• Journal of Korean Ophthalmic Optics Society
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• v.3 no.1
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• pp.21-25
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• 1998

We investigated the optical properties of lead zirconate($PbZrO_3$, PZ) thin films. The PZ films for the measurement of optical properties were prepared on ITO glass by sol-gel method. By post annealing, with annealing temperature $T=700^{\circ}C$, the pyrochlore phase of as-deposited specimen was transformed into the perovskite phase. The surface of films were plat, transmittance were from 60 to 80% at 480~2000nm, and refractive index were from 2.1 to 1.9 at 480~1000nm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.10
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• pp.736-740
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• 2013

In this study, the influence of electrochemical properties by mixing Tetrabutylammonium hydroxide (TBAOH) and ammonium hydroxide (NH4OH) electrode on the dssc. The titanias were prepared using a sol-gel method by mixing Tetrabutylammonium hydroxide and Ammonium hydroxide. The $TiO_2$ nanopowder prepared by sol-gel methode, and to improve the distributed properties of $TiO_2$ nanopowder, the TBAOH and NH4OH was added. The I-V values of cells show that the Tetrabutylammonium has 6.51% efficiency.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2005.04a
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• pp.139-142
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• 2005

This paper describes an automatic finite element (FE) mesh generation for three-dimensional structures consisting of free-form surfaces. This mesh generation process consists of three subprocesses: (a) definition of geometric model, i.e. analysis model, (b) generation of nodes, and (c) generation of elements. One of commercial sol id modelers is employed for three-dimensional sol id structures. Node is generated if its distance from existing node points is similar to the node spacing function at the point. The node spacing function is well control led by the fuzzy knowledge processing. The Delaunay method is introduced as a basic tool for element generation. Automatic generation of FE meshes for three-dimensional sol id structures holds great benefits for analyses. Practical performances of the present system are demonstrated through several mesh generations for three-dimensional complex geometry.

• Journal of Korean society of Dental Hygiene
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• v.1 no.1
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• pp.125-132
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• 2001

This study was carried out to investigate the effect of multi or single application of fluoride plus 0.05% NaF solution on the remineralization of dental caries lesion. The microhardness changes of enamel surface were measured after application of fluoride and precipitation of 0.05% NaF solution on 6 groups of cow's tooth on which the artificial carious lesions were formed first. Test groups were calssified into two step application with NaF, $SnF_2$ and APF under different application time conditions plus 0.05% NaF solution(group I, II, III, IV) and single application with APF plus 0.05% NaF solution (group V) and control(0.05% NaF solution only, group IV). The obtained results were as follows. 1. Regarding microhardness change of enamel surface. microhardness increments in group I(NaF for 1 minute+APF for 3 minutes+0.05% NaF solution for 1 minute), II($SnF_2$ 1 min+APF 3 min+NaF sol.), III($SnF_2$ 2 min+APF 2 min+NaF sol.), IV(NaF 2 min+APF 2 min+NaF sol.) and V(APF 4 min+NaF sol.) were significantly greater than group VI.(P<0.05) 2. Microhardness changes of shorter application time of $SnF_2$ (group II) were significantly greater than group III. (P<0.05) 3. Microhardness changes were variable with kinds of fluoride, application sequence and application time of fluoride. but had no relation with the number of fluoride application.

• Journal of the Korean Ceramic Society
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• v.26 no.5
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• pp.682-690
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• 1989

Fine mullite powder was prepared by colloidal sol-gel route. Boehmite as a starting material of Al2O3 and silica sol or fumed silica as a starting material of SiO2 were used. $\alpha$-Al2O3, TiO2 and ZrO2 were used as seeding materials. The combination of boehmite and silica was found to be the stoichiometric mullite powder. Techniques for drying used were spray drying, freeze drying, reduced pressure evaporation and drying in a oven. The gelled powder was heated at 130$0^{\circ}C$ for 100min and was attrition-milled for 1~3hrs. The mullite powder obtained was composed of submicrometer, uniform and spherical particles with a narrow size distribution. The mullite powder was characterized by BET, SEM, XRD and IR spectroscopy.

• Analytical Science and Technology
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• v.18 no.1
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• pp.1-4
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• 2005

The stable $Ti(OPr^i)_2(OAc)_2$ sol which reacts with a solution of prehydrolysed $Si(OEt)_4$ was made by addition of acetic acid. The structure evolution of the reaction mixture was monitered by $^1H$, $^{29}Si$ NMR and FT-IR spectroscopy.

• Journal of the Korean Ceramic Society
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• v.35 no.4
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• pp.319-324
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• 1998

Sol-gel derived phosphate water-sioluble glasses containing Cu were prepared. Powder-shape of glasses were added in D.I water used polyethylene bottle. After solution contained glass powder were submerged in water bath on 25$^{\circ}C$ their dissolution behavior/characteristics bactericidal effect and cytotoxicity test were evaluated. The maximum amount of Cu(35 mol%) via sol-gel method was more 5 mol% increased than that with melting process. The stage of total dissolution was more dominant than that of selective leaching dur-ing dissolution due to dissolved amount of glasses increased linearly with time. The ratio of Cu+ to {{{{ {Cu }^{2+ } }} was 3:7 so that the structure of glasses is more predominant 2-dimension chain structure than 3-dimenshion po-lymeric structue. The stage of total dissolution was more dominant than that of selective leaching during dissolution. Bactericidal effect against all bacteria showed that solutions which contained 40 ppm and 100 ppm of Cu killed 80 percentages of bacteria within 2 hours and 100 percentages of those within 12 hours. The results of cytotoxicity test for L929 cells showed no cytotoxicity were observed within 96 hours for dis-solved solution that contains 40 ppm and 100 ppm of Cu.

• Journal of the Korean Ceramic Society
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• v.24 no.6
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• pp.561-571
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• 1987

In case of glass ceramics and powder preparation from the metalakoxide solutions, metalakoxide solutions with a various species of alkoxy groups have unique characteristics. Therefore, in this study, the mixing ability of homogeneous sol, gel morphology and physical properties of gels were investigated by the changes in terms of the different four alkoxy groups, CH3-, C2H5-, i-C3H7-n-C4H9-, along with the catalyst for the purpose of the observation about the homogenous transition range from sol to gel. As a result, when the fixed condition was mol ratio of H2O/Si(OR)4=2.0 and variables were batch composition and addition amount of catalyst, the characteristics of Tetra-normal-Butoxysilane and Tetra-iso-propoxysilane systems had very narrow sol-gel conversion region than Tetramethoxysilane and Tetraethoxysilane system. And silicon-alkoxide, systems having narrow sol-gel conversion region were enlarged by addition of catalyst. In viewpoint of the weight loss of gel produced by hydrolysis of silicon alkoxide systems with different four alkoxy groups, the amounts of weight loss of gel containing large molecular alkoxy groups were much more than those of small molecular alkoxy group.

• Korean Journal of Materials Research
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• v.17 no.3
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• pp.147-151
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• 2007

Cu-free multi-component sol, of which final oxide composition becomes $Bi_{1.9}Pb{0.35}SrCaO,\;Bi_{1.8}Pb_{0.2}SrCaO\;and\;Bi_{1.5}SrCaO$, respectively, was prepared through sol-gel route and coated on a bare Cu substrate. Starting materials were metal-alkoxides as follows.; [$Bi(OC_{2}H_{5})_{3}\;Pb(O^{1}C_{3}H_{7})_{2},\;Sr(O^{i}C_{3}H_{7})_{2},\;Ca(OC_{2}H_{5})_{2}$] as a reagent grade. Transparent light yellowish sol was obtained in the case of $Bi_{1.9}Pb_{0.35}SrCaO\;and\;Bi_{1.8}Pb_{0.2}SrCaO$ composition and $Bi_{1.5}SrCaO$ composition's sol was light greenish. Each sol was repeatedly dip-coated on Cu substrate four times and pre-heated at $400^{\circ}C$ and finally heat-treated in the range of $740{\sim}900^{\circ}C$. In the results, crystalline phases confirmed by XRD were (2201) orthorhombic and monoclinic phases. However, only $Bi_{1.9}Pb_{0.35}SrCaO_{x}$ composition showed pseudo-superconductive behavior after heat-treatment at $900^{\circ}C$ for 12 seconds and then onset temperature was 77 K, even though it did not exhibit zero resistance below Tc.

• Proceedings of the Materials Research Society of Korea Conference
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• 1998.08a
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• pp.67.3-67
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• 1998