Carbon Nanotube Reinforced Composites: Metal and Ceramic ...
Carbon Nanotube Reinforced Composites: Metal and Ceramic ...
Carbon Nanotube Reinforced Composites: Metal and Ceramic ...
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Figure 6.6 Dielectric constant vs frequency for 3Y-TZP/MWNT<br />
nanocomposites. Reproduced with permission from [21].<br />
Copyright Ó (2006) John Wiley & Sons, Inc.<br />
constant of nanocomposites [16]. Figure 6.6 shows the dielectric constant vs frequency<br />
plot for the 3Y-TZP/MWNT nanocomposites at room temperature. The<br />
dielectric constant of pristine 3Y-TZP <strong>and</strong> 3Y-TZP/MWNT nanocomposites containing<br />
nanotubes up to 1 wt% is quite low <strong>and</strong> independent of frequency. At MWNT<br />
concentration 2 wt%, the dielectric constant increases significantly. A pronounced<br />
dependence of the dielectric constant on frequency is observed for the 3Y-TZP/<br />
MWNT nanocomposites with MWNT concentration 2 wt%. In this regard, the<br />
dielectric behavior can be described by Equation 6.6. The dielectric constant can reach<br />
11 200 at 10 3 Hz for the 3Y-TZP/4 wt% MWNT nanocomposite.<br />
6.4<br />
Electromagnetic Interference Shielding<br />
Electromagnetic interference (EMI) shielding has received increasing attention in<br />
the electronic <strong>and</strong> communication industries due to the devices emit radiation at<br />
microwave <strong>and</strong> radio frequencies. The EMI of a material refers to its capability to<br />
reflect <strong>and</strong> absorb electromagnetic radiation at high frequencies. Thus, shielding <strong>and</strong><br />
absorbing are two main methods to prevent <strong>and</strong> attenuate EMI radiation. The EMI<br />
shielding effectiveness (SE) of a material is expressed as the ratio of transmitted<br />
power (ET) to incident power (EI) of an electromagnetic wave <strong>and</strong> measured in<br />
decibels (dB) [26, 27]:<br />
SE ¼ 10 log ET<br />
EI<br />
6.4 Electromagnetic Interference Shieldingj177<br />
: ð6:15Þ<br />
In general, electrical conducting materials such as metals, graphite, conducting<br />
polymers <strong>and</strong> polymer-based composites have been used for EMI shielding