阅读说明：本技术 一种柔性电磁超材料及其制备方法 (Flexible electromagnetic metamaterial and preparation method thereof ) 是由 谭果果 雷镇匡 满其奎 宁明强 陈淑文 李润伟 于 2020-06-12 设计创作，主要内容包括：本发明公开了一种柔性电磁超材料及其制备方法,所述柔性电磁超材料包括磁性复合材料构成的柔性基体和嵌入其中的多个周期性排布的超材料周期单元；所述磁性复合材料为磁性材料和粘接剂复合材料；所述的柔性电磁超材料的几何厚度为t<Sub>1</Sub>,所述t<Sub>1</Sub>的取值范围为0.5～2mm；所述超材料周期单元为圆形片或正方形片,所述圆形片的直径或所述正方形片的边长均小于等于5cm；所述超材料周期单元由柔性导电材料构成。本发明所述的柔性电磁超材料具有磁性材料填充比低、厚度薄以及吸波效能强的优异特性,实现了传统磁性复合材料厚度和密度的同时缩减。此外,本发明所述的电磁超材料还具有良好的柔性和大尺度连续弯折拉伸的特点,在军事与民用领域均有一定应用前景。(The invention discloses a flexible electromagnetic metamaterial and a preparation method thereof, wherein the flexible electromagnetic metamaterial comprises a flexible matrix formed by a magnetic composite material and a plurality of periodic metamaterial units which are embedded in the flexible matrix and are periodically arranged; the magnetic composite material is a composite material of a magnetic material and an adhesive; the geometric thickness of the flexible electromagnetic metamaterial is t 1 Said t is 1 The value range of (A) is 0.5-2 mm; the metamaterial periodic unit is a circular sheet or a square sheet, and the diameter of the circular sheet or the side length of the square sheet is less than or equal to 5 cm; the metamaterial periodic unit is made of flexible conductive materials. The flexible electromagnetic metamaterial has the excellent characteristics of low filling ratio of a magnetic material, thin thickness and strong wave-absorbing effect, and the thickness and the density of the traditional magnetic composite material are reduced at the same time. In addition, the method can be used for producing a composite materialThe electromagnetic metamaterial also has the characteristics of good flexibility and large-scale continuous bending and stretching, and has certain application prospect in the military and civil fields.)

1. The flexible electromagnetic metamaterial is characterized by comprising a flexible matrix made of a magnetic composite material and a plurality of periodic metamaterial units embedded in the flexible matrix;

the magnetic composite material is a composite material of a magnetic material and an adhesive; the geometric thickness of the flexible electromagnetic metamaterial is t₁Said t is₁The value range of (A) is 0.5-2 mm;

the metamaterial periodic unit is in the shape of a circular sheet or a square sheet, and the diameter of the circular sheet or the side length of the square sheet is less than or equal to 5 cm; the metamaterial periodic unit is made of flexible conductive materials.

2. The flexible electromagnetic metamaterial according to claim 1, wherein when the periodic units of metamaterial are in the shape of circular sheets; the radius of the circular sheet is R, and the thickness is t₂The value range of R is 0.1-2mm, and t is₂The value range of (A) is 0.05-0.3 mm.

3. The flexible electromagnetic metamaterial according to claim 1, wherein the periodic units of the metamaterial are square pieces, the side length of each square piece is L, and the thickness of each square piece is t₃The value range of L is 0.1-2mm, and t is₃The value range of (A) is 0.05-0.3 mm.

4. The flexible electromagnetic metamaterial according to claim 1, wherein the distance between the centers of any two nearest neighboring periodic units of the metamaterial is d, and the value of d ranges from 0.5 mm to 5 mm.

5. The flexible electromagnetic metamaterial according to claim 1, wherein the flexible substrate is formed by bonding a first flexible substrate and a second flexible substrate, the periodic unit of the metamaterial is embedded on the upper surface of the first flexible substrate, the vertical distance from the lower surface of the periodic unit of the metamaterial to the lower surface of the first flexible substrate is h, and the value range of h is 0.1-1.9 mm.

6. The flexible electromagnetic metamaterial according to any one of claims 1 to 5, wherein in the magnetic composite material, the mass fraction of the magnetic material is in a range of 10% to 90%, and the balance is the binder.

7. The flexible electromagnetic metamaterial according to any one of claims 1 to 5, wherein the magnetic material is a metal magnetic material, ferrite, carbonyl iron, nickel zinc ferrite, or a rare earth soft magnetic material.

8. The flexible electromagnetic metamaterial according to any one of claims 1 to 5, wherein the adhesive is paraffin, liquid silicone, polyurethane or nitrile rubber.

9. The flexible electromagnetic metamaterial according to any one of claims 1 to 5, wherein the flexible conductive material is metallic copper, metallic silver, metallic gold, or a liquid metallic EGaIn alloy.

10. A preparation method of the flexible electromagnetic metamaterial according to any one of claims 1 to 5, comprising the following steps:

(1) calculating the return loss of the flexible electromagnetic metamaterial with different structure sizes according to the types of the magnetic material and the adhesive in the magnetic composite material, the mass fraction ratio of the magnetic material and the type of the flexible conductive material by utilizing a line scanning model in CST simulation software to obtain the structure size with the maximum return loss;

the structure size is the geometric thickness of the flexible electromagnetic metamaterial, the shape and the thickness of the metamaterial periodic unit, the center distance between any two nearest metamaterial periodic units and the vertical distance from the lower surface of the metamaterial periodic unit to the lower surface of the first flexible substrate;

(2) based on the structural size with the largest return loss calculated by CST simulation software, a first flexible substrate is obtained by casting, and a vacancy with the same shape and thickness as the metamaterial periodic unit is reserved on the upper surface of the first flexible substrate;

(3) placing a flexible conductive material in the vacancy of the upper surface of the first flexible substrate;

(4) and covering the second flexible substrate and bonding the second flexible substrate to the first flexible substrate with the metamaterial periodic unit by using a universal glue to obtain the flexible electromagnetic metamaterial.

Technical Field

The invention relates to the field of electromagnetic wave absorption, in particular to a flexible electromagnetic metamaterial and a preparation method thereof.

Technical Field

With the progress of electronic information and communication technology, various electronic and communication devices penetrate into the aspects of daily life of people, on one hand, great convenience is brought to the life of people, on the other hand, electromagnetic pollution generated by the electronic devices influences the health of people, and electromagnetic waves generated by too many electronic devices are easy to interfere with each other to influence normal use. Furthermore, with the development of anti-stealth technology, stealth technology is also greatly promoted. Therefore, the electromagnetic wave absorbing material has a wide application in both military use and civil use. The traditional wave-absorbing material mainly requires strong absorption performance, but with the development of times, more requirements are provided for the wave-absorbing material, and the novel wave-absorbing material is required to have the characteristics of thinness, lightness, width and strength so as to meet more complex application environments.

Among the existing wave-absorbing material types, the magnetic material is the most developed and improved type, but because the wave-absorbing mechanism is applied singly, the existing magnetic material needs higher filling ratio and larger thickness to achieve strong absorption (the research on the wave-absorbing mechanism and the improvement of the wave-absorbing performance of ferrite magnetic materials advances [ J ]. the chemical development, 2015,34 (11)). This results in that the magnetic material is generally thick and heavy in practical use, which greatly limits the application of the electromagnetic wave absorbing material.

Metamaterials are a class of materials that achieve specific physical properties by artificially building precise geometries and dimensions. The electromagnetic properties of the metamaterial can be expressed by equivalent medium theory, namely equivalent permeability and equivalent dielectric constant. By reasonably regulating and controlling the geometric parameters of the metamaterial, the metamaterial can generate electromagnetic resonance with electromagnetic waves so as to quickly lose the energy of the electromagnetic waves.

The traditional wave-absorbing material, especially the wave-absorbing patch material with silica gel as the matrix and high-performance absorbent, realizes the absorption of electromagnetic waves through higher magnetic conductivity and magnetic loss (the application and the current research status of the wave-absorbing material matrix [ J ]. electronic elements and materials, 2011,030(004): 79-83). However, the improvement of the magnetic conductivity and the magnetic loss is accompanied with the increase of the filling ratio of the magnetic material, the improvement of the performance sacrifices the weight of the wave-absorbing material, and most of the thickness is thicker. Taking spherical carbonyl iron with wide application as an example, the mass filling ratio of the spherical carbonyl iron in the X wave band is more than 70 percent and the thickness is about 2mm to realize the wave absorbing performance of-20 dB and higher.

By combining the advantages of the traditional wave-absorbing material and the metamaterial, the development of the novel thin-layer low-density electromagnetic metamaterial has important significance for radar stealth, electromagnetic interference resistance of civil electronic equipment and the like.

Disclosure of Invention

The invention aims to provide a flexible electromagnetic metamaterial and a preparation method thereof, and the design and preparation method can reduce the density and thickness of the wave-absorbing material through the combined action of a special electromagnetic resonance wave-absorbing mechanism of the metamaterial and excellent magnetic loss performance of a magnetic material, so as to achieve the aim of reducing the thickness of the wave-absorbing material.

The technical scheme provided by the invention for solving the technical problems is as follows:

a flexible electromagnetic metamaterial comprises a flexible matrix made of a magnetic composite material and a plurality of periodic metamaterial units embedded in the flexible matrix, wherein the periodic metamaterial units are periodically arranged; the magnetic composite material is a composite material of a magnetic material and an adhesive; the geometric thickness of the flexible electromagnetic metamaterial is t₁Said t is₁The value range of (A) is 0.5-2 mm; the metamaterial periodic unit is in the shape of a circular sheet or a square sheet, and the diameter of the circular sheet or the side length of the square sheet is less than or equal to 5 cm; the metamaterial periodic unit is made of flexible conductive materials.

The flexible electromagnetic metamaterial prepared by the invention realizes the reduction of the contradiction between the density and the thickness of the material on the premise of ensuring a stronger wave-absorbing effect through the combined action of the special electromagnetic resonance wave-absorbing mechanism of the metamaterial and the excellent magnetic loss performance of the magnetic material.

In the magnetic composite material, the mass fraction of the magnetic material accounts for 10-90%, and the balance is adhesive.

The flexible substrate is formed by bonding a first flexible substrate and a second flexible substrate, the metamaterial periodic unit is embedded on the upper surface of the first flexible substrate, the vertical distance from the lower surface of the metamaterial periodic unit to the lower surface of the first flexible substrate is h, and the range of the metamaterial periodic unit is 0.1-1.9 mm.

The bonding is bonding by universal glue.

The magnetic material is preferably a soft magnetic material because of its excellent high-frequency loss characteristics.

The soft magnetic material includes but is not limited to ferrite, carbonyl iron, nickel zinc ferrite or rare earth soft magnetic material.

The adhesive includes, but is not limited to, paraffin, liquid silicone, polyurethane or nitrile rubber, and preferably a polymer material with flexible and bending-resistant properties, such as liquid silicone.

The geometric thickness of the magnetic composite material is defined as t₁Said t is₁The value range of (A) is 0.5-2 mm.

The shape of the metamaterial periodic unit is a circular sheet or a square sheet.

The radius of the circular sheet is R, and the value range of R is 0.1-2 mm.

The thickness of the circular sheet is t₂Said t is₂The value range of (A) is 0.05-0.3 mm.

The side length of the square sheet is L, and the value range of L is 0.1-2 mm.

The thickness of the square sheet is t₃Said t is₃The value range of (A) is 0.05-0.3 mm.

The center-to-center distance between any two nearest neighbor metamaterial periodic units is d, and the value range of d is 0.5-5 mm.

The flexible conductive material is preferably a metal with good conductivity, including but not limited to copper, silver, gold, or liquid metal.

The flexible conductive material is preferably further preferably a liquid metal with good flexibility, including but not limited to an EGaIn alloy.

Further, in order to obtain the optimal structural parameters, for the magnetic composite materials with different proportions and the materials with different period units, the geometric structural parameters corresponding to the required or set performance indexes are obtained through CST simulation calculation.

The invention also provides a preparation method of the flexible electromagnetic metamaterial, which comprises the following steps:

(1) calculating the return loss of the flexible electromagnetic metamaterial with different structure sizes according to the types, mass ratios and the types of the magnetic materials and the adhesives in the magnetic composite material by utilizing a line scanning model in CST simulation software, and obtaining the structure size with the maximum return loss;

the structure size is the geometric thickness of the flexible electromagnetic metamaterial, the shape and the thickness of the metamaterial periodic unit, the center distance between any two nearest metamaterial periodic units and the vertical distance from the lower surface of the metamaterial periodic unit to the lower surface of the first flexible substrate;

(2) based on the structural size with the largest return loss calculated by CST simulation software, a first flexible substrate is obtained by casting, and a vacancy with the same shape and thickness as the metamaterial periodic unit is reserved on the upper surface of the first flexible substrate;

(3) placing a flexible conductive material in the vacancy of the upper surface of the first flexible substrate;

(4) and covering the second flexible substrate and bonding the second flexible substrate to the first flexible substrate with the metamaterial periodic unit by using a universal glue to obtain the flexible electromagnetic metamaterial.

The invention has the following beneficial effects:

1. by embedding the metamaterial periodic unit in the magnetic composite material, the magnetic material can obtain strong absorption at 2-18 GHz even at low filling ratio and low thickness, and the wave absorption rate is more than 90%.

2. By adjustingGeometrical dimensions (R, t) of periodic units of metamaterial₂，L，t₃) And the spatial positions (h and d) of the periodic units of the metamaterial in the magnetic composite material can regulate and control the position and the intensity of an absorption peak.

3. The liquid metal is used as the material of the metamaterial periodic unit, so that the flexible electromagnetic metamaterial has excellent flexibility and bendability, can still recover the original structure after large-scale deformation, and does not influence the wave-absorbing performance.

4. The invention has the characteristics of simple structure, light weight, small thickness and deformation resistance, can be attached to the surface of an application object, and has certain application potential in the military and civil fields.

Drawings

Fig. 1 is a schematic view of a wave-absorbing effect of the electromagnetic metamaterial prepared in example 1.

Fig. 2 is a schematic view of a wave-absorbing effect of the electromagnetic metamaterial prepared in example 2.

Fig. 3 is a schematic view of a wave-absorbing effect of the electromagnetic metamaterial prepared in example 3.

Fig. 4 is a schematic view of a wave-absorbing effect of the electromagnetic metamaterial prepared in example 4.

Fig. 5 is a schematic view of a wave-absorbing effect of the electromagnetic metamaterial prepared in example 5.

Fig. 6 is a schematic view of a wave-absorbing effect of the electromagnetic metamaterial prepared in example 6.

FIG. 7 is a schematic structural diagram of an electromagnetic metamaterial.

Detailed Description

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention, including any reference to the above-described embodiments. Various modifications to these embodiments will be readily apparent to those skilled in the art. The general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.