Patent Application
20130330511
In thin composites, absorption of electromagnetic (EM) waves having gigahertz frequencies, referred to herein as gigahertz EM absorption, can be accomplished by allowing for multiple layers of composites, each layer having an effective index of refraction increasing in magnitude along a stacking direction of such layers. Such structures (often referred to as Salisbury screens) can be tuned for either specific frequencies or for limited block of frequencies in the EM radiation spectrum. By construction, such structures can present nearly optimal performance for normal incident EM waves having gigahertz frequencies, whereas such structures can fail to exhibit absorption of off-normal incident EM waves with gigahertz frequencies.
Another approach to forming a material that exhibits absorption of EM waves having gigahertz frequencies generally entails adding magnetic inclusions into a thin composite in a manner such that the effective permeability (μ) of the resulting composite is substantially equal to the effective permittivity (ε) thereof, with μ and ε typically being complex numbers. Yet, at gigahertz frequencies, most magnetic inclusions that are typically employed have small (e.g., about 1 to about 20) real values and small (e.g., about 0 to about 1) imaginary values for μ/μ0, while the composites incorporating such inclusions also typically are electrically conductive and thus have a large imaginary value for ε/ε0. In such typical scenarios, reflection off the composite commonly poses a problem to attaining satisfactory gigahertz EM absorption. Various other magnetic materials have been utilized in other approaches without yielding broadband absorption.
The disclosure relates to materials having textured surfaces and exhibiting absorption of electromagnetic (EM) waves with gigahertz frequencies, referred to as gigahertz EM waves. A textured surface can comprise a plurality of protrusions that can permit absorption of the gigahertz EM waves. Morphology of the plurality of protrusions can control the absorption properties, e.g., absorption coefficients or specific frequency of absorbed EM radiation, of such materials. The morphology can include one or more of size of the protrusions in the plurality of protrusions, surface packing of such protrusions, surface coverage of the textured surface of the materials, effective density of carriers in the materials having the textured surface, or the like. While various exemplary embodiments and related aspects of the disclosure are illustrated with textured slabs, the materials having the textured surface can adopt other shapes. The materials having textured surfaces as described herein present enhanced gigahertz EM absorption when compared to materials formed from the same compound but without textured surfaces.
Additional aspects, features, or advantages of the subject disclosure will be set forth in part in the description which follows and annexed drawings, and in part will be apparent from such description and drawings, or may be learned by practice of the subject disclosure. The advantages of the disclosure can be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the subject disclosure.
The accompanying drawings are incorporated and illustrate exemplary embodiment(s) of the disclosure and together with the description and claims appended hereto serve to explain various principles, features, or aspects of the subject disclosure.
The subject disclosure may be understood more readily by reference to the following detailed description of exemplary embodiments of the subject disclosure and to the Figures and their previous and following description.
Before the present materials, compounds, compositions, articles, devices, and/or methods are disclosed and described, it is to be understood that the subject disclosure is not limited to specific coating materials, slabs, thin films, or the like, and surface shaping processes for absorption of electromagnetic radiation having gigahertz frequencies. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.
As used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise
Ranges may be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.
In the subject specification and in the claims which follow, reference may be made to a number of terms which shall be defined to have the following meanings: “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.
Throughout the description and claims of this specification, the word “comprise” and variations of the word, such as “comprising” and “comprises,” means “including but not limited to,” and is not intended to exclude, for example, other additives, components, integers or steps. “Exemplary” means “an example of” and is not intended to convey an indication of a preferred or ideal embodiment. “Such as” is not used in a restrictive sense, but for explanatory purposes.
Reference will now be made in detail to the various embodiment(s), aspects, and features of the subject disclosure, example(s) of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like parts.
As described in greater detail below, in various aspects, the disclosure relates to materials having a textured surface and exhibiting absorption of EM waves having gigahertz frequencies. The textured surface can comprise a plurality of protrusions that can permit gigahertz EM absorption. Morphology of the plurality of protrusions can control the absorption properties (e.g., absorption coefficients or specific frequency of absorbed EM radiation) of such materials. The morphology can include one or more of size of the protrusions in the plurality of protrusions, surface packing of such protrusions, surface coverage of the textured surface of the materials, effective density of carriers in the materials having the textured surface, or the like. While various exemplary embodiments and related aspects of the disclosure are illustrated with textured slabs, the materials having the textured surface in accordance with the disclosure can adopt other shapes.
Referring to the drawings,
In one embodiment, the substrate portion 115 and the textured portion 120 can be monolithic. As illustrated in diagram 140, the surface shaping process 150 can form a textured portion 160 comprising a plurality of protrusions from machining the substrate 105 according to a predetermined design (e.g., a specific desired morphology) for the plurality of structural members. In addition or in the alternative, the shaping process 150 can form the textured portion 160 comprising the plurality of protrusions from etching the substrate 105 according to a predetermined mask design effective to yield the plurality of structural members. The predetermined mask can comprise material resilient to a chemical etcher or plasma, the material occluding portions of the substrate according to a desired pattern of structural members. Etching of the masked substrate under controlled conditions (time of exposure to etching agent, strain applied to the substrate, etc.) as part of the surface shaping process 110 yields the plurality of protrusions. It should be appreciated that the surface process 150 embodies the surface shaping process 110. It should also be appreciated that the textured portion 160 embodies the textured portion 120, and the substrate portion 155 embodies the substrate portion 115.
In another embodiment, the material having the textured portion 120 and the substrate portion 115 can be formed from a plurality of two or more materials. As illustrated in diagram 160, the surface shaping process 110 can include a deposition process 170 that can coat the substrate 105 with a layer 180. The material of the layer 180 generally is different from the material of substrate 105. For example, the material of substrate 105 can be a first conductive thermoplastic composite, and the material of the layer 180 can be a second conductive thermoplastic composite. The coated substrate comprising a substrate portion 175 and the layer 180 can be further processed according to a surface shaping process 185 to yield a textured portion 190, comprising a plurality of protrusions, and the substrate portion 175. In one implementation, the coated substrate can be machined according to a predetermined design for the plurality of protrusions. In another implementation, the coated substrate can be etched according to a predetermined mask design effective to yield the plurality of protrusions. It should be appreciated that the textured portion 190 embodies the textured portion 120 described herein.
In other embodiments, the surface shaping process 110 can permit forming the textured portion 120 from adhesive bonding of each structural member of a plurality of members to the substrate 105. In still other embodiments, the surface shaping process 110 can permit forming the textured portion 120 from ultrasonic welding of each protrusion of the plurality of protrusion to the substrate.
In one embodiment, the substrate 105 can be a thin, electrically conductive material. The substrate 105 can have a thickness smaller than about 2 mm. In one aspect, the electrically conductive material can be an electrically conductive thermoplastic composite. The electrically conductive thermoplastic composite can comprise a plurality conductive fibers dispersed in a polymer matrix. The plurality of conductive fibers can define a specific volumetric loading of the polymer matrix. As an example, the electrically conductive thermoplastic composite can be a Faradex® compound, produced by SABIC Innovative Plastics of Pittsfield, Mass. The electrically conductive material can have permittivity ε and permeability μ, with an effective index of refraction n having a real part √{square root over (εμ)}, and the textured portion 120 can have structural members with characteristic sizes (height size, base diameter size, etc.) of the order of λ/√{square root over (εμ)}. Here, λ is a wavelength of electromagnetic radiation impinging onto the textured portion 120. In such scenario, for wavelengths of EM radiation having gigahertz frequencies, e.g., λ in the range from about 1 cm to about 30 cm, and values of √{square root over (εμ)} in the range from about 5 to about 40, the structural members of the texture portion 120 can have characteristic sizes of the order of 0.1 mm to 100 mm. Accordingly, when the surface shaping process 110 produces the textured portion 120 with structural members having such characteristic sizes, the incident gigahertz EM radiation can be absorbed at the composite material. Without intending to be bound by theory, modeling, or simulation, gigahertz EM absorption in the textured portion 120 can be understood as a result of multiple scattering—as opposed to a single scattering event in substrate 105—of the EM radiation in directions substantially parallel to a surface of the composite material and normal to the direction of incidence of such radiation. Multiple scattering of the gigahertz EM radiation can permit additional absorption to occur at the textured portion 120.
In one embodiment, the textured portion 120 can be a textured surface of the substrate 105 that results from treating (e.g., texturizing) the substrate 105 with the surface shaping process 110 to produce a plurality of protrusions located at a surface of the substrate 105. The plurality of protrusions embody the plurality of structural members discussed herein. Treating the substrate 105 with the surface shaping process 110 can yield a textured slab exhibiting absorption of electromagnetic radiation at gigahertz frequencies. To at least such end, the surface shaping process 110 can yield protrusions with characteristic sizes of the order of λ/√{square root over (εμ)}, with λ being the wavelength of electromagnetic radiation having gigahertz frequencies, and ε and μ being the permittivity and permeability, respectively, of material of the substrate 105. In one embodiment, the gigahertz frequencies can span the range from about 1 GHz to about 20 GHz. The textured slab can have a thickness in the range from about 1 mm to about 60 mm.
In another embodiment, a material having a textured surface formed according aspects described herein can comprise a substrate (e.g., substrate 105) of a first material, and an assembly of a second material coupled to the substrate, the assembly comprising a plurality of protrusions (e.g., textured portion 190) located at a surface of the substrate the substrate and the assembly forming a textured slab that exhibits absorption of electromagnetic radiation at gigahertz frequencies. Such material can be referred to as a coating material.
In certain implementations, the textured slab can have a thickness from the group of about 10 mm, about 8 mm, about 6 mm, about 4 mm, about 3 mm, and about 2 mm. In other implementations, the textured can have a thickness in the range of about 2 mm to about 10 mm. With respect to the substrate, in one aspect, the substrate can have a thickness in the range of about 1 mm to about 2 mm. In another aspect, the substrate can have a thickness smaller than about 2 mm. In yet another aspect, the substrate can have a thickness greater than about 1 mm.
The gigahertz frequencies can span the range from about 1 GHz to about 20 GHz. As illustrated herein (see, e.g.,
In certain embodiments, the plurality of protrusions forms a disordered array. In additional or alternative embodiments, the plurality of protrusions forms an ordered array. In one aspect, for an ordered array, the plurality of protrusions is arranged in a periodic lattice, such as a square lattice or a hexagonal lattice. As described herein, the periodic lattice can be represented by a plurality of lattice vectors, each lattice vector representing a single protrusion of the plurality of protrusions. In addition or in the alternative, the periodic lattice can be a lattice with a basis, the basis comprising two protrusions of the plurality of protrusions. The morphology of the plurality of protrusions in the coating material can comprise uniform shapes. In one aspect, each of the plurality of protrusions can have a shape comprising a circular base in contact with the surface of the substrate. In another aspect, each of the plurality of protrusions can have a shape comprising a confined base (e.g., a base of finite spatial extent) in contact with the surface of the substrate, the confined base being a lamina having a predetermined perimeter (e.g., a circumference, a parallelogram, etc.). In yet another aspect, each of the plurality of protrusions can have a shape having an aspect ratio smaller than about 4; however, protrusions having larger aspect ratios also are contemplated. It should be appreciated that for the plurality of protrusions described herein, large aspect ratios (e.g., larger than about 4) can enhance gigahertz absorption at the textured surfaces of the disclosure since, for example, reflection at such surfaces can be reduced when the gradient of the effective index of refraction is reduced in a direction normal to a surface having the plurality of protrusions.
In one embodiment, the first material and the second material can be substantially the same, the first material being a conductive thermoplastic composite. As described herein, the conductive thermoplastic composite comprises a plurality of conductive fibers dispersed in a polymer matrix. The plurality of conductive fibers can define a specific volumetric loading of the polymer matrix. In such scenario, the textured slab can be monolithically formed from machining the substrate (e.g., substrate 105) according to a predetermined design for the plurality of protrusions. In one aspect, the textured slab is monolithically formed from etching the substrate according to a predetermined mask design effective to yield the plurality of protrusions. Such etching can embody the surface shaping process 110. In another aspect, the textured slab can be formed from injection molding (e.g., another embodiment of surface shaping process 110) of a monolithic slab (e.g., substrate 105) of the conductive thermoplastic composite utilizing a textured mold shaped according to a predetermined design of protrusions to be formed onto the textured slab. While such injection molding approach is described in reference to the conductive thermoplastic composite, such approach can be utilized for other materials. In yet another aspect, the textured slab can be formed from compression molding (e.g., yet another embodiment of surface shaping process 110) of a monolithic slab (e.g., substrate 105) of the conductive thermoplastic composite followed by processing (e.g., machining or etching) of the compressed monolithic slab to yield a desired treated surface having the plurality of protrusions. While such compression molding approach is described in reference to the conductive thermoplastic composite, such approach can be utilized for other materials.
In another embodiment, the first material is a first conductive thermoplastic composite, and the second material is a second conductive thermoplastic composite. In such scenario, in one implementation, the textured slab is monolithically formed from (i) coating the substrate with a second material; and (ii) machining the coated substrate according to a predetermined design for the plurality of protrusions. In another implementation, the textured slab is monolithically formed from (i) coating the substrate with a second material; and (ii) etching the coated substrate according to a predetermined mask design effective to yield the plurality of protrusions.
In certain embodiments, substrate materials and assembly materials that are substantially the same or different, the textured slab of the coating material of the disclosure, can be formed from adhesive bonding of each protrusion of the plurality of protrusion to the substrate. In addition or in the alternative, the textured slab can be formed from ultrasonic welding of each protrusion of the plurality of protrusion to the substrate.
Optical properties of the materials with textured surfaces of the disclosure can be analyzed through experiment and simulation.
Absorption spectrum and reflectance spectrum are measured and simulated for normal incidence of an EM wave having a gigahertz frequency within a broadband portion (e.g., from 1 GHz to about 20 GHz) of the EM radiation spectrum. As shown in
As illustrated in
Materials having textured surfaces with disorder also can exhibit gigahertz EM absorption, as illustrated in
It should be appreciated that the various aspects of absorption of EM radiation at gigahertz frequencies disclosed in
While the systems, devices, apparatuses, protocols, processes, and methods have been described in connection with exemplary embodiments and specific illustrations, it is not intended that the scope be limited to the particular embodiments set forth, as the embodiments herein are intended in all respects to be illustrative rather than restrictive.
Unless otherwise expressly stated, it is in no way intended that any protocol, procedure, process, or method set forth herein be construed as requiring that its acts or steps be performed in a specific order. Accordingly, in the subject specification, where description of a process or method does not actually recite an order to be followed by its acts or steps or it is not otherwise specifically recited in the claims or descriptions of the subject disclosure that the steps are to be limited to a specific order, it is no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps or operational flow; plain meaning derived from grammatical organization or punctuation; the number or type of embodiments described in the specification or annexed drawings, or the like.
It will be apparent to those skilled in the art that various modifications and variations can be made in the subject disclosure without departing from the scope or spirit of the subject disclosure. Other embodiments of the subject disclosure will be apparent from consideration of the specification and annexed drawings, and practice of the subject disclosure as described herein. It is intended that the specification, illustrations in the annexed drawings, and examples be considered as non-limiting illustrations only, with a true scope and spirit of the disclosure being indicated by the following claims.
