A fundamental aspect of the growth process of alumina scale on a metal with dispersion of CeO2 nanoparticles

The dispersion of CeO2 nanoparticles resulted in a decrease of the oxidation rate of an ultrafine-grained Ni2Al3 at 1000 degrees C. The reason is explained as follows. During oxidation many Ce ions are released from the CeO2 nanoparticles that are enveloped by the inward growing alpha-Al2O3 from the scale/metal interface due to an increased solubility. The Ce ions transport outward along grain boundaries of the scale, retarding the diffusion of Al ions for the thickening of the outer theta-Al2O3. This explanation is consistent with an observation that many CeO2 nano-precipitates appeared mainly in the near-surface zone of the formed alumina scale. (C) 2011 Elsevier Ltd. All rights reserved.