• Tribology and Lubricants
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• v.35 no.2
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• pp.106-113
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• 2019

We investigated the application of tetrahedral amorphous carbon (ta-C) coatings to fabricate a glass lens manufactured using a glass molding process (GMP). In this work, ta-C coatings with different thickness (50, 100, 150 and 200 nm) were deposited on a tungsten carbide (WC-Co) mold using the X-bend filter of a filtered cathode vacuum arc. The effects of thickness on mechanical and tribological properties of the coating were studied. These ta-C coatings were characterized by atomic force microscopy, scanning electron microscopy, nano-indentation measurements, Raman spectrometry, Rockwell-C tests, scratch tests and ball on disc tribometer tests. The nano-indentation measurements showed that hardness increased with an increase in coating thickness. In addition, the G-peak position in the Raman spectra analysis was right shifted from 1520 to $1586cm^{-1}$, indicating that the $sp^3$ content increased with increasing thickness of ta-C coatings. The scratch test showed that, compared to other coatings, the 100-nm-thick ta-C coating displayed excellent adhesion strength without delamination. The friction test was carried out in a nitrogen environment using a ball-on-disk tribometer. The 100-nm-thick ta-C coating showed a low friction coefficient of 0.078. When this coating was applied to a GMP, the life time, i.e., shot counts, dramatically increased up to 2,500 counts, in comparison with Ir-Re coating.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.2
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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.

• Journal of Surface Science and Engineering
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• v.25 no.2
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• pp.82-89
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• 1992

The effect of interlayer coating of Ni and Ti on corrosion behavior was studied in TiN ion plated steel plate. Interlayer coating was carried out in a single and bi-layer to a various thickness combination prior to final TiN coating of $2\mu\textrm{m}$. Corrosion behavior was evaluated by anodic polarization test in 1N H2SO4 as well as salt spray test. Porosity of each coating was also tested by using SO2 test. Corrosion resistance was improved with increasing the thickness of Ni interlayer coating and Ni-Ti interlayer coating markedly enhanced the corrosion resistance. Ni/Ti interlayer coating of $2\mu\textrm{m}$/2$\mu\textrm{m}$ prior to $2\mu\textrm{m}$ TiN coating decreased the corrosion current density of active range by an order of 4 and that of passive range by an order of 1. This improvement was associated with the retardation of corrosive agent penetration with increasing coating thickness and inherent corrosion resistance of Ni and Ti interlayers, Ni/Ti interlayers coating were also very effective in improvement of corrosion resistance under salt atmosphere.

• Journal of the Semiconductor & Display Technology
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• v.22 no.4
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• pp.119-123
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• 2023

This study is normal orientation technology of slit coating equipment to improve the quality of curved displays. Currently, the demand for curved displays is increasing significantly due to advantages such as screen immersion or design in various industries. Accordingly, changes in the display coating process are essential. In the curved display coating process, unlike the existing flat coating process, the nozzle must be rotated along the curvature of the curved surface to spray the coating solution. The coating solution must be applied while maintaining a uniform thickness. If the thickness of the coating liquid applied to the target surface is non-uniform, the quality of the product may be degraded such as image quality deterioration and light spreading. This paper presents technology and experimental results for keeping the nozzle of slit coating equipment perpendicular to the curved surface and is expected to contribute to the quality improvement of curved displays.

• Journal of the Semiconductor & Display Technology
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• v.2 no.1
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• pp.25-29
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• 2003

The fluid flow, mass transfer, heat transfer and film thickness variation during the spin coating process are numerically studied. The model is said to be I-dimensional because radial variations in film thickness, concentration and temperature are ignored. The finite difference method is employed to solve the equations that are simplified using the similarity transformation. In early time, the film thinning is due to the radial convective outflow. However that slows during the first seconds of spinning so the film thinning due to evaporation of solvent becomes sole. The time varing film thickness is analyzed according to the wafer spin speed, the various solvent fraction in the coating liquid, and the various solvent vapor fraction in the bulk of the overlying gas during the spin coating is estimated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.7 s.166
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• pp.1245-1252
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• 1999

The sliding wear behavior of $Al_2O_3/NiCr$ coating deposited on steel(SM45C) was investigated under lubrication. The parameters of sliding wear are normal loads, coating thickness. As a result, the wear resistance of $Al_2O_3/NiCr$ coating was remarkably greater than that of $Al_2O_3$ coating. The optimized coating thickness was found to be $300{\mu}m$ to ensure good anti-wear. The bond coating played important role in decreasing residual stress. The residual stress had much influence on wear mechanism. These results were correlated with the stress state of coating and the microstructure of coating.

• The Journal of Internal Korean Medicine
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• v.35 no.2
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• pp.157-174
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• 2014

Objectives : The aims of this study were to evaluate the diagnostic values of tongue coating thickness and sterno-costal angle as the quantitative diagnostic indicators in functional dyspepsia. Methods : We surveyed 60 functional dyspepsia patients recruited by the clinical trial, 'Clinical Trial for Evaluation on Availability of tongue diagnosis system (CTS-1000) : a Pilot study'. The patients were classified into three groups according to Rome III criteria for functional dyspepsia, and categorized into five groups according to Instrument of pattern identification for functional dyspepsia. Nepean dyspepsia index-Korean version (NDI-K) score, tongue coating thickness (percentage of tongue coating by tongue diagnosis system (CTS-1000), and weight of tongue coating by microbalance), sterno-costal angle, duration of illness and body mass index (BMI) were investigated. Results : Among the 5 types by instrument of pattern identification for functional dyspepsia, a significant difference of percentage of tongue coating was found. Percentage of tongue coating and weight of tongue coating showed significant correlation with total NDI-K score. Sterno-costal angle showed strong positive correlation with BMI and also showed significant difference between the non-overweight (BMI<23, n=32) and overweight ($BMI{\geq}23$, n=28) groups. Conclusions : Tongue coating thickness showed its potential as a new quantitative diagnostic indicator of functional dyspepsia. Further studies on the sterno-costal angle are anticipated to evaluate its potential as a new quantitative diagnostic indicator.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.217-218
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• 2011

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.66 no.2
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• pp.94-97
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• 2017

A method of improving the anti-fouling characteristics of porcelain insulators was proposed in this study. Functional coating was performed as a method of reducing the surface contamination of the porcelain insulators. The functional coating was applied on a ceramic substrate, which has the same material as the porcelain insulators. After coating the ceramic substrate 2, 3, 4, and 5 times alternately in the horizontal and vertical directions, the surface characteristics according to the thickness of the coating film were analyzed. The optimal process was selected to coat the surfaces of the post insulators and long rod insulators, which are the representative porcelain insulators. After coating, heat treatment was performed for 1 hour at $200^{\circ}C$ in a furnace to secure the durability of the coating film. Compared to the uncoated insulators, the insulators with the functional coating showed significantly improved anti-fouling characteristics as well as excellent adhesion to the coated insulator surface.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2955-2960
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• 2007

To control the coating thickness of zinc in the process of continuous hot-dip galvanizing, it is known from early day that the gas wiping through an air knife system is the most effective because of the obtainable of uniformity of coating thickness, possibility of thin coating, working ability in high speed and simplicity of control. But, the gas wiping using in the galvanizing process brings about a problem of splashing from the strip edge for a certain high speed of coating. And, it is known that the problem of splashing is caused mainly by the existence of separation bubble at the neighbor of the strip surface. In theses connections, in the present study, we proposed two kinds of air knife systems having the same expansion rate of nozzle, and the jet structures and coating thicknesses from a conventional and new proposed nozzles are compared. In numerical analysis, the governing equations consisted of two-dimensional time dependent Navier-Stokes equations, standard ${\kappa}-{\varepsilon}$ turbulence model to solve turbulence stress and so on are employed. As a result, it is found that it had better to use the constant rate nozzle from the point view of the energy saving to obtain the same coating thickness. Also, to reduce the size of separation bubble and to enhance the cutting ability at the strip, it is recommendable to use an air knife having the constant expansion rate nozzle.