Interface structures in nanocrystalline materials

Grain boundary and triple junction structures in nanocrystalline palladium & titanium thin films and in nanocrystalline thorium dioxide powder and sintered pellets have been studied. Amorphous packets with bright contrast are seen in many of the grain boundary junctions and are considered to form as a result of the relaxation of triple junction disclinations. The varying degrees of relaxation of disclinations in NC's lead to a variety of grain boundary structures and are also responsible for the random variation in its lattice parameter in the different nanocrystalline grains. Nanocrystalline state has been suggested to be a desirable microstructural criterion for solid state amorphization. Further it is: to be pointed out that no special features which could be attributed to the nature of bonding in the two materials were seen in this study. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.