A ceramic modified carbon-carbon composite nose cone and preparation method thereof

Abstract

The present invention discloses a preparation method of a ceramic-modified carbon / carbon composite nose cone, which is characterized in that: a carbon fiber preform with a hemispherical front end and a conical rear end is placed in a chemical vapor deposition furnace, and chemical vapor deposition of the PyC interface layer and the SiC interface layer is repeated to obtain a carbon / carbon green body containing a (PyC / SiC) x interface layer. Then, the carbon / carbon green body is placed in a chemical vapor deposition furnace to perform chemical vapor deposition of a carbon matrix to obtain a carbon / carbon porous body. The carbon / carbon porous body is subjected to resin carbon densification to obtain a carbon / carbon composite material. Finally, the carbon / carbon composite material is placed in a chemical vapor deposition furnace again to sequentially perform chemical vapor deposition of an SiC coating and an HfC coating, thereby obtaining the ceramic-modified carbon / carbon composite nose cone.

Description

Technical Field

[0001] The invention relates to a ceramic modified carbon-carbon composite material nose cone and a preparation method thereof, belonging to the technical field of composite material preparation. Background Art

[0002] Hypersonic speed usually refers to a vehicle with a service Mach number greater than 5, powered by an air-breathing engine or a combination of engines, and capable of long-distance flight in the atmosphere and across the atmosphere. Its applications include hypersonic cruise missiles, hypersonic aircraft, and space planes. Hypersonic aircraft are defined as an important research direction in the aerospace field in many countries, and a series of research plans have been formulated. It is hailed as the third revolution in the history of world aerospace after propellers and air-breathing propulsion aircraft. Compared with traditional aircraft, hypersonic aircraft are more maneuverable during service, have faster speeds, and have shorter reaction times. As military equipment, they can enhance combat capabilities and effectively improve the survivability of aircraft. Hypersonic aircraft are of great significance in both military and civilian fields, and are hailed as the new commanding heights of technology in the aerospace field of this century.

[0003] Aerodynamic heat and thermal protection are an unavoidable problem in the development of hypersonic aircraft, namely the "thermal barrier" problem. When the aircraft is in service at hypersonic speed, the gas at the front of the aircraft will be affected by the shock wave, which converts the kinetic energy of the gas into thermal energy, thereby increasing the temperature of the gas. The heat transfer from the high-temperature gas to the wall will cause aerodynamic heating problems. At the same time, as the temperature of the incoming gas increases, the vibration energy of the gas will be excited, the gas molecules will dissociate, and the atoms will ionize, which is the high-temperature gas effect. For example, the US X-43A hypersonic aircraft uses C / C composite materials in high-temperature parts such as the nose cone, the leading edge of the wing, and the tail. The temperature reached 2093°C during the test (9.8 Mach).

[0004] The severe aerodynamic thermal environment will cause the thermal protection system of the aircraft to be subjected to extremely large thermal loads, which may cause deformation of the structure and ablation of the thermal protection material, which will lead to serious consequences such as weakened performance or even failure of the thermal protection system of the aircraft. The deformation and ablation of the thermal protection system will in turn affect the external flow field of the aircraft, thereby changing the aerodynamic thermal environment of the external flow field. At present, the main thermal protection materials are refractory metals, C / C composites, ceramic-based composites, etc. Refractory metals are difficult to become ideal thermal protection materials for hypersonic aircraft due to their high cost, high density, difficult processing and poor oxidation resistance. Therefore, C / C composites and ceramic composites are the development direction of thermal protection materials.

[0005] C / C composite material is a lightweight, high-temperature resistant thermal structural composite material composed of carbon fiber and matrix carbon / graphite. It has excellent properties such as high specific strength, ablation resistance, thermal shock resistance, high thermal conductivity, low thermal expansion coefficient, stable friction coefficient, and low wear rate; especially in an inert atmosphere within 2 000 ℃, the strength increases with the increase of temperature, and it has a low ablation rate and good ablation shape stability in an instantaneous specific service environment above 3 500 ℃. The anti-oxidation C / C composite material containing SiC-HfC coating has the characteristic of zero ablation in a near-space hypersonic environment with high temperature and oxygen at 2 200 ℃. These excellent characteristics under extremely harsh conditions have made C / C composite materials the basic prerequisite for the development of cutting-edge high-tech fields in aerospace.

[0006] However, the high temperature oxidation resistance of C / C composites is poor. Pure C / C composites begin to oxidize rapidly at 500-600°C, and the components decompose, thereby losing the performance of the composites and causing structural damage. Therefore, antioxidant protection is necessary.

[0007] There are usually two ways to protect C / C composites from oxidation: one is matrix modification, which is to modify the carbon fibers and matrix carbon to improve their antioxidant capacity; the other is surface coating protection, which uses high-temperature resistant coatings to isolate oxygen from the matrix to achieve the purpose of oxidation resistance.

[0008] In the process of preparing SiC and HfC coatings by CVD, the precursors trichloromethylsilane (MTS) and HfCl4 are vaporized and immersed in the CVD furnace in gas form for reaction. However, the conventional industrial CVD deposition furnace lacks effective thermal protection for these two gas pipelines, resulting in the solidification of MTS and HfCl4 in the pipeline, causing the molar ratio of the mixed raw gas to be distorted and the pipeline to be blocked. Existing CVD deposition furnaces are mostly designed for brake discs and carbon-carbon crucibles. The deposition of thick-walled preforms such as nose cones causes uneven deposition and a large difference in density inside and outside, especially when depositing SiC and HfC coatings. The density difference is even greater. Summary of the invention

[0009] In view of the deficiencies in the prior art, an object of the present invention is to provide a method for preparing a carbon-ceramic nose cone of a hypersonic aircraft.

[0010] The second object of the present invention is to provide a carbon ceramic nose cone of a hypersonic aircraft prepared by the above preparation method.

[0011] In order to achieve the above object, the present invention adopts the following technical solution:

[0012] The invention discloses a method for preparing a ceramic modified carbon-carbon composite nose cone, wherein a carbon fiber preform with a hemispherical front end and a conical rear end is placed in a chemical vapor deposition furnace, and chemical vapor deposition of a pyrolytic carbon (PyC) interface layer and a SiC interface layer is repeated to obtain a (PyC / SiC)-containing x The carbon / carbon blank is placed in a chemical vapor deposition furnace for chemical vapor deposition of a carbon matrix to obtain a carbon / carbon porous body, the carbon / carbon porous body is densified with resin carbon to obtain a carbon / carbon composite material, and finally the carbon / carbon composite material is placed in a chemical vapor deposition furnace for chemical vapor deposition of a SiC coating and a HfC coating in sequence to obtain a ceramic modified carbon-carbon composite nose cone. The chemical vapor deposition furnace comprises a heat exchanger, a furnace body, a heating element, a furnace chamber, a graphite gas screen, an air inlet pipe, an air outlet pipe, and a deposition chamber. The heat exchanger is located outside the furnace body. The device heats the intake air with the exhaust gas as the heat source, the heating element is located on the outside of the furnace to provide a heat source for the furnace, the furnace is divided into a number of deposition chambers by partitions, any deposition chamber is provided with a graphite gas screen with the same shape as the sample to be deposited and smaller in size than the sample to be deposited, during any chemical vapor deposition, any sample to be deposited is placed in any deposition chamber and covered on the outside of the graphite gas screen, the intake air heated in the heat exchanger is divided into a number of routes and respectively enters from the bottom center of any deposition chamber, and after being screened by the graphite gas, acts on the sample to be deposited, and chemical vapor deposition is performed on the sample to be deposited.

[0013] In the present invention, all chemical vapor depositions, such as chemical vapor deposition of PyC interface layer and SiC interface layer, chemical vapor deposition of carbon matrix, chemical vapor deposition of SiC coating and HfC coating, are placed in a chemical deposition furnace with the same configuration and adopt the same air intake method. The samples to be deposited include carbon fiber preforms, carbon-carbon blanks, and carbon / carbon composite materials.

[0014] In the present invention, the raw material gas, dilution gas and carrier gas entering the chemical vapor deposition furnace are all intake gases.

[0015] In a preferred solution, the air inlet pipe, the air outlet pipe and the heat exchanger are all wrapped with an asbestos layer.

[0016] In the present invention, the exhaust gas outlet temperature is increased by wrapping the intake pipe, the exhaust pipe and the heat exchanger with an asbestos layer, and then the exhaust gas is used to preheat the intake air to avoid the intake temperature being too low, which may lead to pipe blockage and low deposition efficiency. In addition, by increasing the exhaust gas outlet temperature, it is also possible to avoid condensation of reaction by-products in the exhaust pipe to block the pipeline. For example, in the prior art, the exhaust gas outlet pipeline of a common deposition furnace is cooled by circulating water, and the temperature of the exhaust gas outlet pipeline drops suddenly, which may easily lead to pipeline blockage and increase the workload of cleaning and maintenance.

[0017] In a preferred embodiment, the pore size distribution density of the graphite gas sieve is 0.2-0.5 pores / cm 2 .

[0018] In a preferred embodiment, in the graphite gas sieve, the aperture size of the hemispherical front end is 0.4-0.6 cm, the aperture size of the conical rear end is 0.3-0.5 cm, the aperture size of the hemispherical front end is greater than the aperture size of the conical rear end, and the aperture size at the junction of the front end and the rear end is the same as the aperture size of the hemispherical front end.

[0019] In a preferred embodiment, the distance between the graphite gas screen and the sample to be deposited is ≤3 cm.

[0020] The inventors found that by using a graphite gas sieve and setting the distribution and size of the aperture according to the above scheme, and controlling the distance between the sieve and the sample to be deposited to ≤3cm, the density distribution of the nose cone of the special-shaped part can be made uniform. If the setting is unreasonable, it will affect the overall uniformity. For example, if the distance between the graphite gas sieve and the sample to be deposited is too large, deposition will occur on the surface, resulting in a density difference between the inside and the outside.

[0021] In the actual operation process, in order to obtain a coating with uniform composition and ensure uniform deposition effect, the present invention also strengthens the thermal field uniformity monitoring, uses thermocouples, and adds multiple temperature measurement points. Where the mixed gas enters the graphite gas screen, 2, 3, and 3 temperature measurement points are added at the top, middle, and bottom of the graphite gas screen to ensure that the temperature of the gas reaches the required deposition temperature after leaving the graphite gas screen, and the temperature difference of the 8 temperature measurement points at the top, middle, and bottom is ≤10°C.

[0022] In a preferred embodiment, the carbon fiber preform is a 4D carbon fiber braid or a 2.5D needle-punched carbon fiber preform, and the density of the carbon fiber preform is 0.7-0.8 g / cm 3 .

[0023] Further preferably, the 4D carbon fiber woven part is obtained by three-dimensional four-directional weaving of carbon fibers with a tensile modulus of 4500-4900 MPa.

[0024] Further preferably, the 2.5D needle-punched carbon fiber preform is formed by alternately laying a non-woven fabric and a mesh tire, continuously needle-punching in the X and Y directions, and then needle-punching the carbon fiber in the Z direction to obtain the carbon fiber preform.

[0025] The preferred solution is to place a carbon fiber preform with a hemispherical front end and a conical rear end in a chemical vapor deposition furnace, first perform chemical vapor deposition of a PyC interface layer, then perform chemical vapor deposition of a SiC interface layer, and then repeat the chemical vapor deposition of the PyC interface layer and the SiC interface layer 1 to 2 times, respectively, to obtain a carbon fiber preform containing (PyC / SiC) x (x=2 or 3) Carbon / carbon body of the carbon / carbon body of the interface layer.

[0026] Further preferably, the chemical vapor deposition of the PyC interface layer is carried out under nitrogen protection, first heating to 500-600°C at a heating rate of 5-8°C / min, then heating to 900-1000°C at a heating rate of 3-5°C / min, and then introducing nitrogen as a dilution gas and propylene as a carbon source gas in sequence, wherein the volume flow ratio of propylene to nitrogen is 1:1-3, and the internal pressure of the reactor is controlled to maintain 1-3kPa, and the deposition is carried out for 3-5h.

[0027] The heating is divided into two stages, with a fast heating speed in the front stage and a slow heating speed in the back stage. This not only increases the heating speed but also ensures that the temperature difference in the deposition furnace does not exceed the standard.

[0028] Further preferably, the chemical vapor deposition of the SiC interface layer is carried out under the protection of argon, firstly heating to 500-600°C at a heating rate of 5-8°C / min, then heating to 1000-1100°C at a heating rate of 3-5°C / min, and then introducing hydrogen and trichloromethylsilane (MTS) in sequence, wherein the volume flow ratio of trichloromethylsilane to hydrogen is 1:1-2, and the internal pressure of the reactor is controlled to maintain 1-3kPa, and the deposition is carried out for 2-4h.

[0029] In the actual operation process, after the temperature is raised to 1000-1100°C, hydrogen is introduced. After the temperature in the furnace is stabilized, trichloromethylsilane (MTS) is introduced into the reactor by bubbling.

[0030] In a preferred embodiment, the chemical vapor deposition of the carbon matrix is ​​carried out under nitrogen protection, firstly heating the temperature to 500-600°C at a heating rate of 5-8°C / min, then heating the temperature to 900-1000°C at a heating rate of 3-5°C / min, and then introducing nitrogen as a diluent gas and propylene as a carbon source gas in sequence, wherein the volume flow ratio of propylene to nitrogen is 1:1-3, and the internal pressure of the reactor is controlled to maintain 1-3kPa, and the deposition is carried out for 400-600h.

[0031] In the actual operation process, when the carbon matrix is ​​deposited, machining is performed once in the middle, and the taken out material is subjected to surface treatment to open the closed pores.

[0032] In a preferred embodiment, the density of the carbon / carbon porous body is 1.4-1.6 g / cm 3 .

[0033] In a preferred embodiment, during the resin densification process, the obtained carbon / carbon porous body is added to the impregnating agent for impregnation, and then solidified to obtain a solidified body, which is then carbonized and cracked, and then the impregnation-solidification-carbonization and cracking are repeated 2-3 times to obtain a density of ≥1.8g / cm 3The carbon / carbon composite material, the impregnating agent, by mass percentage, is composed of 3-8% polycarbosilane, 1-5% polycarbohafnium, 1%-3% phosphoric acid, and the balance is resin, and the resin is selected from at least one of phenolic resin, furfural resin, and furan resin.

[0034] The present invention, in the process of resin densification, that is, adding a small amount of polycarbosilane and polycarbohafnium, can introduce amorphous SiC and HfC components, which are distributed in the carbon matrix and the surface layer, which is equivalent to introducing a transition layer, and the transition layer components include resin carbon, SiC and HfC. The subsequent SiC and HfC coatings can be effectively combined with the carbon matrix, thereby alleviating the thermal stress concentration phenomenon caused by the large difference in thermal expansion coefficients between the subsequent SiC and HfC coatings and the carbon matrix, improving the service life of the SiC and HfC coatings, and enhancing the thermal protection effect. In addition, a small amount of phosphoric acid is added to accelerate the curing reaction of the resin on the one hand, and phosphoric acid can reduce the activation energy of the reaction, thereby increasing the reaction rate, and on the other hand, improve the thermal stability, chemical resistance and mechanical properties of the epoxy resin.

[0035] Further preferably, the impregnation process is to place the carbon / carbon porous body into an impregnation kettle, preheat the impregnation kettle to 50-75°C while evacuating the kettle, keep warm for 1-3 hours, then absorb the impregnating agent also preheated to 50-75°C into the impregnation kettle, pressurize it with nitrogen to 1-2MPa, and impregnate it at a constant temperature for 2-3 hours.

[0036] During the impregnation process, the impregnation kettle and the carbon / carbon porous material are preheated so that the temperature of the carbon-carbon material body matches the temperature of the impregnant, thereby improving the uniformity of the impregnation. In addition, preheating the impregnation kettle can also remove gas and moisture adsorbed in the porous body.

[0037] Further preferably, the curing temperature is 160-200° C., the curing time is 2-3 h, and the curing pressure is 1.5-2.0 MPa.

[0038] Further preferably, the carbonization cracking process is: firstly heating to 500-600°C at a heating rate of 0.5-1°C / min; then heating to 700-800°C at a heating rate of 0.1-0.5°C / m and keeping warm for 2-3h, and the pressure of carbonization cracking is 105-110kPa.

[0039] In a preferred embodiment, the chemical vapor deposition of the SiC coating is carried out under the protection of argon, firstly heating the temperature to 500-600°C at a heating rate of 5-8°C / min, then heating the temperature to 1000-1100°C at a heating rate of 3-5°C / min, and then introducing hydrogen and trichloromethylsilane (MTS) in sequence, wherein the volume flow ratio of trichloromethylsilane to hydrogen is 1:1-3, and the internal pressure of the reactor is controlled to maintain 1-3kPa, and the deposition is carried out for 3-5h.

[0040] In a preferred embodiment, the chemical vapor deposition of the HfC coating is carried out under the protection of argon, firstly the temperature is increased to 600-800°C at a heating rate of 5-8°C / min, then the temperature is increased to 1200-1300°C at a heating rate of 3-5°C / min, and then hydrogen, methane and hafnium tetrachloride are introduced in sequence, wherein the flow ratio of methane to hydrogen is 1:5-8, and the volume flow ratio of hafnium tetrachloride to hydrogen is 1-3:1, the internal pressure of the reactor is controlled to maintain 1-3kPa, and the deposition is carried out for 3-5h.

[0041] The present invention also provides a ceramic-modified carbon-carbon composite material nose cone prepared by the above preparation method.

[0042] Principle of the Invention

[0043] The present invention adopts two methods, namely, matrix modification and surface coating protection, to improve the material structure design and preparation process on the premise of meeting the mechanical properties of the composite material, so that the C / C composite material has anti-oxidation properties and improves the thermal protection system performance of the aircraft nose cone.

[0044] 1. Carbon fiber preform: The present invention adopts carbon fiber with a tensile modulus of 4500-4900MPa, woven in 4D (three-dimensional four-directional) and 2.5D (XY direction non-weft cloth mesh layer, Z direction needle punching) structures, and an integral nose cone thermal protection structure with a hemispherical front end and a conical rear end. The density of the formed carbon fiber preform reaches 0.7-0.8g / cm 3 , fully ensuring the strength of the carbon-carbon composite material skeleton.

[0045] 2. Preparation of multi-layer interface layer: In order to protect carbon fiber and effectively improve the mechanical properties of carbon-carbon composite materials, it is essential to prepare an interface layer with a moderate thermal expansion coefficient and a dense and complete interface layer. The present invention adopts CVD (chemical vapor deposition) method to prepare a pyrolytic carbon interface layer and a SiC interface layer. The pyrolytic carbon (PyC) interface is the most commonly used interface to improve the bonding between carbon fiber and matrix because of its typical layered structure and good chemical compatibility with SiC. The SiC layer acts as an oxygen barrier layer in the interface, which can hinder the diffusion of oxygen and protect the oxidation of the PyC interface sublayer. SiC is oxidized at high temperature to generate a glass phase. While healing the cracks in the interface, an oxide oxygen barrier layer is generated to hinder the oxidation of the carbon fiber and PyC interface. Studies have shown that the multi-layer interface can well improve the mechanical properties of the composite material. During the stretching process, the cracks deflected multiple times between the matrix and the interface, between the interface sublayers, and between the interface and the fiber, which effectively improved the mechanical properties of the composite material. Therefore, the present invention introduces a SiC interface layer on the basis of the PyC interface layer to obtain (PyC / SiC) x (x=1 or 2 or 3) interface.

[0046] The coating prepared by CVD method is uniform, dense and of high purity. The preparation of SiC interface and SiC coating uses H2 as carrier gas, and trichloromethylsilane (MTS) is brought into the deposition furnace by bubbling. High-purity Ar and H2 are used as dilution gas and reaction gas. The reaction temperature is 1000-1100℃, and the SiC interface deposition time is 3-5h. The reaction equation is as follows:

[0047] CH3SiCl3→SiC+3HCl

[0048] 3. CVD deposition of carbon matrix: using propylene, propane and natural gas as carbon sources, the carbon matrix is ​​deposited in a low vacuum environment at 900-1000℃, so that the density of the composite material reaches 1.4-1.6g / cm 3 CVD deposition of pyrolytic carbon (PyC) interface and carbon matrix uses nitrogen as diluent gas and protective gas, and generates pyrolytic carbon through chemical reactions such as thermal decomposition, dehydrogenation and condensation of propylene, propane and natural gas. The deposition time of pyrolytic carbon (PyC) interface and carbon matrix is ​​3-5h and 400-600h.

[0049] 4. Resin carbon densification: Phenolic resin, furfural resin and furan resin are used as the main liquid precursors. The impregnating agent also contains 3-8% by mass of polycarbosilane and 1-5% by mass of polycarbohafnium, and 1%-3% of phosphoric acid. The composite body prepared in the previous process is immersed in the liquid phase. It can be immersed under vacuum or high pressure. After the impregnation is completed, it is cured and carbonized under 105-110kPa and 700-800℃ to make the density of the composite material reach 1.8g / cm 3 above.

[0050] 5. Preparation of SiC coating on composite surface: Chemical vapor deposition is a very effective method for preparing coatings. Its advantage is that it can prepare high melting point material coatings at lower temperatures, has very good surface coverage, and can deposit coatings on large areas and complex products.

[0051] 6. Preparation of HfC coating on composite surface: The melting point of HfC is as high as 3890℃ and the melting point of its oxide is 2810℃. It has the characteristics of high hardness, strong anti-erosion ability, corrosion resistance and good chemical stability. Therefore, HfC is one of the most ideal coating materials for nozzles and throat liners of solid rocket engines. The advantages of HfC as an ultra-high temperature candle protection coating material on the surface of composite materials are: it has a low oxygen diffusion coefficient under ultra-high temperature conditions; (it has excellent phase stability; the oxidation products will not catalyze its further oxidation. In addition, after oxidation with ceramics, a unique and uniform layered structure is formed: a carbide layer that is well bonded to the matrix, a dense carbon oxide transition layer, and a porous oxide with good thermal shock resistance and anti-erosion ability on the outside. The formation of this structure can form a good ablation protection system on the surface of the composite material. HfC coating was prepared on the surface of C / C composite material using the HfCl4-CH4-H2 reaction system.

[0052] The modified C / C composite material introduced with ceramic by chemical vapor deposition can be prepared by the following formula:

[0053] HfCl4(g)+CH4(g)+H2(g)→HfC(s)+HCl(g)+H2(g) (1)

[0054] CH4→[C]+H2 (2)

[0055] HfCl4+H2→HfCl X +HCl (x=0,1,2,3) (3)

[0056] HfCl X +[C]→HfC+Cl (x=0,1,2,3) (4)

[0057] Cl+H2→HCl (5)

[0058] Among them, (1) is the overall reaction equation, and (2)(3)(4)(5) are the reaction process equations. [C] represents the carbon source produced by gaseous precursors such as propylene and natural gas. The deposition process mainly undergoes the decomposition of gaseous precursors (2)(3), the diffusion of decomposition products to the material boundary layer, and partial adsorption on the material surface, and finally reacts thereon to generate HfC (4). The byproduct HCl of the reaction diffuses outward through the boundary layer (5).

[0059] Advantages and positive effects of the present invention

[0060] 1. High modulus carbon fiber is introduced to weave into a high-density, integrally formed nose cone carbon fiber preform. The overall mechanical properties are higher than those of the combined, low-density preform, and the structure has high reliability.

[0061] Second, introduce a multi-layer composite interface layer on the carbon fiber surface, (PyC / SiC) x (x=1 or 2 or 3) interface, protecting the carbon fiber and hindering the oxidation of the interface between the carbon fiber and PyC. The multi-layer interface can greatly improve the mechanical properties of the composite material. During the stretching process, the cracks deflected multiple times between the matrix and the interface, between the interface sublayers, and between the interface and the fiber, which effectively improved the mechanical properties of the composite material.

[0062] 3. SiC coating and HfC coating are introduced on the surface of the composite material. The single HfC coating is combined with the C / C composite material matrix. Due to the mismatch of thermal expansion effect, under the thermal shock effect, the junction between the HfC coating and the C / C composite material matrix will crack, thereby causing the HfC coating to fail, causing the ablation of the C / C composite material to intensify, affecting the service life. To solve this problem, a SiC coating is introduced between the HfC coating and the C / C composite material matrix. The linear expansion coefficient of SiC is between that of C and HfC, which can better make up for this defect. In addition, in the process of resin carbon densification in the present invention, a certain mass ratio of polycarbosilane and a certain mass ratio of polycarbohafnium are also added to the impregnant. After curing, a small amount of amorphous SiC and HfC are formed on the carbon matrix and the surface, which is equivalent to a transition layer, so that the subsequent coating is more firmly combined. In the high-temperature environment of application, SiC reacts with oxygen to generate SiO2, whose melting point is 1,723°C; HfC reacts with oxygen to generate HfO2, whose melting point is 2,785°C. The self-healing antioxidant multiphase oxide film composed of liquid SiO2 and solid HfO2 generated in situ on the surface of the composite material can resist the erosion of high-speed airflow and the inward diffusion of oxidizing atmosphere. This is the main reason why the composite material has excellent ultra-high temperature and ablation resistance.

[0063] 4. The chemical vapor deposition furnace proposed in the present invention includes components such as a heat exchanger, a heating element, a graphite gas screen (with multiple holes and a gas guide device), an air inlet pipe and an air outlet pipe, etc., which can deposit multiple layers of products at the same time, optimize the gas flow field, and ensure more uniform and reliable deposition. The raw material inlet gas is preheated by the outlet gas, preheated by the heat exchanger, and enters the furnace body in multiple ways, and enters the nose cone blank through the holes of the graphite gas screen to deposit the required substances, effectively avoiding MTS and solidification in the HfCl4 pipeline, and the nose cone base and surface deposition are more uniform. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 Schematic diagram of a chemical vapor furnace.

[0065] Figure 2 Flow chart of the nose cone preparation process. DETAILED DESCRIPTION

[0066] In the following embodiments, the chemical vapor deposition furnace used includes a heat exchanger, a furnace body, a heating element, a furnace chamber, a graphite gas screen, an air inlet pipe, an air outlet pipe, and a deposition chamber. The heat exchanger is located outside the furnace body, and the air inlet is heated by the heat exchanger using the air outlet as a heat source. The heating element is located outside the furnace chamber to provide a heat source for the furnace chamber. The furnace chamber is divided into a number of deposition chambers by partitions, and any deposition chamber is provided with a graphite gas screen having the same shape as the sample to be deposited and a smaller size than the sample to be deposited. During any chemical vapor deposition, any sample to be deposited is placed in any deposition chamber and covered with the outside of the graphite gas screen. The air inlet heated by the heat exchanger is divided into a number of routes and respectively enters from the bottom center of any deposition chamber. After being screened by graphite gas, it acts on the sample to be deposited, and chemical vapor deposition is performed on the sample to be deposited.

[0067] The air inlet pipe, air outlet pipe and heat exchanger are all wrapped with a 10-centimeter-thick asbestos layer.

[0068] Example 1

[0069] Step 1: Weaving of the prefabricated body

[0070] The tensile strength is 4500MPa and the volume density is 1.75g / cm 3 Carbon fiber, in the XY direction, consists of a layer of PANCF non-woven fabric and a layer of PANCF mesh fabric. The carbon fiber is needle-punched in both directions in the Z direction, and the non-woven fabric is alternately laid at 0° / 90°. The weight percentage of non-woven fabric and mesh felt is 80:20, and the volume density of the preform is 0.75g / cm 3 The outer diameter of the front hemisphere of the nose cone is 285mm, the inner diameter is 115mm, the front radius of the rear cone is 285mm, the rear radius is 500mm, the height is 600mm, and the thickness is 85mm.

[0071] Step 2: Preparation of multi-layer interface layer

[0072] The carbon / carbon composite material obtained in step 1 and a customized graphite gas screen are placed in a low-pressure chemical vapor deposition furnace, wherein the pore size distribution density of the graphite gas screen is 0.5 pores / cm 2 In the graphite gas screen, the aperture size of the hemispherical front end is 0.5 cm, and the aperture size of the conical rear end is 0.4 cm. The distance between the graphite gas screen and the sample to be deposited is 0.3 cm. Turn on the vacuum system to keep the gas deposition furnace in a low pressure state (less than 100 Pa); introduce nitrogen protection, turn on the heating system, and heat up to 500°C at a rate of 5°C / min; after heating to 1000°C at a rate of 3°C / min, introduce nitrogen. After the temperature in the furnace stabilizes, introduce propylene and ensure that C3H6 / N2=1 / 1.5. Control the internal pressure of the reactor to maintain 1 kPa, and deposit for 4 hours to obtain the PyC pyrolytic carbon interface layer.

[0073] The carbon / carbon composite material obtained by the above-mentioned deposition process of the pyrolytic carbon interface layer is placed in a low-pressure chemical vapor deposition furnace, and the vacuum system is turned on to keep the vapor deposition furnace in a low-pressure state (less than 100Pa); argon protection is introduced, and the heating system is turned on, and the temperature is increased to 500°C at a rate of 5°C / min; the temperature is increased to 1100°C at a rate of 3°C / min, and hydrogen is introduced. After the temperature in the furnace is stable, trichloromethylsilane (MTS) is brought into the reactor by bubbling as a dilution and protective gas, ensuring that MTS / H2=1 / 2, and the internal pressure of the reactor is controlled to maintain 1kPa, and the deposition is carried out for 2 hours to obtain the SiC interface layer.

[0074] The above-mentioned process of depositing pyrolytic carbon and depositing SiC is repeated to obtain a (PyC / SiC)2 multilayer interface on the carbon fiber surface.

[0075] Step 3: Preparation of carbon matrix

[0076] Place the carbon / carbon composite material blank obtained in step 2 into a low-pressure chemical vapor deposition furnace, turn on the vacuum system to keep the vapor deposition furnace at a low pressure (less than 100Pa); introduce nitrogen protection, turn on the heating system, and heat up to 500°C at a rate of 5°C / min; after heating to 1000°C at a rate of 3°C / min, introduce nitrogen. After the temperature in the furnace stabilizes, introduce propylene and ensure that C3H6 / N2=1 / 1.5, control the internal pressure of the reactor to maintain 1kPa, and deposit for 300 hours. The carbon matrix is ​​deposited on the carbon / carbon composite material, and the density can reach 1.35g / cm 3 The removed material was subjected to surface treatment to open the closed pores and then placed in a low-pressure chemical vapor deposition furnace to repeat the CVD deposition process for 300 hours to obtain a density of 1.6 g / cm 3 Carbon / carbon composite material green body.

[0077] Step 4: Preparation of resin carbon matrix

[0078] Put the body to be impregnated into the impregnation kettle, evacuate and heat the impregnation kettle to 65°C, and keep it warm for 1 hour. Add a certain amount of furfural resin to the preheating kettle, and add 5% by mass of polycarbosilane and 2% by mass of polycarbohafnium ethane, and 3% by mass of phosphoric acid to the impregnating agent. Start the stirring equipment before heating the preheating kettle each time, and heat the preheating kettle to 65°C and keep it warm for 10 minutes; while the impregnation kettle is evacuated, open the feed valve between the impregnation kettle and the preheating kettle, suck the resin into the impregnation kettle, stop evacuating the impregnation kettle, and fill it with nitrogen and pressurize it to 2MPa. The impregnation kettle is kept at a constant temperature of 65°C and a constant pressure of 2MPa for 2 hours; after the impregnation is completed, release the pressure and open the feed valve between the impregnation kettle and the preheating kettle to press the excess resin back into the preheating kettle; after the impregnation kettle is re-filled with N2 and pressurized to 1.6Pa, heat up and cure, the curing temperature is 180°C, and the time is 2h.

[0079] After curing, the component was placed in a carbonization furnace and carbonized at 800°C for 2 hours. Vacuum was applied and the temperature was increased to 600°C at a rate of 0.5°C / min. The temperature was increased to 800°C at a rate of 0.2°C / min and the pressure was 105kPa.

[0080] The above process was repeated two to three times to make the composite material density reach 1.82 g / cm 3 .

[0081] Step 5: Preparation of SiC coating on composite surface

[0082] The carbon / carbon composite material obtained in step 5 is placed in a low-pressure chemical vapor deposition furnace, and the vacuum system is turned on to keep the vapor deposition furnace at a low pressure (less than 100Pa); argon protection is introduced, and the heating system is turned on, and the temperature is increased to 500°C at a rate of 5°C / min; the temperature is increased to 1100°C at a rate of 3°C / min, and the argon is extracted and hydrogen is introduced. After the temperature in the furnace is stable, trichloromethylsilane (MTS) is brought into the reactor by bubbling as a dilution and protective gas, ensuring that MTS / H2=1 / 3, and the internal pressure of the reactor is controlled to maintain 1kPa, and the deposition is performed for 3 hours to obtain a SiC coating.

[0083] Step 6: Preparation of HfC coating on composite surface

[0084] Place the carbon / carbon composite material containing SiC coating obtained in step 5 into a low-pressure chemical vapor deposition furnace, turn on the vacuum system to keep the vapor deposition furnace at a low pressure (less than 100Pa); introduce argon protection, turn on the heating system, and heat up to 800℃ at a rate of 5℃ / min; after heating to 1300℃ at a rate of 3℃ / min, argon is extracted and hydrogen is introduced. After the temperature in the furnace stabilizes, methane is introduced, and CH4 / H2=1 / 6, CH4 / HfCl4=3 / 1, the internal pressure of the reactor is controlled to maintain 3kPa, and deposition is carried out for 3 hours.

[0085] After the deposition process is completed, the product is protected by argon gas and cooled with the furnace. After room temperature, the product is taken out to obtain a finished nose cone. The test data of the nose cone obtained in Example 1 is shown in Table 1:

[0086] Table 1

[0087] Project Name Bending strength Compressive strength Thermal expansion coefficient (1000℃) Line ablation rate Numeric 233MPa 325MPa <![CDATA[1.2×10 -6 / ℃]]> <![CDATA[0.42μm·s -1 ]]>

[0088] Example 2

[0089] Step 1: Weaving of the prefabricated body

[0090] The tensile strength is 4200MPa and the volume density is 1.78g / cm 3 Carbon fiber, in the XY direction, consists of a layer of PANCF non-woven fabric and a layer of PANCF mesh fabric. The carbon fiber is needle-punched in both directions in the Z direction. The non-woven fabric is alternately laid at 0° / 90°. The weight percentage of non-woven fabric and mesh felt is 75:25. The volume density of the preform is 0.80g / cm 3 The outer diameter of the front hemisphere of the nose cone is 285mm, the inner diameter is 115mm, the front radius of the rear cone is 285mm, the rear radius is 500mm, the height is 600mm, and the thickness is 85mm.

[0091] Step 2: Preparation of multi-layer interface layer

[0092] The carbon / carbon composite material obtained in step 1 and a customized graphite gas screen are placed in a low-pressure chemical vapor deposition furnace, wherein the pore size distribution density of the graphite gas screen is 0.5 pores / cm 2In the graphite gas screen, the aperture size of the hemispherical front end is 0.5 cm, the aperture size of the conical rear end is 0.4 cm, and the distance between the graphite gas screen and the sample to be deposited is 0.2 cm. Turn on the vacuum system to keep the vapor deposition furnace in a low pressure state (less than 100 Pa); introduce nitrogen protection, turn on the heating system, and heat up to 500°C at a rate of 5°C / min; after heating to 980°C at a rate of 3°C / min, introduce nitrogen. After the temperature in the furnace stabilizes, introduce propylene, and ensure that C3H6 / N2=1 / 1, control the internal pressure of the reactor to maintain 1 kPa, and deposit for 5 hours to obtain the PyC pyrolytic carbon interface layer.

[0093] The carbon / carbon composite material obtained by the above-mentioned deposition of the pyrolytic carbon interface layer is placed in a low-pressure chemical vapor deposition furnace, and the vacuum system is turned on to keep the vapor deposition furnace in a low-pressure state (less than 100Pa); argon protection is introduced, and the heating system is turned on, and the temperature is increased to 600°C at a rate of 5°C / min; the temperature is increased to 1050°C at a rate of 3°C / min, and hydrogen is introduced. After the temperature in the furnace is stable, trichloromethylsilane (MTS) is brought into the reactor by bubbling as a dilution and protective gas, ensuring that MTS / H2=1 / 2, and the internal pressure of the reactor is controlled to maintain 1-3kPa, and the deposition is performed for 4 hours to obtain the SiC interface layer.

[0094] The above-mentioned process of depositing pyrolytic carbon and depositing SiC was repeated twice to obtain a (PyC / SiC)3 multilayer interface on the carbon fiber surface.

[0095] Step 3: Preparation of carbon matrix

[0096] Place the carbon / carbon composite material blank obtained in step 2 into a low-pressure chemical vapor deposition furnace, turn on the vacuum system to keep the vapor deposition furnace at a low pressure (less than 100Pa); introduce nitrogen protection, turn on the heating system, and heat up to 500°C at a rate of 5°C / min; after heating to 980°C at a rate of 3°C / min, introduce nitrogen. After the temperature in the furnace stabilizes, introduce propylene and ensure that C3H6 / N2=1 / 1, control the internal pressure of the reactor to maintain 1kPa, and deposit for 350 hours to deposit a carbon matrix on the carbon / carbon composite material with a density of 1.35g / cm 3 The removed product was subjected to surface treatment to open the closed pores and then placed in a low-pressure chemical vapor deposition furnace to repeat the CVD deposition process for 200 hours to obtain a density of 1.6 g / cm 3 Carbon / carbon composite material green body.

[0097] Step 4: Preparation of resin carbon matrix

[0098] Put the body to be impregnated into the impregnation kettle, evacuate and heat the impregnation kettle to 75℃, and keep it warm for 1 hour. Add a certain amount of phenolic resin to the preheating kettle, and add 8% by mass of polycarbosilane and 3% by mass of polycarbohafnium ane and 2% by mass of phosphoric acid to the impregnant. Start the stirring equipment before heating the preheating kettle each time, and heat the preheating kettle to 75℃ and keep it warm for 10 minutes; while the impregnation kettle is evacuated, open the feed valve between the impregnation kettle and the preheating kettle, suck the resin into the impregnation kettle, stop evacuating the impregnation kettle, and fill it with nitrogen and pressurize it to 1.5MPa. Keep the impregnation kettle at a constant temperature of 75℃ and a constant pressure of 1.5MPa for 2 hours; after the impregnation is completed, release the pressure and open the feed valve between the impregnation kettle and the preheating kettle to press the excess resin back into the preheating kettle; after the impregnation kettle is re-filled with N2 and pressurized to 1.5MPa, heat it up and cure it, the curing temperature is 180℃, and the time is 2h.

[0099] After curing, the component was placed in a carbonization furnace and carbonized at 800°C for 2 hours. Vacuum was applied and the temperature was increased to 600°C at a rate of 0.5°C / min. The temperature was increased to 780°C at a rate of 0.3°C / min and the pressure was 110 kPa.

[0100] Repeat the above process two to three times to make the density of the composite material reach 1.8g / cm 3 above.

[0101] Step 5: Preparation of SiC coating on composite surface

[0102] The carbon / carbon composite material obtained in step 5 is placed in a low-pressure chemical vapor deposition furnace, and the vacuum system is turned on to keep the vapor deposition furnace in a low pressure state (less than 100Pa); argon protection is introduced, and the heating system is turned on. The heating rate is 6°C / min, and the temperature is raised to 500°C; the heating rate is 3°C / min, and after the temperature is raised to 1050°C, hydrogen is introduced. After the temperature in the furnace is stable, trichloromethylsilane (MTS) is brought into the reactor by bubbling as a dilution and protective gas, ensuring that MTS / H2=1 / 3, and the internal pressure of the reactor is controlled to maintain 1kPa, and the deposition is performed for 5 hours to obtain a SiC coating.

[0103] Step 6: Preparation of HfC coating on composite surface

[0104] Place the carbon / carbon composite material containing SiC coating obtained in step 5 into a low-pressure chemical vapor deposition furnace, turn on the vacuum system to keep the vapor deposition furnace at a low pressure (less than 100Pa); introduce argon protection, turn on the heating system, and heat up to 800℃ at a rate of 5℃ / min; after heating to 1300℃ at a rate of 3℃ / min, argon is extracted and hydrogen is introduced. After the temperature in the furnace stabilizes, methane is introduced, and CH4 / H2=1 / 5, CH4 / HfCl4=2 / 1, the internal pressure of the reactor is controlled to maintain 3kPa, and deposition is carried out for 5 hours.

[0105] After the deposition process is completed, the product is protected by argon and cooled with the furnace. After room temperature, the product is taken out to obtain a finished nose cone. The test data of the nose cone obtained in Example 2 is shown in Table 2:

[0106] Table 2

[0107] Project Name Bending strength Compressive strength Thermal expansion coefficient (1000℃) Line ablation rate Numeric 325MPa 410MPa <![CDATA[1.6×10 -6 / ℃]]> <![CDATA[0.13μm·s -1 ]]>

[0108] Example 3

[0109] Step 1: Weaving of the prefabricated body

[0110] The tensile strength is 4500MPa and the volume density is 1.79g / cm 3 Carbon fiber, in the XY direction, consists of a layer of PANCF non-woven fabric and a layer of PANCF mesh fabric. The carbon fiber is needle-punched in both directions in the Z direction, and the non-woven fabric is alternately laid at 0° / 90°. The weight percentage of non-woven fabric and mesh felt is 78:22, and the volume density of the preform is 0.79g / cm 3 The outer diameter of the front hemisphere of the nose cone is 285mm, the inner diameter is 115mm, the front radius of the rear cone is 285mm, the rear end is 500mm, the height is 600mm, and the thickness is 85mm.

[0111] Step 2: Preparation of interface layer

[0112] The carbon / carbon composite material obtained in step 1 and a customized graphite gas screen are placed in a low-pressure chemical vapor deposition furnace, wherein the pore size distribution density of the graphite gas screen is 0.5 pores / cm 2In the graphite gas screen, the aperture size of the hemispherical front end is 0.5 cm, and the aperture size of the conical rear end is 0.4 cm. The distance between the graphite gas screen and the sample to be deposited is 0.1 cm. Turn on the vacuum system to keep the gas deposition furnace in a low pressure state (less than 100 Pa); introduce nitrogen protection, turn on the heating system, and heat up to 600°C at a rate of 6°C / min; after heating to 950°C at a rate of 3°C / min, introduce nitrogen. After the temperature in the furnace stabilizes, introduce propylene, and ensure that C3H6 / N2=1 / 1, control the internal pressure of the reactor to maintain 1kPa, and deposit for 4 hours to obtain the PyC pyrolytic carbon interface layer.

[0113] The carbon / carbon composite material obtained by the above-mentioned deposition of the pyrolytic carbon interface layer is placed in a low-pressure chemical vapor deposition furnace, and the vacuum system is turned on to keep the vapor deposition furnace at a low pressure state (less than 100Pa); argon protection is introduced, and the heating system is turned on, and the temperature is increased to 600°C at a rate of 6°C / min; the temperature is increased to 1080°C at a rate of 4°C / min, and hydrogen is introduced. After the temperature in the furnace is stable, trichloromethylsilane (MTS) is brought into the reactor by bubbling as a dilution and protective gas, ensuring that MTS / H2=1 / 2.5, and the internal pressure of the reactor is controlled to maintain 1-3kPa, and the deposition is performed for 3 hours to obtain the SiC interface layer.

[0114] Step 3: Preparation of carbon matrix

[0115] Place the carbon / carbon composite material blank obtained in step 2 into a low-pressure chemical vapor deposition furnace, turn on the vacuum system to keep the vapor deposition furnace at a low pressure (less than 100Pa); introduce nitrogen protection, turn on the heating system, and heat up to 600°C at a rate of 5°C / min; heat up to 950°C at a rate of 3°C / min, and then introduce nitrogen. After the temperature in the furnace stabilizes, introduce propylene and ensure that C3H6 / N2=1 / 1, control the internal pressure of the reactor to maintain 1kPa, and deposit for 250 hours to deposit a carbon matrix on the carbon / carbon composite material with a density of 1.25g / cm 3 The removed product was subjected to surface treatment to open the closed pores and then placed in a low-pressure chemical vapor deposition furnace to repeat the CVD deposition process for 250 hours to obtain a density of 1.55 g / cm 3 Carbon / carbon composite material green body.

[0116] Step 4: Preparation of resin carbon matrix

[0117] Put the body to be impregnated into the impregnation kettle, evacuate and heat the impregnation kettle to 70°C, and keep it warm for 2 hours. Add a certain amount of furfural resin to the preheating kettle, and add 6% by mass of polycarbosilane, 5% by mass of polycarbohafnium ethane, and 1% by mass of phosphoric acid to the impregnating agent. Before heating the preheating kettle each time, the stirring equipment must be started, and the preheating kettle must be heated to 70°C and kept warm for 60 minutes; while the impregnation kettle is evacuated, open the feed valve between the impregnation kettle and the preheating kettle, and suck the resin into the impregnation kettle. The impregnation kettle stops evacuating, and is filled with nitrogen and pressurized to 1.8MPa. The impregnation kettle is kept at a constant temperature of 70°C and a constant pressure of 1.8MPa for 2 hours; after the impregnation is completed, release the pressure and open the feed valve between the impregnation kettle and the preheating kettle to press the excess resin back into the preheating kettle; after the impregnation kettle is re-filled with N2 and pressurized to 1.8MPa, heat up and cure, the curing temperature is 180°C, and the time is 3h.

[0118] After curing, the component was placed in a carbonization furnace and carbonized at 800°C for 2 hours. Vacuum was applied and the temperature was increased to 550°C at a rate of 0.5°C / min. The temperature was increased to 790°C at a rate of 0.3°C / min and the pressure was 110 kPa.

[0119] Repeat the above process two to three times to make the density of the composite material reach 1.8g / cm 3 above.

[0120] Step 5: Preparation of SiC coating on composite surface

[0121] The carbon / carbon composite material obtained in step 5 is placed in a low-pressure chemical vapor deposition furnace, and the vacuum system is turned on to maintain a low pressure state (less than 100Pa) in the vapor deposition furnace; argon protection is introduced, and the heating system is turned on, and the temperature is increased at a rate of 8°C / min to 600°C; the temperature is increased at a rate of 3°C / min, and after the temperature is increased to 1080°C, hydrogen is introduced. After the temperature in the furnace is stable, trichloromethylsilane (MTS) is brought into the reactor by bubbling as a dilution and protective gas, ensuring that MTS / H2=1 / 2.5, and the internal pressure of the reactor is controlled to maintain 1kPa, and the deposition is performed for 4 hours to obtain a SiC coating.

[0122] Step 6: Preparation of HfC coating on composite surface

[0123] Put the carbon / carbon composite material containing SiC coating obtained in step 5 into a low-pressure chemical vapor deposition furnace, turn on the vacuum system to keep the vapor deposition furnace at a low pressure (less than 100Pa); introduce argon protection, turn on the heating system, and heat up to 800℃ at a rate of 6℃ / min; after heating to 1350℃ at a rate of 3℃ / min, argon is extracted and hydrogen is introduced. After the temperature in the furnace stabilizes, methane is introduced, and CH4 / H2=1 / 8, CH4 / HfCl4=3 / 1, the internal pressure of the reactor is controlled to maintain 2kPa, and deposition is carried out for 4 hours.

[0124] After the deposition process is completed, the product is protected by argon and cooled in the furnace. After room temperature, the product is taken out to obtain a finished nose cone. The test data of the nose cone obtained in Example 3 is shown in Table 3:

[0125] Table 3

[0126] Project Name Bending strength Compressive strength Thermal expansion coefficient (1000℃) Line ablation rate Numeric 295MPa 382MPa <![CDATA[1.9×10 -6 / ℃]]> <![CDATA[0.21μm·s -1 ]]>

[0127] Comparative Example 1

[0128] The other conditions were the same as those in Example 1, except that the customized graphite gas screen was not used. After the manufacturing process was completed, the finished nose cone was obtained. It was found that the density of the finished green body was uneven, and the density of the shell layer was 0.1-0.3 g / cm higher than that of the core. 3 , the performance test data is shown in Table 4:

[0129] Table 4

[0130] Project Name Bending strength Compressive strength Thermal expansion coefficient (1000℃) Line ablation rate Numeric 85MPa 134MPa <![CDATA[2.6×10 -6 / ℃]]> <![CDATA[1.31μm·s -1 ]]>

[0131] Comparative Example 2

[0132] The other conditions were the same as those in Example 1, except that the interface layer was not prepared on the carbon fiber surface. After the manufacturing process was completed, a finished nose cone was obtained, and the test data were shown in Table 5, and it was found that the ablation rate was high.

[0133] Table 5

[0134] Project Name Bending strength Compressive strength Thermal expansion coefficient (1000℃) Line ablation rate Numeric 215MPa 399MPa <![CDATA[1.7×10 -6 / ℃]]> <![CDATA[0.96μm·s -1 ]]>

[0135] Comparative Example 3

[0136] The other conditions were the same as those in Example 1, except that polycarbosilane and polycarbohafnium were not added to the impregnating agent. After the manufacturing process was completed, a finished nose cone was obtained, and the test data were shown in Table 6:

[0137] Table 6

[0138] Project Name Bending strength Compressive strength Thermal expansion coefficient (1000℃) Line ablation rate Numeric 236MPa 367MPa <![CDATA[1.5×10 -6 / ℃]]> <![CDATA[0.56μm·s -1 ]]>

Claims

1. A method for preparing a ceramic modified carbon-carbon composite nose cone, characterized in that: The carbon fiber preform with a hemispherical front end and a conical rear end is placed in a chemical vapor deposition furnace, and the chemical vapor deposition of the PyC interface layer and the SiC interface layer is repeated to obtain a (PyC / SiC) x The carbon / carbon blank is placed in a chemical vapor deposition furnace for chemical vapor deposition of a carbon matrix to obtain a carbon / carbon porous body, the carbon / carbon porous body is densified with resin carbon to obtain a carbon / carbon composite material, and finally the carbon / carbon composite material is placed in a chemical vapor deposition furnace for chemical vapor deposition of a SiC coating and a HfC coating in sequence to obtain a ceramic modified carbon-carbon composite nose cone. The chemical vapor deposition furnace comprises a heat exchanger, a furnace body, a heating element, a furnace chamber, a graphite gas screen, an air inlet pipe, an air outlet pipe, and a deposition chamber. The heat exchanger is located outside the furnace body. The heat exchanger heats the intake air with the outlet air as the heat source, the heating element is located outside the furnace to provide a heat source for the furnace, the furnace is divided into a plurality of deposition chambers by a partition, any deposition chamber is provided with a graphite gas screen having the same shape as the sample to be deposited and smaller in size than the sample to be deposited, during any chemical vapor deposition, any sample to be deposited is placed in any deposition chamber and covered with the outside of the graphite gas screen, the intake air heated by the heat exchanger is divided into a plurality of routes and respectively enters from the bottom center of any deposition chamber, and after being screened by the graphite gas, acts on the sample to be deposited, so as to perform chemical vapor deposition on the sample to be deposited; The pore size distribution density of the graphite gas sieve is 0.2-0.5 pores / cm 2 ; In the graphite gas sieve, the aperture size of the hemispherical front end is 0.4-0.6 cm, the aperture size of the conical rear end is 0.3-0.5 cm, and the aperture size of the hemispherical front end is greater than the aperture size of the conical rear end, and the aperture size at the junction of the front end and the rear end is the same as the aperture size of the hemispherical front end; The distance between the graphite gas screen and the sample to be deposited is ≤3 cm; During the resin densification process, the obtained carbon / carbon porous body is added to the impregnating agent for impregnation, and then solidified to obtain a solidified body, and then carbonized and cracked, and then the impregnation-solidification-carbonization and cracking are repeated 2-3 times to obtain a density of ≥1.8g / cm 3 The carbon / carbon composite material, the impregnating agent, by mass percentage, is composed of 3-8% polycarbosilane, 1-5% polycarbohafnium, 1%-3% phosphoric acid, and the balance is resin, and the resin is selected from at least one of phenolic resin, furfural resin, and furan resin.

2. The method for preparing a ceramic-modified carbon-carbon composite nose cone according to claim 1, characterized in that: The air inlet pipe, the air outlet pipe and the heat exchanger are all wrapped with an asbestos layer.

3. A method for preparing a ceramic-modified carbon-carbon composite nose cone according to any one of claims 1-2, characterized in that: The carbon fiber preform is a 4D carbon fiber braid or a 2.5D needle-punched carbon fiber preform, and the density of the carbon fiber preform is 0.7-0.8 g / cm 3 .

4. A method for preparing a ceramic-modified carbon-carbon composite nose cone according to any one of claims 1-2, characterized in that: A carbon fiber preform with a hemispherical front end and a conical rear end is placed in a chemical vapor deposition furnace, and chemical vapor deposition of a PyC interface layer is first performed, and then chemical vapor deposition of a SiC interface layer is performed, and then chemical vapor deposition of the PyC interface layer and the SiC interface layer is repeated 1 to 2 times, respectively, to obtain a (PyC / SiC) x (x=2 or 3) Carbon / carbon body of the carbon / carbon body of the interface layer.

5. The method for preparing a ceramic-modified carbon-carbon composite nose cone according to claim 4, characterized in that: The chemical vapor deposition of the PyC interface layer is carried out under nitrogen protection, firstly heating the temperature to 500-600°C at a heating rate of 5-8°C / min, then heating the temperature to 900-1000°C at a heating rate of 3-5°C / min, and then introducing nitrogen as a diluent gas and propylene as a carbon source gas in sequence, wherein the volume flow ratio of propylene to nitrogen is 1:1-3, and the internal pressure of the reactor is controlled to be maintained at 1-3kPa, and the deposition is carried out for 3-5h; The chemical vapor deposition of the SiC interface layer is carried out under the protection of argon, firstly heating the temperature to 500-600°C at a heating rate of 5-8°C / min, then heating the temperature to 1000-1100°C at a heating rate of 3-5°C / min, and then introducing hydrogen and trichloromethylsilane in sequence, wherein the volume flow ratio of trichloromethylsilane to hydrogen is 1:1-2, and the internal pressure of the reactor is controlled to be maintained at 1-3kPa, and the deposition is carried out for 2-4h.

6. A method for preparing a ceramic-modified carbon-carbon composite nose cone according to any one of claims 1-2, characterized in that: The chemical vapor deposition of the carbon matrix is ​​carried out under nitrogen protection, firstly heating the temperature to 500-600°C at a heating rate of 5-8°C / min, then heating the temperature to 900-1000°C at a heating rate of 3-5°C / min, then introducing nitrogen as a diluent gas and propylene as a carbon source gas in sequence, wherein the volume flow ratio of propylene to nitrogen is 1:1-3, the internal pressure of the reactor is controlled to maintain 1-3kPa, and the deposition is carried out for 400-600h; The density of the carbon / carbon porous body is 1.4-1.6 g / cm 3 .

7. A method for preparing a ceramic-modified carbon-carbon composite nose cone according to any one of claims 1-2, characterized in that: The impregnation process is as follows: the carbon / carbon porous body is placed in an impregnation kettle, and the impregnation kettle is preheated to 50-75°C while being vacuumed, and after being kept warm for 1-3 hours, an impregnating agent also preheated to 50-75°C is sucked into the impregnation kettle, and the impregnation kettle is pressurized to 1-2MPa with nitrogen, and the impregnation is carried out at a constant temperature for 2-3 hours; The curing temperature is 160-200°C, the curing time is 2-3h, and the curing pressure is 1.5-2.0MPa; The carbonization cracking process is: firstly heating to 500-600°C at a heating rate of 0.5-1°C / min; then heating to 700-800°C at a heating rate of 0.1-0.5°C / m and keeping warm for 2-3h, and the pressure of carbonization cracking is 105-110kPa.

8. A method for preparing a ceramic-modified carbon-carbon composite nose cone according to any one of claims 1-2, characterized in that: The chemical vapor deposition of the SiC coating is carried out under the protection of argon, firstly the temperature is raised to 500-600°C at a heating rate of 5-8°C / min, then the temperature is raised to 1000-1100°C at a heating rate of 3-5°C / min, and then hydrogen and trichloromethylsilane are introduced in sequence, wherein the volume flow ratio of trichloromethylsilane to hydrogen is 1:1-3, the internal pressure of the reactor is controlled to be maintained at 1-3kPa, and the deposition is carried out for 3-5h; The chemical vapor deposition of the HfC coating is carried out under the protection of argon, firstly the temperature is increased to 600-800°C at a heating rate of 5-8°C / min, then the temperature is increased to 1200-1300°C at a heating rate of 3-5°C / min, and then hydrogen, methane and hafnium tetrachloride are introduced in sequence, wherein the flow ratio of methane to hydrogen is 1:5-8, and the volume flow ratio of hafnium tetrachloride to hydrogen is 1-3:1, the internal pressure of the reactor is controlled to maintain 1-3kPa, and the deposition is carried out for 3-5h.

9. A ceramic-modified carbon-carbon composite nose cone prepared by the preparation method according to any one of claims 1 to 8.

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