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

Morales, Noé J., Goyanes, Silvia, Chiliotte, Claudio, Bekeris, Victoria, Candal, Roberto J., Rubiolo, Gerardo H.
Carbon 2013 v.61 pp. 515-524
acetylene, carbon nanotubes, catalysts, dispersibility, hematite, hydrophilic polymers, nanoparticles, oxidation, pH, particle size, vapors
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 10–50nm) 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 5.7emu/g at an applied field of 18kOe and a coercivity of 520Oe. The hybrid displayed a relatively low pHZPC (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.