When the size of the nano-ferric oxide particles is reduced to the nanometer order, due to the small size effect, surface effect, quantum size effect and macroscopic quantum tunneling effect of the nanoparticles, it has a special difference from the conventional bulk materials. Magnetic properties. This also makes it have special applications in the fields of industry, biomedicine and so on.

1.Magnetic recording material
One of the most important uses of Fe3O4 magnetic particles is to make magnetic recording materials. Due to its small size, the Fe3O4 iron oxide nanoparticles have a magnetic structure from multi-domain to single-domain, and have a very high coercive force. The magnetic recording material can greatly improve the signal-to-noise ratio and improve the image quality. It is also possible to achieve a high density of information records. Nano-sized triiron tetroxide particles must have high coercivity and magnetization, small size, corrosion resistance, friction resistance and temperature adaptation to achieve the best recording results.

2. Microwave absorbing materials
Due to the small size effect of the nano-ferric oxide particles, it has optical properties not possessed by conventional bulk materials, such as optical nonlinearity, as well as light absorption, energy loss during light reflection, etc., and the size of the nanoparticles is very Big interrelationship. Studies have shown that various optical materials prepared by special optics of nano-ferric oxide particles are used in daily life and high-tech fields. The research is still in the laboratory stage now. The quantum size effect of the nano-ferric oxide particles makes it have a blue shift in light absorption at a certain wavelength. The nano-ferric oxide particles have a widening effect on the absorption of light of various wavelengths. Due to its high magnetic permeability, the Fe3O4 magnetic nanopowder can be used as a ferrite absorbing material for microwave absorption.
3. Biomedicine
Magnetic polymer microspheres (immunomagnetic microspheres) are biomedical materials prepared from magnetic nanoparticles and polymer matrix materials. The polymer materials include polystyrene, silane, polyethylene, polyacrylic acid, and starch. , dextran, gelatin, albumin, ethyl cellulose, etc., the skeleton material is mainly an inorganic material having magnetic properties. Because ferroferric oxide nanoparticles have these stable physical properties, have better biocompatibility, higher strength, and are non-toxic and have no side effects, they are widely used in many fields of biomedicine, such as Magnetic resonance imaging, high magnetic separation, targeted drug carriers, tumor hyperthermia techniques, cell labeling and separation, as well as enhanced imaging, contrast agent research, retinal detachment repair surgery, etc.
4. Catalyst carrier
Ferric oxide particles are used as catalysts in many industries, such as the preparation of NH3, high-temperature water-gas shift reactions and natural gas desulfurization reactions. Since the size of the ferroferric oxide nanoparticles is small, the specific surface area is large, the surface smoothness of the nanoparticles is poor, and an uneven atomic step is formed, which increases the contact surface of the chemical reaction. At the same time, with the ferroferric oxide particles as the carrier, the catalyst component covers the surface of the particles, and the catalyst ultrafine particles of the core-shell structure are obtained, which not only maintains the high performance of the catalyst, but also facilitates recovery.
5. Magnetic liquid
Magnetic liquid is a new functional material, which is a highly stable colloidal solution formed by highly dispersing a large number of nano-scale ferromagnetic or ferrimagnetic particles in a liquid carrier liquid. The magnetic liquid in which the particles and the carrier liquid are mixed by the surfactant can exist stably for a long time under the action of the gravity field, the electric field and the magnetic field, and does not cause precipitation and separation. At present, magnetic liquid has been widely used in mineral processing technology, precision grinding, magnetic liquid damping device, magnetic liquid sealing, magnetic liquid bearing, magnetic liquid printing, magnetic liquid lubrication, magnetic liquid fuel, magnetic liquid dye, magnetic liquid velocity sensor and acceleration sensor. , magnetic liquid frequency converter, magnetic liquid gyroscope, underwater low frequency sound wave generator, used for shift register display.