• Journal of Powder Materials
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• v.28 no.5
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• pp.396-402
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• 2021

Stainless steel, a type of steel used for high-temperature parts, may cause damage when exposed to high temperatures, requiring additional coatings. In particular, the Cr₂O₃ product layer is unstable at 1000℃ and higher temperatures; therefore, it is necessary to improve the oxidation resistance. In this study, an aluminide (Fe₂Al₅ and FeAl₃) coating layer was formed on the surface of STS 630 specimens through Al diffusion coatings from 500℃ to 700℃ for up to 25 h. Because the coating layers of Fe₂Al₅ and FeAl₃ could not withstand temperatures above 1200℃, an Al₂O₃ coating layer is deposited on the surface through static oxidation treatment at 500℃ for 10 h. To confirm the ablation resistance of the resulting coating layer, dynamic flame exposure tests were conducted at 1350℃ for 5-15 min. Excellent oxidation resistance is observed in the coated base material beneath the aluminide layer. The conditions of the flame tests and coating are discussed in terms of microstructural variations.

• Journal of the Korean Society of Visualization
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• v.21 no.3
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• pp.15-22
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• 2023

This research introduces an innovative approach for fabricating microstructure surfaces using spray-coating deposition. The resulting surface, referred to as Magnetically Responsive Microstructures (MRM), exhibits hierarchically structured micro-pillar arrays with remarkably high aspect ratios. The fabrication process involves precisely mixing PDMS and hexane with Carbonyl iron powders, followed by ultrasonication and spray-coating on the top of a PDMS substrate placed on the neodymium magnet. The MRM surface shows hydrophobic properties, characterized by a contact angle surpassing 150° and an aspect ratio exceeding 10. Through a comprehensive exploration of critical parameters, including spray amount, magnet-substrate distance, and solution ratio enhanced dynamic tunability and exceptional hydrophobic characteristics are attained. This novel approach holds significant potential for diverse applications in the realm of dynamically tunable microstructures and magnetically responsive surfaces.

• Fashion & Textile Research Journal
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• v.14 no.4
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• pp.635-640
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• 2012

In this study, thermoplastic urethane (TPU) coating yarns were prepared at various extruding temperatures. The fine structure and mechanical properties of resultant TPU coating yarns examined by the wide angle X-ray diffractometer (WAXD), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and tensile test. TPU coating yarns (prepared at extruding temperatures at $175^{\circ}C$) were confirmed as a stable fine structure that obtained excellent tensile strength and flexibility. The C samples prepared by optimized conditions made by TPU woven floor mat. The structure of the woven mat is $4{\times}4$ basket weave and have laminated with the EVA foam to obtained final TPU woven floor mat products. The resultant TPU woven floor mat was obtained to 1.5MN of tensile strength, 22% of the elongation, and 0.2MN of tear strength. The weight loss abrasion and the resilience by the ball rebound of the TPU-woven floor mat was prior to those of the PVC subsequently, we were able to develop a woven floor mat with TPU coating yarn and produce an eco-friendly high valuable woven floor mat using an interior product.

• International Journal of Naval Architecture and Ocean Engineering
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• v.3 no.4
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• pp.242-253
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• 2011

Skin frictional drag reduction efficiency of "stiff" compliant coating was investigated in a wind tunnel experiment. Flat plate compliant coating inserts were installed in a wind tunnel and the measurements of skin frictional drag and velocity field were carried out. The compliant coatings with varying viscoelastic properties had been prepared using different composition. In order to optimize the coating thickness, the most important design parameter, the dynamic viscoelastic properties had been determined experimentally. The aging of the materials (variation of their properties) during half a year was documented as well. A design procedure proposed by Kulik et al. (2008) was applied to get an optimal value for the coating thickness. Along with the drag measurement using the strain balance, velocity and pressure were measured for different coatings. The compliant coatings with the thickness h = 7mm achieved 4~5% drag reduction within a velocity range 30~40 m/s. The drag reduction mechanism of the attenuation of turbulence velocity fluctuations due to the compliant coating was demonstrated. It is envisioned that larger drag reduction effect is obtainable at higher flow velocities for high speed trains and subsonic aircrafts.

• Elastomers and Composites
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• v.53 no.4
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• pp.195-201
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• 2018

Three kinds of rubber compounds were prepared, and their underwater acoustical properties were investigated for anechoic coating. Dynamic mechanical properties of the rubber compounds were measured using a dynamic mechanical analyzer and extended to 100 kHz using time-temperature superposition. The sound speed, reflection coefficient, and attenuation constant were calculated. Silicone rubber showed the lowest reflection coefficient, and nitrile rubber showed the highest attenuation constant. The acoustic properties of nitrile rubber compounds with various compositions were investigated. The sound speed, reflection coefficient, and transmission coefficient of the nitrile rubber in the frequency range of 200-1000 kHz were measured in a water-filled tank.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.1
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• pp.73-80
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• 2008

An improved method to measure the dynamic viscoelastic properties of elastomers is proposed. The method is based on the analysis of forced oscillation of a cylindrical sample loaded with inertial mass. No special equipment or instrumentation other than the ordinary vibration measurement apparatus is required. Typical measurement of the viscoelastic properties of a silicone rubber $Silastic^{(R)}$ S2 were measured over the wide frequency range from 10 Hz to 3 kHz under the action of wide region of deformation from $10^{-4}%$ to 5%. It was shown that modulus of elasticity and loss tangent fall on the single curves when the ratio of load mass to sample mass changed from 1 to 20.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.11
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• pp.344-349
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• 2018

This paper proposes a method of designing the main parameters of the Teflon coating equipment of a guide wire used in medical treatment. The proposed device was designed to be guided by a reel-to-reel method in which the guide wire performs all processes continuously, such as Teflon coating and heat treatment. At this time, the conveyed guide wire vibrates between the rollers, which affects the quality of the coating. Therefore, this paper proposes a dynamic equation of the guide wire to be transported in the longitudinal direction, and design parameters setting method of the feed speed and the interval of the roller supporting the wire is proposed to minimize the vibration amplitude of the guide wire during transport. The Teflon coating of the medical guide wire was carried out based on the developed coating equipment. The target coating thickness of the guide wire was set to less than $10{\mu}m$ in the circumferential direction, and the results were examined by optical microscopy.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.29 no.2
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• pp.7-15
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• 1997

High shear viscosity at several solids levels was measured for a number of pigment slurries and coating colors containing either anionic or amphoteric latex and analyzed according to Mooney and Eiler equations. Maximum packing fraction and intrinsic viscosity were obtained and compared. Eiler equation provides more credible information than Mooney equation on particle packing and intrinsic viscosity. The packing fraction obtained from Eiler equation was slightly greater than that obtained from static FCC measurement indicating the influence of pigment movement under the dynamic condition. Amphoteric latex caused 4-5% increase of maximum packing fraction of a coating color when its pH is lowered from 7 to 6, while anionic latex did not show any significant change in packing characteristics.

• 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.

• Journal of the Korean institute of surface engineering
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• v.34 no.2
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• pp.115-124
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• 2001

Gas wiping process of continuously hot-dip galvanized coating on steel strip has noise and coating problems. To improve the qualify of product, characteristics of air flow on the steel surface must be investigated. In this paper, fluid dynamic model of the gas flow is setup and solved numerically using STAR-CD. The effects of edge baffle, distance between steel plane edge and baffle, inlet pressure, and gap between air knife and strip steel surface are investigated, and it is concluded that edge baffle can reduce over-coating and edge built-up.