Shear thickening fluid with magnetorheological effect and preparation method thereof

Abstract

The invention discloses a shear thickening fluid with a magnetorheological effect and a preparation method thereof, and belongs to the technical field of intelligent materials. The magnetorheological shear thickening fluid consists of the following components in percentage by mass: 15-30% of polyethylene glycol, 15-30% of spherical silicon dioxide and 50-65% of magnetic particles. The preparation method of the magnetorheological shear thickening fluid comprises the following steps: mixing the polyethylene glycol and the spherical silicon dioxide to prepare the shear thickening fluid, adding the magnetic particles, and mixing again to obtain the magnetorheological shear thickening fluid. The raw materials of the magnetorheological shear thickening fluid are easy to obtain, safe and reliable; the preparation method is short in technological process, simple and safe to operate and wide in applicability. The magneto-rheological shear thickening fluid can unify the rate sensitive characteristic of a shear thickening material and the magneto-sensitive characteristic of a magneto-rheological material into a whole, and provides material support for research and development of a damping execution device with self-adaption, self-enhancement and self-adjustment functions and application of the damping execution device to an important engineering structure.

Description

Technical Field

[0001] The invention belongs to the technical field of smart materials, including the technical field of shear thickening fluid and magnetorheological fluid, and specifically relates to a shear thickening fluid with magnetorheological effect and a preparation method thereof. Background Art

[0002] Shear thickening fluid (STF for short) is a type of concentrated particle suspension. When the applied shear rate or shear stress exceeds a critical value, the shear thickening fluid will undergo shear thickening, and its viscosity will increase rapidly, which can increase by several times to dozens of times. The shear thickening phenomenon of shear thickening fluid is characterized by fast response speed and reversible process. When the stress is removed, the fluid will return to its initial state. Shear thickening fluid can achieve performance transformation only under the action of external force, without the need for additional application of electric or magnetic fields.

[0003] The high viscosity of the shear thickening fluid under steady-state shearing and the high energy storage and loss modulus under oscillatory shearing indicate that the shear thickening fluid has good energy absorption characteristics. As a new type of smart material, the shear thickening fluid has great application potential in the fields of shock absorption and vibration isolation, human protection, safe batteries and multifunctional composite materials due to its mechanical properties such as rapid response, large response force and good reversibility.

[0004] Magnetorheological fluid (MRF) is a new type of magnetorheological smart material, the main components of which include magnetic particles, oily carrier fluid and additives. Under the action of an external magnetic field, magnetorheological fluid can produce obvious magnetorheological effects, showing properties similar to those of a solid. When the external magnetic field is removed, the fluid returns to its original flow properties, that is, it undergoes a rapid and reversible conversion between liquid and solid. As a smart material with a wide range of uses and excellent performance, magnetorheological fluids have been widely used in the fields of automobiles, construction, vibration control, etc. in recent years. However, devices based on magnetorheological materials often require the application of an external magnetic field or electric field when working. Once a circuit failure occurs, the device will lose its function and significance. In addition, the magnetic particles in the magnetorheological fluid may agglomerate and adhere under the influence of factors such as a humid atmosphere or external pressure.

[0005] In the field of engineering structure vibration control, magnetorheological materials and shear thickening materials have developed into the two most promising types of intelligent materials. Various vibration reduction devices or intelligent return units developed based on these two types of materials can be widely used in large civil engineering structures to change or adjust the dynamic characteristics of the structure. Magnetorheological materials and shear thickening materials have their own advantages and disadvantages. Magnetorheological materials can rely on external magnetic fields to provide self-adjustment functions for vibration reduction actuators, achieve the goal of controllable performance, and make up for the lack of controllable performance of shear thickening materials; while shear thickening materials can passively respond to external environmental excitations, help vibration reduction actuators achieve self-adaptation and self-enhancement functions, and can effectively improve the disadvantage of magnetorheological materials without protection after power failure. At this stage, magnetorheological materials have become an important filling material for energy-absorbing dampers of civil engineering structures, and shear thickening materials are mainly used in key limit positions of civil engineering structures. Combining the respective characteristics of the two types of materials, unifying the rate-sensitive properties of shear thickening materials and the magnetic sensitivity properties of magnetorheological materials, developing vibration reduction actuators with adaptive, self-enhancing and self-adjusting functions and applying them to seismic vibration reduction of important engineering structures will have very important theoretical significance and engineering practical value. Summary of the invention

[0006] One of the purposes of the present invention is to provide a shear thickening fluid with magnetorheological effect, so as to solve the problem that magnetorheological materials are unprotected after power failure and magnetic particles are prone to agglomeration.

[0007] A second object of the present invention is to provide a method for preparing a shear thickening fluid having a magnetorheological effect.

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] In a first aspect, a shear thickening fluid having a magnetorheological effect, called a magnetorheological shear thickening fluid (MR-STF), comprises a dispersion medium, a dispersed phase and magnetic particles, wherein the dispersion medium is polyethylene glycol and the dispersed phase is spherical silica;

[0010] The magnetorheological shear thickening fluid is composed of 15-30% by weight of polyethylene glycol, 15-30% by weight of spherical silicon dioxide and 50-65% by weight of magnetic particles according to the total weight.

[0011] As a further embodiment of the present invention, the mass ratio of the polyethylene glycol to the spherical silica is 1:0.7-1.8; preferably, the mass ratio of the polyethylene glycol to the spherical silica is 1:0.8-1.5.

[0012] As a further embodiment of the present invention, the molecular weight of the polyethylene glycol is in the range of 200-600.

[0013] As a further embodiment of the present invention, the average particle size of the spherical silica is in the range of 20 nm to 1000 nm; preferably, the average particle size of the spherical silica is in the range of 200 nm to 500 nm.

[0014] As a further embodiment of the present invention, the mass percentage of the magnetic particles, based on the total mass of the magnetorheological shear thickening fluid, includes 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64% or 65%.

[0015] As a further embodiment of the present invention, the magnetic particles are selected from one or more combinations of soft magnetic materials such as iron powder, iron oxide, carbonyl iron, iron carbide, nickel, cobalt, and martensitic stainless steel.

[0016] As a further embodiment of the present invention, the average particle size of the magnetic particles is in the range of 0.1 μm to 100 μm. Preferably, the average particle size of the magnetic particles is in the range of 1 μm to 20 μm.

[0017] In a second aspect, a method for preparing a shear thickening fluid having a magnetorheological effect comprises the following steps:

[0018] S1. Preparation of shear thickening fluid (STF): weighing each component according to mass percentage, mixing polyethylene glycol and spherical silica by ball milling at a mass ratio of 1:0.7 to 1.8 to obtain a shear thickening fluid;

[0019] S2. Preparation of magnetorheological shear thickening fluid (MR-STF): Pour the magnetic particles into the shear thickening fluid obtained in S1, continue ball milling to mix evenly, and obtain magnetorheological shear thickening fluid.

[0020] As a further solution of the present invention, the ball milling time in S1 is 24 to 48 hours, and the ball milling time in S2 is 20 to 28 hours.

[0021] As a further solution of the present invention, the ball milling rotation speed is 180 to 240 rpm.

[0022] It should be noted that the above-mentioned preparation method using ball milling mixing is suitable for preparing a small amount of samples for experimental exploration and testing. A large amount of magnetorheological shear thickening fluid can be prepared by using a high shear homogenizer through a method of fine homogenization and dispersion.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention provides a shear thickening fluid with magnetorheological effect and a preparation method thereof. By combining the respective characteristics of shear thickening materials and magnetorheological materials, the prepared magnetorheological shear thickening fluid can be used in vibration reduction actuators in important engineering structures to provide effective material support, help the vibration reduction actuators to achieve self-adaptation and self-enhancement functions, and improve the protection capability of magnetorheological materials after power failure.

[0025] 2. The present invention utilizes the high specific surface area and large pore volume of spherical silica to improve the dispersibility of magnetic particles in the polyethylene glycol system, which can effectively avoid the sedimentation problem caused by the aggregation of magnetic particles in the magnetorheological shear thickening fluid after power failure. The raw materials of the magnetorheological shear thickening fluid are easy to obtain, safe and reliable; the preparation method has a short process flow, simple and safe operation, and wide applicability. The magnetorheological shear thickening fluid can unify the rate-sensitive properties of shear thickening materials and the magnetic sensitivity properties of magnetorheological materials, providing material support for the development of vibration reduction actuators with adaptive, self-enhancing and self-regulating functions and their application in important engineering structures. Through rational component regulation and configuration, excellent rheological properties and broad application prospects can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be further described below in conjunction with the accompanying drawings.

[0027] Figure 1 is a scanning electron microscope (SEM) image of the spherical silicon dioxide used in the embodiments and comparative examples of the present invention;

[0028] Figure 2 is a scanning electron microscope (SEM) image of the iron powder used in the embodiments and comparative examples of the present invention;

[0029] Figure 3 1 is a comparison diagram of the relationship between shear rate and viscosity of the magnetorheological shear thickening fluid (MR-STF) prepared in Example 2 of the present invention and the shear thickening fluid (STF) prepared in Comparative Example 2;

[0030] Figure 4 is a graph showing the relationship between shear rate and viscosity of the magnetorheological shear thickening fluid (MR-STF) prepared in Example 2 of the present invention under different magnetic fields;

[0031] Figure 5 is a shear stress curve of the magnetorheological shear thickening fluid (MR-STF) prepared in Example 2 of the present invention under different magnetic fields;

[0032] Figure 6 It is a curve diagram showing the change of shear stress of the magnetorheological shear thickening fluid (MR-STF) prepared in Example 1 and Example 2 of the present invention with the magnetic field. DETAILED DESCRIPTION

[0033] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] A shear thickening fluid with magnetorheological effect, called magnetorheological shear thickening fluid (MR-STF), is composed of 15-30% by weight of polyethylene glycol, 15-30% by weight of spherical silica and 50-65% by weight of magnetic particles, based on the total weight; the mass ratio of the polyethylene glycol to the spherical silica is 1:0.7-1.8;

[0035] In a specific embodiment, the molecular weight of polyethylene glycol ranges from 200 to 600.

[0036] In a specific embodiment, the average particle size of the spherical silica is in the range of 20 nm to 1000 nm.

[0037] In a specific embodiment, the magnetic particles are selected from one or more combinations of soft magnetic materials such as iron powder, iron oxide, carbonyl iron, iron carbide, nickel, cobalt, and martensitic stainless steel.

[0038] In a specific embodiment, the average particle size of the magnetic particles ranges from 0.1 μm to 100 μm.

[0039] A method for preparing a shear thickening fluid with magnetorheological effect comprises the following steps:

[0040] S1. Preparation of shear thickening fluid (STF): Weigh each component according to mass percentage, add polyethylene glycol and spherical silica in a mass ratio of 1:0.7 to 1.8 into a ball mill, and mix at room temperature (25 to 30° C.) at a speed of 180 to 240 rpm for 24 to 48 hours to obtain a uniformly mixed shear thickening fluid;

[0041] S2. Preparation of magnetorheological shear thickening fluid (MR-STF): Pour the magnetic particles into the shear thickening fluid obtained in S1, and continue to mix by ball milling at a speed of 180 to 240 rpm for 20 to 28 hours to obtain a magnetorheological shear thickening fluid.

[0042] The SEM images of the spherical silicon dioxide used in the following examples and comparative examples are as follows: Figure 1 As shown, the SEM image of the iron powder used is as follows Figure 2 shown.

[0043] Example 1

[0044] A shear thickening fluid with magnetorheological effect, called magnetorheological shear thickening fluid (MR-STF), is composed of 23.2% by weight of polyethylene glycol, 19.8% by weight of spherical silica and 57% by weight of iron powder, based on the total weight; the molecular weight of the polyethylene glycol is 400;

[0045] The preparation method of the magnetorheological shear thickening fluid comprises the following steps:

[0046] S1. Preparation of shear thickening fluid (STF): Weigh the components according to the above mass percentages, add 4.70 g of polyethylene glycol with a molecular weight of 400 and 4.00 g of spherical silica into a ball mill, and mix them at room temperature at a speed of 200 rpm for 24 h to obtain a uniformly mixed shear thickening fluid;

[0047] S2. Preparation of magnetorheological shear thickening fluid (MR-STF): Pour 11.53 g of magnetic particles into the shear thickening fluid obtained in S1, and continue ball milling at a speed of 200 rpm for 24 h to obtain a magnetorheological shear thickening fluid.

[0048] Comparative Example 1

[0049] A method for preparing a shear thickening fluid (STF) comprises the following steps:

[0050] 4.70 g of polyethylene glycol with a molecular weight of 400 and 4.00 g of spherical silica were added to a ball mill, and the mixture was mixed by ball milling at a speed of 200 rpm for 24 hours at room temperature to obtain a uniformly mixed shear thickening liquid.

[0051] Example 2

[0052] A shear thickening fluid with magnetorheological effect, called magnetorheological shear thickening fluid (MR-STF), is composed of 18.94% by weight of polyethylene glycol, 26.13% by weight of spherical silica and 54.93% by weight of iron powder, based on the total weight; the molecular weight of the polyethylene glycol is 400;

[0053] The preparation method of the magnetorheological shear thickening fluid comprises the following steps:

[0054] S1. Preparation of shear thickening fluid (STF): Weigh the components according to the above mass percentages, add 2.90 g of polyethylene glycol with a molecular weight of 400 and 4.00 g of spherical silica into a ball mill, and mix them at room temperature at a speed of 200 rpm for 24 h to obtain a uniformly mixed shear thickening fluid;

[0055] S2. Preparation of magnetorheological shear thickening fluid (MR-STF): Pour 8.41 g of magnetic particles into the shear thickening fluid obtained in S1, and continue ball milling at a speed of 200 rpm for 24 hours to obtain a magnetorheological shear thickening fluid.

[0056] Comparative Example 2

[0057] A method for preparing a shear thickening fluid (STF) comprises the following steps:

[0058] 2.90 g of polyethylene glycol with a molecular weight of 400 and 4.00 g of spherical silica were added to a ball mill, and the mixture was mixed by ball milling at a speed of 200 rpm for 24 hours at room temperature to obtain a uniformly mixed shear thickening liquid.

[0059] The magnetorheological shear thickening fluid (MR-STF) prepared in Example 1 and Example 2 and the shear thickening fluid (STF) prepared in Comparative Example 1 and Comparative Example 2 were tested for performance:

[0060] Figure 3 The figure is a comparison diagram of the relationship between shear rate and viscosity of the magnetorheological shear thickening fluid (MR-STF) prepared in Example 2 and the shear thickening fluid (STF) prepared in Comparative Example 2; Figure 3 It can be seen that under the same shear rate conditions, the viscosity of the magnetorheological shear thickening fluid is about one order of magnitude higher than that of the shear thickening fluid. The addition of magnetic particle iron powder increases the solid content of the magnetorheological shear thickening fluid, resulting in an increase in its viscosity, and still has a similar shear thickening effect. Magnetic nanoparticle iron powder further promotes the viscosity effect of the shear thickening fluid, thereby improving the performance of the shear thickening fluid.

[0061] Figure 4 The relationship curves of shear rate and viscosity of the magnetorheological shear thickening fluid (MR-STF) prepared in Example 2 under different magnetic fields (0T, 0.20T, 0.40T, 0.60T); Figure 4 It can be seen that under the condition of a magnetic field strength of 0T, the viscosity of the magnetorheological shear thickening fluid is low. When the magnetic field is applied, the magnetic particles in the magnetorheological shear thickening fluid are arranged along the direction of the magnetic field to form a chain structure, which hinders the shearing effect, resulting in a significant increase in its viscosity. With the increase of the magnetic field strength, the viscosity of the magnetorheological shear thickening fluid is further increased. When the magnetic field strength is 0.60T, the viscosity increase is not obvious compared with the viscosity under 0.40T conditions.

[0062] Figure 5 The shear stress curves of the magnetorheological shear thickening fluid (MR-STF) prepared in Example 2 under different magnetic fields (0T, 0.20T, 0.40T, 0.60T); Figure 5It can be seen that with the increase of magnetic field intensity, the chain structure formed by the magnetic particles in the magnetorheological shear thickening fluid along the direction of the magnetic field becomes thicker and more numerous, and the ability to resist shearing is stronger, and the shear stress is greater under the same shear rate conditions.

[0063] Figure 6 The graph of shear stress of magnetorheological shear thickening fluid (MR-STF) prepared in Example 1 and Example 2 as a function of magnetic field; Figure 6 It can be seen that the mass fraction of magnetic particles in the magnetorheological shear thickening fluid prepared in Example 2 is higher, and the chain structure formed under the action of the magnetic field is stronger. Therefore, under the same magnetic field, the magnetorheological shear thickening fluid prepared in Example 2 has a greater shear stress.

[0064] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0065] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A shear thickening fluid having a magnetorheological effect, called a magnetorheological shear thickening fluid, characterized in that: The method comprises a dispersion medium, a dispersion phase and magnetic particles, wherein the dispersion medium is polyethylene glycol and the dispersion phase is spherical silicon dioxide; The magnetorheological shear thickening fluid is composed of 15-30% by weight of polyethylene glycol, 15-30% by weight of spherical silicon dioxide and 50-65% by weight of magnetic particles according to the total weight.

2. A shear thickening fluid with magnetorheological effect according to claim 1, characterized in that: The molecular weight of the polyethylene glycol is in the range of 200-600.

3. The shear thickening fluid with magnetorheological effect according to claim 1, characterized in that: The mass ratio of the polyethylene glycol to the spherical silicon dioxide is 1:0.7-1.

8.

4. A shear thickening fluid with magnetorheological effect according to claim 3, characterized in that: The mass ratio of the polyethylene glycol to the spherical silicon dioxide is 1:0.8-1.

5.

5. The shear thickening fluid with magnetorheological effect according to claim 1, characterized in that: The average particle size of the spherical silicon dioxide is in the range of 20nm to 1000nm.

6. A shear thickening fluid with magnetorheological effect according to claim 5, characterized in that: The average particle size of the spherical silicon dioxide is in the range of 200nm to 500nm.

7. The shear thickening fluid with magnetorheological effect according to claim 1, characterized in that: The magnetic particles are selected from one or more combinations of soft magnetic materials such as iron powder, iron oxide, carbonyl iron, iron carbide, nickel, cobalt, martensitic stainless steel, etc.

8. The shear thickening fluid with magnetorheological effect according to claim 1, characterized in that: The average particle size of the magnetic particles ranges from 0.1 μm to 100 μm.

9. A shear thickening fluid with magnetorheological effect according to claim 8, characterized in that: The average particle size of the magnetic particles ranges from 1 μm to 20 μm.

10. A method for preparing a shear thickening fluid with magnetorheological effect according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Weigh each component according to the mass percentage, and mix the polyethylene glycol and spherical silica in a mass ratio of 1:0.7 to 1.8 by ball milling to obtain a shear thickening liquid; S2. Pour the magnetic particles into the shear thickening liquid obtained in S1, continue ball milling to mix evenly, and obtain a magnetorheological shear thickening liquid.

Images