CN108503351B - Magnetic separation sheet for wireless charging and preparation method thereof - Google Patents
Magnetic separation sheet for wireless charging and preparation method thereof Download PDFInfo
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Abstract
The invention provides a magnetic separation sheet for wireless charging and a preparation method thereof. The method prepares the high Bs and low loss magnetic shield sheet by mixing raw materials, tabletting, presintering at low temperature, doping substances such as trace auxiliary materials and the like, spraying, granulating, pressing and forming, and then discharging glue through a tunnel kiln, sintering in a bell jar furnace and slicing. Meanwhile, the preparation method of the magnetic separation sheet for wireless charging provided by the invention can be used for preparing the magnetic separation sheet in batches so as to meet the production requirement.
Description
Technical Field
The invention relates to the technical field of wireless charging, in particular to a magnetic separation sheet for wireless charging and a preparation method thereof.
Background
As a novel charging mode which is safe, fashionable and convenient, wireless charging is more and more favored by consumers, and is rapidly developed in the fields of consumer electronic products such as mobile phones and computers.
In the working process of the wireless charging equipment, the transmitting end and the receiving end are respectively provided with a coil, the transmitting end coil is connected with a wired power supply and generates an electromagnetic signal, and the receiving end coil induces the electromagnetic signal of the transmitting end so as to generate current to charge the battery. The magnetism isolating sheet attached to the sending end can enhance the magnetic field intensity of the coil and has a high magnetic convergence effect; the magnetic shielding sheet is placed at the receiving end to prevent the metal conductor from attenuating and interfering the magnetic field, so that the metal isolation effect is achieved, the energy waste is prevented, and the charging efficiency is improved. Therefore, the performance effect of the magnetism-shielding sheet plays an important role in wireless charging.
At present, the magnetic shielding sheet is generally made of MnZn ferrite material with high saturation magnetic induction density Bs and low loss characteristic. The preparation process of the magnetic shielding sheet generally comprises the following steps: selecting materials, preparing materials, mixing, presintering, sanding, pulping, spray granulation, pulverizing, molding, sintering and grinding. The magnetic shielding sheet prepared by the process is about 15mm generally. When the magnetism isolating sheet with a large size needs to be prepared, and the central inner hole is small, such as the diameter is 50mm and the aperture of the central inner hole is 5mm, the magnetism isolating sheet prepared by the method has low Bs and high loss due to the fact that the magnetism isolating sheet with the large size cannot fully react in the sintering process, and therefore the magnetic field intensity, the convergence magnetism, the isolation metal and the like of the coil cannot be enhanced in wireless charging equipment.
Disclosure of Invention
The invention provides a magnetism isolating sheet for wireless charging and a preparation method thereof, and aims to solve the problems of low Bs and high loss of the magnetism isolating sheet when the magnetism isolating sheet with a larger size is prepared by the conventional magnetism isolating sheet preparation method.
The invention provides a preparation method of a magnetic separation sheet for wireless charging, which comprises the following steps:
s01: the raw materials for preparing the magnetic shielding sheet are uniformly mixed according to the proportion and then are tabletted to obtain the raw material sheet.
Because the raw materials for preparing the magnetism isolating sheet are uncertain and the proportion is uncertain, the raw materials are mixed according to the preset raw material components and the raw material proportion to form uniform mixed raw materials before the magnetism isolating sheet is prepared by the preparation method of the magnetism isolating sheet for wireless charging provided by the application.
In the present application, Fe is preferably used as the raw material2O3、Mn3O4And ZnO in a mass ratio of Fe2O369.5％、Mn3O423% and ZnO7.5%. In addition, the raw material is preferably Fe2O3MnO and ZnO in a mass ratio of Fe2O365-73% of a zinc oxide, 14-26% of MnO and 3-16% of ZnO. In order to ensure that the prepared magnetic shielding sheet has higher Bs and lower loss, the purity of each component in the raw material is as low as 99.3%.
And tabletting the uniformly proportioned mixed raw materials by a tabletting machine to form a flaky raw material tablet. After the powdery mixed raw material is pressed into the flaky raw material sheet, the situations that the powdery mixed raw material is bonded and difficult to flow during the presintering in the rotary kiln can be avoided, and the large-batch industrial production is further facilitated.
S02: pre-sintering the raw material sheet at the temperature of 950 +/-5 ℃ until the tap density of the pre-sintered raw material sheet is 1.3-1.5 g/cm3。
In order to improve the compactibility of the powder, reduce molding shrinkage and deformation, and cause solid-phase reaction between the raw materials, i.e., the anisotropic permanent magnet becomes ferrite entirely or the soft magnet becomes ferrite partially, the raw material pieces need to be pre-baked in a rotary kiln. Meanwhile, Zn is easy to volatilize and expand at the temperature of 700-900 ℃, so that abnormal expansion can be eliminated in the process of converting the raw material sheet into the ferrite by pre-sintering, and the performance of the magnetic separation sheet is improved.
If the pre-sintering temperature is too low, the solid-phase reaction speed among the components is slow, which is not beneficial to production. If the pre-sintering temperature is too high, solid-phase reaction occurs among the components, oxygen loss and metal volatilization are easily caused, and the subsequent sand grinding is influenced because the particles of reaction products are large. Therefore, in the application, the pre-sintering temperature is 950 +/-5 ℃, the pre-sintering time is 40min, and the tap density of the pre-sintered raw material piece is 1.3-1.5 g/cm3. More preferably, the raw material sheet is calcined at 950 ℃.
S03: and crushing the raw material pieces subjected to pre-sintering to form crushed materials.
S04: mixing the crushed materials, auxiliary materials, polyvinyl alcohol glue and deionized water to form a mixture, and sanding the mixture until the granularity is 0.8-1.5 mu m; the auxiliary materials comprise calcium carbonate, vanadium pentoxide, niobium pentoxide, elementary substance iron and cobaltous oxide.
Mixing the crushed materials, auxiliary materials, polyvinyl alcohol glue and deionized water to form a mixture. In the application, the auxiliary materials comprise calcium carbonate, vanadium pentoxide, niobium pentoxide, elementary substance iron and cobaltous oxide, and the mass of each auxiliary material is 0.3 per thousand, 0.2 per thousand, 1 per thousand and 3.5 per thousand of the total mass of the crushed materials respectively. Namely, the mass of calcium carbonate is 0.3 per mill of the mass of the crushed material, the mass of vanadium pentoxide is 0.3 per mill of the mass of the crushed material, the mass of niobium pentoxide is 0.2 per mill of the mass of the crushed material, the mass of elementary substance iron is 1 per mill of the mass of the crushed material, and the mass of cobaltous oxide is 3.5 per mill of the mass of the crushed material. Further, when the prepared magnetism isolating sheet is soft magnetic, the mass of each auxiliary material cannot exceed 3 per mill of the mass of the crushed materials.
In addition, polyvinyl alcohol glue adopts the polyvinyl alcohol glue that is commonly used in the preparation of current magnetism isolating sheet, and this application does not prescribe a limit to this. In the application, the mass ratio of the polyvinyl alcohol glue to the crushed materials is (0.5-1.5): 100, and the mass ratio of the deionized water to the crushed materials is 1: 2.
The purpose of doping the mixed auxiliary materials, the polyvinyl alcohol glue and the deionized water in the crushed materials is to ensure that the product has certain characteristics. For example, calcium carbonate can increase the resistivity of the magnetic separator sheet and improve the high-frequency characteristics thereof; the cobaltous oxide can improve the temperature characteristic of the magnetism isolating sheet; the simple substance iron can prevent iron deficiency reaction; vanadium pentoxide and niobium pentoxide can reduce the loss of the magnetism isolating sheet and improve the Bs of the magnetism isolating sheet.
The mixture is sanded in a sand mill to promote solid phase reaction and densification and grain growth of the magnetic shielding sheet. Meanwhile, the activity can be increased through sanding refinement so as to facilitate solid-phase reaction in the sintering process. In the sanding process of the mixture, the sanding rotating speed is 2000r/min, and the sanding time is 30-180 min until the mixture is sanded to the granularity of 0.8-1.5 mu m.
S05: and carrying out spray granulation on the mixed material after sanding to obtain spherical particles.
Carrying out spray granulation on the sanded mixture by using a spray tower to obtain spherical particles, wherein the granularity of the spherical particles is required to be 60-180 meshes, the water content is less than 1%, and the apparent density is 1.3-1.45 g/cm3The flow angle is 25-30 degrees. At the moment, the prepared spherical particles are beneficial to pressing into the magnetic column, and the pressed magnetic column is more beneficial to the later-period sufficient water drainage and glue discharge.
S06: pressing the spherical particles into magnetic columns; the green compact density of the magnetic column is 3.0 +/-0.10 g/cm3。
Pressing the spherical particles into magnetic columns with the outer diameter of 50mm and the diameter of more than 20 mm. In the process of pressing and forming the magnetic column, the compact density of the magnetic column is required to be 3.0 +/-0.10 g/cm3. When the compact density of the magnetic column is 3.0 +/-0.10 g/cm3In the process, the distance between the components in the magnetic column is beneficial to the drainage and glue discharge in the tunnel furnace, and is more beneficial to the chemical reaction process and the physical change process in the sintering process.
S07: and the magnetic columns slowly and fully drain water and glue in the tunnel furnace.
During high-temperature sintering, if polyvinyl alcohol glue and deionized water are still left in the magnetic column, magnetic column cracks are easy to appear in the high-temperature sintering process, and solid-phase reaction and a magnetic circuit are affected. Therefore, after the mixture after sanding is pressed into a magnetic column, the magnetic column is placed in a tunnel furnace, and polyvinyl alcohol glue and deionized water in the magnetic column are slowly and fully discharged in a pseudo-burning mode. In order to prevent the magnetic column from generating solid phase reaction in the process of draining water and removing glue, the highest temperature of the tunnel furnace is 600 ℃. Generally, the draining and glue discharging process of the magnetic column is about 6 hours.
S08: and sintering the magnetic column after water drainage and glue removal under the conditions that the nitrogen pressure is 0.2-0.9 Mpa, the compressed air pressure is 0.2-0.8 Mpa, the highest heat preservation temperature is 1330-1450 ℃, the highest temperature rise speed is 4 ℃/min and the maximum temperature drop speed is 4.5 ℃/min to obtain the sintered magnetic column.
Sintering is the whole process of producing ferrite through sintering (densification) and grain growth in a state of lower than the melting temperature of the material. Therefore, the sintering process is a chemical process and a physical process of the material, wherein the chemical process comprises oxidation reduction, solid solution generation and decomposition; physical processes include shrinkage, poly-crystalline growth, and phase changes. Generally, the smaller the particle size of the material is, the larger the surface energy of the material is, the larger the sintering power is, the faster the reaction speed is, and the lower the sintering temperature is, so that the particle size of the material can be reduced as much as possible by sanding refining before compression molding of the magnetic column, and the sintering temperature is lower.
In addition, because the sintering process is a chemical process and a physical process of the materials, in order to prevent the magnetic column from reacting with other materials in the sintering process, the sintering atmosphere of the magnetic column is nitrogen.
The specific process of sintering comprises three stages of initial stage, middle stage and final stage. At the initial stage of sintering, the particles are in contact with each other, and the pores are dispersed and penetrated. With the rise of temperature, the porosity is continuously reduced, the shrinkage is continuously increased, and the density is continuously increased. In the middle stage of sintering, along with the increase of temperature, interfaces among all particles are gradually combined, pores are gradually closed, the porosity is rapidly reduced, and the shrinkage is remarkably increased. At the end of sintering, the temperature is further increased, the closed porosity is reduced and the density is significantly increased. If the temperature is further increased, the pressure in the closed pores increases sharply, and it is difficult to have shrinkage again, or even become large, so that various properties of the product are deteriorated. After the temperature is kept at the highest temperature for a period of time, the temperature is reduced to take out the sintered magnetic column. In the process of temperature reduction, the temperature reduction speed needs to be strictly controlled to prevent the sintered magnetic columns from cracking.
In conclusion, in order to prepare the low-loss high-Bs magnetic shielding sheet, the atmosphere, pressure, maximum heat preservation temperature, maximum temperature rise speed and maximum temperature drop speed of the sintering process should be strictly controlled. In the application, the magnetic column is sintered in a bell jar furnace under the conditions that the nitrogen pressure is 0.2-0.9 Mpa, the compressed air pressure is 0.2-0.8 Mpa, the highest heat preservation temperature is 1330-1450 ℃, the highest temperature rise speed is 4 ℃/min and the maximum temperature fall speed is 4.5 ℃/min, so that the sintered magnetic column is obtained.
S09: and cutting the sintered magnetic column to obtain the magnetic separation sheet.
And performing linear cutting on the prepared sintered magnetic column by using diamond to obtain the magnetic separation sheet with the required thickness.
The invention also provides a magnetic separation sheet for wireless charging, which is prepared by adopting the method.
The technical scheme provided by the embodiment of the invention can have the following beneficial effects:
the invention provides a magnetic separation sheet for wireless charging and a preparation method thereof. The preparation method comprises the following steps: uniformly mixing the raw materials for preparing the magnetic separation sheet according to the proportion, and tabletting to obtain raw material sheets; pre-sintering the raw material sheet at the temperature of 950 +/-5 ℃ until the tap density of the pre-sintered raw material sheet is 1.3-1.5 g/cm3(ii) a Crushing the raw material pieces subjected to pre-sintering to form crushed materials; mixing the crushed materials, auxiliary materials, polyvinyl alcohol glue and deionized water to form a mixture, and sanding the mixture until the granularity is 0.8-1.5 mu m; carrying out spray granulation on the mixed material after sanding to obtain spherical particles; pressing the spherical particles into magnetic columns; the green density of the magnetic column is 3.0 +/-0.10 g/cm 3; the magnetic columns slowly and fully drain water and glue in the tunnel furnace; after draining water and removing glue, the magnetic column is placed under the conditions that the pressure of nitrogen is 0.2-0.9 Mpa, the pressure of compressed air is 0.2-0.8 Mpa,Sintering under the conditions that the highest heat preservation temperature is 1330-1450 ℃, the highest temperature rise speed is 4 ℃/min and the maximum temperature drop speed is 4.5 ℃/min to obtain a sintered magnetic column; and cutting the sintered magnetic column to obtain the magnetic separation sheet. The method prepares the high Bs and low loss magnetic shield sheet by mixing raw materials, tabletting, presintering at low temperature, doping substances such as trace auxiliary materials and the like, spraying, granulating, pressing and forming, and then discharging glue through a tunnel kiln, sintering in a bell jar furnace and slicing. Meanwhile, the preparation method of the magnetic separation sheet for wireless charging provided by the invention can be used for preparing the magnetic separation sheet in batches so as to meet the production requirement.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
Drawings
In order to more clearly explain the technical solution of the present application, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious to those skilled in the art that other drawings can be obtained according to the drawings without any creative effort.
Fig. 1 is a schematic flow chart of a method for manufacturing a magnetic separator for wireless charging according to an embodiment of the present invention.
Detailed Description
Referring to fig. 1, fig. 1 is a schematic flow chart illustrating a method for manufacturing a magnetic separator for wireless charging according to an embodiment of the present application. The following description of the embodiments is based on fig. 1.
Example 1
The embodiment of the application provides a preparation method of a magnetic separation sheet for wireless charging, which comprises the following steps:
s101: the raw materials for preparing the magnetic shielding sheet are Fe according to the mass ratio2O369.5％、Mn3O4And (3) uniformly mixing 23% and ZnO7.5%, and tabletting to obtain a raw material tablet.
S102: pre-sintering the raw material piece at 950 ℃ until the tap density of the pre-sintered raw material piece is 1.3g/cm3。
S103: and crushing the raw material pieces subjected to pre-sintering to form crushed materials.
S104: mixing the crushed materials, auxiliary materials, polyvinyl alcohol glue and deionized water to form a mixture. The rotational speed when the mixture is sanded is 2000r/min, the sanding time is 180min, and the mixture is sanded to the granularity of 0.8 mu m. The auxiliary materials comprise calcium carbonate, vanadium pentoxide, niobium pentoxide, simple substance iron and cobaltous oxide, wherein the mass of the calcium carbonate, the vanadium pentoxide, the niobium pentoxide, the simple substance iron and the cobaltous oxide is respectively 0.3 per mill, 0.2 per mill, 1 per mill and 3.5 per mill of the total mass of the crushed materials. The mass ratio of the crushed materials to the polyvinyl alcohol glue is 100: 1.5. The mass ratio of the deionized water to the crushed materials is 1: 2.
S105: and carrying out spray granulation on the mixed material after sanding to obtain spherical particles. The spherical particles have a particle size of 60 meshes, a water content of less than 1% and a bulk density of 1.3g/cm3The flow angle is 25 °.
S106: pressing the spherical particles into magnetic columns; the green compact density of the magnetic column is 3.0g/cm3。
S107: and the magnetic column slowly and fully drains water and binder in a tunnel furnace at the temperature of 600 ℃.
S108: and sintering the magnetic column after water and glue drainage under the conditions that the nitrogen pressure is 0.2Mpa, the compressed air pressure is 0.2Mpa, the highest heat preservation temperature is 1330 ℃, the temperature rise speed is 4 ℃/min and the temperature reduction speed is 4.5 ℃/min to obtain the sintered magnetic column.
S109: and cutting the sintered magnetic column to obtain the magnetic separation sheet.
The embodiment of the application provides a magnetic separation sheet for wireless charging, which is prepared by adopting the method.
Example 2
The embodiment of the application provides a preparation method of a magnetic separation sheet for wireless charging, which comprises the following steps:
s201: the raw materials for preparing the magnetic shielding sheet are Fe according to the mass ratio2O369.5％、Mn3O4And (3) uniformly mixing 23% of the raw material and ZnO7.5% of the raw material, and tabletting to obtain the raw material tablet.
S202: mixing the raw materialPresintering the tablets at 948 ℃ until the tap density of the presintered raw material tablets is 1.5g/cm3。
S203: and crushing the raw material pieces subjected to pre-sintering to form crushed materials.
S204: mixing the crushed materials, auxiliary materials, polyvinyl alcohol glue and deionized water to form a mixture. The rotational speed when the mixture is sanded is 2000r/min, the sanding time is 120min, and the mixture is sanded to the granularity of 1.4 mu m. The auxiliary materials comprise calcium carbonate, vanadium pentoxide, niobium pentoxide, simple substance iron and cobaltous oxide, wherein the mass of the calcium carbonate, the vanadium pentoxide, the niobium pentoxide, the simple substance iron and the cobaltous oxide is respectively 0.3 per mill, 0.2 per mill, 1 per mill and 3.5 per mill of the total mass of the crushed materials. The mass ratio of the crushed materials to the polyvinyl alcohol glue is 100: 1.2. The mass ratio of the deionized water to the crushed materials is 1: 2.
S205: and carrying out spray granulation on the mixed material after sanding to obtain spherical particles. The spherical particles have a particle size of 180 meshes, a water content of less than 1% and a bulk density of 1.45g/cm3The flow angle is 30 °.
S206: pressing the spherical particles into magnetic columns; the green compact density of the magnetic column is 2.95g/cm3。
S207: and the magnetic column slowly and fully drains water and binder in a tunnel furnace at the temperature of 550 ℃.
S208: and sintering the magnetic column after water drainage and glue drainage under the conditions that the nitrogen pressure is 0.8Mpa, the compressed air pressure is 0.6Mpa, the highest heat preservation temperature is 1440 ℃, the temperature rise speed is 2.5 ℃/min and the temperature drop speed is 2 ℃/min to obtain the sintered magnetic column.
S209: and cutting the sintered magnetic column to obtain the magnetic separation sheet.
The embodiment of the application provides a magnetic separation sheet for wireless charging, which is prepared by adopting the method.
Example 3
The embodiment of the application provides a preparation method of a magnetic separation sheet for wireless charging, which comprises the following steps:
s301: the raw materials for preparing the magnetic shielding sheet are Fe according to the mass ratio2O3And mixing 65%, MnO 26% and ZnO 9% uniformly, and tabletting to obtain the raw material tablet.
S302: pre-sintering the raw material piece at 945 ℃ until the tap density of the pre-sintered raw material piece is 1.3g/cm3。
S303: and crushing the raw material pieces subjected to pre-sintering to form crushed materials.
S304: mixing the crushed materials, auxiliary materials, polyvinyl alcohol glue and deionized water to form a mixture. The rotational speed when the mixture is sanded is 2000r/min, the sanding time is 90min, and the mixture is sanded to the granularity of 1.2 mu m. The auxiliary materials comprise calcium carbonate, vanadium pentoxide, niobium pentoxide, simple substance iron and cobaltous oxide, wherein the mass of the calcium carbonate, the vanadium pentoxide, the niobium pentoxide, the simple substance iron and the cobaltous oxide is respectively 0.3 per mill, 0.2 per mill, 1 per mill and 3.5 per mill of the total mass of the crushed materials. The mass ratio of the crushed materials to the polyvinyl alcohol glue is 100: 0.8. The mass ratio of the deionized water to the crushed materials is 1: 2.
S305: and carrying out spray granulation on the mixed material after sanding to obtain spherical particles. The spherical particles have a particle size of 100 meshes, a water content of less than 1% and a bulk density of 1.4g/cm3The flow angle was 28 °.
S306: pressing the spherical particles into magnetic columns; the green compact density of the magnetic column is 3.05g/cm3。
S307: and the magnetic column slowly and fully drains water and binder in a tunnel furnace at the temperature of 500 ℃.
S308: and sintering the magnetic column after water and glue drainage under the conditions that the nitrogen pressure is 0.3Mpa, the compressed air pressure is 0.3Mpa, the maximum heat preservation temperature is 1420 ℃, the temperature rising speed is 4 ℃/min and the temperature reducing speed is 4.5 ℃/min to obtain the sintered magnetic column.
S309: and cutting the sintered magnetic column to obtain the magnetic separation sheet.
The embodiment of the application provides a magnetic separation sheet for wireless charging, which is prepared by adopting the method.
Example 4
The embodiment of the application provides a preparation method of a magnetic separation sheet for wireless charging, which comprises the following steps:
s401: the raw materials for preparing the magnetic shielding sheet are Fe according to the mass ratio2O373 percent, MnO14 percent and ZnO13 percent are evenly mixed and then tabletted to obtain a raw material tablet.
S402: pre-burning the raw material sheet at 952 ℃ until the tap density of the pre-burned raw material sheet is 1.4g/cm3。
S403: and crushing the raw material pieces subjected to pre-sintering to form crushed materials.
S404: mixing the crushed materials, auxiliary materials, polyvinyl alcohol glue and deionized water to form a mixture. The rotational speed when the mixture is sanded is 2000r/min, the sanding time is 60min, and the mixture is sanded to the granularity of 1 μm. The auxiliary materials comprise calcium carbonate, vanadium pentoxide, niobium pentoxide, simple substance iron and cobaltous oxide, wherein the mass of the calcium carbonate, the vanadium pentoxide, the niobium pentoxide, the simple substance iron and the cobaltous oxide is respectively 0.3 per mill, 0.2 per mill, 1 per mill and 3.5 per mill of the total mass of the crushed materials. The mass ratio of the crushed materials to the polyvinyl alcohol glue is 100:1. The mass ratio of the deionized water to the crushed materials is 1: 2.
S405: and carrying out spray granulation on the mixed material after sanding to obtain spherical particles. The spherical particles have a particle size of 120 meshes, a water content of less than 1% and a bulk density of 1.42g/cm3The flow angle was 28 °.
S406: pressing the spherical particles into magnetic columns; the green compact density of the magnetic column is 3.0g/cm3。
S407: and the magnetic column slowly and fully drains water and binder in a tunnel furnace at the temperature of 580 ℃.
S408: and (3) sintering the magnetic column after water and glue drainage under the conditions that the nitrogen pressure is 0.8Mpa, the compressed air pressure is 0.7Mpa, the highest heat preservation temperature is 1400 ℃, the temperature rise speed is 3.2 ℃/min and the temperature reduction speed is 4.2 ℃/min to obtain the sintered magnetic column.
S409: and cutting the sintered magnetic column to obtain the magnetic separation sheet.
The embodiment of the application provides a magnetic separation sheet for wireless charging, which is prepared by adopting the method.
Example 5
The embodiment of the application provides a preparation method of a magnetic separation sheet for wireless charging, which comprises the following steps:
s501: the raw materials for preparing the magnetic shielding sheet are Fe according to the mass ratio2O372 percent, MnO22 percent and ZnO16 percent are evenly mixed and then tabletted to obtain a raw material tablet.
S502: pre-burning the raw material sheet at 955 ℃ until the tap density of the pre-burned raw material sheet is 1.5g/cm3。
S503: and crushing the raw material pieces subjected to pre-sintering to form crushed materials.
S504: mixing the crushed materials, auxiliary materials, polyvinyl alcohol glue and deionized water to form a mixture. The rotational speed when the mixture is sanded is 2000r/min, the sanding time is 30min, and the mixture is sanded to the granularity of 1.5 mu m. The auxiliary materials comprise calcium carbonate, vanadium pentoxide, niobium pentoxide, simple substance iron and cobaltous oxide, wherein the mass of the calcium carbonate, the vanadium pentoxide, the niobium pentoxide, the simple substance iron and the cobaltous oxide is respectively 0.3 per mill, 0.2 per mill, 1 per mill and 3.5 per mill of the total mass of the crushed materials. The mass ratio of the crushed materials to the polyvinyl alcohol glue is 100: 0.5. The mass ratio of the deionized water to the crushed materials is 1: 2.
S505: and carrying out spray granulation on the mixed material after sanding to obtain spherical particles. The spherical particles have a particle size of 160 meshes, a water content of less than 1% and a bulk density of 1.3g/cm3The flow angle is 30 °.
S506: pressing the spherical particles into magnetic columns; the green compact density of the magnetic column is 2.9g/cm3。
S507: and the magnetic column slowly and fully drains water and binder in a tunnel furnace with the temperature of 560 ℃.
S508: and sintering the magnetic column after water and glue drainage under the conditions that the nitrogen pressure is 0.5Mpa, the compressed air pressure is 0.5Mpa, the highest heat preservation temperature is 1380 ℃, the temperature rise speed is 3.5 ℃/min and the temperature drop speed is 3.5 ℃/min to obtain the sintered magnetic column.
S509: and cutting the sintered magnetic column to obtain the magnetic separation sheet.
The embodiment of the application provides a magnetic separation sheet for wireless charging, which is prepared by adopting the method.
Example 6
The embodiment of the application provides a preparation method of a magnetic separation sheet for wireless charging, which comprises the following steps:
s601: the raw materials for preparing the magnetic shielding sheet are Fe according to the mass ratio2O372 percent, MnO25 percent and ZnO3 percent are evenly mixed and then tabletted to obtain a raw material tablet.
S602: pre-burning the raw material sheet at 955 ℃ until the tap density of the pre-burned raw material sheet is 1.5g/cm3。
S603: and crushing the raw material pieces subjected to pre-sintering to form crushed materials.
S604: mixing the crushed materials, auxiliary materials, polyvinyl alcohol glue and deionized water to form a mixture. The rotational speed when the mixture is sanded is 2000r/min, the sanding time is 30min, and the mixture is sanded to the granularity of 1.5 mu m. The auxiliary materials comprise calcium carbonate, vanadium pentoxide, niobium pentoxide, simple substance iron and cobaltous oxide, wherein the mass of the calcium carbonate, the vanadium pentoxide, the niobium pentoxide, the simple substance iron and the cobaltous oxide is respectively 0.3 per mill, 0.2 per mill, 1 per mill and 3.5 per mill of the total mass of the crushed materials. The mass ratio of the crushed materials to the polyvinyl alcohol glue is 100: 0.5. The mass ratio of the deionized water to the crushed materials is 1: 2.
S605: and carrying out spray granulation on the mixed material after sanding to obtain spherical particles. The spherical particles have a particle size of 160 meshes, a water content of less than 1% and a bulk density of 1.3g/cm3The flow angle is 30 °.
S606: pressing the spherical particles into magnetic columns; the green compact density of the magnetic column is 3.1g/cm3。
S607: and the magnetic column slowly and fully drains water and binder in a tunnel furnace with the temperature of 590 ℃.
S608: and sintering the magnetic column after water drainage and glue removal under the conditions that the nitrogen pressure is 0.9Mpa, the compressed air pressure is 0.8Mpa, the highest heat preservation temperature is 1450 ℃, the temperature rising speed is 3 ℃/min and the temperature falling speed is 4 ℃/min to obtain the sintered magnetic column.
S609: and cutting the sintered magnetic column to obtain the magnetic separation sheet.
The embodiment of the application provides a magnetic separation sheet for wireless charging, which is prepared by adopting the method.
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
It is to be understood that relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The invention is not limited to the precise arrangements described above and shown in the drawings, and various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.
Claims (10)
1. A preparation method of a magnetic separation sheet for wireless charging is characterized by comprising the following steps:
uniformly mixing the raw materials for preparing the magnetic separation sheet according to the proportion, and tabletting to obtain raw material sheets;
pre-sintering the raw material sheet at the temperature of 950 +/-5 ℃ until the tap density of the pre-sintered raw material sheet is 1.3-1.5 g/cm3；
Crushing the raw material pieces subjected to pre-sintering to form crushed materials;
mixing the crushed materials, auxiliary materials, polyvinyl alcohol glue and deionized water to form a mixture, and sanding the mixture until the granularity is 0.8-1.5 mu m; the auxiliary materials comprise calcium carbonate, vanadium pentoxide, niobium pentoxide, elementary substance iron and cobaltous oxide;
carrying out spray granulation on the mixed material after sanding to obtain spherical particles;
pressing the spherical particles into magnetic columns; the green compact density of the magnetic column is 3.0 +/-0.10 g/cm3；
The magnetic columns slowly and fully drain water and glue in the tunnel furnace;
sintering the magnetic column after draining and removing the glue under the conditions that the nitrogen pressure is 0.2-0.9 Mpa, the compressed air pressure is 0.2-0.8 Mpa, the highest heat preservation temperature is 1330-1450 ℃, the highest temperature rise speed is 4 ℃/min and the maximum temperature drop speed is 4.5 ℃/min to obtain a sintered magnetic column;
and cutting the sintered magnetic column to obtain the magnetic separation sheet.
2. The method according to claim 1, wherein the spherical particles have a particle size of 60 to 180 mesh, a water content of less than 1%, and a bulk density of 1.3 to 1.45g/cm3The flow angle is 25-30 degrees.
3. The method of claim 1, wherein the pre-firing temperature of the raw material sheet is 950 ℃.
4. The preparation method of claim 1, wherein the rotation speed of the mixture during sanding is 2000r/min, and the sanding time is 30-180 min.
5. The production method according to claim 1, wherein the raw material includes Fe in a mass ratio2O369.5％、Mn3O423% and ZnO7.5%.
6. The production method according to claim 1, wherein the raw material includes Fe in a mass ratio2O365-73% of a zinc oxide, 14-26% of MnO and 3-16% of ZnO.
7. The production method according to claim 1, wherein the mass of the calcium carbonate, the vanadium pentoxide, the niobium pentoxide, the elemental iron, and the cobaltous oxide is 0.3%, 0.2%, 1%, and 3.5% respectively of the total mass of the pulverized material.
8. The preparation method of the polyvinyl alcohol glue as claimed in claim 1, wherein the mass ratio of the crushed materials to the polyvinyl alcohol glue is 100 (0.5-1.5).
9. The method of claim 1, wherein the tunnel furnace has a maximum temperature of 600 ℃.
10. A magnetism-isolating sheet for wireless charging, which is prepared by the method for preparing a magnetism-isolating sheet for wireless charging according to any one of claims 1 to 9.
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