Nanofibers testing

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. 

The capacitive properties of nanotubes obtained with Cho et al. s method have been studied by Liu et al. from the same research group.208 Tubular structures were obtained with electrodeposition in acetonitrile solution containing 20 mM EDOT under potentio-static condition at 1.6 V vs. Ag/AgCl while nanofibers were synthesized in lOOmM EDOT and at 1.4 V applied potential. Thin wall nanotubes of PEDOT exhibited a stable specific capacitance of 140 Fg 1, while the specific capacitance for the solid nanofibers was 50Fg 1, under the identical test conditions. Figure 9 compares the... 

The last method to be discussed, which is used to form polymer/ceramic composites by electrospinning, is extremely different to the methods previously described, but worth mentioning. Zuo et al. [129] used a method to create a composite scaffold that is actually the reverse of what most people are doing. Instead of mineralizing the nanofibers, Zuo et al. actually incorporated electrospun polymer nanofibers into a ceramic bone cement in order to form a composite scaffold. It was found that by incorporating electrospun nanofibers into the cement, the scaffold became less brittle and actually behaved similarly to that of a ductile material because of the fibers. Composite scaffolds with different polymers and fiber diameters were then tested in order to determine which scaffold demonstrated the most ideal mechanical properties. However, no cell studies were conducted and this method would most likely be used for a bone substitute instead of for bone regeneration applications. 

Experiments carried out on the same SiC nanofibers show similar catalytic results. The SEM observation of the sample after the desulfurization test shows the presence of inhomogeneous large soUd sulfur particles wrapping the SiC structure where a large part of the catalyst surface was still accessible (Fig. 7.19). The remaining free surface of the catalyst allows one to explain the high desulfurization activity despite the relatively high soUd sulfur deposition on the catalyst surface. 

Fig. 7.19 SEM micrographs of the NiS2/SiC nanofibers composite after the desulfurization test. The solid sulfur formed during the test was present in the form of large particles on the surface of the catalyst.

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