Lightweight high-efficiency high-entropy alloy-hollow carbon fiber wave-absorbing composite material and preparation method thereof

Abstract

The invention discloses a lightweight efficient high-entropy alloy-hollow carbon fiber wave-absorbing composite material and a preparation method, and relates to the technical field of wave-absorbing materials. The preparation method comprises the following steps: adding PAN into N, N-dimethylformamide, and dissolving to obtain a PAN solution; adding ferric acetylacetonate, cobalt acetate tetrahydrate, nickel acetate tetrahydrate, manganese acetate tetrahydrate and cupric acetate monohydrate into the PAN solution, heating and stirring to obtain a coaxial spinning shell layer spinning solution; adding PVP (polyvinyl pyrrolidone) into DMF (dimethyl formamide), dissolving and defoaming to obtain a coaxial spinning core layer spinning solution; respectively filling the two spinning solutions into an injector, and carrying out coaxial electrostatic spinning; and drying, carrying out high-temperature calcination in an argon atmosphere, and carrying out heat preservation to obtain the lightweight high-efficiency high-entropy alloy-hollow carbon fiber wave-absorbing composite material. The FeCoNiMnCu high-entropy alloy wave-absorbing composite material which is low in density, stable in structure, uniform and hollow in fiber structure is obtained by combining a coaxial electrostatic spinning method with high-temperature calcination.

Description

Technical Field

[0001] The invention relates to the technical field of wave-absorbing materials, and in particular to a lightweight and efficient high-entropy alloy-hollow carbon fiber wave-absorbing composite material and a preparation method thereof. Background Art

[0002] The research on electromagnetic wave absorbing materials originated from the application of military stealth fighters, and later expanded to the civilian field, used for the protection or shielding of electronic devices. However, the raw materials of electromagnetic wave absorbing materials in the past were mostly ferromagnetic materials such as ferrite, but these materials have high density, resulting in a large specific gravity of the absorbing materials, which is not conducive to the lightweight of the device. In addition, these materials also have the disadvantages of narrow absorption, weak absorption, and high cost. Carbon-based absorbing materials such as expanded graphite, carbon nanotubes, and graphene are complicated to process and expensive. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a lightweight and efficient high-entropy alloy-hollow carbon fiber absorbing composite material and a preparation method. The present invention uses a coaxial electrospinning method combined with high-temperature calcination to obtain a low-density, structurally stable FeCoNiMnCu high-entropy alloy absorbing composite material with a uniform, hollow fiber structure.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a lightweight and efficient high-entropy alloy-hollow carbon fiber absorbing composite material, comprising the following steps: Step 1: adding polyacrylonitrile PAN into N,N-dimethylformamide to dissolve and obtain a PAN solution; adding ferric acetylacetonate, cobalt acetate tetrahydrate, nickel acetate tetrahydrate, manganese acetate tetrahydrate and copper acetate monohydrate to the PAN solution, heating and stirring to promote the sol-gelation of the metal salt, and using the solution as a coaxial spinning shell spinning solution for standby use; Step 2: Add polyvinyl pyrrolidone (PVP) into N,N-dimethylformamide, dissolve, and remove bubbles to obtain a colorless and transparent PVP solution, which is used as a coaxial spinning core layer spinning solution for standby use; Step 3: The two spinning solutions are respectively loaded into different syringes, the injection speed of the coaxial spinning core layer spinning solution is set to 0.04-0.09mL / h, and the injection speed of the coaxial spinning shell layer spinning solution is set to 0.5-0.9mL / h, and coaxial electrospinning is performed; during the spinning process, the spinning voltage is set to 15-20kV, the distance between the needle and the receiver is 15-18cm, and the speed of the drum receiving device is 100-150r / min; Step 4: Dry the fibers obtained by the spinning, and then calcine the fibers at high temperature in an argon atmosphere. The high temperature calcination is first heated to 600°C-1000°C at a heating rate of 5-10°C / min, and then kept warm to obtain a lightweight and efficient high entropy alloy-hollow carbon fiber absorbing composite material.

[0005] Preferably, step 1: adding polyacrylonitrile PAN to N,N-dimethylformamide, and heating and stirring at 70-90°C to promote dissolution to obtain a 10-15wt% PAN solution; adding ferric acetylacetonate, cobalt acetate tetrahydrate, nickel acetate tetrahydrate, manganese acetate tetrahydrate, and copper acetate monohydrate to the above PAN solution, continuing to heat and stir at 70-90°C for 30-60min, transferring to room temperature, and continuing to stir for 8-12h to promote sol-gelation of the metal salt, and using it as a coaxial spinning shell spinning solution for standby use.

[0006] Preferably, in step 1, the mass ratio of each metal salt, ferric acetylacetonate, cobalt acetate tetrahydrate, nickel acetate tetrahydrate, manganese acetate tetrahydrate, copper acetate monohydrate to PAN is 1:5-1:15, respectively.

[0007] Preferably, step 2: adding polyvinyl pyrrolidone PVP to N,N-dimethylformamide, heating and stirring at 50-80°C to promote dissolution, and vacuum degassing in a vacuum drying oven to obtain a colorless and transparent 20-30wt% PVP solution, which is used as the coaxial spinning core layer spinning solution for standby use.

[0008] Preferably, in step three: the mass ratio of polyacrylonitrile PAN to polyvinyl pyrrolidone PVP is 1:4-1:7.

[0009] Preferably, step three: the above two spinning solutions are respectively loaded into different syringes, the injection speed of the coaxial spinning core layer spinning solution is set to 0.06mL / h, and the injection speed of the coaxial spinning shell layer spinning solution is 0.7mL / h, and coaxial electrospinning is performed; during the spinning process, the spinning voltage is set to 18kV, the distance between the needle and the receiver is 15cm, and the rotation speed of the drum receiving device is 100r / min.

[0010] Preferably, step 4: high temperature calcination and holding time is 1-4 h.

[0011] Further preferably, in step 4: the high temperature calcination holding time is 1-4 h.

[0012] Preferably, step 4: the high temperature calcination temperature is 700°C.

[0013] Preferably, step 4: high temperature calcination is carried out at a heating rate of 5°C / min.

[0014] A lightweight and efficient high entropy alloy-hollow carbon fiber wave absorbing composite material is prepared by adopting the preparation method of the lightweight and efficient high entropy alloy-hollow carbon fiber wave absorbing composite material.

[0015] The beneficial effect of adopting the above technical solution is that the present invention successfully prepares a lightweight and efficient high-entropy alloy-hollow carbon fiber absorbing composite material by utilizing coaxial electrospinning combined with high-temperature calcination.

[0016] (1) The present invention prepares PVP@FeCoNiMnCu / PAN fibers with a core-shell structure by an electrospinning method, and converts the PAN fibers into carbon fibers by subsequent high-temperature calcination. The metal salt is simultaneously reduced in situ to FeCoNiMnCu nano high-entropy alloy particles using carbon as a reducing agent. During the high-temperature calcination process, the PVP of the fiber shell layer is removed to obtain a FeCoNiMnCu high-entropy alloy composite hollow carbon fiber absorber material.

[0017] (2) The present invention adjusts the graphitization degree, crystallization behavior and wall thickness of the hollow fiber by adjusting the calcination temperature to control the decomposition process of PVP and PAN and the growth process of high entropy alloy particles. When the calcination temperature is 700°C, FeCoNiMnCu / HCNF-700 obtains excellent wave absorption performance. At a low filling amount of 5w% and a thickness of 3.15mm, a reflection loss of -59.1 dB can be achieved, and the effective absorption bandwidth can reach 6.4 GHz, corresponding to an effective absorption frequency band of 11.6GHz-18 GHz.

[0018] (3) The present invention uses coaxial electrospinning to prepare FeCoNiMnCu / HCNF high entropy alloy / carbon hollow fiber absorbing composite materials. By introducing a hollow structure, the impedance matching and attenuation constant are optimized, and the absorbing performance is enhanced from three aspects: multiple reflection, interface polarization, and magnetic loss. Finally, at an ultra-low filling amount (5 wt%), a thickness of 3.15 mm, and a frequency of 11.7 GHz, the RLmin of FeCoNiMnCu / HCNF-700 reaches -59.1 dB, and the effective absorption frequency band can reach 6.4 GHz (11.6 GHz-18 GHz), covering the entire Ku band. It is a new type of "thin, light, wide, and strong" absorbing material. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments; Figure 1 It is a schematic diagram of the preparation process of the lightweight and efficient high entropy alloy-hollow carbon fiber absorbing composite material FeCoNiMnCu / HCNF of the present invention; Figure 2 is a SEM image of FeCoNiMnCu / HCNF-700 obtained in Example 1 of the present invention; Figure 3is a TEM image of FeCoNiMnCu / HCNF-700 obtained in Example 1 of the present invention; Figure 4 is the XRD pattern of FeCoNiMnCu / HCNF-700 obtained in Example 1 of the present invention; Figure 5 is the Raman graph of FeCoNiMnCu / HCNF-700 obtained in Example 1 of the present invention; Figure 6 is the room temperature hysteresis loop diagram of FeCoNiMnCu / HCNF-700 obtained in Example 1 of the present invention; Figure 7 is a graph showing the relationship between the dielectric constant and complex magnetic permeability of FeCoNiMnCu / HCNF-700 obtained in Example 1 of the present invention and the frequency; Figure 8 It is a schematic diagram of the theoretical microwave absorption performance of FeCoNiMnCu / HCNF-700 obtained in Example 1 of the present invention. DETAILED DESCRIPTION Example 1

[0020] A method for preparing a lightweight and efficient high entropy alloy-hollow carbon fiber wave absorbing composite material comprises the following steps: 2.5 g of polyacrylonitrile (PAN) was added to 15 mL of N,N-dimethylformamide, and heated and stirred at 80°C to promote dissolution to obtain a 15 wt% PAN solution. 0.353 g of ferric acetylacetonate, 0.249 g of cobalt acetate tetrahydrate, 0.248 g of nickel acetate tetrahydrate, 0.245 g of manganese acetate tetrahydrate, and 0.199 g of copper acetate monohydrate were added to the above solution, and the solution was heated for 30 min, transferred to room temperature, and stirred for 15 h to promote the sol-gelation of the metal salts, and used as the coaxial spinning shell spinning solution.

[0021] Add 12 g of polyvinylpyrrolidone (PVP) into 30 mL of N,N-dimethylformamide, heat and stir at 60°C to promote dissolution, and perform vacuum degassing in a vacuum drying oven to obtain a colorless and transparent 30 wt% PVP solution as the coaxial spinning core layer spinning solution for use.

[0022] The two spinning solutions were respectively loaded into 10 mL plastic syringes. The injection speed of the core layer solution was set to 0.06 mL / h, and the injection speed of the shell layer spinning solution was 0.7 mL / h. During the spinning process, the spinning voltage was set to 18 kV, the distance between the needle and the receiver was 15 cm, and the rotation speed of the roller receiving device was 100 r / min.

[0023] The spun fibers were dried in a drying oven at 70°C for 8 h, and then calcined in an argon atmosphere, first at 700°C at a heating rate of 5°C / min, and then kept at this temperature for 2 h. The samples were named FeCoNiMnCu / HCNF-700. The preparation process of FeCoNiMnCu / HCNF is shown in the figure. Figure 1 shown.

[0024] Figure 2 and Figure 3 This is a microscopic morphology of the lightweight and efficient high entropy alloy-hollow carbon fiber absorbing composite material obtained in this embodiment. It can be observed that the high entropy alloy-hollow carbon fiber has a hollow fiber structure, and FeCoNiMnCu high entropy alloy nanoparticles grow on the surface of the hollow carbon fiber.

[0025] and Figure 4 This is the XRD pattern of the lightweight and efficient high entropy alloy-hollow carbon fiber absorbing composite material obtained in this embodiment, with three diffraction peaks at 44.0°, 51.1° and 75.4°, corresponding to the (111), (200) and (220) crystal planes of the FeCoNiMnCu high entropy alloy FCC phase, respectively.

[0026] Figure 5 This is the Raman graph of the lightweight and efficient high entropy alloy-hollow carbon fiber absorbing composite material obtained in this example. The D peak and G peak in the graph prove the existence of graphite structure in the material.

[0027] Figure 6 The room temperature hysteresis loop of the lightweight and efficient high entropy alloy-hollow carbon fiber absorbing composite material obtained in this embodiment has a low saturation magnetization intensity, which proves that the FeCoNiMnCu high entropy alloy is a typical soft magnetic material.

[0028] Figure 7 Graph showing the relationship between the dielectric constant and complex magnetic permeability of the lightweight, high-efficiency high-entropy alloy-hollow carbon fiber absorbing composite material obtained in this embodiment and the frequency.

[0029] The lightweight and efficient high entropy alloy-hollow carbon fiber absorbing composite material obtained in this embodiment has excellent electromagnetic wave absorption performance and the advantages of lightweight and high efficiency compared with other electromagnetic wave materials. Figure 8The schematic diagram of the theoretical wave absorption performance of the FeCoNiMnCu high entropy alloy-hollow carbon fiber obtained in this embodiment is shown. The lightweight and efficient high entropy alloy-hollow carbon fiber wave absorbing composite material obtained in this embodiment uses paraffin as the matrix, and the filling amount of the lightweight and efficient high entropy alloy-hollow carbon fiber wave absorbing composite material in the matrix (paraffin) is 5wt%, and lightweight and efficient high entropy alloy-hollow carbon fiber wave absorbing composite material / paraffin mixed samples with different thicknesses of 1.9-3.4 mm are prepared. When the thickness of the sample is 3.15mm, the absorption peak of the material at 11.7 GHz reaches -59.1 dB, and the absorption bandwidth is 6.4 GHz (11.6 GHz-18 GHz), which is higher than most materials reported in the literature. Example 2

[0030] 2.5 g of polyacrylonitrile (PAN) was added to 15 mL of N,N-dimethylformamide, and heated and stirred at 80°C to promote dissolution to obtain a 15 wt% PAN solution. 0.353 g of ferric acetylacetonate, 0.249 g of cobalt acetate tetrahydrate, 0.248 g of nickel acetate tetrahydrate, 0.245 g of manganese acetate tetrahydrate, and 0.199 g of copper acetate monohydrate were added to the above solution, and the solution was heated for 30 min, transferred to room temperature, and stirred for 15 h to promote the sol-gelation of the metal salts, and used as the coaxial spinning shell spinning solution.

[0031] Add 12 g of polyvinylpyrrolidone (PVP) into 30 mL of N,N-dimethylformamide, heat and stir at 60°C to promote dissolution, and perform vacuum degassing in a vacuum drying oven to obtain a colorless and transparent 30 wt% PVP solution as the coaxial spinning core layer spinning solution for use.

[0032] The two spinning solutions were respectively loaded into 10 mL plastic syringes. The injection speed of the core layer solution was set to 0.06 mL / h, and the injection speed of the shell layer spinning solution was 0.7 mL / h. During the spinning process, the spinning voltage was set to 18 kV, the distance between the needle and the receiver was 15 cm, and the rotation speed of the roller receiving device was 100 r / min.

[0033] The spun fibers were dried in a drying oven at 70°C for 8 h, and then calcined at high temperature in an argon atmosphere, first at a heating rate of 5°C / min to 600°C, and then kept at this temperature for 2 h. The sample was named FeCoNiMnCu / HCNF-600. Example 3

[0034] 2.5 g of polyacrylonitrile (PAN) was added to 15 mL of N,N-dimethylformamide, and heated and stirred at 80°C to promote dissolution to obtain a 15 wt% PAN solution. 0.353 g of ferric acetylacetonate, 0.249 g of cobalt acetate tetrahydrate, 0.248 g of nickel acetate tetrahydrate, 0.245 g of manganese acetate tetrahydrate, and 0.199 g of copper acetate monohydrate were added to the above solution, and the solution was heated for 30 min, transferred to room temperature, and stirred for 15 h to promote the sol-gelation of the metal salts, and used as the coaxial spinning shell spinning solution.

[0035] Add 12 g of polyvinylpyrrolidone (PVP) into 30 mL of N,N-dimethylformamide, heat and stir at 60°C to promote dissolution, and perform vacuum degassing in a vacuum drying oven to obtain a colorless and transparent 30 wt% PVP solution as the coaxial spinning core layer spinning solution for use.

[0036] The two spinning solutions were respectively loaded into 10 mL plastic syringes. The injection speed of the core layer solution was set to 0.06 mL / h, and the injection speed of the shell layer spinning solution was 0.7 mL / h. During the spinning process, the spinning voltage was set to 18 kV, the distance between the needle and the receiver was 15 cm, and the rotation speed of the roller receiving device was 100 r / min.

[0037] The spun fibers were dried in a drying oven at 70°C for 8 h, and then calcined in an argon atmosphere at high temperature, first at a heating rate of 5°C / min to 800°C, and then kept at this temperature for 2 h. The sample was named FeCoNiMnCu / HCNF-800.

Claims

1. A method for preparing a lightweight and efficient high entropy alloy-hollow carbon fiber absorbing composite material, characterized in that: The steps include: Step 1: adding polyacrylonitrile PAN into N,N-dimethylformamide to dissolve and obtain a PAN solution; adding ferric acetylacetonate, cobalt acetate tetrahydrate, nickel acetate tetrahydrate, manganese acetate tetrahydrate and copper acetate monohydrate to the PAN solution, heating and stirring to promote the sol-gelation of the metal salt, and using the solution as a coaxial spinning shell spinning solution for standby use; Step 2: Add polyvinyl pyrrolidone (PVP) into N,N-dimethylformamide, dissolve, and remove bubbles to obtain a colorless and transparent PVP solution, which is used as a coaxial spinning core layer spinning solution for standby use; Step 3: The two spinning solutions are respectively loaded into different syringes, the injection speed of the coaxial spinning core layer spinning solution is set to 0.04-0.09mL / h, and the injection speed of the coaxial spinning shell layer spinning solution is set to 0.5-0.9mL / h, and coaxial electrospinning is performed; during the spinning process, the spinning voltage is set to 15-20kV, the distance between the needle and the receiver is 15-18cm, and the speed of the drum receiving device is 100-150r / min; Step 4: Dry the fibers obtained by the spinning, and then calcine the fibers at high temperature in an argon atmosphere. The high temperature calcination is first heated to 600°C-1000°C at a heating rate of 5-10°C / min, and then kept warm to obtain a lightweight and efficient high entropy alloy-hollow carbon fiber absorbing composite material.

2. The method for preparing the lightweight and efficient high entropy alloy-hollow carbon fiber absorbing composite material according to claim 1, characterized in that The step 1 is as follows: adding polyacrylonitrile PAN to N,N-dimethylformamide, and heating and stirring at 70-90° C. to promote dissolution, to obtain a 10-15wt% PAN solution; adding ferric acetylacetonate, cobalt acetate tetrahydrate, nickel acetate tetrahydrate, manganese acetate tetrahydrate, and copper acetate monohydrate to the PAN solution, continuing to heat and stir at 70-90° C. for 30-60 minutes, transferring to room temperature, and continuing to stir for 8-12 hours to promote sol-gelation of the metal salt, and using the spinning solution as the coaxial spinning shell layer for standby use.

3. The method for preparing the lightweight and efficient high entropy alloy-hollow carbon fiber absorbing composite material according to claim 1, characterized in that The step 1: the mass ratio of each metal salt, ferric acetylacetonate, cobalt acetate tetrahydrate, nickel acetate tetrahydrate, manganese acetate tetrahydrate, copper acetate monohydrate and PAN is 1:5-1:15 respectively.

4. The method for preparing the lightweight and efficient high entropy alloy-hollow carbon fiber absorbing composite material according to claim 1, characterized in that The second step is to add polyvinyl pyrrolidone (PVP) to N,N-dimethylformamide, heat and stir at 50-80°C to promote dissolution, and perform vacuum degassing in a vacuum drying oven to obtain a colorless and transparent 20-30wt% PVP solution, which is used as the coaxial spinning core layer spinning solution for standby use.

5. The method for preparing the lightweight and efficient high entropy alloy-hollow carbon fiber absorbing composite material according to claim 1, characterized in that Step 3: The mass ratio of polyacrylonitrile PAN to polyvinyl pyrrolidone PVP is 1:4-1:

7.

6. The method for preparing the lightweight and efficient high entropy alloy-hollow carbon fiber absorbing composite material according to claim 1, characterized in that The step three is as follows: the two spinning solutions are respectively loaded into different syringes, the injection speed of the coaxial spinning core layer spinning solution is set to 0.06 mL / h, and the injection speed of the coaxial spinning shell layer spinning solution is set to 0.7 mL / h, and coaxial electrospinning is performed; during the spinning process, the spinning voltage is set to 18 kV, the distance between the needle and the receiver is 15 cm, and the rotation speed of the roller receiving device is 100 r / min.

7. The method for preparing the lightweight and efficient high entropy alloy-hollow carbon fiber absorbing composite material according to claim 1, characterized in that The step 4: high temperature calcination and heat preservation time is 1-4 hours.

8. The method for preparing the lightweight and efficient high entropy alloy-hollow carbon fiber absorbing composite material according to claim 1, characterized in that The step 4: high temperature calcination temperature is 700°C.

9. The method for preparing the lightweight and efficient high entropy alloy-hollow carbon fiber absorbing composite material according to claim 1, characterized in that The step 4: high temperature calcination is carried out at a heating rate of 5°C / min.

10. A lightweight and efficient high entropy alloy-hollow carbon fiber absorbing composite material, characterized in that: The composite material is prepared by the method for preparing a lightweight and efficient high entropy alloy-hollow carbon fiber absorbing composite material as described in any one of claims 1 to 9.

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