Cobalt-iron-silicon compound in-situ modified silicon carbide composite fiber as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of structure-function integrated composite materials, and discloses a cobalt-iron-silicon compound in-situ modified silicon carbide composite fiber as well as a preparation method and application thereof. The method comprises the following steps: dissolving soluble metal cobalt salt and soluble metal iron salt in a tetrahydrofuran solution containing polycarbosilane, then mixing with an ethanol solution of polyvinylpyrrolidone to prepare a spinning solution, and carrying out electrostatic spinning, pre-oxidation and high-temperature heat treatment in an inert atmosphere to finish SiC fiber ceramization and in-situ generation of a CoFeSi compound in one step, so as to obtain the SiC fiber ceramic CoFeSi composite material. The CoFeSi / SiC composite fiber aerogel with the three-dimensional network structure is prepared. The silicide type, the fiber morphology and the aerogel performance can be accurately controlled by regulating and controlling the metal source molar ratio and the heat treatment procedure. The material is light, flexible and resistant to high temperature, and magnetic CoFeSi generated in situ integrates excellent electromagnetic wave absorption and heat insulation performance. The method is simple in process, good in controllability, high in repeatability and suitable for large-scale preparation of the high-performance structure-function integrated material.

Description

Technical Field

[0001] This invention belongs to the field of structure-function integrated composite material technology, and discloses a cobalt-iron-silicon compound in-situ modified silicon carbide composite fiber and its preparation method, as well as the application of the cobalt-iron-silicon compound in-situ modified silicon carbide composite fiber in the fields of high temperature insulation or electromagnetic wave absorption. Background Technology

[0002] As aerospace equipment develops towards hypersonic speeds, long endurance, and stealth capabilities, the next generation of aircraft faces the dual challenges of extreme thermal environments and detection threats. Against this backdrop, developing structural-functional integrated materials that combine lightweight, flexibility, efficient thermal insulation, and broadband electromagnetic wave absorption capabilities has become a key core technology for improving the performance and survivability of next-generation equipment.

[0003] Silicon carbide (SiC) ceramic fibers are considered one of the most promising materials for the aforementioned applications due to their high specific strength, high modulus, excellent oxidation resistance, and high-temperature stability. In particular, three-dimensional aerogel materials constructed from high aspect ratio SiC nanofibers not only inherit the intrinsic high-temperature resistance of SiC ceramics but also possess low density, low thermal conductivity, and good flexibility, making them ideal high-temperature insulation materials. However, as an intrinsic semiconductor, the electromagnetic parameters of intrinsic SiC are difficult to adjust. Its single dielectric loss mechanism results in poor impedance matching characteristics, limited electromagnetic wave loss capability, and a narrow effective absorption bandwidth, severely restricting its direct application in the field of electromagnetic wave absorption.

[0004] To compensate for this deficiency, existing technologies typically attempt to introduce magnetic components (such as Fe, Co, Ni, and their compounds) into the SiC matrix to construct a synergistic mechanism between magnetic and dielectric losses, thereby optimizing impedance matching and enhancing electromagnetic wave attenuation. However, current mainstream post-processing composite technologies (such as electroless plating, magnetron sputtering, and physical coating) involve secondary processing on the surface of already formed SiC fibers, which has significant limitations: First, the interfacial bonding between the introduced magnetic particles and the fiber matrix is ​​weak, and they are prone to detachment under thermal stress or mechanical loads, leading to functional failure; second, the preparation process is complex and costly, and it is difficult to achieve a uniform distribution of the magnetic phase; in addition, the magnetic nanoparticles themselves are easily oxidized at high temperatures, resulting in insufficient stability.

[0005] It is evident that existing technologies struggle to simultaneously ensure a robust bond between the magnetic phase and the SiC matrix while maintaining process simplicity and high-temperature material stability. Therefore, there is an urgent need in this field for a novel technical solution capable of generating a thermally stable and magnetically excellent metal silicide in situ within SiC fibers via a simplified process, thereby achieving efficient and controllable preparation of high-performance structure-function integrated SiC fiber aerogels. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention aims to provide a method for preparing cobalt-iron-silicon compound-modified silicon carbide composite fibers in situ. This method employs in-situ composite technology to introduce high-temperature resistant magnetic metal silicides (CoFeSi) into SiC fibers. By uniformly dispersing cobalt and iron precursors at the molecular level in the spinning solution, precursor fibers are formed through electrospinning. A single heat treatment step then simultaneously achieves the ceramization of SiC fibers and the in-situ growth and robust composite of CoFeSi compound particles on the fiber surface. This method enables precise control of the electromagnetic parameters of the composite material, optimizes the synergistic mechanism of dielectric and magnetic losses, and significantly improves the material's electromagnetic wave absorption capability. The prepared CoFeSi / SiC composite fiber aerogel not only retains its lightweight, high-temperature resistant, and thermally insulating properties but also achieves efficient electromagnetic wave absorption and improved material mechanical properties, providing a new technical approach for the design of structural-functional integrated composite materials in the aerospace field.

[0007] To achieve the above objectives, the present invention employs the following technical solution: a method for preparing cobalt-iron-silicon compound-modified silicon carbide composite fibers, comprising the following steps: S1. At room temperature, polyvinylpyrrolidone (PVP) and anhydrous ethanol are mixed and stirred at a mass ratio of (0.7-1.3):7 to obtain mixture I; S2. Mix polycarbosilane (PCS) and tetrahydrofuran (THF) at a mass ratio of (0.8-1.2):15, then add soluble iron salt and soluble cobalt salt in a molar ratio of 1:1, wherein the mass ratio of soluble cobalt salt to THF is (0.1-0.5):15. Stir until homogeneous to obtain mixture II. S3. Slowly add mixture II dropwise to mixture I, wherein the mass ratio of mixture I to mixture II is 1:(1.8-2.4). After stirring evenly, degas the mixture and obtain the precursor fiber membrane through electrospinning. After vacuum drying, perform pre-oxidation treatment. S4. The pre-oxidized fiber membrane is placed in a protective atmosphere and calcined at 1300-1500 °C for 1-4 h to obtain silicon carbide composite fiber aerogel modified with cobalt iron silicon compound nanoparticles, denoted as CoFeSi / SiC.

[0008] Further improvements to the preparation method of in-situ modified silicon carbide composite fibers using cobalt-iron-silicon compounds: Preferably, the soluble iron salt is iron acetylacetonate and the soluble cobalt salt is cobalt acetylacetonate.

[0009] Preferably, in step S3, the mixture II is slowly added dropwise to the mixture I at a mixing rate of 400-600 r / min for 8-12 h.

[0010] Preferably, the specific parameters for spinning in step S3 are set as follows: high voltage 23-27 KV, spinning solution propulsion speed 1.6-2.5 ml / h, receiving distance 15-20 cm, and collection rotation speed 200-400 rpm.

[0011] Preferably, in step S3, the specific steps of vacuum drying of the precursor fiber membrane are as follows: placing the precursor fiber membrane in a vacuum drying oven at 60-90 ℃ for 12-24 h; then placing it in an oven at 60-120 ℃ for 12-24 h; and finally placing it in an oven at 160-220 ℃ for pre-oxidation for 12-24 h.

[0012] Preferably, in step S3, the vacuum-dried precursor fiber membrane is pre-oxidized by holding it at 150-250 °C for 12-24 h.

[0013] Preferably, in step S4, the calcination heating rate is 2-5 °C / min, and the gas flow rate is 180-250 ml / min.

[0014] Preferably, the protective atmosphere in step S4 is argon.

[0015] The second objective of this invention is to provide a method for preparing cobalt-iron-silicon compound in-situ modified silicon carbide composite fibers as described in any one of the above-mentioned methods, resulting in cobalt-iron-silicon compound in-situ modified silicon carbide composite fibers.

[0016] The third objective of this invention is to provide an application of the above-mentioned cobalt-iron-silicon compound in-situ modified silicon carbide composite fiber in the fields of high-temperature insulation or electromagnetic wave absorption.

[0017] The advantages of this invention compared to the prior art are as follows: 1) This invention provides a method for preparing cobalt-iron-silicon compound-modified silicon carbide composite fibers in situ. Using electrospinning technology, a silicon carbide composite fiber in situ modified with cobalt-iron-silicon compound nanoparticles is prepared, ultimately forming a fiber aerogel with a three-dimensional network structure. The ingenious aspect lies in the uniform mixing of iron-cobalt metal precursors (iron acetylacetone, cobalt acetylacetone) and polymer precursors (polycarbosilane PCS) in the solution stage. This allows the metal elements to react with silicon and carbon elements during subsequent heat treatment, generating CoFeSi compounds "in situ" inside or on the surface of the SiC fiber. Strong interfacial bonding and uniform dispersion are achieved: This invention achieves strong interfacial bonding and uniform dispersion by uniformly dispersing metal sources such as iron acetylacetone and cobalt acetylacetone at the molecular scale in the precursor spinning solution. Through electrospinning, pre-oxidation, and one-step calcination, CoFeSi silicide particles are successfully generated in situ on the surface of the SiC fiber. In this process, the metal source is eventually converted into the target silicide in situ through the oxide intermediate, forming a strong interfacial bond with the SiC fiber matrix. This effectively overcomes the problems of easy particle detachment and weak interfacial bonding that exist in traditional mechanical mixing, chemical deposition or physical coating methods.

[0018] 2) Controllable regulation of material composition and properties: By precisely controlling the molar ratio of iron acetylacetone to cobalt acetylacetone, the composition and content of the magnetic phase in the final composite fiber can be effectively regulated, thereby optimizing its electromagnetic parameters and impedance matching characteristics and improving electromagnetic wave absorption performance. Simultaneously, by finely controlling key process parameters such as calcination temperature and time, the crystal phase of the generated silicide and the microstructure of the fiber can be controlled, thus achieving effective regulation of the material's mechanical properties and high-temperature stability.

[0019] 3) Combining excellent comprehensive performance with good process adaptability: The CoFeSi / SiC composite fiber aerogel prepared by this invention successfully integrates lightweight and flexible physical properties, excellent high-temperature thermal insulation performance, and efficient high-temperature electromagnetic wave absorption capability, achieving structure-function integration. The preparation process is simple, short, and highly repeatable, and requires no complex post-processing steps, possessing the potential for large-scale production. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the preparation process of the present invention.

[0022] Figure 2The images show the XRD patterns of the composite fiber membranes prepared in Examples 1-6 of this invention.

[0023] Figure 3 Images (a), (b), and (c) are scanning electron microscope (SEM) images of the composite fibers FC / SiC-1, FC / SiC-2, and FC / SiC-3 prepared in Examples 1-3, respectively.

[0024] Figure 4 Images (a), (b), and (c) are scanning electron microscope (SEM) images of the composite fibers FC / SiC-4, FC / SiC-5, and FC / SiC-6 prepared in Examples 4-6, respectively.

[0025] Figure 5 This is a transmission electron microscope (TEM) image of the composite fiber FC / SiC-2 nanofibers prepared in Example 2.

[0026] Figure 6 This is a transmission electron microscope (TEM) image of the composite fiber FC / SiC-4 nanofibers prepared in Example 4.

[0027] Figure 7 In the figures (a), (b), (c), and (d), the reflection losses of the composite fibers FC / SiC-2, FC / SiC-4, FC / SiC-5, and FC / SiC-6 prepared in Examples 2, 4, 5, and 6, respectively, are in the frequency range of 2-18 GHz. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0029] The method for preparing high-temperature magnetic metal silicides in situ on the surface of SiC fibers by electrospinning, provided by the present invention, is described in detail below. Contents not described in detail in the embodiments of the present invention are prior art known to those skilled in the art.

[0030] Example 1

[0031] This embodiment provides a method for preparing cobalt-iron-silicon compound-modified silicon carbide composite fibers in situ. The preparation process is as follows: Figure 1 As shown, it includes the following steps: Step A1: At room temperature, 1 g of polyvinylpyrrolidone (PVP) and 6.5 g of anhydrous ethanol (EtOH) are mixed in a mass ratio of 1.07:7 to obtain mixture I. Step B1: Mix 1g of polycarbosilane (PCS) and 15g of tetrahydrofuran (THF) and stir until the solution is clear. Then add 0.3532g of iron acetylacetone (Fe(acac)3) and 0.2571g of cobalt acetylacetone (Co(acac)2), with a molar ratio of 1:1 and a mass ratio of 0.2571:15. Stir until the solution is clear to obtain mixture II. Step C1: Slowly add mixture II dropwise to mixture I, stir for 10 h, and let stand for 1 h to remove bubbles to obtain electrospinning solution; spin the electrospinning solution with the following parameters: high voltage 24 kV, feed speed 2 ml / h, receiving distance 20 cm, and roller speed 300 rpm to obtain precursor fiber membrane; place the precursor fiber membrane in a vacuum drying oven at 70 ℃ for 12 h, then place it in an oven at 80 ℃ for 12 h, and finally place it in an oven at 190 ℃ for pre-oxidation for 24 h; Step D1: The pre-oxidized fiber membrane is placed in a tube furnace with an argon flow rate of 200 ml / min and heated to 1300 ℃ for 2 h at a heating rate of 2 ℃ / min to obtain silicon carbide composite fiber aerogel modified with cobalt iron silicon compound nanoparticles, labeled as FC / SiC-1.

[0032] Example 2

[0033] This embodiment provides a method for preparing cobalt-iron-silicon compound-modified silicon carbide composite fibers in situ. The preparation process is as follows: Figure 1 As shown, the specific steps are the same as in Example 2, except that the process of step D1 is as follows: The pre-oxidized fiber membrane was placed in a tube furnace with an argon flow rate of 200 ml / min and calcined at 1400 °C for 2 h at a heating rate of 2 °C / min to obtain silicon carbide composite fiber aerogel modified with cobalt-iron-silicon compound nanoparticles, labeled as FC / SiC-2.

[0034] Example 3

[0035] This embodiment provides a method for preparing cobalt-iron-silicon compound-modified silicon carbide composite fibers in situ. The preparation process is as follows: Figure 1 As shown, the specific steps are the same as in Example 2, except that the process of step D1 is as follows: The pre-oxidized fiber membrane was placed in a tube furnace with an argon flow rate of 200 ml / min and calcined at 1500 °C for 2 h at a heating rate of 2 °C / min to obtain silicon carbide composite fiber aerogel modified with cobalt-iron-silicon compound nanoparticles, labeled as FC / SiC-3.

[0036] Example 4

[0037] This embodiment provides a method for preparing cobalt-iron-silicon compound-modified silicon carbide composite fibers in situ. The preparation process is as follows: Figure 1 As shown, it includes the following steps: Step A2: At room temperature, mix 1g of polyvinylpyrrolidone (PVP) with 6.5g of anhydrous ethanol (EtOH) at a mass ratio of 1.07:7 and stir to obtain mixture I; Step B2: Mix 1g of polycarbosilane (PCS) and 15g of tetrahydrofuran (THF) and stir until the solution is clear. Then add 0.1766g of iron acetylacetone (Fe(acac)3) and 0.1285g of cobalt acetylacetone (Co(acac)2), with a molar ratio of 1:1 and a mass ratio of 0.1285:15. Stir until the solution is clear to obtain mixture II. Step C2: Slowly add mixture II dropwise to mixture I, stir for 10 h, and let stand for 1 h to remove bubbles to obtain electrospinning solution; spin the electrospinning solution with the following parameters: high voltage 24 kV, feed speed 2 ml / h, receiving distance 20 cm, and roller speed 300 rpm to obtain precursor fiber membrane; place the precursor fiber membrane in a vacuum drying oven at 70 ℃ for 12 h, then place it in an oven at 80 ℃ for 12 h, and finally place it in an oven at 190 ℃ for pre-oxidation for 24 h; Step D2: The pre-oxidized fiber membrane is placed in a tube furnace with an argon flow rate of 200 ml / min and heated to 1400℃ for 2 h at a heating rate of 2 ℃ / min to obtain silicon carbide composite fiber aerogel modified with cobalt iron silicon compound nanoparticles, labeled as FC / SiC-4.

[0038] Example 5

[0039] This embodiment provides a method for preparing cobalt-iron-silicon compound-modified silicon carbide composite fibers in situ. The preparation process is as follows: Figure 1 As shown, the specific steps are the same as in Example 5, except that the process for step B2 is as follows: Step B2: Mix 1g of polycarbosilane (PCS) and 15g of tetrahydrofuran (THF) and stir until the solution is clear. Then add 0.2649g of iron acetylacetone (Fe(acac)3) and 0.1928g of cobalt acetylacetone (Co(acac)2), with a molar ratio of 1:1 and a mass ratio of 0.1928:15. Stir until the solution is clear to obtain mixture II. The final product was a silicon carbide composite fiber aerogel modified with cobalt-iron-silicon compound nanoparticles, labeled FC / SiC-5.

[0040] Example 6

[0041] This embodiment provides a method for preparing cobalt-iron-silicon compound-modified silicon carbide composite fibers in situ. The preparation process is as follows: Figure 1 As shown, the specific steps are the same as in Example 5, except that the process for step B2 is as follows: Step B2: Mix 1g of polycarbosilane (PCS) and 15g of tetrahydrofuran (THF) and stir until the solution is clear. Then add 0.4415g of iron acetylacetone (Fe(acac)3) and 0.3215g of cobalt acetylacetone (Co(acac)2), with a molar ratio of 1:1 and a mass ratio of 0.3215:15. Stir until the solution is clear to obtain mixture II. The final product was a silicon carbide composite fiber aerogel modified with cobalt-iron-silicon compound nanoparticles, labeled as FC / SiC-6.

[0042] Morphology and purity testing

[0043] (1) The preparation method of the present invention is as follows: Figure 1 As shown. X-ray diffraction analysis was used to perform material analysis on the nanofibers prepared in Examples 1-6 of this invention, thereby obtaining the following results. Figure 2 The X-ray diffraction pattern shown is from... Figure 2 It can be seen that the materials in Examples 1-6 are all composed of carbon, silicon carbide, and cobalt iron silicon.

[0044] (2) Figure 3 Images (a), (b), and (c) are scanning electron microscope (SEM) images of the composite fibers FC / SiC-1, FC / SiC-2, and FC / SiC-3 prepared in Examples 1-3, respectively. Figure 4 Images (a), (b), and (c) are scanning electron microscope (SEM) images of the composite fibers FC / SiC-4, FC / SiC-5, and FC / SiC-6 obtained in Examples 4-6, respectively. Figure 3 and Figure 4 It can be seen that the diameter of the composite fiber after heat treatment is approximately 300-600 nm, and the surface particles grow randomly on the silicon carbide fiber with a particle diameter of approximately 60-110 nm.

[0045] (3) Figure 5 This is a transmission electron microscope (TEM) image of the composite fiber FC / SiC-2 nanofibers prepared in Example 2. Figure 6The image shown is a transmission electron microscope (TEM) image of the composite fiber FC / SiC-4 nanofibers prepared in Example 4. It can be seen that the cobalt-iron-silicon microstructures grown in situ on the silicon carbide fibers prepared in this invention are all irregular granular, with a particle size of approximately 50-110 nm.

[0046] (4) Figure 7 In Figures (a), (b), (c), and (d), the reflection losses of the composite fibers FC / SiC-2, FC / SiC-4, FC / SiC-5, and FC / SiC-6 prepared in Examples 2, 4, 5, and 6, respectively, are shown in the 2-18 GHz frequency range. The RL of the FC / SiC-2 nanofibers is also shown. min -64.05 dB, EAB max The RL of FC / SiC-4 nanofibers is 4.16 GHz. min -10.79 dB, EAB max The RL of FC / SiC-5 nanofibers is 0.61 GHz. min -19.60 dB, EAB max The RL of FC / SiC-6 nanofibers is 2.86 GHz. min -20.39 dB, EAB max It is 3.48 GHz.

[0047] In summary, the embodiments of this invention can successfully prepare cobalt-iron-silicon particles firmly loaded on silicon carbide fibers, preventing them from easily detaching. Furthermore, the in-situ growth method using high-temperature pyrolysis is simple in principle and easy to implement. The relatively uniform diameter and continuous length of the SiC fibers also positively contribute to improving the microwave absorption performance of the product.

[0048] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications or improvements not exceeding the scope of the claims should be considered within the protection scope of the present invention.

Claims

1. A method for preparing cobalt-iron-silicon compound-modified silicon carbide composite fibers in situ, characterized in that, Includes the following steps: S1. At room temperature, polyvinylpyrrolidone (PVP) and anhydrous ethanol are mixed and stirred at a mass ratio of (0.7-1.3):7 to obtain mixture I; S2. Mix polycarbosilane (PCS) and tetrahydrofuran (THF) at a mass ratio of (0.8-1.2):15, then add soluble iron salt and soluble cobalt salt in a molar ratio of 1:1, wherein the mass ratio of soluble cobalt salt to THF is (0.1-0.5):

15. Stir until homogeneous to obtain mixture II. S3. Slowly add mixture II dropwise to mixture I, wherein the mass ratio of mixture I to mixture II is 1:(1.8-2.4). After stirring evenly, degas the mixture and obtain the precursor fiber membrane through electrospinning. After vacuum drying, perform pre-oxidation treatment. S4. The pre-oxidized fiber membrane is placed in a protective atmosphere and calcined at 1300-1500 °C for 1-4 h to obtain silicon carbide composite fiber aerogel modified with cobalt iron silicon compound nanoparticles, denoted as CoFeSi / SiC.

2. The method for preparing cobalt-iron-silicon compound-modified silicon carbide composite fibers according to claim 1, characterized in that, The soluble iron salt is iron acetylacetonate, and the soluble cobalt salt is cobalt acetylacetonate.

3. The method for preparing cobalt-iron-silicon compound-modified silicon carbide composite fibers according to claim 1 or 2, characterized in that, In step S3, mixture II is slowly added dropwise to mixture I at a mixing rate of 400-600 r / min for 8-12 h.

4. The method for preparing cobalt-iron-silicon compound-modified silicon carbide composite fiber according to claim 1 or 2, characterized in that, The specific parameters for spinning in step S3 are set as follows: high voltage 23-27 KV, spinning solution propulsion speed 1.6-2.5 ml / h, receiving distance 15-20 cm, and collection rotation speed 200-400 rpm.

5. The method for preparing cobalt-iron-silicon compound-modified silicon carbide composite fiber according to claim 1, characterized in that, In step S3, the specific steps of vacuum drying of the precursor fiber membrane are as follows: place the precursor fiber membrane in a vacuum drying oven at 60-90℃ for 12-24 h; then place it in an oven at 60-120℃ for 12-24 h; and finally place it in an oven at 160-220℃ for pre-oxidation for 12-24 h.

6. The method for preparing cobalt-iron-silicon compound-modified silicon carbide composite fiber according to claim 1, characterized in that, In step S3, the vacuum-dried precursor fiber membrane is pre-oxidized by holding it at 150-250 ℃ for 12-24 h.

7. The method for preparing cobalt-iron-silicon compound-modified silicon carbide composite fiber according to claim 1 or 6, characterized in that, In step S4, the calcination heating rate is 2-5 °C / min, and the gas flow rate is 180-250 ml / min.

8. The method for preparing cobalt-iron-silicon compound-modified silicon carbide composite fiber according to claim 1, characterized in that, The protective atmosphere for step S4 is argon.

9. A cobalt-iron-silicon compound in-situ modified silicon carbide composite fiber prepared by the method of any one of claims 1-8.

10. The application of the cobalt-iron-silicon compound in-situ modified silicon carbide composite fiber as described in claim 9 in the fields of high-temperature insulation or electromagnetic wave absorption.

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