Environmental Engineering Reference
In-Depth Information
treatment in a catalytically grown carbon nanotube sample. They have examined
growth of CNTs on a porous alumina template in order to improve the selectivity
and uniformity of CNTs. They have fabricated well ordered, nanosized pores on a
Si substrate using an anodic oxidation method. Recently developed a simple pro-
cess for selective removal of carbon from single-walled carbon nanotube samples
based on a mild oxidation by carbon dioxide. Some nanotubes were found to be
partially filled with a solid material (probably metallic iron) that seems to catalyze
the nanotube growth. Some regions of the deposit also revealed the presence of
nanoparticles. The present experimental conditions should be suitable to produce
locally structured deposits of carbon nanotubes for various applications. Recently
synthesized straight and bamboo like carbon nanotubes in a methane diffusion
flame using a Ni-Cr-Fe wire as a substrate. The catalyst particles were nickel
and iron oxides formed on the wire surface inside the flame. The carbon growth
over the catalysts has been followed gravimetrically in situ. The reaction was
stopped after different pulse numbers in an attempt to control both the diameters
and the lengths of the carbon nanotubes, which were characterized by transmis-
sion electron microscopy (TEM). Recently prepared two kinds of catalytic lay-
ers onto n-typed silicon substrate nickel by sputtering and iron (III) nitrate metal
oxide by spin coating. For iron (III) nitrate metal oxide 0.5 mol of ferric nitrate
non-anhydrate(Fe
2
(NO
3
)
2
.9H
2
O] ethanol solution was coated onto tubes on both
Ni and iron (III) nitrate metal oxide layers by the HFPECVD (hot filament plasma
enhanced chemical vapor deposition) method [55, 58].
1.1.5.4 GRAFTING OF POLYMERS
The covalent reaction of CNT with polymers is important because the long poly-
mer chains help to dissolve the tubes into a wide range of solvents even at a low
degree of functionalization. There are two main methodologies for the covalent
attachment of polymeric substances to the surface of nanotubes, which are de-
fined as “grafting to” and “grafting from” methods. The former relies on the syn-
thesis of a polymer with a specific molecular weight followed by end group trans-
formation. Subsequently, this polymer chain is attached to the graphitic surface of
CNT. The “grafting from” method is based on the covalent immobilization of the
polymer precursors on the surface of the nanotubes and subsequent propagation
of the polymerization in the presence of monomeric species.
1.1.5.4.1
“GRAFTING TO” METHOD
Recently reported the chemical reaction of CNT and PMMA using ultrasonica-
tion. The polymer attachment was monitored by FT-IR and TEM. As a result of
this grafting, CNT were purified by filtration from carbonaceous impurities and
metal particles. A nucleophilic reaction of polymeric An alternative approach was
reported by the group of researchers MWNT were functionalized with n-butyl-
lithium and subsequently coupled with halogenated polymers. Microscopy
Search WWH ::
Custom Search