• 한국주조공학회지
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• 제18권6호
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• pp.593-603
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• 1998

Commercial ductile iron was coated with titanium and aluminum powders by low pressure plasma spraying and then irradiated with a $CO_2$ laser to produce anti-corrosive TiC composite layer. TiC carbides were precipitated homogeneously in a laser alloyed layer by in-situ reaction between carbon existed in the base metal and titanium with thermal sprayed coating. The formation of gas pores and brittle limited mixing zone with ledeburite microstructure in TiC composite layer were surpressed by the complementary alloying of aluminum. The hardness of TiC composite layer obtained by addition of titanium and aluminum was between 600 and 660 Hv, which was three times as high as the hardness of ferritic ductile iron. From the results of isothermal oxidation at 1123k for 24 hours in air, high temperature oxidation resistance of the TiC composite layer with aluminum was improved and doubled when compared with the TiC composite layer without aluminum.

• 한국군사과학기술학회지
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• 제12권2호
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• pp.206-212
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• 2009

The pressurized spray system with nitrogen gas was designed to fabricate the spherical AN(ammonium nitrate) particles. When AN melt was sprayed from a nozzle with equivalent diameter of 0.28mm into an ambient dry air, the ligament breakup mechanism of the molten AN was found to be responsible for the droplet formation(or disintegration) of AN melt. In the experimental range of spray temperature with $170{\sim}200^{\circ}C$ and atomization pressure with $0.1{\sim}0.4MPa$, the spherical AN particles with mean diameter of $130{\sim}250{\mu}m$ were obtained.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.253-253
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• 2010

The Polymer/MWCNT composite films were fabricated by air-spray method under the 2 kg/$cm^2$ pressure using the multi-walled CNTs solution and the polymer on a $50{\mu}m$ kepton film substrates. We obtained the composite films which were sprayed with the MWCNT dispersion. In order to analysis the microstructure for the fabricated Polymer/MWCNT film, we used the X-ray diffraction (XRD) and SEM.

• 한국전기전자재료학회논문지
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• 제23권4호
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• pp.338-342
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• 2010

Carbon nanotubes (CNTs) have excellent electrical, chemical stability, mechanical and thermal properties. The MWCNT films were investigated as a transparent electrode for the solar cell, OLED, and field-emission display. MWCNT films were fabricated by air spray method, whose process is quite low-costed, using the multi-walled CNTs solution on glass substrates. Moreover, the most stable film was fabricated when the spraying time was 60 sec. The film that was sprayed with the MWCNT dispersion for 60 sec, has 300nm thick. And its electric resistivity, transmittance rate, mobility and carrier concentration are $6{\times}10^{-2}{\Omega}{\cdot}cm$, 50% at ${\lambda}=550mm$, $4.3{\times}10^{-2}cm^2/V{\cdot}s$ and $2.1{\times}10^{21}cm^{-3}$, respectively. Also, absorption energy of MWCNT films show from 3.9 eV to 4.6 eV. Furthermore, we can use MWCNT films fabricated by the spray method for the transparent electrode.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년도 춘계 학술대회 개요집
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• pp.45-47
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• 2006

The rotating components in the hot sections of land-based gas turbine are exposed to severe environments during several tens thousand operation hours at above $1100^{\circ}C$ operation temperature. To protect such components from high temperature oxidation, an intermediate bond coat is applied, typical of a MCrAlY-type metal alloy. This study is concerned with the thermal cyclic behavior of thermal barrier coatings. The MCrAlY bond coatings are deposited by HVOF (High Velocity Oxygen Fuel) method on a nickel-based superalloy (GTD-111). Thermal cyclic tests at $1100^{\circ}C$ in ambient air for various periods of time were used to evaluate the thermal cyclic resistance of the TBC coating. The microstructure and morphology of as-sprayed and of thermal cycled coatings were characterized by scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD).

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1998년도 춘계 학술대회논문집
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• pp.128-137
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• 1998

In this numerical experiment, the preconditioned compressible Navier-Stokes equation is tested to analyze the laminar spray combustion. Sprayed flow field is formulated by Eulerian-Lagrangian system for the gas and liquid phases each. DSF(Deterministic Separated Flow) model was adopted for the sprays with the vortex model to describe transients of individual droplet heating. Simplified single global reaction model approximates methanol-air reaction with and without disk flame holder. The equation system is discretized by finite difference technique and time integrated by LU-SGS. Due to greatly simplified chemical reaction mechanism and the lack of experimental evidences, most of the efforts were devoted to show the applicability and robustness of preconditioned compressible flow calculation algorithm. Computation results in qualitatively reasonable combusting flow field, hence it is believed that further refinement are required to produce quantitatively accurate solutions.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.1-5
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• 2008

An experimental study was performed to develop the rotational fuel injection system of the micro turbojet engine. In this system, fuel is sprayed by centrifugal forces of engine shaft. The test rig was designed and manufactured to get droplet information on combustion space. This experimental apparatus consist of a high speed rotational device(Air-Spindle), fuel feeder, rotational fuel injector and acrylic case. To understand spray characteristics, spray droplet size, velocity and distribution were measured by PDPA (Phase Doppler Particle Analyzer) and spray was visualized by using Nd-Yag laser-based flash photography. From the test results, the length of liquid column from injection orifice is controlled by the rotational speeds and Sauter Mean Diameter(SMD) is decreased with rotational speed. Also, Sauter Mean Diameter is increased as increasing mass flow rate at same rotational speeds.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.602-606
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• 2006

The electrostatic is well known phenomena. The fires and explosions caused by electrostatic occur often in the coating mechanical system. This paper presents various cases of electrostatic hazards, reasons why electrostatic hazards are happened, and methods for preventing electrostatic hazards. Generally the electrostatic can be lead to corona discharging, streaming electrification, and impinging electrification in the coating process. Corona discharging happens at electrostatic spray gun with 70 kV. Streaming electrification occurs at mixing process between paint and thinner, and transportation process with thinner. Impinging electrification is shown when the thinner are sprayed to drums. For the purpose of preventing the electrostatic discharge and damage, conductors should be ground, surface electric potential of should be decreased in using electrostatic shielding and ground, and flow of thinner should be controlled acceptable velocity.

• 반도체디스플레이기술학회지
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• 제9권2호
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• pp.117-121
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• 2010

The composite films were fabricated by air-spray method under the 2 kgf/$cm^2$ pressure using the multi-walled CNTs solution and the nitrocellulose on a 10 ${\mu}m$ polyimide film substrates. We obtained the composite films which were sprayed with the MWCNT dispersion by varying the spray time from 20, 40 and 60sec. The electrical and the optical properties of the sandwiched-structure-composite thin films were investigated by an UV/VIS spectrometer and a Hall Effect equipment. As a result, the optical transmittance of all thin films in the visible range, as well as the electrical conductance shows an available value for the transparent electrode. The carrier concentration and the light transmittance rate for the fabricated sample are between $3.733{\times}10^{10}$ and $6.551{\times}10^{14}cm^{-3}$, around 35 to 95%, respectively.

• 한국자동차공학회논문집
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• 제22권5호
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• pp.20-28
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• 2014

The high velocity oxygen fuel spraying (HVOF) is a kind of surface modification process technology to form the sprayed coating layer after spraying the powder to molten or semi-molten state by the ultra-high speed at the high-temperature heat source and conflicting with a substrate. It is desirable to melt completely the thermal spray powder in order to produce the coating layer with an optimal adhesion, however, because a semi-molten powder in a spray process has the low efficiency and become a factor that degrades the mechanical property by the inducement of pore-forming within the coating layer. To improve the wear resistance, corrosion resistance and heat resistance, in this study, the plungers of high-speed and ultra-high pressure reciprocating hydraulic pumps for oil and water used in ironwork are produced with $420J_2$ and the coating layers of plungers are formed by the powders of WC-Co-Cr and WC-Cr-Ni including the high hardness WC. The surface of these plungers is modified by the super-mirror face grinding machine using variable air pressure developed in this laboratory, and then the characteristics of cross-sectional microstructure, and surface roughness and hardness values between no operation and 100 days-operation are examined and made a comparison. The fine tops and bottoms on surface roughness curve of oil-hydraulic pump plunger sprayed by WC-Cr-Ni are molded more and higher than those of water-hydraulic pump sprayed by WC-Co-Cr because the plunger diameter of oil-hydraulic pump is 0.4 times smaller than that of water-hydraulic pump and the pressure of oil-hydraulic pump exerted on the plunger is operated with the 70 bars higher than that of water-hydraulic pump. As a result, it is found that the values of centerline average surface roughness and maximum height for oil-hydraulic pump plunger are bigger than those of water-hydraulic pump plunger.