• Journal of Welding and Joining
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• 제20권5호
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• pp.120-126
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• 2002

Ni-5%Al alloy powder is widely used as the bond coating powder to improve the adhesive strength between the substrate and coating. The important properties in the bond coating are the deposition efficiency and surface roughness. In this study, it was tried to optimize the plasma spray parameters to maximize the deposition efficiency and surface roughness. In the first step, spray current and hydrogen gas flow rate were optimized in order to increase the deposition efficiency. In the next step, the seven plasma spray variables were selected and optimized to improve both the deposition efficiency and surface roughness using the Taguchi experimental method. By these optimization, the deposition efficiency was improved from about 10 % at the frist time to 51.2 % by the optimization of spray current and hydrogen gas flow rate and finally to 65.2 % by the Taguchi experimental method. The average surface roughness was increased from about $12.9\mu\textrm{m}$ to $15.4\mu\textrm{m}$.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 추계학술대회 논문집
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• pp.391-392
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• 2009

• Journal of Welding and Joining
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• 제18권6호
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• pp.96-101
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• 2000

Sintered alumina ceramic substrate has been used for the insulating substrate for thick Hybrid IC owing to its cheapness and good insulating properties. Some of thick HIC's are important to eliminate the heat emitted from the parts that are mounted on the ceramic substrate. Sintered ceramic substrate can not transfer and emit the heat efficiently. It's been tried to do plasma spray coating of alumina ceramic on the metal substrates that have a good heat emission property. The most important properties to commercialize this ceramic coated metal substrate are surface roughness and deposition efficiency. In this study, plasma spray coating parameters are optimized to minimize the surface roughness and to maximize the deposition efficiency using Taguchi experimental method. By this optimization, the deposition efficiency was greatly improved from 35% at the frist time to 75% finally.

• 한국가시화정보학회지
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• 제21권3호
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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.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.145-148
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• 2006

Cold gas dynamic spray is a relatively new coating process by which coatings can be produced without significant heating during the process. Cold gas dynamic spray is conducted by powder sprayed by supersonic gas jet, and generally called the kinetic spray or cold-spray. Cold-spray was developed in Russia in the early 1980s to overcome the defect of thermal spray method. Its low process temperature can minimize thermal stress and also reduce the deformation of the substrate. Most researches on cold-spray have focused on micro scale coating, but our research team tried to apply this method to macro scale deposition. The macro scale deposition causes deformation of a thin substrate which is usually convex to the deposited side. In this research, the main cause of the deformation was investigated using 6061-T6 aluminum alloy and properties of deposited aluminum layer such as coefficient of thermal expansion, Elastic modulus, hardness, electric conductivity were measured. From the result of the analysis, it was concluded that compressive residual stress was the main reason of substrate deformation while CTE had little effect.

• 한국재료학회지
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• 제24권1호
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• pp.60-65
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• 2014

Fe-based amorphous coatings were fabricated on a soda-lime glass substrate by the vacuum kinetic spray method. The effect of the gas flow rate, which determines particle velocity, on the deposition behavior of the particle and microstructure of the resultant films was investigated. The as-fabricated microstructure of the film was studied by field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HR-TEM). Although the activation energy for transformation from the amorphous phase to crystalline phase was lowered by severe plastic deformation and particle fracturing under a high strain rate, the crystalline phases could not be found in the coating layer. Incompletely fractured and small fragments 100~300 nm in size, which are smaller than initial feedstock material, were found on the coating surface and inside of the coating. Also, some pores and voids occurred between particle-particle interfaces. In the case of brittle Fe-based amorphous alloy, particles fail in fragmentation fracture mode through initiation and propagation of the numerous small cracks rather than shear fracture mode under compressive stress. It could be deduced that amorphous alloy underwent particle fracturing in a vacuum kinetic spray process. Also, it is considered that surface energy caused by the formation of new surfaces and friction energy contributed to the bonding of fragments.

• 한국표면공학회지
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• 제41권6호
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• pp.255-263
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• 2008

Generally, deposition mechanism of diamond particle is mainly embedding effect in the kinetic spray process. Accordingly, in spite of high cost, helium gas was employed as process gas to get high diamond fraction in the composite coating. In this study, the deposition behavior of bronze/diamond by kinetic spray process was compared using different process gas (helium and nitrogen). Bare (mean size of $5{\mu}m$, $20{\mu}m$) and nickel coated diamond (mean size of $26{\mu}m$) were deposited on Al 6061-T6 substrate with fixed process temperature and pressure. For comparison with experimental results, plastic deformation behavior of nickel layer was simulated by finite element analysis (using ABAQUS/Explicit 6.7-2). The size, broken ratio, and fraction of diamond in the composite coating were analyzed through scanning electron microscopy and image analysis method. The uniform distribution and deposition efficiency of diamond particles in the coating layer could be achieved by tailoring the physical properties of the feedstock.

• 한국재료학회지
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• 제24권2호
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• pp.98-104
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• 2014

Vacuum kinetic spray(VKS) is a relatively advanced process for fabricating thin/thick and dense ceramic coatings via submicron-sized particle impact at room temperature. However, unfortunately, the particle velocity, which is an important value for investigating the deposition mechanism, has not been clarified yet. Thus, in this research, VKS average particle velocities were derived by numerical analysis method(CFD: computational fluid dynamics) connected with an experimental approach(SCM: slit cell method). When the process gas or powder particles are accelerated by a compressive force generated by gas pressure in kinetic spraying, a tensile force generated by the vacuum in the VKS system accelerates the process gas. As a result, the gas is able to reach supersonic speed even though only 0.6MPa gas pressure is used in VKS. In addition, small size powders can be accelerated up to supersonic velocity by means of the drag-force of the low pressure process gas flow. Furthermore, in this process, the increase of gas flow makes the drag-force stronger and gas distribution more homogenized in the pipe, by which the total particle average velocity becomes higher and the difference between max. and min. particle velocity decreases. Consequently, the control of particle size and gas flow rate are important factors in making the velocity of particles high enough for successful deposition in the VKS system.

• 전기화학회지
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• 제11권2호
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• pp.95-99
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• 2008

본 연구에서는 ESD(Electrostatic spray deposition) 코팅법을 이용하여 지르코늄 산화물을 티타늄에 코팅한 전극을 제조하였다. 전처리과정에서 티타늄 기판의 에칭 방법 효율과 에칭된 티타늄 기판에 지르코늄 산화물 막의 제조 및 전기 화학적 특성에 대하여 연구하였다. 염산 에칭은 티타늄 기판에 가늘고 균일한 홈이 생성된다. 강력한 산화제로 사용되는 오존과 차아염소산을 생성하는 효과적인 금속 산화물 전극의 제작과 물질의 특성에 대해 고찰하였고 참고문헌을 통해 지그코늄 산화물에 초점을 맞추었다. 지르코늄 산화물 전극의 제작의 재현성을 향상시키기 위한 코팅 방법으로 지르코늄 옥시클로라이드의 ESD 코팅법을 사용하였다. 티타늄 기판 위에 지르코늄 산화물 막의 형성에 대한 테스트로 SEM, XRD, Cyclic voltammery를 수행하였다.

• International Journal of Precision Engineering and Manufacturing
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• 제9권1호
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• pp.51-53
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• 2008

A new nano-particle deposition system (NPDS) was developed for a ceramic and metal coating process. Nano- and micro-sized powders were sprayed through a supersonic nozzle at room temperature and low vacuum conditions to create ceramic and metal thin films on metal and polymer substrates without thermal damage. Ceramic titanium dioxide ($TiO_2$) powder was deposited on polyethylene terephthalate substrates and metal tin (Sn) powder was deposited on SUS substrates. Deposition images were obtained and the resulting chemical composition was measured using X-ray photoelectron spectroscopy. The test results demonstrated that the new NPDS provides a noble coating method for ceramic and metal materials.