Dry magnetorheological fluid material and method of making

Abstract

This invention belongs to the field of magnetorheological smart materials technology, and more specifically, relates to a dry magnetorheological fluid material and its preparation method. The dry magnetorheological fluid material provided by this invention, by mass percentage, comprises: 92-99.75% carbonyl iron powder and 0.25-8% fumed silica. It is prepared by mixing carbonyl iron powder and fumed silica, performing wet ball milling, followed by washing, drying, and sieving. Compared with traditional magnetorheological fluids, no liquid carrier is introduced; instead, air is used as the carrier, eliminating the problem of different densities between the two substances in traditional magnetorheological fluids and solving the sedimentation problem of magnetorheological fluids from the source.

Description

Technical Field

[0001] This invention belongs to the field of magnetorheological smart materials technology, and more specifically relates to a dry magnetorheological fluid material and its preparation method. Background Technology

[0002] Materials whose properties can change significantly in the presence of external stimuli are called smart materials. Magnetorheological smart materials are a type of fast-response smart material that can change its rheological properties according to the intensity of magnetic induction. Magnetorheological fluids were among the first invented magnetorheological smart materials, and their viscosity and rheological properties can be significantly altered under the influence of an external magnetic field. Under the influence of an external magnetic field, magnetorheological fluids transform from a liquid to a semi-solid state, exhibiting non-Newtonian behavior, characterized by yield stress dependent on the magnetic field and an increase in viscosity. Due to their rapid response and high control precision, magnetorheological fluids are widely used in devices such as dampers, brakes, clutches, hydraulic valves, and suspension systems.

[0003] However, the sedimentation problem of magnetorheological fluids (MRFs) has always been one of the main factors affecting their lifespan and performance. Traditional MRFs typically consist of a carrier liquid (such as mineral oil, silicone oil, or water) and highly magnetic micron or nano-sized particles (such as nickel, iron, or carbon-based materials). Due to the significant density difference between the two substances, sedimentation easily occurs after prolonged use under gravity, leading to a weakening of the MRF's viscosity and magnetorheological effect. This can even reduce control precision, affect flowability and system reliability, thus limiting the further development and application of MRFs. To better meet practical engineering needs, researchers have focused on improving the sedimentation properties of MRF materials. Currently, researchers mainly use methods such as reducing particle size, adding thixotropic materials, and adding surfactants. However, although these methods can effectively improve the sedimentation problem of MRFs, the sedimentation problem still occurs after prolonged standing, limiting its engineering applications. Summary of the Invention

[0004] The purpose of this invention is to provide a dry magnetorheological fluid material and its preparation method to solve the problems existing in the prior art, and to achieve that the magnetorheological fluid can maintain a good magnetorheological effect while ensuring high sedimentation stability.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] One of the technical solutions of this invention is to provide a dry magnetorheological fluid material, wherein the raw materials, by mass percentage, include: 92-99.75% carbonyl iron powder and 0.25-8% fumed silica.

[0007] Furthermore, the dry magnetorheological fluid material comprises, by mass percentage, 99.5% carbonyl iron powder and 0.5% fumed silica.

[0008] Furthermore, the dry magnetorheological fluid material is composed of carbonyl iron powder and fumed silica.

[0009] Fumed silica, as a dispersant, helps to increase the gaps between carbonyl iron powder particles, making air the carrier liquid for dry magnetorheological fluid.

[0010] The dry magnetorheological fluid material provided by this invention is composed of carbonyl iron powder and fumed silica. Through a specific preparation method, the fumed silica adheres to the surface of the carbonyl iron powder, eliminating sedimentation caused by the density differences between the two substances and solving the sedimentation problem at its source. Furthermore, the increased spacing between the carbonyl iron powder particles reduces friction and thus enhances their fluidity.

[0011] The second technical solution of the present invention provides a method for preparing the above-mentioned dry magnetorheological fluid material, the steps of which include:

[0012] Carbonyl iron powder and fumed silica are mixed, wet ball milled, washed, dried and sieved to obtain the dry magnetorheological fluid material.

[0013] Furthermore, the wet ball milling process uses ethanol as the dispersion medium, and the ball-to-material ratio is 2-5:1.

[0014] Furthermore, the wet ball milling process is performed at a speed of 100–250 rpm for 5 minutes.

[0015] Optionally, the wet ball milling process is divided into two stages: the first stage is ball milling at 75-100 rpm for 2 minutes, and the second stage is ball milling at 250 rpm for 3 minutes.

[0016] Furthermore, the washing process involves using deionized water.

[0017] Furthermore, the drying process involves vacuum drying at 60-70°C for 12-60 hours.

[0018] Furthermore, the sieving process involves sequentially passing the material through 30-mesh, 50-mesh, and 100-mesh sieves.

[0019] The third technical solution of the present invention provides an application of the above-mentioned dry magnetorheological fluid material in dampers, brakes, clutches, hydraulic valves or suspension systems.

[0020] The present invention discloses the following technical effects:

[0021] Compared with traditional magnetorheological fluids, the dry magnetorheological fluid material of this invention does not introduce a liquid carrier liquid, but uses air as the carrier liquid. This eliminates the problem of different densities between the two substances in traditional magnetorheological fluids, thus solving the sedimentation problem of magnetorheological fluids from the source.

[0022] Fumed silica possesses excellent dispersibility and adsorption properties, exhibits superior stability in most chemical environments, and is resistant to high temperatures and does not easily decompose. This invention incorporates fumed silica, which, through ball milling, adheres to carbonyl iron powder, increasing the interparticle size and allowing air to act as a carrier fluid, thus improving the fluidity of the dry magnetorheological fluid. Simultaneously, at the microscopic level, the microstructure of fumed silica mainly consists of primary particles, secondary aggregates, and tertiary aggregates. The fumed silica forms numerous mesopores and macropores within the secondary and tertiary aggregates, enabling air to enter and preventing direct contact between carbonyl iron powder particles, thus reducing friction between them. Ultimately, this allows the dry magnetorheological fluid to maintain both high sedimentation stability and excellent magnetorheological effects. Attached Figure Description

[0023] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0024] Figure 1 This is a schematic diagram of the preparation process of dry magnetorheological fluid materials.

[0025] Figure 2 The shear stress of the dry magnetorheological fluid in Example 1 changes with the shear rate under magnetic induction intensity.

[0026] Figure 3 The images are SEM images of the final products of Example 1 and Comparative Example 1, where a is Example 1 and b is Comparative Example 1. Detailed Implementation

[0027] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0028] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0029] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0030] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0031] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0032] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0033] Unless otherwise specified, "%" in the specific embodiments of the present invention refers to mass percentage; "parts" refers to "parts by mass"; and "room temperature" and "normal temperature" refer to 20-30℃.

[0034] Unless otherwise specified, all raw materials and reagents used in this invention are commercially available products.

[0035] The carbonyl iron powder was supplied by BASF AG of Germany, and its model number is CD.

[0036] The fumed silica was supplied by Evonik Degussa AG, Germany, and the model number was [model number missing]. 300;

[0037] Anhydrous ethanol was supplied by Taicang Xintai Alcohol Co., Ltd.

[0038] The deionized water was provided by Yangzhou Zhongken Food Co., Ltd.

[0039] Figure 1 This is a schematic diagram of the preparation process of dry magnetorheological fluid materials.

[0040] Example 1

[0041] The preparation steps of dry magnetorheological fluid materials include:

[0042] S1. Mix 0.5 parts of fumed silica and 99.5 parts of carbonyl iron powder, add 28.5 parts of anhydrous ethanol, pour into a ball mill jar, then add ball milling beads, with a ball-to-material ratio of 2:1 (mass ratio), and sequentially undergo ball milling stage one treatment (ball milling at 100 rpm for 2 min) and ball milling stage two treatment (ball milling at 250 rpm for 3 min) to obtain a fumed silica-carbonyl iron powder mixture;

[0043] S2. Pour the mixture of fumed silica and carbonyl iron powder (the product after ball milling) into a Buchner funnel, wash it twice with deionized water, let it stand for 60 min, and then dry it in a vacuum drying oven (60℃) for 48 h.

[0044] S3. After drying, the mixture is passed through 30-mesh, 50-mesh and 100-mesh sieves in sequence to obtain a fumed silica-carbonyl iron powder mixed dry magnetorheological fluid material.

[0045] Example 2

[0046] The preparation steps of dry magnetorheological fluid materials include:

[0047] S1. Mix 2 parts of fumed silica and 98 parts of carbonyl iron powder, add 28.1 parts of anhydrous ethanol, pour into a ball mill jar, then add ball milling beads, with a ball-to-material ratio of 2:1 (mass ratio), and sequentially process through the first stage of ball milling (ball milling at 100 rpm for 2 min) and the second stage of ball milling (ball milling at 250 rpm for 3 min) to obtain a mixture of fumed silica and carbonyl iron powder;

[0048] S2. Pour the mixture of fumed silica and carbonyl iron powder (the product after ball milling) into a Buchner funnel, wash it twice with deionized water, let it stand for 60 min, and then dry it in a vacuum drying oven (60℃) for 48 h.

[0049] S3. After drying, the mixture is passed through 30-mesh, 50-mesh and 100-mesh sieves in sequence to obtain a fumed silica-carbonyl iron powder mixed dry magnetorheological fluid material.

[0050] Example 3

[0051] The preparation steps of dry magnetorheological fluid materials include:

[0052] S1. Mix 8 parts of fumed silica and 92 parts of carbonyl iron powder, add 26.4 parts of anhydrous ethanol, pour into a ball mill jar, then add ball milling beads, with a ball-to-material ratio of 2:1 (mass ratio), and sequentially process through the first stage of ball milling (ball milling at 100 rpm for 2 min) and the second stage of ball milling (ball milling at 250 rpm for 3 min) to obtain a mixture of fumed silica and carbonyl iron powder;

[0053] S2. Pour the mixture of fumed silica and carbonyl iron powder (the product after ball milling) into a Buchner funnel, wash it twice with deionized water, let it stand for 60 min, and then dry it in a vacuum drying oven (60℃) for 48 h.

[0054] S3. After drying, the mixture is passed through 30-mesh, 50-mesh and 100-mesh sieves in sequence to obtain a fumed silica-carbonyl iron powder mixed dry magnetorheological fluid material.

[0055] Comparative Example 1

[0056] The preparation steps of dry magnetorheological fluid materials include:

[0057] S1. Add 28.6 parts of anhydrous ethanol to 100 parts of carbonyl iron powder, pour into a ball mill jar, then add ball milling beads, with a ball-to-material ratio of 2:1 (mass ratio), and sequentially process the first stage of ball milling (ball milling at 100 rpm for 2 min) and the second stage of ball milling (ball milling at 250 rpm for 3 min).

[0058] S2. After ball milling, pour the contents into a Buchner funnel, wash twice with deionized water, let stand for 60 minutes, and then dry in a vacuum drying oven (60℃) for 48 hours.

[0059] S3. After drying, the material is passed through 30-mesh, 50-mesh and 100-mesh sieves in sequence to obtain pure carbonyl iron powder dry magnetorheological material.

[0060] Comparative Example 2

[0061] The preparation steps of dry magnetorheological fluid materials include:

[0062] S1. Mix 0.5 parts of talc powder and 99.5 parts of carbonyl iron powder, add 28.5 parts of anhydrous ethanol, pour into a ball mill jar, then add ball milling beads, with a ball-to-powder ratio of 2:1 (mass ratio), and sequentially process through the first stage of ball milling (ball milling at 100 rpm for 2 min) and the second stage of ball milling (ball milling at 250 rpm for 3 min) to obtain ball-milled talc powder-carbonyl iron powder;

[0063] S2. Pour the ball-milled talc-carbonyl iron powder into a Buchner funnel, wash twice with deionized water, let stand for 60 min, and then dry in a vacuum drying oven (60℃) for 48 h.

[0064] S3. After drying, the powder is passed through 30-mesh, 50-mesh and 100-mesh sieves in sequence to obtain talc-carbonyl iron powder material.

[0065] Comparative Example 3

[0066] The preparation steps of dry magnetorheological fluid materials include:

[0067] S1. Mix 0.5 parts mica powder and 99.5 parts carbonyl iron powder, add 28.5 parts anhydrous ethanol, pour into a ball mill jar, then add ball milling beads, with a ball-to-powder ratio of 2:1 (mass ratio), and sequentially process through the first stage of ball milling (ball milling at 100 rpm for 2 min) and the second stage of ball milling (ball milling at 250 rpm for 3 min) to obtain ball-milled mica powder-carbonyl iron powder;

[0068] S2. Pour the ball-milled mica powder-carbonyl iron powder into a Buchner funnel, wash twice with deionized water, let stand for 60 min, and then dry in a vacuum drying oven (60℃) for 48 h.

[0069] S3. After drying, the material is passed through 30-mesh, 50-mesh and 100-mesh sieves in sequence to obtain mica powder-carbonyl iron powder material.

[0070] Test case

[0071] Rheological test:

[0072] Rheological tests were performed on the samples of Examples 1-3 and Comparative Examples 1-4 using an MCR302 rotational rheometer manufactured by Antonpah GmbH, Austria.

[0073] The shear stress values ​​were measured at 40℃ under conditions of no magnetic field (OFF) and with magnetic field (ON).

[0074] Calculate the ratio (ON / OFF) and difference (ON-OFF) between the two. The larger the ratio and the larger the difference, the higher the adjustable range and the more widely it can be used. The results are shown in Table 1.

[0075] Table 1

[0076]

[0077] As shown in Table 1, the dry magnetorheological fluid materials prepared in Examples 1-3 exhibit excellent shear stress ratios and excellent shear stress differences. Furthermore, Examples 1-3 demonstrate that as the content of fumed silica increases, the fluidity of the dry magnetorheological fluid improves, but the shear stress difference decreases sharply. This indicates that the dry magnetorheological fluid prepared by the method in Example 1 shows the most significant effect, exhibiting better magnetorheological effects and a relatively wider adjustable range. In contrast, for Comparative Examples 1-3, the fluidity of the materials significantly decreases; although a large shear stress difference can be maintained, it cannot meet the design requirements of subsequent devices.

[0078] Figure 2 The figure shows the trend of shear stress of the dry magnetorheological fluid in Example 1 as the shear rate increases under magnetic induction intensity. As can be seen from the figure, the shear stress gradually increases with the increase of magnetic induction intensity, indicating that the shear stress of Example 1 is controllable under the action of the magnetic field.

[0079] Figure 3 The figures show SEM images of the final products of Example 1 and Comparative Example 1, where a represents Example 1 and b represents Comparative Example 1. As can be seen from the figures, b is the SEM image of carbonyl iron powder, and a is the SEM image of the dry magnetorheological fluid material. The white flocculent matter in a is fumed silica, indicating that fumed silica can adhere well to the carbonyl iron powder particles using the method of this invention. The white flocculent matter has an excellent porous structure, allowing air to act as a carrier fluid between materials, avoiding direct contact between carbonyl iron powder particles and reducing friction between them.

[0080] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0081] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A dry magnetorheological fluid material, characterized in that, By mass percentage, the raw materials include: 92-99.75% carbonyl iron powder and 0.25-8% fumed silica; The preparation steps of the dry magnetorheological fluid material include: mixing carbonyl iron powder and fumed silica, performing wet ball milling, washing, drying, and sieving to obtain the dry magnetorheological fluid material; The wet ball milling process uses ethanol as the dispersion medium and the ball-to-material ratio is 2-5:

1. The wet ball milling process is performed at a speed of 100-250 rpm for 5 minutes. The wet ball milling process is divided into two stages: the first stage is ball milling at 75-100 rpm for 2 minutes, and the second stage is ball milling at 250 rpm for 3 minutes.

2. The dry magnetorheological fluid material as described in claim 1, characterized in that, By mass percentage, the raw materials include: 99.5% carbonyl iron powder and 0.5% fumed silica.

3. The dry magnetorheological fluid material as described in claim 1, characterized in that, The dry magnetorheological fluid material is composed of carbonyl iron powder and fumed silica.

4. The method for preparing the dry magnetorheological fluid material according to any one of claims 1 to 3, characterized in that, step include: Carbonyl iron powder and fumed silica are mixed, wet ball milled, washed, dried and sieved to obtain the dry magnetorheological fluid material. The wet ball milling process uses ethanol as the dispersion medium and the ball-to-material ratio is 2-5:

1. The wet ball milling process is performed at a speed of 100-250 rpm for 5 minutes. The wet ball milling process is divided into two stages: the first stage is ball milling at 75-100 rpm for 2 minutes, and the second stage is ball milling at 250 rpm for 3 minutes.

5. The preparation method according to claim 4, characterized in that, The washing process involves using deionized water.

6. The preparation method according to claim 4, characterized in that, The drying process involves vacuum drying at 60-70℃ for 12-60 hours.

7. The preparation method according to claim 4, characterized in that, The sieving process involves sequentially passing the material through 30-mesh, 50-mesh, and 100-mesh sieves.

8. The application of the dry magnetorheological fluid material according to any one of claims 1 to 3 in a damper, brake, clutch, hydraulic valve or suspension system.

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