A 22 ppm ultralow percolation threshold with MWCNT

This paper describes the effect of electric field on the structuration of carbon nanotubes in silicone oil. The particles have been dispersed in the liquid by ultrasounds and diluted in order to vary the filler content. Electrical measurements were performed under different electric fields and over time on each filler content, in order to probe the particles structuration. From a critical value, the electric field was found to both increase the conductivity of the composite and reduce percolation threshold. This effect is further enhanced with time. Spectacular percolation thresholds, as low as 22 ppm have been evidenced. This result was attributed to a strengthening effect between filler contacts. More surprisingly, the conductivity remained high after the electric field was stopped, showing the irreversible nature of this effect. In addition, an analytical model has been developed to describe the conductivity of the composite as a function of three parameters: nanotubes content, time and electric field.