• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.76.1-76.1
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• 2010

Recently, many efforts to solve the durability problem of PEM fuel cell are carried on constantly. However, despite this attention, durability researches of gas diffusion layer (GDL) are not much reported yet. Generally, GDL of PEM fuel cell experiences three external attacks, which are dissolution of water, erosion of gas flow, corrosion of electric potential. In this study, among these degradation factors, carbon corrosion of electric potential was focused and investigated with accelerated carbon corrosion test. Through the test, it is confirmed that carbon corrosion occurred at GDL, and corroded GDL decreased a performance of operating fuel cell. The property changes of GDL were measured with various methods such as air permeability meter, pore distribution analyzer, thermo gravimetric analyzer, and tensile stress test to discover the effects of carbon corrosion. Carbon corrosion caused not only loss of weight and thickness, but also degradation of mechanical strength of GDL. In addition, to analysis the reason of GDL property changes, a surface and a cross section of GDL were observed with scanning electron microscope. After 100 hours test, the GDL showed serious damage in center of layer.

• 한국과학교육학회지
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• 제15권4호
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• pp.437-451
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• 1995

Middle and high school students' conceptual understanding about stoichiometry, gas laws, and diffusion was compared with essay type test and multiple choice test. Whereas achievement of high school students was higher in stoichiometry, that of middle school students who were expected to go to high schools was higher in gas laws and diffusion. When students' achievement was compared to that of American college students, Korean students' achievement was higher in stoichiometry and was similar in gas laws. These results indicate that algorithmic problem solving is more emphasized than conceptual understanding in high schools and that quantitative aspects focused in chemistry education are not helpful in concept understanding. Nevertheless relatively smaller difference between concept understanding and algorithmic problem solving for high school students in this study seems to be from concept learning in middle schools.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.394-394
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• 2012

We fabricated organic-inorganic superlattice films using molecular layer deposition (MLD) and atomic layer deposition (ALD). The MLD is a gas phase process in the vacuum like to atomic layer deposition (ALD) and also relies on a self-terminating surface reaction of organic precursor which results in the formation of a monolayer in each sequence. In the MLD process, 'Alucone' is very famous organic thin film fabricated using MLD. Alucone layers were grown by repeated sequential surface reactions of trimethylaluminum and ethylene glycol at substrate temperature of $80^{\circ}C$. In addition, we developed UV-assisted $Al_2O_3$ with gas diffusion barrier property better than typical $Al_2O_3$. The UV light was very effective to obtain defect-free, high quality $Al_2O_3$ thin film which is determined by water vapor transmission rate (WVTR). Ellipsometry analysis showed a self-limiting surface reaction process and linear growth of each organic, inorganic film. Composition of the organic films was confirmed by infrared (IR) spectroscopy. Ultra-violet (UV) spectroscopy was employed to measure transparency of the organic-inorganic superlattice films. WVTR is calculated by Ca test. Organic-inorganic superlattice films using UV-assisted $Al_2O_3$ and alucone have possible use in gas diffusion barrier for OLED.

• 한국건설순환자원학회논문집
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• 제6권4호
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• pp.245-251
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• 2018

최근 구조물의 유지관리의 중요성이 부각되면서 자기치유 콘크리트 기술 분야의 연구가 활발히 이루어지고 있다. 이에 반해서 자기치유 성능을 평가하기 위한 척도는 부족한 실정이다. 균열폭을 측정하기 위한 방법으로 시각적인 방법이 1차적으로 사용되고 있으나 시편 내부의 균열폭을 관찰하기가 어려우며, 비균질한 균열특성으로 인해 표면에 대한 국부적인 측정만 할 수 있는 단점이 있다. 균열에 대한 간접적인 평가 방법으로 투수실험이 널리 활용되고 있지만 물의 점성으로 인한 문제가 있으며, 또한 실험 중 시편내부 물질의 용출될 가능성이 존재한다. 본 연구에서는 기체확산 특성을 활용한 균열폭 평가 방법을 제안하고자 하였다. 아크릴로 이상화된 직선균열을 제작하여 균열폭, 두께에 따른 시편의 확산계수를 분석하였다. 실험결과를 통하여 균열폭과 확산계수는 선형관계에 있음을 보였고, 두께와 확산계수는 역수의 관계에 있음을 증명하였다.

• 한국건설순환자원학회논문집
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• 제9권3호
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• pp.375-382
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• 2021

자기치유 콘크리트는 직접적인 보수보강 없이도 스스로 구조물의 균열을 치유하여 효율적으로 콘크리트 구조물의 수명연장이 가능하다는 측면에서 각광받고 있다. 현재 자기치유 콘크리트는 전 세계적으로 활발히 연구가 진행되고 있는 분야이지만 대부분의 연구는 치유 성능의 향상에 초점을 맞추고 있기 때문에 객관적으로 치유성능을 평가하는 방법은 부족한 실정이다. 자기치유 콘크리트의 성능평가에 활용하기 위해 기체확산실험 방법이 개발된 바가 있지만, 시편의 포화도 및 실험시의 온습도 등과 같은 환경조건의 통제가 필요하다는 단점이 있다. 따라서 본 연구에서는 기체 확산 실험시에 필요한 환경조건을 대폭 완화하여 적용성을 향상시키고자 하였다. 아울러 실험시간을 단축시키고자 사전 안정화 과정을 도입하였고, 약 20분이내의 실험시간에서 3%이내의 오차 수준으로 균열폭의 추정이 가능하였다.

• 한국표면공학회지
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• 제36권1호
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• pp.99-107
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• 2003

The diffusion coefficient of Xe-133 was obtained from an annealing test. The specimens were made from a UO$_2$ single crystal powder with natural enrichment. Weight and grain size were 300mg and ($23\mu\textrm{m}$, respectively. Oxygen potentials were obtained from an oxygen sensor. Released fractions were obtained from both results of gamma scans and quantitative analysis with MCNP code, The annealing test was performed at three temperatures at once. Diffusion coefficients of Xe-133 were calculated using slope of Booth theory in each O/M ratios. Activation energy and the pre-exponential factor of the diffusion coefficient were obtained. The activation energy of near stoichiomeric $UO_2$ is 310 kJ/mol. The measured values of near stoichiometric $UO_2$ are very close to other data available. Diffusion coefficients increase with hyper-stoichiometry, due to higher concentration of cation vacancies.

• 전기화학회지
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• 제5권1호
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• pp.7-12
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• 2002

염수 전해 공정에서 산소음극형 가스화산전극의 적용에 대해 연구, 조사하였다. 가스확산전극은 반응층, 가스확산층, 급 전체로 구성된다. 반응층은 친수성 카본블랙, 소수성 카본블랙, PTFE(polytetrafluoroethylene), 은거울반응이나 함침법에 의해 담지된 은 촉매로 제조하였다. 가스확산충은 소수성 카본블랙과 PTFE로 제조되며, 반응층 내에 사용되는 급전체는 Ni망을 사용하였다. 실험에 의하면 함침법에 의해 Ag촉매를 반응충 카본에 담지시켜 제작된 전극$(Ag\;10wt\%$,바인더 $20wt\%)$이 산소음극 과전압이 약 700mv, 전해조에 장착하여 측정한 전해전압(전해 조건이 $80^{\circ}C,\;32wt\%$ 가성소다 그리고 $300 mA/cm^2$의 전류 밀도)이 약 2.2V로 가장 우수한 결과를 나타내었다. 이는 기존 공정의 전해전압 3.4V에 비해 $30\%$이상 저감된 결과이다. 또한 개발된 가스확산 전극은 염수 분해용 전해 공정에서 3개월 연속 운전이 가능하였다.

• 한국건설순환자원학회논문집
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• 제8권1호
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• pp.143-151
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• 2020

최근 자기치유 콘크리트의 연구가 활발히 진행되고 있으며, 구조물의 유지관리에 활용하기 위한 다양한 방법이 시도되고 있다. 하지만 자기치유 콘크리트의 기술적인 발전과는 달리, 성능을 평가하기 위한 방법은 불충분한 실정이다. 비록 표면관찰과 투수실험을 통해서 균열의 치유를 관찰하는 방법이 널리 실행되고 있지만, 현미경 관찰을 통한 표면관찰 방법은 국부적인 지점의 관찰은 전체적인 성능을 평가하기에는 불충분할 수 있으며, 투수실험의 경우에는 물질용출 및 점성으로 인한 손실을 고려해야 한다. 상기의 두 실험방법의 단점을 보완한 기체확산실험이 개발되었지만, 실제 치유가 발생한 시편을 대상으로의 검증은 이루어지지 않았다. 따라서 본 연구에서는 치유가 발생한 모르타르 시편에 대해 기체확산실험을 진행하였고, 기체확산실험에 의한 자기치유 평가의 적정성을 검증하였다.

• 열처리공학회지
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• 제13권4호
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• pp.224-230
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• 2000

Garbon steel(SM35C) was gas nitrocarburized at $580^{\circ}C$ in $55%N_2-40%NH_3-5%CO_2$ mixed gas atmosphere, and then the steel was induction hardened at $850^{\circ}C$. The microstructure of gas nitrocarburized surface layer was observed by optical microscope and SEM. The phase analysis was carried out by X-ray diffraction method. The mechanical properties of gas nitrocarburized SM35C steel was evaluated by hardness, wear and fatigue test. The thickness of compound and diffusion layer were increased with increasing the gas nitrocarburizing time and the densest compound layer was obtained at 3 hours gas nitrocarburizing time. In case of 15sec induction hardening after gas nitrocarburizing, the surface hardness was decreased from 800Hv to 630Hv owing to the decomposition of compound layer, but wear resistance was increased because of increased hardness of diffusion layer. The fatigue strength of induction hardened steel after gas nitrocarburizing, $58kgf/mm^2$, was higher than $41.5kg/mm^2$ of gas nitrocarburized steel and $45kg/mm^2$ of induction hardened steel, respectively.

• Journal of Welding and Joining
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• 제15권6호
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• pp.32-40
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• 1997

Solid state diffusion bonding is the joining process performed by creep and diffusion, which is accelerated by heating below melting temperature and proper pressing, in vacuum or shielding gas atmosphere. By this process we can obtain sufficient joint which can't be expected from the fusion welding. For Ti-6Al-4V alloy, the optimum solid state diffusion bonding condition and mechanical properties of the joint were found, and micro void morphology at bond interface was observed by SEM. The results of tensile test showed sufficient joint, whose mechanical properties are similar to that of base metal. 850$^{\circ}$C, 3MPa is considered as the optimum bonding condition. Void morphology at interface is long and flat at the initial stage. As the percentage of bonded area increases, however, small and round voids are found. Variation of void shape can be explained as follows. As for the void shrinkage mechanism, at the initial stage, power law creep is the dominant, but diffusion mechanism is dominant when the percentage of bonded area is increased.