Manganese zinc ferrite high-frequency high-impedance material and preparation process thereof

Abstract

The invention relates to the technical field of manganese zinc ferrite materials, and particularly discloses a manganese zinc ferrite high-frequency high-impedance material and a preparation process thereof. The manganese zinc ferrite high-frequency high-impedance material is prepared from the following raw materials: Fe2O3, Mn3O4, ZnO, a carbon nanotube loaded rare earth oxide composite material, P2O5, Co2O3 and CaCO3. The preparation raw materials of the carbon nanotube loaded rare earth oxide composite material comprise a multi-walled carbon nanotube and a rare earth salt, and the mass ratio of the multi-walled carbon nanotube to the rare earth salt is 1: (0.12-0.14). According to the invention, the loss capability of the manganese zinc ferrite material to electromagnetic interference is enhanced, and the problem that the magnetic conductivity and impedance of the material are reduced in a high-frequency environment is solved.

Description

Technical Field

[0001] This invention relates to the field of manganese-zinc ferrite materials technology, and in particular to manganese-zinc ferrite high-frequency high-impedance materials and their preparation process. Background Technology

[0002] As electronic devices continue to evolve towards miniaturization, integration, and higher frequencies, the resulting electromagnetic interference (EMI) problems are becoming increasingly prominent. An effective way to solve or reduce electromagnetic pollution and improve the EMI immunity of electronic devices is to adopt electromagnetic compatibility (EMC) design, which requires a large amount of EMI-resistant materials. Manganese-zinc ferrite, as an important soft magnetic material, determines its electromagnetic shielding effectiveness based on its impedance characteristics at high frequencies.

[0003] Currently, conventional manganese-zinc ferrite materials are widely used in the field of electromagnetic shielding. Existing manganese-zinc ferrite materials typically have a high iron content, often referred to as iron-rich formulations (i.e., the molar fraction of Fe₂O₃ in the main formulation exceeds 50%), in order to obtain a high initial permeability. However, when iron-rich formulations are sintered and cooled in a reducing atmosphere, their spinel structure contains a significant amount of Fe. 2+ The presence of Fe forms 2+ with Fe 3+ The electron migration channels between them induce ion relaxation polarization, causing a sharp decrease in resistivity, making it difficult to adapt to use in high-frequency environments. Summary of the Invention

[0004] To enhance the material's ability to withstand electromagnetic interference and improve its impedance characteristics at high frequencies, this application provides a manganese-zinc ferrite high-frequency high-impedance material and its preparation process.

[0005] Firstly, the manganese-zinc ferrite high-frequency high-impedance material provided in this application adopts the following technical solution: Manganese-zinc ferrite high-frequency high-impedance material, by weight, comprises the following components: Fe2O3 47.5-49 parts, Mn3O4 25-30 parts, ZnO 15-20 parts, carbon nanotube supported rare earth oxide composite material 3-5 parts, P2O5 0.1-0.3 parts, Co2O3 0.1-0.3 parts, CaCO3 0.4-0.8 parts; The raw materials for preparing the carbon nanotube-supported rare earth oxide composite material include multi-walled carbon nanotubes and rare earth salts, and the mass ratio of the multi-walled carbon nanotubes to rare earth salts is 1:(0.12-0.14).

[0006] By adopting the above technical solution, this application uses Fe2O3, Mn3O4, and ZnO as the main components. Compared with the iron-rich formula, this application reduces the amount of Fe2O3 and adopts an iron-poor formula. The spinel structure has a lower content of ferrous ions and contains ZnO or MnO. (1–n)Zn n The presence of a nonmagnetic phase (O) results in high resistivity, low eddy current loss, and high permeability even at high frequencies in iron-poor MnZn ferrite. Adding carbon nanotubes to support rare earth oxide composites fills the pores within the manganese-zinc ferrite grains, increasing the material density and grain boundary resistance. Multi-walled carbon nanotubes, with their large specific surface area and good conductivity, provide an excellent support for rare earth oxides, allowing for uniform dispersion on their surface. Rare earth elements in rare earth salts possess unique electronic structures and chemical properties; in high-frequency environments, these elements can suppress Fe... 2+ with Fe 3+ The formation of electron migration channels between the two reduces the occurrence of ion relaxation polarization, thereby improving the resistivity of the material. On the other hand, the synergistic effect of multi-walled carbon nanotubes and rare earth oxides improves the microstructure of the material, enhances the material's ability to withstand electromagnetic interference, and improves the impedance characteristics of the material at high frequencies.

[0007] Furthermore, the addition of calcium carbonate causes it to dissociate into calcium oxide and carbon dioxide at high temperatures. Calcium oxide reacts with impurities such as silicon and aluminum in the iron ore to form calcium silicate and calcium aluminate, reducing the adverse effects of impurities on the material. During sintering, P2O5 segregates at grain boundaries, increasing the number of metal ion vacancies near the grain boundaries and accelerating grain boundary movement. This promotes grain growth and densification, increasing the initial permeability. Co2O3 inhibits Fe... 2+ The emergence of [the technology] reduces the impact of ambient temperature changes on the permeability of manganese-zinc ferrite magnetic rings.

[0008] Preferably, the rare earth salt comprises samarium nitrate and dysprosium nitrate in a mass ratio of 1:(0.3-0.5).

[0009] By adopting the above technical solution, samarium nitrate and dysprosium nitrate work synergistically to optimize the microstructure of manganese-zinc ferrite materials and suppress Fe in the spinel structure. 2+ with Fe 3+ The formation of electron migration channels between them reduces ion relaxation polarization, thereby avoiding a sharp drop in resistivity, improving the impedance characteristics of the material at high frequencies, enhancing the ability of manganese-zinc ferrite materials to be used at frequencies above 1MHz, and thus improving the electromagnetic shielding effectiveness of the material.

[0010] Preferably, the preparation method of the carbon nanotube-supported rare earth oxide composite material includes the following steps: (1) Add multi-walled carbon nanotubes to an acid solution, stir ultrasonically, filter, wash and dry to obtain carboxylated carbon nanotubes; (2) Dissolve samarium nitrate in water to obtain samarium nitrate solution, and dissolve dysprosium nitrate in water to obtain dysprosium nitrate solution; disperse carboxylated carbon nanotubes in water to obtain a dispersion, add samarium nitrate solution and dysprosium nitrate solution to the dispersion, stir evenly, add alkaline solution, heat and react for 10-12 hours, cool to room temperature, wash the precipitate several times, and dry to obtain carbon nanotube-supported rare earth oxide composite material.

[0011] By employing the above technical solution, carboxylated carbon nanotubes contain a large number of oxygen-containing functional groups on their surface, resulting in a significant negative charge. Upon addition of rare earth salt solution, rare earth metal ions are deposited on the surface of the carboxylated carbon nanotubes through electrostatic adsorption, forming crystal nuclei. After a hydrothermal reaction, the rare earth metal oxides are bonded to the carbon nanotubes via non-covalent bonds. The rare earth oxides formed during the preparation process can interact with other components in the manganese-zinc ferrite, altering the crystal structure and electron cloud distribution, increasing the energy barrier for electron migration, and further inhibiting electron movement in Fe... 2+ with Fe 3 + Migration between.

[0012] Secondly, the preparation process of the manganese-zinc ferrite high-frequency high-impedance material provided in this application adopts the following technical solution: The preparation process of manganese-zinc ferrite high-frequency high-impedance materials includes the following steps: S1: Select high-purity Fe2O3, Mn3O4 and ZnO; S2: Fe2O3, Mn3O4, ZnO, P2O5, Co2O3, and CaCO3 are mixed and placed in a ball mill to obtain a mixture through ball milling. S3: The mixture is pre-sintered, crushed and sieved to obtain pre-sintered material; S4: Carbon nanotube-supported rare earth oxide composite material is added to the pre-sintered material, mixed evenly, binder is added, mixed and granulated, and the pre-sintered material is subjected to a molding process to obtain a green body of a predetermined shape. S5: The green body is sintered, the oxygen partial pressure is adjusted, and after heat preservation, annealing and cooling, a manganese zinc ferrite high-frequency high-impedance material is obtained.

[0013] Preferably, the purity of Fe2O3, Mn3O4 and ZnO in step S1 is greater than or equal to 99%.

[0014] By adopting the above technical solution, high-purity raw materials can reduce the possibility of impurities introducing additional ions, avoid impurities affecting the crystal structure and ion distribution of the material, thereby ensuring that the manganese-zinc ferrite material has good electromagnetic properties, especially at high frequencies, it can maintain high impedance characteristics and improve its electromagnetic shielding effectiveness in high-frequency environments.

[0015] Preferably, in step S2, zirconia balls are used as the ball milling medium, the ball-to-material ratio is controlled at 3:1-5:1, the grinding time is 8-12 hours, the ball milling speed is 200-300 r / min, and the average particle size of the mixture obtained after grinding is 0.5-1.2 μm.

[0016] By adopting the above technical solution, the average particle size of the mixture is controlled to be 0.5-1.2μm through ball milling. When the particle size of the mixture is fine and uniform, the specific surface area of ​​the reaction can be increased, the reaction can be more complete, and a fine-grained structure can be obtained, thereby improving the consistency and stability of the material.

[0017] Preferably, the pre-firing temperature in step S3 is 800-900℃, and the pre-firing time is 2-4h.

[0018] By adopting the above technical solution, the pre-firing temperature is controlled at 800-900℃, so that various oxides undergo preliminary solid-phase reaction to form some ferrite, thereby improving the sintering activity of the powder, reducing the shrinkage and deformation of the product during sintering, and improving the compressibility of the powder, making it easier to form.

[0019] Preferably, in step S4, the molding process adopts dry pressing or isostatic pressing. The dry pressing pressure is 100-200MPa and the holding time is 1-2min. The isostatic pressing pressure is 200-300MPa and the holding time is 2-3min.

[0020] By adopting the above technical solution and controlling the molding pressure, the green body can have a suitable density, reduce the porosity of the material after sintering, improve the mechanical and magnetic properties of the material, and at the same time reduce the generation of cracks and maintain the integrity and performance of the material.

[0021] Preferably, in step S4, the adhesive is a 5wt%-8wt% PVA solution, and the mass ratio of the pre-burned material to the adhesive is 1:(0.3-0.4).

[0022] By adopting the above technical solution, since the brittle pre-fired powder has low bonding force and is difficult to form, the addition of binder granulation makes the powder agglomerate into particles of appropriate size and moderate moisture content, thereby improving compressibility and increasing the flowability of the powder to form a green body with uniform density distribution.

[0023] Preferably, in step S5, the sintering temperature is 1260-1380℃, the heating rate is 2-5℃ / min, the holding time is 3-6h, the annealing temperature is 600-800℃, the annealing time is 2-4h, and the oxygen partial pressure is 3-6%.

[0024] By adopting the above technical solution, the sintering atmosphere of the iron-poor material in this application is controlled as a weak oxidizing atmosphere, which is conducive to the discharge of gas inside the billet as much as possible, and to improving the product density and magnetic permeability.

[0025] This application has the following beneficial effects: This application uses Fe2O3, Mn3O4, and ZnO as the main components. Compared with the iron-rich formulation, this application reduces the amount of Fe2O3 and adopts an iron-poor formulation. The spinel structure has a low content of ferrous ions and contains ZnO or MnO. (1–n) Zn n The presence of a nonmagnetic phase (O) results in high resistivity, low eddy current loss, and high permeability even at high frequencies in iron-poor MnZn ferrite. Adding carbon nanotubes to support rare earth oxide composites fills the pores within the manganese-zinc ferrite grains, increasing the material density and grain boundary resistance. Multi-walled carbon nanotubes, with their large specific surface area and good conductivity, provide an excellent support for rare earth oxides, allowing for uniform dispersion on their surface. Rare earth elements in rare earth salts possess unique electronic structures and chemical properties; in high-frequency environments, these elements can suppress Fe... 2+ with Fe 3+ The formation of electron migration channels between the two reduces the occurrence of ion relaxation polarization, thereby improving the resistivity of the material. On the other hand, the synergistic effect of multi-walled carbon nanotubes and rare earth oxides improves the microstructure of the material, enhances the material's ability to withstand electromagnetic interference, and improves the impedance characteristics of the material at high frequencies.

[0026] Furthermore, the addition of calcium carbonate causes it to dissociate into calcium oxide and carbon dioxide at high temperatures. Calcium oxide reacts with impurities such as silicon and aluminum in the iron ore to form calcium silicate and calcium aluminate, reducing the adverse effects of impurities on the material. During sintering, P2O5 segregates at grain boundaries, increasing the number of metal ion vacancies near the grain boundaries and accelerating grain boundary movement. This promotes grain growth and densification, increasing the initial permeability. Co2O3 inhibits Fe... 2+ The emergence of [the technology] reduces the impact of ambient temperature changes on the permeability of manganese-zinc ferrite magnetic rings. Detailed Implementation

[0027] The present application will be further described in detail below with reference to the embodiments.

[0028] Preparation Example Preparation Example 1 Preparation of carbon nanotube-supported rare earth oxide composite materials: (1) Add 30g of multi-walled carbon nanotubes to 100mL of nitric acid solution (68wt%), stir ultrasonically for 30min, filter, wash and dry to obtain carboxylated carbon nanotubes. (2) 2.8 g of samarium nitrate was dissolved in 28 mL of water to obtain samarium nitrate solution, and 0.8 g of dysprosium nitrate was dissolved in 8 mL of water to obtain dysprosium nitrate solution; carboxylated carbon nanotubes were dispersed in 300 mL of water to obtain dispersion, samarium nitrate solution and dysprosium nitrate solution were added dropwise to dispersion, stirred evenly, ammonia water was added dropwise to adjust the pH value of the mixed solution to 9, and the mixed system was transferred to a hydrothermal reactor, heated to 180℃ and reacted for 10 h, cooled to room temperature, and the precipitate was washed three times alternately with distilled water and ethanol, and then freeze-dried to obtain carbon nanotube-supported rare earth oxide composite material.

[0029] Preparation Example 2 Preparation of carbon nanotube-supported rare earth oxide composite materials: (1) Add 40g of multi-walled carbon nanotubes to 100mL of nitric acid solution (68wt%), stir ultrasonically for 35min, filter, wash and dry to obtain carboxylated carbon nanotubes. (2) Dissolve 3.7g of samarium nitrate in 37mL of water to obtain samarium nitrate solution, and dissolve 1.5g of dysprosium nitrate in 15mL of water to obtain dysprosium nitrate solution; disperse carboxylated carbon nanotubes in 400mL of water to obtain dispersion, add samarium nitrate solution and dysprosium nitrate solution dropwise to dispersion, stir evenly, add ammonia water dropwise, adjust the pH value of the mixed solution to 10, transfer the mixed system to a hydrothermal reactor, heat to 180℃ and react for 11h, cool to room temperature, wash the precipitate three times alternately with distilled water and ethanol, freeze dry, and obtain carbon nanotube-supported rare earth oxide composite material.

[0030] Preparation Example 3 Preparation of carbon nanotube-supported rare earth oxide composite materials: (1) Add 50g of multi-walled carbon nanotubes to 100mL of nitric acid solution (68wt%), stir ultrasonically for 35min, filter, wash and dry to obtain carboxylated carbon nanotubes. (2) 4.6 g of samarium nitrate was dissolved in 46 mL of water to obtain samarium nitrate solution, and 2.4 g of dysprosium nitrate was dissolved in 24 mL of water to obtain dysprosium nitrate solution; carboxylated carbon nanotubes were dispersed in 500 mL of water to obtain dispersion, samarium nitrate solution and dysprosium nitrate solution were added dropwise to dispersion, stirred evenly, ammonia water was added dropwise to adjust the pH value of the mixed solution to 11, and the mixed system was transferred to a hydrothermal reactor, heated to 180℃ and reacted for 12 h, cooled to room temperature, and the precipitate was washed three times alternately with distilled water and ethanol, and then freeze-dried to obtain carbon nanotube-supported rare earth oxide composite material.

[0031] Preparation Example 4 The difference between this preparation example and preparation example 2 is that samarium nitrate is replaced by dysprosium nitrate.

[0032] Preparation Example 5 The difference between this preparation example and Preparation Example 2 is that dysprosium nitrate is replaced by samarium nitrate. Example

[0033] Example 1 The high-frequency, high-impedance manganese-zinc ferrite material comprises: 475g Fe2O3, 250g Mn3O4, 15g ZnO, 30g carbon nanotube-supported rare earth oxide composite material (prepared in Example 1), 1g P2O5, 1g Co2O3, and 4g CaCO3.

[0034] The preparation process of the manganese-zinc ferrite high-frequency high-impedance material in this embodiment includes the following steps: S1: Select Fe2O3 with a purity of 99.9%, Mn3O4 with a purity of 99%, and ZnO with a purity of 99%. S2: Fe2O3, Mn3O4, ZnO, P2O5, Co2O3, and CaCO3 are mixed and placed in a ball mill. Zirconia balls are used as the ball milling medium. The ball-to-material ratio is controlled at 3:1, the grinding time is 8 hours, and the ball milling speed is 200 r / min. After grinding, a mixture with an average particle size of 0.5 μm is obtained. S3: The mixture is pre-calcined at 800℃ for 2 hours, then crushed and sieved to obtain the pre-calcined material; S4: Carbon nanotube-supported rare earth oxide composite material is incorporated into the pre-fired material, mixed evenly, and 5 wt% PVA solution is added. The mass ratio of pre-fired material to PVA solution is controlled at 1:0.3. The mixture is granulated and then the pre-fired material is dry-pressed at a pressure of 100 MPa for 1 min to obtain a preform of a predetermined shape. S5: The green body is sintered at 1260℃, the oxygen partial pressure is adjusted to 3%, held for 3 hours, annealed at 600℃ for 2 hours, and after cooling, a manganese-zinc ferrite high-frequency high-impedance material is obtained.

[0035] Example 2 The high-frequency, high-impedance manganese-zinc ferrite material comprises: 480g Fe2O3, 280g Mn3O4, 18g ZnO, 40g carbon nanotube-supported rare earth oxide composite material (prepared in Example 2), 2g P2O5, 2g Co2O3, and 6g CaCO3.

[0036] The preparation process of the manganese-zinc ferrite high-frequency high-impedance material in this embodiment includes the following steps: S1: Select Fe2O3 with a purity of 99.9%, Mn3O4 with a purity of 99%, and ZnO with a purity of 99%. S2: Fe2O3, Mn3O4, ZnO, P2O5, Co2O3, and CaCO3 are mixed and placed in a ball mill. Zirconia balls are used as the ball milling medium. The ball-to-material ratio is controlled at 4:1, the grinding time is 10 hours, and the ball milling speed is 250 r / min. After grinding, a mixture with an average particle size of 0.8 μm is obtained. S3: The mixture is pre-fired at 850℃ for 3 hours, then crushed and sieved to obtain the pre-fired material; S4: Carbon nanotube-supported rare earth oxide composite material is incorporated into the pre-fired material, mixed evenly, and 7wt% PVA solution is added. The mass ratio of pre-fired material to PVA solution is controlled at 1:0.3. The mixture is granulated and then the pre-fired material is dry-pressed at a pressure of 150MPa for 21min to obtain a preform of the predetermined shape. S5: The green body is sintered at 1320℃, the oxygen partial pressure is adjusted to 4%, the holding time is 5h, and the annealing time is 3h at 700℃. After cooling, a manganese-zinc ferrite high-frequency high-impedance material is obtained.

[0037] Example 3 The high-frequency, high-impedance manganese-zinc ferrite material comprises: 490g Fe2O3, 300g Mn3O4, 200g ZnO, 50g carbon nanotube-supported rare earth oxide composite material (prepared in Example 3), 3g P2O5, 3g Co2O3, and 8g CaCO3.

[0038] The preparation process of the manganese-zinc ferrite high-frequency high-impedance material in this embodiment includes the following steps: S1: Select Fe2O3 with a purity of 99.9%, Mn3O4 with a purity of 99%, and ZnO with a purity of 99%. S2: Fe2O3, Mn3O4, ZnO, P2O5, Co2O3, and CaCO3 are mixed and placed in a ball mill. Zirconia balls are used as the ball milling medium. The ball-to-material ratio is controlled at 5:1, the grinding time is 12 hours, and the ball milling speed is 300 r / min. After grinding, a mixture with an average particle size of 1.2 μm is obtained. S3: The mixture is pre-fired at 900℃ for 4 hours, then crushed and sieved to obtain the pre-fired material; S4: Carbon nanotube-supported rare earth oxide composite material is incorporated into the pre-sintered material, mixed evenly, and 8 wt% PVA solution is added. The mass ratio of pre-sintered material to PVA solution is controlled at 1:0.4. The mixture is granulated and the pre-sintered material is subjected to isostatic pressing at a pressure of 250 MPa and a holding time of 3 min to obtain a green body of the predetermined shape. S5: The green body is sintered at 1380℃, the oxygen partial pressure is adjusted to 5%, the holding time is 6h, and the annealing time is 4h at 800℃. After cooling, a manganese-zinc ferrite high-frequency high-impedance material is obtained.

[0039] Example 4 The difference between this embodiment and Embodiment 2 is that the amount of Fe2O3 used is 580g, that is, the mass ratio of Fe2O3, Mn3O4 and ZnO is 0.58:0.28:0.18.

[0040] Comparative Example Comparative Example 1 The difference between the manganese-zinc ferrite high-frequency high-impedance material and Example 2 is that the carbon nanotube-supported rare earth oxide composite material prepared in Example 4 is used.

[0041] Comparative Example 2 The difference between the manganese-zinc ferrite high-frequency high-impedance material and Example 2 is that the carbon nanotube-supported rare earth oxide composite material prepared in Example 5 is used.

[0042] Comparative Example 3 The difference between the manganese-zinc ferrite high-frequency high-impedance material and Example 2 is that the carbon nanotube-supported rare earth oxide composite material is replaced with multi-walled carbon nanotubes.

[0043] Comparative Example 4 The difference between the manganese-zinc ferrite high-frequency high-impedance material and Example 2 is that the carbon nanotube-supported rare earth oxide composite material is replaced by Sm2O3 by mass.

[0044] Comparative Example 5 The difference between the manganese-zinc ferrite high-frequency high-impedance material and Example 2 is that P2O5 is replaced by Co2O3 in equal mass.

[0045] Comparative Example 6 The difference between the manganese-zinc ferrite high-frequency high-impedance material and Example 2 is that Co2O3 is replaced by P2O5 by mass.

[0046] Performance testing 1. Saturation magnetic induction intensity (Bs): Measured using a SY8232 B-HAnalyzer tester; 2. Curie temperature (Tc): Measured using an LCR-4225 inductance analyzer and a dedicated drying oven; 3. Initial permeability (μi): Measured using an Agilent E4991A LCR meter; 4. Impedance (Ω): The impedance was tested at 1MHz, 25MHz and 100MHz using an Agilent E4991A LCR tester.

[0047] Table 1 Based on the comparison between Example 2 and Example 4, and the data in Table 1, it can be seen that: Example 4 increased the amount of Fe2O3, Fe2+ Fe has a high ion content 2+ with Fe 3+ Electron transitions between atoms reduce resistivity. This application reduces the amount of Fe2O3 and uses an iron-poor formulation, resulting in Fe in the spinel structure... 2+ The content is relatively low, containing ZnO or Mn. (1–n) Zn n The presence of the nonmagnetic phase O gives the iron-poor MnZn ferrite a high resistivity, low eddy current loss, and high permeability even at high frequencies.

[0048] Based on the comparison between Example 2 and Comparative Examples 1-2, and the data in Table 1, it can be seen that samarium oxide and dysprosium oxide have a synergistic effect. In Comparative Example 1, only dysprosium oxide was loaded onto carbon nanotubes, and in Comparative Example 2, only samarium oxide was loaded onto carbon nanotubes; the modification effect of both was poor. In this application, dysprosium oxide and samarium oxide are jointly loaded onto carbon nanotubes. In manganese-zinc ferrite materials, both can optimize the microstructure of the material and suppress Fe in the spinel structure. 2+ with Fe 3+ The formation of electron migration channels between them reduces ion relaxation polarization, thereby avoiding a sharp drop in resistivity, improving the impedance characteristics of the material at high frequencies, enhancing the ability of manganese-zinc ferrite materials to be used at frequencies above 1MHz, and thus improving the electromagnetic shielding effectiveness of the material.

[0049] Based on the comparison of Example 2 and Comparative Examples 3-4, and the data in Table 1, it can be seen that multi-walled carbon nanotubes or rare earth oxides alone have poor effects. By adding carbon nanotube-supported rare earth oxide composite materials, the pores inside the manganese-zinc ferrite grains are filled, increasing the material density and thus improving grain boundary resistance.

[0050] Based on the comparison between Example 2 and Comparative Examples 5-6, and the data in Table 1, it can be seen that P2O5 and Co2O3 have a synergistic effect. Combining the advantages of P, Co, and rare earth elements, P2O5 segregates at grain boundaries, increasing the number of metal ion vacancies near the grain boundaries, thereby accelerating grain boundary movement. This promotes grain growth and densification, increasing the initial permeability, while Co2O3 inhibits Fe... 2+ The emergence of [the technology] reduces the impact of ambient temperature changes on the permeability of manganese-zinc ferrite magnetic rings.

[0051] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this specific embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A manganese-zinc ferrite high-frequency, high-impedance material, characterized in that, By weight, it includes the following components: Fe2O3 47.5-49 parts, Mn3O4 25-30 parts, ZnO 15-20 parts, carbon nanotube supported rare earth oxide composite material 3-5 parts, P2O5 0.1-0.3 parts, Co2O3 0.1-0.3 parts, CaCO3 0.4-0.8 parts; The raw materials for preparing the carbon nanotube-supported rare earth oxide composite material include multi-walled carbon nanotubes and rare earth salts, and the mass ratio of the multi-walled carbon nanotubes to rare earth salts is 1:(0.12-0.14).

2. The manganese-zinc ferrite high-frequency high-impedance material according to claim 1, characterized in that, The rare earth salts include samarium nitrate and dysprosium nitrate in a mass ratio of 1:(0.3-0.5).

3. The manganese-zinc ferrite high-frequency high-impedance material according to claim 2, characterized in that, The preparation method of the carbon nanotube-supported rare earth oxide composite material includes the following steps: (1) Add multi-walled carbon nanotubes to an acid solution, stir ultrasonically, filter, wash and dry to obtain carboxylated carbon nanotubes; (2) Dissolve samarium nitrate in water to obtain samarium nitrate solution, and dissolve dysprosium nitrate in water to obtain dysprosium nitrate solution; disperse carboxylated carbon nanotubes in water to obtain a dispersion, add samarium nitrate solution and dysprosium nitrate solution to the dispersion, stir evenly, add alkaline solution, heat and react for 10-12 hours, cool to room temperature, wash the precipitate several times, and dry to obtain carbon nanotube-supported rare earth oxide composite material.

4. The method for preparing the manganese-zinc ferrite high-frequency high-impedance material according to any one of claims 1-3, characterized in that, Includes the following steps: S1: Select high-purity Fe2O3, Mn3O4 and ZnO; S2: Fe2O3, Mn3O4, ZnO, P2O5, Co2O3, and CaCO3 are mixed and placed in a ball mill to obtain a mixture through ball milling. S3: The mixture is pre-sintered, crushed and sieved to obtain pre-sintered material; S4: Carbon nanotube-supported rare earth oxide composite material is added to the pre-sintered material, mixed evenly, binder is added, mixed and granulated, and the pre-sintered material is subjected to a molding process to obtain a green body of a predetermined shape. S5: The green body is sintered, the oxygen partial pressure is adjusted, and after heat preservation, annealing and cooling, a manganese zinc ferrite high-frequency high-impedance material is obtained.

5. The method for preparing the manganese-zinc ferrite high-frequency high-impedance material according to claim 4, characterized in that, In step S1, the purity of Fe2O3, Mn3O4, and ZnO is greater than or equal to 99%.

6. The manganese-zinc ferrite high-frequency high-impedance material according to claim 4, characterized in that, In step S2, zirconia balls are used as the ball milling medium, the ball-to-material ratio is controlled at 3:1 to 5:1, the grinding time is 8 to 12 hours, the ball milling speed is 200 to 300 r / min, and the average particle size of the mixture obtained after grinding is 0.5 to 1.2 μm.

7. The manganese-zinc ferrite high-frequency high-impedance material according to claim 4, characterized in that, In step S3, the pre-firing temperature is 800-900℃ and the pre-firing time is 2-4 hours.

8. The manganese-zinc ferrite high-frequency high-impedance material according to claim 4, characterized in that, In step S4, the molding process adopts dry pressing or isostatic pressing. The dry pressing pressure is 100-200MPa and the holding time is 1-2min. The isostatic pressing pressure is 200-300MPa and the holding time is 2-3min.

9. The manganese-zinc ferrite high-frequency high-impedance material according to claim 4, characterized in that, In step S4, the adhesive is a 5wt%-8wt% PVA solution, and the mass ratio of the pre-burned material to the adhesive is 1:(0.3-0.4).

10. The manganese-zinc ferrite high-frequency high-impedance material according to claim 4, characterized in that, In step S5, the sintering temperature is 1260-1380℃, the heating rate is 2-5℃ / min, the holding time is 3-6h, the annealing temperature is 600-800℃, the annealing time is 2-4h, and the oxygen partial pressure is 3-6%.

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