XRD and HREM studies of nanocrystalline Cu and Pd.

摘要

Consolidated powders of nanocrystalline Cu and Pd have been studied by x-ray diffraction (XRD) and high resolution electron microscopy (HREM) as part of an investigation of the mechanical behavior of nanocrystalline pure metals. XRD line broadening measurements were made to estimate grain size, qualitative grain size distribution and average long range strains in a number of samples. Mean grain sizes range from 4--60 nm and have qualitatively narrow grain size distributions. Long range lattice strains are of the order of 0.2--3% in consolidated samples. These strains apparently persist and even increase in Cu samples after annealing at 0.35 Tm (498K) for 2h, accompanied by an apparent increase in grain size of (ge)2x. Grain size, grain size distribution width and internal strains vary somewhat among samples produced under apparently identical processing conditions. HREM studies show that twins, stacking faults and low-index facets are abundant in as-consolidated nanocrystalline Cu samples. Methodology, results, and analysis of XRD and HREM experiments are presented. 17 refs., 2 figs., 2 tabs.