Carbon nanotubes have mechanical properties that are far in excess of conventional fibrous materials used in engineering polymer composites. Effective reinforcement of polymers using carbon nanotubes is difficult due to poor dispersion and alignment of the nanotubes along the same axis as the applied force during composite loading. This paper reviews the mechanical properties of carbon nanotubes and their polymer composites to highlight how many previously prepared composites do not effectively use the excellent mechanical behaviour of the reinforcement. Nanomechanical tests using atomic force microscopy are carried out on simple uniaxially aligned carbon nanotube-reinforced polyvinyl alcohol (PVA) fibres prepared using electrospinning processes. Dispersion of the carbon nanotubes within the polymer is achieved using a surfactant. Young's modulus of these simple composites is shown to approach theoretically predicted values, indicating that the carbon nanotubes are effective reinforcements. However, the use of dispersant is also shown to lower Young's modulus of the electrospun PVA fibres.

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A comparative study has been performed in order to quantify the signal-to-background ratio of Raman measurements in fuel-rich flames using pulsed laser radiation at 532, 489, 355 and 266 nm. For the comparison, spectra were recorded in stable premixed, sooting and non-sooting C 2 H 4 /air flames with equivalence ratios of φ = 1.58, 1.92 and 2.0. The spectra show that the background, consisting mainly of laser-induced emissions from polycyclic aromatic hydrocarbons and from C 2 radicals, changes significantly with the laser wavelength. Although the Raman cross sections increase at shorter wavelength the signal-to-background ratio in the flames investigated is clearly the best for λ = 532 nm and the worst for λ = 266 nm. The presented results show the potential and limitations of concentration measurements by laser Raman scattering in fuel-rich flames and are a valuable aid for the decision of what laser system should be used for measurements in laboratory or practical flames.

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