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Diffusion of 57 Co in Surface Layers of Nickel Oxide and Alumina
Author(s) -
Macey Edward P.,
Stubican Vladimir S.
Publication year - 1993
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1993.tb03827.x
Subject(s) - diffusion , activation energy , non blocking i/o , arrhenius equation , arrhenius plot , ionic bonding , atmospheric temperature range , surface diffusion , analytical chemistry (journal) , thermal diffusivity , nickel oxide , nickel , effective diffusion coefficient , chemistry , grain boundary diffusion coefficient , materials science , ion , thermodynamics , crystallography , adsorption , grain boundary , microstructure , medicine , biochemistry , physics , organic chemistry , chromatography , radiology , magnetic resonance imaging , catalysis
Diffusion of 57 Co isotope on NiO (110) and AI 2 O 3 (0001) surfaces was investigated by using the edge source method. The surface diffusion parameter α D ,Δ, where α is the segregation factor, D , the surface diffusion coefficient, and Δ the thickness of the high‐diffusivity layer, was determined for the temperature range 750°–1200°C. For calculation of experimental results, the Whipple solution was used. The Arrhenius plot shows a break at ∽900°C for the surface diffusion of 57 Co isotope on AI 2 O 3 (0001) plane. Above this temperature, vapor transport seems to be the overriding diffusion mechanism. Below this temperature, ionic transport predominates. The apparent activation energy for the ionic transport was calculated to be 120 ± 12 kj/mol. Ionic transport predominated in the surface diffusion of 57 Co on NiO over the entire investigated temperature range. This can be explained by the weak bond between Co‐vapor species and the NiO surface. The results obtained suggest that the surface diffusion of Co 2+ ion on NiO at 750°C is ∼7 orders and at 1200°C ∼5 orders of magnitude faster than volume diffusion. Activation energies are 139 and 227 kJ/mol, for surface and volume diffusion, respectively.