Self-repairable wave-absorbing composite material, preparation method and application thereof

Abstract

The application discloses a self-repairable wave-absorbing composite material and a preparation method and application thereof. The self-repairable wave-absorbing composite material comprises the following components in percentage by mass: a polyurethane matrix: 30-80%; and a composite wave-absorbing powder: 20-70%. The composite wave-absorbing powder is made of graphene oxide and soft magnetic metal powder through plasma ball milling. The preparation method of the self-repairable wave-absorbing composite material comprises the following steps: 1) preparing a polyurethane prepolymer solution; 2) dispersing the composite wave-absorbing powder in the polyurethane prepolymer solution, and then injecting the composite wave-absorbing powder into a mold for curing and forming, so that the self-repairable wave-absorbing composite material is obtained. The self-repairable wave-absorbing composite material has excellent wave-absorbing performance and mechanical properties, and the material can realize fast self-repairing, thereby guaranteeing the stability of the wave-absorbing performance and the mechanical properties. The composite material is suitable for the fields of 5G communication, new energy vehicles, national defense and military industry and the like.

Description

TECHNICAL FIELD

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

[0002] In recent years, the rapid development of wireless communication has provided great convenience for people's daily life and communication, but the widespread use of various wireless communication devices and consumer electronic products has also led to serious electromagnetic pollution problems. Electromagnetic pollution not only poses potential harm to human health, but also interferes with the stable operation of electronic devices. Therefore, there is an urgent need to develop wave-absorbing composite materials that can efficiently absorb electromagnetic waves in a specific frequency range. However, the substrates of traditional wave-absorbing composite materials are generally general-purpose rubber or plastic, which are prone to mechanical damage during use or internal crack propagation due to material fatigue, ultimately seriously affecting the wave-absorbing performance and service life of the materials, and cannot fully meet the growing practical application requirements.

[0003] Therefore, it is of great significance to develop a wave-absorbing composite material that has excellent wave-absorbing performance and mechanical properties and can achieve rapid self-repair. SUMMARY

[0004] The present application aims to provide a self-repairable wave-absorbing composite material and a preparation method and application thereof.

[0005] The technical solution adopted by the present application is as follows:

[0006] A self-repairable wave-absorbing composite material comprises the following components by mass percentage:

[0007] Polyurethane matrix: 30% to 80%;

[0008] Composite wave-absorbing powder: 20% to 70%.

[0009] Preferably, the composite wave-absorbing powder is made by plasma ball milling of graphene oxide and soft magnetic metal powder.

[0010] Further preferably, the composite wave-absorbing powder is made by a preparation method comprising the following steps: ultrasonic dispersion of graphene oxide in anhydrous ethanol to prepare a graphene oxide dispersion, then adding the graphene oxide dispersion, soft magnetic metal powder, and hard alloy balls into a ball milling tank for plasma ball milling, and after ball milling, the material is taken out for vacuum drying to obtain the composite wave-absorbing powder.

[0011] Preferably, the ultrasonic dispersion is carried out under the condition of ultrasonic power of 100W to 600W, and the ultrasonic dispersion time is 10min to 240min.

[0012] Preferably, the mass ratio of the graphene oxide and the soft magnetic metal powder is 1:10-100.

[0013] Preferably, the soft magnetic metal powder is at least one of carbonyl iron powder, iron silicon aluminum powder, iron silicon chromium powder, and iron nickel powder.

[0014] Preferably, the soft magnetic metal powder has a median particle size (D 50 ) of 1-80 µm.

[0015] Preferably, the total mass of the graphene oxide and the soft magnetic metal powder to the mass of the cemented carbide ball is in the range of 1:10-150.

[0016] Preferably, the plasma ball milling is performed in an argon atmosphere, a nitrogen atmosphere, an oxygen atmosphere, or an air atmosphere, the plasma discharge frequency is 5-12 kHz, the atmosphere pressure is 0.01-0.20 MPa, the ball mill rotation speed is 100-3000 rpm, and the ball milling time is 0.5-48 h.

[0017] Preferably, the vacuum drying is performed at a temperature of 60-100 °C for 3-48 h.

[0018] A method for preparing a self-repairable wave-absorbing composite material as described above comprises the following steps:

[0019] 1) dispersing polytetrahydrofuran diol, isocyanate, and a catalyst in an organic solvent to perform a first nucleophilic addition reaction, and then adding oxalyl dihydrazine and diaminodiphenyl disulfide to perform a second nucleophilic addition reaction, to obtain a polyurethane prepolymer solution;

[0020] 2) dispersing the composite wave-absorbing powder in the polyurethane prepolymer solution, and then injecting into a mold to perform curing and molding, to obtain the self-repairable wave-absorbing composite material.

[0021] Preferably, the molar ratio of the polytetrahydrofuran diol, the isocyanate, the oxalyl dihydrazine, and the diaminodiphenyl disulfide is 1:1.4-2.8:0.2-0.8:0.2-0.8.

[0022] Preferably, the polytetrahydrofuran diol in step 1) has a number average molecular weight of 500-5000.

[0023] Preferably, the polytetrahydrofuran diol in step 1) is subjected to a drying and water removal treatment at a temperature of 80-130 °C for 0.5-6 h.

[0024] Preferably, the isocyanate in step 1) is at least one of toluene diisocyanate, isophorone diisocyanate, and diphenylmethane diisocyanate.

[0025] Preferably, the catalyst in step 1) is at least one of bisisopropylether, dimethylamine, dibutyltin dilaurate.

[0026] Preferably, the organic solvent in step 1) is at least one of dimethylacetamide, dimethylformamide, tetrahydrofuran.

[0027] Preferably, the diamino diphenyl disulfide in step 1) is at least one of 2,2'-diamino diphenyl disulfide, 4,4'-diamino diphenyl disulfide.

[0028] Preferably, the first nucleophilic addition reaction (nucleophilic addition reaction of isocyanate with hydroxyl in polytetrahydrofuran glycol) in step 1) is carried out at a temperature of 60-90℃, and the reaction time is 2-8h.

[0029] Preferably, the first nucleophilic addition reaction in step 1) is carried out in a nitrogen atmosphere or an argon atmosphere.

[0030] Preferably, the second nucleophilic addition reaction (nucleophilic addition reaction of isocyanate with oxalic dihydrazine and amino in diamino diphenyl disulfide) in step 1) is carried out at a temperature of 40-60℃, and the reaction time is 6-12h.

[0031] Preferably, the second nucleophilic addition reaction in step 1) is carried out in a nitrogen atmosphere or an argon atmosphere.

[0032] Preferably, the dispersion in step 2) is stirring, and the stirring time is 1-6h.

[0033] Preferably, the solidification forming in step 2) is carried out at a temperature of 50-100℃, and the solidification forming time is 12-48h.

[0034] The self-repairable wave-absorbing composite material as described above is applied in the field of 5G communication, the field of new energy vehicles, or the field of national defense and military industry.

[0035] Principle of the application: The application utilizes the shear force and collision force generated by mechanical vibration in the plasma ball milling process and the thermal effect generated by plasma bombardment of the powder to quickly turn soft magnetic metal particles into flakes, thereby obtaining greater magnetic permeability and dielectric constant, enhancing the electromagnetic wave loss capacity of the soft magnetic metal material. At the same time, under the action of the shear force generated by mechanical ball milling, the binding force between the graphene oxide layers is weakened, and the graphene oxide nanosheets are peeled off into single-layer or few-layer graphene oxide nanosheets, which are complexed with metal ions on the surface of the soft magnetic metal powder, so that the graphene oxide nanosheets can be uniformly and tightly coated on the surface of the soft magnetic metal flakes to obtain composite wave-absorbing powder; the graphene oxide on the surface layer of the composite wave-absorbing powder is reduced to reduced graphene oxide after plasma reduction, which can provide more polarization sites, enhance interface polarization, increase dielectric loss, and enhance strong ion resonance between the composite wave-absorbing powder, thereby obtaining more excellent wave-absorbing performance. In addition, the residual oxygen-containing groups on the surface of the reduced graphene oxide can react with the free isocyanate groups in the polyurethane prepolymer to form crosslinking points, so that the composite wave-absorbing powder as a cross-linkable filler becomes the crosslinking center of the polyurethane, significantly improving the mechanical properties of the matrix. The absorption of electromagnetic waves by the composite wave-absorbing powder can convert electromagnetic energy into heat energy, achieving rapid heating of the polymer matrix, thereby realizing the rapid self-repairing process of the composite wave-absorbing material.

[0036] The beneficial effects of the application are: the wave-absorbing performance and mechanical properties of the self-repairable wave-absorbing composite material of the application are excellent, and the material can realize rapid self-repairing, ensuring the stability of the wave-absorbing performance and mechanical properties. The composite material is suitable for 5G communication, new energy vehicles, national defense and military industry, etc.

[0037] Specifically:

[0038] 1) The application utilizes plasma excitation to change graphene oxide into reduced graphene oxide, enhancing the electrical conductivity of carbon materials, thereby effectively improving the dielectric loss capacity of the composite wave-absorbing powder. The multiple heterojunction interfaces formed between reduced graphene oxide and soft magnetic metals promote interface polarization, and the reduced graphene oxide has abundant polarization sites, enhancing dipole polarization. In addition, the reduced graphene oxide enhances the plasma resonance between the composite wave-absorbing powder, thereby realizing broadband absorption of electromagnetic waves and significantly enhancing the wave-absorbing performance of the composite powder;

[0039] 2) The oxygen-containing groups on the surface of the composite wave-absorbing powder in the self-repairable wave-absorbing composite material of the present application can cross-link with the polyurethane macromolecules to form covalent bonds, so as to change the composite wave-absorbing powder into additional cross-linking centers of the composite material, which not only improves the dispersibility of the powder in the polyurethane matrix, but also greatly improves the mechanical properties of the composite material. In addition, the composite wave-absorbing powder can efficiently absorb electromagnetic waves to realize magnetic-thermal conversion to rapidly heat the polymer matrix, so as to accelerate the self-repairing speed of the composite material, and the mechanical properties and wave-absorbing properties of the composite material after repair can be restored to the original degree, which helps to prolong the service life of the composite material. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 SEM image of the wave-absorbing composite powder of Example 1.

[0041] Figure 2 Minimum reflection loss-frequency curve of the self-repairable wave-absorbing composite materials of Examples 1-5 and the wave-absorbing composite materials of Comparative Examples 1-2.

[0042] Figure 3 Stress-strain curve of the self-repairable wave-absorbing composite material of Example 1 and the wave-absorbing composite material of Comparative Example 1 before and after fracture self-repairing.

[0043] Figure 4 Minimum reflection loss-frequency curve of the self-repairable wave-absorbing composite material of Example 1 and the wave-absorbing composite material of Comparative Example 1 before and after fracture self-repairing.

[0044] Figure 5 Optical microscope photos of the fracture position of the self-repairable wave-absorbing composite material of Example 1 before and after self-repairing for 10 min. DETAILED DESCRIPTION

[0045] The present application will be further explained and described with reference to specific embodiments.

[0046] Example 1:

[0047] A self-repairable wave-absorbing composite material, which is composed of the following components in mass percentage:

[0048] Polyurethane matrix: 50%;

[0049] Composite wave-absorbing powder (mass ratio of graphene oxide to carbonyl iron powder: 1:80): 50%.

[0050] The preparation method of the composite wave-absorbing powder is as follows: graphene oxide is added into anhydrous ethanol, and a graphene oxide dispersion solution with a concentration of 2.5 mg / mL is prepared under the condition of ultrasonic power of 400 W for 20 min; then the graphene oxide dispersion solution, carbonyl iron powder (with a median particle size of 3 μm) and hard alloy balls are added into a ball milling tank, the mass ratio of graphene oxide to carbonyl iron powder is 1:80, and the total mass of graphene oxide and carbonyl iron powder to the mass of hard alloy balls is 1:25; then the ball milling tank is sealed and installed on a plasma ball mill, vacuumized and filled with argon until the gas pressure in the ball milling tank is 0.05 MPa; the vibration control power and the plasma discharge control power are started, the device running time is set to 20 min, the stopping time is set to 20 min, the cycle working times are set to 30 times, the total ball milling time is controlled to 10 h, the ball mill speed is 2000 rpm, and the discharge frequency is 11 kHz; the plasma ball mill is started to carry out plasma ball milling; after the ball milling is completed, the material is taken out and vacuum dried at a temperature of 80 ℃ for 6 h, and the composite wave-absorbing powder is obtained.

[0051] The preparation method of the self-repairable wave-absorbing composite material is as follows:

[0052] 1) polytetrahydrofuran glycol (with a number average molecular weight of 1000) is dehydrated at 120 ℃ for 30 min, then the polytetrahydrofuran glycol and isophorone diisocyanate are dispersed in dimethylacetamide, 1.5% of dibutyltin dilaurate based on the weight of the polytetrahydrofuran glycol is added, and then the mixture is stirred and reacted at 80 ℃ for 3 h under nitrogen protection, and then the temperature is lowered to 50 ℃, and oxalic dihydrazide and 2,2'-diamino diphenyl disulfide are added and the reaction is continued for 8 h, the molar ratio of polytetrahydrofuran glycol, isophorone diisocyanate, oxalic dihydrazide and 2,2'-diamino diphenyl disulfide is 1:2.2:0.5:0.5, and a polyurethane prepolymer solution is obtained;

[0053] 2) the composite wave-absorbing powder and the polyurethane prepolymer solution are mixed according to a mass ratio of 1:10, stirred for 4 h, and then poured into a polytetrafluoroethylene mold, vacuumized, and reacted at 80 ℃ for 12 h, and the self-repairable wave-absorbing composite material is obtained.

[0054] The scanning electron microscope (SEM) image of the wave-absorbing composite powder of the embodiment is shown in Figure 1 .

[0055] As can be seen from Figure 1 , the surface of the wave-absorbing composite powder is rough, and the reduced graphene oxide is exfoliated into fine nanosheets, and the reduced graphene oxide nanosheets are tightly combined with the flaky carbonyl iron powder.

[0056] Example 2:

[0057] A self-repairable wave-absorbing composite material is composed of the following components in mass percentage:

[0058] Polyurethane matrix: 50%;

[0059] Composite wave-absorbing powder (mass ratio of graphene oxide and carbonyl iron powder is 1:40): 50%.

[0060] The preparation method of the composite wave-absorbing powder is as follows: graphene oxide is added to anhydrous ethanol, and a graphene oxide dispersion solution with a concentration of 5 mg / mL is prepared under the condition of ultrasonic power of 400 W for 20 min; then the graphene oxide dispersion solution, carbonyl iron powder (median particle size of 3 μm) and hard alloy balls are added to a ball milling tank, the mass ratio of graphene oxide and carbonyl iron powder is 1:40, and the mass ratio of the total mass of graphene oxide and carbonyl iron powder to the mass of hard alloy balls is 1:20; then the ball milling tank is sealed and installed on a plasma ball mill, vacuumized and filled with argon to 0.05 MPa of air pressure in the ball milling tank, the vibration control power supply and the plasma discharge control power supply are started, the device running time is set to 20 min, the stop time is set to 20 min, the cycle working times are set to 15 times, the total ball milling time is controlled to 5 h, the ball mill speed is set to 1500 rpm, the discharge frequency is set to 11 kHz, the plasma ball mill is started for plasma ball milling, and after the ball milling is completed, the material is taken out and vacuum dried at a temperature of 80℃ for 5 h to obtain the composite wave-absorbing powder.

[0061] The preparation method of the self-repairable wave-absorbing composite material is as follows:

[0062] 1) Polytetrahydrofuran diol (number average molecular weight of 1000) is dehydrated at 100℃ for 1 h, then the polytetrahydrofuran diol and isophorone diisocyanate are dispersed in dimethylacetamide, 1.5% of dibutyltin dilaurate based on the weight of the polytetrahydrofuran diol is added, and then the mixture is stirred and reacted at 80℃ for 3 h under nitrogen protection, and then the temperature is lowered to 50℃, and oxalic dihydrazide and 2,2'-diaminodiphenyl disulfide are added and the reaction is continued for 8 h, the molar ratio of polytetrahydrofuran diol, isophorone diisocyanate, oxalic dihydrazide and 2,2'-diaminodiphenyl disulfide is 1:2.2:0.4:0.6, to obtain a polyurethane prepolymer solution;

[0063] 2) The composite wave-absorbing powder and the polyurethane prepolymer solution are mixed according to a mass ratio of 1:10, stirred for 5 h, then poured into a polytetrafluoroethylene mold, vacuumized, and reacted at 80℃ for 12 h to obtain the self-repairable wave-absorbing composite material.

[0064] Example 3:

[0065] A self-repairable wave-absorbing composite material is composed of the following components in mass percentage:

[0066] Polyurethane matrix: 70%;

[0067] Composite wave-absorbing powder (mass ratio of graphene oxide to carbonyl iron powder: 1:60): 30%.

[0068] The preparation method of the composite wave-absorbing powder is as follows: graphene oxide is added to anhydrous ethanol, and a graphene oxide dispersion solution with a concentration of 3 mg / mL is prepared under the condition of ultrasonic power of 400 W for 20 min; then the graphene oxide dispersion solution, carbonyl iron powder (median particle size of 3 μm) and hard alloy balls are added to a ball milling tank, the mass ratio of graphene oxide to carbonyl iron powder is 1:60, and the mass ratio of the total mass of graphene oxide and carbonyl iron powder to the mass of hard alloy balls is 1:30; then the ball milling tank is sealed and installed on a plasma ball mill, vacuumized and filled with nitrogen to an air pressure of 0.05 MPa in the ball milling tank, the vibration control power supply and the plasma discharge control power supply are started, the device running time is set to 20 min, the stop time is set to 20 min, the cycle working times are set to 21 times, the total ball milling time is controlled to 7 h, the ball mill speed is set to 1000 rpm, the discharge frequency is set to 11 kHz, the plasma ball mill is started for plasma ball milling, and after the ball milling is completed, the material is taken out and vacuum dried at a temperature of 70 ℃ for 12 h to obtain the composite wave-absorbing powder.

[0069] The preparation method of the self-repairable wave-absorbing composite material is as follows:

[0070] 1) Polytetrahydrofuran diol (number average molecular weight of 2000) is dehydrated at 120 ℃ for 30 min, and then the polytetrahydrofuran diol and toluene diisocyanate are dispersed in dimethylacetamide, 2% of dibutyltin dilaurate based on the weight of the polytetrahydrofuran diol is added, and then the mixture is stirred and reacted at 60 ℃ for 6 h under argon protection, and then the temperature is lowered to 50 ℃, and then oxalic dihydrazide and 4,4'-diaminodiphenyl disulfide are added and the reaction is continued for 10 h, and the molar ratio of polytetrahydrofuran diol, toluene diisocyanate, oxalic dihydrazide and 4,4'-diaminodiphenyl disulfide is 1:2.6:0.7:0.7, to obtain a polyurethane prepolymer solution;

[0071] 2) The composite wave-absorbing powder and the polyurethane prepolymer solution are mixed according to a mass ratio of 3:70, stirred for 4 h, and then poured into a polytetrafluoroethylene mold, vacuumized, and reacted at 80 ℃ for 12 h to obtain the self-repairable wave-absorbing composite material.

[0072] Example 4:

[0073] A self-repairable wave-absorbing composite material is composed of the following components in mass percentage:

[0074] Polyurethane matrix: 50%;

[0075] Composite wave-absorbing powder (mass ratio of graphene oxide to carbonyl iron powder: 1:80): 50%.

[0076] The preparation method of the composite absorbing powder is as follows: adding graphene oxide to anhydrous ethanol, ultrasonicating for 30 minutes under an ultrasonic power of 400 W to prepare a graphene oxide dispersion with a concentration of 2.5 mg / mL, then adding the graphene oxide dispersion, carbonyl iron powder (median particle size of 3 μm) and cemented carbide balls to a ball mill, wherein the mass ratio of graphene oxide to carbonyl iron powder is 1:80, and the ratio of the total mass of graphene oxide and carbonyl iron powder to the mass of cemented carbide balls is 1:50, and then sealing the ball mill and placing it in a plasma assisted vacuum chamber. On the ball mill, evacuate the material and introduce argon until the air pressure in the ball mill is 0.02 MPa. Start the vibration control power supply and the plasma discharge control power supply. Set the equipment running time to 30 minutes, the stop time to 30 minutes, the number of cycles to 40 times, the total ball milling time to 20 hours, the ball mill speed to 1500 rpm, the discharge frequency to 10 kHz, and start the plasma ball mill for plasma ball milling. After the ball milling is completed, take out the material and vacuum dry it at 70°C for 10 hours to obtain a composite absorbing powder.

[0077] The preparation method of the self-repairable wave-absorbing composite material is as follows:

[0078] 1) polytetrahydrofuran diol (number average molecular weight is 1000) is placed at 120 ℃ and dehydrated for 30 minutes, then polytetrahydrofuran diol and isophorone diisocyanate are dispersed in dimethylacetamide, then 2% dibutyltin dilaurate is added based on the weight of polytetrahydrofuran diol, then the reaction is stirred at 80 ℃ for 3 hours under nitrogen protection, then the temperature is lowered to 40 ℃, and then oxalyl dihydrazide and 2,2'-diaminodiphenyl disulfide are added and the reaction is continued for 10 hours, the molar ratio of polytetrahydrofuran diol, isophorone diisocyanate, oxalyl dihydrazide, 2,2'-diaminodiphenyl disulfide is 1:2.2:0.5:0.5, to obtain a polyurethane prepolymer solution;

[0079] 2) The composite absorbing powder and the polyurethane prepolymer solution were mixed in a mass ratio of 1:10, stirred for 4 hours, poured into a polytetrafluoroethylene mold, vacuumed, and reacted at 85° C. for 12 hours to obtain a self-repairing absorbing composite material.

[0080] Example 5:

[0081] A self-repairable wave-absorbing composite material, comprising the following components in percentage by mass:

[0082] Polyurethane matrix: 40%;

[0083] Composite absorbing powder (the mass ratio of graphene oxide and iron-nickel powder is 1:80): 60%.

[0084] The preparation method of the composite wave-absorbing powder is as follows: graphene oxide is added into anhydrous ethanol, and a graphene oxide dispersion solution with a concentration of 2.5 mg / mL is prepared under the condition of ultrasonic power of 400 W for 20 min; then the graphene oxide dispersion solution, iron-nickel powder (with a median particle size of 20 μm) and hard alloy balls are added into a ball milling tank, the mass ratio of the graphene oxide to the iron-nickel powder is 1:80, and the total mass of the graphene oxide and the iron-nickel powder to the mass of the hard alloy balls is 1:25; the ball milling tank is sealed and installed on a plasma ball mill, vacuumized and filled with argon to an air pressure of 0.05 MPa in the ball milling tank, the vibration control power supply and the plasma discharge control power supply are started, the device running time is set to 20 min, the stopping time is set to 20 min, the cycle working times are set to 30 times, the total ball milling time is controlled to 10 h, the ball mill speed is 2000 rpm, the discharge frequency is 11 kHz, the plasma ball mill is started to carry out plasma ball milling, and the material is taken out after the ball milling and vacuum dried at a temperature of 80 ℃ for 6 h, to obtain the composite wave-absorbing powder.

[0085] The preparation method of the self-repairable wave-absorbing composite material is as follows:

[0086] 1) polytetrahydrofuran diol (with a number average molecular weight of 3000) is dehydrated at 120 ℃ for 30 min, then the polytetrahydrofuran diol and isophorone diisocyanate are dispersed in dimethylacetamide, 1% of bisdimethylaminoethyl ether based on the weight of the polytetrahydrofuran diol is added, and then the mixture is stirred and reacted at 70 ℃ for 6 h under nitrogen protection, and then the temperature is lowered to 40 ℃, oxalic dihydrazide and 2,2'-diaminodiphenyl disulfide are added and the reaction is continued for 6 h, the molar ratio of the polytetrahydrofuran diol, isophorone diisocyanate, oxalic dihydrazide and 2,2'-diaminodiphenyl disulfide is 1:2.2:0.2:0.8, to obtain a polyurethane prepolymer solution;

[0087] 2) the composite wave-absorbing powder and the polyurethane prepolymer solution are mixed according to a mass ratio of 3:20, stirred for 3 h, and then poured into a polytetrafluoroethylene mold, vacuumized and reacted at 80 ℃ for 24 h, to obtain the self-repairable wave-absorbing composite material.

[0088] Comparative Example 1

[0089] A wave-absorbing composite material is composed of the following components with the following mass percentages:

[0090] Polyurethane matrix: 50%;

[0091] Wave-absorbing powder (carbonyl iron powder): 50%.

[0092] The preparation method of the above-mentioned wave-absorbing powder is as follows: carbonyl iron powder (with a median particle size of 3 μm) and anhydrous ethanol are added into a ball milling tank, the ratio of the amount of carbonyl iron powder to the amount of anhydrous ethanol is 1 g:2.5 mL, hard alloy balls are further added, the ratio of the mass of carbonyl iron powder to the mass of hard alloy balls is 1:25, the ball milling tank is sealed and installed on a vibrating ball mill, a vibrating control power is started after vacuumizing, the total ball milling time is 10 h, the rotating speed of the ball mill is 2000 rpm, and the material is taken out after the ball milling is completed and is vacuum-dried at 80 ℃ for 3 h, thereby obtaining the wave-absorbing powder (in a sheet shape).

[0093] The preparation method of the above-mentioned wave-absorbing composite material is as follows:

[0094] 1) polytetrahydrofuran diol (with a number average molecular weight of 1000) is dehydrated at 120 ℃ for 30 min, the polytetrahydrofuran diol and isophorone diisocyanate are dispersed in dimethylacetamide, 1.5% of dibutyltin dilaurate based on the weight of the polytetrahydrofuran diol is further added, the mixture is stirred and reacted at 80 ℃ for 6 h under the protection of argon, the molar ratio of the polytetrahydrofuran diol to the isophorone diisocyanate is 1:1, and a polyurethane prepolymer solution is obtained;

[0095] 2) the wave-absorbing powder and the polyurethane prepolymer solution are mixed according to a mass ratio of 1:10, stirred for 4 h, poured into a polytetrafluoroethylene mold, vacuumized, and reacted at 80 ℃ for 24 h, thereby obtaining the wave-absorbing composite material.

[0096] Comparative Example 2:

[0097] A wave-absorbing composite material is composed of the following components in mass percentage:

[0098] polyurethane matrix: 50%;

[0099] composite wave-absorbing powder (with a mass ratio of graphene oxide to carbonyl iron powder of 1:80): 50%.

[0100] The preparation method of the above-mentioned composite wave-absorbing powder is as follows: graphene oxide is added into anhydrous ethanol, and a graphene oxide dispersion liquid with a concentration of 2.5 mg / mL is prepared under the condition of ultrasonic power of 400 W for 20 min, the graphene oxide dispersion liquid and carbonyl iron powder (with a median particle size of 3 μm) are mixed and mechanically stirred for 10 min, the mass ratio of the graphene oxide to the carbonyl iron powder is 1:80, and the mixture is vacuum-dried at 80 ℃ for 6 h, thereby obtaining the composite wave-absorbing powder.

[0101] The preparation method of the above-mentioned wave-absorbing composite material is as follows:

[0102] 1) polytetrahydrofuran diol (number average molecular weight 1000) was placed at 120℃ for 30min to remove water, then the polytetrahydrofuran diol and isophorone diisocyanate were dispersed in dimethylacetamide, 1.5% of dibutyltin dilaurate based on the weight of the polytetrahydrofuran diol was added, then the reaction was stirred at 80℃ for 6h under argon protection, the molar ratio of polytetrahydrofuran diol and isophorone diisocyanate was 1:1, to obtain a polyurethane prepolymer solution;

[0103] 2) the composite wave-absorbing powder and the polyurethane prepolymer solution were mixed according to a mass ratio of 1:10, stirred for 4h, then poured into a polytetrafluoroethylene mold, vacuumized, and reacted at 80℃ for 24h to obtain the wave-absorbing composite material.

[0104] Performance test:

[0105] 1) the minimum reflection loss (RL min ) of the self-repairable wave-absorbing composite materials of examples 1-5 and the wave-absorbing composite materials of comparative examples 1-2 changed with frequency as shown in Figure 2 .

[0106] It can be seen from Figure 2 that the wave-absorbing performance of the self-repairable wave-absorbing composite materials of examples 1-5 was greatly improved compared with the wave-absorbing composite materials of comparative examples 1-2, the minimum reflection loss was obviously reduced, and the effective absorption bandwidth (reflection loss RL <-10dB) was increased.

[0107] 2) the stress-strain curves of the self-repairable wave-absorbing composite material of example 1 and the wave-absorbing composite material of comparative example 1 before and after fracture self-repair are shown in Figure 3 .

[0108] It can be seen from Figure 3 that the tensile strength and self-repair performance of the self-repairable wave-absorbing composite material of example 1 were greatly improved compared with the self-repairable wave-absorbing material of comparative example 1.

[0109] 3) the minimum reflection loss of the self-repairable wave-absorbing composite material of example 1 and the wave-absorbing composite material of comparative example 1 changed with frequency before and after fracture self-repair are shown in Figure 4 .

[0110] It can be seen from Figure 4 that the wave-absorbing performance of the self-repairable wave-absorbing composite material of example 1 could be completely repaired after fracture self-repair, while the wave-absorbing performance of the wave-absorbing composite material of comparative example 1 could not be repaired.

[0111] 4) the optical microscope photos of the fracture position of the self-repairable wave-absorbing composite material of example 1 before and after self-repair for 10min are shown in Figure 5 .

[0112] It can be seen from Figure 5It can be seen that the fracture is flat after self-repairing, and is basically completely repaired, indicating that the self-repairing wave-absorbing composite material of Example 1 has excellent self-repairing performance.

[0113] 5) The wave-absorbing performance and self-repairing performance test results of the self-repairing wave-absorbing composite materials of Examples 1-5 and the wave-absorbing composite materials of Comparative Examples 1-2 are shown in the following table:

[0114] Table 1 Wave-absorbing performance and self-repairing performance test results

[0115]

[0116]

[0117] Note:

[0118] Wave-absorbing performance: concentric circular ring samples with an inner diameter of 3.04 mm and an outer diameter of 7.00 mm are punched out by a puncher, and the complex permittivity and complex permeability of the self-repairing wave-absorbing composite material are tested by a coaxial method, the test frequency range is 2-18 GHz, and according to the transmission line theory, the reflection loss (RL) is calculated using the complex permittivity and complex permeability of the absorber at a given frequency and the thickness of the wave-absorbing material:

[0119] The reflection loss of a single-layer absorber is calculated by formula (1):

[0120] Formula (1): In the formula, Z0 is the impedance of free space, about 377, Z in is the normalized input impedance, and the calculation formula is shown in formula (2):

[0121] Formula (2): Z in = (μ r / ε r ) 1 / 2 tanh[j(2πfd / c)(μ r ε r ) 1 / 2 ], in which μ r is the magnetic permeability of free space and the relative magnetic permeability of the material, ε r is the dielectric constant of free space and the relative dielectric constant of the material, j represents the imaginary part, f is the frequency, d is the sample thickness, and c is the speed of light.

[0122] Self-repairing performance: after splicing the fracture position of the tensile sample, 1-2 drops of ethanol are added to the spliced section, and then heated at 80°C for 10 min to repair, so that the ethanol volatilizes, and the mechanical properties and wave-absorbing performance after repair are tested.

[0123] The mechanical self-repairing efficiency is the ratio of the maximum tensile strength after repair to the strength of the undamaged composite material.

[0124] The self-repairing efficiency of the wave-absorbing performance is a ratio of a coincident part of an effective absorption bandwidth of the composite material after repair to an absorption bandwidth of the undamaged composite material to the absorption bandwidth of the undamaged composite material under the same thickness.

[0125] It can be known from Table 1 that:

[0126] a) Compared with the wave-absorbing composite materials prepared by vibration ball milling or ordinary mechanical blending in Comparative Examples 1-2, the self-repairing wave-absorbing composite materials prepared by plasma ball milling in Examples 1-5 have more excellent wave-absorbing performance, wherein, by adjusting the content of graphene oxide, the type of soft magnetic metal, the plasma ball milling conditions and the proportion of the composite absorber, etc. in Examples 1-5, the reflection loss of the composite material is generally less than -50 dB, and the effective absorption bandwidth is greater than 5 GHz (up to 8.12 GHz), which indicates that after the reduction of graphene oxide, the dielectric loss ability of the composite powder is greatly improved, the graphene oxide on the surface of the composite powder provides more polarization sites, promotes dielectric loss, and at the same time optimizes impedance matching, and more excellent wave-absorbing performance is obtained;

[0127] b) It can be known from the results of Figure 3 that the tensile strength of the self-repairing wave-absorbing composite material with multiple hydrogen bonds and wave-absorbing powder crosslinking centers in Example 1 can be up to 28 MPa, and the elongation at break can be up to 900%, which is greatly improved compared with the ordinary polyurethane in Comparative Example 1, indicating that the multiple hydrogen bonds enhance the hydrogen bond crosslinking center, and the reduced graphene oxide acts as a covalent bond crosslinking center of the composite material, and the two work together to improve the mechanical properties of the composite material. In addition, the combination of disulfide bonds and multiple hydrogen bonds in the self-repairing wave-absorbing composite material of Example 1 endows the composite material with excellent self-repairing performance, and after 10 min of heating repair after tensile fracture, the mechanical repair efficiency can be up to 84%, and the wave-absorbing performance repair efficiency can be up to 100%.

[0128] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement modes, and all shall be included in the protection scope of the present application.

Claims

1. A self-repairable wave-absorbing composite material, characterized in that: The following components are included in mass percentage: Polyurethane matrix: 30% to 80%; Composite absorbing powder: 20% to 70%; The composite wave-absorbing powder is made by plasma ball milling graphene oxide and soft magnetic metal powder; The mass ratio of the graphene oxide to the soft magnetic metal powder is 1:10 to 100; The soft magnetic metal powder is at least one of carbonyl iron powder, sendust powder, iron silicon chromium powder and iron nickel powder; The self-repairable absorbing composite material is prepared by a preparation method comprising the following steps: 1) dispersing polytetramethylene glycol, isocyanate and a catalyst in an organic solvent to carry out a first nucleophilic addition reaction, and then adding oxalyl dihydrazide and diaminodiphenyl disulfide to carry out a second nucleophilic addition reaction to obtain a polyurethane prepolymer solution; and 2) dispersing composite absorbing powder in the polyurethane prepolymer solution, and then injecting the composite absorbing powder into a mold for curing and molding to obtain the self-repairable absorbing composite material.

2. The self-repairable wave-absorbing composite material according to claim 1, characterized in that: The median particle size of the soft magnetic metal powder is 1 μm to 80 μm.

3. The self-repairable wave-absorbing composite material according to claim 1, wherein: The plasma ball milling is carried out in an argon atmosphere, a nitrogen atmosphere, an oxygen atmosphere or an air atmosphere, the plasma discharge frequency is 5kHz to 12kHz, the atmosphere pressure is 0.01MPa to 0.20MPa, the ball mill speed is 100rpm to 3000rpm, and the ball milling time is 0.5h to 48h.

4. The self-repairable wave-absorbing composite material according to claim 1, wherein: The molar ratio of the polytetramethylene glycol, isocyanate, oxalyl dihydrazide and diaminodiphenyl disulfide is 1:1.4-2.8:0.2-0.8:0.2-0.

8.

5. The self-repairable wave-absorbing composite material according to claim 1 or 4, characterized in that: The number average molecular weight of the polytetramethylene glycol in step 1) is 500 to 5000; the isocyanate in step 1) is at least one of toluene diisocyanate, isophorone diisocyanate, and diphenylmethane diisocyanate; and the diaminodiphenyl disulfide in step 1) is at least one of 2,2'-diaminodiphenyl disulfide and 4,4'-diaminodiphenyl disulfide.

6. The self-repairable wave-absorbing composite material according to claim 1 or 4, characterized in that: The first nucleophilic addition reaction in step 1) is carried out at a temperature of 60°C to 90°C, and the reaction time is 2h to 8h; the second nucleophilic addition reaction in step 1) is carried out at a temperature of 40°C to 60°C, and the reaction time is 6h to 12h; the curing molding in step 2) is carried out at a temperature of 50°C to 100°C, and the curing molding time is 12h to 48h.

7. An application of the self-repairable wave-absorbing composite material according to any one of claims 1 to 6 in the field of 5G communications, new energy vehicles or national defense and military industry.

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