• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.409-412
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• 2001

The high purity manganese oxides were made from the dust, generated in AOD process that produces a medium-low carbon ferromanganese and collected in the bag filter. Manganese oxide content in the dust was about 90%, and its phase was confirmed as Mn₃O₄. In the extraction of manganese, because of remaining amorphous MnO₂, the dust was reduced to MnO by roasting with charcoal. The pulp density of the reduced dust can control pH of the solution more than 4 and then Fe ion is precipitated to a ferric hydroxide. Because a ferric hydroxide co precipitates with Si ion etc, Fe, Si ion was removed f개m the solution. Heating made water to be volatized and nitrates was left in reactor Then nitrates were a liquid state and stirring was possible. Among the nitrates in reactor, only the manganese nitrate which have the lowest pyrolysis temperature pyrolyzed into β-MnO₂powder and NO₂(g) at the temperature less than 200℃. When the pyrolysis of manganese nitrate has been completed about 90%, injection of water stopped the pyrolysis. Nitrates of impurity dissolved and the spherical high purity β-MnO₂powders were obtained by filtering and washing. Mn₂O₃or Mn₃O₄ powder could be manufactured from β-MnO₂powder by controlling the heating temperature. Lastly, a manufactured manganese oxide particle has 99.97% purity.

• Journal of Sensor Science and Technology
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• v.20 no.1
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• pp.64-69
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• 2011

Porous manganese oxide porous nanostructures were prepared by amino-acid-mediated solvothermal self assembly reaction and subsequent heat treatment at $600^{\circ}C$. When Mn-precursors were heat-treated at $400-550^{\circ}C$, the sensors did not show significant gas responses. In contrast, the manganese oxide heat-treated at $600^{\circ}C$ showed the significant gas responses, that is, the resistance decrease to 100 ppm $C_3H_8$ ($R_a/R_g$ = 2.17, $R_a$ : resistance in air, $R_g$ : resistance in gas) and the resistance increase to 100 ppm $C_2H_5OH$ ($R_g/R_a$ = 1.92). The opposite change of resistance upon exposure to $C_3H_8$ and $C_2H_5OH$ was discussed in relation to the mixed phases of manganese oxides with different valences.

• Journal of the Korean Ceramic Society
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• v.47 no.6
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• pp.633-637
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• 2010

In this study, lithium manganese oxide spinel ($LiMn_{1.9}Fe_{0.1}Nb_{0.0005}O_4$) as a cathode material of lithium ion secondary batteries is synthesized with spray drying, and in order to increase its crystallinity and electrochemical properties, the granulated $LiMn_{1.9}Fe_{0.1}Nb_{0.0005}O_4$ particle surface is coated with lithium titanium oxide spinel ($Li_4Ti_5O_{12}$) through a sol-gel method. The granulated particles present a higher tap density and lower specific surface area. The crystallinity and discharge capacity of the $Li_4Ti_5O_{12}$ coated material is relatively higher than uncoated material. With the coating layer, the discharge capacity and cycling stability are increased and the capacity fading is suppressed successfully.

• Economic and Environmental Geology
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• v.15 no.4
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• pp.205-219
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• 1982

The Eosangcheon manganese ore deposits occur as supergene weathering deposits along quartz porphyry dikes developed in the Ordovician Heungweolri dolomite and Samtaesan limestone formations. The manganese ores are composed of manganese oxide minerals and associated other minerals. Rancieite and todorokite are abundantly found, and birnessite, nsutite, pyrolusite and chalcophanite are found in minor quantities. Associated other minerals are calcite, gypsum, goethite, lepidocrosite, quartz, and sericite. Microscopic, chemical, X-ray powder diffraction, infrared absorption spectroscopic and differential thermal analyses have been made for manganese oxide minerals and associated other minerals. The relationship of birnessite and rancieite was studied by means of X-ray powder diffraction and infrared absorption spectroscopic analyses. It is assumed that these minerals are closely related to each other in crystal structure, but separate species. The manganese oxide minerals were formed mainly by replacement, precipitation from solution, and recrystallization in the supergene weathering environment. The trend of formation of manganese oxide minerals is: (Rhodochrosite)-(todorokite)-(birnessite, rancieite)-(nsutite, pyrolusite, chalcophanite).

• Korean Journal of Materials Research
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• v.31 no.11
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• pp.608-613
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• 2021

This study investigated the reaction between clay and Mn. Mn was coated using a manganese sulfate on porcelain plate and sintered from 1,100 ℃ to 1,250 ℃. The body begin to shrink around 950 ℃ with the increase in temperature and rapidly progressed after 1,100 ℃. Shrinkage of celadon body was performed at a lower temperature than for other substrates. Quartz, kaolin, and feldspar were the main crystalline phases of the starting materials, but they became mullite and crystobalite during the firing process, and some formed amorphous glass. When manganese sulfate was applied and fired, manganese oxide was fused, and some manganese oxide reacted with the substrate to show a dense microstructure different from that of the substrate; the substrate had pores. The manganese coated porcelain fired at 1,200 ℃ had L^* values of 55.25, 36.87, and 37.13 for the white ware, celadon body, and white mixed ware, respectively; with a^* values of 4.63, 3.07, and 2.15, and b^* values of 7.93 and 3.98, it was found to be 3.42. This result indicated that the color of the surface was affected during firing by the chemical reaction between the substrate and manganese.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.2
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• pp.161-168
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• 2005

The catalytic oxidation of toluene in low concentration was investigated over manganese oxide/$\gamma$-A1$_{2}$O$_{3}$ catalysts. As increased manganese loading, the conversion of toluene increased at a lower temperature. The 18.2wt$\%$ Mn/$\gamma$-Al$_{2}$O$_{3}$ appeared to be the most active catalyst. XRD results indicated that most of the catalysts exist as MnO$_{2}$ and Mn$_{2}$O$_{3}$ crystalline phase. After the reaction, the used and the fresh catalysts were characterized by XPS. For the used catalyst, a prominent feature has increased. TPR profiles of 18.2 wt$\%$ Mn/$\gamma$-Al$_{2}$O$_{3}$ changed significantly as the manganese loading increased at a lower temperature.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.6
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• pp.263-270
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• 2018

Recently, porous ceramic materials with anti-static performance are urgently needed for semiconductor and OLED/LCD display manufacturing industry. In this work, we fabricated porous titanium manganese oxide ceramics having the surface resistivity of $10^8-10^{10}$ ohm and enhanced mechanical strength by partial sintering method using nanosized titanium oxide. By addition of nano-sized titanium oxide in the matrix, neck formation between grains was strengthened, which remarkably increased flexural strength up to 170 MPa (@porosity: 15 %), 110 MPa (@porosity: 31 %), compared to 80 MPa (@porosity: 26 %) for pristine titanium manganese oxide ceramics. We evaluated the performances of our ceramics as air-floating module for OLED flexible display manufacturing devices.

• Economic and Environmental Geology
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• v.19 no.4
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• pp.265-276
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• 1986

The Jangseong manganese deposits are supergene oxidation products of hydrothermal rhodochrosite. The manganese ore veins are developed in the Dongjeom Quartzite, and Dumudong Formation. The deposits consist of primary manganese carbonate ores in the deeper part and manganese oxide ores near the surface. The manganese carbonate ores are composed of rhodochrosite and small amounts of sulfides. The manganese oxide ores are composed of birnessite, nsutite, todorokite, chalcophanite, and pyrolusite. Microscopic, X-ray diffraction, infrared, thermal and EPMA analyses have been made for manganese oxide minerals and other associated minerals. The manganese minerals were formed in the following sequence. Rhodochrosite$\rightarrow$birnessite$\rightarrow$todorokite$\rightarrow$nsutite-pyrolusite. Thermochemical properties of chalcophanite were studied by methods of X-ray powder diffraction, infrared absorption spectroscopic analysis and dehydration experiments. Chalcophanite changes to $4.8{\AA}$ phase at $90{\sim}110^{\circ}C$. Chemical analyses show that the manganese oxide minerals generally have high concentration in Zn.

• Bulletin of the Korean Chemical Society
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• v.19 no.2
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• pp.263-265
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• 1998

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.473-478
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• 2008

In this experimental, selective catalytic reduction (SCR) of NO with NH3 over manganese sulfates and manganese sulfates was investigated with catalytic activity, kinetics, temperature programmed reduction (TPR) and TGA. Manganese oxides showed high catalytic activity for SCR at temperature below $200^{\circ}C$. In case of manganese sulfates, the temperature at which SCR of nitric oxide appears shifted to high temperature with sulfation degree, and the maximum catalytic efficiency decreased. The temperature of the onset of reduction for manganese oxides and manganese sulfates is about $160^{\circ}C$ and over $280^{\circ}C$, respectively. We suggest that the onset of reduction in TPR correlates with the onset of SCR activity. Because the pre-exponential factor of manganese sulfates is lower as 1/1000 times than that of other catalysts, catalytic activity of manganese sulfates for NO showed low. The reduction temperature of natural manganese ore which consists of various metal oxides showed lower than that of pure manganese oxides.