• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.5
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• pp.2529-2535
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• 2013

Sol-gel method was utilized to prepare SPEEK/PWA electrolyte composite membranes. TEOS was used as a precursor and phosphotungstic acid(PWA) as a catalyst for the sol-gel reaction. It was observed through FE-SEM analysis that the PWA and silica nanoparticles were uniformly dispersed into the polymer matrix. The water uptake of SPEEK/PWA/silica composite membranes was less affected by TEOS concentration at higher TEOS contents, while the water uptake decreased as TEOS concentration increased at lower TEOS contents. The proton conductivity of the composite membranes showed similar trend as the water uptake of the composite membranes. The methanol permeability of SPEEK/PWA/silica composite membranes decreased as TEOS concentration increased.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.233-233
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• 2006

[ $Y_{2}O_{2}S:Eu$ ], a red phosphor, coated with silica nanoparticles or nanocomposites composed of silica nanoparticles and polymeric materials such as PMMA and PVP was prepared via sol-gel process. Samples were prepared from four different methods coded P1, P2, P3, and P4. P1 includes a conventional sol-gel process and a dip-coating method while P2 has the same procedure with P1 except that nanocomposites containing both silica nanoparticles and polymer prepared by sol-gel process were used as coating materials. In P3 method, phosphors were dispersed in a solution containing silica precursor, i.e., TEOS and then polymerization was performed to coat onto the phosphors surface while P4 followed the same procedure with P3 except that a solution containing both TEOS and organic monomer were used in preparing coating materials. Among various coating methods examined in this study, uniform coating of phosphor could be achieved by using method P4, i.e., phosphor surface coating in a solution containing hydrophobic monomer and TEOS. Furthermore, $Y_{2}O_{2}S:Eu$ red phosphor coated with nanocomposite composed of PMMA matrix and silica nanoparticles exhibited enhanced PL intensity and long-term stability.

• Korean Chemical Engineering Research
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• v.48 no.4
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• pp.428-433
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• 2010

Waterborne polyurethane(WPU) was synthesized from isophorone diisocyanate(IPDI), poly(tetramethylene glycol)(PTMG), dimethylol propionic acid(DMPA), triethylamine(TEA), ethylenediamine(EDA) and 3-aminopropyl triethoxysilane(APS) as a coupling agent. Subsequently, WPU/silica nanocomposites with different silica contents(0 to 8 wt%) were prepared by performing sol-gel reactions with tetraethylorthosilicate in the WPU matrix. The average particle size of the nanocomposite solutions increased with increasing TEOS content. Also, the prepared nanocomposites showed better thermal stability than pure WPU.

• Corrosion Science and Technology
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• v.18 no.5
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• pp.168-174
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• 2019

The sol-gel methodology has been applied successfully in the synthesis of a novel hybrid coating based on dimethoxymethyl-n-octadecylsilane precursor. The newly synthesized parent coating was functionalized further with two commercially-available corrosion-inhibitive pigments Moly-$white^{(R)}$ 101-ED and Hfucophos $Zapp^{(R)}$, applied to mild steel panels, and immersed continuously in 3.5% NaCl electrolytic solution for 288 h. The corrosion protection performance of the prepared functional coatings was evaluated using electrochemical impedance spectroscopy (EIS) and DC polarization techniques. An enhancement in the barrier properties has been revealed from the electrochemical characterization data of the hybrid films, in comparison with untreated mild steel substrates following long-term immersion in 3.5% NaCl. The corrosion resistance properties of the newly developed coatings over mild steel substrates found to be largely dependent on the type of the loaded inhibitive pigment in which the Moly-white inhibitor has a positive impact on the corrosion protection performance of the parent coating, while an opposite behavior was observed upon mixing the base polymeric matrix with the commercially-available Zapp corrosion inhibitor.

• Bulletin of the Korean Chemical Society
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• v.30 no.10
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• pp.2387-2392
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• 2009

A composite film of multi-walled carbon nanotube (MWCNT)/sol-gel-derived zinc oxide(ZnO)/Nafion has been utilized as an efficient immobilization matrix for the construction of a highly sensitive and stable tris(2,2'-bipyridyl) ruthenium(II) (Ru(${bpy)_3}^{2+})$ electrogenerated chemiluminescence (ECL) sensor. The electrochemical and ECL behaviors of Ru(${bpy)_3}^{2+})$ ion-exchanged into the composite film were strongly dependent upon the sol-gel preparation condition, the amount of MWCNT incorporated into the ZnO/Nafion composite film, and the buffer solution pH. The synergistic effect of MWCNTs and ZnO in the composite films increased not only the sensitivity but also the long-term stability of the ECL sensor. The present ECL sensor based on the MWCNT/ZnO/Nafion gave a linear response ($R^2$ = 0.999) for tripropylamine concentration from 500 nM to 1.0 mM with a remarkable detection limit (S/N = 3) of 15 nM. The present ECL sensor showed outstanding long-term stability (94% initial signal retained for 5 weeks). Since the present ECL sensor exhibits large response towards NADH, it could be applied as a transduction platform for the ECL biosensor in which the NADH is produced from the dehydrogenase-based enzymatic reaction in the presence of NA$D^+$ cofactor.

• Bulletin of the Korean Chemical Society
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• v.26 no.2
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• pp.241-247
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• 2005

A series of proton conductive inorganic-organic hybrid membranes doped with phosphoric acid ($H_3PO_4$) and/or triethylphosphate (PO(OEt)$_3$) have been prepared by sol-gel process with 3-glycidoxypropyltrimethoxysilane (GPTMS), 3-aminopropyltriethoxysilane (APTES) and tetraethoxysilane (TEOS) as precursors. High proton conductivity of 3.0 ${\times}$ $10^{-3}$ S/cm with composition of 50TEOS-30GPTMS-20APTES-50$H_3PO_4$ was obtained at 120 ${^{\circ}C}$ under 50% relative humidity. Thermal stability of membrane was significantly enhanced by the presence of SiO$_2$ framework up to 250 ${^{\circ}C}$. XRD revealed that the gels are amorphous. IR spectra showed a good complexation of $H_3PO_4$ in the matrix. The conductivity under 75% relative humidity was significantly improved by addition of APTES due to the increase in concentration of defected site in hybrid matrix. The effect of PO(OEt)$_3$, humidifying time, and heat-treatment were also investigated. PO(OEt)$_3$ had no improvement on conductivity and conductivity increased with humidifying time, however, decreased with heating temperature.

• Elastomers and Composites
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• v.53 no.2
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• pp.57-66
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• 2018

Styrene-butadiene rubber (SBR), reinforced with different contents of silica (with or without modification using silane coupling agents), was prepared by a modified sol-gel method involving hydrolyzation of tetraethoxysilane over an acid catalyst. The structures of the as-prepared samples were characterized using various techniques, such as scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. The mechanical properties of the as-prepared samples were discussed in detail. The results revealed an increasing of the storage modulus (G') with increase in the silica content without modification. In contrast, G' decreased after modification using silane coupling agents, indicating a reduction in the silica-silica interaction and improved dispersion of silica in the SBR matrix. Both tensile stress and hardness increased with increase in the silica content (with modification) in the SBR matrix, albeit with low values compared to the samples with un-modified silica, except for the case of silica modified using (3-glycidyloxypropyl) trimethoxysilane (GPTS). The latter observation can be attributed to the special structure of GPTS and the effort of oxygen atom lone-pair.

• Journal of Electrochemical Science and Technology
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• v.7 no.4
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• pp.277-285
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• 2016

There is a growing demand for simple, cost-effective, and accurate analytical tools to determine the concentrations of biological and environmental compounds. In this study, a stable electroactive thin film of cobalt hexacyanoferrate (Cohcf) was prepared as an in situ chemical precipitant using electrostatic adsorption of $Co^{2+}$ on a silicate sol-gel matrix (SSG)-modified indium tin oxide electrode pre-adsorbed with $[Fe(CN)_6]^{3-}$ ions. The modified electrode was characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical techniques. Electrocatalytic oxidation of hydrazine on the modified electrode was studied. An electrochemical sensor for hydrazine was constructed on the SSG-Cohcf-modified electrode. The oxidation peak currents showed a linear relationship with the hydrazine concentration. This study provides insight into the in situ growth and stability behavior of Cohcf nanostructures and has implications for the design and development of advanced electrode materials for fuel cells and sensor applications.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.4 s.33
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• pp.69-73
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• 2004

A series of $H_3PO_4$-doped composite membranes based on poly(vinyl alcohol)(PVA) and silica have been prepared by sol-gel process. The proton conductivity, as well as properties of swelling, methanol permeation, was measured in this study. The proton conductivity increased with the molar ratio of $H_3PO_4$ to silica. With the silica content increasing, swelling degree decreased and methanol permeability showed a slight increase. It suggested that the former was mainly determined by hydrophilicity of the membrane, while the latter was dominated by the interconnectivity of matrix. According to the value of on, the optimal conformations of these composite membranes were 60, 70, 80 wt.$\%$ of PS-x in membranes, where x were 1.5, 1.0, and 0.5, respectively. These composite membranes were thermal stability up to $200^{\circ}C$.

• Progress in Superconductivity and Cryogenics
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• v.4 no.1
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• pp.26-29
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• 2002

Polyimide-epoxysilane (coupling agent) composites were reacted with oligomeric PDMS, a condensation product of difunctional silane, by a sol-gel process and were then dried into films. And then, the surface, mechanical, and electric properties were measured. The study showed that PDMS existed in the polymide matrix by the use of FT-IR. In the mechanical properties, the maximum elongation and toughness was increased in the polyimide with silane-groups. But the maximum tensile strength was slightly decreased. And the intensive dispersion of the silane-groups on the surface of polyimide was ascertained through XPS measurement. In the electric properties. AC break down voltage was increased by increasing the amount of difunctional silane. This experiment showed that PDMS added polyimide had better mechanical and electric properties than classical materials.