• Journal of the Korean Ceramic Society
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• v.34 no.5
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• pp.483-490
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• 1997

Al2O3/metal composites were fabricated by oxidation and reaction of molten Al-alloy into two types of commercial Al2O3-SiO2 fibrous insulation board. The growth rate, composition and microstructure of these materials were described. An AlZnMg(7075) alloy was selected as a parent alloy. Mixed polycrystalline fiber and glass phase fiber were used as a filler. The growth surface of an alloy was covered with and without SiO2. SiO2 powder was employed as a surface dopant to aid initial oxidation of Al-alloy. Al-alloy, SiO2, fiber block and growth inhibitor CaSiO3 were packed sequentially in a alumina crucible and oxidized in air at temperature range 90$0^{\circ}C$ to 120$0^{\circ}C$. The growth rate of composite layer was calculated by measuring the mass increasement(g) per unit surface($\textrm{cm}^2$). XRD and optical microscope were used to investigate the composition and phase of composites. The composite grown at 120$0^{\circ}C$ and with SiO2 dopant showed rapid growth rate. The growth behavior differed a little depending on the types of fiber used. The composites consist of $\alpha$-Al2O3, Al, Si and pore. The composite grown at 100$0^{\circ}C$ exhibited better microstructure compared to that grown at 120$0^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.11
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• pp.1014-1019
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• 2006

The influence of the number of solution coatings on the densification of the PZT thick films was studied. PZT powder and PZT precursor solution was prepared by a sol-gel method and PZT thick films were fabricated by the screen-printing method on the alumina substrates. The powder and solution of composition were (A) PZT(80/20)/PZT(20/80), (B) PZT(70/30)/PZT(30/70) and (C) PZT(60/40)/PZT(40/60), (D) PZT(52/48)/PT. The coating and drying procedure was repeated 4 times. And then the PZT precursor solution was spin-coated on the PZT thick films. A concentration of a coating solution was 0.5 moth and the number of coating was repeated from 0 to 6. The porosity of the thick films was decreased with increasing the number of coatings and the PZT thick films with 6-times coated showed the dense microstructure and thickness of about $60{\mu}m$. A grain size was increased with increasing the coating number. All PZT thick films showed the typical XRD patterns of a typical perovskite polycrystalline structure. The relative dielectric constant of PZT thick films was improved 30-100% as the number of coatings.

• Journal of the Korean Applied Science and Technology
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• v.9 no.1
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• pp.47-54
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• 1992

The natural antioxidant such as e-tocopherol and synthetic antioxidant BHT were used to compare antioxidative effects of those antioxidants from the physico-chemical properties and fatty acid composition changes in the soybean oil due to number of frying. The composition of frying oil were consisted of a group(Fresh oil), B gorup(Fresh oil added with 0.05% ${\alpha}$-tocopherol), C group(Fresh oil added with 0.2% ${\alpha}$-tocopherol), D group(Fresh oil added with 0.1% BHT), E group(Tocopherol removed oil from oil by active alumina column chromatography The results obtained were as follws : 1. The color was determined by the Lovibond colorimeter color intensity increased number of frying oil. 2, The acid value, TBA value and Carbonyl value were increased number of frying oil. 3. Natural antioxidants less effective than BHT but effect of ${\alpha}$-tocopherol was very similar to that of BHT. 4. The order of antioxidative effect was 0.1% BHT, 0.2% ${\alpha}$-tocopherol, 0.05% ${\alpha}$-tocopherol, fresh oil, tocopherol remove oil.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.378-379
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• 2009

High intensity metal halide discharge lamp performance, specifically the generated luminous flux and light color content, depends critically on the arc tube design. Factors influencing the design and consequent lamp efficacy include : lamp size, geometry, arc tube composition, fill chemistry, electrode design and excitation modes. Shaping of Polycrystalline Alumina(PCA) can be realized by conventional ceramic processes. Several processes are applied nowadays. Well-known in the ceramic high pressure field for decades are the pressing and the extrusion method. Newly developed slurry and precious forming technologies give the one-body seamless tubes, which improve thickness uniformity and lighting performance. Now, we reported some optical properties with different arc tube structures of ceramic metal halide lamps.

• Journal of the Korean Ceramic Society
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• v.15 no.2
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• pp.66-71
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• 1978

The cobalt blue spinel stains (main composition; CoO:$Al_2O_3$=1 : 1) in CoO-NiO-$Al_2O_$3 and $CoO-Al_2O_3-Cr_2O_3$ system were prepared by the calcination of each component oxides to be adequate for the factory. The color development, the change of the lattice constnat of the spinel and its application to colored glazes were studied. The results were summarized as follows. 1) In CoO-Al_2O_3$ spinel, the excess addition of each component hardly made any variation in lattice constantand alumina-rich spinel specimens caused the brilliant blue color fade. 2) An increase of $Ni^{2+}$ in $CoO-NiO-Al_2O_3$ system, made the lattice constnat of the $CoO-Al_2O_3$ spinel smaller, and an increase of $Cr^{3+}$ in $CoO-Al_2O_3-Cr_2O_3$, larger. 3) Glazed stains under lead glaze were colored nearly same dark blue color fade.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1242_1243
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• 2009

The heterolayered BT-BNT thick films were fabricated by screen printing techniques on alumina substrates electrodes with Pt. We report the improved ferroelectric and dielectric properties in the heterolayered teteragonal/rhombohedral structure composed of the BT and the BNT thick films. We investigated the effects of deposition conditions on the structural and electrical properties of the heterolayered BT-BNT thick films. The dielectric properties of the heterolayered BT-BNT thick films were superior to those of single composition BNT, and those values for the heterolayered BT-BNT thick films were 1455, 0.025 and $12.63{\mu}C/cm^2$.

• Journal of the Korean institute of surface engineering
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• v.30 no.3
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• pp.167-174
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• 1997

WC-C0 base cemented carbides were plasma nitrided to obtain more hadened surface layer. The surface hardness of Hv1338 which is higher than a non-treated ane by 30%, and the hardened layer thickness of about 50$\mu\textrm{m}$ were obtained by the treatment of 3hrs under the conditions of $550^{\circ}C$, and 5torr of gas pressure of which composition was 1:1 of $N_2:H_2$. The nitrided surfaces has WIN and W2N phases in the non-coated samples and AIN phase in the alumina coated sampled as the results of X-ray results, and showed surface roughnness of 5$\mu\textrm{m}$ which were caused by the sputtering action of the plasma gasee. The hardenened layer exihibits an enhanced wear resistance the cuttability test.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.632-635
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• 2003

[ $(Ba,Sr,Ca)TiO_3$ ] powders, prepared by the sol-gel method, were mixed with organic vehicle and the BSCT thick films were fabricated by the screen printing techniques on alumina substrates. The dielectric properties were investigated for various composition ratio and $Nb_2O_5$ doping contents. All the BSCT thick films, sintered at $1420^{\circ}C$, showed the typical XRD patterns of a perovskite polycrystalline structure. The Curie temperature and the relative dielectric constant decreased with increasing Ca content and $Nb_2O_5$ doping amount. The relative dielectric constant, dielectric loss and tunability of the BSCT(50/40/10) thick films doped with 1.0wt% $Nb_2O_5$ were 1410, 0.65% and 17.29% respectively.

• Transactions on Electrical and Electronic Materials
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• v.8 no.3
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• pp.125-130
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• 2007

DLC coating on ceramics is very useful for manufacturing the materials with hardness and low friction. Adhesion of DLC thin film on ceramics, on the other hand, is usually very weak. Adhesion of DLC film depends on many parameters such as contamination and chemical bonding between thin film and substrate. In this study, adhesion of DLC film on ceramics was improved by the intermediate layer when the plasma immersion ion deposition (PIID) technique was applied. It is found that the chemical composition and the thickness of intermediate layer have significantly an effect on the adhesion of DLC thin film on $Al_2O_3$.

• The Korean Journal of Ceramics
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• v.4 no.3
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• pp.171-175
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• 1998

$Al_2O_3$-TiC composites were prepared from aluminum, titanium oxide, and carbon fibers by self-propagating high-temperature synthesis(SHS). After the SHS reaction, the TiC phase in the sample was found either fibrous or non-fibrous shape. The fraction of the fibrous TiC phase varied with the amount of $Al_2O_3$ diluent addition. The optimum amount of diluent to make fibrous carbide was determined to be 30%. The fibers were hollow inside and made of multiple grains with a composition of titanium carbide. The hollow fiber formation mechanism was suggested and discussed. The synthesized powders were consolidated to dense composites by hot pressing at $1750^{\circ}C$ under 30 MPa.