Mössbauer study of carbon coated iron magnetic nanoparticles produced by simultaneous reduction/pyrolysis

Abstract

Magnetic iron nanoparticles immersed in a carbon matrix were produced by a combined process of controlled dispersion of Fe 3+ ions in sucrose, thermal decomposition with simultaneous reduction of iron cores and the formation of the porous carbonaceous matrix. The materials were prepared with iron contents of 1, 4 and 8 in %wt in sucrose and heated at 400, 600 and 800 • . The samples were analyzed by XRD, Mössbauer spectroscopy, magnetization measurements, TG, SEM and TEM. The materials prepared at 400 • are composed essentially of Fe 3 O 4 particles and carbon, while treatments at higher temperatures, e.g. 600 and 800 • produced as main phases Fe 0 and Fe 3 C. The Mössbauer spectra of samples heated at 400 • showed two sextets characteristic of a magnetite phase and other contributions compatible with Fe 3+ and Fe 2+ phases in a carbonaceous matrix. Samples treated at temperatures above 600 • showed the presence of metallic iron with concentrations between 16-43%. The samples heated at 800 • produced higher amounts of Fe 3 C (between 20% and 58%). SEM showed for the iron 8% sample treated at 600-800 • C particle sizes smaller than 50 nm. Due to the presence of Fe 0 particles in the carbonaceous porous matrix the materials have great potential for application as magnetic adsorbents.

Iron: a versatile element to produce materials for environmental applications

“…In this process, first Fe 3+ ions are solubilized in aqueous sucrose and upon thermal decomposition the iron is reduced to form magnetic particles surrounded by a nanometric layer of more organized graphitic carbon entrapped in an amorphous carbonaceous matrix ( Figure 13). 44 Studies of these materials as Pd catalysts support in hydrogenation reactions showed promising results with the full conversion of the substrate 1,5-COD (1,5-cyclooctadiene).…”

Carbon-coated CoFe–CoFe2O4 composite particles with high and dual-band electromagnetic wave absorbing properties

“…The saturation magnetization (M s ), remanent magnetization (M r ) and coercivity (H c ) of the CoFe 2 O 4 particles are 64.27 emu g −1 , 4.17 emu g −1 , and 94.09 Oe, respectively. M s decreases to 59.10 emu g −1 after the carbon layer is introduced since the carbon is non-ferromagnetic [20], but H c increases apparently to 389.38 Oe due to the pinning effects of the carbon atom [21,22]. The carbon atom will infiltrate the interior of the submicrosphere through the gap between nanocrystals and be attached to the surface of the nanocrystals.…”

Mössbauer Study on the Conversion of Different Iron-Based Catalysts Used in Carbon Nanotube Synthesis

“…Several Mössbauer studies have already been presented in the past. However, the studies were focused on different aspects, such as a study of the spatial distribution of the catalyst along the aligned CNTs' forests [25] or others [26,27]. We seek to provide a direct comparison between the different situations and their outcomes that are commonly encountered in CNTs' preparation, i.e., synthesis (i) with a sufficient source of carbon, (ii) with an insufficient amount of carbon and (iii) with a partially oxidised catalyst.…”