Preparation method of dustproof and anti-interference soft magnetic ferrite core

Abstract

The invention relates to the field of electronic materials, and discloses a preparation method of a dustproof and anti-interference soft magnetic ferrite magnetic core, and the magnetic core comprises the following components by mass: 50-54 parts of ferric oxide; 24 to 28 parts of manganese oxide; 20 to 24 parts of zinc oxide; 0.4 to 0.6 part of niobium pentoxide; 0.1 to 0.3 part of gadolinium oxide; the surface of the magnetic core is covered with a dynamic response coating, and the coating comprises the following components in parts by mass: 7-9 parts of titanium carbide nanosheets; 75 to 85 parts of polydimethylsiloxane; the mass ratio of niobium pentoxide to gadolinium oxide is (2.5: 1)-(3.5: 1), the dynamic response coating material further comprises 6-8 parts of a mesoporous silica loaded lithium chloride compound, and the pore diameter of mesoporous silica is 4-6 nanometers. A temperature-sensitive-humidity-sensitive composite coating structure is adopted, surface dynamic deformation and conductive path self-adjustment are triggered, dust separation and charge dissipation are synchronously achieved through component cooperation, and functional failure chain reaction caused by environmental factors is blocked.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic materials, and particularly to a preparation method of a dust-proof and anti-interference soft ferrite magnetic core. Background Art

[0002] As a core component of high-frequency electronic devices, soft ferrite magnetic cores are widely used in fields such as power modules, communication base stations, and new energy vehicles. With the miniaturization of devices and the complexity of working conditions, the magnetic cores are faced with multiple challenges such as dust intrusion, temperature and humidity fluctuations, and high-frequency electromagnetic interference. Although traditional magnetic core materials have been continuously optimized in terms of basic properties such as magnetic permeability and loss, the split design of their surface protection and electromagnetic shielding functions makes it difficult to cope with the degradation of comprehensive performance in complex environments, severely restricting their application in high-reliability scenarios.

[0003] In current technologies, two types of solutions are mainly adopted for the protection of magnetic cores: one is to coat a static dust-proof layer (such as silicone resin or epoxy resin) on the surface of the magnetic core to reduce dust adhesion through physical isolation; the other is to optimize the internal electromagnetic structure of the magnetic core (such as doping rare earth elements) to improve the shielding efficiency in specific frequency bands. However, the static coating cannot respond to changes in environmental temperature and humidity, and is prone to electrostatic accumulation under high temperature and high humidity, which instead exacerbates dust adsorption; while the electromagnetic structure optimization solutions mostly focus on single-frequency band shielding and do not consider the impedance mismatch on the surface of the magnetic core caused by dust intrusion, resulting in a significant attenuation of the shielding efficiency in actual working conditions.

[0004] Existing technologies design the dust-proof and anti-interference functions in isolation, lacking a dynamic coordination mechanism. Especially in an environment with alternating temperature and humidity, dust adsorption and electromagnetic interference form a positive feedback effect - dust accumulation causes local electric field distortion, exacerbating electromagnetic leakage; while electromagnetic interference promotes the charged adsorption of dust, leading to irreversible deterioration of the electrothermal performance of the magnetic core. This design concept of functional fragmentation has become a bottleneck restricting the long-term stable operation of magnetic cores in complex working conditions. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technologies, the present invention provides a preparation method of a dust-proof and anti-interference soft ferrite magnetic core, which solves the technical problem of the synergistic degradation of performance caused by the fragmentation of the dust-proof and electromagnetic interference protection functions of existing soft ferrite magnetic cores in complex environments.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions: A dust-proof and anti-interference soft ferrite magnetic core, comprising the following components in parts by mass:

[0007] Ferric oxide: 50 - 54 parts;

[0008] Manganese oxide: 24 - 28 parts;

[0009] Zinc oxide: 20 - 24 parts;

[0010] Niobium pentoxide: 0.4 - 0.6 parts;

[0011] Gadolinium oxide: 0.1 - 0.3 parts;

[0012] The surface of the magnetic core is covered with a dynamic response coating, and the coating comprises components in the following parts by mass:

[0013] Titanium carbide nanosheets: 7 - 9 parts;

[0014] Polydimethylsiloxane: 75 - 85 parts;

[0015] N-isopropylacrylamide microgel: 4 - 6 parts.

[0016] Preferably, the mass ratio of the niobium pentoxide to the gadolinium oxide is 2.5:1 to 3.5:1.

[0017] Preferably, the lateral size of the titanium carbide nanosheets is 0.5 - 2 μm, and the sheet thickness is 1 - 5 nm.

[0018] Preferably, the dynamic response coating material further comprises 6 - 8 parts of mesoporous silica supported lithium chloride complex, wherein:

[0019] The pore diameter of the mesoporous silica is 4 - 6 nm;

[0020] The loading amount of lithium chloride is 25 - 35% of the mass of the mesoporous silica.

[0021] Preferably, the viscosity of the polydimethylsiloxane is 5000 - 8000 mPa·s, and the mass ratio of the polydimethylsiloxane to the titanium carbide nanosheets is (9:1) to (8:2).

[0022] The present invention also provides a preparation method of a dust-proof and interference-proof soft magnetic ferrite magnetic core, comprising the following steps:

[0023] Step 1, mixing ferric oxide, manganese oxide, zinc oxide, niobium pentoxide, and gadolinium oxide to form a precursor powder;

[0024] Step 2, forming a gradient doping layer on the surface of the magnetic core substrate by magnetron sputtering;

[0025] Step 3, spraying a dynamic response coating on the surface of the gradient doping layer and curing.

[0026] Preferably, the step 1 comprises the following sub-steps:

[0027] Wet ball milling: mixing each component with deionized water according to a solid-liquid ratio of 1:2 - 1:3, using zirconia grinding balls for ball milling, with a rotation speed of 280 - 320 revolutions per minute and a time of 20 - 28 hours;

[0028] Spray drying: Feed the ball-milled slurry into a spray drying tower with an inlet temperature of 180 - 220 °C, an outlet temperature of 70 - 90 °C, and an atomization pressure of 0.3 - 0.5 MPa to obtain spherical powder with a particle size of 10 - 50 microns.

[0029] Preferably, step two includes the following sub-steps:

[0030] First layer sputtering: Conduct DC sputtering on the surface of the substrate at a power of 480 - 520 W. The working gas is a mixed gas of argon and oxygen with a gas pressure of 0.4 - 0.6 Pa and a sputtering time of 55 - 65 minutes to form a dense nanocrystalline layer with a grain size of 50 - 80 nm.

[0031] Second layer sputtering: Switch to the pulsed sputtering mode with a frequency of 190 - 210 Hz, a duty cycle of 25 - 35%, the target rotates at 4 - 6 revolutions per minute, and the sputtering angle deflects dynamically synchronously by ±10 - 20° with a sputtering time of 35 - 45 minutes to form a concentration gradient distribution layer of niobium pentoxide and gadolinium oxide.

[0032] Third layer sputtering: Reduce the power to 90 - 110 W, use a pure argon environment with a gas pressure of 0.2 - 0.4 Pa and a sputtering time of 15 - 25 minutes to generate an amorphous ferrite protective layer with a thickness ≤ 1 micron.

[0033] Preferably, step two further includes the following steps:

[0034] When the target rotation speed is 4 - 5 revolutions per minute, the duty cycle of pulsed sputtering is 25 - 30%;

[0035] When the target rotation speed is 5 - 6 revolutions per minute, the duty cycle of pulsed sputtering is 30 - 35%;

[0036] The rate of dynamic deflection of the sputtering angle is 2 - 4° per second, and the deflection direction is opposite to the target rotation direction.

[0037] Preferably, step three includes the following sub-steps:

[0038] Plasma activation: Place the sputtered magnetic core in a vacuum chamber, introduce argon, and conduct plasma treatment at a power of 90 - 110 W for 4 - 6 minutes;

[0039] Asymmetric electrostatic spraying:

[0040] Spraying on the edge area: The electric field bias voltage is +4.5 - 5.5 kV, the spraying distance is 13 - 17 cm, the liquid flow rate is 0.18 - 0.22 ml / min, and it lasts for 2.5 - 3.5 minutes;

[0041] Central area spraying: Electric field bias voltage is +1.8 - 2.2 kV, spraying distance is 13 - 17 cm, liquid flow rate is 0.18 - 0.22 ml / min, lasting for 0.8 - 1.2 minutes;

[0042] UV curing: Use a UV light source with a wavelength of 360 - 370 nm, light intensity of 75 - 85 mW / cm², irradiate for 8 - 12 minutes to form a thickness gradient coating with an edge thickness of 8 - 10 μm and a center thickness of 2 - 3 μm.

[0043] The present invention provides a preparation method for a dust - proof and interference - proof soft ferrite magnetic core. It has the following beneficial effects:

[0044] 1. The present invention adopts a temperature - sensitive and humidity - sensitive composite coating structure to trigger surface dynamic deformation and self - regulation of the conductive path. The prior art relies on a static dust - proof layer, which cannot cope with the coupling effect of temperature and humidity, resulting in the superposition of dust adsorption and electrostatic interference. This solution realizes dust detachment and charge dissipation simultaneously through component synergy, blocking the chain reaction of functional failure caused by environmental factors.

[0045] 2. The gradient sputtering process and the construction of high - resistance phases at grain boundaries in the present invention form a composite electromagnetic barrier, breaking through the frequency - domain response bottleneck of traditional magnetic cores. In conventional solutions, due to the disordered arrangement of magnetic domains and grain - boundary leakage, the electromagnetic shielding efficiency drops sharply in the high - frequency band. This technology forms a wide - band interference isolation layer through a dual mechanism of permeability improvement and eddy - current suppression.

[0046] 3. The present invention constructs a micro - nano interlocking structure on the substrate surface through plasma activation, and combines chemical bonding to inhibit the penetration of water and oxygen. Traditional coatings are prone to peeling under humid and hot conditions due to weak interfacial bonding force, forming dust - adsorption gaps. This technology maintains the continuous coverage integrity of the coating through physical anchoring and chemical - bond synergy.

[0047] 4. The present invention realizes the controllability of the rigidity and flexibility of the micro - gel network through UV light - intensity regulation, solving the problem of mutual exclusion between response rate and durability. In existing processes, due to the mismatch of curing parameters, the coating is prone to cracking or response hysteresis. This solution ensures the co - existence of dust - proof and conductive functions and the ability to resist mechanical damage through dynamic cross - linking degree balance. Brief Description of the Drawings

[0048] Figure 1 It is a schematic flow chart of the method of the present invention. Detailed Embodiments

[0049] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0050] An embodiment of the present invention provides a dust-proof and anti-interference soft ferrite magnetic core, which comprises components in the following parts by mass:

[0051] Iron oxide: 50 - 54 parts;

[0052] Manganese oxide: 24 - 28 parts;

[0053] Zinc oxide: 20 - 24 parts;

[0054] Niobium pentoxide: 0.4 - 0.6 part;

[0055] Gadolinium oxide: 0.1 - 0.3 part;

[0056] The surface of the magnetic core is covered with a dynamic response coating, and the coating comprises components in the following parts by mass:

[0057] Titanium carbide nanosheets: 7 - 9 parts;

[0058] Polydimethylsiloxane: 75 - 85 parts;

[0059] N-isopropylacrylamide microgel: 4 - 6 parts.

[0060] The Fe-Mn-Zn ternary system optimizes the magnetocrystalline anisotropy through the Fe 2+ / Fe 3+ ratio, Mn 2+ suppresses the high-frequency hysteresis loss, and Zn 2+ expands the lattice spacing to reduce the eddy current loss.

[0061] Function of niobium pentoxide (Nb2O5): React with FeO during sintering to form an insulating phase NbFeO 3 , cover the grain boundaries to form a high-resistance layer (grain boundary resistivity > 1×10 8 Ω·cm), and block the high-frequency eddy current path.

[0062] Synergy of gadolinium oxide (Gd2O3): The ionic radius of Gd 3+ (0.094nm) and Fe 3+ (0.064nm) difference induces lattice distortion, refines the grain size to 50 - 80nm, suppresses the magnetic domain wall pinning effect, and improves the magnetic permeability (1200 - 1250).

[0063] If Nb2O5 is excessive (> 3.5:1), the unreacted Nb2O5 accumulates at the grain boundaries, forming a brittle phase that causes the magnetic core to break; if Gd2O3 is excessive (< 2.5:1), excessive lattice distortion causes magnetic domain chaos, and the magnetic permeability drops by more than 20%.

[0064] Synergistic optimization: This ratio ensures that the NbFeO3 insulating phase continuously covers the grain boundaries while Gd 3+The lattice distortion of is controlled within 3% - 5% to achieve the balance between magnetic permeability and mechanical strength.

[0065] Ultra-thin TiC nanosheets (thickness ≤ 5 nm) form a conductive network with a percolation threshold < 0.5 vol% in the polydimethylsiloxane (PDMS) matrix, ensuring that the coating resistivity is adjustable within the range of 10 3 -10 6 Ω·cm.

[0066] When the lateral size > 2 μm, the stacking gap of the nanosheets increases and dust is easily embedded; when < 0.5 μm, the conductive path is discontinuous and the electrostatic dissipation efficiency decreases by 40%.

[0067] The 4 - 6 nm pore diameter of mesoporous SiO2 limits the deliquescence rate of LiCl and gradually releases Cl - ions at humidity > 60% RH, forming a dynamic ion conductive path with the -Si-O- chains in PDMS and reducing the resistivity by 2 - 3 orders of magnitude.

[0068] The liquid film generated by the deliquescence of LiCl reduces the surface energy (contact angle < 30°), making it easier for dust to detach under the airflow disturbance.

[0069] When the viscosity < 5000 mPa·s, the coating has too good leveling property and cannot form a thickness gradient; when > 8000 mPa·s, the spraying atomization particles coarsen, resulting in a porosity > 15%.

[0070] When the mass ratio of PDMS:TiC > 9:1, the conductive network is incomplete; when < 8:2, the flexibility of the coating decreases by 60% and the resistance change rate after bending > 20%.

[0071] The mass ratio of niobium pentoxide to gadolinium oxide is 2.5:1 to 3.5:1.

[0072] The lateral size of the titanium carbide nanosheets is 0.5 - 2 microns and the sheet thickness is 1 - 5 nanometers.

[0073] The dynamic response coating material also includes 6 - 8 parts of mesoporous silica supported lithium chloride complex, where:

[0074] The pore diameter of the mesoporous silica is 4 - 6 nanometers;

[0075] The loading amount of lithium chloride is 25 - 35% of the mass of mesoporous silica.

[0076] The viscosity of the polydimethylsiloxane is 5000 - 8000 mPa·s, and its mass ratio with the titanium carbide nanosheets is (9:1) to (8:2).

[0077] The preparation method of a dust-proof and interference-proof soft ferrite magnetic core described below can be referred to in correspondence with a dust-proof and interference-proof soft ferrite magnetic core described above.

[0078] Please refer to the attached Figure 1 , a preparation method of a dust-proof and interference-proof soft ferrite magnetic core, comprising the following steps:

[0079] Step 1: Mix ferric oxide, manganese oxide, zinc oxide, niobium pentoxide, and gadolinium oxide to form a precursor powder;

[0080] Step 2: Form a gradient doping layer on the surface of the magnetic core substrate by magnetron sputtering;

[0081] Step 3: Spray a dynamic response coating on the surface of the gradient doping layer and cure it.

[0082] Step 1 includes the following sub-steps:

[0083] Wet ball milling: Mix each component with deionized water at a solid-liquid ratio of 1:2 - 1:3, perform ball milling with zirconia grinding balls, at a rotation speed of 280 - 320 revolutions per minute for 20 - 28 hours;

[0084] Spray drying: Feed the ball-milled slurry into a spray drying tower, with an inlet temperature of 180 - 220 °C, an outlet temperature of 70 - 90 °C, and an atomization pressure of 0.3 - 0.5 MPa to obtain spherical powder with a particle size of 10 - 50 microns.

[0085] Step 2 includes the following sub-steps:

[0086] First layer sputtering: Perform DC sputtering on the substrate surface at a power of 480 - 520 W, with a working gas being a mixed gas of argon and oxygen, at a pressure of 0.4 - 0.6 Pa for 55 - 65 minutes to form a dense nanocrystalline layer with a grain size of 50 - 80 nm;

[0087] Second layer sputtering: Switch to the pulse sputtering mode, with a frequency of 190 - 210 Hz, a duty cycle of 25 - 35%, the target rotates at 4 - 6 revolutions per minute, and the synchronous dynamic deflection sputtering angle is ±10 - 20°, for 35 - 45 minutes to form a niobium pentoxide and gadolinium oxide concentration gradient distribution layer;

[0088] Third layer sputtering: Reduce the power to 90 - 110 W, use a pure argon environment, at a pressure of 0.2 - 0.4 Pa for 15 - 25 minutes to generate an amorphous ferrite protective layer with a thickness ≤ 1 micron.

[0089] Step 2 also includes the following steps:

[0090] When the target rotation speed is 4 - 5 revolutions per minute, the duty cycle of pulse sputtering is 25 - 30%;

[0091] When the rotation speed of the target is 5 - 6 revolutions per minute, the duty cycle of pulsed sputtering is 30 - 35%;

[0092] The rate of dynamic deflection of the sputtering angle is 2 - 4° per second, and the deflection direction is opposite to the rotation direction of the target.

[0093] Step three includes the following sub - steps:

[0094] Plasma activation: Place the sputtered magnetic core in a vacuum chamber, introduce argon gas, and perform plasma treatment at a power of 90 - 110 watts for 4 - 6 minutes;

[0095] Asymmetric electrostatic spraying:

[0096] Spraying on the edge area: Electric field bias voltage +4.5 - 5.5 kV, spraying distance 13 - 17 cm, liquid flow rate 0.18 - 0.22 ml / min, for 2.5 - 3.5 minutes;

[0097] Spraying on the central area: Electric field bias voltage +1.8 - 2.2 kV, spraying distance 13 - 17 cm, liquid flow rate 0.18 - 0.22 ml / min, for 0.8 - 1.2 minutes;

[0098] UV curing: Use a UV light source with a wavelength of 360 - 370 nm, light intensity of 75 - 85 mW / cm², irradiate for 8 - 12 minutes to form a thickness - gradient coating with an edge thickness of 8 - 10 μm and a central thickness of 2 - 3 μm.

[0099] In this embodiment, after weighing ferric oxide (50 - 54 parts by mass), manganese oxide (24 - 28 parts by mass), zinc oxide (20 - 24 parts by mass), niobium pentoxide (0.4 - 0.6 parts by mass) and gadolinium oxide (0.1 - 0.3 parts by mass) according to the ratio, they are mixed with deionized water at a solid - liquid ratio of 1:2 - 1:3 to form a slurry. As an option, zirconia grinding balls are used for ball milling. The diameter gradient of the grinding balls is set to three levels of 3 mm, 5 mm, and 8 mm, and the mass ratios are 40%, 35%, and 25% respectively to balance impact crushing and grinding efficiency.

[0100] Specifically, the ball - milling rotation speed is controlled at 280 - 320 revolutions per minute, and the ball - milling time is 20 - 28 hours. When the rotation speed is lower than 280 revolutions per minute, the d90 particle size of the powder is >50 μm, and the grain size after sintering coarsens to more than 150 nm; while when the rotation speed is higher than 320 revolutions per minute, over - refinement of the powder (d90 < 10 μm) will lead to a 15% - 20% increase in the secondary agglomeration rate of particles during the subsequent spray - drying process. In a possible implementation, a polyammonium acrylate dispersant accounting for 0.5% - 1.2% of the total mass of the powder is added synchronously during the ball - milling process. Its molecular chain adsorbs on the particle surface and inhibits agglomeration through electrostatic repulsion.

[0101] In this embodiment, through the synergistic effect of wet ball milling and spray drying, atomic-level dispersion of niobium pentoxide and gadolinium oxide in the ferrite matrix is achieved. Specifically, niobium pentoxide is broken to the sub-micron level (0.2 - 0.8 μm) during ball milling, and a Nb-O-Fe pre-reaction interface is formed with the surface of iron oxide through mechanochemical action, reducing the activation energy for the subsequent sintering to generate the NbFeO3 phase. Due to its relatively high density (7.41 g / cm 3 ), gadolinium oxide is enriched on the surface layer of powder particles driven by the centrifugal force field during the spray drying process, providing a composition transition basis for the gradient sputtering process.

[0102] In a possible implementation, the powder after spray drying needs to be pre-sintered at 400 - 500 °C for 2 - 3 hours to remove residual moisture and organic substances and preliminarily form a spinel phase (FeMnZnO4) skeleton structure. When the pre-sintering temperature exceeds 500 °C, niobium pentoxide and gadolinium oxide will react prematurely to form coarse NbFeO3 and GdFeO3 phases, resulting in the failure of composition regulation during the subsequent gradient sputtering process.

[0103] In this embodiment, the gradient sputtering process includes three sputtering sub-steps, corresponding to DC sputtering, pulsed sputtering, and amorphous protective layer sputtering respectively. Specifically, after the precursor powder prepared in step one is pressed and sintered to form a magnetic core matrix, the surface grain size is 80 - 100 nm, and the surface roughness Ra is 20 - 30 nm. It is necessary to further adjust it to the target state through the sputtering process.

[0104] In a possible implementation, the first layer of sputtering uses the DC mode, the power is set to 480 - 520 watts, the working gas is a mixed gas of argon and oxygen (volume ratio 9:1 to 8:2), and the gas pressure is 0.4 - 0.6 Pa. When the oxygen proportion > 12%, the oxide layer on the target surface thickens to more than 50 nm, and the sputtering rate decreases > 35%; when the oxygen proportion < 8%, the oxygen vacancy concentration in the deposited film layer exceeds 1×10 20 cm -3 , resulting in a 22% increase in the lattice distortion rate. The substrate preheating temperature is controlled at 200 - 250 °C to balance the atomic migration energy and the amorphous phase formation threshold.

[0105] In this embodiment, the second layer of sputtering switches to the pulsed mode, with a frequency of 190 - 210 Hz, a duty cycle of 25 - 35%, a target rotation speed of 4 - 6 revolutions per minute, and the sputtering angle dynamically deflects ±10 - 20°.

[0106] Specifically, the high ionization rate (>80%) of pulsed sputtering enables the deep implantation of niobium pentoxide and gadolinium oxide ions into the substrate, forming a concentration gradient distribution from the surface to the interior: the surface layer has an Nb content of 1.2 - 1.5 at% and a Gd content of 0.4 - 0.5 at%, while the interior has an Nb content of 0.3 - 0.5 at% and a Gd content of 0.1 - 0.2 at%. The dynamic deflection sputtering angle expands the coverage range of the ion beam current to 120°, and the deviation of the film thickness uniformity is < ±3%. If the deflection angle > 20°, the excessive ion incident angle leads to chaotic grain orientation and a 18 - 22% decrease in magnetic permeability.

[0107] In this embodiment, the sputtering power of the third layer is reduced to 90 - 110 W, a pure argon environment (atmospheric pressure 0.2 - 0.4 Pa) is adopted, and the sputtering time is 15 - 25 minutes to generate an amorphous ferrite protective layer with a thickness ≤ 1 μm. Specifically, 0.5 - 1.2 at% of trace carbon is introduced into the amorphous layer, which is derived from the pyrolysis product of ammonium polyacrylate remaining after spray drying in step one. The carbon atoms fill the interstitial spaces of the amorphous network, increasing the hardness of the protective layer to 8.5 - 9.5 GPa, and the diagonal length of the indentation in the Vickers hardness test is ≤ 15 μm.

[0108] In a possible implementation, when the sputtering power < 90 W, the deposition rate < 0.5 nm / s, and the film density is insufficient (density < 4.2 g / cm 3 ); when the power > 110 W, the substrate temperature rise > 100 °C induces partial crystallization of the amorphous layer (crystallization rate > 30%), and the hardness drops below 6 GPa. The amorphous protective layer reduces the penetration rate of the subsequent spraying solvent by > 90%, avoiding chemical erosion reactions at the substrate - coating interface.

[0109] Example 1:

[0110] Substrate components (parts by mass):

[0111] Iron(III) oxide: 52 parts;

[0112] Manganese(II) oxide: 26 parts;

[0113] Zinc oxide: 22 parts;

[0114] Niobium pentoxide: 0.5 part;

[0115] Gadolinium oxide: 0.2 part.

[0116] Wet ball milling:

[0117] Ratio of material to liquid (raw material: water): 1:2.5;

[0118] Ball milling speed: 300 revolutions per minute;

[0119] Ball milling time: 24 hours;

[0120] Material of grinding ball: zirconia (diameter 3 mm).

[0121] Spray drying:

[0122] Inlet temperature: 200 °C;

[0123] Outlet temperature: 80 °C;

[0124] Atomization pressure: 0.4 MPa;

[0125] Powder particle size: 30 ± 10 μm.

[0126] Magnetron sputtering gradient doping:

[0127] The first layer:

[0128] Power: 500 W (DC);

[0129] Gas ratio (Ar:O2): 95:5;

[0130] Air pressure: 0.5 Pa;

[0131] Sputtering time: 60 minutes;

[0132] Grain size: 60 ± 10 nm.

[0133] The second layer:

[0134] Sputtering mode: pulse (frequency 200 Hz);

[0135] Target rotation speed: 5 r / min;

[0136] Duty cycle: 30%;

[0137] Dynamic deflection of sputtering angle: ±15° (deflection rate 3° / s);

[0138] Sputtering time: 40 minutes;

[0139] Nb2O5 concentration gradient: 1.2 at% on the surface layer → 0.3 at% inside.

[0140] The third layer:

[0141] Power: 100 W;

[0142] Gas: pure argon (99.999%);

[0143] Air pressure: 0.3 Pa;

[0144] Sputtering time: 20 minutes;

[0145] Amorphous layer thickness: 0.8 μm.

[0146] Dynamic response coating:

[0147] Coating components:

[0148] Titanium carbide nanosheets: 8 parts (lateral size 1.2 μm, thickness 3 nm);

[0149] PDMS: 80 parts (viscosity 6000 mPa·s);

[0150] NIPAM microgel: 5 parts (LCST 32 °C);

[0151] Mesoporous SiO2@LiCl composite: 7 parts (pore size 5 nm, LiCl loading 30%);

[0152] Plasma activation:

[0153] Argon flow rate: 20 sccm;

[0154] Power: 100 W;

[0155] Treatment time: 5 minutes.

[0156] Electrostatic spraying:

[0157] Edge area: +5 kV, spraying distance 15 cm, flow rate 0.2 mL / min, for 3 minutes; Central area: +2 kV, spraying distance 15 cm, flow rate 0.2 mL / min, for 1 minute. UV curing:

[0158] Wavelength: 365 nm;

[0159] Light intensity: 80 mW / cm 2 ;

[0160] Time: 10 minutes;

[0161] Coating thickness: 9 μm at the edge, 2.5 μm at the center.

[0162] Example 2:

[0163] Substrate components:

[0164] Iron(III) oxide: 54 parts;

[0165] Manganese oxide: 28 parts;

[0166] Zinc oxide: 24 parts;

[0167] Niobium pentoxide: 0.6 parts;

[0168] Gadolinium oxide: 0.3 parts.

[0169] Wet ball milling:

[0170] Ball milling speed: 320 revolutions per minute;

[0171] Ball milling time: 28 hours.

[0172] Magnetron sputtering:

[0173] The first layer:

[0174] Power: 520 watts;

[0175] Sputtering time: 65 minutes.

[0176] The second layer:

[0177] Target rotation speed: 6 revolutions per minute;

[0178] Duty cycle: 35%;

[0179] Deflection angle: +20°.

[0180] The third layer:

[0181] Power: 110 watts;

[0182] Amorphous layer thickness: 1 micron.

[0183] Dynamic response coating:

[0184] Titanium carbide nanosheets: 9 parts;

[0185] PDMS: 85 parts;

[0186] Mesoporous SiO2@LiCl composite: 8 parts (pore diameter 6 nm).

[0187] Spraying parameters:

[0188] Edge electric field: +5.5 kV, for 3.5 minutes;

[0189] Central electric field: +2.2 kV, for 1.2 minutes.

[0190] Example 3:

[0191] Matrix components:

[0192] Iron(III) oxide: 50 parts;

[0193] Manganese oxide: 24 parts;

[0194] Zinc oxide: 20 parts;

[0195] Niobium pentoxide: 0.4 parts;

[0196] Gadolinium oxide: 0.1 part.

[0197] Wet ball milling:

[0198] Ball milling speed: 280 revolutions per minute;

[0199] Ball milling time: 20 hours.

[0200] Magnetron sputtering:

[0201] The first layer:

[0202] Power: 480 watts;

[0203] Sputtering time: 55 minutes.

[0204] The second layer:

[0205] Target rotation speed: 4 revolutions per minute;

[0206] Duty cycle: 25%.

[0207] Deflection angle: +10°

[0208] The third layer:

[0209] Power: 90 watts;

[0210] Amorphous layer thickness: 0.5 micrometers.

[0211] Dynamic response coating:

[0212] Titanium carbide nanosheets: 7 parts;

[0213] PDMS: 75 parts;

[0214] Mesoporous SiO2@LiCl composite: 6 parts (pore diameter 4 nanometers).

[0215] Spraying parameters:

[0216] Edge electric field: +4.5 kV, for 2.5 minutes;

[0217] Central electric field: +1.8 kV, for 0.8 minutes.

[0218] Comparative example 1:

[0219] Compared with Example 1, the difference is that NIPAM microgel is not added to the dynamic response coating, and the rest are the same.

[0220] Comparative example 2:

[0221] Compared with Example 1, the difference is that the magnetron sputtering gradient doping process is cancelled (only single-layer sputtering is carried out, power 500 watts, time 60 minutes), and the rest are the same.

[0222] Comparative example 3:

[0223] Compared with Example 2, the difference is that the mesoporous SiO2@LiCl composite is replaced with an equal amount of ordinary silica powder (non-mesoporous structure, no LiCl loading), and the rest are the same.

[0224] Comparative Example 4:

[0225] Compared with Example 2, the difference lies in that plasma activation is not carried out before spraying, and the rest are the same.

[0226] Comparative Example 5:

[0227] Compared with Example 3, the difference lies in that niobium pentoxide is not added to the matrix component, and the rest are the same.

[0228] Comparative Example 6:

[0229] Compared with Example 3, the difference lies in that the ultraviolet curing light intensity is increased to 100 mW / cm 2 , and the rest are the same.

[0230] Test Example 1: Description of the environmental adaptability verification experiment of the dynamic response coating

[0231] Control group: Examples 1 - 3 vs. Comparative Example 1 (removing NIPAM), Comparative Example 3 (replacing mesoporous SiO2@LiCl).

[0232] Experimental procedure

[0233] Sample preparation:

[0234] Examples 1 - 3: Prepare a complete magnetic core (including NIPAM microgel, mesoporous SiO2@LiCl) according to the claims;

[0235] Comparative Example 1: Remove the NIPAM microgel, and the other components are the same as those in Example 1;

[0236] Comparative Example 3: Replace mesoporous SiO2@LiCl with ordinary SiO2 powder, and the other components are the same as those in Example 2.

[0237] Temperature responsiveness test:

[0238] Place the sample in an incubator and heat it uniformly from 25°C to 45°C (rate 2°C / minute);

[0239] Use a laser confocal microscope to measure the change in the surface roughness (Ra) of the coating;

[0240] Expose to a dust environment (concentration 5 mg / m 3 ) at 45°C for 24 hours, and weigh the dust adhesion amount.

[0241] Humidity responsiveness test:

[0242] Place the sample in a humidity chamber, and gradually increase the humidity from 50% RH to 80% RH (interval of 30 minutes for every 10% RH);

[0243] Use a four-probe resistivity meter to record the real-time change in surface resistivity;

[0244] The electrostatic adsorption test (dust quantity measurement) was carried out under the condition of 80% RH.

[0245] Extreme working condition simulation:

[0246] The sample was placed in an environment of 85 °C + 80% RH for 48 hours;

[0247] The adhesion of the coating (critical load value) was tested by a scratch tester;

[0248] The coating cracking / peeling was visually inspected and observed by SEM.

[0249] Data recording and analysis:

[0250] The data of each group were compared and the performance difference rate was calculated;

[0251] The significance difference (p < 0.05) was verified by using statistical method (t-test).

[0252] Table 1 Data recording table of environmental adaptability experiment for Test Example 1

[0253]

[0254] As can be seen from Table 1 above:

[0255] By comparing the performance differences between the examples and the comparative examples in this experiment, the strong correlation between the environmental self-adaptive mechanism of the dynamic response coating and its components / structures was revealed. The thermosensitive property of NIPAM microgel stems from the LCST (lower critical solution temperature) phase transition behavior of its molecular chains: when the environmental temperature exceeds 32 °C, the hydrophobic segments of the microgel rapidly curl up, causing the internal porosity of the coating to jump from 15% to 35%. This dynamic open-pore structure not only reduces the electrostatic adsorption force of dust by increasing the surface roughness (Ra increases from 0.8 μm to 2.1 μm), but also accelerates heat dissipation by enhancing air convection, thereby suppressing the dust adhesion rate below 12% under high-temperature working conditions (the adhesion rate of Comparative Example 1 soars to 32.7% due to the absence of this component).

[0256] The humidity response mechanism of the mesoporous SiO2@LiCl composite depends on its unique "confined effect - ion dissociation" synergistic effect: when the humidity > 60% RH, the LiCl loaded in the mesopores absorbs moisture and dissociates into Li + and Cl - , forming a continuous conductive network in the pore channels, reducing the surface resistivity from 10 9 Ω·m to 10 6 Ω·m. This process effectively conducts the surface static charges and inhibits the Coulomb force adsorption of dust (the resistivity of Comparative Example 3 only drops to 10 8Ω·m, the electrostatic adsorption capacity increases by 65%). It should be noted that the mesoporous confinement of LiCl also delays the ion migration rate and avoids the deliquescence failure of the coating in a high-humidity environment, which is manifested as zero peeling of the coating in the extreme test at 85°C / 80% RH (in Comparative Example 3, 18.3% peeling occurs due to the absence of this structure).

[0257] The component synergy effect further amplifies the technical advantages: the pore regulation of NIPAM and the charge conduction of SiO2@LiCl are complementary, making the response speed (3 - 5 seconds) of the coating under the coupled action of temperature and humidity more than 6 times faster than that of traditional materials. This rapid self-adaptive ability not only solves the problem of performance fluctuations under complex working conditions (the SE volatility of Example 1 < 8%), but also significantly improves the coating life by reducing the accumulation of interfacial stress (the adhesion retention rate of Example 1 after 500 hours of damp heat cycling > 95%). The deep coupling of experimental data and mechanism fully verifies the scientificity and inescapability of the component limitations in the claims.

[0258] Test Example 2: Verification Experiment Description of the Optimization Mechanism of the Electromagnetic Performance of the Magnetic Core

[0259] Control Group: Examples 1 - 3 vs. Comparative Example 2 (canceling gradient sputtering), Comparative Example 5 (removing Nb2O5).

[0260] Experimental Procedures

[0261] Sample Preparation:

[0262] Examples 1 - 3: Prepare the magnetic core according to the claims (including the gradient sputtering layer and Nb2O5 / Gd2O5 doping);

[0263] Comparative Example 2: Cancel gradient sputtering and only perform single-layer sputtering (power 500W, time 60 minutes);

[0264] Comparative Example 5: Remove Nb2O5 from the substrate, and other components are the same as in Example 3.

[0265] Frequency Domain Characteristic Test:

[0266] Use an impedance analyzer (Agilent4294A) to measure the frequency response curve of the magnetic permeability (μ) in the range of 1 MHz - 1 GHz;

[0267] Test the variation of the electromagnetic shielding effectiveness (SE) with frequency through the coaxial flange method.

[0268] Loss Characteristic Test:

[0269] Use a vibrating sample magnetometer (VSM) to measure the coercivity (Hc);

[0270] The eddy current loss was measured by a power analyzer (Yokogawa WT1800) (continuously for 10 minutes at an input power of 50 W);

[0271] The grain boundary resistivity was measured using the four-probe method (Keithley 2450).

[0272] Structural analysis:

[0273] The cross-section of the magnetic core was cut by focused ion beam (FIB), and the composition distribution of the gradient sputtering layer was analyzed by SEM-EDS line scanning;

[0274] The grain boundary phase morphology and the existence of the high-resistance NbFeO3 phase were observed using a transmission electron microscope (TEM).

[0275] Extreme working condition verification:

[0276] The magnetic core was placed in a high-temperature environment of 85 °C for 100 hours, and the magnetic permeability attenuation rate was tested;

[0277] Exposed for 48 hours at 90% RH humidity to detect changes in eddy current loss

[0278] Table 2 Record table of experimental data on the electromagnetic properties of the magnetic core in Test Example 2

[0279]

[0280] As can be seen from Table 2 above:

[0281] In this experiment, through the synergistic effect of the gradient sputtering process and Nb2O5 doping, the deep mechanism of the improvement of the high-frequency electromagnetic properties of the magnetic core was revealed. The gradient sputtering process forms a concentration gradient of Nb2O5 and Gd2O3 (surface Nb content 1.18 at%, internal reduced to 0.35 at%) from the surface to the inside of the magnetic core by hierarchically regulating the sputtering power (480 W → 520 W → 560 W) and the target deflection angle. This gradient distribution induces a continuous change in magnetic crystal anisotropy, prompting the magnetic domains to flip orderly along the preset path in the alternating field (magnetic permeability of the example is 1200 - 1250), while in the comparative example 2 with uniform sputtering, due to the aggravation of the magnetic domain pinning effect, the magnetic permeability drops sharply to 895, and at the same time the eddy current loss surges by 83%.

[0282] Nb2O5 doping reacts with the ferrite matrix during sintering to form a nano-scale high-resistance NbFeO3 phase (grain boundary resistivity 1.2×10 8 Ω·cm), and its insulating property effectively blocks the high-frequency leakage current at the grain boundaries. In comparative example 5, due to the removal of Nb2O5, only a low-resistance FeO phase (resistivity 5.5×10 6Ω·cm), resulting in the eddy current loss (155 W / kg) reaching 1.8 times that of the example. It is worth noting that the grain refinement effect of gradient sputtering (grain size of 65 nm in the example) further inhibits the expansion of the eddy current circulation path, while the grains of the single-layer sputtered comparative example 2 are coarsened to 150 nm, increasing the eddy current loop area and exacerbating energy dissipation.

[0283] The synergistic optimization of process and components ultimately achieved a breakthrough in the stability of high-frequency magnetic cores. The magnetic domain regulation of gradient sputtering and the improvement of grain boundary resistance of Nb2O5 are complementary: the former reduces the hysteresis loss (coercivity of 8 A / m in the example), and the latter inhibits the eddy current loss (75 - 85 W / kg). Together, they reduce the total loss by 56% compared to the comparative example. This synergistic effect is more significant under extreme conditions - the permeability decay rate of the example is <5% in an 85°C / 90% RH environment, while that of comparative examples 2 / 5 exceeds 25% due to structural instability. The in-depth coupling of experimental data and mechanism verifies the irreplaceability of process parameters and component ratios in the claims, providing core support for the construction of patent technology barriers.

[0284] Test Example 3: Experimental description of process parameter criticality verification

[0285] Control group: Examples 1 - 3 (standard process parameters) vs. Comparative Example 4 (canceling plasma activation), Comparative Example 6 (ultraviolet light intensity exceeding the limit).

[0286] Experimental steps

[0287] Sample preparation:

[0288] Examples 1 - 3: After plasma activation (power 300 W, Ar / O2 mixed gas) according to the claims, spray the coating and perform ultraviolet curing (light intensity 80 mW / cm 2 , wavelength 365 nm);

[0289] Comparative Example 4: Cancel plasma activation and directly spray the coating;

[0290] Comparative Example 6: Increase the ultraviolet curing light intensity to 100 mW / cm 2 , and other steps are the same as those in Example 3.

[0291] Coating uniformity test:

[0292] Use a white light interferometer (Zygo NewView 9000) to measure the coating thickness distribution and calculate the thickness difference between the edge and the center (CV value);

[0293] Observe the surface porosity through SEM (Hitachi SU5000), and use ImageJ software to statistically analyze the pore distribution density.

[0294] Interface reliability test:

[0295] The adhesion of the coating was tested using a tensile testing machine (Instron 5967) according to the ASTM D4541 standard;

[0296] The sample was placed in a damp heat cycling chamber ( humidity 90% RH, cycled 100 times), and the number of interfacial cracks was observed.

[0297] Dynamic response rate test:

[0298] In an environment with sudden changes in temperature and humidity (25 °C / 50% RH → 45 °C / 80% RH), the response time for the coating resistivity to change to a steady state was recorded;

[0299] The change rate of the coating resistance and the crack propagation were tested using a bending testing machine (repeatedly bent 180° 50 times).

[0300] Data acquisition and processing:

[0301] Each group of tests was repeated 5 times, and the average value was taken after removing outliers;

[0302] Analysis of variance (ANOVA) was used to verify the significance of differences between groups (p < 0.05).

[0303] Table 3 Record table of experimental data on the criticality of process parameters in Test Example 3

[0304]

[0305]

[0306] As can be seen from Table 3 above:

[0307] This experiment reveals the deep regulation mechanism of the critical thresholds of plasma activation and ultraviolet curing parameters on the coating performance. Plasma activation bombards the substrate surface with high-energy ions, forming micro-pits and functional groups (such as -OH, -COOH) at the nanoscale, reducing the wetting angle of the coating precursor solution from 75° to 12°, and significantly improving the spreading uniformity (the thickness deviation CV of the example ≤ 6.3%, and that of Comparative Example 4 reaches 14.8%). At the same time, the interfacial chemical bonding induced by plasma (the proportion of C-O-Fe bonds is 22%) greatly enhances the adhesion (8.1 - 8.5 MPa in the example), while in Comparative Example 4, due to the lack of bonding, the number of interfacial cracks after damp heat cycling increased sharply to 17, verifying the blocking effect of plasma on the penetration of water and oxygen at the interface.

[0308] The regulation of ultraviolet light intensity directly affects the dynamic response ability of the coating through the free radical crosslinking density. In the example, 80 mW / cm 2The light intensity stabilizes the crosslinking degree of the microgel network at 65 - 70%, retaining sufficient freedom of chain segment movement to achieve rapid deformation (response time: 3.2 - 4.1 seconds). In Comparative Example 6 (100 mW / cm 2 ), due to excessive crosslinking (crosslinking degree > 85%), the movement of the microgel is hindered, the response time is extended to 10.4 seconds, and microcracks are induced due to stress concentration after bending (resistance change rate +21.3%). This non-linear relationship between crosslinking degree and flexibility reversely proves the insurmountability of the ultraviolet parameter range in the claims.

[0309] The process synergy further amplifies the technical advantages: the interface bonding enhanced by plasma activation and the coating flexibility regulated by ultraviolet curing complement each other, enabling the coating to achieve the best balance between dynamic response and mechanical durability. The resistance change rate of the example remains < 5% after 50 times of 180° bending, while in Comparative Examples 4 / 6, due to the overlimit of a single process parameter, the performance shows a cliff-like deterioration, such as a 62% decrease in adhesion and the number of cracks.

[0310] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A dust-proof and anti-interference soft ferrite magnetic core, characterized in that, Comprising the following components in parts by mass: Iron(III) oxide: 50 - 54 parts; Manganese oxide: 24 - 28 parts; Zinc oxide: 20 - 24 parts; Niobium pentoxide: 0.4 - 0.6 part; Gadolinium oxide: 0.1 - 0.3 part; The surface of the magnetic core is covered with a dynamic response coating, and the coating comprises the following components in parts by mass: Titanium carbide nanosheets: 7 - 9 parts; Polydimethylsiloxane: 75 - 85 parts; N-isopropylacrylamide microgels: 4 - 6 parts.

2. The dust-proof and anti-interference soft ferrite magnetic core according to claim 1, characterized in that, The mass ratio of niobium pentoxide to gadolinium oxide is 2.5:1 to 3.5:

1.

3. A dust-proof and anti-interference soft ferrite magnetic core according to claim 1, characterized in that, The lateral size of the titanium carbide nanosheets is 0.5 - 2 microns, and the sheet thickness is 1 - 5 nanometers.

4. A dust-proof and anti-interference soft ferrite magnetic core according to claim 1, characterized in that, The dynamic response coating material further comprises 6 - 8 parts of mesoporous silica supported lithium chloride complex, wherein: The pore diameter of the mesoporous silica is 4 - 6 nanometers; The loading amount of lithium chloride is 25 - 35% of the mass of the mesoporous silica.

5. A dust-proof and anti-interference soft ferrite magnetic core according to claim 1, characterized in that The viscosity of the polydimethylsiloxane is 5000 - 8000 mPa·s, and its mass ratio to the titanium carbide nanosheets is (9:1) to (8:2).

6. A preparation method of a dust-proof and interference-proof soft magnetic ferrite core, according to any one of claims 1-5, a dust-proof and interference-proof soft magnetic ferrite core, characterized in that, Including the following steps: Step 1: Mix iron(III) oxide, manganese oxide, zinc oxide, niobium pentoxide, and gadolinium oxide to form a precursor powder; Step 2: Form a gradient doping layer on the surface of the magnetic core substrate by magnetron sputtering; Step 3: Spray the dynamic response coating on the surface of the gradient doping layer and cure it.

7. The preparation method of a dust-proof and anti-interference soft ferrite magnetic core according to claim 6, characterized in that, The said Step 1 includes the following sub-steps: Wet ball milling: Mix each component with deionized water at a solid-liquid ratio of 1:2 - 1:3, perform ball milling with zirconia grinding balls, the rotation speed is 280 - 320 revolutions per minute, and the time is 20 - 28 hours; Spray drying: Feed the ball mill slurry into a spray drying tower, the inlet temperature is 180 - 220 °C, the outlet temperature is 70 - 90 °C, and the atomization pressure is 0.3 - 0.5 MPa to obtain spherical powder with a particle size of 10 - 50 microns.

8. The preparation method of a dust-proof and interference-proof soft ferrite magnetic core according to claim 6, characterized in that, The said Step 2 includes the following sub-steps: First layer sputtering: Perform DC sputtering on the substrate surface at a power of 480 - 520 W, the working gas is a mixed gas of argon and oxygen, the gas pressure is 0.4 - 0.6 Pa, and the sputtering time is 55 - 65 minutes to form a dense nanocrystalline layer with a grain size of 50 - 80 nanometers; Second layer sputtering: Switch to the pulsed sputtering mode, the frequency is 190 - 210 Hz, the duty cycle is 25 - 35%, the target rotates at 4 - 6 revolutions per minute, and the sputtering angle is synchronously and dynamically deflected by ±10 - 20°, and the sputtering time is 35 - 45 minutes to form a concentration gradient distribution layer of niobium pentoxide and gadolinium oxide; Third layer sputtering: Reduce the power to 90 - 110 W, use a pure argon environment, the gas pressure is 0.2 - 0.4 Pa, and the sputtering time is 15 - 25 minutes to generate an amorphous ferrite protective layer with a thickness ≤ 1 micron.

9. The preparation method of a dust-proof and anti-interference soft ferrite magnetic core according to claim 6, characterized in that, The said Step 2 further includes the following steps: When the target rotation speed is 4 - 5 revolutions per minute, the duty cycle of pulsed sputtering is 25 - 30%; When the target rotation speed is 5 - 6 revolutions per minute, the duty cycle of pulsed sputtering is 30 - 35%; The rate of dynamic deflection of the sputtering angle is 2 - 4° per second, and the deflection direction is opposite to the target rotation direction.

10. The preparation method of a dust-proof and interference-proof soft ferrite magnetic core according to claim 6, characterized in that, The said Step 3 includes the following sub-steps: Plasma activation: Place the sputtered magnetic core in a vacuum chamber, introduce argon gas, and perform plasma treatment at a power of 90 - 110 watts for 4 - 6 minutes; Asymmetric electrostatic spraying: Edge area spraying: Electric field bias +4.5 - 5.5 kV, spraying distance 13 - 17 cm, liquid flow rate 0.18 - 0.22 ml / min, for 2.5 - 3.5 minutes; Central area spraying: Electric field bias +1.8 - 2.2 kV, spraying distance 13 - 17 cm, liquid flow rate 0.18 - 0.22 ml / min, for 0.8 - 1.2 minutes; UV curing: Use a UV light source with a wavelength of 360 - 370 nm, light intensity 75 - 85 mW / cm², irradiate for 8 - 12 minutes to form a thickness gradient coating with an edge thickness of 8 - 10 μm and a central thickness of 2 - 3 μm.

Images