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1
Pfretzschner, Hans-Ulrich. "Iron oxides in fossil bone". Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 220, n. 3 (11 giugno 2001): 417–29. http://dx.doi.org/10.1127/njgpa/220/2001/417.
Testo completo
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Kim, I. H., W. S. Kim e D. S. Rhee. "Photocatalytic Activity of Fe/Ti Mixed Oxide for Degrading Humic Acid in Water". Advanced Materials Research 717 (luglio 2013): 95–100. http://dx.doi.org/10.4028/www.scientific.net/amr.717.95.
Testo completoAbstract (sommario):
The comparative experiments for removing humic acid as environmental pollutant were conducted by adsorption on iron oxide, photooxidation in the presence of titanium dioxide catalyst and combined adsorption-photooxidation by iron-titanium mixed metal oxides, where all these active components were immobilized on polypropylene granules. The main purpose of the work was the combination of adsorption and photocatalytic oxidation processes to remove humic acid. The granules with iron-titanium mixed oxide for treating humic acid gave much better results with 1.2~3 times higher removal rates comparing to the other two single coated oxides at certain pH values. And the order of removal efficiency according to pH was the same as for single iron oxide-coated granules. The ratio 1:2 of iron oxide/titanium dioxide was found optimal for maximal decolorization of humic acid solution. The total organic carbon decrease of humic acid in each experiments, when it was pre-equilibrated with mixed oxides-coated granules in the dark for 30 min and without pre-equilibration, was very similar. The results suggested that the mechanism of humic acid removal may be not only a respectively combined adsorption and photooxidation by iron oxide and titanium oxides, but an enhanced photooxidation reaction as a result of concentrating humic acid on titanium oxide surface by iron oxide.
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Jeong, D., K. Kim e W. Choi. "Accelerated dissolution of iron oxides in ice". Atmospheric Chemistry and Physics Discussions 12, n. 8 (13 agosto 2012): 20113–34. http://dx.doi.org/10.5194/acpd-12-20113-2012.
Testo completoAbstract (sommario):
Abstract. Iron dissolution from mineral dusts and soil particles is vital as a source of bioavailable iron in various environmental media. In this work, the dissolution of iron oxide particles trapped in ice was investigated as a~new pathway of iron supply. The dissolution experiments were carried out in the absence and presence of various organic complexing ligands under dark condition. In acidic pH conditions (pH 2, 3, and 4), the dissolution of iron oxides was greatly enhanced in the ice phase compared to that in water. The dissolved iron was mainly in the ferric form, which indicates that the dissolution is not a reductive process. The extent of dissolved iron was greatly affected by the kind of organic complexing ligands and the type of iron oxides. The iron dissolution was most pronounced with high surface area iron oxides and in the presence of strong iron binding ligands. The enhanced dissolution of iron oxides in ice is mainly ascribed to the "freeze concentration effect", which concentrates iron oxide particles, organic ligands, and protons in the liquid-like ice grain boundary region and accelerates the dissolution of iron oxides. The ice-enhanced dissolution effect gradually decreased when decreasing the freezing temperature from −10 °C to −196 °C, which implies that the presence and formation of the liquid-like ice grain boundary region play a critical role. The proposed phenomenon of enhanced dissolution of iron oxides in ice may provide a new pathway of bioavailable iron production. The frozen atmospheric ice with iron-containing dust particles in the upper atmosphere thaws upon descending and may provide bioavailable iron upon deposition onto the ocean surface.
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Jeong, D., K. Kim e W. Choi. "Accelerated dissolution of iron oxides in ice". Atmospheric Chemistry and Physics 12, n. 22 (23 novembre 2012): 11125–33. http://dx.doi.org/10.5194/acp-12-11125-2012.
Testo completoAbstract (sommario):
Abstract. Iron dissolution from mineral dusts and soil particles is vital as a source of bioavailable iron in various environmental media. In this work, the dissolution of iron oxide particles trapped in ice was investigated as a new pathway of iron supply. The dissolution experiments were carried out in the absence and presence of various organic complexing ligands under dark condition. In acidic pH conditions (pH 2, 3, and 4), the dissolution of iron oxides was greatly enhanced in the ice phase compared to that in water. The dissolved iron was mainly in the ferric form, which indicates that the dissolution is not a reductive process. The extent of dissolved iron was greatly affected by the kind of organic complexing ligands and the surface area of iron oxides. The iron dissolution was most pronounced with high surface area iron oxides and in the presence of strong iron binding ligands. The enhanced dissolution of iron oxides in ice is mainly ascribed to the "freeze concentration effect", which concentrates iron oxide particles, organic ligands, and protons in the liquid like ice grain boundary region and accelerates the dissolution of iron oxides. The ice-enhanced dissolution effect gradually decreased when decreasing the freezing temperature from −10 to −196 °C, which implies that the presence and formation of the liquid-like ice grain boundary region play a critical role. The proposed phenomenon of enhanced dissolution of iron oxides in ice may provide a new pathway of bioavailable iron production. The frozen atmospheric ice with iron-containing dust particles in the upper atmosphere thaws upon descending and may provide bioavailable iron upon deposition onto the ocean surface.
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BRUCHAJZER, ELŻBIETA, BARBARA FRYDRYCH e JADWIGA SZYMAŃSKA. "Iron oxides – calculated on Fe Documentation of proposed values of occupational exposure limits (OELs)". Podstawy i Metody Oceny Środowiska Pracy 33, n. 2(92) (29 giugno 2017): 51–87. http://dx.doi.org/10.5604/01.3001.0009.9360.
Testo completoAbstract (sommario):
Iron (III) oxide, (Fe2O3, nr CAS 1309-37-1) in natural conditions occurs as iron ore. The most common (hematite) contains about 70% pure iron. Iron (III) oxide is used as a red dye in ceramics, glass and paper industries and as a raw material for abrasive metalworking (cutting). Iron (II) oxide, (FeO, CAS 1345-25-1) occurs as a mineral wurtzite and is used as a black dye in cosmetics and as a component of tattoo ink. Iron (II) iron (III) oxide (Fe3O4, CAS 1309-38-2; 1317- -61-9) is a common mineral. It has strong magnetic properties (so called magnetite). It occurs in igneous rocks (gabbro, basalt). It is the richest and the best iron ore for industry. Occupational exposure to iron oxides occurs in the mining and metallurgical industry in the production of iron, steel and its products. Welders, locksmiths, lathes and workers employed in milling ores and polishing silver are exposed to iron oxides. According to data from the State Sanitary Inspection, in 2013, 389 people in Poland were exposed to iron oxide in concentrations exceeding the current NDS (5 mg/m3) and in 2014 – 172 people. After single and multiple intratracheal and inhalation exposure of animals, transient intensification of oxidative stress and inflammatory reactions were reported. Iron (III) oxide did not cause genotoxic and carcinogenic effects. In literature, there are no data on its effects on fertility, reproduction and pregnancy. Data on chronic toxicity of iron oxides for humans exposed in working environment are limited. In epidemiological studies, all information presented in the documentation comes from observations of people exposed to the combined effects of iron oxides and other factors. It is not stated whether occupational exposure was related to the specific iron oxide and to what concentrations workers were exposed. The most commonly encountered toxic effect in the occupational exposure of iron ore miners and iron welders and welders was minor lung fibrosis lesions and iron-silicon dust (as seen in the RTG study). Siderose is the occupational disease of miners and iron ore metallurgists. Moreover, cases of lung cancer have been reported in miners, steel workers and welders, but they were caused by total exposure to other compounds, including radioactive radon, carcinogenic chromium, manganese, nickel, other oxides (SiO2, ZnO, CO, NO, NO2, MgO) as well as exhaust gases from diesel engines. According to IARC, iron (III) oxide belongs to group 3 (cannot be classified as carcinogenic to humans). Iron (III) oxides can accumulate in a lung tissue, this process may be responsible for the occurrence of fibrosis sites, particularly in higher parts of external lung parts. These effects were visible in the X-ray examination only. Pneumoconiosis (siderosis) caused by exposure to iron oxides is usually asymptomatic (lack of clinical symptoms and changes in lung function parameters). The basis for the proposed MAC-TWA value for inhalable iron oxide fraction was NOAEL of 10 mg Fe/m3. People exposed for more than 10 years to iron (III) oxide had no pulmonary changes. After application of an uncertainty factor of 2 (for differences in personal sensitivity in humans), the MAC-TWA value for the iron oxide fraction was proposed at 5 mg/m3 (calculated as Fe). The same observations on humans were the basis for calculating the MAC-TWA value for respirable fraction of iron (III) oxide. On 12% of workers exposed to respirable fraction at mean concentrations of 10 ÷ 15 mg/m3, changes in pulmonary X-ray were observed. The value of 10 mg/m3 was assumed as LOAEL. After applying the appropriate uncertainty coefficients, the MAC-TWA value for the iron oxide respirable fraction was proposed at 2.5 mg/m3. The authors propose to leave the short-term value (STEL) of 10 mg/m3 for inhaled fraction for iron oxides and to introduce STEL value of 5 mg/m3 for respirable fraction. It is recommended to label the substances with "I" - irritant substance.
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Plemiannikov, Mykola, e Nataliіa Zhdanіuk. "Determination of the influence of temperature, concentration of ferric oxides and oxidative conditions of glass boiling on the displacement of the equilibrium of ferric oxides Fе2O3↔FеO". Technology audit and production reserves 3, n. 1(71) (29 giugno 2023): 10–14. http://dx.doi.org/10.15587/2706-5448.2023.283267.
Testo completoAbstract (sommario):
The object of research is the state of equilibrium of ferrum(II) and ferrum(III) oxides in glass melts at temperatures of 1000–1400 °С, welded in oxidizing, neutral and reducing conditions with a content of ferrum oxides up to 1.5 %. This problem is relevant in the following aspects. The first aspect of this problem is the unwanted coloring of the glass: FeO colors the glass blue, and Fe2O3 – yellow. The combined presence of ferrum(II) oxide and ferrum(III) oxide determines the gradations of glass shades that fall on the green spectrum. The second aspect concerns the thermophysics of processes of boiling glasses containing iron oxides. Ferrum(II) oxide causes a strong absorption band of infrared radiation in the region of 1.1 μm. This becomes an obstacle to the volumetric heating of glass in the processes of cooking, forming, and annealing. The third aspect of the problem concerns the structure of glasses and glass-crystalline materials with an increased content of iron oxides. Iron oxides significantly affect the processes of glass structuring, as ferrum(III) oxide is a typical network former, and ferrum(II) oxide is a typical modifier. The state of FeO↔Fe2O3 equilibrium in glass is significantly influenced by the glass cooking environment, the total amount of iron oxides, and the temperature of the melt. The glass brewing environment has the greatest influence on the balance of iron oxides in the glass. The share of FeO oxide in the total amount of iron oxides (FeO+Fe2O3) increases sharply when moving from an oxidizing medium to a neutral one and then to a reducing one. During thermostating at a temperature of 1400 °С, the proportion of FeO in the glass increases by 1.4–1.7 times during cooking in an oxidizing environment, by 1.2–1.3 times in a neutral environment, and by approximately 1.1 times in a reducing environment. At the same time, this growth is more noticeable in glasses with a lower iron content. Thus, the equilibrium state of FeO↔Fe2O3 in glass significantly affects the technological and operational properties of silicate melts and the final glass. The ratio of formed oxides of trivalent and divalent ferrum was studied by chemical (titrometric) analysis. The research results can be used in practice to develop the composition of glasses with an increased content of iron oxides.
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Zhang, Lin, Di Lun Sheng, Rui Zhang, En Yi Chu, Ju Peng Liu e Sheng Li Zhou. "Preparation of Self-Assembled Iron Oxide Nanorings with Nano-Aluminum". Applied Mechanics and Materials 446-447 (novembre 2013): 210–13. http://dx.doi.org/10.4028/www.scientific.net/amm.446-447.210.
Testo completoAbstract (sommario):
To make fuels and oxides react better, Iron oxide nanoring was synthesized using hydrothermal method and then self-assembled with nano aluminum particles. Iron oxide were characterized by hollow column morphology with outer diameters of 200-240nm, inner diameters of 90-120nm and heights of 120-150nm using SEM and TEM. Iron oxide and aluminum were evenly distributed and contact closely by self-assembly.The touch of fuels and oxides increased effectively.While the ultrasonically-mixed sample scattered randomly and aggregated seriously. Self-assembly is proved to be a effective method for the touch and distribution of oxides and fuels.
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Zhu, Yi. "The influence of iron oxides on wheel–rail contact: A literature review". Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit 232, n. 3 (11 gennaio 2017): 734–43. http://dx.doi.org/10.1177/0954409716689187.
Testo completoAbstract (sommario):
In contrast to other third-body layers – such as water, oil, sand, and leaves – iron oxides exert a constant influence on the friction and wear of wheel–rail contact. However, studies that focus on the influence of iron oxides have not been conducted systematically until the 21st century. This study is a comprehensive presentation of early and recent research works related to the influence of iron oxides on the wheel–rail contact. The characteristics of iron oxides in general and those between railway wheels and rails are discussed. A comparison of various laboratory tests and their relation to actual conditions is also presented. The authors find that the influence of various types of iron oxides on friction and adhesion differs. The thickness of the iron oxide layer also affects the friction and wear. However, the results obtained from laboratory rigs differ from those obtained in field testing. Therefore, it is critical to formulate a standard procedure that produces iron oxides that are similar to those observed in the field. Compared to the case of wheel–rail friction and adhesion, the influence of iron oxides on wear is not so well investigated. Thus, further research in those areas is warranted.
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Al-Hamawandi, M. J., D. R. Azeez e D. K. Ali. "Behavior and Distribution of Free Iron Oxides in Some Soil Orders in Iraq". IOP Conference Series: Earth and Environmental Science 1252, n. 1 (1 dicembre 2023): 012067. http://dx.doi.org/10.1088/1755-1315/1252/1/012067.
Testo completoAbstract (sommario):
Abstract This study was conducted to investigating the behavior of free iron oxides in some soil orders in Iraq. Soil samples were collected from five Pedons for soil orders Entisols, Aridisols, Inceptisols, Vertisols and Mollisols. Total free iron oxides (Fed) were extracted by CBD, amorphous iron oxides by acid ammonium oxalate and iron oxide linked with organic matter by alkaline Sodium pyrophosphate. the distribution of iron oxides in (Fep) to crystallized iron oxides were compared. The results showed that (Fed-Feo) there is no particular direction that controls the vertical distribution of Fed Mollisols and Vertisols pedons excelled in the content of Fed compared to the other orders. Amorphous Feo accumulates in surface horizons and Mollisols pedon was excelled on all pedons in Feo content followed by Vertisols, Inceptisols, Aridisols and Entisols. The Pedons of Inceptisols, Aridisols and Entisols soil order contain higher amounts of crystalline Fed-O oxides compared to the Mollisols and Vertisols as well the vertical distribution taken a different pattern for all pedons. (Fep) was low compared to other forms of iron oxides and is accumulated in surface soil horizon in all pedons.
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Moro, Koua, Aimé Serge Ello, Konan Roger Koffi e N’goran Séverin Eroi. "Mixed Maghemite/Hematite Iron Oxide Nanoparticles Synthesis for Lead and Arsenic Removal from Aqueous Solution". Journal of Nanomaterials 2023 (26 aprile 2023): 1–8. http://dx.doi.org/10.1155/2023/8216889.
Testo completoAbstract (sommario):
This work focused on the synthesis of iron oxide nanoparticles by the coprecipitation method with three basic solutions, namely, NH4OH, KOH, and NaOH. The synthesized iron oxides were characterized by various techniques such as XRD, MET, BET, and a SQUID magnetometer. The results showed nanosized particles of 13.2, 9.17, and 8.42 nm and different phases associated to maghemite and maghemite/hematite. The surface areas were 113, 94, and 84 m2/g and the magnetization strength were 58, 61, and 75 emu/g to iron oxides synthesized with NaOH, KOH, and NH4OH, respectively. The magnetic iron oxides obtained using NaOH were more efficient in the removal of lead and arsenic by adsorption than iron oxides obtained with KOH and NH4OH. However, the magnetic strength decreases using NaOH and KOH. The highest adsorption capacities attained for lead and arsenic removal were 16.6 and 14 mg/g, respectively, using NaOH-based iron oxides.
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Nurhadi, Mukhamad, Ratna Kusumawardani, Teguh Wirawan, Sin Yuan Lai e Hadi Nur. "Synergistic Ti-Fe Oxides on Fishbone-Derived Carbon Sulfonate: Enhanced Styrene Oxidation Catalysis". Indonesian Journal of Chemistry 23, n. 6 (6 dicembre 2023): 1514. http://dx.doi.org/10.22146/ijc.80667.
Testo completoAbstract (sommario):
Fishbone-derived carbon sulfonate, modified through incipient wetness impregnation with titanium tetraisopropoxide and iron nitrate salts, displays catalytic activity in the oxidation of styrene with hydrogen peroxide (H2O2) as an oxidant. This was done to develop a cost-effective, non-toxic, and environmentally friendly bimetallic oxide catalyst, incorporating titanium and iron oxides on mesoporous-derived carbon fishbone to enhance styrene conversion and benzaldehyde selectivity in styrene oxidation using aqueous H2O2. The catalyst, featuring a combination of titanium and iron oxides on the surface of the fishbone-derived carbon sulfonate, demonstrates higher catalytic activity than single oxide catalysts, such as titanium or iron oxides alone. Factors influencing the catalyst's performance are investigated by using FTIR, XRD, XRF, SEM, and BET surface area. The results reveal that the presence of both titanium and iron oxides on the surface of the fishbone-derived carbon sulfonate and the catalyst's surface area creates a synergistic effect, the primary factors affecting its catalytic activity in styrene oxidation using H2O2 as an oxidant.
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Howitt, Julia A., Darren S. Baldwin, Gavin N. Rees e Barry T. Hart. "Facilitated Heterogeneous Photodegradation of Dissolved Organic Matter by Particulate Iron". Environmental Chemistry 1, n. 3 (2004): 197. http://dx.doi.org/10.1071/en04005.
Testo completoAbstract (sommario):
Environmental Context. Iron oxides, as suspended minerals or as a colloidal phase, are common in Australian freshwater systems. Freshwater systems are also loaded with carbon-based substances, ‘dissolved organic matter’, but not all is biologically available as food to freshwater organisms. However, photochemical interactions between these iron oxides and dissolved organic matter provide a mechanism for biologically resistant carbon to re-enter the food web. Suspended iron oxides thus need to be considered in carbon cycles in aquatic ecosystems. Abstract. The photochemical degradation of dissolved organic matter (DOM) derived from the leaves of River Red Gum (Eucalyptus camaldulensis) was examined, with a particular focus on the photochemical generation of CO2, consumption of O2, and the effect of particulate iron minerals on these photochemical reactions. Solutions of leaf leachate were irradiated with ultraviolet and visible light in the presence and absence of amorphous iron oxides. Addition of fresh iron oxide was found to increase the rate of photodegradation of the organic matter by up to an order of magnitude compared to the reactions without added iron oxide. The ratio of CO2 produced to O2 consumed was ~1:1 in both the presence and absence of iron oxyhydroxide. The reactivity of the iron oxides was dependent on the preparation method and decreased with increased storage time. These results suggest that photochemical reactions on particle surfaces should be considered when examining carbon transformation in aquatic ecosystems, especially at sites with potential for the production of iron oxyhydroxides.
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Szpunar, Jerzy A., e Bae Kyun Kim. "High Temperature Oxidation of Steel; New Description of Structure and Properties of Oxide". Materials Science Forum 539-543 (marzo 2007): 223–27. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.223.
Testo completoAbstract (sommario):
The quality of steel sheets is strongly affected by the surface defects that can be generated during hot rolling and are often related to scales removal operation. These defects are related to rather complex high temperature oxidation processes. In order to reduce an occurrence of the defects, it is necessary to understand better the formation of iron oxides during high temperature oxidation, the structure of the interfaces with the substrate and between different oxide phases. However, due to the lack of good experimental research tools details of iron oxide microstructures were not investigated. Conventional methods, such as backscattered electron images or fractography can only provide general characteristics of microstructures like grain morphology and grain size. In this paper the microstructure, phase distribution and texture in oxide formed during high temperature oxidation of iron and low carbon steels are investigated. The oxide microstructures are characterized by orientation imaging microscopy (OIM) on the cross-sectional area of the oxide layers. It is demonstrated that OIM using electron backscattered diffraction (EBSD) techniques, can be used to distinguish grains having different phase composition and orientation and can become invaluable tool for visualizing the oxide microstructure, texture and also can be used to study oxide defects. The three different iron oxides phases can be distinguished and the characteristics of oxides with different oxidation histories compared The characteristics of high temperature oxidation microstructure of iron are presented with description of iron oxide defects and cracking as well as the illustration of the interfacial microstructure between the layered iron oxides.
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Ma, Chuan Guo, Hai Jun Zheng, Xiao Ming Li e Liang Gao. "Preparation and Microwave Absorbing Properties of Iron Oxides/Carbon Nanotubes Compounds". Advanced Materials Research 548 (luglio 2012): 133–37. http://dx.doi.org/10.4028/www.scientific.net/amr.548.133.
Testo completoAbstract (sommario):
A Series of iron oxides/CNTs compounds were prepared using a method of impregnation with iron nitrate solution and followed thermal decomposition. The compounds were characterized by the means of scanning electronic microscope, X-ray diffraction and thermogravimetic analysis. The dielectric and microwave-absorbing properties of EP composites containing the different compounds were further measured in a specific frequency range. The results show that: CNTs show reduction at a high temperature, and can make products of the thermal decomposition of iron nitrate produce iron oxide nanoparticles with different valence states at different temperatures. With increasing decomposition temperature, the iron oxides in CNTs composites in turn are Fe2O3, Fe3O4, FeO and Fe. Compared with pure CNTs, these iron oxides/CNTs composites have better microwave absorbing properties in the wavebands of 7.5GHz ~ 15GHz and 26.5GHz ~ 40GHz. Among those iron oxides /CNTs compounds, Fe3O4/CNTs compound has the best microwave absorbing property.
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Kupková, M., M. Kupka, R. Oriňaková e R. Gorejová. "Corrosion characteristics of sintered heterogeneous materials composed of iron and iron oxides". Koroze a ochrana materialu 64, n. 3 (1 ottobre 2020): 72–78. http://dx.doi.org/10.2478/kom-2020-0011.
Testo completoAbstract (sommario):
Abstract In a coronary angioplasty or orthopaedic surgery, metallic implants are often used to provide mechanical support to the healing tissues. In some situations, this support is really needed only temporarily. After tissue recovery, the implant no longer provides any benefits and can trigger adverse reactions. An optimal solution might be the short-term implants which are able to decompose in situ and can be readily excreted from the body. Iron-based materials are promising candidates for application in biodegradable devices. For the successful application, the ability to control the material’s corrosion rate is important. In this contribution, the corrosion of iron-iron oxide composites is investigated. In order to obtain such materials, iron-oxide granules were incompletely reduced, compacted and sintered. Materials consisting of a pure iron and iron oxides were obtained. Specimens from as-sintered materials and materials reduced once again after sintering were prepared. Potentiodynamic polarization testing in Hanks’ solution indicated that specimens underwent a galvanic corrosion, where the release of ferrous ions from iron surfaces represents the anodic reaction and the oxygen reduction on surfaces of both iron and iron oxides represents the cathodic reaction. Changes in the content of oxides resulted in anticipated shifts in corrosion potential and apparent corrosion current density.
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Latta, Drew E., Christopher A. Gorski e Michelle M. Scherer. "Influence of Fe2+-catalysed iron oxide recrystallization on metal cycling". Biochemical Society Transactions 40, n. 6 (21 novembre 2012): 1191–97. http://dx.doi.org/10.1042/bst20120161.
Testo completoAbstract (sommario):
Recent work has indicated that iron (oxyhydr-)oxides are capable of structurally incorporating and releasing metals and nutrients as a result of Fe2+-induced iron oxide recrystallization. In the present paper, we briefly review the current literature examining the mechanisms by which iron oxides recrystallize and summarize how recrystallization affects metal incorporation and release. We also provide new experimental evidence for the Fe2+-induced release of structural manganese from manganese-doped goethite. Currently, the exact mechanism(s) for Fe2+-induced recrystallization remain elusive, although they are likely to be both oxide-and metal-dependent. We conclude by discussing some future research directions for Fe2+-catalysed iron oxide recrystallization.
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Liu, Ming Da, Feng Jiang, Hui Sun, Dan Yang, Yu Long Zhang e Yao Jing Wang. "Effect of Silicon on Phosphorus Adsorption of Two Synthetic Iron Oxides". Advanced Materials Research 726-731 (agosto 2013): 325–30. http://dx.doi.org/10.4028/www.scientific.net/amr.726-731.325.
Testo completoAbstract (sommario):
Iron oxides play an important role in controlling P activity and availability in environmental systems. Two iron oxides (goethite and ferrihydrite) were synthesized characterized by X-ray diffraction, transmission electron microscopy and N2 adsorption method. To investigate the effect of silicon on phosphorus adsorption of them, batch equilibration method was used. Attempts were made to explore the mechanisms involved by eliminating effects of pH and accompany ions. Results reveal that the ability of two kinds of iron oxides adsorbed phosphorus were as follows: ferrihydrite > goethite. Compared with the control, silicon inhibited the adsorption of phosphorus on two iron oxides, and this effect increased with the increasing of silicon content. Langmuir, Freundlich and Temkin equations could be used to describe the adsorption characteristics of phosphorus on iron oxides well, but the Langmuir model was optimal. With silicon addition, the adsorption equilibrium constants (K) decreased of the phosphorus absorbed on iron oxide, the free energy(ΔG)dropping degree increased, the maximum adsorption capacity(Xm)and maximum buffering capacity (MBC) reduced.
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Kupková, Miriam, Martin Kupka, Renáta Oriňáková e Radka Gorejová. "Microstructure, Stiffness and Corrosion of Bare and Phosphated Specimens Made by Sintering of Structured Iron-Iron Oxide Spheres". Defect and Diffusion Forum 405 (novembre 2020): 411–16. http://dx.doi.org/10.4028/www.scientific.net/ddf.405.411.
Testo completoAbstract (sommario):
Granulated iron oxide particles were incompletely reduced to structured particles comprised metallic iron and residual iron oxides. Structured particles were pressed into prismatic compacts and sintered. Some of sintered specimens were subsequently phosphatized and calcined. Specimens with an iron phosphate coating were found stiffer than specimens without coating. In Hanks' solution, a galvanic corrosion was induced by more noble iron oxides coupled to a less noble metallic iron. This could explain higher corrosion potentials and higher rates of iron dissolution in comparison with a pure iron. The coating of specimens with iron phosphates shifted corrosion potentials towards more negative values and slowed down the dissolution of iron. This was most likely caused by a reduction in oxygen flow through the coating to iron-oxide cathodes, which has enhanced the influence of diffusion control on the kinetics of reduction reaction.
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AWAD, Hamdy Ahmed Mohamed, e Aleksey Valer’evich NASTAVKIN. "Mineralogical and geochemical studies of gabbroids in the East Central Desert, Egypt". NEWS of the Ural State Mining University 59, n. 3 (15 settembre 2020): 41–51. http://dx.doi.org/10.21440/2307-2091-2020-3-41-51.
Testo completoAbstract (sommario):
Relevance of the work. The study area is limited to the Central-Eastern Desert of Egypt, represented by various rock units in addition to the gabbro rock containing iron oxides. Research Objective. This work is devoted to detailed studies of the geology of gabbroid rock minerals and iron oxides. Methodology. This work includes both field work (creation of a new geological map for various rock units in the study area) and laboratory work (preparation of thin sections for petrographic and mineralogical studies using a polarizing microscope and a scanning electron microscope SEM). Results and their application. Exploration and extraction of ore deposits and minerals in the eastern desert of Egypt is one of the most important goals for increasing the rate of mining in the country, which leads to economic recovery and meeting the needs of society. Previous work has focused on evaluating and studying economically mineral resources in the Central-Eastern Desert of Egypt. This place is considered one of the most promising mineral deposits in addition to the available iron oxide minerals. Geological studies show that the mineralization of iron oxide in the study area is mainly associated with gabbroid rocks, which carry iron oxide minerals in the form of groups and lenses in the lower part of the Earth’s layers, which is associated with magma rich in iron oxides. According to field studies, we found that iron minerals are represented by lenses up to 3 m thick, alternating with rock. Conclusions. The chemical analysis of minerals based on iron oxides was discovered using a scanning electron microscope (SEM) used to determine the chemical composition of these minerals, which are classified as minerals such as ilmenite and magnetite. Actually geochemical studies have shown that they have a high content of total iron oxides.
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Li, Ningjie, Jieyu Yu, Xiaojie Wang, Liu Chen, Hong Jiang e Wenjie Zhang. "Growth, Oxidative Stress and Ability to Degrade Tetrabromobisphenol A of Phanerochaete chrysosporium in the Presence of Different Nano Iron Oxides". Water 16, n. 4 (14 febbraio 2024): 567. http://dx.doi.org/10.3390/w16040567.
Testo completoAbstract (sommario):
In order to improve the performance of white rot fungi, especially the model species Phanerochaete chrysosporium in tetrabromobisphenol A (TBBPA) degradation, the strategy of synergizing Phanerochaete chrysosporium with nano iron oxides was considered; however, the effects of different nano iron oxides on Phanerochaete chrysosporium are still unknown. In this study, 20 nm γ-Fe2O3, 30 nm α-Fe2O3, 20 nm Fe3O4, and 200 nm Fe3O4 were used, and the fungal growth, oxidative stress, and ability to degrade TBBPA were monitored. The results showed that the addition of four nano iron oxides did not inhibit the growth of Phanerochaete chrysosporium. The effective antioxidant defense system of Phanerochaete chrysosporium could cope with almost all oxidative pressure induced by 200 nm Fe3O4. But when the size of nano iron oxide became significantly smaller or when the type of iron oxide changed from Fe3O4 to Fe2O3, a higher intracellular hydrogen peroxide (H2O2) content, lower intracellular superoxide dismutase (SOD) and catalase (CAT) activities and higher extracellular lactate dehydrogenase (LDH) activity were induced. When nano iron oxides synergized with Phanerochaete chrysosporium, the removal of TBBPA in all groups was slightly improved and mostly due to the degradation of TBBPA, with smaller iron oxides showing more enhancement for the degradation of TBBPA, while 200 nm Fe3O4 only enhanced the adsorption of TBBPA. The enhanced degradation of TBBPA showed no significant correlation with lignin-degrading enzyme activities but was closely correlated with the intracellular H2O2 concentration.
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Van Dam, Remke L., Wolfgang Schlager, Mark J. Dekkers e Johan A. Huisman. "Iron oxides as a cause of GPR reflections". GEOPHYSICS 67, n. 2 (marzo 2002): 536–45. http://dx.doi.org/10.1190/1.1468614.
Testo completoAbstract (sommario):
Iron oxides frequently occur as secondary precipitates in both modern and ancient sediments and may form bands or irregular patterns. We show from time-domain reflectometry (TDR) field studies that goethite iron-oxide precipitates significantly lower the electromagnetic wave velocity of sediments. Measured variations in magnetic permeability do not explain this decrease. The TDR measurements and a dielectric mixing model also show that neither electrical conductivity nor relative permittivity of the solid material are altered significantly by the iron-oxide material. From drying during all of the measurements, the amount of iron oxides appears to correlate with the volumetric water content, which is the result of differences in water retention capacity between goethite and quartz. These variations in water content control relative permittivity and explain the observed variation in electromagnetic wave velocity. Using 2-D synthetic radar sections, we show that the pattern of iron-oxide precipitation may have a profound influence on the GPR reflection configuration and can cause major difficulties in interpretation.
22
Kajitani, Tsuyoshi, Tomohiro Nozaki e Kei Hayashi. "Thermoelectric Iron Oxides". Advances in Science and Technology 74 (ottobre 2010): 66–71. http://dx.doi.org/10.4028/www.scientific.net/ast.74.66.
Testo completoAbstract (sommario):
P- and N-type thermoelectric iron oxides were developed. The p- and n-type thermoelectric iron oxides were based on delafossite-type CuFeO2 and spinel-type Fe3O4, respectively. The dimensionless figure of merit, ZT, of the bulk p- and n-type iron oxides were 0.15 and 0.10 at 1200K, respectively. The ZT values were improved by the introduction of nano-voids. The physical properties of these iron oxides are structurally unique because of the triangular, or “Kagome,” arrangement of FeO6 octahedra. The delafossite-type CuFeO2 becomes anti-ferromagnet at temperatures less than 20K. The inverse spinel-type Fe3O4 is a ferrimagnet at room temperature. In both crystals, the iron ions are assumed to be in the high-spin state.
23
Gareev, Kamil G. "Diversity of Iron Oxides: Mechanisms of Formation, Physical Properties and Applications". Magnetochemistry 9, n. 5 (27 aprile 2023): 119. http://dx.doi.org/10.3390/magnetochemistry9050119.
Testo completoAbstract (sommario):
Iron oxide compounds have naturally formed during the whole of Earth’s history. Synthetic compositions with iron oxides are produced with the use of various techniques and widely used for scientific and applied purposes. This review considers an attempt to classify all the information on different iron oxide compound formation mechanisms and intended applications in biomedicine, catalysis, waste remediation, geochemistry, etc. All the literature references analyzed were divided into several groups by their number of included iron oxide compounds: compositions containing only one compound (e.g., magnetite or wüstite), including various polymorphs of iron(III) oxide (α-, β-, γ-, ε-, ζ-, δ-Fe2O3); compositions with two different distinguishable iron oxide phases (e.g., maghemite and hematite); compositions containing non-crystalline phases (amorphous iron oxide or atomic clusters); and compositions with mixed iron oxide phases (indistinguishable separate iron oxide phases). Diagrams on the distribution of the literature references between various iron oxide compounds and between various applications were built. Finally, the outlook on the perspectives of further iron oxide studies is provided.
24
Zhang, Ming Huan, Qing Shao, Lu Yuan, Guang Wen Zhou e Yi Qian Wang. "Mechanism of the Oxidation of Iron". Advanced Materials Research 709 (giugno 2013): 106–9. http://dx.doi.org/10.4028/www.scientific.net/amr.709.106.
Testo completoAbstract (sommario):
A layered structure of different iron oxides was produced by thermal oxidation of iron. The structure and microstructure of different layers were examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Selected area electron diffraction (SAED) was used to identify the structures of the different oxide layers. Two different structures of Fe2O3were found to co-exist. Based on our observation, a possible oxidation mechanism for iron was proposed. The results shed light on the oxidation process of metals and provide insight into the synthesis of iron oxides.
25
Tarutis, W. J., e R. F. Unz. "Iron and manganese release in coal mine drainage wetland microcosms". Water Science and Technology 32, n. 3 (1 agosto 1995): 187–92. http://dx.doi.org/10.2166/wst.1995.0140.
Testo completoAbstract (sommario):
The primary mechanisms responsible for the removal and retention of iron, manganese, and sulfate in constructed wetlands receiving acidic mine drainage (AMD) include the formation of metal oxides and sulfides within the sediments. This study was initiated to determine the kinetics of metal ion liberation, under reducing conditions, from synthetic and naturally occurring iron and manganese oxides typically found in AMD precipitates. Rates of metal ion liberation were determined during time series incubations of an organic substrate (spent mushroom compost) to which five metal oxides of varying crystallinity (amorphous and crystalline oxides of iron and manganese; natural AMD oxide) were added. All experiments were carried out in silicone-sealed polycarbonate centrifuge tubes incubated at 22°C for a period of 3, 7, 10, 14, 21 or 28 days. Tubes were sacrificed after each incubation period and were analyzed for redox potential, pH, sulfide, and metals. All tubes exhibited reducing potentials within 3 days coupled with rapidly increasing concentrations of iron and manganese. Liberation of iron and manganese decreased with increasing mineral crystallinity (amorphous > natural AMD ≫ crystalline). The results suggest that metal ion liberation from oxide minerals may be an important source of iron and manganese within constructed wetlands receiving AMD.
26
Bil'genov, A., A. R. Tabylbaeva e P. A. Gamov. "Influence of Temperature and Holding Time on Number and Size of Metal Particles during Solid-Phase Reduction of Iron by Carbon". Solid State Phenomena 316 (aprile 2021): 496–501. http://dx.doi.org/10.4028/www.scientific.net/ssp.316.496.
Testo completoAbstract (sommario):
There is a lack of complete understanding of the mechanism and kinetics of reduction of metals from oxides. This paper presents results and methods of a series of experiments on direct reduction of metals by solid carbon in the form of graphite from a complex oxide with a low iron content in a laboratory muffle furnace at temperatures of 1300, 1400, 1500, 1600 °C and holding time of 1, 3, 5, 7 hours. The statistical analysis of amount and average size of reduced iron particles inside the oxide was studied. Dependence of amount and average size of the reduced iron particles on temperature and time of reduction is presented. The phenomena of iron crystals’ growth, occurring as a result of changes in the crystal lattice of oxide, was studied under experimental conditions. The influence of temperature and holding time on iron particles’ nucleation and their growth in the crystal lattice of a complex oxide were compared. Investigation of mechanism of metals’ reduction from complex oxides and influence of experimental conditions on the nucleation and growth enables to identify new patterns in the process of reduction of metals from their oxides, in general.
27
Setina, Janina, Alona Gabrene, Inna Juhnevica e Gundars Mezinskis. "Characterization of Iron Oxide Nanoparticles for Sol-Gel Dip-Coating Method Prepared Thin Films". Advanced Materials Research 704 (giugno 2013): 275–80. http://dx.doi.org/10.4028/www.scientific.net/amr.704.275.
Testo completoAbstract (sommario):
The paper describes two methods of syntheses of iron oxides, microstructure and morphology of magnetite nanoparticles. Nanocomposite thin films of SiO2/Fe3O4 have been prepared with sol-gel dip coating technique: dip-coating from SiO2/Fe3O4 sol and encapsulation magnetite between two SiO2 layers. Structural and morphological characteristics of iron oxides particles and prepared film were analyzed by X-Ray Diffraction, SEM, FTIR, DTA, AFM. AFM topography of surface and measurements of roughness has shown that using iron oxide encapsulation between two SiO2 layers to provide the even distribution of iron oxide, results as high quality films with low Rq values 1.5 2.7 nm.
28
Litter, Marta I., e Miguel A. Blesa. "Photodissolution of iron oxides II: The lack of efficiency of thiocyanate". Canadian Journal of Chemistry 68, n. 5 (1 maggio 1990): 728–30. http://dx.doi.org/10.1139/v90-114.
Testo completoAbstract (sommario):
Thiocyanate does not enhance, and even inhibits, the photochemical dissolution of iron oxides at 254 nm. At low SCN− concentrations, surface complexes [Formula: see text] are formed only to a small extent due to the low affinity for the surface by the monovalent anion, and electron-hole pairs essentially recombine. At higher ligand concentrations, only the homogeneous photolysis of SCN− is observed. At 450 nm, there is no appreciable light absorption by the oxide but homogeneous photolysis of FeIII—SCN− complexes produces FeII, which dissolves the oxide by a reductive mechanism. Keywords: iron oxides photodissolution, thiocyanate heterogeneous photochemistry, metal oxides surface complexation.
29
Hamed, Mai Hussein, David N. Mueller e Martina Müller. "Thermal phase design of ultrathin magnetic iron oxide films: from Fe3O4 to γ-Fe2O3 and FeO". Journal of Materials Chemistry C 8, n. 4 (2020): 1335–43. http://dx.doi.org/10.1039/c9tc05921k.
Testo completoAbstract (sommario):
Thermodynamically “active” oxide interfaces alter the standard iron oxide phase diagram of complex heterostructures. By controlling the effective oxygen pressure, selected iron oxides phases can be designed through a thermal phase design.
30
Siddhartha, O. Sai, e S. V. Satyanarayana. "Iron Oxides' Influence on the Thermal Decomposition of Pure Ammonium Perchlorate: A Comprehensive Review". Scholars International Journal of Chemistry and Material Sciences 7, n. 04 (9 aprile 2024): 35–44. http://dx.doi.org/10.36348/sijcms.2024.v07i04.001.
Testo completoAbstract (sommario):
The combustion of ammonium perchlorate (AP) has long been a focal point in the development of solid rocket propellants, with particular attention paid to the catalytic effects of iron oxides. Beginning in the 1950s, researchers have diligently studied the kinetics and mechanisms underlying AP combustion, with a focus on both micron-sized and nano-sized iron oxide catalysts due to their widespread application in rocket formulations worldwide. This research effort specifically excludes investigations involving alternative iron oxide-based catalysts, such as doped or mixed oxides, or supported iron oxides, as they are not commonly utilized in major rocket propellant formulations. Despite variations in specific parameters like activation energy and heat of dissociation, the fundamental understanding of AP decomposition with iron oxides remains consistent with earlier findings. Notably, micron-sized catalysts have minimal impact on the low-temperature decomposition (LTD) of AP but can influence high-temperature decomposition (HTD) by altering decomposition temperatures and reducing activation energy. In contrast, nano-sized catalysts tend to accelerate the reaction to such an extent that the LTD phase is often bypassed altogether due to the rapid consumption of NH3, a crucial component in the process. However, the transition to nano-sized particles presents a new challenge: the propensity for particle agglomeration. Current research endeavours are therefore dedicated to devising effective strategies to mitigate this issue and harness the full potential of nano-sized iron oxide catalysts in rocket propellant formulations.
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BENDRE, YU V., V. F. GORYUSHKIN, N. A. KOZYREV, R. A. SHEVCHENKO e N. V. OZNOBIKHINA. "THERMODYNAMIC ASPECTS OF OXIDES REDUCING BY ALUMINUM AND TITANIUM AT THE THERMIT WELDING OF RAILS". Ferrous Metallurgy. Bulletin of Scientific , Technical and Economic Information 77, n. 12 (28 dicembre 2021): 1291–95. http://dx.doi.org/10.32339/0135-5910-2021-12-1291-1295.
Testo completoAbstract (sommario):
During aluminothermic welding of rails, formation of aluminum oxides can take place, which become centers of residual stresses forming resulting in cracks formation followed by fracture and destruction of the welding joint. It was proposed to add titanium scrap in the form of preliminary made powders to the welding thermites composition. At the replacement of aluminum by titanium, titanium oxides formation takes place providing higher resistance against cracks formation. Comparative estimation of thermodynamic properties [∆rH°(T), ∆rG°(T)] of thermite reactions with aluminum and titanium in the systems metal oxide – aluminum and metal oxide – titanium under standard conditions presented. As reaction components for calculation of thermodynamic properties, oxides of iron, manganese, silicon and chrome were used. Thermodynamic analysis of 6 reactions with aluminum and 30 reactions with titanium were carried out. It was established that all the reactions under consideration are thermodynamically probable. However, reactions of both aluminum and titanium with iron oxides had the highest probability and correspondently the highest heat generation. Reducing of silicon oxide had the lowest probability and correspondently the lowest heat generation. The reaction with oxides of manganese and chrome had an intermediate position. By the reducing ability titanium is not worse than aluminum and in reactions with iron oxide even exceeds it, particularly in the temperature range over 2000 K. Enthalpies of reducing reactions of iron oxide by titanium is in the same area of values as the enthalpies of reaction of reducing by aluminum. A thermodynamic analysis showed that application of titanium as a reducing agent at the thermit welding is quite acceptable along with aluminum.
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Zhang, Yuzhe, Bin Wang, Qian Cheng, Xinling Li e Zhongyu Li. "Removal of Toxic Heavy Metal Ions (Pb, Cr, Cu, Ni, Zn, Co, Hg, and Cd) from Waste Batteries or Lithium Cells Using Nanosized Metal Oxides: A Review". Journal of Nanoscience and Nanotechnology 20, n. 12 (1 dicembre 2020): 7231–54. http://dx.doi.org/10.1166/jnn.2020.18748.
Testo completoAbstract (sommario):
How to remove harmful heavy metal ions from waste batteries or lithium cells efficiently has been the focus of scholars. More and more metal oxides had been used to deal with the pollution of heavy metal caused by waste batteries in recent years. Nanostructured metal oxides have great potential because of their large comparative areas. The adsorption for these heavy metal ions can be further improved by using modified metal oxides as adsorbents. At present, iron oxide is widely used in this field. Other metal oxides have also been studied in removing these heavy metal ions. Compared to other metal oxides, the adsorbents made of iron oxide are easy to be separated from the reaction system. pH value in the solution can affect the activity of adsorption sites on metal oxides adsorbents and change the distribution of ions in solution. As a result, pH value can significantly influence the adsorption of metal oxides adsorbents for heavy metal ions from waste batteries or lithium cells.
33
Liu, Xiangqian, e Weihua Hu. "Iron oxide/oxyhydroxide decorated graphene oxides for oxygen reduction reaction catalysis: a comparison study". RSC Advances 6, n. 35 (2016): 29848–54. http://dx.doi.org/10.1039/c5ra28038a.
Testo completo
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Long, Nguyet Viet. "INVESTIGATION OF SURFACES OF NOVEL IRON OXIDES WITH GRAIN AND GRAIN BOUNDARY". Vietnam Journal of Science and Technology 56, n. 1A (4 maggio 2018): 226. http://dx.doi.org/10.15625/2525-2518/56/1a/12527.
Testo completoAbstract (sommario):
Hierarchical nano/microscale α-Fe2O3 iron oxide particle system was prepared by an improved and modified polyol method with the use of NaBH4 agent with high heat treatment at 900 °C in air. Here, α-Fe2O3 iron oxide particles with different shapes were analyzed. The morphologies of the surfaces of α-Fe2O3 iron oxide particles show the oxide structures with the different nano/microscale ranges of grain sizes. In this research, we have found that grain and grain boundary growth limits can be determined in α-Fe2O3 iron oxide structure. This leads to the possibility of producing new iron oxide structures with distribution of desirable size grain and grain boundary. With α-Fe2O3 structure obtained, the magnetic properties of the α-Fe2O3 iron oxide system are different from those of previously reported studies. in national and international studies.Keywords: Iron iron oxides, α-Fe2O3, chemical polyol methods, heat treatment.
35
Cong, Zhiyuan, Shaopeng Gao, Wancang Zhao, Xin Wang, Guangming Wu, Yulan Zhang, Shichang Kang, Yongqin Liu e Junfeng Ji. "Iron oxides in the cryoconite of glaciers on the Tibetan Plateau: abundance, speciation and implications". Cryosphere 12, n. 10 (5 ottobre 2018): 3177–86. http://dx.doi.org/10.5194/tc-12-3177-2018.
Testo completoAbstract (sommario):
Abstract. Cryoconite is a mixture of impurities and ice visually represented by dark colors present in the ablation zone of glaciers. As an important constituent of light-absorbing impurities on the glacier surface, iron oxides influence the radiative properties of mineral dust and thus its impact on ice melting processes. In particular, the distinct optical properties between hematite and goethite (the major iron oxide species) highlight the necessity to obtain accurate knowledge about their abundance and geochemical behavior. Cryoconite samples from five glaciers in different regions of the Tibetan Plateau (TP) and surroundings were studied. The iron abundance in the cryoconite from TP glaciers ranged from 3.40 % to 4.90 % by mass, in accordance with typical natural background levels. Because the light absorption capacity of mineral dust essentially depends on the presence of iron oxides (i.e., free iron), iron oxides were extracted and determined using diffuse reflectance spectroscopy. The ratios of free to total iron for the five glaciers ranged from 0.31 to 0.70, emphasizing that iron in the form of oxides should be considered rather than total iron in the albedo and radiative modeling. Furthermore, the goethite content in iron oxides (in mass fraction) ranged from 81 % to 98 %, showing that goethite was the predominant form among the glaciers. Using the abundance and speciation of iron oxides as well as their optical properties, the total light absorption was quantitatively attributed to goethite, hematite, black carbon (BC) and organic matters at 450 and 600 nm wavelengths. We found that the goethite played a stronger role than BC at shorter wavelengths for most glaciers. Such findings were essential to understand the relative significance of anthropogenic and natural effects, and then taking the proper mitigation measures.
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Ozeki, Sumio, e Hiroyuki Uchiyama. "Magnetoadsorption of nitric oxide on iron oxides". Journal of Physical Chemistry 92, n. 23 (novembre 1988): 6485–86. http://dx.doi.org/10.1021/j100334a003.
Testo completo
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Karimi, N., Henri Buscail, Frédéric Riffard, F. Rabaste, Régis Cueff, Christophe Issartel, Eric Caudron e Sébastien Perrier. "Effect of Lanthanum Sol-Gel Coating on the Oxidation Behaviour of the AISI 304 Steel at 1000°C". Materials Science Forum 595-598 (settembre 2008): 733–41. http://dx.doi.org/10.4028/www.scientific.net/msf.595-598.733.
Testo completoAbstract (sommario):
The aim of the present work is to investigate the effect of Lanthanum surface addition on the oxidation behaviour of the AISI 304 stainless steel, in air, at 1000°C. The in situ X-ray diffraction (XRD) analyses on the blank steel reveal that after the first 10h oxidation, a change in the structural composition of the oxide scale occurs. During the first ten hours oxidation an initial growth of chromia and Mn1,5Cr1,5O4 is observed. After 10 h oxidation, chromia is not detected anymore and iron-containing oxides such as hematite (Fe2O3) and iron chromite (FeCr2O4) are observed in the outer part of the scale. With blank AISI 304 specimens, the iron-containing oxides are generally not very protective and show severe spallation during cooling to room temperature due to thermal stresses. They do not allow a good adherence of the corrosion layer under thermal cycling. On the Lanthanum coated AISI 304 Stainless Steel the oxidation rate is 10 times lower. In situ XRD analyses show the absence of iron containing oxides. It reveals the formation of a fine convoluted Cr2O3 layer associated with the formation of the mixed oxides Mn1,5Cr1,5O4 and LaCrO3. LaCrO3 is found to be located at the oxide/steel interface. Our results show that, even though the scale formed under isothermal conditions is not composed of iron containing oxides, Lanthanum sol-gel coating does not prevent spallation during thermal cycling at 1000°C.
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Ye, Zhi Guo, Xian Liang Zhou, Hui Min Meng, Xiao Zhen Hua, Ying Hu Dong e Ai Hua Zou. "The Electrochemical Characterization of Electrochemically Synthesized MnO2-Based Mixed Oxides for Supercapacitor Applications". Advanced Materials Research 287-290 (luglio 2011): 1290–98. http://dx.doi.org/10.4028/www.scientific.net/amr.287-290.1290.
Testo completoAbstract (sommario):
Nanostructured elements, including: manganese-molybdenum (Mn-Mo) oxide, manganese-molybdenum-tungsten (Mn-Mo-W) oxide, manganese-molybdenum-iron (Mn-Mo-Fe) oxide, manganese-molybdenum-cobalt (Mn-Mo-Co) oxide, manganese-vanadium-tungsten (Mn-V-W) oxide, manganese-vanadium-iron (Mn-V-Fe) oxide and manganese-iron (Mn-Fe) oxide, have been anodically deposited onto titanium substrates by employing an iridium dioxide interlayer (Ti/IrO2anode). The electrochemical characteristics of the resultant oxide deposits have been investigated by cyclic voltammetry (CV) in an aqueous 0.1 M Na2SO4solution. The voltammetric behaviors of the oxide deposits observed are significantly influenced by the doped elements. Molybdenum doping is found to be advantageous at improving the capacitance characteristics of anodically deposited manganese oxide. Comparatively, iron and vanadium doping are found to be unfavorable. The structure and crystallinity of these deposits have been identified by X-ray diffraction (XRD). The surface morphologies of these oxides were acquired from field emission scanning electron microscopes (FESEM). The high values of electrical parameters for the doped deposits are attributed to the net-like and sponge-like nanostructure, and low crystallinity of the doped manganese oxides. The deposit of Mn-Mo oxides exhibits an excellent capacitive-like behavior, possessing the maximum specific capacitance of 810 F g-1at a CV scan rate of 5 mV s-1in aqueous 0.1 M Na2SO4solution.
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Photos-Jones, E., A. Cottier, A. J. Hall e L. G. Mendoni. "Kean Miltos: The Well-Known Iron Oxides of Antiquity". Annual of the British School at Athens 92 (novembre 1997): 359–71. http://dx.doi.org/10.1017/s0068245400016737.
Testo completoAbstract (sommario):
The island of Kea in the North Cyclades was well known in antiquity for its miltos, a naturally occurring red iron oxide valued for its colour and wide range of applications. By combining geological field work, physico-chemical analytical techniques, simulation (heating) experiments as well as simple laboratory tests, this paper describes the study of Kean iron oxides in an attempt to characterize this material which is still largely elusive in the archaeological record. The present work corroborates previous observations about the superior quality of some Kean iron oxides. Furthermore, it puts forward the hypothesis that miltos may have been considered an industrial mineral, and as such may have been used as an umbrella term for a variety of materials including mineralogically distinct purple as well as red iron oxides.
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Owonubi, Ayodele. "Pedogenic Forms of Iron in Soils Developed from Four Parent Materials". JOURNAL OF TROPICAL SOILS 25, n. 1 (22 gennaio 2020): 47. http://dx.doi.org/10.5400/jts.2020.v25i1.47-52.
Testo completoAbstract (sommario):
Information on the distribution of various forms of iron in soils are valuable in the study of soil genesis. The objective of this study was to to evaluate the pedogenic forms of iron in soils developed over basement complex and basaltic parent materials of the study area. Geologic units considered in the basement complex area were granite gneiss, biotite granite and migmatite. Stratified random sampling formed the basis for field work. Soil sampling was carried out by digging at least two soil profile pits in each geologic unit. Organically bound, amourphous and total iron oxides were estimated using 0.1 M sodium pyrophosphate, acidified (pH 3) ammonium oxalate, and dithionite-citrate-bicarbonate method, respectively. The total Fe in the soil samples were determined after a mixed acid digestion. In general, total iron fractions were statistically similar among the soils of basement complex geologic units but significantly lower than those of soils derived from basaltic rocks. However, the distribution of iron oxide fractions was similar among the basement and basaltic geologic units. Furthermore, there were significant differences in the distribution of iron oxides in the B horizons of basement complex derived soils. Consequently, the quantity of iron oxides in the B horizon was in the order migmatite > biotite granite > granite gneiss. About 70% of total iron oxides in the soils over granite gneiss, biotite granite and basaltic rocks was amorphous in nature. Furthermore, total iron oxides constitute less than 20% of total clay both in the basement complex and basaltic soils.
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Birchall, Thomas, Christopher Hallett, Ann Vaillancourt e Krzysztof Ruebenbauer. "A study of iron–tungsten oxides and iron–chromium–tungsten oxides". Canadian Journal of Chemistry 66, n. 4 (1 aprile 1988): 698–702. http://dx.doi.org/10.1139/v88-121.
Testo completoAbstract (sommario):
A 57Fe Moessbauer study of the Fe2O3–WO3 and Fe2O3–Cr2O3–WO3 systems has been carried out. Single phase materials could be prepared having the composition Fe2−xWO6−3x/2 (x = 0.28), the stoichiometric Fe2WO6 always contained detectable amounts of α-Fe2O3. The iron tungstates are found to be unstable to prolonged heating at 1000 °C. The Cr2−yFeyWO6 (0 < y ≤ 2) system was shown to be of the trirutile type when y ≤ 1.7 but multiphasic when y ≥ 1.7, these latter phases have structures based upon the iron and chromium tungstate phases, respectively. The Moessbauer parameters for the Cr2−xFeyWO6 compositions do not appear to behave in the same fashion as the related Fe2−xCrxTeO6 system.
42
Halim, K. S. Abdel, A. A. El-Geassy, M. I. Nasr, Mohamed Ramadan, Naglaa Fathy e Abdulaziz S. Al-ghamdi. "Characteristics and applications of iron oxides reduction processes". Polish Journal of Chemical Technology 26, n. 1 (1 marzo 2024): 39–50. http://dx.doi.org/10.2478/pjct-2024-0005.
Testo completoAbstract (sommario):
Abstract The present review handles the main characteristics of iron oxide reduction and its industrial applications. The reduction of iron oxide is the basis of all ironmaking processes, whether in a blast furnace or by direct reduction and/or direct smelting processes. The reduction characteristics of iron ores control the efficiency of any ironmaking process and the quality of the produced iron as well. Many controlling parameters should be considered when discussing the reducibility of iron ores such as equilibrium phase diagrams, reduction temperature, pressure, gas composition, and the nature of both iron ores and reducing agent. The different factors affecting the main routes of ironmaking will be highlighted in the present review to give a clear picture for each technology. Moreover, further innovations regarding the reduction of iron oxides such as reduction by green hydrogen will be discussed.
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Kapelyushin, Yu, V. Roshchin e A. Roshchin. "Beneficiation of Vanadium and Titanium Oxides by Using Selective Extraction of Iron in Low-Titanium Magnetite Concentrate". Solid State Phenomena 265 (settembre 2017): 913–18. http://dx.doi.org/10.4028/www.scientific.net/ssp.265.913.
Testo completoAbstract (sommario):
Issues with existing vanadium beneficiation stimulate the development of new technologies for wasteless production of vanadium. The present work investigates a possibility of beneficiation of vanadium and titanium oxides in a low-titanium magnetite concentrate by using selective reduction and extraction of iron. Iron was selectively reduced by coal without melting and separated from the oxide (slag) phase during further smelting operation. After the liquid-phase separation vanadium and titanium oxides were accumulated in a slag phase. The following products were produced: slag, containing vanadium and titanium oxides, and iron with relatively low carbon content. The content of vanadium and titanium in a final product has increased in comparison to the initial concentrate.
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Sheshukov, O. Yu, M. A. Mikheenkov, E. A. Vyaznikova, A. S. Bykov e L. B. Vedmid’. "Changes in phase composition of soderites of the bakal deposit at heating". Izvestiya Visshikh Uchebnykh Zavedenii. Chernaya Metallurgiya = Izvestiya. Ferrous Metallurgy 61, n. 11 (24 dicembre 2018): 891–97. http://dx.doi.org/10.17073/0368-0797-2018-11-891-897.
Testo completoAbstract (sommario):
The article presents the results of a study of formation mechanism of magnesia-ferrite when heated siderites of the Bakal deposit with different iron oxide content in an inert and oxidizing atmosphere. It was established that in the case of firing in an inert atmosphere, the decomposition of siderite with high iron content begins at a lower temperature and the enthalpy of such decomposition is less. This effect can be explained by the different phase composition of the samples. The main phases formed under conditions of oxidative firing are hematite and magnesia-ferrite. The amount of hematite and magnesia-ferrite produced in the samples with different iron oxide content during firing in an oxidizing atmosphere is different. Siderite with high content of iron oxides contains more hematite in the firing products than magnesia-ferrite, and siderite with a low content of iron oxides contains more magnesia-ferrite in the firing products than hematite. Formed under conditions of oxidative firing magnesia-ferrites are solid solutions and differ in the degree of substitution of iron and magnesium ions. In siderites with high content of iron oxides, the degree of substitution of magnesium ions with iron ions is greater than in samples with a low content of iron oxides. Since the siderites of the Bakal deposit are poor ore formations, the considerable amount of magnesia-ferrite formed in them during firing makes it difficult to separate silicate and iron-oxide firing products by traditional enrichment methods. Wustite in the products of oxidative firing is not detected, because under these conditions it is in a metastable state and in the presence of a weakly oxidizing atmosphere is converted into magnetite. The scientific novelty is the explanation of the mechanism of siderite decomposition and the description of products of such decomposition. Understanding of the mechanism of decomposition of siderite from the Bakal deposit made it possible to develop the technology of reductive firing of siderite to facilitate separation of its products, and which consists in the regulation of the phase composition of silicate products of reductive firing, ensuring the collapse of magnesia-ferrite and output of iron oxide in a separate phase. The developed technology can be used to provide high-quality enrichment of siderite from the Bakal deposit.
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Axinte, Ciprian, Claudia Nadejde, Manuela Ursache, Anton Airinei, Aurelian Cirlescu, Mihaela Racuciu e Dorina Creangă. "Magnetic Submicron Powder Preparation and Characterization". Materials Science Forum 672 (gennaio 2011): 281–85. http://dx.doi.org/10.4028/www.scientific.net/msf.672.281.
Testo completoAbstract (sommario):
The goal of this experimental study was to present a comparative analysis of iron oxides powders obtained by two alternative methods, i.e. the co-precipitation at high temperature from aqueous reaction medium of iron oxides and, respectively, the solvent free method for the preparation magnetite at room temperature. Vibrational absorption spectra evidenced the dominancy of magnetite in both samples, while the X-ray diffractograms revealed the submicron size as well as the presence of additional iron oxide, in the second sample prepared by solvent free method.
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Alimin, A., L. O. Kadidae, L. Agusu, L. O. Ahmad, S. J. Santosa e A. Asria. "Formation Mechanisms of Co-existence of α-Fe and Iron Oxides Nanoparticles Decorated on Carbon Nanofibers by a Simple Liquid Phase Adsorption-Thermal Oxidation". Journal of New Materials for Electrochemical Systems 25, n. 3 (31 agosto 2022): 200–205. http://dx.doi.org/10.14447/jnmes.v25i3.a07.
Testo completoAbstract (sommario):
We propose formation mechanisms of co-existence of α-Fe and iron oxides nanoparticles decorated on CNFs. The α-Fe nanoparticles are produced via oxidation-reduction mechanisms, which occur in liquid phase adsorption (LPA) assisted by ultrasonic energy, while α-Fe2O3 nanoparticles are thermally formed through mechanisms of Lewis acidbase. In addition, Fe3O4 is thermally formed by reducing Fe2O3 by CNFs. Liquid phase adsorption assisted by ultrasonic energy under ambient temperature using Fe(NO3)3•9H2O as a precursor of iron oxides and α-Fe has been applied. Then, as prepared, Fe(III)@CNFs were thermally calcined at 573 K under air atmosphere in various holding times ranging from 0.5 to 2 h. XRD data confirmed that α- Fe2O3 and Fe3O4 had been successfully grown onto CNFs. Moreover, the presence of the iron oxides and iron nanoparticles was studied by the SEMEDX technique. The iron oxide nanoparticles appeared after a heating period of 0.5h. However, at a holding time of 0.5 h, we found an exciting and unexpected phenomenon where oxygen content is zero percent while Fe is 0.23 wt %. It implies that α-Fe nanoparticles were formed earlier than α-Fe2O3 and Fe3O4 as the proposed mechanisms. Formation mechanisms of iron and its oxides such as α-Fe2O3 and Fe3O4 decorated on CNFs through liquid-phase adsorption followed by thermally treatment technique in this work is expected to give significant contribution in the field of nanocomposite materials, especially for anode materials based on iron oxides.
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Figueroa, Raquel A., e Allison A. MacKay. "Sorption of Oxytetracycline to Iron Oxides and Iron Oxide-Rich Soils". Environmental Science & Technology 39, n. 17 (settembre 2005): 6664–71. http://dx.doi.org/10.1021/es048044l.
Testo completo
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Huo, Jian Zhen. "Preparation of Composite Iron Oxides via Hydrothermal Process". Advanced Materials Research 583 (ottobre 2012): 162–66. http://dx.doi.org/10.4028/www.scientific.net/amr.583.162.
Testo completoAbstract (sommario):
Composite iron oxides are very important advanced materials. In this paper different types of iron oxides α-FeOOH, α-Fe2O3 and composite oxide NiFe2O4 were synthesized via a simple hydrothermal method at 180°C for 10 h. The phases and morphologies of the products were characterized by X-ray diffractometer and high-resolution transmission electron microscopy. The results indicated that α-FeOOH nanorods were prepared when mole concentration of NaOH solution was 3M. By increasing the concentration of NaOH to 5M and 8M, we obtained qusi-fusiform α-Fe2O3 single-crystallines and composite oxide NiFe2O4 nanocrystals, respectively. Our experiments showed that both the concentration of NaOH solution and existence of sulphate ions affect the formation of varying morphologies of the products.
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Kesavan, V., D. Dhar, Y. Koltypin, N. Perkas, O. Palchik, A. Gedanken e S. Chandrasekaran. "Nanostructured amorphous metals, alloys, and metal oxides as new catalysts for oxidation". Pure and Applied Chemistry 73, n. 1 (1 gennaio 2001): 85–91. http://dx.doi.org/10.1351/pac200173010085.
Testo completoAbstract (sommario):
The oxidation of cyclohexane with molecular oxygen in the presence of isobutyraldehyde catalyzed by nanostructured iron and cobalt oxides and iron oxide supported on titania has been studied. Nanostructured cobalt oxide on MCM-41 is found to be efficient for catalytic aerobic epoxidation of olefins.
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El Khalloufi, Mohammed, e Gervais Soucy. "Oxide Reduction Treatment with a Thermal Plasma Torch: A Case Study". Minerals 14, n. 5 (24 aprile 2024): 443. http://dx.doi.org/10.3390/min14050443.
Testo completoAbstract (sommario):
This article presents the findings of a study on oxide reduction utilizing a novel reducing plasma torch, employing greenhouse gases such as CO2 and CH4 as plasma gases. The primary aim of this investigation is to establish the viability of this approach. The innovative plasma torch was employed to reduce various oxides, including aluminum oxide, iron oxide, and titanium oxide, as well as a mixed oxide composition, employing a CO2/CH4 molar ratio of 1:1 within a spouted bed reactor. Following plasma treatment, X-ray diffraction (XRD) analysis was conducted to examine the metallic phases, notably titanium, iron, and aluminum. SEM–EDS observations were carried out to assess microstructural changes and identify elemental compositions pre- and post-plasma treatment. The results demonstrate that within the conical section of the reactor, titanium oxide experiences partial reduction, resulting in limited titanium production, while aluminum oxide and iron oxides (magnetite and hematite) undergo reduction to yield aluminum and iron, respectively. Thermodynamic calculations, performed using Factsage software version 8.3, were utilized to predict stable-phase formations following plasma treatment for each material.