X-ray absorption study in nanocrystalline Fe, Co, Ni and Cu metallic powders

The X-ray absorption was investigated for nanocrystalline, bulk, and oxides of Fe, Co, Ni, and Ctr. From the k edge spectrum? measurements, we have fo und that the band lengths in both nanocrystalline and bulk metallic powders we studied are roughly the same. However the coordination number in nanocr ystalline samples for Fe and Co is 8.6 and 7.4 respectively, which is a lit tle bit larger than that of bulk samples, and it is 11.7 and 11.2 for Ni an d Ctr, which is a little bit smaller than that of bulk samples. Difference between their crystal structure is used to explain our experimental results . The mean-square disorder factor of nanocrystalline samples is always larg er than that of the bulk samples. This indicates that both ordered and diso rdered crystalline phases may exist in nanocrystalline metallic powders. (C ) 1999 Acta Metallurgica Inc.