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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 paper, the heating mechanism and influencing factors of magnetite particles in a 63 kHz alternating magnetic field and 7 kA/m were studied and the results from in vivo heating experiments suggest that magnetite particle can generate enough energy to heat tumor tissue and perform effective hyperthermia.

141 citations

Journal ArticleDOI
14 Jun 1990-Nature
TL;DR: In this article, electron microscopy data obtained from a sequence of samples of Onondaga Limestone from an east-west traverse across northern New York was used to unambiguously show that magnetite spheres are derived by alteration and replacement of framboidal pyrite.
Abstract: LIMESTONES are an important source of palaeomagnetic data, with magnetite the dominant carrier of the magnetization. Because the magnetite is present in low concentrations, however, it has been directly observed only rarely and in trace amounts in acid-treated separates. Such residues are composed primarily of spheres, the ultimate origin of which has been enigmatic7. Yet interpretation of the palaeomagnetic data depends on a knowledge of the origin of the magnetite, which has been inferred to carry either a chemical or a viscous remanent magnetization. Here we present electron microscope data obtained from a sequence of samples of Onondaga Limestone from an east–west traverse across northern New York, which unambiguously show that magnetite spheres are derived by alteration and replacement of framboidal pyrite. Remagnetization is thus caused by chemical, rather than viscous, processes. This chemical remanent magnetization is compatible with a fluid-mediated event occurring on a regional scale, induced by tectonic stress of Alleghenian (late Palaeozoic) age.

141 citations

Journal ArticleDOI
TL;DR: Nitrate removal was most rapid at low pH (2-4); however, the formation of a black oxide film at pH 5 to 8 temporarily halted or slowed the reaction unless the system was augmented with Fe(2+), Cu( 2+), or Al(3+).
Abstract: Under anoxic conditions, zerovalent iron (Fe(0)) reduces nitrate to ammonium and magnetite (Fe3O4) is produced at near-neutral pH. Nitrate removal was most rapid at low pH (2-4); however, the formation of a black oxide film at pH 5 to 8 temporarily halted or slowed the reaction unless the system was augmented with Fe(2+), Cu(2+), or Al(3+). Bathing the corroding Fe(0) in a Fe(2+) solution greatly enhanced nitrate reduction at near-neutral pH and coincided with the formation of a black precipitate. X-ray diffractometry and scanning electron microscopy confirmed that both the black precipitate and black oxide coating on the iron surface were magnetite. In this system, ferrous iron was determined to be a partial contributor to nitrate removal, but nitrate reduction was not observed in the absence of Fe(0). Nitrate removal was also enhanced by augmenting the Fe(0)-H2O system with Fe(3+), Cu(2+), or Al(3+) but not Ca(2+), Mg(2+), or Zn(2+). Our research indicates that a magnetite coating is not a hindrance to nitrate reduction by Fe(0), provided sufficient aqueous Fe(2+) is present in the system.

141 citations

Journal ArticleDOI
TL;DR: In this paper, a collection of 50 submarine intrusive rocks, including doleritic sill rocks, fresh and serpentinized cumulate gabbroses and cumulate peridotites, and lherzolites, are reported to have originated in Layers 2B, 3B and 4 respectively.
Abstract: Summary Measurements of natural remanent magnetization (nrm), Curie temperature, ferrimagnetic and paramagnetic susceptibility, saturation induced and remanent magnetizations, coercive forces, alternating field properties and viscous magnetization are reported for 50 submarine intrusive rocks drilled during Legs 30, 37 and 45 of DSDP. The collection includes doleritic sill rocks, fresh and serpentinized cumulate gabbros and serpentinized cumulate peridotites, and serpentinized lherzolites believed to have originated in Layers 2B, 3B and 4 respectively. Magnetite, with a Curie temperature between 520 and 580°C, is the principal magnetic mineral in all samples. There is no indication of maghemitization or of metamorphism to greenschist facies or above. The magnetite in the doleritic and cumulate gabbros is a product of deuteric alteration of titanomagnetite and pyroxene; the stable nrm is a primary trm. The magnetite in the serpentinized rocks is a secondary product of serpentinization; the stable nrm is a crm. In most rock types, the magnetite is of single-domain or pseudo-single-domain size and soft components of nrm are small. The magnetite grain size in some of the doleritic gabbros is much coarser; these rocks acquire large viscous magnetizations, which however are readily removed by alternating field cleaning. The cleaned nrms of Legs 30 and 45 rocks have approximately dipole inclinations but the nrms of most of the mutually intruded Leg 37 units have been dispersed by tectonic rotations. The doleritic gabbros and the serpentinized peridotites have stable, directionally coherent nrms ≳ 10-3emu cm-3 in intensity. Their counterparts in Layers 2B and 3B/4 are likely contributors to oceanic magnetic anomalies. Layer 3B cumulate gabbros and tectonic serpentinites in the middle and upper crust are less likely anomaly sources.

140 citations

Journal ArticleDOI
20 Oct 2004-Langmuir
TL;DR: The preparation of hybrid temperature-sensitive microgels which include magnetite nanoparticles in their structure, which possess a low critical solution temperature (LCST) in water solutions, with a rapid decrease of the particle size being observed at elevated temperatures.
Abstract: In the present paper, we report the preparation of hybrid temperature-sensitive microgels which include magnetite nanoparticles in their structure. Polymeric microgels have been prepared by surfactant-free emulsion copolymerization of acetoacetoxyethyl methacrylate (AAEM) and N-vinylcaprolactam (VCL) in water with a water-soluble azo-initiator. The obtained microgels possess a low critical solution temperature (LCST) in water solutions, with a rapid decrease of the particle size being observed at elevated temperatures. Magnetite was deposited directly into microgels, leading to the formation of composite particles which combine both temperature-sensitive and magnetic properties. The influence of magnetite load on microgel size, morphology, swelling-deswelling behavior, and stability is discussed.

140 citations


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