Nanoporous Au foams: variation of effective Young's modulus with ligament size

This work focuses on the effects of ligament size on the mechanical behavior of NP Au foams. NP Au structures with ligament diameter between 5 and 200 nm have been fabricated by selective Ag dissolution from Ag70Au30alloys prepared by mechanical alloying and subsequent annealing. Nanoindentation experiments indicate that the effective Young's modulus increases as the ligament thickness decreases. The stiffening of NP Au foams with fine ligaments is ascribed to size effects connected with surface stress states. It is shown that a phenomenological model accounting for disorder and surface contributions to Young's modulus correctly predicts the observed behavior.