Ferrite permanent magnet material and method for producing the same

Abstract

The application belongs to the technical field of permanent magnetic materials, and particularly relates to a ferrite permanent magnetic material and a preparation method thereof. The ferrite permanent magnetic material comprises a base material and an additive material, and the base material comprises, by weight fraction, 80-90 parts of iron oxide, 5-10 parts of strontium oxide, 8-12 parts of nano-magnesium oxide and 2-3 parts of barium carbonate. The additive material comprises an additive and a dispersing aid. The additive comprises calcium carbonate, silicon dioxide and bismuth oxide. The ferrite permanent magnetic material obtained by optimizing the formula and the preparation method is free of cracks, has high density, and effectively improves the coercive force, intrinsic coercive force and remanence, and has excellent overall performance and good processing performance.

Description

Technical Field

[0001] This invention belongs to the field of permanent magnet materials technology, specifically relating to a ferrite permanent magnet material and its preparation method. Background Technology

[0002] Ferrites are ferromagnetic metal oxides. Based on their magnetic properties and applications, ferrites can be classified into five types: soft magnets, permanent magnets, gyromagnets, rectangular magnets, and piezomagnetic magnets. In motors, ferrites are mostly used as permanent magnet materials.

[0003] Permanent magnet ferrites can be classified into isotropic and anisotropic materials based on differences in manufacturing processes. Both types of materials have the same composition. Anisotropic permanent magnets have higher performance; they are produced by magnetic field forming followed by firing, and the easy magnetization axes of their particles are aligned consistently along the direction of the external field. Therefore, anisotropic materials are generally used.

[0004] In recent years, due to the increasing demands for miniaturization and high performance in electronic components, the performance requirements for permanent magnet ferrites have also become increasingly stringent. However, existing permanent magnet ferrites still have certain performance defects, such as microcracks introduced by impurities in raw materials, and a decrease in remanence due to additives added during the manufacturing process or poor condition control. These defects directly affect the performance of permanent magnet ferrites in use.

[0005] Therefore, developing a high-performance ferrite permanent magnet material is expected to solve the above-mentioned shortcomings. Summary of the Invention

[0006] In view of the above-mentioned shortcomings mentioned in the background art, the purpose of this invention is to provide a ferrite permanent magnet material and its preparation method. The ferrite permanent magnet material obtained by the formula and preparation method is crack-free, has high density, and effectively improves its coercivity, intrinsic coercivity and remanence, with excellent overall performance.

[0007] To achieve the above objectives, the present invention provides a ferrite permanent magnet material, which comprises a base material and additives. The base material, by weight, comprises: 80-90 parts of iron oxide, 5-10 parts of strontium oxide, 8-12 parts of nano-magnesium oxide, and 2-3 parts of barium carbonate. The additives include additives and dispersants. The additives include calcium carbonate, silicon dioxide, and bismuth oxide.

[0008] This technical solution optimizes the raw materials and proportions of ferrite permanent magnet materials, effectively improving the material's density, anti-interference ability, and magnetic properties. Adding a certain amount of nano-magnesium oxide, due to its unique characteristics and high purity, not only replaces part of the ferrite material but also controls the silica content in the product, thereby improving the product's performance stability and resistance to magnetic aging and interference. Adding a certain amount of barium carbonate as a barium source increases magnetic saturation intensity, promotes ferrite powder crystallization, and enhances the product's magnetic properties. Controlling the ratio of calcium carbonate to silica ensures that coercivity is improved without decreasing remanence. Simultaneously, adding a certain amount of bismuth oxide alters the material's microstructure, refines the grains, and improves the magnetic properties of the ferrite permanent magnet material, further enhancing coercivity, intrinsic coercivity, and remanence. It also improves the material's stability and processing performance.

[0009] Furthermore, in the above technical solution, the mass ratio of calcium carbonate, silicon dioxide and bismuth oxide is 1:1:0.3-0.8.

[0010] Furthermore, in the above technical solution, the dispersing agent is prepared by mixing citric acid, ammonia, sodium hydroxide, and water in a mass ratio of 1:0.6-1.2:0.5-0.8:0.8-1.2; the mass concentration of the ammonia is 20-30%. Specifically, in the preparation of the dispersing agent, citric acid is first dissolved in water, then ammonia is added and stirred until homogeneous, and then sodium hydroxide is added and stirred until homogeneous. The amount of sodium hydroxide added is sufficient to control the pH of the solution between 5 and 7. This technical solution uses a low-cost, environmentally friendly mixed aqueous dispersant, which has a good dispersion effect and requires no additional removal, thus not affecting the product yield.

[0011] Furthermore, in the above technical solution, the mass ratio of the base material to the additive material is controlled at 100:0.6-1.

[0012] This invention also provides a method for preparing ferrite permanent magnet materials, comprising the following steps: (1) Prepare each raw material, pre-dry the solid raw materials, and weigh each raw material according to the proportion for later use; (2) First mix the base materials, then add the additives, mix evenly and add them into the ball mill, and add half of the dispersing agent and water for wet ball milling; (3) After dehydrating the wet material obtained in step (2), the wet material is molded in one step using an automatic molding press; (4) The material formed in step (3) is pre-sintered in sections for 1-2 hours, and then crushed. (5) Add the pulverized material from step (4) into the grinder, add the other half of the dispersing agent, grind, and sieve; (6) After dehydrating the grinding product from step (5), it is then subjected to secondary molding in a magnetic field using an automatic molding press; (7) The material formed in step (6) is first subjected to low temperature treatment for 3-6 hours, and then subjected to high temperature sintering for 2-3 hours to obtain ferrite permanent magnet material.

[0013] This technical solution combines drying, wet grinding, one-time molding, pre-sintering, grinding, secondary molding, and sintering processes to obtain ferrite permanent magnet materials with high density and no cracks. Drying effectively removes moisture and other substances from the raw materials, resulting in more accurate batching. Wet grinding ensures uniform particle size and good dispersion, which is beneficial for subsequent molding and sintering. Pre-sintering is performed in stages with progressively increasing temperatures, improving material density. Grinding further reduces particle size and improves uniformity. Secondary molding, performed in a magnetic field, enables grain orientation, increasing magnetic induction and coercivity. Low-temperature pre-sintering reduces raw material inhomogeneity and shrinkage, improving product performance.

[0014] Furthermore, in step (2) of the above technical solution, the mass ratio of material, milling beads and water in wet ball milling is 1:6-8:1.5-1.8, and the milling time is 2-4 hours.

[0015] Furthermore, in step (3) of the above technical solution, the moisture content of the dehydrated material is 30-45%; in step (4), the segmented pre-sintering method is as follows: first, the temperature is raised to 950±20℃ at a rate of 2-5℃ / min and held for 0.5-1h, and then the temperature is raised to 1300±20℃ at a rate of 5-10℃ / min and held for 0.5-1h; the average particle size after pulverization is 1-5μm.

[0016] Furthermore, in step (5) of the above technical solution, the grinding power is 5-10kW, the rotation speed is 50-80r / min, the grinding time is 10-15h, and the average particle size of the grinding slurry is 0.1-0.5μm.

[0017] Furthermore, in step (6) of the above technical solution, the moisture content of the dehydrated material is 25-32%, and the magnetic field for compression molding is 1800-2000Gs.

[0018] Furthermore, in step (7) of the above technical solution, the temperature of the low-temperature treatment is 400-600℃; the temperature of the high-temperature sintering is 1160-1230℃.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention optimizes the raw materials and proportions of ferrite permanent magnet materials, effectively improving the material's density, anti-interference ability, and magnetic properties. By adding nano-magnesium oxide, not only can some ferrite material be replaced, but the silica content in the product can also be controlled, thereby improving the product's performance stability and resistance to magnetic aging and interference. Adding barium carbonate as a barium source can increase magnetic saturation strength, promote ferrite powder crystallization, and enhance the product's magnetic properties. By controlling the ratio of calcium carbonate to silica, remanence is maintained while coercivity is improved. Simultaneously, the addition of a certain amount of bismuth oxide alters the material's microstructure, refines the grains, and improves the magnetic properties of the ferrite permanent magnet material, further enhancing coercivity and remanence. It also improves the material's stability and processing performance. The resulting ferrite permanent magnet material is crack-free, high-density, and has good magnetic properties, effectively improving its coercivity and remanence, exhibiting excellent overall performance.

[0020] 2. The preparation method of this invention combines raw material preparation, wet grinding, one-time molding, pre-sintering, grinding, secondary molding, and sintering processes to optimize preparation conditions and parameters. The material has uniform particle size, good formability, and excellent production performance, resulting in ferrite permanent magnet materials with good comprehensive performance and high yield. Detailed Implementation

[0021] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the raw materials used in the following examples are all commercially available products and can be purchased from the market.

[0022] The above-described technical features of the present invention and the technical features specifically described below (such as in the embodiments) can be combined with each other to form new or preferred technical solutions.

[0023] The raw materials involved in the various embodiments of the present invention are either commercially available products or can be prepared according to existing methods.

[0024] The specific content of the present invention will be further explained and described below with reference to the embodiments.

[0025] Example 1 A ferrite permanent magnet material comprises base materials and additives. The base materials, by weight, include: 85 parts iron oxide, 6 parts strontium oxide, 10 parts nano-magnesium oxide, and 2 parts barium carbonate. The additives include additives and dispersants. The mass ratio of calcium carbonate, silicon dioxide, and bismuth oxide in the additives is 1:1:0.4. The dispersant is prepared by mixing citric acid, ammonia (25%), sodium hydroxide, and water in a mass ratio of 1:1:0.6:1. The mass ratio of base materials to additives is controlled at 100:0.6.

[0026] Its preparation method includes the following steps: (1) Prepare each raw material, pre-dry the solid raw materials, and weigh each raw material according to the above proportions for later use; (2) First mix the base materials, then add the additives, mix evenly and add them into the ball mill, and add half of the dispersant and water for wet ball milling; the mass ratio of materials, ball mill beads and water is 1:7:1.6, and the ball milling time is 3h; (3) After dehydrating the wet material obtained in step (2) to a moisture content of 35%, the wet material is formed in one step using an automatic forming press; (4) The material formed in step (3) is first heated to 950±20℃ at a rate of 3℃ / min and held for 0.5h, then heated to 1300±20℃ at a rate of 6℃ / min and held for 1h, and then crushed to an average particle size of 1-5μm. (5) Add the pulverized material from step (4) into a grinder, add the other half of the dispersing agent, grind, and sieve. The grinding power is 6kW, the rotation speed is 6r / min, the grinding time is 12h, and the average particle size of the grinding slurry is 0.1-0.5μm. (6) After dehydrating the grinding product from step (5) to a moisture content of 30%, the product is then subjected to secondary molding in a magnetic field of 2000Gs using an automatic molding press. (7) The material formed in step (6) is first treated at 400℃ for 6 hours, and then sintered at 1160℃ for 3 hours to obtain ferrite permanent magnet material.

[0027] Example 2 A ferrite permanent magnet material comprises a base material and additives. The base material, by weight, includes: 90 parts iron oxide, 10 parts strontium oxide, 8 parts nano-magnesium oxide, and 3 parts barium carbonate. The additives include additives and dispersants. The mass ratio of calcium carbonate, silicon dioxide, and bismuth oxide in the additives is 1:1:0.8. The dispersant is prepared by mixing citric acid, ammonia (25%), sodium hydroxide, and water in a mass ratio of 1:1.2:0.5:1.2. The mass ratio of the base material to the additives is controlled at 100:0.6.

[0028] Its preparation method includes the following steps: (1) Prepare each raw material, pre-dry the solid raw materials, and weigh each raw material according to the above proportions for later use; (2) First mix the base materials, then add the additives, mix evenly and add them into the ball mill, and add half of the dispersant and water for wet ball milling; the mass ratio of materials, ball mill beads and water is 1:6:1.5, and the ball milling time is 4h; (3) After dehydrating the wet material obtained in step (2) to a moisture content of 30%, the wet material is formed in one step using an automatic forming press; (4) The material formed in step (3) is first heated to 950±20℃ at a rate of 5℃ / min and held for 0.5h. Then the temperature is increased to 1300±20℃ at a rate of 10℃ / min and held for 0.5h. Then it is crushed to an average particle size of 1-5μm. (5) Add the pulverized material from step (4) into a grinder, add the other half of the dispersing agent, grind, and sieve. The grinding power is 5kW, the rotation speed is 80r / min, the grinding time is 15h, and the average particle size of the grinding slurry is 0.1-0.5μm. (6) After dehydrating the grinding product of step (5) to a moisture content of 25%, it is then subjected to secondary molding in a magnetic field of 1800Gs using an automatic molding press. (7) The material formed in step (6) is first treated at 500℃ for 5 hours, and then sintered at 1200℃ for 2 hours to obtain ferrite permanent magnet material.

[0029] Example 3 A ferrite permanent magnet material comprises base materials and additives. The base materials, by weight, include: 80 parts iron oxide, 5 parts strontium oxide, 12 parts nano-magnesium oxide, and 2 parts barium carbonate. The additives include additives and dispersants. The mass ratio of calcium carbonate, silicon dioxide, and bismuth oxide in the additives is 1:1:0.3. The dispersant is prepared by mixing citric acid, ammonia (25%), sodium hydroxide, and water in a mass ratio of 1:0.6:0.8:0.8. The mass ratio of base materials to additives is controlled at 100:1.

[0030] Its preparation method includes the following steps: (1) Prepare each raw material, pre-dry the solid raw materials, and weigh each raw material according to the above proportions for later use; (2) First mix the base materials, then add the additives, mix evenly and add them into the ball mill, and add half of the dispersant and water for wet ball milling; the mass ratio of materials, ball mill beads and water is 1:8:1.8, and the ball milling time is 2 hours. (3) After dehydrating the wet material obtained in step (2) to a moisture content of 45%, the wet material is formed in one step using an automatic forming press; (4) The material formed in step (3) is first heated to 950±20℃ at a rate of 2℃ / min and held for 1h, then heated to 1300±20℃ at a rate of 5℃ / min and held for 1h, and then crushed to an average particle size of 1-5μm. (5) Add the pulverized material from step (4) into a grinder, add the other half of the dispersing agent, grind, and sieve. The grinding power is 5-10kW, the rotation speed is 50-80r / min, the grinding time is 10-15h, and the average particle size of the grinding slurry is 0.1-0.5μm. (6) After dehydrating the grinding product from step (5) to a moisture content of 32%, it is then subjected to secondary molding in a magnetic field of 1900Gs using an automatic molding press. (7) The material formed in step (6) is first treated at 600℃ for 3 hours, and then sintered at 1160℃ for 2 hours to obtain ferrite permanent magnet material.

[0031] Comparative Example 1 A ferrite permanent magnet material, which differs from Example 1 in that it does not contain bismuth oxide in the additives, but is otherwise the same as Example 1.

[0032] Comparative Example 2 A ferrite permanent magnet material, which differs from Example 1 in that the base material does not contain nano-magnesium oxide, but is otherwise the same as Example 1.

[0033] Comparative Example 3 A ferrite permanent magnet material, which differs from Example 1 in that it does not contain barium carbonate in the base material, but is otherwise the same as Example 1.

[0034] Comparative Example 4 A ferrite permanent magnet material, which differs from Example 1 in that its preparation method is different: Its preparation method includes the following steps: (1) Prepare each raw material and weigh each raw material according to the above proportions for later use; (2) First mix the base materials, then add the additives, mix evenly and add them into the ball mill, and add the dispersant and water for wet ball milling; the mass ratio of materials, ball mill beads and water is 1:7:1.6, and the ball milling time is 6h; (3) After dehydrating the wet material obtained in step (2) to a moisture content of 35%, the wet material is shaped using an automatic molding press; (4) Keep the material formed in step (3) at 1300±20℃ for 1h, and then crush it to an average particle size of 1-5μm; (5) Add the crushed material from step (4) into a grinder, add water for grinding, and sieve. The grinding power is 6kW, the rotation speed is 6r / min, the grinding time is 12h, and the average particle size of the grinding slurry is 0.1-0.5μm. (6) After dehydrating the grinding product from step (5) to a moisture content of 30%, it is then subjected to secondary molding in an automatic molding press; (7) The material formed in step (6) is sintered at 1160℃ for 3 hours to obtain ferrite permanent magnet material.

[0035] Test case The density and magnetic properties of the ferrite permanent magnet materials obtained in Examples 1-3 and Comparative Examples 1-4: remanent magnetic induction (Br), coercivity (Hcb), intrinsic coercivity (Hcj), and maximum energy product (BH). max The test was conducted, and the results are shown in Table 1.

[0036] Table 1

[0037] As can be seen from the results in Table 1, the ferrite permanent magnet material prepared by the formulation and preparation method of this invention has a high density, a remanent magnetic induction intensity of over 4500 Gs, an intrinsic coercivity of over 5500 Oe, and excellent overall performance. However, due to differences in formulation or preparation methods, the properties of Comparative Examples 1-4 all showed a certain degree of decline. Specifically, Comparative Example 1, without the addition of nano-magnesium oxide, also showed a slight decrease in overall performance, but its cost was higher, and its resistance to magnetic aging and interference was worse. Comparative Example 2, without the addition of barium carbonate, had poorer crystallinity, directly affecting its magnetic properties. Comparative Example 3, with its additives lacking bismuth oxide, showed a change in additive content, directly affecting the grain size and magnetic properties. Comparative Example 4, due to different preparation methods, such as failure to remove impurities from raw materials, lack of segmented sintering, absence of dispersant in secondary grinding, and failure to form in a magnetic field, directly affected the particle size, density, and orientation of the material, thus affecting its magnetic properties.

[0038] Finally, it should be emphasized that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A ferrite permanent magnet material, characterized in that, The ferrite permanent magnet material is composed of base materials and additives. The base materials, by weight, are: 80-90 parts iron oxide, 5-10 parts strontium oxide, 8-12 parts nano magnesium oxide, and 2-3 parts barium carbonate. The additives are composed of additives and dispersants. The additive is composed of calcium carbonate, silicon dioxide, and bismuth oxide; The mass ratio of calcium carbonate, silicon dioxide, and bismuth oxide is 1:1:0.3-0.8; The mass ratio of the base material to the additives is controlled at 100:0.6-1; The preparation method of the ferrite permanent magnet material includes the following steps: (1) Prepare each raw material, pre-dry the solid raw materials, and weigh each raw material according to the proportion for later use; (2) First mix the base materials, then add the additives, mix evenly and add them into the ball mill, and add half of the dispersing agent and water for wet ball milling; (3) After dehydrating the wet material obtained in step (2), the wet material is molded in one step using an automatic molding press; (4) The material formed in step (3) is pre-sintered in sections for 1-2 hours and then crushed. The pre-sintering method is as follows: first, the temperature is raised to 950±20℃ at a rate of 5-10℃ / min and held for 0.5-1 hours, and then the temperature is raised to 1300±20℃ at a rate of 2-5℃ / min and held for 0.5-1 hours. (5) Add the pulverized material from step (4) into the grinder, add the other half of the dispersing agent, grind, and sieve; (6) After dehydrating the grinding product of step (5), it is subjected to secondary molding in a magnetic field using an automatic molding press; wherein the moisture content of the dehydrated material is 25-32%, and the magnetic field for compression molding is 1800-2000Gs. (7) The material formed in step (6) is first subjected to low temperature treatment for 3-6 hours, and then subjected to high temperature sintering for 2-3 hours to obtain ferrite permanent magnet material.

2. The ferrite permanent magnet material according to claim 1, characterized in that, The dispersing agent is prepared by mixing citric acid, ammonia, sodium hydroxide and water in a mass ratio of 1:0.6-1.2:0.5-0.8:0.8-1.2; the mass concentration of the ammonia is 20-30%.

3. A method for preparing a ferrite permanent magnet material as described in any one of claims 1-2, characterized in that, Includes the following steps: (1) Prepare each raw material, pre-dry the solid raw materials, and weigh each raw material according to the proportion for later use; (2) First mix the base materials, then add the additives, mix evenly and add them into the ball mill, and add half of the dispersing agent and water for wet ball milling; (3) After dehydrating the wet material obtained in step (2), the wet material is molded in one step using an automatic molding press; (4) The material formed in step (3) is pre-sintered in sections for 1-2 hours and then crushed. The pre-sintering method is as follows: first, the temperature is raised to 950±20℃ at a rate of 5-10℃ / min and held for 0.5-1 hours, and then the temperature is raised to 1300±20℃ at a rate of 2-5℃ / min and held for 0.5-1 hours. (5) Add the pulverized material from step (4) into the grinder, add the other half of the dispersing agent, grind, and sieve; (6) After dehydrating the grinding product of step (5), it is subjected to secondary molding in a magnetic field using an automatic molding press; wherein the moisture content of the dehydrated material is 25-32%, and the magnetic field for compression molding is 1800-2000Gs. (7) The material formed in step (6) is first subjected to low temperature treatment for 3-6 hours, and then subjected to high temperature sintering for 2-3 hours to obtain ferrite permanent magnet material.

4. The method for preparing a ferrite permanent magnet material according to claim 3, characterized in that, In step (2), during wet ball milling, the mass ratio of material, milling beads and water is 1:6-8:1.5-1.8, and the milling time is 2-4 hours.

5. The method for preparing a ferrite permanent magnet material according to claim 3, characterized in that, In step (3), the moisture content of the dehydrated material is 30-45%; the average particle size after crushing is 1-5μm.

6. The method for preparing a ferrite permanent magnet material according to claim 3, characterized in that, In step (5), the grinding power is 5-10kW, the rotation speed is 50-80r / min, the grinding time is 10-15h, and the average particle size of the grinding slurry is 0.1-0.5μm.

7. The method for preparing a ferrite permanent magnet material according to claim 3, characterized in that, In step (7), the temperature for low-temperature treatment is 400-600℃; the temperature for high-temperature sintering is 1160-1230℃.

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