• Journal of the Korean Chemical Society
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• v.20 no.1
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• pp.35-42
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• 1976

Amine salts of five tetrahedral and three octahedral oxalatoferrate(Ⅲ) complexes have been prepared including pyridinium salts of unreported oxalate complex ions $[FeC_2O_4Br_2]^-,$ $[FeC_2O_4(NCS)_4]^{3-}$ and $[Fe_2(C_2O_4)_3Cl_4]^{4-},$ the latter being most photoreactive. The structural aspects of these new complex ions as well as of other oxalatoferrates(III) have been discussed based on their analytical data and infrared spectra. The results of molar conductivity and magnetic susceptibility measurements of all these oxalatoferrate(III) complexes were also presented.

• Korean Journal of Materials Research
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• v.11 no.1
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• pp.34-38
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• 2001

Intermetallics of Fe-28%Al($Fe_3Al$) and Fe-28%Al-4%Cr($Fe_3Al-4Cr$) were oxidized at 1073, 1273 and 1473k in air for up to 17 days. The oxidation resistance of$Fe_3Al-4Cr$ was basically similar to or better than that of $Fe_3Al$. The oxide scales formed on $Fe_3Al$ consisted essentially of pure ${\alpha}-AL_2O_3$, while those formed on $Fe_3Al-4Cr$ consisted of ${\alpha}-AL_2O_3$ having dissolved iron and chromium ions. The preferential outward diffusion of substrate elements to form the outer oxide layer led to the formation of Kirkendall voids at the oxide-matrix interface. The scales formed on $Fe_3Al(-4Cr)$ were thin and dense up to 1273K, but they spalled easily at 1473K, accompanied by more weight gains.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.4
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• pp.625-628
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• 2008

Ba-Zn ferrite powders for electromagnetic insulator were synthesized by self-propagating high-temperature synthesis(SHS) with a reaction of $xBaO_2+(1-x)ZnO+0.5Fe_2O_3+Fe{\rightarrow}Ba_xZn_{1-x}Fe_2O_4$. In this study, phase indentification of SHS products was carried out by using x-ray diffractometry and quasi-nano sized Ba-Zn powders were prepared by a pulverizing process. SHS mechanism was studied by thermodynamical analysis about oxidation reaction among $BaO_2,\;ZnO,\;Fe_2O_3$, and Fe. As oxygen pressure increases from 0.25 MPa to 1.0 MPa, the SHS reactions occur well and make clearly the SHS products. X-ray analysis shows that final SHS products formed with the ratio of $BaO_2/ZnO$ of 0.25, 1.0 and 4.0, are mainly $Ba_xZn_{1-x}Fe_2O_4$. Based on thermodynamical evaluation, the heat of formation increases in the order of $ZnFe_2O_4,\;BaFe_2O_4$, and $Ba_xZn_{1-x}Fe_2O_4$. This supports that $Ba_xZn_{1-x}Fe_2O_4$ phase is predominately formed during SHS reaction. The SHS reactions to form $Ba_xZn_{1-x}Fe_2O_4$ depends on oxygen partial pressure, and the heat of formation during the SHS reaction. The SHS reactions tends to occur well with increasing the oxygen partial pressure and BaO2/ZnO ratio in the reactants This means that the SHS reaction for the formation of Ba-Zn ferrite includes the reduction of BaO2/ZnO and the oxidation of Fe. $Ba_xZn_{1-x}Fe_2O_4$ powders after pulverizing is agglomeratedwith a size of about $50{\mu}m$, in which quasi-nano sized particles with about 300nm are present.

• Resources Recycling
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• v.26 no.4
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• pp.95-100
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• 2017

In this study, $Fe_2O_3$ was added as a flux to decrease melting temperature and refine during melting of Cu powder from scraped surface of the waste PCB (printed circuit board). The effect of $Fe_2O_3$ ratio to Cu powder and temperature on the recovery of Cu and content of impurities were investigated. It was found that the recovery of Cu was increased with increasing addition ratio of $Fe_2O_3$ and reaction temperature. The contents of O, Si and Fe in Cu phase were also decreased with increasing addition ratio of $Fe_2O_3$ and temperature. The formation of fayalite ($2FeO{\cdot}SiO_2$) and iron oxides phases in the slag was confirmed by XRD analysis after reaction with $Fe_2O_3$. Therefore, it was considered that the decrease of melting temperature and viscosity of slag by formation of fayalite slag contributed remarkably to the Cu recovery.

• Journal of the Korean Ceramic Society
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• v.45 no.3
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• pp.179-184
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• 2008

(40-x)BaO${\cdot}xFe_2O_3{\cdot}60P_2O_5$ glasses with $5{\leq}x{\leq}35mol%$ were investigated by ESR spectroscopy. Two resonances observed near g=2.0 and g=4.3. The line at g=4.3 disappeared with the increase of the $Fe_2O_3$ content. The resonance at $g{\approx}2.0$ displayed characteristic signal consisting of superposed extremely broad and narrow components. The broader one indicates the presence of the association of two or more $Fe^{3+}$ ions, antiferromagnetically and the narrow one is related to the microclusters involving iron ions. Temperature dependence of the ESR integrated intensity revealed short-range antiferromagnetic character for $x{\geq}15mol%$.

• Bulletin of the Korean Chemical Society
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• v.18 no.7
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• pp.743-749
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• 1997

Local structure refinement of the BaFe1-xSnxO3-y system (x=0.00-0.50) has been carried out with Fe K-edge x-ray absorpion spectroscopic studies. It is found out that the Fe ions are placed in two different symmetric sites such as tetrahedral and octahedral sites in the compounds by comparison with Fe K-edge x-ray absorption near edge structure (XANES) spectrum of the γ-Fe2O3 compound as a reference. Small absorption peaks of dipole-forbiden transitions appear at a pre-edge region of 7111 eV due to the existence of Fe ions in the tetrahedral and octahedral sites. The peak intensity decreases with the substitution amount of Sn ion. Three different absorption peaks of 1s→4p dipole-allowed transition appear on the energy region between 7123 and 7131 eV. The peaks correspond to 1s→4p main transition of Fe ions in tetrahedral and octahedral sites and 1s→4p transition followed by the shakedown process of ligand to metal charge transfer. The bond distances between Fe ions in the tetrahedral site and nearest neighboring oxygen atom (Fe-4O), and those in octahedral site (Fe-6O) are determined with the extended x-ray absorption fine structure (EXAFS) analysis. Two different interatomic distances increase with the substitution amount of Sn ion and also the bond lengths of Fe-4O are shorter than those of Fe-6O in all compounds.

• Applied Microscopy
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• v.45 no.3
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• pp.177-182
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• 2015

The boiler tubes of X20CrMoV12.1 used in fossil-fired power plants were obtained and analyzed for the effect of water treatment on the steam corrosion-induced oxide scale in an effort to better understand the oxide formation mechanism, as well as pertinent method of maintenance and lifetime extension. The specimens were analyzed using various microscopy and microanalysis techniques, with focuses on the effect of water treatment on the characters of scale. X-ray diffraction analysis showed that the scales of specimens were composed of hematite ($Fe_2O_3$), magnetite ($Fe_3O_4$), and chromite ($FeCr_2O_4$). Electron backscatter diffraction analysis showed that the oxides were present in the following order on the matrix: outer $Fe_2O_3$, intermediate $Fe_3O_4$, and inner $FeCr_2O_4$. After all volatile treatment or oxygenated treatment, a dense protective $Fe_2O_3$ layer was formed on the $Fe_3O_4$ layer of the specimen, retarding further progression of corrosion.

• Journal of the Korean Magnetics Society
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• v.6 no.4
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• pp.225-234
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• 1996

Needle-like $\alpha-Fe_{2}O_{3}$ particles as precursor for magnetic recording media were prepared directly from amorphous ferric hydroxide in the aqueous solution by hydrothermal reaction. Ellipsoidal or rectangular $\alpha-Fe_{2}O_{3}$ particles were formed in the range of pH 10.75~11.75. The length and acicularity of $\alpha-Fe_{2}O_{3}$ particles were decreased gradually with increasing of citric acid concentration. The formation of needle-like $\alpha-Fe_{2}O_{3}$ particles was inhibited above citric acid concentration of $1.5{\times}10^{-4}\;mol$. We can synthesize $\alpha-Fe_{2}O_{3}$ particles with the most superior acicularity at $140^{\circ}C$ and can not expect a good needle-like particles above $220^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.53 no.4
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• pp.400-405
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• 2016

Ferric oxide (${\alpha}-Fe_2O_3$, hematite) is an n-type semiconductor; due to its narrow band gap ($E_g=2.1eV$), it is a highly attractive and desirable material for use in solar hydrogenation by water oxidation. However, the actual conversion efficiency achieved with $Fe_2O_3$ is considerably lower than the theoretical values because the considerably short diffusion length (2-4 nm) of holes in $Fe_2O_3$ induces excessive charge recombination and low absorption. This is a significant hurdle that must be overcome in order to obtain high solar-to-hydrogen conversion efficiency. In consideration of this, it is thought that elemental doping, which may make it possible to enhance the charge transfer at the interface, will have a marked effect in terms of improving the photoactivities of ${\alpha}-Fe_2O_3$ photoanodes. Herein, we report on the synthesis by pulsed electrodeposition of ${\alpha}-Fe_2O_3$-based anodes; we also report on the resulting photoelectrochemical (PEC) properties. We attempted Ti-doping to enhance the PEC properties of ${\alpha}-Fe_2O_3$ anodes. It is revealed that the photocurrent density of a bare ${\alpha}-Fe_2O_3$ anode can be dramatically changed by controlling the condition of the electrodeposition and the concentration of $TiCl_3$. Under optimum conditions, a modified ${\alpha}-Fe_2O_3$ anode exhibits a maximum photocurrent density of $0.4mA/cm^2$ at 1.23 V vs. reversible hydrogen electrode (RHE) under 1.5 G simulated sunlight illumination; this photocurrent density value is about 3 times greater than that of unmodified ${\alpha}-Fe_2O_3$ anodes.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.06a
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• pp.285-291
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• 2004

As a part of assessment of the structural material for the molten salt handling system, corrosion behavior of Inconel 718, X-750, Haynes 75 and Haynes 263 alloys in the molten salt of LiCl-Li$_2$O-O$_2$was investigated in the range of temperature; $650^{\circ}C$, time; 24~168h, $Li_2O$; 3wt%, mixed gas; Ar~10%$O_2$. In the molten salt of LiCl-$Li_2O-O_2$, the order corrosion rate was Haynes 263 ＜ Haynes 75 ＜ Inconel X-750 ＜ Inconel 718. Haynes 263 alloy showed the highest corrosion resistance among the examined alloys. Corrosion products of alloys were as fellows: Haynes 75: $Cr_2O_4$, $NiFe_2O_4$, $LiNiO_2$, $Li_2NiFe_2O_4$, Inconel 718; $Cr_2O_4$, $NiFe_2O_4$, Haynes 263; $Li(Ni,Co)O_2$, $NiCr_2O_4$, $LiTiO_2$, Inconel X-750; $Cr_2O_3$, $NiFe_2O_4$,$FeNi_3$, (Al,Nb,Ti)$O_2$. Haynes 263 showed local corrosion behavior and Haynes 75, Inconel 718 and Inconel X-750 showed uniform corrosion behavior.