• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전기물성,응용부문
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• pp.79-81
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• 2004

$TiO_2-SnO_2$ thin films are fabricated using sol-gel method. The thickness of thin films increase about $0.03{\sim}0.04{\mu}m$ every a dipping. The permittivity and dissipation factor of $TiO_2-SnO_2$ thin films decrease with increasing frequency. Thin films show semiconductive characteristics above $400^{\circ}C$.

• 한국분말재료학회지
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• 제25권3호
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• pp.257-262
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• 2018

The coupling of two semiconducting materials is an efficient method to improve photocatalytic activity via the suppression of recombination of electron-hole pairs. In particular, the coupling between two different phases of $TiO_2$, i.e., anatase and rutile, is particularly attractive for photocatalytic activity improvement of rutile $TiO_2$ because these coupled $TiO_2$ powders can retain the benefits of $TiO_2$, one of the best photocatalysts. In this study, anatase $TiO_2$ nanoparticles are synthesized and coupled on the surface of rutile $TiO_2$ powders using a microemulsion method and heat treatment. Triton X-100, as a surfactant, is used to suppress the aggregation of anatase $TiO_2$ nanoparticles and disperse anatase $TiO_2$ nanoparticles uniformly on the surface of rutile $TiO_2$ powders. Rutile $TiO_2$ powders coupled with anatase $TiO_2$ nanoparticles are successfully prepared. Additionally, we compare the photocatalytic activity of these rutile-anatase coupled $TiO_2$ powders under ultraviolet (UV) light and demonstrate that the reason for the improvement of photocatalytic activity is microstructural.

• 분석과학
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• 제19권5호
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• pp.376-382
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• 2006

In this work, pitch/activated carbon/$TiO_2$ composite were prepared by $CCl_4$ solvent method with different mixing ratios. The BET surface area of pitch/activated carbon/$TiO_2$ composite has a significantly increase with increasing activated carbon content in pitch/activated carbon/$TiO_2$ composite. The surface structure and elemental compositions of the composite were studied by SEM and EDX, respectively. The SEM results were presented to the characterization of porous texture on the pitch/activated carbon/$TiO_2$ composite. And EDX data was shown the presence of C, O, S, Ti and other elements. The structural properties of the composite were studied in XRD measurements. The $TiO_2$ crystal phases of the pitch/activated carbon/$TiO_2$ composite had lots of rutile-type structure which transforms from anatase-type with a little of anatase-type structure. The photocatalytic activities of the composite were evaluated using a photo-decomposition method under UV lamp. The pitch/activated carbon/$TiO_2$ composites were observed better photocatalytic activity than that of pristine $TiO_2$.

• 한국세라믹학회지
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• 제34권6호
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• pp.583-590
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• 1997

The effects of Mn2O3 and Y2O3 additives on the microstructure and dielectric properties of Sr(Zr, Ti)O3 have been investigated. Powders with Sr(Zr1-xTix)O3(0$\leq$x$\leq$0.1) composition were prepared by the conventional solid state processing from commercial TiO2 and precipitation-processed ZrO2. The powders containing sintering additives of Mn2O3 and Y2O3 were compacted and then sintered at 1,55$0^{\circ}C$ for 4 h to get>97% relative density. Mn2O3 suppressed the grain growth and Y2O3 enhanced the density of sintered body. The oxidation state of Mn ions were determined by a chemical wet method and EPR spectroscopy. Mn ions were present as Mn2+ and Mn4+ in SrZrO3, while as Mn3+ and Mn4+ in Ti-substituted Sr(Zr, Ti)O3. With the substitution of Ti, the lattice parameters of SrZrO3 decreased and its dielectric constant increased with remarkable decrease in Q value. The dielectric constant of Sr(Zr, Ti)O3 was in the range of 30 to 40, Q values 1,200~5,400 at 6 GHz and temperature coefficient of resonant frequency -67~100 ppm/K.

• 공업화학
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• 제32권6호
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• pp.599-606
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• 2021

본 연구는 질소산화물 제거를 위하여 암모니아를 환원제로 사용하는 선택적 촉매 환원법에 있어 지지체에 셀레늄을 첨가하여 300 ℃ 이하에서 V₂O₅/WO₃/TiO₂의 반응 활성을 증진시키기 위한 실험 및 반응특성 연구를 수행하였다. 졸-겔법으로 Se-TiO₂ 및 TiO₂를 합성하였으며, 이를 지지체로 하여 V₂O₅/WO₃/TiO₂ 및 V₂O₅/WO₃/Se-TiO₂ 촉매를 제조하여 상용 촉매와 반응 활성을 비교하였다. 실험 결과, 졸-겔법으로 합성한 TiO₂를 사용한 촉매의 탈질 효율이 상용 TiO₂를 사용하여 제조한 촉매보다 낮은 결과를 보였으나 셀레늄을 첨가함에 따라 탈질 효율이 증진되었다. 따라서 BET, XRD, Raman, H₂-TPR 및 FT-IR분석을 통하여 셀레늄의 첨가가 촉매의 구조에 미치는 영향을 분석하였으며 셀레늄 첨가에 의한 비표면적의 증가와 단량체 및 복합체 바나듐 종의 형성이 반응 특성에 미치는 영향을 확인하였다.

• Transactions on Electrical and Electronic Materials
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• 제6권5호
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• pp.210-213
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• 2005

The $BaTiO_3/SrTiO_3$ heterolayered thick films were fabricated by the screen printing method on alumina substrates. The effect of the sintering temperature on the microstructure and dielectric properties of the $BaTiO_3/SrTiO_3$ thick films has been investigated. The relative dielectric constant and dielectric loss at 1 MHz of the $BaTiO_3/SrTiO_3$ heterolayered thick films with sintering temperature of $1350^{\circ}C$ were about 751 and 1.74, respectively. The remanent polarization $(P_r)$ of the pure $(Ba_{0.5}Sr_{0.5})TiO_3$ and $BaTiO_3/SrTiO_3$ heterolayered films are approximately $5.1\;{\mu}C/cm^2$ and $10\;{\mu}C/cm^2$. This study suggests that the design of the $BaTiO_3/SrTiO_3$ heterolayered thick films capacitor with different phase should be an effective method to enhance the dielectric and ferroelectric performance in devices.

• 청정기술
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• 제14권3호
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• pp.204-210
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• 2008

비가수분해 솔-젤법에 의하여 여러 가지 조성의 $V_{2}O_{5}-TiO_2$ 촉매를 합성하여 특성분석을 실시하고 황화수소의 선택 산화반응에 대한 촉매성능을 고찰하였다. 이 $V_{2}O_{5}-TiO_2$ 촉매는 높은 표면적을 가지고 VOx가 작은 입자로 잘 분산되어 있었고, 환원성도 우수한 것으로 나타났다. 그러나 12 wt% 이상의 바나디아 담지량부터는 결정성 $V_{2}O_5$가 관찰되어 $H_{2}S$의 전환율을 감소시키는 결과를 초래하였다. 이 방법으로 제조된 $V_{2}O_{5}-TiO_2$ 촉매는 통상의 제로젤(xerogel) 촉매나 함침 촉매에 비해 높은 반응활성을 보여 주었고, 암모니아와 물이 포함된 조건에서도 황화수소를 선택 산화시켜 이산화황을 거의 발생시키지 않고 환경 친화적이고 안전한 물질인 원소 황(sulfur)과 티오황산암모늄(ATS)으로 회수할 수 있었다.

• 한국진공학회지
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• 제9권4호
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• pp.373-378
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• 2000

실리콘 기판 위에서 $TiO_2$와 $Bi_2O_3$의 박막 성장은 반응속도론 측면에서 커다란 차이를 보였지만, $Bi_4Ti_3O_{12}$(BIT) 박막의 성장은 주로 $TiO_2$ 성장 거동에 의해 지배를 받았다. 그 결과 BIT 박막은 bismuth가 부족한 조성을 가지게 되었다. 박막 내에 부족한 bismuth의 양을 보충해줌으로써 이러한 문제점을 해결하고자 펄스 주입 유기 금속 화학 기상 증착(MOCVD) 방법을 사용하였다. 이러한 펄스 주입법에 의해 bismuth의 양은 증가하였고 또한, 박막의 깊이 방향으로의 조성이 균일해졌고 $Bi_4Ti_3O_{12}$과 Si사이의 계면이 향상되었다. 게다가, $Bi_4Ti_3O_{12}$ 박막의 결정성은 크게 향상되었고 누설 전류 밀도는 연속 주입법에 비해 1/2에서 1/3정도 낮아졌다. 시계 방향의 C-V 이력 곡선이 관찰되었고 이로 인해 펄스 주입법에 의해 증착된 $Bi_4Ti_3O_{12}$ 박막은 강유전성에 의해 스위칭이 됨을 알 수 있었다.

• 한국세라믹학회지
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• 제55권2호
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• pp.140-144
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• 2018

$ZnO/TiO_2$ nanocomposites were synthesized via a modified sol-gel technique by incorporating 30 and 70 wt% $TiO_2$ nanopowder into a ZnO sol-gel matrix. Zinc acetate dihydrate was used as the ZnO precursor and de-ionized water as the solvent, while titanium oxysulfate was employed for the synthesis of $TiO_2$ nanopowder. The synthesized $ZnO/TiO_2$ nanocomposites were characterized by x-ray diffraction, UV-vis spectroscopy, scanning electron microscopy, and transmission electron microscopy. The $ZnO/TiO_2$ nanocomposites showed both the ZnO (wurtzite) and $TiO_2$ (anatase) phases. The average ZnO crystallite size of the $ZnO/TiO_2$ nanocomposites was found to be about 26.3 nm. The TEM results confirmed that spherical $TiO_2$ particles were embedded in the ZnO matrix. $TiO_2$ particles attached onto the rod-like ZnO particles were also observed. The $ZnO/TiO_2$ nanocomposites exhibited optical absorption properties superior to those of pure ZnO and $TiO_2$.

• 한국세라믹학회지
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• 제32권7호
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• pp.761-768
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• 1995

Double layered BaTiO3 thin films with high dielectric constant as well as good insulating property were prepared for the application to low voltage driving thin film electroluminescent (TFEL) device. BaTiO3 thin films were formed by rf-magnetron sputtering technique. Amorphous and polycrystalline BaTiO3 thin films were deposited at the substrate temperatures of room temperature and 55$0^{\circ}C$, respectively. Two kinds of films prepared under these conditions showed high resistivity and high dielectric constant. The figure of merit (=$\varepsilon$r$\times$Eb.d) of polycrystalline BaTiO3 thin film was very high (8.43$\mu$C/$\textrm{cm}^2$). The polycrystalline BaTiO3 showed a substantial amount of leakage current (I), under the high electric field above 0.5 MV/cm. The double layered BaTiO3 thin film, i.e., amorphous BaTiO3 layer coated polycrystalline BaTiO3 thin film, was prepared by the new stacking method and showed very good dielectric and insulating properties. It showed a high dielectric constant fo 95 and leakage current density of 25 nA/$\textrm{cm}^2$ (0.3MV/cm) with the figure of merit of 20$\mu$C/$\textrm{cm}^2$. The leakage current density in the double layered BaTiO3 was much smaller than that in polycrystalline BaTiO3 under the high electric field. The saturated brightness of the devices using double layered BaTiO3 was about 220cd/$m^2$. Threshold voltage of TFEL devices fabricated on double layered BaTiO3 decreased by 50V compared to the EL devices fabricated on amorphous BaTiO3.