Flexible high-temperature-resistant wave-absorbing material and production process thereof

Abstract

The invention relates to a flexible high-temperature-resistant wave-absorbing material and a production process thereof, the flexible high-temperature-resistant wave-absorbing material comprises an upper layer and a lower layer, and the upper layer is prepared from the following raw materials in parts by mass: 5-20 parts of heteroatom doped porous Co-C particles, 0.2-0.4 part of AgNWs, 10-15 parts of carboxyl-terminated nitrile rubber, 60-90 parts of bisphenol F epoxy resin, 10-20 parts of DDM, 15-25 parts of acetone and 0.5-0.8 part of 2-ethyl-4-methylimidazole; the lower layer is prepared from the following raw materials in parts by mass: 20 to 30 parts of heteroatom doped porous Co-C particles, 0.3 to 0.4 part of AgNWs, 20 to 25 parts of carboxyl-terminated nitrile rubber, 60 to 80 parts of bisphenol F epoxy resin, 10 to 20 parts of DDM, 0.5 to 0.8 part of 2-ethyl-4-methylimidazole and 15 to 20 parts of acetone. The prepared material has lower reflectivity under the condition of small proportion of wave-absorbing filler, and is not easy to attenuate at high temperature.

Description

TECHNICAL FIELD

[0001] The application relates to a wave-absorbing material, in particular to a flexible high-temperature-resistant wave-absorbing material and a production process thereof. BACKGROUND

[0002] With the rapid development of 5G communication, artificial intelligence, Internet of Things and other technologies, electronic devices tend to be highly integrated and high-frequency. Due to the increase of power density of electronic components and the increase of electromagnetic wave reflection and crosstalk influence in high-frequency signal transmission, especially the high-temperature processes such as reflow soldering, solidification and thermal compression bonding involved in chip packaging, and the need to go through multiple thermal cycles, the problem of heat resistance and electromagnetic compatibility is increasingly prominent.

[0003] The wave-absorbing material is mainly composed of an absorbent and a substrate. The absorbent is a sheet-shaped soft magnetic powder, and the substrate is generally a thermoplastic elastomer. The sheet shape of the absorbent can improve the magnetic permeability and thus improve the absorption efficiency. The higher the sheet shape of the absorbent, the higher the dielectric constant and the lower the surface resistivity, which is not conducive to impedance matching. In addition, as a patch material, the wave-absorbing material is directly attached to the surface of the chip. If the content of the dielectric wave-absorbing agent is too high, the surface resistivity will be too low, which may cause short circuit of the chip and also cause high hardness and poor bonding effect.

[0004] The existing flexible wave-absorbing film for chip packaging is prepared by methods such as electrospinning hot pressing, spin coating solidification, and laminated compounding. However, it usually requires a high thickness and a large proportion of wave-absorbing fillers, has the disadvantages of easy agglomeration, weak interlayer bonding, low production capacity, poor bonding effect, and cannot achieve a good balance between flexibility, insulation and wave-absorbing performance. In addition, it performs poorly in high-temperature resistance and cannot meet higher use requirements. SUMMARY

[0005] In order to make the flexible wave-absorbing material have better high-temperature resistance and wave-absorbing performance, the application provides a flexible high-temperature-resistant wave-absorbing material and a production process thereof.

[0006] In a first aspect, the application provides a flexible high-temperature-resistant wave-absorbing material, which comprises an upper layer and a lower layer. The upper layer comprises the following raw materials in parts by mass: 5-20 parts of heteroatom-doped porous Co-C microparticles, 0.2-0.4 parts of AgNWs, 10-15 parts of carboxyl-terminated nitrile rubber, 60-90 parts of bisphenol F epoxy resin, 10-20 parts of DDM, 15-25 parts of acetone, and 0.5-0.8 parts of 2-ethyl-4-methylimidazole. The lower layer comprises the following raw materials in parts by mass: 20-30 parts of heteroatom-doped porous Co-C microparticles, 0.3-0.4 parts of AgNWs, 20-25 parts of carboxyl-terminated nitrile rubber, 60-80 parts of bisphenol F epoxy resin, 10-20 parts of DDM, 0.5-0.8 parts of 2-ethyl-4-methylimidazole, and 15-20 parts of acetone.

[0007] By adopting the above scheme, the upper and lower layer components are reasonably arranged, carboxyl-terminated butyl nitrile rubber and bisphenol F epoxy resin are used as the matrix, a cross-linked structure can be formed, the rubber forms a certain "island-in-sea structure" in the epoxy resin to better absorb impact energy, the overall flexibility of the material is improved, and certain mechanical strength is also provided.

[0008] Metal Co has a face-centered cubic structure and high saturation magnetization, which can provide excellent magnetic properties. By wrapping the Co particles with a carbon layer to form a porous structure, Co oxidation is prevented, and a large number of Co-C heterogeneous interfaces are formed, which enhances interface polarization, prolongs the path of electromagnetic waves, and enhances absorption efficiency. N and P doping in the carbon matrix forms a large number of defect sites, enhancing defect polarization. The doping of heteroatoms into porous Co-C particles makes Co more uniformly and stably dispersed in the system. The non-graphitized carbon with a porous structure formed by the combination of the two is not suitable for continuous conduction paths, avoiding short circuits, and is more suitable for use in the preparation of chip packaging and other electrically self-contained devices. By setting the gradient impedance, the electromagnetic wave reflection is reduced. By limiting the low Co-C content in the upper layer to the high Co-C content in the lower layer, a continuous impedance gradient is formed, impedance matching from air to material is achieved, reflection is reduced, and absorption efficiency is improved. The upper layer has good impedance matching, and the lower layer has good energy loss effect through magnetic and dielectric reinforcement. At the same time, the interface between the upper and lower layers is well integrated through flow casting, step pre-curing and hot pressing, forming a double-layer structure. The interlayer has high bonding strength through the embedding and cross-linking of fillers, and the magnetic loss of Co-C particles and the dielectric loss of AgNWs form a complement, covering a wider frequency range. The electromagnetic coupling effect between Co particles and AgNWs enhances the local electromagnetic field, promoting the conversion of electromagnetic wave energy to heat energy.

[0009] Preferably, the preparation steps of the heteroatom-doped porous Co-C particles include: dissolving cobalt nitrate hexahydrate in methanol to obtain a cobalt nitrate hexahydrate solution, dissolving 2-methylimidazole in methanol to obtain a 2-methylimidazole solution, mixing the 2-methylimidazole solution and the cobalt nitrate hexahydrate solution, stirring, centrifuging and washing, adding melamine and diammonium hydrogen phosphate, and reacting under inert atmosphere protection to obtain heteroatom-doped hollow Co-C particles.

[0010] By adopting the above scheme, the Co 2+The pyridine nitrogen atom is coordinated with 2-methyl imidazole to assemble into a crystal with a sodalite topology structure, the ligand is pyrolyzed at high temperature, the residual carbon atoms are reorganized into a nitrogen-doped porous carbon network, and nano Co particles are reduced and anchored, the metal Co provides natural resonance magnetic loss, the porous carbon provides conductive loss and dipole polarization dielectric loss, the Co-carbon heterojunction enhances the interface polarization loss, N and P doping form a large number of defect sites in the carbon matrix to enhance defect polarization, and small-size Co particles can avoid electromagnetic wave reflection caused by eddy current effect, so that the heteroatom-doped porous Co-C particles prepared have small size, uniform and stable wave absorption effect, and the prepared wave absorption material has better flexibility and is better adapted to the small deformation in the packaging process.

[0011] Preferably, the cobalt nitrate hexahydrate solution further comprises sodium dodecyl benzene sulfonate, and the mass ratio of cobalt nitrate hexahydrate, sodium dodecyl benzene sulfonate and methanol is (3-4) : (7.5-8.2) : (0.01-0.03).

[0012] Preferably, the stirring is ultrasonic stirring, the power is 250-350 W, and the frequency is 35-45 kHz.

[0013] By adding a certain mass of sodium dodecyl benzene sulfonate and limiting the stirring speed, it is possible to inhibit the excessive growth of the crystal by adsorbing on the surface of the crystal nucleus through steric hindrance, and the particle size of the particles assembled is more suitable for the wave absorption material system, and the sodalite topology structure is more typical and stable.

[0014] Preferably, the inert atmosphere is an Ar-H2 mixed atmosphere, and the volume fraction of H2 is 4-7%.

[0015] By adopting the above scheme, the reduction effect is enhanced, Co 2+ is fully reduced, and hydrogen further etches the carbon network, thereby increasing the porosity of the prepared heteroatom-doped porous Co-C particles, and the dielectric loss of the product is stronger.

[0016] Preferably, the heteroatom-doped porous Co-C particles comprise epoxy silane modified heteroatom-doped porous Co-C particles and polyethylene glycol grafted heteroatom-doped porous Co-C particles in a mass ratio of 1: (0.5-2.5).

[0017] Preferably, the molecular weight of the polyethylene glycol is 2000-4000.

[0018] Through the above scheme, the epoxy silane modified system is more compatible, the system is more stable, thereby realizing better absorption of electromagnetic waves, and better dispersion can be realized by cross-linking with the carboxyl-terminated butylnitrile rubber distributed in the island structure, the wave-absorbing network is more uniformly and reasonably distributed, and the performance of the prepared wave-absorbing material is better. The flexible chain segment of polyethylene glycol is compatible with the butadiene segment of butylnitrile rubber, can reduce the van der Waals force between the heteroatom-doped porous Co-C particles, further reduce agglomeration, and improve flexibility and interfacial bonding strength by inserting flexible long chains.

[0019] Preferably, the heteroatom-doped hollow Co-C particles in the upper layer are BN-coated heteroatom-doped hollow Co-C particles, and the preparation steps include: dispersing the heteroatom-doped hollow Co-C particles in ethanol, adding trimethyl borate and urea, protecting in an inert atmosphere, heating, and keeping the reaction temperature to obtain BN-coated heteroatom-doped hollow Co-C particles.

[0020] Preferably, the mass ratio of the heteroatom-doped hollow Co-C particles, trimethyl borate, and urea in the upper layer is 1:(0.2-0.8):(0.12-0.55).

[0021] Preferably, the mass ratio of the heteroatom-doped hollow Co-C particles, trimethyl borate, and urea in the upper layer is 80:13:15.

[0022] By coating the heteroatom-doped hollow Co-C particles in the upper layer with BN, the Co particles inside are provided with unparalleled protection, ensuring that the wave-absorbing performance is stable and not oxidized for a long time under high heat, after packaging, and during the service life, and excellent impedance matching is achieved through the BN shell and the porous structure, which can more effectively absorb rather than reflect electromagnetic waves, preventing secondary interference to the surrounding chips. The upper and lower layers cooperate to form a gradient impedance matching and synergistic loss, and a smooth impedance transition layer from air to lower dielectric in the upper layer to higher dielectric-magnetic in the lower layer is constructed, achieving better performance with less wave-absorbing filler addition and thinner wave-absorbing material.

[0023] Preferably, the mass ratio of the heteroatom-doped porous Co-C particles in the upper layer to the heteroatom-doped porous Co-C particles in the lower layer is (12-14):25.

[0024] By limiting the mass ratio of the heteroatom-doped porous Co-C particles in the upper and lower layers, the wave-transmitting and wave-absorbing performance between the layers is more matched, the magnetic loss gradient is more reasonable, and the wave-absorbing performance of the prepared wave-absorbing material is better.

[0025] Preferably, the AgNWs in the upper layer are short-diameter AgNWs with a diameter of 15-25 nm and a length of 5-10 μm, and the AgNWs in the lower layer are long-diameter AgNWs with a diameter of 25-35 nm and a length of 15-25 μm.

[0026] By limiting the size and content of the AgNWs, after the upper and lower layers are hot-pressed to obtain the wave-absorbing material, the short-diameter AgNWs not only form a better "interlaced network" in the gaps between the long-diameter AgNWs in the lower layer, but also are uniformly and closely distributed in the system, and the multiple scattering paths of electromagnetic waves are increased, the energy dissipation is strengthened, and the wave-absorbing material obtained has better wave-absorbing performance.

[0027] Preferably, the AgNWs are carbon-deposited AgNWs, and the preparation steps include: depositing a 2-3 nm carbon layer on the surface of the AgNWs by CVD.

[0028] By depositing the carbon layer, the stability of the AgNWs is improved, the AgNWs are less likely to be oxidized and attenuated, and the compatibility with the Co-C carbon matrix is better, thereby further improving the stability of the system.

[0029] In a second aspect, the present application provides a production process of a flexible high-temperature-resistant wave-absorbing material, which comprises the following preparation steps: mixing heteroatom-doped porous Co-C particles, AgNWs, carboxyl-terminated nitrile rubber, epoxy resin, and curing agent to obtain a lower layer slurry, casting the lower layer slurry on a substrate, and heat-treating to form a pre-cured layer; mixing heteroatom-doped porous Co-C particles, an AgNWs dispersion, carboxyl-terminated nitrile rubber, phenolic epoxy resin, silane coupling agent, curing agent, accelerator, and solvent to obtain an upper layer slurry, and casting the upper layer slurry on the pre-cured layer; and gradient temperature increasing and hot-pressing treatment, and removing the substrate to obtain the flexible high-temperature-resistant wave-absorbing material.

[0030] Preferably, the pre-curing is 80℃ curing for 20-30 min, the gradient temperature increasing process comprises: 120℃ curing for 40-60 min, 150℃ curing for 40-60 min, and 180℃ curing for 40-60 min, the hot-pressing treatment pressure is 4-5 MPa, the temperature is 100-120℃, and the time is 5-10 min.

[0031] After the pre-curing, the lower layer has a certain support strength, while retaining a certain crosslinking activity and deformation ability, the epoxy matrix at the interface between the upper and lower layers forms physical intercalation and a certain chemical bridging, and the interface bonding strength of the wave-absorbing material obtained is greater. Meanwhile, the process control of the gradient temperature increasing process makes the heat release more uniform, and the internal stress is reduced, and the gradient of the dense wave-absorbing material system formed after the hot-pressing is uniform and reasonable, and the performance of the "interlaced wave-absorbing network" between the wave-absorbing fillers is good.

[0032] In summary, the present application has the following beneficial effects: The application provides a gradient designed double-layer flexible high-temperature resistant wave-absorbing material, realizes better impedance matching of the upper layer and better absorption efficiency of the lower layer through different raw material settings in the upper and lower layers. The application provides a kind of heteroatom doped porous Co-C microparticle and its preparation method, and further preferably a certain mass ratio of epoxy silane modified heteroatom doped porous Co-C microparticle and polyethylene glycol grafted heteroatom doped porous Co-C microparticle are crosslinked with system components, and the synergistic use of winding makes the porous structure resonate magnetic loss, conductive loss, dipole polarization dielectric loss, interface polarization loss, etc. Commonly used, the material realizes better wave-absorbing performance, flexibility and high-temperature resistance under the addition of less filler.

[0033] The application further adds a certain mass ratio of sodium dodecyl benzene sulfonate to the cobalt nitrate hexahydrate solution and limits the stirring speed, optimizes the growth of microparticles, and further enhances the performance of the product by passing a certain mass of hydrogen.

[0034] The application provides a preparation process of a double-layer wave-absorbing material, and the preparation process has the advantages of simple preparation steps and good interlayer bonding effect through pre-curing, curing and hot-pressing treatment with a certain temperature gradient. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0036] Figure 1 The preparation process structure schematic diagram provided by the present application is shown in the figure, wherein 1 is the upper layer, 2 is the lower layer, and 3 is the glass substrate. DETAILED DESCRIPTION

[0037] In order to further help understand the technical solutions of the present application, the following will provide more specific description of the technical solutions of the present application by providing several specific implementation examples. All the described embodiments are only part of the embodiments of the present application, not all; The specific embodiments below can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The reaction devices, monomer compounds and the like involved in the following embodiments are commercially available.

[0038] The specific embodiments below can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0039] The following examples are further illustrations of the application and are not intended to limit the present application in any way.

[0040] Preparation Example Preparation Example 1: Heteroatom-doped porous Co-C microparticles: Dissolve 3.5 g of cobalt nitrate hexahydrate in 100 ml of methanol to obtain a cobalt nitrate hexahydrate solution, dissolve 7.8 g of 2-methylimidazole in 100 ml of methanol to obtain a 2-methylimidazole solution, quickly pour the 2-methylimidazole solution into the cobalt nitrate hexahydrate solution, stir at 800 rpm for 6 hours, centrifuge at 8000 rpm for 10 min, wash with methanol for 3 times, vacuum dry at 60°C to obtain an intermediate product, disperse the intermediate product in 100 ml of ethanol, add 3 g of melamine and 2 g of diammonium hydrogen phosphate, under argon protection, heat at 1°C / min to 600°C, keep the temperature for 2 hours, and naturally cool to room temperature to obtain the heteroatom-doped porous Co-C microparticles.

[0041] Preparation Example 2: Heteroatom-doped porous Co-C microparticles: Dissolve 3.5 g of cobalt nitrate hexahydrate in 100 ml of methanol to obtain a cobalt nitrate hexahydrate solution, dissolve 7.8 g of 2-methylimidazole and 0.02 g of sodium dodecyl benzene sulfonate in 100 ml of methanol to obtain a 2-methylimidazole solution, quickly pour the 2-methylimidazole solution into the cobalt nitrate hexahydrate solution, stir at 800 rpm for 6 hours, centrifuge at 8000 rpm for 10 min, wash with methanol for 3 times, vacuum dry at 60°C to obtain an intermediate product, disperse the intermediate product in 100 ml of ethanol, add 3 g of melamine and 2 g of diammonium hydrogen phosphate, under argon protection, heat at 1°C / min to 600°C, keep the temperature for 2 hours, and naturally cool to room temperature to obtain the heteroatom-doped porous Co-C microparticles.

[0042] Preparation Example 3: Heteroatom-doped porous Co-C microparticles: Dissolve 3.5 g of cobalt nitrate hexahydrate in 100 ml of methanol to obtain a cobalt nitrate hexahydrate solution, dissolve 7.8 g of 2-methylimidazole and 0.01 g of sodium dodecyl benzene sulfonate in 100 ml of methanol to obtain a 2-methylimidazole solution, quickly pour the 2-methylimidazole solution into the cobalt nitrate hexahydrate solution, stir at 800 rpm for 6 hours, centrifuge at 8000 rpm for 10 min, wash with methanol for 3 times, vacuum dry at 60°C to obtain an intermediate product, disperse the intermediate product in 100 ml of ethanol, add 3 g of melamine and 2 g of diammonium hydrogen phosphate, under argon protection, heat at 1°C / min to 600°C, keep the temperature for 2 hours, and naturally cool to room temperature to obtain the heteroatom-doped porous Co-C microparticles.

[0043] Preparation Example 4: Heteroatom-doped porous Co-C microparticles: A solution of 3.5 g of cobalt nitrate hexahydrate was prepared by dissolving the cobalt nitrate hexahydrate in 100 ml of methanol. A solution of 2-methylimidazole was prepared by dissolving 7.8 g of 2-methylimidazole and 0.02 g of sodium dodecylbenzenesulfonate in 100 ml of methanol. The solution of 2-methylimidazole was quickly poured into the solution of cobalt nitrate hexahydrate, and stirred at 800 rpm for 6 hours. The mixture was centrifuged at 8000 rpm for 10 minutes, and washed with methanol three times. The mixture was dried at 60°C under vacuum to obtain an intermediate product. The intermediate product was dispersed in 100 ml of ethanol, and 3 g of melamine and 2 g of diammonium hydrogen phosphate were added. The mixture was heated at a rate of 1°C / min to 600°C under a mixed gas atmosphere of hydrogen and argon containing 5 vol% of hydrogen, and reacted at 600°C for 2 hours. The mixture was naturally cooled to room temperature to obtain heteroatom-doped porous Co-C microparticles.

[0044] Preparation Example 5: Epoxy silane-modified heteroatom-doped porous Co-C microparticles The heteroatom-doped porous Co-C microparticles prepared in Preparation Example 4 were subjected to oxygen plasma treatment at an oxygen flow rate of 15 seem, a reaction vacuum of 0.1 mbar, and a plasma power of 100 W for 5 minutes to activate the microparticles. The activated microparticles were then added to 450 ml of a 60 wt% ethanol aqueous solution, and 5 g of KH-560 was added to the solution. The mixture was stirred at 70°C for 1.5 hours. The mixture was filtered, washed with deionized water three times, and dried at 60°C under vacuum for 1 hour to obtain epoxy silane-modified heteroatom-doped porous Co-C microparticles.

[0045] Preparation Example 6: Amino silane-modified heteroatom-doped porous Co-C microparticles The heteroatom-doped porous Co-C microparticles prepared in Preparation Example 4 were subjected to oxygen plasma treatment at an oxygen flow rate of 15 seem, a reaction vacuum of 0.1 mbar, and a plasma power of 100 W for 5 minutes to activate the microparticles. The activated microparticles were then added to 450 ml of a 60 wt% ethanol aqueous solution, and 5 g of KH-550 was added to the solution. The mixture was stirred at 70°C for 1.5 hours. The mixture was filtered, washed with deionized water three times, and dried at 60°C under vacuum for 1 hour to obtain amino silane-modified heteroatom-doped porous Co-C microparticles.

[0046] Preparation Example 7: PEG2000-grafted heteroatom-doped porous Co-C microparticles The heteroatom-doped porous Co-C microparticles prepared in Preparation Example 4 were activated by oxygen plasma treatment at an oxygen flow rate of 15 seem, a reaction vacuum of 0.1 mbar, and a plasma treatment of 100 W for 5 minutes, and then were added to 450 ml of a 60 wt% ethanol aqueous solution, 5 g of KH-550 was further added, and the mixture was uniformly dispersed, stirred, and reacted at 70°C for 1.5 hours. Then, 20 g of PEG2000 was added, 120 ml of ethanol was added, and the mixture was stirred and reacted at 70°C for 4 hours under N2 protection. After the reaction, the mixture was centrifuged at 8000 rpm for 10 minutes, washed with anhydrous ethanol three times, and vacuum dried at 60°C for 4 hours to obtain PEG2000-grafted heteroatom-doped porous Co-C microparticles.

[0047] Preparation Example 8: PEG1000-grafted heteroatom-doped porous Co-C microparticles The heteroatom-doped porous Co-C microparticles prepared in Preparation Example 4 were activated by oxygen plasma treatment at an oxygen flow rate of 15 seem, a reaction vacuum of 0.1 mbar, and a plasma treatment of 100 W for 5 minutes, and then were added to 450 ml of a 60 wt% ethanol aqueous solution, 5 g of KH-550 was further added, and the mixture was uniformly dispersed, stirred, and reacted at 70°C for 1.5 hours. Then, 20 g of PEG1000 was added, 120 ml of ethanol was added, and the mixture was stirred and reacted at 70°C for 4 hours under N2 protection. After the reaction, the mixture was centrifuged at 8000 rpm for 10 minutes, washed with anhydrous ethanol three times, and vacuum dried at 60°C for 4 hours to obtain PEG1000-grafted heteroatom-doped porous Co-C microparticles.

[0048] Preparation Example 9: BN-coated heteroatom-doped hollow Co-C microparticles The heteroatom-doped porous Co-C microparticles prepared in Preparation Example 4 were dispersed in 250 ml of ethanol, 6.5 g of trimethyl borate and 7.5 g of urea were added, and the mixture was stirred at 300 rpm for 15 minutes. The mixture was heated to 180°C under argon protection, and reacted at 180°C for 2 hours. The reaction mixture was centrifuged at 8000 rpm for 10 minutes, washed with ethanol three times, and then was heated to 800°C at a rate of 5°C / min under argon protection. The mixture was kept at 800°C for 1 hour, and then was cooled to room temperature. The mixture was vacuum dried at 50°C for 6 hours to obtain BN-coated heteroatom-doped hollow Co-C microparticles. Example

[0049] Example 1 Preparation of raw materials: The upper layer raw materials included 13 g of the heteroatom-doped porous Co-C microparticles prepared in Preparation Example 1, 0.3 g of short-diameter AgNWs, 12 g of carboxyl-terminated butylnitrile rubber, 70 g of bisphenol F epoxy resin, 15 g of DDM, 20 g of acetone, and 0.7 g of 2-ethyl-4-methylimidazole. Lower layer raw materials: heteroatom-doped porous Co-C microparticles 25 g, long-diameter AgNWs 0.3 g, carboxyl-terminated butyl nitrile rubber 22 g, bisphenol F epoxy resin 70 g, DDM 15 g, 2-ethyl-4-methyl imidazole 0.7 g, acetone 17 g.

[0050] The lower layer raw materials were mixed uniformly, cast on a glass substrate, and pre-cured at 80°C for 25 min to form a pre-cured layer. The upper layer raw materials were mixed uniformly by mass, cast on the pre-cured layer, cured at 120°C for 50 min, cured at 150°C for 50 min, cured at 180°C for 50 min, and then treated by hot pressing at 4 MPa and 110°C for 5 min. The glass substrate was removed to obtain a flexible high-temperature-resistant wave-absorbing material.

[0051] Example 2 Raw material weighing preparation: Upper layer raw materials: heteroatom-doped porous Co-C microparticles prepared in Preparation Example 1 20 g, short-diameter AgNWs 0.3 g, carboxyl-terminated butyl nitrile rubber 12 g, bisphenol F epoxy resin 70 g, DDM 15 g, acetone 20 g, 2-ethyl-4-methyl imidazole 0.7 g; Lower layer raw materials: heteroatom-doped porous Co-C microparticles prepared in Preparation Example 1 25 g, long-diameter AgNWs 0.3 g, carboxyl-terminated butyl nitrile rubber 22 g, bisphenol F epoxy resin 70 g, DDM 15 g, 2-ethyl-4-methyl imidazole 0.7 g, acetone 17 g.

[0052] The lower layer raw materials were mixed uniformly, cast on a glass substrate, and pre-cured at 80°C for 25 min to form a pre-cured layer. The upper layer raw materials were mixed uniformly by mass, cast on the pre-cured layer, cured at 120°C for 50 min, cured at 150°C for 50 min, cured at 180°C for 50 min, and then treated by hot pressing at 4 MPa and 110°C for 5 min. The glass substrate was removed to obtain a flexible high-temperature-resistant wave-absorbing material.

[0053] Example 3 Raw material weighing preparation: Upper layer raw materials: heteroatom-doped porous Co-C microparticles prepared in Preparation Example 2 13 g, short-diameter AgNWs 0.3 g, carboxyl-terminated butyl nitrile rubber 12 g, bisphenol F epoxy resin 70 g, DDM 15 g, acetone 20 g, 2-ethyl-4-methyl imidazole 0.7 g; Lower layer raw materials: heteroatom-doped porous Co-C microparticles prepared in Preparation Example 2 25 g, long-diameter AgNWs 0.3 g, carboxyl-terminated butyl nitrile rubber 22 g, bisphenol F epoxy resin 70 g, DDM 15 g, 2-ethyl-4-methyl imidazole 0.7 g, acetone 17 g.

[0054] The lower layer raw material is mixed uniformly, cast on a glass substrate, pre-cured at 80℃ for 25min to form a pre-cured layer, the upper layer raw material is mixed uniformly according to the mass, cast on the pre-cured layer, cured at 120℃ for 50min, 150℃ for 50min, 180℃ for 50min, then treated at 4MPa, 110℃ for 5min, and the glass substrate is removed to obtain a flexible high-temperature-resistant wave-absorbing material.

[0055] Example 4 Raw material weighing preparation: The upper layer raw material: heteroatom-doped porous Co-C microparticles 13g, short-diameter AgNWs 0.3g, carboxyl-terminated butyl nitrile rubber 12g, bisphenol F epoxy resin 70g, DDM 15g, acetone 20g, 2-ethyl-4-methylimidazole 0.7g; The lower layer raw material: heteroatom-doped porous Co-C microparticles 25g, long-diameter AgNWs 0.3g, carboxyl-terminated butyl nitrile rubber 22g, bisphenol F epoxy resin 70g, DDM 15g, 2-ethyl-4-methylimidazole 0.7g, acetone 17g.

[0056] The lower layer raw material is mixed uniformly, cast on a glass substrate, pre-cured at 80℃ for 25min to form a pre-cured layer, the upper layer raw material is mixed uniformly according to the mass, cast on the pre-cured layer, cured at 120℃ for 50min, 150℃ for 50min, 180℃ for 50min, then treated at 4MPa, 110℃ for 5min, and the glass substrate is removed to obtain a flexible high-temperature-resistant wave-absorbing material.

[0057] Example 5 Raw material weighing preparation: The upper layer raw material: heteroatom-doped porous Co-C microparticles 13g, short-diameter AgNWs 0.3g, carboxyl-terminated butyl nitrile rubber 12g, bisphenol F epoxy resin 70g, DDM 15g, acetone 20g, 2-ethyl-4-methylimidazole 0.7g; The lower layer raw material: heteroatom-doped porous Co-C microparticles 25g, long-diameter AgNWs 0.3g, carboxyl-terminated butyl nitrile rubber 22g, bisphenol F epoxy resin 70g, DDM 15g, 2-ethyl-4-methylimidazole 0.7g, acetone 17g.

[0058] The lower layer raw material is mixed uniformly, cast on a glass substrate, pre-cured at 80℃ for 25min to form a pre-cured layer, the upper layer raw material is mixed uniformly according to the mass, cast on the pre-cured layer, cured at 120℃ for 50min, 150℃ for 50min, 180℃ for 50min, then treated at 4MPa, 110℃ for 5min, and the glass substrate is removed to obtain a flexible high-temperature-resistant wave-absorbing material.

[0059] Example 6 Raw material preparation: Upper layer raw material: heteroatom-doped porous Co-C microparticles prepared in Preparation Example 1 13 g, long-diameter AgNWs 0.3 g, carboxyl-terminated butyl nitrile rubber 12 g, bisphenol F epoxy resin 70 g, DDM 15 g, acetone 20 g, 2-ethyl-4-methyl imidazole 0.7 g; Lower layer raw material: heteroatom-doped porous Co-C microparticles prepared in Preparation Example 1 25 g, long-diameter AgNWs 0.3 g, carboxyl-terminated butyl nitrile rubber 22 g, bisphenol F epoxy resin 70 g, DDM 15 g, 2-ethyl-4-methyl imidazole 0.7 g, acetone 17 g.

[0060] The lower layer raw material was mixed uniformly and cast on a glass substrate, and pre-cured at 80°C for 25 min to form a pre-cured layer. The upper layer raw material was mixed uniformly according to the mass, and cast on the pre-cured layer. The material was cured at 120°C for 50 min, at 150°C for 50 min, and at 180°C for 50 min, and then treated by hot pressing at 4 MPa and 110°C for 5 min. The glass substrate was removed to obtain a flexible high-temperature-resistant wave-absorbing material.

[0061] Example 7 Raw material preparation: Upper layer raw material: heteroatom-doped porous Co-C microparticles prepared in Preparation Example 1 13 g, long-diameter AgNWs 0.3 g, carboxyl-terminated butyl nitrile rubber 12 g, bisphenol F epoxy resin 70 g, DDM 15 g, acetone 20 g, 2-ethyl-4-methyl imidazole 0.7 g; Lower layer raw material: epoxy-silane modified heteroatom-doped porous Co-C microparticles prepared in Preparation Example 5 10 g, PEG2000 grafted heteroatom-doped porous Co-C microparticles prepared in Preparation Example 7 15 g, long-diameter AgNWs 0.3 g, carboxyl-terminated butyl nitrile rubber 22 g, bisphenol F epoxy resin 70 g, DDM 15 g, 2-ethyl-4-methyl imidazole 0.7 g, acetone 17 g.

[0062] The lower layer raw material was mixed uniformly and cast on a glass substrate, and pre-cured at 80°C for 25 min to form a pre-cured layer. The upper layer raw material was mixed uniformly according to the mass, and cast on the pre-cured layer. The material was cured at 120°C for 50 min, at 150°C for 50 min, and at 180°C for 50 min, and then treated by hot pressing at 4 MPa and 110°C for 5 min. The glass substrate was removed to obtain a flexible high-temperature-resistant wave-absorbing material.

[0063] Example 8 Raw material preparation: Upper layer raw material: heteroatom-doped porous Co-C microparticles prepared in Preparation Example 1 13 g, long-diameter AgNWs 0.3 g, carboxyl-terminated butyl nitrile rubber 12 g, bisphenol F epoxy resin 70 g, DDM 15 g, acetone 20 g, 2-ethyl-4-methyl imidazole 0.7 g; Lower layer raw materials: epoxy silane modified heteroatom doped porous Co-C particles prepared in Preparation Example 5 10 g, PEG1000 grafted heteroatom doped porous Co-C particles prepared in Preparation Example 8 15 g, long diameter AgNWs 0.3 g, carboxyl-terminated butyl nitrile rubber 22 g, bisphenol F epoxy resin 70 g, DDM 15 g, 2-ethyl-4-methylimidazole 0.7 g, acetone 17 g.

[0064] The lower layer raw materials were mixed uniformly, cast on a glass substrate, and pre-cured at 80°C for 25 min to form a pre-cured layer. The upper layer raw materials were mixed uniformly by mass, cast on the pre-cured layer, and cured at 120°C for 50 min, at 150°C for 50 min, and at 180°C for 50 min, and then treated by hot pressing at 4 MPa and 110°C for 5 min. The glass substrate was removed to obtain a flexible high-temperature-resistant wave-absorbing material.

[0065] Example 9 Raw material weighing preparation: Upper layer raw materials: heteroatom doped porous Co-C particles prepared in Preparation Example 1 13 g, short diameter AgNWs 0.3 g, carboxyl-terminated butyl nitrile rubber 12 g, bisphenol F epoxy resin 70 g, DDM 15 g, acetone 20 g, 2-ethyl-4-methylimidazole 0.7 g; Lower layer raw materials: amino silane modified heteroatom doped porous Co-C particles prepared in Preparation Example 6 10 g, PEG2000 grafted heteroatom doped porous Co-C particles prepared in Preparation Example 7 15 g, short diameter AgNWs 0.3 g, carboxyl-terminated butyl nitrile rubber 12 g, bisphenol F epoxy resin 70 g, DDM 15 g, acetone 20 g, 2-ethyl-4-methylimidazole 0.7 g; The lower layer raw materials were mixed uniformly, cast on a glass substrate, and pre-cured at 80°C for 25 min to form a pre-cured layer. The upper layer raw materials were mixed uniformly by mass, cast on the pre-cured layer, and cured at 120°C for 50 min, at 150°C for 50 min, and at 180°C for 50 min, and then treated by hot pressing at 4 MPa and 110°C for 5 min. The glass substrate was removed to obtain a flexible high-temperature-resistant wave-absorbing material.

[0066] Example 10 Raw material weighing preparation: The upper layer raw material: the heteroatom-doped porous Co-C microparticles 13 g, short diameter AgNWs 0.3 g, carboxyl-terminated butyl nitrile rubber 12 g, bisphenol F epoxy resin 70 g, DDM 15 g, acetone 20 g, 2-ethyl-4-methyl imidazole 0.7 g; the lower layer raw material: the epoxy silane modified heteroatom-doped porous Co-C microparticles 5 g, the PEG2000 grafted heteroatom-doped porous Co-C microparticles 20 g, long diameter AgNWs 0.3 g, carboxyl-terminated butyl nitrile rubber 22 g, bisphenol F epoxy resin 70 g, DDM 15 g, 2-ethyl-4-methyl imidazole 0.7 g, acetone 17 g.

[0067] The lower layer raw material was mixed uniformly, cast on a glass substrate, and pre-cured at 80°C for 25 min to form a pre-cured layer. The upper layer raw material was mixed uniformly by mass, cast on the pre-cured layer, cured at 120°C for 50 min, cured at 150°C for 50 min, cured at 180°C for 50 min, and then treated by hot pressing at 4 MPa and 110°C for 5 min. The glass substrate was removed to obtain a flexible high-temperature-resistant wave-absorbing material.

[0068] Example 11 Raw material weighing preparation: The upper layer raw material: the BN-coated heteroatom-doped porous Co-C microparticles 13 g, short diameter AgNWs 0.3 g, carboxyl-terminated butyl nitrile rubber 12 g, bisphenol F epoxy resin 70 g, DDM 15 g, acetone 20 g, 2-ethyl-4-methyl imidazole 0.7 g; the lower layer raw material: the epoxy silane modified heteroatom-doped porous Co-C microparticles 10 g, the PEG2000 grafted heteroatom-doped porous Co-C microparticles 15 g, long diameter AgNWs 0.3 g, carboxyl-terminated butyl nitrile rubber 22 g, bisphenol F epoxy resin 70 g, DDM 15 g, 2-ethyl-4-methyl imidazole 0.7 g, acetone 17 g.

[0069] The lower layer raw material was mixed uniformly, cast on a glass substrate, and pre-cured at 80°C for 25 min to form a pre-cured layer. The upper layer raw material was mixed uniformly by mass, cast on the pre-cured layer, cured at 120°C for 50 min, cured at 150°C for 50 min, cured at 180°C for 50 min, and then treated by hot pressing at 4 MPa and 110°C for 5 min. The glass substrate was removed to obtain a flexible high-temperature-resistant wave-absorbing material.

[0070] Comparative example Comparative example 1 Raw material weighing preparation: The upper layer raw material: spinel ferrite 13 g, short diameter AgNWs 0.3 g, carboxyl-terminated butyl nitrile rubber 12 g, bisphenol F epoxy resin 70 g, DDM 15 g, acetone 20 g, 2-ethyl-4-methyl imidazole 0.7 g; Lower layer raw materials: spinel ferrite 25 g, long-diameter AgNWs 0.3 g, carboxyl-terminated butylnitrile rubber 22 g, bisphenol F epoxy resin 70 g, DDM 15 g, 2-ethyl-4-methylimidazole 0.7 g, acetone 17 g.

[0071] The lower layer raw materials were mixed uniformly, cast on a glass substrate, pre-cured at 80°C for 25 min to form a pre-cured layer, the upper layer raw materials were mixed uniformly according to the mass, cast on the pre-cured layer, cured at 120°C for 50 min, cured at 150°C for 50 min, cured at 180°C for 50 min, and then treated at 4 MPa and 110°C for 5 min, and the glass substrate was removed to obtain a flexible high-temperature-resistant wave-absorbing material.

[0072] Performance test test one: the peak reflectivity I of the product in the frequency band of 1 GHz to 18 GHz was tested according to the test standard GJB2038A-2011, and the test results were summarized in Table 1; Test two: the product was aged at 300°C for 30 s (referring to the commonly used process parameters of reflow soldering and adding redundancy), and then cooled to room temperature, repeated 10 times, and then repeated test one, to obtain the reflectivity II after aging, and the high-temperature attenuation rate was calculated according to (reflectivity I-reflectivity II) / reflectivity I x 100%.

[0073] Table 1 Reflectance I (dB) High temperature decay rate (%) Example 1 -14.2 8.2 Example 2 -11.4 8.3 Example 3 -16.8 8.0 Example 4 -14.9 8.0 Example 5 -17.1 7.8 Example 6 -13.1 8.2 Example 7 -23.4 6.5 Example 8 -19.2 7.1 Example 9 -19.0 7.0 Example 10 -18.5 8.2 Example 11 -28.1 5.3 Comparative Example 1 -7.1 13.1 It can be seen from Examples 1-2 and Comparative Example 1 in combination with Table 1 that the flexible wave-absorbing material is prepared by hot pressing the double-layer structure and limiting the components and mass of each layer, and the prepared wave-absorbing material has good reflectivity and high-temperature resistance.

[0074] It can be seen from Examples 1, 3-6 in combination with Table 1 that the preparation process of the heteroatom-doped porous Co-C particles is limited, a certain mass of sodium dodecyl benzene sulfonate is added, the process parameters are limited, a certain mass ratio of hydrogen is introduced, the epoxy silane modification and PEG2000 modification are respectively carried out, and the structure of AgNWs is limited, which further improves the structural stability and wave-absorbing performance of the prepared wave-absorbing material.

[0075] It can be seen from Examples 1, 7-11 in combination with Table 1 that the heteroatom-doped porous Co-C particles in the upper and lower layers are respectively modified differently, which improves the gradient impedance matching and wave-absorbing effect, and the prepared wave-absorbing material has better performance.

[0076] The specific embodiments are only an explanation of the present application, and are not a limitation of the present application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the specification, but as long as the modifications are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A flexible high-temperature resistant wave-absorbing material, characterized in that: The upper layer comprises the following raw materials by mass fraction: 5-20 parts of the heteroatom-doped porous Co-C microparticles, 0.2-0.4 parts of AgNWs, 10-15 parts of carboxyl-terminated butyl nitrile rubber, 60-90 parts of bisphenol F epoxy resin, 10-20 parts of DDM, 15-25 parts of acetone, and 0.5-0.8 parts of 2-ethyl-4-methylimidazole; and the lower layer comprises the following raw materials by mass fraction: 20-30 parts of the heteroatom-doped porous Co-C microparticles, 0.3-0.4 parts of AgNWs, 20-25 parts of carboxyl-terminated butyl nitrile rubber, 60-80 parts of bisphenol F epoxy resin, 10-20 parts of DDM, 0.5-0.8 parts of 2-ethyl-4-methylimidazole, and 15-20 parts of acetone. 2.The flexible high-temperature-resistant wave-absorbing material according to claim 1, characterized in that: The preparation steps of the heteroatom-doped porous Co-C microparticles include: dissolving cobalt nitrate hexahydrate in methanol to obtain a cobalt nitrate hexahydrate solution, dissolving 2-methylimidazole in methanol to obtain a 2-methylimidazole solution, mixing the 2-methylimidazole solution and the cobalt nitrate hexahydrate solution, stirring, centrifugal washing, adding melamine and diammonium hydrogen phosphate, heating under inert atmosphere protection, and cooling to obtain the heteroatom-doped porous Co-C microparticles. 3.The flexible high-temperature-resistant wave-absorbing material according to claim 2, characterized in that: The cobalt nitrate hexahydrate solution further comprises sodium dodecylbenzenesulfonate, and the mass ratio of cobalt nitrate hexahydrate, sodium dodecylbenzenesulfonate, and methanol is (3-4):(7.5-8.2):(0.01-0.03). 4.The flexible high-temperature-resistant wave-absorbing material according to claim 2, characterized in that: The inert atmosphere is Ar and H2 mixed gas, and the volume fraction of H2 is 4-7%. 5.The flexible high-temperature-resistant wave-absorbing material according to claim 1, characterized in that: The heteroatom-doped porous Co-C microparticles comprise epoxy silane modified heteroatom-doped porous Co-C microparticles and polyethylene glycol grafted heteroatom-doped porous Co-C microparticles at a mass ratio of 1:(0.5-2.5). 6.The flexible high-temperature-resistant wave-absorbing material according to claim 1, characterized in that: The heteroatom-doped porous Co-C microparticles in the upper layer are BN-coated heteroatom-doped porous Co-C microparticles, and the preparation steps include: dispersing the heteroatom-doped porous Co-C microparticles in ethanol, adding trimethyl borate and urea, heating under inert atmosphere protection, and cooling to obtain the BN-coated heteroatom-doped porous Co-C microparticles. 7.The flexible high-temperature-resistant wave-absorbing material according to claim 1, characterized in that: The mass ratio of the heteroatom-doped porous Co-C microparticles in the upper layer to the heteroatom-doped porous Co-C microparticles in the lower layer is (12-14):

25. 8.The flexible high-temperature-resistant wave-absorbing material according to claim 1, characterized in that: The AgNWs in the upper layer are short-diameter AgNWs with a diameter of 15-25 nm and a length of 5-10 μm, and the AgNWs in the lower layer are long-diameter AgNWs with a diameter of 25-35 nm and a length of 15-25 μm.

9. A production process of the flexible high-temperature-resistant wave-absorbing material according to any one of claims 1-8, characterized in that: The method comprises the following steps: weighing the lower layer raw materials by mass, uniformly mixing the raw materials, casting the raw materials on a substrate, and heat treating to form a pre-cured layer; uniformly mixing the upper layer raw materials by mass, casting the raw materials on the pre-cured layer, gradient heating and hot pressing, and removing the substrate to obtain the flexible high-temperature-resistant wave-absorbing material. 10.The production process of a flexible high-temperature-resistant wave-absorbing material according to claim 9, characterized in that: The pre-curing is 80℃ for 20-30min, the process of gradient temperature rising includes: 120℃ for 40-60min, 150℃ for 40-60min, 180℃ for 40-60min, the hot-pressing treatment pressure is 4-5MPa, temperature is 100-120℃, time is 5-10min.

Images