• Journal of the Korean Ceramic Society
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• v.52 no.1
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• pp.56-60
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• 2015

Discontinuous, polycrystalline $Al_2O_3$-dispersed TZP fibers were prepared by the centrifugal spinning of a colloidal $ZrO_2$ sol containing Y and Al nitrates and poly(vinyl alcohol). Factors affecting the rheological properties of the sols, such as sol concentrations, aging, and the amounts and types of additives, were investigated by measuring the shear viscosities. The flow characteristics of the sols were studied in relation to the spinnability by measuring the viscosity with respect to the shear rate. The spinnability was obtained through the addition of a polymer which increases the viscosity to a range of optimum viscosity values for spinning. Aging the sols containing the additives did not noticeably change the sol viscosities at room temperature up to 30 days. The flow behavior of the spinnable sols progressively changed from nearly Newtonian to pseudoplastic with an increase in the sol concentration.

• Journal of the Korean Society of Safety
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• v.13 no.1
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• pp.85-91
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• 1998

Sol-gel derived silica films were prepared by dip-coating onto polymethylmethacylate with Tetraethoxysilane(TEOS) as starting materials. Film properties such as viscosity and thickness were investigated as a function of dip speed, waterprecursor ratio, sol aging time. IR spectra of the gel films prepared from TEOS at various R are given. At small values of R the absorption peaks assignable to C-H vibration in $-OC_2H_5$ groups are observed around 3000 and 1500-1300 $cm^{-1}$. These bands indicate that the -$-OC_2H_5$ groups are retained in the gel at small values of R because of incomplete hydrolysis of TEOS. Film behaviour was interpreted in terms of the dependence of hydrolysis and condensation rates on the interplay between sol pH and waterprecursor ratio. Film thickness was found to increase by approximately a factor of two as waterprecursor ratio increased from two to six. Film thickness also increased with sol prepolymerization time. Surface quality was correlated with processing conditions.

• Journal of the Korean Ceramic Society
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• v.28 no.5
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• pp.365-372
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• 1991

LAS (lithium aluminosilicate) sol was synthesized using the hydrolysis-condensation reaction of TEOS, chelated Al(OBus)3 and Li-salt with H2O in alcohol (EtOH+2-Propanol) medium. Effects of important reaction parameters on the properties of sol and gel-derived LAS were examined. The crystallization of the sol-gel derived LAS with ${\beta}$-spodumene composition began at ∼600$^{\circ}C$, and a series of polymorphic transformations occurred as temperature was increased to 1100$^{\circ}C$: amorphous LAS\longrightarrowhexagonal LiAl(SiO3)2\longrightarrow${\beta}$-spodumene. Lowering Li content in the gel enhanced densification and retarded the crystallization significantly. Optimum reaction conditions of LAS sol formation for thin coating applications were derived from rheological measurements, and these can be summarized as: H2O/total alkoxides molar ratio=4, pH=∼2.5, and aging time of ∼250h.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.110-110
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• 2000

Sol-Gel법은 산화물 전구체(precursor) 상태인 Sol상태로부터 가수분해, 중, 축합반응을 거쳐 최종적으로 Gel 산화물을 합성하는 방법이며 기존의 세라믹스를 합성할 수 있고 고순도의 균질한 화합물을 용이하게 얻을 수 있는 특징이 있다. 최근 전자부품이 소형, 경량화되는 추세에 따라 전자 세라믹스분야에서도 박막화가 대두되고 있는 가운데 Sol-Gel법은 dipping, spining 및 spray 법등을 이용하여 박막의 제작이 가능하며 CVD, PVD, sputtering 법등과 같은 박막제작에 비하여 장비가 복잡하지 않으면서 제작기법이 간단한 이점을 가지고 있다. 소재면에서 볼 때 TiO2 물질은 물리적, 화학적으로 안정하고 굴절율, 착샐율 및 반사율 등이 우수한 재료로서 세라믹스 콘센서, 압전소자, 습도센서와 가스센서분야등에 있어서 중요한 위치를 점하고 있어서 연구자들에게 많은 관심을 가지게 하였다. 본 연구에서는 Sol-Gel법에 의해 TiO2 Sol을 합성한 후 dipping 법으로 박막을 제작하고 박막의 전기전도 특성 및 습도센서소재로의 개발을 위해 습도감지특성에 주목하였고 경시변화로 인해 생성된 Gel powder의 물성에 대해서도 검토하였다.

• Journal of the Korean Ceramic Society
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• v.33 no.1
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• pp.110-118
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• 1996

• Journal of the Korean Ceramic Society
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• v.36 no.11
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• pp.1178-1182
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• 1999

• Journal of the Korean Ceramic Society
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• v.41 no.6
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• pp.471-475
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• 2004

TiO$_2$, SiO$_2$, and PBA(Pseudo Boehemite Alumina) sol were prepared by sol-gel process. The particle sizes of these sol exhibited uniform 10∼30 nm. As the amount of SiO$_2$ sol increased, the temperature of phase transition (from anatase phase to rutile phase) was raised temperature than $600^{\circ}C$, which attributed to the enhanced photocatalyst properties. Also, the anatase phase was obtained with very small amount of the rutile phase from the addition of SiO$_2$ (10∼30 wt%) at annealing temperature of 120$0^{\circ}C$. The specimen with 20 wt% SiO$_2$ sol exhibited the maximum photocatalyst properties. But, the specimen with PBA sol did not affect photocatalytic activity due to the presence of rutile phase.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.7
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• pp.1491-1496
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• 2005

We fabricated the $Pb_{0.72}La_{0.28}TiO_3$ (PLT(28)) thin film successfully by using the sol-gel method and characterized it to evaluate its potential for being utilized as the capacitor dielectrics of ULSI DRAMs. In our sol-gel process, the acetates were used as the starting materials. Through the TGA-DTA analysis, we established the excellent fabrication conditions of the sol-gel method for the PLT(28) thin film. We obtained the dense and crack-free PLT(28) thin film of $100\%$ perovskite phase by drying at $350^{\circ}C$ after each coating and final annealing at $650^{\circ}C$. Electrical properties of PLT(28) thin film were measured through formation on the $Pt/Ti/SiO_2/Si$ substrate and its dielectric constant and leakage current density were measured as 936 and $1.1{\mu}A/cm^2$, respectively.

• Textile Coloration and Finishing
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• v.26 no.4
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• pp.297-304
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• 2014

In this study, we investigated the relationship between the adsorption property of Methyl violet or Tartrazine dye onto silica sol surface and surface charge density of the sol. The adsorption ratio of Methyl violet dye on silica sol decreased to 74% and 92% for the 68nm and 94nm silica sol, respectively, at dye concentration of $175{\mu}g/m^2$. However, the adsorption ratio of Tartrazine dye on 68nm and 94nm silica sol was about 0% for both of them. The surface charge density is $-0.40C/m^2$, $-0.26C/m^2$ for 68nm and 94nm silica sol, respectively. The amount of Methyl violet dye adsorbed on silica sol increased with an increase of surface charge density of particle at the same concentration of the dye. The adsorbed amount of the silica having high surface charge density is larger at high pH domain. But adsorbed amount of the silica having low surface charge density is larger at low pH domain.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.865-868
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• 2005

We fabricated the $Pb_{0.72}La_{0.28}TiO_3 (PLT(28))$ thin film successfully by using the sol-gel method and characterized it to evaluate its potential for being utilized as the capacitor dielectrics of ULSI DRAMs. In our sol-gel process, the acetates were used as the starting materials. Through the TGA-DTA analysis, we established the excellent fabrication conditions of the sol-gel method for the PLT(28) thin film. We obtained the dense and crack-free PLT(28) thin film of 100% perovskite phase by drying at 350$^{\circ}C$ after each coating and final annealing at 650$^{\circ}C$. Electrical properties of PLT(28) thin film were measured through formation on the Pt/Ti/SiO$_2$/Si substrate and its dielectric constant and leakage current density were measured as 936 and 1.1${\mu}$A/cm$^2$, respectively