CN103680798B - A kind of preparation method of perfluoro polyether oil based magnetic liquid - Google Patents

Abstract

The invention discloses a preparation method of a perfluoropolyether oil _- based magnetic liquid, which is composed of bare _Fe3O4 magnetic nanoparticles, perfluoropolyether carboxylic acid surfactants and perfluoropolyether oil-based Prepared in three parts. Firstly, bare Fe ₃ O ₄ nanoparticles with an average particle size of 10nm were prepared by chemical co-precipitation method; then, perfluoropolyether carboxylic acid surfactant was used to modify it; finally, the modified The final Fe ₃ O ₄ magnetic nanoparticles are blended with the perfluoropolyether oil-based carrier fluid to form a uniform and stable perfluoropolyether oil-based magnetic liquid with a saturation magnetization of 14-600Gs. The magnetic liquid has special properties such as superior chemical corrosion resistance, high and low temperature resistance, and absolutely non-combustible, and can work stably for a long time at pH=1~14, -40°C~200°C, especially suitable for military industries such as space stations and aerospace field.

Description

A kind of preparation method of perfluoropolyether oil-based magnetic liquid

technical field

The invention relates to the field of surface modification and dispersion of nanometer powder, in particular to a preparation method of perfluoropolyether oil-based magnetic liquid.

Background technique

Magnetic liquid is a new type of nano-functional material, which is highly dispersed magnetic particles coated with surfactants in the base carrier liquid to form a colloidal suspension with nano-scale, "solid-liquid" two-phase homogeneous and stable mixing , in the gravitational field, magnetic field, electric field, centrifugal field does not occur layered settlement. Because it has both the magnetism of solid materials and the fluidity of liquid materials, it can be quickly magnetized under the action of an external magnetic field to become magnetic. When the external magnetic field is removed, the magnetism disappears immediately, without coercive force and residual magnetism, that is, it shows Excellent superparamagnetism, so it has a series of special physical and chemical properties, nano characteristics and fluidity, and is widely used in aerospace, machinery, energy, materials, chemical industry, biopharmaceutical and other fields.

According to the different types of carrier liquid and surfactant, the magnetic liquid can be divided into: water-based, kerosene-based, gasoline-based, synthetic ester-based, polyglycol-based, polyphenylene ether-based, silicon hydrocarbon-based magnetic liquid. In patent ZL95108828.9, the inventor used the thermal decomposition method to prepare metal magnetic liquid in a specially developed device. The preparation device is complicated, the process is cumbersome, the required thermal decomposition temperature is high, and the energy loss is large, which is not suitable for popularization and large-scale production; In the patent CN1741207A, no surface activity is added, and the nanoparticles are peptized in an acidic solution, and only physical adsorption of the electric double layer is used to prevent inter-particle agglomeration. The separation force is large, the prepared nanoparticles and magnetic liquid are unstable, and can only be used in a weakly acidic environment; in patent CN102063992A, paraffin is used as the base carrier liquid, and the magnetic liquid is prepared by plasma activation method, which needs to be completely isolated from oxygen. The temperature in the reaction chamber is as high as 200°C, and the AC pulse current voltage is as high as 10kV. The reaction device is complicated, the cost is high, and it is especially dangerous to the operator; the patent ZL200510064275.2 adopts the method of mixing and heating the surfactant and the carrier liquid to 80℃～100℃, after cooling to room temperature, add a low-volatility concentrator to it, and react with evaporated carbonyl iron powder in a reaction furnace at 182℃. This method requires a special reaction furnace, and the added concentrator is Low-boiling hydrocarbon ketone organic solvents not only introduce impurities into magnetic liquid products, but also the volatilization of these concentrates will cause harm to operators and the environment. The above-mentioned patents are for the preparation of conventional magnetic liquids. In the patent CN101514284B, fluoroether magnetic materials are mentioned, that is, firstly, perfluoropolyether oil and silicone oil are used as the base carrier liquid, put in a high-pressure reactor at 1MPa, stirred at 100°C for 90min, pressurized at 2MPa, stirred at 150°C for 120min, when When the temperature and pressure return to room temperature and normal pressure, add the iron-nickel alloy nanoparticles prepared by the liquid phase method into the reactor, and stir at 0.5MPa and 60°C for 180min to obtain a magnetic sealing material. In the reaction, the iron-nickel alloy nanoparticles The particles are coated with oleic acid by electric arc method, which requires anaerobic high vacuum, high pressure and high temperature in the reaction kettle mixed with perfluoropolyether oil and silicone oil, and the most important thing is the viscosity of the prepared magnetic material As high as 1.1*10 ⁵ mPa·s is close to semi-solid, and is no longer a magnetic liquid in the traditional sense.

Ester-based, kerosene-based, gasoline-based, and water-based magnetic fluids have reached a mature and practical stage, but with the expansion of the scope of application of these types of magnetic fluids, their disadvantages have become increasingly prominent, such as: cannot be used in high and low temperature environments, cannot It is resistant to acid and alkali, cannot seal corrosive media, cannot withstand radiation, cannot be used in extreme special environments such as space stations, etc., and perfluoropolyether oil-based magnetic fluids are both fluorine ethers because their surfactants and base carrier liquids are Such substances have stable chemical properties and have many special properties, which can overcome the above-mentioned defects in the use of special environments, and have strong application value.

Contents of the invention

The technical problem to be solved by the present invention is: to overcome the deficiencies of the prior art, to provide a perfluoropolyether oil-based oil base that is resistant to acid and alkali corrosion, high and low temperature, non-combustible, high magnetization, and good stability and can be applied to extreme environments. The preparation method of the magnetic liquid, and the preparation process except the vacuum drying step of the modified Fe ₃ O ₄ magnetic nanoparticles, the entire preparation process does not need to be filled with nitrogen or take other measures to exclude oxygen interference, and is completed under an oxygen environment. The device is simple, easy to operate and low energy consumption.

To achieve the above object, the present invention takes the following technical solutions:

A method for preparing a perfluoropolyether oil-based magnetic liquid comprises three parts: magnetic nanoparticles, a surfactant, and a base carrier liquid.

The above-mentioned magnetic nanoparticles are Fe ₃ O ₄ particles, which are prepared by a co-precipitation method, with a particle size of 8-18 nm and an average particle size of 10 nm.

The above-mentioned surfactants are perfluoropolyether carboxylic acids. The selection of surfactants is very important for the preparation of magnetic liquids. It is related to whether the magnetic liquids can be successfully prepared and whether the magnetic liquids have application value. Preparation is the key problem to be solved first, because it plays the role of dispersing particles, improving particle surface properties and matching with base carrier liquid in the process of magnetic liquid preparation.

The base carrier liquid mentioned above is perfluoropolyether oil. The choice of base carrier liquid must comprehensively consider factors such as chemical structural formula, viscosity, molecular weight, and service temperature, and must be strictly matched with the above-mentioned perfluoropolyether carboxylic acid surfactants, which can Stable co-dissolution with it, these are the prerequisites for the preparation of magnetic liquids. The perfluoropolyether oil-based carrier liquid has the following structure: CF ₃ -{[O-CF(CF ₃ )-CF ₂ ] _n -(O-CF ₂ ) _m }-O-CF ₃ , where m+n= 4~60, m/n=18~1200.

The concrete operation of a kind of preparation method of perfluoropolyether oil-based magnetic liquid is as follows:

(1) Preparation of bare Fe ₃ O ₄ magnetic nanoparticles

The ionic equation of the reaction is: Fe ²⁺ +2Fe ³⁺ +8OH ^- =Fe ₃ O ₄ +4H ₂ O, according to the molar ratio of Fe ²⁺ : Fe ³⁺ =1:1.5~2 Add deionized water to prepare Fe ²⁺ , Fe ³⁺ iron salt precursor solution, control the temperature of the water bath at 32-92°C, install and debug the reaction device, and seal the reaction three-necked bottle with a sealant stopper when no material is added. Pour the prepared Fe ³⁺ solution into the three-necked bottle, stirring at a speed of 100-600r/min, when the temperature is close to the preparation reaction temperature, add FeCl ₂ or FeSO ₄ powder, reduce the stirring to 100-150r/min and continue to stir and dissolve Evenly, monitor the internal temperature of the iron-salt mixture at any time. When the temperature exceeds the preparation reaction temperature by 1-2°C, slowly pour into 25% concentrated ammonia water in a molar ratio of Fe ³⁺ : ammonia water = 1:4-8, and the reaction solution immediately turns It is black, the rotating speed is adjusted to 300-600r/min, the precipitation reaction time is 5-30min, and the bare Fe ₃ O ₄ magnetic nanoparticles are prepared.

(2) Coating modification of bare Fe ₃ O ₄ magnetic nanoparticles with perfluoropolyether carboxylic acid surfactants

On the basis of the above step (1), the perfluoropolyether carboxylic acid surfactant can be added to the reaction three-necked flask simultaneously with 25% concentrated ammonia water, or 25% concentrated ammonia water can be added first, and then added after reacting for 5-30 minutes Perfluoropolyether carboxylic acid surfactant. It can be added while stirring, or it can be added under standing conditions. It can be added after the process of preparing Fe ₃ O ₄ is finished and the three-necked reaction flask is still in the first water bath, or it can be added after the three-necked reaction flask is moved into the second water bath used for coating reaction. The temperature of the water bath used for coating is controlled at 52-92°C. Any one of the above-mentioned adding methods can be used, and the ratio of the exposed magnetic particles (g) to the surfactant (ml) is: 40:1～1:1 Add the perfluoropolyether carboxylic acid surfactant, and then Stirring is started at 400-700 r/min, the coating time is 30-120 min, and the coated Fe ₃ O ₄ magnetic nanoparticles are prepared.

(3) Treatment of Fe ₃ O ₄ magnetic nanoparticles after coating

Take out the three-necked flask after the coating reaction in the above step (2), transfer the reaction liquid into a 1000ml beaker, settle under the magnetic stand, and wash it repeatedly with deionized water for 5-7 times until no Cl ^- and SO ₄ ^2- And until pH=7. Move the obtained magnetic particles into a watch glass, put them into a vacuum oven for drying, the vacuum degree is -0.1Mpa, the heating temperature is 30-90°C, and the drying time is generally 24-48 hours.

(4) High-energy ball milling or ultrasonic vibration to make perfluoropolyether oil-based magnetic liquid

Weigh the dried magnetic particles obtained in the above step (3) and mix them with perfluoropolyether oil-based carrier liquid according to the ratio of modified magnetic particles (g) to base carrier liquid (ml) 1:20-2:1. At this time, the perfluoropolyether carboxylic acid surfactant can also be added to the mixture, and the addition ratio is 50-20:0-5 according to the magnetic particle and the perfluoropolyether carboxylic acid surfactant (g:ml). To further modify and make up for the magnetic particles that have not been fully coated. High-energy ball milling or ultrasonic oscillation is used for mixing and dispersing. The temperature can reach 50-80°C during high-speed oscillation. In order to prevent oxidation caused by temperature rise, the method of cooling at intervals is adopted. The cooling range is 0.7°C/min-2°C/min. High-energy ball milling Or end of ultrasound 1h ~ 20h. One of them can be used alone, or both methods can be used in combination to prepare the crude product of perfluoropolyether oil-based magnetic liquid, and the crude product can be precipitated on the magnetic base or high-speed centrifuged to remove the large particles settled from the bottom layer, and this process can be repeated. Step 3 to 5 times, take the upper black uniform mixed solution as perfluoropolyether oil-based magnetic liquid.

The deionized water used in the above steps (1)(3) is produced by an ultrapure water machine, and the resistivity of the deionized water is 18.2MΩ.cm (25°C).

The frequency of the ultrasonic disperser used in the above step (4) is 40kHZ, the grinding capacity of the high-energy ball mill is 50ml*3, and the power is 50kW.

Perfluoropolyether oil-based magnetic fluid has such superior characteristics, it all depends on the performance of its surfactant and base carrier liquid. Perfluoropolyether carboxylic acid surfactants and perfluoropolyether oil-based carrier fluids are all fluoroether substances, which have excellent chemical stability. Almost all drugs except fluorine do not react with them and are not Boiling sulfuric acid, fuming nitric acid, HF, strong oxidant, molten caustic soda and other strong acids, strong bases and strong corrosive substances attack, the molecular structure and chemical composition remain unchanged; the performance of high and low temperature resistance is excellent, and the viscosity is slightly reduced at low temperature -40 °C Increase, but the fluidity is not affected, chemical decomposition and aging do not occur at 290 ° C, no carbon or deposits, no toxic gas is emitted; almost all drugs except fluorine solvents cannot dissolve it, such as hydrocarbons , water, steam, chemical solvents, etc.; it will never burn, has no flash point, no spontaneous ignition point, and will not react with the combustion medium oxygen, which itself can be used as an explosion-proof heat medium.

Compared with the prior art, the present invention has the following advantages:

1. A perfluoropolyether oil-based magnetic liquid that can meet the needs of extreme special environments has been prepared. Long-term immersion in pH = 1-14 acid-base liquid has no effect, and it can be stable for a long time at -40 ° C ~ 200 ° C Work, the particles are evenly distributed, no agglomeration, no coagulation, and fluidity remains unchanged, while some conventional magnetic liquids have already volatilized, frozen or cracked and lost their use value. The magnetic liquid of the present invention solves the long-standing problem of special sealing requirements for important equipment in industries such as aerospace, machinery, chemical industry, pharmacy, and biology. As a key material, it has promoted breakthroughs in the localization of cutting-edge equipment in fields such as national defense, military industry, and manned spaceflight. Broaden the application environment and use medium of magnetic liquids, and be used in fields where conventional surfactants cannot be used or adding a large amount of conventional surfactants has no effect.

2. The perfluoropolyether oil-based magnetic liquid prepared by the present invention has a saturation magnetization of 14 to 600 Gs as measured by a vibrating sample magnetometer, and the magnetization and viscosity can be adjusted arbitrarily.

3. The perfluoropolyether oil-based magnetic liquid of the present invention is absolutely nonflammable.

4. The preparation method of the perfluoropolyether oil-based magnetic liquid prepared by the present invention is simple, the yield is high, and the requirements for equipment are low.

Description of drawings

Figure 1 is the magnetization curve of perfluoropolyether oil-based magnetic liquid.

Figure 2 is a TEM image of magnetic particles coated with a perfluoropolyether carboxylic acid surfactant.

Fig. 3 is an XRD spectrum of magnetic particles coated with a perfluoropolyether carboxylic acid surfactant.

Fig. 4 is an FTIR spectrum of magnetic particles coated with perfluoropolyether carboxylic acid surfactant.

detailed description

Example 1

(1) Preparation of bare Fe ₃ O ₄ magnetic nanoparticles

Weigh 5.40g FeCl ₃ and dissolve it in 400ml deionized water, prepare a 0.05mol/L solution at room temperature for later use, and control the temperature of the water bath at 32°C. Pour the prepared Fe3 ⁺ solution into the there-necked flask with a stirring speed of 300r/min. When the temperature is close to the preparation reaction temperature of 32°C, add 1.98g of _FeCl2 powder, reduce the stirring speed to 100r/min and continue to stir and dissolve evenly. Monitor the internal temperature of the iron-salt mixture at any time. When the temperature reaches 31-32°C, slowly pour in 20ml of 25% concentrated ammonia water, and the reaction solution will immediately turn black. Adjust the rotation speed to 200r/min, and the reaction time to 30min. Bare _Fe3O4 magnetic nanoparticles _.

(2) Coating modification of bare Fe ₃ O ₄ magnetic nanoparticles with perfluoropolyether carboxylic acid surfactants

On the basis of the above step (1), add 1 ml of perfluoropolyether carboxylic acid surfactant without taking out the three-neck reaction flask and without stopping the stirring. Then move the reaction three-neck flask into another water bath for coating reaction. The temperature of the coated water bath is controlled at 62°C, stirring is started at 300r/min, and the coating time is 120min to prepare coated Fe ₃ O ₄ magnetic nanoparticles.

(3) Treatment of Fe ₃ O ₄ magnetic nanoparticles after coating

Take out the three-neck flask after the coating reaction in the above step (2), transfer the reaction solution into a 1000ml beaker, settle on the magnetic stand, and wash it repeatedly with deionized water for 5 to 7 times until there is no ^Cl- and pH in the test lotion. = up to 7. The obtained magnetic particles were transferred into a watch glass and dried in a vacuum drying oven with a vacuum degree of -0.1Mpa, a heating temperature of 80°C, and a drying time of 24 hours.

(4) High-energy ball milling or ultrasonic vibration to make perfluoropolyether oil-based magnetic liquid

Mix the dried magnetic particles (g) obtained in the above step (3) with the perfluoropolyether oil-based carrier liquid (ml) in a ratio of 1:20. Use the method of ultrasonic dispersion to disperse, ultrasonic 1h, get the crude product, precipitate the crude product on the magnetic base to remove the large particles settled in the bottom layer, repeat this step 3 times, take the upper black uniform mixed solution as perfluoropolyether oil The base magnetic liquid has a saturation magnetization of 14GS. The magnetic liquid is absolutely non-flammable, has no flash point, no self-ignition point, and can work stably at pH=1~14, -40°C~200°C. It can be used in magnetic liquid sealing liquid structures, especially for military radar rotary joints, Military and aerospace fields such as tank perimeter mirrors, space station portholes, and moon landing buffers.

Example 2

(1) Preparation of bare Fe ₃ O ₄ magnetic nanoparticles

Weigh 54.0g FeCl ₃ and dissolve it in 400ml deionized water, prepare a 0.5mol/L solution at room temperature for later use, and control the temperature of the water bath at 42°C. Pour the prepared Fe3 ⁺ solution into the there-necked flask with a stirring speed of 300r/min. When the temperature is close to the preparation reaction temperature of 42°C, add 27.80g of _FeSO4 powder, reduce the stirring speed to 100r/min and continue to stir and dissolve evenly. Monitor the internal temperature of the iron-salt mixture at any time. When the temperature reaches 41-42°C, pour 120ml of 25% concentrated ammonia water slowly, and the reaction solution will immediately turn black. Adjust the rotation speed to 400r/min, and the reaction time to 15min. Bare _Fe3O4 magnetic nanoparticles _.

(2) Coating modification of bare Fe ₃ O ₄ magnetic nanoparticles with perfluoropolyether carboxylic acid surfactants

On the basis of the above step (1), 7 ml of perfluoropolyether carboxylic acid surfactant was added without taking out the three-necked reaction flask and without stopping the stirring. Then move the reaction three-necked flask into another water bath for coating reaction. The temperature of the coated water bath is controlled at 72°C, the stirring is started at 400r/min, and the coating time is 45min to prepare coated Fe ₃ O ₄ magnetic nanoparticles.

(3) Treatment of Fe ₃ O ₄ magnetic nanoparticles after coating

Take out the three-neck flask after the coating reaction in the above step (2), transfer the reaction solution into a 1000ml beaker, settle on the magnetic stand, and wash it repeatedly with deionized water for 5 to 7 times, until there is no ^Cl- and SO in the test washing solution. ₄ ^2- and until pH=7. The obtained magnetic particles were transferred into a watch glass and dried in a vacuum drying oven with a vacuum degree of -0.1Mpa, a heating temperature of 30°C, and a drying time of 24 hours.

(4) High-energy ball milling or ultrasonic vibration to make perfluoropolyether oil-based magnetic liquid

Mix the dried magnetic particles (g) obtained in the above step (3) with the perfluoropolyether oil-based carrier liquid (ml) in a ratio of 1:12, and no perfluoropolyether carboxylic acid surfactant is added. Use the method of ultrasonic dispersion to disperse, ultrasonic 5h, get the crude product, precipitate the crude product on the magnetic base to remove the large particles settled in the bottom layer, repeat this step 3 times, take the upper black uniform mixed solution as perfluoropolyether oil The base magnetic liquid has a saturation magnetization of 205GS. This magnetic liquid is absolutely non-flammable, has no flash point, no self-ignition point, and can work stably at pH=1~14, -40°C~200°C. It can be used for magnetic liquid sealing liquid structure Among them, it is especially suitable for military and aerospace fields such as military radar rotary joints, tank perimeter mirrors, space station portholes and lunar landing buffers.

Example 3

(1) Preparation of bare Fe ₃ O ₄ magnetic nanoparticles

Weigh 54.0g FeCl ₃ and dissolve it in 400ml deionized water, prepare a 0.5mol/L solution at room temperature for later use, and control the temperature of the water bath at 52°C. Pour the prepared Fe3 ⁺ solution into the there-necked flask with a stirring speed of 300r/min. When the temperature is close to the preparation reaction temperature of 52°C, add 27.80g of _FeSO4 powder, reduce the stirring speed to 100r/min and continue to stir and dissolve evenly. Monitor the internal temperature of the iron-salt mixture at any time. When the temperature reaches 51-52°C, pour 150ml of 25% concentrated ammonia water slowly, and the reaction solution will immediately turn black. Adjust the rotation speed to 400r/min, and the reaction time to 10min. Bare _Fe3O4 magnetic nanoparticles _.

(2) Coating modification of bare Fe ₃ O ₄ magnetic nanoparticles with perfluoropolyether carboxylic acid surfactants

On the basis of the above step (1), 8 ml of perfluoropolyether carboxylic acid surfactant was added without taking out the three-necked reaction flask and without stopping the stirring. Then move the reaction three-necked flask into another water bath for coating reaction. The temperature of the coated water bath is controlled at 72°C, the stirring is started at 500r/min, and the coating time is 60min to make coated Fe ₃ O ₄ magnetic nanoparticles.

(3) Treatment of Fe ₃ O ₄ magnetic nanoparticles after coating

Take out the three-neck flask after the coating reaction in the above step (2), transfer the reaction solution into a 1000ml beaker, settle on the magnetic stand, and wash it repeatedly with deionized water for 5 to 7 times, until there is no ^Cl- and SO in the test washing solution. ₄ ^2- and until pH=7. The obtained magnetic particles were transferred into a watch glass and dried in a vacuum drying oven with a vacuum degree of -0.1Mpa, a heating temperature of 50°C, and a drying time of 24 hours.

(4) High-energy ball milling or ultrasonic vibration to make perfluoropolyether oil-based magnetic liquid

Mix the dried magnetic particles (g) obtained in the above step (3) with the perfluoropolyether oil-based carrier liquid (ml) in a ratio of 1:8, and no perfluoropolyether carboxylic acid surfactant is added. The method of high-energy ball milling was used to disperse for 5 hours to obtain a crude product. The crude product was precipitated on a magnetic base to remove the large particles settled from the bottom layer. This step was repeated 3 times, and the upper black uniform mixture was taken as perfluoropolyether oil-based magnetic Liquid, the saturation magnetization is 416GS, the magnetic liquid is absolutely non-flammable, has no flash point, no self-ignition point, can work stably at pH=1~14, -40°C~200°C, and can be used in the structure of magnetic liquid sealing liquid, It is especially suitable for military and aerospace fields such as military radar rotary joints, tank perimeter mirrors, space station portholes, and moon landing buffers.

Example 4

(1) Preparation of bare Fe ₃ O ₄ magnetic nanoparticles

Weigh 54.0g FeCl ₃ and dissolve it in 400ml of deionized water, prepare a 0.5mol/L solution at room temperature for later use, control the temperature of the water bath at 72°C, pour the prepared Fe ³⁺ solution into the three-necked bottle, and stir at a speed of 400r /min, when the temperature is close to 72°C, add 30.80g FeSO ₄ powder, reduce the stirring speed to 100r/min, continue stirring to dissolve evenly, monitor the internal temperature of the iron-salt mixture at any time, when the temperature reaches 71-72°C, slowly Pour in 150ml of 25% concentrated ammonia water, the reaction solution turns black immediately, adjust the rotation speed to 500r/min, and the reaction time is 13min, to prepare bare Fe ₃ O ₄ magnetic nanoparticles.

(2) Coating modification of bare Fe ₃ O ₄ magnetic nanoparticles with perfluoropolyether carboxylic acid surfactants

On the basis of the above step (1), move the reaction three-necked flask into a water bath at 80°C, start stirring at 600r/min, then add 11ml of perfluoropolyether carboxylic acid surfactant, and coat for 120min to make a wrapped Coated Fe ₃ O ₄ magnetic nanoparticles.

(3) Treatment of Fe ₃ O ₄ magnetic nanoparticles after coating

Take out the three-neck flask after the coating reaction in the above step (2), transfer the reaction solution into a 1000ml beaker, settle on the magnetic stand, and wash it repeatedly with deionized water for 5 to 7 times, until there is no ^Cl- and SO in the test washing solution. ₄ ^2- and until pH=7. The obtained magnetic particles were transferred into a watch glass and dried in a vacuum drying oven with a vacuum degree of -0.1Mpa, a heating temperature of 60°C, and a drying time of 36 hours.

(4) High-energy ball milling or ultrasonic vibration to make perfluoropolyether oil-based magnetic liquid

Mix the dried magnetic particles (g) obtained in the above step (3) with the perfluoropolyether oil-based carrier liquid (ml) in a ratio of 2:1.8, and add a perfluoropolyether carboxylic acid surfactant to the mixture, Add according to the ratio of magnetic particles (g) to perfluoropolyether carboxylic acid surfactant (ml) at 20:1 to further modify and compensate for the incompletely coated magnetic particles. The method of high-energy ball milling is used for dispersion, and the temperature of the instrument is stopped every 1h to 3h, and the high-energy ball milling is finished after 12h. To obtain a crude product, precipitate the crude product on a magnetic base to remove the precipitated large particles, repeat this step 3 to 5 times, take the upper black uniform mixed solution as a perfluoropolyether oil-based magnetic liquid, and the saturation magnetization is 600Gs. The magnetic liquid is absolutely non-flammable, has no flash point, no self-ignition point, and can work stably at pH=1~14, -40°C~200°C. It can be used in magnetic liquid sealing liquid structures, especially for military radar rotary joints, Military and aerospace fields such as tank perimeter mirrors, space station portholes, and moon landing buffers.

Claims (8)

1. A preparation method of perfluoropolyether oil-based magnetic liquid, at first prepared bare Fe by co _- precipitation O ₄ magnetic nanoparticles with an average particle diameter of 10nm, and then using perfluoropolyether carboxylic acid surfactant The exposed Fe ₃ O ₄ magnetic nanoparticles were coated and modified, and then the modified Fe ₃ O ₄ magnetic nanoparticles were stably suspended in the perfluoropolyether oil-based carrier liquid by high-energy ball milling or ultrasonic vibration method. The grinding capacity of the high-energy ball mill is 50ml*3, the power is 50kW, and the ultrasonic dispersion frequency is 40kHZ. Finally, the magnetic seat precipitation or high-speed centrifugation is used to remove the large particles that cannot be stably suspended to obtain the perfluoropolyether oil-based magnetic liquid. It is characterized in that the perfluoropolyether oil-based carrier fluid has the following structure: CF ₃ -{[O-CF(CF ₃ )-CF ₂ ] _n -(O-CF ₂ ) _m }-O-CF ₃ , where m+ n=4～60, m/n=18～1200. 2. the preparation method of a kind of perfluoropolyether oil _- based magnetic liquid according to claim ₁ is characterized in that exposed Fe O magnetic nanoparticles g and the addition of perfluoropolyether carboxylic acid surfactant ml The ratio is: 40:1～1:1. 3. The preparation method of a kind of perfluoropolyether oil-based magnetic liquid according to claim ₁ , characterized in that the modified _Fe3O4 magnetic nanoparticles g and the addition of perfluoropolyether oil-based carrier liquid ml The ratio is: 1:20～2:1. 4. The preparation method of a kind of perfluoropolyether oil-based magnetic liquid according to claim 1, characterized in that the perfluoropolyether carboxylic acid surfactant is added again in the process of high-energy ball milling or ultrasonic vibration, and the addition ratio is according to The ratio of modified Fe ₃ O ₄ magnetic nanoparticles g to perfluoropolyether carboxylic acid surfactant ml is 50-20:0.1-5, so as to further modify and make up for the incompletely coated magnetic particles. 5. the preparation method of a kind of perfluoropolyether oil-based magnetic liquid according to claim ₁ is characterized in that except the modified _{Fe3O4magnetic} nanoparticle vacuum drying step, the whole preparation process does not need to be filled with nitrogen or Take other measures to eliminate oxygen interference, all done in an aerobic environment. 6. The preparation method of a kind of perfluoropolyether oil-based magnetic liquid according to claim 1, wherein deionized water is used as reaction medium and detergent in the preparation, it is characterized in that the resistivity of deionized water at 25°C is 18.2 MΩ.cm. 7. The preparation method of a kind of perfluoropolyether oil-based magnetic liquid according to claim 1, characterized in that the balls in the high-energy ball mill are made of agate, and the particle diameters are respectively 2mm, 4mm, and 6mm. 8. the preparation method of a kind of perfluoropolyether oil-based magnetic liquid according to claim ₁ is characterized in that for reducing high _- energy ball milling and ultrasonic process Fe in O Oxidation due to heating up, take interval cooling method, The cooling range is 0.7°C/min to 2°C/min.