Mechanical properties of nanocrystalline nanoporous platinum

The mechanical behavior of nanocrystalline, nanoporous platinum (NP Pt) is investigated using a combination of experimental measurements and molecular dynamics (MD) simulations. The NP Pt considered in this work is characterized by an hierarchical internal structure with comparable characteristic strut thickness t and grain size D. The hardness of NP Pt with typical strut thickness t= 2-10 nm is measured by nanoindentation experiments to be H-f =0.2-1.3 GPa. Using standard scaling assumptions, a characteristic individual strut strength can be estimated from the hardness measurements as sigma(s) = 0.3-2.5 GPa. These values compare reasonably well with the ones obtained from MD simulations of isolated struts, represented as nanowires with crystalline structure similar to the experimentally observed NP Pt. The findings suggest that for nanocrystalline NP structures with t D the strength of individual struts decreases gradually with decreasing strut size, so that the overall mechanical strength remains relatively high. The simulations provide insight into the underlying deformation mechanisms and behavior within the struts during mechanical loading. In particular, as struts decrease in size, they accommodate strain primarily through grain boundary plasticity, such as sliding. However, as strut size increases, dislocations begin to play a larger role in accommodating strain. (c) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.