The optimal structure-conductivity relation in epoxy-phthalocyanine nanocomposites.
Phthalcon-11 (aquocyanophthalocyaninatocobalt (III)) forms semiconducting nanocrystals that can be dispersed in epoxy coatings to obtain a semiconducting material with a low percolation threshold. We investigated the structure-conductivity relation in this composite and the deviation from its optimal realization by combining two techniques. The real parts of the electrical conductivity of a Phthalcon-11/epoxy coating and of Phthalcon-11 powder were measured by dielectric spectroscopy as a function of frequency and temperature. Conducting atomic force microscopy (C-AFM) was applied to quantify the conductivity through the coating locally along the surface. This combination gives an excellent tool to visualize the particle network. We found that a large fraction of the crystals is organized in conducting channels of fractal building blocks. In this picture, a low percolation threshold automatically leads to a conductivity that is much lower than that of the filler. Since the structure-conductivity relation for the found network is almost optimal, a drastic increase in the conductivity of the coating cannot be achieved by changing the particle network, but only by using a filler with a higher conductivity level.
Huijbregts
L J
LJ
Technische Universiteit Eindhoven, P.O. Box 513, 5600 MB Eindhoven, The Netherlands. L.J.Huijbregst@tue.nl
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Brokken-Zijp
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Kemerink
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Chen
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Goeje
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Yuan
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Michels
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