Composite magnetorheological fluid

Abstract

The present invention discloses a composite magnetorheological fluid, comprising: anisotropic magnetic powder, the content of which is in the range of 0.05-5% of the total weight of the composite magnetorheological fluid; isotropic magnetic powder at the micron scale, the content of which is in the range of 70-90% of the total weight of the composite magnetorheological fluid; a carrier liquid, and an additive added to the carrier liquid, the content of which is the balance of the composite magnetorheological fluid.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetorheological fluids. More specifically, the present invention relates to the preparation of composite magnetorheological fluids using a combination of isotropic magnetic powder and anisotropic magnetic powder. Background Art

[0002] Magnetorheological fluid is a liquid whose viscosity changes with the application of a magnetic field. It is a stable suspension system composed of soft magnetic particles with high magnetic permeability and low remanence evenly dispersed in a non-magnetic carrier liquid through the action of a surfactant. The working principle of magnetorheological fluid is as follows: under the action of an external magnetic field, each particle is polarized into a magnetic dipole, and the dipoles attract each other to form a chain-like structure between the two magnetic pole plates, which acts like a bridge across the pole plates, hindering the normal flow of the fluid and giving it the characteristics of a solid-like substance. When the external magnetic field is removed, the fluid returns to its original state, that is, the magnetorheological fluid undergoes a rapid and reversible conversion between the liquid state and the solid state. The degree of solidification has a stable and reversible relationship with the current intensity, that is, by controlling the current intensity, the shear yield strength of the solidified magnetorheological fluid can be precisely controlled.

[0003] For many years, there have been many researchers on magnetorheological fluids, and currently, they have been gradually applied to various devices to control damping forces, such as shock absorbers, vibration absorbers, artificial limbs, and elastic seats. The rheology of magnetorheological fluid under the action of a magnetic field is instantaneous, reversible, and the shear yield strength after rheology has a stable corresponding relationship with the magnetic field strength, making it very easy to achieve intelligent control. Therefore, magnetorheological fluid is an intelligent material with wide applications and excellent performance, and the application fields of magnetorheological fluids are expanding rapidly.

[0004] Traditional magnetorheological fluids have a remanence phenomenon. The magnetic response particles with remanence dispersed in the magnetorheological fluid cannot completely return to the free-flowing state after the magnetic field is removed due to the remanence of the particles, interfering with the control process of the magnetorheological fluid working device. The existence of remanence is a common problem in the prior art, and this defect will become more prominent as the use time delays. This will not only lead to poor performance of the magnetorheological fluid and its application equipment, but especially will cause low control response performance and reliability of the fluid or equipment, and there will also be a defect of short service life.

[0005] In order to reduce the coercive force, traditional magnetorheological fluids tend to increase the particle size of the magnetic particles, such as setting them to the micron level. For example, reference can be made to US Patent US6203717B1, which brings another prominent problem, that is, the magnetic particles are prone to sedimentation in the magnetorheological fluid. The sedimentation of magnetic particles directly leads to a short service life, low reliability of the magnetorheological fluid, and ultimately the failure of the magnetorheological fluid.

[0006] In addition, traditional magnetorheological fluids not only have poor anti-settling performance, but also their anti-shear strength performance needs to be improved. For example, compared with the nano-magnetorheological fluids previously invented by the inventors of the present application (refer to, for example, the Chinese patent applications No. 201510538070.7, No. 201510537836.X and the PCT application WO 2017036337A1 of the inventors), at the same volume percentage of magnetic powder particle content, their anti-shear strength is lower than that of the nano-magnetorheological fluids invented by the inventors. Therefore, when applied to, for example, the electromagnetic suspension of an automobile, the excitation coil of the magnetorheological fluid shock-absorbing tube containing traditional magnetorheological fluid must adopt a double-coil configuration, which makes it difficult to miniaturize the magnetorheological fluid shock-absorbing tube and also increases the cost; if a single-coil configuration is adopted, the response time of the magnetorheological fluid shock-absorbing tube to vibration is longer, which is unacceptable for magnetorheological fluid shock-absorbing devices that need to quickly respond to vibration.

[0007] In the nano-magnetorheological fluids previously invented by the inventors, the anisotropic magnetic powder has higher magnetic saturation and faster response speed. Therefore, under a magnetic field, the anisotropic magnetic powder chains have stronger binding force, so the anisotropic magnetorheological fluid can provide stronger anti-shear yield strength under the action of a magnetic field.

[0008] However, nano-magnetorheological fluids still have their inherent defects. For example, their preparation process has a long time, complex processes, high environmental protection requirements, and higher material costs, resulting in a higher cost than traditional magnetorheological fluids. In addition, the specific surface area (specific surface energy) of the anisotropic magnetic powder is relatively large. Therefore, the magnetorheological fluid is relatively thick, the second Newtonian region of the magnetorheological fluid is relatively large, the initial force is relatively large, and the controllable range is limited to a certain extent. The anisotropic magnetic powder may affect the high-shear-rate flow performance of the magnetorheological fluid under zero magnetic field due to its anisotropic shape, such as a relatively large aspect ratio, making the second Newtonian region unstable under zero magnetic field, which is not conducive to device control and shock-absorption control. The so-called second Newtonian region refers to that non-Newtonian fluids will exhibit the performance of Newtonian fluids at high shear rates, that is, the viscosity is constant, and the shear force increases linearly with the increase of the shear rate. Because the kinematic viscosity of the second Newtonian region is constant and is conducive to control, it is the main control region of the magnetorheological fluid.

[0009] In view of the above and other concepts, the present invention is proposed.

[0010] The information included in this background art section of the specification of the present invention, including any references cited herein and any of their descriptions or discussions, is included only for the purpose of technical reference and is not considered to be the subject matter limiting the scope of the present invention. Summary of the Invention

[0011] The present invention is proposed in view of the above and many other concepts. The present invention aims to solve the above technical defects and other problems.

[0012] In this regard, the present invention conceives a better solution to solve the above technical problems and other technical problems. By mixing different magnetic powders to prepare magnetorheological fluids, more advantages can be achieved, especially in terms of cost and comprehensive performance, as well as a wider range of application scenarios.

[0013] Anisotropic magnetic powders have higher magnetic saturation and faster response speeds. Therefore, anisotropic magnetic powders have stronger binding forces when forming chains under a magnetic field. So, anisotropic magnetorheological fluids can provide stronger anti-shear yield strength under the action of a magnetic field. However, anisotropic magnetorheological fluids also have their disadvantages, such as material cost and process cost defects. The specific surface area (and specific surface energy) of anisotropic magnetic powders is relatively large. Therefore, the magnetorheological fluid is relatively thick, the second Newtonian region of the magnetorheological fluid is relatively large, the initial force is relatively large, and the controllable range is limited to a certain extent. Due to the anisotropy of the shape of anisotropic magnetic powders and a relatively large aspect ratio, the high-shear-rate flow performance of the magnetorheological fluid under zero magnetic field is affected, making the second Newtonian region unstable under zero magnetic field, which is not conducive to control.

[0014] The present invention proposes to mix a certain proportion of anisotropic magnetic powders with ordinary isotropic magnetic powders, carrier liquids, and other additives to prepare the composite magnetorheological fluid of the present invention. In other words, anisotropic magnetic powders can be added to traditional magnetorheological fluids to obtain the composite magnetorheological fluid of the present invention, which can form a structure similar to "reinforced concrete" or so-called "fiber-reinforced composite materials" under a magnetic field. Among them, the anisotropic magnetic powders that can quickly form chains (or "bridge") in the direction of the magnetic force lines under the action of a magnetic field are similar to "reinforcing bars", and the isotropic magnetic powders are similar to "cement". Under a magnetic field, the anisotropic magnetic powders in the composite magnetorheological fluid quickly form chains, and the isotropic magnetic powders are magnetically attracted to their adjacent isotropic magnetic powders to form an "interwoven" morphology similar to the "reinforced concrete" structure, whose binding force is greater than that of traditional magnetorheological fluids, the response to the magnetic field is faster, and the morphology is more stable. And this kind of magnetorheological fluid of the present invention can provide higher anti-shear strength. At the same time, this kind of magnetorheological fluid of the present invention can at least partially overcome the above-mentioned disadvantages of anisotropic magnetorheological fluids, and can at least partially maintain the advantages of traditional magnetorheological fluids, and improves the anti-settling property compared with traditional magnetorheological fluids.

[0015] According to one aspect of the present invention, there is provided a composite magnetorheological fluid, comprising: anisotropic magnetic powder, the content of which is in the range of 0.05-5% of the total weight of the composite magnetorheological fluid; isotropic magnetic powder on the micron scale, the content of which is in the range of 70-90% of the total weight of the composite magnetorheological fluid; and a carrier liquid and additives added to the carrier liquid, the content of which is the balance of the composite magnetorheological fluid.

[0016] According to one embodiment, the isotropic magnetic powder is iron powder, and its particle size is in the range of about 0.1-50 microns, for example, in the range of about 0.1-20 microns, 0.2-10 microns or 0.2-5 microns.

[0017] According to one embodiment, the anisotropic magnetic powder is selected from at least one of flaky, strip-shaped, needle-shaped, rod-shaped, cylindrical, dendritic, spherical-like anisotropic magnetic powder and single-crystal anisotropic magnetic powder.

[0018] According to one embodiment, the average particle size or the minimum single-dimensional size of the anisotropic magnetic powder is less than 99 nanometers, for example, in the range of 0.1-99 nanometers, preferably between 0.1-80 nanometers, more preferably between 0.2-50 nanometers, and further preferably between 0.5-20 nanometers.

[0019] According to one embodiment, the average particle size or the minimum single-dimensional size of the anisotropic magnetic powder is in the range of about 100-900 nanometers, for example, in the range of 100-500 nanometers, or between 100-200 nanometers.

[0020] According to one embodiment, the material of the anisotropic magnetic powder is selected from iron, iron alloy, iron-cobalt alloy, iron-platinum alloy, iron oxide, iron nitride, iron carbide, iron carbonyl, nickel, cobalt, chromium dioxide, FePt, SmCo, NdFeB, stainless steel, silicon steel, or a combination of these materials.

[0021] According to one embodiment, the iron alloy is an iron-cobalt alloy or an iron-platinum alloy.

[0022] According to one embodiment, the carrier liquid is an organic liquid, such as mineral oil, synthetic oil, α-olefin, silicone oil or a combination thereof.

[0023] According to one embodiment, the content of the anisotropic magnetic powder is in the range of 0.1-3% of the total weight of the composite magnetorheological fluid, preferably in the range of 0.5-1%.

[0024] According to one embodiment, the additive comprises at least one of the following: surfactant, dispersant, anti-settling agent, organic thixotropic agent, thickening agent, antioxidant, lubricant, viscosity regulator, flame retardant, organoclay rheological additive, sulfur-containing compound, and any combination thereof.

[0025] According to one embodiment, the additive includes at least one of the following: C16-18 alcohol polyoxyethylene ether, condensate of C12-14 alcohol and ethylene oxide, isomeric tridecanol polyoxyethylene ether, isomeric decanol polyoxyethylene ether, oleyl alcohol polyoxyethylene ether, octyldecanol polyoxyethylene ether, octylphenol polyoxyethylene ether, polyethylene glycol stearate, polyoxyethylene stearate, castor oil polyoxyethylene ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyethylene glycol, polypropylene glycol, polyoxyethylene-polyoxypropylene, alkylphenol polyoxyethylene-polyoxypropylene ether, allyl alcohol polyoxyalkylene ether, polyoxyethylene-polyoxypropylene copolymer, methoxypolyethylene glycol, methoxypolypropylene glycol, fatty alcohol ether phosphate, phenolic ether phosphate, isotridecanol phosphate, lauryl phosphate, potassium salt of fatty alcohol ether phosphate, potassium salt of fatty alcohol ether phosphate, potassium salt of phenolic ether phosphate, potassium salt of isotridecanol ether phosphate, potassium salt of lauryl phosphate, dodecylamine polyoxyethylene ether, octadecylamine polyoxyethylene ether, tallow amine polyoxyethylene ether, fatty acid diethanolamide, coconut fatty acid diethanolamide, styrenephenol, glycerol polyether, castor oil phosphate, triglycerol oleate, (Z)-9-octadecenoic acid 1,2,3-propanetriyl ester, pentaerythritol oleate, trimethylolpropane oleate, ammonium salt of nonylphenol polyoxyethylene ether sulfate, ammonium salt of styrenephenol polyoxyethylene ether sulfate, polyether modified silicone oil, and fluorocarbon surfactant.

[0026] According to one embodiment, the additive includes at least one of the following: 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, hindered amine, 2,6-di-tert-butyl-4-methylphenol, N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine, n-octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, tris(2,4-di-tert-butylphenyl) phosphite, pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], isooctyl oleate, trimellitate, neopentyl polyol ester, ditrimethylolpropane ester, neopentyl glycol dioleate, diisooctyl sebacate, diisooctyl adipate, trimethylolpropane coconut oleate, diethyl phthalate, tributyl phosphate, dioctyl phosphate, diethyl adipate, epoxidized soybean oil, polyol benzoate, dioctyl terephthalate, and dioctyl phthalate.

[0027] According to one embodiment, the anisotropic magnetic powder is shape anisotropic and / or magnetocrystalline anisotropic and / or stress-induced magnetic anisotropic.

[0028] According to one embodiment, the composite magnetorheological fluid does not undergo significant sedimentation during at least one week of standing at room temperature.

[0029] The main advantages of the present invention are as follows. The composite magnetorheological fluid of the present invention not only retains the excellent mechanical properties of the anisotropic magnetorheological fluid under a magnetic field, but also takes into account the good fluidity of the traditional magnetorheological fluid under zero magnetic field. The fluid has a stable and wide second Newtonian region, and the initial kinematic viscosity of the fluid is relatively low, so that the control range of the magnetorheological device is wider and more stable, and so on. At the same time, compared with the traditional magnetorheological fluid, the present invention also improves the anti-settling performance of the fluid.

[0030] More embodiments of the present invention can also achieve other beneficial technical effects that are not listed one by one. Some of these other technical effects may be described below, and can be expected and understood by those skilled in the art after reading the present invention.

[0031] This "Summary of the Invention" section aims to introduce in a simplified form the concepts and selections that will be further described below in the "Detailed Description" to help the reader more easily understand the present invention. The Summary of the Invention is not intended to identify the key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. All of the above features are to be understood as merely exemplary, and more features and purposes regarding the process steps can be collected from the disclosure of the present invention. A more comprehensive display of the features, details, practicality, and advantages of the present invention will be provided in the following written description of various embodiments of the present invention, illustrated in the drawings, and defined in the appended claims. Therefore, many restrictive interpretations of the Summary of the Invention may not be understood without further reading the entire specification, the claims, and the drawings. Brief Description of the Drawings

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly describe the drawings required for use in the embodiments or the description of the prior art.

[0033] By referring to the following description in conjunction with the drawings, the above features and advantages of these embodiments and other features and advantages, as well as the manner of achieving them, will become more apparent, and the embodiments of the present invention can be better understood. In the drawings:

[0034] Figure 1 is a schematic diagram showing the morphology of an embodiment of the composite magnetorheological fluid of the present invention after applying a magnetic field.

[0035] Figure 2 Schematically shows the magnetic field scanning stress curves of the composite magnetorheological fluids of the present invention with different anisotropic magnetic powder contents (shear rate 0.1 -s ).

[0036] Figure 3Schematically shows the relationship between the shear resistance strength of the composite magnetorheological fluid of the present invention and the content of anisotropic magnetic powder in the composite magnetorheological fluid under an 800 mT magnetic field (shear rate 0.1 -s ).

[0037] Figure 4 Schematically shows the comparative test results of the shear resistance strength between various composite magnetorheological fluids of the present invention with different contents (higher) of anisotropic magnetic powder and traditional magnetorheological fluids at different shear rates under zero magnetic field and at a temperature of 40°C.

[0038] Figure 5 Schematically shows the comparative test results of the shear resistance strength between various composite magnetorheological fluids of the present invention with different contents (lower) of anisotropic magnetic powder and traditional magnetorheological fluids at different shear rates under zero magnetic field and at a temperature of 40°C.

[0039] Figure 6 Shows the zero magnetic field viscosity of the composite magnetorheological fluid obtained by uniformly adding 2% of different types of anisotropic magnetic powder to the traditional magnetorheological fluid.

[0040] Figure 7 Shows the comparative test of the shear stress (i.e., shear resistance strength) under magnetic field of the composite magnetorheological fluid obtained by uniformly adding 2% of different types of anisotropic magnetic powder to the traditional magnetorheological fluid.

[0041] Figure 8 Shows the comparative test of the anti-settling performance between the composite magnetorheological fluid obtained by adding 0.5% of anisotropic magnetic powder to the traditional magnetorheological fluid and the traditional magnetorheological fluid. Detailed implementation manners

[0042] In the following descriptions of the drawings and the detailed implementation manners, the details of one or more embodiments of the present invention will be elaborated. From these descriptions, the drawings, and the claims, other features, objectives, and advantages of the present invention can be clearly understood.

[0043] It should be understood that the embodiments illustrated and described are not limited to the details of the construction and arrangement of the components set forth in the following description or illustrated in the drawings. The illustrated embodiments can be other embodiments and can be implemented or executed in various ways. Each example is provided by way of explaining rather than limiting the disclosed embodiments.

[0044] In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the present invention without departing from the scope or essence of the disclosure of the present invention. For example, features illustrated or described as part of one embodiment can be used with another embodiment to still produce additional embodiments. Accordingly, the disclosure of the present invention covers such modifications and variations that fall within the scope of the appended claims and their equivalent elements.

[0045] Similarly, it is to be understood that the phrases and terms used herein are for the purpose of description and should not be regarded as restrictive. For example, the use of "comprising", "having" or "provided with" and their variations herein is intended to include open-endedly the items listed thereafter, their equivalents as well as additional items.

[0046] The present invention will be explained and described in more detail below with reference to specific embodiments of the present invention in conjunction with the accompanying drawings.

[0047] Ordinary magnetic powder, i.e., ordinary isotropic magnetic powder, can be those disclosed in, for example, conventional magnetorheological fluids, such as those described in U.S. Patent No. US6203717B1, which is incorporated herein by reference. Typical isotropic magnetic powder generally has a substantially spherical shape, can be obtained by, for example, water atomization process, and generally has a particle size on the micron scale, for example, a particle size of about 1 micron. For other patents related to ordinary magnetorheological fluids and magnetic powder, reference can also be made to, for example, U.S. Patent Applications 2575360, 2661825, 2886151, 5645752, 7393463B2, 6203717B1, and 2006 / 0033069A1, etc., the relevant contents of which are also incorporated herein by reference as if they were described in the application. Of course, in the present invention, the particle size of the ordinary isotropic magnetic powder is not limited to the above, but can have a larger or smaller range of particle sizes, for example, in the range of about 0.1 - 50 microns, such as varying in the ranges of about 0.1 - 20 microns, 0.2 - 10 microns, 0.2 - 5 microns.

[0048] Anisotropic magnetic powder can be obtained, for example, from Chinese Patent Applications No. 201510538070.7, No. 201510537836.X and PCT Application WO 2017036337A1 invented by the inventor before. The relevant contents of these patent applications are also incorporated herein by reference as if they were described in this application. The anisotropic magnetic powder may have, for example, a nano-scale size, for example, its average particle size or minimum single-dimensional size is generally less than 99 nanometers, for example, in the range of 0.1 - 99 nanometers, for example, between 0.1 - 80 nanometers, between 0.2 - 50 nanometers, between 0.5 - 20 nanometers, and so on. However, in the present invention, the size of the anisotropic magnetic powder is not limited to the above nano-scale range, but may have a larger particle size or particle size range, for example, the average particle size or minimum single-dimensional size is in the range of about 0.1 - 900 nanometers, 0.1 - 500 nanometers, 0.1 - 200 nanometers, and so on.

[0049] The following describes the composite magnetorheological fluid of the present invention and its preparation process with specific examples.

[0050] Example I

[0051] Prepare the carrier liquid of the composite magnetorheological fluid. Mineral oil, synthetic oil, α-olefin, silicone oil, etc. can be used as the carrier liquid, and these can all be purchased on the market.

[0052] Prepare the additives of the composite magnetorheological fluid. The additives that can be selected include but are not limited to organic clay, molybdenum disulfide, fumed silica, etc., and these can all be purchased on the market.

[0053] The steps of a preparation process of the composite magnetorheological fluid are as follows.

[0054] Step 1: Dispersing the additive

[0055] The process that can be adopted in this step can be selected from one of the following:

[0056] 1. Add organic clay and fumed silica at room temperature into the container of an ultrasonic stirrer (such as model JM-1018), and perform ultrasonic stirring and dispersion treatment for about 20 minutes at a stirring frequency of about 30 Hz;

[0057] 2. Add organic clay and fumed silica at room temperature into a circulating sand grinding device (such as model YSN-0.2L), and perform sand grinding and stirring dispersion (rotation speed 500 rpm, linear velocity 12 m / s) for about 30 minutes; and

[0058] 3. Add the organoclay and fumed silica at room temperature to a high-speed centrifugal dispersion device (such as model TFS-2.2) for dispersion treatment for about 5 minutes, where the linear velocity of the centrifugal rotation is between 12 m / s and 37 m / s.

[0059] Step 2: Preparing the solution and mixing

[0060] Provide anisotropic magnetic powders (such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 5% of the total weight of the magnetorheological fluid), such as nanoscale flaky anisotropic magnetic powders, dendritic anisotropic magnetic powders, and spherical-like anisotropic magnetic powders, as the anisotropic magnetic powders added to the carrier fluid.

[0061] Configure the basic components of the carrier fluid with 12% mineral oil or synthetic oil and 5% by weight of α-olefin based on the total weight of the composite magnetorheological fluid components, and various other types of additives accounting for approximately 2% of the total weight can be added. Examples of the additives include anti-settling agents, dispersants, lubricants, and antioxidants, etc.

[0062] The anti-settling agents and dispersants in the additives may include at least one of C16-18 alcohol polyoxyethylene ether, C12-14 alcohol and ethylene oxide condensate, isomeric tridecyl alcohol polyoxyethylene ether, isomeric decyl alcohol polyoxyethylene ether, oleyl alcohol polyoxyethylene ether, octyldecanol polyoxyethylene ether, octylphenol polyoxyethylene ether, polyethylene glycol stearate, polyoxyethylene stearate, castor oil polyoxyethylene ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyethylene glycol, polypropylene glycol, polyoxyethylene polyoxypropylene, alkylphenol polyoxyethylene polyoxypropylene ether, allyl alcohol polyoxyalkyl ether, polyoxyethylene-polyoxypropylene copolymer, methoxypolyethylene glycol, methoxypolypropylene glycol, fatty alcohol ether phosphate, phenol ether phosphate, isomeric tridecyl alcohol phosphate, lauryl phosphate, fatty alcohol ether phosphate potassium salt, fatty alcohol ether phosphate potassium salt, phenol ether phosphate potassium salt, isomeric tridecyl ether phosphate potassium salt, lauryl phosphate potassium salt, dodecylamine polyoxyethylene ether, octadecylamine polyoxyethylene ether, tallow amine polyoxyethylene ether, fatty acid diethanolamide, coconut fatty acid diethanolamide, styrenephenol, glycerol polyether, castor oil phosphate, triglycerol oleate, (Z)-9-octadecenoic acid-1,2,3-propanetriyl ester, pentaerythritol oleate, trimethylolpropane oleate, nonylphenol polyoxyethylene ether sulfate ammonium salt, styrenephenol polyoxyethylene ether ammonium sulfate, polyether-modified silicone oil, fluorocarbon surfactant.

[0063] The antioxidants and lubricants in the additive may include at least one of 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, hindered amine, 2,6-di-tert-butyl-4-methylphenol, N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine, n-octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, tris(2,4-di-tert-butylphenyl) phosphite, pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], isooctyl oleate, trimellitate, neopentyl polyol ester, ditrimethylolpropane tetraester, neopentyl glycol dioleate, diisooctyl sebacate, diisooctyl adipate, trimethylolpropane cocoate, diethyl phthalate, trioctyl phosphate, dioctyl phosphate, diethyl adipate, epoxidized soybean oil, polyol benzoate, dioctyl terephthalate, dioctyl phthalate.

[0064] After stirring the above carrier liquid at a low speed with a stirrer for about 10 minutes, add the weighed remaining solid additives such as 1.5% of organoclay and fumed silica slowly at a low speed with a closed oscillating feeder of model GZVF for example. After the addition is completed, disperse the carrier liquid at a high speed with this oscillating feeder for about 30 - 60 minutes to obtain the prepared carrier liquid.

[0065] Put the prepared carrier liquid into a low-speed stirring device (model JB200-D for example), and add anisotropic magnetic powder while stirring slowly at a low speed. For example, the anisotropic magnetic powder can be slowly added to the carrier liquid with an oscillating feeder.

[0066] After that, add ordinary magnetic powder with an oscillating feeder, such as isotropic iron powder with a particle size in the range of about 0.1 - 1 micron. For example, it can be added slowly and uniformly first, and as the addition of iron powder increases, the rotation speed of the oscillating feeder can be gradually increased.

[0067] After all the magnetic powder is added, raise the linear speed of stirring of the low-speed stirring device to a high speed of about 7 - 10 m / s for example, and stir at this high speed for 2 hours.

[0068] Finally, vacuum dry the carrier liquid with added magnetic powder in a vacuum oven (model 202-0B for example) at a temperature of about 40 - 60 °C for 5 hours to discharge the air mixed in the process.

[0069] After that, weigh and package to obtain the finished product of the composite magnetorheological fluid of the present invention.

[0070] Example II

[0071] This example is basically the same as Example I in terms of preparation process, steps, equipment, raw materials, components, parameters, etc. The difference lies in that single-crystal anisotropic magnetic powder is used for the anisotropic magnetic powder, and the added single-crystal anisotropic magnetic powder accounts for 2% of the total weight of the magnetorheological fluid.

[0072] Testing

[0073] 1. Anti-settling test

[0074] 1. Description of the sedimentation system

[0075] The fundamental cause of the sedimentation problem in MRF is the significant density difference between the dispersed phase (taking carbonyl iron powder as an example, with a density of 7.8 g / mL) and the continuous phase (carrier fluid, 1 g / mL). Under the action of gravity, the particles continuously sink to the bottom of the container. Generally, in the upper part of the container, there appears a clear supernatant liquid area that only contains the carrier fluid (transparent or non-transparent, depending on the properties of the carrier fluid), and a clear dividing line is formed in its lower part, which is called the "mud line". In the lower area next to the mud line, the particle concentration remains unchanged for a certain period of time at the beginning, so it is called the "initial concentration area". At the bottom of the container, the particles continuously accumulate, and after a certain time, they are squeezed and hardened under the action of gravity and other forces to form a sedimentation area with the highest concentration and uniform distribution. Obviously, there must be a transition area between the initial concentration area and the sedimentation area, which is called the "variable concentration area", and its concentration will change significantly with time and height. The dividing line between the initial concentration area and the variable concentration area is named the "gel line". As the name implies, the reason is that the variable concentration area seems to be in a very viscous "gel state". The dividing line between the variable concentration area and the sedimentation area is named the "sedimentation line", which represents the starting line of the downward formation of the sedimentation area.

[0076] 2. Visual measurement scheme for the anti-sedimentation test of magnetorheological fluid

[0077] Take a 15 ml test tube and pour 10 ml of traditional magnetorheological fluid and composite magnetorheological fluid added with anisotropic magnetic powder respectively, and place them vertically and statically. Observe and record the scale where the mud line is located every 7 days, continuously observe for about 1 month, and draw a mud line sedimentation curve graph.

[0078] As Figure 8 shown, by measuring the distance from the bottom of the test tube to the top of the fluid - liquid level height, and measuring the distance from the bottom of the test tube to the top of the sedimented magnetic powder - sedimented magnetic powder height, the height value of the transparent layer can be determined. And, using the following equation, the sedimentation rate (Ratio) can be calculated:

[0079] Sedimentation rate Ratio = (Liquid level height (cm) - Sedimented magnetic powder height (cm)) / Liquid level height (cm) × 100%

[0080] The results of the visual test are as Figure 8As shown Figure 8 It shows the comparison of the anti-settling performance test results and data between the composite magnetorheological fluid obtained by adding 0.5% anisotropic magnetic powder to the traditional magnetorheological fluid and the traditional magnetorheological fluid. As Figure 8 shown, the test results indicate that in all the anti-settling tests for 7 days, 14 days, 21 days, and 28 days, the settling rate of this composite magnetorheological fluid is less than that of the traditional magnetorheological fluid, that is, the anti-settling performance of this composite magnetorheological fluid is slightly better than that of the traditional magnetorheological fluid. That is to say, adding an appropriate amount of anisotropic magnetic powder to the traditional magnetorheological fluid can also appropriately improve the anti-settling performance of the traditional magnetorheological fluid.

[0081] 2. Zero magnetic field viscosity test

[0082] For the zero magnetic field viscosity detection and the shear stress detection under magnetic field of the composite magnetorheological fluid of the present invention, a rheometer of model MCR302 produced by Anton-Paar company is used. The detection system is a parallel plate detection system of model PP20 / MRD / TI. The upper heating unit in the detection unit is a semiconductor heating unit and a water bath circulation unit of model MRD170+H-PTD200. The lower heating unit in the detection unit is an oil bath circulation unit of model VT2. The magnetic field unit in the detection unit is an external magnetic field unit of model PS-DC / MR / 1T.

[0083] For the zero magnetic field viscosity detection, 2 ml of the sample is placed in the flat sample cell of the parallel plate detection system, and scan from 0 to 1200 -s kinematic viscosity at 40 °C.

[0084] As Figure 4 can be seen, the magnetic powder concentrations of both the traditional magnetorheological fluid and the composite magnetorheological fluid with 1% added anisotropic magnetic powder are approximately 81%, while the magnetic powder concentration of the magnetorheological fluid prepared with pure anisotropic magnetic powder with comparable mechanical properties is approximately 65%. However, the kinematic viscosity of the anisotropic magnetorheological fluid with a magnetic powder concentration of 65% is much greater than that of the traditional magnetorheological fluid and the composite magnetorheological fluid with a magnetic powder concentration of approximately 81% - this is because the magnetic powder particle size of the anisotropic magnetic powder in the magnetorheological fluid prepared with pure anisotropic magnetic powder is generally nanoscale, which affects the magnitude of the initial force of the damper and the control range of the damper.

[0085] Figure 5 It schematically shows the comparison test results of the anti-shear strength between various composite magnetorheological fluids with different contents (lower) of anisotropic magnetic powder of the present invention and the traditional magnetorheological fluid at zero magnetic field and 40 °C temperature under different shear rates. As Figure 5As shown, in the present invention, adding a small amount of anisotropic magnetic powder to traditional magnetorheological fluid results in a composite magnetorheological fluid that has little change in the kinematic viscosity of the traditional magnetorheological fluid under zero magnetic field. In this way, the composite magnetorheological fluid of the present invention can not only maintain the excellent physical and chemical properties of the traditional magnetorheological fluid, such as kinematic viscosity performance, and has good fluidity under zero magnetic field, but also provide superior mechanical properties, such as shear strength after applying a magnetic field, and so on.

[0086] Figure 6 Shows the zero magnetic field viscosity of the composite magnetorheological fluid obtained by uniformly adding 2% of different types of anisotropic magnetic powder to the traditional magnetorheological fluid. As Figure 6 shown, after testing, there is no substantial correlation or influence between the zero magnetic field viscosity and the type of anisotropic magnetic powder added. However, generally speaking, the flaky anisotropic magnetic powder has the greatest influence on the zero magnetic field viscosity, and the dendritic anisotropic magnetic powder has the least influence on the zero magnetic field viscosity, but these influences are not substantial and do not affect the actual industrial application of the composite magnetorheological fluid of the present invention.

[0087] 3. Detection of anti-shear strength under magnetic field

[0088] For the zero magnetic field viscosity detection and the shear strength detection under magnetic field of this patent, a rheometer of model MCR302 produced by Anton-Paar company is used. The detection system is a parallel plate detection system of model PP20 / MRD / TI. The upper heating unit in the detection unit is a semiconductor heating unit and a water bath circulation unit of model MRD170+H-PTD200. The lower heating unit in the detection unit is an oil bath circulation unit of model VT2. The magnetic field unit in the detection unit is an external magnetic field unit of model PS-DC / MR / 1T.

[0089] For the shear strength detection under magnetic field, 2 ml of the sample is placed in the flat sample cell of the parallel plate detection system, and the scanning current is 0 - 4.5 A, that is, the shear stress at 40 °C under a magnetic field of 0 - 900 mT.

[0090] As Figure 2 shown, it shows that the shear strength under magnetic field of the composite magnetorheological fluid added with different proportions of anisotropic magnetic powder has all increased.

[0091] As Figure 3 shown, it shows the relationship between the action of adding different proportions of anisotropic magnetic powder on the shear stress of the magnetorheological fluid under magnetic field. Figure 3The test is a comparison of the mechanical tests of the composite magnetorheological fluid obtained by adding anisotropic magnetic powder to the traditional magnetorheological fluid under the magnetic field. From the test results, it can be seen that in the composite magnetorheological fluid of the present invention, when the amount of anisotropic magnetic powder added ranges from greater than 0% to about 0.1% to about 0.3% to about 0.5% of the total weight of the magnetorheological fluid, the anti-shear strength performance of the composite magnetorheological fluid under the magnetic field gradually rises to the highest peak value. Then, as the amount of anisotropic magnetic powder added increases, from about 0.5% to 1% addition amount, the anti-shear strength performance of the composite magnetorheological fluid under the magnetic field gradually decreases until at about 1% addition amount of anisotropic magnetic powder, its anti-shear strength is equivalent to that at about 0.1% addition amount. After that, when the addition amount of anisotropic magnetic powder increases from about 1% to about 2%, the anti-shear strength of the composite magnetorheological fluid under the magnetic field remains basically unchanged until when the addition amount of anisotropic magnetic powder increases from about 2% to about 3%, the anti-shear strength has a small increase as a whole. That is to say, when the amount of anisotropic magnetic powder added ranges from greater than 0% to about 3% of the total weight of the magnetorheological fluid, the anti-shear strength of the composite magnetorheological fluid under the magnetic field is greater than that of the traditional magnetorheological fluid.

[0092] Figure 7 shows the detection of the anti-shear strength under the magnetic field of the composite magnetorheological fluid with 2% of different types of anisotropic magnetic powder uniformly added to the traditional magnetorheological fluid. As Figure 7 shown, through the detection of the anti-shear strength under the magnetic field, the results show that the type of anisotropic magnetic powder has a greater impact on the anti-shear strength of the magnetorheological fluid under the magnetic field. Among them, the anti-shear strength is greater when dendritic anisotropic magnetic powder is added, and the shear force is smaller when single-crystal anisotropic magnetic powder is added. Generally speaking, no matter what type of appropriate anisotropic magnetic powder is added to the traditional magnetorheological fluid, it can substantially improve some properties of the traditional magnetorheological fluid, such as the anti-shear strength performance.

[0093] The foregoing description of several embodiments of the present invention has been presented for purposes of illustration. The foregoing description is not intended to be exhaustive nor to limit the invention to the precise features and / or forms disclosed.

[0094] Obviously, many modifications and variations can be made in light of the above teachings, and these all fall within the scope of the present invention. The scope of the present invention is defined only by the appended claims. The appended claims are intended to cover all such modifications and variations.

Claims

1. A composite magnetorheological fluid, characterized in that, The composite magnetorheological fluid comprises: Flaky anisotropic magnetic powder, the content of which is in the range of 0.1-3% of the total weight of the composite magnetorheological fluid; Isotropic magnetic powder on the micron scale, the content of which is in the range of 70-90% of the total weight of the composite magnetorheological fluid; and A carrier liquid and additives added to the carrier liquid, the content of which is the balance of the composite magnetorheological fluid; Wherein, the isotropic magnetic powder is iron powder, and its particle size is in the range of 0.1-50 microns; and Wherein, the average particle size or the minimum single-dimensional size of the flaky anisotropic magnetic powder is in the range of 0.1-99 nanometers.

2. The composite magnetorheological fluid according to claim 1, wherein The particle size of the isotropic magnetic powder is in the range of 0.1-20 microns.

3. The composite magnetorheological fluid according to claim 2, wherein The particle size of the isotropic magnetic powder is in the range of 0.2-5 microns.

4. The composite magnetorheological fluid according to claim 1, wherein The average particle size or the minimum single-dimensional size of the anisotropic magnetic powder is between 0.1-80 nanometers.

5. The composite magnetorheological fluid according to claim 4, wherein The average particle size or the minimum single-dimensional size of the anisotropic magnetic powder is between 0.2-50 nanometers.

6. The composite magnetorheological fluid according to claim 5, wherein The average particle size or the minimum single-dimensional size of the anisotropic magnetic powder is between 0.5-20 nanometers.

7. The composite magnetorheological fluid according to any one of claims 1-5, characterized in that, The material of the anisotropic magnetic powder is selected from iron, iron alloy, iron-cobalt alloy, iron-platinum alloy, iron oxide, iron nitride, iron carbide, iron carbonyl, nickel, cobalt, chromium dioxide, FePt, SmCo, NdFeB, stainless steel, silicon steel, or a combination of these materials.

8. The composite magnetorheological fluid according to any one of claims 1-5, characterized in that, The carrier liquid is an organic liquid.

9. The composite magnetorheological fluid according to claim 8, wherein, The organic liquid is white oil, α-olefin, silicone oil, or a combination thereof.

10. The composite magnetorheological fluid according to claim 1, characterized in that, The content of the anisotropic magnetic powder is in the range of 0.5-1% of the total weight of the composite magnetorheological fluid.

11. The composite magnetorheological fluid according to any one of claims 1-5, characterized in that, The additives include at least one of the following: C16-18 alcohol polyoxyethylene ether, C12-14 alcohol and ethylene oxide condensate, isomeric tridecyl alcohol polyoxyethylene ether, isomeric decyl alcohol polyoxyethylene ether, oleyl alcohol polyoxyethylene ether, octyldecanol polyoxyethylene ether, octylphenol polyoxyethylene ether, polyethylene glycol stearate, stearic acid polyoxyethylene ester, castor oil polyoxyethylene ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyethylene glycol, polypropylene glycol, polyethylene glycol-polypropylene glycol, alkylphenol polyoxyethylene-polypropylene glycol ether, allyl alcohol polyoxyalkyl ether, polyethylene-polypropylene copolymer, methoxy polyethylene glycol, methoxy polypropylene glycol, fatty alcohol ether phosphate, phenol ether phosphate, isomeric tridecyl alcohol phosphate, lauryl phosphate, fatty alcohol ether phosphate potassium salt, fatty alcohol ether phosphate potassium salt, phenol ether phosphate potassium salt, isomeric tridecyl ether phosphate potassium salt, lauryl phosphate potassium salt, dodecylamine polyoxyethylene ether, octadecylamine polyoxyethylene ether, tallow amine polyoxyethylene ether, fatty acid diethanolamide, coconut fatty acid diethanolamide, styrene phenol, glycerol polyether, castor oil phosphate, triglycerol oleate, (Z)-9-octadecenoic acid-1,2,3-propanetriyl ester, pentaerythritol oleate, trimethylolpropane oleate, nonylphenol polyoxyethylene ether sulfate ammonium salt, styrene phenol polyoxyethylene ether ammonium sulfate, polyether modified silicone oil, and fluorocarbon surfactant.

12. The composite magnetorheological fluid according to any one of claims 1-5, characterized in that, The additive contains at least one of the following: 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, hindered amine, 2,6-di-tert-butyl-4-methylphenol, N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexanediamine, n-octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tris(2,4-di-tert-butylphenyl)phosphite, pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), isooctyl oleate, trimellitate, neopentyl polyol ester, ditrimethylolpropane tetraester, neopentyl glycol dioleate, diisooctyl sebacate, diisooctyl adipate, trimethylolpropane cocoate, diethyl phthalate, trioctyl phosphate, dioctyl phosphate, diethyl adipate, epoxidized soybean oil, polyol benzoate, dioctyl terephthalate, and dioctyl phthalate.

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