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Carbon Nanotube Reinforced Composites: Metal and Ceramic ...

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Figure 5.29 SEM fractographs of spark plasma sintered (a) Si3N4<br />

at 1500 C for 3 min under 50 MPa <strong>and</strong> (b) Si3N4/1 wt% MWNT<br />

nanocomposite at 1500 C for 3 min under 100 MPa.<br />

Reproduced with permission from [120]. Copyright Ó (2005)<br />

Elsevier.<br />

They reported that CNTs were missing in the nanocomposite hipped at 20 MPa for 3 h<br />

due to the destruction of CNTs during prolonged processing treatment.<br />

<strong>Carbon</strong> nanotubes survived in the nanocomposite hipped at 2 MPa for 1 h. However,<br />

the composite is porous having coarser grain structure [120]. On the other h<strong>and</strong>,<br />

SPS results in denser composites with nanocrystalline structure (Figure 5.29(a)<br />

<strong>and</strong> (b)). Ball milling MWNT, Si 3N 4 <strong>and</strong> sintering aids in ethanol under sonication<br />

do not provide sufficient dispersion of CNTs. MWNTs are mainly located in<br />

intergranular regions, <strong>and</strong> clustering of nanotubes can be readily seen in the<br />

micrographs.<br />

References<br />

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(2005) Toughening of hard<br />

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2–8.<br />

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