• Journal of Ocean Engineering and Technology
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• 제28권4호
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• pp.338-344
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• 2014

The purpose of this study was to evaluate the dispersion degree of particles using a nanoindentation test for titanium oxide nanoparticles/epoxy resin nanocomposites. Thus, the effects of the particle size and weight fraction, dispersion agent, and position of the sample on the modulus and degree of particle dispersion in the nanocomposites were investigated. As a result, the dispersion degree of large particles was found to be better than that of smaller particles in composites. It could be found that the aggregation or agglomeration of small particles with large surface energy occurred more easily in nanocomposites because of the large specific surface area. The moduli of the upper side of the film-shaped sample obtained from a nanoindentation test were low scattering, while the values for the bottom side were high scattering. Thus, the dispersion situation of the nanoparticles on the upper side of film-shaped samples could be considered to be better than that for the bottom side. This could be concluded due to the non-uniform nanoparticle dispersion in the same sample. The modulus obtained from nanoindentation test increased slightly with the content of nanoparticles and increased with the indented depth for the same sample. The latter is presumably due to the increase in the accumulated particles facing the indenter with the indented depth. The nanoindentation test was found to be a useful method to evaluate the dispersion status of nanoparticles in nanocomposites.

• Economic and Environmental Geology
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• 제33권1호
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• pp.1-18
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• 2000

Lens shaped and stratiform titanomagnetite orebodies in the Boreumdo iron mine are closely associated with amphibolite which intruded into Precambrian metasediments. Mineralogical and petrochemical analyses of amphilbolite and titanomagnetite ores were carried out in order to interpret the origin of amphilbolite and the genesis of titanomagnetite ore deposits. Amphibolites belong to orthoamphilbolite interms of Niggli value and mineralogy, and are characterized by the occurrence of relict olivine. The amphilbolites responsible for titanomagnetite mineralization have extremely high content of $TiO_2$, ranging from 2.12 to 4.59 wt.% with the average value of 3.43 wt.%. Amphibole minerals in amphibolites are consist mainly of calcic amphiboles such as hornblende, ferroan pargasitic hornblende and tremolite. Most plagioclases belong to andesine ($An_{30-50}$\ulcorner). The metamorphic temperature and geobarometric pressure which are calculated by the calcic amphibole-plagioclase geothermometer and calcic amphilbole geobarometer are estimated to be 537$^{\circ}C$~579$^{\circ}C$(avg. 555$^{\circ}C$) and 2.9~6.6 kbar (avg. 4.5 kbars), respectively. It shows a typical amphibolite facies. Based on the mineral chemistry and petrochemisty of amphibolites and iron ores which are composed mainly of titanomagnetite and ilmenite in the Boreumdo iron mine, the titaniferous oxide melts could be immiscibly separatd from the titaniferous ultrabasic magma. The genesis of the Boreumdo titanomagnetite ore deposits are analogous to the Soyeonpyeongdo and Yonchon iron ore deposits in terms of their mineralogy, mineral chemistry and geologic setting.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 한국윤활학회 2002년도 제35회 춘계학술대회
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• pp.215-225
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• 2002

In order to enhance the thermal stability of binder materials of bonded type solid lubricants, several combinations of metal-alkoxide based sol-gel materials such as methyltrimethoxysilane(MTMOS), $titaniumisopropoxide(Ti(Opr^{j})_{4})$, $zirconiumisopropoxide(Zr(Opr^{j})_{4})$ and $aluminumbutoxide(Al(Obu^{t})_{4})$ were chemically modified by epoxy-, acrylic- and fluoro-silane compounds, respectively, in this work. Friction and wear characteristics of these hybrid ceramic materials were tested with a micro tribe-tester where a reciprocating steel ball slid on a test material, and the tribological property was also evaluated with respect to both heat-curing temperature and tile time. Test results generally showed that hybrid ceramic materials modified by epoxy-silane compounds had a low friction compared to others. And the higher heat-curing temperature and the longer heat treatment time resulted in the higher friction and the lower wear. IR spectroscopic analyses revealed that it was caused mainly by the increased metal oxide content in hybrid ceramics when the heat-curing temperature was over $320^{\circ}C$.

• Journal of the Korean Ceramic Society
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• 제38권3호
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• pp.274-279
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• 2001

Pt/Ti/Si 기판 위에 성장시킨 박막 전지용 비정질 산화 바나듐 박막에 고상 전해질 박막 LiPON을 이용하여 전고상형 박막전지를 제작하여 충-방전 시험을 시행하였다. 이렇게 제작된 전고상형 박막전지는 500 사이클 이상까지 평균 15$\mu$Ah의 방전용량을 나타내었으나 초기 사이클 영역부터 방전 용량의 감소가 일어나기 시작했다. 박막 전지의 방전 용량 감소에 따른 비정질 산화 바나듐 박막의 구조적 특성 변화를 관찰하기 위하여 고분해능 현미경 분석을 시행하였다. 충-방전을 하지 않은 초기의 산화 바나듐 박막은 입계를 갖지 않고 다결정 특성을 보이지 않는 완전한 비정질 특성을 보였고 이는 TED 결과와 일치하였다. 그러나 450번의 반복적인 충-방전을 시행한 후의 비정질 산화 바나듐 박막 내에는 microcrystalline 형태의 산화 바나듐의 형성됨을 고분해능 전자 현미경 분석을 통해 발견할 수 있었다. 비정질 산화바나듐 박막의 방전 용량 감소의 원인인 Li의 비가역적 탈-삽입은 비정질 내에 형성된 microcrystalline에 의해 유발된다고 사료된다. 또한 LiPON 전해질 박막과 산화 바나듐 박막사이의 계면에 Li 이온과 산화바나듐과의 반응에 의해 형성된 계면 층에 발견할 수 있었는데 이러한 계면 층 역시 Li 확산과 계면 저항에 영향을 주어 방전 용량 감소에 원인으로 작용한다.

• Transactions on Electrical and Electronic Materials
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• 제14권1호
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• pp.36-38
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• 2013

Eight sample panels using an indium tin oxide(ITO)-coated glass substrate were fabricated, with barrier ribs formed of 55 ${\mu}m$ height and 10 ${\mu}m$ width. The upper and lower substrates were designed with the same panel condition, so a cell gap of 110 ${\mu}m$ was obtained. The charged particles in a cell consisted of $TiO_2$ (for white color) or carbon black (black color), negative or positive charge control agents, and a polymer. The average diameter of the two types of particles was commonly 10 ${\mu}m$, and their q/m value was -4.5 ${\mu}C/g$ and +4.5 ${\mu}C/g$, respectively. The electrically opposite particles mixed by an agitator were loaded into their cells by a simple particle-loading method. The discharging process proceeded at a humidity of 80% and a temperature of $30^{\circ}C$. Reflectivity was measured depending on discharging time, and a hysteresis curve by bias voltage obtained for comparison between the neutralized and non-neutralized panel, in which the superior optical property of the neutralized panel was ascertained.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제25권2호
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• pp.91-95
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• 2012

ZnO thin films were deposited on p-type 4H-SiC substrate by pulsed laser deposition. ZnO nanowires were formed on p-type 4H-SiC substrate by furnace. Ti/Au electrodes were deposited on ZnO thin film/SiC and ZnO nanowire/SiC structures, respectively. Structural and crystallographical properties of the fabricated ZnO thin film/SiC and ZnO nanowire/SiC structures were investigated by field emission scanning electron microscope and X-ray diffraction. In this work, resistance and sensitivity of ZnO thin film/SiC gas sensor and ZnO nanowire/SiC gas sensor were measured at $300^{\circ}C$ with various CO gas concentrations (0%, 90%, 70%, and 50%). Resistance of gas sensor decreases at CO gas atmosphere. Sensitivity of ZnO nanowire/SiC gas sensor is twice as big as sensitivity of ZnO thin film/SiC gas sensor.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.290-290
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• 2013

플라즈마 전해산화(Plasma Electrolytic Oxidation)란 저 농도의 알칼리 전해액을 매개로, 고전압을 가해 미세 플라즈마 방전을 유도하여 Al, Mg, Ti 등의 금속표면을 산화시켜 고내식성, 초경합금 수준의 내마모성, 탁월한 절연성과 고경도성을 가지는 산화막을 형성시키는 기술로 전자, 자동차, 의료, 섬유, 해양, 석유화학 산업에 이르기까지 광범위한 분야에 적용되어 우수한 물성을 확보할 수 있는 차세대의 표면처리 기술이다. 본 연구에서는 6061 알루미늄 합금을 이용하여 다양한 전해액 조건에서 플라즈마 전해산화 공정으로 Al2O3 산화막을 형성시켰다. 산화막의 조성 및 미세구조는 XRD와 FE-SEM, EDS를 이용하여 분석하였다. 형성된 산화막은 회색에서 밝은 회색으로 시편 전면에 고르게 나타났다. 전해액 조성을 바꾸어줌에 따라 각기 다른 표면 특성을 가지는 산화막을 얻을 수 있었고, 그에 따른 물성 변화를 분석하였다. 특히 Si 이온 농도를 조절함으로써 피막 성장인자와 표면 미세구조를 제어할 수 있었다.

• Proceedings of the KAIS Fall Conference
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• 한국산학기술학회 2011년도 춘계학술논문집 2부
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• pp.836-839
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• 2011

염료감응형 태양전지의 상대전극으로 MWCNT(multi-walled carbon nanotube)의 농도 (0.01~0.06g)를 달리하여 FTO(fluorine-doped tin oxide) glass에 분산시켜 상대전극을 만들었다. 그리고 glass/FTO/$TiO_2$/Dye(N719)/electrolyte(C6DMII,GSCN)/MWCNT/FTO/glass 구조를 가진 0.45$cm^2$급 DSSC(dye-sensitized solar cells) 소자를 만들었다. 소자의 미세구조, 분산정도, 광특성은 각각 광학현미경, SEM, source measure unit (Keithley model 2400) 장비를 이용하여 확인하였다. MWCNT 농도 증가와 FTO의 거친 표면형상에 따라 비선형적으로 MWCNT 분산면적이 증가하였고, MWCNT 농도 0.06g일 때 FTO 표면에 전체적으로 MWCNT가 완전히 분산됨을 확인하였다. 소자의 광변환 효율은 MWCNT 분산면적에 비례하는 효율을 보였고, MWCNT 분산농도인 0.06g 일 때 4.49%의 광변환 효율을 얻을 수 있었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.581-584
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• 2002

In this work, a CPW resonator was designed and fabricated to investigate the basic microwave properties, such as effective dielectric constant, of BST thin films. Their properties were used as basic data to simulate and design CPW tunable bandpass filter. We also report on gold/$Ba_{0.5}Sr_{0.5}TiO_3$(BST) ferroelectric thin film C-band tunable bandpass filters(BPFs) designed and fabricated on magnesium oxide substrates using CPW structure. The 2 pole filter was designed for a center frequency of 5.88 GHz with a bandwidth of 9 %. The BST based CPW filter offers a high sensitivity parameter as well as a low loss parameter. The tuning range for the bandpass filter with CPW structure was determined to be 170 MHz.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.746-748
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• 2002

The effect of $MnO_2$ addition in $0.05Pb(Sn_{0.5}Sb_{0.5})O_3-0.8PbZrO_3-0.15PbTiO_3$(0.05PSS-0.8PZ-0.15PT) ceramics on crystal structure and electrical properties were studied. The sintering temperature and time were $1230^{\circ}C{\sim}1270^{\circ}C$ and 2hr, respectively. Then crystal structure, dielectric and pyroelectric properties were investigated. All the poled specimens showed the lower dielectric constant and $tan{\delta}$ than the unpoled specimens. Dielectric constant at 1kHz of the 0.05PSS-0.8PZ-0.15PT(MnO2 0.3wt%) system specimen sintered at $1250^{\circ}C$ for 2hr were 270 and showed the lowest $tan{\delta}$ of 0.2% after poling of $2kV_{DC}/mm$ at $150^{\circ}C$ for 30 minutes. Pyroelectric coefficient was maximum value of $50nC/cm^2K$ and Curie temperature was $224^{\circ}C$.