Coating of zinc ferrite particles with a conducting polymer, polyaniline.

Particles of zinc ferrite, ZnOFe2O3, were coated with polyaniline (PANI) phosphate during the in situ polymerization of aniline in an aqueous solution of phosphoric acid. The PANI-ferrite composites were characterized by FTIR spectroscopy. X-ray photoelectron spectroscopy was used to determine the degree of coating with a conducting polymer. Even a low content of PANI, 1.4 wt%, resulted in the 45% coating of the particles' surface. On the other hand, even at high PANI content, the coating of ferrite surface did not exceeded 90%. This is explained by the clustering of hydrophobic aniline oligomers at the hydrophilic ferrite surface and the consequent irregular PANI coating. The conductivity increased from 2 x 10(-9) to 6.5 S cm(-1) with increasing fraction of PANI phosphate in the composite. The percolation threshold was located at 3-4 vol% of the conducting component. In the absence of any acid, a conducting product, 1.4 x 10(-2) Scm(-1), was also obtained. As the concentration of phosphoric acid increased to 3 M, the conductivity of the composites reached 1.8 S cm(-1) at 10-14 wt% of PANI. The ferrite alone can act as an oxidant for aniline; a product having a conductivity 0.11 S cm(-1) was obtained after a one-month immersion of ferrite in an acidic solution of aniline.