• Resources Recycling
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• v.25 no.5
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• pp.50-56
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• 2016

Extraction behaviour of silver from nitric acid solutions by Cyanex 301 as an extractant was examined. Detailed studies have been conducted to evaluate the effect of different variables influencing the extraction such as concentration of nitric acid and extractant, phase ratio(O/A) and synergism of mixed extractant. The extraction behaviour of associated metals namely Ca, Al, Fe, Zn and Sr has been investigated. The extraction results show that Ag can be extracted effectively by Cyanex 301 and selectively extracted from 3.0M $HNO_3$ using 5% Cyanex 301. Impurity metals loaded in organic phase can be effective scrubbed by 4.0M HCl. Finally, pure silver solution can be obtained efficiently by thiourea as a stripping reagent.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.12
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• pp.601-605
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• 2004

In this paper, we investigated ionic impurities and physical properties by change of carbon black content, which is asemiconductive material for underground power transmission. Specimens were made into sheet form with three existing resins and nine specimens for measurement. The ionic impurities of the specimens were measured using anICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometer), and the density of specimens was measured by a density meter. Specific heat (Cp) was then measured using aDSC (Differential Scanning Calorimetry). The ranges of measurement temperature were from 0[$^{\circ}C$] to 200[$^{\circ}C$], and heating temperature was 4[$^{\circ}C$/min]. Ionic impurities were measured to be high according to increases in the content of carbon black from this experimental result and density was also increased according to these properties. In particular, the impurity content values of A1 and A2, and existing resins, were measured at more than 4000[ppm]. Specific heat from the DSC results was lowered according to augmentation in the content of carbon black. The ionic impurities of carbon black containing Fe, Co, Mn, Al and Zn are forms of rapidly passed kinetic energy that increase the number of times breaking occurs during unit time with the near particles according to an increase in the vibration of particles by the applied heat energy.

• Journal of the Korean Ceramic Society
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• v.29 no.5
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• pp.357-366
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• 1992

Residual organics were considered as impurity in Sol-Gel method. The purpose of this study was to find the conditions to contain as much residual organics as possible in silica gel prepared from TEOS(tetraethylortho-silicate) by Sol-Gel method. Residual organics are to be expected to have reduction effect on synthesizing Si3N4 from silica gel. The results of this study are follows: 1) The maximum content of entrapped carbon was 19.8 wt.%(C/SiO2=0.25 wt.ratio) in silica gel synthesized under the conditions 1.5 fold mole water for incomplete hydrolysis, 2.5 fold mole phenol as a solvent and 0.1 fold mole HCl as a catalyst to TEOS. 2) Silica gel with organics entrapped by Sol-Gel method had a positive effect on the formation of Si3N4 compared with commercial silica gel. 3) Sintered body of synthesized $\alpha$-Si3N4 with Y2O3 and Al2O3 as additives at 175$0^{\circ}C$ in N2 atmosphere showed bending strength, 602$\pm$20 MPa and frature toughness 4.45$\pm$0.15 MPa.m1/2.

• Journal of the Korean Ceramic Society
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• v.31 no.11
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• pp.1330-1336
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• 1994

Ta2O5 films were deposited on the p-Si(100) substrates by ECR-PECVD and annealed in O2 atmosphere. The thicknesses of Ta2O5/SiO2 layers were measured by an ellipsometer and a cross-sectional TEM. Annealing in O2 atmosphere enhanced the stoichiometry of the Ta2O5 film and reduced the impurity carbon content. Ta2O5 films were crystallized at the annealing temperatures above 75$0^{\circ}C$. The best leakage current characteristics and the maximum dielectric constant of Ta2O5/SiO2 film capacitor were observed in the specimen annealed at $700^{\circ}C$ and 75$0^{\circ}C$, respectively. The flat band voltage of the Al/Ta2O5/SiO2/p-Si MOS capacitor was varied in the range of -0.6~-1.6 V with the annealing temperature. The conduction mechanism in the Ta2O5 film, the variation of the effective oxide charge density with the annealing temperature, and the effective electric field distribution in the Ta2O5/SiO2 double layer were also discussed.

• Proceedings of the IEEK Conference
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• 2001.06b
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• pp.49-52
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• 2001

The electrochemical characteristics of Alalloy thin film with low impurity concentrations AIZr deposited by using do magnetron co-sputtering deposition are investigated for the applications as gate bus line in the TFT-LCD panel. AlZr thin films were deposited various atomic percent of Zr. For increasing Zr atomic percent the hillock density was decreased and the resistivity was increased. The deposited thin films show the decrease of resistivity and the increase of grain size after the RTA at 300 $^{\circ}C$for 20 min.. Moreover, the resistivity of AIZr does not show appreciable grain size dependence after RTA. It is concluded that the decrease of resistivity after RTA is due to the increase of grain size. The annealed AIZr(at.0.9%) is found to be hillock free. The electrode potentials of AIZr were less than ITO's (-1.4V) and the etching rate of AIZr(at.0.9%) was 3.8587ng/sec. in KOH(10%) solution. Caculation results reveal that the AIZr(at.0.9%) thin film can be applicable to gate line of 25" UXGA class TFT-LCD panels and can not be applicable to data line.line.

• Journal of the Korean Society for Heat Treatment
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• v.23 no.6
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• pp.338-343
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• 2010

Mechanical properties and microstructures of medium carbon high manganese steels were investigated in terms of alloying elements such as Mn, C contents, and heat treatment condition. Austenite volume fraction was increased with increasing Mn content, leading to hardness decrease in the range of Mn content of above 10% after quenching and tempering. Such results are also supported by microstructural analysis and X-ray diffraction in that the increase in mangaese content results in the increase in austenite fraction. Studies on tempering condition indicated that not only hardness and tensile strength but also charpy impact values were reduced as tempering temperature were raised in the range of $250^{\circ}C$ to $600^{\circ}C$. It was also observed that fracture mode was changed from dimple to intergranular fracture. Such results are thought to be due to very fine carbide precipitation or impurity segreagation at grain boundaries as tempering temperature goes up. Heat treatment of Fe-5Mn-2Si-1Al-0.4C can be optimized by austenitizing at $850^{\circ}C$, air cooling and tempering at $250^{\circ}C$, resulting in 1950 MPa in Tensile strength, 17% in elongation and 23.3 $J/cm^2$ in charpy impact energy with high work hardening characteristics.

• Journal of Korea Foundry Society
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• v.18 no.4
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• pp.357-363
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• 1998

Microstructure of A356 aluminium alloys cast in a permanent mold was investigated by optical microscope and image analyzer, with particular respect to the shape and size distribution of iron intermetallics known as ${\beta}-phase$ ($Al_5FeSi$). Morphologies of the ${\beta}-phase$ was found to change gradually with the Be:Fe ratio like these. In Be-free alloys, ${\beta}-phase$ with needlelike morphology was well developed, but script phase was appeared when the Be:Fe ratio is above 0.2:1. With the Be:Fe ratios of 0.4:1-1:1, script phase as well as Be-rich phase was also observed. In case of higher Be addition, above 1:1, Be-rich phase was observed on all regions of the specimens, and increasing of the Be:Fe ratios gradually make the Be-rich phase coarse. It was also observed that the ${\beta}-phase$ with needlelike morphology was coarsened with increase of the Fe content in Be-free alloys. However, in Be-added alloys, length and number of these ${\beta}-phases$ were considerably decreased with the increased Be:Fe ratio. It was concluded that Fe impurity element to be crystallized into needlelike intermetallics was tied up by Be addition element, and new phases were crystallized into script or Be-rich intermetallics.

• Journal of Korea Foundry Society
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• v.14 no.1
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• pp.28-34
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• 1994

Metallurgical-grade polycrystalline silicon was directionally solidified at growth rates of $0.2{\sim}1.0mm/min$ by using split type, reusable graphite molds which were coated with $Si_3N_4$ powder. The resultant grain sizes of the silicon ingots and the shapes of the solid/liquid(S/L) interfaces were investigated. X-ray diffraction was used to determine the preferred orientation in each of the silicon ingots. The impurity content of the silicon was analyzed and the resistivities of the ingots were measured. During the growth of an ingot, the shape of the S/L interface was concave to the silicon melt, and the resistivity decreased. The presence of Al which can be acting as a carrier, is thought to be the main factor causing such a decrease in resistivity. When a growth rate of 0.2㎜/min was used, the preferred orientation was found to be (111).

• Korean Journal of Materials Research
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• v.30 no.11
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• pp.573-580
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• 2020

YAG (Yttrium Aluminum Garnet, Y₃Al₅O₁₂) has excellent plasma resistance and recently has been used as an alternative to Y₂O₃ as a chamber coating material in the semiconductor process. However, due to the presence of an impurity phase and difficulties in synthesis and densification, many studies on YAG are being conducted. In this study, YAG powder is synthesized by an organic-inorganic complex solution synthesis method using PVA polymer. The PVA solution is added to the sol in which the metal nitrate salts are dissolved, and the precursor is calcined into a porous and soft YAG powder. By controlling the molecular weight and the amount of PVA polymer, the effect on the particle size and particle shape of the synthesized YAG powder is evaluated. The sintering behavior of the YAG powder compact according to PVA type and grinding time is studied through an examination of its microstructure. Single phase YAG is synthesized at relatively low temperature of 1,000 ℃ and can be pulverized to sub-micron size by ball milling. In addition, sintered YAG with a relative density of about 98 % is obtained by sintering at 1,650 ℃.

• Journal of Environmental Science International
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• v.28 no.6
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• pp.553-559
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• 2019

In this study, zeolitic materials at $Na_2CO_3/CFA$ ratio of 0.6 - 1.8 were synthesized from coal fly ash from a thermal power plant using a fusion/hydrothermal method. The zeolitic materials were found to have cubic crystals structure and X-ray diffraction (XRD) peaks of Na-A zeolite by XRD and SEM analysis. When the zeolitic materials were synthesized from the coal fly ash, the XRD peaks of the zeolitic materials at $Na_2CO_3/CFA$ ratios of 0.9-1.8 had the same location as the XRD peaks of commercial Na-A zeolite. The XRD peaks of the Na-A zeolite ($Na_{12}Al_{12}Si_{12}O_{48}27.4H_2O$) were confirmed in the $2{\theta}$ in the range of 7.18-34.18. However, it was also confirmed that peaks of $CaCO_3$, an impurity inhibiting synthesis of Na-A zeolite from CaO and $Na_2CO_3$ in the coal fly ash, occurred in the XRD peaks of the zeolitic materials at $Na_2CO_3/CFA$ ratio of 1.5-1.8. The crystallinities of the zeolitic materials tended to increase gradually within the $Na_2CO_3/CFA$ ratio range of 0.6-1.8.