A conductive electromagnetic ceramic nanofiber aerogel and its preparation method and application

Abstract

The present invention discloses a conductive electromagnetic ceramic nanofiber aerogel, a preparation method thereof and an application thereof. The preparation method comprises the following steps: mixing an aqueous solution of polyethylene oxide and tetraethyl orthosilicate to prepare precursor nanofibers; curing, pyrolyzing and cooling the precursor nanofibers, and uniformly dispersing them in an aqueous phase to obtain an aqueous dispersion of SiO2 nanofibers; mixing the aqueous dispersion of SiO2 nanofibers, an aqueous dispersion of graphene oxide and ZIF-67 powder uniformly, and then performing liquid nitrogen freezing treatment; freeze-drying the product after the liquid nitrogen freezing treatment and annealing it in an inert atmosphere to obtain a conductive electromagnetic ceramic nanofiber aerogel. The ultra-light, biomimetic porous, conductive and magnetic ceramic nanofiber aerogel provided by the present invention utilizes the strong binding points of graphene with renewable flexible SiO2 nanofibers and magnetic components to construct an interconnected highly porous aerogel with good mechanical elasticity.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials, and particularly relates to a conductive and magnetic ceramic nanofiber aerogel and a preparation method and application thereof. Background Art

[0002] The statements herein merely provide background art related to the present invention and do not necessarily constitute prior art.

[0003] Advances in electronic communication technologies and the complexity of operating environments have led to an increased demand for multifunctional devices with excellent comprehensive performance, including higher requirements for thermal management and protection against electromagnetic radiation and interference. To address these challenges, it has become crucial to develop integrated structural materials with characteristics such as light weight, high mechanical strength, efficient heat insulation, and effective electromagnetic wave absorption performance. Among them, ceramic aerogels have attracted much attention due to their low density, low thermal conductivity, and excellent chemical / thermal stability. These characteristics make them suitable for functional applications in harsh environments. For example, silica (SiO 2 ) aerogel particles prepared by a one-pot method exhibit a significantly low thermal conductivity of 14.4 mW·m -1 ·K -1 , which makes them promising materials for reducing carbon emissions resulting from heating and cooling demands. However, different from elastic and compressible components such as polymers, nanocarbon, and metal nanowires, the inherent brittleness and stiffness of ceramics pose significant challenges in the scalable preparation of lightweight and strong ceramic aerogels and their multifunctional applications.

[0004] Efforts to address the brittleness of ceramic aerogels have mainly focused on constructing reinforced ceramic networks using continuous ceramic nanofibers. Recently, ceramic aerogels composed of SiO 2 nanofibers with a large aspect ratio, silicon carbide (SiC) nanofibers, or crystalline metal oxide nanofibers have shown extraordinary elasticity and compressibility. SiO 2 nanofiber aerogels have received great attention due to their high porosity, ultra-low density, large specific surface area, chemical stability, and high temperature resistance, making them suitable for thermal insulation applications. However, the point-to-point contact between fibers in SiO 2 nanofiber aerogels makes them prone to collapse or fatigue failure under high stress conditions. To solve this problem, polymers such as polyacrylonitrile, poly(alkoxysilane), poly(vinyl alkoxysiloxane), and polyrotaxane have been widely used to improve the mechanical properties of ceramic aerogels. These polymers form bonds with Si-O-Si, strengthening the connection between SiO 2 fibers and effectively reducing the SiO 2Brittleness of ceramic aerogels. However, the low decomposition temperature (∼150 °C) of these polymers limits their use in high-temperature applications, compromising the thermal insulation performance of ceramic aerogels. Inorganic Al 2 O 3 , ZrO, aluminoborosilicate (AlBSi) sol, polycrystalline mullite fibers, and other fibers have been incorporated into SiO 2 fiber ceramic aerogels to optimize mechanical properties. However, the random distribution and weak interfacial bonding between the inorganic reinforcing phase and the ceramic aerogel components significantly limit the improvement of compressive and buckling properties. SUMMARY OF THE INVENTION

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a conductive and magnetic ceramic nanofiber aerogel and its preparation method and application. The ultra-light, biomimetic porous, conductive, and magnetic ceramic nanofiber aerogel provided by the present invention utilizes the strong binding points of graphene with renewable flexible SiO 2 nanofibers and MOF-derived magnetic metal / carbon composites to construct an interconnected highly porous aerogel with good mechanical elasticity. The hydrophobic ceramic aerogel exhibits multifunctionality such as electromagnetic wave absorption, magnetothermal conversion, biocidal antibacterial, good thermal stability, and thermal insulation performance under extreme conditions, and has a wide range of applications.

[0006] To achieve the above object, the present invention is realized through the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a conductive and magnetic ceramic nanofiber aerogel, comprising the following steps:

[0008] Mix an aqueous solution of polyethylene oxide and tetraethyl orthosilicate, and prepare precursor nanofibers;

[0009] After curing, pyrolyzing, and cooling the precursor nanofibers, uniformly disperse them in an aqueous phase to obtain a SiO 2 nanofiber aqueous dispersion;

[0010] Mix the SiO 2 nanofiber aqueous dispersion, graphene oxide aqueous dispersion, and ZIF-67 powder uniformly, and then perform liquid nitrogen freezing treatment;

[0011] Freeze-dry the product after liquid nitrogen freezing treatment and anneal it in an inert atmosphere to obtain a conductive and magnetic ceramic nanofiber aerogel.

[0012] Polyethylene oxide is used as a thickening agent and adhesive, which is beneficial for subsequent solution blowing spinning.

[0013] Further carbonization of ZIF-67 can obtain magnetic metal cobalt / carbon composite derivatives.

[0014] Perform liquid nitrogen freezing treatment. As ice crystals grow during freezing, a porous material is obtained.

[0015] Annealing can, on the one hand, reduce graphene oxide to reduced graphene oxide to obtain a certain electrical conductivity; on the other hand, it can carbonize ZIF-67 to obtain a magnetic metal / carbon composite material.

[0016] In some embodiments, in the mixed solution of polyethylene oxide and tetraethyl orthosilicate, the mass percentage of polyethylene oxide is 3-7%, and the mass percentage of tetraethyl orthosilicate is 15-30%.

[0017] In some embodiments, a precursor nanofiber is prepared by a continuous roll-to-roll solution blowing spinning method.

[0018] Preferably, when preparing the precursor nanofiber, the ambient humidity is 15-30%.

[0019] In some embodiments, the curing method is to first heat and pre-cure at 90-120 °C for 10-15 h, and then heat and cure at 150-250 °C for 20-30 h. The first stage is mainly a water evaporation process and a preliminary shaping of solvent evaporation; the second stage is to further stabilize the fiber structure. In some embodiments, the pyrolysis method is as follows: first heat the precursor nanofiber to 600-700 °C at a rate of 0.5-1.5 °C / min, then heat it to 1100-1300 °C at a rate of 2.5-4 °C / min, and hold it at 1100-1300 °C for 0.5-1.5 h. The second step can be heated faster because the fiber structure is basically stable.

[0020] In some embodiments, the SiO 2 The method for obtaining the nanofiber aqueous dispersion is as follows: Add the prepared SiO 2 nanofibers to water, first stir magnetically for 0.5-1.5 h, then perform tip sonication for 20-40 min, and finally perform oscillation treatment for 10-30 min to obtain the SiO 2 nanofiber aqueous dispersion.

[0021] In some embodiments, in the mixed system of SiO 2 nanofibers, GO, and ZIF-67, the mass percentage of SiO 2 nanofibers is 2%-20%, the mass percentage of GO is 60%-90%, and the mass percentage of ZIF-67 is 0%-50%, not 0.

[0022] In some embodiments, the graphene oxide GO aqueous dispersion is prepared by the Hummer method.

[0023] In some embodiments, the annealing temperature is 450-1100° C., and the annealing time is 0.5-4.5 h.

[0024] In a second aspect, the present invention provides a conductive magnetic ceramic nanofiber aerogel prepared by the preparation method.

[0025] In a third aspect, the present invention provides applications of the conductive magnetic ceramic nanofiber aerogel in electromagnetic wave absorption, magnetothermal conversion, photothermal conversion, thermal insulation materials, sensor devices, electrode materials, biomedical materials, antibacterial materials, supporting materials or wearable flexible electronics.

[0026] The beneficial effects achieved by one or more embodiments of the present invention are as follows:

[0027] The biomimetic porous ceramic nanofiber aerogel was successfully prepared by ice template freeze drying and annealing treatment. This is an ultra-light and strong biomimetic porous conductive magnetic ceramic nanofiber aerogel. Secondly, the sustainable, low-density and high-aspect-ratio SiO2 that constitutes the ceramic aerogel was mass-produced using a continuous roll-to-roll solution blowing process. 2 Nanofibers.

[0028] Renewable and flexible SiO 2 The strong bonding points of nanofibers to graphene enable the effective integration of MOF-derived magnetic nanoparticles with synergistic mechanical reinforcement, thus enabling the production of highly porous but strong conductive magnetic ceramic aerogels. The synergistic effect of dielectric and MOF-derived magnetic components, coupled with the different cell walls and biomimetic pores imparted by different freezing methods, enhances the multiple reflections of electromagnetic waves, contributing to the excellent electromagnetic wave absorption performance of the composite aerogels. In addition, the hydrophobic ceramic aerogels demonstrate the multifunctionality of magnetothermal conversion, wireless therapy, in vivo antibacterial applications, and magnetothermal deicing. SiO 2 Nanofibrous aerogels also exhibit good thermal stability and thermal insulation under harsh and extreme conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0030] Figure 1 This is a SEM image of the conductive magnetic ceramic nanofiber aerogel provided in Example 1.

[0031] Figure 2 This is a large-area sample photo of the conductive magnetic ceramic nanofiber aerogel provided in Example 2.

[0032] Figure 3Demonstration of the lightweight and hydrophobic properties of the electromagnetic conductive ceramic nanofiber aerogel provided for Example 3.

[0033] Figure 4 Mechanical resilience of the electromagnetic conductive ceramic nanofiber aerogel provided for Example 4 under different cyclic compressive strains.

[0034] Figure 5 Electromagnetic wave absorption performance of the electromagnetic conductive ceramic nanofiber aerogel provided for Example 5.

[0035] Figure 6 Magnetothermal conversion performance of the electromagnetic conductive ceramic nanofiber aerogel provided for Example 6, where: (a) magnetothermal curve of the aerogel under a 78 mT magnetic field, (b) magnetothermal curves of the aerogel under different magnetic field strengths, and (c) fitting curve of the saturated temperature and magnetic field of the aerogel after working for 30 s.

[0036] Figure 7 For Example 7, the electromagnetic conductive ceramic nanofiber aerogel: (a) photograph as an efficient magnetothermal de-icing device; (b) typical antibacterial function of the aerogel under a 90 mT (M+) magnetic field and the aerogel without a magnetic field (M-) against Escherichia coli (green and red dots represent live bacteria and dead bacteria, respectively).

[0037] Figure 8 For Example 8, the electromagnetic conductive ceramic nanofiber aerogel: (a) infrared thermogram for 1800 s on a hot plate; (b) placing a paper boat on the aerogel heated by an alcohol lamp. Detailed implementation manners

[0038] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0039] The present invention will be further described below in conjunction with examples.

[0040] Example 1

[0041] 5.0 parts by mass of a 15 wt% PEO solution was added to an aqueous solution of 12.0 parts by mass of TEOS, and magnetically stirred for 4 h to obtain a homogeneous solution. Under the condition of 20% relative humidity, the obtained solution was directly used for blowing to obtain precursor nanofibers. The precursor nanofibers were cured in an electric blast box at 100 °C (1 °C / minute) for 12 h and at 200 °C (3 °C / minute) for 24 h to stabilize the fiber structure. Then, it was pyrolyzed in argon: first heated to 650 °C at a rate of 1 °C / minute, then heated from 650 °C to 1200 °C at a rate of 3 °C / minute, and continuously maintained at 1200 °C for 1 h. Finally, it was naturally cooled to obtain SiO 2 nanofibers. The nanofibers were dispersed in deionized water using tip sonication to obtain an aqueous dispersion of SiO 2 nanofibers: First, the above-mentioned SiO 2 nanofibers were dispersed in deionized water and magnetically stirred for 1 h; then tip sonication was carried out at 250 W for 30 minutes; finally, an aqueous dispersion of SiO 2 nanofibers was obtained by using an oscillator for 20 minutes.

[0042] 1.6 parts by mass of Co(NO 3 ) 2 ·6H 2 O was dissolved in 25.0 parts by mass of deionized water to obtain a clear solution. 3.4 parts by mass of C 4 H 6 N 2 was dissolved in 25.0 parts by mass of deionized water. Then the Co(NO 3 ) 2 ·6H 2 O solution was added to the above solution and stirred for 30 min. Finally, after standing at room temperature for 12 h, it was washed and dried several times with deionized water and methanol, and finally a leaf-shaped purple powder of ZIF-67 was obtained.

[0043] The GO aqueous dispersion (1.0 wt%) prepared by the Hummer method and the prepared SiO 2The nanofiber aqueous dispersion (0.5 wt%) was mixed at a volume ratio of 8:2, and then 30 mg of the above-mentioned ZIF-67 purple powder was added to 10 g of the dispersion. After stirring and sonication, a homogeneous dispersion was obtained. Then the mixture dispersion was poured into a mold with a metal substrate (a Teflon cube mold, where the lower bottom is a metal base, mainly because the metal base has faster heat transfer. When placed in liquid nitrogen, a one-way pore wall structure from bottom to top will be formed), and immersed in liquid nitrogen for directional freezing treatment. After freezing, the sample was placed in a freeze dryer (-80 °C, 1 Pa) for about 24 hours to obtain a light purple aerogel. Subsequently, the aerogel was annealed in a nitrogen atmosphere at 600 °C for 2 hours to obtain the final conductive electromagnetic ceramic nanofiber aerogel.

[0044] The SEM image of the prepared conductive electromagnetic ceramic nanofiber aerogel is as Figure 1 shown. The presence of oriented, dense and complete aerogel cell walls indicates a strong interfacial interaction between graphene and SiO 2 and shows minimal morphological damage during annealing. Transmission electron microscopy (TEM) images show that cobalt particles with an average size of about 20 nm are uniformly dispersed on graphene sheets without agglomeration. In addition, the interplanar spacings of the lattice fringes are 0.20 nm and 0.17 nm, corresponding to the (200) and (111) crystal planes of Co respectively, confirming the successful reduction of cobalt during the pyrolysis process.

[0045] Example 2

[0046] 5.0 parts by mass of a 15 wt% PEO solution was added to 12.0 parts by mass of an aqueous TEOS solution, and magnetically stirred for 4 h to obtain a homogeneous solution. Under the condition of 30% relative humidity, the obtained solution was directly used for blowing to obtain precursor nanofibers. The precursor nanofibers were cured in an electric blast furnace at 100 °C (1 °C / minute) for 12 hours and 200 °C (3 °C / minute) for 24 hours to stabilize the fiber structure. Then, pyrolysis was carried out in argon: first, it was heated to 650 °C at a rate of 1 °C / minute, then heated from 650 °C to 1200 °C at a rate of 3 °C / minute, and continuously maintained at 1200 °C for 1 hour. Finally, it was naturally cooled to obtain SiO 2 nanofibers. The nanofibers were dispersed in deionized water using tip sonication to obtain an aqueous dispersion of SiO 2 nanofibers. First, the above-mentioned SiO 2 nanofibers were dispersed in deionized water and magnetically stirred for 1 h. Then tip sonication was carried out at 250 W for 30 minutes. Finally, an aqueous dispersion of SiO 2 nanofibers was obtained by using an oscillator for 20 minutes.

[0047] Dissolve 2.5 parts by mass of Co(NO 3 ) 2 ·6H 2 O in 25.0 parts by mass of deionized water to obtain a clear solution. Dissolve 3.4 parts by mass of C 4 H 6 N 2 in 25.0 parts by mass of deionized water. Then add the Co(NO 3 ) 2 ·6H 2 O solution to the above solution and stir for 30 min. Finally, after standing at room temperature for 12 h, wash and dry several times with deionized water and methanol to finally obtain leaf-shaped purple ZIF-67 powder.

[0048] Mix the GO aqueous dispersion (1.0 wt%) prepared by the Hummer method and the prepared SiO 2 nano-fiber aqueous dispersion (0.5 wt%) in a volume ratio of 8:2. Then add 50 mg of the above purple ZIF-67 powder to 10 g of the dispersion. After stirring and ultrasonic treatment, a uniform dispersion is obtained. Then pour the mixture dispersion into a mold with a metal substrate and immerse it in liquid nitrogen for directional freezing treatment. After freezing, place the sample in a freeze dryer (-80 °C, 1 Pa) for about 24 h to obtain a light purple aerogel. Subsequently, anneal the aerogel in a nitrogen atmosphere at 800 °C for 2 h to obtain the final electromagnetic conductive ceramic nano-fiber aerogel.

[0049] A large-area sample photo of the electromagnetic conductive ceramic nano-fiber aerogel is as Figure 2 shown. Using the scalable method and excellent mechanical properties of SiO 2 and rGO, a large-area and robust composite aerogel (20 cm in diameter) was successfully prepared. The introduction of magnetic Co makes the lightweight composite aerogel easy to be adsorbed by a magnet, expanding the application potential of the composite aerogel.

[0050] Example 3

[0051] Add 5.0 parts by mass of a 15 wt% PEO solution to an aqueous solution of 12.0 parts by mass of TEOS, and stir magnetically for 4 h to obtain a uniform solution. Under the condition of 20% relative humidity, directly use the obtained solution for blowing to obtain precursor nano-fibers. Cure the precursor nano-fibers in an electric blast furnace at 100 °C (1 °C / minute) for 12 h and 200 °C (3 °C / minute) for 24 h to stabilize the fiber structure. Then, pyrolyze in argon: first heat it to 650 °C at a rate of 1 °C / minute, then heat it from 650 °C to 1200 °C at a rate of 3 °C / minute, and continuously hold at 1200 °C for 1 h. Finally, cool naturally to obtain SiO2 Nanofibers. The nanofibers were dispersed in deionized water using tip sonication to obtain SiO 2 aqueous nanofiber dispersion. First, the above-mentioned SiO 2 nanofibers were dispersed in deionized water and magnetically stirred for 1 h. Then, tip sonication was carried out at 250 W for 30 minutes. Finally, an SiO 2 aqueous nanofiber dispersion was obtained by using an oscillator for 20 minutes.

[0052] 1.6 parts by mass of Co(NO 3 ) 2 ·6H 2 O was dissolved in 25.0 parts by mass of deionized water to obtain a clear solution. 3.4 parts by mass of C 4 H 6 N 2 was dissolved in 25.0 parts by mass of deionized water. Then, the Co(NO 3 ) 2 ·6H 2 O solution was added to the above solution and stirred for 30 min. Finally, after standing at room temperature for 12 h, it was washed and dried several times with deionized water and methanol, and finally, leaf-shaped purple ZIF-67 powder was obtained.

[0053] The GO aqueous dispersion (1.0 wt%) prepared by the improved Hummer method and the prepared SiO 2 aqueous nanofiber dispersion (0.5 wt%) were mixed at a volume ratio of 8:2, and then 30 mg of the above purple ZIF-67 powder was added to 10 g of the dispersion. After stirring and sonication, a uniform dispersion was obtained. Then, the mixture dispersion was poured into a mold with a metal substrate and immersed in liquid nitrogen for directional freezing treatment. After freezing, the sample was placed in a freeze dryer (-80 °C, 1 Pa) for about 24 h to obtain a light purple aerogel. Subsequently, the aerogel was annealed in a nitrogen atmosphere at 1000 °C for 2 h to obtain the final electromagnetic conductive ceramic nanofiber aerogel.

[0054] The light weight and hydrophobic properties of the electromagnetic conductive ceramic nanofiber aerogel are shown as Figure 3 shown. The prepared composite aerogel showed stability when placed on setaria viridis, demonstrating its light weight property. In addition, the mixed aerogel showed good hydrophobicity with a water contact angle of 135°, which is beneficial to achieving reliability and durability in practical applications.

[0055] Example 4

[0056] 30.0 parts by mass of a 15 wt% PEO solution was added to 45.0 parts by mass of an aqueous solution of TEOS, and magnetically stirred for 4 h to obtain a homogeneous solution. Under the condition of 20% relative humidity, the obtained solution was directly used for blowing to obtain precursor nanofibers. The precursor nanofibers were cured in an electric blast box at 100 °C (1 °C / minute) for 12 h and at 200 °C (3 °C / minute) for 24 h to stabilize the fiber structure. Then, pyrolysis was carried out in argon: first, it was heated to 650 °C at a rate of 1 °C / minute, then heated from 650 °C to 1200 °C at a rate of 3 °C / minute, and continuously maintained at 1200 °C for 1 h. Finally, it was naturally cooled to obtain SiO 2 nanofibers. The nanofibers were dispersed in deionized water using tip sonication to obtain an aqueous dispersion of SiO 2 nanofibers. First, the above-mentioned SiO 2 nanofibers were dispersed in deionized water and magnetically stirred for 1 h. Then, tip sonication was carried out at 250 W for 30 minutes. Finally, an aqueous dispersion of SiO 2 nanofibers was obtained by using an oscillator for 20 minutes.

[0057] 1.6 parts by mass of Co(NO 3 ) 2 ·6H 2 O was dissolved in 25.0 parts by mass of deionized water to obtain a clear solution. 3.4 parts by mass of C 4 H 6 N 2 was dissolved in 25.0 parts by mass of deionized water. Then the Co(NO 3 ) 2 ·6H 2 O solution was added to the above solution and stirred for 30 min. Finally, after standing at room temperature for 12 h, it was washed and dried several times with deionized water and methanol, and finally a leaf-shaped purple powder of ZIF-67 was obtained.

[0058] The GO aqueous dispersion (1.0 wt%) prepared by the improved Hummer method and the prepared aqueous dispersion of SiO 2 nanofibers (0.5 wt%) were mixed at a volume ratio of 8:2, and then 30 mg of the above-mentioned purple powder of ZIF-67 was added to 10 g of the dispersion. After stirring and sonication, a homogeneous dispersion was obtained. Then the mixture dispersion was poured into a mold with a metal substrate and immersed in liquid nitrogen for directional freezing treatment. After freezing, the sample was placed in a freeze dryer (-80 °C, 1 Pa) for about 24 h to obtain a light purple aerogel. Subsequently, the aerogel was annealed in a nitrogen atmosphere at 800 °C for 2 h to obtain the final conductive electromagnetic ceramic nanofiber aerogel.

[0059] The mechanical resilience of the electromagnetic conductive ceramic nanofiber aerogel under different cyclic compressive strains is as Figure 4 shown. The compression stress-strain curves of the composite aerogel were tested at maximum strains of 30%, 45%, 60% and 75%. The results show that the magnetic composite aerogel maintained its original shape under various strains, indicating its good mechanical resilience and structural stability.

[0060] Example 5

[0061] 5.0 parts by mass of a 15 wt% PEO solution was added to an aqueous solution of 12.0 parts by mass of TEOS, and magnetically stirred for 4 h to obtain a homogeneous solution. Under the condition of 20% relative humidity, the obtained solution was directly used for blowing to obtain precursor nanofibers. The precursor nanofibers were cured in an electric blast box at 100 °C (1 °C / minute) for 12 h and 200 °C (3 °C / minute) for 24 h to stabilize the fiber structure. Then, it was pyrolyzed in argon: first heated to 650 °C at a rate of 1 °C / minute, then heated from 650 °C to 1200 °C at a rate of 3 °C / minute, and continuously maintained at 1200 °C for 1 h. Finally, it was naturally cooled to obtain SiO 2 nanofibers. The nanofibers were dispersed in deionized water using tip sonication to obtain a SiO 2 nanofiber aqueous dispersion. First, the above-mentioned SiO 2 nanofibers were dispersed in deionized water and magnetically stirred for 1 h. Then, tip sonication was carried out at 250 W for 30 minutes. Finally, a SiO 2 nanofiber aqueous dispersion was obtained by using an oscillator for 20 minutes.

[0062] 1.6 parts by mass of Co(NO 3 ) 2 ·6H 2 O was dissolved in 25.0 parts by mass of deionized water to obtain a clear solution. 3.4 parts by mass of C 4 H 6 N 2 was dissolved in 25.0 parts by mass of deionized water. Then the Co(NO 3 ) 2 ·6H 2 O solution was added to the above solution and stirred for 30 min. Finally, after standing at room temperature for 12 h, it was washed and dried several times with deionized water and methanol, and finally a leaf-shaped ZIF-67 purple powder was obtained.

[0063] The GO aqueous dispersion (1.0 wt%) prepared by the Hummer method and the prepared SiO 2The nanofiber aqueous dispersion (0.5 wt%) was mixed at a volume ratio of 8:2, and then 30 mg of the above-mentioned ZIF-67 purple powder was added to 10 g of the dispersion. After stirring and sonication, a homogeneous dispersion was obtained. Then, the mixture dispersion was poured into a mold with a metal substrate and immersed in liquid nitrogen for directional freezing treatment. After freezing, the sample was placed in a freeze dryer (-80 °C, 1 Pa) for about 24 hours to obtain a light purple aerogel. Subsequently, the aerogel was annealed in a nitrogen atmosphere at 800 °C for 2 hours to obtain the final electromagnetic conductive ceramic nanofiber aerogel.

[0064] The electromagnetic wave absorption performance of the electromagnetic conductive ceramic nanofiber aerogel is as Figure 5 shown. The electromagnetic conductive ceramic nanofiber aerogel achieved a reflection loss value of -69.2 dB at a thickness of 2.6 mm, corresponding to a frequency of 16.3 GHz, achieving excellent electromagnetic wave absorption performance at low thickness. Among them, the maximum effective absorption bandwidth value was 7.12 GHz (3.0 mm) respectively.

[0065] Example 6

[0066] 5.0 parts by mass of a 15 wt% PEO solution was added to 12.0 parts by mass of an aqueous TEOS solution, and magnetically stirred for 4 h to obtain a homogeneous solution. Under the condition of 20% relative humidity, the obtained solution was directly used for blowing to obtain precursor nanofibers. The precursor nanofibers were cured in an electric blast furnace at 100 °C (1 °C / minute) for 12 hours and 200 °C (3 °C / minute) for 24 hours to stabilize the fiber structure. Then, it was pyrolyzed in argon: first heated to 650 °C at a rate of 1 °C / minute, then heated from 650 °C to 1200 °C at a rate of 3 °C / minute, and continuously maintained at 1200 °C for 1 hour. Finally, it was naturally cooled to obtain SiO 2 nanofibers. The nanofibers were dispersed in deionized water using tip sonication to obtain an aqueous dispersion of SiO 2 nanofibers. First, the above-mentioned SiO 2 nanofibers were dispersed in deionized water and magnetically stirred for 1 h. Then, tip sonication was carried out at 250 W for 30 minutes. Finally, an aqueous dispersion of SiO 2 nanofibers was obtained by using an oscillator for 20 minutes.

[0067] 1.6 parts by mass of Co(NO 3 ) 2 ·6H 2 O was dissolved in 25.0 parts by mass of deionized water to obtain a clear solution. 3.4 parts by mass of C 4 H 6 N 2Dissolve it in 25.0 parts by mass of deionized water. Then add the Co(NO 3 ) 2 ·6H 2 O solution to the above solution and stir for 30 min. Finally, after standing at room temperature for 12 h, wash and dry several times with deionized water and methanol to finally obtain leaf-shaped purple ZIF-67 powder.

[0068] Mix the GO aqueous dispersion (1.0 wt%) prepared by the improved Hummer method and the prepared SiO 2 nano-fiber aqueous dispersion (0.5 wt%) at a volume ratio of 8:2. Then add 30 mg of the above purple ZIF-67 powder to 10 g of the dispersion. After stirring and sonication, a homogeneous dispersion is obtained. Then pour the mixture dispersion into a mold with a metal substrate and immerse it in liquid nitrogen for directional freezing treatment. After freezing, place the sample in a freeze dryer (-80 °C, 1 Pa) for about 24 h to obtain a light purple aerogel. Subsequently, anneal the aerogel in a nitrogen atmosphere at 800 °C for 2 h to obtain the final electromagnetic conductive ceramic nano-fiber aerogel. By the same method, SiO 2 aerogel and SiO 2 / rGO aerogel are respectively prepared only by controlling the addition or not of GO and ZIF-67.

[0069] The magnetothermal conversion performance of the electromagnetic conductive ceramic nano-fiber aerogel is as Figure 6 shown, where: (a) the magnetothermal curve of the aerogel under a 78 mT magnetic field, (b) the magnetothermal curves of the aerogel under different magnetic field intensities, and (c) the fitting curve of the saturation temperature and magnetic field of the aerogel after working for 30 s. When the composite aerogel is placed under a 78 mT alternating magnetic field in a coil with alternating current, overall uniform heating is generated under the action of the 78 mT alternating magnetic field. Within 17 s, they rapidly rise from room temperature to 54 °C and maintain a uniform and stable equilibrium temperature. This indicates a contactless and uniform magnetothermal response. When the magnetic field is turned off, the temperature rapidly drops from 54 °C to 36 °C within 5 s. In contrast, the non-magnetic aerogel without MOF derivatives does not undergo magnetothermal conversion but experiences temperature changes due to the heating of the alternating current coil. The magnetothermal conversion characteristics under different magnetic field intensities are further explored. The composite aerogel reaches equilibrium temperatures of 38 °C, 44 °C, 50 °C, 54 °C, and 66 °C under magnetic fields of 48 mT, 60 mT, 70 mT, 78 mT, and 90 mT respectively. The temperature of the aerogel can be controlled by adjusting the intensity of the external magnetic field, and it is found that the relationship between the equilibrium temperature and the magnetic field intensity is linear.

[0070] Example 7

[0071] 5.0 parts by mass of a 15 wt% PEO solution was added to 12.0 parts by mass of an aqueous TEOS solution, and magnetically stirred for 4 h to obtain a homogeneous solution. Under the condition of 20% relative humidity, the obtained solution was directly used for blowing to obtain precursor nanofibers. The precursor nanofibers were cured in an electric blast furnace at 100 °C (1 °C / minute) for 12 h and at 200 °C (3 °C / minute) for 24 h to stabilize the fiber structure. Then, it was pyrolyzed in argon: first heated to 650 °C at a rate of 1 °C / minute, then heated from 650 °C to 1200 °C at a rate of 3 °C / minute, and continuously maintained at 1200 °C for 1 h. Finally, it was naturally cooled to obtain SiO 2 nanofibers. The nanofibers were dispersed in deionized water using tip sonication to obtain an aqueous dispersion of SiO 2 nanofibers. First, the above-mentioned SiO 2 nanofibers were dispersed in deionized water and magnetically stirred for 1 h. Then, tip sonication was carried out at 250 W for 30 minutes. Finally, an aqueous dispersion of SiO 2 nanofibers was obtained by using an oscillator for 20 minutes.

[0072] 1.6 parts by mass of Co(NO 3 ) 2 ·6H 2 O was dissolved in 25.0 parts by mass of deionized water to obtain a clear solution. 3.4 parts by mass of C 4 H 6 N 2 was dissolved in 25.0 parts by mass of deionized water. Then the Co(NO 3 ) 2 ·6H 2 O solution was added to the above solution and stirred for 30 min. Finally, after standing at room temperature for 12 h, it was washed and dried several times with deionized water and methanol, and finally a leaf-shaped purple powder of ZIF-67 was obtained.

[0073] The GO aqueous dispersion (1.0 wt%) prepared by the improved Hummer method and the prepared aqueous dispersion of SiO 2 nanofibers (0.5 wt%) were mixed at a volume ratio of 8:2, and then 90 mg of the above purple powder of ZIF-67 was added to 10 g of the dispersion. After stirring and sonication, a homogeneous dispersion was obtained. Then the mixture dispersion was poured into a mold with a metal substrate and immersed in liquid nitrogen for directional freezing treatment. After freezing, the sample was placed in a freeze dryer (-80 °C, 1 Pa) for about 24 h to obtain a light purple aerogel. Subsequently, the aerogel was annealed in a nitrogen atmosphere at 800 °C for 2 h to obtain the final electromagnetic conductive ceramic nanofiber aerogel.

[0074] The photo of the electromagnetic conductive ceramic nanofiber aerogel (a) as an efficient magnetic thermal de-icing device; (b) the typical antibacterial function of the aerogel under a 90 mT (M+) magnetic field and the aerogel without a magnetic field (M-) against Escherichia coli (green and red dots represent live bacteria and dead bacteria) as Figure 7 shown. The hydrophobicity, mechanical properties, and stable magnetic induction heating performance of the aerogels allow for rapid magnetic thermal de-icing behavior. These aerogels can rapidly melt ice within 120 seconds under a 90 mT magnetic field, indicating their suitability for use under harsh conditions. In addition, when the aerogel sprayed with Escherichia coli was exposed to a low magnetic field of 90 mT for 15 minutes, the treated bacteria were observed by confocal laser scanning microscopy. It was found that the equilibrium temperature reached by the aerogel was not conducive to the survival of bacteria, resulting in a significant reduction in the number of bacteria. This highlights the potential of the wireless heating performance of the composite aerogel in antibacterial applications.

[0075] Example 8

[0076] Add 5.0 parts by mass of a 15 wt% PEO solution to 12.0 parts by mass of an aqueous solution of TEOS, and magnetically stir for 4 h to obtain a homogeneous solution. Under the condition of 20% relative humidity, the obtained solution was directly used for blowing to obtain precursor nanofibers. The precursor nanofibers were cured in an electric blast box at 100 °C (1 °C / minute) for 12 h and at 200 °C (3 °C / minute) for 24 h to stabilize the fiber structure. Then, pyrolysis was carried out in argon: first, it was heated to 650 °C at a rate of 1 °C / minute, then heated from 650 °C to 1200 °C at a rate of 3 °C / minute, and continuously maintained at 1200 °C for 1 h. Finally, it was naturally cooled to obtain SiO 2 nanofibers. The nanofibers were dispersed in deionized water using tip sonication to obtain a SiO 2 nanofiber aqueous dispersion. First, the above-mentioned SiO 2 nanofibers were dispersed in deionized water and magnetically stirred for 1 h. Then, tip sonication was carried out at 250 W for 30 minutes. Finally, a SiO 2 nanofiber aqueous dispersion was obtained by using an oscillator for 20 minutes.

[0077] Dissolve 1.6 parts by mass of Co(NO 3 ) 2 ·6H 2 O in 25.0 parts by mass of deionized water to obtain a clear solution. Dissolve 3.4 parts by mass of C 4 H 6 N 2 in 25.0 parts by mass of deionized water. Then add Co(NO 3 ) 2 ·6H 2The O solution was added to the above solution and stirred for 30 min. Finally, after standing at room temperature for 12 h, it was washed and dried several times with deionized water and methanol, and finally purple leaf-shaped ZIF-67 powder was obtained.

[0078] The GO aqueous dispersion (1.0 wt%) prepared by the improved Hummer method and the prepared SiO 2 nano-fiber aqueous dispersion (0.5 wt%) were mixed at a volume ratio of 7:3, and then 30 mg of the above purple ZIF-67 powder was added to 10 g of the dispersion. After stirring and ultrasonic treatment, a uniform dispersion was obtained. Then the mixture dispersion was poured into a mold with a metal substrate and immersed in liquid nitrogen for directional freezing treatment. After freezing, the sample was placed in a freeze dryer (-80 °C, 1 Pa) for about 24 h to obtain a light purple aerogel. Subsequently, the aerogel was annealed in a nitrogen atmosphere at 800 °C for 2 h to obtain the final electromagnetic conductive ceramic nano-fiber aerogel. The electromagnetic conductive ceramic nano-fiber aerogel (a) infrared thermogram on a hot plate for 1800 s and (b) a paper boat placed on the aerogel heated by an alcohol lamp. The infrared image intuitively illustrates the heat transfer characteristics of the composite aerogel. Compared with the hot area at the bottom, the top of the aerogel always remains at a lower temperature, indicating that the aerogel effectively blocks heat. The excellent heat insulation performance of the aerogel enables it to effectively block the infrared radiation generated by the hot plate for more than 30 min, achieving infrared stealth. In addition, the composite aerogel effectively protects the paper boat from rapid combustion by isolating the flame under the iron net.

[0079] Combined with the above examples, it can be seen that the electromagnetic conductive ceramic nano-fiber aerogel provided by the present invention has excellent mechanical strength, excellent dielectric properties, electromagnetic wave absorption properties, magnetothermal conversion properties, antibacterial properties, heat insulation and heat preservation properties, etc. The preparation method of the present invention is simple and efficient, easy to realize large-scale production, and has broad application prospects.

[0080] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a conductive magnetic ceramic nanofiber aerogel, characterized in that: The steps include: Precursor nanofibers are prepared by mixing polyethylene oxide and an aqueous solution of ethyl silicate; The precursor nanofibers are solidified, pyrolyzed, cooled, and then uniformly dispersed in a water phase to obtain an aqueous dispersion of SiO2 nanofibers; The SiO2 nanofiber aqueous dispersion, graphite oxide dispersion and ZIF-67 powder are uniformly mixed and then subjected to liquid nitrogen freezing treatment; The product after liquid nitrogen freezing treatment is freeze-dried and annealed in an inert atmosphere to obtain a conductive magnetic ceramic nanofiber aerogel; In the mixed solution of polyethylene oxide and ethyl silicate, the mass percentage of polyethylene oxide is 3-7%, and the mass percentage of ethyl silicate is 15-30%; The precursor nanofibers were prepared by continuous roll-to-roll solution blowing method; In the mixed system of SiO2 nanofibers, GO and ZIF-67, the mass percentage of SiO2 nanofibers is 2%-20%, the mass percentage of GO is 60%-90%, and the mass percentage of ZIF-67 is 0%-50%, which is not 0.

2. The method for preparing the conductive magnetic ceramic nanofiber aerogel according to claim 1, characterized in that: When preparing the precursor nanofibers, the ambient humidity is 15-30%.

3. The method for preparing the conductive magnetic ceramic nanofiber aerogel according to claim 1, characterized in that: The curing method comprises firstly heating at 90-120° C. for pre-curing for 10-15 hours, and then heating at 150-250° C. for curing for 20-30 hours.

4. The method for preparing the conductive magnetic ceramic nanofiber aerogel according to claim 1, characterized in that: The pyrolysis method is as follows: firstly, the precursor nanofiber is heated to 600-700°C at a rate of 0.5-1.5°C / min, then heated to 1100-1300°C at a rate of 2.5-4°C / min, and maintained at 1100-1300°C for 0.5-1.5h.

5. The method for preparing the conductive magnetic ceramic nanofiber aerogel according to claim 1, characterized in that: The method for obtaining the SiO2 nanofiber aqueous dispersion is as follows: adding the prepared SiO2 nanofiber into water, firstly magnetically stirring for 0.5-1.5h, then performing a tip ultrasonic treatment for 20-40min, and finally performing an oscillation treatment for 10-30min to obtain the SiO2 nanofiber aqueous dispersion.

6. The method for preparing the conductive magnetic ceramic nanofiber aerogel according to claim 1, characterized in that: The annealing temperature is 450-1100° C., and the annealing time is 0.5-4.5 h.

7. A conductive magnetic ceramic nanofiber aerogel, characterized in that: Prepared by the preparation method described in any one of claims 1 to 6.

8. Application of the conductive magnetic ceramic nanofiber aerogel according to claim 7 in electromagnetic wave absorption, magnetothermal conversion, photothermal conversion, thermal insulation materials, sensor devices, electrode materials, biomedical materials, antibacterial materials, supporting materials or wearable flexible electronics.

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