In-situ atomic layer deposition MoS2 coated N-CNF coated MXene composite nanofiber wave-absorbing aerogel and preparation method thereof

Abstract

The invention discloses an in-situ atomic layer deposition MoS2 coated N-CNF and MXene composite nanofiber wave-absorbing aerogel and a preparation method thereof, and the wave-absorbing aerogel is composed of N-CNF and MXene composite nanofibers with MXene nanosheets distributed in a nebula shape, and atomic layer deposition MoS2, the MXene nanosheets are distributed in a nebula shape in N-CNF, and a conductive layer formed by crosslinking MoS2 is wrapped on N-CNF (at) MXene nanofibers. The preparation method comprises the following steps: treating an MXene nanosheet with a surfactant, drying to obtain the MXene nanosheet, and dispersing the MXene nanosheet into a DMF (Dimethyl Formamide) solution of PAN to obtain a PAN-coated MXene electrostatic spinning solution; carrying out electrostatic spinning to prepare PAN (at) MXene nanofiber aerogel; preparing an N-CNF (at) MXene aerogel; and carrying out in-situ atomic layer deposition on the MoS2 to coat the N-CNF (at) MXene composite nanofiber aerogel, so as to prepare the N-CNF (at) MXe ne (at) MoS2 composite nanofiber wave-absorbing aerogel. The conductivity loss and relaxation loss of the absorber are enhanced by a heterogeneous interface in the wave-absorbing aerogel prepared by the preparation method disclosed by the invention; a heterogeneous interface formed by the deposited MoS2 film and the N-CNF improves the impedance matching characteristic of electromagnetic waves.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic wave absorbing materials, and in particular to an in-situ atomic layer deposited MoS2-coated N-CNF@MXene composite nanofiber absorbing aerogel and a preparation method thereof. Background Art

[0002] The development of wireless communication technology has promoted great progress in society. The emergence of new communication technologies such as 5G has brought unprecedented convenience to human normal life. However, the development of these new communication technologies has aggravated the problem of electromagnetic pollution. Electromagnetic pollution can affect the normal operation of electronic equipment and pose a potential threat to human health. Therefore, electromagnetic pollution and interference have become an urgent problem to be solved. To solve this problem, it is very important to develop efficient electromagnetic wave absorbing materials that can convert electromagnetic waves into heat and then dissipate them.

[0003] As a typical one-dimensional nanomaterial with a high aspect ratio, carbon nanofibers not only entangle with each other to form a network structure, but also form a heterogeneous interface with other material surfaces, which is beneficial to the polarization loss of electromagnetic waves. Two-dimensional MXene nanosheets have excellent electrical conductivity, unique two-dimensional structure, large specific surface area and rich functional groups, making them a very promising electromagnetic wave absorption material and a potential candidate material for solving these problems. However, with the emergence of higher demands, the excellent electrical conductivity of MXene nanosheets may lead to impedance mismatch. Moreover, the strong van der Waals interaction between MXene nanosheets leads to the tendency of nanosheets to stack themselves, which hinders the multiple reflection and scattering of electromagnetic waves and affects the electromagnetic wave absorption performance of MXene nanosheets. MXene nanosheets are added to N-CNF to construct a nebula-shaped distribution MXene with local aggregation and overall dispersion, which shows greater prospects in the field of microwave absorption than single MXene nanosheets or N-CNF. Adding MXene nanosheets to N-CNF to construct a nebula-shaped MXene with local aggregation and overall dispersion, and preparing it into N-CNF@MX ene aerogel can effectively increase the polarization interface and promote the transfer of electrons between different N-CNFs, which is conducive to the formation of a conductive loop to improve the absorption performance. The heterogeneous interface between MXene nanosheets and N-CNF can effectively improve impedance matching. Constructing an N-CNF / MoS2 heterogeneous interface on the surface of N-CNF can effectively improve impedance matching and thus improve electromagnetic wave absorption performance. Uniformly depositing MoS2 on the conductive layer composed of N-CNF is still a challenging task.

[0004] The high conformality and uniform and controllable number of layers of atomic layer deposition technology make it the best choice for constructing N-CNF / MoS2 heterogeneous interfaces. Atomic layer deposition technology deposits a target thickness of MoS2 film on a complex N-CNF structure by controlling the number of cycles, realizing the preparation of a N-CNF@MXene@MoS2 composite absorbing aerogel based on atomic layer deposition technology.

[0005] Chinese patent "Application No.: 202210079170.8" discloses a hollow porous nanocarbon fiber and its preparation method. The invention obtains a skin-core composite nanofiber by electrospinning, and obtains a hollow porous nanocarbon fiber after pre-oxidation and carbonization. The effective absorption bandwidth covers 3.9GHz-6.5GHz. Chinese patent "Application No.: 202210803203.9" discloses a method for preparing a sandwich-type absorbing carbon fiber. The invention prepares a modified mesophase asphalt by mixing mesophase asphalt with carbon nanotubes, heating it to a molten state, pressurizing it, and spinning it to obtain a mesophase asphalt fiber precursor. The precursor is then oxidized and carbonized to obtain a carbon fiber with excellent electromagnetic absorption performance. Summary of the invention

[0006] Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention proposes an in-situ atomic layer deposition MoS2 coated N-CNF@MXene composite nanofiber absorbing aerogel and a preparation method thereof. Since MXene nanosheets are prone to self-stacking, the present invention disperses MXene nanosheets in N-CNF to construct a nebula-shaped distribution of MXene, so as to reduce the occurrence of MXene nanosheet self-stacking, optimize aerogel impedance matching, and enhance the conductivity of N-CNF; by enhancing the conductivity loss and polarization loss, the electromagnetic wave absorption capacity is improved. At the same time, due to the lack of functional groups on the surface of N-CNF, the N-CNF / MoS2 heterogeneous interface is formed by plasma treatment and MoS2 is deposited on its surface, which greatly improves the impedance matching and wave absorption performance. The absorbing aerogel prepared by the present invention has the advantages of conductivity, low density, and high specific surface area.

[0007] Technical solution: To solve the above technical problems, the present invention proposes an in-situ atomic layer deposition MoS2 coated N-CNF@MXene composite nanofiber absorbing aerogel. The composite absorbing aerogel is composed of N-CNF, MXene nanosheets and MoS2 film, including N-CNF / MoS2 and MXene / N-CNF heterogeneous interfaces, and has a unique structure with high porosity formed by cross-linking of N-CNF / MoS2 heterogeneous nanofibers. The aerogel has the advantages of conductivity, low density and high specific surface area.

[0008] The in-situ atomic layer deposited MoS2 coated N-CNF@MXene composite nanofiber absorbing aerogel of the present invention is composed of N-CNF@MXene composite nanofibers with nebula-shaped distributed MXene nanosheets and atomic layer deposited MoS2, and has a structure in which nebula-shaped distributed MXene nanosheets in N-CNF and a conductive layer composed of MoS2 cross-linked with each other is wrapped on the N-CNF@MXene nanofibers.

[0009] The method for preparing the in-situ atomic layer deposition MoS2-coated N-CNF@MXene composite nanofiber wave-absorbing aerogel of the present invention comprises the following steps:

[0010] (1) Preparation of MXene nanosheets: measuring HCl solution, weighing Ti3AlC2 and LiF, adding them to the HCl solution for reaction, washing the solution to neutrality; ultrasonically treating the neutral solution; centrifuging to remove Al; adding a surfactant to the MXene aqueous solution; drying in an oven to obtain MXene nanosheets;

[0011] (2) Preparing an electrospinning solution: Weigh PAN powder, add PAN to DMF, heat and stir to dissolve PAN, and obtain a PAN-DMF solution; add the weighed MXene nanosheets treated with a surfactant to the PAN-DMF solution, stir to disperse the MXene nanosheets in the PAN-DMF solution; and obtain a PAN@MXene electrospinning solution.

[0012] (3) Preparation of PAN@MXene nanofiber aerogel by electrospinning: The PAN@MXene electrospinning solution is placed in an electrospinning syringe, and the electrospinning environment temperature, humidity, feed rate, spinning voltage, deionized water receiver rotation speed, and spinning distance are set, and then electrospinning is performed to obtain a PAN@MXene nanofiber aqueous dispersion; the PAN@MXene nanofiber aqueous dispersion prepared by electrospinning is subjected to liquid nitrogen directionally freezing and freeze-drying to obtain a PAN@MXene nanofiber aerogel.

[0013] (4) Preparation of N-CNF@MXene aerogel: The prepared PAN@MXene nanofiber aerogel is placed in a tubular furnace, pre-oxidized and heated in air, then kept warm; then heated in an argon atmosphere, then kept warm for reduction; then cooled to obtain N-CNF@MXene aerogel.

[0014] (5) In situ atomic layer deposition of MoS2 coated N-CNF@MXene composite nanofiber aerogel to prepare N-CNF@MXene@MoS2 composite nanofiber absorbing aerogel: After plasma cleaning, the N-CNF@MXene aerogel is placed in the reaction chamber of the atomic layer deposition equipment, and the reaction chamber is heated and kept warm; MoCl5 and H2S pulses are introduced into the heated reaction chamber to obtain N-CNF@MXene@MoS2 composite nanofiber absorbing aerogel.

[0015] In step (5), the former precursor is flushed before the latter precursor pulse starts, and MoCl5 and H2S are flushed with nitrogen at a flow rate of 50-300sccm before the H2S pulse starts; the heating temperature of the MoCl5 precursor is 190-300°C, and the H2S precursor is maintained at room temperature. The two precursors are loaded into the reaction chamber with nitrogen at the same flow rate of 50-200sccm; the number of cycles is 10-1200 times, and N-CNF@MXene@MoS2 composite absorbing aerogel is obtained. The specific process is to introduce MoCl5 and H2S pulses into the heating reaction chamber to obtain N-CNF@MXene@MoS2 composite absorbing aerogel: MoCl5 and H2S are loaded into the heating reaction chamber by nitrogen for pulsing. Before the pulsing, MoCl5 and H2S are flushed with nitrogen at a flow rate of 50-300sccm; the flushing time for MoCl5 is 60-200s; the heating temperature of MoCl5 is 190-300℃; the flushing time for H2S is 60-200s; the temperature of H2S is 20-25℃.

[0016] In step (5), the plasma cleaning time is 1-5 minutes; the temperature of the heating reaction chamber is 450-750°C, the heating time is 50-80 minutes, and the insulation time is 60-90 minutes; the MoCl5 and H2S pulse time parameters are: MoCl5 pulse time is 1-3 seconds; H2S pulse time is 1-3 seconds.

[0017] In step (1), the concentration of HCl solution is 36%, the ratio of Ti3AlC2 to LiF is one of 1:1 and 1:1.2, and the reaction time is 36-48 hours; the ultrasonic treatment power is 200W-300W, and the ultrasonic treatment time is 1-4 hours; the speed of centrifugal removal of Al is 3500-5000r / min, and the centrifugation time is 10-30min; the surfactant is hexadecyltrimethylammonium bromide or hexadecyldimethylethylammonium bromide, the concentration of the surfactant solution is 0.5-2M, and the immersion time is 1-5 hours; the drying temperature is 60-80°C.

[0018] In step (2), the mass fraction of PAN in the DMF solution of PAN is one of 8wt.%, 10wt.%, 12wt.%, the stirring temperature is 50-80°C, and the stirring time is 24h; the mass fraction of MXene in the PAN@MXene electrospinning solution is one of 2wt.%, 4wt.%, 6wt.%, 8wt.%, 10wt.%, 12wt.%, 14wt.%, and the stirring time is 24-36h.

[0019] In step (3), the electrospinning environment temperature is set to 25-40°C; the ambient humidity is 30-45%; the feed rate is 0.5-1.5 mL / min; the spinning voltage is 10.5-18 kV; the speed of the deionized water receiver end is 200-400 r / min; the receiver speed is 40-120 r / min, the spinning distance is 10-15 cm; the concentration of the PAN@MXene nanofiber aqueous dispersion is 10-50 mg / mL; and the freeze-drying time is 48-72 h.

[0020] In step (4), during the pre-oxidation process, the heating rate of PAN@MXene nanofiber aerogel is 1-5°C / min, and the temperature is raised to 220-300°C and kept warm for 1-2h; the heating rate of PAN@MXene nanofiber aerogel in argon is 2-5°C / min, the insulation temperature is 600-900°C, the insulation time is 2-6h, and the flow rate of argon is 20-150sccm.

[0021] In step (4), the density of N-CNF@MXene aerogel is 10-50 mg / cm 3 , the average pore size is 10-150 μm, the carbon nanofiber diameter is 100-200 nm, and the MXene nanosheets are distributed in a nebula-like manner in the N-CNF@MXene nanofibers.

[0022] In step (5), the density of the N-CNF@MXene@MoS2 composite nanofiber absorbing aerogel based on atomic layer deposition is 15 to 60 mg / cm -3 The porosity is 99-99.8%; the diameter of N-CNF is 100-200nm, and the thickness of MoS2 film deposited on the surface of in-situ grown N-CNF is 100-200nm. The carbon nanofiber wrapped with MoS2 is 200-400nm, and the MoS2 deposited on the surface of in-situ deposited N-CNF is 100-200nm.

[0023] Working principle: The invented in-situ atomic layer deposited MoS2 coated N-CNF@MXene composite nanofiber absorbing aerogel is composed of N-CNF@MXene composite nanofibers with nebula-like distribution of MXene nanosheets and atomic layer deposited MoS2, containing rich N-CNF / MoS2 and MXene / N-CNF heterogeneous interfaces, and has a unique structure of nebula-like distribution of MXene nanosheets in N-CNF and a conductive layer composed of cross-linked MoS2 wrapped on the N-CNF@MXene nanofibers.

[0024] The preparation method is as follows: (1) etching, washing, treating MXene nanosheets with a surfactant, drying to obtain MXene nanosheets, and uniformly dispersing them in a PAN DMF solution to obtain a PAN@MXene electrospinning solution; (2) performing electrospinning, collecting the PAN@MXene nanofibers produced by electrospinning with deionized water, and performing liquid nitrogen-based directional freezing, followed by freeze drying to obtain a PAN@MXene nanofiber aerogel; (3) pre-oxidizing the PAN@MXene nanofiber aerogel in air, and then reducing it by heating in argon to obtain a N-CNF@MXene aerogel; (4) uniformly depositing MoS2 on the nanofibers in the N-CNF@MXene aerogel by atomic layer deposition to obtain a MoS2 in-situ deposited and coated N-CNF@MXene@MoS2 composite nanofiber absorbing aerogel. The N-CNF in this material contains nebula-like distributed MXene nanosheets, and the heterogeneous interface formed by the N-CNF enhances the conductivity loss and relaxation loss of the absorber; the in-situ grown MoS2 forms a conductive layer on the surface of N-CNF@MXene, and the conductive loss of electromagnetic waves is enhanced; the heterogeneous interface formed by the uniformly deposited MoS2 film and N-CNF improves the impedance matching characteristics of electromagnetic waves, thereby further enhancing the wave absorption performance.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following advantages: the present invention disperses MXene nanosheets into N-CNF to achieve a nebula-like distribution of MXene nanosheets in N-CNF, thereby alleviating the self-stacking of MXene nanosheets, improving the impedance matching of the composite aerogel, and achieving the effect of increasing the polarization interface and conductive loss; depositing MoS2 on the N-CNF@MXene nanofibers to form a large number of heterogeneous interfaces is conducive to improving polarization losses and improving impedance matching, thereby improving the electromagnetic wave attenuation ability of the composite aerogel. Compared with other preparation methods of composite aerogel absorbing materials, the preparation method of the in-situ atomic layer deposition Mo S2 coated N-CNF@MXene composite nanofiber absorbing aerogel of the present invention has the advantages of unique MXene nanosheet distribution structure, effective alleviation of MXene self-nanosheet stacking problem, simple and feasible process, and simple and precise control of MoS2 thickness. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the SEM image and structural schematic diagram of the in-situ atomic layer deposited MoS2-coated N-CNF@MXene composite nanofiber absorbing aerogel nanofiber of the present invention; the one-dimensional structure with a high aspect ratio is N-CNF@MXene with in-situ grown Mo S2.

[0027] Figure 2 These are the TEM and EDS images of the nebula-like distributed MXene in the N-CNF@MXene composite nanofiber absorbing aerogel coated with in-situ atomic layer deposition MoS2 of the present invention; the fibrous structure is N-CNF@MXene, and the material on its surface is deposited MoS2.

[0028] Figure 3 This is the curve of reflection loss value changing with frequency at different thicknesses of the in-situ atomic layer deposited MoS2-coated N-CNF@MXene composite nanofiber absorbing aerogel sample of the present invention.

[0029] Figure 4 This is the SEM image of the N-CNF@MXene composite nanofiber absorbing aerogel sample coated with in-situ atomic layer deposition MoS2 of the present invention; the fibrous structure is N-CNF@MXene@MoS2, and the material on the surface is deposited MoS2. DETAILED DESCRIPTION

[0030] Figure 1 In the SEM image and structural schematic diagram of the in-situ atomic layer deposited MoS2-coated N-CNF@MXene composite nanofiber absorbing aerogel nanofiber of the present invention, the one-dimensional structure with a high aspect ratio is N-CNF@MXene with in-situ grown MoS2.

[0031] Figure 2In the TEM image and EDS image of the nebula-like distribution of MXene in the in-situ atomic layer deposited MoS2-coated N-CNF@MXene composite nanofiber absorbing aerogel of the present invention, the fibrous structure is N-CNF@MXene, and the substance on its surface is deposited MoS2.

[0032] Embodiment 1:

[0033] The in-situ atomic layer deposited MoS2-coated N-CNF@MXene composite nanofiber absorbing aerogel of the present invention is composed of N-CNF@MXene@MoS2 composite nanofibers and has a unique structure of nebula-shaped distributed MXene.

[0034] The preparation method of the in-situ atomic layer deposition MoS2 coated N-CNF@MXene composite nanofiber absorbing aerogel of the present invention comprises the following steps:

[0035] (1) Preparation of electrospinning solution: 60 mL of HCl solution was measured, 3 g of Ti3AlC2 and 3 g of LiF were weighed and added to the HCl solution for reaction for 24 h, and the solution was washed until neutral; the neutral solution was ultrasonically treated at 200 W for 3 h, and Al was removed by centrifugation at a speed of 4000 r / min for 30 min; the surfactant hexadecyltrimethylammonium bromide (CTAB) was added to the MXene aqueous solution, and the concentration of the surfactant solution in the solution after preparation was 1 M. After soaking for 2 h, the solution was dried in an oven at 75 °C.

[0036] (2) Preparation of electrospinning solution: Weigh 1 g of PAN powder and add it to 9 g of DMF. Heat and stir at 60 °C for 24 h. The mass fraction of PAN is 10 wt.%. Add MXene nanosheets and stir for 24 h. The mass fraction of MXene is 12 wt.%. Obtain PAN@MXene electrospinning solution.

[0037] (3) Preparation of PAN@MXene nanofiber aerogel by electrospinning: The PAN@MXene electrospinning solution was placed in an electrospinning syringe. The electrospinning environment temperature was 25°C, the ambient humidity was 30%, the feed rate was 0.5 mL / min, and the spinning voltage was 13 kV. The speed of the deionized water receiver end was 260 r / min, the spinning distance was 12 cm, and spinning was started to obtain a PAN@MXene nanofiber aqueous dispersion with a concentration of 35 mg / mL. The PAN@MXene nanofiber aqueous dispersion was frozen with liquid nitrogen and freeze-dried for 50 h to obtain a PAN@MXene nanofiber aerogel.

[0038] (4) Preparation of N-CNF@MXene aerogel: The prepared PAN@MXene nanofiber aerogel was placed in a tubular furnace and subjected to pre-oxidation treatment at a heating rate of 1.5°C / min to 240°C and kept warm for 2 h; the temperature was increased in an argon atmosphere at a heating rate of 3°C / min; the aerogel was carbonized at a temperature of 900°C for 4 h at an argon flow rate of 120 sccm; after cooling, N-CNF@MXene aerogel was obtained.

[0039] (5) In situ atomic layer deposition of MoS2 coated N-CNF@MXene composite nanofiber aerogel to prepare N-CNF@MXene@MoS2 composite absorbing aerogel: The N-CNF@MXene aerogel was plasma cleaned for 5 min; the aerogel was placed in the reaction chamber of the atomic layer deposition equipment, the reaction chamber was heated and kept warm, and then the insulation temperature was 600 ° C, the heating time was 60 min, and the insulation time was 70 min; MoCl5 and H2S pulses were started, the MoCl5 pulse time was 1 s and the H2S pulse time was 1 s, and the former precursor was flushed before the latter precursor pulse started, and the flushing gas was nitrogen with a flow rate of 150 scc m; the flushing time for the MoCl5 precursor is 150 s, the flushing time for the H2S precursor is 150 s, the heating temperature of the MoCl5 precursor is 190°C, the H2S precursor is kept at room temperature, and nitrogen gas with a flow rate of 160 sccm of the two precursors is loaded into the reaction chamber; the number of cycles is 800, and N-CNF@MXene@Mo S2 composite absorbing aerogel is obtained.

[0040] Figure 3 The curve of reflection loss value versus frequency for the sample of Example 1 at a thickness of 1-5 mm is shown in the figure. It is found that the sample has the best absorption loss when the thickness is 3.5 mm, and the minimum reflection loss value corresponding to this thickness is -78.3 dB, indicating that the best impedance matching is achieved at this thickness.

[0041] Embodiment 2:

[0042] (1) Preparation of electrospinning solution: 60 mL of HCl solution was measured, 3 g of Ti3AlC2 and 3.6 g of LiF were weighed and added to the HCl solution for reaction for 36 h, and the solution was washed until neutral; the neutral solution was ultrasonically treated at 260 W for 3 h, and Al was removed by centrifugation at a speed of 3600 r / min for 15 min; the surfactant hexadecyl dimethyl ethyl ammonium bromide (EHDAB) was added to the MXene aqueous solution, and the concentration of the surfactant solution in the solution after preparation was 2 M. After soaking for 5 h, the solution was dried in an oven at 60 °C.

[0043] (2) Preparation of electrospinning solution: Weigh 1.2 g of PAN powder and add it to 8.8 g of DMF. Heat and stir at 80 °C for 24 h. The PAN mass fraction is 12 wt.%. Add MXene nanosheets and stir for 36 h. The MXene mass fraction is 10 wt.%. Obtain PAN@MXene electrospinning solution.

[0044] (3) Preparation of PAN@MXene nanofiber aerogel by electrospinning: The PAN@MXene electrospinning solution was placed in an electrospinning syringe. The electrospinning environment temperature was 30°C, the ambient humidity was 35%, the feed rate was 1.1 mL / min, and the spinning voltage was 12 kV. The speed of the deionized water receiver was 400 r / min, the spinning distance was 15 cm, and spinning was started to obtain a PAN@MXene nanofiber aqueous dispersion with a concentration of 15 mg / mL. The PAN@MXene nanofiber aqueous dispersion was frozen with liquid nitrogen and freeze-dried for 60 h to obtain a PAN@MXene nanofiber aerogel.

[0045] (4) Preparation of N-CNF@MXene aerogel: The prepared PAN@MXene nanofiber aerogel was placed in a tubular furnace and subjected to pre-oxidation treatment. The pre-oxidation heating rate was 3°C / min, the temperature was raised to 290°C, and the temperature was kept at this temperature for 1.5 h; the temperature was raised in an argon atmosphere at a heating rate of 2°C / min; the aerogel was carbonized at a temperature of 750°C for 6 h and an argon flow rate of 80 sccm; after cooling, N-CNF@MXene aerogel was obtained.

[0046] (5) In situ atomic layer deposition of MoS2 coated N-CNF@MXene composite nanofiber aerogel to prepare N-CNF@MXene@MoS2 composite absorbing aerogel: The N-CNF@MXene aerogel was plasma cleaned for 2 min; the aerogel was placed in the reaction chamber of the atomic layer deposition equipment, the reaction chamber was heated and kept warm, and then the insulation temperature was 500 °C, the heating time was 50 min, and the insulation time was 80 min; MoCl5 and H2S pulses were introduced, and the MoCl5 pulse The time is 2.5s and the H2S pulse time is 2.5s. The former precursor is flushed before the latter precursor pulse starts. The flushing gas is nitrogen with a flow rate of 120sccm; the flushing time of the MoCl5 precursor is 80s, and the flushing time of the H2S precursor is 80s. The heating temperature of the MoCl5 precursor is 290°C, and the H2S precursor is kept at room temperature. The two precursors are loaded into the reaction chamber with nitrogen at a flow rate of 80sccm; the number of cycles is 450, and N-CNF@MXene@Mo S2 composite absorbing aerogel is obtained.

Claims

1. An in-situ atomic layer deposition MoS2 coated N-CNF@MXene composite nanofiber microwave absorbing aerogel, characterized by: It is composed of N-CNF@MXene composite nanofibers with nebula-like distribution of MXene nanosheets and atomic layer deposited MoS2, and has a structure in which MXene nanosheets are distributed in a nebula-like manner in N-CNF and a conductive layer composed of MoS2 cross-linked with each other is wrapped on the N-CNF@MXene nanofibers.

2. A method for preparing the in-situ atomic layer deposition MoS2-coated N-CNF@MXene composite nanofiber absorbing aerogel as claimed in claim 1, characterized in that: The following steps are involved: (1) Preparation of MXene nanosheets: HCl solution was measured, Ti3AlC2 and LiF were weighed and added to the HCl solution for reaction, the washing solution was neutral, the neutral solution was ultrasonically treated, Al was removed by centrifugation, a surfactant was added to the MXene aqueous solution, and the solution was dried in an oven to obtain MXene nanosheets; (2) preparing an electrospinning solution: weighing PAN powder, adding PAN to DMF, heating and stirring to dissolve PAN, and obtaining a PAN-DMF solution; adding the weighed MXene nanosheets treated with a surfactant to the PAN-DMF solution, stirring to disperse the MXene nanosheets in the PAN-DMF solution, and obtaining a PAN@MXene electrospinning solution; (3) Preparation of PAN@MXene nanofiber aerogel by electrospinning: placing the PAN@MXene electrospinning solution in an electrospinning syringe, setting the electrospinning environment temperature, humidity, feed rate, spinning voltage, deionized water receiver rotation speed, spinning distance, and then performing electrospinning to obtain a PAN@MXene nanofiber aqueous dispersion, and subjecting the PAN@MXene nanofiber aqueous dispersion prepared by electrospinning to liquid nitrogen directional freezing and freeze drying to obtain a PAN@MXene nanofiber aerogel; (4) Preparation of N-CNF@MXene aerogel: The prepared PAN@MXene nanofiber aerogel was placed in a tubular furnace, pre-oxidized and heated in air, then heated in argon, heated and reduced, and cooled to obtain N-CNF@MXene aerogel; (5) In situ atomic layer deposition of MoS2 coated N-CNF@MXene composite nanofiber aerogel to prepare N-CNF@MXene@MoS2 composite nanofiber absorbing aerogel: The N-CNF@MXene aerogel was plasma cleaned and placed in the reaction chamber of the atomic layer deposition equipment. After the reaction chamber was heated and kept warm, MoCl5 and H2S pulses were introduced into the heated reaction chamber to obtain N-CNF@MXene@MoS2 composite absorbing aerogel.

3. The method for preparing the in-situ atomic layer deposition MoS2-coated N-CNF@MXene composite nanofiber microwave absorbing aerogel according to claim 2, characterized in that: In step (5), the plasma cleaning time is 1-5 minutes; the temperature of the heating reaction chamber is 450-750°C, the heating time is 50-80 minutes, and the insulation time is 60-90 minutes; the MoCl5 and H2S pulse time parameters are: MoCl5 pulse time is 1-3 seconds; H2S pulse time is 1-3 seconds.

4. The method for preparing the in-situ atomic layer deposition MoS2-coated N-CNF@MXene composite nanofiber microwave absorbing aerogel according to claim 2, characterized in that: In step (5), MoCl5 and H2S pulses are introduced into the heating reaction chamber to obtain N-CNF@MXene@MoS2 composite absorbing aerogel, and the process is: MoCl5 and H2S are loaded into the heating reaction chamber by nitrogen for pulsing. Before the pulsing, MoCl5 and H2S are flushed with nitrogen at a flow rate of 50-300sc cm; the flushing time for MoCl5 is 60-200s; the heating temperature of MoCl5 is 190-300℃; the flushing time for H2S is 60-200s; the temperature of H2S is 20-25℃.

5. The method for preparing the in-situ atomic layer deposition MoS2-coated N-CNF@MXene composite nanofiber microwave absorbing aerogel according to claim 2, characterized in that: In step (1), the concentration of the HCl solution is 36%, the ratio of Ti3AlC2 to LiF is one of 1:1 and 1:1.2, and the reaction time is 36-48 hours; the ultrasonic treatment power is 200W-300W, and the ultrasonic treatment time is 1-4 hours; the speed of centrifugal removal of Al is 3500-5000r / min, and the centrifugation time is 10-30min; the surfactant is hexadecyltrimethylammonium bromide or hexadecyldimethylethylammonium bromide, the concentration of the surfactant solution is 0.5-2M, and the immersion time is 1-5 hours; the drying temperature is 60-80°C.

6. The method for preparing the in-situ atomic layer deposition MoS2-coated N-CNF@MXene composite nanofiber microwave absorbing aerogel according to claim 2, characterized in that: In step (2), the mass fraction of PAN in the PAN DMF solution is one of 8wt.%, 10wt.%, 12wt.%, the stirring temperature is 50-80°C, and the stirring time is 24h; the mass fraction of MXene in the PAN@MXene electrospinning solution is one of 2wt.%, 4wt.%, 6wt.%, 8wt.%, 10wt.%, 12wt.%, 14wt.%, and the stirring time is 24-36h.

7. The method for preparing the in-situ atomic layer deposition MoS2-coated N-CNF@MXene composite nanofiber microwave absorbing aerogel according to claim 2, characterized in that: In step (3), the electrospinning environment temperature is set to 25-40°C; the ambient humidity is 30-45%; the feed rate is 0.5-1.5 mL / min; the spinning voltage is 10.5-18 kV; the speed of the deionized water receiver end is 200-400 r / min; the spinning distance is 10-15 cm; the concentration of the PAN@MXene nanofiber aqueous dispersion is 10-50 mg / mL; and the freeze-drying time is 48-72 h.

8. The method for preparing the in-situ atomic layer deposition MoS2-coated N-CNF@MXene composite nanofiber microwave absorbing aerogel according to claim 2, characterized in that: In step (4), during the pre-oxidation process, the heating rate of the PAN@MXene nanofiber aerogel is 1-5°C / min, and the temperature is raised to 220-300°C and kept warm for 1-2h; the heating rate of the PAN@MXene nanofiber aerogel in argon is 2-5°C / min, the insulation temperature is 600-900°C, the insulation time is 2-6h, and the flow rate of argon is 20-150sccm.

9. The method for preparing the in-situ atomic layer deposition MoS2-coated N-CNF@MXene composite nanofiber microwave absorbing aerogel according to claim 2, characterized in that: In step (4), the density of the N-CNF@MXene aerogel is 10 to 50 mg / cm 3 , the average pore size is 10-150 μm, the carbon nanofiber diameter is 100-200 nm, and the MXene nanosheets are distributed in a nebula-like manner in the N-CNF@MXene nanofibers.

10. The method for preparing the in-situ atomic layer deposition MoS2-coated N-CNF@MXene composite nanofiber microwave absorbing aerogel according to claim 2, characterized in that: In step (5), the density of the composite nanofiber absorbing aerogel is 15 to 60 mg / cm 3 , the porosity is 99-99.8%; the carbon nanofibers wrapped with MoS2 are 200-400nm, and the MoS2 deposited on the surface of the in-situ deposited N-CNF is 100-200nm.

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