Changes In Current Efficiency Research Articles

Effect of Tween 80 on electrochemical deposition of cobalt from sulphate solutions

Cobalt is an essential engineering metal among the less abundant metals found in the earth crust with wide range of applications. However due to the scarcity of resources, it is required to produce the metal in a cost effective manner to meet the supply demands. Cobalt is produced by electrodeposition from chloride or sulphate media, the latter being a widely used method. The use of additives in the electrolytic bath during electrodeposition from sulphate solutions can not only solve issues related to current efficiencies, but also result in production of uniform, smooth and bright deposits of the metal. The present work investigates the effect of Tween 80 a non-ionic additive, on the electrodeposition of cobalt. The concentration of the additive Tween 80 was varied over a range of 1–50 mg/L to evaluate the changes in current efficiency, specific energy consumption and quality of electrodeposited cobalt metal. The results indicated that, apart from increasing the current efficiency, the additive produced bright cobalt deposits. A maximum current efficiency of 98.1% was achieved with 20 mg/L Tween 80 in the electrolytic bath. X-ray diffraction studies have revealed that direction is the most preferred orientation of crystal growth during cobalt electrodeposition. However it is shifted to at higher concentrations (50 mg/L) of the additive. Scanning electron micrographs indicate that smooth, compact and uniform deposits of cobalt are obtained at 20 mg/L beyond which there is deterioration in the quality of deposits. Cyclic voltammetric studies indicated polarization of the cathode in the presence of Tween 80. This behaviour was also reflected in the decrease of the rate of electron transfer as evident from exchange current density (i0) values.

Study of shifting of recombination zone in multi-emissive layer organic light emitting devices and its effect on color stability

Color stability in multi-emissive layer organic light emitting devices (Me-OLEDs) has been investigated. Me-OLEDs were based on multiple emitters with a common host CBP doped with three dopants, BCzVBi, Ir(ppy)3 and Ir(btp)2acac for blue, green and red emission. A major variation in CIE coordinates were found from (0.312, 0.294) to (0.236, 0.267) with increase in voltage from 6 to 9V. This coordinate shift in Me-OLEDs has been attributed to the shifting of recombination zone with increase in voltage. In order to support our experimental observation, the EL spectrum of Me-OLEDs has been expressed as a linear combination of EL intensities of OLEDs with its individual constituting layers as emitters. In this way, the contribution of each layer in the EL spectrum of Me-OLEDs has been evaluated at each voltage. It has been observed from these calculations that the contribution of red emitter decreases from 47% to 33.33% and blue emitter increases from 38% to 51.67% with the increase in voltage from 6 to 9V. This supports our hypothesis of shifting of recombination zone with the change in voltage. This shifting has been attributed to the field dependency of electron mobility in CBP. Me-OLED with CBP layers between the emitters was fabricated to improve the color stability. Significant improvement in color stability was achieved without changes in current efficiency in Me-OLED with interlayers.

OLED소자의 수명에 미치는 다층 보호막의 영향

Multilayer passivation film on OLED with organic/inorganic hybrid structure as to diminish the thermal stress and expansion was researched to protect device from the direct damage of and and improve life time characteristics. Red OLED doped with 1 vol.% Rubrene in was used as a basic device. The films consist of ITO(150 nm)/ELM200_HIL(50 nm)/ELM002_HTL(30 nm)/: 1 vol.% Rubrene(30 nm)/(30 nm) and LiF(0.7 nm)/Al(100 nm) which were formed in that order. Using LiF/ as a buffer layer was determined because it significantly improved life time characteristics without suffering damage in the process of forming passivation film. Multilayer passivation film on buffer layer didn`t produce much change in current efficiency, while the half life time at 1,000 of OLED/LiF//E1/ was 710 hours which showed about 1.5 times longer than OLED/LiF//E1 with 498 hours. futhermore, OLED/LiF//E1//E1/ with 1301 hours showed about twice than OLED/LiF//E1/ which demonstrated that superior characteristics of life time was obtained in multilayer passivation film. Through the above result, it was suggested using LiF/ as a buffer layer could reduce the damage from the difference of thermal expansion coefficient in OLED with protective films, and epoxy layer in multilayer passivation film could function like a buffer between inorganic layers with relatively large thermal stress.

Electrodeposition conditions of metallic nickel in electrolytic membrane reactor

The process parameters were optimized for the electrodeposition of nickel in an electrolytic membrane reactor. Nickel(II) and boric acid concentrations, pH and temperature were varied to evaluate the changes in current efficiency and specific energy consumption of nickel electrodeposition. The catholyte was aqueous nickel(II) sulfate and boric acid, and the anolyte was sulfuric acid solution. An anionic membrane separated the anolyte from the catholyte while maintained a conductive path between the two compartments. The results indicated that the cathode current efficiency increased with the increase of nickel concentration, pH and boric acid concentration, and decreased with the increase of current density and stirring rate. A maximum current efficiency of 97.15% was obtained under the optimized conditions of electrolyte composition of 40 g/L Ni and 40 g/L boric acid at temperature of 42 °C and pH of 6 with a cathode current density of 300 A/m2.

Electrodeposition of nanocrystalline nickel by using rotating cylindrical electrodes

In this research, nanocrystalline nickel (14–25 nm) was electrodeposited on rotating cylindrical electrodes in a modified Watts bath. Saccharin was used as a grain refiner. The effect of cathode rotation speed and saccharin concentration on the grain size was studied by transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis. The preferred orientation of deposits progressively changed from a (2 2 0), (2 0 0), and (1 1 1) fiber texture for a saccharin free bath to a (1 1 1) and (2 0 0) double fiber texture for a bath containing 5 g l −1 saccharin. Cathode rotation enhanced the intensity of (1 1 1) peak relative to (1 0 0). The effect of cathode rotation speed, current density, and saccharin concentration on the coating microhardness was investigated. The maximum recorded hardness was 620 HV for 14 nm grain size. The effect of current density and saccharin concentration on morphology was observed by scanning electron microscopy (SEM). The current efficiency changes were studied as a result of saccharin concentration.

Effects of cobalt, temperature and certain impurities upon cobalt electrowinning from sulfate solutions

The effects of cobalt concentration, temperature and the presence of zinc, copper and iron ions in the electrolyte on current efficiency and cathodic quality were investigated by cyclic voltammetry and galvanostatic methods during cobalt electrowinning. The results showed that high cathodic efficiency of cobalt deposition was obtained from solutions containing cobalt concentration in the range 30–60 g l−1. Current efficiency increased from 94% to 97% with increase in cobalt concentration to 60 g l−1 at 20 °C. It was also found that increase in temperature to 50 °C enhanced the cobalt deposition reaction, along with the rate of hydrogen evolution, resulting in little change in current efficiency. The presence of foreign cations in the electrolyte not only adversely affects current efficiency but also promotes cracking and peeling.

Effect of Mg2+, Li+, Na+ and K+ on the electrocrystallization of nickel from aqueous sulfate solutions containing boric acid

The effects of metal ions such as Mg2+, Li+, Na+ and K+ on the cathodic current efficiency, deposit morphology, crystallographic orientation and polarization behaviour during nickel deposition on stainless steel from aqueous sulfate solutions containing boric acid were investigated. There was virtually no change in current efficiency in presence of these metal ions, but changes were observed in the deposit morphologies and crystal orientations even though all the deposits looked bright, smooth and coherent. Changes were also observed in the polarization behaviour during nickel electrocrystallization in presence and absence of boric acid. An attempt has been made to correlate the effect of these metal ions on various parameters studied.

パラジウムめっきリードフレームの曲げ特性に及ぼす下地ニッケルめっきの析出条件の影響

In the palladium plating leadframe, nickel and palladium are plated over the whole surface including outerleads in the leadframe manufacturing process. Users have pointed out plating film cracks after bending of outerleads. The most thickness of the plating film is nickel.We changed nickel plating conditions and studied the influence on plating film cracks, with the following results: (1) Nickel plating film from a sulfamate bath produces fewer cracks than that from a Watt's bath and is suitable for the underlayer of palladium plating film. (2) Internal stress in nickel plating film rises abruptly when the sulfamate bath pH exceeds 5.0. Even then, cracks did not grow larger, indicating no correlation between internal stress and crack extent. (3) Plating conditions should be monitored to maintain plating thickness because current efficiency changes with plating conditions. Their influence on cracks is small.

The effects of Dowfroth, antimony and Saponin on zinc electrowinning from Kidd Creek electrolyte

The effects of Dowfroth alone and in combination with antimony and Saponin on zinc deposition current efficiency and polarization and on the morphology and orientation of 6h and 24h zinc deposits electrowon at 500 Am−2 and 38°C from Kidd Creek zinc electrolyte were determined. Dowfroth, at concentrations as low as 7 mg dm−3, was strongly polarizing, changed the preferred deposit orientation from basal to intermediate and decreased the current efficiency and zinc deposit quality. Dowfroth had a positive interaction with antimony such that certain combinations of these reagents maximized current efficiency and improved the deposit quality. Saponin combined with various concentrations of Dowfroth resulted in a <1% change in current efficiency and did not modify the preferred deposit orientation. At optimum Dowfroth + antimony combinations, the addition of Saponin again did not affect significantly the current efficiency. The preferred deposit orientation was either [1 0 1][1 1 2] or [1 0 1] depending on the combination of these reagents employed. Tests run for 24h for selected combinations of Dowfroth, antimony and Saponin confirmed the results obtained for the 6h studies.