• Korean Journal of Materials Research
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• v.11 no.5
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• pp.398-404
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• 2001

Effects of coating treatment of metallic Cu film on SiC for Al/SiC composite were studied. The Copper was deposited on SiC by electroless plating method. Al/sic composite was fabricated at temperature range of $670^{\circ}C$ to 90$0^{\circ}C$ under vacuum atmosphere. The wetting behavior of Al/SiC composite were analysed by SEM and XRD. The coating treatment on SiC improved wettability of Al melt on SiC considerably comparing to the non coated SiC. This improved wettability seems strongly concerned to the increase of chemical reactivity between coated layer and Al matrix. The improvement of wettability of Al melt on the Cu coated SiC was closely related to in the initial stage of reaction. The metallic film played an important role in reducing the interfacial free energy and breaking down the aluminum oxide film through the reaction with Al melt. The wetting behavior of the as-received SiC with Al melt was not uniform, indicated by the contact angles from less than $97^{\circ}$to more than $97^{\circ}$.

• Journal of the Korean Ceramic Society
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• v.45 no.9
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• pp.561-566
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• 2008

Carbon fiber fabric-silicon carbide composites were fabricated by liquid silicon infiltration (LSI) process. The porous two-dimensional carbon fiber fabric performs were prepared by 13 plies of 2D-plain-weave fabric in a three laminating method, [0/90], [${\pm}45$], [$0/90/{\pm}45$] lay-up, respectively. Before laminating, a thin pyrolytic carbon (PyC) layer deposited on the surface of 2D-plain weave fabric sheets as interfacial layer with $C_3H_8$ and $N_2$ gas at $900^{\circ}C$. A densification of the preforms for $C_f-Si-SiC$ matrix composite was achieved according to the LSI process at $1650^{\circ}C$ for 30 min. in vacuum atmosphere. The bending strength of the each composite were measured and the microstructural consideration was performed by a FE-SEM.

• Journal of the Korean Ceramic Society
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• v.47 no.1
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• pp.75-81
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• 2010

The feasibility of using the thin film technology in utilizing lanthanum strontium manganite (LSM) for a solid oxide fuel cell (SOFC) cathode in a low-temperature regime is investigated in this study. Thin film LSM cathodes were fabricated using pulsed laser deposition (PLD) on anode-supported SOFCs with yttria-stabilized zirconia (YSZ) electrolytes. Although cells with a 1 ${\mu}m$-thick LSM cathode showed poor low-temperature cell performance compared to that of a cell with a bulk-processed cathode due to the lack of a triple-phase boundary length, the cell with 200 nm-thick gadolinia-doped ceria (GDC) inserted between the LSM and YSZ showed enhanced performance and more stable operation characteristics in a comparison of a cell without a GDC layer. We postulate that the GDC layer likely improved the cathode adhesion, therefore contributing to the improvement of the cell performance instead of serving as an interfacial reaction buffer.

• Journal of the Microelectronics and Packaging Society
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• v.6 no.1
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• pp.51-58
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• 1999

The effects of glass composition on the wettability and reactivity with $ZrO_2$substrate was evaluated and fabrication variables and glass compositions was investigated. Various glass compositions was investigated. Alkaline earth silicate glass show good wettability and lower viscosity and crystallization of glass could be prevented by $B_2O_3$.The sealant glass begin to wet on $ZrO_2$substrate below $900^{\circ}C$ and porosity occurred in various glass compositions, the crystallization and porosity in the glass could be prevented by the addition of flux into glass composition. But flowability and reactivity of glass with $ZrO_2$substrate was enhanced. Processing variables should be optimized to reduce the porosity by enhancing the sintering of glass powder. Many silicate glasses were investigated for the applications of high temperature sealants. Wetting and bonding of glass was good enough to seal together between $ZrO_2$and other ceramic components of SOFC. But porosity and reaction layer were occurred in the sealant glass. It will be possible to produce glass sealant without porosity and reaction layer at the interface by optimization of processing variable and modify the glass compositions. In present study, wettability of glass-filler composite was investigated. The porosity, shape of filler and interfacial reactions of sealant glass with fillers were examined.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.5
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• pp.654-664
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• 2006

Statement of problem: There has been a eat interest in the use of titanium for fixed and removable prostheses in recent because of its excellent biocompatibility. However, the melting temperature and chemical reactivity of titanium necessities casting system different from those used in conventional casting. The current titanium casting systems are based on an electric-arc design for melting the metal in an argon atmosphere and its exclusive investment. Despite the new development in Ti casting system, inadequate mold filling and internal porosity are frequently observed casting defects. Purpose : The purposes of this study were to compare the castibility and reaction layer of the casting titanium under the two casting machines and their investment condition. Material and method: coping and machine-milled titanium coping according to the casting methods and the marginal configurations. The total 28 specimens were used, and these are divided into 4 groups according to 2 casting machines and 2 investments. The castings were analyzed using x-ray microanalysis and microhardness testing. The reaction layer between margin of titanium casting and the investments was observed and analyzed with scanning electron microscope. Result: 1. Castabiliy of casting titanium specimen was best in the group of centrifugal casting machine and Selevest $CB^{\circledR}$ and good that of Selevest CB and pressure differential casting machine, Rematitan plus and centrifugal casting machine, Rematitan plus and pressure differential casting machine in order. 2. There was no significanct correlation in titanium castability in respect of casting machine. However ANOVA indicated that Selevest $CB^{\circledR}$ groups had significantly better castability than Rematitan $plus^{\circledR}$ groups.(p<0.05) 3. There was a significant microhardness difference between centrifugal casting machine groups and pressure differential groups.(p<0.05) Titanium castings in centifugal groups had significantly harder than those in pressure differential groups. 4. The addition of zirconia decreased interfacial reactivity. Conclusion: above result revealed that of the castability of titanium casting specimens had little correlation in casting machines and was better in magnesia-based investment contained ZrO2 groups. However in order to practice casting titanium in clininic, its castability should be improved, also there should be more research on factor of castability so that long-span prothesis and removable partial denture metla frame may be casted completly.

• Journal of the Korean Electrochemical Society
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• v.1 no.1
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• pp.33-39
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• 1998

To AC impedance study was performed in this study on the interfacial reaction between organic electrolyte and amorphous tungsten oxides thin film, cathodically coloring oxide, prepared by e-beam evaporation method in the 1 M $LiClO_4/PC$ organic solution. The electrochemical reactions at the interface were analyzed by the transient method and the complex impedance spectroscopy. The impedance spectrums showed that the electro-chemical intercalation of lithium cations was consisted of the following three steps; the first step, the charge transfer reaction of lithium cation at the interface between amorphous tungsten oxides thin film and the organic electrolyte, the second step, the adsorption of lithium atom on the surface of amorphous tungsten oxides thin film, and then the third step, the absorption and the diffusion of lithium atom into amorphous tungsten oxides thin layer. The bleaching and the coloring characteristics of amorphous tungsten oxides thin film were explained in terms of thermodynamic and kinetic variables, the simulated $R_{ct},\;C_{dl},\;D$ and $\sigma_{Li}$ by CNLS fitting method. Especially it was found that the limiting values of electrochromic reaction were the molar ratio of lithium, y=0.167 and the electrode potential, E=2.245 V (vs. Li).

• Korean Journal of Materials Research
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• v.9 no.3
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• pp.288-294
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• 1999

In the flip chip interconnection using solder bump, the Under Bump Metallurgy (UBM) is required to perform multiple functions in its conversion of an aluminum bond pad to a solderable surface. In this study, various UBM systems such as $Al 1\mu\textrm{m} / Ti 0.2\mu\textrm{m} / Cu 5\mu\textrm{m}, Al 1\mu\textrm{m} / Ti 0.2\mu\textrm{m} / Cu 1\mu\textrm{m}, al 1\mu\textrm{m}/Ni 0.2\mu\textrm{m} / Cu 1\mu\textrm{m} and Al 1\mu\textrm{m}/Pd 0.2\mu\textrm{m} / Cu 1\mu\textrm{m}$ for flip chip interconnection using the low melting point eutectic 63Sn-37Pb solder were investigated and compared to their metallurgical properties. $100\mu\textrm{m}$ size bumps were prepared for using an electroplating process. The effects of the number of reflows and aging time on the growth of intermetallic compounds(IMC) were investigated. $Cu_6Sn_5$ and $Cu_3Sn$ IMC were abserved after aging treatment in the UBM system with thick coper $(Al 1\mu\textrm{m}/Ti 0.2\mu\textrm{m}/Cu 5\mu\textrm{m})$. However only the $Cu_6Sn_5$ was detected in the UBM system with $1\mu\textrm{m}$ thick copper even after 2 reflow and 7 day aging at $150^{\circ}C$. Complete Cu consumption by Cu-Sn IMC growth gives rise to a direct contact between solder inner layer such as Ti, Ni and Pd, and hence to possibly cause reactions between two of them. In this study, however, only for the Pd case, IMC of PdSn. was observed by Cu consumption. UBM interfacial reactions with s이der affected the adhesion strength ot s이der balls after s이der reflow and annealing treatment.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.3
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• pp.106-110
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• 2014

The passivation property of $Al_2O_3$ thin film formed using atomic layer deposition (ALD) for the application of crystalline Si solar cells was investigated using microwave photoconductance decay (${\mu}$-PCD). After post-annealing at $400^{\circ}C$ for 5 min, $Al_2O_3$ thin film exhibited the structural stability having amorphous nature without the interfacial reaction between $Al_2O_3$ and Si. The post-annealing at $400^{\circ}C$ for 5 min led to an increase in the relative effective lifetime of $Al_2O_3$ thin film. This could be associated with the field effective passivation combined with surface passivation of textured Si. The capacitance-voltage (C-V) characteristics of the metal-oxide-semiconductor (MOS) with $Al_2O_3$ thin film post-annealed at $400^{\circ}C$ for 5 min was carried out to evaluate the negative fixed charge of $Al_2O_3$ thin film. From the relationship between flatband voltage ($V_{FB}$) and equivalent oxide thickness (EOT), which were extracted from C-V characteristics, the negative fixed charge of $Al_2O_3$ thin film was calculated to be $2.5{\times}10^{12}cm^{-2}$, of which value was applicable to the passivation layer of n-type crystalline Si solar cells.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.1 s.34
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• pp.41-46
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• 2005

A systematic investigation of shear testing was conducted to find a relationship between Ni-Sn intermetallic spatting and the brittle fracture observed in electroless Ni(P)/solder interconnection. Brittle fracture was found in the solder joints made of Sn-3.5Ag, while only ductile fracture was observed in a Cu-containing solder (Sn-3.0Ag-0.5Cu). For Sn-3.0Ag-0.5Cu joints, $(Ni,Cu)_3Sn_4$ and/or $(Cu,Ni)_6Sn_5$ compound were formed at the interface without spatting from the Ni(P) film. For Sn-3.5Ag, $Ni_3Sn_4$ compound was formed and brittle fracture occurred in solder pads where $Ni_3Sn_4$ had spalled. From the analysis of fractured surfaces, it was found that the brittle fracture occurs through the $Ni_3SnP$ layer formed between $Ni_3Sn_4$ intermetallic layer and the Ni(P) film. Since the $Ni_3SnP$ layer is getting thicker during/ after $Ni_3Sn_4$ spatting, suppression of $Ni_3Sn_4$ spatting is crucial to ensure the reliability of Ni(P)/solder system.

• Korean Chemical Engineering Research
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• v.48 no.2
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• pp.172-177
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• 2010

This study reports the high-temperature oxidation kinetics, ASR(area specific resistance), and interfacial microstructure of metallic interconnects coated with conductive oxides in oxidation atmosphere at $800^{\circ}C$, The conductive material LSC($La_{0.8}Sr_{0.2}CoO_3$, prepared by Solid State Reaction) was coated on the Crofer22APU. The contact behavior of coating layer/metal substrate was increased by sandblast. The electrical conductivity of the LSC coated Crpfer22APU was measured by a DC two probe four wire method for 4000hr, in air at $800^{\circ}C$. Microstructure and composition of the coated layer interface were investigated by SEM/EDS. These results show that a coated LSC layer prevents the formation and growth of oxide scale such as $Cr_2O_3$ and enhances the long-term stability and electrical performance of metallic interconnects for SOFCs.