阅读说明：本技术 一种高频高Q值FeSiAl@MnZn铁氧体软磁复合磁粉芯及其制备方法 (High-frequency high-Q-value FeSiAl @ MnZn ferrite soft magnetic composite magnetic powder core and preparation method thereof ) 是由 刘明 董璇 于 2021-08-30 设计创作，主要内容包括：本发明公开了一种高频高Q值FeSiAl@MnZn铁氧体软磁复合磁粉芯及其制备方法,主要包括粉末粒度筛选,化学共沉淀法包覆MnZn铁氧体壳层,复合磁粉预烧,压制成型,退火等步骤。此方法未对FeSiAl粉末进行扁平化和磷化处理,不仅化简了实验流程,减少了环境污染,而且可以实现更好的包覆效果,有效隔绝了金属磁粉颗粒之间的电接触,提高了复合磁粉芯的磁导率和品质因数,拓宽了FeSiAl磁粉芯的应用频率范围。本发明实施流程简单,反应时间短,易于大规模生产和工业化应用。(The invention discloses a high-frequency high-Q-value FeSiAl @ MnZn ferrite soft magnetic composite magnetic powder core and a preparation method thereof. The method does not carry out flattening and phosphorization treatment on the FeSiAl powder, not only simplifies the experimental process and reduces the environmental pollution, but also can realize better coating effect, effectively isolates the electric contact among the metal magnetic powder particles, improves the magnetic conductivity and the quality factor of the composite magnetic powder core and widens the application frequency range of the FeSiAl magnetic powder core. The method has the advantages of simple implementation flow, short reaction time and easy large-scale production and industrial application.)

1. A high-frequency high-Q-value FeSiAl @ MnZn ferrite soft magnetic composite magnetic powder core is characterized in that the high-frequency high-Q-value FeSiAl @ MnZn ferrite soft magnetic composite magnetic powder core is obtained by cold press molding and stress relief annealing of a mixture of FeSiAl @ MnZn ferrite composite magnetic powder, a binder and a release agent; the FeSiAl @ MnZn ferrite composite magnetic powder comprises FeSiAl magnetic powder and a MnZn ferrite coating layer coated on the surface of the FeSiAl magnetic powder.

2. The high-frequency high-Q-value FeSiAl @ MnZn ferrite soft magnetic composite magnetic powder core as claimed in claim 1, wherein the FeSiAl magnetic powder comprises the following components in percentage by mass: si: 8% -13%, Al: 4% -7% of Fe and the balance of Fe;

in the FeSiAl @ MnZn ferrite composite magnetic powder, Fe²⁺：Zn²⁺：Mn²⁺In a molar ratio of 2: x: (1-x), wherein x is 0-1, x is not equal to 0 and x is not equal to 1;

in the FeSiAl @ MnZn ferrite composite magnetic powder core, the mass of the MnZn ferrite coating layer is 0.5-10% of that of the FeSiAl magnetic powder.

3. The high frequency high Q FeSiAl @ MnZn ferrite soft magnetic composite powder core of claim 1, wherein the binder is instant sodium silicate having a mass of 0.5 wt.% to 2 wt.% of the mass of the FeSiAl @ MnZn ferrite soft magnetic composite powder; the release agent adopts zinc stearate, and the mass of the zinc stearate is 0.5-2 wt% of that of the FeSiAl @ MnZn ferrite composite magnetic powder.

4. A preparation method of a high-frequency high-Q-value FeSiAl @ MnZn ferrite soft magnetic composite magnetic powder core is characterized by comprising the following steps of:

forming a MnZn ferrite coating layer on the surface of the FeSiAl magnetic powder by a chemical coprecipitation method to obtain a FeSiAl @ MnZn ferrite precursor;

presintering the FeSiAl @ MnZn ferrite precursor at the temperature of 400-700 ℃ in the air atmosphere, and preserving heat for 1-3h to obtain FeSiAl @ MnZn ferrite composite magnetic powder;

uniformly mixing the FeSiAl @ MnZn ferrite composite magnetic powder, a binder and a release agent, carrying out cold press molding on the mixture, and then carrying out stress relief annealing in an inert atmosphere to obtain the FeSiAl @ MnZn ferrite composite magnetic powder core.

5. The preparation method of the high-frequency high-Q FeSiAl @ MnZn ferrite soft magnetic composite magnetic powder core according to claim 4, wherein the process of forming the MnZn ferrite clad layer on the surface of the FeSiAl magnetic powder by a chemical coprecipitation method to obtain the FeSiAl @ MnZn ferrite precursor comprises the following steps:

adding the Fe-Mn-Zn mixed salt solution into a deionized water suspension of FeSiAl magnetic powder and uniformly stirring to obtain a mixture A;

and continuously stirring the mixture A, adding NaOH solution into the mixture A to adjust the pH value to 9-11 for reaction, and obtaining a FeSiAl @ MnZn ferrite precursor after the reaction is finished.

6. The method for preparing the high-frequency high-Q FeSiAl @ MnZn ferrite soft magnetic composite magnetic powder core according to claim 5, wherein FeCl is adopted as an iron salt in a Fe-Mn-Zn mixed salt solution₂Or FeSO₄Zinc salt is ZnCl₂Or ZnSO₄The manganese salt is MnCl₂Or MnSO₄(ii) a In the chemical coprecipitation process, the temperature is 50-80 ℃, NaOH solution is added, and then stirring is carried out for 20-40min, wherein the stirring speed is 50-160 rpm.

7. The preparation method of the high-frequency high-Q-value FeSiAl @ MnZn ferrite soft magnetic composite magnetic powder core according to claim 4, wherein the FeSiAl magnetic powder comprises the following components in percentage by mass: si: 8% -13%, Al: 4% -7% of Fe and the balance of Fe; the mesh number of the FeSiAl magnetic powder is more than 200 meshes;

in the FeSiAl @ MnZn ferrite composite magnetic powder, Fe²⁺：Zn²⁺：Mn²⁺In a molar ratio of 2: x: (1-x), wherein x is 0-1;

in the FeSiAl @ MnZn ferrite composite magnetic powder core, the mass of the MnZn ferrite coating layer is 0.5-10% of that of the FeSiAl magnetic powder.

8. The method of claim 4, wherein the binder is instant sodium silicate, and the mass of instant sodium silicate is 0.5 wt.% to 2 wt.% of the mass of the FeSiAl @ MnZn ferrite composite magnetic powder; the release agent adopts zinc stearate, and the mass of the zinc stearate is 0.5-2 wt% of that of the FeSiAl @ MnZn ferrite composite magnetic powder.

9. The method for preparing the high-frequency high-Q FeSiAl @ MnZn ferrite soft magnetic composite magnetic powder core according to claim 4, wherein the cold press molding pressure is 1300-2400MPa, the cold press pressurizing rate is 1-10MPa/s, and the pressure maintaining time is 5-400 s.

10. The method for preparing a high-frequency high-Q FeSiAl @ MnZn ferrite soft magnetic composite magnetic powder core as claimed in claim 4, wherein the annealing temperature is 500-850 ℃ during the stress relief annealing, the heat preservation time is 0.5-2h, and argon or nitrogen is used as inert gas.

Technical Field

The invention belongs to the technical field of magnetic material and device preparation, and particularly relates to a high-frequency high-Q-value FeSiAl @ MnZn ferrite soft magnetic composite magnetic powder core and a preparation method thereof.

Background

The magnetic powder core is a soft magnetic material formed by mixing and pressing magnetic material powder and an insulating medium. Compared with other alloy materials, FeSiAl has the characteristics of high saturation magnetic flux density, good temperature stability, high saturation magnetization and the like, so that the FeSiAl can be used for higher power. These characteristics make the magnetic powder core have the advantages that other magnetic materials are difficult to compare with in many application occasions, and the magnetic powder core is widely applied to energy storage filter inductors, power transformer magnetic cores, choke coils, switching power supplies and the like at present.

With the rapid development of electronic information technology, higher requirements are put on the performance of magnetic elements. Miniaturization, high frequency and power of magnetic elements have become a necessary trend of development, and the key to the performance of the magnetic elements lies in the magnetic powder core. Magnetic powder cores can be classified into the following types according to the powder containing a magnetic material: iron powder core, iron silicon aluminum powder core, high magnetic flux density powder core, permalloy and ferrite powder core. In recent years, the sendust core has a larger initial permeability and a better temperature stability, so that the sendust core becomes a mainstream of the current magnetic powder core application and has a wide market prospect. But the high-frequency magnetic performance is poor, the quality factor and the magnetic conductivity are sharply reduced under high frequency, and the loss is sharply increased, which seriously limits the application of the high-frequency magnetic material in high frequency.

Disclosure of Invention

In order to solve the problems in the prior art, the invention aims to provide the high-frequency high-Q-value FeSiAl @ MnZn ferrite soft magnetic composite magnetic powder core and the preparation method thereof.

The technical scheme adopted by the invention is as follows:

a high-frequency high-Q-value FeSiAl @ MnZn ferrite soft magnetic composite magnetic powder core is obtained by cold press molding and stress relief annealing of a mixture of FeSiAl @ MnZn ferrite composite magnetic powder, a binder and a release agent; the FeSiAl @ MnZn ferrite composite magnetic powder comprises FeSiAl magnetic powder and a MnZn ferrite coating layer coated on the surface of the FeSiAl magnetic powder.

Preferably, the FeSiAl magnetic powder comprises the following components in percentage by mass: si: 8% -13%, Al: 4% -7% of Fe and the balance of Fe;

the FeSiAl @ MnZn ferrite is compoundedIn the magnetic powder, Fe²⁺：Zn²⁺：Mn²⁺In a molar ratio of 2: x: (1-x), wherein x is 0-1, x is not equal to 0 and x is not equal to 1;

in the FeSiAl @ MnZn ferrite composite magnetic powder core, the mass of the MnZn ferrite coating layer is 0.5-10% of that of the FeSiAl magnetic powder.

Preferably, the binder is instant sodium silicate, and the mass of the instant sodium silicate is 0.5-2 wt.% of the mass of the FeSiAl @ MnZn ferrite composite magnetic powder; the release agent adopts zinc stearate, and the mass of the zinc stearate is 0.5-2 wt% of that of the FeSiAl @ MnZn ferrite composite magnetic powder.

The invention also provides a preparation method of the high-frequency high-Q-value FeSiAl @ MnZn ferrite soft magnetic composite magnetic powder core, which comprises the following steps of:

forming a MnZn ferrite coating layer on the surface of the FeSiAl magnetic powder by a chemical coprecipitation method to obtain a FeSiAl @ MnZn ferrite precursor;

presintering the FeSiAl @ MnZn ferrite precursor at the temperature of 400-700 ℃ in the air atmosphere, and preserving heat for 1-3h to obtain FeSiAl @ MnZn ferrite composite magnetic powder;

uniformly mixing the FeSiAl @ MnZn ferrite composite magnetic powder, a binder and a release agent, carrying out cold press molding on the mixture, and then carrying out stress relief annealing in an inert atmosphere to obtain the FeSiAl @ MnZn ferrite composite magnetic powder core.

Preferably, the process of forming a MnZn ferrite coating layer on the surface of the FeSiAl magnetic powder by a chemical coprecipitation method to obtain the FeSiAl @ MnZn ferrite precursor comprises the following steps:

adding the Fe-Mn-Zn mixed salt solution into a deionized water suspension of FeSiAl magnetic powder and uniformly stirring to obtain a mixture A;

and continuously stirring the mixture A, adding NaOH solution into the mixture A to adjust the pH value to 9-11 for reaction, and obtaining a FeSiAl @ MnZn ferrite precursor after the reaction is finished.

Preferably, FeCl is used as the iron salt in the Fe-Mn-Zn mixed salt solution₂Or FeSO₄Zinc salt is ZnCl₂Or ZnSO₄The manganese salt is MnCl₂Or MnSO₄(ii) a In the chemical coprecipitation process, the temperature is 50-80 DEGAnd adding NaOH solution, and stirring for 20-40min at the stirring speed of 50-160 rpm.

Preferably, the FeSiAl magnetic powder comprises the following components in percentage by mass: si: 8% -13%, Al: 4% -7% of Fe and the balance of Fe; the mesh number of the FeSiAl magnetic powder is more than 200 meshes;

in the FeSiAl @ MnZn ferrite composite magnetic powder, Fe²⁺：Zn²⁺：Mn²⁺In a molar ratio of 2: x: (1-x), wherein x is 0-1, x is not equal to 0 and x is not equal to 1;

in the FeSiAl @ MnZn ferrite composite magnetic powder core, the mass of the MnZn ferrite coating layer is 0.5-10% of that of the FeSiAl magnetic powder.

Preferably, the binder is instant sodium silicate, and the mass of the instant sodium silicate is 0.5-2 wt.% of the mass of the FeSiAl @ MnZn ferrite composite magnetic powder; the release agent adopts zinc stearate, and the mass of the zinc stearate is 0.5-2 wt% of that of the FeSiAl @ MnZn ferrite composite magnetic powder.

Preferably, the cold press molding pressure is 1300-2400MPa, the cold press pressurizing rate is 1-10MPa/s, and the pressure maintaining time is 5-400 s.

Preferably, during the stress relief annealing, the annealing temperature is 500-850 ℃, the heat preservation time is 0.5-2h, and the inert gas adopts argon or nitrogen.

The invention has the following beneficial effects:

in the high-frequency high-Q-value FeSiAl @ MnZn ferrite soft magnetic composite magnetic powder core, the MnZn ferrite coating layer is coated on the surface of the FeSiAl magnetic powder, and the MnZn ferrite has high resistivity and can effectively reduce the eddy current loss of the surface of the FeSiAl magnetic powder under high frequency by coating the MnZn ferrite on the surface of the FeSiAl magnetic powder, so that the high-frequency characteristic of the FeSiAl soft magnetic powder is improved, the quality factor and the magnetic conductivity of the FeSiAl magnetic powder under high frequency are improved, and the composite magnetic powder core can be applied to higher frequency. In addition, the MnZn ferrite coating layer has high and stable strength and is friction-resistant, so that the direct contact between barrier metal particles can be ensured in the process of press forming, the quality factor can be effectively improved, and the problems that an insulating layer is easy to decompose at high temperature, the coating layer is easy to damage and discontinuous, the thickness is difficult to control and the like in the process of press forming of the magnetic powder core in the conventional insulating coating method are solved.

In the preparation method, the MnZn ferrite coating layer is formed on the surface of the FeSiAl magnetic powder by a chemical coprecipitation method, so that the continuous, uniform and compact MnZn ferrite coating layer can be formed on the surface of the FeSiAl magnetic powder. The FeSiAl magnetic powder used in the invention is not subjected to flattening treatment, and is beneficial to forming a more uniform and compact coating layer in the coating process. In the pressing process of cold press forming, compression forming is needed under a large pressure, and in the process, a large number of defects caused by internal stress are generated in the magnetic powder core, and the existence of the defects can seriously affect the performance of the magnetic powder core. Generally, the larger the pressing pressure, the larger the internal stress generated inside the magnetic powder core. In order to eliminate the defect caused by the internal stress and further improve the magnetic conductivity of the magnetic powder core, the pressed magnetic powder core needs to be annealed, and the annealing can fully release the stress in the magnetic powder core and improve the comprehensive performance of the magnetic powder core. In conclusion, the FeSiAl magnetic powder is coated by the MnZn ferrite with the soft magnetic property, so that the problem of magnetic dilution caused by a non-magnetic coating agent is solved, and the FeSiAl magnetic powder is not subjected to flattening and phosphating treatment, so that a more uniform and compact coating layer is favorably formed, and the environmental pollution is reduced. The insulating layer prepared by the method has higher temperature stability. Sintering the pressed magnetic ring in an inert atmosphere to remove stress to obtain the high-frequency high-Q FeSiAl @ MnZn ferrite composite magnetic powder core.

Drawings

FIG. 1 shows the permeability characteristics of FeSiAl magnetic powder core and FeSiAl @ MnZn ferrite composite magnetic powder core with frequency according to the embodiment of the present invention.

FIG. 2 is a graph showing the Q-factor variation with frequency of FeSiAl magnetic powder cores and FeSiAl @ MnZn ferrite composite magnetic powder cores in the examples of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, various embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood, however, that in various embodiments of the invention, numerous technical details are set forth in order to provide a better understanding of the present application. However, the technical solution claimed in the present application can be implemented without these technical details and various changes and modifications based on the following embodiments.

The invention relates to a preparation method of a FeSiAl @ MnZn ferrite composite magnetic powder core with high magnetic conductivity and high Q value under high frequency, which comprises the following steps:

s1, selecting powder: taking mechanically crushed FeSiAl powder, wherein the components in percentage by weight are Si: 8% -13%, Al: 4 to 7 percent of Fe, and the balance of Fe. And (3) sieving the crushed FeSiAl powder through a 200-mesh sieve, and taking the sieved powder.

S2, preparation of a coating agent solution: according to three metal elements Fe in MnZn ferrite²⁺：Zn²⁺：Mn²⁺2: x: (1-x), wherein x is 0-1, x is not equal to 0 and x is not equal to 1, iron salt, zinc salt and manganese salt are respectively weighed, dissolved in deionized water, and stirred to be completely dissolved to obtain a Fe-Mn-Zn mixed salt solution;

s3, a coating process: pouring the FeSiAl powder obtained in the step S1 into deionized water with the same mass as the iron-silicon-aluminum powder to prepare a suspension, heating to 50-80 ℃, adding the Fe-Mn-Zn mixed salt solution obtained in the step S2, uniformly stirring, adding 1mol/L NaOH solution, continuously stirring, adjusting the pH value of the solution to 9-11, and continuously heating, stirring and reacting for 20-40min to obtain a FeSiAl @ MnZn ferrite precursor;

s4, pre-sintering of the composite magnetic powder: alternately washing the FeSiAl @ MnZn ferrite precursor by using deionized water and absolute ethyl alcohol, drying for 24h at 60 ℃, then placing in a muffle furnace, presintering at 400-700 ℃ in an air atmosphere at the heating rate of 3-5 ℃/min, and preserving heat for 1-3h to obtain FeSiAl @ MnZn ferrite composite magnetic powder;

s5, magnetic powder core forming: powdery instant sodium silicate and zinc stearate are uniformly mixed with FeSiAl @ MnZn ferrite composite magnetic powder, and the magnetic ring with the size of 18mm in outer diameter, 8mm in inner diameter and 6.5mm in height is obtained after cold press molding. Annealing the magnetic ring in an inert atmosphere to remove stress, wherein the heating rate is 3-5 ℃/min, and keeping the temperature for 0.5-2h to obtain the FeSiAl @ MnZn ferrite composite magnetic powder core.

Wherein, FeCl is adopted as the ferric salt in S2₂Or FeSO₄Zinc salt is ZnCl₂Or ZnSO₄The manganese salt is MnCl₂Or MnSO₄. The stirring speed in S3 is 50-160 rpm. The FeSiAl @ MnZn ferrite composite magnetic powder core is described in S4, wherein the MnZn ferrite is 0.5-10% of the mass of the FeSiAl magnetic powder. The pressure of the cold pressing in the S5 is 1300MPa-2400MPa, the pressurizing rate of the cold pressing is 1-10MPa/S, and the pressure maintaining time is 5-400S. S5, the addition amount of the sodium silicate and the zinc stearate relative to the FeSiAl @ MnZn ferrite composite magnetic powder is as follows: sodium silicate 0.5-2 wt.%, zinc stearate 0.5-2 wt.%. The annealing temperature of S5 is 500-850 ℃. And the inert atmosphere of S5 is argon or nitrogen.

In the scheme of the invention, a chemical coprecipitation method is adopted, so that a continuous, uniform and compact MnZn ferrite coating layer is synthesized on the surface of the FeSiAl magnetic powder. The MnZn ferrite has high resistivity, and is coated on the surface of the FeSiAl metal magnetic powder, so that the eddy current loss of the FeSiAl metal magnetic powder under high frequency can be effectively reduced, and further, the high-frequency characteristic of the FeSiAl metal magnetic powder is improved. The FeSiAl magnetic powder used in the invention is not subjected to flattening treatment, so that a more uniform and compact coating layer can be formed in the coating process. In addition, the MnZn ferrite is a ferrimagnetic material and has higher resistivity, and the coating amount and the form of the ferrite in the FeSiAl @ MnZn ferrite composite magnetic powder can be adjusted by controlling the reaction temperature, the reaction time, the PH value, the sintering temperature and the quality of various reactants of coprecipitation. According to the invention, the MnZn ferrite coating layer is formed on the surface of the FeSiAl magnetic powder by a chemical coprecipitation method, so that the quality factor of the composite magnetic powder core under high frequency is improved, and the composite magnetic powder core can be applied to higher frequency. The MnZn ferrite coating layer has high and stable strength and friction resistance, and can ensure the direct contact between barrier metal particles in the process of press forming of the FeSiAl magnetic powder core, thereby effectively improving the quality factor, and overcoming the problems that an insulating layer is easy to decompose at high temperature, the coating layer is easy to damage, is discontinuous, the thickness is difficult to control and the like in the process of press forming of the magnetic powder core in the conventional insulation coating method at home and abroad at present. Compared with the FeSiAl powder insulation coating in the prior art, the invention has the outstanding characteristics that the soft magnetic MnZn ferrite is used for coating, so that the dilution of the nonmagnetic insulation coating on the magnetic powder core magnetic conductivity is overcome; in addition, the FeSiAl powder is not flattened and phosphated in the implementation process, so that the experimental process is simplified, the pollution to the environment is reduced, and a better coating effect can be realized. The FeSiAl @ MnZn ferrite composite magnetic powder core prepared by the scheme of the invention has the advantages that the frequency stability of the magnetic conductivity and the Q value under high frequency are both obviously improved, and the application frequency range is widened.

Example 1

1. Taking mechanically crushed FeSiAl powder, wherein the components in percentage by weight are Si: 9%, Al: 6 percent and the balance of Fe. And (4) sieving the FeSiAl powder with a 200-mesh sieve, and taking undersize products.

2. And coating a MnZn ferrite insulating layer on the surface of the FeSiAl powder by a chemical coprecipitation method, wherein the coprecipitation temperature is 70 ℃, and the reaction time is 30 min.

3. With anhydrous FeCl₂、ZnCl₂·4H₂O and anhydrous MnCl₂As reactant, according to Fe²⁺：Zn²⁺：Mn²⁺In a molar ratio of 2: 0.9: 0.1, respectively weighing chloride salt, dissolving in deionized water to obtain FeCl₂-ZnCl₂-MnCl₂The salt solution is mixed.

4. According to the MnZn ferrite: the mass ratio of FeSiAl is 0.5: 99.5 the mechanically crushed FeSiAl powder is weighed, poured into deionized water and heated to 70 ℃. FeCl of corresponding amount is slowly dropped into the heated FeSiAl magnetic powder₂-ZnCl₂-MnCl₂And (3) mixing the salt solution, uniformly stirring, then dripping 1mol/L NaOH solution, continuously stirring, adjusting the pH value of the solution to 11, and reacting for 30min to obtain the FeSiAl @ MnZn ferrite precursor.

5. Alternately washing the FeSiAl @ MnZn ferrite precursor by using absolute ethyl alcohol and deionized water for several times until the precursor is clean, then placing the precursor in a drying box, drying the precursor for 24 hours at the temperature of 60 ℃, placing the dried FeSiAl @ MnZn ferrite precursor in a muffle furnace for presintering at the temperature of 500 ℃, and preserving the heat for 3 hours to obtain the FeSiAl @ MnZn ferrite composite magnetic powder.

6. Adding 0.5 wt.% of sodium silicate and 0.5 wt.% of zinc stearate, pressurizing at the rate of 1MPa/s, keeping the pressure for 120s, cold-pressing and molding at 2400MPa, and annealing at 800 ℃ for 0.5h in a nitrogen atmosphere to obtain the FeSiAl @ MnZn ferrite composite magnetic powder core.

And (3) winding 10 turns of enameled copper wires around the sintered magnetic powder core, and testing to obtain the FeSiAl @ MnZn ferrite composite magnetic powder core with the effective magnetic permeability of 43.62 and the Q value of 70.19 at 400kHz under the test frequency of 100 kHz.

Example 2

1. Taking mechanically crushed FeSiAl powder, wherein the components in percentage by weight are Si: 9%, Al: 6 percent and the balance of Fe. The FeSiAl powder is screened by a 200-mesh screen, and the undersize is taken.

2. And coating a MnZn ferrite insulating layer on the surface of the crushed FeSiAl powder by a chemical coprecipitation method, wherein the coprecipitation temperature is 70 ℃, and the reaction time is 30 min.

3. With anhydrous FeCl₂、ZnCl₂·4H₂O and anhydrous MnCl₂As a reactant, Fe²⁺：Zn²⁺：Mn²⁺In a molar ratio of 2: 0.5: 0.5 respectively weighing chloride salt, dissolving in deionized water to obtain FeCl₂-ZnCl₂-MnCl₂The salt solution is mixed.

4. According to the MnZn ferrite: the mass ratio of FeSiAl is 3: 97 the crushed FeSiAl powder is weighed and poured into deionized water with the mass equivalent to that of the FeSiAl powder, and the mixture is heated to 70 ℃. FeCl of corresponding amount is slowly dropped into the heated FeSiAl magnetic powder₂-ZnCl₂-MnCl₂And mixing the salt solution, uniformly stirring, then dripping 1mol/L NaOH solution, continuously stirring, adjusting the pH value of the solution to 10.5, and reacting for 30min to obtain the FeSiAl @ MnZn ferrite precursor.

5. Alternately washing the FeSiAl @ MnZn ferrite precursor by using absolute ethyl alcohol and deionized water for several times until the precursor is clean, then placing the precursor in a drying box, drying the precursor for 24 hours at the temperature of 60 ℃, placing the dried FeSiAl @ MnZn ferrite precursor in a muffle furnace for presintering at the temperature of 600 ℃, and preserving the heat for 3 hours to obtain the FeSiAl @ MnZn ferrite composite magnetic powder.

6. Adding 2 wt.% of sodium silicate and 2 wt.% of zinc stearate, pressurizing at the rate of 10MPa/s and holding pressure for 60s, cold-pressing and molding at 2100MPa, and annealing at 700 ℃ for 1h in a nitrogen atmosphere to obtain the FeSiAl @ MnZn ferrite composite magnetic powder core.

And (3) winding 10 turns of enameled copper wires on the sintered magnetic powder core, and testing to obtain the FeSiAl @ MnZn ferrite composite magnetic powder core with the effective magnetic permeability of 47.93 and the Q value of 53.8 at 400kHz under the test frequency of 100 kHz.

Example 3

1. Taking mechanically crushed FeSiAl powder, wherein the components in percentage by weight are Si: 8%, Al: 5 percent and the balance of Fe. And (3) sieving the crushed FeSiAl powder through a 200-mesh sieve, and taking the sieved substances.

2. And coating a MnZn ferrite insulating layer on the surface of the crushed FeSiAl powder by a chemical coprecipitation method, wherein the coprecipitation reaction temperature is 70 ℃, and the reaction time is 30 min.

3. With anhydrous FeCl₂、ZnCl₂·4H₂O and anhydrous MnCl₂As a reactant, Fe²⁺：Zn²⁺：Mn²⁺In a molar ratio of 2: 0.2: 0.8 respectively weighing chloride salt, dissolving in deionized water to obtain FeCl₂-ZnCl₂-MnCl₂The salt solution is mixed.

4. According to the MnZn ferrite: the mass ratio of FeSiAl is 9: 91, weighing the crushed FeSiAl powder, pouring the powder into deionized water with the mass equivalent to that of the FeSiAl powder, and heating to 70 ℃. FeCl of corresponding amount is slowly dropped into the heated FeSiAl magnetic powder₂-ZnCl₂-MnCl₂And mixing the salt solution, uniformly stirring, then dripping 1mol/L NaOH solution, continuously stirring, adjusting the pH value of the solution to 9.3, and reacting for 20min to obtain the FeSiAl @ MnZn ferrite precursor.

5. Alternately washing the FeSiAl @ MnZn ferrite precursor by using absolute ethyl alcohol and deionized water for several times until the precursor is clean, then placing the precursor in a drying box, drying the precursor for 24 hours at the temperature of 60 ℃, placing the dried FeSiAl @ MnZn ferrite precursor in a muffle furnace for presintering at the temperature of 700 ℃, and preserving the temperature for 2 hours to obtain the FeSiAl @ MnZn ferrite composite magnetic powder.

6. Adding 1.5 wt.% of sodium silicate and 1 wt.% of zinc stearate, pressurizing at the rate of 10MPa/s and holding pressure for 60s, cold-pressing and molding at 2400MPa, and annealing at 800 ℃ for 0.5h in a nitrogen atmosphere to obtain the FeSiAl @ MnZn ferrite composite magnetic powder core.

And (3) winding 10 turns of enameled copper wires around the sintered magnetic powder core, and testing to obtain the FeSiAl @ MnZn ferrite composite magnetic powder core with the effective magnetic permeability of 62.32 and the Q value of 62.64 at 400kHz under the test frequency of 100 kHz.

Example 4

1. Taking mechanically crushed FeSiAl powder, wherein the components in percentage by weight are Si: 13%, Al: 7 percent and the balance of Fe. And (3) sieving the crushed FeSiAl powder through a 200-mesh sieve, and taking the sieved substances.

2. And coating a MnZn ferrite insulating layer on the surface of the crushed FeSiAl powder by a chemical coprecipitation method, wherein the coprecipitation reaction temperature is 70 ℃, and the reaction time is 40 min.

3. With anhydrous FeCl₂、ZnCl₂·4H₂O and anhydrous MnCl₂As a reactant, Fe²⁺：Zn²⁺：Mn²⁺In a molar ratio of 2: 0.8: 0.2 respectively weighing sulfate, dissolving in deionized water to obtain FeCl₂-ZnCl₂-MnCl₂The salt solution is mixed.

4. According to the MnZn ferrite: the mass ratio of FeSiAl is 3: 97, weighing the crushed FeSiAl powder, pouring the powder into deionized water with the mass equivalent to that of the FeSiAl powder, and heating to 70 ℃. Slowly dripping a corresponding amount of FeSO into the heated FeSiAl magnetic powder₄-ZnSO₄-MnSO₄And mixing the salt solution, uniformly stirring, then dripping 1mol/L NaOH solution, continuously stirring, adjusting the pH value of the solution to 10.3, and reacting for 30min to obtain the FeSiAl @ MnZn ferrite precursor.

5. Alternately washing the FeSiAl @ MnZn ferrite precursor by using absolute ethyl alcohol and deionized water for several times until the precursor is clean, then placing the precursor in a drying box, drying the precursor for 24 hours at the temperature of 60 ℃, placing the dried FeSiAl @ MnZn ferrite precursor in a muffle furnace for presintering at the temperature of 500 ℃, and preserving the temperature for 1 hour to obtain the FeSiAl @ MnZn ferrite composite magnetic powder.

6. Adding 1.5 wt.% of sodium silicate and 1 wt.% of zinc stearate, pressurizing at the rate of 5MPa/s, maintaining the pressure for 15s, cold-pressing and molding at 1500MPa, and annealing at 550 ℃ for 2h in a nitrogen atmosphere to obtain the FeSiAl @ MnZn ferrite composite magnetic powder core.

And (3) winding 10 turns of enameled copper wires around the sintered magnetic powder core, and testing to obtain the FeSiAl @ MnZn ferrite composite magnetic powder core with the effective magnetic permeability of 34.26 and the Q value of 43.38 at 400kHz under the test frequency of 100 kHz.

Example 5

1. Taking mechanically crushed FeSiAl powder, wherein the components in percentage by weight are Si: 9%, Al: 6 percent and the balance of Fe. And (3) sieving the crushed FeSiAl powder through a 200-mesh sieve, and taking the sieved substances.

2. And coating a MnZn ferrite insulating layer on the surface of the crushed FeSiAl powder by a chemical coprecipitation method, wherein the coprecipitation reaction temperature is 70 ℃, and the reaction time is 30 min.

3. With anhydrous FeCl₂、ZnCl₂·4H₂O and anhydrous MnCl₂As a reactant, Fe²⁺：Zn²⁺：Mn²⁺In a molar ratio of 2: 0.4: 0.6 respectively weighing chloride salt, dissolving in deionized water to obtain FeCl₂-ZnCl₂-MnCl₂The salt solution is mixed.

4. According to the MnZn ferrite: the mass ratio of FeSiAl is 1: 99, weighing the crushed FeSiAl powder, pouring the powder into deionized water with the mass equivalent to that of the FeSiAl powder, and heating to 70 ℃. FeCl of corresponding amount is slowly dropped into the heated FeSiAl magnetic powder₂-ZnCl₂-MnCl₂And (3) mixing the salt solution, uniformly stirring, then dripping 1mol/L NaOH solution, continuously stirring, adjusting the pH value of the solution to 9, and reacting for 20min to obtain the FeSiAl @ MnZn ferrite precursor.

5. Alternately washing the FeSiAl @ MnZn ferrite precursor by using absolute ethyl alcohol and deionized water for several times until the precursor is clean, then placing the precursor in a drying box, drying the precursor for 24 hours at the temperature of 60 ℃, placing the dried FeSiAl @ MnZn ferrite precursor in a muffle furnace for presintering at the temperature of 500 ℃, and preserving the heat for 3 hours to obtain the FeSiAl @ MnZn ferrite composite magnetic powder.

6. Adding 1.5 wt.% of sodium silicate and 1 wt.% of zinc stearate, pressurizing at the rate of 5MPa/s and the dwell time of 400s, cold-pressing and molding under 1700MPa, and annealing for 1h in a nitrogen atmosphere at 700 ℃ to obtain the FeSiAl @ MnZn ferrite composite magnetic powder core.

And (3) winding 10 turns of enameled copper wires around the sintered magnetic powder core, and testing to obtain the FeSiAl @ MnZn ferrite composite magnetic powder core with the effective magnetic permeability of 70 and the Q value of 61.07 at 400kHz under the test frequency of 100 kHz.

FIG. 1 shows the effective permeability versus frequency for FeSiAl magnetic powder cores and FeSiAl @ MnZn ferrite composite magnetic powder cores prepared in the three examples. As can be seen from FIG. 1, in the frequency range of 100kHz-1MHz, the magnetic permeability of the coated composite magnetic powder core shows better frequency stability, and the effective magnetic permeability is higher. The ferrite belongs to soft magnetic materials, the ferrite-coated magnetic powder core can overcome the problem of magnetic dilution caused by non-magnetic coating, and the ferrite-coated magnetic powder core has increased resistivity, thereby improving the frequency stability of the effective magnetic conductivity of the magnetic powder core.

FIG. 2 shows the quality factor versus frequency for FeSiAl magnetic powder cores and FeSiAl @ MnZn ferrite composite magnetic powder cores prepared in the three examples. As can be seen from FIG. 2, the coated composite magnetic powder core has a higher quality factor at high frequencies in the range of the rate 100kHz-1 MHz. This is because the FeSiAl particles are effectively isolated after ferrite coating, and the contact between the particles is reduced, so that the loss is reduced and the quality factor is increased. From this, it is known that the MnZn ferrite cladding has a positive effect of improving the quality factor of the FeSiAl magnetic powder core.

In summary, the method mainly comprises the steps of powder granularity screening, coating of a MnZn ferrite shell layer by a chemical coprecipitation method, pre-sintering of composite magnetic powder, press forming and annealing. The preparation method does not carry out flattening and phosphorization treatment on the FeSiAl powder, not only simplifies the experimental process and reduces the environmental pollution, but also can realize better coating effect, effectively isolates the electric contact among the metal magnetic powder particles, improves the magnetic conductivity and quality factor of the composite magnetic powder core and widens the application frequency range of the FeSiAl magnetic powder core. The method has the advantages of simple implementation flow, short reaction time and easy large-scale production and industrial application.

The above description is only a preferred embodiment of the present invention, and it should be noted that modifications and embellishments can be made without departing from the core technology of the present invention, and the modifications and embellishments also belong to the protection scope of the present invention. Any changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.