• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.202-206
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• 2009

We studied the spray characteristics of the high-speed rotating fuel injection system. The diameter of in-line injection orifices are varied from 1mm to 5mm and the number of in-line injection orifices are varied from 3 to 12. Droplet size, velocity and spray distribution were measured by the PDPA(Phase Doppler Particle Analyzer) system and spray was visualized. From the test results, the liquid column generated from the injection orifice is mainly controlled by the rotational speeds. Also diameter of injection orifices and number of injection orifices have influence on the diameters of droplet. Consequently, we find out that the basic mechanism of controlling the droplet size is the liquid film thickness in the injection orifice.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1499-1502
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• 2005

Dense $BaMgAl_{10}O_{17}:Eu^{2+}$ phosphor particles with a spherical shape have been synthesized through spray pyrolysis method using basic aluminum nitrate precursor as a spray solution. This $BaMgAl_{10}O_{17}:Eu^{2+}$ particles prepared by the spray pyrolysis have shown the stronger emission intensity compared to the commercially-available $BaMgAl_{10}O_{17}:Eu^{2+}$. However, thermal stability of the BAM:Eu b lue phosphor is very poor due to changing from $Eu^{2+}$ to $Eu^{3+}$ at the thermal process, so brightness of the phosphor decreases. To improve the thermal stability of the dense BAM:Eu phosphor, the spherical BAM:Eu particles were coated with pure $BaMgAl_{10}O_{17}$ layer using the hydrolysis reaction in a solution system. The synthesized powders were characterized by XRD, SEM and PL. On the other hand, the emission properties of the BAM:Eu phosphors coated with $BaMgAl_{10}O_{17}$ layer before and after thermal treatment at $500^{\circ}C$ for 30 min were estimated under VUV excitation. The brightness of the coated phosphor was higher than that of the uncoated phosphor. Also, the coating thickness of BAM layer in the BAM:Eu particles was optimized.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.265-266
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• 2006

The chemical conversion coating formed on magnesium alloy investigated for low cost and harmless in environment by using the colloidal silica as the main component. The film formed in 298 K is thick, the film, which was thought combination of Si-O, was formed. The film formed in 313 K is thinner than that in 298 K. The quantity of film formed at high temperature such as 333 K and 353 K is smaller than dissolved quantity. At the anodic polarization experiment, corrosion resistance in sealing by hot water after chemical conversion treatment in basic solution condition get worse than that in comparison with basic solution condition. In salt spray test, the ratio of black rust on specimen that did not conducted chemical conversion treatment was five times or more compared with those of chemical conversion treated specimen. The film thickness of chemical conversion coating produced by alkali treatment process is thinner than in comparison with that of specimen produced in basic chemical conversion treatment solution condition. It is thought, however, that it showed good corrosion resistance during salt spray test because the area of microcracks is small.

• Progress in Superconductivity
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• v.12 no.1
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• pp.68-73
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• 2010

Y123 films have been deposited on $LaAlO_3$ (100) single-crystal and IBAD substrates by spray pyrolysis method using nitrate precursors. Ultrasonic atomization was adopted to decrease the droplet size, spraying angle and its moving velocity toward substrate for introducing the preheating tube furnace in appropriate location. A small preheating tube furnace was installed between spraying nozzle and substrate for fast drying and enhanced decomposition of precursors. C-axis oriented films were obtained on both LAO and IBAD substrates at deposition temperature of around $710{\sim}750^{\circ}C$ and working pressures of 10~15 torr. Thick c-axis epitaxial film with the thickness of $0.3{\sim}0.6\;{\mu}m$ was obtained on LAO single-crystal by 10 min deposition. But the XRD results of the film deposited on IBAD template at same deposition condition showed that the buffer layers of the IBAD metal substrate was affected by long residence of metal substrate at high temperature for YBCO deposition.

• Journal of the Korean institute of surface engineering
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• v.30 no.5
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• pp.333-346
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• 1997

Plasma spray processes for functional coatings of tubular SOFC ( Soild oxide Fuel Cell).consisting of air electrode, oxide electrolyte, an fuel electrode, are optimized by fully saturated fractional factorial testing. Material and electric characteristics of each coating are analtsed by the implementation of SEM and optical microscope for evaluating microstructure and porosity, X-ray diffraction method for investigating compositional change between raw powder and sprayed coating, and Van der Pauw method for measuring electrical conductivity. LSM ($La_{0.65}Sr_{0.35}MnO_3$air electrode and Ni-YSL fuel electrode coatings have porosities of around 23~30% sufficient for effective fuel and oxidant gas supply to electrochemical reaction interfaces and electrical conductivities of around 90 S/cm and 1000 S/cm, respectively, enough for acting as current collecting electrodes. YSZ($ZrO_2-8mol%Y_2O_3$) electrolyte film has a high ionic conductivities of 0.05~0.07 S/cm at $1000^{\circ}C$ in air atmosphere, but appears to be somewhat too porous to reduce the thickness. for enhancing the cell efficiency. A unit tubular SOFC has beem fabricated by the optimized plasma spray processes for each functional coating and the cell. Its electrochemical chracteristics are investigated by measuring voltage-current and power density with variation of operationg temperature, radio of fuel to air gas flowrates, and total gas flowrate of reactants.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.8
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• pp.620-623
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• 2013

The carbon nanotube / poly-vinylidene fluoride (CNT/PVDF) composite films for the nano-generator devices were fabricated by spray coating method using the CNT/PVDF solution, which was prepared by adding PVDF pellets into the CNT dispersed N-Methyl-2-pyrroli-done (NMP) solution. The flexible CNT/PVDF composite films were investigated by the scanning electron microscopy, which revealed that the CNTs were uniformly dispersed in the PVDF matrix and thickness of the films was approximately $20{\mu}m$. Fourier transform infra-red spectra were used to investigate crystal structure of the as-spray-coated CNT/PVDF films, and we found that they revealed extremely large portion of the ${\beta}$ phase PVDF. The capacitance of the CNT/PVDF films increased by adding CNTs into the PVDF matrix, and finally saturated. However, the resistance didn't show any saturation effect in the CNT concentration range of 0~4 wt%. Finally, the resulting nano-generator devices revealed reasonable current output after given mechanical stress.

• Corrosion Science and Technology
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• v.7 no.6
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• pp.370-374
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• 2008

In this study, we evaluated anti-corrosion properties of both commercial unleaded and lead epoxy primer for automotive substrate before applying to actual painting lines by salt spray test, and cyclic corrosion test, potentiodynamic test and electrochemical impedance spectroscopy. The difference in the corrosion resistance between automotive epoxy primers contained $Bi(OH)_{3}$ and leaded one was investigated. And it was also discussed the effect of zinc phosphate pretreatment to the epoxy primers. The specimen coated epoxy primer contained $Bi(OH)_{3}$ showed 0.5 V higher corrosion potential than that of bare steel. The result of salt spray test did not indicate remarkable difference of corrosion resistance in all specimens above $10{\mu}m$ thickness up to 1200 hours. In the cyclic corrosion test, epoxy primers contained $Bi(OH)_{3}$ on phosphated substrate performed good corrosion properties until 800 hours. The epoxy primer contained $Bi(OH)_{3}$ performed the equivalent corrosion resistance as leaded coating on phosphated steel, but slightly inferior to that of leaded on bare steel. These results show that the pre-treatment of zinc phosphate is effective as well as pigment changing in performing anti-corrosion properties in automotive bodies.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.432-432
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• 2010

Organic light emitting diodes (OLED) thin films were fabricated by Electrostatic spray deposition (ESD). In this study, we reported the thickness, morphology, current efficiency, luminescence of OLED fabricated by ESD. These results were compared with the spin coating method, and showed that also ESD is a good fabrication method for OLED because of its characteristics similar with the results using spin coating. The active layer consists of organic blends with Poly(N-vinylcarbazole) (PVK), 2-(4-Biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD), N,N'-Bis(3-methylphenyl) -N,N'-bis(phenyl)-benzidine (TPD), Tris(2-phenylpyridine)iridium(III) (Ir(ppy)3), and the structure of OLED consists of aluminum (Al), lithium fluoride (LiF), organic blends, PEDOT:PSS and Indium-tin-oxide (ITO), which was used as the top cathode, cathode interfacial layer, emitting layer and bottom anode, respectively. The results suggest that Electrostatic spray deposition is a promising method for the next generation of OLED fabrication since it has a probability fabricating large-area thin films.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.16-19
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• 2011

An experimental study on the spray characteristics of Gas-centered swirl coaxial injectors(GCSCI) for high-performance staged combustion rocket engines has been carried out using cold flow tests. In this study, water and gaseous nitrogen are used as working fluids and a back-lit photography technique with image processing for the measurements of spray characteristics. Our study is focused on the effect of injector geometries like as gap thickness of liquid nozzle and gas nozzle and momentum flux ratio for fundamental understanding of the injectors.

• Corrosion Science and Technology
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• v.22 no.4
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• pp.257-264
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• 2023

Ti-6Al-4V alloys are mainly used as dental materials due to their excellent biocompatibility, corrosion resistance, and chemical stability. However, they have a low bioactivity with bioinertness in the body. Therefore, they could not directly bond with human bone. To improve their applications, their bone bonding ability and bone formation capacity should be improved. Thus, the objective of this study was to improve the bioinert surface of titanium alloy substrate to show bioactive characteristics by performing surface modification using wollastonite powder. Commercial bioactive wollastonite powder was successfully deposited onto Ti-6Al-4V alloy using a room temperature spray process. It was found that wollastonite-coated layer showed homogeneous microstructure and uniform thickness. Corrosion resistance of Ti-6Al-4V alloy was also improved by plasma electrolytic oxidation treatment. Its wettability and bioactivity were also greatly increased by wollastonite coating. Results of this study indicate that both plasma electrolytic oxidation treatment and wollastonite coating by room temperature spray process could be used to improve surface bioactivity of Ti-6Al-4V alloy substrate.