• Transactions on Electrical and Electronic Materials
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• v.7 no.3
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• pp.129-133
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• 2006

Ferroelectric PZT heterolayered thick films were fabricated by the alkoxide-based sol-gel method. PZT(20/80) and PZT(80/20) paste were made and alternately screen-printed on the alumina substrates. The coating and drying procedure was repeated 4 times to form the heterolayered thick films. The thickness of the PZT heterolayered thick films was approximately $60{\mu}m$. All PZT thick films showed the typical XRD patterns of a polycrystalline rhombohedral structure. And in the PZT thick films sintered at $1100^{\circ}C$, the pyrochlore phase was observed due to the evaporation of PbO. The relative dielectric constant and the dielectric loss of the PZT thick films sintered at $1050^{\circ}C$ were 445.2 and 1.90 % at 1 kHz, respectively. The remanent polarization and coercive field of the PZT thick films sintered at $1050^{\circ}C$ were $14.15{\mu}C/cm^2$ and 19.13 kV/cm, respectively.

• Transactions on Electrical and Electronic Materials
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• v.8 no.4
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• pp.149-152
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• 2007

[ $(Ba_{0.6}Sr_{0.3}Ca_{0.1})TiO_3$ ](BSCT) thick films doped with 0.1 mol% $MnCO_3\;and\;Yb_2O_3(0.1{\sim}0.7mol%)$ were fabricated by the screen printing method on the alumina substrates. And the structural and electrical properties as a function of $Yb_2O_3$ amount were investigated. The exothermic peak was observed at around $680^{\circ}C$ due to the formation of the poly crystalline perovskite phase. The lattice constants of the BSCT thick film doped with 0.7 mol% is 0.3994 nm. The specimen doped with 0.7 mol% $Yb_2O_3$ showed dense and uniform grains with diameters of about $4.2{\mu}m$. The average thickness of all BSCT thick films was approximately $70{\mu}m$. Relative dielectric constant and dielectric loss of the specimen doped with 0.7 mol% $Yb_2O_3$ were 2823 and 3.4%, respectively. The Curie temperature of the BSCT thick films doped with 0.1 mol% $Yb_2O_3$ was $46^{\circ}C$.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.6
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• pp.119-126
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• 2014

Micro-holes of conductive ceramic are required in micro structures. Micro-electrical discharge machining (Micro-EDM) is an effective machining method since EDM is as process for shaping hard metals and complex-shaped holes by spark erosion in all kinds of electro-conductive materials. However, as the depth of micro hole increases, the machining condition becomes more unstable due to inefficient removal of debris between the electrode and the workpiece. In this paper, micro-EDM was performed to evaluate machining characteristic such as electrode wear, machining time, taper angle, radial clearance with varying voltage and ultrasonic vibration on 10 vol.% Carbon-nanotube reinforced conductive $Al_2O_3$ composite fabricated by spark plasma sintering in previous research.

• Elastomers and Composites
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• v.44 no.3
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• pp.329-335
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• 2009

Four series of novel liquid crystalline polyurethanes were synthesized by the polyaddition reaction of diisocyanates such as 2,6-tolylene diisocyanate (2,6-TDI), 2,5-tolylene diisocyanate (2,5-TDI), 2,4-tolylene diisocyanate (2,4-TDI), and 1,4-phenylene diisocyanate (1,4-PDI) with 4,4'-bis(5-hydroxypentoxy)biphenyl (BP5). 4,4'-bis(5-hydroxypentoxy)biphenyl exhibited a smectic type mesophase. Mesophase was found for all synthesized liquid crystalline polyurethanes except 1,4-PDI/BP5. The structures and the thermal properties of polyurethanes were studied by using FT-IR and ^1H$ NMR spectroscopy, DSC measurements and a polarizing microscope equipped with a heating stage.

• Journal of the Semiconductor & Display Technology
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• v.10 no.1
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• pp.95-99
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• 2011

$(1-x)BaTiO_3+(x)Cd_5(PO_4)_3Cl$ ceramics were prepared by the conventional ceramic technique, i.e., solid state reaction at high temperature. The concentration of $Cd_5(PO_4)_3C$ was varied from 0.01 to 0.15 mole fraction. In order to study the phase transitions of our ceramics, the Raman scattering spectra were measured as functions of concentration x and temperature. It was found that the soluble limit of $Cd_5(PO_4)_3Cl$ in $BaTiO_3$ was the x=0.05 composition and $BaTiO_3$ phase disappeared above x=0.10. A new phase identified as $Ba_4Ti_3P_2O_{15}$ was detected in all samples of our compositions. The Curie temperature shifts up to $130^{\circ}C$ as the concentration x increases from zero to 0.05 and shift down to $95^{\circ}C$ as further increases to 0.08. For the increase of the Curie temperature, it is suggested that it can result from the inhibition of displacement of $Ti^{4+}$ in the distorted octahedron due to well dispersed $Ba_4Ti_3P_2O_{15}$ and $Cd_5(PO_4)_3Cl$ phase.

• Journal of Digital Convergence
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• v.11 no.9
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• pp.319-324
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• 2013

The old man has different characteristics than those which have ages. To experience a variety of different environments and has tendencies because. Therefore, all the old uniform to the progress of art therapy is not possible and when you feel the need for self-treatment is effective participation hayeoyaman looks. Art therapy through the medium of art to express the inner feelings that are kept on the image of the elderly because of the feelings that naturally help revealing, emotion plays a role in mitigating the crisis. Art therapy in the treatment of non-verbal means of means of self-defense, so receives less control is reduced. In addition, the opportunity to use art media sensation itself reduced stimulation of the elderly a sense of the way so you are valued as a very useful educational program.

• The Journal of Korean Academy of Prosthodontics
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• v.35 no.3
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• pp.544-556
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• 1997

All ceramic restorations except In-Ceram Alumina system gave a good esthetics and an exellent marginal fidelity. The flexural strength of them had about 150MPa, so the indication is only single crown. By using In-ceram Alumina System(450Mpa), it is thought to be possible to construct bridge for its high flexural strength. But the prognosis is unclear, The purposes of this study are to clear short term prognosis of In-Ceram bridge restorations, to elucidate its clinical significance. Among 22 In-Ceram Bridge restored in our department, 11 In-Ceram bridges with follow up were used. The period of placement is from 1 to 18 months. The results were as follows : 1. Among follow up 11 bridges, 2 bridges were fractured. One is 4 unit in maxillary lateral incisors, the other is 3 unit bridge in maxillary canine and premolar. Including 11 bridge without follow up, failure rate is very low(2/22). 2. The fracture sites are connector areas between abutment and pontic. To maintain In-Ceram bridge for long term period, it is needed to remove the nonphysiologic occlusal force and to have sufficient thickness of alumina core. For estabilishing clinical use of In-Ceram bridges, it is thought to need clinical research during long term period.

• Journal of the Korean Society of Safety
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• v.28 no.1
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• pp.18-23
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• 2013

The purpose of this study were to develop and validate a prototype slipmeter used on-site floor. The developed slipmeter was dreg sled type. It measured static coefficient of friction(SCOF). The developed slipmeter was evaluated with ASTM 2508-11 which use four different standard surfaces(polished granite, glazed porcelain, vinyl composite tile, and ceramic tile). The SCOF was then measured with developed slipmeter under the three different contaminants and seven different floors. The test results of slipmeter were also compared with those of BOT-3000, floor surface roughness, and human perception. The test results revealed that developed slipmeter successfully ranked all four standard surfaces and differentiated among standard surfaces with varying degrees of slipperiness. The developed slipmeter couldn't properly measure slipperiness under the two kind of floors(polished tile, ground steel plate) and one kind of contaminant(glycerol). The test results of developed slipmeter had stronger correlation with those of BOT-3000 and floor roughness under the water and detergent solution than under the glycerol. The test results of developed slipmeter also showed stronger correlation with those of BOT-3000 and surface roughness than those of human perception. The newly developed slipmeter had been found to give consistent results under the test conditions except for two kind of floors(polished tile, ground steel plate) and one kind of contaminant(glycerol).

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.5
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• pp.242-242
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• 2004

The composites were fabricated 61 vol.%α-α-SiC and 39vol.% WC powders with the liquid forming additives of 12wt% Al₂O₃＋Y₂O₃ by pressureless annealing at 1700, 1800, 1900℃ for 4 hours. The result of phase analysis of composites by XRD revealed α-SiC(2H), WC, and YAG($Al_5Y_3O_{12}$) crystal phase. The relative density, the flexural strength, fracture toughness and Young′s modulus showed respectively the highest value of 99.4%, 375.76㎫, 5.79㎫ㆍ$m^{\frac{1}{2}}$, and 106.43㎬ for composite by pressureless annealing temperature 1900℃ at room temperature. The electrical resistivity showed the lowest value of 1.47×$10^{-3}$/Ω·㎝ for composite by pressureless annealing temperature 1900℃ at 25℃. The electrical resistivity of the α-SiC-WC composites was all positive temperature cofficient resistance (PTCR) in the temperature ranges from 25℃ to 500℃.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.5
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• pp.241-247
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• 2004

The composites were fabricated 61 vol.%$\alpha$-$\alpha$-SiC and 39vol.% WC powders with the liquid forming additives of 12wt% $Al_2$O$_3$＋Y$_2$O$_3$ by pressureless annealing at 1700, 1800, 190$0^{\circ}C$ for 4 hours. The result of phase analysis of composites by XRD revealed $\alpha$-SiC(2H), WC, and YAG(Al$_{5}$ Y$_3$O$_{12}$ ) crystal phase. The relative density, the flexural strength, fracture toughness and Young's modulus showed respectively the highest value of 99.4%, 375.76㎫, 5.79㎫ㆍm$\frac{1}{2}$, and 106.43㎬ for composite by pressureless annealing temperature 190$0^{\circ}C$ at room temperature. The electrical resistivity showed the lowest value of 1.47${\times}$10$^{-3}$ $\Omega$$.$cm for composite by pressureless annealing temperature 190$0^{\circ}C$ at $25^{\circ}C$. The electrical resistivity of the $\alpha$-SiC-WC composites was all positive temperature cofficient resistance (PTCR) in the temperature ranges from $25^{\circ}C$ to 50$0^{\circ}C$.