyanate on electrodeposition processes involving cobalt, nickel and lead could be predicted by regarding the thiocyanate as a bridging anion for deposition the transition elements and merely as a blocking agent for the deposition of the non-transition elements. 1. (1) Voltammetric methods showed that the thiocyanate increased the rate of deposition of the transition elements, cobalt and nickel, but only inhibited the deposition of the non-transition elements lead and hydrogen. 2. (2) Current efficiency measurements showed that addition of thiocyanate ions increased the current efficiency for the deposition of the transition elements cobalt and nickel, but decreased the current efficiency for deposition of the non-transition element lead. 3. (3) Alloy deposition studies showed that addition of thiocyanate ions increased the percentage of cobalt and nickel in cobalt-lead and Ni-Pb alloys.

Current Efficiency Measurements in Laboratory Aluminium Cells—XI. Anode Gas Composition and Anode Consumption

The anode gas composition and the anode consumption were measured in a small laboratory aluminium electrolysis cell. The anode gas was found to be 100% CO2(g), and the carbon consumption of a prebaked anode decreased slightly with increasing anodic current density towards a value of about 110% of the theoretical consumption. For a graphite anode a slight increase was observed, and the consumptions were higher, in the range 135–150%. From the increase in anode consumption with increasing temperature it was concluded that selective oxidation of prebaked anodes may be the main reason for the excess anode consumption. For graphite anodes, however, the gas evolution and electrolyte stirring may rather be the main cause for the high anode consumption values.

Current Efficiency Measurements in Laboratory Aluminium Cells—XII. Low-Melting Bath

Electrolysis with a low-melting cryolite bath containing 20 mass% aluminium fluoride and 3 mass% lithium fluoride showed that the current efficiency could be improved by 1.2% for each 10°C reduction in temperature in the range from 890 to 940°C. The main problems encountered with the use of such a low-melting bath were increased cathodic overvoltage, shorter time before the onset of an anode effect, and possible formation of solid cryolite on the cathode. Part of the reason was the low convection in the bath in the small laboratory aluminium cell. The results are encouraging with respect to achieving better current efficiencies with the use of low-melting baths in aluminium electrolysis.

Current Efficiency Measurements in Laboratory Aluminium Cells—X. Anodic Overvoltage and Potential Decay Curves

AbstractAnodic overvoltage and potential decay curves on a graphite anode were measured in a laboratory aluminium electrolysis cell, by use of the steady state and current interruption technique. The anodic overvoltage vs the logarithm of the current density showed straight lines, with a Tafel coefficient of 0.51 V and a Tafel slope of 0.27 V. The potential decay curves were smooth with a rapid initial decrease, depending on the current density. The double layer capacitance was found to be in the range from 600 to 950 μF·cm−2. These experimental data were used to discuss the rate-determining step in the anode reaction mechanism.

Current Efficiency Measurements in Laboratory Aluminium Cells—XII. Low-Melting Bath

Current Efficiency Measurements in Laboratory Aluminium Cells—XII. Low-Melting Bath

Current Efficiency Measurements in Laboratory Aluminium Cells—XI. Anode Gas Composition and Anode Consumption

The anode gas composition and the anode consumption were measured in a small laboratory aluminium electrolysis cell. The anode gas was found to be 100% CO2(g), and the carbon consumption of a prebaked anode decreased slightly with increasing anodic current density towards a value of about 110% of the theoretical consumption. For a graphite anode a slight increase was observed, and the consumptions were higher, in the range 135–150%. From the increase in anode consumption with increasing temperature it was concluded that selective oxidation of prebaked anodes may be the main reason for the excess anode consumption. For graphite anodes, however, the gas evolution and electrolyte stirring may rather be the main cause for the high anode consumption values.

Current Efficiency Measurements in Laboratory Aluminium Cells—X. Anodic Overvoltage and Potential Decay Curves

Anodic overvoltage and potential decay curves on a graphite anode were measured in a laboratory aluminium electrolysis cell, by use of the steady state and current interruption technique. The anodic overvoltage vs the logarithm of the current density showed straight lines, with a Tafel coefficient of 0.51 V and a Tafel slope of 0.27 V. The potential decay curves were smooth with a rapid initial decrease, depending on the current density. The double layer capacitance was found to be in the range from 600 to 950 μF·cm−2. These experimental data were used to discuss the rate-determining step in the anode reaction mechanism.

Current Efficiency Measurements in Laboratory Aluminium Cells—IX. Cathodic Overvoltage on Aluminium-Copper Aloys

Current Efficiency Measurements in Laboratory Aluminium Cells—IX. Cathodic Overvoltage on Aluminium-Copper Aloys

Current Efficiency Measurements in Laboratory Aluminium Cells—VIII. Current, Temperature and Cathode Alloy Composition (Al–Cu), Al-Diffusivity

Current Efficiency Measurements in Laboratory Aluminium Cells—VIII. Current, Temperature and Cathode Alloy Composition (Al–Cu), Al-Diffusivity

Current Efficiency Measurements in Laboratory Aluminium Cells—VIII. Current, Temperature and Cathode Alloy Composition (Al–Cu), Al-Diffusivity

Abstract The current efficiency in a small laboratory aluminium electrolysis cell was measured as a function of cell current, cathode alloy composition (Al–Cu) and bath temperature. The current efficiency was found to increase with increasing current density, increasing copper content in the cathode alloy and decreasing temperature. The diffusivity of aluminium dissolved in the bath was calculated to be 9·10−5cm2 s−1 at 970°C. Practical implications of the results on the current efficiency in industrial cells are discussed.

Current Efficiency Measurements in Laboratory Aluminium Cells—IX. Cathodic Overvoltage on Aluminium-Copper Aloys

Abstract Cathodic overvoltage measurements on aluminium-copper alloys in cryolite melts were made by a steady-state interruption technique. For a cathodic current density of 1 A·cm−2 at 960°C the cathodic overvoltage was 160 mV. The results were used to calculate the electrical field strength and the thickness of the diffusion layer. The diffusivities of Na+ and F− ions in molten cryolite at 1000°C were found to be 9.1·10−5cm2s−1 and 4.9·10−5cm2s−1, which agree well with the data reported in the literature.