• Tribology and Lubricants
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• v.20 no.5
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• pp.237-244
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• 2004

Micro/nano tribological characteristics of PTFE coating films were experimentally studied. PTFE (polytetrafluoroethylene) modified polyethylene and low molecular weight PTFE were used as a coating materials. These films were deposited on Si-wafer (100) by IBAD (ion beam assisted deposition) method. The Ar ion beam sputtering was performed to change the surface topography of films using a hollow cathode ion gun under different Ar ion dose conditions in a vacuum chamber. Micro/nano tribological characteristics, water wetting angles and roughness were measured with a micro tribotester, SPM (scanning probe microscope), contact anglemeter and profilometer, respectively. The durability of the films were measured with macro tribotester. Results showed that the PTFE coating surfaces were converted to hydrophobic. The water contact angle of coated surfaces and surface roughness increased with the coating thickness. Adhesion and friction in micro and nano scale were governed by magnitude of normal load in soft material such as PTFE films. As the increase of sputtering time on low molecular weight PTFE films, the surface roughness was increased and nano adhesion and friction were decreased. The nano tribological characteristics of surfaces are mainly improved by chemical modification such as PTFE coating and given a synergy effect by the physical modification such as topographic modification.

• Biomaterials and Biomechanics in Bioengineering
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• v.1 no.1
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• pp.13-25
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• 2014

In the current study, a drug-eluting stent coated with biodegradable polymers and sirolimus was developed by using an ultrasonic nanocoater and characterized in aspects of surface smoothness and coating thickness. In addition, in vitro release profiles of sirolimus by changing top coating layer with different biodegradable polymers were investigated. Smooth surfaces with variable thickness could be fabricated by optimizing polymer concentration, flow rate, nozzle-tip distance, gas pressure, various solvents and ultrasonic power. Smooth surface could be generated by using volatile solvents (acetone, chloroform, and methylene chloride) or post-treating with solvent vapor. Coating thickness could be controlled by varying injection volume or polymer concentration, and higher concentration could reduce the coating time while obtaining the same thickness. The thickness measurement was the most effectively performed by a conventional cutting method among three different methods that were investigated in this study. Release profiles of sirolimus were effectively controlled by changing polymers for top layer. PLGA made the release rate 3 times faster than PDLLA and PLLA and all top layers prevented burst release at the initial phase of profiles. Our results will provide useful and informative knowledge for developing drug-eluting stents, especially coated with biodegradable polymers.

• Journal of Hydrogen and New Energy
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• v.21 no.4
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• pp.313-320
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• 2010

Carbon cloth was impregnated into PTFE emulsion. PTFE is a fluoropolymer used as a coating material in various fields due to its hydrophobicity and excellent mechanical properties. In this study, PTFE emulsion was prepared different particle size of 5~500 nm and $3{\sim}5{\mu}m$. FE-SEM and FT-IR spectroscopy were used microscopic observation and investigation of chemical structure change after PTFE coating. Mass variations, gas permeability and water contact angles were analyzed to determine a GDL performance of PTFE coated carbon cloth. PTFE coated carbon cloth show different mass increase according as PTFE concentration and the number of coating times. Water contact angle of PTFE coated carbon cloth was not effected by size of PTFE particle and the number of coating time; meanwhile, gas permeability was rapidly changed at carbon cloth coated by emulsion with size of $3{\sim}5{\mu}m$ PTFE particle.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05e
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• pp.35-39
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• 2003

An ageing characteristics of RTV coating materials by corona discharge have been studied. The recovery of a hydrophobicity of RTV coating materials with the thickness of $300{\mu}m$ was in identical with a bulk silicone materials. The hydrophobicity of RTV coating materials has been almost lost when its were discharged during 40 seconds by corona with 10kV, and recovered after about 45 hours. But the resistivity of RTV coating materials has not been recovered after 45 hours, even though after 80 hours the 95% of initiation resistivity value has been recovered. There was no critical compounds(such as Si and Al) changes on RTV surfaces by the corona discharge treatment until 100 seconds. In the test of arc erosion, it was seen that the coating sample with silicone rubber as a base material have more longer bum-out time than other samples with FRP or glass base.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.467-471
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• 2005

In this paper, experimental methods about the flow behavior of thin polymer film by various edge patterns in the spin coating process for stable cover layer coating of a blu-ray disc is described. The blu-ray disc, a next-generation optical disc format over 25GB, consists of a 1.1m thick substrate and a 0.1mm tick cover layer. Generally, cover layer on the blu-ray disc is made by the polymer spin coating process. However, it is hard to secure sufficient coating uniformity around the rim on the cover layer. In order to get the uniform thickness deviation and to minimize the bead around the rim, the edge of the disc substrate can be modified into various patterns, such as normal plain, trench, step and chamfer pattern, etc, around the rim on the disc and experimented with various parameters, such as surface tension, viscosity, coating time, temperature and rotation speed, etc. And the optimal shape of the rim was tried to get by 3 dimensional computer simulation of the polymer expulsion process.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.39 no.2 s.120
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• pp.17-24
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• 2007

PEA(Print Evenness Analyzer) Module can be utilized as a tool to evaluate print mottle. The tester is de-signed to measure the uniformity of liquid penetration into paper at very short contact time. To evaluate effects of base paper properties on print mottle, the experiments were performed with 3 types of base pa-per whose sizing degree, roughness and porosity were varied. Coated papers were produced with high solid coating color (70%) and low solid coating color (67%). Uniformity of water absorption into base paper and coated paper was measured with PEA. It was found that, in order to minimize print mottle, base paper shall be produced with a high sizing degree and low roughness and the concentration of coating color shall be kept as high as possible, providing that it has proper rheology properties for coating process.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.34 no.2
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• pp.223-230
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• 1998

Recently, with the rapid development in the industries such as mechanical plants, automobiles, ships and marine structures, it is enlarged by the use of the SS 41 steel. This mechanical plants and marine structures are exposed m corrosion because of Cl-under marine environments. To protect their accidents, mainly applied anti-corrosion epoxy coating and various protective its structures. In this study, corrosion control characteristics on the epoxy coating were investigated by the galvanic corrosion of impressed voltage tester under marine environments The main results obtained are as follows; 1. Corrosion current density of amine-epoxy coating becomes more increased than that of other epoxy coating and the time area rate of pin hole and pit until 5% becomes most rapid. 2. The potential of SUS 304 stainless steel(cathode) for Al-epoxy coating is nearly zero potential. 3. Corrosion current density of Amine-epoxy by shot blast becomes more decreased than that of not shot blast and cathodic potential becomes more noble. 4. As distance of anode and cathode is more decreased, corrosion current density of epoxy coating is more increased and cathodic potential becomes less noble.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.6
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• pp.1-7
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• 2014

Gas turbines for generation are operated under high temperatures, high pressures and in corrosive environments for long periods of time. This environment causes serious damage to these parts. Therefore, the material, coating, and cooling technology used with a gas turbine are important factors with regard to turbine blade development. One method that can be used to protect a product from harsh conditions is the coating technology. A turbine blade undergoes very aggressive thermal stress and experiences high-temperature fatigue. In order to reduce the surface temperature of the components and protect the blade from high-temperature flames, a thermal barrier coating (TBC) is applied to its substrate. This study confirms the applicability of an inspection system for the turbine blade coating layer using an artificial heat source.

• Journal of the Korean institute of surface engineering
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• v.19 no.3
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• pp.92-108
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• 1986

An electroplating on the lead frame fabricated from domestic copper plate was studied experimentally. In this study, nickel was plated on the thin copper lead frame and silver layer was coated on the nickel film in the cyanide electrolyte. The effect of process variables such as current density, plating time, coating thickness and flow rate of electrolytic solution on the properties of coating was investigated. Some samples on each step were fabricated during electroplating. The results obtained from polarization measurement, observation of SEM photograph, adhesion test of coating and microhardness test are as follows. On silver plating, polarization resistance of potentiostatic cathodic polarization curve is reduced as the flow rate of Ag electrolytic solution increases. And above resistance is also reduced when the minor chemicals of sodium cyanide and sodium carbonate are added in potassium silver cyanide bath. The reduced polarization resistance makes silver deposition on the cathode easy. An increase in the current density and the coating thickness causes the particle size of deposit to coarsen, and consequently the Knoop microhardness of the coating decreases. On selective plating an increase in the flow rate of plating solution lead to do high speed plating with high current density. In this case, the surface morphology of deposit is of fine microstructure with high Knoop hardness. An increasing trend of the adhesion of coating was shown with increasing the current density and flow rate of electrolytic solution.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1930-1932
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• 2005

Colloidal Silica(CS)/methyltrimethoxy silane(MTMS) and CS/MTMS/epoxy silane(Es) sol solutions were prepared in variation with synthesizing parameters such as kinds of CS, kinds of silane and reaction time. In order to understand its physical and chemical properties, sol-gel coating films on glass were fabricated. In the case of CS/MTMS sol, the coating films had high contact angle and more enhanced flat surface than those in the case of CS/MTMS/ES sol. Also, the coating films obtained from single CS had a better flat surface than those obtained from mixed CS. In the case of thermal stability, thermal dissociation of CS/MTMS and CS/MTMS/ES sol-gel coating films did not occur up to $550^{\circ}C$ and $440^{\circ}C$ respectively. The thickness of coating films obtained from CS/MTMS sol increased than those of CS/MTMS/ES sol. In addition, the coating films obtained from single CS were more thicker than those obtained from mixed CS.