Silicone oil-based rare earth Dy < 3 + > doped Fe3O4 magnetic fluid and preparation method thereof

Abstract

The invention relates to the field of nanotechnology, and particularly discloses a silicone oil-based rare earth Dy < 3 + > doped Fe3O4 magnetic fluid and a preparation method thereof.The preparation method comprises the following steps that S1, FeSO4. 4H2O, FeC13. 6H2 O and Dy (NO3) 3.5 H2O are mixed with water to prepare a metal salt solution, and the metal salt solution is heated to 55-75 DEG C and then mixed with ammonia water to react to prepare rare earth Dy < 3 + > doped Fe3O4 nanoparticles; s2, adding hydrochloric acid into the reaction liquid obtained in S1 to adjust the pH value to 5.5-6.5, then adding a silane coupling agent, heating and mixing, washing the obtained product with water and ethanol until the pH value is neutral, and drying to obtain modified nano magnetic particles; and S3, adding the modified nano magnetic particles into silicone oil for dispersion, and finally removing the precipitate to obtain the silicone oil-based rare earth Dy < 3 + > doped Fe3O4 magnetic fluid. The magnetic fluid obtained by the preparation method provided by the invention has the advantages of high and low temperature resistance, oxidation resistance, good magnetic performance, high hydrophobicity and the like, and the preparation cost can be reduced.

Description

Technical Field

[0001] The present invention relates to the field of nanotechnology, and in particular to a silicone oil-based rare earth Dy 3+ Doped Fe3O4 magnetic fluid and preparation method thereof. Background Art

[0002] Magnetic fluid is a stable "solid-liquid" two-phase colloidal solution formed by magnetic particles with a diameter less than 10 nm coated with surfactants and dispersed in a base carrier liquid. It consists of three parts: nanoscale magnetic particles, surfactants and base carrier liquid. Due to its superparamagnetism and anisotropy under the action of a magnetic field, magnetic fluid has many unique properties, such as magnetic viscosity, magneto-optical properties, magnetocaloric properties, etc., and is therefore widely used in many fields, such as sealing, lubrication, grinding, heat transfer, dampers, sensors and medical instruments.

[0003] The main methods for preparing magnetic fluids are ball milling, chemical coprecipitation and peptization. Among them, chemical coprecipitation is the most common method, but this method is time-consuming, has low yield, and the surfactant coating rate is not high, which greatly reduces the solubility of the modified particles in the carrier liquid, thereby affecting the stability and service life of the prepared magnetic fluid.

[0004] CN116864286 A discloses a method for preparing a high saturation magnetization gadolinium ferrite / silicone oil magnetic liquid. By adjusting the ion ratio, gadolinium ferrite nanomagnetic particles with high saturation magnetization are prepared. On this basis, the particles are double-layered chemically coated, and then the coated particles are dispersed in silicone oil with high viscosity to prepare a gadolinium ferrite / silicone oil-based magnetic liquid with high saturation magnetization. It focuses on adjusting the gadolinium element iron element ion ratio to optimize the performance of the magnetic fluid, but does not pay attention to the purity of the ferromagnetic fluid. Summary of the invention

[0005] The present invention provides a silicone oil-based rare earth Dy 3+ The invention discloses a doped Fe3O4 magnetic fluid and a preparation method thereof. The magnetic fluid is resistant to high and low temperatures, is resistant to oxidation, has good magnetic properties, has high hydrophobicity, and can reduce preparation costs.

[0006] The technical solution of the present invention is to provide a silicone oil-based rare earth Dy 3+ The preparation method of doped Fe3O4 magnetic fluid comprises the following steps: S1. Mix FeSO4·4H2O, FeC13·6H2O and Dy(NO3)3·5H2O with water to prepare a metal salt solution. Heat the metal salt solution and ammonia solution to 55-75°C respectively and then mix them to react and prepare rare earth Dy 3+ Doped Fe3O4 nanoparticles; S2, hydrochloric acid is added to the reaction solution obtained in S1 to adjust the pH to 5.5-6.5, and then a silane coupling agent is added, heated and mixed, and the obtained product is washed with water and ethanol until the pH is neutral, and dried to obtain modified nano-magnetic particles; S3, adding the modified nano magnetic particles into silicone oil for dispersion, and finally removing the precipitate to obtain silicone oil-based rare earth Dy 3+ Doped Fe3O4 magnetic fluid.

[0007] Optionally, the molar ratio of FeSO4·4H2O, FeC13·6H2O and Dy(NO3)3·5H2O is 1:1.2~1.6:0.018~0.022.

[0008] Optionally, the molar ratio of FeSO4·4H2O, FeC13·6H2O and Dy(NO3)3·5H2O is 1:1.4:0.02.

[0009] Optionally, the concentration of the ammonia solution is 0.8-1.2 mol / L, and the amount added is controlled so that the pH of the reaction solution after the reaction is 8-10.

[0010] Optionally, the reaction time in S1 is 0.5-1.5 h.

[0011] Optionally, the silane coupling agent in S2 is KH550; the heating temperature is 65-80° C., the stirring speed during mixing is 300-550 r / min, and the time is 20-30 min.

[0012] Optionally, the modified nanomagnetic particles in S2 are vacuum dried at a temperature of 60-80° C. for 5-12 hours.

[0013] Optionally, the volume mass ratio of silicone oil to modified nanomagnetic particles in S3 is 0.5-10 mL / g, the dispersion time is 5-30 min, and the temperature is controlled at 60-80°C.

[0014] The present invention also relates to Dy obtained by the preparation method 3+ Doped Fe3O4 magnetic fluid.

[0015] The present invention also relates to the Dy 3+ Application of doped Fe3O4 magnetic fluid in fluid machinery shaft sealing.

[0016] The present invention has the following beneficial effects: The method comprises mixing a divalent iron salt solution and a trivalent iron salt solution and a dysprosium nitrate solution uniformly, adding an excess amount of an alkaline solution to react, adding an appropriate amount of a surfactant to perform surface modification treatment on the dysprosium nitrate solution after the reaction is completed, and finally precipitating, repeatedly washing and drying to obtain a surface-modified rare earth Dy 3+Doped Fe3O4 nanoparticles. The nanoparticles are added to silicone oil for ultrasonic dispersion to obtain high-performance silicone oil-based rare earth Dy 3+ Compared with pure Fe3O4 nanoparticles, the Dy 3+ The doped Fe3O4 nanoparticles have superparamagnetism, high saturation magnetization and good magnetic properties.

[0017] The present invention uses an ammonia solution as the alkaline solution. Compared with using a strong alkaline solution, more ammonium salts generated in the reaction exist in the solution, and the purity of Fe3O4 obtained by the reaction is higher. When preparing the magnetic fluid in the later stage, the coupling agent can be more coated on the Fe3O4. Silicone oil is used as the carrier liquid of the magnetic fluid, which enhances the dispersibility and stability of the particles in the solution, and improves the magnetic properties and life of the magnetic fluid.

[0018] The preparation method of the invention has a simple process, is easy to control, has low cost, and is convenient for realizing industrialized mass production. DETAILED DESCRIPTION

[0019] The experimental methods in the following examples are conventional methods unless otherwise specified. The materials used in the following examples are commercially available products unless otherwise specified.

[0020] The present invention relates to a silicone oil-based rare earth Dy 3+ The preparation method of doped Fe3O4 magnetic fluid comprises the following steps: S1. Mix FeSO4·4H2O, FeC13·6H2O and Dy(NO3)3·5H2O with water to prepare a metal salt solution. Heat the metal salt solution to 55-75°C and then mix it with ammonia water to react and prepare rare earth Dy 3+ Doped Fe3O4 nanoparticles; S2, hydrochloric acid is added to the reaction solution obtained in S1 to adjust the pH to 5.5-6.5, and then a silane coupling agent is added, heated and mixed, and the obtained product is washed with water and ethanol until the pH is neutral, and dried to obtain modified nano-magnetic particles; S3, adding the modified nano magnetic particles into silicone oil for dispersion, and finally removing the precipitate to obtain silicone oil-based rare earth Dy 3+ Doped Fe3O4 magnetic fluid.

[0021] Preparation of rare earth Dy 3+ When doping Fe3O4 nanoparticles, the reaction involved is: Fe 2+ +x Dy 3+ +(2-x)Fe 3+ +8 OH - → Dy x Fe 3-x O4+4 H2O.

[0022] In the ferrite unit cell structure, oxygen ions are closely packed to form a tetrahedral void (referred to as A site) and an octahedral void (referred to as B site). 3+ With a larger magnetic moment, it is easy to fill the B site with a larger gap, so that the magnetic moment of the B site increases, thereby increasing the magnetism of the entire magnetic particle and enhancing the magnetism of the magnetic fluid. 3+ The increase of ions, when more B sites are filled, will change the proximity of magnetic ions at the B sites, relatively weaken the super exchange between AB sites, resulting in negative exchange between BB, weakening the total magnetic moment, and reducing the overall magnetic properties of the magnetic fluid. The molar ratio of FeSO4·4H2O, FeC13·6H2O and xDy(NO3)3·5H2O (where x represents the molar amount of dysprosium nitrate pentahydrate) in S1 is 1:1.2~1.6:0.018~0.022; preferably 1:1.4:0.02. When x=0.02 in the reaction formula, Dy in the dysprosium aqueous solution 3+ The occupied B-type vacancy just makes the magnetism of the B position increase without generating negative exchange, and will not weaken the super exchange between the AB positions, so that the overall magnetic properties of the magnetic fluid reach the optimal theoretical Fe 2+ , Fe 3+ 、Dy 3+ The molar ratio is 1:1.98:0.02, but due to Fe 2+ It will be partially oxidized to Fe during the preparation process 3+ , so Fe 2+ :Fe 3+ The molar ratio should be less than 1:1.98. 2+ , Fe 3+ 、Dy 3+ When the molar ratio is 1:1.4:0.02, the effect is better.

[0023] During the reaction in S1, the temperature is controlled at 55°C-75°C, and the growth of the crystal nucleus is accelerated by heating, but the temperature should not be too high, otherwise the stability of the grains will be reduced, thereby reducing the growth rate of the grains; stirring during the mixed reaction is helpful for the rapid reaction, but the speed should not be too fast, otherwise the agglomeration of particles and the fusion of grain boundaries will be reduced, inhibiting the growth of the particles; preferably, the stirring speed is controlled at 300-400rad / min. Regarding the reaction time in S1, if it is too short, the reaction cannot be fully completed, affecting the stability and saturation magnetization of the magnetic particles; if the reaction time is too long, the generated nanomagnetic particles will be too large and easily oxidized, which is not conducive to the next step of dispersion; the reaction time of the present invention is preferably controlled at 0.5-1.5h.

[0024] The concentration of the ammonia solution in S1 is 0.8-1.2 mol / L, preferably 1 mol / L, and the amount added is controlled to control the pH of the reaction solution to be 8-10 after the reaction; preferably pH 9, at which time Fe 3+ 、Dy 3+ with Fe 2+ All completely precipitated.

[0025] The silane coupling agent in S2 is preferably KH550; the heating temperature is 65-80°C, the stirring speed during mixing is 300-550r / min, and the time is 20-30min. The silane coupling agent can only be hydrolyzed and coated under acidic conditions, so the pH needs to be adjusted to acidic before adding the silane coupling agent in the present invention, preferably controlling the pH to 5.5-6.5 to avoid too small a pH value, otherwise excessive hydrogen ions will react with the nanomagnetic particles, destroying their crystal structure and causing them to lose their magnetism.

[0026] In the preferred embodiment, the modified nano-magnetic particles in S2 are vacuum dried, preferably at a drying temperature of 60-80°C for 5-12 hours. The volume mass ratio of silicone oil to modified nano-magnetic particles in S3 is 0.5-10 mL / g, the dispersion time is 5-30 min, and the temperature is controlled at 60-80°C; the silicone oil is preferably 2-methyl silicone oil with a viscosity of 1900 cSt.

[0027] The embodiments of the present invention will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0028] Example 1 Silicone oil based rare earth Dy 3+ The preparation method of the doped Fe3O4 magnetic fluid comprises the following steps: (1) At room temperature, use an electronic balance to accurately weigh 5.6 g FeSO4·4H20, 9.45 g FeC13·6H20, and 0.2 g Dy(NO3)3·5H2O.

[0029] (2) Take 500 ml of ultrapure water and add the three materials into the water respectively. Stir mechanically at a speed of 350 rad / min to mix thoroughly. Place the mixture in a water bath and heat it to above 55°C.

[0030] (3) Pour 1 mol / lL ammonia water into the above mixed solution until the reaction pH value reaches 9 and react for 1.5 h.

[0031] (4) Use an electronic balance to accurately weigh 5 g of silane coupling agent A1120.

[0032] (5) Slowly add hydrochloric acid solution to the above solution until the pH reaches 6.5, add the weighed silane coupling agent A1120 to the solution, heat the water bath to 80°C, and stir at 350 rad / min for 40 min.

[0033] (6) Place the obtained product on a magnetic stand and wash it alternately with ultrapure water and ethanol until the pH value is close to 7.

[0034] (7) The obtained product was placed in a vacuum drying oven at 80 °C for 8 h.

[0035] (8) Weigh 2 g of the nanomagnetic particles using an electronic balance and add them to 30 mL of silicone oil.

[0036] (9) Use an electric stirrer for mechanical stirring for 48 hours and ultrasonic dispersion for 30 minutes.

[0037] (10) Place the prepared sample on a magnetic stand and let it rest for 30 minutes, then pour out the upper silicone oil. The resulting black and shiny liquid is silicone oil-based rare earth Dy 3+ Doped Fe3O4 magnetic fluid.

[0038] Example 2 Same as Example 1, except that the molar ratio of FeSO4·4H2O, FeC13·6H2O and Dy(NO3)3·5H2O is adjusted to 1:1.4:0.018.

[0039] Example 3 Same as Example 1, except that the molar ratio of FeSO4·4H2O, FeC13·6H2O and Dy(NO3)3·5H2O is adjusted to 1:1.4:0.022.

[0040] Example 4 Same as Example 1, except that the molar ratio of FeSO4·4H2O, FeC13·6H2O and Dy(NO3)3·5H2O is adjusted to 1:1.4:0.018; and the silane coupling agent A1120 is replaced by A1100.

[0041] Example 5 Same as Example 4, except that the molar ratio of FeSO4·4H2O, FeC13·6H2O and Dy(NO3)3·5H2O is adjusted to 1:1.4:0.02;.

[0042] Example 6 Same as Example 4, except that the molar ratio of FeSO4·4H20, FeC13·6H20 and Dy(NO3)3·5H2O is adjusted to 1:1.4:0.022.

[0043] Example 7 Same as Example 1, except that the molar ratio of FeSO4·4H2O, FeC13·6H2O and Dy(NO3)3·5H2O is adjusted to 1:1.4:0.018; and the silane coupling agent A1120 is replaced by KH550.

[0044] Example 8 Same as Example 7, except that the molar ratio of FeSO4·4H2O, FeC13·6H2O and Dy(NO3)3·5H2O is adjusted to 1:1.4:0.02;.

[0045] Example 9 Same as Example 7, except that the molar ratio of FeSO4·4H2O, FeC13·6H2O and Dy(NO3)3·5H2O is adjusted to 1:1.4:0.022.

[0046] Comparative Example 1 is the same as Example 1, except that the aqueous ammonia solution is replaced by a sodium hydroxide solution of equal concentration.

[0047] The magnetic fluids obtained in the above embodiments and comparative examples were tested respectively, and the specific data are shown in Table 1. The test principles of pressure resistance, high speed life and high temperature life are similar. Add magnetic fluid into the sealing element, and observe the leakage of the sealing element by continuously applying pressure. Once leakage occurs, the surface material reaches the pressure resistance limit. The same applies to high speed and high temperature life.

[0048] Redispersibility refers to the ability of powder or concentrated fluid to re-form a uniform and stable dispersion system after adding a dispersion medium (such as water, solvent), which is detected by a laser particle size analyzer.

[0049] Yield stress refers to the minimum shear stress required for a fluid to start flowing. It is a key parameter for characterizing the rheological properties of non-Newtonian fluids (such as toothpaste, paint, mud, gel, etc.). It is obtained by rotational rheometer testing.

[0050] The sedimentation stability can be qualitatively obtained through intuitive observation. The fluid is placed in a transparent test tube with a scale, kept at a constant temperature and allowed to stand. The height of the sedimentation interface is regularly observed and recorded, and the sedimentation stability parameters are calculated to determine the fluid sedimentation stability.

[0051] Table 1

[0052] As can be seen from the table above, the performance of the prepared magnetic fluid is relatively optimal when the silane coupling agent KH550 is used as the surfactant of the nanomagnetic particles and the silane coupling agent KH550 and the dysprosium doping amount are selected to be 0.02 molar ratio.

[0053] The above embodiments describe the preferred implementation of the present invention, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A silicone oil-based rare earth Dy 3+ The preparation method of doped Fe3O4 magnetic fluid is characterized in that: The following steps are involved: S1. Mix FeSO4·4H2O, FeC13·6H2O and Dy(NO3)3·5H2O with water to prepare a metal salt solution. Heat the metal salt solution to 55-75°C and then mix it with ammonia water to react and prepare rare earth Dy 3+ Doped Fe3O4 nanoparticles; S2, hydrochloric acid is added to the reaction solution obtained in S1 to adjust the pH to 5.5-6.5, and then a silane coupling agent is added, heated and mixed, and the obtained product is washed with water and ethanol until the pH is neutral, and dried to obtain modified nano-magnetic particles; S3, adding the modified nano magnetic particles into silicone oil for dispersion, and finally removing the precipitate to obtain silicone oil-based rare earth Dy 3+ Doped Fe3O4 magnetic fluid.

2. The preparation method according to claim 1, characterized in that: The molar ratio of FeSO4·4H2O, FeC13·6H2O and Dy(NO3)3·5H2O is 1:1.2~1.6:0.018~0.

022.

3. The preparation method according to claim 2, characterized in that: The molar ratio of FeSO4·4H20, FeC13·6H20 and Dy(NO3)3·5H2O is 1:1.4:0.

02.

4. The preparation method according to claim 1, characterized in that: The concentration of the ammonia solution is 0.8-1.2 mol / L, and the amount added is controlled to control the pH of the reaction solution to be 8-10 after the reaction.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The reaction time in S1 is 0.5-1.5h.

6. The preparation method according to claim 1, characterized in that: The silane coupling agent in S2 is KH550; the heating temperature is 65-80°C, the stirring speed during mixing is 300-550r / min, and the time is 20-30min.

7. The preparation method according to claim 1, characterized in that: The modified nano-magnetic particles in S2 are vacuum dried at a temperature of 60-80° C. for 5-12 hours.

8. The preparation method according to claim 1, characterized in that: The volume mass ratio of silicone oil to modified nano-magnetic particles in S3 is 0.5-10 mL / g, the dispersion time is 5-30 min, and the temperature is controlled at 60-80°C.

9. Dy obtained by the preparation method according to any one of claims 1 to 8 3+ Doped Fe3O4 magnetic fluid.

10. Dy according to claim 9 3+ Application of doped Fe3O4 magnetic fluid in fluid machinery shaft sealing.

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