Synthesis, structure and electromagnetic properties of mesoporous Fe3O4 aerogels by sol–gel method

• Fe3O4 aerogels possess quite low density and large specific surface area.
• The porous Fe3O4 aerogels show superparamagnetism and high saturation magnetization.
• We study the influences of concentration, molar ratios of reactants and calcinations on the textural and magnetic properties.
• The porous material with electromagnetic properties can be a microwave absorbent.

The Fe3O4 aerogels have been prepared by the sol–gel method and subsequent supercritical drying with CO2, FeCl3·6H2O, FeCl2·4H2O and propylene oxide was used as precursor and gelling accelerator, respectively. The result from XRD indicated that the aerogels were composed of nano-crystals. XPS was employed to further characterize the structure of products and confirmed the existence of Fe and O. SEM and TEM showed a fine microstructure of the as-prepared aerogels with three dimensional network, and the skeletons of aerogels were consist of interconnected nanoparticles. The Fe3O4 aerogels also possessed quite low density (0.249–0.393 m2 g−1), large specific surface area (60.26–330.20 m2 g−1) and superior saturation magnetization (14.64–52.28 emu g−1). Moreover, the textural and magnetic properties of the aerogels could be controlled by solution concentration, molar ratio of propylene oxide (PO) to Fe3+ and calcination temperature. The fabricated Fe3O4 aerogels exhibited certain electromagnetic properties in the frequency range of 2–18 GHz, and the maximum value of tan δe and tan δm is 0.07 and 0.27, respectively.