Graphene-mxene composite aerogel and preparation method and application thereof
By preparing a multi-layered gradient graphene-MXene composite aerogel, the problems of high brittleness and limited functionality of MXene aerogel were solved, achieving a dynamic infrared stealth effect with high compression resilience and broadband microwave absorption, which is suitable for electronic communications and aerospace fields.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SOUTH CHINA UNIV OF TECH
- Filing Date
- 2024-03-27
- Publication Date
- 2026-05-19
AI Technical Summary
Existing MXene aerogels are brittle and have poor compression resilience due to the lack of covalent cross-linking between the layers, and they also lack dynamic infrared stealth and broadband microwave absorption capabilities.
A multi-layered gradient graphene-MXene composite aerogel was formed by preparing an aqueous dispersion of graphene oxide and performing bidirectional cryogenic casting. The interfacial bonding was enhanced by the physical entanglement and chemical cross-linking of graphene oxide and MXene, and the graphene-MXene composite aerogel was formed by annealing.
A multilayer gradient structure of graphene-MXene composite aerogel was achieved, exhibiting excellent compression resilience, dynamic infrared stealth performance, and broadband microwave absorption capabilities, making it suitable for applications in electronic communications and aerospace.
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Figure CN118324129B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of aerogel materials technology, specifically to a graphene-MXene composite aerogel, its preparation method, and its applications. Background Technology
[0002] MXene is a transition metal carbon and / or nitride with a two-dimensional layered structure, widely used in energy storage, heat conduction, microwave absorption (electromagnetic shielding), infrared stealth, and photothermal conversion. MXene exhibits self-assembly properties similar to graphene oxide, making it suitable for preparing three-dimensional aerogels. However, MXene aerogels are brittle due to the lack of covalent cross-linking between MXene sheets, making them prone to layer dislocation and structural collapse under stress. CN114705082A discloses a 3D aerogel-based phase change composite material with dual infrared stealth and visible light camouflage functions and its preparation method. The method involves first mixing graphene oxide, MXene dispersion, and a reducing agent, followed by freeze-drying to prepare a graphene-MXene composite aerogel. This is then impregnated with a phase change material and sprayed with thermochromic ink, ultimately yielding an aerogel with dual infrared and visible light camouflage functions. However, this 3D aerogel-based phase change composite material has a simple structural design, poor compression resilience, and lacks broadband microwave absorption capabilities.
[0003] Therefore, it is of great significance to develop an MXene aerogel material with excellent compression resilience and dual functions of dynamic infrared stealth and broadband microwave absorption. Summary of the Invention
[0004] The purpose of this invention is to provide a graphene-MXene composite aerogel, its preparation method, and its application.
[0005] The technical solution adopted in this invention is:
[0006] A method for preparing a graphene-MXene composite aerogel includes the following steps:
[0007] 1) Prepare a series of graphene-MXene aqueous dispersions with the same graphene oxide concentration but different MXene concentrations;
[0008] 2) Inject the graphene oxide-MXene aqueous dispersion into molds of the same size and then perform bidirectional cryogenic casting to obtain graphene oxide-MXene frozen blocks;
[0009] 3) Multiple graphene oxide-MXene frozen blocks were surface-bonded in order of MXene content from low to high / from high to low, and then placed at room temperature to allow the bonding surface to partially melt before bidirectional freeze casting and freeze drying to obtain graphene oxide-MXene composite aerogel.
[0010] 4) Anneal the graphene oxide-MXene composite aerogel in a protective atmosphere to obtain the graphene-MXene composite aerogel.
[0011] Preferably, the graphene oxide sheet diameter in step 1) is 5 μm to 200 μm.
[0012] Preferably, the MXene in step 1) is Ti3C2T. x Ti3CNT x Ti2CT x V2CT x Ti 1.6 Nb 0.4 CT x At least one of the following, wherein T represents a terminal group and x represents the number of terminal groups.
[0013] Preferably, the MXene in step 1) has a sheet diameter of 1 μm to 500 μm.
[0014] Preferably, the concentration of graphene oxide in the graphene oxide-MXene aqueous dispersion in step 1) is 2 mg / mL to 40 mg / mL, and the concentration of MXene is 2 mg / mL to 40 mg / mL.
[0015] Preferably, the mass ratio of graphene oxide to MXene in the graphene oxide-MXene aqueous dispersion in step 1) is 1:0.1 to 12.5.
[0016] Preferably, step 1) is specifically operated as follows: mixing MXene aqueous dispersions of different concentrations with graphene oxide aqueous dispersions of the same concentration in equal volumes, then performing ultrasonic dispersion, followed by heating and mechanical stirring to obtain a series of graphene oxide-MXene aqueous dispersions with the same graphene oxide concentration and different MXene oxide concentrations.
[0017] Preferably, the ultrasonic dispersion is performed under conditions of ultrasonic power of 200W to 600W, and the ultrasonic dispersion time is 30min to 90min.
[0018] Preferably, the heating temperature is 60℃~90℃.
[0019] Preferably, the stirring is carried out at a mixer speed of 200 rpm to 800 rpm for a stirring time of 20 min to 80 min.
[0020] Preferably, the number of graphene oxide-MXene frozen blocks in step 2) is 2 to 5.
[0021] Preferably, the size of the mold in step 2) is 7.5mm~30mm×6mm~30mm×7.5mm~30mm.
[0022] Preferably, in step 2), the bidirectional cryogenic casting uses liquid nitrogen or a low-temperature water bath to create a cold source, and a copper bridge is used to conduct the cold source. The casting time is 15 min to 60 min.
[0023] Preferably, in step 3), the bidirectional cryogenic casting uses liquid nitrogen or a low-temperature water bath to create a cold source, and a copper bridge is used to conduct the cold source. The casting time is 5 min to 30 min.
[0024] Preferably, the freeze-drying in step 3) is carried out at a temperature of -70℃ to -40℃ for a time of 48h to 108h.
[0025] Preferably, the protective atmosphere in step 4) is an argon atmosphere or a nitrogen atmosphere.
[0026] Preferably, the annealing operation in step 4) is as follows: first, control the heating rate to 2℃ / min~10℃ / min to raise the temperature from room temperature (25℃±5℃) to 200℃~600℃, then keep it at that temperature for 1h~5h, and then let it cool naturally to room temperature.
[0027] A graphene-MXene composite aerogel, which is prepared by the above-described method.
[0028] Preferably, the overall density of the graphene-MXene composite aerogel is 4.5 mg / cm³. 3 ~25.5mg / cm 3 .
[0029] Application of a graphene-MXene composite aerogel as described above in the preparation of communication equipment or aerospace equipment.
[0030] The beneficial effects of the present invention are: the graphene-MXene composite aerogel of the present invention has a multi-layer gradient structure, excellent compression resilience, and dual functions of dynamic infrared stealth and broadband microwave absorption. Moreover, its preparation method is simple and can be widely used in fields such as electronic communication and aerospace.
[0031] Specifically:
[0032] 1) The graphene-MXene composite aerogel of the present invention has good electrothermal conversion characteristics. When energized, the temperature of the composite aerogel will increase with the increase of the voltage (2V~5V) applied at its two ends. The heating time is short (5s~30s). The composite aerogel has good temperature stability. By adjusting the voltage, the temperature of the aerogel can be made consistent with the ambient temperature, thereby giving the composite aerogel excellent dynamic infrared stealth performance.
[0033] 2) The graphene-MXene composite aerogel of the present invention has a multi-layer gradient structure. Different gradient layers can absorb microwaves of different frequencies, thereby achieving full-band microwave absorption in the range of 2GHz to 18GHz, with an effective absorption bandwidth of up to 16GHz, which significantly exceeds the effective absorption bandwidth of existing aerogels (5GHz to 9GHz).
[0034] 3) This invention uses bidirectional cryogenic casting to orient MXene and graphene oxide along a direction parallel to the nanosheets. Physical entanglement and chemical cross-linking occur between MXene and graphene oxide nanosheets, significantly enhancing the interfacial bonding between them. The adjacent layers of the multilayer gradient structure have gradient-varying compressive strength, which can effectively buffer compressive stress, thereby increasing the compressive resilience of the composite aerogel (it can withstand more than 90% of the compressive strain, and can be cyclically compressed more than 5000 times when the compressive strain is controlled at 80%). Moreover, the microstructure of the composite aerogel remains relatively stable during large strain cyclic compression and will not be damaged. Attached Figure Description
[0035] Figure 1 This is a flowchart illustrating the preparation process of the graphene-MXene composite aerogel of the present invention.
[0036] Figure 2 This is a physical image of the graphene-MXene composite aerogel from Example 1.
[0037] Figure 3 This is a SEM image of the cross-section of the graphene-MXene composite aerogel in Example 2.
[0038] Figure 4 The graph shows the compression rebound test results of the graphene-MXene composite aerogel in Example 3 at 90% strain.
[0039] Figure 5 The graph shows the microwave absorption performance test results of the graphene-MXene composite aerogel in Example 5.
[0040] Figure 6 The graph shows the temperature changes of the graphene-MXene composite aerogel in Example 1 under different voltages.
[0041] Figure 7 The image shows the infrared stealth test results of the graphene-MXene composite aerogel in Example 1 at 50°C. Detailed Implementation
[0042] The present invention will be further explained and described below with reference to specific embodiments.
[0043] Example 1:
[0044] A graphene-MXene composite aerogel is prepared as follows (preparation flowchart shown). Figure 1 As shown):
[0045] 1) 4.5 mL of Ti3C2T at concentrations of 2 mg / mL, 6 mg / mL, and 10 mg / mL was added. x The aqueous dispersions (with sheet diameters of 1 μm to 50 μm) were added to 4.5 mL of an aqueous dispersion of graphene oxide (with sheet diameters of 5 μm to 50 μm) with a concentration of 8 mg / mL. The dispersions were then ultrasonically dispersed for 90 min at an ultrasonic power of 200 W. After heating to 90 °C, the dispersions were mechanically stirred for 20 min at a stirrer speed of 800 rpm to obtain three types of graphene oxide-MXene aqueous dispersions with the same graphene oxide concentration but different MXene concentrations.
[0046] 2) The graphene oxide-MXene aqueous dispersion was injected into three silicone rubber molds with a size of 30mm×10mm×30mm. Liquid nitrogen was used as the cold source and copper bridge was used to conduct the cold source. The two-way cryogenic casting was carried out for 20 minutes to obtain the graphene oxide-MXene frozen block.
[0047] 3) Three graphene oxide-MXene frozen blocks were surface-bonded in order of increasing MXene content, and then placed at room temperature to allow the bonding surface to partially melt. Liquid nitrogen was then used as the cold source, and copper bridge was used to conduct the cold source for bidirectional freeze casting for 10 minutes. Finally, the blocks were freeze-dried at -70℃ (cold trap temperature of the freeze dryer) for 48 hours to obtain graphene oxide-MXene composite aerogel.
[0048] 4) Place the graphene oxide-MXene composite aerogel in a tube furnace, fill it with nitrogen gas at a flow rate of 50 mL / min, and control the heating rate to increase from room temperature (25℃) to 400℃ at a rate of 5℃ / min. Hold the temperature for 2 hours, and then allow it to cool naturally to room temperature to obtain the graphene-MXene composite aerogel (overall density of 4.8 mg / cm³). 3 ).
[0049] A physical image of the graphene-MXene composite aerogel in this embodiment is shown below. Figure 2 As shown.
[0050] Depend on Figure 2 It can be seen that the graphene-MXene composite aerogel of this embodiment does not bend the fluff of dandelion when placed on it, indicating that its density is very low.
[0051] Example 2:
[0052] A graphene-MXene composite aerogel is prepared as follows (preparation flowchart shown). Figure 1 As shown):
[0053] 1) 4.5 mL of Ti3CNT at concentrations of 15 mg / mL, 20 mg / mL, and 25 mg / mL were added. x The aqueous dispersions (with sheet diameters of 50 μm to 100 μm) were added to 4.5 mL of an aqueous dispersion of graphene oxide (with sheet diameters of 100 μm to 200 μm) with a concentration of 20 mg / mL. The dispersions were then ultrasonically dispersed for 30 min at an ultrasonic power of 600 W. After heating to 60 °C, the dispersions were mechanically stirred for 20 min at a stirrer speed of 800 rpm to obtain three types of graphene oxide-MXene aqueous dispersions with the same graphene oxide concentration but different MXene concentrations.
[0054] 2) The graphene oxide-MXene aqueous dispersion was injected into three silicone rubber molds with a size of 30mm×10mm×30mm. Liquid nitrogen was used as the cold source and copper bridge was used to conduct the cold source. The two-way cryogenic casting was carried out for 20 minutes to obtain the graphene oxide-MXene frozen block.
[0055] 3) Three graphene oxide-MXene frozen blocks were surface-bonded in order of increasing MXene content, and then placed at room temperature to allow the bonding surface to partially melt. Liquid nitrogen was then used as the cold source, and copper bridge was used to conduct the cold source for bidirectional freeze casting for 10 minutes. Finally, the blocks were freeze-dried at -40℃ (cold trap temperature of the freeze dryer) for 108 hours to obtain graphene oxide-MXene composite aerogel.
[0056] 4) Place the graphene oxide-MXene composite aerogel in a tube furnace, fill it with nitrogen gas at a flow rate of 50 mL / min, and control the heating rate to rise from room temperature (25℃) to 600℃ at a rate of 10℃ / min. Hold the temperature for 2 hours, then allow it to cool naturally to room temperature to obtain the graphene-MXene composite aerogel (overall density 14.4 mg / cm³). 3 ).
[0057] The scanning electron microscope (SEM) image of the cross-section of the graphene-MXene composite aerogel in this embodiment is shown below. Figure 3 As shown.
[0058] Depend on Figure 3 It can be seen that the graphene-MXene composite aerogel has a three-layer gradient structure. The higher the mass ratio of graphene to MXene, the looser the pore structure of the corresponding aerogel layer. Conversely, the lower the mass ratio of graphene to MXene, the denser the pore structure of the corresponding aerogel layer.
[0059] Example 3:
[0060] A graphene-MXene composite aerogel is prepared as follows (preparation flowchart shown). Figure 1 As shown):
[0061] 1) 4.5 mL of Ti3CNT at concentrations of 30 mg / mL, 35 mg / mL, and 40 mg / mL were added. x The aqueous dispersions (with sheet diameters of 400 μm to 500 μm) were added to 4.5 mL of an aqueous dispersion of graphene oxide (with sheet diameters of 100 μm to 200 μm) at a concentration of 35 mg / mL. The dispersions were then ultrasonically dispersed for 60 min at an ultrasonic power of 400 W. After heating to 80 °C, the dispersions were mechanically stirred for 60 min at a stirrer speed of 400 rpm to obtain three types of graphene oxide-MXene aqueous dispersions with the same graphene oxide concentration but different MXene concentrations.
[0062] 2) The graphene oxide-MXene aqueous dispersion was injected into three silicone rubber molds with a size of 30mm×10mm×30mm. Liquid nitrogen was used as the cold source and copper bridge was used to conduct the cold source. The two-way cryogenic casting was carried out for 20 minutes to obtain the graphene oxide-MXene frozen block.
[0063] 3) Three graphene oxide-MXene frozen blocks were surface-bonded in order of increasing MXene content, and then placed at room temperature to allow the bonding surface to partially melt. Liquid nitrogen was then used as the cold source, and copper bridge was used to conduct the cold source for bidirectional freeze casting for 10 minutes. Finally, the blocks were freeze-dried at -50℃ (cold trap temperature of the freeze dryer) for 72 hours to obtain graphene oxide-MXene composite aerogel.
[0064] 4) Place the graphene oxide-MXene composite aerogel in a tube furnace, fill it with nitrogen gas at a flow rate of 50 mL / min, and control the heating rate to increase from room temperature (25℃) to 400℃ at a rate of 5℃ / min. Hold the temperature for 2 hours, then allow it to cool naturally to room temperature to obtain the graphene-MXene composite aerogel (overall density of 25.2 mg / cm³). 3 ).
[0065] Example 4:
[0066] A graphene-MXene composite aerogel is prepared as follows (preparation flowchart shown). Figure 1 As shown):
[0067] 1) 3.4 mL of Ti3C2T at concentrations of 10 mg / mL, 20 mg / mL, 30 mg / mL, and 40 mg / mL was added. xThe aqueous dispersions (with sheet diameters of 400 μm to 500 μm) were added to 3.4 mL of an aqueous dispersion of graphene oxide (with sheet diameters of 100 μm to 200 μm) at a concentration of 25 mg / mL. The dispersions were then ultrasonically dispersed for 90 min at an ultrasonic power of 200 W. After heating to 60 °C, the dispersions were mechanically stirred for 80 min at a stirrer speed of 200 rpm to obtain four types of graphene oxide-MXene aqueous dispersions with the same graphene oxide concentration but different MXene concentrations.
[0068] 2) The graphene oxide-MXene aqueous dispersion was injected into four silicone rubber molds with dimensions of 30mm×7.5mm×30mm. Liquid nitrogen was used as the cold source, and copper bridge was used to conduct the cold source. The two-way cryogenic casting was carried out for 15 minutes to obtain the graphene oxide-MXene frozen block.
[0069] 3) Four graphene oxide-MXene frozen blocks were surface-bonded in order of increasing MXene content, and then placed at room temperature to allow the bonding surface to partially melt. Liquid nitrogen was then used as the cold source, and copper bridge was used to conduct the cold source for bidirectional freeze casting for 5 minutes. Finally, the blocks were freeze-dried at -40℃ (cold trap temperature of the freeze dryer) for 48 hours to obtain graphene oxide-MXene composite aerogel.
[0070] 4) Place the graphene oxide-MXene composite aerogel in a tube furnace, fill it with nitrogen gas at a flow rate of 120 mL / min, and control the heating rate to rise from room temperature (25℃) to 400℃ at a rate of 10℃ / min. Hold the temperature for 2 hours, then allow it to cool naturally to room temperature to obtain the graphene-MXene composite aerogel (overall density of 18.1 mg / cm³). 3 ).
[0071] Example 5:
[0072] A graphene-MXene composite aerogel is prepared as follows (preparation flowchart shown). Figure 1 As shown):
[0073] 1) 2.7 mL of Ti3CNT at concentrations of 2 mg / mL, 10 mg / mL, 20 mg / mL, 30 mg / mL, and 40 mg / mL were added. x The aqueous dispersions (with sheet diameters of 300 μm to 400 μm) were added to 2.7 mL of an aqueous dispersion of graphene oxide (with sheet diameters of 100 μm to 200 μm) at a concentration of 20 mg / mL. The dispersions were then ultrasonically dispersed for 30 min at an ultrasonic power of 600 W. After heating to 90 °C, the dispersions were mechanically stirred for 20 min at a stirrer speed of 800 rpm to obtain five types of graphene oxide-MXene aqueous dispersions with the same graphene oxide concentration but different MXene concentrations.
[0074] 2) The graphene oxide-MXene aqueous dispersion was injected into five silicone rubber molds with a size of 30mm×6mm×30mm. Liquid nitrogen was used as the cold source and copper bridge was used to conduct the cold source. The two-way cryogenic casting was carried out for 15 minutes to obtain the graphene oxide-MXene frozen block.
[0075] 3) Five graphene oxide-MXene frozen blocks were surface-bonded in order of increasing MXene content, and then placed at room temperature to allow the bonding surface to partially melt. Liquid nitrogen was then used as the cold source, and copper bridge was used to conduct the cold source for bidirectional freeze casting for 5 minutes. Finally, the blocks were freeze-dried at -70℃ (cold trap temperature of the freeze dryer) for 108 hours to obtain graphene oxide-MXene composite aerogel.
[0076] 4) Place the graphene oxide-MXene composite aerogel in a tube furnace, fill it with nitrogen gas at a flow rate of 20 mL / min, and control the heating rate to rise from room temperature (25℃) to 400℃ at a rate of 2℃ / min. Hold the temperature for 2 hours, and then allow it to cool naturally to room temperature to obtain the graphene-MXene composite aerogel (overall density of 14.5 mg / cm³). 3 ).
[0077] Example 6:
[0078] A graphene-MXene composite aerogel is prepared as follows (preparation flowchart shown). Figure 1 As shown):
[0079] 1) 6.8 mL of Ti3CNT at concentrations of 20 mg / mL and 40 mg / mL were added. x Aqueous dispersions of graphene oxide (sheet diameter 300μm~400μm) were added to 6.8mL of 10mg / mL aqueous dispersions of graphene oxide (sheet diameter 100μm~200μm), and then ultrasonically dispersed for 90min at an ultrasonic power of 200W. After heating to 60℃, the dispersions were mechanically stirred for 80min at a stirrer speed of 200rpm to obtain two types of graphene oxide-MXene aqueous dispersions with the same graphene oxide concentration but different MXene concentrations.
[0080] 2) The graphene oxide-MXene aqueous dispersion was injected into two silicone rubber molds with a size of 30mm×15mm×30mm respectively. Liquid nitrogen was used as the cold source and copper bridge was used to conduct the cold source. The two-way cryogenic casting was carried out for 30 minutes to obtain the graphene oxide-MXene frozen block.
[0081] 3) Two graphene oxide-MXene frozen blocks were surface-bonded together, and then placed at room temperature to allow the bonding surface to partially melt. Liquid nitrogen was then used as the cold source, and copper bridge was used to conduct the cold source for bidirectional freeze casting for 20 minutes. Finally, the blocks were freeze-dried at -40℃ (cold trap temperature of the freeze dryer) for 48 hours to obtain graphene oxide-MXene composite aerogel.
[0082] 4) Place the graphene oxide-MXene composite aerogel in a tube furnace, fill it with nitrogen gas at a flow rate of 20 mL / min, and control the heating rate to rise from room temperature (25℃) to 400℃ at a rate of 10℃ / min. Hold the temperature for 2 hours, then allow it to cool naturally to room temperature to obtain the graphene-MXene composite aerogel (overall density of 16.8 mg / cm³). 3 ).
[0083] Example 7:
[0084] A graphene-MXene composite aerogel is prepared as follows (preparation flowchart shown). Figure 1 As shown):
[0085] 1) 6.8 mL of Ti3C2T at concentrations of 2 mg / mL and 40 mg / mL were added. x The aqueous dispersions (with sheet diameters of 200 μm to 300 μm) were added to 6.8 mL of an aqueous dispersion of graphene oxide (with sheet diameters of 100 μm to 200 μm) at a concentration of 20 mg / mL. The dispersions were then ultrasonically dispersed for 30 min at an ultrasonic power of 600 W. After heating to 60 °C, the dispersions were mechanically stirred for 20 min at a stirrer speed of 800 rpm to obtain two types of graphene oxide-MXene aqueous dispersions with the same graphene oxide concentration but different MXene concentrations.
[0086] 2) The graphene oxide-MXene aqueous dispersion was injected into two silicone rubber molds with a size of 30mm×15mm×30mm respectively. Liquid nitrogen was used as the cold source and copper bridge was used to conduct the cold source. The two-way cryogenic casting was carried out for 30 minutes to obtain the graphene oxide-MXene frozen block.
[0087] 3) Two graphene oxide-MXene frozen blocks were surface-bonded together, and then placed at room temperature to allow the bonding surface to partially melt. Liquid nitrogen was then used as the cold source, and copper bridge was used to conduct the cold source for bidirectional freeze casting for 20 minutes. Finally, the blocks were freeze-dried at -40℃ (cold trap temperature of the freeze dryer) for 108 hours to obtain graphene oxide-MXene composite aerogel.
[0088] 4) Place the graphene oxide-MXene composite aerogel in a tube furnace, fill it with nitrogen gas at a flow rate of 120 mL / min, and control the heating rate to rise from room temperature (25℃) to 600℃ at a rate of 10℃ / min. Hold the temperature for 2 hours, then allow it to cool naturally to room temperature to obtain the graphene-MXene composite aerogel (overall density of 14.8 mg / cm³). 3 ).
[0089] Comparative Example 1:
[0090] An MXene aerogel is prepared as follows:
[0091] 27 mL of Ti3C2T with a concentration of 20 mg / mL was added. x Aqueous dispersions (with sheet diameters of 400μm to 500μm) were injected into silicone rubber molds measuring 30mm × 30mm × 30mm. Liquid nitrogen was used as the cold source, and a copper bridge was employed for conductive cooling. The mixture was then cryogenically cast for 30 minutes, followed by freeze-drying at -70℃ (cold trap temperature of the freeze dryer) for 48 hours to obtain MXene aerogel (overall density of 20.0 mg / cm³). 3 ).
[0092] Comparative Example 2:
[0093] A graphene-MXene composite aerogel is prepared as follows:
[0094] 1) Add 13.5 mL of Ti3C2T solution with a concentration of 20 mg / mL. x Aqueous dispersions of graphene oxide (sheet diameter 400μm~500μm) were added to 13.5mL of 10mg / mL aqueous dispersions of graphene oxide (sheet diameter 100μm~200μm), and then ultrasonically dispersed for 30min at an ultrasonic power of 600W. After heating to 60℃, the dispersions were mechanically stirred for 20min at a stirrer speed of 800rpm to obtain an aqueous dispersion of graphene oxide-MXene.
[0095] 2) Inject the graphene oxide-MXene aqueous dispersion into a silicone rubber mold with a size of 30mm×30mm×30mm, and then use liquid nitrogen as a cold source and copper bridge to conduct the cold source for bidirectional cryogenic casting for 30 minutes to obtain the graphene oxide-MXene frozen block.
[0096] 3) The graphene oxide-MXene frozen block was freeze-dried at a temperature of -70℃ (cold trap temperature of the freeze dryer) for 48 hours to obtain graphene oxide-MXene composite aerogel.
[0097] 4) Place the graphene oxide-MXene composite aerogel in a tube furnace, fill it with nitrogen gas at a flow rate of 120 mL / min, and control the heating rate to rise from room temperature (25℃) to 600℃ at a rate of 10℃ / min. Hold the temperature for 2 hours, then allow it to cool naturally to room temperature to obtain the graphene-MXene composite aerogel (overall density of 12.0 mg / cm³). 3 ).
[0098] Performance testing:
[0099] The compression rebound test results of the graphene-MXene composite aerogel in Example 3 at 90% strain are shown in the figure below. Figure 4 As shown in the figure, the microwave absorption performance test results of the graphene-MXene composite aerogel in Example 5 are as follows. Figure 5 As shown in the figure, the temperature change of the graphene-MXene composite aerogel in Example 1 under different voltages is as follows. Figure 6 As shown in the figure, the infrared stealth test results of the graphene-MXene composite aerogel in Example 1 at 50°C are as follows. Figure 7 As shown in the table below, the performance test data of the aerogels of Examples 1-7 and Comparative Examples 1-2 are as follows:
[0100] Table 1. Performance test data of aerogels from Examples 1-7 and Comparative Examples 1-2.
[0101]
[0102] Note:
[0103] Compression strength: The test was conducted in accordance with "GB / T 7757-2009 Determination of compressive stress-strain properties of vulcanized rubber or thermoplastic rubber", with a compression rate of 5 mm / min and a test temperature of 25℃±2℃.
[0104] Compression cycle count: The test was conducted in accordance with "GB / T 7757-2009 Determination of compressive stress-strain properties of vulcanized rubber or thermoplastic rubber". The strain was set to 80%, the compression rate was 50 mm / min, and the test temperature was 25℃±2℃. When the permanent deformation of the aerogel exceeded 10%, the corresponding number of compression cycles was recorded.
[0105] Minimum Reflection Loss (RL) min Effective Absorption Bandwidth (EAB): Tests were conducted according to "GB / T 32596-2016 General Specification for Electromagnetic Shielding Absorbers". The coaxial method was used to test the electromagnetic parameters of the aerogel, and then the RL of the aerogel was calculated. min and EAB;
[0106] Heating time and temperature change range: When a voltage of 2V to 5V is applied, an infrared thermal imager is used to record the temperature change range of the aerogel surface after heating time and voltage changes, with the highest temperature being 300℃.
[0107] Depend on Figure 4 It can be seen that the graphene-MXene composite aerogel in Example 3 can still return to its initial height after being compressed to 90% strain, indicating that it has excellent compression resilience.
[0108] Depend on Figure 5 It can be seen that the graphene-MXene composite aerogel in Example 5 can effectively achieve broadband microwave absorption at a relatively low thickness, with a maximum effective absorption bandwidth of 16.0 GHz (2.0 GHz to 18.0 GHz), and its microwave absorption performance is excellent.
[0109] Depend on Figure 6 It can be seen that as the applied voltage increases, the temperature of the graphene-MXene composite aerogel in Example 1 gradually increases, and the temperature stability is good.
[0110] Depend on Figure 7 It can be seen that at a voltage of 3V, the temperature of the graphene-MXene composite aerogel in Example 1 reaches about 50°C. In infrared imaging, the graphene-MXene composite aerogel blends into the background color, indicating that the graphene-MXene composite aerogel has excellent dynamic infrared stealth performance.
[0111] As shown in Table 1:
[0112] 1) The MXene aerogel in Comparative Example 1 could not recover from compression, while the graphene-MXene composite aerogel (without gradient structure) in Comparative Example 2 underwent permanent deformation after 100 cycles of compression, indicating that graphene enhanced the compression recovery performance of the MXene aerogel. In addition, the introduction of graphene helps to adjust the impedance matching of the graphene-MXene composite aerogel, thereby reducing the minimum reflection loss of the composite aerogel, increasing the effective absorption bandwidth, and improving the wave absorption performance. However, graphene also reduces the resistance of the composite aerogel, making it take longer to heat up when energized.
[0113] 2) Compared with the MXene aerogel of Comparative Example 1 and the graphene-MXene composite aerogel of Comparative Example 2, the graphene-MXene composite aerogel of Example 1 has higher compressive strength and only undergoes permanent deformation after 500 cycles of compression, indicating that the multilayer gradient structure can improve the compression recovery performance of the aerogel. In addition, the multilayer gradient structure also improves the microwave absorption bandwidth of the aerogel. This is mainly because the increase in the number of aerogel layers is conducive to the absorption of microwaves in different frequency bands. After the microwaves of different frequency bands are absorbed, they are superimposed, thereby achieving a larger effective absorption bandwidth.
[0114] 3) In Examples 1-3, different types of MXene were used and the concentration of MXene aqueous dispersion was increased to obtain graphene-MXene composite aerogels with a three-layer gradient structure and different compressive strengths. As the concentration of MXene increased, the temperature range of the graphene-MXene composite aerogel gradually increased, thus covering a temperature range of 40℃ to 300℃, achieving dynamic infrared stealth at an ambient temperature of 40℃ to 300℃. The performance of the graphene-MXene composite aerogels in Examples 1-3 was superior to that of the MXene aerogel in Comparative Example 1 and Comparative Example 2, indicating that the graphene-MXene composite aerogels corresponding to different types of MXene have better mechanical, microwave absorption, and dynamic infrared stealth properties. In Examples 3-6, as the concentration of graphene-MXene increased, the temperature range of the graphene-MXene composite aerogel gradually increased, thus covering a temperature range of 40℃ to 300℃, achieving dynamic infrared stealth at an ambient temperature of 40℃ to 300℃. The increased number of gradient layers in the Xene composite aerogel significantly increases the number of cyclic compressions and further improves the effective absorption bandwidth, indicating that the more gradient layers there are, the better the compression resilience of the aerogel. Furthermore, it further confirms that different gradient layers can absorb microwaves of different frequencies; therefore, the more gradient layers there are, the wider the microwave absorption bandwidth becomes. The graphene-MXene composite aerogels in Examples 6 and 7 both have two-layer gradient structures, but by increasing the concentration difference between the two layers, the microwave absorption bandwidth of the aerogel can also be improved. This is mainly because when the MXene concentration difference is small, the microwave absorption frequency bands corresponding to different gradient layers have a wide overlap range. The greater the MXene concentration difference between different gradient layers, the narrower the overlap range of the microwave absorption bands between different gradient layers, and the wider the corresponding effective absorption frequency band.
[0115] In summary, compared with MXene aerogel and graphene-MXene composite aerogel without gradient structure, the graphene-MXene composite aerogel of the present invention has a macroscopically tunable multilayer gradient structure. The graphene-MXene composite aerogel has higher compressive strength, more cycles of compression, better dynamic infrared stealth performance and broadband absorption performance, and is suitable for use as a multifunctional stealth composite material in fields such as electronic communication and aerospace.
[0116] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.
Claims
1. A method for preparing a graphene-MXene composite aerogel, characterized in that, Includes the following steps: 1) Prepare a series of graphene-MXene aqueous dispersions with the same graphene oxide concentration but different MXene concentrations; 2) Inject the graphene oxide-MXene aqueous dispersion into molds of the same size and then perform bidirectional cryogenic casting to obtain graphene oxide-MXene frozen blocks; 3) Multiple graphene oxide-MXene frozen blocks were surface-bonded in order of MXene content from low to high / from high to low, then placed at room temperature to allow the bonding surface to partially melt before bidirectional freeze casting and freeze drying to obtain graphene oxide-MXene composite aerogel. 4) Anneal the graphene oxide-MXene composite aerogel in a protective atmosphere to obtain the graphene-MXene composite aerogel. In step 1), the mass ratio of graphene oxide to MXene in the graphene oxide-MXene aqueous dispersion is 1:0.1 to 12.
5. Step 3) The number of graphene oxide-MXene frozen blocks is 2 to 5.
2. The preparation method according to claim 1, characterized in that: Step 1) The graphene oxide sheet diameter is 5μm to 200μm; Step 1) The MXene is Ti3C2T x Ti3CNT x Ti2CT x V2CT x Ti 1.6 Nb 0.4 CT x At least one of them, wherein T represents a terminal group, x The number of terminal groups is indicated; the diameter of the MXene in step 1) is 1 μm to 500 μm.
3. The preparation method according to claim 1 or 2, characterized in that: In step 1), the concentration of graphene oxide in the graphene oxide-MXene aqueous dispersion is 2 mg / mL to 40 mg / mL, and the concentration of MXene is 2 mg / mL to 40 mg / mL.
4. The preparation method according to claim 1, characterized in that: Step 2) The bidirectional cryogenic casting uses liquid nitrogen to create a cold source and a copper bridge to conduct the cold source. The casting time is 15 min to 60 min.
5. The preparation method according to claim 1, characterized in that: Step 3) The bidirectional cryogenic casting uses liquid nitrogen to create the cold source and a copper bridge to conduct the cold source. The casting time is 5 min to 30 min. Step 3) The freeze drying is carried out at a temperature of -70℃ to -40℃ for 48 h to 108 h.
6. The preparation method according to any one of claims 1, 2 and 5, characterized in that: Step 4) The specific operation of annealing is as follows: first, control the heating rate to 2℃ / min~10℃ / min to raise the temperature from room temperature to 200℃~600℃, then keep it at that temperature for 1h~5h, and then let it cool naturally to room temperature.
7. A graphene-MXene composite aerogel, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 6.
8. The graphene-MXene composite aerogel according to claim 7, characterized in that: The overall density of the graphene-MXene composite aerogel is 4.5 mg / cm³. 3 ~25.5mg / cm 3 .
9. The application of the graphene-MXene composite aerogel as described in claim 7 or 8 in the preparation of aerospace equipment.