Nanocomposites and nanomaterials

Influence of addition filler’s type on tunnel conductivity of carbon/polymer composites
Perets Yu.S.1, Vovchenko L.L.1, Matzui L.Yu.1, Yakovenko O.S.1, Lazarenko O.A.1
1 Department of Physics, Kyiv National Taras Shevchenko University, Volodymyrs’ka str., 64, Kyiv, 01033, Ukraine.
E-mail: yu.s.perets@gmail.com

In this paper, the influence of various parameters on the temperature dependences of the resistance of mono and hybrid polymer composites (CMs) was investigated. In order to understand exactly how the composition of the polymer CMs affects the temperature dependence of the resistance, several types of CMs have been investigated. Type one is monofiller CMs in which the polymer type was varied. The second type is hybrid CMs in which carbon filler (GNPs or MWCNTs) was combined with different kinds of the second filler (boron nitride, barium hexafferite, magnetite). The electric resistance of the samples was measured by two-probe and four-probe method in temperature region 6 K - 300 K.
Percolation parameters, the distance between filler particles and other parameters of all of the investigated CMs were estimated using expression [1]:
	(1)
where δ — thickness of the polymer layer, j — density of the tunnel current, V — potential difference, e and m — charge and mass of an electron, h — Planck constant, λ — height of the barrier (in case of the epoxy λ  1 еV [1]), w — cross-sectional tunneling value.
It was shown that in mono CMs with GNPs the distance between the particles when overcoming the percolation threshold is about 0.35 nm which is 10 times lower than that of CMs with CNTs. The addition of a dielectric filler to the CMs reduces its resistance, indicating that the particles are delaminated and unraveled. GNPs become a binder for MWCNTs in CMs where carbon fillers are mixed in different ratios and thus increase the number of electrically conducting chains and reduce resistance of the hybrid composite.

1.	Hu N., Karube Y., Arai M., Watanabea T., Yand C., Lia Y., Liua Y., Fukunagab H. Investigation on sensitivity of a polymer/carbon nanotube composite strain sensor // Carbon. – 2010.- 48, N 3. P. 680–687.