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RISS 인기검색어
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- 저자 : 오정석(Jeong Seong Oh) (검색결과 6 건)
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스텔라이트 합금 용사 코팅의 피로 강도에 미치는 후열처리의 영향
오정석,이창규,Oh Jeong Seong,Komotori Jun,Rhee Chang Kyu 한국분말야금학회 2005 한국분말재료학회지 (KPMI) Vol.12 No.2
The effect of post-heat treatment on the coating characteristics and the fatigue strength of the gas flame thermally sprayed Stellite alloy coatings on $0.35\%$ carbon steel were investigated. The fatigue fracture surfaces of the heat treated samples were observed using SEM (Scanning Electron Microscopy). For as-sprayed samples, there was considerable scattering in the fatigue life due to the presence of the pores in the coating. After the post-heat treatment to improve the microstructural characteristics of the coating layer, the fatigue strength of the specimens was greatly improved, increasing with increasing the coating thickness. For the specimens with the 0.3mm and 0.5mm thick coating, the fatigue cracks originated in the substrate region just below the interface. On the contrary, for the specimens with the 1.0mm thick coating, they nucleated at the pore within the coating, and the fatigue strength was 2.6 times higher than that of the substrate due to the high fatigue resistance of the coating.
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오정석,이성훈,김광제,Oh, Jeong-Seok,Lee, Seong-Hoon,Kim, Kwang-Jea The Rubber Society of Korea 2011 엘라스토머 및 콤포지트 Vol. No.
The effects of chopped kenaf fiber concentration on mechanical property of polypropylene (PP) composite are investigated. The addition of kenaf increased the tensile strength, flexural modulus, impact strength, specific gravity, and HDT, while decreased the elongation%, flexural strength, and melt flow index. The increase of mechanical properties is due to increased surface area contacting between fiber and polymer matrix and fiber-fiber interaction. Volatile extractives in the kenaf seemed to decrease the interfacial adhesion between kenaf surface and PP. 일정한 길이로 분쇄한 케냐프섬유를 일정한 비율로 PP수지에 복합화하여 섬유의 함량에 따른 기계적특성을 조사하였다. 케냐프 섬유의 함량이 증가할수록 인장강도, 굴곡탄성률, 충격강도, 비중, 열변형온도가 증가하는 경향을 나타내었으나 신장률, 굴곡강도, 용융유동지수는 감소하는 경향을 나타내었다. 기계적물성증가의 원인은 섬유와 PP간의 계면접촉면적의 증가와 섬유간의 연결간섭으로 고찰되었다. 케냐프섬유내에 존재하는 증발성추출물질이 PP와 의 계면접착에 있어서 감소에 영향을 미치는 것으로 고려된다.
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전기선 폭발법에 의해 제조된 Cu-Ni 합금 나노 분말의 윤활 특성
오정석(Jeong Seong Oh),이창규(Chang Kyu Rhee) 한국트라이볼로지학회 2005 한국트라이볼로지학회 학술대회 Vol.2005 No.6
Cu-Ni alloy nanoparticles were synthesized by a pulsed wire evaporation method in an inert gas, having the average size of l60㎚ approximately. The effect of Cu-Ni alloy nanoparticles as additives to oil on the tribological properties was studied. The worn surfaces were characterized by SEM and EDS. Cu-Ni alloy nanoparticles mixed with oil showed the low coefficient of friction and low wear rate in comparison to pure oil. The Cu-Ni agglomerates were shown to get compressed. The observed plowing tracks are associated with the shear of agglomerated and compressed Cu-Ni nanoparticles in the interface, The surfaces of the rubbed with oil + Cu-Ni nanoparticles were found to be covered by the film. EDS analysis revealed that this film was consisted of a copper. The Cu-Ni film protects the surfaces of direct contact and thus decreases the wear rates of samples. It was clearly demonstrated that Cu-Ni alloy nanopowders as additives were able to restore the worn surface and to preserve the friction surfaces from wear.
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나노 케냐프 셀룰로오스가 폴리프로필렌 복합소재의 물성 증가에 미치는 영향
오정석(Jeong Seok Oh),이성훈(Seong Hoon Lee),범석훈(Sug Hun Bumm),김광제(Kwang Jea Kim) 한국고분자학회 2013 폴리머 Vol.37 No.5
나노입자크기의 케냐프섬유를 폴리프로필렌에 첨가하였을 시, 복합소재의 물성변화를 관찰하였다. 천연크기의케냐프섬유를 나노입자크기의 케냐프섬유로 대체하였을 시, 그 복합소재의 인장강도, 휨강도, 충격강도, 열변형온도가 증가한 반면에, 용융지수, 연신율(%), 충격강도 등이 감소하였다. 이는 나노입자크기의 케냐프섬유가 폴리프로필렌과 접촉하는 표면적의 증가와 섬유표면에 존재하는 휘발성 추출물질 등의 불순물의 감소에 따른 것으로 판단된다. The effects of nano size kenaf cellulose fiber on mechanical property of polypropylene (PP) composite were investigated. The addition of nano-kenaf in place of natural kenaf showed higher tensile strength, flexural strength, impact strength, and heat deflection temperature compared to the natural kenaf filled PP composite, while it shows lower melt flow index, elongation%, and flexural modulus. These seemed to be due to the increased surface area of nano-kenaf fiber contacting PP matrix and reduced impurities such as volatile extractives on the fiber surface.
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Jeong Seok Oh(오정석),Seong-Hoon Lee(이성훈),Kwang-Jea Kim(김광제) 한국고분자학회 2015 폴리머 Vol.39 No.1
나노케냐프 섬유가 포함된 셀룰로스 섬유를 알카리(NaOH)로 처리 후 PP 수지에 첨가하여 물성에 미치는 영향에 대하여 조사하였다. 알카리를 섬유에 처리한 효과로는 M.I., 신장율, 충격강도가 증가하는 반면 인장강도, 휨모듈러스, 열변형온도가 처리하지 않은 섬유에 비해 감소하였다. 알카리를 나노섬유에 처리하였을 때 섬유표면의 불순물과 화학물질을 제거하여 섬유표면의 특성을 변화시켜서 나노섬유와 PP 수지간의 계면간 접착력을 감소시키고 PP의 특성을 변화시키는 것으로 보인다. The surface of nano-kenaf containing cellulose fibers was treated with alkali (NaOH) and their effects on the physical properties of the polypropylene (PP) composite were investigated. The treatment of alkali on the fibers increased the melt flow index (M.I.), elongation%, and impact strength, while it decreased the tensile strength, flexural modulus and heat deflection temperature (HDT) of the compound compared to the untreated one. It seemed the alkali treatment on the nano-kenaf fiber changed the character of the fiber due to removal of impurities and chemicals on the surface and resulted in decreased interfacial adhesion between the nano-fiber surface and the PP matrix and changed the character of the PP.
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케냐프섬유로 강화된 PP복합재료내의 섬유의 함량이 기계적특성 향상에 미치는 효과
오정석 ( Jeong Seok Oh ),이성훈 ( Seong Hoon Lee ),김광제 ( Kwang Jea Kim ) 한국고무학회 2011 엘라스토머 및 콤포지트 Vol.46 No.2
일정한 길이로 분쇄한 케냐프섬유를 일정한 비율로 PP수지에 복합화하여 섬유의 함량에 따른 기계적특성을 조사하였다. 케냐프 섬유의 함량이 증가할수록 인장강도, 굴곡탄성률, 충격강도, 비중, 열변형온도가 증가하는 경향을 나타내었으나 신장률, 굴곡강도, 용융유동지수는 감소하는 경향을 나타내었다. 기계적물성증가의 원인은 섬유와 PP간의 계면접촉면적의 증가와 섬유간의 연결간섭으로 고찰되었다. 케냐프섬유내에 존재하는 증발성추출물질이 PP와 의 계면접착에 있어서 감소에 영향을 미치는 것으로 고려된다. The effects of chopped kenaf fiber concentration on mechanical property of polypropylene (PP) compositeare investigated. The addition of kenaf increased the tensile strength, flexural modulus, impact strength, specific gravity, and HDT, while decreased the elongation%, flexural strength, and melt flow index. The increase of mechanical propertiesis due to increased surface area contacting between fiber and polymer matrix and fiber-fiber interaction. Volatile extractives in the kenaf seemed to decrease the interfacial adhesion between kenaf surface and PP.
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