Structural transitions in aqueous suspensions of natural graphite

The electric conductivity $\sigma $ and plastic viscosity $\eta$ of aqueous suspensions at different volume fraction of graphite $\phi $ and concentration of nonionic surfactant (Triton X-305) are investigated. The correlations between conductivity and rheological properties are discussed. A model of structural transitions in aqueous graphite suspensions is discussed. Two structural transitions, corresponding to changes in electrical and rheomechanical properties, are identified as percolation and sol-gel transitions, respectively. An unusual initial decrease of the bulk electrical conductivity with graphite volume fraction $\phi $ increase was observed in surfactant solution. This fact is explained as a result of isolating coating formation around the graphite particles.