• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.12
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• pp.8-13
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• 2001

Cerium oxide ($CeO_2$) thin film has been proposed as a buffer layer between the ferroelectric thin film and the Si substrate in Metal-Ferroelectric-Insulator-Silicon (MFIS) structures for ferroelectric random access memory (FRAM) applications. In this study, $CeO_2$ thin films were etched with $Cl_2$/Ar gas mixture in an inductively coupled plasma (ICP). Etch properties were measured for different gas mixing ratio of $Cl_2$($Cl_2$+Ar) while the other process conditions were fixed at RF power (600 W), dc bias voltage (-200 V), and chamber pressure (15 mTorr). The highest etch rate of $CeO_2$ thin film was 230 ${\AA}$/min and the selectivity of $CeO_2$ to $YMnO_3$ was 1.83 at $Cl_2$($Cl_2$+Ar gas mixing ratio of 0.2. The surface reaction of the etched $CeO_2$ thin films was investigated using x-ray photoelectron spectroscopy (XPS) analysis. There is a Ce-Cl bonding by chemical reaction between Ce and Cl. The results of secondary ion mass spectrometer (SIMS) analysis were compared with the results of XPS analysis and the Ce-Cl bonding was monitored at 176.15 (a.m.u). These results confirm that Ce atoms of $CeO_2$ thin films react with chlorine and a compound such as CeCl remains on the surface of etched $CeO_2$ thin films. These products can be removed by Ar ion bombardment.

• Applied Chemistry for Engineering
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• v.20 no.2
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• pp.234-240
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• 2009

$Mg(OH)_2$ particles were prepared by precipitation and a hydrothermal treatment to examine the effect of $MgCl_2$ concentration, alkali type and concentration, temperature, hydrothermal treatment on the formation of $Mg(OH)_2$ particles using full factorial design, as one of DOE (Design of experiment) methods. The primary particle size is similar to the secondary particle size for the samples after the hydrothermal treatment, where the average particle size of $Mg(OH)_2$ increased with increasing the concentration of $MgCl_2$ and hydrothermal temperature and decreasing alkali/Mg molar ratio. On the other hand, for the samples prepared from precipitation, the secondary particle size is larger than the primary particles due to aggregation. The difference in alkaline source is that the particles prepared from $NH_4OH$ exhibit the larger size with better dispersion than those from NaOH. Low density polyethylene and ethylene-co-vinyl acetate (LDPE-EVA) resin composed of the smaller secondary particle size of $Mg(OH)_2$ shows a higher limited oxygen index (LOI) at 50 and 55% loading, but the smaller primary particle size may result in a better grade in UL-94 tests. At the high loading of 60%, all samples with any preparation methods exhibit V-0 grade but the LOI value depends on not only primary particle size but also dispersion state.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.530-534
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• 2011

The synthesis of dimethyl carbonate by liquid phase oxidative carbonylation of methanol was studied under batch reaction system. Reaction factors such as effect on various metals, anion containing in copper catalyst, temperature, carbon monoxide and oxygen molar ratio and copper content were investigated. In particular $CuCl_2{\cdot}2H_2O$ showed the excellent of the methanol conversion 65.2%, DMC selectivity 96.6% reaction condition under 1.0 g, $150^{\circ}C$, MeOH/CO/$O_2$=0.2/0.215/0.05 (molar ratio). $CuCl_2$ led to corrosion of the reactor. Thus, a new catalyst system using supports was investigated to resolve these corrosion problem. Influence on various supports were examined and copper catalyst supported on zeolite Y showed the most excellent activity on the formation of dimethyl carbonate. The amount of Fe dissolved during the reaction using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometer) was compared with catalysts, calcined Cu/zeolite Y showed the lower value below 5% than $CuCl_2-2H_2O$.

• Journal of the Korean Electrochemical Society
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• v.2 no.3
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• pp.156-162
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• 1999

Various types of iron oxide based materials as a cathode of lithium secondary battery have been prepared and their electrochemical characteristics have been also observed. In order to understand the fundamental characteristics of iron oxide electrode, three kinds of iron oxides such as iron oxides formed by direct oxidation of iron plate or iron powders and FeOOH powders were tested with cyclic voltammetry. The oxidation and reduction peaks due to the reaction of intercalation and deintercalation were not observed for the iron oxide prepared with iron plate and FeOOH powders. In case of iron oxide prepared from iron powders, only one reduction peak was observed. A layered form of $LiFeO_2$ was synthesized directly from $FeCl_3\cdot6H_2O,\;NaOH\;and\;LiOH$ and LiOH by hydrothermal reaction. The effect of NaOH on the electrode performance was examined. When increasing NaOH, it provides the electrode with less discharge capacity and efficiency, however, decreasing rate of discharge capacity became smaller. $LiFeO_2$ synthesized with the molar ratio of $NaOH/FeCl_3/LiOH$, 2/1/7 showed the largest capacity, but the discharging efficiency was sharply decreased after 30 cycles.

• Korean Journal of Soil Science and Fertilizer
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• v.2 no.1
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• pp.27-30
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• 1969

The present notes summarize the results obtained from the effect of soil-solution ratio on pH values of soils having widely different physico-chemical characteristics. The pH was determined in deionized water N-KCl and 0.01 M $CaCl_2$ solution The results obtained are: 1. With deionized water, the pH values increase with the increase in soil-solution ratio. The increase is more in upland soils than in paddy soils. 2. With N-KCl solution, there is also an increase in pH values with the increase in soil-solution ratio but the increase is less than the corresponding increase with deionized water. 3. With 0.01 M $CaCl_2$ solution, there is practically no change in pH values with the increase in soil-solution ratio except for saline soils. 4. In case of saline soils, the pH increase even in case of 0.01 M $CaCl_2$ solution with increase in soil-solution ratio, the reason for increase may be due to decrease of electric potential by high concentration of salts.

• Bulletin of the Korean Chemical Society
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• v.25 no.2
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• pp.280-284
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• 2004

The optimum conditions for the most effective precipitate of surfactant complex of sodium alkylsulfate with cetylpyridinium chloride were studied in the aqueous solution. The parameters such as the alkyl chain length of anionic surfactants, molar ratio of two surfactants, temperature and the concentration of added NaCl in the aqueous solution were correlatively studied for the productivity of the precipitate formation. By the productivity, the optimum conditions to produce complex of anionic surfactant with cationic surfactant were the longer alkyl chain, equivalent molar ratio between anionic and cationic surfactants, 0 $^{\circ}C$ and 1.5 M NaCl.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.186-190
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• 1997

Corrosion of steel reinforcement is the most significant factor of deterioration in reinforced concrete structures. It breaks down the passive film and allows the steel to be corroded severely at a high rate. The main object of this study is to determine the critical chloride ion concentrations in the pore solutions and chloride binding effect of cement pastes. It is found that binding chloride ion ratio of cement is between 0.04% and 0.3% and Cl/OH in pore solution under 0.3.

• Korean Journal of Soil Science and Fertilizer
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• v.47 no.6
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• pp.540-546
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• 2014

Acid mine drainage sludge (AMDS) has been classified as mine waste and generally deposited in land. For this reason, studies have been conducted to examine the possibility of recycling AMDS as an amendment for heavy metal stabilization in soil. The main objective of this study was to evaluate heavy metal stabilization efficiency of AMDS comparing with the widely used lime stone. Also, optimum mixing ratio was evaluated for enhancing heavy metal stabilization. AMDS and limestone were mixed at the ratio of 0:100, 25:75, 50:50, 75:25, and 100:0 with five different heavy metal solutions ($100mg\;L^{-1}$ of $NaAsO_2$, $CdCl_2$, $CuCl_2$, $Pb(NO_3)_2$, and $ZnSO_4{\cdot}7H_2O$). The amendments were added at a rate of 3% (w/v). In order to determine the stabilization kinetics, samples were collected at different reaction time of 0, 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024 minutes. The heavy metal stabilization by AMDS was faster and higher than those of limestone for all examined heavy metals. While limestone showed only 20% of arsenic (As) stabilization after 1,024 minutes, 96% of As was stabilized within 1 minute by AMDS. The highest effect on the stabilization of heavy metal (loid) was observed, when the two amendments were mixed at a ratio of 1:1. These results indicated that AMDS can be effectively used for heavy metal stabilization in soil, especially for As, and the optimum mixing ratio of AMDS and lime was 1:1 at a rate of 3% (w/v).

• Journal of the Korean Chemical Society
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• v.16 no.4
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• pp.249-256
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• 1972

Hadong-Kaolin was treated with aqueous sodium hydroxide solution. The crystalline structure was studied by X-ray powder diffraction method. The optimum conditions for various crystal formation were as follows: Crystal Concentration Temp. reating time Halloysite 1~4 N NaOH $60^{\circ}C$ 0.5${\sim}$4 hr Sodium A zeolite 0.5${\sim}$2 N NaOH 80${\sim}$$100^{\circ}C$ 6${\sim}$20 hr Hydoxysodalite > 4 N NaOH 80${\sim}$$100^{\circ}C$ > 4 hr The ratio of $Na_2O to SiO_2$ for crystallizing sodium A zeolite was 0.5-1.5. The $Ca^{++}$ ion exchange capacity of produced sodium A zeolite for 0.2 N $CaCl_2$ solution at $25^{\circ}C$ was amounted to 65% of theoretical value.

• Journal of the Korean Electrochemical Society
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• v.4 no.4
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• pp.139-145
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• 2001

Various compositions of iron oxide based materials as a cathode of lithium secondary battery have been fabricated and tested with electrochemical method. A layered form of $LiFeO_2$ was synthesized by mixing and heating the initial materials of $FeCl_3\;6H_2O,\;LiOH$ and NaOH at low temperature. The effect of changing the precursors composition was investigated. As a result, when increasing the additive amount of NaOH, the capacity of the electrode is decreased but the performance and declining rate of capacity became smaller. $LiFeO_2$ synthesized with the weight ratio of $NaOH/FeCl_3/LiOH,\;2/1/7$ showed the largest capacity, but the discharging efficiency was sharply decreased after 30 cycles. Charge-discharge tests of lithium cells with $LiFeO_2$ cathode having the layer structure were performed. This cell showed the reversibility in the range of 1.5-4.5V of cell voltage. By using CPR method, chemical diffusion coefficients were measured in 1M $LiPF_6/EC/DEC$ solution. The value of chemical diffusion coefficient decreased with increasing the lithium content x, In 0.5$10^{-11}^cm^2/s$.