CN111439995B - A kind of high-performance Co-free hexagonal permanent ferrite material and preparation method thereof - Google Patents

Abstract

The invention discloses a high-performance Co-free hexagonal permanent magnetic ferrite material and a preparation method thereof, mainly aiming at the problems of relative shortage of strategic cobalt resources and high price and the like in China, and mainly solving the key technical problems in the following two aspects in the field of permanent magnetic ferrite: firstly, the main component completely replaces Co ions, so that the production cost is greatly reduced, and the method has great strategic significance for relieving the relative shortage of the cobalt resources in China; secondly, it has high B_rHigh H_cjHegao (BH)_maxThe air gap flux density and the overload multiple of the permanent magnet motor can be improved, the number of magnetic shoes required by the motor is reduced, and the small-size high-efficiency and high-stability of the permanent magnet motor are realized. The performance index of the high-performance Co-free hexagonal permanent magnetic ferrite material prepared by the invention is higher than that of the high-performance La-Co in the marketThe material is a hexagonal permanent magnetic ferrite material, and the final performance indexes are as follows: residual magnetic induction B_rMore than or equal to 460 mT; intrinsic coercive force H_cjMore than or equal to 370 kA/m; magnetic coercive force H_cbNot less than 330 kA/m; maximum magnetic energy product (BH)_max≥41kJ/m³。

Description

A kind of high-performance Co-free hexagonal permanent ferrite material and preparation method thereof

technical field

The invention belongs to the technical field of preparation of ferrite materials, in particular to a high-performance Co-free hexagonal permanent magnet ferrite material and a preparation method thereof.

Background technique

The rapid development of strategic emerging industries such as high-end equipment, new energy vehicles, smart health, and smart home urgently requires small, efficient, and high-stability permanent magnet motor systems; It has exceeded one hundred billion. With the pace of technological innovation and industrial structure upgrading in the field of permanent magnet motors, permanent magnet ferrite materials in the upstream of the industrial chain have also been rapidly developed and adjusted. Many well-known magnetic companies at home and abroad, such as Japan's TDK, FDK, Hitachi Metals, China's Hengdian East Magnetics, Jiangfen Magnetic Materials, Sinosteel Tianyuan, etc., actively target market demand, focus on technological innovation, technology development orientation, and constantly promote permanent magnets The main technical means of the high-end ferrite material is to use La-Co combined doping to control the main formula system and optimize the process structure, so as to form a relatively stable high-performance hexagonal permanent ferrite covering the La-Co system in all directions. Material.

However, with the rapid development of economic globalization in recent years, strategic non-renewable resources are increasingly exhausted, and building a resource-saving and environment-friendly society has become an increasingly pursued goal. The average content of cobalt used in the field of permanent magnet ferrite in the earth's crust is only 0.001%, while China's cobalt resources mainly come from cobalt associated minerals, and the cost of production and utilization is high. At present, the market price of Co ₃ O ₄ is about 340,000/ tons, mostly relying on foreign imports, posing a potential threat to the development of the national economy. Therefore, the research and preparation of high-performance Co-free hexagonal permanent magnet ferrite materials has become a major demand for the development of the national economic strategy.

For the research and preparation of high-performance Co-free hexagonal permanent ferrite materials, the performance indicators of Ca-La substituted hexagonal permanent ferrite materials published by National Chiao Tung University in Korea are: residual magnetic induction intensity B _r ≤ 340mT, intrinsic coercivity The force H _cj ≤ 218kA/m, the maximum magnetic energy product of the material is not listed. The residual magnetic induction intensity and intrinsic coercive force of the material are both low, which cannot be compared with the performance indicators of the market high-performance La-Co series hexagonal permanent magnet ferrite materials (residual magnetic induction intensity B _r ≥ 450mT, intrinsic coercive force H _cj ≥ 358kA /m, the maximum magnetic energy product (BH) _max ≥38kJ/m ³ ) is matched. German Siemens Technology Co., Ltd. uses traditional oxide ceramic method to prepare SrFe ₁₁ AlO ₁₉ permanent magnet ferrite material. Its performance indicators are: residual magnetic induction intensity B _r ≤ 260mT, intrinsic coercivity H _cj ≤ 500kA/m, not listed The maximum magnetic energy product of a material. Although the intrinsic coercivity of the material has reached the performance index of the high-performance La-Co series hexagonal permanent magnet ferrite material on the market, its residual magnetic induction intensity is low, which cannot meet the requirements of high efficiency and high air gap magnetic density of permanent magnet motors. South Korea's Samsung Electronics Automotive R&D team has announced a Mn-Zn substituted hexagonal permanent magnet ferrite material. Its performance indicators are: residual magnetic induction intensity B _r ≤ 430mT, intrinsic coercivity H _cj ≤ 250kA/m, maximum magnetic energy product ( BH) _max ≤ 36kJ/m ³ . Anhui University of China uses La-Cu to replace the hexagonal permanent magnet ferrite material. Its performance indicators are: residual magnetic induction intensity B _r ≤ 420mT, intrinsic coercivity H _cj ≤ 235kA/m, maximum magnetic energy product (BH) _max ≤ 32kJ /m ³ . Although the residual magnetic induction intensity and maximum magnetic energy product of the above two materials are close to the performance indicators of the high-performance La-Co series hexagonal permanent magnet ferrite materials on the market, their intrinsic coercivity is low, which cannot meet the overload multiple and high performance of the permanent magnet motor. stability requirements.

In addition, in the published patent CN1664964, a non-substituted hexagonal permanent magnet ferrite material is published, and its performance indicators are: residual magnetic induction intensity B _r ≤ 378mT, intrinsic coercive force H _cj ≤ 222kA/m, maximum magnetic energy Product (BH) _max ≤ 26kJ/m ³ . The residual magnetic induction intensity, intrinsic coercive force and maximum magnetic energy product of the product are far from the performance indicators of the high-performance La-Co series hexagonal permanent ferrite materials on the market. The performance index of a high coercivity hexagonal permanent magnet ferrite material (SrFe _12-x Al _x O ₁₉ , 0.3≤x≤0.5) published by patent CN105060870A is: residual magnetic induction intensity B _r ≤ 370mT, intrinsic coercivity H _cj ≤400kA/m, maximum magnetic energy product (BH) _max ≤25kJ/m ³ . The intrinsic coercivity of the product reaches the performance index of high-performance La-Co series hexagonal permanent magnet ferrite materials on the market, but its residual magnetic induction intensity and maximum magnetic energy product are low, which cannot meet the requirements of small, high-efficiency and high air-gap magnetic density of permanent magnet motors. demand. Patent CN106745298A discloses an enhanced hexagonal permanent magnet ferrite material (SrFe _12-x Ce _x O ₁₉ , 0.3≤x≤0.5), its performance index is: specific saturation magnetization σ _s ≤ 60.7emu/g, intrinsic The coercivity H _cj ≤ 345kA/m, the maximum magnetic energy product and density of the material are not given. Although the intrinsic coercivity of the product is close to the performance index of the high-performance La-Co series hexagonal permanent magnet ferrite material on the market, its specific saturation magnetization is far from it (σ _s ≥ 72emu/g).

Based on the above, the current Co-based hexagonal permanent magnet ferrite materials for electric motors have the problem that their properties cannot have high B _r , high H _cj and high (BH) _max .

SUMMARY OF THE INVENTION

The purpose of the present invention is to, in view of the above-mentioned problems, to provide a high-performance Co-free hexagonal permanent ferrite material and a preparation method thereof whose performance index is better than that of the high-performance La-Co series hexagonal permanent ferrite material on the market.

The technical scheme of the present invention is achieved as follows: a high-performance Co-free hexagonal permanent ferrite material, whose components are composed of main components and additives, is characterized in that:

According to the molar percentage of the main components, the main components include: 1.38-4.46 mol% CaCO ₃ , 2.15-6.15 mol % La ₂ O ₃ , 1.38-5.38 mol % SrCO ₃ , 73.5-82.2 mol % Fe ₂ O ₃ , 1.15- 5.77mol% Al ₂ O ₃ , 1.92～6.54mol% ZnO, 1.69～7.31mol% CuO;

According to the weight percentage of main components, calculated in terms of oxides, the additives include: 0.01-0.08wt% La ₂ O ₃ , 0.03-0.09wt% Al ₂ O ₃ , 0.08-0.18wt% H ₃ BO ₃ , 0.08-0.38wt% %CaCO ₃ , 0.18-0.38 wt% SiO ₂ , 0.12-0.72 wt% Ca(C ₆ H ₁₁ O ₇ ) ₂ , 0.12-0.72 wt % HO(CH ₂ CH ₂ O) _n H.

The high-performance non-Co-based hexagonal permanent magnet ferrite material according to the present invention, according to the molar percentage of main components, the main components include: 2.18-3.46 mol% CaCO ₃ , 2.55-4.15 mol % La ₂ O ₃ , 2.18- 4.23mol% SrCO ₃ , 78.5～81.2mol% Fe ₂ O ₃ , 2.15～4.77mol% Al ₂ O ₃ , 3.04～5.54mol% ZnO, 2.69～5.31mol% CuO;

According to the weight percentage of main components, calculated in terms of oxides, the additives include: 0.03-0.06wt% La ₂ O ₃ , 0.05-0.07wt% Al ₂ O ₃ , 0.10-0.16wt% H ₃ BO ₃ , 0.18-0.28wt% % CaCO ₃ , 0.24-0.34 wt % SiO ₂ , 0.22-0.62 wt % Ca(C ₆ H ₁₁ O ₇ ) ₂ , 0.22-0.62 wt % HO(CH ₂ CH ₂ O) _n H.

The high-performance non-Co-based hexagonal permanent ferrite material according to the present invention, according to the molar percentage of the main components, the main components include: 2.54mol% CaCO ₃ , 2.92mol% La ₂ O ₃ , 2.23mol% SrCO ₃ , 80.54mol% Fe ₂ O ₃ , 4.08mol% Al ₂ O ₃ , 4.54mol% ZnO, 3.15mol% CuO;

According to the weight percentage of the main components, calculated as oxides, the additives include: 0.04wt% La ₂ O ₃ , 0.06wt% Al ₂ O ₃ , 0.14wt% H ₃ BO ₃ , 0.21wt% CaCO ₃ , 0.29wt% SiO ₂ , 0.52 wt% _Ca ( _C6H11O7 ) ₂ , _0.48 wt% HO( _{CH2CH2O ) nH} .

The high-performance Co-free hexagonal permanent magnet ferrite material of the present invention has the following performance indicators:

Residual magnetic induction intensity B _r ≥ 460mT;

Intrinsic coercivity H _cj ≥370kA/m;

Magnetic coercivity H _cb ≥330kA/m;

Maximum magnetic energy product (BH) _max ≥41kJ/m ³ .

A high-performance non-Co-based hexagonal permanent magnet ferrite material, the performance index of the material is:

Residual magnetic induction intensity B _r ≥ 460mT;

Intrinsic coercivity H _cj ≥370kA/m;

Magnetic coercivity H _cb ≥330kA/m;

Maximum magnetic energy product (BH) _max ≥41kJ/m ³ .

The high-performance non-Co-based hexagonal permanent magnet ferrite material of the present invention is composed of main components and additives, and the main components include: CaCO ₃ , La ₂ O ₃ , SrCO ₃ , Fe ₂ O ₃ , Al ₂ O ₃ , ZnO, CuO; the additives include: La ₂ O ₃ , Al ₂ O ₃ , H ₃ BO ₃ , CaCO ₃ , SiO ₂ , Ca(C ₆ H ₁₁ O ₇ ) ₂ , HO(CH ₂ CH ₂ O) _n H.

A preparation method of a high-performance Co-free hexagonal permanent ferrite material, characterized in that: comprising the following steps:

a) Material formula selection

According to the molar percentage of main components, 1.38-4.46mol% CaCO ₃ , 2.15-6.15mol% La ₂ O ₃ , 1.38-5.38mol% SrCO ₃ , 73.5-82.2mol% Fe ₂ O ₃ , 1.15-5.77mol% Al ₂ O ₃ , 1.92-6.54mol% ZnO, 1.69-7.31mol% CuO;

b) One time ball milling

Mix the above powder evenly in the ball mill, and control the particle size of the powder between 0.7 and 0.9 μm;

c) Burn-in

Drying the ball abrasive obtained in step b), and pre-sintering it in a furnace at 1050 to 1150 ° C for 2 to 4 hours;

d) Doping with additives

The following additives are added to the powder obtained in step c) by weight: 0.01-0.08wt% La ₂ O ₃ , 0.03-0.09wt% Al ₂ O ₃ , 0.08-0.18wt% H ₃ BO ₃ , 0.08-0.38wt% CaCO _3. 0.18-0.38wt% SiO ₂ , 0.12-0.72wt% Ca(C ₆ H ₁₁ O ₇ ) ₂ , 0.12-0.72wt% HO(CH ₂ CH ₂ O) _n H;

e) Secondary ball milling

The powder obtained in step d) is ball-milled in a ball mill, and the particle size of the powder is controlled between 0.5 and 0.7 μm;

f) Forming

Dewatering the ball-milling slurry obtained in step e) to make the water content of the slurry 35-50%, pressing and molding under a wet-pressing magnetic field molding machine, the molding magnetic field strength is 7.5-14.5 kOe, and the pressure holding time is 6-12 s ;

g) Sintering

The blank obtained in step f) is sintered in a sintering furnace, and a pressure of 100-500 N is applied to the upper part of the blank, and the temperature is kept at 1080-1180° C. for 2.5-5.5 hours.

The invention mainly aims at the problems of relatively poor and expensive strategic cobalt resources in China, and provides a high-performance Co-free hexagonal permanent magnet ferrite material and a preparation method thereof, and mainly solves the following two key technical problems in the field of permanent magnet ferrite. : First, the main component completely replaces Co _ions , and the production cost is greatly _reduced , which is of great strategic significance for alleviating the relative _shortage of cobalt resources in China; The air-gap magnetic density and overload multiple of the permanent magnet motor reduce the number of magnetic tiles required by the motor, and realize the small, high-efficiency and high stability of the permanent magnet motor.

The high-performance non-Co-based hexagonal permanent ferrite material prepared by the invention has a performance index higher than that of the high-performance La-Co series hexagonal permanent ferrite material on the market, and its final performance index is as follows:

Residual magnetic induction intensity B _r ≥ 460mT;

Intrinsic coercivity H _cj ≥370kA/m;

Magnetic coercivity H _cb ≥330kA/m;

Maximum magnetic energy product (BH) _max ≥41kJ/m ³ .

Description of drawings

FIG. 1 shows a scanning electron microscope photo of the hexagonal permanent magnet ferrite material in Example 1 of the present invention.

FIG. 2 shows a scanning electron microscope photograph of the hexagonal permanent magnet ferrite material in Example 2 of the present invention.

FIG. 3 shows a scanning electron microscope photo of the hexagonal permanent magnet ferrite material in Example 3 of the present invention.

FIG. 4 shows a scanning electron microscope photo of the hexagonal permanent magnet ferrite material in Example 4 of the present invention.

FIG. 5 is a scanning electron microscope photograph of the hexagonal permanent magnet ferrite material according to Embodiment 5 of the present invention.

Fig. 6 shows the scanning electron microscope photograph of the hexagonal permanent magnet ferrite material of Comparative Example 1 of the present invention.

Fig. 7 shows the scanning electron microscope photograph of the hexagonal permanent magnet ferrite material of Comparative Example 2 of the present invention.

FIG. 8 shows a scanning electron microscope photograph of the hexagonal permanent magnet ferrite material of Comparative Example 3 of the present invention.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings.

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

Aiming at the problems that strategic cobalt resources in China are relatively poor and expensive, the present invention provides a Co-free hexagonal permanent ferrite material with high B _r , high H _cj and high (BH) _max and a preparation method thereof. Its guiding ideology is: magnetic domain theory, ion occupancy mechanism, crystal-promoting competitive sintering mechanism, electrostatic steric hindrance mechanism, and magnetic stress theory. First, by selecting high-purity CaCO ₃ , La ₂ O ₃ , SrCO ₃ , Fe ₂ O ₃ , Al ₂ O ₃ , ZnO and CuO as raw materials, the ion occupancy and single domain of hexagonal permanent ferrite materials were deeply analyzed The critical size is controlled by a combination of various metal ions, and the optimal formula range is formulated to achieve high coercivity and high magnetic induction intensity; Mechanism of structure and dispersion properties of magnetic slurry, study of the effects of La ₂ O ₃ , Al ₂ O ₃ , H ₃ BO ₃ , CaCO ₃ and SiO ₂ on the grain boundary properties of calcium gluconate and polyethylene glycol Influence on the dispersion characteristics of magnetic slurry, the optimal additive formula is formulated; finally, under the premise of the above-mentioned formulation, additives and powder preparation process optimization, based on the magnetic stress theory sintering technology, the grains grow uniformly and finely flaky. Finally, a Co-free hexagonal permanent magnet ferrite material with high B _r , high H _cj and high (BH) _max was prepared.

The high-performance non-Co-based hexagonal permanent ferrite material _of the present invention is composed of main components and additives. 2.15～6.15mol% La ₂ O ₃ , 1.38～5.38mol% SrCO ₃ , 73.5～82.2mol% Fe ₂ O ₃ , 1.15～5.77mol% Al ₂ O ₃ , 1.92～6.54mol% ZnO, 1.69～7.31mol% CuO.

The additives are calculated in terms of oxides according to the weight percentage of the main components, and specifically include: 0.01-0.08wt% La ₂ O ₃ , 0.03-0.09wt% Al ₂ O ₃ , 0.08-0.18wt% H ₃ BO ₃ , 0.08-0.38 wt% CaCO ₃ , 0.18-0.38 wt% SiO ₂ , 0.12-0.72 wt% Ca(C ₆ H ₁₁ O ₇ ) ₂ (calcium gluconate), 0.12-0.72 wt % HO(CH ₂ CH ₂ O) _n H( polyethylene glycol).

In terms of the main components of the present invention, on the one hand, the substitution of La ³⁺ +Al ³⁺ can increase the critical size of the single domain, enhance the magnetocrystalline anisotropy, and significantly improve the coercivity of the sintered sample; on the other hand, Cu ²⁺ occupies Fe 2a (↑) and 4f ₂ (↓) crystal sites in ³⁺ , and the occupation ratio is about 1:2, Zn ²⁺ preferentially occupies 4f ₁ (↓) crystal site in Fe ³⁺ , which is beneficial to control the saturation magnetic induction of sintered samples At the same time, the main formula introduces an appropriate amount of low-melting CuO, which can reduce the pre-sintering temperature, reduce energy consumption, and improve the density of the sintered body.

In terms of additives, the present invention introduces trace amounts of La ₂ O ₃ and Al ₂ O ₃ to repair the lattice defects generated in the pre _- sintering process and improve the purity _of the sintered samples; Decompose to form B ₂ O ₃ glass phase, which is enriched at grain boundaries to inhibit grain growth and improve coercivity; doping with CaCO ₃ and SiO ₂ refines grains, narrows particle distribution, and improves remanence orientation; adding glucose Calcium acid forms an electric double layer structure on the surface of ferrite, introduces polyethylene glycol, adsorbs on the surface of particles, hinders the agglomeration between particles, and plays the role of dispersing magnetic particles.

Since the magnetostrictive coefficient λ _s <0 of the hexagonal permanent ferrite material, during the sintering process, a setter plate with a certain weight is placed on the ferrite magnetic sheet to improve the c-axis orientation of the crystal grains. That is: introducing metal ions such as La ³⁺ and Al ³⁺ through the main formula, increasing the critical size of the single domain, regulating the ion occupancy distribution, and achieving high coercivity and high saturation magnetic induction; The composite additive can optimize the characteristics of grain boundaries and realize the maximization of single domain particle size and densified growth; the combination of ionic and steric dispersants can build an electric double layer structure and steric hindrance effect, control the viscosity of the slurry, and realize the Dispersion between magnetic particles; based on the theoretical model of magnetic stress, the c-axis orientation of the magnetic moment of the crystal grains is controlled to achieve uniform and fine flake growth.

The preparation method of the high-performance Co-free hexagonal permanent magnet ferrite material of the present invention comprises the following steps:

a) Material formula selection

According to the molar percentage of main components, 1.38-4.46mol% CaCO ₃ , 2.15-6.15mol% La ₂ O ₃ , 1.38-5.38mol% SrCO ₃ , 73.5-82.2mol% Fe ₂ O ₃ , 1.15-5.77mol% Al ₂ O ₃ , 1.92-6.54 mol % ZnO, 1.69-7.31 mol % CuO.

b) One time ball milling

The above powders are mixed evenly in a ball mill, and the particle size of the powder is controlled between 0.7 and 0.9 μm.

c) Burn-in

The ball abrasive obtained in step b) is dried, and pre-fired in a furnace at 1050-1150° C. for 2-4 hours.

d) Doping with additives

The following additives are added to the powder obtained in step c) by weight: 0.01-0.08wt% La ₂ O ₃ , 0.03-0.09wt% Al ₂ O ₃ , 0.08-0.18wt% H ₃ BO ₃ , 0.08-0.38wt% CaCO _3. 0.18-0.38wt% SiO ₂ , 0.12-0.72wt% Ca(C ₆ H ₁₁ O ₇ ) ₂ (calcium gluconate), 0.12-0.72wt% HO(CH ₂ CH ₂ O) _n H (polyethylene di alcohol).

e) Secondary ball milling

The powder obtained in step d) is ball-milled in a ball mill, and the particle size of the powder is controlled between 0.5-0.7 μm.

f) Forming

Dewatering the ball-milling slurry obtained in step e) to make the water content of the slurry 35-50%, pressing and molding under a wet-pressing magnetic field molding machine, the molding magnetic field strength is 7.5-14.5 kOe, and the pressure holding time is 6-12 s .

g) Sintering

The blank obtained in step f) is sintered in a sintering furnace, and a pressure of 100-500 N is applied to the upper part of the blank, and the temperature is kept at 1080-1180° C. for 2.5-5.5 hours.

h) test

The sample obtained in step g) is tested for permanent magnet properties, and the residual magnetic induction intensity _Br , intrinsic coercivity H _cj , magnetic induction coercivity H _cb and maximum magnetic energy product (BH) _max of the material adopt AMT-4A permanent magnet properties Automatic gauge test.

The high-performance non-Co-based hexagonal permanent magnet ferrite material of the present invention has residual magnetic induction intensity B _r ≥460mT, intrinsic coercive force Hcj ≥370kA/m, magnetic induction coercive force _{Hcb ≥330kA} /m, maximum magnetic energy product (BH) _max ≥ 41kJ/m ³ .

The specific embodiments 1 to 5 of the present invention and the comparative examples 1 to 3 include the following steps:

a) Select the formula, the main components of Examples 1-5 are CaCO ₃ , La ₂ O ₃ , SrCO ₃ , Fe ₂ O ₃ , Al ₂ O ₃ , ZnO, CuO, and the main components of Comparative Examples 1-3 are CaCO ₃ , La ₂ O ₃ , SrCO ₃ , Fe ₂ O ₃ ; the proportions of the corresponding main components are shown in the table below, in molar percentages, calculated as oxides.

b) One time ball milling, the above material powder is mixed evenly in the ball mill, and the particle size of the powder is controlled between 0.7 and 0.9 μm.

c) pre-sintering, drying the ball abrasive obtained in step b), and pre-sintering in a furnace at 1070° C. for 3.5 hours.

d) Add additives, add the powder obtained in step c) into additives according to weight ratio: La ₂ O ₃ , Al ₂ O ₃ , H ₃ BO ₃ , CaCO ₃ , SiO ₂ , Ca(C ₆ H ₁₁ O ₇ ) ₂ (calcium gluconate), HO(CH ₂ CH ₂ O) _n H (polyethylene glycol), H ₃ BO ₃ , CaCO ₃ , SiO ₂ , Ca(C ₆ H in Comparative Example 1-3 ₁₁ O ₇ ) ₂ (calcium gluconate); the proportions of the corresponding additives are shown in the following table, calculated by the mass percentage of the main component and calculated as oxides.

e) secondary ball milling, the powder obtained in step d) is ball milled in a ball mill, and the particle size of the powder is controlled between 0.5 and 0.7 μm.

f) Forming, dewatering the ball-milled slurry obtained in step e) to make the water content of the slurry 38%, pressing and molding under a wet-pressing magnetic field molding machine, the molding magnetic field strength is 8.5kOe, and the pressure holding time is 7s.

g) sintering, placing the blank obtained in step f) in a sintering furnace for sintering, and applying a pressure of 100-500 N on the upper part of the blank, and keeping the temperature at 1120° C. for 3.5 hours.

h) Test, the samples obtained in step g) are tested for permanent magnetic properties. The residual magnetic induction intensity B _r , the intrinsic coercive force H _cj , the magnetic induction coercive force H _cb and the maximum magnetic energy product (BH) _max of the material adopt AMT- 4A permanent magnet characteristic automatic measuring instrument test.

After the above process, a high-performance Co-free hexagonal permanent magnet ferrite material was prepared. The performance indicators are as follows:

The test results of Examples 1-5 and Comparative Examples 1-3 are as follows:

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (5)

1. A preparation method of a high-performance Co-free hexagonal permanent magnetic ferrite material is characterized by comprising the following steps: the method comprises the following steps:

a) material formulation selection

According to the mole percentage of the main component, 1.38-4.46 mol percent of CaCO is adopted₃、2.15～6.15mol％La₂O₃、1.38～5.38mol％SrCO₃、73.5～82.2mol％Fe₂O₃、1.15～5.77mol％Al₂O₃、1.92～6.54mol％ZnO、1.69～7.31mol％CuO；

b) One-step ball milling

Uniformly mixing the above material powder in a ball mill, wherein the particle size of the powder is controlled to be 0.7-0.9 μm;

c) pre-firing

Drying the ball-milled material obtained in the step b), and pre-burning in a furnace at 1050-1150 ℃ for 2-4 hours;

d) additive

Adding the following additives into the powder obtained in the step c) according to the weight ratio: 0.01 to 0.08 wt% of La₂O₃、0.03～0.09wt％Al₂O₃、0.08～0.18wt％H₃BO₃、0.08～0.38wt％CaCO₃、0.18～0.38wt％SiO₂、0.12～0.72wt％Ca(C₆H₁₁O₇)₂、0.12～0.72wt％HO(CH₂CH₂O)_nH；

e) Secondary ball milling

Ball-milling the powder obtained in the step d) in a ball mill, wherein the particle size of the powder is controlled to be 0.5-0.7 mu m;

f) shaping of

Dehydrating the ball-milling slurry obtained in the step e) to ensure that the water content of the slurry is 35-50%, and performing compression molding under a wet-pressing magnetic field forming machine, wherein the magnetic field intensity of the formed slurry is 7.5-14.5 kOe, and the pressure maintaining time is 6-12 s;

g) sintering

And f), placing the blank obtained in the step f) in a sintering furnace for sintering, applying 100-500N pressure on the upper part of the blank, and preserving heat for 2.5-5.5 hours at the temperature of 1080-1180 ℃.

2. The high-performance Co-free hexagonal permanent magnetic ferrite material prepared by the preparation method of claim 1 comprises the following components in percentage by weight:

according to the mole percentage of the main components, the main components comprise: 1.38 to 4.46 mol% CaCO₃、2.15～6.15mol％La₂O₃、1.38～5.38mol％SrCO₃、73.5～82.2mol％Fe₂O₃、1.15～5.77mol％Al₂O₃、1.92～6.54mol％ZnO、1.69～7.31mol％CuO；

By weight of principal componentThe additive comprises the following components in percentage by weight calculated by oxide: 0.01 to 0.08 wt% of La₂O₃、0.03～0.09wt％Al₂O₃、0.08～0.18wt％H₃BO₃、0.08～0.38wt％CaCO₃、0.18～0.38wt％SiO₂、0.12～0.72wt％Ca(C₆H₁₁O₇)₂、0.12～0.72wt％HO(CH₂CH₂O)_nH。

3. The high-performance Co-free hexagonal permanent magnetic ferrite material according to claim 2, wherein: according to the mole percentage of the main components, the main components comprise: 2.18 to 3.46 mol% CaCO₃、2.55～4.15mol％La₂O₃、2.18～4.23mol％SrCO₃、78.5～81.2mol％Fe₂O₃、2.15～4.77mol％Al₂O₃、3.04～5.54mol％ZnO、2.69～5.31mol％CuO；

The additive comprises the following components in percentage by weight of main components and calculated by oxides: 0.03 to 0.06 wt% of La₂O₃、0.05～0.07wt％Al₂O₃、0.10～0.16wt％H₃BO₃、0.18～0.28wt％CaCO₃、0.24～0.34wt％SiO₂、0.22～0.62wt％Ca(C₆H₁₁O₇)₂、0.22～0.62wt％HO(CH₂CH₂O)_nH。

4. The high-performance Co-free hexagonal permanent magnetic ferrite material according to claim 3, wherein: according to the mole percentage of the main components, the main components comprise: 2.54 mol% CaCO₃、2.92mol％La₂O₃、2.23mol％SrCO₃、80.54mol％Fe₂O₃、4.08mol％Al₂O₃、4.54mol％ZnO、3.15mol％CuO；

The additive comprises the following components in percentage by weight of main components and calculated by oxides: 0.04 wt% La₂O₃、0.06wt％Al₂O₃、0.14wt％H₃BO₃、0.21wt％CaCO₃、0.29wt％SiO₂、0.52wt％Ca(C₆H₁₁O₇)₂、0.48wt％HO(CH₂CH₂O)_nH。

5. The high performance Co-free hexagonal permanent ferrite material of claim 2, 3 or 4, wherein: the performance indexes of the material are as follows:

residual magnetic induction B_r≥460mT；

Intrinsic coercive force H_cj≥370kA/m；

Magnetic coercive force H_cb≥330kA/m；

Maximum magnetic energy product (BH)_max≥41kJ/m³。

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