• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.99-99
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• 2010

Polymer nanocomposite has been attracting much attention as a new insulation material, since homogeneous dispersion of nm-sized inorganic fillers can improve various properties significantly. In this paper, various kinds of epoxy based nanocomposites were made and AC breakdown strength of Nano-TiO2 and micro-silica filler mixture of epoxy based composites were studied by sphere to sphere electrode. Moreover, nano- and micro-filler combinations were adopted as an approach toward practical application of nanocomposite insulation materials. Nano-TiO2 particle size is about 10nm and composites ratio was resin (100) : hardener (82) : accelerator (1.5). AC breakdown test was performed at room temperature (25 [$^{\circ}C$], 80 [$^{\circ}C$] and 100 [$^{\circ}C$] in the vicinity of Tg (90[$^{\circ}C$]). And thermal conductivity were measured by ASTM-D5470.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.29-29
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• 2010

Engineering plastics have excellent electrical properties, mechanical strength and various characteristic which include chemical resistance, environmental resistance, weatherability at a wide temperature range. It has good characteristic(light weight, good productivity) as compare with epoxy or porcelain insulators. However, engineering plastics not suited to outdoor insulator because it isn't hydrophobic. Therefore, to over come these critical problems, we improve the surface insulation characteristics of engineering plastic by coating micro-, nano- size inorganic fillers added to RTV-SIR(Room temperature vulcanized-silicone rubber) at this plastic surface. The effect is analyzed through salt-fog test, tracking test. In conclusion, the engineering plastic coated RTV with micro-$Al_2O_3$20[phr], nano-Al(OH)3 1 ~ 3[phr] improved much better than the others.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.2
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• pp.138-145
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• 1998

The $(Pb_{0.9}Ca_{0.1})TiO_3$[PCT] thin films have been deposited by sol-gel processing on Si-wafer and ITO glass substrates. The creak-free films have been obtained by rapid thermal annealing at $700^{\circ}C$ for 10 minute and characterized by XRD, SEM and electrical measurements. Their tetragonality c/a was 1.041 and grain size was $0.15{\sim}0.2{\mu}m$. When the electrode system of sample was Au/PCT/ITO(MFM) and film thickness was $0.8{\mu}m$, dielectric constant, dielectric loss and Curie temperature were about 149, 0.085 and $449^{\circ}C$ at 10kHz, respectively. Spontaneous polarization $P_s$, remnant polarization $P_r$ and coercive field $E_c$ were about $5.29{\mu}C/cm^2$, $4.15{\mu}C/cm^2$ and 82kV/cm calculated by hysteresis loop.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.3
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• pp.242-248
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• 2008

The structural, optical and electrical properties of ZnO films doped with 1.5 at% of 3A materials(B, Al, Ga, In) were studied by sol-gel process. The films were found to be c-axis (002) oriented hexagonal structure on glass substrate, when post heated at 500 $^{\circ}C$. The surface of the films showed a uniform and nano size microstructure and the crystalline size of doped films decreased. The lattice constants of ZnO:B/Al/Ga increased than that of ZnO, while ZnO:In decreased. All the films were highly transparent(above 90 %) in the visible region. The energy gaps of ZnO:B/Al/Ga were increased a little, but that of ZnO:In was not changed. The resistivities of ZnO:Al/Ga/In were less than 0.1 $\Omega$cm. All the films showed a semiconductor properties in the light or temperature, however ZnO:In was less sensitive to it. A figure of merit of ZnO:In had the highest value of 0.025 $\Omega^{-1}$ in all samples.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.1
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• pp.56-60
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• 2014

The polyimide composite membranes were prepared with polyimide composite solutions including graphenes by using the phase inversion method. The morphologies of these membranes were significantly changed according to the graphene loadings in composite solutions and the solvent systems of the composite solutions. The finger-like macro-voids were formed in the hollow fiber membranes which were prepared in the NMP solvent system with a small amount of ethanol. As increasing the content of the viscous alcohols such as glycerol or 1,3-propanediol in the composite solution, however, the morphologies of the hollow fiber membranes were changed to sponge-like types. In case of flat membranes, the increase of graphene content in polyimide composites causes that their membranes change from the finger-like macro-porous to sponge-like morphologies.

• Korean Journal of Materials Research
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• v.23 no.6
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• pp.344-352
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• 2013

First, a purified sludge was calcined at various temperatures viz. 800, 900, 1000, 1100 and $1200^{\circ}C$ per hour. Subsequently 100 wt% of ware from Geryong mountain was mixed with 5~25 wt% of a purified sludge. Then the ware was treated at $1250^{\circ}C$ in an electric kiln to test a bending strength. The physicochemical property of the prepared ware was characterized by XRD, Raman and SEM analysis. Among the different percentage, 25 wt% of a ware in a purified sludge calcined at $1000^{\circ}C$ showed 689 $kg/cm^2$ strength. Also the purified sludge calcined at $1000^{\circ}C$ was adequate physical properties than the other composites. Further to enhance the physical strength, 3 wt% $TiO_2$ (a mineralizer) was added into the ware and the strength was increased up to 731 $kg/cm^2$. The composites exhibit absorption and porosity rates of 0.17% and 0.39% respectively.

• Korean Journal of Materials Research
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• v.27 no.2
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• pp.113-118
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• 2017

Natural and expandable graphites were chemically treated in acidic aqueous solutions such as acetic acid or mixtures of acetic acid and nitric acid. Structures and thermal conductivities of the as-treated graphites were characterized in detail. Both graphites were significantly oxidized in the mixed acidic solution of $H_2SO_4$ and $HNO_3$, which condition was generally used for the oxidation of carbon nanotubes. This considerable oxidation of graphites caused a depression of their thermal conductivity. The structural characteristics, obtained by XRD and XPS, show that the graphites treated in the relatively weak acidic conditions (acetic acid or mixture of acetic acid and nitric acid) were quite similar to the untreated graphites. However, the thermal conductivities of both acidic-treated graphites were remarkably increased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.185-190
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• 2003

In this paper, it was demonstrated that the organic thin film transistors were fabricated by the organic gate insulators with vapor deposition polymerization (VDP) processing. In order to form polyimide as a gate insulator, vapor deposition polymerization process was also introduced instead of spin-coating process, where polyimide film was co-deposited by high-vacuum thermal evaporation from 4,4'-oxydiphthalic anhydride (ODPA) and 4,4'-oxydianiline (ODA) and 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and ODA, and cured at $150^{\circ}C$ for 1hr. Electrical output characteristics in our organic thin film transistors using the staggered-inverted top-contact structure obtained to the saturated slop in the saturation region and the subthreshold non-linearity in the triode region. Field effect mobility, threshold voltage, and on-off current ratio in $0.45\;{\mu}m$ thick gate dielectric layer were about $0.17\;cm^2/Vs$, -7 V, and $10^6\;A/A$, respectively. Details on the explanation of compared to organic thin-film transistors (OTFTS) electrical characteristics of ODPA-ODA and 6FDA-ODA as gate insulators by fabricated thermal co-deposition method.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.3
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• pp.240-245
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• 2006

Recently, as the road capacity reaches the limit and environmental problems becomes serious, there is gradually increased a need for railroad vehicles that are environment-friendly and have time regularity, reliability, and safety. Accordingly, in addition to conventional railroad vehicles, lots of vehicles are being newly developed. In this study, temperature sensors were adhered to transformer that is used in KHST(Korean High-Speed Train) to verify variation of temperature characteristics about transformer synthetically and efficiently. In the case that temperature of transformer exceeds reference temperature for running of KHST, overheating of transformer may cause a fatal accident of vehicle. Therefore, after on-line measuring system was constructed in vehicle, oil temperature and tank temperature were measured on real-time. Characteristics and main specifications of transformer in KHST were described in this paper. Also, measuring system for temperature measurement of transformer was explained in brief. Temperature data of transformer was acquired using measuring system, KRRI(Korea Railroad Research Institute) analyzed characteristic in contrast with comparing with temperature of transformer about month, running speed and running time.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.5
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• pp.423-429
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• 2001

PbS, CuS and (Pb,Cu)S thin films were chemically deposited on glass from alkaline baths containing lead acetate, copper chloride, thiourea and triethanolamine. The deposition, optical, resistivity and thermal electric properties of these films were studied. PbS thin films showed a hexagonal structure and CuS thin films showed amorphous. The crystalline of (Pb,Cu)S thin films was obtained by heat treatment at 200$\^{C}$ and the deposition ratio of Pb to Cu showed 7:3. The energy gap of PbS, CuS and (Pb,Cu)S thin films were 1.7, 2.1 and 2.4 eV, respectively. Sheet resistance of PbS thin films was less affected on thermal annealing, but hose of (Pb,Cu)S and CuS thin films were more reduced about 3 orders of magnitude. All of those thin films indicated p type semiconductor in temperature ranging 30$\^{C}$ to 150$\^{C}$.