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옥경민,김경록,김태완,김동현,박희대,성열문,박홍채,윤석영,Ok, Kyung-Min,Kim, Kyeong-Lok,Kim, Tae-Wan,Kim, Dong-Hyun,Park, Hee-Dae,Sung, Youl-Moon,Park, Hong-Chae,Yoon, Seog-Young 한국결정성장학회 2013 韓國結晶成長學會誌 Vol.23 No.1
이차상의 편석, 분말의 조성 및 합성방법은 $La_{0.8}Sr_{0.2}Ga_{0.8}Mg_{0.1}Co_{0.1}O_{3-{\delta}}$(LSGMC) 물질의 전도도에 영향을 미친다. 조성이 균일하고 순도가 높은 분말을 얻기 위해 GNP(Glycine nitrate process)를 이용하여 고체산화물 연료전지의 전해질재료인 $La_{0.8}Sr_{0.2}Ga_{0.8}Mg_{0.1}Co_{0.1}O_{3-{\delta}}$를 합성하였다. 자발연소반응 시, 글리신의 양에 따른 물질의 특성을 확인하기 위하여, 글리신/양이온 비를 0.5, 1, 1.5, 2, 2.5로 변화시켜 분말을 합성하였다. 합성된 분말의 단상의 perovskite상 동정 및 소결체의 미세구조 변화를 XRD와 SEM을 이용하여 분석하였다. 조성비가 1.5인 경우, 상대적으로 치밀하며, $800^{\circ}C$에서 0.131 $Scm^{-1}$의 우수한 전기전도특성을 나타냈다. 또한, $25{\sim}800^{\circ}C$ 사이의 온도에서 열팽창거동이 선형을 나타내었다. Conductivity of LSGMC materials were affected by secondary phase segregation, composition and synthetic route. $La_{0.8}Sr_{0.2}Ga_{0.8}Mg_{0.1}Co_{0.1}O_{3-{\delta}}$ (LSGMC) powders were prepared using the glycine nitrate process to produce high surface area and compositionally homogeneous powders. The powders were synthesized with different 0.5, 1, 1.5, 2, 2.5 of glycine/cation molar ratios. A single perovskite phase from the synthesized powders was characterized with X-ray diffraction patterns. The obtained sintered pellets showed the dense grain microstructure. In case of 1.5 molar ratio, its density was higher than the others. The electrical conductivity measured at $800^{\circ}C$ was observed to be 0.131 $Scm^{-1}$. In addition, the linear thermal expansion behavior was indicated between $25^{\circ}C$ and $800^{\circ}C$.
나노점토가 연질 폴리우레탄/점토 다공성 나노복합체의 기계적 특성에 미치는 영향
옥경민,김규헌,김경록,김동현,김춘환,박홍채,윤석영,Ok, Kyung-Min,Kim, Kyu-Heon,Kim, Kyeong-Lok,Kim, Dong-Hyun,Kim, Chun-Hwan,Park, Hong-Chae,Yoon, Seog-Young 한국재료학회 2013 한국재료학회지 Vol.23 No.7
Flexible polyurethane/clay porous nanocomposite foams were synthesized using natural and organically modified montmorillonite clays such as bentonite, closite 10A and closite 30B. The content of nanoclays was varied from 1 to 5 wt% of polyol. Dispersion of clay in Polyurethane(PU) matrix was investigated by X-ray diffraction(Cu-$K{\alpha}$ rays of wavelength $1.54{\AA}$) using an X-ray diffractometer. Also, we determined that the thermal resistance of PU foam increased with added clay, compared to that of pure PU foam. The cell size and the fraction of open cells of the precursor foam were controlled by the addition of clay to the polyurethane foam. Modified clays were found to be more efficient cell openers than the unmodified clay. In addition, the tensile strength and elongation of the polyurethane/clay porous nanocomposites were examined. Increasing clay content increased the mechanical properties of the composites, such as tensile strength, and elongation at break. However, increasing the content over 5 wt% deteriorated the properties of the composites. We found that the nanofillers(bentonite, closite 10A and closite 30B) improved the thermal stability of the nanocomposite foam. The nanocomposite foam containing 3 wt% of closite 30B exhibited the best tensile strength and thermal stability.
동결-젤 주조 공정 기반 삼차부틸알코올을 이용한 단일방향 기공구조를 가지는 이상인산칼슘 세라믹 지지체의 제조 및 특성평가
김경록,옥경민,김동현,박홍채,윤석영,Kim, Kyeong-Lok,Ok, Kyung-Min,Kim, Dong-Hyun,Park, Hong-Chae,Yoon, Seog-Young 한국세라믹학회 2013 한국세라믹학회지 Vol.50 No.4
Porous biphasic calcium phosphate scaffolds were fabricated by a freeze-gel casting technique using a tertiary-butyl alcohol (TBA)-based slurry. After sintering, unidirectional macropore channels of scaffolds aligned regularly along the TBA ice growth direction were tailored simultaneously with micropores formed in the outer wall of the pore channels. The crystallinity, micro structure, pore configuration, bulk density, and compressive strength for the scaffolds were investigated with X-ray diffractometery, scanning electron microscopy analysis, a water immersion method, and a universal test machine. The results revealed that the sintered porosity and pore size generally resulted in a high solid loading which resulted in low porosity and small pore size, which relatively increased the higher compressive strength. After being sintered at $1100-1300^{\circ}C$, the scaffolds showed an average porosity and compressive strength in the range 35.1-74.9% and 65.1-3.0 MPa, respectively, according to the processing conditions.