Nanodusting of RENi5 intermetallic grains through nucleation and growth of carbon nanotubes (RE = Rare-Earth)

The kinetics of the methane decomposition at NdNi5 catalyst powder has been studied by means of the thermogravimetry in the temperature range from 475 to 525 degrees C. The catalytic reaction yields the dusting of the catalyst particles, the size of which is in the domain of microns, in nanocrystals, which are encapsulated at one of the ends of the multiwalled carbon nanotubes with these last being the only carbon-containing byproduct of the reaction. Microscopy and spectroscopic techniques have been employed to characterize both the catalyst nanocrystals and multiwalled carbon nanotubes. The experimental kinetics exhibit an induction period, which is temperature dependent, before the steady state is reached. The behavior of these curves has been described by a kinetic model, the physical basis of which lays on the interplay between the nucleation process of the carbon nanotubes and the detachment of the intermetallic nanosingle crystal from the catalyst grain with these being the locus of the catalytic process.