Well-aligned carbon nanotubes (CNTs) with different shapes, namely coiled CNTs ( CCNTs), V-shape CNTs (VCNTs) and ribbon-like CNTs (RCNTs), were prepared by floating catalyst chemical vapor deposition (FC-CVD) using triethylsilane and ferrocene as catalyst precursors and xylene as carbon source. The products were characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction and energy dispersive spectrometer. The experimental results indicated that triethylsilane limited the catalyst effectivity in the formation of the novel shapes. When the mole ratio of ferrocene and triethylsilane reached 10:1, the array morphology was maintained and several shapes appeared. It inferred that the catalyst particles were formed by two phases, namely Fe-C-Si solid solution and cementite Fe3C. The different absorption and desorption rates of carbon atoms between this two phases as well as the catalyst morphology change during the growth consequently lead to the formation of CCNTs and RCNTs. As for the VCNTs, it concluded that the partial inactivation of catalysts lead to two separated growth areas of CNTs which formed this CNTs. A mechanism is proposed to explain the relationships between the adding of triethylsilane and the formation of the novel structure. (C) 2015 Elsevier B.V. All rights reserved.