Alignment of dispersed multiwalled carbon nanotubes in low strength AC electrical fields.

The possibilities to use electricity as a tool to induce alignment of multiwall carbon nanotubes suspended in water with help of a non-ionic surfactant have been investigated. Several different experiments were made using various field strengths and frequencies of 15-140 V/cm and 0.1-500 Hz respectively. The experiments were recorded by filming the processes through a reflected light microscope. Each movie is between 15-45 seconds long and is adequate to estimate orientation rates and alignment directions. It was observed that the alignment rate increased with increasing field strength and that the system is less sensitive at lower frequencies. Both field strength and frequency can be used to control the speed and degree of orientation. At low frequencies, the suspension is forced to oscillate in a pumping fashion between the electrodes. The nanotubes are forced to align with the fluid streamlines rather than with the field lines. At higher frequencies, the oscillation ceases. Alignment rate increases with increasing field strengths. The MWNTs are fully aligned in less than 1 s for an electrical field > or = 70 V/cm and frequency > 20 Hz. A similar experiment was carried out for a non-ideal MWNT/H2O dispersion system. It was observed that the MWNTs aligned in the same fashion as before but after a few minutes a transition occurred. The MWNTs moved quickly towards each other and a network consisting of mainly aligned MWNTs was created. The MWNT movement slowed down after the network had branched out to connect the electrodes. The alignment of CNTs in an applied electrical field seems to be an efficient, quick, and cheap method with many advantages. The method opens doors to many interesting and exciting possibilities for production of novel materials with unique properties. Both alignment of separated MWNTs and the creation of aligned MWNTs in networks are of interest from an engineering point of view.