Nanocrystalline magnetic conductive sheet and preparation method thereof, and spliced magnetic shielding sheet

Abstract

To overcome the problem that existing magnetic shielding materials struggle to balance saturation magnetic induction and loss characteristics, this invention provides a nanocrystalline magnetic permeable sheet, its preparation method, and a spliced ​​magnetic shielding sheet. The nanocrystalline magnetic permeable sheet is composed of Fe. (100‑x‑y‑z‑α‑β‑γ) Co x Cu y M z Si α B β X γ Wherein, M includes one or more of Nb, V, Mo, Ta, W, Zr, Hf, Ti, Cr, Mn, Al, Sc, Y, Zn, and Sn; X includes one or more of C, Ge, P, Ga, Sb, In, and S; 0.1≤x≤10, 0.2≤y≤1.5, 1≤z≤5, 1≤α≤18, 5≤β≤15, 0≤γ≤3, and satisfies 18≤y+z+α+β+γ≤26; the saturation magnetic induction intensity B of the nanocrystalline magnetic permeable sheet is... s The permeability is 1.25~1.75 T; at a test frequency of 128kHz, the real part of the permeability μ' is 100~10000 and the imaginary part of the permeability μ” is 2~7000; at a test frequency of 360kHz, the real part of the permeability μ' is 95~5500 and the imaginary part of the permeability μ” is 2~5800.

Description

Technical Field

[0001] This invention belongs to the field of magnetic shielding materials technology, specifically relating to a nanocrystalline magnetic shielding sheet and its preparation method, as well as spliced ​​magnetic shielding sheets. Background Technology

[0002] In recent years, nanocrystalline soft magnetic alloys have been widely used in shielding applications for wireless power charging (WPC), heated tobacco products (HNB), and various high-frequency power supplies due to their relatively high saturation magnetic induction, low high-frequency loss, and high high-frequency permeability. Magnetic shielding materials are required in mobile phone wireless charging receiver modules, and nanocrystalline magnetic sheets have become the mainstream magnetic shielding material solution for mobile phone wireless charging receivers due to their excellent soft magnetic properties and ultra-thin thickness. Major brands such as Apple, Samsung, and Huawei all use nanocrystalline magnetic sheets as their magnetic shielding material. PMI's heated tobacco products use induction heating, and a shielding material is needed around the electromagnetic induction heating coil to prevent magnetic field leakage. High-frequency power supplies, such as the main transformer of an onboard charger (OBC), experience significant radiated interference that can affect the operation of other power electronic devices, also requiring additional shielding materials for protection.

[0003] In existing methods for fabricating nanocrystalline magnetic shielding sheets, typical FINEMET® type nanocrystalline materials are often used as the core magnetic conductive material. However, this material has a low saturation magnetic induction intensity of only 1.24T. Therefore, after being processed into a magnetic conductive sheet for wireless charging, it cannot achieve high-power wireless charging functions such as 30W and above within the constraints of the overall thickness. Currently, the nanocrystalline materials used in mass production have a saturation magnetic induction of only 1.24T due to their composition, which cannot meet the requirements of high-power applications. Although increasing the thickness of a single-layer nanocrystalline strip can enhance its saturation current characteristics, it will increase high-frequency losses, thereby increasing the heat generation of the entire magnetic sheet and rendering it unusable. Furthermore, increasing the thickness of a single-layer nanocrystalline strip leads to an increase in the overall thickness of the magnetic sheet, which does not conform to the customer's design requirements for thinner and lighter designs. In addition, in recent years, many domestic and foreign enterprises and research institutes have increased the Fe content in FeCuNbSiB alloys to improve the saturation magnetic induction intensity of the material itself. However, due to the reduction of the content of elements such as Nb and Si, the crystallization process is not as controllable as that of FINEMET type nanocrystals, and grain coarsening is very likely to occur, which deteriorates the loss characteristics of the alloy itself and increases the energy consumption of the magnetic shielding sheet material. Summary of the Invention

[0004] To address the problem that existing magnetic shielding materials struggle to balance saturation magnetic induction intensity and loss characteristics, this invention provides a nanocrystalline magnetic conductive sheet, its preparation method, and a spliced ​​magnetic shielding sheet.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0006] On the one hand, the present invention provides a nanocrystalline magnetic permeable sheet, the composition of which is Fe (100-x-y-z-α-β-γ) Co x Cu y M z Si α B β X γ Wherein, M includes one or more of Nb, V, Mo, Ta, W, Zr, Hf, Ti, Cr, Mn, Al, Sc, Y, Zn, and Sn, and X includes one or more of C, Ge, P, Ga, Sb, In, and S, 0.1≤x≤10, 0.2≤y≤1.5, 1≤z≤5, 1≤α≤18, 5≤β≤15, 0≤γ≤3, and satisfies 18≤y+z+α+β+γ≤26;

[0007] The saturation magnetic induction intensity B of the nanocrystalline magnetic permeable sheet s The value is 1.25~1.75 T;

[0008] The nanocrystalline magnetic permeable sheet has a real permeability μ' of 100~10000 and an imaginary permeability μ” of 2~7000 at a test frequency of 128kHz, and a real permeability μ' of 95~5500 and an imaginary permeability μ” of 2~5800 at a test frequency of 360kHz.

[0009] The nanocrystalline magnetic permeable sheet contains a Co7Fe3 phase, and the volume percentage of the Co7Fe3 phase in the nanocrystalline magnetic permeable sheet is 0.01~8%.

[0010] Optionally, 70≤100-xyz-α-β-γ≤85, 0.1≤x≤10.

[0011] Optionally, at least 50% of the volume of the nanocrystalline magnetic sheet is composed of grains with a grain size of less than 50 nm.

[0012] Optionally, the nanocrystalline magnetic sheet has a broken magnetic texture, and magnetic sheet gaps are formed along the broken magnetic texture to divide the nanocrystalline magnetic sheet into multiple unit magnetic sheets.

[0013] Optionally, the broken magnetic texture includes multiple polygonal textures, which are enclosed shapes formed by multiple cracks connecting at their ends, and the multiple polygonal textures are arranged at intervals to form a honeycomb-like pattern.

[0014] Optionally, the magnetic fracture pattern includes multiple spider web-like patterns, which are arranged at intervals on the nanocrystalline magnetic sheet. The spider web-like patterns include multiple radial cracks and multiple transverse cracks. The multiple radial cracks are arranged radially outward from the center of the spider web-like patterns, and the transverse cracks connect two adjacent radial cracks.

[0015] Furthermore, the present invention provides a method for preparing a nanocrystalline magnetically permeable thin film as described above, comprising the following steps:

[0016] The composition is Fe (100-x-y-z-α-β-γ) Co x Cu y M z Si α B β X γ The alloy is prepared into an amorphous alloy strip by single-roll rapid quenching; wherein M includes one or more of Nb, V, Mo, Ta, W, Zr, Hf, Ti, Cr, Mn, Al, Sc, Y, Zn, Sn, and X includes one or more of C, Ge, P, Ga, Sb, In, S, 0.1≤x≤10, 0.2≤y≤1.5, 1≤z≤5, 1≤α≤18, 5≤β≤15, 0≤γ≤3, and satisfies 18≤y+z+α+β+γ≤26;

[0017] Amorphous alloy strips are annealed to obtain single-layer nanocrystalline ribbons.

[0018] The nanocrystalline ribbon is stacked in multiple layers, or not, and then subjected to magnetic fragmentation treatment. The single or multiple layers of the magnetically fragmented nanocrystalline ribbon are then composited, or not, to obtain the nanocrystalline magnetic sheet.

[0019] Optionally, the annealing process can be a single annealing process or a double annealing process.

[0020] Optionally, the annealing process is a single annealing process, including the following operations:

[0021] The temperature is increased at a rate of 1~10℃ / min to 0~50℃ below the crystallization initiation temperature of the alloy strip, held at this temperature T1 for 10~60min, then increased at a rate of 0.5~3℃ / min to above the crystallization peak temperature, held at this temperature T2 for 30~240min, where T2 is 10~100℃ above the crystallization initiation temperature, and then cooled to below 200℃ before being removed from the furnace; or,

[0022] The annealing process is a two-stage annealing process, including the following operations:

[0023] The temperature is increased at a rate of 1–10 °C / min to 0–50 °C below the crystallization initiation temperature of the alloy strip, and held at this temperature (T1) for 10–60 min. Then, the temperature is increased at a rate of 0.5–3 °C / min to above the crystallization peak temperature, and held at this temperature (T2) for 30–240 min. The temperature is then decreased to below 200 °C, and the temperature is increased again at a rate of 1–8 °C / min to 0–50 °C below the crystallization initiation temperature of the alloy strip, and held at this temperature (T3) for 10–60 min. Then, the temperature is increased at a rate of 0.5–3 °C / min to above the crystallization peak temperature, and held at this temperature (T4) for 20–240 min. Finally, the temperature is decreased to below 200 °C before being removed from the furnace. The temperatures of T3 and T4 are 5–50 °C higher than those of T1 and T2, respectively.

[0024] Optionally, during the annealing process, the amorphous alloy strip is transported to the annealing equipment in a roll-to-roll manner. During annealing, tension of 1~100MPa is applied to the amorphous alloy strip along its length direction to promote the orientation of nanocrystals along the length direction and improve the magnetic anisotropy of the prepared nanocrystalline strip in the length direction.

[0025] Optionally, the outermost layer of the single-layer nanocrystalline ribbon or the multi-layer stacked nanocrystalline ribbon before magnetic crushing is protected by double-sided adhesive, with one side being double-sided adhesive and the other side being either double-sided adhesive or single-sided adhesive.

[0026] Optionally, the magnetic crushing process is carried out using a circular roller pressing method;

[0027] The surface of the roller is provided with a plurality of pits, which are spaced apart on the surface of the roller; or...

[0028] The surface of the roller is provided with a plurality of protrusions, which are spaced apart on the surface of the roller.

[0029] Furthermore, the present invention provides a spliced ​​magnetic shielding sheet, comprising multiple nanocrystalline magnetic permeable sub-sheets spliced ​​together. The nanocrystalline magnetic permeable sub-sheets are selected from the nanocrystalline magnetic permeable thin sheets described above or nanocrystalline magnetic permeable thin sheets prepared by the preparation method described above. The nanocrystalline magnetic permeable sub-sheets exhibit magnetic anisotropy. The planar direction of the nanocrystalline magnetic permeable sub-sheets has a first direction and a second direction perpendicular to the first direction. The DC relative permeability (μ) of the first direction and the second direction is... r Different values ​​result in different relative permeability (μ) of DC. r The direction with a higher magnetization value is defined as the easy magnetization direction. The easy magnetization directions of each of the nanocrystalline magnetic sub-sheets are different and are perpendicular to the radial magnetic field direction generated by the wireless charging coil of the mobile phone.

[0030] Optionally, each of the nanocrystalline magnetic conductive sub-pieces is arranged in a ring array around the center of the spliced ​​magnetic shielding sheet, and the direction perpendicular to the easy magnetization direction of each of the nanocrystalline magnetic conductive sub-pieces is arranged radially outward from the center of the spliced ​​magnetic shielding sheet.

[0031] According to the nanocrystalline magnetically permeable sheet provided by the present invention, Co is used to replace part of the Fe. Theoretically, from the perspective of atomic magnetic moment, replacing Fe with Co, which has a lower magnetic moment, will directly reduce the average atomic magnetic moment of the material, thereby leading to a decrease in saturation magnetization and saturation magnetic induction B. s While the magnetic flux density decreases, contrary to conventional understanding, the inventors discovered that through a specific annealing process, the doped Co forms a Co7Fe3 phase in the nanocrystalline magnetic permeable sheet, in addition to the α-Fe nanocrystalline phase and the Fe3Si phase. Furthermore, by controlling the volume percentage of the Co7Fe3 phase in the nanocrystalline magnetic permeable sheet to be 0.01%~8%, it is beneficial to maintain low high-frequency losses while increasing the saturation magnetic induction intensity of the nanocrystalline magnetic permeable sheet. Specifically, in this application, the saturation magnetic induction intensity B of the nanocrystalline magnetic permeable sheet... s The permeability ranges from 1.25 to 1.75 T. At a test frequency of 128 kHz, the imaginary part of permeability μ” is 2 to 7000, and at a test frequency of 360 kHz, the imaginary part of permeability μ” is 2 to 5800. The mechanism is speculated to be that the presence of the Co7Fe3 phase leads to the formation of Co-Co and Fe-Co atom pairs in the alloy. The exchange interaction between these two atom pairs is stronger than that between Fe-Fe pairs. Cobalt atoms can promote a more consistent arrangement of the magnetic moments of the surrounding iron atoms, thereby increasing the average atomic magnetic moment of each iron atom. Co simultaneously promotes the precipitation of α-Fe(Co) nanocrystalline phase, resulting in higher macroscopic saturation magnetic induction and stronger exchange interactions that stabilize magnetic order. This achieves higher saturation magnetic induction without significantly increasing the ferromagnetic element content (Fe+Co). Furthermore, because the ferromagnetic element content is not substantially increased, a higher proportion of crystal-forming and refining elements (such as Cu, M, Si, and B) are retained, ensuring nanocrystal formation, grain refinement, and the stability of the nanocrystalline structure. This reduces eddy current losses and avoids the problem of decreased nanocrystal quantity and coarse grains caused by simply increasing iron content, which would lead to increased hysteresis losses. In addition, under the Fe-Co atomic exchange interaction, the magnetostriction coefficient λ of the material is significantly reduced, and the grains are refined. The decrease in magnetostriction coefficient reduces the hysteresis loss of the material, and the refinement of grains reduces the eddy current loss. In summary, the nanocrystalline magnetic conductive sheet provided by this invention breaks through the technical bottleneck that existing nanocrystalline materials cannot simultaneously achieve high saturation magnetic induction intensity and low high-frequency loss. Through reasonable composition design and process optimization, it achieves a synergistic improvement in saturation magnetic induction intensity and loss characteristics, providing a better magnetic shielding material solution for high-power wireless charging and other application scenarios. Attached Figure Description

[0032] Figure 1 This is a flowchart of the annealing process provided by the present invention;

[0033] Figure 2 This is a photograph of the broken magnetic texture provided in the first embodiment of the present invention;

[0034] Figure 3 This is a photograph of the broken magnetic texture provided in the second embodiment of the present invention;

[0035] Figure 4 This is a schematic diagram of the shape cutting of the nanocrystalline magnetic permeable sheet provided in the third embodiment of the present invention;

[0036] Figure 5 This is a schematic diagram of the shape of the spliced ​​magnetic shielding sheet provided in the third embodiment of the present invention;

[0037] Figure 6 This is a schematic diagram of the shape cutting of the nanocrystalline magnetic permeable sheet provided in the fourth embodiment of the present invention;

[0038] Figure 7 This is a schematic diagram of the shape of the spliced ​​magnetic shielding sheet provided in the fourth embodiment of the present invention;

[0039] Figure 8 The image shown is the XRD pattern obtained in Embodiment 1 of the present invention. Detailed Implementation

[0040] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0041] In the description of this invention, the term "saturation magnetic induction intensity B" is used. s "Bs" refers to the maximum stable magnetic flux density (Bs) of a nanocrystalline soft magnetic material, which no longer increases with the increase of the applied magnetic field. The unit is Tesla (T). This parameter directly determines the material's ability to withstand high-power magnetic fields: the higher the Bs, the greater the magnetic flux the material can carry with the same thickness and volume, and the less likely it is to experience magnetic saturation.

[0042] In the description of this invention, the term "real part of permeability μ'" is a core parameter characterizing the magnetic permeability and magnetic flux conduction efficiency of soft magnetic materials under alternating magnetic fields (such as high-frequency wireless charging magnetic fields), reflecting the material's ability to guide, concentrate, and conduct magnetic fields. The higher the value of μ', the stronger the material's ability to gather and conduct magnetic field lines, the higher the magnetic shielding efficiency, and the better the coupling efficiency and energy transmission capability of the wireless charging module. A stable μ' under high-frequency conditions can ensure the stable magnetic properties of the magnetic shielding sheet within the operating frequency range, meeting the magnetic permeability and magnetic shielding requirements of scenarios such as mobile phone wireless charging and high-frequency power supply shielding.

[0043] In the description of this invention, the term "imaginary part of permeability μ" is a parameter characterizing the magnetic loss of soft magnetic materials in an alternating magnetic field. It reflects the amount of energy dissipated as heat during the magnetization and demagnetization cycles, mainly including hysteresis loss and eddy current loss. The smaller μ is, the lower the energy loss and the less heat generated when the material operates at high frequencies; conversely, an excessively large μ will lead to a significant temperature rise and increased loss in the magnetic shielding sheet.

[0044] In the description of this invention, the term "DC relative permeability (μ)" is used. r "" refers to the dimensionless parameter obtained by dividing the ratio of the internal magnetic induction intensity (B) to the external magnetic field intensity (H) of a soft magnetic material in a DC magnetic field environment by the free permeability (μ0, a constant). The formula for its calculation is:

[0045]

[0046] This parameter is a core indicator characterizing the DC magnetization capability of soft magnetic materials, directly reflecting the material's ability to guide and concentrate magnetic field lines under a constant magnetic field: the higher the μᵣ value, the easier it is for the material to be magnetized in a DC magnetic field, and the stronger the effect of converging and conducting magnetic field lines; the lower the μᵣ value, the more difficult it is to magnetize the material, and the greater the resistance to magnetic field line conduction.

[0047] This invention provides a nanocrystalline magnetic thin film for wireless charging, the composition of which is Fe. (100-x-y-z-α-β-γ) Co x Cu y M z Si α B β X γ Wherein, M includes one or more of Nb, V, Mo, Ta, W, Zr, Hf, Ti, Cr, Mn, Al, Sc, Y, Zn, and Sn, and X includes one or more of C, Ge, P, Ga, Sb, In, and S, 0.1≤x≤10, 0.2≤y≤1.5, 1≤z≤5, 1≤α≤18, 5≤β≤15, 0≤γ≤3, and satisfies 18≤y+z+α+β+γ≤26;

[0048] The saturation magnetic induction intensity B of the nanocrystalline magnetic permeable sheet s The value is 1.25~1.75 T;

[0049] The nanocrystalline magnetic permeable sheet has a real permeability μ' of 100~10000 and an imaginary permeability μ” of 2~7000 at a test frequency of 128kHz, and a real permeability μ' of 95~5500 and an imaginary permeability μ” of 2~5800 at a test frequency of 360kHz.

[0050] The nanocrystalline magnetic permeable sheet contains a Co7Fe3 phase, and the volume percentage of the Co7Fe3 phase in the nanocrystalline magnetic permeable sheet is 0.01% to 8%.

[0051] The nanocrystalline magnetically permeable sheet, through formulation design, uses Co to replace part of the Fe. Theoretically, from the perspective of atomic magnetic moment, replacing Fe with Co, which has a lower magnetic moment, will directly reduce the average atomic magnetic moment of the material, thereby leading to a decrease in saturation magnetization and saturation magnetic induction B. s While the magnetic flux density decreases, contrary to conventional understanding, the inventors discovered that through a specific annealing process, the doped Co forms a Co7Fe3 phase in the nanocrystalline magnetic permeable sheet, in addition to the α-Fe nanocrystalline phase and the Fe3Si phase. Furthermore, by controlling the volume percentage of the Co7Fe3 phase in the nanocrystalline magnetic permeable sheet to be 0.01%~8%, it is beneficial to maintain low high-frequency losses while increasing the saturation magnetic induction intensity of the nanocrystalline magnetic permeable sheet. Specifically, in this application, the saturation magnetic induction intensity B of the nanocrystalline magnetic permeable sheet... sThe permeability ranges from 1.25 to 1.75 T. At a test frequency of 128 kHz, the imaginary part of permeability μ” is 2 to 7000, and at a test frequency of 360 kHz, the imaginary part of permeability μ” is 2 to 5800. The mechanism is speculated to be that the presence of the Co7Fe3 phase leads to the formation of Co-Co and Fe-Co atom pairs in the alloy. The exchange interaction between these two atom pairs is stronger than that between Fe-Fe pairs. Cobalt atoms can promote a more consistent arrangement of the magnetic moments of the surrounding iron atoms, thereby increasing the average atomic magnetic moment of each iron atom. Co simultaneously promotes the precipitation of α-Fe(Co) nanocrystalline phase, resulting in higher macroscopic saturation magnetic induction and stronger exchange interactions that stabilize magnetic order. This achieves higher saturation magnetic induction without significantly increasing the ferromagnetic element content (Fe+Co). Furthermore, because the ferromagnetic element content is not substantially increased, a higher proportion of crystal-forming and refining elements (such as Cu, M, Si, and B) are retained, ensuring nanocrystal formation, grain refinement, and the stability of the nanocrystalline structure. This reduces eddy current losses and avoids the problem of decreased nanocrystal quantity and coarse grains caused by simply increasing iron content, which would lead to increased hysteresis losses. In addition, under the Fe-Co atomic exchange interaction, the magnetostriction coefficient λ of the material is significantly reduced, and the grains are refined. The decrease in magnetostriction coefficient reduces hysteresis loss, and grain refinement reduces eddy current loss. In summary, the nanocrystalline magnetic sheet provided by this invention significantly improves the saturation magnetic induction intensity of the material without significantly reducing amorphous forming elements and crystallization process controlling elements. This expands the applicable charging power range of the magnetic sheet, and through the coupling effect of ferromagnetic elements, the overall magnetic loss is controlled to a level lower than or comparable to that of typical nanocrystalline materials. The resulting magnetic sheet for wireless charging can increase charging power by more than 30% with the same overall thickness.

[0052] In some embodiments, the volume percentage of the Co7Fe3 phase in the nanocrystalline magnetic sheet can be tested and calculated using the following methods:

[0053] The Rietveld full-spectrum fitting method is adopted. Its principle is as follows: based on the crystal structure model, the entire XRD spectrum (rather than a single peak) is calculated, and the experimental data is fitted by the least squares method, while refining the structural parameters and phase content.

[0054] The formula is:

[0055]

[0056] Wherein, Si: scaling factor of phase i (proportional to its content).

[0057] Z: Number of chemical formula units in the unit cell

[0058] M: Chemical formula weight

[0059] V: Unit cell volume

[0060] step:

[0061] 1. Input the crystal structure file (CIF) of each phase.

[0062] 2. Set refinement parameters (peak shape, background, cell parameters, etc.).

[0063] 3. The software automatically fits the data and outputs the mass fraction of each phase.

[0064] In a preferred embodiment, 70≤100-xyz-α-β-γ≤85, 0.1≤x≤10.

[0065] A reasonable ratio of Fe and Co elements can further promote the uniform formation of the Co7Fe3 phase. While improving the saturation magnetic induction intensity of the nanocrystalline magnetic permeable sheet, it reduces the fluctuation of high-frequency loss and avoids the problem of high-frequency loss caused by excessive Co content or the inability to effectively improve the saturation magnetic induction intensity due to insufficient Co content. This makes the performance of the nanocrystalline magnetic permeable sheet more targeted, adaptable to the personalized use needs in different scenarios, and improves the compatibility and practicality of the product. At the same time, it should be noted that the selection of Co content needs to take into account the final ratio of Fe element. Specifically, when the Co content increases, the Fe element content should be reduced to avoid a significant decrease in the content of other elements.

[0066] In some embodiments, at least 50% of the volume of the nanocrystalline magnetic sheet is composed of grains with a grain size of less than 50 nm.

[0067] A sufficiently high volumetric content of refined nanocrystalline structure can significantly reduce high-frequency eddy current losses and hysteresis losses, reduce heat generation of the magnetic sheet during high-frequency operation, and prevent heat from affecting the normal operation of the equipment or damaging the magnetic sheet. At the same time, fine and uniform grains can improve the stability of the material's magnetic permeability and the uniformity of saturation magnetic induction intensity, enhance the magnetic shielding effect, prevent magnetic field leakage, and make it suitable for scenarios with high requirements for loss control and shielding performance.

[0068] In some embodiments, the nanocrystalline magnetic sheet has a broken magnetic texture, and magnetic sheet gaps are formed along the broken magnetic texture to divide the nanocrystalline magnetic sheet into multiple unit magnetic sheets.

[0069] By incorporating fragmented magnetic textures and gaps on nanocrystalline magnetic sheets, the sheets are divided into multiple unit sheets, effectively solving the problem of excessive eddy current losses during high-frequency operation. The segmentation of unit sheets shortens the eddy current path, significantly reducing eddy current losses and further minimizing heat generation. Simultaneously, it avoids the decrease in permeability caused by eddy current effects, ensuring the stability of high-frequency magnetic permeability.

[0070] like Figure 2 As shown, in the first embodiment provided by the present invention, the broken magnetic texture includes multiple polygonal textures, which are enclosed shapes formed by multiple cracks connecting at their ends, and the multiple polygonal textures are arranged at intervals to form a honeycomb-like pattern.

[0071] The honeycomb-like arrangement ensures uniform distribution of the unit magnetic sheets and consistent eddy current path lengths. Furthermore, the polygonal texture guarantees the independence of each unit magnetic sheet, preventing localized overheating caused by excessively high eddy current losses and ensuring uniform overall temperature. In addition, the honeycomb-like texture design facilitates mass production (such as roll forming), ensuring consistency and precision of the broken magnetic texture, thus improving production efficiency and product yield.

[0072] like Figure 3 As shown, in the second embodiment provided by the present invention, the broken magnetic texture includes multiple spider web-like textures, which are arranged at intervals on the nanocrystalline magnetic sheet. The spider web-like texture includes multiple radial cracks and multiple transverse cracks. The multiple radial cracks are arranged radially outward from the center of the spider web-like texture, and the transverse cracks connect two adjacent radial cracks.

[0073] Designing the magnetic fragmentation pattern as a spiderweb-like pattern containing radial and transverse cracks can minimize eddy current losses caused by magnetic field cutting and improve energy conversion efficiency; the transverse cracks connect adjacent radial cracks, further segmenting the eddy current path and enhancing the loss control effect.

[0074] In other embodiments provided by the present invention, the broken magnetic texture can also be a texture pattern capable of forming multiple unit magnetic sheets, such as a grid pattern, an irregular broken pattern, etc.

[0075] Another embodiment of the present invention provides a method for preparing a nanocrystalline magnetically permeable sheet as described above, comprising the following steps:

[0076] The composition is Fe (100-x-y-z-α-β-γ) Co x Cu y M z Si α B β X γThe alloy is prepared into an amorphous alloy strip by single-roll rapid quenching; wherein M includes one or more of Nb, V, Mo, Ta, W, Zr, Hf, Ti, Cr, Mn, Al, Sc, Y, Zn, Sn, and X includes one or more of C, Ge, P, Ga, Sb, In, S, 0.1≤x≤10, 0.2≤y≤1.5, 1≤z≤5, 1≤α≤18, 5≤β≤15, 0≤γ≤3, and satisfies 18≤y+z+α+β+γ≤26;

[0077] Amorphous alloy strips are annealed to obtain single-layer nanocrystalline ribbons.

[0078] The nanocrystalline ribbon is stacked in multiple layers, or not, and then subjected to magnetic fragmentation treatment. The single or multiple layers of the magnetically fragmented nanocrystalline ribbon are then composited, or not, to obtain the nanocrystalline magnetic sheet.

[0079] Among them, the single-roll rapid quenching method is used to quickly prepare amorphous alloy strips with excellent uniformity, laying a good foundation for subsequent nanocrystallization and ensuring the uniformity of material composition and thickness; annealing is used to precisely control the transformation of amorphous strips to nanocrystalline state, avoid grain coarsening, and ensure the stability of the magnetic properties of the material; and magnetic fragmentation treatment can adjust the eddy current loss of the magnetic sheet according to the needs, adapting to different high-frequency scenarios.

[0080] This preparation method is based on the Fe provided above. (100-x-y-z-α-β-γ) Co x Cu y M z Si α B β X γ The alloy design eliminates the need for complex equipment and processes, enabling mass production, reducing production costs, and ensuring consistent product performance. The resulting nanocrystalline magnetic sheets possess advantages such as high saturation magnetic induction intensity and low high-frequency loss, making them suitable for various scenarios including wireless charging, HNB, and high-frequency power shielding, demonstrating strong practicality.

[0081] In some embodiments, the annealing process is a single annealing process or a double annealing process.

[0082] In some embodiments, the annealing process is a single annealing process, including the following operations:

[0083] The temperature is increased at a rate of 1~10℃ / min to 0~50℃ below the crystallization initiation temperature of the alloy strip, held at this temperature T1 for 10~60min, then increased at a rate of 0.5~3℃ / min to above the crystallization peak temperature, held at this temperature T2 for 30~240min, where T2 is 10~100℃ above the crystallization initiation temperature, and then cooled to below 200℃ before being removed from the furnace; or,

[0084] The annealing process is a two-stage annealing process, including the following operations:

[0085] The temperature is increased at a rate of 1–10 °C / min to 0–50 °C below the crystallization initiation temperature of the alloy strip, and held at this temperature (T1) for 10–60 min. Then, the temperature is increased at a rate of 0.5–3 °C / min to above the crystallization peak temperature, and held at this temperature (T2) for 30–240 min. The temperature is then decreased to below 200 °C, and the temperature is increased again at a rate of 1–8 °C / min to 0–50 °C below the crystallization initiation temperature of the alloy strip, and held at this temperature (T3) for 10–60 min. Then, the temperature is increased at a rate of 0.5–3 °C / min to above the crystallization peak temperature, and held at this temperature (T4) for 20–240 min. Finally, the temperature is decreased to below 200 °C before being removed from the furnace. The temperatures of T3 and T4 are 5–50 °C higher than those of T1 and T2, respectively.

[0086] like Figure 1 As shown, in some embodiments, during the annealing process, the amorphous alloy strip is transported to the annealing equipment in a roll-to-roll manner. During annealing, tension of 1~100MPa is applied to the amorphous alloy strip along its length direction to promote the orientation of nanocrystals along the width direction and improve the magnetic anisotropy of the prepared nanocrystalline strip in the width direction.

[0087] The roll-to-roll method is suitable for continuous batch production, which greatly improves the efficiency of the annealing process, reduces labor costs, and ensures the uniformity of thin strip annealing.

[0088] It should be noted that in some embodiments, such as when applied to the spliced ​​magnetic shielding sheet described below, there are certain requirements for the magnetic anisotropy of the nanocrystalline magnetic permeable sheet. In this embodiment, applying tension along the length direction can promote the orientation of the nanocrystals along the width direction, improve the magnetic anisotropy of the nanocrystalline strip in the width direction, and significantly improve the permeability and saturation magnetic induction intensity in this direction. More importantly, this preparation method uses Fe as described above. (100-x-y-z-α-β-γ) Co x Cu y M z Si α B β X γIn this alloy, Co is added to replace part of the Fe. During annealing, Co selectively dissolves and precipitates with Fe, forming a Co7Fe3 phase with uniaxial magnetic anisotropy. Compared to the polycrystalline disordered arrangement of pure Fe-based nanocrystals (without Co), the Co7Fe3 phase has a clear crystallographic preferred orientation. Its magnetic moments tend to align along specific crystal axes, naturally possessing the structural basis for magnetic anisotropy. This provides a structural carrier for the directional alignment under tension, thus forming a synergistic effect with the tension. This causes the distorted lattice to recover and recrystallize perpendicular to the tension direction (the width direction of the nanocrystal strip), leading to the directional alignment of the Co7Fe3 phase's crystal axis and the growth direction of the nanocrystal grains perpendicular to the tension direction. Compared to Fe-based nanocrystals without Co, the lattice distortion introduced by Co can enhance the material's response sensitivity to external tension. Under relatively small tension, the grains and the Co7Fe3 phase can be oriented, avoiding strip breakage due to excessive tension. At the same time, the oriented grains and phase structure are more stable, thereby strengthening the orientation consistency of the magnetic moment along the tension direction and improving magnetic anisotropy. This makes it suitable for fields with high requirements for magnetic anisotropy of nanocrystalline magnetic sheets.

[0089] In some embodiments, the width of the amorphous alloy strip is 10~215mm and the thickness is 10~30μm.

[0090] In some embodiments, the outermost layer of the single-layer nanocrystalline ribbon or the multi-layer stacked nanocrystalline ribbon before magnetic fragmentation is protected by double-sided adhesive, with one side being double-sided adhesive and the other side being either double-sided adhesive or single-sided adhesive.

[0091] By applying adhesive to both sides for protection, the nanocrystalline ribbon undergoes a subsequent magnetic fragmentation process. The surface forms a cracked pattern, and both sides are protected and fixed by adhesive films. This prevents small fragments from shifting, promoting a uniform crack pattern, and also reduces the likelihood of peeling or protrusion, thus preventing defects in appearance or performance. Subsequently, the magnetically fragmented nanocrystalline sheets are laminated in multiple layers. During the lamination process, the magnetically fragmented nanocrystalline ribbon is protected by adhesive films on both sides, further reducing the chance of fragment peeling and protrusion during lamination. This significantly ensures the appearance and performance yield of the multi-layer laminated nanocrystalline magnetic sheets.

[0092] In addition, the gaps in the nanocrystalline ribbon after the magnetic crushing treatment of the present invention do not need to be filled with an adhesive layer, or only a small amount of colloid is used for filling. After double-sided adhesive coating for protection, the magnetic crushing treatment is carried out. The surface of the nanocrystalline ribbon forms cracks and both sides are protected and fixed by adhesive film. On the one hand, small fragments are not easy to move, which is conducive to generating uniform crack patterns. On the other hand, it is not easy to peel off or protrude, thus preventing poor appearance or performance.

[0093] In some embodiments, the number of layers in the multilayer stack is 2 to 18, and adjacent nanocrystalline ribbon layers are bonded and fixed together with double-sided adhesive. By stacking an appropriate number of layers, a good magnetic fragmentation structure can be ensured while saving the number of double-sided adhesive protection layers and reducing the overall thickness of the magnetically conductive sheet.

[0094] In some embodiments, the magnetic crushing process is carried out by a circular roller pressing method.

[0095] In some embodiments, it is suitable for forming such Figure 2 The magnetic texture shown is provided with multiple pits on the surface of the roller, and the multiple pits are spaced apart on the surface of the roller.

[0096] In some embodiments, it is suitable for forming such Figure 3 The magnetic texture shown is provided with multiple protrusions on the surface of the roller, and the multiple protrusions are spaced apart on the surface of the roller.

[0097] In other embodiments, to form other magnetic crushing patterns, other magnetic crushing structures may be provided on the surface of the roller, such as providing transverse or longitudinal blades; or magnetic crushing may be performed without using a roller, using a flat plate for crushing, and at the same time, providing corresponding magnetic crushing structures on the flat plate.

[0098] Furthermore, the present invention provides a spliced ​​magnetic shielding sheet, comprising multiple nanocrystalline magnetic permeable sub-sheets spliced ​​together. The nanocrystalline magnetic permeable sub-sheets are selected from the nanocrystalline magnetic permeable thin sheets described above or nanocrystalline magnetic permeable thin sheets prepared by the preparation method described above. The nanocrystalline magnetic permeable sub-sheets exhibit magnetic anisotropy. The planar direction of the nanocrystalline magnetic permeable sub-sheets has a first direction and a second direction perpendicular to the first direction. The DC relative permeability (μ) of the first direction and the second direction is... r Different values ​​result in different relative permeability (μ) of DC. r The direction with a higher magnetization value is defined as the easy magnetization direction. The easy magnetization directions of each of the nanocrystalline magnetic sub-sheets are different and are perpendicular to the radial magnetic field direction generated by the wireless charging coil of the mobile phone.

[0099] The spliced ​​magnetic shielding sheet, through the splicing design of multiple nanocrystalline magnetic permeable sub-sheets with magnetic anisotropy, precisely adapts to the radial magnetic field generated by the wireless charging coil of a mobile phone. Compared with traditional single-structure magnetic shielding sheets, it achieves a dual breakthrough in magnetic performance and application adaptability: First, the nanocrystalline magnetic permeable sub-sheets possess clear magnetic anisotropy, with the DC relative permeability (μ) in the first and second directions within the plane being significantly different. rThere are significant differences. By arranging the sub-pieces so that the easy magnetization direction of each sub-piece is perpendicular to the radial magnetic field direction of the coil, compared with a single magnetic shielding sheet, the spliced ​​magnetic shielding sheet provided by this invention can make the magnetic flux conduction in the magnetic shielding sheet smoother, effectively reduce magnetic field reflection and high-frequency loss, greatly improve magnetic conduction efficiency, and avoid interference from magnetic field leakage of precision electronic components inside the mobile phone. Secondly, the sub-pieces are made of nanocrystalline magnetic permeable sheets prepared by the optimized composition and process of this application, which have both high saturation magnetic induction intensity of 1.25~1.75T and low high-frequency loss (the imaginary part of permeability μ” is 2~7000 at the test frequency of 128kHz and 2~5800 at the test frequency of 360kHz). It can meet the magnetic shielding requirements of high-power wireless charging without increasing the thickness of the magnetic sheet, ensuring charging safety and equipment lifespan.

[0100] In some embodiments, each of the nanocrystalline magnetic conductive sub-sheets is arranged in a ring array around the center of the spliced ​​magnetic shielding sheet, and the direction perpendicular to the easy magnetization direction of each of the nanocrystalline magnetic conductive sub-sheets is arranged radially outward from the center of the spliced ​​magnetic shielding sheet.

[0101] The radially arranged easy magnetization directions perfectly align with the radial magnetic field generated by the wireless charging coil of the mobile phone. This fully utilizes the advantageous magnetic conduction direction of the nanocrystalline magnetic subsheets, resulting in a shorter magnetic field conduction path and lower resistance within the magnetic shielding sheet. This minimizes magnetic field loss, further improving magnetic shielding efficiency while reducing overall losses. The annular distribution of easy magnetization directions ensures uniform permeability across all areas of the magnetic shielding sheet, guaranteeing uniform conduction of the magnetic flux generated by the coil throughout the entire shielding area. This avoids fluctuations in charging efficiency caused by localized differences in magnetic properties, resulting in a more stable high-power charging process.

[0102] like Figure 4 The diagram shown is a schematic representation of the shape cutting of the nanocrystalline magnetic permeable sheet provided in the third embodiment of the present invention. It yields four isosceles triangles with 90° vertices. Correspondingly, the easy magnetization direction of the nanocrystalline magnetic permeable sheet is perpendicular to the centerline of the isosceles triangles. Figure 4 The cut nanocrystalline magnetic permeable sheets are spliced ​​together, with the apex corners of each nanocrystalline magnetic permeable sheet joined together to obtain, as shown in the figure. Figure 5 The square-shaped spliced ​​magnetic shielding sheet is shown. In this case, the easy magnetization direction of the nanocrystalline magnetic conductive sheet is set around the center of the spliced ​​magnetic shielding sheet, and the direction perpendicular to the easy magnetization direction radiates outward from its apex point.

[0103] like Figure 6 The diagram shown is a schematic of the shape cutting of the nanocrystalline magnetic permeable sheet provided in the fourth embodiment of the present invention, resulting in six sectors with 60° apex angles. Correspondingly, the easy magnetization direction of the nanocrystalline magnetic permeable sub-sheet is perpendicular to the direction of the bisector along the apex angle. Figure 6The cut nanocrystalline magnetic permeable sheets are spliced ​​together, with the apex corners of each nanocrystalline magnetic permeable sheet joined together to obtain, as shown in the figure. Figure 7 The circular spliced ​​magnetic shielding sheet shown has the easy magnetization direction of the nanocrystalline magnetic sub-sheet arranged around the center of the spliced ​​magnetic shielding sheet, and the direction perpendicular to the easy magnetization direction radiates outward from its apex point.

[0104] The present invention will be further illustrated by the following examples.

[0105] Example 1

[0106] This embodiment illustrates the nanocrystalline magnetic thin film for wireless charging and its preparation method disclosed in this invention, including the following steps:

[0107] Fe was prepared by single-roll rapid quenching method. bal. Co3Cu 0.8 Nb 2.9 Si 11.5 The B8 strip, with a width of 65 mm and a thickness of 17 μm, initially exhibited a completely amorphous microstructure. The strip was divided into approximately 1 kg rolls and placed in an inert atmosphere-protected annealing furnace for crystallization annealing. The specific annealing process was as follows: the temperature was increased to 460 °C at a rate of 5 °C / min and held for 30 min; then increased to 560 °C at a rate of 2 °C / min and held for 90 min; finally, the temperature was lowered to 200 °C and removed from the furnace. The annealing temperature was 560 °C, and the annealing time was 90 min. Testing revealed that its microstructure was a two-phase structure composed of nanoscale crystalline phases and amorphous residual phases, with the nanoscale crystalline phase accounting for over 50% of the volume and a grain size of approximately 13.9 nm. X-ray diffraction analysis of the nanocrystalline strip yielded the following XRD pattern: Figure 8 As shown, phase analysis revealed the presence of Co7Fe3 and Fe3Si phases.

[0108] The annealed strip is then coated with a double-sided acrylic resin adhesive with a PET base layer, and the film thickness is 3μm. The coated magnetic sheet is then subjected to magnetic crushing treatment using a magnetic crushing roller. The crushed double-layer nanocrystalline strip is then laminated in two layers to obtain the four-layer nanocrystalline magnetic sheet for high-power wireless charging.

[0109] Example 2

[0110] This embodiment illustrates the nanocrystalline magnetic thin film for wireless charging and its preparation method disclosed in this invention, including the following steps:

[0111] Fe was prepared by single-roll rapid quenching method. bal. Co1Cu1Nb3Si 15.5The B7 strip, with a width of 65 mm and a thickness of 17 μm, initially exhibited a completely amorphous microstructure. The strip was divided into approximately 1 kg rolls and placed in an inert atmosphere-protected annealing furnace for crystallization annealing. The specific annealing process was as follows: the temperature was increased to 460 °C at a rate of 6 °C / min and held for 30 min; then increased to 560 °C at a rate of 1.5 °C / min and held for 90 min; finally, the temperature was lowered to 200 °C in the furnace before removal from the furnace. The annealing temperature was 560 °C, and the annealing time was 90 min. Testing revealed that its microstructure was a two-phase structure composed of nanoscale crystalline phases and amorphous residual phases, with the nanoscale crystalline phase accounting for over 50% of the volume and a grain size of approximately 12.6 nm.

[0112] The annealed strip is then coated with a double-sided acrylic resin adhesive with a PET base layer, and the film thickness is 3μm. The coated magnetic sheet is then subjected to magnetic crushing treatment using a magnetic crushing roller. The crushed double-layer nanocrystalline strip is then laminated in two layers to obtain the four-layer nanocrystalline magnetic sheet for high-power wireless charging.

[0113] Example 3

[0114] This embodiment illustrates the nanocrystalline magnetic thin film for wireless charging and its preparation method disclosed in this invention, including the following steps:

[0115] Fe was prepared by single-roll rapid quenching method. bal. Co3Cu 0.8 Nb 2.1 Si 11.5 The B9 strip, with a width of 65 mm and a thickness of 17 μm, initially exhibited a completely amorphous microstructure. The strip was divided into approximately 1 kg rolls and placed in an inert atmosphere-protected annealing furnace for crystallization annealing. The specific annealing process was as follows: the temperature was increased to 460 °C at a rate of 5 °C / min and held for 30 min; then increased to 550 °C at a rate of 1 °C / min and held for 90 min; finally, the temperature was lowered to 200 °C in the furnace before removal from the furnace. The annealing temperature was 550 °C, and the annealing time was 90 min. Testing revealed that its microstructure was a two-phase structure composed of nanoscale crystalline phases and amorphous residual phases, with the nanoscale crystalline phase accounting for over 50% of the volume and a grain size of approximately 14.0 nm.

[0116] The annealed strip is then coated with a double-sided acrylic resin adhesive with a PET base layer, and the film thickness is 3μm. The coated magnetic sheet is then subjected to magnetic crushing treatment using a magnetic crushing roller. The crushed double-layer nanocrystalline strip is then laminated in two layers to obtain the four-layer nanocrystalline magnetic sheet for high-power wireless charging.

[0117] Example 4

[0118] This embodiment illustrates the nanocrystalline magnetic thin film for wireless charging and its preparation method disclosed in this invention, including the following steps:

[0119] Fe was prepared by single-roll rapid quenching method. bal. Co2Cu 0.8 Nb 2.2 Si 11 The B7 strip, with a width of 65 mm and a thickness of 17 μm, initially exhibits a completely amorphous microstructure. The strip is divided into small rolls of approximately 1 kg each and placed in an inert atmosphere-protected annealing furnace for crystallization annealing. The specific annealing process is as follows: The temperature is increased to 460°C at a rate of 5°C / min and held for 30 min; then increased to 550°C at a rate of 3°C / min and held for 90 min; finally, the temperature is lowered to 200°C in the furnace before removal. This process is repeated twice: the strip is heated to 460°C at a rate of 5°C / min and held for 30 min; then increased to 550°C at a rate of 3°C / min and held for 30 min; finally, the temperature is lowered to 200°C in the furnace before removal. The annealing temperature is 550°C, and the annealing time is 90 min. Tests revealed that its microstructure is a two-phase structure composed of a nano-crystalline phase and an amorphous residual phase, with the nano-crystalline phase accounting for more than 50% of the volume and the grain size being approximately 15.2 nm.

[0120] The annealed strip is then coated with a double-sided acrylic resin adhesive with a PET base layer, and the film thickness is 3μm. The coated magnetic sheet is then subjected to magnetic crushing treatment using a magnetic crushing roller. The crushed double-layer nanocrystalline strip is then laminated in two layers to obtain the four-layer nanocrystalline magnetic sheet for high-power wireless charging.

[0121] Example 5

[0122] This embodiment illustrates the nanocrystalline magnetic thin film for wireless charging and its preparation method disclosed in this invention, including the following steps:

[0123] Fe was prepared by single-roll rapid quenching method. bal. Co 10 Cu 0.8 Nb 2.5 Si 11.5The B8 strip, with a width of 65 mm and a thickness of 17 μm, initially exhibited a completely amorphous microstructure. This strip was divided into approximately 1 kg rolls and placed in an inert atmosphere-protected annealing furnace for crystallization annealing at 560°C for 90 minutes. Testing revealed a dual-phase microstructure consisting of a nanoscale crystalline phase and an amorphous residual phase, with the nanoscale crystalline phase accounting for over 50% of the volume and a grain size of approximately 13.5 nm.

[0124] The annealed strip is then coated with a double-sided acrylic resin adhesive with a PET base layer, and the film thickness is 3μm. The coated magnetic sheet is then subjected to magnetic crushing treatment using a magnetic crushing roller. The crushed double-layer nanocrystalline strip is then laminated in two layers to obtain the four-layer nanocrystalline magnetic sheet for high-power wireless charging.

[0125] Comparative Example 1

[0126] This comparative example is used to illustrate the nanocrystalline magnetic thin film for wireless charging and its preparation method disclosed in this invention, including the following steps:

[0127] Fe was prepared by single-roll rapid quenching method. bal. Cu1Nb3Si 15.5 The B7 strip, with a width of 65 mm and a thickness of 17 μm, initially exhibited a completely amorphous microstructure. This strip was divided into approximately 1 kg rolls and placed in an inert atmosphere-protected annealing furnace for crystallization annealing at 560°C for 90 minutes. Testing revealed a dual-phase microstructure consisting of a nanoscale crystalline phase and an amorphous residual phase, with the nanoscale crystalline phase accounting for over 50% of the volume and a grain size of approximately 12.5 nm.

[0128] The annealed strip is then coated with a double-sided acrylic resin adhesive with a PET base layer, and the film thickness is 3μm. The coated magnetic sheet is then subjected to magnetic crushing treatment using a magnetic crushing roller. The crushed double-layer nanocrystalline strip is then laminated in two layers to obtain the four-layer nanocrystalline magnetic sheet for high-power wireless charging.

[0129] Comparative Example 2

[0130] This comparative example is used to illustrate the nanocrystalline magnetic thin film for wireless charging and its preparation method disclosed in this invention, including the following steps:

[0131] Fe was prepared by single-roll rapid quenching method. bal. Cu 0.8 Nb 2.1 Si 11.8 B 9.6The strip, with a width of 65 mm and a thickness of 17 μm, initially exhibited a completely amorphous microstructure. The strip was divided into small rolls of approximately 1 kg each and placed in an inert atmosphere-protected annealing furnace for crystallization annealing at 550℃ for 90 minutes. Testing revealed that its microstructure was a dual-phase structure composed of a nanoscale crystalline phase and an amorphous residual phase, with the nanoscale crystalline phase accounting for over 50% of the volume and a grain size of approximately 15.5 nm.

[0132] The annealed strip is then coated with a double-sided acrylic resin adhesive with a PET base layer, and the film thickness is 3μm. The coated magnetic sheet is then subjected to magnetic crushing treatment using a magnetic crushing roller. The crushed double-layer nanocrystalline strip is then laminated in two layers to obtain the four-layer nanocrystalline magnetic sheet for high-power wireless charging.

[0133] The crystallization initiation temperature and crystallization peak temperature of Examples 1-5 and Comparative Examples 1-2 are shown in Table 1:

[0134] Table 1

[0135]

[0136] Performance testing

[0137] The following performance tests were performed on the nanocrystalline magnetic permeable sheets prepared in Examples 1-5 and Comparative Examples 1-2:

[0138] Volume percentage of Co7Fe3 phase in nanocrystalline magnetic thin films: Rietveld full-spectrum fitting method was used for testing.

[0139] Saturation magnetic induction intensity B s Test: The test was conducted using a VSM (Vibrating Sample Magnetometer).

[0140] Permeability (real part μ' and imaginary part μ) test: The sample after demagnetization was stamped into a ring with an outer diameter of 19.9 mm and an inner diameter of 8.8 mm and placed in the test fixture corresponding to Keysight 4990a. The calculated L and Rs were obtained by testing.

[0141] Inductance L test: The sample composed of 4 layers of nanocrystals after magnetic fragmentation was stamped into a standard square with an outer size of 55×55mm, attached to a coil with an initial inductance of 6.2μH, and measured directly using an LCR meter.

[0142] Quality factor Q test: The sample composed of 4 layers of nanocrystals was stamped into a standard square with an outer size of 55×55mm and attached to a coil with an initial inductance of 6.2μH. The quality factor Q was calculated by measuring L and Rs (equivalent resistance) with an LCR meter. Q = ω·L / Rs.

[0143] Saturation current test: Connect an LCR meter to a bias current source and apply current while measuring L. As the current increases, L will decrease. Define the current corresponding to a 2.5% decrease in L as the saturation current Is.

[0144] The test results are entered into Table 2.

[0145] Table 2

[0146]

[0147] As can be seen from the test results in Table 2, the nanocrystalline magnetic permeable sheets prepared by this invention all formed a Co7Fe3 phase with a specific volume ratio. Compared with traditional FeCuNbSiB-based nanocrystalline materials without this phase, the saturation magnetic induction intensity was effectively improved. The improvement in saturation magnetic induction was particularly significant in some embodiments, breaking through the performance bottleneck of traditional materials. Simultaneously, the nanocrystalline magnetic permeable sheets of this invention maintained a level comparable to traditional materials in terms of the real part of high-frequency permeability, while the imaginary part of permeability did not show a significant increase. This achieved a balance between high saturation magnetic induction intensity and low high-frequency loss, solving the problem that existing materials struggle to synergistically improve these two core properties. Samples with different Co7Fe3 phase volume ratios exhibited corresponding performance variation patterns. A reasonable phase ratio can better balance saturation magnetic induction and loss characteristics, while an excessively high Co7Fe3 phase ratio leads to a decrease in saturation magnetic induction. In terms of inductance performance, the samples of this invention were basically on par with traditional materials, ensuring the basic magnetic conduction capability. The quality factor was also maintained at a good level, and the overall saturation current index was superior. The saturation current of some embodiments was significantly improved, meaning that the material can carry higher charging power and is suitable for high-power wireless charging applications. Traditional materials, if their saturation magnetism is simply increased, will be accompanied by a significant increase in high-frequency losses and a decrease in quality factor. However, the material of this invention avoids this problem by optimizing its composition and process, and achieves synergistic optimization of performance.

[0148] Example 6

[0149] This embodiment illustrates the nanocrystalline magnetic thin film for wireless charging and its preparation method disclosed in this invention, including most of the operational steps in Example 1, with the following differences:

[0150] The aforementioned amorphous strip was subjected to continuous roll-to-roll annealing. During the annealing process, a tension of 20 MPa was applied to the strip, the annealing temperature was 590 °C, and the annealing time was 30 s. Testing revealed that its microstructure was a two-phase structure composed of a nanoscale crystalline phase and an amorphous residual phase, with the nanoscale crystalline phase accounting for more than 50% of the volume and a grain size of approximately 13.6 nm.

[0151] Comparative Example 3

[0152] This comparative example is used to illustrate the nanocrystalline magnetic thin film for wireless charging and its preparation method disclosed in this invention. It includes most of the operational steps in Comparative Example 1, but the difference lies in:

[0153] The aforementioned amorphous strip was subjected to continuous roll-to-roll annealing. During the annealing process, a tension of 20 MPa was applied to the strip, the annealing temperature was 590 °C, and the annealing time was 30 s. Testing revealed that its microstructure was a two-phase structure composed of a nanoscale crystalline phase and an amorphous residual phase, with the nanoscale crystalline phase accounting for more than 50% of the volume and a grain size of approximately 12.3 nm.

[0154] Performance testing

[0155] The following performance tests were performed on the nanocrystalline magnetic permeable sheets prepared in Examples 1, 6, 1, and 3:

[0156] Magnetic anisotropy test: The material after tension roll annealing was coated with a film, resulting in a 4-layer structure. This 4-layer structure was then stamped into four quarter-circle arcs, dividing a 20×8mm ring into four equal parts. The central diameter direction of one set of arcs was aligned with the easy magnetization axis, while the other set was perpendicular to it. These four arcs were then joined together to form a complete 19.8×8.8mm ring, which was then placed in a Keysight 4990A instrument for inductance and Q-value testing. After measuring the inductance, the permeability was calculated.

[0157] The test results are entered into Table 3.

[0158] Table 3

[0159]

[0160] As shown in Table 3, the samples treated with tension roll annealing all exhibited obvious magnetic anisotropy. In this assembly scheme, the magnetic permeability μ'=1000 was achieved by setting the easy magnetization direction of the sample perpendicular to the diameter direction. The value of μ” in this state is significantly lower than that in the state where the easy magnetization direction is the same as the diameter direction, and also lower than that of the sample without an easy magnetization direction. Compared with the traditional non-magnetic anisotropic design sample, μ” was further optimized while ensuring that μ' reaches the expected value, and a better balance was achieved between magnetic permeability and magnetic loss control.

[0161] Furthermore, compared with the sample without the Co7Fe3 phase, the sample containing the Co7Fe3 phase exhibits a better μ” value when the easy magnetization direction is perpendicular to the external magnetic field under the same magnetic anisotropy control method. This indicates that the composition design of the present invention, combined with the magnetic anisotropy control process, can more effectively reduce magnetic loss while achieving the target μ’, making the high-frequency performance of the magnetic shielding material more suitable for the application requirements of wireless charging.

[0162] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A nanocrystalline magnetically permeable thin sheet, characterized in that, Its composition is Fe (100-x-y-z-α-β-γ) Co x Cu y M z Si α B β X γ Wherein, M includes one or more of Nb, V, Mo, Ta, W, Zr, Hf, Ti, Cr, Mn, Al, Sc, Y, Zn, and Sn, and X includes one or more of C, Ge, P, Ga, Sb, In, and S, 0.1≤x≤10, 0.2≤y≤1.5, 1≤z≤5, 1≤α≤18, 5≤β≤15, 0≤γ≤3, and satisfies 18≤y+z+α+β+γ≤26; The saturation magnetic induction intensity B of the nanocrystalline magnetic permeable sheet s The value is 1.25~1.75 T; The nanocrystalline magnetic permeable sheet has a real permeability μ' of 100~10000 and an imaginary permeability μ” of 2~7000 at a test frequency of 128kHz, and a real permeability μ' of 95~5500 and an imaginary permeability μ” of 2~5800 at a test frequency of 360kHz. The nanocrystalline magnetic permeable sheet contains a Co7Fe3 phase, and the volume percentage of the Co7Fe3 phase in the nanocrystalline magnetic permeable sheet is 0.01~8%.

2. The nanocrystalline magnetic permeable sheet according to claim 1, characterized in that, 70≤100-xyz-α-β-γ≤85, 0.1≤x≤10。 3. The nanocrystalline magnetic permeable sheet according to claim 1, characterized in that, At least 50% of the volume of the nanocrystalline magnetic sheet is composed of grains with a grain size of less than 50 nm.

4. The nanocrystalline magnetic permeable sheet according to claim 1, characterized in that, The nanocrystalline magnetic sheet has a broken magnetic texture, and magnetic sheet gaps are formed along the broken magnetic texture to divide the nanocrystalline magnetic sheet into multiple unit magnetic sheets.

5. The nanocrystalline magnetic permeable sheet according to claim 4, characterized in that, The broken magnetic texture includes multiple polygonal textures, which are enclosed shapes formed by the connection of multiple cracks at their ends. The multiple polygonal textures are arranged at intervals to form a honeycomb-like pattern.

6. The nanocrystalline magnetic permeable sheet according to claim 4, characterized in that, The magnetic fracture pattern includes multiple spider web-like patterns, which are arranged at intervals on the nanocrystalline magnetic sheet. The spider web-like patterns include multiple radial cracks and multiple transverse cracks. The multiple radial cracks are arranged radially outward from the center of the spider web-like patterns, and the transverse cracks connect two adjacent radial cracks.

7. A method for preparing a nanocrystalline magnetically permeable thin film according to any one of claims 1 to 6, characterized in that, The following steps are included: The composition is Fe (100-x-y-z-α-β-γ) Co x Cu y M z Si α B β X γ The alloy is prepared into an amorphous alloy strip by single-roll rapid quenching; wherein M includes one or more of Nb, V, Mo, Ta, W, Zr, Hf, Ti, Cr, Mn, Al, Sc, Y, Zn, Sn, and X includes one or more of C, Ge, P, Ga, Sb, In, S, 0.1≤x≤10, 0.2≤y≤1.5, 1≤z≤5, 1≤α≤18, 5≤β≤15, 0≤γ≤3, and satisfies 18≤y+z+α+β+γ≤26; Amorphous alloy strips are annealed to obtain single-layer nanocrystalline ribbons. The nanocrystalline ribbon is stacked in multiple layers, or not, and then subjected to magnetic fragmentation treatment. The single or multiple layers of the magnetically fragmented nanocrystalline ribbon are then composited, or not, to obtain the nanocrystalline magnetic sheet.

8. The method for preparing nanocrystalline magnetically permeable thin films according to claim 7, characterized in that, The annealing process can be a single annealing process or a double annealing process.

9. The method for preparing nanocrystalline magnetically permeable thin films according to claim 7, characterized in that, The annealing process is a single annealing process, including the following operations: The temperature is increased at a rate of 1~10℃ / min to 0~50℃ below the crystallization initiation temperature of the alloy strip, held at this temperature T1 for 10~60min, then increased at a rate of 0.5~3℃ / min to above the crystallization peak temperature, held at this temperature T2 for 30~240min, where T2 is 10~100℃ above the crystallization initiation temperature, and then cooled to below 200℃ before being removed from the furnace; or, The annealing process is a two-stage annealing process, including the following operations: The temperature is increased at a rate of 1–10 °C / min to 0–50 °C below the crystallization initiation temperature of the alloy strip, and held at this temperature (T1) for 10–60 min. Then, the temperature is increased at a rate of 0.5–3 °C / min to above the crystallization peak temperature, and held at this temperature (T2) for 30–240 min. The temperature is then decreased to below 200 °C, and the temperature is increased again at a rate of 1–8 °C / min to 0–50 °C below the crystallization initiation temperature of the alloy strip, and held at this temperature (T3) for 10–60 min. Then, the temperature is increased at a rate of 0.5–3 °C / min to above the crystallization peak temperature, and held at this temperature (T4) for 20–240 min. Finally, the temperature is decreased to below 200 °C before being removed from the furnace. The temperatures of T3 and T4 are 5–50 °C higher than those of T1 and T2, respectively.

10. The method for preparing nanocrystalline magnetically permeable thin films according to claim 7, characterized in that, During the annealing process, the amorphous alloy strip is fed into the annealing equipment in a roll-to-roll manner. During annealing, tension of 1~100MPa is applied to the amorphous alloy strip along its length direction to promote the orientation of nanocrystals along the length direction and improve the magnetic anisotropy of the prepared nanocrystalline strip in the length direction.

11. The method for preparing nanocrystalline magnetically permeable thin films according to claim 7, characterized in that, Before the magnetic fragmentation treatment, the outermost layer of the single-layer nanocrystalline ribbon or the multi-layer stacked nanocrystalline ribbon is protected by double-sided adhesive, with one side being double-sided adhesive and the other side being either double-sided adhesive or single-sided adhesive.

12. The method for preparing nanocrystalline magnetically permeable thin films according to claim 7, characterized in that, The magnetic fragmentation process is carried out using a circular roller pressing method. The surface of the roller is provided with a plurality of pits, which are spaced apart on the surface of the roller; or... The surface of the roller is provided with a plurality of protrusions, which are spaced apart on the surface of the roller.

13. A spliced ​​magnetic shielding sheet, characterized in that, The assembly comprises multiple interconnected nanocrystalline magnetic permeable sheets, wherein the nanocrystalline magnetic permeable sheets are selected from the nanocrystalline magnetic permeable sheets described in any one of claims 1 to 6 or prepared by the preparation method described in any one of claims 7 to 12, wherein the nanocrystalline magnetic permeable sheets exhibit magnetic anisotropy, and wherein the planar direction of the nanocrystalline magnetic permeable sheets contains a first direction and a second direction perpendicular to the first direction, wherein the DC relative permeability (μ) of the first direction and the second direction is... r Different values ​​result in different relative permeability (μ) of DC. r The direction with a higher magnetization value is defined as the easy magnetization direction. The easy magnetization directions of each of the nanocrystalline magnetic sub-sheets are different and are perpendicular to the radial magnetic field direction generated by the wireless charging coil of the mobile phone.

14. The spliced ​​magnetic shielding sheet according to claim 13, characterized in that, Each of the nanocrystalline magnetic conductive sub-pieces is arranged in a ring array around the center of the spliced ​​magnetic shielding sheet, and the direction perpendicular to the easy magnetization direction of each of the nanocrystalline magnetic conductive sub-pieces is arranged radially outward from the center of the spliced ​​magnetic shielding sheet.

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