Organometallic synthesis of colloidal α-/β-NiAl nanoparticles and selective aluminum oxidation in α-Ni1-xAlx nanoalloys

Mirza Cokoja, Harish Parala, Alexander Birkner, Osama Shekhah, Maurits W.E. Van Den Berg, Roland A. Fischer*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

A novel soft chemical synthesis of Ni1-xAlx nanoparticles (0.09 ≤ x ≤ 0.50) by cohydrogenolysis of [Ni(cod) 2] (1) with [(AlCp*)4] (2) or with [(Me 3N)AlH3] (3) in nonaqueous solution is presented (cod = 1,5-cyclooctadiene, Cp* = 1,2,3,4,5-cyclopentadienyl). The treatment of equimolar amounts of 1 and 2 in mesitylene solution under 3 bar of H2 at 150°C gave a brown-black colloidal solution of intermetallic β-NiAl particles, characterized by transmission electron microscopy/energy dispersive X-ray analysis (TEM/EDX) and powder X-ray diffraction (XRD). The solution was stable under 3 bar of H2 at 150°C for up to 8 h. The β-NiAl colloids were treated postsynthesis with 17O-enriched 1-adamantanecarboxylic acid (ACA) as a surface capping group, giving nearly monodisperse α-NiAl colloids that were stable under argon at room temperature for weeks. The coordination of ACA at the α-NiAl surface was studied by 17O NMR and IR spectroscopy. A series of α-Ni 1-xAlx samples with a variety of compositions (x = 0.50, 0.33, 0.25, 0.17, 0.09) were prepared analogously, and the samples were characterized by means of elemental analysis (ICP), XRD, and TEM/EDX. Air oxidation of α-Ni1-xAlx nanoparticles leads to core-shell particles of the type (Al2O3) δ/2@Ni1-xAlx-δ (0.09 ≤ x ≤ 0.50; x > δ). XRD, X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS) analyses showed that the Ni core is protected against oxidation down to an Al content of about 10 atom %.

Original languageEnglish (US)
Pages (from-to)5721-5733
Number of pages13
JournalChemistry of Materials
Volume19
Issue number23
DOIs
StatePublished - Nov 13 2007

ASJC Scopus subject areas

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

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