• Journal of Korea Foundry Society
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• v.40 no.6
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• pp.135-145
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• 2020

Aluminum cast iron has excellent oxidation resistance, sulfurization resistance, and corrosion resistance. However, the ductility at room temperature is insufficient, and at temperatures above 600?, the strength drops sharply and practicality is limited. In the case of heat-resistant cast iron, high-temperature materials containing Cr and Ni account for 30 to 50% or more. However, these high-temperature materials are expensive. Aluminum heat-resistant cast iron is considered as a substitute for expensive heat-resistant materials. Oxidation due to the aging temperature and holding time conditions increases more in 0 wt.% Al-cast iron than in 2 and 4 wt.% Al-cast iron according to oxidized weight and gravimetric oxide layer thickness measurements. As a result of observing the cross-section of the oxide layer, it was found to contain 0 wt.% of Al-cast iron silicon oxide-containing SiO₂ or Fe₂SiO₄ oxide film. In cast iron containing aluminum, the thickness of the internal oxide layer due to aluminum increases as the aging temperature and retention time increase, and the amount of the iron oxide layer generated on the surface decreases.

• Bulletin of the Korean Chemical Society
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• v.30 no.11
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• pp.2577-2583
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• 2009

Presented are the formation of iron oxide layers on evaporator tubes in an actual fossil power plant operated under all volatile treatment (AVT) condition and an experimental simulation of iron oxide formation in the presence of ferrous and ferric ions. After actual operations for 12781 and 36326 hr in the power plant, two iron oxide layers of magnetite on the evaporator tubes were found: a continuous inner layer and a porous outer layer. The experimental simulation (i.e., artificial corrosion in the presence of ferrous and ferric ions at 100 ppm level for 100 hr) reveals that ferrous ions turn the continuous inner oxide layer on tube metal to cracks and pores, while ferric ions facilitate the production of porous outer oxide layer consisting of large crystallites. Based on a comparison of the oxide layers produced in the experimental simulation with those observed on the actually used tubes, we propose possible routes for oxid layer formation schematically. In addition, the limits of the proposed corrosion routes are discussed in detail.

• Korean Journal of Materials Research
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• v.24 no.7
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• pp.363-369
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• 2014

This is the study on diffusion of ceramic body oxide compounds to glaze. For ceramic bodies, no ferrous oxides contain white ware, celadon, and 3 wt% iron oxides contained white ware was used in this experiment. These ceramic bodies were glazed by transparency glaze, iron oxides contained glaze, and glaze made by pine tree ash that treated in 1240 degree, under reduction condition for an hour. An electron probe microanalyzer(EPMA) was used to study diffusion of oxides and to calculate distance of ceramics bodies. As a result, only iron oxide and magnesium oxide from the body diffused to glaze, and also made a band which shown very thin layer of iron oxide and magnesium oxide between the body and glaze. The densest band of iron oxide formed 100 to $150{\mu}m$ in the glaze, and the densest band of magnesium oxide was found 50 to $100{\mu}m$ in the glaze. Therefore, it could be concluded that iron oxide in the body is diffused to the glaze and it affects the color of glaze, even though iron oxide exists in the glaze. Furthermore, the thickness of the glaze has an effect on the color of celadon.

• Particle and aerosol research
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• v.9 no.4
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• pp.209-219
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• 2013

We have used the modified diffusion flame burner to synthesize silica coated iron oxide nanoparticles having enhanced superparamagnetic property. Silica-encapsulated iron oxide particles were directly observed using a high resolution transmission electron microscope. From the energy dispersive X-ray spectroscopy (EDS) and zeta potential measurements, the iron oxide particles were found to be completely covered by a silica coating layer. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) measurements revealed that the iron oxide core consists of ${\gamma}-Fe_2O_3$ rather than ${\alpha}-Fe_2O_3$. Our magnetization measurements support this conclusion. Biocompatibility test of the silica-coated iron oxide nanoparticles is also conducted using the protein adsorption onto the coated particle.

• Tribology and Lubricants
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• v.17 no.6
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• pp.459-466
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• 2001

In this study, the effects of oxide layer formed on the contact parts of TiN coated ball and steel disk on friction characteristics in various sliding conditions were investigated. AISI52100 steel ball was used for the substrate of coated ball specimens, which were prepared by depositing TiN coating with 1(m in coating thickness. AISI1045 steel was used for the disk type counter-body. To investigate the effect of oxide layer on the contact parts of two materials, the tests were performed both in air for forming oxide layer on the contact parts and in nitrogen environment to avoid oxidation. From the test results, the frictional characteristic between the two materials was predominated by iron oxide layer that formed on wear tract of counter-body and this layer caused friction transition and high friction. And the adhesive wear occurred from steel disk to TiN coated ball caused the formation of oxide layer on counter parts between the two materials.

• Journal of Powder Materials
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• v.21 no.6
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• pp.422-428
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• 2014

In this study, the reduction kinetics and behaviors of oxides in the water-atomized iron powder have been evaluated as a function of temperature ranging $850-1000^{\circ}C$ in hydrogen environment, and compared to the reduction behaviors of individual iron oxides including $Fe_2O_3$, $Fe_3O_4$ and FeO. The water-atomized iron powder contained a significant amount of iron oxides, mainly $Fe_3O_4$ and FeO, which were formed as a partially-continuous surface layer and an inner inclusion. During hydrogen reduction, a significant weight loss in the iron powder occurred in the initial stage of 10 min by the reduction of surface oxides, and then further reduction underwent slowly with increasing time. A higher temperature in the hydrogen reduction promoted a high purity of iron powder, but no significant change in the reduction occurred above $950^{\circ}C$. Sequence reduction process by an alternating environment of hydrogen and inert gases effectively removed the oxide scale in the iron powder, which lowered reduction temperature and/or shortened reduction time.

• 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 the Korean institute of surface engineering
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• v.31 no.2
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• pp.101-108
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• 1998

The effect of oxidation-reduction heating conditions on coating adherence of hot-dip galvanized steel containing silicon has beeninvestigated. The presence of a stbke sillicon oxide formed on the steel surface has been shown to be very detrimenal to proper wetting by liquid zinc. When the steel has more than the critical sillicon content neeled to from a stable external oxide, the use of oxidation-reduction method has been found successful in obtaining a good quality, coated product with excellence adhreence. This can be explained by the formation of an iron oxide. The iron oxrtion of the scale is reduced, leaving the stable oxides dispersed in a fresh metallic iron surface layer. This reduced iron surface is easily wetted by the liquid zinc and excellent adherence is obtained.

• Journal of the Korean institute of surface engineering
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• v.33 no.4
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• pp.281-288
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• 2000

To understand the effect of Fe on the oxidation behavior of TiAl alloys, TiAl-(2, 4, 6at% )Fe were oxidized at 800 and 90$0^{\circ}C$ in air. The oxidation resistance of TiAl-Fe alloys increased with increasing an iron content. The scales formed consisted of an outer $TiO_2$ layer, an intermediate $A1_2$$O_3$ layer, and an inner mixed ($TiO_2$+$A1_2$$O_3$) layer, being similar to other common TiAl alloys. But, the scales formed on TiAl-Fe alloys were generally thin compared to those formed on pure TiAl, and contained dissolved iron. Below the oxide scale, an oxygen affected zone was formed. This beneficial effects of Fe on increasing the oxidation resistance and scale adherence of TiAl alloys were attributed to the refinement of oxide grains, increased scale adherence and the enhanced alumina-forming tendency.

• Journal of Korea Foundry Society
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• v.20 no.4
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• pp.240-246
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• 2000

Surface layer properties such as composition, phase, hardness, and oxide layer condition are very important if the main failure mechanism of metals is wear. Generally, stable and dense oxide layers are known to decrease the wear rate of metals by prohibition of metallic junction occurred between bare metals. Addition of Si above 4 wt% to DCI(Ductile Cast Iron) is reported to enhance the significant oxidation resistance by forming the silicon-rich surface layer which inhibits further oxidation. And addition of up to 2 wt% Mo to high Si ductile iron produces significant increases in high temperature tensile strength, creep strength, thermal fatigue resistance and oxidation resistance. High pressure wear characteristics of unalloyed DCI(Ductile cast Iron), 4.46 wt% Si ductile iron, 4.3 wt% Si-0.52 wt% Mo ductile iron were investigated through unlubricated pin-on-disc wear test. Wear test was carried out at speed of 23m/min, under pressure of 3 MPa and 3.3 MPa. Wear surfaces of each specimen were observed by SEM to determine the wear mechanism under high pressure wear condition. Addition of Si 4.46 wt% severely deteriorated wear property of ductile iron compared to unalloyed DCI. But combined addition of Si 4.3 wt%andMo0.52wt%decreasedthefrictioncoefficient(${\mu}$)ofductileironsandremarkablydelayedthemild-severeweartransition.