A method for producing in situ a pyrolytic bond of a tantalum carbide composite coating

Abstract

This invention relates to the field of semiconductor materials technology, and discloses a tantalum carbide coating and its preparation method by pyrolysis-bonded in-situ growth. Along the substrate surface from the inside out, the tantalum carbide coating includes a transition layer and a tantalum carbide coating layer. The transition layer includes tantalum carbide and 0-8 wt% hafnium carbide. The preparation method includes the following steps: vaporizing the raw materials separately, then mixing them to obtain a mixed precursor gas; preheating the substrate material at high temperature, then pyrolyzing the mixed precursor gas through a plasma flame, allowing it to settle onto the substrate material surface, and cooling it to obtain a tantalum carbide coating on the substrate material surface. Through a high-temperature pyrolysis-bonded in-situ growth process, a tantalum carbide coating is formed and attached to the substrate surface, and a hafnium carbide-containing transition layer is also formed between the substrate and the tantalum carbide coating. This results in a tantalum carbide coating with higher bonding ability, uniform thickness, high density, and high surface finish. This preparation method has higher production efficiency and lower cost.

Description

Technical Field

[0001] This invention relates to the field of semiconductor materials technology, and more specifically, to a method for preparing a tantalum carbide coating and its in-situ pyrolytic bonding. Background Technology

[0002] In the field of semiconductor crystal growth, graphite is frequently used as a raw material for preparing heating elements, crucibles, insulation containers, flow guides, and insulation materials due to its excellent thermal conductivity, structural strength, and temperature resistance at high temperatures. In the crystal growth of first-generation semiconductor silicon, high-purity graphite materials were sufficient at approximately 1700℃. However, the crystal growth of third-generation semiconductor silicon carbide is mostly carried out in smaller chambers with more complex atmospheres, including vapors of Si, C, and SiC; and the processing temperature needs to reach approximately 2000-2200℃. The high temperature causes graphite to form volatiles and particles in the chamber, significantly affecting crystal quality and leading to crystal defects such as carbon inclusions. In epitaxial growth, graphite disks with silicon carbide coatings are generally used. However, for homoepitaxial growth of silicon carbide, the temperature is around 1600℃. Under these conditions, silicon carbide is prone to phase transitions, thus losing protection for the graphite matrix.

[0003] Based on the above, a proposed solution is to treat the graphite substrate with a tantalum carbide coating to address these issues. Tantalum carbide has a high melting point of 3880℃, maintains good mechanical properties at high temperatures, and exhibits excellent high-temperature resistance to chemical corrosion, ablation oxidation, and high-temperature mechanical properties.

[0004] Currently, methods for growing tantalum carbide coatings on graphite substrates mainly include chemical vapor deposition (CVD) and coating sintering. In the field of semiconductor materials, CVD is often used to grow tantalum carbide coatings. However, the CVD process is difficult, and it is hard to precisely control conditions such as airflow. Therefore, CVD coatings can only be deposited on the graphite substrate surface, and the coatings are prone to peeling off. Furthermore, the process is complex and costly. In practical applications, once the CVD coating peels off the graphite substrate, pitting corrosion occurs at the peeled-off portion. This not only causes contamination of the equipment with volatiles and carbon particles but also leads to defects in the final product, reducing the lifespan of the graphite device.

[0005] Based on the above, there is an urgent need for a method to prepare tantalum carbide coatings on the surface of graphite devices that can enable the tantalum carbide coatings to have high comprehensive performance. Summary of the Invention

[0006] The technical problem to be solved by this invention:

[0007] Currently, in the field of semiconductor materials, devices are mostly made from graphite. To protect the stability of the material and performance of graphite devices during production or use, a technique of coating the surface of graphite devices with tantalum carbide has been proposed. The main method used for coating graphite devices with tantalum carbide is chemical vapor deposition (CVD). However, practical applications have shown that the CVD-based tantalum carbide coating has a processing cycle of over one week, resulting in high costs. Furthermore, the difference in thermal expansion coefficients between the coating and the interface leads to thermal fatigue and detachment, failing to achieve a long-term, beneficial protective effect.

[0008] The technical solution adopted in this invention is as follows:

[0009] This invention provides a tantalum carbide composite coating, which includes a transition layer and a tantalum carbide coating along the inner-outward direction of the substrate surface. The transition layer includes tantalum carbide and hafnium carbide, and the hafnium carbide accounts for 0-10 wt% of the transition layer.

[0010] Preferably, the transition layer thickness is 5-20 μm and the tantalum carbide coating thickness is 30-65 μm.

[0011] This invention also provides a method for preparing the above-mentioned tantalum carbide composite coating by pyrolysis and in-situ bonding, comprising the following steps:

[0012] S1 feedstock vaporization:

[0013] Tantalum source, carbon source and hafnium source are vaporized respectively to form vaporized tantalum source, vaporized carbon source and vaporized hafnium source;

[0014] S2 mixed precursor gas;

[0015] Vaporized tantalum source, vaporized carbon source and vaporized hafnium source are fed into the mixing pipe at different flow rates using hydrogen or rare gas, and mixed to obtain mixed precursor gas;

[0016] S3 is used to prepare tantalum carbide coatings:

[0017] First, the substrate material is placed in the reaction chamber for preheating. Then, the mixed precursor gas is pyrolyzed by plasma flame, settled onto the surface of the substrate material, and cooled to obtain the tantalum carbide coating on the surface of the substrate material.

[0018] Preferably, in step S3, the preheating temperature is 1900-2500℃.

[0019] Preferably, the temperature is controlled at ≥2600℃ during pyrolysis.

[0020] Preferably, in step S1, the mass ratio of tantalum source, carbon source and hafnium source is 1:2:0.02-0.06.

[0021] Preferably, in step S2, during the initial gas flow, the gas flow rate of the tantalum source is controlled to be 300-800 g / h, the gas flow rate of the carbon source is 600-1600 g / h, and the gas flow rate of the hafnium source is 100-180 g / h, to form a transition layer.

[0022] Preferably, in step S2, during the later stage of gas transmission, the gas flow rate of the tantalum source is controlled to be 300-800 g / h, the gas flow rate of the carbon source is 600-1600 g / h, and the gas flow rate of the hafnium source is 0, to form a tantalum carbide coating.

[0023] Preferably, in step S2, the flow rate of hydrogen or rare gas is controlled to be 20-50 L / h.

[0024] Preferably, the ventilation time is 4-6 hours.

[0025] The beneficial effects of this invention are as follows:

[0026] This invention employs a high-temperature pyrolysis process combined with an in-situ reaction sintering process to form and attach a tantalum carbide coating on the surface of a graphite substrate. By controlling the amount of each component and the gas flow rate, the content of the raw material components in the coating decreases sequentially from the surface of the graphite substrate outwards, forming a tantalum carbide coating with a gradient content. Experiments have shown that the tantalum carbide coating produced in this way has significantly higher bonding ability, as well as uniform thickness, strong density, and high surface smoothness.

[0027] In this process, the content of hafnium source component in the raw materials is significantly lower than that of carbon source and tantalum source. Under the condition of using a limited gas flow rate, in the initial gas flow stage, a transition layer containing tantalum carbide and hafnium carbide can be formed on the surface near the graphite substrate, in which the content of hafnium carbide gradually decreases from about 8% to 0. In the subsequent gas flow stage, a pure tantalum carbide coating that has a major protective effect on the graphite substrate is mainly formed to achieve the thermal field design and corrosion resistance requirements of the silicon carbide crystal growth process.

[0028] In the transition layer near the graphite matrix, hafnium carbide can be dissolved into tantalum carbide, which significantly improves the elastic modulus of tantalum carbide. Experiments have shown that the elastic modulus can be increased by more than 15%. In the subsequent sintering process, the density of the material can be further improved.

[0029] From a technological perspective, this invention employs a pyrolysis-in-situ growth method. On one hand, ultrafine powders deposited through pyrolysis react on the surface of a graphite substrate to form a tantalum carbide film, which then diffuses into the solid phase within the graphite substrate. On the other hand, ultrafine tantalum powder reacts with the graphite substrate to produce tantalum carbide. Using this process, the film generated by the ultrafine powder effectively fills the pores on the graphite substrate surface, ensuring coating density. Simultaneously, the coating formed by the reaction of the powder and the graphite substrate can penetrate below the surface layer of the graphite substrate, resulting in better adhesion between the coating and the graphite substrate, thus meeting higher application requirements.

[0030] Furthermore, compared to the traditional CVD method for preparing surface coatings of semiconductor crystal devices, the pyrolysis-combined in-situ growth method of this invention offers significantly higher production efficiency. Specifically, the CVD method requires more than 7 days to achieve a surface coating thickness of 50 μm or greater on graphite devices, while the pyrolysis-combined in-situ growth method of this invention can produce a coating thickness of over 50 μm in just 6 hours, resulting in a significantly shorter production cycle and lower production costs. Attached Figure Description

[0031] Figure 1 This is an electron microscope image of the tantalum carbide coating on the surface of the graphite device in Example 1;

[0032] Figure 2 This is an electron microscope image of the tantalum carbide coating on the surface of the graphite device in Example 6. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0034] This invention provides a tantalum carbide composite coating, which includes a transition layer and a tantalum carbide coating along the direction from the inside to the outside of the substrate surface. The transition layer includes tantalum carbide and hafnium carbide, with hafnium carbide accounting for 0-10 wt% of the transition layer. The tantalum carbide coating includes tantalum carbide.

[0035] The transition layer has a thickness of 5-20 μm, and the tantalum carbide coating has a thickness of 30-65 μm. The total thickness of the tantalum carbide composite coating is 35-85 μm, preferably 45-70 μm. If the thickness of the tantalum carbide composite coating is too large, it will easily fall off due to increased stress. If the thickness is too small, it will lead to insufficient corrosion resistance.

[0036] The present invention also provides a method for preparing the above-mentioned tantalum carbide composite coating by pyrolysis and in-situ formation, comprising the following steps:

[0037] (1) Place TaCl5, chlorinated paraffin and HfCl4 in separate vaporization chambers for vaporization to form vaporized TaCl5, vaporized chlorinated paraffin and vaporized HfCl4 respectively;

[0038] (2) Vaporized TaCl5, vaporized chlorinated paraffin and vaporized HfCl4 are fed into the mixing pipe at different flow rates by H2 or rare gas and mixed to obtain a mixed precursor.

[0039] The mass ratio of chlorinated paraffin to TaCl5 is 2:1; the flow rate of hydrogen or rare gas is controlled at 20-50 L / h; during the initial gas flow, the flow rate of tantalum source is controlled at 300-800 g / h, carbon source at 600-1600 g / h, and hafnium source at 100-180 g / h to form a transition layer; during the later gas flow, the flow rate of tantalum source is controlled at 300-800 g / h, carbon source at 600-1600 g / h, and hafnium source at 0 to form a tantalum carbide coating; and the overall gas flow time is 4-6 hours.

[0040] Those skilled in the art can reasonably adjust the aeration rate of each substance according to the overall processing volume of the material. The core is to continuously introduce carbon and tantalum sources, while gradually reducing the chromium source from the initial amount to 0, so as to form a process layer containing chromium carbide in the middle and a tantalum carbide coating without chromium carbide on the outermost layer.

[0041] (3) The graphite device is placed in a high-temperature chamber for preheating. The preheating temperature in the high-temperature chamber is 1900-2500℃. Then, the mixed gas is sent into a high-temperature plasma flame for pyrolysis. The center temperature of the high-temperature plasma flame is ≥5700℃ and the edge temperature is ≥2600℃. Ultrafine tantalum powder and carbon powder are generated. The generated ultrafine tantalum powder and carbon powder are deposited on the surface of the graphite device and react on the surface of the graphite device to generate tantalum carbide, which is attached to the surface of the graphite substrate. The thickness of the tantalum carbide coating is 40-60μm.

[0042] (4) The graphite device is cooled at a cooling rate of 5℃ / min to obtain a graphite device with a tantalum carbide coating on the surface.

[0043] In this invention, the flow rate and time of HfCl4 entering the mixing pipe are controlled. Initially, the flow rate of HfCl4 is high, and it gradually decreases over time. HfCl4 is only introduced for a short period of time in the initial stage, so that the part of the transition layer in contact with the graphite device is a composite layer with a high HfCl4 content. Along the surface of the graphite device outward, the hafnium carbide concentration is set in a gradient. In the subsequent stage, the HfCl4 content drops to 0, and the tantalum carbide coating begins to form.

[0044] In this invention, the innermost layer of the coating near the graphite device contains 8-10 wt% hafnium carbide, and the hafnium carbide content gradually decreases to 0 from the inner layer of the coating outward, forming a hafnium carbide doped transition layer with a gradient concentration decreasing. Specifically, the thickness of the hafnium carbide doped gradient transition layer is 0.1-10 μm, preferably 1-3 μm.

[0045] <Example>

[0046] Example 1

[0047] 2 kg TaCl5, 4 kg chlorinated paraffin, and 0.08 kg HfCl4 were placed in separate vaporization chambers and vaporized. The vaporized precursors were then fed into a mixing pipe to be mixed to form a precursor gas.

[0048] The above-mentioned well-mixed precursor gas is sent into a high-temperature plasma flame for pyrolysis using Ar carrier gas, and the pyrolysis generates components such as Ta, Hf, C, and Cl2 gas.

[0049] During this period, the flow rate of Ar was controlled at 30 L / h; the flow rate of HfCl4 was reduced from an initial flow rate of 160 g / h to 0 at a rate of 160 g / h, while the remaining mixed gas was uniformly and stably ventilated at a flow rate of 400 g / h for TaCl5 and 800 g / h for chlorinated paraffin for 4 hours.

[0050] The ultrafine powder generated by pyrolysis includes Ta, Hf, and C, with a particle size controlled in the range of 3-10 μm. It settles onto the surface of a graphite device that has been placed in a high-temperature chamber at 2200℃. The settled powder generates a tantalum carbide film through in-situ reaction and adheres to the graphite substrate, forming a tantalum carbide coating of about 60 μm.

[0051] A graphite substrate with an attached tantalum carbide film is cooled to room temperature at a rate of 5°C / min to obtain a graphite device with a tantalum carbide coating.

[0052] Example 2

[0053] 2 kg TaCl5, 4 kg chlorinated paraffin, and 0.10 kg HfCl4 were placed in separate vaporization chambers and vaporized. The vaporized precursors were then fed into a mixing pipe to mix and form a precursor gas.

[0054] The above-mentioned well-mixed precursor gas is sent into a high-temperature plasma flame for pyrolysis using Ar carrier gas, and the pyrolysis generates components such as Ta, Hf, C, and Cl2 gas.

[0055] During this period, the flow rate of Ar was controlled at 30 L / h; the flow rate of HfCl4 was reduced from an initial flow rate of 160 g / h to 0 at a rate of 160 g / h, while the remaining mixed gas was uniformly and stably ventilated at a flow rate of 400 g / h for TaCl5 and 800 g / h for chlorinated paraffin for 4 hours.

[0056] The ultrafine powder generated by pyrolysis includes Ta, Hf, and C, with a particle size controlled in the range of 3-10 μm. It settles onto the surface of a graphite device that has been placed in a high-temperature chamber at 2400℃. The settled powder generates a tantalum carbide film through in-situ reaction and adheres to the graphite substrate, forming a tantalum carbide coating of about 52 μm.

[0057] A graphite substrate with an attached tantalum carbide film is cooled to room temperature at a rate of 5°C / min to obtain a graphite device with a tantalum carbide coating.

[0058] Example 3

[0059] 1.6 kg TaCl5, 3.2 kg chlorinated paraffin, and 0.06 kg HfCl4 were placed in separate vaporization chambers and vaporized. The vaporized precursors were then fed into a mixing pipe to mix and form a precursor gas.

[0060] The above-mentioned well-mixed precursor gas is sent into a high-temperature plasma flame for pyrolysis using Ar carrier gas, and the pyrolysis generates components such as Ta, Hf, C, and Cl2 gas.

[0061] During this period, the flow rate of Ar was controlled at 30 L / h; the flow rate of HfCl4 was reduced from an initial flow rate of 150 g / h to 0 at a rate of 150 g / h, while the remaining mixed gas was uniformly and stably ventilated at a flow rate of 400 g / h for TaCl5 and 800 g / h for chlorinated paraffin for 4 hours.

[0062] The ultrafine powder generated by pyrolysis includes Ta, Hf, and C, with a particle size controlled in the range of 3-10 μm. It settles onto the surface of a graphite device that has been placed in a high-temperature chamber at 2200℃. The settled powder generates a tantalum carbide film through in-situ reaction and adheres to the graphite substrate, forming a tantalum carbide coating of about 36 μm.

[0063] A graphite substrate with an attached tantalum carbide film is cooled to room temperature at a rate of 5°C / min to obtain a graphite device with a tantalum carbide coating.

[0064] Example 4

[0065] 1.8 kg TaCl5, 3.6 kg chlorinated paraffin, and 0.06 kg HfCl4 were placed in separate vaporization chambers and vaporized. The vaporized precursors were then fed into a mixing pipe to mix and form a precursor gas.

[0066] The above-mentioned well-mixed precursor gas is sent into a high-temperature plasma flame for pyrolysis using Ar carrier gas, and the pyrolysis generates components such as Ta, Hf, C, and Cl2 gas.

[0067] During this period, the flow rate of Ar was controlled at 30 L / h; the flow rate of HfCl4 was reduced from an initial flow rate of 165 g / h to 0 at a rate of 165 g / h; and the remaining mixed gas was uniformly and stably ventilated at a flow rate of 360 g / h for TaCl5 and 700 g / h for 4 hours.

[0068] The ultrafine powder generated by pyrolysis includes Ta, Hf, and C, with a particle size controlled in the range of 3-10 μm. It settles onto the surface of a graphite device that has been placed in a high-temperature chamber at 2200℃. The settled powder generates a tantalum carbide film through in-situ reaction and adheres to the graphite substrate, forming a tantalum carbide coating of about 32 μm.

[0069] A graphite substrate with an attached tantalum carbide film is cooled to room temperature at a rate of 10 °C / min to obtain a graphite device with a tantalum carbide coating.

[0070] Example 5

[0071] 1.8 kg TaCl5, 3.6 kg chlorinated paraffin, and 0.065 kg HfCl4 were placed in separate vaporization chambers and vaporized. The vaporized precursors were then fed into a mixing pipe to mix and form a precursor gas.

[0072] The above-mentioned well-mixed precursor gas is sent into a high-temperature plasma flame for pyrolysis using Ar carrier gas, and the pyrolysis generates components such as Ta, Hf, C, and Cl2 gas.

[0073] During this period, the flow rate of Ar was controlled at 30 L / h; the flow rate of HfCl4 was reduced from an initial flow rate of 165 g / h to 0 at a rate of 165 g / h; and the remaining mixed gas was uniformly and stably ventilated at a flow rate of 410 g / h for TaCl5 and 820 g / h for 4 hours.

[0074] The ultrafine powder generated by pyrolysis includes Ta, Hf, and C, with a particle size controlled in the range of 3-10 μm. It settles onto the surface of a graphite device that has been placed in a high-temperature chamber at 2200℃. The settled powder generates a tantalum carbide film through in-situ reaction and adheres to the graphite substrate, forming a tantalum carbide coating of about 45 μm.

[0075] A graphite substrate with an attached tantalum carbide film was cooled to room temperature at a rate of 6 °C / min to obtain a graphite device with a tantalum carbide coating.

[0076] Example 6

[0077] 2.4 kg TaCl5, 4.8 kg chlorinated paraffin, and 0.12 kg HfCl4 were placed in separate vaporization chambers and vaporized. The vaporized precursors were then fed into a mixing pipe to mix and form a precursor gas.

[0078] The above-mentioned well-mixed precursor gas is sent into a high-temperature plasma flame for pyrolysis using Ar carrier gas, and the pyrolysis generates components such as Ta, Hf, C, and Cl2 gas.

[0079] During this period, the flow rate of Ar was controlled at 30 L / h; the flow rate of HfCl4 was reduced from an initial flow rate of 120 g / h to 0 at a rate of 120 g / h; and the remaining mixed gas was uniformly and stably ventilated at a flow rate of 500 g / h for TaCl5 and 1000 g / h for chlorinated paraffin for 5 hours.

[0080] The ultrafine powder generated by pyrolysis includes Ta, Hf, and C, with a particle size controlled in the range of 3-10 μm. It settles onto the surface of a graphite device that has been placed in a high-temperature chamber at 2200℃. The settled powder generates a tantalum carbide film through in-situ reaction and adheres to the graphite substrate, forming a tantalum carbide coating of about 65 μm.

[0081] A graphite substrate with an attached tantalum carbide film was cooled to room temperature at a rate of 12 °C / min to obtain a graphite device with a tantalum carbide coating.

[0082] <Comparative Example>

[0083] Comparative Example 1

[0084] (1) The graphite device is placed in the reaction chamber and the graphite substrate is fixed by a fixing bracket made of molded graphite with tantalum carbide coating. Then the reaction chamber is heated to 2200℃. The heating rate during the heating process is 9.2℃ / min.

[0085] (2) 1 kg of solid tantalum pentachloride powder is loaded into the gasification chamber for gasification to form gaseous tantalum pentachloride. The temperature of the gasification chamber is 160℃ and the pressure is 50 kPa.

[0086] (3) Gaseous tantalum pentachloride (99.99% purity) is introduced into the reaction chamber using argon gas, while hydrogen gas is simultaneously introduced into the vaporization chamber to react and form a tantalum carbide coating on the graphite substrate surface. The flow rate of the mixed gas consisting of gaseous tantalum pentachloride and the carrier is 2 L / min, and the flow rate of hydrogen gas is 1 L / min. The molar ratio of gaseous tantalum pentachloride, hydrogen, and argon gas in the reaction chamber is 3:5:4, the reaction temperature is 2200℃, the reaction pressure is 100 mmHg, and the reaction time in the reaction chamber is 6 h.

[0087] (4) After the reaction is complete, start cooling at a rate of 1.7℃ / min (without any auxiliary means, the temperature will drop from 2200℃ to room temperature in about 24 hours). After the temperature drops to room temperature, open the furnace lid.

[0088] (5) Change the position of the fixed support to expose its contact with the graphite matrix, and then repeat the above steps (1) to (4), wherein the reaction time in the reaction chamber in (3) is 2h, and other parameters are not changed.

[0089] Comparative Example 2

[0090] (1) The graphite device that has been calcined and surface treated is placed in a CVD high-temperature furnace, and then the reaction chamber is heated to 2200℃. The heating rate during the heating process is 9℃ / min, and the pressure of the reaction chamber during the heating process is 400Pa.

[0091] (2) 1 kg of solid tantalum pentachloride powder is loaded into the gasification chamber for gasification to form gaseous tantalum pentachloride. The temperature of the gasification chamber is 150℃ and the pressure is 60 kPa.

[0092] (3) Gaseous tantalum pentachloride (99.99% purity) was introduced into the reaction chamber using argon gas, while a mixture of hydrogen and methane (9:2 molar ratio) was simultaneously introduced into the vaporization chamber to form a tantalum carbide coating on the graphite substrate. The flow rate of the gas mixture consisting of gaseous tantalum pentachloride and the support was 5 L / min, and the flow rate of hydrogen was 2 L / min. The reaction temperature was 2200℃, the reaction pressure was 10 kPa, and the reaction time in the reaction chamber was 72 h.

[0093] (4) After the reaction is complete, start cooling at a rate of 1.7℃ / min. After cooling to room temperature, open the furnace lid.

[0094] (5) Change the position of the fixed support to expose its contact point with the graphite matrix, and then repeat steps (1) to (4) above. In step (3), the reaction time in the reaction chamber is 24 hours, and other parameters are not changed.

[0095] (6) Cool the graphite substrate with tantalum carbide film attached to room temperature at a rate of 3℃ / min to obtain a graphite device with tantalum carbide coating.

[0096] <Experimental Example>

[0097] Samples: Examples 1-6, Comparative Examples 1-2

[0098] (1) Electron microscopy scanning experiment

[0099] like Figure 1 Here is an electron microscope image of the tantalum carbide coating on the surface of the graphite device in Example 1, as shown. Figure 2 This is an electron microscope image of the tantalum carbide coating on the surface of the graphite device in Example 6. Figure 1 and Figure 2 It can be seen that the tantalum carbide coating on the surface of the graphite device can bond tightly with the graphite device, reducing the risk of coating peeling off.

[0100] (2) Coating temperature resistance test

[0101] Take graphite device samples with tantalum carbide coatings on the surface prepared in Examples 1-6 and Comparative Examples 1-2 respectively, place them in a high-temperature vacuum furnace, heat them to 2000°C within 5 minutes, and then cool them to below 100°C. Repeat the above heating and cooling process 3 times and record the damage to the coating on the surface of the graphite device.

[0102] The graphite device sample was then placed in a liquid nitrogen container from room temperature and left to stand for 1 minute. After being removed, it was left to stand at room temperature for 1 minute. This process was repeated 3 times, and the extent of damage to the coating on the surface of the graphite device was recorded.

[0103] Among them, the rapid heating shock resistance level refers to the number of times a sample can remain unbroken after being placed in a temperature difference of 2000℃ and room temperature alternately. "A" means more than 100 times, "B" means more than 50 times and less than 100 times, and "C" means less than 50 times.

[0104] The binding strength resistance to extreme cold shock rating refers to the number of times a sample can remain intact after being placed in a liquid nitrogen container and then in a temperature difference of room temperature, alternating between the two. "A" means it can withstand 10 or more extreme cold shocks, "B" means it can withstand 5-10 extreme cold shocks, and "C" means it can withstand less than 5 extreme cold shocks.

[0105] The above experimental results are summarized and recorded in Table 1 below:

[0106] Table 1. Damage to the coatings of different graphite devices under different conditions.

[0107]

[0108] The withstand performance under specific conditions (the time it takes for the rod to break under a flow rate of 2 liters per minute of ammonia gas at 1700℃ and 50 Pa pressure) is divided into three different levels:

[0109] Grade A: Withstands 20 hours without breakage;

[0110] Grade B: Failure within 20 hours;

[0111] Grade C: Failure within 10 hours.

[0112] As shown in Table 1 above, the tantalum carbide coating on the surface of the graphite device prepared by Examples 1-2 has a significantly lower degree of damage under harsh environments such as extremely high temperature and extremely low temperature than the tantalum carbide coating on the graphite device prepared by Comparative Examples 1-2. This indicates that the preparation process of the tantalum carbide coating on the surface of the graphite device proposed in this invention can make the surface coating have significantly better temperature resistance.

[0113] (3) Fracture tolerance test of graphite devices:

[0114] Tantalum carbide coatings were prepared on the surface of cylindrical graphite devices using the methods of Examples 1-2 and Comparative Examples 1-2, respectively. The graphite devices had a diameter of 3 mm and a length of 100 mm. These cylindrical graphite devices were placed in a high-temperature environment of 50 Pa and 1700 °C, with ammonia gas introduced at a flow rate of 2 L / min. The fracture tolerance time of the cylindrical graphite devices was recorded and summarized in Table 2 below.

[0115] Table 2. Fracture resistance of tantalum carbide coatings on different round bar graphite devices

[0116] Tolerance Example 1 A Example 2 A Example 3 B Example 4 A Example 5 A Example 6 B Comparative Example 1 C Comparative Example 2 B

[0117] As shown in Table 2 above, compared with the graphite devices with tantalum carbide coatings prepared by the method of Comparative Examples 1-2, the method of Examples 1-2 to prepare tantalum carbide coatings on the surface of graphite devices can make the coated graphite device materials have a significantly stronger ability to maintain material integrity in extremely high or low temperature environments, that is, it has more outstanding extreme temperature resistance performance overall.

[0118] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A tantalum carbide composite coating, characterized in that, Along the substrate surface from the inside out, there is a transition layer and a tantalum carbide coating. The transition layer is composed of tantalum carbide and hafnium carbide, with hafnium carbide accounting for 0-10 wt% of the transition layer. The innermost layer of the coating near the graphite substrate contains 8-10 wt% hafnium carbide. From the inner layer of the coating outward, the hafnium carbide content gradually decreases to 0, forming a hafnium carbide doped transition layer with a gradient concentration decreasing.

2. The tantalum carbide composite coating of claim 1, wherein, The transition layer thickness is 5-20μm, and the tantalum carbide coating thickness is 30-65μm.

3. A method for preparing the tantalum carbide composite coating by pyrolysis and in-situ formation according to claim 1, characterized in that, Includes the following steps: S1 Raw material vaporization: Tantalum source, carbon source and hafnium source are vaporized respectively to form vaporized tantalum source, vaporized carbon source and vaporized hafnium source; S2 Mixed precursor gas; Vaporized tantalum source, vaporized carbon source and vaporized hafnium source are fed into the mixing pipe at different flow rates using hydrogen or rare gas, and mixed to obtain mixed precursor gas; S3 Preparation of tantalum carbide coating: First, the substrate material is placed in the reaction chamber for preheating. Then, the mixed precursor gas is pyrolyzed by plasma flame, settled onto the surface of the substrate material, and cooled to obtain the tantalum carbide coating on the surface of the substrate material.

4. The method of claim 3, wherein the method is characterized by, In step S3, the preheating temperature is 1900-2500℃.

5. The method of claim 4, wherein the method is characterized by: During pyrolysis, the temperature should be controlled at ≥2600℃.

6. The method according to any one of claims 3 to 5, c h a r a c t e r i s e d b y In step S1, the mass ratio of tantalum source, carbon source and hafnium source is 1:2:0.02-0.

06.

7. The method of claim 6, wherein the method is characterized by, In step S2, during the initial gas flow, the gas flow rate of the tantalum source is controlled at 300-800 g / h, the gas flow rate of the carbon source is 600-1600 g / h, and the gas flow rate of the hafnium source is 100-180 g / h to form a transition layer.

8. The method of claim 7, wherein the method is characterized by, In step S2, during the later stage of ventilation, the gas flow rate of the tantalum source is controlled to be 300-800 g / h, and the gas flow rate of the carbon source is controlled to be 600-1600 g / h, to form a tantalum carbide coating.

9. The method of claim 8, wherein the method is characterized by, In step S2, the flow rate of hydrogen or rare gas is controlled to be 20-50 L / h.

10. The method of claim 8, wherein the method is characterized by, Ventilation time is 4-6 hours.

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