• Journal of the Korean Electrochemical Society
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• v.3 no.4
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• pp.235-240
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• 2000

Screen-printing and doctor blade method were investigated and proposed as an electrode coating process for high power capacitor. CV measured from the amorphous $MnO_2$ electrode prepared by screen-printing shows closer to ideal capacitor characteristics. Specific capacitances calculated from CVs with potential scan rate of 50mV/s were 5.8, 81.8, and 172.0 F/g for electrode thickness of $140{\mu}m,\;24{\mu}m,\; 3{\mu}m$, respectively. Assumed that utilization of active $MnO_2$ in electrode of screen-printing is $100\%$, those were $3.4\%$ in one of paste method and $47.6\%$ in one of doctor blade method. The screen-printing can be good technique to coat thin film on current collector for high power application.

• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.269-279
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• 1996

The porous armophous catalysts, composed of $SiO_2-TiO_2-V_2O_5$ were prepared through SOL-GEL process by differing the preparation parameters. Selected the optimum SOL-GEL catalyst which has the best NO removal activity through the screening test, and repeated coating it on the cordierite monolith which is the freely through and inert. And examined the NOx, SOx simultaneous removal effect under S. C. R. condition. In addition to its characterization performances by the DTA, TGA, BET, $NH_3$ and NO TPD, ESCA, XRD etc.

• Journal of the Korean Ceramic Society
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• v.33 no.11
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• pp.1195-1202
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• 1996

To prepare the dielectric thin films of (Pb1-xSrx)TiO3 (x=0.1, 0.2, 0.3, 0.35, 0.5) by the sol-gel process titanium (IV) isopropoxide (Ti[OCH(CH3)2]4) and Pb Sr, acetate were used therefore the thin films were fabricated by dip-coating method. Stability of the sol decreased with addition of Sr content thin films could be fabricated up to 35mol% Over this range precipitation of sol occured thin films couldn't be obtained. Transmittance of thin films at visible range decreased with the increase of heat-treatment temperature but exhibited transmit-tance above 60% in all case. Moreover transmittance of thin films at visible range slightly increased with of addition of Sr,. When thin film containing 30 mol% srontium was heated at 600℃ the best perovskite phase was obtained. The dielectric constant (ε) was 280 and dielectric loss factor (tan δ) was 0.021 and curie tempera-ture (Tc) decreased with the increase of addition of Sr.

• Journal of the Korean Magnetics Society
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• v.2 no.1
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• pp.15-21
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• 1992

Acicular ${\gamma}-Fe_{2}O_{3}$ particles were heated at $90^{\circ}C$ in alkaline solution containing mixed solution of dyadic metal with $Co^{+2}/Fe^{+2}$ ratio of 0.5. When cobalt content was increased, the coercivity of resultant product increased linearly, and surface area decreased. The cobalt ferrite was grown epitaxially on the surface ${\gamma}-Fe_{2}O_{3}$ crystal, and the increase of coercivity was attributed to the crystalline magnetic anisotropy of the cobalt ferrite which is conform to coating layer. We can expect superior magnetic properties above normal ratio of 2. The progress of reaction has an effect on coercivity of cobalt ferrite epitaxial iron oxide. The stability of temperature and the change om standin& of $Co-{\gamma}-Fe_{2}O_{3}$ was largely influenced by the composition of coating layer.

• Journal of Surface Science and Engineering
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• v.44 no.3
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• pp.82-88
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• 2011

A uniform chromium-free conversion coating treated with an alkaline phosphate- permanganate solution was formed on the AZ 31 magnesium alloy. The effect of acid pickling on the morphology and on the corrosion resistance of the alkaline phosphate-permanganate conversion coating was investigated. The chemical composition and phase structure of conversion coating layer were determined via optical microscopy, SEM, EDS, XPS and XRD. Results show that the conversion coatings are relatively uniform and continuous, with thickness 1.8 to $2.4\;{\mu}m$. The alkaline phosphate-permanganate conversion coating was mainly composed of elements Mg, O, P, Al and Mn. The conversion-coated layers were stable compounds of magnesium oxide and spinel ($MgAl_2O_4$). These compounds were excellent inhibitors to corrosion. The electrochemical corrosion behaviors of coatings in 3.5 wt.% NaCl solutions were evaluated by electrochemical impedance spectroscopy, potentiodynamic polarization technique. EIS results showed a polarization resistance of $0.1\;k{\Omega}$ for the untreated Mg and $16\;k{\Omega}$ for the alkaline phosphate-permanganate conversion treatment sample, giving an improvement of about 160 times. The results of the electrochemical measurements demonstrated that the corrosion resistance of the AZ 31 magnesium alloy was improved by the alkaline phosphate-permanganate conversion treatment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.11a
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• pp.65-66
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• 1994

This paper describes study on the preparation of ferrite powder for bonded mallets. The specimen which has the basic composition of SrO$.$nF$_2$O$_3$ with n=5.9 is in nonstoichiomatric region. Calcination is performed under N$_2$ atmosphere 1175$^{\circ}C$, 1200$^{\circ}C$, 1225$^{\circ}C$, 1250$^{\circ}C$ and 1275$^{\circ}C$ respectively. Then, Cooling is carried out in the furnace. In order to increase coecivity and obtain uniform grain size, we add to the specimen 0.7wt%CaCO$_3$, 0.3wt % SiO$_2$, 0.5wt%Na$_2$SiO$_3$ and 0.5wr% Al$_2$O$_3$. Also, in order to increase milling effect, carbon coating on sample particles is tried. As the result, single magnetic domain partic1e with Size of 1$\mu\textrm{m}$ in obtained and magnetic properties are improved.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.2
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• pp.66-69
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• 2003

Various semiconductor nanowires such as GaN, GaP, InP, Si$_3$N$_4$, SiO$_2$/Si, and SiC were coated conformally with aluminum oxide (Al$_2$O$_3$) layers by atomic layer deposition (ALD) using trimethylaluminum (TMA) and distilled water ($H_2O$) at a temperature of 20$0^{\circ}C$. Transmission electron microscopy (TEM) revealed that A1203 cylindrical shells conformally coat the semiconductor nanowires. This study suggests that the ALD of $Al_2$O$_3$ on nanowires is a promising method for preparing cylindrical dielectric shells for coaxially gated nanowire field-effect transistors.

• Journal of Powder Materials
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• v.29 no.6
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• pp.468-476
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• 2022

Yttria-stabilized zirconia (YSZ) has a low thermal conductivity, high thermal expansion coefficient, and excellent mechanical properties; thus, it is used as a thermal barrier coating material for gas turbines. However, during long-time exposure of YSZ to temperatures of 1200℃ or higher, a phase transformation accompanied by a volume change occurs, causing the YSZ coating layer to peel off. To solve this problem, YSZ has been doped with trivalent and tetravalent oxides to obtain coating materials with low thermal conductivity and suppressed phase transformation of zirconia. In this study, YSZ is doped with trivalent oxides, Nd₂O₃, Yb₂O₃, Al₂O₃, and tetravalent oxide, TiO₂, and the thermal conductivity of the obtained materials is analyzed according to the composition; furthermore, the relative density change, microstructure change, and m-phase formation behavior are analyzed during long-time heat treatment at high temperatures.

• Journal of Powder Materials
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• v.5 no.1
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• pp.28-34
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• 1998

Plasma sprayed ceramic coatings are widely used in various industrial fields to improve their properties or to reduce the production cost. The ceramic powders for plasma spray coating have been mainly manufactured by spray drying or fused+crushed process. In this study, chromium oxide which has better mechanical properties than those of the other ceramic was selected and agglomerated chromium oxide powders for plasma spray coating were produced by spray drying process with a various processing condition. The large hollow powders and the harsh surfaced powders are formed at high slurry feed rate more than 163 g/min. and low binder concentration less than 2wt%, respectively. These powders cause the considerable decrease of flowability and apparent density. The powders produced by spray drying process have the spherical shape with the mean size of 45 ${\mu}m$, but these are shown lower apparent density and flowability than the powders produced by fused+crushed powders. The plasma spray coated layers by spray dried powders are shown a different microstructure with that by fused+crushed powders in porosity shape, but their properties such as density, hardness and bond strength are similar.

• Journal of the Korean Ceramic Society
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• v.23 no.3
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• pp.53-61
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• 1986

A gas sensor which has been made by wet process had fabricated by coating each of the mixture on alumina tube and firing at 85$0^{\circ}C$ for 3hrs. A gas concentration such $H_2$, CO, $C_3H_8$, $C_2H_2$ and $CH_4$ vs its detection voltage characteristics has been in-vestigated on $SnO_2-In_2O_3-MgO$ system doped with PdO, $La_2O_3$, $ThO_2$, NiO and $Nb_2O_5$ The optimum sensitivity composition for various gases were 90w/o $SnO_2$-9w/o $In_2O_3$-1w/o MgO for $H_2$, $C_2H_2$ CO and $C_3H_8$ and 95w/o $SnO_2$-4w/o $In_2O_3$-1w/o MgO for $CH_4$. The sample which has been made by wet process than dry process had predominated sensitivity for each gases and particle size of the sample coprecipitated with PH=9 was 0.1${\mu}{\textrm}{m}$ The $SnO_2$-In2_O_3-MgO$ system doped with 2w/o $Nb_2O_5$ and NiO was the most sensitive for $H_2$ and $C_2H_2$ gas. In $SnO_2$-In2_O_3-MgO$ system doped with $ThO_2$ the sensitivity of $H_2$ gas was decreased but CO gas was in-creased when dopant con was increased.