NMR Observation of Melting and Diffusion in Al/Al-Oxide Nanophase Composites

P. Apte and B. H. Suits
High temperature 27Al NMR measurements of Al/Al-Oxide nanophase composites produced by consolidation of nanoscale Al particles which have been passivated by exposure to air are reported. The Al metal is observed to melt at the same temperature in all the samples independent of grain size and without a change in the shape of the sample. The results here confirm previous thermal measurements which show that the Al metal melts without apparent grain growth in these materials. On the other hand, the temperature for the onset of rapid atomic diffusion, as estimated from NMR line widths, shows a significant sample dependence. Heated samples exhibit a factor of five increase in hardness and yet remain electrically conducting.

NanoStructured Materials 10, 917-922 (1998).

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