• Bulletin of the Korean Chemical Society
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• v.26 no.2
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• pp.248-252
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• 2005

Synthetic layered double hydroxides (LDHs), [$Mg_4Al_2(OH)_{12}]CO_3{\cdot}nH_2O$, were prepared in the submicron size of plate-like polycrystals. Anion-exchange reactions with various linear dicarboxylic acids were performed to produce LDH/organic hybrid materials by solvothermal treatment in toluene. X-ray powder diffraction spectra for the products indicated that the interlayer spacings of LDHs remarkably changed, up to 20 $\AA$ when 1,10-decanedicarboxylic acid anions were intercalated as an organic guest. Dicarboxylates-LDHs samples could be also re-exchanged consecutively with other dicarboxylic acids or carbonate without serious destruction of layer structure under the scanning electron microscopic observation.

• Carbon letters
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• v.2 no.2
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• pp.99-104
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• 2001

Partial mesophase (PM) pitch precursor was prepared from fluidized catalytic cracking-decant oils (FCC-DO) by chemical reaction in the presence of $Br_2$. The PM pitch heated-treatment at $420^{\circ}C$ for 9 h exhibited the softening point of $297^{\circ}C$ with 23% yield, and 55% anisotropic content. The PM pitch precursor was melt-spun through circular nozzle by pressurized $N_2$, stabilized at $310^{\circ}C$, carbonized at $700^{\circ}C$, $1000^{\circ}C$, and $1200^{\circ}C$. The enough stabilization introduced 16.4% of the oxygen approximately. The stacking height ($L_{c002}$) and interlayer spacing ($d_{002}$) of the as-spun fibers were 4.58 nm and $3.45{\AA}$ and the value became minimum and maximum at $700^{\circ}C$ respectively in the carbonization procedure. The tensile strength increased with an increase in the heat treatment temperature exhibiting highest value of 750 MPa at $1200^{\circ}C$ carbonization.

• Journal of Welding and Joining
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• v.19 no.1
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• pp.75-81
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• 2001

The metallurgical study of microconstituents in transient liquid phase bonded joints of Ni-base single crystal superalloys, CMSX-2 and CMSX-4 was investigated employing MBF-80 insert metal. TLP bonding of specimens was carried out at 1,373~1,523K for 0~19.6ks in vacuum. Three types of microconstituents ; needle-like constituent, dot-like constituent and abnormal shape constituent were formed in the bonded interlayer during TLP bonding operation. All these microconstituents were identified as boride. Microconstituents contain a large percentage of Cr in the early stage of bonding. As increasing the holding time, the amount of Cr was decreased and the amount of W, Co and Re were increased. From the analysis results of electron diffraction pattern by TEM, composition of elements in microconstituents were into MBlongrightarrowM$_{5}$B$_3$longrightarrowM$_2$B type with the increased in holding time. It can be explained by the fact that the relative amount of boron in microconstituents was decreased when the holding time was increased.d.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.594-597
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• 2003

In the present study, the piezoelectricity and polarization of multilayer ceramic actuator, being designed to stack PMN-PZ-PT ceramic layers and Ag-Pd electrode layers alternatively, were investigated under a consideration of geometric factor, the volume ratio of the ceramic to the electrode layers. The actuators were fabricated by tape casting of 0.2Pb(Mg1/3Nb2/3)O3-0.38PbZrO3-0.42PbTiO3 followed by lamination and burnout & co-firing processes. The actuators of 10 10 0.62 nm3 in size were formed in a way that 60 200 m thick ceramics were stacked alternatively with 5 m thick electrode layer. Increases in polarization and electric field-induced displacement with thickness of the ceramic layer were attributed to change of 90o/180o domain ratio, which was affected by interlayer internal stress. The piezoelectricity and actuation behaviors were found to depend upon the volume ratio (or thickness ratio) of ceramic to electrode layers.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.139-139
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• 2012

With angle resolved photoemission spectroscopy (ARPES), the surface electronic band structures of Pt3Co (111) and Pt3Ni (111) single crystals are investigated, which allow to study the bonding interaction between chemically absorbed atomic oxygen and its surfaces. The d-band electrons of subsurface TM are separated from the direct chemical bonding with atomic oxygen. That is, the TM does not contribute to direct chemical bonding with oxygen. From the density functional theory (DFT) calculations, it is identified that the main origin of improved oxygen absorption property, i.e. softening of Pt-O bonding, is due to the suppression of Pt surface-states which is generated from change of interlayer potential, i.e. charge polarization, between Pt-top and TM-subsurface. Our results point out the critical roles of subsurface TM in modifying surface electronic structures, which in turn can be utilized to tune surface chemical properties.

• Korean Journal of Materials Research
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• v.21 no.10
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• pp.550-555
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• 2011

A high-quality CIGS film with a selenization process needs to be developed for low-cost and large-scale production. In this study, we used $Cu_2In_3$, CuGa and $Cu_2Se$ sputter targets for the deposition of a precursor. The precursor deposited by sputtering was selenized in Se vapor. The precursor layer deposited by the co-sputtering of $Cu_2In_3$, CuGa and $Cu_2Se$ showed a uniform distribution of Cu, In, Ga, and Se throughout the layer with Cu, In, CuIn, CuGa and $Cu_2Se$ phases. After selenization at $550^{\circ}C$ for 30 min, the CIGS film showed a double-layer microstructure with a large-grained top layer and a small-grained bottom layer. In the AES depth profile, In was found to have accumulated near the surface while Cu had accumulated in the middle of the CIGS film. By adding a Cu-In-Ga interlayer between the co-sputtered precursor layer and the Mo film and adding a thin $Cu_2Se$ layer onto the co-sputtered precursor layer, large CIGS grains throughout the film were produced. However, the Cu accumulated in the middle of CIGS film in this case as well. By supplying In, Ga and Se to the CIGS film, a uniform distribution of Cu, In, Ga and Se was achieved in the middle of the CIGS film.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.362-365
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• 2005

Currently Chemical Mechanical Planarization (CMP) has become an essential step in the overall semiconductor wafer fabrication technology. Especially the CMP pad conditioner, one of the diamond tools, is required to have strong diamond retention. Strong cohesion between diamond grits and metal matrix prevents macro scratch on the wafer. If diamond retention is weak, the diamond will be pulled out of metal matrix. The pulled diamond grits are causative of macro scratch on wafer during CMP process. Firstly, some results will be reported of cohesion between diamond grits and metal matrix on the diamond tools prepared by three different manufacturing methods. A measuring instrument with sharp cemented carbide connected with a push-pull gauge was manufactured to measure the cohesion between diamond grits and metal matrix. The retention force of brazed diamond tool was stronger than the others. The retention force was also increased in proportion to the contact area of diamond grits and metal matrix. The brazed diamond tool has a strong chemical combination of the interlayer composed of chrome in metal matrix and carbon which enhance the interfacial cohesion strength between diamond grits and metal matrix. Secondly, we measured real-time data of the coefficient of friction and the pad wear rate by using CMP tester (CETR, CP-4). CMP pad conditioner samples were manufactured by brazed, electro-plated and sintered methods. The coefficient of friction and the pad wear rate were shown differently according to the arranged diamond patterns. Consequently, the coefficient of friction is increased according as the space between diamonds is increased or the concentration of diamonds is decreased. The pad wear rate is increased according as the degree of diamond protrusion is increased.

• Journal of the Korean Magnetics Society
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• v.10 no.2
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• pp.62-66
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• 2000

Annealing cycle number and nonmagnetic layer thickness dependences of interlayer coupling field ( $H_{inf}$ ) and coercivity ( $H_{cf}$ ) of free magnetic layer on NiMn alloy-spin valve films (SVF) were investigated. The SVF is Glass (7059)/N $i_{81}$F $e_{l9}$(70 $\AA$)/Co(10 $\AA$)/Cu(t $\AA$)/Co(15 $\AA$)N $i_{81}$$Fe_{19}$(35 $\AA$)/N $i_{25}$M $n_{75}$(250 $\AA$)Ta(50 $\AA$) films, it were fabricated using the dc sputtering method at different pinning layer thickness and nonmagnetic spacer thickness (Cu thickness; 30 $\AA$, 35 $\AA$, 40 $\AA$) of NiMn alloy with 25 at.%. Ni In case that Cu thickness of SVF is 35 $\AA$ and peak exchange coupling field ( $H_{ex}$) was 620 Oe, while coercivity $H_{c}$ = 280 Oe and MR ratio showed 2.5%. As for $H_{inf}$ and $H_{cf}$ , every SVF increased up to the stabilized values with the increase of annealing cycle number 15, which were $H_{inf}$ of 120 Oe and $H_{cf}$ of 75 Oe. The increase of $H_{cf}$ with the annealing cycle number seems to be caused by the effective reduction of Cu layer thickness due to the increase of interfacial mixing of Cu layer and Co layer. In addition, the $H_{inf}$ and $H_{cf}$ dependences of free NiFe layer by the interfacial mixing effect were appeared the different aspects when Cu layer becomes more thinner and thicker than Cu layer thickness of 35 $\AA$, respectively.ively....

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.89-92
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• 2001

Drop weight impact tests were performed to investigate the impact behavior of carbon fiber/epoxy composite laminates reinforced by short fibers and other interleaving materials. Characterization techniques, such as cross-sectional fractography and scanning acoustic microscopy, were employed quantitatively to assess the internal damage of some composite laminates. Scanning electron microscopy was used to observe impact damage and fracture modes on specimen fracture surfaces. The results show that composite laminates experience various types of fracture; delamination, intra-ply cracking, matrix cracking and fiber breakage depending on the interlayer materials. Among the composite laminates tested in this study, the composites reinforced by Zylon fibers showed very good impact damage resistance with medium level of damage, while the composites interleaved by poly(ethylene-co-acrylic acid) (PEEA) film is expected to deteriorate the bulk strength due to the reduction of fiber volume fraction, even though the damaged area is significantly reduced.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.8-11
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• 1997

This study makes SrTiO$_{3}$ with nonpolarity among ferroelectrics by RF sputtering as dielectric layer, produces thin film of Si/SrTiO$_{3}$ and Si/Ti/SrTiO$_{3}$ of MOS structure using Ti as buffer layer, measures and examines the electrical features with optical refractive index, absorption rate, permittivity, photon energy and as a result, ferroelectrics oscillation occurrs by the interaction within a film by light temperature and the absorption of thin film with Ti as buffer layer is increased. It is found that the pea\ulcorner of permittivity value of Ti/SrTiO$_{3}$ thin film has low values and is appeared late and as dipole which is found in dielectric is shown, the experiment satisfies the theory In the nature of permittivity by photon energy, imaginary value is higher and current variation slope of thin film of thickness SrTiO$_{3}$ has lower values in reverse bias.