• Journal of radiological science and technology
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• v.10 no.1
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• pp.75-83
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• 1987

The insulating oil used for X-ray tube housing were degraded by X-ray irrdiation, high temperature and high anode voltage for normal operation. This study was measured the conduction current-X-ray dose, heating degradation, time, temperature and electric field characteristics and the dependense of electrode materials and gap length in the X-ray irradiatied insulating oil under of D.C voltage. The obtained results can be summarized as following. 1. The conduction current of X-ray irradiated insulating oil is more about $2.5{\sim}3$ times as large as than that of non x-ray irradiated, and is become saturation phenomena after some degree. 2. The conduction current of many times heating x-ray irradiated insulating oil is more than that of a few times heating. 3. The higher temperature x-ray irradiated insulating oil is increased, the more conduction current, and that is increased about ten times as large as when it's temperatures is increased to $80^{\circ}C\;at\;30^{\circ}C$, twenty five times at $100^{\circ}C$. 4. The dependence of electrode materials is appeared at the low electric field, and the small gap length with Fe > Cu > Al. 5. The low electric field than 3000 v/cm is appeared Ohm's law region, and the high is become saturation region at the I-E characteristics. 6. The larger gap length is become, the more conduction current is increased at the same electric field.

• Applied Chemistry for Engineering
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• v.30 no.6
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• pp.659-666
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• 2019

Proton exchange membrane fuel cells (PEMFCs) generate electricity by electrochemical reactions of hydrogen and oxygen. PEMFCs are expected to alternate electric power generator using fossil fuels with various advantages of high power density, low operating temperature, and environmental-friendly products. PEMFCs have widely been used in a number of applications such as fuel cell vehicles (FCVs) and stationary fuel cell systems. However, there are remaining technical issues, particularly the long-term durability of each part of fuel cells. Degradation of a carbon supported-platinum catalyst in the anode and cathode follows various mechanistic origins in different fuel cell operating conditions, and thus accelerated stress test (AST) is suggested to evaluate the durability of electrocatalyst. In this article, comparable protocols of the AST durability test are intensively explained.

• Journal of Microbiology and Biotechnology
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• v.28 no.8
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• pp.1360-1366
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• 2018

The fungi associated with termites secrete enzymes such as laccase (multi-copper oxidase) that can degrade extracellular wood matrix. Laccase uses molecular oxygen as an electron acceptor to catalyze the degradation of organic compounds. Owing to its ability to transfer electrons from the cathodic electrode to molecular oxygen, laccase has the potential to be a biocatalyst on the surface of the cathodic electrode of a microbial fuel cell (MFC). In this study, a two-chamber MFC using the laccase-producing fungus Galactomyces reessii was investigated. The fungus cultured on coconut coir was placed in the cathode chamber, while an anaerobic microbial community was maintained in the anode chamber fed by industrial rubber wastewater and supplemented by sulfate and a pH buffer. The laccase-based biocathode MFC (lbMFC) produced the maximum open circuit voltage of 250 mV, output voltage of 145 mV (with a $1,000{\Omega}$ resistor), power density of $59mW/m^2$, and current density of $278mA/m^2$, and a 70% increase in half-cell potential. This study demonstrated the capability of laccase-producing yeast Galactomyces reessii as a biocatalyst on the cathode of the two-chamber lbMFC.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.6
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• pp.670-676
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• 2016

Hydrogen town in Republic of Korea was established in 2013. Hydrogen as a byproduct produced by various processes of factories is used in hydrogen town facilities. As cell performance is affected by contaminations in fuel gas, various standards about impurities of fuel have been determined by many countries. This study shows performance degradation of single cell with impurities concentrations. Traces of carbon monoxide (CO) and hydrogen sulfide ($H_2S$)can cause considerable cell performance losses. For comparing the performances by poisoning of CO, acceleration test, I-V curve, constant current are performed. Both the CO and $H_2S$ poisoning rate are a function of their concentration. With the higher concentrations the higher poisoning rates are observed. And, it was confirmed that, oxidation behavior and side reaction generation are not affected. Under the lower $H_2S$ concentration condition, the poisoning rate is much higher than that of CO because of its different adsorption intensity. It can be possible that the result of this study can be used for enacting regulation as a baseline data.

• Korean Chemical Engineering Research
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• v.53 no.4
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• pp.412-416
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• 2015

To evaluate the performance and durability of membrane, measurement of hydrogen crossover is needed during PEMFC(Proton Exchange Membrane Fuel Cells) operation. In this work, concentration of hydrogen at cathode was analysed by gas chromatograph during operation suppling with air instead of inert gas into the cathode. The hydrogen permeated through membrane reacted with oxygen at cathode and then the concentration of hydrogen was lower than in case inert gas was supplied. Hydrogen concentration decreased as the flow rate of air increased at cathode. Increase of temperature, humidity and pressure of anode gas enhanced the hydrogen concentration at cathode. The hydrogen concentration was about 5.0 ppm at current density of $120mA/cm^2$ during general PEMFC operation.

• Korean Journal of Materials Research
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• v.10 no.4
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• pp.301-304
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• 2000

A new triode type Co-silicided Si FEA(field emitter array) was realized by Co-silicidation of Co coated Si FEA and its field emission properties were investigated. The field emission properties of the fabricated device through the unit pixel with $45{\times}45$ tip array in the area of $250{\mu\textrm{m}}{\times}250{\mu\textrm{m}}$ under high vacuum condition of $10^{-8}Torr$ were as follows : the turn-on voltage was about 35V and the anode current was about $1.2\mu\textrm{A}(0.6㎁/tip)$ at the bias of $V_A=500V\;and\; V_G=55V$. The fabricated device showed the stable electrical characteristics without degradation of field emission current for the long term operation except for the initial transient state. The low turn-on voltage and the high current stability of the Co-silicided Si FEA were due to the thermal and chemical stability and the low work function of silicide layer formed at the surface of Si tip.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.4
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• pp.461-466
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• 2020

There are many application fields of electrical energy storage such as load shifting, integration with renewables, frequency or voltage supports, and so on. Especially, the frequency regulation is needed to stabilize the electric power system, and there have to be more than 1 GW as power reserve in Korea. Ni-rich layered oxide cathode materials have been investigated as a cathode material for Li-ion batteries because of their higher discharge capacity and lower cost than lithium cobalt oxide. Nonetheless, most of them have been investigated using small coin cells, and therefore, there is a limit to understand the deterioration mode of Ni-rich layered oxides in commercial high energy Li-ion batteries. In this paper, the pouch-type 20 Ah-scale Li-ion full cells are fabricated using Ni-rich layered oxides as a cathode and graphite as an anode. Above all, two test conditions for the application of frequency regulation were established in order to examine the performances of cells. Then, the electrochemical performances of two types of Ni-rich layered oxides are compared, and the long-term performance and degradation mode of the cell using cathode material with high nickel contents among them were investigated in the frequency regulation conditions.

• Journal of the Korean Electrochemical Society
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• v.27 no.1
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• pp.47-54
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• 2024

In this study, ZIF67/rGO was used to minimize the battery life degradation due to the insulating properties of sulfur and the elution of lithium polysulfide. ZIF67 wrapped in rGO creates more space within the carbon sponge and can hold a large amount of sulfur. The sulfur@ZIF67/rGO composite was synthesized and prepared as a sponge to enhance the sulfur retention capacity. The result showed a high initial capacity, with a value of about 1093 mAh g^-1 and a capacity retention rate of 84% after 100 cycles. The high interaction with sulfur through the complexation of cobalt and carbon confirmed that ZIF67/rGO exhibits high performance as a carrier for sulfur, the anode active material of lithium-sulfur batteries, and the high initial capacity and improved capacity retention rate were confirmed.

• Transactions of the Korean hydrogen and new energy society
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• v.6 no.2
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• pp.53-63
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• 1995

A 100kW class stack consisting of 10 molten carbonate fuel cells has been fabricated. Internally manifold stack has been tested for endurance. Each cell in the stack had an electrode area of $100cm^2$ and reactant gases were distributed in each cells in a cross-flow configuration. Initial and long term operation performance of the stack was investgated as a function of gas utilization using a specially designed small scale stack test facility. It was possible to have a stack with an output of more than 100W using an anode gas of 72% $H_2/18%$ $CO_2/10%H_2O$ and cathode gas of 33% $O_2/67%$ $CO_2$ and 70% Air 30% $CO_2$. The output and voltage of the stack at a current 15A($150mA/cm^2$) and gas utilization of 0.4 showed 125.8W and 8.39V respectively by elapsed time of 310 hours operation. In long term operation characteristics, the voltage drop of 52.4mV/1000hour was observed after more than 1,840 hours operation. Among the voltage drop, the OCV loss was highest than other voltage loss such as internal resistance and electrode polarization. Non uniformity of 2voltages and degradation of cell voltage in the stack was observed in according to changing the utilization rate after a long term operation. Further work for increasing the performance prolonging the life of the stack are required.

• Journal of the Korea Organic Resources Recycling Association
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• v.23 no.2
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• pp.47-52
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• 2015

A microbial fuel cell (MFC) is a device that can be obtained electricity from a variety of organic through the catalytic reaction of the microorganism. The MFC can be applied to various fields, and research is required to promote the performance of the microbial fuel cell for commercialization. The lower performance of an MFC is due to oxygen reduction at the cathode and the longer time of microbial degradation at anode. The MFC amount of power is sufficient but, in consideration of many factors, as a renewable energy, now commonly power density as compared to Nafion117 it is an ion exchange membrane used is PP (Poly Propylene) from 80 to about 11 fold higher, while reducing the cost to process wastewater is changed to a microporous non-woven fabric of a low cost, it may be energy-friendly environment to generate electricity. All waste, in that it can act as a bait for microorganisms, sustainability of the microbial fuel cell is limitless. The latest research on the optimization and performance of the operating parameters are surveyed and through the SSaM-GG(Smart, Shared, and Mutual- Green Growth) or GG-SSaM(Green Growth - Smart, Shared, and Mutual) as the concept of sustainable development in MFC, the middle indices are developed in this study.