Abstract The activation energies,the preexponential factors and the corresponding self-diffusion coefficients for a nanocrystalline material in various diffusion conditions were calculated. Based on comparison of the calculated self-diffusions with the experimentally measured one, it is suggested that the diffusion model in nanocrystals is a complex one with the combination of the boundary diffusion by the vacancy mechanism and the internal surface diffusion of atoms along internal surfaces of boundary voids. CHEN Da, professor, Department of Materials Science, Shanghai Jiaotong University, Shanghai 200030
