Core−shell Nanostructured Nanopowders along (CeO_<i>x</i>)_<i>x</i>(Al₂O₃)_1−<i>x</i>Tie-Line by Liquid-Feed Flame Spray Pyrolysis (LF-FSP)

Abstract

We report here the synthesis of (CeOx)1−x(Al2O3)x mixed-metal oxide nanopowders with molar ratios that span the CeOx−Al2O3 composition range. Liquid-feed flame spray pyrolysis (LF-FSP) of mixtures of N(CH2CH2O)3Al (alumatrane) and Ce(O2CCH2CH3)(OH) precursors dissolved in ethanol were aerosolized with O2, combusted at temperatures of 1500−2000 °C and rapidly quenched thereafter to provide (CeOx)1−x(Al2O3)x nanopowders of selected compositions. All powders exhibit average particle sizes (APSs) < 20 nm and corresponding surface areas of ≥50 m2/g when produced at rates of 100−300 g/h. The as-processed powders were characterized in terms of phase, size, specific surface area, composition, and morphology by BET, XRD, XRF, SEM, TEM, STEM, XEDS, XPS, FT-IR, and TGA-DTA. Surprising core−shell nanostructured nanopowders are observed in the Ce−Al−O system at CeOx rich concentrations (≥15 mol %). In addition, evidence is presented for the incorporation of Ce3+ ions in the δ-alumina lattice at the lowest concentrations and Ce-magnetoplumbite (CeAl11O18) at 5−10 mol % CeOx concentrations.