CN108231322B

CN108231322B - Sintered neodymium-iron-boron magnet deposited with composite film and preparation method thereof

Info

Publication number: CN108231322B
Application number: CN201711408854.3A
Authority: CN
Inventors: 宋振纶; 丁雪峰; 胡方勤; 杨丽景; 姜建军; 郑必长; 武秉晖
Original assignee: Baotou Hidyee Technology Co ltd; Ningbo Institute of Material Technology and Engineering of CAS
Current assignee: Baotou Hidyee Technology Co ltd; Ningbo Institute of Material Technology and Engineering of CAS
Priority date: 2017-12-22
Filing date: 2017-12-22
Publication date: 2020-06-16
Anticipated expiration: 2037-12-22
Also published as: CN108231322A

Abstract

The invention discloses a sintered neodymium-iron-boron magnet deposited with a composite film, which comprises a sintered neodymium-iron-boron magnet and the composite film deposited on the outer surface of the sintered neodymium-iron-boron magnet by a magnetron sputtering method; the element composition of the composite film comprises necessary element Tb and/or Dy and optional element Cu, and the composite film is a co-sputtering mixed film or an alternate mixed film. The invention provides a sintered neodymium-iron-boron magnet deposited with a composite film, the coercive force of the sintered neodymium-iron-boron magnet is obviously improved, and the production cost is obviously reduced.

Description

Sintered neodymium-iron-boron magnet deposited with composite film and preparation method thereof

Technical Field

The invention relates to the technical field of rare earth permanent magnet materials, in particular to a sintered neodymium-iron-boron magnet deposited with a composite film and a preparation method thereof.

Background

The sintered Nd-Fe-B permanent magnet material is increasingly widely applied in the fields of wind power generation, power automobiles and the like, the fields all require the magnet to work stably at high temperature, and the high-temperature stability and the coercive force of the magnet are closely related.

At present, magnetism is improvedThe bulk coercive force method is mostly realized by improving the magnetocrystalline anisotropy field, and the addition of heavy rare earth elements is an effective method for improving the magnetocrystalline anisotropy field of the sintered neodymium iron boron magnet. In general, a certain amount of heavy rare earth elements Dy and Tb are added in the sintering process to replace the main phase Nd of the magnet₂Fe₁₄Nd of B, form (Nd, Dy/Tb)₂Fe₁₄B, its anisotropy field is stronger than Nd₂Fe₁₄Phase B, coercive force is improved. But the modification method has the disadvantages that on one hand, the modification method consumes heavy rare earth with high amount, and heavy rare earth Dy and Tb are expensive and have scarce resources; on the other hand, Dy, Tb and Fe dispersed in the main phase are antiferromagnetically coupled, which results in the reduction of the remanence and the maximum energy product of the magnet, so a new solution is needed.

Many research results show that the grain boundary diffusion treatment technology is a good method for improving the coercive force of the sintered neodymium iron boron. Usually, the heavy rare earth elements or compounds thereof are attached to the surface of the magnet by adopting the modes of coating, sticking, evaporating, sputtering and the like, and then the components of the magnet are regulated and controlled by heat treatment, diffusion and permeation and tempering, the microstructure tissue is optimized, and the coercive force of the magnet is improved.

The magnetron sputtering coating method not only consumes the heavy rare earth elements and has less coercive force, but also obviously improves the coercive force, and the heavy rare earth elements are diffused along the grain boundary of the sintered neodymium iron boron, and a small part of the heavy rare earth elements are diffused into the main phase from the grain boundary, thereby avoiding the reduction of remanence and maximum energy product caused by excessive heavy rare earth elements in the main phase. In addition, the magnetron sputtering coating method also has the following advantages: the binding force with the substrate is good, the film forming speed is stable and controllable, the film thickness is accurately controlled, the activity of the vacuum coating layer is high, the diffusion is easy, and the surface post-treatment of the sample after heat treatment is simple.

However, because the price of heavy rare earth elements is high, finding a method or structure which can greatly reduce the preparation cost under the condition of improving the same coercive force still remains a problem to be solved in the field.

Disclosure of Invention

Aiming at the problems, the invention provides the sintered neodymium-iron-boron magnet deposited with the composite film, the coercive force of the sintered neodymium-iron-boron magnet is obviously improved, and the production cost is obviously reduced.

The specific technical scheme is as follows:

a sintered NdFeB magnet deposited with a composite film comprises a sintered NdFeB magnet and the composite film deposited on the outer surface of the sintered NdFeB magnet through a magnetron sputtering method;

the element composition of the composite film comprises necessary element Tb and/or Dy and optional element Cu, and the composite film is a co-sputtering mixed film or an alternate mixed film.

The composite film deposited on the outer surface of the sintered neodymium-iron-boron magnet comprises two forms:

one is to deposit a mixed film containing different elements at one time by a co-sputtering mode; one method is to prepare a mixed film containing different elements after multiple depositions by an alternate sputtering method.

Preferably, the co-sputtered mixed film has an elemental composition including Tb_x1Cu_1-x1、Dy_x2Cu_1-x2、 Tb_x3Dy_1-x3、Tb_x4Dy_y1Cu_1-(x4+y1)(ii) a The x 1-x 4 and y1 represent the percentage content of atoms, and the x 1-x 4 and the y1 are respectively and independently selected from 0-1; more preferably, x 1-x 4 and y1 are respectively and independently selected from 0.65-0.8; more preferably, the co-sputtered mixed thin film has an elemental composition of Tb_0.8Cu_0.2。

Preferably, the alternately mixed thin film alternately sputters essential element thin films and optional element thin films, and sputters one-time essential element thin films and one-time optional element thin films as an alternate period, the alternate period is at least one, and the content of each element in each alternate period is continuously adjustable, and can be the same or different; further preferably, the alternating period is selected from 1 to 10000.

Preferably, the elemental composition of the alternating mixed thin film includes Tb_x5Cu_1-x5、Dy_x6Cu_1-x6、Tb_x7Dy_y2Cu_1-(x7+y2)(ii) a X 5-x 7 and y2 represent atomic percentage content and are independently selectedFrom 0 to 1; further preferably, the nitrogen-containing organic silicon compound is independently selected from 0.65-0.8; more preferably, the alternating mixed thin film has an element composition of Tb_0.8Cu_0.2。

Further preferably, the alternating mixed film is formed by sputtering a necessary element film and then sputtering an optional element film.

With the composition of sputtering element as Tb_0.8Cu_0.2Experiments show that when the mixed thin film with the same thickness and an alternate period is sputtered, the Tb thin film is firstly sputtered and deposited, and when the Cu thin film is then sputtered and deposited, the improvement effect of the coercive force is better than that of the Tb thin film which is firstly sputtered and deposited and then sputtered and deposited.

Further preferably, the alternating period is at least 4.

Preferably, the thickness of the composite film is 1 to 12 μm.

The invention also discloses a preparation method of the sintered neodymium-iron-boron magnet deposited with the composite film, which comprises the following steps:

1) pretreating a sintered neodymium-iron-boron magnet sample;

2) carrying out ion activation treatment on the pretreated sintered neodymium iron boron magnet sample;

3) depositing a composite film on the outer surface of the sintered neodymium iron boron magnet sample subjected to the ion activation treatment by a magnetron sputtering method;

4) and (3) carrying out thermal diffusion and tempering treatment on the sintered neodymium iron boron magnet sample treated in the step 3).

Preferably, in the step 1), the pretreatment comprises oil removal, acid washing, alcohol ultrasonic treatment and blow drying; the method specifically comprises the following steps: the method comprises the steps of firstly removing oil on the surface of a sintered neodymium iron boron magnet by using oil removing powder, then cleaning the sintered neodymium iron boron magnet by using a nitric acid solution with the dilution concentration of 3-5 vol%, finally ultrasonically cleaning the magnet by using deionized water and absolute ethyl alcohol, removing impurities attached to the surface, and blow-drying by using a blower for later use.

Preferably, in the step 2), the pretreated sintered neodymium iron boron magnet sample is placed in a magnetron sputtering vacuum chamber, and the vacuum chamber is vacuumized to 5 × 10^-3～5×10^-4Pa, then filling high-purity argon (the purity is more than or equal to 9)9.999%) was subjected to ion activation treatment.

The ion activation treatment process comprises the following steps: ionizing high purity Ar to Ar in a vacuum chamber using an ion source⁺Applying negative bias to attract high-energy Ar on a sintered NdFeB magnet sample⁺Bombarding the surface of the sample, and further removing impurities and an oxide layer to generate a clean surface. Preferably, the working parameters of the ion source are vacuum degree of 0.2-0.6 Pa, anode voltage of 100-200V, anode current of 0.5-1.5A, negative bias of 200-400V and activation time of 20-40 min.

Preferably, in step 3), the target material for magnetron sputtering includes a Dy target material, a Tb target material, a Cu target material, a TbCu alloy target material, a DyCu alloy target material and a TbDyCu alloy target material; the working pressure is 0.1-3 Pa, and the target power density is 1-7W/cm²。

When co-sputtering mixed films are deposited, two sputtering methods can be adopted:

one is to open the metal target material of the element to be deposited at the same time, adjust the angle between the targets, make the glow overlap, control the power of the target separately, prepare the mixed film with continuously changing content; taking the preparation of TbCu co-sputtering mixed film as an example, Tb target and Cu target are simultaneously started for deposition.

The other is to directly start the alloy target containing the element to be deposited, and the components of the deposited film are different along with the difference of the components of the target; taking the preparation of the TbCu co-sputtering mixed film as an example, only the TbCu alloy target needs to be started for deposition.

When the alternate mixed film is deposited, the metal target material of the element to be deposited is started simultaneously, so that the sample passes below each target in sequence, and the time for stopping the sample below each target is controlled, namely the thickness of each element film can be controlled; the alternation times can be controlled by controlling the times of the sample passing through the target; periodically reversed films can be prepared by changing the direction of sample transport. Here, the periodicity refers to the order of depositing the essential element film and the optional element film.

And 4), performing high-temperature thermal diffusion and tempering treatment on the sintered neodymium iron boron magnet deposited with the heavy rare earth composite film. Preferably, the temperature of the thermal diffusion is 800-1000 ℃, and the heat preservation time is 1-40 h; the temperature of the tempering treatment is 400-600 ℃, and the heat preservation time is 1-5 h.

Compared with the prior art, the invention has the following advantages:

1. the method for preparing the film is flexible and simple, the content control of each element of the prepared magnetron sputtering mixed heavy rare earth film is simple and convenient, and the composition of the film has various changes; the diffusion depth and the diffusion percentage of various elements are synchronously analyzed, the improvement degree of the coercive force is tested, and the method has important significance for optimizing the components of the film and reducing the consumption of the valuable rare earth Tb.

2. The method for preparing the heavy rare earth alternating multilayer film by adopting the magnetron sputtering method can be one period or a plurality of periods. And the content of each element is continuously adjustable in one period. The arrangement order, the periodic rule and the diffusion depth of two elements penetrating into the magnet are detected, and the diffusion order and the diffusion difficulty degree of various heavy rare earth elements can be obtained.

3. The heavy rare earth film prepared by the magnetron sputtering method has the advantages of good film substrate binding force, high coating activity, easy diffusion, small heavy rare earth consumption and resource saving.

4. Compared with the traditional process, the method has the advantages that only little low-binding-force powder is remained on the surface of the magnet after the grain boundary diffusion, the subsequent treatment is simple, and the magnet can be used only by one-step simple cleaning or grinding and polishing.

Drawings

Fig. 1 is a schematic structural diagram of a sintered ndfeb magnet with a deposited composite thin film prepared in example 1 (upper diagram) and example 2 (lower diagram), respectively;

fig. 2 is a schematic structural diagram of a sintered ndfeb magnet with a deposited composite thin film prepared in example 3 (upper diagram) and example 4 (lower diagram), respectively;

fig. 3 is a schematic structural diagram of sintered ndfeb magnets deposited with composite films, prepared in example 5 (upper diagram) and example 6 (lower diagram), respectively;

FIG. 4 is a schematic structural diagram of a sintered NdFeB magnet deposited with a composite thin film prepared in example 7;

fig. 5 is a schematic structural view of a sintered ndfeb magnet deposited with a composite film prepared in example 10; FIG. 6 is a schematic structural view of a sintered NdFeB magnet deposited with a composite thin film prepared in example 11; fig. 7 is a schematic structural view of the sintered ndfeb magnet deposited with the composite thin film prepared in example 12.

Detailed Description

The method comprises the steps of depositing a heavy rare earth element film on the surface of a sintered neodymium iron boron magnet by using a magnetron sputtering method, taking a heavy rare earth layer as a diffusion source, carrying out high-temperature heat treatment diffusion on the heavy rare earth element, enabling the heavy rare earth element to enter the interior of the magnet along a main phase grain boundary, replacing atoms on the edge layer of the main phase grain with a part of the heavy rare earth element, forming a magnetic hardening layer, and improving the coercive force of the magnet.

The present invention is further illustrated by the following examples, which are provided for the purpose of illustration only and are not intended to be limiting.

Example 1

Carrying out oil removal, rust removal and blow-drying treatment on the sintered neodymium iron boron magnet with the size of phi 10mm multiplied by 3mm, which specifically comprises the following steps: the method comprises the steps of firstly removing oil on the surface of a sintered neodymium iron boron magnet by using oil removing powder, then cleaning the sintered neodymium iron boron magnet by using a nitric acid solution with the dilution concentration of 3-5 vol%, finally ultrasonically cleaning the magnet by using deionized water and absolute ethyl alcohol, removing impurities attached to the surface, and blow-drying by using a blower for later use.

The vacuum degree of the vacuum chamber is pumped to 1 x 10^-3Pa, then filling high-purity Ar (the purity is more than or equal to 99.999%) into the vacuum chamber, and carrying out ion activation sample treatment.

The ion activation process comprises ionizing high-purity Ar into Ar by adopting an ion source in a vacuum chamber⁺Applying negative bias voltage to the sintered Nd-Fe-B magnet sample to attract high-energy Ar⁺Bombarding the surface of the sample, and further removing impurities and an oxide layer to generate a clean surface.

The working parameters of the ion source are vacuum degree of 0.4Pa, anode voltage of 150V, anode current of 1A, negative bias of 300V and activation time of 30 min.

The heavy rare earth film is prepared by adopting a magnetron sputtering method, a pure Dy target material, a pure Tb target material, a pure Cu target material, a TbCu alloy target material, a DyCu alloy target material and a TbDyCu alloy target material are arranged in a vacuum chamber, the working air pressure is 0.3Pa, and the heavy rare earth films with different thicknesses and different compositions can be obtained by opening different target materials and controlling the film coating time.

In this embodiment, only the pure Tb target is turned on, and the coating time is controlled to obtain a pure Tb film with a film thickness of 2 μm.

And then carrying out high-temperature thermal diffusion and tempering treatment on the sintered neodymium-iron-boron magnet deposited with the heavy rare earth film. The high-temperature thermal diffusion temperature is 950 ℃, and the heat preservation time is 20 hours; the tempering temperature is 450 ℃, and the heat preservation time is 4 hours.

Example 2

The preparation process is the same as that in example 1, except that only the pure Dy target material is opened during the deposition of the heavy rare earth film, and the film coating time is controlled to obtain the pure Dy film with the film thickness of 2 μm.

Example 3

The preparation process is the same as that in the example 1, and the difference is only that when the heavy rare earth film is deposited, the Dy target and the Tb target are simultaneously opened, the angle between the targets is adjusted, the targets are overlapped in glow, the power of the targets is controlled, and the Dy/Tb co-sputtering mixed film with the thickness of 2 mu m is prepared.

Example 4

The preparation process is the same as that in the example 1, and the difference is only that when the heavy rare earth film is deposited, the Dy target and the Cu target are simultaneously opened, the angle between the targets is adjusted, the targets are overlapped in glow, the power of the targets is controlled, and the Dy/Cu co-sputtering mixed film with the thickness of 2 mu m is prepared.

Example 5

The preparation process is the same as that in the embodiment 1, and the difference is only that when the heavy rare earth film is deposited, the TbCu alloy target material is started, and the coating time is controlled to obtain Tb with the film thickness of 2 mu m_0.8Cu_0.2Co-sputtering the mixed film.

Example 6

The preparation process is the same as that in the example 1, and the difference is only that when the heavy rare earth film is deposited, a TbDyCu alloy target is started, and the film coating time is controlled to obtain the Tb/Dy/Cu co-sputtering mixed film with the film thickness of 2 mu m.

Examples 7 to 9

The preparation process is the same as that in the embodiment 1, and the difference is only that when the heavy rare earth film is deposited, the sample sequentially passes through the lower parts of the opened Tb target material and the Cu target material, the time of stopping the sample under each target is controlled, the thickness of each film is controlled, and the multi-period alternating film can be prepared by controlling the times of passing the sample under the target.

Tb in examples 7 to 9, each having a film thickness of 2 μm_0.8Cu_0.2The films were mixed alternately, but the number of alternation was 1, 2, and 4 in this order.

Example 10

The preparation process is the same as that in example 1, except that in the process of depositing the heavy rare earth film, the sample sequentially passes through the lower parts of the opened Dy target material and the opened Cu target material, the time for stopping the sample under each target is controlled, the thickness of each film is controlled, and the alternating mixed film with the film thickness of 2 mu m in different periods can be prepared by controlling the times for passing the sample under the target

Example 11

The preparation process is the same as that of example 7, except that, when the heavy rare earth film is deposited, the sample sequentially passes through the opened Cu target and the opened Tb target to prepare Cu with the film thickness of 2 mu m and the alternation frequency of 1_0.2Tb_0.8The films were mixed alternately.

Example 12

The preparation process was the same as in example 10 except that, in depositing the heavy rare earth film, the sample was passed through the opened Cu target and Dy target in order to prepare a Cu/Dy alternate mixed film having a film thickness of 2 μm.

The following table 1 shows the magnetic property data of the sintered ndfeb magnets with the deposited composite films prepared in examples 1, 2, 5, 7 to 9 and 11, respectively, and the magnetic property data of the original sintered ndfeb magnets are given as a comparison.

TABLE 1

Comparing the data in table 1, it was found that the coercivity was increased by 5.6kOe for the sample prepared in example 1 compared to the original nd fe-b magnet, while the coercivity was increased by 6.7kOe for the sample prepared in example 5 and the Tb usage was reduced by 20%. The effect is best, and the purpose of partially replacing Tb by Cu is realized.

Compared with the magnetic performance of the samples prepared in the embodiments 7-9, the coercive force is improved more obviously after the alternation times are increased, and the heavy rare earth utilization effect is better. Comparing the magnetic properties of the samples prepared in example 7 and example 11, the example 7 in which heavy rare earth elements are deposited first is better in the effect of improving the coercivity.

Claims

1. A preparation method of a sintered NdFeB magnet deposited with a composite film is characterized by comprising the following steps:

1) pretreating a sintered neodymium-iron-boron magnet sample;

4) carrying out thermal diffusion and tempering treatment on the sintered neodymium iron boron magnet sample treated in the step 3);

the sintered neodymium-iron-boron magnet deposited with the composite film comprises a sintered neodymium-iron-boron magnet and the composite film deposited on the outer surface of the sintered neodymium-iron-boron magnet through a magnetron sputtering method;

the element composition of the composite film comprises necessary elements Tb and/or Dy and optional elements Cu, and the composite film is an alternate mixed film; the alternate mixed film is obtained by depositing necessary elements and optional elements after alternate sputtering;

the alternate mixed film marks the film of the element necessary for sputtering once and the film of the element selectable once as an alternate period, and the alternate period is at least 4.

2. The method for preparing sintered NdFeB magnet with deposited composite film as claimed in claim 1, wherein the composition of alternate mixed film elements comprises Tb_x5Cu_1-x5、Dy_x6Cu_1-x6Or Tb_x7Dy_y2Cu_1-(x7+y2)；

The x 5-x 7 and y2 represent the percentage content of atoms, and the x 5-x 7 are respectively selected from 0-1.

3. The method of claim 1, wherein the alternately mixed films are formed by sputtering a film of an essential element and then a film of an optional element.

4. The method for preparing the sintered NdFeB magnet with the deposited composite film according to claim 1, wherein the thickness of the composite film is 1-12 μm.

5. The method for preparing the sintered NdFeB magnet with the deposited composite film according to claim 1, wherein the pretreatment in step 1) comprises degreasing, pickling, alcohol ultrasonic treatment and blow drying.

6. The method for preparing the sintered NdFeB magnet with the deposited composite film as claimed in claim 1, wherein in the step 2), the pretreated sintered NdFeB magnet sample is placed in a magnetron sputtering vacuum chamber and is vacuumized to 5 x 10^-3～5×10^-4And Pa, filling high-purity argon again, and performing ion activation treatment.

7. The method for preparing a sintered ndfeb magnet with a deposited composite film according to claim 1, wherein in step 3), the target material for magnetron sputtering includes a Dy target material, a Tb target material, and a Cu target material;

the working pressure is 0.1-3 Pa, and the target power density is 1-7W/cm²。

8. The method for preparing the sintered NdFeB magnet with the deposited composite film according to claim 1, wherein in the step 4), the temperature of the thermal diffusion is 800-1000 ℃, and the temperature of the tempering treatment is 400-600 ℃.