Nanodiamonds intercalated with metals: structure and diamond-graphite phase transitions

We used X-ray diffraction, small-angle X-ray scattering, and scanning electron microscopy (SEM) to study the diamond graphite phase transition in detonation nanodiamond (ND) intercalated with Cu, Ni, Co and Fe for the first time. The study has been made before and after annealing in hydrogen and argon. The SEM data obtained support the idea of the hierarchic structure of ND with a size of primary cluster of about 5 nm. There are several levels of aggregation of primary clusters. We have shown that all the samples of ND are surface fractals. It means the structure can be characterized by three parameters: coherent scattering region (CSR), the size of scatterer A and fractal dimensionality D. The transition degree was identified by X-ray diffractometry from the peaks of bulk nanographite. Scanning electron microscopy was used to determine the sizes of metallic and carbon aggregates. We have found from the CRS, A and D data that the intercalation does not practically change the diamond core at annealing in hydrogen and its size is similar to that reported earlier. However the changes of the scatterer size and fractal dimensionality depend on type of intercalated metals in hydrogen annealing. (C) 2004 Elsevier B.V All rights reserved.