• Bulletin of the Korean Chemical Society
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• 제24권1호
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• pp.86-90
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• 2003

Reverse-Water-Gas-Shift reaction (RWGSR) was carried out over the ZnO, $Al_2O_3,\;and\;ZnO/Al_2O_3$ catalysts at the temperature range from 400 to 700 ℃. The ZnO showed good specific reaction activity but this catalyst was deactivated. All the catalysts except the $ZnO/Al_2O_3$ catalyst (850 ℃) showed low stability for the RWGSR and was deactivated at the reaction temperature of 600 ℃. The $ZnO/Al_2O_3$ catalyst calcined at 850 ℃ was stable during 210 hrs under the reaction conditions of 600 ℃ and 150,000 GHSV, showing CO selectivity of 100% even at the pressure of 5 atm. The high stability of the $ZnO/Al_2O_3$ catalyst (850 ℃) was attributed to the prevention of ZnO reduction by the formation of $ZnAl_2O_4$ spinel structure. The spinel structure of $ZnAl_2O_4$ phase in the $ZnO/Al_2O_3$ catalyst calcined at 850 ℃ was confirmed by XRD and electron diffraction.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.343-343
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• 2011

ZnO has been introduced as one of the good candidates for next generation opto-electronics. Recently, ZnO is known to be suitable for the transparent electrode in organic solar cells and light emitting devices. The contact with n-type organic material has been studied due to the n-type properties of ZnO. However, the surface of ZnO has shown different electronic property with respect to its surface orientation. Therefore, it is presumed that there are differences in the interfacial electronic structures between organic materials and ZnO with different orientation. Therefore, it is required to classify the interfacial electronic structures according to the surface orientation of ZnO. In this study, we measured the interfacial electronic structures between the ZnO substrate having various orientations and a typical n-type organic material, tris-(8-hydroxyquinoline) aluminum (Alq3). In-situ x-ray and ultraviolet photoelectron spectroscopy measurements revealed the interfacial electronic structures. We found the changes in the electronic structures with respect to the orientation of ZnO substrate and it could be used to improve the contact between ZnO and Alq3.

• 한국세라믹학회지
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• 제29권2호
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• pp.161-165
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• 1992

Nonlinear exponents and electron trap density variations were observered in ZnO-Bi2O3-MnO2 ternary ZnO varistors as a function of heat treatment temperature. Three kinds of ZnO varistor compositions were selected; i.e. 99.0 ZnO-0.5 Bi2O3-0.5 MnO2, 98.5 ZnO-1.0 Bi2O3-0.5 MnO2, and 98.0 ZnO-1.5 Bi2O3-0.5 MnO2 in mol%. Sintering was done at 1150$^{\circ}C$ for three hours, and heat treatments were done at 500$^{\circ}C$, 700$^{\circ}C$, and 900$^{\circ}C$. When heat treated at 500$^{\circ}C$, nonlinear exponents were increased regardless of the Bi2O3 amount. Increasing heat treatment temperature above 500$^{\circ}C$ resulted in lowering nonlinear exponents. Nonlinear exponents seem to be related to the 0.17 and 0.33 eV electron traps which are possibly of intrinsic origin.

• 한국세라믹학회지
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• 제40권3호
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• pp.262-267
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• 2003

Off-axis 고주파 마그네트론 스퍼터링법으로 사파이어(0001) 기판 위에 이종에피텍셜 ZnO 박막을 제조하였다. ZnO 박막의 결정성은 증착압력, RF power 그리고 기판온도의 공정조건 변화에 많은 영향을 받았으며, 스퍼터링된 입자의 적당한 kinetic energy와 기판표면에서의 표면이동도(surface mobility)가 조화를 이룰 때 결정성이 우수한 이종에피텍셜 박막을 을 얻을 수 있었다. 이종에피텍셜 ZnO 박막의 Photoluminescence(PL) 특성 측정 결과, 저온(17K)에서 약 3.36 eV의 자외선 영역 발광을 관찰할 수 있었으며, 상온에서도 3.28 eV의 자외선 영역 발광을 관찰할 수 있었다. ZnO 박막을 산소 분위기에서 열처리함에 따라 결정성은 향상되는 반면 자외선 영역의 발광은 급격히 감소하는 경향을 보였다.

• 전기전자학회논문지
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• 제22권3호
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• pp.712-715
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• 2018

ZnO 시드 막 위에 수열합성법으로 나노로드를 성장시켰다. 고주파 스퍼터링으로 증착한 ZnO 박막을 $600^{\circ}C$에서 열처리한 후 시드 막으로 사용하였다. 성장된 ZnO 나노로드를 $400^{\circ}C$ 및 $800^{\circ}C$에서 열처리하였다. ZnO 나노로드의 열처리에 따른 구조적 및 광학적 특성을 고찰하였다. ZnO 나노로드를 $400^{\circ}C$에서 열처리함으로써 강도가 크고 반폭치가 좁은 자외선 피크를 얻을 수 있었다.

• 전자공학회논문지 IE
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• 제43권4호
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• pp.8-12
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• 2006

본 논문에서는 $SiO_2-ZnO-B_2O_3$ 계 및 $P_2O_5$-ZnO-BaO 계의 반사율과 유전특성을 $TiO_2$의 양에 따라 조사하였다. 반사율은 $TiO_2$ 함량이 증가함에 따랴 감소하였다 여기서 $P_2O_5$-ZnO-BaO계는 $SiO_2-ZnO-B_2O_3$ 계보다 더 낮은 반사율을 나타내었으며, 유전상수는 $P_2O_5$-ZnO-BaO 계가 $SiO_2-ZnO-B_2O_3$ 계보다 높았다. 두 계 모두 유전상수는 $TiO_2$의 양에 따라 증가하는 특성을 보였다. 이 결과는 높은 반사율과 항복특성이 요구되는 PDP디스플레이의 후면 유전층에 적용할 수 있을 것으로 생각된다.

• 한국재료학회지
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• 제25권6호
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• pp.300-304
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• 2015

Nanorod ZnO and spherical nano ZnO for gas sensors were prepared by hydrothermal reaction method and hydrazine method, respectively. The nano-ZnO gas sensors were fabricated by a screen printing method on alumina substrates. The gas sensing properties were investigated for hydrocarbon gas. The effects of Co concentration on the structural and morphological properties of the nano ZnO:Co were investigated by X-ray diffraction and scanning electron microscope (SEM), respectively. XRD patterns revealed that nanorod and spherical ZnO:Co with a wurtzite structure were grown with (100), (002), (101) peaks. The sensitivity of nanorod and spherical ZnO:Co sensors was measured for 5 ppm $CH_4$ and $CH_3CH_2CH_3$ gas at room temperature by comparing the resistance in air with that in target gases. The highest sensitivity to the $CH_4$ and $CH_3CH_2CH_3$ gas of spherical nano ZnO:Co sensors was observed at Co 6 wt%. The spherical nano ZnO:Co sensor exhibited a higher sensitivity to hydrocarbon gas than nanorod ZnO.

• 대한전기학회논문지
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• 제43권4호
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• pp.613-619
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• 1994

Dielectric properties of Ba(ZnS11/3TTaS12/3T)OS13T+x ZnO(x=0, 0.4, 0.8, 1.0 wt%) ceramics have been investigated at microwave frequencies. With excess ZnO, the sinterability was improved and the dielectric constant($\varepsilon$S1rT) and the unloaded quality factor(QS1UT) were increased. The structure changed into hexagonal from pseudocubic as being annealed at 140$0^{\circ}C$ in excess ZnO composition. Also, the temperature coefficient of the resonant frequency ($\tau$S1fT) turned into (-)ppm/$^{\circ}C$ when sintered at 155$0^{\circ}C$ for 2 hours. But the specimen sintered in ZnO muffling showed increased density and $\varepsilon$S1rT but lowerde QS1uT. Among the specimen investigated, expecially the composition added with 0.4wt% excess ZnO showed the most optimum dielectric values ($\varepsilon$S1rT=28, QS1uT x f=120000GHz) better than those of original Ba(ZnS11/2T TaS12/3T)OS13T ceramics.

• 한국자기학회지
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• 제18권1호
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• pp.43-47
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• 2008

[ $ZnO-Bi_2O_3-Al_2O_3-B_2O_3-SiO_2$ ] nano-glass를 sol-gel 법으로 제조 하였다. 평균 입자 크기는 60.3 nm였으며 매우 균일한 입도 분포를 가졌다. Nano-glass를 NiZnCu ferrite의 저온소성용 소결조제로 사용하였으며 NiZnCu ferrite에 nano-glass를 첨가한 후 $840{\sim}900^{\circ}C$에서 2시간 소결을 진행하였다. 소결성 및 자기적 특성에 대해 연구하였으며 밀도, 수축율, 초투자율, 품질계수, 및 포 화자화값을 측정하였다. nano-glass를 0.5 wt% 첨가하여 $900^{\circ}C$에서 소결한 토로이달 core 시편의 초투자율은 1 MHz에서 측정 시 193.3의 값을 가졌다. 초투자율과 포화자화값은 소결온도가 증가함에 따라 증가하는 경향을 나타내었다. sol-gel 법에 의해 제조된 $ZnO-Bi_2O_3-Al_2O_3-B_2O_3-SiO_2$ nano-glass를 칩인덕터용 NiZnCu ferrite의 저온 소결조제로 사용 가능함을 알 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.47-50
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• 2002

ZnO nanowires were coated conformally with aluminum oxide ($Al_{2}O_{3}$) material by atomic layer deposition (ALD). The ZnO nanowires were first synthesized on a Si (100) substrate at $1380^{\circ}C$ from ball-milled ZnO powders by a thermal evaporation procedure with an argon carrier gas without any catalysts; the length and diameter of these ZnO nanowires are $20\sim30{\mu}m$ and $50{\sim}200$ nm, respectively. $Al_{2}O_{3}$ films were then deposited on these ZnO nanowires by ALD at a substrate temperature of $300^{\circ}C$ using trimethylaluminum (TMA) and distilled water ($H_{2}O$). Transmission electron microscopy (TEM) images of the deposited ZnO nanowires revealed that 40nm-thick $Al_{2}O_{3}$ cylindrical shells surround the ZnO nanowires.