Mechanisms for the Oxidation of Fe3O4

Feitknecht, W.; Gallagher, K. J.

doi:10.1038/228548a0

Cited by 80 publications

(41 citation statements)

References 6 publications

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“…It is know that bivalent iron from magnetite is easily prone to oxidation. 28 Indeed, a local oxidation of magnetite can be brought about by the laser beam during the Raman experiment. 29 The Raman spectrum of the nanostructures (Fig.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of magnetic microtubes decorated with nanowires and cells

et al. 2018

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ARTICLES YOU MAY BE INTERESTED INStudy on the mechanism of a manganese-based catalyst for catalytic NO X flue gas denitration AIP Advances 8, 045004 (2018); https://doi.org/10.1063/1.4989431The effect of surface wettability on the performance of a piezoelectric membrane pump AIP Advances 8, 045010 (2018) Antiferromagnetic and ferrimagnetic microtubes decorated with nanowires have been obtained during thermal oxidation process, which was assisted by in situ electrical resistivity measurements. The synthesis route including heat treatment and electrical current along with growth mechanism are presented. This simple method and the ability to tune in the magnetic moment of the obtained microtubes going from a nonmagnetic-like to a large magnetization saturation open an avenue for interesting applications. In vitro experiments involving adherence, migration, and proliferation of fibroblasts cell culture on the surface of the microtubes indicated the absence of cytotoxicity for this material. We have also calculated both torque and driving magnetic force for these microtubes with nanowires and cells as a function of external magnetic field gradient which were found to be robust opening the possibility for magnetic bio micro-robot device fabrication and application in biotechnology.

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Section: Resultsmentioning

confidence: 99%

Synthesis of magnetic microtubes decorated with nanowires and cells

et al. 2018

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“…This applies whether or not a-Fe203 nuclei are present (13,23). The present study (results (iii)) suggests that uptake of water from the gas phase by magnetite is associated with non-stoichiometry in the latter (Fe3-,04-,, 0 < x I l), presumably because the protons of the water can be accommodated in the cation vacancies, concomitantly stabilizing the spinel structure (22)(23)(24)(25)58); thus, coarsely crystalline, stoichiometric Fe304 oxidizes to a-Fe203 even when prepared by a "wet" method (36) (results (ii)).…”

Section: Discussionmentioning

confidence: 99%

“…Fe203"), although thermodynamically unstable Maghemite forms in nature either through the with respect to hematite (a-Fe20,) and not usually oxidation of magnetite (Fe30,) if this is sufficiently considered a common mineral, does occur widely finely-divided (3,(8)(9)(10)(11)(12)(13)(14)(15), through the oxidation at in terrestrial (notably highly-weathered tropical) ambient temperatures of aqueous iron(II) via Presoils (1,2), has been reported to be an important cipitated "green rusts" under conditions of limited secondary mineral in certain subvolcanic hy-0 2 supply (i.e., slow reaction) (16,17), and ~ossibly drothermal breccia bodies (3), appears to be a through dehydration of lepidocrocite (Y-F~O(OH)) major constituent of the sands of Mars (4,5), and (1,(18)(19)(20) although a redox cycle may be involved has even been said to be the substance responsible in this last case (l,21). Whatever the mechanism, it appears that the presence of water is necessary for 'To whom correspondence should be addressed.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of the magnetite–maghemite–hematite transformation, with special reference to hydrothermal systems

Swaddle¹,

Oltmann²

1980

Can. J. Chem.

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. Maghemite, prepared in the usual way (but with exclusion of silica, e.g., from glassware) by precipitation of non-stoichiometric magnetite Fe3-,O,-, in aqueous MOH (M = Na, K) followed by air oxidation, picks up moisture from the air to reach the limiting composition MsH,-sFe50,. where 6 -0.02-0.03 for fresh material, but changes under hydrothermal conditions because of ion exchange. Despite the role of absorbed moisture in stabilizing maghernite, formation of the latter from Fe3-,O,-, is markedly retarded, and its decomposition to u-Fe,03 greatly accelerated, under hydrothermal conditions relative to the rates of the corresponding reactions of the dry solids. The rate of hydrothermal decomposition of maghemite is strongly retarded by silica. Over the range 160-187°C at least, silica-free maghemite decomposes in water according to the empirical equation -In ( I -a ) = (kt)", whereu is the fractional extent of decomposition. and 11 -2.5 for neutral water (with k = 1.3 x s-I at 160°C and 3.1 x 10-5s-' at 175°C) but approaches unity, without major effects on the overall time-scale of reaction, at high [MOH]. The mechanistic significance of these and previous results are considered; the hydrothermal conversion of maghemite to hematite evidently proceeds by ii dissolution-reprecipitation sequence. THOMAS WILSON SWADDLE et P~~I L L I P~L T M A N N .Can. J . Chem. 58, 1763 (1980). La maghemite. preparee de manitre habituelle (mais avec elimination de la silice par exemple celle de la verrerie) par precipitation de la magnetite non stoechiometrique Fe,-,O,_, dans du MOH aqueux (M = Na, K) suivie d'une oxydation a I'air, absorbe I'humiditC de I'air pour atteindre une composition limite de MsHI+,Fe5O, ou 6 -0.02-0.03 pour le produit fr-ais, mais il se produit des changements dans des conditions hydrothermiques pa; suite de I'echange d'ions. En depit du r6le de I'humidite absorbee en tant que stabilisatrice de la maghernite, la formation de cette derniere B partir de Fe3+,0,_, est fortement retiirdee et sa dCcomposition en Fe203 u est grandement accClerCe dans des conditions hydrothermiques s'apparentant aux vitesses des reactions correspondantes des solides secs. La vitesse de decomposition hydrothermique de la maghemite est fortement retardee par la silice. Au moins dans I'intervalle de 160-187"C, la maghemite depourvue de silice se decompose dans I'eau selon I'equation empirique In (1 -a ) =

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“…potentiel de passivation (-250 mV) présentent moins d'intérêt puisque leur sélectivité se dégrade dès 100° C (11) [12]. Leur évolution en cours de traitement thermique est absolument analogue à celle obtenue par voie chimique (6), nous la présentons figure 12. Jusqu'à 200° C la diffraction électronique ne permet pas de [13][14][15]. Les [Variations of depth of external zone (part b Fig.…”

Section: Introductionunclassified