Graphene composite aerogel and application thereof

Abstract

The invention provides graphene composite aerogel and application thereof. The graphene composite aerogel comprises a framework and a one-dimensional carbon material, the framework comprises a plurality of graphene sheet layers, and the plurality of graphene sheet layers are stacked in the thickness direction; a porous structure is arranged between any two adjacent graphene sheet layers along the thickness direction; the one-dimensional carbon material is distributed on the graphene sheet layer, and the axial direction of the one-dimensional carbon material is parallel to the plane where the graphene sheet layer is located; the thickness direction is perpendicular to the plane where the graphene sheet layers are located, so that the problem of poor compression resistance of the graphene aerogel in the prior art is solved.

Description

Technical Field

[0001] This invention relates to the field of aerogel materials technology, and more specifically, to a graphene composite aerogel and its applications. Background Technology

[0002] Aerogels are porous solid materials characterized by low density, high porosity, and large specific surface area. They are widely used in aerospace exploration, microwave absorbing materials, environmental protection, high-efficiency catalysis, and supercapacitors. Since the 1930s, a series of aerogels with different materials, structures, and properties have been synthesized. Graphene, with its high thermal conductivity, low density, and good electrical conductivity, has become a new material for preparing thermally conductive aerogels. Currently, graphene aerogels suffer from low mechanical properties. Although existing porous graphene frameworks possess a certain degree of high compressibility and resilience in a single direction, they are prone to damage under high-intensity pressure in practical applications, losing their compressive and resilience properties. Therefore, improving the compressive strength of graphene aerogels while maintaining structural integrity and high horizontal thermal conductivity is a pressing issue that needs to be addressed. Summary of the Invention

[0003] The main objective of this invention is to provide a graphene composite aerogel and its application, so as to solve the problem of poor compressive strength of graphene aerogel in the prior art.

[0004] To achieve the above objectives, according to one aspect of the present invention, a graphene composite aerogel is provided, comprising a framework and a one-dimensional carbon material;

[0005] The framework consists of multiple graphene sheets stacked along the thickness direction; there is a porous structure between any two adjacent graphene sheets along the thickness direction.

[0006] One-dimensional carbon materials are distributed on graphene sheets, and the axis of the one-dimensional carbon materials is parallel to the plane in which the graphene sheets are located.

[0007] The thickness direction is perpendicular to the plane containing the graphene sheets.

[0008] Furthermore, the graphene sheets are curved, and any two adjacent graphene sheets along the thickness direction overlap to form a porous structure.

[0009] Furthermore, the horizontal thermal conductivity of the graphene composite aerogel along the plane of the graphene sheets ranges from 20 W / mK to 70 W / mK.

[0010] Furthermore, the graphene composite aerogel exhibits a longitudinal thermal conductivity of 1 W / mK to 10 W / mK along its thickness direction under a test pressure of 206 kPa.

[0011] Furthermore, after being subjected to a high-pressure compression treatment of 40,000 kPa for 10 seconds, the graphene composite aerogel exhibited a compression ratio of greater than or equal to 70% under a test pressure of 206 kPa.

[0012] Furthermore, after being subjected to a high-pressure treatment of 40,000 kPa for 10 seconds, the graphene composite aerogel exhibits a rebound rate of greater than or equal to 90% under a test pressure of 100 kPa.

[0013] Furthermore, after being subjected to a high-pressure treatment of 40000 kPa for 10 seconds, the graphene composite aerogel was subjected to 1000 cycles of compression at 90% strain, and the stress value change rate was less than or equal to 10%.

[0014] Furthermore, the density of the graphene composite aerogel is 0.02 g / cm³. 3 Up to 0.15 g / cm 3 .

[0015] Furthermore, the porosity of the graphene composite aerogel is 70% to 90%.

[0016] Furthermore, the specific surface area of ​​the graphene composite aerogel is 100 m². 2 / g to 1000m 2 / g.

[0017] Furthermore, the pore volume of the graphene composite aerogel is 0.1 cm³. 3 / g to 2.0cm 3 / g.

[0018] Furthermore, by volume percentage, macropores with a pore size of 150 μm to 500 μm account for ≥70%.

[0019] Furthermore, by volume percentage, the proportion of pores with a diameter of 10 μm to 50 μm is less than or equal to 30%.

[0020] Furthermore, the graphene composite aerogel has an average pore size of 150 μm to 500 μm.

[0021] Furthermore, the content of one-dimensional carbon material in the graphene composite aerogel is 1% to 20% by weight.

[0022] Furthermore, by weight percentage, the carbon content in the graphene composite aerogel is greater than or equal to 99%.

[0023] Furthermore, the Raman spectrum of the graphene composite aerogel exhibits D and G peaks, with an area ratio of ID to G peaks. D / I G Less than 0.01.

[0024] Furthermore, the pores between any two adjacent graphene sheets along the thickness direction are oriented along the plane of the graphene sheets to form an ordered honeycomb-like porous structure.

[0025] Furthermore, the thickness of the graphene sheets ranges from 1 nm to 5 nm.

[0026] Furthermore, one-dimensional carbon materials include one or more of carbon nanotubes, functionalized carbon nanotubes, carbon fibers, aramid fibers, and polyoxadiazole fibers.

[0027] Furthermore, one-dimensional carbon materials include carbon nanotubes, which include at least one of single-walled carbon nanotubes, oligo-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0028] Furthermore, one-dimensional carbon materials include carbon nanotubes, which include single-walled carbon nanotubes with a length of 5 μm to 50 μm and a diameter of 1 nm to 4 nm.

[0029] Furthermore, one-dimensional carbon materials include carbon nanotubes, which include oligowalled carbon nanotubes with a length of 5 μm to 50 μm and a diameter of 2 nm to 10 nm.

[0030] Furthermore, one-dimensional carbon materials include carbon nanotubes, which include multi-walled carbon nanotubes with a length of 5 μm to 50 μm and a diameter of 7 nm to 30 nm.

[0031] Furthermore, the one-dimensional carbon material includes functionalized carbon nanotubes, which include at least one of functionalized single-walled carbon nanotubes, functionalized oligo-walled carbon nanotubes, and functionalized multi-walled carbon nanotubes.

[0032] Furthermore, the one-dimensional carbon material includes functionalized carbon nanotubes, which include functionalized single-walled carbon nanotubes with a length of 5 μm to 50 μm and a diameter of 1 nm to 6 nm.

[0033] Furthermore, the one-dimensional carbon material includes functionalized carbon nanotubes, which include functionalized oligowalled carbon nanotubes with a length of 5 μm to 50 μm and a diameter of 2 nm to 15 nm.

[0034] Furthermore, the one-dimensional carbon material includes functionalized carbon nanotubes, which include functionalized multi-walled carbon nanotubes with a length of 5 μm to 50 μm and a diameter of 7 nm to 40 nm.

[0035] Furthermore, the one-dimensional carbon material includes carbon fibers with a length of 1 μm to 200 μm and a diameter of 5 μm to 20 μm.

[0036] Furthermore, the one-dimensional carbon material includes aramid fibers with a length of 0.1 mm to 5 mm and a diameter of 5 μm to 20 μm.

[0037] Furthermore, the one-dimensional carbon material includes polyoxadiazole fibers with a length of 0.1 mm to 5 mm and a diameter of 5 μm to 20 μm.

[0038] According to one aspect of the present invention, the above-described graphene composite aerogel is provided as a thermally conductive material in a thermal management system.

[0039] By applying the technical solution of this invention, a high-strength one-dimensional carbon material is introduced into the skeleton of graphene aerogel to improve the skeleton strength and resist external pressure. The introduction of the one-dimensional carbon material is attached to the graphene sheets as a reinforcing material, which significantly improves the support strength of the three-dimensional skeleton while achieving a high compression ratio.

[0040] The graphene composite aerogel based on the present invention is not prone to collapse under strong external pressure and has good recovery resilience. After the strong external pressure is unloaded, the skeleton can recover quickly and maintain the high compression resilience and high compression ratio of the original skeleton. Attached Figure Description

[0041] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0042] Figure 1 SEM image of a cross section along the thickness direction in the reduced graphene oxide composite aerogel prepared in Example 1;

[0043] Figure 2 This is a partial view of the graphene sheets in the graphene composite aerogel prepared in Example 1;

[0044] Figure 3 This is a SEM image of a cross-section along the thickness direction in the graphene composite aerogel prepared in Example 1.

[0045] Figure 4 This is a load-time variation graph of the graphene composite aerogel under 90% compressive strain in Example 1;

[0046] Figure 5 The load-stroke variation diagram is shown for the graphene composite aerogel in Example 1 under 90% compressive strain. Detailed Implementation

[0047] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0048] As described in the background section, existing graphene composite aerogels suffer from poor compressive strength, with the framework prone to collapse and irreversible elasticity under high pressure. To address these issues, this invention provides a composite aerogel and its applications.

[0049] According to one aspect of the present invention, a graphene composite aerogel is provided, comprising a framework and a one-dimensional carbon material; the framework comprises a plurality of graphene sheets stacked along the thickness direction; a porous structure is formed between any two adjacent graphene sheets along the thickness direction; the one-dimensional carbon material is distributed on the graphene sheets and the axial direction of the one-dimensional carbon material is parallel to the plane in which the graphene sheets are located; the thickness direction is perpendicular to the plane in which the graphene sheets are located.

[0050] The graphene composite aerogel provided by this invention improves the strength of the graphene aerogel framework by introducing high-strength one-dimensional carbon material into it, thereby enhancing the framework's resistance to external pressure. The one-dimensional carbon material acts as a reinforcing material attached to the graphene sheets, achieving a high compressibility while significantly improving the support strength of the three-dimensional framework. Based on this invention, the graphene composite aerogel framework is less prone to collapse under strong external pressure and exhibits good recovery resilience. After the external pressure is unloaded, the framework can quickly recover, maintaining the original framework's high compressibility and resilience, as well as its high compressibility.

[0051] In some embodiments, the graphene sheets are curved, and any two adjacent graphene sheets overlap along the thickness direction to form a porous structure, which can enhance the support strength and resilience of the three-dimensional framework along the thickness direction. In this application, the thickness direction refers to the direction perpendicular to the plane containing the graphene sheets.

[0052] In some embodiments, the horizontal thermal conductivity of the graphene composite aerogel along the plane of the graphene sheets is 20 W / mK to 70 W / mK. Specifically, the horizontal thermal conductivity can be 20 W / mK, 25 W / mK, 30 W / mK, 31 W / mK, 32 W / mK, 33 W / mK, 34 W / mK, 35 W / mK, 36 W / mK, 37 W / mK, 38 W / mK, 39 W / mK, 40 W / mK, 41 W / mK, 42 W / mK, 43 W / mK, 44 W / mK, 45 W / mK, 50 W / mK, 60 W / mK, or 70 W / mK. Of course, other values ​​within the above range are also possible and are not limited here. Preferably, it is 30 W / mK to 45 W / mK.

[0053] In some embodiments, the graphene composite aerogel exhibits a longitudinal thermal conductivity of 1 W / mK to 10 W / mK along its thickness direction under a test pressure of 206 kPa. Specifically, the longitudinal thermal conductivity can be 1 W / mK, 1.2 W / mK, 1.5 W / mK, 2 W / mK, 2.5 W / mK, 3 W / mK, 3.5 W / mK, 4 W / mK, 4.5 W / mK, 5 W / mK, 6 W / mK, 7 W / mK, 7 W / mK, 9 W / mK, or 10 W / mK. Of course, other values ​​within the above range are also possible and are not limited here. In principle, as a thermally conductive material, the higher the longitudinal and horizontal thermal conductivity of aerogel, the better. This invention has found that the horizontal and longitudinal thermal conductivity of composite aerogels are closely related to the pore size and porosity, carbon fiber loading and uniformity, lattice integrity of graphene sheets, and graphene sheet thickness, among other structural properties. Composite aerogels with longitudinal and horizontal thermal conductivity within the above-mentioned ranges have high supporting strength and resilience along the thickness direction of graphene sheets. They possess high horizontal thermal conductivity while also exhibiting high compressive strength, high resilience, and structural integrity.

[0054] In some embodiments, after being subjected to a high-pressure compression treatment of 40000 kPa for 10 s, the graphene composite aerogel exhibits a compression ratio of greater than or equal to 70% under a test pressure of 206 kPa. The compression ratio of the graphene composite aerogel after being subjected to high pressure is closely related to structural performance parameters such as the carbon loading of one-dimensional carbon materials and the load uniformity, which are related to support strength and resilience. This invention has found that graphene composite aerogels with compression ratios within the above range have a high one-dimensional carbon material loading and load uniformity on the graphene sheets, and thus exhibit high support strength and resilience.

[0055] In some embodiments, after being subjected to a high-pressure treatment of 40,000 kPa for 10 seconds, the graphene composite aerogel exhibits a rebound rate of greater than or equal to 90% under a test pressure of 100 kPa. The compression rebound rate of the graphene composite aerogel after high pressure is closely related to structural performance parameters such as the loading amount and load uniformity of one-dimensional carbon materials, which are related to support strength and rebound performance. This invention has found that in graphene composite aerogels with a rebound rate within the above range, the graphene sheets have a high loading amount and load uniformity of one-dimensional carbon materials. Therefore, the graphene composite aerogel has high support strength and rebound performance. After the external high pressure (40,000 kPa) is unloaded, the skeleton can recover quickly and maintain the high compression rebound performance and high compression ratio of the original skeleton.

[0056] In some embodiments, after being subjected to a 40,000 kPa high-pressure compression treatment for 10 seconds, the graphene composite aerogel undergoes 1,000 cycles of cyclic compression at 90% strain, and the stress change rate is less than or equal to 10%. The stress change rate of the graphene composite aerogel after cyclic compression is related to structural performance parameters such as the loading amount of one-dimensional carbon material, the load uniformity, and the pore arrangement in the graphene composite aerogel, which are related to support strength and resilience. Graphene composite aerogels with a change rate within the above range have a higher one-dimensional carbon material loading amount and load uniformity, so as to obtain higher support strength and compression cycle performance after being subjected to high pressure, and have a more uniform pore arrangement in the graphene composite aerogel so that the graphene composite aerogel can be uniformly stressed under external force and reduce stress concentration points, so that the graphene composite aerogel has higher support strength and resilience. After being subjected to a 40,000 kPa high-pressure compression treatment for 10 seconds, it can still be cyclically compressed 1,000 times at 90% deformation, and the skeleton can still maintain structural integrity.

[0057] In some embodiments, the density of the graphene composite aerogel is 0.02 g / cm³. 3 Up to 0.15 g / cm 3 Specifically, it can be 0.02 g / cm³. 3 0.04g / cm 3 0.06g / cm 3 0.07g / cm 3 0.08g / cm 3 0.09g / cm 3 0.10 g / cm 3 0.11 g / cm 3 0.13g / cm 3 0.15g / cm 3 Of course, other values ​​within the above range are also possible and are not limited here. Graphene composite aerogels with densities within the above range have larger porosity to obtain higher resilience performance, while possessing a high-strength skeleton (graphene sheet density and carbon fiber loading) to obtain higher support strength, thus giving the graphene composite aerogels high support strength and resilience performance.

[0058] In some embodiments, the graphene composite aerogel has a porosity of 70% to 90% and a specific surface area of ​​100 m². 2 / g to 1000m 2 / g, pore volume 0.1cm 3 / g to 2cm 3 / g. Graphene composite aerogels with porosity, specific surface area, and pore volume within the above range have high porosity, high-strength framework, and a high proportion of macropores, which gives them high support strength and resilience.

[0059] In some embodiments, by volume percentage, the proportion of macropores with a pore size of 150 μm to 500 μm in the graphene composite aerogel is greater than or equal to 70%, and the proportion of micropores with a pore size of 10 μm to 50 μm is less than or equal to 30%. Specifically, the following ratios are possible: 70% macropores and 30% micropores; 70% macropores and 25% micropores; 80% macropores and 20% micropores; 80% macropores and 15% micropores; 90% macropores and 5% micropores; 95% macropores and 5% micropores; or 95% macropores and 3% micropores. Other values ​​within the above ranges are also possible and are not limited here. Graphene composite aerogels within the above ranges have a high proportion of macropores and a relatively concentrated pore size distribution, which allows for a higher compressibility. Simultaneously, they can be uniformly stressed under external forces and have fewer stress concentration points, resulting in higher compressive strength and resilience.

[0060] In some embodiments, the average pore size of the graphene composite aerogel is between 150 μm and 500 μm, specifically 150 μm, 200 μm, 220 μm, 250 μm, 270 μm, 300 μm, 320 μm, 350 μm, 400 μm, 450 μm, and 500 μm, or other values ​​within the above range, which are not limited here. Graphene composite aerogels within the above pore size range exhibit high compressibility under external force.

[0061] In some embodiments, the content of one-dimensional carbon material in the graphene composite aerogel is 1% to 20% by weight, specifically 1%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, and 20%, or other values ​​within the above range, which are not limited herein. The loading of one-dimensional carbon material affects the compressive strength and lateral thermal conductivity of the graphene composite aerogel. Within the above ranges, the graphene composite aerogel exhibits high lateral thermal conductivity and high compressive strength in the thickness direction.

[0062] In some embodiments, the carbon content in the graphene composite aerogel is greater than or equal to 99% by weight. Graphene composite aerogels with higher carbon content have higher lattice integrity and higher mechanical strength.

[0063] In some embodiments, the Raman spectrum of the graphene composite aerogel has a D peak and a G peak, and the area ratio of the D peak to the G peak is I. D / I G Less than 0.01, graphene composite aerogel materials have few defects, high graphitization, and high horizontal thermal conductivity.

[0064] In some embodiments, the pores between any two adjacent graphene sheets along the thickness direction in the graphene composite aerogel are oriented along the plane of the graphene sheets to form an ordered honeycomb-like porous structure. The ordered porous structure can further enhance the compressive strength and resilience of the graphene composite aerogel.

[0065] In some embodiments, the thickness of the graphene sheets is 1 nm to 5 nm, specifically 1 nm, 2 nm, 3 nm, 4 nm, or 5 nm, or other values ​​within the above range, which are not limited here. When the thickness of the graphene sheets is within the above size range, the framework of the graphene composite aerogel has high compressive strength and compression resilience.

[0066] In some embodiments, one-dimensional carbon materials include one or more of carbon nanotubes, functionalized carbon nanotubes, carbon fibers, aramid fibers, and polyoxadiazole fibers.

[0067] In some embodiments, the one-dimensional carbon material includes carbon nanotubes, which include at least one of single-walled carbon nanotubes, oligo-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0068] In some embodiments, the one-dimensional carbon material includes carbon nanotubes, which include single-walled carbon nanotubes. The single-walled carbon nanotubes have a length of 5 μm to 50 μm and a diameter of 1 nm to 4 nm. Specifically, the single-walled carbon nanotubes have a length of 5 μm and a diameter of 1 nm, a length of 10 μm and a diameter of 1.5 nm, a length of 20 μm and a diameter of 2 nm, a length of 30 μm and a diameter of 2.5 nm, a length of 40 μm and a diameter of 3 nm, and a length of 50 μm and a diameter of 4 nm. Other values ​​within the above ranges are also possible and are not limited thereto. Carbon nanotubes within the above size range exhibit high mechanical strength, and their loading onto graphene sheets can significantly improve the mechanical strength of the framework.

[0069] In some embodiments, the one-dimensional carbon material includes carbon nanotubes, which include oligowalled carbon nanotubes. The length of the oligowalled carbon nanotubes is 5 μm to 50 μm, and the diameter is 2 nm to 10 nm. Specifically, the oligowalled carbon nanotubes have a length of 5 μm and a diameter of 2 nm, a length of 10 μm and a diameter of 4 nm, a length of 20 μm and a diameter of 5 nm, a length of 30 μm and a diameter of 6 nm, a length of 40 μm and a diameter of 8 nm, a length of 50 μm and a diameter of 10 nm, and other values ​​within the above range are also possible and are not limited herein. Oligowalled carbon nanotubes within the above size range have high mechanical strength, and when loaded onto graphene sheets, they can significantly improve the mechanical strength of the framework.

[0070] In some embodiments, the one-dimensional carbon material includes carbon nanotubes, which include multi-walled carbon nanotubes. The length of the multi-walled carbon nanotubes is 5 μm to 50 μm, and the diameter is 7 to 30 nm. Specifically, the multi-walled carbon nanotubes have a length of 5 μm and a diameter of 7 nm, a length of 10 μm and a diameter of 12 nm, a length of 20 μm and a diameter of 15 nm, a length of 30 μm and a diameter of 20 nm, a length of 40 μm and a diameter of 25 nm, and a length of 50 μm and a diameter of 30 nm. Other values ​​within the above ranges are also possible and are not limited thereto. Multi-walled carbon nanotubes within the above size range exhibit high mechanical strength, and their loading onto graphene sheets can significantly improve the mechanical strength of the framework.

[0071] In some embodiments, the one-dimensional carbon material includes carbon nanotubes, which include at least one of single-walled carbon nanotubes, oligo-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0072] In some embodiments, the one-dimensional carbon material includes functionalized carbon nanotubes, which include functionalized single-walled carbon nanotubes. The length of the functionalized single-walled carbon nanotubes is 5 μm to 50 μm, and the diameter is 1 nm to 6 nm. The functionalized single-walled carbon nanotubes can have a length of 5 μm and a diameter of 1 nm, a length of 10 μm and a diameter of 2 nm, a length of 20 μm and a diameter of 3 nm, a length of 30 μm and a diameter of 4 nm, a length of 40 μm and a diameter of 5 nm, a length of 50 μm and a diameter of 6 nm, or other values ​​within the above range. These functionalized single-walled carbon nanotubes within the above size range exhibit high mechanical strength, and when loaded onto graphene sheets, they can significantly improve the mechanical strength and compressive resilience of the framework.

[0073] In some embodiments, the one-dimensional carbon material includes functionalized carbon nanotubes, which include functionalized oligowalled carbon nanotubes. The length of the functionalized oligowalled carbon nanotubes is 5 μm to 50 μm, and the diameter is 2 nm to 15 nm. Specifically, the functionalized oligowalled carbon nanotubes have a length of 5 μm and a diameter of 2 nm, a length of 10 μm and a diameter of 5 nm, a length of 20 μm and a diameter of 6 nm, a length of 30 μm and a diameter of 8 nm, a length of 40 μm and a diameter of 10 nm, a length of 50 μm and a diameter of 15 nm, and other values ​​within the above range are also possible and are not limited thereto. The functionalized oligowalled carbon nanotubes within the above size range exhibit high mechanical strength, and when loaded onto graphene sheets, they can significantly improve the mechanical strength and compressive resilience of the framework.

[0074] In some embodiments, the one-dimensional carbon material includes functionalized carbon nanotubes, which include functionalized multi-walled carbon nanotubes. The length of the functionalized multi-walled carbon nanotubes is 5 μm to 50 μm, and the diameter is 7 nm to 40 nm. Specifically, the functionalized multi-walled carbon nanotubes have a length of 5 μm and a diameter of 7 nm, a length of 10 μm and a diameter of 15 nm, a length of 20 μm and a diameter of 20 nm, a length of 30 μm and a diameter of 25 nm, a length of 40 μm and a diameter of 30 nm, a length of 50 μm and a diameter of 40 nm, and other values ​​within the above range are also possible and are not limited herein. Functionalized multi-walled carbon nanotubes within the above size range exhibit high mechanical strength, and when loaded onto graphene sheets, they can significantly improve the mechanical strength and compressive resilience of the framework.

[0075] In some embodiments, the one-dimensional carbon material includes carbon fibers with a length of 1 μm to 200 μm and a diameter of 5 μm to 20 μm. Specifically, the length can be 1 μm, 10 μm, 30 μm, 45 μm, 50 μm, 60 μm, 65 μm, 70 μm, 85 μm, 90 μm, 100 μm, 150 μm, 180 μm, or 200 μm, and the diameter can be 5 μm, 7 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 15 μm, 18 μm, or 20 μm. Of course, other values ​​within the above ranges are also possible and are not limited here. Carbon fiber possesses both high mechanical strength and toughness. Carbon fibers within the aforementioned length and diameter range exhibit high mechanical strength and good dispersibility, making them easy to attach to graphene sheets and improving the compressive strength and compression resilience of the skeleton.

[0076] In some embodiments, the one-dimensional carbon material includes aramid fibers with a length of 0.1 mm to 5 mm and a diameter of 5 μm to 20 μm. Specifically, the length can be 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, or 5 mm, and the diameter can be 5 μm, 7 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 15 μm, 18 μm, or 20 μm. Other values ​​within the above ranges are also possible and are not limited thereto. Aramid fibers within the above length and diameter ranges exhibit high mechanical strength and good dispersibility, thus enabling the acquisition of graphene composite aerogels with high mechanical strength.

[0077] In some embodiments, the one-dimensional carbon material includes polyoxadiazole fibers. The length of the polyoxadiazole fibers is 0.1 mm to 5 mm, and the diameter is 5 μm to 20 μm. Specifically, the length can be 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, or 5 mm, and the diameter can be 5 μm, 7 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 15 μm, 18 μm, or 20 μm. Of course, other values ​​within the above range are also possible and are not limited here. Polyoxadiazole fibers within the above length and diameter range have high mechanical strength and good dispersibility in order to obtain graphene composite aerogels with high mechanical strength.

[0078] According to another aspect of the present invention, the above-described graphene composite aerogel is provided as a thermally conductive material in a thermal management system. Graphene itself possesses extremely high thermal conductivity, resulting in a graphene composite aerogel having a layered structure formed by stacking graphene sheets along its thickness direction, which exhibits high lateral thermal conductivity. Furthermore, the graphene composite aerogel possesses excellent compressive strength, making it suitable as a thermally conductive material in a thermal management system.

[0079] This invention also provides a method for preparing graphene composite aerogels, comprising the following steps:

[0080] A wet film containing graphene oxide sheets and one-dimensional carbon material is obtained by coating a mixed slurry containing graphene oxide sheets and one-dimensional carbon material, and the wet film is dried to obtain a composite film.

[0081] A reducing foaming agent was used to chemically reduce and foam the composite membrane to obtain a reduced graphene oxide composite aerogel.

[0082] Graphene oxide composite aerogel was obtained by low-temperature drying and high-temperature graphitization thermal reduction treatment.

[0083] In the process of preparing the composite film through mixing slurry, coating, and drying, under the influence of π-π interactions, graphene oxide sheets assemble and stack along the thickness direction and extend along the plane of the graphene oxide sheets, forming a stacked graphene oxide sheet structure along the thickness direction. One-dimensional carbon materials are initially attached to the graphene oxide sheets through van der Waals forces, hydrogen bonds, and π-π interactions, which further strengthens the connection between the graphene oxide sheets along the plane, ultimately resulting in a composite film containing graphene oxide sheets and one-dimensional carbon materials. By subjecting the composite film containing graphene oxide sheets and one-dimensional carbon materials to chemical reduction foaming treatment, pathways are formed inside the composite film, constructing a three-dimensional framework. Furthermore, while constructing the three-dimensional reduced graphene oxide framework, the stacked structure of the reduced graphene oxide sheets and the one-dimensional carbon materials are maintained. Carbon materials are attached to reduced graphene oxide sheets. In the subsequent high-temperature graphitization thermal reduction process, the thermal reducing gas escapes orderly along the pathways of the three-dimensional reduced graphene oxide framework, thereby maintaining its stacked structure and the attachment of one-dimensional carbon materials. This reduces the deformation of the architecture and stacked structure of the reduced graphene oxide aerogel. Furthermore, by sintering the reduced graphene oxide aerogel at high temperatures, excess oxygen-containing functional groups can be removed and damaged lattices can be repaired. The p orbitals of carbon atoms in adjacent graphene sheets along the plane of the reduced graphene oxide sheets overlap to form π bonds, forming tightly connected graphene sheets. One-dimensional carbon materials are further connected to graphene sheets by π bonds so that one-dimensional carbon materials are firmly attached to graphene sheets, thus obtaining a composite graphene aerogel with high compression resilience and high compressibility.

[0084] In some embodiments, the preparation steps of the mixed slurry are as follows: dispersing graphene oxide sheets and one-dimensional carbon material premixed dry materials in water to form a mixed dispersion, and subjecting the mixed dispersion to high-pressure homogenization and degassing treatment in sequence to obtain the mixed slurry.

[0085] The mixed dispersion is subjected to high-pressure homogenization, which disperses graphene oxide sheets and one-dimensional carbon materials to form a stable slurry system. This facilitates the subsequent self-assembly of graphene oxide sheets and one-dimensional carbon materials to form a uniform film. The high-pressure homogenization process also involves the secondary exfoliation of some graphene oxide sheets, which is beneficial for the uniform loading of one-dimensional carbon materials on the graphene oxide sheets and increases the loading capacity. Taking carbon nanotubes as an example, graphene oxide sheets contain a large number of conjugated π bonds, and the walls of carbon nanotubes are also composed of conjugated carbon atoms. Based on the principle of π-π interaction, a strong attraction is generated between graphene oxide sheets and carbon nanotubes. This attraction allows carbon nanotubes to be stably adsorbed on the surface of graphene oxide sheets. Furthermore, during the high-pressure homogenization process, the particles in the mixed dispersion are subjected to enormous pressure and impact, further breaking down the agglomerates and refining the particle size. This allows carbon nanotubes to be more evenly distributed around the graphene oxide sheet and better adsorbed onto the surface of the graphene oxide sheet. During the coating and drying of the mixed slurry to obtain the composite film, as the solvent gradually evaporates, the graphene oxide sheet and carbon nanotubes will gradually be fixed in the structure of the composite film, maintaining the uniform dispersion state formed by the interaction, and finally forming a composite film in which carbon nanotubes are dispersed on the surface of the graphene oxide sheet.

[0086] In some embodiments, the atomic ratio of carbon atoms to oxygen atoms in the graphene oxide sheet is (1.5–3):1, specifically 1.5:1, 1.8:1, 2:1, 2.1:1, 2.2:1, 2.4:1, 2.5:1, 2.6:1, 2.8:1, 2.9:1, 3:1, etc., and other values ​​within the above range are also possible and are not limited here. It is understood that the high-oxidation-degree graphene oxide sheet used in this invention provides more reduction sites to generate larger and more numerous pores, while also providing more sites for the attachment of one-dimensional carbon materials on the graphene oxide sheet to introduce more one-dimensional carbon materials.

[0087] In some embodiments, the graphene oxide sheet has oxygen-containing functional groups, which include at least one of epoxy, hydroxyl, and carboxyl functional groups, including but not limited to the above-mentioned oxygen-containing functional groups. Other oxygen-containing functional groups that can undergo a reduction reaction with a reducing foaming agent and can generate gas are also applicable to the present invention.

[0088] In some embodiments, the length and width of the graphene oxide sheet are 80 μm to 150 μm. Specifically, the length and width can be independently 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 125 μm, 130 μm, 135 μm, 140 μm, and 150 μm, respectively, or other values ​​within the above range, which are not limited here. Using the above-mentioned larger-sized graphene oxide sheets as raw materials facilitates the loading of one-dimensional carbon materials to obtain higher mechanical properties. In addition, since the graphene oxide sheet structure is large, it will occupy a certain space in the mixed slurry. When one-dimensional carbon materials, such as carbon nanotubes, are added, the presence of the graphene oxide sheet will hinder the direct contact and aggregation between carbon nanotubes, playing a steric hindrance role, thereby improving the dispersion effect of the raw materials in the mixed slurry.

[0089] In some embodiments, the number of layers of the graphene oxide sheet is less than or equal to 8, specifically 1, 2, 3, 4, 5, 6, 7, or 8 layers, preferably 3 to 8 layers. Compared with single-layer graphene, the preparation process of graphene oxide sheets within this layer range is relatively simple and the processing time is short. At the same time, it can ensure the high compressive strength, high compression resilience, and high compression ratio of the graphene skeleton prepared from the graphene oxide sheet, which is beneficial to the commercial continuous production of composite aerogels.

[0090] In some embodiments, graphene oxide sheets and one-dimensional carbon materials are mixed at a speed of 50 rpm to 200 rpm to obtain a premixed dry material. The specific speed can be 50 rpm, 55 rpm, 60 rpm, 80 rpm, 100 rpm, 120 rpm, 140 rpm, 160 rpm, 170 rpm, 180 rpm, 190 rpm, or 200 rpm, or other values ​​within the above range. The mixing time is 30 min to 60 min, or 30 min, 32 min, 35 min, 40 min, 42 min, 45 min, 48 min, 50 min, 52 min, 55 min, 58 min, or 60 min, or other values ​​within the above range.

[0091] In some embodiments, the solid content in the mixed dispersion is 2% to 10%, specifically 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 7%, 8%, 9%, 10%, or other values ​​within the above range, which are not limited here.

[0092] In some embodiments, a planetary mixer is used to prepare the mixed dispersion. The mixing speed is 30 rpm to 50 rpm, specifically 30 rpm, 35 rpm, 40 rpm, 45 rpm, or 50 rpm. Of course, other mixing process conditions within the above range are also acceptable and are not limited here. The dispersion speed is 500 rpm to 5000 rpm, specifically 500 rpm, 1000 rpm, 1500 rpm, 2000 rpm, 3000 rpm, or 5000 rpm. Of course, other dispersion process conditions within the above range are also acceptable and are not limited here. The running time is 5 min to 120 min. Specific process combinations can include stirring speed of 30 rpm, dispersion speed of 1000 rpm, and running time of 30 min; stirring speed of 40 rpm, dispersion speed of 2000 rpm, and running time of 60 min; stirring speed of 45 rpm, dispersion speed of 4000 rpm, and running time of 60 min; stirring speed of 50 rpm, dispersion speed of 5000 rpm, and running time of 90 min. Of course, it can also be one process within the above range, or multiple processes combined and operated in a set order. There are no restrictions here.

[0093] In some embodiments, the pressure of the high-pressure homogenization process is 500 bar to 1250 bar, the temperature of the homogenization process is 10°C to 25°C, and the number of processes is 2 to 4, so that the one-dimensional carbon material is more uniformly loaded on the graphene oxide sheets and a higher one-dimensional carbon material loading is obtained.

[0094] In some embodiments, degassing is performed using a vacuum degassing method at a vacuum pressure of -10 kPa to -200 kPa, a processing temperature of 15 to 25°C, a rotation speed of 500 rpm to 2000 rpm, and a degassing time of 30 s to 10 min. Specifically, it can be one or more of the following processes: 500 rpm for 10 min, 800 rpm for 6 min, 1000 rpm for 3 min, 1200 rpm for 2 min, 1400 rpm for 1.5 min, 1500 rpm for 1 min, and 2000 rpm for 30 s, or a repeated operation of one process. Of course, other values ​​within the above range are also possible and are not limited here.

[0095] In some embodiments, the viscosity of the mixed slurry is between 30,000 cps and 60,000 cps, specifically 30,000 cps, 35,000 cps, 40,000 cps, 42,000 cps, 45,000 cps, 48,000 cps, 50,000 cps, 52,000 cps, 55,000 cps, 58,000 cps, and 60,000 cps. Other values ​​within the above range are also possible and are not limited herein. Mixed slurries within the above viscosity range are beneficial for forming a uniform film layer during coating.

[0096] In some embodiments, the pH value of the mixed slurry is 6 to 9, specifically 6, 6.5, 6.8, 7, 7.2, 7.3, 7.5, 7.8, 8, 8.5, or 9. Of course, other values ​​within the above range are also possible and are not limited here. Within the above pH range, it is beneficial for the dispersion of graphene oxide sheets and one-dimensional carbon materials to form a stable mixed slurry, so that the one-dimensional carbon materials can be uniformly attached to the graphene oxide sheets through π-π interactions, hydrogen bonds, and other interactions during the subsequent self-assembly of graphene oxide sheets.

[0097] In some embodiments, the thickness of the wet film is between 2400 mm and 3500 mm, specifically 2400 mm, 2500 mm, 2600 mm, 2700 mm, 2800 mm, 2900 mm, 3000 mm, 3100 mm, 3200 mm, 3300 mm, 3400 mm, and 3500 mm, or other values ​​within the above range, which are not limited here. The thickness of the wet film affects the thickness of the composite film subsequently produced. A wet film with a thickness within the above range can be assembled into a composite film with a multilayer graphene oxide sheet structure and uniform distribution during the subsequent drying process, which is beneficial for the subsequent foaming to form a graphene composite aerogel material with high porosity and mechanical strength.

[0098] In some embodiments, during the drying process of the wet film, the drying temperature is 60°C to 80°C, and the drying time is 2 hours to 6 hours. Specifically, it can be drying at 60°C for 6 hours, 62°C for 5.5 hours, 65°C for 5 hours, 68°C for 4.5 hours, 70°C for 4 hours, 72°C for 3.5 hours, 75°C for 3 hours, 78°C for 2.5 hours, and 80°C for 2 hours. Of course, other values ​​within the above range are also possible and are not limited here. The drying temperature affects the rate of water evaporation, thereby affecting the appearance and quality of the film. Under the above drying temperature and drying time, it is beneficial for the graphene oxide sheets to be fully assembled with each other and for the graphene oxide sheets and one-dimensional carbon materials, so that the one-dimensional carbon materials are uniformly attached to the graphene oxide sheets to form a composite film with a uniform appearance and compactness, so as to form a graphene composite aerogel material with high porosity and mechanical strength in subsequent foaming.

[0099] In some embodiments, the thickness of the composite film is from 100 μm to 250 μm, specifically 100 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 210 μm, 220 μm, 230 μm, 240 μm, and 250 μm, but other values ​​within the above range are also possible and are not limited herein. Composite films within the above range have a multilayer graphene oxide sheet structure, which is beneficial for subsequent foaming to form graphene composite aerogels with high mechanical strength.

[0100] In some embodiments, the reducing foaming agent comprises a reducing substance and an aqueous solution of a protic acid, the protic acid releasing protons H. + H + It can suppress the ionization of hydrogen ions on graphene oxide, reduce the repulsive force between graphene oxide sheets, and maintain the stacked structure of graphene oxide sheets while building the graphene oxide framework during the reduction foaming process.

[0101] In some embodiments, the reducing agent is selected from at least one of hydrazine hydrate, sodium borohydride, glucose, ascorbic acid, sodium ascorbate, ethylene glycol, hydroiodic acid, acetic acid, dopamine, melamine, sodium hydroxide, and potassium hydroxide, including but not limited to the above substances. Other reducing agents that can react with the oxygen-containing functional groups of graphene oxide sheets to generate gas are also applicable to the present invention. The protic acid is selected from one or a combination of two organic acids and inorganic acids. Organic acids include, but are not limited to, formic acid and acetic acid, and inorganic acids include, but are not limited to, boric acid, carbonic acid, and sulfuric acid.

[0102] In some embodiments, the content of reducing substances in the reducing foaming agent is 1% to 30% by weight, specifically 1%, 2%, 5%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, or 30%, or other values ​​within the above range, which are not limited herein. During the foaming process, bubbles are generated between adjacent reduced graphene oxide sheets, expanding the reduced graphene oxide sheets and thus forming pathways inside the membrane. The reducing foaming substances within the above range can react with the oxygen-containing functional groups in the graphene oxide sheets to rapidly form a graphene oxide composite aerogel with uniform pore size distribution.

[0103] In some embodiments, the content of protic acid in the reducing foaming agent is 0.5% to 2% by weight, specifically 0.5%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, or other values ​​within the above range, which are not limited here. The above low concentration H... +When combined with a reducing agent, the solution can effectively suppress hydrogen ion ionization and reduce the repulsive force between graphene oxide sheets. During the reduction foaming process, it can build a three-dimensional reduced graphene oxide aerogel framework while maintaining the stacked structure of graphene oxide sheets.

[0104] In some embodiments, the temperature of the chemical reduction foaming treatment is from 30°C to 90°C, specifically 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, or 90°C. Of course, other values ​​within the above range are also possible and are not limited here.

[0105] In some embodiments, the chemical reduction foaming treatment time is 5s to 5min, specifically 5s, 15s, 25s, 35s, 45s, 55s, 1min, 1.5min, 2min, 2.5min, 3min, 3.5min, 4min, 4.5min, 5min, or other values ​​within the above range. Preferably, it is 2min to 5min, which is beneficial for the formation of large pores.

[0106] In some embodiments, the chemical reduction foaming process is performed multiple times in descending order of the concentration of reducing substances, so that the composite membrane is fully foamed during the chemical reduction stage.

[0107] In some embodiments, the chemical reduction foaming process is performed in three stages according to the decreasing concentration of the reducing agent. By weight percentage, in the first foaming process, the reducing agent content in the foaming agent is 15% to 30%, and the foaming time is 1 min to 30 min. In the second foaming process, the reducing agent content in the foaming agent is 10% to 20%, and the foaming time is 1 min to 20 min. In the third foaming process, the reducing agent content in the foaming agent is 1% to 10%, and the foaming time is 10 s to 1 min. By adopting a sequential foaming process with decreasing foaming agent concentration and controlling the foaming time for different concentrations, the composite film can be fully foamed.

[0108] In some embodiments, the low-temperature drying treatment is performed at a temperature of 60°C to 400°C for a duration of 5 hours to 20 hours. Specifically, it can be drying at 60°C for 20 hours, at 80°C for 15 hours, at 120°C for 13 hours, at 150°C for 12 hours, at 200°C for 11 hours, at 250°C for 8 hours, at 300°C for 7 hours, at 350°C for 7 hours, and at 400°C for 5 hours. Other values ​​within the above range are also possible and are not limited here. Preferably, the heating rate is less than or equal to 10°C / min. Specifically, it can be 1°C / min, 2°C / min, 4°C / min, 5°C / min, 6°C / min, 8°C / min, or 10°C / min. Other values ​​within the above range are also possible and are not limited here.

[0109] In some embodiments, the high-temperature graphitization thermal reduction treatment is performed at a temperature of 2900°C to 3100°C for a time of 15 to 50 hours. Specifically, it can be performed at 2900°C for 50 hours, 2950°C for 40 hours, 2980°C for 28 hours, 3000°C for 25 hours, 3020°C for 22 hours, 3040°C for 20 hours, 3050°C for 18 hours, or 3100°C for 15 hours. Other values ​​within the above range are also possible and are not limited here. Within the above temperature and time range, the graphene sheets have a high degree of graphitization, and the material has better horizontal thermal conductivity and mechanical properties. Preferably, the heating rate is less than or equal to 5°C / min, specifically 1°C / min, 2°C / min, 3°C / min, 4°C / min, or 5°C / min. Other values ​​within the above range are also possible and are not limited here.

[0110] Because graphene oxide sheets contain numerous oxygen-containing functional groups, during the preparation, coating, and drying of the composite film from mixed slurry, one-dimensional carbon materials, such as aramid fibers and polyoxadiazole fibers, initially adhere to the graphene oxide sheets primarily through van der Waals forces and hydrogen bonds. Through chemical reduction foaming treatment of the composite film containing graphene oxide sheets and one-dimensional carbon materials, the functional groups on the surface of the graphene oxide (GO) sheets are partially reduced to generate reduced graphene oxide (rGO). During the reduction process, gas is generated and gas bubbles are formed between the reduced graphene oxide sheets, expanding the sheets and creating pathways within the composite film. This constructs a three-dimensional reduced graphene oxide framework. Furthermore, while constructing the three-dimensional reduced graphene oxide framework, the stacking structure of the reduced graphene oxide layers and the adhesion of the one-dimensional carbon materials to the reduced graphene oxide layers are maintained. This results in the three-dimensional reduced graphene oxide framework exhibiting excellent compressive strength. Due to the presence of pores and pathways, this three-dimensional reduced graphene oxide possesses… This process facilitates the orderly escape of thermal reducing gases during subsequent high-temperature sintering, reducing deformation of the reduced graphene composite aerogel's architecture and stacking structure, thus maintaining the integrity of the overall graphene composite aerogel structure and resulting in a composite graphene aerogel with high compressive resilience and high compressibility. Furthermore, high-temperature sintering of the reduced graphene oxide aerogel removes excess oxygen-containing functional groups and repairs damaged lattices. The p orbitals of carbon atoms in adjacent graphene sheets along the plane of the reduced graphene oxide sheets overlap to form π bonds, creating tightly connected graphene sheets that enhance the heat dissipation performance of the graphene composite aerogel. Simultaneously, with the generation and escape of thermal reducing gases during graphitization, the reduced graphene oxide sheets are further reduced, creating new micropores between any two adjacent graphene sheets along the thickness direction. These micropores can be distributed around the pores generated by chemical reduction, resulting in a graphene composite aerogel with high heat dissipation, high compressive strength, high compressive resilience, and high compressibility.

[0111] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0112] Example 1

[0113] Step 1: Premix the three dry materials—graphene oxide sheets, carbon nanotubes, and carbon fibers—at a speed of 100 rpm for 30 minutes to obtain a premixed dry material. The graphene oxide sheets have a carbon-to-oxygen atom ratio of 2:1, a length of 100 μm, and a width of 80 μm. The carbon nanotubes are multi-walled carbon nanotubes with a length of 30 μm and a diameter of 15 nm. The carbon fibers have a length of 80 μm and a diameter of 7 μm. The mass ratio of added graphene oxide sheets to one-dimensional carbon material is 9:1, and the mass ratio of added carbon nanotubes to carbon fibers is 8:2.

[0114] A mixed dispersion was prepared by dispersing premixed dry materials in water, and the solid content of the mixed dispersion was 4%. The preparation process of the mixed dispersion was as follows: a planetary mixer was used for stirring. The dispersion was carried out in three steps at a stirring speed of 45 rpm: the first step was to disperse at a stirring speed of 800 rpm for 10 min, the second step was to disperse at a stirring speed of 2000 rpm for 15 min, and the third step was to disperse at a stirring speed of 4000 rpm for 15 min. Then, the dispersion was carried out at a stirring speed of 50 rpm for 30 min.

[0115] The mixed dispersion was subjected to high-pressure homogenization at a pressure of 750 bar, twice, at a temperature of 14°C.

[0116] The homogenized system was deaerated to obtain a mixed slurry with a viscosity of 35000 cps and a pH of 7. The deaeration process was as follows: the deaeration was carried out in two steps, the first step was deaeration at 1000 rpm for 1 min and the second step was deaeration at 2000 rpm for 1 min, the vacuum pressure was -98 kPa and the treatment temperature was 25℃.

[0117] A wet film with a thickness of 2500 μm was obtained by coating the mixed slurry. The wet film was dried at 60°C for 5 hours to obtain a composite film. The composite film includes graphene oxide sheets, carbon nanotubes and carbon fibers, and has a thickness of 150 μm.

[0118] Step 2: An aqueous solution containing reducing substances and protic acid is used as a reducing foaming agent to foam the composite membrane. The specific steps are as follows: The composite membrane is subjected to three chemical reduction foaming treatments in descending order of the concentration of the reducing substance. In the three chemical reduction foaming treatments, the protic acid is acetic acid, and its concentration is 1% by mass percentage of the reducing foaming agent. The selected reducing substance is hydrazine hydrate, and its concentration in the three chemical reduction foaming treatments is 15%, 10%, and 1% by mass percentage of the reducing foaming agent, respectively. The temperature is 40℃, and the soaking time is 2 min, 1 min, and 30 s, respectively. After washing and drying, reduced graphene oxide composite aerogel is obtained.

[0119] Step 3: The obtained reduced graphene oxide composite aerogel is subjected to heat treatment reduction. After heat treatment at low temperature of 300℃ for 7 hours (heating rate of 3℃ / min) and graphitization at high temperature of 3100℃ for 20 hours (graphitization heating rate of 3℃ / min), graphene composite aerogel is obtained.

[0120] Figure 1 SEM image of reduced graphene oxide composite aerogel as an intermediate product. Figure 2 and Figure 3The SEM image of the graphene composite aerogel product shows that the graphene composite aerogel includes a graphene framework formed by stacking graphene sheets along the thickness direction and a porous structure distributed between any two adjacent graphene sheets along the thickness direction; one-dimensional carbon material is distributed on the graphene sheets, and the axis of the one-dimensional carbon material is parallel to the plane where the graphene sheets are located. The structure and performance parameters are shown in Tables 1 and 2. Figure 4 This is a load-time curve showing the load change of the sample during a compression cycle test at 90% compressive strain after being subjected to a high pressure of 40000 kPa for 10 seconds. Figure 5 The load-stroke variation diagram of the sample under 90% compressive strain after being subjected to a high pressure of 40000 kPa for 10 s shows that the sample still has compressive resilience after being subjected to high pressure, and the material structure can still be maintained after 1000 cycles of compression at 90% deformation.

[0121] Example 2

[0122] Step 1: Premix the two dry materials, graphene oxide sheets and carbon fibers, at a speed of 100 rpm for 60 minutes to obtain a premixed dry material. The carbon-oxygen atom ratio in the graphene oxide sheets is 2:1, the length of the graphene oxide sheets is 100 μm and the width is 80 μm, the length of the carbon fibers is 100 μm and the diameter is 10 μm, and the mass ratio of the added graphene oxide sheets to the carbon fibers is 8:2.

[0123] A mixed dispersion was prepared by dispersing premixed dry materials in water, and the solid content of the mixed dispersion was 3.5%. The preparation process of the mixed dispersion was as follows: a planetary mixer was used to carry out three-step dispersion at a stirring speed of 40 rpm. The first step was to disperse at a dispersion speed of 1000 rpm for 10 min, the second step was to disperse at a dispersion speed of 2000 rpm for 15 min, and the third step was to disperse at a dispersion speed of 4000 rpm for 20 min. Then, the dispersion was carried out at a dispersion speed of 50 rpm for 50 min.

[0124] The mixed dispersion was subjected to high-pressure homogenization at a pressure of 650 bar, once, and at a homogenization temperature of 14°C.

[0125] The homogenized system was degassed to obtain a mixed slurry with a viscosity of 30,000 cps and a pH of 7.8. The degassed process was as follows: degassed at 1000 rpm for 2 min, under a vacuum pressure of -98 kPa and a processing temperature of 25℃.

[0126] The mixed slurry is coated to obtain a wet film with a thickness of 2500 mm. The wet film is dried at 60°C for 5 hours to obtain a composite film. The composite film includes graphene oxide sheets and carbon fibers and has a thickness of 100 μm.

[0127] Step 2: An aqueous solution containing reducing substances and protic acid is used as a reducing foaming agent to foam the composite membrane. The specific steps are as follows: The composite membrane is subjected to three chemical reduction foaming treatments in descending order of reducing substance concentration. In the three chemical reduction foaming treatments, the protic acid is carbonic acid, and its concentration is 2% by mass percentage of the reducing foaming agent. The selected reducing substance is potassium hydroxide, and its concentration in the three chemical reduction foaming treatments is 30wt%, 20wt%, and 10wt% by mass percentage of the reducing foaming agent, respectively. The temperature is 70℃, and the soaking time is 20min, 10min, and 10s, respectively. After washing and drying, reduced graphene oxide composite aerogel is obtained.

[0128] Step 3: The obtained reduced graphene oxide composite aerogel is subjected to heat treatment reduction, which involves heat treatment at 400℃ for 5 hours (heating rate 3℃ / min) and graphitization at 2900℃ for 20 hours (graphitization heating rate 3℃ / min) to obtain graphene composite aerogel.

[0129] Example 3

[0130] Step 1: Premix the three dry materials—graphene oxide sheets, polyoxadiazole fibers, and carbon nanotubes—at a speed of 100 rpm for 40 minutes to obtain a premixed dry material. The carbon-to-oxygen atom ratio in the graphene oxide sheet raw material is 2:1. The graphene oxide sheet has a length of 100 μm and a width of 80 μm. The carbon nanotubes are multi-walled carbon nanotubes with a length of 30 μm and a diameter of 20 nm. The polyoxadiazole fibers have a length of 1 mm and a diameter of 7 μm. The mass ratio of the added graphene oxide sheets to the one-dimensional carbon material is 8.5:1.5, and the mass ratio of the added carbon nanotubes to the polyoxadiazole fibers is 1:1.

[0131] A mixed dispersion was prepared by dispersing the premixed dry material in water, and the solid content of the mixed dispersion was 5%. The preparation process of the mixed dispersion was as follows: a planetary mixer was used for stirring. The dispersion was carried out in two steps at a stirring speed of 40 rpm. The first step was a dispersion at a stirring speed of 1000 rpm for 20 min, and the second step was a dispersion at a stirring speed of 3000 rpm for 20 min. Then, the dispersion was carried out at a stirring speed of 50 rpm for 5000 rpm for 60 min.

[0132] The mixed dispersion was then subjected to high-pressure homogenization at a pressure of 850 bar, twice, and at a homogenization temperature of 14°C.

[0133] The homogenized system was deaerated to obtain a mixed slurry with a viscosity of 40,000 cps and a pH of 8. The deaeration process consisted of a first step of deaeration at 1,000 rpm for 1 min and a second step of deaeration at 2,000 rpm for 2 min, with a vacuum pressure of -98 kPa and a processing temperature of 25℃.

[0134] The mixed slurry was coated to obtain a wet film with a thickness of 3000 mm. The wet film was dried at 70°C for 4 hours to obtain a composite film. The composite film includes graphene oxide sheets, carbon nanotubes and polyoxadiazole fibers, and the thickness of the composite film is 200 μm.

[0135] Step 2: An aqueous solution containing reducing substances and protic acids is used as a reducing foaming agent to foam the composite membrane. The specific steps are as follows: The composite membrane is subjected to three chemical reduction foaming treatments in descending order of reducing substance concentration. In the three chemical reduction foaming treatments, formic acid is used in all three treatments, and its concentration is 1.5% by mass percentage of the reducing foaming agent. The selected reducing substance is ascorbic acid, and its concentration in the three chemical reduction foaming treatments is 30wt%, 10wt%, and 5wt% by mass percentage of the reducing foaming agent, respectively. The temperature is 70℃ in all three treatments, and the soaking time is 2min, 1min, and 1min, respectively. After washing and drying, reduced graphene oxide composite aerogel is obtained.

[0136] Step 3: The obtained reduced graphene oxide composite aerogel is subjected to low-temperature heat treatment at 400℃ for 5 hours (heating rate 3℃ / min) and high-temperature graphitization at 3000℃ for 20 hours (graphitization heating rate 3℃ / min) to obtain composite aerogel.

[0137] Example 4

[0138] The only difference from Example 1 is that carbon fiber is replaced with aramid fiber.

[0139] Example 5

[0140] The only difference between this and Example 1 is that the preparation process of the mixed dispersion is as follows: first, the mixture is stirred at 45 rpm and dispersed at 3000 rpm for 30 minutes, and then stirred at 50 rpm and dispersed at 6000 rpm for 30 minutes.

[0141] Example 6

[0142] Unlike Example 1, the mixed dispersion was prepared by stirring at 50 rpm and dispersing at 500 rpm for 60 min.

[0143] Example 7

[0144] The only difference between it and Example 1 is that it has not undergone homogenization.

[0145] Example 8

[0146] The only difference between it and Example 1 is that the homogenization pressure in step one is 300 bar.

[0147] Example 9

[0148] The only difference between it and Example 1 is that the drying temperature in step one is 50°C.

[0149] Example 10

[0150] The only difference between it and Example 1 is that the drying temperature in step one is 90°C.

[0151] Example 11

[0152] The only difference between it and Example 1 is that the carbon-oxygen atom ratio in the graphene oxide sheet is 5:1.

[0153] Example 12

[0154] The only difference between this example and Example 1 is that the concentration of protic acid in step two is 0.5%.

[0155] Example 13

[0156] The only difference between it and Example 1 is that the graphitization temperature in step three is 2600°C.

[0157] Example 14

[0158] The only difference between it and Example 1 is that the graphitization temperature in step three is 3000°C.

[0159] Comparative Example 1

[0160] The only difference between it and Example 1 is that no one-dimensional carbon material was added in step one.

[0161] Performance testing

[0162] The composite aerogels prepared in the examples and comparative examples were subjected to the following tests:

[0163] 1) Scanning electron microscopy (SEM) was used to characterize the graphene composite aerogel, determining its framework size, framework state, and pore size. ImageJ was used to statistically calculate the average pore size and the ratio of large to small pores. The results are shown in Table 1.

[0164] 2) Compression and rebound performance test

[0165] The equipment used was Shimadzu AGS-X500N. Referring to GB / T 343361 "Nano Aerogel Composite Thermal Insulation Products", the sample was cut into 20mm×20mm square sheets. The initial thickness h0 of the sample was measured with a thickness gauge to an accuracy of 0.01mm. The compression speed of the testing machine was 2mm / min. When the sample was compressed to (100±5)kPa, the compression was stopped and the testing machine was held in this position for (5±0.5)min. After that, the sample was removed and allowed to recover for (5±0.5)min. The recovered thickness h' of the sample was measured with a thickness gauge to an accuracy of 0.01mm. The compression rebound rate of the sample was calculated using the following compression rebound rate and rounded to 1%. The calculated compression rebound rate at 100kPa is shown in Table 2.

[0166] The formula for calculating compression rebound rate is:

[0167] In the formula, R is the compression resilience; h0 is the initial thickness in millimeters (mm); and h′ is the recovered thickness in millimeters (mm).

[0168] 3) Compression ratio test

[0169] The LW-9389 steady-state heat flow thermal conductivity tester was used. Referring to ASTM-D5470 "Standard Test Method for Thermal Transfer Properties of Thermally Conductive and Electrically Insulating Materials", the sample was cut into a square piece of 25.4mm × 25.4mm. The thermally conductive sheet-compression ratio test mode was selected, the test pressure was 30psi (i.e., 206Kpa), and the test temperature was 25℃. The sample compression ratio at 206Kpa is shown in Table 2.

[0170] 4) Compression ratio test after pressing under 40000kPa high pressure

[0171] A servo-controlled pressure testing machine (model: DY-2008SFS) was used to apply high pressure to the graphene composite aerogel along the stacking direction of the graphene sheets. The pressure was set to 40,000 kPa and applied at a rate of 2,000 kPa / s. After reaching 40,000 kPa, the pressure was maintained for 10 seconds.

[0172] The compression resilience of the graphene composite aerogel after high-pressure treatment was tested using the method in 2).

[0173] The compressibility of the graphene composite aerogel was tested using the method described in 3).

[0174] Table 2 shows the compression rebound rate at 100 kPa and the compression rate at 206 kPa after being compressed under 40000 kPa.

[0175] 5) Compression cycle test

[0176] The equipment used was Shimadzu AGS-X500N, and the test conditions were as follows: test temperature: 23℃, load sensor: 100N (0.5 grade), test fixture: compression fixture (100mm diameter pressure plate), test rate: 0.3mm / min; the sample was the sample in 4) that had been compressed by 40000kPa and placed in the test environment for 12 hours; the sample size was 5cm×5cm.

[0177] The experimental procedure is as follows: The preload force is set to 0.005 N to ensure full contact between the pressure plate and the specimen; the preload force is kept stable and this state is maintained before proceeding to the next step; the loading speed is set to 0.3 mm / min, and the electronic universal testing machine is started to begin the test; the specimen is compressed to 90% strain, and the load and displacement during the test are monitored; the loading is removed, allowing the specimen to return to its initial position, ensuring complete recovery and stability, and the load and displacement during the test are monitored. The above steps are repeated for a total of 1000 cycles of compression. At each compression to 90% strain, the stress and load values ​​are recorded, and the rate of change of stress after 1000 cycles of compression is calculated. The results are shown in Table 2.

[0178] 6) Horizontal thermal conductivity test

[0179] The equipment used was an LFA-467 Hyper Flash. Referring to ASTM-E1461, "Standard Test Method for Determination of Fixed Thermal Conductivity by Flash Method", the sample was cut into a circular piece with a diameter of 25.4 mm to measure the horizontal thermal diffusivity (i.e., the thermal diffusivity along the direction of the graphene sheet). The horizontal thermal conductivity (i.e., the thermal conductivity along the direction of the graphene sheet) was calculated based on the horizontal diffusivity.

[0180] Horizontal thermal conductivity = horizontal thermal diffusivity × density × specific heat capacity.

[0181] The horizontal thermal diffusivity is measured in m. 2 / s, specific heat capacity is 0.85, unit is J / (kg·K), density is the density of graphene composite aerogel, unit is kg / m³ 3 .

[0182] The horizontal thermal conductivity is shown in Table 1.

[0183] 7) Longitudinal thermal conductivity test

[0184] The equipment used was an LW-9389 steady-state heat flow thermal conductivity tester. Referring to ASTM-D5470 "Standard Test Method for Thermal Transfer Properties of Thermally Conductive and Electrically Insulating Materials", the sample was cut into a square piece of 25.4mm × 25.4mm. The thermal conductivity test mode was selected, and the longitudinal thermal conductivity was tested. The test pressure was 30psi (i.e., 206kPa), and the test temperature was 80℃.

[0185] 8) The surface area was tested using a specific surface area and pore size analyzer (TriStar3000, USA), and the results are shown in Table 1.

[0186] 9) The pore volume was tested using a fully automated mercury porosimetry pore size analyzer (AutoPore V, USA), and the results are shown in Table 1.

[0187] 10) Porosity Testing: The equipment used was a MAY-12450 ceramic porosity tester. The dry sample was placed on the air-filled measuring stage, and after stabilization, its dry, empty weight was measured. The sample was then placed in a water cup for saturation treatment, and subsequently placed on the water-filled measuring stage. After stabilization, the sample's saturated water weight was measured. The sample was then removed and placed on a water-soaked nano-sponge. Excess water was wiped off the sample surface, and after stabilization, the sample was saturated with air, and the porosity was displayed.

[0188] 11)I D / I G Ratio: Defects and crystal structure of the sample were analyzed using Raman spectroscopy, with a continuous scanning range of 100 cm⁻¹ at room temperature. -1 Up to 4000cm -1 The laser wavelength λ is 532nm, and I is calculated using the area ratio. D / I G ratio.

[0189] 12) Density test

[0190] The prepared graphene composite aerogel was cut into small pieces of uniform size, and its thickness, area and mass were measured. The sample density was calculated by ρ = m / v.

[0191] 13) Carbon content test

[0192] A certain amount of sample was weighed and heated to 950℃ in a muffle furnace and held at that temperature. The carbon content was calculated by weighing the percentage of residue after combustion. The carbon mass fraction of the samples was all above 99%, indicating that the graphene composite aerogel has a high carbon content and is free of impurities.

[0193] Table 1

[0194]

[0195] Table 2

[0196]

[0197]

[0198] Note: " / " indicates that the sample underwent irreversible deformation during the test.

[0199] As shown in Tables 1 and 2, compared with Comparative Example 1, the graphene composite aerogels prepared in Examples 1 to 15 of this invention have high compressive resilience and high compression ratio (compression resilience of 98% to 98% at 100 kPa and compression ratio of 70% to 78% at 206 kPa), as well as high support strength and compression cycle performance. After being subjected to strong compression treatment at 40,000 kPa, its compressive resilience and compression ratio remain basically unchanged. After being subjected to strong compression treatment at 40,000 kPa, after 1,000 cycles of compression at 90% deformation, the stress value remains basically unchanged, and the skeleton can still maintain structural integrity.

[0200] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A graphene composite aerogel, characterized by, The graphene composite aerogel comprises a skeleton and one-dimensional carbon materials; The skeleton comprises a plurality of graphene layers stacked along a thickness direction, and each two adjacent graphene layers along the thickness direction have a porous structure therebetween; The one-dimensional carbon materials are distributed on the graphene layers and the axial direction of the one-dimensional carbon materials is parallel to the plane in which the graphene layers are located; The thickness direction is perpendicular to the plane in which the graphene layers are located.

2. The graphene composite aerogel according to claim 1, wherein, The graphene layers are curved, and each two adjacent graphene layers along the thickness direction are face-to-face overlapped to form the porous structure.

3. The graphene composite aerogel of claim 1, wherein, The graphene composite aerogel has at least one of the following characteristics: (1) The horizontal thermal conductivity of the graphene composite aerogel along the plane direction of the graphene layers is 20 W / mK to 70 W / mK; (2) The longitudinal thermal conductivity of the graphene composite aerogel along the thickness direction is 1 W / mK to 10 W / mK under a test pressure of 206 KPa; (3) After the graphene composite aerogel is compressed by a high pressure of 40,000 kPa for 10 s, the compression rate of the graphene composite aerogel is greater than or equal to 70% under a test pressure of 206 KPa; (4) After the graphene composite aerogel is compressed by a high pressure of 40,000 kPa for 10 s, the resilience rate of the graphene composite aerogel is greater than or equal to 90% under a test pressure of 100 KPa; (5) After the graphene composite aerogel is compressed by a high pressure of 40,000 kPa for 10 s, the stress value change rate of the graphene composite aerogel is less than or equal to 10% after 1,000 cycles of compression under a strain of 90%.

4. The graphene composite aerogel according to any one of claims 1 to 3, wherein, The graphene composite aerogel has at least one of the following characteristics: (1) the density of the graphene composite aerogel is 0.02 g / cm 3 to 0.15 g / cm 3 ; (2) The porosity of the graphene composite aerogel is 70% to 90%; (3) the specific surface area of the graphene composite aerogel is 100 m 2 / g to 1000 m 2 / g; (4) the graphene composite aerogel has a pore volume of 0.1 cm 3 / g to 2.0 cm 3 / g.

5. The graphene composite aerogel according to any one of claims 1 to 3, wherein, The graphene composite aerogel has at least one of the following characteristics: (1) The proportion of macropores with a pore size of 150 μm to 500 μm accounts for greater than or equal to 70% in terms of volume percentage; (2) The proportion of micropores with a pore size of 10 μm to 50 μm accounts for less than or equal to 30% in terms of volume percentage; (3) The average pore size of the graphene composite aerogel is 150 μm to 500 μm.

6. The graphene composite aerogel according to any one of claims 1 to 3, wherein, The graphene composite aerogel has at least one of the following characteristics: (1) The content of the one-dimensional carbon materials in the graphene composite aerogel accounts for 1% to 20% in terms of weight percentage; (2) The content of carbon elements in the graphene composite aerogel is greater than or equal to 99% in terms of weight percentage; (3) the graphene composite aerogel has a D peak and a G peak in a Raman spectrum, and an area ratio I D / I G of the D peak and the G peak is less than 0.

01.

7. The graphene composite aerogel according to any one of claims 1 to 3, wherein, The pores between each two adjacent graphene layers along the thickness direction are arranged in an ordered honeycomb-shaped porous structure along the plane direction of the graphene layers; and / or, The thickness of the graphene layers is 1 nm to 5 nm.

8. The graphene composite aerogel according to any one of claims 1 to 3, wherein, The one-dimensional carbon materials comprise one or more of carbon nanotubes, functionalized carbon nanotubes, carbon fibers, aramid fibers, and polyoxadiazole fibers.

9. The graphene composite aerogel of claim 8, wherein, The graphene composite aerogel has at least one of the following characteristics: (1) The one-dimensional carbon materials comprise carbon nanotubes, and the carbon nanotubes comprise at least one of single-walled carbon nanotubes, few-walled carbon nanotubes, and multi-walled carbon nanotubes; (2) the one-dimensional carbon material comprises carbon nanotubes, the carbon nanotubes comprise single-walled carbon nanotubes, the single-walled carbon nanotubes have a length of 5 μm to 50 μm and a diameter of 1 nm to 4 nm; (3) the one-dimensional carbon material comprises carbon nanotubes, the carbon nanotubes comprise few-walled carbon nanotubes, the few-walled carbon nanotubes have a length of 5 μm to 50 μm and a diameter of 2 nm to 10 nm; (4) the one-dimensional carbon material comprises carbon nanotubes, the carbon nanotubes comprise multi-walled carbon nanotubes, the multi-walled carbon nanotubes have a length of 5 μm to 50 μm and a diameter of 7 nm to 30 nm; (5) the one-dimensional carbon material comprises functionalized carbon nanotubes, the functionalized carbon nanotubes comprise at least one of functionalized single-walled carbon nanotubes, functionalized few-walled carbon nanotubes and functionalized multi-walled carbon nanotubes; (6) the one-dimensional carbon material comprises functionalized carbon nanotubes, the functionalized carbon nanotubes comprise functionalized single-walled carbon nanotubes, the functionalized single-walled carbon nanotubes have a length of 5 μm to 50 μm and a diameter of 1 nm to 6 nm; (7) the one-dimensional carbon material comprises functionalized carbon nanotubes, the functionalized carbon nanotubes comprise functionalized few-walled carbon nanotubes, the functionalized few-walled carbon nanotubes have a length of 5 μm to 50 μm and a diameter of 2 nm to 15 nm; (8) the one-dimensional carbon material comprises functionalized carbon nanotubes, the functionalized carbon nanotubes comprise functionalized multi-walled carbon nanotubes, the functionalized multi-walled carbon nanotubes have a length of 5 μm to 50 μm and a diameter of 7 nm to 40 nm; (9) the one-dimensional carbon material comprises carbon fibers, the carbon fibers have a length of 1 μm to 200 μm and a diameter of 5 μm to 20 μm; (10) the one-dimensional carbon material comprises aramid fibers, the aramid fibers have a length of 0.1 mm to 5 mm and a diameter of 5 μm to 20 μm; (11) the one-dimensional carbon material comprises polyoxadiazole fibers, the polyoxadiazole fibers have a length of 0.1 mm to 5 mm and a diameter of 5 μm to 20 μm.

10. Use of graphene composite aerogels according to any one of claims 1 to 9, characterized in that, as a heat-conducting material for use in a thermal management system.

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