Three-dimensional atomic scale analysis of nanostructured materials

The 3-dimensional atom probe (3DAP) has been used to provide atomic-scale m icrocharacterisation of a number of nanostructured materials. Grain boundar y segregation has been investigated in electrodeposited nanocrystalline nic kel and Ni-P. In the nanocrystalline nickel, there was no observable grain boundary segregation in the as-deposited condition. After annealing, carbon and sulphur contamination was found at the boundary of an abnormally-grown grain. In the as-deposited Ni-P alloy, only limited grain boundary segrega tion of P is seen, but annealing produces significant segregation and the f ormation of Ni3P precipitates at grain boundaries. The phase chemistry in a melt-spun amorphous Fe-Si-Cu-Nb-B-Al (FINEMET-type) alloy has also been st udied, and the hetereogeneous nucleation of Fe-Si nanocrystals at Cu precip itates shown conclusively. It is found that at early stages of crystallisat ion, there is only limited partitioning of the Si between the nanocrystals and the amorphous matrix. Atom probe studies of thin layered films have his torically been limited by specimen preparation problems, but recent advance s have now yielded data on metallic multilayer films. This has allowed atom ic-scale measurements of interface chemistry in these films for the first t ime. (C) 2001 Elsevier Science Ltd. All rights reserved.