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Microstructural development of macroporous silicon carbide ceramics during annealing
엄정혜,Masaki Narisawa,김영욱 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.2
Macroporous silicon carbide ceramics with porosities ranging from 67% to 84% were fabricated by a carbothermal reduction process from a carbon-filled polysiloxane and subsequent annealing. Microstructural development during annealing was investigated using scanning electron microscopy (SEM). The grain size increased with an increase in the annealing time and the morphology changed from equiaxed to cube or hexagonal platelets depending on the annealing temperature. By controlling the annealing time and annealing temperature, it was possible to adjust the size and morphology of SiC grains in macroporous SiC ceramics.
엄정혜(??慧) 길림성민족사무위원회 2020 중국조선어문 Vol.225 No.-
일반적으로 련어라고 할 때는 관용적으로 자주 함께 어울려쓰이는 단어결합을 의미한다. 본 론문에서는 결합의 공고성과 의미구조적전일성의 측면에서 련어가 자유로운 단어결합과 성구적인 단어결합과 어떤 차이를 나타내는가를 밝히고 그로부터 조선어련어의 개념을 언어학적으로 정의하려고 한다.
Processing of Kaolin-Based Microfiltration Membranes
엄정혜,김영욱,송인혁 한국세라믹학회 2013 한국세라믹학회지 Vol.50 No.5
Kaolin-based membranes with a pore size of 0.30-0.40 μm were successfully prepared by a simple pressing route using low-cost starting materials, kaolin and sodium borate. The prepared green bodies were sintered at different temperatures ranging between 900 and 1200oC. The sintered membranes were characterized by X-ray diffraction, mercury porosimetry, scanning electron microscopy, and capillary flowmetry. It was observed that the porosity decreased with an increase in both the sintering temperature and the sodium borate content, whereas the flexural strength increased with an increase in both the sintering temperature and the sodium borate content. The air flow rate decreased with an increase in the sodium borate content. The typical porosity, flexural strength, and specific flow rate of the kaolin-based membrane sintered with 5 wt% sodium borate at 1100oC were 37%, 19 MPa, and 1 × 10−3 L/min/cm2, respectively, at a p of 30 psi.
성인 장애인의 장애수용, 장애정체감, 사회적 지지가 비전통적 진로효능감 및 진로흥미에 미치는 영향 - 사회인지진로이론 적용 -
엄정혜,양은주 대구대학교 특수교육재활과학연구소 2016 특수교육재활과학연구 Vol.55 No.1
본 연구는 성인 장애인의 장애수용 및 장애정체감, 사회적 지지가 비전통적 진로효능감 및 진로흥미에 어떻게 영향을 미치는지 사회인지진로이론에 근거하여 탐색해보았다. 연구 대상자는 수도권에 거주하는 성인 장애인 208명으로 정신, 발달, 지적 장애를 제외한 신체 장애인이면서 정규직 직업을 가지고 있지 않은 사람들이었다. 장애수용 척도, 장애정체감 척도, 사회적 지지 척도를 사용하였으며, 본인이 고려하고 있는 직업을 자유롭게 쓰고 각각에 대한 자신의 효능감과 흥미를 보고하도록 하여, 장애인 인구 내에서 비전형적 혹은 비전통적으로 여겨지는 직업에 대한 효능감과 흥미를 측정하였다. 각 변인들 간의 상관분석을 수행하고 사회인지진로이론에 근거하여 설정한 연구 모형을 검증하기 위한 적합도 분석 및 직접, 간접 효과 분석을 실시하였다. 연구 결과, 연구에 사용된 모든 변인들이 유의미한 상관을 보였으며, 연구 모형은 지지되었다. 장애수용이 장애정체감에 유의한 영향을 미쳤으며, 장애수용을 통해 예측된 장애정체감은 다시 비전통적 진로효능감을 매개로 비전통적 진로흥미를 예측한다는 간접효과가 확인되었다. 사회적 지지는 장애정체감을 예측하였고, 비전통적 진로효능감에 대해 장애정체감을 매개로 한 간접효과가 유의미함과 동시에 직접효과 역시 유의미한 것으로 확인되었다.
SiC 필러 함량이 탄소 함유 Polysiloxane으로부터 제조된 고기공률 탄화규소 세라믹스의 미세조직과 꺾임강도에 미치는 영향
엄정혜,김영욱,송인혁 한국세라믹학회 2012 한국세라믹학회지 Vol.49 No.6
Highly porous silicon carbide (SiC) ceramics were fabricated from polysiloxane, SiC and carbon black fillers, AlN-Y2O3 additives, and poly (ether-co-octene) (PEOc) and expandable microsphere templates. Powder mixtures with a fixed PEOc content (30 wt%) and varying SiC filler contents from 0-21 wt% were compression-molded. During the pyrolysis process, the polysiloxane was converted to SiOC, the PEOc generated a considerable degree of interconnected porosity, and the expandable microspheres generated fine cells. The polysiloxane-derived SiOC and carbon black reacted and synthesized nano-sized SiC with a carbothermal reduction during a heattreatment. Subsequent sintering of the compacts in a nitrogen atmosphere produced highly porous SiC ceramics with porosities ranging from 78 % to 82 % and a flexura lstrength of up to ~7 MPa.
Processing of Vermiculite-Silica Composites with Prefer-Oriented Rod-Like Pores
엄정혜,김영욱,이승석,정두화 한국세라믹학회 2012 한국세라믹학회지 Vol.49 No.4
Vermiculite-silica composites with a layered structure were fabricated by adding cellulose fibers as a pore former and by a simple uniaxial pressing and subsequent sintering process. Three different combinations of additives were used and their effects on the compressive strength and thermal conductivity of the composites were investigated. Both compressive strengths (42-128 MPa) and thermal conductivities (0.75-1.48 W/m· K) in the direction perpendicular to the pressing direction (T) were higher than those (19-81 MPa and 0.32-1.04 W/m·K) in the direction parallel to the pressing direction (S) in all samples. The anisotropy in both properties was attributed to the microstructural anisotropy, which was caused by the layered structure developed in the composites.
Effect of Strontium Carbonate Content on Flexural Strength of Clay-Based Membrane Supports
엄정혜,김영욱,송인혁 한국세라믹학회 2015 한국세라믹학회지 Vol.52 No.6
The effect of SrCO3 content on the microstructure, porosity, flexural strength, and pore size distribution of clay-based membrane supports was investigated. Green compacts prepared from low cost materials such as kaolin, bentonite, talc, sodium borate, and strontium carbonate were sintered at 1000oC for 8 h in air. It was possible to control the porosity of the clay-based membrane supports within the range of 33% to 37% by adjusting the SrCO3 content. The flexural strength of the clay-based membrane supports was found to strongly depend on their porosity. In turn, the porosity was affected by the SrCO3 content. The average pore size and flexural strength of the clay-based membrane supports containing 4 wt% SrCO3 were 0.62 μm and 33 MPa at 34% porosity.
엄정혜,서유광,김영욱,이성재 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.3
Silicon carbide (SiC) ceramics were pressureless sintered with 3 vol% Al2O3-Y2O3-AlN additives with the AlN/(Al2O3+AlN) molar ratios of 0-0.75 at 1850-2000 °C for 1 hr and the effects of additive composition (i.e., changes in the AlN/(Al2O3+AlN) molar ratio while maintaining constant Y2O3 content) on the mechanical properties of the pressureless-sintered SiC ceramics were investigated. Self-reinforced microstructures consisting of relatively large platelet SiC grains and relatively small equiaxed grains have been obtained in all specimens when sintered at 1900 °C for 1 h in an argon atmosphere. The achievement of self-reinforced microstructures under such mild conditions (holding for 1 hr at 1900 °C) is caused by the beneficial effects of additive composition and the acceleration of the β→α phase transformation of SiC by seeding, i.e., the addition of 1 vol% α-SiC into β-SiC. The typical flexural strength and fracture toughness of the pressureless-sintered SiC ceramics with an AlN/(Al2O3+AlN) mole ratio of 0.5 were 433 MPa and 6.6 MPa·m1/2 at room temperature, respectively.