Triiron Tetraoxide CAS 1317-61-9

Triiron Tetraoxide is an inorganic substance with the chemical formula Fe3O4. It is a black crystal with magnetism, so it is also called magnetic iron oxide. It cannot be regarded as "ferrous metaferrite" [Fe (FeO₂)₂], nor as a mixture of ferrous oxide (FeO) and ferric oxide (Fe₂O₃), but it can be approximately regarded as a compound of ferrous oxide and ferric oxide (FeO · Fe₂O₃). This substance is insoluble in water, alkali solution, ethanol, ether and other organic solvents. The natural ferric oxide is insoluble in acid solution, and it is easy to oxidize into ferric oxide (Fe₂O₃) in the air under humid conditions. It is usually used as pigment and polishing agent, and can also be used to make audio tapes and telecommunications equipment.

1. Ferroferric oxide is a common magnetic material.

2. The special pure Fe₃O₄ is used as the raw material of recording tape and telecommunication equipment.

3. Natural magnetite is the raw material of ironmaking.

4, for making primer and topcoat.

5 、 Ferric oxide is the main raw material for the production of iron catalyst ( a catalyst ).

6, its hardness is very large, can be used as abrasive. It has been widely used in the field of automobile braking, such as brake pads, brake shoes and so on.

7. Ferroferric oxide has been recognized in the field of welding materials in China. The production of welding rod and welding wire is still in its infancy, and the market prospect is very broad.

8.Fe₃O₄ shows good performance in sewage treatment because of its large specific gravity and strong magnetism.

9, iron oxide can also be used as pigments and polishing agent.

10, we can also through some chemical reactions, such as the use of sodium nitrite and so on, so that the surface of the steel to generate a layer of dense iron oxide, to prevent or slow down the corrosion of steel, such as firearms, saw blade surface blue, black. Commonly known as ' roast blue '.

11. Make special electrode.

1. Precipitation method

Precipitation method is the most commonly used method for preparing nano particles because of its simple operation, low cost, high purity and uniform composition, which is suitable for large-scale production. At the same time, the dispersion of nanoparticles can be improved by adding organic dispersants or complexing agents to the precipitation mixture, and the disadvantage of easy agglomeration of nanoparticles can be overcome. Common precipitation methods include coprecipitation, hydrolytic precipitation, ultrasonic precipitation, alcohol salt solution and chelate decomposition.

(1) Coprecipitation method:

By coprecipitation method, precipitants are added to the solution containing various cations to allow all ions to precipitate completely. In order to obtain uniform precipitation, the salt solution containing various cations is usually slowly added to the excessive precipitator for stirring, so that the concentration of all ions greatly exceeds the equilibrium concentration of precipitation, and all components are separated out at the same time in proportion as far as possible.

Its principle is Fe²⁺+2Fe³⁺+8OH ^- → Fe₃O₄+4H₂O.

The molar ratio of Fe²⁺and Fe³⁺has a direct effect on the crystal structure of nano particles prepared by precipitation method; PH value of solution, ion concentration and reaction temperature all affect the size of particles. The main problem of precipitation method is how to prepare nanoparticles with single crystal structure and uniform particle size by controlling reaction conditions. The filtration and washing of external precipitator must also be considered.

The Fe₃O₄ nanoparticles obtained by coprecipitation method are mostly spherical in structure and small in size (5-10nm). However, due to the low temperature of the reaction, the crystallinity of the particles obtained is relatively poor. Moreover, the nano Fe₃O₄ particles prepared by this method are easy to agglomerate among particles during washing, filtering and drying, which will affect the performance of nano Fe₃O₄.

(2) Hydrolysis precipitation method:

Hydrolysis precipitation method is to release OH^- by hydrolysis of alkaline substances. Common alkaline substances include urea, hexamethylene diamine, etc. These substances release OH^- slowly, which is conducive to the formation of uniform nanoparticles when preparing nano Fe₃O₄ particles. Generally, this method can produce nanoparticles with a particle distribution of 7 nm to 39 nm.

(3) Ultrasonic precipitation method:

Ultrasound can produce cavitation effect in the solvent, and the cavitation bubble generated collapses in a very short time of 10-11 seconds, generating a high temperature of about 5000K in the bubble. Compared with the traditional stirring technology, this series of cavitation is easier to achieve mesoscopic uniform mixing, eliminate local concentration unevenness, improve reaction speed, stimulate the formation of new phases, and can also play a shear role in agglomeration, which is conducive to the formation of small particles. The application of ultrasonic technology has no special requirements on the properties of the system, as long as there is a liquid medium for energy transmission. Vijayakumar. R et al. used the radiation of high intensity ultrasound to prepare the superparamagnetic Fe3O4 particles with the particle size of 10 nm from the ferric acetate solution.

(4) Alcoholic salt solution:

By using the reduction effect of sodium acetate ionizing in water to generate acetate, Fe was partially reduced to Fe at about 180 ℃ in a high-pressure reactor. Yonghui Deng and others heated FeCl₃ sodium acetate and ethylene glycol in a high-pressure reactor at 200 ℃ for 8h to prepare superparamagnetic Fe₃O₄ nanoparticles.

(5) Chelate decomposition method:

The principle of this method is that metal ions and appropriate ligands form a stable complex at room temperature. At the appropriate temperature and pH value, the complex is destroyed. The metal ions are released again and react with OH ions in the solution and external precipitators and oxidants to generate insoluble metal oxides, hydroxides, salts and other precipitates of different valence. Further treatment can produce nanoparticles of certain size or even shape.

2. Hydrothermal (solvothermal) method:

Hydrothermal (solvothermal) reaction is a general term for chemical reactions carried out under high temperature and high pressure in fluids such as aqueous solution (organic solvent) or steam. Hydrothermal method is a kind of synthesis for preparing nano powder developed in recent ten years. Fe3O4 prepared by this method has small particle size, uniform particle size, no need of high temperature calcination pretreatment, and can realize multivalent ion doping. However, the hydrothermal method requires the use of high temperature and high pressure resistant equipment, so the cost of this method is high and it is difficult to achieve large-scale production.

Nanometer Fe₃O₄ prepared by hydrothermal method mostly uses inorganic iron salts (FeCl₃ · 6H₂O, FeCl₂ · 4H₂O, FeSO₄) and organic iron salts (ferrocene Fe (C₅H₅)₂) as precursors, hydrazine, polyethylene glycol, PVP, etc. as surfactants, and is synthesized in alkaline solution below 200 ℃.

Shouheng Sun prepared superparamagnetic Fe₃O₄ particles with controllable particle size by hydrothermal method. First, Fe₃O₄ particles with a particle size of 4nm were prepared using Fe (acac) 3 as the Fe source, and then Fe₃O₄ nanoparticles with a particle size of 4nm were prepared by controlling the holding time and other factors.

Zhen Li et al. reported that Fe₃O₄ nanoparticles were prepared using common FeCl₃ · H₂O as precursor instead of expensive Fe (acac)₃.

Yadong Li et al. reported that monodisperse Fe₃O₄ nanoparticles were prepared with FeCl₃ · 6H₂O, NaAC, EG and PEG as raw materials, and the particle size was adjustable.

3. Microemulsion method:

Microemulsion method refers to the formation of lotion by two immiscible solvents under the action of surfactant, that is, the amphiphilic molecules divide the continuous medium into small spaces to form a micro reactor, in which the reactants react to generate solid phase. Due to the limitation of the micro reactor in nucleation, crystal growth, coalescence, clustering and other processes, nano particles with a layer of surfactant and a certain condensed structure and morphology are formed.

The preparation of nanometer catalyst by micro lotion method has the advantages of simple equipment, mild experimental conditions and controllable particle size, which is incomparable to other methods. Therefore, it has become a very interesting technology in the synthesis of nano catalysts. The research on the preparation of nano catalyst by micro lotion method mostly focuses on the control of particle size, while the research on the control of particle monodispersity is relatively less.

4. Sol gel method

This method uses hydrolysis and polymerization of metal alkoxides to prepare uniform sol of metal oxides or metal hydroxides, and then condenses it into transparent gel. The gel is dried and heat treated to prepare oxide ultrafine powder. The disadvantage of Sol gel method is that the use of metal alkoxides as raw materials leads to high cost and long synthesis cycle in the gelling process. At the same time, the application of sol-gel method to prepare nanoparticles with particle size less than 100 nm has not been reported.

In addition, other preparation methods such as microwave method, pyrolytic carbonyl precursor method, ultrasonic method, air oxidation method, pyrolysis reduction method, polyol reduction method, etc. have been reported successively.

The black Fe₃O₄ nanoparticles can be obtained by adding FeSO₄ solution to ammonia solution in the microwave oven for 8s. Alivasatos et al. prepared monodisperse γ- Fe₃O₄ nanoparticles, since then, this method has been widely used in the preparation of monodisperse magnetic oxide nanoparticles. Liu et al. prepared FePt magnetic nanoparticles with a diameter of 3nm by using the polyol reduction method and the reduction reaction of ferrous acetylacetonate and platinum acetylacetonate in the high-temperature liquid phase. The particles were monodisperse under the protection of surfactant. Meng Zhe et al. successfully prepared Fe₃O₄ ultrafine powder with high purity, strong magnetism and spherical distribution by oxidation induction and air oxidation of Fe (OH)₂ suspension at room temperature with pH=10 or so.

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