• 한국세라믹학회지
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• 제36권6호
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• pp.571-576
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• 1999

This paper describes both electromagnetic properties and electromagnetic-wave absorbind (EMA) characteristics of the radar absorbing coating materials in the microwave frequencies. The coating materials are prepared by mixing ferrite powder with epoxy resin polymers. The electromagnetic property and the EMA characteristics of the coating materials are measured in the frequency ranges between 0.2 GHz and 15GHz using the S-parameter method. The results show that the typical coating material has ({{{{ {μ }`_{r } ^{' } }} of about 2 and ({{{{ { ε}`_{r } ^{' } }} of about 4. And the coating materials have a little EMA characteristics in the frequency from 4 to 6 GHz and more improved EMA characteristics around 12 GHz And it is desirable for improvement of the EMA characteristics of the coating materials to properly select electromagnetic properties of constitutional materials inthe interesting frequency ranges.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2002년도 춘계학술발표회 초록집
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• pp.10-11
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• 2002

• 펄프종이기술
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• 제44권5호
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• pp.39-45
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• 2012

For a fundamental study for high concentration pigment coating, the effects of alkali swellable emulsion (ASE) type rheology modifier and surface adsorption emulsion (SAE) type rheology modifier on both the stability and the viscoelastic behavior of a coating color were elucidated. The coating color prepared with SAE type rheology modifier showed superior thermal and mechanical stability than that with ASE type. In the high concentration and high speed coating process, the mechanical stability of a coating color was a key parameter since both impact force and shear force were increased with the increase of coating color concentration and coating speed, respectively.

• 반도체디스플레이기술학회지
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• 제16권4호
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• pp.91-96
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• 2017

In this computational study of optical fiber manufacturing, WOW (wet-on-wet) double coating process on freshly drawn glass fiber has been numerical modelled and simulated using a simplified geometry of typical optical fiber coating apparatus. The numerical domain includes primary and secondary coating dies along with secondary coating cup and the interface between primary and secondary coating liquids are investigated using level set method. Coating liquid viscosity is an important parameter and its dependence on temperature is also considered. Since there would be possibility for pressure and temperature of primary coating liquid to be increased substantially at high fiber drawing speed, the effects of increased pressure and temperature of primary coating liquid are examined on flow patterns of coating liquids in secondary coating cup. In case that both pressure and temperature of primary coating liquid are high enough, liquid interface becomes noticeably unstable and this flow instability could adversely affect the uniform coatings and final quality of produced optical fiber.

• 한국안전학회지
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• 제23권4호
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• pp.25-29
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• 2008

Recently, new functionally graded material(FGM) that has a spatial variation in composition and properties is developed because of its good quality. This material yields the demands for resistance to corrosion and high temperature in turbine blade, wear resistance as in gears and high strength machine parts. Especially coating treatment in FGM surface brings forth a mechanical weak at the interface due to discontinuous stress resulting from a steep material change. It often, leads cracks or spallation in a coating area around an interface. The behavior of propagation cracks in FGMs was here investigated. The interface stresses were reduced because of graded material properties. Also graded material parameter with exponential equation was founded to influence the stress intensity factor. And the resistance curve with FGM coating was slightly increased.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2008년도 추계학술대회 초록집
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• pp.68-68
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• 2008

There are several methods for oxide coating on metals, such as aluminum or carbon nanotubes(CNTs). Usually CVD method is introduced for various oxide coating on CNTs. Another method is electrochemical method which use potential-pH diagram for oxide coating on metal or CNTs. In this experiment, electrochemical coating parameter for oxide coating on aluminum template modified by acids and hydrogen peroxide ($H_2O_2$) were examined. SEM micrographs displayed clearly $Ni(OH)_2$ coating on template. For confirmation of electrochemical method application to EDLC electrode material fabrication, EDS spectrum was analyzed.

• 한국정밀공학회지
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• 제32권2호
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• pp.159-166
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• 2015

Slot-die coating is well known technique to guarantee a uniformly coated layer and is compatible with roll-to-roll process. In actual roll-to-roll slot-die coating process, the lateral difference of coated layer thickness is observed. An experimental study was performed to improve the coating quality. Coating speed and coating gap were selected as the experimental factors. A full factorial, statistical method was conducted to optimize the process conditions. Based on the results of repeated experiment, the lowest deviation of lateral thickness (700 nm, <10%) was achieved at 10 m/min coating speed and $300{\mu}m$ coating gap. This result has significance because such optimized process guideline can be utilized with all process improvement in various coating applications.

• 한국세라믹학회지
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• 제53권6호
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• pp.628-634
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• 2016

The 8 wt% yttria($Y_2O_3$) stabilized zirconia ($ZrO_2$), 8YSZ, a typical thermal barrier coating (TBC) for turbine systems, was fabricated under different starting powder conditions and coating parameters by atmospheric plasma spray (APS) coating process. Four different starting powders were prepared by conventional spray dry method with different additive and process parameter conditions. As a result, large- and small-size spherical-type particles and Donut-type particles were obtained. Dense structure of 8YSZ coating was produced when small size spherical-type or Donut-type particles were used. On the other hand, 8YSZ coating with a porous structure was formed from large-size spherical-type particles. Furthermore, a segmented coating structure with vertical cracks was observed after post heat treatment on the surface of dense structured coating by argon plasma flame at an appropriate gun distance and power condition.

• 반도체디스플레이기술학회지
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• 제23권2호
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• pp.65-70
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• 2024

Using a computational fluid dynamics(CFD) simulation tool, we have provided a coating guideline for slot-die coating with a double layer slot die head. We have analyzed the fluid dynamics in terms of the coating speed, flow rate ratio, and viscosity ratio, which are critical for the stability of coating meniscus. We have identified the common coating defects such as break-up, air entrainment, and leakage by varying the coating speeds. The flow rate ratio is the critical parameter determining the wet film thickness of the top and bottom layers. It is shown that when the flow rate ratio exceeds or equals 1.8, air entrainment occurs due to insufficient hydraulic pressure in the bottom layer, even though the total flow rate remains constant. Furthermore, we have found that the flow of the bottom layer is significantly affected by the viscosity of top layer. The viscosity ratio of 4 or higher obstructs the flow of the bottom layer due to the increased hydraulic resistance, resulting in leakage. Finally, we have demonstrated that as the viscosity ratio increases from 0.1 to 10, the maximum coating speed rises from 0.4 mm/s to 1.6 mm/s, and the minimum wet film thickness decreases from 800 ㎛ to 200 ㎛.

• 한국주조공학회지
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• 제7권2호
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• pp.122-132
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• 1987

Full mold casting process is a new technique offering numerous advantages and promising possibilities. The present study is aimed to bring out the results of experiments carried out to study the effect of pattern coatings on the solidification of 99.5% pure aluminum plate-shaped castings in the various sand molds and the thermal behavior of the molds. The results of the investigation indicate that (i) with increase in pattern coating thickness, the relative chilling power decreases gradually for silica and increases for zircon coating, and (ii) the application of a pattern coating significantly reduces the maximum interface temperature by the mold which is more pronounced in the case of thinner mold wall. The investigation also indicates that Chvorinov's rule is not found to be valid for the casting in the full mold, with or without pattern coating. Therefore in full mold process, the pattern coating thickness will be a very important parameter in the study of thermal behavior.