Multilayer electromagnetic shielding composite material

Abstract

To provide a multilayer material for shielding low frequency electromagnetic waves.SOLUTION: A multilayer material may include a plurality of repeating material alternating layer sets. Each of the repeating alternate layer sets may include a conductive layer and a magnetic layer that includes a continuous layer of a magnetic material. The multilayer material is generally configured to shield electromagnetic waves with frequencies below about 1 MHz. In various embodiments, the conductive layer may include a conductive metal or a two-dimensional transition metal carbide. The multilayer material may be provided as a thin film or may be shaped or sized as flakes for use with a resin composite material to be adhered via a spray coating technique.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates generally to electromagnetic shielding, and more particularly to multi-layer materials for shielding electromagnetic waves having low frequencies, for example, less than about 1 MHz. [Background technology]

[0002] The background description provided is generally intended to provide a context for the present disclosure. The inventors' work, to the extent that it may be described in this Background section, and aspects of the specification that may not otherwise qualify as prior art at the time of filing, are not admitted, either explicitly or implicitly, as prior art against the present technology.

[0003] Electronic devices that use, transmit, or distribute electrical energy create electromagnetic waves, also called electromagnetic interference. Electromagnetic interference is the result of oscillations of electric and magnetic fields, with the waves traveling perpendicular to the direction of propagation. Electromagnetic interference can be harmful to other electronic devices, potentially leading to device degradation or malfunction in some cases.

[0004] Vehicles may have many low frequency noise sources, including prime movers, power control units, batteries, electrical wires, etc. These and other electronic devices may emit low frequency electromagnetic waves with frequencies in the KHz to MHz range. These electromagnetic waves may interfere in harmful ways with other vehicle devices, and may also potentially have negative effects on human health, for example by interfering with devices such as artificial hearts that aid in the electronic control of organs. Unwanted interference has been shielded previously with relatively thick and heavy metal shields. The use of copper, a highly conductive material, and nickel, a highly permeable material, generally does not provide high shielding effectiveness when normalized to mass or thickness.

[0005] The increasing number of electronic devices used within vehicles, especially those operating at faster speeds and smaller sizes, can potentially increase unwanted electromagnetic interference. Summary of the Invention [Problem to be solved by the invention]

[0006] While recent improvements may have been made in shielding electromagnetic interference at higher frequencies (GHz range and above), a need still exists for compact, lightweight, and cost-effective materials for shielding low frequency electromagnetic radiation. [Means for solving the problem]

[0007] This section generally summarizes the disclosure and does not extensively disclose its entire scope or all of its features.

[0008] In one aspect, the present technology provides a multi-layer material for shielding low-frequency electromagnetic waves. The multi-layer material may include a plurality of repeating alternating layer sets of materials. Each repeating alternating layer set may include a conductive layer and a magnetic layer, which may include a continuous layer of a magnetic material. The multi-layer material is configured to shield electromagnetic waves that generally have low frequencies, for example, exhibit frequencies less than about 1 MHz. In some examples, the conductive layer may include a two-dimensional transition metal carbide.

[0009] In another aspect, the present technology provides a sprayable composite composition for shielding low frequency electromagnetic waves. The composite composition includes a liquid resin substrate and a flake-like material disposed within the liquid resin substrate. The flake-like material can include a plurality of repeating alternating material layer sets. Each repeating alternating material layer set can include a conductive layer and a magnetic layer. The magnetic layer can be provided as a continuous layer of magnetic material. Upon application to a substrate or structured component, the composite composition is configured to shield electromagnetic waves having a frequency of less than about 1 MHz.

[0010] In yet another aspect, the present technology provides a method of forming a composite material for shielding low frequency electromagnetic waves. The method includes providing a multilayer material including a plurality of repeating alternating layer sets of material. Each repeating alternating layer set includes a conductive layer and a magnetic layer including a continuous layer of magnetic material. The method includes shaping or sizing the multilayer material into flakes and creating a homogenous mixture of the flakes of the multilayer material and a liquid resin substrate. The method includes applying the homogenous mixture to a substrate or structured component to form a coating. In various aspects, the coating is configured to shield electromagnetic waves having a frequency of less than about 1 MHz.

[0011] Further areas of applicability and further ways of enhancing the disclosed technology will become apparent from the description provided. The description and specific examples in this summary are intended to be illustrative only and are not intended to limit the scope of the disclosure.

[0012] The present teachings will become more fully understood from the detailed description and the accompanying drawings, in which: [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram of a vehicle showing electromagnetic radiation emanating from devices such as a power control unit, a battery, and electrical lines. [Diagram 2] FIG. 2 is a diagram providing a first exemplary representation of a multi-layer material according to various embodiments of the present technology. [Diagram 3] FIG. 3 is a schematic diagram that provides a generalization of potential shielding mechanisms that may contribute to the shielding properties resulting from multilayer materials made according to the present technique. [Figure 4A] FIG. 4A is a diagram providing an additional example representation of a multi-layer material according to embodiments of the present technology that may use different materials within some layers. [Figure 4B] FIG. 4B is a diagram providing an additional example representation of a multi-layer material according to aspects of the present technology that may use different materials within some layers. [Figure 4C] FIG. 4C is a diagram providing an additional example representation of a multi-layer material according to embodiments of the present technology that may use different materials within some layers. [Diagram 5] FIG. 5 is a diagram providing an example representation of a coating including pieces or flakes of multi-layered material according to various embodiments of the present technology. [Figure 6A] FIG. 6A shows an example plot of shielding effectiveness versus frequency for a far-field simulation for a multilayer material having various numbers of layers and a fixed total thickness. [Figure 6B] FIG. 6B shows an example plot of shielding effectiveness versus frequency for a far-field simulation for a multilayer material having various numbers of layers and a fixed total thickness. [Figure 6C] FIG. 6C shows an example plot of shielding effectiveness versus frequency for a far-field simulation for a multilayer material with various numbers of layers and a fixed total thickness.

[0014] The figures described herein are intended to illustrate general features of methods, algorithms and devices among the features of the present technology for the purpose of explaining some aspects. These figures may not precisely reflect the features of any given aspect, and are not necessarily intended to define or limit specific embodiments falling within the scope of this technology. Furthermore, some aspects may incorporate features derived from combinations of figures. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] An effective electromagnetic shielding material must be able to reduce undesirable electromagnetic interference by various mechanisms, including both reflection and absorption and / or interference of electromagnetic waves. For certain types of low frequency interference, there may be a strong need for magnetic field shielding. The present technology provides lightweight, multi-layer composite materials useful as electromagnetic shielding materials, which also address the need for magnetic field shielding that may occur at low frequencies.

[0016] The multilayer composites of the present technology may be particularly useful in vehicles to shield low frequency electromagnetic waves and electromagnetic interference induced from electric and / or magnetic fields that may originate from one or more electronic devices. In various embodiments, the multilayer composites may include multiple repeating alternating layer sets of materials. Each repeating alternating layer set may include a conductive layer and a magnetic layer. As discussed in more detail below, the magnetic layer may include a continuous layer of magnetic material. The multilayer composites are generally configured to shield electromagnetic waves having relatively low frequencies, for example, less than about 1 MHz. In some embodiments, the multilayer composites may be configured to shield electromagnetic waves having frequencies less than about 100 kHz. The conductive layer may include a variety of different materials and configurations to provide high conductivity, and in some non-limiting embodiments may include two-dimensional transition metal carbides. It is contemplated that the multilayer composites may be provided as thin films or layers that can be used alone or in combination with another substrate or structural component. In other uses, the multilayer composites may be shaped and / or sized as small pieces or flakes. In various embodiments, the flakes can be mixed with a suitable substrate, such as a liquid resin, to form a mixture that can be applied / deposited via spray application techniques, for example, to form an electromagnetic shielding coating to be applied onto one or more shaped vehicle components.

[0017] FIG. 1 is a schematic illustration of an exemplary passenger vehicle 20 with front and rear seat occupants 22 in an interior passenger compartment 24. The vehicle 20 may include various components and electronic devices, and is specifically shown with a power control unit 26, a battery 28, and various wires and / or electrical lines 30. For illustrative purposes, the power control unit 26, the battery 28, and the electrical lines 30 are shown with the electromagnetic waves 32a, 32b, 32c that they emit. It is envisioned that the multilayer composite material of the present technology may be used as a thin film, membrane assembly, or coating that serves as an electromagnetic shield for vehicle components. For example, in various embodiments, it is contemplated that the multilayer composite material may be strategically applied or incorporated with other materials, such as insulators, on any substrate or structural component of the vehicle 20 to shield the passenger compartment 24 or other desired interior areas of the vehicle 20 from at least a portion of the electromagnetic waves 32a, 32b, 32c. It should be understood that although various aspects of the present technology may be discussed with reference to an electromagnetic shielding application for use within a vehicle 20, the present disclosure is applicable for non-automotive applications as well and is not intended to be limited in scope in any way. For example, multi-layer composites can be used in combination with many forms of base substrates or similar materials, which can be solid or porous, that provide an underlying structure that supports a thin film, membrane assembly or coating and has the ability to serve as an electromagnetic shield.

[0018] 2 is a schematic diagram providing a first exemplary representation of a multi-layer material 36 according to various embodiments of the present technology. The multi-layer material 36 is specifically shown with a first material layer set 38 and a second material layer set 40, with any number of repeating alternating layer sets positioned between the first and second layer sets 38, 40 to provide a total thickness or height dimension h. Although the thickness dimension h can vary based on many different factors and material properties, in various embodiments, the thickness dimension h can be less than about 200 μm, less than about 150 μm, less than about 100 μm, or even less than about 75 μm. As shown, each layer set 38, 40 can include a conductive layer 42 and a magnetic layer 44. The orientation or assembly sequence of the conductive layer 42 and the magnetic layer 44 within the layer set 38, 40 can vary.

[0019] As briefly mentioned above, an effective electromagnetic shielding material should be able to reduce undesirable electromagnetic interference by various mechanisms. It is generally understood that absorption is typically the primary or primary shielding mechanism, and reflection is often the secondary shielding mechanism. Reflection can include single and multiple reflections, as well as interlayer reflections occurring between distinct layers. FIG. 3 is a schematic diagram providing a generalization of the shielding mechanisms believed to contribute to the resulting shielding of the multilayer material of the present technology. For example, various incident electromagnetic waves 46 can travel in the "y" direction and first contact a surface 48 of the multilayer material 36. A portion of the incident wave 46 can immediately reflect from the surface 48 as a reflected wave 50, while other portions of the incident wave 46 can travel through the various layers as weakened transmitted waves 52, absorbed waves 54, and interlayer reflected waves 56 traveling substantially in the "x" direction. Some waves may ultimately pass as outgoing waves 58, but most likely attenuated with reduced intensity. Without being bound by theory, it is believed that in addition to reflection from the conductive layer 42, the use of the magnetic layer 44, which includes a magnetic material with a high magnetic permeability value, exhibits high shielding capability with respect to magnetic fields, which is highly advantageous when shielding low frequency electromagnetic waves. In particular, impedance mismatch between the various layers can be significant, causing increased internal reflections that can ultimately lead to absorption within the various layers. At low frequencies, it is believed that magnetic permeability has a stronger effect.

[0020] The conductive components provided in the conductive layers 42 of the multi-layer material 36 of the present technology preferably have a relatively high conductivity in order to provide charge carriers for interacting with the electromagnetic field. Many conventional conductive layers useful in electromagnetic shielding include conductive metals. Thus, the conductive layers 42, in their simplest form, can be provided as very thin, highly conductive metals such as metal films or layers. For example, a copper layer disposed between magnetic materials can improve shielding effectiveness due to its relatively high conductivity. In many instances, each conductive layer 42 can be provided with an atomically thin thickness dimension as a thin monolayer, or in some instances with a thickness dimension of about 10 μm to about 50 μm. In some embodiments, the higher conductivity of the conductive layers 42 can improve shielding effectiveness as the thickness dimension increases. Thus, the conductive layers 42 can function as conductive spacers. The conductive layers 42 of different layer sets can generally be provided with substantially the same thickness dimension. In other embodiments, some conductive layers 42 can be provided with different thickness dimensions. In yet other embodiments, it is envisioned that conductive layer 42 may also be provided as a polymer matrix composite that includes a conductive material, such as a conductive metal.

[0021] As an alternative to thin metal films or layers, the present technology also provides for the use of MXene as the conductive layer 42 of the multi-layer material 36. As known in the art, MXene is a family of two-dimensional (2D) transition metal carbides, carbonitrides and nitrides that have been used in many applications. With respect to electromagnetic shielding, MXene exhibits excellent flexibility, is easy to manufacture and process, and exhibits high conductivity at minimal thickness. In various embodiments, MXene can be provided as a thin layer or monolayer, e.g., a layer a few atoms thick. In other embodiments, MXene can be provided as multiple stacked layers forming the conductive layer 42. In embodiments using multiple layers, the layers can include the same or different materials and compositions. The layers can also be provided with the same or different thickness dimensions.

[0022] As is known in the art, an MXene compound or composition generally comprises a two-dimensional inorganic material arranged as a layer having a first and second surface. The MXene layer can be a substantially two-dimensional array of crystalline cells, each of which is an M crystalline cell, such that each X is positioned within an octahedral array of M. n+1 X n where M is at least one Group IIIB, IVB, VB or VIB metal; each X is C, N or a combination thereof; and n=1, 2 or 3.

[0023] MXene compositions have been described in various patents and publications, and for the sake of brevity, various details of the composition, electrical properties, and methods of making the MXene compositions are not included herein. Any known MXene composition should be considered as potentially applicable for use in the present technology. However, for the sake of completeness, M can be at least one of Sc, Y, Lu, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, or W. Some of these compositions contain M n+1 X n has one or more empirical formulas including ScC, TiC, VC, CrC, CrN, ZrC, NbC, HfC, TiC, VC, TaC, TiC, VC, TaC, TiC, VC, TaC, ScN, TiN, VN, CrN, CrN, ZrN, NbN, HfC, TiN, VC, TaC, Ti ... n+1 X n The structure includes Ti3C2, Ti2C, Ta4C3 or (V 1 / 2 Cr 1 / 2 In some other embodiments, M is Ti or Ta and n is 1, 2, or 3, e.g., having an empirical formula of Ti3C2 or Ti2C, where at least one of the surfaces of each layer has a surface termination comprising a hydroxide, oxide, suboxide, or combination thereof.

[0024] In another embodiment, M'2M'' is an octahedral array of M' and M'', where each X is located within the octahedral array of M' and M''. n X n+1 It has an empirical formula of M'' n X exists as a separate two-dimensional array of atoms intercalated (sandwiched) between a pair of two-dimensional arrays of M' atoms, where M' and M'' are different group IIIB, IVB, VB or VIB metals (including where M' and M'' are Ti, V, Nb, Ta, Cr, Mo or combinations thereof), each X is C, N or combinations thereof; n=1 or 2. For completeness, in some embodiments, M' can be Mo and M'' can be Nb, Ta, Ti or V, or combinations thereof. In other embodiments, n is 2, M' can be Mo, Ti, V or combinations thereof, and M'' can be Cr, Nb, Ta, Ti or V, or combinations thereof. In still other embodiments ... n X n+1 comprises Mo2TiC2, Mo2VC2, Mo2TaC2, Mo2NbC2, Mo2Ti2C3, Cr2TiC2, Cr2VC2, Cr2TaC2, Cr2NbC2, Ti2NbC2, Ti2TaC2, V2TaC2, or V2TiC2, preferably Mo2TiC2, Mo2VC2, Mo2TaC2, or Mo2NbC2 or their nitride or carbonitride analogs. In yet another embodiment, M'2M'' n X n +1 includes Mo2Ti2C3, Mo2V2C3, Mo2Nb2C3, Mo2Ta2C3, Cr2Ti2C3, Cr2V2C3, Cr2Nb2C3, Cr2Ta2C3, Nb2Ta2C3, Ti2Nb2C3, Ti2Ta2C3, V2Ta2C3, V2Nb2C3, or V2Ti2C3, preferably Mo2Ti2C3, Mo2V2C3, Mo2Nb2C3, Mo2Ta2C3, Ti2Nb2C3, Ti2Ta2C3, or V2Ta2C3, or nitride or carbonitride analogues thereof.

[0025] In yet other aspects, the present technology may include the use of self-assembled magnetized MXene layers, magnetically doped MXene layers, as well as layers including composites of MXene and various magnetic materials that may provide conductive magnetic composites. Non-limiting examples of Ti3C2MXene based composites include carbon nanotubes-Ti3C2MXene; nanocarbon spheres-Ti3C2MXene; amorphous carbon-TiO2-Ti3O2MXene; ZnO-Ti3C2MXene; Ni0.5Zn0.5Fe2O4-Ti3C2MXene; Fe3O4-Ti3C2MXene; Ba3Co2Fe 24 O 41 -Ti3C2MXene;Ni-Ti3C2MXene;Co3O4-Ti3C2MXene;Co 0.2 Ni 0.4 Zinc 0.4 Fe2O4-Ti3C2MXene; and FeCo-Ti3C2MXene. x Various 2-D Ti3C2TxMXenes in which T represents surface termination groups such as -OH, =O, and -F after etching are also contemplated.

[0026] The magnetic layers 44 of the multi-layer material 36 may be disposed immediately adjacent to the conductive layers 42 of each of the alternating layer sets 38, 40. Similarly, the alternating layer sets 38, 40 may be disposed immediately adjacent to one another. However, in some embodiments, small, discontinuous gaps or pockets 60 (FIG. 3) may optionally be present between some of the alternating layer sets 38, 40. In various embodiments, the magnetic layer 44 includes at least one magnetic material such that the magnetic layer 44 exhibits a relative permeability, which is a measure of the resistance of a material to the formation of a magnetic field, generally greater than 1, greater than 10, greater than 100, and typically in the range of about 100 to about 1,000,000 depending on the material. Permeability is typically measured in H / m (henry / m) or Newtons / Ampere. 2 (NA 2 ) units.

[0027] Non-limiting exemplary materials that may be included in the magnetic layer 44 include various ferromagnetic metals, such as Fe, Ni, Co, and combinations of Si, Bi, K, Cu, Zn, Mn, etc. By way of example, specific materials may include neodymium magnets, austenitic stainless steels, martensitic stainless steels (hardened or annealed), carbon steels, carbonyl iron powder compounds, silicon iron powder compounds, iron powder compounds, Al-Si-Fe powder compounds (Sendust), nickel iron powder compounds, Mo-Fe-Ni powder compounds (Molypermalloy powder, MPP), ferrites (Cobalt, Nickel, Zinc; Magnesium, Manganese, Zinc; Nickel, Zinc; Manganese, Zinc), ferritic stainless steels (hardened), electrical steels, iron (99.8% purity), cobalt-iron, Mu-metal, NANOPERM®, Permalloy, iron (99.95% purity Fe annealed in H), Metglas 2714A (annealed), NANOMET®, and combinations thereof.

[0028] In various embodiments, the magnetic layer 44 may be provided as a continuous layer of material with a high density that is considered distinct from a non-continuous layer that may include isolated magnetic particles. The continuous layer of material may include magnetic particles having particle sizes with major dimensions measured in the nanometer range, sometimes referred to herein as magnetic nanoparticles. In various embodiments, the continuous layer of magnetic material may include a solid layer of magnetic nanoparticles. Such a continuous layer of magnetic material may be formed using various known techniques, including deposition and chemical techniques. In some examples, the continuous layer of magnetic material may include annealed magnetic nanoparticles, and the layer may be formed using an annealing process that fuses the magnetic nanoparticles. The thickness dimension of the magnetic layer may vary based on the selection of materials and the desired properties, and may be in the range of about 1 μm to about 200 μm, about 10 μm to about 100 μm, or about 30 μm to about 50 μm. Thus, in various embodiments, the ratio of the thickness dimension of the conductive layer 42 to the thickness dimension of the magnetic layer 44 may vary and may be within a wide range of about 1:0.01 to about 1:1,000. In other embodiments, the ratio of the thickness dimension of the conductive layer 42 to the thickness dimension of the magnetic layer 44 is from about 1:1 to about 1:4. The magnetic layers 44 of the different layer sets can generally be provided with substantially the same thickness dimension. In other embodiments, some of the magnetic layers 44 can be provided with different thickness dimensions.

[0029] 4A-4C show additional example representations of multi-layer materials according to embodiments of the present technology that may use different materials or different compositions in some layers. Using different materials in one or more of the different layers may affect differences in impedance values, which in turn may affect different electromagnetic shielding properties, such as increased reflection. For example, a multi-layer material may include a first set of alternating layers with a first conductive layer and a first magnetic material; and a second set of alternating layers with a second conductive layer different from the first conductive layer and a second magnetic material different from the first magnetic material. FIGS. 4A-4C provide non-limiting example configurations of multi-layer composite materials with alternating layer sets including different materials.

[0030] As shown in Fig. 4A, the multi-layer material 62 specifically includes three alternating layer sets. Each set may include conductive layers 42a, 42b, 42c with different material compositions, while the magnetic layers 44 each have the same material composition. As shown in Fig. 4B, the multi-layer material 64 similarly includes three alternating layer sets, but each set may provide the same material composition for each conductive layer 42, while each set includes magnetic layers 44a, 44b, 44c with different material compositions. As shown in Fig. 4C, the multi-layer material includes three alternating layer sets, with three different materials in the conductive layers 42a, 42b, 42c and three different materials in the magnetic layers 44a, 44b, 44c.

[0031] The multi-layer composites of the present technology can also be used with additional conductive fillers as known in the art to further affect electromagnetic interference shielding. Non-limiting examples can include various carbon nanotubes, carbon nanofibers, graphene, etc.

[0032] In embodiments where it may not be feasible to use the multilayer composite as a thin film, which in some cases may be too fragile for a particular application, the present technology also contemplates shaping and / or sizing the multilayer composite as small pieces or flakes. In various embodiments, the flakes can be mixed with a suitable substrate, such as a liquid resin, to form a mixture that can be applied / deposited, such as via spray application techniques, to form an electromagnetic shielding coating to be applied, for example, onto one or more vehicle components, which may have complex or three-dimensional shapes.

[0033] FIG. 5 is a schematic diagram providing an exemplary representation of a resulting coating 70 including pieces or flakes 72 of multi-layered material disposed within a resin 74 according to various embodiments of the present technology. An exemplary sprayable composite composition may include any suitable liquid resin substrate with small pieces or flakes 72 provided as a substantially homogenous mixture disposed therein. The dimensions of the flakes 72, also referred to as flaky material, may vary based on the particular application and desired properties. In various embodiments, one or more surface dimensions of the flaky material may be from about 5 μm to about 100 μm. In some cases, the flakes 72 may have substantially uniform dimensions, while in other embodiments, it may be desirable to include flakes 72 with the mixture having different size dimensions, e.g., different aspect ratios of height:width. The flakes 72 may be provided with different types and combinations of materials as well. The flake material may include multiple repeating sets of alternating layers of materials as described above. For example, each repeating alternating layer set can include a conductive layer and a magnetic layer, and the magnetic layer can be provided as a continuous layer of magnetic material. Although the flakes 72 in FIG. 5 are illustrated as generally rectangular shaped, the flake geometries can be substantially more random, with different dimensions as well as various alignments within the resin 74. Upon application of the composite material to a substrate or structured component as a coating, which can be applied using any known spray application suitable for the material, the coating composite composition can be configured to shield electromagnetic waves having frequencies less than about 1 MHz.

[0034] The present technology further provides a method for forming a composite material for shielding low-frequency electromagnetic waves. The method can include providing a multilayer material that includes a plurality of repeating alternating layer sets of materials as described above. For example, each repeating alternating layer set includes a conductive layer and a magnetic layer that can include a continuous layer of magnetic material. The method includes shaping or sizing the multilayer material into flakes, and then producing a homogeneous mixture of the flakes of the multilayer material with a suitable substrate, such as a liquid resin material. The method includes applying the homogeneous mixture to a substrate or structured component to form one or more film coatings. In various embodiments, the resulting coating is configured to shield electromagnetic waves having a frequency of less than about 1 MHz. EXAMPLES

[0035] Various aspects of the present disclosure are further illustrated with reference to the following examples, it being understood that these examples are provided to illustrate particular aspects of the disclosure and should not be construed as limiting the scope of the disclosure in or to any particular aspect.

[0036] 6A-6C each illustrate an exemplary plot of frequency (MHz) vs. shielding effectiveness (dB) for a far-field simulation using one set of multi-layer materials. Each figure compares the same defined total thickness h, but different numbers of repeating layer sets provided (e.g., 2-10 layers or 1-5 repeating layer sets). FIG. 6A illustrates data for a first set of five multi-layer materials, with a total thickness h of 100 μm for each multi-layer material. FIG. 6B illustrates data for a second set of five multi-layer materials, with a total thickness h of 150 μm for each multi-layer material. FIG. 6C illustrates data for a third set of five multi-layer materials, with a total thickness h of 200 μm for each multi-layer material. The properties used in the simulation were a permittivity of 22, a permeability of 1, and a dc of 5e. 5 A conductive layer having a conductivity of 0.025 S / m; and a dielectric constant of 0.025 e 3The magnetic permeability, and 5e 7 The layer contained a repeating set of alternating magnetic layers with a conductivity of 10 ...

[0037] Shielding effectiveness can be considered similar to the measurement of electromagnetic interference shielding efficiency, a term used to characterize the ability of a material to block electromagnetic waves. Total electromagnetic interference shielding efficiency can be considered as the sum of absorption shielding efficiency, reflection shielding efficiency, and multiple internal reflection shielding efficiency. For high electromagnetic interference shielding efficiency values, the contribution of multiple internal reflections is incorporated into the absorption, as re-reflected waves are absorbed as heat (due to internal reflections) or dissipated within the shielding material.

[0038] Besides reflection and absorption, multiple reflection is also a shielding mechanism, which means reflection at various surfaces or interfaces inside a material. However, multiple reflection losses can be neglected if the distance between the reflecting surfaces or interfaces is greater than the skin depth. The electric field of a plane wave penetrating a conductor decreases exponentially with increasing depth of the incoming conductor, so that the electromagnetic wave penetrates only the area near the surface of the conductor. The depth at which the field strength drops to 1 / e of its incident value is called the skin depth: δ = (πfμσ) -1 where f is frequency, μ is magnetic permeability (μ=μ o μ r ), and μ o is 4 × 10 -7 H / m, μ ris the relative permeability and σ is the electrical conductivity. Thus, the skin depth decreases as frequency, electrical conductivity or permeability increases. Using the multi-layer materials of the present technology, the skin depth limit is overcome, where shielding beyond this limit is generally provided from internal reflections.

[0039] The preceding description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses in any manner. The phrase A, B and at least one of C as used herein should be considered to mean the logic (A or B or C) with a non-exclusive logic "OR". Various steps within a method can be performed in different orders without altering the principles of the present disclosure. The disclosure of a range includes the disclosure of all ranges and subranges within all ranges.

[0040] The headings used herein (e.g., "Background" and "Summary") and subheadings are intended for a general organization of the subject matter within the disclosure only and are not intended to limit the disclosure of the technology or any aspect thereof. The recitation of multiple embodiments having stated features is not intended to exclude other embodiments having additional features or other embodiments incorporating different combinations of the stated features.

[0041] As used herein, the terms "comprise" and "include" and variations thereof are intended to be non-limiting, such that a recitation or listing of consecutive items does not exclude other similar items that may also be useful in the devices and methods of the technology. Similarly, the terms "can" and "may" and variations thereof are intended to be non-limiting, such that a statement that an embodiment can or may include certain elements or features does not exclude other embodiments of the technology that do not include those elements or features.

[0042] The broad teachings of the present disclosure can be implemented in a variety of forms. Thus, while the present disclosure includes specific examples, the true scope of the present disclosure should not be so limited, since other modifications will become apparent to those skilled in the art upon review of the specification and the following claims. References herein to an aspect or various aspects mean that a particular feature, structure, or characteristic described in connection with an embodiment or a particular system is included in at least one embodiment or aspect. The appearance of the phrase "in one aspect" (or variations thereof) does not necessarily refer to the same aspect or embodiment. It should also be understood that the various method steps discussed herein need not be performed in the same order as depicted, and that not every method step is required for every aspect or embodiment.

[0043] The above description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment and, where applicable, are interchangeable and usable in selected embodiments even if not specifically shown or described. This, in turn, can be varied in various ways. Such variations should not be considered as departures from the disclosure, and all such modifications are intended to be included within the scope of the present disclosure.

Claims

1. In a multi-layer material for shielding low-frequency electromagnetic waves: a plurality of repeating alternating layer sets of material, each repeating alternating layer set comprising: A conductive layer; a magnetic layer comprising a continuous layer of magnetic material; A multi-layer material comprising: configured to block electromagnetic waves having a frequency less than about 1 MHz; a first set of alternating layers with a first conductive layer and a first magnetic material; and a second set of alternating layers with a second conductive layer different from the first conductive layer and a second magnetic material different from the first magnetic material. Multilayer material.

2. The multi-layer material of claim 1 , wherein the conductive layer comprises a highly conductive metal.

3. The multi-layer material of claim 1 , wherein the conductive layer comprises a two-dimensional transition metal carbide.

4. 10. The multi-layer material of claim 1, wherein the plurality of sets of repeating alternating layers of material have a total thickness dimension of less than about 200 μm.

5. 10. The multi-layer material of claim 1, wherein the plurality of sets of repeating alternating layers of material have a total thickness dimension of less than about 150 μm.

6. 10. The multi-layer material of claim 1, wherein each conductive layer has a thickness dimension of about 10 μm to about 50 μm.

7. 10. The multi-layer material of claim 1, wherein the multi-layer material is configured to shield electromagnetic waves having frequencies less than about 100 kHz.

8. The multi-layer material of claim 1 , wherein the continuous layer of the magnetic material comprises annealed magnetic nanoparticles.

9. The multi-layer material of claim 1 , wherein the continuous layer of the magnetic material comprises a solid layer of magnetic nanoparticles.

10. 10. The multi-layer material of claim 1, wherein said successive layers of said magnetic material exhibit a magnetic permeability number of from about 100 to about 1,000,000.

11. A vehicle component with an electromagnetic shield comprising the multi-layer material of claim 1.

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