• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.11 no.3
• /
• pp.89-95
• /
• 2001

The CZ-silicon crystal was annealed at $1350^{\circ}C$ to dissolve the vacancy type grown-in defects. A this temperature, the equilibrium concentration of the oxygen in the silicon crystal is around $1.7{\times}10^{18}$ which induces the oxygen undersaturation in the silicon crystal. This situation results in the faster dissolution of the grown-in defects in the bulk of the silicon wafer than near the surface. This indicates the possibility that the presence of the higher concentration of silicon interstitial hinders the dissolution of the grown-in defects, which were known to compose of the vacancy clusters with surrounding silicon oxide film. This expectation was confirmed by the observation that the slower dissolution of the grown-in defects near the surface of the silicon wafer in the oxygen atmosphere than in the argon atmosphere. This result is quite opposite to the previous argument hat presence of the excess silicon interstitial leads to faster dissolution of the vacancy type defects.

• Resources Recycling
• /
• v.12 no.4
• /
• pp.30-37
• /
• 2003

A kinetics study on the dissolution reaction of zinc-ferrite has been made with aqueous sulfuric acid in various temperature and concentration. Fraction reacted(R) and apparent rate constant(K) increased with increasing temperature and concentration of sulfuric acid solution. The rate of dissolution is shown by $1-(1-K)^{1/3}=Kt$ for the initial stage of the reaction in aqueous sulfuric acid, where K is apparent rate constant, R is fraction reacted and t is reaction time, respectively. Activation energy associated with reaction was determined to be 16.3 kcal/mole. The dissolution of zinc-ferrite in sulfuric acid solution is dissolved by sto-ichiometric composition, but Fe and Zn did not dissolved, respectively.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2002.05a
• /
• pp.2-2
• /
• 2002

Quartz Crystal Microbalance(QCM)은 표면에 묻은 물질의 미량의 무게변화도 간단히 측정 할 수 있어 반웅기 내에서 일어나는 현상올 in-situ로 즉시 알 수 있는 장점을 가진 장치이 다. 이 장치를 이용하면 초엄계 이산화탄소 내에서 용해도를 알 수 있고, 대상물질이 녹아냐 가는 속도를 측정하면 확산계수를 구할 수 있다. 그리고, 초음파 혼을 반응용기 내에 설치하 고, 초음파 효과를 알아보았다. 먼저 static system에서 초음파 효과를 알아보았다. Cu(acac)2를 대상으로, 밀폐된 용기에서 수행한 실험에서, 액체와 초임계 이산화탄소 내에서 용해속도를 QCM으로 구할 수 있었다. 용해속도로부터 Cu(acac)2의 확산계수를 측정할 수 있었다. 액체 내에선 $10^{-4}{\;}cm2/sec$, 초임계상태에서 $10^{-2}{\;}cm2/sec$의 값을 갖는 것으로 나타 났다. 그리고, 초음파를 사용할 경우 이 확산계수값이 4-5배정도 증가하는 것으로 냐타났다. 이어서 dynamic system에서 반응을 알아보았다. Cyanex를 함유한 C02를 반응용기에 흘리 면서 QCM표면에 묻은 Co이온의 용해속도를 측정하였다. 초음파는 용해도에 아무 역활을 안하는 것으로 나타났다. 주어진 조건에서 13 microgram/gram-cyanex의 용해도를 갖는 것 으로 나타났다.

• Applied Chemistry for Engineering
• /
• v.9 no.3
• /
• pp.388-393
• /
• 1998

The effects of surface area of $UO_2$ pellets($s:0.034{\sim}0.282cm^2/g-UO_2$), concentration of nitric acid(1.5~10N) and temperature($40{\sim}105^{\circ}C$) on the dissolution rate were investigated in this experiment. The results showed that dissolution rate of $UO_2$ pellets was in direct proportion to effective surface area(s) and well fit to linear plot in high surface area. The dissolution rate was expressed as dc/dt = 10.6s at $90^{\circ}C$, [$HNO_3$]=8N, and proportioned to the power 1.42 of $HNO_3$ concentration. And also, the results showed that dissolution rate was sharply increased according to temperature increase in temperature below $90^{\circ}C$, but decreased in temperature above $90^{\circ}C$. Activation energy(E) was evaluated to be 36.3KJ/mol.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.16 no.1
• /
• pp.46-52
• /
• 2008

Oils and chlorinated solvents leaking to the subsurface are entrapped in the soil pore and these are called as nonaqueous phase liquids (NAPL). NAPL entrapped in porous media acts as a continuous source for surface and ground water contamination. This study visualized dissolution of trichloroethylene (TCE) entrapped in porous media and quantified the velocity of TCE dissolution using an image analysis technique. As the water velocity increased, the level of dissolution increased. The results imply that a TCE contaminated region having a high infiltration rate and groundwater velocity may result in severe groundwater contamination. Microscopic images of TCE entrapped in porous media showed that TCE present in the preferential flow paths was easily dissoluted into the water phase. However, TCE present in the stagnant flow region was visualized for long time. The results imply that TCE would be still present in the soil if TCE is detected in goundwater.

• Journal of the Korean Chemical Society
• /
• v.54 no.1
• /
• pp.88-92
• /
• 2010

Isopropyl mercaptan is an important pharmaceutical intermediate and chemical material. And thiourea and triglycol are the main materials for the synthesis of isopropyl mercaptan. Therefore the dissolution of thiourea in triglycol solution is very important for the production of isopropyl mercaptan. The aims of this study are to examine the dissolution kinetics of thiourea in triglycol solution, and to present an alternative process for producing isopropyl mercaptan. In order to investigate the dissolution kinetics of thiourea in triglycol solution, the concentrations of solution and reaction temperature were selected as experimental parameters. It was determined that the dissolution rate of thiourea increased with the increase in solution concentration and temperature. An empirical equation was used in fitting the data. Statistical analysis indicated small errors and the results should be reliable.

• Korean Chemical Engineering Research
• /
• v.48 no.6
• /
• pp.712-716
• /
• 2010

Salting-out technique was adopted to crystallize dye crystals from dye solution. Solubility of dye solution and crystallization kinetics of Reactive Red 218 was investigated. Solubility of dye solution is decreased by higher KCl concentration. The empirical expressions of salting-out crystallization kinetics for Reactive Red 218 in continuous MSMPR crystallizer was $G=6.864{\times}10^{-5}{\Delta}C^{1.207}$ and $B^0=4.8{\times}10^{22}{\Delta}C[1.1{\times}10^{-13}+{({\Delta}C)}^{0.7}{M_T}^2]$.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.10 no.6
• /
• pp.1292-1297
• /
• 2009

This study was performed to investigate solubility, dissolution rate and ash content of solid type fuel additive in gasoline and diesel in order to set up manufacturing standards. From the results, the unfiltered impurities were increased when the fuel additive was added on gasoline and diesel. Also, the unfiltered fuel additive was decreased with respect to increasing the pore size of the filter paper. When one gram of the fuel additive was dissolved in one liter of gasoline at room temperature, the best dissolution rate was about 2 hours. But, almost nothing was dissolved in diesel during 72 hours at $20^{\circ}C$ below zero. At the experiment of ash content, the gasoline which the fuel additive was melted in was showing 28 times more ash content than that was not including the fuel additive. Therefore, it seemed that almost all of ash content was caused by the fuel additive.

• Applied Chemistry for Engineering
• /
• v.3 no.4
• /
• pp.686-693
• /
• 1992

In order to investigate the mechanism of dissolutin of nickel from a matte composed essentially of heazlewoodite and ferronickel, the leaching in an aqueous solution of hydrochloric was carried out at $50-90^{\circ}C$, 0.5-3.ON HCl, and with the particle sizes between $100-160{\mu}m$ and $400-500{\mu}m$. The leaching rate of heazlewoodite was much rapider than that of ferronickel, and the two components were simultaneously dissolved with different reaction rates. Within the experimental range, NiS, an intermediate, was not formed. However a possibility to form a thin layer of NiS on particle surface upon saturating the reaction mixture with $H_2S$ was not excluded. At the initial stage, the activation energy was about 10 kcal/g mol. The reaction occurred at the particle surface, and consequently the particle size decreased with time. The rate of dissoultion for nickel was linearly proportional to the concentration of HCl up to 1.0N.

• 순환기질환의공학회:학술대회논문집
• /
• 2004.11a
• /
• pp.7-8
• /
• 2004