• Title/Summary/Keyword: Metal ion

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Hydrogen and Ethanol Gas Sensing Properties of Mesoporous P-Type CuO

  • Choi, Yun-Hyuk;Han, Hyun-Soo;Shin, Sun;Shin, Seong-Sik;Hong, Kug-Sun
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.08a
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    • pp.222-222
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    • 2012
  • Metal oxide gas sensors based on semiconductor type have attracted a great deal of attention due to their low cost, flexible production and simple usability. However, most works have been focused on n-type oxides, while the characteristics of p-type oxide gas sensors have been barely studied. An investigation on p-type oxides is very important in that the use of them makes possible the novel sensors such as p-n diode and tandem devices. Monoclinic cupric oxide (CuO) is p-type semiconductor with narrow band gap (~1.2 eV). This is composed of abundant, nontoxic elements on earth, and thus low-cost, environment-friendly devices can be realized. However, gas sensing properties of neat CuO were rarely explored and the mechanism still remains unclear. In this work, the neat CuO layers with highly ordered mesoporous structures were prepared by a template-free, one-pot solution-based method using novel ink solutions, formulated with copper formate tetrahydrate, hexylamine and ethyl cellulose. The shear viscosity of the formulated solutions was 5.79 Pa s at a shear rate of 1 s-1. The solutions were coated on SiO2/Si substrates by spin-coating (ink) and calcined for 1 h at the temperature of $200{\sim}600^{\circ}C$ in air. The surface and cross-sectional morphologies of the formed CuO layers were observed by a focused ion beam scanning electron microscopy (FIB-SEM) and porosity was determined by image analysis using simple computer-programming. XRD analysis showed phase evolutions of the layers, depending on the calcination temperature, and thermal decompositions of the neat precursor and the formulated ink were investigated by TGA and DSC. As a result, the formation of the porous structures was attributed to the vaporization of ethyl cellulose contained in the solutions. Mesoporous CuO, formed with the ink solution, consisted of grains and pores with nano-meter size. All of them were strongly dependent on calcination temperature. Sensing properties toward H2 and C2H5OH gases were examined as a function of operating temperature. High and fast responses toward H2 and C2H5OH gases were discussed in terms of crystallinity, nonstoichiometry and morphological factors such as porosity, grain size and surface-to-volume ratio. To our knowledge, the responses toward H2 and C2H5OH gases of these CuO gas sensors are comparable to previously reported values.

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Effect of Fluoride-based Plasma Treatment on the Performance of AlGaN/GaN MISHFET

  • Ahn, Ho-Kyun;Kim, Hae-Cheon;Kang, Dong-Min;Kim, Sung-Il;Lee, Jong-Min;Lee, Sang-Heung;Min, Byoung-Gue;Yoon, Hyoung-Sup;Kim, Dong-Young;Lim, Jong-Won;Kwon, Yong-Hwan;Nam, Eun-Soo;Park, Hyoung-Moo;Lee, Jung-Hee
    • ETRI Journal
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    • v.38 no.4
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    • pp.675-684
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    • 2016
  • This paper demonstrates the effect of fluoride-based plasma treatment on the performance of $Al_2O_3/AlGaN/GaN$ metal-insulator-semiconductor heterostructure field effect transistors (MISHFETs) with a T-shaped gate length of $0.20{\mu}m$. For the fabrication of the MISHFET, an $Al_2O_3$ layer as a gate dielectric was deposited using atomic layer deposition, which greatly decreases the gate leakage current, followed by the deposition of the silicon nitride layer. The silicon nitride layer on the gate foot region was then selectively removed through a reactive ion etching technique using $CF_4$ plasma. The etching process was continued for a longer period of time even after the complete removal of the silicon nitride layer to expose the $Al_2O_3$ gate dielectric layer to the plasma environment. The thickness of the $Al_2O_3$ gate dielectric layer was slowly reduced during the plasma exposure. Through this plasma treatment, the device exhibited a threshold voltage shift of 3.1 V in the positive direction, an increase of 50 mS/mm in trans conductance, a degraded off-state performance and a larger gate leakage current compared with that of the reference device without a plasma treatment.

Crevice Corrosion Properties of PWR Structure Materials Under Reductive Decontamination Conditions (환원제염조건에서 가압경수로 구조재료의 틈부식 특성)

  • Jung, Jun-Young;Park, Sang Yoon;Won, Hui Jun;Choi, Wang Kyu;Moon, Jei Kwon;Park, So Jin
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.12 no.3
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    • pp.199-209
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    • 2014
  • Crevice corrosion tests were conducted to examine the corrosion properties of HYBRID (HYdrazine Base Reductive metal Ion Decontamination) which was developed to decontaminate the PWR primary coolant system. To compare the corrosion properties of HYBRID with commonly existing decontamination agents, oxalic acid (OA) and citric oxalic acid (CITROX) were also examined. Type 304 Stainless Steel (304 SS) and Alloy 600 which are major components of the primary coolant system in Pressurized Water Reactor (PWR) were evaluated. Crevice corrosion tests were conducted under very aggressive conditions to confirm quickly the corrosion properties of primary coolant system structure components which have high corrosion resistance. Pitting and IGA were occurred in crevice surface under OA and CITROX conditions. But localized corrosion was not observed under HYBRID condition. Very low corrosion rate of less than $1.3{\times}10^{-3}{\mu}m/h$ was observed under HYBRID condition for both materials. On the other hand, under OA condition, Alloy 600 indicated comparatively uniform corrosion rate of $4.0{\times}10^{-2}{\mu}m/h$ but 304 SS indicated rapid accelerated corrosion in lower case than pH 2.0. In case of HYBRID condition, general corrosion and crevice corrosion were scarcely occurred. Therefore, material integrity of HYBRID in decontamination of primary coolant system in pressurized water reactor (PWR) reactor was conformed.

Studies on the Enzymatical Properties of Streptomyces sp. S-45 Isolated from Soil (토양(土壤)에서 분리(分離)한 Streptomyces sp. s-45의 효소학적(酵素學的) 성질(性質)에 관한 연구(硏究))

  • Kim, Yeong-Yil;Kim, Yong-Woong;Kim, Kwang-Sik
    • Korean Journal of Soil Science and Fertilizer
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    • v.21 no.2
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    • pp.129-134
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    • 1988
  • Enzymatical properties of Streptomyces sp. S-45 producing chitinase and ${\beta}$-1.3-glucanase isolated from soil were investigated. Chitinase activity was 3.01(U/ml) and ${\beta}$-1.3-glucanase activity was 2.49(U/ml). The optimum medium for mycolytic enzyme production of strain was composed of 0.7% colloidal chitin, 0.3% glucose, 0.5% asparagine, 0.2% peptone, 0.01% NaCl, 0.01% $K_2HPO_4$ and 0.01% $MgSO_4{\cdot}7H_2O$ in intial pH 7.0. The optimal condition for mycolytic enzyme activities were: pH 6.5-7.0, $45-50^{\circ}C$. Enzyme activities were activated by metal ion as $10^{-2}M\;Co^{{+}{+}}$, $Cu^{{+}{+}}$, $Mn^{{+}{+}}$, $Al^{{+}{+}{+}}$ and $10^{-3}M\;Sn^{{+}{+}}$ but $Ag^{{+}{+}}$, $Hg^{{+}{+}}$ inhibited.

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Culture Conditions of E. coli CK1092 for the Production of 2,3-Dihydroxybiphenyl Dioxygenase (2,3-Dihydroxybiphenyl Dioxygenase 생산을 위한 E. coli CK1092의 배양조건)

  • Lee, Jung-Young;Kim, Youngsoo;Lee, Ki-Sung;Min, Kyung-Hee;Kim, Young-Chang;Kim, Chi-Kyung;Lim, Jai-Yun
    • Korean Journal of Microbiology
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    • v.34 no.1_2
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    • pp.20-25
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    • 1998
  • To obtain higher yield of 2,3-dihydroxybiphenyl(2,3-DHBP) dioxygenase by recombinant E. coli CK1092 carrying pcbC gene of Pseudomonas sp. P20, the environmental and physiological factors were investigated and the cultural conditions using jar fermentor were studied. E. coli CKl092 was grown in LB medium supplemented with 2% sucrose, as a basal medium. The effect of various metal ions on the enzyme production was investigated. In particular, the enzyme production increased in the presence of $Fe^{3+}$ and $Fe^{2+}$, and showed the maxium at the concentration of $10^{-5}M$. The enzyme production was increased by 55% in the medium containing $Fe^{3+}$ ($10^{-5}M$) ion. The optimal temperature and initial pH for cell growth were $37^{\circ}C$ and 7.0, respectively. In the culture using a fermentor at $37^{\circ}C$, the optimal conditions for the enzyme production were obtained at the initial pH 7.0, 1 v/v/m of aeration rate, 200 rpm of agitation speed. It was found that enzyme activity was higher when cultivated without pH control than with pH control.

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Effects and Behaviors of Heavy Metals(Cd, Cr, Cu, Pb) in Cement Clinker Reaction (시멘트 클린커 반응에서 중금속(Cd, Cr, Cu, Pb)의 거동과 영향)

  • Hong, Seong-Su;Lee, Taeck-Hong;Lim, Gye-Gyu;Oh, Hea-Kab;Lee, Bong-Han
    • Applied Chemistry for Engineering
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    • v.10 no.5
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    • pp.696-700
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    • 1999
  • The effects and behaviors of heavy metals incoming from industrial by-products were investigated in cement clinker reaction. The raw meal containing 500 ppm of heavy metal ion such as Cu, Cd, Cr, and Pb was calcined at $1450^{\circ}C$ for 30 minutes. Burnability index, fixation concentration of heavy metals in clinker, and apportionment ratio were analyzed. Pb had a minimum fixation concentration of under 5% and Cr had a maximum over 85%. The burnability of Cr containing clinker was lower than that of others as the result of higher value of 3.41% of free lime after calcination at $1450^{\circ}C$. Cu, Cd, and Pb had not any significant effects on the clinker reactitivity. The volatility of heavy metals produced lots of macropores and micropores in clinker and minerals. Cd and Cr were the major apportionments in alite and belite and Cu in interstitial phase. Pb was existed under the detection limit of EDAX analysis due to its higher volatility.

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Durability and Crack Control of Concrete Using Fluosilicates Based Composite (규불화염계 복합 조성물을 혼입한 콘크리트의 균열제어 및 내구성)

  • Yun, Hyun-Do;Yang, Il-Seung;Kim, Do-Su;Khil, Bae-Su;Han, Seung-Gu
    • Journal of the Korea Concrete Institute
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    • v.18 no.1 s.91
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    • pp.57-64
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    • 2006
  • The crack presented in concrete structures causes a structural defect, the durability decrease, and external damages etc. Therefore, it is necessary to improve durability through the effort to control the crack. Fluosilicic acid($H_2SiF_6$) is recovered as aqueous solution which absorbs $SiF_4$ produced from the manufacturing of industrial-graded $H_3PO_4$ or HF. Generally, fluosilicates prepared by the reaction between $H_2SiF_6$ and metal salts. Addition of fluosilicates to cement endows odd properties through unique chemical reaction with the fresh and hardened cement. Mix proportions for experiment were modulated at 0.45 of water to cement ratio and $0.0{\sim}2.0%$ of adding ratio of fluosilicate salt based inorganic compound. To evaluate correlation of concrete strength and adding ratio of fluosilicate salt based inorganic compound, the tests were performed about design strength(21, 24, 27 MPa) with 0.5% of adding ratio of fluosilicate salt based inorganic compound. Applications of fluosilicate salt based inorganic compound to reduce cracks resulted from plastic and drying shrinkage, to improve durability are presented in this paper. Durability was evaluated as neutralization, chloride ion penetration depth, freezing thawing resistant tests and weight loss according reinforcement corrosion. It is ascertained that the concrete added fluosilicate salt based inorganic compound showed m ability to reduce the total area and maximum crack width significantly as compared non-added concrete. In addition, the durability of concrete improved because of resistance to crack and watertightness by packing role of fluosilicate salt based inorganic compound obtained and pozzolanic reaction of soluble $SiO_2$ than non-added concrete.

A Study on Physico-chemical Property and Composition of Velvet Antler and Byproducts in Elk. (Elk종의 녹용과 부산물의 이화학적 특성에 관한 연구)

  • 이길왕
    • Journal of Life Science
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    • v.14 no.3
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    • pp.496-500
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    • 2004
  • This study has been performed for physico-chemical property and composition of sinew, testes, tail, blood and velvet antler in Elk. Amino acid contents in the sinew taurine, alanine, histidine, and lysine were high contained, histidine, glutamic acid, taurine, and lysine were high contained in testes, glutamic acid, lysine, alanine, glycine, and phenylalanine were high contained in tail, histidine, glycine, and lysine were high contained in blood, glutamic acid, lysine, taurine, alanine, and glycine were high contained in velvet antler. And, based on the amount of mineral, $K^{+}$, $Ca^{2+}$, and $P^{+}$ were 444.8, 166.6 and 242.9mg per 100g in sinew, respectively. $K^{+}$, $Ca^{2+}$ and $P^{+}$ were 294.4, 330.5, and 514.3 mg per 100g in testes, respectively, $K^{+}$, $Mg^{2+}$, and $P^{+}$ were 1420.6, 118.4, and 1105.2mg per 100 mg in tail, respectively. Fe3+,-K+, and P+ were 344.1, 1023.6 and 157.2 mg per 100 mg in blood, respectively and $K^{+}$, $Ca^{2+}$ and $P^{+}$ were 888.4, l1533.1 and 14722.0 in velvet antler, respectively. Finaly, difference were found in comparison of composition of free mwtal ion (N $a^{+}$, $K^{+}$, $Mg^{2+}$ and $Ca^2$) bwteen blood, tail, tests, sinew and velvet antler, and composition of free metal in blood higher than those othersd higher than those others.

Adsorption Characterization of Cd by Coal Fly Ash Using Response Surface Methodology (RSM) (반응표면분석법을 이용한 석탄회에서의 Cd 흡착특성에 관한 연구)

  • An, Sangwoo;Choi, Jaeyoung;Cha, Minwhan;Park, Jaewoo
    • Journal of the Korean GEO-environmental Society
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    • v.11 no.1
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    • pp.19-26
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    • 2010
  • The batch experiments and response surface methodology (RSM) have been applied to the investigation of the cadmium (Cd) adsorption by coal fly ash (CFA). CFA having maximum Cd removal mass of 8.51 mg/g were calculated from Langmuir model. Cd removal reaction with different initial pH ranged from 4 to 9. When the initial pH was higher, Cd was removed more by adsorption and precipitation. These results suggest that the lower pH cause an increase of $H^+$ ion concentration which competed with Cd ions for exchange sites in CFA. Also, The Cd adsorption was mathematically described as a function of parameters initial Cd concentration ($X_1$), initial pH ($X_2$), and initial CFA mass ($X_3$) being modeled by use of the Box-Behnken methods. Empirical models were developed to describe relationship between the experimental variables and response. Statistical analysis indicates that tree factors ($X_1$, $X_2$, and $X_3$) on the linear term (main effects), and tree factors ($X_1X_2$, $X_1X_3$, and $X_2X_3$) on the non-linear term (Interaction effect; cross-product) had significant effects, respectively. In this case, the value of the adjusted determination coefficient (adjusted $R^2=0.9280$) was closed to 1, showing a high significance of the model. Statistical results showed the order of Cd removal at experimental factors to be initial initial pH > initial Cd concentration > initial CFA mass.

Removal Characteristics of Heavy Metals in Acid Mine Drainage (AMD) Using Porous Starfish Ceramics (II) - Treatment of AMD in a Column Reactor System (불가사리 소재 다공성 세라믹을 이용한 산성광산배수 내 중금속의 제거특성(II) - 컬럼연속 실험을 통한 산성광산배수의 처리특성)

  • Lee, Yonghwan;Yim, Soobin
    • Journal of the Korean GEO-environmental Society
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    • v.15 no.12
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    • pp.25-34
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    • 2014
  • The objective of this study was to investigate the removal characteristics and the elimination mechanism of heavy metals in Acid Mine Drainage (AMD) using spherical-type porous Zeolite-StarFish ceramics (porous ZSF ceramics) packed in a continuous column reactor system. The average removal efficiencies of heavy metals in AMD were Al 98.7, As 98.7, Cd 96.0, Cu 89.1, Fe 99.5, Mn 94.4, Pb 96.3 and Zn 80.8 % during 110 days of operation time. The average removal capacity of porous ZSF ceramics for heavy metals were measured to be Al 21.76, As 1.52, Cd 1.27, Cu 3.41, Fe 44.83, Mn 3.48, Pb 2.36 and Zn $3.76mg/kg{\cdot}day$. The analysis results of mechanism using SEM, EDS and XRD exhibited that the porous ZSF ceramics could act as a multi-functional ceramics for the removal of heavy metals in AMD through the reactions of precipitation, adsorption and ion-exchange. The experimental results of column reactor system displayed that the porous ZSF ceramics would be a consistently efficient agent for the removal of heavy metals in AMD for a long term.