High-performance neodymium iron boron / silicone rubber composite magnetorheological elastomer and preparation method thereof

Abstract

The invention belongs to the technical field of elastomer materials, and provides a high-performance neodymium iron boron / silicone rubber composite magnetorheological elastomer and a preparation method thereof. The preparation method comprises the following steps: activating neodymium-iron-boron magnetic powder, immersing the neodymium-iron-boron magnetic powder into a dopamine hydrochloride aqueous solution for deposition reaction, and adding a silane coupling agent for condensation reaction to obtain neodymium-iron-boron magnetic powder coated with a PDA-silane composite modified layer; and mixing the neodymium iron boron magnetic powder coated with the PDA-silane composite modified layer with a silicone rubber matrix, and sequentially carrying out curing treatment and magnetization treatment to obtain the high-performance neodymium iron boron / silicone rubber composite magnetorheological elastomer. The method is simple and low in cost, the magnetorheological elastomer with high-strength interface bonding, high magnetic responsiveness, excellent mechanical property, excellent electrical property and excellent thermal stability is successfully prepared, and a material foundation is laid for development of magnetic-force-electricity multifunctional coupling devices, advanced sensors and intelligent drivers.

Description

Technical Field

[0001] This invention relates to the field of elastomer materials technology, and in particular to a high-performance neodymium iron boron / silicone rubber composite magnetorheological elastomer and its preparation method. Background Technology

[0002] Magnetoelastics, as an important class of smart materials, have developed due to the deep integration of fundamental research on magnetic field-mechanical response behavior and application needs. These materials typically consist of ferromagnetic particles (such as NdFeB and carbonyl iron powder) dispersed in a polymeric elastic matrix (such as silicone rubber). Their working mechanism is mainly based on the control of the material's magnetization state by an external magnetic field, inducing macroscopic deformation through magnetostriction or Maxwell stress. Simultaneously, mechanical deformation can also cause changes in the magnetic flux within the material, thereby achieving the coupling and conversion of multiple physical fields such as force, magnetism, and electricity. Researchers began systematically studying ferromagnetic composite materials as early as the mid-20th century. With the rapid development of soft robotics, wearable sensing, and biomedical devices in recent years, magnetoelastics, with their advantages of non-contact control, rapid response, and large degrees of freedom deformation, have once again become a cutting-edge focus of smart materials research.

[0003] However, a significant mismatch exists between the rigid nature of the soft magnetic particles and the flexibility of the polymer matrix, resulting in weak interfacial bonding. Under external loads or alternating magnetic fields, stress concentration and interfacial debonding easily occur. The key problem lies in the insufficient uniformity of magnetic particle dispersion in the matrix. Scanning electron microscopy analysis shows that unmodified NdFeB magnetic powder is unevenly dispersed in the silicone rubber matrix, with obvious voids and separation at the interface (as shown in the attached figure, the unmodified sample exhibits agglomeration and defects). These structural defects directly lead to a decrease in modulus and increased energy dissipation during stretching or compression of the magnetoelastic, and severely limit the material's flexibility. Poor dispersion not only reduces mechanical properties (such as elongation at break) but also affects the magnetic-force coupling efficiency, because uneven dispersion leads to local stress concentration, weakens the overall deformation capacity, and makes the material prone to failure in dynamic applications.

[0004] In previous studies of magnetoelastic effects, the mechano-magnetic coupling coefficient is a key parameter for measuring the efficiency of magnetic flux change in a material under mechanical force, directly affecting the sensitivity of the sensor. Previously, the main method to improve the mechano-magnetic coupling coefficient was to increase the concentration of magnetic particles (such as NdFeB) to optimize performance by enhancing magnetic responsiveness. However, this method has significant limitations: increasing particle concentration leads to uneven dispersion of particles in the polymer matrix (such as silicone rubber), causing agglomeration, thus sacrificing material flexibility, reducing elongation at break, and exacerbating interfacial debonding problems. For example, scanning electron microscopy analysis shows that NdFeB magnetic powder exhibits significant agglomeration and defects in the silicone rubber matrix (such as…). Figure 1As shown in the figure, this limits the effective improvement of the magnetic coupling coefficient and restricts the application of the material in flexible devices.

[0005] In fact, by optimizing dispersion uniformity, the mechanomagnetic coupling coefficient—that is, the conversion efficiency between magnetic field-induced deformation and mechanical response—can be significantly improved without increasing particle concentration. This is because good dispersion ensures uniform stress transmission and enhances the cooperative deformation capability of the interface, thereby improving coupling performance without sacrificing flexibility. However, existing technologies often rely on introducing external components or complex processes, such as liquid metal microfibers, to compensate for insufficient performance, but this increases process complexity and potential risks. The necessity of improved dispersion is particularly prominent in applications requiring high tensile strength (elongation at break >400%), fatigue durability, and stable electrical signal output, such as implantable sensors.

[0006] Previous research has often overlooked the potential to synergistically optimize mechanical, magnetic, and electrical properties by simply improving dispersion. How to enhance flexibility and thus improve the mechano-magnetic coupling coefficient through improved dispersion is an underexplored area in the design of magnetoelastic materials. Existing methods typically sacrifice flexibility for high magnetic response, failing to achieve a balanced optimization of performance.

[0007] Therefore, there is an urgent need to provide a high-performance neodymium iron boron / silicone rubber composite magnetorheological elastomer that can improve interfacial bonding by enhancing dispersion uniformity while suppressing magnetic powder oxidation. This would improve material flexibility and significantly enhance the mechanical-magnetic coupling coefficient without increasing particle concentration, fundamentally solving the problems of weak interfacial bonding and insufficient mechanical and electrical properties of existing materials. Summary of the Invention

[0008] In view of this, the present invention provides a high-performance neodymium iron boron / silicone rubber composite magnetorheological elastomer and its preparation method, so as to solve the problems of weak interfacial bonding and insufficient mechanical and electrical properties of existing magnetorheological elastomers.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for preparing a high-performance neodymium iron boron / silicone rubber composite magnetorheological elastomer, comprising the following steps: 1) The neodymium iron boron magnetic powder is activated and then immersed in an aqueous solution of dopamine hydrochloride to carry out a deposition reaction, thereby obtaining neodymium iron boron magnetic powder coated with a primary coating layer; 2) The neodymium iron boron magnetic powder coated with the primary coating layer is mixed with a silane coupling agent and subjected to a condensation reaction to obtain neodymium iron boron magnetic powder coated with a PDA-silane composite modified layer. 3) The neodymium iron boron magnetic powder coated with the PDA-silane composite modified layer is mixed with the silicone rubber matrix and then subjected to curing and magnetization treatments in sequence to obtain a high-performance neodymium iron boron / silicone rubber composite magnetorheological elastomer.

[0010] Preferably, the particle size of the neodymium iron boron magnetic powder in step 1) is 5~25 μm.

[0011] Preferably, the activation treatment in step 1) specifically involves immersing neodymium iron boron magnetic powder in ethanol and then subjecting it to ultrasonic treatment; the ultrasonic treatment time is 10~30 min, the temperature is 25~40℃, and the power is 200~400 W.

[0012] Preferably, the mass-volume concentration of the dopamine hydrochloride aqueous solution in step 1) is 0.5~3 g / L; and the deposition reaction time is 4~16 h.

[0013] Preferably, the silane coupling agent in step 2) includes silane coupling agent KH-560; the mass ratio of the neodymium iron boron magnetic powder coated with the primary coating layer to the silane coupling agent is 100:0.5~3.

[0014] Preferably, the condensation reaction in step 2) is carried out at a temperature of 50~70℃ for 4~16 h.

[0015] Preferably, the thickness of the PDA-silane composite modified layer in step 2) is 20~50 nm.

[0016] Preferably, the silicone rubber matrix in step 3) comprises room temperature vulcanizing methyl vinyl silicone rubber; the mass ratio of the NdFeB magnetic powder coated with the PDA-silane composite modified layer to the silicone rubber matrix is ​​6~8:2~4.

[0017] Preferably, the curing temperature in step 3) is 50~90℃ and the time is 2~8 h.

[0018] Preferably, the pulsed magnetic field for magnetization in step 3) is 500~3000 mT and the time is 5~10 min.

[0019] The present invention also provides a high-performance NdFeB / silicone rubber composite magnetorheological elastomer prepared by the above-mentioned method for preparing high-performance NdFeB / silicone rubber composite magnetorheological elastomer.

[0020] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention utilizes the synergistic surface modification of dopamine and silane coupling agents to construct a PDA-silane composite modified layer with a thickness of 20-50 nm on the surface of NdFeB magnetic powder. Specifically, the NdFeB magnetic powder is activated and then immersed in an aqueous solution of dopamine hydrochloride for deposition, forming a primary coating layer on the surface of the NdFeB magnetic powder. A silane coupling agent is then added, and the alkoxy group of silane reacts with the phenolic hydroxyl group of PDA to form the PDA-silane composite modified layer. This PDA-silane composite modified layer not only inhibits the oxidation of NdFeB magnetic powder and improves its dispersion stability, but also significantly enhances the interfacial bonding between NdFeB magnetic powder and the silicone rubber matrix, solving the problems of easy oxidation and weak interfacial bonding of NdFeB magnetic powder. This, in turn, improves the mechanical and electrical properties of the magnetorheological elastomer.

[0021] 2. The preparation method described in this invention is simple and low in cost, and successfully prepares a high-performance neodymium iron boron / silicone rubber composite magnetorheological elastomer with high-strength interfacial bonding, high magnetic responsiveness, excellent mechanical and electrical properties and thermal stability, laying a material foundation for the development of multifunctional magnetic-mechanical-electric coupling devices and advanced sensors and intelligent actuators. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0023] Figure 1 The image shows a SEM image of the high-performance NdFeB / silicone rubber composite magnetorheological elastomer prepared in Comparative Example 1; where, Figure 1 In the image, 'a' represents the SEM image at 500x magnification. Figure 1 In the image, b represents the SEM image at 2000x magnification; Figure 2 The image shows a SEM image of the high-performance NdFeB / silicone rubber composite magnetorheological elastomer prepared in Example 4; wherein, Figure 2 In the image, 'a' represents the SEM image at 500x magnification. Figure 2 In the image, b represents the SEM image at 2000x magnification; Figure 3 The images show the X-ray photoelectron spectroscopy (XPS) and Si element peak analysis of the neodymium iron boron / silicone rubber composite magnetorheological elastomers prepared in Example 4 and Comparative Example 1; where, Figure 3 In the figure, 'a' represents the XPS spectra of untreated NdFeB particles and NdFeB particles modified with PDA2@KH560. Figure 3In the diagram, b represents the newly added Si element peak spectrum analysis. Figure 3 (The horizontal axis represents the binding energy, and the vertical axis represents the photoelectron intensity). Figure 4 Transmission electron microscopy (TEM) images of the neodymium iron boron / silicone rubber composite magnetorheological elastomers prepared in Example 4 and Comparative Example 1; wherein, Figure 4 In the diagram, 'a' represents the morphology of NdFeB prepared in Comparative Example 1. Figure 4 In the image, b represents the morphology of NdFeB-PDA2@KH560 prepared in Example 4; Figure 5 The stress-strain curves of the neodymium iron boron / silicone rubber composite magnetorheological elastomers prepared in Example 4 and Comparative Example 1 are shown. Figure 5 (The horizontal axis represents strain, and the vertical axis represents stress). Figure 6 The current-pressure relationship diagrams for the neodymium iron boron / silicone rubber composite magnetorheological elastomers prepared in Example 4 and Comparative Example 1 are shown below. Figure 6 The horizontal axis represents pressure, and the vertical axis represents current. Detailed Implementation

[0024] This invention provides a method for preparing a high-performance neodymium iron boron / silicone rubber composite magnetorheological elastomer, comprising the following steps: 1) The neodymium iron boron magnetic powder is activated and then immersed in an aqueous solution of dopamine hydrochloride to carry out a deposition reaction, thereby obtaining neodymium iron boron magnetic powder coated with a primary coating layer; 2) The neodymium iron boron magnetic powder coated with the primary coating layer is mixed with a silane coupling agent and subjected to a condensation reaction to obtain neodymium iron boron magnetic powder coated with a PDA-silane composite modified layer. 3) The neodymium iron boron magnetic powder coated with the PDA-silane composite modified layer is mixed with the silicone rubber matrix and then subjected to curing and magnetization treatments in sequence to obtain a high-performance neodymium iron boron / silicone rubber composite magnetorheological elastomer.

[0025] In this invention, the particle size of the neodymium iron boron magnetic powder in step 1) is 5~25 μm, preferably 8~22 μm, more preferably 10~20 μm, and even more preferably 15~18 μm.

[0026] In this invention, the activation treatment in step 1) specifically involves immersing neodymium iron boron magnetic powder in ethanol and then subjecting it to ultrasonic treatment; the ultrasonic treatment time is 10-30 min, preferably 12-28 min, more preferably 15-25 min, and even more preferably 20 min; the ultrasonic treatment temperature is 25-40℃, preferably 28-38℃, and even more preferably 30-35℃; the ultrasonic treatment power is 200-400 W, preferably 220-380 W, more preferably 250-350 W, and even more preferably 300-330 W.

[0027] In this invention, the mass-volume concentration of the dopamine hydrochloride aqueous solution in step 1) is 0.5~3 g / L, preferably 0.7~2.5 g / L, more preferably 1~2.2 g / L, and even more preferably 1.5~2 g / L; the deposition reaction time is 4~16 h, preferably 5~15 h, more preferably 6~10 h, and even more preferably 8 h; and the dopamine hydrochloride aqueous solution in the deposition reaction is in excess.

[0028] In this invention, the silane coupling agent in step 2) preferably includes silane coupling agent KH-560; the mass ratio of the neodymium iron boron magnetic powder coated with the primary coating layer to the silane coupling agent is 100:0.5~3, preferably 100:0.8~2.8, more preferably 100:1~2.5, and even more preferably 100:1.5~2.

[0029] In this invention, the temperature of the condensation reaction in step 2) is 50~70℃, preferably 52~65℃, and more preferably 55~60℃; the time of the condensation reaction is 4~16 h, preferably 5~15 h, and more preferably 8~10 h.

[0030] In this invention, the thickness of the PDA-silane composite modified layer in step 2) is 20~50 nm, preferably 22~45 nm, more preferably 25~40 nm, and even more preferably 30~35 nm.

[0031] In this invention, the silicone rubber matrix in step 3) preferably includes room temperature vulcanizing methyl vinyl silicone rubber; the mass ratio of the neodymium iron boron magnetic powder coated with the PDA-silane composite modified layer to the silicone rubber matrix is ​​6~8:2~4, preferably one of 6:4, 7:3, and 8:2.

[0032] In this invention, the curing temperature in step 3) is 50~90℃, preferably 52~85℃, more preferably 55~80℃, even more preferably 60~75℃, and more preferably 65~70℃; the curing time is 2~8 h, preferably 2.5~7 h, more preferably 3~6.5 h, and more preferably 4.5~6 h.

[0033] In this invention, the pulsed magnetic field of the magnetization treatment in step 3) is 500~3000 mT, preferably 600~2500 mT, more preferably 800~2000 mT, and more preferably 1000~1500 mT; the magnetization treatment time is 5~10 min, preferably 5.5~8.5 min, more preferably 6~8 min, and more preferably 7~7.5 min.

[0034] This invention also provides a high-performance NdFeB / silicone rubber composite magnetorheological elastomer prepared by the above-described method for preparing a high-performance NdFeB / silicone rubber composite magnetorheological elastomer. The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0035] Example 1 1) Neodymium iron boron magnetic powder (particle size 5 μm) was immersed in ethanol and activated by ultrasonic cleaning for 20 min at room temperature and 300 W. Then it was immersed in a dopamine hydrochloride aqueous solution with a mass-volume concentration of 1 g / L and stirred at room temperature for 8 h to complete the deposition reaction, thus obtaining neodymium iron boron magnetic powder coated with a primary coating layer. 2) Neodymium iron boron magnetic powder coated with a primary coating layer was mixed with silane coupling agent KH-560 at a mass ratio of 100:1 and subjected to a condensation reaction at 60°C for 8 h to obtain neodymium iron boron magnetic powder coated with a PDA-silane composite modified layer (the thickness of the PDA-silane composite modified layer was 30 nm). 3) Mix 80 wt% of NdFeB magnetic powder coated with PDA-silane composite modified layer with 80 wt% of room temperature vulcanizing methyl vinyl silicone rubber (Ecoflex 00-30), cure at 60℃ for 6 h, and then magnetize under a pulsed magnetic field of 2500 mT using an ACS Scientific IM-10-30 magnetizer for 5 min to obtain a high-performance NdFeB / silicone rubber composite magnetorheological elastomer.

[0036] Example 2 The only difference between Example 2 and Example 1 is that the mass-volume concentration of the dopamine hydrochloride aqueous solution is replaced with 2 g / L, while other reaction conditions remain unchanged.

[0037] Example 3 The only difference between Example 3 and Example 1 is that the mass-volume concentration of the dopamine hydrochloride aqueous solution is replaced with 3 g / L, while other reaction conditions remain unchanged.

[0038] The high-performance NdFeB / silicone rubber composite magnetorheological elastomers prepared in Examples 1-3 were characterized by SEM and TEM. The results showed that when the concentration of dopamine hydrochloride aqueous solution was 2 g / L, the NdFeB magnetic powder was most uniformly dispersed in the silicone rubber matrix, with a nearest neighbor distance variance of 1.3 and a coating layer thickness of 30 nm, exhibiting a dense and complete structure. In contrast, the nearest neighbor distance variances at concentrations of 1 g / L and 3 g / L were 4.2 and 3.8, respectively, indicating a decrease in dispersibility.

[0039] In addition, a universal tensile testing machine was used to test the elongation at break of a 40 mm × 10 mm × 0.5 mm specimen with a gauge length of 20 mm and a tensile rate of 100 mm / min. A Keithley 6514 electrometer was used to test the sensitivity of the high-performance NdFeB / silicone rubber composite magnetorheological elastomers prepared in Examples 1-3. The specimens were the high-performance NdFeB / silicone rubber composite magnetorheological elastomers prepared in Examples 1-3. The results showed that when the concentration of dopamine hydrochloride aqueous solution was 2 g / L, the elongation at break of the magnetorheological elastomer reached 556%, with a sensitivity of 8.42 μA / kPa. When the concentrations of dopamine hydrochloride aqueous solution were 1 g / L and 3 g / L, the elongation at break of the magnetorheological elastomer were 150% and 300%, respectively, with sensitivities of 3.5 μA / kPa and 5.0 μA / kPa, respectively. Therefore, it can be seen that when the concentration of dopamine hydrochloride aqueous solution is 2 g / L, the elongation at break and sensitivity of magnetorheological elastomer are the highest, effectively balancing the interfacial bonding strength and dispersibility of magnetorheological elastomer.

[0040] Example 4 1) Neodymium iron boron magnetic powder (particle size 5 μm) was immersed in ethanol and activated by ultrasonic cleaning at room temperature and 300 W for 20 min. Then it was immersed in a dopamine hydrochloride aqueous solution with a mass volume concentration of 2 g / L and stirred at room temperature for 12 h to complete the deposition reaction, so that PDA was deposited to form an adhesion layer, and neodymium iron boron magnetic powder with a primary coating layer was obtained. 2) Neodymium iron boron magnetic powder coated with a primary coating layer was mixed with silane coupling agent KH-560 at a mass ratio of 100:1 and subjected to a condensation reaction at 60°C for 8 h to obtain neodymium iron boron magnetic powder coated with a PDA-silane composite modified layer (the thickness of the PDA-silane composite modified layer was 30 nm). 3) Mix 80 wt% of NdFeB magnetic powder coated with PDA-silane composite modification layer with 80 wt% of room temperature vulcanizing methyl vinyl silicone rubber (Ecoflex 00-30), cure at 60℃ for 2 h, and then magnetize under a pulsed magnetic field of 2500 mT using an ACS Scientific IM-10-30 magnetizer for 5 min to obtain a high-performance NdFeB / silicone rubber composite magnetorheological elastomer (denoted as NdFeB-PDA2@KH560).

[0041] Comparative Example 1 Neodymium iron boron magnetic powder (particle size D) 50 80 wt% of NdFeB (7.3 μm) was directly mixed with 80 wt% of room temperature vulcanizing methyl vinyl silicone rubber (Ecoflex 00-30). After stirring for 10 min, the mixture was vacuum degassed and injected into a mold. It was then cured at 60 °C for 2 h and then magnetized for 5 min using an ASC Scientific IM-10-30 magnetizer under a pulsed magnetic field of 2500 mT to obtain a high-performance NdFeB / silicone rubber composite magnetorheological elastomer with an anisotropic chain structure.

[0042] The microstructure of the high-performance NdFeB / silicone rubber composite magnetorheological elastomers prepared in Example 4 and Comparative Example 1 was characterized by SEM (scanning electron microscopy), and the results are as follows: Figures 1-2 As shown, where, Figure 1 In Figure 'a', the image of the magnetorheological elastomer in Comparative Example 1 is a SEM image magnified at 500x. Figure 1 In the image, b is the SEM image of the magnetorheological elastomer in Comparative Example 1 at 2000x magnification; Figure 2 In Figure 'a', the image is a SEM image of the magnetorheological elastomer in Example 4 at 500x magnification. Figure 2 In Figure b, the image is a SEM image of the magnetorheological elastomer in Example 4 at 2000x magnification. From... Figure 1 As can be seen from a~b in Comparative Example 1, the NdFeB magnetic powder is unevenly distributed in the silicone rubber matrix, with significant agglomeration. The calculated nearest neighbor distance variance is 5.587, indicating a large number of defects at the interface. Figure 2 As can be seen from a~b in Example 4, the dispersion uniformity of the NdFeB magnetic powder was significantly improved, and the nearest neighbor distance variance decreased to 1.324, indicating a reduction in agglomeration. This confirms that the PDA-silane composite modified layer effectively enhances the compatibility between the particles and the matrix. This improvement stems from the synergistic effect of the adhesion of PDA and the chemical bonding of silane, which reduces interfacial voids and thus optimizes the stress transfer path.

[0043] The high-performance neodymium iron boron / silicone rubber composite magnetorheological elastomers prepared in Example 4 and Comparative Example 1 were characterized by X-ray photoelectron spectroscopy and transmission electron microscopy, and the results are as follows: Figures 3-4 As shown, where, Figure 3 In the figure, 'a' represents the XPS spectra of untreated NdFeB particles and NdFeB particles modified with PDA2@KH560. Figure 3 In the diagram, b represents the newly added Si element peak spectrum analysis. Figure 4 In the image, 'a' represents the morphology of untreated NdFeB particles. Figure 4 In the figure, b represents the morphology of NdFeB particles after modification with PDA2@KH560. Figure 3 XPS analysis results showed that the surface chemical composition of NdFeB particles significantly changed after composite modification with polydopamine (PDA) and KH-560. The XPS broad scan spectrum of unmodified NdFeB particles only showed characteristic peaks for iron (Fe), oxygen (O), and a small amount of impurity carbon (C); while the modified NdFeB-PDA2@KH560 sample showed a characteristic peak for silicon (Si) at a binding energy of 102 eV, and a characteristic peak for nitrogen (N) at 399.6 eV. The Si signal originated from the hydrolysis and condensation products of the silane coupling agent KH560, while the N signal clearly indicated the presence of amino functional groups in PDA. These two newly added characteristic peaks together confirmed that KH560 and PDA were successfully introduced and stably attached to the surface of NdFeB particles. At the morphological level, TEM observation directly revealed the existence and thickness of the surface modification layer. Figure 4 As shown in figure a, the surface of the original NdFeB particles is clear and smooth, without any coating structure. In contrast, NdFeB-PDA2@KH560 particles ( Figure 4 (b) The surface exhibits a continuous and uniform coating layer, with an average thickness of approximately 30.6 nm. This result not only morphologically confirms the successful construction of the PDA2@KH560 composite coating, but also provides a structural basis for improving interfacial interactions in subsequent composite materials.

[0044] The elongation at break and tensile strength of the high-performance NdFeB / silicone rubber composite magnetorheological elastomers prepared in Example 4 and Comparative Example 1 were tested using the same testing method as in Example 1. The results showed that the elongation at break of the magnetorheological elastomer in Comparative Example 1 was only 120%, from... Figure 5It can also be seen that the magnetorheological elastomer (NdFeB) in Comparative Example 1 has low tensile strength and high modulus, which limits its flexible applications; while the magnetorheological elastomer (NdFeB-PDA2@KH560) in Example 4 has a significantly increased elongation at break of 556%, higher tensile strength, and lower modulus, which enhances the material's deformation capacity under the same pressure. This improvement is directly attributed to the strengthening of interfacial bonding, avoiding early failure caused by stress concentration.

[0045] The sensitivity and response range of the high-performance NdFeB / silicone rubber composite magnetorheological elastomers prepared in Example 4 and Comparative Example 1 were tested using an electrometer. The results are as follows: Figure 6 As shown, from Figure 6 As can be seen, the magnetorheological elastomer (NdFeB) in Comparative Example 1 has a sensitivity of 2.78 μA / kPa, a narrow response range (3.5 Pa~1000 kPa), and poor cycle stability. In contrast, the magnetorheological elastomer (NdFeB-PDA2@KH560) in Example 4 exhibits a sensitivity increased to 8.42 μA / kPa, a response range expanded to 3.5 Pa~2000 kPa, and a voltage output increase of 1.3 times under 20 kPa pressure, while maintaining a response time within 3 ms. This demonstrates that modifying NdFeB magnetic powder significantly improves the dispersion uniformity of the powder, making it easier for conductive components to capture changes in the magnetic field, thus enhancing the magneto-electric conversion efficiency.

[0046] Furthermore, the performance degradation of the magnetorheological elastomer in Comparative Example 1 exceeded 20% after immersion in artificial sweat for 168 hours, while the performance degradation of the magnetorheological elastomer in Example 4 was less than 5%, verifying that the PDA-silane composite modified layer formed by the method described in this invention has intrinsic waterproof properties and excellent environmental stability.

[0047] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-performance neodymium iron boron / silicone rubber composite magnetorheological elastomer, characterized in that, Includes the following steps: 1) The neodymium iron boron magnetic powder is activated and then immersed in an aqueous solution of dopamine hydrochloride to carry out a deposition reaction, thereby obtaining neodymium iron boron magnetic powder coated with a primary coating layer; 2) The neodymium iron boron magnetic powder coated with the primary coating layer is mixed with the silane coupling agent and subjected to a condensation reaction to obtain neodymium iron boron magnetic powder coated with a PDA-silane composite modified layer. 3) The neodymium iron boron magnetic powder coated with the PDA-silane composite modified layer is mixed with the silicone rubber matrix and then subjected to curing and magnetization treatments in sequence to obtain a high-performance neodymium iron boron / silicone rubber composite magnetorheological elastomer.

2. The method for preparing a high-performance neodymium iron boron / silicone rubber composite magnetorheological elastomer according to claim 1, characterized in that, The particle size of the neodymium iron boron magnetic powder mentioned in step 1) is 5~25 μm.

3. The method for preparing a high-performance neodymium iron boron / silicone rubber composite magnetorheological elastomer according to claim 2, characterized in that, The activation treatment described in step 1) is as follows: immersing neodymium iron boron magnetic powder in ethanol and then subjecting it to ultrasonic treatment; The ultrasonic treatment time is 10~30 min, the temperature is 25~40℃, and the power is 200~400 W.

4. A method for preparing a high-performance neodymium iron boron / silicone rubber composite magnetorheological elastomer according to any one of claims 1 to 3, characterized in that, The mass concentration of the dopamine hydrochloride aqueous solution in step 1) is 0.5~3 g / L; The deposition reaction time is 4 to 16 hours.

5. The method for preparing a high-performance neodymium iron boron / silicone rubber composite magnetorheological elastomer according to claim 4, characterized in that, The silane coupling agent mentioned in step 2) includes silane coupling agent KH-560; The mass ratio of the neodymium iron boron magnetic powder coated with the primary coating layer to the silane coupling agent is 100:0.5~3.

6. The method for preparing a high-performance neodymium iron boron / silicone rubber composite magnetorheological elastomer according to claim 5, characterized in that, The condensation reaction described in step 2) is carried out at a temperature of 50~70℃ for 4~16 h.

7. The method for preparing a high-performance neodymium iron boron / silicone rubber composite magnetorheological elastomer according to claim 6, characterized in that, The thickness of the PDA-silane composite modified layer in step 2) is 20~50 nm.

8. The method for preparing a high-performance neodymium iron boron / silicone rubber composite magnetorheological elastomer according to claim 7, characterized in that, The silicone rubber matrix mentioned in step 3) includes room temperature vulcanizing methyl vinyl silicone rubber; The mass ratio of the neodymium iron boron magnetic powder coated with the PDA-silane composite modified layer to the silicone rubber matrix is ​​6~8:2~4.

9. The method for preparing a high-performance neodymium iron boron / silicone rubber composite magnetorheological elastomer according to claim 8, characterized in that, The curing process described in step 3) is carried out at a temperature of 50~90℃ for 2~8 hours. The pulsed magnetic field for magnetization in step 3) is 500~3000 mT, and the time is 5~10 min.

10. The high-performance NdFeB / silicone rubber composite magnetorheological elastomer prepared by the method of any one of claims 1 to 9.

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