Graphene-supported carbonaceous dielectric sheets and their electrorheology

Two-dimensional dielectric sheets composed of graphene-supported amorphous carbon were prepared by annealing polyaniline-coated graphene oxide sheets in vacuum. The morphology and structure were characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and Fourier-transform infrared spectroscopy. This showed that annealing the polyaniline-coated graphene oxide had little influence on its plate-like morphology but transformed the graphene oxide core into conducting graphene and the polyaniline shell into insulating nitrogen-enriched amorphous carbon. An electrorheological suspension was prepared by dispersing the graphene-supported carbonaceous sheets in silicone oil and its electrorheological property was investigated by rhelogical tests under electric fields. The suspension demonstrated a strong electrorheological effect. Its yield stress and shear stress were about three times as large as those of a suspension of pure carbonaceous particles at equal electric field strengths. The storage modulus of the suspension was also higher than that of a suspension of pure carbonaceous particles, indicating stronger electrorheological activity. Dielectric measurements indicated that the presence of the graphene core had increased the polarization property, and this is responsible for the increased electrorheological activity. (C) 2012 Elsevier Ltd. All rights reserved.