Carbon nanotubes physical-mechanical

Gavillet, J., Loiseau, A., Joumet, C., Willaime, F., Ducastelle, F. and Chariier, J.-C., Root-growth mechanism for single walled carbon nanotubes. Physical Review Letters, 87 (27), 2001,275504. 

Nardelli, M. B., 8c Bernholc, J. (1999). Mechanical deformations and coherent transport in carbon nanotubes. Physical Review B, 60(24), R16338-R16341. 

Rochefort, A., Avouris, P, Lesage, R, 8c Salahub, D. R. (1999a). Electrical and mechanical properties of distorted carbon nanotubes. Physical Review B, 50(19), 13824-13830. 

Dresselhaus MS, Dresselhaus G, Charlier JC, Hernandez E (2004) Electronic, thermal and mechanical properties of carbon nanotubes. Philosophical Transactions of the Royal Society of London Series A-Mathematical Physical and Engineering Sciences 362 2065-2098. 

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]. 

H. Y. Song, X. W. Zha, The effects of boron doping and boron grafts on the mechanical properties of single-walled carbon nanotubes., Journal of Physics D-Applied Physics 2009,... 

Ivanov LV, Chernykh VP, Kartel NT et al (2008) Study of mechanisms of carbon nanotubes cytotoxicity. In Chemistry, Physics and Technology of Surface Modification. Proceedings of ISC, Kiev 34-36... 

The DNA-carbon nanotube interaction is a complicated and dynamic process. Many studies on this subject have been pursued through a series of techniques, including molecular dynamic simulation, microscopy, circular dichroism, and optical spectroscopy.57,58 Although the detailed mechanism is not fully understood at present, several physical factors have been proposed to be driving DNA-carbon nanotube interactions,46,59-61 such as entropy loss due to confinement of the DNA backbone, van der Waals and hydrophobic (rr-stacking) interactions, electronic interactions between DNA and carbon nanotubes, and nanotube deformation. A recent UV optical spectroscopy study of the ssDNA-SWNT system demonstrated experimentally that... 

The past decade has led to the detection of new carbon allotropes such as fullerenes26 and carbon nanotubes,27 28 in which the presence of five-mem-bered rings allows planar polycyclic aromatic hydrocarbons to fold into bent structures. One notes at the same time that these structures are not objects of controlled chemical synthesis but result from unse-lective physical processes such as laser ablation or discharge in a light arc.29 It should be noted, on the other hand, that, e.g., pyrolytic graphitization processes, incomplete combustion of hydrocarbon precursors yielding carbon black, and carbon fibers30 are all related to mechanisms of benzene formation and fusion to polycyclic aromatic hydrocarbons. 

Attaching chemical functionalities to CNTs can improve their solubility and allow for their manipulation and processability [24]. The chemical functionalization can tailor the interactions of nanotubes with solvents, polymers and biopolymer matrices. Modified tubes may have physical or mechanical properties different from those of the original nanotubes and thus allow tuning of the chemistry and physics of carbon nanotubes. Chemical functionalization can be performed selectively, the metallic SWCNTs reacting faster than semiconducting tubes [25]. 

The different flame-retardant (FR) mechanisms of action of current nanoparticles, such as layered silicates, carbon nanotubes (CNTs), and nano-oxides or -hydroxides, according to their nature and interfacial modifications, are relatively well known and detailed in numerous works.5 13 These mechanisms are rather different from those exhibited by usual FRs and correspond mainly to the following physical, physicochemical, or chemical actions ... 

A. Loiseau, X. Blase, J.C. Charlier, P. Gadelle, C. Journet, C. Laurent and A. Peigney, Synthesis methods and growth mechanisms, in Understanding Carbon Nanotubes. From Basics to Application, Lecture Notes in Physics 677, Springer, 2006. 

Table 5.1. Carbon nanotubes have a high potential to improve the mechanical, physical and electrical properties of polymers, as stated by Thostenson et al. (4). They exhibit an exceptionally high aspect ratio in combination with low density, as well as high strength and stiffness (Coleman et al. (5)), which make them a potential candidate for the reinforcement of polymeric materials.

We review the research on preparation, morphology, especially physical properties and applications of polyurethane (PU)/carbon nanotube (CNT) nanocomposites. First, we provide a brief introduction about the preparation of PU/CNT nanocomposites. Then, the functionalization and the dispersion morphology of CNTs as well as the structures of the nanocomposites are also introduced. After that, we discuss in detail the effects of carbon nanotubes on the physical properties (including mechanical, thermal, electrical, rheological and other properties) of PU/CNT nanocomposites. The potential applications of these nanocomposites are also addressed. Finally, the challenges and the research that needs to be done in the future for achieving high-performance polyurethane/carbon nanotube nanocomposites are prospected. 

The last few years have seen the extensive use of nanoparticles because of the small size of the filler and the corresponding increase in the surface area, allowing to achieve the required mechanical properties at low filler loadings. Nanometer-scale particles including spherical particles such as silica or titanium dioxide generated in-situ by the sol-gel process (4-8), layered silicates (9-12), carbon (13) or clay fibers(14,15), single-wall or multiwall carbon nanotubes (16,17) have been shown to significantly enhance the physical and mechanical properties of rubber matrices. 

In this entry, the principal chemical features of defect populations (defect chemistry) will be described from the restricted viewpoint of crystalline inorganic solids. The influence of defects upon mechanical properties will be excluded and defects that may have greatest relevance to physical properties will be treated from the point of view of chemical importance. Defects in molecular crystals and amorphous and glassy solids will be omitted see Noncrystalline Solids), as will the important areas of alloys see Alloys), thin films see Thin Film Synthesis of Solids), and carbon nanotubes and related nanoparticles see Carbon Fullerenes). References to the literature before 1994 are to be found in the corresponding article in the first edition of this Encyclopedia. ... 

Several growth models are proposed for the carbon nanotubes prepared by the pyrolysis of hydrocarbons on metal surfaces. Baker and Harris [100] suggested a four-step mechanism. In the first step, the hydrocarbon decomposes on the metal surface to release hydrogen and carbon, which dissolves in the particle. The second step involves the diffusion of the carbon through the metal particle and its precipitation on the rear face to form the body of the filament. The supply of carbon onto the front face is faster than the diffusion through the bulk, causing an accumulation of carbon on the front face, which must be removed to prevent the physical... 

Physical sensors are sensitive to external parameters like temperature, pressure, mechanical strain etc. In the process, the sensor generates a signal that can be measured and assigned to a certain value. Carbon nanotubes can be employed to measure a multitude of quantities. Just a few examples shall illushate this versatility here. 

Carbon nanotubes (CNs) were discovered by lijima in 1991 [69], since when they have been regarded as materials of exceptional interest. This high level of interest is not only because of their remarkable electronic properties, their extremely desirable mechanical properties (strength and flexibility), or their good physical and chemical properties [70], but also because of to their potential applications (hydrogen storage, chemical sensors, nanoelectronic devices, components for high performance composites) [71]. 

In this context, nanoporous carbons are extremely interesting materials which can be used either as electrodes of supercapacitors or hydrogen reservoir. They are commercially available at a low cost and under various forms (powder, fibers, foams, fabrics, composites) [3]. They can be obtained with well-developed and controlled porosity [4,5] and with a rich surface functionality [6,7], As far as electrochemistry applications are concerned, very important advantages of carbons are a high electrical conductivity, a good chemical stability in various electrolytic media and the possibility to control wettability by the nature of the surface functionality. When they are not playing the role of active material for the storage process, carbons may be also useful as additive in a composite to improve its physical properties. Particularly carbon nanotubes are able to improve the electrical conductivity and mechanical properties of electrodes [8],... 

CNTs can be combined with various metal oxides for the degradation of some organic pollutants too. Carbon nanotubes/metal oxide (CNT/MO) composites can be prepared by various methods such as wet chemical, sol gel, physical and mechanical methods. To form nanocomposite, CNTs can be combined with various metal oxides like Ti Oj, ZnO, WO3, Fc203, and AI2O3. The produced nanocomposite can be used for the removal of various pollutants. Nanoscale Pd/Fe particles were combined with MWNTs and the resulted composite was used to remove 2,4-dichlorophenol (2,4-DCP). It was reported that the MB adsorption was pH-dependent and adsorption kinetics was best described by the pseudo-second-order model. Iron oxide/CNT composite was reported to be efficient adsorbent for remediation of chlorinated hydrocarbons. The efficiency of some other nanocomposites such as CNT/ alumina, CNT/titania and CNT/ZnO has also been reported [60-62]. 

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