• Resources Recycling
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• v.29 no.5
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• pp.28-37
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• 2020

In this study, the effect of precipitation temperature, ammonium chloride amount and addition method, vanadium and sodium hydroxide content of the solution on the precipitation of ammonium metavanadate were examined by using the sodium vanadate(NaVO₃) solution in alkali region as a starting material. As the pH of solution decreased, the addition amount of ammonium chloride and the vanadium content of the solution increased, the precipitation rate of ammonium metavanadate increased. In this research condition, the basic conditions for obtaining more than 90% of precipitation yield were 10,000mg/L of vanadium content, 2equivalents of ammonium chloride addition, room temperature, and 2 hours of precipitation time. The size of precipitated particles decreased with increasing precipitation rate. Especially when liquid ammonium chloride was injected into the solution, the precipitation rate was the slowest and the particle size of the precipitate was the largest. After the primary precipitation by adding ammonium chloride as a solid, the secondary precipitation was carried out by adding new reactants. At this time, the precipitation with added ammonium chloride solid was not affected by the precipitates present in the solution. However, when liquid ammonium chloride was added, new precipitate was deposited on the surface of the precipitate present in the solution, increasing its size. Due to the difference in ammonium metavanadate solubility to temperature, the precipitation temperature at the vanadium content of 10,000mg/L in the solution affected the precipitation rate of ammonium metavanadate and the precipitation temperature did not affect the precipitation rate at a high concentration of more than 30,000mg/L vanadium content in the solution.

• Korean Journal of Materials Research
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• v.33 no.10
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• pp.406-413
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• 2023

This study used optical and scanning electron microscopy to analyze the surface oxidation phenomenon that accompanies a γ'-precipitate free zone in a directional solidified CM247LC high temperature creep specimen. Surface oxidation occurs on nickel-based superalloy gas turbine blades due to high temperature during use. Among the superalloy components, Al and Cr are greatly affected by diffusion and movement, and Al is a major component of the surface oxidation products. This out-diffusion of Al was accompanied by γ' (Ni₃Al) deficiency in the matrix, and formed a γ'-precipitate free zone at the boundary of the surface oxide layer. Among the components of CM247LC, Cr and Al related to surface oxidation consist of 8 % and 5.6 %, respectively. When Al, the main component of the γ' precipitation phase, diffused out to the surface, a high content of Cr was observed in these PFZs. This is because the PFZ is made of a high Cr γ phase. Surface oxidation of DS CM247LC was observed in high temperature creep specimens, and γ'-rafting occurred due to stress applied to the creep specimens. However, the stress states applied to the grip and gauge length of the creep specimen were different, and accordingly, different γ'-rafting patterns were observed. Such surface oxidation and PFZ and γ'-rafting are shown to affect CM247LC creep lifetime. Mapping the microstructure and composition of major components such as Al and Cr and their role in surface oxidation, revealed in this study, will be utilized in the development of alloys to improve creep life.

• Korean Journal of Materials Research
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• v.14 no.1
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• pp.9-12
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• 2004

Metallic impurities, such as Fe, Cu, and Au, become generation and recombination centers for minority carriers when combined with oxide precipitates or silicon self-interstitial clusters. As these centers may cause leakage and discharge in silicon devices, their prevention through gettering of the metallic impurities is an important issue. In this article, key aspects of intrinsic gettering, such as oxygen control, wafer cleaning, device area denudation, and bulk oxygen precipitation are discussed, and a practical method of implementing intrinsic gettering is outlined.

• Korean Journal of Pharmacognosy
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• v.12 no.2
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• pp.88-93
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• 1981

One hundred and forty-four extracts have been tested for the presence of saponins, using the method of froth formation, precipitate formation by acid hydrolysis, Liebermann-Buchard reaction on the acid hydrolysate, and hemolytic activity of the extracts. Among the samples tested, thirteen extracts showed positive saponin reaction in all the tests employed and one hundred and thirty-six showed positive in one or more tests of saponins. The results are tabulated.

• KSBB Journal
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• v.15 no.4
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• pp.405-407
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• 2000

A novel recovery method was developed to obtain the plant cell and its debris from Taxus chinensis cell cultures By pH control of plant cell cultures plant cell and debris was precipitated. The best pH is between 1.8 and 2.2 to obtain the precipitate of the plant cell and debris. Also paclitaxel is stable in this acidic conditions. This method is very simple an efficient to recover the plant cell and debris from plant cell cultures.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.135-139
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• 2001

According to the requirement of cyanide precipitation-purification technology, adopt the acidized sulfate to precipitate cyanide. Studying the influence of acidity and the dosage of sulfate on precipitation rate of impurity ion in cyanide wastewater, and, on the basis of synthetic precipitation experiments, we obtain principle process of cyanide precipitation-purification to technology.

• Journal of the Korean Ceramic Society
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• v.22 no.5
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• pp.61-65
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• 1985

This stud deals with the conditions for the Formation of Ba-Ferrite by Hydrothemal synthesis Suspensions Containing either iron(III) hydroxide or hydroxide oxide and barium ians were subjected to autoclavings at various temperatures from 150 to 30$0^{\circ}C$. A ferromagnetic precipitate BaO.$6Fe_2O_3$ consisting of hexagonal plate-like particle was obtained by suitable combination of temperature and concentration of KOH

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.10a
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• pp.228-231
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• 1997

A series of load relaxation tests was performed to determine stress-strain rate curves at high temperatures. Constitutive parameters of GBS and GMD were evaluated from the curves using the recently proposed inelastic deformation theory. Tensile tests and Microsturcture investigations showed deformation behavior as the relaxation test results predicted.

• 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 Mineralogical Society of Korea
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• v.24 no.2
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• pp.145-149
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• 2011