• The Korean Journal of Ceramics
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• 제3권1호
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• pp.47-51
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• 1997

The dense sintered bodies of Si/SiC composite with various Si contents could be fabricated by changing the green density in the forming process. The Si/SiC/graphite composites with various graphite contents could be also fabricated by changing a graphite content in the starting composition. Their mechanical and tribological properties were characterized and wear mechanism was also studided. The hardness and strength of the Si/SiC and the Si/SiC/graphite were decreased with increasing the contents of free Si and graphite, respectively. However, the friction coefficient and specific wear rate had no specific relations to their hardness and strength. Adhesion of free Si was a main factor to determine a wear resistance of the Si/SiC composite. In the case of the Si/SiC/graphite, solid lubricationl and liquid reservoir of the graphite particles played the main role of the reduction of the friction force. In the torque test to estimate the possibility of practical of practical applications, the value of torque between the Al2O3 disk and Si/SiC/graphite disk was 1/6 lower compared with two $Al_2O_3$ disks on the basis of 100,000 cycles.

• 자원리싸이클링
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• 제5권4호
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• pp.11-16
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• 1996

부유선별법에 의한 탈묵공정에서 잉크입자와 기포의 부착은 상호간의 충돌에 의한 것인데, 충돌의 가능성은 주로 수력학적 조건에 지배된다. 따라서, 부유선별법에서 미세입자의 제거효율이 낮은 이유는 수력학적 영향에 의해 입자가 기포주위의 수층유선을 따라 흘러내리는 경향이 있으므로 기포와의 충돌이 어렵기 때문이라고 해석되어 진다. 또한, 크고 무거운 잉크입자의 경우에는 기포에 의한 부상과정에서 중력과 점성력 등의 영향을 크게 받으므로 부유선별에 의한 제거가 어렵다고 간주되어 진다. 따라서, 부유선별의 실제공정에서는 계면화학적 측면에서의 조건선정 뿐만 아니라, 잉크입자와 기포의 크기를 조절하는 수력학적 관점에서의 조절이 또한 중요하다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권11호
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• pp.611-616
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• 1999

The introduction of the eddy current braking(ECB) system in HSRT(high speed railway train) is known to be advantageous, in that the system is independent on wheel-rail adhesion coefficient which is greatly affected by weather condition. It also minimize the maintenance of the brake system and does not require any additional electric energy because it is powered form the regenerated power at the time of the braking. In this study, the braking and attraction forces of the ECB are simulated by 2-D FEM and are experimentally verified on a down-scaled prototype. A control algorithm of the ECB is proposed to generate constant braking torque using linear variation of the reference current according to speed. Experimental results shows that the constant torque is generated over all operating speed region by developed control algorithm.

• 한국수소및신에너지학회논문집
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• 제23권5호
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• pp.538-544
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• 2012

The bubbles made of hydrogen and oxygen gases producted by electrolysis disturb the electrolysis, but the behavior of these bubbles in the electrolysis stack isn't clearly defined. In order to study on the behavior of bubbles in the flow pattern of the meshes type separator, the flow visualization experiment was performed by using of a visible alkaline electrolysis stack and a stereoscopic microscope. As the results, a fine size bubbles adhered to the separator's surface in the electrolyte solution have grown large sized bubbles until each bubble's buoyance is lager than the sum of surface adhesion force and weight. And then the large bubbles flow into the upper area of the separator. Also, as wide area of the separator have been occupied by various sized bubbles, the electrolysis efficiency is declined.

• 한국재료학회지
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• 제30권7호
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• pp.327-332
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• 2020

Laser induced surface activation (LISA) technology requires refined selection of process variables to fabricate conductive microcircuits on a general polymer material. Among the process variables, laser mode is one of the crucial factors to make a reliable conductor pattern. Here we compare the continuous wave (CW) laser mode with the pulse wave (PW) laser mode through determination of the surface roughness and circuit accuracy. In the CW laser mode, the surface roughness is pronounced during the implementation of the conductive circuit, which results in uneven plating. In the PW laser mode, the surface is relatively smooth and uniform, and the formed conductive circuit layer has few defects with excellent adhesion to the polymer material. As a result of a change of laser mode from CW to PW, the value of Ra of the polymer material decreases from 0.6 ㎛ to 0.2 ㎛; the value of Ra after the plating process decreases from 0.8 ㎛ to 0.4 ㎛, and a tight bonding force between the polymer source material and the conductive copper plating layer is achieved. In conclusion, this study shows that the PW laser process yields an excellent conductive circuit on a polymeric material.

• Nuclear Engineering and Technology
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• 제50권5호
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• pp.724-730
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• 2018

Chromium and chromium nitride were selected as potential barriers to prevent fuel-clad chemical interaction (FCCI) between the cladding and the fuel material. In this study, ferritic/martensitic HT-9 steel and misch metal were used to simulate the reaction between the cladding and fuel fission product, respectively. Radio frequency magnetron sputtering was used to deposit Cr and CrN films onto the cladding, and the gas flow rates of argon and nitrogen were fixed at certain values for each sample to control the deposition rate and the crystal structure of the films. The samples were heated for 24 h at 933 K through the diffusion couple test, and considerable amount of interdiffusion (max. thickness: $550{\mu}m$) occurred at the interface between HT-9 and misch metal when the argon and nitrogen were used individually. The elemental contents of misch metal were detected at the HT-9 through energy dispersive X-ray spectroscopy due to the interdiffusion. However, the specimens that were sputtered by mixed gases (Ar and $N_2$) exhibited excellent resistance to FCCI. The thickness of these CrN films were only $4{\mu}m$, but these films effectively prevented the FCCI due to their high adhesion strength (frictional force ${\geq}1,200{\mu}m$) and dense columnar microstructures.

• 한국전기전자재료학회논문지
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• 제32권2호
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• pp.129-133
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• 2019

TiN thin films were fabricated using an unbalanced magnetron sputtering (UBMS) system, and their structure and surface characteristics as well as their optical and tribological properties were evaluated. The hardness, elastic modulus, adhesive force, surface roughness, and transmittance of the Ti thin films fabricated using the UBMS system were 11.5 GPa, 103 GPa, 27.5 N, 2.45 nm and 20%, respectively. The TiN films prepared with various proportions of nitrogen as the reaction gas exhibited maximum values for the hardness, elastic modulus, critical load, RMS roughness and transmittance of approximately 19.2 GPa, 182 GPa, 27.3 N, 0.98 nm, and 85%, respectively. Moreover, the TiN thin film fabricated under the condition of 30 sccm nitrogen gas showed the optimal physical properties. In summary, the TiN thin films fabricated using the UBMS system exhibited excellent hardness, elastic modulus, adhesion, and smooth surface in addition to good hydrophilic properties.

• Journal of Industrial and Engineering Chemistry
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• 제67권
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• pp.396-406
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• 2018

In this study, a polydioxanone (PDO) and poly(L-lactic acid) (PLLA) sheath-core biphasic monofilament was designed to develop an esophageal stent with improved mechanical properties and controlled biodegradability. The radial force of PDO/PLLA sheath-core stent was 10.24 N, while that of PDO stent was 5.64 N. Deteriorations of tensile strength, elastic modulus and elongation during degradation test were also delayed on PDO/PLLA group. Hyaluronic acid-dopamine conjugate and $BaSO_4/PDO$ conjugate coating layers provided improved tissue adhesion strength and reasonable X-ray contrast, respectively. Taken all together, the sheath-core filaments with tissue adhesive and radiopaque properties will be useful in designing esophageal stents.

• 마이크로전자및패키징학회지
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• 제29권2호
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• pp.107-112
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• 2022

본 연구에서는 용제를 전혀 사용하지않고 UV경화가 가능한 실버 페이스트를 개발하였다. 무용제(solvent-free) 타입으로 개발한 실버 페이스트의 점도 및 점탄성 측정하였다. 그리고 스크린인쇄로 패턴을 인쇄한 후에 UV경화로 전극도막을 형성시켰다. 형성된 전극도막의 전도성, 연필경도, 접착력에 대해서 평가하였다. 마지막으로 전극도막의 경화특성은 TGA 및 FT-IR로 평가하였다. 이러한 결과를 정리하면 전도성, 접착력, 경화특성에 대해서는 Paste(4), 즉 1.2 ㎛의 구형 실버 파우더와 50 nm 실버 파우더를 72:8%로 혼합한 실버 페이스트가 가장 우수한 물성이 얻어짐을 알 수 있었다.

• 한국지반공학회논문집
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• 제24권8호
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• pp.43-52
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• 2008

본 연구에서는 단철근 네일과 다철근 네일의 인장강도를 조사하기 위해 단철근과 다철근 네일의 극한인발시험과 크리프시험을 수행하였다. 철근과 시멘트 그라우트의 부착력과 인장하중에 의해 유발된 마찰력, 하중전이 특성을 조사하였다. 단철근과 다철근 네일의 현장인발시험과 유한차분해석 프로그램의 하나인 $FLAC^{2D}$를 이용하여 얻은 결과를 분석하고 비교하였다. 다철근 네일의 현장인발시험결과 단철근 네일에 비해 인발파괴하중이 크고 하중전이가 큼을 알 수 있다.