MODELING OF NANOPHASE MATERIALS

Nanophase or nanocrystalline materials are polycrystals in which the grain size ranges typically from a few nanometers to a few tens of nanometers. Under these conditions the volume occupied by the grain boundary region may represent 50% or more of the total material volume. The unique properties of the grain boundary then have a significant influence on the bulk behaviour of the material. A computer model has been developed which treats separately the crystalline and grain boundary regions. By utilizing measured data for nanophase palladium, the model has been used to determine the effective elastic properties of the grain boundary region for that material. The model demonstrates that the Young's modulus varies with grain size in a nonlinear fashion that is not adequately represented by existing theoretical models. With the aid of a model of this type, it is then a relatively simple matter to investigate features such as sensitivity to changes in the grain aspect ratio and the result of adding further phases to form more complex nanocomposite materials.