Biomedical Engineering Reference
In-Depth Information
7.15
Increase in the electrical conductivity of glass and glass-ceramic
matrix composites containing CNTs available in the literature.
et al., 2009) or the structuring of CNTs around large micron-size grains in
glass-ceramic matrices (Subhani, 2012a), while a value
1.0wt% shows a
homogenous dispersion of CNTs with individual CNTs well-separated from
others (Bauhofer and Kovacs, 2009). Higher aspect ratio CNTs give lower
percolation threshold and higher absolute conductivity of the composite
system due to fewer junctions, but are susceptible to alignment effects (i.e.
anisotropy in electrical conductivity) (Otieno et al., 2010). In principle, the
dimensionality constant should provide geometrical information about the
CNT network, whether controlled by agglomeration or excluded volume
effects, as also observed in CNT-polymer composites (Bauhofer and
Kovacs, 2009).
>
Thermal conductivity
The thermal diffusivity (
) and specific heat capacity (Cp) of CNT-glass/
glass-ceramic matrix composites are generally measured by laser flash
technique and differential scanning calorimetry, respectively. Thermal
conductivity (Kc) is then calculated by computing the two measured values
along with sintered density (
α
ρ
) of composites using the following equation:
K
c
¼ a
C
p
r
½
:
7
5
Since CNTs exhibit high individual thermal conductivities greater than
