Corrosion-resistant sintered neodymium-iron-boron permanent magnet and preparation method and application thereof

Abstract

The invention discloses a corrosion-resistant sintered neodymium-iron-boron permanent magnet and a preparation method and application thereof. The corrosion-resistant sintered neodymium-iron-boron permanent magnet comprises a sintered neodymium-iron-boron permanent magnet body and a silane coupling agent hydrophobically modified AlCr coating covering the surface of the sintered neodymium-iron-boron permanent magnet body. The silane coupling agent hydrophobically modified AlCr coating comprises an AlCr coating body and a silane coupling agent cross-linked and coupled to the surface of the AlCr coating body and the inner walls of pores. The preparation method of the corrosion-resistant sintered neodymium-iron-boron permanent magnet comprises the following steps: 1) depositing an AlCr coating on the surface of the sintered neodymium-iron-boron permanent magnet; and 2) carrying out hydrophobic modification on the AlCr coating by adopting a silane coupling agent. The surface of the corrosion-resistant sintered neodymium-iron-boron permanent magnet is covered with the AlCr coating hydrophobically modified by the silane coupling agent, the corrosion-resistant sintered neodymium-iron-boron permanent magnet has excellent magnetic performance and excellent corrosion resistance, the preparation method is simple, and the corrosion-resistant sintered neodymium-iron-boron permanent magnet has very wide application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of surface protection of magnetic materials, and particularly relates to a corrosion-resistant sintered NdFeB permanent magnet, a preparation method thereof, and an application thereof. Background Art

[0002] Sintered NdFeB permanent magnets have excellent magnetic properties and are widely used in permanent magnet motors, microelectronic control, aerospace and other fields. However, the corrosion resistance of sintered NdFeB permanent magnets is poor (sintered NdFeB permanent magnets are composed of the Nd2Fe 14 B main phase and Nd-rich phases located at grain boundaries. As long as there is an aqueous corrosion solution, the Nd-rich phases will corrode rapidly and powder into failure), which greatly restricts the application expansion of sintered NdFeB permanent magnets.

[0003] At present, the corrosion resistance of sintered NdFeB permanent magnets is mainly improved by depositing a protective coating on the surface of the sintered NdFeB permanent magnet (the Nd-rich phase is too active, and the traditional sacrificial anode protection method for steel anti-corrosion is not applicable to sintered NdFeB permanent magnets). For example: 1) electroplating or electroless plating of Zn layer, Ni layer or NiP layer; 2) depositing coatings such as Al layer, ZnAl layer, AlMn layer, etc. by magnetron sputtering; 3) wrapping organic coatings such as epoxy resin layer by spin coating or electrostatic spraying. However, the coatings deposited by electroplating and magnetron sputtering contain hydrophilic pores, and water can penetrate to the substrate through capillary action and cause corrosion. Although the organic coatings formed by spin coating, electrostatic spraying of epoxy resin, etc. can effectively seal the pores and thus obtain a better anti-corrosion effect, the thickness of the organic coatings is generally large, resulting in excessive magnetic loss of the sintered NdFeB permanent magnet, and the organic coatings are usually prone to aging, resulting in a significant reduction in corrosion resistance and not having a long-term stability protection effect.

[0004] Therefore, it is of great significance to develop a sintered NdFeB permanent magnet with both excellent magnetic properties and excellent corrosion resistance. Summary of the Invention

[0005] The purpose of the present invention is to provide a corrosion-resistant sintered NdFeB permanent magnet, a preparation method thereof, and an application thereof.

[0006] The technical solution adopted by the present invention is:

[0007] A corrosion-resistant sintered NdFeB permanent magnet, which comprises a sintered NdFeB permanent magnet and an AlCr coating hydrophobically modified by a silane coupling agent covering the surface of the sintered NdFeB permanent magnet; the composition of the AlCr coating hydrophobically modified by the silane coupling agent includes an AlCr coating and a silane coupling agent crosslinked and coupled on the surface and the inner wall of the pores of the AlCr coating.

[0008] Preferably, the atomic percentage of Al in the AlCr coating is 78% to 82%.

[0009] Preferably, the AlCr coating is composed of an amorphous phase and a microcrystalline phase.

[0010] Preferably, the silane coupling agent is at least one of γ-aminopropyltriethoxysilane (silane coupling agent KH550), γ-aminoethylaminopropyltrimethoxysilane (silane coupling agent KH792), and γ-methacryloxypropyltrimethoxysilane.

[0011] Preferably, the thickness of the silane coupling agent-hydrophobically modified AlCr coating is 3 μm to 4 μm.

[0012] A method for preparing the corrosion-resistant sintered neodymium iron boron permanent magnet as described above includes the following steps:

[0013] 1) Using DC magnetron sputtering or pulsed DC magnetron sputtering, sputter-deposit an Al 80 Cr 20 alloy target on the surface of the sintered neodymium iron boron permanent magnet to form an AlCr coating;

[0014] 2) Immerse the sintered neodymium iron boron permanent magnet treated in step 1) in a silane coupling agent hydrolysis solution for soaking, then take it out for cleaning and drying, and then cure it to form a silane coupling agent-hydrophobically modified AlCr coating, thus obtaining the corrosion-resistant sintered neodymium iron boron permanent magnet.

[0015] Preferably, the sputter deposition in step 1) is carried out under the condition that the temperature is 180°C to 220°C.

[0016] Preferably, the mass percentage content of the silane coupling agent in the silane coupling agent hydrolysis solution in step 2) is 5% to 15%.

[0017] Preferably, the silane coupling agent hydrolysis solution in step 2) is prepared by the following method: Mix the silane coupling agent, water, and ethanol / methanol, and then carry out stirring hydrolysis.

[0018] Preferably, the mass ratio of the silane coupling agent to water is 1:0.3 to 0.5.

[0019] Preferably, the hydrolysis time is 10 h to 15 h.

[0020] Preferably, the soaking time in step 2) is 1 min to 3 min.

[0021] Preferably, the curing in step 2) is carried out under the condition that the temperature is 120°C to 180°C, and the curing time is 30 min to 60 min.

[0022] Application of a corrosion-resistant sintered NdFeB permanent magnet as described above in the fields of permanent magnet motors, microelectronic control, or aerospace

[0023] The beneficial effects of the present invention are as follows: The surface of the corrosion-resistant sintered NdFeB permanent magnet of the present invention is covered with an AlCr coating hydrophobically modified with a silane coupling agent, which has both excellent magnetic properties and excellent corrosion resistance, and its preparation method is simple, having a very broad application prospect.

[0024] Specifically:

[0025] The surface of the corrosion-resistant sintered NdFeB permanent magnet of the present invention is covered with an AlCr coating hydrophobically modified with a silane coupling agent. The AlCr coating has a high hardness, good anti-scratch performance, stable performance, and a small thickness. At the same time, the silanol groups formed by the hydrolysis of the silane coupling agent can form a firm cross-linking coupling on the surface and the inner wall of the pores of the AlCr coating, filling and blocking the pores of the AlCr coating, significantly reducing the capillary penetration of the aqueous corrosion liquid. The synergistic effect of the AlCr coating and the silane coupling agent endows the sintered NdFeB permanent magnet with excellent corrosion resistance without affecting its magnetic properties. Description of the Drawings

[0026] Figure 1 SEM image of the AlCr coating hydrophobically modified with a silane coupling agent on the surface of the corrosion-resistant sintered NdFeB permanent magnet of Example 1.

[0027] Figure 2 XRD pattern of the AlCr coating hydrophobically modified with a silane coupling agent on the surface of the corrosion-resistant sintered NdFeB permanent magnet of Example 1.

[0028] Figure 3 Polarization curve of the corrosion-resistant sintered NdFeB permanent magnet of Example 1 in a 3.5% mass fraction NaCl solution. Detailed Embodiments

[0029] The following combines specific examples to further explain and illustrate the present invention.

[0030] Example 1:

[0031] A corrosion-resistant sintered NdFeB permanent magnet, and its preparation method is as follows:

[0032] 1) Mechanically grind and polish the sintered NdFeB permanent magnet to a mirror surface, then ultrasonically clean it with acetone and absolute ethanol for 10 minutes each, dry it, and then place it on the sample stage in a DC magnetron sputtering system. Then place Al 80 Cr 20The alloy target (target specification: Φ60mm×3mm) is installed on the corresponding target station of the DC magnetron sputtering system, and the distance between the target and the sintered NdFeB permanent magnet is adjusted to 80mm. Then, the sample heating system is turned on to heat the sintered NdFeB permanent magnet to 200°C. Next, the DC magnetron sputtering system is started for DC magnetron sputtering deposition. The sputtering power is 200W, and the deposition time is 2h. Then, the DC magnetron sputtering system is turned off, and the sintered NdFeB permanent magnet is taken out after cooling with the chamber to below 100°C to form an AlCr coating (atomic percentage of Al is 79.27%);

[0033] 2) 2.5g of silane coupling agent KH550, 1.0g of deionized water and 21.5g of absolute ethanol are mixed and magnetically stirred for 12h to prepare a silane coupling agent hydrolysis solution. Then, the sintered NdFeB permanent magnet treated in step 1) is immersed in the silane coupling agent hydrolysis solution for 2min. Next, the sintered NdFeB permanent magnet is taken out and its surface is rinsed with absolute ethanol, and left standing for 15min to volatilize the residual ethanol on the surface. Then, it is placed in a drying oven and cured at 120°C for 60min to form a silane coupling agent hydrophobically modified AlCr coating (thickness is 3.5μm), and a corrosion-resistant sintered NdFeB permanent magnet is obtained.

[0034] Performance test:

[0035] 1) The scanning electron microscope (SEM) image of the silane coupling agent hydrophobically modified AlCr coating on the surface of the corrosion-resistant sintered NdFeB permanent magnet in this example is as Figure 1 shown.

[0036] It can be seen from Figure 1 that: the silane coupling agent hydrophobically modified AlCr coating on the surface of the corrosion-resistant sintered NdFeB permanent magnet is dense, without visible pores and cracks.

[0037] 2) The X-ray diffraction (XRD) image of the silane coupling agent hydrophobically modified AlCr coating on the surface of the corrosion-resistant sintered NdFeB permanent magnet in this example is as Figure 2 shown.

[0038] It can be seen from Figure 2 that: the silane coupling agent hydrophobically modified AlCr coating on the surface of the corrosion-resistant sintered NdFeB permanent magnet is composed of amorphous phase and microcrystalline phase.

[0039] 3) The polarization curve of the corrosion-resistant sintered NdFeB permanent magnet (denoted as Al 80 Cr 20 -KH550) in a 3.5% mass fraction NaCl solution is as Figure 3(The sintered NdFeB permanent magnet without any treatment, the sintered NdFeB permanent magnet with an AlCr coating on its surface, and the sintered NdFeB permanent magnet hydrophobically modified with a silane coupling agent on its surface were used as controls, and were denoted as NdFeB, Al 80 Cr 20 and KH550, respectively, as shown.)

[0040] Note:

[0041] The preparation method of the sintered NdFeB permanent magnet hydrophobically modified with a silane coupling agent on its surface is as follows: Immerse the sintered NdFeB permanent magnet in the silane coupling agent hydrolysis solution (the same as in Example 1) for 2 minutes, then take out the sintered NdFeB permanent magnet and rinse its surface with absolute ethanol, and let it stand for 15 minutes to volatilize the residual ethanol on the surface, obtaining the sintered NdFeB permanent magnet hydrophobically modified with a silane coupling agent on its surface.)

[0042] It can be seen from Figure 3 that: The corrosion current density of the corrosion-resistant sintered NdFeB permanent magnet is only 2.10×10 -8 A / cm 2 , which is two orders of magnitude lower than that of the sintered NdFeB permanent magnet with an AlCr coating on its surface and the sintered NdFeB permanent magnet hydrophobically modified with a silane coupling agent on its surface, indicating its excellent corrosion resistance.)

[0043] Example 2:

[0044] A corrosion-resistant sintered NdFeB permanent magnet, and its preparation method is as follows:

[0045] 1) Mechanically grind and polish the sintered NdFeB permanent magnet to a mirror surface, then ultrasonically clean it with acetone and absolute ethanol for 10 minutes each, dry it, then place it on the sample stage in the DC magnetron sputtering system, and then install the Al 80 Cr 20 alloy target (the target specification is Φ60mm×3mm) on the corresponding target station of the DC magnetron sputtering system, adjust the distance between the target and the sintered NdFeB permanent magnet to 80mm, then turn on the sample heating system to heat the sintered NdFeB permanent magnet to 200°C, then start the DC magnetron sputtering system for DC magnetron sputtering deposition, the sputtering power is 200W, the deposition time is 2h, then turn off the DC magnetron sputtering system and take out the sintered NdFeB permanent magnet after it cools to below 100°C with the chamber, forming an AlCr coating (the atomic percentage of Al is 79.27%);

[0046] 2) Mix 1.25 g of silane coupling agent KH-550, 0.5 g of deionized water and 23.25 g of absolute ethanol, and magnetically stir for 12 h to prepare a silane coupling agent hydrolysis solution. Then immerse the sintered NdFeB permanent magnet treated in step 1) in the silane coupling agent hydrolysis solution for 2 min, take out the sintered NdFeB permanent magnet, rinse the surface with absolute ethanol, and let it stand for 15 min to volatilize the residual ethanol on the surface. Then place it in a drying oven and cure at 180 °C for 30 min to form a silane coupling agent hydrophobic modified AlCr coating (thickness: 3.6 μm), obtaining a corrosion-resistant sintered NdFeB permanent magnet.

[0047] Tested (the test method is the same as that in Example 1), the microstructure of the silane coupling agent hydrophobic modified AlCr coating on the surface of the corrosion-resistant sintered NdFeB permanent magnet in this example is highly similar to that of the silane coupling agent hydrophobic modified AlCr coating on the surface of the corrosion-resistant sintered NdFeB permanent magnet in Example 1.

[0048] Tested (the test method is the same as that in Example 1), the corrosion current density of the corrosion-resistant sintered NdFeB permanent magnet in this example is only 2.62×10 -8 A / cm 2 , having excellent corrosion resistance.

[0049] Example 3:

[0050] A corrosion-resistant sintered NdFeB permanent magnet, and its preparation method is as follows:

[0051] 1) Mechanically grind and polish the sintered NdFeB permanent magnet to a mirror surface, then ultrasonically clean it with acetone and absolute ethanol for 10 min each, dry it, and then place it on the sample stage in a DC magnetron sputtering system. Then install the Al 80 Cr 20 alloy target (target specification: Φ60 mm × 3 mm) on the corresponding target station of the DC magnetron sputtering system, adjust the distance between the target and the sintered NdFeB permanent magnet to 80 mm, then turn on the sample heating system to heat the sintered NdFeB permanent magnet to 200 °C, and then start the DC magnetron sputtering system for DC magnetron sputtering deposition. The sputtering power is 200 W, and the deposition time is 2 h. Then turn off the DC magnetron sputtering system and take out the sintered NdFeB permanent magnet after it cools to below 100 °C with the chamber to form an AlCr coating (atomic percentage of Al: 79.27%);

[0052] 2) Mix 3.75 g of silane coupling agent KH-550, 1.5 g of deionized water and 19.75 g of absolute ethanol, and magnetically stir for 12 h to prepare a silane coupling agent hydrolysis solution. Then immerse the sintered NdFeB permanent magnet treated in step 1) into the silane coupling agent hydrolysis solution for 2 min, take out the sintered NdFeB permanent magnet, rinse the surface with absolute ethanol, let it stand for 15 min to volatilize the residual ethanol on the surface, and then place it in a drying oven to cure at 120 °C for 60 min to form an AlCr coating (with a thickness of 3.4 μm) hydrophobically modified by the silane coupling agent, and obtain a corrosion-resistant sintered NdFeB permanent magnet.

[0053] Tested (the test method is the same as that in Example 1), the microstructure of the AlCr coating hydrophobically modified by the silane coupling agent on the surface of the corrosion-resistant sintered NdFeB permanent magnet in this example is highly similar to that of the AlCr coating hydrophobically modified by the silane coupling agent on the surface of the corrosion-resistant sintered NdFeB permanent magnet in Example 1.

[0054] Tested (the test method is the same as that in Example 1), the corrosion current density of the corrosion-resistant sintered NdFeB permanent magnet in this example is only 3.01×10 -8 A / cm 2 , and it has excellent corrosion resistance.

[0055] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A corrosion-resistant sintered NdFeB permanent magnet, characterized in that, It comprises a sintered neodymium iron boron permanent magnet and an AlCr coating hydrophobically modified with a silane coupling agent covering the surface of the sintered neodymium iron boron permanent magnet; The composition of the AlCr coating hydrophobically modified with the silane coupling agent comprises an AlCr coating and a silane coupling agent crosslinked and coupled on the surface and the inner wall of the pores of the AlCr coating.

2. The corrosion-resistant sintered Nd-Fe-B permanent magnet according to claim 1, wherein: The atomic percentage of Al in the AlCr coating is 78% - 82%.

3. The corrosion-resistant sintered neodymium iron boron permanent magnet according to claim 1 or 2, characterized in that: The AlCr coating is composed of an amorphous phase and a microcrystalline phase.

4. The corrosion-resistant sintered NdFeB permanent magnet according to claim 1 or 2, characterized in that: The silane coupling agent is at least one of γ-aminopropyltriethoxysilane, γ-aminoethylaminopropyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane.

5. The corrosion-resistant sintered neodymium-iron-boron permanent magnet according to claim 1 or 2, wherein: The thickness of the AlCr coating hydrophobically modified with the silane coupling agent is 3μm - 4μm.

6. A method for preparing a corrosion-resistant sintered neodymium iron boron permanent magnet according to any one of claims 1 to 5, characterized in that, It includes the following steps: 1) The AlCr alloy target is sputter-deposited on the surface of the sintered neodymium-iron-boron permanent magnet by DC magnetron sputtering or pulsed DC magnetron sputtering to form an AlCr coating; 80 Cr 20 The AlCr alloy target is sputter-deposited on the surface of the sintered neodymium-iron-boron permanent magnet by DC magnetron sputtering or pulsed DC magnetron sputtering to form an AlCr coating; 2) Immerse the sintered neodymium iron boron permanent magnet treated in step 1) in a silane coupling agent hydrolysis solution for soaking, then take it out for cleaning and drying, and then cure it to form an AlCr coating hydrophobically modified with a silane coupling agent, thus obtaining a corrosion-resistant sintered neodymium iron boron permanent magnet.

7. The preparation method according to claim 6, characterized in that: The sputtering deposition in step 1) is carried out under the condition that the temperature is 180°C - 220°C.

8. The preparation method according to claim 6, characterized in that: The soaking time in step 2) is 1min - 3min.

9. The preparation method according to claim 6 or 8, characterized in that: The curing in step 2) is carried out under the condition that the temperature is 120°C - 180°C, and the curing time is 30min - 60min.

10. Application of a corrosion-resistant sintered neodymium iron boron permanent magnet as described in any one of claims 1 - 5 in the field of permanent magnet motors, the field of microelectronic control, or the field of aerospace.

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