A nickel coating electrodeposited on the surface of sintered neodymium-iron-boron by regulating a magnetic field

Abstract

The application discloses a nickel plating layer on the surface of sintered neodymium-iron-boron by electrodepositing under the regulation of a magnetic field, relates to the technical field of electrodepositing nickel on sintered neodymium-iron-boron, and aims at better utilizing the magnetic field to help electrodepositing and improving performance; the preparation method of the nickel plating layer is directly electrodepositing pure nickel anodes and sintered neodymium-iron-boron cathodes in a magnetic field; the nickel plating layer is in the form of pyramidal dense distribution on the surface of sintered neodymium-iron-boron, and the bottom surface of the pyramid faces the surface of sintered neodymium-iron-boron; when the magnetic field intensity is 0.07T and the magnetic field direction is B||I, the obtained nickel plating layer has the best compactness, and the corrosion resistance and temperature resistance are also the most excellent; the application has the advantages of simple process, easy control, fast speed, low cost, environmental protection, and the ability of stably obtaining the nickel plating layer with more excellent compactness, corrosion resistance and temperature resistance on the surface of sintered neodymium-iron-boron.

Description

Technical Field

[0001] This invention relates to the field of sintered NdFeB electrodeposition nickel plating technology, specifically to a nickel plating layer electrodeposited on the surface of sintered NdFeB by controlling a magnetic field. Background Technology

[0002] As a third-generation permanent magnet material, NdFeB has gradually developed into a magnetic material with a wide range of applications, rapid development speed, and excellent comprehensive performance. It has been widely used in new energy vehicles, energy-saving home appliances, consumer electronics, clean energy and other fields, and has broad application prospects. However, due to its poor stability and corrosion resistance, its practical application is limited.

[0003] In recent years, many researchers have expanded the application fields of electrodeposition by preparing protective layers on NdFeB surfaces, leveraging its advantages of simplicity, ease of operation, low cost, high controllability, and the ability to prepare various types of films. With the development of magnetoelectric technology, magnetic field electrodeposition technology has attracted increasing attention. Introducing a magnetic field into electrodeposition, utilizing its interaction with the electric field and metal ions to induce magnetohydrodynamic (MHD) and magnetization effects, can effectively improve problems such as surface roughness and slow deposition rates, providing the necessary conditions for preparing high-performance coatings. However, currently, the method of electrodepositing nickel coatings on sintered NdFeB surfaces using magnetic fields remains at a basic level of simple synergistic effects. There is a lack of research on how to further optimize the density, corrosion resistance, and heat resistance of nickel coatings by controlling the magnetic field, which undoubtedly represents a significant waste of the synergistic effect of the magnetic field. Therefore, there is an urgent need for a method to solve this problem by electrodepositing nickel coatings on sintered NdFeB surfaces using controlled magnetic fields. Summary of the Invention

[0004] The purpose of this invention is to provide a nickel plating layer electrodeposited on the surface of sintered NdFeB by controlling the magnetic field, so as to better utilize the magnetic field to help improve the performance of electrodeposition.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a nickel plating layer electrodeposited on the surface of sintered NdFeB by controlling a magnetic field. The nickel plating layer is prepared by directly electrodepositing a pure nickel anode and a sintered NdFeB cathode in a magnetic field. The nickel plating layer is densely distributed in a pyramidal shape on the surface of the sintered NdFeB, with the base of the pyramid facing the surface of the sintered NdFeB.

[0006] Preferably, the surfaces between adjacent edges of the pyramid are convex arc surfaces or planes, and the maximum length of the base of the pyramid is less than 3 μm.

[0007] Preferably, the magnetic field strength is 0.035 to 0.2T, the anode and cathode are parallel plates, the current I is perpendicular to the plane of the anode and cathode plates, and the magnetic field direction is B⊥I or B∥I.

[0008] Preferably, the electrodeposition of the nickel plating is carried out in a mixed solution of nickel sulfate, nickel chloride, boric acid and sodium dodecylbenzenesulfonate.

[0009] Preferably, the nickel sulfate solution concentration is 340 g / L, the nickel chloride solution concentration is 45 g / L, the boric acid solution concentration is 45 g / L, and the sodium dodecylbenzenesulfonate solution concentration is 0.1 g / L.

[0010] Preferably, the electrodeposition conditions for the nickel plating are: a constant temperature of 50°C and a current density of 4 A / dm³. 2 Electrodeposition was performed for 1 minute, followed immediately by adjusting the current density to 2.5 A / dm². 2 And deposit for 30 minutes.

[0011] Preferably, the magnetic field strength is 0.07T and the magnetic field direction is B∥I.

[0012] Preferably, in the method for preparing the nickel plating layer, the sintered NdFeB cathode is subjected to pretreatment of degreasing, derusting, and activation in sequence before electrodeposition. The degreasing solution is a solution obtained by dissolving sodium hydroxide, sodium phosphate, sodium carbonate, and OP emulsifier in deionized water in sequence. The derusting solution is prepared by diluting nitric acid, and the activation solution is prepared by diluting hydrochloric acid.

[0013] Another technical solution provided by the present invention: the application of the above-mentioned nickel plating layer in the surface treatment of sintered NdFeB materials.

[0014] Preferably, the nickel plating layer is used to improve the density, corrosion resistance and temperature resistance of the plating layer.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] 1. The process of electrodepositing nickel on the surface of sintered NdFeB by controlling the magnetic field is based on the original electrodeposition process and only requires the addition of a spatial magnetic field. It does not require complex equipment, special templates, or cumbersome steps. The process is simple, easy to control, fast, low in cost and environmentally friendly. It can stably obtain a high-performance nickel coating on the surface of sintered NdFeB.

[0017] 2. The method of preparing a nickel plating layer by electrodepositing on the surface of sintered NdFeB by regulating the magnetic field involves adjusting the temperature, time, current density, and electrolyte concentration of the electrodeposition reaction, thereby improving the density, corrosion resistance, and temperature resistance of the plating layer, and directly or indirectly ensuring the magnetic properties of sintered NdFeB.

[0018] 3. By controlling the magnetic field to electrodeposit a nickel layer on the surface of sintered NdFeB, the sintered NdFeB can obtain better protective performance.

[0019] 4. The nickel plating electrodeposited on the surface of sintered NdFeB by controlling the magnetic field can be easily modified and put into production by existing production units because it only requires ordinary electrodeposition equipment and magnetic field assistance, and is easy to apply and improve. Attached Figure Description

[0020] Figure 1 a and 1b are SEM images of the nickel plating on the surface of the sintered NdFeB in Example 1;

[0021] Figure 2 This is a Tafel polarization curve of the nickel plating on the surface of the sintered NdFeB in Example 1;

[0022] Figure 3 a1 and 3a2 are SEM images of the nickel plating on the surface of the sintered NdFeB in the comparative examples.

[0023] Figure 3 b1 and 3b2 are SEM images of the nickel plating on the surface of the sintered NdFeB in Example 2;

[0024] Figure 3 c1 and 3c2 are SEM images of the nickel plating on the surface of the sintered NdFeB in Example 3;

[0025] Figure 3 d1 and 3d2 are SEM images of the nickel plating on the surface of the sintered NdFeB in Example 1;

[0026] Figure 3 e1 and 3e2 are SEM images of the nickel plating on the surface of the sintered NdFeB in Example 4;

[0027] Figure 4 a is an XRD image of the nickel plating on the surface of sintered NdFeB in Examples 2, 3 and the comparative example;

[0028] Figure 4 b is an XRD image of the nickel plating on the surface of sintered NdFeB in Examples 1, 4 and the comparative example;

[0029] Figure 5 Figure a shows the test results of the temperature resistance of the nickel plating on the surface of sintered NdFeB in Examples 2, 3 and the comparative example;

[0030] Figure 5 b is a graph showing the test results of the temperature resistance of the nickel plating on the surface of sintered NdFeB in Examples 1, 4 and the comparative example;

[0031] Figure 6 a is the Tafel polarization curve of the nickel plating on the surface of sintered NdFeB in Examples 2, 3 and the comparative example;

[0032] Figure 6b is the Tafel polarization curve of the nickel plating on the surface of sintered NdFeB in Examples 1, 4 and the comparative example;

[0033] Figure 2 and Figure 6 The Initial sample is a blank sintered NdFeB sample without nickel plating. Detailed Implementation

[0034] Through theoretical analysis and conceptualization, the inventors conducted numerous experiments based on the proposed design. By applying a random spatial magnetic field, they adjusted the composition and concentration of the plating solution, and compared parameters such as electrodeposition temperature, current density, and time. After determining a method capable of forming a relatively uniform nickel plating layer of a specific shape, they continued to explore further using these optimized parameters. The parameters can be referenced in the following comparative examples:

[0035] Comparative example:

[0036] Prepare an electroplating solution in a 500mL beaker. The solution composition is: 340g / L nickel sulfate hexahydrate, 45g / L nickel chloride hexahydrate, 45g / L boric acid, and 0.1g / L SDBS. Prepare a degreasing solution by dissolving 0.5g sodium hydroxide, 7.5g sodium phosphate, 5g sodium carbonate, and 0.05g OP emulsifier in 100mL of deionized water. Prepare a rust removal solution with 40mL / L nitric acid. Prepare an activation solution with 30mL / L hydrochloric acid.

[0037] Then, the NdFeB sample at the cathode underwent pretreatment including degreasing, derusting, and activation to remove grease and impurities from the sample surface. A pure nickel plate was used as the anode, and the anode and cathode were connected to the positive and negative terminals of a DC power supply via wires, respectively. The current was controlled to be constant at 4 A / dm² at 50°C. 2 Electrodeposition was performed for 1 minute, followed immediately by adjustment to 2.5 A / dm. 2 A Ni coating was obtained by deposition for 30 minutes and then dried at 60°C.

[0038] Based on the above, the inventors also conducted a large number of experiments, applying magnetic fields of different intensities and directions within the electrodeposition space. They found that when the magnetic field strength was 0.035 to 0.2T, the anode and cathode were parallel plates, the current I was perpendicular to the plane of the anode and cathode plates, and the magnetic field direction was B⊥I or B∥I, the performance of the nickel plating was better. The following are some preferred embodiments based on these experimental results.

[0039] Example 1:

[0040] A parallel (B∥I) magnetic field with a magnetic field strength of 0.07T was applied in the electrodeposition space to prepare a Ni coating on the NdFeB surface by electrodeposition. The electrodeposition was carried out in a magnetic field, and the rest of the process was the same as that of the comparative example.

[0041] Figure 1 This is a SEM image of the Ni coating on the sample surface prepared in this embodiment. As can be seen from the image, the Ni coating is pyramidal in shape, with almost all sides being convex arc surfaces and the base size being less than 3 μm. It also exhibits a uniform and dense morphology. This convex pyramid has excellent mechanical strength. In addition, for the same amount of nickel coating, its surface area is smaller than that of conventional needle-shaped or needle-conical nickel coatings, and the adjacent monomers are more tightly connected. From the surface condition, it possesses promising performance.

[0042] Figure 2 The corrosion resistance performance of the blank, comparative example, and this embodiment was compared. The specific test method is as follows: In a 3.5 wt% NaCl solution, using an electrochemical workstation in a standard three-electrode system, the sample was used as the working electrode, and a platinum electrode and a saturated calomel electrode were used as the counter and reference electrodes, respectively, to conduct corrosion resistance performance tests. The Tafel polarization curves show that it exhibits excellent corrosion resistance at a magnetic field strength of 0.07 T (B∥I), with a corrosion current (I0.07). corr =8.305×10 -7 A·cm -2 The corrosion potential (E) decreases. corr (-0.193V) positive shift.

[0043] Figure 4 Figure b includes XRD images of the nickel plating on the sample surface of the comparative example and this embodiment. The substrate peak of the comparative example is obvious, while the substrate peak of this embodiment almost disappears completely, indicating that the density of the nickel plating is effectively improved.

[0044] Figure 5 Section b includes the temperature resistance test results of the nickel plating in the comparative example and the present embodiment, which were conducted under the same conditions. The left side is the comparative example, and the middle side is the present embodiment. Obviously, the irreversible magnetic loss of the present embodiment is greatly reduced, and it has excellent temperature resistance.

[0045] Example 2

[0046] A magnetic field perpendicular to (B⊥I) and with a magnetic field strength of 0.07T was applied in the electrodeposition space to prepare a Ni coating on the NdFeB surface by electrodeposition. The electrodeposition was carried out in a magnetic field, and the rest of the process was the same as that of the comparative example.

[0047] Example 3

[0048] A magnetic field perpendicular to (B⊥I) and with a magnetic field strength of 0.1T was applied in the electrodeposition space to prepare a Ni coating on the NdFeB surface by electrodeposition. The electrodeposition was carried out in a magnetic field, and the rest of the process was the same as that of the comparative example.

[0049] Example 4

[0050] A parallel (B∥I) magnetic field with a magnetic field strength of 0.1T was applied in the electrodeposition space to prepare a Ni coating on the NdFeB surface by electrodeposition. The electrodeposition was carried out in a magnetic field, and the rest of the process was the same as that of the comparative example.

[0051] from Figure 3 As can be seen, when a parallel or perpendicular magnetic field is applied for electrodeposition, the shape of the Ni coating changes from the original needle-like shape to a pyramidal shape, especially when the magnetic field strength is 0.07T(B∥I), it exhibits the most uniform and dense morphology.

[0052] Figure 4 The XRD patterns of the Ni coatings on the sample surfaces prepared in the four examples and comparative examples are shown. It was found that the peaks on the substrate either disappeared or decreased significantly after the application of a magnetic field in the four examples, indicating that the density of the nickel layer deposited by magnetic field electrodeposition using the method of the present invention is improved.

[0053] See Figure 5 All four embodiments exhibited smaller irreversible magnetic losses compared to the comparative examples, and the smallest irreversible magnetic losses at a magnetic field strength of 0.07T(B∥I), demonstrating excellent temperature resistance.

[0054] Figure 2 The corrosion resistance performance of the blank, comparative example, and four embodiments was compared. The specific testing method is as follows: In a 3.5 wt% NaCl solution, using an electrochemical workstation in a standard three-electrode system, the NdFeB sample was used as the working electrode, and a platinum electrode and a saturated calomel electrode were used as the counter and reference electrodes, respectively. The Tafel polarization curves show that the corrosion current decreased and the corrosion potential shifted positively in all four embodiments; clearly, the best corrosion resistance performance was observed at a magnetic field of 0.07 T (B∥I).

[0055] The magnetic field in this invention can be obtained in any way, such as an electromagnetic field, a permanent magnet, or a common magnet. However, in order to save long-term costs in mass production, it is preferable to use a permanent magnet.

[0056] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

[0057] Any aspects of this invention not described in detail are well-known to those skilled in the art.

Claims

1. A nickel plating layer electrodeposited on the surface of sintered NdFeB magnets by controlling a magnetic field, characterized in that: The nickel plating layer is prepared by electrodeposition directly using a pure nickel anode and a sintered NdFeB cathode in a magnetic field; the strength of the magnetic field is 0.035 to 0.2T, the anode and cathode are parallel plates, the current I is perpendicular to the plane of the anode and cathode plates, and the direction of the magnetic field is B⊥I or B∥I; The nickel plating layer is densely distributed in a pyramidal shape on the surface of the sintered NdFeB, with the base of the pyramid facing the surface of the sintered NdFeB.

2. The nickel plating layer electrodeposited on the surface of sintered NdFeB by controlling a magnetic field according to claim 1, characterized in that: The surfaces between adjacent edges of the pyramid are convex arc surfaces or planes, and the maximum length of the base of the pyramid is less than 3 μm.

3. The nickel plating layer electrodeposited on the surface of sintered NdFeB by controlling the magnetic field according to claim 2, characterized in that: The electrodeposition of the nickel plating layer is carried out in a mixed solution of nickel sulfate, nickel chloride, boric acid and sodium dodecylbenzenesulfonate.

4. The nickel plating layer electrodeposited on the surface of sintered NdFeB by controlling a magnetic field according to claim 3, characterized in that: The concentrations of the nickel sulfate solution, nickel chloride solution, boric acid solution, and sodium dodecylbenzenesulfonate solution are 340 g / L, 45 g / L, 45 g / L, and 0.1 g / L, respectively.

5. The nickel plating layer electrodeposited on the surface of sintered NdFeB by controlling a magnetic field according to claim 1, characterized in that: The electrodeposition conditions for the nickel plating were: constant temperature at 50°C and current density of 4 A / dm³. 2 Electrodeposition was performed for 1 minute, followed immediately by adjusting the current density to 2.5 A / dm². 2 And deposit for 30 minutes.

6. The nickel plating layer electrodeposited on the surface of sintered NdFeB by controlling a magnetic field according to claim 1, characterized in that: The magnetic field has a strength of 0.07T and a direction of B∥I.

7. The nickel plating layer electrodeposited on the surface of sintered NdFeB by controlling a magnetic field according to claim 1, characterized in that: In the method for preparing the nickel plating layer, the sintered NdFeB cathode is subjected to pretreatment of degreasing, rust removal and activation in sequence before electrodeposition. The degreasing solution is a solution obtained by dissolving sodium hydroxide, sodium phosphate, sodium carbonate and OP emulsifier in deionized water in sequence. The rust removal solution is prepared by diluting nitric acid and the activation solution is prepared by diluting hydrochloric acid.

8. The application of the nickel plating according to any one of claims 1 to 7 in the surface treatment of sintered NdFeB materials.

9. The application according to claim 8, wherein the nickel plating is used to improve the density, corrosion resistance and temperature resistance of the plating.

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