• Title/Summary/Keyword: MnO$_2$

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The Dielectrical Properties of $(1-x)(Sr_a.Pb_b.Ca_c)TiO_3-xB_i2O_3.TiO_2$ system affected by $Bi_2O_3.3TiO_2$ amounts and $MnO_2$ ($(1-x)(Sr_a.Pb_b.Ca_c)TiO_3-xB_i2O_3.TiO_2$계에서의 $Bi_2O_3.3TiO_2$$MnO_2$첨가에 따른 유전특성에 관한 연구)

  • 박상도;이응상
    • Journal of the Korean Ceramic Society
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    • v.34 no.2
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    • pp.123-130
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    • 1997
  • In this study, (Sr.Pb.Ca)TiO3-Bi2O3.3TiO2(SPCT) systems were investigated to develop a new material which has a high dielectric constant, a low dielectric loss and a small TCC(Temperature Coefficient of Capa-citance), and are suitable for high voltage applications as a function of the additions of Bi2O3.3TiO2 from 5 mol.% to 9 mol.%. The result obtained from our investigation showed that up to 6 mol.% Bi2O3.3TiO ad-dition the dielectric constant increased and it deteriorated at higher concentrations with increasing amount of the acicular grains. As a result of some dopants (SiO2, Nb2O3, MnO2) addition to SPCT, the specimens with MnO2 showed good dielectric properties. The dielectric constant decreased, but the TCC was improved with the addition of MnO2 from 0.15 wt.% to 0.45 wt. %.

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Studies on Spinel Ferrites (I) Effects of Addition of Rare-Earth Oxides on the Magnetic Properties of Mn-Zn Ferrites (Spinel Ferrite에 관한 연구 (I) Mn-Zn계 Ferrite의 자기특성에 대한 희토류산화물의 첨가효과)

  • 김태옥
    • Journal of the Korean Ceramic Society
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    • v.14 no.2
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    • pp.78-81
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    • 1977
  • The effects of variation in composition and the addition of small amount of the rare-earth oxides La2O3, CeO2 and Sm2O3 on the magnetic properties of Mn-Zn system ferrites, 0.5MnO.0.5ZnO.(1+0.1X) Fe2O3(X=-1, 0, 1, 2), were investigated in the range of frequencies of 0.1~100 kHz. It was shown that the magnetic permeability of the specimens with the composition Mn 0.5 Zn 0.5 Fe2O4 was maximum in the Mn-Zn system ferrites, and that the addition of a small amount of the rare-earth oxides to the composition 0.5 MnO.0.5ZnO.0.9 Fe2O3 caused the sharp increase of magnetic permeability and the decrease of the loss factors.

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Preparation and Luminescent Properties of Zn2SiO4:Mn, Ga Phosphors (Zn2SiO\4:Mn, Ga 형광체의 제조와 발광특성)

  • Lee, Ji-Young;Yu, Yun-Sik;Yu, Il
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.22 no.2
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    • pp.158-162
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    • 2009
  • $Zn_2SiO_4$:Mn green phosphors doped with Ga for PDP were synthesized by solid state reaction method. Photoluminescence measurements showed a new emission peak at around 600 nm for $Zn_2SiO_4$:Mn phosphors doped with Ga. Also, the luminescent color with doping $Ga^{3+}$ in the $Zn_2SiO_4$:Mn phosphors changed to green from yellowish green. Consequently, the new peak and charge of the luminescent color in the $Zn_2SiO_4$:Mn, Ga phosphors were attributed to $^2E{\rightarrow}^6A_2$ transition of $Mn^{4+}$.

Low Temperature Selective Catalytic Reduction of NO with $NH_3$ over Mn/$CeO_2$ and Mn/$ZrO_2$ (Mn/$CeO_2$와 Mn/$ZrO_2$ 촉매 상에서 $NH_3$를 사용한 NO의 선택적 촉매 산화 반응)

  • Ko, Jeong Huy;Park, Sung Hoon;Jeon, Jong-Ki;Sohn, Jung Min;Lee, See-Hoon;Park, Young-Kwon
    • Applied Chemistry for Engineering
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    • v.23 no.1
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    • pp.105-111
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    • 2012
  • Manganese (Mn) catalysts were generated using $CeO_2$ and $ZrO_2$supports synthesized by the supercritical hydrothermal method and two different Mn precursors, aimed at an application for a low-temperature selective catalytic reduction process. Manganese acetate (MA) and manganese nitrate (MA) were used as Mn precursors. Effects of the kind and the concentration of the Mn precursor used for catalyst generation on the NOx removal efficiency were investigated. The characteristics of the generated catalysts were analyzed using $N_2$ adsorption-desorption, thermo-gravimetric analysis, X-ray diffraction, and X-ray photoelectron spectroscopy. De-NOx experiments were carried out to measure NOx removal efficiencies of the catalysts. NOx removal efficiencies of the catalysts generated using MA were superior to those of the catalysts generated using MN at every temperature tested. Analyses of the catalyst characteristics indicated that the higher NOx removal efficiencies of the MA-derived catalysts stemmed from the higher oxygen mobility and the stronger interaction with support material of $Mn_2O_3$ produced from MA than those of $MnO_2$ produced from MN.

Electrochemical Properties of LiMn$_2$O$_4$by the Sort of Mixing Materials and Variation of Mole ratios (합성 물질의 종류 및 몰비 변화에 따른 LiMn$_2$O$_4$의 전기화학적 특성)

  • 최형기;박현배;정인성;구할본
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1997.11a
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    • pp.286-289
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    • 1997
  • It was studied that the effect of the mixing materials and the mole ratios on electrochemical properties of LiMn$_2$O$_4$LiMn$_2$O$_4$is prepared by reacting stoichiometric mixture of LiOH.$H_2O$ and MnO$_2$(EMD or CMD) and heating at 80$0^{\circ}C$ for 36h. We obtained properties of crystal structure through X-ray diffraction. LiMn$_2$O was reversible at 4.5V~3.0V and displayed two reduction and oxidation. Optimum synthesis results were obtained by reacting with LiOH.$H_2O$ and MnO$_2$(EMD) at mole ratio 1:2.

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Development of High-performance Supercapacitors Based on MnO2/Functionalized Graphene Nanocomposites (망간산화물/기능화된 그래핀 나노복합체에 기반한 고성능 슈퍼커패시터 개발)

  • Choi, Bong Gill
    • Applied Chemistry for Engineering
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    • v.27 no.4
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    • pp.439-443
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    • 2016
  • In this report, $MnO_2$ nanoparticle-deposited functionalized graphene sheets were prepared and their superior electrochemical performances were demonstrated by cyclic voltammetry, galvanostatic charge-discharge, and impedance analysis. Ionic liquids were employed to functionalize the surface of reduced graphene oxides (RGOs), leading to prevention of the aggregation of RGO sheets and abundant growth sites for deposition of $MnO_2$ nanoparticles. As-prepared $MnO_2/RGO$ nanocomposites were characterized using scanning electron microscope, transition electron microscope, X-ray photoelectron spectroscopy, and X-ray diffraction. Electrochemical properties of $MnO_2/RGO$ electrode were evaluated using $Na_2SO_4$ electrolyte under a three-electrode system. The $MnO_2/RGO$ electrode showed a high specific capacitance (251 F/g), a high rate capability (80.5% retention), and long-term stability (93.6% retention).

Electrical properties of $MnO_2$doped PSN-PNN-PT ceramics ($MnO_2$가 첨가된 PSN-PNN-PT세라믹스의 전기적인 특성)

  • 이종덕;박상만;박기엽
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.07a
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    • pp.959-962
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    • 2001
  • In this study, the piezoelectric and dielectric properties and Temperature stability of resonant frequency with MnO$_2$doped 0.36Pb(Sc$_{1}$2/Nb$_{1}$2/)O$_3$- 0.25Pb(Ni$_{1}$3/Nb$_{2}$3/)O$_3$-0.39PbTiO$_3$(hereafter PSNNT) were investigated. The tetagonality of crystal structure was developed with increasing MnO$_2$additive content. With increasing MnO$_2$additive content, the electromechanical coupling factor and quality factor were increased. Electromechanical coupling k$_{p}$ and quality factor Q$_{m}$ at MnO$_2$doped with 2.0mol% were showed highest value of 55.6% and 252. In the case of specimen for MnO$_2$doped with 2mol%, temperature dependance of resonant frequency had a good properties.ies.

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The relation of the crystal phase and the charge/discharge capacity of $Li[Li_yMn_{2-y}]O_4$ cathode materials substituted Li (Li 치환된 $Li[Li_yMn_{2-y}]O_4$ 정극 활물질의 결정 구조와 충방전 용량과의 관계)

  • Jeong, In-Seong;Gu, Hal-Bon;Park, Bok-Gi;Son, Myeng-Mo;Lee, Heon-Su
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2000.04b
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    • pp.117-120
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    • 2000
  • The relation of crystal phase and charge/discharge capacity of $Li[Li_yMn_{2-y}]O_4$ were studied for different degrees of Li substitution (y). All cathode material showed spinel phase based on cubic phase in X-ray diffraction. Other peaks didn't show in spite of the increase of y value in $Li[Li_yMn_{2-y}]O_4$. Ununiform of $Li[Li_yMn_{2-y}]O_4$ which calcinated by (111) face and (222) face was more stable than that of pure $LiMn_2O_4$. In addition, At TG analysis, calcined $Li[Li_{0.1}Mn_{1.9}]O_4$ exhibited much mass loss at $800{\mu}m$. The cycle performance of the $Li(Li_yMn_{2-y}]O_4$ was improved by the substitution of $Li^{1+}$ for $Mn^{3+}$ in the octahedral sites. Specially, $Li[Li_{0.08}Mn_{1.92}]O_4$ and $Li[Li_{0.1}Mn_{1.9}]O_4$ cathode materials showed the charge and discharge capacity of about 125mAh/g at first cycle, and about 95mAh/g after 70th cycle. It is excellent than that of pure $LiMn_2O_4$, which 125mAh/g at first cycle, 65mAh/g at 70th.

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Synergistically Enhanced Oxygen Evolution Catalysis with Surface Modified Halloysite Nanotube

  • Hyeongwon Jeong;Bharat Sharma;Jae-ha Myung
    • Journal of Electrochemical Science and Technology
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    • v.14 no.1
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    • pp.96-104
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    • 2023
  • Synergistically increased oxygen evolution reaction (OER) of manganese oxide (MnO2) catalyst is introduced with surface-modified halloysite nanotube (Fe3O4-HNTs) structure. The flake shaped MnO2 catalyst is attached on the nanotube template (Fe3O4-HNTs) by series of wet chemical and hydrothermal method. The strong interaction between MnO2 and Fe3O4-HNTs maximized active surface area and inter-connectivity for festinate charge transfer reaction for OER. The synergistical effect between Fe3O4 layer and MnO2 catalyst enhance the Mn3+/Mn4+ ratio by partial replacement of Mn ions with Fe. The relatively increased Mn3+/Mn4+ ratio on MnO2@FHNTs induced 𝜎* orbital (eg) occupation close to single electron, improving the OER performances. The MnO2@FHNTs catalyst exhibited the reduced overpotential of 0.42 V (E vs. RHE) at 10 mA/cm2 and Tafel slope of (99 mV/dec), compared with that of MnO2 with unmodified HNTs (0.65 V, 219 mV/dec) and pristine MnO2 (0.53 V, 205 mV/dec). The present study provides simple and innovative method to fabricate nano fiberized OER catalyst for a broad application of energy conversion and storage systems.

Electrochemical Properties of LiMn2O4-LiNi1/3Mn1/3Co1/3O2 Cathode Materials in Lithium Secondary Batteries (리튬이차전지 양극활물질용 LiMn2O4-LiNi1/3Mn1/3Co1/3O2의 전기화학적 특성)

  • Kong, Ming Zhe;Nguyen, Van Hiep;Gu, Hal-Bon
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.29 no.5
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    • pp.298-302
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    • 2016
  • In this work, $LiMn_2O_4$ and $LiNi_{1/3}Mn_{1/3}Co_{1/3}O_2$ cathode materials are mixed by some specific ratios to enhance the practical capacity, energy density and cycle performance of battery. At present, the most used cathode material in lithium ion batteries for EVs is spinel structure-type $LiMn_2O_4$. $LiMn_2O_4$ has advantages of high average voltage, excellent safety, environmental friendliness, and low cost. However, due to the low rechargeable capacity (120 mAh/g), it can not meet the requirement of high energy density for the EVs, resulting in limiting its development. The battery of $LiMn_2O_4-LiNi_{1/3}Mn_{1/3}Co_{1/3}O_2$ (50:50 wt%) mixed cathode delivers a energy density of 483.5 mWh/g at a current rate of 1.0 C. The accumulated capacity from $1^{st}$ to 150th cycles was 18.1 Ah/g when the battery is cycled at a current rate of 1.0 C in voltage range of 3.2~4.3 V.