Magnetic nanoparticle, and preparation method therefor and use thereof

Abstract

The present application provides a magnetic nanoparticle, and a preparation method therefor and a use thereof. The chemical formula of the magnetic nanoparticle is Sr1-x-yBaxLayFe12-zCozO19, wherein 0≤x≤0.3, 0≤y≤0.3, 0≤z≤0.25, and x, y and z are not 0 at the same time; and the average particle size of the magnetic nanoparticle is 20-40 nm. The magnetic nanoparticle in the present application has a small particle size and exhibit excellent magnetic properties, and can be used in magnetic storage devices to further meet needs for storage of massive data in the information age.

Description

Nanomagnetic particles, preparation method and application thereof Technical Field

[0001] The present application relates to the field of magnetic material technology, for example, a nanomagnetic particle and its preparation method and application. Background Art

[0002] In recent years, as magnetic recording devices have been developing towards higher-density recording, higher and higher requirements have been placed on the magnetic properties of magnetic materials.

[0003] While hexagonal ferrite permanent magnets lack the magnetic properties of rare earth permanent magnets, they offer numerous advantages, including abundant resources, simple preparation processes, and low material costs. They are widely used in motors, sensors, magnetic storage, and other fields, making them the most widely used type of permanent magnet. Hexagonal ferrite permanent magnets are particularly well-suited for magnetic storage devices requiring long-term storage due to their resistance to high temperatures, corrosion, and oxidation. In today's information and data age, with the need for long-term storage of large amounts of both warm and cold data, hexagonal ferrite magnetic storage media have garnered widespread attention.

[0004] CN102076629A discloses a reinforced hexagonal ferrite magnetic material, in which alkali metal is doped.

[0005] CN109836147A discloses a permanent magnet ferrite and a preparation method thereof. The permanent magnet ferrite is composed of 55wt% or more of Sr-based ferrite material and 45wt% or less of Ca-based ferrite material based on the total mass of the permanent magnet ferrite. The Sr-based ferrite material has Sr 1-x La x Fe 3+ 2n-y Co y O 19 Ferrite main phase; the Ca-based ferrite material has Ca x (Sr+Ba) y La 1-x-y Fe 3+ 2n-z Co z O 19 Ferrite main phase.

[0006] The ferrite material described in the above solution has large particle size and poor magnetic properties. Due to the low magnetic properties of ferrite materials, their magnetic storage density is relatively small, which cannot meet the storage needs of huge data in the information age, and has become a key bottleneck restricting its widespread application.

[0007] Summary of the Invention

[0008] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0009] The present application provides a nanomagnetic particle and its preparation method and application. The nanomagnetic particle described in the present application has a small particle size and exhibits excellent magnetic properties. The use of the nanomagnetic particle in magnetic storage devices can further meet the storage needs of huge data in the information age.

[0010] In the first aspect, the present application provides a nanomagnetic particle, the chemical formula of the nanomagnetic particle is Sr 1-x-y Ba x La y Fe 12-z Co z O 19 , wherein 0≤x≤0.3, 0≤y≤0.3, 0≤z≤0.25, x, y and z are not all 0 at the same time, and the average particle size of the nanomagnetic particles is 20 to 40 nm, for example: 20 nm, 25 nm, 30 nm, 35 nm or 40 nm.

[0011] The nanomagnetic particles described in this application have a nanocrystalline structure (average particle size less than 50nm). The nanocrystalline structure increases the coercivity of the material as its grain size decreases. In particular, when the grain size is less than 50nm, a strong exchange coupling effect will occur between adjacent grains, which greatly increases the remanence of the material. At the same time, the magnetic particles have Sr 1-x-y Ba x La y Fe 12-z Co z O 19 Its chemical composition has excellent magnetic properties, making it more suitable for the development of high recording density magnetic storage devices.

[0012] In one embodiment, among the nanomagnetic particles, particles with a particle size of 10 to 40 nm (eg, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, or 40 nm, etc.) account for ≥90%.

[0013] In one embodiment, among the nanomagnetic particles, particles with a particle size greater than 40 nm (for example, 40.5 nm, 41 nm, 43 nm, 45 nm, 48 nm, or 49 nm, etc.) account for ≤5%, for example, 1%, 2%, 3%, 4%, or 5%, etc.

[0014] In one embodiment, among the nanomagnetic particles, particles with a particle size of less than 10 nm (eg, 9 nm, 8 nm, 7 nm, 6 nm, 5 nm, or 3 nm, etc.) account for ≤5%, for example, 1%, 2%, 3%, 4%, or 5%, etc.

[0015] Among the nanomagnetic particles described in the present application, the sum of particles with a particle size of 10-40 nm, a particle size greater than 40 nm, and a particle size less than 10 nm is 100%. For example, particles with a particle size of 10-40 nm account for 95%, particles with a particle size greater than 40 nm account for 3%, and particles with a particle size less than 10 nm account for 2%.

[0016] In one embodiment, when both y and z are not 0, y and z satisfy the relationship: 1≤y / z≤1.5, for example: 1, 1.1, 1.2, 1.36, 1.4 or 1.5, etc.

[0017] In a second aspect, the present application provides a method for preparing the nanomagnetic particles according to the first aspect, the preparation method comprising the following steps:

[0018] (1) Main material A and main material B are mixed in proportion to obtain a mixed material, wherein main material A includes SrCO3 and Fe2O3, and main material B includes any one or a combination of at least two of BaCO3, La2O3 or Co2O3, and the mixed material is mixed with H3BO3 and SrCl2, ground, and then calcined;

[0019] (2) melting the calcined material and flowing it onto a water-cooled roller to obtain an amorphous sheet;

[0020] (3) After the amorphous thin slice is subjected to a heating and crystallization treatment, it is washed to obtain the nanomagnetic particles.

[0021] In the preparation process of nanomagnetic particles in the present application, the addition of H3BO3 and SrCl2 can adjust the viscosity of the melt while promoting the melting of the mixture, thereby affecting the thickness of the amorphous sheet and its cooling rate on the roller, and ultimately affecting the microstructure and properties of the material.

[0022] In one embodiment, the mass of the H3BO3 in step (1) is 15-25% of the mass of the mixed material, for example, 15%, 18%, 20%, 22% or 25%.

[0023] In one embodiment, the mass of the SrCl2 is 10-20% of the mass of the mixed material, for example, 10%, 12%, 15%, 18% or 20%.

[0024] In one embodiment, the grinding method in step (1) comprises ball milling.

[0025] In one embodiment, the calcination temperature is 900-1100°C, for example, 900°C, 950°C, 1000°C, 1050°C or 1100°C.

[0026] In one embodiment, the calcination treatment time is 1 to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours.

[0027] The purpose of the calcination treatment described in this application is to allow the elements to diffuse into each other in the solid state, so as to avoid uneven distribution of the material after melting due to inconsistent density in the subsequent melting process, resulting in insufficient diffusion of atoms and segregation of elemental components.

[0028] In one embodiment, the temperature of the melt treatment in step (2) is 1350-1500°C, for example, 1350°C, 1380°C, 1400°C, 1450°C or 1500°C.

[0029] In one embodiment, the flowing out specifically comprises pouring the melted liquid into a tubular container with a nozzle, and simultaneously introducing air to wet-press the liquid so that the liquid flows out through the nozzle.

[0030] In one embodiment, the rotation speed of the water-cooled roller is 20-30 m / s, for example, 20 m / s, 22 m / s, 25 m / s, 28 m / s or 30 m / s.

[0031] In one embodiment, the temperature of the heating crystallization treatment in step (3) is 550-650°C, for example, 550°C, 580°C, 600°C, 620°C or 650°C.

[0032] The present invention can adjust the size of grains and particles by controlling the crystallization temperature and time. If the temperature is too low, the grain size will be too small, resulting in excessive paramagnetic particles. It may also cause the same particle to contain multiple tiny grains, making the material polycrystalline. If the temperature is too high, the material grains will grow excessively, the particles will be too coarse, and the magnetic properties will be affected.

[0033] In one embodiment, the heating crystallization time is 4 to 6 hours, for example, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours.

[0034] In one embodiment, the washing treatment in step (3) includes placing the material obtained after heating and crystallization in water, adding acid and repeatedly dissolving it until all non-magnetic materials in the material are dissolved and washed away, precipitating the remaining material, and repeatedly washing it with alcohol.

[0035] In one embodiment, the washing is followed by a drying process.

[0036] In one embodiment, the drying temperature is 100-110°C, for example, 100°C, 102°C, 105°C, 108°C or 110°C.

[0037] In a third aspect, the present application provides an application of the nanomagnetic particles as described in the first aspect, wherein the nanomagnetic particles are used in magnetic storage devices.

[0038] Compared with the related art, this application has the following beneficial effects:

[0039] (1) In the preparation process of nanomagnetic particles of the present application, the addition of H3BO3 and SrCl2 can adjust the viscosity of the melt while promoting the melting of the mixture, thereby affecting the thickness of the amorphous sheet and its cooling rate on the roller, and ultimately affecting the microstructure and properties of the material.

[0040] (2) The nanomagnetic particles described in this application have a nanocrystalline structure (average particle size is less than 50nm). The nanocrystalline structure increases the coercivity of the material as its grain size decreases. In particular, when the grain size is less than 50nm, a strong exchange coupling effect will occur between adjacent grains, which greatly increases the remanence of the material. At the same time, the magnetic particles have Sr 1-x-y Ba x La y Fe 12-z Co z O 19 Its chemical composition has excellent magnetic properties, making it more suitable for the development of high recording density magnetic storage devices.

[0041] (3) The nanomagnetic particles described in this application can achieve Ms of more than 77.3emu / g, Mr of more than 45.1emu / g, and Hcj of more than 4.15kOe while ensuring an average particle size below 30nm, showing good magnetic properties.

[0042] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0043] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0044] Example 1

[0045] This embodiment provides a nanomagnetic particle, and the preparation method of the nanomagnetic particle is as follows:

[0046] (1) SrCO3, BaCO3, La2O3, Fe2O3, and Co2O3 are mixed in proportion so that the atomic ratio of each element satisfies Sr 1-x-y Ba x La y Fe 12-z Co z O19 , where x=0, y=0.3, z=0.25, and y / z=1.2, then add 25% of the total weight of the mixture, H3BO3, and 10% of SrCl2, place the mixture in a ball mill, add deionized water, and ball mill for 5 hours, wherein the weight ratio of the material, the ball, and the water is 1:10:1.5, pour the mixed material together with the solution into a container, and then heat and dry at 110°C. The dried powder is placed in a muffle furnace and calcined for 2 hours at a calcination temperature of 1000°C;

[0047] (2) The calcined product is placed in a crucible, heated to 1400°C to melt, and then poured into a tubular container with a nozzle. Air is introduced to apply pressure, causing the liquid to flow through the nozzle onto a water-cooled roller rotating at a high speed (25 m / s), obtaining a thin sheet with an amorphous microstructure;

[0048] (3) The amorphous thin slice is heated at 600°C for 5 hours to crystallize, and the crystallized thin slice is put into water and repeatedly dissolved with hydrochloric acid until the residual non-magnetic SrO, BaO, La2O3, Fe2O3, Co2O3, H3BO3 and SrCl2 in the thin slice are completely dissolved and washed away, and the remaining product is precipitated and repeatedly washed with alcohol, and then dried at 110°C to obtain the nanomagnetic particles. The average particle size of the magnetic powder is 23nm, of which particles with a size of 10 to 40nm account for 95%, particles with a size greater than 40nm account for 2%, and particles with a size less than 10nm account for 3%.

[0049] Example 2

[0050] This embodiment provides a nanomagnetic particle, and the preparation method of the nanomagnetic particle is as follows:

[0051] (1) SrCO3, BaCO3, La2O3, Fe2O3, and Co2O3 are mixed in proportion so that the atomic ratio of each element satisfies Sr 1-x-y Ba x La y Fe 12-z Co z O 19 , where x=0, y=0.3, z=0.25, and y / z=1.2, then add 15% of the total weight of the mixture, H3BO3, and 20% of SrCl2, place the mixture in a ball mill, add deionized water, and ball mill for 5 hours, wherein the weight ratio of the material, balls, and water is 1:10:1.5, pour the mixed material together with the solution into a container, and then heat and dry at 110°C. The dried powder is placed in a muffle furnace and calcined for 3 hours at a calcination temperature of 900°C;

[0052] (2) The calcined product is placed in a crucible, heated to 1350°C to melt, and then poured into a tubular container with a nozzle. Air is introduced to apply pressure, causing the liquid to flow through the nozzle onto a water-cooled roller rotating at a high speed (20 m / s), obtaining a thin sheet with an amorphous microstructure;

[0053] (3) The amorphous thin slice is heated at 550°C for 6 hours to crystallize, and the crystallized thin slice is placed in water and repeatedly dissolved with hydrochloric acid until the residual non-magnetic SrO, BaO, La2O3, Fe2O3, Co2O3, H3BO3 and SrCl2 in the thin slice are completely dissolved and washed away, and the remaining product is precipitated and repeatedly washed with alcohol, and then dried at 110°C to obtain the nanomagnetic particles. The average particle size of the magnetic powder is 28 nm, of which particles with a size of 10 to 40 nm account for 93%, particles with a size greater than 40 nm account for 3%, and particles with a size less than 10 nm account for 4%.

[0054] Example 3

[0055] This embodiment provides a nanomagnetic particle, and the preparation method of the nanomagnetic particle is as follows:

[0056] (1) SrCO3, BaCO3, La2O3, Fe2O3, and Co2O3 are mixed in proportion so that the atomic ratio of each element satisfies Sr 1-x-y Ba x La y Fe 12-z Co z O 19 , where x=0, y=0.3, z=0.2, and y / z=1.5, then add 15% of the total weight of the mixture, H3BO3, and 10% of SrCl2, place the mixture in a ball mill, add deionized water, and ball mill for 5 hours, wherein the weight ratio of the material, the ball, and the water is 1:10:1.5, pour the mixed material together with the solution into a container, and then heat and dry at 110°C. The dried powder is placed in a muffle furnace and calcined for 1 hour at a calcination temperature of 1100°C;

[0057] (2) The calcined product is placed in a crucible, heated to 1500°C to melt, and then poured into a tubular container with a nozzle. Air is introduced to apply pressure, causing the liquid to flow through the nozzle onto a water-cooled roller rotating at a high speed (30 m / s), obtaining a thin sheet with an amorphous microstructure;

[0058] (3) The amorphous thin slice is heated at 650°C for 4 hours to crystallize, and the crystallized thin slice is placed in water and repeatedly dissolved with hydrochloric acid until the residual non-magnetic SrO, BaO, La2O3, Fe2O3, Co2O3, H3BO3 and SrCl2 in the thin slice are completely dissolved and washed away, and the remaining product is precipitated and repeatedly washed with alcohol, and then dried at 110°C to obtain the nanomagnetic particles. The average particle size of the magnetic powder is 23 nm, of which particles with a size of 10 to 40 nm account for 96%, particles with a size greater than 40 nm account for 2%, and particles with a size less than 10 nm account for 2%.

[0059] Example 4

[0060] The only difference between this embodiment and embodiment 1 is that the amount of H3BO3 added is 10% of the mixture, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0061] Example 5

[0062] The only difference between this embodiment and embodiment 1 is that the amount of H3BO3 added is 30% of the mixture, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0063] Example 6

[0064] The only difference between this embodiment and embodiment 1 is that the amount of SrCl2 added is 5% of the mixture, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0065] Example 7

[0066] The only difference between this embodiment and embodiment 1 is that the amount of SrCl2 added is 25% of the mixture, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0067] Comparative Example 1

[0068] (1) SrCO3, BaCO3, La2O3, Fe2O3, and Co2O3 are mixed in proportion so that the atomic ratio of each element satisfies Sr 1-x-y Ba x La y Fe 12-z Co z O 19 , where x=0, y=0.3, z=0.25, and y / z=1.2, then add 15% of the total weight of the mixture, H3BO3, and 20% of SrCl2, place the mixture in a ball mill, add deionized water, and ball mill for 5 hours, wherein the weight ratio of the material, balls, and water is 1:10:1.5, pour the mixed material together with the solution into a container, and then heat and dry at 110°C. The dried powder is placed in a muffle furnace and calcined for 3 hours at a calcination temperature of 900°C;

[0069] (2) The calcined material was placed in water and repeatedly dissolved with hydrochloric acid until all the remaining non-magnetic SrO, BaO, La2O3, Fe2O3, Co2O3, H3BO3, and SrCl2 in the material were dissolved and washed away. The remaining product was precipitated and repeatedly washed with alcohol, and then dried at 110°C to obtain ferrite magnetic powder particles. The average particle size of the magnetic powder was 0.9 μm, which was much larger than the magnetic powder particle size in the embodiment.

[0070] Comparative Example 2

[0071] The only difference between this comparative example and Example 1 is that SrCl2 is not added, and the other conditions and parameters are exactly the same as those in Example 1.

[0072] Comparative Example 3

[0073] The only difference between this comparative example and Example 1 is that x=0, y=0, z=0, and the other conditions and parameters are exactly the same as those in Example 1.

[0074] Performance testing:

[0075] The magnetic materials obtained in the embodiment and the comparative example were tested by VSM analysis to measure the saturation magnetic induction intensity Ms, the residual magnetization intensity Mr and the coercive force Hcj. The test results are shown in Table 1:

[0076] Table 1

[0077] As can be seen from Table 1, from Examples 1-3, the nanomagnetic particles described in the present application can achieve Ms of more than 77.3 emu / g, Mr of more than 45.1 emu / g, and Hcj of more than 4.15 kOe while ensuring an average particle size of less than 30 nm, showing good magnetic properties.

[0078] A comparison of Example 1 and Examples 4-5 shows that, during the preparation of the nanomagnetic particles described in the present application, the amount of H3BO3 added affects their performance. When the amount of H3BO3 added is controlled within 15-25% of the mass of the mixture, the magnetic nanoparticles obtained have better performance. If the amount of boric acid added is too low, the melt viscosity is too high, and the dispersibility on the roller is poor, resulting in an unreasonable particle size distribution, with low Ms, Mr, and Hcj. If the amount of boric acid added is too high, the melt viscosity is too low, the magnetic powder contains more paramagnetic particles smaller than 10 nm, and Ms, Mr, and Hcj are also unsatisfactory.

[0079] By comparing Example 1 with Examples 6-7, it can be seen that during the preparation process of the nanomagnetic particles described in the present application, the amount of SrCl2 added affects its performance. When the amount of SrCl2 added is controlled at 10-20% of the mass of the mixture, the performance of the magnetic nanoparticles obtained is better. If the amount of SrCl2 added is too low, although the particles have a better Hcj, the Ms and Mr are low. If the amount of SrCl2 added is too high, the Ms and Mr of the particles increase slightly, but the Hcj is low.

[0080] From the comparison between Example 1 and Comparative Example 1, it can be seen that the nanomagnetic particles of the present application have a nanocrystalline structure (average particle size is less than 50nm). The nanocrystalline structure makes the coercivity of the material increase as the grain size decreases. In particular, when the grain size is less than 50nm, a strong exchange coupling effect will occur between adjacent grains, which greatly improves the remanence of the material. At the same time, the magnetic particles have Sr 1-x-y Ba x La y Fe 12-z Co z O 19 Its chemical composition has excellent magnetic properties, making it more suitable for the development of high recording density magnetic storage devices.

[0081] From the comparison between Example 1 and Comparative Example 2, it can be seen that without adding SrCl2, the Ms, Mr and Hcj of the material will decrease.

[0082] From the comparison between Example 1 and Comparative Example 3, it can be seen that without the addition of Ba, La and Co to the nanomagnetic particles described in the present application, the Ms, Mr and Hcj of the material all decrease to varying degrees. Although the particle size is small, the magnetic properties deteriorate, making it unsuitable for high-density magnetic storage devices.

[0083] The applicant declares that the above is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Technical personnel in the relevant technical field should understand that any changes or substitutions that can be easily thought of by technical personnel in the relevant technical field within the technical scope disclosed in this application fall within the protection scope and disclosure scope of this application.

Claims

1. A nanomagnetic particle, wherein: The chemical formula of the nanomagnetic particles is Sr 1-x-y Ba x La y Fe 12-z Co z O 19 , wherein 0≤x≤0.3, 0≤y≤0.3, 0≤z≤0.25, x, y and z are not 0 at the same time, and the average particle size of the nanomagnetic particles is 20 to 40 nm.

2. The nanomagnetic particle according to claim 1, wherein Among the nano magnetic particles, particles with a particle size of 10 to 40 nm account for ≥90%.

3. The nanomagnetic particle according to claim 1 or 2, wherein: Among the nano-magnetic particles, particles with a particle size greater than 40 nm account for ≤5%.

4. The nanomagnetic particle according to any one of claims 1 to 3, wherein: Among the nano-magnetic particles, particles with a particle size of less than 10 nm account for ≤5%.

5. The nanomagnetic particle according to any one of claims 1 to 4, characterized in that: When both y and z are not 0, y and z satisfy the relationship: 1≤y / z≤1.

5.

6. A method for preparing the nanomagnetic particles according to any one of claims 1 to 5, comprising the following steps: (1) Main material A and main material B are mixed in proportion to obtain a mixed material, wherein main material A includes SrCO3 and Fe2O3, and main material B includes any one or a combination of at least two of BaCO3, La2O3 or Co2O3, and the mixed material is mixed with H3BO3 and SrCl2, ground and then calcined; (2) melting the calcined material and flowing it onto a water-cooled roller to obtain an amorphous sheet; (3) After heating and crystallizing the amorphous thin slice, washing is performed to obtain the nanomagnetic particles.

7. The preparation method according to claim 6, wherein The mass of the H3BO3 in step (1) is 15-25% of the mass of the mixed material.

8. The preparation method according to claim 6 or 7, wherein: The mass of the SrCl2 is 10-20% of the mass of the mixed material.

9. The preparation method according to any one of claims 6 to 8, wherein: The grinding method in step (1) includes ball milling.

10. The preparation method according to any one of claims 6 to 9, wherein: The calcination temperature is 900-1100°C; Optionally, the calcination treatment time is 1 to 3 hours.

11. The preparation method according to any one of claims 6 to 10, wherein: The temperature of the melting treatment in step (2) is 1350-1500°C.

12. The preparation method according to any one of claims 6 to 11, wherein: The outflowing specifically comprises pouring the melted liquid into a tubular container with a nozzle, and simultaneously introducing air to wet-press the liquid so that the liquid flows out through the nozzle; Optionally, the rotation speed of the water-cooled roller is 20-30 m / s.

13. The preparation method according to any one of claims 6 to 12, wherein: The temperature of the heating crystallization treatment in step (3) is 550-650°C; Optionally, the heating crystallization time is 4 to 6 hours.

14. The preparation method according to any one of claims 6 to 13, wherein: The washing treatment in step (3) comprises placing the material obtained after heating and crystallization in water, adding acid and repeatedly dissolving it until all non-magnetic materials in the material are dissolved and washed away, precipitating the remaining material, and repeatedly washing it with alcohol; Optionally, a drying process is performed after the washing; Optionally, the drying temperature is 100-110°C.

15. A use of the nanomagnetic particles according to any one of claims 1 to 5, wherein: The nano magnetic particles are used in magnetic storage devices.

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