• Bulletin of the Korean Chemical Society
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• 제33권10호
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• pp.3378-3382
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• 2012

A superhydrophobic surface with a water contact angle > $150^{\circ}$ has attracted great interest from both fundamental and practical aspects. In this study, we demonstrated that hydrophobicity of a silica nanotube (SNT) array can be easily controlled by the SNT aspect ratio. In addition, the adhesive and anti-adhesive properties were controlled without modifying the hydrophobic surface. Various silica structures on a polydimethylsiloxane substrate were prepared using the desired alumina template. Bundle-arrayed and bowl-arrayed silica surfaces exhibited extraordinary superhydrophobicity due to the large frontal surface area and hierarchical micro/nanostructure. As the strategy used in this study is biocompatible and a wide range of hydrophobicities are capable of being controlled by the SNT aspect ratio, a hydrophobic surface composed of an SNT array could be an attractive candidate for bioapplications, such as cell and protein chips.

• 멤브레인
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• 제14권3호
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• pp.201-206
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• 2004

열화학적 IS 공정에서 요오드화수소의 분해에 적용하기 위하여 화학증착법(CVD)으로 제조된 silica 막의 안정성을 HI-$H_2O$ 기상 혼합물에서 평가하였다. Si 원천으로 tetraethoxysilane을 사용하여 서로 다른 CVD 온도로 기공크기가 100 nm인 $\alpha$-alumina를 처리하였다. CVD온도는 $700^{\circ}C$, $650^{\circ}C$, $600^{\circ}C$이었다. $600^{\circ}C$에서 수행한 단일 성분의 투과 실험에서 측정한 막의 $H_2$/$N_2$ 선택도는 CVD 온도 $700^{\circ}C$의 M1 막은 43.2, $650^{\circ}C$의 M2 막은 12.6, $600^{\circ}C$의 M3 막은 8.7을 나타내었다. HI-$H_2O$ 기상 혼합물에서 안정성 실험은 $450^{\circ}C$에서 수행하였는데, CVD 온도 $650^{\circ}C$에서 처리된 막이 다른 온도에서 처리된 막보다 더 안정성이 더 좋은 결과를 얻었다.

• 한국재료학회지
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• 제16권12호
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• pp.731-738
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• 2006

It is seriously considered using Al CMP (chemical mechanical planarization) process for the next generation 45 nm Al wiring process. Al CMP is known that it has a possibility of reducing process time and steps comparing with conventional RIE (reactive ion etching) method. Also, it is more cost effective than Cu CMP and better electrical conductivity than W via process. In this study, we investigated 4 different kinds of slurries based on abrasives for reducing scratches which contributed to make defects in Al CMP. The abrasives used in this experiment were alumina, fumed silica, alkaline colloidal silica, and acidic colloidal silica. Al CMP process was conducted as functions of abrasive contents, $H_3PO_4$ contents and pressures to find out the optimized parameters and conditions. Al removal rates were slowed over 2 wt% of slurry contents in all types of slurries. The removal rates of alumina and fumed silica slurries were increased by phosphoric acid but acidic colloidal slurry was slightly increased at 2 vol% and soon decreased. The excessive addition of phosphoric acid affected the particle size distributions and increased scratches. Polishing pressure increased not only the removal rate but also the surface scratches. Acidic colloidal silica slurry showed the highest removal rate and the lowest roughness values among the 4 different slurry types.

• 한국광물학회지
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• 제26권2호
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• pp.101-110
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• 2013

나노크기 매킨나와이트(nanocrystalline mackinawite, FeS)는 높은 비표면적을 지닌 반응성 높은 광물로, 오염된 지하수나 토양의 복원을 위해 널리 사용된다. 또한 매킨나와이트는 혐기성 부식반응에 대해 열역학적으로 안정하고, 황산염 환원미생물의 대사에 의해 재생된다는 장점이 있다. 하지만 매킨나와이트 나노입자는 지하수 흐름에 의해 멀리 확산되거나 입자집적이 일어나 대수층 공극을 막는다. 따라서 현장복원을 위한 투과반응벽(permeable reactive barrier)의 설치를 위해서 나노크기 매킨나와이트에 대한 변형이 필요하다. 이를 위해 본 연구에서는 코팅법을 활용해 매킨나와이트 나노입자를 알루미나(alumina, $Al_2O_3$) 및 활성알루미나(activated alumina) 표면에 증착시켰다. 매킨나와이트의 코팅량은 pH에 따라 현저히 달랐으며, 두 종의 알루미나 모두 약 pH 6.9에서 최대 코팅이 관찰되었다. 이 pH에서 알루미나와 매킨나와이트는 반대의 표면전하(surface charge)를 띠어 두 광물 간 정전기적 인력이 발생하고, 이로 인해 효율적인 코팅이 일어났다. 이 pH에서 알루미나 및 활성 알루미나에 의한 코팅량은 각각 0.038 $mmol{\cdot}FeS/g$과 0.114 $mmol{\cdot}FeS/g$이었다. 혐기성 조건에서 코팅되지 않은 알루미나 및 활성 알루미나, 그리고 최적 pH에서 코팅된 알루미나 및 활성 알루미나를 사용해 아비산염(arsenite) 흡착실험을 수행했다. 코팅되지 않은 활성 알루미나는 코팅되지 않은 알루미나와 비교해 단위질량당 높은 아비산염의 제거를 보여주었으나, 매킨나와이트의 코팅에 의한 흡착량 증가를 보이지 않았다. 활성 알루미나는 높은 비표면적을 지니고 있어 반응성 높은 수산화작용기(hydroxyl functional group)가 다수 존재했고, 이로 인해 코팅된 매킨나와이트에 의한 아비산염의 제거가 중요하지 않았다. 반면 알루미나는 매킨나와이트 코팅에 의해 향상된 아비산염의 제거율을 보였는데, 이것은 알루미나에 존재한 수산화작용기가 아비산염과의 표면배위결합(surface complexation)에 소모되고, 코팅된 매킨나와이트에 의한 부가적인 흡착이 일어났기 때문이다. 코팅된 알루미나는 이전에 연구된 코팅된 실리카와 비교해보면 단위 비표면적당 매킨나와이트의 코팅량이 약 8배 높았으며, 더 높은 아비산염에 대한 흡착력을 보였다. 따라서 본 연구의 결과는 코팅된 알루미나는 투과반응벽의 설치에 적합한 물질이고, 특히 아비산염으로 오염된 지하수의 정화에 유용하게 적용될 수 있음을 지시하고 있다.

• 한국광물학회지
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• 제12권1호
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• pp.11-22
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• 1999

Thermal behavior of dickite was studied by thermal analysis, X-ray diffraction analysis, electron microprobe analysis, and scanning electron microscopy, Dickite has an endothermic peak at about$ 650^{\circ}C$ and an exothermic one at $960^{\circ}C$ in the differential thermal analysis. The endothermic reaction is assigned to the decomposition of dickite to meta-dickite. Hydroxyl radicals are removed from dickite structure by the reaction, resulting in the weight loss about 10.5~14.5% and appearance of a 14$\AA$ phase different from other kaolin minerals. The reaction slowly proceed in the range of $200^{\circ}C$. As the completion of decomposition, aciclular mullite forms at the expense of meta-dickite plates with random crystallographic relationship. Mullites have diverse silica versus alumina ratio. The exothermic reaction without weight loss seems to be due to the formation of spinel and amorphous silica. The spinel phase shows cryptocrystalline globular morphology accompanying a little amount of silica. From spinel phase shows cryptocrystalling globular morphology accompanying a little amount of silica. From this work, it is suggested that mullite is formed from meta-dickite much lower temperature than the reported one in the previous works.

• 한국세라믹학회지
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• 제30권3호
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• pp.189-198
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• 1993

A new pressurized sol-gel coating technique forming membrane layers inside pores of the porous support by the simple operation has been developed. Crack-free and reproducible nanoparticulate silica membranes supported on the porous $\alpha$-alumina tube are synthesized by pressurized coating at 600kPa for 2hr. The pore radius and N2 gas permiability at the room temperature of silica membrane layers are 8$\AA$ and 7.0$\times$10-7mol/$m^2$.s.Pa, respectively. The mechanism of N2 gas transfer through synthesized membrane layers is the perfect Knudeen flow, and the thermal stability of the silica composite membranes is excellent upto 40$0^{\circ}C$.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.9-12
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• 2007

The transport mechanisms of the MTES (methyltriethoxysilane) templating silica/a-alumina composite membrane were evaluated by using four binary and one quaternary hydrogen mixtures through permeation experiments at unsteady- and steady-states. Since the permeation flux in the MTES membrane, through the experimental and theoretical studies, was affected by molecular sieving effects as well as surface diffusion properties, the kinetic and equilibrium separation should be considered simultaneously according to molecular properties. In order to depict the transient multi-component permeation on the templating silica membrane, the GMS (generalized Maxwell-Stefan) and DGM (dust gas model) were adapted to unsteady-state material balance.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.567-568
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• 2006

To investigate the recycle possibility of slurry for the oxide-chemical mechanical polishing (oxide-CMP) application, three kinds of retreated methods were introduced as follows: First, the effects on the addition of silica abrasives and the diluted silica slurry (DSS) on CMP performances were investigated. Second, the characteristics of mixed abrasive slurry (MAS) using non-annealed and annealed alumina ($Al_2O_3$) powder as an abrasive added within DSS were evaluated to achieve the improvement of removal rates (RRs) and within-wafer non-uniformity (WIWNU%). Third, the oxide-CMP wastewater was examined in order to evaluate the possible ways of reusing it. And then, we have discussed the CMP characteristics of silica slurry retreated by mixing of original slurry and used slurry (MOS).

• The Korean Journal of Ceramics
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• 제6권2호
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• pp.159-163
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• 2000

Alumina fibre has been synthesized successfully by sol-gel technique. Boehmite sol was prepared by hydrolyzing aluminium iso-propoxide and peptizing it with nitric acid. The stable sol thus obtained was used for fibre drawing when their viscosity reached the required value as a result of progress of the hydrolyzation and polycondensation reaction. The fibres dried at 11$0^{\circ}C$ for 12 hours were sintered at 1$600^{\circ}C$ for 5 hours. A reasonable sintered density with better microstructure and strength have been attained using 2 wt% of urea, magnesia and silica as sinter additives. Thermal analysis with sintering additives of 2 wt% and phase determination of the heat treated fibres using XRD and FT IR spectra confirms the phase transitions. The observation of surface and cross-section of the fibres were made using SEM. Fibres of uniform circular cross-section is obtained by fixing the shape in a setting solution.

• 한국세라믹학회지
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• 제31권12호
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• pp.1475-1482
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• 1994

Compositionally triphasic boehmite-silica-zirconia composite gels were prepared by a multiphasic sol-gel route. Phase-formation characteristics and densification behavior of the gel compacts were examined with and without $\alpha$-Al2O3 seeding. In the unseeded triphasic gels, both $\alpha$-Al2O3 and mullite crystallize simultaneously at 130$0^{\circ}C$. On the other hand, the $\alpha$-Al2O3 seeding selectively induces the formation of corundum phase ($\alpha$-Al2O3) at a significantly lower temperature (~110$0^{\circ}C$) and facilitates an epitaxial growth of $\alpha$-Al2O3 between 1100~130$0^{\circ}C$. The densification of alumina-mullite-zirconia composite (derived from the triphasic gels) was also enhanced by the $\alpha$-Al2O3 seeding, and this was attributed to the delayed crystallization of mullite in the $\alpha$-Al2O3 seeded gel.