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Final‐Stage Densification During Pressure‐Sintering of CoO
Author(s) -
URICK PAUL A.,
NOTIS MICHAEL R.
Publication year - 1973
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.1151-2916.1973.tb12418.x
Subject(s) - materials science , creep , sintering , grain boundary diffusion coefficient , diffusion , lattice diffusion coefficient , grain boundary , thermodynamics , stress (linguistics) , tracer , composite material , effective diffusion coefficient , microstructure , medicine , linguistics , physics , philosophy , radiology , magnetic resonance imaging , nuclear physics
The final‐stage densification behavior of high‐purity pressure‐sintered CoO was studied as a function of temperature (950° to 1100°C) and applied pressure (6,000 to 11,750 psi). The stress‐temperature regime during densification indicated that Nabarro‐Herring diffusional creep should be the predominant deformation mechanism, whereas the experimental creep rate response as a function of stress level indicated the presence of a threshold stress. Interpretation of the data through use of a diffusion model for hot‐pressing yields effective diffusion coefficients which agree well with those obtained by tracer techniques for Co self‐diffusion. Activation energies of 33,460 and 39,600 cal/mol were obtained at relative densities of 0.90 and 0.95, respectively. On the basis of the observed densification kinetics and microscopic examination, it was concluded that densification is controlled by cation diffusion through the lattice and that oxygen diffusion is enhanced near the grain boundary.