Gradient carbon nanotube fiber needled preform heat dredging ceramic-based composite material and preparation method thereof

Abstract

The invention relates to a gradient carbon nanotube fiber needled preform heat dredging ceramic-based composite material and a preparation method thereof. The method includes; preparing a plurality of carbon nano tube fiber web tire layers and carbon nano tube fiber cloth layers which are alternately laminated with the carbon nano tube fiber web tire layers and are compounded by needling, wherein the carbon nano tube fiber web tire layers comprise carbon nano tube fibers and organic fibers, and the content of the organic fibers is gradually changed layer by layer along the thickness direction of the prefabricated body; forming a carbon interface layer by using a carbon source; decomposing the organic fibers through high-temperature treatment to form pores in gradient distribution; and carrying out impregnation and cracking by using a ceramic precursor to obtain the heat-conducting ceramic-based composite material. According to the pure carbon nanotube fiber needled preform prepared by the method, organic fibers are decomposed through high-temperature treatment, pores in gradient distribution are formed while the heat conductivity is improved, closed pores are avoided, carbon interface deposition and ceramic densification are facilitated, mechanics is improved, the preparation period is shortened, and the cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of ceramic matrix composites, and particularly relates to a high thermal conductivity ceramic matrix composite with a gradient carbon nanotube fiber needle-punched preform as a heat conduction path and a toughening phase, and a preparation method thereof. Background Art

[0002] Under high-speed flight conditions, the thermal structure components of an aircraft will face the test of extreme service conditions. Therefore, extremely stringent requirements are imposed on the thermophysical properties of the materials related to the thermal structure components.

[0003] High thermal conductivity materials can quickly transfer local high heat loads from high-temperature regions to low-temperature regions, rapidly reduce the thermal damage of local structures, and extend the service life of the materials.

[0004] Ceramic matrix composites with fibers as reinforcement and ceramic materials as the matrix are an important part of ultra-high temperature structural composites, combining the two advantages of efficient heat transfer and high temperature heat resistance. In addition to the excellent properties of ceramic materials, they also have the advantages of light weight and high strength of the reinforcing phase fibers.

[0005] Traditional fiber reinforcement materials, such as silicon carbide fibers and carbon fibers, have low graphitization degrees and small graphite crystallite sizes for silicon carbide fibers and ordinary carbon fibers, resulting in low thermal conductivities and difficulty in forming effective heat conduction paths. High thermal conductivity mesophase pitch-based carbon fibers also have problems such as high modulus, brittle texture after graphitization, the need for auxiliary processes for piercing and arranging in the thickness direction, inability to form a three-dimensional continuous preform, weak bonding between carbon fibers and the matrix, in-plane thermal conductivity being about 10 to 100 times that of the thermal conductivity along the thickness, and anisotropy of thermal conductivity.

[0006] Existing fiber reinforcement materials, such as the above-mentioned fiber reinforcement materials, as toughening phases of ceramic matrix composites can no longer meet the requirements for the heat conduction performance, high-temperature shape retention performance, and oxidation resistance performance of materials in extreme environments. Using high-strength, high-thermal conductivity continuous fibers to form an effective heat conduction path and ultra-high temperature ceramics as the main anti-oxidation and anti-ablation materials, the obtained heat conduction ceramic matrix composites can achieve high thermal conductivity while meeting the requirements of long-term oxidation resistance and service reliability. Among them, the fiber reinforcement material, as a toughening phase and the main heat conduction phase, needs to meet the requirements of high strength, high toughness, and high thermal conductivity simultaneously.

[0007] As a typical representative of new high-performance fibers, a one-dimensional macroscopic material composed of oriented carbon nanotubes - carbon nanotube fiber (CNTF) exhibits excellent properties such as light weight, high strength, high toughness, and high thermal conductivity. How to use carbon nanotube fibers to achieve fiber-reinforced preform design and weaving and process matching with ceramic matrices is the key to enabling carbon nanotube fibers to exhibit excellent performance in the preparation of high thermal conductivity ceramic matrix composites. Summary of the Invention

[0008] In order to avoid the problems of rapid deposition on the surface of the preform, slow densification speed in the later stage, and easy formation of closed pores, which require machining to eliminate defects after a certain deposition time, resulting in a long preparation cycle and high cost, a thermal conduction ceramic matrix composite material with high thermal conductivity while meeting the requirements of long-term oxidation resistance and service reliability is obtained. The present invention provides a ceramic matrix composite material with a gradient carbon nanotube fiber needle-punched preform with a volume content increasing from the surface to the center as a thermal conduction path and toughening phase, and a preparation method thereof.

[0009] Specifically, in the first aspect, the present invention provides a preparation method of a gradient carbon nanotube fiber needle-punched preform thermal conduction ceramic matrix composite material, characterized in that the method comprises the following steps;

[0010] (1) Prepare a needle-punched preform, the needle-punched preform includes at least three layers of carbon nanotube fiber web layers and carbon nanotube fiber cloth layers alternately laminated and needle-compounded with the carbon nanotube fiber web layers, wherein the at least three layers of carbon nanotube fiber web layers contain carbon nanotube fibers and organic fibers with a content increasing layer by layer from the middle web layer along the thickness direction of the needle-punched preform to both sides;

[0011] (2) Use a carbon source to form a carbon interface layer on the surface of the fibers of the needle-punched preform to obtain a carbon interface layer preform;

[0012] (3) Perform high-temperature treatment on the carbon interface layer preform to decompose the organic fibers, so that the obtained high-temperature treatment preform forms pores with an increasing number layer by layer from the middle web layer along the thickness direction of the preform to both sides;

[0013] (4) Impregnate and pyrolyze the high-temperature treatment preform with a ceramic precursor to obtain a gradient carbon nanotube fiber needle-punched preform thermal conduction ceramic matrix composite material.

[0014] In the second aspect, the present invention provides a gradient fiber preform thermal conduction ceramic matrix composite material prepared by the method according to the first aspect of the present invention.

[0015] The present invention has the following technical advantages compared with the prior art:

[0016] (1) The present invention selects short-cut carbon nanotube fibers as the web, and prepares fiber cloth with long carbon nanotube fibers, and needle-compounds the web and the fiber cloth to obtain a carbon nanotube fiber needle-punched preform. Based on the characteristics of low density, high strength, and high thermal conductivity of carbon nanotubes, compared with the ceramic matrix composite materials prepared by traditional carbon fiber preforms, the present invention has significant advantages in lightweight, high strength, and high thermal conductivity.

[0017] (2) By mixing organic fibers with different contents in the web preform and through high-temperature treatment, while achieving graphitization, the organic fibers decompose to generate Z-direction pores, thereby forming a gradient structure with the volume content gradually increasing from the outside to the inside. This avoids problems such as rapid deposition on the surface of the preform, slow densification rate in the later stage, easy formation of closed pores, and the need to eliminate defects through machining after a certain deposition time, resulting in long preparation cycles and high costs. At the same time, high-temperature treatment can also improve the thermal conductivity of the carbon nanotube fiber and obtain an efficient heat conduction path. The thermally conductive ceramic matrix composite material prepared by the present invention has higher uniformity, mechanical properties, and thermal properties.

[0018] (3) The present invention can regulate the carbon nanotube fiber content in different directions by adjusting the web density and the fiber content of the non-woven fabric, thereby regulating the heat conduction path in the thermally conductive composite material and preparing a ceramic matrix composite material with thermally conductive properties that can be regulated according to requirements in all directions. Detailed implementation mode

[0019] As described above, the present invention provides a method for preparing a gradient carbon nanotube fiber needle-punched preform thermally conductive ceramic matrix composite material in the first aspect, characterized in that the method comprises the following steps;

[0020] (1) Prepare a needle-punched preform, the needle-punched preform includes at least three or more carbon nanotube fiber web layers and carbon nanotube fiber cloth layers that are alternately laminated and needle-compounded with the carbon nanotube fiber web layers, wherein, the at least three or more carbon nanotube fiber web layers contain carbon nanotube fibers and organic fibers with a content that gradually increases layer by layer from the middle web layer along the thickness direction of the needle-punched preform to both sides;

[0021] (2) Use a carbon source to form a carbon interface layer on the surface of the fibers of the needle-punched preform to obtain a carbon interface layer preform;

[0022] (3) Perform high-temperature treatment on the carbon interface layer preform to decompose the organic fibers, so that the obtained high-temperature treatment preform forms pores with a gradually increasing number layer by layer from the middle web layer along the thickness direction of the preform to both sides;

[0023] (4) Use a ceramic precursor to impregnate and crack the high-temperature treatment preform to obtain a gradient carbon nanotube fiber needle-punched preform thermally conductive ceramic matrix composite material.

[0024] The method of the present invention will be described in more detail below.

[0025] Needle-punched preform

[0026] In the present invention, the needle-punched preform includes at least three layers of carbon nanotube fiber web layers and carbon nanotube fiber cloth layers that are alternately laminated and needle-punched together with the carbon nanotube fiber web layers. Among them, the at least three layers of carbon nanotube fiber web layers contain carbon nanotube fibers and organic fibers whose content increases layer by layer from the middle web layer to both sides along the thickness direction of the needle-punched preform.

[0027] In the present invention, the carbon nanotube fibers used to prepare the carbon nanotube fiber web layers and the carbon nanotube fibers used to prepare the carbon nanotube fiber cloth can be independently commercially obtained or can be prepared by the method provided by the present invention, which includes the following steps:

[0028] (i) Oxidize the carbon nanotubes to remove the amorphous carbon attached to the surface of the catalyst and the carbon nanotubes to expose the metal catalyst;

[0029] (ii) Treat the oxidized carbon nanotubes with an acid to remove the metal catalyst;

[0030] (iii) Wash the carbon nanotubes from which the metal catalyst has been removed with water, and then freeze-dry to obtain purified carbon nanotube raw materials;

[0031] (iv) Disperse the purified carbon nanotube raw materials in an acidic solution and stir evenly to obtain a spinning dope;

[0032] (v) Use the spinning dope to prepare carbon nanotube fibers by a wet spinning process.

[0033] In step (i), the oxidation can be carried out using hydrogen peroxide. Such oxidation is usually weak oxidation, so it can be carried out at room temperature when the hydrogen peroxide solution and the carbon nanotubes are stirred evenly. The content of carbon nanotubes in the hydrogen peroxide is 1 mg / mL to 2.5 mg / mL.

[0034] In step (ii), the acid treatment can use, for example, hydrochloric acid and can be carried out at room temperature.

[0035] In step (iii), when washing the carbon nanotubes from which the metal catalyst has been removed with water (such as deionized water), the carbon nanotubes can be separated by a centrifugation-ultrasonic filtration method, and the washing can be repeated until the filtrate is neutral. The freeze-drying can be carried out at, for example, -20 °C.

[0036] In step (iv), the acidic solution can be concentrated sulfuric acid or an aqueous solution of chlorosulfonic acid; stirring can be carried out using a magnetic stirrer; the concentration of the spinning dope can be a spinning dope with a carbon nanotube concentration of 0.5% by mass to 1.5% by mass (for example, 1% by mass).

[0037] In step (v), continuous carbon nanotube fibers with different electro-mechanical properties can be obtained by regulating the extrusion rate, draw ratio, and coagulation bath components. The extrusion rate can be, for example, from 0.2 m / min to 12 m / min (such as 0.2, 0.5, 1.0, 2.0, 5.0, 8.0, 10.0, or 12.0 m / min), the draw ratio can be from 0.8 to 1.2 (such as 0.8, 0.9, 1.0, 1.1, or 1.2), the coagulation bath can be an acetone coagulation bath and / or a pure water coagulation bath, and it can successively pass through an acetone coagulation bath and a pure water coagulation bath.

[0038] The carbon nanotube fibers used to prepare the carbon nanotube fiber web matrix layer and the carbon nanotube fibers used to prepare the carbon nanotube fiber cloth, whether obtained commercially or prepared by the above method of the present invention, can independently have the following properties: the tensile strength is from 1.0 GPa to 3.2 GPa (such as 1.0, 1.5, 2.0, 2.5, 3.0, or 3.2 GPa), the elongation at break is from 3% to 5% (such as 4%), and the density is from 1.1 g / cm 3 to 1.2 g / cm 3 (such as 1.15 g / cm 3 ), and the thermal conductivity is from 300 W / m·K to 500 W / m·K (such as 300, 350, 400, 450, or 500 W / m·K).

[0039] In some preferred embodiments, the carbon nanotube fiber cloth is a carbon nanotube fiber cloth without weft.

[0040] In the present invention, the volume content of the organic fiber in each of the fiber web matrix layers increases gradually from the middle fiber web matrix layer to both sides along the thickness direction of the preform, so that pores can be formed layer by layer from the middle to both sides along the thickness direction after high-temperature treatment.

[0041] The present invention does not particularly limit the material of the organic fiber, as long as it can decompose to form pores during high-temperature treatment. For example, the organic fiber can be selected from polyethylene fiber, polyester fiber, polypropylene fiber, and polyvinyl alcohol fiber.

[0042] In some preferred embodiments, the volume content of the organic fiber in each of the fiber web matrix layers increases gradually from the middle fiber web matrix layer to both sides along the thickness direction of the preform from 0% to 20% layer by layer. The volume content of the organic fiber in the middle fiber web matrix layer can be 0%, and of course, there can also be a certain amount of organic fiber according to needs. For example, it can contain 1% to 5% by volume of organic fiber, and then gradually increases to 20% by volume.

[0043] In the present invention, the number of layers N of the carbon nanotube fiber web ply is at least three or more, preferably five or more, more preferably seven or more. For example, it can be 3 to 20 layers (such as 3, 5, 10, 15 or 20 layers), or 5 to 20 layers, or 7 to 20 layers. Of course, according to needs, more layers can also be included, such as 25 layers.

[0044] In some embodiments, N is an odd number, and the middle ply of the web ply contains the least amount of organic fiber, and increases towards both sides. In other embodiments, N is an even number, and the two middle plies of the web ply contain the least amount of organic fiber, and then increase towards both sides.

[0045] The increase can be an equal or unequal increase symmetrically, or an equal or unequal increase asymmetrically. In the present invention, symmetric means that the same number of carbon nanotube web plies are symmetrically laid from the middle web ply (which can be one or two middle web plies) along the thickness direction towards both sides, otherwise it is called asymmetric; equal means that the amount of increase in the volume content of the organic fiber in each carbon nanotube fiber web ply increases layer by layer by an equal amount, otherwise it is called an unequal increase.

[0046] For example, when N is an odd number, such as 9 layers, the middle ply of the web ply contains the least amount of organic fiber, such as 0%, and then there are 4 layers on each side, and each layer increases by 5% to 20%, that is, the four layers on each side increase by an increment of 5% from the middle to both sides, and the volume contents are 5%, 10%, 15% and 20% respectively. This is a case of symmetric equal increase. Another example is when N is an even number, such as 10 layers, the two middle plies of the web ply contain the least amount of organic fiber, such as both 0%, and then there are 4 layers on each side, and each layer increases by 5% to 20%, that is, the four layers on each side increase by an increment of 5% from the middle to both sides, and the volume contents are 5%, 10%, 15% and 20% respectively. This is another case of symmetric equal increase. Another example is when N is 12, there are 5 layers on one side, and the volume content of the organic fiber increases equally from the middle to both sides, which are 0%, 5%, 10%, 15%, 20% in sequence; there are 7 layers on the other side, and the volume content of the organic fiber increases unequally from the middle to both sides, which are 0%, 3%, 6%, 9%, 12%, 15%, 18%, 20% in sequence, and the volume content of the organic fiber layer of the two middle carbon nanotube web plies is 0%.

[0047] In the present invention, the carbon nanotube fiber web ply can directly use a commercially available web or a commercially customized web, or can be made from short-cut carbon nanotube fibers obtained by short-cutting the carbon nanotube fibers prepared by the above method of the present invention.

[0048] During short cutting, the carbon nanotube fiber tow (the tow contains 100 - 1000 fibers) can be cut, for example, by the air flow cutting method. Among them, by adjusting the air flow speed and cutting angle, the fiber tow can be cut off by the high-speed air flow. When using the air flow cutting method for cutting, the cutting air flow speed can be 100 m / s to 300 m / s (such as 100, 200 or 300 m / s), the air pressure is 0.5 MPa to 2.0 MPa (such as 0.5, 1.0, 1.5 or 2.0 MPa), the feeding speed of the fiber tow is 10 m / min to 50 m / min (such as 10, 20, 30, 40 or 50 m / min), the tension of the fiber tow is 5 N to 20 N (such as 5, 10, 15 or 20 N), and the diameter of the fiber tow can be 1 mm to 10 mm (such as 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 mm). During short cutting, the fibers can be cut into short fibers with a length of, for example, 6 cm to 9 cm.

[0049] In some other preferred embodiments, the short fibers are short fibers with a length of 6 cm to 9 cm (such as 6, 7, 8 or 9 cm). In the case where there are organic fibers in the carbon nanotube fiber web matrix layer, the length of the organic fibers can be the same or different from that of the short-cut carbon nanotube fibers, but preferably the same length.

[0050] Whether obtained commercially or prepared by the method of the present invention, the areal density of the carbon nanotube fiber web matrix layer is preferably 100 g / m 2 to 200 g / m 2 (such as 100, 120, 140, 160, 180 or 200 g / m 2 ).

[0051] The present invention does not particularly limit the thickness of the obtained needle-punched preform. However, in some preferred embodiments, the thickness of the needle-punched preform is 10 mm to 20 mm (such as 10, 12, 14, 16, 18 or 20 mm).

[0052] In some other preferred embodiments, the needle punching density of the needle punching composite is 60 needles / cm 2 to 100 needles / cm 2 (such as 60, 70, 80, 90 or 100 needles / cm 2 ).

[0053] Carbon interface layer preform

[0054] In the present invention, a carbon interface layer is formed on the surface of the fibers of the needle-punched preform by using a carbon source to obtain a carbon interface layer preform.

[0055] The carbon source for forming the carbon interface layer is usually a hydrocarbon, such as propylene or propane.

[0056] In some preferred embodiments, chemical vapor infiltration (CVI) can be used to deposit a carbon layer on the surface of the fibers (including carbon nanotube fibers and organic fibers) of the needle-punched preform as a transition layer between the fibers and the ceramic matrix, thereby obtaining a framework material.

[0057] The chemical vapor infiltration can be carried out as follows: Place the needle-punched preform in a chemical vapor deposition furnace, and by controlling the heating temperature, a carbon interface layer is formed on the fiber surface after a certain period of time under a vacuum and high-temperature state. The reaction temperature of chemical vapor deposition can be, for example, 900 - 1100 °C (such as 900, 1000, or 1100 °C), and keep the temperature for 50 h to 150 h (such as 50, 100, or 150 h). The pressure in the reaction furnace can be 10 Pa to 150 Pa (such as 10, 50, 100, or 150 Pa).

[0058] The present invention does not particularly limit the thickness of the carbon interface layer. However, in some preferred embodiments, the thickness of the carbon interface layer is 500 nm to 1500 nm (such as 500, 750, 1000, 1250, or 1500 nm).

[0059] High-temperature treated preform

[0060] In the present invention, the carbon interface layer preform is subjected to high-temperature treatment to decompose the organic fibers, so that the obtained high-temperature treated preform forms pores with an increasing number layer by layer from the middle web layer along the thickness direction of the preform to both sides.

[0061] In some preferred embodiments, the treatment temperature of the high-temperature treatment can be 1800 °C to 3200 °C (such as 1800, 2000, 2200, 2400, 2600, 2800, 3000, or 3200 °C).

[0062] Since the carbon nanotube fibers can withstand a very high temperature and there is a large difference in the decomposition temperature from that of the organic fibers in the preform, the mechanical properties of the preform imparted by the carbon nanotube fibers in the web layer will not be affected during the high-temperature treatment. On the contrary, the high-temperature treatment not only decomposes the organic fibers to form gradient pores, but also can improve the thermal conductivity of the carbon nanotube fibers to obtain an efficient heat conduction path, making the prepared thermally conductive ceramic matrix composite material have higher uniformity, as well as higher mechanical and thermal properties, thus bringing multiple benefits from the high-temperature treatment.

[0063] Ceramic matrix composite

[0064] In the present invention, after obtaining the heat-treated preform, the heat-treated preform is impregnated and pyrolyzed with a ceramic precursor to obtain a gradient carbon nanotube fiber needle-punched preform thermally conductive ceramic matrix composite.

[0065] In some preferred embodiments, the ceramic precursor is selected from zirconium-silicon ceramic precursors, zirconium-hafnium ceramic precursors, hafnium-tantalum ceramic precursors, zirconium carbide ceramic precursors, silicon carbide ceramic precursors, hafnium carbide ceramic precursors, and tantalum carbide ceramic precursors.

[0066] In some specific embodiments, the present invention provides a method for preparing a gradient carbon nanotube fiber needle-punched preform thermally conductive ceramic matrix composite, the method comprising the following steps:

[0067] (1) Purify the carbon nanotubes, and then disperse the purified carbon nanotubes in an acidic solution and stir evenly to obtain a spinning dope.

[0068] When purifying the carbon nanotubes, the carbon nanotubes can be mixed with hydrogen peroxide in a certain ratio and then stirred evenly at room temperature to weakly oxidize the carbon nanotubes to remove the amorphous carbon attached to the surface of the catalyst and the carbon nanotubes, thereby exposing the metal catalyst. Then, the carbon nanotubes are mixed and stirred with an acid solution such as hydrochloric acid (concentration 1-2.5 mg / mL) at room temperature to remove the metal catalyst. Finally, the carbon nanotubes are washed, and when washing, a centrifugation-ultrasonic filtration method can be used to wash the carbon nanotubes with water such as deionized water until the filtrate is neutral. Then, the carbon nanotubes are freeze-dried (for example, at -20°C) to obtain the purified carbon nanotube raw material.

[0069] Disperse the purified carbon nanotubes in concentrated sulfuric acid or chlorosulfonic acid solution, and magnetically stir to prepare a carbon nanotube dispersion with a mass fraction of 0.5% to 1.5%.

[0070] (2) Prepare carbon nanotube fibers by a wet spinning process, wherein continuous carbon nanotube fibers with different mechanical properties and electrical properties can be obtained by regulating the extrusion rate, draw ratio, and coagulation bath components.

[0071] In some preferred embodiments, the extrusion rate can be 0.2 m / min to 12 m / min, the draw ratio can be 0.8 - 1.2, and the coagulation bath can sequentially include an acetone coagulation bath and a water (such as pure water) coagulation bath. The carbon nanotube fibers thus prepared are continuous fibers, with a tensile strength of 1.0 GPa to 3.2 GPa, an elongation at break that can be 3% to 5%, and a density that can be 1.1 g / cm 3 to 1.2 g / cm 3 , and a thermal conductivity that can be 300 W / m·K to 500 W / m·K.

[0072] (3) Prepare short-cut fibers. For example, the carbon nanotube fiber bundle can be cut by the air flow cutting method. By adjusting the air flow speed and cutting angle, the fiber bundle can be cut off by the high-speed air flow, so as to obtain short-cut fibers with a length of 5 cm to 9 cm.

[0073] The cutting air flow speed of the air flow cutting method is 100 - 300 m / s, the air flow pressure is 0.5 - 2.0 MPa, the fiber bundle feeding speed is 10 - 50 m / min, the fiber bundle tension is 5 - 20 N, and the fiber bundle diameter is 1 - 10 mm.

[0074] (4) Use the dry-laying process to prepare a uniform carbon nanotube fiber web. The areal density of the carbon nanotube fiber web prepared by the dry-laying process can be 100 g / m 2 to 200 g / m 2 .

[0075] (5) Use carbon nanotube fibers to prepare fiber cloth (such as non-woven cloth). The fiber cloth can be laid on the web or the laid part at 0° / 90°, and needle-punched and laminated layer by layer. Among them, different volume contents of organic fibers can be mixed in each web along the thickness of the preform. The volume content of the organic fibers can gradually decrease from 20% - 0% from the two-side webs to the central web. During needle-punched lamination, continuous needle punching can be carried out layer by layer to obtain a needle-punched preform with a thickness of, for example, 10 mm to 20 mm and a fiber volume content of 30% to 50%. The needle punching density of the needle-punched lamination can be 60 needles / cm 2 to 100 needles / cm 2 , and the areal density of the carbon nanotube fiber non-woven cloth is 200 g / m 2 to 500 g / m 2 .

[0076] (6) Use the chemical vapor infiltration (CVI) method to deposit a carbon layer on the fiber surface in the preform as a transition layer between the fiber and the ceramic matrix to obtain a framework material. The chemical vapor infiltration is to place the gradient needle-punched carbon nanotube fiber preform in a chemical vapor deposition furnace. By controlling the heating temperature, an interface layer with a thickness of 500 nm to 1.5 μm is formed on the fiber surface under the vacuum high-temperature state after a certain time. The chemical vapor deposition reaction temperature is 900 °C to 1100 °C, and it is kept warm for 50 h to 150 h, and the pressure in the reaction furnace is 10 Pa to 150 Pa.

[0077] (7) Place the preform with the deposited carbon interface layer in a high-temperature furnace filled with inert gas for high-temperature treatment, and the temperature is 1800 °C to 3200 °C. The organic fibers in the preform decompose, generating needle holes with a gradient content in the thickness direction, and the thermal conductivity of the carbon nanotube fibers is further improved by high-temperature graphitization.

[0078] (8) The gradient carbon nanotube fiber needle-punched preform is prepared by the precursor infiltration and pyrolysis process and used as the ceramic matrix composite with a heat conduction path and toughening phase; the precursor for preparing the ceramic matrix composite by the precursor infiltration and pyrolysis method is a multi-precursor of zirconium silicon, zirconium hafnium, and hafnium tantalum, or can also be a single precursor of the above types. This step is a well-known technology in the art, and those skilled in the art can prepare a heat conduction ceramic matrix composite with a density of 2.0 g / cm 3 to 4.0 g / cm 3 . The gradient carbon nanotube fiber needle-punched preform heat conduction ceramic matrix composite prepared by the present invention not only has high thermal conductivity, but also reduces the densification uniformity, shortens the preparation cycle, and significantly improves the mechanical and antioxidant properties.

[0079] The present invention provides, in a second aspect, a gradient fiber preform heat conduction ceramic matrix composite prepared by the method according to the first aspect of the present invention.

[0080] Examples

[0081] The present invention will be further described below in conjunction with specific examples. However, it should be understood that these examples are only used to illustrate the present invention, rather than to limit the present invention, and the protection scope of the present invention is not limited to these examples.

[0082] The experimental methods used in the following examples are all conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples can all be obtained commercially unless otherwise specified.

[0083] Example 1

[0084] (1) Mix carbon nanotubes and hydrogen peroxide in a certain ratio (2 mg / mL), stir evenly at room temperature to oxidize the carbon nanotubes, so as to remove the amorphous carbon attached to the surface of the catalyst and carbon nanotubes and expose the metal catalyst contained in the carbon nanotubes; then, mix the oxidized carbon nanotubes with hydrochloric acid (concentration 2 mg / mL and treatment time 4 h) evenly at room temperature to remove the metal catalyst therein; finally, wash the carbon nanotubes from which the metal catalyst has been removed with deionized water until the filtrate is neutral; then, freeze-dry the washed carbon nanotubes (temperature -20 °C) to obtain purified carbon nanotube raw materials; disperse the purified carbon nanotube raw materials in chlorosulfonic acid and stir evenly to prepare a carbon nanotube dispersion with a mass fraction of 1.0%.

[0085] (2) The wet spinning process is adopted, and the carbon nanotube dispersion obtained in step (1) is used to prepare carbon nanotube fibers. The extrusion rate is adjusted to 1.2 m / min, the draw ratio is adjusted to 1.0, and it passes through an acetone coagulation bath and a pure water coagulation bath in sequence. After testing, the tensile strength of the carbon nanotube fibers thus prepared is 3.0 GPa, the elongation at break is 4%, and the density is 1.2 g / cm 3 , and the thermal conductivity is 500 W / m·K.

[0086] (3) The carbon nanotube fiber tow (F CNT ) prepared in step (2) is cut by the air cutting method. The cutting air flow speed is 200 m / s, the air pressure is 1.0 MPa, the fiber tow feeding speed is 20 m / min, the fiber tow tension is 5 N, and the fiber tow diameter is 1 mm, to obtain short fibers with a length of 5 - 9 cm.

[0087] (4) Using the short fibers prepared in step (3), a dry laying process is adopted to prepare a uniform carbon nanotube fiber web (containing 0%, 3%, 6%, 9%, 12%, 15%, 18%, 20% by volume of organic fibers). The areal density of the web is 100 g / m 2 .

[0088] (5) Carbon nanotube fibers prepared in step (2) are used to prepare a weftless cloth with an areal density of 200 g / m 2 . Then, the weftless cloth is layer - by - layer laid on the upper and lower surfaces of the carbon nanotube fiber web prepared in step (4) at 0° / 90° and needled and compounded (after laying one layer of weftless cloth, it is needled and compounded with the already laid part once). Among them, the needled preform contains organic fibers whose volume content gradually decreases from 20% to 0% from both side surfaces to the center direction along the thickness direction (after laying one layer of web and one layer of weftless cloth, a composite layer is formed. The thickness of this composite layer is about 0.7 mm, with a total of 28 layers, 14 layers on each side. The distribution of the organic fiber content from one side surface to the other side surface is as follows: 20% (1), 18% (2), 15% (2), 12% (2), 9% (2), 6% (2), 3% (2), 0% (2), 3% (2), 6% (2), 9% (2), 12% (2), 15% (2), 18% (2), 20% (1), and the numbers in the brackets are the number of layers). Through continuous layer - by - layer needling, a needled preform with a thickness of 20 mm and a fiber volume content of 40% is obtained, in which the weftless cloth and the web are needled and compounded together;

[0089] (6) The needled preform prepared in step (5) is placed in a chemical vapor deposition furnace. The pressure in the furnace is adjusted to 150 Pa, the deposition reaction temperature is adjusted to 900 °C, and it is kept warm for 150 h to obtain a preform with a carbon interface layer formed on the fiber surface.

[0090] (7) Place the preform with the carbon interface layer prepared in step (6) in a high-temperature furnace filled with inert gas for high-temperature treatment at 2400 °C to obtain a high-temperature treated preform. The organic fibers for needle punching in the high-temperature treated preform decompose during the high-temperature treatment, thereby generating pinholes with a gradient content in the thickness direction; moreover, through high-temperature treatment, the carbon nanotube fibers are graphitized, thus further enhancing the thermal conductivity of the obtained preform.

[0091] (8) Prepare a ceramic matrix composite. Using a zirconium silicate precursor as a reactant, impregnate and pyrolyze the high-temperature treated preform by the precursor impregnation pyrolysis method to obtain an F 3 / C-ZrC-SiC ceramic matrix composite with a density of 1.8 g / cm CNT .

[0092] (9) After testing, the tensile strength of the prepared F CNT / C-ZrC-SiC ceramic matrix composite in an inert environment at 1600 °C is 243 MPa, the thermal conductivity in the X / Y direction is 75 W / m·K, and the thermal conductivity in the Z direction is 57 W / m·K.

[0093] Example 2

[0094] The same method as in Example 1 is used, with the difference that in step (5), the volume content of the organic fibers in each carbon nanotube fiber web layer is 0, that is, all web tires without added organic fibers are used, so there are no organic fibers with a layer-by-layer gradient distribution.

[0095] After testing, the tensile strength of the prepared F CNT / C-ZrC-SiC ceramic matrix composite at 1600 °C in an inert environment is 178 MPa, the thermal conductivity in the X / Y direction is 62 W / m·K, and the thermal conductivity in the Z direction is 55 W / m·K.

[0096] Example 3

[0097] The same method as in Example 1 is used, with the difference that steps (1) to (4) are not carried out. In step (5), directly use a T700-12K carbon fiber needle-punched preform with the same parameters (the same preform preparation process, that is, the short-cut fiber length is 5-9 cm, the areal density of the web tire is 100 g / m 2 . The non-woven fabric is a T700-12K carbon fiber non-woven fabric with an areal density of 200 g / m 2 , and the laying method and organic fiber distribution therein are the same) to replace the needle-punched preform prepared in step (5) of Example 1.

[0098] After testing, the prepared C / C-ZrC-SiC ceramic matrix composite has a density of 1.95 g / cm 3 , a tensile strength of 192 MPa in an inert environment at 1600 °C, a thermal conductivity in the X / Y direction of 8 W / (m·K), and a thermal conductivity in the Z direction of 5 W / (m·K).

[0099] Example 4

[0100] The same method as in Example 1 was used, except that in step (3), an ordinary carbon fiber web with the same parameters (i.e., a areal density of 100 g / m 2 ) was used to replace the carbon nanotube fiber web in step (4) of Example 1.

[0101] After testing, the prepared F CNT / C-ZrC-SiC ceramic matrix composite has a density of 1.85 g / cm 3 , a tensile strength of 235 MPa in an inert environment at 1600 °C, a thermal conductivity in the X / Y direction of 76 W / (m·K), and a thermal conductivity in the Z direction of 7 W / (m·K).

[0102] Example 5

[0103] The same method as in Example 1 was used, except that in step (5), an ordinary carbon fiber non-woven fabric with the same areal density (i.e., 200 g / m 2 ) was used to replace the carbon nanotube fiber non-woven fabric in step (5) of Example 1.

[0104] After testing, the prepared F CNT / C-ZrC-SiC ceramic matrix composite has a density of 1.9 g / cm 3 , a tensile strength of 238 MPa in an inert environment at 1600 °C, a thermal conductivity in the X / Y direction of 12 W / (m·K), and a thermal conductivity in the Z direction of 53 W / (m·K).

[0105] Example 6

[0106] The same method as in Example 1 was used, except that in step (4), the areal density of the obtained carbon nanotube fiber web was 200 g / m 2 ; in step (5), the fiber volume content of the prepared needle-punched preform was 45%.

[0107] After testing, the prepared F CNT / C-ZrC-SiC ceramic matrix composite has a density of 1.85 g / cm 3 , a tensile strength of 242 MPa in an inert environment at 1600 °C, a thermal conductivity in the X / Y direction of 78 W / (m·K), and a thermal conductivity in the Z direction of 61 W / (m·K).

[0108] Example 7

[0109] The same method as in Example 1 is adopted, with the difference that in step (5), the areal density of the carbon nanotube fiber non-woven fabric prepared is 300 g / m 2 , and the fiber volume content of the prepared needled preform is 45%.

[0110] After testing, the prepared F CNT / C-ZrC-SiC ceramic matrix composite has a density of 1.81 g / cm 3 , a tensile strength of 258 MPa in an inert environment at 1600 °C, an X / Y-direction thermal conductivity of 103 W / m·K, and a Z-direction thermal conductivity of 51 W / m·K.

[0111] Example 8

[0112] The same method as in Example 1 is adopted, with the difference that in step (5), the areal density of the prepared carbon nanotube fiber non-woven fabric is 300 g / m 2 , and the fiber volume content of the prepared needled preform is 50%. In step (8), a hafnium tantalum precursor is used instead of the zirconium silicon precursor as the reactant to prepare an F 3 / C-HfTaC ceramic matrix composite with a density of 3.2 g / cm CNT .

[0113] After testing, the prepared F CNT / C-HfTaC ceramic matrix composite has a tensile strength of 297 MPa in an inert environment at 1600 °C, an X / Y-direction thermal conductivity of 113 W / m·K, and a Z-direction thermal conductivity of 52 W / m·K.

[0114] Of course, the present invention can also have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding changes and deformations should all fall within the protection scope of the appended claims of the present invention.

Claims

1. A preparation method of a gradient carbon nanotube fiber needle-punched preform thermally conductive ceramic matrix composite, characterized in that The method includes the following steps; (1) Prepare a needle-punched preform, which includes at least three or more carbon nanotube fiber web layers and carbon nanotube fiber cloth layers that are alternately laminated and needle-punched together with the carbon nanotube fiber web layers. Among them, the at least three or more carbon nanotube fiber web layers contain carbon nanotube fibers and organic fibers whose content gradually increases layer by layer from the middle web layer to both sides along the thickness direction of the needle-punched preform; (2) Use a carbon source to form a carbon interface layer on the surface of the fibers of the needle-punched preform to obtain a carbon interface layer preform; (3) Perform high-temperature treatment on the carbon interface layer preform to decompose the organic fibers, so that the obtained high-temperature treatment preform forms pores with a gradually increasing number layer by layer from the middle web layer to both sides along the thickness direction of the preform; (4) Impregnate and pyrolyze the high-temperature treatment preform with a ceramic precursor to obtain a gradient carbon nanotube fiber needle-punched preform thermal conduction ceramic matrix composite.

2. The method according to claim 1, wherein: The carbon nanotube fibers used to prepare the carbon nanotube fiber web carcass layer and the carbon nanotube fibers used to prepare the carbon nanotube fiber cloth independently have the following properties: a tensile strength of 1.0 GPa to 3.2 GPa, an elongation at break of 3% to 5%, and a density of 1.1 g / cm 3 to 1.2 g / cm 3 , and a thermal conductivity of 300 W / m·K to 500 W / m·K.

3. The method according to claim 1, wherein: The volume content of the organic fibers in each of the fiber web layers gradually increases from 0% to 20% layer by layer from the middle web layer to both sides along the thickness direction of the preform.

4. The method according to any one of claims 1 to 3, wherein: The carbon nanotube fiber web layer is made of chopped fibers; Preferably, the chopped fibers are chopped fibers with a length of 6 cm to 9 cm.

5. The method according to any one of claims 1 to 4, wherein: The areal density of the fibrous web base layer is 100 g / m 2 to 200 g / m 2 ; The thickness of the carbon interface layer is 500 nm to 1500 nm; The thickness of the needle-punched preform is 10 mm to 20 mm; and / or The fiber volume content of the needle-punched preform is 30% to 50%.

6. The method according to any one of claims 1 to 5, wherein: The carbon nanotube fiber cloth is a carbon nanotube fiber cloth without weft; and / or The areal density of the carbon nanotube fiber cloth is 200 g / m 2 to 500 g / m 2 .

7. The method according to any one of claims 1 to 6, wherein: The needle punching density of the needle punching composite is 60 needles / cm 2 to 100 needles / cm 2 .

8. The method according to any one of claims 1 to 7, wherein: The ceramic precursor is selected from zirconium-silicon ceramic precursors, zirconium-hafnium ceramic precursors, hafnium-tantalum ceramic precursors, zirconium carbide ceramic precursors, silicon carbide ceramic precursors, hafnium carbide ceramic precursors, and tantalum carbide ceramic precursors; The organic fibers are selected from polyethylene fibers, polyester fibers, polypropylene fibers, and polyvinyl alcohol fibers; The carbon source is a hydrocarbon, preferably selected from propylene or propane.

9. The method according to any one of claims 1 to 8, wherein: The treatment temperature of the high-temperature treatment is 1800 °C to 3200 °C.

10. A gradient fiber preform thermal conduction ceramic matrix composite prepared by the method according to any one of claims 1 to 9.