• Journal of Welding and Joining
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• v.20 no.5
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• pp.87-92
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• 2002

Weldability of Friction Stir Welded(FSW) AZ31B-H24 Mg alloy sheet with 4m thick was evaluated by changing welding speed. The sound welding conditions mainly depended on the suffiicient welding heat input during the process. The insufficient heat input resulted in the void like defect in the weld zone. Higher welding speed caused a larger inner void or lack of bonding. The defects were distributed at the stir zone or the transition region between stir zone and thermo-mechanical affected zone (UE). The size of defects slightly increased with increasing welding speed. These defects had a great effect on the joint strength of weld zone. The weld zone was composed of stir zone, TMAZ and heat affected zone. The stir zone was cosisted of fine recrystallized structure with $5-8\mu\textrm{m}$ in the mean grain size. The hardness of weld zone was near the 60HV, which was slightly lower than that of base metal. The maximum joint strength was about 219MPa that was 75% of that of base metal and the yield strength was also lower than that of base metal partly due to the existance of defects.

• Journal of the Korean Vacuum Society
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• v.14 no.2
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• pp.91-96
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• 2005

The silicon-on-insulator (SOI) wafer fabrication technique has been developed by using ion-cut process, based on proton implantation and wafer bonding techniques. It has been shown by SRIM simulation that 65keV proton implantation is required for a SOI wafer (200nm SOI, 400nm BOX) fabrication. In order to investigate the optimum proton dose and primary annealing condition for wafer splitting, the surface morphologic change has been observed such as blistering and flaking. As a result, effective dose is found to be in the $6\~9\times10^{16}\;H^+/cm^2$ range, and the annealing at $550^{\circ}C$ for 30 minutes is expected to be optimum for wafer splitting. Direct wafer bonding is performed by joining two wafers together after creating hydrophilic surfaces by a modified RCA cleaning, and IR inspection is followed to ensure a void free bonding. The wafer splitting was accomplished by annealing at the predetermined optimum condition, and high temperature annealing was then performed at $1,100^{\circ}C$ for 60 minutes to stabilize the bonding interface. TEM observation revealed no detectable defect at the SOI structure, and the interface trap charge density at the upper interface of the BOX was measured to be low enough to keep 'thermal' quality.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.9
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• pp.969-975
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• 2009

In this paper, bonded wafer analysis system is proposed using laser beam transmission; while the transmission model is derived by simulation. Since the failure of bonded wafer stems in void existence, transmittance deviations caused by the thickness of the void are analyzed and variations of the intensity through the void or defect easily have been recognized then the testing power has been increased. In addition, large screen display on laser study has been done which resulted in acquiring a feasible technique for analysis of the whole bonding surface. In this regard, three approaches are demonstrated in which Halogen lamp, IR lamp and laser have been tested and subsequently by results comparison the optimized technique using laser has been derived.

• Structural Engineering and Mechanics
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• v.53 no.5
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• pp.1017-1030
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• 2015

In this study, the finite element method was used to analyze the distribution of the adhesive shear stresses in the single-lap bonded joint of two plates 2024-T3 aluminum with and without defects. The effects of the adhesive properties (shear modulus, the thickness and the length of the adhesive were highlighted. The results prove that the shear stresses are located on the free edges of the adhesively bonding region, and reach maximum values near the defect, because the concentration of high stress occurs near this area.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.283-284
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• 2018

The rear side surface of tiles act have protrusions that helps secure the adhesion between the tile and the mortar for tile setting. Conventional height of the rear side usually ranges between 1 to 1.5 mm, and the molding method is classified in between press type and compression type during the manufacturing process, with most tiles being produced by the former method. In sites where adhesion failures were observed, tiles were taken to examine the cause of defect. It was determined that height was irregular at the rear side surface. Based on these findings, an experiment was conducted to determine the correlation between the rear surface and the bonding strength of tiles.

• The Korean Journal of Ceramics
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• v.3 no.3
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• pp.163-168
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• 1997

Most of heteroepitaxial $\beta$-SiC thin films have been successfully grown on Si(100) adapting a carburizing process, by which a few atomic layers of substrate surface is chemically converted to very thin SiC layer using hydrocarbon gas sources. Using an organo-silicon precursor, bis-trimethylsilymethane (BTMSM, [$C_7H_{20}Si_2$]), heteropitaxial $\beta$-SiC thin films were successfully grown directy on Si substrate without a carburized buffer layer. The defect density of the $\beta$-SiC thin films deposited without a carburized layer was as low as that of $\beta$-SiC films deposited on carburized buffer layer. In addition, void density was also reduced by the formation of self-buffer layer using BTMSM instead of carburized buffer layer. It seems to be mainly due to the characteristic bonding structure of BTMSM, in which Si-C was bonded alternately and tetrahedrally (SiC$_4$).

• Journal of the Korean Ceramic Society
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• v.25 no.1
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• pp.35-41
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• 1988

In the system of Li2O-MgO-Al2O3-Cr2O3, the crystalline solid solution of LiCrO2 along the pseudo-binary join between rocksalt structure(LiCrO2) and spinel structure(MgCr2O4 or MgAl2O4) have been investigated by x-ray diffraction techniques. In this study, order-disorder phase transition of LiCrO2 was observed and the unit cell of the disordered LiCrO2 structure has been established. It has been found that LiCrO2 makes a solid solution over a wide range with MgAl2O4, while not with MgCr2O4. This difference was explained as being due to the ability of oxygen lattice distortion which depended on the relative sizes and chemical bonding characteristics of the substituted ions.

• Macromolecular Research
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• v.15 no.2
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• pp.134-141
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• 2007

The direct chromatographic separation of enantiomers by chiral stationary phases (CSPs) has been extensively developed over the past two decades, and has now become the most popular method for the analytical and preparative separations of enantiomers. Polysaccharide derivatives coated onto silica gel, as CSPs, playa significantly important role in the enantioseparations of a wide range of chiral compounds using high-performance liquid chromatography (HPLC). Unfortunately, the strict solvent limitation of the mobile phases is the main defect in the method developments of these types of coated CSPs. Therefore, the immobilization of polysaccharide derivatives onto silica gel, via chemical bonding, to obtain a new generation of CSPs compatible with the universal solvents used in HPLC is increasingly important. In this article, our recent studies on the immobilization of polysaccharide derivatives onto the silica gel, as CSPs, through radical copolymerization with various vinyl monomers are reported. Polysaccharide derivatives, with low vinyl content, can be efficiently fixed onto silica gel with high chiral recognition.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.3
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• pp.173-180
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• 2007

In this paper, we have proposed a simple finite element model for separation mode analysis on the roadwheel and track assembly of main battle tank and established a contact stress-based mechanism which could explain the initiation and growth of separation defect occurred during the test of padreplacable track. It was proved that the longitudinal contact shear stress component on the pin hole region of the track shoe body which is parallel to the driving direction is consistent with the crack initiation at the bonding surface between track shoe and wheel-side rubber. The longitudinal shear stress increased locally near the separated region after the separation initiated. So we could assume that the local stress concentration accelerates the separation growth according to the shear mode.

• Journal of the Korean Vacuum Society
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• v.7 no.2
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• pp.150-154
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• 1998

Photoluminescence(PL), XRD, TEM results $5\times1016/\textrm{cm}^2, 1\times10^{17}/\textrm{cm}^2, 3\times10^{17}/\textrm{cm}^2$ Si-implanted $SiO_2$ films on crystalline silicon are reported. At low dose implantation and low annealing temperature, visible PL are observed. The PL spectrum has 7400$\AA$ and 8360$\AA$ peaks. As annealing time increased, the PL intensity are increased and peak positions are changed. The PL spectrum are not observed at high dose implantation and high annealing temperature. For the samples of low dose and high annealing temperature, visible PL are observed at short annealing time (30 minutes) and disappear for more than 1 hour annealing. From XRD and TEM results, silicon cluster are related to nonradiative defects. It is concluded that the origin of visible PL in Si implanted SiO2 films are not nanocrystal but two kinds of radiative defects. The Si-O-O bonding related defects (O rich defects) and Si-Si-O bonding related defects (Si rich defects) are related to the PL spectrum and depend on concentraion of Si implantation, annealing temperature and time.