• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2011.11a
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• pp.5-5
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• 2011

나노섬유를 제조하는 방법 중에는 상분리 현상을 이용한 방법, 자가 조립성을 이용한 방법, 템플레이트를 이용한 방법, 전기방사법이 있으며 특히 전기방사법은 연속적으로 균일한 나노섬유를 제조할 수 있다. 또한 전기방사법은 장비가 간단하며 고분자 blend ratio와 무기재료의 함량에 따라 뛰어난 특성을 나타내는 나노복합섬유를 만들 수 있다. 최근 식물에서 추출한 단백질을 전기방사법을 이용하여 나노입자 및 나노섬유를 제조하고 이를 의료 분야 등에 적용하기 위한 연구가 활발히 진행되고 있으며 이런 식물성 단백질은 동물성 단백질에 비하여 인체 적용이 용이하고 매장량이 풍부한 장점이 있다. 본 연구에서는 전기방사법을 이용하여 옥수수에서 추출한 단백질인 zein의 나노입자 및 나노섬유를 제조하였다. 또한 천연 추출물이 혼입된 복합 나노입자 및 나노섬유를 제조하여 zein이 가진 고유 특성 이외에 천연 추출물의 특성을 추가로 부여해서 더욱 발전된 나노입자 및 나노섬유를 제조하였다. 고분자 농도, 전압, 방사거리 등 다양한 공정변수를 조절하여 최적의 조건을 확립하였으며 제조된 나노입자 및 나노섬유는 field-emission type scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV/vis), fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC)를 이용하여 특성분석을 실시하였다.

• Journal of Soil and Groundwater Environment
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• v.19 no.1
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• pp.63-69
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• 2014

This paper presents the feasibility of using different iron oxides (microscale hematite (HT), microscale magnetite (MT), and nanoscale maghemite (NMH)) in enhancing nitrate reduction by zero-valent iron (Fe(0)) under two solution conditions (artificial acidic water and real groundwater). Addition of MT and NMH into Fe(0) system resulted in enhancement of nitrate reduction compared to Fe(0) along reaction, especially in groundwater condition, while HT had little effect on nitrate reduction in both solutions. Field emission scanning electron microscopy (FESEM) analysis showed association of MT and NMH with Fe(0) surface, presumably due to magnetic attraction. The rate enhancement effect of the minerals is presumed to arise from its role as an electron mediator that facilitated electron transport from Fe(0) to nitrate. The greater enhancement of MT and NMH in groundwater was attributed to surface charge neutralization by calcium and magnesium ions in groundwater, which in turn facilitated adsorption of nitrate on Fe(0) surface.

• Korean Journal of Materials Research
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• v.27 no.12
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• pp.705-709
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• 2017

The electronic and optical characteristics of molybdenum disulphide ($MoS_2$) film significantly vary with its thickness, and thus a rapid and accurate estimation of the number of $MoS_2$ layers is critical in practical applications as well as in basic researches. Various existing methods are currently available for the thickness measurement, but each has drawbacks. Transmission electron microscopy allows actual counting of the $MoS_2$ layers, but is very complicated and requires destructive processing of the sample to the point where it will no longer be useable after characterization. Atomic force microscopy, particularly when operated in the tapping mode, is likewise time-consuming and suffers from certain anomalies caused by an improperly chosen set point, that is, free amplitude in air for the cantilever. Raman spectroscopy is a quick characterization method for identifying one to a few layers, but the laser irradiation causes structural degradation of the $MoS_2$. Optical microscopy works only when $MoS_2$ is on a silicon substrate covered with $SiO_2$ of 100~300 nm thickness. The last two optical methods are commonly limited in resolution to the micrometer range due to the diffraction limits of light. We report here a method of measuring the distribution of the number of $MoS_2$ layers using a low voltage field emission electron microscope with acceleration voltages no greater than 1 kV. We found a linear relationship between the FESEM contrast and the number of $MoS_2$ layers. This method can be used to characterize $MoS_2$ samples at nanometer-level spatial resolution, which is below the limits of other methods.

• Applied Microscopy
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• v.42 no.3
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• pp.129-135
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• 2012

In this study, the changes in hair quality before and after Magic straight perm have been evaluated through a hair damage measurement method. For this, a healthy high school student's (age18 years) wavy hair was selected and permed on the left and right sides. Then, the changes caused by physical methods which were applied during the fl at iron-based Magic straight perm were evaluated based on the hair damage measurement method before and after the Magic straight perm. According to the protein release test after the Magic straight perm, 1.26% in average and 0.14% was observed in Cool Magic straight perm sample. In a field emission scanning electron microscopy (FE-SEM) test, saw teeth-shaped partial desquamation of cuticle cells and impurities were observed in the warm-treated hair sample. In atomic force microscope (AFM), line-profile is a method to represent roughness data on hair. According to analysis on 3-dimensional (3D) images, the hair with Cool Magic straight perm was lower than the hair with Warm Magic perm in terms of the color change of 3D images. In addition, vertical changes were observed in the hair with Cool Magic perm. As a result, irregular surface roughness was observed. This study proposed a method to minimize hair damage by cooling down the heat with the cool hair straightener as soon as the Warm Magic was finished.

• Journal of the Korean Ceramic Society
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• v.49 no.2
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• pp.167-172
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• 2012

Fine diamond powders are synthesized with a 420 ${\phi}$ cubic press and stack-cell composed of Kovar ($Fe_{54}Ni_{29}Co_{17}$) (or Kovar+7 ${\mu}m$-thick Zn electroplated) alloy and graphite disks. The high pressure high temperature (HPHT) process condition was executed at $1500^{\circ}C$ for 280 seconds by varying the nominal pressure of 5.7~10.6 GPa. The density of formation, size, shape, and phase of diamonds are determined by optical microscopy, field emission scanning electron microscopy, thermal gravimetric analysis-differential thermal ammnlysis (TGA-DTA), X-ray diffraction (XRD), and micro-Raman spectroscopy. Through the microscopy analyses, we found that 1.5 ${\mu}m$ super-fine tetrahedral diamonds were synthesized for Zn coated Kovar cell with whole range of pressure while ~3 ${\mu}m$ super-fine diamond for conventional Kovar cell with < 10.6 GPa. Based on $750^{\circ}C$ exothermic reaction of diamonds in TGA-DTA, and characteristic peaks of the diamonds in XRD and micro-Raman analysis, we could confirm that the diamonds were successfully formed with the whole pressure range in this research. Finally, we propose a new process for super-fine diamonds by lowering the pressure condition and employing Zn electroplated Kovar disks.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.291.1-291.1
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• 2014

산화아연 박막은 아연이 코팅된 테프론 기판 위에 졸-겔 스핀코팅 방법을 이용하여 각기 다른 후열처리 온도에서 제작되었다. 산화아연 박막의 후열처리 온도에 따른 구조적, 광학적 특성은 field emission scanning electron microscopy (FE-SEM), X-ray diffractometer, and photoluminescence spectroscope를 이용하여 분석하였다. 후열처리 온도를 달리하여 성장한 모든 산화아연 박막은 수지상(dendrite) 구조를 가지고 있으며, 이 수지상 구조 위에 약 20 nm의 산화아연 입자들이 성장되었다. 후열처리 온도가 증가함에 따라 c-축 배향성이 우세하게 나타났으며, 인장응력도 증가하였다. 후열처리 온도 $400^{\circ}C$에서 Near-band-edge emission (NBE) 피크는 적색편이(red-shift) 하였고, 후열처리 온도가 증가함에 따라 deep-level emission (DLE) 피크의 세기는 감소하였다. 또한 $400^{\circ}C$의 후열처리 온도에서 NBE 피크의 반치폭(FWHM)이 가장 작았으며, INBE/IDLE의 비율이 가장 높았다. 따라서 $400^{\circ}C$의 후열처리 공정에 의해 결정성 및 광학적 특성이 가장 우수한 산화아연 박막을 얻을 수 있었다.

• Korean Journal of Materials Research
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• v.30 no.8
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• pp.399-405
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• 2020

In the present investigation we show the effect of Al doping on the length, size, shape, morphology, and sensing property of ZnO nanorods. Effect of Al doping ultimately leads to tuning of electrical and optical properties of ZnO nanorods. Undoped and Al-doped well aligned ZnO nanorods are grown on sputtered ZnO/SiO₂/Si (100) pre-grown seed layer substrates by hydrothermal method. The molar ratio of dopant (aluminium nitrate) in the solution, [Al/Zn], is varied from 0.1 % to 3 %. To extract structural and microstructural information we employ field emission scanning electron microscopy and X-ray diffraction techniques. The prepared ZnO nanorods show preferred orientation of ZnO <0001> and are well aligned vertically. The effects of Al doping on the electrical and optical properties are observed by Hall measurement and photoluminescence spectroscopy, respectively, at room temperature. We observe that the diameter and resistivity of the nanorods reach their lowest levels, the carrier concentration becomes high, and emission peak tends to approach the band edge emission of ZnO around 0.5% of Al doping. Sensing behavior of the grown ZnO nanorod samples is tested for H₂ gas. The 0.5 mol% Al-doped sample shows highest sensitivity values of ~ 60 % at 250 ℃ and ~ 50 % at 220 ℃.

• Korean Journal of Materials Research
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• v.31 no.10
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• pp.582-585
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• 2021

Y₂O₃:Eu_x (x = 0.005, 0.01, 0.02, 0.03, 0.05, 0.1 mol) phosphors are synthesized with different concentrations of Eu³⁺ ions by solvothermal method. The crystal structure, surface and optical properties of the Eu doped Y₂O₃ phosphors are investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and photoluminescence (PL) and photoluminescence excitation (PLE) analyses. From X-ray diffraction (XRD) results, the crystal structure of the Eu doped Y₂O₃ phosphor is found to be cubic. The maximum emission spectra of the Eu doped Y₂O₃ phosphors are observed at 0.05 mol Eu³⁺ concentration. The photoluminescence of 615 nm in the Eu doped Y₂O₃ phosphors is associated with ⁵D₀ → ⁷F₂ transition of Eu³⁺ ions. The decrease in emission intensity of 0.1 mol Eu doped Y₂O₃ is interpreted by concentration quenching. The International Commission on Illumination (CIE) coordinates of 0.05 mol Eu doped Y₂O₃ phosphor are X = 0.6547, Y = 0.3374.

• Journal of the Korean Vacuum Society
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• v.16 no.3
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• pp.205-209
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• 2007

ZnO thin films were deposited on a Si wafer and a soda lime glass using atomic layer deposition(ALD). The substrate temperature were between $130^{\circ}C{\sim}150^{\circ}C$. The deposition rate of the ZnO film was measured to be $2.72{\AA}$ per cycle. The films were analyzed using field emission scanning electron microscopy(FESEM), X-ray diffractometer(XRD), and Auger electron spectroscopy(AES). Impurity-free ZnO thin films were obtained and the crystallinity was found to be dependant upon the substrate temperature.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.445.1-445.1
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• 2014

Dye-sensitized solar cells (DSSCs) have been widely investigated as a next-generation solar cell because of their simple structure and low manufacturing cost. The $TiO_2$ film with thickness of $8{\sim}10{\mu}m$, which consists of nanoparticles, acts as both a scaffold with a high surface-to-volume ratio for the dye loading and a pathway to remove the electrons. However, charge carriers have to move across many particle boundaries by a hopping mechanism. So, one dimensional nanostructures such as nanotubes, nanorods and nanowires should improve charge carrier transportation by providing a facile direct electron pathway and lowering the diffusion resistance. However, the efficiencies of DSSCs using one dimensional nanostructures are less than the $TiO_2$ nanoparticle-based DSSCs. In this work, the patterned $TiO_2$ film with thickness of $3{\mu}m$ was deposited using photolithography process to decrease of electron pathway and increase of surface area and transmittance of $TiO_2$ films. Properties of the patterned $TiO_2$ films were investigated by various analysis method such as X-ray diffraction, field emission scanning electron microscopy (FESEM) and UV-visible spectrophotometer.