• Journal of the Korean Ceramic Society
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• v.56 no.5
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• pp.483-488
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• 2019

We studied whether chemical strengthening can heal the flaws on soda-lime silicate glass. Artificial surface cracks were introduced on the glass by sharp indentation with various loads of 0.1 to 10 N. Then, the glasses with flaws were treated by ion-exchanging in KNO₃ melt. The change in the dimension of the crack on glass was measured by a digital microscope and a scanning electron microscope. The chemical strengthening treatment enhances the strength of the glass with flaws. It is thought that the melted KNO₃ not only forms the depth of the compressed layer of 7.5 ㎛, but also heals the cracks by infiltrating them and expanding the glass on both sides of the cracks. The critical length (2c) of the cracks on soda-lime glass that can be healed by chemical strengthening is 50 ㎛ or less.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05a
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• pp.70-73
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• 2004

The packaging of the integrated circuits requires knowledge of ceramics and metals to accommodate the fabrication of modules that are used to construct subsystems and entire systems from extremely small components. Composite ceramics (Al$_2$O$_3$-SiO$_2$) were tested for substrates. A stress analysis was conducted for a linear work-hardening metal cylinder embedded in an infinite ceramic matrix. The bond between the metal and ceramic was established at high temperature and stresses developed during cooling to room temperature. The calculations showed that the stresses depend on the mismatch in thermal expansion, the elastic properties, and the yield strength and work hardening rate of the metal. Experimental measurements of the surface stresses have also been made on a Cu/Al$_2$O$_3$-SiO$_2$ceramic system, using an indentation technique. A comparison revealed that the calculated stresses were appreciably larger than the measured surface stresses, indicating an important difference between the bulk and surface residual stresses. However, it was also shown that porosity in the metal could plastically expand and permit substantial dilatational relaxation of the residual stresses. Conversely it was noted that pore clusters were capable of initiating ductile rupture, by means of a plastic instability, in the presence of appreciable tri-axiality. The role of ceramics for packaging of microelectronics will continue to be extremely challenging.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.308-312
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• 2003

The packaging of the integrated circuits requires knowledge of ceramics and metals to accommodate the fabrication of modules that are used to construct subsystems and entire systems from extremely small components. Composite ceramics ($Al_2O_3-SiO_2$) were tested for substrates. A stress analysis was conducted for a linear work-hardening metal cylinder embedded in an infinite ceramic matrix. The bond between the metal and ceramic was established at high temperature and stresses developed during cooling to room temperature. The calculations showed that the stresses depend on the mismatch in thermal expansion, the elastic properties, and the yield strength and work hardening rate of the metal. Experimental measurements of the surface stresses have also been made on a $Cu/Al_2O_3-SiO_2$ ceramic system, using an indentation technique. A comparison revealed that the calculated stresses were appreciably larger than the measured surface stresses, indicating an important difference between the bulk and surface residual stresses. However, it was also shown that porosity in the metal could plastically expand and permit substantial dilatational relaxation of the residual stresses. Conversely it was noted that pore clusters were capable of initiating ductile rupture, by means of a plastic instability, in the presence of appreciable tri-axiality. The role of ceramics for packaging of microelectronics will continue to be extremely challenging.

• Korean Journal of Metals and Materials
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• v.46 no.7
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• pp.464-470
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• 2008

Metallic nanostructures have great potential for bio-chemical sensor applications due to the excitation of localized surface plasmon and its sensitive response to environmental change. Unlike the commonly explored absorption-based sensing, the optical scattering provides single particle detection scheme. For the localized surface plasmon resonance spectroscopy, the metallic nanostructures with controlled shape and size have been usually fabricated on adhesion-layer pre-coated transparent glass substrates. In this study, we calculated the optical scattering properties of plasmonic Au nanodisc using a discrete dipole approximation method and analyzed the effect of adhesion layer on them. Our result also indicates that there is a trade-off between the surface plasmon damping and the capability of supporting nanostructures in determining the optimal thickness of adhesion layer. Marginal thickness of Ti adhesion layer for supporting Au nanostructures fabricated on a silica glass substrate was experimentally analyzed by an adhesion strength test using a nano-indentation technique.

• Korean Journal of Materials Research
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• v.10 no.5
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• pp.321-327
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• 2000

Two kinds of $Al_2O_3/TZP$ composites were prepared using the liquid infiltration of 3Y-TZP and 12Ce-TZP precursors into hte sintered porous $Al_2O_3$. Small TZP additions(~11.0wt%) had increased the strength(19~59%) and fracture toughness(14~157%) of the sintered Al2O3 material($1600^{\circ}C$, 2h). The addition of 3Y-TZP was effective on case of the strength. By the way, in case of the fracture toughness that of 12Ce-TZP was effective. Infiltrated TZP was concentrated on the surface where its grain growth was enhanced and $Al_2O_3$ grain growth was effectively inhibit-ed, when compared to the inner region of the composite. The indentation crack was propagated through both intergranular modes and transgranular and the proportion if intergranular fracture was the larger in $Al_2O_3/12Ce-TZP$.

• Journal of Ocean Engineering and Technology
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• v.25 no.6
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• pp.66-71
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• 2011

Recently, the production of shipbuilding and offshore plant industries, with a trend toward large structures, has led to an increased use of high strength ultra-thick plates. The use of ultra-thick plates increases the welding tasks, and the welding process generates distortion and residual stress in the weldment because of the rapid heating and cooling. Welding distortion and residual stress in the welded structure resulte in many troubles such as deformation and life deterioration. In particular, the welding residual stress has an important effect on welding deformation, fatigue, buckling strength, brittleness, etc. The purpose of this study was to evaluate the residual stress at a multi-pass weldment using an experimental method for EH36 high-tension steel. In this experimental method, AIS3000 was used to measure the residual stress of a welded part, HAZ, and base metal; EPMA and XRD were used to study the material properties.

• Korean Journal of Materials Research
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• v.15 no.12
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• pp.796-801
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• 2005

In order to reduce the weight of glass in architecture, automobile, bottles, displays, a new technique that can strengthen glass was developed using various method. Generally, the strength achieved of glass-ceramics is higher as is 1.he fracture toughness by the formation of a crystalline phase inside glass. In this study, $70SiO_2-20Na_2O-10CaO-10TiO_2$ glasses were irradiated to strengthen by heterogeneous phase using femto-second laser pulse. Laser pulse irradiation of samples was analyzed by DTA, TMA, XRD, nano-indenter and SEM. Samples irradiated by laser had lower value$(3\~4\times10^{-3}Pa)$ of nano indentation which related with mother glass$(8\times10-3Pa)$ than values. Microcracks were occurred around laser irradiation area when femtosecond laser with the repetition rate of 1kHz was used as the light source to induced heterogeneous phase.

• Journal of the Korean Ceramic Society
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• v.37 no.1
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• pp.21-25
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• 2000

Gas pressure sintered silicon nitride based composites with 5 wt% $\beta$-Si3N4 whiskers were prepared, and the variations depending on sintering additives and sintering temperature were studied. Sintering additives were 6 wt% Y2O3-1 wt% MgO(6Y1M), 6 wt%Y2O3-1 wt% Al2O3(6Y1A), 6 wt% Y2O3-1 wt% SiO2(6Y1S), and whiskers were unidirectionally oriented by a modified tape casting technique. Samples were fully densified by gas pressure sintering at 2148 K and 2273 K. As the sintering temperature increased, the size of large elongated grains was increased. Three point flexural strength of 6Y1M and 6Y1M samples was higher than that of 6Y1S sample, and the strength decreased as the sintering temperature increased. The indentation crack length became shorter for the sample sintered at higher temperature, and the difference between the cracks length parallel to and normal to the direction of whisker alignment was decreased. In case of cracks 45$^{\circ}$off the whisker alignment direction, the crack length anisotropy disappeared.

• The Journal of Korean Academy of Prosthodontics
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• v.29 no.2
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• pp.245-265
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• 1991

The purpose of this study was to observe the changes of the elemental transmission and bond strength between the metal and porcelain according to various kinds of ion beam mixing method. ion beam mixing of $meta1/SiO_2$ (silica), $meta1/Al_2O_3$(alumina) interfaces causes reactions when the $Ar^+$ was implanted into bilayer thin films using a 100KeV accelerator which was designed and constructed for this study. A vacuum evaporator used in the $10^{-5}-10^{-6}$ Torr vacuum states for the evaporation. For this study, three kinds of porcelain metal selected, -precious, semiprecious, and non-precious. Silica and alumina were deposited to the metal by the vacuum evaporator, separately. One group was treated by two kinds of dose of the ion beam mixing $(1\times10^{16}ions/cm^2,\;5\times10^{15}ions/cm^2)$, and the other group was not mixed, and analyzed the effects of ion beam mixing. The analyses of bond strength, elemental transmissions were performed by the electron spectroscopy of chemical analysis (ESCA), light and scanning electron microscope, scratch test, and micro Vickers hardness tests. The finding led to the following conclusions. 1. In the scanning electron and light microscopic views, ion beam mixed specimens showed the ion beam mixed indentation. 2. In the micro Vickers hardness and scratch tests, ion beam mixed specimens showed higher strength than that of non mixed specimens, however, nonprecious metal showed a little change in the bond strength between mixed and non mixed specimens. 3. In the scratch test, ion beam mixed specimens showed higher shear strength than that of non treated specimens at the precious and semiprecious groups. 4. In the ESCA analysis, Au-O and Au-Si compounds were formed and transmission of the Au peak was found ion beam mixed $SiO_2/Au$ specimen, simultaneously, in the higher and lower bonded areas, and ion beam mixed $SiO_2/Ni-Cr$ specimen, oxygen, that was transmitted from $SiO_2\;to\;SiO_2/Ni-Cr$ interface combined with 12% of Ni at the interface.

• The korean journal of orthodontics
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• v.31 no.1 s.84
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• pp.149-157
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• 2001

The purpose of this study was to investigate the property of a new Korean stainless steel wire(Jinsung Ind.) comparing with other foreign Products. Five types of stainless steel wires (Standard, Resilient, HI-T of Unitek, Stainless steel of Ormco and Jinsung Ind.) in 0.016x0.022 and 0.019x0.02 were tested to observe for Composition analysis, size difference, tensile properties, flexure bending property, tortion property, surface hardness and surface topography by means of SEM. The findings suggest that: 1. In maximum tensile strength of tensile properties, Unitek Hi-T showed the greatest value, followed by Unitek Resilient, Jinsung Stainless Steel, Ormco Stainless Steel, Unitek Standard in 0.016x0.022, and Unitek Hi-T showed highest value, followed by Jinsung Stainless Steel, Ormco Stainless Steel, Unitek Resilient, Unitek Standard in 0.019x 0.025. 2. In elongation rate, Unitek Standard showed the greatest value, fellowed by Ormco Stainless Steel, Unitek Hi-T, Unitek Resilient, Jinsung Stainless Steel in 0.016x0.022, and Unitek Hi-T showed the highest value, followed by Unitek Standard, Ormco Stainless Steel, Jinsung Stainless Steel, Unitek Resilient in 0.019x0.025. 3. In modulus of elasticity, Jinsung Stainless Steel showed the greatest value, followed by Unitek Hi-T, Unitek Resilient, Ormco Stainless Steel, Unitek Standard in 0.016x0.022, and Unitek Resilient showed the highest value followed by Jinsung Stainless Steel, Ormco Stainless Steel, Unitek Hi-T, Unitek Standard in 0.019x0.025. 4. In bending fatigue test, Jinsung Stainless Steel showed the greatest fracture resistance, followed by Unitek Hi-T, Unitek Standard, Unitek Resilient, Ormco Stainless Steel in 0.016x0.022, and Unitek Hi-T showed the greatest fracture resistance followed by Jinsung Stainless Steel, Unitek Resilient, Unitek Standard, Ormco Stainless Steel in 0.019x0.025. 5. In twist test, Unitek Resilient showed the greatest fracture resistance, followed by Jinsung Stainless Steel, Unitek Hi-7, Ormco Stainless Steel, Unitek Standard in 0.016x0.022, and Jinsung showed the greatest fracture resistance, followed by Unitek Resilient, Unitek Standard, Ormco Stainless Steel, Unitek Hi-T. 6. In surface topography, every products showed indentation and pitting. Jinsung stainless steel wire showed long thin indentation and relatively smooth surface. Unitek wires showed indentation and pitting and Ormco wire showed a lot of irregular pittings.