Carbon nanotubes homogeneous dispersion

Morphology evaluation of nanometric geometry and characteristics of the observed nanostructures. For example, to determine the typology (single or multiwall), the chiral angle, the twisted angle, etc. of carbon nanotubes. Homogeneity to determine the statistical distribution of the various nanomaterials/structures present in a sample or, for example, dispersed into a matrix or in any device. 

Recently, the efficacy of LDHs as catalyst precursors for the synthesis of carbon nanotubes via catalytic chemical vapor deposition of acetylene has been reported by Duan et al. [72]. Nanometer-sized cobalt particles were prepared by calcination and subsequent reduction of a single LDH precursor containing cobalt(II) and aluminum ions homogeneously dispersed at the atomic level. Multi-walled carbon nanotubes with uniform diameters were obtained. 

In order to produce high-performance elastomeric materials, the incorporations of different types of nanoparticles such as layered silicates, layered double hydroxides, carbon nanotubes, and nanosilica into the elastomer matrix are now growing areas of rubber research. However, the reflection of the nano effect on the properties and performance can be realized only through a uniform and homogeneous good dispersion of filler particles in the rubber matrix. 

The viscoelastic properties of carbon nanotube/polymer composites have both practical importance related to composite processing and scientific importance as a probe of the composite dynamics and microstructure. The viscosity for CNT/PU dispersion at mixing is also very important for in-situ formation of polyurethane nanocomposite. Lower viscosity means a better flow ability and more homogenous mixing with isocyanate. Furthermore, low viscosity is very helpful to remove the bubbles before curing, which is a key step for polyurethane preparation. 

The unique two-phase structures of polyurethane that offers the elasticity of rubber combined with the toughness and durability of metal make them one of the most extensively studied and frequently used materials in carbon nanotube related nanocomposites. The main difficulty in developing CNT based polyurethane nanocomposites was how to achieve uniform and homogeneous CNT dispersion. Further investigations on the interactions between carbon nanotubes and two-phase structures are critical for the wider applications of carbon nanotube/polyurethane composites. 

Palladium metal particles with an average diameter of ca. 5 nm were homogeneously dispersed inside carbon nanotubes. Such nanostructured material was an extremely active and selective catalyst for the hydrogenation of the C=C bond of cinnamaldehyde. The high external surfece area of the carbon nanotubes could explain the high reactivity of the catalyst despite its relatively low specific surfece area, i.e. 20 m. g". On the other hand, the high selectivity towards the C=C bond hydrogenation was attributed to the absence of a microporous network and of residual acidic sites in the carbon nanotube catalyst as compared to a commercial activated charcoal. 

Common processes in the production of ceramic or metal composites employ sinter or hot-pressing methods to blend the respective partners. However, these procedures have some serious drawbacks once it comes to the preparation of carbon nanotube composites. Firstly, a wetting of the nanotubes by the composite partner often is complicated, if not impossible, in the solid state, and secondly, it still poses considerable problems to incorporate the tubes into the matrix in a homogeneous and, where possible, individually dispersed way. 

The liquid-phase selective hydrogenation of the C=C bond in a, 3-unsaturated cinnamaldehyde was studied to show the benefit of the use of the CNTs support versus the traditional powder activated charcoal-based catalyst [75, 76]. The catalyst consisted of homogeneous palladium nanoparticles dispersed inside the carbon nanotubes. The characteristics of the Pd-based catalyst have already been detailed above. 

Other nano-fillers have also investigated. Cao et al. [253] reported the utilization of multiwalled carbon nanotubes (MWCNTs) as filler-reinforcement to improve the performance of plasticized starch (PS). The PS/MWCNTs nanocomposites were prepared by a simple method of solution casting and evaporation. The results indicated that the MWCNTs dispersed homogeneously in the PS matrix and formed strong hydrogen bonding with PS molecules. Besides the improvement of mechanical properties, the incorporation of MWCNTs into the PS matrix also led to a decrease in the water sensitivity of the PS-based materials. 

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