Epitaxial NiO hillocks on truncated octahedral nanoparticles of passivatedNi

Epitaxial NiO hillocks on the {111} and {001} facets of truncated octahedra l nanoparticles of Ni have been directly observed by high-resolution transm ission electron microscopy. These nanometer hillocks form a rough shell enc losing the Ni nanoparticle. The epitaxial relationships of NiO on nanoparti cles of Ni are the same as those of NiO on bulk Ni {111} and {001} surfaces . The formation of hillocks is related to the relaxation of the compressive stress in NiO arising from the very large lattice mismatch between NiO and Ni. The compressively stressed epitaxial NiO shell provides effective prot ection to the nanoparticles of Ni against further oxidation. (C) 2001 Ameri can Institute of Physics.