Abstract:
Electric resistivity ρ of graphite (including thermoexfoliated one) are mainly governed both
by its structure and morphology. The analysis of electric properties in this case is strongly
complicated by the presence of the high anisotropy of ρ for graphite crystal and peculiar
conductivity mechanism in the disordered areas at the boundaries of the ordered graphite crystals.
That is why, the mechanisms determining the transport properties of the graphite-based structures
remains still discussible. Here, several speculations concerning the interpretation of ρ(Т)
dependencies for nanocomposite materials (NCM) on the base of thermoexfoliated graphite (TEG)
containing different metal constituent are thoroughly analyzed.
The specimens for investigation were prepared by the compacting of the source materials
under the pressure ranging from 60 to 450 MPa. Metal modifier has been involved into NCM
structure by chemical deposition. The ρ(Т) dependencies within 77-450 К temperature range were
investigated by the routine four-probe method.
Electron microscopy investigation shows that the metal modifier particles 100-300 nm in
size are located at the surface of the graphite platelets (Fig.1). The size of these platelets along a
axis is much greater that along c axis. The X-ray diffraction studies evidence for high extend of
texture of the compacted specimens. Since с axis was oriented along the compacting axis, the
electric current in our experimental geometry flowed in the basis plain for the majority of the
graphite crystallites. The size of the graphite crystallites L along с axis was determined by the width
of (002) and (004) TEG reflections) It is ranged within 70-120 nm (see Table). The values of L
were reduced down to 40-50 nm in a result of impregnation by mineral-organic composition with
the subsequent thermal shock at 800°С
