Iron-cobalt alloy nanoparticles embedded in an alumina xerogel matrix

Guido Ennas*, Andrea Falqui, Giorgio Paschina, Giaime Marongiu

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

Nanocrystalline γ-Al2O3 and FeCo-Al 2O3 nanocomposite xerogels with high surface areas and pore volumes were prepared from alcogels obtained by a fast sol-gel procedure. The formation of γ-Al2O3 occurs via a sequence of stages starting from a disordered pseudo-bohemite phase which around 700°C gives rise to amorphous allumina; this progressively cristallizes as γ-Al2O3, which is stable up to 1100° C, when microcrystalline α-Al2O3 becomes the dominant phase; in the range 1000-1200°C minor traces of δ-Al2O 3 and θ-Al2O3 are present. Xerogels containing iron and cobalt are amorphous up to 700° C; calcination at 800°C gives rise to a spinel phase similar to γ-Al2O 3 where metal ions partially fill the vacancies; at 1000°C γ-Al2O3 progressively disappears to form α-Al2O3 and Co(Fe)Al2O4, which are the only phases present at 1200°C. Reduction in hydrogen flow of the xerogel, previously calcined at 450°C, leads to a nanocomposite constituted of FeCo alloy nanoparticles around 10 nm dispersed into α-Al 2O3 nanocrystalline matrix. Zero-field-cooled (ZFC) and FC magnetic curves are typical of superparamagnetic materials and indicate the occurrence of high-strength particle interactions.

Original languageEnglish (US)
Pages (from-to)6486-6491
Number of pages6
JournalChemistry of Materials
Volume17
Issue number25
DOIs
StatePublished - Dec 13 2005

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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