• The Korean Journal of Ceramics
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• 제6권2호
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• pp.159-163
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• 2000

Alumina fibre has been synthesized successfully by sol-gel technique. Boehmite sol was prepared by hydrolyzing aluminium iso-propoxide and peptizing it with nitric acid. The stable sol thus obtained was used for fibre drawing when their viscosity reached the required value as a result of progress of the hydrolyzation and polycondensation reaction. The fibres dried at 11$0^{\circ}C$ for 12 hours were sintered at 1$600^{\circ}C$ for 5 hours. A reasonable sintered density with better microstructure and strength have been attained using 2 wt% of urea, magnesia and silica as sinter additives. Thermal analysis with sintering additives of 2 wt% and phase determination of the heat treated fibres using XRD and FT IR spectra confirms the phase transitions. The observation of surface and cross-section of the fibres were made using SEM. Fibres of uniform circular cross-section is obtained by fixing the shape in a setting solution.

• 한국세라믹학회지
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• 제32권2호
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• pp.197-208
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• 1995

${\gamma}$-LiAlO2 fibers for fiber reinforced molten carbonate fuel cell (MCFC) matrix have been produced from LiAlO2 complex polymeric sols using the sol-gel process. The stable and spinnable LiAlO2 sols could be synthesized by mixing LiNO3 alcohol solutions in aluminum complex polymeric sols prepared through the condensationpolymerization reaction of 1 more of aluminum tri-sec-butoxide with 0.55 mole of mixed chelates (mole ratio of acetylaceton/triethanolamine=0.25/0.3). It was found that the viscosity range for fiber-spinning should be higher than 30 poise. The defect-free flexible ${\gamma}$-LiAlO2 fibers with the average tensile strength of 350 MPa could be obtained when the spinned fibers were heat-treated to 120$0^{\circ}C$ on the specified heating schedule after dried at room temperature.

• International Journal of Industrial Entomology and Biomaterials
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• 제27권1호
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• pp.180-184
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• 2013

Recently, silk sericin has attracted the attention of researchers owing to its useful properties as a biomaterial including 1) good wound healing and cell activities, 2) fast gelation character, and 3) high water retention property. In the present study, silk sericin was prepared using different extraction times in hot water and the effect of extraction time on the rheological properties of sericin solutions and gels was examined. It was found that the production yield of sericin increased with extraction time. The shear viscosity of sericin solutions and gels decreased with increasing extraction time due to a decrease in sericin molecular weight. When the sericin solution transformed to a gel, the viscosity increased and the shear thinning behavior was more evident. In addition, the shear stress measurements indicated that the slip between the sericin samples and the measuring plate of the rheometer was increased by the gelation of sericin. The compression strength of sericin gel could be increased remarkably (by more than 100 fold) by preparation using the freezing and thawing method.

• 한국세라믹학회지
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• 제46권6호
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• pp.653-656
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• 2009

Alumina bushing used for manufacturing glass fiber was fabricated by gel-casting which can fabricate complex forms. When solid loading is increased, density was increased and shrinkage and absorption were decreased. The sample loading with 57 vol% solid was optimum for alumina suspension, which showed the best physical properties. The cast sample was sintered at $1550{^{\circ}C}$ for two hours with sintering additive, $Y_2O_3$. The result showed that the alumina bushing with $Y_2O_3$ sintering additive has a density of 98%, shrinkage of 11% and bending strength of 196 kg/$cm^2$.

• E2M - 전기 전자와 첨단 소재
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• 제10권1호
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• pp.61-67
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• 1997

We have studied dielectric properties of sol-gel derived tantalum oxide thin films as the insulators. As the sample is annealed from 300.deg. C to 700.deg. C, it is found amorphous below 600.deg. C and crystalline over it. Dielectric constant is maximum(18.6) when Ta$_{2}$O$_{5}$ film was annealed at 400.deg. C. It is found that dielectric strength in Ta$_{2}$O$_{5}$ film annealed at 400.deg. C (1.5MV/cm) increases and then decreases over annealed at 500.deg. C. This phenomenon was attributed to pinhole effect and crystallization. The de conduction properties can be interpreted by Poole-Frenkel effect.ect.

• 대한약학회:학술대회논문집
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• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2-2
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• pp.235.2-235
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• 2003

To develop the buccal delivery system of rhEGF for the treatment of buccal mucosal ulcer, polymer films and hydrogels were investigated. Methods: Hydrogels for thermosenstive sol/gel systems were prepared by the cold method (Schmolka, 1972). And mucoadhesive films were prepared by mixing sod. alginate/polycarbophil 974p. To find an optimum buccal mucosal adhesive gel or film, the gel strength of the poloxamer and sod. alginate/polycarbophil 974p hydrogels were determined by the Simple Rheology Method and their mucoadhesiveness were measured by the Instron (M 4400, Instron Co., U.S.A.) method. (omitted)

• 한국세라믹학회지
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• 제36권8호
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• pp.829-834
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• 1999

산화물 첨가에 의한 불투명화 실리카 에어로겔이 졸-겔 초임게 건조법으로 제조 되었으며 그들의 기계적 강도 및 열전도도 특성이 연구되었다. SiO2-10 mol% TiO2와 SiO2-10 mol% Fe2O3 에어로겔의 압축강도는 순수 실리카 에어로겔의 강도(0.025 MPa)에 비해 훨씬 높은 0.11 MPa과 0.047 MPa 정도 이었으며 TiO2에 의한 불투명화 실리카 에어로겔의 열전도도는 $400^{\circ}C$에서 0.0205 W/m · K 정도로 매우 낮은 값이었다. 순수 실리카 에어로겔의 기계적 강도 증진 및 고온 열전도도 증가를 억제하기 위한 불투명화제로는 TiO2가 Fe2O3에 비해 훨씬 효과적임을 알 수 있었다.

• 한국축산식품학회지
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• 제35권6호
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• pp.841-846
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• 2015

This study was investigated to determine the effect of microbial transglutaminase (MTG) with or without red bean protein isolate (RBPI) on the porcine myofibrillar protein (MP) gel functionality at different pH values (pH 5.75-6.5). Cooking yield (CY, %), gel strength (GS, gf), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) were determined to measure gel characteristics. Since no differences were observed the interaction between 1% RBPI and pH, data were pooled. CY increased with the addition of 1% RBPI, while it was not affected by pH values. GS increased with increased pH and increased when 1% RBPI was added, regardless of pH. There were distinctive endothermic protein peaks, at 56.55 and 75.02℃ at pH 5.75, and 56.47 and 72.43℃ at pH 6.5 in DSC results, which revealed decreased temperature of the first peak with the addition of 1% RBPI and increased pH. In SEM, a more compact structure with fewer voids was shown with the addition of 1% RBPI and increased pH from 5.75 to 6.5. In addition, the three-dimensional structure was highly dense and hard at pH 6.5 when RBPI was added. These results indicated that the addition of 1% RBPI at pH 6.5 in MTG-mediated MP represent the optimum condition to attain maximum gel-formation and protein gel functionality.

• 공업화학
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• 제5권3호
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• pp.443-450
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• 1994

Polyacrylic acid를 NaOH와 $NH_4OH$로 중화시켜 중화도가 다른 polyelectrolyte를 만든 후, 수용액 상에서 ethylene glycol diglycidyl ether(EGDE)로 가교시켜 안정한 상태의 젤을 얻었다. 안정한 젤이 얻어지는 가장 작은 polyelectrolyte의 농도인 $C_{gel}$은 polyelectrolyte의 extended from에도 불구하고 비슷한 분자량의 중성 고분자의 간과 비슷하였다. 전해질 고분자에 대한 scaling이론에 의하면 semi-dilute영역에서의 전해질 고분자용액은 분자량 의존성이 없어야 함에도 불구하고 gelation결과는 중성 고분자와 흡사한 분자량 의존성을 보이며 entanglement 농도인 $C^{**}$와 비교했을 때에도 $C_{gel}$은 훨씬 큰 값을 갖는다. 이는 고분자 전해질의 농도가 진해질수록 용액의 이온세기가 증가하여 extended from에서 coil form으로 변화되기 때문으로 보인다. 고분자 전해질의 중화도에 따른 gelation은 100% 중화된 시료의 $C_{gel}$값과 분자량 의존성에 있어 거의 비슷한 경향을 보이며 이는 고분자 전해질의 conformation변화가 이온세기에 상당히 민감함을 보여 준다. 고분자 전해질 수용액에 추가로 저분자량의 염을 가하면 고분자의 용액 속에서의 크기가 더욱 축소하여 더 큰 $C_{gel}$값을 보인다.

• International Journal of Concrete Structures and Materials
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• 제3권2호
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• pp.97-101
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• 2009

It has been known that acid-resistant concretes on the liquid glass basis have high porosity (up to 18${\sim}$20%), low strength and insufficient water resistance. Therefore they can not be used as materials for load-bearing structural elements. Significant increasing of silicate matrix strength and density was carried out by incorporation of special liquid organic alkali-soluble silicate additives, which block of superficial pores and reduces concrete shrinkage deformation. It was demonstrated that introduction of tetrafurfuryloxisilane additive sharply increases strength, durability and shock resistance of silicate polymer concrete in aggressive media. This effect is attributable to hardening of contacts between silicate binder gel globes and modification of alkaline component owing to "inoculation" of the furan radical. The optimal concrete composition with the increased strength, chemical resistance in the aggressive environments, density and crack resistance was obtained.