• International Journal of Precision Engineering and Manufacturing
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• v.8 no.4
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• pp.27-32
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• 2007

Gears, crucial components in modern precision machinery for power transmission mechanisms, are required to have low contacting noise with high torque transmission, which makes the use of gear-tooth profile modifications and gear-tooth surface crowning extremely efficient and valuable. Due to the shortcomings of current techniques, such as manual rectification, mechanical modification, and numerically controlled rectification, we propose a novel electrochemical gear-tooth profile modification method based on an artificial neural network control technique. The fundamentals of electrochemical tooth-profile modifications based on real-time control and a mathematical model of the process are discussed in detail. Due to the complex and uncertain relationships among the machining parameters of electrochemical tooth-profile modification processes, we used an artificial neural network to determine the required processing electric current as the tooth-profile modification requirements were supplied. The system was implemented and a practical example was used to demonstrate that this technology is feasible and has potential applications in the production of precision machinery.

• Journal of the Korean institute of surface engineering
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• v.43 no.6
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• pp.289-296
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• 2010

The effect of organic additives, thiourea (TU), on the copper electroplated layer of large rectangular size was investigated through physical and various electrochemical techniques. It was found that TU had strong adsorption characteristics on the Ni substrate and affected the initial electroplating process by inducing surface reaction instead of mass transfer in the bulk solution. TU additives had its critical micelle concentration at 200 ppm in copper sulphate solution and showed abrupt change in morphological and electrochemical impedance spectroscopic results around this concentration, which could be related with the destruction of adsorption structure of TU-Cu(I) complex formed at the Ni substrate surface. By conducting a commercial electroplating simulation, when TU additives was included at cmc in the plating solution, it acted as a depolarizer for copper electrodeposition and was effective to reduce the unevenness of copper deposits between centre and edge region at high current densities of 10 ASD.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.7
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• pp.736-745
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• 2009

Fuel cells convert a fuel together with oxygen in a highly efficient electrochemical reaction to electricity and water. Since the electrochemical reaction in the fuel cell stack dose not generate any noise, Fuel cell systems are expected to operated much quieter than combustion engines. However, the tonal noise and the broad band noise caused by a centrifugal compressor and an electric motor cause which is required to feed the ambient air to the cathode of the fuel cell stack with high pressure. In this study, the multi-camber perforated muffler is used to reduce noise. We propose optimized muffler model using an axiomatic design method that optimizes the parameters of perforated muffler while keeping the volume of muffler minimized.

• Journal of Ceramic Processing Research
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• v.19 no.6
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• pp.499-503
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• 2018

In this paper, cobalt embedded in nitrogen and sulfur co-doped carbon nanotubes (CoNSTs) were synthesized for oxygen reduction reaction (ORR) catalysts. The CoNSTs were prepared through a facile heat treatment method without any templates. Different amounts of the metal salt were employed to examine the physicochemical and electrochemical properties of the CoNSTs. The CoNSTs showed the bamboo-like tube morphology with the encased Co nanoparticles in the tubes. Through the x-ray photoelectron spectroscopy analysis, the catalysts exhibited different chemical states of the nitrogen and sulfur species. As a result, the CoNST performed high activity toward the ORR in an acidic condition with the onset potential of 0.863 V (vs. reversible hydrogen electrode). It was clearly demonstrated from the electrochemical characterizations that the quality of the nitrogen and sulfur species significantly influences the ORR activity rather than the total amount of the dopants.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.918-921
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• 2002

Some investigators who have tried to achieve the highly smooth surface finish using electrochemical processes have reported that high current density produced lustrous surfaces while the opposite conditions produced a passive layer and had a tendency to produce a black surface. However, processing at a low current density may produce a non-lustrous surface but the improvement of dimensional accuracy of the surface is significant. The surface with pulse process was a bit more lustrous than with continuous current but the black passive layer still could be found at grooved surface. There are two ways to achieve highly smooth surface finish. One is brushing it with a brush the other is electrochemical machining (ECM) with high current. The former method is the most common polishing practice, but not only may the surface obtained differ from operator to operator, but precision smooth surface on micro grooves are difficult to obtain. The latter one recently has been used to produce a highly smooth surface after EDM process. However, the material removal rate in ECM with high current is relatively high. Hence the original shape of the micro grooves, which was formed by electrochemical micro-machining (EMM) process, may be destroyed. In this study, an electrochemical polishing process using pulse current is adopted as a possible alternative process when micro grooves formed by EMM process should be polished. Mirror-like micro grooves with lustrous and smooth surface can be produced electrochemically with pulse current because the voltage and current used can be lower than the case of continuous current. This study will discuss the accurate control of physical and electrical conditions so as to achieve mirror-like micro grooves with lustrous and smooth surface without destroying the original shape of micro grooves.

• 한국전기화학회:학술대회논문집
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• 2005.07a
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• pp.163-168
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• 2005

• 한국전기화학회:학술대회논문집
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• 2002.04a
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• pp.43-43
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• 2002

• Journal of Electrochemical Science and Technology
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• v.13 no.3
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• pp.362-368
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• 2022

The application of polymer composite electrolyte in all-solid-state lithium-sulfur battery (ASSLSBs) can guarantee high energy density and improve the interface contact between electrolyte and electrode, which has a broader application prospect. However, the inherent insulation of the sulfur-cathode leads to a low electron/ion transfer rate. Carbon materials with high electronic conductivity and electrolyte materials with high ionic conductivity are usually selected to improve the electron/ion conduction of the composite cathode. In this work, PEO-LiTFSI-LLZO composite polymer electrolyte (CPE) with high ionic conductivity was prepared. The ionic conductivity was 1.16×10^-4 and 7.26×10^-4 S cm^-1 at 20 and 60℃, respectively. Meanwhile, the composite sulfur cathode was prepared with Sulfur, reduced graphene oxide and composite polymer electrolyte slurry (S-rGO-CPEs). In addition to improving the ion conductivity in the cathode, CPEs also replaces the role of binder. The influence of different contents of CPEs in the cathode material on the performance of the constructed battery was investigated. The results show that the electrochemical performance of the all-solid-state lithium-sulfur battery is the best when the content of the composite electrolyte in the cathode is 40%. Under the condition of 0.2C and 45℃, the charging and discharging capacity of the first cycle is 923 mAh g^-1, and the retention capacity is 653 mAh g^-1 after 50 cycles.

• Journal of Electrochemical Science and Technology
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• v.15 no.1
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• pp.178-189
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• 2024

This work aims to investigate the efficiency of electrocoagulation (EC) of pistachio processing industrial wastewater (PPIW) using the continuous EC process. The tubular reactor made of stainless steel with an internal diameter of 60 mm was used as a cathode electrode. The effect of some parameters was examined on the removal of chemical oxygen demand (COD) and total phenols (TP) removal efficiency. The influences of the initial pH of wastewater (from 4 to 8), flow rate (from 25 to 125 mL/min), current density (from 7 to 21 mA/cm²), and supporting electrolyte type (NaCl, NaNO₃, and Na₂SO₄), supporting electrolyte concentration (from 10 to 100 mg/L NaCl) on removal efficiency were investigated to determine the best experimental conditions. The examination of the physico-chemical parameters during the EC treatment showed that the best removal efficiency was obtained under conditions where the flow rate was 25 mL/min (20 min reaction time), the pH value was 5.2, and the current density was 21 mA/cm² has set. Under these experimental conditions, COD and TP removal efficiency were found to be 75% and 97%, respectively, while energy consumption was 18.5 kW h/m³. The study results show that the EC can be applied to PPIW pre-treatment.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.4
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• pp.615-618
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• 2016

Electrochemical noise(EN) has been used to analyze the deterioration of coating films of offshore wind substructures. In this study, prototype sensors using EN have been developed to detect the corrosion rate. To verify the reliability of sensors, experiments were conducted both in the laboratory and offshore using probe and standard samples. New analysis and data processing techniques show that the sensor can provide useful information about the corrosion rate.