• Journal of the Korean Ceramic Society
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• v.28 no.9
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• pp.705-711
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• 1991

Alumina precursor sol was obtained by the reaction of Al(OC4H9)3 and acetylacetone in the solvent followed by the partial hydrolysis. This sol was measured by viscosity and the effect of pH. The powders obtained from this sol were calcined at the various temperatures. The transition of crystals and crystal state were investigated at the various temperatures. The powders dried at 90$^{\circ}C$ showed amorphous and ${\gamma}$-Al2O3 at 900$^{\circ}C$, ${\alpha}$-Al2O3 mono-phase at 1050$^{\circ}C$ respectively. As a result of Al27-MASNMR analysis, amorphous and ${\alpha}$-Al2O3 powders showed 6-coordinated Al, ${\gamma}$-Al2O3 4-coordinated Al respectively.

• Journal of the Korean Ceramic Society
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• v.32 no.1
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• pp.17-24
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• 1995

The TEA complex polymeric sol was prepared by the alkoxide sol-gel method. The purpsoe of this experiment was to vefity the particle shape in the sol from the investigation of the rheological properties. TEA retarded hydrolysis rate by the reaction with alkoxide enough to make a stable transparent sol in the wide range of composition. From the results of the viscosity change with time, the optimum mole ratio for spinning was selected as 0.5 mole of TEA, 3 mole of H2O and the optimum viscosity was 104 cPs. The rheological behavior of the sol showed that the particle shape in the sol was linear, which was adequate for fiber drawing.

• Korean Chemical Engineering Research
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• v.54 no.6
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• pp.767-774
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• 2016

Three different alumina sols were prepared by hydrolyzing aluminum isopropoxide as a starting material in methanol solvent, followed by peptizing with acetic acid, nitric acid or hydrochloric acid as a peptizing agent by the Sol-Gel Method. Also, coating solutions were obtained by adding a silane coupling agent, (3-glycidyloxypropyl) trimethoxysilane to the alumina sols, deposited on polycarbonate substrates by dip-coating and densified by thermal curing. The effect of types of peptizing agents was studied on the properties of coating films. As a result, coating films, prepared with hydrochloric acid or nitric acid as a peptizing agent, showed excellent properties of pencil hardness of H or 2H and adhesion of 5B. On the other hand, coating films, prepared with acetic acid as a peptizing agent, exhibited poor properties of pencil hardness of HB and adhesion of 3B.

• Journal of the Korean Applied Science and Technology
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• v.38 no.6
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• pp.1561-1567
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• 2021

In this study, we have studied synthesis of zirconia-alumina composite coating materials via a low-temperature sol-gel process. The zirconia-alumina composites were prepared by coating zirconia precursor, alumina precursor, and organosilane mixture on a polyethylene terephthalate substrate through three steps: sol-gel process, low-temperature photocuring process, and heat treatment process. The structural properties and element analysis of the composites were confirmed by FT-IR and XPS. The coated composite showed a transmittance of 96% or more in the visible light region with a wavelength of 420 nm or more and pencil hardness of 9H or more. In case of the composite of the molar ratio of zirconia and alumina of 1:4, the highest nanoindentation hardness was measured with 1.212 GPa.

• Journal of the Korean Ceramic Society
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• v.30 no.7
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• pp.589-597
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• 1993

The optimum sol solution for making alumina membrane was synthesized by using sol-gel method with aluminium isopropoxide. Two types of supports were made from the $\alpha$-Al2O3 powder. The porosities of supports could be controlled by the forming methods and the heat treatment conditions. After the support was coated with optimum sol solution and heat-treated at 50$0^{\circ}C$ for 1hour, the thickness of crack-free membrane could be controlled reproductively with dipping time.

• Korean Chemical Engineering Research
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• v.45 no.4
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• pp.328-334
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• 2007

Chemical heat pump system of 2-propanol/acetone/hydrogen is most suitable to the recovery of waste heat of power plant. various types of 5 wt% Pt-alumina catalysts were prepared for 2-propanol dehydrogenation using sol-gel method. The characteristics and the dehydrogenation reaction rate of each catalyst were investigated. Pt-alumina xerogel catalyst has excellent reaction rate and good durability in comparison with the existing alumina supported Pt catalysts. Pt-alumina aerogel catalyst had the highest reaction rate in all prepared catalysts, but sufficient aging time was necessary to maintain its reaction rate. A potential advantage of the aerogel catalyst is the fact that the high temperature heat treatment is not required. Without heat treatment or with low temperature heat treatment, the Pt-alumina aerogel catalyst has excellent reaction rate as well as durability and this gives us the economic advantage. Alumina xerogel supported Pt catalyst prepared by incipient wetness method showed good reaction rate, and had good mechanical strength. Blank alumina xerogel prepared by sol-gel method can be used for the support of metal catalysts.

• Applied Chemistry for Engineering
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• v.8 no.4
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• pp.704-707
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• 1997

The preparation of alumina sol for fine chemical field from kaolin-derived aluminum sulfate solution is performed. Noncrystalline AlO(OH) was prepared by dropping ammonia water into aluminum sufate solution with stirring. Acetetic acid was added to form the electrical double layers on the particle surface of the slurry, which resulted in a stable sol. The influence of the reaction temperature, reaction time, acetetic acid concentration on the preparation of alumina sol were investigated. Dispersed colloid particles of AlO(OH) were prepared at the reaction temperature of $50{\sim}90^{\circ}C$ and 1.6 A/C = 1.6 (molar ratio), regardless of the reaction time. Stable alumina sol having a particle size of about 5~10 nm was prepared in the range 1~5 vol% alumina content.

• Membrane Journal
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• v.21 no.3
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• pp.229-235
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• 2011

In this study, mesoporous titania/alumina membranes were prepared by sol-gel method. Pore structure and phase composition of titania/alumina membranes could be changed by calcination temperature. The addition of alumina into titania membranes retarded anatase-to-rutile phase transformation, resulting in stabilization of pore structures. The 5 time dip-coated membrane calcined at $450^{\circ}C$ is about $10.3{\mu}m$ in thickness with an average pore size of 5 nm. Hydrogen and nitrogen permeances through the membrane were $17.1{\times}10^{-7}mol/m^2{\cdot}s{\cdot}Pa$ and $4.7{\times}10^{-7}mol/m^2{\cdot}s{\cdot}Pa$, respectively. These data were explained by the Knudsen diffusion mechanism.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.879-882
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• 1997

This paper aims to clarify the effect of the sol-gel sintered alumina grain and the PbO content of binder on the performance of the vitrified alumina stone for superfinishing the ball bearing race with the vitrified alumina superfinishing stone. The main conclusions obtained were as follows. The stone that contain 8- 11% PbO in binder shows the highest grinding ratio, and increasing or decreasing the PbO contents causes lower grinding ratio. When superfinishing with the stone using the 45% fused alumina and 55% sol-gel sintered alumina grain, the grinding ratio becomes the best, the other ratio of grain contents shows lower performance. With increasing the bending strength of stone, the grinding ratio becomes larger. The roughness of the finished surface is the lowest in case of using the stone of the above mentioned conditions.

• Journal of the Korean Ceramic Society
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• v.29 no.2
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• pp.107-118
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• 1992

Alumina supports for TiO2 ultrafiltration membrane coating were prepared by presintering disk-type preforms at 140$0^{\circ}C$. These supports showed uniform microstructures which had the apparent porosity of 40%, the pore size distribution in the range of 0.1~0.5${\mu}{\textrm}{m}$, and the water flux of 1400ι/$m^2$.h at the pressure difference of 10 atm. The optimum pH and concentration of the TiO2 sol for coating were 0.8 and 1.0 wt%, respectively, and sol particles were identified as rutile forms of 20 nm size. Crack-free alumina-supported rutile TiO2 membranes could be prepared through well controlled drying and heating the gel layer coated by the sol-gel dipping. The pore size of the TiO2 membranes heat-treated at 50$0^{\circ}C$ for 2 hrs was 30~80$\AA$, and their thickness varied from 1.1 to 3.8 ${\mu}{\textrm}{m}$ in accordence with the dipping time (4~40 min). The flux of water through this composite membrane at 10 atm was found to be in the range from 800 to 1100ι/$m^2$.hr depending on the dipping time (10~40 min). The membrane thickness increased linearly with the square root of the dipping time and the slope was 0.62 ${\mu}{\textrm}{m}$/{{{{ SQRT { min} }}.