• Journal of the Korean Ceramic Society
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• v.47 no.5
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• pp.467-473
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• 2010

The objective of this study is to prepare lead-free thick film resistor (TFR) paste compatible with AlN substrate for hybrid microelectronics. For this purpose, CaO-ZnO-$B_2O_3-Al_2O_3-SiO_2$ glass system was chosen as a sintering aid of $RuO_2$. The effects of the weight ratio of CaO to ZnO in glass composition, the glass content and the sintering temperature on the electrical properties of TFR were investigated. $RuO_2$ as a conductive and glass powder were dispersed in an organic binder to obtain printable paste and then thick-film was formed by screen printing, followed by sintering at the range between $750^{\circ}C$ and $900^{\circ}C$ for 10 min with a heating rate of $50^{\circ}C$/min in an ambient atmosphere. The addition of ZnO to glass composition and sintering at higher temperature resulted in increasing sheet resistance and decreasing temperature coefficient of resistance. Using $RuO_2$-based resistor paste containing 40 wt%glass of CaO-20.5%ZnO-25%$B_2O_3$-7%$Al_2O_3$-15%$SiO_2$ composition, it is possible to produce thick film resistor on AlN substrate with sheet resistance of $10.6\Omega/\spuare$ and the temperature coefficient of resistance of 702ppm/$^{\circ}C$ after sintering at $850^{\circ}C$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.2
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• pp.23-33
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• 1991

Mn - Zn Ferrite has the natural characteristics of incongruent melting and the zinc oxide evaporation while the crystal is being grown. As a result of these, it comes into existence to be a non-uniform distribution of cations along the crystal growth axis and also Pt particles are usually precipitated into the crystals in Bridgman method since the melt zone is maintained for a long time in the crucible. These have bad effects on the magnetic properties of ferrites. But, to overcome these faults and then acquire the better single crystals. new modified growth method was developed and the growth factors were investigated as following: melt height in the crucible, surface tension and density of melt, the behavior of melt at interface, the shapes of crucible and solid -liquid interface, powder feeding rate, and the crystal growing speed. In additon, when we analyzed the compositional fluctuations of grown crystals, they were supressed within 1.5 mol% $Fe_20_3$, 2 mol% MnO, ZnO respectively with comparing to initial composition of crystal and the microstructures of crystals on the(110) plane were observed by optical microscope through the chemical etching technique and the magnetic properties were determined.

• Journal of the Korean Ceramic Society
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• v.51 no.3
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• pp.184-189
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• 2014

Electric arc furnace dust (EAFD) is a solid waste generated by the steel-scrap recycling process. It mainly consists of zinc oxides (ZnO), alumina ($Al_2O_3$), iron oxides ($Fe_2O_3$), and silica ($SiO_2$). Here we report the preparation and characterization of blue ceramic pigments using EAFD powder as a starting material. $(Zn(EAFD),Co)Al_2O_4$ blue ceramic pigment was prepared by the solid-state reaction method. The color characteristics of the pigment obtained were compared with those of pure $CoAl_2O_4$. The new pigment was characterized using XRD, CIE-$L^*a^*b^*$ color-measurements, SEM, and EDX. The XRD analysis revealed that the $(Zn(EAFD),Co)Al_2O_4$ pigment was composed of mainly the spinel phase of $(Zn,Co)Al_2O_4$. The $Zn(EAFD)_{0.25}Co_{0.75}Al_2O_4$ pigments showed a vivid blue color with a $b^*$ value of -28.64 and a good glaze stability with a transparent glaze.

• Journal of the Korean Ceramic Society
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• v.17 no.3
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• pp.121-128
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• 1980

In order to obtain the fundamental data for the preparation of ferroxplana $Zn_2Y(Ba_2Zn_2Fe_{12}O_{22})$, which is useful for GHz-band communication, the optimum coprecipitation condition of $Zn(NO_3)_2-6FeCl_3$ in $NH_4OH$ solution and the formation process of the hexagonal ferrite were investigated. By the hot-petroleum-drying and calcining the coprecipitated hydroxide mixture $Zn(OH)_2 +Ba(OH)_2+ 6Fe(OH)_3$, the fine and uniform powder was obtained , whose phase composition and microstructure were studied by X.R.D. and electron microscope. In results, it was found that $Zn_2Y$, BaM and $Zn_2W$ were the representative phases in calcined specimens whose activation energies of crystal growth were about 3, 8, 2.5, $5.4{\times}10^4$ J/mole , respectively. The sintered specimens would be appreciated as useful magnetic cores for the high frequency communication.

• Korean Journal of Materials Research
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• v.11 no.8
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• pp.636-640
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• 2001

In order to improve the optical Performance of green emitting phosphor for plasma display panel (PDP) application, the wet chemical method for preparing $Zn_{2-x}$ $SiO_4$:xMn (xi=0.02. 0.08) phosphor was designed. The spherical phosphor particles were obtained and the size can be between 0.5$\mu\textrm{m}$ and 2$\mu\textrm{m}$. The formation of phosphor, which had the willemite structure, was completed at relatively low temperature of 108$0^{\circ}C$. Also, photoluminescence Properties of the phosphors prepared were investigated under vacuum ultraviolet excitation. In particular, the emission intensity of Zn$_2$SiO$_4$:0.08Mn phosphor having the 1$\mu\textrm{m}$ of particle size was higher than that of commercial phosphor by 40%. The decay time of zinc silicate powder prepared as containing 8 mole% of manganese has been measured as 7.8ms.

• Korean Journal of Materials Research
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• v.11 no.8
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• pp.363-363
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• 2001

In order to improve the optical Performance of green emitting phosphor for plasma display panel (PDP) application, the wet chemical method for preparing $Zn_{2-x}$ $SiO_4$:xMn (xi=0.02. 0.08) phosphor was designed. The spherical phosphor particles were obtained and the size can be between 0.5$\mu\textrm{m}$ and 2$\mu\textrm{m}$. The formation of phosphor, which had the willemite structure, was completed at relatively low temperature of 108$0^{\circ}C$. Also, photoluminescence Properties of the phosphors prepared were investigated under vacuum ultraviolet excitation. In particular, the emission intensity of Zn$_2$SiO$_4$:0.08Mn phosphor having the 1$\mu\textrm{m}$ of particle size was higher than that of commercial phosphor by 40%. The decay time of zinc silicate powder prepared as containing 8 mole% of manganese has been measured as 7.8ms.

• Journal of the Korean institute of surface engineering
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• v.50 no.1
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• pp.42-45
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• 2017

The magnesium-base AZ61 alloy was cast while adding 1% CaO powder into the melt. It was hot extruded, and oxidized at $550-650^{\circ}C$ in air in order to study its microstructure and oxidation behavior. Initially added CaO powder reacted with Al in the melt to $Al_2Ca$ particles that aligned along the extrusion direction. The formed $Al_2Ca$ particles increased the oxidation resistance through forming the superficial CaO scale at the upper part of the thin MgO oxide scale.

• Korean Journal of Materials Research
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• v.9 no.6
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• pp.609-614
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• 1999

The effect of the amount of $SiO_2$dopant on the behavior of $AlO_2$$O_3$-composite formation by melt oxdation of Al-alloy was examined in this paper. The $SiO_2$powder was spread on the top surface of the Al-1Mg-3-Si-5Zn-1Cu alloy in th alumina crucible. The selected amount of each powder was 0.03, 0.10, 0.16g/$\textrm{cm}^2$. The oxidation behavior was determined by observing the weight gain after the heat treatment for 10 hours at 1373K. The macroscopic structure of formed oxide layer was examined by an optical microscope. The top surface and the cross-section of the grown oxide layer were investigated by SEM and analysed by EDX. The $SiO_2$ powder was determined to enhance oxidation by thermit reaction with Al which reduced the growth incubation period of the oxidation layer. As the amount of the $SiO_2$dopant increased, the growth rate decreased due to the precipitated Si which blocked the Al-alloy channel in the composite materials. However, more uniform layer was obtained due to the occurrance of the enhanced oxidation reaction in the whole alloy surface compared to the case of addition of less amount of dopant.

• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.1881-1886
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• 2010

Hydrothermal reaction of zinc(II) salts with 5-sulfoisophthalic acid monosodium salt ($NaO_3SC_6H_3$-1,3-(COOH)$_2$, $NaH_2$-SIP) and 1,10-phenanthroline (phen) led to two new compounds, [Zn(phen)$_3$$\cdot2H_2SIP\cdot4H_2O$ (1) and [Zn(phen)$_2(H_2O)_2]\cdot2H_2SIP\cdot2H_2O$ (2). They were characterized by element analysis, IR spectroscopy, thermalgravimetric analysis (TGA), X-ray powder diffraction (XRD), and single-crystal X-ray diffraction. Both compounds 1-2 represent the first example of Zn/phen/SIP system. The Zn (II) ion in 1 is six-coordinated by six nitrogen atoms from three phen molecules, and the $H_2SIP^-$ ligands engage in the formation of hydrogen bond. The Zn(II) ion in 2 is coordinated by four nitrogen atoms from two phen molecules and two oxygen atoms from two water molecules. Moreover, both 1 and 2 are assembled into 3D supramolecular architectures by hydrogen bonds (O-H$\ldots$O) and $\pi-\pi$ interactions. Solvent water molecules occupying voids of the compounds serve as receptors or donors of the extensive O-H$\ldots$O hydrogen bonds.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.118.2-118.2
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• 2017

Combustion behavior of Fe, CuO, NiO, ZnO and $Fe_2O_3$ powder mixture was carried out by finite element method (FEM) to understand a reaction at iron and metal oxide interface. The FEM was done by using ANSYS Fluent 17.0. Initial and boundary conditions are 1 atmosphere, room temperature, 0.1MPa of oxygen partial pressure, $T_{S1}=1127^{\circ}C$, $T_{S2}=327^{\circ}C$ for a cylindrical shape specimen with dia. $35{\times}80$ [mm]. The maximum combustion temperature is $1537^{\circ}C$ for the condition of conduction, convection and radiation. The combustion temperature and rate are about $847^{\circ}C$ and 3.9mm/sec, respectively. The combustion wave is enough to make ternary ferrite phase like $CuNiZnFe_2O_3$.