H2O2 was employed to pre-oxidize the Zn nano- and microparticles and then oxide films with different thickness coated on the surface of the particles were achieved. TG-DSC examinations were carried out for the Zn nano- and microparticles treated with and without H2O2 pre-oxidization as well as the SEM technologies for the corresponding morphologies of the thermally oxidized products. There are tremendous differences on the thermal behaviors and the morphologies between the nano- and microparticles, namely, the treatment with H2O2 pre-oxidization brought much effect on the Zn nanopartides but little on the Zn microparticles for the thermal behaviors and resulted in ZnO chestnut bur-like particles, needles, and pellets morphologies for nanoparticles, and only chestnut bur-like particles for microparticles after thermal oxidation. The models for vapor-solid (VS) growth mechanism resulted in ZnO nanostructures growth were presented. (c) 2006 Elsevier B.V. All rights reserved.