• Journal of the Korean Ceramic Society
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• v.33 no.2
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• pp.155-162
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• 1996

A Taguchi methodology study of the plasma spraying thermal barrier coating (TBC) layer is presented. The experiment parameters were designed by a L8-style orthogonal arrays approach. A Taguchi analysis was conduc-ted through the results of the coating properties which were affected by plasma spraying parameters. Zirconia (partially stbilized with ytrria: PSZ) was sprayed on TiAl intermetallic compound substrates, The coating layer was characterized by thickness microstructure and porosity using SEM and Image analyzer. The coating quali-ties are discussed with respect to thermal barrier effect thermal cycling test6 and adhesion strength test. An optimum condition of plasma spraying process which are derived from the Taguchi analysis could be found for high quality TBC.

• Journal of the Korean Ceramic Society
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• v.34 no.6
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• pp.601-610
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• 1997

In cofiring of multilayered alumina with tungsten, the change of camber with lamination condition was experimented and the effect of sintering shrinkage of alumina and tungsten was investigated. From the exact measurement of sintering shrinkage of tungsten thick film, as lamination pressure increased, the sintering shrinkage of alumina decreased but that of tungsten thick film was not changed. So it was though that the main factor which induced the sintering shrinkage difference between ceramics and metal with lamination condition was the change of sintering shrinkage of ceramics. In case of high lamination pressure, high green sheet density, the cofired specimen showed low camber due to low shrinkage difference between alumina and tungsten and there was a linear relation between camber and shrinkage difference. It was found that this shrinkage difference could change the thickness of tungsten film and the microstructure within via hole during cofiring.

• Journal of the Korean Ceramic Society
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• v.24 no.2
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• pp.101-110
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• 1987

The relative electrical conductivity of vacuum deposited Al films on a soda-lime(2947) and an alumino boro silicate(7809) glass was investigated with the variation of the relative humidity,temperature and film thickness. The structure and microstructure of Al films before and after exposure to the humidity wereexamined by the X-ray Diffractormenter(XRD) and Scanning Electron Microscope(SEM). As the relative humidity increased, the electrical conductivity of Al films on both glasses was decreased. However, the Al films on 7809 glass showed higher conductivity than that of 2947 glass under the same testing conditions. The decreasing of electrical conductivity was caused by the formation of Aluminum hydroxide which was made by the reaction between the aluminum films and water vapor.

• Journal of the Korean Ceramic Society
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• v.31 no.3
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• pp.330-336
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• 1994

High strength cement composites (W/C=0.1) were prepared by using various blending materials such as SiC whisker and white carbon (hydrated silica: SiO2·nH2O). The effect of various blending materials on the microstructure and strength of the hardened cement paste were investigated in the view of fracture mechanics. The plain specimen showed 101 MPa of flexural strength, 81 GPa of Young's modulus and 1.32 MPam1/2 of fracture toughness. When the blending materials were added to the composites, their values were enhanced to about 110∼138 MPa, 95∼146 GPa and 1.32∼1.87MPam1/2 respectively. The improvement of the mechanical strength for the hardened cement paste may be due to the removal of macropores, the reduction of total porosity, pozzolanic reaction and the increase of various fracture toughening effect.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2006.05a
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• pp.198-201
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• 2006

To produce fine structure with uniform surface of barrier ribs in PDP, acid etching process has been used in manufacture process. It is necessary to understand the mechanism of etching, particularly on the interface of ceramic fillers and matrix glass. We investigated the effect of ceramic fillers (ZnO, $Al_{2}O_3$) on the microstructure of borate glass system to find an etching mechanism of barrier ribs. The harrier ribs was etched with a several steps, dissolving a small amount of residual glass, taking out alumina fillers, and removing a cluster type of ZnO fillers and glass matrix.

• Journal of the Semiconductor & Display Technology
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• v.5 no.3 s.16
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• pp.33-36
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• 2006

To produce a fine structure with uniform surface of barrier ribs in PDP, acid etching process has been used in manufacture process. It is necessary to understand the mechanism of etching, particularly on the interface of ceramic fillers and matrix glass. We investigated the effect of ceramic fillers (ZnO, $Al_2O_3$) on the microstructure of borate glass system to find an etching mechanism of barrier ribs. The barrier ribs was etched with several steps, dissolving a small amount of residual glass, taking out alumina fillers, and removing a cluster type of ZnO fillers and glass matrix.

• Corrosion Science and Technology
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• v.4 no.1
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• pp.23-28
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• 2005

Several plasma-sprayed ceramic coatings with two- and three-layers were characterized and tested for the application of cooling tube coatings of oxygen convert gas recovery system (OG cooling system) in the steel making plant. Thermal cycling tests using a torch heating with compressed air cooling were carried out and characterized before and after the tests. The effects of metallic bond coat as well as ceramic top coat were also studied. Possible failure mechanisms with low carbon steel substrate were assessed in term of microstructure, porosity, bond strength, thermal expansion coefficient, and the phase transformation. Finally, the results of field tests at the OG cooling system are presented and discussed their microstructural degradation. Test results have shown that three-layered coatings perform better than two-layered coatings.

• Journal of the Korean Ceramic Society
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• v.43 no.8 s.291
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• pp.451-457
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• 2006

The solid solutions of ${\alpha}-Si_3N_4$, i.e. ${\alpha}$-sialons, are represented by a general formula of $M_x(Si,Al)_{12}(O,N)_{16}$, in which metal ions (M) dissolve into interstitial sites to stabilize the structure. Processing methods for the fabrication of ${\alpha}/{\beta}$-sialon composites, ${\alpha}-sialon/{\beta}Si_3N_4$ composites, refractory or tough ${\alpha}$-sialon ceramics have been developed to tailor the mechanical properties. Translucent and photoluminescent properties have been investigated recently. A number of applications of ${\alpha}$-sialon ceramics as engineering and optical ceramics are also presented.

• Journal of the Korean Ceramic Society
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• v.29 no.10
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• pp.757-764
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• 1992

The platelet reinforced mullite-zirconia composites were prepared by pressurelss sintering with addition of Al2O3 or SiC platelets. The sintered density of 10 vol% Al2O3 platelet reinforced mullite-zirconia composite was 98.3% at 1700$^{\circ}C$. The fracture strength (290 MPa) and fracture toughness (4.9 MPa$.${{{{ SQRT { m} }}) in the Al2O3 platelet reinforced mullite-zirconia composite were enhanced compared with those of mullite-zirconia due to the crack deflection and load transfer effect of platelets. Whereas, the SiC platelet reinforced mullite-zirconia composite sintered at 1650$^{\circ}C$ showed relatively lower density (95.7%), fracture strength (170 MPa), and fracture toughness (3.9 MPa$.${{{{ SQRT { m} }} than the Al2O3 platelet reinforced mullite-zirconia composite.

• Journal of the Korean Ceramic Society
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• v.30 no.12
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• pp.1007-1014
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• 1993

YBa2Cu3Ox(YBCO) thick films were prepared by a screen printing of the powders, obtained by a coprecipitation in oxalic acid, on the Y2O3-stabilized zirconia substrates and their superconducting properties were determined. TC, JC and the orientation factor of the thick films increased with increasing temperature up to 103$0^{\circ}C$ and then the superconducting properties disappeared with further heat treatments. The optimization of JC was achieved by heating thick films at 103$0^{\circ}C$ for 7min. In this case the TC of the thick film was determined to be 87.5K. It was observed that TC of thick films depends on the orthorhombicity and JC is likely governed by a microstructure of YBCO rather than by the orientation factor.