• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2009년도 춘계학술대회 논문집
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• pp.244-245
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• 2009

Sol-gel coatings of $TiO_2$ have been prepared from $TiO_2$ sol and deposited by dip-coating technique on 316L stainless steel sheets in order to study the electrochemical behaviorin corrosive solutions. The influence of the coatings on the chemical corrosion of the substrate has been evaluated by potentiodynamic polarization curves in different aqueous NaCl solution at $25^{\circ}C$.

• Macromolecular Research
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• 제10권3호
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• pp.174-177
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• 2002

Proton-conducting hybrid materials composed of silica and Nafion polymer were prepared from the sol-gel synthesis of silica in aqueous Nafion solution. The compositions of hybrid proton conductors were adjusted with the changing ratios of tetraethyl orthosilicate to Nafion. The thermal analysis, FTIR, SEM, and X-ray diffraction studies have proved the formation of Nafion/silica hybrid materials and no remarkable phase separation was observed, which led to an assumption that the macromolecular chain of silica and Nafion was homogeneously interlaned.

• Korean Chemical Engineering Research
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• 제56권2호
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• pp.156-161
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• 2018

염소법과 졸-겔법으로 $TiO_2$ 광촉매 분말을 제조하였다. 제조방법 및 조건에 따라 촉매의 결정상 형태(아나타제와 루타일)와 비표면적이 변화하는 것을 알 수 있었다. TTIP-sol로 제조한 광촉매가 염소법이나 TBOT-sol로 제조한 광촉매에 비해 methylene blue (MB) 분해 특성이 더 높았으며, 수용액상의 90% 이상의 MB를 제거할 수 있었다. 실험 결과를 통해 $TiO_2$ 광촉매는 단일 아나타제상와 큰 비표면적을 가지면 유기물 분해 특성을 향상될 수 있는 것을 확인하였다.

• 한국전기전자재료학회논문지
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• 제32권3호
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• pp.246-251
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• 2019

A solvent free, highly concentrated silica-acryl monomer hybrid sol was synthesized using aqueous colloidal silica as a precursor. The effects of the silica particle size, type of surface treatment agent employed, and silica content on the formation of the hybrid sol were systematically studied. The optical and physical properties of the coating solution prepared using the hybrid sol were also characterized. The viscosity of the hybrid sol tended to decrease as the particle size of the silica and the molecular weight of the surface treatment agent increased. The PET substrate coated with MPTMS-Mix (mixture, 70 wt%) solution showed the highest surface hardness (6 H) and low surface roughness ($Ra=0.044{\mu}m$), which could be attributed to an increase in packing density caused by the infiltration of small particles into the pores formed between larger particles.

• 한국재료학회지
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• 제26권10호
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• pp.570-576
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• 2016

Using the ultrasonic pyrolysis method, spherical $SiO_2$ powders were synthesized from aqueous $SiO_2$ sol as a starting material. The effects of pyrolysis conditions such as reaction temperature, $SiO_2$ sol concentration, and physical properties of precursor were investigated for the morphologies of the resulting $SiO_2$ powders. The particle size, shape, and crystallite size of the synthesized $SiO_2$ powders were demonstrated according to the pyrolysis conditions. Generally, the synthesized $SiO_2$ particles were amorphous phase and showed spherical morphology with a smooth surface. It was revealed that increased crystallite size and decreased spherical $SiO_2$ particle size were obtained with increases of the pyrolysis reaction temperature. Also, quantity of spherical $SiO_2$ particles decreased with the decrease in the concentration and surface tension of the precursor.

• 한국분말재료학회지
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• 제10권5호
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• pp.310-317
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• 2003

Two-component ceramic (alumina-zirconia) composites were fabricated by a soft-solution process in which polyethylene glycol (PEG) was used as a polymeric carrier. Metal salts and PEG were dissolved in ethyl alcohol without any precipitation in 1:1 volume ratio of alumina and zirconia. In the non-aqueous system, the flammable solvent made explosive, exothermic reaction during drying process. The reaction resulted in formation of volume expanded, porous precursor powders by a vigorous decomposition of organic components in the precursor sol. The PEG content affected the grain size of sintered composites as well as the morphology of precursor powders. The difference of microstructure in sintered composite was attribute to the solubility and homogeneity of metal cations in precursor sol. At the optimum amount of the PEG polymer, the metal ions were dispersed effectively in solution and a homogeneous polymeric network was formed. It made less agglomerated particles in the precursor sol and affected on uniform grain size in sintered composite.

• 한국응용과학기술학회지
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• 제17권2호
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• pp.144-148
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• 2000

A modification of the sol-gel method to obtain phase pure superconducting oxides is described. The method starts from organic salts of yttrium, barium and copper, such as acetates, and avoids the sudden and uncontrollable decomposition of the organic fraction which occurs if nitrates are used as starting materials. The aqueous solution obtained with citric acid in an alkaline medium is concentrated under vacuum. The solid so prepared is decomposed at about $300^{\circ}C$ thus giving an oxide precursor containing well dispersed yttrium, barium and copper. Pyrolysis at 850 - $920^{\circ}C$ followed by oxygen annealing gives the superconducting orthorhombic 123 phase. The results of TGA/DTA of the precursor, as well as XRD, electrical and magnetic property measurements on the pyrolysis products are presented and discussed.

• 한국응용과학기술학회지
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• 제24권3호
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• pp.246-252
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• 2007

$BaTiO_3$ powders were prepared by sol-gel method from different concentration of KOH aqueous solution and Ba/Ti molar ratio. Particle shape, size and crystal structure of prepared $BaTiO_3$ powders were analyzed by SEM, XRD, and FT-IR. As the result of KOH concentration changing, spherical particles were obtained by condition more than 3 M and particle size decreased as concentration increasing. Different appearance showed between dried and sintered powders against changing of Ba/Ti molar ratio. In case of dried powders, the crystallinity decreased as molar ratio increasing. On the other hand, increased as molar ratio increasing in case of sintered powders.

• Bulletin of the Korean Chemical Society
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• 제27권12호
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• pp.1981-1984
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• 2006

Novel amphiphilic, thermo-responsive polyaspartamides which showed both LCST (lower critical solution temperature), and sol-gel transition were prepared and characterized. The polyaspartamide derivatives were synthesized from polysuccinimide, the polycondensate of aspartic acid monomer, via successive nucleophilic ring-opening reaction by using dodecylamine and N-isopropylethylenediamine (NIPEDA). At the intermediate composition ranges, the dilute aqueous solution exhibited a thermally responsive phase separation due to the presence of LCST. The phase transition temperature was controllable by changing the content of pendent groups. In addition, a physical gelation, i.e. the sol-gel transition was observed from the concentrated solutions, which was elucidated by dynamic viscoelastic measurements. These novel injectable and thermo-responsive hydrogels have potential for various biomedical applications such as tissue engineering and current drug delivery system.

• 한국재료학회지
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• 제26권3호
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• pp.136-142
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• 2016

To study the dispersion factors of silica sol prepared from fumed silica powder, we prepared silica sol under an aqueous system using a batch type bead mill. The dispersion properties of silica sol have a close relationship to dispersion factors such as pH, milling time and speed, the size and amount of zirconia beads, the solid content of fumed silica, and the shape and diameter of the milling impellers. Especially, the silica particles in silica sol were found to show dispersion stability on a pH value above 7, due to the electrostatic repulsion between the particles having a high zeta potential value. The shape and diameter of the impellers installed in the bead mill for the dispersion of fumed silica was very important in reducing the particle size of the aggregated silica. The median particle size ($D_{50}$) of silica sol obtained after milling was also optimized according to the variation of the size and amount of the zirconia beads that were used as the grinding medium, and according to the solid content of fumed silica. The dispersion properties of silica sol were investigated using zeta potential, turbiscan, particle size analyzer, and transmission electron microscopy.