• Journal of Welding and Joining
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• 제27권6호
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• pp.43-48
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• 2009

In this study, Cu-based bulk metallic glass (BMG) coatings were deposited by atmospheric plasma spraying (APS) process with different process conditions (with- and without hydrogen gas). As adding the hydrogen gas, thermal energy in the plasma flame increased and induced difference in the melting state of the Cu-based BMG particles. The microstructure and mechanical properties of the coatings were analyzed using a scanning electron microscope (SEM) with an energy dispersive spectroscopy (EDS) and nano-indentation tester in the light of phase analysis. It was elucidated by the nano-indentation tests that un-melted region was a mainly amorphous phase which showed discrete plasticity observed as the flow serrations on the load.displacement (P - h) curves, and the curves of solidified region showed lower flow serrations as amorphous phase mingled with crystalline phase. Oxides produced during the spraying process had the highest hardness value among the phases and were well mixed with other phases resulted from the increase in melting degree.

• 한국화재소방학회논문지
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• 제23권3호
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• pp.31-39
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• 2009

최근 고층건물의 화재안전성에 대한 문제점이 사회적으로 부각되어지고 있으며, 이러한 고층 건물에 다수 사용되고 있는 CFT기둥 부재에 대한 내화성능을 정량적으로 평가하는 방법이나 기준들이 마련되지 않은 상황이다. 이에 본 연구에서는 고강도 콘크리트를 충전한 CFT 단주를 제작하여 내화실험을 실시하고, 화재시 내화성능평가 및 비정상온도분포해석을 이용한 해석을 수행하여 온도분포해석의 모델링을 제안할 수 있었다. 이것을 기초로 CFT Stub Column의 고온특성 평가결과를 활용하여 화재시 내화시간에 따른 CFT기둥의 잔존내력 예측식을 유도할 수 있었다.

• 한국광물학회지
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• 제25권4호
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• pp.185-195
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• 2012

나노 크기 매킨나와이트(FeS)는 높은 환원력, 흡착성, 그리고 비표면적을 지니고 있어, 염소유기물의 분해와 중금속 및 비금속의 제거에 유용하다. 하지만 매킨나와이트 나노입자는 콜로이드 안정성(colloid stability)의 변화로 지하수 흐름에 따라 쉽게 확산되거나, 입자집적(particle aggregation)에 의해 대수층의 공극을 막을 수 있다. 따라서 투과반응벽(permeable reactive barrier)에 적용하기 위해서 적절한 공학적 변형이 필요하다. 본 연구에서는 코팅법을 적용해 나노크기 매킨나와이트를 변형시킴으로써 본래의 반응성을 유지하고 또한 경제적인 투과반응벽의 설치에 활용하고자 한다. 이를 위해 화학적 처리를 하지 않은 규사(non-treated silica sand, NTS)와 화학적 처리에 의해 불순물이 제거된 규사(chemically treated silica sand, CTS)를 사용해 매킨나와이트를 코팅시켰다. 두 규사 모두 약 pH 5.4에서 매킨나와이트가 최대로 코팅되었으며, 이 pH는 (1) 매킨나와이트의 용해도, (2) 규사 및 매킨나와이트의 표면전하(surface charge)에 의해 영향받았다. 최적 pH에서 NTS와 CTS에 의한 코팅량은 각각 0.101 mmol FeS/g, 0.043 mmol FeS/g으로, NTS 표면에 존재하는 산화철 등의 불순물에 의해 매킨나와이트의 코팅이 현저히 증가했다. 한편 혐기성 조건에서 코팅되지 않은 규사 2종과 최적 pH에서 코팅된 규사 2종을 이용해 아비산염(arsenite)의 흡착실험을 실시했다. pH 7에서 코팅되지 않은 NTS와 코팅된 NTS에 의한 아비산염의 상대적 제거율은 아비산염의 초기 농도에 따라 달라졌다. 낮은 농도에서 코팅되지 않은 NTS가 높은 아비산염의 제거율을 보였으나, 높은 농도에서는 코팅된 NTS가 상대적으로 높은 제거율을 보였다. 이런 차이는 아비산염은 낮은 농도에서 규사 표면에 존재하는 산화물과의 표면배위결합(surface complexation)에 의해 제거되었고, 높은 농도에서 코팅된 매킨나와이트와 반응해 황화비소(arsenic sulfides)로 침전되었기 때문이다. pH 7에서 코팅된 NTS에 비교해 코팅된 CTS는 현저히 낮은 아비산염 제거율을 보였는데, 이는 CTS의 상대적으로 낮은 매킨나와이트 코팅량에 기인했다. 따라서 코팅된 NTS는 코팅된 CTS보다 아비산염의 제거를 위한 투과반응벽의 설치에 더 적합한 물질이며, 특히 아비산염의 오염도가 심한 지하수의 복원에 유용하게 적용될 수 있다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.439-443
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• 2008

Painting process or coating with acrylic film may improve the surface defects of injection molded parts deteriorated by weldlines. flow marks. and etc. However such processes increase the production costs and increase environmental problems. Recently various types of rapid mold heating & cooling technology have been developed in order to improve surface quality of products. In this study. the heating & cooling performance of a telephone case mold is investigated by heat transfer analysis, in which the rapid mold heating & reeling technology is applied. The surface temperature of the mold was measured using thermal image camera and compared with analysis results. The influence of the rapid mold heating & cooling technology on weldline appearance and cycle time increase was also examined.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권5호
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• pp.315-320
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• 2000

This paper presents the fabrication and test of a micropump with an electromagnetic actuator and a pair of aluminum flap valves. The actuator consists of a solenoid coil, a permanent magnet and an actuator diaphragm. The actuator diaphragm is fabricated by the spin coating of silicone rubber. The valve are passive ones and are fabricated by micromachining. The deflection of the fabricated actuator diaphragm is measured with a laser vibrometer. The deflection of the actuator diaphragm is proportional to the input current. The measured deflection of the fabricated diaphragm is $400 \mum$,/TEX> when the input is 118 mApp, and the cut-off frequency is 50 Hz. The maximum flow rate of the fabricated micropump with the electromagnetic actuator is about 5$0 \muell/min$ at 5 Hz when the input current and the duty ratio of the square was are 118 mApp and 50%, respectively.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.185-186
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• 2002

Fretting of fuel rod cladding material, Zircaloy-4 tube, in PWR nuclear power plants must be reduced and avoided. Nowadays the introduction of surface treatments or coatings is expected to be an ideal solution to fretting damage since fretting is closely related to wear. corrosion and fatigue. Therefore. in this study the fretting wear experiment was performed using TiAlN coated Zircaloy-4 tube as the fuel rod cladding and uncoated Zircaloy-4 as on of grids, especially concentrating on the sliding component. Fretting wear resistance of TiAlN coated Zircaloy-4 tubes was improved compared with that of TiN coated tubes and uncoated tubes and fretting wear mechanisms were brittle fracture and plastic flow at lower slip amplitude but severe oxidation and spallation of oxidative layer at higher ship amplitude.

• Bulletin of the Korean Chemical Society
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• 제25권4호
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• pp.560-562
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• 2004

• Corrosion Science and Technology
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• 제3권2호
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• pp.67-71
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• 2004

Galvanized Steel pipes have been widely used in industries and apartments, Unexpected early leakage has been found in an apartment. Tunneling corrosion or penetration was found in the water supply pipes. The chemical compositions of the pipes and properties of coating layer were evaluated. The pipes met the specification of KS D 3507. The cause of early failure was analyzed through the examination of macrostructures and microstructures, It was found that the pipes were failed by grooving corrosion, which resulted from galvanic corrosion of weld bead and matrix.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 추계학술대회 논문집 학회본부
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• pp.261-264
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• 1991

Titanium carbide(TiC) films were deposited on stainless-steel sheets using HCD(Hollow Cathode Discharge) reactive ion plating. Acetylene gas was used as the reactant gas. The characteristics of TiC films were examined by X-Ray diffraction, $\alpha$-step, ESCA(Electron Spectroscopy for Chemical Analysis), and, AES(Auger Electron Spectroscopy). The results were discussed with regard to various deposition conditions(bias voltage, acetylene flow rate, temperature).

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1442-1447
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• 2004

A significant amount of labor hour is being spent for clean up spent abrasives after blasting. So, for improving the efficiency of abrasive(grit) recovery process which acts as the neck of a battle in preceding coating stage, it was established the theoretical background for pneumatic transport technology in the abrasive recovery system as well as experimentally evaluated the effect of design parameters such as flow pattern, saltation velocity and pressure drop on the efficiency of the abrasive recovery system. And, by optimizing the operating parameter such as the length and diameter of suction hose, specification of recovery device, recovery mouth and hose connection method, a method which can dramatical1y increase the efficiency of abrasive recovery system, is derived.