• 한국세라믹학회지
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• 제35권8호
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• pp.878-884
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• 1998

Synthesis of high purity mullite from korean resourceful kaolin and water-soluble aluminium salts was in-vestigated by addition of mullite seed. Single phase of mullite was formed at 1350$^{\circ}C$ however its mullite con-tent was 31-33% Maximum content of mullite synthesized from kaoin aluminium nitrate and 8wt% mul-lite seed was 98% at 1600$^{\circ}C$ for 4 hours.

• 한국세라믹학회지
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• 제16권1호
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• pp.13-20
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• 1979

High purity alumina has been extracted form low grade Korean alunite. Alunite ore was treated by 15% $NH_4OH$ solution, followed by 10% $H_2SO_4$ leaching and metallic impurities such as Fe and Ti were removed by solvent extraction method. Alumina prepared by the extraction process was 99.9% in purity. Hot Petroleum Drying Method has been employed for the preparation of uniformly fine alumina powder, using chemical reagent aluminum sulfate and ammonium aluminum sulfate extrated from Korea alunite. The sinterability of alumina powder prepared by Hot Petroleum Drying Method was shown to be improved in comparison with the one treated by other methods such as ball milling method, but dry pressing was difficult due to the agglomeration of calcined powder. The best slip of alumina powder prepared by Hot Petroleum Drying Method contained a lower soild content than the one treated by other methods. The alumina body formed by soild and drain casting with the former alumina powder showed a higher sintered density.

• Archives of Pharmacal Research
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• 제22권6호
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• pp.614-618
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• 1999

A reversed-phase high-performace liquid chromatographic method was developed to determine the optical purity of metoprolol enantiomers. The enantiomers were converted to diastereomeric derivatives using (-)-menthyl chloroformate reagent. Separation of the enantiomers as diastereomers was achieved by reversed-phase HPLC within 30 min using Inertsil C8 column. This method allowed determination of 0.05% of either enantiomer in the presence of its stereoisomer and method validation showed adequate linearity over the required range. Owing to the reaction condition during the derivatization with (-)-menthyl chloroformate, the possibility of racemization had to be established. Different ratios of (S)-(-)-metoprolol and (R)-(+)-metoprolol were prepared. Enantiomeric separation of these mixtures took place on a chiralcel OD column or, after derivatization with (-)-menthyl chloroformate, on a C8 column. The results form the these two independent separation systems were compared with trace racemization and were in very good agreement. No racemization was found during the experiment.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.149-153
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• 2005

The electron beam machining provides very high resolution up to nanometer scale, hence the E-beam writing technology is rapidly growing in MEMS and nano-engineering areas. In the optical column of the e-beam writer, there are several lenses condensing and focusing electron beams from electron gun with fringing magnetic fields. The polepieces of these lenses are usually made with high purity iron which is hard to fabricate and very expensive. In this paper, the possibility of using polepiece of object lens composed with pure iron and low carbon steel was examined to reduce cost. The magnetic field at object lens was calculated with finite element method, and practical focusing qualities of SEM pictures were observed comparing for the object lens polepieces with pure iron and two type of composed with low carbon steel.

• 한국정밀공학회지
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• 제12권3호
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• pp.62-72
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• 1995

The present study was undertaken to investigate the dry wear mechanism of the alumina ceramics in the purity variation for the wear of STB2. The wear test was carried out under different experimental condition various sliding speed, contact pressure and sliding distance. According as the alumina purity increased, wear volume of the STB2 decreased and minimum value of wear volume was over to high speed side. According as the sliding speed and sliding distance increased, friction coefficient decreased owing to drop of the shear strength, it decresed largely owing to decreased of elastic modulus and thermal conductivity with decrease in alumina purity. Indicative of minimum, value of wear volume, low speed side was abrasive wear, high speed side was wear of heat softening. The friction surface of ceramics protacted by oxide was transfer from STB2.

• Current Optics and Photonics
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• 제7권2호
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• pp.191-199
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• 2023

We propose a dual Fabry-Perot interferometer (DFPI) structure that combines two Fabry-Perot interferometers. The structure is designed to have spectral peaks in the red, green, and blue regions simultaneously, to be applicable to R, G, and B subpixels without any patterning process. The optimized structure has been fabricated on a glass substrate using a thermal evaporation technique. When the DFPI structure was attached to the quantum-dot color-conversion layer, the full width at half maximum values of the green and red spectra decreased by 47.29% and 51.07% respectively. According to CIE 1931 color space, the DFPI showed a 37.66% wider color gamut than the standard RGB color coordinate. Thus it was experimentally proven that the proposed DFPI structure improved color purity. This DFPI structure will be useful in realizing a display with high color purity.

• 한국분말재료학회지
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• 제11권4호
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• pp.294-300
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• 2004

This study for preparation of aluminum nitride (AlN) with high purity was carried out by self-propagating high-temperature synthesis method in two different systems, $Al-N_{2}$ and $Al-N_{2}$-AlN, with the change of nitrogen gas pressure and dilution factor. On the occasion of $Al-N_{2}$ system, unreacted aluminum was detected in the product in spite of high nitrogen pressure, 10 MPa, This may be caused by obstructing nitrogen gas flow to inner part of molten and agglomerate of aluminum, formed in pre-heating zone. In $Al-N_{2}$-AlN system, AlN with a purity of 95% or ever can be prepared in the condition of $f_{Dil}\geq0.5$, $P_{N_{2}}\geq$ 1 MPa, and the purity can be elevated to 98% over in the condition of $f_{Dil}$ = 0.7 and $P_{N_{2}}$ = 10 MPa.

• 한국응용과학기술학회지
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• 제24권2호
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• pp.140-148
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• 2007

As an additional high purification method of p-dioxanone monomer for a high molecular weight polymer, the sweating operation of crystalline layer obtained by layered melt crystallization from p-dioxanone-diethylene glycol system was studied. Purity and yield of p-dioxanone crystal depended mainly on the sweating temperature and sweating time. Increasing sweating time and sweating temperature, the purity of p-dioxanone crystal increase, whereas the yield of that decrease, respectively. Through the optimization of sweating operation, p-dioxanone crystal can be upgraded to very high purity over 99.9 % suited to monomer for polymerization.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2005년도 생물공학의 동향(XVII)
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• pp.566-569
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• 2005

한국산 개비자나무로부터 새로운 개념의 homoharringtonine 분리 및 정제 공정을 개발하였다. 메탄올을 사용한 4회 반복 추출에 의해 biomass로부터 대부분(>99%)의 homoharringtonine을 회수 할 수 있었다. 흡착 공정에서는 활성 백토(active clay)를 사용하여 추출물에 포함되어 있는 식물유래 타르, 왁스 성분을 효과적으로 제거하였다. Silica gel low-pressure chromatography공정을 통해서 순도 52% 이상의 homoharringtonine을 얻었으며, HPLC 공정을 통해 고순도 및 고수율의 homharringtonine을 정제할 수 있었다. 정제된 homoharringtonine의 분자량 및 구조분석을 수행한 결과 표준물질(Homharringtonine)과 동일 물질임을 확인할 수 있었다.

• 자원리싸이클링
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• 제15권2호
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• pp.37-44
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• 2006

국내 흑연광의 총 매장량은 약 260만 톤 정도이지만, 국제경쟁력을 가지지 못해 현재는 일부 광산에서만 채광하고 있다. 그러나 최근 휴대용 전자제품의 수요가 증가함에 따라 2차 전지의 전극에 사용되는 고순도의 흑연을 전량 고가로 수입에 의존하고 있어, 고순도 흑연의 국산화를 위한 연구가 필요한 실정이다. 그러므로 본 연구에서는 고순도 흑연을 생산하기 위한 전처리 단계로서 29.50% F.C.의 원광($D_{50}=69.393{\mu}m$)시료를 attrition mill에서 20분 마광($D_{50}=10.314{\mu}m$)하여 microbubble column을 이용하여 실험한 결과 정선과정 없이도 95% F.C. 이상의 산물을 90%이상의 회수율로 얻을 수 있었다.