• 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.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.156-156
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• 2016

The effect of nitrogen doping on the mechanical and tribological performance of single-layer tetrahedral amorphous carbon (ta-C:N) coatings of up to $1{\mu}m$ in thickness was investigated using a custom-made filtered cathode vacuum arc (FCVA). The results obtained revealed that the hardness of the coatings decreased from $65{\pm}4.8GPa$ to $25{\pm}2.4GPa$ with increasing nitrogen gas ratio, which indicates that nitrogen doping occurs through substitution in the $sp^2$ phase. Subsequent AES analysis showed that the N/C ratio in the ta-C:N thick-film coatings ranged from 0.03 to 0.29 and increased with the nitrogen flow rate. Variation in the G-peak positions and I(D)/I(G) ratio exhibit a similar trend. It is concluded from these results that micron-thick ta-C:N films have the potential to be used in a wide range of functional coating applications in electronics. To achieve highly conductive and wear-resistant coatings in system components, the friction and wear performances of the coating were investigated. The tribological behavior of the coating was investigated by sliding an SUJ2 ball over the coating in a ball-on-disk tribo-meter. The experimental results revealed that doping using a high nitrogen gas flow rate improved the wear resistance of the coating, while a low flow rate of 0-10 sccm increased the coefficient of friction (CoF) and wear rate through the generation of hematite (${\alpha}-Fe_2O_3$) phases by tribo-chemical reaction. However, the CoF and wear rate dramatically decreased when the nitrogen flow rate was increased to 30-40 sccm, due to the nitrogen inducing phase transformation that produced a graphite-like structure in the coating. The widths of the wear track and wear scar were also observed to decrease with increasing nitrogen flow rate. Moreover, the G-peaks of the wear scar around the SUJ2 ball on the worn surface increased with increasing nitrogen doping.

• Journal of the Korean Ceramic Society
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• v.49 no.1
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• pp.95-99
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• 2012

Silicon carbide ceramics are used for oxidation resistive coating films due to their excellent properties like high strength, good oxidation resistance, and good abrasion resistance, but they have poor formability and are prepared by vapor process which is complicated, costly, and sometimes hazardous. In this study, preparation of silicon carbide coating film by liquid process using polymer precursor was attempted. Coating film was prepared by dip coating on substrate followed by heat treatment in argon at $1200^{\circ}C$. By changing the dipping speed, the thickness was controlled. The effects of plasticizer, binder, or fiber addition on suppression of crack generation in the polymer and ceramic films were examined. It was found that fiber additives was effective for suppressing crack generation.

• Transactions of the Society of Information Storage Systems
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• v.2 no.3
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• pp.178-183
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• 2006

A Blu-ray disc, which has a more than 25GB optical capacity, has been known as a promising next-generation optical disc format. It commonly has a 1.1 mm thick substrate and a 0.1 mm thick cover layer for beam transmitting and the protection of the reflecting surface. The cover layer is generally formed by the spin coating process. However, in conventional spin coating, small bumps are formed along the rim of the disc, which results in the fatal reading error. Numerical simulation of the thin film flow behaviors during spin coating with the commercial solver and optimal spinning conditions was obtained. Thickness distribution of the cover layer according to the variation of substrate's edge shape could be calculated as well. By modifying the shape of the substrate edge shape, the bumps along the disc rim could be minimized, and it was proved that the chamfered edge, around $5{\sim}10$ degree, is the simplest and most effective way to minimize the bumps.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.90-90
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• 2017

Cold spray (Cold gas dynamic spray, kinetic spray) is the latest spray coating process that is known as solid state deposition process. In cold spray, inert gases (typically nitrogen and helium) accelerate powder particles prior to impact onto the substrate. Accelerating particles start to deposit onto the substrate after reaching certain critical velocities depending on the coating materials and substrate. Since process gas temperatures are kept below to melting temperature of the coating materials, it is possible to spray temperature sensitive materials such as copper and titanium, nanocrystal materials, and amorphous metals without affecting the phase change and oxide formation. It is also possible to deposit thick coatings because cold spray coatings present compressive residual stresses. This ability to deposit thick coatings is suitable to repair or rebuild parts as an additive manufacturing process. In this presentation, cold spray is introduced and compared to other additive manufacturing processes such as laser and electron beam based processes. It is also presented some applications especially in the view point of additive manufacturing process.

• International journal of advanced smart convergence
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• v.11 no.2
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• pp.59-63
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• 2022

In this study, we study of luminescent solar concentrators comprise thick glass with broadband antireflection coating deposited on the top surfaces and inorganic phosphor layers contacted on the bottom surfaces. Solar cells are contacted to the lateral surfaces of the glass. Experimental results show the broadband antireflection coating increased the short-circuit current of the solar cell.

• Proceedings of the KIEE Conference
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• 2006.07d
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• pp.2211-2212
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• 2006

Ferroelectric PZT (70/30) thick films were fabricated by the screen printing method. And the PZT (30/70) precusor solution were infiltrated by the spin-coating method on the PZT thick films to obtain a densification. All PZT thick films were sintered at $1050^{\circ}C$ for 10 min. Structural properties, such as crystalline structure, microstructures and compositional ratio, of PZT thick films were investigated with the variation of the number of sol coatings using XRD, SEM and EDS, respectively. All PZT thick films exhibited a perovskite polycrystalline structure without a pyrochloer phase. The thickness of PZT thick films, 4-times screen-printed, was approximately $60{\mu}m$. And the densification of the PZT thick films increased with increasing the number of sol coatings.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.579-580
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• 2006

Ferroelectric PZT (70/30) thick films were fabricated by the screen printing method. And the PZT (30/70) Precusor solution were infiltrated by the spin-coating method on the PZT thick films to obtain a densification. All PZT thick films were sintered at $1050^{\circ}C$ for 10min. Structural properties, such as crystalline structure, microstructures and compositional ratio, of PZT thick films were investigated with the variation of the number of sol coatings using XRD, SEM and EDS, respectively. All PZT thick films exhibited a perovskite polycrystalline structure without a pyrochloer phase. The thickness of PZT thick films, 4-times screen-printed, was approximately 60fm. And the densification of the PZT thick films increased with increasing the number of sol coatings.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1245-1246
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• 2006

Ferroelectric PZT (70/30) thick films were fabricated by the screen printing method. And the PZT (30/70) precusor solution were infiltrated by the spin-coating method on the PZT thick films to obtain a densification. All PZT thick films were sintered at $1050^{\circ}C$ for 10 min. Structural properties, such as crystalline structure, microstructures and compositional ratio, of PZT thick films were investigated with the variation of the number of sol coatings using XRD, SEM and EDS, respectively. All PZT thick films exhibited a perovskite polycrystalline structure without a pyrochloer phase. The thickness of PZT thick films, 4-times screen-printed, was approximately $60{\mu}m$. And the densification of the PZT thick films increased with increasing the number of sol coatings.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1705-1706
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• 2006

Ferroelectric PZT (70/30) thick films were fabricated by the screen printing method. And the PZT (30/70) precusor solution were infiltrated by the spin-coating method on the PZT thick films to obtain a densification. All PZT thick films were sintered at $1050^{\circ}C$ for 10 min. Structural properties, such as crystalline structure, microstructures and compositional ratio, of PZT thick films were investigated with the variation of the number of sol coatings using XRD, SEM and EDS, respectively. All PZT thick films exhibited a perovskite polycrystalline structure without a pyrochloer phase. The thickness of PZT thick films, 4-times screen-printed, was approximately $60{\mu}m$. And the densification of the PZT thick films increased with increasing the number of sol coatings.