CN112409653B - Wave absorber, preparation method and application thereof - Google Patents
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Abstract
The invention provides a wave absorber and a preparation method thereof, comprising the following steps of S1: carrying out hydroxylation treatment on various nano silicon dioxide with different particle sizes, wherein the particle size ratio of the large-particle-size nano silicon dioxide to the small-particle-size nano silicon dioxide is more than or equal to 5; s2: weighing hydroxylated nano silicon dioxide, carbonyl iron powder, agate beads and absolute ethyl alcohol according to a preset proportion, and putting the hydroxylated nano silicon dioxide, carbonyl iron powder, agate beads and absolute ethyl alcohol into a ball milling tank; s3: the mixture is subjected to mechanochemical ball milling for a certain time, and the silicon dioxide gradations with different particle diameters are obtained after drying, large particle diameter particles are surrounded by small particle diameter particles, and SiO mainly distributed in a long chain shape is formed 2 The wave absorber of the particle micro-filler network, and the interface of the nano silicon dioxide and carbonyl iron powder are connected through chemical reaction to generate-Si-O-Si-bond. The invention obtains the wave absorber with excellent processing performance and impedance matching performance through the grading of nano silicon dioxide with different particle sizes and a simple mechanochemical ball milling process.
Description
[ field of technology ]
The invention relates to the field of wave absorbers, in particular to a wave absorber, a preparation method and application thereof.
[ background Art ]
The wave absorbing material has very important and wide application in the fields of aerospace, electronic materials and the like, the wave absorbing material is mostly aimed at the working frequency X and Ku wave bands of a radar at present, the wave absorbing capability of the wave absorbing material for a low-frequency wave band is limited by the intrinsic electromagnetic parameters of the wave absorbing material, the working frequency band gradually evolves to a low frequency along with the continuous development of the radar detection technology, and on the basis of increasingly mature development of the 4-20 GHz high-frequency wave absorbing material at home and abroad, the governments of various countries actively explore new camouflage stealth technologies aiming at the detection of the low-frequency meter wave radar. However, most of the research is focused on high-frequency wave-absorbing materials, and the research on low-frequency L (1-2 GHz) and S (2-4 GHz) bands is not comprehensive enough.
Carbonyl iron powder is a metal micro powder wave absorber with excellent performance, and has a mechanism of magnetic loss and dielectric loss, but the impedance matching property of the carbonyl iron powder is poor, the impedance matching property of the carbonyl iron powder can be improved by coating a low dielectric layer on the surface of the carbonyl iron powder, but the existing process is complex, the problem that the environment pollution is large and the batch production cannot be applied exists, and the interface connecting force between a coating layer and the carbonyl iron powder is weak, so that the coating structure of the carbonyl iron powder is easy to damage in the processing process, and the processing performance is poor.
[ invention ]
In order to solve the technical problems, the invention provides a preparation method of a wave absorber, which comprises the following steps of S1: carrying out hydroxylation treatment on various nano silicon dioxide with different particle sizes, wherein the particle size ratio of the large-particle-size nano silicon dioxide to the small-particle-size nano silicon dioxide is more than or equal to 5; s2: weighing hydroxylated nano silicon dioxide, carbonyl iron powder, agate beads and absolute ethyl alcohol according to a preset proportion, and putting the hydroxylated nano silicon dioxide, carbonyl iron powder, agate beads and absolute ethyl alcohol into a ball milling tank; s3: the mixture is subjected to mechanochemical ball milling for a certain time, and the silicon dioxide gradations with different particle diameters are obtained after drying, large particle diameter particles are surrounded by small particle diameter particles, and SiO mainly distributed in a long chain shape is formed 2 The particle micro filler network wave absorber has silicon dioxide coated on the edge and/or surface of the sheet carbonyl iron powder, and the interface between the nanometer silicon dioxide and the carbonyl iron powder is connected through chemical reaction to form-Si-O-Si-bond. The invention uses simple mechanochemical ball milling technology to make carbonyl iron powder flaked, and at the same time, the silicon dioxide network with different grain size fractions is coated on the edge and/or surface of the flaked carbonyl iron powder, and the interface between the nano silicon dioxide and the carbonyl iron powder is connected by chemical reaction to generate-Si-O-Si-bond, thus obtaining a additiveThe wave absorber has good working performance and impedance matching performance. The wave absorber has good combination property with the rubber elastic matrix, and can obtain a ternary interface non-uniform composite material, thereby preparing a low-frequency rubber wave absorbing product with excellent service performance and having good low-frequency application prospect.
In some embodiments of the present invention, the hydroxylation treatment in the step S1 includes activating the nano silica with a mixed solution of concentrated sulfuric acid and hydrogen peroxide, where the mass ratio of the concentrated sulfuric acid to the hydrogen peroxide is 70:30, the reaction temperature is 70-80 ℃, and the reaction time is 0.5-2h.
In some embodiments of the present invention, the particle size of the nano silica in the step S1 is 2nm-100nm, wherein the nano silica is a graded combination of two different particle sizes, and the particle size ratio of the large particle size nano silica to the small particle size nano silica is not less than 5.
In some embodiments of the invention, the large particle size nanosilica has a particle size of 50-100nm and the small particle size nanosilica has a particle size of 2-20nm.
In some embodiments of the invention, the mass ratio of the large particle size nanosilica to the small particle size nanosilica is 2:1.
In some embodiments of the invention, the carbonyl iron powder: nano silicon dioxide: agate: absolute ethanol 100g: (2-5) g: (1000-2000) g (1-2.2) L.
In some embodiments of the present invention, 1-3g of an ester compound may be further added in the step S2.
In some embodiments of the present invention, the ball milling speed in the step S3 is 250-450 r/min, and the ball milling time is 24-48 h.
The invention also discloses a wave absorber obtained by the preparation method and application of the wave absorber in wave absorbing materials.
The invention also discloses a preparation method of the low-frequency flexible rubber wave-absorbing material, which comprises the steps that a. The nitrile rubber, the wave-absorbing agent, the vulcanizing agent sulfur, the accelerator M, the active agent zinc oxide and the plasticizer stearic acid are weighed according to a preset proportion, wherein the proportion by mass part phr is 100:700:3:1:5:2; b. mixing the raw materials on an open type double-roller open mill, packaging with a triangle, passing through the mill for several times, uniformly mixing, and cooling the lower piece to obtain a sizing material; c. and (3) placing the rubber material at normal temperature for more than 24 hours, and then curing and forming to obtain the rubber wave-absorbing material. The wave absorber has good combination property with the rubber elastic matrix, and can obtain a ternary interface non-uniform composite material, thereby preparing a low-frequency rubber wave absorbing product with excellent service performance and having good low-frequency application prospect.
In some embodiments of the invention, the temperature of the curing and molding of the sizing material is 140-150 ℃, the curing pressure is 14-16MPa, and the curing time is 10-12min.
The carbonyl iron powder is flaked by ball milling through a mechanochemical method, and a stronger anisotropic field can be obtained, so that the magnetic permeability is improved, and the absorption and attenuation of the carbonyl iron powder to electromagnetic waves are improved. The carbonyl iron powder after ball milling is in a flat stacking structure, and gaps among the arrangement of the flaky particles can influence the continuity of a conductive network. On the one hand, the invention uses SiO with different particle diameters 2 Grading to form SiO with large particle size surrounded by small particle size and long chain distribution 2 The particle micro-filler network has enough paths to reduce the relaxation time, thereby reducing the dielectric constant and improving the impedance matching performance of electromagnetic wave and material interface. On the other hand, during the ball milling process, a large number of defects are generated at the edges of the flaky particles to form vacancies and dislocation, and free hydroxyl generated by the absolute ethyl alcohol can fill the vacancies to form SiO with abundant hydroxyl on the surface 2 The reaction generates firm-Si-O-Si-bond, siO 2 The three-element interface non-uniformity composite material is formed by the wave-absorbing material which is stably adhered to the surface and/or the edge of the flaked carbonyl iron powder and is adhered to the rubber matrix, and can cause various reflection and propagation paths to enhance the interface loss and scattering loss of electromagnetic wave incidence.
[ description of the drawings ]
FIG. 1 is a scanning electron microscope image of a mixture of nano silica with different particle sizes and carbonyl iron powder before ball milling treatment in example 1 of the invention;
FIG. 2 is a scanning electron microscope image of the wave-absorbing agent obtained in example 1 of the present invention.
[ detailed description ] of the invention
The present invention will be described in further detail with reference to the following examples in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Preparation of wave-absorbing agent
S1, carrying out hydroxylation treatment on two kinds of nano silicon dioxide with different particle sizes, wherein the particle size of the large-particle-size nano silicon dioxide is 50-100nm, the particle size of the small-particle-size nano silicon dioxide is 2-20nm, the particle size ratio of the large-particle-size nano silicon dioxide to the small-particle-size nano silicon dioxide is 5, and the mass ratio of the large-particle-size nano silicon dioxide to the small-particle-size nano silicon dioxide is 2:1; s2: weighing hydroxylated nano silicon dioxide, carbonyl iron powder, agate beads and absolute ethyl alcohol according to a preset proportion, and putting the hydroxylated nano silicon dioxide, carbonyl iron powder, agate beads and absolute ethyl alcohol into a ball milling tank, wherein the carbonyl iron powder is prepared by the following steps: nano silicon dioxide: agate: absolute ethanol 100g: (2-5) g: (1000-2000) g (1.0-2.2) L; s3: the ball milling rotating speed is 250-450 r/min, the ball milling time is 24-48 h, the wave absorbing agent of which the silicon dioxide is coated on the edge and/or the surface of the sheet carbonyl iron powder is obtained after drying, and the interface of the nano silicon dioxide and the carbonyl iron powder is connected through chemical reaction to generate-Si-O-Si-bond.
In other embodiments of the present invention, substances such as glycerol methacrylate, acrylic ester, methyl acetate and the like may be added in the step S2, and the mechanochemical effect generated in the ball milling process may induce chemical reaction with silica, and under the action of mechanical force, si—o bonds of silica particles are broken to generate free radicals, and ester bonds are broken to react with free radical-OH, so that the silica surface has chemically active organic groups, which may further increase the interfacial binding force between nano silica and carbonyl iron powder, and enhance the compatibility between functional nano silica and organic rubber matrix.
In other embodiments of the present invention, the particle size of the nano silica is 2nm-100nm, and the nano silica can be graded by 3 or more than 3 different particle sizes, wherein the particle size ratio of any large particle size nano silica to small particle size nano silica is not less than 5, which is favorable for further improving the coating of the nano silica on carbonyl iron powder and adjusting the impedance matching characteristic of the carbonyl iron powder.
In other embodiments of the present invention, the hydroxylation treatment in step S1 includes activating the nano silica with a mixed solution of concentrated sulfuric acid and hydrogen peroxide, where the mass ratio of the concentrated sulfuric acid to the hydrogen peroxide is 70:30, the reaction temperature is 70-80 ℃, and the reaction time is 0.5-2h. The process can further increase the hydroxyl content of the hydroxylated nano silicon dioxide and activate the hydroxyl on the surface of the silicon dioxide.
In order to further verify the wave absorbing performance and the processing performance of the wave absorbing agent, the wave absorbing material is prepared by blending the wave absorbing agent and rubber, and the wave absorbing performance is evaluated and tested.
Example 1
Preparation of the wave absorber: s1, carrying out hydroxylation treatment on two kinds of nano silicon dioxide with different particle sizes, wherein the particle size of the large-particle-size nano silicon dioxide is 50-100nm, the particle size of the small-particle-size nano silicon dioxide is 2-20nm, the particle size ratio of the large-particle-size nano silicon dioxide to the small-particle-size nano silicon dioxide is 5, and the mass ratio of the large-particle-size nano silicon dioxide to the small-particle-size nano silicon dioxide is 2:1; s2: adding hydroxylated nano silicon dioxide, carbonyl iron powder, agate beads and absolute ethyl alcohol into a ball milling tank according to a preset proportion, wherein the carbonyl iron powder is spherical particles with the particle size of 3-10 mu m, and the carbonyl iron powder is prepared by the steps of: nano silicon dioxide: agate: absolute ethanol 100g:2g:1000 g/1L; s3: the ball milling rotating speed is 250r/min, and the ball milling time is 24h.
Preparation of a wave-absorbing rubber material: a. weighing nitrile rubber, a wave absorber, sulfur as a vulcanizing agent, an accelerator M, zinc oxide as an active agent and stearic acid as a plasticizer according to a preset proportion, wherein the proportion by mass phr is 100:700:3:1:3:2; b. mixing the raw materials on an open type double-roller open mill, packaging with a triangle, passing through the mill for several times, uniformly mixing, and cooling the lower piece to obtain a sizing material; c. placing the rubber material for more than 24 hours at normal temperature, filling the rubber material into a forming die with the length and width of 300 x 300mm and the thickness of 2.0mm, curing at 140-150 ℃, under the curing pressure of 14-16MPa for 10-12 minutes, and curing and forming to obtain the rubber wave-absorbing material.
Referring to fig. 1 and 2, it can be seen from fig. 1 that nano silica and carbonyl iron powder particles in spherical form are transformed into a lamellar microstructure shown in fig. 2 after being subjected to the mechanochemical process according to the present invention, and lamellar edges show a distinct interfacial polarization structural state. At the mark of fig. 2, a micro-filler structure is formed in which large-size particles are surrounded by small-size particles, siO2 particles mainly distributed in a long chain form exist, nano-like substances with rough adhesion exist on the surface of the flaky carbonyl iron powder and the surface connection of the flaky carbonyl iron powder, and a void structure in which the nano-substances exist alone does not exist, which indicates that the micro-filler structure in which the interface of nano-silica and carbonyl iron powder is tightly connected through chemical reaction is formed.
Example 2
Preparation of the wave absorber: s1, carrying out hydroxylation treatment on two kinds of nano silicon dioxide with different particle sizes, wherein the particle size of the large-particle-size nano silicon dioxide is 50-100nm, the particle size of the small-particle-size nano silicon dioxide is 2-10nm, the particle size ratio of the large-particle-size nano silicon dioxide to the small-particle-size nano silicon dioxide is 8, and the mass ratio of the large-particle-size nano silicon dioxide to the small-particle-size nano silicon dioxide is 2:1; s2: adding hydroxylated nano silicon dioxide, carbonyl iron powder, agate beads and absolute ethyl alcohol into a ball milling tank according to a preset proportion, wherein the carbonyl iron powder is spherical particles with the particle size of 3-10 mu m, and the carbonyl iron powder is prepared by the steps of: nano silicon dioxide: agate: absolute ethanol 100g:3g:1500 g/2L; s3: the ball milling rotating speed is 300r/min, and the ball milling time is 30h.
Preparation of the wave-absorbing material: a. weighing nitrile rubber, a wave absorber, sulfur as a vulcanizing agent, an accelerator M, zinc oxide as an active agent and stearic acid as a plasticizer according to a preset proportion, wherein the proportion by mass phr is 100:700:3:1:3:2; b. mixing the raw materials on an open type double-roller open mill, packaging with a triangle, passing through the mill for several times, uniformly mixing, and cooling the lower piece to obtain a sizing material; c. placing the rubber material for more than 24 hours at normal temperature, filling the rubber material into a forming die with the length and width of 300 x 300mm and the thickness of 2.0mm, curing at 140-150 ℃, under the curing pressure of 14-16MPa for 10-12 minutes, and curing and forming to obtain the rubber wave-absorbing material.
Example 3
Preparation of the wave absorber: s1: the method comprises the steps of carrying out hydroxylation treatment on two kinds of nano silicon dioxide with different particle sizes, wherein the particle size of the large-particle-size nano silicon dioxide is 50-100nm, the particle size of the small-particle-size nano silicon dioxide is 2-10nm, the particle size ratio of the large-particle-size nano silicon dioxide to the small-particle-size nano silicon dioxide is 8, and the mass ratio of the large-particle-size nano silicon dioxide to the small-particle-size nano silicon dioxide is 2:1; s2: adding hydroxylated nano silicon dioxide, carbonyl iron powder, agate beads and absolute ethyl alcohol into a ball milling tank according to a preset proportion, wherein the carbonyl iron powder is spherical particles with the particle size of 3-10 mu m, and the carbonyl iron powder is prepared by the steps of: nano silicon dioxide: glycerol methacrylate: agate: absolute ethanol 100g:3g:1.5g:1500 g/2L; s3: the ball milling rotating speed is 400r/min, and the ball milling time is 48h.
Preparation of the wave-absorbing material: a. weighing nitrile rubber, a wave absorber, sulfur as a vulcanizing agent, an accelerator M, zinc oxide as an active agent and stearic acid as a plasticizer according to a preset proportion, wherein the proportion by mass phr is 100:700:3:1:4:3; b. mixing the raw materials on an open type double-roller open mill, packaging with a triangle, passing through the mill for several times, uniformly mixing, and cooling the lower piece to obtain a sizing material; c. placing the rubber material at normal temperature for more than 24 hours, filling the rubber material into a forming die with the length and width of 300mm and the thickness of 2.0mm, curing at 140-150 ℃ and under 14-16MPa for 10-12min, and curing to obtain the rubber wave-absorbing material
Comparative example 4
Preparation of the wave absorber: s1, carrying out hydroxylation treatment on two kinds of nano silicon dioxide with different particle sizes, wherein the particle size of the large-particle-size nano silicon dioxide is 50-100nm, the particle size of the small-particle-size nano silicon dioxide is 2-20nm, the particle size ratio of the large-particle-size nano silicon dioxide to the small-particle-size nano silicon dioxide is 5, and the mass ratio of the large-particle-size nano silicon dioxide to the small-particle-size nano silicon dioxide is 2:1; s2: adding carbonyl iron powder, agate beads and absolute ethyl alcohol into a ball milling tank according to a preset proportion, wherein the carbonyl iron powder is spherical particles with the particle size of 3-10 mu m, and the carbonyl iron powder is prepared by the steps of: agate: absolute ethanol 100g:2g:1000 g/1L; s3: ball milling rotation speed is 250r/min, ball milling time is 24h, and carbonyl iron powder is subjected to flaking ball milling treatment; s4: and physically blending the dried carbonyl iron powder and graded silicon dioxide by a mixing stirrer to prepare the wave absorber.
Preparation of the wave-absorbing material: a. weighing nitrile rubber, a wave absorber, sulfur as a vulcanizing agent, an accelerator M, zinc oxide as an active agent and stearic acid as a plasticizer according to a preset proportion, wherein the proportion by mass phr is 100:700:3:1:3:2; b. mixing the raw materials on an open type double-roller open mill, packaging with a triangle, passing through the mill for several times, uniformly mixing, and cooling the lower piece to obtain a sizing material; c. placing the rubber material for more than 24 hours at normal temperature, filling the rubber material into a forming die with the length and width of 300 x 300mm and the thickness of 2.0mm, curing at 140-150 ℃, under the curing pressure of 14-16MPa for 10-12 minutes, and curing and forming to obtain the rubber wave-absorbing material.
Comparative example 5
Preparation of the wave absorber: s1: the method comprises the step of adding nano silicon dioxide with the same particle size for hydroxylation treatment, wherein the particle size range of the nano silicon dioxide is 80-100nm. S2: adding hydroxylated nano silicon dioxide, carbonyl iron powder, agate beads and absolute ethyl alcohol into a ball milling tank according to a preset proportion, wherein the carbonyl iron powder is spherical particles with the particle size of 3-10 mu m, and the carbonyl iron powder is prepared by the steps of: nano silicon dioxide: agate: absolute ethanol 100g:4g:1000g:1.5L; s3: the ball milling rotating speed is 250r/min, and the ball milling time is 36h.
Preparation of the wave-absorbing material: a. weighing nitrile rubber, a wave absorber, sulfur as a vulcanizing agent, an accelerator M, zinc oxide as an active agent and stearic acid as a plasticizer according to a preset proportion, wherein the proportion by mass phr is 100:700:3:1:3:2; b. mixing the raw materials on an open type double-roller open mill, packaging with a triangle, passing through the mill for several times, uniformly mixing, and cooling the lower piece to obtain a sizing material; c. placing the rubber material for more than 24 hours at normal temperature, filling the rubber material into a forming die with the length and width of 300 x 300mm and the thickness of 2.0mm, curing at 140-150 ℃, under the curing pressure of 14-16MPa for 10-12 minutes, and curing and forming to obtain the rubber wave-absorbing material.
Comparative example 6
Preparation of the wave absorber: s1: according to the scheme, nano silicon dioxide is not added, and the wave absorber is prepared by purely mechanically ball milling carbonyl iron powder. S2: adding carbonyl iron powder, agate beads and absolute ethyl alcohol into a ball milling tank according to a preset proportion, wherein the carbonyl iron powder is spherical particles with the particle size of 3-10 mu m, and the carbonyl iron powder is prepared by the steps of: agate: absolute ethanol 100g:1000 g/2L; s3: the ball milling rotating speed is 300r/min, and the ball milling time is 36h.
Preparation of the wave-absorbing material: a. weighing nitrile rubber, a wave absorber, sulfur as a vulcanizing agent, an accelerator M, zinc oxide as an active agent and stearic acid as a plasticizer according to a preset proportion, wherein the proportion by mass phr is 100:700:3:1:3:2; b. mixing the raw materials on an open type double-roller open mill, packaging with a triangle, passing through the mill for several times, uniformly mixing, and cooling the lower piece to obtain a sizing material; c. placing the rubber material for more than 24 hours at normal temperature, filling the rubber material into a forming die with the length and width of 300 x 300mm and the thickness of 2.0mm, curing at 140-150 ℃, under the curing pressure of 14-16MPa for 10-12 minutes, and curing and forming to obtain the rubber wave-absorbing material.
The wave absorbers prepared in the cases 1 to 6 and paraffin wax are heated in a high-temperature furnace at 50-60 ℃ according to the mass ratio of 80:20, then are quickly taken out, mixed and stirred uniformly to prepare viscous solids, the viscous solids are filled into a coaxial circular mold (the outer diameter of the mold is 7mm, the inner diameter of the mold is 3.04 mm), samples with the thickness of 1-2mm are prepared respectively, and then the complex dielectric constant and the complex magnetic conductivity are measured respectively by a network vector analyzer.
The wave-absorbing materials prepared by mixing the wave-absorbing agents prepared in cases 1 to 6 with the nitrile rubber material respectively were tested for reflectivity and mechanical properties according to GJB2038A-2011 and GBT528-2009, and the results are shown in table 1.
Table 1 results of reflectance and mechanical properties testing of the wave-absorbing materials in different examples
In the above embodiments, the present invention has been described by way of example only, but various modifications of the invention can be made by those skilled in the art after reading the present patent application without departing from the spirit and scope of the invention.
Claims (9)
1. The preparation method of the wave absorber is characterized by comprising the following steps:
s1: carrying out hydroxylation treatment on various nano silicon dioxide with different particle sizes, wherein the particle size ratio of the large-particle-size nano silicon dioxide to the small-particle-size nano silicon dioxide is more than or equal to 5;
s2: weighing hydroxylated nano silicon dioxide, carbonyl iron powder, agate beads and absolute ethyl alcohol according to a preset proportion, and putting the hydroxylated nano silicon dioxide, carbonyl iron powder, agate beads and absolute ethyl alcohol into a ball milling tank;
s3: the mixture is subjected to mechanochemical ball milling and drying to obtain silicon dioxide gradations with different particle diameters, large-particle-diameter particles are surrounded by small-particle-diameter particles, a wave absorber of a SiO2 particle micro-filler network mainly distributed in a long chain shape is formed, and the interface of nano silicon dioxide and carbonyl iron powder is connected through chemical reaction to generate-Si-O-Si-bonds;
wherein the particle size of the nano silicon dioxide in the step S1 is 2nm-100nm, and the carbonyl iron powder in the step S2: nano silicon dioxide: agate beads: absolute ethanol 100g: (2-5) g: (1000-2000) g (1-2.2) L.
2. The preparation method of claim 1, wherein the hydroxylation treatment process in the step S1 comprises the step of activating the nano silicon dioxide by using a mixed solution of concentrated sulfuric acid and hydrogen peroxide, wherein the mass ratio of the concentrated sulfuric acid to the hydrogen peroxide is 70:30, the reaction temperature is 70-80 ℃, and the reaction time is 0.5-2h.
3. The method according to claim 1, wherein the nano silica in the step S1 is a graded combination of two different particle sizes, and the ratio of the large particle size nano silica to the small particle size nano silica is 5-10.
4. The method according to claim 3, wherein the large-particle-diameter nano-silica has a particle diameter of 50 to 100nm and the small-particle-diameter nano-silica has a particle diameter of 2 to 20nm.
5. The method of claim 3, wherein the mass ratio of the large particle size nano silica to the small particle size nano silica is 2:1.
6. The preparation method according to claim 5, wherein 1-3g of ester compound is further added in the step S2.
7. A wave absorber obtained by the production method according to any one of claims 1 to 6.
8. The preparation method of the low-frequency flexible rubber wave-absorbing material is characterized by comprising the following steps of a, weighing nitrile rubber, wave-absorbing agent, vulcanizing agent, accelerator, active agent and plasticizer according to a preset proportion, wherein the proportion by mass portion phr is 100:700:3-4:1-2:3-5:2-4, wherein the wave absorber is a wave absorber obtained by the preparation method of any one of claims 1-6;
b. mixing the raw materials on an open type double-roller open mill, packaging with a triangle, passing through the mill for several times, mixing for 20-30 min, and cooling the lower piece to obtain sizing material;
c. and (3) placing the rubber material at normal temperature for more than 24 hours, and then curing and forming to obtain the rubber wave-absorbing material.
9. The method of claim 8, wherein the curing and molding temperature of the sizing material is 140-150 ℃, the curing pressure is 14-16MPa, and the curing time is 10-12min.
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