A boron nitride modified silicon carbide fiber grown carbon nanotube ceramic matrix composite material and its preparation method

Abstract

The present invention provides a boron nitride modified silicon carbide fiber grown carbon nanotube ceramic matrix composite material and a preparation method thereof. The preparation method comprises the following steps: Step S1, immersing the boron nitride modified silicon carbide fiber in a ferrocene xylene solution with a concentration of 0.02 - 0.2 g / ml for 24 - 72 h; Step S2, using argon as the carrier gas and hydrogen as the protective gas, introducing them into a high-temperature tube furnace, heating to 600 - 1000 °C at a heating rate of 5 - 15 °C / min; Step S3, diffusing the catalyst solution in Step S1 into the high-temperature tube furnace at a diffusion rate of 0.1 - 0.5 sccm, and introducing 1 - 30 sccm of acetylene as the carbon source into the high-temperature tube furnace, and reacting for 5 - 60 min to obtain the boron nitride modified silicon carbide fiber grown carbon nanotube ceramic matrix composite material. The preparation method provided by the present invention realizes the effect of multi-interface synergistic toughening; by controlling conditions such as the morphology, growth density, and length of the carbon nanotubes, the macroscopic mechanical properties of the composite material are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic matrix composites, and particularly relates to a boron nitride modified silicon carbide fiber grown carbon nanotube ceramic matrix composite and a preparation method thereof. Background Art

[0002] Due to the inherent brittleness of ceramic materials, they lack sufficient reliability as structural materials. Ceramic matrix composites have well improved the toughness of materials by introducing fibers and designing a reasonable interface. Ceramic matrix composites are new ceramic materials that gradually developed in the 1980s of the 20th century. Due to the characteristics of ceramic matrix composites such as high temperature resistance, chemical corrosion resistance, oxidation resistance, high strength, high hardness, low linear expansion coefficient, and low thermal conductivity, they have become ideal high-temperature structural materials and have great application potential in environments with harsh requirements for materials such as aeroengines, gas turbines, and nuclear reactors, and have received extensive attention from people.

[0003] The interface layer is an important part of ceramic matrix composites and has functions such as protecting fibers, toughening, and transferring loads. By designing a suitable interface, the toughness of ceramic matrix composites can be increased and the reliability of the composites can be improved through means such as crack deflection and fiber pull-out energy absorption. Boron nitride is a commonly used interface layer for silicon carbide fiber reinforced silicon carbide composites. Boron nitride has a good interfacial bonding strength with silicon carbide fibers. In addition, B 2 O 3 melted at high temperature will dissolve SiO 2 . These molten oxides can inhibit the oxidation reaction of the material, thus showing good oxidation resistance and enhancing the anti-failure ability of the interface layer in a high-temperature oxidation environment.

[0004] Carbon nanotubes have an approximate quasi-one-dimensional structure, low density, good mechanical and mechanical properties, large specific surface area, large aspect ratio, etc., making them good toughening materials. Generally, the toughening mechanisms of carbon nanotubes are as follows:

[0005] 1. Carbon nanotubes enhance the stress transfer ability of the composite material. The formation of a carbon nanotube network helps to evenly distribute the stress field under an external load, improving the impact strength;

[0006] 2. The carbon nanotube network can play the role of a physical network, providing the same effect as a chemical cross-linking structure, showing a morphological change similar to that of elastomer particle reduction, and enhancing the impact toughness of the material;

[0007] 3. Morphological evolution induced by carbon nanotubes;

[0008] 4. Solubilization of immiscible blends induced by carbon nanotubes prevents agglomeration in regions during the melt mixing process, improves compatibility, and results in toughening of the material.

[0009] 5. The nano-bridge effect of carbon nanotubes at the interface, where the carbon nanotubes grow perpendicular to the crack and bridge the crack surface, thus providing closing stress across the entire crack surface. Introducing carbon nanotubes into the interface of immiscible polymer blends can prevent crack initiation and propagation, improve interfacial adhesion, and facilitate stress transfer from one component to another, thereby enhancing the toughness of the material.

[0010] Carbon nanotubes have been widely used in polymer matrix composites, but less attention has been paid to ceramic matrix composites, especially in multi-interface composites. Therefore, the research on introducing carbon nanotubes into ceramic matrix composites for interfacial toughening has far-reaching significance for solving the brittle shortcomings of ceramic materials and preparing ceramic matrix composites with better toughness. Summary of the Invention

[0011] The technical problem to be solved by the present invention is to provide a preparation method of a boron nitride-modified silicon carbide fiber grown carbon nanotube ceramic matrix composite. The method uses floating catalyst chemical vapor deposition to grow carbon nanotubes on boron nitride-coated silicon carbide fibers to achieve the effect of multi-interface synergistic toughening; by controlling conditions such as the morphology, growth density, and length of carbon nanotubes, the macroscopic mechanical properties of the composite are improved.

[0012] The technical solution of the present invention is as follows:

[0013] A preparation method of a boron nitride-modified silicon carbide fiber grown carbon nanotube ceramic matrix composite, comprising the following steps:

[0014] Step S1, soaking the boron nitride-modified silicon carbide fiber in a ferrocene xylene solution with a concentration of 0.02 - 0.2 g / ml for 24 - 72 h;

[0015] Specifically, the concentration of the ferrocene xylene solution can be 0.02 g / ml, 0.05 g / ml, 0.08 g / ml, 0.1 g / ml, 0.15 g / ml, or 0.2 g / ml, or other values within this range; preferably, the concentration of the ferrocene xylene solution is 0.02 g / ml;

[0016] The soaking time can be 24 h, 36 h, 48 h, 60 h, or 72 h, or other values within this range.

[0017] Step S2, using argon as the carrier gas and hydrogen as the protective gas, introducing them into a high-temperature tubular furnace, heating to 600 - 1000 °C at a heating rate of 5 - 15 °C / min;

[0018] Specifically, the reaction temperature can be 600 °C, 650 °C, 700 °C, 750 °C, 800 °C, 850 °C, 900 °C, 950 °C or 1000 °C, or can be a temperature value within this range; preferably, the reaction temperature is 650 - 750 °C; more preferably, the reaction temperature is 700 °C;

[0019] The heating rate can be 5 °C / min, 6 °C / min, 7 °C / min, 9 °C / min, 10 °C / min, 12 °C / min, 14 °C / min or 15 °C / min, or can be other values within this range; preferably, the heating rate is 15 °C / min.

[0020] Step S3: Diffuse the catalyst solution in step S1 into the high-temperature tube furnace at a diffusion rate of 0.1 - 0.5 sccm, and introduce acetylene with a flow rate of 1 - 30 sccm as the carbon source into the high-temperature tube furnace, and the reaction time is 5 - 60 min to obtain a carbon nanotube ceramic matrix composite material with boron nitride modified silicon carbide fibers grown;

[0021] Specifically, the diffusion rate of the catalyst solution can be 0.1 sccm, 0.2 sccm, 0.3 sccm, 0.4 sccm or 0.5 sccm, or can be other values within this range; the acetylene flow rate can be 1 sccm, 5 sccm, 10 sccm, 15 sccm, 20 sccm, 25 sccm or 30 sccm, or can be other values within this range; the reaction time can be 5 min, 10 min, 20 min, 30 min, 40 min, 50 min or 60 min, or can be other values within this range. Preferably, the catalyst solution is diffused into the high-temperature tube furnace at a diffusion rate of 0.4 sccm, acetylene with a flow rate of 20 sccm is introduced into the high-temperature tube furnace, and the reaction time is 20 min.

[0022] Furthermore, the protruding distance of the quartz tube in the high-temperature tube furnace is 5 - 20 cm, such as 5 cm, 10 cm, 15 cm or 20 cm, or can be other values within this range. Preferably, the protruding distance of the quartz tube in the high-temperature tube furnace is 10 cm.

[0023] Further, in step S2, the flow rate of argon is 200 - 1000 sccm, and the flow rate of hydrogen is 20 - 200 sccm. Specifically, the flow rate of argon can be 200 sccm, 300 sccm, 400 sccm, 500 sccm, 800 sccm, 1000 sccm, 1200 sccm, 1500 sccm, 1600 sccm, 1800 sccm or 2000 sccm, or other values within this range; preferably, the flow rate of argon is 400 - 1000 sccm; more preferably, it is 800 sccm. The flow rate of hydrogen can be 20 sccm, 50 sccm, 80 sccm, 100 sccm, 120 sccm, 150 sccm, 180 sccm or 200 sccm, or other values within this range; preferably, the flow rate of hydrogen is 90 - 200 sccm, and more preferably, the flow rate of hydrogen is 180 sccm.

[0024] Further, the silicon carbide fiber is a polycrystalline silicon carbide fiber.

[0025] The present invention also provides a boron nitride - modified silicon carbide fiber - grown carbon nanotube ceramic - matrix composite material, which is prepared by the above - mentioned preparation method.

[0026] Compared with the prior art, the boron nitride - modified silicon carbide fiber - grown carbon nanotube ceramic - matrix composite material and its preparation method provided by the present invention have the following beneficial effects:

[0027] The preparation method of the boron nitride - modified silicon carbide fiber - grown carbon nanotube ceramic - matrix composite material provided by the present invention uses the floating - catalyst chemical vapor deposition method to grow carbon nanotubes on the boron nitride - coated silicon carbide fiber. The boron nitride interface is well - combined with the carbon nanotubes, realizing the multi - interface synergistic toughening effect; by controlling conditions such as the morphology, growth density, and length of the carbon nanotubes, the macroscopic mechanical properties of the composite material are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0029] Figure 1 It is the SEM image of growing carbon nanotubes on the boron nitride interface of the coated silicon carbide fiber in Example 1;

[0030] Figure 2 It is the SEM image of growing carbon nanotubes on the boron nitride interface of the coated silicon carbide fiber in Example 2;

[0031] Figure 3 SEM image of growing carbon nanotubes on the coated silicon carbide fiber boron nitride interface for Example 3;

[0032] Figure 4 SEM image of growing carbon nanotubes on the coated silicon carbide fiber boron nitride interface for Example 4;

[0033] Figure 5 SEM image of growing carbon nanotubes on the coated silicon carbide fiber boron nitride interface for Example 5;

[0034] Figure 6 SEM image of growing carbon nanotubes on the coated silicon carbide fiber boron nitride interface for Example 6;

[0035] Figure 7 Effect diagram of average fracture tensile strength and ultimate tensile strain of different composite materials. Detailed implementation manners

[0036] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention and make the above objects, features, and advantages of the present invention more obvious and understandable, the following further describes the detailed implementation manners of the present invention.

[0037] The endpoints and any values in the ranges disclosed herein are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0038] The boron nitride modified silicon carbide fiber grown carbon nanotube ceramic matrix composite material of the present invention realizes the increase of the toughness and mechanical properties of silicon carbide ceramics by introducing fibers and reasonable interface design. The introduction of fibers has fundamentally changed the fracture behavior of ceramic materials, changing from the original brittle fracture to non-brittle fracture; boron nitride has a lamellar structure similar to graphite and has a moderate interface bonding strength with silicon carbide fibers, and the starting temperature of boron nitride is high, forming a protective condensed oxide B 2 O 3 to maintain passivation near 950 °C, thereby obtaining better oxidation resistance; carbon nanotubes have a quasi-one-dimensional structure, and the large aspect ratio of carbon nanotubes enables good load transfer in the matrix, thereby achieving the purpose of toughening.

[0039] The boron nitride modified silicon carbide fiber grown carbon nanotube ceramic matrix composite material SiC of the present invention f-BN-CNTs / SiC uses BN and CNTs to synergistically reinforce silicon carbide fiber / silicon carbide composites. The presence of multiple interfaces not only protects the fibers from corrosion but also improves the toughness and mechanical properties of the composites.

[0040] The following elaborates in detail on the boron nitride-modified silicon carbide fiber-grown carbon nanotube ceramic matrix composites of the present invention in combination with specific examples.

[0041] Example 1

[0042] A preparation method for boron nitride-modified silicon carbide fiber-grown carbon nanotube ceramic matrix composites includes the following steps:

[0043] (1) Pre-soak the boron nitride-modified silicon carbide fibers in a ferrocene xylene solution with a concentration of 0.02 g / ml for 24 h;

[0044] (2) Use 800 sccm of argon as the carrier gas and 180 sccm of hydrogen as the protective gas to be introduced into a high-temperature tube furnace. The heating rate is 15 °C / min, and the temperature is raised to 650 °C;

[0045] (3) The catalyst solution diffuses into the tube furnace at 0.4 sccm, and 20 sccm of acetylene is introduced into the high-temperature tube furnace as the carbon source. The reaction time is 10 min.

[0046] Please refer to Figure 1 , which is the SEM image of growing carbon nanotubes on the boron nitride interface of the coated silicon carbide fibers in Example 1. The carbon nanotubes uniformly cover the boron nitride interface. The morphology of the grown carbon nanotubes is regular and uniform, and good uniform coverage is achieved on different fibers, but the length of the carbon nanotubes is short and the growth density is low.

[0047] Example 2

[0048] A preparation method for boron nitride-modified silicon carbide fiber-grown carbon nanotube ceramic matrix composites includes the following steps:

[0049] (1) Pre-soak the boron nitride-modified silicon carbide fibers in a ferrocene xylene solution with a concentration of 0.02 g / ml for 24 h;

[0050] (2) Use 800 sccm of argon as the carrier gas and 180 sccm of hydrogen as the protective gas to be introduced into a high-temperature tube furnace. The heating rate is 15 °C / min, and the temperature is raised to 650 °C;

[0051] (3) The catalyst solution diffuses into the tube furnace at 0.4 sccm, and 20 sccm of acetylene is introduced into the high-temperature tube furnace as the carbon source. The reaction time is 20 min.

[0052] Please refer toFigure 2 , which is the SEM image of growing carbon nanotubes on the coated silicon carbide fiber boron nitride interface in Example 2. It can be seen from Figure 2 that by increasing the reaction time, the length of the carbon nanotubes increases, the growth density increases appropriately, and the content of amorphous carbon also increases to a certain extent.

[0053] Example 3

[0054] A preparation method of a boron nitride modified silicon carbide fiber growing carbon nanotube ceramic matrix composite material, comprising the following steps:

[0055] (1) Pre-soak the boron nitride modified silicon carbide fiber in a ferrocene xylene solution with a concentration of 0.02 g / ml for 24 h;

[0056] (2) Use 800 sccm argon as the carrier gas and 180 sccm hydrogen as the protective gas to introduce into the high-temperature tube furnace, with a heating rate of 15 °C / min, and heat up to 700 °C;

[0057] (3) The catalyst solution diffuses into the tube furnace at 0.4 sccm, and 20 sccm acetylene is introduced into the high-temperature tube furnace as the carbon source, and the reaction time is 10 min.

[0058] Please refer to Figure 3 , which is the SEM image of growing carbon nanotubes on the coated silicon carbide fiber boron nitride interface in Example 3. It can be seen from Figure 3 that increasing the synthesis temperature promotes the growth of carbon nanotubes at a faster rate, increases the length, increases the growth density, and the crystallinity of the carbon nanotubes is also better. The increase in the growth density of the carbon nanotubes makes the carbon nanotubes on some fibers grow in an array.

[0059] Example 4

[0060] A preparation method of a boron nitride modified silicon carbide fiber growing carbon nanotube ceramic matrix composite material, comprising the following steps:

[0061] (1) Pre-soak the boron nitride modified silicon carbide fiber in a ferrocene xylene solution with a concentration of 0.02 g / ml for 24 h;

[0062] (2) Use 800 sccm argon as the carrier gas and 180 sccm hydrogen as the protective gas to introduce into the high-temperature tube furnace, with a heating rate of 15 °C / min, and heat up to 700 °C;

[0063] (3) The catalyst solution diffuses into the tube furnace at 0.4 sccm, and 20 sccm acetylene is introduced into the high-temperature tube furnace as the carbon source, and the reaction time is 20 min.

[0064] Please refer to Figure 4, is the SEM image of growing carbon nanotubes on the coated silicon carbide fiber boron nitride interface in Example 4. It can be seen from Figure 4 that increasing the reaction time increases the length of the carbon nanotubes and moderately increases the growth density.

[0065] Example 5

[0066] A preparation method of a carbon nanotube ceramic matrix composite material grown on boron nitride modified silicon carbide fibers includes the following steps:

[0067] (1) Pre-soak the boron nitride modified silicon carbide fibers in a ferrocene xylene solution with a concentration of 0.02 g / ml for 24 h;

[0068] (2) Use 800 sccm argon as the carrier gas and 180 sccm hydrogen as the protective gas and introduce them into a high-temperature tube furnace. The heating rate is 15 °C / min and heat up to 750 °C;

[0069] (3) The catalyst solution diffuses into the tube furnace at 0.4 sccm, and 20 sccm of acetylene is introduced into the high-temperature tube furnace as the carbon source, and the reaction time is 20 min.

[0070] Please refer to Figure 5 , is the SEM image of growing carbon nanotubes on the coated silicon carbide fiber boron nitride interface in Example 5. Combining Figure 3 , Figure 4 and Figure 5 it can be seen that when the reaction temperature continues to increase, the activity of the catalyst particles increases, and agglomeration is more likely to occur, resulting in an increase in the diameter of the grown carbon nanotubes; at the same time, as the synthesis temperature increases, the content of amorphous carbon increases, resulting in a decrease in the purity of the carbon nanotubes.

[0071] Example 6

[0072] A preparation method of a carbon nanotube ceramic matrix composite material grown on boron nitride modified silicon carbide fibers includes the following steps:

[0073] (1) Pre-soak the boron nitride modified silicon carbide fibers in a ferrocene xylene solution with a concentration of 0.02 g / ml for 24 h;

[0074] (2) Use 400 sccm argon as the carrier gas and 90 sccm hydrogen as the protective gas and introduce them into a high-temperature tube furnace. The heating rate is 15 °C / min and heat up to 700 °C;

[0075] (4) The catalyst solution diffuses into the tube furnace at 0.2 sccm, and 10 sccm of acetylene is introduced into the high-temperature tube furnace as the carbon source, and the reaction time is 10 min.

[0076] Please refer to Figure 6, which is the SEM image of growing carbon nanotubes on the coated silicon carbide fiber boron nitride interface in Example 6. From Figure 6 it can be seen that by reducing the gas inlet rate and the catalyst diffusion rate, the growth density of carbon nanotubes decreases, and only a shallow layer covers the boron nitride interface, no longer presenting an array-like morphology.

[0077] Therefore, for the preparation method of the carbon nanotube ceramic matrix composite material grown on the boron nitride modified silicon carbide fiber of the present invention, Example 4 is the preferred example.

[0078] The boron nitride modified silicon carbide fiber composite material SiC f -BN / SiC, the carbon nanotube grown on the surface of silicon carbide fiber composite material SiC f -CNTs / SiC, and the composite material SiC of Example 4 in the present invention f -BN-CNTs / SiC were subjected to mechanical property tests. Among them, the carbon nanotube growth process of the carbon nanotube grown on the surface of silicon carbide fiber composite material is the same as that of Example 4, and the boron nitride modified silicon carbide fiber composite material SiC f -BN / SiC is the same as the boron nitride modified silicon carbide fiber material used in Example 4.

[0079] The test method is: using a universal tensile testing machine to conduct uniaxial tensile tests on the three composite materials, measuring the average fracture tensile strength and the ultimate tensile strain of each composite material. The test results are shown in Figure 7 , where Figure 7 (a) represents the average fracture tensile strength of the material, Figure 7 (b) represents the ultimate tensile strain of the material. From Figure 7 it can be seen that for the composite material SiC f -CNTs / SiC, only CNTs act as the interface, and CNTs cannot completely cover the silicon carbide fiber. Therefore, during the preparation process, the fiber is corroded to a certain extent and degraded, so the mechanical properties are relatively low. Its average tensile fracture strength is only 35.7 MPa, and the ultimate strain is only 0.6%. For the composite material SiC f -BN / SiC uses BN with a similar graphite multi-layer structure as the interface, which has a relatively moderate interface bonding strength, can protect the fiber from corrosion, and plays a role in preventing and deflecting the crack from propagating in the matrix, thus improving the mechanical properties of the micro composite material. Its average tensile fracture strength is 292.8 MPa, and the ultimate tensile strain is 2.1%. For the composite material SiC f-BN-CNTs / SiC uses BN and CNTs to synergistically reinforce silicon carbide fiber / silicon carbide composites. The existence of multiple interfaces not only protects the fibers from corrosion, but also improves the macroscopic mechanical properties of the microcomposites due to the introduction of CNTs. In addition, CNTs can improve the toughness of the composites through mechanisms such as pull-out, fracture, and deflection bridging to extend cracks. Composite material SiC f -BN-CNTs / SiC has the highest average tensile fracture strength of 359.4 MPa, compared with the composite material SiC f -BN / SiC, which is increased by 22.7%; its ultimate tensile strain is 2.2%, compared with the composite material SiC f -BN / SiC has a relatively small increase. Therefore, the design of multiple interfaces of CNTs and BN improves the macroscopic mechanical properties of silicon carbide fiber / silicon carbide composites.

[0080] The above has made a detailed description of the embodiments of the present invention, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations made to these embodiments without departing from the principle and spirit of the present invention still fall within the protection scope of the present invention.

Claims

1. A preparation method of a boron nitride modified silicon carbide fiber grown carbon nanotube ceramic matrix composite material, characterized in that, it includes the following steps: Step S1, soak the boron nitride modified silicon carbide fiber in a ferrocene xylene solution with a concentration of 0.02 g / ml for 24 - 72 h; Step S2, use argon as the carrier gas and hydrogen as the protective gas to introduce into a high-temperature tube furnace, heat up to 700 °C, and the heating rate is 5 - 15 °C / min; among them, the flow rate of argon is 800 sccm, and the flow rate of hydrogen is 180 sccm; Step S3, adopt the floating catalyst chemical vapor deposition method, diffuse the catalyst solution in Step S1 into the high-temperature tube furnace at a diffusion rate of 0.4 sccm, and introduce 20 sccm of acetylene as the carbon source into the high-temperature tube furnace, and the reaction time is 20 min, grow carbon nanotubes on the boron nitride coated silicon carbide fiber to obtain a boron nitride modified silicon carbide fiber grown carbon nanotube ceramic matrix composite material.

2. The preparation method of the boron nitride modified silicon carbide fiber grown carbon nanotube ceramic matrix composite material according to claim 1, characterized in that, the extension distance of the quartz tube in the high-temperature tube furnace is 5 - 20 cm.

3. The preparation method of the boron nitride modified silicon carbide fiber grown carbon nanotube ceramic matrix composite material according to claim 1, characterized in that, the silicon carbide fiber is a polycrystalline silicon carbide fiber.

4. A boron nitride modified silicon carbide fiber grown carbon nanotube ceramic matrix composite material, characterized in that, it is prepared by the preparation method described in any one of claims 1 - 3.

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