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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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TL;DR: In this paper, a theoretical model of grain size dependence of domain transitions in magnetite is presented, which is used to predict the grain size range for pseudosingle domain (PSD) behavior.
Abstract: A theoretical model of grain size dependence of domain transitions in magnetite is presented. This domain model is used to predict the grain size range for pseudosingle domain (PSD) behavior in magnetite. For cubic magnetite particles, the single domain (SD) to two-domain (TD) transition occurs at ∼800 ± 200 A, the TD-three-domain transition occurs at ∼ 1500 A, and the PSD-"true" multidomain (MD) transition occurs at \sim 8\mu m. These results are in fair agreement with experimental results within a factor of 2. Our results indicate that the grain size range for the canonical case of a PSD grain (a TD grain with a single 180° wall) or "PSARK" (subdomain magnetic moment) ranges from ∼700 A for cubic particles of magnetite to \sim3.2 \mu m for a length: width ratio of 5:1. Comparison with grain size distributions of magnetite grains in igneous rocks suggest that the PSARK can be the major contributor to the remanence of these grains.
85 citations
TL;DR: Iron oxide nanoparticles of reduced oxidation state, mainly in the form of magnetite, have been synthesized utilizing a new continuous, gas-phase, nonpremixed flame method using hydrocarbon fuels, which allows for the iron particle formation to be maintained in a more reducing environment.
85 citations
TL;DR: In this paper, the formation of highly reactive species in the interface of Fe 0 /iron oxides mixtures, i.e. Fe 3 O 4 (magnetite), γ-Fe 2 O 3 (maghemite) or α-Fe 3 O 3(hematite) prepared by mechanical grinding and thermal treatment at 200, 400, 600 or 800°C under argon atmosphere, was studied.
Abstract: This work studied the formation of highly reactive species in the interface of Fe 0 /iron oxides mixtures, i.e. Fe 3 O 4 (magnetite), γ-Fe 2 O 3 (maghemite) or α-Fe 2 O 3 (hematite) prepared by mechanical grinding and thermal treatment at 200, 400, 600 or 800 °C under argon atmosphere. Mossbauer spectroscopy, powder X-ray diffraction, scanning electron microscopy, BET surface area and magnetization measurements suggest a strong interaction between the metal and the oxide surfaces at temperature as low as 200 °C, producing highly reactive surface species. These reactive species are readily oxidized when exposed to air at room temperature to form large quantities of Fe 2 O 3 . The treatment at 600 and 800 °C leads to an extensive solid state reaction of Fe 0 with Fe 3 O 4 to produce the phase wustite, FeO, with a strong decrease in BET surface area and reactivity. These thermally treated mixtures Fe 0 /iron oxides were also studied as heterogeneous catalysts to promote the decomposition of H 2 O 2 . The mixtures Fe 0 /Fe 3 O 4 treated at 200 and 400 °C showed a remarkable increase in activity for the H 2 O 2 decomposition. The high reactivity of these samples is discussed in terms of Fe surf 2+ species formed by electron transfer from Fe 0 to Fe 3+ at the interface metal/oxide which are active to initiate the H 2 O 2 decomposition via a Haber–Weiss mechanism. The mixtures Fe 0 /γ-Fe 2 O 3 and Fe 0 /α-Fe 2 O 3 ground and thermally treated were also studied, however much lower activities for the H 2 O 2 decomposition were observed.
85 citations
TL;DR: Novel magnetic nano-carriers around 180 nm in diameter showed higher performance compared to commercially available magnetic beads in terms of purification efficiency of target including extent of non-specific binding protein.
85 citations
TL;DR: In this article, a composite pellet made of Malaysian iron ore with palm kernel shell (PKS) waste was subjected to reduction tests using an electric tube furnace to investigate the effect of temperature and PKS content on reduction rate.
85 citations