• Journal of the Korea Convergence Society
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• v.12 no.5
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• pp.17-22
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• 2021

Eco-friendly magnesium-air battery is a kind of metal-air battery known as a primary battery with a very high theoretical discharge capacity. This battery is also called a metal-fuel cell from the viewpoint of using oxygen in the atmosphere as a cathode active material and magnesium alloy as a fuel. Since battery performance is determined by the properties of the magnesium alloy used as a anode, more research and development of the magnesium alloy electrode as a anode material are required in order to commercialize it as a high-performance battery. In this study, the commercialized magnesium alloys(AZ31, AZ61) were selected and then electrochemical measurements and discharge test were conducted. Electrochemical properties of magnesium alloys were investigated by OCP changes, Tafel parameters and CV measurement, and the feasibilities of AZ61 alloy with excellent discharge capacity(1410mAhg^-1) as electrode materials were evaluated through CC discharge experiments.

• Korean Chemical Engineering Research
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• v.61 no.4
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• pp.517-522
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• 2023

A chemical/mechanical durability test of polymer membrane evaluation method is used in which air and hydrogen are supplied to the proton exchange membrane fuel cell (PEMFC) and wet/dry is repeated in the open circuit voltage (OCV) state. In this protocol, when wet/dry is repeated, voltage increase/decrease is repeated, resulting in electrode degradation. When the membrane durability is excellent, the number of voltage changes increases and the evaluation is terminated due to electrode degradation, which may cause a problem that the original purpose of membrane durability evaluation cannot be performed. In this study, the same protocol as the department of energy (DOE) was used, but oxygen was used instead of air as the cathode gas, and the wet/dry time and flow rate were also increased to increase the chemical/mechanical degradation rate of the membrane, thereby shortening the durability evaluation time of the membrane to improve these problems. The durability test of the Nafion 211 membrane electrode assembly (MEA) was completed after 2,300 cycles by increasing the acceleration by 2.6 times using oxygen instead of air. This protocol also accelerated degradation of the membrane and accelerated degradation of the electrode catalyst, which also had the advantage of simultaneously evaluating the durability of the membrane and the electrode.

• Clean Technology
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• v.19 no.1
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• pp.59-64
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• 2013

Pt/carbon Electrode catalysts for PEMFC were synthesized using colloidal method. PSA (platinum sulfite acid) was used as a Pt precursor and CPA (chloroplatinic acid) was also used to replace relatively expensive PSA. Electrode catalysts prepared using PSA showed Pt particle size less than 3.5 nm and Pt yield higher than 90% in 10~40 wt% Pt loading. Electrode catalysts prepared using CPA also showed Pt particle size less than 4.4 nm and Pt yield higher than 80% in 10~40 wt% Pt loading. The MEA (membrane electrode assembly) using 20 wt% Pt/VXC72 showed equivalent I-V curve comparing with commercial electrode catalyst in single cell test.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.213-213
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• 2003

고온 및 고압의 가혹한 방사선 분위기에서 사용되는 핵연료 피복관은 중성자 조사 및 수소화합물의 생성 등으로 인하여 기계적 성질이 저하된다. 따라서 조사된 핵연료 피복관의 손상기준 확립과 안전성 해석을 위해서는 연성 및 강도 등 기계적 특성을 정확히 이해하여야 할 필요가 있다. 핵연료 피복관의 종 및 횡 방향 인장특성 평가를 위하여 개발된 기존의 다양한 시험법들을 비교하고, 핫셀시험에 적합한 인장시험법을 개발하였다. 피복관의 종방향 인장시편은 튜브시편 또는 게이지부 내에서 균일한 변형률 분포를 얻도록 설계된 도그본 튜브시편(그림 1)을 사용한다. 피복관의 횡방향 인장시험에 사용되는 링시편(그림 2)은 게이지부 내에서 균일한 단축 원환변형율 분포 또는 평면변형율 조건을 나타내도록 설계한다. 연소 또는 조사된 피복관으로부터 시편을 제작하기 위해서는 핫셀 내에서 작업 이 가능한 방전가공기(그림 3)를 사용한다. 피복관의 종방향 인장시험용그립(grip)은 핀-부하형이며, 횡방향 인장시험의 경우는 시험 동안 시편의 곡률이 일정하게 유지 되도록 그립의 형상 및 치수를 결정한다(그림 4). 피복관의 종 및 횡방향 강도와 변형 등 기계적 특성을 평가하기 위한 응력-변형율 곡선은 시험기의 복합 강성(K)을 고려하여 결정한다. 이상과 같이 검토된 인장시험법은 피복관의 안전성 해석(safety analysis)과 관련 규정(regulatory)에서 사용되는 피복관 손상기준(fuel damage criteria)의 개선에 필수적인 자료를 제공한다.

• Journal of the Korean Society of Combustion
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• v.10 no.1
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• pp.20-26
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• 2005

In the present study, catalytic combustion of hydrogen-air premixture in a millimeter scale monolith coated with Pt catalyst was investigated. As the combustor size decreases, the heat loss increases in proportion with the inverse of the scale of combustion chamber and combustion efficiency decreases in a conventional type of combustor. Combustion reaction assisted by catalyst can reduce the heat loss by decreasing the reaction temperature at which catalytic conversion takes place. Another advantage of catalytic combustion is that ignition is not required. Platinum was coated by incipient wetness method on a millimeter scale monolith with cell size of $1{\times}1mm$. Using this monolith as the core of the reaction chamber, temperatures were recorded at various locations along the flow direction. Burnt gas was passed to a gas chromatography system to measure the hydrogen content after the reaction. The measurements were made at various volume flow rate of the fuel-air premixture. The gas chromatography results showed the reaction was complete at all the test conditions and the reacting species penetrated the laminar boundary layer at the honeycomb and made contact with the catalyst coated surface. At all the measuring locations, the record showed monotonous increase of temperature during the measurement duration. And the temperature profile showed that the peak temperature is reached at the point nearest to the gas inlet and decreasing temperature along the flow direction.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.2
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• pp.93-98
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• 2008

To investigate the characteristics of water droplet on the gas diffusion layer from both top-view and side-view of the flow channel, a rig test apparatus was designed and fabricated with prism attached plate. This experimental device is used to simulate the growth of single liquid water droplet and its transport process with various air flow velocity and channel height. The contact angle hysteresis and height of water droplet are measured and analyzed. It is found that droplet tends towards to be instable by decreasing channel height, increasing flow velocity or making GDL more hydrophobic. Also, the simplified force balance model matches with experimental data only in a restricted range of operating conditions and shows discrepancy as the air flow velocity and channel height increases.

• Tribology and Lubricants
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• v.30 no.1
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• pp.21-28
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• 2014

Damage to the cylinder liner of large ship engines, such as scuffing on the surface, can occur very easily because it is operated in a corrosive environment. This scuffing may be due to oil film destruction and corrosive wear caused by water and sulfur included in the fuel, abrasive impurities, and poor lubricants. Thus, a method for monitoring the condition and diagnosing the failure of the cylinder liner and piston ring is needed. In this study, a reciprocating friction and wear test was carried out with a cast iron specimen, which simulated an engine cylinder in a corrosive atmosphere. The lubricants used were base oil, stirred oil with distilled water, a NaCl solution, and dilute sulfuric acid. The friction coefficient and frequency spectrum were measured using a load cell and acceleration sense in each experimental condition. We then used these results to diagnose the failure of the cylinder liner.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.2
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• pp.190-196
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• 2018

Carbon fiber/epoxy composites are typical brittle materials and have low impact properties. Recently, it is important to investigate impact characteristics of carbon fiber composites because of increasing use as automobile parts and high pressure hydrogen vessels of fuel cell electric vehicles for light weight. In this study, the low velocity impact properties of carbon fiber/epoxy composites fabricated by a filament winding method are studied. The low velocity impact properties were measured by performing tests according to ASTM D7136. The low velocity impact simulations were carried out using commercial structural analysis software, Abaqus. The absorbed energy and the delamination shapes were compared between the experimental and simulation results. The numerical analysis method showed that the absorbed energy decreased with the reduced number of cohesive elements in the composite models.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.5
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• pp.455-461
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• 2015

This paper deals with an experimental verification of a temperature-dependent power loss model of a DC/DC converter in severe temperature conditions. The power loss of a DC/DC converter is obtained by summing the losses by the components constituting the converter including switching elements, diodes, inductors, and capacitors. MIL-STD-810F stipulates that any electronic devices must be operable in the temperature ranging from $-50^{\circ}C$ to $70^{\circ}C$. We summarized the temperature-dependent loss models for the converter components. A SEPIC-type converter is designed and built as a target. Using a constant-temperature chamber, a test rig is set up to measure the power loss of the converter. The experimental results confirm the validity of the loss model within 4.5% error. The model can be useful to predict the efficiency of the converter at the operating temperature, and to provide guidelines in order to improve the efficiency.

• Journal of the Korean Ceramic Society
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• v.44 no.4 s.299
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• pp.214-218
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• 2007

The decrease of polarization resistance in cathode is the key point for operating at intermediate temperature SOFC (solid oxide fuel cell). In this study, the influence of Co substitution in B-site at complex perovskite on the electronic conductivity of PSCM ($Pr_{0.3}Sr_{0.7}Co_xMn_{(1-x)}$) was investigated. The PSCM series exhibits excellent MIEC (mixed ionic electronic conductor) properties. The ASR (area specific resistance) of PSCM3773 was $0.174{\Omega}{\cdot}cm^2\;at\;700^{\circ}C$. The activation energy of PSCM3773 was also lower than other compositions of PSCM. The TEC(thermal expansion coefficient) was decreased by addition of Mn. The ASR values were increased gradually during the thermal cycling test of PSCM37773 due to the delamination between electrolyte and cathode materials. The delamination was caused by the difference of TEC.