• Bulletin of the Korean Chemical Society
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• v.30 no.1
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• pp.219-223
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• 2009

$TiO_2$ doped with $Er^{3+\;and\;Yb^{3+}$ was used for fabricating a scattering layer and a nano-crystalline $TiO_2$ electrode layer to be used in dye-sensitized solar cells. The material was prepared using a new sol-gel combustion hybrid method with acetylene black as fuel. The $Er^{3+}$-$Yb^{3+}$ co-doped titanium oxide powder synthesized at 700oC had embossed structure morphology with a size between 27 to 54 nm that agglomerated to produce micron size particles, as observed by the scanning electron micrographs. The XRD patterns showed that the $Er^{3+}$-$Yb^{3+}$ co-doped titanium oxide had an amorphous structure, while using the same method without doping $Er^{3+}\;or\;Yb^{3+},\;TiO_2$ was obtained in the crystallite form with thea dominance of rutile phase. Fabricating a bilayer structure consisting of nano-crystalline $TiO_2$ and the synthesized $Er^{3+}$-$Yb^{3+}$ co-doped titanium oxide showed better scattering property, with an overall increase of 15.6% in efficiency of the solar cell with respect to a single nano-crystalline $TiO_2$ layer.

• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.447-453
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• 2011

The monodisperse spherical $SiO_2$ particles were overcoated with $Y_2O_3:Eu^{3+}$ phosphor layers via a Pechini sol-gel process and the resulting $SiO_2@Y_2O_3:Eu^{3+}$ core-shell phosphors were subsequently annealed at $800^{\circ}C$ at an ambient atmosphere. The crystallographic structure, morphology, and luminescent property of core-shell structured $SiO_2@Y_2O_3:Eu^{3+}$ phosphors were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and photoluminescence (PL). The spherical, nonagglomerated $SiO_2$ particles prepared by a Stober method exhibited a relatively narrow size distribution in the range of 260-300 nm. The thickness of phosphor shell layer in the core-shell particles can be facilely controlled by varying the coating number of $Y_2O_3:Eu^{3+}$ phosphors. The core-shell structured $SiO_2@Y_2O_3:Eu^{3+}$ phosphors showed a strong red emission, which was dominated by the $^5D_0-^7F_2$ transition (610 nm) of $Eu^{3+}$ ion under the ultraviolet excitation (263 nm). The PL emission properties of $SiO_2@Y_2O_3:Eu^{3+}$ phosphors were also compared with pure $Y_2O_3:Eu^{3+}$ nanophosphors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.104-107
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• 2001

The fabricated La-modified lead titanate (PLT) thin flirt without poling treatment was investigated for modulation frequency dependence of pyroelectric properties by the dynamic method. $Pb_{1-x}La_{x}Ti_{1-x/4}O_3$PLT (x=0.1) thin film having 10 mol% La content was deposited on a Pt/$TiO_{x}$/$SiO_2$/Si substrate by sol-gel method. The PLT(10) thin film exhibits a relatively excellent dielectric property. The pyroelectric coefficient (p) of the PLT(10) thin film is 6.6 x $10^{-9}$C/$\textrm{cm}^2$.K without frequency dependence. The figure of merits for the voltage responsivity and specific detectivity are 1.03${\times}$$10^{-11}$/C.cm/J and 1.46 x $10^{-9}$C.cm/J, respectively. The PLT(10) thin film has voltage responsivity ($R_{V}$) of 5.15 V/W at 8 Hz. Noise equivalent power (NEP) and specific detectivity (D＊) of the PLT(10) thin film are 9.93 x $10^{-8}$W/Hz$^{1/2}$ and 1.81 x $10^{6}$ cmHz$^{1/2}$/W at the same frequency of 100 Hz, respectively. The results means that PLT thin film having 10 mol % La content is suitable for the sensing materials of pyroelectric IR sensors.

• Journal of Embryo Transfer
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• v.24 no.4
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• pp.259-263
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• 2009

Salivary lipocalin (SAL1) is a member of the lipocalin protein family that has a property to associate with many lipophilic molecules and was identified as pheromone-binding protein in pigs. Our previous study has shown that SAL1 is expressed in the uterine endometrium in a cell type- and implantation stage-specific manner and secreted into the uterine lumen in pigs. However, function of SAL1 in the uterus during pregnancy in pigs is still not known. To understand physiological function of SAL1 in the uterine endometrium during pregnancy in pigs, it needs to elucidate the ligand(s) for SAL1. Thus, to identify the ligand for SAL1 in the porcine uterus, we collected uterine luminal fluid from pigs on day 12 of pregnancy by flushing with PBS. Proteins from the uterine luminal fluid were separated by ion exchange chromatography and gel filtration. Fractions containing SAL1 protein were pooled and concentrated. Immunoblot analysis confirmed successful purification of SAL1. Then, we extracted lipids from the purified SAL1 protein and analyzed the lipids by liquid chromatography-mass spectrometry, and predicted to be steroid hormones and prostaglandins as SAL1 ligands. Results in this study showed that SAL1 protein in the uterine secretions has a small lipophilic molecule as a natural ligand. Further characterization of ligand extracted from purified SAL1 will be useful for understanding physiological function of SAL1 during pregnancy and its application to increase the pregnancy rate in pigs.

• Applied Biological Chemistry
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• v.39 no.3
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• pp.218-221
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• 1996

With a view to increase utility of ethanol fractioned fish skin gelatin as a food source, efforts of additives on physical properties of the gelatin were investigated. The physical properties such as gel strength, melting Point, gelling point and viscosity of both ethanol-treated and untreated gelatins were improved by adding ferric ion, sugar and ethanol to the gelatin sol, but were deteriorated by the added sodium chloride and acids. Insignificant difference in effect of physical properties on additives such as sodium chloride, sugar and ethanol between ethanol-treated and untreated gelatins were not observed. However, the effect of ferric ion and acids on the physical properties of ethanol-treated gelatin has a greater than that of untreated gelatin.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.286-287
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• 2006

Barium titanate ($BaTiO_3$) glycolate particles were synthesized at temperature as low as $100^{\circ}C$ through glycothermal reaction by using $Ba(OH)_2{\cdot}8H_2O$ and amorphous titanium hydrous gel as precursors and ethylene glycol as solvent. The particle size and morphology of $BaTiO_3$ glycolate powders can be controlled by varying the reaction conditions such as the reaction temperature and Ba:Ti molar ratio of starting precursors. After glycothermal treatment at $220^{\circ}C$ for 24 h in 1.25:1(Ba:Ti), the average particle size of the $BaTiO_3$ glycolate powder was about 200-400 nm and low agglomeration. $BaTiO_3$ powders were formed by heat-treating the glycolate powder in air at $500-1000^{\circ}C$. As a result, the size of $BaTiO_3$ crystallites changed from around 50-300 nm. It is also demonstrated that the size and shape of $BaTiO_3$ particles investigated as a function of calcination temperature. The $BaTiO_3$ particles obtained from optimum synthesis condition were pressed, sintered and measured for the dielectric property. The $BaTiO_3$ ceramics sintered at $1250^{\circ}C$ for 2 h had 98 % of theoretical density. The ceramics have an average grain size of about $1\;{\mu}m$ and displays the high dielectric constant (~3100) and low dielectric loss (<0.1) at room temperature.

• Polymer(Korea)
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• v.35 no.3
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• pp.244-248
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• 2011

Poly(2,6-dimethyl-1,4-phenylene ether) (PPE) was synthesized by oxidative polymerization using various Cu(I)-amine catalyst system. The effects of catalyst/monomer ratio, different amine ligand, and the content of 2,4,6-trimethylphenol (TMP) additive on the polymer yield and molecular weight were investigated by using gel permeation chromatography. The catalytic activity of various Cu-amine systems on the 2,S-dimethylphenol (DMP) polymerization was monitored and compared each other through oxygen-uptake experiment. In addition, the effect of catalyst removal using aqueous EDTA on the thermal stability of the prepared polymer was elucidated by thermogravimetric analysis.

• Journal of Radiation Industry
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• v.9 no.1
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• pp.9-13
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• 2015

Epoxy resin is widely used as aerospace, automobile, construction and electronics due to their good mechanical and electrical properties and environmental advantages. However, the inherent flammability of epoxy resin has limited its application in some field where good flame retardancy is required. Nano clay can enhance the properties of polymers such as flames retardancy and thermal stability. In this study, we have investigated the nanoclay filled epoxy composite, which has good flame retardancy while maintaining high mechanical properties. The cured epoxy resins were obtained using an electron beam curing process. The nano clays were dispersed in epoxy acrylate solution and mechanically stirred. The prepared mixtures were irradiated using an electron beam accelerator. The composites were characterized by gel content and thermal/mechanical properties. Moreover, the flammability of the composite was evaluated by limited oxygen index (LOI). The flame retardancy of nano clay filled epoxy composite was evidently improved.

• Journal of Adhesion and Interface
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• v.15 no.2
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• pp.69-76
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• 2014

Two kinds of epoxy-functionalized alkoxysilane (EAS) compounds (EAS-MS and EAS-ES) were successfully synthesized through the reaction between epoxy resin (YD-128) and aminopropyl trimethoxysilane (APTMS) or aminopropyl triethoxysilane (APTES). By the hydrolysis-polycondensation reaction of EAS compounds with 3-Glycidyloxypropyl trimethoxysilane (GPTMS) and Tetraethyl orthosilicate (TEOS), silica/epoxy nanohybrids could be prepared at various compositions of EAS to GPTMS/TEOS. Prepared nanohybrids were yellow transparent and miscible with various organic solvents. By the reaction silica/epoxy nanohybrids with curing agents (TETA or acrylic acid), cured hybrids films could be obtained. These cured films showed higher thermal stability and mechanical property compared to cured neat epoxy resin. TEM and AFM images showed formation of nano-sized silica nanoparticles within cured hybrid films.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.26 no.1
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• pp.93-106
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• 2000

One phase liquid crystal formula was developed by using of nonionic surfactants, polyols, water and oils and its physical property was investigated. At the system oft to 1 ratio of POE octyldodecyl ether series, which have Y type (branch type) hydrophobic group, and POE glyceryl monostearate series, Y type hydrophilic group, it was examined that the formula at 7:3, 6:4, and 5:5 ratio of nonionic surfactant : polyols, shows L$\alpha$ , a pattern which is a typical characteristic of liquid crystal structure under the cross microscope polarized film. As results of L$\alpha$ phase diagram study, the formula which had high hydrophilic nonionic surfactant and the 7:3 ratio of nonionic surfactant : polyol appeared to increase the amount of oil containment and to be capable of the lamella formation. Besides it was examined that lamellar liquid crystal formula could contain about 25-40% water between lamella layers and it was transformed into w/o emulsion following as water content increased. When the lamella gel was applied into a human skin, it was investigated that it had effectiveness in increasing transepidermal water content of the skin.