High-temperature-resistant, heat-insulating and flame-retardant poly-p-phenylene terephthamide nanofiber composite aerogel as well as preparation method and application thereof

Abstract

The invention discloses a high-temperature-resistant, heat-insulating and flame-retardant poly (p-phenylene terephthamide) nanofiber composite aerogel as well as a preparation method and application thereof. The composite aerogel is prepared by slowly releasing proton to induce gel through a two-step sol-gel method. Firstly, carboxyl on a PAA molecular chain is introduced to interact with deprotonated amido in an ANF molecular chain, so that a part of a hydrogen bond system is recovered, ANF pre-gel is achieved, then Ti2CCl2 is dispersed into the ANF pre-gel system, the gelation process is further completed through protonic acid, and the ANF / Ti2CCl2 / ANF composite material is obtained. The composite aerogel is obtained through an improved directional freeze-drying technology and a solvent replacement method. The prepared composite aerogel combines the high thermal stability of Ti2CCl2 and the excellent mechanical property of ANF, has excellent flame retardance, high temperature resistance and heat shielding effectiveness, has wide application prospects in the fields of electronic heat dissipation, building energy efficiency, solar energy utilization and the like, and can meet the ever-increasing requirements for efficient thermal regulation and thermal protection.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite aerogels, and in particular relates to a high temperature resistant, heat insulating and flame retardant poly(p-phenylene terephthalamide) nanofiber composite aerogel, in particular to a structurally ordered composite aerogel with high efficiency photothermal response, high temperature resistant, heat insulating and flame retardant properties, and also relates to a preparation method and application of the aerogel. Background Art

[0002] The sol-gel method is a commonly used method for preparing nanomaterials or complex structure materials. The process usually starts with dissolving the precursor substance in a solution to form a transparent and stable sol system. By adjusting the temperature, pH value or introducing a gelling agent, the sol is gradually transformed into a gel with a three-dimensional network structure. The three-dimensional network can effectively capture the sol particles and achieve a uniformly dispersed structure. Subsequently, aerogels can be prepared by freeze drying or supercritical fluid drying. The sol-gel method can not only prepare complex materials under relatively mild conditions, but also accurately control the morphology and structure of the materials, while quickly achieving nanoscale uniform dispersion of heterogeneous fillers.

[0003] Poly(p-phenylene terephthalamide) (PPTA) fiber is a high-performance synthetic fiber prepared by polycondensation of p-phenylenediamine and terephthaloyl chloride. It is widely used in high-performance textiles, bulletproof materials and aerospace fields due to its excellent heat resistance, chemical resistance, high strength and high modulus. Aerogel material is an artificial material with ultra-low density, high porosity and high specific surface area. It also has excellent mechanical properties and chemical stability. It has been widely used in protection, thermal insulation, energy and biomedicine. As a new type of nanomaterial, PPTA nanofiber (ANF) is a derivative of PPTA. With its excellent performance, it effectively solves the main problems of traditional aramid fiber such as smooth surface, low chemical reactivity and poor composite reinforcement effect, thus greatly expanding the research on high-performance fiber materials in the functionalization and diversification direction. ANF aerogel prepared by sol-gel method can fully retain the characteristics of nano effect, high specific surface area, low thermal conductivity and low dielectric constant. ANF ​​not only inherits the high strength, high modulus and high temperature resistance of macro aramid fiber, but also has nano properties such as high specific surface area and high aspect ratio. It is a new type of nano building unit with great potential. However, despite its many excellent properties, ANF still has some defects in practical applications, especially in terms of high temperature resistance, heat insulation and flame retardancy:

[0004] 1) Insufficient thermal stability: ANF is prone to thermal degradation in high temperature environments, resulting in a decrease in its mechanical properties. Although PPTA itself has a high thermal decomposition temperature (about 500°C), the thermal stability of ANF is still insufficient under long-term high temperature exposure.

[0005] 2) Limited heat insulation performance: The thermal conductivity of ANF is relatively high, resulting in limited heat insulation performance. In application scenarios that require high-efficiency heat insulation, the heat insulation effect of ANF cannot meet the requirements.

[0006] 3) Insufficient flame retardancy: Although PPTA itself has certain flame retardancy, under extreme conditions (such as high temperature or direct flame action), the flame retardancy of ANF is still insufficient, and it is prone to combustion or thermal decomposition.

[0007] MXene is a class of two-dimensional transition metal carbides, nitrides, or carbonitrides derived from MAX-phase materials. Due to its excellent physical and chemical properties, such as high electrical conductivity, mechanical strength, chemical stability, and surface functionalization ability, this material has been widely used in fields such as energy storage, sensors, catalysis, and electromagnetic shielding. Currently, the main preparation method of MXene is the acid etching method. This method requires using hydrofluoric acid-containing solution or Lewis acid molten salt to selectively etch out the A-layer elements, and then separating the MXene sheets through an intercalating agent. This method not only produces a large amount of waste liquid and waste gas but also limits the types and scale of MXenes. MXene can be synthesized directly from metal raw materials, avoiding the pollution of waste liquid and waste gas generated by the traditional etching method. At the same time, by adjusting the reaction conditions and precursor ratios, precise control of different components and structures can be achieved. Using chemical vapor deposition technology, large-area, uniform, and continuous thin films can be grown on the substrate; by adjusting the temperature and atmosphere, its surface functional groups can be effectively controlled. In addition, by selecting different metal halides, new halogen-containing MXenes (such as Ti2CCl2) can be synthesized, further expanding its application potential. Summary of the Invention

[0008] The present invention aims to provide a poly(p-phenyleneterephthalamide) nanofiber composite aerogel with high temperature resistance, heat insulation, and flame retardancy, as well as its preparation method and application. Through a two-step sol-gel method, the carboxyl groups on the PAA molecular chain interact with the deprotonated amide groups on the ANF molecular chain, partially restoring the hydrogen bond system, pre-gelatinizing ANF, and increasing the viscosity. Then, Ti2CCl2 nanosheets are introduced into the pre-gel system through high-speed shearing, and then protonic acid and solution are introduced to completely gel ANF. The introduction of Ti2CCl2 nanosheets enables the composite aerogel to combine the high thermal stability of Ti2CCl2 with the excellent mechanical properties of ANF, possessing excellent flame retardancy, high temperature resistance, and thermal shielding efficiency.

[0009] To achieve the above objectives, the present invention provides the following technical solutions:

[0010] The present invention provides a preparation method of a composite aerogel by a two-step PAA-induced ANF gel and introducing Ti2CCl2 nanosheets. By means of the sol-gel method, the carboxyl groups on the PAA molecular chain interact with the deprotonated amide groups on the ANF molecular chain, partially restoring the hydrogen bond system, pre-gelatinizing ANF, increasing the viscosity, and then introducing Ti2CCl2 nanosheets into the pre-gel system through high-speed shearing. Subsequently, a protonic acid and a solution are introduced to completely gel ANF. The introduction of Ti2CCl2 nanosheets can significantly improve the performance and functionality of the composite material. Its high thermal conductivity and photothermal conversion ability can be used for thermal management and photothermal response materials; its high strength and two-dimensional structure contribute to enhancing the mechanical properties of the composite material; its low infrared emissivity makes it suitable for infrared stealth applications. At the same time, the halogen groups on the surface endow it with good chemical stability and interfacial binding ability, and excellent thermal shielding efficiency and mechanical properties are achieved through microstructure design.

[0011] In the first aspect of the present invention, a poly(p-phenylene terephthalamide) nanofiber composite aerogel with high temperature resistance, heat insulation and flame retardancy is provided. Through a two-step sol-gel method, the carboxyl groups on the synthesized PAA molecular chain are used to induce the ANF dispersion liquid and pre-gel, and the Ti2CCl2 nanosheets synthesized by high-temperature solid-phase synthesis are introduced into the ANF pre-gel system, fully dispersed and homogenized. Subsequently, ANF is completely gelled through solvent replacement treatment, and a Ti2CCl2 / ANF composite aerogel with an ordered structure is prepared by directional freeze-drying.

[0012] Furthermore, the components of the poly(p-phenylene terephthalamide) nanofiber composite aerogel are as follows by weight: 1 part by weight of the DMSO dispersion liquid of ANF, 0.2 - 0.5 part by weight of the DMSO solution of PAA, 0.5 - 3 part by weight of Ti2CCl2 nanosheets, 0.2 part by weight of the aqueous dispersion liquid of protonic acid; wherein the solvent components for solvent replacement are 20 - 25 parts by volume of tert-butanol, 5 - 15 parts by volume of ethanol, 10 - 20 parts by volume of silane coupling agent, and 40 - 65 parts by volume of deionized water.

[0013] Furthermore, the components of the DMSO dispersion liquid of ANF are 0.5 - 2 parts by weight of ANF, 0.4 - 1.6 parts by weight of potassium hydroxide, and 96.4 - 99.1 parts by weight of DMSO; wherein ANF is prepared by low-temperature condensation polymerization from 0.9 part by weight of p-phenylenediamine, 1.69 part by weight of terephthaloyl chloride, 1.33 part by weight of pyridine, 1.12 part by weight of anhydrous calcium chloride, and 61.68 part by weight of N-methylpyrrolidone.

[0014] Furthermore, the PAA is prepared by low-temperature condensation polymerization from 4.0 parts by weight of 4,4'-diaminodiphenyl ether, 5.026 parts by weight of 3,3',4,4'-biphenyltetracarboxylic dianhydride, and 67.464 parts by weight of N,N-dimethylacetamide.

[0015] In the second aspect of the present invention, a method for preparing the poly(p-phenyleneterephthalamide) nanofiber composite aerogel is provided, which comprises the following steps:

[0016] Step 1: Dissolve 10 parts by weight of anhydrous calcium chloride and pyrrole in a ratio of 1:1.5 in 200 parts by weight of N-methylpyrrolidone, introduce argon gas, dissolve 1 mole part by weight of p-phenylenediamine in N-methylpyrrolidone, and lower the temperature of the system to below 0 °C; dissolve 1.005 mole parts by weight of terephthaloyl chloride in 10 parts by weight of N-methylpyrrolidone, and add it dropwise to the reaction system through a constant pressure funnel. During the dropping process, a protective gas needs to be introduced to avoid the accumulation of heat generated by the rapid reaction, which may affect the progress of the reaction; after the Weissenberg effect appears in the reaction system, end the reaction and collect the reaction product to obtain ANF;

[0017] Step 2: Disperse 0.5 - 1.5 parts by weight of ANF and 0.5 - 1 part by weight of potassium hydroxide in 97.5 - 198.2 parts by weight of dimethyl sulfoxide (DMSO), and mix them at room temperature until completely dissolved to obtain an ANF dispersion with a concentration of 0.5 wt.% - 2;

[0018] Transfer 4 parts by weight of 4,4'-diaminodiphenyl ether (ODA) and 68 parts by weight of N,N-dimethylacetamide (DMAc) to a three-necked flask, disperse ODA in DMAc, stir until completely dissolved, and then lower the temperature of the reaction system to 0 - 4 °C; weigh 5 parts by weight of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and add it to the three-necked flask in batches. After the Weissenberg effect appears, end the reaction to obtain a light yellow viscous PAA liquid;

[0019] Step 3: Take 2.87 parts by weight of nano-Ti powder as the titanium source, 0.4 parts by weight of graphene nanosheets as the carbon source, and 4.6 parts by weight of TiCl4. After fully mixing them evenly under the protection of a nitrogen atmosphere, seal them in a quartz crucible, and then transfer them to a muffle furnace. Heat up to 950 °C within 20 minutes, keep the temperature for reaction for 2 hours to obtain a Ti2CCl2 nano-intermediate, and cool it to room temperature with the furnace and collect it for standby; Ultrasonically disperse 0.5 parts by weight of tannic acid in 20 parts by weight of Tris buffer solution, and then ultrasonically disperse 1 part by weight of the Ti2CCl2 nano-intermediate and add it to the above mixed solution, stir magnetically for 6 hours, wash the reaction product with water, and dry it to obtain Ti2CCl2 nanosheets;

[0020] Step 4: Thoroughly mix 1 part by weight of the ANF dispersion and 0.2 - 0.5 part by weight of the PAA solution using a high-speed shear mixer to pre-gel the ANF dispersion; evenly disperse 0.5 - 3 parts by weight of the Ti2CCl2 nanosheets in the ANF pre-gel system by high-speed shearing as well. Add 0.2 part by weight of a 25 wt.% acetic acid solution to the ANF pre-gel system, transfer it to an oven, raise the temperature to 60 °C, and keep it warm for 30 min. After complete gelation, a Ti2CCl2 / ANF composite gel with two-step slow-release proton-induced gelation is obtained.

[0021] Step 5: Thoroughly mix 25 - 35 parts by volume of tert-butanol, 10 - 20 parts by volume of absolute ethanol, 5 - 10 parts by volume of a silane coupling agent, and 45 - 60 parts by volume of deionized water; transfer the Ti2CCl2 / ANF composite gel to the above mixed solution and transfer it to an oven, raise the temperature to 60 °C, and treat it for 3 hours. After cooling, repeatedly wash it with deionized water to obtain a Ti2CCl2 / ANF composite hydrogel.

[0022] Step 6: Immerse a self-made copper plate mold in liquid nitrogen for pre-cooling, transfer the Ti2CCl2 / ANF composite hydrogel to the copper plate mold, pre-freeze it for 30 min, keep the mold temperature at -30 °C, and dry the frozen Ti2CCl2 / ANF composite hydrogel. After 30 hours, a Ti2CCl2 / ANF composite aerogel with two-step slow-release proton-induced gelation is obtained; immediately anneal the Ti2CCl2 / ANF composite aerogel at 350 °C for 1 - 3 hours to obtain a Ti2CCl2 / ANF composite aerogel with a stable structure.

[0023] Furthermore, the weight ratio of the titanium source, carbon source, and titanium tetrachloride is 2.87:0.4:4.6, where the titanium source includes titanium powder, titanium foil, and titanium sheets, and the carbon source includes graphite, graphene, carbon nanotubes, and carbon foam.

[0024] Furthermore, the concentration of the ANF dispersion is 0.5 - 2 wt.%.

[0025] In the third aspect of the present invention, there is provided the use of the poly(p-phenyleneterephthalamide) nanofiber composite aerogel as a thermal insulation material for building exterior walls, roofs, or energy systems to provide heat insulation and thermal regulation functions.

[0026] In the fourth aspect of the present invention, there is provided the use of the poly(p-phenyleneterephthalamide) nanofiber composite aerogel as an emergency heat source material in clothing, sports equipment, or rescue equipment, where the poly(p-phenyleneterephthalamide) nanofiber composite aerogel can convert thermal energy under available light sources to provide temperature or thermal energy support.

[0027] In the fifth aspect of the present invention, there is provided the application of the above-mentioned poly(p-phenyleneterephthalamide) nanofiber composite aerogel in a hyperthermia device, wherein the poly(p-phenyleneterephthalamide) nanofiber composite aerogel provides local heating through rapid photothermal response to assist in the treatment of muscle pain or arthritis.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1) The poly(p-phenyleneterephthalamide) nanofiber composite aerogel of the present invention is prepared by inducing ANF gel by a two-step method with PAA and introducing Ti2CCl2 nanosheets, so that the prepared composite aerogel combines the high thermal stability of Ti2CCl2 and the excellent mechanical properties of ANF, thus having excellent flame retardancy, high temperature resistance performance, and thermal shielding efficiency, overcoming the technical defects of the prior art in aspects such as high temperature resistance and heat insulation and flame retardancy performance.

[0030] 2) Through optimized design, the present invention uses a compound solvent including tert-butanol, ethanol, deionized water, and silane coupling agent combined with an innovative solvent replacement method to treat the ANF gel, significantly shortening the solvent replacement time and also using the surface modification effect of the coupling agent to effectively reduce the surface tension. During the drying process, this method significantly reduces volume shrinkage and maintains the stability of the aerogel structure.

[0031] 3) The thermal conductivity and photothermal conversion ability of the poly(p-phenyleneterephthalamide) nanofiber composite aerogel of the present invention can be used for thermal management and photothermal response materials; the high strength and two-dimensional structure help to enhance the mechanical properties of the composite material; the low infrared emissivity makes it suitable for infrared stealth applications. At the same time, the halogen groups on the surface endow it with good chemical stability and interfacial bonding ability, and excellent thermal shielding efficiency and mechanical properties are achieved through microstructural design.

[0032] 4) By adopting an improved sol-gel method and introducing photothermal response Ti2CCl2 nanosheets, the high temperature resistant, heat insulating, and flame retardant composite aerogel with ultrafast photothermal response prepared by the present invention can be used for efficient thermal management and personal wearable devices. Description of the Drawings

[0033] Figure 1 Shows the microscopic structure diagrams and element distribution diagrams of ANF and Ti2CCl2 / ANF composite aerogels in the embodiments of the present invention.

[0034] Figure 2 Shows the microscopic structure and composition element distribution diagram of Ti2CCl2 nanosheets in the embodiments of the present invention.

[0035] Figure 3XRD and infrared spectra of ANF, Ti2CCl2 nanosheets and Ti2CCl2 / ANF composite aerogels in the embodiments of the present invention are shown.

[0036] Figure 4 The compression performance of the Ti2CCl2 / ANF composite aerogel in the embodiments of the present invention is shown, where Figure 4 (a) is the compression stress-strain curve of the Ti2CCl2 / ANF composite aerogel, Figure 4 (b) is the compression cycle curve of the Ti2CCl2 / ANF composite aerogel, Figure 4 (c) is the maximum compression strength of the Ti2CCl2 / ANF composite aerogel, Figure 4 (d) is the modulus of the Ti2CCl2 / ANF composite aerogel.

[0037] Figure 5 It is the infrared thermal imaging diagram of the Ti2CCl2 / ANF composite aerogel prepared in the embodiments of the present invention under the condition of near-infrared light illumination. Detailed implementation manners

[0038] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

[0039] The present invention provides a preparation method of a composite aerogel that induces ANF gel by two-step PAA and introduces Ti2CCl2 nanosheets. By means of the sol-gel method, the carboxyl groups on the PAA molecular chain interact with the deprotonated amide groups on the ANF molecular chain, partially restoring the hydrogen bond system, pre-gelatinizing ANF, increasing the viscosity, and then introducing Ti2CCl2 nanosheets into the pre-gel system through high-speed shearing, and then introducing protonic acid and solution to completely gel ANF. The introduction of Ti2CCl2 nanosheets can significantly improve the performance and functionality of the composite material. Its high thermal conductivity and photothermal conversion ability can be used in thermal management and photothermal response materials; its high strength and two-dimensional structure help to enhance the mechanical properties of the composite material; its low infrared emissivity makes it suitable for infrared stealth applications. At the same time, the halogen groups on the surface endow it with good chemical stability and interfacial bonding ability, and excellent thermal shielding efficiency and mechanical properties are achieved through microstructural design.

[0040] PAA is prepared by low-temperature condensation polymerization of aromatic monomers such as 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 4,4'-diaminodiphenyl ether, and p-phenylenediamine. It has excellent heat resistance, wear resistance, corrosion resistance, and electrical insulation properties, and can be used to produce high-strength and wear-resistant textiles such as bulletproof vests and chemical protective clothing. The carboxyl groups on the PAA molecular chain can interact with the hydrogen bond system of the deprotonated PPTA molecular chain to achieve gelation, and at the same time, the rigidity and flexibility of the molecular chain can be regulated by selecting different diamine and dianhydride monomers. The entanglement of the PAA and PPTA molecular chains, as well as the imidization and increase of crosslinking points during heat treatment, can further improve the mechanical strength of the material.

[0041] Ti2CCl2 nanosheets are directly synthesized by a one-step high-temperature direct synthesis method. The reaction precursors are titanium metal powder (Ti), graphene (carbon source), and titanium tetrachloride (TiCl4) mixed evenly in a weight ratio of 2.87:0.4:4.6 and sealed in a crucible. The temperature of the muffle furnace is raised to 950 °C, and then the precursor mixture is immediately transferred to the muffle furnace for heat preservation reaction for 2 hours. At high temperature, Ti2CCl2 nanosheets are formed through solid-state reactions between Ti, TiCl4, and graphene. The direct synthesis method is efficient, scalable, and avoids the by-product pollution of traditional etching methods. The introduction of Ti2CCl2 nanosheets can significantly optimize various properties of the composite material. Its high thermal conductivity and uniform heat conduction ability improve the thermal management performance, its high strength and two-dimensional layered structure enhance the mechanical properties of the material, and its excellent photothermal response and wide-band absorption characteristics endow the material with efficient photothermal conversion ability. In addition, Ti2CCl2 nanosheets have good electrical conductivity and low infrared emissivity, which can achieve electromagnetic shielding and infrared stealth effects; the halogen groups on their surface also enhance the chemical stability and interfacial bonding force of the composite material. By compounding with matrix materials, Ti2CCl2 nanosheets can achieve multi-functional synergistic optimization and are widely used in fields such as wearable devices, military stealth, energy storage devices, electromagnetic shielding, and environmental governance.

[0042] Solvent replacement and drying during the preparation of aerogels are also crucial steps to maintain the integrity of the aerogel structure. Among them, the solvent replacement and drying processes, as key links, directly determine the structure and properties of the aerogel. Through optimized design, the physical and chemical properties of the aerogel can be regulated to meet different application requirements. By using a compound solvent (including tert-butanol, ethanol, deionized water, and silane coupling agent) combined with an innovative solvent replacement method to treat the ANF gel, the solvent replacement time is significantly shortened, and at the same time, the surface modification effect of the coupling agent is utilized to effectively reduce the surface tension. During the drying process, this method significantly reduces volume shrinkage and maintains the stability of the aerogel structure.

[0043] The present invention provides a method for preparing a poly(p-phenyleneterephthalamide) nanofiber composite aerogel with high temperature resistance, heat insulation and flame retardancy, comprising the following steps:

[0044] Step 1: Dissolve 10 parts by weight of anhydrous calcium chloride and pyrrole in a ratio of 1:1.5 in 200 parts by weight of N-methylpyrrolidone, introduce argon, dissolve 1 mole part by weight of p-phenylenediamine in N-methylpyrrolidone, and lower the temperature of the system to below 0 °C; dissolve 1.005 mole parts by weight of terephthaloyl chloride in 10 parts by weight of N-methylpyrrolidone, and add it dropwise to the reaction system through a constant pressure funnel. During the dropping process, a protective gas needs to be introduced to avoid heat accumulation caused by rapid reaction, which affects the progress of the reaction; after the Weissenberg effect appears in the reaction system, end the reaction and collect the reaction product to obtain ANF;

[0045] Step 2: Disperse 0.5 - 1.5 parts by weight of ANF and 0.5 - 1 part by weight of potassium hydroxide in 97.5 - 198.2 parts by weight of dimethyl sulfoxide (DMSO), and mix them at room temperature until completely dissolved to obtain an ANF dispersion with a concentration of 0.5 wt.% - 2;

[0046] Transfer 4 parts by weight of 4,4'-diaminodiphenyl ether (ODA) and 68 parts by weight of N,N-dimethylacetamide (DMAc) to a three-necked flask, disperse ODA in DMAc, stir until completely dissolved, and then lower the temperature of the reaction system to 0 - 4 °C; weigh 5 parts by weight of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and add it to the three-necked flask in batches. After the Weissenberg effect appears, end the reaction to obtain a light yellow viscous PAA liquid;

[0047] Step 3: Take 2.87 parts by weight of nano-Ti powder as the titanium source, 0.4 parts by weight of graphene nanosheets as the carbon source, and 4.6 parts by weight of TiCl4, mix them evenly under the protection of a nitrogen atmosphere, seal them in a quartz crucible, and then transfer them to a muffle furnace. Heat up to 950 °C within 20 minutes, keep the temperature for reaction for 2 hours to obtain a Ti2CCl2 nano-intermediate, and cool it to room temperature with the furnace and collect it for standby; ultrasonically disperse 0.5 parts by weight of tannic acid in 20 parts by weight of Tris buffer solution, and then ultrasonically disperse 1 part by weight of the Ti2CCl2 nano-intermediate and add it to the above mixed solution, stir magnetically for 6 hours, wash the reaction product with water, and dry it to obtain Ti2CCl2 nanosheets;

[0048] Step 4: Thoroughly mix 1 part by weight of the ANF dispersion and 0.2 - 0.5 parts by weight of the PAA solution using a high-speed shear mixer to pre-gel the ANF dispersion; evenly disperse 0.5 - 3 parts by weight of the Ti2CCl2 nanosheets in the ANF pre-gel system by high-speed shearing as well. Add 0.2 parts by weight of 25 wt.% acetic acid solution to the ANF pre-gel system, transfer it to an oven, raise the temperature to 60 °C, and keep it warm for 30 min. After complete gelation, a Ti2CCl2 / ANF composite gel with two-step slow-release proton-induced gelation is obtained.

[0049] Step 5: Thoroughly mix 25 - 35 parts by volume of tert-butanol, 10 - 20 parts by volume of absolute ethanol, 5 - 10 parts by volume of silane coupling agent, and 45 - 60 parts by volume of deionized water; transfer the Ti2CCl2 / ANF composite gel to the above mixed solution and transfer it to an oven, raise the temperature to 60 °C, and process for 3 hours. After cooling, repeatedly wash it with deionized water to obtain a Ti2CCl2 / ANF composite hydrogel.

[0050] Step 6: Immerse the self-made copper plate mold in liquid nitrogen for pre-cooling. Transfer the Ti2CCl2 / ANF composite hydrogel to the copper plate mold, pre-freeze for 30 min, and keep the mold temperature at -30 °C. Dry the frozen Ti2CCl2 / ANF composite hydrogel. After 30 hours, a Ti2CCl2 / ANF composite aerogel with two-step slow-release proton-induced gelation is obtained. Immediately anneal the Ti2CCl2 / ANF composite aerogel at 350 °C for 1 - 3 hours to obtain a Ti2CCl2 / ANF composite aerogel with stable structure.

[0051] Example 1

[0052] Dissolve 10 parts by weight of anhydrous calcium chloride and pyrrole with a mass ratio of 1:1.5 in 200 parts by weight of N-methylpyrrolidone (NMP). Under a protective atmosphere, dissolve 1 mole part of p-phenylenediamine (PDD) in the mixed solvent, and lower the system temperature below 0 °C. Subsequently, dissolve 1.005 mole parts of terephthaloyl chloride (TPC) in 10 parts of NMP, and add it dropwise to the reaction system through a constant-pressure funnel. When the Weissenberg effect appears in the reaction system, terminate the reaction and collect the reaction product to synthesize ANF. Disperse 1.5 parts by weight of ANF and 1 part by weight of potassium hydroxide in 97.5 parts by weight of DMSO to prepare an ANF dispersion with a concentration of 1.5 wt.%, and magnetically stir it to a uniform ANF dispersion.

[0053] Weigh 4 parts by weight of 4,4-diaminodiphenyl ether (ODA), add 68 parts by weight of N,N-dimethylacetamide (DMAc) into a three-necked flask, disperse ODA in DMAc, and completely dissolve it by magnetic stirring. Subsequently, lower the temperature of the reaction system to 0 - 4 °C. Weigh 5 parts by weight of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), add it to the three-necked flask in batches, and stop the reaction after the Weissenberg effect appears in the reaction system. Finally, a light yellow viscous PAA liquid is obtained.

[0054] Take 2.87 parts by weight of nano-Ti powder as the titanium source, 0.4 parts by weight of graphene nanosheets as the carbon source, and 4.6 parts by weight of TiCl4. After mixing them evenly under the protection of a nitrogen atmosphere, seal them in a quartz crucible, and then transfer them to a muffle furnace. Heat up to 950 °C within 20 minutes, hold the reaction for 2 hours to obtain a Ti2CCl2 nano-intermediate, and cool it to room temperature with the furnace and collect it for standby; Ultrasonically disperse 0.5 parts by weight of tannic acid in 20 parts by weight of Tris buffer solution, and then ultrasonically disperse 1 part by weight of the Ti2CCl2 nano-intermediate and add it to the above mixed solution. Stir magnetically for 6 hours, wash the reaction product with water, and dry it to obtain Ti2CCl2 nanosheets;

[0055] Take 1 part by weight of ANF dispersion and 0.1 part by weight of PAA solution. Disperse the PAA solution in the ANF solution by a high-speed shearer. The rich carboxyl groups on the PAA molecular chain can pre-gel the ANF dispersion. Disperse 1 part by weight of Ti2CCl2 nanosheets into the pre-gel of ANF by high-speed shear. Immediately add 0.1 part by weight of acetic acid solution (20 wt.%) to the pre-gel system of ANF, then transfer it to an oven, raise the temperature to 60 °C, hold for 30 min, and let it stand for gelation.

[0056] Take 25 parts by volume of tert-butanol, 10 parts by volume of absolute ethanol, 10 parts by volume of silane coupling agent, and 55 parts by volume of deionized water, and mix these components evenly. Place the Ti2CCl2 / ANF organic gel and the prepared mixed solution in an oven together, raise the temperature to 60 °C for solvent replacement treatment for 3 hours. After the reaction, take out the gel and wash it with deionized water multiple times to remove the residual solvent.

[0057] Immerse the self-made copper mold in liquid nitrogen for pre-cooling. After the temperature cools to -80 °C - -60 °C, transfer the ANF gel to the copper mold for pre-freezing. After 30 min, transfer it to a freeze dryer for freeze-drying.

[0058] Transfer the dry Ti2CCl2 / ANF composite aerogel to a tubular furnace. Under a nitrogen atmosphere, raise the temperature to 350 °C at a heating rate of 2 °C / min, perform annealing treatment for 3 h, and after the heat treatment is completed, cool it to room temperature at 5 °C / min to obtain the hybrid ANF aerogel (ANFT-1).

[0059] After testing, the surface temperature of the prepared hybrid ANF aerogel in a thermal environment of 300 °C is only 150.9 °C, the temperature difference from the ambient temperature is 149.1 °C, the thermal conductivity of the prepared sample is only 0.043, and the thermal decomposition temperature reaches 530 °C.

[0060] Example 2

[0061] Dissolve 10 parts by weight of anhydrous calcium chloride and pyrrole with a mass ratio of 1:1.5 in 200 parts by weight of N-methylpyrrolidone (NMP). Under a protective atmosphere, dissolve 1 mole part of p-phenylenediamine (PDD) in the compound solvent, and lower the temperature of the system below 0 °C. Subsequently, dissolve 1.005 mole parts of terephthaloyl chloride (TPC) in 10 parts of NMP, and add it dropwise to the reaction system through a constant pressure funnel. When the Weissenberg effect appears in the reaction system, terminate the reaction and collect the reaction product to synthesize ANF. Disperse 1.5 parts by weight of ANF and 1 part by weight of potassium hydroxide in 97.5 parts by weight of DMSO to prepare an ANF dispersion with a concentration of 1.5 wt.%, and magnetically stir until a uniform ANF dispersion is obtained.

[0062] Weigh 4 parts by weight of 4,4'-diaminodiphenyl ether (ODA), add 68 parts by weight of N,N-dimethylacetamide (DMAc) to a three-necked flask, disperse ODA in DMAc, and completely dissolve it by magnetic stirring. Subsequently, lower the temperature of the reaction system to 0 - 4 °C. Weigh 5 parts by weight of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), add it to the three-necked flask in batches, and stop the reaction after the Weissenberg effect appears in the reaction system to finally obtain a pale yellow viscous PAA liquid.

[0063] Take 2.87 parts by weight of nano-Ti powder as the titanium source, 0.4 parts by weight of graphene nanosheets as the carbon source, and 4.6 parts by weight of TiCl4. After fully mixing and homogenizing under a nitrogen atmosphere protection, seal it in a quartz crucible, and then transfer it to a muffle furnace and heat it to 950 °C within 20 minutes, hold the reaction for 2 hours to obtain the Ti2CCl2 nano-intermediate, and cool it to room temperature with the furnace and collect it for standby; ultrasonically disperse 0.5 parts by weight of tannic acid in 20 parts by weight of Tris buffer solution, and then ultrasonically disperse 1 part by weight of the Ti2CCl2 nano-intermediate and add it to the above mixed solution, magnetically stir for 6 hours, wash the reaction product, and dry it to obtain Ti2CCl2 nanosheets;

[0064] Take 1 part by weight of the ANF dispersion and 0.1 part by weight of the PAA solution. Disperse the PAA solution in the ANF solution through a high-speed shear machine. The abundant carboxyl groups on the PAA molecular chain can pre-gel the ANF dispersion. Disperse 1.5 parts by weight of the Ti2CCl2 nanosheets into the pre-gel of ANF through high-speed shear. Immediately, add 0.1 part by weight of acetic acid solution (20 wt.%) to the pre-gel system of ANF, then transfer it to an oven, raise the temperature to 60 °C, keep it warm for 30 min, and let it stand still to wait for gelation.

[0065] Take 25 parts by volume of tert-butanol, 10 parts by volume of absolute ethanol, 10 parts by volume of silane coupling agent and 55 parts by volume of deionized water, and mix these components evenly. Place the Ti2CCl2 / ANF organic gel and the prepared mixed solution in an oven together, raise the temperature to 60 °C for solvent replacement treatment for 3 hours. After the reaction is completed, take out the gel and wash it with deionized water multiple times to remove the residual solvent.

[0066] Immerse the self-made copper mold in liquid nitrogen for pre-cooling. After the temperature cools to -80 °C to -60 °C, transfer the ANF gel to the copper mold for pre-freezing. After 30 min, transfer it to a freeze dryer for freeze drying.

[0067] Transfer the dried Ti2CCl2 / ANF composite aerogel to a tube furnace. Under a nitrogen atmosphere, raise the temperature to 350 °C, set the heating rate to 2 °C / min, and perform annealing treatment for 3 h. After the heat treatment is completed, cool it to room temperature at 5 °C / min to obtain the hybrid ANF aerogel (ANFT-2).

[0068] After testing, the surface temperature of the prepared hybrid ANF aerogel in a thermal environment of 300 °C is only 159.4 °C, the temperature difference from the ambient temperature is 140.6 °C, the thermal conductivity of the prepared sample is only 0.0459, and the thermal decomposition temperature reaches 537 °C.

[0069] Example 3

[0070] Dissolve 10 parts by weight of anhydrous calcium chloride and pyrrole with a mass ratio of 1:1.5 in 200 parts by weight of N-methylpyrrolidone (NMP). Under a protective atmosphere, dissolve 1 mole part of p-phenylenediamine (PDD) in the compound solvent, and lower the temperature of the system below 0 °C. Subsequently, dissolve 1.005 mole parts of terephthaloyl chloride (TPC) in 10 parts of NMP, and add it dropwise to the reaction system through a constant pressure funnel. When the Weissenberg effect appears in the reaction system, terminate the reaction and collect the reaction product to synthesize ANF. Disperse 1.5 parts by weight of ANF and 1 part by weight of potassium hydroxide in 97.5 parts by weight of DMSO to prepare an ANF dispersion with a concentration of 1.5 wt.%, and stir magnetically until a uniform ANF dispersion is obtained.

[0071] Weigh 4 parts by weight of 4,4'-diaminodiphenyl ether (ODA), add 68 parts by weight of N,N-dimethylacetamide (DMAc) into a three-necked flask, disperse ODA in DMAc, and completely dissolve it by magnetic stirring. Subsequently, lower the temperature of the reaction system to 0 - 4 °C. Weigh 5 parts by weight of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), add it to the three-necked flask in batches, and stop the reaction after the Weissenberg effect appears in the reaction system, finally obtaining a light yellow viscous PAA liquid.

[0072] Take 2.87 parts by weight of nano-Ti powder as the titanium source, 0.4 parts by weight of graphene nanosheets as the carbon source, and 4.6 parts by weight of TiCl4. After fully mixing them evenly under the protection of a nitrogen atmosphere, seal them in a quartz crucible, then transfer them to a muffle furnace and heat up to 950 °C within 20 minutes, hold the reaction for 2 hours to obtain a Ti2CCl2 nano-intermediate, and cool it to room temperature with the furnace and collect it for standby; Ultrasonically disperse 0.5 parts by weight of tannic acid in 20 parts by weight of Tris buffer solution, then ultrasonically disperse 1 part by weight of the Ti2CCl2 nano-intermediate and add it to the above mixed solution, stir magnetically for 6 hours, wash the reaction product with water, and dry it to obtain Ti2CCl2 nanosheets;

[0073] Take 1 part by weight of the ANF dispersion and 0.1 part by weight of the PAA solution. Disperse the PAA solution in the ANF solution by a high-speed shear machine. The rich carboxyl groups on the PAA molecular chain can pre-gel the ANF dispersion. Disperse 2 parts by weight of the Ti2CCl2 nanosheets into the pre-gel of ANF by high-speed shear, then add 0.1 part by weight of acetic acid solution (20 wt.%) to the pre-gel system of ANF, then transfer it to an oven, raise the temperature to 60 °C, hold for 30 min, and let it stand for gelation.

[0074] Take 25 parts by volume of tert-butanol, 10 parts by volume of absolute ethanol, 10 parts by volume of silane coupling agent, and 55 parts by volume of deionized water, and mix these components evenly. Place the Ti2CCl2 / ANF organic gel and the prepared mixed solution in an oven together, raise the temperature to 60 °C for solvent replacement treatment for 3 hours. After the reaction is completed, take out the gel and wash it with deionized water multiple times to remove the residual solvent.

[0075] Immerse the self-made copper mold in liquid nitrogen for pre-cooling. After the temperature cools to -80 °C to -60 °C, transfer the ANF gel to the copper mold for pre-freezing, and transfer it to a freeze dryer for freeze drying after 30 min.

[0076] Transfer the dry Ti2CCl2 / ANF composite aerogel to a tube furnace. Under a nitrogen atmosphere, raise the temperature to 350 °C at a heating rate of 2 °C / min, perform annealing treatment for 3 h, and after the heat treatment is completed, cool it to room temperature at 5 °C / min to obtain the hybrid ANF aerogel (ANFT-3).

[0077] After testing, the prepared hybrid ANF aerogel has a surface temperature of only 170.4 °C in a thermal environment of 300 °C, a temperature difference from the ambient temperature of 129.6 °C, a thermal conductivity of only 0.0498 for the prepared sample, and a thermal decomposition temperature of up to 538 °C.

[0078] Example 4

[0079] Dissolve 10 parts by weight of anhydrous calcium chloride and pyrrole with a mass ratio of 1:1.5 in 200 parts by weight of N-methylpyrrolidone (NMP). Under a protective atmosphere, dissolve 1 mole part of p-phenylenediamine (PDD) in the complex solvent and lower the system temperature below 0 °C. Subsequently, dissolve 1.005 mole parts of terephthaloyl chloride (TPC) in 10 parts of NMP and add it dropwise to the reaction system through a constant pressure funnel. When the Weissenberg effect appears in the reaction system, terminate the reaction and collect the reaction product to synthesize ANF. Disperse 1.5 parts by weight of ANF and 1 part by weight of potassium hydroxide in 97.5 parts by weight of DMSO to prepare an ANF dispersion with a concentration of 1.5 wt.%, and stir magnetically until a homogeneous ANF dispersion is obtained.

[0080] Weigh 4 parts by weight of 4,4'-diaminodiphenyl ether (ODA), add 68 parts by weight of N,N-dimethylacetamide (DMAc) to a three-necked flask, disperse ODA in DMAc, and completely dissolve it by magnetic stirring. Subsequently, lower the temperature of the reaction system to 0 - 4 °C. Weigh 5 parts by weight of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and add it to the three-necked flask in batches. Stop the reaction after the Weissenberg effect appears in the reaction system to finally obtain a light yellow viscous PAA liquid.

[0081] Take 2.87 parts by weight of nano-Ti powder as the titanium source, 0.4 parts by weight of graphene nanosheets as the carbon source, and 4.6 parts by weight of TiCl4. After fully mixing and homogenizing under a nitrogen atmosphere protection, seal it in a quartz crucible, and then transfer it to a muffle furnace and heat it to 950 °C within 20 minutes, hold the reaction for 2 hours to obtain the Ti2CCl2 nano-intermediate, and cool it to room temperature with the furnace and collect it for standby; ultrasonically disperse 0.5 parts by weight of tannic acid in 20 parts by weight of Tris buffer solution, and then ultrasonically disperse 1 part by weight of the Ti2CCl2 nano-intermediate and add it to the above mixed solution, stir magnetically for 6 hours, wash the reaction product with water, and dry it to obtain Ti2CCl2 nanosheets;

[0082] Take 1 part by weight of the ANF dispersion and 0.1 part by weight of the PAA solution. Disperse the PAA solution in the ANF solution through a high-speed shear machine. The abundant carboxyl groups on the PAA molecular chain can cause the ANF dispersion to pre-gel. Disperse 3 parts by weight of the Ti2CCl2 nanosheets into the pre-gel of ANF through high-speed shear. Immediately, add 0.1 part by weight of acetic acid solution (20 wt.%) to the pre-gel system of ANF, then transfer it to an oven, raise the temperature to 60 °C, keep it warm for 30 min, and let it stand still to wait for gelation.

[0083] Take 25 parts by volume of tert-butanol, 10 parts by volume of absolute ethanol, 10 parts by volume of silane coupling agent, and 55 parts by volume of deionized water. Mix these components evenly. Place the Ti2CCl2 / ANF organogel and the prepared mixed solution in an oven together, raise the temperature to 60 °C for solvent replacement treatment for 3 hours. After the reaction is completed, take out the gel and wash it with deionized water multiple times to remove the residual solvent.

[0084] Immerse the self-made copper mold in liquid nitrogen for pre-cooling. After the temperature cools to -80 °C to -60 °C, transfer the ANF gel to the copper mold for pre-freezing. After 30 min, transfer it to a freeze dryer for freeze drying.

[0085] Transfer the dried Ti2CCl2 / ANF composite aerogel to a tube furnace. Under a nitrogen atmosphere, raise the temperature to 350 °C, set the heating rate to 2 °C / min, perform annealing treatment for 3 h. After the heat treatment is completed, cool it to room temperature at 5 °C / min to obtain the hybrid ANF aerogel (ANFT-4).

[0086] After testing, the surface temperature of the prepared hybrid ANF aerogel in a thermal environment of 300 °C is only 178.0 °C, the temperature difference from the ambient temperature is 122.0 °C, the thermal conductivity of the prepared sample is only 0.0592, and the thermal decomposition temperature reaches 537 °C.

[0087] Example 5

[0088] Dissolve 10 parts by weight of anhydrous calcium chloride and pyrrole with a mass ratio of 1:1.5 in 200 parts by weight of N-methylpyrrolidone (NMP). Under a protective atmosphere, dissolve 1 mole of p-phenylenediamine (PPD) in the compound solvent and lower the temperature of the system below 0 °C. Subsequently, dissolve 1.005 moles of terephthaloyl chloride (TPC) in 10 parts of NMP and add it dropwise to the reaction system through a constant pressure funnel. When the Weissenberg effect appears in the reaction system, terminate the reaction and collect the reaction product to synthesize ANF. Disperse 0.5 part by weight of ANF and 0.5 part by weight of potassium hydroxide in 99 parts by weight of DMSO to prepare an ANF dispersion with a concentration of 0.5 wt.%, and stir magnetically until a uniform ANF dispersion is obtained.

[0089] Weigh 4 parts by weight of 4,4'-diaminodiphenyl ether (ODA), add 68 parts by weight of N,N-dimethylacetamide (DMAc) into a three-necked flask, disperse ODA in DMAc, and completely dissolve it by magnetic stirring. Subsequently, lower the temperature of the reaction system to 0 - 4 °C. Weigh 5 parts by weight of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), add it into the three-necked flask in batches, and stop the reaction after the Weissenberg effect appears in the reaction system, finally obtaining a light yellow viscous PAA liquid.

[0090] Take 2.87 parts by weight of nano-Ti powder as the titanium source, 0.4 parts by weight of graphene nanosheets as the carbon source, and 4.6 parts by weight of TiCl4. After fully mixing them evenly under the protection of a nitrogen atmosphere, seal them in a quartz crucible, and then transfer them to a muffle furnace. Heat up to 950 °C within 20 minutes, hold the reaction for 2 hours to obtain a Ti2CCl2 nano-intermediate, and cool it to room temperature with the furnace for collection and standby; Ultrasonically disperse 0.5 parts by weight of tannic acid in 20 parts by weight of Tris buffer solution, and then ultrasonically disperse 1 part by weight of the Ti2CCl2 nano-intermediate and add it to the above mixed solution. Stir magnetically for 6 hours, wash the reaction product with water, and dry it to obtain Ti2CCl2 nanosheets;

[0091] Take 1 part by weight of ANF dispersion and 0.1 part by weight of PAA solution. Disperse the PAA solution in the ANF solution through a high-speed shear machine. The rich carboxyl groups on the PAA molecular chain can pre-gel the ANF dispersion. Disperse 2 parts by weight of Ti2CCl2 nanosheets into the pre-gel of ANF through high-speed shear. Immediately add 0.1 part by weight of acetic acid solution (20 wt.%) to the pre-gel system of ANF, and then transfer it to an oven. Raise the temperature to 60 °C, hold for 30 min, and let it stand for gelation.

[0092] Take 25 parts by volume of tert-butanol, 10 parts by volume of absolute ethanol, 10 parts by volume of silane coupling agent, and 55 parts by volume of deionized water, and mix these components evenly. Place the Ti2CCl2 / ANF organogel and the prepared mixed solution in an oven together, raise the temperature to 60 °C for solvent replacement treatment for 3 hours. After the reaction, take out the gel and wash it with deionized water multiple times to remove the residual solvent.

[0093] Immerse the self-made copper mold in liquid nitrogen for pre-cooling. After the temperature cools to -80 °C to -60 °C, transfer the ANF gel to the copper mold for pre-freezing. After 30 min, transfer it to a freeze dryer for freeze drying.

[0094] Transfer the dry Ti2CCl2 / ANF composite aerogel to a tubular furnace. Under a nitrogen atmosphere, raise the temperature to 350 °C at a heating rate of 2 °C / min, and perform annealing treatment for 3 h. After the heat treatment is completed, cool it to room temperature at 5 °C / min to obtain the hybrid ANF aerogel (ANFT-5).

[0095] After testing, the surface temperature of the prepared hybrid ANF aerogel in a thermal environment of 300 °C is only 150.8 °C, and the temperature difference from the ambient temperature is 149.2 °C. The thermal conductivity of the prepared sample is only 0.042 W / (m·K), and the thermal decomposition temperature reaches 529 °C.

[0096] Example 6

[0097] Dissolve 10 parts by weight of anhydrous calcium chloride / pyrrole with a mass ratio of 1:1.5 in 200 parts by weight of N-methylpyrrolidone (NMP). Introduce a protective gas, and dissolve 1 part by mole weight of p-phenylenediamine (PDD) in the compounded solvent. Lower the temperature of the system below 0 °C. Dissolve 1.005 parts by mole weight of terephthaloyl chloride (TPC) in 10 parts by weight of NMP, and add it dropwise to the reaction system through a constant pressure funnel. After the Weissenberg effect appears in the reaction system, end the reaction and collect the reaction product to obtain ANF.

[0098] Disperse 1 part by weight of ANF and 1 part by weight of potassium hydroxide in 98 parts by weight of DMSO to prepare an ANF dispersion with a concentration of 1 wt.%, and magnetically stir to obtain a homogeneous ANF dispersion.

[0099] Transfer 4 parts by weight of 4,4'-diaminodiphenyl ether (ODA) and measure 68 parts by weight of N,N-dimethylacetamide (DMAc) into a three-necked flask. Disperse ODA in DMAc and magnetically stir until completely dissolved. Then lower the temperature of the reaction system to 0-4 °C. Weigh 5 parts by weight of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and add it to the three-necked flask in portions. After the Weissenberg effect appears, end the reaction to obtain a pale yellow viscous PAA liquid.

[0100] Take 2.87 parts by weight of nano-Ti powder as the titanium source, 0.4 parts by weight of graphene nanosheets as the carbon source, and 4.6 parts by weight of TiCl4. Mix them evenly under the protection of a nitrogen atmosphere and seal them in a quartz crucible. Then transfer them to a muffle furnace and heat up to 950 °C within 20 minutes, hold the reaction for 2 hours to obtain the Ti2CCl2 nano-intermediate, and cool it to room temperature with the furnace and collect it for standby; ultrasonically disperse 0.5 parts by weight of tannic acid in 20 parts by weight of Tris buffer solution, and then ultrasonically disperse 1 part by weight of the Ti2CCl2 nano-intermediate and add it to the above mixed solution. Magnetically stir for 6 hours, wash the reaction product, and dry it to obtain Ti2CCl2 nanosheets;

[0101] Take 1 part by weight of the ANF dispersion and 0.1 part by weight of the PAA solution. Disperse the PAA solution in the ANF solution through a high-speed shear machine. The abundant carboxyl groups on the PAA molecular chain can cause the ANF dispersion to pre-gel. Disperse 2 parts by weight of the Ti2CCl2 nanosheets into the pre-gel of ANF through high-speed shear. Immediately add 0.1 part by weight of acetic acid solution (20 wt.%) to the pre-gel system of ANF, then transfer it to an oven, raise the temperature to 60 °C, keep it warm for 30 min, and let it stand still to wait for gelation.

[0102] Take 25 parts by volume of tert-butanol, 10 parts by volume of absolute ethanol, 10 parts by volume of silane coupling agent, and 55 parts by volume of deionized water, and mix these components evenly. Place the Ti2CCl2 / ANF organic gel and the prepared mixed solution in an oven together, raise the temperature to 60 °C for solvent replacement treatment for 3 hours. After the reaction is completed, take out the gel and wash it with deionized water multiple times to remove the residual solvent.

[0103] Immerse the self-made copper mold in liquid nitrogen for pre-cooling. After the temperature cools to -80 °C to -60 °C, transfer the ANF gel to the copper mold for pre-freezing. After 30 min, transfer it to a freeze dryer for freeze drying.

[0104] Transfer the dried Ti2CCl2 / ANF composite aerogel to a tubular furnace. Under a nitrogen atmosphere, raise the temperature to 350 °C, set the heating rate to 2 °C / min, perform annealing treatment for 3 h. After the heat treatment is completed, cool it to room temperature at 5 °C / min to obtain the hybrid ANF aerogel (ANFT-6).

[0105] After testing, the surface temperature of the prepared hybrid ANF aerogel in a thermal environment of 300 °C is only 157.6 °C, and the temperature difference from the ambient temperature is 142.4 °C. The thermal conductivity of the prepared sample is only 0.047 W / (m·K), and the thermal decomposition temperature reaches 534 °C.

[0106] Example 7

[0107] Dissolve 10 parts by weight of anhydrous calcium chloride / pyrrole with a mass ratio of 1:1.5 in 200 parts by weight of N-methylpyrrolidone (NMP), introduce a protective gas, dissolve 1 part by mole weight of p-phenylenediamine (PDD) in the compounded solvent, and lower the system temperature below 0 °C. Dissolve 1.005 parts by mole weight of terephthaloyl chloride (TPC) in 10 parts by weight of NMP, and add it dropwise to the reaction system through a constant pressure funnel. After the Weissenberg effect appears in the reaction system, end the reaction and collect the reaction product to obtain ANF.

[0108] Disperse 2 parts by weight of ANF and 2 parts by weight of potassium hydroxide in 96 parts by weight of DMSO to prepare an ANF dispersion with a concentration of 2 wt.%, and magnetically stir to obtain a uniform ANF dispersion.

[0109] Transfer 4 parts by weight of 4,4'-diaminodiphenyl ether (ODA) and measure 68 parts by weight of N,N-dimethylacetamide (DMAc) into a three-necked flask. Disperse ODA in DMAc and magnetically stir until completely dissolved. Then cool the reaction system temperature to 0 - 4 °C. Weigh 5 parts by weight of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and add it to the three-necked flask in portions. After the appearance of the Weissenberg effect, end the reaction to obtain a pale yellow viscous PAA liquid.

[0110] Take 2.87 parts by weight of nano-Ti powder as the titanium source, 0.4 parts by weight of graphene nanosheets as the carbon source, and 4.6 parts by weight of TiCl4. Mix them thoroughly under the protection of a nitrogen atmosphere and seal them in a quartz crucible. Immediately transfer it to a muffle furnace and heat it to 950 °C within 20 minutes, and hold the reaction for 2 hours to obtain a Ti2CCl2 nano-intermediate. Cool it to room temperature with the furnace and collect it for standby; Ultrasonically disperse 0.5 parts by weight of tannic acid in 20 parts by weight of Tris buffer solution, and then ultrasonically disperse 1 part by weight of the Ti2CCl2 nano-intermediate and add it to the above mixed solution. Magnetically stir for 6 hours, wash the reaction product with water, and dry it to obtain Ti2CCl2 nanosheets;

[0111] Take 1 part by weight of the ANF dispersion and 0.1 part by weight of the PAA solution. Disperse the PAA solution in the ANF solution through a high-speed shear machine. The rich carboxyl groups on the PAA molecular chain can pre-gel the ANF dispersion. Disperse 2 parts by weight of the Ti2CCl2 nanosheets into the pre-gel of ANF through high-speed shear. Immediately add 0.1 part by weight of acetic acid solution (20 wt.%) to the pre-gel system of ANF, and then transfer it to an oven, raise the temperature to 60 °C, hold for 30 min, and let it stand for gelation.

[0112] Take 25 parts by volume of tert-butanol, 10 parts by volume of absolute ethanol, 10 parts by volume of silane coupling agent, and 55 parts by volume of deionized water, and mix these components evenly. Place the Ti2CCl2 / ANF organic gel and the prepared mixed solution in an oven and raise the temperature to 60 °C for solvent replacement treatment for 3 hours. After the reaction, take out the gel and wash it with deionized water multiple times to remove the residual solvent.

[0113] Immerse the self-made copper mold in liquid nitrogen for pre-cooling. After the temperature cools to -80 °C to -60 °C, transfer the ANF gel to the copper mold for pre-freezing. After 30 min, transfer it to a freeze dryer for freeze drying.

[0114] Transfer the dry Ti2CCl2 / ANF composite aerogel to a tubular furnace. Under a nitrogen atmosphere, raise the temperature to 350 °C at a heating rate of 2 °C / min, and perform annealing treatment for 3 h. After the heat treatment is completed, cool it to room temperature at 5 °C / min to obtain the hybrid ANF aerogel (ANFT-7).

[0115] After testing, the surface temperature of the prepared hybrid ANF aerogel in a thermal environment of 300 °C is only 162.4 °C, and the temperature difference from the ambient temperature is 137.6 °C. The thermal conductivity of the prepared sample is only 0.049 W / (m·K), and the thermal decomposition temperature reaches 535 °C.

[0116] Due to the use of a two-step method to induce gelation, the introduction of PAA can increase the entanglement between molecular chains at the molecular chain scale. The introduction of Ti2CCl2 nanosheets and the directional structure design can effectively improve the mechanical properties and thermal stability of the material. Figure 1 The microscopic structure diagrams and element distribution diagrams of ANF and Ti2CCl2 / ANF composite aerogels in Example 3 of the present invention are shown. It can be seen from the SEM images that the synthesized ANF exists in the form of nanofibers in the DMSO dispersion, and the diameter of the nanofibers is 20-40 nm. The microscopic structure of the ANF aerogel Figure 1 The designed directional ordered structure can be seen from the local enlarged view. It can be known from the local enlarged view that the skeleton of the aerogel is still composed of nanofibers. Moreover, the element distribution diagram also confirms the introduction of Ti2CCl2. Figure 2 The microscopic structure and composition element distribution diagram of Ti2CCl2 nanosheets in the examples of the present invention are shown. The structure of Ti2CCl2 is as Figure 2 (a) and (b) show that Ti2CCl2 grows on graphene sheets in a high-temperature environment, showing a nanosheet structure with a size of 200-500 nanometers. Figure 2 (d) and (e1-e4) EDS results confirm that the main components of Ti2CCl2 nanosheets are Ti, C, O, and Cl. O may be partial oxidation in a high-temperature environment. The introduction of two-dimensional nanosheets helps to improve the modulus and strength of the composite aerogel, can be used as the skeleton support of the aerogel, and significantly improves its compressive and tensile properties, solving the problems of high brittleness and easy collapse of traditional aerogels.

[0117] Figure 3 The XRD and infrared spectra of ANF, Ti2CCl2 nanosheets, and Ti2CCl2 / ANF composite aerogels in the examples of the present invention are shown. X-ray diffraction (XRD) is used to analyze the phase composition and structural information of aramid nanofibers (ANF), Ti2CCl2, and ANFT composite aerogels. Figure 3It can be seen from (a) that the three broadened diffraction peaks of ANF in XRD are located at 20.5°, 22.8° and 28.6°, corresponding to the (110), (200) and (004) crystal planes of poly(p-phenyleneterephthalamide) (PPTA). For the Ti2CCl2 nanosheets, its lattice parameter was calculated as Its diffraction pattern is consistent with that of the samples prepared by the direct synthesis method in the literature, which also confirms the successful preparation of Ti2CCl2 nanosheets. The chemical components and functional groups of aramid nanofibers (ANF), Ti2CCl2 and ANFT hybrid aerogels were verified by Fourier transform infrared spectroscopy (FTIR). Figure 3 (b) For the ANFT hybrid aerogel, its FTIR spectrum retains the main characteristic peaks of ANF and Ti2CCl2. The ANFT composite aerogel combines the characteristics of Ti2CCl2 and ANF in terms of structure, and the enhancement or change of its physical and chemical properties provides support for its performance in thermal management or other applications. Figure 4 The stress-strain curves and 500-cycle compression performance of the Ti2CCl2 / ANF composite aerogels prepared in Examples 1 to 4 of the present invention are shown to characterize the mechanical properties and fatigue resistance of the composite aerogels. It can be seen from the figure that its ultimate compression performance is 536 KPa. During the loading process of ultimate compression, the obtained stress-strain (σ-ε) curve shows a typical three-stage deformation: (1) Due to the bending of nanofibers, it shows a typical linear elastic region at low strain (ε < 20%). (2) In the plateau region of 20% < ε < 50%, it is related to the elastic buckling of porous materials. (3) A high-strain densification region appears at ε > 50%. When the maximum value of strain increases from 20% to 80%, the maximum stress of the ANF aerogel increases sharply from 35.39 kPa to 536.4 kPa, indicating that the Ti2CCl2 / ANF composite aerogel has strong compressive ability under high-strain conditions. The aerogel was subjected to 1, 100, 200, 300 and 500 cycles of loading within a fixed compression strain range (40%) to evaluate its durability and fatigue performance. The compression stress of the first loading is the highest, and the curve shows a steep shape, indicating that the material has a high elastic recovery ability during the initial deformation. As the number of cycles increases (from Cycle 100 to Cycle 500), the curve gradually flattens, and the compression stress decreases slightly. This indicates that slight plastic deformation occurs during the repeated loading process of the material, or the bearing capacity decreases due to the loss of pore structure. Despite the stress attenuation, after the 300th cycle, the curve change tends to be stable, indicating that the ANF hybrid aerogel has a certain structural stability and durability.

[0118] The introduction of Ti2CCl2 nanosheets effectively realizes the ultrafast photothermal response of the composite aerogel. Figure 5The infrared thermal imaging picture shows the temperature distribution change of the ANF composite aerogel prepared in Example 3 of the present invention under photothermal response, providing the visualization characteristics of the thermal management performance of the material when heated by light. From Figure 5 it can be seen the dynamic process of the material heating up with time under photothermal irradiation. At the initial state, the surface temperature of the aerogel is close to the ambient temperature. At 12.6 seconds, the surface temperature of the aerogel has risen to 105 °C, and the absolute temperature difference from the environment is 78 °C. The rapid temperature rise in a short time indicates that the ANF composite aerogel can efficiently absorb light energy and convert it into heat energy. The ANF composite aerogel has the characteristics of rapid heating, efficient photothermal conversion, and excellent heat insulation performance. In the future, by adjusting the material composition, its photothermal response speed and efficiency can be further optimized to meet the needs of more application scenarios.

[0119] The Ti2CCl2 / ANF nanofiber composite aerogel of the present invention is prepared by a two-step slow-release proton-induced gelation method. First, the carboxyl groups on the PAA molecular chain interact with the deprotonated amide groups in the ANF molecular chain to restore part of the hydrogen bond system, realizing the pre-gelation of ANF. Then, Ti2CCl2 is dispersed into the pre-gelation system of ANF, and the gelation process is further completed using a protonic acid. Finally, through an improved directional freeze-drying technique and solvent replacement method, a composite aerogel with ultrafast photothermal response, low density, and high porosity is obtained. The composite aerogel combines the high thermal stability of Ti2CCl2 and the excellent mechanical properties of ANF, demonstrating excellent photothermal conversion efficiency and rapid temperature response characteristics. The composite aerogel prepared by the two-step slow-release proton-induced gelation method has a low density (0.0425 g / cm 3 )、high porosity (96.38%) and excellent thermal conductivity (0.0592 W / m·K). This material also has excellent flame retardancy and high temperature resistance (530 °C). The composite aerogel has high-efficiency thermal shielding performance, excellent thermal stability and mechanical properties. Its ultrafast photothermal response, low density, high porosity, good flame retardancy and high temperature resistance make this material an ideal thermal management material. The composite aerogel has broad application prospects in the fields of electronic heat dissipation, building energy efficiency, solar energy utilization, military protection, etc., and can meet the growing demand for efficient thermal regulation and thermal protection. It can be used as a thermal insulation material for building exterior walls, roofs or energy systems to provide heat insulation and thermal regulation functions; it can convert heat energy under available light sources to provide temperature or heat energy support, and can be used as an emergency heat source material in clothing, sports equipment or rescue equipment; it can also provide local heating through rapid photothermal response to assist in treating muscle pain or arthritis.

[0120] It should be noted that the embodiments described above are only the preferred embodiments of the present invention. For those of ordinary skill in the art, without departing from the principle of the present invention, several modifications, improvements, and equivalent substitutions can be made to the present invention, and these modifications, improvements, and equivalent substitutions are also considered to fall within the protection scope of the claims of the present invention.

Claims

1. A high temperature resistant, heat insulating and flame retardant poly(p-phenylene terephthalamide) nanofiber composite aerogel, characterized in that: Through a two-step sol-gel method, the carboxyl groups on the synthesized PAA molecular chain were used to induce ANF dispersion and pre-gelation, and the Ti2CCl2 nanosheets synthesized at high temperature solid phase were introduced into the ANF pre-gel system and fully dispersed. Subsequently, the ANF was completely gelled by solvent replacement treatment, and the structurally ordered Ti2CCl2 / ANF composite aerogel was prepared by directional freeze-drying.

2. The high temperature resistant, heat insulating and flame retardant poly(p-phenylene terephthalamide) nanofiber composite aerogel according to claim 1, characterized in that: The components of the poly(p-phenylene terephthalamide) nanofiber composite aerogel are, by weight: 1 part by weight of DMSO dispersion of ANF, 0.2-0.5 parts by weight of DMSO solution of PAA, 0.5-3 parts by weight of Ti2CCl2 nanosheets, and 0.2 parts by weight of aqueous dispersion of protonic acid; wherein the solvent component used for solvent replacement is 20-25 parts by volume of tert-butyl alcohol, 5-15 parts by volume of ethanol, 10-20 parts by volume of silane coupling agent, and 40-65 parts by volume of deionized water.

3. The high temperature resistant, heat insulating and flame retardant poly(p-phenylene terephthalamide) nanofiber composite aerogel according to claim 2, characterized in that: The components of the DMSO dispersion of ANF are 0.5-2 parts by weight of ANF, 0.4-1.6 parts by weight of potassium hydroxide and 96.4-99.1 parts by weight of DMSO; wherein ANF is prepared by low-temperature condensation polymerization of 0.9 parts by weight of p-phenylenediamine, 1.69 parts by weight of terephthaloyl chloride, 1.33 parts by weight of pyridine, 1.12 parts by weight of anhydrous calcium chloride and 61.68 parts by weight of N-methylpyrrolidone.

4. The high temperature resistant, heat insulating and flame retardant poly(p-phenylene terephthalamide) nanofiber composite aerogel according to claim 2, characterized in that: The PAA is prepared by low-temperature condensation polymerization of 4.0 parts by weight of 4,4'-diaminodiphenyl ether, 5.026 parts by weight of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 67.464 parts by weight of N,N-dimethylacetamide.

5. A method for preparing the poly(p-phenylene terephthalamide) nanofiber composite aerogel according to any one of claims 1 to 4, characterized in that: The steps include: Step 1: dissolving 10 parts by weight of anhydrous calcium chloride and pyrrole in a ratio of 1:1.5 in 200 parts by weight of N-methylpyrrolidone, introducing argon, dissolving 1 part by weight of p-phenylenediamine in N-methylpyrrolidone, and lowering the system temperature to below 0°C; dissolving 1.005 parts by weight of terephthaloyl chloride in 10 parts by weight of N-methylpyrrolidone, and adding the mixture dropwise to the reaction system through a constant pressure funnel, and introducing protective gas during the dropwise addition process to avoid heat accumulation generated by the rapid reaction and affecting the reaction; after the Weissenberg effect appears in the reaction system, terminating the reaction and collecting the reaction product to obtain ANF; Step 2: Disperse 0.5-1.5 parts by weight of ANF and 0.5-1 parts by weight of potassium hydroxide in 97.5-198.2 parts by weight of dimethyl sulfoxide (DMSO), and mix at room temperature until completely dissolved to obtain an ANF dispersion with a concentration of 0.5wt.% to 2; 4 parts by weight of 4,4-diaminodiphenyl ether ODA and 68 parts by weight of N,N-dimethylacetamide DMAc were transferred to a three-necked flask, ODA was dispersed in DMAc, and stirred until completely dissolved, and then the temperature of the reaction system was lowered to 0-4°C; 5 parts by weight of 3,3',4,4'-biphenyltetracarboxylic dianhydride BPDA were weighed and added to the three-necked flask in batches, and the reaction was terminated after the Weissenberg effect appeared to obtain a light yellow PAA viscous liquid; Step 3: 2.87 parts by weight of nano-Ti powder as a titanium source, 0.4 parts by weight of graphene nanosheets as a carbon source, and 4.6 parts by weight of TiCl4 are fully mixed under the protection of a nitrogen atmosphere and then sealed in a quartz crucible, and then transferred to a muffle furnace and heated to 950°C within 20 minutes, and kept warm for reaction for 2 hours to obtain a Ti2CCl2 nano intermediate, which is then cooled to room temperature with the furnace and collected for later use; 0.5 parts by weight of tannic acid is ultrasonically dispersed in 20 parts by weight of Tris buffer, and then 1 part by weight of Ti2CCl2 nano intermediate is ultrasonically dispersed and added to the above mixed solution, magnetically stirred for 6 hours, the reaction product is washed with water, and dried to obtain Ti2CCl2 nanosheets; Step 4: 1 part by weight of the ANF dispersion and 0.2-0.5 parts by weight of the PAA solution are fully mixed by a high-speed shearing machine to pre-gel the ANF dispersion; 0.5-3 parts by weight of Ti2CCl2 nanosheets are also uniformly dispersed in the ANF pre-gel system by high-speed shearing, 0.2 parts by weight of 25wt.% acetic acid solution is added to the ANF pre-gel system, and the system is transferred to an oven and heated to 60°C for 30 minutes. After complete gelation, a two-step slow-release proton-induced gel Ti2CCl2 / ANF composite gel is obtained; Step 5: 25-35 parts by volume of tert-butyl alcohol, 10-20 parts by volume of anhydrous ethanol, 5-10 parts by volume of silane coupling agent and 45-60 parts by volume of deionized water are fully mixed; the Ti2CCl2 / ANF composite gel is transferred to the above mixed solution and transferred to an oven, the temperature is increased to 60°C, and the treatment is carried out for 3 hours. After cooling, the Ti2CCl2 / ANF composite hydrogel is repeatedly washed with deionized water to obtain the Ti2CCl2 / ANF composite hydrogel; Step 6: Immerse the homemade copper plate mold in liquid nitrogen for pre-cooling, transfer the Ti2CCl2 / ANF composite hydrogel to the copper plate mold, pre-freeze for 30 minutes, maintain the mold temperature at -30°C, dry the frozen Ti2CCl2 / ANF composite hydrogel, and obtain the two-step sustained-release proton-induced gel Ti2CCl2 / ANF composite aerogel after 30 hours; then anneal the Ti2CCl2 / ANF composite aerogel at 350°C for 1 to 3 hours to obtain a structurally stable Ti2CCl2 / ANF composite aerogel.

6. The method according to claim 5, characterized in that The weight ratio of the titanium source, the carbon source and titanium tetrachloride is 2.87:0.4:4.6, wherein the titanium source includes titanium powder, titanium foil and titanium sheet, and the carbon source includes graphite, graphene, carbon nanotubes and carbon foam.

7. The method according to claim 5, characterized in that The concentration of the ANF dispersion is 0.5-2 wt.%.

8. Use of the poly(p-phenylene terephthalamide) nanofiber composite aerogel according to any one of claims 1 to 4 as a thermal insulation material in a building exterior wall, roof or energy system, characterized in that: Used to provide thermal insulation and heat regulation.

9. Use of the poly(p-phenylene terephthalamide) nanofiber composite aerogel according to any one of claims 1 to 4 as an emergency heat source material in clothing, sports equipment or rescue equipment, characterized in that: The poly(p-phenylene terephthalamide) nanofiber composite aerogel can convert thermal energy under an available light source to provide temperature or thermal energy support.

10. Use of the poly(p-phenylene terephthalamide) nanofiber composite aerogel according to any one of claims 1 to 4 in a thermal therapy device, characterized in that: The poly(p-phenylene terephthalamide) nanofiber composite aerogel provides local heating through rapid photothermal response to assist in the treatment of muscle pain or arthritis.

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