Nanotube Composites with Other Materials

Besides combinations with polymers as mentioned above, there are also some composites of carbon nanotubes with other, and especially with inorganic materials. These are, in most cases, metals or ceramic compounds like aluminum oxide. 

The intention is again to use the properties of the nanotubes for an improvement of the materials characteristics. The main focus in doing so is on mechanical reinforcement. 

Common processes in the production of ceramic or metal composites employ sinter or hot-pressing methods to blend the respective partners. However, these procedures have some serious drawbacks once it comes to the preparation of carbon nanotube composites. Firstly, a wetting of the nanotubes by the composite partner often is complicated, if not impossible, in the solid state, and secondly, it still poses considerable problems to incorporate the tubes into the matrix in a homogeneous and, where possible, individually dispersed way. 

---

Composites with Other Polymers Besides the composite materials presented so far, a multitude of further polymer composites with carbon nanotubes has been prepared and studied regarding their properties. After all, any given polymer is suitable to some extent to interact with different carbon nanotubes (pristine or functionalized). The number and range of possible combinations surpass the scope of this text, so the examples mentioned below inevitably have to remain incomplete. 

Functionalization of CNTs is of special importance for diverse applications as it can lead not only to the improvement of their solubility but also to their ability to be coupled with other materials creating composites with fascinating characteristics (Hirsch 2002). Irradiation-mduced defects normally increase the reactivity of nanotubes at the surface. Thus, functional groups can be attached to both graphene and nanotubes in spedlic areas (Guo et al. 2005 Salah et al. 2009 Fedoseeva et al. 2010). The induced defects in the jjp -bonded carbon systems due to focused electron and ion beams are governed by the knock-on displacement of carbon atoms, creating vacancies and interstitials in the nanotubes (Krasheninnikov and Nordlund 2010). 

In this section, consideration will be given to research in which conducting polymers have been combined with other materials to create a composite with improved actuation properties. This might involve the incorporation of a stiffer material (e.g. carbon nanotubes) to improve the stresses produced, or the inclusion of a gel to increase the amount of strain generated, albeit in a weaker actuator. 

My original plan had been to develop theories for mixtures of liquid crystals with other materials, such as semiflexible polymers, spherical particles, rodlike polymers, nanotubes, surfactant molecules, or membranes. Currently, in 2011, the theoretical studies of the liquid crystal composites are almost completed up to nanotubes. Of course, there are various problems unresolved and it is likely to take about ten more years. 

Encapsulation of other material into carbon nanotubes would also open up a possibility for the applications to electrodevices. By applying the template method, perfect encapsulation of other material into carbon nanotubes became possible. No foreign material was observed on the outer surface of carbon nanotubes. The metal-filled uniform carbon nanotubes thus prepared can be regarded as a novel onedimensional composite, which could have a variety of potential applications (e.g novel catalyst for Pt metal-filled nanotubes, and magnetic nanodevice for Fe304-filled nanotubes). Furthermore, the template method enables selective chemical modification of the inner surface of carbon nanotubes. With this technique, carbon... 

An interesting question arises considering composites with multiwalled carbon nanotubes. In such materials there are two possible ways of stress relief upon mechanical strain On one hand, like in other fiber-reinforced composites, the interfacial interaction may be overcome by the mechanical forces so the polymer peels from the nanotubes. On the other hand, however, the individual walls of the MWNT may slide one inside another like a sword in a sheath (so-called interwaU sliding. Figure 3.85). Both effects may occur to varying extents depending on how strongly the multiwalled tubes are bound to the matrix. 

Metal matrix nanocomposites are those having metal as the continuous phase or matrix and other nanoparticles like carbon nanotube as the reinforced materials. These types of composites can be classified as continuous and noncontinuous. One of the more important nanocomposites is Carbon nanotube reinforced metal matrix composite, which is an emerging new material with the high tensile strength and electrical conductivity of carbon nanotube materials. In addition to carbon nanotube metal matrix composites, boron nitride reinforced metal matrix composites and carbon nitride metal matrix composites are the new research areas on metal matrix nanocomposites [9,10]. 

---