Composite carbon nanofibers

Therefore, it can be seen from the above expression that is closely related to absorption loss (SE ). SE is also important for porous structures (e.g., foams) and for certain type of filled composites (carbon nanofibers [CNFs]/carbon nanotubes [CNTs]/graphene-filled polymers) or for certain design geometries (e.g., honeycomb lattices) [1,2,9,13,81]. It can be neglected in the case of a shield having thick absorbing elements due... 

Figure 6.15 TEM images of composite carbon nanofibers (a) long nanotubes formed at 850°C (b) curved nanotubes formed at 700°C. Reprinted with permission from Hou and Reneker (2004). Copyright 2004. John Wiley Sons.

Effect of oxidative treatments on catalytic property of carbon nanofiber composite... 

Sonoelectrochemistry has also been used for the efficient employment of porous electrodes, such as carbon nanofiber-ceramic composites electrodes in the reduction of colloidal hydrous iron oxide [59], In this kind of systems, the electrode reactions proceed with slow rate or require several collisions between reactant and electrode surface. Mass transport to and into the porous electrode is enhanced and extremely fast at only modest ultrasound intensity. This same approach was checked in the hydrogen peroxide sonoelectrosynthesis using RVC three-dimensional electrodes [58]. 

M.E., Evans, D.E., Ku, B.K., Crouch, K. and Eloover, M.D. (2007) Identification and characterization of potential sources of worker exposure to carbon nanofibers during polymer composite laboratory operations./. Occup. Environ. Hyg., 4 (12), D125-D130. 

The obtained carbon nanofibers were used for the synthesis of composite materials MgH2-CNF, whose hydrogen storage characteristics were thoroughly studied. 

The investigation of hydrogen sorption properties of the MgH2-CNF composites, obtained by mechanochemical treatment of mixtures of the components, testifies about availability of use of carbon nanofibers for creation of hydrogen storage composite materials. 

Abstract. A chemical composition and structural parameters of specially prepared catalyst for the pyrolytic synthesis of carbon nanomaterials have been studied by X-ray diffraction, Mossbauer spectroscopy and electron microscopy. A plenty of chemical transformations in the catalyst have been monitored. The inert (Mgi xFxO) and active, very fine particles of the catalyst (MgFe204) components which are involved in the process of carbon nanofibers were revealed. 

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. 

FIGURE 29 SEM images of carbon ceramic composites made from (A) sucrose (Cord-SUC) (B) polyfurfuryl alcohol (Cord-PFA) (C) carbon nanofibers (Cord-CNF). 

The oxidation behavior of the composite after 2 h of growth allowed the calculation of the carbon nanofiber stoechiometry inside the composite used as catalyst support for the low temperature H2S oxidation, -i.e. about 20 wt.%. 

R. Viera, C. Pham-Huu, N. Keller, and M. J. Ledoux, New carbon nanofiber/graphite felt composite for use as catalyst support for hydrazine catalytic decomposition, Chem. Commun., (2002) 954-955. 

Several monolithic enzyme biocatalysts were prepared and characterized with carbon coatings consisting of carbonized sucrose, carbonized polyfurfuryl alcohol, and carbon nanofibers. The coated carbon monoliths were also compared with an integral (composite) carbon monolith. A lipase from Candida antarctica was adsorbed on the monolithic supports. Adsorption on carbon coatings can be very effective, depending on the carbon microstructure. For a high lipase loading. 

The above polyolefin copolymers have also been used to prepare conventional composites and nanocomposites. However, similar to the case of polymer blends, not too many studies have been reported thus far. Recently, Kelarakis et al. (49) have mixed 10 wt% of surface-modified carbon nanofiber (MCNF) with propylene-ethylene random copolymer (propylene 84.3%). The MCNF acted as a nucleating agent for crystallization of the a-form of PP in the matrix. During deformation at room temperature, strain-induced crystallization took place, while the transformation from the 7-phase to a-phase also occurred for both unfilled and 10 wt% MCNF-filled samples. The tensile strength of the filled material was consistently higher than that of pure copolymer. These results are illustrated in Fig. 8.27. 

XPS is primarily a surface technique, as the escape depth of the photoelectrons ranges from 2 to 5 nm, and it would therefore primarily yield information on the composition of the most external surface of the carbon nanofibers. For this reason should it be possible to obtain the surface oxygen content from XPS [28]. In this regard, it was suggested that 80-90 % peak area... 

Ji, L. and Zhang, X. Generation of activated carbon nanofibers from electrospun polyacrylonitrile-zinc chloride composites for use as anodes in hthium-ion batteries. Electrochem. Commun. 2009,11(3), 684-687. 

The fabrication and electrical properties of carbon nanofiber-polystyrene composites and their potential applications for EMI shielding have been reported [42]. Being lightweight is a key technological requirement for the development of practical EMI shielding systems. Thus the fabrication of foam structures to further reduce the weight of carbon nonofiber-ploymer composites has been recently demonstrated and simple preparation routine has been reported [43] by which this novel foam structure can be prepared. 

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