AU2020102143A4 - Preparation method of graphene polyimide composite sponge precursor-based thermal-conductive film - Google Patents
Preparation method of graphene polyimide composite sponge precursor-based thermal-conductive film Download PDFInfo
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 348
- 229910021389 graphene Inorganic materials 0.000 title claims abstract description 315
- 239000004642 Polyimide Substances 0.000 title claims abstract description 156
- 229920001721 polyimide Polymers 0.000 title claims abstract description 156
- 239000002131 composite material Substances 0.000 title claims abstract description 117
- 239000002243 precursor Substances 0.000 title claims abstract description 87
- 238000002360 preparation method Methods 0.000 title claims abstract description 26
- 229920005575 poly(amic acid) Polymers 0.000 claims abstract description 131
- 238000010438 heat treatment Methods 0.000 claims abstract description 76
- 239000000243 solution Substances 0.000 claims abstract description 64
- 238000000034 method Methods 0.000 claims abstract description 49
- 239000011259 mixed solution Substances 0.000 claims abstract description 42
- 239000007864 aqueous solution Substances 0.000 claims abstract description 37
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 32
- 238000007731 hot pressing Methods 0.000 claims abstract description 32
- 238000000137 annealing Methods 0.000 claims abstract description 17
- 230000003647 oxidation Effects 0.000 claims abstract description 16
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 16
- 238000001035 drying Methods 0.000 claims abstract description 12
- 238000005087 graphitization Methods 0.000 claims abstract description 12
- 238000004108 freeze drying Methods 0.000 claims abstract description 11
- 238000007710 freezing Methods 0.000 claims abstract description 4
- 230000008014 freezing Effects 0.000 claims abstract description 4
- 238000002156 mixing Methods 0.000 claims abstract description 4
- ZMANZCXQSJIPKH-UHFFFAOYSA-N Triethylamine Chemical compound CCN(CC)CC ZMANZCXQSJIPKH-UHFFFAOYSA-N 0.000 claims description 48
- VLDPXPPHXDGHEW-UHFFFAOYSA-N 1-chloro-2-dichlorophosphoryloxybenzene Chemical compound ClC1=CC=CC=C1OP(Cl)(Cl)=O VLDPXPPHXDGHEW-UHFFFAOYSA-N 0.000 claims description 22
- 238000003756 stirring Methods 0.000 claims description 15
- HLBLWEWZXPIGSM-UHFFFAOYSA-N 4-Aminophenyl ether Chemical compound C1=CC(N)=CC=C1OC1=CC=C(N)C=C1 HLBLWEWZXPIGSM-UHFFFAOYSA-N 0.000 claims description 10
- 150000004985 diamines Chemical class 0.000 claims description 10
- 239000000178 monomer Substances 0.000 claims description 10
- 239000007787 solid Substances 0.000 claims description 10
- 239000002798 polar solvent Substances 0.000 claims description 9
- 238000004140 cleaning Methods 0.000 claims description 8
- 238000001914 filtration Methods 0.000 claims description 8
- 230000009467 reduction Effects 0.000 claims description 6
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- 238000002203 pretreatment Methods 0.000 claims description 3
- 238000005406 washing Methods 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 claims description 2
- 239000006185 dispersion Substances 0.000 abstract description 5
- 239000002253 acid Substances 0.000 abstract description 4
- 238000003763 carbonization Methods 0.000 abstract description 2
- 238000011065 in-situ storage Methods 0.000 abstract description 2
- 238000006116 polymerization reaction Methods 0.000 abstract description 2
- 239000008367 deionised water Substances 0.000 description 25
- 229910021641 deionized water Inorganic materials 0.000 description 25
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 25
- 238000001816 cooling Methods 0.000 description 24
- 230000008569 process Effects 0.000 description 16
- 239000002002 slurry Substances 0.000 description 14
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical group CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 description 13
- 230000006872 improvement Effects 0.000 description 13
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 12
- 239000000843 powder Substances 0.000 description 12
- 239000007788 liquid Substances 0.000 description 7
- 238000009210 therapy by ultrasound Methods 0.000 description 7
- 239000000835 fiber Substances 0.000 description 6
- 229910052757 nitrogen Inorganic materials 0.000 description 6
- 238000006068 polycondensation reaction Methods 0.000 description 6
- 239000002244 precipitate Substances 0.000 description 6
- 239000011343 solid material Substances 0.000 description 6
- 230000007123 defense Effects 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 229920000642 polymer Polymers 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 230000003993 interaction Effects 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 238000005452 bending Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 125000000524 functional group Chemical group 0.000 description 2
- 230000017525 heat dissipation Effects 0.000 description 2
- 125000005462 imide group Chemical group 0.000 description 2
- 239000012774 insulation material Substances 0.000 description 2
- 230000010354 integration Effects 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- XMWRBQBLMFGWIX-UHFFFAOYSA-N C60 fullerene Chemical compound C12=C3C(C4=C56)=C7C8=C5C5=C9C%10=C6C6=C4C1=C1C4=C6C6=C%10C%10=C9C9=C%11C5=C8C5=C8C7=C3C3=C7C2=C1C1=C2C4=C6C4=C%10C6=C9C9=C%11C5=C5C8=C3C3=C7C1=C1C2=C4C6=C2C9=C5C3=C12 XMWRBQBLMFGWIX-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910021393 carbon nanotube Inorganic materials 0.000 description 1
- 239000002041 carbon nanotube Substances 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000007385 chemical modification Methods 0.000 description 1
- 230000021615 conjugation Effects 0.000 description 1
- 239000003431 cross linking reagent Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000003989 dielectric material Substances 0.000 description 1
- 229920006351 engineering plastic Polymers 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
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- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
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- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
- C04B35/52—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite
- C04B35/522—Graphite
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- C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
- C04B35/52—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite
- C04B35/524—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite obtained from polymer precursors, e.g. glass-like carbon material
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Abstract
The present application discloses a preparation method of a graphene polyimide composite
sponge precursor-based thermal-conductive film, including the steps of: mixing a graphene oxide
aqueous solution with a polyimide precursor solution to obtain a graphene oxide/polyamic acid
mixed solution, and freezing the graphene oxide/polyamic acid mixed solution to obtain a
graphene oxide/polyamic acid frozen sponge, drying by a freeze-drying method to obtain a
graphene oxide/polyamic acid composite sponge, placing the graphene oxide/polyamic acid
composite sponge in a resistance vacuum hot-pressing furnace, performing hot-pressing oxidation
pretreatment and mechanical pressurization to obtain a reduced graphene oxide/polyimide
composite film; and then performing vacuum thermal annealing and mechanical pressurization to
obtain a graphene/polyimide carbon film, placing in a high-temperature graphitization furnace,
and graphitizing the carbon film by adopting a gradient heating method. By adopting the technical
solution of the present application, the dispersion of graphene is improved; and the obtained film
has certain flexibility, high mechanical strength, better electrical and thermal conductivities, and
the preparation process is simple.
Drawings
icecrystals
graphene oxide/ polyamic
in-situ polymerization method acid mixed solution
cold sources
freeze-drying method
graphene oxide/ polyamic highly-oriented graphene
acid mixed solution oxide/polyamic acid composite sponge
oStres
Stress
graphitization treatment
hot-pressing oxidation pretreatment
hot-pressing oxidation
carbonization treatment
FIG.1
FIG.2
Description
Drawings
icecrystals
graphene oxide/ polyamic in-situ polymerization method acid mixed solution
cold sources freeze-drying method
graphene oxide/ polyamic highly-oriented graphene acid mixed solution oxide/polyamic acid composite sponge
Stress oStres
graphitization treatment
hot-pressing oxidation pretreatment
hot-pressing oxidation carbonization treatment
FIG.1
FIG.2
Editorial Note 2020102143 There is only eighteen pages of the description
Description
Technical Field
[0001] The present application relates to the technical field of composite materials, and particularly relates to a preparation method of a graphene polyimide composite sponge precursor-based thermal-conductive film.
Background Art
[0002] Nowadays, with the progress of science and technology, the development of lightweight and high electronic integration of modem military equipment is facing increasingly severe thermal management challenges. For example, the high integration of large-scale high-power electronic components in electronic weapons, ultra-high-speed aircrafts, remote sensing satellites, radars and the like will cause serious heat concentration problems, which has a fatal threat to the operating stability and safety reliability of the key components of military equipment. Meanwhile, the complex thermal interface in highly integrated equipment also puts forward the unique requirement of flexibility for thermal management materials.
[0003] With the discovery of graphene, more and more scientists have focused on this potential emerging material. Graphene, as another stable nano-carbon simple substance following fullerene and carbon nanotubes, is an ideal two-dimensional material, with high electrical and thermal-conductivities. Graphene has great application potential as a novel thermal-conductive film, because it is isotropic, and the thermal conduction in the sheet has no directionality. In addition, the graphene oxide film can be prepared by assembly of reduced graphene oxide, which is an economical and simple preparation process The graphene oxide contains rich oxygen-containing functional groups, and can be uniformly dispersed in an organic solvent and an aqueous solution The graphene oxide serving as a raw material has advantages that the area of the graphene oxide sheet is relatively large and adjustable; the grain boundary scattering of phonons in the transmission process is reduced due to a continuous sheet structure, thereby being beneficial to the improvement of the thermal conductivity; in addition, due to the fact that abundant oxygen-containing functional groups on the graphene oxide sheet can generate hydrogen bonds, large conjugation 7 bonds and other strong interactions, improving the mechanical properties of the graphene film.
[0004] Polyimide (PI), as a special engineering plastic with the advantages such as good molding process ability, high mechanical strength and good heat stability, can be widely used in thermal insulation materials, sound insulation materials, catalyst carriers and dielectric materials. It refers to a class of polymers containing imide rings in the main chain, among which polymers containing imide structures are the most important. In the 1950s, with the rapid development of aviation, aerospace, chemical industry and other fields, people have higher and higher requirements for the strength and thermal resistance of materials. Polyimide has just met this urgent demand and achieved rapid development. Therefore, polyimide is widely used in various fields of the national economy. In addition, the precursor of the polyimide can be converted into an aqueous solution by chemical modification, and is expected to homogeneously compounded with the graphene aqueous dispersion; and after thermal annealing, the obtained graphene polyimide composite film has excellent mechanical properties, but the thermal and electrical conductivities are still poor.
[0005] In summary, although nowadays the graphene thermal-conductive film has entered the market, the complex preparation process and poor mechanical properties cause the graphene film with the near-perfect thermal conductive property at present cannot be widely applied to the field of heat dissipation. Therefore, it is a problem that needs to be addressed urgently to achieve a greater property improvement by obtaining stronger interaction through uniform dispersion of graphene in a polymer and reduction of interface thermal resistance.
Summary of the Invention
[0006] In view of the technical problems, the present application discloses a preparation method of a graphene polyimide composite sponge precursor-based thermal-conductive film, and solves the problems of the existing graphene composite film in terms of mechanical performance, electrical and thermal conductivities.
[0007] Therefore, the technical solution of the present application is as follows: a preparation method of a graphene polyimide composite sponge precursor-based thermal-conductive film includes the steps of: step Si, preparing a graphene oxide aqueous solution; step S2, preparing a polyimide precursor solution; step S3, mixing the graphene oxide aqueous solution with the polyimide precursor solution to obtain a graphene oxide/polyamic acid mixed solution; step S4, freezing the graphene oxide/polyamic acid mixed solution to obtain a graphene oxide/polyamic acid frozen sponge; step S5, drying the graphene oxide/polyamic acid frozen sponge by adopting a freeze-drying method to obtain a graphene oxide/polyamic acid composite sponge; step S6, placing the graphene oxide/polyamic acid composite sponge in a resistance vacuum hot-pressing furnace, and adopting a hot-pressing oxidation pretreatment method to realize the reduction of graphene oxide and the imidization of polyamic acid ; and meanwhile performing mechanical pressurization to obtain a reduced graphene oxide/polyimide composite film; further, a preparation method of the reduced graphene oxide/polyimide composite film in the step S6 is a dimension reduction method;
[0008] step S7, placing the reduced graphene oxide/polyimide composite film in a resistance vacuum hot-pressing furnace, and carbonizing the graphene and polyimide by adopting a vacuum thermal annealing; and meanwhile performing mechanical pressurization to obtain a graphene/polyimide carbon film; and stepS8, placing the graphene/polyimide carbon film in a high-temperature graphitization furnace, and graphitizing the graphene/polyimide carbon film by adopting a gradient heating method to obtain the graphene polyimide composite sponge precursor-based thermal-conductive film.
[0009] By adopting the technical solution of the present application, graphene is uniformly dispersed in the polymer, the interface thermal resistance is reduced, and the obtained film has high thermal and electrical conductivities, and has relatively high tensile strength and certain flexibility.
[0010] As a further improvement of the present application, in the step S3, a concentration of graphene oxide in the graphene oxide aqueous solution is 1-10 mg/mL. Preferably, the concentration of graphene oxide in the graphene oxide aqueous solution is 4-6 mg/mL.
[0011] As a further improvement of the present application, the step S includes: adding deionized water into a graphene oxide slurry, and stirring for 60-120 min at a stirring speed of 100-700 r/min; and performing ultrasonic treatment for 30-60 min at a frequency of 10-100 KHz to obtain the graphene oxide aqueous solution; As a further improvement of the present application, in the step S3, a concentration of polyamic acid in the polyimide precursor solution is 15-20 mg/mL.
[0012] As a further improvement of the present application, in the step S3, a concentration of graphene oxide in the graphene oxide/polyamic acid mixed solution is 10 wt%-90 wt%. Further, the concentration of graphene oxide is preferably from 60 wt% to 90 wt%.
[0013] As a further improvement of the present application, in the step S6 and the step S7, a pressure of the mechanical pressurization is 20 MPa-30 MPa, the pressure is maintained and then the pressure is released until the temperature drops to 200°C.
[0014] As a further improvement of the present application, in the step S6, a thermal annealing temperature of the hot-pressing oxidation pretreatment method is 300°C-350°C, and the temperature is kept constant for 1 h -1.5 h.
[0015] As a further improvement of the present application, in the step S7, a temperature of the vacuum thermal annealing is 900°C-1000°C, and the temperature is kept constant for 2 h -2.5 h.
[0016] As a further improvement of the present application, in the step S8, the conditions of the gradient heating method are as follows: heating to 1200°C at a heating rate of 20°C/min, changing the heating rate to 10°C/min, heating to 2200°C, keeping the temperature constant for 30 min, continuing to heat to 2800°C at a heating rate of 5°C/min, keeping the temperature constant for 120 min, and dropping to a room temperature.
[0017] As a further improvement of the present application, the step S2 includes: dispersing a monomer diamine diaminodiphenyl ether in a polar solvent, and then adding a pyromellitic dianhydride, wherein a molar ratio of the pyromellitic dianhydride to the monomer diamine diaminodiphenyl ether is 100:95-99; stirring to fully react to obtain a polyamic acid (PAA) solution; after the reaction is finished, washing, filtering, cleaning and drying to obtain a solid; and uniformly stirring the solid and a triethylamine (TEA) aqueous solution to obtain a water-soluble polyimide precursor solution. Further, the polar solvent is dimethylacetamide.
[0018] Specifically, the preparation method of the graphene polyimide composite sponge precursor-based thermal-conductive film includes: 1, preparing a graphene oxide aqueous solution: adding deionized water into a graphene oxide slurry, and stirring for 60-120 minat a stirring speed of 100-700 r/min; and performing ultrasonic treatment for 30-60 min at a frequency of -100 KHz to obtain a graphene oxide aqueous solution;
[0019] wherein, the graphene oxide slurry is prepared by adopting a modified Hummers method ; wherein, a concentration of the graphene oxide slurry is 20 mg/mL; the concentration of graphene oxide in the graphene oxide aqueous solution is 1 mg/mL-10 mg/mL, preferably 4 mg/mL-6 mg/mL;
[0020] 2, preparing a polyimide precursor solution: uniformly dispersing a monomer diamine diaminodiphenyl ether (ODA) powder in a polar solvent dimethylacetamide (DMAc) solution by using an electromagnetic stirrer; continuously adding a small amount of pyromellitic dianhydride (PMDA) powder into the mixed solution, stirring for 5 h to fully react to obtain a polyamic acid (PAA) solution; the molar concentration ratio of PMDA to ODA is 100:95-99; after the polycondensation reaction is finished, washing the stirred solution with a large amount of deionized water to obtain yellow precipitate polyamic acid fibers; removing residual deionized water after filtering, cleaning and drying to obtain a solid with a mass fraction of 5%; and taking the solid material corresponding to 1 g of PAA solution, together with 0.48 g of triethylamine (TEA) solution and 18.52 mL of deionized water, and stirring at a room temperature for 6 h to obtain the water-soluble polyimide precursor.
[0021] wherein a concentration of polyamic acid in the polyimide precursor solution is 15-20 mg/mL;
[0022] 3, preparing a graphene oxide/polyamic acid mixed solution: mixing the graphene oxide aqueous solution obtained in the step 1 with the polyimide precursor solution obtained in the step 2, and stirring for 2 h to fully react to obtain graphene oxide/polyamic acid mixed solutions with different concentrations.
[0023] wherein a concentration of graphene oxide in the graphene oxide/polyamic acid mixed solution is 10 wt%-90 wt%, preferably 60wt% -90 wt%;
[0024] 4, preparing a highly-oriented graphene oxide/polyamic acid frozen sponge: directionally freezing the graphene oxide/polyamic acid mixed solution obtained in the step 3 with liquid nitrogen to obtain highly-oriented graphene oxide/polyamic acid frozen sponges with different shapes.
[0025] 5 preparing a highly-oriented graphene oxide/polyamic acid composite sponge: drying the highly-oriented graphene oxide/polyamic acid frozen sponge obtained in the step 4 by adopting a freeze-drying method to obtain the highly-oriented graphene oxide/polyamic acid composite sponge;
[0026] 6, preparing a reduced graphene oxide/polyimide composite film: placing the highly-oriented graphene oxide/polyamic acid composite sponge obtained in the step 5 in a resistance vacuum hot-pressingfurnace, and adopting a hot-pressing oxidation pretreatment to realize the reduction of graphene oxide and imidization of polyamic acid through a one-step method; when heating to 200°C, performing mechanical pressurization under a pressure of 20-30 MPa; continuously heating to 300°C-350°C and keeping the temperature constant for 1 h -1.5 h; then start cooling, and when the temperature drops to 200°C, releasing the pressure; and continuously cooling to a room temperature to obtain the reduced graphene oxide/polyimide composite film;
[0027]7, preparing a graphene/polyimide carbon film: placing the reduced graphene oxide/polyimide composite film obtained in the step 6 in a resistance vacuum hot-pressing furnace, and carbonizing the graphene and polyimide by adopting a high-temperature vacuum thermal annealing process; when heating to 200°C, performing mechanical pressurization under a pressure of 20 MPa -30 MPa; continuously heating to 900°C-1000°C, and keeping the temperature constant for 2 h -2.5 h; then start cooling, and when the temperature drops to 200°C, releasing the pressure; and continuously cooling to a room temperature to obtain the graphene/polyimide carbon film; and
[0028] 8, preparing a graphene/polyimide composite sponge precursor-based thermal-conductivefilm: placing the graphene/polyimide carbon film obtained in the step 7 in a high-temperature graphitization furnace, and graphitizing the graphene/polyimide carbon film by adopting a gradient heating method; heating to 1200°C at a heating rate of 20°C/min, changing the heating rate to 10°C/min, heating to 2200°C and keeping the temperature constant for 30 min, continuing heating to 2800°Cat a heating rate of 5°C/min and keeping the temperature constant for 120 min; and dropping to a room temperature to obtain the graphene/polyimide composite sponge precursor-based thermal-conductive film.
[0029] The present application also discloses a graphene polyimide composite sponge precursor-based thermal-conductive film obtained by the preparation method of the graphene polyimide composite sponge precursor-based thermal-conductive film of any one of above.
[0030] Compared with the prior art, the present application has the following beneficial effects: firstly, the preparation method is simple in process and low in cost; by adopting graphene oxide as a raw material, the sheet area is relatively large and adjustable, and the continuous sheet structure results in a reduced grain boundary scattering of phonons in the transmission process, which facilitates the improvement of the thermal conductivity; the graphene oxide is used as a cross-linking agent of polyamic acid by utilizing oxygen-containing groups on the graphene oxide sheet, so that the highly-oriented three-dimensional graphene oxide/polyamic acid composite sponge can be constructed, which improves the dispersion of graphene, has certain flexibility, high mechanical strength and better electrical and thermal conductivities, and is expected to be a heat dissipation material of a flexible device to be applied to actual electronic equipment;
[0031] secondly, according to the technical solution, a dimension reduction method is adopted, polyamic acid is crosslinked and imidized under the action of pressure and thermal annealing ; meanwhile graphene oxide can be reduced into graphene by a one-step hot-pressing oxidation pretreatment process; effective interfacial contact is established to generate strong interaction between sheets, and then the defects of a composite film sample are reduced through a high-temperature vacuum thermal annealing process and a graphitization treatment process. By the present application, the mechanical performance of the film is improved, the thermal and the electrical conductivities of the film are increased, making the thermal and the electrical conductivities more stable and excellent; and
[0032] thirdly, according to the technical solution, the thickness and flexibility of the graphene film can be controlled by adjusting the concentration of the dispersion liquid, the mechanical pressure, the thermal annealing temperature and the reaction time; and the preparation method can be widely applied to industrial production.
Brief Description of the Drawings
[0033] FIG. 1 is a schematic diagram of a preparation process of Example 1.
[0034] FIG. 2 is a photograph of a highly-oriented graphene oxide/polyamic acid composite sponge prepared in Example 1.
[0035] FIG. 3 shows photographs of a graphene/polyimide composite sponge precursor-based thermal-conductive film prepared in Example 1 and flexibility thereof.
[0036] FIG. 4 shows a graph that indicates a relative electrical resistance change rate of the graphene/polyimide composite sponge precursor-based thermal-conductive film of Example 1 after 10000 bending cycles.
Detailed Description of the Invention
[0037] Preferred embodiments of the present application are described in further detail below.
[0038] Example 1 A graphene/polyimide composite sponge precursor-based thermal-conductive film, with a schematic diagram of a preparation process being shown in FIG. 1, is prepared by the steps of: 1, preparing a graphene oxide aqueous solution: 20 mL of graphene oxide slurry was measured, added with deionized water, and stirred for 60 min at a stirring speed of 700 r/min; and ultrasonic treatment was performed for 30 min at a frequency of 100 KHz to obtain the graphene oxide aqueous solution;
[0039] wherein the concentration of the graphene oxide slurry is 20 mg/mL; the concentration of graphene oxide in the graphene oxide aqueous solution is 5 mg/mL;
[0040] 2, preparing a polyimide precursor solution: 1.98g of monomer diamine diaminodiphenyl ether (ODA) powder was uniformly dispersed in 83 mL of a polar solvent dimethylacetamide (DMAc) solution by using an electromagnetic stirrer; 2.18 g of pyromellitic dianhydride (PMDA) powder was added into the mixed solution continuously in a small amount, and stirred for 5 h to fully react to obtain a polyamic acid (PAA) solution; wherein the molar concentration ratio of PMDA to ODA is 100: 99;
[0041] after the polycondensation reaction was finished, the stirred solution was washed with a large amount of deionized water to obtain yellow precipitate polyamic acid fibers; residual deionized water was removed after filtering, cleaning and drying to obtain a solid with a mass fraction of 5%; the solid material corresponding to 1 g of PAA solution was taken together with
0.48 g of triethylamine (TEA) solution and 18.52 mL of deionized water, and stirred at a room temperature for 6 h to obtain the water-soluble polyimide precursor;
[0042] wherein the concentration of polyamic acid in the polyimide precursor solution is 20 mg/mL;
[0043]3, preparing a graphene oxide/polyamic acid mixed solution: the graphene oxide aqueous solution obtained in the step 1 was mixed with the polyimide precursor solution obtained in the step 2, and stirred for 2 h to fully react to obtain graphene oxide/polyamic acid mixed solutions with different concentrations;
[0044] wherein the concentration of graphene oxide in the graphene oxide/polyamic acid mixed solution is 70 wt%;
[0045] 4, preparing a highly-oriented graphene oxide/polyamic acid frozen sponge: the graphene oxide/polyamic acid mixed solution obtained in the step 3 was directionally frozen with liquid nitrogen to obtain highly-oriented graphene oxide/polyamic acid frozen sponges with different shapes;
[0046] 5, preparing a highly-oriented graphene oxide/polyamic acid composite sponge: the highly-oriented graphene oxide/polyamic acid frozen sponge obtained in the step 4 was dried by adopting a freeze-drying method to obtain the highly-oriented graphene oxide/polyamic acid composite sponge;
[0047] 6, preparing a reduced graphene oxide/polyimide composite film: the highly-oriented graphene oxide/polyamic acid composite sponge obtained in the step 5 was placed in a resistance vacuum hot-pressing furnace, and graphene oxide was reduced and polyamic acid was imidized through a one-step method by adopting a hot-pressing oxidation pretreatment process; when heating to 200°C, mechanical pressurization was performed with a pressure of 25 MPa; followed by continuously heating to 350°C, and the temperature was kept constant for 1 h; then cooling was started, and when the temperature dropped to 200°C, the pressure was released; and cooling was continued to a room temperature to obtain the reduced graphene oxide/polyimide composite film;
[0048] 7, preparing a graphene/polyimide carbon film: the reduced graphene oxide/polyimide composite film obtained in the step 6 was placed in a resistance vacuum hot-pressing furnace, and graphene and polyimide was carbonized by adopting a high-temperature vacuum thermal annealing process; when heating to 200°C, mechanical pressurization was performed with a pressure of 25 MPa; followed by continuously heating to 1000°C, and the temperature was kept constant for 2 h; then cooling was started, and when the temperature dropped to 200°C, the pressure was released; and cooling was continued to a room temperature to obtain the graphene/polyimide carbon film; and
[0049] 8, preparing a graphene/polyimide composite sponge precursor-based thermal-conductive film: the graphene/polyimide carbon film obtained in the step 7 was placed in a high-temperature graphitization furnace, and the graphene/polyimide carbon film was graphitized by adopting a gradient heating method; the temperature was raised to 1200°C at a heating rate of 20°C/min, then the heating rate was changed to 10°C/min, followed by heating to 2200°C, and the temperature was kept constant for 30 min; heating was continued to 2800°Cat a heating rate of 5°C/min and the temperature was kept constant for 120 min; and then the temperature dropped to a room temperature to obtain the graphene/polyimide composite sponge precursor-based thermal-conductive film.
[0050] The photograph of the highly-oriented graphene oxide/polyamic acid composite sponge prepared in the step 5 of Example 1 is shown in FIG. 2, from which it can be seen that the highly-oriented graphene oxide/polyamic acid composite sponge is yellowish brown and flat in surface, the inner sheet after cutting is in an oriented tube bundle structure along the crystal growth direction, and the vertical direction is in a honeycomb-like porous structure. The structure has positive influence on the formation of the graphene/polyimide composite sponge precursor-based thermal-conductive film at the later stage.
[0051] The graphene/polyimide composite sponge precursor-based thermal-conductive film prepared in the step 8 of Example 1 and the flexible photographs thereof are shown in FIG. 3, from which it can be seen that the prepared low-defect graphene film is smooth in surface and free of wrinkles or bubbles; and it has certain flexibility, and can be bent 180 and folded into various shapes. A graph of a relative electrical resistance change rate of the graphene/polyimide composite sponge precursor-based thermal-conductive film prepared in the step 8 of Example 1 after 10000 bending cycles, is shown in FIG. 4, from which it can be seen that the resistance is not obviously increased, indicating a good operating stability.
[0052] The thermal conductivity and the electrical conductivity of the samples were tested, and the thermal conductivity of the graphene/polyimide composite sponge precursor-based thermal-conductive film is 1467 W m-1 K-1, the electrical conductivity reaches 1.8x105 S m-1, and the numerical values are equivalent to that of the graphene composite film with high thermal and electrical conductivities reported at present. Meanwhile, the graphene/polyimide composite sponge precursor-based thermal-conductive film prepared by the embodiment has relatively high tensile strength, reaching up to 150 MPa, about 4 times that of the current graphene film, and has certain flexibility, meeting the practical application requirements in the fields of national defense military equipment and intelligent electronics.
[0053] Example 2
A graphene/polyimide composite sponge precursor-based thermal-conductive film is prepared by the steps of: 1, preparing a graphene oxide aqueous solution: 20 mL of graphene oxide slurry was measured, added with deionized water, and stirred for 60 min at a stirring speed of 700 r/min; and ultrasonic treatment was performed for 30 min at a frequency of 100 KHz to obtain the graphene oxide aqueous solution;
[0054] wherein the concentration of the graphene oxide slurry is 20 mg/mL; the concentration of graphene oxide in the graphene oxide aqueous solution is 5 mg/mL;
[0055] 2, preparing a polyimide precursor solution: 1.98g of monomer diamine diaminodiphenyl ether (ODA) powder was uniformly dispersed in 83 mL of a polar solvent dimethylacetamide (DMAc) solution by using an electromagnetic stirrer; 2.18 g of pyromellitic dianhydride (PMDA) powder was added into the mixed solution continuously in a small amount, and stirred for 5 h to fully react to obtain a polyamic acid (PAA) solution; wherein the molar concentration ratio of PMDA to ODA is 100: 99;
[0056] after the polycondensation reaction was finished, the stirred solution was washed with a large amount of deionized water to obtain yellow precipitate polyamic acid fibers; residual deionized water was removed after filtering, cleaning and drying to obtain a solid with a mass fraction of 5%; the solid material corresponding to 1 g of PAA solution was taken together with 0.48 g of triethylamine (TEA) solution and 18.52 mL of deionized water, and stirred at a room temperature for 6 h to obtain the water-soluble polyimide precursor;
[0057] wherein the concentration of polyamic acid in the polyimide precursor solution is 20 mg/mL;
[0058] 3, preparing a graphene oxide/polyamic acid mixed solution: the graphene oxide aqueous solution obtained in the step 1 was mixed with the polyimide precursor solution obtained in the step 2, and stirred for 2 h to fully react to obtain graphene oxide/polyamic acid mixed solutions with different concentrations;
[0059] wherein the concentration of graphene oxide in the graphene oxide/polyamic acid mixed solution is 90 wt%;
[0060] 4, preparing a highly-oriented graphene oxide/polyamic acid frozen sponge: the graphene oxide/polyamic acid mixed solution obtained in the step 3 was directionally frozen with liquid nitrogen to obtain highly-oriented graphene oxide/polyamic acid frozen sponges with different shapes;
[0061] 5, preparing a highly-oriented graphene oxide/polyamic acid composite sponge: the highly-oriented graphene oxide/polyamic acid frozen sponge obtained in the step4 was dried by adopting a freeze-drying method to obtain the highly-oriented graphene oxide/polyamic acid composite sponge;
[0062] 6, preparing a reduced graphene oxide/polyimide composite film: the highly-oriented graphene oxide/polyamic acid composite sponge obtained in the step 5 was placed in a resistance vacuum hot-pressing furnace, and graphene oxide was reduced and polyamic acid was imidized through a one-step method by adopting a hot-pressing oxidation pretreatment process; when heating to 200°C, mechanical pressurization was performed with a pressure of 30 MPa; followed by continuously heating to 300°C, and the temperature was kept constant for 1.5 h; then cooling was started, and when the temperature dropped to 200°C, the pressure was released; and cooling was continued to a room temperature to obtain the reduced graphene oxide/polyimide composite film;
[0063] 7, preparing a graphene/polyimide carbon film: the reduced graphene oxide/polyimide composite film obtained in the step 6 was placed in a resistance vacuum hot-pressing furnace, and graphene and polyimide was carbonized by adopting a high-temperature vacuum thermal annealing process; when heating to 200°C, mechanical pressurization was performed with a pressure of 30 MPa; followed by continuously heating to 900°C, and the temperature was kept constant for 2.5 h; then cooling was started, and when the temperature dropped to 200°C, the pressure was released; and cooling was continued to a room temperature to obtain the graphene/polyimide carbon film; and
[0064] 8, preparing a graphene/polyimide composite sponge precursor-based thermal-conductivefilm: the graphene/polyimide carbon film obtained in the step 7 was placed in a high-temperature graphitization furnace, and the graphene/polyimide carbon film was graphitized by adopting a gradient heating method; the temperature was raised to 1200°C at a heating rate of 20°C/min, then the heating rate was changed to 10°C/min, followed by heating to 2200°C, and the temperature was kept constant for 30 min; heating was continued to 2800°Cat a heating rate of 5°C/min and the temperature was kept constant for 120 min; and then the temperature dropped to a room temperature to obtain the graphene/polyimide composite sponge precursor-based thermal-conductivefilm.
[0065] The thermal and electrical conductivities of the samples were tested, and the thermal conductivity of the graphene/polyimide composite sponge precursor-based thermal-conductive film is 1450 W m-1 K-1, the electrical conductivity reaches 1.75x10 5 S m-1, and the numerical values are equivalent to that of the graphene composite film with high thermal and electrical conductivities reported at present. Meanwhile, the graphene/polyimide composite sponge precursor-based thermal-conductive film prepared by the embodiment has relatively high tensile strength, reaching up to 147 MPa, about 4 times that of the current graphene film, and has certain flexibility, meeting the practical application requirements in the fields of national defense military equipment and intelligent electronics.
[0066] Example 3 A graphene/polyimide composite sponge precursor-based thermal-conductive film is prepared by the steps of: 1, preparing a graphene oxide aqueous solution: 20 mL of graphene oxide slurry was measured, added with deionized water, and stirred for 120min at a stirring speed of 100 r/min; and ultrasonic treatment was performed for 60 minutes at a frequency of 10KHz to obtain the graphene oxide aqueous solution;
[0067] wherein the concentration of the graphene oxide slurry is 20 mg/mL; the concentration of graphene oxide in the graphene oxide aqueous solution is 4mg/mL;
[0068] 2, preparing a polyimide precursor solution: 1.98g of monomer diamine diaminodiphenyl ether (ODA) powder was uniformly dispersed in 83 mL of a polar solvent dimethylacetamide (DMAc) solution by using an electromagnetic stirrer; 2.18 g of pyromellitic dianhydride (PMDA) powder was added into the mixed solution continuously in a small amount, and stirred for 5 h to fully react to obtain a polyamic acid (PAA) solution; wherein the molar concentration ratio of PMDA to ODA is 100: 99; after the polycondensation reaction was finished, the stirred solution was washed with a large amount of deionized water to obtain yellow precipitate polyamic acid fibers; residual deionized water was removed after filtering, cleaning and drying to obtain a solid with a mass fraction of 5%; the solid material corresponding to 1 g of PAA solution was taken together with 0.48 g of triethylamine (TEA) solution and 18.52 mL of deionized water, and stirred at a room temperature for 6 h to obtain the water-soluble polyimide precursor;
[0069] wherein the concentration of polyamic acid in the polyimide precursor solution is 20 mg/mL;
[0070] 3, preparing a graphene oxide/polyamic acid mixed solution: the graphene oxide aqueous solution obtained in the step 1 was mixed with the polyimide precursor solution obtained in the step 2, and stirred for 2 h to fully react to obtain graphene oxide/polyamic acid mixed solutions with different concentrations;
[0071] wherein the concentration of graphene oxide in the graphene oxide/polyamic acid mixed solution is 60 wt%;
[0072] 4, preparing a highly-oriented graphene oxide/polyamic acid frozen sponge: the graphene oxide/polyamic acid mixed solution obtained in the step 3 was directionally frozen with liquid nitrogen to obtain highly-oriented graphene oxide/polyamic acid frozen sponges with different shapes;
[0073] 5, preparing a highly-oriented graphene oxide/polyamic acid composite sponge: the highly-oriented graphene oxide/polyamic acid frozen sponge obtained in the step 4was dried by adopting a freeze-drying method to obtain the highly-oriented graphene oxide/polyamic acid composite sponge;
[0074] 6, preparing a reduced graphene oxide/polyimide composite film: the highly-oriented graphene oxide/polyamic acid composite sponge obtained in the step 5 was placed in a resistance vacuum hot-pressing furnace, and graphene oxide was reduced and polyamic acid was imidized through a one-step method by adopting a hot-pressing oxidation pretreatment process; when heating to 200°C, mechanical pressurization was performed with a pressure of 20 MPa; followed by continuously heating to 300°C, and the temperature was kept constant for 1.5 h; then cooling was started, and when the temperature dropped to 200°C, the pressure was released; and cooling was continued to a room temperature to obtain the reduced graphene oxide/polyimide composite film;
[0075] 7, preparing a graphene/polyimide carbon film: the reduced graphene oxide/polyimide composite film obtained in the step 6 was placed in a resistance vacuum hot-pressing furnace, and graphene and polyimide was carbonized by adopting a high-temperature vacuum thermal annealing process; when heating to 200°C, mechanical pressurization was performed with a pressure of 20 MPa; followed by continuously heating to 900°C, and the temperature was kept constant for 2.5 h; then cooling was started, and when the temperature dropped to 200°C, the pressure was released; and cooling was continued to a room temperature to obtain the graphene/polyimide carbon film; and
[0076] 8, preparing a graphene/polyimide composite sponge precursor-based thermal-conductivefilm: the graphene/polyimide carbon film obtained in the step 7 was placed in a high-temperature graphitization furnace, and the graphene/polyimide carbon film was graphitized by adopting a gradient heating method; the temperature was raised to 1200°C at a heating rate of 20°C/min, then the heating rate was changed to 10°C/min, followed by heating to 2200°C, and the temperature was kept constant for 30 min; heating was continued to 2800°Cat a heating rate of 5°C/min and the temperature was kept constant for 120 min; and then the temperature dropped to a room temperature to obtain the graphene/polyimide composite sponge precursor-based thermal-conductivefilm.
[0077] The thermal and electrical conductivities of the samples were tested, and the thermal conductivity of the graphene/polyimide composite sponge precursor-based thermal-conductive film is 1380 W m-1 K-1, the electrical conductivity reaches 1.68x10 5 S m-1, and the numerical values are equivalent to that of the graphene composite film with high thermal and electrical conductivities reported at present. Meanwhile, the graphene/polyimide composite sponge precursor-based thermal-conductive film prepared by the embodiment has relatively high tensile strength, reaching up to 137 MPa, about 4 times that of the current graphene film, and has certain flexibility, meeting the practical application requirements in the fields of national defense military equipment and intelligent electronics.
[0078] Example 4 A graphene/polyimide composite sponge precursor-based thermal-conductive film is prepared by the steps of: 1, preparing a graphene oxide aqueous solution: 20 mL of graphene oxide slurry was measured, added with deionized water, and stirred for 120min at a stirring speed of 100 r/min; and ultrasonic treatment was performed for 60 min at a frequency of 10KHz to obtain the graphene oxide aqueous solution;
[0079] wherein the concentration of the graphene oxide slurry is 20 mg/mL; the concentration of graphene oxide in the graphene oxide aqueous solution is 6mg/mL;
[0080] 2, preparing a polyimide precursor solution: 1.98g of monomer diamine diaminodiphenyl ether (ODA) powder was uniformly dispersed in 83 mL of a polar solvent dimethylacetamide (DMAc) solution by using an electromagnetic stirrer; 2.18 g of pyromellitic dianhydride (PMDA) powder was added into the mixed solution continuously in a small amount, and stirred for 5 h to fully react to obtain a polyamic acid (PAA) solution; wherein the molar concentration ratio of PMDA to ODA is 100: 99; after the polycondensation reaction was finished, the stirred solution was washed with a large amount of deionized water to obtain yellow precipitate polyamic acid fibers; residual deionized water was removed after filtering, cleaning and drying to obtain a solid with a mass fraction of 5%; the solid material corresponding to 1 g of PAA solution was taken together with 0.48 g of triethylamine (TEA) solution and 18.52 mL of deionized water, and stirred at a room temperature for 6 h to obtain the water-soluble polyimide precursor;
[0081] wherein the concentration of polyamic acid in the polyimide precursor solution is 20 mg/mL;
[0082] 3, preparing a graphene oxide/polyamic acid mixed solution: the graphene oxide aqueous solution obtained in the step 1 was mixed with the polyimide precursor solution obtained in the step 2, and stirred for 2 h to fully react to obtain graphene oxide/polyamic acid mixed solutions with different concentrations;
[0083] wherein the concentration of graphene oxide in the graphene oxide/polyamic acid mixed solution is 90 wt%;
[0084] 4, preparing a highly-oriented graphene oxide/polyamic acid frozen sponge: the graphene oxide/polyamic acid mixed solution obtained in the step 3 was directionally frozen with liquid nitrogen to obtain highly-oriented graphene oxide/polyamic acid frozen sponges with different shapes;
[0085] 5, preparing a highly-oriented graphene oxide/polyamic acid composite sponge: the highly-oriented graphene oxide/polyamic acid frozen sponge obtained in the step 4 was dried by adopting a freeze-drying method to obtain the highly-oriented graphene oxide/polyamic acid composite sponge;
[0086]6, preparing a reduced graphene oxide/polyimide composite film: the highly-oriented graphene oxide/polyamic acid composite sponge obtained in the step 5 was placed in a resistance vacuum hot-pressing furnace, and graphene oxide was reduced and polyamic acid was imidized through a one-step method by adopting a hot-pressing oxidation pretreatment process; when heating to 200°C, mechanical pressurization was performed with a pressure of 25 MPa; followed by continuously heating to 350°C, and the temperature was kept constant for 1 h; then cooling was started, and when the temperature dropped to 200°C, the pressure was released; and cooling was continued to a room temperature to obtain the reduced graphene oxide/polyimide composite film;
[0087] 7, preparing a graphene/polyimide carbon film: the reduced graphene oxide/polyimide composite film obtained in the step 6 was placed in a resistance vacuum hot-pressing furnace, and graphene and polyimide was carbonized by adopting a high-temperature vacuum thermal annealing process; when heating to 200°C, mechanical pressurization was performed with a pressure of 25 MPa; followed by continuously heating to 1000°C, and the temperature was kept constant for 2 h; then cooling was started, and when the temperature dropped to 200°C, the pressure was released; and cooling was continued to a room temperature to obtain the graphene/polyimide carbon film; and
[0088] 8, preparing a graphene/polyimide composite sponge precursor-based thermal-conductivefilm: the graphene/polyimide carbon film obtained in the step 7 was placed in ahigh-temperature graphitization furnace, and the graphene/polyimide carbon film was graphitized by adopting a gradient heating method; the temperature was raised to 1200°C at a heating rate of 20°C/min, then the heating rate was changed to 10°C/min, followed by heating to 2200°C, and the temperature was kept constant for 30 min; heating was continued to 2800°Cat a heating rate of 5°C/min and the temperature was kept constant for 120 min; and then the temperature dropped to a room temperature to obtain the graphene/polyimide composite sponge precursor-based thermal-conductivefilm.
[0089] The thermal and electrical conductivities of the samples were tested, and the thermal conductivity of the graphene/polyimide composite sponge precursor-based thermal-conductive film is 1460 W m-1 K-1, the electrical conductivity reaches 1.76x10 5 S m-1, and the numerical values are equivalent to that of the graphene composite film with high thermal and electrical conductivities reported at present. Meanwhile, the graphene/polyimide composite sponge precursor-based thermal-conductive film prepared by the embodiment has relatively high tensile strength, reaching up to 146 MPa, about 4 times that of the current graphene film, and has certain flexibility, meeting the practical application requirements in the fields of national defense military equipment and intelligent electronics.
[0090] Example 5 A graphene polyimide composite sponge precursor-based thermal-conductive film is prepared by the steps of: 1, preparing a graphene oxide aqueous solution: 20 mL of graphene oxide slurry was measured, added with deionized water, and stirred for 120min at a stirring speed of 100 r/min; and ultrasonic treatment was performed for 60 min at a frequency of 1OKHz to obtain the graphene oxide aqueous solution;
[0091] wherein the concentration of the graphene oxide slurry is 20 mg/mL; the concentration of graphene oxide in the graphene oxide aqueous solution iS6 mg/mL;
[0092] 2, preparing a polyimide precursor solution: 1.98g of monomer diamine diaminodiphenyl ether (ODA) powder was uniformly dispersed in 83 mL of a polar solvent dimethylacetamide (DMAc) solution by using an electromagnetic stirrer; 2.18g of pyromellitic dianhydride (PMDA) powder was added into the mixed solution continuously in a small amount, and stirred for 5 h to fully react to obtain a polyamic acid (PAA) solution; wherein the molar concentration ratio of PMDA to ODA is 100: 95; after the polycondensation reaction was finished, the stirred solution was washed with a large amount of deionized water to obtain yellow precipitate polyamic acid fibers; residual deionized water was removed after filtering, cleaning and drying to obtain a solid with a mass fraction of 5%; the solid material corresponding to 1 g of PAA solution was taken together with 0.48 g of triethylamine (TEA) solution and 18.52 mL of deionized water, and stirred at a room temperature for 6 h to obtain the water-soluble polyimide precursor;
[0093] wherein the concentration of polyamic acid in the polyimide precursor solution is mg/mL;
[0094] 3, preparing a graphene oxide/polyamic acid mixed solution: the graphene oxide aqueous solution obtained in the step 1 was mixed with the polyimide precursor solution obtained in the step 2, and stirred for 2 h to fully react to obtain graphene oxide/polyamic acid mixed solutions with different concentrations;
[0095] wherein the concentration of graphene oxide in the graphene oxide/polyamic acid mixed solution is 10 wt%;
[0096] 4, preparing a highly-oriented graphene oxide/polyamic acid frozen sponge: the graphene oxide/polyamic acid mixed solution obtained in the step 3 was directionally frozen with liquid nitrogen to obtain highly-oriented graphene oxide/polyamic acid frozen sponges with different shapes;
[0097] 5, preparing a highly-oriented graphene oxide/polyamic acid composite sponge: the highly-oriented graphene oxide/polyamic acid frozen sponge obtained in the step 4 was dried by adopting a freeze-drying method to obtain the highly-oriented graphene oxide/polyamic acid composite sponge;
[0098] 6, preparing a reduced graphene oxide/polyimide composite film: the highly-oriented graphene oxide/polyamic acid composite sponge obtained in the step 5 was placed in a resistance vacuum hot-pressing furnace, and graphene oxide was reduced and polyamic acid was imidized through a one-step method by adopting a hot-pressing oxidation pretreatment process; when heating to 200°C, mechanical pressurization was performed with a pressure of 25 MPa; followed by continuously heating to 350°C, and the temperature was kept constant for 1 h; then cooling was started, and when the temperature dropped to 200°C, the pressure was released; and cooling was continued to a room temperature to obtain the reduced graphene oxide/polyimide composite film;
[0099] 7, preparing a graphene/polyimide carbon film: the reduced graphene oxide/polyimide composite film obtained in the step 6 was placed in a resistance vacuum hot-pressing furnace, and graphene and polyimide was carbonized by adopting a high-temperature vacuum thermal annealing process; when heating to 200°C, mechanical pressurization was performed with a pressure of 25 MPa; followed by continuously heating to 1000°C, and the temperature was kept constant for 2 h; then cooling was started, and when the temperature dropped to 200°C, the pressure was released; and cooling was continued to a room temperature to obtain the graphene/polyimide carbon film; and
[0100] 8, preparing a graphene/polyimide composite sponge precursor-based thermal-conductivefilm: the graphene/polyimide carbon film obtained in the step 7 was placed in ahigh-temperature graphitization furnace, and the graphene/polyimide carbon film was graphitized by adopting a gradient heating method; the temperature was raised to 1200°C at a heating rate of 20°C/min, then the heating rate was changed to 10°C/min, followed by heating to 2200°C, and the temperature was kept constant for 30 min; heating was continued to 2800°Cat a heating rate of 5°C/min and the temperature was kept constant for 120 min; and then the temperature dropped to a room temperature to obtain the graphene/polyimide composite sponge precursor-based thermal-conductivefilm.
[0101] The thermal and electrical conductivities of the sample were tested, and the thermal conductivity of the graphene polyimide composite sponge precursor-based thermal-conductive film is 1330 Wm-'K-1, the electrical conductivity reaches 1.xO 5 Sm-1, and the numerical values are equivalent to that of the graphene composite film with high thermal and electrical conductivities reported at present. Meanwhile, the graphene polyimide composite sponge precursor-based thermal-conductive film prepared by the embodiment has relatively high tensile strength, reaching up to 126 MPa, about 3.5 times that of the current graphene film, and has certain flexibility, meeting the practical application requirements in the fields of national defense military equipment and intelligent electronics.
[0102] The foregoing is a further detailed description of the present application, taken in conjunction with specific preferred embodiments, and is not to be construed as limiting the present application to those specific embodiments. It will be apparent to those skilled in the art that various modifications and improvements can be made in the present application without departing from the spirit or scope of the present application.
Editorial Note 2020102143 There is only two pages of the claim
Claims (10)
1.A preparation method of a graphene polyimide composite sponge precursor-based thermal-conductive film, characterized by comprising the steps of: step S1, preparing a graphene oxide aqueous solution; step S2, preparing a polyimide precursor solution; step S3, mixing the graphene oxide aqueous solution with the polyimide precursor solution to obtain a graphene oxide/polyamic acid mixed solution; step S4, freezing the graphene oxide/polyamic acid mixed solution to obtain a graphene oxide/polyamic acid frozen sponge; step S5, drying the graphene oxide/polyamic acid frozen sponge by adopting a freeze-drying method to obtain a graphene oxide/polyamic acid composite sponge; step S6, placing the graphene oxide/polyamic acid composite sponge in a resistance vacuum hot-pressing furnace, and adopting a hot-pressing oxidation pretreatment method to realize the reduction of graphene oxide and the imidization of polyamic acid ; and meanwhile performing mechanical pressurization to obtain a reduced graphene oxide/polyimide composite film; step S7, placing the reduced graphene oxide/polyimide composite film in a resistance vacuum hot-pressing furnace, and carbonizing the graphene and polyimide by adopting a vacuum thermal annealing; and meanwhile performing mechanical pressurization to obtain a graphene/polyimide carbon film; and stepS8, placing the graphene/polyimide carbon film in a high-temperature graphitization furnace, and graphitizing the graphene/polyimide carbon film by adopting a gradient heating method to obtain the graphene polyimide composite sponge precursor-based thermal-conductive film.
2. The preparation method of a graphene polyimide composite sponge precursor-based thermal-conductive film of claim 1, characterized in that in the step S3, a concentration of graphene oxide in the graphene oxide aqueous solution is 1-10 mg/mL.
3. The preparation method of a graphene polyimide composite sponge precursor-based thermal-conductive film of claim 1, characterized in that in the step S3, a concentration of polyamic acid in the polyimide precursor solution is 15-20 mg/mL.
4. The preparation method of a graphene polyimide composite sponge precursor-based thermal-conductive film of claim 1, characterized in that in the step S3, a concentration of graphene oxide in the graphene oxide/polyamic acid mixed solution is 10 wt%- 9 0 wt%.
5. The preparation method of a graphene polyimide composite sponge precursor-based thermal-conductive film of claim 1, characterized in that in the step S6 and the step S7, a pressure of the mechanical pressurization is 20 MPa-30 MPa, the pressure is maintained and then the pressure is released until the temperature drops to 200°C.
6. The preparation method of a graphene polyimide composite sponge precursor-based thermal-conductive film of claim 5, characterized in that in the step S6, a thermal annealing temperature of the hot-pressing oxidation pretreatment methodis300°C-350°C, and the temperature is kept constant for 1 h -1.5 h.
7. The preparation method of a graphene polyimide composite sponge precursor-based thermal-conductive film of claim 5, characterized in that in the step S7, a temperature of the vacuum thermal annealing is 900°C-1000C, and the temperature is kept constant for 2 h -2.5 h.
8. The preparation method of a graphene polyimide composite sponge precursor-based thermal-conductive film of claim 5, characterized in that in the stepS8, the conditions of the gradient heating method are as follows: heating to 1200°C at a heating rate of 20°C/min, changing the heating rate to 10°C/min, heating to 2200°C, keeping the temperature constant for 30 min, continuing to heat to 2800°C at a heating rate of 5°C/min, keeping the temperature constant for 120 min, and dropping to a room temperature.
9. The preparation method of a graphene polyimide composite sponge precursor-based thermal-conductive film of any one of claims 1-8, characterized in thatthe step S2 comprises: dispersing a monomer diamine diaminodiphenyl ether in a polar solvent, and then adding a pyromellitic dianhydride, wherein amolar ratio of the pyromellitic dianhydride to the monomer diamine diaminodiphenyl ether is 100:95-99; stirring to fully react to obtain a polyamic acid (PAA) solution; after the reaction is finished, washing, filtering, cleaning and drying to obtain a solid; and uniformly stirringthe solid and a triethylamine (TEA) aqueous solution to obtain a water-soluble polyimide precursor solution.
10. A graphene polyimide composite sponge precursor-based thermal-conductive film, characterized by being obtained by the preparation method of a graphene polyimide composite sponge precursor-based thermal-conductive film of any one of claims 1-9.
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