One-step chemical vapor deposition synthesis of magnetic CNT-hercynite (FeAl2O4) hybrids with good aqueous colloidal stability

A multiwall carbon nanotube (MWCNT)/hercynite (FeAl2O4) hybrid nanomaterial was synthesized by one-step chemical vapor deposition (CVD) using acetylene as precursor and FeOx-AlOOH xerogel as catalyst. The hybrid material was composing by hercynite nanoparticles (diameter 10-50 nm) intimately attached to the walls of the MWCNTs. The diameter of the MWCNTs was related to particle size of the catalyst. The hybrid nanomaterial exhibited a characteristic magnetic behavior that can be considered as a combination of superparamagnetism and ferromagnetism, with a saturation magnetization of 5.7 emu/g at an applied field of 18 kOe and a coercivity of 520 Oe. The hybrid displayed a relatively low pH(ZPC) (approx. 3.2) and formed very stable aqueous suspensions at pH 5.5. Controlled oxidation of the hybrid generated oxidized functional groups, as -OH and -COOH, and promoted the transformation of hercynite to hematite. Due to the high dispersibility of the hybrid in water, it presents an interesting potential as nanofiller for hydrophilic polymers. (C) 2013 Elsevier Ltd. All rights reserved.