Carbon Nanotube Reinforced Composites: Metal and Ceramic ...

Figure 1.15 In situ tensile deformation of
individual single-walled CNT in a transmission
electron microscope. (a)–(d) Tensile elongation
of a SWNT under a constant bias of 2.3 V.
Arrowheads mark kinks and arrows indicate
features at the ends of the nanotube that are
almost unchanged during elongation. Images
are scaled to the same magnification.
Jacobsen et al. used the vibration-reed method to measure the stiffness of VGCF and
found an average elastic modulus of 680 GPa [152]. Ishioka et al. reported that straight
VGCFs have an average Young s modulus of 163 GPa and an average tensile strength
of 2.05 GPa based on tensile measurements Further, impurities and metal catalysts
in VGCFs can result in very low stiffness [153]. Uchida et al. calculated the elastic
modulus of the two-layered nanofiber to be 100–775 GPa, depending on the degree of
misorientation of graphite layers [13].
1.6
Physical Properties of Carbon Nanotubes
1.6.1
Thermal Conductivity
1.6 Physical Properties of Carbon Nanotubesj29
(e), (f) Tensile elongation of a SWNT at room
temperature without bias. Images are scaled to
the same magnification. (g) Low magnification
image showing fracture in midsection of a
nanotube at room temperature. Reproduced
with permission from [151]. Copyright Ó (2006)
Nature Publishing Company.
The in-plane thermal conductivity of graphite crystal is very high, that is, 3080–
5150 W m 1 K 1 at room temperature [154]. However, the c-axis thermal conductivity
of graphite is very low because its interlayer is bounded by weak van der Waals
forces [155]. The thermal conductivity of graphite generally increases markedly as
the temperature is reduced [156], and closely related to their lattice vibrations
or phonons. Contribution to a finite in-plane thermal conductivity of graphite at low