• 한국태양에너지학회 논문집
• /
• 제33권4호
• /
• pp.31-38
• /
• 2013

The chemical composition of the black Cr solar selective coatings electrodeposited were investigated for property analysis by using a XPS(X-ray photoelectron spectroscopy) before and after annealing in air at $300^{\circ}C{\sim}500^{\circ}C$ for 120 hours. Black Cr selective coating exposed by solar radiation for 5 months was compared with annealed sample. In addition, The Cu solar selective coatings were prepared by thermal oxidation method for low temperature application. The samples obtained were characterized by using the optical reflectance measurements by using a spectrometer. Optical properties of oxidized Cu solar coatings were solar absorptance $({\alpha}){\simeq}0.62$ and thermal emittance $({\epsilon}){\simeq}0.41(100^{\circ}C)$. In the as-prepared Cr black selective coating, the surface of the coating was found to have Cr hydroxide and Cr. The Cr hydroxide of the major component was converted to $Cr_2O_3$ or $CrO_3$ form after annealing at $500^{\circ}C$ with the desorption of water molecules. The black Cr selective coating was degraded significantly at temperature of $500^{\circ}C$. The main optical degradation modes of this coating were diffusion of Cu substrate materials.

• Bulletin of the Korean Chemical Society
• /
• 제35권3호
• /
• pp.886-890
• /
• 2014

The properties of magnetic material of Nd-Fe-B are highly affected by various factors such as particle size, magnetic anisotropy, phase purity and crystal structure. Incorporation of excess neodymium was carried out in various percentages so that it will adjust the proportion of neodymium in the host crystal after reduction treatment and finally help to improve magnetic property of a material. The interdiffusion of Nd-Fe and boron was studied for various compositions and their effect on magnetic property was understood with theoretical concepts. The factors such as amount of hard and soft phase in the reduction treated product is also responsible for the possible exchange coupling between hard and soft phase magnets for better magnetic properties.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2010년도 추계학술대회 초록집
• /
• pp.75.2-75.2
• /
• 2010

Polymer electrolyte fuel cells (PEFCs) have received a lot of attention as a power source for both stationary and mobile applications due to their attractive feature. In general, the performance of PEFCs is highly affected by the property of the electrodes. A PEFC electrode essentially consists of a gas diffusion layer and a catalyst layer. The gas difusion layer is highly porous and hydrophobicized with PTFE polymer. The catalyst layer usually contains electrocatalyst, proton conducting polymer, even PTFE as additive. Particularly, the proton conducting ionomer helps to increase the catalytic activity at three-phase boundary and catalyst utilization. Futhermore, it helps to retain moisture, resulting in preventing the electrodes from membrane dehydration. The most widely used proton conducting ionomer is perfluorinated sulfonic acid polymer, namely, Nafion from DuPont due to its high proton conductivity and good mechanical property. However, there are great demands for alternative ionomers based on non-fluorinated materials in terms of high temperature availability, environmental adaptability and production cost. In this study, the electrodes with the various content of the sulfonated poly(ether sulfone) ionomer in the catalyst layer were prepared. In addition, we evaluated electrochemical properties of the prepared electrodes containing the various amount of the ionomers by using the cyclic voltammetry and impedance spectroscopy to find an optimal ionomer composition in the catalyst layer.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
• /
• pp.188.1-188.1
• /
• 2014

Aluminum is widely used as a material for electrode on silicon based devices. Especially, aluminum films are used as backside and front-side electrodes in silicon quantum dot (QD) solar cells. In this point, the diffusion of aluminum is very important for the enhancement of power conversion efficiency by improvement of contact property. Aluminum was deposited on a Si (100) wafer and a Si QD layer by ion beam sputter system with a DC ion gun. The Si QD layer was fabricated by $1100^{\circ}C$ annealing of the $SiO_2/SiO_1$ multilayer film grown by ion beam sputtering deposition. Cs ion beam with a low energy and a grazing incidence angle was used in SIMS depth profiling analysis to obtain high depth resolution. Diffusion behavior of aluminum in the Al/Si and Al/Si QD interfaces was investigated by secondary ion mass spectrometry (SIMS) as a function of heat treatment temperature. It was found that aluminum is diffused into Si substrate at $450^{\circ}C$. In this presentation, the effect of heat treatment temperature and Si nitride diffusion barrier on the diffusion of Al will be discussed.

• 한국안전학회지
• /
• 제37권2호
• /
• pp.1-9
• /
• 2022

Most factories deal with toxic or flammable chemicals in their industrial processes. These hazardous substances pose a risk of leakage due to accidents, such as fire and explosion. In the event of chemical release, massive casualties and property damage can result; hence, quantitative risk prediction and assessment are necessary. Several methods are available for evaluating chemical dispersion in the atmosphere, and most analyses are considered neutral in dispersion models and under far-field wind condition. The foregoing assumption renders a model valid only after a considerable time has elapsed from the moment chemicals are released or dispersed from a source. Hence, an initial dispersion model is required to assess risk quantitatively and predict the extent of damage because the most dangerous locations are those near a leak source. In this study, the dispersion model for initial consequence analysis was developed with three-dimensional unsteady advective diffusion equation. In this expression, instantaneous leakage is assumed as a puff, and wind velocity is considered as a coordinate transform in the solution. To minimize the buoyant force, ethane is used as leaked fuel, and two different diffusion coefficients are introduced. The calculated concentration field with a molecular diffusion coefficient shows a moving circular iso-line in the horizontal plane. The maximum concentration decreases as time progresses and distance increases. In the case of using a coefficient for turbulent diffusion, the dispersion along the wind velocity direction is enhanced, and an elliptic iso-contour line is found. The result yielded by a widely used commercial program, ALOHA, was compared with the end point of the lower explosion limit. In the future, we plan to build a more accurate and general initial risk assessment model by considering the turbulence diffusion and buoyancy effect on dispersion.

• 대한기계학회논문집B
• /
• 제34권2호
• /
• pp.157-163
• /
• 2010

고체산화물연료전지는 세라믹 물질로 이루어지며, 세라믹 물질의 물성치는 작동조건에 따라 달라진다. 따라서, 높은 신뢰성을 가지는 시뮬레이션 모델을 개발하기 위해서는 세라믹 물질의 물성치를 정확하게 예측할 수 있어야한다. 본 논문에서는 고체산화물연료전지의 성능에 영향을 미치는 여러가지 물성치를 선택하고 그 물성치를 위한 시뮬레이션 모델이 개발되었다. 개회로전압을 위한 깁스에너지, 활성화손실을 위한 교환전류밀도, 저항손실을 위한 전기전도도가 계산되었다. 또한, 다공성 전극 내부의 물질전달 해석을 위해서 분자확산과 누센확산을 함께 고려하는 유효확산계수가 계산되었다. 이러한 계산과정 후에 물성치 모델과 전기화학반응 모델이 동시에 시뮬레이션 되었다. 해석코드의 검증을 위해서 전산해석 결과는 실험결과 및 Chan 등에 의해서 수행된 이전 연구결과와 비교되었다.

• 한국재료학회지
• /
• 제8권12호
• /
• pp.1090-1098
• /
• 1998

Rf 마그네트론 반응성 스퍼터링법으로 $RuO_2$박막을 Si 및 Ru/Si 기판 위에 증착한 뒤 산소 분위기 (1atm)에서 열처리를 하여 RuO$_2$박막의 열적 안정성 및 확산방지 특성을 연구하였다.$ RuO_2$박막은 산소 분위기 $700^{\circ}C$에서 10분까지 안정하여, 산소와 실리콘에 대한 우수한 확산방지 특성을 나타내었다 $750^{\circ}C$ 열처리시, 우선 성장 방위에 관계없이 RuO$_2$박막 표면 및 내부에서 휘발 반응이 일어남과 동시에 확산방지 특성은 저하되었다. 그러나 80$0^{\circ}C$ 열처리 시에는 $750^{\circ}C$ 열처리와는 다른 미세구조를 나타내었다. 이러한 열처리 온도에 따른 휘발반응에는 RuO$_2$의 표면 결함구조인 $RuO_3$와 증착시 박막내 함유된 과잉산소에 의한 결함 구조가 영향을 주는 것으로 판단된다.

• 한국재료학회지
• /
• 제10권2호
• /
• pp.160-165
• /
• 2000

Sputter Cu(1-4.5at.%Mg) alloy를 100mTorr이하의 산소압력에서 온도를 증가시키며 열처리하였을 때 표연과 계면에서 형성된 MgO의 확산방지막 특성을 살펴보았다 먼저, $Cu(Mg)/SiO_2/Si$ 구조의 샘플을 열처리했을 때 계면에서는 $2Mg+SiO_2{\rightarrow}2MgO+Si$의 화학반응에 의해 MgO가 형성되는데 이 MgO충에 의해 Cu가 $SiO_2$로 확산되는 것이 현저하게 감소하였다. TiN/Si 기판 위에서도 Cu(Mg)과 TiN 계면에 MgO가 형성되어 Cu(4.5at.%Mg)의 경우 $800^{\circ}C$까지 Cu와 Si의 확산을 방지할 수 있었다. 표면에 형성된 MgO위에 Si을 증착하여 $Si/MgO(150\;{\AA})/Cu(Mg)/SiO_2/Si$구조로 만든 후 열처리했을 때 $150\;{\AA}$의 MgO는 $700^{\circ}C$까지 Si과 Cu의 확산을 방지할 수 있었다. 표면에 형성된 MgO($150\;{\AA}$)의 누설전류특성은 break down 5V, 누설전류 $10^{-7}A/\textrm{cm}^2$의 값을 나타냈다. 또한 $Si_3N_4/MgO$ 이중구조에서는 매우 낮은 누설전류밀도를 나타냈으며 MgO에 의해 $Si_3N_4$ 증착시 안정적인 계면이 형성됨을 확인하였다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
• /
• pp.208-211
• /
• 2003

In this paper, mechanical property of electric epoxy with water aging was discussed. We studied mechanical property of elastic resin after absorption in water from 0 to 484 hour. As a result, diffusion factor of elastic epoxy showed $20-21{\times}10^{-4}mm^2/s$ and general epoxy showed $9.5{\times}10^{-4}mm^2/s$. Elastic property increased linearly according to amount of addictives and decreased elastic property according to amount of water absorption. Tensile strength was reduced to add to addictives. It was effected by water absorption of micro-void of elastic epoxy. Hardness inclined to decrease after increasing according to absorbed time.

• 한국결정성장학회지
• /
• 제18권1호
• /
• pp.15-21
• /
• 2008

탄화규소(SiC)는 산화저항성, 내식성, 고온 강도 및 열전도 특성 등의 기계적 특성이 매우 우수한 재료로 알려져 있지만, 강한 공유결합성으로 인하여 그 소결이 매우 어려운 재료이다. 본 연구에서는 치밀한 탄화규소 소결체를 제조하기 위하여 카본 및 보론을 소결 첨가제로하여 열간 가압 소결법을 적용하여 탄화규소 소결체를 제작하여 그 특성을 평가하였다. 카본의 첨가는 탄화규소의 소결을 촉진하는 역할을 하여 비정상 입성장을 억제하기 때문에 미세하고 균일한 미세구조를 형성하였기 때문에 탄화규소 소결체의 기계적 특성을 향상시키는 것을 확인 할 수 있었다. 또한 차본의 첨가는 소결 중 보론의 첨가에 의해 발생하는 탄화규소의 6H 구조에서 4H 구조로의 상전이를 억제함을 알 수 있었다.