Structure of nanometer-sized polycrystalline iron investigated by positron lifetime spectroscopy

Positron Annihilation in Magnetite Nanopowders Prepared by Co-Precipitation Method

“…Alternatively, it is possible that not large drop observed for the τ 1 component is caused by a small reducing of vacancy cluster volumes. The first component, τ 1 , is related to positrons trapped in free volumes in the region of grain boundaries (GB) [14]. In support of this interpretation the results of calculations carried out in [15] can also be cited.…”

“…In support of this interpretation the results of calculations carried out in [15] can also be cited. The second component corresponds to positrons trapped in nanovoids located in triple points [14]. Its intensity I 2 monotonically decreases from about 82% for nanoparticles of mean size 6.6 nm to 72% for that of 11.8 nm.…”

Characterization of densified fully stabilized nanometric zirconia by positron annihilation spectroscopy

“…99, 024313 ͑2006͒ possible. Schaefer et al 25 reported that crystal interfaces are the primary positron traps in nanocrystalline metals. However, in ionic materials the structure of the grain boundary can be quite complex.…”

Oxidation Resistance of Nanocrystalline Alloys

“…Similarly, EXFAS investigation of nanocrystalline Fe and Pd indicated a large reduction in the atomic coordination number, supporting the idea of a very disordered structure at the interfaces [52][53][54][55][56]. Positron-lifetime spectroscopy measurements showed a large density of vacancy-like defects in grain boundaries and relatively large free volume at the triple points arising from misorientationinduced atomic instability of these sites [57]. Elastic relaxation of the interfaces occurred with a very different parameter than conventional coarse grain size polycrystalline materials.…”