GNT: Graphene and Nanotubes
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PhD defence on carbon nanotube growth mechanisms
Thesis of Université Paris XI
CEA de Saclay SPAM/LFP Group "édifice nanométrique"
Celia Castro
will defend her PhD works in Material Chemistry
on Thursday 17 December at 14h30 at Neurospin in amphithéâtre J. Talairach
Growth mechanisms of aligned carbon nanotubes :
nanotube-catalyst relations
Abstract
The field of nanoscience which is developing intensively, carbon nanotubes (CNTs)
are attracting strong interest because of their particular properties resulting of their special
structure. To control and optimize manufacturing processes, it is important to understand the
Francis Perrin, allows the continuous and rapid growth of aligned and clean Multi-Walled
CNT by the simultaneous injection of liquid carbonaceous precursor (toluene) and catalyst
precursor (metallocene).
Our main objective was to understand how the chemical transformation of metallocene
into catalyst particles, what is the exact nature of catalyst particles, what are the parameters
controlling their activity and finally how the catalytic species progress to enable the growth of
CNTs. From an experimental approach involving a systematic study of products all along the
furnace for different thermodynamic (flow and cooling step) and chemical (concentration of
precursors, introduction of reducing gas) conditions, we demonstrate a homogeneous
nucleation of particles of iron in the gas phase occurring before the isothermal area followed
by their gradual deposition along the furnace. The catalytic particles located at the base of the
aligned nanotube carpet are semi-molten iron saturated with carbon that is fed continuously
by the catalytic species which diffuse all along the CNT carpet to its base.
The field of nanoscience which is developing intensively, carbon nanotubes (CNTs)
are attracting strong interest because of their particular properties resulting of their special
structure. To control and optimize manufacturing processes, it is important to understand the
mechanisms governing their growth. Among the synthesis methods of CNTs, the aerosolassisted
CCVD (Catalyst Chemical Vapor Deposition) process, developed in LaboratoireFrancis Perrin, allows the continuous and rapid growth of aligned and clean Multi-Walled
CNT by the simultaneous injection of liquid carbonaceous precursor (toluene) and catalyst
precursor (metallocene).
Our main objective was to understand how the chemical transformation of metallocene
into catalyst particles, what is the exact nature of catalyst particles, what are the parameters
controlling their activity and finally how the catalytic species progress to enable the growth of
CNTs. From an experimental approach involving a systematic study of products all along the
furnace for different thermodynamic (flow and cooling step) and chemical (concentration of
precursors, introduction of reducing gas) conditions, we demonstrate a homogeneous
nucleation of particles of iron in the gas phase occurring before the isothermal area followed
by their gradual deposition along the furnace. The catalytic particles located at the base of the
aligned nanotube carpet are semi-molten iron saturated with carbon that is fed continuously
by the catalytic species which diffuse all along the CNT carpet to its base.
8:05am, 2/12/09