Ultra-Fine Spherical Particles of γ-Alumina: Electron Microscopy of Crystal Structure and Surface Morphology at Atomic Resolution

The γ-alumina particles are produced by a dry method developed by the author. Three types of structures, tentatively called δ' (orthorhombic; Pmn21; a=8.2, b=16.4, c=11.8 Å), θ1 (monoclinic; B2/b; a=11.1, b=12.1, c=17.7 Å, β=103° ) and θ2 (monoclinic, B2/m; a=11.1, b=12.1, c=2.9 Å, β=103°) are found. The particle is spherical but facetted with flat {111} and {100} surfaces; {110} surfaces consist of many small {111} facets. As a new approach to ceramics and catalysis research, surface morphology of a neck portion of two coalescing particles, and clusters of Rh6(CO)16 impregnated on the particles are demonstrated for the first time.