Preparation method of cobalt / attapulgite / carbon nanocomposite fiber with wave absorbing performance

Abstract

The present invention belongs to the technical field of microwave-absorbing materials, and specifically relates to a method for preparing a cobalt / attapulgite / carbon nanocomposite fiber with microwave-absorbing properties. The preparation method comprises the following steps: mixing a magnetic metal salt, a polymer, a solvent, and nano-attapulgite in a specific proportion, reacting under heating conditions and at room temperature to obtain a mixed spinning solution; electrospinning the mixed spinning solution to obtain composite nanofibers; and carbonizing the obtained composite nanofibers to obtain a cobalt / attapulgite / carbon nanocomposite fiber with microwave-absorbing properties. The present invention has the beneficial effect that, due to the adoption of the above-mentioned technical solution, the carbon nanocomposite fiber of the present invention combines excellent properties such as light weight, strong absorption, a wide effective absorption bandwidth, and a low filling ratio. The carbon nanofibers have excellent dielectric properties, electrical conductivity, thermal stability, and low density. Carbon nanofibers are expected to be used to produce ideal microwave-absorbing materials.

Description

Technical Field

[0001] The invention belongs to the technical field of wave-absorbing materials, and in particular relates to a method for preparing cobalt / attapulgite / carbon nanocomposite fibers with wave-absorbing properties. Background Art

[0002] Currently, existing microwave absorbing materials primarily include ferrites, metal alloys, and graphite. These materials offer high absorption strength, but their narrow absorption bandwidth and high density limit their further development. Ferrite and metal alloy absorbers, in particular, are particularly limited by their high density. In recent years, in-depth research on polymer-derived ceramics, such as silicon carbide (SiC) and silicon nitride (Si3N4), has revealed their excellent high-temperature semiconductor properties and piezoresistive characteristics, demonstrating their potential application in microwave absorbing materials and promising prospects for use as microwave absorbers. However, these polymer-derived ceramics exhibit poor microwave absorption performance.

[0003] Silicon boron carbon nitride (SiBCN) ceramics, characterized by their lightweight, low thermal expansion coefficient, high hardness, high modulus, corrosion resistance, and excellent resistance to high temperatures, oxidation, and creep, are important ultra-high-temperature ceramic systems, widely used in high-temperature engines, turbines, nuclear reactor walls, high-temperature sensors, catalyst heat exchange systems, combustion systems, thermal protection systems, and aerospace equipment and high-tech fields. Due to their excellent properties, SiBCN ceramics are gaining increasing attention in the research of microwave absorbing materials for use in harsh environments. However, the current relatively narrow effective absorption bandwidth and low electromagnetic wave attenuation coefficient of SiBCN ceramics significantly limit their development as microwave absorbers, and their electromagnetic wave absorption performance still needs to be improved.

[0004] Existing technologies also use metal-organic framework derivatives to become excellent composite electromagnetic absorbing materials, but there are many shortcomings. The performance of the absorber still has a lot of room for improvement, mainly because it is necessary to meet the requirements of low thickness and achieve a wide effective absorption band. The preparation process is complex, time-consuming, and has low yield, and most of them use highly toxic organic solvents. The current absorbers are mainly binary composite materials. There is very little research on the performance of ternary and multi-component composite materials, and the relationship between the properties of each component and the electromagnetic parameters is still vague. Summary of the Invention

[0005] The present invention discloses a method for preparing cobalt / attapulgite / carbon nanocomposite fibers with wave-absorbing properties, which solves the above-mentioned technical problems and other technical problems in the prior art.

[0006] In order to solve the above technical problems, the technical solution of the present invention is: a method for preparing cobalt / attapulgite / carbon nanocomposite fibers with wave absorbing properties, the preparation method specifically comprising the following steps:

[0007] S1) mixing a magnetic metal salt, a polymer, a solvent, and nano-attapulgite in a certain ratio, and reacting them under heating conditions and at room temperature to obtain a mixed spinning solution;

[0008] S2) electrospinning the mixed spinning solution obtained in S1) to obtain composite nanofibers;

[0009] S3 carbonizes the obtained composite nanofiber to obtain cobalt / attapulgite / carbon nanocomposite fibers with wave absorbing properties.

[0010] Furthermore, the ratio of the magnetic metal salt, polymer, solvent and nano-attapulgite in S1) is 8:9:81:2.

[0011] Furthermore, the magnetic metal salt is one or more of iron salt, nickel salt and cobalt salt;

[0012] The polymer is one or more of polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, polyvinyl pyrrolidone, polyethylene, polyvinyl chloride and polyamide;

[0013] The solvent is one or more of ultrapure water, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, acetone, methanol and ethanol;

[0014] The nano-attapulgite is obtained by refining attapulgite ore.

[0015] Further, the specific steps of S3) are:

[0016] S3.1) Place the dried composite nanofibers in a quartz boat and place it in a tube furnace;

[0017] S3.2) Evacuating the tube furnace or introducing an inert atmosphere, carbonizing the tube furnace by heating in stages, and cooling the tube furnace to room temperature to obtain composite carbon nanofibers;

[0018] S3.3) The composite carbon nanofibers obtained in S3.2) are calcined and carbonized to obtain cobalt / attapulgite / carbon nanocomposite fibers with microwave absorbing properties.

[0019] Furthermore, the specific process of the segmented heating in S3.2) is as follows:

[0020] First, heat to 280-320℃ at a heating rate of 1-4.5℃ / min and keep warm for 0.8-1.2 hours;

[0021] Then continue to heat up to 550-1200℃ at a rate of 1-4℃ / min and keep warm for 0.5h-3h.

[0022] Furthermore, the vacuum degree of the evacuation in S2) is 0.1 Pa; the inert atmosphere includes inert gases nitrogen and argon.

[0023] Another object of the present invention is to provide a cobalt / attapulgite / carbon nanocomposite fiber having wave absorbing properties, wherein the cobalt / attapulgite / carbon nanocomposite fiber is prepared by the above-mentioned preparation method.

[0024] Furthermore, the cobalt / attapulgite / carbon nanocomposite fiber has a carbon nanofiber skeleton with a spiral bending shape, the nano-attapulgite Al, Si, Mg and O elements are distributed near the outer end of the bending area of ​​the carbon nanofiber skeleton, the C element is evenly distributed in the composite fiber, and the Co element is randomly distributed in the composite fiber in the form of particles.

[0025] The nanocomposite fiber has a saturation magnetization of not less than 9.2emu / g and a coercive force of not less than 223.4Oe; the effective absorption bandwidth of the cobalt / attapulgite / carbon nanocomposite fiber is 5.60GHz, the minimum RL can reach -34.34dB, and the filling ratio in paraffin is 12%.

[0026] An application of the Co / ATP / C nanocomposite fiber prepared by the above preparation method in magnetic materials, wave absorbing materials or shielding materials.

[0027] The mechanism of the present invention is as follows: ATP, a natural, rod-like, hydrous magnesium-aluminum silicate clay mineral, is incorporated into an absorber. Due to its unique one-dimensional nanostructure, well-developed honeycomb-like intracrystalline pores, and large specific surface area, its introduction into the absorber can form a complex structure with multiple interfaces and multiple pores. This not only generates strong interfacial polarization and dipole polarization, enhancing polarization losses, but also enhances the reflection and scattering of electromagnetic waves within the absorber, thus increasing electromagnetic wave attenuation. Furthermore, the bending deformation of the ATP under high-temperature calcination results in a curved carbon fiber structure, which extends the electromagnetic wave propagation path and enhances electromagnetic wave loss and attenuation.

[0028] The present invention has the following beneficial effects: Due to the adoption of the above-mentioned technical solution, the carbon nanocomposite fibers of the present invention combine excellent properties such as light weight, strong absorption, a wide effective absorption bandwidth, and a low filling ratio. The carbon nanofibers also have excellent dielectric properties, electrical conductivity, thermal stability, and low density. This makes it possible to utilize carbon nanofibers to create ideal microwave absorbing materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a flowchart of a method for preparing cobalt / attapulgite / carbon nanocomposite fibers with wave absorbing properties.

[0030] Figure 2These are scanning electron microscope photos of the composite fibers prepared in Examples 1, 2, and 3 of the present invention.

[0031] Figure 3 These are the hysteresis loops of the composite fibers prepared in Examples 1, 2, and 3 of the present invention.

[0032] Figure 4 HAADF-STEM images of the composite fibers prepared in Example 1 and Example 3 of the present invention and EDX element distribution images of C, Co, O, Mg, Al and Si.

[0033] Figure 5 These are pictures showing the wave absorption performance of the composite fibers prepared in Examples 1 and 3 of the present invention. DETAILED DESCRIPTION

[0034] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0035] like Figure 1 As shown, the present invention provides a method for preparing a cobalt / attapulgite / carbon nanocomposite fiber with wave absorbing performance, and the preparation method specifically comprises the following steps:

[0036] S1) mixing a magnetic metal salt, a polymer, a solvent, and nano-attapulgite in a certain ratio, and reacting them under heating conditions and at room temperature to obtain a mixed spinning solution;

[0037] S2) electrospinning the mixed spinning solution obtained in S1) to obtain composite nanofibers;

[0038] S3 carbonizes the obtained composite nanofiber to obtain cobalt / attapulgite / carbon nanocomposite fibers with wave absorbing properties.

[0039] The ratio of the magnetic metal salt, polymer, solvent and nano-attapulgite in the S1) is 8:9:81:2.

[0040] The magnetic metal salt is one or more of iron salt, nickel salt and cobalt salt;

[0041] The polymer is one or more of polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, polyvinyl pyrrolidone, polyethylene, polyvinyl chloride and polyamide;

[0042] The solvent is one or more of ultrapure water, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, acetone, methanol and ethanol;

[0043] The nano-attapulgite is obtained by refining attapulgite ore.

[0044] The specific steps of S3) are:

[0045] S3.1) Place the dried composite nanofibers in a quartz boat and place it in a tube furnace;

[0046] S3.2) Evacuating the tube furnace or introducing an inert atmosphere, carbonizing the tube furnace by heating in stages, and cooling the tube furnace to room temperature to obtain composite carbon nanofibers;

[0047] S3.3) The composite carbon nanofibers obtained in S3.2) are calcined and carbonized to obtain cobalt / attapulgite / carbon nanocomposite fibers with microwave absorbing properties.

[0048] The specific process of the segmented heating in S3.2) is as follows:

[0049] First, heat to 280-320℃ at a heating rate of 1-4.5℃ / min and keep warm for 0.8-1.2 hours;

[0050] Then continue to heat up to 550-1200℃ at a rate of 1-4℃ / min and keep warm for 0.5h-3h.

[0051] Furthermore, the vacuum degree of the evacuation in S2) is 0.1 Pa; the inert atmosphere includes inert gases nitrogen and argon.

[0052] A cobalt / attapulgite / carbon nanocomposite fiber with wave absorbing performance is prepared by adopting the above-mentioned preparation method.

[0053] The cobalt / attapulgite / carbon nanocomposite fiber has a carbon nanofiber skeleton in a spirally curved shape, the nano-attapulgite Al, Si, Mg and O elements are distributed near the outer end of the bending area of ​​the carbon nanofiber skeleton, the C element is uniformly distributed in the composite fiber, and the Co element is randomly distributed in the composite fiber in the form of particles.

[0054] The nanocomposite fiber has a saturation magnetization of not less than 9.2emu / g and a coercive force of not less than 223.4Oe. The cobalt / attapulgite / carbon nanocomposite fiber has a frequency of 5.60GHz (12.4-18.0GHz), a minimum RL of -34.34dB, and a filling ratio of 12% in paraffin.

[0055] An application of the Co / ATP / C nanocomposite fiber prepared by the above preparation method in magnetic materials, wave absorbing materials or shielding materials.

[0056] Example 1:

[0057] (1) 0.0200 g (0.2 wt%) of ATP was mixed into 8.30 mL of deionized water, which was placed in a water bath and magnetically stirred at 60°C for 20 min, followed by ultrasonic treatment for 1 h to allow the ATP to be completely dispersed in the deionized water to obtain a uniform suspension. 0.9000 g (9 wt%) of PVA was then added thereto, and magnetically stirred at 80°C for 2 h to completely dissolve the PVA. Finally, 0.8000 g (8 wt%) of Co(Ac)2 was added to the mixed solution, and stirred at 50°C for 2 h. Finally, the solution was stirred at 20°C for 14 h to obtain a Co(Ac)2 / ATP / PVA / H2O mixed spinning solution;

[0058] (2) The spinning solution was placed in a syringe and fixed to the electrospinning apparatus. The solution propagation rate was set to 0.24 mL / h, and the distance between the spinning needle and the collecting plate was set to 12 cm. Spinning was then performed at a DC voltage of 15 kV. Finally, the resulting polymer composite fiber was placed in a constant temperature drying oven and dried at 60°C for 15 h.

[0059] (3) The dried polymer fiber precursor is placed in a quartz boat and carbonized at high temperature in a tube furnace under vacuum conditions. First, the sample is heated to 300°C at a heating rate of 2.5°C / min, and then kept warm for 1 hour to stabilize the structure of the composite carbon nanofiber. Then, the temperature is continued to be raised to 550°C at a rate of 2.5°C / min, and kept warm at 550°C for 1 hour. After the insulation is completed, the sample is naturally cooled to room temperature in a vacuum to obtain the composite carbon nanofiber. The sample obtained at a calcination temperature of 550°C is named S550.

[0060] Example 2:

[0061] (1) 0.0200 g (0.2 wt%) of ATP was mixed into 8.30 mL of deionized water, which was placed in a water bath and magnetically stirred at 60°C for 20 min. The mixture was then ultrasonically treated for 1 h to allow the ATP to be completely dispersed in the deionized water to obtain a uniform suspension. 0.9000 g (9 wt%) of PVA was then added and magnetically stirred at 80°C for 2 h to completely dissolve the PVA. Finally, 0.8000 g (8 wt%) of Co(Ac)2 was added to the mixed solution and stirred at 50°C for 2 h. The solution was stirred at 20°C for 14 h to obtain a Co(Ac)2 / ATP / PVA / H2O mixed spinning solution.

[0062] (2) The spinning solution was placed in a syringe and fixed to the electrospinning apparatus. The solution propagation rate was set to 0.24 mL / h, and the distance between the spinning needle and the collecting plate was set to 12 cm. Spinning was then performed at a DC voltage of 15 kV. Finally, the resulting polymer composite fiber was placed in a constant temperature drying oven and dried at 60°C for 15 h.

[0063] (3) The dried polymer fiber precursor was placed in a quartz boat and carbonized at high temperature in a tube furnace under vacuum conditions. First, the sample was heated to 300°C at a heating rate of 2.5°C / min and then kept at this temperature for 1 hour to stabilize the structure of the composite carbon nanofibers. The temperature was then continued to be raised to 650°C at a rate of 2.5°C / min and kept at this temperature for 1 hour. After the holding period, the sample was naturally cooled to room temperature in a vacuum to obtain the composite carbon nanofibers. The sample obtained at the calcination temperature of 650°C was named S650.

[0064] Example 3:

[0065] (1) 0.0200 g (0.2 wt%) of ATP was mixed into 8.30 mL of deionized water, which was placed in a water bath and magnetically stirred at 60°C for 20 min. The mixture was then ultrasonically treated for 1 h to allow the ATP to be completely dispersed in the deionized water to obtain a uniform suspension. 0.9000 g (9 wt%) of PVA was then added and magnetically stirred at 80°C for 2 h to completely dissolve the PVA. Finally, 0.8000 g (8 wt%) of Co(Ac)2 was added to the mixed solution and stirred at 50°C for 2 h. The solution was stirred at 20°C for 14 h to obtain a Co(Ac)2 / ATP / PVA / H2O mixed spinning solution.

[0066] (2) The spinning solution was placed in a syringe and fixed to the electrospinning apparatus. The solution propagation rate was set to 0.24 mL / h, and the distance between the spinning needle and the collecting plate was set to 12 cm. Spinning was then performed at a DC voltage of 15 kV. Finally, the resulting polymer composite fiber was placed in a constant temperature drying oven and dried at 60°C for 15 h.

[0067] (3) The dried polymer fiber precursor was placed in a quartz boat and carbonized at high temperature in a tube furnace under vacuum conditions. First, the sample was heated to 300°C at a heating rate of 2.5°C / min and then kept at this temperature for 1 hour to stabilize the structure of the composite carbon nanofiber. Then, the temperature was continued to be raised to 750°C at a rate of 2.5°C / min and kept at 750°C for 1 hour. After the insulation, the sample was naturally cooled to room temperature in a vacuum to obtain the composite carbon nanofiber. The sample obtained at a calcination temperature of 750°C was named S750.

[0068] like Figure 2As shown in the SEM photos of S550, S650 and S750 prepared in Examples 1 to 3, it can be seen that the diameter of the fiber is about 100nm, and all the fibers have a spiral-like curved shape, which shows that the addition of ATP has an effect on the growth of the fiber. As the calcination temperature increases, the surface of the fiber becomes obviously rougher, and the large particles on the fiber gradually increase. This is because the increase in calcination temperature is conducive to the growth of nanoparticles in the fiber. Figure 2 In Figure c, a certain degree of cracking can be found in the fiber, which indicates that ATP has been significantly decomposed and its structure has collapsed at a calcination temperature of 750°C.

[0069] like Figure 2 a in the figure is the XRD pattern of S550, S650 and S750. Due to the low calcination temperature, the crystallinity of the composite fiber of S550 is poor, so no obvious diffraction peak appears. As the calcination temperature increases, the crystallinity of the composite fiber increases and the diffraction peak becomes sharper. The diffraction peaks of S650 and S750 at 44.2°, 51.5° and 75.6° correspond to the (111), (200) and (220) crystal planes of Co, respectively (PDF#15-0806). The characteristic peaks at 36.5° and 42.4° correspond to the (111) and (200) crystal planes of CoO, respectively (PDF#43-1004). The diffraction peak at 26.3° of the three samples corresponds to the (011) crystal plane of SiO2 (PDF#47-1144), which is caused by the decomposition of ATP. In the XRD pattern of S750, the diffraction peaks at 28.4°, 47.3°, and 56.1° correspond to the (111), (200), and (220) crystal planes of Si (PDF#27-1402). The (040) and (241) diffraction peaks of MgAl2O4 (PDF#47-0254) can be seen at 36.5° and 53.6°, respectively. The diffraction peak at 35.6° is attributed to the (111) crystal plane of SiC (PDF#29-1129). This indicates that the high temperature of calcination at 750°C and the reduction effect of carbon fibers destroyed the structure of ATP, further decomposing it and producing new phases.

[0070] Figure 3 The hysteresis loops of Co / ATP / C nanocomposite fibers calcined at different temperatures are shown in the figure. As can be seen from the figure, when the external magnetic field is 15000 Oe, the magnetic induction intensity of S550 is not fully saturated. This is because the crystallinity of Co in the obtained composite fiber is poor and the magnetic properties are very weak under the calcination condition of 550℃. s This is because the increase in sintering temperature improves the crystallinity of Co and enhances its magnetism. s48.0emu / g and 51.1emu / g respectively, which are lower than the M of bulk Co. s (162.6emu / g), which may be due to the presence of non-magnetic carbon fibers and ATP in the composite fibers [ . Figure 3 The enlarged image shows the residual magnetization intensity (M r ) are 9.2emu / g and 15.6emu / g respectively. c ) are 223.4Oe and 553.6Oe, respectively, which are much higher than the H c Value (10.0Oe)

[100] This may be related to the existence of single domain size of nanomagnetic particles and the anisotropic dispersion characteristics of the particles in the fibers.

[0071] HAADF images and element distribution photos of S550 are shown in the figure below. Figure 4 As shown in ag. From the HAADF photo, we can see that Figure 4 In a, there are dense and small particles in the fiber. Figure 4 It can be found from the bd that the three elements C, Co and O are evenly distributed throughout the fiber. Figure 4 From the dg in the image, we can see that there are rod-shaped substances at the location where the fiber curls, and they are mainly composed of O, Mg, Al, and Si. This proves that the curled structure of the fiber is caused by the presence of ATP. In addition, in addition to the main location of ATP, Mg, Al, and Si elements are also distributed in other areas of the fiber, indicating that there is a certain degree of decomposition in ATP during the roasting process. The HAADF image and element distribution photos of S750 are shown in the figure. Figure 4 As shown in hn. Figure 4 It can be found in the h that at a calcination temperature of 750℃, the particles in the fiber condense together to form larger particles, and are randomly distributed throughout the fiber with different sizes. From the distribution diagram of various elements, it can be seen that the C element is evenly distributed in the fiber, such as Figure 4 The i and Co elements in the fiber are dispersed in the form of particles, such as Figure 4 In j; O element is mainly distributed in and around the particles, indicating the existence of oxides, such as Figure 4 k in; combined Figure 4As can be seen from the kn, the four elements Al, Si, Mg, and O are mainly distributed near the outer end of the fiber bending area, indicating that the effect of ATP gives the fiber a curved structure. In the distribution diagram of the three elements Al, Si, and Mg, no obvious rod-like structure is seen, indicating that the structure of ATP is destroyed at the calcination temperature of 750°C. Due to the further decomposition of ATP, Al, Si, Mg, and O are also distributed in other areas. Combined with the element distribution photos of Co and O, Al, Mg, and Si, it can be found that Co exists as relatively small particles in the area where the carbon nanofibers bend, indicating that the presence of nano-ATP creates a certain resistance to the growth of Co nanoparticles. The bending of nanocarbon fibers is mainly due to the strong van der Waals mutual attraction between ATP and PVA molecular chains. During the high-temperature calcination process, the structure of the carbon nanofibers is continuously compressed. This mutual attraction causes the inner wall of the fiber to easily shrink during the compression process, thereby causing the fiber structure to bend.

[0072] The reflection loss (RL) value is the main indicator to describe the performance of the absorbing material. From the curves of RL changes with frequency of the three samples, Figure 5 It can be seen from the ac that when the thickness of S550 is 2.5mm, at 15.76GHz, the minimum RL can reach -46.67dB, and the effective bandwidth is 5.60GHz (12.4-18.0GHz), which basically achieves full coverage of the Ku band at high frequencies. At a thickness of 3mm, the effective bandwidth can reach 6.72GHz (9.92-16.64GHz), achieving broadband absorption of electromagnetic waves. At 12.4GHz, the minimum RL can reach -34.34dB. When the thickness of S650 is 2mm, the minimum RL is -34.67dB, and the effective bandwidth is 5.72GHz (12.24-17.96GHz), which also basically covers the entire Ku band. It can be found that S550 has the best wave absorption performance, followed by S650. From the RL three-dimensional image, Figure 5 It can be seen from the df in that the thicker the sample, the lower the electromagnetic wave frequency when the RL peak appears, and the matching thickness of S650 is thinner than that of S550.

[0073] The above describes in detail the method for preparing a cobalt / attapulgite / carbon nanocomposite fiber with microwave-absorbing properties provided in the examples of this application. The description of the above examples is intended only to facilitate understanding of the method and core concept of this application. Furthermore, those skilled in the art will appreciate that variations in the specific implementation and scope of application are possible based on the principles of this application. Therefore, this description should not be construed as limiting this application.

[0074] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different nouns to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criteria for distinction. For example, "including" and "comprising" mentioned throughout the specification and claims are open-ended terms, so they should be interpreted as "including / including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve the technical problems within a certain error range and basically achieve the technical effects. The subsequent description in the specification is a preferred embodiment of the present application, but the description is for the purpose of illustrating the general principles of the present application, and is not used to limit the scope of the present application. The scope of protection of the present application shall be as defined in the attached claims.

[0075] It should also be noted that the terms "include," "comprises," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product or system comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such product or system. In the absence of further limitations, an element defined by the phrase "comprises a..." does not exclude the presence of other identical elements in the product or system comprising the element.

[0076] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0077] The above description shows and describes several preferred embodiments of the present application. However, as previously mentioned, it should be understood that the present application is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Instead, the present application can be used in various other combinations, modifications, and environments and can be modified within the scope of the application concept described herein through the above teachings or technology or knowledge in the relevant field. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present application should be protected by the claims appended hereto.

Claims

1. A method for preparing a cobalt / attapulgite / carbon nanocomposite fiber having microwave absorbing properties, the method comprising the following steps: S1) mixing a cobalt salt, a polymer, a solvent, and nano-attapulgite in a ratio of 8:9:81:2, and reacting the mixture under heating and at room temperature to obtain a mixed spinning solution, wherein the nano-attapulgite is obtained by refining attapulgite ore; S2) electrospinning the mixed spinning solution obtained in S1) to obtain composite nanofibers; S3) carbonizing the obtained composite nanofibers to obtain cobalt / attapulgite / carbon nanocomposite fibers with microwave absorbing properties; The specific steps of S3) are: S3.1) Place the dried composite nanofibers in a quartz boat and place it in a tube furnace; S3.2) Evacuating the tube furnace or introducing an inert atmosphere to a vacuum degree of 0.1 Pa, wherein the inert atmosphere includes nitrogen and argon, carbonizing the tube furnace by staged heating, and cooling the tube furnace to room temperature to obtain composite carbon nanofibers; The specific process of the segmented heating is: First, heat to 280-320℃ at a heating rate of 1-4.5℃ / min and keep warm for 0.8-1.2 hours; Then continue to heat up to 550-1200℃ at a rate of 1-4℃ / min and keep warm for 0.5h-3h; S3.3) The composite carbon nanofibers obtained in S3.2) are calcined and carbonized to obtain cobalt / attapulgite / carbon nanocomposite fibers having microwave absorbing properties.

2. The preparation method according to claim 1, characterized in that The polymer is one or more of polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, polyvinyl pyrrolidone, polyethylene, polyvinyl chloride and polyamide; The solvent is one or more of ultrapure water, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, acetone, methanol and ethanol.

3. A cobalt / attapulgite / carbon nanocomposite fiber with microwave absorbing properties, characterized in that: The cobalt / attapulgite / carbon nanocomposite fiber is prepared by the preparation method according to any one of claims 1 to 2.

4. The cobalt / attapulgite / carbon nanocomposite fiber according to claim 3, characterized in that The cobalt / attapulgite / carbon nanocomposite fiber has a carbon nanofiber skeleton in a spirally curved shape, the nano-attapulgite Al, Si, Mg and O elements are distributed near the outer end of the bending area of ​​the carbon nanofiber skeleton, the C element is uniformly distributed in the composite fiber, and the Co element is randomly distributed in the composite fiber in the form of particles.

5. The cobalt / attapulgite / carbon nanocomposite fiber according to claim 3, characterized in that The saturation magnetization of the nanocomposite fiber is not less than 9.2 emu / g, and the coercive force is not less than 223.4 Oe. The effective absorption bandwidth of the cobalt / attapulgite / carbon nanocomposite fiber is 5.60 GHz, and the minimum RL can reach −34.34 dB.

6. Use of the cobalt / attapulgite / carbon nanocomposite fiber prepared by the preparation method according to any one of claims 1 to 2 in magnetic materials, wave absorbing materials or shielding materials.

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