• Korean Journal of Materials Research
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• v.22 no.10
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• pp.526-530
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• 2012

Silica-based ceramic-matrix composites have shown promise as advanced materials for many applications such as chemical catalysts, ceramics, pharmaceuticals, and electronics. $SiO_2$-CuO-$CeO_2$ multi-component powders and their thin film, using an oxalic acid template as a chelating agent, have larger surface areas and more uniform pore size distribution than those of inorganic acid catalysts. $SiO_2$-CuO-$CeO_2$ composite powders were synthesized using tetraethylorthosilicate, copper (II) nitrate hemi (pentahydrate), and cerium (III) nitrate hexahydrate with oxalic acid as template or pore-forming agent. The process of thermal evolution, the phase composition, and the surface morphology of these powders were monitored by thermogravimetry-differential thermal analysis (TG-DTA), X-ray diffractometry (XRD), field-emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectrometry (EDXS). The mesoporous property of the powders was observed by Brunner-Emmett-Teller surface (BET) analysis. The improved surface area of this powder template with oxalic acid was $371.4m^2/g$. This multi-component thin film on stainless-steel was prepared by sol-gel dip coating with no cracks.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.23 no.1
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• pp.9-15
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• 2017

To identify applicability for packaging material of polyvinyl alcohol (PVA)/boric acid (BA) coating solution with highly-enhanced water vapor and oxygen barrier properties, the PET/PVA-BA/OPP multi-layer films were prepared through comma coating and lamination process. The oxygen and water vapor permeabilities, and tensile strength of as-prepared multi-layer films were investigated before and after pressure cooker test (PCT). Although oxygen and water vapor permeabilites, and mechanical properties of PET/PVA-BA/OPP multi-layer films was decreased after PCT, their properties were highly enhanced as increase of BA contents in PVA matrix. This is strongly related with enhanced cross-linking density in PVA-BA layer. In storage test of seasoned-laver, the PET/PVA-BA/OPP multi-layer films were comparatively effective to suppress the increase in peroxide value originating from oxidation of seasoned-laver. Comparing the commercially available PP/Al-metallized PP for seasoned-laver packaging, however, PET/PVA-BA/OPP multi-layer films did not show any advantage in water activity. This is due to higher water vapor permeation properties of as-prepared multi-layer films. Therefore, further studies are required to enhance the water vapor permeation in PET/PVA-BA/OPP multi-layer films.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.1
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• pp.1-8
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• 2015

To produce the white light, there are a single chip method using the blue light and phosphor coating, a multi chip method by mixing R, G, B light.. Multi chip method is proper for the smart lighting system by controling color and color temperature. And color rendering of single chip LED is good by even spectral distribution. To apply application technic like smart light system, this paper analyzed the properties of single chip LED and RGB multi chip LED, and implemented the 2 part subject evaluation for single chip LED and RGB multi chip LED. The first part is comparison of properties for single chip LED and RGB multi chip and second part is color appearance evaluation of 8 colors in each lighting environment.

• Progress in Superconductivity
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• v.9 no.2
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• pp.167-172
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• 2008

We fabricated $YBa_2Cu_3O_{7-x}$(YBCO) films on (00l) $LaAlO_3$ substrates prepared by metal organic deposition(MOD) method using trifluoroacetate(TFA) solution. The films with various thicknesses were prepared by repeating the dip-coating and calcining processes. The effects of film thickness on phase formation, microstructures, and critical properties were evaluated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The microstructure and resultant critical current($I_C$) and critical current density($J_C$) varied remarkably with film thickness: The ($I_C$) value increased from 39 to 160 A/cm-width as the number of coatings increased from one to four, while the corresponding $J_C$ was measured to be in the range of $0.84-1.21\;MA/cm^2$. Both the $I_C$ and $J_C$ decreased when an additional coating was applied due to microstructural degradation, indicating that the optimum thickness is in the range of $1.1-1.8\;{\mu}m$. The possible cause for the decrease in the $I_C$ and $J_C$ value for film thicker than $1.8\;{\mu}m$ include non-uniform thickness, increased surface roughness, and the poor formability of the YBCO phase and texture arising from the insufficient heat treatment time with respect to the increased thickness.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.5
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• pp.467-476
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• 2006

We fabricated the YBCO films on LAO substrate using the TFA-MOD method and evaluated the effects of heat treatment temperature and film thickness on the microstructure, degree of texture, and critical properties. The calcining and firing were peformed at the temperature range of $370^{\circ}C-460^{\circ}C\;and\;750^{\circ}C-800^{\circ}C$, respectively. For the films fired at $775^{\circ}C$ after calcining at $400^{\circ}C-430^{\circ}C$showed highest critical temperature (Tc-onset) of 89.5 K and critical current (Ic) of 40A/cm-width which corresponds to critical current density (Jc) of $1.8MA/cm^2$. The highest critical properties are probably attributed to the formation of purer YBCO phase, stronger biaxial texture, and higher oxygen content, according to the XRD, pole-figure, SEM, Raman analysis. From the multi-coated films, the Ic increased from 39 to 169 A/cm-width as the coating repeated to four times, while the corresponding Jc was measured from once to be in the range of $0.8-1.2MA/cm^2$. Both Ic and Jc degraded as the coating repeated further, indicating that the optimum thickness is in the range of $1.0{\mu}m-1.7{\mu}m$.

• Composites Research
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• v.31 no.3
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• pp.83-87
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• 2018

An object in the Low Earth Orbit (LEO) is affected by many environmental conditions unlike earth's surface such as, Atomic oxygen (AO), Ultraviolet Radiation (UV), thermal cycling, High Vacuum and Micrometeoroids and Orbital Debris (MMOD) impacts. The effect of all these parameters have to be carefully considered when designing a space structure, as it could be very critical for a space mission. Polybenzimidazole (PBI) is a high performance thermoplastic polymer that could be a suitable material for space missions because of its excellent resistance to these environmental factors. A thin coating of PBI polymer on the carbon epoxy composite laminate (referred as CFRP) was found to improve the energy absorption capability of the laminate in event of a hypervelocity impact. However, the overall efficiency of the shield also depends on other factors like placement and orientation of the laminates, standoff distances and the number of shielding layers. This paper studies the effectiveness of using a PBI coating on the front bumper in a multi-shock shield design for enhanced hypervelocity impact resistance. A thin PBI coating of 43 micron was observed to improve the shielding efficiency of the CFRP laminate by 22.06% when exposed to LEO environment conditions in a simulation chamber. To study the effectiveness of PBI coating in a hypervelocity impact situation, experiments were conducted on the CFRP and the PBI coated CFRP laminates with projectile velocities between 2.2 to 3.2 km/s. It was observed that the mass loss of the CFRP laminates decreased 7% when coated by a thin layer of PBI. However, the study of mass loss and damage area on a witness plate showed CFRP case to have better shielding efficiency than PBI coated CFRP laminate case. Therefore, it is recommended that PBI coating on the front bumper is not so effective in improving the overall hypervelocity impact resistance of the space structure.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.44 no.5
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• pp.32-38
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• 2012

This study was carried out to elucidate the potential in substitution of SB latex with eco-friendly starch based bio-binder as a coating binder. The part of SB latex in coating color of pre- and top layer was substituted with starch based bio-binder in order to evaluate the characteristics of coating color and coated paper, and printability. The viscosity and water retention of coating color were increased by substitution of SB latex with starch based bio-binder. Roughness of coated paper was increased by substitution with starch based bio-binder, although there was not significant changes in roughness when SB latex is used as a binder in pre-coating color. Brightness and whiteness of coated paper were not affected, but opacity and print mottle were improved by substitution with starch based bio-binder. The interesting result observed was that dry-pick did not affected significantly, and ink set-off was improved by starch based bio-binder. It is expected that starch based bio-binder can be commercialized if the systematic further research works are carried out.

• Journal of the Korean institute of surface engineering
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• v.44 no.5
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• pp.226-231
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• 2011

Graphene was coated on STS 316L by electro spray coating method to improve its properties of corrosion resistance and contact resistance. Exfoliated graphite (graphene) was made of the graphite by chemical treatment. Graphene is distributed using dispersing agent, and STS 316L was coated with diffuse graphene solution by electro spray coating method. The structure of the exfoliated graphite was analyzed using XRD and the coating layer of surface was analyzed by using SEM. Analysis showed that multi-layered graphite structure was destroyed and it was transformed into fine layers graphene structure. And the result of SEM analysis on the surface and the cross section, graphene layer was uniformly formed with 3~5 ${\mu}m$ thickness on the surface of substrate. Corrosion resistance test was applied in the corrosive solution which is similar to the PEM fuel cell stack inside. And interfacial contact resistance test was measured to simulate the internal operating conditions of PEM fuel cell stack. The results of measurements show that stainless steel coated with graphene was improved in corrosion resistance and surface contact resistance than stainless steel without graphene coating layer.

• Journal of the Korean Ceramic Society
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• v.36 no.4
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• pp.391-402
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• 1999

Characteristics of composite electrolytes which were prepared by coating a thin film of YSZ (yttria sta-bilized zirconia : (ZrO2)0.92 (Y2O3)0.08) on YDC (yttria doped ceria : Ce0.8Y0.2O1.9) with mixed conductivity have been investigated in order to develop the low-temperature solid oxide fuel cell. The thickness (t) of spin-coated YSZ thin films after the heat-treatment at 600$^{\circ}C$ was increased proportionally to the sol con-centrations (C) while the decrease in its thickness with the spin rate ($\omega$) could be expressed in the e-quation of ln t=9.49-0.53 ln $\omega$(0.99mol//s sol conc.) When the sol concentration and the spin rate being less than 0.99 mol/l and higher than 1000 rpm respectively reliable YSZ/YDC composite electrolytes could be obtained by multi-coating although several micro-cracks were observed in singly coated YSZ film surfaces. The dense YSZ film with a 1$\mu\textrm{m}$ thickness was prepared by coating of 0.99 mol/l YSZ sol five-times at 2000 rpm followed by heat-treatment at 1400$^{\circ}C$ for 2h, The adhesion between YSZ film and YDC substrate was found to be very good. The open circuit voltages of H2/O2 single cell with YSZ/YDC composite electrolytes were 0.79∼0.82 V at 800$^{\circ}C$ and 0.75∼0.77V at 900$^{\circ}C$ The open circuit voltage was inversely proportioned to the thickness ratio of YSZ thin film (1$\mu\textrm{m}$) to YDC substrate(0.28-2.22 mm)

• Polymer(Korea)
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• v.33 no.6
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• pp.620-624
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• 2009

Biomedical metal implants have been used clinically for replacement, restoration, or improvement of injury bodies based on high mechanical properties, but it has some risks such as the inflammatory, late thrombosis, or restenosis due to the low biocompatibility and toxicity. In various techniques of surface treatment developed to preserve these drawbacks, this study examined the electrospray coating technology with biodegradable poly (lactic-co-glycoic acid) (PLGA) on metal surface. Based on fundamental examination of electrospraying and solution parameters, the surface morphology of coated film was closely related to the boiling point of solvent, in-flight distance, and droplet size. The thickness of polymer film was linearly proportional to the emerged volume. This result exhibits that the polymeric droplets were continuously deposited on the polymer film. Therefore, the electrospray coating technology might be applied into the fabrication of single/multi-layered polymer film in nano-/micro-thickness and the control of the topology for biomedical metal implants including stents.