CN109650870B

CN109650870B - Slurry of flake ferrite material and preparation method and application thereof

Info

Publication number: CN109650870B
Application number: CN201910067429.5A
Authority: CN
Inventors: 苏艳锋; 黄慧博; 单震; 於扬栋; 王媛珍; 包宇航
Original assignee: Hengdian Group DMEGC Magnetics Co Ltd
Current assignee: Hengdian Group DMEGC Magnetics Co Ltd
Priority date: 2019-01-24
Filing date: 2019-01-24
Publication date: 2021-07-16
Anticipated expiration: 2039-01-24
Also published as: CN109650870A

Abstract

The invention relates to slurry of a flake ferrite material, a preparation method and application thereof. The invention adopts a step-by-step ball milling method, the particle size D50 of the slurry obtained by mixing the raw materials through the first ball milling and the pass ball milling is 0.8-1.5 mu m, the particle size D99 is 2.5-5.5 mu m, the particle size distribution range of the slurry is narrow, the influence of the residual material on the yield is avoided by adopting the pass ball milling, and the obtained slurry can be used for preparing the thin-sheet ferrite material by tape casting.

Description

Slurry of flake ferrite material and preparation method and application thereof

Technical Field

The invention relates to the field of ferrite materials, in particular to slurry of a flake ferrite material and a preparation method and application thereof.

Background

With the continuous development of electronic information technology, communication has fully entered the wireless era. In the technology using magnetic field near field coupling, although the application frequencies of the electronic tag RFID, NFC and wireless charging technology are different, there is a commonality in demand for a soft magnetic material that is required to have a sheet-like ultra-thin shape as a shield for enhancing the antenna inductance and shielding a metal environment. The thickness requirement of the magnetic-isolating sheet at the receiving end is generally lower than 0.1mm, the thickness of the magnetic-isolating sheet at the transmitting end of the charger is generally 0.5-1.5mm, the sheet ferrite material is generally prepared by adopting a tape-casting process, firstly, ferrite powder, a solvent, a dispersing agent, a binding agent and other auxiliary agents are prepared into uniform and consistent slurry, then, the solvent is volatilized by a tape-casting machine to prepare a sheet green body with a certain thickness, and the green body can be cut into magnetic-isolating sheets with various shapes after being sintered, filmed and softened. The key point of the casting method for preparing the ferrite sheet is the preparation of slurry, the quality of the slurry determines the casting yield, and the preparation process of the slurry strongly influences the performance and yield of subsequent sintering. At present, a rolling ball milling and batch feeding mode is generally adopted for preparing slurry, the slurry preparation mode has few related equipment and simple process, but the slurry with small powder particle size is difficult to obtain due to low ball milling efficiency. And the dispersion capability is poor, agglomerated particles which cause the appearance defects of products often exist in slurry, the particle size distribution is wide, the shrinkage consistency is poor during sintering, severe deformation is generated, and the sintering yield is low. And moreover, the residual materials in the ball milling tank of each batch are more, and the residual materials can be mixed with the next batch and then continuously ball milled, so that the consistency among the batches is influenced.

CN103833340A discloses slurry for an NFC magnetic sheet, which consists of ferrite powder and an organic system and is prepared by the following steps: sequentially adding a dispersing agent, an organic solvent and ferrite powder into a ball milling tank, and performing ball milling in sequence; then, sequentially adding a plasticizer and a binder, and carrying out secondary ball milling; and (3) selectively adding or not adding an auxiliary agent, and performing vacuum defoaming to obtain the slurry for the NFC magnetic sheet. The scheme has the defects that the particle size distribution of the obtained slurry is not uniform, and the product consistency is influenced by the residual materials.

CN104073660A discloses a method for preparing a metal soft magnetic composite material by tape casting, which mainly comprises the following steps: 1) mixing a passivating agent and a solvent according to the mass fraction of 0.1-5% of the passivating agent to obtain a passivating solution, mixing the passivating solution and magnetic metal powder according to the mass ratio of 0.01-1, stirring, and drying to obtain passivating powder; 2) mixing passivation powder, an organic solvent, a dispersant, a binder and a plasticizer, uniformly stirring, filtering by a screen mesh, and defoaming to prepare uniformly dispersed slurry; 3) tape casting; 4) drying and curing. The scheme is not ball milled, and the prepared slurry has wide particle size distribution range.

CN104766686A discloses a novel NFC magnetic sheet slurry and a preparation method thereof, which consists of ferrite powder and a water-based system, wherein the water-based system contains water, a surface treatment agent, an adhesive and a defoaming agent; and is prepared by the following steps: (1) putting the surface treating agent, ferrite powder and water into a ball milling tank, and carrying out ball milling in sequence; (2) after primary ball milling, adding a defoaming agent and an adhesive, and carrying out secondary ball milling; (3) and taking out the slurry after secondary ball milling, and performing vacuum defoaming to obtain the slurry for the NFC magnetic sheet. The slurry obtained by the scheme still has the problems of uneven grinding and wide particle size distribution range of the obtained slurry.

Although the above documents provide methods for preparing slurry for tape casting, the above documents still have the problems of wide particle size distribution range and large particle size of the prepared slurry, low solid content of residue and green bodies in the ball milling process, and low yield of the prepared sheet-type ferrite material; meanwhile, the existence of the residual materials can influence the consistency of the granularity of the slurry, so that the development of a preparation method of the slurry for preparing the flake ferrite material by tape casting and the slurry thereof are of great significance.

Disclosure of Invention

The invention aims to provide slurry of a sheet ferrite material and a preparation method and application thereof, the invention adopts a step-by-step ball milling method, the particle size D50 of the slurry after the preparation raw materials are subjected to first ball milling mixing and pass ball milling is 0.8-1.5 mu m, D99 is 2.5-5.5 mu m, the particle size distribution range of the slurry is narrow, the influence of residual materials on the yield is avoided by adopting pass ball milling, and the obtained slurry is used for preparing the sheet ferrite material by tape casting.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides a method for preparing a slurry for casting a sheet-type ferrite material, the method comprising the steps of:

(1) mixing a dispersing agent, a solvent and ferrite powder for first ball milling and mixing;

(2) performing secondary ball milling on the product obtained in the step (1) by adopting a pass ball milling method;

(3) mixing the product obtained in the step (2) with an auxiliary agent, stirring and mixing the mixture to obtain slurry;

(4) and (4) filtering and defoaming the product obtained in the step (3) to obtain the slurry.

The thickness of the thin-sheet ferrite material is thin (generally the thickness is less than or equal to 1.5mm), the thin-sheet ferrite material prepared by the casting method requires that the cast slurry particles are uniformly distributed, the particle size is small, and the agglomeration condition is less. The slurry prepared by the preparation method of the slurry has narrow particle size distribution range, and can ensure the shrinkage consistency in the sintering process. Meanwhile, the dispersibility of ferrite powder in a solvent is improved by step-by-step ball milling, the utilization rate of a binder and other auxiliaries is greatly improved, the content of the binder in the traditional rolling ball mill pulping is generally more than 6.5%, and the content of the binder in the slurry obtained by the preparation method is 2.5-6%, so that the solid content of a green body is improved.

According to the slurry preparation method, the pass-through ball milling is adopted in the step (2) for the second ball milling, so that the particle size of slurry particles can be effectively reduced, and the pass-through ball milling is flowing feeding, so that the accumulation of residual materials in a ball mill can be prevented, and the consistency of the particle size of the slurry is improved.

Preferably, the particle size of the ferrite powder in the step (1) is D50: 2.0 to 10.0 μm (exemplary include 2 μm, 4 μm, 6 μm, 8 μm, or 10 μm, etc.), D99: 20 to 60 μm (exemplary include 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, or 60 μm, etc.), preferably D50: 2.0 to 4.0 μm, D99: 25 to 45 μm.

Preferably, the ball-to-material ratio of the first ball-milling mixture in the step (1) is (3-8):1, such as 3:1, 4:1, 5:1, 6:1, 7:1 or 8:1, and the like, and is preferably 5: 1.

Preferably, the grinding balls of the first ball-milling material mixing in the step (1) comprise grinding balls with a first size and grinding balls with a second size, and the size of the grinding balls with the first size is smaller than that of the grinding balls with the second size.

Preferably, the first size grinding balls in step (1) have a diameter of 5-7mm, such as 5mm, 5.5mm, 6mm, 6.5mm or 7mm, and preferably 6.5 mm.

Preferably, the diameter of the second size grinding ball in the step (1) is 8-10mm, such as 8mm, 8.5mm, 9mm, 9.5mm or 10mm, and the like, and is preferably 9 mm.

Preferably, the number ratio of the first size grinding balls to the second size grinding balls in the step (1) is (300: 800):1, such as 300:1, 350:1, 400:1, 450:1, 500:1, 550:1, 600:1, 650:1, 700:1, 750:1 or 800:1, etc., preferably 500: 1.

Preferably, the rotating speed of the first ball milling mixing in the step (1) is 60-240r/min, such as 60r/min, 80r/min, 100r/min, 140r/min, 180r/min, 220r/min or 240 r/min.

Preferably, the time for the first ball milling mixing in the step (1) is 30-120min, such as 30min, 60min, 80min, 100min or 120 min.

Preferably, the particle size D50 of the product obtained in step (1) is 1.5-3.2. mu.m, such as 1.5. mu.m, 1.8. mu.m, 2.1. mu.m, 2.4. mu.m, 2.7. mu.m, 2.9. mu.m or 3.2. mu.m, etc., preferably 1.8-2.4. mu.m.

Preferably, the grinding balls of the pass-through ball milling in the step (2) are zirconium balls.

Preferably, the diameter of the milling balls of the pass ball mill of step (2) is 0.2 to 10mm, such as 0.2mm, 0.5mm, 1mm, 1.5mm, 2.5mm, 3.5mm, 4mm, 6mm, 8mm or 10mm, etc., preferably 0.5 to 1.5 mm.

Preferably, the flow rate through the ball mill in step (2) is 10-100mL/s, such as 10mL/s, 20mL/s, 30mL/s, 40mL/s, 50mL/s, 60mL/s, 70mL/s, 80mL/s, 90mL/s, or 100mL/s, and the like.

Preferably, the particle size D50 of the product obtained in step (2) is 0.8-1.5. mu.m, such as 0.8. mu.m, 1. mu.m, 1.2. mu.m, 1.3. mu.m or 1.5. mu.m, etc., preferably D50 is 1-1.3. mu.m.

Preferably, the particle size D99 of the product obtained in step (2) is 2.5-5.5 μm, such as 2.5 μm, 2.8 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm or 5.5 μm, etc., and D99 is 2.8-3.5 μm.

Preferably, the slurry mixing time in the step (3) is 3-10h, such as 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10 h.

Preferably, the auxiliary agent in step (3) comprises a plasticizer and/or a binder.

Preferably, the viscosity of the slurry obtained in step (4) at 25 ℃ is 1800-5000 mPas, for example 1800-, 2000-, 2200-, 2400-, 2800-, 3200-, 3600-, 3900-, 4500-, 4800-or 5000-mPas, preferably 2200-4500 mPas.

As a preferred technical scheme, the preparation method of the slurry for preparing the flake ferrite material by casting comprises the following steps:

(1) mixing a dispersing agent, a solvent and ferrite powder to perform primary ball-milling mixing, wherein the ball-to-material ratio of the primary ball-milling mixing is (3-8):1, the diameter of the first-size grinding ball is 5-7mm, the diameter of the second-size grinding ball is 8-10mm, the number ratio of the first-size grinding ball to the second-size grinding ball is (300-;

(2) performing secondary ball milling on the product obtained in the step (1) by adopting pass ball milling, wherein the grinding balls of the pass ball milling are zirconium balls, the diameter of each grinding ball is 0.5-1.5mm, and the flow rate of the pass ball milling is 10-100 mL/s;

(3) mixing the product obtained in the step (2), a binder and a plasticizer, and stirring and mixing the mixture for 3-10 hours;

In a second aspect, the invention provides a slurry for preparing a flake ferrite material by casting, which comprises the following components in percentage by weight:

preferably, the slurry is prepared by the preparation method for preparing the slurry for preparing the flake ferrite material by casting according to the first aspect.

Preferably, the particle size D50 of the slurry is 0.8-1.5 μm, such as 0.8 μm, 1 μm, 1.2 μm, 1.3 μm or 1.5 μm, etc., preferably 1-1.3 μm.

Preferably, the particle size D99 of the slurry is 2.5-5.5 μm, such as 2.5 μm, 2.8 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm or 5.5 μm, etc., preferably 2.8-3.5 μm.

The mass percentage of the ferrite powder in the slurry adopted by the invention is 65-78%, such as 65%, 68%, 70%, 72%, 75% or 78%; the mass percentage of the dispersant is 0.25-0.5%, such as 0.25%, 0.3%, 0.35%, 0.4%, 0.45% or 0.5%; the mass percentage of the binder is 2.5-6%, such as 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5% or 6%; the mass percentage of the plasticizer is 1-5%, such as 1%, 2%, 3%, 4% or 5%; the balance of solvent; the components and the content of the slurry can be matched with the preparation method of the slurry for preparing the sheet-type ferrite material by tape casting to obtain the slurry with uniform particle size distribution and smaller particle size, so that the yield of the prepared sheet-type manganese-zinc soft magnetic ferrite material is improved.

Compared with the traditional ball milling mode, the slurry for preparing the sheet ferrite material by tape casting has the advantages that the step-by-step ball milling method is adopted, so that ferrite powder particles sintered at higher temperature are more refined, the particle size distribution is optimized, and the content of a binder is far lower than that of the slurry prepared by other processes; the slurry provided by the invention increases the dissolving capacity of the binder and the wetting capacity of the ferrite powder, so that the slurry has excellent consistency and leveling property, the stability of casting thickness is ensured, the defect of poor appearance is reduced, and the performance and yield of the product are improved.

Preferably, the ferrite powder comprises any one of nickel-copper-zinc ferrite powder, manganese-zinc ferrite powder and nickel-zinc ferrite, and is preferably manganese-zinc ferrite powder.

Preferably, the manganese-zinc ferrite powder comprises a main component and an auxiliary component; mn in the main component₃O₄In a molar percentage of 36-39 mol%, Fe₂O₃The mol percent is 50.0-54.0mol percent, and the rest is ZnO; the mass fractions of the auxiliary components calculated by the respective oxides are respectively as follows, wherein the total mass of the main components is 100 percent:

preferably, the dispersant comprises any one or a mixture of at least two of castor oil, fish oil and oleic acid, such as a mixture of castor oil and fish oil, a mixture of castor oil and oleic acid, a mixture of fish oil and oleic acid or a mixture of castor oil, fish oil and oleic acid, and the like.

Preferably, the binder comprises polyvinyl butyral (PVB).

Preferably, the plasticizer comprises Dibutyl phthalate (DBP) and/or xylene formate.

Preferably, the solvent includes any one or a mixture of at least two of ethanol, xylene, n-propanol and ethyl acetate, such as a mixture of ethanol and xylene, a mixture of ethanol and n-propanol, a mixture of ethanol and ethyl acetate, a mixture of xylene and n-propanol, a mixture of xylene and ethyl acetate or a mixture of n-propanol and ethyl acetate, and the like.

Preferably, the solvent is a mixture of any two of ethanol, xylene, n-propanol and ethyl acetate, and the weight mixing ratio of the solution is (1-3):1, such as 1:1, 1:1.5, 1:2, 1:2.5 or 1:3, and the like, preferably 1:1.

As a preferable technical scheme, the slurry for preparing the flake ferrite material by casting comprises the following components in percentage by weight:

preferably, the solvent is a mixture of ethanol and xylene in a weight ratio of 1:1.

In a third aspect, the invention provides a preparation method of a thin sheet type manganese-zinc soft magnetic ferrite material, wherein the preparation method is obtained by casting and sintering the slurry according to the second aspect.

Preferably, the method comprises the steps of:

(1) preparing slurry;

(2) tape casting;

(3) and sintering to obtain the thin sheet type manganese-zinc soft magnetic ferrite material.

Preferably, the method for preparing a slurry according to the step (1) employs the method for preparing a slurry for casting a sheet-type ferrite material according to the first aspect.

The preparation method of the flake-type manganese-zinc soft magnetic ferrite material adopts the preparation method of the slurry for preparing the flake-type ferrite material by tape casting according to the first aspect; the obtained slurry has narrow particle size distribution range, and the content of the binder required by the slurry is reduced, so that the solid content of the green body is improved, and the yield of the preparation method of the sheet type manganese-zinc soft magnetic ferrite material is improved.

Preferably, the thickness of the cast green body of step (2) is 0.03-3mm, such as 0.03mm, 0.05mm, 0.1mm, 0.5mm, 1.2mm, 1.5mm or 3mm, etc., preferably 0.05-1 mm.

Preferably, the sintering in step (3) comprises a temperature rising stage, a temperature holding stage and a temperature reducing stage.

Preferably, the rate of the warming phase is 1.5-3 deg.C/min, such as 1.5 deg.C/min, 1.7 deg.C/min, 1.9 deg.C/min, 2.1 deg.C/min, 2.3 deg.C/min, 2.5 deg.C/min, 2.7 or 3 deg.C/min, and the like.

Preferably, the temperature of the heat preservation stage is 1150-1300 ℃, such as 1150 ℃, 1200 ℃, 1250 ℃, 1290 ℃ or 1300 ℃, and preferably 1250-1290 ℃.

Preferably, the incubation time of the incubation period is 2-5h, such as 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h, etc.

Preferably, the warming phase is carried out in air.

Preferably, the incubation phase is performed under an equilibrium atmosphere.

Preferably, the equilibrium atmosphere has an oxygen content of 0.5% to 1%, such as 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%, etc., with the remainder being nitrogen.

Preferably, the temperature reduction stage is performed in a nitrogen atmosphere.

As a preferable technical scheme of the invention, the preparation method of the flake manganese zinc soft magnetic ferrite material is obtained by casting and sintering the slurry according to the second aspect.

Preferably, the method comprises the steps of:

(1) preparing a slurry by the method for preparing a slurry for casting a sheet-type ferrite material as described in the first aspect;

(2) casting to obtain a green body with the thickness of 0.03-3 mm;

(3) sintering at 1250-; and obtaining the thin sheet type manganese-zinc soft magnetic ferrite material.

In a fourth aspect, the present invention provides a thin-sheet type manganese-zinc soft magnetic ferrite material prepared by the method for preparing a thin-sheet type manganese-zinc soft magnetic ferrite material according to the third aspect, wherein the thickness of the thin-sheet type manganese-zinc soft magnetic ferrite material is 0.03-1.5mm, such as 0.03mm, 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 1mm, 1.2mm or 1.5mm, etc.

Preferably, the thickness deviation of the sheet type manganese-zinc soft magnetic ferrite material in any square area of 5mm multiplied by 5mm is less than or equal to 5 mu m.

The thickness deviation testing method comprises the steps of selecting square areas of 5mm multiplied by 5mm optionally on the sheet type manganese-zinc soft magnetic ferrite material, randomly selecting 10 points in each square area, testing the thickness of the square areas, and calculating the variance of the testing results to obtain the thickness deviation.

In a fifth aspect, the invention provides a use of the sheet-type manganese-zinc soft magnetic ferrite material according to the fourth aspect as a magnetism-isolating sheet.

Preferably, the magnetism isolating sheet is used for an NFC device and a wireless charging device.

Compared with the prior art, the invention has at least the following beneficial effects:

(1) the preparation method of the slurry adopts step-by-step ball milling to ensure that the particle size distribution range D50 of the prepared slurry is 0.8-1.5 mu m, the particle size distribution range D99 is 2.5-5.5 mu m, the particle size distribution range is narrow, the content of the required binder is low, so that the solid content of a green blank is improved, and the yield of the obtained sheet type manganese-zinc soft magnetic ferrite material is more than or equal to 78%;

(2) the preparation method of the slurry adopts a mode of combining the first ball milling mixing and the second ball milling to solve the problem of residual material accumulation in the ball milling of a single ball milling tank, thereby obtaining the slurry with narrower particle size distribution range.

(3) The thickness of the thin-sheet type manganese-zinc soft magnetic ferrite material prepared by the preparation method of the thin-sheet type manganese-zinc soft magnetic ferrite material is 0.03-1.5mm, and compared with the thin-sheet type manganese-zinc soft magnetic ferrite material prepared by slurry obtained by ball milling of a single ball milling tank, the surface smoothness of the thin-sheet type manganese-zinc soft magnetic ferrite material is also obviously improved, the thickness deviation in any 5mm multiplied by 5mm square region is less than or equal to 5 mu m, and the thin-sheet type manganese-zinc soft magnetic ferrite material can meet the requirement of being used as a magnetism isolating sheet.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

In the embodiment, manganese zinc ferrite powder for wireless charging is selected to prepare a thin sheet type manganese zinc soft magnetic ferrite material with the size of 100 multiplied by 100mm and the thickness of 0.03-1.0 mm.

Example 1

The preparation method of the thin-sheet type manganese-zinc soft magnetic ferrite material comprises the following steps:

(1) slurry preparation

In the embodiment, manganese-zinc ferrite powder is used as ferrite powder, a mixed solution of ethanol and xylene in a weight ratio of 1:1 is used as a solvent, castor oil is used as a dispersant, polyvinyl butyral is used as a binder, and dibutyl phthalate is used as a plasticizer; based on 100 percent of mass of the slurry, the mass percent of the manganese-zinc ferrite powder is 71.5 percent, the mass percent of the dispersing agent is 0.5 percent, the mass percent of the binding agent is 2.8 percent, the mass percent of the plasticizer is 1.2 percent, and the mass percent of the solvent is 24 percent.

The preparation of the slurry comprises the following steps:

(a) adding a dispersing agent, a solvent and ferrite powder into a ball mill for first ball milling and mixing; the diameter of a grinding ball of a first size is 6.5mm, the diameter of a grinding ball of a second size is 9mm, and the number ratio of the first size grinding ball to the second size grinding ball is 500: 1; the ball milling time is 0.5h, the ball milling rotating speed is 65r/min, and the ball-to-material ratio is 3.7: 1;

(b) performing secondary ball milling on the product obtained in the step (a) by adopting pass ball milling, wherein the diameter of a milling ball is 1-2mm, and the flow of a ball mill is 30 mL/s;

(c) mixing the product obtained in the step (b), a binder and a plasticizer, stirring and mixing the mixture for 5 hours;

(d) and (c) filtering and defoaming the product obtained in the step (c) to obtain the slurry.

(2) Tape casting and sintering

And carrying out tape casting on the prepared slurry on a tape casting machine to prepare a green body with the thickness of 0.5mm, cutting the green body into a certain size, laminating, and sintering to obtain the thin sheet type manganese-zinc soft magnetic ferrite material, wherein the sintering comprises a heating stage, a heat preservation stage and a cooling stage, the heating rate is 2 ℃/min, the heat preservation temperature is 1250 ℃, the time is 2 hours, the temperature is naturally reduced, and the sintering is carried out under the atmosphere with the oxygen content of 0.5-1% (the rest is nitrogen).

The particle size of the product after the first ball milling and mixing, the particle size of the prepared slurry, the yield of the thin sheet type manganese-zinc soft magnetic ferrite material, the complex permeability and the thickness are shown in table 1.

Example 2

This example differs from example 1 in that: replacing the solvent in the step (1) with a mixed solution of n-propanol and xylene in an equal weight ratio of 1: 1; replacing the ball material ratio in the step (a) with 4.4: 1; replacing the diameter of the grinding ball in the step (b) with 3-5 mm.

Example 3

This example differs from example 1 in that: replacing the solvent in the step (1) with a mixed solution of ethanol and ethyl acetate in an equal weight ratio of 1: 1; based on 100 percent of mass of the slurry, the mass percent of the manganese-zinc ferrite powder is 69 percent, the mass percent of the dispersing agent is 0.3 percent, the mass percent of the binding agent is 2.5 percent, the mass percent of the plasticizer is 1 percent, and the mass percent of the solvent is 27.2 percent; replacing the ball material ratio in the step (a) with 7.1: 1; replacing the diameter of the grinding ball in the step (b) with 5-8 mm; the flow rate of the ball mill was replaced with 20 mL/s.

Example 4

This example differs from example 1 in that: replacing the solvent in the step (1) with a mixed solution of n-propanol and ethyl acetate in an equal weight ratio of 1: 1; based on 100 percent of mass of the slurry, the mass percent of the manganese-zinc ferrite powder is 72 percent, the mass percent of the dispersing agent is 0.4 percent, the mass percent of the binding agent is 2.5 percent, the mass percent of the plasticizer is 1.1 percent, and the mass percent of the solvent is 24 percent; replacing the ball material ratio in the step (a) with 7.5: 1; replacing the diameter of the grinding ball in the step (b) with 0.5-2 mm.

Example 5

This example differs from example 1 in that: replacing the solvent in the step (1) with a mixed solution of n-propanol and xylene in an equal weight ratio of 1: 1; replacing the ball material ratio in the step (a) with 7.4: 1; replacing the diameter of the grinding ball in the step (b) with 8-10 mm; the flow rate of the ball mill was replaced with 20 mL/s.

Example 6

(1) slurry preparation

In the embodiment, manganese-zinc ferrite powder is used as ferrite powder, a mixed solution of ethanol and xylene with a mass ratio of 3:1 is used as a solvent, fish oil is used as a dispersing agent, polyvinyl butyral is used as a binder, and xylene formate is used as a plasticizer; based on 100 percent of mass of the slurry, the mass percent of the manganese-zinc ferrite powder is 78 percent, the mass percent of the dispersing agent is 0.25 percent, the mass percent of the binding agent is 6 percent, the mass percent of the plasticizer is 1 percent, and the mass percent of the solvent is 14.75 percent.

The preparation of the slurry comprises the following steps:

(a) adding a dispersing agent, a solvent and ferrite powder into a ball mill to perform first ball milling and mixing; the diameter of a grinding ball of a first size is 5mm, the diameter of a grinding ball of a second size is 10mm, and the number ratio of the first size grinding ball to the second size grinding ball is 300: 1; the ball milling time is 1.5h, the ball milling rotating speed is 200r/min, and the ball-material ratio is 5: 1;

(b) performing secondary ball milling on the product obtained in the step (a) by adopting pass ball milling, wherein the diameter of a milling ball is 9-10mm, and the flow of a ball mill is 100 mL/s;

(c) mixing the product obtained in the step (b), a binder and a plasticizer, stirring and mixing the mixture for 10 hours;

(2) Tape casting and sintering

And carrying out tape casting on the prepared slurry on a tape casting machine to prepare a green body with the thickness of 0.5mm, cutting the green body into a certain size, laminating, and sintering to obtain the thin sheet type manganese-zinc soft magnetic ferrite material, wherein the sintering comprises a heating stage, a heat preservation stage and a cooling stage, the heating rate is 3 ℃/min, the heat preservation temperature is 1290 ℃, the time is 5 hours, the temperature is naturally reduced, and the heating and the sintering are carried out in an atmosphere with the oxygen content of 0.5-1% (the rest is nitrogen).

Example 7

(1) slurry preparation

In the embodiment, manganese-zinc ferrite powder is used as ferrite powder, a mixed solution of ethanol and xylene with a mass ratio of 1:3 is used as a solvent, oleic acid is used as a dispersing agent, polyvinyl butyral is used as a binder, and a mixed ester of dibutyl phthalate and xylene formate with a weight ratio of 1:1 is used as a plasticizer; based on 100 percent of mass of the slurry, the mass percent of the manganese-zinc ferrite powder is 65 percent, the mass percent of the dispersing agent is 0.5 percent, the mass percent of the binding agent is 2.5 percent, the mass percent of the plasticizer is 5 percent, and the mass percent of the solvent is 27 percent.

The preparation of the slurry comprises the following steps:

(a) adding a dispersing agent, a solvent and ferrite powder into a ball mill to perform first ball milling and mixing; the diameter of a grinding ball of a first size is 7mm, the diameter of a grinding ball of a second size is 8mm, and the number ratio of the first size grinding ball to the second size grinding ball is 800: 1; the ball milling time is 0.5h, the ball milling rotating speed is 60r/min, and the ball-material ratio is 3.5: 1;

(b) performing secondary ball milling on the product obtained in the step (a) by adopting pass ball milling, wherein the diameter of a milling ball is 1-2mm, and the flow of a ball mill is 10 mL/s;

(c) mixing the product obtained in the step (b), a binder and a plasticizer, stirring and mixing the mixture for 3 hours;

(2) Tape casting and sintering

And carrying out tape casting on the prepared slurry on a tape casting machine to prepare a green body with the thickness of 0.5mm, cutting the green body into a certain size, laminating, and sintering to obtain the thin sheet type manganese-zinc soft magnetic ferrite material, wherein the sintering comprises a heating stage, a heat preservation stage and a cooling stage, the heating rate is 3 ℃/min, the heat preservation temperature is 1150 ℃, the time is 5 hours, the temperature is naturally reduced, and the heating and the sintering are carried out in an atmosphere with the oxygen content of 0.5-1% (the rest is nitrogen).

Example 8

This example differs from example 1 in that: the manganese zinc ferrite powder is replaced by nickel copper zinc ferrite powder with equal weight.

The nickel-copper-zinc ferrite powder comprises Fe₂O₃The molar percentage of the CuO is 48 mol%, the molar percentage of the CuO is 11 mol%, the molar percentage of the ZnO is 23 mol%, and the molar percentage of the Ni is 18 mol%.

The particle size of the product after the first ball milling and mixing and the particle size of the slurry obtained in this example are shown in table 1.

Example 9

This example differs from example 1 in that: the manganese-zinc ferrite powder was replaced with nickel-zinc ferrite powder of the same weight, and the other conditions were exactly the same as in example 1.

The nickel-copper-zinc ferrite powder comprises Fe₂O₃The molar percentage of (A) is 56 mol%, the molar percentage of ZnO is 25 mol%, and the molar percentage of Ni is 19 mol%.

Example 10

This example differs from example 1 in that: replacing the grinding balls of the first ball milling and mixing in the step (a) with the same number of grinding balls with single size, wherein the diameter of the grinding balls is 6.5 mm.

Example 11

This example differs from example 1 in that: replacing the grinding balls of the first ball milling and mixing in the step (a) with the same number of grinding balls with single size, wherein the diameter of the grinding balls is 9 mm.

Example 12

This example differs from example 1 in that: replacing the flow rate of the ball mill in the step (b) from 30mL/s to 100 mL/s.

Example 13

This example differs from example 1 in that: replacing the flow rate of the ball mill in the step (b) from 30mL/s to 10 mL/s.

Example 14

This example differs from example 1 in that: replacing the flow rate of the ball mill in the step (b) from 30mL/s to 5 mL/s.

Example 15

This example differs from example 1 in that: replacing the flow rate of the ball mill in the step (b) from 30mL/s to 120 mL/s.

Comparative example 1

This comparative example differs from example 1 in that: replacing the ball milling time in the step (a) with 4h, and replacing the ball milling rotating speed with 50 r/min; other conditions were exactly the same as in step (a) of example 1; and (c) not carrying out the steps (b) and (c), adding a binder and a plasticizer into the ball milling tank 0.5h after the step (a), carrying out ball milling again, and carrying out the step (d) to obtain the slurry, wherein the time of ball milling again is 18h, and the rotating speed of ball milling again is 50 r/min.

The particle size of the slurry prepared in this comparative example, the yield, the complex permeability and the thickness of the sheet-type manganese-zinc soft magnetic ferrite material are shown in table 1.

Comparative example 2

The difference between this pair of examples and example 1 is that: replacing a solvent with a mixed solution of ethanol and n-propanol with an equal weight ratio of 1:1, wherein the mass percentage of the manganese-zinc ferrite powder is 72%, the mass percentage of the dispersing agent is 0.6%, the mass percentage of the binding agent is 2.2%, the mass percentage of the plasticizer is 1.1%, and the mass percentage of the solvent is 24.1%, based on 100% of the slurry; replacing the ball milling time in the step (a) with 4h, and replacing the ball milling rotating speed with 50 r/min; and (c) not carrying out the steps (b) and (c), adding a binder and a plasticizer into the ball milling tank 0.5h after the step (a), carrying out ball milling again, and carrying out the step (d) to obtain the slurry, wherein the ball milling again lasts for 18h, and the rotating speed of the ball milling again is 50 r/min.

A method for testing the performance of the thin sheet type Mn-Zn soft magnetic ferrite materials obtained in examples 1 to 15 and comparative examples 1 to 2 comprises the following steps:

(a) testing the granularity of the product after the first ball milling and mixing, and testing the granularity by adopting a laser granularity meter;

(b) particle size testing of the slurry: the method for testing the granularity of the slurry is the same as that of the product after the first ball milling and mixing;

(c) and (3) testing yield: screening appearance qualified products (the qualified products refer to products without the defect characteristics of deformation, warping and concave-convex points) in the thin sheet type manganese-zinc soft magnetic ferrite material obtained in the step (2) and then weighing; the total weight of the sintered qualified product is the total weight of the sintered qualified product; counting the finished product rate of casting and sintering according to the weight, namely the finished product rate is the total weight of sintered ferrite powder;

(d) and (3) magnetic permeability test: after coating films on two sides of the obtained sheet type manganese-zinc soft magnetic ferrite material, punching sample rings with the diameter of 19.9mm multiplied by 8.8mm by using a die to test the magnetic conductivity, wherein the test conditions are that the frequency is 200kHz and the temperature is 25 ℃;

(e) testing the thickness of the thin sheet type manganese-zinc soft magnetic ferrite material: and (3) optionally selecting 25 points on the thin sheet type manganese-zinc soft magnetic ferrite material to test the thickness of the thin sheet type manganese-zinc soft magnetic ferrite material, and averaging to obtain the thickness of the thin sheet type manganese-zinc soft magnetic ferrite material.

The methods of examples 1 to 15 and comparative examples 1 to 2 were repeated 100 times each, and the yield of casting and sintering, i.e., yield ═ total fired weight/weight of ferrite powder, was counted by weight, and the average of the yield and the average of complex permeability of each group of examples were counted, and the results are shown in table 1:

TABLE 1

As can be seen from table 1, the magnetic permeability μ 'and the yield of the thin sheet type mn-zn soft magnetic ferrite materials obtained in examples 1 to 15 are both higher than those of comparative examples 1 to 2, the yields of the thin sheet type mn-zn soft magnetic ferrite materials obtained in examples 1 to 15 are not less than 78%, and the yields of comparative examples 1 to 2 are not more than 68%, so that the yield of the thin sheet type mn-zn soft magnetic ferrite materials prepared by the slurry process of the step ball milling can be obviously improved, the magnetic permeability μ' of the thin sheet type mn-zn soft magnetic ferrite materials obtained in examples 1 to 15 is not less than 742.31, and the magnetic permeability μ 'of the comparative examples 1 to 2 is not more than 637.52, thereby the magnetic permeability μ' of the thin sheet type mn-zn soft magnetic ferrite materials prepared by the slurry process of the step ball milling can be obviously improved; comparing example 1 and examples 10-11, it can be seen that the use of two sizes of balls for the first ball mill mix is superior to the use of only one size of balls; when the flow rate of the ball mill for the second ball milling was > 100mL/s or < 10mL/s, it was found that the particle size distribution of the resulting slurry was broad and the yield was low by combining examples 1 and 12 to 15.

The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.

Claims

1. A preparation method of slurry for preparing a flake ferrite material by casting is characterized by comprising the following steps:

(1) dispersing agent, solvent and D50: 2.0 to 10.0 μm, D99: mixing ferrite powder of 20-60 mu m, and performing first ball milling mixing to obtain a product with the particle size D50 of 1.5-3.2 mu m;

(2) performing secondary ball milling on the product obtained in the step (1) by adopting a pass ball mill with a grinding ball diameter of 0.2-10mm to obtain a product with the particle size D50 of 0.8-1.5 mu m and the particle size D99 of 2.5-5.5 mu m;

(3) mixing the product obtained in the step (2) with an auxiliary agent, stirring and mixing the mixture to obtain slurry; the auxiliary agent comprises a plasticizer and a binder;

(4) filtering and defoaming the product obtained in the step (3) to obtain the slurry, wherein the viscosity of the slurry at 25 ℃ is 1800-5000mPa & s;

the grinding balls of the first ball-milling material mixing comprise grinding balls with a first size and grinding balls with a second size, and the diameter of the grinding balls with the first size is 5-7 mm; the diameter of the second size grinding ball is 8-10 mm; the number ratio of the first size grinding balls to the second size grinding balls is (300- & lt800) & gt 1;

the flow rate of the passing ball milling in the step (2) is 10-100 mL/s;

the solvent is a mixture of any two of ethanol, xylene, n-propanol and ethyl acetate, and the weight mixing ratio of the solvent is 1:1.

2. The method of claim 1, wherein the ferrite powder of step (1) has a particle size of D50: 2.0 to 4.0 μm, D99: 25 to 45 μm.

3. The preparation method of claim 1, wherein the ball-to-material ratio of the first ball-milled mixture in the step (1) is (3-8): 1.

4. The method of claim 3, wherein the first ball mill mix of step (1) has a ball to material ratio of 5: 1.

5. The method of claim 1, wherein the first size balls of step (1) have a diameter of 6.5 mm.

6. The method of claim 1, wherein the second size balls of step (1) have a diameter of 9 mm.

7. The method of claim 1, wherein the ratio of the number of first size balls to the number of second size balls in step (1) is 500: 1.

8. The preparation method of claim 1, wherein the rotation speed of the first ball milling mixture in the step (1) is 60 to 240 r/min.

9. The preparation method of claim 1, wherein the time for the first ball milling mixing in step (1) is 30-120 min.

10. The process according to claim 1, wherein the product obtained in step (1) has a particle size D50 of 1.8 to 2.4. mu.m.

11. The method of claim 1, wherein the milling balls of the pass-through ball milling of step (2) are zirconium balls.

12. The method of claim 1, wherein the passing ball mill of step (2) has a diameter of 0.5 to 1.5 mm.

13. The process according to claim 1, wherein the product obtained in step (2) has a particle size D50 of 1 to 1.3 μm.

14. The process according to claim 1, wherein the product obtained in step (2) has a particle size D99 of 2.8 to 3.5. mu.m.

15. The method according to claim 1, wherein the slurry mixing time in the step (3) is 3 to 10 hours.

16. The process according to claim 1, wherein the slurry obtained in step (4) has a viscosity of 2200-4500 mPas at 25 ℃.

17. The method of claim 1, comprising the steps of:

18. The slurry for preparing the flake ferrite material by casting is characterized by comprising the following components in percentage by weight:

the slurry is prepared by the preparation method of the slurry for preparing the flake ferrite material by casting according to any one of claims 1 to 17.

19. The slurry of claim 18, wherein the ferrite powder comprises any one of nickel copper zinc ferrite powder, manganese zinc ferrite powder, and nickel zinc ferrite.

20. The slurry of claim 19, wherein the ferrite powder is manganese zinc ferrite powder.

21. The slurry of claim 20, wherein the manganese zinc ferrite powder comprises a primary component and a secondary component; mn in the main component₃O₄In a molar percentage of 36-39 mol%, Fe₂O₃The mol percent is 50.0-54.0mol percent, and the rest is ZnO; the mass fraction of the auxiliary components calculated by the respective oxides is calculated by taking the total mass of the main components as 100%Respectively as follows:

22. the slurry of claim 18, wherein the dispersant comprises any one of castor oil, fish oil, and oleic acid, or a mixture of at least two thereof.

23. The slurry of claim 18, wherein said binder comprises polyvinyl butyral.

24. The slurry of claim 18, wherein the plasticizer comprises dibutyl phthalate and/or xylene formate.

25. The slurry according to claim 18, comprising the following components in weight percent:

26. the slurry of claim 18, wherein the solvent is a mixture of ethanol and xylene in a weight ratio of 1:1.

27. A method for preparing a thin sheet type manganese-zinc soft magnetic ferrite material, characterized in that the method is obtained by casting and sintering the slurry according to any one of claims 18 to 26.

28. The method of claim 27, comprising the steps of:

(1) preparing slurry;

(2) tape casting;

(3) sintering to obtain the thin sheet type manganese-zinc soft magnetic ferrite material;

the method for preparing a slurry according to the step (1) adopts the method for preparing a slurry for casting a sheet-type ferrite material according to any one of claims 1 to 17;

the sintering in the step (3) comprises a heating stage, a heat preservation stage and a cooling stage; the temperature raising stage is carried out in the air; the heat preservation stage is carried out in a balanced atmosphere, wherein the balanced atmosphere contains 0.5-1% of oxygen, and the balance is nitrogen; the cooling stage is carried out in a nitrogen atmosphere.

29. The method of claim 28, wherein said cast green body of step (2) has a thickness of 0.03 to 3 mm.

30. The method of claim 29, wherein said cast green body of step (2) has a thickness of 0.05 to 1 mm.

31. The method of claim 28, wherein the ramp-up phase is at a rate of 1.5 to 3 ℃/min.

32. The method as set forth in claim 28, wherein the temperature of the incubation stage is 1150-1300 ℃.

33. The method of claim 32, wherein the temperature of the incubation stage is 1250-.

34. The method of claim 28, wherein the incubation period is 2 to 5 hours.

35. The thin sheet-type manganese-zinc soft magnetic ferrite material prepared by the preparation method according to any one of claims 27 to 34, wherein the thickness of the thin sheet-type manganese-zinc soft magnetic ferrite material is 0.03 to 1.5 mm.

36. The sheet-type Mn-Zn soft magnetic ferrite material according to claim 35, wherein a thickness deviation in any 5mm x 5mm square area of the sheet-type Mn-Zn soft magnetic ferrite material is not more than 5 μm.

37. Use of the thin sheet-type manganese-zinc soft magnetic ferrite material according to claim 35, as a magnetism-shielding sheet.

38. Use according to claim 37, wherein the magnetic separator is used in NFC devices and wireless charging devices.