Radar and infrared compatible stealth filler, PEEK composite material, preparation method and application

Abstract

The invention belongs to the technical field of functional materials, and particularly relates to radar and infrared compatible stealth filler, a PEEK composite material, a preparation method and application. The filler comprises a core structure and MoSe2 nanoflowers coated on the surface of the core structure, the core structure is a cobalt-nitrogen doped carbon coated multi-walled carbon nanotube, and is obtained by pyrolyzing a dimethyl imidazole cobalt coated multi-walled carbon nanotube. Magnetic metal cobalt is introduced, a generated magnetic-electric synergistic loss mechanism is beneficial to optimization of impedance matching parameters, the radar stealth performance of the filler is improved, then a low-infrared-emissivity material MoSe2 nanoflower is uniformly grown through a one-step solvothermal method, the filler has the infrared stealth performance, a semiconductor material MoSe2 further has certain radar stealth performance, and the infrared stealth performance of the filler is improved. The nanometer flower-shaped structure is beneficial to multiple times of reflection and scattering of incident electromagnetic waves, and the radar and infrared compatible stealth function is achieved through accurate composition regulation and structural design.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials, and particularly relates to a filler for radar and infrared compatible stealth, a PEEK composite material, a preparation method and an application thereof. Background Art

[0002] With the rapid development of information technology, modern military reconnaissance systems have formed a multi-band, multi-dimensional, all-weather three-dimensional detection network. Among them, radar detection is still the cornerstone technology of military detection (accounting for about 60% - 80%), while the proportion of infrared detection is continuously increasing (accounting for 20% - 40%). In modern warfare, the stealth ability of military equipment is one of the core technologies to improve its survival probability, penetration ability and combat effectiveness. With the rapid development of detection technology, it is currently difficult for single-band (such as radar or infrared) stealth materials to effectively avoid multi-compound detection. Therefore, developing multi-spectral compatible (such as radar-infrared compatible) stealth materials is particularly important for enhancing the concealment, surprise attack and sustained combat capabilities of weapons and equipment in complex battlefield environments. However, the preparation of radar-infrared compatible stealth materials faces great difficulties because there are inherent contradictions between the two stealth mechanisms. Radar stealth materials require high absorption rate and low reflectivity, while infrared stealth materials require high reflectivity and low absorption rate. At the same time, radar stealth materials will convert electromagnetic waves into heat for attenuation, which will also cause the surface temperature of military equipment to rise, which is very unfavorable for infrared stealth. Therefore, solving the inherent contradiction between these two mechanisms is the key to achieving radar-infrared compatible stealth. Due to the conflict in the design principles of traditional single-band stealth materials, previous studies have basically achieved the purpose of multi-band compatible stealth through the repeated superposition of different functional coatings, which has led to an increase in the weight of military facilities and the complexity of the structure. At the same time, the multi-layer coating is vulnerable to environmental erosion or mechanical stress delamination and fails. This greatly increases the later maintenance cost of military facilities. Therefore, it is very necessary to develop a multi-band compatible stealth material with integrated structural functions through component and structure design, thereby reducing the load of weapons and equipment, improving its durability and reducing the later maintenance requirements.

[0003] Polyetheretherketone (PEEK) is a semi-crystalline special engineering plastic, which is widely used in the military field due to its excellent physical and chemical properties, such as the production of fighter fairings, fuselages, and unmanned aerial vehicles. These components, as the key sources of radar scattering and infrared radiation in military weapons, play a crucial role in achieving the radar and infrared compatible stealth capabilities of weaponry. At the same time, to reduce the later maintenance costs and extend the service life, the development of a structural-functional integrated polyetheretherketone (PEEK) composite material with both infrared and radar compatible stealth capabilities has become a key technical direction for coping with modern multi-spectrum detection threats and promoting the lightweight and intelligent development of advanced equipment. It should be noted that the microwave absorption performance of PEEK is extremely low. Therefore, it is usually necessary to compound advanced stealth materials with the PEEK matrix, combine structural design and composition optimization to achieve effective absorption of electromagnetic waves and efficient regulation of thermal radiation characteristics, break through the limitations of single function, vulnerable coating, and redundant weight in traditional stealth technologies, and achieve the purpose of compatible stealth. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a filler, a PEEK composite material, a preparation method, and an application for radar and infrared compatible stealth. The stealth material prepared using the filler of the present invention has the function of radar and infrared compatible stealth.

[0005] The present invention provides a filler for radar and infrared compatible stealth, including a core structure, and MoSe2 nanoflowers coated on the surface of the core structure;

[0006] The core structure is multi-walled carbon nanotubes coated with cobalt-nitrogen doped carbon, and the cobalt-nitrogen doped carbon has a metal-organic framework structure.

[0007] Preferably, the mass ratio of the core structure to the MoSe2 nanoflowers is 1:1.4 to 1:4.3.

[0008] The present invention also provides a preparation method for the filler for radar and infrared compatible stealth described in the above technical solution, including the following steps:

[0009] Perform the first pyrolysis on the multi-walled carbon nanotubes coated with cobalt dimethylimidazole in an inert atmosphere to obtain multi-walled carbon nanotubes coated with cobalt-nitrogen doped carbon;

[0010] Mix the multi-walled carbon nanotubes coated with cobalt-nitrogen doped carbon, a molybdenum source, a selenium source, a reducing agent, water, and a polar organic solvent for a solvothermal reaction, and perform the second pyrolysis on the obtained solid in an inert atmosphere to obtain the filler for radar and infrared compatible stealth.

[0011] Preferably, the mass ratio of the multi-walled carbon nanotubes to the cobalt dimethylimidazole in the multi-walled carbon nanotubes coated with cobalt dimethylimidazole is 1:3.9 to 1:15.9.

[0012] Preferably, the temperature of the first pyrolysis is 600 - 800 °C and the time is 2 - 4 h.

[0013] Preferably, the molar ratio of Mo in the molybdenum source to the mass of the cobalt - nitrogen - doped carbon - coated multi - walled carbon nanotubes is (0.5 - 1) mmol:(30 - 90) mg; the temperature of the solvothermal reaction is 200 - 240 °C and the time is 12 - 48 h.

[0014] The present invention also provides a PEEK composite material with radar - and - infrared compatible stealth performance, which comprises polyether ether ketone and fillers dispersed in the polyether ether ketone. The fillers are the radar - and - infrared compatible stealth fillers described in the above technical solution or the radar - and - infrared compatible stealth fillers obtained by the above preparation method.

[0015] Preferably, the mass ratio of the fillers to the polyether ether ketone is 1:1 - 1:10.

[0016] The present invention also provides a preparation method of the PEEK composite material with radar - and - infrared compatible stealth performance described in the above technical solution, which comprises the following steps:

[0017] Wet - mix the polyether ether ketone and the fillers and then carry out compression molding to obtain the composite material with radar - and - infrared compatible stealth performance.

[0018] The present invention also provides the application of the radar - and - infrared compatible stealth fillers or the PEEK composite materials with radar - and - infrared compatible stealth performance described in the above technical solution in the field of multi - functional compatible stealth or camouflage.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention provides a radar - and - infrared compatible stealth filler, which comprises a core structure and MoSe2 nanoflowers coated on the surface of the core structure; the core structure is cobalt - nitrogen - doped carbon - coated multi - walled carbon nanotubes, and the cobalt - nitrogen - doped carbon has a metal - organic framework structure.

[0021] The cobalt-nitrogen doped carbon material generated by the pyrolysis of cobalt dimethyl imidazolium (ZIF-67) in multi-walled carbon nanotubes coated with cobalt dimethyl imidazolium contains magnetic metal cobalt, which is beneficial to improve the magnetic permeability of the filler and enhance the magnetic loss performance of electromagnetic waves; the highly conductive multi-walled carbon nanotubes (MWCNTs) and molybdenum diselenide (MoSe2) with semiconductor properties can promote the dielectric loss of the filler to electromagnetic waves. The MoSe2 nanoflowers coated on the surface of the core structure construct a multi-layer heterogeneous structure, which contains multiple heterogeneous interfaces. At the same time, the polar functional groups with different charges on the surface of MWCNTs and the large number of defects generated during the pyrolysis process further enhance the interface polarization and dipole polarization loss of the filler. When the electromagnetic wave is incident on the surface of the stealth material including the filler, the special flower-like morphology of the MoSe2 nanoflowers and the three-dimensional network formed by the overlap of multi-walled carbon nanotubes help the electromagnetic wave to be reflected and scattered multiple times, extend the propagation path, dissipate the electromagnetic wave, and improve the microwave absorption performance. The present invention coats MoSe2 nanoflowers on the surface of cobalt-nitrogen doped carbon coated multi-walled carbon nanotubes, which on the one hand optimizes impedance matching parameters and improves the radar stealth performance of the filler, and on the other hand enables the filler to have infrared stealth performance, thereby achieving the function of radar and infrared compatible stealth.

[0022] The present invention also provides a radar and infrared compatible stealth PEEK composite material, which has excellent radar stealth performance, electromagnetic wave absorption performance and infrared stealth performance, and the preparation method is simple, the product morphology is easy to control, and has broad application prospects in radar stealth technology, microwave absorption and electromagnetic shielding, infrared camouflage, etc. The multifunctional and compatible stealth of polyetheretherketone composite materials helps to comprehensively enhance the "integrated detection and strike" armed capabilities of military weapons, improve the survivability and air defense capabilities of weapon systems, effectively improve the combat performance and electronic warfare capabilities of weapons and equipment, and extend their service life.

[0023] The data of the embodiment show that the MWCNTs@Co-NC@MoSe2 multilayer heterogeneous structure filler prepared by the present invention can achieve excellent stealth performance when the filling amount is 33wt%. When the matching thickness of the composite material is 2.1mm, the minimum reflection loss is -50.00dB; when the matching thickness is 2.0mm, the maximum effective absorption bandwidth is 6.84GHz. The radar stealth performance simulation is carried out using CST software. The results show that when the theta angle is 0 degrees, the radar scattering cross section reduction value can reach 18.5dB·m 2 , indicating that the composite material has excellent radar stealth performance. The possibility of composite materials as infrared stealth materials was verified by using infrared thermal imaging equipment, and the results showed that the composite material also has excellent infrared stealth performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 It is the preparation flow chart of the MWCNTs@Co-NC@MoSe2 / PEEK composite material in Example 1;

[0026] Figure 2 It is the XRD pictures of MWCNTs, ZIF-67, Co-NC, MWCNTs@ZIF-67, MWCNTs@Co-NC, MoSe2 nanoflowers, and MWCNTs@Co-NC@MoSe2;

[0027] Figure 3 It is the SEM pictures of ZIF-67 (a1~a2), Co-NC (b1~b2), MWCNTs@ZIF-67 (c1~c2), MWCNTs@Co-NC (d1~d2), MoSe2 nanoflowers (e1~e2), and MWCNTs@Co-NC@MoSe2 (f1~f2);

[0028] Figure 4 It is the EDS spectrum of MWCNTs@Co-NC@MoSe2;

[0029] Figures 5 to 7 They are the radar wave absorption performance diagrams of the MWCNTs@Co-NC@MoSe2 / PEEK composite materials prepared in Examples 1 to 3 respectively, where Figure 5 is Example 1, Figure 6 is Example 2, Figure 7 is Example 3;

[0030] Figure 8 It is the radar stealth performance diagram of the MWCNTs@Co-NC@MoSe2 / PEEK composite material prepared in Example 1;

[0031] Figure 9 It is the infrared thermal imaging diagram of the MWCNTs@Co-NC@MoSe2 / PEEK composite material prepared in Example 1 under different heating times. Detailed implementation manners

[0032] The present invention provides a filler for radar and infrared compatible stealth, including a core structure and MoSe2 nanoflowers coated on the surface of the core structure;

[0033] The nuclear structure is multi-walled carbon nanotubes coated with cobalt-nitrogen-doped carbon; the cobalt-nitrogen-doped carbon has a metal-organic framework structure.

[0034] In the present invention, the mass ratio of the cobalt-nitrogen-doped carbon-coated multi-walled carbon nanotubes (MWCNTs@Co-NC) to the MoSe2 nanoflowers is preferably 1:1.4 to 1:4.3, and specifically can be 1:1.41, 1:2.12 or 1:4.23.

[0035] In the present invention, the cobalt-nitrogen-doped carbon-coated multi-walled carbon nanotubes are preferably obtained by pyrolyzing multi-walled carbon nanotubes coated with cobalt dimethylimidazole.

[0036] The radar and infrared compatible stealth filler provided by the present invention is a nano-filler with a three-dimensional scabbard structure, having good dispersibility, uniform morphology and particle size, and no obvious agglomeration phenomenon. It has a unique microscopic morphology, excellent polarization ability and electromagnetic loss ability, can maintain suitable dielectric constant and magnetic permeability in a wide frequency range, has good impedance matching characteristics and very excellent electromagnetic wave absorption performance. After mixing the filler with the matrix material (PEEK), due to the presence of multi-walled carbon nanotubes, the scattered MWCNTs will overlap with each other to form a three-dimensional network structure.

[0037] The present invention also provides a preparation method of the radar and infrared compatible stealth filler described in the above technical solution, including the following steps:

[0038] Pyrolyzing the multi-walled carbon nanotubes coated with cobalt dimethylimidazole in an inert atmosphere to obtain cobalt-nitrogen-doped carbon-coated multi-walled carbon nanotubes;

[0039] Mixing the cobalt-nitrogen-doped carbon-coated multi-walled carbon nanotubes, molybdenum source, selenium source, reducing agent, water and polar organic solvent for a solvothermal reaction, and pyrolyzing the obtained solid in an inert atmosphere to obtain the radar and infrared compatible stealth filler.

[0040] In the present invention, unless otherwise specified, the materials and equipment used are all commercially available products in the art.

[0041] The present invention pyrolyzes the multi-walled carbon nanotubes coated with cobalt dimethylimidazole to obtain cobalt-nitrogen-doped carbon-coated multi-walled carbon nanotubes.

[0042] In the present invention, the preparation method of the multi-walled carbon nanotubes coated with cobalt dimethylimidazole preferably includes the following steps:

[0043] Mixing multi-walled carbon nanotubes, cobalt source, organic ligand and alcohol organic solvent, and carrying out room temperature aging to obtain multi-walled carbon nanotubes coated with cobalt dimethylimidazole (MWCNTs@ZIF-67).

[0044] In the present invention, the diameter of the multi-walled carbon nanotubes (MWCNTs) is preferably 100 - 300 nm, and the length is preferably 5 - 20 μm. The multi-walled carbon nanotubes used in the specific embodiments of the present invention are purchased from Showa Corporation of Japan. The multi-walled carbon nanotubes of the present invention have a large self-conductivity and good conductance loss performance.

[0045] In the present invention, the cobalt source preferably includes one or more of cobalt acetate tetrahydrate, cobalt nitrate hexahydrate, cobalt chloride hexahydrate, and cobalt sulfate hexahydrate, and more preferably cobalt nitrate hexahydrate.

[0046] In the present invention, the organic ligand is preferably 2-methylimidazole. The molar ratio of the cobalt source to the organic ligand is preferably 1:4 - 1:8, more preferably 1:4 - 1:6, and still more preferably 1:4.

[0047] In the present invention, the alcoholic organic solvent is preferably methanol.

[0048] In the present invention, the molar ratio of the cobalt source to the volume of the alcoholic organic solvent is preferably (3.44 - 13.74) mmol:50 mL, more preferably (3.44 - 6.88) mmol:50 mL, and still more preferably 3.44 mmol:50 mL.

[0049] In the present invention, the molar ratio of the organic ligand to the volume of the alcoholic organic solvent is preferably (13.75 - 54.98) mmol:50 mL, more preferably (13.75 - 27.52) mmol:50 mL, and still more preferably 13.75 mmol:50 mL.

[0050] In the present invention, the mixing of the multi-walled carbon nanotubes, cobalt source, organic ligand, and alcoholic organic solvent is preferably as follows: the multi-walled carbon nanotubes, cobalt source, and a part of the alcoholic organic solvent are first mixed to obtain a first solution; the organic ligand and the remaining alcoholic organic solvent are second mixed to obtain a second solution; then the first solution and the second solution are mixed. The first mixing preferably includes ultrasonic treatment and magnetic stirring. The time of ultrasonic treatment is preferably 15 - 60 min, more preferably 15 - 45 min, and still more preferably 30 min. The power of ultrasonic treatment is preferably 500 W, and the frequency is preferably 20 kHz. The time of magnetic stirring is preferably 1 - 6 h, more preferably 2 - 4 h, and still more preferably 3 h. With the first mixing method and time of the present invention, MWCNTs and Co 2+ can interact with each other sufficiently.

[0051] In the present invention, the mixing is preferably carried out under stirring. The rotation speed of stirring is preferably 300 - 500 rpm, more preferably 400 - 500 rpm, and the time is preferably 1 - 2 h, more preferably 1.5 - 2 h.

[0052] In the present invention, the temperature for aging at room temperature is preferably 20 to 35 °C, the time is preferably 12 to 24 h, more preferably 18 to 24 h; after aging at room temperature, it preferably further includes: solid-liquid separation, washing and drying the obtained solid; the solid-liquid separation is preferably centrifugation; the washing reagent is preferably methanol, and the number of washing times is preferably 3 times; the drying is preferably vacuum drying, and the temperature of the vacuum drying is preferably 60 °C.

[0053] In the present invention, the mass ratio of multi-walled carbon nanotubes (MWCNTs) to cobalt dimethylimidazole (ZIF-67) in the cobalt dimethylimidazole-coated multi-walled carbon nanotubes is preferably 1:3.96 to 1:15.82, more preferably 1:3.96 to 1:7.91, still more preferably 1:3.96 to 1:5.27, and specifically can be 1:3.96, 1:5.27, 1:7.91 or 1:15.82. Due to the different ratios of multi-walled carbon nanotubes to the cobalt source, the dielectric loss ability (generated by multi-walled carbon nanotubes) and magnetic loss ability (generated by metallic cobalt) are different, and the impedance matching degree is also different. If the amount of multi-walled carbon nanotubes is too large and the proportion of metallic elements is small, the conductance loss of the material is too large at this time, the impedance is mismatched, and the skin effect is likely to occur on the surface of the material, causing a large amount of reflection of the incident electromagnetic wave and unable to effectively enter the interior of the material for loss.

[0054] In the present invention, the inert atmosphere preferably includes an argon atmosphere or a nitrogen atmosphere, and the first pyrolysis is preferably carried out in a tubular furnace.

[0055] In the present invention, the temperature of the first pyrolysis is preferably 600 to 800 °C, specifically can be 600 °C, 700 °C, 750 °C or 800 °C, the time is preferably 2 to 4 h, more preferably 2 to 3 h; the heating rate from room temperature to the temperature of the first pyrolysis is preferably 2 to 10 °C / min, more preferably 2 to 8 °C / min, still more preferably 2 to 5 °C / min. The main purpose of the first pyrolysis is to generate magnetic metallic cobalt with magnetic loss ability by pyrolyzing ZIF-67. The pyrolysis temperature and time described in the present invention have good reduction effect, and the magnetic loss performance of the obtained material is high, which is beneficial to realizing the stealth function.

[0056] Cobalt dimethylimidazole (ZIF-67) is a zeolitic imidazole-based metal organic framework material, a complex of metal salt and organic ligand, with a dodecahedral structure. Through pyrolysis, the cobalt salt can be reduced to a magnetic metal element, introducing magnetic loss, and basically maintaining the original dodecahedral structure. The pore structure of the pyrolysis product is also conducive to multiple reflections and scattering of electromagnetic waves after incidence. Cobalt-nitrogen doped carbon-coated multi-walled carbon nanotubes have both conductivity loss and magnetic loss. The heterogeneous interface formed during the pyrolysis process is conducive to the interfacial polarization loss of the material, and the defects introduced during the pyrolysis process and the functional groups on the surface of the material are conducive to the dipole polarization loss of the material.

[0057] After obtaining the cobalt-nitrogen doped carbon-coated multi-walled carbon nanotubes, the present invention mixes the cobalt-nitrogen doped carbon-coated multi-walled carbon nanotubes, a molybdenum source, a selenium source, a reducing agent, water and a polar organic solvent to carry out a solvothermal reaction, and performs a second pyrolysis on the obtained solid in an inert atmosphere to obtain a radar and infrared compatible stealth filler.

[0058] In the present invention, the molybdenum source preferably includes one or more of molybdenum acetylacetonate, sodium molybdate dihydrate, ammonium molybdate tetrahydrate and molybdenum trioxide, and more preferably molybdenum acetylacetonate.

[0059] In the present invention, the ratio of the amount of Mo in the molybdenum source to the mass of cobalt-nitrogen doped carbon-coated multi-walled carbon nanotubes is preferably (0.5-1) mmoL:(30-90) mg, more preferably (0.5-0.75) mmoL:(30-60) mg, specifically 0.5 mmoL:30 mg, 0.5 mmoL:60 mg or 0.5 mmoL:90 mg.

[0060] In the present invention, the selenium source is preferably Se powder.

[0061] In the present invention, the reducing agent preferably includes hydrazine hydrate or sodium borohydride, and the volume ratio of the amount of the selenium source to the reducing agent is preferably (1-2) mmoL:(4-8) mL, more preferably (1-1.5) mmoL:(4-6) mL, and even more preferably 1 mmoL:4 mL.

[0062] In the present invention, the polar organic solvent preferably includes N,N-dimethylformamide (DMF) or dimethyl sulfoxide (DMSO), and the ratio of the amount of the molybdenum source to the volume of the polar organic solvent is preferably (0.5-1) mmoL:(80-160) mL, more preferably (0.5-1) mmoL:(80-120) mL.

[0063] In the present invention, the water is preferably deionized water, and the volume ratio of the water to the polar organic solvent is preferably (20 - 40):80, more preferably (20 - 30):80. The addition of deionized water in the present invention can regulate the polarity of the solvent to affect the nucleation process, avoid excessive aggregation of particles, thereby optimizing the two-dimensional structure and properties of the material, and facilitating the progress of the reaction.

[0064] In the present invention, the mixing of the cobalt-nitrogen-doped carbon-coated multi-walled carbon nanotubes, molybdenum source, selenium source, reducing agent, water and polar organic solvent is preferably as follows: the selenium source and the reducing agent are mixed for the third time to carry out an oxidation-reduction reaction to obtain a third mixed solution; the molybdenum source, cobalt-nitrogen-doped carbon-coated multi-walled carbon nanotubes, polar organic solvent and water are mixed and dispersed to obtain a fourth mixed solution; the third mixed solution is added dropwise to the fourth mixed solution. The temperature of the oxidation-reduction reaction is preferably room temperature, and the time is preferably 24 h. The mixing and dispersion preferably include ultrasonic treatment and stirring. The time of the ultrasonic treatment is preferably 1 h, and the time of the stirring is preferably 3 h.

[0065] In the present invention, the solvothermal reaction is preferably carried out in a stainless steel autoclave.

[0066] In the present invention, the temperature of the solvothermal reaction is preferably 200 - 240 °C, more preferably 210 - 230 °C, still more preferably 220 °C, and the time is preferably 12 - 48 h, more preferably 12 - 36 h, still more preferably 24 h. During the solvothermal process, a layer of MoSe2 nanoflowers (shell) grows uniformly on the surface of the MWCNTs@Co-NC material acting as the core structure, thereby preparing the MWCNTs@Co-NC@MoSe2 filler with a three-dimensional scabbard structure. The prepared molybdenum diselenide nanoflower structure has the ability of dielectric loss and can be used for radar stealth. At the same time, its infrared emissivity is low and it can be used for infrared stealth.

[0067] In the present invention, after the solvothermal reaction, it preferably further includes: after the obtained reaction solution is cooled to room temperature, solid-liquid separation is carried out, and the obtained solid is washed and dried. The washing reagents include ethanol and deionized water, and the drying is preferably vacuum drying at 70 °C.

[0068] In the present invention, the inert atmosphere preferably includes an argon atmosphere or a nitrogen atmosphere, and the second pyrolysis is preferably carried out in a tube furnace.

[0069] In the present invention, the temperature of the second pyrolysis is preferably 600 °C, and the time is preferably 2 - 6 h, more preferably 3 - 5 h, and still more preferably 4 h. The function of the second pyrolysis is to improve the crystallinity of the material and remove the residual selenium powder. MoSe2 with high crystallinity is more likely to form a regular flower-like structure, which is beneficial to the multiple reflection and scattering of electromagnetic waves between layers, prolongs the propagation path, and enhances the attenuation of electromagnetic waves; moreover, the product after pyrolysis has higher purity. The pyrolysis process described in the present invention helps to exert the electromagnetic wave attenuation mechanism.

[0070] The present invention also provides a PEEK composite material with radar and infrared compatible stealth performance, which includes polyetheretherketone and fillers dispersed in the polyetheretherketone. The fillers are the radar and infrared compatible stealth fillers described in the above technical solution or the radar and infrared compatible stealth fillers obtained by the preparation method described in the above technical solution.

[0071] In the present invention, the mass ratio of the filler to the polyetheretherketone is preferably 1:1 - 1:10, more preferably 1:1.5 - 1:5, and still more preferably 1:2. Specifically, it can be 33:67, 35:65, 50:50, 40:60, 20:80 or 10:90. The mass ratio described in the present invention will neither hinder the realization of the stealth function due to insufficient filler addition, nor cause the skin effect due to excessive filler addition and too high carbon material content, resulting in the reflection of electromagnetic waves on the material surface, thereby affecting the stealth function.

[0072] The present invention also provides a preparation method for the PEEK composite material with radar and infrared compatible stealth performance described in the above technical solution, which includes the following steps:

[0073] Wet-mix the polyetheretherketone and the filler and then carry out compression molding to obtain a composite material with radar and infrared compatible stealth performance.

[0074] In the present invention, the polyetheretherketone (PEEK) is a high molecular material with excellent physical and chemical properties, including high strength, high temperature resistance (long-term use temperature is 260 °C), chemical stability and wear resistance.

[0075] In the present invention, the polyetheretherketone is preferably polyetheretherketone ultrafine powder, the particle size of the polyetheretherketone ultrafine powder is preferably 650 mesh, and the melt index is preferably 20 g / 10 min.

[0076] In the present invention, the wet mixing of the polyetheretherketone and the filler is preferably: dispersing the polyetheretherketone and the filler in an organic solvent, performing solid-liquid separation, drying the obtained solid to obtain a mixed powder. The dispersion is preferably carried out under stirring, the stirring time is preferably 1 - 48 h, more preferably 12 - 48 h, specifically it can be 12 h, 24 h or 48 h. The present invention has no special requirements for the stirring speed; the organic solvent preferably includes acetone.

[0077] In the present invention, the compression molding is preferably pressing, and there are no special requirements for the mold of the compression molding. The pressing preferably includes cold pressing and hot pressing; the pressure of the cold pressing is preferably 30 MPa, the temperature is preferably normal temperature, the time of the cold pressing is preferably 5-20 min, more preferably 10-15 min; the hot pressing includes the first hot pressing and the second hot pressing, the temperatures of the first hot pressing and the second hot pressing are independently preferably 350-380 °C, more preferably 360-380 °C, the pressure of the first hot pressing is preferably normal pressure, the time is preferably 10-60 min, more preferably 10-30 min; the pressure of the second hot pressing is preferably 10-50 MPa, more preferably 10-40 MPa, specifically it can be 30 MPa, the time is preferably 10-60 min, more preferably 10-40 min, specifically it can be 10 min, 15 min or 40 min.

[0078] The PEEK composite material with radar and infrared compatible stealth provided by the present invention has excellent radar stealth performance, electromagnetic wave absorption performance and infrared stealth performance, and the preparation method is simple, and the product morphology is easy to control.

[0079] The present invention also provides the application of the filler or PEEK composite material with radar and infrared compatible stealth described in the above technical solution in the field of multifunctional compatible stealth or camouflage.

[0080] In the present invention, by enhancing magnetic loss, conductance loss, polarization loss and multiple reflections and scattering, optimizing the impedance matching performance, the probability of electromagnetic wave reflection on the material surface is reduced. The MWCNTs@Co-NC@MoSe2 stealth filler can form a three-dimensional network structure by overlapping each other in the composite material. Due to the inconsistent distribution of the filler in each plane, the electric field distribution, magnetic field distribution and energy loss density inside the material are also inconsistent, constructing a multi-layer heterogeneous structure, improving the macroscopic anisotropy performance of the material, and further enhancing the electromagnetic wave dissipation.

[0081] In order to further illustrate the present invention, the filler, PEEK composite material with radar and infrared compatible stealth, preparation method and application provided by the present invention will be described in detail below with reference to the drawings and embodiments, but they cannot be understood as limiting the protection scope of the present invention.

[0082] In the examples and comparative examples of the present invention, the multi-walled carbon nanotubes (MWCNTs) used were purchased from Showa Co., Ltd. of Japan, and the specific dimensions were: diameter 100-300 nm, length 5-20 μm; the particle size of the polyether ether ketone ultrafine powder was 650 mesh, and the melt index was 20 g / 10 min.

[0083] Comparative Example 1

[0084] 1. Weigh 200 mg of MWCNTs and dissolve them in 50 mL of methanol containing 2 g of Co(NO3)2·6H2O. Sonicate strongly (power: 500 W, frequency: 20 kHz) for 30 min, and then stir magnetically for 3 h. Let MWCNTs and Co 2+ interact fully. Mix the above solution with 50 mL of methanol containing 2.26 g of 2-methylimidazole. Stir the mixture at a rotation speed of 500 rpm for 2 h and age it at room temperature for another 24 h. Finally, collect the black product by centrifugation, wash it three times with methanol, and then dry it overnight in a vacuum oven at 60 °C to obtain a purple-black powder, MWCNTs@ZIF-67.

[0085] 2. Put the prepared MWCNTs@ZIF-67 powder into a tubular furnace filled with argon, heat it to 600 °C at a heating rate of 2 °C / min, and pyrolyze it at 600 °C for 2 h to obtain a black powder, MWCNTs@Co-NC-600.

[0086] 3. Uniformly disperse 10 parts by weight of MWCNTs@Co-NC-600 and 90 parts by weight of PEEK ultrafine powder in acetone, filter and dry them for later use. First, cold-press the uniformly dispersed MWCNTs@Co-NC-600 / PEEK mixed powder in a mold for 15 minutes, then heat it to 380 °C and hold for 10 minutes. Subsequently, increase the pressure to 30 MPa and press for 15 minutes to obtain the MWCNTs@Co-NC-600 / PEEK composite material.

[0087] Comparative Example 2

[0088] The difference from Comparative Example 1 is that the pyrolysis temperature in Step 2 is different. In this comparative example, the pyrolysis temperature is 700 °C, and the other steps are the same.

[0089] Step 2 obtains a black powder, MWCNTs@Co-NC-700.

[0090] Step 3 obtains the MWCNTs@Co-NC-700 / PEEK composite material.

[0091] Comparative Example 3

[0092] The difference from Comparative Example 1 is that the pyrolysis temperature in Step 2 is different. In this comparative example, the pyrolysis temperature is 800 °C, and the other steps are the same.

[0093] Step 2 obtains a black powder, MWCNTs@Co-NC-800.

[0094] Step 3 obtains the MWCNTs@Co-NC-800 / PEEK composite material.

[0095] Comparative Example 4

[0096] The difference from Comparative Example 3 is that the mass of MWCNTs in Step 1 is different. In this comparative example, 100 mg of MWCNTs was weighed, and the other steps were the same.

[0097] The following Example 1 is carried out according to Figure 1 the preparation flow chart shown to prepare the MWCNTs@Co-NC@MoSe2 / PEEK composite material.

[0098] Example 1

[0099] 1. The preparation method of MWCNTs@ZIF-67 is the same as that of Comparative Example 1.

[0100] 2. The prepared MWCNTs@ZIF-67 powder is put into a tubular furnace filled with argon, heated to 800 °C at a heating rate of 2 °C / min, and pyrolyzed at 800 °C for 2 h to obtain MWCNTs@Co-NC-800 black powder.

[0101] 3. 0.079 g of Se powder and 4 mL of hydrazine hydrate are fully mixed in a 5 mL beaker and reacted completely at room temperature for 24 hours to obtain Solution A. Subsequently, 0.163 g of molybdenum acetylacetonate and 30 mg of MWCNTs@Co-NC-800 are dispersed in 80 mL of DMF and stirred vigorously (500 rpm). After mixing evenly, 20 mL of deionized water is added, ultrasonicated for 1 hour, and stirred for 3 hours to obtain Dispersion B. While continuously stirring, Solution A is added dropwise to Dispersion B to ensure thorough mixing. Then the obtained mixture is transferred to a 250 mL stainless steel autoclave and reacted at 220 °C for 24 hours. Vacuum dried at 70 °C. Finally, the obtained powder is put into a tubular furnace filled with Ar and pyrolyzed at 600 °C for 4 h to increase crystallinity and remove residual selenium powder. The obtained product is denoted as MWCNTs@Co-NC-800@MoSe2.

[0102] 4. 33 parts by weight of MWCNTs@Co-NC-800@MoSe2 and 67 parts by weight of PEEK ultrafine powder are uniformly dispersed in acetone, filtered and dried for later use. The uniformly dispersed MWCNTs@Co-NC-800@MoSe2 / PEEK mixed powder is first cold pressed (room temperature, 30 MPa) in a mold for 15 minutes, then heated to 380 °C (atmospheric pressure) and kept for 10 minutes, and then the pressure is increased to 30 MPa and pressed for 15 minutes to obtain the MWCNTs@Co-NC-800@MoSe2 / PEEK composite material.

[0103] Example 2

[0104] The difference from Example 1 is only that:

[0105] In Step 3, 0.163 g of molybdenum acetylacetonate and 60 mg of MWCNTs@Co-NC-800 were dispersed in 80 mL of DMF and stirred vigorously. After mixing evenly, 20 mL of deionized water was added, followed by sonication for 1 hour and stirring for 3 hours to obtain Dispersion B.

[0106] In Step 4, 33 parts by weight of MWCNTs@Co-NC-800@MoSe2 and 67 parts by weight of PEEK ultrafine powder were evenly dispersed in acetone, filtered, dried, and reserved for use.

[0107] Example 3

[0108] The difference from Example 1 is only that:

[0109] In Step 3, 0.163 g of molybdenum acetylacetonate and 90 mg of MWCNTs@Co-NC-800 were dispersed in 80 mL of DMF and stirred vigorously. After mixing evenly, 20 mL of deionized water was added, followed by sonication for 1 hour and stirring for 3 hours to obtain Dispersion B.

[0110] In Step 4, 33 parts by weight of MWCNTs@Co-NC-800@MoSe2 and 67 parts by weight of PEEK ultrafine powder were evenly dispersed in acetone, filtered, dried, and reserved for use.

[0111] Example 4

[0112] The difference from Example 1 is only that:

[0113] In Step 4, 50 parts by weight of MWCNTs@Co-NC-800@MoSe2 and 50 parts by weight of PEEK ultrafine powder were evenly dispersed in acetone, filtered, dried, and reserved for use.

[0114] Example 5

[0115] The difference from Example 1 is only that:

[0116] In Step 4, 40 parts by weight of MWCNTs@Co-NC-800@MoSe2 and 60 parts by weight of PEEK ultrafine powder were evenly dispersed in acetone, filtered, dried, and reserved for use.

[0117] Example 6

[0118] The difference from Example 1 is only that:

[0119] In Step 4, 20 parts by weight of MWCNTs@Co-NC-800@MoSe2 and 80 parts by weight of PEEK ultrafine powder were evenly dispersed in acetone, filtered, dried, and reserved for use.

[0120] Example 7

[0121] The difference from Example 1 is only that:

[0122] In Step 4, 10 parts by weight of MWCNTs@Co-NC-800@MoSe2 and 90 parts by weight of PEEK ultrafine powder were uniformly dispersed in acetone, and after filtration and drying, they were reserved for use.

[0123] The test was carried out with reference to GJB 5239-2004 "Test Method for Absorbing Performance of Radio Frequency Absorbing Materials". Table 1 shows the test results of the composite materials obtained in the comparative examples and examples. Sample size: outer diameter 7 mm, inner diameter 3 mm, thickness 2 mm. The thickness in Table 1 is the simulated thickness.

[0124] Table 1 Test Results of Composite Materials Obtained in Comparative Examples and Examples

[0125]

[0126]

[0127] It can be seen from Table 1 that excellent stealth performance can be achieved when the filler content in Example 1 is 33 wt%. When the matching thickness is 2.1 mm, the minimum reflection loss is -50.00 dB. When the matching thickness is 2.0 mm, the maximum effective absorption bandwidth is 6.84 GHz.

[0128] Unless otherwise specified below, MWCNTs@Co-NC@MoSe2 are all composite materials prepared in Example 1.

[0129] Figure 2 XRD patterns of MWCNTs, ZIF-67, Co-NC, MWCNTs@ZIF-67, MWCNTs@Co-NC, MoSe2 nanoflowers, and MWCNTs@Co-NC@MoSe2. Among them, the preparation methods of ZIF-67, Co-NC, and MoSe2 nanoflowers refer to Example 1, and the corresponding substances can be not added.

[0130] The prepared ZIF-67 shows multiple diffraction peaks that can be clearly observed at 2θ < 30°, which is highly consistent with the simulated results of ZIF-67 (PDF#671073), confirming the successful preparation of ZIF-67. The obtained ZIF-67 precursor was pyrolyzed at high temperature in a tubular furnace to obtain nitrogen-doped carbon containing metal Co particles (Co-NC). The original crystal diffraction peaks disappeared and new diffraction peaks appeared. Among them, the three strong diffraction peaks at 2θ = 44.2°, 51.4°, and 75.9° correspond to the (111), (200), and (220) crystal planes of Co (PDF#15-0806), respectively, further confirming that the crystal structure changed during high-temperature pyrolysis. The characteristic diffraction peaks of Co confirm that Co 2+ was reduced to Co after high-temperature treatment of ZIF-67. In addition, a weak diffraction peak of the graphite carbon (002) crystal plane can be observed near 2θ = 26.1°. This is because the organic ligands of ZIF-67 decompose at high temperature to form a carbon skeleton, and the broad peak shape is due to the low crystallinity. In the XRD pattern of WMCNTs@ZIF-67, the graphite carbon diffraction peaks of multi-walled carbon nanotubes and the characteristic peaks of ZIF-67 appear simultaneously, further proving the successful growth of ZIF-67 on MWCNTs. In the XRD pattern of MoSe2 after heat treatment, four obvious diffraction peaks at 2θ = 13.1°, 31.8°, 37.7°, and 56.1° are attributed to the (002), (100), (103), and (110) planes of the 2H-MoSe2 phase, respectively, which is consistent with the standard card (PDF#29-0914). This can prove that the prepared sample is the MoSe2 required for the experiment. The XRD spectrum of the MWCNTs@Co-NC@MoSe2 sample contains both the characteristic crystal planes of MoSe2 and the characteristic diffraction peaks of MWCNTs and Co-NC, proving that MoSe2 nanoflowers were successfully coated on the surface of MWCNTs@Co-NC.

[0131] Figure 3 SEM images of ZIF-67 (a1~a2), Co-NC (b1~b2), MWCNTs@ZIF-67 (c1~c2), MWCNTs@Co-NC (d1~d2), MoSe2 nanoflowers (e1~e2), and MWCNTs@Co-NC@MoSe2 (f1~f2).

[0132] As Figure 3As shown in (a1) and (a2), the synthesized ZIF-67 has a uniform dodecahedral structure with a smooth surface. (b1) and (b2) are the surface morphologies of the product Co-NC obtained by pyrolyzing ZIF-67 at high temperature, showing obvious collapse and shrinkage. Some particles still retain the original dodecahedral structure because when the metal-organic complex thermally decomposes at high temperature, gas is released, resulting in a decrease in the internal pressure of the crystal and causing the structure to collapse. As can be seen from (c1) and (c2), the red characters in (c2) are the diameter of ZIF-67, 1.259 μm. All ZIF-67 particles are interspersed by MWCNTs to form a unique three-dimensional network structure, and ZIF-67 is evenly dispersed on the surface of MWCNTs. After high-temperature calcination treatment, the material still maintains the original network structure, and the previously smooth surface has undergone significant shrinkage and collapse, as shown in Figure 3 (d1) and (d2) in the figure, which is similar to the morphological change of ZIF-67. Figure 3 (e1) and (e2) in the figure are the SEM images of MoSe2 nanoflowers after heat treatment. The results show that the flower-like contour of MoSe2 nanoflowers is clear after heat treatment, and the size of a single nanoflower is about 500 nm. From the scanning electron microscope of MWCNTs@Co-NC@MoSe2 Figure 3 (f1) and (f2) in the figure, it can be clearly seen that a layer of MoSe2 nanoflowers has grown uniformly on the rough surface of MWCNTs@Co-NC. The resulting core-shell structure contains multiple heterogeneous interfaces. At the same time, the flower-like structure is conducive to multiple reflections and scattering of incident electromagnetic waves, increasing the transmission path of electromagnetic waves, which is beneficial to further optimizing impedance matching and electromagnetic parameters, thereby improving the electromagnetic wave absorption performance.

[0133] Figure 4 is the EDS spectrum of MWCNTs@Co-NC@MoSe2.

[0134] To further confirm the successful preparation of MWCNTs@Co-NC@MoSe2, EDS was used to analyze its element distribution. It can be found from the EDS element mapping diagram of the selected area of the image that Mo and Se elements are evenly distributed in the outer layer, and Co, N, C, and O elements exist in the inner layer, which further proves that MoSe2 is evenly wrapped around the MWCNTs@Co-NC composite material, forming a core-shell structure. These results are consistent with the SEM analysis.

[0135] Figures 5 to 7 is the electromagnetic wave absorption performance diagram of the MWCNTs@Co-NC@MoSe2 / PEEK composite materials prepared in Examples 1-3, where Figure 5 is Example 1, Figure 6 is Example 2, Figure 7It is Example 3; namely, the three-dimensional reflection loss performance diagrams (a1 - c1), two-dimensional reflection loss performance diagrams (a2 - c2), and reflection loss performance curves (a3 - c3) of Examples 1, 2, and 3 (with the addition amount of MWCNTs@Co-NC@MoSe2 being 33 wt.%) at different thicknesses in the range of 2 - 18 GHz.

[0136] As Figure 5 shown in (a1) - (a3) therein, Example 1 exhibits the best electromagnetic absorption characteristics. When the matching thickness is 2.1 mm, the RL min value is -50.00 dB (11.88 GHz), while when the matching thickness is 2.0 mm, the corresponding EAB max has increased to 6.84 GHz. The absorption performance of Example 2 (see Figure 6 (b1) - (b3) therein) is weaker compared to Example 1. When the matching thickness is 2.8 mm, the RL min value reaches -47.20 dB (7.39 GHz), and the corresponding EAB max is 6.39 GHz (1.7 mm). As can be seen from Figure 7 (c1) - (c3) therein, the electromagnetic wave absorption ability of Example 3 is the weakest. When the matching thickness is 2.3 mm, the RL min value is only -12.45 dB (18 GHz), and when the matching thickness is 1.3 mm, the maximum EAB max is only 1.26 GHz.

[0137] The radar stealth performance simulation was carried out using CST software. Figure 8 It is the radar stealth performance diagram of the MWCNTs@Co-NC@MoSe2 / PEEK composite material prepared for Example 1. Among them, (a) is the three-dimensional simulation diagram of the monostatic RCS of the Example 1 specimen, (b) is the two-dimensional simulation diagram of the monostatic RCS of the Example 1 specimen, (c) is the RCS simulation curve of the Example 1 specimen and the perfect conductor, and (d) is the RCS reduction value of the Example 1 specimen at scanning angles of 0°, 15°, 30°, 45°, 60°, and 75° respectively. The results show that when the theta angle is 0 degree, the reduction value of its radar cross section can reach 18.5 dB·m 2 , indicating that the material described in the present invention has very excellent radar stealth performance.

[0138] The thermal camouflage performance of the MWCNTs@Co-NC@MoSe2 / PEEK composite material was systematically evaluated using an infrared thermal imager. The sample was placed on a heating platform at a constant temperature of 60 °C, and infrared thermal imaging photos at different heating times were recorded using a calibrated Fotric-226 infrared camera. Figure 9Infrared thermal imaging diagrams of the MWCNTs@Co-NC@MoSe2 / PEEK composite material prepared in Example 1 at different heating times, where the temperatures of (a) to (f) are 24.9 °C, 25.9 °C, 26.1 °C, 26.3 °C, 26.3 °C, and 26.6 °C, respectively. The results show that the upper surface temperature of the sample increased from 24.9 °C to 26.6 °C, and the sample exhibited an excellent thermal camouflage efficiency of 56%. These results confirm that the prepared MWCNTs@Co-NC@MoSe2 / PEEK composite material has good infrared camouflage performance.

[0139] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. People can also obtain other embodiments according to the embodiments of the present invention without creative labor, and these embodiments all belong to the protection scope of the present invention.

Claims

1. A filler for radar and infrared compatible stealth, characterized in that, It includes a core structure and MoSe2 nanoflowers coated on the surface of the core structure; The core structure is multi-walled carbon nanotubes coated with cobalt-nitrogen-doped carbon, and the cobalt-nitrogen-doped carbon has a metal-organic framework structure.

2. The radar and infrared compatible stealth filler according to claim 1, wherein The mass ratio of the core structure to the MoSe2 nanoflowers is 1:1.4 to 1:4.

3.

3. The preparation method of the radar and infrared compatible stealth filler according to claim 1 or 2, characterized in that It includes the following steps: Perform first pyrolysis on multi-walled carbon nanotubes coated with cobalt dimethylimidazole in an inert atmosphere to obtain multi-walled carbon nanotubes coated with cobalt-nitrogen-doped carbon; Mix the multi-walled carbon nanotubes coated with cobalt-nitrogen-doped carbon, molybdenum source, selenium source, reducing agent, water and polar organic solvent to carry out a solvothermal reaction, and perform second pyrolysis on the obtained solid in an inert atmosphere to obtain a filler with radar and infrared compatible stealth.

4. The preparation method according to claim 3, characterized in that, The mass ratio of the multi-walled carbon nanotubes to cobalt dimethylimidazole in the multi-walled carbon nanotubes coated with cobalt dimethylimidazole is 1:3.9 to 1:15.

9.

5. The preparation method according to claim 3 or 4, characterized in that, The temperature of the first pyrolysis is 600 to 800 °C, and the time is 2 to 4 h.

6. The preparation method according to claim 3, characterized in that, The molar ratio of Mo in the molybdenum source to the mass of the multi-walled carbon nanotubes coated with cobalt-nitrogen-doped carbon is (0.5 to 1) mmol:(30 to 90) mg; the temperature of the solvothermal reaction is 200 to 240 °C, and the time is 12 to 48 h.

7. A PEEK composite material compatible with radar and infrared stealth, characterized in that, It includes polyetheretherketone and a filler dispersed in the polyetheretherketone, and the filler is the filler with radar and infrared compatible stealth described in claim 1 or 2 or the filler with radar and infrared compatible stealth obtained by the preparation method described in any one of claims 3 to 6.

8. The PEEK composite material according to claim 7, wherein The mass ratio of the filler to the polyetheretherketone is 1:1 to 1:

10.

9. The preparation method of the PEEK composite material with radar and infrared compatible stealth as claimed in claim 7 or 8, characterized in that, It includes the following steps: Wet-mix the polyetheretherketone and the filler and then perform compression molding to obtain a composite material with radar and infrared compatible stealth.

10. Application of the filler with radar and infrared compatible stealth described in claim 1 or 2 or the PEEK composite material with radar and infrared compatible stealth described in claim 7 or 8 in the field of multi-functional compatible stealth or camouflage.

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