Nanofibers nucleation

Keywords Nanofiber Nucleation Branching Fiber network Additive... 

Sone and Samuel (2004) continued the studies of mineralization on PA nanofibers by utilizing the same PA described above to nucleate and grow CdS nanocrystals. In this case, the negatively charged phosphate and carboxylate groups bind to Cd, and CdS was formed after diffusion of H2S gas. A low Cd to PA ratio led to the formation of CdS nanocrystals that were 3-5 nm in diameter. An intermediate ratio of... 

Fig. 59 a SEM image of a glass/ZnO nucleation layer/ZnO nanocarpet structure. The ZnO nanofibers are grown from an aqueous solution of zinc nitrate, and the nucleation layer is spin-coated from a zinc acetate solution, b SEM image of P3HT intercalated into the nanocarpet structure. (Reprinted from [280], 2006, with permission from Elsevier)... 

As mentioned in the introduction, the interaction between metal hydroxide and carbon inevitably will be quite subtle. From a study of the DP of nickel hydroxide onto carbon nanofibers, van der Lee et al. [45] concluded that the carboxylic acid groups are key anchoring and nucleation sites on the support surface for the deposition of nickel hydroxide. Surface oxidation of carbon nanofibers typically introduces one COOH group per square nanometer. Nickel ions may adsorb onto these groups. This is what the authors found, as can be inferred from the results shown in Figure 5.7. 

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. 

Nucleation on Polymer Nanofibers and their Controllable Conversion to Protective Layers Preliminary Theoretical Study... 

Keywords polymer nanofibers, nanospider, nucleation, energy barrier. 

Since the diameter of nanofibers is the thickness of several atoms, the system of nanofibers exhibits a very large specific surface, which may be exploited to be an active site for (heterogeneous) nucleation. Generally, nucleation is the formation of a very small amount of a new, product phase (so-called clusters) from the parent phase by fluctuations. Boltzmannian probability that a clusters (consisting of n-particles) will be formed within metastable original phase is given by... 

Above expression is valid when the clusters form at random sites within the bulk of original phase (so-called homogeneous nucleation). In the case of heterogeneous nucleation, the clusters are formed on foreign surfaces placed within the system (impurities, walls of the vessel, wafers or certain base materials - e g. nanofibers) and the necessary energy of clusters formation on flat surface reads (see, e g. [4]) ... 

Figure 1 Heterogeneous nucleation on a) flat substrate b) on surface of nanofiber (or radius R).

Energy (10) plays an essential role governing the process of formation of cluster on surface of nanofiber, because its maximal value represents the so-called nucleation barrier which has to be overcome to obtain stable, growable cluster. It may be also readily proved that... 

From the figure it is clear that due to homogeneous nucleation of graphene the formation of imiform growing PANl nanofibers has been accelerated and results nanofibrillar morphology of PANl on the surface of the... 

Acids can act as dopants for polyaniline therefore, if the nanofibers are first doped with these acids, and subsequently exposed to the metal ions, precipitates should be formed on the surface of the nanofibers, leading to inorganic-polyaniline nanofiber composites. This idea has been applied in Section 7.3.5 to improve the detection of H2S. Another possibility is to use nanofibers as nucleation seeds to collect inorganic nanoparticles from supersaturated solutions [148]. 

Nanofibers which form self-organized fibrous networks in organogels are sometimes found to have a 3D crystalUne order [15-18,21]. The formation of fibers, therefore, takes place in most cases via a crystallization process [ 15-18,21], including nucleation and growth [22-32]. 

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