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윤중열,김해두,박천홍,Yun, Jung-Yeul,Kim, Hai-Doo,Park, Chun-Hong 한국세라믹학회 2002 한국세라믹학회지 Vol.39 No.10
표면층과 내부간의 기공구조가 다른 다공질체를 제조하기 위해 입자크기가 다른 두 종류의 분체를 이용하여 다공질 성형체를 제조하였다. 두 층간의 소결 수축율을 동일하게 제어하기 위해 성형밀도 변화에 따른 소결밀도 변화를 예측할 수 있는 Ford's equation을 도입하여 소결 수축율을 동일한 조건을 구하였다. 제조된 다공질체는 미세구조와 통기도를 조사함으로서 기공의 이중 구조화 여부를 평가하였다. SEM 관찰결과 기공크기가 다른 두 층으로 구성되어 있는 것을 확인하였다. 각 층의 통기도는 출발 입자크기와 기공율이 클수록 증가하였으며, 이중 기공구조를 갖는 시편의 통기도는 기공크기가 작은 층의 특성에 의존하였다. In order to fabricate double-layered porous materials powders of different particle sizes were pressed stepwise. Ford's equation which predicts the fired density with the change in pressed density was employed in order to adjust the difference in sintering shrinkage of the green body with double-layered porous structure. Double-layered porous materials were characterized by investigating microstructures and permeability. SEM micrographs showed the distinct difference in pore sizes of double-layered porous material. Permeability of single-layered porous material increased by increasing the starting particle sizes and porosity as well. Permeability of the double-layered porous material depends largely on the layer of small pore diameter.
Fabrication of Fe Foam using Slurry Coating Process
윤중열,박다희,양상선,왕제필,Yun, Jung-Yeul,Park, Dahee,Yang, Sangsun,Wang, Jei-Pil The Korean Institute of Resources Recycling 2017 資源 리싸이클링 Vol.26 No.6
메탈폼은 매우 많은 기공을 포함하는 세포상 구조를 갖는 고체금속을 일컫는다. 특히 관통 기공 같은 개기공들은 고온용 필터 및 촉매 지지체 등으로 산업적으로 많이 사용되고 있다. 본 연구에서는 슬러리 코팅공정으로 90% 이상의 기공율과 2 mm 이상의 기공크기를 갖는 Fe 폼을 제조하였다. 이때 Fe 분말과 $Fe_2O_3$ 분말의 혼합비를 달리하여 기공율과 기공크기를 제어하였다. 이를 위해 우선 분말, 증류수 및 폴리비닐알콜(PVA)를 균일하게 혼합하여 슬러리를 제조하였다. $Fe_2O_3$ 분말의 혼합 비율이 증가할수록 PU 폼에 코팅된 슬러리의 양이 증가한 반면 Fe 폼의 수축 및 기공율은 각각 감소하였다. Metal foams have a cellular structure consisting of a solid metal containing a large volume fraction of pores. In particular, open pores which are penetrable pores are necessary for industrial applications such as in high temperature filters and as support for catalysts. In this study, Fe foam with greater than 90% porosity and 2-mm pore size was successfully fabricated using a slurry coating process and the pore properties were characterized. The Fe and $Fe_2O_3$ powder mixing ratios were controlled to produce Fe foam samples with different pore sizes and porosity. First, the slurry was prepared through the uniform mixing of powders, distilled water, and polyvinyl alcohol(PVA). The amount of slurry coated with the PU foam increased with increasing $Fe_2O_3$ mixing powder ratio, but the shrinkage and porosity of the Fe foams decreased, respectively, with increasing $Fe_2O_3$ mixing powder ratio.
정전 분무 공정을 이용한 Fecralloy 나노 입자가 코팅된 Fecralloy Foil의 제조
윤중열,양상선,구혜영,이혜문,Yun, Jung-Yeul,Yang, Sang-Sun,Koo, Hye-Young,Lee, Hye-Moon 한국분말야금학회 2011 한국분말재료학회지 (KPMI) Vol.18 No.6
Fecralloy is the promising materials for high temperature exhaust filtering system due to the excellent its oxidation resistance property. In this research, Fecralloy nanoparticles coated Fecralloy thin foil was prepared by a single nozzle electrospray system in order to increase surface area of Fecralloy foil. Fecralloy nanoparticles were fabricated by electrical wire explosion method in ethanol using Fecralloy wires as a source material. Electrospray modes with applied D.C voltages to Fecralloy colloidal solution were investigated to make a stable cone-jet mode. Coated layers with and without additional heat treatment were observed by FE-SEM (field emission-scanning electron microscope) and tape test for evaluating their adhesion to substrate were performed as well.
최성환,윤중열,이혜문,공영민,김병기,이기안,Choi, Sung-Hwan,Yun, Jung-Yeul,Lee, Hye-Mun,Kong, Young-Min,Kim, Byoung-Kee,Lee, Kee-Ahn 한국분말야금학회 2011 한국분말재료학회지 (KPMI) Vol.18 No.2
This study investigated the high temperature oxidation behavior of Ni-22.4%Fe-22%Cr-6%Al (wt.%) porous metal. Two types of open porous metals with different pore sizes of 30 PPI and 40 PPI (pore per inch) were used. A 24-hour TGA test was conducted at three different temperatures of $900^{\circ}C$, $1000^{\circ}C$ and $1100^{\circ}C$. The results of the BET analysis revealed that the specific surface area increased as the pore size decreased from 30 PPI to 40 PPI. The oxidation resistance of porous metal decreased with decreasing pore size. As the temperature increased, the oxidation weight gain of the porous metal also increased. Porous metals mainly created oxides such as $Al_2O_3$, $Cr_2O_3$, $NiAl_2O_4$, and $NiCr_2O_4$. In the 40 PPI porous metal with small pore size and larger specific surface area, the depletion of stabilizing elements such as Al and Cr occurred more quickly during oxidation compared to the 30 PPI porous metal. Ni-Fe-Cr-Al porous metal's high-temperature oxidation micro-mechanism was also discussed.
이동원,윤중열,신선명,김인수,왕제필,Lee, Dong-Won,Yun, Jung-Yeul,Shin, Shun-Myung,Kim, In-Soo,Wang, Jei-Pil 한국분말야금학회 2013 한국분말재료학회지 (KPMI) Vol.20 No.3
The study on the fabrication of iron powder from forging scales using hydrogen gas has been conducted on the effect of hydrogen partial pressure, temperature, and reactive time. The mechanism for the reduction of iron oxides was proposed with various steps, and it was found that reduction pattern might be different depending on temperature. The iron content in the scale and reduction ratio of oxygen were both increased with increasing reactive time at 0.1atm of hydrogen partial pressure. On the other hand, for over 30 minutes at 0.5 atm of hydrogen partial pressure, the values were found to be almost same. In the long run, iron metallic powder was obtained with over 90% of iron content and an average size of its powder was observed to be about $100{\mu}m$.
연소합성법에 의한 발열성 다공질 MoSi<sub>2</sub>계 재료의 제조
송인혁,윤중열,김해두,Song, In-Hyuck,Yun, Jung-Yeul,Kim, Hai-Doo 한국세라믹학회 2004 한국세라믹학회지 Vol.41 No.1
본 연구에서는 SHS 공정에 의하여 기공의 크기를 조절함으로서 전기저항 발열 특성을 가지는 다공성 $MoSi_2$를 제조하는 공정에 관하여 연구하였다. 결함이 억제된 다공질 재료를 제조하기 위하여 Si 함량 변화 및 예열 공정을 실시하였으며, 성형체 제조에 사용되는 Mo 분말의 크기 변화에 따른 가공 형성 거동에 대하여 연구하였다. 실험 결과 합성된 $MoSi_2$ 입자의 크기는 Mo 입자의 크기와는 관계없이 연소 합성시 발열되는 발열양에 의해 좌우되었으며, 기공의 크기는 Mo 입자의 크기에 따라 결정되었다. 또한 가공 경사 $MoSi_2$ 다공질 재료를 만들기 위하여 150-300${\mu}m$ Mo 분말과 4-5${\mu}m$ Mo 분말을 단계별로 5층으로 혼합하여 합성한 결과 거시적으로 순차적인 기공 크기 분포를 나타내었으며, 이를 통하여 포집 효율등이 우수한 다공성 발열체 재료의 제조가 가능하였다. In this study, SHS process has been employed to fabricate porous $MoSi_2$ material with electric-resistive heating capability through the control of pore size. The preform for SHS reaction was consisted of molybdenum powder with different sizes and silicon powder with different contained quantity. The size of the $MoSi_2$ particles thus formed was determined by the generated heat of combustion, not by the size of molybdenum powder. However, the pore size of $MoSi_2$ composite was proportional to the particle size of molybdenum powder. that is the coarser the molybdenum powder used, the larget the formed pore size. Based on these results, the porous $MoSi_2$ composite could be fabricated with a desired pore size. By orienting the porous molybdenum disilicide-based material in the form of pore size gradient, porous materials used for filters with improved dirt-holding capacity can be manufactured.