Neodymium-iron-boron magnet and preparation method thereof

Abstract

The invention relates to a neodymium-iron-boron magnet and a preparation method thereof, and belongs to the technical field of neodymium-iron-boron magnets. The neodymium-iron-boron magnet comprises the following components: acrylic resin, vinyl epoxy resin, modified neodymium-iron-boron magnetic powder, a graphene complex, a curing agent and a lubricant, the neodymium-iron-boron magnet prepared by the method shows excellent stability, mechanical strength and high temperature resistance, so that the overall magnetic performance of the magnet is improved. In addition, the magnet is low in manufacturing cost, excellent in performance, high in cost performance and capable of meeting the requirements of more scenes.

Description

Technical Field

[0001] The invention belongs to the technical field of NdFeB magnets and relates to NdFeB magnets and a preparation method thereof. Background Art

[0002] The combination of thermosetting or thermoplastic polymers and magnetic materials forms composite materials with magnetic functions, which is crucial to the national economic development. The NdFeB magnetic composite material, which is composed of magnetic NdFeB powder and non-magnetic thermosetting or thermoplastic polymer materials, has the advantages of low density and easy processing into high-precision dimensions and complex shapes. It also has excellent mechanical properties and supports large-scale automated production. This material has been increasingly widely used in high-tech fields such as new energy vehicle motors, home appliances, electronic technology, automation control, computers and satellites.

[0003] Bonded NdFeB magnets are increasingly in demand due to their diverse shapes and flexible magnetization methods. Given the active nature of NdFeB materials, they are extremely susceptible to corrosion, so bonded NdFeB magnets are usually composed of an NdFeB matrix and a protective layer covering the surface. The usual preparation process involves first preparing an NdFeB matrix, and then coating the protective layer on the surface of the matrix by electroplating or electrophoresis. When preparing the NdFeB matrix, acetone is often used as a solvent to prepare the binder solution, while zinc stearate is used as a lubricant to enhance the fluidity of the powder. However, zinc stearate is easily volatilized during the curing process of the magnet, resulting in surface defects, and has limited effect as a single lubricant. In addition, NdFeB magnetic powder is easily adsorbed on the surface by oxygen and moisture in high temperature, humidity, electrochemical environment and hydrogen-containing conditions, resulting in oxidative corrosion, which limits its wide application in industry. Summary of the invention

[0004] The purpose of the present invention is to provide a neodymium iron boron magnet and a preparation method thereof. The neodymium iron boron magnet prepared by the present invention exhibits excellent stability, mechanical strength and high temperature resistance, thereby improving the overall magnetic properties of the magnet. In addition, the magnet has a low production cost, excellent performance, high cost performance, and can meet the needs of more scenarios.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A neodymium iron boron magnet comprises the following components by weight: 6.2-7.6 parts of acrylic resin, 1.8-2.2 parts of vinyl epoxy resin, 80-90 parts of modified neodymium iron boron magnetic powder, 6-8 parts of graphene composite, 0.4-0.6 parts of curing agent and 0.8-1.2 parts of lubricant.

[0007] As a preferred technical solution of the present invention, the lubricant is formed by mixing zinc stearate and zinc sorbate in a mass ratio of 2:1.2-1.4; the curing agent is one or more of benzoyl peroxide, cumene hydroperoxide, tert-butyl hydroperoxide, 2,4-dichlorobenzoyl peroxide and dodecyl peroxide;

[0008] As a preferred technical solution of the present invention, the method for preparing the modified NdFeB magnetic powder comprises the following steps:

[0009] Step S1, under nitrogen protection, mixing NdFeB magnetic powder and anhydrous ethanol, slowly adding silane coupling agent after heating, stirring and mixing, removing the solvent by rotary evaporation, and vacuum drying to constant weight to obtain pretreated NdFeB magnetic powder;

[0010] Step S2: Under nitrogen protection, the pretreated NdFeB magnetic powder and anhydrous ethanol are mixed and then ultrasonically treated, the composite monomer and initiator are added, stirred and heated, the solid is filtered out, washed three times with anhydrous ethanol, and vacuum dried to constant weight to obtain modified NdFeB magnetic powder.

[0011] As a preferred technical solution of the present invention, in step S1, the heating is to 60°C; the stirring and mixing is to stir at a speed of 500-800rpm for 6-8h; the vacuum drying temperature is 80°C; the mass ratio of the NdFeB magnetic powder, anhydrous ethanol and silane coupling agent is 16-18:45-50:1.8-2.1; the silane coupling agent is vinyl triethoxysilane; and the NdFeB magnetic powder impregnated with the silane coupling agent can initially prevent its oxidation.

[0012] As a preferred technical solution of the present invention, in step S2, the ultrasonic treatment is ultrasonic treatment at a power of 300-400W for 15-20min; the stirring and heating is stirring at a temperature of 65-72°C for 5-6h; the temperature of the vacuum drying is 85°C; the mass ratio of the pretreated NdFeB magnetic powder, anhydrous ethanol, composite monomer and initiator is 20-22:50-55:3.2-3.5:0.10-0.12; the composite monomer is composed of cardanol, trans-2-hexenal and glycidyl methacrylate in a mass ratio of 3.0-3.4:1.4-1.6:0.8-1.1.

[0013] As a preferred technical solution of the present invention, the preparation method of the graphene complex comprises the following steps: ultrasonically mixing graphene, ethanol solution and cysteine, filtering out solid matter, and vacuum drying to constant weight to obtain the graphene complex.

[0014] As a preferred technical solution of the present invention, the ultrasonic mixing is performed at a power of 600-800W for 20-30min; the temperature of the vacuum drying is 80°C; and the mass ratio of the graphene, ethanol solution and cysteine ​​is 10-12:30-40:5.2-5.4.

[0015] A method for preparing the above-mentioned NdFeB magnet comprises the following steps: mixing acrylic resin, vinyl epoxy resin, modified NdFeB magnetic powder, graphene composite, curing agent and lubricant, melt-extruding at 110-120°C, and curing at 150-160°C to obtain the magnet.

[0016] Beneficial effects of the present invention:

[0017] The NdFeB magnet prepared by the present invention exhibits excellent stability, mechanical strength and high temperature resistance, thereby improving the overall magnetic properties of the magnet. In addition, the magnet has low production cost, excellent performance, high cost performance, and can meet the needs of more scenarios. DETAILED DESCRIPTION

[0018] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0019] Example 1

[0020] A neodymium iron boron magnet comprises the following components by weight: 6.2 parts of acrylic resin, 1.8 parts of vinyl epoxy resin, 80 parts of modified neodymium iron boron magnetic powder, 6 parts of graphene composite, 0.4 parts of curing agent and 0.8 parts of lubricant; the lubricant is a mixture of zinc stearate and zinc sorbate in a mass ratio of 2:1.2; the curing agent is benzoyl peroxide;

[0021] The preparation method of the modified NdFeB magnetic powder comprises the following steps:

[0022] Step S1, under nitrogen protection, mixing NdFeB magnetic powder and anhydrous ethanol, slowly adding silane coupling agent after heating, stirring and mixing, removing the solvent by rotary evaporation, and vacuum drying to constant weight to obtain pretreated NdFeB magnetic powder; wherein the heating is to 60°C; the stirring and mixing is to stir at a speed of 500 rpm for 6 hours; the vacuum drying temperature is 80°C; the mass ratio of NdFeB magnetic powder, anhydrous ethanol and silane coupling agent is 16:45:1.8; the silane coupling agent is vinyl triethoxysilane;

[0023] Step S2, under nitrogen protection conditions, mixing the pretreated NdFeB magnetic powder and anhydrous ethanol and then performing ultrasonic treatment, adding the composite monomer and initiator, stirring and heating, filtering the solid, washing it with anhydrous ethanol three times, and vacuum drying it to constant weight to obtain modified NdFeB magnetic powder; wherein the ultrasonic treatment is ultrasonic treatment at a power of 300 W for 15 minutes; the stirring and heating is stirring at a temperature of 65° C. for 5 hours; the temperature of the vacuum drying is 85° C.; the mass ratio of the pretreated NdFeB magnetic powder, anhydrous ethanol, composite monomer and initiator is 20:50:3.2:0.10; the composite monomer is composed of cardanol, trans-2-hexenal, and glycidyl methacrylate in a mass ratio of 3.0:1.4:0.8.

[0024] The method for preparing the graphene composite comprises the following steps:

[0025] After ultrasonically mixing graphene, ethanol solution and cysteine, filtering out solids, and vacuum drying to constant weight, a graphene composite is obtained. The ultrasonic mixing is performed at a power of 600 W for 20 minutes; the vacuum drying temperature is 80° C.; and the mass ratio of graphene, ethanol solution and cysteine ​​is 10:30:5.2.

[0026] A method for preparing a NdFeB magnet comprises the following steps: mixing acrylic resin, vinyl epoxy resin, modified NdFeB magnetic powder, graphene composite, curing agent and lubricant, and then melt-extruding at 110 DEG C, and curing at 150 DEG C to obtain the NdFeB magnet.

[0027] Example 2

[0028] A neodymium iron boron magnet comprises the following components by weight: 6.9 parts of acrylic resin, 2 parts of vinyl epoxy resin, 85 parts of modified neodymium iron boron magnetic powder, 7 parts of graphene composite, 0.5 parts of curing agent and 1.0 parts of lubricant; the lubricant is a mixture of zinc stearate and zinc sorbate in a mass ratio of 2:1.3; the curing agent is benzoyl peroxide;

[0029] The preparation method of the modified NdFeB magnetic powder comprises the following steps:

[0030] Step S1, under nitrogen protection, mixing NdFeB magnetic powder and anhydrous ethanol, slowly adding silane coupling agent after heating, stirring and mixing, removing the solvent by rotary evaporation, and vacuum drying to constant weight to obtain pretreated NdFeB magnetic powder; wherein the heating is to 60°C; the stirring and mixing is to stir at a speed of 650rpm for 7h; the vacuum drying temperature is 80°C; the mass ratio of NdFeB magnetic powder, anhydrous ethanol and silane coupling agent is 17:48:2; the silane coupling agent is vinyltriethoxysilane;

[0031] Step S2, under nitrogen protection conditions, mixing the pretreated NdFeB magnetic powder and anhydrous ethanol and then performing ultrasonic treatment, adding the composite monomer and initiator, stirring and heating, filtering the solid, washing it three times with anhydrous ethanol, and vacuum drying it to constant weight to obtain modified NdFeB magnetic powder; wherein the ultrasonic treatment is ultrasonication at a power of 350 W for 18 minutes; the stirring and heating is stirring at a temperature of 68° C. for 5.5 hours; the vacuum drying temperature is 85° C.; the mass ratio of the pretreated NdFeB magnetic powder, anhydrous ethanol, composite monomer and initiator is 21:52:3.4:0.11; the composite monomer is composed of cardanol, trans-2-hexenal, and glycidyl methacrylate in a mass ratio of 3.2:1.5:1.

[0032] The method for preparing the graphene composite comprises the following steps:

[0033] After ultrasonically mixing graphene, ethanol solution and cysteine, filtering out solids, and vacuum drying to constant weight, a graphene composite is obtained. The ultrasonic mixing is performed at a power of 700 W for 25 minutes; the vacuum drying temperature is 80° C.; and the mass ratio of graphene, ethanol solution and cysteine ​​is 11:35:5.3.

[0034] A method for preparing a NdFeB magnet comprises the following steps: mixing acrylic resin, vinyl epoxy resin, modified NdFeB magnetic powder, graphene composite, curing agent and lubricant, melt extruding at 115°C, and curing at 155°C to obtain the magnet.

[0035] Example 3

[0036] A neodymium iron boron magnet comprises the following components by weight: 7.6 parts of acrylic resin, 2.2 parts of vinyl epoxy resin, 90 parts of modified neodymium iron boron magnetic powder, 8 parts of graphene composite, 0.6 parts of curing agent and 1.2 parts of lubricant; the lubricant is a mixture of zinc stearate and zinc sorbate in a mass ratio of 2:1.4; the curing agent is benzoyl peroxide;

[0037] The preparation method of the modified NdFeB magnetic powder comprises the following steps:

[0038] Step S1, under nitrogen protection, mixing NdFeB magnetic powder and anhydrous ethanol, slowly adding silane coupling agent after heating, stirring and mixing, removing the solvent by rotary evaporation, and vacuum drying to constant weight to obtain pretreated NdFeB magnetic powder; wherein the heating is to 60°C; the stirring and mixing is to stir at a speed of 800 rpm for 8 hours; the vacuum drying temperature is 80°C; the mass ratio of NdFeB magnetic powder, anhydrous ethanol and silane coupling agent is 18:50:2.1; the silane coupling agent is vinyl triethoxysilane;

[0039] Step S2, under nitrogen protection conditions, mixing the pretreated NdFeB magnetic powder and anhydrous ethanol and then performing ultrasonic treatment, adding the composite monomer and initiator, stirring and heating, filtering the solid, washing it with anhydrous ethanol three times, and vacuum drying it to constant weight to obtain modified NdFeB magnetic powder; wherein the ultrasonic treatment is ultrasonication at a power of 400 W for 20 minutes; the stirring and heating is stirring at a temperature of 72° C. for 6 hours; the vacuum drying temperature is 85° C.; the mass ratio of the pretreated NdFeB magnetic powder, anhydrous ethanol, composite monomer and initiator is 22:55:3.5:0.12; the composite monomer is composed of cardanol, trans-2-hexenal, and glycidyl methacrylate in a mass ratio of 3.4:1.6:1.1.

[0040] The method for preparing the graphene composite comprises the following steps:

[0041] After ultrasonically mixing graphene, ethanol solution and cysteine, filtering out solids, and vacuum drying to constant weight, a graphene composite is obtained. The ultrasonic mixing is performed at a power of 800 W for 30 minutes; the vacuum drying temperature is 80° C.; and the mass ratio of graphene, ethanol solution and cysteine ​​is 12:40:5.4.

[0042] A method for preparing a NdFeB magnet comprises the following steps: mixing acrylic resin, vinyl epoxy resin, modified NdFeB magnetic powder, graphene composite, curing agent and lubricant, and then melt-extruding at 120°C, and curing at 160°C to obtain the NdFeB magnet.

[0043] Comparative Example 1

[0044] Compared with Example 3, Comparative Example 1 is different in that vinyltriethoxysilane is not used, and the other components, preparation steps and parameters are the same.

[0045] Comparative Example 2

[0046] Compared with Example 3, the difference in Comparative Example 2 is that cardanol is not used, and the other components, preparation steps and parameters are the same.

[0047] Comparative Example 3

[0048] Compared with Example 3, Comparative Example 3 is different in that trans-2-hexenal is not used, and the remaining components, preparation steps and parameters are the same.

[0049] Comparative Example 4

[0050] Compared with Example 3, Comparative Example 4 is different in that glycidyl methacrylate is not used, and the remaining components, preparation steps and parameters are the same.

[0051] Comparative Example 5

[0052] Compared with Example 3, Comparative Example 5 is different in that cysteine ​​is not used, and the other components, preparation steps and parameters are the same.

[0053] The NdFeB magnets prepared in Examples 1-3 and Comparative Examples 1-5 were subjected to the following performance tests, respectively. The test results are shown in Table 1.

[0054] Table 1

[0055]

[0056]

[0057] It can be seen from the test results in Table 1 that compared with comparative examples 1-5, the NdFeB magnets prepared in Examples 1-3 of the present invention have excellent stability, mechanical strength and high temperature resistance, which improves the comprehensive magnetic properties of the magnets while reducing the manufacturing cost. The prepared magnets have good performance and high cost performance and can meet more occasions.

[0058] Through comparative analysis, it can be seen that this is because the present invention uses vinyltriethoxysilane to hydrophobically modify the surface of NdFeB magnetic powder and introduces unsaturated carbon-carbon double bonds, so that the composite monomer can undergo in-situ polymerization reaction on its surface. Cardanol can form a protective film on the surface of the magnetic material through its own antioxidant property to prevent its oxidation from causing a decrease in mechanical properties and magnetic properties. The long carbon chain it contains can act as a lubricant, which can give NdFeB magnetic powder excellent fluidity, reduce friction between particles, and prevent its agglomeration. The active functional groups of hexenal and glycidyl methacrylate can increase the compatibility between NdFeB magnetic powder and resin, and improve the high temperature resistance, mechanical strength and toughness of the magnet material; cardanol and trans-2-hexenal are both natural materials and are biodegradable. While meeting environmental protection requirements, trans-2-hexenal can also utilize the mutual grafting of amino and aldehyde groups to promote the combination of graphene composites and modified NdFeB magnetic powder. Graphene can also play a lubricating and reinforcing role, significantly improving the mechanical strength and high temperature resistance of the magnet material.

[0059] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any indirect modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A neodymium iron boron magnet, characterized in that: The composition includes the following components by weight: 6.2-7.6 parts of acrylic resin, 1.8-2.2 parts of vinyl epoxy resin, 80-90 parts of modified NdFeB magnetic powder, 6-8 parts of graphene composite, 0.4-0.6 parts of curing agent and 0.8-1.2 parts of lubricant; The method for preparing the modified NdFeB magnetic powder comprises the following steps: Step S1, under nitrogen protection, mixing NdFeB magnetic powder and anhydrous ethanol, slowly adding silane coupling agent after heating, stirring and mixing, removing the solvent by rotary evaporation, and vacuum drying to constant weight to obtain pretreated NdFeB magnetic powder; Step S2: Under nitrogen protection, the pretreated NdFeB magnetic powder and anhydrous ethanol are mixed and then ultrasonically treated, the composite monomer and initiator are added, stirred and heated, the solid is filtered out, washed three times with anhydrous ethanol, and vacuum dried to constant weight to obtain modified NdFeB magnetic powder.

2. The NdFeB magnet according to claim 1, characterized in that: The lubricant is prepared by mixing zinc stearate and zinc sorbate in a mass ratio of 2:1.2-1.4; the curing agent is one or more of benzoyl peroxide, cumene hydroperoxide, tert-butyl hydroperoxide, 2,4-dichlorobenzoyl peroxide and dodecanoyl peroxide.

3. The NdFeB magnet according to claim 1, characterized in that: In step S1, the temperature is raised to 60°C; the stirring and mixing is stirred at a speed of 500-800 rpm for 6-8 hours; and the vacuum drying temperature is 80°C.

4. The NdFeB magnet according to claim 1, characterized in that: In step S1, the mass ratio of the NdFeB magnetic powder, anhydrous ethanol and silane coupling agent is 16-18:45-50:1.8-2.1; the silane coupling agent is vinyl triethoxysilane.

5. The NdFeB magnet according to claim 1, characterized in that: In step S2, the ultrasonic treatment is performed at a power of 300-400 W for 15-20 min; the stirring and heating is performed at a temperature of 65-72° C. for 5-6 h; and the vacuum drying temperature is 85° C.

6. The NdFeB magnet according to claim 1, characterized in that: In step S2, the mass ratio of the pretreated NdFeB magnetic powder, anhydrous ethanol, composite monomer and initiator is 20-22:50-55:3.2-3.5:0.10-0.12; the composite monomer is composed of cardanol, trans-2-hexenal and glycidyl methacrylate in a mass ratio of 3.0-3.4:1.4-1.6:0.8-1.

1.

7. The NdFeB magnet according to claim 1, characterized in that: The preparation method of the graphene complex comprises the following steps: ultrasonically mixing graphene, ethanol solution and cysteine, filtering out solid matter, and vacuum drying to constant weight to obtain the graphene complex.

8. The NdFeB magnet according to claim 7, characterized in that The ultrasonic mixing is performed at a power of 600-800 W for 20-30 min; the vacuum drying temperature is 80° C.; and the mass ratio of the graphene, ethanol solution and cysteine ​​is 10-12:30-40:5.2-5.

4.

9. A method for preparing a NdFeB magnet as claimed in any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: mixing acrylic resin, vinyl epoxy resin, modified NdFeB magnetic powder, graphene composite, curing agent and lubricant, and then melt-extruding at 110-120° C. and curing at 150-160° C. to obtain the product.

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