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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 conducted a comprehensive study of the crystallography and magnetic properties of bullet-shaped magnetosomes formed by uncultivated giant rod magnetotactic bacteria (referred to as MYR-1), recently discovered in Lake Miyun.
97 citations
TL;DR: In this article, the sulfate-methane transition (SMT) has been encountered at shallow depths of a few meters below the seafloor, where sulfate diffusing downward from the bottom water is met and reduced by methane rising from deeper in the sediment column, intense alteration affects the detrital magnetic mineral assemblage.
97 citations
TL;DR: In this paper, the second-neighbor Coulomb interaction of the cations on the octahedral sites was investigated and the Verwey temperature shift as a function of the substituent concentration was determined from the temperature dependence of the resistivity.
Abstract: Magnetite single crystals Fe32xMxO4 doped with M5Ni, Co, Mg, Al, Ga, and Ti were grown and annealed under a controlled atmosphere to produce homogeneous and oxygen stoichiometric samples. The cation vacancy concentration of the samples was proved to be lower than 10 26 by means of magnetic disaccommodation spectroscopy. The Verwey temperature shift as function of the substituent concentration was determined from the temperature dependence of the resistivity. The systematics of the transition temperature shift as function of the concentration and nature of the substituents is indicative that the mechanism of the transition is related to the second-neighbor Coulomb interaction of the cations on the octahedral sites. @S0163-1829~98!00846-7#
97 citations
TL;DR: In this article, stable suspensions of superparamagnetic iron oxide nanoparticles stabilized with unmodified polyethylene glycol (PEG) at four molecular weights (2000, 4000, 6000 and 10,000 Da) and several PEG/iron ratios were obtained.
96 citations
TL;DR: In this paper, the reaction-transport code CRUNCH is used to investigate the iron-clay interactions at 50°C over a period of 10,000 years, which are the conditions considered here to represent the mean temperature value and the expected timescale for the corrosion stage.
Abstract: In the context of deep geological disposal of high level radioactive wastes, the interactions between iron and clay-rich materials may lead to adverse transformations of clay minerals with a potential loss of confining properties such as swelling and capacity to exchange cations. Such transformations have been experimentally observed at temperatures starting at ca. 80 °C, where smectites contained in a mixture of bentonite and iron powder are transformed into iron-rich serpentine-type minerals. The reaction-transport code CRUNCH is used to investigate the iron–clay interactions at 50 °C over a period of 10,000 years, which are the conditions considered here to represent the mean temperature value and the expected timescale for the corrosion stage. The aim is to predict the nature and quantity of corrosion product, calculate the chemistry of water (essentially the pH) and the mineralogical transformation in the system containing the canister, an optional engineered barrier (bentonite) and the host-rock (argillite). The results of the calculations show that at the interface with the canister, where steel corrosion occurs, the iron is partly immobilized by the precipitation of iron oxides (essentially magnetite) and small amounts of siderite. The pH stabilizes at high values, between 10 and 11, at this location. In the bentonite or the argillite in contact with the container, the primary clay minerals are destabilized and iron-rich serpentine-like minerals precipitate as observed in the experiments (cronstedtite and berthierine). These minerals show low cation exchange and swelling capacities. The results also show that the interactions between iron and clay may lead to significant porosity changes in the system. A reduction of the porosity is predicted at the surface of the steel canister, due to the precipitation of iron oxides. Porosity increase is predicted in the clay material due to the dissolution of the primary clay minerals. The effect of these porosity changes have yet to be observed experimentally and assessed with regard to the confinement capability of the repository near field, especially by considering the mechanical aspects in the case with and without the engineered barrier.
96 citations