A ceramic injection-molded 3D wound face type Ni-Zn ferrite material and a preparation method thereof

Abstract

The application provides a ceramic injection molding 3D winding surface type Ni-Zn ferrite material and a preparation method thereof. The material is composed of Fe2O3 45wt%-49wt%, NiO 18wt%-33wt%, ZnO 22wt%-33wt%, CuO 5wt%-7wt%, SnO2 0.2wt%-1.0wt%, Co3O4 0.3wt%-0.7wt% and modified multi-walled carbon nanotubes 1.2wt%-1.5wt% by weight. The modified multi-walled carbon nanotubes are multi-walled carbon nanotubes loaded with Fe2O3 / Fe3O4 on the surface. The material is suitable for ceramic injection molding, can accurately form the required curved surface, thin wall and fine groove of the 3D winding surface type, can improve the sintering density by adding SnO2, can optimize the powder dispersibility by adding the modified multi-walled carbon nanotubes, can greatly improve the material fluidity and forming stability, can avoid the problem of low magnetic core precision, can adjust the magnetic crystal anisotropy by adding Co3O4, can reduce the permeability fluctuation rate at low temperature, can improve the mechanical strength after debinding and sintering, and can reduce damage in use. The material has the advantages of long service life, reasonable component design, simple implementation, and easy popularization and implementation.

Description

Technical Field

[0001] This application belongs to the field of ferrite material production technology, specifically relating to a Ni-Zn ferrite material suitable for ceramic injection molding 3D wound surface and its preparation method. Background Technology

[0002] In existing technologies, ferrite materials, due to their excellent magnetism, low loss, and stability, are the core components of inductors, transformers, and communication electronic components. They are crucial for the high-frequency and miniaturized development of electronic devices, directly affecting equipment performance and market competitiveness. However, traditional ferrite cores are mostly produced by uniaxial pressing or isostatic pressing, which can only produce simple shapes such as blocks and rings. They cannot accurately form the curved surfaces, thin walls, and fine grooves required for 3D winding surfaces, hindering the research and mass production of 3D winding surface ferrite cores and making it difficult to meet the needs of high-frequency communications, new energy, and other fields.

[0003] In existing technologies, the industry has introduced ceramic injection molding (CIM) technology, which mixes ferrite powder with organic binders and injects them into the mold to fabricate magnetic cores with complex shapes, breaking through traditional bottlenecks. However, existing ferrite materials suitable for ceramic injection molding have the following shortcomings: traditional ferrites have poor flowability and molding stability, making it difficult to fill the fine structure of 3D winding surfaces, resulting in low core precision and poor surface quality; after debinding and sintering, the density, permeability, and rate of change of permeability relative to temperature of ferrite cannot meet the requirements of low-temperature and high-frequency applications. After sintering, the mechanical strength of ferrite is insufficient, the service life is short, and it is not suitable for low-temperature applications. It is easily damaged during winding or use, affecting the reliability of the components.

[0004] Therefore, there is an urgent need to improve ferrite materials suitable for ceramic injection molding 3D winding surfaces, enhance their molding adaptability and core performance, meet the needs of high-frequency power supplies, low-temperature applications, communications and other fields, and promote the upgrading of electronic component technology. Summary of the Invention

[0005] This application aims to address the technical problems in the prior art, where traditional ferrite cores, produced by powder pressing, can only produce simple shapes and cannot accurately form the structures required for 3D winding surfaces. Furthermore, ferrites produced by ceramic injection molding suffer from poor fluidity and molding stability, low core precision, insufficient mechanical strength after debinding and sintering, unsuitability for low-temperature applications, large permeability fluctuations under low-temperature conditions, and short service life. Therefore, this application proposes a Ni-Zn ferrite material suitable for ceramic injection molding of 3D winding surfaces and its preparation method.

[0006] This application adopts the following scheme: a Ni-Zn ferrite material suitable for ceramic injection molding 3D wound surface type, which, by weight, is composed of the following components: Fe2O3 45wt%-49wt%, NiO 18wt%-33wt%, ZnO 22wt%-33wt%, CuO 5wt%-7wt%, SnO2 0.2wt%-1.0wt%, Co3O4 0.3wt%-0.7wt%, and modified multi-walled carbon nanotubes 1.2wt%-1.5wt%;

[0007] The modified multi-walled carbon nanotubes are multi-walled carbon nanotubes with Fe2O3 / Fe3O4 supported on their surface.

[0008] In some feasible embodiments, the method for preparing the modified multi-walled carbon nanotubes includes the following steps:

[0009] Step 101. Activated multi-walled carbon nanotubes, 1 mol / L ferric nitrate solution, and anhydrous ethanol are added to the reaction vessel in a mass ratio of 1:(8-10):(0.8-1.2). After dispersing at room temperature and 1000-1200 rpm for 10 min, a pre-dispersed system is obtained.

[0010] Step 102. Add concentrated ammonia to the pre-dispersion system prepared in step 101. When the pH of the reaction system is 10, stop adding concentrated ammonia. React the reaction system at room temperature and 100-150 rpm for 25-30 hours. After filtration, washing and drying, crude modified multi-walled carbon nanotubes are obtained.

[0011] Step 103. Transfer the crude modified multi-walled carbon nanotubes prepared in step 102 to a sintering furnace and sinter at 400°C with air introduced for 2 hours. After sintering, cool down to room temperature with a mixture of N2 and H2 to obtain the modified multi-walled carbon nanotubes.

[0012] In some feasible embodiments, the volume ratio of N2 to H2 is 3:1.

[0013] In some feasible embodiments, the heating rate during sintering is 6°C / min, and the cooling rate during cooling is 10°C / min.

[0014] In some feasible embodiments, step 101, the preparation method of activated multi-walled carbon nanotubes includes the following steps: multi-walled carbon nanotubes and mixed acid solution are added into a stirred tank in a mass ratio of 1:6, activated for 12 hours under the conditions of 1200rpm-1500rpm and 130℃ oil bath, and then filtered, washed with deionized water until neutral, and dried to obtain the activated multi-walled carbon nanotube product.

[0015] In some feasible embodiments, the mixed acid solution is obtained by mixing a 1 mol / L nitric acid solution and a 1 mol / L sulfuric acid solution at a volume ratio of 5:2.

[0016] In practical implementation, after activation with strong acid, multi-walled carbon nanotubes (MWCNTs) undergo surface etching to create defective channels. Simultaneously, numerous oxygen-containing functional groups (-COOH, -OH) are introduced, significantly increasing the surface area of ​​the MWCNTs and providing abundant loading sites for Fe₂O₃ / Fe₃O₄. The oxygen-containing functional groups at these loading sites then coordinate with Fe through these bonds. 3+ By combining and loading a large number of Fe(OH)3 precursor particles onto the surface of multi-walled carbon nanotubes under alkaline conditions, and then oxidizing them in air, modified multi-walled carbon nanotubes with a large amount of Fe2O3 / Fe3O4 loaded on the surface are obtained. The multi-walled carbon nanotubes loaded with Fe2O3 / Fe3O4 not only have enhanced magnetism, but can also bond with Fe2O3 in the ferrite matrix through Fe-O-Fe bonds, thereby improving the interfacial bonding force of the ferrite material.

[0017] In some feasible embodiments, the sintering density of the ferrite material is 4.9 g / cm³. 3 -5.5g / cm 3 .

[0018] In some feasible embodiments, the initial permeability μi of the ferrite is 425H / m-480H / m, and the rate of change of the permeability of the ferrite relative to the temperature is defined as Δui under the conditions of -40℃ to 25℃, wherein Δui satisfies the following relationship 0<Δui<1, and the Curie temperature Tc of the ferrite material is 135℃-150℃.

[0019] To address the technical problems raised in this application, this application also provides a method for preparing Ni-Zn ferrite materials suitable for ceramic injection molding 3D wound surface type, comprising the following steps:

[0020] Step 201. Transfer Fe2O3, NiO, ZnO, CuO, SnO2, Co3O4 and modified multi-walled carbon nanotubes sequentially into a dry mixing vessel according to the preset target ratio. After dispersing for 20 minutes at room temperature and 1600rpm-2200rpm, powder A is obtained.

[0021] Step 202. Transfer the powder A prepared in step 201 to a calcining furnace and calcine it at 840℃-860℃ with air introduced for 420min-540min to obtain calcined material B.

[0022] Step 203. Transfer the calcined material B and dispersant prepared in step 202 to a ball mill. After wet ball milling for 2-5 hours with steel balls as the ball milling medium, slurry C is obtained. Polyethylene glycol is selected as the dispersant.

[0023] Step 204. Transfer the slurry C prepared in step 203 and polyvinyl alcohol to a spray granulator, and spray dry it under the conditions of output pressure of 0.5MPa-1.5MPa and output temperature of 150℃-200℃ to obtain powder D.

[0024] Step 205. Transfer the powder D prepared in step 204 to the mold and press it to obtain a green blank. Then transfer the green blank to the sintering furnace and sinter it at 1050℃-1150℃ with air introduced for 120min-150min to obtain the finished Ni-Zn ferrite material suitable for ceramic injection molding 3D wound surface type.

[0025] In some feasible embodiments, in step 203, the particle size range of slurry C is 1.0 μm-1.8 μm.

[0026] In some feasible embodiments, in step 204, the mass of polyvinyl alcohol is 1.5wt%-3.2wt% of the total mass of slurry C.

[0027] In some feasible embodiments, in step 205, the compaction density of the green body is 3.1 g / cm³. 3 -3.6g / cm 3 .

[0028] To address the technical problems raised in this application, this application also provides an application of Ni-Zn ferrite material suitable for ceramic injection molding 3D wound surface type, which is used to manufacture filter inductors.

[0029] Compared with the prior art, this application has the following beneficial effects:

[0030] This application provides a Ni-Zn ferrite material suitable for ceramic injection molding 3D wound surface and its preparation method. It is composed of Fe2O3 45wt%-49wt%, NiO 18wt%-33wt%, ZnO 22wt%-33wt%, CuO 5wt%-7wt%, SnO2 0.2wt%-1.0wt%, Co3O4 0.3wt%-0.7wt%, and modified multi-walled carbon nanotubes 1.2wt%-1.5wt%, wherein the modified multi-walled carbon nanotubes are multi-walled carbon nanotubes with Fe2O3 / Fe3O4 surface-loaded. This material is suitable for ceramic injection molding, enabling precise molding of curved surfaces, thin walls, and fine grooves required for 3D winding surfaces. The addition of SnO2 enhances sintering density, while the inclusion of modified multi-walled carbon nanotubes optimizes powder dispersion, significantly improving material flowability and molding stability, thus avoiding the problem of low core precision. Furthermore, the addition of Co3O4 regulates magnetocrystalline anisotropy, working synergistically with the modified multi-walled carbon nanotubes to reduce permeability fluctuations at low temperatures, improve mechanical strength after debinding and sintering, and reduce damage during use. It boasts advantages such as long service life, rational component design, ease of implementation, and convenient promotion and implementation. Attached Figure Description

[0031] Figure 1 These are the permeability variation curves of the ferrite magnetic rings in Examples 1-3 of this application in the temperature range of -40℃ to Tc;

[0032] Figure 2 These are the permeability variation curves of the ferrite magnetic rings in Embodiment 1 and Comparative Example 1 of this application in the temperature range of -40℃ to Tc;

[0033] Figure 3 These are the permeability variation curves of the ferrite magnetic rings in Embodiment 1 and Comparative Example 2 of this application in the temperature range of -40℃ to Tc;

[0034] Figure 4 These are the permeability variation curves of the ferrite magnetic rings in Embodiment 1 and Comparative Example 3 of this application in the temperature range of -40℃ to Tc;

[0035] Figure 5 These are the permeability variation curves of the ferrite magnetic rings in Embodiment 1 and Comparative Example 4 of this application in the temperature range of -40℃ to Tc. Detailed Implementation Example 1

[0036] (1) The preparation method of activated multi-walled carbon nanotubes includes the following steps: multi-walled carbon nanotubes and mixed acid solution are added into a stirred tank in a mass ratio of 1:6. After activation for 12 hours under the conditions of 1200 rpm and 130℃ oil bath, the activated multi-walled carbon nanotubes are then filtered, washed with deionized water until neutral, and dried to obtain the finished product.

[0037] The mixed acid solution is obtained by mixing a 1 mol / L nitric acid solution and a 1 mol / L sulfuric acid solution in a volume ratio of 5:2.

[0038] (2) The preparation method of modified multi-walled carbon nanotubes includes the following steps:

[0039] Step 101. Activated multi-walled carbon nanotubes, 1 mol / L ferric nitrate solution, and anhydrous ethanol are added to the reaction vessel in a mass ratio of 1:8:0.8. After dispersing at room temperature and 1000 rpm for 10 min, a pre-dispersed system is obtained.

[0040] Step 102. Add concentrated ammonia to the pre-dispersion system prepared in step 101. When the pH of the reaction system is 10, stop adding concentrated ammonia. After reacting the reaction system at room temperature and 100 rpm for 25 h, filter, wash and dry in sequence to obtain crude modified multi-walled carbon nanotubes.

[0041] Step 103. Transfer the crude modified multi-walled carbon nanotubes prepared in step 102 to a sintering furnace and sinter at 400°C with air introduced for 2 hours. After sintering, cool down to room temperature with a mixture of N2 and H2 to obtain the modified multi-walled carbon nanotubes.

[0042] In step 103, the volume ratio of N2 to H2 is 3:1. During the sintering process, the heating rate is 6℃ / min, and during the cooling process, the cooling rate is 10℃ / min.

[0043] (3) A method for preparing 3D wound surface Ni-Zn ferrite materials suitable for ceramic injection molding, comprising the following steps:

[0044] Step 201. According to the composition table shown in Table 1, Fe2O3, NiO, ZnO, CuO, SnO2, Co3O4 and modified multi-walled carbon nanotubes are sequentially transferred to a dry mixing vessel and dispersed at room temperature and 1600 rpm for 20 min to obtain powder A.

[0045] Step 202. Transfer the powder A obtained in step 201 to a calcining furnace and calcine it at 840°C with air introduced for 420 minutes to obtain calcined material B.

[0046] Step 203. Transfer the calcined material B and dispersant prepared in step 202 to a ball mill. After wet ball milling for 2 hours with steel balls as the ball milling medium, slurry C is obtained. The particle size range of the obtained slurry C is 1.2 μm.

[0047] Step 204. Transfer the slurry C prepared in step 203 and polyvinyl alcohol to a spray granulator, and spray dry it at an output pressure of 0.5 MPa and an output temperature of 150°C to obtain powder D. The mass of polyvinyl alcohol is 1.6 wt% of the total mass of slurry C.

[0048] Step 205. Transfer the powder D prepared in step 204 into a mold and press it to obtain a green body. Then transfer the green body to a sintering furnace and sinter it at 1050℃ with air circulation for 120 minutes to obtain a finished Ni-Zn ferrite material suitable for ceramic injection molding 3D wound surface type. The pressing density of the green body is 3.1 g / cm³. 3 . Example 2

[0049] (1) The preparation method of activated multi-walled carbon nanotubes includes the following steps: multi-walled carbon nanotubes and mixed acid solution are added into a stirred tank in a mass ratio of 1:6. After activation for 12 hours under the conditions of 1300 rpm and 130℃ oil bath, the activated multi-walled carbon nanotubes are obtained by filtration, washing with deionized water until neutral, and drying.

[0050] The mixed acid solution is obtained by mixing a 1 mol / L nitric acid solution and a 1 mol / L sulfuric acid solution in a volume ratio of 5:2.

[0051] (2) The preparation method of modified multi-walled carbon nanotubes includes the following steps:

[0052] Step 101. Activated multi-walled carbon nanotubes, 1 mol / L ferric nitrate solution, and anhydrous ethanol are added to the reaction vessel in a mass ratio of 1:9:1. After dispersing at room temperature and 1100 rpm for 10 min, a pre-dispersed system is obtained.

[0053] Step 102. Add concentrated ammonia to the pre-dispersion system prepared in step 101. When the pH of the reaction system is 10, stop adding concentrated ammonia. After reacting the reaction system at room temperature and 120 rpm for 27 h, filter, wash and dry in sequence to obtain crude modified multi-walled carbon nanotubes.

[0054] Step 103. Transfer the crude modified multi-walled carbon nanotubes prepared in step 102 to a sintering furnace and sinter at 400°C with air introduced for 2 hours. After sintering, cool down to room temperature with a mixture of N2 and H2 to obtain the modified multi-walled carbon nanotubes.

[0055] In step 103, the volume ratio of N2 to H2 is 3:1. During the sintering process, the heating rate is 6℃ / min, and during the cooling process, the cooling rate is 10℃ / min.

[0056] (3) A method for preparing 3D wound surface Ni-Zn ferrite materials suitable for ceramic injection molding, comprising the following steps:

[0057] Step 201. According to the composition table shown in Table 1, Fe2O3, NiO, ZnO, CuO, SnO2, Co3O4 and modified multi-walled carbon nanotubes are sequentially transferred to a dry mixing vessel and dispersed at room temperature and 2000 rpm for 20 min to obtain powder A.

[0058] Step 202. Transfer the powder A prepared in step 201 to a calcining furnace and calcine it at 850°C with air introduced for 500 minutes to obtain calcined material B.

[0059] Step 203. Transfer the calcined material B and dispersant prepared in step 202 to a ball mill. After wet ball milling for 3 hours with steel balls as the ball milling medium, slurry C is obtained. The particle size range of the obtained slurry C is 1.5 μm.

[0060] Step 204. Transfer the slurry C prepared in step 203 and polyvinyl alcohol to a spray granulator, and spray dry it at an output pressure of 1 MPa and an output temperature of 170°C to obtain powder D. The mass of polyvinyl alcohol is 2 wt% of the total mass of slurry C.

[0061] Step 205. Transfer the powder D prepared in step 204 into a mold and press it to obtain a green body. Then transfer the green body to a sintering furnace and sinter it at 1100℃ with air circulation for 125 minutes to obtain a finished Ni-Zn ferrite material suitable for ceramic injection molding 3D wound surface type. The pressing density of the green body is 3.4 g / cm³. 3 . Example 3

[0062] (1) The preparation method of activated multi-walled carbon nanotubes includes the following steps: multi-walled carbon nanotubes and mixed acid solution are added into a stirred tank in a mass ratio of 1:6. After activation for 12 hours under the conditions of 1300 rpm and 130℃ oil bath, the activated multi-walled carbon nanotubes are obtained by filtration, washing with deionized water until neutral, and drying.

[0063] The mixed acid solution is obtained by mixing a 1 mol / L nitric acid solution and a 1 mol / L sulfuric acid solution in a volume ratio of 5:2.

[0064] (2) The preparation method of modified multi-walled carbon nanotubes includes the following steps:

[0065] Step 101. Activated multi-walled carbon nanotubes, 1 mol / L ferric nitrate solution, and anhydrous ethanol are added to the reaction vessel in a mass ratio of 1:10:1.2. After dispersing at room temperature and 1200 rpm for 10 min, a pre-dispersed system is obtained.

[0066] Step 102. Add concentrated ammonia to the pre-dispersion system prepared in step 101. When the pH of the reaction system is 10, stop adding concentrated ammonia. After reacting the reaction system at room temperature and 150 rpm for 30 h, filter, wash and dry in sequence to obtain crude modified multi-walled carbon nanotubes.

[0067] Step 103. Transfer the crude modified multi-walled carbon nanotubes prepared in step 102 to a sintering furnace and sinter at 400°C with air introduced for 2 hours. After sintering, cool down to room temperature with a mixture of N2 and H2 to obtain the modified multi-walled carbon nanotubes.

[0068] In step 103, the volume ratio of N2 to H2 is 3:1. During the sintering process, the heating rate is 6℃ / min, and during the cooling process, the cooling rate is 10℃ / min.

[0069] (3) A method for preparing 3D wound surface Ni-Zn ferrite materials suitable for ceramic injection molding, comprising the following steps:

[0070] Step 201. According to the composition table shown in Table 1, Fe2O3, NiO, ZnO, CuO, SnO2, Co3O4 and modified multi-walled carbon nanotubes are sequentially transferred to a dry mixing vessel and dispersed at room temperature and 2200 rpm for 20 min to obtain powder A.

[0071] Step 202. Transfer the powder A prepared in step 201 to a calcining furnace and calcinate it at 860°C with air introduced for 540 minutes to obtain calcined material B.

[0072] Step 203. Transfer the calcined material B and dispersant prepared in step 202 to a ball mill. After wet ball milling for 5 hours with steel balls as the ball milling medium, slurry C is obtained. The particle size range of the obtained slurry C is 1.8 μm.

[0073] Step 204. Transfer the slurry C prepared in step 203 and polyvinyl alcohol to a spray granulator, and spray dry it at an output pressure of 1.5 MPa and an output temperature of 200°C to obtain powder D. The mass of polyvinyl alcohol is 1.5 wt%-3.2 wt% of the total mass of slurry C.

[0074] Step 205. Transfer the powder D prepared in step 204 into a mold and press it to obtain a green body. Then transfer the green body to a sintering furnace and sinter it at 1150℃ with air circulation for 120-150 minutes to obtain a finished Ni-Zn ferrite material suitable for ceramic injection molding 3D wound surface type. The pressing density of the green body is 3.6 g / cm³. 3 .

[0075] Comparative Example 1

[0076] The difference between Comparative Example 1 and Example 2 is that the modified multi-walled carbon nanotubes in the ferrite were removed and replaced with Fe2O3, while the process of the remaining components remained unchanged.

[0077] Comparative Example 2

[0078] The difference between Comparative Example 2 and Example 2 is that Co3O4 in the ferrite is removed and replenished with Fe2O3, while the process of the remaining components remains unchanged.

[0079] Comparative Example 3

[0080] The difference between Comparative Example 3 and Example 2 is that the modified multi-walled carbon nanotubes and Co3O4 in the ferrite were removed at the same time and replenished with Fe2O3, while the process of the remaining components remained unchanged.

[0081] Comparative Example 4

[0082] The difference between Comparative Example 4 and Example 2 is that the modified multi-walled carbon nanotubes are replaced with multi-walled carbon nanotubes, while the processes for the other components remain unchanged.

[0083] Table 1. Component Tables of Examples 1-3 and Comparative Examples 1-4

[0084]

[0085] The ferrite magnetic rings (outer diameter 20 mm, inner diameter 12 mm, thickness 5 mm, with a groove 1 mm long, 0.5 mm wide, and 0.3 mm deep on the outer surface) prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to the following tests:

[0086] Test 1: Referring to GB / T 6060.2-2006 "Surface Roughness Comparison Samples for Grinding, Turning, Boring, Milling, Shaping and Planing Surfaces", a laser diameter gauge with an accuracy of ±0.001mm was used to test the radial error of the outer circle / inner circle of the ferrite magnetic rings (outer diameter 20mm, inner diameter 12mm, thickness 5mm) prepared in Examples 1-3 and Comparative Examples 1-4, i.e. the surface accuracy error.

[0087] Test 2: Referring to SJ / T 11610-2016 "Inspection Methods for Dimensions and Appearance of Electronic Ceramic Parts", a 400x metallographic microscope was used to observe the filling integrity of the fine grooves with a width of 0.5 mm and a depth of 0.3 mm on the ferrite magnetic rings prepared in Examples 1-3 and Comparative Examples 1-4, and the filling area ratio, i.e., the groove filling rate, was calculated.

[0088] Test 3: Referring to GB / T 3655-2008 "Method for Measuring the Magnetic Properties of Electrical Steel Strips (Sheets)," copper wire with a diameter of 0.25 mm was wound around the strips in Examples 1-3 and Comparative Examples 1-4. The prepared ferrite magnetic ring was wound with 10 turns. The Curie temperature Tc of the magnetic ring and the initial permeability μi of the ferrite magnetic ring were measured using an HP-4294A LCR meter, a TMJ-9712B controllable constant temperature and humidity chamber, and an HP-4263B LCR meter. The permeability μi of the ferrite magnetic ring was measured under the conditions of -40℃ to 25℃ (constant temperature every 5℃ for 30 min) and a magnetic field strength of 500 A / m. The relative temperature change rate Δui of the permeability was calculated using the formula Δui=[μi(T+ΔT)-μi(T)] / μi(T)×100% (where ΔT=5℃, T represents the test points at -40℃-20℃). The permeability change curve of the ferrite magnetic ring in the temperature range of -40℃ to Tc was plotted. Figures 1-5 As shown;

[0089] Test 4: Referring to GB / T 13818-2009 "Test Method for Bending Properties of Molding Plastics", the bending strength of the ferrite magnetic rings prepared in Examples 1-3 and Comparative Examples 1-4 was tested using the three-point bending method (span 15 mm, loading speed 2 mm / min). At the same time, referring to GB / T 25995-2010 "Test Method for Density and Apparent Porosity of Fine Ceramics", the volume density of the above magnetic rings was tested using the Archimedes' displacement method with deionized water as the medium. The test results are shown in Tables 2 and 3 below.

[0090] Table 2. Results of Tests 1, 2, and 4

[0091]

[0092] Table 3 Test Results Table

[0093]

[0094]

[0095] As shown in Tables 2 and 3, this application provides a Ni-Zn ferrite material suitable for ceramic injection molding of 3D wound surfaces. By doping the metal oxide matrix with multi-walled carbon nanotubes (Fe2O3 / Fe3O4-MWCNTs) loaded with Fe2O3 / Fe3O4, the ferrite material is more suitable for ceramic injection molding processes, and can accurately form the curved surfaces, thin walls and fine grooves required for 3D wound surfaces. By adding Co3O4 to adjust the magnetocrystalline anisotropy, and with the synergistic effect of the modified multi-walled carbon nanotubes, the magnetic permeability fluctuation rate at low temperature is reduced, the mechanical strength after debinding and sintering is improved, and damage during use is reduced.

[0096] Specifically, in Examples 1-3, after activation with strong acid, multi-walled carbon nanotubes (MWCNTs) underwent surface etching to create defective channels. Simultaneously, numerous oxygen-containing functional groups (-COOH, -OH) were introduced, significantly increasing the surface area of ​​the MWCNTs and providing a large number of loading sites for Fe2O3 / Fe3O4. The oxygen-containing functional groups at these loading sites then interact with Fe through coordination bonds. 3+ By combining and loading a large number of Fe(OH)3 precursor particles onto the surface of multi-walled carbon nanotubes under alkaline conditions, and then oxidizing them in air, modified multi-walled carbon nanotubes with a large amount of Fe2O3 / Fe3O4 loaded on the surface are obtained. The multi-walled carbon nanotubes loaded with Fe2O3 / Fe3O4 not only have enhanced magnetism, but can also bond with Fe2O3 in the ferrite matrix through Fe-O-Fe bonds, thereby improving the interfacial bonding force of the ferrite material.

[0097] Furthermore, in ferrite materials, the oxygen-containing functional groups (-COOH) in Fe2O3 / Fe3O4-MWCNTs interact with the metal cations (NiO and ZnO) on the surface of NiO and ZnO. ²+ Zn ²+Coordination bonds are formed, and the Fe2O3 / Fe3O4 shell and Fe2O3 in the matrix are bonded through Fe-O-Fe bonds, breaking the agglomerates formed by van der Waals forces in traditional powders. This significantly improves the interfacial bonding force and dispersion uniformity of ferrite materials, thereby significantly improving the fluidity of slurry C in step 203, allowing it to fully fill the mold, reducing radial deviation, and ultimately improving the surface precision of the sintered ferrite to 0.02mm-0.03mm (0.09mm in Comparative Example 1), and the groove filling rate to 95%-98% (80% in Comparative Example 1). Especially in Examples 2 and 3, due to the finer and more uniformly dispersed loaded particles, the fine grooves with a width of 0.5mm and a depth of 0.3mm can be completely filled without voids or material shortages. In Comparative Example 1 (Fe2O3 / Fe3O4-MWCNTs removed), Fe2O3, NiO and other powders agglomerated severely due to van der Waals forces, resulting in poor fluidity of the slurry C and an inability to uniformly fill the mold during molding, thus reducing the surface finish and groove filling degree. In Comparative Example 4 (MWCNTs replacing Fe2O3 / Fe3O4-MWCNTs), the unmodified MWCNTs had no oxygen-containing functional groups on their surface and were dispersed only by physical mixing. Voids still existed at the interface between them and the ferrite matrix, which could not effectively break up the agglomeration, thus reducing the surface finish and groove filling degree.

[0098] Furthermore, in Examples 1-3, the high conductivity of Fe2O3 / Fe3O4-MWCNTs can rapidly conduct magnetic field energy, reducing energy loss from magnetic domain movement at low temperatures. The magnetic domain fit between the loaded Fe2O3 / Fe3O4 and Fe2O3 in the ferrite matrix can effectively improve the magnetic moment orientation of the ferrite material, enhance the magnetic field response capability of the ferrite, and effectively improve the initial permeability of the ferrite. In the ferrite matrix, the Co in Co3O4 3+ It can enter the Ni-Zn ferrite spinel lattice and replace part of the Fe. 3+The position reduces the anisotropy constant of the magnetocrystalline material, alleviates the domain pinning effect, and makes the relative temperature change rate Δui of the ferrite permeability more gradual (Δui=11.63% at -40℃ in Example 2, and Δui=16.59% at -40℃ in Comparative Example 2). In the ferrite matrix, the high thermal conductivity of Fe2O3 / Fe3O4-MWCNTs can suppress the generation of lattice defects during sintering, and Co3O4 can form coordination bonds with Fe2O3 / Fe3O4-MWCNTs, optimizing the internal interface performance of the ferrite and improving the uniformity of Co3O4 distribution, thereby significantly improving the magnetic order of the ferrite. Together, these factors increase the Curie temperature Tc of the ferrite from 93℃ in Comparative Example 3 to 148℃ in Example 3, and ensure the stability of the magnetic structure at low temperatures. In Comparative Example 2 (without Co3O4), the anisotropy constant of the magnetocrystalline material is relatively high, making it difficult for the domain walls to move at low temperatures. Therefore, at -40℃, the permeability of the ferrite decreases to 478 H / m, and Δui increases to 16.59%, resulting in a significant decrease in permeability stability. In Comparative Example 3, both Co3O4 and Fe2O3 / Fe3O4-MWCNTs are eliminated simultaneously. The synergistic effect of the magnetic domains disappears, the magnetic moment orientation decreases, and the high thermal conductivity component in the system is missing. This makes it impossible to more effectively suppress lattice defects during the sintering process. Therefore, at -40℃, the permeability of the ferrite decreases to 448 H / m, Δui increases to 17.89%, and the Curie temperature Tc decreases significantly, failing to meet the requirements for use in low-temperature scenarios. In Comparative Example 4, the MWCNTs surface was not loaded with Fe2O3 / Fe3O4, resulting in a decrease in the overall interfacial bonding strength of the ferrite, which could not effectively transfer magnetic field energy. The magnetic order inside the ferrite was reduced, which could not effectively suppress lattice defects during the sintering process. Therefore, at -40℃, Δui increased to 15.66%, and the magnetic permeability stability was reduced.

[0099] In terms of mechanical properties, in Examples 1-3, Fe2O3 / Fe3O4-MWCNTs form a supporting framework inside the ferrite matrix. During sintering, the Fe2O3 / Fe3O4 loaded on the surface of MWCNTs can combine with the metal oxides in the ferrite matrix, thereby effectively suppressing the formation of sintering voids and significantly improving the density and mechanical strength of the ferrite material, resisting mechanical stress during the winding process.

[0100] Specifically, in Examples 1-3, Fe2O3 / Fe3O4-MWCNTs are distributed within the ferrite matrix. The Fe2O3 / Fe3O4 on their surface is bonded to the matrix via Fe-O-Fe bonds, reducing interfacial porosity and effectively transferring the internal stress of the ferrite matrix. The high thermal conductivity of Fe2O3 / Fe3O4-MWCNTs within the ferrite matrix effectively inhibits abnormal grain growth during ferrite sintering, refines the ferrite grain size, reduces porosity formation, and improves the density and mechanical strength of the ferrite. As shown in Table 2, the bulk density of the ferrite magnetic rings in Examples 1-3 reaches 4.92 g / cm³. 3 -4.99g / cm 3 (Comparative Example 1: 4.28 g / cm³) 3 The density of the sample increased by 15%-20%, and the flexural strength increased by 123-134 MPa (compared to 96 MPa in Comparative Example 1). Example 3, due to the highest MWCNT content (1.5 wt%), the most uniform load, and the most significant skeleton reinforcement effect, achieved a flexural strength of 134 MPa, capable of withstanding 20-30 MPa radial pressure during winding without cracking. In Comparative Example 1, the Fe2O3 / Fe3O4-MWCNTs skeleton was removed. During sintering, grain agglomeration increased the porosity of the conductive ferrite, and the pores easily became stress concentration points during stress transmission, thus reducing the flexural strength to 96 MPa and the bulk density to 4.28 g / cm³. 3 In Comparative Example 3, both the Fe2O3 / Fe3O4-MWCNTs framework and Co3O4 were simultaneously removed. The ferrite lacked both framework support and a high thermal conductivity component to optimize the lattice, leading to increased lattice defects. Consequently, the flexural strength decreased to 90 MPa, and the bulk density decreased to 3.93 g / cm³. 3 It is prone to cracking during winding.

[0101] This application provides a Ni-Zn ferrite material suitable for ceramic injection molding 3D wound surface type, which is composed of Fe2O3 45wt%-49wt%, NiO 18wt%-33wt%, ZnO 22wt%-33wt%, CuO 5wt%-7wt%, SnO2 0.2wt%-1.0wt%, Co3O4 0.3wt%-0.7wt%, and modified multi-walled carbon nanotubes 1.2wt%-1.5wt%, wherein the modified multi-walled carbon nanotubes are multi-walled carbon nanotubes with Fe2O3 / Fe3O4 surface loaded. Among them, Fe2O3 / Fe3O4-MWCNTs solve the problem of powder agglomeration and improve the adaptability of ferrite ceramics to injection molding. The magnetic domain synergy between Fe2O3 / Fe3O4-MWCNTs and Fe2O3, combined with the magnetocrystalline anisotropy adjustment of Co3O4, optimizes the magnetic order, permeability stability and Curie temperature of the ferrite matrix; and introduces a supporting framework into the ferrite matrix to improve the density and mechanical strength of the ferrite material. It has the advantages of long service life, reasonable composition design, simple implementation and easy promotion and implementation.

[0102] The embodiments provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A Ni-Zn ferrite material suitable for ceramic injection molding 3D wound surface type, characterized in that, By weight fraction, it consists of the following components: Fe2O3 45wt%-49wt%, NiO 18wt%-33wt%, ZnO 22wt%-33wt%, CuO 5wt%-7wt%, SnO2 0.2wt%-1.0wt%, Co3O4 0.3wt%-0.7wt%, and modified multi-walled carbon nanotubes 1.2wt%-1.5wt%. The modified multi-walled carbon nanotubes are multi-walled carbon nanotubes with Fe2O3 / Fe3O4 supported on their surface.

2. The Ni-Zn ferrite material suitable for 3D wound surface profile of ceramic injection molding according to claim 1, characterized in that, The method for preparing the modified multi-walled carbon nanotubes includes the following steps: Step 101. Activated multi-walled carbon nanotubes, 1 mol / L ferric nitrate solution, and anhydrous ethanol are added to the reaction vessel in a mass ratio of 1:(8-10):(0.8-1.2). After dispersing at room temperature and 1000-1200 rpm for 10 min, a pre-dispersed system is obtained. Step 102. Add concentrated ammonia to the pre-dispersion system prepared in step 101. When the pH of the reaction system is 10, stop adding concentrated ammonia. React the reaction system at room temperature and 100-150 rpm for 25-30 hours. After filtration, washing and drying, crude modified multi-walled carbon nanotubes are obtained. Step 103. Transfer the crude modified multi-walled carbon nanotubes prepared in step 102 to a sintering furnace and sinter at 400°C with air introduced for 2 hours. After sintering, cool down to room temperature with a mixture of N2 and H2 to obtain the modified multi-walled carbon nanotubes.

3. The Ni-Zn ferrite material suitable for 3D wound surface profile of ceramic injection molding according to claim 2, characterized in that, In step 101, the preparation method of activated multi-walled carbon nanotubes includes the following steps: multi-walled carbon nanotubes and mixed acid solution are added into a stirred tank in a mass ratio of 1:6, activated for 12 hours under the conditions of 1200rpm-1500rpm and 130℃ oil bath, and then filtered, washed with deionized water until neutral, and dried to obtain activated multi-walled carbon nanotubes.

4. The Ni-Zn ferrite material suitable for 3D wound surface type ceramic injection molding according to claim 3, characterized in that, The mixed acid solution is obtained by mixing a 1 mol / L nitric acid solution and a 1 mol / L sulfuric acid solution at a volume ratio of 5:

2.

5. A Ni-Zn ferrite material suitable for ceramic injection molding 3D wound surface type according to claim 1, characterized in that... The initial permeability μi of the ferrite is 425H / m-480H / m. Under the conditions of -40℃ to 25℃, the rate of change of the permeability of the ferrite relative to the temperature is defined as Δui, where Δui satisfies the following relationship 0<Δui<1. The Curie temperature Tc of the ferrite material is 135℃-150℃.

6. The Ni-Zn ferrite material suitable for 3D wound surface profile of ceramic injection molding according to claim 1, characterized in that, The sintering density of the ferrite material is 4.9 g / cm³. 3 -5.5g / cm 3 .

7. A method for preparing a 3D wound surface Ni-Zn ferrite material suitable for ceramic injection molding according to any one of claims 1-6, characterized in that, Includes the following steps: Step 201. Transfer Fe2O3, NiO, ZnO, CuO, SnO2, Co3O4 and modified multi-walled carbon nanotubes sequentially into a dry mixing vessel according to the preset target ratio. After dispersing for 20 minutes at room temperature and 1600rpm-2200rpm, powder A is obtained. Step 202. Transfer the powder A prepared in step 201 to a calcining furnace and calcine it at 840℃-860℃ with air introduced for 420min-540min to obtain calcined material B. Step 203. Transfer the calcined material B and dispersant prepared in step 202 to a ball mill. Under the condition that the ball milling medium is steel balls, wet ball mill for 2-5 hours to obtain slurry C. Step 204. Transfer the slurry C prepared in step 203 and polyvinyl alcohol to a spray granulator, and spray dry it under the conditions of output pressure of 0.5MPa-1.5MPa and output temperature of 150℃-200℃ to obtain powder D. Step 205. Transfer the powder D prepared in step 204 to the mold and press it to obtain a green blank. Then transfer the green blank to the sintering furnace and sinter it at 1050℃-1150℃ with air introduced for 120min-150min to obtain a Ni-Zn ferrite material suitable for ceramic injection molding 3D wound surface type.

8. The method for preparing a 3D wound surface Ni-Zn ferrite material suitable for ceramic injection molding according to claim 7, characterized in that, In step 203, the particle size range of slurry C is 1.0 μm-1.8 μm.

9. A method for preparing a 3D wound surface Ni-Zn ferrite material suitable for ceramic injection molding according to claim 7, characterized in that, In step 204, the mass of polyvinyl alcohol is 1.5wt%-3.2wt% of the total mass of slurry C.

10. A method for preparing a 3D wound surface Ni-Zn ferrite material suitable for ceramic injection molding according to claim 7, characterized in that, In step 205, the compaction density of the green body is 3.1 g / cm³. 3 -3.6g / cm 3 .

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