• Journal of the Korean Ceramic Society
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• v.45 no.10
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• pp.584-588
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• 2008

Porous hydroxyapatite(HA) and HA-coated porous $Al_2O_3$ possessing pore characteristics required for bone substitutes were prepared by a slurry foaming method combined with gelcasting. The HA coating was deposited by heating porous $Al_2O_3$ substrates in an aqueous solution containing $Ca^{2+}$ and ${PO_4}^{3-}$ ions at $65{\sim}95^{\circ}C$ under ambient pressure. The pore characteristic, microstructure, and compressive strength were investigated and compared for the two kinds of samples. The porosity of the samples was about 81% and 80% for HA and $Al_2O_3$, respectively with a highly interconnected network of spherical pores with size ranging from 50 to $250{\mu}m$. The porous $Al_2O_3$ sample showed much higher compressive strength(25 MPa) than the porous HA sample(10 MPa). Fairly dense and uniform HA coating(about $2{\mu}m$ thick) was deposited on the porous $Al_2O_3$ sample. Since the compressive strength of cancellous bone is $2{\sim}12$ MPa, both the porous HA and HA-coated porous $Al_2O_3$ samples could be successfully utilized as scaffolds for bone repair. Especially the latter is expected suitable for load bearing bone substitutes due to its excellent strength.

• Progress in Superconductivity
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• v.6 no.2
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• pp.142-145
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• 2005

YBCO coated conductors have been fabricated with a newly developed oxide-precursor-based MOD process. The precursor solution was synthesized with low cost YBCO powders as starting materials and YBCO coated conductors have been deposited on IBAD substrate ($CeO_2$/IBAD-YSZ/SS). YBCO coated conductor prepared by dip coating shows transport $I_c$ of 15A/cm-w at 77 K. Microstructural and crystallographic analyses indicate that YBCO layer was grown in epitaxy with substrate and exhibited well-developed dense microstructure. Also discussed are processing and analysis of YBCO coated conductor by slot-die web coating method. It was shown that this oxide-based MOD process provides a low cost route to coated conductor with high $J_c$.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.167.1-167.1
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• 2014

We report a facile method to fabricate superhydrophobic, transparent and conductive film using multi-walled carbon nanotubes (MWCNTs) which are coated by polydimethylsiloxane (PDMS). In order to prepare a film, PDMS coated MWCNTs were dispersed in solvents and the solution was drop-casted on substrates. It was demonstrated that the PDMS coating enhanced the dispersion of MWCNTs in diverse solvents such as dimethyl formamide(DMF) and acetone without the use of acids or surfactants, which are the common methods. In the case of DMF solvent, dispersion of MWCNT was improved by 40 % upon PDMS-coating of MWCNT. Enhanced dispersion of MWCNTs made it possible to fabricate transparent and conductive film homogeneously on the substrate and PDMS-coating on MWCNTs also made the surface hydrophobic. We can fabricate a uniform and multifunctional MWCNT film (transparent, conductive, superhydrophobic and flexible) which is applicable on large area without any physical damage and expensive equipment.

• Corrosion Science and Technology
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• v.9 no.5
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• pp.175-186
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• 2010

The auto industry is demanding more ductile high-strength steel grades to build lighter and stronger car bodies. The hot-dip galvanizing problems of these new steel grades are creating a demand for an improved method to control zinc wettability. The simplest way to improve zinc wettability on industrial hot-dip galvanizing lines is to increase the strip immersion temperature at zinc bath entry for enhancing the aluminothermic reaction. However, this practice increases the reactivity due to overheating the zinc in the snout which induces the formation of brittle Fe-Zn compounds at the strip/coating interface with the formation of higher amounts of dross in the zinc bath and snout contamination. Thus, this simple practice can only be utilized for short production periods of one to two hours without deteriorating coating quality. This problem has been solved by employing a technique that allows the use of a higher and attuned strip immersion temperature at zinc bath entry while still maintaining a constantly low zinc bath temperature. This has been proven to provide the solution for both the improved wettability and a significant reduction in the amounts of dross in the zinc bath.

• Journal of Periodontal and Implant Science
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• v.38 no.3
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• pp.453-466
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• 2008

Purpose: The purpose of this research is to study about initial adhesion, proliferation and activation of osteoblast to titanium surface treated with machined, hydroxyapatite coating, resorbable blast material blasting and anodizing method. Material and Methods: After treating the titanium surface of each block with machined, impurities were removed and sterilized. The number of cells attached from cultured osteoblast of respective experimental groups were measured at 1, 4, 7, and 14day and alkaline phosphatase, calcium, and inorganic phosphate concentration of cultured solution was measured. Result: Anodizing group showed the highest rate of cell attachment and proliferation activity. RBM treated group showed the highest increasing on their alkaline phosphatase activity, on the calcium apposition, on inorganic phosphate apposition of 1 and 4 days in cultured osteoblast to compare with other groups. Conclusion: On the basis of these findings, we conclude that surface modification of titanium was profoundly effected on the attachment, proliferation and activation of osteoblast in initial stage osseointegration.

• Journal of the Korean Ceramic Society
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• v.54 no.3
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• pp.200-204
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• 2017

Molybdenum (Mo), an electrode material of alkali metal thermal-to-electric converters (AMTEC), facilitates grain growth behavior and forms Mo-Na-O compounds at high operating temperatures, resulting in reduced performance and shortened lifetime of the cell. Mo/TiN composite materials have been developed to provide a solution for such issues. Mo is a metal that possesses excellent electrical properties, and TiN is a ceramic compound with high-temperature durability and catalytic activity. In this study, a dip-coating process with an organic solvent-based slurry was used as an optimal coating method to achieve homogeneity and stability of the electrodes. Cell performance was evaluated under various conditions such as the number of coatings, ranging from 1 to 3 times, and heat treatment temperatures of $800-1100^{\circ}C$. The results confirmed that the cell yielded a maximum power of 9.99 W for the sample coated 3 times and heat-treated at $900^{\circ}C$.

• Membrane Journal
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• v.10 no.3
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• pp.130-138
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• 2000

Polyethersulfone (PES) asymmetric membranes for gas separation were prepared by dry/wet phase inversion method and their separation properties for CO$_2$ and N$_2$ gases were investigated. The effects of important variables such as composition of casting solution and evaporation time in preparation of asymmetric gas membrane on membrane morphology and the separation properties were analyzed and the optimum condition of membrane preparation was established. To compensate the defects like pinholes existed on skin layer of the membrane prepared, the membranes were coated with silicone resin. By comparing separation properties after coating with those before coating, we found that the coating of silicone resin was effective to enhance the separation properties. The casting solution mainly used in this study consisted of PES, N-methyl-2-pyrrolidone, acetone, ethanol and distilled water was used as coagulation agent. It was shown that the selectivity for CO$_2$/N$_2$ was getting higher but the permeability decreases, as the contents of PES and volatile organic solvent and evaporation time increased. The selectivity for CO$_2$/N$_2$ and permeability of CO$_2$ of the membrane prepared under the optimum condition were found to be 61 and 21 GPU, respectively.

• Journal of the Korean institute of surface engineering
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• v.49 no.2
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• pp.202-210
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• 2016

This study was intended to investigate the effect of the amount of magnesium addition and heat treatment in the Al-Mg coating film in order to improve corrosion resistance of aluminum coating. Al-Mg alloy films were deposited on cold rolled steel by physical vapor deposition sputtering method. Heat treatment was fulfilled in an nitrogen atmosphere at the temperature of $400^{\circ}C$ for 10 min. The morphology was observed by SEM, component and phase of the deposited films were investigated by using GDLS and XRD, respectively. The corrosion behaviors of Al-Mg films were estimated by exposing salt spray test at 5 wt.% NaCl solution and measuring polarization curves in deaerated 3 wt.% NaCl solution. With the increase of magnesium content, the morphology of the deposited Al-Mg films changed from columnar to featureless structure and particle size was became fine. The x-ray diffraction data for deposited Al-Mg films showed only pure Al peaks. However, Al-Mg alloy peaks such as $Al_3Mg_2$ and $Al_{12}Mg_{17}$ were formed after heat treatment. All the sputtered Al-Mg films obviously showed good corrosion resistance compared with aluminum and zinc films. And corrosion resistance of Al-Mg film was increased after heat treatment.

• Progress in Superconductivity
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• v.8 no.1
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• pp.59-64
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• 2006

High $J_c\;YBa_2Cu_3O_x$ superconducting films were fabricated by MOD method using fluorine-free dichloroacetic acid(DCA) as chelating solvent for preparing precursor solution. Coating solutions were prepared by dissolving Y-, Ba- and Cu-acetates in DCA solvent followed by drying in rota vapor to obtain the blue gel that is diluted in methanol and 2-methoxyethanol for adjusting the cation concentration. DCA-MOD precursor solution was coated on a single crystal(001) $LaAlO_3(LAO)$ substrate by a dip coating method with a speed of 25 mm/min. Coated films were calcined at lower temperature up to $500^{\circ}C$ in flowing oxygen atmosphere with a 7.2% humidity. Conversion heat treatment was performed at various temperatures of $780{\sim}810^{\circ}C$ for 2 h in flowing Ar gas containing 1000 ppm oxygen with a humidity of 9.45%. SEM observations showed that films have very dense microstructures for the films prepared at the temperature higher than $800^{\circ}C$ regardless of diluting solvent; methanol or 2-methoxyethanol. X-ray diffraction analysis showed that YBCO grains grew with a (001) preferred orientation. A High critical current density($J_c$) of 1.28 $MA/cm^2$(@77 K and self-field) was obtained id. the YBCO film prepared using 2-methoxyethanol as a solvent.

• Journal of Korean Ophthalmic Optics Society
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• v.3 no.1
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• pp.217-222
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• 1998

Coating films of $SiO_2-TiO_2-AgO$ have been prepared on soda-lime-silica slide glasses and single crystal silicon wafer by the sol-gel method using a spin-coating technique. Commercially available tetraethyl orthosilicate, titanium trichloride, and silver-nitrates were used as starting materials. The heat treatment temperature of this coating films was $500^{\circ}C$ properly, obtained from TG-DTA result. The films with thickness of 310 nm were prepared by 5 times coating. In the case of l0 mol% AgO, the film showed a crack-free and smooth surface, but the higher Ago content exhibited the more pin hole and the segregated cluster of AgO. The IR absorbance of the films decreased in the range of 400 nm to 700 nm with the increase of annealing temperature. And the reflectance of the coating films decreased and the color was changed light yellow to white yellow with the increase of Ago content.