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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, the degree of stoichiometry in magnetite is quantitatively measured by determining the ratio of Fe2+ to Fe3+ using powder X-ray diffraction (pXRD).
Abstract: A solid solution can exist of magnetite (Fe3O4) and maghemite (γ-Fe2O3), which is commonly referred to as nonstoichiometric or partially oxidized magnetite. The degree of stoichiometry in magnetite is quantitatively measured by determining the ratio of Fe2+ to Fe3+. Magnetite stoichiometry ( x = Fe2+/Fe3+) strongly influences several physical properties, including the coercitivity, sorption capacity, reduction potential, and crystalline structure. Magnetite stoichiometry has been extensively studied, although very little work exists examining the stoichiometry of nanoparticulate samples (<<100 nm); when the stoichiometry was measured for nanoparticulate samples, it was not validated with a secondary technique. Here, we review the three most common techniques to determine magnetite stoichiometry: (1) acidic dissolution; (2) Mossbauer spectroscopy; and (3) powder X-ray diffraction (pXRD), specifically with nanoparticulate samples in mind. Eight samples of nonstoichiometric magnetite were synthesized with x ranging from 0 to 0.50 and with the particle size kept as similar as possible (BET specific surface area = 63 ± 7 m2/g; particle size ≈ 20 nm). Our measurements indicate excellent agreement between stoichiometries determined from Mossbauer spectra and by acidic dissolution, suggesting that Mossbauer spectroscopy may be a useful means for estimating magnetite stoichiometry in nanoparticulate, multi-phases samples, such as those found in the environment. A significant linear correlation was also observed between the unit-cell length ( a ) of magnetite measured by pXRD and magnetite stoichiometry, indicating that pXRD may also be useful for determining particle stoichiometry, especially for mixed phased samples.
206 citations
TL;DR: In this paper, a commercial promoted precipitated iron catalyst (100 Fe/5 Cu/4.2 K/25 SiO2 by weight) was characterized after different pretreatment conditions and after Fischer-Tropsch (FT) synthesis in a fixed bed reactor.
206 citations
TL;DR: In this paper, magnetic poly epsilon-caprolactone (PCL) nanoparticles were prepared in a well shaped spherical form by the o/w emulsion method.
205 citations
TL;DR: In this paper, an improved approach for the coating of superparamagnetic magnetite nanoparticles with shells of amorphous silica is described. But it is not shown that the magnetic core-shell structure is superparamagntic.
204 citations
TL;DR: In this article, the authors designed encapsulated magnetite graphene oxide inside a non-toxic alginate bead as a high-performance green chemical for the uptake of Cr(VI) and As(V) in water treatment applications (mGO/bead).
204 citations