The fly ash cenospheres (FACs) were pretreated with gamma-aminopropyltriethoxy silane (APS), and the outward amino groups are favorable to the following in situ growth of polyaniline as a conducting polymer layer on the surfaces of FACs to form FAC/polyaniline core shell structural composites. Mullite/polyaniline composites were also fabricated by further converting the FACs to mullite. The as-prepared samples were characterized by zeta potential measurements, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, as well as thermogravimetric analyses. The results of this study indicate that FACs can be successfully modified by APS, and that due to the action of APS, uniform and continuous polymer layer in the FAC/polyaniline composites was obtained under the given in situ polymerization condition. After dipping in 2.0% HF solution for 1h, the FAC cores changed into porous mullite so as to prepare mullite/polyaniline composites. (C) 2012 Elsevier B.V. All rights reserved.