A nickel-zinc ferrite material and its preparation method and use

Abstract

The present invention relates to a nickel-zinc ferrite material, a preparation method, and uses thereof. The nickel-zinc ferrite material comprises raw materials including main components and additives. The main components include Fe2O3, NiO, ZnO, and CuO, and the additives include Bi2O3, Co2O3, and ZrO2. Based on 100 mol% of the total amount of the main components, Fe2O3 accounts for 65 mol%-66.7 mol%, NiO accounts for 10.6 mol%-13 mol%, ZnO accounts for 17 mol%-20 mol%, and CuO accounts for 2 mol%-4.5 mol%. By regulating the ratio of the main components of the raw materials, the nickel-zinc ferrite has advantages such as high wide-temperature and high-bandwidth magnetic permeability. The material can be better applied to transformers and wireless charging fields, thereby improving wireless charging efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of soft ferrites, and in particular to a nickel-zinc ferrite material and a preparation method and application thereof. Background Art

[0002] With the rapid development and upgrading of electronic product technology in recent years, ferrite cores have been widely used in medical devices, mobile phone wireless charging, new energy vehicle charging stations, LED lighting, rainproof power supplies for outdoor lighting projects, smart homes, household appliances, and high-performance computers. The widespread application of ferrites in various industries, including communications, IT, automotive, aerospace, shipbuilding, and defense weapon systems, has necessitated high-frequency components that are suitable for surface mounting and soldering, as well as possessing excellent strength. The miniaturization and thinness of surface-mount components have placed even higher demands on the magnetic and electrical properties of NiZn materials. This requires components to possess high magnetic permeability, high stability, and long life. Globally, emerging industries such as new energy, 5G communications, artificial intelligence, and fast-charging power supplies will continue to see growing demand for high-performance magnetic core materials, particularly in the wireless charging sector, providing us with broad opportunities for development.

[0003] The advantages of NiZn soft ferrite materials are mainly reflected in its high resistivity, low power consumption and high frequency characteristics. 2+ NiZn ferrite is not easily priced, and its high resistivity reduces losses in high-frequency applications, making it particularly suitable for high-frequency applications above 1 MHz. Furthermore, the sintering process for NiZn ferrite is simple, requiring no atmosphere protection and maintaining a relatively low sintering temperature, making it compatible with LTCC (low-temperature co-fired ceramic) processes. NiZn ferrite also boasts a wide bandwidth and low transmission loss, making it commonly used in high-frequency electromagnetic interference (EMI) protection and surface-mount devices integrating high-frequency power and interference immunity.

[0004] However, NiZn soft ferrite material also has some drawbacks. Its performance is inferior to that of MnZn ferrite in the low-frequency range. Furthermore, compared to MnZn ferrite, NiZn ferrite development has been relatively slow and on a smaller scale. This may be due to NiZn ferrite's insufficient performance in low-frequency applications, which has limited its development in certain areas. While the magnetic permeability of currently used NiZn soft ferrite materials ranges from 500 to 700, the Curie temperature is only 120°C and the Bs is below 360mT. Consequently, products made with NiZn material suffer from low inductance, low energy conversion efficiency, and high losses when current is applied.

[0005] Research progress in NiZn soft ferrite materials has focused on formula optimization, additive applications, sintering process improvements, one-step synthesis methods, doping research, and the application of nanotechnology. These improvements help enhance the material's performance and meet the demands of high-frequency applications. Formula is a crucial factor in determining the performance of ferrite materials. By adjusting the ratio of NiO, ZnO, and Fe2O3, the magnetic properties of ferrites can be optimized, particularly for high-frequency applications.

[0006] In the existing technology, NiZn soft magnetic ferrite materials have the defects of insufficient broadband performance, high sintering temperature, and poor temperature stability of eddy current loss and power loss. Therefore, how to provide a preparation method of nickel-zinc ferrite material with excellent broadband performance, high temperature stability and a low sintering temperature has become a problem that needs to be solved urgently. Summary of the Invention

[0007] In order to solve the above technical problems, the purpose of the present invention is to provide a nickel-zinc ferrite material, a preparation method and use thereof. The nickel-zinc ferrite material of the present invention has the advantages of high magnetic permeability and high Curie temperature, which solves the problem of broadband magnetic permeability stability and high Bs problem of the material at low and high temperatures, thereby improving the applicability of power magnetic products such as wireless charging magnetic plates, common-mode inductors, pulse transformers, and laminated magnetic beads / inductors.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a nickel-zinc ferrite material, the raw materials of which include a main component and an additive, the main component including Fe2O3, NiO, ZnO and CuO, and the additives including Bi2O3, Co2O3 and ZrO2;

[0010] Taking the total amount of the main component as 100 mol%, Fe2O3 is 65 mol%-66.7 mol%, for example, it can be 65wt%, 65.2wt%, 65.4wt%, 65.6wt%, 65.8wt%, 66.0wt%, 66.2wt%, 66.4wt%, 65.5wt% or 66.7wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0011] Based on the total amount of the main components as 100 mol%, NiO is 10.6 mol%-13 mol%, for example, it can be 10.6wt%, 10.8wt%, 11.0wt%, 11.2wt%, 11.4wt%, 11.6wt%, 11.8wt%, 12.0wt%, 12.2wt%, 12.4wt%, 12.6wt%, 12.8wt% or 13wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0012] Based on the total amount of the main components as 100 mol%, ZnO is 17 mol%-20 mol%, for example, it can be 17wt%, 17.5wt%, 18wt%, 18.5wt%, 19wt%, 19.5wt% or 20wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0013] Based on the total amount of the main component as 100 mol%, CuO is 2 mol%-4.5 mol%, for example, it can be 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt% or 4.5wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0014] Based on the total mass of the main component as 100wt%, the mass fraction of the additive is 0.4wt%-2.0wt%, for example, it can be 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt% or 2.0wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0015] The present invention achieves a higher magnetic permeability and higher Tc of nickel-zinc ferrite materials at high frequencies by regulating the ratio between the main components of the raw materials. Fe2O3 mainly determines the magnetic permeability and Curie temperature Tc, ZnO regulates the magnetic permeability and Curie temperature Tc values, CuO reduces the sintering temperature, and NiO mainly determines the magnetoelectric properties of the material at low temperatures. When the Fe2O3 content is not within the range, the magnetic permeability is low and the impedance value Z is also low. Since it is necessary to ensure the broadband high impedance value characteristic, the contents of Fe2O3, ZnO, CuO and NiO need to be adjusted to achieve this. The nickel-zinc ferrite of the present invention has the advantages of high wide-temperature and high broadband magnetic permeability, and can be better applied to transformers and wireless charging fields, making wireless charging more efficient.

[0016] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0017] Preferably, based on the total mass of the main component as 100wt%, Bi2O3 is 0.3wt%-1.5wt%, for example, it can be 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt% or 1.5wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] The present invention can uniformly grow FeBi2O4 with spinel structure by adding Bi2O3. 3+ The K1 value is very large, so the amount of CoFe2O4 in the composition determines to a large extent the imaginary part of the complex permeability of the material, thereby improving the high permeability performance of the ferrite under wide frequency band. When Bi-Zr and nickel-zinc ferrite undergo solid-phase reaction, they mainly grow on the grain boundaries, and the Bi2O3 content exceeds 1.5wt%, which will cause crystallization on the magnet surface, resulting in lower permeability and smaller Bs value.

[0019] Preferably, based on the total mass of the main component as 100wt%, Co2O3 is 0.1wt%-0.3wt%, for example, it can be 0.1wt%, 0.15wt%, 0.2wt%, 0.25wt% or 0.3wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] Preferably, based on the total mass of the main components as 100wt%, ZrO2 is 0.03wt%-0.1wt%, for example, it can be 0.03wt%, 0.04wt%, 0.05wt%, 0.06wt%, 0.07wt%, 0.08wt%, 0.09wt% or 0.1wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] The present invention adjusts the ratio between additives in the raw materials, and the combined substitution of Co and Bi improves the magnetic permeability to achieve high-frequency and high-impedance values. The combined substitution of Bi, Co and Zr adjusts the wide-temperature magnetic permeability to achieve broadband and high-permeability performance.

[0022] When the content of each additive is within the scope of the present invention, the requirements of magnetic permeability and high impedance value Z can be met at the same time; after adding Bi2O3, FeBi2O4 with spinel structure can be uniformly grown. 3+The K1 value is very large, so the CoFe2O4 content in the composition largely determines the imaginary part of the material's complex permeability, thereby improving the ferrite's high permeability performance over a wide bandwidth. During the solid-state reaction between Bi-Zr and nickel-zinc ferrite, growth primarily occurs on grain boundaries. However, if the sintering aid Bi2O3 content exceeds 1.5wt%, it will cause surface crystallization, resulting in lower permeability and a smaller Bs value. Without the addition of a sintering aid, raw sintering occurs, leading to lower permeability. The addition of zirconia can achieve excellent magnetic properties at low temperatures.

[0023] In a second aspect, the present invention provides a method for preparing the nickel-zinc ferrite material as described in the first aspect, the preparation method comprising the following steps:

[0024] (1) mixing the main component, the ball material and the solvent in a mass ratio of 1:(4-8):(0.5-1.2) for the first ball milling, and then performing the first spray granulation to obtain the spray granulated material;

[0025] (2) the spray granulated material is pre-fired to obtain a pre-fired material;

[0026] (3) mixing the pre-calcined material, additives, binder, dispersant and defoamer and performing a second ball milling to obtain a slurry;

[0027] (4) the slurry is subjected to a second spray granulation and molding to obtain a blank;

[0028] (5) The blank is subjected to microwave sintering to obtain nickel-zinc ferrite material.

[0029] The present invention adopts the method of microwave sintering, which can mainly use a lower sintering temperature, so that NiZnCu ferrite obtains more excellent magnetoelectric properties. The advantage of using microwave sintering for ferrite materials is that it can achieve rapid and uniform heating, improve sintering efficiency and product uniformity. Microwave sintering directly absorbs microwave energy through the dielectric loss of the material, thereby heating and sintering. This heating method has a fast heating rate, high energy utilization rate, high heating efficiency, and is safe, hygienic and pollution-free. Microwave sintering can also improve the microstructure and performance of the material. Due to its unique heating mechanism, it can promote grain growth, obtain ultrafine grain structure materials, and significantly improve the microstructure of the material. In addition, microwave sintering can reduce the sintering temperature, and rapid temperature increase can suppress the growth of grain structure, obtain a more uniform fine grain microstructure, and have less internal pores.

[0030] Preferably, the solvent in step (1) comprises water.

[0031] Preferably, the rotation speed of the first ball milling in step (1) is 200 rpm-400 rpm, for example, it can be 200 rpm, 220 rpm, 240 rpm, 260 rpm, 280 rpm, 300 rpm, 320 rpm, 340 rpm, 360 rpm, 380 rpm or 400 rpm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0032] Preferably, the diameter of the balls used in the first ball milling in step (1) is 5 mm to 10 mm, for example, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm or 10 mm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] Preferably, the time for the first ball milling in step (1) is 20 min-60 min, for example, it can be 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] Preferably, the pre-calcination temperature in step (2) is 780°C-950°C, for example, it can be 780°C, 790°C, 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C, 900°C, 910°C, 920°C, 930°C, 940°C or 950°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0035] Preferably, the pre-burning time in step (2) is 2h-4h, for example, 2h, 2.5h, 3h, 3.5h or 4h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0036] Preferably, the binder in step (3) comprises any one or a combination of at least two of ethyl cellulose, polyvinyl alcohol or polyvinyl butyral. Typical but non-limiting combinations include a combination of ethyl cellulose and polyvinyl alcohol, a combination of polyvinyl alcohol and polyvinyl butyral, a combination of ethyl cellulose and polyvinyl butyral, and a combination of ethyl cellulose, polyvinyl alcohol and polyvinyl butyral.

[0037] Preferably, the dispersant in step (3) comprises any one or a combination of at least two of castor oil, citric acid, triethanolamine, polyacrylamide or phosphates. Typical but non-limiting combinations include a combination of castor oil and citric acid, a combination of triethanolamine and polyacrylamide, a combination of polyacrylamide and phosphate, a combination of castor oil, citric acid and triethanolamine, a combination of triethanolamine, polyacrylamide and phosphate, a combination of castor oil, citric acid, triethanolamine and phosphate, and a combination of castor oil, citric acid, triethanolamine, polyacrylamide and phosphate.

[0038] Preferably, the defoaming agent in step (3) includes any one or a combination of at least two of n-octanol, polyethers, mineral oil or non-silicone defoaming agents. Typical but non-limiting combinations include a combination of n-octanol and polyethers, a combination of mineral oil and non-silicone, a combination of polyethers and mineral oil, a combination of n-octanol, polyethers and non-silicone defoaming agents, and a combination of n-octanol, polyethers, mineral oil and non-silicone defoaming agents.

[0039] Preferably, the diameter of the balls used in the second ball milling in step (3) is 5 mm to 10 mm, for example, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm or 10 mm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0040] The present invention further optimizes the diameter of the balls in the second ball milling to 5mm-10mm to obtain a slurry with a suitable particle size, thereby promoting sintering molding. Compared with the traditional ball milling ball diameter of 12mm, the present invention uses balls with a smaller diameter. The particle size of the slurry obtained by ball milling is smaller and the grain size distribution is more uniform, thereby improving the accuracy and consistency of sample grinding.

[0041] Preferably, the ball-to-material ratio of the second ball milling in step (3) is (3-5):1, for example, it can be 3:1, 4:1 or 5:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] Preferably, the second ball milling in step (3) includes a first-stage ball milling and a second-stage ball milling.

[0043] Preferably, the rotation speed of the first stage ball milling in step (3) is 50 rpm-300 rpm, for example, it can be 50 rpm, 100 rpm, 150 rpm, 200 rpm, 250 rpm or 300 rpm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0044] Preferably, the time for the first stage ball milling in step (3) is 10 min-20 min, for example, it can be 10 min, 12 min, 14 min, 16 min, 18 min or 20 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0045] Preferably, the rotation speed of the second stage ball milling in step (3) is 400 rpm-600 rpm, for example, it can be 4400 rpm, 4420 rpm, 440 rpm, 460 rpm, 480 rpm, 500 rpm, 520 rpm, 540 rpm, 560 rpm, 580 rpm or 600 rpm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0046] Preferably, the time for the second stage ball milling in step (3) is 50 min-150 min, for example, it can be 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, 130 min, 140 min or 150 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0047] Preferably, the mass ratio of the pre-sintered material, water, binder, dispersant and defoamer in step (3) is 100:(40-150):(4-20):(0.1-2):(0.001-0.0025), for example, it can be 100:40:4:0.1:0.001, 100:50:4:0.1:0.001, 100:60:4:0.1:0.001, 100:100:4:0.2:0.001, 100:120:4:0.3:0.001, 100:100:4:0.4:0.5:0.001, 100:120:4:0.6:0.001, 100:100:4:0.7:0.001, 100:100:4:0.8:0.001, 100:100:4:0.9:0.001, 100:110:4:0.1:0.001, 100:120:4:0.1:0.001, 100:110:4:0.2:0.001, 100:110:4:0.3:0.001, 100:110:4:0. 0:100:10:0.15:0.002, 100:60:4:0.5:0.002, 100:60:4:1:0.002, 100:60:4:1.5:0.002, 100:60:4:2:0.002, 100:60:4:0.5:0.0015, 100:60:4:0.5:0.0025 or 100:150:20:2:0.025, but not limited to the listed values, other values ​​not listed within the numerical range are also applicable.

[0048] Preferably, the particle size distribution X50 of the slurry in step (3) is 0.5 μm-0.8 μm, for example, it can be 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm or 0.8 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0049] Preferably, the particle size distribution X90 of the slurry in step (3) is 1.25 μm-1.8 μm, for example, it can be 1.25 μm, 1.3 μm, 1.35 μm, 1.4 μm, 1.45 μm, 1.5 μm, 1.55 μm, 1.6 μm, 1.65 μm, 1.7 μm, 1.75 μm or 1.8 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0050] The present invention selects balls with appropriate ball diameters to ball-mill the raw materials to obtain a slurry with a narrower particle size distribution and a more uniform slurry particle size distribution. The slurry under this particle size distribution is conducive to reducing the subsequent sintering temperature. In addition, the distribution of grain size also affects the magnetic domain diameter. When the grain size in the slurry is too large, it will lead to loose sintering and the occurrence of raw burning, which in turn leads to low magnetic permeability. When the grain size in the slurry is too small, the grain morphology will grow abnormally, which will greatly reduce the high-frequency magnetic permeability.

[0051] Preferably, the average size of the particles produced by the second spray granulation in step (4) is 30 μm to 200 μm, for example, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm or 200 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0052] Preferably, the density of the blank in step (4) is 3.10 g / cm 3 -3.25g / cm 3 , for example, it can be 3.10 g / cm 3 、3.15g / cm 3 、3.20g / cm 3 or 3.25g / cm 3 , but not limited to the listed values, other unlisted values ​​within the numerical range are also applicable.

[0053] Preferably, the size of the blank in step (4) is H25mm×15mm×10mm, where H represents a ring with an outer diameter of 25mm, an inner diameter of 15mm and a height of 10mm, which is a standard green blank.

[0054] Preferably, the distributed microwave sintering process in step (5) includes a first heating step, a second heating step, a first cooling step, and a second cooling step.

[0055] Preferably, the heating rate of the first heating in step (5) is 0.5°C / min-1.5°C / min, for example, it can be 0.5°C / min, 0.6°C / min, 0.7°C / min, 0.8°C / min, 0.9°C / min, 1.0°C / min, 1.1°C / min, 1.2°C / min, 1.3°C / min, 1.4°C / min or 1.5°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0056] Preferably, the target temperature of the first heating in step (5) is 550°C-750°C, for example, it can be 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, 710°C, 720°C, 730°C, 740°C or 750°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0057] Preferably, the first heating holding time in step (5) is 2h-7h, for example, it can be 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h or 7h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0058] Preferably, the heating rate of the second heating in step (5) is 1°C / min-3°C / min, for example, it can be 1°C / min, 1.2°C / min, 1.4°C / min, 1.6°C / min, 1.8°C / min, 2.0°C / min, 2.2°C / min, 2.4°C / min, 2.6°C / min, 2.8°C / min or 3°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0059] Preferably, the target temperature of the second heating in step (5) is 750°C-1050°C, for example, it can be 750°C, 850°C, 950°C, 1000°C or 1050°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0060] The present invention combines microwave sintering with distributed sintering. Microwave sintering further improves energy efficiency. Compared with traditional sintering methods, it reduces the highest sintering temperature and further optimizes the final temperature of the second heating step to 750°C-950°C. The resulting nickel-zinc ferrite material has even better performance. If the temperature is too low, it will burn prematurely, resulting in low magnetic permeability, especially at low temperatures and high frequencies. If the temperature is too high, not only will the ferrite material's performance not be improved, but it will also increase losses and increase manufacturing costs.

[0061] Preferably, the second heating holding time in step (5) is 2h-5h, for example, it can be 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0062] Preferably, the cooling rate of the first cooling in step (5) is 2°C-5°C / min, for example, it can be 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min, 4°C / min, 4.5°C / min or 5°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0063] Preferably, the target temperature of the first cooling in step (5) is 500°C-600°C, for example, it can be 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C or 600°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0064] Preferably, the cooling rate of the second cooling in step (5) is 1°C / min-4°C / min, for example, it can be 1°C / min, 1.5°C / min, 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min or 4°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0065] Preferably, the target temperature of the second cooling in step (5) is 40°C-50°C, for example, it can be 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C or 50°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0066] The present invention adopts the method of heating and cooling in stages in order to control the uniform growth of grains and make the ferrite morphology more compact, which is conducive to maintaining the magnetic permeability at high and low temperatures and the magnetoelectric properties at high frequencies.

[0067] As a preferred technical solution of the preparation method of the present invention, the preparation method comprises the following steps:

[0068] (1) mixing the main component, the ball material and water in a mass ratio of 1:(4-8):(0.5-1.2) at a first ball milling speed of 50 rpm-300 rpm for 20 min-60 min, and then performing a first spray granulation to obtain a spray granulated material;

[0069] (2) pre-calcining the spray granulated material at 780° C. to 950° C. for 2 h to 4 h to obtain a pre-calcined material;

[0070] (3) Pre-sintered material, additives, binder, dispersant and defoamer were mixed in a mass ratio of 100:(40-150):(4-20):(0.1-2):(0.001-0.0025, and Bi2O3 was added in an amount of 0.3wt%-1.5wt%, Co2O3 in an amount of 0.1wt%-0.3wt%, and ZrO2 in an amount of 0.03wt%-0.1wt% to perform a second ball milling. The balls used in the milling process are 5 mm and 10 mm in diameter at a weight ratio of 1:1. The ball-to-material ratio of the second ball milling is (3-5):1. The second ball milling includes a first stage of ball milling at 50 rpm to 200 rpm for 10 min to 20 min and a second stage of ball milling at 400 rpm to 600 rpm for 50 min to 150 min to obtain a slurry with a particle size distribution X50 of 0.5 μm to 0.8 μm and X90 of 1.25 μm to 1.8 μm.

[0071] (4) The slurry is subjected to a second spray granulation to obtain particles with an average size of 30 μm-200 μm, and the density is 3.10 g / cm 3 -3.25g / cm 3 , the volume of the blank is H25mm×15mm×10mm;

[0072] (5) The blank is subjected to microwave sintering, and the sintering process is as follows: first heating the temperature to 550°C-750°C at a heating rate of 0.5°C / min-1.5°C / min and keeping the temperature for 2h-7h, then heating the temperature to 750°C-1050°C at a heating rate of 1°C / min-3°C / min and keeping the temperature for 2h-5h, then cooling the temperature to 500°C-600°C at a cooling rate of 2°C-5°C / min, and then cooling the temperature to 40°C-50°C at a cooling rate of 1°C / min-4°C / min to obtain a nickel-zinc ferrite material.

[0073] In a third aspect, the present invention provides a use of the nickel-zinc ferrite material as described in the first aspect, wherein the nickel-zinc ferrite material is used for a broadband wireless charging magnetic sheet, and the magnetic permeability of the nickel-zinc ferrite material at 25°C is ≥1000, and the magnetic permeability under 1MHz test conditions is ≥1000.

[0074] The nickel-zinc ferrite material of the present invention is used for broadband wireless charging magnetic sheets and has excellent broadband magnetic permeability, which gives it obvious advantages in the fields of high-frequency communication, electronic countermeasures, and anti-electromagnetic interference, and can provide a wider operating frequency range and better performance.

[0075] Preferably, the nickel-zinc ferrite material is used in the fields of aerospace, automobile, communication and new energy materials.

[0076] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0077] Compared with the prior art, the present invention has at least the following beneficial effects:

[0078] (1) The present invention achieves a higher magnetic permeability value and a higher Tc at high frequencies for nickel-zinc ferrite materials by regulating the ratio between the main components of the raw materials. When the Fe2O3 content is not within the range, the magnetic permeability is low and the impedance value Z is also low. Since it is necessary to ensure the broadband high impedance value characteristic, the contents of Fe2O3, ZnO, CuO and NiO need to be adjusted to achieve this. The nickel-zinc ferrite of the present invention has the advantages of high magnetic permeability over a wide temperature range and high magnetic permeability over a wide frequency range, and can be better applied to the fields of transformers and wireless charging, making wireless charging more efficient.

[0079] (2) The present invention adopts a microwave sintering method. The advantage of using microwave sintering for ferrite materials is that it can achieve rapid and uniform heating, improve sintering efficiency and product uniformity. Microwave sintering directly absorbs microwave energy through the dielectric loss of the material, thereby heating and sintering. This heating method has a fast heating speed, high energy utilization, high heating efficiency, and is safe, hygienic and pollution-free. Microwave sintering can also improve the microstructure and performance of the material. Due to its unique heating mechanism, it can promote grain growth, obtain ultrafine grain structure materials, and significantly improve the microstructure of the material. In addition, microwave sintering can reduce the sintering temperature, and the rapid heating can inhibit the growth of grain structure, obtaining a more uniform fine-grained microstructure with less internal pores.

[0080] (3) The nickel-zinc ferrite material of the present invention is used for broadband wireless charging magnetic sheets. The magnetic permeability of the nickel-zinc ferrite material at 25°C is ≥1000, and the magnetic permeability under 1MHz test conditions is ≥1000. It has excellent broadband magnetic permeability, which gives it obvious advantages in high-frequency communications, electronic countermeasures, anti-electromagnetic interference and other fields, and can provide a wider operating frequency range and better performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 This is an SEM image of the nickel-zinc ferrite material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0082] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0083] In the following examples, unless otherwise specified, all reagents and consumables were purchased from conventional reagent manufacturers in the field; unless otherwise specified, the experimental methods and technical means used were conventional methods and means in the field.

[0084] Example 1

[0085] This embodiment provides a nickel-zinc ferrite material. The nickel-zinc ferrite material includes a main component and additives. Based on 100 mol% of the total amount of the main component, Fe2O3 accounts for 65.68 mol%, NiO accounts for 11.05 mol%, ZnO accounts for 20 mol%, and CuO accounts for 3.27 mol%. Based on 100 wt% of the total mass of the main component, Bi2O3 accounts for 0.36 wt%, Co2O3 accounts for 0.15 wt%, and ZrO2 accounts for 0.05 wt%.

[0086] The preparation method of the nickel-zinc ferrite material provided in this embodiment comprises the following steps:

[0087] (1) mixing the main component, the ball material and water in a mass ratio of 1:6:1, performing the first ball milling for 40 minutes at a first ball milling speed of 200 rpm-400 rpm, and then performing the first spray granulation to obtain a spray granulated material;

[0088] (2) the spray granulated material is fed into a rotary kiln at a feed rate of 150 kg / h and pre-fired at 890° C. for 3 h to obtain a pre-fired material;

[0089] (3) according to the mass ratio of pre-calcined material: water: ethyl cellulose: citric acid: n-octanol being 100:60:10:1:0.0015, Bi2O3: Co2O3: ZrO2 = 0.36wt%: 0.15wt%: 0.05wt% additives were added, all the raw materials were mixed and subjected to a second ball milling, the ball diameter of the second ball milling was 8mm, the ball-to-material ratio of the second ball milling was 3:1, and the second ball milling included a first stage ball milling at 180rpm for 10min and a second stage ball milling at 500rpm for 60min to obtain a slurry with a particle size distribution X50 of 0.58μm and X90 of 1.35μm;

[0090] (4) The slurry is subjected to a second spray granulation to obtain particles with an average size of 30 μm-200 μm, and the density is 3.10 g / cm 3 -3.25g / cm 3 , the volume of the blank is H25mm×15mm×10mm;

[0091] (5) The blank is subjected to microwave sintering, and the sintering process is as follows: first heating to 650°C at a heating rate of 1°C / min and keeping warm for 5 hours, then heating to 750°C at a heating rate of 1.3°C / min and keeping warm for 3 hours, then cooling to 500°C at a cooling rate of 2.3°C / min in an air atmosphere, and then cooling to 50°C at a cooling rate of 3°C / min in an air atmosphere to obtain a nickel-zinc ferrite material.

[0092] The SEM image of the prepared nickel-zinc ferrite material is shown in Figure 2. Figure 1 As shown, the grain size of the nickel-zinc ferrite material is uniform and all within 20 μm.

[0093] Example 2

[0094] This embodiment provides a nickel-zinc ferrite material. The nickel-zinc ferrite material includes a main component and additives. Based on 100 mol% of the total amount of the main component, Fe2O3 accounts for 65.6 mol%, NiO accounts for 11.5 mol%, ZnO accounts for 19.6 mol%, and CuO accounts for 3.3 mol%. Based on 100 wt% of the total mass of the main component, Bi2O3 accounts for 0.6 wt%, Co2O3 accounts for 0.17 wt%, and ZrO2 accounts for 0.05 wt%.

[0095] The preparation method of the nickel-zinc ferrite material provided in this embodiment comprises the following steps:

[0096] (1) mixing the main component, the ball material, and water in a mass ratio of 1:6.5:0.5, performing the first ball milling for 40 minutes at a first ball milling speed of 350 rpm, and then performing the first spray granulation to obtain a spray granulated material;

[0097] (2) the spray granulated material is fed into a rotary kiln at a feed rate of 150 kg / h and pre-fired at 850° C. for 3 h to obtain a pre-fired material;

[0098] (3) According to the mass ratio of pre-calcined material: water: ethyl cellulose: citric acid: n-octanol being 100:60:10:0.6:0.001, Bi2O3: Co2O3: ZrO2 = 0.6wt%: 0.17wt%: 0.05wt% additives were added, all the raw materials were mixed and subjected to a second ball milling, the ball diameter of the second ball milling was 10 mm, the ball-to-material ratio of the second ball milling was 3:1, and the second ball milling included a first stage ball milling at 100 rpm for 10 min and a second stage ball milling at 400 rpm for 120 min to obtain a slurry with a particle size distribution X50 of 0.62 μm and X90 of 1.38 μm;

[0099] (4) The slurry is subjected to a second spray granulation to obtain particles with an average size of 30 μm-200 μm, and the density is 3.10 g / cm 3 -3.25g / cm 3 , the volume of the blank is H25mm×15mm×10mm;

[0100] (5) The blank is subjected to microwave sintering, and the sintering process is as follows: first heating the temperature to 650°C at a heating rate of 2.5°C / min and keeping the temperature for 4 hours, then heating the temperature to 850°C at a heating rate of 1.3°C / min and keeping the temperature for 2.5 hours, then cooling the temperature to 500°C at a cooling rate of 6°C / min in an air atmosphere, and then cooling the temperature to 50°C at a cooling rate of 7°C / min in an air atmosphere to obtain a nickel-zinc ferrite material.

[0101] Example 3

[0102] This embodiment provides a nickel-zinc ferrite material. The nickel-zinc ferrite material includes a main component and additives. Based on 100 mol% of the total amount of the main component, Fe2O3 accounts for 65 mol%, NiO accounts for 12.8 mol%, ZnO accounts for 19.27 mol%, and CuO accounts for 2.93 mol%. Based on 100 wt% of the total mass of the main component, Bi2O3 accounts for 0.8 wt%, Co2O3 accounts for 0.19 wt%, and ZrO2 accounts for 0.06 wt%.

[0103] The preparation method of the nickel-zinc ferrite material provided in this embodiment comprises the following steps:

[0104] (1) The main component, ball material and water were mixed in a mass ratio of 1:5:0.8 and ball milled for 40 minutes at a first ball milling speed of 350 rpm, and then spray granulated to obtain a spray granulated material;

[0105] (2) the spray granulated material is fed into a rotary kiln at a feed rate of 150 kg / h and pre-fired at 800° C. for 3 h to obtain a pre-fired material;

[0106] (3) according to the mass ratio of pre-calcined material: water: polyvinyl alcohol: castor oil: polyether being 100:60:12:1.2:0.002, Bi2O3: Co2O3: ZrO2=0.8wt%:0.19wt%:0.06wt% additives were added, all raw materials were mixed and subjected to a second ball milling, the ball diameter of the second ball milling was 6mm, the ball-to-material ratio of the second ball milling was 4:1, and the second ball milling included a first stage ball milling at 200rpm for 10min and a second stage ball milling at 550rpm for 120min to obtain a slurry with a particle size distribution X50 of 0.68μm and X90 of 1.48μm;

[0107] (4) The slurry is subjected to a second spray granulation to obtain particles with an average size of 30 μm-200 μm, and the density is 3.10 g / cm 3 -3.25g / cm 3 , the volume of the blank is H25mm×15mm×10mm;

[0108] (5) The blank is subjected to microwave sintering, and the sintering process is as follows: first heating the temperature to 750°C at a heating rate of 2°C / min and keeping the temperature for 5 hours, then heating the temperature to 900°C at a heating rate of 3°C / min and keeping the temperature for 5 hours, then cooling the temperature to 600°C at a cooling rate of 4°C / min in an air atmosphere, and then cooling the temperature to 50°C at a cooling rate of 6.5°C / min in an air atmosphere to obtain a nickel-zinc ferrite material.

[0109] Example 4

[0110] This embodiment provides a nickel-zinc ferrite material. The nickel-zinc ferrite material includes a main component and additives. Based on 100 mol% of the total amount of the main component, Fe2O3 accounts for 66.6 mol%, NiO accounts for 12.68 mol%, ZnO accounts for 17.4 mol%, and CuO accounts for 3.32 mol%. Based on 100 wt% of the total mass of the main component, Bi2O3 accounts for 1.0 wt%, Co2O3 accounts for 0.2 wt%, and ZrO2 accounts for 0.075 wt%.

[0111] The preparation method of the nickel-zinc ferrite material provided in this embodiment comprises the following steps:

[0112] (1) The main component, ball material and water were mixed in a mass ratio of 1:3.5:0.6 and ball milled for 40 minutes at a first ball milling speed of 350 rpm, and then spray granulated to obtain a spray granulated material;

[0113] (2) the spray granulated material is fed into a rotary kiln at a feed rate of 150 kg / h and pre-fired at 930° C. for 2.5 h to obtain a pre-fired material;

[0114] (3) according to the mass ratio of pre-calcined material: water: polyvinyl alcohol: castor oil: polyether being 100:60:10:1:0.0015, Bi2O3: Co2O3: ZrO2=1.0wt%:0.2wt%:0.075wt% additives were added, all raw materials were mixed and subjected to a second ball milling, the ball diameter of the second ball milling was 7mm, the ball-to-material ratio of the second ball milling was 3.3:1, and the second ball milling included a first stage ball milling at 150rpm for 15min and a second stage ball milling at 600rpm for 120min to obtain a slurry with a particle size distribution X50 of 0.7μm and X90 of 1.5μm;

[0115] (4) The slurry is subjected to a second spray granulation to obtain particles with an average size of 30 μm-200 μm, and the density is 3.10 g / cm 3 -3.25g / cm 3 , the volume of the blank is H25mm×15mm×10mm;

[0116] (5) The blank is subjected to microwave sintering, and the sintering process is as follows: first heating the temperature to 750°C at a heating rate of 1.25°C / min and keeping the temperature for 2 hours, then heating the temperature to 920°C at a heating rate of 1.6°C / min and keeping the temperature for 3 hours, then cooling the temperature to 600°C at a cooling rate of 2.7°C / min in an air atmosphere, and then cooling the temperature to 40°C at a cooling rate of 2°C / min in an air atmosphere to obtain a nickel-zinc ferrite material.

[0117] Example 5

[0118] This embodiment provides a nickel-zinc ferrite material. The nickel-zinc ferrite material includes a main component and additives. Based on 100 mol% of the total amount of the main component, Fe2O3 accounts for 66 mol%, NiO accounts for 11.45 mol%, ZnO accounts for 19.5 mol%, and CuO accounts for 3.05 mol%. Based on 100 wt% of the total mass of the main component, Bi2O3 accounts for 1.2 wt%, Co2O3 accounts for 0.25 wt%, and ZrO2 accounts for 0.09 wt%.

[0119] The preparation method of the nickel-zinc ferrite material provided in this embodiment comprises the following steps:

[0120] (1) mixing the main component, the ball material, and water in a mass ratio of 1:6:1.1, performing the first ball milling for 40 minutes at a first ball milling speed of 350 rpm, and then performing the first spray granulation to obtain a spray granulated material;

[0121] (2) the spray granulated material is fed into a rotary kiln at a feed rate of 150 kg / h and pre-fired at 930° C. for 3 h to obtain a pre-fired material;

[0122] (3) According to the mass ratio of pre-calcined material: water: polyvinyl butyral: triethanolamine: mineral oil being 100:50:10:1:0.0025, Bi2O3: Co2O3: ZrO2 = 1.2wt%: 0.25wt%: 0.09wt% additives were added, all raw materials were mixed and subjected to a second ball milling, the ball diameter of the second ball milling was 6mm, the ball-to-material ratio of the second ball milling was 3.5:1, and the second ball milling included a first stage ball milling at 120rpm for 10min and a second stage ball milling at 450rpm for 120min to obtain a slurry with a particle size distribution X50 of 0.75μm and X90 of 1.52μm;

[0123] (4) The slurry is subjected to a second spray granulation to obtain particles with an average size of 30 μm-200 μm, and the density is 3.10 g / cm 3 -3.25g / cm 3 , the volume of the blank is H25mm×15mm×10mm;

[0124] (5) The blank is subjected to microwave sintering, and the sintering process is as follows: first heating the temperature to 550°C at a heating rate of 0.55°C / min and keeping the temperature for 5 hours, then heating the temperature to 780°C at a heating rate of 1.2°C / min and keeping the temperature for 5 hours, then cooling the temperature to 560°C at a cooling rate of 5°C / min in an air atmosphere, and then cooling the temperature to 50°C at a cooling rate of 8°C / min in an air atmosphere to obtain a nickel-zinc ferrite material.

[0125] Example 6

[0126] This embodiment provides a nickel-zinc ferrite material. The nickel-zinc ferrite material includes a main component and additives. Based on 100 mol% of the total amount of the main component, Fe2O3 accounts for 65.9 mol%, NiO accounts for 11.4 mol%, ZnO accounts for 18.5 mol%, and CuO accounts for 4.2 mol%. Based on 100 wt% of the total mass of the main component, Bi2O3 accounts for 1.5 wt%, Co2O3 accounts for 0.3 wt%, and ZrO2 accounts for 0.1 wt%.

[0127] The preparation method of the nickel-zinc ferrite material provided in this embodiment comprises the following steps:

[0128] (1) mixing the main component, the ball material and water in a mass ratio of 1:5:1 and performing the first ball milling for 40 minutes at a first ball milling speed of 350 rpm, and then performing the first spray granulation to obtain a spray granulated material;

[0129] (2) the spray granulated material is fed into a rotary kiln at a feed rate of 150 kg / h and pre-fired at 910° C. for 2.5 h to obtain a pre-fired material;

[0130] (3) According to the mass ratio of pre-calcined material: water: polyvinyl butyral: triethanolamine: mineral oil being 100:60:10:1:0.0015, Bi2O3: Co2O3: ZrO2 = 1.5wt%: 0.3wt%: 0.1wt% additives were added, all raw materials were mixed and subjected to a second ball milling, the ball diameter of the second ball milling was 8 mm, the ball-to-material ratio of the second ball milling was 4:1, and the second ball milling included a first stage ball milling at 230 rpm for 10 min and a second stage ball milling at 460 rpm for 90 min to obtain a slurry with a particle size distribution X50 of 0.72 μm and X90 of 1.68 μm;

[0131] (4) The slurry is subjected to a second spray granulation to obtain particles with an average size of 30 μm-200 μm, and the density is 3.10 g / cm 3 -3.25g / cm 3 , the volume of the blank is H25mm×15mm×10mm;

[0132] (5) The blank is subjected to microwave sintering, and the sintering process is as follows: first heating the temperature to 600°C at a heating rate of 1.5°C / min and keeping the temperature for 5 hours, then heating the temperature to 820°C at a heating rate of 3°C / min and keeping the temperature for 5 hours, then cooling the temperature to 500°C at a cooling rate of 5.7°C / min in an air atmosphere, and then cooling the temperature to 50°C at a cooling rate of 6°C / min in an air atmosphere to obtain a nickel-zinc ferrite material.

[0133] Examples 7-9

[0134] The compositions of the nickel-zinc ferrite materials provided in Examples 7-9 are shown in Table 1. The method for preparing the nickel-zinc ferrite materials differs from that in Example 1 only in that the mass percentage of the additives in the raw materials is adjusted according to Table 1, and the rest of the preparation method remains unchanged.

[0135] Example 10

[0136] This embodiment provides a nickel-zinc ferrite material, which differs from Example 1 only in that, when preparing the nickel-zinc ferrite material, the diameter of the balls used in the second ball milling in step (3) is 12 mm.

[0137] Example 11

[0138] This embodiment provides a nickel-zinc ferrite material, which differs from embodiment 1 only in that, when preparing the nickel-zinc ferrite material, the maximum temperature of the second sintering in step (5) is 1060°C.

[0139] Example 12

[0140] This embodiment provides a nickel-zinc ferrite material, which differs from embodiment 1 only in that, when preparing the nickel-zinc ferrite material, the maximum temperature of the second sintering in step (5) is 700°C.

[0141] Comparative Examples 1-8

[0142] The compositions of the nickel-zinc ferrite materials provided in Comparative Examples 1-8 are shown in Table 1. The method for preparing the nickel-zinc ferrite materials differs from that in Example 1 only in that the mass percentages of the main components in the raw materials are adaptively adjusted according to Table 1.

[0143] Comparative Example 9

[0144] This comparative example provides a nickel-zinc ferrite material, which differs from Example 1 only in that, when preparing the nickel-zinc ferrite material, silicon dioxide is additionally added to the additives added in step (3), wherein the mass percentage of silicon dioxide is 0.003 wt%, and the total mass percentage of the four additives is kept unchanged, and the mass percentage of the remaining additives is reduced proportionally with the added mass.

[0145] Comparative Example 10

[0146] This comparative example provides a nickel-zinc ferrite material, which differs from Example 1 only in that, when preparing the nickel-zinc ferrite material, step (5) adopts a traditional sintering method.

[0147] Test method: The sintered magnetic rings with an outer diameter of 25 mm, an inner diameter of 15 mm, and a height of 10 mm obtained from Examples 1-9 and Comparative Examples 1-10 were tested for inductance using an Agilent E4991. The magnetic permeability μi was then calculated based on the size factor. The magnetic permeability μi at various frequencies and the magnetic permeability at various temperatures were tested using an LCR magnetic material tester and a high and low temperature controllable oven. The test results are shown in Table 2. The compositions and contents of Examples 1-9 and Comparative Examples 1-10 are shown in Table 1. "SPEC" in Table 1 indicates the range of the content of each substance, and "SPEC" in Table 2 indicates the standard value of the sintering performance of the test formula.

[0148] Table 1

[0149]

[0150]

[0151] Table 2

[0152]

[0153]

[0154]

[0155] The test results show that:

[0156] (1) It can be seen from Examples 1-6 that the present invention achieves a higher magnetic permeability value and a higher Tc of the nickel-zinc ferrite material at high frequencies by regulating the ratio between the main components of the raw materials. When the Fe2O3 content is not within the range, the magnetic permeability is low and the impedance value Z is also low. Since it is necessary to ensure the broadband high impedance value characteristic, the contents of Fe2O3, ZnO, CuO and NiO need to be adjusted to achieve this. The nickel-zinc ferrite material has a magnetic permeability of ≥1000 at 25°C and a magnetic permeability of ≥1000 under 1MHz test conditions. It can be better applied to the fields of transformers and wireless charging, making wireless charging more efficient.

[0157] (2) By comparing Example 1 with Examples 7-9, it can be seen that the present invention can simultaneously meet the requirements of magnetic permeability and high impedance value Z by further controlling the contents of the three additives within an appropriate range. When the content of one of the additives exceeds the preferred range of the present invention, its magnetic permeability decreases significantly and cannot meet the SPEC standard requirements for use.

[0158] (3) By comparing Example 1 with Example 10, it can be seen that the present invention further optimizes the ball diameter used in the ball milling process to 5mm-10mm to obtain a slurry with a suitable particle size, thereby promoting sintering molding. Compared with the traditional ball milling ball diameter of 12mm, the present invention uses a smaller diameter ball, and the particle size of the slurry obtained by ball milling is smaller and the grain size distribution is more uniform, thereby improving the accuracy and consistency of sample grinding.

[0159] (4) By comparing Example 1 with Examples 11-12, it can be seen that the present invention further optimizes the maximum temperature range of microwave sintering to obtain a nickel-zinc ferrite material with even better performance. If the temperature is too low, it will be sintered prematurely, resulting in low magnetic permeability. If the temperature is too high, not only will the performance of the ferrite material not be improved, but it will also increase losses, leading to increased manufacturing costs.

[0160] (5) It can be seen from Example 1 and Comparative Examples 1-8 that the present invention achieves a higher magnetic permeability value and a higher Tc of the nickel-zinc ferrite material at high frequencies by regulating the ratio between the main components of the raw materials. When the Fe2O3 content is not within the range, the magnetic permeability is low and the impedance value Z is also low. Since it is necessary to ensure the broadband high impedance value characteristic, the contents of Fe2O3, ZnO, CuO and NiO need to be adjusted to achieve this.

[0161] (6) It can be seen from Example 1 and Comparative Example 9 that if a sintering aid silica is added, the purity and magnetic permeability of the material will be affected. The additive of the present invention does not add a sintering aid silica, which simplifies the production process and reduces costs. Not using a silica additive helps to maintain the uniform characteristics of the sintered grains of the material and avoid abnormal grain growth, thereby obtaining a nickel-zinc ferrite material with better magnetic permeability.

[0162] (7) It can be seen from Example 1 and Comparative Example 10 that the advantage of microwave sintering of ferrite materials is that it can achieve rapid and uniform heating, improve sintering efficiency and product uniformity. Microwave sintering directly absorbs microwave energy through the dielectric loss of the material, thereby heating and sintering. This heating method has a fast heating rate, high energy utilization rate, high heating efficiency, and is safe, hygienic and pollution-free. Microwave sintering can also improve the microstructure and performance of the material. Due to its unique heating mechanism, it can promote grain growth, obtain ultrafine grain structure materials, and significantly improve the microstructure of the material. In addition, microwave sintering can reduce the sintering temperature, and rapid heating can inhibit the growth of grain structure, obtain a more uniform fine grain microstructure, and have less internal pores. When using traditional sintering methods, not only is the efficiency low, but uniform sintering of grains cannot be achieved, and the magnetic properties of the ferrite material obtained are also greatly reduced.

[0163] In summary, the present invention achieves a higher magnetic permeability value and a higher Tc of the nickel-zinc ferrite material at high frequency by regulating the ratio between the main components of the raw materials, adopts a microwave sintering method to improve the sintering efficiency and product uniformity, and at the same time improves the microstructure and performance of the material. Due to its unique heating mechanism, it can promote grain growth, obtain ultrafine grain structure materials, and significantly improve the magnetic permeability value of the material. The magnetic permeability of the prepared nickel-zinc ferrite material at 25°C is ≥1000, and the magnetic permeability under 1MHz test conditions is ≥1000.

[0164] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A nickel-zinc ferrite material, characterized in that: The raw materials include main components and additives, the main components include Fe2O3, NiO, ZnO and CuO, and the additives are Bi2O3, Co2O3 and ZrO2; Based on the total amount of the main components as 100 mol%, Fe2O3 is 65 mol%-66.7 mol%, NiO is 10.6 mol%-13 mol%, ZnO is 17 mol%-20 mol%, and CuO is 2 mol%-4.5 mol%; Based on the total mass of the main component as 100wt%, the total mass fraction of the additive is 0.4wt%-2.0wt%; based on the total mass of the main component as 100wt%, Bi2O3 is 0.3wt%-1.5wt%, Co2O3 is 0.1wt%-0.3wt%, and ZrO2 is 0.03wt%-0.1wt%; The nickel-zinc ferrite material is prepared by the following preparation method, which comprises: The main component, the ball material and the solvent are mixed and then subjected to a first ball milling and pre-sintering to obtain a pre-sintered material; the pre-sintered material and the additive are mixed and then subjected to a second ball milling, forming and microwave sintering to obtain a nickel-zinc ferrite material; The diameter of the balls in the second ball milling is 5mm-10mm; The microwave sintering includes a first temperature increase, a second temperature increase, a first temperature decrease, and a second temperature decrease; The target temperature of the second heating is 750°C-1050°C.

2. A method for preparing the nickel-zinc ferrite material according to claim 1, characterized in that: The preparation method comprises the following steps: (1) The main component, the ball material and the solvent are mixed and ball milled for the first time, and then the spray granulation is performed for the first time to obtain the spray granulated material; (2) The spray granulated material is pre-fired to obtain a pre-fired material; (3) Mixing the pre-sintered material, additives, binder, dispersant and defoamer and performing a second ball milling to obtain a slurry; (4) The slurry is subjected to a second spray granulation and molding to obtain a blank; (5) The blank is subjected to microwave sintering to obtain nickel-zinc ferrite material; The diameter of the balls in the second ball milling in step (3) is 5 mm to 10 mm; The microwave sintering process in step (5) includes a first heating process, a second heating process, a first cooling process, and a second cooling process; The target temperature of the second heating is 750°C-1050°C.

3. The preparation method according to claim 2, characterized in that The mass ratio of the main component, ball material and solvent in step (1) is 1:(4-8):(0.5-1.2).

4. The preparation method according to claim 2, characterized in that The solvent in step (1) includes water.

5. The preparation method according to claim 2, characterized in that The rotation speed of the first ball milling in step (1) is 200 rpm-400 rpm.

6. The preparation method according to claim 2, characterized in that The diameter of the balls used in the first ball milling in step (1) is 5 mm to 10 mm.

7. The preparation method according to claim 2, characterized in that The time of the first ball milling in step (1) is 20 min to 60 min.

8. The preparation method according to claim 2, characterized in that The pre-firing temperature in step (2) is 780°C-950°C.

9. The preparation method according to claim 2, characterized in that The pre-burning time in step (2) is 2h-4h.

10. The preparation method according to claim 2, characterized in that The adhesive in step (3) includes any one of ethyl cellulose, polyvinyl alcohol or polyvinyl butyral, or a combination of at least two of them.

11. The preparation method according to claim 2, characterized in that The dispersant in step (3) includes any one of castor oil, citric acid, triethanolamine, polyacrylamide or phosphates, or a combination of at least two of them.

12. The preparation method according to claim 2, characterized in that The defoaming agent in step (3) includes any one of n-octanol, polyethers or mineral oil, or a combination of at least two of them.

13. The preparation method according to claim 2, characterized in that The ball-to-material ratio of the second ball milling in step (3) is (3-5):

1.

14. The preparation method according to claim 2, characterized in that The second ball milling in step (3) includes a first-stage ball milling and a second-stage ball milling.

15. The preparation method according to claim 2, characterized in that In step (3), the rotation speed of the ball milling in the first stage is 50 rpm-300 rpm.

16. The preparation method according to claim 2, characterized in that The time of the first stage ball milling in step (3) is 10 min to 20 min.

17. The preparation method according to claim 2, characterized in that The rotation speed of the ball milling in the second stage of step (3) is 400 rpm-600 rpm.

18. The preparation method according to claim 2, characterized in that The time of the second stage ball milling in step (3) is 50 min-150 min.

19. The preparation method according to claim 2, characterized in that: The mass ratio of the pre-burned material, water, adhesive, dispersant and defoaming agent in step (3) is 100:(40-150):(4-20):(0.1-2):(0.001-0.0025).

20. The preparation method according to claim 2, characterized in that The particle size distribution X50 of the slurry in step (3) is 0.5 μm-0.8 μm, and X90 is 1.25 μm-1.8 μm.

21. The preparation method according to claim 2, characterized in that The average size of the particles produced by the second spray granulation in step (4) is 30 μm to 200 μm.

22. The preparation method according to claim 2, characterized in that The density of the blank in step (4) is 3.10 g / cm 3 -3.25g / cm 3 The size of the blank is H25mm×15mm×10mm.

23. The preparation method according to claim 2, characterized in that The first heating rate is 0.5°C / min-1.5°C / min.

24. The preparation method according to claim 2, characterized in that The target temperature of the first heating is 550°C-750°C.

25. The preparation method according to claim 2, characterized in that The first heating holding time is 2h-7h.

26. The preparation method according to claim 2, characterized in that The second heating rate is 1°C / min-3°C / min.

27. The preparation method according to claim 2, characterized in that The second heating holding time is 2h-5h.

28. The preparation method according to claim 2, characterized in that The cooling rate of the first cooling is 2°C-5°C / min.

29. The preparation method according to claim 2, characterized in that The target temperature of the first cooling step is 500°C-600°C.

30. The preparation method according to claim 2, characterized in that The second cooling rate is 1°C / min-4°C / min.

31. The preparation method according to claim 2, characterized in that The target temperature of the second cooling process is 40°C-50°C.

32. The preparation method according to claim 2, characterized in that The preparation method comprises the following steps: (1) Mixing the main component, ball material and water in a mass ratio of 1: (4-8): (0.5-1.2) at a first ball milling speed of 50 rpm-300 rpm for 20 min-60 min, and then performing the first spray granulation to obtain a spray granulated material; (2) The spray granulated material is pre-calcined at 780°C-950°C for 2h-4h to obtain a pre-calcined material; (3) Mix the pre-sintered material, additives, binder, dispersant and defoamer in a mass ratio of 100:(40-150):(4-20):(0.1-2):(0.001-0.0025, and add Bi2O3 at 0.3wt%-1.5wt%, Co2O3 at 0.1wt%-0.3wt%, and ZrO2 at 0.03wt%-0.1wt% for the second ball milling. The balls used in the milling process are 5 mm and 10 mm in diameter at a weight ratio of 1:

1. The ball-to-material ratio of the second ball milling is (3-5):

1. The second ball milling includes a first stage of ball milling at 50 rpm to 200 rpm for 10 min to 20 min and a second stage of ball milling at 400 rpm to 600 rpm for 50 min to 150 min to obtain a slurry with a particle size distribution X50 of 0.5 μm to 0.8 μm and X90 of 1.25 μm to 1.8 μm. (4) The slurry is subjected to a second spray granulation to obtain particles with an average size of 30 μm-200 μm, and the density is 3.10 g / cm 3 -3.25g / cm 3 , the volume of the blank is H25mm×15mm×10mm; (5) The blank is subjected to microwave sintering, and the microwave sintering process is as follows: first heating the temperature to 550°C-750°C at a heating rate of 0.5°C / min-1.5°C / min and keeping the temperature for 2h-7h, then heating the temperature to 750°C-1050°C at a heating rate of 1°C / min-3°C / min and keeping the temperature for 2h-5h, then cooling the temperature to 500°C-600°C at a cooling rate of 2°C-5°C / min, and then cooling the temperature to 40°C-50°C at a cooling rate of 1°C / min-4°C / min to obtain nickel-zinc ferrite material.

33. A use of the nickel-zinc ferrite material according to claim 1, characterized in that: The nickel-zinc ferrite material is used for a broadband wireless charging magnetic sheet. The magnetic permeability of the nickel-zinc ferrite material at 25° C. is ≥1000, and the magnetic permeability under 1 MHz test conditions is ≥1000.

34. The use according to claim 33, characterized in that The nickel-zinc ferrite material is used in the fields of aerospace, automobile, communication and new energy materials.

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