Preparation method of fiber preform SiC nanowire with large length-diameter ratio
The catalytic cracking method is used to grow SiC nanowires in situ in prefabricated fibers, which solves the problems of high preparation cost and difficulty in controlling SiC nanowires, and achieves uniform distribution and high yield of high-performance SiC nanowires, improves the mechanical properties of composite materials, and is suitable for aerospace and other fields.
Patent Information
- Application Number
- CN202510605831.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-12
- Publication Date
- 2025-08-15
AI Technical Summary
The existing SiC nanowires are costly and difficult to control in preparation, especially in large-size components, which is difficult to meet the demand for high-performance composite materials in the aerospace field.
By using catalytic cracking, large-length-to-diameter SiC nanowires are grown in situ in the fiber prefabricated body by preparing polycarbosilane solution and adding catalyst, combined with vacuum impregnation and heat treatment processes, large-length-to-diameter SiC nanowires are grown in situ, controlling the element ratio of Si to C, and achieving uniform distribution.
SiC nanowires with large length-to-diameter ratio, high purity and high yield were prepared, which improved the mechanical properties of the composite material, was suitable for large-sized components, simplified the preparation process, reduced costs, and was suitable for industrial production.
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Figure CN120483741A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of SiC nanowire preparation, and particularly relates to a method for preparing SiC nanowires with a large aspect ratio as a fiber preform. Background Art
[0002] Fiber reinforced silicon carbide ceramic matrix composites (C f / SiC) composite materials have been widely used in aerospace, high-performance weapons and equipment, optical components and other fields due to their excellent properties such as low density, high specific modulus and high temperature resistance. The rapid development of aerospace has put great pressure on C f / SiC composite materials put forward higher requirements, such as higher specific strength, higher reliability, etc.
[0003] SiC nanowires combine the inherent advantages of SiC with the quantum effects of one-dimensional nanomaterials. They have been applied to fields such as mesoscopic physics and nanodevice preparation, becoming one of the research hotspots. The strength of SiC nanowires is extremely high (50GPa), close to the theoretical value and remains stable under extreme environments. The local elongation of SiC nanowires exceeds 200%, and the overall fracture strain is 28%, showing excellent ductility. Yang et al. (see: Single-crystal SiC nanowires with athin carbon coating for stronger and tougher ceramic composites, Advanced Materials, Vol. 17, No. 12, June 7, 2005) used the CVI process to deposit a large number of SiC nanowires on the fiber surface and coated the nanowire surface with a layer of pyrolytic carbon. The strength of the composite material increased from 380 to 750MPa, and the fracture toughness increased from 9.5 to 20.3MPam 1 / 2 Pei et al. (see: Effect of in situ grown SiC nanowires on6] microstructure and mechanical properties of C / SiC composites, Ceramics International, Vol. 40, No. 4, May 2014) used a polymer precursor pyrolysis method to in situ grow SiC nanowires and prepare a matrix containing nanowires. The study found that the introduction of SiC nanowires increased the flexural strength of the composite material by 92%. A large number of studies have shown that the introduction of SiC nanowires can effectively improve the mechanical properties of C / SiC composites. f Mechanical properties of SiC / SiC composites.
[0004] Currently, there are two methods for adding nanowires: directly adding nanowires to the precursor solution and synthesizing nanowires in situ on the fiber. The former method makes it difficult to evenly disperse the nanowires in the solution and is a complex process. The latter method is applicable to all composite material preparation processes and allows the nanowires to be evenly distributed within the fiber preform.
[0005] Currently, the main reported methods for in situ growth of SiC nanowires are chemical vapor deposition (CVD) and catalytic cracking. However, the CVD method suffers from difficulties in controlling the preparation process, resulting in uneven distribution of the grown SiC nanowires and unsuitability for large-scale components. The catalytic cracking method primarily uses polycarbosilane (PCS) as the raw material, and most studies have used solid PCS as the raw material. However, solid PCS decomposes rapidly, making the catalytic reaction rate difficult to control. Summary of the Invention
[0006] In order to overcome the shortcomings of high preparation cost and difficult control of the preparation process of SiC nanowires, the present invention proposes a method for preparing SiC nanowires with a large aspect ratio as a fiber preform.
[0007] The technical solution adopted by the present invention to solve the technical problem is:
[0008] A method for preparing SiC nanowires with a large aspect ratio as a fiber preform comprises the following steps:
[0009] Step 1: Prepare polycarbosilane solution
[0010] Polycarbosilane and an organic solvent are placed in a container and stirred until they are mutually dissolved and the solution is clear, thereby obtaining a polycarbosilane solution; the mass fraction of the polycarbosilane in the polycarbosilane solution is 1% to 50%.
[0011] Step 2: Add catalyst to polycarbosilane solution
[0012] The catalyst is added to the polycarbosilane solution, ultrasonically dispersed for 10 to 30 minutes, and stirred until the catalyst is completely dissolved to obtain a polycarbosilane solution containing the catalyst, i.e., mixed solution 1.
[0013] The mass of the catalyst is 1% to 10% of the mass of the polycarbosilane.
[0014] Step 3: Vacuum impregnation of fiber preform
[0015] The fiber preform is immersed in the mixed solution 1 and vacuum impregnated for 20 minutes to 60 minutes to obtain a pretreated fiber preform.
[0016] The fibers of the fiber preform are carbon fibers or SiC fibers, and the structure of the fiber preform is two-dimensional lamination, three-dimensional needle punching, or three-dimensional weaving.
[0017] Step 4: Heat treatment
[0018] The pretreated fiber preform is placed in a crucible, and the crucible containing the pretreated fiber preform is placed in a tubular furnace. Argon gas is introduced into the tubular furnace to heat treat the pretreated fiber preform at a temperature of 1200° C. to 1600° C. for a time of 1 h to 4 h to obtain a fiber preform with a large aspect ratio SiC nanowire.
[0019] In the method for preparing the above-mentioned fiber preform with a large aspect ratio SiC nanowire, the polycarbosilane comprises solid polycarbosilane and hyperbranched polycarbosilane, and the mass ratio of the solid polycarbosilane to the hyperbranched polycarbosilane is 0.1-100.
[0020] The organic solvent is ethanol, toluene, or xylene.
[0021] In the above-mentioned method for preparing SiC nanowires with a large aspect ratio as a fiber preform, the catalyst is ferrocene or nickelocene.
[0022] In the above-mentioned method for preparing the fiber preform SiC nanowire with a large aspect ratio, the stirring time is 1 hour to 2 hours.
[0023] The beneficial effects of the present invention are:
[0024] A method for preparing SiC nanowires with a large aspect ratio from a fiber preform has a simple preparation process. By regulating the ratio of linear polycarbosilane (i.e., solid polycarbosilane) to hyperbranched polycarbosilane, the elemental ratio of Si to C is precisely controlled. This ensures that the supersaturation of gaseous Si and C molecules in the catalyst mother nucleus during the cracking process is moderate, reaching an equilibrium state, avoiding premature cessation of growth or excessively rapid growth, and thus achieving controllable preparation of SiC nanowires.
[0025] A method for preparing SiC nanowires with a large aspect ratio from a fiber preform has low requirements for equipment and processing conditions. It can effectively utilize the cracking products of polycarbosilane to grow SiC nanowires in situ. The preparation process uses atmospheric pressure equipment, making this method safer and more reliable than chemical vapor deposition.
[0026] A method for preparing SiC nanowires with a large aspect ratio from a fiber preform is disclosed. The SiC nanowires are prepared by a catalytic cracking method, and their combination with fiber-reinforced silicon carbide ceramic-based composites is easily achieved. The method is independent of the configuration of the preform and is conducive to engineering and industrial production.
[0027] A method for preparing SiC nanowires with a large aspect ratio from a fiber preform. The prepared SiC nanowires have a large aspect ratio (aspect ratio of 200), a diameter of only 300 nm, and a length of 60 μm. The nanowires prepared by this method have high yield and high purity, and contain little ceramic residue in the fiber preform.
[0028] A method for preparing SiC nanowires with a large aspect ratio in a fiber preform, in which SiC nanowires with a large aspect ratio are grown in situ within the fiber preform through a catalytic cracking method combined with a precursor impregnation pyrolysis method. This method overcomes the problem that carbon fibers cannot strengthen composite materials at the submicron scale, increases the matrix cracking stress of the composite material, and achieves strengthening and toughening.
[0029] A method for preparing SiC nanowires with a large aspect ratio from a fiber preform uses solid polycarbosilane and liquid polycarbosilane as main raw materials. The high aspect ratio SiC nanowires are grown in situ within the fiber preform via a catalytic cracking method. This method is independent of the fiber preform configuration, and the catalytic cracking rate is easily controlled. This method effectively addresses the problems of high SiC nanowire preparation cost, difficult-to-control preparation process, and unsuitability for large-sized components. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 This is a flowchart of the preparation process of Example 1 of the present invention;
[0031] Figure 2 This is the microscopic morphology of the SiC nanowire with a large aspect ratio of the fiber preform of Example 1 of the present invention, wherein: Figure 2 a is the micromorphology of SiC nanowires with large aspect ratio in the fiber preform. Figure 2 b is the microscopic morphology of SiC nanowires at a higher magnification;
[0032] Figure 3 This is a transmission electron microscope image of a fiber preform with a large aspect ratio SiC nanowire according to an embodiment of the present invention, wherein: Figure 3 a is the transmission electron microscopy morphology of a single SiC nanowire. Figure 3 b is the transmission electron microscope morphology of a single SiC nanowire at a higher magnification. Figure 3 c is the distribution diagram of C element in SiC nanowires, Figure 3 d is the distribution diagram of Si element in SiC nanowires;
[0033] Figure 4 This is a size distribution diagram of SiC nanowires with a large aspect ratio in a fiber preform prepared in Example 1 of the present invention, wherein: Figure 4 a is the SiC nanowire diameter distribution, Figure 4 b is the length distribution of SiC nanowires. DETAILED DESCRIPTION
[0034] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0035] Example 1
[0036] A method for preparing SiC nanowires with a large aspect ratio as a fiber preform, the preparation process is as follows Figure 1 As shown, the following steps are included:
[0037] Step 1: Solid polycarbosilane, hyperbranched polycarbosilane and an organic solvent (including but not limited to ethanol, toluene, and xylene) are weighed respectively according to a ratio and placed in a container for stirring until the polycarbosilane and the organic solvent are completely miscible and the solution is clear and transparent, thereby preparing a polycarbosilane solution with a mass fraction of 1% to 50%, wherein the mass ratio of the solid polycarbosilane to the hyperbranched polycarbosilane is between 0.1 and 100.
[0038] Step 2: Weigh a catalyst (including but not limited to ferrocene, nickelocene, etc.) with a mass of 1% to 10% of the mass of the polycarbosilane, and add it to the polycarbosilane solution. After ultrasonic dispersion for 10 to 30 minutes, continue stirring for 1 to 2 hours until the catalyst is completely dissolved to obtain a mixed solution 1, that is, a polycarbosilane solution with added catalyst.
[0039] Step 3: Immerse the pre-prepared fiber preform (the preform fibers include but are not limited to carbon fibers and SiC fibers, and the preform structure includes but is not limited to two-dimensional lamination, three-dimensional needle punching, three-dimensional weaving, etc.) in the mixed solution 1 and vacuum impregnate for 20 to 60 minutes to obtain a pretreated fiber preform.
[0040] Step 4: Place the pretreated fiber preform in a crucible, then place it in a tube furnace, and after passing argon, heat treat it at a temperature of 1200℃~1600℃ for 1~4h to in-situ grow SiC nanowires in the fiber preform, i.e., SiC nanowires with a large aspect ratio in the fiber preform. The micromorphology of the prepared SiC nanowires with a large aspect ratio in the fiber preform is shown in the attached figure. Figure 2 The transmission electron microscope image of the prepared fiber preform with large aspect ratio SiC nanowires is shown in the attached figure. Figure 3 shown. Figure 2 This is the micromorphology of SiC nanowires with a large aspect ratio in the fiber preform. It can be seen that the SiC nanowires grow in the fiber preform and have a relatively large aspect ratio. Figure 3 This is a transmission electron microscope image of SiC nanowires with a large aspect ratio in the fiber preform. It can be seen that the SiC nanowires are cylindrical and the main elements are Si and C.
[0041] The size distribution of SiC nanowires with large aspect ratio in the prepared fiber preform is as follows Figure 4 As shown, Figure 4 a is the SiC nanowire diameter distribution, Figure 4 b is the length distribution of SiC nanowires. Figure 4 The average diameter of SiC nanowires is about 300 nm. Figure 4 b The average length of the SiC nanowires is 60 μm, and the calculated aspect ratio of the SiC nanowires is about 200.
Claims
1. A method for preparing SiC nanowires with a large aspect ratio as a fiber preform, characterized in that: The following steps are involved: Step 1: Prepare polycarbosilane solution: Putting polycarbosilane and an organic solvent in a container, stirring until they are mutually dissolved and the solution is clear, thereby obtaining a polycarbosilane solution; The mass fraction of the polycarbosilane in the polycarbosilane solution is 1% to 50%; Step 2: Add catalyst to polycarbosilane solution: Add the catalyst to the polycarbosilane solution, ultrasonically disperse for 10 to 30 minutes, and stir until the catalyst is completely dissolved. A polycarbosilane solution with a catalyst added is obtained, i.e., mixed solution 1; The mass of the catalyst is 1% to 10% of the mass of the polycarbosilane; Step 3: Vacuum impregnation of fiber preform: Immersing the fiber preform in the mixed solution 1 and vacuum impregnating for 20 to 60 minutes to obtain a pretreated fiber preform; The fibers of the fiber preform are carbon fibers or SiC fibers, and the structure of the fiber preform is two-dimensional lamination, three-dimensional needle punching, or three-dimensional weaving; Step 4: Heat treatment: The pretreated fiber preform is placed in a crucible, and the crucible containing the pretreated fiber preform is placed in a tubular furnace. Argon gas is introduced into the tubular furnace to heat treat the pretreated fiber preform at a temperature of 1200° C. to 1600° C. for a time of 1 h to 4 h to obtain a fiber preform with a large aspect ratio SiC nanowire.
2. The method for preparing SiC nanowires with a large aspect ratio as a fiber preform according to claim 1, characterized in that: The polycarbosilane comprises solid polycarbosilane and hyperbranched polycarbosilane, and the mass ratio of the solid polycarbosilane to the hyperbranched polycarbosilane is 0.1 to 100; The organic solvent is ethanol, toluene, or xylene.
3. The method for preparing SiC nanowires with a large aspect ratio as a fiber preform according to claim 1, characterized in that: The catalyst is ferrocene or nickelocene.
4. The method for preparing SiC nanowires with a large aspect ratio as a fiber preform according to claim 1, characterized in that: The stirring time is 1 h to 2 h.