• Title/Summary/Keyword: $C_2O_2H_4$

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Synthesis and Sintering of Cordierite by using Coprecipitation Method (공침법에 의한 Cordierite분말의 합성 및 소결에 관한 연구)

  • 한문희;박금철
    • Journal of the Korean Ceramic Society
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    • v.27 no.7
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    • pp.899-906
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    • 1990
  • The cordierite powders were prepared from Mg(NO3)2.6H2O, Al(NO3)3.9H2O and colloidal silica by the coprecippitation method, and the sintering behavior of the powders were investigated. Two different methods were applied for producing the precursor powders. The one was to added the aqueous solution of Mg(NO3)2.6H2O and Al(NO3)3.9H2O to NH4OH to adjust pH at 10 where the colloidal silica of pH 10 was added. The other wa to add the aqueous solution of Mg(NO3)2.6H2O and Al(NO3)3.9H2O to the colloidal silica with NH4OH to control the final mixture to be at pH 10. It was confirmed that more homogeneous powders were obtained from the latter method. The firing linear shrinkage of the powder compacts fabricated from the calcined powder between 90$0^{\circ}C$ and 110$0^{\circ}C$ was found to be larger as the calcination temperature was low. But all of them stopped shrinking around 120$0^{\circ}C$. The powder compacts, fabricated using the calcined powders at 90$0^{\circ}C$ and 95$0^{\circ}C$ for 2hours and sintered at 142$0^{\circ}C$ for 2hours, showed relative density of 93-96%, 3-point bending strength of 81-83MPa, KIC of 1.9-2.4 MPam1/2 and thermal expansion coefficient of 0.213-0.732$\times$10-6$^{\circ}C$.

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Thermodynamic and Physical Properties of (NH4)2MnCl4·2H2O by Nuclear Magnetic Resonance Relaxation Times

  • Kim, Yoo Young
    • Journal of the Korean Magnetic Resonance Society
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    • v.23 no.2
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    • pp.40-45
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    • 2019
  • The phase transition temperatures and thermodynamic properties of $(NH_4)_2MnCl_4{\cdot}2H_2O$ grown by the slow evaporation method were studied using differential scanning calorimetry and thermogravimetric analysis. A structural phase transition occurred at temperature $T_{C1}$ (=264 K), whereas the changes at $T_{C2}$ (=460 K) and $T_{C3}$ (=475 K) seemed to be chemical changes caused by thermal decomposition. In addition, the chemical shift and the spin-lattice relaxation time $T_{1{\rho}}$ were investigated using $^1H$ magic-angle spinning nuclear magnetic resonance (MAS NMR), in order to understand the role of $NH_4{^+}$ and $H_2O$. The rise in $T_{1{\rho}}$ with temperature was related to variations in the symmetry of the surrounding $H_2O$ and $NH_4{^+}$.

Photo-induced Isomerization and Polymerization of (Z,Z)-Muconate Anion in the Gallery Space of [LiAl2(OH)6]+ Layers

  • Rhee, Seog-Woo;Jung, Duk-Young
    • Bulletin of the Korean Chemical Society
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    • v.23 no.1
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    • pp.35-40
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    • 2002
  • Photoreaction of guest organic anions in layered organic-inorganic hybrid materials was investigated. The layered hybrids were synthesized by an anion-exchange reaction of $[LiAl_2(OH)_6]Cl{\cdot}yH_2O$ layered double hydroxide with aqueous (Z,Z)- and (E,E)-muconates under inert atmospheric condition, to give new organicinorganic hybrids of $[LiAl_2(OH)_6]_2[(Z,Z)-C_6H_4O_4]{\cdot}zH_2O$ and $[LiAl_2(OH)_6]_2[(E,E)-C_6H_4O_4]{\cdot}H_2O$, respectively. The basal spacings calculated by XRPD of intercalates indicate that muconate anions have almost vertical arrangements against the host $[LiAl_2(OH)_6]^+$ lattices in the interlayer of organic-inorganic hybrid materials. When UV light was irradiated on the suspension of $[LiAl_2(OH)_6]_2[(Z,Z)-C_6H_4O_4]{\cdot}zH_2O$, the (Z,Z)-muconate anions of the gallery space of hybrids were polymerized in the aqueous media while it was isomerized into more stable (E,E)-muconate in the methanollic suspension in the presence of catalytic amount of molecular iodine. All the products were characterized using elemental analysis, TGA, XRPD, FT-IR, $^1H$ NMR and $^{13}C$ CP-MAS NMR.

Cationic Iridium(I) Complex of Ethyl Cinnamate and Hydrogenation of Unsaturated Esters with Iridium(I)-Perchlorato Complex

  • Yang, Kyung-Joon;Chin, Chong-Shik
    • Bulletin of the Korean Chemical Society
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    • v.7 no.6
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    • pp.466-468
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    • 1986
  • Reaction of $Ir(ClO_4)(CO)(PPh_3)_2$ with trans-$C_6H_5CH$ = $CHCO_2C_2H_5$ produces a new cationic iridium(I) complex, [Ir (trans-$C_6H_5CH$ = $CHCO_2C_2H_5)(CO)(PPh_3)_2]ClO_4$ where trans-$C_6H_5CH$ = $CHCO_2C_2H_5$ seems to be coordinated through the carbonyl oxygen rather than through the $\pi$-system of the olefinic group according to the spectral data. It has been found that Ir$(ClO_4)(CO)(PPh_3)_2$ catalyzes the hydrogenation of $CH_2$ = $CHCO_2C_2H_5$, trans-$CH_3CH$ = $CHCO_2C_2H_5$ and trans-$C_6H_5CH$ = $CHCO_2C_2H_5$ to $CH_3CH_2CO_2C_2H_5$, $CH_3CH_2CH_2CO_2C_2H_5$ and $C_6H_5CH_2CH_2CO_2C_2H_5$, respectively at room temperature under the atmospheric pressure of hydrogen. The relative rates of the hydrogenation of the unsaturated esters are mostly understood in terms of steric reasons.

A Study on Comparison of Heat Transfer Characteristic and Heat Storage Capability of $C_{28}H_{58}$ and $Na_4P_2O_7{\cdot}10H_2O$ ($C_{28}H_{58}$$Na_4P_2O_7{\cdot}10H_2O$의 전열특성 및 축열성능 비교에 관한 연구)

  • Yim, Chang-Soon;Kim, Jun-Keun;Cho, Nam-Cheol;Kim, Young-Ki
    • Solar Energy
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    • v.11 no.2
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    • pp.41-50
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    • 1991
  • Heat transfer phenomena and temperature characteristics in heat storage and release process in the heat storage system using PCM(Phase Change material) were studied experimentally. The melting points of Octacosane paraffin($C_{28}H_{58}$) and sodium pyrophosphate decahydrate ($Na_4P_2O_7{\cdot}10H_2O$) used for phase change materials are $62^{\circ}C$ and $79^{\circ}C$ respectively. Experiments were performed in order to investigate temperature distributions, the heat storage quantity and the release quantity on octacosane paraffin and sodium pyrophosphate decahydrate for heat storage and release in the heat storage system. Furthermore the comparison of these characteristics between paraffin and $Na_4P_2O_7{\cdot}10H_2O$ were evaluated. In case of the paraffin, temperature slowly increased at early heat storage process by natural convection, while temperature of $Na_4P_2O_7{\cdot}10H_2O$ rapidly increased the dominant role played by conduction at early heat storage processing Also, during the heat storage and release process in case of the paraffin, it was observed that the variation of temperature of the neighborhood of wall and center in the top and bottom of the tube exhibited a great difference, however in $Na_4P_2O_7{\cdot}10H_2O$, it was observed that the variation of temperature exhibited a little difference. And heat storage quantity of each PCM of identity mass in heat storage process was shown that $Na_4P_2O_7{\cdot}10H_2O$ exhibited more by 16 percents than paraffin.

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Reliability Analysis of 4H-SiC CMOS Device for High Voltage Power IC Integration (고전압 Power IC 집적을 위한 4H-SiC CMOS 신뢰성 연구)

  • Kang, Yeon-Ju;Na, Jae-Yeop;Kim, Kwang-Soo
    • Journal of IKEEE
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    • v.26 no.1
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    • pp.111-118
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    • 2022
  • In this paper, we studied 4H-SiC CMOS that can be integrated with high-voltage SiC power devices. After designing the CMOS on a 4H-SiC substrate, we compared the electrical characteristics with the reliability of high temperature operation by TCAD simulation. In particular, it was confirmed that changing HfO2 as the gate dielectric for reliable operation at high temperatures improves the thermal properties compared to SiO2. By researching SiC CMOS devices, we can integrate high-power SiC power devices with SiC CMOS for excellent performance in terms of efficiency and cost of high-power systems.

Molybdenum(Ⅴ)-Oxo Complexes with Oxygen, Nitrogen and Sulfur Donors. Synthesis, Spectral and Electrochemical Properties (산소, 질소, 그리고 황 주개 원자의 몰리브덴(Ⅴ)-산소 착물 합성과 분광학적 및 전기화학적 성질)

  • Kim, Hee-Jung;Koo, Bon-Kweon
    • Journal of the Korean Chemical Society
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    • v.39 no.6
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    • pp.434-439
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    • 1995
  • Six-coordinate molybdenum(Ⅴ)-oxo complexes, (R4N)[MoO(NCS)2L](R=CH3, C2H5, n-C4, H9) with S-methyl-3-(2-hydroxy-x-phenyl)methylenedithiocarbazate(L1: x=5-H) and its derivatives (L2:x=5-CH3, L3: x=3-CH3O, L4: x=5,6-C4H4 and L5: x=5-NO2) have been synthesized and the structural, spectral and electrochemical properties of the complexes have been characterized by elemental analysis, molar conductivity, UV-Vis, IR, 1H NMR, and CV (cyclic voltammetry).

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SiC/SiO2 Interface Characteristics in N-based 4H-SiC MOS Capacitor Fabricated with PECVD and NO Annealing Processes (PECVD와 NO 어닐링 공정을 이용하여 제작한 N-based 4H-SiC MOS Capacitor의 SiC/SiO2 계면 특성)

  • Song, Gwan-Hoon;Kim, Kwang-Soo
    • Journal of IKEEE
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    • v.18 no.4
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    • pp.447-455
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    • 2014
  • In this research, n-based 4H-MOS Capacitor was fabricated with PECVD (plasma enhanced chemical vapor deposition) process for improving SiC/$SiO_2$ interface properties known as main problem of 4H-SiC MOSFET. To overcome the problems of dry oxidation process such as lower growth rate, high interface trap density and low critical electric field of $SiO_2$, PECVD and NO annealing processes are used to MOS Capacitor fabrication. After fabrication, MOS Capacitor's interface properties were measured and evaluated by hi-lo C-V measure, I-V measure and SIMS. As a result of comparing the interface properties with the dry oxidation case, improved interface and oxide properties such as 20% reduced flatband voltage shift, 25% reduced effective oxide charge density, increased oxide breakdown field of 8MV/cm and best effective barrier height of 1.57eV, 69.05% reduced interface trap density in the range of 0.375~0.495eV under the conduction band are observed.

Partial oxidation of n-butane over ceria-promoted nickel/calcium hydroxyapatite (세리아가 첨가된 니켈/칼슘 하이드록시 아파타이트 촉매 상의 부탄 부분산화 연구)

  • Kwak, Jung-Hun;Lee, Sang-Yup;Kim, Mi-So;Nam, Suk-Woo;Lim, Tae-Hoon;Hong, Seong-Ahn;Yoon, Ki-June
    • 한국신재생에너지학회:학술대회논문집
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    • 2007.11a
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    • pp.89-92
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    • 2007
  • Partail oxidation(POX) of n-butane was investigated in this research by employing ceria-promoted Ni/calcium hydroxyapatite catalysts ($Ce_xNi_{2.5}Ca_{10}(OH)_2(PO_4)_6$ ; x = $0.1{\sim}0.3$) which had recently been reported to exhibit good catalytic performance in POX of methane and propane. The experiments were carried out with changing ceria content, $O_2/n-C_4H_{10}$ ratio and temperature. As the $O_2/n-C_4H_{10}$ feed ratio increased up to 2.75, n-$C_4H_{10}$ conversion and $H_2$ yield increased and the selectivity of methane and other hydrocarbons decreased. But with $O_2/n-C_4H_{10}$ = 3.0, $n-C_4H_{10}$ conversion and $H_2$ yield decreased. This is considered due to that too much oxygen may inhibit the reduction of Ni or induce the oxidation of Ni, which results in poor catalytic activity. The optimum $O_2/n-C_4H_{10}$ ratio lay between 2.50 and 2.75. $Ce_{0.1}Ni_{2.5}Ca_{10}(OH)_2(PO_4)_6$ showed the highest $n-C_4H_{10}$ conversion and $H-2$ yield on the whole. In durability tests, higher hydrogen yield and better catalyst stability were obtained with the $O_2/n-C_4H_{10}$ ratio of 2.75 than with the ratio of 2.5.

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Structural characterization of ladder-type cadmium(II) citrate complex, (C3H12N2)[{Cd(H2O)(C6H5O7)}2]·6H2O

  • Kim, Chong-Hyeak;Lee, Sueg-Geun
    • Analytical Science and Technology
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    • v.20 no.4
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    • pp.355-360
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    • 2007
  • The title complex, $(C_3H_{12}N_2)[\{Cd(H_2O)(C_6H_5O_7)\}_2]{\cdot}6H_2O$, I, has been prepared and its structure characterized by FT-IR, EDS, elemental analysis, ICP-AES, and X-ray single crystallography. It is triclinic system, $P{\bar{1}}$ space group with a = 10.236(2), b = 11.318(2), c = $13.198(2){\AA}$, ${\alpha}=77.95(1)^{\circ}$, ${\beta}=68.10(1)^{\circ}$, ${\gamma}=78.12(1)^{\circ}$, V = $1373.5(3){\AA}^3$, Z = 2. Complex I has constituted by protonated 1,3-diaminopropane cations, citrate coordinated cadmium(II) anions, and free water molecules. The central cadmium atoms have a capped trigonal prism geometry by seven coordination with six oxygen atoms of three different citrate ligands and one water molecule. Citrate ligands are bridged to three different cadmium atoms. Each cadmium atom is linked by carboxylate and hydroxyl groups of citrate ligand to construct an one-dimensional ladder-type assembly structure. The polymeric crystal structure is stabilized by three-dimensional networks of the intermolecular O-H${\cdots}$O and N-H${\cdots}$O hydrogen-bonding interaction.