• Journal of Energy Engineering
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• v.11 no.3
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• pp.247-253
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• 2002

Natural manganese ore was selected as main active component for a non-zinc desulfurization sorbent used in the gas clean-up process of the integrated gasification combined cycle (IGCC) because of excellent H$_2$S removal efficiency and economical aspect . In this study, the regeneration characteristics of sorbent after desulfurization reaction were determined in a thermobalance reactor and a fixed bed reactor in the temperature range of 350~55$0^{\circ}C$. The mixed gases of oxygen and nitrogen are used as the regeneration reaction gases for manganese sorbent. According to Mn-S-O phase diagram, the manganese sorbent has a low regeneration efficiency in medium temperature due to formation of MnSO$_4$ and the regeneration temperature must be over 85$0^{\circ}C$. To improve that problem, ammonia and steam was added in regeneration mixed gases. Effect of new regeneration method was determined by XRD and difference of desulfurization through multicycle tests.

• Journal of the Korean Electrochemical Society
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• v.4 no.1
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• pp.1-5
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• 2001

Composite ratio of $LiMn_2O_4$ in cathode was optimized as function of specific surface area. Binder has to be used as possible as little, and it should maintain adhesive property between cathode composite and current collector even though in electrolytes. For this purpose, We used 'Hot Roll Pressing' method, and it was effective. To prevent separation of cathode composite from current collector, PVDF(Polyvinylidenefluoride) has to be mixed more than $1.1\%$ in weight ratio to sum of surface area of lithium manganese oxide and conducting agents. Specific internal resistance was reduced as by increasing electrical conductivity of cathode. And Ratio of 2C rate discharge capacity to 0.2C rate discharge capacity was increased by $17\%$, as increasing electrical conductivity from 0.019 mS/cm to 0.036 mS/cm.

• Applied Chemistry for Engineering
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• v.28 no.2
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• pp.193-197
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• 2017

In this study, we report on the catalyst process installed in conjunction with a wet plasma electrostatic precipitator to remove the oil mist and fine dust emitted from large-size grill restaurants. The multi-stage catalyst module reduced odor through catalytic reaction of acetaldehyde on catalysts even at an ambient temperature with ozone as an oxidant readily produced in a wet plasma electrostatic precipitator. Two types of manganese-based catalysts, $Mn_2O_3$ and $CuMnO_x$ were fabricated by extrusion molding for structured catalysts in practical applications, and the optimum conditions for high removal efficiencies of acetaldehyde and ozone were determined. When two optimized catalysts were applied in a two-stage catalyst module, the removal efficiency of acetaldehyde and ozone were ${\geq}85%$ and 100% respectively at the space velocity of $10,000h^{-1}$ and the reaction temperature of $100^{\circ}C$.

• Resources Recycling
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• v.11 no.4
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• pp.44-50
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• 2002

Characteristics on the sulfuric acid leaching of zinc and manganese from the spent zinc-carbon battery powders obtained by cushing and magnetic separation, were investigated with the variation of sulfuric acid concentration, reaction temperature, stir-ring speed and solid/liquid ratio. The sample powders were composed of Zn metal, ZnO, $MnO_2$ and $Mn_2$$O_3$. and it was found that the selective leaching of zinc was difficult in this system. At the condition of S/L ratio 1:10, IM H$_2$$SO_4$, $60^{\circ}C$ and 200 rpm, leaching rate of Zn and Mn are 92% and 35% respectively. The concentration of Zn and Mn in the leaching solution are 19.5 g/l, 7.8 g/l and pH of that solution is 0.75. It was confirmed at reducing agent should be added to increase e leaching rate of manganese with sulfuric acid.

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.4
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• pp.443-448
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• 2010

The objective of this study was to assess the catalytic activities of manganese oxide (MnO, $MnO_2$, $Mn_2O_3$, and $Mn_3O_4$) catalysts for odors (acetaldehyde and propionaldehyde) removal. We used a fixed bed reactor as the experimental apparatus and the catalytic performance were carried out over the temperature range of $200{\sim}470^{\circ}C$. The properties and performance of catalysts were characterized by the X-ray diffraction (XRD) and Brunauer Emmett Teller (BET). The catalytic activities of manganese oxide catalysts for acetaldehyde combustion were in the order of MnO < $MnO_2$ < $Mn_2O_3$ < $Mn_3O_4$, and it is similar to that of propionaldehyde combustion. We also confirmed that the reactions have well followed the kinetic model of Power-Rate Law and the reaction order (n) is 1 for both of the acetaldehyde and propionaldehyde combustion. In addition, the reaction activation energy of acetaldehyde and propionaldehyde combustion over $Mn_3O_4$ were found to be $72.42\;kJmol^{-1}$ for 487~503 K and $51.14\;kJmol^{-1}$ for 473~533 K, respectively.

• Applied Chemistry for Engineering
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• v.23 no.1
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• pp.119-123
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• 2012

This study presents the effect of oxygen on the $NH_3$ selective catalytic reduction (SCR) by Mn/$TiO_2$ catalyst. The lattice oxygen of catalysts is participate in the low temperature SCR, and the gaseous oxygen directly takes part in the rexoidtion of reduced catalyst. These redox properties of oxygen an play important role in SCR activity and the available capability of lattice oxygen depends on the manganese oxidation state of the catalyst surface. $MnO_2$ species has a higher redox property than that of $Mn_2O_3$ species on deposited $TiO_2$ surface and these manganese oxide states strongly depend on the $TiO_2$ surface area.

• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.137-141
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• 2005

The CMR properties and magnetic properties of sulphospinels $Zn_xFe_{1-x}Cr_2S_4$ have been explored by X-ray diffraction, magnetoresistance measurement, and $M\ddot{o}ssbauer$ spectroscopy. The crystal structures in the range of x=0.05, 0.1, 0.2 are cubic at room temperature. Magnetoresistance measurement indicates that these system is semiconducting below about 160 K. The temperature of maximum magnetoresistance is almost consistent with Curie temperature. The Zn substitutions for Fe occur to increase the Jahn-Teller relaxation and the electric quadrupole shift. CMR properties could be explained with Jahn-Teller effect, and half-metallic electronic structure, which is different from both the double exchange interactions of manganite La-Ca-Mn-O system and the triple exchange interactions of chalcogenide $Cu_xFe_{1-x}Cr_2S_4$.

• Journal of the Korean Magnetics Society
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• v.19 no.3
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• pp.94-99
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• 2009

We have studied the effects of oxygen partial pressure change on the physical properties of the $La_{0.7}Ca_{0.3}MnO_3$ thin films grown by Pulsed laser Deposition. Contrary to the previous reports, thin films of high curie temperature were successfully synthesized at very low oxygen partial pressure ($1.0{\times}10^{-5}$, $1.0{\times}10^{-6}Torr$). These observations indicate that the shape of plasma plume and the kinetic energy of the ablated species in it play an important role in determining the quality of samples. We also fabricated p-n heterojunction of $La_{0.7}Ca_{0.3}MnO_3$ and Nb-doped $SrTiO_3$. The current-voltage curves show rectifying behavior and, furthermore, the current responses to the applied magnetic field, indicating a potential possibility of device applications.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.5
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• pp.362-366
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• 2000

$Li_{0.44}MnO_2$cathode material has high reversibility during lithium insertion processes and is not easily damaged through over-charging or over-discharging. $Mn_2O_3$is often present as an impurity phase, and reduce the electrochemical capacity of electrode because this phase is electrochemically inert. Adding of excess NaOH reduced the $Mn_2O_3$to the content under undetectable by X-ray diffraction. Because the capacity can be increased in the cathode materials with larger unit cell, some of the manganese was replaced with titanium having larger ion size, and powders with the formula $Li_{0.44}T_{iy}Mn_{1-y}O_2$(where y = 0.11, 0.22, 0.33, 0.44, and 0.55) was synthesized and characterized. A maximum reversible capacity of 150 mAh/g was obtained for $Li/P(EO)_8$LiTFSI/$Li_{0.44}Ti_{0.22}Mn_{0.78}O_2$cells in electrochemical potential spectroscopy (ECPS) experiments. Cells with the titanium-doped manganese oxides exhibited a fade rate of 0.12 % or less per cycle.

• Applied Biological Chemistry
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• v.37 no.5
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• pp.414-420
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• 1994

Birnessite, pyrolusite and hausmannite were synthesized and tested for the ability to oxidize Cr(III) to Cr(VI). These oxides differed in zero point of charge, surface area, and crystallinity. The kinetic study showed that Cr(III) oxidation on the Mn-oxide surface is a first-order reaction. The reaction rate was various for different oxide at different conditions. Generally the reaction by hausmannite, containing Mn(III), was faster than the others, and oxidation by pyrolusite was much slower. Solution pH and initial Cr(III) concentration had a significant effect on the reaction. Inhibited oxidation at higher pH and initial Cr(III) concentration could be due to the chance of Cr(III) precipitation or complexing on the oxide surface. Oxidations by birnessite and hausmannite were faster at lower pH, but pyrolusite exhibited increased oxidation capacity at higher pH in the range between 3.0 and 5.0. Reactions were also temperature sensitive. Although calculated activation energies for the oxidation reactions at pH 3.0 were higher than the general activation energy for diffusion, there is no experimental evidence to suggest which reaction is the rate limiting step.