Triiron Tetraoxide Hardness With Great Magnetic Properties
Iron oxide is a commonly used magnetic material, also known as iron oxide black, black or gray-blue. Iron oxide is a ferrite, that is, Fe2 + Fe3 + (Fe3 + O4) (ie FeFe (FeO4) in front of 2 + and 3 + represents the valence of iron). In Fe3O4, iron was two valence, an iron atom was +2 price, two iron atoms were +3 price, so that iron oxide can be seen as a compound composed of FeO and Fe2O3, can be expressed as FeO 〃Fe2O3, and can not be said to be a mixture of FeO and Fe2O3, it is pure matter.
The hardness of iron oxide is very large, with magnetic, can be seen as ferrous oxide and iron oxide composition of the compound, reverse spinel type, cubic crystal system. In the external magnetic field can be directional movement, particle size within a certain range with superparamagnetism, and in addition to alternating electromagnetic field can produce heat and other characteristics, its chemical stability, and therefore a wide range of uses.
Preparation of nano - ferric oxide
The preparation method of nano-particles mainly includes:
Physical methods for the preparation of nanoparticles are generally vacuum condensing method, physical pulverization method, mechanical ball milling method. However, the sample prepared by physical method has a low purity, poor particle distribution, easy to be oxidized, and difficult to prepare nanoparticles below 10 nm, so it is rarely adopted in industrial production and testing.
Chemical methods are coprecipitation, sol-gel method, microemulsion method, hydrolysis method, hydrothermal method and so on. The particles with the nanoparticles obtained by chemical method are generally of good quality, small particle size, easy operation method and low production cost. It is the main method of research and production.
1, coprecipitation method:
Precipitation method is in a soluble salt solution containing two or more metal ions, adding a suitable precipitant to uniformly precipitate or crystallize the metal ions, and then dehydrating or thermally decomposing the precipitate to produce nanometer powder.
2, sol-gel method:
Sol - Gel method is a new process for the preparation of monodisperse metal oxide particles in liquid phase developed by Japanese scientists.
3, microemulsion method:
Microemulsion is a thermodynamically stable system of transparent, isotropic and low viscosity composed of oil, water and surfactant. The nonpolar substance which is insoluble in water is used as the dispersion medium, and the aqueous solution of the reactant is dispersed Phase, the surfactant is an emulsifier, forming a water-in-oil or oil-in-water microemulsion.
4, hydrothermal method:
The hydrothermal method is a method in which water is used as a reaction medium in a high-temperature, high-pressure reaction environment in a closed autoclave, and a precursor which is usually insoluble or insoluble is dissolved to crystallize it.
Application of nano - iron oxide
When the size of ferric oxide is reduced to the nanometer level, it has a special effect such as the small size effect, the surface effect, the quantum size effect and the macroscopic quantum tunneling effect of the nanoparticles, nature. Which also makes it in the industrial, biomedical and other fields have a special application.
Magnetic polymer microspheres (also known as immunomagnetic microspheres) are biomedical materials prepared from magnetic nanoparticles and polymeric skeletal materials. Polymeric materials include polystyrene, silane, polyethylene, polyacrylic acid , Starch, dextran, gelatin, albumin, ethyl cellulose, etc., the skeleton material is mainly a magnetic inorganic material. Fe3O4 is widely used in many fields of biomedical, such as magnetic resonance imaging, magnetic separation and targeting, because of its stable material properties, good biocompatibility, high strength and non-toxic side effects. Drug carrier, tumor hyperthermia, cell labeling and isolation.
2, magnetic liquid:
Magnetic liquid is a new type of functional material, it will be a large number of nano-scale ferromagnetic or ferrous magnetic particles highly dispersed in the liquid carrier in the composition of a highly stable colloidal solution, particles and carrier liquid through the surfactant Mixed magnetic liquid even in the gravity field, electric field, magnetic field can also be long-term stability of the existence, does not produce precipitation and separation. At present, the magnetic fluid has been widely used in mineral processing technology, precision grinding, magnetic liquid damping device, magnetic liquid seal, magnetic liquid bearings, magnetic liquid printing, magnetic liquid lubrication, magnetic liquid fuels, magnetic liquid dyes, magnetic liquid velocity sensors and acceleration sensors , Magnetic liquid frequency converter, magnetic liquid gyroscope, underwater low frequency sound wave generator, for the shift register display.
3, the catalyst carrier:
Fe3O4 particles are used as catalysts in many industrial reactions. Due to the small size, specific surface area of Fe3O4 nanoparticles, and the surface of nano-particles rough, the formation of uneven atomic steps, increasing the chemical reaction of the contact surface. At the same time, the Fe3O4 particles as the carrier, the catalyst composition on the surface of the particles, the preparation of nuclear - shell structure of the catalyst ultrafine particles, both to maintain the catalytic performance of the catalyst, but also easy to recover the catalyst. Therefore, Fe3O4 particles are widely used in catalyst carrier research.
4, Microwave absorbing material:
The quantum size effect of nanoparticles makes it have a blue shift phenomenon for some wavelength of light absorption. The nanoparticle powder has a broadening of the absorption of light at various wavelengths. Fe3O4 magnetic nano-powder because of the high permeability, can be used as a ferrite absorbing material, used in microwave absorption.
5, magnetic recording material:
Another important use of nanometer Fe3O4 magnetic particles is used to make magnetic recording materials. Nano Fe3O4 because of its small size, the magnetic structure from the multi-domain into a single domain, with a very high coercive force, used to do magnetic recording material can greatly improve the signal to noise ratio, improve image quality, and can achieve high information records density. In order to achieve the best recording results, nano Fe3O4 particles must have a higher coercive force and residual magnetization, smaller size, corrosion resistance, abrasion resistance and adaptable temperature changes.
6, magnetic seal:
Magnetic fluid, also known as magnetic fluid or ferromagnetic fluid, with the magnetic field can control its physical properties, with a liquid carrier of the mobility, lubricity and sealing. It is composed of nanoscale (10nm below) the strong magnetic particles dispersed in a certain degree of liquid formed in a stable colloid system. Can be used as a mechanical seal of the rotary shaft seal (dynamic seal), the use of magnetic liquid is both a fluid and magnetic material characteristics, it can be adsorbed in the permanent magnet or electromagnet gap, so that two relatively moving objects are sealed. The formation of liquid O-ring, for precision instruments, precision machinery, gas seals, vacuum seals, pressure seals, etc.; dynamic seal the most widely used, can achieve zero leakage, with a small amount of sealing liquid, shock, no mechanical wear, , Low power consumption, no aging, self-lubricating, long life, wide speed range, simple structure, the accuracy of the shaft and finish requirements are not high, reliable sealing and so on.