• Journal of the Korean institute of surface engineering
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• v.56 no.6
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• pp.443-450
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• 2023

SiC/SiC_f CMC is vulnerable to water vapor corrosion at a high temperature of 1500℃. So, EBC (Environmental Barrier Coating) materials are required to protect Si-based CMCs. Ytterbium silicates are reported to have coefficient of thermal expansion (CTE) similar to that of the base material, such as SiC/SiC_f CMC. When the EBC are materials exposed to high temperature environment, the interface between ytterbium silicates and SiC/SiC_f CMC is not separated, and the coating purpose can be safely achieved. For the perspective of EBC applications, thermally grown oxide (TGO) layer with different CTE is formed by the reaction with water vapor in EBC, which leads to a decrease in life time. In this study, we prepare two types of ytterbium silicates to observe the corrosion behavior during the expose to high temperature and water vapor. In order to observe this behavior, the steam-jet furnace is prepared. In addition, phase formation of these ytterbium silicates is analyzed with microstructures by the before/after steam-jet evaluation at 1500℃ for 100 h.

• Journal of the Korean institute of surface engineering
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• v.48 no.5
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• pp.218-226
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• 2015

The goal of this study is to investigate a metal cladding that contains SiC composites as a protective layer and analysis the characteristics of the specimens on high temperature oxidation To make SiC composites, the current process needs a high temperature (about $1100^{\circ}C$) for the infiltration of fixing materials such as SiC. To improve this situation, we need a low temperature process. In this study, we developed a low temperature process for making SiC composites on the metal layer, and we have made two kinds: cladding with protective SiC composites made by polycarbosilane(PCS), and a PCS filling method using supercritical carbon dioxide. A corrosion test at $1200^{\circ}C$ in a mixed steam and Ar atmosphere was performed on these specimens. The result show that the cladding with protective SiC composites have excellent oxidation suprression rates. This study can be said to have developed new metal cladding with enhanced durability by using SiC composite as protective films of metal cladding instead of simple coating film.

• Transactions of Materials Processing
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• v.24 no.6
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• pp.405-410
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• 2015

Sheet-forming of Mg alloys is conducted at elevated temperatures (250℃) due to the low formability at room temperature. The high-temperature process often gives rise to surface damage on the alloy (i.e. galling.) In the current study, the frictional characteristics of DLC coating slid against an AZ31 Mg alloy at various temperatures were investigated. The coating has been used widely for low-friction processes. Dry-sliding friction and galling characteristics of an AZ31 Mg alloy (disk), which slid against uncoated and a DLC-coated STD-61 steel (pin), were investigated using a reciprocating-sliding tribometer at room temperature and 250℃. To represent the real sliding phenomena during a sheet metal forming process, single-stroke tests were used (10mm stroke length) rather than a reciprocating long sliding-distance test. The DLC coating suppressed adhesion between the alloy and the tool steel at room temperature, and exhibited a low friction coefficient. However, during sliding at 250℃, severe adhesion occurred between the two surfaces, which resulted in a high friction coefficient and galling.

• Journal of the Korean Ceramic Society
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• v.52 no.5
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• pp.338-343
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• 2015

To prevent an interfacial reaction between the anode and the electrolyte layer during the conventional high-temperature co-firing process, an anode-supported type cell with a thin-film electrolyte was fabricated by low-temperature ceramic thick film coating process. Ni-GDC cermet composite was used as the anode material and YSZ was used as the electrolyte material. Open circuit voltage and maximum power density were found to strongly depend on the surface uniformity of the anode functional layer. By optimizing the microstructure of the anode functional layer, the open circuit voltage and maximum powder density of the cell increased to 1.11 V and $1.35W/cm^2$, respectively, at $750^{\circ}C$. When a GDC barrier layer was applied between the YSZ electrolyte and the LSCF cathode, the cell showed good stability, with almost no degradation up to 100 h. Anode-supported type SOFCs with high performance and good stability were fabricated using a coating process.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.82.2-82.2
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• 2010

The development of bipolar plate having high efficiency and chemical properties has a major impact on fuel cell applications commercialization. Even though graphite bipolar plate has high electric conductivity and chemical resistance, it has demerits about mass production and brittle property for commercialization. Hence, metallic bipolar plate can be substitute for fuel cell bipolar plate. Although its inadequate corrosion behavior under PEMFC environment lead to a deterioration of membrane by dissolved metal ions, metallic bipolar plate for PEMFC is more suitable for automotive and residential power generation system because of its high mechanical strength, low gas permeability and applicability to mass production. Therefore, several types of coating has been applied to prevent corrosion and oxide film growth and to achieve more high durability. This work presents durability of coated metal bipolar plate for low temperature PEMFC which made for fuel cell vehicle. This results showed surface treatment increase long-term durability, even electric conductivity and corrosion resistance.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.6
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• pp.895-900
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• 2013

Several plasma spray and metallurgical surface coatings such as $Al_2O_3$, $Cr_2O_3$, WC-Ni, and chromizing coating have been examined for their application in environments with high temperature, wear, and corrosion. The chromizing coating is different from others coatings in the manufacturing process the surface. These coatings' characteristics were tested experimentally, and the results were compared. WC-Ni shows good performance against thermal barrier, wear, and corrosion and is one of the best candidates for the environment considered herein. These coatings were studied for their application in the steel manufacturing industry. The most commonly required functions in this industry are thermal and wear resistance.

• Journal of ILASS-Korea
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• v.13 no.4
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• pp.193-199
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• 2008

Spray coating is a versatile surface modification technology in which coating is built-up based on the successive deposition of micron-scaled particles. Depending on the coating materials, the coatings can meet the required mechanical properties, corrosion resistance, and other properties of base materials. Spraying processes are mainly classified into thermal and kinetic spraying according to their bonding mechanism and deposition characteristics. Specifically, thermal spraying process can be further classified into many categories based on the design and mechanism of the process, such as frame spraying, arc spraying, atmospheric plasma spraying (APS), and high velocity oxygen-fuel (HVOF) spraying, etc. Kinetic spraying or cold gas dynamic spraying is a newly emerging coating technique which is low-temperature and high-pressure coating process. In this paper, overall view of thermal and kinetic spray coating technologies is discussed in terms of fundamentals and industrial applications. The technological characteristics and bonding mechanism of each process are introduced. Deposition behavior and properties of technologically remarkable materials are reviewed. Furthermore, industrial applications of spray coating technology and its potentials are prospected.

• Carbon letters
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• v.8 no.2
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• pp.91-94
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• 2007

The application of Carbon and graphite based materials in unprotected environment is limited to a temperature of $450^{\circ}C$ or so because of their susceptibility to oxidation at this temperature and higher. To over come these obstacles a low cost chemical vapour reaction process (CVR) was developed to give crystalline and high purity SiC coating on graphite and isotropic C/C composite. CVR is most effective carbothermal reduction method for conversation of a few micron of carbon layer to SiC. In the CVR method, a sic conversation layer is formed by reaction between carbon and gaseous reagent silicon monoxide at high temperature. Characterization of SiC coating was carried out using SEM. The other properties studied were hardness density and conversion efficiency.

• Journal of the Semiconductor & Display Technology
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• v.18 no.3
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• pp.12-18
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• 2019

The protective double layer polymer coatings on silica optical fibers are realized by wet-on-wet liquid coating process and they play an important role in final quality of mass produced optical fibers. This numerical study aims to analyze the effects of secondary coating die design parameters by employing two dimensional axisymmetric model of coating cup and coating die geometry and computational fluid dynamics simulations which include temperature dependent viscosity of polymer coating liquids and viscous dissipation heating. Under high speed fiber drawing conditions and pressurized coating liquid supply, the effects of converging die angle are investigated in order to appreciate the change of coating liquid flow patterns such as flow recirculation zone near coating die as well as primary and secondary coating layer thicknesses. The auxiliary coating die to converging coating die is also tested and the results find that this concept is advantageous in achieving stable double layer coatings on silica glass fiber.

• Korean Journal of Materials Research
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• v.27 no.11
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• pp.577-582
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• 2017

Self-cleaning and photocatalytic $TiO_2$ thin films were prepared by a facile sol-gel method followed by spin coating using peroxo titanic acid as a precursor. The as-prepared thin films were heated at low temperature($110^{\circ}C$) and high temperature ($400^{\circ}C$). Thin films were characterized by X-ray diffraction(XRD), Field-emission scanning electron microscopy(FESEM), UV-Visible spectroscopy and water contact angle measurement. XRD analysis confirms the low crystallinity of thin films prepared at low temperature, while crystalline anatase phase was found the for high temperature thin film. The photocatalytic activity of thin films was studied by the photocatalytic degradation of methylene blue dye solution. Self-cleaning and photocatalytic performance of both low and high temperature thin films were compared.