• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.44.2-44.2
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• 2009

BCP powder was synthesized using microwave hydrothermal process with mixed calcium hydroxide and phosphoric acid. After using replica method, porous BCP scaffold was fabricated. PU (Poly Urethane) was used as the fugitive skeleton to fabricate the porous scaffold. BCP powder was mixed in PVB (Polyvinyl butyral) and ethanol solution and then applied to the PU foam by dip coating. After several times of coating and the subsequent oven drying the coated PU foam was burnt out at $750^{\circ}C$ at air to remove the PU. The resulting networked porous composites were sintered at $1250^{\circ}C$, $1300^{\circ}C$ and $1350^{\circ}C$ in microwave furnace for 30 minutes. Material properties of the porous bodies like compressive strength and porosity were investigated. Detailed microstructure of the BCP porous body was characterized by SEM and XRD and TEM techniques. In our experiments, the relationship between mechanical property and viscosity of powder, sintering temperature was investigated.

• Korean Journal of Materials Research
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• v.18 no.4
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• pp.211-217
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• 2008

A $ZrO_2$ coating solution containing $ZrO_2$ photo-catalysis, which is transparent in visible light, was prepared by the hydrolysis of alkoxide, and thin films on the $SiO_2$ glass substrate were formed in a dipcoating method. These thin films were heat-treated at temperatures ranging from $250^{\circ}C-800^{\circ}C$ and their characteristics were subjected to thermal analysis, XRD, spectrometry, SEM, EDS, contact angle measurement, and AFM. Tetragonal $ZrO_2$ phase was found in the thin film heat treated at $450^{\circ}C$, and anatase $TiO_2$ phase was detected in the thin film heat-treated at $600^{\circ}C$ and above. The thickness of the films was approximately 300 nm, and the roughness was 0.66 nm. Thus, the film properties are excellent. The films are super hydrophilic with a contact angle of $4.0^{\circ}$; moreover, they have self-cleaning effect due to the photo catalytic property of anatase $TiO_2$.

• Journal of the Korean Ceramic Society
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• v.27 no.5
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• pp.583-588
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• 1990

Glass films in the binary system B2O3-SiO2 and Al2O3-SiO2 were prepared on soda-lime-silica slide glass by the dip-coating technique from TEOS and boric acid or aluminum nitrate. Thickness of the films varying with viscosity and withdrawal speed were measured and effect of composition and firing temperature on the properties such as transmittance and refractive index were investigated. nM2O3.(100-n)SiO2(M=B or Al) films containing up to 20mol% B2O3 and 40mol% Al2O3 were transparent. Maximum transmittance at visible range were obtained for the sample containing 15mol% Ba2O3 and 32.5mol% Al2O3 and heat-treated at 50$0^{\circ}C$, respectively. Refractive index of the film containing 15mol% B2O3 was mininum in the B2O3-SiO2 binary system and minimal refractive index was appeared at the film containing 32.5mol% Al2O3. In IP spectra, addition of B2O3 were increased absorption peak intensity of B-O and Si-O-B bond and addition of Al2O3 were decreased absorption peak intensity of Si-O bond, respectively.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1998-2000
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• 2005

The effects of the addition of nanocrystalline Y2O3 powder on the microstructure and superconducting properties have been investigated in YBCO films prepared by TFA-MOD process. Precursor solution doped with extra $Y_2O_3$ Powder was prepared by adding $Y_2O_3$ powder into a stoichiometic precursor solution with a cation ratio of Y:Ba:Cu=1:2:3. Coating solutions with and without $Y_2O_3$ doping were coated on $LaAlO_3(100)$ single crystal by a dip coating method, cacination and conversion heat treatments were performed at the controlled atmosphere containing water vapor Current carry capacity(Jc) of YBCO film was enhanced about 50% by $Y_2O_3$ doping. It is thought that the enhancement of Jc is due to the better connectivity of YBCO grains and/or the flux pinning by the presence of nanocrystalline $Y_2O_3$ Particles embedded in YBCO grains.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2001-2003
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• 2005

Various organic acid were used in order to prepare new metalorganic deposition solution for high quality $REBa_2Cu_3O_{7-{\delta}}$ (RE=Y, Eu, Gd) films. Prepared fluorine free MO precursor solution was coated on single crystal (001) $LaAlO_3$ (LAO) by dip coating method. Processing parameters such as oxygen partial pressure, water vapor, ramping rate and pyrolysis temperature etc havebeen controlled in order to make high $J_c$ films with a good epitaxial relationship with substrate. 0.5 micron-thick film was obtained by single coating and no crack appeared after calcination. Oxygen partial pressure was varied in the range of $100{\sim}1,000 ppm$ and conversion heat treatment was carried out at the temperature of $725{\sim}765^{\circ}C$. A critical transition temperature $(T_{c0})$ of 90K and a critical transport current density $(J_c)$ of $>0.5MA/cm^2$ (77K and self-field) were demonstrated for the YBCO film on (001) oriented LAO substrates with a thickness of 0.5 micron. $I_c$ was determined by utilizing a transport measurement. SEM and XRD investigations confirmed that films were grown epitaxially onto the LAO single crystal substrate. It is thought that fluorine free new MOD solutionis promising for high quality REBCO films.

• Textile Coloration and Finishing
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• v.15 no.3
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• pp.161-167
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• 2003

The preparations of deodorizing fibers using $TiO_2$ have been investigated. The fibers were coated with $TiO_2$ for the purpose of deodorizing by dipping fibers into the $TiO_2$ sol solutions and calcined at $450^\circ{C}$, $500^\circ{C}$ and $750^\circ{C}$ for 1 h after coating. The surface structure of the coated fibers was studied with XRD on the different preparation conditions of calcination temperatures. The deodorizing function of the prepared fibers was studied by the determination of the decomposing capability for $NH_3,\;CH_3SH\;and\;CH_3CHO$. The deodorant activity(D.A.) of these deodoriBing fibers was measured by chromogenic gas detector tubes. The deodorizing effect of the prepared fibers were shown to be similar for the three model compounds; 5wt% $TiO_2$ sol solution calcined at $450^\circ{C}$ < 5 wt% $TiO_2$ sol solution calcined at $500^\circ{C}$< 5 wt% TiO$_2$ sol solution calcined at $750^\circ{C}$.

• Korean Journal of Metals and Materials
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• v.50 no.8
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• pp.575-582
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• 2012

Medium carbon steel was aluminized by hot dipping into molten Al or Al-1 at% Si baths. After hot-dipping in these baths, a thin Al-rich topcoat and a thick alloy layer rich in $Al_5Fe_2$ formed on the surface. A small amount of FeAl and $Al_3Fe$ was incorporated in the alloy layer. Silicon from the Al-1 at% Si bath was uniformly distributed throughout the entire coating. The hot dipping increased the microhardness of the steel by about 8 times. Heating at $700-1000^{\circ}C$, however, decreased the microhardness through interdiffusion between the coating and the substrate. The oxidation at $700-1000^{\circ}C$ in air formed a thin protective ${\alpha}-Al_2O_3$ layer, which provided good oxidation resistance. Silicon was oxidized to amorphous silica, exhibiting a glassy oxide surface.

• Korean Journal of Metals and Materials
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• v.46 no.2
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• pp.58-64
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• 2008

Surface-void defects observed on the galvannealed(GA) steel sheets in Interstitial-free high-strengthened steels containing Si and Mn have been investigated using the combination of the FIB(Focused Ion Beam) and FE-TEM(Field Emission-Transmission Electron Microscope) techniques. The scanning ion micrographs of cross-section microstructure of defects showed that these defects were identified as craters which were formed on the projecting part of the substrate surface. Also, those craters were formed on the Si or Mn-Si oxides film through the whole interface between galvannealed coating and steel substrate. Interface enrichments and oxidations of the active alloying elements such as Si and Mn during reduction annealing process for galvanizing were found to interrupt Zn and Fe interdiffusion during galvannealing process. During galvannealing, Zn and Fe interdiffusion is preferentially started on the clean substrate surface which have no oxide layer on. And then, during galvannealing, crater is developed with consumption of molten zinc on the oxide layer.

• Membrane Journal
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• v.25 no.5
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• pp.422-430
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• 2015

The present study announces that the pH value of seed coating solution makes a significant effect on the microstructure of silicalite-1 zeolite layer formed on ${\alpha}$-alumina support. Seed with an average diameter of 75 nm was dispersed in ethanol to prepare three kinds of seed coating solutions with different pH values, and dip-coated on the support. The pH value was controlled to be 2.2, 7.0, and 9.3, respectively. In the secondary growth process, pH 7 seed solution resulted an uniform, 3 to $4{\mu}m$ thick, completely covered, and 100 nm grained silicalite-1 zeolite separation layer. The uniformity and completeness were explained by a uniform, closely packed, multi-layered, and completely covered seed coating in the pH 7 condition. In the condition, ${\alpha}$-alumina support and seed are oppositely charged: support is positively charged (8.4 mV) and seed, negatively (-1.7 mV). The opposite charging induced a strong electrostatic attraction between seed and support, which made the good seed coating state. On the other hand, pH 2.2 and pH 9.3 seed solutions resulted non-uniform, partially covered, and around $1{\mu}m$ grained zeolite separation layer, since seed and support are the same sign charged in the conditions. The same sign charging induced a strong electrostatic repulsion between seed and support which caused a low coverage of seed. It could be concluded that the pH value of seed coating solution is a key parameter to determine the microstructure of silicalite-1 zeolite separation layer.

• Korean Journal of Optics and Photonics
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• v.13 no.3
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• pp.197-203
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• 2002

The TiO$_2$ coating solutions were synthesized with different concentrations (T1-0.7N, T2-2.0N) of hydrochloric acid used as catalyst. and TiO$_2$ thin films were prepared by sol-gel dip coating. Their structural and optical properties were examined as a function of calcination temperature. XRD results showed that T1 thin films calcined at 400~80$0^{\circ}C$ had the anatase phase, while those calcined at 100$0^{\circ}C$ had the rutile phase. T2 thin films calcined at 40$0^{\circ}C$ and $600^{\circ}C$ had the anatase phase, with the rutile phase for calcination at 80$0^{\circ}C$. Crystallinity of T2 thin films was superior to that of T1 thin films. The crystallite size of TiO$_2$ thin films increased with increasing calcination temperature, and the crystallite size of anatase phase in T2 thin films was larger than that in T1 thin films, but the crystallite size of rutile phase in T2 thin films was smaller. The surface morphology of the films showed that the films were formed more densely in the rutile phase than in the anatase phase, this phenomenon appeared conspicuously in T2 thin films. The transmittance of the samples with thin films on quartz glass calcined at 100$0^{\circ}C$ was significantly reduced at wavelength range about 300-700 nm due to the increased absorption originating from the change of crystallite phase and composition of the films and the scattering effect originating from increasing crystallite size. The refractive index of TiO$_2$ thin films increased, and hence the film thickness as well as the porosity of TiO$_2$ thin films decreased with increasing calcination temperature. Furthermore, the refractive index of T2 thin films was higher than T1 thin films, and porosity of T2 films was lower.