High-thermoelectricity gel of anisotropic structure, and preparation method and application thereof

Abstract

The application discloses a kind of high thermoelectric aerogel of anisotropic structure and preparation method and application thereof, belong to aerogel material preparation field.Preparation method includes the following steps: (1) preparation aramid nanofiber dispersion liquid;(2) preparation MXene;(3) preparation alkali MXene;(4) preparation aerogel precursor solution;(5) directional freezing method is prepared to obtain high thermoelectric aerogel.The aerogel provided by the application is treated with the double promotion strategy of directional structure and chemical modification MXene to aramid-based aerogel, which greatly synergistically improves the thermoelectric performance of aerogel material, greatly synergistically improves the high temperature early warning performance of aerogel;At the same time, the aerogel provided by the application has low density, good flexibility and processability, meets the use demand of fire-fighting material.

Description

Technical Field

[0001] This invention belongs to the field of aerogel preparation technology, specifically relating to an anisotropic high-thermal electrogel, its preparation method, and its application. Background Technology

[0002] Firefighting suits are crucial equipment for protecting firefighters during fire rescue operations in extreme temperature conditions. The thermal protection performance of firefighting suits primarily relies on the insulation layer within a multi-layered fabric system, effectively protecting firefighters from environmental heat hazards during high-temperature exposure. Aerogels, with their excellent low density and thermal insulation properties, are promising candidates for highly efficient thermal insulation in firefighting suits, offering high insulation performance while reducing weight. Among them, aramid nanofiber (ANF)-based aerogels, with their superior thermal stability and porous structure at the nano and micro scales, are the preferred choice for insulation layers in firefighting suits, significantly suppressing heat conduction and convection within the aerogel skeleton under high radiant heat exposure. Unfortunately, ANF-based insulation layers in firefighting suits can still undergo thermal decomposition and cracking under prolonged exposure to extreme temperatures (≥400°C), endangering firefighter safety. Integrating intelligent temperature sensing into ANF-based composite aerogels offers a novel solution for monitoring and preventing pyrolysis damage in firefighting suits. This proactive strategy can provide firefighters with early warnings before the insulation layer decomposes under extreme fire conditions, extending the lifespan of fire suits and effectively ensuring personal safety. Recent advances in temperature-responsive materials have sparked great interest in developing temperature-sensitive aerogels for fire suits. To date, traditional high-temperature warning aerogels based on thermally resistive materials have a key drawback: their electrical signal transmission heavily relies on an external power source. Therefore, such aerogels not only increase the complexity of the temperature sensing system but also pose a risk of power failure due to prolonged exposure to high temperatures. In contrast, thermoelectric gels are considered effective temperature-sensing materials for fire suits, capable of directly converting heat into voltage upon exposure to high temperatures. The voltage intensity is directly related to changes in temperature difference. For example, patent document CN117210961A provides a core-sheath structure thermoelectric gel fiber with repeatable warnings, high sensitivity, and self-powered performance.

[0003] However, the inherent isotropic porous structure of traditional thermoelectric aerogels leads to mechanical constraints and short discontinuous charge carrier transport paths, limiting their effectiveness in high-temperature warning applications. Therefore, fabricating a high-thermoelectric-performance aerogel for high-temperature warning applications in fire suits remains a significant challenge.

[0004] Therefore, this invention is proposed. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide an anisotropic high thermoelectric gel, its preparation method and application, and the resulting aerogel has high thermoelectric properties and good high temperature early warning performance.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing anisotropic high-thermal-electrogel, comprising the following steps:

[0008] (1) Preparation of aramid nanofiber dispersion;

[0009] (2) Preparation of MXene;

[0010] (3) Preparation of alkalized MXene;

[0011] (4) Preparation of aerogel precursor solution: Add the alkalized MXene obtained in step (3) to DMSO solvent, stir to obtain mixture I; then add montmorillonite to DMSO solvent, stir to obtain mixture II; mix mixture I and mixture II with the aramid nanofiber dispersion obtained in step (1), stir to obtain aerogel precursor solution.

[0012] (5) A high-temperature electrogel was prepared by directional freezing.

[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 and stirring at room temperature for 5 to 10 days to obtain 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 with hydrochloric acid, stirring and then slowly adding Ti3AlC2, stirring again; washing and centrifuging after stirring until the pH value of the supernatant is greater than 6, and obtaining the precipitate;

[0015] The precipitate was mixed with deionized water and subjected to ultrasonic treatment to obtain a single-layer MXene nanosheet dispersion. The obtained single-layer MXene nanosheet dispersion was then centrifuged again and subsequently 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 and then centrifuging and washing to obtain a precipitate; and drying the obtained precipitate under vacuum to obtain alkalized MXene.

[0017] As a preferred embodiment of the technical solution of the present invention, in step (4), the ratio of the amount 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 directional freeze-drying under liquid nitrogen conditions, and then solidifying the frozen aerogel precursor in a coagulation bath; next, cleaning the solidified aerogel precursor, then performing solvent exchange in a mixed solution, and performing freeze-drying after the exchange treatment to obtain aerogel AM; finally, immersing the aerogel AM in DMSO solvent containing CH3NH3PbI3 and performing vacuum drying to obtain thermo-electrogel.

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

[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 was obtained by dissolving CH3NH3PbI3 in the solvent DMSO; the vacuum drying of the aerogel AM was 2-8 h.

[0022] Secondly, the present invention seeks protection for the high-thermal electrogel prepared by the above method.

[0023] Thirdly, the present invention provides the application of the high-temperature electrogel obtained above in high-temperature / gas early warning, such as high-temperature early warning for fire suits.

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

[0025] The aerogel provided by this invention employs a dual enhancement strategy of imparting a directional structure and chemically modifying MXene to aramid-based aerogels, which greatly synergistically improves the thermoelectric properties of the aerogel material and significantly enhances its high-temperature warning performance.

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

[0027] The aerogel provided by this invention has low density, good flexibility and processability, which meets the requirements for use in fire protection materials. Attached Figure Description

[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 a SEM image of the cross-sectional oriented pores of the aerogel obtained in Example 1.

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

[0031] Figure 4 This is a demonstration of the different shapes and flexibility of the aerogel obtained in Example 1.

[0032] Figure 5 The results show the thermoelectric properties of the aerogels obtained in Example 1 and Comparative Examples 1-3.

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

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

[0035] Figure 8 This is an optical image of the gas visualization detection performance in Example 1. Detailed Implementation

[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] It should also be emphasized that, unless otherwise specified in the examples, the conditions should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products. For example, aramid fiber was purchased from Shanghai Mingxi Industrial Co., Ltd.; montmorillonite (analytical grade AR) was from Wokai and purchased from Aladdin Biochemical Technology Co., Ltd.

[0038] This invention provides a method for preparing anisotropic high-thermal-electrogels, comprising the following steps:

[0039] (1) Preparation of aramid nanofiber dispersion;

[0040] (2) Preparation of MXene;

[0041] (3) Preparation of alkalized MXene;

[0042] (4) Preparation of aerogel precursor solution: Add the alkalized MXene obtained in step (3) to DMSO solvent, stir to obtain mixture I; then add montmorillonite to DMSO solvent, stir to obtain mixture II; mix mixture I and mixture II with the aramid nanofiber dispersion obtained in step (1), stir to obtain aerogel precursor solution.

[0043] (5) A high-temperature electrogel was prepared by directional freezing.

[0044] The above technical solution employs a dual strategy (imparting a directional structure and chemically modifying MXene) to enhance the thermoelectric properties of aramid nanofiber (ANFs)-based aerogels, thereby endowing them with more sensitive high-temperature early warning performance. In nature, human or animal muscle tissue possesses anisotropic and ordered structures, giving muscles high mechanical strength and directional molecular transport channels, providing inspiration for developing high-performance thermoelectric high-temperature early warning aerogels based on ANFs. Inspired by the directional structure of human muscle tissue, directional freezing technology imparts a directional structure to the aerogel, enhancing electron transport. Simultaneously, chemical modification (alkalization) of the MXene material with sodium hydroxide converts the fluorine-containing functional groups on the MXene surface into hydroxyl groups (-OH). Alkali treatment of MXene disrupts the electrostatic balance between MXene layers, preventing the electrostatic repulsion between MXene layers from compensating for the high surface energy and inducing wrinkling of the MXene sheets. Simultaneously, sodium ions (Na... + The insertion of MXene increases the interlayer spacing, effectively inhibits the re-accumulation of MXene sheets, facilitates the formation of an open three-dimensional porous structure, promotes electron transport, and improves the electrochemical performance of the material.

[0045] In harsh fire environments, especially in some industrial sites, there may be leaks of toxic gases (NH3). Prolonged exposure to high levels of NH3 can cause serious effects on humans (such as irritation to the eyes, throat, skin, and respiratory tract), and can often lead to 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 for ensuring the safety of firefighters.

[0046] By loading CH3NH3PbI3, the aerogel acquires the ability to visually detect NH3 gas, filling the gap in traditional fire suits' inability to detect toxic gases and further enhancing the safety of firefighters in complex fire scenes. This aerogel can be directly used as a thermal insulation layer in fire suits, achieving a triple function of "thermal barrier—temperature sensing—gas warning," significantly improving the safety of firefighters in complex fire scenes. Future applications can also be expanded to industrial high-temperature protection, wearable devices, and other fields. This dual-function integration solves the technical bottleneck of traditional firefighting equipment's inability to simultaneously cope with high temperatures and toxic gases. Its signal transmission and visual gas warning characteristics provide firefighters with comprehensive safety assurance in complex fire environments. This research innovatively combines thermoelectric conversion with gas sensing technology.

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

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

[0049] The obtained precipitate was mixed with deionized water and subjected to ultrasonic treatment to obtain a single-layer MXene nanosheet dispersion. The obtained single-layer MXene nanosheet dispersion was then centrifuged again and subsequently freeze-dried to obtain MXene. More specifically, the amount of lithium fluoride used was 1–2.5 g; the concentration of hydrochloric acid was 8–15 mol / L, and the amount used was 10–30 mL; the amount of Ti3AlC2 used was 0.5–2 g.

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

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

[0052] In some embodiments, step (5) specifically includes: adding the aerogel precursor solution obtained in step (4) into a mold, then performing directional freeze-drying under liquid nitrogen conditions, followed by solidifying the frozen aerogel precursor in a coagulation bath; then, washing the solidified aerogel precursor, then performing solvent exchange in a mixed solution, and finally performing freeze-drying to obtain aerogel AM; finally, immersing the aerogel AM in a DMSO solvent containing CH3NH3PbI3 and performing vacuum drying to obtain thermo-electrogel. The directional freezing device can use existing mature equipment, can be processed according to existing technology, or can be self-made. If self-made, it can be assembled in the following manner: pouring liquid nitrogen into a liquid nitrogen basin (the specifications can be 24cm in diameter and 14cm in height), placing a copper block (the specifications can be 6cm*1cm*1.5cm) at the bottom of the basin, placing a mold containing the aerogel precursor solution on the copper block, and foam treatment can be performed around the mold. Traditional thermoelectrogels exhibit an inherently isotropic porous structure, leading to mechanical confinement and short, discontinuous carrier transport paths, resulting in poor mechanical and electrical properties, which limits their effectiveness in temperature sensing applications. By constructing anisotropic, oriented, ordered structures through directional freezing, aerogels can be endowed with high mechanical strength and oriented molecular transport channels, enhancing their mechanical properties and electrical conductivity, thus achieving more sensitive high-temperature early warning performance.

[0053] More specifically, in step (5), the directional freeze-drying temperature is -196℃, and the time is 10–30 min; the coagulation bath is composed of a mixture of ethanol and acetic acid in a volume ratio of 7:3, and the coagulation treatment temperature is -18℃, with a time of 8–24 h. Using an ethanol-acetic acid mixture as the coagulation bath, with acetic acid as a proton donor, provides abundant hydrogen ions (H+). + This process enhances the formation of hydrogen bonds between fibers, thereby achieving high regeneration and reinforcement of nanofibers. Simultaneously, the strategic addition of ethanol mitigates excessive skeletal shrinkage caused by low surface tension, maintaining structural stability and integrity.

[0054] More specifically, 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; solvent exchange is carried out to inhibit the formation of ice crystals during subsequent freeze-drying and to maintain the microstructure of the aerogel.

[0055] The DMSO solvent containing CH3NH3PbI3 is obtained by dissolving CH3NH3PbI3 in DMSO solvent, and the preferred concentration of CH3NH3PbI3 is 0.25 g / mL; the aerogel AM is vacuum dried for 2–8 h. By introducing CH3NH3PbI3, the limitation of traditional high-temperature early warning sensors in lacking visual monitoring function for hazardous gases is overcome.

[0056] Example 1

[0057] A method for preparing an anisotropic high-thermal-electrogel includes the following steps:

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

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

[0060] The precipitate was mixed with deionized water and ultrasonically treated for 2.5 h 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 alkalized MXene: 100 mg of MXene obtained in step (2) was dispersed in 60 mL of 5 wt% sodium hydroxide solution, stirred at 30 °C for 4 h, and then centrifuged and washed to obtain a precipitate; the precipitate was dried under vacuum at 60 °C for 12 h to obtain alkalized MXene.

[0062] (4) Preparation of aerogel precursor solution: Add the alkalized MXene obtained in step (3) to DMSO solvent and stir for 3 hours to obtain mixture I; then add montmorillonite to DMSO solvent and stir for 3 hours to obtain mixture II; mix mixture I and mixture II with the aramid nanofiber dispersion obtained in step (1) and stir to obtain aerogel precursor solution; wherein, the ratio of alkalized MXene, montmorillonite and aramid nanofiber dispersion is 2:1:4;

[0063] (5) High-temperature electrogel was prepared by directional freezing: The aerogel precursor solution obtained in step (4) was added to a polytetrafluoroethylene mold, and then directionally freeze-dried in liquid nitrogen for 20 min (temperature -196℃) using a directional freezing device. Then, the frozen aerogel precursor was solidified in a coagulation bath (temperature -18℃, the coagulation bath was obtained by mixing ethanol and acetic acid in a volume ratio of 7:3) for 18 h. Next, the solidified aerogel precursor was washed, and then mixed with a solvent. The aerogel AM was obtained by solvent exchange in a solution (prepared by mixing tert-butanol and water in a volume ratio of 1:1) for 5 h, followed by freeze drying for 18 h. Finally, the aerogel AM was completely immersed in DMSO solvent containing CH3NH3PbI3 and vacuum dried at 100 °C for 3 h to obtain a thermo-electrogel. The DMSO solvent containing CH3NH3PbI3 was obtained by dissolving CH3NH3PbI3 in DMSO solvent, and the concentration of CH3NH3PbI3 was 0.25 g / mL.

[0064] Example 2

[0065] A method for preparing an anisotropic high-thermal-electrogel includes the following steps:

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

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

[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 alkalized MXene: 100 mg of MXene obtained in step (2) was dispersed in 60 mL of 6 wt% sodium hydroxide solution, stirred at 30 °C for 4 h, and then centrifuged and washed to obtain a precipitate; the precipitate was dried under vacuum at 60 °C for 12 h to obtain alkalized MXene.

[0070] (4) Preparation of aerogel precursor solution: Add the alkalized MXene obtained in step (3) to DMSO solvent and stir for 3 hours to obtain mixture I; then add montmorillonite to DMSO solvent and stir for 3 hours to obtain mixture II; mix mixture I and mixture II with the aramid nanofiber dispersion obtained in step (1) and stir to obtain aerogel precursor solution; wherein, the ratio of alkalized MXene, montmorillonite and aramid nanofiber dispersion is 2:1:4;

[0071] (5) High-temperature electrogel was prepared by directional freezing: The aerogel precursor solution obtained in step (4) was added to a polytetrafluoroethylene mold, and then directionally freeze-dried in liquid nitrogen for 20 min (temperature -196℃) using a directional freezing device. Then, the frozen aerogel precursor was solidified in a coagulation bath (temperature -18℃, the coagulation bath was obtained by mixing ethanol and acetic acid in a volume ratio of 7:3) for 18 h. Next, the solidified aerogel precursor was washed, and then mixed with a solvent. The aerogel AM was obtained by solvent exchange in a solution (prepared by mixing tert-butanol and water in a volume ratio of 1:1) for 6 hours, followed by freeze-drying for 18 hours. Finally, the aerogel AM was completely immersed in DMSO solvent containing CH3NH3PbI3 and vacuum-dried at 100°C for 3 hours to obtain a thermo-electrogel. The DMSO solvent containing CH3NH3PbI3 was obtained by dissolving CH3NH3PbI3 in DMSO solvent, and the concentration of CH3NH3PbI3 was 0.25 g / mL.

[0072] Example 3

[0073] A method for preparing an anisotropic high-thermal-electrogel includes the following steps:

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

[0075] (2) Preparation of MXene: 1.6g of lithium fluoride was mixed with 30mL of 12mol / L hydrochloric acid and magnetically stirred for 50min. Then, 1.1g of Ti3AlC2 was slowly added and stirred again for 18h. After stirring, the mixture was repeatedly washed with distilled water and centrifuged at 3000rpm for 10min until the pH of the supernatant was greater than 6 to obtain the 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 alkalized MXene: 100 mg of MXene obtained in step (2) was dispersed in 60 mL of 6 wt% sodium hydroxide solution, stirred at 30 °C for 5 h, and then centrifuged and washed to obtain a precipitate; the precipitate was dried under vacuum at 60 °C for 12 h to obtain alkalized MXene.

[0078] (4) Preparation of aerogel precursor solution: Add the alkalized MXene obtained in step (3) to DMSO solvent and stir for 3 hours to obtain mixture I; then add montmorillonite to DMSO solvent and stir for 3 hours to obtain mixture II; mix mixture I and mixture II with the aramid nanofiber dispersion obtained in step (1) and stir to obtain aerogel precursor solution; wherein, the ratio of alkalized MXene, montmorillonite and aramid nanofiber dispersion is 2:1:4;

[0079] (5) High-temperature electrogel was prepared by directional freezing: The aerogel precursor solution obtained in step (4) was added to a polytetrafluoroethylene mold, and then directionally freeze-dried in liquid nitrogen for 20 min (temperature -196℃) using a directional freezing device. Then, the frozen aerogel precursor was solidified in a coagulation bath (temperature -18℃, the coagulation bath was obtained by mixing ethanol and acetic acid in a volume ratio of 7:3) for 20 h. Next, the solidified aerogel precursor was washed, and then mixed with a solvent. The aerogel AM was obtained by solvent exchange in a solution (prepared by mixing tert-butanol and water in a volume ratio of 1:1) for 6 hours, followed by freeze-drying for 18 hours. Finally, the aerogel AM was completely immersed in DMSO solvent containing CH3NH3PbI3 and vacuum-dried at 100°C for 3 hours to obtain a thermo-electrogel. The DMSO solvent containing CH3NH3PbI3 was obtained by dissolving CH3NH3PbI3 in DMSO solvent, and the concentration of CH3NH3PbI3 was 0.25 g / mL.

[0080] Comparative Example 1

[0081] Compared to Example 1, Comparative Example 1 used a freezer freezing method for processing, while all other steps were the same. Specifically, a method for preparing an anisotropic high-temperature electrogel includes the following steps:

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

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

[0084] The precipitate was mixed with deionized water and ultrasonically treated for 2.5 h 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 alkalized MXene: 100 mg of MXene obtained in step (2) was dispersed in 60 mL of 5 wt% sodium hydroxide solution, stirred at 30 °C for 4 h, and then centrifuged and washed to obtain a precipitate; the precipitate was dried under vacuum at 60 °C for 12 h to obtain alkalized MXene.

[0086] (4) Preparation of aerogel precursor solution: Add the alkalized MXene obtained in step (3) to DMSO solvent and stir for 3 hours to obtain mixture I; then add montmorillonite to DMSO solvent and stir for 3 hours to obtain mixture II; mix mixture I and mixture II with the aramid nanofiber dispersion obtained in step (1) and stir to obtain aerogel precursor solution; wherein, the ratio of alkalized MXene, montmorillonite and aramid nanofiber dispersion is 2:1:4;

[0087] (5) High-temperature electrogel was prepared by refrigerator freezing method: The aerogel precursor solution obtained in step (4) was added to a polytetrafluoroethylene mold, and the mold was placed in the freezer layer (temperature -18℃) for freezing for 24h. Then, the frozen aerogel precursor was solidified in a coagulation bath (temperature -18℃, the coagulation bath was obtained by mixing ethanol and acetic acid in a volume ratio of 7:3) for 18h. Then, the solidified aerogel precursor was washed and then placed in a mixed solution (by volume ratio of ethanol and acetic acid) for 18h. The aerogel AM was obtained by solvent exchange for 6 hours in a mixture of tert-butanol and water (with a product ratio of 1:1), followed by freeze-drying for 18 hours. Finally, the aerogel AM was completely immersed in DMSO solvent containing CH3NH3PbI3 and vacuum-dried at 100°C for 3 hours to obtain the thermoelectrogel. The DMSO solvent containing CH3NH3PbI3 was obtained by dissolving CH3NH3PbI3 in DMSO solvent, and the concentration of CH3NH3PbI3 was 0.25 g / mL.

[0088] Comparative Example 2

[0089] Compared to Example 1, Comparative Example 2 used ordinary MXene without alkalization treatment. Specifically, a method for preparing an anisotropic high-thermal-electrogel includes the following steps:

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

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

[0092] The precipitate was mixed with deionized water and ultrasonically treated for 2.5 h 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) Preparation of aerogel precursor solution: MXene obtained in step (2) is added to DMSO solvent and stirred for 3 hours to obtain mixture I; then montmorillonite is added to DMSO solvent and stirred for 3 hours to obtain mixture II; mixture I and mixture II and aramid nanofiber dispersion obtained in step (1) are mixed and stirred to obtain aerogel precursor solution; wherein, the ratio of MXene, montmorillonite and aramid nanofiber dispersion is 2:1:4;

[0094] (4) High-temperature electrogel was prepared by directional freezing: The aerogel precursor solution obtained in step (3) was added to a polytetrafluoroethylene mold, and then directionally freeze-dried in liquid nitrogen for 20 min (temperature -196℃) using a directional freezing device. Then, the frozen aerogel precursor was solidified in a coagulation bath (temperature -18℃, the coagulation bath was obtained by mixing ethanol and acetic acid in a volume ratio of 7:3) for 18 h. Next, the solidified aerogel precursor was washed, and then mixed with a solvent. The aerogel AM was obtained by solvent exchange in a solution (prepared by mixing tert-butanol and water in a volume ratio of 1:1) for 5 h, followed by freeze drying for 18 h. Finally, the aerogel AM was completely immersed in DMSO solvent containing CH3NH3PbI3 and vacuum dried at 100 °C for 3 h to obtain a thermo-electrogel. The DMSO solvent containing CH3NH3PbI3 was obtained by dissolving CH3NH3PbI3 in DMSO solvent, and the concentration of CH3NH3PbI3 was 0.25 g / mL.

[0095] Comparative Example 3

[0096] Compared to Example 1, Comparative Example 3 used ordinary MXene without alkalization treatment and employed a freezer freezing method. Specifically,

[0097] A method for preparing an anisotropic high-thermal-electrogel includes the following steps:

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

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

[0100] The precipitate was mixed with deionized water and ultrasonically treated for 2.5 h 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) Preparation of aerogel precursor solution: MXene obtained in step (2) is added to DMSO solvent and stirred for 3 hours to obtain mixture I; then montmorillonite is added to DMSO solvent and stirred for 3 hours to obtain mixture II; mixture I and mixture II and aramid nanofiber dispersion obtained in step (1) are mixed and stirred to obtain aerogel precursor solution; wherein, the ratio of MXene, montmorillonite and aramid nanofiber dispersion is 2:1:4;

[0102] (4) High-temperature electrogel was prepared by refrigerator freezing method: The aerogel precursor solution obtained in step (3) was added to a polytetrafluoroethylene mold, and the mold was placed in the freezer layer (temperature -18℃) for freezing for 24h. Then, the frozen aerogel precursor was solidified in a coagulation bath (temperature -18℃, the coagulation bath was obtained by mixing ethanol and acetic acid in a volume ratio of 7:3) for 18h. Then, the solidified aerogel precursor was washed and then placed in a mixed solution (by volume ratio of ethanol and acetic acid) for 18h. The aerogel AM was obtained by solvent exchange for 6 hours in a mixture of tert-butanol and water (with a product ratio of 1:1), followed by freeze-drying for 18 hours. Finally, the aerogel AM was completely immersed in DMSO solvent containing CH3NH3PbI3 and vacuum-dried at 100°C for 3 hours to obtain the thermoelectrogel. The DMSO solvent containing CH3NH3PbI3 was obtained by dissolving CH3NH3PbI3 in DMSO solvent, and the concentration of CH3NH3PbI3 was 0.25 g / mL.

[0103] Figure 1 This is a SEM image of the aerogel prepared in Example 1. Figure 1 The top view, perpendicular to the axis of the aerogel, shows a honeycomb-like porous scaffold structure in cross-section. See also... Figure 2 Parallel to the axis, the aerogel consists of a layered structure with large-scale parallel channels, exhibiting a highly ordered layered structure with ANFs as the main framework. The interlayer spacing is approximately 20 μm, similar to the structure of human muscle tissue.

[0104] Directed pores act as scattering centers, significantly increasing the scattering probability of phonons in the propagation path, reducing the heat transfer path in the solid, and thus lowering the thermal conductivity κ. This increases the temperature difference between the two ends of the aerogel, thereby improving its thermoelectric properties. The directed pore structure allows charge carriers to be transported rapidly along the continuous framework, reducing conductivity loss caused by pores. The directed structure suppresses lateral scattering of charge carriers, thus relatively preserving σ while lowering κ, improving the power factor (PF = σS). 2 (where S is the Seebeck coefficient).

[0105] See further Figure 3 The aerogel can be safely placed on flower petals without causing any damage to the flower, demonstrating its ultralight properties; its density is only 0.041 g·cm³. -3 This property gives aerogel a greater advantage when used as a thermal insulation layer in fire suits.

[0106] See further Figure 4Aerogels possess extremely high processability, allowing them to be processed into any desired shape, including hearts, rectangles, and triangles, without breaking during processing. Simultaneously, aerogels exhibit exceptional flexibility; they can be bent or folded without breaking, withstand significant bending deformation, and demonstrate remarkable resilience.

[0107] See further Figure 5 Connect the two ends of the aerogel sample to a multimeter, then place it on a heating plate to adjust the temperature at both ends of the aerogel. Adjust the heating plate to 200, 300, and 400°C respectively, and record the DC voltage output data on the multimeter. The test results are as follows: Figure 5 As shown, the image is a temperature-voltage bar graph of different samples at different temperatures. Figure 5 As shown in Table 1, the greater the temperature difference between the two ends of the thermoelectric aerogel, the higher the generated voltage, as the heating plate temperature increases. With a fixed heating plate temperature, the voltage generated in Example 1 > the voltage generated in Control Example 1 > the voltage generated in Control Example 2 > the voltage generated in Control Example 3. This indicates that chemical treatment of MXene and the use of directional freezing, along with the synergistic effect of dual orbitals, significantly improve the thermoelectric properties of the aerogel.

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

[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 A high-temperature early warning system was constructed by connecting the sample to a millivolt alarm. The sample was heated in contact with an alcohol lamp; the heated aerogel rapidly generated an electric current, triggering the warning light. This system was then applied to fire suits to improve the safety of firefighters during fire rescues. To further test the high-temperature early warning sensitivity of the aerogel at different temperatures, the aerogel was connected to a millivolt alarm to construct a high-temperature early warning system. The aerogel was then placed on heating plates at 200℃, 300℃, and 400℃, and under an alcohol lamp flame, respectively, to test the early warning sensitivity of different aerogels under various test conditions. The test results showed that the aerogel prepared by directional freezing and chemically modified MXene exhibited highly efficient thermoelectric conversion performance, effectively improving the sensitivity of the high-temperature early warning. See [link to specific results] for details. Figure 7 As shown in Table 2.

[0111] Table 2. Time test results of high temperature warning in Example 1 and Comparative Examples 1-3

[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 8A novel approach using CH3NH3PbI3 (MAPbI3) combined with aerogel was developed for visual monitoring of NH3 in complex fire conditions, overcoming the limitation of traditional high-temperature early warning sensors that lack the ability to visually attenuate hazardous gases. The aerogel was fixed in a chamber and purged with air. Subsequently, NH3 gas at a concentration of 40 ppm was injected for testing at room temperature, and the aerogel exhibited sensitivity to NH3. Upon exposure to NH3, the appearance of the aerogel in Example 1 underwent a visual change 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 rescues.

[0114] The present invention has been illustrated through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of individual raw materials in the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. The application of an anisotropic high-thermal-electrogel in high-temperature / gas early warning, characterized in that, The preparation of anisotropic high-thermal-electrogels includes the following steps: (1) Preparation of aramid nanofiber dispersion; (2) Preparation of MXene; (3) Preparation of alkalized MXene; (4) Preparation of aerogel precursor solution: Add the alkalized MXene obtained in step (3) to DMSO solvent, stir to obtain mixture I; then add montmorillonite to DMSO solvent, stir to obtain mixture II; mix mixture I and mixture II with the aramid nanofiber dispersion obtained in step (1), stir to obtain aerogel precursor solution. (5) A high-temperature electrogel was prepared by directional freezing method; The specific steps of step (5) include: adding the aerogel precursor solution obtained in step (4) into a mold, then performing directional freeze-drying under liquid nitrogen conditions, and then solidifying the frozen aerogel precursor in a coagulation bath; next, cleaning the solidified aerogel precursor, then performing solvent exchange in a mixed solution, and performing freeze-drying after the exchange treatment to obtain aerogel AM; finally, immersing the aerogel AM in a DMSO solution containing CH3NH3PbI3 and performing vacuum drying to obtain high-temperature electrogel. In step (5), the directional freeze-drying temperature is -196 ℃ and the time is 10~30 min; the composition of the coagulation bath is: ethanol and acetic acid mixed in a volume ratio of 7:3, the coagulation treatment temperature is -18 ℃ and the time is 8~24 h.

2. The application according to claim 1, characterized in that, The specific steps of step (1) include: adding aramid and potassium hydroxide into DMSO solvent and stirring at room temperature for 5-10 days to obtain aramid nanofiber dispersion.

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

4. The application according to claim 1, characterized in that, 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 drying the precipitate under vacuum to obtain alkalized MXene.

5. The application according to claim 1, characterized in that, In step (4), the ratio of alkalized MXene, montmorillonite, and aramid nanofiber dispersion is 2:1:

4.

6. The application according to claim 1, characterized in that, 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 2~12h; The DMSO solution containing CH3NH3PbI3 was obtained by dissolving CH3NH3PbI3 in the solvent DMSO; the aerogel AM was vacuum dried for 2-8 hours.

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