• Korean Journal of Materials Research
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• v.14 no.8
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• pp.547-551
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• 2004

The sulfidation behaviour of Fe-XAl-0.3Y(X=5, 10, 14, 25 $wt.\%$) alloys was investigated at 1123 K in $H_2/H_{2}S$ gas atmosphere for $1\sim24$ hrs using SEM/EDX, XRD and EPMA. The weight changes of Fe-XAl-0.3Y alloys followed the parabolic rate law, Sulfidation rates of iron aluminide alloys with high Al content were one-twentieth lower than that of 5Al alloys. This is due to the formation of protective $Al_{2}O_3$ oxides on the surface of 10Al, 14Al and 25Al alloys. By calculating partial pressure of impurity oxygen contained $H_2/H_{2}S$ gas, the $Al_{2}O_3$ oxides formation could be explained using Fe-Al-S-O thermodynamic stability diagram. The sulfidation product scales of the 5Al alloy showed that thick iron sulfide scale(FeS) containing porosities formed during early stages of sulfidation. With continued sulfidation, aluminum sulfide was formed at the alloy/scale interface.

• Proceedings of the KSEEG Conference
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• 2003.04a
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• pp.3-6
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• 2003

Southwest Hokkaido (Sapporo-Iwanai district) in the Northeast Japan arc (Fig. 1) is one of the best places to test the correlation among tectonic regime, stress field, magmatic style and hydrothermal mineralization. This paper reviews the Miocene to Pleistocene tectonic framework, geology, magmatic style and stress field of southwest Hokkaido, and correlates them with different types of deposits (Kuroko, epithermal base-metal and precious-metal). (omitted)

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.81-81
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• 2003

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.32 no.4
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• pp.411-420
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• 1996

The structure of the scale formed on the surface of Fe - Cr - X alloys exposed to 1143K high sulfidation($Ps_2$ = 1.11$\times$$10^-7$ atm, $Po_2$ = 3.11$\times$$10^-20$ atm) or sulfidation/oxidation(($Ps_2$= 1.06$\times$$10^-7$ atm, ($Po_2$ = 3.11$\times$$10^-18$ atm) environment has been observed and analysed using XRD, SEM/EDS. To investigate the possibility of protective film formed on the surface of the alloys, Aluminium, Nickel were selected as alloying elements. Thermodynamic phase stability diagram was used to predict the reaction path of scale formed on Fe - Cr - X alloys. Parabolic rate constant($K_p$) value with 6wt% Al in Fe - 25Cr alloy decreased significantly compared with the Fe - 25Cr alloy without 6wt% Al. Since thin layer of defect free sulfide film, (Al, Cr)Sx, was formed at the alloy/scale interface. Fe - rich sulfide scale at outer layer and Cr - rich sulfide scale containing porosity at inner layer of Fe - 25Cr alloy have been observed. The reaction path for these scales could be predicted by the thermodynamic stability diagram.

• Journal of the Korean institute of surface engineering
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• v.54 no.2
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• pp.43-52
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• 2021

The Ni-based superalloy, Inconel 740, was corroded between 800 and 1100℃ for up to 100 hr in air and Ar-0.2%SO₂ gas in order to study its corrosion behavior in air and sulfur/oxygen environment. It displayed relatively good corrosion resistance in both environment, because its corrosion was primarily dominated by not sulfidation but oxidation especially in Ar-0.2%SO₂ gas. Such was attributed to the thermodynamic stability of oxides of alloying elements when compared to corresponding sulfides. The scales consisted primarily of Cr₂O₃, together with some NiAl₂O₄, MnCr₂O₄, NiCrMnO₄, and rutile-TiO₂. Sulfur from SO₂ gas made scales prone to spallation, and thicker. It also widened the internal corrosion zone when compared to air. The corrosion resistance of IN740 was mainly indebted to the formation of protective Cr₂O₃-rich oxides, and suppression of the sulfide formation.

• Journal of Energy Engineering
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• v.5 no.2
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• pp.123-130
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• 1996

Reduction, sulfidation, and regeneration reactions were performed using domestic and Australian iron ore in order to develop a desulfurizing sorbent for the high temperature desulfurization process that is one of major processes in the integrated coal gasification combined cycle (IGCC) system. A TGA (Thermogravimetric Analysis) reactor and a fixed-bed reactor were used. Some basic kinetic information was obtained from BET surface area measurements, SEM photos, cyclic reactions, reaction temperature changes and TGA curves of the sorbents. The rates of both desulfurization and regeneration increased with increasing reaction temperature in the range of 500-700$^{\circ}C$.

• Journal of the Korean institute of surface engineering
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• v.52 no.5
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• pp.251-257
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• 2019

Fe-9Cr-2W steels were corroded at $600-800^{\circ}C$ for up to 100 hr in ($Na_2SO_4-K_2SO_4-Fe_2O_3$)-($CO_2-0.3%SO_2-6%O_2$) mixed gas. The poor condition samples formed thick oxide scales that consisted primarily of $Fe_2O_3$ as the major oxide and $Fe_3O_4$, FeO as the minor one through preferential oxidation of Fe. Fe-9Cr-2W steels corroded fast, forming thick and non-protective scale. The scale divided into the outer and inner layer, which consisted of the outer Fe-O layer and the inner (Fe,Cr)-O layer containing some (Fe,Cr)-S.

• Journal of Soil and Groundwater Environment
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• v.28 no.1
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• pp.15-24
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• 2023

A persulfate(PS)/sulfidated microscale zero-valent iron(S-mZVI) system was tested for treating a soil contaminated with phenol. Sulfidation of bare mZVI was conducted using a mechanochemical process utilizing a ball mill in order to improve persulfate activation capacity and stability of unmodified mZVI. The synthesized S-mZVI performed markedly better than the bare mZVI in activating PS. The optimum molar ratio of sulfur to mZVI was around 0.12. In the soil slurry experiments, a very rapid and complete removal of phenol was observed at the optimum molar ratios of PS to S-mZVI of 2:1 and PS to phenol of 16:1. The phenol removal efficiencies decreased as the water content of the slurries decreased. This was believed to be due to increased soil oxidant demand as the amount of soil was increased as relative to the water content. To evaluate the field applicability of the process, slurry experiments adopting high soil contents were carried out that simulated in-situ soil mixing conditions. These experiments resulted in substantially compromised degradation efficiencies of 54.3% and 43.8% within 4 hours. The current study generally shows that the PS/S-mZVI process has a potential to be developed into a remediation technology for soils contaminated with organics.

• Economic and Environmental Geology
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• v.25 no.4
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• pp.397-416
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• 1992

In the present study, three clay deposits, named the Seongsan, Ogmaesan and Haenam deposits, were investigated. The altered zones are recognized in the hydrothermally altered rocks of the clay deposits from the center of the alteration to the margin: Kaolin, Kaolin-Quartz, Quartz, Sericite and Chlorite zones in the Seongsan deposits; Quartz zone, Alunite zone, Kaolin zone, Sericite zone and Chlorite zone in the Ogmaesan deposits; Quartz zone, Pyrophyllite zone, Sericite zone and Chlorite zone in the Haenam deposits. These zones can be grouped into two types of alteration: Acidic alteration such as Pyrophyllite zone, Alunite zone, Quartz zone, Kaolin zone, Kaolin-Quartz zone and a part of Sericite zone; Propylitic alteration such as Chlorite zone and a part of Sericite zone. All clay deposits belong to high-sulfidation (acid-sulfate) system. The rocks of the acidic alterations are composed of pyrophyllite, alunite, kaolin minerals, sericite, quartz and pyrite. On the basis of bulk chemical compositions, it was found that some components such as $SiO_2$, $TiO_2$, $Fe_2O_3$, FeO, MgO, CaO, $K_2O$ and $Na_2O$ were mobilized considerably from the original rocks. The mobility of these major elements is related to, and controls, mineral assemblages in each altered zone. Polytypes of sericite are determined as $2M_1$ and 1M by X-ray diffraction method. The amount of $2M_1$ is nearly equal to that of 1M in the Seongsan deposits whereas $2M_1$ is less and higher than that of 1M in the Ogmaesan and the Haenam deposits. These facts indicate that formation temperature of sericite is relatively high in the Haenam deposits, moderate in the Seongsan deposits, and low in the Ogmaesan deposits. The ratios of Na/(K+Na) for alunite in the Ogmaesan deposits determined by electron microprobe analyzer (EPMA) are higher than those in the Seongsan deposits. Thus, the alunite of the Ogmaesan deposits must have been formed from the solutions with relatively high aqueous Na/(K+Na) ratios and low pH at a high temperature rather than that of the Seongsan deposits. From all data, it is clarified that alunite is hypogene in origin, and has been formed by oxidation of hydrogen sulfide in the steam-heated environment, and that alunite has been produced by the spectacular solfataric alteration observed at the surface of some present-day hydrothermal systems.

• Economic and Environmental Geology
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• v.48 no.4
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• pp.273-285
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• 2015

The extensive hydrothermal deposits have been found, for the first time, on the western TA25 seamount caldera in the Tonga arc. The seafloor hydrothermal vents are active and immature, emitting the transparent fluids of which temperatures range from $150^{\circ}C$ to $242^{\circ}C$ (average=$203^{\circ}C$). The recovered hydrothermal sulfides are mainly composed of sphalerite, pyrite, marcasite, galena, chalcopyrite, covellite, tennantite, enargite and sulfates such as barite, gypsum/anhydrite. Predominant sphalerite categorize it into Zn-rich hydrothermal ore body. Zn-rich sulfide ores have minor enargite, indicating that mineralization occurred in high sulfidation environment. The proportion and FeS content of sphalerite increase from outside to inside of the hydrothermal ores, respectively. In particular, sphalerite has a great silver content (up to ~10 wt.%). Chalcopyrite is more frequently observed in mound than in the chimney, implying mineralization temperature in the mound is higher than in the chimney. Homogenization temperatures and salinities from fluid inclusions in barite at the mound range from $148^{\circ}C$ to $341^{\circ}C$ (average=$213^{\circ}C$) and 0.4 to 3.6 equiv. wt.% NaCl, respectively. Homogenization temperatures suggest that sulfides in the mound mineralized at a higher temperature (${\geq}200^{\circ}C$) than in the chimney.