阅读说明：本技术 一种柔性射频段负介电和负磁导率吸波材料的制备方法 (Preparation method of flexible radio-frequency-band negative dielectric and negative magnetic conductivity wave-absorbing material ) 是由 范润华 张子栋 刘峣 孙凯 解培涛 范润德 范国华 于 2018-08-29 设计创作，主要内容包括：本发明涉及一种具有负介电和负磁导率的吸波材料制备方法,特别涉及一种具有具有柔性的聚合物基双负材料制备方法,该发明可应用于电磁屏蔽、吸波、波导领域。上述负介电材料的制备方法,包括：步骤1,利用固相反应法制备钇铁石榴石粉体；步骤2,将钇铁石榴石粉体与聚苯胺粉体以一定比例混合；步骤3,将混合粉料压力成型为具有一定形状的复合材料。本发明制备的双负材料,其介电常数在10MHz-1GHz频段可为负值,磁导率在100MHz-1GHz频段可为负值。聚苯胺的电导率对产品性能具有决定性影响,通过聚苯胺的选择和控制聚苯胺的体积分数,可实现对双负性能的调控,进而实现不同的吸波性能。由于聚苯胺具有柔性,本发明可将材料制备成薄膜或涂层,用于可穿戴的电磁产品。(The invention relates to a preparation method of a wave-absorbing material with negative dielectric and negative magnetic conductivity, in particular to a preparation method of a polymer-based double-negative material with flexibility. The preparation method of the negative dielectric material comprises the following steps: step 1, preparing yttrium iron garnet powder by using a solid-phase reaction method; step 2, mixing yttrium iron garnet powder and polyaniline powder in a certain proportion; and 3, pressure molding the mixed powder into a composite material with a certain shape. The dielectric constant of the prepared double-negative material can be a negative value in a frequency band of 10MHz-1GHz, and the magnetic conductivity can be a negative value in a frequency band of 100MHz-1 GHz. The conductivity of the polyaniline has a decisive influence on the product performance, and the regulation and control of the double negative performance can be realized by selecting the polyaniline and controlling the volume fraction of the polyaniline, so that different wave-absorbing properties are realized. Due to the flexibility of polyaniline, the material can be prepared into a film or a coating to be used for wearable electromagnetic products.)

1. A preparation method of a flexible microwave absorbing material with radio frequency band negative dielectric and negative magnetic conductivity is characterized by comprising the following steps:

step 1: preparing YIG powder by a solid-phase reaction method, and preparing yttrium iron garnet powder by a solid-phase reaction: mixing yttrium oxide and iron oxide powder according to a molar ratio of 3:5, performing ball milling, drying, performing a 1300 ℃ solid phase reaction, and sieving (300 meshes) to obtain yttrium iron garnet powder; the yttrium iron garnet powder used in the step 1 can also use other industrial grade powder, and the grain diameter is between 1 and 20 mu m;

step 2: mixing yttrium iron garnet powder and polyaniline powder according to a certain proportion, wherein the polyaniline is conductive polyaniline, the particle size is 1-5 μm, the direct current conductivity is 0.1-10 (omega. cm) -1, and the direct current conductivity of the conductive polyaniline used in the invention is one of key parameters; the volume ratio of the yttrium iron garnet powder in the composite powder ranges from 60% to 95%; the mixing means is a ball mill and dry milling; when a planetary ball mill is used for mixing, the total ball-material ratio is 2 (the optimal ratio), the ball milling rotating speed is 240r/min, and the ball milling time is 0.5-2 hours; when a vibration ball mill is used for mixing materials, the ball-material ratio is 1-3, low-frequency vibration is carried out for 14-24 seconds, then high-frequency vibration is carried out for 60-120 seconds, and circulation is carried out for 3-6 times;

and step 3: pressure molding the mixed powder obtained in the step (2) into a composite material with a certain shape, wherein the size of a mold is designed according to the size of the material to be prepared; the molding mode is hot press molding or pressure molding without heating; firstly, pouring powder into a mould, and preheating for 20-40min at 60-100 ℃ when hot-press molding; then pressurizing to 20MPa-50MPa, maintaining the pressure for 30min, and relieving the pressure when cooling to room temperature, wherein the pressure relief rate is 5MPa/min-30 MPa/min, and the cooling mode can be natural cooling or circulating water cooling; when the pressure forming is carried out without heating, slowly pressurizing to 10MPa, maintaining the pressure for 10min, then pressurizing to 30MPa-50MPa, maintaining the pressure for 30min, and the pressure relief rate is 5MPa/min-30 MPa/min.

Technical Field

The invention relates to a preparation method of a wave-absorbing material with negative dielectric and negative magnetic conductivity, in particular to a preparation method of a polymer-based negative dielectric and negative magnetic conductivity super-structure composite material with flexibility.

Background

Materials with both negative permittivity and negative permeability are called double negative materials and were first realized in 2001 in the form of metamaterials. Later, the metamaterial is rapidly developed in the fields of stealth, perfect imaging, radar antennas, wireless power transmission and the like, and is called as a hotspot of scientific research and technical innovation. The novel electromagnetic properties of metamaterials are largely dependent on the geometric size, shape and arrangement of periodically ordered structural units, rather than on the intrinsic properties of the materials of which they are composed, and therefore their properties are referred to as artificial properties. From the perspective of the composition and the micro-morphology of the material, the realization of the double negative property through the intrinsic property of the material is also significant. In percolation composites, certain composites can achieve negative dielectric constants and negative permeability when the conductive filler content exceeds the percolation threshold. Metallic fillers such as nickel, copper, iron, silver, etc. are often used as conductive fillers, while aluminum oxide, yttrium iron garnet, and polymers are often used as insulating matrices. Copper-yttrium iron garnet, silver-yttrium iron garnet, iron-aluminum oxide, nickel-aluminum oxide, and the like have been reported to achieve negative dielectric constant and negative permeability. However, these composite materials are prepared by combining the conductive filler with the insulating matrix, and there are few reports on combining the insulating filler with the conductive matrix, especially on the dual negative performance of the radio frequency band.

Negative permeability can be achieved in ferromagnetic resonance bands in ferromagnetic materials, such as ferromagnetic metals and alloys, or in ferrites. The magnetic resonance frequency of the yttrium iron garnet is near 1GHz, the negative magnetic conductivity can be realized, and the frequency band of the negative magnetic conductivity can be regulated and controlled by applying a bias external magnetic field. According to the Drude model, the metal material has a negative dielectric constant below the characteristic frequency of the plasma, and thus, the negative dielectric constant and the negative permeability can be simultaneously realized by compounding different metal nanoparticles with YIG. For example, silver or copper particles are composited with porous YIG by a process of impregnation reduction, and the copper particles and YIG particles may also be bonded together by an epoxy resin.

Polymeric materials are also used to make negative dielectric materials due to their advantages of being lightweight, flexible, and amenable to large scale fabrication. The polyaniline, polypyrrole and other conductive high polymer materials can be used for compounding with YIG to prepare a double negative material. When the conductive polymer material is used to replace a metal material, sintering and thermal reduction processes can be avoided in the process, and meanwhile, the composite material can have certain flexibility. The composite material has important application in the field of wave absorption.

Disclosure of Invention

The invention provides a preparation method of a double-negative material in order to realize a flexible wave-absorbing material with negative dielectric and negative magnetic conductivity. The preparation scheme provided by the invention is as follows:

step 1: preparing YIG powder by a solid-phase reaction method. Preparing yttrium iron garnet powder by using a solid-phase reaction: mixing yttrium oxide and iron oxide powder according to a molar ratio of 3:5, ball-milling, drying, carrying out a 1300 ℃ solid phase reaction, and sieving (300 meshes) to obtain yttrium iron garnet powder. The yttrium iron garnet powder used in the step 1 can also use other industrial grade powder, and the grain diameter is between 1 and 20 mu m.

Step 2: mixing yttrium iron garnet powder and polyaniline powder in a certain proportion. Wherein, the polyaniline is conductive polyaniline, the particle diameter is 1 μm-5 μm, the direct current conductivity is 0.1-10 (omega. cm) -1, and the direct current conductivity of the conductive polyaniline used in the invention is one of the key parameters. The volume ratio of the yttrium iron garnet powder in the composite powder is 60-95%. The mixing method is ball milling and dry milling. When a planetary ball mill is used for mixing, the total ball-material ratio is 2 (the optimal ratio), the ball milling rotating speed is 240r/min, and the ball milling time is 0.5-2 hours; when a vibration ball mill is used for mixing materials, the ball material ratio is 1-3, low-frequency vibration is carried out for 14-24 seconds, then high-frequency vibration is carried out for 60-120 seconds, and circulation is carried out for 3-6 times.

And step 3: and (3) pressure-forming the mixed powder obtained in the step (2) into a composite material with a certain shape. The size of the mould is designed according to the size of the material to be prepared. The molding mode is hot press molding or only pressure molding without heating. The powder is poured into a mould and preheated for 20-40min at 60-100 ℃ during hot-press molding. Then pressurizing to 20MPa-50MPa, maintaining the pressure for 30min, and relieving the pressure when cooling to the room temperature, wherein the pressure relief rate is 5MPa/min-30 MPa/min, and the cooling mode can be natural cooling or circulating water cooling. When the pressure forming is carried out without heating, slowly pressurizing to 10MPa, maintaining the pressure for 10min, then pressurizing to 30MPa-50MPa, maintaining the pressure for 30min, and the pressure relief rate is 5MPa/min-30 MPa/min.

The invention provides a preparation method of a flexible wave-absorbing material, which has the following beneficial effects:

1) the raw materials used in the invention can be directly used as industrial raw materials, and the process is simple and the energy consumption is low;

2) the conductivity of polyaniline has a decisive influence on the product performance, and the regulation and control on the double negative performance can be realized by controlling the volume fractions of yttrium iron garnet and polyaniline;

3) the double negative material prepared by the invention has certain flexibility, can be prepared into a film and is used for wearable electromagnetic products.

Drawings

FIG. 1 is an SEM photograph of an yttrium iron garnet powder used in examples;

FIG. 2 is an SEM image of a pure polyaniline bulk material;

FIG. 3 shows the double negative properties of YIG/polyaniline composites.

Detailed Description

In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following detailed description is made with reference to specific embodiments and accompanying drawings.

The above-described scheme is further illustrated below with reference to specific examples. It should be understood that these examples are for illustrative purposes and are not intended to limit the scope of the present invention. The conditions used in the examples may be further adjusted according to the conditions of the particular manufacturer, and the conditions not specified are generally the conditions in routine experiments.

The invention provides a preparation method of a super-structure composite material with stable weak negative dielectric property, and the specific material dosage and the experimental process are shown in the following examples.