Electromagnetic shielding material and method for manufacturing the same

Abstract

The application provides an electromagnetic shielding material and a preparation method thereof, and relates to the technical field of electromagnetic shielding materials.The electromagnetic shielding material comprises the following components in terms of molar percentage: 16-99.5% of n-type semiconductor metal oxide and 0.5-2% of rare earth material.In essence, the n-type semiconductor metal oxide is a metallic conductor.Doping the rare earth material into the n-type semiconductor metal oxide can reduce the lattice scattering of the n-type semiconductor metal oxide and increase the free carrier concentration, thereby greatly reducing the square resistance.The lower the square resistance is, the higher the linear reflection part of the shielding efficiency is, that is, under the same thickness, the n-type semiconductor metal oxide after the doping system material can block stronger electromagnetic waves.Therefore, the electromagnetic shielding material provided by the application has stronger electromagnetic shielding efficiency.

Description

Technical Field

[0001] This application relates to the field of electromagnetic shielding materials technology, and in particular to an electromagnetic shielding material and its preparation method. Background Technology

[0002] Transparent conductive oxide (TCO) is a core material in fields such as displays, touch screens, and photovoltaics. However, the current electromagnetic shielding effectiveness (SE) of TCO materials is only 10-15 dB, which cannot meet the requirements for higher broadband electromagnetic shielding. Summary of the Invention

[0003] This application provides an electromagnetic shielding material and its preparation method to solve the problem of poor electromagnetic shielding effectiveness of existing TCO materials.

[0004] In a first aspect, embodiments of this application provide an electromagnetic shielding material comprising the following molar percentage components: 16% to 99.5% of n-type semiconductor metal oxides and 0.5% to 2% of rare earth materials.

[0005] Optionally, the n-type semiconductor metal oxide includes In2O3 and SnO2, the rare earth material includes La2O3 and Nd2O3, and the proportions of each component in the electromagnetic shielding material by molar percentage are: In2O3 97~98%, SnO2 1~2%, La2O3 0.2~1%, Nd2O3 0.2~1%.

[0006] Optionally, the n-type semiconductor metal oxide includes ZnO and Al2O3, the rare earth material includes CeO2 and Y2O3, and the proportions of each component in the electromagnetic shielding material by molar percentage are: ZnO 98~99%, Al2O3 0.5~1%, CeO2 0.2~0.8%, Y2O3 0.1~0.5%.

[0007] Optionally, the n-type semiconductor metal oxide includes AZO, the rare earth material includes La2O3, and the electromagnetic shielding material further includes single-walled carbon nanotubes and rare earth coupling agents. The proportions of each component in the electromagnetic shielding material by molar percentage are as follows: AZO 87.5~91.5%, La2O3 0.5%, single-walled carbon nanotubes 6~8%, and rare earth coupling agents 1~2%.

[0008] Optionally, the n-type semiconductor metal oxide includes CoFe2O4, the rare earth material includes Y2O3, and the electromagnetic shielding material further includes PI and a rare earth dispersant. The proportions of each component in the electromagnetic shielding material by molar percentage are as follows: CoFe2O4 16~20%, Y2O3 0.6~1%, PI 75~85%, and rare earth dispersant 1~2%.

[0009] Secondly, embodiments of this application also provide a method for preparing an electromagnetic shielding material, the method comprising: Obtain a first mixture comprising the following components in molar percentage: 16% to 99.5% n-type semiconductor metal oxide and 0.5% to 2% rare earth materials; The first mixture is processed to obtain the electromagnetic shielding material.

[0010] Optionally, the n-type semiconductor metal oxide includes In2O3 and SnO2, and the rare earth material includes La2O3 and Nd2O3. The proportions of each component in the first mixture by molar percentage are: In2O3 97~98%, SnO2 1~2%, La2O3 0.2~1%, Nd2O3 0.2~1%. The process of treating the first mixture to obtain the electromagnetic shielding material includes: Anhydrous ethanol was added to the first mixture to obtain a second mixture; Under the first conditions, the second mixture is ball-milled using a ball mill to obtain a third mixture. The first conditions include: a ball-to-material ratio of 10:1 and a ball mill speed of ≥300 r / min. The third mixture is sequentially dried, pressed into shape, and sintered with oxygen to obtain the first target material; The first target material is subjected to a first thin film deposition process and annealing to obtain the electromagnetic shielding material. The parameters of the first thin film deposition process are: power 170~190W, substrate temperature 200~210℃, Ar:O2=20:1, pressure 0.4~0.6Pa, deposition rate 2nm / s, and thickness 150nm.

[0011] Optionally, the n-type semiconductor metal oxide includes ZnO and Al2O3, and the rare earth material includes CeO2 and Y2O3. The molar percentages of each component in the first mixture are as follows: ZnO 98~99%, Al2O3 0.5~1%, CeO2 0.2~0.8%, Y2O3 0.1~0.5%. The process of treating the first mixture to obtain the electromagnetic shielding material includes: Anhydrous ethanol was added to the first mixture to obtain a fourth mixture; Under the second condition, the fourth mixture is ball-milled to obtain the fifth mixture. The second condition includes: ball-to-material ratio of 8:1 and rotation speed of 250~260hr / min. The fifth mixture is dried, pressed into shape, and sintered with oxygen to obtain the second target material; The second target material is subjected to a second thin film deposition process and ultraviolet ozone treatment to obtain the electromagnetic shielding material. The parameters of the second thin film deposition process are: power 150-160W, substrate temperature 160~185℃, Ar:O2=30:1, pressure 0.3~0.6Pa, deposition rate 1.6~2.0nm / s, and thickness 100nm.

[0012] Optionally, the n-type semiconductor metal oxide includes AZO, the rare earth material includes La2O3, and the first mixture further includes single-walled carbon nanotubes and a rare earth coupling agent. The proportions of each component in the first mixture by molar percentage are as follows: AZO 87.5~91.5%, La2O3 0.5%, single-walled carbon nanotubes 6~8%, and rare earth coupling agent 1~2%. The process of obtaining the first mixture includes: The AZO, La2O3, and single-walled carbon nanotubes were added to a polar organic solvent and ultrasonically dispersed to obtain a sixth mixture. A rare earth coupling agent is added to the sixth mixture, and the mixture is stirred at a temperature of 50℃-70℃ to obtain the first mixture; The process of treating the first mixture to obtain the electromagnetic shielding material includes: Obtain a base layer, wherein the base layer is made of La2O3-doped AZO; The first mixture is spin-coated onto the substrate and cured at a temperature of 110℃-130℃ to obtain the electromagnetic shielding material.

[0013] Optionally, the n-type semiconductor metal oxide includes CoFe2O4, the rare earth material includes Y2O3, and the first mixture further includes PI and a rare earth dispersant. The proportions of each component in the first mixture by molar percentage are as follows: CoFe2O4 16~20%, Y2O3 0.6~1%, PI 75~85%, and rare earth dispersant 1~2%. The process of obtaining the first mixture includes: The CoFe2O4, Y2O3, and rare earth dispersant were added to a polar organic solvent and ultrasonically dispersed to obtain a seventh mixture. The PI was added to the seventh mixture, and the mixture was stirred and reacted at a temperature of 40°-60° to obtain the first mixture. The process of treating the first mixture to obtain the electromagnetic shielding material includes: The first mixture is coated into a film and then subjected to gradient curing to obtain the electromagnetic shielding material.

[0014] In the technical solution provided in this application, n-type semiconductor metal oxide is essentially a metallic conductor. Doping rare earth materials into n-type semiconductor metal oxide can reduce lattice scattering and increase the free carrier concentration, thereby significantly reducing sheet resistance. The lower the sheet resistance, the higher the linear reflection portion of the shielding effectiveness. That is, at the same thickness, the n-type semiconductor metal oxide after doping the system material can block stronger electromagnetic waves. Therefore, the electromagnetic shielding material of this application has stronger electromagnetic shielding effectiveness. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is one of the structural schematic diagrams of the electromagnetic shielding material provided in the embodiments of this application; Figure 2 This is the second schematic diagram of the structure of the electromagnetic shielding material provided in the embodiments of this application; Figure 3 This is a schematic flowchart of the preparation method of the electromagnetic shielding material provided in the embodiments of this application. Detailed Implementation

[0017] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0018] This application provides an electromagnetic shielding material.

[0019] The electromagnetic shielding material comprises the following components in molar percentage: 16%~99.5% n-type semiconductor metal oxide and 0.5%~2% rare earth materials.

[0020] The n-type semiconductor metal oxide can be: indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), or fluorine-doped tin oxide (FTO). n-type semiconductor metal oxides possess electronic conductivity and a wide bandgap. The wide bandgap refers to the fact that most n-type TCO materials have a bandgap greater than 3.0 eV. The photon energy of visible light (approximately 1.6 ~ 3.2 eV) is insufficient to excite electrons to cross this bandgap. Therefore, visible light cannot be absorbed by the material but passes directly through it. Thus, n-type semiconductor metal oxides can simultaneously exhibit the characteristics of being metallic (conductive) and transparent (non-light-absorbing).

[0021] The rare earth material may be: La, Ce, Nd, or Y.

[0022] In this application, n-type semiconductor metal oxides are essentially metallic conductors. Doping n-type semiconductor metal oxides with rare earth materials reduces lattice scattering and increases the free carrier concentration, thereby significantly reducing sheet resistance. The lower the sheet resistance, the higher the linear reflection portion of the shielding effectiveness. That is, at the same thickness, the doped n-type semiconductor metal oxide can block stronger electromagnetic waves. Therefore, the electromagnetic shielding material of this application has stronger electromagnetic shielding effectiveness.

[0023] Optionally, the n-type semiconductor metal oxide includes In2O3 and SnO2, the rare earth material includes La2O3 and Nd2O3, and the proportions of each component in the electromagnetic shielding material by molar percentage are: In2O3 97~98%, SnO2 1~2%, La2O3 0.2~1%, Nd2O3 0.2~1%.

[0024] In this embodiment, the preferred composition is: In2O3 97.5%, SnO2 1.5%, La2O3 0.5%, Nd2O3 0.5%.

[0025] like Figure 1 As shown, La 3+ The ionic radius is greater than that of In 3+ With its relatively large ionic radius, La preferentially occupies grain boundary sites when introduced into the In₂O₃ lattice. This effectively suppresses abnormal grain growth during high-temperature processing or long-term use, preventing resistivity drift caused by grain coarsening. Therefore, this material exhibits excellent stability and a significantly extended lifespan under high-temperature and high-humidity conditions.

[0026] Neodymium (Nd) is a rare-earth magnetic element with unpaired f electrons. In traditional ITO systems, electromagnetic shielding primarily relies on the reflection loss of free electrons. This embodiment, by introducing Nd, not only maintains the high conductivity of the matrix (reflection loss) but also introduces a magnetic loss mechanism (absorption loss). The presence of Nd enhances the material's ability to absorb electromagnetic waves, thus achieving a dual shielding mechanism of reflection and absorption, significantly improving the material's electromagnetic shielding effectiveness.

[0027] The large ionic radii of La and Nd induce microscopic expansion of the lattice, thereby releasing the tensile internal stress generated during thin film deposition. This stress release makes the thin film structure more relaxed, significantly improving the adhesion and bending resistance of the film on flexible substrates. The material is less prone to microcracks under repeated bending conditions, making it more suitable for applications in flexible displays and flexible shielding.

[0028] It should be noted that although the SnO2 content (1-2%) is slightly lower than that of traditional ITO (typically 5-10%), the introduction of La and Nd optimizes the lattice defect structure and reduces the scattering of charge carriers by grain boundaries. This synergistic effect maintains high carrier mobility while keeping the Sn doping level low, achieving a good balance between low sheet resistance and high transmittance, and reducing raw material costs.

[0029] Experiments have shown that for ITO materials, La / Nd rare earth doping has achieved a synergistic improvement in flexibility, stability and conductivity, increasing the number of bending cycles from <100 to over 500, and reducing the sheet resistance change rate at high temperatures to <5%, while maintaining low sheet resistance (8-12) and high light transmittance (>89%). Furthermore, the rare earth doped target material can be directly adapted to existing magnetron sputtering production lines without the need for large-scale equipment modifications, thus reducing mass production costs.

[0030] Optionally, the n-type semiconductor metal oxide includes ZnO and Al2O3, the rare earth material includes CeO2 and Y2O3, and the proportions of each component in the electromagnetic shielding material by molar percentage are: ZnO 98~99%, Al2O3 0.5~1%, CeO2 0.2~0.8%, Y2O3 0.1~0.5%.

[0031] In this embodiment, the preferred composition is: ZnO 98.7%, Al2O3 0.8%, CeO2 0.3%, Y2O3 0.2%.

[0032] like Figure 2 As shown, Ce (cerium) has a unique variable valence state property (it can be found in Ce). 3+ and Ce 4(Conversion between +). When CeO2 is introduced into the ZnO lattice, Ce can act as a highly efficient donor dopant source, providing a large number of free electrons to the conduction band. This electron donor effect works synergistically with Al doping, significantly increasing the free carrier concentration in the thin film, thereby effectively reducing the resistivity of the material and improving the conductivity and electromagnetic shielding effectiveness of the thin film.

[0033] Y 3+ The radius of the yttrium ion is significantly larger than that of Zn. 2+ This size difference causes Y ions to tend to aggregate at grain boundaries, generating a strong grain boundary pinning effect. This pinning effect effectively limits abnormal grain growth in the film during high-temperature treatment or long-term aging, preventing a sharp increase in resistivity due to grain coarsening. Therefore, this material exhibits excellent stability under high temperature and high humidity environments, solving the problem of easy aging of traditional AZO.

[0034] The introduction of rare earth ions (Ce, Y) alters the stress distribution within the crystal lattice, thus releasing stress. Simultaneously, the pinning effect of Y on the grains refines the grain size. The smaller grains and optimized stress state make the film more flexible, less prone to microcracks during bending or folding. This significantly improves the film's applicability on flexible substrates and solves the problem of performance degradation after repeated bending of traditional AZO, despite its greater flexibility than ITO.

[0035] Ce doping enhances the high conductivity of electromagnetic wave reflection loss, while the microstructural inhomogeneities introduced by Ce and Y increase the scattering path of electromagnetic waves. While maintaining high visible light transmittance, this composite system provides excellent electromagnetic shielding performance, making it particularly suitable for applications sensitive to electromagnetic interference, such as flexible displays and touchscreens.

[0036] Experiments have shown that by doping AZO materials with rare earth elements such as Ce, Y, and La, the problems of conductivity fluctuation and poor weather resistance have been solved. The sheet resistance has been reduced from 15-20 to 8-12, the transmittance remains above 88% after 500 hours of UV aging, and the number of flexible bending cycles has exceeded 10,000. It is suitable for roll-to-roll flexible production lines, and the cost is only 30-40% of that of ITO.

[0037] Optionally, the n-type semiconductor metal oxide includes AZO, the rare earth material includes La2O3, and the electromagnetic shielding material further includes single-walled carbon nanotubes and rare earth coupling agents. The proportions of each component in the electromagnetic shielding material by molar percentage are as follows: AZO 87.5~91.5%, La2O3 0.5%, single-walled carbon nanotubes 6~8%, and rare earth coupling agents 1~2%.

[0038] In this embodiment, the preferred configuration is 90% La-doped AZO (0.5 mol% La2O3 doping), 8% single-walled carbon nanotubes (SWCNTs), and 2% rare earth coupling agent.

[0039] As a metal oxide ceramic material, AZO is inherently brittle. This embodiment introduces high aspect ratio single-walled carbon nanotubes (SWCNTs), which, like nanoscale reinforcing bars, construct a three-dimensional interpenetrating network structure between AZO grains. When the film is subjected to bending forces, the SWCNT network effectively transfers stress and prevents the propagation of microcracks, thereby significantly improving the material's elongation at break. This "rigid-flexible" structure allows the film to maintain good integrity after repeated bending, making it ideal for flexible display and flexible shielding applications.

[0040] AZO is an inorganic ceramic, while SWCNT has relatively inert surface properties. Direct mixing of the two can easily lead to agglomeration and poor bonding. Rare earth coupling agents play a crucial molecular bridging role in the composite system, connecting the inorganic oxide on one end through chemical bonding and the carbon nanotubes on the other end through physical entanglement. This not only solves the agglomeration problem of SWCNT in the slurry and achieves uniform dispersion at the nanoscale, but also significantly enhances the interfacial bonding strength between the inorganic matrix and the reinforcing phase, prevents interlayer delamination, and improves the overall density of the composite material.

[0041] The material contains two sets of conductive channels: one is the electronic conductivity of the AZO matrix itself, and the other is the contact conductivity formed by the SWCNT network. These two conductive networks work together to not only further reduce the sheet resistance of the film, but more importantly, enhance the absorption loss in electromagnetic shielding. Compared with traditional metal films that mainly rely on reflection to shield electromagnetic waves, this composite material can dissipate more electromagnetic wave energy, thus providing superior and more stable electromagnetic shielding performance while maintaining high light transmittance.

[0042] Optionally, the n-type semiconductor metal oxide includes CoFe2O4, the rare earth material includes Y2O3, and the electromagnetic shielding material further includes PI and a rare earth dispersant. The proportions of each component in the electromagnetic shielding material by molar percentage are as follows: CoFe2O4 16~20%, Y2O3 0.6~1%, PI 75~85%, and rare earth dispersant 1~2%.

[0043] In this embodiment, the preferred solution is 18% Y-doped CoFe2O4 (0.8 mol% Y2O3 doping), 80% PI, and 2% rare earth dispersant.

[0044] CoFe2O4 (cobalt ferrite) is a typical soft magnetic material. Unlike ITO / AZO, which mainly relies on reflecting electromagnetic waves, this material utilizes the natural resonance and domain wall resonance mechanisms within the magnetic particles to convert the energy of incident electromagnetic waves into heat energy. This "absorption-type shielding" can significantly reduce secondary reflection (secondary pollution) of electromagnetic waves, especially providing excellent shielding against low-frequency or mid-frequency magnetic field interference, thus solving the problem of poor magnetic field shielding ability of traditional conductive films.

[0045] PI (polyimide) accounts for as much as 75-85% of the matrix. PI is a high-performance flexible polymer material, which makes the prepared electromagnetic shielding film have excellent flexibility and bending resistance, and can be attached to curved or irregularly shaped devices. At the same time, the material has low density and light weight, making it very suitable for lightweight shielding needs in portable electronic devices, wearable devices or aerospace fields.

[0046] Y 3+ The ionic radius of (yttrium ion) and Fe 3+ Similarly, the introduction of Y₂O₃ allows it to enter the lattice of CoFe₂O₄ for site substitution, thereby fine-tuning the lattice constant and optimizing the material's permeability and magnetic loss characteristics, resulting in a better impedance match to free space. This rare-earth doping enhances the material's saturation magnetic induction, broadens the absorption frequency band, and simultaneously helps improve the interfacial bonding between inorganic particles and the polymer matrix, preventing the material from cracking when bent.

[0047] Magnetic powders are prone to agglomeration, leading to uneven shielding performance. Rare earth dispersants can form a steric hindrance or electrostatic repulsion layer on the particle surface, ensuring that CoFe2O4 nanoparticles are uniformly dispersed at the molecular level in the PI matrix. This guarantees the uniformity and consistency of shielding effectiveness and also improves the stability of the material.

[0048] like Figure 3 As shown, this application also provides a method for preparing an electromagnetic shielding material, comprising the following steps: Step 101: Obtain a first mixture, the first mixture comprising the following molar percentage components: 16%~99.5% n-type semiconductor metal oxide, 0.5%~2% rare earth materials; Step 102: Process the first mixture to obtain the electromagnetic shielding material.

[0049] Among them, n-type semiconductor metal oxide is essentially a metallic conductor. Doping rare earth materials into n-type semiconductor metal oxide can reduce lattice scattering and increase the concentration of free carriers, thereby significantly reducing sheet resistance. The lower the sheet resistance, the higher the linear reflection part of the shielding effectiveness. That is, at the same thickness, the n-type semiconductor metal oxide after doping the system material can block stronger electromagnetic waves. Therefore, the first mixture has stronger electromagnetic shielding effectiveness.

[0050] Based on the first mixture, a drying and molding process is carried out to obtain the electromagnetic shielding material.

[0051] Optionally, the n-type semiconductor metal oxide includes In2O3 and SnO2, and the rare earth material includes La2O3 and Nd2O3. The proportions of each component in the first mixture by molar percentage are: In2O3 97~98%, SnO2 1~2%, La2O3 0.2~1%, Nd2O3 0.2~1%. The process of treating the first mixture to obtain the electromagnetic shielding material includes: Anhydrous ethanol was added to the first mixture to obtain a second mixture; Under the first conditions, the second mixture is ball-milled using a ball mill to obtain a third mixture. The first conditions include: a ball-to-material ratio of 10:1 and a ball mill speed of ≥300 r / min. The third mixture is sequentially dried, pressed into shape, and sintered with oxygen to obtain the first target material; The first target material is subjected to a first thin film deposition process and annealing to obtain the electromagnetic shielding material. The parameters of the first thin film deposition process are: power 170~190W, substrate temperature 200~210℃, Ar:O2=20:1, pressure 0.4~0.6Pa, deposition rate 2nm / s, and thickness 150nm.

[0052] In this embodiment, obtaining the electromagnetic shielding material includes the following steps: Raw material processing: In2O3, SnO2, La2O3 and Nd2O3 powders were dried at 120℃ for 2h, mixed in the above proportion to obtain the first mixture, anhydrous ethanol was added (to obtain the second mixture), and ball milled for 6h (ball-to-material ratio 10:1, speed 300r / min) to obtain the third mixture.

[0053] Target material preparation: The mixed slurry was spray-dried (inlet air 180℃, outlet air 80℃), pressed into shape (200MPa), and sintered at 1500℃ in an oxygen atmosphere for 5h to obtain the first target material with a density of 99.2%.

[0054] Thin film deposition: magnetron sputtering deposition, with the following parameters: power 180W, substrate temperature 200℃, Ar:O2=20:1, pressure 0.5Pa, deposition rate 2nm / s, and thickness 150nm. Post-processing: Annealing at 160℃ for 30 minutes to obtain the electromagnetic shielding material.

[0055] In this process, anhydrous ethanol is used as the medium for prolonged mechanical activation under high-speed ball milling conditions of ≥300 r / min. This process completely breaks down the agglomerates of the raw material powder, enabling the addition of extremely small amounts (molar ratio of only 0.2%~1%) of rare earth elements (La2O3, Nd2O3) to achieve homogeneous mixing with the matrix powder (In2O3) at the microscale. This lays a uniform foundation for subsequent target preparation and sputtering, avoiding localized resistivity anomalies in the thin film caused by uneven doping.

[0056] During thin film deposition, the substrate temperature is controlled at 200–210°C. This medium-low temperature heating provides sufficient surface migration energy, promoting the rearrangement of thin film atoms on the substrate and significantly improving the crystallinity of the film. High crystallinity means fewer grain boundary defects, thereby reducing carrier scattering and further reducing sheet resistance; at the same time, thermal stress matching reduces the internal stress of the film and improves the adhesion between the film and the substrate.

[0057] The Ar:O2 ratio in the sputtering gas pressure was set to 20:1, which is a low-oxygen environment. The low oxygen partial pressure is conducive to the formation of an appropriate amount of intrinsic oxygen vacancies in the In2O3 lattice. These oxygen vacancies, acting as donor levels, can provide a large number of free electrons, thereby significantly improving the conductivity of the thin film. This ratio strikes a good balance between high transmittance and high conductivity.

[0058] Optionally, the n-type semiconductor metal oxide includes ZnO and Al2O3, and the rare earth material includes CeO2 and Y2O3. The molar percentages of each component in the first mixture are as follows: ZnO 98~99%, Al2O3 0.5~1%, CeO2 0.2~0.8%, Y2O3 0.1~0.5%. The process of treating the first mixture to obtain the electromagnetic shielding material includes: Anhydrous ethanol was added to the first mixture to obtain a fourth mixture; Under the second condition, the fourth mixture is ball-milled to obtain the fifth mixture. The second condition includes: ball-to-material ratio of 8:1 and rotation speed of 250~260hr / min. The fifth mixture is dried, pressed into shape, and sintered with oxygen to obtain the second target material; The second target material is subjected to a second thin film deposition process and ultraviolet ozone treatment to obtain the electromagnetic shielding material. The parameters of the second thin film deposition process are: power 150-160W, substrate temperature 160~185℃, Ar:O2=30:1, pressure 0.3~0.6Pa, deposition rate 1.6~2.0nm / s, and thickness 100nm.

[0059] In this embodiment, obtaining the electromagnetic shielding material includes the following steps: Raw material pretreatment: ZnO, Al2O3, CeO2, and Y2O3 powders were dried at 120℃ for 2 hours and mixed to obtain the first mixture. Anhydrous ethanol was added to the first mixture (to obtain the fourth mixture), and the mixture was ball-milled for 4 hours (ball-to-material ratio 8:1, speed 250 r / min) to obtain the fifth mixture. Target material preparation: spray drying (inlet air 160℃, outlet air 70℃), pressing molding (180MPa), sintering in air atmosphere at 1300℃ for 4h to obtain a second target material with a density of 98.6%; Thin film deposition: magnetron sputtering deposition, with the following parameters: power 150W, substrate temperature 180℃, Ar:O2=30:1, pressure 0.4Pa, deposition rate 1.8nm / s, and thickness 100nm. Post-processing: Ultraviolet ozone treatment for 15 minutes (power 30W) to obtain the electromagnetic shielding material.

[0060] During thin film deposition, the Ar:O2 ratio in the sputtering gas reaches as high as 30:1. This extremely high argon ratio implies an extremely low oxygen partial pressure environment. This environment is conducive to inducing a large number of intrinsic oxygen vacancies in the ZnO lattice. As effective electron donors, oxygen vacancies significantly increase the free carrier concentration of the thin film, thereby significantly reducing sheet resistance, improving the film's ability to reflect electromagnetic waves, and achieving high shielding effectiveness.

[0061] AZO thin films readily adsorb water molecules or organic pollutants from the air. These impurities trap free electrons, leading to a decrease in surface conductivity. Ultraviolet ozone treatment effectively removes surface impurities and passivates surface dangling bonds, reducing surface electron scattering. This treatment step, without damaging the bulk structure of the film, further improves its transmittance and stabilizes its surface resistivity, preventing performance drift over time.

[0062] Optionally, the n-type semiconductor metal oxide includes AZO, the rare earth material includes La2O3, and the first mixture further includes single-walled carbon nanotubes and a rare earth coupling agent. The proportions of each component in the first mixture by molar percentage are as follows: AZO 87.5~91.5%, La2O3 0.5%, single-walled carbon nanotubes 6~8%, and rare earth coupling agent 1~2%. The process of obtaining the first mixture includes: The AZO, La2O3, and single-walled carbon nanotubes were added to a polar organic solvent and ultrasonically dispersed to obtain a sixth mixture. A rare earth coupling agent is added to the sixth mixture, and the mixture is stirred at a temperature of 50℃-70℃ to obtain the first mixture; The process of treating the first mixture to obtain the electromagnetic shielding material includes: Obtain a base layer, wherein the base layer is made of La2O3-doped AZO; The first mixture is spin-coated onto the substrate and cured at a temperature of 110℃-130℃ to obtain the electromagnetic shielding material.

[0063] In this embodiment, obtaining the electromagnetic shielding material includes the following steps: La-doped AZO and SWCNT were added to NMP and ultrasonically dispersed for 30 min (200 W) to obtain the sixth mixture; Add rare earth coupling agent, stir at 60°C for 2 hours to obtain the first mixture; La-doped AZO substrate was deposited by magnetron sputtering (50 nm), followed by spin coating of composite slurry (3000 r / min, 30 s). The electromagnetic shielding material is obtained by curing at 120℃ for 30 minutes.

[0064] SWCNTs (single-walled carbon nanotubes) are prone to aggregation and difficult to disperse uniformly. This embodiment breaks up agglomeration through ultrasonic dispersion and incorporates a rare-earth coupling agent. The coupling agent constructs molecular bridges between the inorganic particles (AZO) and organic nanotubes (SWCNTs), undergoing a chemical reaction at 50°C-70°C to achieve compatibility modification. This not only ensures highly uniform dispersion of all components in the slurry but also significantly enhances the interfacial bonding strength between the inorganic matrix and the nanotubes, preventing interlayer delamination of the composite material under stress and significantly improving the mechanical properties of the film.

[0065] This embodiment employs a layered fabrication strategy. The bottom layer is a dense La-doped AZO thin film, providing a smooth surface and good basic conductivity. The upper layer is a spin-coated AZO / SWCNT composite layer. The dense substrate layer overcomes the surface roughness problem easily caused by spin-coated powder, ensuring the optical transmittance of the film. The SWCNT network in the composite layer provides excellent flexibility and electromagnetic shielding absorption performance. This structure achieves a complementary advantage between the high conductivity of inorganic materials and the high flexibility of carbon nanotubes.

[0066] Optionally, the n-type semiconductor metal oxide includes CoFe2O4, the rare earth material includes Y2O3, and the first mixture further includes PI and a rare earth dispersant. The proportions of each component in the first mixture by molar percentage are as follows: CoFe2O4 16~20%, Y2O3 0.6~1%, PI 75~85%, and rare earth dispersant 1~2%. The process of obtaining the first mixture includes: The CoFe2O4, Y2O3, and rare earth dispersant were added to a polar organic solvent and ultrasonically dispersed to obtain a seventh mixture. The PI was added to the seventh mixture, and the mixture was stirred and reacted at a temperature of 40°-60° to obtain the first mixture. The process of treating the first mixture to obtain the electromagnetic shielding material includes: The first mixture is coated into a film and then subjected to gradient curing to obtain the electromagnetic shielding material.

[0067] In this embodiment, obtaining the electromagnetic shielding material includes the following steps: Y-doped CoFe2O4 and rare earth dispersant were added to NMP and ultrasonically dispersed for 40 min (250 W) to obtain the seventh mixture; Add PI precursor and stir at 50°C for 1 hour to obtain the first mixture; Spray coating to form a film (wet film 50μm), gradient curing: 80℃ / 1h→120℃ / 1h→180℃ / 2h; The electromagnetic shielding material is obtained by cooling to room temperature.

[0068] This embodiment employs a gradient curing process instead of a one-step high-temperature curing. Gradual heating avoids surface skinning and internal bubbles caused by rapid solvent evaporation, as well as film cracking due to thermal stress concentration. Gradual heating helps eliminate residual thermal stress in the PI matrix during curing, significantly improving film smoothness. This process allows sufficient time for polymer chains to rearrange on the substrate surface, thereby greatly enhancing the adhesion between the film and the substrate and preventing the shielding layer from peeling off.

[0069] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An electromagnetic shielding material, characterized in that, The electromagnetic shielding material comprises the following components in molar percentage: 16%~99.5% n-type semiconductor metal oxide and 0.5%~2% rare earth materials.

2. The electromagnetic shielding material according to claim 1, characterized in that, The n-type semiconductor metal oxide includes In2O3 and SnO2, the rare earth material includes La2O3 and Nd2O3, and the proportions of each component in the electromagnetic shielding material by molar percentage are as follows: In2O3 97~98%, SnO2 1~2%, La2O3 0.2~1%, Nd2O3 0.2~1%.

3. The electromagnetic shielding material according to claim 1, characterized in that, The n-type semiconductor metal oxide includes ZnO and Al2O3, the rare earth material includes CeO2 and Y2O3, and the proportions of each component in the electromagnetic shielding material by molar percentage are as follows: ZnO 98~99%, Al2O3 0.5~1%, CeO2 0.2~0.8%, Y2O3 0.1~0.5%.

4. The electromagnetic shielding material according to claim 1, characterized in that, The n-type semiconductor metal oxide includes AZO, the rare earth material includes La2O3, and the electromagnetic shielding material further includes single-walled carbon nanotubes and rare earth coupling agents. The proportions of each component in the electromagnetic shielding material by molar percentage are as follows: AZO 87.5~91.5%, La2O3 0.5%, single-walled carbon nanotubes 6~8%, and rare earth coupling agents 1~2%.

5. The electromagnetic shielding material according to claim 1, characterized in that, The n-type semiconductor metal oxide includes CoFe2O4, the rare earth material includes Y2O3, and the electromagnetic shielding material further includes PI and a rare earth dispersant. The proportions of each component in the electromagnetic shielding material by molar percentage are as follows: CoFe2O4 16~20%, Y2O3 0.6~1%, PI 75~85%, and rare earth dispersant 1~2%.

6. A method for preparing an electromagnetic shielding material, characterized in that, The method includes: Obtain a first mixture comprising the following components in molar percentage: 16% to 99.5% n-type semiconductor metal oxide and 0.5% to 2% rare earth materials; The first mixture is processed to obtain the electromagnetic shielding material.

7. The method for preparing the electromagnetic shielding material according to claim 6, characterized in that, The n-type semiconductor metal oxide includes In2O3 and SnO2, and the rare earth material includes La2O3 and Nd2O3. The proportions of each component in the first mixture by molar percentage are as follows: In2O3 97~98%, SnO2 1~2%, La2O3 0.2~1%, Nd2O3 0.2~1%. The process of treating the first mixture to obtain the electromagnetic shielding material includes: Anhydrous ethanol was added to the first mixture to obtain a second mixture; Under the first conditions, the second mixture is ball-milled using a ball mill to obtain a third mixture. The first conditions include: a ball-to-material ratio of 10:1 and a ball mill speed of ≥300 r / min. The third mixture is sequentially dried, pressed into shape, and sintered with oxygen to obtain the first target material; The first target material is subjected to a first thin film deposition process and annealing to obtain the electromagnetic shielding material. The parameters of the first thin film deposition process are: power 170~190W, substrate temperature 200~210℃, Ar:O2=20:1, pressure 0.4~0.6Pa, deposition rate 2nm / s, and thickness 150nm.

8. The method for preparing the electromagnetic shielding material according to claim 6, characterized in that, The n-type semiconductor metal oxide includes ZnO and Al2O3, and the rare earth material includes CeO2 and Y2O3. The proportions of each component in the first mixture, in molar percentage terms, are as follows: ZnO 98~99%, Al2O3 0.5~1%, CeO2 0.2~0.8%, Y2O3 0.1~0.5%. The process of treating the first mixture to obtain the electromagnetic shielding material includes: Anhydrous ethanol was added to the first mixture to obtain a fourth mixture; Under the second condition, the fourth mixture is ball-milled to obtain the fifth mixture. The second condition includes: ball-to-material ratio of 8:1 and rotation speed of 250~260hr / min. The fifth mixture is dried, pressed into shape, and sintered with oxygen to obtain the second target material; The second target material is subjected to a second thin film deposition process and ultraviolet ozone treatment to obtain the electromagnetic shielding material. The parameters of the second thin film deposition process are: power 150-160W, substrate temperature 160~185℃, Ar:O2=30:1, pressure 0.3~0.6Pa, deposition rate 1.6~2.0nm / s, and thickness 100nm.

9. The method for preparing the electromagnetic shielding material according to claim 6, characterized in that, The n-type semiconductor metal oxide includes AZO, the rare earth material includes La2O3, and the first mixture further includes single-walled carbon nanotubes and a rare earth coupling agent. The proportions of each component in the first mixture by molar percentage are as follows: AZO 87.5~91.5%, La2O3 0.5%, single-walled carbon nanotubes 6~8%, and rare earth coupling agent 1~2%. The process of obtaining the first mixture includes: The AZO, La2O3, and single-walled carbon nanotubes were added to a polar organic solvent and ultrasonically dispersed to obtain a sixth mixture. A rare earth coupling agent is added to the sixth mixture, and the mixture is stirred at a temperature of 50℃-70℃ to obtain the first mixture; The process of treating the first mixture to obtain the electromagnetic shielding material includes: Obtain a base layer, wherein the base layer is made of La2O3-doped AZO; The first mixture is spin-coated onto the substrate and cured at a temperature of 110℃-130℃ to obtain the electromagnetic shielding material.

10. The method for preparing the electromagnetic shielding material according to claim 6, characterized in that, The n-type semiconductor metal oxide includes CoFe2O4, the rare earth material includes Y2O3, and the first mixture further includes PI and a rare earth dispersant. The proportions of each component in the first mixture by molar percentage are as follows: CoFe2O4 16~20%, Y2O3 0.6~1%, PI 75~85%, and rare earth dispersant 1~2%. The process of obtaining the first mixture includes: The CoFe2O4, Y2O3, and rare earth dispersant were added to a polar organic solvent and ultrasonically dispersed to obtain a seventh mixture. The PI was added to the seventh mixture, and the mixture was stirred and reacted at a temperature of 40°-60° to obtain the first mixture. The process of treating the first mixture to obtain the electromagnetic shielding material includes: The first mixture is coated into a film and then subjected to gradient curing to obtain the electromagnetic shielding material.

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