A method for producing an mb2-sic composite fiber

Abstract

The application discloses a preparation method of MB2-SiC composite fibers, which comprises the following steps: mixing and stirring a mixed solution A composed of sorbitol, boric acid, acetic acid and ethanol, a solution B composed of an alcoholate of M metal and acetic acid, a solution C composed of PCS and THF, and a solution D composed of PVP and ethanol, obtaining primary spun fibers through electrostatic spinning, and obtaining MB2-SiC composite fibers through heat treatment, wherein M is at least one of zirconium and hafnium. In the preparation of boride ceramic fibers, silicon-containing substances are introduced, and silicon carbide is generated in situ, so that small grains of MB2 and SiC are uniformly distributed on long fibers, the aspect ratio of the fibers can be improved, the advantages of boride fibers are retained, and the carbon content of the boride fibers is reduced, and thus the oxidation resistance of the overall ceramic fibers is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of composite fibers, and particularly relates to a preparation method of boride-silicon carbide composite fibers. BACKGROUND

[0002] With the rapid development of aerospace technology, higher requirements are put forward for the materials used in the hot end parts of modern aircraft. Ultra-high temperature ceramics (UHTC) have become one of the attractive candidate materials for high-temperature applications due to their high melting point and strong high-temperature chemical stability. Among them, boride ultra-high temperature ceramics have the advantages of low theoretical density and excellent wear resistance, and have become a research hotspot. However, the brittleness and high-temperature environmental oxidation resistance of borides are still not satisfactory, which may lead to unpredictable catastrophic failure, so the mechanical properties of boride ceramics must be improved before their potential applications are fully realized.

[0003] The introduction of a second phase is one of the successful strategies to improve the mechanical properties of bulk boride ceramics. Currently, both carbides and borides are expected to be excellent second phase materials for improving the mechanical properties of boride ceramics. For example, Zhang et al. (Oxid Met (2016) 85:311-320) studied the oxidation behavior of ZrB2-SiC composites with different SiC powder additions at 1273 and 1473 K in air for 12 h, and the results showed that the oxidation layers formed were different when the SiC content was different, and when the SiC content was 30wt%, a borosilicate glass could be formed on the top layer, showing the highest oxidation resistance; Chen et al. (Ceramics International 49 (2023) 28030-28035) synthesized high aspect ratio ZrB2 rod-like crystals by a molten salt-mediated boron / carbon thermal reduction method, which can improve the problem of poor fracture toughness of bulk ZrB2 ceramics.

[0004] However, the prior art has the problems of insufficient toughening performance of 0-dimensional silicon carbide particles alone, and high content of amorphous carbon in boride short-cut ceramic fibers affecting the oxidation resistance of the fibers. SUMMARY

[0005] In view of the above problems in the prior art, the present application provides a preparation method of MB2-SiC composite fibers, in order to improve the aspect ratio of the fibers and reduce the carbon content of the boride fibers, thereby improving the oxidation resistance of the overall ceramic fibers.

[0006] To achieve the above object, the present application adopts the following technical solutions:

[0007] A preparation method of MB2-SiC composite fibers, comprising the following steps:

[0008] Step 1, sorbitol, boric acid and acetic acid and ethanol are mixed and heated to clarify to obtain a mixed solution A; the alkoxide of M metal is mixed with acetic acid and heated to clarify to obtain solution B; PCS is added to THF and stirred to dissolve to obtain solution C; PVP is added to ethanol and stirred to dissolve to obtain solution D; wherein M is at least one of zirconium and hafnium;

[0009] Step 2, solution A and solution B are mixed and heated to clarify to obtain solution E;

[0010] Step 3, solution C, solution D and solution E are mixed and stirred to obtain an electrospinning solution, and then electrospinning is performed to obtain a primary spun fiber;

[0011] Step 4, the primary spun fiber is dried and then heat treated in an argon atmosphere to obtain an MB2-SiC composite fiber.

[0012] Further, when preparing the mixed solution A, the molar ratio of carbon in sorbitol to boron in boric acid is 4.5-5.5:3, the volume ratio of acetic acid to ethanol is 4:5.5-5.5, and the mass ratio of boric acid to acetic acid is 1:2.7-3. The heating temperature during preparation is 60-70℃.

[0013] Further, the molar ratio of M metal contained in the alkoxide of M metal in solution B to boron contained in boric acid in mixed solution A is 1:6; the volume ratio of the alkoxide of M metal in solution B to acetic acid is 1:1.2-1.6; and the heating temperature during preparation of solution B is 60-70℃.

[0014] Further, the mass ratio of PCS to THF in solution C is 1:7-21.

[0015] Further, the mass ratio of PVP to ethanol in solution D is 1:5.5-6.

[0016] Further, the temperature of the heating and stirring in step 2 is 70-80℃.

[0017] Further, the mixing and stirring time in step 3 is 6-10h, and the volume ratio of solution E to solution C, solution D is 1:1.1:1.4.

[0018] Further, the parameters of the electrospinning in step 3 are: flow rate 1.5-3ml / h, voltage 18-22KV, receiving distance 13-18cm.

[0019] Further, in step 4, the drying is performed in a 60-80℃ oven for 2-4h, and the heat treatment is performed at 1400-1550℃ for 2-4h.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] 1. The present application provides a preparation method of MB2-SiC composite fiber, which introduces silicon-containing substances in the preparation of boride ceramic fiber, generates silicon carbide in situ, and uniformly distributes the small crystal grains of MB2 and SiC on the long fiber, thereby improving the aspect ratio of the fiber, retaining the advantages of boride fiber, and reducing the carbon content of boride fiber to improve the overall oxidation resistance of the ceramic fiber.

[0022] 2. The present application adopts a preparation method process of precursor mixing and in-situ growth, which is simple and easy to operate. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0024] Figure 1 It is a flowchart of the present application.

[0025] Figure 2 It is a data graph of ZrB2-SiC composite fiber prepared in Example 1 of the present application, wherein (a) is a scanning electron microscope photo of the as-spun fiber, (b) is an XRD graph of ZrB2-SiC composite fiber, (c) and (d) are scanning electron microscope photos of ZrB2-SiC composite fiber at different magnifications.

[0026] Figure 3 It is a transmission electron microscope data of ZrB2-SiC composite fiber prepared in Example 1 of the present application, wherein (a) is a TEM morphology graph of ZrB2-SiC composite fiber, (b) is a high-resolution graph of SiC lattice spacing calibration, (c) is a high-resolution graph of ZrB2 lattice spacing calibration, and (d) is a polycrystalline diffraction ring calibration graph of ZrB2-SiC composite fiber.

[0027] Figure 4 It is an EDS energy spectrum data graph of ZrB2-SiC composite fiber prepared in Example 1 of the present application, wherein (a) is an EDS morphology graph of ZrB2-SiC composite fiber, (b) is a total EDS spectrum graph of Zr, B, Si and C element distribution, (c) is an EDS graph of C element distribution, (d) is an EDS graph of Zr element distribution, (e) is an EDS graph of B element distribution, and (f) is an EDS graph of Si element distribution.

[0028] Figure 5Data graphs of the HfB2-SiC composite fiber prepared in Example 2 of the present application, wherein: (a) is a scanning electron microscope photo of the as-spun fiber, (b) is an XRD graph of the HfB2-SiC composite fiber, (c), (d) are scanning electron microscope photos of the HfB2-SiC composite fiber at different magnifications.

[0029] Figure 6 Data graphs of the (Zr 0.5 Hf 0.5 )B2-SiC composite fiber prepared in Example 3 of the present application, wherein: (a) is a scanning electron microscope photo of the as-spun fiber, (b) is an XRD graph of the (Zr 0.5 Hf 0.5 )B2-SiC composite fiber, (c), (d) are scanning electron microscope photos of the (Zr 0.5 Hf 0.5 )B2-SiC composite fiber at different magnifications. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application is further described in detail below in combination with examples, and all other examples obtained by those skilled in the art without making any creative efforts on the premise of the examples in the present application all belong to the scope of protection of the present application.

[0031] Example 1

[0032] The present example provides a preparation method of ZrB2-SiC composite fiber, and the preparation flow is shown in Figure 1 , which specifically comprises the following steps:

[0033] Step 1, 6.2 g of boric acid and 5.5 g of sorbitol are added into a mixed solvent composed of 16 mL of acetic acid and 20 mL of ethanol, heated and stirred at 70℃ until clear, to obtain a mixed solution A. 7.5 mL of zirconium n-propyl alcohol is added into 12 mL of acetic acid, heated and stirred at 70℃ until turbid, to obtain a solution B. 2 g of PCS is added into 24 mL of THF, stirred until the PCS is dissolved, to obtain a solution C. 4.09 g of PVP is added into 31 mL of ethanol, stirred until the PVP is dissolved, to obtain a solution D.

[0034] Step 2, the solution A and the solution B are mixed and heated and stirred at 70℃ until clear, to obtain a solution E.

[0035] Step 3, the solution C, the solution D and the solution E are mixed and stirred at room temperature for 8 h, to obtain an electrospinning solution, and then electrospinning is performed to obtain an as-spun fiber, and the electrospinning parameters are as follows: flow rate 2 mL / h, voltage 20 KV, receiving distance 15 cm.

[0036] Step 4, after the as-spun fiber is dried in an oven at 60℃ for 2h, it is placed in a tube furnace and calcined at 1400℃ for 3h under argon atmosphere with a heating rate of 2℃ / min, to obtain ZrB2-SiC composite fiber.

[0037] The as-spun fiber and ZrB2-SiC composite fiber prepared in this example are observed by scanning electron microscope. As shown in Figure 2 (a), the diameter of the as-spun fiber is about 1μm, and the surface is smooth with good morphology. As shown in Figure 2 (c) and Figure 2 (d), the diameter of the ZrB2-SiC composite fiber is about 300nm.

[0038] The ZrB2-SiC composite fiber prepared in this example is subjected to phase determination by X-ray diffractometer, as shown in Figure 2 (b), it can be seen that the composite fiber is composed of zirconium boride and silicon carbide.

[0039] The ZrB2-SiC composite fiber prepared in this example is observed by transmission electron microscope. As shown in Figure 3 (a), the surface of the fiber is smooth, but the fiber is composed of multiple small grains inside. As shown in Figure 3 (b) and Figure 3 (c), the particles on the fiber are identified as ZrB2 and SiC particles. As shown in Figure 3 (d), the diffraction pattern is a polycrystalline diffraction ring, which is also identified as ZrB2 and SiC.

[0040] The ZrB2-SiC composite fiber prepared in this example is observed by EDS energy spectrum. As shown in Figure 4 , the fiber is composed of multiple ZrB2 and SiC small grains inside, with a large contrast between the distribution areas of Zr and Si.

[0041] Example 2

[0042] This example provides a preparation method of HfB2-SiC composite fiber, and the preparation process is shown in Figure 1 , which specifically comprises the following steps:

[0043] Step 1, 6.2g of boric acid and 5.5g of sorbitol are added to a mixed solvent composed of 16mL of acetic acid and 20mL of ethanol, heated and stirred at 70℃ until clear, to obtain a mixed solution A. 9.3mL of hafnium n-propylate is added to 12mL of acetic acid, heated and stirred at 70℃ until turbid, to obtain solution B. 2g of PCS is added to 24mL of THF, stirred until PCS is dissolved, to obtain solution C. 4.3g of PVP is added to 31mL of ethanol, stirred until PVP is dissolved, to obtain solution D.

[0044] Step 2, mix solution A and solution B and heat stir at 70℃ until clear to obtain solution E.

[0045] Step 3, mix solution C, solution D and solution E and stir at room temperature for 8h to obtain electrospinning solution, then electrospinning to obtain as-spun fiber, the electrospinning parameters are: flow rate 2mL / h, voltage 20KV, receiving distance 15cm.

[0046] Step 4, after the as-spun fiber is dried in an oven at 60℃ for 2h, it is placed in a tube furnace and calcined at 1500℃ for 2h under argon atmosphere at a heating rate of 2℃ / min to obtain HfB2-SiC composite fiber.

[0047] The as-spun fiber and HfB2-SiC composite fiber prepared in this example are observed by scanning electron microscope. As shown in Figure 5 (a), the diameter of the as-spun fiber is about 1μm, the surface is smooth and the morphology is good. As shown in Figure 5 (c) and Figure 5 (d), the diameter of the HfB2-SiC composite fiber is about 800nm.

[0048] The HfB2-SiC composite fiber prepared in this example is subjected to phase determination by X-ray diffractometer, as shown in Figure 5 (b), it can be seen that the composite fiber is composed of hafnium boride and silicon carbide.

[0049] Example 3

[0050] This example provides a preparation method of (Zr 0.5 Hf 0.5 )B2-SiC composite fiber, and the preparation process is as shown in Figure 1 , which specifically comprises the following steps:

[0051] Step 1, 6.2g of boric acid and 5.5g of sorbitol are added to a mixed solvent composed of 16mL of acetic acid and 20mL of ethanol, heated and stirred at 70℃ until clear to obtain mixed solution A. 3.75mL of zirconium n-propyl alcohol and 4.65mL of hafnium n-propyl alcohol are added to 12mL of acetic acid, heated and stirred at 70℃ until turbid to obtain solution B. 2g of PCS is added to 24mL of THF and stirred until PCS is dissolved to obtain solution C. 4.28g of PVP is added to 31mL of ethanol and stirred until PVP is dissolved to obtain solution D.

[0052] Step 2, mix solution A and solution B and heat stir at 70℃ until clear to obtain solution E.

[0053] Step 3, solution C, solution D and solution E are mixed and stirred at room temperature for 8h to obtain an electrospinning solution, and then electrospinning is carried out to obtain a spun fiber, and the electrospinning parameters are: flow rate 2mL / h, voltage 20KV, receiving distance 15cm.

[0054] Step 4, the spun fiber is dried in an oven at 60℃ for 2h, then placed in a tube furnace, heated to 1500℃ at a heating rate of 2℃ / min under argon atmosphere, and calcined for 2h to obtain (Zr 0.5 Hf 0.5 )B2-SiC composite fiber.

[0055] The spun fiber and (Zr 0.5 Hf 0.5 )B2-SiC composite fiber prepared in the embodiment are observed by scanning electron microscopy. As shown in (a), the diameter of the spun fiber is about 1.2μm, the surface is smooth, and the morphology is good. As shown in (c) and (d), the diameter of the (Zr Figure 6 Hf Figure 6 )B2-SiC composite fiber is about 800nm. Figure 6 The (Zr 0.5 Hf 0.5 )B2-SiC composite fiber prepared in the embodiment is subjected to phase determination by X-ray diffractometer, and as shown in (b), it can be seen that the composite fiber is composed of zirconium hafnium boride and silicon carbide.

[0056] Figure 6 The (Zr 0.5 Hf 0.5 )B2-SiC composite fiber prepared in the embodiment is subjected to phase determination by X-ray diffractometer, and as shown in (b), it can be seen that the composite fiber is composed of zirconium hafnium boride and silicon carbide.

[0057] As can be seen from the above, the MB2-SiC composite fiber can be prepared by the present application, which not only can make the small grains of the two substances uniformly distributed on the long fiber and retain the original characteristics, but also is easy to operate by the in-situ growth method of precursor mixing.​

Claims

1. A method for producing an MB2-SiC composite fiber, characterized by, The method comprises the following steps: Step 1, mixing sorbitol, boric acid, acetic acid and ethanol and heating and stirring until clear to obtain a mixed solution A; mixing an alcoholate of M metal with acetic acid and heating and stirring until uniform to obtain a solution B; adding PCS to THF and stirring until the PCS is dissolved to obtain a solution C; adding PVP to ethanol and stirring until the PVP is dissolved to obtain a solution D; wherein M is at least one of zirconium and hafnium; In the preparation of the mixed solution A, the molar ratio of carbon in sorbitol to boron in boric acid is 4.5-5.5:3, the volume ratio of acetic acid to ethanol is 4:5.5-5.5, and the mass ratio of boric acid to acetic acid is 1:2.7-3; The molar ratio of M metal contained in the alcoholate of M metal in the solution B to boron contained in boric acid in the mixed solution A is 1:6, and the volume ratio of the alcoholate of M metal in the solution B to acetic acid is 1:1.2-1.6; The mass ratio of PCS to THF in the solution C is 1:7-21; The mass ratio of PVP to ethanol in the solution D is 1:5.5-6; Step 2, mixing solution A and solution B and heating and stirring until clear to obtain a solution E; Step 3, mixing solution C, solution D and solution E according to a volume ratio of solution E to solution C to solution D of 1:1.1:1.4, stirring uniformly to obtain an electrospinning solution, and then electrospinning to obtain a primary spun fiber; Step 4, drying the primary spun fiber and then heat treating under an argon atmosphere to obtain an MB2-SiC composite fiber.

2. The method of producing an MB2-SiC composite fiber according to claim 1, characterized by: The heating temperature in the preparation of the mixed solution A is 60-70℃.

3. The method of producing an MB2-SiC composite fiber according to claim 1, characterized by: The heating temperature in the preparation of the solution B is 60-70℃.

4. The method of producing an MB2-SiC composite fiber according to claim 1, characterized by: The temperature of the heating and stirring in step 2 is 70-80℃.

5. The method of producing an MB2-SiC composite fiber according to claim 1, characterized by: The time of the mixing and stirring in step 3 is 6-10 h.

6. The method of producing an MB2-SiC composite fiber according to claim 1, characterized by, The parameters of the electrospinning in step 3 are: flow rate 1.5-3 mL / h, voltage 18-22 KV, and receiving distance 13-18 cm.

7. The method of producing an MB2-SiC composite fiber according to claim 1, characterized by: In step 4, the drying is performed in an oven at 60-80℃ for 2-4 h, and the heat treatment is performed at 1400-1550℃ for 2-4 h.

8. An MB2-SiC composite fiber prepared by the method of any one of claims 1-7.

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