A method for preparing a catalyst-free SiC nanowire array and application thereof in biomedical materials

Abstract

The application discloses a preparation method of catalyst-free growth of SiC nanowire arrays and application of the SiC nanowire arrays in biomedical materials, and belongs to the technical field of ceramic preparation. The preparation method comprises the following steps: first, depositing a pyrolytic carbon layer on the surface of a carbon fiber preform; then, vacuum impregnating the carbon fiber preform in a monocrystalline nanometer silicon powder dispersion liquid; finally, performing normal-pressure heat treatment on the impregnated preform in a mixed gas atmosphere composed of oxygen and argon in a static closed environment to obtain the catalyst-free growth of SiC nanowire arrays. In the preparation process, metal impurities are not introduced, the growth of highly ordered SiC nanowire arrays is realized by the reaction of monocrystalline nanometer silicon particles and a small amount of oxygen in a static closed environment, the interlaminar shear strength of carbon / carbon composite materials can be significantly improved, and the problem of residual metal catalysts in the growth of SiC nanowire arrays in a carbon fiber preform in the prior art is solved.

Description

Technical Field

[0001] This invention relates to the field of ceramic preparation technology, specifically to a method for preparing SiC nanowire arrays without a catalyst and its application in biomedical materials. Background Technology

[0002] Carbon / carbon composites, with their multiple advantages including biocompatibility, mechanical compatibility, wear resistance, chemical stability, and radiation permeability, have shown broad application prospects in biomedical fields such as artificial joints, bone repair, and dental implants. Although high preparation costs and insufficient long-term in vivo behavioral studies are current challenges, with the optimization of preparation processes and the deepening of clinical research, carbon / carbon composites are expected to become an important choice for next-generation high-performance biomedical materials.

[0003] Carbon / carbon composites are typically fabricated using laminated, braided, or needle-punched preforms, followed by densification processes such as chemical vapor infiltration or liquid-phase impregnation carbonization. Due to the high inertness of the carbon fiber surface and the lack of strong chemical bonds between the carbon fiber and the matrix carbon, the fiber / matrix interface is weak. Furthermore, residual pores, microcracks, and residual stress caused by thermal mismatch during fabrication make the material highly susceptible to delamination failure along the interlaminar plane when subjected to loads in the thickness direction. Studies have shown that the interlaminar shear strength of most two-dimensional lay-up carbon / carbon composites is far lower than their in-plane tensile strength; this anisotropy is far greater than that of metallic materials and significantly higher than that of resin-based or ceramic-based composites.

[0004] SiC possesses excellent biocompatibility, resistance to body fluid corrosion, absence of NMR artifacts, tunable mechanical properties, and intrinsic antibacterial properties due to its nano-morphology, making it suitable for various biomedical applications such as orthopedics and dentistry. Growing SiC nanowires on the surface of carbon fibers effectively increases the slip resistance between fibers and the matrix, significantly improving the interlaminar shear properties of carbon / carbon composites. The inherent weakness of interlaminar bonds in carbon / carbon composites stems from the low bonding strength resulting from the physical bonding between layers relying solely on pyrolytic carbon or pitch carbon. After in-situ growth of SiC nanowires between the fiber layers, a robust nanowire / carbon "mechanical interlocking" structure is formed with the subsequently densified carbon matrix. The rough surface of the nanowires, even exhibiting a periodic step structure, significantly enhances the mechanical interlocking with the matrix. Furthermore, a small number of chemical bonds (such as C–Si–C bonds) may form between SiC and the carbon matrix, further improving the interfacial bonding strength.

[0005] However, the morphology of SiC nanowires, particularly orderly array structures and random dispersions, significantly differs in their effect on improving the shear strength of carbon / carbon composites. Numerous studies have shown that ordered SiC nanowire arrays are more efficient and significantly enhance the interlaminar shear strength of carbon / carbon composites compared to randomly distributed SiC nanowires. On one hand, orderly SiC nanowire arrays can form a vertically connected three-dimensional network bridging structure between the composite layers. These nanowires are arranged orderly along the thickness direction or at specific angles, directly bridging the interfaces between carbon fiber layers. When the interlaminar region is subjected to shear loads, the nanowire array acts like miniature "steel bars," effectively transferring stress from one layer of fiber to another, inhibiting crack initiation and propagation at the interface. While randomly shaped SiC nanowires can also provide some overall reinforcement, their random orientation and entanglement make it difficult to form directional, efficient load transfer channels. Stress often concentrates at localized entanglements, potentially becoming crack initiation points. On the other hand, the interfacial bonding between ordered nanowire arrays and the matrix is ​​more uniform and controllable. SiC nanowire arrays, prepared through vapor-phase growth or catalyst-assisted directional fabrication, can form a regularly arranged "nanobrush" structure on the surface of a fiber cloth. During subsequent deposition of pyrolytic carbon, the matrix can uniformly encapsulate each nanowire, forming a robust mechanical and chemical bonding interface. This structure not only increases the tortuosity of the shear fracture path but also avoids stress concentration caused by localized nanowire agglomeration. Conversely, randomly distributed SiC nanowires occupy a large volume fraction, inducing porosity and defects in the pyrolytic carbon matrix. Furthermore, excessive nanowires in localized areas can exacerbate the mismatch in thermal expansion coefficients, leading to unfavorable microcracks upon cooling. Therefore, SiC nanowire arrays, with their ordered arrangement, optimized stress transfer path, and uniform interfacial bonding, significantly outperform randomly morphological SiC nanowires in improving the interlaminar shear strength of carbon / carbon composites. This difference between "order" and "disorder" in microstructure determines whether the nanoreinforcing phase can move from "discrete dispersion" to "highly efficient load-bearing," representing a crucial direction for future interface engineering of high-performance biomedical carbon / carbon composites.

[0006] In existing background technologies, common methods for preparing silicon carbide (SiC) nanowire arrays mainly include template-assisted chemical vapor deposition (TACVD), direct vapor-liquid-solid (VLS) growth, and anodic oxidation. Among these, direct VLS growth is widely used for the directional growth of SiC nanowire arrays within carbon fiber preforms due to its controllable process and tunable structure. This method typically employs metal catalysts (such as iron (Fe), nickel (Ni), and gold (Au)) that react with silicon and carbon sources at high temperatures to form eutectic alloy droplets. These alloy droplets effectively absorb gaseous silicon (Si) and carbon (C) sources. When the dissolved Si and C reach supersaturation within the droplets, solid SiC nanowires preferentially precipitate from the bottom of the droplets, and a well-organized nanowire array structure is gradually constructed by controlling the growth direction. Therefore, direct VLS growth exhibits significant advantages in the in-situ growth of SiC nanowire arrays within carbon fiber preforms and is currently one of the widely recognized and effective techniques.

[0007] However, this method still faces a significant challenge in practical applications: because the nucleation and growth of nanowires are highly dependent on the guidance of metal catalyst particles, these catalysts inevitably remain in the nanowire array system after the reaction, either attached to the nanowire tips or embedded within the product. These metal residues not only reduce the overall purity of the SiC nanowire product but may also negatively impact its interfacial properties, thermal stability, and subsequent processing adaptability. Especially in biomedical applications, residual metal elements (such as Fe and Ni) may trigger biotoxicity or immune rejection reactions, significantly reducing the biocompatibility and safety of the material, thus limiting the further promotion of this method in high-purity, high-performance, and bio-related applications. Therefore, developing a metal catalyst-free preparation method while maintaining SiC nanowire array growth has become a key challenge in the current technological landscape. Summary of the Invention

[0008] To address the aforementioned technical problems, the present invention aims to provide a method for preparing SiC nanowire arrays without a catalyst and its application in biomedical materials, thereby resolving the issue of residual metal catalysts in the existing technology for growing SiC nanowire arrays in carbon fiber preforms.

[0009] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: In a first aspect, the present invention provides a method for preparing a catalyst-free SiC nanowire array, comprising the following steps: S1, Deposition of pyrolytic carbon layer: A carbon fiber preform containing a pyrolytic carbon layer was obtained by depositing a pyrolytic carbon layer on the surface of a carbon fiber preform using a chemical vapor infiltration method. S2. Preparation of single-crystal nano-silicon dispersion: Single-crystal nano-silicon powder was placed in anhydrous ethanol and a dispersant was added. The mixture was then magnetically stirred and ultrasonically dispersed to obtain a single-crystal nano-silicon dispersion. S3, Vacuum Impregnation: The carbon fiber preform containing pyrolytic carbon layer obtained in S1 was vacuum impregnated in a single crystal nano-silicon powder dispersion to obtain the impregnated preform. Growth of S4 and SiC nanowire arrays: The impregnated preform obtained from S3 was placed in a mixed atmosphere of oxygen and argon and subjected to atmospheric pressure heat treatment in a static closed environment to obtain a carbon fiber preform for growing SiC nanowire arrays, thus obtaining a catalyst-free grown SiC nanowire array.

[0010] The beneficial effects of this invention are as follows: This invention proposes a catalyst-free method for preparing SiC nanowire arrays. Single-crystal silicon nanoparticles are used as raw materials and introduced into a preform containing a pyrolytic carbon layer via vacuum impregnation. The SiC nanowire array is then grown in a static environment under an argon atmosphere containing a small amount of oxygen. This method utilizes trace amounts of oxygen to promote the oxidation of single-crystal silicon nanoparticles and their reaction with pyrolytic carbon, inducing the formation of SiC nanowire arrays. Simultaneously, maintaining a sealed environment within the furnace during SiC growth effectively reduces gas disturbance within the preform, ensuring the ordered nature of the grown SiC nanowire array. This achieves the growth of SiC nanowire arrays within a carbon fiber preform without any residual metal catalyst.

[0011] Furthermore, the carbon fiber preform in S1 is a 2.5D needle-punched carbon fiber preform.

[0012] Furthermore, in the chemical vapor permeation process in S1, the carbon source gas is a mixture of methane and propane, with a flow rate ratio of methane to propane of 1:(0.2~0.6) and a total flow rate of 40~80 L / min.

[0013] Furthermore, the deposition temperature in S1 was 1080~1150 ℃, the deposition time was 12~16 h, and the deposition pressure was 1~10 kPa.

[0014] Furthermore, the concentration of the single-crystal nano-silicon powder dispersion in S2 is 10~15 mg / mL, and the amount of dispersant added is 1%~2% of the mass of the single-crystal nano-silicon particles.

[0015] Furthermore, the particle size of the single-crystal nano-silicon powder in S2 is 100~300 nm, the dispersion medium is anhydrous ethanol, and the dispersant is sodium polyacrylate.

[0016] Furthermore, the magnetic stirring speed is 100~1500 rpm, and the stirring time is 0.5~1 h; the ultrasonic power is 300~600 W, and the ultrasonic time is 0.5~1.5 h.

[0017] Furthermore, the vacuum impregnation pressure in S3 is 6~10 kPa, and the impregnation time is 5~15 min.

[0018] Furthermore, after vacuum impregnation in S3, freeze-drying is performed at a temperature of -50 to -30 ℃, a vacuum degree of 10 to 30 Pa, and a drying time of 24 to 48 h.

[0019] Furthermore, the ratio of oxygen to argon in S4 is 1:(7~12).

[0020] Furthermore, after argon and oxygen are introduced into S4, the inlet and outlet are closed to maintain a sealed static environment for heating.

[0021] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: The present invention adopts a static closed environment growth strategy. By controlling the filling of oxygen and argon into the furnace and then closing the inlet and outlet, a small amount of oxygen is used to participate in the reaction, which effectively reduces the gas flow inside the preform and ensures the high orderliness of the grown SiC nanowire array.

[0022] Furthermore, the heat treatment temperature in S4 is 1520~1580 ℃, and the holding time is 0.5~1 h.

[0023] In a second aspect, the present invention provides a catalyst-free SiC nanowire array, which is prepared by the above-described preparation method.

[0024] The beneficial effects of the present invention are as follows: the SiC nanowire array prepared by the present invention has high orderliness and can form a three-dimensional network bridging structure along the thickness direction, providing a directional and efficient stress transfer path, thereby significantly improving the interlaminar shear strength of the composite material.

[0025] A third aspect of the present invention provides the application of the above-described catalyst-free SiC nanowire array in the preparation of carbon / carbon composite materials.

[0026] In a fourth aspect, the present invention provides a method for preparing a catalyst-free grown SiC nanowire array-doped carbon / carbon composite material, wherein the carbon fiber preform with grown SiC nanowire array obtained in S4 is subjected to pyrolysis carbon densification by chemical vapor infiltration to obtain a catalyst-free grown SiC nanowire array-doped carbon / carbon composite material.

[0027] The beneficial effects of this invention are as follows: This invention completes the preparation of carbon / carbon composite materials by pyrolyzing carbon densification of carbon fiber preforms with grown SiC nanowire arrays. By utilizing the highly ordered SiC nanowire array, the shear strength of the carbon / carbon composite material is significantly improved, while avoiding the residue of metal catalysts, thus eliminating safety risks for the application of carbon / carbon composite materials in biomedical materials.

[0028] Furthermore, in the chemical vapor permeation process, the carbon source gas is natural gas, with a flow rate of 0.8~1 m³. 3 / h.

[0029] Furthermore, the deposition temperature was 1030~1100 ℃, the deposition time was 24~48 h, and the thermocouple migration rate was 125~500 μm / h.

[0030] In a fifth aspect, the present invention provides a catalyst-free SiC nanowire array-doped carbon / carbon composite material, which is prepared by the above-described preparation method.

[0031] In a sixth aspect, the present invention provides the application of the above-described catalyst-free SiC nanowire array or catalyst-free SiC nanowire array doped carbon / carbon composite material in the preparation of biomedical materials.

[0032] The beneficial effects of this invention are as follows: the SiC nanowire array or carbon / carbon composite material prepared by this invention has no metal catalyst residue, which fundamentally eliminates the risk of metal ions causing cytotoxicity or immune rejection. It has excellent biocompatibility, good structural and performance designability, and excellent interlaminar shear strength, and can be widely used in biomedical materials.

[0033] The present invention has the following beneficial effects: 1. This invention eliminates the need for metal catalysts (such as Fe, Ni, Au, etc.) required in the traditional VLS method, and instead utilizes the reaction of single-crystal silicon nanoparticles with trace amounts of oxygen to induce the growth of SiC nanowire arrays. No metal impurities are introduced during the preparation process, and the final product contains no catalyst residue, fundamentally eliminating the risk of metal ions triggering cytotoxicity or immune rejection reactions.

[0034] 2. This invention employs a growth strategy in a static, closed environment. By controlling the introduction of oxygen and argon into the furnace and then closing the inlet and outlet, a small amount of oxygen is used in the reaction, effectively reducing airflow disturbance inside the preform and ensuring the high orderliness of the grown SiC nanowire array. Compared to randomly distributed SiC nanowires, the ordered array obtained by this invention can form a three-dimensional network bridging structure along the thickness direction, providing a directional and efficient stress transfer path, significantly increasing the tortuosity of the shear fracture path, thereby significantly improving the interlaminar shear strength of the composite material and making the material less prone to delamination failure when subjected to loads in the thickness direction.

[0035] 3. Simplified process, controllable cost, and excellent structural and performance designability. The raw materials used in this invention are simple, the overall process is significantly simplified, raw material costs are greatly reduced, and no toxic or harmful precursors are involved. Furthermore, by controlling the size of the silicon nanoparticles, micro-oxidation temperature and time, impregnation concentration, and high-temperature reaction parameters (temperature, holding time, etc.), the diameter, distribution density, and growth orientation of SiC nanowires can be effectively controlled, thereby optimizing the mechanical properties and microstructure of the composite material as needed, exhibiting excellent process adaptability and product designability. Attached Figure Description

[0036] Figure 1 Flowchart of the preparation process of carbon / carbon composite materials doped with SiC nanowire arrays; Figure 2 The image shows the XRD pattern of the single-crystal nano-silicon particles used in S1 of Example 1. Figure 3 This is a spot scan of the energy spectrum of the single-crystal silicon nanoparticles used in S1 in Example 1; Figure 4 This is the energy spectrum spot scan of the SiC nanowire array obtained in S4 of Example 1; Figure 5 This is a scanning electron microscope image of the SiC nanowire array obtained in S4 of Example 1; Figure 6 Drawings of interlaminar shear testing equipment and molds; Figure 7 These are images showing the damage to samples after interlaminar shear tests in Examples 1-3 and Comparative Example 1; Figure 8 The load-displacement curves of the carbon / carbon composite material prepared in Comparative Example 1 are shown. Figure 9 The load-displacement curve of the SiC nanowire array-doped carbon / carbon composite material prepared in Example 1 is shown. Figure 10 This is a load-displacement curve of the SiC nanowire array-doped carbon / carbon composite material prepared in Example 2. Figure 11The image shows the load-displacement curves of the SiC nanowire array-doped carbon / carbon composite material prepared in Example 3. Detailed Implementation

[0037] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0038] Example 1: A method for preparing SiC nanowire array-doped carbon / carbon composite material includes the following steps: S1. Deposition of pyrolytic carbon layer on the surface of carbon fiber preform: A 2.5D needle-punched carbon fiber preform was placed in a chemical vapor infiltration furnace, using a methane-propane mixture as the carbon source gas. The methane to propane flow ratio was 1:0.2, the total flow rate was 40 L / min, the deposition temperature was 1080 ℃, the deposition time was 12 h, and the deposition pressure was 1 kPa. A thin and uniform layer of pyrolytic carbon was deposited on the carbon fiber surface to obtain a carbon fiber preform containing a pyrolytic carbon layer.

[0039] S2. Preparation of single-crystal nano-silicon dispersion: First, weigh an appropriate amount of 100 nm single-crystal silicon nanoparticles at a concentration of 10 mg / mL and place them in anhydrous ethanol. Add sodium polyacrylate as a dispersant, with a content of 1% of the mass of the single-crystal silicon nanoparticles. Then, perform magnetic stirring (1000 rpm, 0.5 h) and ultrasonic dispersion (300 W, 0.5 h) in sequence to obtain a uniform and stable single-crystal silicon nanoparticle dispersion. S3, Vacuum impregnation to introduce nano-silicon particles: Then, the carbon fiber preform containing the pyrolytic carbon layer obtained in S1 was immersed in the single-crystal nano-silicon dispersion obtained in S2, and both were placed in a vacuum impregnation chamber. The vacuum was drawn to 6 kPa and impregnated for 5 min. The nano-silicon particles were introduced into the internal pores of the preform by using negative pressure. After the impregnation was completed, the preform was taken out and freeze-dried at -50 ℃ and 10 Pa vacuum for 24 h to obtain the carbon fiber preform with the introduction of single-crystal nano-silicon particles.

[0040] Growth of S4 and SiC nanowire arrays: First, the preform obtained from S3 was placed in a tube furnace, and oxygen and argon were introduced at a volume ratio of 1:7, and the inlet and outlet were closed. Then, the temperature was raised to 1520 °C and held for 0.5 h to grow SiC nanowire arrays in a static and sealed environment. Finally, after the reaction was completed, the temperature was cooled to room temperature to obtain a carbon fiber preform with grown SiC nanowire arrays.

[0041] S5. Pyrolytic carbon densification of carbon fiber preforms: The carbon fiber preform with SiC nanowire array grown in S4 was placed in a gradient chemical vapor infiltration furnace with natural gas as the carbon source and a flow rate of 0.8 m³ / s. 3 The deposition temperature was 1030 °C, the thermocouple migration rate was 125 μm / h, and the deposition time was 24 h. The pyrolytic carbon was further densified to obtain a SiC nanowire array-doped carbon / carbon composite material.

[0042] Example 2: A method for preparing SiC nanowire array-doped carbon / carbon composite material includes the following steps: S1. Deposition of pyrolytic carbon layer on the surface of carbon fiber preform: A 2.5D needle-punched carbon fiber preform was placed in a chemical vapor infiltration furnace, using a methane-propane mixture as the carbon source gas. The methane to propane flow ratio was 1:0.4, the total flow rate was 60 L / min, the deposition temperature was 1115 ℃, the deposition time was 14 h, and the deposition pressure was 5.5 kPa. A thin and uniform layer of pyrolytic carbon was deposited on the carbon fiber surface to obtain a carbon fiber preform containing a pyrolytic carbon layer.

[0043] S2. Preparation of single-crystal nano-silicon dispersion: First, weigh an appropriate amount of single-crystal silicon nanoparticles with a particle size of 200 nm at a concentration of 12.5 mg / mL and place them in anhydrous ethanol. Add sodium polyacrylate as a dispersant, with a content of 1.5% of the mass of the single-crystal silicon nanoparticles. Then, perform magnetic stirring (1300 rpm, 0.75 h) and ultrasonic dispersion (450 W, 1 h) to obtain a uniform and stable single-crystal silicon nanoparticle dispersion. S3, Vacuum impregnation to introduce nano-silicon particles: Then, the carbon fiber preform containing the pyrolytic carbon layer obtained in S1 was immersed in the single-crystal nano-silicon dispersion obtained in S2, and both were placed in a vacuum impregnation chamber. The vacuum was drawn to 8 kPa and impregnated for 10 min. The nano-silicon particles were introduced into the internal pores of the preform by using negative pressure. After the impregnation was completed, the preform was taken out and freeze-dried at -40 ℃ and 20 Pa vacuum for 36 h to obtain the carbon fiber preform with the introduction of single-crystal nano-silicon particles.

[0044] Growth of S4 and SiC nanowire arrays: First, the preform obtained from S3 was placed in a tube furnace, and oxygen and argon were introduced at a volume ratio of 1:10, and the inlet and outlet were closed. Then, the temperature was raised to 1550 °C and held for 0.75 h to grow SiC nanowire arrays in a static and sealed environment. After the reaction was completed, the preform was cooled to room temperature to obtain the carbon fiber preform with grown SiC nanowire arrays.

[0045] S5. Pyrolytic carbon densification of carbon fiber preforms: The carbon fiber preform with SiC nanowire array grown in S4 was placed in a gradient chemical vapor infiltration furnace with natural gas as the carbon source and a flow rate of 0.9 m³ / s. 3 The deposition temperature was 1060 °C, the thermocouple migration rate was 312.5 μm / h, and the deposition time was 36 h. The pyrolytic carbon was further densified to obtain a SiC nanowire array-doped carbon / carbon composite material.

[0046] Example 3: A method for preparing SiC nanowire array-doped carbon / carbon composite material includes the following steps: S1. Deposition of pyrolytic carbon layer on the surface of carbon fiber preform: A 2.5D needle-punched carbon fiber preform was placed in a chemical vapor infiltration furnace, using a methane-propane mixture as the carbon source gas. The methane to propane flow ratio was 1:0.6, the total flow rate was 80 L / min, the deposition temperature was 1150 ℃, the deposition time was 16 h, and the deposition pressure was 10 kPa. A thin and uniform layer of pyrolytic carbon was deposited on the carbon fiber surface to obtain a carbon fiber preform containing a pyrolytic carbon layer.

[0047] S2. Preparation of single-crystal nano-silicon dispersion: First, weigh an appropriate amount of single-crystal silicon nanoparticles with a particle size of 300 nm at a concentration of 15 mg / mL and place them in anhydrous ethanol. Add sodium polyacrylate as a dispersant, with a content of 2% of the mass of the single-crystal silicon nanoparticles. Then, perform magnetic stirring (1500 rpm, 1 h) and ultrasonic dispersion (600 W, 1.5 h) in sequence to obtain a uniform and stable single-crystal silicon nanoparticle dispersion. S3, Vacuum impregnation to introduce nano-silicon particles: Then, the carbon fiber preform containing the pyrolytic carbon layer obtained in S1 was immersed in the single-crystal nano-silicon dispersion obtained in S2, and both were placed in a vacuum impregnation chamber. The vacuum was drawn to 10 kPa and impregnated for 15 min. The negative pressure was used to introduce the nano-silicon particles into the internal pores of the preform. After the impregnation was completed, the preform was taken out and freeze-dried at -30 ℃ and 30 Pa vacuum for 48 h to obtain the carbon fiber preform with the introduction of single-crystal nano-silicon particles.

[0048] Growth of S4 and SiC nanowire arrays: First, the preform obtained from S3 was placed in a tube furnace, and oxygen and argon were introduced at a volume ratio of 1:12, and the inlet and outlet were closed. Then, the temperature was raised to 1580 °C and held for 1 h to grow SiC nanowire arrays in a static and sealed environment. After the reaction was completed, the preform was cooled to room temperature to obtain carbon fiber preforms with grown SiC nanowire arrays.

[0049] S5. Pyrolytic carbon densification of carbon fiber preforms: The carbon fiber preform with SiC nanowire array grown in S4 was placed in a gradient chemical vapor infiltration furnace with natural gas as the carbon source and a flow rate of 1 m³ / s. 3 The deposition temperature was 1100 °C, the thermocouple moving rate was 500 μm / h, and the deposition time was 48 h. The pyrolytic carbon was further densified to obtain a SiC nanowire array-doped carbon / carbon composite material.

[0050] Comparative Example 1: A carbon / carbon composite material, the preparation method of which differs from that of Example 1, is that no single-crystal nano-silicon powder is added in S2, while the remaining steps are the same as in Example 1.

[0051] Comparative Example 2: A carbon / carbon composite material, the preparation method of which differs from that of Example 2, is that no single-crystal nano-silicon powder is added in S2, while the remaining steps are the same as in Example 2.

[0052] Comparative Example 3: A carbon / carbon composite material, the preparation method of which differs from that of Example 3, is that no single-crystal nano-silicon powder is added in S2, while the remaining steps are the same as in Example 3.

[0053] After S4 treatment, SiC nanowire arrays were successfully grown on the surface of the carbon fiber preform. The grown nanowire arrays grew vertically on the carbon fiber surface, were neatly arranged, and had uniform thickness, exhibiting a good array effect.

[0054] Experimental Example 1: Phase Analysis The products obtained in Examples 1-3 have basically the same characteristics. The following tests are conducted using Example 1 as an example: The single-crystal silicon nanoparticles used in Example 1 were subjected to XRD and energy dispersive spectroscopy (EDS) analyses. The SiC nanowire array prepared in S4 of Example 1 was subjected to EDS spot scanning and scanning electron microscopy. The results are as follows: Figures 2-5 As shown.

[0055] The results showed that the original single-crystal silicon nanoparticles were elemental silicon with a pure surface free of impurities. After S4 heat treatment, the energy dispersive spectroscopy results showed that carbon peaks appeared in the nanowires, with no other impurities, indicating that the array formed was composed of pure SiC nanowires. Scanning electron microscopy showed that SiC nanowire arrays were successfully grown on the surface of the carbon fiber preform. The grown nanowire arrays grew vertically on the carbon fiber surface, were neatly arranged, and had uniform thickness, exhibiting a good array effect.

[0056] Experimental Example 2: Interlaminar Shear Performance Test Interlaminar shear tests were performed on the carbon / carbon composite materials prepared in Examples 1-3 and Comparative Examples 1-3, respectively.

[0057] According to the standard GB / T 40388-2021 for testing the shear properties of carbon / carbon composites, the shear properties of the composites were tested using the shear test mode of a CMT5304-2kN electronic universal testing machine. The specimen dimensions were 20 (±0.5) mm × 26 (±0.5) mm × 10 (±0.5) mm, and the specimen was cut parallel to the lamination direction of the non-woven fabric. The load application rate for the shear test was 0.3 mm / min. During loading, the computer collected and recorded the load-displacement curves via sensors. The shear strength was obtained using the following formula:

[0058] In the formula: τ Shear strength / MPa; F Maximum load / N; A 0 represents the initial area of ​​the shear surface in mm. 2 .

[0059] The shear performance test process is as follows: Figure 6 As shown, it includes a shear test fixture and a sample from Example 1 before testing.

[0060] The products obtained from Comparative Examples 1 to 3 have basically the same characteristics. The following analysis of shear failure behavior is based on Comparative Example 1 as an example: Images of the fractured specimens after shear tests of Examples 1-3 and Comparative Example 1 are shown below. Figure 7 As shown, the load-displacement correlation data during shear testing of different materials are respectively as follows: Figures 8-11 As shown in Table 1, the shear strength results are as follows.

[0061] Table 1 Shear strength test results

[0062] Depend on Figures 8-11It can be seen that the carbon / carbon composite materials prepared by growing SiC nanowire arrays on the surface of carbon fiber preforms in Examples 1-3 still maintain their typical "pseudoplastic" fracture behavior. Table 1 shows that the interlaminar shear strength of the SiC nanowire array-doped carbon / carbon composite materials prepared according to the process of this invention is improved compared to the carbon / carbon composite materials without SiC nanowire array doping; among them, the sample in Example 3 with SiC nanowire array doping has the highest shear strength reaching 38.9 MPa, while the shear strength of the undoped carbon / carbon composite material is only 26.5 MPa. The shear strength of this invention is improved by 46.8%, and the interlaminar shear performance is significantly improved.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing SiC nanowire arrays without a catalyst, characterized in that, Includes the following steps: S1, Deposition of pyrolytic carbon layer: A carbon fiber preform containing a pyrolytic carbon layer was obtained by depositing a pyrolytic carbon layer on the surface of a carbon fiber preform using a chemical vapor infiltration method. S2. Preparation of single-crystal nano-silicon dispersion: Single-crystal nano-silicon powder was placed in anhydrous ethanol and a dispersant was added. The mixture was then magnetically stirred and ultrasonically dispersed to obtain a single-crystal nano-silicon dispersion. S3, Vacuum Impregnation: The carbon fiber preform containing pyrolytic carbon layer obtained in S1 is immersed in the single crystal nano-silica powder dispersion obtained in S2 and vacuum impregnated to obtain the impregnated preform. Growth of S4 and SiC nanowire arrays: The impregnated preform obtained from S3 was subjected to atmospheric pressure heat treatment in a mixed atmosphere of oxygen and argon under static closed environment to obtain a carbon fiber preform for growing SiC nanowire arrays, thus obtaining a catalyst-free grown SiC nanowire array. The volume ratio of oxygen to argon in S4 is 1:(7~12). The heat treatment temperature is 1520~1580 ℃, and the holding time is 0.5~1 h.

2. The method for preparing SiC nanowire arrays without catalyst growth according to claim 1, characterized in that, In the chemical vapor permeation process described in S1, the carbon source gas is a mixture of methane and propane, with a flow rate ratio of methane to propane of 1:(0.2~0.6) and a total flow rate of 40~80 L / min. The deposition temperature was 1080~1150 ℃, the deposition time was 12~16 h, and the deposition pressure was 1~10 kPa.

3. The method for preparing a catalyst-free SiC nanowire array according to claim 1, characterized in that, The concentration of the single-crystal nano-silicon powder dispersion in S2 is 10~15 mg / mL, and the amount of dispersant added is 1%~2% of the mass of the single-crystal nano-silicon particles; The particle size of the single-crystal nano-silicon powder is 100~300 nm, the dispersion medium is anhydrous ethanol, and the dispersant is sodium polyacrylate. The vacuum impregnation pressure in S3 is 6~10 kPa, and the impregnation time is 5~15 min; After vacuum impregnation, the product is freeze-dried at a temperature of -50 to -30 ℃, a vacuum degree of 10 to 30 Pa, and a drying time of 24 to 48 h.

4. A catalyst-free SiC nanowire array growth method, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 3.

5. The application of the catalyst-free grown SiC nanowire array according to claim 4 in the preparation of carbon / carbon composite materials.

6. A method for preparing a catalyst-free SiC nanowire array-doped carbon / carbon composite material, characterized in that, The carbon fiber preform with grown SiC nanowire array obtained in S4 of claim 1 is densified by pyrolysis using chemical vapor infiltration to obtain a carbon / carbon composite material with SiC nanowire array doped without catalyst growth.

7. The method for preparing catalyst-free SiC nanowire array-doped carbon / carbon composite material according to claim 6, characterized in that, The chemical vapor infiltration method used for the pyrolytic carbon densification employs natural gas as the carbon source gas, with a flow rate of 0.8~1.0 m³ / s. 3 / h; The deposition temperature was 1030~1100 ℃, the deposition time was 24~48 h, and the thermocouple migration rate was 125~500 μm / h.

8. A catalyst-free SiC nanowire array-doped carbon / carbon composite material, characterized in that, It is prepared by the preparation method according to any one of claims 6 or 7.

9. The application of the catalyst-free grown SiC nanowire array of claim 4 or the catalyst-free grown SiC nanowire array doped carbon / carbon composite material of claim 8 in the preparation of biomedical materials.

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