Annealing study of Fe2O3 nanoparticles: Magnetic size effects and phase transformations

Xu, X.N.; Wolfus, Y.; Shaulov, A.; Yeshurun, Y.; Felner, I.; Nowik, I.; Koltypin, Yuri; Gedanken, Aharon

doi:10.1063/1.1457544

Cited by 81 publications

(49 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The superparamagnetic magnetite nanoparticles comprise 45.2% of the sample and are the source of two well-defined double quadrupolar unfolding spectra corresponding to the Fe 2+ and Fe 3+ species of magnetite, respectively. The doublet represents the fraction of small particles in which longrange magnetic ordering is absent (Xu et al, 2002). These doublets are characteristic of magnetite with SP properties, and their presence supports the results obtained by susceptibility measurements.…”

Section: Mössbauer Spectroscopysupporting

confidence: 72%

Natural magnetite nanoparticles from an iron-ore deposit: size dependence on magnetic properties

et al. 2009

View full text Add to dashboard Cite

We report on the discovery of magnetite nanoparticles ranging in size from 2 to 14 nm in the mineralized zones of the Peña Colorada iron-ore deposit, southern Mexico. Micrometric scale magnetite was magnetically reduced and divided into distinct size ranges: 85-56 μm, 56-30 μm, 30-22 μm, 22-15 μm, 15-10 μm, 10-7 μm and 7-2 μm. Nanometric-scale magnetite in the size range 2-14 nm was identified. The magnetite was characterized by X-ray diffraction, transmitted and reflected light microscope, high-resolution transmission electron microscopy (TEM), high angle annular dark field, Mössbauer spectroscopy and its magnetic properties. Crystallographic identification of nanostructures was performed using high-resolution TEM. Characteristic changes were observed when the particles make the size transition from micro-to nanometric sizes, as follows: (1) frequency-dependent magnetic susceptibility percentage (χ FD %) measurements show high values (13%) for the 2-14 nm fractions attributed to dominant fractions of superparamagnetic particles; (2) variations of χ FD % < 4.5% in fractions of 56-0.2 μm occur in association with the presence of microparticles formed by magnetite aggregates of nanoparticles (<15 nm) embedded in berthierine; (3) Mössbauer spectroscopy results identified a superparamagnetic fraction; (4) nanometric and 0.2-7 μm grain size magnetite particles require a magnetic field up to 152 mT to reach saturation during the isothermal remanent magnetization experiment; (5) coercivity and remanent magnetization of the magnetite increase when the particle size decreases, probably due to parallel coupling effects; (6) twomagnetic susceptibility versus temperature experiments of the same 2-14 nm sample show that the reversibility during the second heating is due to the formation of new magnetite nanoparticles and growth of those already present during the first heating process.

show abstract

Section: Mössbauer Spectroscopysupporting

confidence: 72%

Natural magnetite nanoparticles from an iron-ore deposit: size dependence on magnetic properties

et al. 2009

View full text Add to dashboard Cite

show abstract

“…The hyperfine parameters of this doublet (Table 2) are similar to those reported previously for Fe 2 O 3 nanoparticles prepared by other synthetic routes. [62][63][64][65] The non-Lorentzian shape of the doublet is caused by the distribution of the quadrupole splitting and reflects the distorted symmetry of the charge distribution around the Fe 3+ cores. The Mössbauer spectrum at 5 K in an external magnetic field of 5 T was measured to determine the phase composition of sample A1 ( Figure 5, a).…”

Section: The Effect Of Decomposition Temperature On the Crystal Strucmentioning

confidence: 99%

The Effect of Surface Area and Crystal Structure on the Catalytic Efficiency of Iron(III) Oxide Nanoparticles in Hydrogen Peroxide Decomposition

et al. 2010

View full text Add to dashboard Cite

Iron(II) oxalate dihydrate has been used as a readily decomposable substance for the controlled synthesis of nanosized iron(III) oxides. The polymorphous composition, particle size and surface area of these iron oxide nanoparticles were controlled by varying the reaction temperature between 185 and 500°C. As-prepared samples were characterized by XRD, low-temperature and in-field Mössbauer spectroscopy, BET surface area and the TEM technique. They were also tested as heterogeneous catalysts in hydrogen peroxide decomposition. At the selected temperatures, the formed nanomaterials did not contain any traces of amorphous phase, which is known to considerably reduce the catalytic efficiency of iron(III) oxide catalysts. As the thickness of the sample (≈ 2 mm) was above the critical value, a temporary temperature increase ("exo effect") was observed during all quasiisothermal decompositions studied, irrespective of the reaction temperature. Increasing the reaction temperature resulted in a shift of the exo effect towards shorter times and an increased content of maghemite phase. The maghemite content decreases above 350°C as a result of a thermally in-

show abstract

“…Many of these materials were coated, to provide an inert and biologically compatible outer shell made of silica [67] , gold [43,57,76] or carbon [71,73] . [36,48] . The 4 nm Co NPs with fcc, hcp and epsilon phases have blocking temperatures of -143 ° C, 1 ° C and 17 ° C, respectively [49] .…”

Section: Biomedicalmentioning

confidence: 99%

Application of alternative energy forms in catalytic reactor engineering

Houlding

Rebrov

2012

Green Processing and Synthesis

View full text Add to dashboard Cite

This review provides a general overview of recent applications of magnetic nanoparticles for controlled radiofrequency (RF) heating in catalytic synthesis, mass transfer enhancement in laminar fl ow and magnetic separation. By directly delivering RF energy to magnetic materials, issues such as long heating periods and energy losses can be minimized. The main mechanisms of RF heating are briefl y reviewed. The effect of nanoparticles size, shape and composition on the effi ciency of RF heating is discussed. RF energy has been shown to be effective in many applications, however, it is still not used in chemicals due to high equipment costs.

show abstract

Annealing study of Fe2O3 nanoparticles: Magnetic size effects and phase transformations

Cited by 81 publications

References 19 publications

Natural magnetite nanoparticles from an iron-ore deposit: size dependence on magnetic properties

Natural magnetite nanoparticles from an iron-ore deposit: size dependence on magnetic properties

The Effect of Surface Area and Crystal Structure on the Catalytic Efficiency of Iron(III) Oxide Nanoparticles in Hydrogen Peroxide Decomposition

Application of alternative energy forms in catalytic reactor engineering

Contact Info

Product

Resources

About