• Bulletin of the Korean Chemical Society
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• v.20 no.11
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• pp.1313-1318
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• 1999

Lewis bases were employed to control the stoichiometry of ferrite film prepared by light enhanced plating (LEP) technique. When 2,2'-bipyridyl was used as a Lewis base, conversion electron Mosbauer spectroscopy (CEMS) and x-ray powder diffraction (XRD) experiments showed that the main component of the ferrite films was metal-deficient magnetite (Fe3(1-δ)O4). Nonstoichiometry and roughness of LEP films were increased by the addition of 2,2'-bipyridyl. Using ethylenediaminetetraacetate (EDTA) as a Lewis base, produced film that was a mixture of magnetite and Υ-FeO(OH). No low temperature transition (Verwey transition) of magnetite was detected in resistivity and ac-susceptibility measurements for the LEP films. Surface morphology of the LEP films was observed by atomic force microscopy (AFM). The size of dominant particles was about 0.2 μm.

• Resources Recycling
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• v.2 no.2
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• pp.27-38
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• 1993

In this study, we investigated the grinding and sedimentation(elutriation) process of the dusts for the effective separation of high purity iron and iron oxides. For characterization of the dust, particle size distribution and chemical composition, were examined. The results obtained in this study may be summarized as follows : 1. The converter CF(clarifier) dust of the Pohang 1st, 2nd steel making factory and EC(Evaporation Cooler), EP(Eltrostatic precititator) dust of the Kwangyang 2nd steel making factory are composed $\alpha$-Fe(21~50%), FeO(wustite)$Fe_3$$O_4$(magnetite), $Fe_2$$O_3$, CaO, $Al_2$$O_3$, $SiO_2$, and etc. 2. Pure iron has ductile characteristic in nature, particle size of the pure iron increase by increasing the grinding time. On the other hand, it is conformed that bo고 particles of hematite and magnetite become less than 325 mesh after 10 minutes grinding. 3. By applying the elutriation technique for the EC dust of the Kwangyang 2nd steel making factory, the iron powder of high content more than 99.17% of pure Fe was recovered with 37.8% yield at grinding time for 40 minutes. 4. By applying the elutriation technique for the CF dust of the Pohang 2nd steel making factory, the iron powder of high content more than 98.38% of pure Fe was recovered with 44.42% yield at grinding time for 40 minutes. 5. When magnetic separation was performed using plastic bonding magnet of 70 gauss, more than 98% Fe grade of iron powder was recovered in the size range +65 -200 mesh but the recovery of it was low.

• Journal of the Korean institute of surface engineering
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• v.40 no.6
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• pp.250-253
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• 2007

Plasma nitrocarburizing and plasma oxidizing treatments were performed to improve the wear and corrosion resistance of SKD 11 steel. Plasma nitrocarburizing was conducted for 12 h at $520^{\circ}C$ in the nitrogen, hydrogen and methane atmosphere to produce the $\varepsilon-Fe_{2-3}(N,C)$ phase. It was found that the compound layer produced by plasma nitrocarburising was predominantly composed of $\varepsilon-phase$, with a small proportion of $\gamma'-Fe_4(N,C)$ phase. The thickness of the compound layer was about $5{\mu}m$ and the diffusion layer was about $150{\mu}m$ in thickness, respectively. Plasma post oxidation was performed on the nitrocarburized samples with various oxygen/hydrogen ratio at constant temperature of $500^{\circ}C$ for 1 hour. The very thin magnetite($Fe_3O_4$) layer $1-2{\mu}m$ in thickness on top of the compound layer was obtained by plasma post oxidation. It was confirmed that the corrosion characteristics of the nitrocarburized compound layer could be further improved by the application of the superficial magnetite layer.

• Journal of the Korean Magnetics Society
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• v.21 no.5
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• pp.157-162
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• 2011

The effect of ferrous/ferric molar ratio and precipitants on the formation of nano size magnetite particle was investigated by coprecipitation method. Ferrous sulfate and ferric sulfate were used as iron sources and sodium hydroxide and ammonium hydroxide was used as a precipitant. Single phase magnetite was synthesized with all of experiment conditions (ferrous/ferric molar ratios and precipitants). Particle size was smaller, and particle size distribution was narrower when NaOH was used than $NH_4OH$ was used. The crystallinity and particle size was increased and narrower particle size distribution with increasing molar ratio ferrous/ferric sulfate with the same precipitant. Super paramagnetism could be obtained at all of experiment conditions. The highest saturation magnetization (72 emu/g) was obtained when the ferrous/ferric molar ratio was 2.5 and precipitant was used $NH_4OH$.

• Macromolecular Research
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• v.14 no.2
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• pp.209-213
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• 2006

The ring-opening polymerization of D,L-lactide initiated by tin(II) 2-ethylhexanoate $(Sn(Oct)_2)$ on the surface-initiated magnetite $(Fe_{3}O_4)$ nanoparticles was performed at $130^{\circ}C$. The effects of the polymer molar mass and concentration on the amount of surface polymer were investigated. The number average molecular weights, $M_n$, obtained by both NMR and GPC methods fit well within the accuracy of the applied methods and ranged from 1,100 to $4,040g\;mol^{-1}$. A surface functionalization density of up to 625 initiation sites per particle was obtained. The composition of various core-shell particles was determined by TGA, with results indicating magnetite $(Fe_{3}O_4)$ contents, ${\mu}m$, between 17 and 59 wt%. Under the influence of a magnetic field, the heating generated by superparamagnetic core-shell particles suspended in toluene presented guidelines for an optimization of magnetic particle systems with respect to an application for hyperthermia.

• Resources Recycling
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• v.11 no.3
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• pp.31-36
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• 2002

Magnetic separation was carried out in order to improve the magnetite grade of the spent iron oxide catalyst, that was composed with magnetite, ceria and soluble alkaline salt. The recovery of magnetite from the spent iron oxide catalyst was over 99%, and the magnetite contents was upgraded to about 80% from 70% via wet type magnetic separation at 500 Gauss. This improvement was due to the removal of alkaline salt by water instead of the magnetic separation.

• Resources Recycling
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• v.1 no.1
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• pp.14-22
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• 1992

As a basic study to recover the copper from the copper converter slag, the characterisitcs of converter slag was studied. The results obtained in this work are as follows. 1. The copper converter slag is composed of Cu, $Cu_2$S, $Fe_3$$O_4$, Fayalite and silicate. 2. It is supposed that magnetite in converter slag is oxidized to hematite at $720^{\circ}C$ and this phase is soluted to fayalite. 3. As the converter slag is added in the water solution, pH increased and the heavy metal ions in the water are adsorbed on the slag. 4. Work index of the converter slag cooled for the 10 hour and the 2 hour are 25~27 kWh/ton and 35 kWh/ton, respectively. 5. In the case of grinding test of converter slag, fayalite in converter slag is easily grinded than magnetite in converter slag.

• Journal of the Mineralogical Society of Korea
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• v.15 no.3
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• pp.231-240
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• 2002

Microbial metal reduction influences the biogeochemical cycles of carbon and metals as well as plays an important role in the bioremediation of metals, radionuclides, and organic contaminants. The use of bacteria to facilitate the production of magnetite nanoparticles and the formation of carbonate minerals may provide new biotechnological processes for material synthesis and carbon sequestration. Metal-reducing bacteria were isolated from a variety of extreme environments, such as deep terrestrial subsurface, deep marine sediments, water near Hydrothemal vents, and alkaline ponds. Metal-reducing bacteria isolated from diverse extreme environments were able to reduce Fe(III), Mn(IV), Cr(VI), Co(III), and U(VI) using short chain fatty acids and/or hydrogen as the electron donors. These bacteria exhibited diverse mineral precipitation capabilities including the formation of magnetite ($Fe_3$$O_4$), siderite ($FeCO_3$), calcite ($CaCO_3$), rhodochrosite ($MnCO_3$), vivianite [$Fe_3$($PO_4$)$_2$ .$8H_2$O], and uraninite ($UO_2$). Geochemical and environmental factors such as atmospheres, chemical milieu, and species of bacteria affected the extent of Fe(III)-reduction as well as the mineralogy and morphology of the crystalline iron mineral phases. Thermophilic bacteria use amorphous Fe(III)-oxyhydroxide plus metals (Co, Cr, Ni) as an electron acceptor and organic carbon as an electron donor to synthesize metal-substituted magnetite. Metal reducing bacteria were capable of $CO_2$conversion Into sparingly soluble carbonate minerals, such as siderite and calcite using amorphous Fe(III)-oxyhydroxide or metal-rich fly ash. These results indicate that microbial Fe(III)-reduction may not only play important roles in iron and carbon biogeochemistry in natural environments, but also be potentially useful f3r the synthesis of submicron-sized ferromagnetic materials.

• Bulletin of the Korean Chemical Society
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• v.34 no.5
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• pp.1457-1461
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• 2013

The $Fe_3O_4$-core and Ag-shell ($Fe_3O_4@Ag$ nanoeggs) were prepared through the encapsulation of 3-aminopropyltriethoxysilane-coated magnetite nanoparticle in nano-Ag shell by a simple chemically controlled procedure. The $Fe_3O_4@Ag$ nanoeggs were characterized by scanning electron microscopy, transmission electron microscopy, UV-vis spectrum and superconducting quantum interference device magnetometer, respectively. A detailed analysis is provided of how the hydrolysis and condensation of 3-aminopropyltriethoxysilane and the pH value are vital in fabricating the $Fe_3O_4@Ag$ nanoeggs. The prepared $Fe_3O_4@Ag$ nanoeggs possessed uniform size, improved monodispersity, stability against aggregation and high magnetization, which were utilized for the detection of latent fingerprints deposited onto different surfaces. The experimental results showed that the latent fingerprints developed with the $Fe_3O_4@Ag$ nanoeggs powders exhibited excellent ridge details with minimal background staining.

• The Journal of the Petrological Society of Korea
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• v.3 no.1
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• pp.1-19
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• 1994

We present petrography, mode and chemistry data for Fe-Ti oxide minerals from the Mesozoic granitoids in South Korea. Magnetites from the Daebo Uurassic) granites are nearly pure $Fe_3O_4$, while those from the Bulgugsa (Cretaceous) granites contain considerable amounts of Mn and Ti. This is probably related to rapid cooling of the Bulgugsa granites compared with slow cooling of Daebo granites, which is supported by geologic relations and hornblende geobarometry results of Cho and Kwon (1994) on the emplacement depth for these granites. The composition of ilmenite does not shew appreciable difference between the Daebo and Bulgugsa granites. However, $Fe_2O_3$ contents are higher for the ilmenites coexisting with magnetite than for those without magnetite. In the temperature vs. oxygen fugacity diagram, the Bulgugsa granites plot near Ni-NiO and QFM buffer curves, although only two samples show greater than the granite solidus temperature. The mode data suggest that both magnetite- and ilmenite-series exist in Daebo and Bulgusa granites from the Kyonggi massif, Ogcheon belt and Youngnam massif, while only magnetite-series exists in Bulgugsa granites from the Kyongsang basin. Many ilmenite-series granites occur in the Ogcheon belt, which might be related to assimilation of carboniferous sediments in the belt. The proportion (44 : 56) between ilmenite- and magnetite-series for the Daebo granites is significantly different from that of Ishihara et al. (1981) who showed, using magnetic susceptibility data, predominance of ilmenite-series (more than 70%) for the Daebo granites, which can be mainly attributed to preference in sampling and to wrong assignment of age for some plutons. We also found magnetite in weakly-magnetized Kanghwa granite which was formerly classified as ilmenite-series by Ishihara et al. (1981). The proportion of ilmenite-series increases in the order of hornblende biotite granite, biotite granite and two mica granite. We conclude from these observations that the ilmeniteseries granites might have originated from contamination of carboniferous crustal material and/or such source material.