57 Fe transmission Mössbauer spectroscopy (TMS) and back scattered conversion electron Mössbauer spectroscopy (CEMS) measurements were carried out on Fe-filled multiwalled carbon nanotubes (Fe-MWCNTs) grown by chemical vapor deposition with ferrocene as precursor. Samples of Fe-MWCNTs material deposited on the inner wall of the quartz tube reactor and samples of aligned Fe-MWCNTs grown perpendicularly to the oxidized Si substrate were characterised by the TMS method. The data show that Fe phases encapsulated within the carbon nanotubes comprise ␣-Fe, ␥-Fe, and Fe 3 C in different percentage ratio depending on the sample preparation. These results are in a good accordance with the previously measured magnetic characteristics and with the structural data found by x-ray diffraction as well by selected area electron diffraction methods and allow a new complementary characterization of the Fe(Fe-alloy)-MWCNT systems. The CEMS method applied for the characterization of metal containing MWCNTs reveals that close to the top surface of the aligned Fe-MWCNTs samples only the ␥-Fe phase is found. This technique shows an additional potential for further investigation of the spatial distribution of the crystalline phases in the depth of aligned Fe-MWCNT samples.

A detailed study of the interaction of methanol with an iron-molybdenum oxide catalyst has been performed by in situ 57-Fe Mo ¨ssbauer spectroscopy. The main experiments have been carried out with a methanol-air mixture (3.5, 5.5, and 10.2 vol % CH 3 OH) in the temperature range 473-673 K. The initial interaction with methanol has been found to lead to the appearance and accumulation of lattice vacancies and formation of nonstoichiometric iron(III) molybdate. The amount of vacancies is a function of temperature and of the redox potential of the reaction mixture. The initial product of the reduction with a CH 3 OH/Ar gas mixture is again iron(III) molybdate with anion vacancies. Prolonged reduction at T ) 573 K results in the formation of β-FeMoO 4 . The data elucidate the peculiarities of the catalyst stability and some of the reactions for its deactivation.

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