A multi-nebulizer-based aerosol-assisted system for the synthesis of magnetic iron mixed metal oxides nanoparticles (MFe2O4, M = Fe2+, Ni2+, Mn2+, Co2+, Zn2+)

Toward scaling up magnetic nanoparticle synthesis from laboratories to the industry, this study reports on the development of a multi-nebulizer-based aerosol-assisted system. The developed system consists of three main parts: a sprayer, an electric heater tunnel, and a rotating magnetic collector. The sprayer consists of a peristaltic pump and two homemade glass concentrate pneumatic nebulizers with untreated fused silica capillaries. High purity nitrogen gas was used as the carrier gas for the generation of aerosols of the reagents pumped into the nebulizers. The angle between the two nebulizers was 35°. The electric heater tunnel consists of 6 tungsten filaments covered by cylindrical stainless steel plates. A dimmer was also used to preset the tunnel temperature. The tunnel temperature was measured using an infrared thermometer. The aerosol generated from the sprayer travel inside the hot tunnel (250–330 °C) for the further reaction of the precursor reagents and desolvation of the synthesized nanoparticles. The rotating magnetic collector consists of a cylindrical neodymium permanent magnet located inside a stainless steel cylindrical plate. The cylindrical complex is rotated using a gearbox DC motor to collect the synthesized MNPs exiting from the electric heater tunnel. Using the developed system, Fe₃O_4, CoFe₂O_4, MnFe₂O_4, NiFe₂O₄, and ZnFe₂O₄ were synthesized successfully. XRD, VSM, and FE-SEM analysis were utilized to characterize the synthesized nanoparticles. The SEM images of the synthesized nanoparticles showed that all synthesized nanoparticles were spherical (except for ZnFe₂O₄). The average diameters were 121.13, 43.19, 33.21, 33.28, and 33.63 nm for Fe₃O_4, CoFe₂O_4, MnFe₂O_4, NiFe₂O₄, and ZnFe₂O₄ nanoparticles using the developed method under the optimized conditions for each nanoparticle. As compared with similar methods such as the spray pyrolysis and aerosol-assisted chemical vapor deposition, the developed method can be utilized for the synthesis of magnetic nanoparticles of relatively higher magnetization at lower temperatures.