DISTINGUISHING NANOCRYSTALLINE SOLIDS FROM FINE-PARTICLE ENSEMBLES USING MOSSBAUER-SPECTROSCOPY

Nanocrystalline solids, formed by compacting fine powders, have been p roclaimed to possess a new structure. Specific characteristics have be en reported from Mossbauer studies, and these appear to confirm and re inforce a model of crystalline cores isolated by disordered, low-densi ty grain boundaries. In measurements of three compacted samples, we we re unable to reproduce the characteristics expected. Reasons are sugge sted as to why the results differ between similarly-prepared samples. It is pertinent to enquire whether any of the previously reported Moss bauer characteristics of fine-particle compacts require a new structur al model, or whether all the results can be simply understood in terms of particle agglomerates. Reference to the literature reveals that th ere is no distinction.