• 자원리싸이클링
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• 제16권1호
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• pp.28-36
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• 2007

폐 ITO 타겟을 염산에 용해시킨 복합 산용액을 원료로 하여 자체기술에 의해 개발한 분무열분해 반응장치를 통하여 평균입도가 50nm이하인 나노 ITO 분말을 제조하였으며, 반응온도 및 원료용액의 농도 등의 반응인자들의 변화에 따른 ITO 분말의 특성을 파악하였다. 반응온도가 $800^{\circ}C$로부터 $1100^{\circ}C$로 변화함에 따라 생성된 ITO 분말의 평균 입도는 40nm로부터 100nm정도까지 증가하고 있었으며, 조직도 점점 치밀화되면서 각각의 입자들이 독립된 다각형 형태를 나타내었으며, 입도분포는 더욱 불균일하게 나타나고 있었다. 또한 반응온도 증가에 따라 XRD 피크의 강도는 증가하였으며 비표면적은 감소하고 있었다. 원료용액 내의 인듐 성분의 농도가 50g/l로부터 400g/l로 증가됨에 따라 생성된 ITO 분말의 평균입도는 점점 증가하는 반면 입도분포는 더욱 불균일 하였다. 농도가 50g/l인 경우에는 ITO 분말의 평균입도는 30nm 이하이면서 입도분포는 비교적 균일하게 나타나고 있었다. 반면 농도가 포화농도에 가까운 400g/l인 경우에는 분말들의 입도분포는 20nm 정도부터 100nm 이상까지 공존하는 매우 불균일한 형태를 나타내고 있었다. 농도가 증가함에 따라 XRD 피크의 강도는 점점 증가하였으며 비표면적은 점점 감소하였다.

• 한국산학기술학회논문지
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• 제14권2호
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• pp.585-591
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• 2013

페키지형 발전시스템용 라디에이터를 균일한 두께로 코팅할 수 있는 로봇자동화 시스템을 개발하였다. 이 시스템은 스프레이 건을 부착한 6축 로봇, 로봇을 주행방향으로 이송하는 주행대차, 공압과 함께 도료와 신너를 공급하는 장치, 제어장치 및 로봇경로 오프라인프로그램으로 구성되어 있다. 최적운전 조건으로 코팅로봇 자동화 시스템을 사용하여 라디에이터를 코팅한 결과, 평균 코팅두께가 $43{\mu}m$로서 규정치인 $25-100{\mu}m$을 만족하였다. OLP를 활용한 코팅로봇 자동화 시스템의 생산성은 기존 수작업의 12.6 배로 향상되었다.

• Tribology and Lubricants
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• 제34권5호
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• pp.175-182
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• 2018

Accumulation of coal ash at the boiler wall reduces combustion and fuel efficiency. The design of a wall blower is important to effectively remove coal ash. We present numerical results for the removal of coal ash from boiler walls of domestic coal-fired power plants, associated with the computational fluid dynamics for the flow from spray nozzle to boiler wall. The numerical model simulates an erosion process in which the multiphase fluid comprising saturated vapor and fluid water is sprayed from the nozzle, and the water particles impact the boiler wall. We adopt the Finnie erosion model for water particles. We obtain the erosion rate density as a function of nozzle angle and its injection angle. As excessive coal ash removal usually induces damage to the boiler wall, the removal operation typically focuses on a large area with uniform depth rather than the maximum removal of coal ash at a specific location. In order to estimate the removal performance of the wall blower nozzle considering several functionality and reliability factors, we evaluate the optimal injection and nozzle angles with respect to the biggest cumulative and highest erosion rates, as well as the widest range and lowest standard deviation of the erosion rate distribution.

• International Journal of Aeronautical and Space Sciences
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• 제18권2호
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• pp.270-278
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• 2017

This paper describes development procedure and verification test results of a bi-propellant thruster using hydrogen peroxide and kerosene. The design thrust of the thruster is about 500 N and six swirl type coaxial injectors were used. The passage type manifolds were employed for the injector head to reduce the response time. The passage was designed to minimize stagnation points and recirculation region to ensure uniform flow distribution and sufficient cooling performance through flow analysis using Fluent. A catalytic igniter using hydrogen peroxide was installed at the center of the injector head. The propellant feeding and spray characteristics were confirmed by hydraulic tests. Combustion tests were performed on design and off-design points to analyze combustion characteristics under various mixture ratio conditions. The combustion test results show that combustion efficiency was over 95 % and chamber pressure fluctuation were less than 1.5 % under all test conditions.

• 한국기계가공학회지
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• 제10권5호
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• pp.131-136
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• 2011

Many researchers are recently studying about Electroactive polymer(EAP). But it has a physical limitation, because of property of material. Carbon nanotube(CNT) is known as the promising material which has excellent electro-mechanical characteristics and is mostly defect-free. It is expected that a successful synthesis of CNT and Nafion known as a primary material for IPMC would make a great improvement on its electro-mechanic feature. This study focuses on the method of synthesis of CNT with Nafion which improves electro-mechanical characteristic. To come up with mechanical dispersion with Nafion and Isopropyl Alcohol(IPA), we dispersed Single-walled carbon nanotubes(SWCNTs). For a uniformly layer of CNT, we used a spray gun on a hot plate by a simplified method. We fabricated a disperse SWCNT/Nafion composite uniformly. Through the use of the E-beam evaporator to form an uniform electrode layer, we consummated the IPMC actuator. This result shows improving 1.5 times mechanical properties about driving force in IPMC.

• 한국가시화정보학회지
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• 제12권2호
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• pp.9-12
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• 2014

Conventional electrospray and air spray methods have the vulnerabilities of limited flow rate (throughput) and droplet size, respectively. Since high throughput with uniform size of droplet is required for various applications, an improved technique should be adopted. Here, we report a combined system of an air pressure and an electric field and evaluate the atomization performance of it. The air flow allowed applying high flow rate range and the electric field reinforced the atomization process to generate fine droplets. A correlation between two forces was investigated by comparing the droplet produced by each method. The atomized droplets were measured and visualized by image processing and a particle image velocimetry (PIV). The quantitative results were achieved from the parametric space and the effect of both forces was analyzed. The motion of charged droplets followed the outer electric field rather than the complex vortex in the shear layer so that the droplets accelerated directly toward the grounded collector.

• 대한기계학회논문집B
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• 제25권5호
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• pp.660-665
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• 2001

Ultrafine particles have been widely used in many high technology industrial areas. The spherical nonagglomerated and uniform nanometer-size SiO$_2$particles are synthesized by the direct injection of TEOS(Tetraethyorthosilicate) using electro-hydrodynamic spraying method. Electro-hydrodynamic spraying can generate submicron-size TEOS droplets having high electric charges by applying a high electric field between the liquid injection nozzle and the reaction tube. These TEOS droplets are evaporated, and thermally decomposed or oxidized to produce nanometresized SiO$_2$particles in the reaction tube. Spherical, nonagglomerated and ultrafine particles are generated in various conditions and examined by using SEM and SMPS. As the total gas flow rate in the furnace changes from 1.5 lpm, the mean diameter of SiO$_2$particle decreases from 120 nm to 68 nm. The synthesized particle charging fractions are also investigated.

• 한국표면공학회지
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• 제27권3호
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• pp.158-165
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• 1994

Cu-Cr alloy thin film requires good quality of etching be used for TAB technology. The etched cross sec-tion was clean enough when the etching was performed in 0.1M $FeCl_3$ solution at $50^{\circ}C$. The etching rate was increased with the amount of $KMnO_4$. For enhanced profile of cross section and rate, the spray etchning was found to be superior compared to the immersion etching. A series of experiments were performed to improve the uniformity of the current distribution in electrodeposition onto the substrate with lithographic patterns. Copper was electrodeposited from quiescent-solution, paddle-agitated-solution, and air-bubbled-solution to in-vestigate the effect of the fluid flow. The thickness profile of the specimen measured by profilmetry has the non uniformity at feature scale in quiescent-solution, because of the longitudinal vortex roll caused by the natural convection. However, uniform thickness profile was achieved in paddle-agitated or air bubbled solu-tion.

• 설비공학논문집
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• 제29권8호
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• pp.437-445
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• 2017

Because of improvement of living standards and increased use of ice at home, built-in ice makers are of interest. In this study, refrigeration cycle of a unitary ice maker for residential usage was optimized using R-404A. Optimization was achieved through a search for proper refrigerant charge amount. For the present ice maker producing ice for 24 cups, the optimum charge amount was 200 g. In this configuration, the ice making cycle time was 17 minutes 53 seconds, ice production was 1.27 kg/h and COP was 0.310. After initial start-up, condensation and evaporation temperatures gradually decreased with time. As ice builds in the cup, heat transfer performance of the evaporator decreases, that results in decrease of evaporation and condensation temperatures. Replacement of existing slit nozzles with individual circular hole nozzles improved ice production capacity by 10 percent. Through visualization of ice formation in the ice cup, growth rate of the ice in the cup was relatively uniform.

• Journal of Magnetics
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• 제16권3호
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• pp.304-307
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• 2011

High performance Nd-Fe-B magnets can be manufactured by both sintering and hot deformation. The corrosion behaviors of the magnets prepared by the two processes were compared. Effect of microstructure on the corrosion resistance of Nd-Fe-B magnets was also investigated. A neutral salt spray test (NSS) was performed for the different-processed magnets. The weight losses of the samples after the corrosion test were measured. The corrosion microstructures were observed using a scanning electron microscope. It shows that the corrosion resistance of hot deformed magnets is much better than that of the sintered ones because the grain size and the distribution of Nd-rich phases of the hot deformed magnets are much finer and more uniform than those of the sintered ones. The different microstructure between the sintered and the hot deformed magnets causes the different corrosion behavior.