• Applied Chemistry for Engineering
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• v.28 no.5
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• pp.513-520
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• 2017

The application possibility of an alternative new method with low energy consumption was studied for the eco-friendly fabrication of foamed glasses from waste glasses. As a result, fabricating temperature can be reduced under $300^{\circ}C$ without using various expensive inorganic oxidants. The foamed glass can be fabricated at a proper mixing ratio of the waste glass powder, water glass, little surfactant and bubble stabilizer by induction heating method. In the experimental range, the assured optimal condition is 4 min heating on the induction machine with a steel-container ($100mm{\times}100mm{\times}20mm$) and followed by evaporating and drying process for 11 min with 110 g of glass powder, 80 g of water glass, 3 g of surfactant and 0.2 g of bubble stabilizer. When the foamed glass was fabricated at the optimal condition, the density of the glass was $0.85g/cm^3$ and the heat conduction was $0.052W/h{\cdot}K$. In addition, the compressive strength of the glass was above $50kg/cm^2$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.4
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• pp.349-358
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• 2000

Fabrication and Characterization of Bi$_{2}$/Sr$_{2}$/CaCu$_{2}$/O$_{8}$(Bi2212) superconductor thick films were fabricated successfully on C tapes by liquid reaction between Cu-free precursors of Bi$_{x}$/SrCaO/$_{y}$(x=1.2-2) and Cu tapes. Cu-free Bi-Sr-Ca-O powder mixtures were screen-printed on Cu tapes and heat-treated at 850-87$0^{\circ}C$ for several minutes in air oxygen nitrogen and low oxygen pressure. In order to obtain the optimum heat-treatment condition we studied the effect of the precursor composition the printing thickness and the heat-treatment atmosphere on the superconducting properties of Bi2212 films and the reaction mechanism. Microstructures and phases of thick films were analyzed by films and the reaction mechanism. Microstructures and phases of thick films were analyzed by optical microscope and XRD. The electric properties of superonducting films were examined by the four probe method. At heat-treatment temperature the thick films were in a partially molten state by liquid reaction between CuO of the oxidized copper tape and the precursors which were printed on Cu tapes. During the heat-treatment procedure Bi2212 superconducting particle nucleate and grow in preferred orientations.ons.s.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.232-235
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• 2002

Recently developed liquid silicone rubber (LSR) can be cured by platinum catalyzed additional hydrosilylation mechanism and has the advantage of no byproduct compared to traditional millable peroxide curing silicone rubber. We investigated the characteristics of dielectric breakdown of silicone rubber and adhesion properties between semi-conductive LSR and insulating LSR for high voltage application of pre-molded joint (PMJ). In order to understand the dielectric breakdown characteristics, we used the sheet samples and the paired type rogowski insert electrode system. The breakdown strength and adhesion strength of LSR (E-3) were superior to those of several silicone rubbers. Adhesion strength could be improved by curing at high temperature without post-curing process or enhanced by post-curing process. When LSR (E-3) was cured at $(150^{\circ}C{\times}10min$ semi-conductive )${\times}$ ($175^{\circ}C{\times}10min$ insulation), it showed the high breakdown strength with low standard deviation, and good adhesion strength. In this results, we could apply this process to the fabrication of PMJ without post-curing.

• Korean Journal of Materials Research
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• v.25 no.6
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• pp.279-287
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• 2015

In order to prepare anode materials for high power lithium ion secondary batteries, carbon composites were fabricated with a mixture of petroleum pitch and coke (PC) and a mixture of petroleum pitch, coke, and natural graphite (PC-NG). Although natural graphite has a good reversible capacity, it has disadvaantages of a sharp decrease in capacity during high rate charging and potential plateaus. This may cause difficulties in perceiving the capacity variations as a function of electrical potential. The coke anodes have advantages without potential plateaus and a high rate capability, but they have a low reversible capacity. With PC anode composites, the petroleum pitch/cokes mixture at 1:4 with heat treatment at $1000^{\circ}C$ (PC14-1000C) showed relatively high electrochemical properties. With PC-NG anode composites, the proper graphite contents were determined at 10~30 wt.%. The composites with a given content of natural graphite and remaining content of various petroleum pitch/cokes mixtures at 1:4~4:1 mass ratios were heated at $800{\sim}1200^{\circ}C$. By increasing the content of petroleum pitch, reversible capacity increased, but a high rate capability decreased. For a given composition of carbonaceous composite, the discharge rate capability improved but the reversible capacity decreased with an increase in heat treatment temperature. The carbonaceous composites fabricated with a mixture of 30 wt.% natural graphite and 70 wt.% petroleum pitch/cokes mixture at 1:4 mass ratio and heat treated at $1000^{\circ}C$ showed relatively high electrochemical properties, of which the reversible capacity, initial efficiency, discharge rate capability (retention of discharge capacity in 10 C/0.2 C), and charge capacity at 5 C were 330 mAh/g, 79 %, 80 %, and 60 mAh/g, respectively.

• Journal of Surface Science and Engineering
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• v.49 no.6
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• pp.595-603
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• 2016

Rare-earth zirconates, including lanthanum zirconate and gadolinium zirconate, have been investigated as ones of the most promising candidates for next-generation thermal barrier coating (TBC) materials due to their excellent properties such as low thermal conductivity, chemical stability at high temperature and so on. In this study, TBCs with three compositions, in the $La_2O_3-Gd_2O_3-ZrO_2$ system with reduced rare-earth contents from $RE_2Zr_2O_7$ compositions, were fabricated by using suspension plasma spray with different suspension preparation methods. The phase formation, microstructure, and thermal properties of TBCs were examined. In particular, each coating exhibited single fluorite phase and a dense, vertically-separated microstructure. The potential of coatings with rare-earth zirconates for TBC applications was also discussed.

• Journal of the Korean Ceramic Society
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• v.36 no.1
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• pp.89-96
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• 1999

Manufacturing conditions of the porous alumina mold were established to overcome various limits of the gypsum mold. For the preparations of the porous alumina mold, an activated charcoal was added to the Al2O3 with the wt% variation and then mixed. The binary slurry was study dispersed based on the examination of the ESA and rheological behaviro. The cylinder type alumina mold was cast in the gyspum mold and characterized by the shrinkage rate at the variable sintering temperature and the resistance against wear. It was proper to make a sintering of the Al2O3 by the surface diffusion which was non-shrinkage sintering mechansim, and intergranular neck growed stronger while sintering was being made. We studied a sintering by three categories; 1) thermodynamic method below 1,000$^{\circ}C$, 2) kinetic method above 1,000$^{\circ}C$ and 3) combined method. In the results of the respective works, combined method was superiro to the others. The prepared Al2O3 mold had relatively high strength, low drying rate, the resistance against the acid or base and good casting behavior.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.39 no.2
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• pp.6-10
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• 2002

Al films (1000~4000${\AA}$)were deposited on glass and polymer(polyethersulfine) plastic substrates by DC-magnetron sputtering for plastic-based flat-panel displays. A stepped heating process was used both to improve the electrical characteristics and to diminish the thermal expansion of the polymer substrates. Following this procedure, we could succeed in sputtering Al films without any cracking or shrinkage of the polymer substrates. The treatment temperatures and deposited process of Al films were under 200$^{\circ}C$. Also, this low temperature fabrication process allows the application of plastic substrates. Scanning Electrom Microscopy, Atomic Force Microscopy, X-ray Dffractometry, and electrical measurements such as resistivity measurements were performed to investigate the properties of deposited the Al films and their reliability. 

• Korean Journal of Optics and Photonics
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• v.31 no.2
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• pp.96-104
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• 2020

A catadioptric omnidirectional zoom optical system using a hybrid lens (COZOSH) that performs simultaneously two functions of a lens and a mirror was designed at the visible wavelength range for daytime unmanned surveillance, and its performance was analyzed. The hybrid lens has lots of advantages in terms of fabrication and assembly of a COZOSH, because of the obviation of a lens boring process and reduction of the number of optical components. Additionally, we designed the COZOSH to expand the compressed inner-image region of a donut image at low spatial frequencies. As a result, the optimized design performance of the optical system that satisfies all initial design specifications was obtained from calculation of the modulation transfer function, spot diagram, and tolerance analysis. We confirmed that the COZOSH is a passively athermalized optical system under conditions of temperature variation from -30℃ to 50℃, by using athermalization analysis during zooming.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.13.1-13.1
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• 2009

Transparent electronics has attracted many interests, for it can open new applications for consumer electronics, transportation, business, and military. Among them, display backplane, thin film transistor (TFT) array would be the most attractive application. Many researchers have been investigating oxide semiconductors for transparent channel material of TFT since the report for transparent amorphous oxide semiconductor (TAOS) TFT by Hosono group and ZnO TFT by Wager group. Especially, oxide TFTs have been intensively investigated during a couple of years since the first demonstration of ZnO-TFT driving AM-OLED. Many papers regarding the fabrication and performance of oxide TFTs, and active matrix display driven by oxide TFTs have been reported. Now lots of people have confidence in the competitiveness of oxide TFTs for the backplane of AM-Display. Especially, high mobility, uniformity, fairly good stability, and low cost process make oxide TFTs applied even to a large size AM-OLED. Last year, Samsung mobile display, former SID, reported 12" AM-OLED driven by IZGO-TFT and it seems that the remained issue for the mass production is the bias temperature stability. Here, we will introduce the application of oxide TFT and important issue for oxide TFT to be used for the direct printing.

• Journal of Hydrogen and New Energy
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• v.17 no.2
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• pp.204-211
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• 2006

The electrolyte in the solid oxide fuel cell must be dense enough to avoid gas leakage and thin enough to reduce the ohmic resistance. In order to manufacture the thin and dense electrolyte layer, 8 mol% $Y_2O_3$ stabilized-$ZrO_2$ (8YSZ) electrolyte layers were coated on the porous tubular substrate by the novel vacuum slurry dip-coating process. The effects of the slurry concentration, presintering temperature, and vacuum pressure on the thickness and the gas permeability of the coated electrolyte layers have been examined in the vacuum slurry coating process. The vacuum-coated electrolyte layers showed very low gas permeabilities and had thin thicknesses. The single cell with the vacuum-coated electrolyte layer indicated a good performance of $495\;mW/cm^2$, 0.7 V at $700^{\circ}C$. The experimental results show that the vacuum dip-coating process is an effective method to fabricate dense thin film on the porous tubular substrate.