Characterization of Nanosized Maghemite Particles Prepared by Microemulsion Using an Ionic Surfactant

Abstract

We have characterized a system of maghemite, γ -Fe 2 O 3 , nanosized particles prepared by a microemulsion method using an ionic surfactant. The Mössbauer spectra from 21 to 298 K evolve from a totally magnetically split signal at low temperatures to a single superparamagnetic (sp) doublet at 298 K with a blocking temperature of ≈150 K. The real component of the AC susceptibility (5 ν 10 4 Hz) displays a behavior characteristic of a system of interacting particles. A broad distribution of the particle sizes is revealed by the much higher average energy barrier obtained by AC susceptibility than Mössbauer.

Colloidal Synthesis and Characterization of Tetrapod-Shaped Magnetic Nanocrystals

“…This is also consistent with the Mo ¨ssbauer spectra above 80 K (spectra a-d) which show a quadrupole splitting in agreement with the literature values for γ-Fe 2 O 3 . 27,28 Similar conclusions can be drawn from the analysis of other samples.…”

Characterization of iron hydroxide/oxide nanoparticles prepared in microemulsions stabilized with cationic/non-ionic surfactant mixtures

“…9. The pictures show an agglomerate of many (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) single crystals. This agglomerate exhibits oval-shaped (or elongated) clumps which encounter a clear sintering upon calcination.…”

“…Iron oxide nanoparticles (haematite, maghemite, magnetite) can be prepared by different methods such as sol-gel [13], precipitation [14], microwave synthesis [15], hydrothermal synthesis [16], microemulsion [17][18][19]. Here we report a water-in-oil microemulsion route to synthesize iron oxide nanoparticles.…”

Characterization of &#947- and α-Fe₂O₃ nano powders synthesized by emulsion precipitation-calcination route and rheological behaviour of α-Fe₂O₃

“…Micronic acicular maghemite was prepared either directly from FeOOH or through a topotatic oxidation of magnetite (Bate, 1975). Maghemite nanoparticles have been obtained by co-precipitation of FeCl 3 and FeCl 2 in an alkali medium, (Massart, 1981), microemulsion method with ionic surfactants, (Tueros et al, 2003) or physical methods such as high-energy ballmilling (Randrianantoandro et al, 2001). Hematite nanoparticles with different structures have also been synthesized by various methods, such as the sol-gel process (Woo et al, 2003), thermal oxidation of iron metal (Wen et al, 2005), forced hydrolysis (Musi´c et al, 2003), hydrothermal method (Cao et al, 2005;Giria et al, 2005;Baruwati et al, 2006;Jia et al, 2007), gas-phase flame synthesis (Kumfer et al, 2010), ultrasonic spray pyrolysis (Gurmen and Ebin, 2010).…”