• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1234_1235
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• 2009

The Langmuir-Blodgett (LB) method has been one of the most suitable techniques for fabricating organic thin films with well-controlled structures, compositions and thickness at the molecular level. We investigated the surface activity of dendrimer films at air-water interface by $\pi$-A isotherm. Also, we attempted to fabricate a G3-9Ph dendritic silsequioxane LB films. And their surface morphologies were observed by atomic force microscopy (AFM).

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.99-102
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• 2003

Reactions between 48Sn-52In solder and under bump metallurgies(UBM) such as 100nm $Ti/8{\mu}m$ Cu and 300nm Al/400nm Ni(V)/400nm Cu have been investigated, and the shear strength of 48Sn-52In solder bumps on each UBM has been evaluated. While intermetallic compounds with two different morphologies were continuously thickened on Ti/Cu with repeating the reflow process, the intermetallics on Al/Ni(V)/Cu spalled into the solder with increasing the number of reflow times. The solder bumps on Ti/Cu exhibited higher shear strength than those on Al/Ni(V)/Cu.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1293-1294
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• 2008

The Langmuir-Blodgett (LB) method has been one of the most suitable techniques for fabricating organic thin films with well-controlled structures, compositions and thickness at the molecular level. We investigated the surface activity of dendrimer films at air-water interface by ${\pi}$-A isotherm. Also, we attempted to fabricate a 1G(4,3)-chloride dendrimer LB films. And their surface morphologies were observed by atomic force microscopy (AFM).

• The Korean Journal of Ceramics
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• v.3 no.1
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• pp.13-17
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• 1997

It is identified that the diamond films grown o bias-treated (100) silicon showed different surface morphologies and film textures according to the initial applied dc bias voltage at the same growth condition. The highly oriented diamond film (HODF) was successfully grown on -200 V bias-treated silicon substrate in which the heteroepitaxial relation of $(100)_{dimond}//(100)_{si}\; and\; [110]_{diamond}//[110]_{si}$ was identified. On the contrary, the heteroepitaxial relation was considerably disturbed in the samples bias-voltage was a key factor in growing the highly oriented diamond film on (100) silicon substrate. Considering the experimental results, we proposed a new model about heteroepitaxial diamond growth on silicon, in which 9 diamond unit cell are matched with 4 silicon cells and the bond covalency of both atoms is satisfied via the intermediate layer at the interface as well.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.320-323
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• 2000

We attempted to fabricate polyurethane derivatives (PU-CN, PU-DCM) LB films by using LB method. Also, we investigated the monolayer behavior at the air-water interface by surface pressure-area ($\pi$-A) isotherms. And, the surface morphologies and the physicochemical properties of LB films were investigated by atomic force microscopy (AFM) and UV-vis spectroscopy, respectively. Also, the electrical properties of polyurethane derivatives LB films were investigated by using the conductivity and the dielectric constant. In the AFM images, we conclude that surface morphology of PU-DCM LB films is smooth and homogeneous and has optimal hydrophobicity and good stability, whereas PU-CN LB films give rougher surfaces with more excess material. In the I-V characteristics, the conductivity is different as to the polyurethane derivatives, it is considered that this phenomena could be described by the difference of lumophore pendant which was adhered at PU main chain.

• Journal of Surface Science and Engineering
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• v.45 no.5
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• pp.188-192
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• 2012

The hetero junction on dielectrics and ferrite for LTCC was prepared by using NiCuZn ferrite. The shrinkage behaviour of ferrite tapes in combination with a dielectric tape was investigated. The characteristics of NiCuZn ferrite were investigated using XRD (X-ray diffractometer), Dilatometer, FE-SEM (Field emission scanning electron microscope), EDS (Energy dispersive spectrometer). NiCuZn ferrite calcined at $700^{\circ}C$ had a good apparent density and initial permeability of magnetic properties. The shrinkage rate of the NCZF700 ferrite and dielectric material was similar. The multilayer revealed dense, uniform morphologies with excellent interface quality. Diffusion of hetero junction such as dielectric and ferrite was not occuring at $900^{\circ}C$.

• Journal of Korea Foundry Society
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• v.23 no.5
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• pp.276-285
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• 2003

In the undercooled melt of $Pd_{40}Cu_{30}Ni_{10}P_{20}$ alloy, the solidification behavior including nucleation and growth of crystals at the micrometer level has been observed in-situ by use of a confocal scanning laser microscope combined with an infrared image furnace. The $Pd_{40}Cu_{30}Ni_{10}P_{20}$ alloy specimens were cooled from the liquid state to glass transition temperature. 575 K, at various cooling late under a helium gas flow. According to the cooling rate, the morphologies of the solidification front are changed among various types, irregular jog like front, columnar dendritic front, cellular grain, star like shape jog and fine grain, etc. The velocities of the solid-liquid interface are measured to be $10^{-5}{\sim}10^{-8}$ m/s which are at least two orders higher than the theoretical crystal growth rates. Combining the morphologies observed in terms of cooling rates and their solidification behaviors, we conclude that phase separation takes place in the undercooled molten $Pd_{40}Cu_{30}Ni_{10}P_{20}$ alloy. The continuous cooling transformation (CCT) diagram was constructed from solidification onset time at various linear cooling conditions with different rate. The CCT diagram suggests that the critical cooling rate for glassy solidification is about 1.5 K/s, which is in agreement with the previous calorimetric findings.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.4
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• pp.510-525
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• 2000

The effects of pretreatment of Co-Cr alloy, including two adhesive primers that contain either MDP or MAC-10, and silicoating on the bond The result sobtained as follows; o Strength of 4-META/MMA-TBB resin were investigated using FT-IR, SEM, and EDAX. o In the SEM observation of surface morphologies, the sandblasted specimen exibited a very rough surface, whereas the surfaces of the two groups primed with either MDP or MAC-10 were covered with a layer of primer, and the surface morphology of the silicoated specimen remained almost the same after sandblasting. o Before the thermocycling tests, the group treated with MDP demonstrated the highest mean tensile bond strength and the sandblasted group showed the lowest bond strength. o After 20,000 thermocyling, the mean tensile bond strength of the sandblasted group exhibited a 50% reduction in bond strength, while the others showed a $20\sim30%$ reduction. o Observation of the metal-resin interface revealed that in all groups the resin permeated the rough surface formed by sandblasting thereby producing a mechanical bond between the metal and the resin. It was also found that thermocycling resulted in a gap formation at the metal-resin interface of the specimens, and the sandblasted group exhibited a larger gap width than the other groups. o In fracture mode, all specimens indicated a cohesive fracture within the resin before thermocycling. However, thermocyling produced adhesive failure at the edge of the resin-metal interface in most specimens. The sandblasted group, which exhibited the lowest bond strength after thormocycling, also demonstrated the largest area of adhesive failure.

• Transactions on Electrical and Electronic Materials
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• v.18 no.4
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• pp.181-184
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• 2017

Multilayer ceramics in which piezoelectric layers of $0.90Pb(Zr_{0.48}Ti_{0.52})O_3-0.05Pb(Mn_{1/3}Sb_{2/3})O_3-0.05Pb(Zn_{1/3}Nb_{2/3})O_3$ (0.90PZT-0.05PMS-0.05PZN) stack alternately with silver electrode layers were prepared by an advanced low-temperature co-fired ceramic (LTCC) method. The electrical properties and bonding strength of the multilayers were associated with the interface morphologies between the piezoelectric and silver-electrode layers. Usually, the inner silver electrodes are fabricated by sintering silver paste in multi-layer stacks. To improve the interface bonding strength, piezoelectric powders of 0.90PZT-0.05PMS-0.05PZN with an average particle size of $23{\mu}m$ were added to silver paste to form a gradient interface. SEM observation indicated clear interfaces in multilayer ceramics without powder addition. With the increase of piezoelectric powder addition in the silver paste, gradient interfaces were successfully obtained. The multilayer ceramics with gradient interfaces present greater bonding strength as well as excellent piezoelectric properties for 30~40 wt% of added powder. On the other hand, over addition greatly increased the resistance of the inner silver electrodes, leading to a piezoelectric behavior like that of bulk ceramics in multilayers.

• Korean Journal of Materials Research
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• v.11 no.4
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• pp.312-318
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• 2001

The mechanical and electrical properties of Cu-Nb filamentary nanocomposite fabricated by the bundling and drawing process were examined. The strength increased gradually with increasing Nb content while the ductility was insensitive to Nb content. The ratio of yield stresses at 293K and 75K are found to be 치ose to that of Young's moduli in various Cu-Nb nanocomposites, suggesting that athermal obstacles primarily control the strength. The fracture morphologies show ductile fractures irrespective of Nb contents. Secondary cracking along the interfaces between subelemental wires was occasionally observed and the frequency of secondary cracking increased with increasing Nb content. The conductivity and the resistivity ratio decreased with increasing Nb content. The decrease of the conductivity and the resistivity ratio(${\rho}_{293k}$/$\{rho}_{75k}$) can be explained by the increasing contribution of interface scattering.