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Preparation methods of magnetic nanomaterials content sharing

by:Transmart     2022-12-25

Preparation method of magnetic nanomaterial

Among a large number of well-known magnetic materials, the application of materials with high saturation magnetization but low stability is limited to a certain extent because they cannot meet the requirements of high saturation magnetization and high stability at the same time. At present, there are only a few kinds of magnetic particles that can be used as magnetic particles, mainly metal oxides, such as ferric oxide (Fe2O3), MFe2O4 (M=Co, Mn, Ni), ferric oxide (Fe3O4), binary and Ternary alloys, such as metal iron, cobalt, nickel and their iron-cobalt alloys, nickel-iron alloys, and neodymium-iron-boron (NdFeB), lanthanum-cobalt alloy (LaCo) alloys, etc., their stability (that is, oxidation resistance) decreases successively, But the saturation magnetization increases in the above order. The development of nanotechnology has made the application of these magnetic materials possible. At present, the nanotechnology of magnetic materials has become a development trend of material science.

The preparation technology of magnetic nanomaterials determines its properties and is related to the final industrial application. At present, the preparation technology of magnetic nanomaterials can be classified into many kinds, one is divided into physical method and chemical method; the other is classified according to the state of matter, such as solid phase method, liquid phase method and gas phase method. Among them, the solid-phase method includes amorphous crystallization method and high-energy ball milling method; the liquid-phase method includes spray method, deposition method, evaporation method, sol-gel method, solvent volatilization decomposition method and electrodeposition method; gas-phase method includes molten metal reaction method , Gas condensation method, vacuum evaporation method, sputtering method, laser induction method, electric heating evaporation method, mixed plasma method and chemical vapor deposition method, etc.

Each of these methods has its advantages and disadvantages:

1. The sol-gel method uses metal-organic or inorganic compounds as precursors to be solidified through solutions, sols, and gels. The advantages are simple process, many reaction species, uniform product particles, easy process control, good dispersion, and easy realization. High purification, short reaction cycle, and low reaction temperature, but the preparation cost is high, and high-temperature calcination is required, which is unfavorable for the synthesis of small-sized magnetic nanoparticles;

2. Amorphous crystallization method is a method to realize nanocrystallization through annealing heat treatment on the basis of amorphous;

3. The high-energy ball milling method is in the high-energy ball mill, through the frequent collision of tens of micron magnetic material coarse particles with grinding balls, grinding pots and particles, so that these micron solid particles are repeatedly squeezed, deformed, Strong plastic deformation such as fracture and welding will increase the defect density on the surface of magnetic material particles, and the grains will gradually refine until nano-scale magnetic particles are formed.

4. The ball milling method is easy to operate and the cost is low, but the magnetic nanomaterials prepared by this method are easy to introduce impurities, and it is difficult to obtain uniform and fine particles. At the same time, there are poor dispersion, many crystal defects, and stable particles. The shortcomings of low performance and high energy consumption.

5. The mechanical alloying method can prepare high-melting point metals and alloy nanomaterials that are difficult to obtain by conventional methods. It can also prepare nano-intermetallic compounds, solid solutions of mutually immiscible systems, and nanocrystalline ceramic composite materials. The process is simple and The efficiency is high, so it is an effective process method for preparing magnetic nanomaterials.

6. The sputtering method is a relatively mature method with large output, relatively simple process, low cost, and easy control of grain size, but the disadvantage is that there are inevitably some defects on the surface of the roller, so the strips produced by this method There are defects such as microcracks, and only two-dimensional magnetic nanomaterial thin strips can be prepared by this method.

7. The precipitation method includes co-precipitation method, uniform precipitation method and direct precipitation method. Co-precipitation method is suitable for preparing oxides. It is to add a precipitant to the mixed metal salt solution to obtain a solution with uniform components, and then perform thermal decomposition. The feature is simple and easy, but the product has low purity and large particle size; the direct precipitation method is to make the metal cation in the solution react directly with the precipitant to form a precipitate; the uniform precipitation method is to add the precipitant solution to the metal salt solution Stir constantly, so that the precipitant is slowly generated in the solution, eliminating the inhomogeneity of the precipitant.

8. The chemical vapor deposition method is also called the gas phase chemical reaction method. The prepared product has fine particles, uniform shape and good dispersibility.

9. The pyrolysis method is to heat and decompose organometallic compounds in high-boiling organic solvents to prepare nanoparticles.

10. The microemulsion method is to pass two kinds of immiscible liquids through surfactant molecules as an interface film to form a thermodynamically stable and isotropic dispersion system, which can limit the processes of nucleation, growth, coalescence, and agglomeration. In a tiny spherical droplet, spherical particles can be formed, and further agglomeration between particles is avoided. Therefore, the nanoparticle particle size distribution obtained by this method is narrow, and the monodispersity, interfacial property and stability are good. At the same time, Compared with other methods, it also has the advantages of simple experimental equipment, easy control of particle size, low energy consumption, and wide adaptability.

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