Papers by Keyword: Hollow Nanoparticle

Abstract: . In intermetallic compounds, random vacancy motion is not possible as it would disrupt the equilibrium ordered arrangement of atoms on lattice sites. In view of this limitation, various atomistic models have been proposed, which allow atom-vacancy exchanges to take place without concomitant long range disordering. For a L12 -type A3B structure, the major element A diffuses faster than the minor element B. The trend is attributed to the different diffusing paths; A atoms can diffuse through site exchanges with a neighbouring vacancy on its own sublattice, while the jump of a B atom to a neighbouring site always creates wrong bonds. For L10-type structures such as γ-TiAl, significant diffusion anisotropy is observed; Ti atoms diffuse on the Ti sublattice, while Al atoms also diffuse on the Ti sublattice. The formation of hollow metal oxide nanoparticles through the oxidation process has been studied by transmission electron microscopy for Cu, Zn, Al, Pb and Ni. The hollow structure is obtained as a result of vacancy aggregation, resulting from the rapid outward diffusion of metal ions through the oxide layer during the oxidation process. This suggests the occurrence of two different diffusion processes in the formation of hollow oxides.

Abstract: The formation of hollow metal oxide nanoparticles through oxidation process has been studied by transmission electron microscopy for Cu, Zn, Al, Pb and Ni in order to clarify the detailed formation mechanism of hollow oxide nanoparticles and their governing factors. For Cu, Zn, Al and Ni nanoparticles, hollow oxide nanoparticles are obtained as a result of vacancy aggregation in the oxidation processes. These results arise from faster outward diffusion of metal ions through the oxide layer in the oxidation processes. On the other hand, Pb nanoparticles turn to solid PbO, because the diffusivity difference DPb < DO in PbO leads to no formation of vacancy clusters.

Abstract: The influence of nonequilibrium vacancy distribution, generated by a difference of intrinsic fluxes of components under limited efficiency of vacancy sinks/sources, on various diffusion processes, is analyzed. Interdiffusion, reactive diffusion, reactive phase growth under electric current, spinodal decomposition, collapse of compound nanoshells, ripening are considered.