Carbon nanotube bags: catalytic formation, physical properties, two-dimensional alignment and geometric structuring of densely filled carbon tubes.
In: Chemistry--A European Journal, Jg. 7 (2001) ; Nr. 13, S. 2888-2895
Zeitschriftenaufsatz / Fach: Chemie
The catalytic CVD synthesis, using propyne as carbon precursor and Fe(NO3)3 as catalyst precursor inside porous alumina, gives carbon nanotube (CNT) bags in a well-arranged two-dimensional order. The tubes have the morphol. of bags or fibers, since they are completely filled with smaller helicoidal CNTs. This morphol. has so far not been reported for CNTs. Owing to the dense filling of the outer mother CNTs with small helicoidal CNTs, the resulting CNT fibers appear to be stiff and show no sign of inflation, as sometimes obsd. with hollow CNTs. The fiber morphol. was obsd. by raster electron microscopy (REM), transmission electron microscopy (TEM), and at. force microscopy (AFM). The carbon material is graphitic as deduced from spectroscopic studies (X-ray diffraction, Raman and electron energy loss spectroscopy (EELS)). From Mossbauer studies, the presence of two different oxidn. states (Fe0 and FeIII) of the catalyst is proven. Geometric structuring of the template by two different methods has been studied. Inkjet catalyst printing shows that the tubes can be arranged in defined areas by a simple and easily applied technique. Laser-structuring creates grooves of nanotube fibers embedded in the alumina host. This allows the formation of defined architectures in the mm range. Results on hydrogen absorption and field emission properties of the CNT fibers are reported.