阅读说明：本技术 复合型磁流变流体 (Composite magnetorheological fluid ) 是由 秦浩 梁燕玲 于 2020-12-07 设计创作，主要内容包括：本发明披露了一种复合型磁流变流体,包括：各向异性的磁粉,其含量在所述复合型磁流变流体的总重量的0.05-5％的范围内；微米尺度的各向同性的磁粉,其含量在所述复合型磁流变流体的总重量的70-90％的范围内；载液,和添加到所述载液中的添加剂,其含量为所述复合型磁流变流体的余量。(The invention discloses a composite magnetorheological fluid, which comprises: anisotropic magnetic powder in an amount within the range of 0.05-5% by weight of the total weight of the composite magnetorheological fluid; micrometer isotropic magnetic powder, the content of which is in the range of 70-90% of the total weight of the composite magnetorheological fluid; a carrier fluid, and an additive added to the carrier fluid in an amount to balance the composite magnetorheological fluid.)

1. A composite magnetorheological fluid comprising:

anisotropic magnetic powder in an amount within the range of 0.05-5% by weight of the total weight of the composite magnetorheological fluid;

micrometer isotropic magnetic powder, the content of which is in the range of 70-90% of the total weight of the composite magnetorheological fluid;

carrying a liquid; and

and additives added to the carrier fluid in an amount to balance the composite magnetorheological fluid.

2. A composite magnetorheological fluid according to claim 1, the isotropic magnetic powder being iron powder having a particle size in the range of about 0.1 to 50 microns, such as in the range of about 0.1 to 20 microns, 0.2 to 10 microns or 0.2 to 5 microns.

3. The composite magnetorheological fluid of claim 1 or 2, wherein the anisotropic magnetic powder is selected from at least one of sheet, strip, needle, rod, cylinder, dendrite, spheroidal anisotropic magnetic powder and single crystal anisotropic magnetic powder.

4. A composite magnetorheological fluid according to any one of claims 1 to 3, the anisotropic magnetic particles having an average particle size or smallest single dimensional dimension of less than 99 nm, such as in the range of 0.1 to 99 nm, preferably between 0.1 and 80 nm, more preferably between 0.2 and 50 nm, even more preferably between 0.5 and 20 nm.

5. A composite magnetorheological fluid according to any one of claims 1 to 3, wherein the anisotropic magnetic particles have an average particle size or a minimum single dimensional size in the range of about 100-900 nm, such as at 100-500 nm or between 100-200 nm.

6. A composite magnetorheological fluid according to any one of the preceding claims, wherein the anisotropic magnetic powder is of a material selected from iron, iron alloys, iron-cobalt alloys, iron-platinum alloys, iron oxides, iron nitrides, iron carbides, iron carbonyls, nickel, cobalt, chromium dioxide, FePt, SmCo, NdFeB, stainless steel, silicon steel or combinations of these materials.

7. A composite magnetorheological fluid according to any one of the preceding claims, in which the carrier liquid is an organic liquid such as a mineral oil, a synthetic oil, an alpha-olefin, a silicone oil or a combination thereof.

8. A composite magnetorheological fluid according to any one of the preceding claims, wherein the anisotropic magnetic powder is present in an amount in the range from 0.1 to 3%, preferably in the range from 0.5 to 1% by weight based on the total weight of the magnetorheological fluid.

9. A composite magnetorheological fluid according to any one of the preceding claims, wherein the additives comprise at least one of: c16-18 alcohol polyoxyethylene ether, C12-14 alcohol-ethylene oxide condensate, isomeric tridecanol polyoxyethylene ether, oleyl alcohol polyoxyethylene ether, capryl decanol 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 polyoxyethylene ether, polyoxyethylene-polyoxypropylene copolymer, methoxypolyethylene glycol, methoxypolypropylene glycol, fatty alcohol ether phosphate, phenol ether phosphate, isotridecyl alcohol phosphate, lauryl phosphate, fatty alcohol ether phosphate potassium, phenol ether phosphate potassium, isotridecyl alcohol ether phosphate potassium, ethylene oxide condensate, isotridecyl alcohol polyoxyethylene, ethylene oxide condensate, ethylene oxide, propylene oxide, lauryl phosphate potassium salt, lauryl amine polyoxyethylene ether, octadecylamine polyoxyethylene ether, tallow amine polyoxyethylene ether, fatty acid diethanolamide, coconut oil 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 ammonium sulfate salt, styrene phenol polyoxyethylene ether ammonium sulfate salt, polyether modified silicone oil and fluorocarbon surfactant.

10. A composite magnetorheological fluid according to any one of the preceding claims, wherein the additives comprise at least one of: 6-ethoxy-2, 2, 4-trimethyl-1, 2-dihydroquinoline, hindered amine, 2, 6-di-tert-butyl-4-methylphenol, N' -bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine, N-octadecyl-beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate, tris (2, 4-di-tert-butylphenyl) phosphite, pentaerythrityl-tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], isooctyl oleate, trimellitate, neopentyl polyol ester, dipentaerythritol 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.

Technical Field

The invention relates to the technical field of magnetorheological fluids. More particularly, the present invention relates to the production of composite magnetorheological fluids using a combination of isotropic and anisotropic magnetic powders.

Background

Magnetorheological fluids are liquids whose viscosity changes with the application of a magnetic field. The stable suspension system is formed by uniformly dispersing soft magnetic particles with high magnetic permeability and low remanence in a non-magnetic carrier liquid through the action of a surfactant. The working principle of the magnetorheological fluid is as follows: under the action of an external magnetic field, each particle is polarized into a magnetic dipole, the dipoles attract each other, and a chain-bundle-shaped structure formed between the two magnetic pole plates is transversely arranged between the pole plates like a bridge, so that the normal flow of fluid is blocked, and the solid-like characteristic is generated. When the external magnetic field is removed, the fluid is restored to the original state, namely the magnetorheological fluid is rapidly and reversibly converted between the liquid state and the solid state. The solid state degree and the current intensity form a stable and reversible relation, namely the shear yield strength of the solid state magnetorheological fluid can be accurately controlled by controlling the current intensity.

Magnetorheological fluids have been used for many years to control damping forces in a variety of devices, such as shock absorbers, body prostheses, and flexible seats. The rheological behavior of the magnetorheological fluid under the action of the magnetic field is instantaneous and reversible, and the shear yield strength after the rheological behavior has a stable corresponding relation with the magnetic field strength, so that the intelligent control is very easy to realize. Therefore, the magnetorheological fluid is an intelligent material with wide application and excellent performance, and the application field of the magnetorheological fluid is rapidly expanded.

The traditional magnetorheological fluid has a remanence phenomenon, and after a magnetic field is removed, magnetic response particles dispersed in the magnetorheological fluid and having remanence can not completely recover to a free flowing state due to the remanence of the particles, so that the control process of a working device of the magnetorheological fluid is disturbed. The existence of residual magnetism is a common problem in the prior art, and the defect is more prominent along with the delay of the use time, which not only can lead to the poor performance of the magnetorheological fluid and the applied equipment thereof, but also can lead to the poor control response performance and reliability of the fluid or the equipment, and also has the defect of short service life.

In order to reduce the coercivity, conventional magnetorheological fluids tend to increase the size of the magnetic particles, such as on the order of microns, as can be seen, for example, in U.S. patent No. US6203717B1, which presents another significant problem, namely the tendency of the magnetic particles to settle in the magnetorheological fluid. The settling of the magnetic particles directly results in short service life, low reliability of the magnetorheological fluid and ultimately failure of the magnetorheological fluid.

Furthermore, not only the anti-settling property of the conventional magnetorheological fluid is poor, but also the anti-shear strength property of the conventional magnetorheological fluid is to be improved, for example, compared with the nano magnetorheological fluid invented by the inventor of the present application (see, for example, chinese patent application nos. 201510538070.7, 201510537836.x and PCT application WO 2017036337a1 of the inventor of the present application), the anti-shear strength of the conventional magnetorheological fluid is lower than that of the nano magnetorheological fluid invented by the inventor of the present application under the same volume percentage of magnetic powder particle content. Therefore, in the case of application to an electromagnetic suspension of an automobile, for example, the excitation coil of the magnetorheological fluid damper containing the conventional magnetorheological fluid must be configured with a double coil, which makes the magnetorheological fluid damper difficult to miniaturize and more costly; if a single coil configuration is used, the magnetorheological fluid damper tube will have a longer response time to vibration, which is unacceptable for magnetorheological fluid damper devices that require a fast response to vibration.

In the nano magnetorheological fluid invented by the inventor before, the anisotropic magnetic powder has higher magnetic saturation and faster response speed, so that the anisotropic magnetic powder chains have stronger bonding force under a magnetic field, and the anisotropic magnetorheological fluid can provide stronger anti-shearing yield strength under the action of the magnetic field.

However, the nano magnetorheological fluid still has inherent defects, such as long preparation process time, complex process, high environmental protection requirement and higher material cost, so that the cost is higher than that of the traditional magnetorheological fluid. In addition, the specific surface area (specific surface energy) of the anisotropic magnetic powder is large, so that the magnetorheological fluid is thick, the second Newton region of the magnetorheological fluid is large, the initial force is 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 the zero magnetic field due to the anisotropic shape, such as the large aspect ratio, so that the second newton region is unstable under the zero magnetic field, which is not beneficial to device control and vibration damping control. The second Newtonian region is that the non-Newtonian fluid can show the performance of the Newtonian fluid under the condition of high shear rate, namely, the viscosity is constant, the shear force linearly increases along with the increase of the shear rate, and the second Newtonian region is favorable for control due to the constant kinematic viscosity, so that the second Newtonian region is the main control region of the magnetorheological fluid.

The present invention has been made in view of the above and other concepts.

The information included in this background section of the specification of the present invention, including any references cited herein and any descriptions or discussions thereof, is included for technical reference purposes only and is not to be taken as subject matter which would limit the scope of the present invention.

Disclosure of Invention

The present invention has been made in view of the above and other more conception. The present invention is directed to addressing the above technical shortcomings and other problems.

In this respect, the present invention contemplates better solutions to the above-mentioned technical problems, as well as other technical problems, by mixing different magnetic powders to prepare a magnetorheological fluid, achieving further advantages, in particular in terms of cost and overall performance, and a wider range of application scenarios.

The anisotropic magnetic powder has higher magnetic saturation and faster response speed, so the chain of the anisotropic magnetic powder has stronger bonding force under a magnetic field, the anisotropic magnetorheological fluid can provide stronger shear-resistant yield strength under the action of the magnetic field, but the anisotropic magnetorheological fluid also has the defects of material cost and process cost, the specific surface area (and specific surface energy) of the anisotropic magnetic powder is larger, so the magnetorheological fluid is thicker, the second Newton region of the magnetorheological fluid is larger, the initial force is larger, and the controllable range is limited to a certain extent. The anisotropic magnetic powder has large aspect ratio due to shape anisotropy, and influences the high shear rate flowing property of the magnetorheological fluid under the zero magnetic field, so that the second Newton region is unstable under the zero magnetic field and is not beneficial to control.

The invention provides a method for preparing the composite magnetorheological fluid by mixing a combination of anisotropic magnetic powder and common isotropic magnetic powder in a certain proportion, carrier liquid and other additives. In other words, anisotropic magnetic powder can be added to a conventional magnetorheological fluid to obtain the composite magnetorheological fluid of the present invention, which can form a structure similar to "steel bar cement" or a so-called "fiber reinforced composite material" under a magnetic field, wherein the anisotropic magnetic powder capable of rapidly forming chains (or "bridging") in the direction of magnetic lines of force under the action of the magnetic field is similar to "steel bar", and the isotropic magnetic powder is similar to "cement". Under the magnetic field, the anisotropic magnetic powder in the composite magnetorheological fluid is quickly chained, the isotropic magnetic powder and the adjacent isotropic magnetic powder are connected through magnetic attraction, so that an interwoven form similar to a reinforced cement structure is formed, the binding force of the composite magnetorheological fluid is larger than that of the traditional magnetorheological fluid, the reaction to the magnetic field is quicker, and the form is more stable. And the magnetorheological fluids of the present invention provide increased shear strength. At the same time, the magnetorheological fluid of the present invention may at least partially overcome the disadvantages of anisotropic magnetorheological fluids as described above, and may at least partially retain the advantages of conventional magnetorheological fluids, with improved resistance to settling compared to conventional magnetorheological fluids.

According to an aspect of the present invention, there is provided a composite magnetorheological fluid comprising: anisotropic magnetic powder in an amount within the range of 0.05-5% by weight of the total weight of the composite magnetorheological fluid; micrometer isotropic magnetic powder, the content of which is in the range of 70-90% of the total weight of the composite magnetorheological fluid; and a carrier fluid and additives added to the carrier fluid in an amount to balance the composite magnetorheological fluid.

According to one embodiment, the isotropic magnetic powder is an iron powder having a particle size in the range of about 0.1-50 microns, such as in the range of about 0.1-20 microns, 0.2-10 microns, or 0.2-5 microns.

According to an embodiment, the anisotropic magnetic powder is selected from at least one of a sheet-like, bar-like, needle-like, rod-like, cylindrical, dendritic, spheroidal anisotropic magnetic powder and a single crystal anisotropic magnetic powder.

According to an embodiment, the anisotropic magnetic powder has an average particle size or smallest single dimension smaller than 99 nm, for example in the range of 0.1-99 nm, preferably between 0.1-80 nm, more preferably between 0.2-50 nm, even more preferably between 0.5-20 nm.

According to an embodiment, the average particle size or the minimum single dimension of the anisotropic magnetic powder is in the range of about 100-900 nm, such as 100-500 nm, or between 100-200 nm.

According to an embodiment, the material of the anisotropic magnetic powder is selected from iron, iron alloys, iron-cobalt alloys, iron-platinum alloys, iron oxides, iron nitrides, iron carbides, iron carbonyls, nickel, cobalt, chromium dioxide, FePt, SmCo, NdFeB, stainless steel, silicon steel, or combinations of these materials.

According to an embodiment, the iron alloy is an iron-cobalt alloy or an iron-platinum alloy.

According to an embodiment, the carrier liquid is an organic liquid, such as mineral oil, synthetic oil, alpha-olefin, silicone oil, or a combination thereof.

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

According to an embodiment, the additive comprises at least one of the following: surfactants, dispersants, anti-settling agents, organic thixotropic agents, thickeners, antioxidants, lubricants, viscosity modifiers, flame retardants, organoclay-based rheological additives, sulfur-containing compounds, and any combination thereof.

According to an embodiment, the additive comprises at least one of the following: c16-18 alcohol polyoxyethylene ether, C12-14 alcohol-ethylene oxide condensate, isomeric tridecanol polyoxyethylene ether, oleyl alcohol polyoxyethylene ether, capryl decanol 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 polyoxyethylene ether, polyoxyethylene-polyoxypropylene copolymer, methoxypolyethylene glycol, methoxypolypropylene glycol, fatty alcohol ether phosphate, phenol ether phosphate, isotridecyl alcohol phosphate, lauryl phosphate, fatty alcohol ether phosphate potassium, phenol ether phosphate potassium, isotridecyl alcohol ether phosphate potassium, ethylene oxide condensate, isotridecyl alcohol polyoxyethylene, ethylene oxide condensate, ethylene oxide, propylene oxide, lauryl phosphate potassium salt, lauryl amine polyoxyethylene ether, octadecylamine polyoxyethylene ether, tallow amine polyoxyethylene ether, fatty acid diethanolamide, coconut oil 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 ammonium sulfate salt, styrene phenol polyoxyethylene ether ammonium sulfate salt, polyether modified silicone oil and fluorocarbon surfactant.

According to an embodiment, the additive comprises 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' -bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine, N-octadecyl-beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate, tris (2, 4-di-tert-butylphenyl) phosphite, pentaerythrityl-tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], isooctyl oleate, trimellitate, neopentyl polyol ester, dipentaerythritol 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.

According to an embodiment, the anisotropic magnetic powder is shape anisotropic and/or magnetocrystalline and/or stress induced magnetic anisotropy.

According to one embodiment, the composite magnetorheological fluid does not settle significantly during standing at room temperature for a period of at least 1 week.

The composite magnetorheological fluid has the main advantages that the composite magnetorheological fluid not only keeps excellent mechanical properties of anisotropic magnetorheological fluid under a magnetic field, but also has good fluidity of the traditional magnetorheological fluid under a zero magnetic field, the fluid has a second Newtonian region with wide stability, and the initial kinematic viscosity of the fluid is lower, so that the control range of a magnetorheological device is wider and more stable, and the like. Meanwhile, compared with the traditional magneto-rheological fluid, the anti-settling performance of the fluid is also improved.

Further embodiments of the invention are also capable of achieving other advantageous technical effects not listed, which other technical effects may be partially described below and which would be expected and understood by one skilled in the art after reading the present invention.

The summary of the invention section is intended to introduce a selection of concepts and options in a simplified form that are further described below in the detailed description of the invention to assist the reader in understanding the invention. This summary is not intended to identify 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 exemplary only and further features and objects with respect to process steps may be gleaned from the present disclosure. A more complete appreciation of the features, details, utilities, and advantages of the present invention will be provided in the following written description of various embodiments of the invention, illustrated in the accompanying drawings, and defined in the appended claims. Accordingly, many non-limiting interpretation of the summary of the invention may not be understood without further reading the entire specification, claims and drawings.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the embodiments or the description of the prior art will be briefly described below.

The above features and advantages and other features and advantages of these embodiments, and the manner of attaining them, will become more apparent and the embodiments of the invention will be better understood by reference to the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic diagram schematically illustrating the configuration of an embodiment of the composite magnetorheological fluid of the invention after application of a magnetic field.

FIG. 2 is a schematic representation of the magnetic field scan stress curve (shear rate 0.1) for a composite magnetorheological fluid having different anisotropic powder contents of the present invention^-s)。

FIG. 3 is a schematic representation of the relationship between the shear strength of the composite magnetorheological fluid of the invention and the anisotropic magnetic powder content in the composite magnetorheological fluid at a magnetic field of 800mT (shear rate 0.1)^-s)。

Fig. 4 schematically shows the results of comparative testing of the shear strength of various composite magnetorheological fluids of the present invention having different (higher) anisotropic magnetic powder contents at different shear rates at a temperature of 40 c at zero magnetic field compared to conventional magnetorheological fluids.

Fig. 5 schematically shows the results of comparative testing of the shear strength of various composite magnetorheological fluids of the present invention having different (lower) anisotropic magnetic powder contents at different shear rates at a temperature of 40 c at zero magnetic field versus conventional magnetorheological fluids.

Fig. 6 shows the zero field viscosity of a composite magnetorheological fluid to which 2% of different types of anisotropic magnetic powders are added collectively in a conventional magnetorheological fluid.

Fig. 7 shows a comparison of shear stress (i.e., shear strength) tests under the magnetic field of a composite magnetorheological fluid with a uniform addition of 2% of different types of anisotropic magnetic powders to a conventional magnetorheological fluid.

Fig. 8 shows a comparison of the settling resistance test of a composite magnetorheological fluid obtained by adding 0.5% anisotropic magnetic powder to a conventional magnetorheological fluid.

Detailed Description

The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

It is to be understood that the embodiments illustrated and described are not limited in application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The illustrated embodiments are capable of other embodiments and of being practiced or of being carried out in various ways. Examples are provided by way of explanation of the disclosed embodiments, not limitation.

Indeed, it will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments of the present invention without departing from the scope or spirit of the disclosure. For instance, features illustrated or described as part of one embodiment, can be used with another embodiment to yield a still further embodiment. Thus, the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents.

Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. For example, the use of "including," "having," or "provided" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

The invention will be explained and explained in more detail below with reference to specific embodiments of the invention and with reference to the drawings.

Common magnetic powders, i.e. common isotropic magnetic powders, may be, for example, those disclosed in conventional magnetorheological fluids, see, for example, US6203717B1, which is incorporated herein by reference. A typical isotropic magnetic powder generally has a substantially spherical shape, obtainable, for example, by a water atomization process or the like, and generally has a particle size on the micrometer scale, for example, a particle size of about 1 micrometer or so. See also, for example, U.S. patent applications 2575360, 2661825, 2886151, 5645752, 7393463B2, 6203717B1, and 2006/0033069a1, the relevant contents of which are also incorporated herein by reference as if set forth in the present application, and several other patents related to magnetorheological fluids and magnetic particles. Of course, in the present invention, the particle size of the ordinary isotropic magnetic powder is not limited to the above, but may have a larger or smaller range of particle size, for example, in the range of about 0.1 to 50 micrometers, for example, in the range of about 0.1 to 20 micrometers, 0.2 to 10 micrometers, 0.2 to 5 micrometers.

Anisotropic magnetic powders are available, for example, from chinese patent application No.201510538070.7, No.201510537836.x and PCT application WO 2017036337a1, previously invented by the inventors, the relevant contents of which are also incorporated by reference in the present application, as described in the application. The anisotropic magnetic powder may for example have a size in the nanometer range, e.g. its average particle size or smallest single dimension is typically smaller than 99 nm, e.g. in the range of 0.1-99 nm, e.g. between 0.1-80 nm, between 0.2-50 nm, between 0.5-20 nm, etc. However, in the present invention, the size of the anisotropic magnetic powder is not limited to the above-mentioned nano-scale range, but may have a larger particle diameter or a range of particle diameters, for example, an average particle diameter or a minimum single-dimensional size in a range of about 0.1 to 900 nm, 0.1 to 500 nm, 0.1 to 200 nm, or the like.

The composite magnetorheological fluid and the preparation process thereof are described below by combining specific examples.

Example I

A carrier liquid for a composite magnetorheological fluid is prepared, and mineral oil, synthetic oil, α -olefin, silicone oil, or the like is used, and these are commercially available.

Additives for preparing the composite magnetorheological fluid, which may be selected include, but are not limited to, organoclays, molybdenum disulfide, fumed silica, and the like, are commercially available.

The preparation process of the composite magnetorheological fluid comprises the following steps.

Step one, dispersing the additive

The process employable in this step may be one selected from the group consisting of:

1. adding organoclay and fumed silica at room temperature into a container of an ultrasonic stirrer (such as type JM-1018), and performing ultrasonic stirring dispersion treatment for about 20 minutes at a stirring frequency of about 30 Hz;

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

3. the organoclay and fumed silica at room temperature are dispersed in a high-speed centrifugal dispersing apparatus (e.g., model No. TFS-2.2) for about 5 minutes, wherein the linear velocity of the centrifugal rotation is between 12m/s and 37 m/s.

Step two, liquid preparation and mixed material treatment

Anisotropic magnetic powder, such as nano-scale flake anisotropic magnetic powder, dendritic anisotropic magnetic powder, or quasi-spherical anisotropic magnetic powder, is provided as anisotropic magnetic powder added to the carrier liquid in a proportion (e.g., 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 5%) based on the total weight of the magnetorheological fluid.

The base of the carrier fluid is formulated with 12% by weight of mineral or synthetic oil, 5% by weight of alpha-olefin, based on the total weight of the composite magnetorheological fluid composition, and other various types of additives may be added at about 2% by weight of the total weight. Examples of additives include anti-settling agents, dispersants, lubricants, and antioxidants, among others.

The anti-settling agent and dispersant in the additive can comprise C16-18 alcohol polyoxyethylene ether, C12-14 alcohol and ethylene oxide condensate, isomeric tridecanol polyoxyethylene ether, isomeric dodecyl alcohol polyoxyethylene ether, oleyl alcohol polyoxyethylene ether, octyl decyl alcohol polyoxyethylene ether, octyl phenol 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, polyoxyethylene polyoxypropylene, alkylphenol polyoxyethylene polyoxypropylene ether, allyl alcohol polyoxyethylene ether, polyoxyethylene-polyoxypropylene copolymer, methoxypolyethylene glycol, methoxypolypropylene glycol, fatty alcohol ether phosphate, phenol ether phosphate, isotridecyl alcohol phosphate, lauryl phosphate, fatty alcohol ether phosphate potassium salt, ethylene oxide stearate, polyoxyethylene castor oil polyoxyethylene ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty, At least one of potassium salt of phenol ether phosphate, potassium salt of isotridecanol ether phosphate, potassium salt of lauryl phosphate, laurylamine polyoxyethylene ether, stearylamine polyoxyethylene ether, tallow amine polyoxyethylene ether, fatty acid diethanolamide, coconut oil 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 ammonium sulfate salt, styrene phenol polyoxyethylene ether ammonium sulfate salt, polyether modified silicone oil and fluorocarbon surfactant.

The antioxidant and lubricant in the additive may include 6-ethoxy-2, 2, 4-trimethyl-1, 2-dihydroquinoline, hindered amine, 2, 6-di-tert-butyl-4-methylphenol, N' -bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine, N-octadecyl beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate, tris (2, 4-di-tert-butylphenyl) phosphite, pentaerythrityl tetrakis [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], isooctyl oleate, trimellitate, neopentyl polyol, neopentyl glycol dioleate, diisooctyl sebacate, pentaerythritol, At least one of diisooctyl adipate, trimethylolpropane cocooleate, diethyl phthalate, trioctyl phosphate, dioctyl phosphate, diethyl adipate, epoxidized soybean oil, polyol benzoate, dioctyl terephthalate and dioctyl phthalate.

After the carrier liquid is stirred for about 10 minutes at a low speed by a stirrer, a closed oscillation feeder of the GZVF type is used for slowly adding 1.5 percent of the weighed balance of solid additive organic clay, fumed silica and the like at a low speed, and after the addition is finished, the oscillation feeder is used for carrying out high-speed dispersion treatment on the carrier liquid for about 30-60 minutes to obtain the prepared carrier liquid.

The prepared carrier liquid is put into a low-speed stirring device (model is JB200-D for example), and the anisotropic magnetic powder is added while stirring slowly at low speed, for example, the anisotropic magnetic powder can be slowly added into the carrier liquid by using a vibration feeder.

Thereafter, a conventional magnetic powder, such as an isotropic iron powder having a particle size in the range of about 0.1-1 micron, is added using a vibratory feeder. For example, the iron powder may be added slowly and at a constant speed, and the rotation speed of the oscillating feeder may be gradually increased as the iron powder is added.

After the addition of all the magnetic powder is completed, the linear speed of stirring by the low-speed stirring apparatus is raised to a high speed of, for example, about 7 to 10m/s, and stirred at the high speed for 2 hours.

Finally, the carrier liquid added with the magnetic powder is subjected to vacuum drying in a vacuum oven (model is 202-0B for example) at the temperature of about 40-60 ℃ for 5 hours, and air mixed in the process is discharged.

And weighing and packaging to obtain the composite magnetorheological fluid finished product.

Example II

This example is substantially the same as example I in terms of the manufacturing process, steps, equipment, raw materials, components, parameters, etc., except that single crystal anisotropic magnetic powder is used for the anisotropic magnetic powder, and the single crystal anisotropic magnetic powder added accounts for 2% of the total weight of the magnetorheological fluid.

Testing

First, anti-settling test

1. Description of the sedimentation System

The underlying cause of the MRF settling problem is the very different density difference between the dispersed phase (density 7.8g/m L, for example carbonyl iron powder) and the continuous phase (carrier fluid, 1g/m L). The particles continue to sink to the bottom of the vessel under the influence of gravity. The upper part of the container generally presents a transparent (or non-transparent, depending on the nature of the carrier liquid) supernatant liquid zone containing only the carrier liquid, and a clear dividing line, called a "mud line", is formed in the lower part. The lower region immediately below the mudline, which has a particle concentration that remains constant for an initial period of time, is referred to as the "initial concentration zone". And (3) continuously accumulating the particles at the bottom of the container, and mutually extruding the particles under the action of gravity and the like after a certain time to harden and harden the particles to form a deposition area with the maximum concentration and uniform distribution. Obviously, there must be a transition zone between the initial concentration zone and the deposition zone, called "variable concentration zone", whose concentration varies considerably with time and height. The boundary between the initial concentration region and the variable concentration region is named "gel line" because, as the name suggests, the variable concentration region appears as a very viscous "gel state". The boundary between the variable concentration region and the deposition region is designated as a "deposition line" indicating the starting line for forming the deposition region downward.

2. Visual measurement scheme for anti-settling test of magnetorheological fluids

And (3) respectively filling 10ml of the traditional magnetorheological fluid and 10ml of the composite magnetorheological fluid added with the anisotropic magnetic powder into a 15ml test tube, and vertically standing. And observing and recording scales where the mud lines are located every 7 days, continuously observing for about 1 month, and drawing a mud line settlement curve chart.

As shown in fig. 8, the height of the transparent layer can be determined by measuring the distance from the bottom of the tube to the top of the fluid-the height of the liquid surface, and measuring the distance from the bottom of the tube to the top of the settled magnetic particles-the height of the settled magnetic particles. Also, using the following equation, the sedimentation rate (Ratio) can be calculated:

the sedimentation rate Ratio is (liquid level height (cm) — height of sedimented magnetic particles (cm))/liquid level height (cm) × 100%

The visual test results are shown in fig. 8. Fig. 8 shows the results and data of anti-settling performance tests of a composite magnetorheological fluid obtained by adding 0.5% anisotropic magnetic powder to a conventional magnetorheological fluid. As shown in fig. 8, the test results show that the compound magnetorheological fluid has a lower sedimentation rate than the conventional magnetorheological fluid in all of the 7-day, 14-day, 21-day and 28-day anti-sedimentation tests, i.e., the compound magnetorheological fluid has slightly better anti-sedimentation performance than the conventional magnetorheological fluid. That is, the anti-settling performance of the traditional magnetorheological fluid can be properly improved by adding a proper amount of anisotropic magnetic powder into the traditional magnetorheological fluid.

Two, zero magnetic field viscosity test

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

For zero magnetic field viscosity detection, 2ml of sample is placed in a flat plate sample groove of a parallel plate type detection system, and 0-1200 th of scanning is carried out^-sKinematic viscosity at 40 ℃.

As can be seen from fig. 4, the magnetic powder concentration of the conventional magnetorheological fluid and the composite magnetorheological fluid containing 1% of anisotropic magnetic powder are both about 81%, and the magnetic powder concentration of the magnetorheological fluid prepared from pure anisotropic magnetic powder with the mechanical properties equivalent to those of the conventional magnetorheological fluid is about 65%. However, the kinematic viscosity of the anisotropic magnetorheological fluid with the 65% magnetic powder concentration is far greater than that of the conventional magnetorheological fluid and the composite magnetorheological fluid with the magnetic powder concentration of about 81%, because the magnetic powder particle size of the anisotropic magnetic powder in the magnetorheological fluid prepared from the pure anisotropic magnetic powder is generally in a nanometer level, the initial force of the damper and the control range of the damper are influenced.

Fig. 5 schematically shows the results of comparative testing of the shear strength of various composite magnetorheological fluids of the present invention having different (lower) anisotropic magnetic powder contents at different shear rates at a temperature of 40 c at zero magnetic field versus conventional magnetorheological fluids. As shown in fig. 5, in the present invention, the composite magnetorheological fluid obtained by adding a small amount of anisotropic magnetic powder to the conventional magnetorheological fluid has little change to the kinematic viscosity of the conventional magnetorheological fluid under a zero magnetic field, so that the composite magnetorheological fluid of the present invention can maintain the excellent physicochemical properties of the conventional magnetorheological fluid, such as kinematic viscosity, and has good fluidity under a zero magnetic field, and can provide excellent mechanical properties, such as shear strength after a magnetic field is added, etc.

Fig. 6 shows the zero field viscosity of a composite magnetorheological fluid to which 2% of different types of anisotropic magnetic powders are added collectively in a conventional magnetorheological fluid. As shown in fig. 6, no substantial correlation or influence was detected between the zero field viscosity and the type of anisotropic magnetic powder added. However, in general, the influence of the flake anisotropic magnetic powder on the zero field viscosity is the largest, and the influence of the dendritic anisotropic magnetic powder on the zero field viscosity is the smallest, but these influences are not substantial, and do not influence the practical industrial application of the composite magnetorheological fluid of the present invention.

Third, shear strength detection under magnetic field

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

For the detection of the shear strength under the magnetic field, 2ml of a sample is placed in a flat plate sample groove of a parallel plate type detection system, and the scanning current is 0-4.5A, namely the shear stress at 40 ℃ under the magnetic field of 0-900 mT.

As shown in FIG. 2, it is shown that the shear strength of the composite magnetorheological fluid with different proportions of anisotropic magnetic powder is improved.

As shown in FIG. 3, the action relationship of the addition of different proportions of anisotropic magnetic powder to the shear stress of the magnetorheological fluid in the magnetic field is shown. The test of fig. 3 is a comparison of mechanical tests of a composite magnetorheological fluid obtained by adding anisotropic magnetic powder to a conventional magnetorheological fluid under a magnetic field. From the test results, it can be seen that the shear strength performance of the composite magnetorheological fluid under a magnetic field is gradually increased to the highest peak value when the anisotropic magnetic powder is added in the composite magnetorheological fluid of the invention from more than 0% to about 0.1% to about 0.3% to about 0.5% of the total weight of the magnetorheological fluid. Then, as the addition amount of the anisotropic magnetic powder increases, the shear strength performance of the composite magnetorheological fluid under a magnetic field gradually decreases from about 0.5% to 1% of the addition amount until the shear strength is equivalent to that of about 0.1% of the addition amount at about 1% of the addition amount of the anisotropic magnetic powder. Thereafter, the shear strength of the composite magnetorheological fluid under the magnetic field remains substantially constant when the addition amount of the anisotropic magnetic powder is increased from about 1% to about 2%, and the shear strength as a whole increases to a small extent when the addition amount of the anisotropic magnetic powder is increased from about 2% to about 3%. That is, the composite magnetorheological fluid has a greater shear strength under magnetic field than conventional magnetorheological fluids when the amount of anisotropic magnetic powder added is increased from greater than 0% to about 3% of the total weight of the magnetorheological fluid.

FIG. 7 shows the shear strength measurements under magnetic field of a composite magnetorheological fluid with 2% of different types of anisotropic magnetic powder added together in a conventional magnetorheological fluid. As shown in FIG. 7, the shear strength under the magnetic field was examined, and the results showed that the type of the anisotropic magnetic powder has a large influence on the shear strength under the magnetic field of the magnetorheological fluid. Wherein, the added dendritic anisotropic magnetic powder has higher shearing strength, and the added single crystal anisotropic magnetic powder has smaller shearing force. In summary, no matter what kind of proper amount of anisotropic magnetic powder is added into the traditional magnetorheological fluid, the partial performance of the traditional magnetorheological fluid, such as the shear strength performance, is substantially improved.

The foregoing description of several embodiments of the invention has been presented for the purposes of illustration and description. The foregoing description is not intended to be exhaustive or to limit the invention to the precise features and/or forms disclosed.

Obviously, many modifications and variations are possible in light of the above teaching and are within the scope of the invention. The scope of the invention is only limited by the appended claims. It is intended that the appended claims cover all such modifications and variations.