• 전기학회논문지
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• 제63권9호
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• pp.1233-1238
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• 2014

In this thesis, it is investigated the characteristics of Dye Sensitized Solar Cell (DSSC) according to variation of $TiO_2$ thickness (6, 12, 18, and $24{\mu}m$) and three distinct $TiO_2$ sintering temperatures (350, 450 and $550^{\circ}C$) by XRD, SEM, I-V and UV-Vis spectrophotometer. According to sintering temperature, $TiO_2$ was transformed into the anatase structure at $350^{\circ}C$, rutile structure at $550^{\circ}C$ and further into the two structure at $450^{\circ}C$. With increasing thickness up to $18{\mu}m$ and sintering temperature up to $450^{\circ}C$, respectively, the irradiance rate increased in the range of 9~26 percent and 2.80~5.10 percent. Whereas a further increase to $24{\mu}m$ and $550^{\circ}C$, the irradiance rate decrease in the range of 4~11 percent and 30~47 percent. The conversion efficiency increased in the range of 2.80~5.01 and 3.03~5.01 with increasing thickness up to $18{\mu}m$ and sintering temperature up to $450^{\circ}C$. By contrast, increase to $24{\mu}m$ and $550^{\circ}C$, the conversion efficiency decreased in the range of 3.31~5.01 and 2.80~3.89, respectively. The DSSC that thickness of $TiO_2$ were $18{\mu}m$ and sintered at $450^{\circ}C$ exhibited the most excellent characteristics, in which open-circuit voltage, short-circuit current, Fill Factor and conversion efficiency are 0.69 V, $11.4mA/cm^2$, 0.64 and 5.01%, respectively.

• 전기화학회지
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• 제14권1호
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• pp.27-32
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• 2011

Cr을 첨가한 $Li_4Ti_5O_{12}$의 전기화학적 특성을 고찰하였다. 산화물에 금속원자가 치환될 경우에 결정구조가 변화되며, $Li_4Ti_5O_{12}$의 전기화학적 특성이 변화하게 된다. 졸-겔법을 이용하여 $Li_4Ti_{5-x}Cr_xO_{12}$ (x = 0~0.2)를 제조하였으며, 전기로에서 $800{\sim}850^{\circ}C$로 공기중에서 12시간 동안 열처리하였다. 시료의 물리적인 특성은 TG-DTA, XRD, SEM, FT-IR을 사용하여 측정하였으며, 전기화학적인 특성은 0.01~2.0V의 범위에서 배터리충방전기를 사용하여 측정하였다. $Li_4Ti_5O_{12}$는 1C에서 169.9 mAh/g의 용량을 나타내었으며, 0.1C로 변화되었을 경우에 초기용량의 97.5%를 나타내었다. $Li_4Ti_{4.9}Cr_{0.1}O_{12}$ 시료는 1C에서 193.8 mAh/g의 용량을 보였으며, 0.1C에서는 초기용량의 98.8%를 나타내었다.

• Bulletin of the Korean Chemical Society
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• 제33권9호
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• pp.3043-3047
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• 2012

To investigate the scattering layer effect of a $TiO_2$ multilayer in dye-sensitized solar cells (DSSCs), we designed a new DSSC system, assembled with a CdS-$TiO_2$ scattering layer electrode. A high-magnification SEM image exhibited hollyhock-like particles with a width of 1.5-2.0 ${\mu}m$ that were aggregated into 10-nm clumps in a hexagonal petal shape. The efficiency was higher in the DSSC assembled with a CdS-$TiO_2$ scattering layer than in the DSSC assembled with $TiO_2$-only layers, due to the decreased resistance in electrochemical impedance spectroscopy (EIS). The short-circuit current density ($J_{sc}$) was increased by approximately 7.26% and the open-circuit voltage ($V_{oc}$) by 2.44% over the 1.0 wt % CdS-$TiO_2$ composite scattering layer and the incident photon-to-current conversion efficiency (IPCE) in the maximum peak was also enhanced by about 5.0%, compared to the DSSC assembled without the CdS-$TiO_2$scattering layer.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.206-206
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• 2010

정보화 기술이 급속히 발전함에 따라서 보다 많은 양의 data를 전송, 처리, 저장 하게 되면서 이를 처리 할 수 있는 대용량, 고속, 비휘발성의 차세대 메모리의 개발이 요구 되고 있다. 이 중 저항 변화 메모리(ReRAM)는 일반적으로 전이금속산화물을 이용한 MIM 구조로서 적당한 전기 신호를 가하면 저항이 높아서 전도되지 않는 상태(Off state)에서 저항이 낮아져 전도가 가능한 상태(On state)로 바뀌는 메모리 특성을 가진다. ReRAM은 비휘발성 메모리이며 종래의 비휘발성 기억소자인 Flash memory 보다 access time이 $10^5$배 이상 빠르며, 2~5V 이하의 낮은 전압에서 동작이 가능하다. 또한 구조가 간단하여 공정상의 결함을 현저히 줄일 수 있다는 점 등 많은 장점들이 있어서 Flash memory를 대체할 수 있는 유력한 후보로 여겨지고 있다. 저항 변화의 특징을 잘 나타내는 물질에는 $TiO_2$, $Al_2O_3$, $NiO_2$, $HfO_2$, $ZrO_2$등의 많은 전이금속산화물들이 있다. 본 연구에서는 Reactive DC-magnetron Sputtering 방법과 DC-magnetron sputter를 이용하여 Ti를 증착한 후 Oxidation 방법으로 각각 증착한 $TiO_2$박막을 사용하여 저항변화특성을 관찰하였다. $TiO_2$상부에 Atomic Layer Deposition (ALD)를 이용하여 $HfO_2$ 박막을 증착하여 표면처리를 하고, 또한 $TiO_2$에 다른 전이 금속박막 층을 추가 증착하여 저항변화 특성에 접합한 조건을 찾는 연구를 진행하였다. 하부 전극과 상부 전극 물질로는 Si 100 wafer 위에 Pt 또는 TiN을 사용하였다. 저항변화 특성을 평가하기 위해 Agilent E5270B를 이용하여 current-voltage (I-V)를 측정하였다. X-ray Diffraction (XRD)를 이용하여 증착 된 전기금속 박막 물질의 결정성을 관찰했으며, Atomic Force Microscopy (AFM)을 이용하여 증착 된 샘플의 표면을 관찰했다. SEM과 TEM을 통해서는 sample의 미세구조를 확인 하였다.

• 분석과학
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• 제11권2호
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• pp.79-87
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• 1998

최근의 소비자들은 waterproof 기능을 가진 광범위한 UV 차단 제품을 선호하며, 피부 안전성에도 많은 관심을 가지고 있다. NR method로 세포 자극성(in-vitro)을 실험한 결과, UV-B의 자외선 차단제들은 0.08 w/v% 이상에서 세포의 생존율이 떨어졌고, UV-A의 자외선 차단제들은 0.06 w/v% 이상에서 세포의 생존율이 떨어졌다. 무기 자외선 차단제들의 patch-test는 각각 10.5와 11.25 이하로 피부에 자극성은 없었다. UV 흡수 곡선, UV-B는 octyl methoxycinnamate(OMC), UV-A는 butyl methoxy dibenzoylmethane(BMDM) 가장 적합하였다. 따라서, 유기 자외선 차단제는 OMC와 BMDM이 nylon과 polyethylene에 코팅된 원료인 $Nylonpoly^{TM}$ UVA/UVB을 사용하였다. 무기 자외선 차단제는 zinc oxide(ZnO)와 titanium dioxide($TiO_2$)를 사용하였다. ZnO와 $TiO_2$의 혼합 비율은 6:4가 적당하였다. 총 UV차단제의 함량은 ZnO 6%, $TiO_2$ 4%와 $Nylonpoly^{TM}$ UVA/UVB 5%를 썬 스크린 크림에 혼합하였다. In-vi-tro의 SPF값은 38.9이었다. 응용으로, 동일 함량을 넣은 O/W type과 W/S type의 썬 스크린 크림을 만들어 시간 경과에 따른 SPF를 측정한 결과, SPF가 O/W type보다 W/S type이 5배 이상 오래 지속되었다. 이것은 해수욕, 등산, 스키를 탈 경우에 효과적이다. 본 연구는 자외선 차단제의 피부 트러블을 최소화하고자 하였으며, 매끄러움성, 피부 안전성과 자외선 차단 효과가 우수한 화장품이라고 생각되어진다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.385-385
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• 2010

In this work, we have investigated the etching characteristics of $TiO_2$ and selectivity of $TiO_2$ over $SiO_2$ thin films as resistance in ReRAM using the inductively coupled plasma. The etch rate and selectivity were measured by varying the $BCl_3$ addition into Ar plasma. The maximum etchrate was obtained at 110.1nm/min at $BCl_3$/Ar=5sccm/10sccm, 500W for RFpower, -100v for DC-bias voltage, and 2Pa for the process pressure. The etched $TiO_2$ surface was investigated with X-ray photo electron spectroscopy. We explained the etching mechanism in two etch mechanisms, physiclas puttering and chemical reaction.

• 한국광물학회지
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• 제15권1호
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• pp.78-84
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• 2002

New pyrochlore-type phases($A_2$$B_2$$O_{7}$) were synthesized in the systems: CaO-C$eO_2$-T$iO_2$, CaO-$UO_2$(T$hO_2$)-Z$rO_2$, CaO-$UO_2$(T$hO_2$)-$Gd_2$$O_3$-T$iO_2$-Z$rO_2$, 및 CaO-T$hO_2$-S$nO_2$. The starting materials were pressed with the pressure of 200~400 MPa and sintered at 1500~ 155$0^{\circ}C$ for 4~8 hours in air and at 1300~ 135$0^{\circ}C$ for 5 ~50 hours under oxygen atmosphere. The products were characterized using XRD, SEM/EDS and TEM. In the bulk compositions of CaCe$Ti_2$$O_{7}$, CaTh$Zr_2$$O_{7}$,($Ca_{0.5}$ Gd$Th_{0.5}$)(ZrTi)$O_{7}$) ($Ca_{0.5}$Gd$Th_{0.5}$)(ZrTi)$O_{7}$, ($Ca_{0.5}$G$dU_{0.5}$)(ZrTi)$O_{7}$ and CaTh$Sn_2$$O_{7}$ , pyrochlore was the major phase, together with other oxide phase $of_2$$O_{7}$ fluorite structure. In the samples with target compositions CaU$Zr_2$$O_2$및 $Ca_{0.5}$ G$dU_{0.5}$)$Zr_2$T$iO_{7}$ pyrochlore was not identified, but a fluorite-structured phase was detected. The formation factor as the stable phase depended on crystal chemical characteristics of the actinide and lanthanide elements of the system concerned.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2018년도 춘계학술대회 논문집
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• pp.75-75
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• 2018

Commercially pure titanium (CP-Ti) and Ti-6Al-4V alloys have been widely used in implant materials such as dental and orthopedic implants due to their corrosion resistance, biocompatibility, and good mechanical properties. However, surface modification of titanium and titanium alloys is necessary to improve osseointegration between implant surface and bone. Especially, when titanium oxide nanotubes are formed on the surface of titanium alloy, cell adhesion is greatly improved. In addition, plasma electrolytic oxide (PEO) coatings have a good safety for osseointegration and can easily and quickly form coatings of uniform thickness with various pore sizes. Recently, the effects of bone element such as magnesium, zinc, strontium, silicon, and manganese for bone regeneration are researching in dental implant field. The purpose of this study was researched on the surface morphology of PEO-treated Ti-6Al-4V alloy after anodic titanium oxide treatmentusing various instruments. Ti-6Al-4V ELI disks were used as specimens for nanotube formation and PEO-treatment. The solution for the nanotube formation experiment was 1 M $H_3PO_4$ + 0.8 wt. % NaF electrolyte was used. The applied potential was 30V for 1 hours. The PEO treatment was performed after removing the nanotubes by ultrasonics for 10 minutes. The PEO treatment after removal of the nanotubes was carried out in the $Ca(CH_3)_2{\cdot}H_2O+(CH_3COO)_2Mg{\cdot}4H_2O+Mn(CH_3COO)_2{\cdot}4H_2O+Zn(CH_3CO_2)_2Zn{\cdot}2H_2O+Sr(CH_2COO)_2{\cdot}0.5H_2O+C_3H_7CaO_6P$ and $Na_2SiO_3{\cdot}9H_2O$ electrolytes. And the PEO-treatment time and potential were 3 minutes at 280V. The morphology changes of the coatings on Ti-6Al-4V alloy surface were observed using FE-SEM, EDS, XRD, AFM, and scratch tester. The morphology of PEO-treated surface in 5 ion coating solution after nanotube removal showed formation or nano-sized mesh and micro-sized pores.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.263-266
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• 2001

In this paper, we investigated dielectric properies for BST thin films that was deposited on MgO/Si substrates using RF magnetron sputtering. In here, MgO film was used to perform that a diffusion b arrier between the BST film and Si substrate and a buffer layer to assist the BST film growth. A d eposition condition for MgO films was RF Power of 50W, substrate temperature of room temperature and the working gas ratio of Ar:O$_2$ were varied from 90:10 to 60:47. Finally we manufactured the cap acitor of Al/BST/MgO/Si/Al structure to know electrical properties of this capacitor through I-V, C-V measurement. In the results, C-V aha racteristic curves was shown a ferroelectric property so we measured P-E. A remanent poliazation and coerceive electric field was present 2$\mu$C/cm$^2$ and -27kV/cm respectively at Ar:O$_2$=90:10. And a va clue of dielectric constant was 86 at Ar:02=90:10.

• 동력기계공학회지
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• 제19권6호
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• pp.26-32
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• 2015

The purpose of this study is to investigate the de-NOx performance characteristics according to the $TiO_2$ crystal structures ratio of $V_2O_5$ SCR catalysts. The anatase(100%) SCR catalyst showed the highest desorption peak of 80ppm at about $250^{\circ}C$, and $NH_3$ was not desorbed at $500^{\circ}C$. It can be confirmed that there was many $NH_3$ desorbed at a high temperature among other various crystal structures, which is because the catalyst was more acidized to increase the intensity of acid sites as the content of subacid sulfate ions($NH_2SO_4$) in the rutile phase increases. The anatase/rutile(7%/93%) SCR had the smallest width of de-NOx performance drop according to thermal aging, and had strong durability against thermal aging.