High-heat electrical gel with anisotropic structure as well as preparation method and application of high-heat electrical gel

Abstract

The invention discloses a high-thermal-conductivity aerogel with an anisotropic structure and a preparation method and application thereof, and belongs to the field of aerogel material preparation. The preparation method comprises the following steps: (1) preparing an aramid nanofiber dispersion liquid; (2) preparing MXene; (3) preparing alkalized MXene; (4) preparing an aerogel precursor solution; and (5) preparing the high-heat electrical gel by adopting a directional freezing method. According to the aerogel provided by the invention, the aramid fiber-based aerogel is endowed with double improvement strategy treatment of a directional structure and chemical modified MXene, so that the thermoelectric performance of the aerogel material is greatly improved in a synergistic manner, and the high-temperature early warning performance of the aerogel is greatly improved in a synergistic manner; meanwhile, the aerogel provided by the invention has low density, good flexibility and machinability, and meets the use requirements of fire-fighting materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of aerogel preparation, and in particular relates to a high-temperature electrical gel with an anisotropic structure, a preparation method and an application thereof. Background Art

[0002] Turnout gear is a crucial piece of equipment for protecting firefighters during firefighting and rescue operations under extreme temperature conditions. The thermal performance of turnout gear primarily relies on the insulation layer within the multilayer fabric system, which effectively shields firefighters from ambient heat hazards during high-temperature exposure. Aerogels, with their exceptional low density and thermal insulation properties, are a promising candidate for efficient thermal insulation in turnout gear, enabling them to reduce weight while simultaneously providing high thermal insulation. Aramid nanofiber (ANFs)-based aerogels, with their excellent thermal stability and porous structure at the nano and micro scales, are a promising candidate for the thermal insulation layer of turnout gear. They significantly inhibit heat conduction and convection within the aerogel skeleton under high radiant heat exposure. Unfortunately, ANFs-based insulation layers in turnout gear can still undergo thermal decomposition and cracking after prolonged exposure to extreme temperatures (≥400°C), compromising firefighter safety. Integrating intelligent temperature sensing into ANFs-based composite aerogels offers a novel solution for monitoring and preventing pyrolytic damage in turnout gear. This proactive strategy can provide firefighters with early warnings before the insulation layer thermally decomposes under extreme fire conditions, extending the life of fire suits and effectively ensuring personal safety. Recent advances in temperature-responsive materials have sparked great interest in the development of temperature-sensitive aerogels for fire suits. To date, traditional high-temperature warning aerogels based on thermal resistance materials have a key flaw: their electrical signal transmission is heavily dependent on an external power supply. Therefore, this type of aerogel not only increases the complexity of the temperature sensing system, but also poses the risk of power failure due to long-term exposure to high temperature conditions. In contrast, thermoelectric gels are considered to be effective temperature sensing materials in fire suits. When exposed to high temperatures, they can directly convert heat into voltage, and the voltage intensity is directly related to the change in temperature difference. For example, patent document CN117210961A provides a thermoelectric gel fiber with a skin-core structure that has the properties of repeatable warning, high sensitivity and self-power supply.

[0003] However, the inherent isotropic porous structure of conventional thermoelectric gels leads to mechanical limitations and short discontinuous carrier transport paths, which limits their efficacy in high-temperature warning applications. Therefore, fabricating an aerogel with high thermoelectric performance for high-temperature warning applications in firefighting uniforms remains a great challenge.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide an anisotropic high-thermal electrical gel and its preparation method and application. The obtained aerogel has high thermoelectricity and good high-temperature warning performance.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a high-temperature electrical gel with an anisotropic structure, comprising the following steps:

[0008] (1) preparing an aramid nanofiber dispersion;

[0009] (2) Preparation of MXene;

[0010] (3) Preparation of alkalized MXene;

[0011] (4) Preparing an aerogel precursor solution: adding the alkalized MXene obtained in step (3) to a DMSO solvent and stirring to obtain a mixture I; then adding montmorillonite to the DMSO solvent and stirring to obtain a mixture II; mixing the mixture I and the mixture II and the aramid nanofiber dispersion obtained in step (1), and stirring to obtain an aerogel precursor solution;

[0012] (5) High-temperature electrical gel was prepared by directional freezing method.

[0013] As a preferred embodiment of the technical solution of the present invention, the specific steps of step (1) include: adding aramid and potassium hydroxide into DMSO solvent, stirring at room temperature for 5 to 10 days, and obtaining an aramid nanofiber dispersion.

[0014] As a preferred embodiment of the technical solution of the present invention, the specific steps of step (2) include: mixing lithium fluoride and hydrochloric acid, stirring, slowly adding Ti3AlC2, and stirring again; after stirring, washing and centrifuging until the pH value of the supernatant is greater than 6 to obtain a precipitate;

[0015] The obtained precipitate is mixed with deionized water and subjected to ultrasonic treatment to obtain a single-layer MXene nanosheet dispersion; then, the obtained single-layer MXene nanosheet dispersion is centrifuged again and then freeze-dried to obtain MXene.

[0016] As a preferred embodiment of the technical solution of the present invention, the specific steps of step (3) include: dispersing the MXene obtained in step (2) in a sodium hydroxide solution, stirring, centrifuging, and washing to obtain a precipitate; and vacuum drying the obtained precipitate to obtain the alkaline MXene.

[0017] As a preferred embodiment of the technical solution of the present invention, in step (4), the usage ratio of alkalized MXene, montmorillonite, and aramid nanofiber dispersion is 2:1:4.

[0018] As a preferred embodiment of the technical solution of the present invention, the specific steps of step (5) include: adding the aerogel precursor solution obtained in step (4) into a mold, then performing directionally freeze-drying under liquid nitrogen conditions, and then solidifying the frozen aerogel precursor in a coagulation bath; then, washing the solidified aerogel precursor, and then performing solvent exchange in the mixed solution, and freeze-drying after the exchange treatment to obtain aerogel AM; finally, immersing the aerogel AM in a DMSO solvent containing CH3NH3PbI3 and performing vacuum drying to obtain a thermoelectric gel.

[0019] As a preferred embodiment of the technical solution of the present invention, in step (5), the temperature of directional freeze-drying is -196°C and the time is 10 to 30 minutes; the composition of the coagulation bath is: a mixture of ethanol and acetic acid in a volume ratio of 7:3, the coagulation treatment temperature is -18°C, and the time is 8 to 24 hours.

[0020] As a preferred embodiment of the technical solution of the present invention, in step (5), the mixed solution is obtained by mixing tert-butanol and water in a volume ratio of 1:1; the solvent exchange time is 2 to 12 hours;

[0021] The DMSO solvent containing CH3NH3PbI3 is obtained by dissolving CH3NH3PbI3 in the solvent DMSO; the vacuum drying of the aerogel AM is 2 to 8 hours.

[0022] In a second aspect, the present invention seeks to protect the high-temperature electrical gel prepared by the above method.

[0023] In a third aspect, the present invention provides the use of the high-temperature electrical gel obtained above in high-temperature / gas warning, such as high-temperature warning for fire-fighting clothing.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The aerogel provided by the present invention uses a dual improvement strategy of imparting a directional structure to the aramid-based aerogel and chemically modifying MXene, which greatly synergistically improves the thermoelectric properties of the aerogel material and greatly synergistically improves the high-temperature warning performance of the aerogel.

[0026] The aerogel provided by the present invention, by loading CH3NH3PbI3, enables the aerogel to have the function of visual detection of NH3 gas, filling the gap that traditional fire-fighting suits cannot sense toxic gases; the aerogel can be directly used as the thermal insulation layer of fire-fighting suits, realizing the triple functions of "thermal barrier - temperature perception - gas warning", further improving the safety of firefighters in complex fire scenes.

[0027] The aerogel provided by the present invention has low density, good flexibility and processability, and meets the use requirements of fire-fighting materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a top-view SEM image of the honeycomb structure of the aerogel obtained in Example 1.

[0029] Figure 2 This is an SEM image of the cross-section oriented pores of the aerogel obtained in Example 1.

[0030] Figure 3 This is an example diagram of the lightweight nature of the aerogel obtained in Example 1.

[0031] Figure 4 The different shapes and flexibility of the aerogel obtained in Example 1 are demonstrated.

[0032] Figure 5 The thermoelectric performance results of the aerogels obtained in Example 1 and Comparative Examples 1 to 3 are shown.

[0033] Figure 6 This is an optical image of the high temperature warning performance of Example 1.

[0034] Figure 7 The results are a comparison of the high temperature warning sensitivity of the aerogels obtained in Example 1 and Comparative Examples 1 to 3.

[0035] Figure 8 This is an optical image of the gas visualization detection performance of Example 1. DETAILED DESCRIPTION

[0036] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] It should be emphasized that, where specific conditions are not specified in the examples, conventional conditions or those recommended by the manufacturer were followed. Reagents or instruments used without manufacturer identification are commercially available. For example, aramid fiber was purchased from Shanghai Mingxi Industrial Co., Ltd.; montmorillonite (analytical grade AR) was purchased from Aladdin Biochemical Technology Co., Ltd. under the brand name Wokai.

[0038] The present invention provides a method for preparing a high-temperature electrical gel with an anisotropic structure, comprising the following steps:

[0039] (1) preparing an aramid nanofiber dispersion;

[0040] (2) Preparation of MXene;

[0041] (3) Preparation of alkalized MXene;

[0042] (4) Preparing an aerogel precursor solution: adding the alkalized MXene obtained in step (3) to a DMSO solvent and stirring to obtain a mixture I; then adding montmorillonite to the DMSO solvent and stirring to obtain a mixture II; mixing the mixture I and the mixture II and the aramid nanofiber dispersion obtained in step (1), and stirring to obtain an aerogel precursor solution;

[0043] (5) High-temperature electrical gel was prepared by directional freezing method.

[0044] In the above technical solution, a dual strategy (imparting directional structure and chemically modifying MXene) is adopted to enhance the thermoelectric properties of aramid nanofiber (ANFs)-based aerogels, thereby giving them more sensitive high-temperature warning performance. In nature, the muscle tissue of humans or animals has anisotropic and ordered structures, which gives the muscles high mechanical strength and directional molecular transmission channels, providing inspiration for the development of high-performance thermoelectric high-temperature warning aerogels based on ANFs. Inspired by the directional structure of human muscle tissue, the directional freezing technology gives the aerogel a directional structure and enhances electron transport. At the same time, the MXene material is chemically modified (alkalized) with sodium hydroxide, which can convert the fluorine-containing functional groups on the surface of the MXene material into hydroxyl groups (-OH). Alkali treatment of MXene will destroy the electrostatic balance between the MXene layers, making the electrostatic repulsion between the MXene layers unable to compensate for the high surface energy, inducing wrinkling of the MXene sheets. At the same time, sodium ions (Na + ) increases the interlayer spacing of MXene sheets, effectively inhibits the re-accumulation of MXene sheets, and is conducive to the formation of an open three-dimensional porous structure, which facilitates electron transport and improves the electrochemical properties of the material.

[0045] In harsh fire environments, particularly in industrial sites, toxic gas (NH3) leaks may occur. Long-term exposure to high levels of NH3 by firefighters can not only cause severe human effects (such as irritation to the eyes, throat, skin, and respiratory tract), but can also often cause explosions when concentrations exceed a certain level. However, NH3 is colorless and diffuses rapidly, making it difficult to detect with the naked eye. Therefore, the ability to visually monitor NH3 is crucial to ensuring firefighter safety.

[0046] By loading CH3NH3PbI3, the aerogel is endowed with the ability to visually detect NH3 gas, filling the gap in traditional firefighting suits' inability to sense toxic gases and further improving the safety of firefighters in complex fire scenes. The aerogel can be directly used as the thermal insulation layer of firefighting suits, achieving the triple functions of "thermal barrier - temperature sensing - gas warning", significantly improving the safety of firefighters in complex fire scenes. In the future, it can also be expanded to areas such as industrial high-temperature protection and wearable devices. This dual-functional integration solves the technical bottleneck of traditional firefighting equipment's inability to cope with high temperatures and toxic gases at the same time. Its signal transmission and visual gas warning characteristics provide firefighters with all-round safety protection in complex fire environments. This research pioneered the combination of thermoelectric conversion and gas sensing technology.

[0047] In some embodiments, step (1) comprises adding aramid and potassium hydroxide to a DMSO solvent and stirring at room temperature for 5 to 10 days to obtain an aramid nanofiber dispersion. More specifically, the amount of aramid is 1 to 2 g, the amount of potassium hydroxide is 1 to 2 g, and the amount of DMSO solvent is 50 to 150 mL.

[0048] In some embodiments, the specific steps of step (2) include: mixing lithium fluoride and hydrochloric acid, stirring, and slowly adding Ti3AlC2, and stirring again; after stirring, washing, centrifuging, until the pH value of the supernatant is greater than 6, to obtain a precipitate;

[0049] The resulting precipitate is mixed with deionized water and ultrasonically treated to obtain a monolayer MXene nanosheet dispersion. The resulting monolayer MXene nanosheet dispersion is then centrifuged again and freeze-dried to yield MXene. Specifically, the amount of lithium fluoride used is 1-2.5 g; the amount of hydrochloric acid used is 10-30 mL at a concentration of 8-15 mol / L; and the amount of Ti3AlC2 used is 0.5-2 g.

[0050] In some embodiments, step (3) comprises the following steps: dispersing the MXene obtained in step (2) in a sodium hydroxide solution, stirring, centrifuging, and washing to obtain a precipitate; and vacuum drying the obtained precipitate to obtain an alkalized MXene. More specifically, the amount of MXene used is 50 to 200 mg, the concentration of the sodium hydroxide solution is 3 to 10 wt%, and the amount of the sodium hydroxide solution used is 20 to 100 mL; the stirring temperature is 25 to 40°C, and the stirring time is 2 to 8 hours; the vacuum drying temperature is 50 to 70°C, and the drying time is 6 to 24 hours. MXene is an emerging two-dimensional transition metal carbide / carbonitride with a unique thermoelectric effect and excellent electrical conductivity. However, the random stacking of MXene nanosheets will limit the full utilization of its surface area and electrical conductivity. Chemical modification (alkalization) of the MXene material with sodium hydroxide can convert the fluorine-containing functional groups on the surface of the MXene material into hydroxyl groups (-OH), providing more active surface sites. Alkali treatment of MXene will destroy the electrostatic balance between MXene layers and induce wrinkling of MXene sheets. + ) increases the interlayer spacing of MXene sheets, effectively inhibits the re-accumulation of MXene sheets, and is conducive to the formation of an open three-dimensional porous structure, which facilitates electron transport and improves the electrochemical performance of the material.

[0051] In some embodiments, in step (4), the ratio of the amount of alkalized MXene, montmorillonite, and aramid nanofiber dispersion is 2:1:4.

[0052] In some embodiments, the specific steps of step (5) include: adding the aerogel precursor solution obtained in step (4) to a mold, then performing directional freeze drying under liquid nitrogen conditions, and then solidifying the frozen aerogel precursor in a coagulation bath; then, washing the solidified aerogel precursor, then performing solvent exchange in the mixed solution, and freeze drying after the exchange process to obtain aerogel AM; finally, immersing the aerogel AM in a DMSO solvent containing CH3NH3PbI3 and vacuum drying to obtain a thermoelectric gel. The directional freezing device can use existing mature equipment, or can be processed with reference to existing technology, or can be homemade. If homemade is used, it can be assembled in the following form: liquid nitrogen is poured into a liquid nitrogen basin (the specifications can be 24 cm in diameter and 14 cm in height), a copper block (the specifications can be 6 cm*1 cm*1.5 cm) is placed at the bottom of the basin, and a mold containing the aerogel precursor solution is placed on the copper block. The mold can be foamed around. Conventional thermoelectric gels exhibit an inherently isotropic porous structure, resulting in mechanical limitations and the shortest discontinuous carrier transport pathways, resulting in poor mechanical and electrical properties, which limits their effectiveness in temperature sensing applications. By using a directional freezing method, an anisotropic, directional, ordered structure is constructed, which can give the aerogels high mechanical strength and directional molecular transport pathways, enhancing their mechanical properties and electrical conductivity, and achieving more sensitive high-temperature warning performance.

[0053] More specifically, in step (5), the temperature of directional freeze drying is -196°C and the time is 10 to 30 minutes; the composition of the coagulation bath is: a mixture of ethanol and acetic acid with a volume ratio of 7:3, the coagulation treatment temperature is -18°C and the time is 8 to 24 hours. The ethanol and acetic acid mixed solution is used as the coagulation bath, and acetic acid is used as a proton donor to provide abundant hydrogen ions (H + ), enhancing the formation of hydrogen bonds between fibers, thereby achieving a high degree of regeneration and reinforcement of nanofibers. At the same time, the strategic addition of ethanol alleviates the excessive contraction of the skeleton caused by low surface tension, maintaining the stability and integrity of the structure.

[0054] More specifically, in step (5), the mixed solution is obtained by mixing tert-butyl alcohol and water in a volume ratio of 1:1; the solvent exchange time is 2 to 12 hours; the solvent exchange is performed to inhibit the formation of ice crystals during the subsequent freeze-drying process and maintain the microstructure of the aerogel;

[0055] The CH3NH3PbI3-containing DMSO solvent is prepared by dissolving CH3NH3PbI3 in DMSO. The concentration of CH3NH3PbI3 is preferably 0.25 g / mL. The aerogel AM is vacuum-dried for 2 to 8 hours. The introduction of CH3NH3PbI3 overcomes the limitation of traditional high-temperature warning sensors in lacking the ability to visualize hazardous gases.

[0056] Example 1

[0057] A method for preparing a high-temperature electrical gel with an anisotropic structure comprises the following steps:

[0058] (1) Preparation of aramid nanofiber dispersion: 1.5 g of aramid and 1.5 g of potassium hydroxide were added to 80 mL of DMSO solvent and stirred at room temperature for 7 days to obtain an aramid nanofiber dispersion;

[0059] (2) Preparation of MXene: 1.6 g of lithium fluoride was mixed with 20 mL of 12 mol / L hydrochloric acid, and 1 g of Ti3AlC2 was slowly added after magnetic stirring for 40 min. The mixture was stirred for another 24 h. After stirring, the mixture was repeatedly washed with distilled water and centrifuged at 3000 rpm for 10 min until the pH value of the supernatant was greater than 6 to obtain a precipitate.

[0060] The obtained precipitate was mixed with deionized water and ultrasonically treated for 2.5 hours to obtain a single-layer MXene nanosheet dispersion; then, the obtained single-layer MXene nanosheet dispersion was centrifuged again at 3000 rpm and then freeze-dried to obtain MXene;

[0061] (3) Preparation of alkaline MXene: 100 mg of MXene prepared in step (2) was dispersed in 60 mL of 5 wt% sodium hydroxide solution, stirred at 30°C for 4 h, centrifuged, and washed to obtain a precipitate; the obtained precipitate was vacuum-dried at 60°C for 12 h to obtain the alkaline MXene;

[0062] (4) Preparing an aerogel precursor solution: adding the alkalized MXene obtained in step (3) to a DMSO solvent and stirring for 3 h to obtain a mixture I; then adding montmorillonite to the DMSO solvent and stirring for 3 h to obtain a mixture II; mixing the mixture I and the mixture II and the aramid nanofiber dispersion obtained in step (1) and stirring to obtain an aerogel precursor solution; wherein the amount ratio of the alkalized MXene, montmorillonite and aramid nanofiber dispersion is 2:1:4;

[0063] (5) A high-temperature electrical gel was prepared by a directional freezing method: the aerogel precursor solution obtained in step (4) was added to a polytetrafluoroethylene mold, and then a directional freezing device was used to perform directional freeze drying in liquid nitrogen for 20 minutes (temperature -196°C), and then the frozen aerogel precursor was solidified in a coagulation bath (temperature of -18°C, the coagulation bath was obtained by mixing ethanol and acetic acid in a volume ratio of 7:3) for 18 hours; then, the solidified aerogel precursor was washed and then placed in a mixed solution. The aerogel AM was obtained by solvent exchange in a liquid (obtained by mixing tert-butanol and water in a volume ratio of 1:1) for 5 hours, and then freeze-dried for 18 hours to obtain the aerogel AM; finally, the aerogel AM was completely immersed in a DMSO solvent containing CH3NH3PbI3 and vacuum-dried at 100°C for 3 hours to obtain the thermoelectric gel; wherein the DMSO solvent containing CH3NH3PbI3 was obtained by dissolving CH3NH3PbI3 in the solvent DMSO, and the concentration of CH3NH3PbI3 was 0.25 g / mL.

[0064] Example 2

[0065] A method for preparing a high-temperature electrical gel with an anisotropic structure comprises the following steps:

[0066] (1) Preparation of aramid nanofiber dispersion: 1.5 g of aramid and 1.5 g of potassium hydroxide were added to 100 mL of DMSO solvent and stirred at room temperature for 10 days to obtain an aramid nanofiber dispersion;

[0067] (2) Preparation of MXene: 1.6 g of lithium fluoride was mixed with 25 mL of 12 mol / L hydrochloric acid, and 1 g of Ti3AlC2 was slowly added after magnetic stirring for 50 min. The mixture was stirred for another 18 h. After stirring, the mixture was repeatedly washed with distilled water and centrifuged at 3000 rpm for 8 min until the pH value of the supernatant was greater than 6 to obtain a precipitate.

[0068] The obtained precipitate was mixed with deionized water and ultrasonically treated for 3 hours to obtain a single-layer MXene nanosheet dispersion; then, the obtained single-layer MXene nanosheet dispersion was centrifuged again at 3000 rpm and then freeze-dried to obtain MXene;

[0069] (3) Preparation of alkaline MXene: 100 mg of MXene prepared in step (2) was dispersed in 60 mL of 6 wt% sodium hydroxide solution, stirred at 30°C for 4 h, centrifuged, and washed to obtain a precipitate; the obtained precipitate was vacuum-dried at 60°C for 12 h to obtain the alkaline MXene;

[0070] (4) Preparing an aerogel precursor solution: adding the alkalized MXene obtained in step (3) to a DMSO solvent and stirring for 3 h to obtain a mixture I; then adding montmorillonite to the DMSO solvent and stirring for 3 h to obtain a mixture II; mixing the mixture I and the mixture II and the aramid nanofiber dispersion obtained in step (1) and stirring to obtain an aerogel precursor solution; wherein the amount ratio of the alkalized MXene, montmorillonite and aramid nanofiber dispersion is 2:1:4;

[0071] (5) A high-temperature electrical gel was prepared by a directional freezing method: the aerogel precursor solution obtained in step (4) was added to a polytetrafluoroethylene mold, and then a directional freezing device was used to perform directional freeze drying in liquid nitrogen for 20 minutes (temperature -196°C), and then the frozen aerogel precursor was solidified in a coagulation bath (temperature of -18°C, the coagulation bath was obtained by mixing ethanol and acetic acid in a volume ratio of 7:3) for 18 hours; then, the solidified aerogel precursor was washed and then placed in a mixed solution. The aerogel AM was obtained by solvent exchange in a liquid (obtained by mixing tert-butanol and water in a volume ratio of 1:1) for 6 hours, and then freeze-dried for 18 hours to obtain the aerogel AM; finally, the aerogel AM was completely immersed in a DMSO solvent containing CH3NH3PbI3 and vacuum-dried at 100°C for 3 hours to obtain the thermoelectric gel; wherein the DMSO solvent containing CH3NH3PbI3 was obtained by dissolving CH3NH3PbI3 in the solvent DMSO, and the concentration of CH3NH3PbI3 was 0.25 g / mL.

[0072] Example 3

[0073] A method for preparing a high-temperature electrical gel with an anisotropic structure comprises the following steps:

[0074] (1) Preparation of aramid nanofiber dispersion: 1.5 g of aramid and 1.5 g of potassium hydroxide were added to 100 mL of DMSO solvent and stirred at room temperature for 7 days to obtain an aramid nanofiber dispersion;

[0075] (2) Preparation of MXene: 1.6 g of lithium fluoride was mixed with 30 mL of 12 mol / L hydrochloric acid, and 1.1 g of Ti3AlC2 was slowly added after magnetic stirring for 50 min, and stirred again for 18 h. After stirring, the mixture was repeatedly washed with distilled water and centrifuged at 3000 rpm for 10 min until the pH value of the supernatant was greater than 6 to obtain a precipitate.

[0076] The obtained precipitate was mixed with deionized water and ultrasonically treated for 3 hours to obtain a single-layer MXene nanosheet dispersion; then, the obtained single-layer MXene nanosheet dispersion was centrifuged again at 3000 rpm and then freeze-dried to obtain MXene;

[0077] (3) Preparation of alkaline MXene: 100 mg of MXene prepared in step (2) was dispersed in 60 mL of 6 wt% sodium hydroxide solution, stirred at 30°C for 5 h, centrifuged, and washed to obtain a precipitate; the obtained precipitate was vacuum-dried at 60°C for 12 h to obtain the alkaline MXene;

[0078] (4) Preparing an aerogel precursor solution: adding the alkalized MXene obtained in step (3) to a DMSO solvent and stirring for 3 h to obtain a mixture I; then adding montmorillonite to the DMSO solvent and stirring for 3 h to obtain a mixture II; mixing the mixture I and the mixture II and the aramid nanofiber dispersion obtained in step (1) and stirring to obtain an aerogel precursor solution; wherein the amount ratio of the alkalized MXene, montmorillonite and aramid nanofiber dispersion is 2:1:4;

[0079] (5) A high-temperature electrical gel was prepared by a directional freezing method: the aerogel precursor solution obtained in step (4) was added to a polytetrafluoroethylene mold, and then a directional freezing device was used to perform directional freeze drying in liquid nitrogen for 20 minutes (temperature -196°C), and then the frozen aerogel precursor was solidified in a coagulation bath (temperature was -18°C, and the coagulation bath was obtained by mixing ethanol and acetic acid in a volume ratio of 7:3) for 20 hours; then, the solidified aerogel precursor was washed and then The aerogel AM was obtained by solvent exchange in a liquid (obtained by mixing tert-butanol and water in a volume ratio of 1:1) for 6 hours, and then freeze-dried for 18 hours to obtain the aerogel AM; finally, the aerogel AM was completely immersed in a DMSO solvent containing CH3NH3PbI3 and vacuum-dried at 100°C for 3 hours to obtain the thermoelectric gel; wherein the DMSO solvent containing CH3NH3PbI3 was obtained by dissolving CH3NH3PbI3 in the solvent DMSO, and the concentration of CH3NH3PbI3 was 0.25 g / mL.

[0080] Comparative Example 1

[0081] Compared with Example 1, the refrigerator freezing method was used in Comparative Example 1, and the remaining steps were the same. Specifically, a method for preparing an anisotropic high-temperature electrical gel comprises the following steps:

[0082] (1) Preparation of aramid nanofiber dispersion: 1.5 g of aramid and 1.5 g of potassium hydroxide were added to 80 mL of DMSO solvent and stirred at room temperature for 7 days to obtain an aramid nanofiber dispersion;

[0083] (2) Preparation of MXene: 1.6 g of lithium fluoride was mixed with 20 mL of 12 mol / L hydrochloric acid, and 1 g of Ti3AlC2 was slowly added after magnetic stirring for 40 min. The mixture was stirred for another 24 h. After stirring, the mixture was repeatedly washed with distilled water and centrifuged at 3000 rpm for 10 min until the pH value of the supernatant was greater than 6 to obtain a precipitate.

[0084] The obtained precipitate was mixed with deionized water and ultrasonically treated for 2.5 hours to obtain a single-layer MXene nanosheet dispersion; then, the obtained single-layer MXene nanosheet dispersion was centrifuged again at 3000 rpm and then freeze-dried to obtain MXene;

[0085] (3) Preparation of alkaline MXene: 100 mg of MXene prepared in step (2) was dispersed in 60 mL of 5 wt% sodium hydroxide solution, stirred at 30°C for 4 h, centrifuged, and washed to obtain a precipitate; the obtained precipitate was vacuum-dried at 60°C for 12 h to obtain the alkaline MXene;

[0086] (4) Preparing an aerogel precursor solution: adding the alkalized MXene obtained in step (3) to a DMSO solvent and stirring for 3 h to obtain a mixture I; then adding montmorillonite to the DMSO solvent and stirring for 3 h to obtain a mixture II; mixing the mixture I and the mixture II and the aramid nanofiber dispersion obtained in step (1) and stirring to obtain an aerogel precursor solution; wherein the amount ratio of the alkalized MXene, montmorillonite and aramid nanofiber dispersion is 2:1:4;

[0087] (5) A high-temperature electrical gel was prepared by a refrigerator freezing method: the aerogel precursor solution obtained in step (4) was added to a polytetrafluoroethylene mold, and the mold was placed in a refrigerator freezer (temperature of -18 ° C) for 24 hours. The aerogel precursor after freezing was then solidified in a coagulation bath (temperature of -18 ° C, the coagulation bath was obtained by mixing ethanol and acetic acid in a volume ratio of 7:3) for 18 hours; then, the aerogel precursor after solidification was washed and then in a mixed solution (by volume ratio of 7:3) for 24 hours. The aerogel AM was obtained by solvent exchange for 6 hours, and then freeze-dried for 18 hours to obtain the aerogel AM; finally, the aerogel AM was completely immersed in a DMSO solvent containing CH3NH3PbI3 and vacuum-dried at 100°C for 3 hours to obtain the thermoelectric gel; wherein the DMSO solvent containing CH3NH3PbI3 was obtained by dissolving CH3NH3PbI3 in the solvent DMSO, and the concentration of CH3NH3PbI3 was 0.25 g / mL.

[0088] Comparative Example 2

[0089] Compared with Example 1, in Comparative Example 2, ordinary MXene was used without alkalization treatment. Specifically, a method for preparing an anisotropic high-temperature electrical gel comprises the following steps:

[0090] (1) Preparation of aramid nanofiber dispersion: 1.5 g of aramid and 1.5 g of potassium hydroxide were added to 80 mL of DMSO solvent and stirred at room temperature for 7 days to obtain an aramid nanofiber dispersion;

[0091] (2) Preparation of MXene: 1.6 g of lithium fluoride was mixed with 20 mL of 12 mol / L hydrochloric acid, and 1 g of Ti3AlC2 was slowly added after magnetic stirring for 40 min. The mixture was stirred for another 24 h. After stirring, the mixture was repeatedly washed with distilled water and centrifuged at 3000 rpm for 10 min until the pH value of the supernatant was greater than 6 to obtain a precipitate.

[0092] The obtained precipitate was mixed with deionized water and ultrasonically treated for 2.5 hours to obtain a single-layer MXene nanosheet dispersion; then, the obtained single-layer MXene nanosheet dispersion was centrifuged again at 3000 rpm and then freeze-dried to obtain MXene;

[0093] (3) Preparing an aerogel precursor solution: adding the MXene obtained in step (2) to a DMSO solvent and stirring for 3 h to obtain a mixture I; then adding montmorillonite to a DMSO solvent and stirring for 3 h to obtain a mixture II; mixing the mixture I, the mixture II and the aramid nanofiber dispersion obtained in step (1) and stirring to obtain an aerogel precursor solution; wherein the amount ratio of MXene, montmorillonite and aramid nanofiber dispersion is 2:1:4;

[0094] (4) A high-temperature electrical gel was prepared by a directional freezing method: the aerogel precursor solution obtained in step (3) was added to a polytetrafluoroethylene mold, and then a directional freezing device was used to perform directional freeze drying in liquid nitrogen for 20 minutes (temperature -196°C), and then the frozen aerogel precursor was solidified in a coagulation bath (temperature of -18°C, the coagulation bath was obtained by mixing ethanol and acetic acid in a volume ratio of 7:3) for 18 hours; then, the solidified aerogel precursor was washed and then placed in a mixed solution. The aerogel AM was obtained by solvent exchange in a liquid (obtained by mixing tert-butanol and water in a volume ratio of 1:1) for 5 hours, and then freeze-dried for 18 hours to obtain the aerogel AM; finally, the aerogel AM was completely immersed in a DMSO solvent containing CH3NH3PbI3 and vacuum-dried at 100°C for 3 hours to obtain the thermoelectric gel; wherein the DMSO solvent containing CH3NH3PbI3 was obtained by dissolving CH3NH3PbI3 in the solvent DMSO, and the concentration of CH3NH3PbI3 was 0.25 g / mL.

[0095] Comparative Example 3

[0096] Compared with Example 1, in Comparative Example 3, ordinary MXene was used without alkalization treatment; and a refrigerator freezing method was used. Specifically,

[0097] A method for preparing a high-temperature electrical gel with an anisotropic structure comprises the following steps:

[0098] (1) Preparation of aramid nanofiber dispersion: 1.5 g of aramid and 1.5 g of potassium hydroxide were added to 80 mL of DMSO solvent and stirred at room temperature for 7 days to obtain an aramid nanofiber dispersion;

[0099] (2) Preparation of MXene: 1.6 g of lithium fluoride was mixed with 20 mL of 12 mol / L hydrochloric acid, and 1 g of Ti3AlC2 was slowly added after magnetic stirring for 40 min. The mixture was stirred for another 24 h. After stirring, the mixture was repeatedly washed with distilled water and centrifuged at 3000 rpm for 10 min until the pH value of the supernatant was greater than 6 to obtain a precipitate.

[0100] The obtained precipitate was mixed with deionized water and ultrasonically treated for 2.5 hours to obtain a single-layer MXene nanosheet dispersion; then, the obtained single-layer MXene nanosheet dispersion was centrifuged again at 3000 rpm and then freeze-dried to obtain MXene;

[0101] (3) Preparing an aerogel precursor solution: adding the MXene obtained in step (2) to a DMSO solvent and stirring for 3 h to obtain a mixture I; then adding montmorillonite to a DMSO solvent and stirring for 3 h to obtain a mixture II; mixing the mixture I, the mixture II and the aramid nanofiber dispersion obtained in step (1) and stirring to obtain an aerogel precursor solution; wherein the amount ratio of MXene, montmorillonite and aramid nanofiber dispersion is 2:1:4;

[0102] (4) A high-temperature electrical gel was prepared by a refrigerator freezing method: the aerogel precursor solution obtained in step (3) was added to a polytetrafluoroethylene mold, and the mold was placed in a freezer layer of a refrigerator (temperature of -18°C) for 24 hours. The aerogel precursor after freezing was then solidified in a coagulation bath (temperature of -18°C, the coagulation bath was obtained by mixing ethanol and acetic acid in a volume ratio of 7:3) for 18 hours; then, the aerogel precursor after solidification was washed and then in a mixed solution ( The aerogel AM was obtained by solvent exchange for 6 hours, and then freeze-dried for 18 hours to obtain the aerogel AM; finally, the aerogel AM was completely immersed in a DMSO solvent containing CH3NH3PbI3 and vacuum-dried at 100°C for 3 hours to obtain the thermoelectric gel; wherein the DMSO solvent containing CH3NH3PbI3 was obtained by dissolving CH3NH3PbI3 in the solvent DMSO, and the concentration of CH3NH3PbI3 was 0.25 g / mL.

[0103] Figure 1 is a SEM image of the aerogel prepared in Example 1. Figure 1 The top view, perpendicular to the axis of the aerogel, shows the porous scaffold structure with a honeycomb structure in cross section. Figure 2 The aerogel is composed of a layered structure with large-scale parallel channels, showing a highly ordered layered structure with ANFs as the main skeleton. The interlayer spacing is about 20 μm, which is similar to the structure of human tissue muscle.

[0104] Directed pores act as scattering centers, significantly increasing the probability of phonon scattering in the propagation path, reducing the solid heat transfer path, and thus reducing thermal conductivity κ. The temperature difference between the two ends of the aerogel is increased, thereby improving thermoelectric performance. The directional pore structure allows carriers to be quickly transmitted along the continuous skeleton, reducing the conductivity loss caused by pores. The directional structure inhibits the lateral scattering of carriers, thereby reducing κ while relatively retaining σ, improving the power factor (PF = σS 2 , S is the Seebeck coefficient).

[0105] See further Figure 3 The aerogel can be safely placed on the petals without causing any damage to the flowers, demonstrating the ultra-light properties of the aerogel, with a density of only 0.041 g·cm -3 This property gives aerogel a better advantage when used as a thermal insulation layer in firefighting clothing.

[0106] See further Figure 4Aerogel has extremely high processability and can be processed into any desired shape, including heart-shaped, rectangular and triangular, without breaking during the processing. At the same time, aerogel has extremely high flexibility and can be bent and folded without breaking. It can withstand large bending deformation and has excellent flexibility.

[0107] See further Figure 5 , connect the two ends of the aerogel sample to a multimeter, and then place it on a heating plate to adjust the temperature of the two ends of the aerogel. Adjust the heating plate to 200, 300, and 400℃ respectively, and record the output DC voltage data on the multimeter. The test results are as follows Figure 5 As shown in the figure, the picture is a temperature-voltage bar graph of different samples at different temperatures. Figure 5 As shown in Table 1, as the heating plate temperature increases, the greater the temperature difference across the thermoelectric gel, the higher the voltage generated. With the heating plate temperature fixed, the voltage generated by Example 1 > the voltage generated by Control Example 1 > the voltage generated by Control Example 2 > the voltage generated by Control Example 3. This demonstrates that the chemical treatment of MXene and the directional freezing method, through a dual-track synergistic effect, significantly enhance the thermoelectric performance of the aerogel.

[0108] Table 1 Thermoelectric performance test results of Example 1 and Comparative Examples 1 to 3

[0109] 200℃ 300℃ 400℃ Example 1 4.26mv 8.64mv 14.32mv Comparative Example 1 2.9mv 4.62mv 8.43mv Comparative Example 2 1.8mv 3.2mv 6.3mv Comparative Example 3 0.46mv 1.67mv 3.2mv

[0110] See further Figure 6 , connect the sample to a millivolt alarm, build a high-temperature warning system, use an alcohol lamp to contact heat the sample, the aerogel is heated, quickly generates current, and triggers the warning light. It is applied to firefighting suits to improve the safety of firefighters in fire scenes. In order to further test the high-temperature warning sensitivity of aerogels at different temperatures, the aerogels are connected to a millivolt alarm to build a high-temperature warning system. The aerogels are then placed on heating plate platforms at 200°C, 300°C, and 400°C, and under the flame of an alcohol lamp to test the warning sensitivity of different aerogels under different test conditions. The test results show that the aerogels prepared by directional freezing and chemically modified MXene exhibit efficient thermoelectric conversion performance, which effectively improves the sensitivity of high-temperature warnings. For specific results, see Figure 7 and as shown in Table 2.

[0111] Table 2 Test results of high temperature warning time of Example 1 and Comparative Examples 1 to 3

[0112] 200℃ 300℃ 400℃ Flame Example 1 13.6 s 8.2s 4.2s 1.3s Comparative Example 1 17.3s 14.7s 8.6s 5.4s Comparative Example 2 19.1s 16.4s 14.1s 8.3s Comparative Example 3 23.3s 18.4s 16.1s 12.2s

[0113] See further Figure 8, using CH3NH3PbI3 (MAPbI3) combined with aerogel for visual monitoring of NH3 in complex fire situations, which solves the limitation of traditional high-temperature early warning sensors that lack the visual reduction function of dangerous gases. The aerogel was fixed in a chamber and purged with air. Subsequently, 40ppm concentration of NH3 gas was injected and tested at room temperature. The aerogel showed sensitivity to NH3. When exposed to NH3, the appearance of the aerogel in Example 1 underwent a visual transformation from black to yellow. Visual monitoring of NH3 gas can provide an intuitive and rapid response, improving firefighters' risk awareness in fire environments during firefighting operations and rescue.

[0114] While the present invention is illustrated by the aforementioned embodiments, the present invention is not limited to these embodiments, nor does it necessarily rely on these embodiments for implementation. Those skilled in the art will appreciate that any improvements to the present invention, equivalent replacements for individual raw materials in the present invention, additions of auxiliary ingredients, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing anisotropic high-temperature electrical gel, characterized in that: The steps include: (1) preparing an aramid nanofiber dispersion; (2) Preparation of MXene; (3) Preparation of alkalized MXene; (4) Preparing an aerogel precursor solution: adding the alkalized MXene obtained in step (3) to a DMSO solvent and stirring to obtain a mixture I; then adding montmorillonite to the DMSO solvent and stirring to obtain a mixture II; mixing the mixture I and the mixture II and the aramid nanofiber dispersion obtained in step (1), and stirring to obtain an aerogel precursor solution; (5) High-temperature electrical gel was prepared by directional freezing method.

2. The method for preparing an anisotropic high-temperature electrical gel according to claim 1, characterized in that: The specific steps of step (1) include: adding aramid and potassium hydroxide into DMSO solvent, stirring at room temperature for 5 to 10 days, and obtaining aramid nanofiber dispersion.

3. The method for preparing a high-temperature electrical gel with an anisotropic structure according to claim 1, characterized in that: The specific steps of step (2) include: mixing lithium fluoride and hydrochloric acid, stirring, slowly adding Ti3AlC2, and stirring again; after the stirring is completed, washing, centrifuging until the pH value of the supernatant is greater than 6 to obtain a precipitate; The obtained precipitate is mixed with deionized water and subjected to ultrasonic treatment to obtain a single-layer MXene nanosheet dispersion; then, the obtained single-layer MXene nanosheet dispersion is centrifuged again and then freeze-dried to obtain MXene.

4. The method for preparing an anisotropic high-temperature electrical gel according to claim 1, characterized in that: The specific steps of step (3) include: dispersing the MXene prepared in step (2) in a sodium hydroxide solution, stirring, centrifuging, and washing to obtain a precipitate; and vacuum drying the obtained precipitate to obtain the alkaline MXene.

5. The method for preparing an anisotropic high-temperature electrical gel according to claim 1, characterized in that: In step (4), the ratio of the amount of alkalized MXene, montmorillonite, and aramid nanofiber dispersion is 2:1:

4.

6. The method for preparing an anisotropic high-temperature electrical gel according to claim 1, characterized in that: The specific steps of step (5) include: adding the aerogel precursor solution obtained in step (4) into a mold, then performing directionally freeze-drying under liquid nitrogen conditions, and then solidifying the frozen aerogel precursor in a coagulation bath; then, washing the solidified aerogel precursor, and then performing solvent exchange in the mixed solution, and freeze-drying after the exchange treatment is completed to obtain aerogel AM; finally, immersing the aerogel AM in a DMSO solvent containing CH3NH3PbI3 and performing vacuum drying to obtain a thermoelectric gel.

7. The method for preparing anisotropic high-temperature electrical gel according to claim 6, characterized in that: In step (5), the temperature of directional freeze drying is -196°C, and the time is 10 to 30 minutes; the composition of the coagulation bath is: a mixture of ethanol and acetic acid with a volume ratio of 7:3, the coagulation treatment temperature is -18°C, and the time is 8 to 24 hours.

8. The method for preparing anisotropic high-temperature electrical gel according to claim 6, characterized in that: In step (5), the mixed solution is obtained by mixing tert-butyl alcohol and water in a volume ratio of 1:1; the solvent exchange time is 2 to 12 hours; The DMSO solvent containing CH3NH3PbI3 is obtained by dissolving CH3NH3PbI3 in the solvent DMSO; the vacuum drying of the aerogel AM is 2 to 8 hours.

9. A high-temperature electrical gel prepared by the method according to any one of claims 1 to 8.

10. Use of the high-temperature electrical gel according to claim 9 in high-temperature / gas early warning.

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