Structural transitions in aqueous suspensions of natural graphite

The electric conductivity σ and viscosity η of aqueous suspensions at different volume fraction of graphite ϕ 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 electrical connectivity and rigidity (or sol–gel) percolation transitions, respectively. An unusual initial decrease of the bulk electrical conductivity with graphite volume fraction ϕ increase was observed in the surfactant solution. This fact is explained as a result of an isolating coating formation around the graphite particles.