• 보존과학연구
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• s.29
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• pp.65-90
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• 2008

This study examines the status and the physical features of Paraloid B-72 layers with examination of microstructure and analysis of organic matters. Paraloid B-72 layers were coated on samples from the colour layer of outer wall painting in Mireuk hall in Geumsan temple. On the basis of the previous examination result, it has made the samples which are similar to outer wall in Mireuk hall in Geumsan temple. The samples can be divided into two, one; 5% Paraloid B-72 coating and another is without coating. Then samples have been experimented under the compulsive environments of infrared radiation and immersion, thereafter compared the results of the damages and physical features between two samples. As a result of the comparison, the sample with Paraloid B-72 had more serious cracks, exfoliations and peeling layers than that of without Paraloid B-72. Otherwise, in the examination of ultraviolet radiation, the sample with Paraloid B-72 coating showed weaker physical properties, less density in structure of colour layer and less hardness in surface of colour layer than the sample without coating. The percentage of moisture content after the ultraviolet radiation was higher in the sample without Paraloid B-72 than the sample with Paraloid B-72 coating. Observing the conditions before the ultraviolet radiation, the sample with Paraloid B-72 coating demonstrated lower rate in moisture evaporation rate than the sample without Paraloid B-72. As a consequence, in examination of this samples, the change of physical features are increased in the sample with Paraloid B-72 coating than that without Paraloid B-72 when compulsive environment of heat, moisture and ultraviolet rays for a short term are imposed.

• Nuclear Engineering and Technology
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• v.49 no.5
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• pp.1031-1043
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• 2017

A structural model for stress distributions of coated Zircaloy subjected to realistic incore pressure difference, thermal expansion, irradiation-induced axial growth, and creep has been developed in this study. In normal operation, the structural integrity of coating layers is anticipated to be significantly challenged with increasing burnup. Strain mismatch between the zircaloy and the coated layer, due to their different irradiation-induced axial growth, and creep deformation are found to be the most dominant causes of stress. This study suggests that the compatibility of the high temperature irradiation-induced strains (axial growth and creep) between zircaloy and the coating layer and the capability to undergo plastic strain should be taken as key metrics, along with the traditional focus on chemical protectiveness.

• Nuclear Engineering and Technology
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• v.54 no.12
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• pp.4693-4697
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• 2022

Parylene coating was adopted on CdZnTe (CZT) detector as a mechanical protection layer after wet passivation with hydrogen peroxide (H₂O₂) and ammonium fluoride (NH₄F). Wet chemical passivant lose their effectiveness when exposed to the ambient conditions for a long time. Parylene coating could protect the effectiveness of passivation, by mechanically blocking the exposure to the ambient conditions. Stability of CZT detector was tested with the measurement of leakage current density and response to radio-isotopes. When the enough thickness of parylene (>100 ㎛) is adopted, parylene is a promising protection layer thereby ensuring the performance and long-term stability of CZT detectors.

• Corrosion Science and Technology
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• v.3 no.1
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• pp.20-25
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• 2004

In order to clarify the durability of protective coatings for maritime steel structures, various anti-corrosive organic coated steel samples were exposed for twelve years in semitropical marine environment at Miyakojima Island, Okinawa, JAPAN. Samples were various organic coated steel pipes, 4.0 m in length and 150 mm in diameter. While the bare steel pipe entirely corroded in 4.5 mm thickness in four and half years, these organic coated steel pipes exhibited protective appearances after twelve-year-exposure except for the defect in the coatings. Polyethylene (PE) lining pipe exhibited a good protective performance. Urethane painted pipe was also good but some barnacles stuck to its surface. A combination of petrolatum tape and FRP cover showed sufficient corrosion resistance for steel surface. The correlation in results between exposure and laboratory acceleration test was examined. It was found that salt spray test (SST) results corresponded to rusted area of scratched portion and that adhesion change of coating layer corresponded to the rotating immersion test result. Among the on-site measured data, volume resistivity is utilized for the index of corrosion protection performance of organic coating.

• Journal of Korea Foundry Society
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• v.17 no.3
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• pp.276-285
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• 1997

The effect of wheel surface condition on solidification behavior of Al-Cu ribbon was investigated in order to establish extreme levels of heat extraction. The condition of wheel surface was changed either by heating the wheel surface up to $200^{\circ}C$ or by coating boron nitride(BN) onto the the rim of a wheel. Heating the wheel surface up to $200^{\circ}C$ improved the wetting behavior between the molten metal and the rotating wheel, leading to an increase in the ratio of columnar structure to the entire thickness of Al-4.3wt%Cu and Al-33.2wt%Cu ribbons. For Al-4.3wt%Cu ribbon, assuming one grain as a single heterogeneous nucleation event at the contact point, the nucleation density with the wheel surface heated to $200^{\circ}C$, was $4{\times}10^6/mm^2$, and in the cases of BN coating with thin and thick layers, $10^5/mm^2$ and $5{\times}10^4/mm^2$, respectively. The largest cooling capacity of the wheel corresponded to the heated wheel surface, and as the thickness of BN coating layer increased, the cooling capacity of the wheel gradually decreased.

• Journal of the Korean institute of surface engineering
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• v.37 no.3
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• pp.152-157
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• 2004

Ti-Al-N ($Ti_{75}$ $Al_{25}$ N) and Ti-Al-Si-N ($Ti_{69}$ $Al_{23}$ $Si_{8}$N) coatings synthesized by a DC magnetron sputtering technique were studied comparatively with respect to phase characterization and high-temperature oxidation behavior. $Ti_{69}$ $Al_{23}$ $Si_{ 8}$N coating had a nanocomposite microstructure consisting of nanosized(Ti,Al,Si)N crystallites and amorphous $Si_3$$N_4$, with smooth surface morphology. Ti-Al-N coating of which surface $Al_2$$O_3$ layer formed during oxidation suppressed further oxidation. It was sufficiently stable against oxidation up to about $700^{\circ}C$. Ti-Al-Si-N coating showed better oxidation resistance because both surface Ab03 and near-surface $SiO_2$ layers suppressed further oxidation. XRD, GDOES, XPS, and scratch tests were performed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.2
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• pp.608-613
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• 2010

This study is on development of UV-cured water soluble coating composition which have more improved anti-cigar burning to prevent a surface of PVC tile from damage of heat. To make an anti-cigar burning coating solution, thermostable agent that synthesize main materials phosphorus compound, guanidine and ammonium phosphate dibasic used temporary flame retardants, changing their contents from 10 to 30wt% against quantities of resin and compounded. After coating PVC tiles using bar-coating method that can adjust a thickness, we estimated surface properties of coated layer such as anti-cigar burning, adhesive power, chemical resistance, thickness of coating, and so on. Results showed that a coating composition added 30 wt% of phosphorus compound and coated with No.12 bar-coater had the best optimized surface property in anti-cigar burning effect, adhesive power and chemical resistance. Also, we could find anti-cigar burning effect was improved as thermostable agents content and coating thickness increased.

• Journal of the Korean institute of surface engineering
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• v.33 no.1
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• pp.38-47
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• 2000

A Ti(CN) layer was formed on aluminum alloy by using diethylamino titanium, hydrogen and nitrogen with the pulsed DC PACVD process. Effect of process parameters such as precursor evaporation temperature, duty ratio, frequency, voltage, $H_2$/$N_2$gas ratio on the properties of Ti(CN) layer were investigated. The layer thus obtained had high hardness and low friction coefficient. Detailed results on the hardness, surface morphology, XRD, WDS analysis, wear test and scratch test of this layer are presented.

• Journal of the Korean institute of surface engineering
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• v.45 no.6
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• pp.264-271
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• 2012

Due to the good corrosion resistance and machinability, copper alloy is commonly employed for shipbuilding, hydroelectric power and tidal power industries. The Cu alloy, however, has poor durability, and the seawater application at fast flow condition becomes vulnerable to cavitation damage leading to economic loss and risking safety. The HVOF(High Velocity Oxygen Fuel) thermal spray coating with WC-10Co4Cr were therefore introduced as a replacement for chromium or ceramic to minimize the cavitation damage and secure durablility under high-velocity and high-pressure fluid flow. Cavitation test was conducted in seawater at $15^{\circ}C$ and $25^{\circ}C$ with an amplitude of $30{\mu}m$ on HVOF WC-10Co4Cr coatings produced by thermal spray. The cavitation at $15^{\circ}C$ and $25^{\circ}C$ exposed the substrate in 12.5 hours and in 10 hours, respectively. Starting from 5 hours of cavitation, the coating layer continued to show damage by higher than 160% over time when the temperature of seawater was elevated from $15^{\circ}C$ to $25^{\circ}C$. Under cavitation environment, although WC-10Co4Cr has good wear resistance and durability, increase in temperature may accelerate the damage rate of the coating layer mainly due to cavitation damage.

• Corrosion Science and Technology
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• v.11 no.6
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• pp.263-269
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• 2012

Copper alloys are commonly applied to ship's propellers, pumps and valves which are serviced in seawater due to their good castability and corrosion resistance. In the environment of high flow velocity, however, erosion damage predominates over corrosion damage. In particular, the cavitation in seawater environment accelerates surface damage to copper alloys, resulting in degradation of products and economic losses and also threatening safety. The surface was coated with WC-27NiCr by high velocity oxygen fuel(HVOF) spraying technique to attain durability and cavitation resistance of copper alloys under high velocity/pressure flow. The cavitation test was performed for the WC-27NiCr coating deposited by HVOF in seawater at the amplitude of $30{\mu}m$ with seawater temperature. The cavitation at $15^{\circ}C$ caused exfoliation of the coating layer in 17.5 hours while that of $25^{\circ}C$ caused the exfoliation in 12.5 hours. When the temperature of seawater was elevated to $25^{\circ}C$ from $15^{\circ}C$, more damage was induced by over 160%. Although WC-27NiCr has good durability, corrosion resistance and eletrochemical stability, the cavitation damage rate of the coating layer could remarkably increase at the elevated temperatures under cavitation environments.