کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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1448928 | 988687 | 2010 | 10 صفحه PDF | دانلود رایگان |

Novel wedge-geometry, dual-layer alumina samples, both undoped and 500 ppm Y3+-doped, were studied in the temperature regime 1250–1400 °C to determine the effect of Y3+ on oxygen grain-boundary transport in alumina. The samples consisted of a wedge-shaped, single-phase alumina top layer, diffusion bonded to an alumina/Ni substrate containing a fine, uniform dispersion of Ni marker particles (0.5 vol.%). The extent of the alumina spinel oxidation layer was measured as a function of the wedge thickness for a series of heat-treatment conditions. Models of the transport behavior were used to derive values for the rate constants (k) in both the alumina top layer and the alumina/Ni substrate. It was found that the presence of yttrium slows oxygen grain-boundary diffusion in alumina by a factor of ∼5 (at 1300 °C), and increases the corresponding activation enthalpy for oxidation from 407 ± 20 to 486 ± 34 kJ mol−1. Microstructural observations suggested that yttrium also slows Ni outward diffusion. A comparison of the different k values revealed that, at 1300 °C, the presence of Ni alone enhances transport by a factor of ∼2 relative to undoped alumina.
Journal: Acta Materialia - Volume 58, Issue 7, April 2010, Pages 2442–2451