Explosive compaction of nanocrystalline alumina powder.

Nano ceramics have special properties: they are superhard, frictionless and have very fine pores. These special properties are shown only with grain sizes below 100 nanometers (nm). It is very difficult to retain this small grain size during conventional consolidation of powders and subsequent sinter processes. A key to solve this problem could be the explosive consolidation with shock pressures up to similar to 30 GPa. Experiments with nano Al2O3 - powder which was produced by the "exploding wire technique" with a mean crystallite size of similar to 60 nm showed that almost 100% of crytalline density is achievable by explosive consolidation. By SEM - and XRD - Analysis is found that phase transitions occur and as a result of high shock wave treatment lattice distortion in the material decreases and subgrain size increases.