Magnetorheological fluid and method for producing same

Abstract

The application discloses a kind of magnetorheological fluid and preparation method thereof, belong to magnetorheological fluid technical field, overcome the defects that sedimentation stability and magnetorheological effect of magnetorheological fluid in prior art are difficult to simultaneously optimize.The magnetorheological fluid of the application includes carrier liquid 40-90 parts, magnetic particle 10-60 parts by mass fraction;The carrier liquid is eutectic solvent.The magnetorheological fluid of the application simultaneously improves the sedimentation stability and magnetorheological effect of magnetorheological fluid.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of magnetorheological fluids, and particularly relates to a magnetorheological fluid and a preparation method thereof. BACKGROUND

[0002] The magnetorheological fluid is a colloidal suspension formed by dispersing magnetic particles in a carrier liquid, and is a kind of magnetic response intelligent fluid. When a magnetic field is applied, the magnetic particles form a chain structure along the direction of the magnetic field, and the magnetorheological fluid changes from a liquid state to a solid-like state. When the magnetic field is removed, the magnetorheological fluid can recover from the solid-like state to the liquid state. By applying a variable magnetic field, the material properties can be controllably changed. Due to the characteristics of the magnetorheological fluid, such as fast response to the magnetic field, noiseless operation, insensitivity to a small amount of dust or pollutants, and easy control, the magnetorheological fluid is widely used in various mechanical engineering fields, such as dampers, shock absorbers, brakes, etc.

[0003] The sedimentation of the magnetic particles is caused by the density difference between the particles and the carrier liquid. Too fast sedimentation will lead to a decrease in the rheological effect of the magnetorheological fluid, thereby reducing the application value thereof. In order to solve this problem, researchers have proposed many strategies, such as preparing magnetic particles with special morphology to slow down the sedimentation by reducing the particle density or coating the surface of the magnetic particles to reduce agglomeration to slow down the sedimentation. These strategies effectively improve the sedimentation stability of the magnetorheological fluid, but at the same time, the magnetism of the magnetic particles is reduced, thereby reducing the magnetorheological effect of the magnetorheological fluid. SUMMARY

[0004] Therefore, the technical problem to be solved by the present application is to overcome the defects in the prior art that the sedimentation stability and the magnetorheological effect of the magnetorheological fluid are difficult to be simultaneously optimized, so as to provide a new magnetorheological fluid which has excellent rheological properties and excellent sedimentation stability.

[0005] To this end, the present application provides the following technical solutions.

[0006] The present application provides a magnetorheological fluid, which comprises, in mass parts, 40-90 parts of a carrier liquid and 10-60 parts of magnetic particles; the carrier liquid is a eutectic solvent.

[0007] Further, the carrier liquid comprises a hydrogen bond donor and a hydrogen bond acceptor.

[0008] Further, the carrier liquid further comprises water.

[0009] Preferably, the sum of the mass of the hydrogen bond donor and the hydrogen bond acceptor accounts for 95-100% of the total mass of the carrier liquid.

[0010] Further, the hydrogen bond donor is 1,3-propanediol, 1,4-butanediol, glycerol or urea.

[0011] The hydrogen bond acceptor is choline chloride.

[0012] Further, the molar ratio of the hydrogen bond acceptor and the hydrogen bond donor is 1:1-1:4.

[0013] For example, the molar ratio of the hydrogen bond acceptor and the hydrogen bond donor is 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5 or 1:4.

[0014] Further, the magnetic particles include at least one of Fe3O4 irregular nanoparticles, SiO2-coated Fe3O4 irregular nanoparticles, acid-treated SiO2-coated Fe3O4 irregular nanoparticles, amino-modified Fe3O4 irregular nanoparticles, or SiO2-coated carbonyl iron spherical particles.

[0015] Specifically, the particle size of the amino-modified Fe3O4 irregular nanoparticles is 50-400 nm.

[0016] Specifically, the particle size of the SiO2-coated carbonyl iron spherical particles is 400 nm-1.1 μm.

[0017] The application also provides a preparation method of the magneto-rheological fluid, including the following steps:

[0018] Obtaining the magnetic particles;

[0019] Preparing the carrier liquid;

[0020] Adding the magnetic particles into the carrier liquid and stirring uniformly to obtain the magneto-rheological fluid.

[0021] Further, the preparation method of the magnetic particles includes:

[0022] Dispersing Fe3O4 irregular nanoparticles in a mixed solution containing ethanol, water and ammonia, stirring and adding tetraethyl orthosilicate, continuing to stir for 20-30 h, separating and drying to obtain SiO2-coated Fe3O4 irregular nanoparticles.

[0023] Further, the SiO2-coated Fe3O4 irregular nanoparticles are soaked in acid solution to obtain acid-treated SiO2-coated Fe3O4 irregular nanoparticles.

[0024] Further, the preparation method of the magnetic particles includes:

[0025] Dispersing Fe3O4 irregular nanoparticles in a mixed solution containing ethanol, water and ammonia, stirring and adding tetraethyl orthosilicate and 3-aminopropyltrimethoxysilane, continuing to stir for 20-30 h, separating and drying to obtain amino-modified Fe3O4 irregular nanoparticles.

[0026] The technical scheme of the application has the following advantages:

[0027] The magnetorheological fluid provided by the application comprises, in mass parts, 40-90 parts of carrier liquid and 10-60 parts of magnetic particles; the carrier liquid is a eutectic solvent.

[0028] The application uses a eutectic solvent as the carrier liquid, and the research direction is transferred from modification of the magnetic particles to the carrier liquid and the interface action between the magnetic particles and the carrier liquid, so that the magnetic properties of the magnetic particles can be avoided from being reduced, and the magnetorheological effect of the magnetorheological fluid can be avoided from being reduced. Compared with the traditional carrier liquid silicon oil, the eutectic solvent has a strong hydrogen bond network inside, and the hydrogen bond action between the surface groups of the magnetic particles and the molecules of the eutectic solvent can improve the sedimentation stability and the magnetorheological effect of the magnetorheological fluid. In addition, the eutectic solvent has the advantages of green environmental protection, easy degradation, easy preparation, low cost and high adjustability. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the specific embodiments of the application or the technical solutions in the prior art, the drawings needed in the following specific embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0030] Figure 1 The yield stress of the magnetorheological fluid of Examples 1-4 and Comparative Example 1 changes with the magnetic field intensity;

[0031] Figure 2 The sedimentation rate of the magnetorheological fluid of Examples 1-4 and Comparative Example 1 changes with time;

[0032] Figure 3 The yield stress of the magnetorheological fluid of Examples 5-8 and Comparative Example 2 changes with the magnetic field intensity;

[0033] Figure 4 The sedimentation rate of the magnetorheological fluid of Examples 5-8 and Comparative Example 2 changes with time;

[0034] Figure 5 The yield stress of the magnetorheological fluid of Examples 9-12 and Comparative Example 3 changes with the magnetic field intensity;

[0035] Figure 6 The sedimentation rate of the magnetorheological fluid of Examples 9-12 and Comparative Example 3 changes with time;

[0036] Figure 7 The yield stress of the magnetorheological fluid of Examples 13-16 and Comparative Example 4 changes with the magnetic field intensity;

[0037] Figure 8 The sedimentation rate of the magnetorheological fluid of Examples 13-16 and Comparative Example 4 changes with time;

[0038] Figure 9 Graph of yield stress of the magnetorheological fluid of Example 17-21, Example 11 and Comparative Example 3 as a function of magnetic field strength;

[0039] Figure 10 Graph of sedimentation rate of the magnetorheological fluid of Example 17-21, Example 11 and Comparative Example 3 as a function of time;

[0040] Figure 11 Graph of yield stress of the magnetorheological fluid of Example 22, Example 11 and Comparative Example 3 as a function of magnetic field strength;

[0041] Figure 12 Graph of sedimentation rate of the magnetorheological fluid of Example 22, Example 11 and Comparative Example 3 as a function of time;

[0042] Figure 13 Graph of yield stress of the magnetorheological fluid of Example 23-26 and Example 11 as a function of magnetic field strength;

[0043] Figure 14 Graph of yield stress of the magnetorheological fluid of Example 27 and Comparative Example 5 as a function of magnetic field strength;

[0044] Figure 15 Graph of sedimentation rate of the magnetorheological fluid of Example 27 and Comparative Example 5 as a function of time. DETAILED DESCRIPTION

[0045] The following examples are provided to better enable those skilled in the art to further understand and practice the application, and are not intended to limit the scope of the application in any way. Any product derived from the application or from the combination of the application with other prior art features is intended to fall within the scope of the application.

[0046] Unless otherwise indicated, conventional methods of laboratory preparation, molecular biology, chemistry, and pharmacology, which are well within the purview of the skilled artisan, are employed in the examples. Unless otherwise indicated, all reagents and instruments are commercially available and are conventional in the art.

[0047] The Fe3O4 irregular nanoparticles used in the examples and comparative examples were purchased from Shanghai Micron Biochemical Co., Ltd., 99.5%, 20 nm. The silicone oil was purchased from Sigma Aldrich, 100 cst.

[0048] (1) Fe3O4 irregular nanoparticles as magnetic particles

[0049] The magnetic particles of the magnetorheological fluids of Examples 1-4 were all Fe3O4 irregular nanoparticles, and the compositions of the carrier fluids are shown in Table 1.

[0050] The magnetorheological fluid was prepared as follows: Hydrogen bond acceptors and hydrogen bond donors were mixed according to the combinations shown in Table 1, and heated and stirred at 80°C until a transparent and homogeneous liquid was formed. Random Fe3O4 nanoparticles were added to the carrier liquids of Examples 1-4, and stirred until homogeneous to obtain the magnetorheological fluid. The mass content of magnetic particles in the magnetorheological fluid was 30 wt%.

[0051] Table 1. Combinations of hydrogen bond acceptors and hydrogen bond donors in eutectic solvents of Examples 1-4

[0052]

[0053] Comparative Example 1

[0054] This comparative example is basically the same as Example 1, except that the carrier liquid in this comparative example is silicone oil.

[0055] Experimental Example 1

[0056] Rheological properties were measured using a rotational rheometer (MCR 302, Anton Paar, Austria). The logarithmically increasing shear rates ranged from 0.1 to 100 s⁻¹. -1 The shear stress-shear rate curves were measured under different magnetic fields. All experiments were conducted at 25°C. The yield stress of the magnetorheological fluid under different magnetic field strengths was obtained by fitting the shear rate-shear stress curves using the Bingham plasticity model.

[0057] The sedimentation stability of the magnetorheological fluid was evaluated using a visual observation method. The magnetorheological fluid was placed in test tubes and observed visually at room temperature. The evolution of the sedimentation rate over time was used to assess sedimentation stability. Here, the sedimentation rate is defined as the percentage of the mudline height relative to the total fluid height. Figure 1 The graph shows the yield stress of the magnetorheological fluid in Examples 1-4 and Comparative Example 1 as a function of magnetic field strength. Figure 1 It can be seen that when no magnetic field is applied, Examples 1-3 and Comparative Example 1 have similar yield stresses. However, when a magnetic field is applied, the yield stresses of the magnetorheological fluids in Examples 1-4 are much higher than those in Comparative Example 1, indicating that the rheological properties of Examples 1-3 are better than those of Comparative Example 1. Figure 2 The graph shows the change in sedimentation rate of the magnetorheological fluid in Examples 1-4 and Comparative Example 1 over time. Figure 2 It can be seen that the settlement stability of Examples 1-4 is better than that of Comparative Example 1.

[0058] (2) Random Fe3O4 nanoparticles coated with SiO2 are used as magnetic particles

[0059] The carrier liquid of Examples 5 to 8 is the same as that of Examples 1 to 4, respectively, except that the magnetic particles of Examples 5 to 8 are SiO2-coated Fe3O4 irregular nanoparticles.

[0060] Preparation of SiO2-coated Fe3O4 irregular nanoparticles: 10 g of Fe3O4 irregular nanoparticles were dispersed in a solution containing 320 ml of ethanol, 80 ml of water, and 8 ml of ammonia water (28 wt%), with constant mechanical stirring and the addition of 6 ml of tetraethyl orthosilicate. After mechanically stirring the suspension under nitrogen for 24 hours, the magnetic particles were separated using a magnet and washed several times with deionized water and ethanol. SiO2-coated Fe3O4 irregular nanoparticles were obtained after drying at 50°C for 12 hours.

[0061] Comparative Example 2

[0062] This comparative example is substantially the same as Example 5, except that the carrier liquid in this comparative example is silicone oil.

[0063] Test Example 2

[0064] The rheological properties and sedimentation stability of Examples 5 to 8 and Comparative Example 2 were tested.

[0065] Figure 3 The graph of the yield stress of the magnetorheological fluids of Examples 5 to 8 and Comparative Example 2 as a function of the magnetic field strength is shown in Figure 1. Figure 3 As can be seen, the yield stress of the magnetorheological fluids of Examples 5 to 8 is higher than that of Comparative Example 2 after the application of a magnetic field, indicating that the rheological properties of Examples 5 to 8 are superior to those of Comparative Example 2. Figure 4 The graph of the sedimentation rate of the magnetorheological fluids of Examples 5 to 8 and Comparative Example 2 as a function of time is shown in Figure 2. Figure 4 As can be seen, the sedimentation stability of Examples 5 to 8 is superior to that of Comparative Example 2.

[0066] (3) Acid-treated SiO2-coated Fe3O4 irregular nanoparticles as magnetic particles

[0067] The carrier liquid of Examples 9 to 12 is the same as that of Examples 5 to 8, respectively, except that the magnetic particles of Examples 9 to 12 are acid-treated SiO2-coated Fe3O4 irregular nanoparticles.

[0068] Preparation of acid-treated SiO2-coated Fe3O4 irregular nanoparticles: The prepared SiO2-coated Fe3O4 irregular nanoparticles were soaked in 1 mol·L -1 of hydrochloric acid for 12 hours to obtain acid-treated SiO2-coated Fe3O4 irregular nanoparticles.

[0069] Comparative Example 3

[0070] This comparative example is substantially the same as Example 9, except that the carrier fluid in this comparative example is silicone oil.

[0071] Test Example 3

[0072] The rheological properties and sedimentation stability of Examples 9-12 and Comparative Example 3 were tested.

[0073] Figure 5 The graph of the yield stress of the MR fluids of Examples 9-12 and Comparative Example 3 as a function of magnetic field strength is shown in Figure 2. From Figure 2, it can be seen that Examples 9-12 and Comparative Example 3 have similar yield stress when no magnetic field is applied, but the yield stress of the MR fluids of Examples 9-12 is higher than that of Comparative Example 3 when a magnetic field is applied, indicating that the rheological properties of Examples 9-12 are superior to those of Comparative Example 3. Figure 5 Figure 6 The graph of the sedimentation rate of the MR fluids of Examples 9-12 and Comparative Example 3 as a function of time is shown in Figure 3. From Figure 3, it can be seen that the sedimentation stability of Examples 9-12 is superior to that of Comparative Example 3. Figure 6

[0074] (4) Amino-modified Fe3O4 irregular nanoparticles as magnetic particles

[0075] The carrier fluids of Examples 13-16 are the same as those of Examples 1-4, respectively, and Examples 13-16 differ from Examples 1-4 in that the magnetic particles of Examples 13-16 are amino-modified Fe3O4 irregular nanoparticles.

[0076] Preparation of the amino-modified Fe3O4 irregular nanoparticles: 10 g of Fe3O4 irregular nanoparticles were dispersed in a solution containing 320 ml of ethanol, 80 ml of water, and 8 ml of aqueous ammonia (28 wt%), and mechanical stirring was continued while 6 ml of tetraethyl orthosilicate and 24 ml of 3-aminopropyltrimethoxysilane were added. After the above suspension was mechanically stirred under nitrogen for 24 hours, the resulting magnetic particles were separated using a magnet and washed several times with deionized water and ethanol. The amino-modified Fe3O4 irregular nanoparticles were obtained after drying at 50°C for 12 hours.

[0077] Comparative Example 4

[0078] This comparative example is substantially the same as Example 13, except that the carrier fluid in this comparative example is silicone oil.

[0079] Test Example 4

[0080] The rheological properties and sedimentation stability of Examples 13-16 and Comparative Example 4 were tested.

[0081] Figure 7 The graph of the yield stress of the MR fluids of Examples 13-16 and Comparative Example 4 as a function of magnetic field strength is shown in Figure 4. From Figure 4, it can be seen that Examples 13-16 and Comparative Example 4 have similar yield stress when no magnetic field is applied, but the yield stress of the MR fluids of Examples 13-16 is higher than that of Comparative Example 4 when a magnetic field is applied, indicating that the rheological properties of Examples 13-16 are superior to those of Comparative Example 4. Figure 7 ​​It can be seen that the yield stress of the magnetorheological fluids of Examples 13-16 is higher than that of Comparative Example 4 when a magnetic field is applied, indicating that the rheological properties of Examples 13-16 are superior to those of Comparative Example 4. Figure 8 Fig. 4 is a graph showing the change of the sedimentation rate of the magnetorheological fluids of Examples 13-16 and Comparative Example 4 with time. It can be seen that the sedimentation stability of Examples 13-16 is superior to that of Comparative Example 4. Figure 8 Fig. 4 is a graph showing the change of the sedimentation rate of the magnetorheological fluids of Examples 13-16 and Comparative Example 4 with time. It can be seen that the sedimentation stability of Examples 13-16 is superior to that of Comparative Example 4.

[0082] (5) Mole ratio of hydrogen bond acceptor and hydrogen bond donor

[0083] The magnetorheological fluids of Examples 17-21 are basically the same as those of Example 11, the hydrogen bond acceptor is choline chloride, the hydrogen bond donor is glycerol, and the magnetic particles are acid-treated irregular SiO2-coated Fe3O4 nanoparticles. The difference is that the mole ratio of the hydrogen bond acceptor and the hydrogen bond donor is 1:1.5, 1:2.5, 1:3, 1:3.5, and 1:4, respectively.

[0084] Test Example 5

[0085] The rheological properties and sedimentation stability of Examples 17-21 were tested.

[0086] Figure 9 Fig. 5 is a graph showing the change of the yield stress of the magnetorheological fluids of Examples 17-21, Example 11, and Comparative Example 3 with magnetic field strength. It can be seen that the yield stress of Examples 17-21, Example 11, and Comparative Example 3 is similar when no magnetic field is applied, but the yield stress of Examples 17-21 and Example 11 is higher than that of Comparative Example 4 when a magnetic field is applied. This indicates that the rheological properties of Examples 17-21 and Example 11 are superior to those of Comparative Example 3. Figure 9 Fig. 5 is a graph showing the change of the yield stress of the magnetorheological fluids of Examples 17-21, Example 11, and Comparative Example 3 with magnetic field strength. It can be seen that the yield stress of Examples 17-21, Example 11, and Comparative Example 3 is similar when no magnetic field is applied, but the yield stress of Examples 17-21 and Example 11 is higher than that of Comparative Example 4 when a magnetic field is applied. This indicates that the rheological properties of Examples 17-21 and Example 11 are superior to those of Comparative Example 3. Figure 10 Fig. 6 is a graph showing the change of the sedimentation rate of the magnetorheological fluids of Examples 17-21, Example 11, and Comparative Example 3 with time. It can be seen that the sedimentation stability of Examples 17-21 and Example 11 is superior to that of Comparative Example 3. Figure 10 Fig. 6 is a graph showing the change of the sedimentation rate of the magnetorheological fluids of Examples 17-21, Example 11, and Comparative Example 3 with time. It can be seen that the sedimentation stability of Examples 17-21 and Example 11 is superior to that of Comparative Example 3.

[0087] This test example proves that the magnetorheological fluids with different mole ratios of hydrogen bond acceptor and hydrogen bond donor can simultaneously improve the magnetorheological properties and sedimentation stability of the magnetorheological fluids.

[0088] (6) Carrier liquid including hydrogen bond acceptor, hydrogen bond donor, and water

[0089] The magnetorheological fluid of Example 22 is basically the same as that of Example 11, the hydrogen bond acceptor is choline chloride, the hydrogen bond donor is glycerol, and the magnetic particles are acid-treated irregular SiO2-coated Fe3O4 nanoparticles. The difference is that the carrier liquid further includes water. The content of water in Example 22 is 5wt% of the mass of the carrier liquid.

[0090] Test Example 6

[0091] The rheological properties and the sedimentation stability of the magnetorheological fluid of Example 22 were tested.

[0092] Figure 11 The graph of the yield stress of the magnetorheological fluid of Example 22 and Comparative Example 3 as a function of the magnetic field strength is shown in Figure 2. Figure 11 It can be seen that the yield stress of Example 22 and Comparative Example 3 is similar when no magnetic field is applied, while the yield stress of the magnetorheological fluid of Example 22 is higher than that of Comparative Example 3 when a magnetic field is applied. This indicates that the rheological properties of Example 22 are superior to those of Comparative Example 3. Figure 12 The graph of the sedimentation rate of the magnetorheological fluid of Example 22 and Comparative Example 3 as a function of time is shown in Figure 3. Figure 12 It can be seen that the sedimentation stability of Example 22 (water content of 5wt%) is superior to that of Comparative Example 3.

[0093] (7) Different magnetic particle content in the magnetorheological fluid

[0094] Examples 23-26 are substantially the same as Example 11, except that the mass content of the magnetic particles in the magnetorheological fluid is 20wt%, 40wt%, 50wt%, and 60wt%, respectively.

[0095] Test Example 7

[0096] The magnetorheological properties of the magnetorheological fluid of Examples 23-26 were tested.

[0097] Figure 13 The graph of the yield stress of the magnetorheological fluid of Examples 23-26 as a function of the magnetic field strength is shown in Figure 4. Figure 13 It can be seen that the greater the mass fraction of the magnetic particles, the greater the yield stress of the magnetorheological fluid.

[0098] Example 27

[0099] This example is substantially the same as Example 3, except that the magnetic particles in this example are SiO2-coated carbonyl iron spherical particles, which are purchased from BASF SE, Germany.

[0100] Comparative Example 5

[0101] This comparative example is substantially the same as Example 27, except that the carrier liquid of this comparative example is silicone oil.

[0102] Test Example 8

[0103] The rheological properties and the sedimentation stability of the magnetorheological fluid of Example 27 and Comparative Example 5 were tested.

[0104] Figure 14 The graph of the yield stress of the magnetorheological fluid of Example 27 and Comparative Example 5 as a function of the magnetic field strength is shown in Figure 5. Figure 15 ​A graph showing the change in the sedimentation rate of the magnetorheological fluid of Example 27 and Comparative Example 5 with time. From this Figure 14 , 15 It is known that the rheological properties and the sedimentation stability of the magnetorheological fluid of Example 27 are superior to those of Comparative Example 5.

[0105] Obviously, the above examples are merely illustrative in nature and are not intended to limit the scope of the embodiments. For purposes of conformance with the known art, the following common general knowledge to those skilled in the art can be made on the basis of the above description: further variations or changes in different forms can be made. Here, it is not necessary and also impossible to exhaust all the embodiments. The obvious changes or variations derived therefrom are still within the scope of protection of the present application.

Claims

1. A magnetorheological fluid, characterized in that, By mass, it comprises 40-90 parts of carrier liquid and 10-60 parts of magnetic particles; the carrier liquid is a eutectic solvent. The carrier fluid includes a hydrogen bond donor and a hydrogen bond acceptor; The combined mass of the hydrogen bond donor and the hydrogen bond acceptor accounts for 95-100% of the total mass of the carrier fluid; The hydrogen bond donor is 1,3-propanediol, 1,4-butanediol, glycerol, or urea; The hydrogen bond acceptor is choline chloride.

2. The magnetorheological fluid according to claim 1, characterized in that, The carrier fluid also includes water.

3. The magnetorheological fluid according to claim 1, characterized in that, The molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:1 to 1:

4.

4. The magnetorheological fluid according to any one of claims 1-3, characterized in that, The magnetic particles include at least one of the following: Fe3O4 random nanoparticles, Fe3O4 random nanoparticles coated with SiO2, Fe3O4 random nanoparticles coated with SiO2 after acidification treatment, Fe3O4 random nanoparticles modified with amino groups, or carbonyl iron spherical particles coated with SiO2.

5. A method for preparing the magnetorheological fluid according to any one of claims 1-4, comprising the following steps: Obtain magnetic particles; Preparation of carrier fluid; Magnetic particles are added to the carrier liquid and stirred evenly to obtain a magnetorheological fluid.

6. The method for preparing the magnetorheological fluid according to claim 5, characterized in that, The method for preparing the magnetic particles includes: Fe3O4 random nanoparticles were dispersed in a mixed solution containing ethanol, water and ammonia, stirred and tetraethyl orthosilicate was added, and stirring was continued for 20-30 hours. After separation and drying, Fe3O4 random nanoparticles coated with SiO2 were obtained.

7. The method for preparing magnetorheological fluid according to claim 6, characterized in that, The Fe3O4 random nanoparticles coated with SiO2 were soaked in an acid solution to obtain acid-treated Fe3O4 random nanoparticles coated with SiO2.

8. The method for preparing magnetorheological fluid according to claim 5, characterized in that, The method for preparing the magnetic particles includes: Fe3O4 random nanoparticles were dispersed in a mixed solution containing ethanol, water and ammonia, stirred and then tetraethyl orthosilicate and 3-aminopropyltrimethoxysilane were added. The mixture was stirred for 20-30 hours, separated and dried to obtain amino-modified Fe3O4 random nanoparticles.

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