Anelasticity study on interfaces of nanocrystalline Au and nanoporous Au

The grain boundary region and pore play an essential role in nanostructured materials. In the present study, nanoporous (np-) Au prepared by dealloying (DA np-Au) is studied by means of the anelasticity measurement referring to the nanocrystalline (n-) Au prepared by the gas-deposition method (GD n-Au). In GD n-Au>0.99 (the subscript, >0.99, denotes the relative density of the specimen referring to the bulk density), the linear increase in the internal friction above 200 K (Q>200 K−1) and a broad peak at about 100 K (PL) are observed. In GD n-Au0.81 containing nanopores, broad peaks at about 220 K (PH1) and 260 K (PH2) as well as PL and Q>200 K−1 are observed. In DA np-Au0.4, PL, PH2 and no Q>200 K−1 are observed. Densification of DA np-Au0.4 by pressing causes a significant increase in both PH1 and PH2, and annealing at 360 K cancels the effect of pressing. These results are discussed in the light of the characteristic grain boundary properties in nanostructured materials.