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Powder Technology, Vol.160, No.3, 229-233, 2005
Fabrication of Fe-, Ni- and FeNi-coated Al2O3 core-shell microspheres by heterogeneous precipitation
The precursors with NiCO(3)center dot 2Ni(OH)(2)center dot 2H(2)O-, Fe(2)O(3)center dot nH(2)O-, or both of NiCO(3)center dot 2Ni(OH)(2)center dot 2H(2)O- and Fe203-nH20-coated alumina microspheres were prepared, respectively, by the aqueous heterogeneous precipitation using metal salts, ammonium hydro-carbonate and alpha-Al2O3 micropowders as the starting materials. Subsequently, magnetic metallic Ni-, alpha-Fe- and gamma-FeNi-coated alumina core-shell structural microspheres were successfully obtained by thermal reduction of the as-prepared precursors at 700 C for 2 h, respectively. Optimized precipitation processing parameters of the concentration of alumina micropowders (15 g/L), the rate of adding reactants (5 mL/min) and pH value were determined by a trial and error method. Powders of the precursors and the resultant metal (Ni, alpha-Fe, gamma-FeNi alloy)-coated alumina micropowders were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The experimental results show that it is possible to adjust metal coating thicknesses and fabricate multilayer structured metal/ceramics core-shell microspherical powder materials and these materials may be applied for high performance of functional materials and devices. (c) 2005 Elsevier B.V. All rights reserved.