Low Current Efficiency Research Articles

Photo-modulated thin film transistor based on dynamic charge transfer within quantum-dots-InGaZnO interface

The temporal development of next-generation photo-induced transistor across semiconductor quantum dots and Zn-related oxide thin film is reported in this paper. Through the dynamic charge transfer in the interface between these two key components, the responsibility of photocurrent can be amplified for scales of times (∼104 A/W 450 nm) by the electron injection from excited quantum dots to InGaZnO thin film. And this photo-transistor has a broader waveband (from ultraviolet to visible light) optical sensitivity compared with other Zn-related oxide photoelectric device. Moreover, persistent photoconductivity effect can be diminished in visible waveband which lead to a significant improvement in the device's relaxation time from visible illuminated to dark state due to the ultrafast quenching of quantum dots. With other inherent properties such as integrated circuit compatible, low off-state current and high external quantum efficiency resolution, it has a great potential in the photoelectric device application, such as photodetector, phototransistor, and sensor array.

On the Design of Power-Rail ESD Clamp Circuits With Gate Leakage Consideration in Nanoscale CMOS Technology

CMOS technology has been widely used to produce many integrated circuits. However, the thinner gate oxide in nanoscale CMOS technology seriously increases the difficulty of electrostatic discharge (ESD) protection design. The power-rail ESD clamp circuit has been the key circuit to perform the whole-chip ESD protection scheme. Some ESD detection circuits were developed to trigger on ESD devices across the power rails to quickly discharge ESD current away from the internal circuits. Therefore, on-chip ESD protection circuits must be designed with the consideration of standby leakage to minimize the power consumption and the possibility of malfunction to normal circuit operation. The design of power-rail ESD clamp circuits with low standby leakage current and high efficiency of layout area in nanoscale CMOS technology is reviewed in this paper. The comparisons among those power-rail ESD clamp circuits are also discussed.

A Power Conditioning Stage Based on Analog-Circuit MPPT Control and a Superbuck Converter for Thermoelectric Generators in Spacecraft Power Systems

A thermoelectric generator (TEG) is a very important kind of power supply for spacecraft, especially for deep-space missions, due to its long lifetime and high reliability. To develop a practical TEG power supply for spacecraft, a power conditioning stage is indispensable, being employed to convert the varying output voltage of the TEG modules to a definite voltage for feeding batteries or loads. To enhance the system reliability, a power conditioning stage based on analog-circuit maximum-power-point tracking (MPPT) control and a superbuck converter is proposed in this paper. The input of this power conditioning stage is connected to the output of the TEG modules, and the output of this stage is connected to the battery and loads. The superbuck converter is employed as the main circuit, featuring low input current ripples and high conversion efficiency. Since for spacecraft power systems reliable operation is the key target for control circuits, a reset–set flip-flop-based analog circuit is used as the basic control circuit to implement MPPT, being much simpler than digital control circuits and offering higher reliability. Experiments have verified the feasibility and effectiveness of the proposed power conditioning stage. The results show the advantages of the proposed stage, such as maximum utilization of TEG power, small input ripples, and good stability.

High-performance green phosphorescent top-emitting organic light-emitting diodes based on FDTD optical simulation

We have successfully applied finite-difference time-domain (FDTD) method in top-emitting organic light-emitting diodes (TOLEDs) for structure optimization, demonstrating good agreement with experimental data. A mixed host with both hole transport and electron transport materials is employed for the green phosphorescent emitter to avoid charge accumulation and broaden the recombination zone. The resulting TOLEDs exhibit ultra-high efficiencies, low current efficiency roll-off, and a highly saturated color, as well as hardly detectable spectrum shift with viewing angles. In particular, a current efficiency of 127.0cd/A at a luminance of 1000cd/m2 is obtained, and maintains to 116.3cd/A at 10,000cd/m2.

Regenerating spent acid produced by HZSM-5 zeolite preparation by bipolar membrane electrodialysis

A large amount of acid wastewaters containing sodium chloride (NaCl) is usually generated during the production of HZSM-5 zeolite (H-form Zeolite Socony Mobile Five). It can cause contamination of the environment if discharged directly. In this study, a method was reported to regenerate hydrochloric acid (HCl) and sodium hydroxide (NaOH) from the acid wastewater by bipolar membrane electrodialysis (BMED). The effects of operation parameters, such as initial base concentration and current density, on the spent acid solution regeneration were investigated. The results indicated that the initial concentration of sodium hydroxide had little or no effect on the acid wastewater regeneration. But it was also demonstrated that current density have a great influence on the acid wastewater regeneration, and a higher current density applied to the BMED stack usually resulted in lower current efficiency and higher energy consumption. After the operation of BMED process, the comparison between the recycled acid solution and the pure acid solution illustrates the recycled acid solution by BMED process can replace the pure acid solution completely. Therefore, this experiment can not only achieve the elimination of environmental pollution, but also the recycling of resources.

Current efficiency of Ga electrodeposition under different anions concentrations

The gallium electrodeposition from alkaline solution has a very low current efficiency, the reason for which is still not quite understood. The effects of electrode materials used for gallium electrodeposition, as well as the effects of NaOH concentration and the anions concentrations in the solution, including SO42-, SiO32-, CO32-, AlO2-, F-, and Cl-, on the deposition were analyzed in this study. The suitable materials of SUS316-SUS316 were suggested for the gallium electrodeposition. Based on the electrode couples, the NaOH concentration of 4 mol.L-1 for gallium electrodeposition exhibits the greatest current efficiency. Moreover, the current efficiency would decrease in the electrolyte along with the increasing concentration of the anions, except that, 0.2 mol.L-1 Cl- in the solution slightly improves the current efficiency of gallium electrodeposition. Moreover, the gallium deposited on the cathode from the solution with 0.6 mol.L-1 SiO32- appears tiny black in color and coarse. Meanwhile, SUS304 is shown to be not suitable to be used as cathode for the gallium electrodeposition from the alkaline solution.

The Evolution of Søderberg Aluminum Cell Technology in North and South America

In the 1940s, the horizontal stud Soderberg cells were considered to be superior to the small 30-kA Hall prebake cells, which at that time operated at a lower current efficiency and higher energy consumption. The amperage was first increased on the Soderberg cells from 30 kA to 50–60 kA and then later to 90–120 kA by basically increasing the anode length and the number of anode studs. Due to the increase in demand for aluminum metal, the less expensive Soderberg smelters proliferated in the 1940s to the 1970s in North and South America. In the 1970s, 24 Soderberg smelters located in North and South America had a primary aluminum capacity over 3 million tpy. The largest operating Soderberg smelter, Companhia Brasileira de Aluminio, has a plant capacity over 470000 tpy and started the last new Soderberg potline in 2007. However, poor magnetics inherent with end-to-end Soderberg cell busbar design limited any further increase in amperage while the side-to-side prebake cells were able to operate more efficiently at 200 kA and higher. Compared with prebake technology, Soderberg cells are now less efficient and have higher production costs, they are more difficult to automate and they have the greatest environmental and health challenges. Health studies from the middle of the 1970s showing a clear link between Soderberg tar fume exposure and the incidence of various types of cancer lead companies to propose a program of replacement. As a result, today there are only five Soderberg smelters operating in North and South America with a capacity of <1 million tpy.

710 3価クロムめっき浴における電極反応の調査(OS7-(3),OS7 オーガナイズドセッション《精密/微細加工と評価》)

Our laboratory has been developing a chromium plating bath using trivalent chromium as one of the alternative process. It is, however, difficult to comprehend complex behavior of reaction occurring at the electrodes of the plating bath. So, the purpose of this study is to elucidate the reactions and the change of bath composition during the electro deposition. The authors surveyed the composition of gases generated from the various types of bathes by the electrode reaction with gas chromatography, and evaluated the ratio of electric current used for the gas generation. It became obvious that the ratio greatly depends on the bath composition, especially the ratio becomes very low in the trivalent chromium bath. We have concluded that the lower current efficiency is owing to the reaction that Cl_2 generated at the anode dissolves in the bath again as hypochlorous acid.

Experimental Research of Spouted Particulate Electrodes on Removal of Copper Wastewater

In this research, heavy metal copper was chosen for this study, with its sulfate solution simulated wastewater, using spouted particulate electrodes to purify wastewater and recycle metal copper. Experimental studied the effects on different conditions of electrodeposition, such as pH, constant current, copper ion concentration, the size of the cathode particle and nitrogen sparging. The results showed the optimum conditions were that pH was 3.0, constant current was 10.0A, the size of cathode particle was 1.8mm and with nitrogen sparging. In particular, nitrogen sparging not only reduced dissolved oxygen in wastewater to prevent the metal back to solution, but also handled the problem of low current efficiency due to concentration polarization and electrochemical polarization.

Structure, microhardness and corrosion behaviour of nanostructured CoP coatings obtained by direct current and pulse plating

Abstract A previously designed electrolyte to obtain nanocrystalline CoP (nCoP) alloys has been modified to overcome some process drawbacks, mainly bath instability and low current efficiencies. Moreover, the influence of some plating conditions, such as the anode material/configuration or the hydrodynamic regime, has been analysed to try to optimize the coatings characteristics and, at the same time, reducing production costs. Using the modified electrolyte, air agitation and a cobalt anode, nCoP alloys with low phosphorous content (1–2 wt%) and good properties can be obtained both using galvanostatic pulse plating (PP) and direct current (DC) electrodeposition. With these conditions the bath stability, the current efficiency and also the current distribution are significantly increased. Although PP and DC coatings have similar characteristic, PP alloys show smaller grain sizes and this results in an increased microhardness after annealing. This annealing has a side effect on the coatings, which is the cracking of the layer and its obvious impact on its protective performance. Despite this, these nCoP alloys are promising as alternative to traditional electroplated hard chromium coatings.

Characterization of Nickel-Antimony Doped Tin Oxide Electrodes Prepared via Sol-Gel Dip-Coating Method

Nickel and antimony doped tin oxide (NATO) electrodes were prepared by sol-gel dip-coating method. The effect of doping levels was investigated via scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The electrochemical ozone generation efficiency was also tested. The results showed that sol-gel prepared electrodes had a smoother surface morphology and lower current efficiency for ozone generation than electrodes prepared by traditional pyrolysis method. The nickel and antimony doping lead to a decrease in the crystallites size, while its effects on ozone generation efficiency were complex.

Electroplating Using Ionic Liquids

Electroplating is a key technology in many large-scale industrial applications such as corrosion-resistant and decorative coatings. Issues with current aqueous processes, such as toxicity of reagents and low current efficiencies, can often be overcome by using ionic liquids, and this approach has turned ionometallurgy into a fast-growing area of research. This review outlines the interactions in ionic liquids that are responsible for the advantageous properties of these solvents in electroplating. It summarizes recent research in which these properties have been analyzed or exploited and highlights fundamental issues in research and technology that need to be addressed.

Tungsten Oxide Buffer Layers Fabricated in an Inert Sol‐Gel Process at Room‐Temperature for Blue Organic Light‐Emitting Diodes

WO3 deposition from tungsten ethoxide precursor solutions at room temperature is demonstrated. The W(OEt)6 precursor can be converted under inert conditions and hence avoids sample contamination with oxygen, opening a pathway to more stable devices. The stoichiometry of all WO3 layers and the optoelectronic performance of the respective SMOLEDs well match thermally evaporated WO3 and its corresponding SMOLEDs. The solution processed WO3 hole injection layers enable the fabrication of blue phosphorescent OLEDs with low onset voltage and current efficiencies of up to 14 cd A(-1) .

Novel Three-Phase Three-Level-Stacked Neutral Point Clamped Grid-Tied Solar Inverter With a Split Phase Controller

Characterized by the low leakage current and high efficiency, a three-level neutral point clamped (3L-NPC) inverter becomes more popular for a transformerless photovoltaic grid connected system. The three-level-stacked neutral point clamped (3L-SNPC) structure is a derivative of 3L-NPC providing more advantages such as a double apparent switching frequency and parallel load current paths. In this paper, the power loss distribution and features of 3L-SNPC are analyzed first when applied to solar inverters. Based on the analysis, a novel 3L-SNPC leg structure is proposed for solar applications in order to reduce the power loss particularly for the low power range, given the fact that solar inverters generally operate in the low power range during most of the daytime. Then, a two-stage solar inverter topology, applying the proposed structure to the phase leg, is described. Further, a split phase controller is applied for the two-stage solar inverter, consisting of the maximum power point tracking control, optimized dc-link voltage control, and grid current control. Finally, a new dead-time elimination pulsewidth modulation strategy is proposed and conveniently implemented to each phase based on the split phase controller. Experimental results are illustrated to demonstrate the applicability of the proposed topology and controller.

Clean post-processing of 2-amino-1-propanol sulphate by bipolar membrane electrodialysis for industrial processing of 2-amino-1-propanol

2-Amino-1-propanol (AMP) is a key intermediate compound in the production of antibiotics, with increasing demand in industry. In this study, we propose a newly designed bipolar membrane electrodialysis (BMED) system with a novel three-compartment configuration for the processing of AMP from the AMP sulphate solution. The operational parameters were investigated for optimizing the performance of this novel BMED stack, compared to the traditional two-compartment BMED stack in the pilot scale experiment. The experimental results indicate that this novel type of BMED stack offers a better performance for AMP processing than the conventional two-compartment BMED stack. The optimum performance was observed at the current density ranging from 40 to 60mAcm−2 and a spacer thickness of 0.70mm. The corresponding current efficiency and energy consumption reached up to 53.4% and 3.135kWhkg−1, respectively. The two-compartment BMED stack was found to have a low current efficiency (39.8%) and a high energy consumption (3.864kWhkg−1). Pilot-scale experiments for an industrial application of this novel BMED stack have been applied, demonstrating that the BMED process is feasible and economically alternative for AMP purification in the industry.

Highly Efficient, Ultra‐Low Energy Consumption Process for Phenol Wastewater Treatment with Ultra‐Low Carbon Emission

AbstractPhenol is one of the main pollutants in phenol wastewater and has been proved non‐biodegradable. In this study, based on strongly ring‐opening capability of boron doped diamond film electrode, a highly efficient and energy‐saving method with ultra‐low carbon emission is established through a combination of electrochemical oxidation and biological degradation. On one hand, electrochemical oxidation as pretreatment can solve the critical problem that phenol wastewater is a biological recalcitrant. On the other hand, the relatively low current efficiency during the late stage of electrochemical oxidation can be solved by follow‐up biological treatment, thus reduce the energy consumption and the cost significantly. More importantly, the carboxylic acids (oxidized from phenol) can be fully used as carbon source (no additional carbon source is added) for microbial growth instead of being oxidized to carbon dioxide and water through selecting optimizing sequencing batch reactor access time, so the carbon emission is greatly reduced. The results showed that it can save about 76.5% energy consumption and about 51.2% chemical oxygen demand can be used to maintain microorganism self‐reproduction. This is significant that this combined technology not only runs highly effectively at low cost, but also reduces the emission of greenhouse gas, carbon dioxide, thus environment friendly with wide application prospects.

High Temperature Electrolysis for Liquid Iron Production

Iron metal is traditionally produced by carbothermic reduction in a blast furnace; an effective, but capital and energy intensive method that produces large amounts of CO2, SO2 and a variety of other contaminating byproducts. An alternative route to produce iron might be electrolysis in aqueous, molten salts or oxide based electrolytes. This paper focuses on the behaviour of iron ions and electrowinning of iron at temperatures from 1400 - 1550 °C. Experiments were performed in molten oxide mixtures of SiO2, MgO, Al2O3 and CaO.Fe2O3 was the source of iron. Iron could be deposited on molybdenum cathodes from molten oxide electrolytes containing dissolved Fe2O3, although at very low current efficiency.

Decolourization and degradation of C.I. Acid Red 73 by anodic oxidation and the synergy technology of anodic oxidation coupling nanofiltration

This work is conducted to study ability of anodic oxidation treatment azo dye C.I. Acid Red 73 (AR73) using the electrodes of Y doped Ti/SnO2–Sb electrodes prepared by thermal decomposition and Ti/SnO2–Sb electrodes prepared by electrodeposition. It has been shown that doping Y can enhances the electrochemical activity of the electrodes, but the accelerated service life was slightly reduced. Both the lifetime and electrochemical activity of Ti/SnO2–Sb electrodes prepared by electrodeposition in a new Sn–Sb electrodeposition bath outperform the Ti/SnO2–Sb electrodes prepared by thermal decomposition. Moreover, the effect of varying wastewater process indexes (initial pH (4–10), the addition of NaCl (0–9mM) and initial dye concentration (0.5–2.0gL−1)) on the performance of anodic oxidation using Ti/SnO2–Sb electrodes prepared by electrodeposition was investigated followed by the performance indicators analyses including color, chemical oxygen demand (COD), current efficiency and specific energy consumption. Finally, the synergy technology of anodic oxidation coupling nanofiltration was adopted to treat AR73 wastewater in order to overcome the low current efficiency of anodic oxidation. Preliminary results have shown that the synergy technology could cost-effectively treat AR73 wastewater.

Through-Silicon-Via (TSV) Filling by Electrodeposition of Cu with Pulse Current at Ultra-Short Duty Cycle

Through-Si-via (TSV) filling with electrodeposited Cu was performed with a pulse current consisting of very a short duty cycle to achieve 3D interconnection in high density integrated circuit (IC) devices. Low frequency was unacceptable in this condition, because a highly acidic electrolyte attacked the seed layer and Cu deposit obtained with low current efficiency during comparably longer off time period. An increased frequency critically enhanced the filling rate of Cu, which was mainly related to the improvement of the current efficiency and lower dissolution rate. In pulse conditions, high density nanoscale twin structure and strain fields were observed, which were caused by induced stress during the on-time because of high peak current density. Application of pulse deposition reduced thermal extrusion of Cu that was related to the imperfect microstructure of the deposited Cu.

Influence of silver content and MnSO4 addition on performance of different lead–silver alloys during polarisation and decay periods

The electrochemical activity and the corrosion properties of five commercial lead anodes were examined by the conventional polarisation methods and the electrochemical impedance spectroscopy method. The results show that the anode Pb–0·62Ag alloy had a lower overpotential for anode reaction than the others. The corrosion resistance after polarisation of the anode Pb–0·62Ag alloy was higher than that of the Pb–0·29Ag–0·1Ca alloy, Pb–0·58Ag alloy and Pb–0·67Ag alloy, but lower than that of the anode Pb–0·72Ag alloy. However, the anode Pb–0·72Ag alloy had the highest overpotential. When anodes Pb–0·72Ag alloy and Pb–0·62Ag alloy were used, the cathode current efficiencies were higher, while anodes Pb–0·29Ag–0·1Ca alloy, Pb–0·58Ag alloy and Pb–0·67Ag alloy gave lower current efficiency. Regarding these several factors, the anode Pb–0·62Ag alloy is the best choice.On a examiné l’activité électrochimique et les propriétés de corrosion de cinq anodes commerciales en plomb, au moyen des méthodes conventionnelles de polarisation et de la méthode de spectroscopie d’impédance électrochimique. Les résultats montrent que l’anode de Pb–0·62Ag avait une surtension plus basse que celle des autres pour la réaction de l’anode. La résistance à la corrosion après la polarisation de l’anode de Pb–0·62Ag était plus élevée que pour l’anode de Pb–0·29Ag–0·1Ca, l’anode de Pb–0·58Ag ou l’anode de Pb–0·67Ag, mais plus basse que celle de l’anode de Pb–0·72Ag. Cependant, l’anode de Pb–0·72Ag avait la surtension la plus élevée. Lorsqu’on utilisait les anodes de Pb–0·72Ag ou de Pb–0·62Ag, le rendement du courant de la cathode était plus élevé, alors que les anodes de Pb–0·29Ag–0·1Ca, de Pb–0·58Ag et de Pb–0·67Ag donnaient un rendement de courant plus bas. Par rapport aux divers facteurs, l’anode de Pb–0·62Ag constitue le meilleur choix.