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The reaction principle and method of ferroferric oxide magnetic particles

wallpapers News 2021-11-25
The reaction principle and method of ferroferric oxide magnetic particles
Ferroferric oxide has ferromagnetism. If the particle radius is at the nanometer level, it is called ferromagnetic particles.
Since 2013, a large number of pieces of literature on the preparation of nano-Fe3O4 have emerged, and some new preparation processes have also continued to appear. The traditional methods for preparing nano-Fe3O4 mainly include the precipitation method, hydrothermal (solvothermal) method, micro emulsification method, and sol-gel method. Emerging preparation methods such as microwave method, pyrolysis carbonyl precursor method, ultrasonic method, air oxidation method, pyrolysis-reduction method, polyol reduction method, etc., are gradually becoming the research focus of scholars. In the related preparation methods of Fe3O4, new types of surfactants and preparation systems have also made breakthroughs. Surfactants are not limited to SDS, PEG, CTAB, citric acid, oleic acid, etc., and NSOCMCS and polyacrylamide as modifiers have also been reported. The preparation system also successively appeared in the ethanol-water system, n-propanol-water, propylene glycol-water system, and so on.
The precipitation method is the most commonly used method for preparing nanoparticles due to its simple process operation and low cost, high product purity, and uniform composition, and is suitable for large-scale production. At the same time, by adding an organic dispersant or complexing agent to the precipitation mixture, the dispersibility of nanoparticles can be improved, and the shortcomings of easy agglomeration of nanoparticles can be overcome. Commonly used precipitation methods include co-precipitation, hydrolytic precipitation, ultrasonic precipitation, alkoxide hydrolysis, and chelate decomposition.
The hydrothermal (solvothermal) reaction is a general term for chemical reactions carried out in fluids such as aqueous solutions (organic solvents) or steam under high temperatures and pressure. The hydrothermal method is a synthesis of nano-powders developed in the past ten years. The Fe3O4 prepared by this method has a small particle size, relatively uniform particle size, does not require high-temperature calcination pretreatment, and can achieve the doping of multivalent ions. miscellaneous. However, since the hydrothermal method requires the use of high-temperature and high-pressure equipment, the cost of this method is relatively high and it is difficult to achieve large-scale production.
The preparation of nano-Fe3O4 by hydrothermal method mostly uses inorganic iron salts (FeCl3·6H2O, FeCl2·4H2O, FeSO4) and organic iron salts (ferrocene Fe(C5H5)2) as precursors, with hydrazine and polyethylene glycol, PVP, etc. as surfactants, synthesized under alkaline solution conditions below 200℃.
Showing Sun prepared superparamagnetic Fe3O4 particles with controllable particle size by hydrothermal method. First, Fe(acac)3 was used as the Fe source to prepare Fe3O4 particles with a particle size of 4nm, and then Fe3O4 particles with a particle size of 4nm were used as seeds. By controlling the holding time and other factors, the particles were prepared with particle sizes of 6, 8, and 12 respectively. , 16nm Fe3O4 nanoparticles.
Zhen Li et al. reported the use of common FeCl3·H2O instead of expensive Fe(acac)3 as a precursor to prepare Fe3O4 nanoparticles.
Yadong Li et al. reported that FeCl3·6H2O, NAC, EG, and PEG were used as raw materials to prepare monodisperse Fe3O4 nanoparticles with adjustable particle size.
The micro emulsification method refers to the formation of an emulsion by two immiscible solvents under the action of surfactants, that is, amphiphilic molecules divide the continuous medium into tiny spaces to form a microreactor, in which the reactants react to form a solid phase. The processes of nucleation, crystal growth, coalescence, and agglomeration are restricted by the microreactor, so as to form nanoparticles that are wrapped with a layer of surfactant and have a certain condensed structure and morphology.
The preparation of nano-catalysts by the microemulsion method has the advantages of simple equipment, mild experimental conditions, and controllable particle size, which are unmatched by other methods. Therefore, it has become a very interesting technology in the synthesis of nanocatalysts. The research on the preparation of nanocatalysts by the microemulsion method mostly focuses on the control of particle size, and there are relatively little researches on the control of particle monodispersity.
The sol-gel method uses the hydrolysis and polymerization of metal alkoxides to prepare a uniform sol of metal oxides or metal hydroxides and then concentrates them into a transparent gel. The gel is dried and heat-treated to obtain superfine oxide powder. The disadvantages of the Sol-gel method are that the use of metal alkoxides as raw materials leads to high costs and a long synthesis cycle in the gelation process. At the same time, the application of the sol-gel method to prepare nanoparticles with a particle size of less than 100nm has not been reported yet.
In addition, other preparation methods such as microwave method, pyrolysis carbonyl precursor method, ultrasonic method, air oxidation method, pyrolysis-reduction method, polyol reduction method, etc. have been reported successively.
Hai Yanbing et al. added FeSO4 solution to ammonia solution in a microwave oven for 8 seconds to obtain black Fe3O4 nanoparticles. Alivasatos et al. used the pyrolysis carbonyl precursor method to prepare monodisperse γ-Fe3O4 nanoparticles. Since then, this method has been widely used in the preparation of monodisperse magnetic oxide nanoparticles. Liu et al. used the polyol reduction method to prepare FePt magnetic nanoparticles with a diameter of 3nm by the reduction reaction of ferrous acetylacetonate and platinum acetylacetonate in a high-temperature liquid phase. The particles were monodisperse under the protection of surfactants. state. Meng Zhe et al. successfully prepared Fe3O4 ultrafine powder with high purity, strong magnetism, and spherical distribution by using oxidation induction and air oxidation Fe(OH)2 suspension in an environment with pH=10 at room temperature.

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