• 한국세라믹학회지
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• 제43권10호
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• pp.666-672
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• 2006

GDC20($Ce_{0.8}Gd_{0.2}O_{1.9}$) powder was synthesized by oxalate co-precipitation and milling and its thermal decomposition, phase formation, and sinterability were investigated. As-prepared precipitates were non-crystalline due to the milling process and completely decomposed at 400$^{\circ}C$ The powder calcined at 800$^{\circ}C$ for 2 h contained fine p]sty particles with an average size of 0.69 $\mu$m. Attrition milling of the calcined powder for 2 h had a little milling effect, resulting in a slight decrease in the particle size to 0.45 $\mu$m. The milled powder consisted of small spherical primary particles and some large particles, which had been agglomerated during calcination. Due to the excellent sinterability of the powder, sintering of the powder compacts for 4 h showed relative densities of 78.7% at 1000$^{\circ}C$ and 97.8% at 1300$^{\circ}C$, respectively. Densification was found to almost complete at temperature above 1200$^{\circ}C$ and a dense and homogeneous microstructure was obtained. A rapid grain growth occurred between 1200$^{\circ}C$ and 1300$^{\circ}C$. Grains in 0.1$\sim$0.5 $\mu$m sizes at 1200$^{\circ}C$ grew to 0.2$\sim$2 $\mu$m and their size distribution became broader at 1300$^{\circ}C$.

• 한국세라믹학회지
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• 제39권7호
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• pp.649-656
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• 2002

Zn(NO$_3$)$_2$ 수용액과 urea[CO(NH$_2$)$_2$]를 이용한 침전법과 Self-Assembled Monolayers(SAMs)를 이용한 microcontact printing 방법으로 미세 패턴화된 ZnO 박막을 Al/si0$_2$/si 기판 위에 제조하였다. Zn(NO$_3$)$_2$와 urea를 혼합하여 제조한 Zn(OH)$_2$ 박막은 침전온도와 urea 량이 증가할수록 Zn(OH)$_2$의 침전량이 증가하였고 Zn(NO$_3$)$_2$와 urea의 반응 시간이 증가함에 따라, Zn(OH)$_2$ 박막의 두께와 입자 크기가 증가하였다. Zn(NO$_3$)$_2$와 urea의 혼합비를 1 : 8, 용액의 침전 온도를 오일 bath내에서 8$0^{\circ}C$, 반응시간을 1시간으로 하여 Al/SiO$_2$/Si 기판 위에 침전된 Zn(OH)$_2$ 박막을 $600^{\circ}C$에서 1시간 동안 열처리하여, 미세 패턴을 형성하기 위한 균질한 크기의 ZnO 박막을 제조할 수 있었다. Microcontact printing방법으로 소수성과 친수성 SAMs인 Octadecylphosphonic Acid(OPA)와 2-Carboxyethylphosphonic Acid(CPA)를 각각 Al/SiO$_2$/Si 기판 위에 선택적으로 흡착한 후에 친수성 SAM인 CPA위에 Zn(OH)$_2$를 침전시켜 미세 패턴화된 ZnO 박막을 제조할 수 있었다

• 한국재료학회지
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• 제6권3호
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• pp.275-281
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• 1996

YIG 전구체 분말은 요소의 열분해반응을 이용한 균일침전법에 의해서 질산염으로부터 제조하였다. 침전은 철이온이 먼저 침전한 후 이트륨이온이 침전하는 과정으로 이루어졌다. YGI전구체 분말은 철산화물과 비정질로 구성되어 있으며 그 분말의 대략적인 화학식은 2.5Fe2O3.Y3(OH)9-2x(CO3)x.nH2O로 되어있다. YIG 전구체 분말의 열분해과정은 dehydration, 철산화물의 recrystallization, yttrium carbonate 및 yttrium oxide의 형성과 고상반응등 여러단계로 구성되어 있다. 열처리온도가 증가함에 따라 Y2O3와 Fe2O3의 고상반응에 의해 YFeO3 intermediate을 경유해서 YIG상이 형성됨을 확인하였다. 단일상의 YIG는 120$0^{\circ}C$에서 6시간 공기중에서 소성함에 의해서 얻을 수 있었다.

• 한국세라믹학회지
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• 제31권8호
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• pp.835-840
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• 1994

In this study, the synthesis of Ba2Ti9O20 powder having chemically homogeneous and highly pure fine particle size distribution was attempted by the oxalate method. And the effects of ZrO2 addition was investigated. The four compositions (X=0, 0.028, 0.048, 0.068) of Ba2(Ti9-x, Zrx)O20 were prepared by precipitation reaction of BaCl2, TiCl4, and ZrOCl2, with oxalic acid and NH4OH acting as a precipitating agent and a pH regulator respectively, in aqueous solution. In case of 4.8 mol% ZrO2 addition, the single phase Ba2Ti9O20 was obtained at 120$0^{\circ}C$ and its dielectric properties was excellent showing K=40.5, Q=4621 at 5.4 GHz.

• 미생물학회지
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• 제20권4호
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• pp.183-188
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• 1982

Clostidium botulinum type B가 생성하는 독소를 정제할 수 있는 방법을 연구하였다. 정제과정은 독소를 ammonium sulfate로 배양액에서 침전시켜 추출한후 Polymin P를 처리하여 핵산 및 기타 단백질을 최대한 제거한 후 Sephaex G-I00에서 gel fiItration을 시키고 DEAE-Sephadex로 이온교환 크로마토그래피를 시켰다. 이러한 과정으로 정제된 독소의 회수율은 17%였으며 SDS-polyacrylamide gel electrophoresis 결과 하나의 선을 나타내 동질성을 증명하였다. 정제된 독소의 분자량은 163,000이였으며 $\beta$-mercaptoethanol을 사용하여 환원시킨 결과 분자량 106,000과 56,000의 하위 단위체로 분리되었다.

• 한국분말재료학회지
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• 제10권5호
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• pp.310-317
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• 2003

Two-component ceramic (alumina-zirconia) composites were fabricated by a soft-solution process in which polyethylene glycol (PEG) was used as a polymeric carrier. Metal salts and PEG were dissolved in ethyl alcohol without any precipitation in 1:1 volume ratio of alumina and zirconia. In the non-aqueous system, the flammable solvent made explosive, exothermic reaction during drying process. The reaction resulted in formation of volume expanded, porous precursor powders by a vigorous decomposition of organic components in the precursor sol. The PEG content affected the grain size of sintered composites as well as the morphology of precursor powders. The difference of microstructure in sintered composite was attribute to the solubility and homogeneity of metal cations in precursor sol. At the optimum amount of the PEG polymer, the metal ions were dispersed effectively in solution and a homogeneous polymeric network was formed. It made less agglomerated particles in the precursor sol and affected on uniform grain size in sintered composite.

• 한국분말재료학회지
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• 제9권5호
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• pp.346-351
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• 2002

Pure and fine, two-component titanate powders (barium titanate, calcium titanate etc.) were synthesized by an ethylene glycol method. Titanium isopropoxide and other metal ionic salts were dissolved in liquid-type ethylene glycol without any precipitation. In non-aqueous system, the amount of ethylene glycol affected the solubility and homogeneity of metal cation sources in the solution. At the optimum amount of the polymer, the metal ions were dispersed effectively in solution and a homogeneous polymeric network was formed. Most of the synthesized powders had sub-micron or nano-size primary particles after calcination and the agglomerated calcined powders were easily ground by ball milling process. All synthesized titanate powders had stable crystallization behavior at low temperature and high specific surface area after ball milling. The crystallization behavior and the microstructures of the calcined powders were affected on the ethylene glycol content.

• 대한화장품학회지
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• 제25권4호
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• pp.43-50
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• 1999

The planarized $SiO_2$ particles were prepared by two-step reduction method of making much smaller particles, micron-sized ones, to improve spreadability, adherence, and smoothness. Various pigments known as flaky extender usually have terrace layers on their surfaces, but $SiO_2$ particles in this study exhibit a smooth surface structure. These single $SiO_2$ particles were used as core particles to prepare the composite particles coated with ultra fine $TiO_2$ particles by a homogeneous precipitation method. The thickness and the morphology of the deposited $TiO_2$ layers could be modified by adjusting the reactant concentrations, the reaction time and the temperature. The characteristics of $SiO_2/TiO_2$ composite in the field of color cosmetics are to give an UV-cut effect and to enhance the chroma of human skin color, one of optical properties.

• Fibers and Polymers
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• 제4권4호
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• pp.195-198
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• 2003

Epoxidized polybutadiene (EPB) was prepared by polybutadiene (PB) with m-chloroperbenzoic acid (MCPBA) in homogeneous solution. EPB was blended with poly(3-hydroxybutyrate) (PHB) up to 30 wt% by solution-precipitation procedure. The thermal decomposition of PHB/EPB blends was studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and differential thermal analysis (DTA). The thermograms of PHB/EPB blends contained a two-step degradation process, while that of pure PHB sample exhibited only one-step degradation process. This degradation behavior of PHB/EPB blends, which have a higher thermal stability as measured by maximum decomposition temperature and residual weight, is probably due to crosslinking reactions of the epoxide groups in the EPB component with the carboxyl chain ends of PHB fragments during the degradation process, and the occurrence of such reactions can be assigned to the exothermic peaks in their DTA thermograms.

• 한국식물병리학회지
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• 제14권6호
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• pp.559-562
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• 1998

Odontoglossum ringspot virus (ORSV) was finally purified from ORSV-infected orchid plants by diethylaminoethyl (DEAE) cellulose anion exchange column chromatography. The virus was reliably eluted by potassium chloride at the concentration from 0.1 M to 0.13 M. Partial purification was done by solubilization with Triton X-100 (allkylphenoxypolyethoxy ethanol) and precipitation with polyethylene glycol (PEG; MW 8,000). The finally purified ORSV represented one distinct homogeneous band and the molecular weight of its capsid protein was about 17,500 Dalton in electrophoretic analysis. Electron microscopy showed not only intact particles ranged from 280 nm to 340 nm in length, but also segmented particles that final 140 nm to 220 nm and even disks. Enzyme-linked immunosorbent assay (ELISA) showed that final yield was 12 mg/100 g of the infected leaves. Bioassay demonstrated that the purified ORSV had the normal infectivity to orchid plants and Nicotiana glutionsa. Based on these data, anion exchange column chromatography could be efficiently applied to the purification of ORSV and other viruses similar to ORSV.