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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 authors studied the magnetic properties of marine sediments from the California continental borderland (San Pedro, Santa Catalina, and San Nicolas basins) in order to quantitatively assess the effects of sediment diagenesis on magnetic minerals.
Abstract: The rock magnetic properties of marine sediments from the California continental borderland (San Pedro, Santa Catalina, and San Nicolas basins) have been studied in order to quantitatively assess the effects of sediment diagenesis on magnetic minerals. Previous studies have noted that the natural remanent magnetization in these sediments, primarily carried by detrital magnetite, decays to 10% or less of its surface value soon after deposition. This decrease is caused by magnetite dissolution related to sediment diagenesis and is unrelated to paleoclimatic variations or changes in the regional influx of detrital magnetic material. Detailed rock magnetic measurements show that shifts to softer remanent coercivity and differences in the rate and degree of magnetic intensity loss with depth can be related to the dissolution process. The shift to softer remanent coercivity is related to a coarsening of the magnetic mineral grain sizes with depth due to preferential dissolution of the finest-grained magnetic material. The intensity decreases, which are linearly proportional to magnetite concentration decreases, indicate that dissolution occurs with rate constants ranging from 0.3 to 1.6 kyr−1. The rate constants, sulfide concentrations, and magnetite grain size estimates from the borderland are consistant with previous studies of magnetite dissolution. Our results demonstrate the importance of both sulfide and magnetite surface area in the dissolution process. Anomalous peaks in viscous remanence within the sediments suggest the authigenic growth of greigite and its subsequent transformation to pyrite.
145 citations
TL;DR: In this paper, it was found that the ratio of magnetite to hematite in the surface oxide film appears to increase with increasing water vapor pressure, ascending temperature, and extending oxidation time.
Abstract: Laser Raman spectroscopy (LRS) has been applied for the detection and characterization of thin corrosion films formed on iron in air at a temperature range from 100 to 150 C. In situ ellipsometric measurements have also been conducted for quantitative estimations of the film growth kinetics. It is found that (1) the oxidation of iron in dry air leads to the formation of a surface oxide film composed primarily of magnetite and (2) the water vapor in air accelerates the formation of hematite. The ratio of magnetite to hematite in the surface oxide film appears to increase with (1) increasing water vapor pressure, (2) ascending temperature, and (3) extending oxidation time.
144 citations
TL;DR: In this article, a single iron precursor (iron(III) ethoxide) and an amphiphilic poly(ethylene oxide)-block-poly(propylene oxide)-poly(poly(methylene oxide) triblock copolymer (PEO100/PPO65/PEO 100) as a soft template were used to synthesize spherical mesoporous magnetite (Fe3O4) aggregates with wormhole-like pore structure.
Abstract: Spherical mesoporous magnetite (Fe3O4) aggregates with a wormhole-like pore structure were successfully synthesized for the first time using a single iron precursor (iron(III) ethoxide) and an amphiphilic poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) triblock copolymer (PEO100–PPO65–PEO100) as a soft template In this synthesis, the interaction between the iron precursor and the triblock copolymer self-assemblies in ethanol leads to the assembly of magnetite nanocrystals into spherical mesoporous aggregates These aggregates were characterized using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, standard and high-resolution transmission electron microscopy, 57Fe Mossbauer spectroscopy, and X-ray diffraction, confirming the formation of pure-phase Fe3O4 particles with monodisperse morphology (about 130 nm in diameter), three-dimensional wormhole-like mesopores, and highly crystalline spinel structure In addition, a formation mechanism for this material in the present system is proposed, based on the analysis of results The mesoporous magnetite has a high specific surface area of 1656 m2 g−1, and relatively large pores with a mean size of 52 nm The magnetic susceptibility data demonstrate that this material exhibits superparamagnetic behavior
144 citations
TL;DR: In this article, uniform iron oxide magnetic nanoparticles, with sizes in the range 9-22 nm, have been synthesized by thermal decomposition of an iron oleate complex in 1-octadecene, controlling reaction parameters related to the nucleation and growth processes.
Abstract: Uniform iron oxide magnetic nanoparticles, with sizes in the range 9–22 nm, have been synthesized by thermal decomposition of an iron oleate complex in 1-octadecene, controlling reaction parameters related to the nucleation and growth processes. After transferring to water through a ligand substitution process, nanoparticles display very good magnetic and magneto-thermal properties. The relationship between these properties and the size and size distribution of the particles is discussed. The colloidal stability of the nanoparticles dispersed in common biological buffers has also been studied.
144 citations
TL;DR: In this article, the effects of various metal additives in the reduced iron oxide on the production of hydrogen from water have been examined at a temperature range 373-873 K. The authors suggested that Rh metal would catalyze the dissociation of H2O at low temperature while the compound oxides formed between iron and additives mitigate the coagulation of iron and iron oxide particles during repeated reaction cycles.
144 citations