阅读说明：本技术 一种频带可调的柔性多层吸波材料及其制备方法 (Frequency band adjustable flexible multilayer wave-absorbing material and preparation method thereof ) 是由 张恒宇 肖红 陈剑英 王焰 梁高勇 冯硕 季惠 孟令卿 施楣梧 于 2020-11-12 设计创作，主要内容包括：本发明公开了一种频带可调的柔性多层吸波材料及其制备方法。所述柔性多层吸波材料为下述1)或2)：1)由吸波织物层与频率选择织物层或与电磁波反射织物层按照任意顺序叠放构成的双层吸波材料；2)由频率选择织物层、吸波织物层和电磁波反射织物层按照任意顺序叠放构成的多层吸波材料,频率选择织物层由频率选择织物制成,频率选择织物为具有可设计谐振频点的织物；吸波织物层由吸波织物制成,吸波织物为含有吸波剂的织物。本发明通过仿真模拟,高效设计出不同频段所需的FSF单元周期排列及尺寸,并将具有滤波作用的FSF与吸波织物、电磁波反射织物以不同叠放顺序、层组合进行叠层,可调控层复合材料在不同工作频带内实现宽频高强吸收,提高工作效率。(The invention discloses a frequency band adjustable flexible multilayer wave-absorbing material and a preparation method thereof. The flexible multilayer wave-absorbing material is 1) or 2) as follows: 1) the double-layer wave-absorbing material is formed by stacking a wave-absorbing fabric layer and a frequency-selecting fabric layer or an electromagnetic wave reflecting fabric layer in any order; 2) the multilayer wave-absorbing material is formed by stacking a frequency selection fabric layer, a wave-absorbing fabric layer and an electromagnetic wave reflection fabric layer in any order, wherein the frequency selection fabric layer is made of frequency selection fabric, and the frequency selection fabric is fabric with a designable resonance frequency point; the wave-absorbing fabric layer is made of wave-absorbing fabric, and the wave-absorbing fabric is fabric containing a wave-absorbing agent. According to the invention, through simulation, the periodic arrangement and the size of the FSF units required by different frequency bands are efficiently designed, the FSF with the filtering function, the wave-absorbing fabric and the electromagnetic wave reflecting fabric are laminated in different stacking sequences and layer combinations, the adjustable layer composite material realizes broadband high-strength absorption in different working frequency bands, and the working efficiency is improved.)

1. A flexible multilayer wave-absorbing material with adjustable frequency band is 1) or 2) as follows:

1) the double-layer wave-absorbing material is formed by stacking a wave-absorbing fabric layer and a frequency-selecting fabric layer or an electromagnetic wave reflecting fabric layer in any order;

2) the multilayer wave-absorbing material is formed by stacking a frequency selection fabric layer, a wave-absorbing fabric layer and an electromagnetic wave reflection fabric layer in any order;

the frequency selective fabric layer is made of frequency selective fabric, and the frequency selective fabric is fabric with designable resonance frequency points;

the wave-absorbing fabric layer is made of wave-absorbing fabric, and the wave-absorbing fabric is fabric containing a wave-absorbing agent;

the electromagnetic wave reflecting fabric is made of an electromagnetic wave reflecting fabric, and the electromagnetic wave reflecting fabric is a fabric with metal conductive characteristics.

2. The flexible multilayer wave absorbing material of claim 1, wherein: the designable resonance frequency point refers to a resonance frequency point realized by a specific periodic structure obtained through electromagnetic simulation calculation;

the frequency selective fabric comprises a patch type fabric or a pore type fabric;

the patch type fabric is formed by plating or pasting a periodic conductive metal layer on a flexible fabric substrate;

the conductive metal layer is a metal layer formed by silver, copper, aluminum, nickel or zinc;

the pore type fabric is formed by manufacturing a periodic array open pore structure on the conductive fabric.

3. A flexible multilayer wave-absorbing material according to claim 1 or 2, characterized in that: the wave absorbing agent is any one of carbonyl iron, hydroxyl nickel, hydroxyl cobalt, ferrite, silicon carbide, barium titanate, graphite, silicon nitride, iron nitride, carbon fiber and zinc oxide;

the wave-absorbing fabric is formed by coating the wave-absorbing agent on a fabric substrate or by soaking the wave-absorbing agent in a three-dimensional fabric.

4. A flexible multilayer wave absorbing material according to claim 3, characterized in that: the surface density of the wave-absorbing fabric is 200g/m²～4000g/m²；

The fabric substrate is any one of the following 1) to 3):

1) cotton fiber fabric, viscose fiber fabric or blended or interwoven fabric of cotton fiber and viscose fiber;

2) polyester fabric, nylon fabric, vinylon fabric, polypropylene fabric or blended or interwoven fabric of polyester, nylon, vinylon and/or polypropylene;

3) aramid fabric, ultra-high molecular weight polyethylene fiber fabric or blended or interwoven fabric of aramid and ultra-high molecular weight polyethylene fiber.

5. A flexible multilayer wave-absorbing material according to any one of claims 1 to 4, characterized in that: the electromagnetic wave reflecting fabric is a fabric with a metal plated on the surface or a fabric woven by metal yarns;

the metal is silver, copper, aluminum, nickel and/or zinc;

the metal yarn is a yarn formed of silver, copper, aluminum, nickel and/or zinc.

6. A flexible multilayer wave-absorbing material according to any one of claims 1 to 5, characterized in that: the frequency selection fabric layer, the wave-absorbing fabric layer and the electromagnetic wave reflection fabric layer are stacked in any order to form 2-5 layers of wave-absorbing materials.

7. A preparation method of the flexible multilayer wave-absorbing material in any one of claims 1 to 6, comprising the following steps:

s1, performing analog calculation on the periodic arrangement and the size of the resonant units with different shapes by using an electromagnetic simulation means to obtain resonant units with different resonant frequency points and frequency response characteristics, and manufacturing the frequency selection fabric by taking the fabric as a substrate;

s2, mixing the wave absorbing agent and the polymer to obtain a mixture, uniformly stirring, and scraping the mixture on a fabric substrate or soaking the three-dimensional fabric in the mixture to obtain the wave absorbing fabric;

s3, coating the metal slurry on the fabric or weaving the metal yarn into woven fabric or knitted fabric to obtain the electromagnetic wave reflecting fabric;

s4, stacking the frequency selection fabric, the wave-absorbing fabric and the electromagnetic wave reflection fabric in any order by adopting a physical bonding mode to obtain the flexible multilayer wave-absorbing material.

8. The method of claim 7, wherein: in step S2, the polymer is any one of aqueous polyurethane, oil-based polyurethane, polyvinyl alcohol, and polyvinyl chloride;

the mass ratio of the wave absorbing agent to the polymer is 1-9: 1 to 4.

9. The production method according to claim 7 or 8, characterized in that: in step S3, the metal paste is coated by chemical plating, electroplating or magnetron sputtering.

Technical Field

The invention relates to a frequency band adjustable flexible multilayer wave-absorbing material and a preparation method thereof, belonging to the technical field of microwave absorbing materials.

Background

The wave-absorbing material needs to meet two conditions, namely, the impedance of the material and the free space is equivalent as much as possible, and the wave-absorbing material has high electromagnetic wave loss capacity so as to convert the electromagnetic wave energy into heat energy or other forms of energy to the maximum extent and cannot generate secondary pollution like an electromagnetic shielding material. Commonly used wave absorbers are carbonyl iron, ferrite, and the like. For example, carbonyl iron is a high-permeability wave-absorbing material that attenuates electromagnetic waves by hysteresis loss and eddy current loss, but is often accompanied by problems of thickness, poor mechanical properties, and the like in order to achieve an absorption effect.

Different devices have different working frequency bands, and in order to ensure the normal operation of the devices and the safety of the surrounding environment of the devices, a wave-absorbing material with adjustable working frequency band and a preparation method thereof are needed. The Frequency Selective Surface (FSS) is a periodic structure that has a selective transmission effect on electromagnetic waves. By taking the preparation method of the frequency selective surface FSS as a reference, the Frequency Selective Fabric (FSF) can be formed by periodically arraying the conductive units on the surface of the non-conductive fabric or by periodically arraying holes on the conductive fabric, so that the electromagnetic wave in a specific frequency band can be transmitted, and the electromagnetic wave in other frequency bands can be cut off. The fabric can meet the requirement of air permeability and can also meet the protection requirement.

The single wave-absorbing material often has the defects of poor impedance matching, limited absorption performance and narrow wave-absorbing frequency band. The patent application (CN 106469858A) discloses a wave absorbing body structure, a metal plate, a honeycomb layer and a resistor sheet are stacked in multiple layers to obtain the wave absorbing material with wide frequency band and strong absorption, but the metal plate has large weight, the total thickness of the composite material exceeds 20cm, the patent application (CN10983029A) discloses a wave absorbing composite material and a preparation method thereof, in particular to a preparation method of an impedance matching layer/a three-dimensional graphene layer/a low-frequency electromagnetic loss layer, and the wave absorbing material has a wider wave absorbing frequency band at low frequency; patent application (CN 108092006 a) discloses a layered broadband radar wave absorbing plate and a method for preparing the same, and patent application (CN 105744816B) discloses an electromagnetic wave shielding composite film, wherein the two patent applications disclose methods for preparing a multilayer wave absorbing film, and the layer composite materials in the above patents can improve the absorptivity of electromagnetic waves, but cannot realize selective transmission of electromagnetic waves in a certain specific frequency band, and do not have the flexibility and air permeability peculiar to fabrics.

At present, a multi-layer composite material which can efficiently regulate and control the wave-absorbing frequency band of the wave-absorbing material and meet the requirements of the wave-absorbing material on softness and air permeability is lacked.

Disclosure of Invention

The invention aims to provide a frequency band adjustable flexible multilayer wave-absorbing material which is composed of a Frequency Selective Fabric (FSF), a wave-absorbing fabric and an electromagnetic wave reflecting fabric, and can reduce the weight of the composite wave-absorbing material, widen the effective wave-absorbing frequency band, increase the wave-absorbing strength, endow the multilayer composite wave-absorbing material with soft, broadband and high wave-absorbing characteristics, and particularly, realize the adjustment of the working frequency band of the wave-absorbing material through the FSF.

The flexible multilayer wave-absorbing material with adjustable frequency band provided by the invention is 1) or 2) as follows:

1) double-layer wave-absorbing material formed by stacking wave-absorbing fabric layers and frequency-selective fabric layers or electromagnetic wave reflecting fabric layers in any order

2) The multilayer wave-absorbing material is formed by stacking a frequency selection fabric layer, a wave-absorbing fabric layer and an electromagnetic wave reflection fabric layer in any order;

the frequency selective fabric layer is made of frequency selective fabric, and the frequency selective fabric is fabric with designable resonance frequency points;

the wave-absorbing fabric layer is made of wave-absorbing fabric, and the wave-absorbing fabric is fabric containing a wave-absorbing agent;

the electromagnetic wave reflecting fabric is made of an electromagnetic wave reflecting fabric, and the electromagnetic wave reflecting fabric is a fabric with metal conductive characteristics.

In the flexible multilayer wave-absorbing material, the designable resonance frequency point refers to a resonance frequency point realized by a specific periodic structure obtained through electromagnetic simulation calculation;

wherein, the resonance unit can be in a cross shape, a Yelu spray cooling shape, a circular shape or a U shape;

the frequency selective fabric comprises a patch type fabric or a pore type fabric;

the patch type fabric is formed by plating or pasting a periodic conductive metal layer on a flexible fabric substrate;

the conductive metal layer is a metal layer formed by silver, copper, aluminum, nickel or zinc;

the pore type fabric is formed by manufacturing a periodic array open pore structure on the conductive fabric.

In the flexible multilayer wave-absorbing material, the wave-absorbing agent can be any one of carbonyl iron, hydroxyl nickel, hydroxyl cobalt, ferrite, silicon carbide, barium titanate, graphite, silicon nitride, iron nitride, carbon fiber and zinc oxide;

the wave-absorbing fabric is formed by coating the wave-absorbing agent on a fabric substrate or by soaking the wave-absorbing agent in a three-dimensional fabric.

In the flexible multilayer wave-absorbing material, the surface density of the wave-absorbing fabric can be 200g/m²～4000g/m²；

The fabric substrate is any one of the following 1) to 3):

1) cotton fiber fabric, viscose fiber fabric or blended or interwoven fabric of cotton fiber and viscose fiber;

2) polyester fabric, nylon fabric, vinylon fabric, polypropylene fabric or blended or interwoven fabric of polyester, nylon, vinylon and/or polypropylene;

3) aramid fabric, ultra-high molecular weight polyethylene fiber fabric or blended or interwoven fabric of aramid and ultra-high molecular weight polyethylene fiber.

In the flexible multilayer wave-absorbing material, the electromagnetic wave reflecting fabric can be a fabric with a metal plated on the surface or a fabric woven by metal yarns;

the metal may be silver, copper, aluminum, nickel and/or zinc;

the metal yarn may be a yarn formed of silver, copper, aluminum, nickel and/or zinc.

In the flexible multilayer wave-absorbing material, the frequency selection fabric layer, the wave-absorbing fabric layer and the electromagnetic wave reflection fabric layer are stacked in any order to form 2-5 layers of wave-absorbing material, as shown in fig. 2;

according to any stacking sequence, for example, the frequency selection fabric layer and the wave-absorbing fabric layer are sequentially stacked to obtain a double-layer wave-absorbing fabric, the wave-absorbing fabric layer and the electromagnetic wave reflection fabric layer are sequentially stacked to obtain a double-layer composite wave-absorbing fabric, the wave-absorbing fabric layer, the frequency selection fabric layer and the electromagnetic wave reflection fabric layer are sequentially stacked to obtain three wave-absorbing fabrics, the frequency selection fabric layer, the wave-absorbing fabric layer and the electromagnetic wave reflection fabric layer are sequentially stacked to obtain three wave-absorbing fabrics, the wave-absorbing fabric layer, the frequency selection fabric layer, the wave-absorbing fabric layer and the electromagnetic wave reflection fabric layer, and four wave-absorbing fabrics are sequentially stacked.

In the wave-absorbing material, each layer takes the fabric as a substrate, can be bent, and has flexibility compared with the layer composite materials of the metal plate layer composite wave-absorbing material and other media; and when the wave absorbing layer adopts the three-dimensional spacing fabric, the spacing fabric has larger pores, and the frequency selection layer and the reflecting layer both take the fabric as the substrate, so the air permeability is better.

The invention also provides a preparation method of the flexible multilayer wave-absorbing material, which comprises the following steps:

s1, performing analog calculation on the periodic arrangement and the size of the resonant units with different shapes by using an electromagnetic simulation means to obtain resonant units with different resonant frequency points and frequency response characteristics, and manufacturing the frequency selection fabric by taking the fabric as a substrate;

s2, mixing the wave absorbing agent and the polymer to obtain a mixture, uniformly stirring, and scraping the mixture on a fabric substrate or soaking the three-dimensional fabric in the mixture to obtain the wave absorbing fabric;

s3, coating the metal slurry on the fabric or weaving the metal yarn into woven fabric or knitted fabric to obtain the electromagnetic wave reflecting fabric;

s4, stacking the frequency selection fabric, the wave-absorbing fabric and the electromagnetic wave reflection fabric in any order by adopting a physical bonding mode to obtain the flexible multilayer wave-absorbing material.

In the above preparation method, in step S2, the polymer may be any one of aqueous polyurethane, oil-based polyurethane, polyvinyl alcohol and polyvinyl chloride;

the mass ratio of the wave absorbing agent to the polymer can be 1-9: 1 to 4.

In the above preparation method, in step S3, the metal paste is coated by electroless plating, electroplating or magnetron sputtering.

According to the invention, through simulation, the periodic arrangement and the size of the FSF units required by different frequency bands are efficiently designed, the FSF with the filtering function, the wave-absorbing fabric and the electromagnetic wave reflecting fabric are laminated in different stacking sequences and layer combinations, the adjustable layer composite material realizes broadband high-strength absorption in different working frequency bands, and the working efficiency is improved.

Drawings

Fig. 1 is a schematic structural diagram of FSFs of different shapes and types, which are cross-shaped, yersinia cooling, circular and U-shaped from left to right, wherein gray is a conductive part and white is a non-conductive part.

FIG. 2 is a schematic structural diagram of a multilayer composite wave-absorbing material.

Detailed Description

The experimental procedures used in the following examples are all conventional procedures unless otherwise specified.

Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.

Example 1 double-layer composite wave-absorbing fabric

Selecting the FSF resonance units in a cross shape, wherein the distance between the resonance units is 30mm, the resonance frequency point is 3.96GHz, and coating conductive silver paste on the polyester woven fabric by adopting screen printing according to the periodical arrangement and the size of the simulation design to manufacture the patch type FSF as shown in figure 1; mixing barium titanate and waterborne polyurethane according to the mass ratio of 3:1, mechanically stirring for 5min, uniformly mixing, and blade-coating on cotton woven fabric as wave-absorbing fabric with the surface density of 625g/m². The double-layer composite wave-absorbing fabric is obtained by laminating the wave-absorbing fabric on the upper part and the wave-absorbing fabric on the lower part according to the frequency, and the thickness of the double-layer composite wave-absorbing fabric is 0.66 mm.

Within the test range of 2-18GHz, the reflectivity peak value is-17.3 dB, the bandwidth less than-5 dB is 9.4GHz, and the bandwidth less than-10 dB is 5.7GHz, so that the wave-absorbing material can effectively absorb electromagnetic waves.

Example 2 three-layer wave-absorbing fabric

Selecting an FSF resonance unit with a U-shaped shape, a resonance unit interval of 20mm and a resonance frequency point of 4.78GHz, and coating conductive copper paste on the cotton knitted fabric by adopting screen printing according to the periodical arrangement and the size of the analog design to manufacture the patch type FSF, as shown in figure 1; mixing zinc oxide and polyvinyl alcohol (molecular weight is 1000) according to a mass ratio of 1:1, mechanically stirring for 5min, uniformly mixing, soaking the terylene three-dimensional space fabric in the mixture for 15min, airing at room temperature to obtain the wave-absorbing fabric with the surface density of 714g/m². By adopting the mode of chemical platingThe copper-nickel mixed slurry is coated on the polyester knitted fabric to be used as the electromagnetic wave reflecting fabric. Three layers of wave-absorbing fabrics with the thickness of 0.78mm are obtained by sequentially laminating the wave-absorbing layer on the upper part, the FSF in the middle part and the electromagnetic wave reflecting fabric on the bottom part.

Within the test range of 2-18GHz, the reflectivity peak value is-18 dB, the bandwidth less than-5 dB is 6.2GHz, and the bandwidth less than-10 dB is 3.4GHz, so that the wave-absorbing material has a wider effective wave-absorbing frequency band.

Example 3 three-layer wave-absorbing fabric

Selecting the FSF resonance units with the shape of a circular ring, the distance between the resonance units being 20mm, the resonance frequency point being 6GHz, coating conductive copper paste on the polyester woven fabric by adopting screen printing, and then tearing off the resonance units by utilizing laser engraving according to the period arrangement and the size of the simulation design to manufacture the pore FSF, as shown in figure 1; mixing graphite and oil-based polyurethane according to a mass ratio of 11:20, mechanically stirring for 5min, uniformly mixing, soaking the terylene three-dimensional space fabric in the mixture for 20min, airing the mixture at room temperature to serve as a wave-absorbing layer, wherein the surface density is 1250g/m². Silver yarn is used as a raw material to weave a woven fabric as an electromagnetic wave reflecting fabric. And then sequentially laminating the FSF on the upper part, the wave-absorbing fabric in the middle and the electromagnetic wave reflecting fabric at the bottom to obtain three layers of wave-absorbing fabrics with the thickness of 0.91 mm.

Within the test range of 2-18GHz, the reflectivity peak value is-14.6 dB, the bandwidth less than-5 dB is 12.1GHz, the bandwidth less than-10 dB is 2.8GHz, and therefore, the wave-absorbing material is wider in the frequency band less than-5 dB and can meet the requirement of absorption of more than 90% of electromagnetic waves.

Example 4 three-layer wave-absorbing Material

Selecting the FSF resonance units to be circular, the distance between the resonance units to be 15mm, the resonance frequency point to be 7.8GHz, selecting the FSF resonance units to be U-shaped, the distance between the resonance units to be 20mm, and the resonance frequency point to be 2.6GHz, and coating conductive silver paste on the polyester woven fabric by adopting screen printing according to the periodical arrangement and the size of the simulation design to manufacture the patch type FSF as shown in figure 1; mixing carbonyl iron powder and waterborne polyurethane according to the mass ratio of 7:10, mechanically stirring for 5min, uniformly mixing, and blade-coating on nylon woven fabric with the surface density of 926.7g/m²To doIs wave-absorbing fabric. And then sequentially laminating the circular FSF on the upper part, the wave-absorbing fabric in the middle and the U-shaped FSF on the bottom layer to obtain three layers of wave-absorbing materials with the thickness of 0.85 mm.

Within the test range of 2-18GHz, the reflectivity peak value is-21.9 dB, the bandwidth less than-5 dB is 9.8GHz, and the bandwidth less than-10 dB is 6.4GHz, so that the wave-absorbing material can realize the absorption of 99% of electromagnetic waves and can realize effective absorption within a wider frequency band.

Example 5 four layers of wave absorbing Material

Selecting the FSF resonant unit to be a Yelu spreading cold shape, the distance between the resonant units to be 15mm and the resonant frequency point to be 12GHz, coating conductive copper paste on the polyester woven fabric by adopting screen printing, and then tearing off the resonant unit part by utilizing laser engraving according to the period arrangement and the size of the simulation design to manufacture a pore FSF, as shown in figure 1; mixing silicon carbide and oil-based polyurethane 9:1, mechanically stirring for 5min, uniformly mixing, and then blade-coating on a cotton knitted fabric to obtain the wave-absorbing fabric 1 with the surface density of 1004.5g/m²(ii) a Mixing carbonyl iron powder and oil-based polyurethane according to a mass ratio of 4:3, mechanically stirring for 5min, uniformly mixing, and blade-coating on a polyester knitted fabric to serve as a wave-absorbing layer 2 with the surface density of 2618g/m²(ii) a And coating the copper-nickel mixed slurry on the polyester knitted fabric in a chemical plating mode to obtain the electromagnetic wave reflecting fabric. Four layers of wave-absorbing materials are obtained by laminating the upper layer to the bottom layer according to the sequence of the wave-absorbing layer 1, the frequency selection layer, the wave-absorbing layer 2 and the electromagnetic wave reflection fabric, and the thickness of the wave-absorbing materials is 1.7 mm.

Within the test range of 2-18GHz, the peak value of double reflectivity is-24.8 dB and-20.6 dB, and the bandwidths less than-10 dB are respectively corresponding to 3.8GHz and 3.2GHz, so that the wave-absorbing material can realize high-strength absorption of electromagnetic waves in multiple frequency bands, and the frequency selection surface has obvious regulation and control effect on the wave-absorbing frequency bands.