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

Abstract

The γ-alumina particles are produced by a dry method developed by the author. Three types of structures, tentatively called δ' (orthorhombic; Pmn2 1 ; a =8.2, b =16.4, c =11.8 Å), θ 1 (monoclinic; B2/b; a =11.1, b =12.1, c =17.7 Å, β=103° ) and θ 2 (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 Rh 6 (CO) 16 impregnated on the particles are demonstrated for the first time.