• Tribology and Lubricants
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• 제19권5호
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• pp.251-258
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• 2003

New method and device for the on-line measurement of soot concentration in a diesel engine oil are proposed, where the measurement principle is based mainly on attenuated internal total reflection. The detector were evaluated in various ranges of contaminated oils by carbon black particles. It was found that the proposed detector could be well used to monitor the oil deterioration due to soot contamination. Operational range of the detector was found from 0 to 5 mass percentage of soot content. Test results with water and fuel dilution showed that these effects were not remarkable. However, adsorption of carbon black particles onto the measurement surface was considered to be a critical problem of the detector. Effects of particle deposition on the interface was experimentally evaluated with the oil temperature and flow turbulence and discussed throughout this work.

• 수산해양기술연구
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• 제28권3호
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• pp.295-305
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• 1992

The critical strain energy release rate and the failure mechanisms of glass-carbon epoxy resin hybrid composites are investigated in the temperature range of the ambient temperature to 8$0^{\circ}C$. The direction of laminates and the volume fraction are [(+45, -45, 0, 0) sub(2) ] sub(s), 50%, respectively. The major failure mechanisms of these composites are studied using the scanning electron microscope for the fracture surface. Results are summarized as follows: 1) The critical strain energy release rate shows a maximum at ambient temperature and it tends to decrease as temperature goes up. 2) The critical strain energy release rate increases as the content of glass increases, and especially shows dramatic increase for the high glass fiber content specimens. 3) Major failure mechanisms can be classfied such as localized shear yielding, fiber-matrix debonding, matrix micro-cracking, and fiber pull-out and/or delamination.

• Elastomers and Composites
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• 제33권5호
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• pp.363-369
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• 1998

UV를 이용하여 반응성 모노머인 아크릴아미드를 SBR에 광그라프트 시키는데 있어서 주요한 인자인 모노머 농도, 조사시간 그리고 카본블랙의 함량이 모노머의 그라프트율에 미치는 영향을 살펴보았다. 광개시제로는 benzophenone을 사용하였다. 아크릴아미드의 그라프트율을 측정하기 위하여 FT-IR ATR과 증류수를 이용하여 정접촉각을 측정하였다. 아크릴아미드의 함량과 UV 조사시간이 증가함에 따라 그라프트율은 증가하였으며 또한 접촉각은 감소하는 현상을 나타내었다. SBR중 카본블랙 함량이 증가함에 따라 그라프트율이 증가함을 알 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.144-147
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• 2000

The effect of accelerated aging test on ethylene-propylene-diene monomer(EPDM) rubber used for outdoor insulation was studied by X-ray photoelectron spectroscopy(XPS), scanning electron microscope(SEM), FFT spectrum alalysis, and electrical pulse counts using PC by oscilloscope(300 MHz). In electrical alalysis, FFT spectrum analysis indicated arcing caused a significant increase in the third harmonic content of the leakage current of polluted insulator. Also, pulse counts increased as aging time. The surface oxygen and aluminum content were found to increase and that of carbon and nitrogen were found to decrease with time. The detailed XPS analysis indicated that the concentration of carbon in C-C decreased and concentration of highly oxidized carbons increased with time, which was due to the oxidation of EPDM rubber polymer SEM analysis indicated that crack and erosion of EPDM rubber occurred with time.

• Elastomers and Composites
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• 제49권3호
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• pp.204-209
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• 2014

단일벽 카본나노튜브 (SWCNT)/에폭시 복합체에 sodium-montmorillonite ($Na^+$-MMT)을 첨가하여 MMT크기와 MMT/SWCNT 비율이 복합체의 기계적 전기적 성질에 미치는 영향에 대하여 살펴보았다. 다른 크기를 갖는 3종류의 MMT를 사용하였으며, 모두 SWCNT의 분산에 효과적임을 알 수 있었다. MMT함량이 증가함에 따라 SWCNT/에폭시 복합체의 기계적인 성질은 증가하였으며, 임계함량에 도달한 후에는 감소하기 시작하였다. 그러나 표면전기저항은 MMT 함량이 증가함에 따라 감소하였으며, 임계함량에 도달한 후 증가하기 시작하였다. 최대 기계적 성질과 최소 전기특성은 임계 MMT/SWCNT 비율은 MMT 크기에 크게 의존하였으며, 이는 MMT크기가 증가함에 따라 감소하였다.

• Corrosion Science and Technology
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• 제13권5호
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• pp.170-177
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• 2014

Polyurethane coating was designed to give a hydrophobic property on its surface by modifying it with hydroxyl terminated polydimethylsiloxane and then effects of surface hydrophobic tendency, water transport behavior and hence corrosion protectiveness of the modified polyurethane coating were examined using FT-IR/ATR spectroscopy, contact angle measurement and electrochemical impedance test. As results, the surface of polyurethane coating was changed from hydrophilic to hydrophobic property due primarily to a phase separation tendency between polyurethane and modifier by the modification. The phase separation tendency is more appreciable when modified by polydimethylsiloxane with higher content. Water transport behavior of the modified polyurethane coating decreased more in that with higher hydrophobic surface property. The decrease in the impedance modulus ${\mid}Z{\mid}$ at low frequency region in immersion test for polyurethane coatings was associated with the water transport behavior and surface hydrophobic properties of modified polyurethane coatings. The corrosion protectiveness of the modified polyurethane coated carbon steel generally increased with an increase in the modifier content, confirming that corrosion protectiveness of the modified polyurethane coating is well agreed with its water transport behavior.

• Geomechanics and Engineering
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• 제12권3호
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• pp.399-415
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• 2017

A series of direct shear tests were conducted to investigate the frictional properties of the interface between structures and the filling soil of Chongqing airport fourth stage expansion project. Two types of structures are investigated, one is low carbon steel and the other is the bedrock sampled from the site. The influence of soil water content, surface roughness and material types of structure were analyzed. The tests show that the interface friction and shear displacement curve has no softening stage and the curve shape is close to the Clough-Duncan hyperbola, while the soil is mainly shear contraction during testing. The interface frictional resistance and normal stress curve meets the Mohr-Coulomb criterion and the derived friction angle and frictional resistance of interface increase as surface roughness increases but is always lower than the internal friction angle and shear strength of soil respectively. When surface roughness is much larger than soil grain size, soil-structure interface is nearly shear surface in soil. In addition to the geometry of structural surface, the material types of structure also affects the performance of soil-structure interface. The wet interface frictional resistance will become lower than the natural one under specific conditions.

• 대한기계학회논문집B
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• 제36권10호
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• pp.1033-1041
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• 2012

본 논문에서는 석탄의 물리적 화학적 구조에 의한 직접탄소 연료전지 내부의 전기화학 반응 특성의 변화에 대하여 연구하였다. 석탄의 구조, 표면적 및 기공체적, 작용기의 분포 등을 분석하기 위하여 다양한 분석 기법(TGA, XRD, BET, XPS)을 사용하였다. 석탄 내부에 존재하는 탄소의 강력한 결정구조는 연료의 비표면적 및 기공크기를 축소시켜 고 전류밀도 영역에서 급격한 포텐셜의 감소를 초래한다. 표면에 분포하는 작용기는 저전류 밀도 영역에서의 전기화학 반응에 영향을 미치며, 제한 전류밀도 및 최대 전력밀도는 전체 탄소의 양과 밀접한 상관관계를 가지고 있다는 것을 확인할 수 있었다. 전해질의 물질전달 향상 및 작동온도에 의한 영향도 논하였다.

• Corrosion Science and Technology
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• 제15권5호
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• pp.226-236
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• 2016

316L stainless steels have been widely used in many engineering fields, because of their high corrosion resistance and good mechanical properties. However, welding or aging treatment may induce intergranular corrosion and stress corrosion cracking etc. Since these types of corrosion are closely related to the formation of chromium carbide in grain boundaries, the alloys are controlled by methods such as the lowering of carbon content, solution heat treatment. This work focused on the intergranular corrosion mechanism of slightly-sensitized and Ultrasonic Nano-crystal Surface Modification (UNSM)-treated 316L stainless steel. Samples were sensitized for 1, 5, and 48 hours at $650^{\circ}C$ in $N_2$ gas atmosphere. Subsequently UNSM treatments were carried out on the surface of the samples. The results were discussed on the basis of the sensitization by chromium carbide and carbon segregation, the residual stress and grain refinement. Even though chromium carbide was not precipitated, the intergranular corrosion rate of 316L stainless steel was drastically increased with aging time, and it was confirmed that the increased intergranular corrosion rate of slightly-sensitized (not carbide formed) 316L stainless steel was due to the carbon segregation along the grain boundaries. However, UNSM treatment improved the intergranular corrosion resistance of aged stainless steels, and its improvement was due to the reduction of carbon segregation and the grain refinement of the outer surface, including the introduction of compressive residual stress.

• 한국표면공학회지
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• 제43권2호
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• pp.105-110
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• 2010

Electroless nickel plating on porous carbon substrate for the application of MCFC electrodes was investigated. Acidic and alkaline bath were used for the electroless nickel plating. The pore sizes of carbon substrates were 16-20 ${\mu}m$ and over 20 ${\mu}m$. The carbon surface was changed from hydrophobic to hydrophilic after immersing the substrate in an ammonia solution for 40 min at $60^{\circ}C$. The contact angle of water was decreased from $85^{\circ}C$ to less than $20^{\circ}$ after ammonia pretreatment. The deposition rate in the alkaline bath was higher than that in the acidic bath. The deposition rate was increased with increasing pH in both acidic and alkaline bath. The content of phosphorous in nickel deposit was decreased with increasing pH in both acidic and alkaline bath. The contents of phosphorous is low in alkaline bath. The minimum concentration of $PdCl_2$ for the electroless nickel plating was 10 ppm in alkaline bath and 5 ppm in acidic bath. The thickness of nickel was not affected by the concentration of $PdCl_2$.