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CNT composites

CNT possess high elastic modulus and tensile strength as high as 1 TPa and 200 GPa, respectively and hence it is used as strong, light, and tough fibers for nanocomposite structures. To attain the strength CNT has to be distributed homogeneously throughout the matrix. This requires a good interfacial bonding. From various research findings the fallowing is summarized.
Ceramic composites
To obtain composits several techniques are used. For example in one case glass rods were used as additives to reinforce inorganic Ceramics. Silicon glass rods were synthesized by using surfactantcarbon nanotube co-micelles as templates to obtain100% enhancement on hardness in the presence of 6 wt % of CNTs. Here surfactant help to improve the dispersion of single-wall carbon nanotubes leading to a significant improvement of mechanical properties. In other cases poly (vinylidene fluoride) was adopted to assist the dispersion and serve as a glue to increase the interfacial adhesion in the composites.
Unlike carbon fibers, the as-prepared CNTs tend to form bundles due to van der Waals forces, and it is difficult to separate them individually. Defects found in compacts are usually due to agglomerations or inhomogeneous distribution of components. From the viewpoint of colloidal processing, multicomponents could be distributed evenly when they possess similar surface properties. Successful surface modification of silicon nitride powder with aluminum or other colloidal sintering agent proved more homogeneity in the green compacts compared with that of conventionally prepared samples.
It is also possible to coat the surface of CNTs with alumina, to improve the homogeneous distribution od carbon nanotubes in the ceramic matrix by properly binding the two phases more tight after sintering. A colloidal processing route is an effective way to improve the mechanical properties of carbon nanotube-alumina composites. By adjusting the surface properties of the alumina powder and that of CNTs, it is feasible to make them bind together with attractive electrostatic forces, which produces strong cohesion between two phases after sintering.

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