• Applied Chemistry for Engineering
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• v.10 no.1
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• pp.1-5
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• 1999

The dispersing performance of oligomer-type anionic surfactants ($C_mD-Na$), cooligomers of diethylester maleate and alkylvinylether of different alkyl chain lengths or polymerization degree were studied on the aqueous suspension of iron dxide or titanium dioxide particles which are hydrophilic pigments. The dispersion behavior of oligomer-type surfactants for these dispersoids, although anion charges on the surface of pigments particles showed different dispersing properties, was dependent upon the side alkyl chain length. Oligomer-type surfactants having more than $C_8$ side alkyl chain exhibited large dispersing action for relatively hydrophobic ${\alpha}-Fe_2O_3$ and Anatase $TiO_2$ in the concentration range of more than 0.1% oligomer-type surfactant solutions.

• Journal of the Korean Institute of Gas
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• v.24 no.5
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• pp.39-46
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• 2020

This paper is considered about centerline segregation of API 5L steel used in pipeline. Mn/S, Nb and C were known as segregated elements in the centerline of pipe thickness. The Mn usually was accompanied by S consisting of long viscous shape. Microstructure of the centerline was composed of MnS and Nb/Ti indusions including oxide. The segregation effect in centerline region was analyzed by OM, SEM/EDS and micro Vickers hardness. The Mn, Nb and C are retarded elements in transformation from austenite to ferrite or martensite. These elements could derive a bainitic microstructure as a kind of martensite, which is different from difference and element segregation between in matrix and centerline derived from steel melting and heat treatment.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.88-88
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• 2009

실리콘 이종접합 태양전지 제작을 위한 주요 요소기술 중 TCO/a-Si:H 간의 계면 특성은 태양전지 효율을 결정하는 주요 인자이다. 일반적으로 투명전도 산화막으로는 ZnO:Al 또는 ITO 가 사용되고 있으며 Zn, In, Sn, O 등의 확산과 Si원소의 확산으로 TCO/a-Si:H 계면에서 $SiO_x$가 생성되어 태양전지 충진률을 감소시키는 영향을 미친다. 따라서 본 연구에서는 TCO/a-Si 계면에서 확산을 방지 하면서 패시베이션 역할을 하는 완충층을 삽입하여 실리콘 이종접합 태양전지의 효율을 높이는 연구를 수행하였다. 완충층으로 사용된 ZnO:Al의 수소화와 Zn 박막, $TiO_2$ 박막의 전기 광학적 특성을 분석하였고 AES 분석을 통해 $SiO_x$의 생성과 각 원소의 확산정도를 분석하고, CTLM을 이용하여 TCO/완충층/a-Si 간의 접촉저항을 측정하였다. 결과적으로 완충층으로 사용된 $TiO_2$(5nm)는 광특성에 큰 감소요인 없이 전기적 특성과 접촉저항 특성이 우수하였으며, 원소들간의 확산방지층으로도 우수한 특성을 보였다. ZnO:Al의 수소화는 SIMS 분석 결과 수소원소들이 계면쪽에 위치하지 않고 표면쪽에 다수 존재함으로써 패시베이션 특성을 크게 보이지 않았으나 AZO 박막의 전기적 특성은 크게 향상 시켰다. 그밖에 완충층으로 사용된 Zn 박막은 두께가 두꺼원 질수록 접촉저항의 감소를 가져왔으나 광학적 특성이 크게 감소하면서 효율적인 광포획 특성을 가지지 못하였다. 본 연구를 통하여 TCO/a-Si:H 간의 완충층 삽입을 통해 접촉저항을 낮추고 원소간의 확산을 억제하여 계면 패시베이션 특성을 향상 시킬수 있었다.

• Journal of Sensor Science and Technology
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• v.23 no.5
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• pp.337-341
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• 2014

For various additives doped-$VO_2$ critical temperature sensors using the nature of semiconductor to metal transition, the crystallinity, microstructure, and temperature vs. resistance characteristics were systematically investigated. As a starting material of $VO_2$ sensor, vanadium pentoxide ($V_2O_5$) powders were used, and CaO, SrO, $Bi_2O_3$, $TiO_2$, and PbO dopants were used, respectively. The $V_2O_5$ powders with dopants were mixed with a vehicle to form paste. This paste was silk screen-printed on $Al_2O_3$ substrates and then $V_2O_5$-based thick films were heat-treated at $500^{\circ}C$ for 2 hours in $N_2$ gas atmosphere for the reduction to $VO_2$. From X-ray diffraction analysis, $VO_2$ phases for pure $VO_2$, and CaO and SrO-doped $VO_2$ thick films were confirmed and their grain sizes were 0.57 to $0.59{\mu}m$. The on/off resistance ratio of the $VO_2$ sensor in phase transition temperature range was $5.3{\times}10^3$ and that of the 0.5 wt.% CaO-doped $VO_2$ sensor was $5.46{\times}10^3$. The presented critical temperature sensors could be commercialized for fire-protection and control systems.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.319-319
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• 2013

Even though the fabrication methods of metal oxide based thin film capacitor have been well established such as RF sputtering, Sol-gel, metal organic chemical vapor deposition (MOCVD), ion beam assisted deposition (IBAD) and pulsed laser deposition (PLD), an applicable capacitor of printed circuit board (PCB) has not realized yet by these methods. Barium Strontium Titanate (BST) and other high-k ceramic oxides are important materials used in integrated passive devices, multi-chip modules (MCM), high-density interconnect, and chip-scale packaging. Thin film multi-layer technology is strongly demanded for having high capacitance (120 nF/$mm^2$). In this study, we suggest novel multi-layer thin film capacitor design and fabrication technology utilized by plasma assisted deposition and photolithography processes. Ba0.6Sr0.4TiO3 (BST) was used for the dielectric material since it has high dielectric constant and low dielectric loss. 5-layered BST and Pt thin films with multi-layer sandwich structures were formed on Pt/Ti/$SiO_2$/Si substrate by RF-magnetron sputtering and DC-sputtering. Pt electrodes and BST layers were patterned to reveal internal electrodes by photolithography. SiO2 passivation layer was deposited by plasma-enhanced chemical vapor deposition (PE-CVD). The passivation layer plays an important role to prevent short connection between the electrodes. It was patterned to create holes for the connection between internal electrodes and external electrodes by reactive-ion etching (RIE). External contact pads were formed by Pt electrodes. The microstructure and dielectric characteristics of the capacitors were investigated by scanning electron microscopy (SEM) and impedance analyzer, respectively. In conclusion, the 0402 sized thin film multi-layer capacitors have been demonstrated, which have capacitance of 10 nF. They are expected to be used for decoupling purpose and have been fabricated with high yield.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.438-439
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• 2013

Microelectronic devices의 접촉저항의 향상을 위해 Metal silicides의 형성 mechanism과 전기적 특성에 대한 연구가 많이 이루어지고 있다. 지난 수십년에 걸쳐, Ti silicide, Co silicide, Ni silicide 등에 대한 개발이 이루어져 왔으나, 계속적인 저저항 접촉 소재에 대한 요구에 의해 최근에는 Rare earth silicide에 관한 연구가 시작되고 있다. Rare-earth silicide는 저온에서 silicides를 형성하고, n-type Si과 낮은 schottky barrier contact (~0.3 eV)를 이룬다. 또한, 비교적 낮은 resistivity와 hexagonal AlB2 crystal structure에 의해 Si과 좋은 lattice match를 가져 Si wafer에서 high quality silicide thin film을 성장시킬 수 있다. Rare earth silicides 중에서 ytterbium silicide는 가장 낮은 electric work function을 갖고 있어 낮은 schottky barrier 응용에서 쓰이고 있다. 이로 인해, n-channel schottky barrier MOSFETs의 source/drain으로써 주목받고 있다. 특히 ytterbium과 molybdenum co-deposition을 하여 증착할 경우 thin film 형성에 있어 안정적인 morphology를 나타낸다. 또한, ytterbium silicide와 마찬가지로 낮은 면저항과 electric work function을 갖는다. 그러나 ytterbium silicide에 molybdenum을 화합물로써 높은 농도로 포함할 경우 높은 schottky barrier를 형성하고 epitaxial growth를 방해하여 silicide film의 quality 저하를 야기할 수 있다. 본 연구에서는 ytterbium과 molybdenum의 co-deposition에 따른 silicide 형성과 전기적 특성 변화에 대한 자세한 분석을 TEM, 4-probe point 등의 다양한 분석 도구를 이용하여 진행하였다. Ytterbium과 molybdenum을 co-deposition하기 위하여 기판으로 $1{\sim}0{\Omega}{\cdot}cm$의 비저항을 갖는 low doped n-type Si (100) bulk wafer를 사용하였다. Native oxide layer를 제거하기 위해 1%의 hydrofluoric (HF) acid solution에 wafer를 세정하였다. 그리고 고진공에서 RF sputtering 법을 이용하여 Ytterbium과 molybdenum을 동시에 증착하였다. RE metal의 경우 oxygen과 높은 반응성을 가지므로 oxidation을 막기 위해 그 위에 capping layer로 100 nm 두께의 TiN을 증착하였다. 증착 후, 진공 분위기에서 rapid thermal anneal(RTA)을 이용하여 $300{\sim}700^{\circ}C$에서 각각 1분간 열처리하여 ytterbium silicides를 형성하였다. 전기적 특성 평가를 위한 sheet resistance 측정은 4-point probe를 사용하였고, Mo doped ytterbium silicide와 Si interface의 atomic scale의 미세 구조를 통한 Mo doped ytterbium silicide의 형성 mechanism 분석을 위하여 trasmission electron microscopy (JEM-2100F)를 이용하였다.

• Journal of Conservation Science
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• v.8 no.1 s.11
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• pp.10-15
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• 1999

The chemical compositions and microstructure of the punch'ong excavated from Bokwangri, Kangnung were investigated by the scanning electron microscope (SEM) with an energy dispersive X-ray spectrometer (EDS), X-ray diffractometer (XRD), and dilatometer. The compositions of body were $SiO_2(73-78\%),\;Al_2O_3(13-16\%)$, $RO{\cdot}R_2O(4-5\%,\;R=Ca,\;Mg,\;Na,\;K),\;R_xO_y(3-6\%,\;R=Fe,Ti)$ in weight ratio, which were higher silica and flux $(RO{\cdot}R_2O)$ but lower alumina. Owing to the high content$(21-30\%)$ of calcium oxide the glaze is considered lime type. Firing temperature range for the ceramic was presumed to about $1150^{\circ}C$.

• Journal of Sensor Science and Technology
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• v.10 no.3
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• pp.173-179
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• 2001

The currently used semiconductor pressure sensors are piezoresistive and capacitive type. Especially, semiconductor micro pressure sensors have a great deal of attention because of their small size. However, its fabrication processes are difficult, so that its yield is poor. For the purpose of resolving the drawbacks of the existing silicon pressure sensors, we demonstrate a new type of pressure sensor using PSFET(pressure sensitive field effect transistor) and investigate its operational characteristics. We used PZT(Pb(Zr,Ti)$O_3$) as a pressure sensing material. PZT thin films were deposited on a gate oxide of MOSFET by an rf-magnetron sputtering method. To abtain the stable phase, perovskite structure, furnace annealing technique have been employed in PbO ambient. The sensitivity of the PSFET was 0.38 mV/mmHg.

• Korean Journal of Materials Research
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• v.14 no.11
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• pp.813-820
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• 2004

The electrolytic reduction of spent oxide fuel involves the liberation of oxygen in a molten LiCl electrolyte, which is a chemically aggressive environment that is very corrosive for typical structural materials. So, it is essential to choose the optimum material for the process equipment handling molten salt. In this study, corrosion behavior of Haynes 263, 75, and Inconel X-750, 718 in molten salt of $LiCl-Li_{2}O$ under oxidation atmosphere was investigated at $650^{\circ}C\;for\;72\sim360$ hours. At $3\;wt\%\;of\;Li_{2}O$, Haynes 263 alloy showed the highest corrosion resistance among the examined alloys, and up to $8\;wt\%\;of\;Li_{2}O$, Haynes 75 exhibited the highest corrosion resistance. Corrosion products were formed $Li(Ni,Co)O_2,\;LiNiO_2\;and\;LiTiO_2\;and\;Cr_{2}O_3$ on Haynes 263, $Cr_{2}O_3,\;NiFe_{2}O_4,\;LiNiO_2,\;Li_{2}NiFe_{2}O_4,\;Li_{2}Ni_{8}O_10$ and Ni on Haynes 75, $Cr_{2}O_3,\;(Al,Nb,Ti)O_2,\;NiFe_{2}O_4,\;and\;Li_{2}NiFe_{2}O_4$ on Inconel X-750 and $Cr_{2}O_3,\;NiFe_{2}O_4\;and\;CrNbO_4$ on Inconel 718, respectively. Haynes 263 showed local corrosion behavior and Haynes 75, Inconel X-750, 718 showed uniform corrosion behavior.

• Applied Chemistry for Engineering
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• v.8 no.4
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• pp.679-684
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• 1997

The major constituents in spent FCC catalysts are Si, Al, Fe, Ti, alkali metals and some others. The spent catalyst is also composed small amounts of rare metals such as Ce, Nd, Ni and V. The selective adsorption and concentration of Ce and Nd from the leaching solution of spent FCC catalysts with sulfuric acid($0.25mol/dm^3$) were carried out by the column method with a chelate resin having a functional group of aminophosphoric acid type. Ce and Nd were separated from eluate liquor containing Al, Nd and V by the precipitation process with oxalic acid. Vanadium is purified from chloride ion coexistance by solvent extraction, employing tri-n-octyl phosphine oxide as extractant with Al in the raffinate solution. Rare metals with the purity of 99 percent were obtained from the spent FCC catalyst.