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기계적 합금화 p-type FeSi<sub>2</sub>의 플라즈마 용사 성형 및 열전 특성
최문관,어순철,김일호,Choi Mun-Gwan,Ur Soon-Chul,Kim IL-Ho 한국재료학회 2004 한국재료학회지 Vol.14 No.3
P-type $\beta$-FeSi$_2$ with a nominal composition of $Fe_{0.92}Mn_{0.08}Si_2$ powders has been produced by mechanical alloying process. As-milled powders were spray dried and consolidated by atmospheric plasma thermal spraying as a rapid sintering process. As-milled powders were of metastable state and fully transformed to $\beta$-$FeSi_2$ phase by subsequent isothermal annealing. However, as-thermal sprayed $Fe_{0.92}Mn_{0.08}Si_2$ consisted of untransformed mixture of $\alpha$-$Fe_2Si_{5}$ and $\varepsilon$-FeSi phases. Isothermal annealing has been carried out to induce transformation to the thermoelectric semiconducting $\beta$-$FeSi_2$ phase. Isothermal annealing at $845^{\circ}C$ in vacuum gradually led to the thermoelectric semiconducting $\beta$-$FeSi_2$ phase transformation, but some residual metallic $\alpha$ and $\varepsilon$ phases were unavoidable even after prolonged annealing. Thermoelectric properties of $\beta$-$FeSi_2$ materials before and after isothermal annealing were evaluated. Seebeck coefficient increased and electric conductivity decreased with increasing annealing time due to the phase transition from metallic phases to semiconducting phases. Thermoelectric properties showed gradual increment, but overall properties appeared to be inferior to those of vacuum hot pressed specimens.
기계적 합금화에 의해 제조된 Skutterudite CoSb<sub>3</sub>의 열전특성
최문관,조경원,어순철,김일호,Choi Moon-Kwan,Cho Hyoung-Won,Ur Soon-Chul,Kim Il-Ho 한국재료학회 2004 한국재료학회지 Vol.14 No.11
Skutterudite $CoSb_3$ powders were produced by mechanical alloying (MA) of elemental powders using a nominal stoichiometric composition. Annealing of MA powders under specific condition led to a complete phase transformation to a semiconducting ${\delta}-CoSb_3$. Single phase $CoSb_3$ was successfully produced by vacuum hot pressing using MA powders without subsequent annealing. Phase transformations during mechanical alloying and hot pressing were systematically investigated using XRD and SEM. Thermoelectric properties as a function of temperature were evaluated for the hot pressed specimens and compared with results of analogous studies.
경계 요소법을 이용한 다양한 부유체의 동유체력 계수 계산
최문관,구원철 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.11
본 연구에서는 선박의 내항성능을 평가할 때 중요하게 고려되는 동유체력 계수인 부가질량 계수와 파랑 감쇠계수를 2차원 경계 요소법을 사용하여 주파수 영역에서 계산하였다. 동유체력 계수는 선박형상의 복잡성과 계산 시간의 지연 등으로 인해 경험식이나 약산식에 의한 계산방법이 보편적이지만, 각 형상에 따른 오차가 증가할 수 있는 가능성이 있다. 본 논문에서는 각기 다른 형상의 부유체의 부가질량과 감쇠계수를 계산하여, Lewis form등으로 형상을 근사화하여 약산식으로 계산한 값과 비교 분석 하였다. 또한 Green 함수법을 사용한 결과 및 실험결과와 비교하여 각 계산법에 따른 부유체 형상과 해저면 영향에 따른 차이를 분석하였다. 이를 통해 시간영역에서 슬래밍이 포함된 선박의 복잡한 거동 문제에 적용할 수 있는 가능성을 고찰하였다.
파랑 중 선체에 작용하는 Global Load 계산을 위한 약산식 검토
최문관,박인규,구원철 대한조선학회 2012 대한조선학회 학술대회자료집 Vol.2012 No.5
This paper considers an analytical practice about global loads on the hull of ships. Ships experience significant vibrations on the hull induced by incident waves in the ocean. The vibrations are usually classified as either whipping or springing, depending on whether the vibration mode is transient or steady state. In this study, a numerical analysis is performed about vertical motions of ships in time domain and results are compared with the simplified formula from Guidelines through the parametric study.
파랑 중 선체에 작용하는 Global Load 계산을 위한 약산식 검토
최문관,박인규,구원철 한국해양환경·에너지학회 2012 한국해양환경공학회 학술대회논문집 Vol.2012 No.5
This paper considers an analytical practice about global loads on the hull of ships. Ships experience significant vibrations on the hull induced by incident waves in the ocean. The vibrations are usually classified as either whipping or springing, depending on whether the vibration mode is transient or steady state. In this study, a numerical analysis is performed about vertical motions of ships in time domain and results are compared with the simplified formula from Guidelines through the parametric study.
김영진,최문관,서준형,김병렬,조계홍 한국자원리싸이클링학회 2020 資源 리싸이클링 Vol.29 No.6
석탄재로부터 희토류 회수에 관한 연구 자료를 분석 및 검토하였다. 석탄재로부터 희토류 회수를 위해 적용된 선별 실험은 주로 PC 보일러로부터 발생된 석탄재를 대상으로 입도분리, 자력, 비중 및 부유선별법 등을 이용해 연구하였다. 선별 공정을 통해 희토류 성분의 농축 가능한 수준은 수 천 ppm 정도로 낮게 확인되었고, 선별 공정 이후 회수된 산물을 대상으로 습식 제련 공정을 통한 추가 농축 처리가필요한 것으로 확인되었다. 침출 공정에서는 석탄재의 희토류 성분을 침출 향상을 위해 알칼리 용융과 같은 전처리 후, 침출공정에 적용하는 것이 효율적인 공정으로 확인되었다. 세계적 희토류 회수 시스템의 개발이 아직은 미흡한 것으로 확인되었으나, 석탄재에 포함된 희토류 회수 연구는 계속 진행될 것으로 보고되었다. 국내에서는 석탄재 중 희토류 회수를 위한 회수 기술이 매우 부족한 상황으로 선별, 침출 등의 기술 개발이 시급한 실정이다. This study aims to introduce and review on the recovery technologies of rare earth elements(REEs) from coal ash. Many researchers have been carried out by various beneficiation processes, such as particle size separation, magnetic separation, specific gravity, and flotation to recover rare earth elements from coal ash generated from Pulverized Coal(PC) boiler. Through the beneficiation process, it was confirmed that concentration of rare earth elements was much lower than the 4,700 ppm, and that additional enrichment treatment through wet process was needed for the products recovered after the beneficiation process. It was confirmed that the rare earth elements contained in coal ash were applied to the leaching process after pretreatment such as alkali-fusion to improve leaching efficiency. Although beneficiation and leaching methods have been studied, its optimum recovery technologies for rare earth elements not been confirmed up to now, research on the recovery of rare earth contained in coal ash is reported to continue. In case of Korea, the technology for the recovery of rare earth elements from coal ash and coal by-product could not been confirmed up to present. In these reasons, it is urgent to develop technologies such as beneficiation and leaching process continuously.