The radiolysis of boehmite (aluminum oxyhydroxide) and gibbsite (aluminum hydroxide) at various phases along their thermal degradation to alumina (aluminum oxide) has been investigated using a variety of analytical techniques. Breakup of the surface is observed due to water loss and leads to the development of pits rather than a delamination of the layered structure. Radiolysis of boehmite and gibbsite leads to the production of H2 with a yield in the former considerably greater than in the latter. With increasing thermal dehydration of these compounds, the yield of H2 increases with a maximum very near to the point where the major transition to alumina occurs. The yield of H2 decreases beyond this transition as the compounds more completely convert to alumina. The presences of adsorbed water increases the yield of H2 while the production of O2 is much less than expected from the stoichiometry. Electron paramagnetic resonance spectroscopy show the presence of H atoms in boehmite but not in gibbsite. H atoms formed in the interstitial regions are believed to be the precursor to H2, with the main reactions occurring at the material surface. Oxygen seems to be captured within the matrix leading to the formation of oxygen centered radicals.

Thermal and radiolytic degradation of boehmite and gibbsite

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