Interface structures in nanocrystalline materials

Grain boundary and triple junction structures in nanocrystalline palladium & titanium thin films and in nanocrystalline thorium dioxide powder and sin tered 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 d egrees of relaxation of disclinations in NC's lead to a variety of grain bo undary 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 so lid state amorphization. Further it is: to be pointed out that no special f eatures which could be attributed to the nature of bonding in the two mater ials were seen in this study. (C) 2001 Acta Materialia Inc. Published by El sevier Science Ltd. All rights reserved.