High-performance composite wave-absorbing material, preparation method and application thereof

Abstract

The application discloses a kind of high-performance composite wave-absorbing materials and preparation method, application, it is related to composite wave-absorbing material technical field, the composite wave-absorbing material is dispersed in polydimethylsiloxane matrix by core-shell structure material formation, the core-shell structure material is magnetic particle as core, with wave-transparent nanoparticle-containing liquid metal as shell, the thickness of the liquid metal shell layer is accurately controlled by adding amount and chemical etching process, the chemical etching process is controlled layer by layer thinning to pre-formed thick shell layer, the composite surface with gradient impedance matching function is formed by the network of partially exposed silicon dioxide and residual liquid metal outside shell layer, the wave-absorbing performance of the composite wave-absorbing material obtained is excellent, and preparation method is convenient, easy to control, and application range is wider.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite wave-absorbing materials, in particular to a high-performance composite wave-absorbing material and a preparation method and application thereof. BACKGROUND

[0002] At present, common electromagnetic wave-absorbing materials are mainly based on magnetic metal powder, which covers Fe, Co, Ni and other metal single substances and alloy powder, and realizes the absorption and weakening of electromagnetic waves through mechanisms such as magnetic hysteresis loss, eddy current loss and natural resonance loss. However, such wave-absorbing agents have some defects that cannot be ignored, such as easy oxidation, poor corrosion resistance, large density, and poor absorption performance in the low frequency band, making it difficult to achieve wideband wave-absorbing effect alone.

[0003] For example, the patent application document with publication number "CN107979964A" proposes an electromagnetic wave-absorbing sheet. The absorbing sheet is made of a composite material of electromagnetic wave-absorbing agent and high molecular resin, which is attached to the required part to absorb and attenuate the incident electromagnetic wave through the electromagnetic wave-absorbing material, and convert it into heat energy or other forms of energy, thereby achieving the purpose of absorbing electromagnetic waves. However, the electromagnetic wave-absorbing performance of the absorbing sheet is insufficient, and further research and development of composite wave-absorbing patches with more excellent wave-absorbing performance are still needed.

[0004] For another example, the patent application with publication number "CN113603149A" obtains core-shell structure γ-Fe2O3@SiO2 particles with good wave-absorbing performance and ferromagnetic behavior, but the coating process is complex and not conducive to large-scale production, and the wave-absorbing performance also has room for improvement.

[0005] In addition, the patent application document with publication number "CN110283461A" discloses a tunable electromagnetic wave-absorbing material based on liquid metal, which adheres to the outside of the equipment and can absorb electromagnetic waves at room temperature, but its maximum reflection loss is only 50dB, so its wave-absorbing performance still needs to be further improved. SUMMARY

[0006] The purpose of the present application is to provide a high-performance composite wave-absorbing material and a preparation method and application thereof, to solve the problem of poor wave-absorbing performance of electromagnetic wave-absorbing materials in the prior art.

[0007] The present application is achieved by the following technical solutions:

[0008] A high-performance composite wave-absorbing material, the composite wave-absorbing material is formed by dispersing core-shell structure material in a polydimethylsiloxane matrix, wherein the core-shell structure material accounts for 50-90wt%, and the polydimethylsiloxane matrix accounts for 10-50wt%.

[0009] The core-shell structure material has magnetic particles as the core and liquid metal containing wave-transparent nanoparticles as the shell. In the core-shell structure material, the magnetic particles account for 70-99 wt%, and the liquid metal containing wave-transparent nanoparticles accounts for 1-30 wt%. In the liquid metal containing wave-transparent nanoparticles, the wave-transparent nanoparticles account for 1-55 wt%, and the liquid metal accounts for 45-99 wt%.

[0010] The silica nanoparticles in the liquid metal shell layer are structured into a three-dimensionally connected channel network, which can guide the incident electromagnetic wave from the material surface to the magnetic core and enhance energy dissipation through multiple reflections and scattering during the guiding process.

[0011] The thickness of the liquid metal shell layer is precisely controlled by adding an amount and a chemical etching process. The chemical etching process controllably thins the pre-formed thick shell layer layer by layer, so that a composite surface with a gradient impedance matching function is formed on the outside of the shell layer, which is composed of a partially exposed silica network and residual liquid metal.

[0012] Further, the wave-transparent nanoparticles are at least one of silica, zinc oxide or aluminum oxide.

[0013] Further, the wave-transparent nanoparticles are silica nanoparticles with a particle size of 5-100 nm. In the present application, the particle size of the wave-transparent nanoparticles affects the connectivity of the channels and the scattering characteristics of the electromagnetic wave. Smaller particles with a particle size in the range of 5-30 nm are more conducive to forming continuous channels, and larger particles with a particle size in the range of 30-100 nm are more conducive to enhancing the microscopic scattering effect in the shell layer.

[0014] Further, the magnetic particles are at least one particle of ferrite, carbonyl iron, iron, cobalt, nickel and alloys thereof.

[0015] Further, the magnetic particles are spherical carbonyl iron.

[0016] Further, the liquid metal is selected from at least one of gallium, indium, tin, bismuth, aluminum, copper.

[0017] Further, the polydimethylsiloxane is at least one of hydroxyl-terminated polydimethylsiloxane, amino-terminated polydimethylsiloxane, alkoxy-terminated polydimethylsiloxane, and carboxyl-terminated polydimethylsiloxane.

[0018] Further, the thickness of the shell layer in the core-shell structure material is 5-30% of the diameter of the magnetic particles. The thickness of the shell layer is designed so that the silica channels can form an effective transmission path and provide sufficient scattering and reflection space in the shell layer.

[0019] A preparation method of a high-performance composite wave-absorbing material, comprising the following steps:

[0020] S1, preparing raw materials according to the raw material ratio as described above, for standby;

[0021] S2, adding liquid metal and wave-transparent nanoparticles into an automatic grinder, and grinding for 10-60 min at a speed of 100-2000 rpm to obtain liquid metal containing wave-transparent nanoparticles;

[0022] S3, adding the liquid metal containing wave-transparent nanoparticles in step S2 and magnetic particles into an automatic grinder, and grinding for 1-30 min at a speed of 100-1000 rpm to obtain an initial core-shell structure material;

[0023] S4, placing the initial core-shell structure material in step S3 in a chemical etchant, controlling the temperature to be 15-40 DEG C, and processing for 1-30 min to obtain a core-shell structure material with wave-transparent nanoparticles exposed on the surface;

[0024] S5, placing the core-shell structure material in step S4 and a polydimethylsiloxane matrix into a container, stirring for 1-30 min using a stirrer at a speed of 100-1000 rpm, and drying to obtain a high-performance composite wave-absorbing material.

[0025] Further, in step S4, the chemical etchant is at least one selected from a 0.1-0.5 mol / L hydrochloric acid ethanol solution and a 0.05-0.3 mol / L sulfuric acid ethanol solution.

[0026] Further, in step S5, the drying method is heating in an oven at 50-150 DEG C for 1-5 h.

[0027] The high-performance composite wave-absorbing material as described above or obtained by the preparation method as described above is applied to electromagnetic compatibility and protection of 5G communication equipment, automatic driving radar, radar cover, unmanned aerial vehicle, and electromagnetic compatibility and protection function of stealth coating.

[0028] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0029] I. In the present application, a high-performance composite wave-absorbing material is proposed, which has high-efficiency electromagnetic wave absorption performance. By constructing a three-dimensional interconnected channel network of silicon dioxide in the liquid metal shell layer, efficient absorption of electromagnetic waves is achieved, and the specific mechanism includes: guiding directional transmission of electromagnetic waves to avoid disordered scattering loss; multiple reflection and scattering at the interface to enhance dissipation; forming a gradient impedance matching path to reduce interface reflection loss. The core-shell structure material realizes the synergistic effect of magnetic loss and dielectric loss, and the wave-absorbing performance is adjusted by precisely controlling the core-shell ratio and channel parameters. The minimum reflection loss is less than -67.31 dB in the frequency range of 2-18 GHz, which is much better than the existing wave-absorbing materials.

[0030] II. In the present application, a high-performance composite wave-absorbing material is proposed, which solves the problem of precise control of nanoscale shell thickness by traditional mechanical methods, and can realize nanoscale customization of shell thickness. The etching process exposes part of the internal silicon dioxide network, forming a "silicon dioxide / liquid metal" composite gradient layer at the outermost layer of the material, which greatly optimizes the impedance matching and is the key to ultra-high-efficiency wave-absorbing performance.

[0031] III. In the present application, a high-performance composite wave-absorbing material is proposed, which realizes the synergistic maximization of multiple loss mechanisms by combining "silicon dioxide wave channel" with "magnetic core". By adjusting the particle size of silicon dioxide as a parameter and optimizing the shell thickness by chemical etching, the magnetic loss and dielectric loss reach the best balance for specific application scenarios. The silicon dioxide channel efficiently "infuses" electromagnetic waves into the magnetic core to excite magnetic loss, and the multiple scattering of the channel itself and the interface polarization enhance dielectric loss.

[0032] IV. In the present application, a high-performance composite wave-absorbing material is proposed, which has ultra-strong wave-absorbing performance, as well as light weight, good flexibility, strong weather resistance, and can be conformally attached to any complex curved surface. The high-performance composite wave-absorbing material can be applied in 5G communication equipment, automatic driving radar, radar cover, electromagnetic compatibility and protection of unmanned aerial vehicles, and electromagnetic compatibility and protection function in stealth coating, which has great market potential and value. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is the reflection loss diagram of examples 1-6.

[0034] Figure 2 is the reflection loss diagram of comparative examples 1-6.

[0035] Figure 3 is the flowchart of preparing the high-performance composite wave-absorbing material in the present application.

[0036] Figure 4 is the schematic diagram of the wave-transparent nanoparticle silicon dioxide channel network in the present application.

[0037] Figure 5 is a SEM image of spherical carbonyl iron.

[0038] Figure 6 is a SEM image of liquid metal coated magnetic core-shell structure material microspheres containing wave-transparent nanoparticles.

[0039] Figure 7 is a photo of a high-performance composite wave-absorbing material product prepared in the present application.

[0040] Figure 8 is Figure 7 is a SEM image of the cross section of the product in DETAILED DESCRIPTION

[0041] The present application will be further described in conjunction with the following examples, but the embodiments of the present application are not limited thereto.

[0042] In the present application, the polydimethylsiloxane is at least one of hydroxyl-terminated polydimethylsiloxane, amino-terminated polydimethylsiloxane, alkoxy-terminated polydimethylsiloxane, and carboxyl-terminated polydimethylsiloxane. In the following examples, hydroxyl-terminated polydimethylsiloxane is taken as an example for testing, which is purchased from Shenzhen Boyang Organic Silicon Material Co., Ltd., and the model is BY-300.

[0043] In the present application, the wave-transparent nanoparticles can be selected from one of silica, zinc oxide, or aluminum oxide nanoparticles, and preferably the particle size of the silica nanoparticles is 5-100 nm. In the following examples, nano-silica is taken as an example for illustration.

[0044] In the present application, the magnetic particles are at least one particle selected from ferrite, carbonyl iron, iron, cobalt, nickel, and alloys thereof. In the following examples, spherical carbonyl iron and spherical iron-silicon-aluminum are taken as examples for illustration.

[0045] In the present application, the liquid metal is selected from at least one of gallium, indium, tin, bismuth, aluminum, and copper.

[0046] In the present application, the chemical etchant is at least one of an ethanol solution of hydrochloric acid with a concentration of 0.1-0.5 mol / L and an ethanol solution of sulfuric acid with a concentration of 0.05-0.3 mol / L. In the following examples, a dilute ethanol solution of sulfuric acid with a concentration of 0.1 mol / L is taken as an example for illustration.

[0047] Example 1

[0048] Reference Figure 3 , a high-performance composite wave-absorbing material is prepared by the following method steps:

[0049] Step 1, preparation of liquid metal

[0050] Take gallium 68.5 parts, indium 21.5 parts and tin 10 parts by weight, mix uniformly and then add to the crucible; heat to 280℃, keep for 6h, then cool to room temperature to obtain liquid metal, and then place the liquid metal in a container under inert atmosphere protection for standby.

[0051] Step two, preparation of liquid metal containing nanosilica

[0052] Take 2 parts of silica microspheres with a diameter of 50nm and 98 parts of liquid metal in step one by weight, mix the two materials and then put them into a mortar, control the rotation speed at 500rpm for 5min to obtain liquid metal containing nanosilica.

[0053] Step three, preparation of initial core-shell structure material

[0054] Take 5 parts of liquid metal containing nanosilica in step two and 95 parts of spherical carbonyl iron by weight, mix the two materials and then put them into a mortar, control the rotation speed at 500rpm for 5min to obtain initial core-shell structure material. The SEM image of spherical carbonyl iron is shown in Figure 5 .

[0055] Step four, preparation of core-shell structure material

[0056] Disperse the initial core-shell structure material in step three in a 0.1mol / L dilute sulfuric acid ethanol solution, magnetically stir at room temperature (25℃) for 10min to accurately etch the liquid metal shell layer and expose part of the silica network inside the shell layer to the surface. After etching, wash the sample with anhydrous ethanol by centrifugation or filtration for 3 times to completely remove the residual acid and reaction products. Then, dry the washed core-shell structure material in a vacuum oven at 60℃ for 4h to obtain the core-shell structure material, as shown in Figure 6 , Figure 6 is the SEM image of liquid metal coated with magnetic core-shell structure material microspheres containing wave-transparent nanoparticles.

[0057] Step five, preparation of high-performance composite wave-absorbing material

[0058] Take 70 parts of core-shell structure material and 30 parts of polydimethylsiloxane by weight, put the core-shell structure material and polydimethylsiloxane into a container, stir with a stirrer at a rotation speed of 300rpm for 5min to obtain a composite material; then transfer the composite material to a mold and heat in an oven at a temperature of 90℃ for 2h to obtain a high-performance composite wave-absorbing material, as shown in Figure 7 、 8 , Figure 7 is a product photo of high-performance composite wave-absorbing material, Figure 8 is the SEM image of the cross section of the product.

[0059] Example 2

[0060] Reference Figure 3 A high-performance composite wave-absorbing material was prepared by the following method steps:

[0061] Step one, preparation of liquid metal

[0062] According to parts by weight, take gallium 68.5 parts, indium 21.5 parts and tin 10 parts of three raw materials, mix evenly and then add to the crucible; heat to 280℃, keep warm for 6h, then cool to room temperature, get liquid metal, and then put the liquid metal in a container under inert atmosphere protection for standby.

[0063] Step two, preparation of liquid metal containing nano-silicon dioxide

[0064] According to parts by weight, take 2 parts of silica microspheres with a diameter of 30nm and 98 parts of liquid metal in step one, mix the two materials and put them into a mortar, control the speed at 500rpm for 5min, get liquid metal containing nano-silicon dioxide.

[0065] Step three, preparation of initial core-shell structure material

[0066] According to parts by weight, take 5 parts of liquid metal containing nano-silicon dioxide in step two and 95 parts of spherical carbonyl iron, mix the two materials and put them into a mortar, control the speed at 500rpm for 5min, get initial core-shell structure material.

[0067] Step four, preparation of core-shell structure material

[0068] Disperse the initial core-shell structure material in step three in a 0.1mol / L dilute sulfuric acid ethanol solution, stir magnetically at room temperature (25℃) for 10min, accurately etch the liquid metal shell layer, and at the same time expose the internal silicon dioxide network to the surface of the shell layer. After etching, wash the sample with anhydrous ethanol by centrifugation or filtration for 3 times to completely remove the residual acid and reaction products. Then, dry the washed core-shell structure material in a vacuum oven at 60℃ for 4h to get the core-shell structure material.

[0069] Step five, preparation of high-performance composite wave-absorbing material

[0070] According to parts by weight, take 70 parts of core-shell structure material in step four and 30 parts of polydimethylsiloxane, put the core-shell structure material and polydimethylsiloxane into a container, stir with a stirrer at a speed of 300rpm for 5min to get a composite material; then transfer the composite material to a mold and heat in an oven at a temperature of 90℃ for 2h to get a high-performance composite wave-absorbing material.

[0071] Example 3

[0072] Reference Figure 3 A high-performance composite wave-absorbing material is prepared by the following steps:

[0073] Step 1, preparation of liquid metal

[0074] According to weight parts, take gallium 68.5 parts, indium 21.5 parts and tin 10 parts of three raw materials, mix uniformly and then add to the crucible; heat to 280℃, keep warm for 6h, and then cool to room temperature to obtain liquid metal, and then place the liquid metal in a container under inert atmosphere protection for standby.

[0075] Step 2, preparation of liquid metal containing nano-silicon dioxide

[0076] According to weight parts, take 2 parts of silica microspheres with a diameter of 100 nm and 98 parts of liquid metal in step 1, mix the two materials and then put them into a mortar, control the rotation speed at 500 rpm and mix for 5 min to obtain liquid metal containing nano-silicon dioxide.

[0077] Step 3, preparation of initial core-shell structure material

[0078] According to weight parts, take 5 parts of liquid metal containing nano-silicon dioxide in step 2 and 95 parts of spherical carbonyl iron, mix the two materials and then put them into a mortar, control the rotation speed at 500 rpm and mix for 5 min to obtain the initial core-shell structure material.

[0079] Step 4, preparation of core-shell structure material

[0080] Disperse the initial core-shell structure material in step 3 in a dilute sulfuric acid ethanol solution with a concentration of 0.1 mol / L, and magnetically stir at room temperature (25℃) for 10 min to accurately etch the liquid metal shell layer and expose part of the silicon dioxide network on the surface of the shell layer. After etching, the sample is washed with anhydrous ethanol by centrifugation or filtration for 3 times to completely remove the residual acid and reaction products. Then, the washed core-shell structure material is dried in a vacuum oven at 60℃ for 4h to obtain the core-shell structure material.

[0081] Step 5, preparation of high-performance composite wave-absorbing material

[0082] According to weight parts, take 70 parts of the core-shell structure material in step 4 and 30 parts of polydimethylsiloxane, put the core-shell structure material and polydimethylsiloxane into a container, and stir with a stirrer at a rotation speed of 300 rpm for 5 min to obtain a composite material; then transfer the composite material to a mold and heat in an oven at a temperature of 90℃ for 2h to obtain a high-performance composite wave-absorbing material.

[0083] Example 4

[0084] Reference Figure 3 A high-performance composite wave-absorbing material is prepared by the following steps:

[0085] Step one, preparation of liquid metal

[0086] According to parts by weight, take gallium 68.5 parts, indium 21.5 parts and tin 10 parts of three raw materials, mix evenly and then add to the crucible; heat to 280℃, keep warm for 6h, then cool to room temperature, get liquid metal, and then put the liquid metal in a container under inert atmosphere protection, ready for use.

[0087] Step two, preparation of liquid metal containing nano-silicon dioxide

[0088] According to parts by weight, take 1 part of silica microspheres with a diameter of 50nm and 99 parts of liquid metal in step one, mix the two materials and put them into a mortar, control the speed at 500rpm for 5min, get liquid metal containing nano-silicon dioxide.

[0089] Step three, preparation of initial core-shell structure material

[0090] According to parts by weight, take 5 parts of liquid metal containing nano-silicon dioxide in step two and 95 parts of spherical carbonyl iron, mix the two materials and put them into a mortar, control the speed at 500rpm for 5min, get initial core-shell structure material.

[0091] Step four, preparation of core-shell structure material

[0092] Disperse the initial core-shell structure material in step three in a 0.1mol / L dilute sulfuric acid ethanol solution, stir magnetically at room temperature (25℃) for 10min, accurately etch the liquid metal shell layer, and at the same time expose the internal silicon dioxide network to the surface of the shell layer. After etching, wash the sample with anhydrous ethanol by centrifugation or filtration for 3 times to completely remove the residual acid and reaction products. Then, dry the washed core-shell structure material in a vacuum oven at 60℃ for 4h, get the core-shell structure material.

[0093] Step five, preparation of high-performance composite wave-absorbing material

[0094] According to parts by weight, take 70 parts of core-shell structure material in step four and 30 parts of polydimethylsiloxane, put the core-shell structure material and polydimethylsiloxane into a container, stir with a stirrer at a speed of 300rpm for 5min, get the composite material; then transfer the composite material to a mold and heat in an oven at a temperature of 90℃ for 2h, get the high-performance composite wave-absorbing material.

[0095] Example 5

[0096] Reference Figure 3 A high-performance composite wave-absorbing material is prepared by the following steps:

[0097] Step 1, preparation of liquid metal

[0098] According to weight parts, take gallium 68.5 parts, indium 21.5 parts and tin 10 parts of three raw materials, mix uniformly and then add to the crucible; heat to 280℃, keep warm for 6h, and then cool to room temperature to obtain liquid metal, and then place the liquid metal in a container under inert atmosphere protection for standby.

[0099] Step 2, preparation of liquid metal containing nano-silicon dioxide

[0100] According to weight parts, take 3 parts of silica microspheres with a diameter of 50 nm and 97 parts of liquid metal in step 1, mix the two materials and then put them into a mortar, control the rotation speed at 500 rpm and mix for 5 min to obtain liquid metal containing nano-silicon dioxide.

[0101] Step 3, preparation of initial core-shell structure material

[0102] According to weight parts, take 5 parts of liquid metal containing nano-silicon dioxide in step 2 and 95 parts of spherical carbonyl iron, mix the two materials and then put them into a mortar, control the rotation speed at 500 rpm and mix for 5 min to obtain the initial core-shell structure material.

[0103] Step 4, preparation of core-shell structure material

[0104] Disperse the initial core-shell structure material in step 3 in a dilute sulfuric acid ethanol solution with a concentration of 0.1 mol / L, and magnetically stir at room temperature (25℃) for 10 min to accurately etch the liquid metal shell layer and expose part of the silicon dioxide network on the surface of the shell layer. After etching, the sample is washed with anhydrous ethanol by centrifugation or filtration for 3 times to completely remove the residual acid and reaction products. Then, the washed core-shell structure material is dried in a vacuum oven at 60℃ for 4h to obtain the core-shell structure material.

[0105] Step 5, preparation of high-performance composite wave-absorbing material

[0106] According to weight parts, take 70 parts of the core-shell structure material in step 4 and 30 parts of polydimethylsiloxane, put the core-shell structure material and polydimethylsiloxane into a container, and stir with a stirrer at a rotation speed of 300 rpm for 5 min to obtain a composite material; then transfer the composite material to a mold and heat in an oven at a temperature of 90℃ for 2h to obtain the high-performance composite wave-absorbing material.

[0107] Example 6

[0108] ReferenceFigure 3 A high-performance composite wave-absorbing material is prepared by the following steps:

[0109] Step one, preparing liquid metal

[0110] According to weight parts, take gallium 68.5 parts, indium 21.5 parts and tin 10 parts of three raw materials, mix uniformly and then add to the crucible; heat to 280℃, keep warm for 6h, and then cool to room temperature to obtain liquid metal, and then place the liquid metal in a container under inert atmosphere protection for standby.

[0111] Step two, preparing liquid metal containing nano-silicon dioxide

[0112] According to weight parts, take 2 parts of silica microspheres with a diameter of 50nm and 98 parts of liquid metal in step one, mix the two materials and then put them into a mortar, control the rotation speed at 500rpm for 5min to obtain liquid metal containing nano-silicon dioxide.

[0113] Step three, preparing initial core-shell structure material

[0114] According to weight parts, take 5 parts of liquid metal containing nano-silicon dioxide in step two and 95 parts of spherical iron-silicon-aluminum, mix the two materials and then put them into a mortar, control the rotation speed at 500rpm for 5min to obtain initial core-shell structure material.

[0115] Step four, preparing core-shell structure material

[0116] Disperse the initial core-shell structure material in step three in a 0.1mol / L dilute sulfuric acid ethanol solution, magnetically stir at room temperature (25℃) for 10min to accurately etch the liquid metal shell layer and expose part of the silicon dioxide network on the surface of the shell layer. After etching, wash the sample with anhydrous ethanol by centrifugation or filtration for 3 times to completely remove the residual acid and reaction products. Then, dry the washed core-shell structure material in a vacuum oven at 60℃ for 4h to obtain the core-shell structure material.

[0117] Step five, preparing high-performance composite wave-absorbing material

[0118] According to weight parts, take 70 parts of core-shell structure material in step four and 30 parts of polydimethylsiloxane, put the core-shell structure material and polydimethylsiloxane into a container, stir with a stirrer at a rotation speed of 300rpm for 5min to obtain a composite material; then transfer the composite material to a mold and heat in an oven at a temperature of 90℃ for 2h to obtain a high-performance composite wave-absorbing material.

[0119] Comparative example 1

[0120] A preparation method of a composite wave-absorbing material:

[0121] Take 70 parts of spherical carbonyl iron and 30 parts of polydimethylsiloxane by weight, put the two materials into a container, and stir with a stirrer at a speed of 300 rpm for 5 min.

[0122] Put the composite material obtained in the above step into a mold, and heat in an oven at a temperature of 90℃ for 2h to obtain a composite wave-absorbing material.

[0123] Comparative Example 2

[0124] A liquid metal coated carbonyl iron core-shell structure composite wave-absorbing material is prepared by the following method:

[0125] Step 1, preparation of liquid metal

[0126] Take 68.5 parts of gallium, 21.5 parts of indium and 10 parts of tin by weight, mix them uniformly and then add them to a crucible; heat to 280℃, keep for 6h, then cool to room temperature to obtain liquid metal, and then place the liquid metal in a container under inert atmosphere protection for standby.

[0127] Step 2, preparation of core-shell structure material

[0128] Take 5 parts of liquid metal and 95 parts of carbonyl iron by weight, and the carbonyl iron is selected as spherical carbonyl iron. Mix the two materials and then put them into a mortar, and stir with a stirrer at a speed of 300 rpm for 5 min.

[0129] Step 3, preparation of liquid metal coated carbonyl iron core-shell structure composite wave-absorbing material

[0130] Take 70 parts of the core-shell structure material of step 2 and 30 parts of polydimethylsiloxane by weight, put them into a container, and stir with a stirrer at a speed of 300 rpm for 5 min. Then put the composite material into a mold, and heat in an oven at a temperature of 90℃ for 2h to obtain a high-performance composite wave-absorbing material.

[0131] Comparative Example 3

[0132] A preparation method of a silicon dioxide and carbonyl iron composite wave-absorbing material, comprising the following steps:

[0133] Put nano-silicon dioxide, spherical carbonyl iron and polydimethylsiloxane into a container, 1.4 parts of silicon dioxide, 68.6 parts of spherical carbonyl iron and 30 parts of polydimethylsiloxane by weight, and stir with a stirrer at a speed of 300 rpm for 5 min.

[0134] The composite material obtained in the above step is transferred into a mold, and is added into an oven at a temperature of 90 DEG C for 2h, to obtain the composite wave-absorbing material.

[0135] Comparative Example 4

[0136] A preparation method of a nano-silica coated carbonyl iron powder composite wave-absorbing material, comprising the following steps:

[0137] Step one, 10g of carbonyl iron powder is added into 100ml of ethanol and 10ml of water, and is ultrasonically treated for 20min; then 5ml of tetraethyl orthosilicate is weighed, and is added into the above solution, and is stirred for 30min to obtain a mixture;

[0138] Step two, 5ml of ammonia solution is weighed, and is added dropwise into the mixture of step one, and is stirred at room temperature for 3h for hydrolysis, and is vacuum filtered, and the obtained precipitate is washed with anhydrous ethanol for 3 times, and is dried at 60 DEG C for 10h, to obtain the nano-silica coated carbonyl iron powder;

[0139] Step three, the nano-silica coated carbonyl iron and polydimethylsiloxane are put into a container, and the nano-silica coated carbonyl iron material is 70 parts, and the polydimethylsiloxane is 30 parts by weight, and a stirrer with a rotating speed of 300rpm is used to stir for 5min;

[0140] The composite material obtained in the above step is transferred into a mold, and is added into an oven at a temperature of 90 DEG C for 2h, to obtain the composite wave-absorbing material.

[0141] Comparative Example 5

[0142] A preparation method of a liquid metal coated carbonyl iron core-shell structure and polydimethylsiloxane composite wave-absorbing material containing dispersed nano-silica, comprising the following steps:

[0143] Step one, preparation of liquid metal

[0144] 68.5 parts of gallium, 21.5 parts of indium and 10 parts of tin are taken as three raw materials, and are mixed uniformly, and then are added into a crucible; the temperature is increased to 280 DEG C, and is kept for 6h, and then is cooled to room temperature, to obtain the liquid metal; the liquid metal is placed in a container under the protection of inert atmosphere, and is ready for use.

[0145] Step two, preparation of core-shell structure material

[0146] The spherical carbonyl iron and the liquid metal are weighed according to the component formula, and are mixed, and then are put into a mortar, and the rotating speed is controlled to 500rpm for mixing for 5min.

[0147] Step three, preparation of liquid metal coated carbonyl iron core-shell structure and polydimethylsiloxane composite wave-absorbing material containing dispersed nano-silica

[0148] Put the obtained core-shell structure material, and spherical nanometer silicon dioxide and polydimethylsiloxane into a container, and stir for 5 min at a stirring speed of 300 rpm.

[0149] Put the obtained composite material into a mold, and add it into an oven at a temperature of 90℃ for 2 h to obtain a composite wave-absorbing material.

[0150] Comparative Example 6

[0151] A spherical iron-silicon-aluminum and polydimethylsiloxane composite wave-absorbing material is prepared by the following steps:

[0152] Put the spherical iron-silicon-aluminum and polydimethylsiloxane into a container, and stir for 5 min at a stirring speed of 300 rpm.

[0153] Put the obtained composite material into a mold, and add it into an oven at a temperature of 90℃ for 2 h to obtain a composite wave-absorbing material.

[0154] Comparative Example 7

[0155] A high-performance composite wave-absorbing material is prepared by the following steps:

[0156] Step 1, preparation of liquid metal

[0157] Take gallium 68.5 parts, indium 21.5 parts and tin 10 parts by weight, mix them uniformly, and then add them into a crucible; heat to 280℃, keep for 6 h, and then cool to room temperature to obtain a liquid metal; and then place the liquid metal in a container under inert atmosphere protection for standby.

[0158] Step 2, preparation of liquid metal containing nanometer silicon dioxide

[0159] Take 2 parts of silica microspheres with a diameter of 50 nm and 98 parts of the liquid metal in step 1 by weight, mix the two materials, and then put them into a mortar, mix for 5 min at a speed of 500 rpm to obtain a liquid metal containing nanometer silicon dioxide.

[0160] Step 3, preparation of initial core-shell structure material

[0161] Take 5 parts of the liquid metal containing nanometer silicon dioxide in step 2 and 95 parts of spherical carbonyl iron-silicon-aluminum by weight, mix the two materials, and then put them into a mortar, mix for 5 min at a speed of 500 rpm to obtain a core-shell structure material.

[0162] Step 4, preparation of high-performance composite wave-absorbing material

[0163] Take 70 parts of the core-shell structure material in step four and 30 parts of polydimethylsiloxane by weight, put the core-shell structure material and polydimethylsiloxane into a container, and stir with a stirrer at a speed of 300 rpm for 5 min to obtain a composite material; then transfer the composite material to a mold and heat in an oven at a temperature of 90℃ for 2h to obtain a high-performance composite wave-absorbing material.

[0164] Performance test.

[0165] The reflection loss of the composite wave-absorbing materials obtained in Examples 1-6 and Comparative Examples 1-7 was tested, and the results are shown in Table 1. The reflection loss test results of Examples 1-6 are shown in Table 1. Figure 1 The reflection loss test results of Comparative Examples 1-6 are shown in Table 1. Figure 2 .

[0166] The test method for reflection loss is as follows: the electromagnetic parameters of the sample are measured by a vector network analyzer, and the reflection loss value Zin is calculated according to the following formula:

[0167] .

[0168] Table 1

[0169]

[0170] According to the statistical results in Table 1, it can be seen that:

[0171] Example 1 and Comparative Example 1, the present application adopts a liquid metal containing wave-transparent nanoparticles to coat magnetic particles to form a core-shell structure composite wave-absorbing material, compared with the material in which the magnetic particles are directly dispersed in the polydimethylsiloxane matrix, the minimum reflection loss is greatly improved from -16.94dB to -67.31dB, and the improvement effect is significant.

[0172] Example 1 and Comparative Example 2, compared with the composite wave-absorbing material in which the liquid metal coated magnetic particles are simply dispersed in the polydimethylsiloxane matrix, the present application adds wave-transparent nanoparticles to the liquid metal, realizing the dual action of magnetic loss and dielectric loss, and the minimum reflection loss is improved from -19.39dB to -67.31dB.

[0173] Example 1 and Comparative Examples 3-4, compared with the nanosilica coated carbonyl iron wave-absorbing material and the composite wave-absorbing material in which the material is dispersed in polydimethylsiloxane, in the present scheme, the minimum reflection loss is significantly improved by the combination of multiple wave-absorbing materials and the superposition of multiple wave-absorbing methods. At the same time, compared with Comparative Examples 2 and 4, the wave-absorbing performance of the present scheme is not only significantly better than that of the liquid metal coated magnetic particles and the nanosilica coated magnetic particles, but also better than the simple superposition of the performances of the two.

[0174] As can be seen from the comparison between Example 1 and Comparative Example 5, the present application can improve the wave absorption performance by nearly one time by using the special process of “preparing liquid metal containing wave-transparent nanoparticles, coating the core-shell structure material with carbonyl magnetic particles, and finally dispersing in the polydimethylsiloxane matrix”, compared with the method of “mixing the liquid metal coated with carbonyl iron with nanoparticles and then dispersing in the polydimethylsiloxane matrix”.

[0175] In addition, the comparison between Example 1 and Comparative Example 7 shows that etching the outer layer of the core-shell structure liquid metal and exposing the silica channel can significantly improve the electromagnetic wave absorption.

[0176] As can be seen from Examples 1-3, adding wave-transparent particles of different sizes can have a certain influence on the performance when preparing the composite wave-absorbing material, which is mainly because the wave-transparent particles can affect the connectivity of the channel and the scattering characteristics of the electromagnetic wave. In Examples 1, 2 and 3, 50 nm, 30 nm and 100 nm wave-transparent particles are respectively selected, and the obtained composite wave-absorbing materials all have relatively optimal wave-absorbing performance, and the minimum reflection loss is-67.31 dB, -59.89 dB and -55.47 dB respectively. A large number of experiments have verified that the wave-transparent particles of 5-100 nm can be selected in the present application, and the smaller particle size of 5-30 nm is beneficial to form a continuous channel, and the larger particle size of 30-100 nm can enhance the micro scattering effect in the shell layer.

[0177] As can be seen from Examples 1 and 6, other magnetic metals can also achieve the improvement of the minimum reflection loss by using the method of the present application.

[0178] As can be seen from all the examples and comparative examples, the wave-absorbing performance of the present application is better than the simple superposition of the prior art, and the performance of the composite wave-absorbing material is significantly improved. Moreover, the special structure (liquid metal containing nano-silica as the shell, coated with magnetic material) of the present application has better wave-absorbing performance than the simple mixture of the three. Figure 4 , Figure 4 is a schematic diagram of wave-transparent nanoparticle-silica channel network.

[0179] As can be seen from Examples 1-6, the composite wave-absorbing materials with different performances can be obtained by adjusting the ratio of liquid metal, wave-transparent nanoparticles and magnetic particles, so as to meet the demand of different application scenarios for the material.

[0180] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Any simple modification or equivalent change made according to the technical essence of the present application to the above embodiment falls within the protection scope of the present application.

Claims

1. A high-performance composite wave-absorbing material, characterized in that: The composite wave-absorbing material is formed by dispersing the core-shell structure material in a polydimethylsiloxane matrix, wherein the core-shell structure material accounts for 50-90 wt%, and the polydimethylsiloxane matrix accounts for 10-50 wt%. The core-shell structure material has a magnetic particle as a core and a liquid metal containing wave-transparent nanoparticles as a shell, wherein the magnetic particle accounts for 70-99 wt%, and the liquid metal containing wave-transparent nanoparticles accounts for 1-30 wt%; in the liquid metal containing wave-transparent nanoparticles, the wave-transparent nanoparticles account for 1-55 wt%, and the liquid metal accounts for 45-99 wt%. The thickness of the liquid metal shell layer is precisely controlled by adding an amount and a chemical etching process, the chemical etching process is used to controllably thin the pre-formed thick shell layer layer by layer, and a composite surface with a gradient impedance matching function is formed on the outside of the shell layer by a network of partially exposed silicon dioxide and residual liquid metal.

2. The high-performance composite wave-absorbing material according to claim 1, characterized in that: The wave-transparent nanoparticles are silicon dioxide nanoparticles, zinc oxide nanoparticles, or aluminum oxide nanoparticles.

3. The high-performance composite wave-absorbing material according to claim 2, characterized in that: The wave-transparent nanoparticles are silicon dioxide nanoparticles with a particle size of 5-100 nm.

4. The high-performance composite wave-absorbing material according to claim 1, characterized in that: The magnetic particle is at least one particle selected from the group consisting of ferrite, carbonyl iron, iron, cobalt, nickel, and alloys thereof.

5. The high-performance composite wave-absorbing material according to claim 4, characterized in that: The magnetic particle is spherical carbonyl iron.

6. The high-performance composite wave-absorbing material according to claim 1, characterized in that: The liquid metal is at least one selected from the group consisting of gallium, indium, tin, bismuth, aluminum, and copper.

7. The high-performance composite wave-absorbing material according to claim 1, characterized in that: The polydimethylsiloxane is at least one selected from the group consisting of hydroxyl-terminated polydimethylsiloxane, amino-terminated polydimethylsiloxane, alkoxy-terminated polydimethylsiloxane, and carboxyl-terminated polydimethylsiloxane.

8. The high-performance composite wave-absorbing material according to claim 1, characterized in that: The thickness of the shell layer in the core-shell structure material is 5-30% of the diameter of the magnetic particle.

9. A method for preparing high-performance composite wave-absorbing material, characterized in that, The method comprises the following steps: S1, preparing raw materials according to the raw material ratio of claim 1; S2, adding the liquid metal and the wave-transparent nanoparticles into an automatic grinder, grinding at a speed of 100-2000 rpm for 10-60 min to obtain the liquid metal containing wave-transparent nanoparticles; S3, adding the liquid metal containing wave-transparent nanoparticles in step S2 and the magnetic particle into an automatic grinder, grinding at a speed of 100-1000 rpm for 1-30 min to obtain the initial core-shell structure material; S4, placing the initial core-shell structure material in step S3 in a chemical etching agent, controlling the temperature to be 15-40℃, and processing for 1-30 min to obtain the core-shell structure material with the wave-transparent nanoparticles exposed on the surface; S5, placing the core-shell structure material in step S4 and the polydimethylsiloxane matrix into a container, stirring using a stirrer at a speed of 100-1000 rpm for 1-30 min, and drying to obtain the high-performance composite wave-absorbing material.

10. The method for preparing a high-performance composite microwave absorbing material according to claim 9, characterized in that: In step S4, the chemical etching agent is at least one selected from the group consisting of a 0.1-0.5 mol / L hydrochloric acid ethanol solution and a 0.05-0.3 mol / L sulfuric acid ethanol solution.

11. The method for preparing a high-performance composite microwave absorbing material according to claim 9, characterized in that: In step S5, the drying method is heating in an oven at 50-150℃ for 1-5 h.

12. The high-performance composite wave-absorbing material according to any one of claims 1-8 or the high-performance composite wave-absorbing material obtained by the preparation method according to claims 9-11, which is applied in electromagnetic compatibility and protection of 5G communication equipment, automatic driving radar, radar cover, unmanned aerial vehicle, and electromagnetic compatibility and protection function of stealth coating.

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