• Journal of the Korean Ceramic Society
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• v.29 no.5
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• pp.403-409
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• 1992

The titania membrane thickness coated on the porous alumina support by the sol-gel method was analyzed using the slipcasting model. The thickness of calcined membrane layers increased linearly from 1.3 to 3.8 ${\mu}{\textrm}{m}$ with the square root of the dipping time (4~40 min). Growth rates of the thickness of wet gels and calcined layers were well described quantitatively by the slipcasting model. Through the regression of experimental data using model equations, the permeability and the pressure drop across wet gels, and the thickness and their growth rate constants of wet gels and calcined layers could be determined. It was also known that the gellation concentration of the TiO2 sol used in this work and the porosity of wet gel layes were 25 mol/ι and 0.53, respectively.

• Journal of the Korean Ceramic Society
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• v.30 no.2
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• pp.115-122
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• 1993

Transparent Al2O3 and TiO2 clear sols prepared by hydrolysis and subsequent peptization were mixed into wet gel. EDS analysis for this gel showed that wet gel was extremely homogeneous in chemical composition. Calcination of the wet gel at 120$0^{\circ}C$ for 50 minutes resulted in Al2O3-TiO2 nanocomposite powders where TiO2 particles of 101~102 nanometer were dispersed in the Al2O3 matrix. Both powders were sintered for 4 hours in the temperature range over 1500~1$650^{\circ}C$ with and without 5wt% MgO sintering aid. Among these sintered bodies, nanocomposite powder compacts sintered at 1$650^{\circ}C$ for 4 hours with 5wt% MgO showed the most dense structure with the grain size under 5${\mu}{\textrm}{m}$ and highest relative density of 98.2%.

• Journal of the Korean Ceramic Society
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• v.33 no.12
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• pp.1394-1402
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• 1996

The Silica gel with the density of 0.2g/cm3 and porosity of 90% was synthesized. The silica wet gel was dried and heat-treated under the ambient pressure after modification of the wet gel surface by TMCS. Specific surface area total pore volume and mean pore radius of dried gel were all increased with increasing heat treatment temperature and confirmed about 1400m2/g, 4.5cc/g and 8 nm respectively after heat treatment above 25$0^{\circ}C$. But the pore size distribution of dried gel was in the range of 1-100nm and was almost indepen-dent of temperature. As the result of external shape pore characteristics and microstructure of gel using SEM similar properties were observed between the silica gel synthesized in this study and the silica aerogel through the super critical drying.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.39 no.3
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• pp.36-40
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• 2007

It has been problematic to repulp the dry broke treated with permanent wet strength agents like PAE, UF and MF. Solution type GPAM has the benefit of easy repulping but it has problems of cocross-linking and tends to gel. Therefore, the product concentration must be lower than 10% to reduce the gel generation problem. We developed emulsion type GPAM by an inverse emulsion technology to resolve both the repulping problem with permanent wet strength agents and the stability problem of GPAM solution products.

• Korean Journal of Food Science and Technology
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• v.27 no.5
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• pp.690-696
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• 1995

Properties of dry milled rice flours made of paddy with different moisture content (12.6, 18.4 and 24.4%) were compared with those of wet milled rice flour. Among dry milled rice flour, the higher moisture content of paddy the finer particle size and the more distinct shape of starch were observed. As the moisture content of paddy increased, L (lightness) value and water absorption index of rice flour were increased, while setback in amylogram and water soluble index were decreased. Lower gel consistency and gel strength were found in dry milled rice flours than in wet milled rice flour, while no significant difference was found among dry milled rice flours. Enthalpy for melting crystalline of retrograded gels was higher in dry milled rice flours made of paddy with 24.4% moisture content than in other dry milled rice flours. Wet milled rice flour had lower retrogradation enthalphy than dry milled rice flours.

• Journal of the Korean Ceramic Society
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• v.22 no.2
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• pp.39-43
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• 1985

This study presents the results of an overall effort to detemine the applicability of the chemical wet process informing lead titanate electronic ceramics. Although pure lead titanate has not proven to be an important technological materials when prepared via conventional processing procedures this work is interesting as a study of chemical wet processing and a way of preparing pbTiO3 for study. The result obtained from this experiment were as follows ; Optimum synthesis condition which synthesize PbTiO3 by chemical wet process was obtained by firing at 50$0^{\circ}C$ after mixing $Pb(OH)_2$- gel and $Ti(OH)_4$ -gel at 7$0^{\circ}C$ for 4 hours.

• Journal of Energy Engineering
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• v.21 no.1
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• pp.43-46
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• 2012

A fluidized bed drying approach was utilized to the synthesis of water glass based silica aerogel powders. The effects of the fluidized bed drying conditions such as the superficial velocity and temperature of hot air and bead size as well as bead/wet-gel ratio, on the physical properties such as tapping density and productivity of the aerogel powders were systematically investigated. The experimental results showed that the amount of beads mixed with wet-gels in the fluidized bed column has the most profound impact on the fluidization efficiency, greatly enhancing the yield of the aerogel powders up to 98% with a proper bead/wet-gel weight ratio as compared to 72% without using beads. No significant change was observed in the tapping density over a wide range of the fluidized drying condition. Consequently the fluidized bed drying approach shows a good promise as an alternative route for the large-scale production of the aerogel powders.

• The Korean Journal of Ceramics
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• v.6 no.1
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• pp.37-42
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• 2000

To reduce shrinkage and the possibility of fracture during ambient pressure drying, it is of great importance to increase the strength and stiffness of the wet gels. In this paper is presented the strengthening and stiffening of wet silica gels prepared from sodium silicate (water glass) as well as properties of the corresponding xerogels. By washing gels containing different initial silica contents in water solutions at elevated pH, a maximum in shear modulus of ~4 MPa was obtained. The maximum stiffness enabled xerogels with bulk density of 0.28g/$\textrm{cm}^3$ to be made regardless of silica content and washing conditions. However, by aging the wet gels in a solution providing fresh monomers to the gel network, a shear modulus of 20 MPa was obtained after 27h. By this method monolithic xerogels with a density down to ~0.2g/$\textrm{cm}^3$ was prepared. The results are compared to alkoxide based gels.

• Journal of the Korean Ceramic Society
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• v.47 no.6
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• pp.553-559
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• 2010

The synthesis behavior of nanoporous silica aerogel in the macroporous ceramic structure was observed using TEOS as a source material and glycerol as a DCCA(dry control chemical additive). Silica aerogel in the macroporous ceramic structure were synthesized through a sono-gel process. The wet gel in the macroporous ceramic structure were aged in ethanol for 72 h at $50^{\circ}C$. The aged wet gel was dried under supercritical drying condition. The addition of glycerol has a role of giving the uniform pore size distribution. The reproducibility of aerogel in the macroporous ceramic was improved in the glycerol(0.05 mol%) added to the silica sol and TEOS : $H_2O$=1 : 12.

• Journal of the Korean Ceramic Society
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• v.45 no.10
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• pp.644-650
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• 2008

It has been proposed that the Cao-$SiO_2$ binary system can be good basic composition of bioactive glasses and glass-ceramics. In the present study, various kinds of Cao-$SiO_2$ gels were prepared by sol-gel method in order to control the microstructure which are related to their dissolution rate, induction period of apatite formation in body environment. Characterization of the gels were done by wet chemical analysis, SEM observation, FT-IR spectroscopy and XRD. The gelation time decreased with CaO content. However, the volume of all the dried gel decreased to 50% of the wet gels irrespective of increasement of CaO content. All the Cao-$SiO_2$ gels were amorphous and contained a large amount of silanol groups on their surfaces after heat treatment up to $800^{\circ}C$. The interconnected structure of the gel changed to agglomerated spherical powders when Ca content exceed to 20 mol%. Most of the Cao-$SiO_2$ gel showed amorphous when heat-treated up to $900^{\circ}C$. However, quartz and cristobalite was produced when heat-treated at $1000^{\circ}C$ and resultant microstructure of the gel contained microporous structure.