Nickel-zinc magnetic core material and preparation process thereof

Abstract

The invention provides a nickel-zinc magnetic core material and a preparation process thereof, and the preparation process comprises the following steps: carrying out first ball milling on Fe2O3 powder, ZnO powder and NiO powder to obtain a mixture; pre-sintering the mixture for the first time, and crushing to obtain a first pre-sintered material; adding carbonyl iron powder and Bi2O3 into the pre-sintered material, mixing, and carrying out secondary ball milling to obtain a blended material; pre-sintering the blended material for the second time, and crushing to obtain a second pre-sintered material; and adding an adhesive and a defoaming agent into the second pre-sintered material for spray granulation, pressing and sintering to obtain the nickel-zinc magnetic core material. The prepared nickel-zinc magnetic core material is uniform in grain size and high in density, the resistivity of the material is greatly improved, and the high-frequency eddy current loss is remarkably reduced.

Description

Technical Field

[0001] This invention relates to the field of magnetic core material preparation technology, specifically to a nickel-zinc magnetic core material and its preparation process. Background Technology

[0002] Nickel-zinc ferrite is an important soft magnetic material, widely used in high-frequency inductors, transformers, and electromagnetic interference suppression components due to its high resistivity, low high-frequency loss, and good magnetic properties. With the development of electronic devices towards higher frequencies, miniaturization, and integration, higher requirements are being placed on the performance (such as initial permeability, saturation flux density, and high-frequency loss) and fabrication processes of nickel-zinc magnetic core materials.

[0003] Traditional nickel-zinc ferrite preparation processes suffer from problems such as uneven grain size and insufficient density, which limit further improvement in material properties. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a nickel-zinc magnetic core material and its preparation process.

[0005] A process for preparing a nickel-zinc magnetic core material includes the following steps: Fe2O3 powder, ZnO powder and NiO powder were ball-milled for the first time to obtain a mixture. The mixture is pre-fired for the first time and then crushed to obtain the first pre-fired material; After adding carbonyl iron powder and Bi2O3 to the pre-calcined material and mixing, a second ball milling was performed to obtain a blend. The blend is pre-fired a second time and then crushed to obtain the second pre-fired material; The second pre-burned material is mixed with binder and defoamer, sprayed and granulated, pressed, and sintered to obtain the nickel-zinc magnetic core material.

[0006] Preferably, the mass ratio of Fe2O3 powder, ZnO powder and NiO powder is (6-6.5):(2-2.5):(1-1.5).

[0007] Preferably, the mass ratio of Fe2O3 powder, carbonyl iron powder, and Bi2O3 material is (6-6.5):(1.6-2.0):(0.5-1.2).

[0008] Preferably, the ball mill speed for the first ball milling is 200-400 rpm, and the time is 2-8 hours.

[0009] Preferably, the heating rate for the first pre-firing is 1-5°C / minute, the pre-firing temperature is 850°C-1000°C, and the holding time is 1-4 hours.

[0010] Preferably, the second ball milling speed is 150-300 rpm and the time is 1-4 hours.

[0011] Preferably, the heating rate of the second pre-firing is 2-5°C / min, the pre-firing temperature is 750°C-900°C, and the holding time is 0.5-2 hours.

[0012] Preferably, the adhesive is polyvinyl alcohol, and the addition amount is about 0.8% - 1.5% of the dry weight of the powder; the defoamer is polydimethylsiloxane, and the addition amount is about 0.1% - 0.3% of the dry weight of the powder; the inlet temperature is 200 - 300°C; and the outlet temperature is 80 - 120°C.

[0013] Preferably, in the sintering step, the temperature is increased to the discharge temperature at 1-1.5°C / min, held for 1-2 hours, and the discharge temperature is 300-500°C; the sintering temperature is increased at 3-4°C / min, held for 2-6 hours, and the sintering temperature is 1050°C-1250°C; the temperature is decreased to 600°C at 1-3°C / min, and then cooled in the furnace.

[0014] The beneficial effects of this invention are as follows: This invention achieves uniform mixing of Fe2O3, ZnO, and NiO powders through a first ball milling process; a first pre-calcination process converts most of the raw materials into the desired ferrite phase, resulting in a more chemically stable ferrite phase during final sintering; a second ball milling process, incorporating carbonyl iron powder and Bi2O3 into the first pre-calcined material, allows Bi2O3 particles to adhere to the surface of the pre-calcined ferrite particles and carbonyl iron powder, achieving mechanical mixing and initial activation; and a second pre-calcination process further enhances the uniform mixing of Fe2O3, ZnO, and NiO powders. The initial liquefaction, wetting, and encapsulation of ferrite particles and the highly active carbonyl iron powder are oxidized to Fe2O3 and connected to the surface of the ferrite particles, thus "connecting" the ferrite particles to form aggregates. Through sintering, Bi2O3 melts again, and through particle rearrangement and dissolution-precipitation mechanisms, it greatly promotes material transport, eliminates porosity, and achieves material densification. Ferrite grains grow in the liquid phase, forming a final uniform microstructure, and Bi2O3 is eventually enriched at the grain boundaries, forming a grain boundary phase, which significantly reduces high-frequency eddy current losses. Detailed Implementation

[0015] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Example 1

[0017] (1) Weigh the raw materials according to the mass ratio Fe2O3: ZnO: NiO = 6.2: 2.2: 1.2, and perform the first ball milling at 300 rpm for 4 hours to obtain the mixture.

[0018] (2) The mixture is pre-fired for the first time. The temperature is increased to 920°C at 2°C / min, and the temperature is held for 2 hours. After cooling in the furnace, it is crushed to obtain the first pre-fired material.

[0019] (3) Add carbonyl iron powder and Bi2O3 to the first pre-burned material, so that Fe2O3: carbonyl iron powder: Bi2O3 = 6.2:1.8:0.7 (mass ratio), and perform a second ball milling at 250 rpm for 2 hours to obtain a blend.

[0020] (4) The blend is pre-fired a second time. The temperature is increased to 830°C at 3°C / min, held for 1 hour, cooled in the furnace and then crushed to obtain the second pre-fired material.

[0021] (5) Add 1.2% of the dry weight of polyvinyl alcohol (PVA) and 0.2% of polydimethylsiloxane to the second pre-burned material for spray granulation. The inlet temperature is 250°C and the outlet temperature is 100°C.

[0022] (6) The granulated particles are biaxially compressed under a pressure of 100 MPa.

[0023] (7) Sintering the green blank: heat up to 400°C at 1°C / min to remove the glue, and hold for 1.5 hours; then heat up to 1150°C at 3°C / min and hold for 4 hours; finally cool down to 600°C at 2°C / min and cool with the furnace to obtain nickel-zinc magnetic core material.

[0024] Example 2

[0025] (1) Weigh the raw materials according to the mass ratio of Fe2O3: ZnO: NiO = 6.5: 2.0: 1.0, and perform the first ball milling at a speed of 350 rpm for 3 hours to obtain the mixture.

[0026] (2) The mixture is pre-fired for the first time. The temperature is increased to 950°C at 3°C / min and held for 1.5 hours. After cooling in the furnace, it is crushed to obtain the first pre-fired material.

[0027] (3) Add carbonyl iron powder and , making Fe2O3: carbonyl iron powder: = 6.5 : 2.0 : 1.2 (mass ratio). A second ball milling process was performed at 200 rpm for 3 hours to obtain the blend.

[0028] (4) The blend is pre-fired a second time by heating it to 860°C at 4°C / min, holding it at that temperature for 0.5 hours, cooling it in the furnace, and then crushing it to obtain the second pre-fired material.

[0029] (5) Add 1.5% PVA and 0.3% polydimethylsiloxane by dry weight of powder to the second pre-burned material for spray granulation. The inlet temperature is 280°C and the outlet temperature is 90°C.

[0030] (6) The granulated particles are biaxially compressed under a pressure of 120 MPa.

[0031] (7) Sintering the green blank: heat up to 350°C at 1.5°C / min to remove the glue, and hold for 2 hours; then heat up to 1180°C at 4°C / min and hold for 3 hours; finally cool down to 600°C at 1°C / min and cool with the furnace to obtain nickel-zinc magnetic core material.

[0032] Example 3

[0033] (1) Weigh the raw materials according to the mass ratio of Fe2O3: ZnO: NiO = 6: 2.5: 1.5, and perform the first ball milling at a speed of 320 rpm for 3.5 hours to obtain the mixture.

[0034] (2) The mixture is pre-fired for the first time. The temperature is increased to 900°C at 2°C / min and held for 2.5 hours. After cooling in the furnace, it is crushed to obtain the first pre-fired material.

[0035] (3) Add carbonyl iron powder and Bi2O3 to the first pre-calcined material, so that Fe2O3: carbonyl iron powder: Bi2O3 = 6: 1.6: 0.5 (mass ratio). Perform a second ball milling at 270 rpm for 1.5 hours to obtain a blend.

[0036] (4) The blend is pre-fired a second time by heating it to 860°C at 4°C / min, holding it at that temperature for 0.5 hours, cooling it in the furnace, and then crushing it to obtain the second pre-fired material.

[0037] (5) Add 1.5% PVA and 0.3% polydimethylsiloxane by dry weight of powder to the second pre-burned material for spray granulation. The inlet temperature is 280°C and the outlet temperature is 90°C.

[0038] (6) The granulated particles are biaxially compressed under a pressure of 120 MPa.

[0039] (7) Sintering the green blank: heat up to 350°C at 1.5°C / min to remove the glue, and hold for 2 hours; then heat up to 1180°C at 4°C / min and hold for 3 hours; finally cool down to 600°C at 1°C / min and cool with the furnace to obtain nickel-zinc magnetic core material.

[0040] Example 4

[0041] (1) Weigh the raw materials according to the mass ratio of Fe2O3: ZnO: NiO = 6.5: 2.5: 1.0, and perform the first ball milling at a speed of 200 rpm for 8 hours to obtain the mixture.

[0042] (2) The mixture is pre-fired for the first time. The temperature is increased to 850°C at 1°C / min, and the temperature is held for 1 hour. After cooling in the furnace, it is crushed to obtain the first pre-fired material.

[0043] (3) Add carbonyl iron powder and Bi2O3 to the first pre-calcined material, so that Fe2O3: carbonyl iron powder: Bi2O3 = 6.5:1.7:1.2 (mass ratio). Perform a second ball milling at 220 rpm for 2.5 hours to obtain a blend.

[0044] (4) The blend is pre-fired a second time. The temperature is increased to 820°C at 2°C / min, held for 1 hour, cooled in the furnace and then crushed to obtain the second pre-fired material.

[0045] (5) Add 1.4% PVA and 0.25% polydimethylsiloxane by dry weight of powder to the second pre-burned material for spray granulation. The inlet temperature is 240°C and the outlet temperature is 90°C.

[0046] (6) The granulated particles are bidirectionally pressed into shape under a pressure of 90 MPa.

[0047] (7) Sintering the green blank: heat up to 380°C at 1.2°C / min to remove the glue, and hold for 2 hours; then heat up to 1170°C at 3.5°C / min and hold for 5 hours; finally cool down to 600°C at 1.5°C / min and cool with the furnace to obtain nickel-zinc magnetic core material.

[0048] Example 5

[0049] (1) Weigh the raw materials according to the mass ratio of Fe2O3: ZnO: NiO = 6.5: 2.5: 1.0, and perform the first ball milling at a speed of 400 rpm for 2 hours to obtain the mixture.

[0050] (2) The mixture is pre-fired for the first time. The temperature is increased to 1000°C at 5°C / min and held for 4 hours. After cooling in the furnace, it is crushed to obtain the first pre-fired material.

[0051] (3) Add carbonyl iron powder and Bi2O3 to the first pre-calcined material, so that Fe2O3: carbonyl iron powder: Bi2O3 = 6.5:1.7:1.2 (mass ratio). Perform a second ball milling at 220 rpm for 2.5 hours to obtain a blend.

[0052] (4) The blend is pre-fired a second time. The temperature is increased to 820°C at 2°C / min, held for 1 hour, cooled in the furnace and then crushed to obtain the second pre-fired material.

[0053] (5) Add 1.4% PVA and 0.25% polydimethylsiloxane by dry weight of powder to the second pre-burned material for spray granulation. The inlet temperature is 240°C and the outlet temperature is 90°C.

[0054] (6) The granulated particles are bidirectionally pressed into shape under a pressure of 90 MPa.

[0055] (7) Sintering the green blank: heat up to 380°C at 1.2°C / min to remove the glue, and hold for 2 hours; then heat up to 1170°C at 3.5°C / min and hold for 5 hours; finally cool down to 600°C at 1.5°C / min and cool with the furnace to obtain nickel-zinc magnetic core material.

[0056] Example 6

[0057] (1) Weigh the raw materials according to the mass ratio of Fe2O3: ZnO: NiO = 6.4: 2.0: 1.6, and perform the first ball milling at a speed of 340 rpm for 3 hours to obtain the mixture.

[0058] (2) The mixture is pre-fired for the first time. The temperature is increased to 980°C at 4°C / min and held for 1.5 hours. After cooling in the furnace, it is crushed to obtain the first pre-fired material.

[0059] (3) Add carbonyl iron powder and Bi2O3 to the first pre-calcined material, so that Fe2O3: carbonyl iron powder: Bi2O3 = 6.4:1.6:0.8 (mass ratio). Perform a second ball milling at 150 rpm for 4 hours to obtain a blend.

[0060] (4) The blend is pre-fired a second time. The temperature is increased to 750°C at 2°C / min, held for 2 hours, cooled in the furnace and then crushed to obtain the second pre-fired material.

[0061] (5) Add 1.1% PVA and 0.18% polydimethylsiloxane by dry weight of powder to the second pre-burned material for spray granulation. The inlet temperature is 270°C and the outlet temperature is 85°C.

[0062] (6) The granulated particles are biaxially compressed under a pressure of 115 MPa.

[0063] (7) Sintering the green blank: heat up to 350°C at 1.5°C / min to remove the glue, and hold for 2 hours; then heat up to 1180°C at 4°C / min and hold for 3 hours; finally cool down to 600°C at 1°C / min and cool with the furnace to obtain nickel-zinc magnetic core material.

[0064] Example 7

[0065] (1) Weigh the raw materials according to the mass ratio of Fe2O3: ZnO: NiO = 6.4: 2.0: 1.6, and perform the first ball milling at a speed of 340 rpm for 3 hours to obtain the mixture.

[0066] (2) The mixture is pre-fired for the first time. The temperature is increased to 980°C at 4°C / min and held for 1.5 hours. After cooling in the furnace, it is crushed to obtain the first pre-fired material.

[0067] (3) Add carbonyl iron powder and Bi2O3 to the first pre-calcined material, so that Fe2O3: carbonyl iron powder: Bi2O3 = 6.4:1.6:0.8 (mass ratio). Perform a second ball milling at 300 rpm for 1 hour to obtain a blend.

[0068] (4) The blend is pre-fired a second time by heating it to 900°C at 5°C / min, holding it at that temperature for 0.5 hours, cooling it in the furnace, and then crushing it to obtain the second pre-fired material.

[0069] (5) Add 1.1% PVA and 0.18% polydimethylsiloxane by dry weight of powder to the second pre-burned material for spray granulation. The inlet temperature is 270°C and the outlet temperature is 85°C.

[0070] (6) The granulated particles are biaxially compressed under a pressure of 115 MPa.

[0071] (7) Sintering the green blank: heat up to 350°C at 1.5°C / min to remove the glue, and hold for 2 hours; then heat up to 1180°C at 4°C / min and hold for 3 hours; finally cool down to 600°C at 1°C / min and cool with the furnace to obtain nickel-zinc magnetic core material.

[0072] Example 8

[0073] (1) Weigh the raw materials according to the mass ratio of Fe2O3: ZnO: NiO = 6.5: 1.8: 1.2, and perform the first ball milling at a speed of 330 rpm for 4 hours to obtain the mixture.

[0074] (2) The mixture is pre-fired for the first time. The temperature is increased to 940°C at 2°C / min, and the temperature is held for 2 hours. After cooling in the furnace, it is crushed to obtain the first pre-fired material.

[0075] (3) Add carbonyl iron powder and The Fe2O3:carbonyl iron powder:Bi2O3 ratio was adjusted to 6.5:2.0:0.9 (mass ratio). A second ball milling process was then performed at 240 rpm for 2 hours to obtain the blend.

[0076] (4) The blend is pre-fired a second time. The temperature is increased to 850°C at 3°C / min and held for 2 hours. After cooling in the furnace, it is crushed to obtain the second pre-fired material.

[0077] (5) Add 1.2% PVA and 0.2% polydimethylsiloxane by dry weight of powder to the second pre-burned material for spray granulation. The inlet temperature is 260°C and the outlet temperature is 100°C.

[0078] (6) The granulated particles are biaxially compressed under a pressure of 120 MPa.

[0079] (7) Sintering the green blank: heat up to 300°C at 1°C / min to remove the glue, and hold for 1 hour; then heat up to 1050°C at 3°C / min and hold for 2 hours; finally cool down to 600°C at 1°C / min and cool with the furnace to obtain nickel-zinc magnetic core material.

[0080] Example 9

[0081] (1) Weigh the raw materials according to the mass ratio of Fe2O3: ZnO: NiO = 6.5: 1.8: 1.2, and perform the first ball milling at a speed of 330 rpm for 4 hours to obtain the mixture.

[0082] (2) The mixture is pre-fired for the first time. The temperature is increased to 940°C at 2°C / min, and the temperature is held for 2 hours. After cooling in the furnace, it is crushed to obtain the first pre-fired material.

[0083] (3) Add carbonyl iron powder and The Fe2O3:carbonyl iron powder:Bi2O3 ratio was adjusted to 6.5:2.0:0.9 (mass ratio). A second ball milling process was then performed at 240 rpm for 2 hours to obtain the blend.

[0084] (4) The blend is pre-fired a second time. The temperature is increased to 850°C at 3°C / min, held for 2 hours, cooled in the furnace and then crushed to obtain the second pre-fired material.

[0085] (5) Add 1.2% PVA and 0.2% polydimethylsiloxane by dry weight of powder to the second pre-burned material for spray granulation. The inlet temperature is 260°C and the outlet temperature is 100°C.

[0086] (6) The granulated particles are biaxially compressed under a pressure of 120 MPa.

[0087] (7) Sintering the green blank: heat up to 500°C at 1.5°C / min to remove the glue, and hold for 2 hours; then heat up to 1250°C at 4°C / min and hold for 6 hours; finally cool down to 600°C at 3°C / min and cool with the furnace to obtain nickel-zinc magnetic core material.

[0088] Comparative Example 1 Compared to Example 1, the second pre-calcination step was omitted. That is, after the first pre-calcination and crushing, carbonyl iron powder and... A second ball milling process was performed, and the resulting blend was then directly spray-granulated, pressed, and sintered (the sintering process was the same as in Example 1).

[0089] Comparative Example 2 Compared with Example 1, the addition of carbonyl iron powder and Bi2O3 material, as well as the secondary ball milling and second pre-calcination steps, were omitted.

[0090] The performance of the magnetic core materials prepared in Examples 1-9 and Comparative Examples 1-2 of this invention was tested, and the results are shown in the table below.

[0091]

[0092] Results analysis and discussion: The magnetic permeability of Comparative Example 1 is lower than that of Example 1 with a similar composition, indicating that the two pre-firing processes are more conducive to forming a complete and uniform microstructure, thereby improving the magnetic permeability. The Bs value of Comparative Example 2 is the lowest, at only 380 mT, which indicates that the single pre-firing process cannot fully utilize the activity of carbonyl iron powder to improve Bs, which may lead to insufficient densification. The losses of all examples are significantly lower than those of Comparative Examples 1 and 2, which strongly demonstrates the great advantage of the two pre-firing process in reducing losses.

[0093] The test results fully demonstrate that the present invention, through a combination of two pre-firing processes and a specific component ratio, successfully improves the performance of nickel-zinc magnetic core materials. Compared with the traditional single pre-firing process (Comparative Examples 1 and 2), the materials prepared by the present invention exhibit significant advantages in key performance indicators such as permeability, saturation flux density, and especially power loss, and can meet the needs of high-performance nickel-zinc ferrite materials in different application scenarios.

[0094] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A process for preparing a nickel-zinc magnetic core material, characterized in that, Includes the following steps: Fe2O3 powder, ZnO powder and NiO powder were ball-milled for the first time to obtain a mixture. The mixture is pre-fired for the first time and then crushed to obtain the first pre-fired material; After adding carbonyl iron powder and Bi2O3 to the pre-calcined material and mixing, a second ball milling was performed to obtain a blend. The blend is pre-fired a second time and then crushed to obtain the second pre-fired material; The second pre-burned material is mixed with binder and defoamer, sprayed and granulated, pressed, and sintered to obtain the nickel-zinc magnetic core material.

2. The preparation process according to claim 1, characterized in that, The mass ratio of Fe2O3 powder, ZnO powder and NiO powder is (6-6.5):(2-2.5):(1-1.5).

3. The preparation process according to claim 1, characterized in that, The mass ratio of Fe2O3 powder, carbonyl iron powder, and Bi2O3 material is (6-6.5):(1.6-2.0):(0.5-1.2).

4. The preparation process according to claim 1, characterized in that, The first ball milling operation is performed at a speed of 200-400 rpm for 2-8 hours.

5. The preparation process according to claim 1, characterized in that, The heating rate for the first preheating is 1-5°C / minute, the preheating temperature is 850°C - 1000°C, and the holding time is 1-4 hours.

6. The preparation process according to claim 1, characterized in that, The second ball milling operation was performed at a speed of 150-300 rpm for 1-4 hours.

7. The preparation process according to claim 1, characterized in that, The second preheating process involves a heating rate of 2-5°C / minute, a preheating temperature of 750°C-900°C, and a holding time of 0.5-2 hours.

8. The preparation process according to claim 1, characterized in that, The adhesive is polyvinyl alcohol, and the addition amount is about 0.8% - 1.5% of the dry weight of the powder; the defoamer is polydimethylsiloxane, and the addition amount is about 0.1% - 0.3% of the dry weight of the powder. The inlet temperature is 200 - 300°C and the outlet temperature is 80 - 120°C.

9. The preparation process according to claim 1, characterized in that, In the sintering step, the temperature is increased to the discharge temperature at 1-1.5°C / min, and held for 1-2 hours, with the discharge temperature being 300-500°C; the sintering temperature is increased at 3-4°C / min, and held for 2-6 hours, with the sintering temperature being 1050°C-1250°C; the temperature is then decreased to 600°C at 1-3°C / min, and then cooled in the furnace.

10. A nickel-zinc magnetic core material, prepared by the preparation process described in any one of claims 1-9.

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