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Magnetite

About: Magnetite is a research topic. Over the lifetime, 10277 publications have been published within this topic receiving 278071 citations.


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Journal ArticleDOI
TL;DR: In this article, the microwave properties of natural rubber based composites in the 1-12 GHz frequency range were determined by the conductive carbon black/magnetite hybrid fillers obtained by impregnation at different ratios between carbon and magnetite phase.
Abstract: The study presents the microwave properties of natural rubber based composites in the 1–12 GHz frequency range as determined by the conductive carbon black/magnetite hybrid fillers obtained by impregnation at different ratios between carbon and magnetite phase. It has been established that, the changes in the investigated properties exhibit a resonance character in the 3–9 GHz range and are caused by alternations both of frequency and the ratio between the hybrid phases. The real and imaginary parts of permittivity and permeability, dielectric and magnetic loss angle tangent and conductivity have been also determined. The composite comprising a hybrid filler whose carbon:magnetite phase ratio is 90:10 has turned to be the most successful. The good microwave characteristics of the composite are related to the dielectric and magnetic losses, as well as to the achieved optimal permittivity of the composite at the given ratio of the carbon and magnetite phase. The percent content of the conductive filler has a significant impact upon EMI SE of the composites. The introduction of Fe3O4 into the hybrid filler has a crucial role for decreasing the reflection by the composites surface.

74 citations

Journal ArticleDOI
TL;DR: In this article, the reduction of porous spheres of hematite by stages through the intermediate oxides and also continuously to iron by CO/CO2 mixtures at temperatures of 600 to 900°C (873 to 1173 K).
Abstract: Non-topochemical behavior was studied during reduction of porous spheres of hematite by stages through the intermediate oxides and also continuously to iron by CO/CO2 mixtures at temperatures of 600 to 900°C (873 to 1173 K). The behavior became more nearly topochemical as temperature increased. Shrinking occurred during the reduction of hematite to magnetite and of magnetite to wustite, whereas swelling was observed during the reduction of wiistite to iron. Shrinking was greater, and swelling less, at higher temperatures. The total surface area of the solid decreased with increasing extent of reduction during each of the three stages. A non-topochemical model was developed which satisfies, better than previously proposed models, the reduction data for the single reactions and the three reactions occurring simultaneously. The model provides for variation in particle size and local changes in porosity and effective diffusivity. An empirical “sintering exponent” was introduced to describe changes in reacting surface area.

74 citations

Journal ArticleDOI
01 Dec 2008-Gff
TL;DR: Magnetite-apatite iron ores of the Kiruna type, unaffected by deformation, have structures and textures similar to those of igneous rocks as discussed by the authors, and the best examples are the El Laco deposits in northern Chile which resemble lava flows, pyroclastic deposits and dikes.
Abstract: Magnetite-apatite iron ores of the Kiruna type, unaffected by deformation, have structures and textures similar to those of igneous rocks. The best examples are the El Laco deposits in northern Chile which resemble lava flows, pyroclastic deposits and dikes. El Laco magnetites have δ18O values between 2.3 and 4.2‰ (V-SMOW). Magnetite from ore with a magmatic texture has a mean of 3.7‰, and the mean for magnetite intergrown with pyroxene in veins is 2.4‰. Oxygen isotope data given here, fluid inclusion results and geological evidence indicate that ore formation took place in a cooling magmatic system. Major orebodies resembling lava flows and near-vent pyroclastic deposits crystallized from magma at ca. 1000°C. Fluids from cooling magma deposited magnetite and pyroxene (±apatite) at ca. 800°C in fissures and open spaces, now present as veins cutting major orebodies. There is little evidence for significant magnetite precipitation during hydrothermal conditions. A large province of magnetite-apatit...

74 citations

Journal ArticleDOI
TL;DR: In this paper, thermophilic iron-reducing bacteria obtained from two sedimentary basins in Virginia and Colorado, USA, reduced amorphous Fe(III) oxyhydroxide to form magnetite-rich (>60% in most samples) iron oxides in acetate- or H{sub 2/CO-sub 2}-enriched cultures.

74 citations

Journal ArticleDOI
TL;DR: It is shown that unstable NPs with a mixed wustite–magnetite composition can be oxidized to pure maghemite by extending the reaction time or using an oxidizing agent.
Abstract: Iron fatty acid complexes (IFACs) are prepared via the dissolution of porous hematite powder in hot unsaturated fatty acid The IFACs are then decomposed in five different organic solvents under reflux conditions in the presence of the respective fatty acid The XRD analysis results indicate that the resulting NPs comprise a mixture of wustite, magnetite, and maghemite phases The solvents with a higher boiling point prompt the formation of larger NPs containing wustite as the major component, while those with a lower boiling point produce smaller NPs with maghemite as the major component In addition, it is shown that unstable NPs with a mixed wustite–magnetite composition can be oxidized to pure maghemite by extending the reaction time or using an oxidizing agent

74 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023570
20221,277
2021367
2020478
2019494
2018446