• The Korean Journal of Ceramics
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• v.4 no.2
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• pp.156-161
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• 1998

We have measured changes of the non-stoichiometry, $\Delta\delta$, in Fe-doped nicked oxide , by thermogravimetry for four iron fractions, x=0.01, 0.031, 0.057 and 0.10, and three temperatures, T=1273, 1373 and 1473 K. The obtained data can be modelled by a defect structure in which substitutional trivalent iron ions, FeNi, are compensated by cation vacancies, $V_{Ni}$", and (4:1)-clusters. These clusters consist of tetravalent interstitial iron, $Fe_i\;^4$

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.2
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• pp.77-83
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• 2014

The purpose of this study was to figure out the impacts of iron oxide types and dosages to bloating when producing artificial lightweight aggregates by utilization of recycled resources such as bottom-ash, reject-ash and dredgedsoil. In order to figure out chemical characteristics of raw materials, XRD and XRF analyses were performed. 50 wt% of dredged-soil, 15 wt% of bottom-ash and 35wt.% of reject-ash were mixed, then the amount of iron oxide was varied at 5 to 30 wt% with intervals of 5 wt% with $Fe_2O_3$ and $Fe_3O_4$ respectively. As molded aggregates were sintered by rapid sintering in intervals of $40^{\circ}C$ from $1060^{\circ}C$ to $1180^{\circ}C$, specific gravity and water absorption were measured. As a result, the artificial lightweight aggregate with iron oxide of 10~15 vol% showed the lowest specific gravity, and it was identified that the more iron oxide vol% increases, the more specific gravity increases because of liquid phase sintering.

• Journal of the Korean Society of Safety
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• v.35 no.5
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• pp.128-136
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• 2020

In the present experimental study, the effect of water-based iron(III) oxide nanofluid on the MFB(Minimum Film Boiling) point during quenching was investigated. As the highly heated test specimen, the cylindrical stainless steel rod was used, and as the test fluids, the water-based iron(III) oxide nanofluids of 0.001 and 0.01 vol% concentrations were prepared with the pure water. To examine the effect of location in the test specimen, the thermocouples were installed at the bottom and middle of wall, and center in the test specimen. Through a series of experiments, the experimental data about the influences of nanofluid concentrations, the number of repeated experiments, and locations in the test specimen on the reaching time to MFB point, MFBT(Minimum Film Boiling Temperature), and MHF(Minimum Heat Flux) were obtained. As a result, with increasing the concentration of nanofluid and the number of repeated experiments, the reaching time to MFB point was reduced, but the MFBT and MHF were increased. In addition, it was found that the effect of water-based iron(III) oxide nanofluid on the MFB point at the bottom of wall in the test specimen was observed to be greater than that at the middle of wall and center. In the present experimental ranges, as compared with the pure water, the water-based iron(III) oxide nanofluid showed that the maximum reduction of reaching time to MFB point was about 53.6%, and the maximum enhancements of MFBT and MHF were about 31.1% and 73.4%, respectively.

• Journal of Conservation Science
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• v.36 no.5
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• pp.393-404
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• 2020

We observed changes in the properties of the glaze layer according to the content of iron oxide and inferred the composition, content, and environment of the materials used in the past during the production process of black ware. First, experiments were conducted using different ratios of iron oxide, feldspar, calcite, and ash at different temperatures and firing environments; the characteristics of glaze were classified into five groups in the oxidation environment. Different properties were identified in the reducing environment above 1200℃. The crystal identified in the experiment was similar to the glaze characteristics in the excavated black ware. The crystal phase appeared in four groups: band shape, circular, arborescent phase, and needle crystal, depending on the change in the content of iron oxide. However, the difference in crystals did not appear significantly at high temperatures. In addition, crystals of glaze were divided into two groups depending on the component ratio. The presence or absence of feldspar is thought to affect crystallinity and amorphous iron oxide and the changes in the glaze layer changed substantially depending on the amount of iron oxide. In particular, it was confirmed that the aspects of iron oxide in the oxidation and reduction environments were different and, therefore, crystallization due to the firing environment also affected the optical characteristics.

• Journal of Korea Foundry Society
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• v.10 no.2
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• pp.154-161
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• 1990

The microstructures of sintered products of $Fe_2O_3$or $Fe_3O_4$-Oxide added cast iron powder was investigated. And the effects of particle size distribution was investigated too. As the result, the structures of sintered products did not related to the species of Fe-Oxide. Th porosity of sintered products was decreased in size and spherodized with increasing sintering temperature, decreasing Fe-Oxide quantity. Fe-Oxide itself did not hinder sintering of cast iron powder particularly, therefore sintering could be occurred without termination of reduction of it. And the sintered products of finer particle size distribution had finer and more spherodized porosity, and had minimized the deviation of size and shape of porosity.

• Journal of the Korean institute of surface engineering
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• v.26 no.3
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• pp.109-114
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• 1993

Black magnetite film could be formed on Invar steel for shadows mask by iron electroplating in thickness of 0.46~0.63$\mu\textrm{m}$ on Invar steel and subsequent oxidation of iron by immersion in strongly alkaline soution for 30~60 minutes. blackness degreed of magnetite oxide film on Invar was C20BL90 in comparision of color chart of Dainippon Ink & Chemicals Inc. Co. and adhesion test showed excellent adhesion of oxide film on substrate. Magnetite oxide film grew up on iron in hot strongly alkaline solution according to 'Sato-Cohen' oxide film growth model.

• Korean Journal of Materials Research
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• v.16 no.11
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• pp.687-691
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• 2006

Synthesis of Iron oxides by air oxidation of $FeSO_4$ solutions in the presence of NaOH, Diethylenetriamine (DETA), Butylamine (BA) and influence of ultrasonic wave were investigated by XRD, SEM and particle size analyzer. As the DETA addition increased to 0.05 mol, $Fe_3O_4$ was formed with goethite($\alpha$- FeOOH) and $Fe_3O_4$ single phase was formed above 0.18mol of DETA. As the BA addition increased, the XRD peak intensity of (020) face of lepidocrocite($\gamma$-FeOOH) was developed until the formation of $Fe_3O_4$ and reduced the size of the iron oxide particles formed. Ultrasonic wave reduced the size of the iron oxide particles but gave little effects on the iron oxide particles synthesized by amine.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.3
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• pp.341-349
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• 2010

It is well known that manganese is hard to oxidize under neutral pH condition in the atmosphere while iron can be easily oxidized to insoluble iron oxide. The purpose of this study is to identify removal mechanism of manganese in the D water treatment plant where is treating bank filtered water in aeration and rapid sand filtration. Average concentration of iron and manganese in bank filtered water were 5.9 mg/L and 3.6 mg/L in 2008, respectively. However, their concentration in rapid sand filtrate were only 0.11 mg/L and 0.03 mg/L, respectively. Most of the sand was coated with black colored manganese oxide except surface layer. According to EDX analysis of sand which was collected in different depth of sand filter, the content of i ron in the upper part sand was relatively higher than that in the lower part. while manganese content increased with a depth. The presence of iron and manganese oxidizing bacteria have been identified in sand of rapid sand filtration. It is supposed that these bacteria contributed some to remove iron and manganese in rapid sand filter. In conclusion, manganese has been simultaneously removed by physicochemical reaction and biological reaction. However, it is considered that the former reaction is dominant than the latter. That is, Mn(II) ion is rapidly adsorbed on ${\gamma}$-FeOOH which is intermediate iron oxidant and then adsorbed Mn(II) ion is oxidized to insoluble manganese oxide. In addition, manganese oxidation is accelerated by autocatalytic reaction of manganese oxide. The iron and manganese oxides deposited on the surface of the sand and then are aged with coating sand surface.

• Resources Recycling
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• v.21 no.1
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• pp.75-81
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• 2012

Porous pellets for immobilizing heavy metals were manufactured from coal tailings and iron oxide powder. Coal tailings was pulverized and mixed with iron oxide powder. The mixed powder was granulated into spherical pellets and roasted. Over $1100^{\circ}C$, residual coal in coal tailings reduced iron oxide to ZVI(Zero-Valent Iron). The pellets have 34.63% of porosity, 1.31 g/mL of bulk density, and 9.82.urn median pore diameter. The pellets were reacted with synthetic solutions containing each heavy metals: arsenic(V), copper(II), chrome(VI), and cadmium(II), respectively. On the test of immobilizing heavy metal, the pellets made at $1100^{\circ}C$ were superior to the other pellets made under $1000^{\circ}C$. Immobilizing over 99.9% of 10ppm heavy metal solutions required I hour for arsenic, 2 hours for chrome, and 4 hours for copper. However, immobilizing capacity of cadmium was inferior to that of the other metals and it was decreased in reversely proportion to initial concentration of the solutions.

• Journal of the Korean institute of surface engineering
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• v.25 no.2
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• pp.66-72
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• 1992

Magnetite film on iron surface could be coated in strongly alkaline solution (12M NaH\OH) which contained additives such as NaHCO3, KCl and NaNO2, Iron plate was immersed in boiling solution ($130^{\circ}C$) contained above mentioned additives for 1 hour. There are some microcracks and these cracks proved to be the sites for the initiation of corrosion when immersed in 3% NaCl solution. To improve corrosion resistance of the coated steel plate, chromating was done as a post treatment. Chromate film was formed on magnetite oxide film potentiostatically at-918mV/SCE for five minutes at temperature of $70^{\circ}C$ in the alkaline solution containing 5g/l Na2Cr2O7.2H2O.Cr3O4 was electrodeposited on magnetite oxide film and Cr2O3 was electrodeposited on iron surface which was assumed as surface revealed due to microcracks. Increased corrosion resistance of chromated magnetite oxide film was proved in salt spray test & immersion test.