FeS Layer Research Articles

Metal-organic framework derived FeS/MoS2 composite as a high performance anode for sodium-ion batteries

Abstract Considering the superior performances of MOF-based and MoS2-based materials, a flower-like FeS/MoS2 composite is synthetized using MIL-100(Fe) as a precursor. Electronic density of states and band structure are simulated by density functional theory (DFT) calculations, which prove that FeS/MoS2 heterostructure exhibits metallic behavior. Unique structure and powerful hetero-interface synergistic effect of FeS/MoS2 is conducive to improve the stability of sodium-ion batteries (SIBs). It provides reversible capacities of 464 and 365 mA h g−1 at 0.1 and 1.0 A g−1. When the current density increases to 5 A g−1, FeS/MoS2 delivers a high capacity of 325 mA h g−1 with a capacity retention rate (71.1%). Moreover, it can maintain a stable specific capacity of 331 mA h g−1 at 2.0 A g−1 after 200 cycles. Adsorption energy calculated by DFT indicates that more Na atoms may be trapped on the top of Mo atom between FeS and MoS2 layers. This study may stimulate the interesting of multivariate-MOFs/ covalent organic frameworks (COFs) composite emerging two-dimensional materials and facilitate the application of composite electrode in high-performance SIBs.

Investigation of Corrosion Behavior of Drain Pipes of Process Compressors in Direct Reduction Unit.

Corrosion is a natural process in the destruction of industrial components. Corrosion can be intensified and finally led to destruction where there are temperature increase and microbial agents in addition to the main causes of corrosion. Process compressors were employed in order to meet the gas pressure and flow of the process in the direct reduction unit, and carbon steel pipes were used to separate water from the gas. However, these pipes are punctured and leak water and gas in less time in comparison with the other units. In order to examine the destruction reasons, several samples of the destructed pipe were provided, and they were studied by scanning electron microscopy (SEM) and EDS. The results showed that, besides regular agents like high temperature and acidic medium, microbial corrosion by sulfate-reducing bacteria and H2S gas effect lead to intensifying local and sub-sediment corrosion so that the component will be destructed in less time. The presence of FeS layer will result in severe local corrosion.

Removal of Sb(III) by sulfidated nanoscale zerovalent iron: The mechanism and impact of environmental conditions

Pollution of Sb(III) in water has caused great concern in recent years. Nanoscale zero-valent iron (nZVI) can detoxify Sb(III) polluted water, but the rapid passivation and low adsorption capacity limit its practical application. Hence, this study provides a new and efficient nanotechnology to remove Sb(III) using the sulfidated nanoscale zero-valent iron (S-nZVI). The S-nZVI exhibits higher Sb(III)-removal efficiency than pristine nZVI under both aerobic and anoxic conditions. The adsorption capacity of Sb(III) by optimized S-nZVI (465.1 mg/g) is 6 times as high as that of the pristine nZVI (83.3 mg/g) under aerobic conditions. The results indicate that Sb(III) and Sb(V) can be immobilized on the surface of S-nZVI by forming Fe-S-Sb precipitates. Moreover, characterization results demonstrate that the existence of S2− can not only activate H2O2 to produce hydroxyl radical, but also accelerate the cycle of Fe3+/Fe2+ to improve the efficiency of Fenton reaction. Therefore, S-nZVI can produce more hydroxyl radicals to oxidize Sb (III) to Sb (V) and results in 2.3-fold higher oxidation rate of Sb(III) compared to pristine nZVI. The formed FeS layer on the S-nZVI surface can also improve the release ability of Fe2+ and accelerate the formation of nZVI corrosion products. S-nZVI thus holds great potential to be applied in antimony removal.

No FeS layer in Mercury? Evidence from Ti/Al measured by MESSENGER

In this study we investigate the likeliness of the existence of an iron sulfide layer (FeS matte) at the core-mantle boundary (CMB) of Mercury by comparing new chemical surface data obtained by the X-ray Spectrometer onboard the MESSENGER spacecraft with geochemical models supported by high-pressure experiments under reducing conditions. We present a new data set consisting of 233 Ti/Si measurements, which combined with Al/Si data show that Mercury's surface has a slightly subchondritic Ti/Al ratio of 0.035 ± 0.008. Multiphase equilibria experiments show that at the conditions of Mercury's core formation, Ti is chalcophile but not siderophile, making Ti a useful tracer of sulfide melt formation. We parameterize and use our partitioning data in a model to calculate the relative depletion of Ti in the bulk silicate fraction of Mercury as a function of a putative FeS layer thickness. By comparing the model results and surface elemental data we show that Mercury most likely does not have a FeS layer, and in case it would have one, it would only be a few kilometers thick (<13km). We also show that Mercury's metallic Fe(Si) core cannot contain more than ∼1.5 wt.% sulfur and that the formation of this core under reducing conditions is responsible for the slightly subchondritic Ti/Al ratio of Mercury's surface.

Corrosion of 15Mo3 carbon steel superheater tubes in waste incineration plants: A comparison between a field‐returned tube and laboratory tests

AbstractIn this study, a field‐returned superheater tube of carbon steel 16Mo3 (1.5415) was analyzed in detail. In addition to cross‐section analysis, different scales were investigated layer by layer using microscopic, diffraction, and spectroscopic techniques. The corrosion products can be divided into three layers: The layer adjacent to the metallic tube surface was an iron‐ and chlorine‐rich scale, followed by an FeS layer present at the gas flow side, and the outermost layer was an iron oxide scale consisting of Fe3O4 and α‐Fe2O3. The different mechanisms responsible for the structure of such scale formation and the different corrosion products formed at the tube are discussed. Furthermore, the root cause for the disability to form a protective scale under such conditions was identified by comparison with results from laboratory tests.

Mercury's thermal evolution controlled by an insulating liquid outermost core?

The weak intrinsic magnetic field of Mercury is intimately tied to the structure and cooling history of its metallic core. Recent constraints about the planet's internal structure suggest the presence of a FeS layer overlying a silicon-bearing core. We performed 4-electrode resistivity experiments on core analogues up to 10 GPa and over wide temperature ranges in order to investigate the insulating properties of core materials. Our results show that the FeS layer is liquid and insulating, and that the electrical resistivity of a miscible Fe-Si(-S) core is comparable to the one of an immiscible Fe-S, Fe-Si core. The difference in electrical resistivity between the FeS-rich layer and the underlying Fe-Si(-S) core is at least 1 log unit at pressure and temperature conditions relevant to Mercury's interior. Estimates of the lower bound of thermal conductivity for FeS and Fe-Si(-S) materials are calculated using the Wiedemann-Franz law. A thick (>40 km) FeS-rich shell is expected to maintain high temperatures across the core, and if temperature in this layer departs from an adiabat, then this might affect the core cooling rate. The presence of a liquid and insulating shell is not inconsistent with a thermally stratified core in Mercury and is likely to impact the generation and sustainability of a magnetic field.

Inhibiting the sp2 carbon deposition by adjunction of sulphurous species in refractory ceramics subjected to CO and H2 reducing atmosphere

The formation of sp2 carbon by the Boudouard reaction significantly damages the refractory ceramics. Sulphur is an efficient way to prevent the carbon deposition catalysed by Fe3C, in the presence of H2. Thermogravimetric analysis was carried out on Fe2O3 samples exposed to a CO/H2 gas mixture at 600 °C. Solid sulphur was mixed with Fe2O3 powder or continually added in the form of gas into the CO/H2 reducing gas. The samples were characterised by X-ray diffraction, Raman spectroscopy, SEM and TEM. The addition of 100 ppm of sulphur species in the gas prevents the formation of carbon. The mechanism that governs the inhibition of the reaction is proposed, in which the formation of a thin protective FeS layer (0.5–1 nm) is involved. This study paves the way to an effective solution to inhibit the sp2 carbon deposition in the refractories by poisoning the Fe3C catalyst with sulphur.

Palygorskite-supported sulfide-modified nanoscale zero-valent iron for Congo red removal

ABSTRACTIn this work, the optimum conditions for the synthesis of nano zero valent iron sulfide were studied in detail using orthogonal experiment. The palygorskite-supported sulfide-modified nanoscale zero-valent iron (S-nZVI/P) was prepared, characterized, and further applied to remove Congo red (CR) in aqueous solutions. The results of structural characterization showed that the Fe0 was coated with FeS layers. The influence of sulfidation conditions on the removal rat e of CR was investigated in detail, and the results revealed that S-nZVI/P prepared at 30°C with a Fe/S ratio of 1 was found to effectively remove CR. Moreover, S-nZVI/P showed a significantly enhanced removal rate towards CR as compared with nZVI/P and nZVI, suggesting that sulfidation treatment is a promising method to improve the reactivity of nZVI.

A new intercalated iron sulfide (C2H8N2)0.4Fe2S2 from solvothermal route: Synthesis, structure and tunable magnetism

In this work, a new intercalated FeS compound: (C2H8N2)0.4Fe2S2 was synthesized via the solvothermal route. The product is stable in air and shows the micron-sized plate shape. Structure refinement indicates that (C2H8N2)0.4Fe2S2 adopts the I4/m space group with the lattice constants a=3.6906(6) and c=20.4215(11) Å. The [FeS] layer crystallizes into the anti-fluorite structure with edge-sharing tetrahedrons and the C2H8N2 molecules are inserted in between the layers. (C2H8N2)0.4Fe2S2 is the first intercalated FeS compound reported up to now that contains the electroneutral guest layers. This specific feature leads to the paramagnetic behavior without any magnetic transition in the measured temperature range. Furthermore, we find that the ferromagnetic interaction can also be easily induced in this compound by inserting the extra Fe in between the layers, indicating the controllable magnetism of the title compound. The absence of superconductivity in (C2H8N2)0.4Fe2S2 is mainly due to the external pressure on FeS layers induced by En intercalation.

Top-down freezing in a Fe–FeS core and Ganymede’s present-day magnetic field

Ganymede’s core most likely possesses an active dynamo today, which produces a magnetic field at the surface of ∼ 719 nT. Thermochemical convection triggered by cooling of the core is a feasible power source for the dynamo. Experiments of different research groups indicate low pressure gradients of the melting temperatures for Fe–FeS core alloys at pressures prevailing in Ganymede’s core ( < 10 GPa). This may entail that the core crystallizes from the top instead of from the bottom as is expected for Earth’s core. Depending on the core sulfur concentration being more iron- or more sulfur-rich than the eutectic concentration either snowing iron crystals or a solid FeS layer can form at the top of the core. We investigate whether these two core crystallization scenarios are capable of explaining Ganymede’s present magnetic activity. To do so, we set up a parametrized one-dimensional thermal evolution model. We explore a wide range of parameters by running a large set of Monte Carlo simulations. Both freezing scenarios can explain Ganymede’s present-day magnetic field. Dynamos of iron snow models are rather young ( < 1 Gyr), whereas dynamos below the FeS layer can be both young and much older ( ∼ 3.8 Gyr). Successful models preferably contain less radiogenic heat sources in the mantle than the chondritic abundance and show a correlation between the reference viscosity in the mantle and the initial core sulfur concentration.

Factors influencing degradation of trichloroethylene by sulfide-modified nanoscale zero-valent iron in aqueous solution

Sulfide-modified nanoscale zero-valent iron (S/NZVI) has been considered as an efficient material to degrade trichloroethylene (TCE) in groundwater. However, some critical factors influencing the dechlorination of TCE by S/NZVI have not been investigated clearly. In this study, the effects of Fe/S molar ratio, initial pH, dissolved oxygen and particle aging on TCE dechlorination by S/NZVI (using dithionite as sulfidation reagent) were studied. Besides, the feasibility of reactivation of the aged-NZVI by sulfidation treatment was looked into. The results show that the Fe/S molar ratio and initial pH significantly influenced the TCE dechlorination, and a higher TCE dechlorination was observed at Fe/S molar ratio of ∼60 under alkaline condition. Spectroscopic analyses demonstrate that the enhanced TCE dechlorination was associated with the presence of FeS on the surface of S/NZVI. Dissolved oxygen had little effect on TCE dechlorination by S/NZVI, revealing that the FeS layer could be able to alleviate the surface passivation of NZVI caused by oxidation. Aging of S/NZVI up to 10–20 d only slightly decreased the dechlorination efficiency of TCE. Although an obvious drop in dechorination efficiency was observed for the S/NZVI aged for 30 d, it still exhibited a higher reactivity than the bare NZVI. This indicates that sulfidation of NZVI did prolong its lifetime. Additionally, sulfidation treatment was used to reactivate the aged NZVI, and the results show that the reactivated NZVI even had higher reactivity than the fresh NZVI, suggesting that sulfidation treatment would be a promising method to reactivate the aged NZVI.

Sulfide-modified zerovalent iron for enhanced antimonite sequestration: Characterization, performance, and reaction mechanisms

Zerovalent iron (ZVI) is commonly used for water treatment under aerobic conditions such as sequestration of metals. Sulfide-modified ZVI (S-ZVI) is attracting increasing attention for its easy preparation and high reactivity with environmental pollutants. The processes responsible for contaminant removal can be a complex mixture of redox, sorption, and coprecipitation processes. In this paper, ZVI and S-ZVI were used to sequester antimonite (Sb(III)). The rates of Sb(III) sequestration were determined in open, well-mixed, batch reactors. The effects of various experimental variables were investigated, including pH, iron dose, initial concentrations of Sb(III), aging time of the ZVI and S-ZVI, addition of Fe2+, mixing rate, etc. The results showed that S-ZVI can significantly enhance the Sb(III) sequestration, and under basic conditions in this study, the kobs (0.018 min−1) obtained in the S-ZVI system was approximately 15 times higher than the 0.0012 min−1 obtained in the ZVI system. Solid phase characterizations were conducted to assess the influence of sulfidation on the morphology and surface geochemistry of ZVI. Scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) confirmed the presence of sulfur. X-ray photoelectron spectroscopy (XPS) indicated the oxidation of Sb(III) to Sb(V) and adsorption and coprecipitation onto the iron oxides is the mainly sequestration process. The FeS layer on ZVI is more conductive than oxides and therefore accelerates electron transfer. In addition sulfidation promotes the corrosion of iron and the formation of ferrous iron, which further enhances the ferric iron oxide formation, thereby favoring adsorption and oxidation of Sb(III).

Study of the Corrosive Behavior of the AISI 1020 Steel in Acid Crude Oil by Microscopic Techniques (LM, AFM and SEM/EDX) and Raman Spectroscopy

Microscopic techniques were combined to study the influence of corrosion rate on the morphologic behavior of AISI 1020 steel specimens submitted to thermal degradation of a typical acid crude oil (total acid number (TAN) = 2.1390 mg KOH g-1 and total sulfur (S) = 0.7778 wt.%). The techniques used were light microscopy (LM), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDX), atomic force microscopy (AFM) as well as Raman spectroscopy. Assays were performed in six different degradation time (t = 6, 12, 24, 36, 48 and 72 h) at 320 oC. After the exposure of the specimens to petroleum, a reduction above 37% in the TAN after t = 72 h was observed, with a maximum corrosion rate during the first periods of degradation (t = 6 and 12 h). Correlating the TAN and corrosion rate data with the microscopic data, the images of LM, AFM, and SEM/EDX showed that after 6 h of exposure to petroleum, a passivation film was formed on the surface of the steel. This film consisted of two layers, an external one, formed of FeS, and an internal one, composed of iron oxides and oxyhydroxides. However, after 48 h of thermal degradation, this morphology was altered to a single layer of FeS coating the steel surface.

Syntheses and characterizations of multinuclear, chain and layer silver(I) complexes assembled from bispyridine analogues of pyridinyl-hexahydropyrimidine

Coordination chemistry of pyridinyl-hexahydropyrimidine has not been studied to date, despite that the organic chemistry and coordination chemistry involving rigid bispyridine (bipy), pyrimidine and their derivatives have been widely reported. In this paper, the one-pot reaction of AgX (X = NO3− and ClO4−) with three rigid-flexible bispyridine analogues, 2-(pyridin-n-yl)hexahydropyrimidine [n =4 (L1), 3 (L2), 2 (L3)], lead to the formation of seven complexes, namely, [AgL1(NO3)]n·n(H2O) (1), [AgL1(NO3)]n (2), [Ag6(L1)4(NO3)6]·6(H2O) (3), [AgL1(CH3CN)]n·n(ClO4) (4), [Ag2(L2)2(NO3)(H2O)]n·n(NO3)·n(H2O) (5), [Ag3(L2)3(CH3CN)2]n0.3n(ClO4) (6), and [Ag2(L3)2(NO3)2] (7), which have been characterized by elemental analysis, IR, TG, PL, powder and single-crystal X-ray diffraction. Structural analyses indicate that the conformational transformations of L1-L3 cause diverse structures. In 1 and 2, L1 presents modes I and II which connects adjacent Ag(I) into fes layers. In contrast, modes III and I in 3 and 4 join adjacent Ag(I) into hexanuclear and ladder chain structures. Complexes 5 and 6 show the same ladder chain structures with the L2 displaying the same coordination mode IV. L3 in 7 exhibits tripodal mode V to connect adjacent two Ag(I), thus forming dinuclear unit. Interestingly, adjacent dinuclear units are further joined by intermolecular hydrogen bonds to form kgd layer. Luminescent investigation reveals that 4 and 6 exhibit emissions from 443 to 581nm.

Magnetism at the Interface of Magnetic Oxide and Nonmagnetic Semiconductor Quantum Dots.

Engineering interfaces specifically in quantum dot (QD) heterostructures provide several prospects for developing multifunctional building block materials. Precise control over internal structure by chemical synthesis offers a combination of different properties in QDs and allows us to study their fundamental properties, depending on their structure. Herein, we studied the interface of magnetic/nonmagnetic Fe3O4/CdS QD heterostructures. In this work, we demonstrate the decrease in the size of the magnetic core due to annealing at high temperature by the decrease in saturation magnetization and blocking temperature. Furthermore, surprisingly, in a prominently optically active and magnetically inactive material such as CdS, we observe the presence of substantial exchange bias in spite of the nonmagnetic nature of CdS QDs. The presence of exchange bias was proven by the increase in magnetic anisotropy as well as the presence of exchange bias field (HE) during the field-cooled magnetic measurements. This exchange coupling was eventually traced to the in situ formation of a thin antiferromagnetic FeS layer at the interface. This is verified by the study of Fe local structure using X-ray absorption fine structure spectroscopy, demonstrating the importance of interface engineering in QDs.

Superconductivity and magnetism in iron sulfides intercalated by metal hydroxides.

Inspired by naturally occurring sulfide minerals, we present a new family of iron-based superconductors. A metastable form of FeS known as the mineral mackinawite forms two-dimensional sheets that can be readily intercalated by various cationic guest species. Under hydrothermal conditions using alkali metal hydroxides, we prepare three different cation and metal hydroxide-intercalated FeS phases including (Li1-x Fe x OH)FeS, [(Na1-x Fe x )(OH)2]FeS, and K x Fe2-y S2. Upon successful intercalation of the FeS layer, the superconducting critical temperature Tc of mackinawite is enhanced from 5 K to 8 K for the (Li1-x Fe x OH) δ+ intercalate. Layered heterostructures of [(Na1-x Fe x )(OH)2]FeS resemble the natural mineral tochilinite, which contains an iron square lattice interleaved with a hexagonal hydroxide lattice. Whilst heterostructured [(Na1-x Fe x )(OH)2]FeS displays long-range magnetic ordering near 15 K, K x Fe2-y S2 displays short range antiferromagnetism.

Corrosion of Fe-(9~37) wt. %Cr Alloys at 700–800 °C in (N2, H2O, H2S)-Mixed Gas

Fe-(9, 19, 28, 37) wt. %Cr alloys were corroded at 700 and 800 °C for 70 h under 1 atm of N2, 1 atm of N2/3.2%H2O mixed gas, and 1 atm of N2/3.1%H2O/2.42%H2S mixed gas. In this gas composition order, the corrosion rate of Fe-9Cr alloy rapidly increased. Fe-9Cr alloy was always non-protective. In contrast, Fe-(19, 28, 37) wt. %Cr alloys were protective in N2 and N2/3.2%H2O mixed gas because of the formation of the Cr2O3 layer. They, however, became nonprotective in N2/3.1%H2O/2.42%H2S mixed gas because sulfidation dominated to form the outer FeS layer and the inner Cr2S3 layer containing some FeCr2S4.

Tribological properties of lead-free Cu–FeS composites under dry sliding condition

Abstract

Characterization of Magnetite Scale Formed in Naphthenic Acid Corrosion

Naphthenic acid corrosion (NAC) is one of the major concerns for corrosion engineers in refineries. Iron sulfide (FeS) scales, formed from sulfur compound corrosion, are traditionally considered to be semi-protective and lower NAG However, no relationship has been found between protectiveness and the characteristics of FeS scale. In this study, the corrosive processes of refineries have been probed with laboratory experiments using a model sulfur compound and petroleum-derived naphthenic acids. The morphology and composition of scales were analyzed with a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and convergent beam electron diffraction (CBED). These high resolution microscopy techniques revealed the presence of an iron oxide (Fe3O4 or magnetite) layer on metal surfaces under a FeS layer in the scale. The presence of an oxide scale was correlated with the NAP acid activity during the experiments. It is postulated that the formation of the Fe3O4 layer resulted from the decomposition of iron naphthenates at high temperatures.

Kinetics and Microstructure of Sulfonitriding of Die-Steels

Sulfonitriding is one of the surface treatments of die made of steels for forging and casting. In this surface treatment, annealing under NH3 and H2S containing atmosphere provides the formation of top sulfide layer on the nitrided zone. The surface sulfide zone has anti-seizure and lubrication effects during forging and casting processes. In this study, microstructure development and its kinetics in sulfonitriding of die-steels. Commercial die-steels, JIS-SKT4 and JIS-SKD61, were used. Those steels were annealed under gas-mixture of N2 and H2S at 520°C for 0.5 h and NH3for 2.5 h. Microstructure of the samples was observed by using scanning electron microscopy (SEM) and electron probe micro-analyzer (EPMA). Phase identification of the samples was conducted with X-ray diffraction (XRD). Chemical profile from the surface was obtained by using glow discharge spectroscopy (GDS). A thin continuous layer with 2 -3 μm in thickness was developed on the surface of die-steels. XRD revealed the formation of FeS after sulfonitriding process. The FeS layer was so dense without significant pore network. Results of GDS and EPMA shows that the surface FeS layer include nitrogen and Cr. Inner nitrided zone consisted of mainly Fe3N. Repeating the sulfonitriding process, thickness of the top FeS layer and Fe3N zone increase parabolically. As a result of the marker experiments with Al2O3 particles, top FeS layer was developed by the outward diffusion of Fe and Fe3N zone was grown with inward diffusion of N. Because open pore network in the top FeS layer was not observed, inward diffuses of nitrogen passing through the top FeS layer occurs during sulfonitriding process.