Nanocarbon composites

Vilatela, J.J. and D. Eder, Nanocarbon composites and hybrids in sustainability A Review. 

Nanocarbon composites can be broadly divided into three kinds, each with some possible subdivisions. Examples of these composites and their schematic representations are presented in Fig. 8.1. The first type corresponds to composites where the nanocarbon is used as a filler added to a polymer matrix analogous, for example, to rubber reinforced with carbon black (CB). The second consists of hierarchical composites with both macroscopic fibers and nanocarbon in a polymer, such as a carbon fiber laminate with CNTs dispersed in the epoxy matrix. The third type is macroscopic fibers based... 

Fig. 8.1 Electron micrographs of different nanocarbon composite types (top) and their schematic representation (bottom). The nanocarbons can be dispersed as a filler (left), combined with macroscopic fibers in a hierarchical composite (middle), or assembled as a continuous nanostructured fiber (right). Micrographs from references [7, 8, 9], with kind permission from Elsevier (2010, 2008, 2009).

The author is grateful to R. Guzman-Villoria for useful discussions about hierarchical nanocarbon composites and to N. Krol for text editing and acknowledges financial support from MINECO (Spain) through its Juan de la Cierva Program and FP7-Marie Curie Action-CIG. 

Carbon Nanotube and Carbon Nanofiber Nanocomposites. The discovery of single-wall carbon nanotubes (SWNT) has renewed focus on composites with SWNT, multiwalled carbon nanotube (MWNT) and carbon nanofiber (CNF) reinforcements, together referred to as ID Nanocarbon composites (39). These constituents offer promise for new lightweight materials with incredible mechanical, electrical, and thermal properties. ID Nanocarbon materials are envisioned as multifunctional materials, eg single materials used for structures as well as electrical and/or thermal conductors. One example is electronics in a space satellite that need to be lightweight and mechanically supported, have the excess heat dissipated, and be protected from electromagnetic interference (EMI). Other examples are structures that are also batteries and structures that store hydrogen for fuel cells. 

Makunin, A. V., Tchecherin, N. G. (2011). Polymer and Nanocarbon Composites from Cosmic Technologies, Ed. M., Universitetskaya kniga 150p. 

Nalidixic acid, 3 29 21 104, 123, 215 year of disclosure or market introduction, 3 6t N-alkylation reactions of aniline, 2 785-786 microwaves in, 16 557-558 Naltrexone drug delivery, 9 65—66 Nameplate capacities, 23 547-548 Nametre viscometer, 21 739 NAND arrays, 22 258 Nanoaluminum composites, 10 19, 20 Nanoassemblies, shell and core cross-linked, 20 489-490 Nanocar, 24 62 Nanocarbon materials, 1 718-722 Nanoceramics, 1 705-708 Nanoclays, 11 313-314... 

Nanocarbon structures such as fullerenes, carbon nanotubes and graphene, are characterized by their weak interphase interaction with host matrices (polymer, ceramic, metals) when fabricating composites [99,100]. In addition to their characteristic high surface area and high chemical inertness, this fact turns these carbon nanostructures into materials that are very difficult to disperse in a given matrix. However, uniform dispersion and improved nanotube/matrix interactions are necessary to increase the mechanical, physical and chemical properties as well as biocompatibility of the composites [101,102]. 

Incorporation of nanocarbons into polymer composites and hybrids... 

Tab. 4.3 Percolation threshold and conductivity for electrical transport using different types of nanocarbons in polymer composites.

The filler route has proved to be very efficient to obtain isotropic composites with relatively large improvements in matrix properties at small mass (volume) fractions of nanocarbon. For example, electrical percolation in epoxy has been obtained with only 0.0025 wt% of multi-wall nanotubes (MWNTs) [12]. Similarly, a 2.7-fold increase in matrix modulus has been observed on addition of 0.6 vol% MWNTs to polyvinyl alcohol (PVA) [13]. Although more modest compared to the previous two examples, a... 

In this simple form, this expression is a good first approximation to compare the experimental reinforcement achieved upon addition of filler to the matrix, to the theoretical prediction [11]. It provides a measure of how efficiently the properties of the nanofiller are exploited in the composite, but also enables the comparison with the level of reinforcement achieved using other fillers. Note, in addition, that equation (8.2) sets an upper limit between Efl5 = 200 GPa and / = 1000 GPa, depending on whether the nanocarbon is randomly or perfectly oriented (without taking q0 into account). 

Due to their high aspect ratio, nanocarbons dispersed in a polymer matrix can form a percolating conductive network at very low volume fractions (< 0.1 %). The conductivity of a composite above the transition from an insulator can be described by the statistical percolation using an excluded volume model [22,23] to yield the following expression ... 

While conductivities of nanocarbons dispersed in polymers fall short of those of metals, a variety of applications can be unlocked by turning an insulating matrix into a conductor, which requires only small volume fractions that can therefore keep the system viscosity at a level compatible with composite processing techniques. Of particular interest are novel functionalities of these conductive matrices that exploit the presence of a conductive network in them, such as structural health monitoring (SHM) based on changes in electrical resistance of the nanocarbon network as it is mechanically deformed [30]. 

Fig. 8.4 Plots of relative change in electrical resistance against tensile deformation of a CNT/epoxy composite (a) shows the various characteristics of the piezoresistivity of nanocarbon networks linear resistance change in the elastic regime, nonlinear region after inelastic deformation and the permanent electrical resistance drop due to plastic deformation (image adapted from [30]) ...

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