ISSN:
1551-2916
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
The microstructure of transition aluminas obtained via the dehydration of boehmite has been characterized by using transmission electron microscopy (TEM). The presence of γ-, δ-, and θ-aluminas was identified by using selected-area electron diffraction. Modifications that resulted from the reordering of aluminum vacancies on octahedral sites in a cubic close-packed oxygen network have been detected and analyzed by using high-resolution transmission electron microscopy (HRTEM) combined with image simulations. A good correspondence of the observed and calculated images confirmed the ordering of vacant octahedral sites located on {011} and {011} planes that formed a zigzag configuration along the 〈010〉 direction. Two more arrangements of empty octahedral sites, but now concentrated on {001} planes, have been determined in the sintered powder-gel agglomerates. Structure analysis suggested that the modifications are all associated with the rearrangement of vacant sites during the phase transformation from gamma-alumina to δ-alumina, and further to theta-alumina, and may be driven by configuration entropy minimization.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1151-2916.1998.tb02527.x
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