Aerogel fiber with adjustable proportion of solid core and porous shell, and preparation method and application thereof
By adjusting the ratio of solid core to porous shell in aerogel fibers, and using time-dependent swelling and freeze-drying methods to prepare composite structures, the problem of poor mechanical properties of aerogel fibers is solved, achieving flexible performance control and renewability, making it suitable for electromagnetic shielding and thermal conduction/insulation applications.
Patent Information
- Application Number
- CN202311826048.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-27
- Publication Date
- 2026-05-15
- Estimated Expiration
- 2043-12-27
AI Technical Summary
The porous framework structure of existing aerogel fibers results in poor mechanical properties, making them difficult to use in extreme environments. Furthermore, the microstructure is difficult to control, affecting their thermal conductivity, insulation, electromagnetic shielding, and electromagnetic wave reflection/absorption properties.
By controlling the timed swelling time of aerogel fibers and adjusting the ratio of solid core to porous shell, a solid core-porous shell composite structure was prepared using timed swelling and freeze-drying methods, thus achieving precise control of the microstructure.
The mechanical properties of aerogel fibers have been improved, enabling flexible switching between thermal conductivity/insulation and electromagnetic shielding properties. They are also renewable and customizable to meet the needs of different application scenarios.
Smart Images
Figure CN117779229B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of aerogel fiber composite materials technology, specifically to an aerogel fiber with an adjustable solid core-porous shell ratio, its preparation method, and its application. Background Technology
[0002] Aerogel fiber, as a novel fiber material, possesses numerous advantages such as high porosity, large specific surface area, and low density. Its porous structure effectively restricts internal air convection, heat radiation, and heat conduction, resulting in fabrics with excellent thermal insulation properties. Furthermore, the porous structure of aerogel fiber can effectively optimize the impedance matching characteristics between the fiber surface and electromagnetic waves, and it is often used in the development of absorption-oriented electromagnetic shielding fabrics.
[0003] However, the loose, porous skeleton structure inside aerogel fibers leads to the deterioration of their mechanical properties. Fabrics woven from aerogel fibers are mostly unable to withstand large-scale twisting, bending, and stretching deformations.
[0004] Currently, a common technical approach is to enhance the mechanical strength of the porous skeleton of aerogel fibers, thereby improving the overall strength of the aerogel fiber. However, the strength improvement of a loose porous skeleton is limited, and therefore cannot adequately meet the needs of people for the use of fibers or textiles in extreme environments.
[0005] Currently, those skilled in the art have introduced continuous solid polyimide long fibers into polyimide aerogel fibers using a rubber tube forming method. These fibers achieve an impressive tensile strength of 150 MPa over a wide temperature range and exhibit excellent thermal insulation properties. However, this strategy of using macroscopically sized long fibers to enhance the mechanical properties of aerogel fibers makes it difficult to achieve precise control over the microscopic structure within the aerogel fibers, particularly the accurate adjustment of the ratio of solid cores to porous shells.
[0006] Furthermore, changes in the internal microstructure of aerogel fibers directly affect various fiber properties, such as thermal insulation, thermal management, electrical conductivity, electromagnetic shielding, and electromagnetic wave reflection / absorption characteristics. However, due to the generally small diameter of aerogel fiber materials, typically sub-millimeter, micrometer, or even nanometer scale, it is currently not possible to precisely control the internal microstructure of aerogel fibers at a small scale. Summary of the Invention
[0007] In view of the above problems, the present invention provides an aerogel fiber with an adjustable solid core-porous shell ratio, a preparation method and application, which realizes precise control of the solid core-porous shell ratio. Composite aerogel fibers with different solid core-porous shell ratios exhibit significantly different thermal conductivity / insulation properties, electromagnetic shielding properties and electromagnetic wave reflection / absorption characteristics, thereby greatly improving the mechanical properties of composite aerogel fibers. Moreover, the aerogel fibers also have renewability and reproducibility.
[0008] This invention provides an aerogel fiber with an adjustable solid core-porous shell ratio. The aerogel fiber includes a solid core and a porous shell. By controlling the timed swelling time of the aerogel fiber, the ratio of the solid core to the porous shell can be arbitrarily adjusted; the ratio of the solid core to the porous shell is 1-3:3-1. This invention also provides a method for preparing the aerogel fiber with an adjustable solid core-porous shell ratio, comprising:
[0009] Step 1: Prepare opaque precursor spinning solution: Weigh an appropriate amount of polyvinyl alcohol and dissolve it to obtain a polyvinyl alcohol solution;
[0010] The polyvinyl alcohol solution is mixed with a multi-walled carbon nanotube aqueous dispersion to obtain a polyvinyl alcohol-carbon nanotube mixture. Acrylamide and an acrylamide crosslinking agent are added to the polyvinyl alcohol-carbon nanotube mixture to obtain an opaque precursor spinning solution.
[0011] Preferably, the specific steps for obtaining the opaque precursor spinning solution in step 1 include:
[0012] Weigh out polyvinyl alcohol and add it to deionized water. Heat and stir to dissolve the polyvinyl alcohol to obtain a polyvinyl alcohol solution. Continue to heat the polyvinyl alcohol solution to evaporate half of the volume of deionized water. After cooling to room temperature, a high-viscosity aqueous dispersion of polyvinyl alcohol is obtained.
[0013] Weigh out the multi-walled carbon nanotube aqueous dispersion, slowly add the multi-walled carbon nanotube aqueous dispersion to the polyvinyl alcohol high viscosity aqueous dispersion, while stirring vigorously, and after mixing evenly, obtain a mixed dispersion.
[0014] Acrylamide and acrylamide crosslinking agent were added to the mixed dispersion, and the mixture was stirred continuously at room temperature to obtain an opaque precursor spinning solution.
[0015] Preferably, the mass ratio of polyvinyl alcohol to acrylamide is 2-10:5-10; and the volume of deionized water is 20 mL.
[0016] Furthermore, the mass of the polyvinyl alcohol is 1-5g. Preferably, the heating temperature is 85-95°C, and the volume of the high-viscosity polyvinyl alcohol aqueous dispersion is 10mL.
[0017] Furthermore, the heating temperature is 90°C.
[0018] The multi-walled carbon nanotube aqueous dispersion is a 10-15 wt% multi-walled carbon nanotube aqueous dispersion; the volume of the multi-walled carbon nanotube aqueous dispersion is 5-15 mL.
[0019] Furthermore, the multi-walled carbon nanotube aqueous dispersion is a 13wt% multi-walled carbon nanotube aqueous dispersion.
[0020] Preferably, the stirring intensity of the vigorous stirring is 1600 rpm;
[0021] Preferably, the ratio of acrylamide to acrylamide crosslinking agent is 250-500:3-6;
[0022] Preferably, the acrylamide crosslinking agent comprises: N,N-methylenebisacrylamide;
[0023] Furthermore, the mass of the acrylamide is 2.5-5g; the mass of the N,N-methylenebisacrylamide is 0.003-0.006g.
[0024] Preferably, the continuous stirring time is 12 hours.
[0025] Step 2: Preparation of solid structure fibers: The opaque precursor spinning solution is placed in a coagulation bath and soaked to obtain hydrogel fibers; the hydrogel fibers are then processed to obtain solid structure fibers.
[0026] Preferably, the specific steps for obtaining the solid structural fiber include:
[0027] Prepare a coagulation solution and place the coagulation solution in a coagulation bath; inject the opaque precursor spinning solution into the rotating coagulation bath through a pump-controlled syringe, soak, and obtain fully cross-linked hydrogel fibers.
[0028] The fully cross-linked hydrogel fibers are washed and dried with deionized water to obtain solid structure fibers, which are then collected by a rotating collection shaft.
[0029] Furthermore, the specific steps for preparing the coagulant include:
[0030] Weigh out N'N'N'N-tetramethylethylenediamine and ammonium persulfate and mix them to obtain a coagulant.
[0031] Furthermore, the volume ratio of N'N'N'N-tetramethylethylenediamine to ammonium persulfate is 1:1;
[0032] Furthermore, the N'N'N'N-tetramethylethylenediamine has a volume of 20-30 mL; the ammonium persulfate has a volume of 20-30 mL.
[0033] Furthermore, the soaking time is 30 seconds.
[0034] Furthermore, the pump-controlled injector includes a 16-20G needle and a syringe body with an inner diameter of 15mm, and an injection speed of 0.25-0.75mm·min. -1 ;like Figure 1 As shown in (a);
[0035] Step 3: The solid structure fiber is treated by timed swelling and freeze-drying to synthesize aerogel fiber with an adjustable ratio of solid core to porous shell.
[0036] Preferably, the specific steps for obtaining aerogel fibers with an adjustable ratio of solid core to porous shell include:
[0037] The solid fiber structure was directly immersed in deionized water for timed swelling. Figure 1 (b);
[0038] After the swelling time is reached, the solid fiber structure is quickly removed from the deionized water and its surface moisture is dried with filter paper to obtain the swollen fiber.
[0039] The swollen fibers were immersed in liquid nitrogen and then rapidly frozen to obtain rapidly frozen fibers.
[0040] The frozen fibers are dried in a freeze dryer at -80℃ for 24-72 hours to form aerogel fibers with an adjustable ratio of solid core to porous shell.
[0041] Preferably, the freezing time is 10s-15s, and the freezing temperature is -196℃ at normal pressure.
[0042] Preferably, the swelling time is 0-300s. As the swelling time increases, the proportion of solid cores in the fiber gradually decreases, while the proportion of porous shells gradually increases.
[0043] It is understandable that when the timed swelling time is 0s, that is, no timed swelling is performed, and non-porous solid aerogel fibers are obtained;
[0044] When the swelling time is 300s, the fibers are fully swollen, resulting in a fully porous aerogel fiber without a solid core.
[0045] Furthermore, the time for the timed swelling is 30-90 seconds.
[0046] In one embodiment of the present invention, the aerogel fiber with an adjustable ratio of solid core to porous shell is renewable and reproducible.
[0047] One embodiment of the present invention further includes a method for achieving the renewability and reproducible customizability using aerogel fibers with an adjustable ratio of solid core to porous shell, the specific steps of which include:
[0048] Regeneration of aerogel fibers: Aerogel fibers with an adjustable ratio of solid core to porous shell are selected and immersed in deionized water. The aerogel fibers rapidly absorb water, forming fully swollen hydrogel fibers. After heat drying, the fully swollen hydrogel fibers form dry, dense, solid structure fibers. These dry, dense solid structure fibers are then immersed in deionized water, with precise control over the immersion time. After rapid freezing and freeze-drying, aerogel fibers with an adjustable ratio of solid core to porous shell are obtained again. Figure 6 As shown in (a);
[0049] Customization of aerogel fibers: Select any solid core and porous shell ratio of aerogel fibers that can be adjusted and immerse them in deionized water to obtain fully swollen hydrogel fibers. After the fully swollen hydrogel fibers are heat-dried, a customized swelling time is set, and the fibers are immersed in deionized water according to the customized swelling time. The immersion time in deionized water is precisely controlled. After rapid freezing and freeze-drying, customized aerogel fibers with an adjustable solid core and porous shell ratio are obtained.
[0050] In another embodiment of the present invention, the regeneration process of the aerogel fiber specifically involves: the aerogel fiber rapidly absorbing water to form a fully swollen hydrogel fiber; after the fully swollen hydrogel fiber is heat-dried, a dry and dense solid structure fiber is formed; the dry and dense solid structure fiber is then immersed in deionized water for a precisely controlled immersion time of 30 seconds; after rapid freezing and freeze-drying, an aerogel fiber with an adjustable ratio of solid core to porous shell is obtained again, defined as composite aerogel fiber PPAF-30s. Figure 6 As shown in (a);
[0051] In another embodiment of the present invention, the regeneration process of aerogel fibers specifically involves: selecting aerogel fibers with an adjustable ratio of solid core to porous shell and immersing them in deionized water. The aerogel fibers rapidly absorb water, forming fully swollen hydrogel fibers. After heat drying, the fully swollen hydrogel fibers are formed into dry and dense solid structure fibers. These dry and dense solid structure fibers are then immersed in deionized water for a precise immersion time of 60 seconds. After rapid freezing and freeze-drying, aerogel fibers with an adjustable ratio of solid core to porous shell are obtained again, defined as composite aerogel fiber PPAF-60s. Figure 6 As shown in (a);
[0052] In another embodiment of the present invention, the regeneration process of aerogel fibers specifically involves: selecting aerogel fibers with an adjustable ratio of solid core to porous shell and immersing them in deionized water. The aerogel fibers rapidly absorb water, forming fully swollen hydrogel fibers. After heat drying, the fully swollen hydrogel fibers are formed into dry and dense solid structure fibers. These dry and dense solid structure fibers are then immersed in deionized water for a precise immersion time of 90 seconds. After rapid freezing and freeze-drying, aerogel fibers with an adjustable ratio of solid core to porous shell are obtained again, defined as composite aerogel fiber PPAF-90s. Figure 6 As shown in (a).
[0053] In another embodiment of the present invention, the customization of the aerogel fiber is specifically as follows: taking the composite aerogel fiber PPAF-30s as an example, the composite aerogel fiber PPAF-30s is soaked in deionized water. The composite aerogel fiber PPAF-30s quickly absorbs water and forms a fully swollen hydrogel fiber. After the fully swollen hydrogel fiber is heat-dried, a dry and dense solid structure fiber is formed. The dry and dense solid structure fiber is then soaked in deionized water. The customized swelling time is 60s, and the soaking time in water is precisely controlled to be 60s. After rapid freezing and freeze-drying treatment, the composite aerogel fiber PPAF-60s is obtained. Figure 6 (b)
[0054] This invention rapidly transfers fully swollen hydrogel fibers to liquid nitrogen for quick freezing, preventing further water penetration into the inner core layer of the fiber. After freeze-drying, the wet hydrogel fiber shell is transformed into a porous aerogel shell, while the solid, non-porous inner core remains unchanged, thus enabling the aerogel fiber to be regenerated.
[0055] The present invention also provides the application of aerogel fibers with an adjustable ratio of solid core to porous shell.
[0056] Preferably, the aerogel fiber with an adjustable ratio of solid core to porous shell is used in electromagnetic shielding and in the thermal conductivity / insulation of fiber fabrics, such as... Figure 4 .
[0057] The aerogel fibers prepared by this invention can be woven into fiber fabrics, and their thermal conductivity / thermal insulation properties can be freely switched. It can be understood that if strong thermal insulation performance is required, the proportion of porous shells can be adjusted to be as high as possible, and if good thermal conductivity of the fiber fabric is required, the proportion of solid cores of the aerogel fibers can be made as high as possible.
[0058] The electromagnetic wave reflection / absorption characteristics of the aerogel fibers prepared by this invention can be switched arbitrarily when woven into fiber fabrics. It can be understood that if the fiber fabric needs to absorb more electromagnetic waves, the proportion of porous shells in the aerogel fibers can be increased; if the fiber fabric needs to strongly reflect electromagnetic waves, the proportion of solid cores in the aerogel fibers can be increased.
[0059] The technical solution of this invention uses time-induced swelling and freeze-drying to obtain composite aerogel fibers with an adjustable ratio of solid core to porous shell. A solid core layer is introduced into the aerogel fiber to construct a solid core-porous shell aerogel fiber with a porous shell layer covering the solid core layer. This not only retains its inherent aerogel properties but also significantly improves its mechanical strength, achieving precise control of the internal microstructure of the composite aerogel fiber.
[0060] The aerogel fiber with a solid core-porous shell composite structure prepared by this invention can achieve different properties by adjusting the proportion of the core and shell, giving it strong repeatability and flexibility in performance control, and meeting the needs of people in different application scenarios in actual use.
[0061] The technical solution of this invention uses the time-swelling method to prepare aerogel fibers with an adjustable ratio of solid core to porous shell. The aerogel fibers have a solid core and a porous shell with the same composition and no obvious dividing interface. The tensile mechanical properties can be adjusted to a large extent. A higher proportion of solid core results in stronger mechanical properties.
[0062] Compared with the prior art, the present invention has at least the following beneficial effects:
[0063] (1) The aerogel fiber prepared by the present invention has an adjustable ratio of solid core and porous shell. The two parts, "core" and "shell", are completely identical and tightly bound. In actual use, there will be no phase separation. The ratio of solid core to porous shell in the aerogel fiber can also be adjusted to achieve the control of the internal microstructure of the fiber.
[0064] (2) By changing the time of swelling, the present invention regulates the microstructure inside the aerogel fiber. Different microstructures exhibit different thermal insulation performance, electromagnetic shielding performance, and electromagnetic wave reflection / absorption characteristics.
[0065] (3) The aerogel fiber prepared by the present invention with adjustable ratio of solid core and porous shell has renewability and repeatability. Renewability ensures durability in actual use, and repeatability shows its potential to change its performance according to actual use needs. Attached Figure Description
[0066] The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention.
[0067] Figure 1 This is a schematic diagram of the preparation process of aerogel fibers with an adjustable ratio of solid core to porous shell prepared in Examples 1-3 of the present invention.
[0068] Figure 2 This is a schematic diagram of cross-sectional scanning electron microscope images of three different solid core and porous shell ratios of aerogel fibers prepared in Examples 1-3 of the present invention.
[0069] Figure 3 This is a schematic diagram of the stress-strain curves of the aerogel fibers with adjustable ratio of solid core to porous shell prepared in Examples 1-3 of the present invention.
[0070] Figure 4 (a) is a schematic diagram of infrared photographs of three fabrics woven from aerogel fibers with adjustable ratios of solid core and porous shell prepared in Examples 1-3 of the present invention.
[0071] Figure 4 (b) is a schematic diagram of the thermal conductivity of three fabrics woven from aerogel fibers with three different ratios of solid core and porous shell prepared in Examples 1-3 of the present invention.
[0072] Figure 4 (c) is a schematic diagram of the temperature-time curves of three fabrics woven from aerogel fibers with three different ratios of solid core and porous shell prepared in Examples 1-3 of the present invention.
[0073] Figure 5 (a) is a schematic diagram of the electromagnetic shielding efficiency curves of three fabrics of aerogel fibers with three different ratios of solid core and porous shell prepared in Examples 1-3 of the present invention.
[0074] Figure 5(b) is a schematic diagram of the average electromagnetic shielding efficiency and power absorption coefficient “A”, reflection coefficient “R” and transmission coefficient “T” of three fabrics of aerogel fibers with three different proportions of solid core and porous shell prepared in Examples 1-3 of the present invention.
[0075] Figure 6 (a) is a schematic diagram of the renewability of aerogel fibers with adjustable ratio of solid core to porous shell prepared in Examples 4-6 of the present invention.
[0076] Figure 6 (b) is a schematic diagram of the repeatable customization process of aerogel fibers with adjustable ratio of solid core to porous shell prepared in Examples 4-6 of the present invention. Detailed Implementation
[0077] To better understand the above-described objectives, features, and advantages of the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other. Furthermore, the present invention can be implemented in other ways different from those described herein; therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.
[0078] A specific embodiment of the present invention, such as Figure 1-6 This invention discloses an aerogel fiber with an adjustable solid core-porous shell ratio, its preparation method, and its applications. To illustrate the effectiveness of the method proposed in this invention, a specific embodiment is provided below to describe the above technical solution in detail. The specific implementation steps are as follows:
[0079] Example 1:
[0080] Preparation of opaque precursor spinning solution: 2g of polyvinyl alcohol (PVA) was added to 20mL of deionized water, heated and stirred at 90℃ to dissolve the PVA, and excess water was evaporated. After cooling to room temperature, 10mL of high-viscosity PVA aqueous dispersion was finally obtained.
[0081] Take 10 mL of 13 wt.% multi-walled carbon nanotubes (MWCNTs) aqueous dispersion and slowly add it to a high-viscosity polyvinyl alcohol (PVA) aqueous dispersion, while stirring vigorously at 1600 rpm until the mixture is homogeneous and a mixed dispersion is obtained.
[0082] Add 3.5g of acrylamide (AM) and 0.003g of N'N-methylenebisacrylamide (MBA) to the mixed dispersion, stir at room temperature for 12h, and the opaque precursor spinning solution is prepared.
[0083] Preparation of solid structure fibers: such as Figure 1 As shown in (a);
[0084] Add 25 mL of N'N'N'N-tetramethylethylenediamine (TMEDA) and 25 mL of ammonium persulfate (APS) aqueous solution (2 mol / L). -1 The mixture is stirred to obtain a coagulated liquid; the coagulated liquid is then placed in a coagulation bath.
[0085] The opaque precursor spinning solution was spun at a rate of 0.5 mm / min. -1 The propellant is extruded from the needle of the pump-controlled injector into a rotating coagulation bath, where it is immersed for 30 seconds to produce fully cross-linked hydrogel fibers; the inner diameter of the needle of the pump-controlled injector is 840 μm, and the inner diameter of the syringe tube is 15 mm.
[0086] After rinsing and drying, the hydrogel fibers are obtained as solid structure fibers, which are then collected by a rotating collection shaft.
[0087] Solid structure fibers are directly immersed in deionized water, and the swelling time is precisely controlled to be 30 seconds. After the swelling time is completed, the fibers are quickly removed from the deionized water and the surface moisture is absorbed with filter paper to obtain swollen fibers.
[0088] The swollen fibers were rapidly immersed in liquid nitrogen for quick freezing to obtain the quick-frozen fibers.
[0089] The frozen fibers were dried in a freeze dryer at -80°C for 48 hours to finally form composite aerogel fiber PPAF-30s;
[0090] The solid core to porous shell ratio of the composite aerogel fiber PPAF-30s is 3:1; the composite aerogel fiber PPAF-30s is woven into PPAF-30s fiber fabric through a textile process.
[0091] After the above steps, the thermal insulation performance of the PPAF-30s fiber fabric obtained in this embodiment is as follows: Figure 4 As shown.
[0092] Example 2
[0093] The swelling time in step 3 of implementation 1 is set to 60s, and other processing methods remain unchanged, finally obtaining composite aerogel fiber PPAF-60s, wherein the ratio of solid core to porous shell in composite aerogel fiber PPAF-60s is 1:1; composite aerogel fiber PPAF-60s is woven through textile process to obtain PPAF-60s fiber fabric.
[0094] After the above steps, the thermal insulation performance of the PPAF-60s fiber fabric obtained in this embodiment is as follows: Figure 4 As shown.
[0095] Example 3
[0096] The swelling time in step 3 of implementation 1 is set to 90s, and other processing methods remain unchanged, finally obtaining composite aerogel fiber PPAF-90s, in which the ratio of solid core to porous shell in composite aerogel fiber PPAF-90s is 1:3.
[0097] PPAF-90s composite aerogel fiber is woven into PPAF-90s fiber fabric through a textile process.
[0098] After the above steps, the thermal insulation performance of the PPAF-90s fiber fabric obtained in this embodiment is as follows: Figure 4 As shown.
[0099] Example 4
[0100] Regeneration of composite aerogel fiber PPAF-30s: The composite aerogel fiber PPAF-30s obtained in Example 1 was immersed in deionized water. The composite aerogel fiber PPAF-30s rapidly absorbed water, forming a fully swollen hydrogel fiber. After heat drying, the hydrogel fiber formed a dry, dense, solid fiber structure. The dry, dense, solid fiber structure was then immersed in deionized water for a precisely controlled immersion time of 30 seconds, thus obtaining composite aerogel fiber PPAF-30s again. Figure 6 As shown in (a);
[0101] Customization of composite aerogel fiber PPAF-30s: The composite aerogel fiber PPAF-30s in Example 1 was repeatedly customized to obtain composite aerogel fibers PPAF-60s or PPAF-90s in Example 2 or 3. The soaking time in deionized water during the regeneration process of composite aerogel fiber PPAF-30s was changed to 60s or 90s to obtain hydrogel fibers with different degrees of swelling. After rapid freezing and freeze drying, composite aerogel fibers PPAF-60s or PPAF-90s were obtained, realizing the repeatability of aerogel fiber customization. Figure 6 (b)
[0102] Example 5
[0103] Regeneration of composite aerogel fiber PPAF-60s: The composite aerogel fiber PPAF-60s obtained in Example 2 was immersed in deionized water. The composite aerogel fiber PPAF-60s rapidly absorbed water, forming a fully swollen hydrogel fiber. After heat drying, the hydrogel fiber formed a dry, dense, solid fiber structure. The dry, dense, solid fiber structure was then immersed in deionized water for a precisely controlled immersion time of 60 seconds, thus obtaining composite aerogel fiber PPAF-60s again. Figure 6 As shown in (a);
[0104] Customization of composite aerogel fiber PPAF-60s: The composite aerogel fiber PPAF-60s of Example 2 was repeatedly customized to obtain the composite aerogel fiber PPAF-30s or PPAF-90s of Example 1 or 3. The soaking time of composite aerogel fiber PPAF-60s in deionized water was changed to 30 or 90s to obtain hydrogel fibers with different degrees of swelling. After rapid freezing and freeze drying, composite aerogel fiber PPAF-30s or PPAF-90s was obtained, realizing the repeatability of fiber customization. Figure 6 (b)
[0105] Example 6
[0106] Regeneration of composite aerogel fiber PPAF-90s: The composite aerogel fiber PPAF-90s obtained in Example 3 was immersed in deionized water. The composite aerogel fiber PPAF-90s rapidly absorbed water, forming a fully swollen hydrogel fiber. After heat drying, the hydrogel fiber formed a dry, dense, solid structure fiber. The dry, dense, solid structure fiber was then immersed in deionized water for a precisely controlled immersion time of 90 seconds, thus obtaining composite aerogel fiber PPAF-90s again. Figure 6 As shown in (a);
[0107] Customization of composite aerogel fiber PPAF-90s: The composite aerogel fiber PPAF-90s of Example 3 was repeatedly customized to obtain the composite aerogel fiber PPAF-30s or PPAF-60s of Example 1 or 2. The soaking time of composite aerogel fiber PPAF-90s in deionized water was changed to 30 or 60s to obtain hydrogel fibers with different degrees of swelling. After rapid freezing and freeze drying, composite aerogel fiber PPAF-30s or PPAF-60s was obtained, realizing the repeatability of fiber customization. Figure 6 (b)
[0108] Following the above steps, the internal microstructures of the composite aerogel fibers PPAF-30s, PPAF-60s, and PPAF-90s in Examples 1, 2, and 3 were obtained as follows: Figure 2 As shown; Figure 2 The image shows cross-sectional scanning electron microscope (SEM) images of three different fibers, revealing significant differences in the internal structure of the aerogel fibers, exhibiting highly varying core-shell ratios. With increasing swelling time, the proportion of solid core structures gradually decreases, while the proportion of porous shell structures gradually increases, and the fiber diameter gradually increases. This demonstrates precise control over the internal microstructure of the aerogel fibers.
[0109] After the above steps, the tensile strength test results of composite aerogel fibers PPAF-30s, PPAF-60s, and PPAF-90s in Examples 1, 2, and 3 are as follows: Figure 3 As shown, with the extension of swelling time, the proportion of solid cores in the composite aerogel fiber decreases, its tensile stress gradually decreases, and its strain gradually increases. The higher the proportion of solid cores, the better the mechanical properties of the aerogel fiber.
[0110] After the above steps, the thermal insulation performance of the PPAF-30s fiber fabric, PPAF-60s fiber fabric, and PPAF-90s fiber fabric obtained in Examples 1, 2, and 3 is as follows: Figure 4 As shown, there are significant differences in the thermal insulation performance of PPAF-30s fiber fabric, PPAF-60s fiber fabric and PPAF-90s fiber fabric (the temperature of the planar heat source is 200℃). With the extension of swelling time, the proportion of porous shell structure increases, its thermal conductivity gradually decreases, the stable plateau temperature gradually decreases and the heating rate gradually slows down, thus achieving the regulation of thermal insulation performance.
[0111] The electromagnetic shielding performance of composite aerogel fibers PPAF-30s, PPAF-60s, and PPAF-90s is as follows: Figure 5 As shown, Figure 5 In (a, b), the electromagnetic shielding efficiency (SE) of the three fibers first increases and then decreases with the increase of the proportion of porous shell structure in the aerogel fiber, with PPAF-60s showing the highest electromagnetic shielding efficiency. Figure 5 In (b), as the proportion of porous shell structure in the aerogel fiber increases, its power absorption coefficient "A" increases significantly, while its power reflection coefficient "R" decreases considerably. This indicates that the fabric's absorption capacity for electromagnetic waves gradually increases, while its reflection capacity gradually decreases. The electromagnetic shielding mechanism changes from reflection-dominant to absorption-dominant, which is more conducive to reducing secondary electromagnetic pollution and exhibits "green" electromagnetic shielding characteristics. This allows for the regulation of electromagnetic shielding performance and electromagnetic wave reflection / absorption characteristics.
[0112] Composite aerogel fibers PPAF-30s, PPAF-60s, and PPAF-90s possess renewable and reproducible customizability, such as... Figure 6As shown, since one of the main components of this aerogel fiber is polyacrylamide (PAM), it rapidly absorbs water when soaked in water, forming a fully swollen hydrogel fiber. After heat drying, this hydrogel fiber forms a dense, non-porous solid fiber. Then, this dried, non-porous solid fiber is soaked in water again. Because the fiber absorbs water from the outside in, by precisely controlling the soaking time, fibers with the same degree of swelling as before can be obtained, with a wet hydrogel shell on the outside and a solid, non-porous, dry core on the inside. Finally, it is rapidly transferred to liquid nitrogen for quick-freezing to prevent further water penetration into the inner core layer. After freeze-drying, the wet hydrogel shell transforms into a porous aerogel shell, while the inner solid, non-porous core layer remains unchanged, ultimately resulting in the regeneration of the aerogel fiber. Figure 6 (a)).
[0113] For reproducible customization, by appropriately extending or shortening the soaking time during fiber regeneration, fibers with different degrees of swelling can be obtained. After rapid freezing and freeze-drying, aerogel fibers with core-shell composite structures of different proportions of solid cores and porous shells are finally obtained, achieving reproducible customization of fibers. Figure 6 (b)).
[0114] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for preparing aerogel fibers with an adjustable solid core-porous shell ratio, characterized in that, include: Step 1: Prepare opaque precursor spinning solution: Weigh an appropriate amount of polyvinyl alcohol and dissolve it to obtain a polyvinyl alcohol solution; The polyvinyl alcohol solution was mixed with a multi-walled carbon nanotube aqueous dispersion to obtain a polyvinyl alcohol-carbon nanotube mixture. Acrylamide and an acrylamide crosslinking agent were added to the polyvinyl alcohol-carbon nanotube mixture to obtain an opaque precursor spinning solution. Step 2: Preparation of solid structure fibers: Immerse the opaque precursor spinning solution in a coagulation bath to obtain hydrogel fibers; process the hydrogel fibers to obtain solid structure fibers. Step 3: The solid structure fiber is treated with time-dependent swelling and freeze-drying methods to obtain aerogel fiber with an adjustable ratio of solid core to porous shell. Specific steps include: The solid fiber structure was directly immersed in deionized water for timed swelling. After the swelling time is reached, the solid fiber structure is removed from the deionized water, and the surface moisture is dried to obtain the swollen fiber. The swollen fibers were immersed in liquid nitrogen and then rapidly frozen to obtain rapidly frozen fibers. The frozen fibers are dried in a freeze dryer at -100~-80℃ for 24-72 hours to form aerogel fibers with an adjustable ratio of solid core to porous shell. The swelling time is 30-300 seconds.
2. The preparation method according to claim 1, characterized in that, The specific steps for obtaining the opaque precursor spinning solution described in step 1 include: Weigh out polyvinyl alcohol and add it to deionized water. Heat and stir to dissolve the polyvinyl alcohol to obtain a polyvinyl alcohol solution. Continue to heat the polyvinyl alcohol solution to evaporate some of the deionized water. After cooling to room temperature, obtain a polyvinyl alcohol aqueous dispersion. Weigh out the multi-walled carbon nanotube aqueous dispersion, slowly add the multi-walled carbon nanotube aqueous dispersion to the polyvinyl alcohol aqueous dispersion, and stir vigorously until the mixture is homogeneous to obtain a mixed dispersion. Acrylamide and acrylamide crosslinking agent were added to the mixed dispersion, and the mixture was stirred continuously at room temperature to obtain an opaque precursor spinning solution.
3. The preparation method according to claim 2, characterized in that, The mass ratio of polyvinyl alcohol to acrylamide to acrylamide crosslinking agent is 50-250: 125-250: 1.5-3.
4. The preparation method according to claim 2, characterized in that, The acrylamide crosslinking agent includes: N,N-methylenebisacrylamide.
5. The preparation method according to claim 2, characterized in that, The multi-walled carbon nanotube aqueous dispersion is a 10-15 wt% multi-walled carbon nanotube aqueous dispersion. The volume of the multi-walled carbon nanotube aqueous dispersion is 5-15 mL.
6. The preparation method according to claim 1, characterized in that, The specific steps for obtaining the solid structural fiber include: Prepare a coagulation solution and place the coagulation solution in a coagulation bath; inject the opaque precursor spinning solution into the rotating coagulation bath through a pump-controlled syringe to immerse it and obtain fully cross-linked hydrogel fibers. The fully cross-linked hydrogel fibers are washed and dried with deionized water to obtain solid structure fibers, which are then collected by a rotating collection shaft.