Composite material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of tantalum carbide materials, and provides a composite material and a preparation method and application thereof.The preparation method of the composite material comprises the following steps that (1) plasma oxidation treatment is conducted on the surface of a base material, and the base material subjected to oxidation treatment is obtained; (2) in the presence of a first gas system for depositing tantalum carbide, performing first deposition on the surface of the oxidized substrate to obtain a first preform containing a tantalum carbide coating; 3) performing second deposition on the surface of the first preform in the presence of hafnium carbide particles and a second gas system for depositing tantalum carbide to obtain a second preform containing a hafnium carbide-tantalum carbide coating; and (4) carrying out heat treatment on the second prefabricated body to obtain the composite material. The coating on the surface of the base material in the composite material prepared by the method is tough and compact, and the base material and the coating on the surface of the base material have strong binding force.

Description

Technical Field

[0001] The present invention relates to the technical field of tantalum carbide materials, and particularly relates to a composite material, a preparation method thereof, and Background Art

[0002] The extreme operating conditions faced by solid rocket propulsion systems pose severe challenges to ultra-high temperature materials, especially in the context of the rapid development of the aerospace field. Carbon-based materials are renowned for their high specific strength, excellent thermal conductivity, suitable thermal shock resistance, and good mechanical properties at high temperatures. These characteristics make them highly favored in the aerospace industry, especially for applications such as rocket nozzles, nose tips, and leading edges of gas turbine engine components. However, carbon-based materials are prone to oxidation in high-temperature oxidation environments, and have disadvantages such as poor tolerance to ammonia and insufficient wear resistance, resulting in latent degradation and gradually being unable to meet the increasingly stringent usage requirements, severely limiting their application potential at high temperatures.

[0003] On the other hand, tantalum carbide (TaC) ceramics have a melting point as high as 3880 °C, extremely high hardness (Mohs hardness is 9 - 10), relatively large thermal conductivity (22 W·m -1 ·K -1 ), flexural strength (340 - 400 MPa), and a small coefficient of thermal expansion (6.6×10 -6 K -1 ). In addition, TaC exhibits excellent thermochemical stability and outstanding physical properties. Therefore, TaC coatings have been widely used in many fields such as aerospace thermal protection, single crystal growth, energy electronics, and medical devices. Compared with bare graphite or SiC-coated graphite, TaC coatings show better chemical corrosion resistance, and are particularly suitable for growing GaN or AlN single crystals in MOCVD equipment and growing SiC single crystals in PVT equipment, significantly improving the quality of the grown single crystals. However, the bonding force between a single tantalum carbide coating and a carbon-based material is weak, prone to cracking, resulting in product failure. Summary of the Invention

[0004] The object of the present invention is to overcome the above problems existing in the prior art, and provide a composite material and a preparation method thereof. The coating on the surface of the substrate in the composite material prepared by this method is tough and dense, and there is a strong bonding force between the substrate and the coating on its surface.

[0005] To achieve the above object, the first aspect of the present invention provides a preparation method of a composite material, which includes the following steps:

[0006] (1) Perform plasma oxidation treatment on the surface of the substrate to obtain the substrate after oxidation treatment;

[0007] (2) In the presence of a first gas system for depositing tantalum carbide, a first deposition is carried out on the surface of the substrate after oxidation treatment to obtain a first preform with a tantalum carbide coating;

[0008] (3) In the presence of hafnium carbide particles and a second gas system for depositing tantalum carbide, a second deposition is carried out on the surface of the first preform to obtain a second preform with a hafnium carbide - tantalum carbide coating;

[0009] (4) The second preform is heat - treated to obtain the composite material.

[0010] The second aspect of the present invention provides a composite material, which is the composite material prepared by the preparation method described in the first aspect.

[0011] The third aspect of the present invention provides the application of the composite material described in the second aspect as a high - temperature resistant material.

[0012] The present invention adopts the above - mentioned technical solutions and has the following beneficial effects:

[0013] In the present invention, by first depositing a thin layer of TaC and then adding HfC powder while depositing the TaC layer, a heterogeneous nucleation environment is created, which promotes the mutual solubility of HfC and TaC. A dense and tough HfC - TaC layer is deposited at a lower temperature. With a certain period of heat treatment, the pores, cracks and defects on the coating surface can be greatly reduced, thereby improving the bonding performance between the coating and the substrate, and enhancing the high - temperature resistance and ablation resistance of the composite material.

[0014] By adding HfC powder during the deposition of the TaC layer in a single - deposition manner, the present invention can effectively reduce the reaction temperature, enabling deposition to be carried out at around 1000 °C. This can greatly reduce the production cost and save the time for heating and cooling.

[0015] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed herein. In this article, unless otherwise specified, data ranges include endpoints. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The SEM image of the surface of the composite material prepared in Example 1 of the present invention is shown.

[0017] Figure 2 The XRD pattern of the surface of the composite material prepared in Example 1 of the present invention is shown. Detailed Embodiments

[0018] The following provides a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for explaining and illustrating the present invention, and are not used to limit the present invention.

[0019] Unless otherwise defined, all scientific and technical terms used in the present invention have the same meaning as commonly understood by those skilled in the technical field to which the present invention pertains.

[0020] The first aspect of the present invention provides a method for preparing a composite material, the method comprising the following steps:

[0021] (1) Perform plasma oxidation treatment on the surface of the substrate to obtain the oxidized substrate;

[0022] (2) Perform a first deposition on the surface of the oxidized substrate in the presence of a first gas system for depositing tantalum carbide to obtain a first preform with a tantalum carbide coating;

[0023] (3) Perform a second deposition on the surface of the first preform in the presence of hafnium carbide particles and a second gas system for depositing tantalum carbide to obtain a second preform with a hafnium carbide - tantalum carbide coating;

[0024] (4) Perform heat treatment on the second preform to obtain the composite material.

[0025] The substrate can be, for example, at least one of a carbon - based substrate, a silicon - based substrate, and a SiC substrate, and can be a substrate or a substrate already attached with a transition layer (for example, the substrate can include a carbon - based substrate and a SiC coating attached to the carbon - based substrate).

[0026] In some embodiments, the substrate is a carbon - based substrate.

[0027] In some embodiments, the carbon - based substrate is graphite (such as isostatic graphite) or carbon fiber reinforced carbon, etc.

[0028] In some embodiments, the thermal expansion coefficient of the carbon - based substrate is 4×10 -6 / K - 7.5×10 -6 / K, the density is 1.7 - 2.2 g / cm 3 , the porosity is 5 - 25%, and the grain size is below 5 μm.

[0029] In some embodiments, the method further includes pre-treating the substrate before plasma oxidation treatment. The substrate surface can be made to have a certain roughness and / or impurities on the substrate surface can be removed through the pre-treatment. Processes including but not limited to grinding, sandblasting, plasma treatment, etc. can be used to make the substrate surface have a certain roughness (Ra is 0.2 μm - 2 μm) and high cleanliness, ensuring the tight bonding between the coating and the substrate.

[0030] The way to remove impurities can be, for example, to perform a cleaning treatment on the substrate. The cleaning treatment can be water washing or acid washing, and can be rinsing and / or immersion washing, and can be carried out by conventional means in the art as long as the impurities on the substrate surface can be removed. It should be understood that after cleaning, drying treatment can be carried out and then used for the subsequent deposition process. Among them, the drying method can be a conventional drying method, such as drying using a vacuum dryer or blowing air, etc. (it can be dried at 100 - 300 °C for more than 2 h). An oxygen-containing atmosphere (the oxygen concentration can be, for example, 200 ppm - 500 ppm) can also be introduced to oxidize and remove or purge and clean the substrate surface and / or the particles on the surface.

[0031] Plasma oxidation is an effective method widely used in material surface modification technology. It uses high-energy active particles in the plasma to bombard the material surface, changing its surface chemical composition, structure, and properties. It has been found that compared with conventional oxidation treatment methods, using plasma oxidation can improve the bonding performance between the substrate and the coating.

[0032] During the plasma oxidation treatment process, generally, plasma is first generated. For example, in a plasma reaction chamber, plasma can be generated through gas discharge. The gas used to form the plasma can be a conventional gas in the art, such as oxygen and an optional auxiliary gas (such as argon or helium). The obtained plasma can be used to treat the substrate. For example, the graphite substrate to be treated can be placed in the plasma reaction chamber to expose it to the plasma. The high-energy active particles in the plasma bombard the surface of the graphite substrate and react with the surface of the graphite substrate to form an oxide layer. After the oxidation treatment is completed, the substrate can be washed with deionized water to remove the reaction residues, and then dried in an oven.

[0033] The plasma oxidation treatment can be carried out under the conventional conditions in the art as long as the oxidation effect can be achieved. In some embodiments, the conditions of the plasma oxidation treatment include: the power is 120 - 180 W (such as 120 W, 130 W, 140 W, 150 W, 160 W, 170 W, 180 W), the discharge frequency is 10 - 15 MHz (such as 10 MHz, 11 MHz, 12 MHz, 13 MHz, 14 MHz, 15 MHz), and the time is 5 - 20 min (such as 5 min, 10 min, 15 min, 20 min).

[0034] In some embodiments, the mass ratio of C element to O element on the surface of graphite (substrate) is 10 - 20, such as 10, 12, 14, 16, 18, 20.

[0035] In some embodiments, C element and O element on the graphite surface exist in the forms of C - C, C - OH, and C - O - C.

[0036] In some embodiments, on the graphite surface, the content of C - C is 82 - 92 wt% (such as 82 wt%, 85 wt%, 88 wt%, 90 wt%, 92 wt%), the content of C - OH is 5 - 12 wt% (such as 5 wt%, 7 wt%, 9 wt%, 10 wt%, 12 wt%), and the content of C - O - C is 1 - 7 wt% (such as 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%).

[0037] In some embodiments, the mass ratio of C element to O element on the surface of the substrate after the oxidation treatment is 14 or less (such as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14), and preferably 1 - 12.

[0038] In some embodiments, C element and O element on the surface of the substrate after the oxidation treatment exist in the forms of C - C, C - OH, C - O - C, and - COOH.

[0039] In some embodiments, on the surface of the substrate after the oxidation treatment, the content of C - C is 65 - 85 wt% (such as 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%), the content of C - OH is 8 - 18 wt% (such as 8 wt%, 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%), the content of C - O - C is 2 - 15 wt% (such as 2 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%), and the content of - COOH is 2 - 10 wt% (such as 2 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt%).

[0040] In some embodiments, the first deposition method and the second deposition method are each independently CVD deposition. The equipment used can be a CVD vapor deposition furnace. The substrate can be horizontally placed in the deposition reaction chamber first, the furnace door is closed, the reaction chamber is pumped to a vacuum below 200 Pa, and then the temperature is raised to the deposition temperature at a rate of 2°C / min - 10°C / min. The first deposition and the second deposition can be carried out continuously, that is, the deposition process is not interrupted.

[0041] In some embodiments, the first gas system and the second gas system each independently include a Ta source, a C source, a reducing gas, and a diluting gas.

[0042] In some embodiments, the Ta source gas contains at least one of TaF5, TaCl5, and TaBr5. The Ta source gas can be obtained by sublimation of Ta source powder or particles. The Ta source powder can be obtained by grinding (such as ball milling) Ta source solid particles in an inert atmosphere (such as argon). Preferably, the particle size Dv50 of the Ta source powder can be below 1 mm, such as 100 μm, 200 μm, 400 μm, 500 μm, 600 μm, 800 μm, 900 μm.

[0043] In some embodiments, the C source gas contains at least one of CH4, C2H4, C2H6, C3H6, and C3H8.

[0044] In some embodiments, the reducing gas is hydrogen.

[0045] In some embodiments, the diluting gas can be an inert gas, that is, another gas that does not react with other components. For example, it can be argon Ar or helium He.

[0046] In some embodiments, the particle size Dv50 of hafnium carbide particles is 2 - 8 μm, such as 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm. When the particle size Dv50 of hafnium carbide particles is within this range, the densification of the coating and the bonding force between the substrate and the coating can be further improved. At the same time, more nucleation sites can be provided to improve densification. The HfC powder can be ball milled to this range by the ball milling method, and Dv50 can be measured by a laser particle size analyzer.

[0047] In some embodiments, in the first gas system and the second gas system, the molar ratio of tantalum element to carbon element is each independently 1:0.5 - 1 (such as 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1).

[0048] In some embodiments, during the second deposition process, the molar amount ratio of hafnium element to tantalum element is 1:5 - 10.

[0049] In some embodiments, in the first gas system and the second gas system, the molar ratio of tantalum element to reducing gas is independently 1:0.5 - 5 (such as 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5).

[0050] In some embodiments, in the first gas system and the second gas system, the molar ratio of tantalum element to diluting gas is independently 1:50 - 100 (such as 1:50, 1:60, 1:70, 1:80, 1:90, 1:100).

[0051] In some embodiments, in the first gas system and the second gas system, the flow rate of the tantalum source is independently 20 - 60 g / min (such as 20 g / min, 30 g / min, 40 g / min, 50 g / min, 60 g / min).

[0052] In some embodiments, the flow rate of HfC is 3 - 10 g / min (such as 3 g / min, 5 g / min, 7 g / min, 9 g / min, 10 g / min).

[0053] In some embodiments, the conditions of the first deposition result in a tantalum carbide coating with a thickness of 0.1 - 0.2 μm (such as 0.1 μm, 0.15 μm, 0.2 μm).

[0054] In some embodiments, the conditions of the first deposition include: a deposition temperature of 1050 - 1300 °C (such as 1050 °C, 1100 °C, 1150 °C, 1200 °C, 1250 °C, 1300 °C), a pressure of 1 kPa - 5 kPa (such as 1 kPa, 2 kPa, 3 kPa, 4 kPa, 5 kPa), and a time of 10 - 30 min (such as 10 min, 15 min, 20 min, 25 min, 30 min).

[0055] The time point when the first deposition ends can be counted from the time point when HfC is introduced. At the end of the first deposition, TaC grains are in the seed crystal state under high - temperature conditions. After adding HfC powder, it is beneficial for HfC to dissolve in TaC, and can also greatly reduce the nucleation energy of TaC, thereby being more conducive to nucleation and improving the density of the composite coating, enhancing the toughness and high - temperature resistance of the coating.

[0056] In some embodiments, the conditions of the second deposition result in a hafnium carbide - tantalum carbide coating with a thickness of 20 - 40 μm (such as 20 μm, 25 μm, 30 μm, 35 μm, 40 μm).

[0057] In some embodiments, the conditions for the second deposition include: a deposition temperature of 1050 - 1300 °C (such as 1050 °C, 1100 °C, 1150 °C, 1200 °C, 1250 °C, 1300 °C), a pressure of 1 kPa - 5 kPa (such as 1 kPa, 2 kPa, 3 kPa, 4 kPa, 5 kPa), and a time of 2 h - 4 h (such as 2 h, 2.5 h, 3 h, 3.5 h, 4 h).

[0058] In some embodiments, the conditions for the heat treatment include: a temperature of 1100 - 1500 °C (such as 1100 °C, 1200 °C, 1300 °C, 1400 °C, 1500 °C), a pressure of 3 kPa - 7 kPa (such as 3 kPa, 4 kPa, 5 kPa, 6 kPa, 7 kPa), and a time of 2 h - 4 h (such as 2 h, 2.5 h, 3 h, 3.5 h, 4 h). By heat-treating the coating, the lattice distortion caused by solid solution is eliminated, the internal stress is reduced, and further, the pores, cracks, etc. in the coating can be further reduced.

[0059] After obtaining the final product, a vacuum cooling operation can be performed. The specific operation method can be a conventional operation method in the art. For example, after the last deposition is completed, the inside of the furnace can be pumped down to below 200 Pa, and the temperature can be gradually reduced to room temperature at a cooling rate of 2 - 10 °C / min. Subsequently, Ar or N2 with a flow rate of 20 - 200 L / min is introduced to adjust the pressure to atmospheric pressure, and then the furnace is opened to take out the product.

[0060] The second aspect of the present invention provides a composite material, which is the composite material prepared by the preparation method described in the first aspect.

[0061] In some embodiments, the composite material includes a substrate (with an oxygen-containing surface) and a composite coating on the surface of the substrate. The composite coating includes a TaC coating adjacent to the substrate and an HfC - TaC coating on the other side of the TaC coating.

[0062] The hafnium carbide - tantalum carbide coating has a dense surface, no fine pores that can cause coating failure, and relatively large grains. In some embodiments, the average grain size on the surface of the HfC - TaC coating is 15 - 40 μm (such as 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm).

[0063] In the present invention, the grain size can be observed on the surface of the coating by an optical microscope or a scanning electron microscope and measured and calculated using Image J software.

[0064] In some embodiments, in the composite coating, the content of Ta element is 36-46 at% (such as 36 at%, 38 at%, 40 at%, 42 at%, 44 at%, 46 at%), the content of Hf element is 5-12 at% (such as 5 at%, 7 at%, 9 at%, 10 at%, 11 at%, 12 at%), and the content of C element is 40-55 at% (such as 40 at%, 45 at%, 50 at%, 55 at%). Herein, at% refers to atomic percentage.

[0065] In some embodiments, the thickness of the HfC-TaC coating is 10-40 μm (such as 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm).

[0066] In some embodiments, the thickness of the TaC coating is below 0.5 μm (such as 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm).

[0067] In some embodiments, the thickness of the composite coating is 10-40 μm (such as 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm).

[0068] In the present invention, the measuring method for the content of each element is energy dispersive X-ray spectroscopy. Points are taken in the coating area for point scanning to obtain the content of each element.

[0069] For the parameters regarding the thickness of each coating, refer to the first aspect.

[0070] The third aspect of the present invention provides the application of the composite material described in the second aspect as a high-temperature resistant material.

[0071] The composite material can be used as a semiconductor material, for example, and can be applied to fields such as single crystal growth, energy electronics, aerospace, semiconductors, and energy vehicles.

[0072] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention. The present invention will be described in detail below with specific embodiments, and these embodiments are for understanding rather than limiting the present invention.

[0073] Unless otherwise specified, the materials, reagents, etc. used in the following embodiments can be obtained from commercial channels.

[0074] The present invention will be described in detail below in conjunction with specific embodiments, which are used for understanding rather than limiting the present invention.

[0075] In the following examples, the graphite sheet used as the substrate has a surface including C element and O element in the forms of C-C, C-OH, and C-O-C. The mass ratio of C element to O element is 13.28, and the content of C-C is 87.04 wt%, the content of C-OH is 8.8 wt%, and the content of C-O-C is 4.09 wt%.

[0076] Example 1

[0077] (1) In the plasma reaction chamber, the surface of the graphite sheet is subjected to plasma oxidation. The plasma gas is oxygen. After the plasma treatment is completed, the graphite sheet is washed with deionized water to remove the plasma reaction residues, and then the graphite sheet is dried in a drying oven. Among them, the conditions of plasma oxidation include: the treatment power is 150 W, and plasma discharge is carried out for 10 min at a discharge frequency of 13 MHz.

[0078] After plasma oxidation, the surface of the graphite sheet includes C element and O element in the forms of C-C, C-OH, C-O-C, and -COOH. The mass ratio of C element to O element is 4.18, and the content of C-C is 74.31 wt%, the content of C-OH is 10.52 wt%, the content of C-O-C is 10.58 wt%, and the content of -COOH is 6.59 wt%.

[0079] (2) Under an Ar atmosphere, the TaCl5 powder is subjected to ball milling treatment to make its powder particle size less than 500 μm; the HfC powder is subjected to ball milling treatment to make its powder particle size Dv50 about 5 μm.

[0080] (3) The graphite substrate is placed in the furnace body of the CVD deposition furnace, the furnace door is closed, the reaction chamber is evacuated to a vacuum below 200 Pa, the temperature is raised to 1200 °C, the pressure is controlled at 3 kPa, and Ar is introduced and stabilized for 20 min. Then TaCl5, H2, Ar, and CH4 are introduced into the CVD deposition furnace. After deposition for 20 min, the HfC powder pipeline is opened to deposit the HfC-TaC coating for 3 h. Among them, the molar ratio of TaCl5, CH4, H2, and Ar is 1:0.6:2:80. Among them, the molar ratio of HfC to TaCl5 is 1:6.

[0081] (4) After the deposition is completed, the coating is heat-treated at 1300 °C and a pressure of 5 kPa for 3 h to obtain the composite material.

[0082] Among them, the thickness of the TaC coating is 0.15 μm, the thickness of the HfC-TaC coating is 33 μm, and the average grain size on the surface of the HfC-TaC coating is 18 μm. In the composite coating, the content of Ta element is 42 at%, the content of Hf element is 8 at%, and the content of C element is 50 at%. The SEM image and XRD pattern of the coating surface are respectively as Figure 1 and Figure 2 shown.

[0083] Example 2

[0084] (1) In a plasma reaction chamber, plasma oxidation is performed on the surface of a graphite sheet. The plasma gas is oxygen. After the plasma treatment is completed, the graphite sheet is washed with deionized water to remove the residues of the plasma reaction, and then the graphite sheet is dried in a drying oven. Among them, the conditions of plasma oxidation include: the treatment power is 130 W, and plasma discharge is carried out for 5 min at a discharge frequency of 15 MHz.

[0085] After plasma oxidation, the surface of the graphite sheet includes C element and O element existing in the forms of C-C, C-OH, C-O-C, and -COOH. The mass ratio of C element to O element is 11.27, and the content of C-C is 79.2 wt%, the content of C-OH is 14.93 wt%, the content of C-O-C is 2.02 wt%, and the content of -COOH is 3.85 wt%.

[0086] (2) Under an Ar atmosphere, ball milling treatment is performed on TaCl5 powder to make its powder particle size less than 500 μm; ball milling treatment is performed on HfC powder to make its powder particle size Dv50 about 3 μm.

[0087] (3) Place the graphite substrate in a CVD deposition furnace, close the furnace door, evacuate the reaction chamber to a vacuum below 200 Pa, raise the temperature to 1100 °C, control the pressure to 1 kPa, and introduce Ar after stabilizing for 20 min. Then, TaCl5, H2, Ar, and CH4 are introduced into the CVD deposition furnace. After depositing for 10 min, the HfC powder pipeline is opened to deposit the HfC-TaC coating, and the deposition is carried out for 2.5 h. Among them, the molar ratio of TaCl5, CH4, H2, and Ar is 1:0.8:3:60. Among them, the molar ratio of HfC to TaCl5 is 1:8.

[0088] (4) After the deposition is completed, the coating is heat-treated at 1150 °C and a pressure of 4 kPa for 3.5 h to obtain the composite material.

[0089] Among them, the thickness of the TaC coating is 0.1 μm, the thickness of the HfC-TaC coating is 25 μm, and the average grain size on the surface of the HfC-TaC coating is 12 μm. In the composite coating, the content of Ta element is 40 at%, the content of Hf element is 6 at%, and the content of C element is 54 at%.

[0090] Example 3

[0091] (1) In the plasma reaction chamber, plasma oxidation is carried out on the surface of the graphite sheet. The plasma gas is oxygen. After the plasma treatment is completed, the graphite sheet is washed with deionized water to remove the residues of the plasma reaction, and then the graphite sheet is dried in a drying oven. Among them, the conditions of plasma oxidation include: the treatment power is 170 W, and plasma discharge is carried out for 15 min at a discharge frequency of 11 MHz.

[0092] After plasma oxidation, the surface of the graphite sheet includes C element and O element in the forms of C-C, C-OH, C-O-C, and -COOH. The mass ratio of C element to O element is 3.06, and the content of C-C is 70.24 wt%, the content of C-OH is 10.54 wt%, the content of C-O-C is 12.09 wt%, and the content of -COOH is 7.13 wt%.

[0093] (2) Under an Ar atmosphere, ball milling treatment is carried out on TaCl5 powder to make its powder particle size less than 500 μm; ball milling treatment is carried out on HfC powder to make its powder particle size Dv50 about 7 μm.

[0094] (3) Put the graphite substrate into the CVD deposition furnace, close the furnace door, evacuate the reaction chamber to a vacuum below 200 Pa, raise the temperature to 1300 °C, control the pressure to 5 kPa, and stably introduce Ar for 20 min. Then introduce TaCl5, H2, Ar, and CH4 into the CVD deposition furnace. After deposition for 30 min, open the HfC powder pipeline to deposit the HfC-TaC coating for 3.5 h. Among them, the molar ratio of TaCl5, CH4, H2, and Ar is 1:1:4:100. Among them, the molar ratio of HfC to TaCl5 is 1:10.

[0095] (4) After the deposition is completed, raise the furnace body temperature to 1450 °C, and carry out heat treatment on the coating for 2.5 h at a pressure of 6 kPa to obtain the composite material.

[0096] Among them, the thickness of the TaC coating is 0.2 μm, the thickness of the HfC-TaC coating is 28 μm, and the average grain size on the surface of the HfC-TaC coating is 10 μm. In the composite coating, the content of Ta element is 45 at%, the content of Hf element is 10 at%, and the content of C element is 45 at%.

[0097] Comparative Example 1

[0098] The operation was carried out according to the method described in Example 1, except that the graphite sheet was not subjected to plasma oxidation treatment.

[0099] Comparative Example 2

[0100] The operation was carried out according to the method described in Example 1, except that the graphite sheet was subjected to thermal oxidation treatment instead of plasma oxidation treatment. The conditions of the oxidation treatment included heating the graphite to 600 °C in an air atmosphere and oxidizing for 10 min.

[0101] After thermal oxidation, the surface of the graphite sheet included C element and O element in the forms of C-C, C-OH, C-O-C and -COOH. The mass ratio of C element to O element was 15, and the content of C-C was 85 wt%, the content of C-OH was 10 wt%, the content of C-O-C was 2 wt%, and the content of -COOH was 1 wt%.

[0102] Example 4

[0103] The operation was carried out according to the method described in Example 1, except that the processing power of plasma oxidation was 100 W.

[0104] After plasma oxidation, the surface of the graphite sheet included C element and O element in the forms of C-C, C-OH, C-O-C and -COOH. The mass ratio of C element to O element was 11.59, and the content of C-C was 81 wt%, the content of C-OH was 16 wt%, the content of C-O-C was 2 wt%, and the content of -COOH was 1 wt%.

[0105] Comparative Example 3

[0106] The operation was carried out according to the method described in Example 1, except that instead of depositing a TaC layer on the surface of the graphite sheet after plasma oxidation treatment, an HfC-TaC coating was directly deposited. That is, in step (3), the temperature was raised to 1200 °C, the pressure was controlled at 3 kPa, Ar was introduced and stabilized for 20 min, and then TaCl5, H2, Ar and CH4 were introduced into the CVD deposition furnace, and at the same time, the HfC powder pipeline was opened to deposit the HfC-TaC coating.

[0107] Comparative Example 4

[0108] Operate according to the method described in Example 1, except that HfCl4 is used instead of HfC when depositing the HfC-TaC coating. Specifically, in step (3), the temperature is raised to 1500 °C, the pressure is controlled at 1 kPa, Ar is introduced and stabilized for 20 min, then TaCl5, H2, Ar, and CH4 are introduced into the CVD deposition furnace. After depositing for 20 min, the HfCl4 pipeline is opened to deposit the HfC-TaC coating for 5 h. After the deposition is completed, the coating is heat-treated at 1600 °C and a pressure of 5 kPa for 3 h to obtain the composite material.

[0109] Example 5

[0110] Operate according to the method described in Example 1, except that TaCl5, H2, Ar, and CH4 are introduced into the CVD deposition furnace. After depositing for 40 min, the HfC powder pipeline is opened to deposit the HfC-TaC coating.

[0111] Example 6

[0112] Operate according to the method described in Example 1, except that TaCl5, H2, Ar, and CH4 are introduced into the CVD deposition furnace. After depositing for 5 min, the HfC powder pipeline is opened to deposit the HfC-TaC coating.

[0113] Example 7

[0114] Operate according to the method described in Example 1, except that in step (3), the temperature is raised to 1500 °C, the pressure is controlled at 6 kPa, Ar is introduced and stabilized for 20 min, then TaCl5, H2, Ar, and CH4 are introduced into the CVD deposition furnace. After depositing for 30 min, the HfC powder pipeline is opened to deposit the HfC-TaC coating for 5 h. After the deposition is completed, the coating is heat-treated at 1600 °C and a pressure of 8 kPa for 3 h to obtain the composite material.

[0115] Example 8

[0116] Operate according to the method described in Example 1, except that in step (3), the temperature is raised to 800 °C, the pressure is controlled at 1 kPa, Ar is introduced and stabilized for 20 min, then TaCl5, H2, Ar, and CH4 are introduced into the CVD deposition furnace. After depositing for 10 min, the HfC powder pipeline is opened to deposit the HfC-TaC coating for 2 h. After the deposition is completed, the coating is heat-treated at 900 °C and a pressure of 2 kPa for 3 h to obtain the composite material.

[0117] Example 9

[0118] Operate according to the method described in Example 1, except that the molar ratio of HfC to TaCl5 is 1:12.

[0119] Among them, in the composite coating, the content of Ta element is 53 at%, the content of Hf element is 3 at%, and the content of C element is 44 at%.

[0120] Example 10

[0121] Operate according to the method described in Example 1, except that the molar ratio of HfC to TaCl5 is 1:3.

[0122] Among them, in the composite coating, the content of Ta element is 49 at%, the content of Hf element is 4 at%, and the content of C element is 47 at%.

[0123] Example 11

[0124] Operate according to the method described in Example 1, except that the Dv50 of the particle size of HfC is 9 μm.

[0125] Example 12

[0126] Operate according to the method described in Example 1, except that the Dv50 of the particle size of HfC is 1.5 μm.

[0127] Example 13

[0128] Operate according to the method described in Example 1, except that the molar ratio of TaCl5, CH4, H2, and Ar is 1:0.6:5:80. Among them, in the composite coating, the content of Ta element is 51 at%, the content of Hf element is 4 at%, and the content of C element is 35 at%.

[0129] Example 14

[0130] Operate according to the method described in Example 1, except that the molar ratio of TaCl5, CH4, H2, and Ar is 1:0.6:1:80. Among them, in the composite coating, the content of Ta element is 38 at%, the content of Hf element is 5 at%, and the content of C element is 57 at%.

[0131] Comparative Example 5

[0132] Operate according to the method described in Example 1, except that no heat treatment is performed after deposition. Among them, in the composite coating, the content of Ta element is 49 at%, the content of Hf element is 4 at%, and the content of C element is 45 at%.

[0133] Test Example

[0134] Perform performance evaluation on the composite materials prepared in the examples and comparative examples. The specific method is as follows.

[0135] (1) Evaluation of thermal shock resistance

[0136] The sample to be tested was heated to 2000 °C at a heating rate of 10 °C / min and held for 1 h, then purged with argon at 100 L / min and air-cooled to 500 ± 20 °C. Then, it was observed whether there were obvious cracks on the surface of the sample. After observing no cracks on the surface, it was continued to be put into the thermal shock furnace for heating. If cracks appeared, the test was stopped. This operation was cycled until cracking occurred, and the result was expressed by the number of cycles at cracking. For example, if the number of cycles was 45 times, it meant the cracking test at 45 cycles. The results are shown in Table 1.

[0137] (2) Evaluation of fracture toughness

[0138] According to the indentation method, a Vickers hardness tester was used to test the polished composite material sample with a load of 100 gf (≈0.98 N) to test the fracture toughness. The test results are shown in Table 1.

[0139] Table 1

[0140]

[0141]

[0142] It can be seen from the comparison between Examples 1-4 and Comparative Examples 1 and 2 that treating the graphite flakes by plasma oxidation can significantly improve the thermal shock resistance and fracture toughness of the composite material, and the performance of the composite material can be further improved under the preferred treatment conditions.

[0143] It can be seen from the comparison between the examples and Comparative Examples 3 and 4 that the technical solution of the present invention can significantly improve the thermal shock resistance and fracture toughness of the composite material by first depositing a thin layer of TaC and then adding HfC powder while depositing the TaC layer. In particular, the prior deposition of a thin layer of TaC layer makes a greater contribution to the improvement of the performance of the composite material. It can be seen from the data of Comparative Example 5 that when no heat treatment is carried out, the thermal shock resistance of the material will be significantly reduced, which is related to the fact that heat treatment can eliminate part of the stress.

[0144] It can be seen from the comparison between Example 1 and Examples 5-14 that adopting the preferred deposition conditions in the present invention is beneficial to improving the performance of the composite material.

[0145] It should be noted that in this text, the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of additional identical elements in the process, method, article or device including that element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in the reverse order according to the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0146] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a composite material, characterized in that: The method comprises the following steps: (1) performing plasma oxidation treatment on the surface of the substrate to obtain an oxidized substrate; (2) performing a first deposition on the surface of the oxidized substrate in the presence of a first gas system for depositing tantalum carbide to obtain a first preform containing a tantalum carbide coating; (3) performing a second deposition on the surface of the first preform in the presence of hafnium carbide particles and a second gas system for depositing tantalum carbide to obtain a second preform containing a hafnium carbide-tantalum carbide coating; (4) Heat treating the second preform to obtain the composite material.

2. The preparation method according to claim 1, characterized in that: The conditions of plasma oxidation treatment include: power of 120-180W, discharge frequency of 10-15MHz, and time of 5-20min.

3. The preparation method according to claim 1, characterized in that: The substrate is a carbon-based substrate; The first gas system and the second gas system each independently include a Ta source, a C source, a reducing gas and a diluting gas; The conditions of the first deposition are such that the thickness of the tantalum carbide coating is 0.1-0.2 μm; The conditions of the second deposition are such that the thickness of the hafnium carbide-tantalum carbide coating is 20-40 μm.

4. The preparation method according to claim 1, characterized in that: In the first gas system and the second gas system, the molar ratio of tantalum element, carbon element, reducing gas and diluent gas is independently 1:0.5-1:0.5-5:50-100; In the second deposition process, the molar ratio of hafnium element to tantalum element is 1:5-10; The particle size Dv50 of hafnium carbide particles is 2-8μm 。 5. The preparation method according to claim 3, characterized in that: The Ta source comprises at least one of TaF5, TaCl5 and TaBr5; The C source comprises at least one of CH4, C2H4, C2H6, C3H6 and C3H8; The reducing gas is H2; The diluent gas is Ar or He.

6. The preparation method according to claim 1, characterized in that: The first deposition method and the second deposition method are each independently CVD deposition.

7. The preparation method according to claim 6, characterized in that: The conditions of the first deposition include: a deposition temperature of 1050-1300° C., a pressure of 1 kPa-5 kPa, and a time of 10-30 min; The conditions of the second deposition include: deposition temperature of 1050-1300°C, pressure of 1 kPa-5 kPa, and time of 2 h-4 h; The heat treatment conditions include: temperature of 1100-1500°C, pressure of 3kPa-7kPa, and time of 2h-4h.

8. A composite material, characterized in that The composite material is a composite material prepared by the preparation method according to any one of claims 1 to 7.

9. The composite material according to claim 8, characterized in that The composite material comprises a substrate and a composite coating located on the surface of the substrate, wherein the composite coating comprises a TaC coating and a HfC-TaC coating; The average grain size on the surface of HfC-TaC coating is 15-40 μm; In the composite coating, the content of Ta element is 36-46at%, the content of Hf element is 5-12at%, and the content of C element is 40-55at%.

10. Use of the composite material according to claim 8 or 9 as a high temperature resistant material.

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