Liquid-feed flame spray pyrolysis (LF-FSP) for combinatorial processing of nanooxide powders along the (ZrO2)1-x(Al2O3)x tie-line.: Phase segregation and the formation of core-shell nanoparticles

We report here the synthesis of (ZrO2)(1-x)(Al2O3), nanooxide powders with molar ratios that span the ZrO2-Al2O3 composition range. Liquid-feed flame spray pyrolysis (LF-FSP) of mixtures of N(CH2CH2O)(3)AI (alumatrane) and Zr(CH3CH2COO)(2)(OH)(2) precursors dissolved in ethanol, were aerosolized with O-2, combusted at temperatures of 1500-2000 degrees C and rapidly quenched thereafter to provide (ZrO2)(1-x)(Al2O3), nanopowders of selected compositions. All powders exhibit average particle sizes (APSs) < 20 nm and corresponding surface areas of approximate to 50 m(2)/g when produced at rates of 100-300 g/h. The as-processed powders were characterized in terms of phase, APS, specific surface area, composition, and morphology by BET, XRD, XRF, SEM, TEM, FT-IR, and TGA-DTA. The presence of delta-alumina and tetragonal zirconia is observed over most of the compositions studied. Furthermore, this phase segregation leads to the formation or core-shell materials. Evidence is presented suggesting the incorporation of Z1(-2+/3+) ions above the published solubility limit of ZrO2 in delta-alumina.