Mössbauer transmission and back-scattered conversion electron study of Fe nanowires encapsulated in multi-walled carbon nanotubes

Fe-57 transmission Mossbauer spectroscopy (TMS) and back scattered conversion electron Mossbauer 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 alpha-Fe, gamma-Fe, and Fe3C 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 gamma-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. (C) 2004 American Institute of Physics.