• Journal of the Korean Ceramic Society
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• v.26 no.1
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• pp.132-138
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• 1989

High purity(99.99%) spherical particles of hydrated Basic Aluminum Salts(BAS) were prepared by a homogeneous precipitation process utilizing the urea decomposition reaction and characterized by XRD, SEM, TG-DTA, IR and PSA methods. Amorphous hydrated BAS was precipitated in the range of pH 4~6. The molar ratio [Al3+]/[SO42-] for the precipitate particles was about 3.7. With increasing the concentration of aluminum sulfate the precipitation of the hydrated BAS occurred slowly and the precipitate particles with a narrow size distribution were fine(1-2${\mu}{\textrm}{m}$ in diameter). At temperatures in the range 400$^{\circ}$to 95$0^{\circ}C$, desulfurization and dehydroxylization resulted in weight loss with 22%. When the precipitate particles were thermally treated, the crystlline ${\gamma}$-Al2O3 was identifited by XRD at 50$0^{\circ}C$ and ${\gamma}$-Al2O3 particles were transformed into $\alpha$-Al2O3 at 100$0^{\circ}C$. A vermicular network was produced by calcining at 125$0^{\circ}C$ for 30min.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.307-310
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• 2005

Ageing behavior of the Al-Mg-Si alloy was modeled for the use of optimization of Al forging product. Typical precipitates of Al-Mg-Si alloy are a wide variety of metastable phases (e.g. GP zones, $\beta',\beta'$). These rod shaped particles take a role to hinder the dislocation movement. The precipitation sequence in Al-Mg-Si alloys is quite complex and the strength of precipitate particles differs with the ageing condition. In the present study, the ageing behavior of Al-Mg-Si alloy was investigated by using an industrial grade Al 6061 alloy forged product, which was a perform for an Al impeller for turbo charger. The precipitate hardening models by Esmaeili's approach were used for the analysis of ageing behavior.

• Progress in Superconductivity and Cryogenics
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• v.22 no.3
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• pp.7-12
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• 2020

Electromechanical properties of REBCO CC tapes are known to be limited by defects (cracks) that form in the brittle REBCO layer. These defects could be inherently acquired during the CC tapes' manufacturing process, such as slitting, and which can be initiated at the CC tapes' edges. If propagated and long enough, they are believed to cause critical current degradation and can substantially decrease the delamination strength of CC tapes. Currently, commercially available CC tapes from various manufacturers utilize different growth techniques for depositing the REBCO layers on the substrates in their CC tapes preparation. Their epitaxial techniques, unfortunately, cannot perfectly avoid the formation of particles, in which sometimes acts as current blocking defects, known as outgrowths. Collective research regarding the composition, size, and formation of these particles for various CC tapes with different deposition techniques are particularly uncommon in a single study. Most importantly, these particles might interact in one way or another to the existing cracks. Therefore, systematic investigation on the interactions between the cracks' development mechanism and particles on the REBCO superconducting layers of practical CC tapes are of great importance, especially in the design of superconducting devices. Here, a proper etching process was employed for the CC tapes to expose and observe the REBCO layers, clearly. The scanning electron microscope, field emission scanning microscope, and energy-dispersive x-ray spectroscopy were utilized to observe the interactions between cracks and particles in various practical CC tapes. Particle compositions were identified whether as non-superconducting or superconducting and in what manner it interacts with the cracks were studied.

• Microbiology and Biotechnology Letters
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• v.40 no.2
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• pp.157-162
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• 2012

In this study, we have for the first time applied increased surface area fractional precipitation in order to decrease the particle size of the anticancer agent paclitaxel from plant cell cultures. When compared with the case where no surface area increasing material was employed, the addition of ion exchange resin as a surface area increasing material resulted in a considerable decrease in the size of the paclitaxel precipitate. When ion exchange resin was used, the paclitaxel particles were four to five times smaller, having less than a 20 ${\mu}m$ radius, than those obtained in the absence of ion exchange resin. This is presumably because the growth of paclitaxel particles was impeded by the addition of ion exchange resin. The size of the paclitaxel precipitate also depended on the material used to increase the surface area, a result considered to be due to differences in the affinity between the particular ion exchange resin used and the paclitaxel particles. The yield of paclitaxel was significantly improved when ion exchange resin was used as a material to increase surface area. Paclitaxel, with a reduced particle size due to the addition of a surface area increasing material during the fractional precipitation process, is believed to be particularly useful for practical applications of the drug.

• Journal of the Korean Ceramic Society
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• v.34 no.10
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• pp.1009-1014
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• 1997

Ammonia gas was blown into the solution of zirconium ion to induce precipitation of supersaturated zirconium ion at gas-liquid interface with increase in pH. The influence of pH on the phase and particle size of precipitate and calcined powders has been investigated. At pH 4.5 of zirconium solution, maximum yield of 98.7% was obtained. Above pH 4.5, there was no more increase of yield. Above pH 5.5, large aggregates consisting of primary particles were observed in precipitate and calcined powders. At pH 4.5, almost aggregate-free fine spherical zirconia powders were obtained.

• Journal of the Mineralogical Society of Korea
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• v.9 no.2
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• pp.64-70
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• 1996

Early weathering products of anorthosite were investigated by using scanning electron microscopy in order to trace the development of halloysite particles and aggregates. Tiny short tubes or spheres precipitate on the plagioclase surface in the initial stage of weathering and form the compact globular aggregates. With continued growth, several globules are coalesced into wrinkled halloysite aggregates, and short tubes or spheres in globules grow into long tubes forming sheaf-like aggregates. Particle shape of halloysite varies with changing supersaturation degree of weathering solution, and determines the morphology of halloysite aggregates.

• Journal of the Korean Chemical Society
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• v.13 no.2
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• pp.157-164
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• 1969

Aoolphane was treated with 30% Hydrochloric acid at $18^{\circ}C$ for two hows with stirring in order to obtain the insoluble form of SiO2 gel and to extract quantitatively both $Al_2O_3$as and $Fe_2O_3AlCl_3{\cdot}6H_2O Fe$ and $Cl_3{\cdot}6H_2O$ forms, respectively, at the same time. $SiO_2$ gel was filtered and to the filterate Ammonia was added to precipitate $Al(OH)_3[Fe(OH)_3 Contaminated ]$ The precipitate was separated by filteration and the filterate was recovered as the form of $NH_4Cl$. The precipitate was treated with 200g (NaOH)/l Concentration of NaOH a little excessively to the equivalent at $65~70^{\circ}C$ as $Fe(OH)_3$ formed was insoluble, it was filtered of and to the filterate containing $NaAl(OH)_4(OH_2)_2$Carbon dioxide gas was bubbled at $50^{\circ}C~90^{\circ}C$ to obtain the precipitate with excellent filterability and crystallinity. The product was certified to be Dawsonite $(NaAl(OH)_2CO_3)$ by X-Ray diffraction analysis at below $40^{\circ}C$, when $CO_2$ gas was bubbled into the relatively lower concentration of $NaAl(OH)_4(OH_2)_2$ solution, the precipitate of very fine particles was formed, which was hard to filter and with the Composition of $\alpha-Al_2O_3-H_2O$ (Boehmite).

• Applied Microscopy
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• v.36 no.2
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• pp.47-55
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• 2006

In this paper a transmission electron microscope (TEM) observation of fine Cu precipitates distributed randomly in Al-2.5Cu-1.5Mg wt.% alloy is first reported. This new observation happened to occur when an ion milling was peformed to remove oxides on the specimen, particularly, aged 100 hours at $150^{\circ}C$. Meanwhile the oxides were identified to be $Cu_2O$ particles. For this work involved with analysis of diffraction rings, the formulation of the electron diffraction rings pattern for powder particles was made. Finally the significance of this unexpected ion milling effort on the alloy was discussed

• Korean Journal of Materials Research
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• v.8 no.2
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• pp.126-130
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• 1998

Aluminum sulfate, $AI_{2}(SO_4)_3\cdot18H_2O$ was prepared by adding of kaolin-dissolved sulphuric acid into ethanol and its thermal decomposition behavior was discussed. As-synthesized high purity precipitate particles were platelike shapes of $2\mu\textrm{m}$ size. With increasing drop rate of leach liquor into ethanol, the crystallite sizes of the precipitate decreased. The apparent activation energies for dehydration and sulfate decomposition of the precipitate were $11.9Kcal mol^{-1}$ and $48.2kcal mol^{-1}$ respectively.

• Journal of the Korean Ceramic Society
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• v.24 no.3
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• pp.215-222
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• 1987

${\alpha}$-Ferric Hydrous Oxide and ${\alpha}$-Ferric Oxide were obtained as following processes that Ferric Nitrate solution was adjusted to pH 6-8 with Ammonium Hydroxide, refluxed the Iron precipitate for 1 hr. at 80$^{\circ}C$, washed it with water and Methanol (95%), dried it to obtain ${\alpha}$-Ferric Hydrous Oxide at 60$^{\circ}C$, and then heated in atmosphere to prepare ${\alpha}$-Ferric Oxide for 1 hr. at 450$^{\circ}C$. Mica particles cleaned with ultrasonicator (45KHz) in water were mixed with Ferric Nitrate solution and treated it to adsorb ${\alpha}$-Ferric Oxide on the surface of mica particles by using the abovementioned processes, but the heated temperature was at 500$^{\circ}C$. The maximum wavelength of reflected light on the surface of mica-${\alpha}$-Ferric Oxide (50%) was appeared at 546nm but -Ferric Oxide free mica only was at 436 nm. The maximum wavelength was shifted to longer when the weight ratios of ${\alpha}$-Ferric Oxide to mica was changed from 1% to 50%.