Thixotropic behavior and particulate aggregation in a suspension of carbon nanotubes

The present study dealt with the evaluation of the particulate aggregation in a suspension of multi-walled carbon nanotubes using fractal theory and rheological properties including thixotropy. The multi-walled carbon nanotubes are dispersed in Newtonian glycerol in the concentration range between 0.2 and 0.45 wt%. Rheological measurement was performed for the suspension at various dispersion times up to 300 min. The suspension showed thixotropy, shear-thinning behavior, and yield stress. It also exhibited plateaus of storage modulus in frequency and strain sweep tests. As the dispersion time increases, thixotropy, low-shear viscosities, and yield stress increase, and then their increasing rates slow down. Suspension's electrical conductivity also showed similar behavior as that of thixotropy with the dispersion time. Viscoelastic behavior was combined with a fractal concept to provide the fractal dimensions of the flocs in the suspension at various dispersion times. The fractal dimension tends to decrease with the dispersion time. Conclusively it is interpreted that as the dispersion proceeds flocs become smaller and chain-like, then the reduced and thinned flocs build the wider range of network structures at rest state.