Electrical resistivity of compacted TEG and TEG-Fe under compression

Electric resistivity of compacted composite materials (CM) based on thermoexfoliated graphite TEG and TEG–Fe3O4+Fe under compression (along a-axis or C-axis) has been investigated by four-probe method. The estimation of the effective Yung module along a-axis Eeff(a) for compacted TEG gives the values ∼1.6 GP a that is higher than Eeff(C) along C-axis—1.0 GPa. The fixing of iron particles on TEG surface leads to increase of Eeff(a) up to 2.4 GPa. It was shown that several different processes could occur under compression of specimens: additional compacting of specimen under loading due to plastic deformation (the improvement of contact between particles, R decreases); specimen micro-rupture (R increases); the rotation of graphite macro-planes (Ra increases due to anisotropy of TEG particles' resistivity ρ); the increasing of contact areas between TEG particles and contact pressure at compressing (the decrease of R, that is reversible in a case of elastic deformation of specimens). The irreversible changes in the value of normalized resistance R/R0 were shown to be in direct proportion to the plastic deformation εplast at compression along a-axis while R/R0 (σ) has maximum at compression along C-axis.