The evolution of iron in over-exchanged Fe/ZSM5 prepared via chemical vapor deposition of FeCl 3 was studied at each stage of the synthesis. Different characterization techniques (EXAFS, HR-XANES, 57 Fe Mössbauer spectroscopy, 27 Al NMR, EELS, HR-TEM, XRD, N 2 physisorption, and FTIR spectroscopy) were applied in order to correlate the changes occurring in the local environment of the Fe atoms with migration and aggregation phenomena of iron at micro-and macroscopic scale. Mononuclear isolated Fe-species are formed upon FeCl 3 sublimation, which are transformed into binuclear Fe-complexes during washing. During calcination, iron detached from the Brønsted sites migrates to the external surface of the zeolite, finally leading to significant agglomeration. Nevertheless, agglomeration of Fe can be strongly suppressed by adequately tuning the conditions of the calcination.  2002 Elsevier Science (USA). All rights reserved.

In this paper, the presence of a considerable number of Co (3-4 nm) and Pd (1-4 nm) particles in the inner tube (4-9 nm inner diameter) of carbon nanofibers is demonstrated with TEM and XPS. Oxidation of freshly grown fibers in nitric acid resulted in opening of the inner tube of the fibers and in creating adsorption sites on the internal and external surface of the fibers needed for anchoring of the metal precursors. It is demonstrated that analysis with TEM tilt series is a very powerful tool to locate the actual position of the metal particles, i.e. on the external or internal surface of the fibers. The fraction of metal present in the inner core of the fibers varied from 10-15% for Pd to 28-34% for Co, depending on the synthesis method.