• Title/Summary/Keyword: Manganese Oxide

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Preparation of Manganese Oxide Powders by Spray Pyrolysis and its Electrochemical Characterization (Spray Pyrolysis에 의한 Manganese Oxide 입자의 제조 및 전기화학적 특성)

  • Choi, Won-Chang;Byun, Dong-Jin;Lee, Jung-Kee;Park, Dal-Keun;Kim, Hyeon-Joong
    • Korean Journal of Materials Research
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    • v.11 no.11
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    • pp.936-940
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    • 2001
  • Spray pyrolysis is a favorable technique to form complex mixed-metal oxide powders with high purity in high temperature region. Manganese oxide powders were prepared by spray pyrolysis from an aqueous solution of $Mn(NO_3)_2$. Powders were formed in the temperature range of 500~$700^{\circ}C$ under the constant pressure of 300torr. All the powders have hydrous forms. When the temperature was increased, the size and the surface area of the particles decreased. An electrochemical capacitors were made with manganese oxide electrodes and KOH electrolyte. With the temperature decreased, capacitors showed high capacitance. Capacitor which was prepared with powders formed in the temperature $500^{\circ}C$ demonstrated specific capacitances as high as 83F/g.

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Mechanisms of Formation of Manganese Oxide Minerals in the Manganese Deposits of the Taebaeg Mt. Region, Korea (太白山地區 망간鑛床에 있어서 酸化망간鑛物의 生成機構)

  • Kim, Soo-Jin;Cho, Hyen-Goo;Choi, Hun-Soo
    • Journal of the Mineralogical Society of Korea
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    • v.5 no.1
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    • pp.1-5
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    • 1992
  • The manganese oxide ores in the Taebaeg Mt. region have been formed by supergene weathering of the primary hydrothermal or sedimentary manganese ores. The supergenesis is controlled by the physical chemistry of the descending groundwater in the supergene zone. It includes the fundamental geological processes, such as dissolution, oxidation, transportation, precipitation, and crystallization and recrystallization. However, the fundamental mechanisms for the formation of various manganese oxide minerals are 1) replacement, 2) precipitation from solution, and 3) solid state crystallization and recrystallization. Various textures and structures of ores have been formed by these processes. Detailed paragenetic sequence of manganese oxide minerals in each ore deposit is summerized.

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Synthesis of Alumina-Grafted Manganese Oxide Particles Using Surfactants through Coprecipitation Method and Their Thermal Properties

  • Kwon, Boseong;Park, Jun-Hwan;Jang, Seong-Cheol;Oh, Seong-Geun
    • Bulletin of the Korean Chemical Society
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    • v.34 no.12
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    • pp.3559-3564
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    • 2013
  • Alumina particles were grafted onto the surface of manganese oxide particles via the coprecipitation process using surfactant and cosurfactant. The phase of Mn/Al salts (Phase I) and the phase of precipitation agent (Phase II) were prepared in aqueous surfactant solution, separately. Phase II was added into Phase I and the reaction was performed to form the precursors of composites through hydrogen bonding between $Mn(OH)_2$ and $Al(OH)_3$ prepared by the reaction of Mn/Al salts with the precipitation agent. The alumina-grafted manganese oxide particles were obtained as a final product after calcination. The concentrations of Al salt and surfactant were varied to investigate their effects on the formation and the crystallinity of composites. In addition, the crystal structure of products could be controlled by changing the calcination temperature. Through thermal analyses, it was found that the thermal stability of manganese oxide was improved by the introduction of alumina on its surface.

Effect of Ni addition on anodically deposited $MnO_2$ film (Anodic deposition된 $MnO_2$ 막에 있어서 Ni 첨가 영향)

  • Kim, Bong-Seo;Lee, Dong-Yoon;Lee, Hee-Woong;Chung, Won-Sub
    • Proceedings of the KIEE Conference
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    • 2003.07c
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    • pp.1535-1537
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    • 2003
  • Manganese oxide electrode was designed to improve electrical conductivity for dimensionally stable anode(DSA) using discreet variation (DV)-X${\alpha}$ method. It was calculated in DV-X${\alpha}$ method that the addition of nickel to manganese oxide reduce the energy band gap of manganese oxide electrode. Therefore, it is estimated that nickel in 3 additive elements of Ti, Ni and Sn is the best candidate to improve the electrical conductivity of manganese oxide. The anodically deposited manganese oxide which was produced in 0.2M $MnSO_4$ and 0.2M (Mn,Ni)$SO_4$ solution had $MnSO_4$ structure which was identified by XRD. The $MnSO_4$ films produced in both solutions over than 50mA/$cm^2$ of current density and long deposition time of 600sec showed low adhesion with Ti substrate.

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Chromatographic Enrichment of Lithium Isotopes by Hydrous Manganese(IV) Oxide

  • Kim, Dong Won
    • Bulletin of the Korean Chemical Society
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    • v.22 no.5
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    • pp.503-506
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    • 2001
  • Separation of lithium isotopes was investigated by chemical ion exchange with a hydrous manganese(IV) oxide ion exchanger using an elution chromatography. The capacity of manganese(IV) oxide ion exchanger was 0.5 meq/g. One molar CH3COO Na solution was used as an eluent. The heavier isotope of lithium was enriched in the solution phase, while the lighter isotope was enriched in the ion exchanger phase. The separation factor was calculated according to the method of Glueckauf from the elution curve and isotopic assays. The single stage separation factor of lithium isotope pair fractionation was 1.021.

Effects of Manganese and Carbon on the HAZ Microstructural Evolution in Titanium Oxide Steel (티타늄 산화물강 열영향부 조직변태에 미치는 망간 및 탄소의 영향)

  • 방국수
    • Journal of Welding and Joining
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    • v.22 no.2
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    • pp.78-84
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    • 2004
  • Effects of manganese and carbon on the HAZ microstructural evolution in 500㎫ grade titanium oxide steels were investigated. Microstructural evolution primarily depends on supercooling. When cooled at 3$^{\circ}C$/s in 0.15%C-1.5%Mn steel, grain boundary and Widmanst tten ferrite formed at 640 and 62$0^{\circ}C$, respectively, followed by competitive formation of acicular ferrite and upper bainite inside of grain at 58$0^{\circ}C$. With an increase of manganese, degree of supercooling increased while critical cooling rate for the formation of gain boundary ferrite decreased. Consequently, the amount of acicular ferrite in HAZ was decreased in 2.0%Mn after initial increase in 1.0 and 1.5%Mn. Therefore, optimum supercooling should be maintained to accelerate acicular ferrite formation in titanium oxide steels. Low carbon steel, 0.11%C-1.5%Mn, showed larger amount of acicular ferrite than higher carbon steel because of effectiveness of diffusionless transformation in low carbon steel.

Electrodeposited Nano-flakes of Manganese Oxide on Macroporous Ni Electrode Exhibiting High Pseudocapacitance

  • Gobal, F.;Jafarzadeh, S.
    • Journal of Electrochemical Science and Technology
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    • v.3 no.4
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    • pp.178-184
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    • 2012
  • A porous nickel (P-Ni) substrate was prepared by selective leaching of zinc from pressed pellets containing powders of Ni & Zn in 4 M NaOH solution. Anodic deposition of manganese oxide onto the porous Ni substrate ($MnO_x$/P-Ni) formed nano-flakes of manganese oxide layers as revealed in SEM studies. Pseudocapacitance of this oxide electrode was evaluated by cyclic voltammetry (CV) and chronopotentiometry (CHP) in 2 M NaOH solution. The specific capacitance of the Mn oxide electrode was as high as 1515 F $g^{-1}$, which was ten times higher than Mn oxide deposited on a flat Ni-ribbon. 80% of capacity was retained after 200 charge/discharge cycles. The system showed no loss of activity in dry form over period of days. The impedance studies indicated highly conducting $MnO_x$/P-Ni substance and the obtained specific capacitance from impedance data showed good agreement with the charge/discharge measurements.

Catalytic Oxidation of Toluene by Manganese Oxide: (II) Support and Precursor Effect (망간 산화물에 의한 톨루엔 촉매 산화 반응: (II) 담체 및 전구물질 영향)

  • Cheon Tae-Jin;Choi Sung-Woo;Lee Chang-Soep
    • Journal of Korean Society for Atmospheric Environment
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    • v.21 no.3
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    • pp.277-284
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    • 2005
  • Catalytic oxidation of toluene in low concentrations was investigated over various supports. As the manganese oxides loading was increased, the conversion of toluene increased at a lower temperature. The 18.2 $wt\%$ $Mn/\gamma-Al_2O_3$ appeared to be the most active catalyst. Among the supports, $\gamma-Al_2O_3$ was more active than $TiO_2$ and $SiO_2$. Manganese oxide catalysts prepared from manganese nitrate precursor were better for complete oxidation of toluene than those prepared from manganese sulfate and chloride precursor because sulfate from manganese sulfate and chloride from chloride manganese remained even after the calcination by XRD (X-Ray Diffraction) analyses.

Characteristics and Preparation of Manganese Oxide Electrode by Using Pulse Voltammetry Electrodeposition for Electrolysis (펄스 전착법을 이용한 전기분해용 망간 산화물 전극의 제조 및 특성)

  • Yang, Jeong-Jin;Lee, Mi-Young;Kim, Jeong-Sik;Shin, Hyun-Soo;Park, Soo-Gil
    • Journal of the Korean Electrochemical Society
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    • v.13 no.2
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    • pp.138-144
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    • 2010
  • In order to investigate the electrochemical propertied of titanium electrode for electrolysis, manganese oxide was electrodeposited on surface of mesh titanium by pulse voltammetry. The morphological changes and impedance results of manganese oxide electrodeposited electrode were analyzed by SEM and EDX. The size of electrodeposited manganese oxide on mesh titanium was increased with first cycle pulse time increase, and approximately 100 non-uniform manganese oxide was grown at 10 ms pulse polarization time. Charge transfer resistance($R_{ct}$) of near the overpotential was analyzed by EIS measurement and the feasibility of prepared electrode was evaluated by the overpotential calculated from Tafel plots.