title: Uniform nanosized goethite particles obtained by aerial oxidation in the FeSO4-Na2CO3 system.
abstract: Pure goethite particles in the nanometer size range (from approximately 200 to approximately 80 nm) with an elongated shape (axial ratio from approximately 5 to approximately 8) useful as iron precursors for magnetic recording have been prepared by oxidation of the suspensions resulting from the addition of sodium carbonate to Fe(II) sulfate aqueous solutions under a restrictive set of experimental conditions (Fe(II) concentration, carbonate/Fe(II) mole ratio, temperature, and air flow rate). In all cases, the goethite particles were formed by a dissolution-recrystallization mechanism through an intermediate green-rust phase. The particle size was determined by the carbonate/Fe(II) ratio (which controls the formation pH), the FeSO(4) concentration, and the air flow rate. The smallest particles (length 80 nm) were obtained for a high carbonate/Fe(II) mole ratio (>/=3), a low Fe(II) concentration (0.075 mol dm(-3)), and an air flow rate of 2 dm(3) min(-1). The goethite particles were also characterized by the electron diffraction and high-resolution TEM finding that they were monocrystalline, having the crystalline c axis parallel to the longest particle dimension.
authors.affiliation: Instituto de Ciencia de Materiales de Sevilla (CSIC-UNSE), Americo Vespucio s/n, Isla de La Cartuja, Seville, 41092, Spain.
authors.forename: Raúl
authors.initials: R
authors.lastname: Pozas
authors.forename: Manuel
authors.initials: M
authors.lastname: Ocaña
authors.forename: M Puerto
authors.initials: MP
authors.lastname: Morales
authors.forename: Carlos J
authors.initials: CJ
authors.lastname: Serna