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Preparation of Poly(vinylpyrrolidone) Coated Iron Oxide Nanoparticles for Contrast Agent (조영제로 활용하기 위한 폴리(비닐피롤리돈)이 코팅된 산화철 나노 입자의 제조)

  • Lee Ha Young;Lim Nak Hyun;Seo Jin A;Khang Gilson;Kim Jungahn;Lee Hai Bang;Cho Sun Hang
    • Polymer(Korea)
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    • v.29 no.3
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    • pp.266-270
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    • 2005
  • Iron oxide nanoparticles were prepared by the thermal decomposition of iron pentacarbonyl (Fe(CO)5) Poly(vinylpyrrolidone) (PVP) was used as surface-modifying agent to control the size of the iron oxide nanoparticles. The crystalline structure of PVP coated iron oxide nanoparticles was determined by XRD. The size of PVP coated iron oxide nanoparticles was determined by TEM and ELS. The particle sizes of PVP coated iron oxide nanoparticles were controlled by adjusting the molar ratio of PVP/Fe (CO)5, solvent and molecular weight of PVP Particle sizes increased with increasing PVP content. Spherical 50\~100 nm sized iron oxide nanoclusters were produced when dimethylformamide was used as a solvent. And well-defined 10 nm iron oxide nanoparticles were produced in Carbitol. The prepared PVP coated iron oxide nanoparticles exhibited a well-dispersed property in water. The results obtained in this study confirmed the feasibility of the PVP-coated iron oxide nanoparticles as a biomaterial for MRI contrast agent.

Fabrication of TiO2 Electrode Containing Scattering Particles in Dye-Sensitized Solar Cells (산란 입자를 포함하는 염료감응 태양전지용 TiO2 전극 제조)

  • Lee, Jin-Hyoung;Lee, Tae-Kun;Kim, Cheol-Jin
    • Journal of the Microelectronics and Packaging Society
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    • v.18 no.2
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    • pp.57-62
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    • 2011
  • The energy conversion efficiency of DSSCs (Dye-Sensitized Solar Cells) is dependent on the powder size, the structure, and the morphology of TiO2 electrode. The higher efficiency is obtained with high surface area of the nanoanatase-TiO2 powder adsorbed onto a lot more of the dye. Also, the enhancement of light scattering increases the efficiency with high adsorption of the dye. Powder size, crystalline phase, and shape of TiO2 obtained by hydrothermal method have 15-20 nm, anatase and round. TiO2 electrode has fabricated with the mixture of scattering TiO2 particle with 0.4 μm in nano-sized powder. Conversion efficiency of series of DSSCs was measured with volume fraction of scattering particle. Photovoltaic characteristics of DSSCs with 10% scattering particles are 3.51 mA for Jsc (short circuit current), 0.79 V for Voc(open circuit potential), filling factor 0.619 and 6.86% for efficiency. Jsc was improved by 11% and enhancement of efficiency by 0.77% compared with that of no scattering particles. The confinement of inserted light by light scattering particles has more increase of the injection of exiton(electron-hole pair) and decrease of moving path in electron. Efficiencies of DSSCs with more than 10% for scattering particles have reduced with increasing the pore in the TiO2 electrode.

Residual Stress and Elastic Modulus of Y2O3 Coating Deposited by EB-PVD and its Effects on Surface Crack Formation

  • Kim, Dae-Min;Han, Yoon-Soo;Kim, Seongwon;Oh, Yoon-Suk;Lim, Dae-Soon;Kim, Hyung-Tae;Lee, Sung-Min
    • Journal of the Korean Ceramic Society
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    • v.52 no.6
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    • pp.410-416
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    • 2015
  • Recently, a new Y2O3 coating deposited using the EB-PVD method has been developed for erosion resistant applications in fluorocarbon plasma environments. In this study, surface crack formation in the Y2O3 coating has been analyzed in terms of residual stress and elastic modulus. The coating, deposited on silicon substrate at temperatures higher than 600C, showed itself to be sound, without surface cracks. When the residual stress of the coating was measured using the Stoney formula, it was found to be considerably lower than the value calculated using the elastic modulus and thermal expansion coefficient of bulk Y2O3. In addition, amorphous SiO2 and crystalline Al2O3 coatings were similarly prepared and their residual stresses were compared to the calculated values. From nano-indentation measurement, the elastic modulus of the Y2O3 coating in the direction parallel to the coating surface was found to be lower than that in the normal direction. The lower modulus in the parallel direction was confirmed independently using the load-deflection curves of a micro-cantilever made of Y2O3 coating and from the average residual stress-temperature curve of the coated sample. The elastic modulus in these experiments was around 33 ~ 35 GPa, which is much lower than that of a sintered bulk sample. Thus, this low elastic modulus, which may come from the columnar feather-like structure of the coating, contributed to decreasing the average residual tensile stress. Finally, in terms of toughness and thermal cycling stability, the implications of the lowered elastic modulus are discussed.

An Introduction to Kinetic Monte Carlo Methods for Nano-scale Diffusion Process Modeling (나노 스케일 확산 공정 모사를 위한 동력학적 몬테칼로 소개)

  • Hwang, Chi-Ok;Seo, Ji-Hyun;Kwon, Oh-Seob;Kim, Ki-Dong;Won, Tae-Young
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.41 no.6
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    • pp.25-31
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    • 2004
  • In this paper, we introduce kinetic Monte Carlo (kMC) methods for simulating diffusion process in nano-scale device fabrication. At first, we review kMC theory and backgrounds and give a simple point defect diffusion process modeling in thermal annealing after ion (electron) implantation into Si crystalline substrate to help understand kinetic Monte Carlo methods. kMC is a kind of Monte Carlo but can simulate time evolution of diffusion process through Poisson probabilistic process. In kMC diffusion process, instead of. solving differential reaction-diffusion equations via conventional finite difference or element methods, it is based on a series of chemical reaction (between atoms and/or defects) or diffusion events according to event rates of all possible events. Every event has its own event rate and time evolution of semiconductor diffusion process is directly simulated. Those event rates can be derived either directly from molecular dynamics (MD) or first-principles (ab-initio) calculations, or from experimental data.

Growth of Graphene Films from Solid-state Carbon Sources

  • Kwak, Jinsung;Kwon, Tae-Yang;Chu, Jae Hwan;Choi, Jae-Kyung;Lee, Mi-Sun;Kim, Sung Youb;Shin, Hyung-Joon;Park, Kibog;Park, Jang-Ung;Kwon, Soon-Yong
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.181.2-181.2
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    • 2014
  • A single-layer graphene has been uniformly grown on a Cu surface at elevated temperatures by thermally processing a poly (methyl methacrylate) (PMMA) film in a rapid thermal annealing (RTA) system under vacuum. The detailed chemistry of the transition from solid-state carbon to graphene on the catalytic Cu surface was investigated by performing in-situ residual gas analysis while PMMA/Cu-foil samples being heated, in conjunction with interrupted growth studies to reconstruct ex-situ the heating process. We found that the gas species of mass/charge (m/e) ratio of 15 (CH3+) was mainly originated from the thermal decomposition of PMMA, indicating that the formation of graphene occurs with hydrocarbon molecules vaporized from PMMA, such as methane and/or methyl radicals, as precursors rather than by the direct graphitization of solid-state carbon. We also found that the temperature for dominantly vaporizing hydrocarbon molecules from PMMA and the length of time, the gaseous hydrocarbon atmosphere is maintained, are dependent on both the heating temperature profile and the amount of a solid carbon feedstock. From those results, we strongly suggest that the heating rate and the amount of solid carbon are the dominant factors to determine the crystalline quality of the resulting graphene film. Under optimal growth conditions, the PMMA-derived graphene was found to have a carrier (hole) mobility as high as 2,700cm2V1s1 at room temperature, which is superior to common graphene converted from solid carbon.

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Properties of AlN epilayer grown on 6H-SiC substrate by mixed-source HVPE method (6H-SiC 기판 위에 혼합소스 HVPE 방법으로 성장된 AlN 에피층 특성)

  • Park, Jung Hyun;Kim, Kyoung Hwa;Jeon, Injun;Ahn, Hyung Soo;Yang, Min;Yi, Sam Nyung;Cho, Chae Ryong;Kim, Suck-Whan
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.30 no.3
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    • pp.96-102
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    • 2020
  • In this paper, AlN epilayers on 6H-SiC (0001) substrate are grown by mixed source hydride vapor phase epitaxy (MS-HVPE). AlN epilayer of 0.5 ㎛ thickness was obtained with a growth rate of 5 nm per hour. The surface of AlN epilayer grown on 6H-SiC (0001) substrate was investigated by field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDS). Dislocation density was considered through HR-XRD and related calculations. A fine crystalline AlN epilayer with screw dislocation density of 1.4 × 109 cm-2 and edge dislocation density of 3.8 × 109 cm-2 was confirmed. The AlN epilayer on 6H-SiC (0001) substrate grown by using the mixed source HVPE method could be applied to power devices.

Hydrogen production using CdS-TiO2 composite photocatalysts (CdS-TiO2 복합 광촉매계에 의한 수소제조)

  • Kim, Soo-Sun;Jang, Jum-Suk;So, Won-Wook;Kim, Kwang-Je;Moon, Sang-Jin
    • Journal of Hydrogen and New Energy
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    • v.11 no.4
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    • pp.161-169
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    • 2000
  • In the case of photocatalytic hydrogen production from water, the performance-property relationships of CdS-TiO2 film type composite catalysts were investigated. To control the physical properties of the primary particles, the mixture of CdS and TiO2 nano-sols prepared by the sol-gel method at room temperature was hydrothermally treated at 240oC for 12hr. The film electrodes were prepared by the casting method. The photocurrents measured by a photoelectrochemical method and the hydrogen production rates measured by a photochemical method were closely dependent on the physical properties such as crystalline form, primary particle size and CdS/TiO2 mole ratio, and these varied in the range of 1.2~2.6 mA/cm2 and 1.01.6×103mol/hr, respectively.

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In-situ Observations of Gas Phase Dynamics During Graphene Growth Using Solid-State Carbon Sources

  • Kwon, Tae-Yang;Kwak, Jinsung;Chu, Jae Hwan;Choi, Jae-Kyung;Lee, Mi-Sun;Kim, Sung Youb;Shin, Hyung-Joon;Park, Kibog;Park, Jang-Ung;Kwon, Soon-Yong
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.08a
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    • pp.131-131
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    • 2013
  • A single-layer graphene has been uniformly grown on a Cu surface at elevated temperatures by thermally processing a poly(methyl methacrylate) (PMMA) film in a rapid thermal annealing (RTA) system under vacuum. The detailed chemistry of the transition from solid-state carbon to graphene on the catalytic Cu surface was investigated by performing in-situ residual gas analysis while PMMA/Cu-foil samples being heated, in conjunction with interrupted growth studies to reconstruct ex-situ the heating process. The data clearly show that the formation of graphene occurs with hydrocarbon molecules vaporized from PMMA, such as methane and/or methyl radicals, as precursors rather than by the direct graphitization of solid-state carbon. We also found that the temperature for vaporizing hydrocarbon molecules from PMMA and the length of time the gaseous hydrocarbon atmosphere is maintained, which are dependent on both the heating temperature profile and the amount of a solid carbon feedstock are the dominant factors to determine the crystalline quality of the resulting graphene film. Under optimal growth conditions, the PMMA-derived graphene was found to have a carrier (hole) mobility as high as ~2,700 cm2V-1s-1 at room temperature, superior to common graphene converted from solid carbon.

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Property of Nickel Silicides with Hydrogenated Amorphous Silicon Thickness Prepared by Low Temperature Process (나노급 수소화된 비정질 실리콘층 두께에 따른 저온형성 니켈실리사이드의 물성 연구)

  • Kim, Jongryul;Choi, Youngyoun;Park, Jongsung;Song, Ohsung
    • Korean Journal of Metals and Materials
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    • v.46 no.11
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    • pp.762-769
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    • 2008
  • Hydrogenated amorphous silicon(a-Si : H) layers, 120 nm and 50 nm in thickness, were deposited on 200 nmSiO2/single-Si substrates by inductively coupled plasma chemical vapor deposition(ICP-CVD). Subsequently, 30 nm-Ni layers were deposited by E-beam evaporation. Finally, 30 nm-Ni/120 nm a-Si : H/200 nmSiO2/single-Si and 30 nm-Ni/50 nm a-Si:H/200 nmSiO2/single-Si were prepared. The prepared samples were annealed by rapid thermal annealing(RTA) from 200C to 500C in 50C increments for 30 minute. A four-point tester, high resolution X-ray diffraction(HRXRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and scanning probe microscopy(SPM) were used to examine the sheet resistance, phase transformation, in-plane microstructure, cross-sectional microstructure, and surface roughness, respectively. The nickel silicide on the 120 nm a-Si:H substrate showed high sheet resistance(470Ω/) at T(temperature) < 450C and low sheet resistance (70Ω/) at T > 450C. The high and low resistive regions contained ζNi2Si and NiSi, respectively. In case of microstructure showed mixed phase of nickel silicide and a-Si:H on the residual a-Si:H layer at T < 450C but no mixed phase and a residual a-Si:H layer at T > 450C. The surface roughness matched the phase transformation according to the silicidation temperature. The nickel silicide on the 50 nm a-Si:H substrate had high sheet resistance(1kΩ/) at T < 400C and low sheet resistance (100Ω/) at T > 400C. This was attributed to the formation of δNi2Si at T > 400C regardless of the siliciation temperature. An examination of the microstructure showed a region of nickel silicide at T < 400C that consisted of a mixed phase of nickel silicide and a-Si:H without a residual a-Si:H layer. The region at T > 400C showed crystalline nickel silicide without a mixed phase. The surface roughness remained constant regardless of the silicidation temperature. Our results suggest that a 50 nm a-Si:H nickel silicide layer is advantageous of the active layer of a thin film transistor(TFT) when applying a nano-thick layer with a constant sheet resistance, surface roughness, and δNi2Si temperatures > 400C.

Immobilization of As and Pb in Contaminated Soil Using Bead Type Amendment Prepared by Iron NanoparticlesImpregnated Biochar (철 나노 입자가 담지된 바이오차 기반 비드 형태 안정화제를 이용한 비소 및 납 오염토양의 안정화)

  • Choi, Yu-Lim;Kim, Dong-Su;Kang, Tae-Jun;Yang, Jae-Kyu;Chang, Yoon-Young
    • Journal of Environmental Impact Assessment
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    • v.30 no.4
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    • pp.247-257
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    • 2021
  • In this work, Iron Nano-Particles Impregnated BioChar/bead (INPBC/bead) soil amendment was developed to increase biochar's reactivity to As in soil and preventing possible wind loss. Prior to preparation of INPBC/bead, INPBC was produced utilizing lignocellulosic biomass and Fe(III) solution in a hydrothermal method, followed by a calcination process. Then, the bead type amendment, INPBC/bead was produced by cross-linking reaction of alginate with INPBC. FT-IR, XRD, BET, and SEM-EDS analyses were utilized to characterize the as-synthesised materials. The particle size range of INPBC/bead was 1-4 mm, and different oxygen-containing functional groups and Fe3O4 crystalline phase were produced on the surface of INPBC/bead, according to the characterization results. The soil cultivation test was carried out in order to assess the stabilization performance of INPBC/bead utilizing As and Pb-contaminated soil obtained from an abandoned mining location in South Korea. After 4 weeks of culture, TCLP and SPLP extraction tests were performed to assess the stabilization efficacy of the amendment. The TCLP and SPLP findings revealed that raising the application ratio improved stabilizing efficiency. The As stabilization efficiency was determined to be 81.56 % based on SPLP test findings for a 5% in (w/w) INPBC/bead treatment, and the content of Pb in extracts was reduced to the limit of detection. According to the findings of this study, INPBC/bead that can maintain pH of origin soil and minimize wind loss might be a potential amendment for soil polluted with As and heavy metals.