Carbon Nanomaterials-Based Composites

Multiwalled carbon nanotubes (MWCNT) are relatively easy to synthesize and cheaper compared to either double-walled or single-walled carbon nanotubes. Hence they have been investigated for incorporation into BC. The electrical conductivity of BC-MWCNT composite depends on various factors such as 1) average length of MWCNT 2) their concentration in the precursor solution 3) type of surfactant used for dispersing the nanotubes and 4) immersion time for dispersing the nanotubes in the BC matrix. Yoon et al. [57] studied the effect of these variables on the overall electrical conductivity by using two surfactants. Cetyl trimethylammonium bromide (CTAB) 

---

Figure 17.18 Schematic shows the typical synthesis method of carbon nanomaterials-based BC composite.

Since the discovery of SWNTs, they have been expected to become the building blocks of the next generation of functional nanomaterials. However, their strong cohesive property and poor solubility have restricted the use of SWNTs for fundamental and applied research fields. One method to overcome these problems is to make the SWNTs more soluble by wrapping them with polymers [31]. At the same time, the fabrication of high-performance carbon nanotube (CNT)-based composites is driven by the ability to create anisotropy at the molecular level to obtain appropriate functions. 

With the advent of nanomaterials, different types of polymer-based composites developed as multiple scale analysis down to the nanoscale became a trend for development of new materials with new properties. Multiscale materials modeling continue to play a role in these endeavors as well. For example, Qian et al. [257] developed multiscale, multiphysics numerical tools to address simulations of carbon nanotubes and their associated effects in composites, including the mechanical properties of Young s modulus, bending stiffness, buckling, and strength. Maiti [258] also used multiscale modeling of carbon nanotubes for microelectronics applications. Friesecke and James [259] developed a concurrent numerical scheme to evaluate nanotubes and nanorods in a continuum. 

The intent of the investigations currently performed in the field of creation of different compositions based on carbon nanomaterials is to moderate the processes of these materials dehydrogenation and increase hydrogen capacity of some of them. 

Although much progress has been made in both synthesis and purification of carbon nanomaterials, commercial samples still contain nanostrucmres of different size, shape, and composition. As-produced carbon nanomaterials are frequently composed of mixtures of CNTs, fullerenes, carbon onions, amorphous carbon and graphite, which are structurally different and possess different reactivity. Since the oxidation kinetics are closely related to structural features, reaction rates and activation energies are expected to differ for the distinct carbon forms, which is an important issue for oxidation-based purification or surface functionalization. In analogy to graphite [3-6], oxidation of a carbon nanostmcture [7-9] can be described by a first-order reaction, with respect to the carbon component. 

In the nanotechnology field, carbon-based materials and associated composites have received special attention both for fundamental and applicative research. In the first kind, carbon compounds may be included, often taking the form of a hollow spheres, ellipsoids, or mbes. Spherical and ellipsoidal carbon nanomaterials are referred to as fullerenes, while cylindrical ones are called nanombes and nanofibers. In the second class, one includes composite materials that combine carbon nanoparticles with other nanoparticles, or nanoparticles with large bulk-type materials. The unique properties of these various types of nanomaterials provide novel electrical, catalytic, magnetic, mechanical, thermal, and other features that are desirable for applications in commercial, medical, military, and enviromnental sectors. This is the case for conducting polymers (CPs) and carbon nanombes (CNTs) [1-5]. 

However, the storage capability from the fiber electrode based on bare carbon nanomaterial is poor owing to the double-layer capacitance mechanism. Therefore, pseudocapac-itive materials, such as metallic oxide and conducting polymer can also be incorporated into the CNT fiber to enhance the capacitance. For example, CNT/PANI composite fibers... 

Carbon-based polymer nano composites represent an interesting type of advanced materials with structural characteristics that allow them to be applied in a variety of fields. Functionalization of carbon nanomaterials provides homogeneous dispersion and strong interfacial interaction when they are incorporated into polymer matrices. These features confer superior properties to the polymer nanocomposites. This chapter focuses on nanodiamonds, carbon nanotubes and graphene due to their importance as reinforcement fillers in polymer nanocomposites. The most common methods of synthesis and functionalization of these carbon nanomaterials are explained and different techniques of nanocomposite preparation are briefly described. The performance achieved in polymers by the introduction of carbon nanofillers in the mechanical and tribological properties is highlighted, and the hardness and scratching behavior of the nanocomposites are also discussed. 

Electrochemical biosensor performance such as sensitivity, protein stability, selectivity or reproducibility have been improved due to the use of different carbonaceous materials and combination of them. To improve the sensitivity of a electrochemical biosensor is necessaiy to increase the enzyme amount in a proper immobilization manner. CNTs are good candidates and in this regard, some authors combine carbon nanomaterials with conducting polymers, which gives rise the biosensor special properties due to the synergic effect of the individual components. The electrochemical determination of lactate by the use of lactate oxidase (LOx) based SPE platform takes advantages of the combination of MW-CNT and conductive polysulfone polymer, and such an electrochemical biosensor was successfully applied for the quantification of lactate in wine and beer. In some cases, the inconvenient is the low stability associated with the deleterious interaction of the enzyme LOx with the composite CNT/polymer substrate. 

Conductive Polymer Composites Based on Carbon Nanomaterials... 

Fig. 3 Most studied nanomaterials in past two decades conductive polymer composites based on carbon nanomaterials (Graphene, SWCNT, and Fullerene from L-R Figs, taken from Refs. [85-87])...

---