Iron-cobalt nano-particles, preparation method thereof and application of iron-cobalt nano-particles in magnetorheological fluid

Abstract

The invention belongs to the technical field of magnetorheological fluid preparation, and particularly relates to iron-cobalt nanoparticles, a preparation method of the iron-cobalt nanoparticles and application of the iron-cobalt nanoparticles in magnetorheological fluid. The iron-cobalt nanoparticles contain iron and cobalt, are amorphous and spherical, and have an average particle size of 20-35 nm. The iron-cobalt nano-particles are excellent in magnetization performance, the saturation magnetization of the iron-cobalt nano-particles can reach 220 emu / g, and compared with ferromagnetic nano-particles, the saturation magnetization of the iron-cobalt nano-particles can be improved by 44.7%. Moreover, the magnetorheological fluid prepared on the basis of the iron-cobalt nanoparticles is excellent in performance, the zero-field viscosity of the magnetorheological fluid can be as low as 0.63 Pa.s, and the maximum shear stress corresponding to the shear rate of 0.1 s <-1 > under a 1T magnetic field can reach 68KPa.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetorheological fluid preparation, and in particular relates to iron-cobalt nanoparticles, a preparation method thereof, and application thereof in magnetorheological fluid. Background Art

[0002] Magnetorheological fluid (MRF) is a smart material composed primarily of magnetic particles, a carrier fluid, and additives. Under the influence of an external magnetic field, it can reversibly transform from liquid to solid within milliseconds, exhibiting excellent magnetorheological properties. MRF has broad application prospects in shock absorbers, clutches, dampers, and other applications. The performance of MRF depends primarily on the characteristics of the magnetic particles, including particle size, morphology, and saturation magnetization.

[0003] At present, the magnetic particles commonly used in magnetorheological fluids mainly include iron powder, carbonyl iron powder, ferrite, etc. CN114551022B discloses a high-performance magnetorheological fluid, which contains magnetic micron particles and composite stacked magnetic nanoparticles, and improves the anti-sedimentation and shear yield stress of the magnetorheological fluid under low magnetic field through the two-phase composite magnetic conductive particles. CN111233046A discloses a hollow magnetic Fe3O4 nano-doped microsphere for magnetorheological fluid, which has a lower density and better dispersibility and stability, and can improve the compatibility of magnetic particles in the base carrier liquid. CN106548847A discloses a magnetorheological fluid, which contains magnetic particles, a carrier liquid, a surfactant, a thixotropic agent, a lubricant, a desiccant and an anti-corrosion agent, and has better anti-sedimentation and anti-agglomeration capabilities.

[0004] In terms of magnetic particle materials, iron-cobalt alloy has attracted much attention due to its higher saturation magnetization intensity and has gradually become one of the main magnetic particle materials for the preparation of magnetorheological fluids. Summary of the Invention

[0005] Based on this, the present invention uses a method for preparing nanoparticles by DC arc plasma evaporation. By optimizing the mass ratio of iron and cobalt, as well as the density of DC electricity in the DC arc plasma evaporation method, iron-cobalt nanoparticles with excellent saturation magnetization can be prepared. The magnetorheological fluid prepared based on the iron-cobalt nanoparticles has excellent zero-field viscosity and shear stress.

[0006] In order to achieve the above object, the present invention can adopt the following technical solutions:

[0007] On one hand, the present invention provides an iron-cobalt nanoparticle. The iron-cobalt nanoparticle contains iron and cobalt, is amorphous and spherical, and has an average particle size of 20nm-35nm.

[0008] Another aspect of the present invention provides a method for preparing the above-mentioned iron-cobalt nanoparticles, the preparation method comprising: preparing an iron-cobalt alloy by a DC arc plasma evaporation method; wherein the mass ratio of iron to cobalt in the iron-cobalt alloy is (2.5-3.5):2; the DC current density in the DC arc plasma evaporation method is 250A / cm 2 -310A / cm 2 .

[0009] More preferably, in the above preparation method, the mass ratio of iron to cobalt in the iron-cobalt alloy is 3:2; the current density of the DC current in the DC arc plasma evaporation method is 270A / cm 2 .

[0010] Preferably, in the above preparation method, the DC current in the DC arc plasma evaporation method is 80A-120A; and / or the voltage is 20V-30V.

[0011] In another aspect, the present invention provides a magnetorheological fluid comprising the iron-cobalt nanoparticles of the present invention, dimethyl silicone oil, and an additive, wherein the additive comprises a preservative and a dispersant.

[0012] Preferably, in the magnetorheological fluid, the preservative is benzotriazole; and / or the dispersant is polyether-modified siloxane.

[0013] More preferably, in the magnetorheological fluid, the mass of the iron-cobalt nanoparticles is 35wt%-45wt% of the dimethyl silicone oil; and / or the mass of the preservative is 0.8wt%-1.2wt% of the dimethyl silicone oil; and / or the mass of the dispersant is 0.4wt%-0.6wt% of the dimethyl silicone oil.

[0014] More preferably, in the magnetorheological fluid, the mass of the iron-cobalt nanoparticles is 40 wt % of the dimethyl silicone oil; and / or the mass of the preservative is 1 wt % of the dimethyl silicone oil; and / or the mass of the dispersant is 0.5 wt % of the dimethyl silicone oil.

[0015] Another aspect of the present invention provides a method for preparing the magnetorheological fluid of the present invention, the preparation method comprising: mixing iron-cobalt nanoparticles, dimethyl silicone oil and an additive to prepare the magnetorheological fluid.

[0016] Preferably, in the above preparation method, high-speed shearing and / or ultrasonic treatment is performed during the mixing process.

[0017] The beneficial effects of the present invention include:

[0018] (1) The iron-cobalt nanoparticles provided by the present invention have excellent magnetization properties, and their saturation magnetization intensity can reach 220emu / g. Compared with ferromagnetic micron particles, the saturation magnetization intensity can be increased by 44.7%.

[0019] (2) The magnetorheological fluid provided by the present invention has excellent performance. Its zero-field viscosity can be as low as 0.63 Pa·s, and the maximum shear stress corresponding to a shear rate of 0.1s-1 under a 1T magnetic field can reach 68KPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 These are SEM images of the iron-cobalt nanoparticles prepared in Example 1 and the ferromagnetic micron particles prepared in Comparative Example 1; wherein (a) is the ferromagnetic micron particles prepared in Comparative Example 1, and (b) is the iron-cobalt nanoparticles prepared in Example 1. DETAILED DESCRIPTION

[0021] The examples are provided to better illustrate the present invention, but are not intended to limit the present invention to the examples. Therefore, non-essential improvements and adjustments to the embodiments made by those skilled in the art based on the above-mentioned invention still fall within the scope of protection of the present invention.

[0022] The terms used herein are only used to describe specific embodiments and are not intended to limit the present disclosure. Unless the context has a significantly different meaning, expressions in the singular include expressions in the plural. As used herein, it should be understood that terms such as "include", "have", "comprise" and the like are intended to indicate the presence of features, numbers, operations, components, parts, elements, materials or combinations. The terms of the present invention are disclosed in the specification and are not intended to exclude the possibility that one or more other features, numbers, operations, components, parts, elements, materials or combinations thereof may exist or may be added. As used herein, " / " may be interpreted as "and" or "or", depending on the circumstances.

[0023] In a first aspect, an embodiment of the present invention provides an iron-cobalt nanoparticle, which contains iron and cobalt, is amorphous and spherical, and has an average particle size of 20 nm to 35 nm.

[0024] It should be noted that the iron-cobalt nanoparticles provided by the present invention have excellent magnetic properties and physicochemical properties, and have broad application prospects in the fields of magnetorheological fluids, catalysts, biomedicine, etc. The iron-cobalt nanoparticles in the present embodiment have higher specific surface area and more uniform particle size distribution due to their amorphous amorphous structure and spherical morphology, thereby showing more excellent magnetic properties (saturation magnetization can reach 220emu / g) and dispersibility. The average particle size in the present invention is 20nm-35nm, such as 23nm, 25nm, 28nm, 30nm or 32nm etc.

[0025] In a second aspect, an embodiment of the present invention provides a method for preparing the above-mentioned iron-cobalt nanoparticles, the preparation method comprising: preparing an iron-cobalt alloy by a DC arc plasma evaporation method; wherein the mass ratio of iron to cobalt in the iron-cobalt alloy is (2.5-3.5):2; the DC current density in the DC arc plasma evaporation method is 250A / cm 2 -310A / cm 2 .

[0026] It should be noted that the present invention controls the mass ratio of iron and cobalt and the current density of the direct current in the DC arc plasma evaporation method to prepare iron-cobalt nanoparticles with excellent performance. The mass ratio of iron and cobalt can be (2.5-3.5):2, such as 2.7:2, 3:2 or 3.2:2. When the mass ratio is 3:2, the saturation magnetization of the prepared iron-cobalt nanoparticles is the largest. In addition, when the mass ratio is lower than 2.5:2 or greater than 3.5:2, the saturation magnetization of the prepared iron-cobalt nanoparticles will decrease significantly. In addition, the current density is 250A / cm 2 -310A / cm 2 , for example 270A / cm 2 、290A / cm 2 or 300A / cm 2 etc., where the current density is 270A / cm 2 The saturation magnetization intensity of the iron-cobalt nanoparticles prepared is higher, and when the current density is less than 250A / cm 2 or >310A / cm 2 When the saturation magnetization of the prepared iron-cobalt nanoparticles decreases significantly.

[0027] In some specific examples, in the above preparation method, the DC current in the DC arc plasma evaporation method is 80A-120A; and / or the voltage is 20V-30V.

[0028] It should be noted that the DC current in the DC arc plasma evaporation method of the present invention can be 80A-120A, such as 90A, 100A or 110A, etc.; and / or the voltage can be 20V-30V, such as 25V, 27V or 29V, etc.

[0029] In some specific examples, the above preparation method may include the following steps:

[0030] (1) Target pretreatment and installation

[0031] 1) Using Fe-Co alloy target (purity ≥ 99.99%), process it into a disc with a diameter of 50mm-100mm and a thickness of 5mm-10mm by wire cutting;

[0032] 2) Polish the target surface with 400-mesh and 800-mesh sandpaper in sequence until the roughness Ra is less than or equal to 0.8 μm;

[0033] 3) Soak the target in anhydrous ethanol and ultrasonically clean it to remove grease and oxidation layer;

[0034] 4) Fix the target material to the water-cooled copper electrode with bolts, connect the high-voltage cable to the top of the electrode, and pass cooling water (flow rate 5-10L / min, water temperature 15±2℃) to the bottom;

[0035] (2) Vacuum system preparation and arc triggering

[0036] 1) Start the mechanical pump and molecular pump combined system to increase the vacuum degree of the chamber to ≤5×10-3Pa;

[0037] 2) Start the high-voltage pulse module (5-10kV) to break through the insulating membrane between the electrodes and generate the initial arc;

[0038] 3) Immediately switch to DC power supply after arc is triggered, and the current density is controlled at 250A / cm 2 -310A / cm 2 (current fluctuation <±1%), voltage stable at 20V-30V, current 80A-120A;

[0039] (3) Argon pressure control

[0040] 1) The argon pressure of the main gas line is set to 0.2MPa-0.3MPa;

[0041] 2) The mass flow meter (MFC) dynamically adjusts the flow rate to stabilize the plasma plume and maintain the target evaporation rate in the range of 5-8g / min. At the same time, the auxiliary gas line argon pressure is set to 0.05MPa, and the laminar flow mode is used to guide the airflow to wrap around the arc edge, directly suppressing droplet splashing to a droplet ratio of <0.1%;

[0042] (4) Arc plasma evaporation and nanoparticle nucleation

[0043] 1) The arc plasma temperature is as high as 8000-10000K, causing the target material to evaporate into gaseous atoms instantly;

[0044] 2) Gaseous atoms are rapidly cooled in an argon environment and condensed into nuclei through collisions, forming nanoparticle prototypes;

[0045] (5) Particle growth inhibition

[0046] 1) A helium nozzle array (aperture 0.5 mm) is embedded in the bottom of the vacuum chamber in a ring structure (10 mm spacing), resembling a multi-porous shower head to evenly cover the high-temperature particle flow path;

[0047] 2) The distance between the nozzle and the evaporation zone of the copper crucible is precisely controlled at 50 mm, forcing the particle growth time to be shortened to <1 ms, inhibiting grain coarsening and heterogeneous agglomeration;

[0048] (6) Annealing

[0049] 1) Under the protection of high-purity argon (oxygen content <10ppm, laminar flow rate 50L / min, Re <500), iron-cobalt nanoparticles (0-50nm) were first annealed at 400℃×2h to eliminate internal stress and then slowly cooled (<50℃ / h) to 200℃.

[0050] 2) then heating the mixture at 600°C for 1 hour in a 1T axial uniform magnetic field (uniformity >95%) to achieve oriented magnetic domain alignment, and finally air-cooling the mixture to room temperature to obtain iron-cobalt nanoparticles.

[0051] In a third aspect, an embodiment of the present invention provides a magnetorheological fluid comprising the iron-cobalt nanoparticles of the present invention, dimethyl silicone oil, and an additive, wherein the additive comprises a preservative and a dispersant.

[0052] It should be noted that, based on the excellent saturation magnetization of the iron-cobalt nanoparticles of the present invention, they can be combined with dimethyl silicone oil and additives to produce a magnetorheological fluid with excellent performance; additives are well known in the art, such as preservatives and dispersants. Furthermore, the magnetorheological fluid prepared in this invention can exhibit a zero-field viscosity as low as 0.63 Pa·s, and a maximum shear stress of 68 kPa at a shear rate of 0.1 s⁻¹ in a 1 T magnetic field.

[0053] In some specific examples, in the magnetorheological fluid, the preservative is benzotriazole; and / or the dispersant is polyether-modified siloxane.

[0054] It should be noted that, in the magnetorheological fluid of the present invention, the preservative and the dispersant are both well known in the art. For example, the preservative may be benzotriazole; and / or the dispersant may be polyether-modified siloxane.

[0055] In some specific examples, in the magnetorheological fluid, the mass of the iron-cobalt nanoparticles is 35wt%-45wt% of the dimethyl silicone oil; and / or the mass of the preservative is 0.8wt%-1.2wt% of the dimethyl silicone oil; and / or the mass of the dispersant is 0.4wt%-0.6wt% of the dimethyl silicone oil.

[0056] It should be noted that in the magnetorheological fluid of the present invention, the mass of the iron-cobalt nanoparticles is 35wt%-45wt% of the dimethyl silicone oil, for example, 37wt%, 40wt% or 42wt%; the mass of the preservative can be 0.8wt%-1.2wt% of the dimethyl silicone oil, for example, 0.9wt%, 1wt% or 1.1wt%; the mass of the dispersant can be 0.4wt%-0.6wt% of the dimethyl silicone oil, for example, 0.45wt%, 0.5wt% or 0.55wt%.

[0057] In some specific examples, in the magnetorheological fluid, the mass of the iron-cobalt nanoparticles can be preferably 40 wt% of the dimethyl silicone oil; the mass of the preservative can be preferably 1 wt% of the dimethyl silicone oil; and / or the mass of the dispersant can be preferably 0.5 wt% of the dimethyl silicone oil. The magnetorheological fluid prepared with these amounts exhibits better performance.

[0058] In a fourth aspect, an embodiment of the present invention provides a method for preparing the magnetorheological fluid of the present invention, the preparation method comprising: mixing iron-cobalt nanoparticles, dimethyl silicone oil and an additive to prepare the magnetorheological fluid.

[0059] It should be noted that the preparation method of the magnetorheological fluid of the present invention is simple, and iron-cobalt nanoparticles, dimethyl silicone oil and additives are mixed, and the mixing method is well known in the art.

[0060] In some specific examples, in the above preparation method, high-speed shearing and / or ultrasonic treatment is performed during the mixing process.

[0061] It should be noted that the magnetorheological fluid of the present invention can be subjected to high-speed shearing or ultrasonic treatment during the mixing process. Preferably, high-speed shearing combined with ultrasonic treatment can produce a magnetorheological fluid with better performance.

[0062] In order to better understand the present invention, the content of the present invention is further explained below with reference to specific examples, but the content of the present invention is not limited to the following examples.

[0063] In the following examples, the DC arc plasma evaporation system comes from Beijing Chuangshi Weina Technology Co., Ltd., the vacuum system (including the vacuum chamber) comes from Beijing Zhongke Keyi Co., Ltd., the argon ion bombardment device (surface treatment equipment) comes from Beijing Chuangshi Weina Technology Co., Ltd., the gas flow control system (including the mass flow meter MFC) comes from Beijing Qixing Huachuang Electronics Co., Ltd., the helium forced cooling system (customized integrated equipment) comes from Chengdu Aotai Medical Systems Co., Ltd., and the annealing equipment (two-step annealing furnace) comes from Hefei Kejing Materials Technology Co., Ltd.

[0064] Example of preparation of iron-cobalt nanoparticles

[0065] Example 1

[0066] (1) Target pretreatment and installation

[0067] 1) Using an Fe-Co alloy target (Fe:Co (mass ratio) = 3:2, purity ≥ 99.99%), wire-cut into a disk with a diameter of 50 mm and a thickness of 10 mm;

[0068] 2) Polish the target surface with 400-mesh and 800-mesh sandpaper in sequence until the roughness Ra is less than or equal to 0.8 μm;

[0069] 3) Soak the target in anhydrous ethanol and ultrasonically clean it for 20 minutes to remove grease and oxidation layer;

[0070] 4) Fix the target to the water-cooled copper electrode with bolts, connect the high-voltage cable to the top of the electrode, and pass cooling water (flow rate 5L / min, water temperature 15±2℃) to the bottom;

[0071] (2) Vacuum system preparation and arc triggering

[0072] 1) Start the mechanical pump and molecular pump combined system to increase the vacuum degree of the chamber to ≤5×10-3Pa;

[0073] 2) Start the high-voltage pulse module (5-10kV) to break through the insulating membrane between the electrodes and generate the initial arc;

[0074] 3) Immediately switch to DC power supply after arc is triggered, and the current density is controlled at 270A / cm 2 (current fluctuation <±1%), voltage stable at 25V, current 100A;

[0075] (3) Argon pressure control

[0076] 1) The argon pressure of the main gas line is set to 0.3MPa;

[0077] 2) The mass flow meter (MFC) dynamically adjusts the flow rate to stabilize the plasma plume and maintain the target evaporation rate in the range of 5-8g / min. At the same time, the auxiliary gas line argon pressure is set to 0.05MPa, and the laminar flow mode is used to guide the airflow to wrap around the arc edge, directly suppressing droplet splashing to a droplet ratio of <0.1%;

[0078] (4) Arc plasma evaporation and nanoparticle nucleation

[0079] 1) The arc plasma temperature is as high as 8000-10000K, causing the target material to evaporate into gaseous atoms instantly;

[0080] 2) Gaseous atoms are rapidly cooled in an argon environment and condensed into nuclei through collisions, forming nanoparticle prototypes;

[0081] (5) Particle growth inhibition

[0082] 1) A helium nozzle array (aperture 0.5 mm) is embedded in the bottom of the vacuum chamber in a ring structure (10 mm spacing), resembling a multi-porous shower head to evenly cover the high-temperature particle flow path;

[0083] 2) The distance between the nozzle and the evaporation zone of the copper crucible is precisely controlled at 50 mm, forcing the particle growth time to be shortened to <1 ms, inhibiting grain coarsening and heterogeneous agglomeration;

[0084] (6) Annealing

[0085] 1) Under the protection of high-purity argon (oxygen content <10ppm, laminar flow rate 50L / min, Re <500), iron-cobalt nanoparticles (0-50nm) were first annealed at 400℃×2h to eliminate internal stress and then slowly cooled (<50℃ / h) to 200℃.

[0086] 2) then heating the mixture at 600°C for 1 hour in a 1T axial uniform magnetic field (uniformity >95%) to achieve oriented magnetic domain alignment, and finally air-cooling the mixture to room temperature to obtain iron-cobalt nanoparticles.

[0087] Example 2

[0088] Example 2 is substantially the same as Example 1, and the difference between Example 2 and Example 1 is that in Example 2, the Fe:Co (mass ratio) in the Fe-Co alloy target is 2.5:2, and the rest is the same as Example 1, and iron-cobalt nanoparticles are prepared.

[0089] Example 3

[0090] Example 3 is substantially the same as Example 1, and the difference between Example 3 and Example 1 is that in Example 3, the Fe:Co (mass ratio) in the Fe-Co alloy target is 3.5:2, and the rest is the same as Example 1, and iron-cobalt nanoparticles are prepared.

[0091] Example 4

[0092] Example 4 is substantially the same as Example 1. The difference between Comparative Example 4 and Example 1 is that in Example 4, the current density is controlled at 250 A / cm 2 , the voltage is stabilized at 25 V, the current is 100 A, and the other conditions are the same as in Example 1 to prepare iron-cobalt nanoparticles.

[0093] Example 5

[0094] Example 5 is substantially the same as Example 1. The difference between Example 5 and Example 1 is that in Example 5, the current density is controlled at 310 A / cm 2 , the voltage is stabilized at 25 V, the current is 100 A, and the other conditions are the same as in Example 1 to prepare iron-cobalt nanoparticles.

[0095] Comparative Example 1

[0096] Comparative Example 1 is substantially the same as Example 1, and the difference between Comparative Example 1 and Example 1 is that in Comparative Example 1, the Fe-Co alloy target material is a single iron material, and the rest is the same as Example 1, to prepare ferromagnetic micron particles.

[0097] Comparative Example 2

[0098] Comparative Example 2 is substantially the same as Example 1. The difference between Comparative Example 1 and Example 1 is that in Comparative Example 1, the Fe:Co (mass ratio) in the Fe-Co alloy target is 2:2, and the rest is the same as Example 1, to prepare iron-cobalt nanoparticles.

[0099] Comparative Example 3

[0100] Comparative Example 3 is substantially the same as Example 1. The difference between Comparative Example 2 and Example 1 is that in Comparative Example 2, the Fe:Co (mass ratio) in the Fe-Co alloy target is 3:2, and the rest is the same as Example 1, to prepare iron-cobalt nanoparticles.

[0101] Comparative Example 4

[0102] Comparative Example 4 is substantially the same as Example 1. The difference between Comparative Example 4 and Example 1 is that in Comparative Example 4, the current density is controlled at 230 A / cm 2 , the voltage is stabilized at 25 V, the current is 100 A, and the other conditions are the same as in Example 1 to prepare iron-cobalt nanoparticles.

[0103] Comparative Example 5

[0104] Comparative Example 5 is substantially the same as Example 1. The difference between Comparative Example 4 and Example 1 is that in Comparative Example 5, the current density is controlled at 350 A / cm 2 , the voltage is stabilized at 25 V, the current is 100 A, and the other conditions are the same as in Example 1 to prepare iron-cobalt nanoparticles.

[0105] The iron-cobalt nanoparticles prepared in Example 1 and the ferromagnetic micron particles prepared in Comparative Example 1 were observed using SEM. Figure 1 As shown, the results show that the iron-cobalt nanoparticles are amorphous and non-crystalline; the particles are spherical with an average particle size of 27 nm; the ferromagnetic micron particles are micron particles (>1 μm) with irregular morphology, wide particle size distribution, high surface roughness, and generally low crystallinity.

[0106] Preparation Example of Magnetorheological Fluid

[0107] Example 6

[0108] Dimethyl silicone oil (viscosity 100 mPa·s, viscosity index>300) (as a base liquid), benzotriazole (BTA) (as a preservative), polyether-modified siloxane (molecular weight 2000 Da) (as a dispersant) and iron-cobalt nanoparticles (Example 1) were sheared (5000 rpm) and dispersed in a high-speed shear disperser (SGN / Sijun GRS2000 / 4) for 1 hour, and ultrasonically treated (40 kHz / 300 W pulse) while shearing to obtain a magnetorheological fluid; wherein the mass fraction of benzotriazole (BTA) in the dimethyl silicone oil was 1.0 wt %, the mass fraction of polyether-modified siloxane (molecular weight 2000 Da) in the dimethyl silicone oil was 0.5 wt %, and the mass fraction of iron-cobalt nanoparticles in the dimethyl silicone oil was 40 wt %.

[0109] Example 7 to Example 10

[0110] In Examples 7 to 10, the iron-cobalt nanoparticles prepared in Examples 2 to 5 were used in accordance with the preparation method in Example 6 to prepare different magnetorheological fluids.

[0111] Example 11

[0112] Example 11 is substantially the same as Example 6. The difference between Example 11 and Example 6 is that only ultrasound is used and a high-speed shearing disperser is not used for shearing. Other steps are the same as Example 6 to prepare a magnetorheological fluid.

[0113] Example 12

[0114] Example 12 is substantially the same as Example 6. The difference between Example 12 and Example 6 is that only a high-speed shearing disperser is used for shearing, and ultrasound is not used. Other steps are the same as Example 6, and a magnetorheological fluid is prepared.

[0115] Comparative Examples 6 to 10

[0116] Comparative Examples 6 to 10 are different magnetorheological fluids prepared by using the iron-cobalt nanoparticles prepared in Comparative Examples 1 to 5 according to the preparation method in Example 6.

[0117] Performance Testing

[0118] The saturation magnetization of the iron-cobalt nanoparticles or ferromagnetic micron particles prepared in Examples 1 to 5 and Comparative Examples 1 to 5 was tested according to the standard GB / T 13888-2009. The results are shown in Table 1 below.

[0119] Table 1 Saturation magnetization of iron-cobalt nanoparticles prepared in Examples and Comparative Examples

[0120]

[0121]

[0122] It can be seen from Table 1 above that the saturation magnetization of the iron-cobalt nanoparticles prepared in Examples 1 to 5 is significantly higher than that of the ferromagnetic micron particles and iron-cobalt nanoparticles prepared in the comparative example; wherein:

[0123] Comparison of Example 1 with Comparative Example 1 shows that the saturation magnetization of the iron-cobalt nanoparticles prepared in Example 1 is significantly higher than that of the ferromagnetic micronized particles prepared in Comparative Example 1, with the saturation magnetization being increased by 44.7%.

[0124] By comparing Examples 1 to 3 with Comparative Examples 2 and 3, it can be seen that when the Fe:Co (mass ratio) in the Fe-Co alloy target is (2.5-3.5):2, the saturation magnetization intensity of the iron-cobalt nanoparticles prepared is significantly higher than that of the iron-cobalt nanoparticles prepared when the Fe:Co (mass ratio) in the Fe-Co alloy target is 2:2 and 3:2; among them, the saturation magnetization intensity of the iron-cobalt nanoparticles prepared when the Fe:Co (mass ratio) is 3:2 is the highest;

[0125] Comparison of Example 1, Example 4 and Example 5 with Comparative Example 4 and Comparative Example 5 shows that the current density is controlled at 250 A / cm 2 -310 A / cm 2 The saturation magnetization intensity of the iron-cobalt nanoparticles prepared at this time is significantly higher than that of the nanoparticles prepared at a current density of 230 A / cm 2 and 350A / cm 2 The iron-cobalt nanoparticles prepared by the current density was controlled at 270A / cm 2 The saturation magnetization intensity of the iron-cobalt nanoparticles prepared when

[0126] Furthermore, the zero-field viscosity and the maximum shear stress corresponding to a shear rate of 0.1 s⁻¹ in a 1 T magnetic field of the magnetorheological fluids prepared in Examples 6 to 12 and Comparative Examples 6 to 10 were tested in accordance with the JB / T 12512-2015 standard. The test results are shown in Table 2 below.

[0127] Table 2 Performance test of magnetorheological fluid prepared in Examples and Comparative Examples

[0128]

[0129]

[0130] It can be seen from Table 2 above that the zero-field viscosity of the magnetorheological fluids prepared in Examples 6 to 12 is significantly lower than that of the magnetorheological fluids prepared in Comparative Examples 6 to 10; wherein:

[0131] Comparison of Example 6 with Comparative Example 6 shows that the zero-field viscosity of the magnetorheological fluid prepared in Example 6 is significantly lower than that of the magnetorheological fluid prepared in Comparative Example 1, indicating that the iron-cobalt nanoparticles are superior to the ferromagnetic microparticles.

[0132] By comparing Examples 6 to 8 with Comparative Examples 7 and 8, it can be seen that the zero-field viscosity of the magnetorheological fluid based on the iron-cobalt nanoparticles prepared when the Fe:Co (mass ratio) in the Fe-Co alloy target is (2.5-3.5):2 is significantly lower than that of the magnetorheological fluid based on the iron-cobalt nanoparticles prepared when the Fe:Co (mass ratio) in the Fe-Co alloy target is 2:2 and 3:2; among them, the magnetorheological fluid based on the iron-cobalt nanoparticles prepared when the Fe:Co (mass ratio) is 3:2 has the lowest zero-field viscosity;

[0133] Comparison of Example 6, Example 9 and Example 10 with Comparative Example 9 and Comparative Example 10 shows that based on the current density being controlled at 250 A / cm 2 -310 A / cm 2 The zero-field viscosity of the magnetorheological fluid with iron-cobalt nanoparticles prepared at this time is significantly lower than that based on the current density controlled at 230A / cm 2 and 350A / cm 2 The magnetorheological fluid of iron-cobalt nanoparticles prepared by the method of the invention is characterized by that the current density is controlled at 270A / cm 2 The zero-field viscosity of the magnetorheological fluid with iron-cobalt nanoparticles prepared at is the lowest;

[0134] By comparing Example 6 with Example 11 and Example 12, it can be seen that the zero-field viscosity of the magnetorheological fluid prepared by using both a high-speed shear disperser and ultrasound is lower than that of the magnetorheological fluid prepared by using only a high-speed shear disperser or ultrasound.

[0135] In addition, it can be seen from Table 2 above that the maximum shear stress corresponding to the shear rate of 0.1s-1 under a 1T magnetic field of the magnetorheological fluids prepared in Examples 6 to 12 is significantly higher than that of the magnetorheological fluids prepared in Comparative Examples 6 to 10; wherein:

[0136] Comparison of Example 6 with Comparative Example 6 shows that the maximum shear stress corresponding to a shear rate of 0.1 s-1 under a 1 T magnetic field of the magnetorheological fluid prepared in Example 6 is significantly higher than that of the magnetorheological fluid prepared in Comparative Example 1, indicating that the iron-cobalt nanoparticles are superior to the ferromagnetic microparticles.

[0137] By comparing Examples 6 to 8 with Comparative Examples 7 and 8, it can be seen that the maximum shear stress corresponding to the shear rate of 0.1s-1 under 1T magnetic field of the magnetorheological fluid based on the iron-cobalt nanoparticles prepared when the Fe:Co (mass ratio) in the Fe-Co alloy target is (2.5-3.5):2 is significantly greater than the magnetorheological fluid based on the iron-cobalt nanoparticles prepared when the Fe:Co (mass ratio) in the Fe-Co alloy target is 2:2 and 3:2; among them, the maximum shear stress corresponding to the shear rate of 0.1s-1 under 1T magnetic field of the magnetorheological fluid based on the iron-cobalt nanoparticles prepared when the Fe:Co (mass ratio) is 3:2 is the largest;

[0138] Comparison of Example 6, Example 9 and Example 10 with Comparative Example 9 and Comparative Example 10 shows that based on the current density being controlled at 250 A / cm 2 -310 A / cm 2 The maximum shear stress of the magnetorheological fluid of iron-cobalt nanoparticles prepared at a shear rate of 0.1s-1 under a 1T magnetic field is significantly greater than that of the magnetorheological fluid based on the current density controlled at 230A / cm 2 and 350A / cm 2 The magnetorheological fluid of iron-cobalt nanoparticles prepared by the method of the invention is characterized by that the current density is controlled at 270A / cm 2 The maximum shear stress corresponding to the shear rate of 0.1s-1 under the 1T magnetic field of the magnetorheological fluid of iron-cobalt nanoparticles prepared at this time is the largest;

[0139] By comparing Example 6 with Example 11 and Example 12, it can be seen that the maximum shear stress corresponding to the shear rate of 0.1s-1 under a 1T magnetic field of the magnetorheological fluid prepared by using a high-speed shear disperser and ultrasound at the same time is higher than that of the magnetorheological fluid prepared by using only a high-speed shear disperser or ultrasound.

[0140] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be covered by the scope of the claims of the present invention.

Claims

1. Iron-cobalt nanoparticles, characterized in that The iron-cobalt nanoparticles contain iron and cobalt, are amorphous and spherical, and have an average particle size of 20nm-35nm.

2. The method for preparing iron-cobalt nanoparticles according to claim 1, characterized in that: The preparation method comprises: preparing an iron-cobalt alloy by a DC arc plasma evaporation method; wherein, In iron-cobalt alloy, the mass ratio of iron to cobalt is (2.5-3.5):2; The DC current density in the DC arc plasma evaporation method is 250A / cm 2 -310A / cm 2 .

3. The preparation method according to claim 2, characterized in that In iron-cobalt alloy, the mass ratio of iron to cobalt is 3:2; The DC arc plasma evaporation method uses a DC current density of 270 A / cm 2 .

4. The preparation method according to claim 2 or 3, characterized in that The DC current in the DC arc plasma evaporation method has a current of 80A-120A; and / or a voltage of 20V-30V.

5. Magnetorheological fluid, characterized in that The invention comprises the iron-cobalt nanoparticles according to claim 1, dimethyl silicone oil and an auxiliary agent, wherein the auxiliary agent comprises a preservative and a dispersant.

6. The magnetorheological fluid according to claim 5, characterized in that The preservative is benzotriazole; and / or The dispersant is polyether-modified siloxane.

7. The magnetorheological fluid according to claim 5 or 6, characterized in that: The mass of the iron-cobalt nanoparticles is 35wt%-45wt% of the dimethyl silicone oil; and / or The mass of the preservative is 0.8wt%-1.2wt% of dimethyl silicone oil; and / or The mass of the dispersant is 0.4wt%-0.6wt% of the dimethyl silicone oil.

8. The magnetorheological fluid according to claim 7, characterized in that The mass of the iron-cobalt nanoparticles is 40 wt% of the dimethyl silicone oil; and / or The mass of the preservative is 1 wt% of dimethyl silicone oil; and / or The mass of the dispersant is 0.5 wt% of dimethyl silicone oil.

9. The method for preparing a magnetorheological fluid according to any one of claims 5 to 8, characterized in that: The preparation method comprises the following steps: mixing iron-cobalt nanoparticles, dimethyl silicone oil and an auxiliary agent to prepare a magnetorheological fluid.

10. The preparation method according to claim 9, characterized in that High shear and / or ultrasonic treatment is performed during mixing.

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