The development of porous microstructures during the dehydration of boehmite

used to follow the low-temperature dehydration of boehmite, and show that a coherent skeleton of y-AlzO 3 with a porous texture is produced. For material fired in air the development ofa number of pore systems i described. Of these the most important, as far as the dehydration process is concerned, is a lamellar pore system parallel to (ooI) ~ and having a regular spacing of the order of 35-4 o/~. A much faster dehydration process is induced by exposure to the electron beam and results in the formation of a more randomly oriented pore structure. The observed microstrueture and the calculated internal surface area are compared with the results of previous adsorption studies. T H E ultimate product of thermal treatment of the hydroxides and oxyhydroxides of aluminium is the thermodynamically stable form of aluminium oxide, ~-A1203 (corundum). However, with the exception of diaspore, dehydration of the various species of aluminium hydroxide produces a series of metastable intermediate aluminas before final conversion to ~-A1203. The identity of the transition alumina species found in a particular dehydration sequence is characteristic of the starting material. In the case of boehmite the sequence is (Stumpf et al., I95O; Lippens and d