Abstract

Mesoporous magnetite (Fe₃O₄) was successfully synthesized on a large scale by direct pyrolysis of ferric nitrate-EG (EG = ethylene glycol) gel in a one-end closed horizontal tube furnace in the air without using any template, additions, and carrier gas. The as-synthesized mesoporous Fe₃O₄ were characterized by powder X-ray diffraction (XRD), infrared spectra (IR), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), Brunauer–Emmett–Teller (BET), Barrett–Joyner–Halenda (BJH), and thermal gravimetric analysis (TGA). Results from TEM showed that the as-obtained Fe₃O₄ has mesoporous structure formed by the loose agglomeration of nanoparticles with diameter of about 6 nm, which was also confirmed by small-angle XRD and nitrogen adsorption analysis. Furthermore, vibrating sample magnetometer (VSM) measurements indicated that the saturated magnetization of the as-obtained mesoporous Fe₃O₄ was ferromagnetic with the saturation magnetization (Ms) and coercivity (Hc) of 46 emu/g and 136 Oe, respectively. In addition, a possible growth mechanism of mesoporous Fe₃O₄ was also discussed.

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Research highlights

Mesoporous magnetite (Fe₃O₄) was successfully synthesized by direct pyrolysis of ferric nitrate-EG (EG = ethylene glycol) gel in a horizontal tube furnace in the air. The as-prepared mesoporous Fe₃O₄ was formed by the loose agglomeration of nanoparticles with diameter of about 6 nm. Mesoporous Fe₃O₄ with the BET surface area and total pore volume of 145 m²/g and 0.12 cm³/g were obtained at 400 °C for 12 h.