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팔당호 표층 퇴적물에 함유된 중금속의 입도 의존성에 관한 연구
신경용,전상호,Shin, Kyung-Yong,Jun, Sang-Ho 한국환경보건학회 2012 한국환경보건학회지 Vol.38 No.5
Objective: The purpose of this study was to present the standard deviation of the elemental normalization of concentration of selected heavy metals in the surface sediment of Lake Paldang. Methods: Grain size dependency of selected heavy metal concentrations in the surface sediments of Lake Paldang was analyzed by the extrapolation method. The heavy metal concentrations were the sum of all fractions. Results: Cd and Cu showed an increase of the coefficient of determination($r^2$) in the fractional content of particle size, from <256 ${\mu}m$ to <20 ${\mu}m$, and a decrease from <20 ${\mu}m$ to <1 ${\mu}m$. The normalized concentration of Cd and Cu by extrapolation at 50% <20 ${\mu}m$ were 0.8 mg/kg, 37.0 mg/kg, 57.6 mg/kg and 201.7 mg/kg respectively. Conclusions: The normalized concentrations in the sediment of Lake Paldang are 1.5-2.0 times higher than mean average concentration. We concluded that in interpretation of heavy metal concentration in the sediment of Lake Paldang, normalization of grain size dependency should be considered.
니켈기 Inconel 740H 초내열합금과 고Cr계 Gr.92 내열강의 이종금속 용접부의 미세조직 및 크리프 파단 특성
신경용,이지원,한정민,이경운,공병욱,홍현욱 대한금속·재료학회 2018 대한금속·재료학회지 Vol.56 No.5
Microstructure evolution and the creep fracture characteristics of dissimilar welds between Ni-based superalloy Inconel 740H and High Cr ferritic steel Gr.92 were investigated. The dissimilar welds were fabricated by shielded metal arc (SMA) welding process with Ni-based austenitic Inconel 182 superalloy. Postweld heat treatment at 760 oC for 4 hours was conducted to temper the fresh martensite formed in the heat-affected zone (HAZ) of Gr.92, and to form γ΄ strengthener in Inconel 740H. The weld interface between the Gr.92 and weld metal was characterized by a discrete line with minimal inter-diffusion, whilst the weld interface on the Inconel 740H side showed an unmixed zone having epitaxial columnar growth from the base metal. It was observed that the fresh untempered martensite formed at the Gr.92-sided coarse-grained HAZ next to the weld interface during PWHT. This may be due to higher Ni contents diffused from the Ni-based weld metal. A sharp increase in hardness was detected at the coarse-grained HAZ of Gr.92 while the hardness minimum occurred at the fine-grained and intercritical HAZ (FG/IC HAZ). Fracture after creep at 650 oC/80 MPa and 700 oC/35 MPa occurred at the FG/IC HAZ of Gr.92, commonly known as a type IV fracture. This may be attributed to the strain localization at the FG/IC HAZ due to the smaller grain size as well as the lowest hardness. The elemental migration across the weld interface was not significant. It was also found that a needle-like Nb-rich δ-phase formed at the interdendritic region of the weld metal after creep at 700 oC/35 MPa.
페놀수지/알루미나 복합 활성탄소중공사막을 이용한 응축성 기체 분리
신경용,박유인,김범식,구기갑 한국막학회 2010 멤브레인 Vol.20 No.4
탄소막은 고분자막에 비해 높은 선택성과 투과성, 열적, 화학적 안정성을 가지고 있어 기체 분리, 특히 휘발성 유기화합물(VOCs) 분리막으로 많은 관심을 받고 있다. 활성탄소중공사막은 기공 표면(pore wall)에 형성된 흡착성 미세기공에 의해 선택적으로 응축성 성분이 흡착, 확산되는 흡착-확산 기구에 의해 흡착성-비흡착성 물질이 분리된다. 본 연구에서는 다공성 알루미나 중공사막 지지체에 phenolic resin (novolac type)을 코팅한 후 산화, 탄화 및 활성화 등의 열분해 과정을 통해 막 표면과 기공 표변에 흡착성 미세기공이 형성된 활성탄소중공사막을 제조하였다. 또한 열분해 조건에 따른 phenol/alumina 복합 활성탄소중공사막의 물리적 특성과 기체 투과특성에 대해 살펴보았다. 그 결과, 제조된 phenol/alumina 복합 활성탄소중공사막이 휘발성 유기물질의 대부분을 차지하고 있는 탄화수소를 선택적으로 분리 회수하는데 매우 효과적인 특성을 갖고 있음을 확인할 수 있었다. 따라서 본 연구에서 개발된 phenol/alumina 복합 활성탄소중공 사막은 VOCs의 분리, 농축에 매우 효과적으로 활용 가능할 것으로 기대된다. Carbon membrane materials have received considerable attention for the gas separation including hydrocarbon mixture of ingredients of the volatile organic compounds(VOCs) because they possess their higher selectivity, permeability, and thermal stability than the polymeric membranes. The use of activated carbon membranes makes it possible to separate continuously the VOCs mixture by the selective adsorption-diffusion mechanism which the condensable components are preferentially adsorbed in to the micropores of the membrane. The activated carbon hollow fiber membranes with uniform adsorptive micropores on the wall of open pores and the surface of the membranes have been fabricated by the carbonization of a thin film of phenolic resin deposited on porous alumina hollow fiber membrane. Oxidation, carbonization, and activation processing variables were controlled under different conditions in order to improve the separation characteristics of the activated carbon membrane. Properties of activated carbon hollow fiber membranes and the characterization of a gas permeation by pyrolysis conditions were studied. As the result, the activated carbon hollow fiber membranes with good separation capabilities by the molecular size mechanism as well as selective adsorption on the pores surface followed by surface diffusion effective in the recovery hydrocarbons have been obtained. Therefore, these activated carbon membranes prepared in this study are shown as promising candidate membrane for separation of VOCs.