Small angle neutron scattering from nanocrystalline palladium as a function of annealing

Small angle neutron scattering (SANS) has been measured from samples of nanocrystalline palladium (n-Pd) in the as-compacted state or annealed for 100, 300, or 800 deg C as part of a study of mechanical properties and their correlation with changes in internal structure. Analysis of the scattering data shows the presence of at least three classes of scatters. On the basis that grain boundaries in fcc nanocrystalline metals are found to be similar to grain boundaries in coarse-grained metals, and that the latter have been shown not to contribute measureably to SANS in coarse-grained samples, it was decided to see if other types of defects could account for the observed scattering. The total volume fraction of scatters calculated from the invariant coincides with the value obtained by density measurement if it is assumed that, in both cases, voids are the primary defects involved.