Tomography and High-Resolution Electron Microscopy Study of Surfaces and Porosity in a Plate-like γ-Al₂O₃

Abstract

Morphological and surface characteristics of γ-Al 2 O 3 are topics of high relevance in the field of catalysis. Using tomography and high-resolution transmission electron microscopy (TEM) imaging, we have studied the surface characteristics of a model γ-Al 2 O 3 synthesized in the shape of platelets and macroscopically defined by (110) Al 2 O 3 and (111) Al 2 O 3 surface facets. We show that the dominant (110) Al 2 O 3 surface of the synthesized γ-Al 2 O 3 is not atomically flat but undergoes a significant reconstruction, forming nanoscale (111) Al 2 O 3 facets. In addition to high-resolution imaging, tomographic analysis was carried out, enabling an examination of the pores/voids, which were found to be mostly enclosed within the bulk and inaccessible to gases or solvents carrying precursors for metal particles. Tomographic analysis shows that the surfaces of the pores are defined exclusively by (100) Al 2 O 3 and (111) Al 2 O 3 facets. The importance of these findings is discussed in the context of relative surface energies of low index surfaces and ethanol desorption characteristics.