UBC Theses and Dissertations
Creep of compacts of colloidal boehmite (A100H) during dehydroxylation St-Jacques, Robert Gustave
A compressive creep study of cold compacted colloidal boehmite has been carried out during the dehydroxylation reaction. The creep tests were made as a function of temperature, applied stress and the relative density of the cold compact. The activation energy for creep has been found to be 9.1 ± 1.5 Kcal/mole. The total creep rate was due to the stress associated with the neck formation at the points of contact and the applied stress. The creep rate is proportional to the applied stress. The final form of the total creep rate equation is ė =[0.144 exp ( formula omitted )+2.2x10ˉ⁷σ] sec ˉ¹. Electron photomicrographs of fractured surfaces of deformed specimens revealed the presence of contact points in the aligned fibers, confirming the existence of the driving force for shrinkage. Equations relating the change in length and the strength of a compact with time have been tested with the experimental data, which indicated that the rate controlling mechanism may be volume diffusion for the creep process.
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