A heat-conducting and heat-insulating integrated graphene fiber aerogel as well as a preparation method and application thereof

Abstract

This invention discloses an integrated thermally conductive and insulating graphene fiber aerogel, its preparation method, and its applications. The graphene fiber aerogel is composed of at least one stacked basic functional unit. The basic functional unit includes a layer of highly thermally conductive dense graphene film and a layer of highly thermally insulating porous graphene fiber aerogel. The graphene fiber aerogel and the graphene film achieve in-situ self-fusion at the molecular scale through carbon-carbon covalent bonds, forming an integrated and stable interface structure. The in-plane thermal conductivity of the material was tested using a laser flare method, reaching as high as 364 W / mK; the normal thermal conductivity of the material was tested using a steady-state heat flow method, reaching as high as 0.119 W / mK; a high-power pulsed laser (power density 100 W / cm², pulse width 1 s) was used to simulate thermal shock, and an infrared thermal imager was used to record the temperature rise curves of the front impact point and the back side of the material. The time required for the back side temperature to reach 100°C was as high as 18 s.

Description

Technical Field

[0001] This invention belongs to the technical field of nano-carbon materials and high-temperature thermal protection materials, specifically relating to an integrated thermally conductive and insulating graphene fiber aerogel, its preparation method, and its application. Background Technology

[0002] Thermal protection systems face severe technical challenges when dealing with localized transient high heat flux shocks caused by lasers, engine jets, and explosive shock waves. Traditional single-function thermal protection materials face a fundamental technical paradox. Ideal protective materials need asymmetric thermal regulation capabilities: extremely high lateral thermal conductivity on the heated surface to facilitate heat dissipation, reduce localized thermal stress, and prevent localized overheating; simultaneously, extremely high thermal insulation performance in the thickness direction to protect sensitive back-end components. However, single-phase material systems struggle to overcome the limitations of their physical properties. While traditional porous thermal insulation materials such as ceramic-based porous fiber felts possess low isotropic thermal conductivity, they are prone to localized overheating at the impact point under high-power-density transient thermal shocks due to impeded in-plane heat expansion, leading to material ablation failure or burn-through. Conversely, while high thermal conductivity graphene films or metal foils can rapidly homogenize temperatures through excellent in-plane thermal conductivity, their thickness is typically only a few hundred micrometers, offering almost no thermal insulation in the thickness direction. Heat quickly penetrates the material, exposing the back-end equipment to high-temperature threats.

[0003] To overcome the performance limitations of single materials, researchers have attempted to directly combine thermally conductive and insulating layers into assemblies. However, this direct stacking approach presents more complex interfacial challenges in practical applications. When two different materials are combined using simple mechanical stacking or traditional adhesive processes, a significant interfacial thermal resistance forms between the layers. This interface acts like a "barrier" in the heat flow channel, severely hindering the conduction of heat from the thermally conductive layer to the insulating layer, significantly reducing the efficiency of the intended "lateral diffusion" synergistic mechanism. More importantly, due to the significant difference in the coefficients of thermal expansion between high thermal conductivity materials (such as metals and graphite) and high thermal insulation materials (such as ceramics), enormous thermal stress is generated at the interface under intense thermal cycling or external stress, causing warping, debonding, or even delamination of the multilayer composite material, rendering the overall structure's protective function completely ineffective. Furthermore, in extreme high-temperature environments, commonly used organic adhesives decompose and fail, while inorganic binders may introduce new reactive and brittle phases, further deteriorating interfacial stability and thermal management performance under extreme temperatures.

[0004] In summary, the core of the current technological dilemma lies in the fact that single materials are limited by inherent physical laws, resulting in limited functionality; while simple multiphase material combinations cannot overcome the thermo-mechanical synergistic failure problem caused by the mismatch between interfacial thermal resistance and thermal expansion coefficients, making it difficult to achieve the ideal effect of multifunctional synergy. Therefore, developing an integrated material with a stable multilayer interfacial microstructure under extreme thermal operating environments and possessing efficient local thermal shock protection functions has become an inevitable choice and a key technological breakthrough for overcoming the bottleneck of transient thermal shock protection and meeting the development needs of next-generation high-end equipment. Summary of the Invention

[0005] To address the problems of high interfacial thermal resistance, weak bonding, and insufficient elasticity in existing composite laminated materials, this invention provides an integrated thermally conductive and insulating graphene fiber aerogel. This graphene fiber aerogel is composed of at least one stacked basic functional unit. The basic functional unit includes a layer of highly thermally conductive dense graphene film and a layer of highly thermally insulating porous graphene fiber aerogel. During the filtration process of the long fibers, negative pressure drives the fluid to generate downward pressure, causing the underlying short fibers to shrink and reconstruct into a dense and smooth membrane substrate, eliminating microscopic pores and opening continuous phonon transport channels. Simultaneously, some long fibers embed into surface defects of the short fibers under solvent dragging, forming a deep interfacial interpenetrating network. This physical interlocking process not only builds a "thermal bridge" to repair heat flow interruptions but also achieves crucial interfacial mechanical enhancement through fiber entanglement. The graphene fiber aerogel and graphene film achieve in-situ self-fusion at the molecular scale through carbon-carbon covalent bonds, forming an integrated and stable interfacial structure. The in-plane thermal conductivity of the material was tested using the laser flare method and found to be as high as 364 W / mK; the normal thermal conductivity of the material was tested using the steady-state heat flow method and found to be as high as 0.119 W / mK; a high-power pulsed laser (power density 100 W / cm², pulse width 1 s) was used to simulate thermal shock, and an infrared thermal imager was used to record the temperature rise curves of the front impact point and the back side of the material. The time required for the back side temperature to reach 100 ℃ could be as high as 18 s.

[0006] Specifically, the preparation method of the graphene fiber aerogel of the present invention is as follows: (1) Prepare a spinning solution containing graphene oxide in a mass ratio of not less than 1:9 and a high molecular weight polymer with a molecular weight of not less than 1 million, such as polyvinyl alcohol (PVA), polyethylene oxide (PEO), sodium polyacrylate (PAAS), etc. The solvent of the spinning solution is a polar solvent, such as water, DMF, etc.

[0007] (2) Composite gel fibers are obtained by spinning using spinning solution; the coagulation bath used in spinning is a 10wt%-20wt% ionic solution, specifically a multivalent ion that can crosslink with graphene oxide, including one or more of calcium ions, aluminum ions, and iron ions.

[0008] (3) The composite gel fiber is processed into short fibers with a length of less than 5 mm and long fibers with a length of more than 1 cm; short fiber dispersion and long fiber dispersion are prepared respectively, and the solvent is a polar solvent such as ethanol / ethyl acetate; (4) The short fiber dispersion is filtered on the filter membrane so that it self-fusions to form an initial, relatively dense thin film substrate on the filter membrane; (5) The long fiber dispersion is uniformly dispersed on the above-mentioned film substrate and subjected to secondary vacuum filtration. When the long fibers are stacked together, they form a three-dimensional porous aerogel structure. At the same time, some of the fibers will interpenetrate, entangle and fuse with the underlying film substrate to form a strong mechanical interlock and preliminary physical bond to obtain graphene fiber aerogel unit; (6) Repeat steps (4)-(5) to assemble and dry the obtained graphene fiber aerogel units; the drying is carried out at 25 ℃ and under a certain pressure (0-0.5 MPa) for 48 h to promote the formation of strong hydrogen bond interactions between the original physical contact points and the graphene oxide sheets.

[0009] (7) Reduce and graphitize to obtain thermally conductive and heat-insulating integrated graphene fiber aerogel.

[0010] During the filtration process of long fibers, negative pressure drives the fluid to generate strong downward pressure, causing the underlying short fibers to shrink and reconstruct into a dense and smooth membrane substrate, eliminating microscopic pores and opening continuous phonon transport channels. Simultaneously, some long fibers, dragged by the solvent, embed into surface defects of the short fibers, forming a deep interpenetrating network. This physical interlocking process not only builds a "thermal bridge" to repair heat flow interruptions but also achieves crucial interfacial mechanical enhancement through fiber entanglement. Thanks to the perfect matching of thermal expansion coefficients of homologous materials, this interpenetrating structure effectively resists thermal stress shear caused by drastic temperature changes, endowing the system with excellent interfacial structural stability and avoiding the delamination and debonding defects common in traditional heterogeneous laminated materials. Furthermore, the strong lateral shear force generated by the abrupt change in flow velocity between layers exerts a "horizontal combing" effect on the underlying short fibers, inducing them to highly oriented along the two-dimensional plane. This multi-effect synergy of physical compaction, interfacial interpenetration, and flow field orientation not only ensures the robustness and reliability of the macroscopically integrated material but also maximizes the in-plane thermal conductivity, ensuring that transient heat flow can rapidly diffuse in all directions without dead zones.

[0011] Furthermore, the spinning method described in step (2) is one of blow spinning, wet spinning, dry spinning, or electrospinning.

[0012] Furthermore, the filtration method in steps (4) and (5) is vacuum filtration.

[0013] Furthermore, the reduction method in step (7) is chemical reduction using a reducing agent, which is one of hydroiodic acid vapor, hydroiodic acid, or hydrazine hydrate vapor. Preferably, the reduction is carried out at a high temperature of 95 degrees Celsius for 12 hours in a hydroiodic acid vapor atmosphere.

[0014] Further, the graphitization method in step (7) is as follows: in an inert atmosphere, the temperature is raised to 1000 ℃ at a heating rate of 2-5 ℃ / min and held for 1 h; then the temperature is further raised to 2800 ℃ and held for 2 hours, followed by furnace cooling. During this process, the polymer is completely carbonized and partially graphitized, and the graphene oxide is deeply reduced and its lattice structure is repaired, forming a highly graphitized pure carbon structure. More importantly, at high temperatures, adjacent graphene sheets form a strong π-π conjugation and covalent cross-linking effect at the original physical contact points through the rearrangement and connection of carbon atoms, thereby realizing the in-situ self-fusion interpenetrating interface between the graphene film and the graphene fiber aerogel, ultimately obtaining an integrated functional unit of all carbon.

[0015] Furthermore, the number of repetitions in step (6) is 0-50 times, preferably 1-20 times.

[0016] The thermally conductive and heat-insulating integrated graphene fiber aerogel prepared in this invention is obtained by cross-lamination of graphene film and graphene aerogel; wherein the thickness of graphene film is 1-100 micrometers and the thickness of graphene aerogel is 0.5-100 millimeters.

[0017] The density of the thermally conductive and insulating integrated graphene fiber aerogel is no greater than 0.1 g / cm³. 3 .

[0018] The present invention also provides applications of the above-mentioned integrated thermal insulation graphene fiber aerogel.

[0019] The advantages of this invention are: (1) By using graphene fibers with the same chemical composition as precursors for films and aerogels, molecular-scale interpenetration was achieved through hierarchical control of fiber length and high-temperature graphitization induction, forming a fusion interface connected by π-π conjugation and strong covalent cross-linking, fundamentally solving the technical bottlenecks of heterogeneous material interface delamination and excessive thermal expansion characteristics. The introduction of carbon-based covalent interfaces prevents the material from delaminating and warping under severe thermal cycling, avoiding delamination problems under thermal cycling or mechanical vibration, and resulting in a long service life.

[0020] (2) In addition, an innovative heat flow regulation model of "in-plane thermal conduction and diffusion + normal thermal insulation and hindrance" was proposed, which integrates two materials with opposite thermal properties at the molecular / nanoscale. This strong anisotropy is the core of its efficient thermal shock protection. Faced with local thermal shock, the surface graphene film can instantly "spread" heat in the horizontal direction, greatly reducing the local heat flux density; the bottom graphene fiber aerogel effectively blocks the downward transfer of heat. This synergistic mechanism of "horizontal thermal conduction followed by vertical thermal insulation" can improve the heat delay time (i.e., the time for the back to reach the critical temperature) and improve the problem of local heat concentration in the material compared with a single material.

[0021] (3) The overall density can be as low as 0.1 g / cm³ by adopting an all-carbon micro-nano structure design. 3 The following technologies meet the stringent weight reduction requirements of aerospace materials. The fibrous aerogel framework endows the material with excellent compression resilience and vibration fatigue resistance, while the graphitized structure ensures structural stability and performance retention across a wide temperature range, especially at high temperatures. The production process combines mature spinning technology with continuous assembly technology. By controlling spinning parameters, fiber length distribution, and the number of stacked layers, the material's density, porosity, and thermal conductivity / insulation properties can be precisely controlled, possessing the potential to fabricate large-area, complex-shaped devices and facilitating industrial scale-up. Attached Figure Description

[0022] Figure 1 The SEM morphology of the thermally conductive and insulating integrated graphene fiber aerogel prepared in Example 1 is shown.

[0023] Figure 2 The image shows the SEM morphology of the interface between the graphene fiber and the film in Example 1.

[0024] Figure 3 The stress-strain curve of Example 1 under 60% compression at high temperature (2000℃) is shown.

[0025] Figure 4 The stress-strain curve of Example 1 under 60% compression at room temperature (25℃) is shown. Detailed Implementation

[0026] The following examples are provided to further illustrate the present invention and are intended to explain the invention, not to limit its scope. Unless otherwise specified, all figures are expressed in parts by weight and weight percentages.

[0027] Unless otherwise specified, the raw materials used in this invention are all conventional commercially available products; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0028] The embodiments of the present invention will be further described below with reference to several examples.

[0029] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0030] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0031] Example 1 (1) Use a 10 mg / g aqueous solution of graphene oxide, add 1% sodium polyacrylate (PAAS), mix and stir at a mass ratio of 1:1 until completely dissolved to obtain a spinning solution.

[0032] (2) Using a blown spinning equipment, under the conditions of an airflow rate of 3 L / min, a spinning solution extrusion speed of 20 mL / h, and a receiving distance of 30 cm, the spinning solution was blown into a coagulation bath in which 20% calcium chloride aqueous solution and anhydrous ethanol were mixed in a 1:1 ratio to prepare GO / PAAS composite gel fibers with an average diameter of 10 micrometers.

[0033] (3) The obtained composite gel fibers were washed with ethanol to remove cross-linked ions-calcium, and then cut into two types of GO / PAAS composite gel fibers with lengths of ~1 mm (short fiber) and ~10 cm (long fiber), respectively, and prepared into a dispersion with ethanol.

[0034] (4) Take 5 mL of the dispersion prepared from short fibers formed by spinning solution and perform vacuum filtration to form a self-fusion film with a thickness of about 5 μm on the cellulose filter membrane. Then take 15 mL of the dispersion prepared from long fibers formed by spinning solution and perform secondary filtration to form a fiber aerogel layer with a thickness of about 5 mm on the film, thus obtaining the "film-aerogel" prefabricated functional unit.

[0035] (5) Dry the preform at 0.5 MPa and 25 °C for 48 h.

[0036] (6) The dried preform was chemically reduced at 95 degrees Celsius for 12 hours in a hydroiodic acid vapor atmosphere.

[0037] (7) The chemically reduced preform is placed in a tube furnace and heated to 1000°C at 2°C / min under argon protection. It is held for 1 hour, then heated to 2800°C and held for 2 hours. It is then cooled with the furnace.

[0038] (8) After removal, a single integrated thermal insulation functional unit was obtained, with a density of 0.074 g / cm³. Its graphene film layer thickness is approximately 4 μm; the graphene fiber aerogel layer thickness is approximately 2 mm. Its SEM morphology is as follows: Figure 1 As shown, according to Figure 2 It can be seen that the graphene fiber and the film have a good fusion interface. The stress-strain mechanical properties of the fabricated integrated thermal insulation functional unit were tested at 2000 ℃ and 25 ℃, respectively. Figure 3 , 4 As shown, the mechanical properties of the integrated thermal insulation functional unit are similar under high and low temperature conditions, indicating that it has good high temperature stability.

[0039] (9) Performance testing: The material's normal thermal conductivity was measured to be 0.123 W / mK using the laser flare method; the in-plane thermal conductivity was measured to be 347 W / mK using the steady-state heat flow method; and thermal shock was simulated using a high-power pulsed laser (power density 100 W / cm², pulse width 1 s), with infrared thermal imagers recording the temperature rise curves at the impact point on the front and back of the material. The test results show that the time required for the back surface temperature of the material to reach 100 °C is 8 s.

[0040] Example 2 (1) Repeat steps 1-4 of Example 1 to prepare 3 identical functional units.

[0041] (2) Stack the three units directly and dry them at a pressure of 0.5 MPa and a temperature of 25 °C.

[0042] (3) Repeat steps 6-8 of Example 1 to finally obtain a thermally conductive and insulating integrated laminated material with a total thickness of approximately 6.1 mm. The density is 0.078 g / cm³.

[0043] (4) Performance testing: The in-plane thermal conductivity of the material was measured to be 337 W / mK using the laser flare method; the normal thermal conductivity was measured to be 0.127 W / mK using the steady-state heat flow method. Thermal shock was simulated using a high-power pulsed laser (power density 100 W / cm², pulse width 1 s), and the temperature rise curves of the front and back sides of the material were recorded using an infrared thermal imager. The test results show that the time required for the back side temperature to reach 100 ℃ is 17 s.

[0044] Example 3 (1) Repeat steps 1-3 of Example 1.

[0045] (2) A dispersion of short fibers formed by spinning solution was taken from 5 mL and vacuum filtered to form a self-fusion film with a thickness of about 5 μm on the cellulose filter membrane. A dispersion of long fibers formed by spinning solution was taken from 7.5 mL and vacuum filtered again to form a fiber aerogel layer with a thickness of about 2.5 mm on the film, thus obtaining a "film-aerogel" preform. Two identical functional units were prepared.

[0046] (3) Stack the two units directly and dry them at a pressure of 0.5 MPa and a temperature of 25 °C.

[0047] (4) Repeat steps 6-8 of Example 1 to obtain a thermally conductive and insulating integrated laminated material with a total thickness of approximately 2.06 mm. The density is 0.081 g / cm³.

[0048] (5) Performance testing: The in-plane thermal conductivity of the material was measured to be 352 W / mK using the laser flare method; the normal thermal conductivity was measured to be 0.125 W / mK using the steady-state heat flow method. Thermal shock was simulated using a high-power pulsed laser (power density 100 W / cm², pulse width 1 s), and the temperature rise curves of the front and back sides of the material were recorded using an infrared thermal imager. The test results show that the time required for the back side temperature to reach 100 ℃ is 13 s.

[0049] Example 4 (1) Repeat steps 1-3 of Example 1.

[0050] (2) Take 5 mL of the short fiber dispersion formed by spinning solution and perform vacuum filtration to form a self-fusion film with a thickness of about 5 μm on the cellulose filter membrane. Then take 3 mL of the long fiber dispersion formed by spinning solution and perform a second vacuum filtration to form a fiber aerogel layer with a thickness of about 1 mm on the film to obtain a "film-aerogel" preform. Five identical functional units were prepared.

[0051] (3) Stack the five units directly and dry them at a pressure of 0.5 MPa and a temperature of 25 °C.

[0052] (4) Repeat steps 6-8 of Example 1 to obtain a thermally conductive and insulating integrated laminated material with a total thickness of approximately 2.1 mm. The density is 0.085 g / cm³.

[0053] (5) Performance testing: The in-plane thermal conductivity of the material was measured to be 364 W / mK using the laser flare method; the normal thermal conductivity was measured to be 0.119 W / mK using the steady-state heat flow method. Thermal shock was simulated using a high-power pulsed laser (power density 100 W / cm², pulse width 1 s), and the temperature rise curves of the front and back sides of the material were recorded using an infrared thermal imager. The test results show that the time required for the back side temperature to reach 100 ℃ is 18 s.

[0054] Example 5 (1) Use a 10 mg / g aqueous solution of graphene oxide, add 1 wt% sodium polyacrylate (PAAS), mix and stir at a mass ratio of 1:9 until completely dissolved to obtain a spinning solution.

[0055] (2) Using a blown spinning equipment, under the conditions of an airflow rate of 3 L / min, a spinning solution extrusion speed of 20 mL / h, and a receiving distance of 30 cm, the spinning solution was blown into a coagulation bath in which 20% calcium chloride aqueous solution and anhydrous ethanol were mixed in a 1:1 ratio to prepare GO / PAAS composite gel fibers with an average diameter of 10 micrometers.

[0056] (3) The obtained composite gel fibers were washed with ethanol to remove crosslinking ions, and then cut into two types of GO / PAAS composite gel fibers with lengths of ~1 mm (short fiber) and ~10 cm (long fiber), respectively, and prepared into a dispersion with ethanol.

[0057] (4) Take 5 mL of the dispersion prepared from short fibers formed by spinning solution and perform vacuum filtration to form a self-fusion film with a thickness of about 5 μm on the cellulose filter membrane. Then take 15 mL of the dispersion prepared from long fibers formed by spinning solution and perform secondary filtration to form a fiber aerogel layer with a thickness of about 5 mm on the film, thus obtaining the "film-aerogel" preform.

[0058] (5) Dry the preform at 0.5 MPa and 25 °C for 48 h.

[0059] (6) The dried preform was chemically reduced at 95 degrees Celsius for 12 hours in a hydroiodic acid vapor atmosphere.

[0060] (7) The chemically reduced preform is placed in a tube furnace and heated to 1000°C at 2°C / min under argon protection. It is held for 1 hour, then heated to 2800°C and held for 2 hours. It is then cooled with the furnace.

[0061] (8) After removal, a single integrated thermal insulation functional unit is obtained with a density of 0.073 g / cm³. Its graphene film layer thickness is about 4 μm; the graphene fiber aerogel layer thickness is about 2 mm.

[0062] (9) Performance testing: The material's normal thermal conductivity was measured to be 0.098 W / mK using the laser flare method; the in-plane thermal conductivity was measured to be 125 W / mK using the steady-state heat flow method; thermal shock was simulated using a high-power pulsed laser (power density 100 W / cm², pulse width 1 s), and the temperature rise curves of the front and back sides of the material were recorded using an infrared thermal imager. The test results show that the time required for the back side temperature of the material to reach 100 °C is 10 s.

[0063] Example 6 The only difference from Example 1 is that the fibers are ~10 cm long, and their thermal conductivity is similar to that of Example 1.

[0064] Example 7 The only difference from Example 1 is the short fiber (~5 mm), and its thermal conductivity is similar to that of Example 1.

[0065] Comparative Example 1 (Single Fiber Aerogel) (1) Repeat steps 1 and 2 of Example 1. Cut the obtained composite gel fibers into GO / PAAS composite gel fibers with a length of ~10 cm (long fiber).

[0066] (2) Take 15 mL of the long fiber dispersion formed by spinning solution and vacuum filter it to form a fiber aerogel layer with a thickness of about 5 mm, and obtain the aerogel preform. Dry the preform at 25 ℃ and 0.5 MPa pressure for 48 h and then perform chemical reduction.

[0067] (3) The chemically reduced preform is placed in a tube furnace and heated to 1000℃ at 2℃ / min under argon protection. It is held for 1 hour and then heated to 2800℃ and held for 2 hours. It is then cooled with the furnace.

[0068] (4) After removal, a single graphene fiber aerogel layer is obtained. Its thickness is about 1.94 mm and its density is 0.071 g / cm³.

[0069] (5) Performance testing: The in-plane thermal conductivity of the material was measured to be 0.093 W / mK using the laser flare method and 0.081 W / mK using the steady-state heat flow method. Thermal shock was simulated using a high-power pulsed laser (power density 100 W / cm², pulse width 1 s), and the temperature rise curves of the front and back sides of the material were recorded using an infrared thermal imager. The test results show that the time required for the back side temperature to reach 100 °C is 5 s.

[0070] Comparative Example 2 has only a short fiber layer (1) Use a 10 mg / g aqueous solution of graphene oxide, add 1% sodium polyacrylate (PAAS), mix and stir at a mass ratio of 1:1 until completely dissolved to obtain a spinning solution.

[0071] (2) Using a blown spinning equipment, under the conditions of an airflow rate of 3 L / min, a spinning solution extrusion speed of 20 mL / h, and a receiving distance of 30 cm, the spinning solution was blown into a coagulation bath in which 20% calcium chloride aqueous solution and anhydrous ethanol were mixed in a 1:1 ratio to prepare GO / PAAS composite gel fibers with an average diameter of 10 micrometers.

[0072] (3) Cut the obtained composite gel fibers into GO / PAAS composite gel fibers with a length of ~1 mm (short fiber).

[0073] (4) Take 5 mL of spinning solution to form short fibers and a portion of coagulation bath for vacuum filtration, and form a self-fusion film of about 5 μm thickness on the cellulose filter membrane.

[0074] (5) Dry the preform at 0.5 MPa and 25 °C for 48 h.

[0075] (6) The dried preform was chemically reduced at 95 degrees Celsius for 12 hours in a hydroiodic acid vapor atmosphere.

[0076] (7) The chemically reduced preform is placed in a tube furnace and heated to 1000°C at 2°C / min under argon protection. It is held for 1 hour, then heated to 2800°C and held for 2 hours. It is then cooled with the furnace.

[0077] (8) A graphene film with a thickness of 4 micrometers was obtained.

[0078] Table 1. Comparison of thermal properties of integrated thermally conductive and insulating graphene fiber aerogels

[0079] The above embodiments describe in detail the structure, features, and effects of the present invention. The above description is only a preferred embodiment of the present invention. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, shall still fall within the scope of protection of the present invention if they do not exceed the scope covered by the specification.

Claims

1. A method for preparing a thermally-conducting and thermally- insulating integrated graphene fiber aerogel, characterized by, It includes the following steps: (1) Prepare a spinning solution, wherein the spinning solution includes graphene oxide and a polymer with a molecular weight of not less than 1 million, and the mass ratio of the graphene oxide to the polymer is not less than 1:

9. (2) Composite gel fibers are obtained by spinning using spinning solution; (3) The composite gel fibers are processed into short fibers with a length of no more than 5 mm and long fibers with a length of 10-100 mm respectively; (4) The short fiber dispersion is filtered on the filter membrane to form a thin film substrate on the filter membrane surface; (5) The long fiber dispersion was filtered on the film substrate to obtain graphene fiber aerogel units. (6) Repeat steps (4)-(5) to assemble and dry the obtained graphene fiber aerogel units; (7) Reduce and graphitize to obtain thermally conductive and heat-insulating integrated graphene fiber aerogel.

2. The method of claim 1, wherein, The spinning method described in step (2) is one of blow spinning, wet spinning, dry spinning, or electrospinning.

3. The method of claim 1, wherein, The filtration method in steps (4) and (5) is vacuum filtration.

4. The method of claim 1, wherein, The reduction method in step (7) is to use a reducing agent for chemical reduction, wherein the reducing agent is one of hydroiodic acid vapor, hydroiodic acid, or hydrazine hydrate vapor.

5. The method of claim 1, wherein, The graphitization method in step (7) is as follows: in an inert atmosphere, the temperature is increased to 1000 ℃ at a heating rate of 2-5 ℃ / min and held for 1 h; then the temperature is increased to 2800 ℃ and held for 2 hours, and then cooled with the furnace.

6. The method of claim 1, wherein, The number of repetitions in step (6) is 0-50 times.

7. A thermally conductive and insulating integrated graphene fiber aerogel prepared by the method as described in claim 1.

8. The thermally and electrically conductive integrated graphene fiber aerogel of claim 7, wherein, The integrated thermally conductive and insulating graphene fiber aerogel is obtained by cross-lamination of graphene film and graphene aerogel.

9. The thermally and electrically conductive integrated graphene fiber aerogel of claim 7, wherein, The heat-conducting and heat-insulating integrated graphene fiber aerogel has a density of not more than 0.1 g / cm 3 .

10. An application of the thermally conductive and insulating integrated graphene fiber aerogel as described in claim 7.

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