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Manufacture of electrical and magnetic graded and anisotropic materials for novel manipulations of microwaves.

Grant PS, Castles F, Lei Q, Wang Y, Janurudin JM, Isakov D, Speller S, Dancer C, Grovenor CR - Philos Trans A Math Phys Eng Sci (2015)

Bottom Line: While aspects of ST theory have been confirmed using these structures, they are often disadvantaged by narrowband operation, high losses and difficulties in implementation.A key aim is to highlight the limitations and possibilities of various manufacturing approaches, to constrain designs to those that may be achievable.The article focuses on polymer-based nano- and microcomposites in which interactions with microwaves are achieved by loading the polymers with high-permittivity and high-permeability particles, and manufacturing approaches based on spray deposition, extrusion, casting and additive manufacture.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK patrick.grant@materials.ox.ac.uk.

ABSTRACT
Spatial transformations (ST) provide a design framework to generate a required spatial distribution of electrical and magnetic properties of materials to effect manipulations of electromagnetic waves. To obtain the electromagnetic properties required by these designs, the most common materials approach has involved periodic arrays of metal-containing subwavelength elements. While aspects of ST theory have been confirmed using these structures, they are often disadvantaged by narrowband operation, high losses and difficulties in implementation. An all-dielectric approach involves weaker interactions with applied fields, but may offer more flexibility for practical implementation. This paper investigates manufacturing approaches to produce composite materials that may be conveniently arranged spatially, according to ST-based designs. A key aim is to highlight the limitations and possibilities of various manufacturing approaches, to constrain designs to those that may be achievable. The article focuses on polymer-based nano- and microcomposites in which interactions with microwaves are achieved by loading the polymers with high-permittivity and high-permeability particles, and manufacturing approaches based on spray deposition, extrusion, casting and additive manufacture.

No MeSH data available.


Related in: MedlinePlus

Magnetically aligned anisotropic composites composed of Fe flakes in epoxy. (a,b) Electron micrographs show preferential alignment of the flakes due to the applied magnetic field. The insets indicate the direction of the magnetic field (black arrows) with respect to the sample geometry and the orientation of the exposed section (pale blue) (scale bars, 50 μm). (c) Photograph of the samples and the stripline measurement apparatus used to retrieve the effective permeability of the composite. (d) The real part of the relative permeability as a function of frequency for three types of sample, showing the induced anisotropy of the magnetically aligned samples.
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RSTA20140353F2: Magnetically aligned anisotropic composites composed of Fe flakes in epoxy. (a,b) Electron micrographs show preferential alignment of the flakes due to the applied magnetic field. The insets indicate the direction of the magnetic field (black arrows) with respect to the sample geometry and the orientation of the exposed section (pale blue) (scale bars, 50 μm). (c) Photograph of the samples and the stripline measurement apparatus used to retrieve the effective permeability of the composite. (d) The real part of the relative permeability as a function of frequency for three types of sample, showing the induced anisotropy of the magnetically aligned samples.

Mentions: Bulk composites are typically isotropic in terms of ε′ and μ′ but these properties in a composite can be contrived to be anisotropic with suitable processing: for example, the alignment of magnetic particles in an external magnetic field applied to an epoxy-based Fe-containing composite during curing, as shown in figure 2. Anisotropic superstructures may also be contrived using arrangements of bulk isotropic materials: for example, if an isotropic composite is formed into a regular array of uniformly oriented rods, it behaves as a homogeneous, but anisotropic, material for wavelengths much larger than the distance between the rods [22].Figure 2.


Manufacture of electrical and magnetic graded and anisotropic materials for novel manipulations of microwaves.

Grant PS, Castles F, Lei Q, Wang Y, Janurudin JM, Isakov D, Speller S, Dancer C, Grovenor CR - Philos Trans A Math Phys Eng Sci (2015)

Magnetically aligned anisotropic composites composed of Fe flakes in epoxy. (a,b) Electron micrographs show preferential alignment of the flakes due to the applied magnetic field. The insets indicate the direction of the magnetic field (black arrows) with respect to the sample geometry and the orientation of the exposed section (pale blue) (scale bars, 50 μm). (c) Photograph of the samples and the stripline measurement apparatus used to retrieve the effective permeability of the composite. (d) The real part of the relative permeability as a function of frequency for three types of sample, showing the induced anisotropy of the magnetically aligned samples.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4528831&req=5

RSTA20140353F2: Magnetically aligned anisotropic composites composed of Fe flakes in epoxy. (a,b) Electron micrographs show preferential alignment of the flakes due to the applied magnetic field. The insets indicate the direction of the magnetic field (black arrows) with respect to the sample geometry and the orientation of the exposed section (pale blue) (scale bars, 50 μm). (c) Photograph of the samples and the stripline measurement apparatus used to retrieve the effective permeability of the composite. (d) The real part of the relative permeability as a function of frequency for three types of sample, showing the induced anisotropy of the magnetically aligned samples.
Mentions: Bulk composites are typically isotropic in terms of ε′ and μ′ but these properties in a composite can be contrived to be anisotropic with suitable processing: for example, the alignment of magnetic particles in an external magnetic field applied to an epoxy-based Fe-containing composite during curing, as shown in figure 2. Anisotropic superstructures may also be contrived using arrangements of bulk isotropic materials: for example, if an isotropic composite is formed into a regular array of uniformly oriented rods, it behaves as a homogeneous, but anisotropic, material for wavelengths much larger than the distance between the rods [22].Figure 2.

Bottom Line: While aspects of ST theory have been confirmed using these structures, they are often disadvantaged by narrowband operation, high losses and difficulties in implementation.A key aim is to highlight the limitations and possibilities of various manufacturing approaches, to constrain designs to those that may be achievable.The article focuses on polymer-based nano- and microcomposites in which interactions with microwaves are achieved by loading the polymers with high-permittivity and high-permeability particles, and manufacturing approaches based on spray deposition, extrusion, casting and additive manufacture.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK patrick.grant@materials.ox.ac.uk.

ABSTRACT
Spatial transformations (ST) provide a design framework to generate a required spatial distribution of electrical and magnetic properties of materials to effect manipulations of electromagnetic waves. To obtain the electromagnetic properties required by these designs, the most common materials approach has involved periodic arrays of metal-containing subwavelength elements. While aspects of ST theory have been confirmed using these structures, they are often disadvantaged by narrowband operation, high losses and difficulties in implementation. An all-dielectric approach involves weaker interactions with applied fields, but may offer more flexibility for practical implementation. This paper investigates manufacturing approaches to produce composite materials that may be conveniently arranged spatially, according to ST-based designs. A key aim is to highlight the limitations and possibilities of various manufacturing approaches, to constrain designs to those that may be achievable. The article focuses on polymer-based nano- and microcomposites in which interactions with microwaves are achieved by loading the polymers with high-permittivity and high-permeability particles, and manufacturing approaches based on spray deposition, extrusion, casting and additive manufacture.

No MeSH data available.


Related in: MedlinePlus