Preparation method of a kind of perception protection function integration heat-accumulating and heat-insulating aerogel fiber and fiber

Abstract

The application provides a preparation method and a fiber of a sensing and protection function integrated heat storage and insulation aerogel fiber, and the method comprises the following steps: step 1, dispersing a flame-retardant functional agent in a polyacrylonitrile solution by shearing-ultrasonic, and preparing a flame-retardant oriented fiber membrane by high-speed air jet spinning combined with directional magnetic guide orientation; step 2, uniformly anchoring heat storage and insulation phase change microspheres on the surface of the flame-retardant oriented fiber obtained in step 1 by ultrasonic atomization-electrostatic spraying, and obtaining a flame-retardant thermal barrier yarn by combining a directional magnetic guide bunching technology; step 3, preparing a core-shell structure crimped fiber by eccentric coaxial phase separation spinning with the flame-retardant thermal barrier yarn as a core layer and thermoelectric nanosheets as an outer layer, and synchronously modifying a precursor sol on the outer layer of the fiber, and combining directional freezing-induced micropore formation to prepare the sensing and protection function integrated heat storage and insulation aerogel fiber. The application has a wide prospect in the fields of extreme environment thermal protection and thermal energy utilization, and provides a method for preventing thermal runaway.

Description

Technical Field

[0001] This invention relates to the field of advanced functional fiber materials that integrate sensing and protection in extreme environments, specifically to a method for preparing a heat-storing aerogel fiber that integrates sensing and protection functions. Background Technology

[0002] Currently, the demand for advanced functional fiber materials for thermal protection is undergoing profound changes in fields such as personal thermal management, industrial safety, emergency rescue, deep-earth engineering, and aerospace. Traditional thermal protection materials mainly focus on passive barrier functions, such as using aerogels, ceramic fibers, and multilayer composite materials to achieve efficient thermal insulation. Although these materials have made significant progress in resisting extreme external thermal environments, their nature remains primarily limited to passive barriers. They cannot perceive the material's own thermal state, structural integrity, and external thermal threats in real time, and it is even more difficult to provide critical information to the control system.

[0003] With increasing environmental complexity and stricter safety standards, thermal protection systems face higher demands. For example, in lithium-ion battery thermal runaway protection, in addition to insulation to slow heat spread, early in-situ detection of abnormal temperature rises or thermal shock locations in individual battery cells is required. This provides early warning to the battery management system, enabling a shift from passive protection to active intervention. In the field of emergency rescue protective equipment, materials need to possess excellent flame retardancy, heat insulation, and breathability. Real-time monitoring of the flame temperature and heat flux density on the outer surface of clothing, as well as the temperature and humidity microclimate inside the clothing, and even identification of fabric damage, will greatly enhance firefighters' environmental awareness and survival probability. In aerospace thermal protection systems, which withstand extreme thermal loads, embedding distributed sensing capabilities to provide real-time feedback on the temperature field, strain field, and ablation state of different parts of the material is crucial for aircraft structural health monitoring and safety assessment.

[0004] However, achieving integrated sensing and protection functions still faces significant technical challenges. Existing technologies often employ the method of attaching independent temperature or strain sensors to the surface of traditional protective materials. However, such external sensors can easily compromise the integrity of the protective structure, while also increasing system complexity, weight, and the risk of failure. Therefore, developing protective materials with sensing capabilities has become a key path to overcome these technological bottlenecks.

[0005] Developing a thermal insulation aerogel fiber that integrates sensing and protection functions will break through the limitations of traditional protective materials that only possess passive protection capabilities, and promote the development of thermal protection systems towards intelligence, lightweighting, and integration. While providing excellent physical protection, this material can sense environmental and its own critical status information in real time, providing data support for active thermal management, early safety warnings, and accurate damage assessment. It represents a crucial technological direction and core breakthrough for addressing extreme thermal safety challenges. Summary of the Invention

[0006] Objective of the Invention: The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a method and fiber for preparing an integrated sensing and protective heat-storing aerogel fiber. The method involves dispersing a flame-retardant functional agent in a polyacrylonitrile solution using shearing and ultrasonication, followed by high-speed air-jet spinning combined with directional magnetic orientation to prepare a flame-retardant oriented fiber membrane. Then, heat-storing phase change microspheres are uniformly anchored onto the surface of the flame-retardant oriented fiber obtained in step S1 using ultrasonic atomization and electrostatic spraying. Combined with directional magnetic bundling technology, a flame-retardant thermal barrier yarn is obtained. Finally, using the flame-retardant thermal barrier yarn as the core layer and thermoelectric nanosheets as the outer layer, a core-shell structured crimped fiber is prepared by eccentric coaxial phase separation spinning. Simultaneously, a precursor sol is modified on the outer layer of the fiber, and combined with directional cryogenic induction of micropore formation, an integrated sensing and protective heat-storing aerogel fiber is prepared.

[0007] The method includes the following steps:

[0008] Step 1: The flame retardant functional agent is dispersed in a polyacrylonitrile solution by shear-ultrasound, and a flame retardant oriented fiber membrane is prepared by high-speed air-jet spinning combined with directional magnetic orientation.

[0009] Step 2: By ultrasonic atomization-electrostatic spraying, heat-storing phase change microspheres are uniformly anchored on the surface of the flame-retardant oriented fiber membrane obtained in Step 1. Combined with directional magnetic induction bundling technology, flame-retardant thermal barrier yarn is obtained.

[0010] Step 3: Using flame-retardant thermal barrier yarn as the core layer and thermoelectric nanosheets as the outer layer, core-shell structured crimped fibers are prepared by eccentric coaxial phase separation spinning. Simultaneously, precursor sol is modified on the outer layer of the fiber, and combined with directional freezing to induce micropore formation, an integrated sensing and protective heat-insulating aerogel fiber is prepared.

[0011] Preferably, in step 1, the concentration of polyacrylonitrile in the mixed solution is 0.80~2.00 mol / L, and the flame retardant is one or more of organic halogen flame retardants, organic phosphorus flame retardants, organic nitrogen flame retardants, and inorganic flame retardants, with a mass fraction ratio of flame retardant to polyacrylonitrile of 0.1:1~0.5:1.

[0012] Preferably, in step 1, the solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, sulfolane, ethyl nitrate, thiocyanate, perchlorate, zinc chloride, lithium bromide, and concentrated nitric acid, and the mass fraction ratio of the solvent to polyacrylonitrile is 8.4:1 to 16.7:1.

[0013] Preferably, in step 1, a solution blowing spinning process is carried out with an airflow of 200~800Pa, the solution flow rate is set to 5~60mL / h, and a magnetic field is used at the same time. The magnetic field direction is perpendicular to the spinning and drawing direction, and the intensity is 0.4~0.7T. The average diameter of the resulting flame-retardant oriented fiber is 200~400nm.

[0014] Preferably, in step 2, the heat storage and insulation phase change microspheres are one or more of paraffin@silicon dioxide, n-tetracosane@silicon dioxide, n-tetracosane@calcium carbonate, and n-tetracosane@ferric oxide, and the thickness of the heat storage and insulation phase change microlayer obtained by spraying is 1~50µm (the heat storage and insulation phase change microspheres form a heat storage and insulation phase change microlayer on the fiber surface).

[0015] Preferably, in step 2, the vibration frequency of the ultrasonic atomization-electrostatic spraying is set to 15~120kHz, the electrostatic voltage is 1~60kV, the magnetic field strength of the directional magnetic induction bundle is 0.4~0.7T, and the magnetic field direction is perpendicular to the spinning and drawing direction.

[0016] Preferably, in step 3, the thermoelectric nanosheets are one or more of graphene, chalcogenides, black phosphorus and MXene, the precursor sol is one of aramid sol, polyimide sol, silica sol, graphene sol and cellulose sol, and the porosity of the aerogel fibers is 83%~99%.

[0017] Preferably, in step 3, the core-shell structure layer thickness ratio of the flame-retardant thermal barrier yarn (core layer) and the thermoelectric nanosheet (shell layer) is 2:1 to 1:2, and the core-shell structure layer thickness ratio of the thermoelectric nanosheet (core layer) and the precursor sol (shell layer) is 2:1 to 1:2.

[0018] Preferably, in step 3, the coagulation bath in the eccentric coaxial phase separation spinning technology is a mixture of acid solution and deionized water. The acid solution is one or more of formic acid, acetic acid, hydrochloric acid, nitric acid, chlorosulfonic acid, phosphoric acid, and sulfuric acid. The H2O of the acid solution in the coagulation bath is... + The concentration is 0~4 mol / L, and the spinning draw ratio is 1~4.

[0019] In another aspect, the present invention also provides fibers prepared according to the method, wherein the limiting oxygen index is 20.9-40% and the room temperature thermal conductivity is 0.021-0.033 W / m. -1 K -1 At 25℃, the high-temperature thermal conductivity is 0.079~0.092 W / m². -1 K -1With a thermoelectric figure of merit of 1.07~1.23 and a Seebeck coefficient of 4.3~9.0μV / K at 300℃, it has excellent thermal insulation, flame retardancy and thermoelectric properties, and realizes integrated sensing and protection functions. It can be applied in personal thermal management in extreme environments, battery thermal runaway protection, emergency rescue protection equipment, deep earth engineering, aerospace thermal protection and thermal energy utilization.

[0020] The beneficial effects of this invention are as follows:

[0021] (1) This invention uses directional magnetic orientation applied simultaneously with high-speed air jetting to prepare flame-retardant oriented fiber membranes. Compared with electrospinning, the fiber membrane is fluffy and porous, with slow air propagation speed, and has certain heat insulation properties. At the same time, the mechanical properties of the oriented fibers are enhanced. (2) Ultrasonic atomization-electrostatic spraying makes the heat-storing phase change microspheres more uniformly anchored on the fiber membrane, forming a continuous and dense thermal barrier layer. (3) Aerogel fibers obtained by directional freezing during eccentric coaxial phase separation spinning have higher strength along the axial orientation compared with aerogel fibers synthesized by traditional wet spinning. At the same time, the inner fiber acts as a skeleton, supporting the outer aerogel to a certain extent and enhancing its strength. (4) The aerogel network structure constructed in this invention has abundant micro-nano pores with a porosity of 83%~99% and a room temperature thermal conductivity of 0.021~0.033 W / m. -1 K -1 At 25℃, the high-temperature thermal conductivity is 0.079~0.092 W / m. -1 K -1 @300℃, with excellent heat insulation and warmth preservation performance, and the addition of flame retardant functional agent makes the fiber have flame retardant properties, providing a new idea for the research of thermal management and thermal protection; (5) This invention uses thermoelectric nanosheets to construct a conductive network structure, continuously monitor the temperature and output signals to realize early sensing, providing a method for preventing thermal runaway.

[0022] The technical solution proposed in this invention enables the fiber to not only possess excellent mechanical, thermal insulation, and flame retardant properties, achieving a synergistic effect of thermal insulation and flame retardancy, but also to integrate sensing and protective functions. The fiber has a tensile strength of 21.9~44.3 MPa, a limiting oxygen index of 20.9%~40%, and a room temperature thermal conductivity of 0.021~0.033 W / m². -1 K -1 At 25℃, the high-temperature thermal conductivity is 0.079~0.092 W / m. -1 K -1 With a thermoelectric figure of merit of 1.07~1.23 and a Seebeck coefficient of 4.3~9.0 μV / K at 300℃, it is a high-performance sensing and protection fusion material with broad application prospects. Attached Figure Description

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0024] Figure 1 This is a schematic diagram of the method flow of the present invention.

[0025] Figure 2 This is a scanning electron microscope image of the MPP / PAN oriented fiber membrane in Example 1.

[0026] Figure 3 This is a scanning electron microscope image of the heat storage and insulation phase change microspheres in Example 1.

[0027] Figure 4 This is a scanning electron microscope image of the MPP / PAN@Mxene@ANF aerogel fiber in Example 1. Detailed Implementation

[0028] like Figure 1 As shown, the present invention provides a method for preparing an integrated heat-storing and insulating aerogel fiber with sensing and protective functions, comprising the following steps.

[0029] Step S11, Preparation of flame-retardant oriented fiber membrane: Polyacrylonitrile is uniformly dissolved in N,N-dimethylformamide by shear-ultrasound, and then melamine polyphosphate is uniformly dispersed in polyacrylonitrile solution by shear-ultrasound and placed in a syringe (the concentration of polyacrylonitrile is 1.78 mol / L, and the concentration of melamine polyphosphate is 0.53 mol / L). While high-speed air jetting, directional magnetic orientation is achieved (the magnetic field direction is perpendicular to the spinning and drawing direction, the magnetic field strength is 0.4T, the solution jet spinning process is carried out with a compressed air flow of 200Pa, and the solution flow rate is set to 5mL / h) to prepare MPP / PAN oriented fiber membrane with an average fiber diameter of 346nm.

[0030] Step S12, preparation of flame-retardant thermal barrier yarn: dissolve docosane@ferric oxide phase change microspheres in deionized water, and then uniformly anchor them onto flame-retardant oriented fibers by ultrasonic atomization-electrostatic spraying (vibration frequency of 60kHz, electrostatic voltage of 30kV). Then, prepare MPP / PAN yarn by directional magnetic induction bundling technology (magnetic field direction is perpendicular to the spinning and drawing direction, magnetic field strength is 0.4T).

[0031] Step S13, preparing integrated sensing and protective thermal insulation aerogel fiber: MPP / PAN yarn is passed through the inner layer of a coaxial spinning needle of model 22G and placed into a coagulation bath of 5000mL acetic acid and 4500mL deionized water to obtain 10% acetic acid concentration. The yarn is connected to the roller through a yarn guide. At the same time, Mxene solution is connected to the outer layer spinneret of the coaxial spinning needle of model 20G. Under the thrust of the pusher, the solution is squeezed into the coagulation bath with a draw ratio of 1.5 and wound onto the roller along with the yarn to obtain MPP / PAN@Mxene hydrogel fiber. Then, the MPP / PAN@Mxene hydrogel fibers were removed from the roller, passed through the inner layer of a 20G coaxial spinning needle, and placed in a 5000mL coagulation bath (10% acetic acid concentration) prepared by mixing 500mL of acetic acid with 4500mL of deionized water. The fibers were then connected to the roller via a yarn guide. Simultaneously, the aramid sol was connected to the outer layer of an 18G coaxial spinning needle and extruded into the coagulation bath under the action of a pusher. The draw ratio was 1.5, and the fibers were wound onto the roller along with the yarn to obtain MPP / PAN@Mxene@ANF hydrogel fibers. The MPP / PAN@Mxene@ANF hydrogel fibers were then removed from the roller and placed in deionized water for 24 hours, followed by exchange in a 50% tert-butanol solution for 24 hours. Finally, the MPP / PAN@Mxene@ANF hydrogel fibers were removed from the 50% tert-butanol solution and directionally frozen for 24 hours. The sample was then placed in a freeze dryer, with the cold trap temperature controlled at -40℃ and the vacuum degree at 55Pa. After 24 hours, MPP / PAN@Mxene@ANF aerogel fibers were obtained.

[0032] Embodiment 2 of the present invention provides an integrated sensing and protective heat-storing aerogel fiber and its preparation method, including the following steps.

[0033] Step S21, Preparation of flame-retardant oriented fiber membrane: Polyacrylonitrile is uniformly dissolved in N,N-dimethylformamide by shear-ultrasound, and then melamine polyphosphate is uniformly dispersed in the polyacrylonitrile solution by shear-ultrasound and placed in a syringe (the concentration of polyacrylonitrile is 1.94 mol / L, and the concentration of melamine polyphosphate is 0.19 mol / L). While high-speed air jetting, directional magnetic orientation is achieved (the magnetic field direction is perpendicular to the spinning and drawing direction, the magnetic field strength is 0.5T, and the solution jet spinning process is carried out with a compressed air flow of 500Pa, and the solution flow rate is set to 15mL / h) to prepare an MPP / PAN oriented fiber membrane with an average fiber diameter of 300nm.

[0034] Step S22, preparation of flame-retardant thermal barrier yarn: dissolve docosane@ferric oxide phase change microspheres in deionized water, and then uniformly anchor them onto flame-retardant oriented fibers by ultrasonic atomization-electrostatic spraying (vibration frequency of 120kHz, electrostatic voltage of 60kV). Then, prepare MPP / PAN yarn by directional magnetic induction bundling technology (magnetic field direction is perpendicular to the spinning and drawing direction, magnetic field strength is 0.5T).

[0035] Step S23, preparing integrated sensing and protective thermal insulation aerogel fiber: MPP / PAN yarn is passed through the inner layer of a coaxial spinning needle of model 22G and placed into a coagulation bath of 5000mL acetic acid and 4500mL deionized water to obtain 10% acetic acid concentration. The yarn is connected to the roller through a yarn guide. At the same time, Mxene solution is connected to the outer layer spinneret of the coaxial spinning needle of model 20G and squeezed into the coagulation bath under the action of a pusher. The draw ratio is 2, and the yarn is wound onto the roller to obtain MPP / PAN@Mxene hydrogel fiber. Then, the MPP / PAN@Mxene hydrogel fibers were removed from the roller, passed through the inner layer of a 20G coaxial spinning needle, and placed in a 5000mL coagulation bath (10% acetic acid concentration) prepared by mixing 500mL of acetic acid with 4500mL of deionized water. The fibers were then connected to the roller via a yarn guide. Simultaneously, the aramid sol was connected to the outer layer of an 18G coaxial spinning needle and extruded into the coagulation bath under the thrust of a pusher. The draw ratio was 2, and the fibers were wound onto the roller along with the yarn to obtain MPP / PAN@Mxene@ANF hydrogel fibers. The MPP / PAN@Mxene@ANF hydrogel fibers were then removed from the roller and placed in deionized water for 24 hours, followed by solvent exchange in a 50% tert-butanol solution for 24 hours. Finally, the MPP / PAN@Mxene@ANF hydrogel fibers were removed from the 50% tert-butanol solution and directionally frozen for 24 hours. The sample was then placed in a freeze dryer, with the cold trap temperature controlled at -40℃ and the vacuum degree at 55Pa. After 24 hours, MPP / PAN@Mxene@ANF aerogel fibers were obtained.

[0036] Embodiment 3 of the present invention provides an integrated sensing and protective heat-storing aerogel fiber and its preparation method, including the following steps.

[0037] Step S31, Preparation of flame-retardant oriented fiber membrane: Polyacrylonitrile is uniformly dissolved in N,N-dimethylformamide by shear-ultrasound, and then melamine polyphosphate is uniformly dispersed in the polyacrylonitrile solution by shear-ultrasound and placed in a syringe (the concentration of polyacrylonitrile is 1.86 mol / L, and the concentration of melamine polyphosphate is 0.37 mol / L). Oriented by high-speed air jetting and directional magnetic permeation (the magnetic field direction is perpendicular to the spinning and drawing direction, the magnetic field strength is 0.6 T, the solution jet spinning process is carried out with a compressed air flow of 650 Pa, and the solution flow rate is set to 25 mL / h) to prepare an MPP / PAN oriented fiber membrane with an average fiber diameter of 333 nm.

[0038] Step S32, preparation of flame-retardant thermal barrier yarn: dissolve n-dodecane@ferric oxide phase change microspheres in deionized water, and then uniformly anchor them onto flame-retardant oriented fibers by ultrasonic atomization-electrostatic spraying (vibration frequency of 60kHz, electrostatic voltage of 30kV). Then, prepare MPP / PAN yarn by directional magnetic induction bundling technology (magnetic field direction is perpendicular to the spinning and drawing direction, magnetic field strength is 0.6T).

[0039] Step S33, Preparation of integrated sensing and protective thermal insulation aerogel fiber: Flame-retardant thermal barrier yarn is passed through the inner layer of a coaxial spinning needle of model 22G and placed into a coagulation bath of 5000mL acetic acid and 4500mL deionized water to obtain 10% acetic acid concentration. The yarn is connected to the roller through a yarn guide. At the same time, Mxene solution is connected to the outer layer spinneret of the coaxial spinning needle of model 20G and squeezed into the coagulation bath under the action of a pusher. The draw ratio is 2, and the yarn is wound onto the roller to obtain MPP / PAN@Mxene hydrogel fiber. Then, the MPP / PAN@Mxene hydrogel fibers were removed from the roller, passed through the inner layer of a 20G coaxial spinning needle, and placed in a 5000mL coagulation bath (10% acetic acid concentration) prepared by mixing 500mL of acetic acid with 4500mL of deionized water. The fibers were then connected to the roller via a yarn guide. Simultaneously, the aramid sol was connected to the outer layer of an 18G coaxial spinning needle and extruded into the coagulation bath under the thrust of a pusher. The draw ratio was 2, and the fibers were wound onto the roller along with the yarn to obtain MPP / PAN@Mxene@ANF hydrogel fibers. The MPP / PAN@Mxene@ANF hydrogel fibers were then removed from the roller and placed in deionized water for 24 hours, followed by exchange in a 50% tert-butanol solution for 24 hours. Finally, the MPP / PAN@Mxene@ANF hydrogel fibers were removed from the 50% tert-butanol solution and directionally frozen for 24 hours. The sample was then placed in a freeze dryer, with the cold trap temperature controlled at -40℃ and the vacuum degree at 55Pa. After 24 hours, MPP / PAN@Mxene@ANF aerogel fibers were obtained.

[0040] Embodiment 4 of the present invention provides an integrated sensing and protective heat-storing aerogel fiber and its preparation method, including the following steps.

[0041] Step S41, Preparation of flame-retardant oriented fiber membrane: Polyacrylonitrile is uniformly dissolved in N,N-dimethylformamide by shear-ultrasound, and then melamine polyphosphate is uniformly dispersed in the polyacrylonitrile solution by shear-ultrasound and placed in a syringe (the concentration of polyacrylonitrile is 0.80 mol / L, and the concentration of melamine polyphosphate is 0.99 mol / L). Oriented by high-speed air jetting and directional magnetic permeation (the magnetic field direction is perpendicular to the spinning and drawing direction, the magnetic field strength is 0.7T, the solution jet spinning process is carried out with a compressed air flow of 800 Pa, and the solution flow rate is set to 60 mL / h) to prepare an MPP / PAN oriented fiber membrane with an average fiber diameter of 400 nm.

[0042] Step S42, preparing flame-retardant thermal barrier yarn: dissolve docosane@ferric oxide phase change microspheres in deionized water, and then uniformly anchor them onto flame-retardant oriented fibers by ultrasonic atomization-electrostatic spraying (vibration frequency of 15kHz, electrostatic voltage of 1kV). Then, prepare MPP / PAN yarn by directional magnetic induction bundling technology (magnetic field direction is perpendicular to the spinning and drawing direction, magnetic field strength is 0.7T).

[0043] Step S43, preparing integrated sensing and protective thermal insulation aerogel fiber: The flame-retardant thermal barrier yarn is passed through the inner layer of the coaxial spinning needle (model 22G) and placed into a coagulation bath with a concentration of 10% acetic acid (500mL) obtained by mixing acetic acid with 4500mL of deionized water. The yarn is then connected to the roller via a yarn guide. At the same time, the Mxene solution is connected to the outer layer spinneret of the coaxial spinning needle (model 20G) and extruded into the coagulation bath under the action of a pusher. The draw ratio is 4, and the yarn is wound onto the roller to obtain MPP / PAN@Mxene hydrogel fiber. Then, the MPP / PAN@Mxene hydrogel fibers were removed from the roller, passed through the inner layer of a 20G coaxial spinning needle, and placed in a 5000mL coagulation bath (10% acetic acid concentration) prepared by mixing 500mL of acetic acid with 4500mL of deionized water. The fibers were then connected to the roller via a yarn guide. Simultaneously, the aramid sol was connected to the outer layer of an 18G coaxial spinning needle and extruded into the coagulation bath under the thrust of a pusher. The draw ratio was 4, and the fibers were wound onto the roller along with the yarn to obtain MPP / PAN@Mxene@ANF hydrogel fibers. The MPP / PAN@Mxene@ANF hydrogel fibers were then removed from the roller and placed in deionized water for 24 hours, followed by exchange in a 50% tert-butanol solution for 24 hours. Finally, the MPP / PAN@Mxene@ANF hydrogel fibers were removed from the 50% tert-butanol solution and directionally frozen for 24 hours. The sample was then placed in a freeze dryer, with the cold trap temperature controlled at -40℃ and the vacuum degree at 55Pa. After 24 hours, MPP / PAN@Mxene@ANF aerogel fibers were obtained.

[0044] Comparative Example 1 of this invention provides a high-strength, high-elasticity, flame-retardant thermal barrier aerogel fiber and its preparation method, which basically adopts the method of preparing integrated sensing and protective thermal insulation aerogel fiber in Example 1. The difference is that the aerogel fiber in this example is a pure protective material, not an integrated sensing and protective material. Specifically: Polyacrylonitrile is uniformly dissolved in N,N-dimethylformamide by shear-ultrasound, and then melamine polyphosphate is uniformly dispersed in the polyacrylonitrile solution by shear-ultrasound and placed in a syringe (the concentration of polyacrylonitrile is 1.78 mol / L, and the concentration of melamine polyphosphate is 0.53 mol / L). Simultaneously, directional magnetic orientation is achieved by high-speed air jetting (the magnetic field direction is perpendicular to the spinning and drawing direction, the magnetic field strength is 0.4T, and the solution jet spinning process is carried out with a compressed air flow of 200 Pa, and the solution flow rate is set to 5 mL / h), to prepare an MPP / PAN oriented fiber membrane with an average fiber diameter of 346 nm. Docosane@Fe3O4 phase change microspheres were dissolved in deionized water and uniformly anchored onto MPP / PAN oriented fibers via ultrasonic atomization-electrostatic spraying (vibration frequency 60kHz, electrostatic voltage 30kV). MPP / PAN yarn was then prepared using directional magnetic induction bundling technology (magnetic field direction perpendicular to the spinning and drawing direction, magnetic field strength 0.4 T). The MPP / PAN yarn was passed through the inner layer of a coaxial spinning needle (model 22G) and placed in a coagulation bath containing 500mL of acetic acid and 4500mL of deionized water (500mL, 10% acetic acid concentration). The yarn was then connected to a roller via a yarn guide. Simultaneously, aramid sol was connected to the outer spinneret of the coaxial spinning needle (model 20G) and extruded into the coagulation bath under the action of a pusher. The draw ratio was 1.5, and the yarn was wound onto the roller to obtain MPP / PAN@ANF hydrogel fibers. Then, the MPP / PAN@ANF hydrogel fibers were removed from the roller and placed in deionized water for 24 hours, followed by exchange in a 50% tert-butanol solution for 24 hours. Finally, the MPP / PAN@ANF hydrogel fibers were removed from the 50% tert-butanol solution and directionally frozen for 24 hours. The frozen sample was then placed in a freeze dryer with the cold trap temperature controlled at -40°C and the vacuum degree at 55 Pa. After 24 hours, MPP / PAN@ANF aerogel fibers were obtained.

[0045] Comparative Example 2 of this invention provides a high-strength, high-elasticity thermal barrier sensing aerogel fiber and its preparation method, which basically adopts the method of Example 1 to prepare an integrated sensing and protective thermal insulation aerogel fiber. The difference is that this example does not use flame-retardant additives to modify the fiber membrane. Specifically, polyacrylonitrile is uniformly dissolved in N,N-dimethylformamide with ultrasonic assistance and placed in a syringe (the concentration of polyacrylonitrile is 2.00 mol / L). Simultaneously, directional magnetic orientation is achieved through high-speed air jetting (the magnetic field direction is perpendicular to the spinning and drawing direction, the magnetic field strength is 0.4 T, and the solution jet spinning process is performed with a compressed air flow of 200 Pa, and the solution flow rate is set to 5 mL / h), to prepare a PAN-oriented fiber membrane with a fiber diameter of 200 nm. Docosane@Fe3O4 phase change microspheres were dissolved in deionized water and uniformly anchored onto oriented fibers via ultrasonic atomization-electrostatic spraying (vibration frequency 60kHz, electrostatic voltage 30kV). PAN yarn was then prepared using directional magnetic induction bundling technology (magnetic field direction perpendicular to the spinning and drawing direction, magnetic field strength 0.4T). The thermal barrier yarn was passed through the inner layer of a coaxial spinning needle (model 22G) and placed in a coagulation bath containing 500mL of acetic acid and 4500mL of deionized water (500mL, 10% acetic acid concentration). The yarn was connected to a roller via a yarn guide. Simultaneously, an Mxene solution was connected to the outer spinneret of the coaxial spinning needle (model 20G). The solution was extruded into the coagulation bath under the action of a pusher, with a draw ratio of 1.5, and wound onto the roller along with the yarn to obtain MPP / PAN@Mxene hydrogel fibers. Then, the MPP / PAN@Mxene hydrogel fibers were removed from the roller, passed through the inner layer of a 20G coaxial spinning needle, and placed in a 5000mL coagulation bath (10% acetic acid concentration) prepared by mixing 500mL acetic acid with 4500mL deionized water. The mixture was then connected to the roller via a yarn guide. Simultaneously, the aramid sol was connected to the outer layer spinneret of the 18G coaxial spinning needle. Under the thrust of a pusher, the aramid sol was extruded into the coagulation bath at a draw ratio of 1.5 and wound onto the roller along with the yarn to obtain MPP / PAN@Mxene@ANF hydrogel fibers. The MPP / PAN@Mxene@ANF hydrogel fibers were then removed from the roller and placed in deionized water for 24 hours, followed by 24 hours of exchange in a 50% tert-butanol solution. Finally, the MPP / PAN@Mxene@ANF hydrogel fibers were removed from the 50% tert-butanol solution and directionally frozen for 24 hours. The sample was then placed in a freeze dryer, with the cold trap temperature controlled at -40℃ and the vacuum degree at 55 Pa. After 24 hours, MPP / PAN@Mxene@ANF aerogel fibers were obtained.

[0046] Comparative Example 3 of this invention provides an aerogel fiber and its preparation method, which basically adopts the method of Comparative Example 1 to prepare aerogel fibers. The difference is that the aerogel fiber in this example is an aramid aerogel fiber, with a non-coaxial structure, no thermoelectric nanosheets for sensing, and no flame-retardant thermal barrier yarn reinforcement. Specifically, aramid sol is connected to a spinneret of model 18G, and extruded into a coagulation bath under the thrust of a pusher, and wound along the yarn onto a roller to obtain the desired hydrogel fiber. Then, the hydrogel fiber is removed from the roller and placed in deionized water for 24 hours, with the deionized water being replaced every 8 hours. The deionized water is then replaced with a 50% tert-butanol solution, and solvent exchange continues for 12 hours. Finally, the hydrogel fiber is removed from the 50% tert-butanol solution and directionally frozen for 24 hours. The frozen sample is placed in a freeze dryer, with the cold trap temperature controlled at -40℃ and the vacuum degree at 55 Pa, and aramid aerogel fibers are obtained after 24 hours.

[0047] The structural characterization and performance testing are as follows:

[0048] Scanning electron microscopy observation: MPP / PAN oriented fiber membranes were observed using a field emission scanning electron microscope (model SU8220, HITACHI). Figure 2 ), n-dodecane@Fe3O4 phase change microspheres ( Figure 2 ) and the microstructure of MPP / PAN@Mxene@ANF aerogel fibers ( Figure 4 ).

[0049] Mechanical property testing: The tensile properties of the composite material were tested using a universal tensile testing machine (model 5900) from Instron, USA. At least three parallel samples were tested in each group, and the average value of the results was taken.

[0050] Room temperature thermal conductivity test: The thermal conductivity of the composite material was tested according to the national standard GB / T 34336-2017 "Nanoporous aerogel composite thermal insulation products". At least 3 parallel samples were tested in each group, and the average value of the results was taken.

[0051] High-temperature thermal conductivity test: The material was heated to 300°C using a protective hot plate method and the high-temperature thermal conductivity of the composite material was tested. Referring to the report by Schenk et al. [Adv. Funct. Mater. 35, no.43(2025): 2506814.], at least 3 parallel samples were tested in each group, and the average value of the results was taken.

[0052] Limiting oxygen index test: The limiting oxygen index of composite materials is tested according to the international standard ISO 4589-2:2017 "Plastics - Determination of flammability by oxygen index method - Part 2: Test at room temperature". At least 15 parallel samples are tested in each group, and the average value is taken as the result.

[0053] Seebeck coefficient test: The Seebeck coefficient of the composite material is measured using a thermoelectric performance tester. At least three parallel samples are tested in each group, and the average value of the results is taken.

[0054] Thermoelectric figure of merit (ZT) test: Taking into account the material’s electrical conductivity (σ), Seebeck coefficient (α), thermal conductivity (κ), and temperature (T), the calculation formula is ZT = (α²Tσ) / κ. At least 3 parallel samples are tested in each group, and the average value of the results is taken.

[0055] The experimental results are as follows:

[0056] like Figure 2 As shown, the MPP / PAN oriented fiber membrane synthesized in Example 1 has an average fiber diameter of 346 nm. Figure 3 Scanning electron microscope image of n-dodecane@ferric oxide phase transition microspheres, showing typical core-shell structure features, with an average diameter of 1613 nm. Figure 4 The image shows a scanning electron microscope image of MPP / PAN@Mxene@ANF aerogel fibers prepared by shear-induced orientation spinning technology. The aerogel fibers are oriented and arranged, and the n-dodecane@ferric oxide phase change microspheres are uniformly distributed inside the MPP / PAN@ANF aerogel fibers.

[0057] Table 1 compares the test results of tensile strength, elastic modulus, limiting oxygen index, room temperature thermal conductivity, high temperature thermal conductivity, Seebeck coefficient, and thermoelectric figure of merit of the aerogel fibers obtained in the examples and comparative examples.

[0058] Table 1. Test results of mechanical properties, flame retardant and thermal insulation properties, and thermoelectric properties of aerogel fibers.

[0059]

[0060] Compared to Comparative Examples 1 and 3, Examples 1-4 exhibit a higher thermoelectric figure of merit (Figure of Good Character) and Seebeck coefficient (Figure of Seebeck coefficient) of 1.07-1.23, and a higher Figure of Good Character (Figure of Good Character) of 4.3-9.0 μV / K. This is because the introduction of thermoelectric nanosheets enables thermoelectric conversion, thereby sensing temperature changes. Compared to Comparative Examples 1 and 3, Examples 1-4 demonstrate higher tensile strength (21.9-44.3 MPa) and elastic modulus (589-667 MPa), exhibiting superior mechanical properties. This is due to the enhanced strength resulting from axial orientation, while the support of the core yarn further strengthens the fiber. Compared to Comparative Examples 2 and 3, Examples 1-4 have a limiting oxygen index (LOI) of 20.9%-40%, with the synergistic effect of the flame retardant and aramid fibers contributing to their excellent flame-retardant properties. The room temperature thermal conductivity of Examples 1-4 and Comparative Examples 1-3 is 0.021-0.033 W / m². -1 K -1@25℃, and the high-temperature thermal conductivity of the fiber is 0.079~0.092Wm. -1 K -1 At 300℃, the nanoscale pores of aerogel fibers firmly encapsulate air into a thermal insulation cavity, preventing it from moving freely and transferring heat, thus inhibiting heat convection and heat conduction. At the same time, the hollow structure of the heat-storing and insulating phase change microspheres can also inhibit heat conduction, giving it good thermal insulation performance and forming a highly efficient and dense thermal barrier.

[0061] This demonstrates that the technical solution proposed in this invention enables MPP / PAN@Mxene@ANF aerogel fibers to possess excellent heat insulation and flame retardant effects, thermoelectric conversion, and sensing performance, thereby achieving integrated sensing and protection functions.

[0062] This invention provides a method for preparing an integrated sensing and protective thermal insulation aerogel fiber and the fiber itself. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A method for preparing an integrated sensing and protective thermal insulation aerogel fiber, characterized in that, Includes the following steps: Step 1: The flame retardant functional agent is dispersed in a polyacrylonitrile solution by shear-ultrasound, and a flame retardant oriented fiber membrane is prepared by high-speed air-jet spinning combined with directional magnetic orientation. Step 2: By ultrasonic atomization-electrostatic spraying, heat-storing phase change microspheres are uniformly anchored on the surface of the flame-retardant oriented fiber membrane obtained in Step 1. Combined with directional magnetic induction bundling technology, flame-retardant thermal barrier yarn is obtained. Step 3: Using flame-retardant thermal barrier yarn as the core layer and thermoelectric nanosheets as the outer layer, core-shell structured crimped fibers are prepared by eccentric coaxial phase separation spinning. Simultaneously, precursor sol is modified on the outer layer of the fiber, and combined with directional freezing to induce micropore formation, an integrated sensing and protective heat-insulating aerogel fiber is prepared.

2. The method as described in claim 1, characterized in that, In step 1, the concentration of polyacrylonitrile in the mixed solution is 0.80~2.00mol / L, and the flame retardant is one or more of the following: organic halogen flame retardant, organic phosphorus flame retardant, organic nitrogen flame retardant, and inorganic flame retardant. The mass fraction ratio of the flame retardant to polyacrylonitrile is 0.1:1~0.5:

1.

3. The method as described in claim 1, characterized in that, In step 1, the solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, sulfolane, ethyl nitrate, thiocyanate, perchlorate, zinc chloride, lithium bromide, and concentrated nitric acid, and the mass fraction ratio of the solvent to polyacrylonitrile is 8.4:1 to 16.7:

1.

4. The method as described in claim 1, characterized in that, In step 1, a solution blowing spinning process is carried out with an airflow of 200~800Pa, and the solution flow rate is set to 5~60mL / h. At the same time, a magnetic field is applied, with the direction of the magnetic field perpendicular to the spinning and drawing direction and the intensity of 0.4~0.7T. The average diameter of the resulting flame-retardant oriented fiber is 200~400nm.

5. The method as described in claim 1, characterized in that, In step 2, the heat storage and insulation phase change microspheres are one or more of the following: paraffin@silica, n-tetracosane@silica, n-tetracosane@calcium carbonate, and n-tetracosane@ferric oxide. The thickness of the heat storage and insulation phase change microlayer obtained by spraying is 1~50µm.

6. The method as described in claim 1, characterized in that, In step 2, the vibration frequency of the ultrasonic atomization-electrostatic spraying is set to 15~120kHz, the electrostatic voltage is 1~60kV, the magnetic field strength of the directional magnetic induction bundle is 0.4~0.7T, and the magnetic field direction is perpendicular to the spinning and drawing direction.

7. The method as described in claim 1, characterized in that, In step 3, the thermoelectric nanosheets are one or more of graphene, chalcogenides, black phosphorus and MXene, the precursor sol is one of aramid sol, polyimide sol, silica sol, graphene sol and cellulose sol, and the porosity of the aerogel fiber is 83%~99%.

8. The method as described in claim 1, characterized in that, In step 3, the core-shell structure layer thickness ratio of the flame-retardant thermal barrier yarn and the thermoelectric nanosheet is 2:1 to 1:2, and the core-shell structure layer thickness ratio of the thermoelectric nanosheet and the precursor sol is 2:1 to 1:

2.

9. The method as described in claim 1, characterized in that, In step 3, the coagulation bath in the eccentric coaxial phase separation spinning technology is a mixture of acid solution and deionized water. The acid solution is one or more of formic acid, acetic acid, hydrochloric acid, nitric acid, chlorosulfonic acid, phosphoric acid, and sulfuric acid. The H₂ content of the acid solution in the coagulation bath is... + The concentration is 0~4 mol / L, and the spinning draw ratio is 1~4.

10. The fiber prepared by the method according to any one of claims 1 to 9, characterized in that, The fiber has a limiting oxygen index of 20.9-40% and a room temperature thermal conductivity of 0.021-0.033 W / m². -1 K -1 At 25℃, the high-temperature thermal conductivity is 0.079~0.092 W / m². -1 K -1 At 300℃, the thermoelectric figure of merit is 1.07~1.23, and the Seebeck coefficient is 4.3~9.0μV / K.

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