Nanofiber-Nanotube Composites

These geometries are particularly appealing for filtration-type applications, in sensors, and in highly effective composite design. But, at least for the present, the fahrication routes for these more exotic nanofiher-hased constructs remain too expensive for high-volume applications. Most have yet to he moved out of the laboratory into pilot-plant scale before their viability in volume applications can be meaningfully discussed. 

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The properties of a nanocomposite are determined by the stmcture and properties of the nanoelements, which form it. One of the main tasks in making nanocomposites is building the dependence of the stmcture and shape of the nanoelements forming the basis of the composite on their sizes. This is because with an increase or a decrease in the specific size of nanoelements (nanofibers, nanotubes, nanoparticles, and so on), their physical— mechanical properties such as coefficient of elasticity, strength, deformation parameter, and so on, are varying over one order [1-5]. 

T. Yang, N. Zhou, Y. Zhang, W. Zhang, K. Jiao, and G. Li, Synergistically improved sensitivity for the detection of specific DNA sequences using polyaniline nanofibers and multi-walled carbon nanotubes composites. Biosens. Bioelectron., 24, 2165—2170 (2009). 

Qi, R. Guo, R. Shen, M. Cao, X. Zhang, L. Xu, J. Electrospun poly (lactic-co-glycolic acid)/halloysite nanotube composite nanofibers for drug encapsulation and sustained release. J. Mater. Chem. 2010, 20 (47), 10622-10629. 

Scanning electron microscopy (SEM) is one of the very useful microscopic methods for the morphological and structural analysis of materials. Larena et al. classified nanopolymers into three groups (1) self-assembled nanostructures (lamellar, lamellar-within-spherical, lamellar-within-cylinder, lamellar-within-lamellar, cylinder within-lamellar, spherical-within-lamellar, and colloidal particles with block copolymers), (2) non-self-assembled nanostructures (dendrimers, hyperbranched polymers, polymer brushes, nanofibers, nanotubes, nanoparticles, nanospheres, nanocapsules, porous materials, and nano-objects), and (3) number of nanoscale dimensions [uD 1 nD (thin films), 2 nD (nanofibers, nanotubes, nanostructures on polymeric surfaces), and 3 nD (nanospheres, nanocapsules, dendrimers, hyperbranched polymers, self-assembled structures, porous materials, nano-objects)] [153]. Most of the polymer blends are immiscible, thermodynamically incompatible, and exhibit multiphase structures depending on the composition and viscosity ratio. They have two types of phase morphology sea-island structure (one phase are dispersed in the matrix in the form of isolated droplets, rods, or platelets) and co-continuous structure (usually formed in dual blends). 

He L X and Tjong S C (2010) Effect of temperature on electrical conduction behavior of polyvinyl-idene fluoride nanocomposites with carbon nanotubes and nanofibers, Curr Nanosci 6 520-524. Bhattacharyya A R, Sreekumar T V, Liu T, Kumar S, Ericson L M, Hauge H and Smalley R E (2003) Crystallization and orientation in polypropylene/single wall carbon nanotube composite. Polymer 44 2373-2377. 

Almecija D, Blond D, Sader J E, Colemanb J N and Boland J J (2009) Mechanical properties of individual electrospun polymer-nanotube composite nanofibers, Carbon 47 2253-2258. 

The Science of Nanomaterials is proving to be one of the most attractive and promising fields for technological development in this century. In the scientific literature several terms related to Nanoscience can be found, of which it is worth highlighting nanoparticles, nanocrystals, nanofibers, nanotubes and nano-composites. In fact, all these are related to nanostructured materials, which have well-defined structural features. The physical and chemical properties of materials at the nanometer scale (usually set in the range of 1-100 nm) are of immense interest and increasing importance for future technological applications. Nanostructured materials often exhibit different properties when compared to other materials. 

Wiemann K, Kaminsky W, Gojny FH, Schulte K (2005) Synthesis and properties of syndiotactic poly(propylene)/carbon nanofiber and nanotube composites prepared by in situ polymerization with metallocene/MAO catalysts. Macromol Chem Phys 206 1472-1478... 

Sandler, J., et al.. Crystallization of carbon nanotube and nanofiber polypropylene composites. Journal of Macromolecular Science - Physics, 2003. B42(3—4) p. 479-488. 

Shaffer, M., Sandler, J. Carbon Nanotube/Nanofiber Polymer Composites. In Processing and Properties of Nanocomposites, Advani, S. G., Ed., World Scientific New Jersey, 2007 1-59. 

Shaffer M, Kinloch IA. Prospects for nanotube and nanofiber composites. Composites Science and Technology. 2004 Nov 64(15) 2281-2. 

Lee H, Mall S, He P, Shi DL, Narasimhadevara S, Yeo-Heung Y, Shanov V, Schulz MJ (2007) Characterization of carbon nanotube/nanofiber-reinforced polymer composites using an instrumented indentation technique. Composites Part B 38 58-65... 

One of the features of the catalysts for production of carbon nanofibers and especially nanotubes consists in a big role of catalyst particle size besides the catalyst chemical composition. The size can not be assigned in advance, and only the change of synthesis method or synthesis condition allows to produce the most active particles. Chemical composition of the catalyst can be changed during pyrolysis. 

A test matrix of about 20 different carbon samples, including commercial carbon fibers and fiber composites, graphite nanofibers, carbon nanowebs and single walled carbon nanotubes was assembled. The sorbents were chosen to represent a large variation in surface areas and micropore volumes. Both non-porous materials, such as graphites, and microporous sorbents, such as activated carbons, were selected. Characterization via N2 adsorption at 77 K was conducted on the majority of the samples for this a Quantachrome Autosorb-1 system was used. The results of the N2 and H2 physisorption measurements are shown in Table 2. In the table CNF is used to designate carbon nanofibers, ACF is used for activated carbon fibers and AC for activated carbon. 

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