• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.2
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• pp.59-64
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• 2014

Crystallographic phases of Plasma electrolytic oxidized Al alloy, A1050, were investigated. The electrolyte of PEO was $Na_2Si_2O_3$ and KOH. Unipolar pulse, $ 2000{\mu}sec$ with $400{\mu}sec+420V$ impulse, were applied for 2 min, 5 min, 15 min, and 30 min. ${\gamma}-Alumina$, as well as ${\alpha}-alumina$, was main crystal phase. ${\gamma}-Alumina$ was appeared in the beginning, then the amount of ${\alpha}-alumina$ was increased with time, but the amount of ${\gamma}-Alumina$ remained constant without any increasing. So, it is concluded that plasma gas produce ${\gamma}-Alumina$ at the first, and then ${\gamma}-Alumina$ transform ${\alpha}-alumina$ finally. During the transformation, high temperature of micro plasma gives transformation energy.

• Clean Technology
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• v.10 no.1
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• pp.47-51
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• 2004

현재 반도체 공정에서 사용되는 세정기술은 대부분이 1970년대 개발된 RCA 세정법인 과산화수소를 근간으로 하는 습식 세정으로, 표면의 입자를 제거하기 위한 SC-1 세정액은 강력한 산화제인 과산화수소에 의한 표면과 입자의 산화와 암모니아에 의한 표면의 에칭이 동시에 일어나 입자를 표면으로부터 분리시킨다. 금속 불순물을 제거하기 위한 SC-2 세정액은 염산과 과산화수소 혼합액을 사용하며 금속 불순물을 용해시켜 알칼리나 금속 이온을 형성하거나 용해 가능한 화합물을 형성시켜 제거한다. 또한 황산과 과산화수소를 혼합한 Piranha 세정액은 효과적인 유기물 제거제로서 웨이퍼에 오염된 유기물을 용해 가능한 화합물로 만들거나 과산화수소에 의해 형성되는 산화막내에 오염물을 포함시켜 불산 용액으로 산화막을 제거할 때 함께 제거된다. 최근 금속과 산화막을 동시에 제거하기 위해 희석시킨 불산에 과산화수소를 첨가한 세정공정이 사용되고 있으며 불산에 의해 표면의 산화막이 제거될 때 산화막내에 포함된 금속 불순물을 동시에 제거시킬 수 있다. 그러나 이와 같이 습식세정액 내에 공통적으로 포함되어 있는 과산화수소의 분해는 그만큼 가속화되어 사용되는 화학 약품의 양이 그만큼 증가하게 되고 조작하기 어려운 단점도 있다. 이를 해결하기 위해 환경친화적인 관점으로 화학약품의 사용을 최소화하는 등 RCA세정을 보완하는 연구가 계속 진행되고 있다. 본 연구에서는 RCA세정법을 환경적으로 대체할 수 있는 세정에 사용되는 전리수의 pH변화에 따른 전리수 분석을 하였다. 전리수의 제조를 위하여 전해질로는 NH4CI (HCI:H2O:NH4OH=1:1:1)를 사용하였다. pH 11 이상, ORP -700mV~-850mV인 환원수와 pH 3 이하, ORP 1000mV~1200mV인 산화수를 제조하였으며, 초순수를 첨가하여 pH 7.2와 ORP 351.1mV상태까지 조절하였다. 이렇게 만들어진 산화수와 환원수를 시간 변화와 pH 변화에 따라 Clean Room 안에서 FT-IR과 접촉각 측정기로 실험하였다. FT-IR분석에서 산화수는 pH가 높아질수록, 환원수는 낮아질수록 흡수율이 낮아졌다. 접촉각 실험에서는 산화수의 pH가 높아질수록 환원수의 pH가 낮아질수록 접촉각이 커짐을 확인하였다. 결론적으로 전리수를 이용하여 세정을 하면, 접촉성을 조절할 수 있어 반도체 세정을 가능하게 할 수 있으며, 환경친화적인 결과를 도출할 것으로 전망된다.

• Journal of the Korean Chemical Society
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• v.26 no.6
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• pp.378-382
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• 1982

Green crystalline salts of substituted pyridinium oxopentachloromolybdates(V) were obtained from concentrated hydrochloric acid solution of molybdenum(V)-thiocyanate extract. $MoOCl_3(X-py)_2$ (X-py were 4-and 3-cyanopyridine, 2-amino-4-picoline and 4-acetylpyridine) were obtained by reflux of the corresponding substituted pyridinium salts of oxopentachloromolybdates(Ⅴ) in absolute ethanol. ($X-pyH_2$)[$MoOCl_5$]$H_2$O containing the $MoO^{3+}$ group are dissolved and hydrolysed in water but $MoOCl_3(X-py)_2$ are insoluble in water, alcohol and acetone. The complexes are paramagnetic compounds.

• Journal of the Korean Chemical Society
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• v.37 no.1
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• pp.83-91
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• 1993

The eletrochemical behavior of light lanthanide complexes has been investigated by several electrochemical techniques in alkaline solutions. The composition of the complexes was determined by spectrophotometric method to be 1 : 1 and reduction mechanism was two steps 1 electron transfer reaction. The half wave potential of first peak depended on pH and cathodic current showed remarkably adsorptive properties. The results of DC and CV investigation demonstrated the quise-reversible nature of the electron transfer. The anion radical formed after first one electron reduction process, dimerizes to form dimer. The apparent irreversible behavior of the second wave is a result of the existence of a fast protonation following the second electron transfer. An exhaustive electrolysis was carried out at controlled potential of -1.80 V, deep blue color of the solution became progressively weaker, and then the solution became colorless solution. The final product of an exhaustive electrolysis is electro-inactive. The appearance of four steps may be explained by the fact the reduction of Ln-OCP elucidated ECEC mechanism.

• Applied Microscopy
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• v.38 no.1
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• pp.11-19
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• 2008

To examine the effect of the electrolyzed alkaline reduced water (ERW) on animal immunity, by employing Echinostoma hortense that is a parasite in the small intestine, the immune response of C57BL/6 was examined. To C57BL/6 mice, Echinostoma hortense metacercaria 15 per animal was in oculate dorsally, the worm was collected after 2 weeks, and the change of goblet cells and mast cells in the mucosa of small intestine was examined, and by using a protein chip, the change of cytokines in the serum was compared and observed. As a result, average 8.3 worms were collected from the C57BL/6 mice infected with E. hortense, and in the group fed with the ERW, average 10 worms were collected. In regard to the examination of the change of goblet cells, in the experimental group infected with E. hortense and fed with the ERW, average 4.3 worms per villus were detected, hence, it was found that the expression of goblet cells was low (p<0.001). Regarding the examination of the change of mast cells, similarly, in the group infected with E. hortense and fed with the ERW, average 11 worms per villus were detected, and it appears to be less than control group (p<0.001). Regarding the expression of cytokines in mouse serum, in comparison of the experiment group infected with E. hortense and control group, in the expression of the Th1 cytokines IL-6, IL-$1{\beta}$, IFN-${\gamma}$, TNF-${\alpha}$, and IL-2, and the Th2 cytokines IL-4, IL-5, IL-10, and IL-13, a significant difference was not detected. In our study, it was found that in the infection of E. hortense, the ERW mediates its effect on the number of goblet cells and mast cells in the intestinal mucosa, and simultaneously, the worm expulsion was delayed, and thus the conclusion that the ERW mediated its effect on the intestinal immunity of mice was obtained.

• Clean Technology
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• v.22 no.1
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• pp.16-28
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• 2016

Textile industry is considered as one of the most polluting sectors in terms of effluent composition and volume of discharge. It is well known that the effluents from textile dying industry contain not only chromatic substances but also large amounts of organic compounds and insolubles. The azo dyes generate huge amount of pollutions among many types of pigments. In general, the electrochemical treatments, separating colors and organic materials by oxidation and reduction on electrode surfaces, are regarded as simpler and faster processes for removal of pollutants compared to other wastewater treatments. In this paper the electrochemical degradation characteristics of dye wastewater containing CI Direct Blue 15 were analyzed. The experiments were performed with various anode materials, such as RuO₂/Ti, PtO₂/Ti, IrO₂/Ti and graphite, with stainless steel for cathode. The optimal anode material was located by changing operating conditions like electrolyte concentration, current density, reaction temperature and initial pH. The degradation efficiency of dye wastewater increased in proportion to the electrolyte concentration and the current density for all anode materials, while the temperature effect was dependent on the kind. The performance orders of anode materials were RuO₂/Ti > PtO₂/Ti > IrO₂/Ti > graphite in acid condition and RuO₂/Ti > IrO₂/Ti > PtO₂/Ti > graphite in neutral and basic conditions. As a result, RuO₂/Ti demonstrated the best performance as an anode material for the electrochemical treatment of dye wastewater.

• Resources Recycling
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• v.16 no.5
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• pp.8-12
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• 2007

Anhydrous magnesium chloride, dehydration product from magnesium chloride hydrate is a general raw material to prepare electrolytic magnesium. However, the dehydration is not trivial and can be accompanied by hydrolysis leading to the production of undesirable hydroxy chloride compounds of magnesium. Therefore, dehydration process is actually the most complicated and hardest in the electrolysis methods for the production of magnesium. In this work, the influence of dehydrating temperature has been studied at the temperature range from $200^{\circ}C$ to $600^{\circ}C$ in air and HCl gas atmosphere individually to compare the results. With increasing of dehydration temperature MgOHCl and MgO were obtained in air. On the other hand, when the temperature was increased above $300^{\circ}C$ anhydrous magnesium chlorides were prepared in HCl gas atmosphere. Anhydrous magnesium chloride was formed at near $300^{\circ}C$ and completely crystallized at about $500^{\circ}C$. All of the HCl used as atmosphere gas in the dehydration was recovered as hydrochloric acid solution at a water vessel up to 41% by weight at $20^{\circ}C$.

• Clean Technology
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• v.18 no.4
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• pp.426-431
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• 2012

Carbon-rich coal can be utilized as a fuel for direct carbon fuel cell (DCFC). However, left-behind ash after the electrochemical oxidation may hinder the electrochemical reactions. In this study, we produced ash-free coal (AFC) by thermal extraction and then tested it as a fuel for DCFC. DCFC was built based on solid oxide electrolyte and the electrochemical performance of AFC mixed with $K_2CO_3$ was compared with AFC only. Significantly enhanced power density was found by catalytic steam gasification of AFC. However, an increase of the power density by catalytic pyrolysis was negligible. This result indicated that a catalyst activated the steam gasification reactions, producing much more $H_2$ and thus increasing the power density, compared to AFC only. Results of a quantitative analysis showed much improved kinetics in AFC with $K_2CO_3$ in agreement with DCFC results. A secondary phase of potassium on yttria-stabilized zirconia (YSZ) surface was observed after the cell operation. This probably caused poor long-term behavior of AFC with $K_2CO_3$. A thin YSZ (30 ${\mu}m$ thick) was found to be higher in the power density than 0.9 mm of YSZ.

• Journal of the Korean Chemical Society
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• v.26 no.6
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• pp.383-388
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• 1982

$Mo_2O_4Cl_2$$(X-py)_4{\cdot}2H_2$O and $(X-pyH)_4$[$Mo_2O_4(NCS)_6)$]${\cdot}H_2$O have been prepared. The infrared, electronic and reflectance spectra, molar conductances and magnetic susceptibility data of complexes are reported. $Mo_2O_4Cl_2$$(X-py)_4{\cdot}2H_2$O (X-py were 3-and 4-cyanopyridine, nicotinamide, 3,5-lutidine and 2-amino-4-picoline) were obtained by hydrolysis of the corresponding substituted pyridinium oxopentachloromolybdates(Ⅴ). Addition of water and substituted pyridines to molybdenum(Ⅴ)-thiocyanate ethylacetate extract yielded brown compounds, $(X-pyH)_4$[$Mo_2O_4(NCS)_6)$]${\cdot}H_2$O where X-py were pyridine, ${\alpha}$, 3-bromopyridine 3,5-lutidine, 3-benzoylpyridine and 4-acetylpyridine. Binuclear, $Mo_2O_4Cl_2(X-py)_4{\cdot}2H_2$ prepared from hydrolysis of $(X-pyH)_2[MoOCl_5]{\cdot}H_2O$ were diamagnetic and nonelectrolytes. The anion of $(X-pyH)_4$[$Mo_2O_4(NCS)_6)$]${\cdot}H_2$O was formulated as dimer and electrolyte.

• Journal of the Korea Concrete Institute
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• v.21 no.6
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• pp.689-696
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• 2009

In this study, electro-deposition method was applied to heal cracks in various blended concrete. The performance of the method was indirectly monitored by measuring impressed voltage, electrolyte, galvanic current monitoring, linear polarization resistance, and directly by image analysis of the cracks. The indirect and direct monitoring values are compared to develop guidelines for relating the indirect measures to actual crack healing. As a result, It was found that impressed voltage was convergence to 2.9V after 20000 minutes. From the galvanic current test results of artificial crack healing, the corrosion resistance showed that the order of 0.4 $>$ 0.6 $>$ 0.5 water to cement ratio. Furthermore, in view of binder, the corrosion resistance order was calculated OPC $>$ 60%GGBS $>$ 10%SF $>$ 30%PFA. Finally, It was found that 76.47% of healed crack surface calculated from the artificial crack healing technique using electrochemical deposition method.