Defects in nanocrystalline Pd and submicrocrystalline Cu by EXAFS

EXAFS spectra of nanocrystalline (nc) Pd and submicrocrystalline (smc) Cu a re presented, nc-Pd samples with a grain size of 15 nm have been prepared b y gas condensation technique, and submicrocrystalline Cu samples with a gra in size of 100 nm have been prepared by severe plastic deformation. EXAFS m easurements of powder nc-Pd samples with optimal thickness were performed u sing synchrotron radiation, and rolled smc-Cu by laboratory EXAFS spectrome ter, As a result of mathematical treatment, atomic density distribution fun ctions have been determined. The results obtained show that in comparison with coarse-grained crystallin e standards the decrease of the first neighbor coordination numbers N is 5- 6% for nc-Pd, and 3% for smc-Cu. For interpretation of the obtained results , the numerical simulation of the atomic structure with modelling to cut of f the bond lengths for grain boundary and to create vacancies during sample preparation is performed. (C) 2000 Elsevier Science B.V. All rights reserv ed.