• Journal of the Korean Vacuum Society
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• v.20 no.3
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• pp.225-232
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• 2011

Reactive ion etching (RIE) technique for maskless surface texturing of mc-silicon solar wafers has been applied and succeed in fabricating a grass-like black-silicon with an average reflectance of $4{\pm}1%$ in a wavelength range of 300~1,200 nm. In order to investigate the optimized texturing conditions for mass production of high quantum efficiency solar cell Surface characteristics such as the spatial distribution of average reflectance, micrscopic surface morphology and minority carrier lifetime were monitored for samples from saw-damaged $15.6{\times}15.6\;cm^2$ bare wafer to key-processed wafers as well as the mc-Si solar cells. We observed that RIE textured wafers reveal lower average reflectance along from center to edges by 1% and referred the origin to the non-uniform surface structures with a depth of 2 times deeper and half-maximum width of 3 times. Samples with anti-reflection coating after forming emitter layer also revealed longer minority carrier lifetime by 40% for the edge compared to wafer center due to size effects. As results, mc-Si solar cells with RIE-textured surface also revealed higher efficiency by 2% and better external quantum efficiency by 15% for edge positions with higher height.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.199-199
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• 2013

최근 단파장 광전 소자와 고출력 고주파 전자 소자에 대한 수요 때문에 넓은 밴드갭 에너지를 갖는 반도체에 관심이 많다. 이중에서, ZnO는 우수한 화학 및 역학적 안정성, 수소 플라즈마 내구성과 저가 제조의 장점 때문에 광전자 소자 개발 분야에 적합한 산화물 투명 전극으로 관심을 끌고 있다. 불순물이 도핑되지 않은 ZnO는 본질적으로 산소 빈자리 (vacancy)와 아연 격자틈새 (interstitial)와 같은 자체의 결함으로 말미암아 n형의 극성을 갖기 때문에, 반도체 소자로 응용하기 위해서는 도핑 운반자의 농도와 전도성을 제어하는 것이 필요하다. 본 연구에서는 박막 제조시 제어성, 안정성과 용이하게 성장이 가능한 졸겔 (sol-gel) 방법을 사용하여 사파이어와 석영 기판 위에 Cu가 도핑된 ZnO 박막을 성장시켰으며, 그것의 구조, 표면 형상, 평균 투과율, 광학 밴드갭 에너지를 계산하였다. 특히, Cu의 몰 비를 0, 0.01, 0.03, 0.05, 0.07, 0.1 mol로 변화시키면서 ZnO:Cu 박막을 성장시켰다. ZnO:Cu 졸은 zinc acetate dihydrate, 2-methoxyethanol (용매), momoethanolamine (MEA, 안정제)을 사용하여 제조하였다. 상온에서 2-methoxyethanol과 MEA가 혼합된 용액에 zinc acetate dihydrate (Zn)을 용해시켰다. 이때 MEA와 Zn의 몰 비는 1로 유지하였다. 이 용액을 $60^{\circ}C$ 가열판 (hot plate)에서 24 h 동안 자석으로 휘젓으며 혼합하여 맑고 균일한 용액을 얻었다. 이 용액을 3000 rpm 속도로 회전하는 스핀 코터기의 상부에 장착된 사파이어와 석영 기판 위에 주사기 (syringe)를 사용하여 한 방울 떨어뜨려 30 s 동안 스핀한 다음에, 용매를 증발시키고 유기물 찌꺼기를 제거하기 위하여 $300^{\circ}C$에서 10분 동안 건조시킨다. 기판 위에 코팅하는 작업에서 부터 건조 작업까지를 10회 반복한 다음에, 1 h 동안 전기로에 장입하여 석영 기판 위에 증착된 시료는 $550^{\circ}C$에서, 사파이어 기판은 $700^{\circ}C$에서 열처리를 수행하였다. Cu의 몰 비 0, 0.01, 0.03, 0.05, 0.07, 1로 성장된 ZnO:Cu 박막에 대한 x선 회절 분석의 결과에 의하면, 모든 ZnO:Cu 박막의 경우에 관측된 34.3o의 피크는 ZnO (002) 면에서 발생된 회절 패턴을 나타낸다. 이것은 JCPDS #80-0075에 제시된 회절상과 일치하였으며, ZnO:Cu 박막이 기판에 수직인 c-축을 따라 우선 배향됨을 나타낸다. 사파이어 기판 위에 증착된 박막의 경우에, Cu의 몰 비가 점점 증가함에 따라(002)면 회절 피크의 세기는 전반적으로 증가하여 0.07 mol에서 최대를 나타내었으나, 석영 기판 위에 증착된 박막의 경우에는 0.05 mol에서 최대를 보였다. 외선-가시광 분광계를 사용하여 서로 다른 Cu의 몰 비로 성장된 ZnO:Cu 박막에서 광학 흡수율 (absorbance) 스펙트럼을 측정하였으며, 이 데이터를 사용하여 평균 투과율을 계산한 결과, 투과율은 Cu의 몰 비에 따라 현저한 차이를 나타내었다. Cu의 몰 비가 0.07 mol일 때 평균 투과율은 80%로 가장 높았으며, 0.03 mol에서는 30%로 최소이었다. 광학밴드갭 에너지는 Tauc 모델을 사용하여 계산하였고, 결정 입자의 형상과 크기와의 상관 관계를 조사하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.272-277
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• 2019

In this paper, a manufacturing method of an anti-glare cover glass on LCD for outdoor use is proposed. The main specification of cover glass is hardness and anti-glare. Hardness is achieved by using the tempered glass, and anti-glare(AG) film is laminated to meet anti-glare specification no the tempered glass. However, the AG film is difficult to maintain the AG performance continuously because the abrasion resistance of the PET film itself is as weak as about 3H. Therefore, a novel production procedure using screen printing method is proposed. The proposed coating is implemented by applying $ZnO-B_2O_3-SiO_2$ powder on glass surface and the glass is made with enhanced hardness through tempering process. In order to apply the ZBS powder uniformly on the glass surface, a screen printing process is used. The main parameters to be considered in screen printing are the oil concentration and mesh opening size. Because the amount of ZBS powder applied to the printing process is controlled by these two parameters, the correlativity is confirmed through the experiments. In order to evaluate the performance of the proposed method, the haze, surface roughness and transmittance are selected as the performance index and are compared with the AG film. As a result of comparison, it is verified that the transmittance of the proposed tempered glass is 83.1%, which is slightly lower than 89.5% of AG film, but the hardness is more than double to 7H.

• Analytical Science and Technology
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• v.21 no.3
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• pp.237-243
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• 2008

Nano core shell structures of $TiO_2$ particles coated on surface of ZnO nanoparticles were prepared by the polymerized complex and sol-gel method. The average particle size of ZnO by the polymerized complex method showed 100 nm and the average particle size of $TiO_2$ by the sol-gel method showed below 10 nm. The average particle size of $ZnO@TiO_2$ nano core shell struture represented about 150 nm. The agglomeration between the ZnO particles using the polymerized complex method was highly controlled by the uniform absorption of $TiO_2$ colloid on the spherical ZnO surfaces. The driving force of heterogeneous bonding between ZnO and $TiO_2$ was induced by the Coulomb force. The ZnO and $TiO_2$ particles electrified with + and - charges, respectively, resulted in strong bonding by the difference of iso-electric point (IEP) when they laid neutrality pH area, depending on the heterogeneous surface electron electrified by the different zeta potential on the pH values.

• Composites Research
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• v.37 no.3
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• pp.204-208
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• 2024

De-icing/anti-icing fluid is essential for removing ice formation on aircraft. It chemically removes ice using organic solvents, which can cause damage to the topcoat surface in the process. In this study, glycol-based deicing/anti-icing fluid was used to remove ice, and the resulting damage to the topcoat was examined. USB microscope was used to observe the formation and growth of ice, while a confocal microscope was employed to observe the surface morphology after treatment with de-icing/anti-icing fluid. Additionally, coating thickness measurements and Fourier transform infrared (FT-IR) analysis were conducted to investigate the physical and chemical changes on the surface. The repeated application of de-icing/anti-icing fluid showed a reduction in the ice formation rate and an increase in the growth rate. Damage during the pressurization process and surface damage to the polyurethane topcoat caused by ethylene glycol were observed during the de-icing process. Although no chemical changes were detected, the analysis revealed that surface uniformity decreased, with physical damage such as cracks and undulations forming on the surface. It was confirmed that while de-icing/anti-icing fluid is effective in removing ice, it also causes surface damage.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.43 no.1
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• pp.61-68
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• 2017

The key quality attributes of the pressed powder, one of base makeup products, are skin-affinity and spreadability. In general, there was a limit to meet skin-affinity and spreadability simultaneously, which are opposite attributes each other. In this study, air jet mill process was tried to satisfy two main properties. Skin-affinity was improved by a wet coating of sericite with a mixture of lauroyl lysine (LL) and sodium cocoyl glutamate (SCG). The application of mono-dispersed polymethyl methacrylate (PMMA) and diphenyl dimethicone/vinyl diphenyl dimethicone/silsesquioxane crosspolymer (DDVDDSC) improved both qualities. Air jet mill process has been mainly applied in the pharmaceutical and food industries, and is a method used for processing powder materials in cosmetic field. In this study, we were able to complete makeup cosmetics with an optimum particle size $6.8{\mu}m$ by combining the air jet mill process at the manufacturing stage. It was confirmed that the Ti element was uniformly distributed throughout the cosmetics by EDS mapping, and that the corners of the tabular grains were rounded by SEM analysis. It is considered that this can provide an effect of improving the spreadability when the cosmetic is applied to the skin by using a makeup tool. LL with excellent skin compatibility and SCG derived from coconut with little skin irritation were wet coated to further enhance the adhesion of sericite. SEM images were analyzed to evaluate effect of the dispersion and uniformity of PMMA on spreadability. With the spherical shapes of similar size, it was found that the spreading effect was further increased when the distribution was homogeneously mono-dispersed. The dispersion and spreadability of PMMA were confirmed by measuring the kinetic friction and optimal content was determined. The silicone rubber powder, DDVDDSC, was confirmed by evaluating the hardness, spreading value, and drop test. Finally, it was found that the dispersion of PMMA and silicone rubber powder affected spreadability. Such makeup cosmetics have excellent stability in drop test while having appropriate hardness, and good stability over time. Taken together, it is concluded that air jet mill process can be utilized as a method to improve skin-affinity and spreadability of the pressed powder.

• Journal of the Korean Electrochemical Society
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• v.23 no.2
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• pp.25-38
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• 2020

Photoelectrochemical water splitting has been considered as the most promising technology for generating hydrogen energy. Transition metal dichalcogenide (TMD) compounds have currently attracted tremendous attention due to their outstanding ability towards the catalytic water-splitting hydrogen evolution reaction (HER). Herein, we report the synthesis method of various transition metal dichalcogenide including MoS₂, MoSe₂, WS₂, and WSe₂ nanosheets as excellent catalysts for solar-driven photoelectrochemical (PEC) hydrogen evolution. Photocathodes were fabricated by growing the nanosheets directly onto Si nanowire (NW) arrays, with a thickness of 20 nm. The metal ion layers were formed by soaking the metal chloride ethanol solution and subsequent sulfurization or selenization produced the transition metal chalcogenide. They all exhibit excellent PEC performance in 0.5 M H₂SO₄; the photocurrent reaches to 20 mA cm^-2 (at 0 V vs. RHE) and the onset potential is 0.2 V under AM1.5 condition. The quantum efficiency of hydrogen generation is avg. 90%. The stability of MoS₂ and MoSe₂ is 90% for 3h, which is higher than that (80%) of WS₂ and WSe₂. Detailed structure analysis using X-ray photoelectron spectroscopy for before/after HER reveals that the Si-WS₂ and Si-WSe₂ experience more oxidation of Si NWs than Si-MoS₂ and Si-MoSe₂. This can be explained by the less protection of Si NW surface by their flake shape morphology. The high catalytic activity of TMDs should be the main cause of this enhanced PEC performance, promising efficient water-splitting Si-based PEC cells.

• Food Science and Preservation
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• v.20 no.5
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• pp.659-667
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• 2013

This study was performed to determine the effects of the blanching condition (immersion ratio 1:15 (w/v) for 3 min at $95^{\circ}C$, and solution containing 1% sodium chloride) and selected forming agents (dextrin DE=10, dextrin DE=20, ${\beta}$-cyclodextrin; each forming agents added 5%) on the phytochemical compounds and quality characteristics of Ligularia fischeri leaves. The moisture was not affected by the forming agent. The color of a, b and chroma values were low in the blanching treatment groups and were significantly lowest with ${\beta}$-cyclodextrin (CD). The polyphenol and flavonoid contents in the blanching treatment groups were higher than those in the non-blanching-treatment group. The ascorbic acid content was higher in the non-blanching-treatment group and was significantly highest in the group treated with dextrin (DE=10) whereas the blanching treatment groups showed lower dehydroascorbic acid content than the non-blanching-treatment group. The water absorption was higher in the non-blanching-treatment group and was significantly highest in the group treated with CD. The water solubility in the blanching treatment groups treated with dextrin (DE=20) and CD was higher than that in the blanching treatment group treated with DE=10. The total chlorophyll and chlorophyll a and b contents were high in the blanching treatment group treated with CD, and for the total carotenoid contents, the same tendency as that seen with the chlorophyll content was observed. With regard to the particle diameter, those in the blanching treatment groups were lower than that in the non-blanching-treatment group and was significantly lowest in the blanching treatment groups treated with DE=20 and CD. The result of SEM observation showed that the spray-dried powders in blanching treatment groups treated with the DE=20 and CD forming agents had uniform particle distribution.