• Resources Recycling
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• v.18 no.6
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• pp.30-37
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• 2009

Silica sol was prepared from the mixture of sodium silicate solution and oxidized silicate solution in which sodium had been removed by sol-gel process. The properties of sodium silicate solution and silicate solution thus prepared were characterized by yellow silicomolydate method. Moreover, the formation and growth of silica sol from sodium silicate solution was investigated. Sodium silicate solution with 2% of $SiO_2$ contains 95% of reactive silicate, and 50% of reactive silicate participates sol-gel reaction. From the results of FT-IR analysis, it was found that the intensity of silanol bond decreased and the intensity of siloxane bond increased with increasing reaction temperature. Zeta potential of silica sol prepared at each condition was -40~-60 mV and it could be known that silica sol in this study was well dispersed. The silica sol with 5~10 nm size could be prepared by heating the mixed solution of sodium silicate and silicate solution. And the silica sol grew into about 20 nm as silicate solution was added to silica sol solution.

• Resources Recycling
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• v.16 no.5
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• pp.31-35
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• 2007

The formation of silica sol from sodium silicate solution and the growth of silica sols were investigated in this study. The $SiO_2$ content of 2% in sodium silicate solution was proper to oxidize sodium silicate with sulfuric acid. After the removal of sodium ions in sodium silicate solution, the pH of silicate solution had to be controlled above 9 for a stable silicate solution. The silica sol, which size is about 10 nm, could be prepared by heating the mixed solution of sodium silicate and silicate solution removed sodium ions at pH 10 and 80. And the silica sol grew into about 50 nm as silicate solution was added to silica sol solution.

• Proceedings of the Membrane Society of Korea Conference
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• 1996.10a
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• pp.55-57
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• 1996

다공성 무기막은 높은투과도와 뛰어난 내열.내화학성, 그리고 경제성 때문에 기존의 PSA공정이나 증류와 같은 고에너지 분리공정을 대체하는 공정으로 각광을 받고 있다. 무기재료막의 제조하는 방법으로 주로 알콕사이드를 사용하는 솔-젤법(1)과 금속(2) 또는 기상반응(3)을 이용하는 화학증착법이 사용된다. 또한 고온에서 수소를 연속적으로 분리하여 화학평형에 기인한 한계를 극복하여 높은 수율을 얻고자하는 막반응기에 관한 연구가 활발히 진행되고 있다. 본 연구에서는 $\alpha$-알루미나 지지체의 미세한 다공성 구조 내부에서 TEOS(Tetraethylorthosilicate)와 산성의 알코올-물 혼합물을 확산시켜 실리카 솔을 생성시킴과 동시에 젤화시켜 기공의 크기를 감소시켜 막을 제조하였다. 이렇게 제조된 막은 높은 투과도와 낮은 수소선택도(selectivity=3-4)를 보였고, 두번째 단계로 silica sol을 제조하여 진공 하에서 dip-coating을 행하였다. 이렇게 2단계로 기공 구조를 개선시킨 실리카 막은 저압에서 상대적으로 높은 수소의 분리도(selectivity=5-7)를 보였으며 여전히 높은 투과도를 갖는다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.123-123
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• 2012

초소수성 표면은 150도 이상의 높은 물 접촉각과 10도 이하의 낮은 sliding angle을 가지며 self-cleaning, anti-contamination 기능을 갖고 있는 것이 특징이다. 재료표면의 친수성과 소수성을 제어하기 위해서는 화학적 인자인 물질의 표면에너지나 물리적 인자인 표면 거칠기를 조절하는 방법이 있다. 초소수성 표면을 구현하기 위해서는 표면의 거칠기를 증가시키거나 표면 에너지를 낮춰야 하는데 고체 표면의 거칠기를 증가시키기 위해서는 일반적으로 표면에 microscale과 nanoscale의 계층구조를 형성시키는 방법이 사용된다. 자연계에 매우 풍부하게 존재하는 실리카는 내구성과 내마모성, 화학적 안정성, 고온 안정성 등을 지니고 있으며 인체에 무해하기 때문에 다양한 종류의 전자기기 및 부품의 내외장 코팅에 적용이 검토되고 있다. 이러한 관점에서 본 연구에서는 초소수성 코팅층을 구현하는 하나의 방법으로서 졸-겔방법으로 실리카 졸을 합성하여 전기분무법을 사용하여 microscale의 실리카 입자 코팅층을 형성하였으며, 표면 미세구조 조절 및 계층구조 형성과 불소화처리 공정을 통하여 초소수성 실리카 코팅층을 제조하였다. 이러한 초소수성 실리카 코팅층의 표면거칠기, 자외선 영향향, 내구성 등을 초소수성 관점에서 평가하였다.

• Polymer(Korea)
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• v.29 no.3
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• pp.242-247
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• 2005

Two kinds of colloidal silica(CS)/silane sol solutions were prepared in variation with synthesizing parameters such as kinds of CS, ratio of CS to silane and reaction time. Such sol solutions were obtained from 1034A Cs/methyl-trimethoxysilane(MTMS) and HSA CS/MTMS solutions. In the case of 1034A CS/MTMS CS/silane sol, coating film had high contact angle and more enhanced flat surface than those in the case of HSA CS/MTMS sol. In the case of thermal stability, thermal dissociation of 1034A CS/MTMS sol did not occur up to $550^{circ}$. The thickness of coating film obtained from 1034A CS/MTMS sol increased with increasing the amount of MTMS. The hardness of coating films obtained from 1034A CS/MTMS sol decreased with increasing the amount of MTMS. Surface free energy of CS/silane sol-gel coating film decreased with increasing amount of MTMS.

• Resources Recycling
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• v.17 no.6
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• pp.34-42
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• 2008

The properties of sodium silicate solution were surveyed by using the yellow silicomolybdic method, and the formation of silica sol from sodium silicate solution and the growth of silica sol were investigated in this study. The $SiO_2$ content of 2 wt% in sodium silicate solution was proper to oxidize sodium silicate with sulfuric acid. After the removal of sodium ions in sodium silicate solution, the pH of silicate solution had to be controlled above 9 for the stabilization of silicate solution. The condensation between silicic acid species and silica nuclei surfaces has been studied at $20{\sim}80^{\circ}C$ and pH 10 in silicate solutions with silica nuclei. The reaction falls into two kinetics regimes, limited at high silicic acid species concentration by polymerization, but at lower concentration by a process whereby deposited silicic acid species condenses further to silica. The overall condensation is first-order in silicic acid species concentration, proceeded toward to pseudo equilibrium concentration, $C_x$, rather than the solubility of amorphous silica. The heat of solution of amorphous silica was 3.34 kcal/mol and exhibits an Arrhenius temperature dependence with an apparent activation energy of 3.16 kcal/mol in the range of $20{\sim}80^{\circ}C$.

• Proceedings of the Korea Crystallographic Association Conference
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• 2003.11a
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• pp.22-22
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• 2003

• Proceedings of the Membrane Society of Korea Conference
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• 1996.04a
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• pp.51-52
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• 1996

무기막을 기체 분리 및 분리막 반응기에 적용하려면 특정 기체에 대한 선택도 뿐만 아니라 절대 투과 속도 또한 높아야 한다. 박막 담지 무기막은 다공성 지지체를 사용하여 그위 또는 그 기공 내에 선택적 투과성을 지니는 막을 합성한 형태로서, 되도록 얇은 선택적 투과막을 지지체에 제조함으로써 투과도를 향상시킬 수 있다. 고온에서 수소에 투과성이 있는 실리카막의 경우 기공의 크기기 4nm 정도인 다공성 유리를 지지체로 하여 화학증착법으로 제조하는 연구가 많이 수행되어 왔으며 400$\circ$ 이상의 온도에서 막을 통한 수소의 투과도는 0.1 cm$^3$[STP]/min-atm-cm$^2$ 수준이었다. 본 연구에서는 실리카 담지 무기막의 수소 투과성 향상을 위하여 기공의 크기가 다공성 유리보다 큰 다공성 알루미나를 지지체로 사용하였으며, 이 지지체의 기공 내부에 솔-젤 및 화학증착법에 의하여 실리카 막을 합성하고 고온에서의 기체 투과 특성을 살펴보았다.

• Polymer(Korea)
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• v.28 no.5
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• pp.391-396
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• 2004

In order to overcome drawbacks in the conventional preparation of epoxy/silica nanocomposites, such as formation of micro voids and dimensional instability caused by evolution of volatile by-products during curing reaction, a novel preparation method using Si-N precursor has been proposed. When prepared through in-situ reaction of epoxy curing reaction with sol-gel reaction of Si-N precursor, methyltripiperidinylsilane (MTPS) which does not produce by-products during reaction, epoxy/silica nanocomposites of extremely even dispersion of inorganic phase could be successfully prepared, resulting in high enhancement of mechanical and thermal properties as well as outstanding transparency.

• Journal of Conservation Science
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• v.23
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• pp.1-10
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• 2008

Consolidants based on tetraethoxysilane (TEOS) such as alkoxysilanes have been widely used for the consolidation of decaying stone heritages. Low-viscosity alkoxysilanes penetrate inside the decaying stone and polymerize within the porous structure of the decaying stone, significantly increasing the cohesion of the material. However, TEOS-based consolidants suffer from practical drawbacks, such as crack formation of the gel during the drying phase due to the developed capillary force, which is typical for TEOS-based consolidants. We prepared new consolidants TEOS-based consolidants containing flexible (3-glycidoxypropyl)trimethoxysilane (GPTMS) and silica nanoparticles (or polyhedral oligomeric silsesquioxanes (POSS)) in order to reduce capillary force development during gel drying. Since the consolidants should have a good interaction with the component of the stone in order to connect the isolate grains of decaying stone, the adhesion interaction of the developed consolidants on the surface of the granite was macroscopically investigated by the ISO 2409 cross cutting test. The adhesion interaction decreased with the addition of silica nanoparticle and POSS while it increased with the addition of GPTMS in TEOS solution.