• 대한화학회지
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• 제35권4호
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• pp.422-426
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• 1991

천연 규산 알루미늄 광인 할로이사이트 광물로부터 고순도 ${\alpha}-Al_2O_3$을 합성하기 위해 ${\alpha}-Al_2O_3$의 전구물질인 수산화 알루미늄과 암모니움 명반을 합성하였다. 이들에 대한 열분해 반응기구는 열분석, XRD 및 IR 측정으로부터 규명되었고, 열분해로부터 얻어진 ${\alpha}-Al_2O_3$의 미세구조 및 비표면적은 SEM 및 BET 측정에 의해 수행되었다. 이때 ${\alpha}-Al_2O_3$ 입자의 크기는 모두 ${\phi}$ = 0.1∼0.5 ${\mu}$m이었으나, 비표면적의 크기는 암모니움 명반으로부터 얻어진 경우(89.0 m$^2$/g)가 수산화 알루미늄으로부터 얻어진 경우(7.3 m$^2$/g)보다 매우 높은 결과를 얻었다.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2003년도 춘계총회 및 연구발표회 초록집
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• pp.208.1-208
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• 2003

• 한국막학회:학술대회논문집
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• 한국막학회 2005년도 춘계 총회 및 학술발표회
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• pp.46-48
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• 2005

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2005년도 추계학술발표회
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• pp.765-766
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• 2005

• 한국응용과학기술학회지
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• 제15권3호
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• pp.55-60
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• 1998

The sodium ${\alpha}-sulfo$ fatty acid vinyl ester oligomers, which are oligomer type surfactants were prepared by polymerization with fatty acid vinyl acetate. The ${\alpha}-sulfonation$ of fatty acid vinyl ester oligomers were carried by direct addition of sulfur trioxide. The dispersing performance of oligomer type anionic surfactants and sodium dodecyl sulfate(SDS) in the aqueous suspension of iron oxide and titanium dioxide particles was evaluated by particle size distribution and zeta-potential measurement. As results, the particles of iron oxide and titanium dioxide were flocculated by addition of small amount of oligomer type anionic surfactants and sodium dodecyl sulfate(SDS), then the flocks redispersed by more addition of oligomer type anionic surfactants and SDS. The flocculation, redispersion process was observed in lower concentration range of oligomer type anionic surfactants than SDS. Especially, the dispersing action of sodium ${\alpha}-sulfo$ palmitic acid vinyl ester oligomer was better than sodium ${\alpha}-sulfo$ lauric acid vinyl ester oligomer.

• 한국전기전자재료학회논문지
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• 제22권6호
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• pp.501-505
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• 2009

$TiO_2$ nano-particle paste was prepared by ethyl cellulose, $\alpha$-terpineol and bis(2-ethylhexyl) phthalate (dioxcyl phthalate) for dye-sensitized solar cells (DSSCs). Dispersion and absorbance of $TiO_2$ photoanode films was controlled by adding different amount of ethyl cellulose and $\alpha$-terpineol. The morphology of prepared $TiO_2$ films was studied by field emission scanning electron microscopy (FE-SEM) and the optical properties of $TiO_2$ films were measured by UV/vis spectra. Photovoltaic-current density was observed to determine the electrochemical response of DSSCs. Energy conversion efficiency was obtained about 7.1% at ethyl cellulose and $\alpha$-terpineol at optimal mixed ratio (as ethyl cellulose: 0.1 g; $\alpha$-terpineol: 1.5 ml) under illumination with AM 1.5($100\;Wcm^{-2}$) simulated sunlight.

• 한국세라믹학회지
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• 제52권4호
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• pp.273-278
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• 2015

${\alpha}-Al_2O_3$ was synthesized by solvothermal synthesis using ${\alpha}-Al_2O_3$ seed, precursor of fine boehmite (Al(OOH)) or gibbsite ($Al(OH)_3$), and 1, 4-butanediol solvent. The seed content and precursor type were selected as variables in order to synthesize ${\alpha}-Al_2O_3$. The formation time of ${\alpha}-Al_2O_3$ was reduced and the size of the particles was decreased with addition of the seed. When the seed content was increased, the size of the synthesized ${\alpha}-Al_2O_3$ was reduced. Morphologies of the as-synthesized ${\alpha}-Al_2O_3$ with ${\alpha}-Al_2O_3$ seed were polyhedron-shaped, while the shape was plate-like or polyhedral without the seed, depending on the additives or the average particle size of the boehmite precursor. The aggregation of as-synthesized ${\alpha}-Al_2O_3$ from boehmite was smaller than that from gibbsite. As-synthesized ${\alpha}-Al_2O_3$, with 140 nm size, was obtained by using the seed and boehmite precursor.

• 열처리공학회지
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• 제29권2호
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• pp.51-55
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• 2016

The P/M processing of titanium aluminide using amorphous TiAl is developed by which it is possible to overcome inherent fabricability problems and to obtain a fine microstructure. A high quality amorphous TiAl powder produced by reaction ball milling shows clear glass transition far below a temperature at the onset of crystallization in differential scanning calorimetry above a heating rate of 0.05 K/s. We obtained a fully dense compact of amorphous TiAl powders, encapsulated in a vacuumed can, via viscous flow by hot isostatic pressing (HIP). Isothermally annealing of HIP'ed amorphous compact under a pressure of 196 MPa shows a progressive growth of ${\gamma}-TiAl$ phase with ${\alpha}2$ ($Ti_3Al$), which is characterized by increasing sharpness of X-ray peaks with temperature. Fully dense HIP'ed compact of titanium aluminide TiAl shows a high hardness of 505 Hv, suggesting strengthening mechanisms by sub-micron sized grain of ${\gamma}-TiAl$ and particle-dispersion by second phase constituent, ${\alpha}2$.

• Journal of Magnetics
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• 제5권2호
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• pp.40-43
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• 2000

Acicular $\alpha-FeOOH\; and\; Ba(OH)_2\cdot8H_2O$ are starting materials in this study. This paper presents the characteristics of the contents of citric acid and heating condition for preparing acicular barium ferrite powder. They control particle shape, crystalline phase, magnetic properties of acicular barium ferrite powder So the effects of the contents of citric acid and heating condition are studied. The experimental condition for starting materials were 800~1000$\circ C$ in firing and 0~40 wt% citric acid, respectively, Ba-ferrite particles fired at the range of 800 $\circ C$to 900 $\circ C$ were maintained as acicular particle shape, but there were mixed particles of acicular and round shape after fired at 950 $\circ C$. Ba-ferrite powder of the single phase was obtained in firing at 900~1000$\circ C$ and with 20 wt.% citric acid. There were unreacted phase of $\alpha-Fe_2O_3 \;and \; BaFe_2O_4$ phases as a second phase in case of sintering at below 850 $\circ C$. Acicular barium ferrite powder of single phase was also produced in firing at 900 $\circ C$ with 20 wt.% citric acid. The saturation magnetization of single phase of acicular $BaFe_12O_19$powder was about 51 emu/g and coercivity was about 4200 Oe.

• 한국의류학회지
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• 제34권7호
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• pp.1175-1183
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• 2010

This study investigates the effect of polarity of oily soil on adhesion of oily and particulate soil to PET fabric in oily/particulate mixed soil systems. The potential energy of interaction between two particles was examined as a fundamental environment of adhesion of soil to fabrics. The ${\zeta}$-potential of ${\alpha}-Fe_2O_3$ particles was measured by a microelectrophoresis method, and the potential energy of interaction between two particles was calculated by using the Verwey-Overbeek theory. The ${\zeta}$-potential of particle and the potential energy of interaction between two particles was slightly influenced by the polarity and type of oily soil, but increased with the increased anionic surfactant concentration and amount of oily soil. The adhesion of oily soil to fabric increased with the additional amount of polarity of oily soil and decreased surfactant concentration that was relatively high at a temperature of $60^{\circ}C$ surfactants solution. The adhesion of ${\alpha}-Fe_2O_3$ particle to PET fabric decreased with an increased amount and polarity of oily soil and increased surfactant concentration Although some similarity exists, the general trend of the adhesion to fabric by particulate soil differ from oily soil.