• 한국세라믹학회지
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• 제26권4호
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• pp.539-549
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• 1989

Polycrystalline TiO2 thin films were deposited on Si and Al2O3 substrates by CVD method. Ethyl titanate, Ti(OC2H5)4, was used as a source material for Ti and O, and Ar was used for carrier gas. In the surface chemical reaction controlled deposition condition, the apparent activation energy of 6.74 Kcal/mole was obtained, and the atomic adsorption on substrate surface was proved to be governed by Rideal-Elley mechanism. In the mass transfer controlled deposition condition, the deposition rate was in a good agreement with the result which was calculated by the simple boundary layer theory. It was also observed that TiO2 thin films show different surface morphology according to the different deposition mechanism, which was fixed by deposition conditions. This phenomenon could be well explained by the surface perturbation theory.

• 한국세라믹학회지
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• 제20권3호
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• pp.243-249
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• 1983

This study has examined on the effect for the fitting in porcelain body of MgO-SiO system. The mixture was made of correponding in the theoretical composition of enstatite with Kyul Sung Talc and sea water magnesia cake. Hyup Jin Kaolin as clay minerals to give the mixture plasticity was added 10% by weight of the mixture. Feldspar was added inv various kinds of 1%-20% by weight of the above mixture. After the physical properties and microstructures were carefully examined the following results were obtained. 1. The addition amount of feldspar should generally be from 5% to 10% by weight of the mixture to be good for the properties of the strength and the range of the firing temperature. 2. The 5% addition amount of feldspar was good for the apparent bulk density. 3. 5% and 10% additions showed up stably excellant with respect to the various properties Therefore when we considered the apparent bulk density and the thermal shock resistance 5% addition amount of feldspar showed the most excellant properties between $1350^{\circ}C$ and $1400^{\circ}C$.

• 한국세라믹학회지
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• 제31권3호
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• pp.235-240
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• 1994

The electric and magnetic properties of Mg1.9-2xMn0.05Fe4xO4+${\gamma}$+2wt% Al2O3, and its microstructure have been investigated as a function of ferrite composition (x=0.45, 0.5, 0.55). The microstructure turned out to be independent on the ferrite composition. The resistivity was decreased with increasing Fe contents, whereas the Curie temperature decreased. Saturation magnetization was varied from 1741 to 2022 G with composition, and squareness ratio (SR), coercive force (BHc) were decreased and increased with increasing Fe contents respectively, so the sample which SR and BHc were 0.97 Oe and 1.49 Oe can be attainable at x=0.45.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.189.1-189.1
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• 2013

Titanium dioxide (TiO2) is a wide bandgap semiconductor possessing photochemical stability and thus widely used for photocatalysis. However, enhancing photocatalytic efficiency is still a challenging issue. In general, the efficiency is affected by physio-chemical properties such as crystalline phase, crystallinity, exposed crystal facets, crystallite size, porosity, and surface/bulk defects. Here we propose an alternative approach to enhance the efficiency by studying interfaces between thin TiO2 layers to be stacked; that is, the interfacial phenomena influencing on the formation of porous structures, controlling crystallite sizes and crystallinity. To do so, multi-layered TiO2 thin films were fabricated by using a sol-gel method. Specifically, a single TiO2 thin layer with a thickness range of 20~40 nm was deposited on a silicon wafer and annealed at $600^{\circ}C$. The processing step was repeated up to 6 times. The resulting structures were characterized by conventional electron microscopes, and followed by carrying out photocatalytic performances. The multi-layered TiO2 thin films with enhancing photocatalytic efficiency can be readily applied for bio- and gas sensing devices.

• 한국물환경학회지
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• 제23권2호
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• pp.274-280
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• 2007

The photochemical decolorization of Rhodamine B (RhB) in water has been carried out by photo-Fenton process. The effect of applied $H_2O_2$, $Fe^{2+}$ dose, solution pH and UV dose have been studied. The influence of constituent processes of photo-Fenton such as UV, $H_2O_2$ and Fenton has been investigated. Comparison of RhB removal was made between the photo-Fenton and $UV/H_2O_2$ process. The results obtained showed that the optimum dosage of $Fe^{2+}$ and $H_2O_2$ were 0.0031 mmol and 0.625 mol, respectively. pH 3 is found to be the optimum pH of for photo-Fenton process. pH and UV dose strongly influenced the decolorization of RhB in photo-Fenton process. The photo-Fenton and $UV/H_2O_2$ processes showed similar decolorization and seem to be appropriate for the decolorization of dye wastewater.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2009년도 추계학술대회 초록집
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• pp.185-185
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• 2009

Polypropylene beads (PP) coated with $TiO_2$ thin films were prepared by a rotating cylindrical plasma chemical vapor deposition (PCVD) reactor and were used to remove phenol in aqueous solution. The $TiO_2$ thin films of 416 nm thickness were coated on the PP particles uniformly. As the number of $TiO_2$-coated PP beads increases, the phenol is degraded faster, because of larger total surface area of photocatalysts for photodegradation. This study shows that a rotating cylindrical PCVD reactor can be a good method to prepare the particles coated with high-quality $TiO_2$ thin films, which can be applied to the pollutant removal by a photodegradation reaction of $TiO_2$ with high efficiency.

• Korean Journal of Chemical Engineering
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• 제36권2호
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• pp.191-196
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• 2019

The phase of Cu,Zn,Al precursors strongly affects the activity of their final catalysts. Herein, the Cu,Zn,Al precursor was prepared by precipitation of $Al^{3+}$ onto primitive, amorphous Cu,Zn precipitate. This precursor turned out to be a phase mixture of zincian malachite and hydrotalcite in which the latter phase was less abundant compared to the co-precipitated precursor. The final catalyst derived from this precursor exhibited a little higher copper surface area and methanol synthesis activity than the co-precipitated counterpart. Therefore, the two precursor phases need to be mixed in an adequate proportion for the preparation of active $Cu/ZnO/Al_2O_3$ catalyst.

• 한국세라믹학회지
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• 제56권1호
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• pp.77-83
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• 2019

MgO-C refractories are used in basic furnaces and steel ladles due to their many desirable properties, such as excellent thermal shock resistance via low thermal expansion, and high thermal conductivity. However, the mechanical and thermal properties of the refractory continuously deteriorate by spalling phenomena and pore generation due to the oxidation of graphite, used as a carbon source, indicating that the characteristics and performance of MgO-C refractories need to be improved by using a new material or composition. In this study, the use of a Hertzian indentation test as a method for determining the damage and fracture behavior of an MgO-C refractory is described. The results highlight that Hertzain indentation tests can be one of the important evaluation tools for quasi-plastic damage accumulation of MgO-C refractories during falling process of scrap metal.

• 암석학회지
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• 제4권1호
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• pp.20-30
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• 1995

이 연구는 경기육괴에 속하는 춘천 동부 지역의 구봉산층군내 각섬암(구본산 각섬암) 및 그 남동부의 상걸리 지역 용두리 편마암 복함체내에 산출되는 각섬암(상걸리 각섬암)에 대한 야외관계 및 주성분 원소의 특징을 보고하며, 그 기원을 토의 한다. 많은 경우에 주변 변성퇴적암과 조화적인 산출상태를 보이는 춘천 각섬암의 화학적 특징을 화성기원임을 나타낸다. $SiO_2$ 함량이 45~53 wt%인 이들 각섬암의 원암은 현무암질로 대부분 비알칼리 계열이 솔리아이트에 속한다. MgO 변화그림에서 $Na_2O$, $Fe_2O_3$, $Al_2O_3$ 는 전반적으로 분산되는 반면, CaO는 MgO와 정비례하고 $SiO_2$, $TiO_2$, $P-2O_5$, $K_2O$는 MgO와 반비례하는 경향을 보인다. 이들 주성분 원소의 변화는 현무암질 마그마의 감람석, 단사휘석, 사장석의 정출과 관련된 분화 결과로 GUTJR될 수 있다. 강걸리 각섬암은 구봉산 각섬암에 비해 낮은 MgO를 가져보다 분화된 암석임을 보이는데, 두 각섬암의 불호정원소의 비 $TiO_2/P_2O_5$의 차이는 모 마그마의 성인이 다름을 시사한다. 주성분 원소를 이용한 지구조 판별 그림에서 추천 각섬암을 그원암이 판내부환경에서 정치한 현무암질암임을 시사하여, 옥천대 각섬암의 그것과 유사하다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1689-1691
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• 1999

The conduction characteristics of $Pr_6O_{11}$-based ZnO varistor were investigated. ZnO-$Pr_6O_{11}$-CoO-$Sm_2O_3$-based ZnO varistor were sintered at $1300^{\circ}C$ and $1350^{\circ}C$ in the addition range $0.0\sim2.0mol%$ $Sm_2O_3$, respectively. ZnO varistors which are added with 1.0mol% at each temperature exhibited best excellent conduction characteristics, namely the nonlinear exponent was 42.05 at $1300^{\circ}C$, 36.79 at $1350^{\circ}C$ and leakage current was $9.16{\mu}A$ at $1300^{\circ}C$, $11.7{\mu}A$ at $1350^{\circ}C$. Consequently, it is estimated that ZnO-$Pr_6O_{11}$-CoO-$Sm_2O_3$-based ZnO varistors, which $Sm_2O_3$ is added 1.0mol% is to be used as a basic composition of $Pr_6O_{11}$-based ZnO varistors.