摘要
Positron lifetime results showed that there are two kinds of interfacial defects in the nanocrystalline alloys obtained by crystallization of the amorphous alloy, namely free-volume-sized and nanovoid-sized defects. The former is smaller than a monovacancy; the latter is of the size of several monovacancies and is usually situated at the intersections of several interfaces. In comparison with the nanovoid-sized defect, though the free-volume-sized defect is a shallow trapping potential, the quantity can be as much as 90% of all defects. It should be noted that nanovoids can change remarkably in both size and concentration with grain growth. So it is imaginable that this type of defect will exert a great influence on the interfacial structure and properties of nanocrystalline materials. So far, reports in this aspect are still meager.
