• 한국표면공학회지
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• 제40권5호
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• pp.241-244
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• 2007

$MgF_2$/Cr/$MgF_2$, $MgF_2$/Cu/$MgF_2$ and $MgF_2$/Al/$MgF_2$ multi-layered thin films were fabricated by evaporation system. $MgF_2$ and Cr(Cu, And Al) was selected as a low refractive index material and mid reflector layer, respectively. Optical properties including color effect were systematically studied in terms of different film layer by using spectrophotometer. Experimental results were compared to the simulation result. The films consistings of $MgF_2$/Cr/$MgF_2$, $MgF_2$/Cu/$MgF_2$, $MgF_2$/Al/$MgF_2$ multi-layered thin films showed wavelength range of $430{\sim}780nm$, typically color range between greenish yellow and orange at view angle of $45^{\circ}$. It was confirmed that this experimental result was well matched with simulation result.

• 한국재료학회지
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• 제28권8호
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• pp.435-439
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• 2018

MA Al alloys are examined to determine the effects of alloying of Mg and Cu and rolling on tensile deformation behavior at 748 K over a wide strain rate range($10^{-4}-10^3/s$). A powder metallurgy aluminum alloy produced from mechanically alloyed pure Al powder exhibits only a small elongation-to-failure(${\varepsilon}_f$ < ~50%) in high temperature(748 K) tensile deformation at high strain rates(${\acute{\varepsilon}}=1-10^2/s$). ${\varepsilon}_f$ in MA Al-0.5~4.0Mg alloys increases slightly with Mg content(${\varepsilon}_f={\sim}140%$ at 4 mass%). Combined addition of Mg and Cu(MA Al-1.5%Mg-4.0%Cu) is very effective for the occurrence of superplasticity(${\varepsilon}_f$ > 500%). Warm-rolling(at 393-492 K) tends to raise ${\varepsilon}_f$. Lowering the rolling-temperature is effective for increasing the ductility. The effect is rather weak in MA pure Al and MA Al-Mg alloys, but much larger in the MA Al-1.5%Mg-4.0%Cu alloy. Additions of Mg and Cu and warm-rolling of the alloy cause a remarkable reduction in the logarithm of the peak flow stress at low strain rates (${\acute{\varepsilon}}$< ~1/s) and sharpening of microstructure and smoothening of grain boundaries. Additions of Mg and Cu make the strain rate sensitivity(the m value) larger at high strain rates, and the warm-rolling may make the grain boundary sliding easier with less cavitation. Grain boundary facets are observed on the fracture surface when ${\varepsilon}_f$ is large, indicating the operation of grain boundary sliding to a large extent during superplastic deformation.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.373-373
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• 2011

$Cu(In,Ga)Se_2$(CIGS) 박막 태양전지는 Chalcopyrite계 박막 태양전지로 Cu, In, Ga, Se 각 원소의 조성을 적절히 조절하여 박막을 성장시킨다. 성장시킨 CIGS 박막은 광흡수계수가 105cm-1로 다른 물질 보다 뛰어나고 직접 천이형 반도체로서 얇은 두께로도 고효율의 박막 제작이 가능하다. 얇은 두께로도 충분히 빛의 흡수가 가능하지만, cell 표면 반사에 의한 광 손실은 cell 효율을 떨어뜨리게 된다. 본 연구에서는 CIGS 박막 태양전지의 광 흡수 향상을 위해 굴절률이 1.86인 ITO 위에 ITO보다 굴절률이 작은 $MgF_2$ (n=1.377) [1]를 80, 100, 120, 140 nm로 증착하여 $MgF_2$/Al/Ni/ITO/i-ZnO/CdS/CIGS/Mo/SLG 시료를 제작하고, optical reflectance, Quantum Efficiency를 이용하여 분석하였다. optical reflectance 분석 결과, $MgF_2$ AR coating을 한 경우, 두께가 두꺼워짐에 따라 광 반사도가 감소하는 경향을 보였다. 또한 AR coating 두께가 커짐에 따라 fluctuation이 점점 커지며, 파형이 장파장 쪽으로 shift하는 것을 관찰 할 수 있었다. Quantum efficiency (QE)를 분석한 결과 $MgF_2$ AR coating 할 경우, 측정된 대부분의 파장에서 QE가 향상되는 것을 확인할 수 있었다. 하지만 AR coating 두께에 따른 변화는 뚜렷한 차이를 보이지 않았다. AR coating 결과, JSC가 증가하여 efficiency가 향상되는 것을 확인 할 수 있다. 그러나 $MgF_2$ AR coating 80~140 nm 범위에서 cell 효율 변화의 뚜렷한 차이는 관찰할 수 없었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.251-254
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• 2001

This paper describes an efficiency improvement of buried contact solar cell (BSCS) with a structure of MgF$_2$/CeO$_2$/Ag/Cu/Ni grid/n$^{+}$ emitter/p-type Si base/p$^{+}$/Al. Theoretical and experimental investigations were performed on a double layer antireflection (DLAR) coating of MgF$_2$/CeO$_2$. We investigated CeO$_2$ films as an AR layer because they have a proper refractive index of 2.46 and demonstrate the same lattice constant as Si substrate. An optimized DLAR coating shewed a reflectance as low as 2.04 % in the wavelengths ranged from 0.4 ${\mu}{\textrm}{m}$ to 1.1 ${\mu}{\textrm}{m}$. BCSC cell efficiency was improved from 16.2 % without any AR coating to 19.9 % by employing DLAR coatings. Further details on MgF$_2$/CeO$_2$ DLAR coatings on the BCSC cells are presented in this paper.per.

• Journal of Electrochemical Science and Technology
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• 제11권2호
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• pp.140-147
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• 2020

This paper presents a hypothesis and its experimental validation that ∆E (E_sec,corr - E_corr) of cyclic polarization curve of an Al-Zn-Mg-Cu alloy decreases firstly and then increases with the increasing of corrosion rate or corroded fraction F_corr of alloy surface. The minimum value of ∆E is obtained when F_corr ≈ 50%. In addition, a proportional relationship between ∆E and |50% - F_corr| was found. This non-monotonic relation between ∆E and extent of localized corrosion indicates that additional attention should be paid on using ∆E to assess localized corrosion behaviour of Al-Zn-Mg-Cu alloys.

• 한국주조공학회지
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• 제20권1호
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• pp.38-45
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• 2000

The remelting for recycling or thin aluminum scrap, such as aluminum chip generally involves melting of these pieces submerged in molten salt flux. In this study, the effects of salt flux compositions and alloying elements on the aluminum dropletscoalescence and oxide film removal were studied in 99.8%Al, Al-1.01%Cu, Al-1.03%Si, and Al-1.38%Mg alloys as a function of holding time at $740^{\circ}C$ Salt fluxes based on NaCl-KCl(1:1) with addition of 5wt.% fluorides(NaF, $Na_3AlF_6$, $CaF_2$) or 5 wt.% chloride($MgCl_2$, $AlCl_3$) were used. The experimental results show that NaCl-KCl(1:1) with addition of 5 wt.% fluorides exhibits better coalescence ability than that with chlorides. The oxide film is not removed by NaCl-KCl(1:1) with addition of 5 wt.%chlorides, while it is removed by NaCl-KCl(1:1) with addition of 5 wt.% fluorides. The aluminum droplets coalescence and oxide film removal by salt fluxes are related to interfacial tension tension between metal and salt flux.

• 한국대기환경학회지
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• 제14권6호
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• pp.631-642
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• 1998

Fall-out particles were collected by the modified British deposit gauges at 35 sampling sites in Suwon area from January to November, 1996. Twenty chemical species (Al. Ba, Cd, Cr, K, Pb, Sb, Zn, Cu, Fe, Ni, V, F-, Cl-, NO3-, 5042-, Na+, NH4+, Mg2+, and Ca2+) were analyzed by AAS and If. The purposes of this study were to estimate qualitatively various emission sources of the fell-out particle by applying multivariate statistical techniques such as factor analysis, multiple regression analysis, and discriminant analysis. During the study, outlier sites were determined by a z-score method. Cl-, Na+, Mg2+, and SO42- were highly correlated due to their common marine related source. Wind speed was the most influential factor for the deposition fluxes of the particle itself and all the chemical species as well. When applying the factor analysis, 8 source patterns were qualitatively obtained, such as marine source, soil source, oil burning source, Cr related source, tire source, Cd related source, agriculture source, and F- related source. As a result of the multiple regression analysis, we could suggest that some chemical compounds may possibly exist in the form of CaSO4, NaN03, NaCl, MgC12, (NH4)2SO4, NaF, and CaCl2 in the fall-out particles. Finally, spatial and seasonal classification study performed by a discriminant analysis showed th.at SO42-, Ca2+, Cl-, and Fe were dominant in the group of spatial pattern; however, SO42-, Cl-, Al, and V were in the group of seasonal pattern.

• Archives of Metallurgy and Materials
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• 제64권2호
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• pp.617-622
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• 2019

This study investigated the effect of T6 heat treatment on the microstructure and scratch wear behavior of hypoeutectic Al-12wt.%Si alloy manufactured by extrusion. Microstructural observation identified spherical eutectic Si phases before and after the heat treatment of alloys (F, T6). Phase analysis confirmed Al matrix and Si phase as well as Al₂Cu and Al₃Ni, Mg₂Si in both alloys. In particular, Al₂Cu was finer and more evenly distributed in T6 alloy. This resulted in Vickers hardness of T6 alloy that was 2.3 times greater compared to F alloy. The scratch wear test was conducted using constant load scratch test (CLST) mode and multi-pass scratch test (MPST) mode. The scratch coefficient and worn out volume obtained by such were used to evaluate wear properties before and after heat treatment. In the case of T6 alloy, its scratch coefficient was lower than F alloy in all load ranges. After 15 repeated tests to measure worn out volume, F alloy and T6 alloy measured 1.2×10^-1 mm³ and 7.8×10^-2 mm³, respectively. In other words, the wear resistance of T6 alloy were confirmed to be better than those of F alloy. In addition, this study attempted to identify the microstructural factors that contribute to the better scratch wear resistance of T6 alloy and wear mechanism from surface and cross-section observations after the wear tests.

• 한국환경보건학회지
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• 제30권5호
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• pp.455-468
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• 2004

The purpose of this paper is to understand the time series and origin of a chemical component and to compare the difference during yellow sand episodes for analysis $PM_{10}$ chemical components in the region of west in Korean Peninsula, 1999-2001. An annual mean concentration of $PM_{10}$ is $29.1\;{\mu}g/m^3$. A monthly mean and standard deviation of $PM_{10}$ concentration are very high in spring but there is no remarkably seasonal variation. Also, water soluble ionic component of $PM_{10}$ be influenced by double more total anion than total cation, be included $NO_{3}^-\;and\;SO_{4}^{2-}$ for the source of acidity and $NH_{4}^+$ to neutralize. Tracer metals of $PM_{10}$ slowly increases caused by emitted for soil and ocean (Fe, Al, Ca, Mg, Na) and Zn, Pb, Cu, Mn for anthropogenic source. According to method of enrichment factor (E.F) and statistics, assuming that the origin of metal component in $PM_{10}$ most of element in the Earth's crust e.g. Mg, Ca, Fe originates soil and Cu, Zn, Cd, Pb derives from anthropogenic sources. The ionic component for $Na^{+}\;Cl^-,\;Mg^{2+}\;and\;Ca^{2+}$ and Mg, Al, Ca, Fe originated by soil component largely increase during yellow sand period and then tracer metal component as Pb, Cd, Zn decrease. According to factor analysis, the first group is ionic component ($Na^+,\;Mg^{2+},\;Ca^{2+}$) and metal component (Na, Fe, Mn and Ni) be influenced by soil. The second group, Mg, Cr also be influenced by soil particle.

• 자원환경지질
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• 제42권3호
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• pp.217-234
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• 2009

본 연구에서는 부산광역시 기장군 일광면 일대 농업지역의 지하수 수질과 농약에 의한 오염 특성을 요인분석을 이용하여 규명하였다. 1, 2, 3차의 수질분석에 의하면, 무기성분($Ca^{2+}$, $Na^+$, $Mg^{2+}$, $K^+$, $Zn^{2+}$, $Cu^{2+}$, $Fe^{2+}$, $Al^{3+}$, $NO_3\;^-$, $Cl^-$, $SO_4\;^{2-}$, $F^-$, $SiO_2$)의 평균농도는 2차조사에서 대체로 높게 나타났으며, 살충제인 carbofuran과 제초제 alachlor는 2차조사에서 과반수가 넘는 지하수공에서 검출이 되었다. 이는 강수량의 증가로 인해서 지하수내로 오염물질의 용출량이 늘어났기 때문으로 판단된다. 요인분석과 수질조성에 의하면, $SiO_2$, $HCO_3\;^-$, $F^-$을 제외한 무기성분들은 인위적인 오염(화학비료, 퇴비, 유기물의 분해, 축산폐수, 생활하수), 염수, 물-광물 반응의 영향을 받고 있다. 인위적인 오염을 대표하는 $NO_3\;^-$평균농도는 먹는물 기준보다 약 4${\sim}$5배 초과하고 있다. 또한, 염수의 영향은 해안에서부터 멀수록 작아지는 것으로 판단된다.