CN113321844A - Graphene/polyimide composite foam wave-absorbing material with oriented pore structure and preparation method thereof - Google Patents

Graphene/polyimide composite foam wave-absorbing material with oriented pore structure and preparation method thereof Download PDF

Info

Publication number
CN113321844A
CN113321844A CN202110615275.6A CN202110615275A CN113321844A CN 113321844 A CN113321844 A CN 113321844A CN 202110615275 A CN202110615275 A CN 202110615275A CN 113321844 A CN113321844 A CN 113321844A
Authority
CN
China
Prior art keywords
graphene
composite foam
polyamic acid
graphene oxide
pore structure
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
CN202110615275.6A
Other languages
Chinese (zh)
Other versions
CN113321844B (en
Inventor
王子成
刘天西
张亚伟
李双双
唐新伟
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Jiangnan University
Original Assignee
Jiangnan University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Jiangnan University filed Critical Jiangnan University
Priority to CN202110615275.6A priority Critical patent/CN113321844B/en
Publication of CN113321844A publication Critical patent/CN113321844A/en
Application granted granted Critical
Publication of CN113321844B publication Critical patent/CN113321844B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/28—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K3/00—Materials not provided for elsewhere
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2201/00—Foams characterised by the foaming process
    • C08J2201/04—Foams characterised by the foaming process characterised by the elimination of a liquid or solid component, e.g. precipitation, leaching out, evaporation
    • C08J2201/048—Elimination of a frozen liquid phase
    • C08J2201/0484—Elimination of a frozen liquid phase the liquid phase being aqueous
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2379/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen with or without oxygen, or carbon only, not provided for in groups C08J2361/00 - C08J2377/00
    • C08J2379/04—Polycondensates having nitrogen-containing heterocyclic rings in the main chain; Polyhydrazides; Polyamide acids or similar polyimide precursors
    • C08J2379/08—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/02—Elements
    • C08K3/04—Carbon
    • C08K3/042—Graphene or derivatives, e.g. graphene oxides

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Carbon And Carbon Compounds (AREA)
  • Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)

Abstract

The invention discloses a graphene/polyimide composite foam wave-absorbing material with an oriented pore structure and a preparation method thereof, and belongs to the technical field of porous composite foam wave-absorbing materials and preparation thereof. The graphene/polyimide composite foam material with the oriented laminated pore structure is obtained by compounding graphene oxide and polyamide acid and performing a bidirectional ice template method, vacuum freeze drying and thermal imidization treatment process. The graphene/polyimide composite foam material with the oriented pore structure has excellent electromagnetic wave absorption performance and a wider absorption frequency range, is simple and easy to operate in the preparation process, is green and pollution-free, and is expected to be applied to the fields of aerospace, military equipment, civil electric appliances and the like.

Description

Graphene/polyimide composite foam wave-absorbing material with oriented pore structure and preparation method thereof
Technical Field
The invention relates to a graphene/polyimide composite foam wave-absorbing material with an oriented pore structure and a preparation method thereof, belonging to the technical field of porous composite foam wave-absorbing materials and preparation thereof.
Background
With the development of society and the progress of science and technology, various electronic and electrical equipment and communication equipment bring convenience to daily life of people, and simultaneously, a large amount of electromagnetic pollution is inevitably brought to the health and living environment of people. In recent years, research and development of high-performance electromagnetic wave absorbing materials with strong absorption capacity and wide absorption frequency band has become one of the hot spots in the field of material research. The traditional wave-absorbing material comprises ferrite, carbonyl iron and the like, and has the characteristics of large magnetic loss and wide absorption frequency band. But the defects of larger density, high processing cost, difficult processing, poor corrosion resistance and the like seriously hinder the popularization and the application of the alloy in the fields of aerospace, military equipment and civil electric appliances. Carbon foam, as a porous material having a three-dimensional conductive network, has advantages of low density, high processability, and good corrosion resistance, and thus has received much attention and research. The special porous structure in the carbon foam material increases the specific surface area in the material, so that incident electromagnetic waves can perform energy dissipation in a multiple reflection/scattering mode among the porous structures in the material.
However, in conventional carbon foams, carbon/polymer syntactic foams have a large impedance mismatch at the surface of the syntactic foam due to the carbon-based conductive phase wrapping up on the surface of the polymer insulating phase during assembly, which eventually results in a large reflection of incident electromagnetic waves with only a small fraction of the waves able to enter the interior of the foam; the pore size structure of polymeric pyrolytic foam materials (e.g., wood, cotton, butts, bread, etc.) is strongly dependent on the source of the raw materials, is less programmable and controllable, and generally results in a random pore structure that is also isotropic, making precise design and controllable adjustment of the internal pore structure and pore size of the material on a microscopic scale difficult.
Disclosure of Invention
[ problem ] to provide a method for producing a semiconductor device
The carbon foam material has high conductivity due to the internal special structure, so that incident electromagnetic waves are reflected in a large quantity, impedance mismatching is generated between the incident electromagnetic waves and the wave-absorbing material, the incident electromagnetic waves are prevented from entering the material, and then the electromagnetic waves cannot be effectively attenuated and dissipated. Most of conventionally obtained carbon foam materials are isotropic random porous structures, incident electromagnetic waves are insufficient in multiple reflection and scattering degrees in the materials, the energy attenuation degree is low, and the like, so that the optimization of structural design for enhancing the microwave absorption performance is urgently needed.
[ technical solution ] A
In order to solve the technical problems, the invention provides a polyimide/graphene composite foam wave-absorbing material with an oriented pore structure and a preparation method thereof, and aims to overcome the defects of small microwave absorption amount, low multiple reflection and scattering degree of incident electromagnetic waves in the material, low energy attenuation degree and the like caused by surface impedance mismatch of a graphene foam material.
The graphene/polyimide composite foam wave-absorbing material with the oriented porous structure is obtained by compounding graphene oxide and polyamide acid and by a bidirectional ice template method, a vacuum freeze-drying technology and a heat treatment process. The introduction of the polyimide can improve the mechanical strength of the composite foam wave-absorbing material on one hand; on the other hand, the problem of material surface impedance mismatch caused by high conductivity of the graphene material is solved, more electromagnetic waves are promoted to be incident into the material, and therefore the electromagnetic waves are attenuated and dissipated in the material. Under the influence of the oriented laminated pore structure in the material, on one hand, electromagnetic waves are subjected to multiple reflection and scattering to a greater extent between the laminated pore structures in the material after being incident on the material, and on the other hand, propagation paths of the electromagnetic waves after entering the material are increased, so that the maximum energy attenuation and dissipation of the incident electromagnetic waves between the laminated pore structures are realized.
Specifically, the invention firstly provides a preparation method of a graphene/polyimide composite foam wave-absorbing material with an oriented pore structure, and the method comprises the following steps: preparing a graphene oxide dispersion liquid with a certain concentration under an ultrasonic condition; preparing a polyamic acid/triethylamine aqueous solution in ultrapure water; mixing the graphene oxide dispersion liquid and the polyamic acid/triethylamine aqueous solution under magnetic stirring to obtain a graphene oxide/polyamic acid composite liquid, and obtaining graphene oxide/polyamic acid composite foam through a sol-gel method, a two-way ice template method and a freeze drying process; and then carrying out thermal imidization treatment on the graphene oxide/polyamide acid composite foam in an inert atmosphere to obtain the graphene/polyimide composite foam wave-absorbing material.
In one embodiment of the present invention, the mass ratio (concentration ratio) of the graphene oxide, the water-soluble polyamic acid, and the triethylamine is (0-20 mg/mL): (0-40 mg/mL): 0-20 mg/mL), wherein the three components are not 0 at the same time.
In one embodiment of the present invention, the concentration ratio of the water-soluble polyamic acid to triethylamine is preferably 2: 1.
In one embodiment of the present invention, the raw flake graphite used for preparing graphene oxide has a size of 80 to 350 mesh, and is prepared by Hummers method.
In one embodiment of the present invention, the water-soluble polyamic acid is prepared by the following method: firstly, dissolving a diamine monomer in a polar solvent, then adding a dicarboxylic anhydride monomer, carrying out polymerization reaction in an ice-water bath, then adding organic amine, and continuing the reaction to obtain a water-soluble polyamic acid sol; solvent exchange and freeze drying to obtain water soluble polyamic acid.
In one embodiment of the present invention, the diamine monomer includes any one of p-phenylenediamine or 4, 4' -diaminodiphenyl ether; the binary anhydride monomer comprises any one of biphenyl tetracarboxylic dianhydride or pyromellitic dianhydride; the polar solvent includes any one of N-methylpyrrolidone, N '-dimethylacetamide, or N, N' -dimethylformamide; the organic amine includes any one of triethylamine or dipropylamine.
In one embodiment of the invention, the molar ratio of the diamine monomer, the dicarboxylic anhydride monomer and the organic amine is (0-1): 0-1.
In one embodiment of the present invention, the sol-gel method, the two-way ice template method, and the vacuum freeze-drying method include: pouring the composite liquid into a bidirectional freezing mould, wherein the sol-gel time is 12-15 h, and then carrying out vacuum freeze drying, wherein the freezing temperature is-50 to-120 ℃, and the freezing time is 6-8 h; the vacuum degree is 0.1-2 Pa, and the drying time is 72-96 h.
In one embodiment of the present invention, the bottom bi-directional freezing mold is an angled wedge-shaped open cubic mold.
In one embodiment of the present invention, the angle of the wedge formed by the polydimethylsiloxane material used in the two-way ice template method is 10 to 30 °.
In one embodiment of the present invention, the thermal imidization treatment process includes: carrying out heat treatment for 1-4 h at 25-300 ℃ in an inert atmosphere; the inert atmosphere is any one of nitrogen, helium or argon.
In one embodiment of the present invention, the heat treatment procedure of the thermal imidization treatment process is preferably 80-120 ℃ for 1-3 hours, 180-220 ℃ for 1-3 hours, 280-320 ℃ for 1-3 hours, and most preferably 100 ℃ for 1 hour, 200 ℃ for 1 hour, and 300 ℃ for 1 hour.
The invention also provides the graphene/polyimide composite foam wave-absorbing material with the oriented pore structure prepared by the method.
Moreover, the invention also provides electronic equipment, military equipment and precise electronic instruments which contain the graphene/polyimide composite foam wave-absorbing material.
Finally, the invention provides the application of the preparation method or the graphene/polyimide composite foam wave-absorbing material in the fields of aerospace, military equipment, civil electric appliances and magnetic protection.
The invention has the beneficial effects that:
(1) the invention adopts a bidirectional ice template technology to successfully prepare the graphene/polyimide composite foam wave-absorbing material with the oriented pore structure, and can be used for the application of wide-frequency strong microwave absorption;
(2) according to the impedance matching principle in the electromagnetic wave absorption theory, the surface impedance matching of the composite foam wave-absorbing material is improved by introducing the high-impedance polyimide component, so that more electromagnetic waves are made to enter the material, and the attenuation and dissipation of the electromagnetic waves in the material are realized;
(3) under the influence of the oriented laminated pore structure in the material, on one hand, the graphene/polyimide composite foam with the oriented pore structure generates multiple reflection and scattering to a greater extent between the laminated pore structures in the material after electromagnetic waves enter the material, and on the other hand, increases the propagation path of the electromagnetic waves after entering the material, thereby realizing the maximum energy attenuation and dissipation of the incident electromagnetic waves between the laminated pore structures.
(4) The introduction of the polyimide can improve the mechanical strength of the composite foam on one hand; on the other hand, the problem of material surface impedance mismatch caused by high conductivity of the graphene material is solved, more electromagnetic waves are promoted to be incident into the material, and therefore the electromagnetic waves are attenuated and dissipated in the material. Under the influence of the oriented layered pore structure in the material, on one hand, after the electromagnetic wave is incident to the material, multiple reflection and scattering occur to a greater extent between the layered pore structures in the material, and on the other hand, the propagation path of the electromagnetic wave after entering the material is increased, so that the maximum energy attenuation and dissipation of the incident electromagnetic wave between the layered pore structures are realized.
Drawings
FIG. 1 is a representation of the micro-morphology of the wave-absorbing material in examples 1-2: (a) a top view cross-section of a unidirectional graphene/polyimide syntactic foam; (b) a top cross-sectional view of a bi-directional graphene/polyimide syntactic foam. .
Fig. 2 is a wave-absorbing effect diagram of the unidirectional graphene/polyimide composite foam prepared in example 2: (a) a three-dimensional reflection loss map; (b) the effective absorption bandwidth map.
FIG. 3 is a wave-absorbing effect diagram parallel to the direction of the oriented lamellar pore structure in example 1: (a) a three-dimensional reflection loss map; (b) the effective absorption bandwidth map.
FIG. 4 is a wave-absorbing effect diagram perpendicular to the direction of the oriented lamellar pore structure in example 1: (a) a three-dimensional reflection loss map; (b) the effective absorption bandwidth map.
Detailed Description
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.
The method for measuring the electromagnetic wave absorbing performance of the graphene/polyimide composite foam comprises the following steps: and measuring the electromagnetic parameters of the wave-absorbing material by using an Agilent 8720ET vector network analyzer in a frequency range of 0.5-18 GHz through a coaxial line method.
The method for characterizing the internal micro-morphology of the graphene/polyimide composite foam comprises the following steps: the microscopic morphology of the wave-absorbing material is observed and researched by using a field emission scanning electron microscope (Hitachi S-4800) under the voltage of 5 kV.
Example 1
(1) Preparing graphene oxide: adding 2g of 325-mesh crystalline flake graphite, 240mL of concentrated sulfuric acid and 27mL of concentrated phosphoric acid into a 500mL three-neck flask, mechanically stirring for 30min, slowly adding 12g of potassium permanganate, controlling the temperature in a water bath to be 50 ℃, continuously stirring at a constant speed for 12h, slowly pouring the mixed solution into a beaker containing 400mL of deionized water after the reaction is finished, and uniformly stirring with a glass rod. Aqueous hydrogen peroxide was added dropwise to the mixture, and stirred until the solution became golden yellow, and left to stand overnight. Centrifuging the mixed solution to remove residual acid, metal ions and the like in the mixed solution; and then respectively adopting a dilute HCl solution and deionized water to wash for multiple times until the pH value is close to 5-6, and carrying out vacuum freeze drying on the obtained graphene oxide for later use.
(2) Preparation of Water-soluble Polyamic acid: n, N '-dimethylacetamide is used as a solvent, and a polyamic acid solution with the solid content of 15% is prepared by condensation polymerization reaction of 4, 4' -diaminodiphenyl ether and pyromellitic dianhydride in an equal molar ratio in an ice-water bath. The specific process is as follows: 8.0096g of 4,4 '-diaminodiphenyl ether is dissolved in 95.57g N, N' -dimethylacetamide, 8.7248g of pyromellitic dianhydride is added, and the mixture reacts for 5 hours in an ice-water bath. Then, 4.0476g of triethylamine is added into the mixture, and the mixture is reacted for 5 hours to prepare a water-soluble polyamic acid solution with the solid content of 15 percent; precipitating the prepared water-soluble polyamic acid by using deionized water, precipitating the prepared water-soluble polyamic acid in the deionized water by flowing the prepared water-soluble polyamic acid, and finally performing vacuum freeze drying (the temperature is minus 80 ℃, and the vacuum degree is below 10 Pa) to obtain the water-soluble polyamic acid for later use.
(3) Preparing a bidirectional freezing mold: a square copper sheet (with the side length of 2cm and the thickness of 1mm) is used as a freezing surface, a silica gel square tube (with the inner side length of 2cm and the height of 2cm) is stuck on the copper sheet, the copper sheet is placed on an inclined platform with the gradient of 15 degrees, then a dimethyl siloxane (PDMS) precursor solution is poured until the whole surface of the copper sheet is just covered, and then the two-way freezing mold is obtained by curing at the temperature of 80 ℃ for 2 hours.
(4) Preparing graphene/polyimide composite foam: and (3) uniformly compounding the graphene oxide obtained in the step (1), the polyamic acid obtained in the step (2) and triethylamine according to the concentration ratio of 2:2: 1. The specific operation is as follows: preparing a graphene oxide dispersion liquid with the concentration of 10mg/mL under an ultrasonic condition; preparing a polyamic acid/triethylamine aqueous solution with the polyamic acid concentration of 10mg/mL and the concentration ratio of the polyamic acid to the triethylamine of 2:1 in ultrapure water; and mixing the graphene oxide dispersion liquid and the polyamic acid/triethylamine aqueous solution under magnetic stirring to obtain the graphene oxide/polyamic acid composite liquid. Pouring the graphene oxide/polyamide acid composite foam into a bidirectional freezing mold, freezing for 6 hours at the temperature of-70 ℃, and then carrying out vacuum freeze drying (the vacuum degree is 0.1-2 Pa, and the drying time is 72 hours) to obtain the graphene oxide/polyamide acid composite foam. And then carrying out heat treatment on the graphene oxide/polyamic acid composite foam in a nitrogen atmosphere, wherein the heat treatment procedures are as follows in sequence: and finally obtaining the graphene/polyimide composite foam material with the oriented pore structure at 100 ℃ for 1h, 200 ℃ for 1h and 300 ℃ for 1h, and naming the graphene/polyimide composite foam material as rGO/PI.
Example 2
Preparing a one-way freezing mold: a square copper sheet (with the side length of 2cm and the thickness of 1mm) is used as a freezing surface, and a silica gel square tube (with the inner side length of 2cm and the height of 2cm) is stuck on the copper sheet, so that the unidirectional freezing mold can be obtained.
The present embodiment is different from embodiment 1 in that: and (3) pouring the graphene oxide and polyamic acid composite solution obtained in the step (4) in the embodiment 1 into a one-way freezing mold, and performing the same low-temperature freezing process (-70 ℃, 6h) and vacuum freeze drying (the vacuum degree is 0.1-2 Pa, and the drying time is 72h) to obtain the graphene oxide/polyamic acid composite foam. And then carrying out heat treatment on the composite foam material under the nitrogen atmosphere (100 ℃ for 1 h; 200 ℃ for 1 h; 300 ℃ for 1h) to finally obtain the unidirectional graphene/polyimide composite foam material.
Micro-morphology characterization and microwave absorption performance test
The composite foams prepared in examples 1-2 were subjected to microscopic morphology characterization and microwave absorption performance tests, and the results are shown in FIGS. 1-4.
FIG. 1 is a representation of the microscopic morphology of the syntactic foam of examples 1-2: (a) a top view cross-section of a unidirectional graphene/polyimide syntactic foam; (b) a top cross-sectional view of a bi-directional graphene/polyimide syntactic foam. As shown in fig. 1(a), the cross-sectional microstructure of the unidirectional graphene/polyimide composite foam in a plan view is an isotropic porous structure, and has a honeycomb-like shape and a pore size of about 50 μm. However, the internal microstructure of the graphene/polyimide composite foam prepared by the bidirectional ice template method is an oriented layered structure, and shows obvious anisotropy, and the distance between lamellar pores is about 50 μm, so that the result proves the effectiveness of the bidirectional freezing method for successfully constructing the oriented layered pore structure.
Fig. 2 is a wave-absorbing effect diagram of the unidirectional graphene/polyimide composite foam prepared in example 2: (a) a three-dimensional reflection loss map; (b) the effective absorption bandwidth map. Freezing with a one-way freezing mold at-70 deg.C for 6 h; the addition concentration of the graphene oxide and the water-soluble polyamic acid is 10mg/mL, and the unidirectional graphene/polyimide composite foam material prepared by the method is 10mg/mL, and has weaker microwave absorption strength. As shown in FIG. 2(a), when the sample thickness is 5.00mm and the frequency is 10.48GHz, the minimum value RL of the microwave reflection loss of the sample isminOnly-9.37 dB.
FIG. 3 shows example 1The wave-absorbing effect chart in the direction parallel to the oriented laminar pore structure: (a) a three-dimensional reflection loss map; (b) the effective absorption bandwidth map. Freezing with a bidirectional freezing mold at-70 deg.C for 6 h; the addition concentration of the graphene oxide and the water-soluble polyamic acid is 10mg/mL, and the bidirectional graphene/polyimide composite foam material prepared by 10mg/mL has weaker microwave absorption intensity in a direction parallel to the orientation pore structure. As shown in FIG. 3(a), when the sample thickness is 1.8mm and the frequency is 16.25GHz, the minimum value RL of the microwave reflection loss of the sample isminAt-8.48 dB, which also confirms that the attenuation of the incident electromagnetic wave parallel to the direction of the laminar pore structure is ineffective.
FIG. 4 is a wave-absorbing effect diagram perpendicular to the direction of the oriented lamellar pore structure in example 1: (a) a three-dimensional reflection loss map; (b) the effective absorption bandwidth map. Freezing with a one-way freezing mold at-70 deg.C for 6 h; the addition concentration of the graphene oxide and the water-soluble polyamic acid is 10mg/mL, and the unidirectional graphene/polyimide composite foam material prepared by 10mg/mL has the maximum microwave absorption intensity and the effective absorption bandwidth in the direction perpendicular to the oriented laminar pore structure. As shown in FIG. 4(a), when the sample thickness is 4.75mm and the frequency is 9.25GHz, the minimum value RL of the microwave reflection loss of the sample isminReaching-61.29 dB; at this time, the effective absorption bandwidth reaches 5.51GHz (7.06-12.57 GHz). In addition, as can be seen from fig. 4(b), the maximum effective absorption bandwidth of the sample can reach 5.86GHz (9.25-15.11 GHz) at a sample thickness of 3.84mm, covering X and Ku bands. As described above, the great improvement of the microwave absorption performance of the bidirectional graphene/polyimide composite foam can be attributed to the reasonable construction of the oriented layered pore structure in the material, which can effectively promote the electromagnetic wave to generate a greater degree of multiple reflection and scattering between the layered pore structures after being incident into the material perpendicular to the oriented layered pore structure, and meanwhile, the successful construction of the oriented layered pore structure can also increase the propagation path of the electromagnetic wave after entering the material, thereby realizing the maximum layer-by-layer energy attenuation and dissipation of the incident electromagnetic wave between the layered pore structures.
Example 3
This example is different from example 1 inCharacterized in that: and (3) uniformly compounding the graphene oxide obtained in the step (1), the polyamic acid obtained in the step (2) and triethylamine according to the concentration ratio of 1:2: 1. The specific operation is as follows: preparing a graphene oxide dispersion liquid with the concentration of 10mg/mL under an ultrasonic condition; preparing a polyamic acid/triethylamine aqueous solution with the concentration of the polyamic acid being 20mg/ml and the concentration ratio of the polyamic acid to the triethylamine being 2:1 in ultrapure water; and mixing the graphene oxide dispersion liquid and the polyamic acid/triethylamine aqueous solution under magnetic stirring to obtain the graphene oxide/polyamic acid composite liquid. Pouring the composite foam into a bidirectional freezing mold, and performing low-temperature freezing process (-70 ℃, 6h) and vacuum freeze drying (the vacuum degree is 0.1-2 Pa, and the drying time is 72h) to obtain the graphene oxide/polyamide acid composite foam. And then carrying out heat treatment on the graphene oxide/polyamic acid composite foam in a nitrogen atmosphere, wherein the heat treatment procedures are as follows in sequence: and (3) obtaining the graphene/polyimide composite foam material at 100 ℃ for 1h, 200 ℃ for 1h and 300 ℃ for 1 h. Minimum value RL of reflection loss of the composite foam when the thickness is 4.99mm and the frequency is 8.725GHzminIs-35.91 dB, corresponding effective absorption bandwidth (RL)<-10dB) is 5.25GHz (6.80-12.05 GHz).
Example 4
The present embodiment is different from embodiment 1 in that: and uniformly compounding the graphene oxide, the polyamide acid and the triethylamine according to the concentration ratio of 2:1: 0.5. The specific operation is as follows: preparing a graphene oxide dispersion liquid with the concentration of 10mg/mL under an ultrasonic condition; preparing a polyamic acid/triethylamine aqueous solution with the polyamic acid concentration of 5mg/ml and the concentration ratio of the polyamic acid to the triethylamine of 2:1 in ultrapure water; and mixing the graphene oxide dispersion liquid and the polyamic acid/triethylamine aqueous solution under magnetic stirring to obtain the graphene oxide/polyamic acid composite liquid. Pouring the composite foam into a bidirectional freezing mold, and performing the same low-temperature freezing process (-70 ℃, 6h) and vacuum freeze drying (the vacuum degree is 0.1-2 Pa, and the drying time is 72h) to obtain the graphene oxide/polyamic acid composite foam. And then carrying out heat treatment on the composite material in a nitrogen atmosphere (100 ℃ for 1h, 200 ℃ for 1h, 300 ℃ for 1h) to finally obtain the graphene/polyimide composite foam material. Reflection loss of the syntactic foam at a thickness of 5mm and a frequency of 11.0GHzMinimum value RLminIs-10.38 dB, corresponding effective absorption bandwidth (RL)<-10dB) is 1.40GHz (10.21-11.61 GHz).
Example 5
The present embodiment is different from embodiment 1 in that: and (3) pouring the graphene oxide/polyamic acid composite liquid obtained in the step (4) into a bidirectional freezing mold, and performing low-temperature freezing process (-50 ℃, 6h) and vacuum freeze drying (the vacuum degree is 0.1-2 Pa, and the drying time is 72h) to obtain the graphene oxide/polyamic acid composite foam. And then carrying out heat treatment on the graphene oxide/polyamic acid composite foam in a nitrogen atmosphere, wherein the heat treatment procedures are as follows in sequence: and (3) obtaining the graphene/polyimide composite foam material at 100 ℃ for 1h, 200 ℃ for 1h and 300 ℃ for 1 h. Minimum value RL of reflection loss of the composite foam when the thickness is 5mm and the frequency is 9.43GHzminIs-18.45 dB, corresponding effective absorption bandwidth (RL)<-10dB) is 4.92GHz (7.49-12.41 GHz).
Example 6
The present embodiment is different from embodiment 1 in that: and pouring the graphene oxide/polyamide acid composite liquid into a bidirectional freezing mold, and performing low-temperature freezing process (-90 ℃, 6h) and vacuum freeze drying (the vacuum degree is 0.1-2 Pa, and the drying time is 72h) to obtain the graphene oxide/polyamide acid composite foam. And then carrying out heat treatment on the graphene oxide/polyamic acid composite foam in a nitrogen atmosphere, wherein the heat treatment procedures are as follows in sequence: and (3) obtaining the graphene/polyimide composite foam material at 100 ℃ for 1h, 200 ℃ for 1h and 300 ℃ for 1 h. Minimum value RL of reflection loss of the composite foam when the thickness is 5mm and the frequency is 8.81GHzminIs-26.16 dB, corresponding effective absorption bandwidth (RL)<-10dB) is 4.98GHz (6.80-11.78 GHz).
Example 7
The present embodiment is different from embodiment 1 in that: preparing a graphene oxide dispersion liquid with the concentration of 5mg/mL under an ultrasonic condition; preparing a polyamic acid/triethylamine aqueous solution with the polyamic acid concentration of 5mg/ml and the concentration ratio of the polyamic acid to the triethylamine of 2:1 in ultrapure water; mixing the graphene oxide dispersion liquid and the polyamic acid/triethylamine aqueous solution under magnetic stirring to obtain the graphene oxide/polyamic acid compositeAnd (4) mixing the liquid. Pouring the composite foam into a bidirectional freezing mold, and performing the same low-temperature freezing process (-70 ℃, 6h) and vacuum freeze drying (the vacuum degree is 0.1-2 Pa, and the drying time is 72h) to obtain the graphene oxide/polyamic acid composite foam. And then carrying out heat treatment on the composite material in a nitrogen atmosphere (100 ℃ for 1h, 200 ℃ for 1h, 300 ℃ for 1h) to finally obtain the graphene/polyimide composite foam material. Minimum value RL of reflection loss of the composite foam when the thickness is 3.34mm and the frequency is 17.74GHzminIs-11.99 dB, corresponding effective absorption bandwidth (RL)<-10dB) is 0.61GHz (17.39-18.00 GHz).
Example 8
The present embodiment is different from embodiment 1 in that: preparing a graphene oxide dispersion liquid with the concentration of 20mg/mL under an ultrasonic condition; preparing a polyamic acid/triethylamine aqueous solution with the concentration of the polyamic acid being 20mg/ml and the concentration ratio of the polyamic acid to the triethylamine being 2:1 in ultrapure water; and mixing the graphene oxide dispersion liquid and the polyamic acid/triethylamine aqueous solution under magnetic stirring to obtain the graphene oxide/polyamic acid composite liquid. Pouring the composite foam into a bidirectional freezing mold, and performing the same low-temperature freezing process (-70 ℃, 6h) and vacuum freeze drying (the vacuum degree is 0.1-2 Pa, and the drying time is 72h) to obtain the graphene oxide/polyamic acid composite foam. And then carrying out heat treatment on the composite material in a nitrogen atmosphere (100 ℃ for 1h, 200 ℃ for 1h, 300 ℃ for 1h) to finally obtain the graphene/polyimide composite foam material. Minimum value of reflection loss RL of the syntactic foam when the thickness is 2.23mm and the frequency is 18.0GHzminIs-28.40 dB, corresponding effective absorption bandwidth (RL)<-10dB) is 3.41GHz (14.59-18.00 GHz).
Comparative example 1
This comparative example differs from example 1 in that: graphene oxide obtained in the step (1) in example 1 is placed in ultrapure water to prepare a graphene oxide dispersion liquid with a concentration of 10mg/mL under an ultrasonic condition, the graphene oxide dispersion liquid is poured into a bidirectional freezing mold, and graphene oxide foam is obtained through the same low-temperature freezing process (-70 ℃, 6h) and vacuum freeze drying (the vacuum degree is 0.1-2 Pa, and the drying time is 72 h). Then heat treating at 100 deg.C for 1h, 200 deg.C for 1h, 300 deg.C for 1h under nitrogen atmosphere to obtain final productA raw graphene oxide foam material. Minimum value of reflection loss RL of the foam when the thickness is 5mm and the frequency is 10.74GHzminIs-5.40 dB, corresponding effective absorption bandwidth (RL)<-10dB) is 0.
Comparative example 2
This comparative example differs from example 1 in that: the water-soluble polyamic acid obtained in step (2) in example 1 and triethylamine were mixed at a concentration ratio of 2:1 to prepare an aqueous solution. The specific operation is as follows: preparing a polyamic acid/triethylamine aqueous solution with the polyamic acid concentration of 10mg/mL and the concentration ratio of the polyamic acid to the triethylamine of 2:1 in ultrapure water, pouring the polyamic acid/triethylamine aqueous solution into a two-way freezing mold, and performing the same low-temperature freezing process (-70 ℃, 6h) and vacuum freeze drying (the vacuum degree is 0.1-2 Pa, and the drying time is 72h) to obtain the polyamic acid foam. Then, the mixture is subjected to heat treatment under the nitrogen atmosphere, and the heat treatment procedures are as follows: 1h at 100 ℃, 1h at 200 ℃ and 1h at 300 ℃ to finally obtain the polyimide foam material. Minimum value of reflection loss RL of the foam when the thickness is 3.8mm and the frequency is 16.51GHzminIs-1.96 dB, corresponding effective absorption bandwidth (RL)<-10dB) is 0.
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (10)

1. A preparation method of a graphene/polyimide composite foam wave-absorbing material with an oriented pore structure is characterized by comprising the following steps: preparing a graphene oxide dispersion liquid with a certain concentration under an ultrasonic condition; preparing a polyamic acid/triethylamine aqueous solution in ultrapure water; mixing the graphene oxide dispersion liquid and the polyamic acid/triethylamine aqueous solution under magnetic stirring to obtain a graphene oxide/polyamic acid composite liquid, and obtaining graphene oxide/polyamic acid composite foam through a sol-gel method, a two-way ice template method and a freeze drying process; and then carrying out thermal imidization treatment on the graphene oxide/polyamide acid composite foam in an inert atmosphere to obtain the graphene/polyimide composite foam wave-absorbing material.
2. The method according to claim 1, wherein the mass ratio (concentration ratio) of the graphene oxide, the water-soluble polyamic acid, and the triethylamine is (0-20 mg/mL): (0-40 mg/mL): 0-20 mg/mL), and the three are not 0 at the same time.
3. The preparation method according to claim 1, wherein the sol-gel method, the two-way ice template method and the vacuum freeze-drying comprise: pouring the composite liquid into a bidirectional freezing mould, wherein the sol-gel time is 12-15 h, and then carrying out vacuum freeze drying, wherein the freezing temperature is-50 to-120 ℃, and the freezing time is 6-8 h; the vacuum degree is 0.1-2 Pa, and the drying time is 72-96 h.
4. The preparation method according to claim 3, wherein the angle of the wedge shape in the bidirectional ice template method is in the range of 10-30 °.
5. The method according to claim 1, wherein the thermal imidization treatment process includes: carrying out heat treatment for 1-4 h at 25-300 ℃ in an inert atmosphere; the inert atmosphere is any one of nitrogen, helium or argon.
6. The method according to claim 5, wherein the thermal imidization treatment process comprises a thermal treatment procedure of 80-120 ℃ for 1-3 hours, 180-220 ℃ for 1-3 hours, and 280-320 ℃ for 1-3 hours.
7. The method according to any one of claims 1 to 6, wherein the water-soluble polyamic acid is prepared by: firstly, dissolving a diamine monomer in a polar solvent, then adding a dicarboxylic anhydride monomer, carrying out polymerization reaction in an ice-water bath, then adding organic amine, and continuing the reaction to obtain a water-soluble polyamic acid sol; solvent exchange and freeze drying to obtain water soluble polyamic acid.
8. The graphene/polyimide composite foam wave-absorbing material with the oriented pore structure, which is prepared according to any one of claims 1 to 7.
9. Electronic equipment, military equipment and precise electronic instruments containing the graphene/polyimide composite foam wave-absorbing material with the oriented pore structure as claimed in claim 8.
10. The graphene/polyimide composite foam wave-absorbing material with the oriented pore structure in claim 8 is applied to the fields of aerospace, military equipment, civil electric appliances and magnetic protection.
CN202110615275.6A 2021-06-02 2021-06-02 Graphene/polyimide composite foam wave-absorbing material with oriented pore structure and preparation method thereof Active CN113321844B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202110615275.6A CN113321844B (en) 2021-06-02 2021-06-02 Graphene/polyimide composite foam wave-absorbing material with oriented pore structure and preparation method thereof

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202110615275.6A CN113321844B (en) 2021-06-02 2021-06-02 Graphene/polyimide composite foam wave-absorbing material with oriented pore structure and preparation method thereof

Publications (2)

Publication Number Publication Date
CN113321844A true CN113321844A (en) 2021-08-31
CN113321844B CN113321844B (en) 2023-01-31

Family

ID=77421452

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202110615275.6A Active CN113321844B (en) 2021-06-02 2021-06-02 Graphene/polyimide composite foam wave-absorbing material with oriented pore structure and preparation method thereof

Country Status (1)

Country Link
CN (1) CN113321844B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116515163A (en) * 2023-05-06 2023-08-01 四川大学 Structure/wave absorbing integrated composite material prepared by in-situ foaming filling aramid fiber honeycomb and application thereof

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120328785A1 (en) * 2010-04-02 2012-12-27 Pusan National University Industry-University Cooperation Foundation Polyimide nanocomposite and method for preparing same
CN109912833A (en) * 2019-02-11 2019-06-21 东华大学 A kind of polyimide aerogels and preparation method thereof
CN110818945A (en) * 2019-12-03 2020-02-21 四川大学 Polyimide/graphene composite aerogel with ordered pore structure and preparation method and application thereof

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120328785A1 (en) * 2010-04-02 2012-12-27 Pusan National University Industry-University Cooperation Foundation Polyimide nanocomposite and method for preparing same
CN109912833A (en) * 2019-02-11 2019-06-21 东华大学 A kind of polyimide aerogels and preparation method thereof
CN110818945A (en) * 2019-12-03 2020-02-21 四川大学 Polyimide/graphene composite aerogel with ordered pore structure and preparation method and application thereof

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
杨苗: "冰模板法制备长程有序多孔材料", 《中国优秀博硕士学位论文全文数据库(硕士) 工程科技I辑》 *
石安富等: "《工程塑料手册》", 31 March 2003, 上海科学技术出版社 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116515163A (en) * 2023-05-06 2023-08-01 四川大学 Structure/wave absorbing integrated composite material prepared by in-situ foaming filling aramid fiber honeycomb and application thereof

Also Published As

Publication number Publication date
CN113321844B (en) 2023-01-31

Similar Documents

Publication Publication Date Title
Zhou et al. Comparison in dielectric and microwave absorption properties of SiC coated carbon fibers with PyC and BN interphases
CN111548529B (en) Polyimide-based graphene composite foam material with multilevel structure and preparation method thereof
Wu et al. A self-assembly method for the fabrication of a three-dimensional (3D) polypyrrole (PPy)/poly (3, 4-ethylenedioxythiophene)(PEDOT) hybrid composite with excellent absorption performance against electromagnetic pollution
CN110818945A (en) Polyimide/graphene composite aerogel with ordered pore structure and preparation method and application thereof
CN112047386A (en) Heating modified MXene/ferroferric oxide composite wave-absorbing material and preparation method thereof
Hutagalung et al. Effect of MnO2 additive on the dielectric and electromagnetic interference shielding properties of sintered cement-based ceramics
CN113321844B (en) Graphene/polyimide composite foam wave-absorbing material with oriented pore structure and preparation method thereof
CN113088077B (en) Polyimide/multi-walled carbon nanotube composite aerogel and preparation method and application thereof
CN114832741B (en) Preparation method of heat-conducting wave-absorbing composite aerogel and heat-conducting wave-absorbing composite aerogel
CN114920978B (en) Preparation method of aerogel with electromagnetic shielding and sound absorption functions
Ma et al. Multifunctional and magnetic MXene composite aerogels for electromagnetic interference shielding with low reflectivity
CN114568009A (en) Fe-MOF derived graphene-based magnetic composite aerogel wave-absorbing material and preparation method thereof
CN112265982A (en) Preparation method of N-doped graphene/graphene nanoribbon composite aerogel
CN115915738A (en) HOF-derived one-dimensional Ni-doped magnetic carbon-based nano composite material and preparation method thereof
Guo et al. Biomass-based electromagnetic wave absorption materials with unique structures: a critical review
CN108530100B (en) Carbon-based wave absorption film and preparation method thereof
CN114071982A (en) Honeycomb reduced graphene oxide foam/nickel nanoparticle wave absorbing agent and preparation method thereof
CN109971420B (en) Preparation method and application of one-dimensional zirconium dioxide/carbon nanotube nano composite material
CN112094426B (en) Impedance gradual change type graphene-based polyimide composite foam wave-absorbing material
CN112646372A (en) Polyimide film with low dielectric constant and application thereof
CN111302324A (en) Magnetic microporous carbon-based wave-absorbing composite material and preparation method thereof
Kim et al. Highly omnidirectional and frequency tunable multilayer graphene-based monopole patch antennas
CN115650286A (en) rGO/MXene/TiO 2 /Fe 2 Preparation method of C multi-stage heterostructure porous microsphere wave-absorbing material
CN112911915B (en) Corrosion-resistant graphene-based magnetic composite foam wave-absorbing material and preparation method thereof
CN115920790B (en) Preparation method of multifunctional nitrogen-doped carbon aerogel

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant