Crystallization of Magnetic Iron Oxide Nanoparticles during Chemical Synthesis from Iron Salt Solutions with Exposure to Ultrasound

Iron oxide nanopowders are synthesized via chemical precipitation. It is shown that synthesis produces an iron oxide phase with a magnetite structure (either a magnetite–maghemite solid solution or a mixture of this solid solution and goethite). The sizes of the CSR and particles for the main phase are 10–20 nm. The synthesized iron oxide powders have developed surfaces, specific surface area SBET ≈ 92 and 117 m2/g, and identical fairly large specific pore volumes ( V_P_/P_0→ 0.99_ = 0.35 cm3/g). It is shown that additional in situ ultrasonic treatment of the magnetic iron oxide nanoparticles in the mother liquor results in abrupt oxidation of iron(II) ions and creates a nonmagnetic impurity phase of goethite.