Internal friction of nanocrystalline silver

Low frequency internal friction and shear modulus of nanocrystalline silver were measured by both force vibration and free decay methods. The specimen s were prepared by inert gas condensation and in situ warm compaction. The average grain size of the specimens was 52 nm. An internal friction peak wa s observed around 450 K. The activation energy of the peak was measured to be 0.88 (+/-0.1) eV, in agreement with that of grain boundary diffusion in silver. The internal friction peak is suggested to be associated with grain boundary relaxation.