Apparatus and Control Method for Preparing Graphite-Based Tantalum Carbide Coatings

Abstract

This invention discloses an apparatus and control method for preparing graphite-based tantalum carbide coatings. The apparatus includes a vacuum sintering furnace and a rotating system. The interior space of the vacuum sintering furnace forms a reaction chamber. The rotating system includes a graphite disk, a motor, and connecting components. The graphite disk is disposed within the reaction chamber of the vacuum sintering furnace. N receiving spaces for accommodating the graphite substrate are defined on the inner sidewall of the graphite disk. These receiving spaces are evenly distributed on the inner sidewall of the graphite disk, and a clamping component for fixing the graphite substrate is connected to the upper edge of each receiving space. The motor is mounted on the outer sidewall of the vacuum sintering furnace and is electrically connected to the control system of the vacuum sintering furnace. The connecting components penetrate the sidewall of the vacuum sintering furnace, with one end fixedly connected to the outer sidewall of the graphite disk and the other end fixedly connected to the output end of the motor. This invention can reduce the coefficient of thermal expansion between the coating and the substrate, increase the bonding force, improve the density of the coating, and solve the technical problems of cracks and pores in the coating.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to an apparatus and control method for preparing a graphite-based tantalum carbide coating. Background Technology

[0002] Related technologies indicate that during the growth of third-generation semiconductor silicon carbide crystals, the growth interface environment differs between the crystal's axial center and edges, leading to increased crystal yield at the edges. Furthermore, defects are easily generated at the crystal edges due to the influence of graphite. Additionally, to achieve further diameter expansion of silicon carbide crystals, controlling the crystallization quality at the edges becomes particularly crucial as the crystal diameter and thickness increase.

[0003] In the industry, tantalum carbide coatings are commonly used to address the crystal quality issues at the aforementioned edges. Currently, the main methods for applying tantalum carbide coatings to third-generation semiconductor graphite components are chemical vapor deposition (CVD) and high-temperature curing sintering. The CVD method for preparing TaC coatings requires the source material TaCl5. TaCl5 vaporizes at 500K, and the vaporized TaCl5 is poured into the CVD furnace as a gas source, where it is deposited along with other introduced reducing atmospheres to form TaC. The reaction process is as follows:

[0004] TaCl5+C m H n +H2→TaC+HCl+H2

[0005] When using CVD to prepare TaC coatings, the process control is good and the coating composition and structure can be designed. However, due to the presence of residual thermal stress, the prepared coating is prone to cracking. Moreover, Ta2C is easily generated during TaC deposition. In addition, the requirements for equipment performance and maintenance are relatively strict, and the preparation cost is high.

[0006] The high-temperature curing and sintering method involves adding activators and binders to TaC powder, applying it to the surface of a graphite matrix material for curing, and then sintering it at high temperature. This method has a lower cost, but the coating after sintering has poor density, and the coating is prone to leaving pores after the activators and binders escape. Summary of the Invention

[0007] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention provides an apparatus for preparing a graphite-based tantalum carbide coating, which can improve coating efficiency, reduce costs, reduce the coefficient of thermal expansion between the coating and the substrate, increase adhesion, improve coating density, and solve the technical problems of cracks and pores in the coating.

[0008] The present invention also proposes a method for controlling the apparatus for preparing graphite-based tantalum carbide coatings using the above-described device.

[0009] An apparatus for preparing a graphite-based tantalum carbide coating according to a first aspect of the present invention includes a vacuum sintering furnace and a rotating system. The interior space of the vacuum sintering furnace forms a reaction chamber. The rotating system includes a graphite disk, a motor, and connecting components. The graphite disk is disposed within the reaction chamber. N receiving spaces for accommodating a graphite substrate are defined on the inner sidewall of the graphite disk. The receiving spaces are evenly distributed on the inner sidewall of the graphite disk. The relationship between the depth d1 of the receiving space and the height or depth d2 of the graphite substrate is: 1 / 2*d2≤d1≤2 / 3*d2. A clamping component for fixing the graphite substrate is connected to the outer edge of each receiving space. The motor is installed on the outer sidewall of the vacuum sintering furnace. The motor is electrically connected to the control system of the vacuum sintering furnace. The connecting components penetrate the sidewall of the vacuum sintering furnace, with one end fixedly connected to the outer sidewall of the graphite disk and the other end fixedly connected to the output end of the motor. In this solution, a mixture of tantalum carbide powder is placed inside a graphite substrate. A space is used to hold the graphite substrate. After the entire graphite substrate is placed in the space, a clamping device fixes it to a graphite disk. A motor is then started, causing the graphite disk to rotate, which in turn causes the graphite substrate to rotate continuously. The tantalum carbide powder mixture rolls inside the graphite substrate and, under strong centrifugal force, continuously impacts the inner wall of the graphite substrate, accumulating and penetrating to the surface of the inner wall, forming a tantalum carbide coating. This increases the bonding force between the graphite substrate and the tantalum carbide coating, solving the defects of poor coating density after high-temperature curing sintering and the tendency for pores to remain in the coating after the activator and binder overflow. Simultaneously, it improves coating efficiency and quality.

[0010] The method for controlling the apparatus for preparing a graphite-based tantalum carbide coating according to the second aspect of the present invention is as follows:

[0011] In the first stage, a tantalum carbide mixture is loaded into a graphite matrix. After installing the graphite cap, the graphite matrix is ​​placed into the receiving space and clamped and fixed in the receiving space by clamping components. The vacuum sintering furnace control system controls the vacuum system to evacuate the reaction chamber to 1.22-1.32 Pa, and high-purity argon gas is introduced into the reaction chamber through the gas supply pipe. The vacuum is then evacuated to below 5 Pa, and this process is repeated M times. When the set amount of argon gas has been introduced, the gas supply pipe is closed. Finally, high-purity argon gas is introduced into the reaction chamber through the gas supply pipe to maintain the pressure in the reaction chamber at 45-65 Pa. Afterward, the vacuum sintering furnace control system controls the motor of the rotating system to work and controls the motor speed to 400-600 r / min. At the same time, the vacuum sintering furnace control system controls the resistance heater to work, and the temperature measuring gun monitors the temperature in the reaction chamber in real time through the temperature measuring tube.

[0012] This stage lasts for 168-200 hours, with the temperature of the reaction chamber maintained at 50-60℃. In the last 50 hours of this stage, the control system controls the resistance heater to slowly raise the temperature of the reaction chamber to 1650-1950℃, with a heating rate of 50℃ / min or less.

[0013] In the second stage, high-purity hydrogen gas is introduced into the reaction chamber through a gas pipeline at a flow rate of 5-7 sccm. The pressure in the reaction chamber is controlled at 150-200 Pa, and the temperature of the reaction chamber is heated to 2250-2280℃ within 5 hours. At the same time, the control system controls the motor speed to drop to 0 and then maintains the temperature for 50 hours. At this temperature, sintering treatment is carried out on the graphite substrate to coat its inner wall with tantalum carbide coating.

[0014] In the third stage, the cooling rate is controlled at 50℃ / min or below to cool the temperature to 1600-1800℃. At the same time, the pressure in the reaction chamber is increased to 300Pa. This process condition is maintained for 6-8 hours, while the hydrogen flow rate is still controlled at 5-7 sccm. After that, the cooling rate is controlled at 50℃ / min or below to reduce the temperature to 1200-1600℃, and the high-purity hydrogen is shut off. At this time, the hydrogen flow rate is 0 sccm. Finally, the cooling rate is controlled at 50℃ / min or below to cool the temperature in the reaction chamber to below 800℃, and the pressure is increased to 1.5 kPa. At the same time, the argon flow rate is increased to 7000 sccm. After cooling with the furnace for 48 hours, the furnace is opened and samples are taken. At this time, the inner wall of the graphite matrix is ​​coated with tantalum carbide, completing the preparation of the graphite-based tantalum carbide coating.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1) This invention uses centrifugal force to press a tantalum carbide mixture onto the inner wall of a graphite matrix. Under the action of strong centrifugal force, the tantalum carbide mixture continuously impacts the inner wall of the graphite matrix, accumulates and penetrates to the surface layer of the inner wall of the graphite matrix to form a tantalum carbide coating. This increases the bonding force between the graphite matrix and the tantalum carbide coating, and solves the defects such as poor coating density after high-temperature curing sintering and easy pores left in the coating after the activator and binder overflow. At the same time, it improves coating efficiency and reduces the production cost of enterprises.

[0017] 2) This invention utilizes the physical and mechanical principle of collision and extrusion to effectively improve the bonding force between the graphite matrix and the tantalum carbide coating, partially offsetting the cracking caused by the inherent thermal expansion coefficient problem between the graphite part and the coating.

[0018] 3) This invention solves the defects of residual thermal stress leading to cracks or the formation of Ta2C during carbonization during the preparation of tantalum carbide coatings, effectively improving the quality of graphite-based tantalum carbide coatings. Furthermore, this invention has low equipment performance requirements, low equipment manufacturing costs, and is easy to maintain, further effectively reducing enterprise production costs.

[0019] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the apparatus for preparing a graphite-based tantalum carbide coating according to an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the rotating system of an apparatus for preparing a graphite-based tantalum carbide coating according to an embodiment of the present invention;

[0022] Figure 3 yes Figure 2 Side view;

[0023] Figure 4 This is an XRD analysis image of a graphite-based tantalum carbide coating prepared using the apparatus for preparing graphite-based tantalum carbide coatings according to an embodiment of the present invention.

[0024] Figure 5 This is a cross-sectional SEM image of a graphite-based tantalum carbide coating prepared using the apparatus for preparing graphite-based tantalum carbide coatings according to an embodiment of the present invention.

[0025] Figure 6 This is a surface SEM image of a graphite-based tantalum carbide coating prepared by the apparatus for preparing graphite-based tantalum carbide coating according to an embodiment of the present invention.

[0026] Figure 7 yes Figure 6 EDS image of the coating at point 1 in the middle;

[0027] Figure 8 yes Figure 6 EDS image of the coating at point 2 in the middle;

[0028] Figure 9 This is a schematic diagram of the standard Gibbs free energy of TaC formed at 1400-2600℃. Attached image description:

[0030] 100: Apparatus for preparing graphite-based tantalum carbide coatings;

[0031] 10: Vacuum sintering furnace; 11: Resistance heater; 12: Furnace body; 13: Pressure gauge;

[0032] 20: Motor; 21: Graphite disk; 22: Connecting component;

[0033] 30: Graphite crucible; 31: Tantalum carbide raw material powder; 32: Tantalum sphere; 33: Graphite lid;

[0034] 40: Temperature gun; 41: Stand; 42: Temperature tube;

[0035] 50: Stove frame;

[0036] 60: Gas pipeline:

[0037] 71: Graphite ring; 72: Graphite bolt. Detailed Implementation

[0038] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0039] The following disclosure provides numerous different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples. Such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. Additionally, examples of various specific processes and materials are provided in this invention; however, those skilled in the art will recognize the applicability of other processes and / or the use of other materials.

[0040] The following is for reference. Figures 1 to 9An apparatus 100 for preparing a graphite-based tantalum carbide coating according to an embodiment of the present invention is described, comprising a vacuum sintering furnace 10 and a rotating system. The rotating system includes a graphite disk 21, a motor 20, and a connecting component 22. The graphite disk 21 is disposed in the reaction chamber of the vacuum sintering furnace 10. N receiving spaces for accommodating graphite crucibles 30 are defined on the inner sidewall of the graphite disk 21. The receiving spaces are evenly distributed on the inner sidewall of the graphite disk 21. The relationship between the depth d1 of the receiving space and the height or depth d2 of the graphite crucible 30 is: 1 / 2*d2≤d1≤2 / 3*d2. Each receiving space is connected to a clamping component for fixing the graphite crucible 30 at its outer edge. The motor 20 is mounted on the outer sidewall of the vacuum sintering furnace 10. The motor 20 is electrically connected to the control system of the vacuum sintering furnace 10. The connecting component 22 penetrates the sidewall of the vacuum sintering furnace 10, with one end fixedly connected to the outer sidewall of the graphite disk 21 and the other end fixedly connected to the output end of the motor 20. In this embodiment, the graphite crucible 30 is taken as an example. The connecting component 22 can be a connecting shaft. One end of the connecting shaft is threadedly fixed to the graphite disk 21, and the other end is fixedly connected to the output end of the motor 20. The motor 20 drives the graphite disk 21 to rotate through the connecting shaft.

[0041] refer to Figure 2 and Figure 3 As shown, in some embodiments, the accommodating space of the present invention is cylindrical, matching the graphite crucible. The clamping components include a graphite ring 71 and graphite bolts 72. The diameter of the graphite ring 71 is slightly larger than the diameter of the accommodating space. The graphite ring 71 is located at the opening of the accommodating space, fixedly connected to the inner sidewall of the graphite disk 21, and coaxially arranged with the accommodating space. At least three graphite bolts 72 are provided, preferably four, evenly distributed on the sidewall of the graphite ring 71, penetrating the graphite ring 71, and threadedly connected to the graphite ring 71. In use, the graphite crucible is first placed in the accommodating space, and then the graphite bolts 72 are tightened inward, so that the ends of the four graphite bolts 72 are pressed against the sidewall of the graphite crucible, thereby fixing the graphite crucible.

[0042] Of course, the clamping component can also be other structures capable of clamping and fixing the graphite crucible. For example, the clamping component may include at least three sets of graphite clamps and graphite bolts 72. The three sets of graphite clamps are evenly distributed on the outer edge of the receiving space and fixedly installed on the graphite disk 21. The sidewalls of the three sets of graphite clamps are all perforated with graphite bolts 72 for clamping the graphite crucible, and the graphite bolts 72 are threadedly connected to the graphite clamps. To clamp the graphite crucible more securely, this embodiment preferably has four sets of graphite clamps evenly distributed at the upper edge of the receiving space to ensure that the graphite crucible will not come out of the receiving space due to strong centrifugal force when rotating. Specifically, after the graphite crucible is placed into the receiving space, the graphite bolts 72 on the graphite clamps are tightened, so that the part of the graphite crucible exposed outside the receiving space is clamped by the four graphite bolts 72 around it.

[0043] refer to Figure 1 As shown, in some embodiments of the present invention, two sets of rotating systems are provided and arranged symmetrically. Furthermore, to improve the efficiency of preparing tantalum carbide coatings on graphite crucibles, in some embodiments, four receiving spaces for accommodating graphite crucibles can be opened on the inner sidewall of the graphite disk 21 of each rotating system. In actual use, the two graphite disks 21 can simultaneously prepare tantalum carbide coatings on the inner walls of eight graphite crucibles, greatly improving the efficiency of coating preparation.

[0044] In this embodiment, the coefficient of thermal expansion of the eight graphite crucibles is preferably 7.0 × 10⁻⁶. -6 ~8.0×10 -6 / K, this range corresponds to the coefficient of thermal expansion of tantalum carbide (6.9 × 10⁻⁶). -6 ~7.8×10 -6 The coefficient of thermal expansion (C / K) is close to that of tantalum carbide. If the C / K coefficient is too large or too small, the difference between it and the C / K coefficient of tantalum carbide will increase, easily generating large tensile or compressive stresses. This results in poor coating density and porosity, leading to larger tensile or compressive stresses. Furthermore, the density of the graphite crucible is preferably around 1.52–2.0 g / cm³. Under these conditions, graphite is porous. In this embodiment, the porosity of the graphite crucible is preferably 1.5 g / cm³. μ At this point, it is beneficial for tantalum to penetrate into the surface of the graphite crucible during the reaction process, and the resulting tantalum carbide coating can be more firmly and tightly bonded to the graphite crucible.

[0045] refer to Figure 1As shown, in some embodiments of the present invention, the vacuum sintering furnace 10 mainly consists of a furnace body 12, a pressure gauge 13, a resistance heater 11, a temperature measuring gun 40, a gas supply pipe 60, a vacuum system, and a furnace frame 50. The internal space of the furnace body 12 forms a reaction chamber. During operation, the gas supply pipe 60 at the bottom of the reaction chamber supplies a mixture of hydrogen and argon gas. The pressure gauge 13 is installed on the top wall of the furnace body 12 to monitor the pressure inside the reaction chamber. The pressure gauge 13 is connected to the control system of the vacuum sintering furnace 10. The resistance heaters 11 are symmetrically installed at the top and bottom of the reaction chamber. The heater 11 is electrically connected to the control system of the vacuum sintering furnace 10. The resistance heater 11 is used to provide heating conditions for the reaction chamber. The temperature measuring gun 40 is installed outside the vacuum sintering furnace 10 through the bracket 41. The temperature measuring tube 42 passes through the side wall of the vacuum sintering furnace 10 opposite to the temperature measuring gun 40. In other words, the temperature measuring tube 42 passes through the side wall of the vacuum sintering furnace 10 and is fixed to the side wall of the vacuum sintering furnace 10. The axes of the temperature measuring gun 40 and the temperature measuring tube 42 are on the same straight line, so that the temperature measuring gun 40 can monitor the temperature in the reaction chamber through the temperature measuring tube 42. The gas inlet of the gas pipe 60 is connected to the process gas pipeline, and its outlet is connected to the reaction chamber. In this embodiment, the gas pipe 60 is connected to the hydrogen process gas pipeline and the argon process gas pipeline respectively. The vacuum system's pumping end is connected to the reaction chamber, and its outlet is connected to the tail gas treatment system. The vacuum system is electrically connected to the control system of the vacuum sintering furnace 10. The furnace body 12 is installed on the furnace frame 50. The furnace wall of the vacuum sintering furnace 10 is a hollow structure, and its interior is filled with cooling water to form a cold water system.

[0046] Based on the above device, the specific control method of this embodiment is as follows (the graphite crucible 30 in this embodiment is taken as an example):

[0047] In the first stage, the tantalum carbide mixture is loaded into a graphite crucible. After installing the graphite cap 33, the graphite crucible is placed into the receiving space and clamped and fixed in the receiving space by clamping components. The vacuum system of the vacuum sintering furnace 10 controls the vacuum system to evacuate the reaction chamber to 1.22-1.32 Pa, preferably 1.28 Pa, and high-purity argon gas is introduced into the reaction chamber through the gas supply pipe 60 to fill it. The vacuum is then reduced to below 5 Pa, and this process is repeated 3 times. After the set amount of argon gas has been introduced, the gas supply pipe is closed. 60. Finally, high-purity argon gas is introduced into the reaction chamber through the gas supply pipe 60 to maintain the pressure in the reaction chamber at 45-65 Pa, preferably 50 Pa. Then, the control system of the vacuum sintering furnace 10 (hereinafter referred to as the "control system") controls the operation of the motor 20 of the rotating system and controls the speed of the motor 20 to 400-600 r / min, preferably 550 r / min. At the same time, the control system controls the operation of the resistance heater 11, and the temperature measuring gun 40 monitors the temperature in the reaction chamber in real time through the temperature measuring tube 42.

[0048] This stage lasts for 168-200 hours, preferably 180 hours, with the temperature of the reaction chamber maintained at 50-60°C, preferably 50°C. During the last 50 hours of this stage, the control system controls the resistance heater 11 to heat the temperature inside the reaction chamber to 1650-1950°C, preferably 1750°C, with the heating rate controlled at 50°C / min or less, preferably 20°C / min.

[0049] Specifically, if sintering is performed directly at 2250℃-2280℃ or above, preferably 2265℃, the effect of coating tantalum carbide onto the graphite crucible will be greatly reduced, or even no coating effect will appear. The sintered tantalum carbide will exist in the form of powder rather than film. However, this stage of the process allows the tantalum carbide mixture to easily obtain a tantalum carbide coating in the form of film rather than powder. Therefore, this stage of the process is very important and necessary.

[0050] The technical effect to be achieved in this stage is that after the reaction chamber reaches a certain temperature and pressure, the tantalum carbide mixed powder in the reaction chamber undergoes continuous force collisions with the inner wall of the graphite crucible under the action of tantalum balls 32, at a rotation speed of 400-600 r / min. In the initial stage of the process, the temperature is maintained at 50-60℃, and the flowing tantalum carbide mixed powder is in an adherent state, which further promotes the cold extrusion process between the tantalum carbide mixed powder particles and the porous graphite wall. Under continuous collisions, some of the tantalum carbide mixed powder penetrates into the surface of the graphite crucible through the porous graphite wall, providing a basis for the subsequent thermal reaction. In the last 50 hours of the first stage of the process, the temperature gradually rises to 1650-1950℃. Under heating conditions, a small portion of the powder that has penetrated into or mechanically welded into the surface of the graphite wall or deposited on the inner wall of the graphite crucible forms an initial deposit of a certain thickness. As the temperature increases, the reaction proceeds further. During this process, some of the tantalum that has penetrated the graphite wall reacts with the carbon in the graphite wall to form tantalum carbide. This forms an intermediate layer, similar to a transition layer between the graphite and the tantalum carbide coating, reducing the coefficient of thermal expansion between the two and providing adhesion for the subsequent coating. Therefore, the first stage of the process in this invention is particularly important. By appropriately combining the tantalum carbide mixed powder composition, temperature, pressure, gas flow rate, and processing time, the thickness of the initial reaction layer can be controlled.

[0051] In the second stage, high-purity hydrogen gas is introduced into the reaction chamber through the gas supply pipe 60 at a flow rate of 5-7 sccm, preferably 6 sccm. The pressure in the reaction chamber is controlled at 150-200 Pa, preferably 150.5 Pa, and the temperature of the reaction chamber is raised to 2250-2280℃, preferably 2265℃, within 5 hours. At the same time, the control system controls the speed of motor 20 to drop to 0, and then maintains the temperature for 50 hours. At this temperature, sintering treatment is carried out in the graphite crucible to coat its inner wall with tantalum carbide.

[0052] The technical effect to be achieved in this stage is to activate and convert the residual tantalum and carbon in the tantalum carbide mixed powder into tantalum carbide through this processing technology. The purpose of adding some tantalum carbide powder to the tantalum carbide mixed powder is to improve the crystallinity of tantalum carbide formed by tantalum and carbon. Specifically, firstly, after the first stage treatment, the pressure in the reaction chamber is reduced to about 150-200 Pa, preferably 150.5 Pa, with the rotation speed at zero. Then, a reducing atmosphere such as hydrogen or a mixture thereof is introduced at 5-7 sccm, preferably 6 sccm, to adjust the pressure in the reaction chamber to 150-200 Pa, preferably 150.5 Pa, while the reaction chamber is reheated. The temperature is slowly heated to 2250℃-2280℃ for 5 hours, and the treatment is carried out at this temperature for 50 hours. At this temperature, sintering is performed in a graphite crucible to coat its inner wall with a tantalum carbide coating.

[0053] To address the stress generated in the coating, in the third stage, the pressure in the reaction chamber is increased to 300 Pa, and the cooling rate is controlled at 50°C / min or less, preferably a heating rate of 20°C / min, to cool the temperature in the reaction chamber to 1600-1800°C, preferably 1750°C. This process is maintained for 6-8 hours, preferably 6.5 hours, while the hydrogen flow rate remains controlled at 5-7 sccm, preferably 6 sccm. Afterward, the cooling rate is controlled at 50°C / min or less, preferably a heating rate of 20°C / min, to lower the temperature to 1200-1600°C. The temperature is set at 1280-1550℃, more preferably 1300-1500℃. High-purity hydrogen gas is turned off, and the pressure in the reaction chamber is maintained at 300 Pa. At this time, the hydrogen gas flow rate is 0 sccm. Finally, the cooling rate is controlled at 50℃ / min or less, preferably 20℃ / min, to cool the temperature of the reaction chamber to below 800℃ and increase the pressure to 1.5 kPa. At the same time, the argon gas flow rate is increased to 7000 sccm. After cooling with the furnace for 48 hours, the furnace is opened and samples are taken. At this time, the inner wall of the graphite crucible is coated with tantalum carbide, completing the preparation of the tantalum carbide coating on the inner wall of the graphite crucible.

[0054] In the above steps, hydrogen and argon are preferably high-purity gases with a purity of 99.99% or higher and an oxygen content of 5 ppm or lower.

[0055] refer to Figure 4 The image shows the XRD analysis of a graphite-based tantalum carbide coating, which can be obtained using well-known methods. Specifically, phase analysis was performed using X-ray diffraction (XRD, Bruker D8 Advance) on a prepared sample from a graphite crucible. The diffraction target was a Cu target with Kα radiation, the scan rate was set to 2° / min, and the diffraction plane angle ranged from 20° to 90°. Figure 4It can be seen that the diffraction peak of the sample was determined to be TaC (JCPDS Card No. 04-001-2976) by comparison with the JCPDS card.

[0056] refer to Figure 5 As shown, a cross-sectional SEM image of a graphite-based tantalum carbide coating prepared using this invention can be obtained by well-known methods. Specifically, microstructure analysis was performed using a Quanta-250 scanning electron microscope (SEM, SU3500), analyzing the surface and cross-sectional morphology of the coating sample. Simultaneously, selected area composition analysis (EDS) was performed on two regions. (Reference) Figure 5 , Figure 6 , Figure 7 , Figure 8 As shown in Table 1, the tantalum carbide coating on the surface of the graphite crucible prepared using this invention is relatively smooth and dense, with no obvious peeling. Combined with XRD analysis, its morphology and composition indicate that the coating is stable TaC.

[0057] Table 1

[0058] Ta (at.%) C(at.%) Position 1 44.4 55.6 Position 2 35.0 65.0

[0059] refer to Figure 9 As shown in the diagram, the standard Gibbs free energy of TaC formation at 1400-2600℃ is illustrated. Calculations using HSC software show that tantalum and carbon have relatively high Gibbs free energies in the range of 2300-2400℃.

[0060] In some embodiments, the tantalum carbide mixture of the present invention includes a plurality of tantalum spheres 32 and tantalum carbide raw material powder 31, wherein the mass ratio of the total mass of the tantalum spheres 32 to the mass ratio of the tantalum carbide raw material powder 31 is 2.3:1; wherein the tantalum carbide raw material powder 31 is composed of tantalum powder, tantalum carbide powder, and carbon powder in a mass ratio of 5:3:2; of course, other ratios can be selected according to actual needs. The diameter of the tantalum spheres 32 can be 3mm, 4mm, or 5mm, preferably 5mm. In this embodiment, the particle size of the tantalum powder, tantalum carbide powder, and carbon powder is 300-500 mesh, preferably 500 mesh, but 350 mesh, 450 mesh, etc. can also be selected. The binder is a polyester organic material, preferably polyvinyl alcohol.

[0061] The preparation method of tantalum carbide raw material powder 31 in this embodiment includes the following steps:

[0062] S1 mixes 300-mesh tantalum powder, tantalum carbide powder, and carbon powder in a mixer at a weight ratio of 5:3:2. Then, a binder is added, the mass of which is 1 / 10 of the total mass of the tantalum powder, tantalum carbide powder, and carbon powder. The mixture is then cured at 80°C to form a solid. The solid is then pulverized in a powder mill to obtain raw material powder.

[0063] S2 dissolves polyvinyl alcohol in a water bath at a temperature above 100°C. Then, raw material powder 1 is mixed with polyvinyl alcohol at a temperature above 100°C at a mass ratio of 1:0.55 to obtain tantalum carbide raw material powder 31. The tantalum carbide raw material powder 31 is in a fluid state, which further increases the adhesion of the reaction of tantalum carbide raw material powder 31.

[0064] Other components of the apparatus and method for preparing graphite-based tantalum carbide coatings according to embodiments of the present invention, such as vacuum sintering furnaces, motors, etc., and their operation, are known to those skilled in the art and will not be described in detail here.

[0065] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0066] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0067] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0068] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0069] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0070] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. An apparatus for preparing a graphite-based tantalum carbide coating, characterized in that, include A vacuum sintering furnace, wherein the internal space of the vacuum sintering furnace constitutes a reaction chamber; A rotating system includes a graphite disk, a motor, and connecting components. The graphite disk is disposed within the reaction chamber. N receiving spaces for accommodating graphite substrates are defined on the inner sidewall of the graphite disk. The receiving spaces are evenly distributed on the inner sidewall of the graphite disk. The relationship between the depth d1 of the receiving space and the height or depth d2 of the graphite substrate is: 1 / 2*d2≤d1≤2 / 3*d2. Each receiving space has a clamping component connected to its outer edge for fixing the graphite substrate. The motor is installed on the outer sidewall of the vacuum sintering furnace. The motor is electrically connected to the control system of the vacuum sintering furnace. The connecting components penetrate the sidewall of the vacuum sintering furnace, with one end fixedly connected to the outer sidewall of the graphite disk and the other end fixedly connected to the output end of the motor.

2. The apparatus for preparing a graphite-based tantalum carbide coating according to claim 1, characterized in that, The receiving space is cylindrical, and the clamping component includes a graphite ring and graphite bolts. The diameter of the graphite ring is larger than the diameter of the receiving space. The graphite ring is located at the opening of the receiving space, fixedly connected to the inner sidewall of the graphite disk, and coaxially arranged with the receiving space. At least three graphite bolts are provided, evenly distributed on the sidewall of the graphite ring, penetrating the graphite ring, and threadedly connected to the graphite ring.

3. The apparatus for preparing a graphite-based tantalum carbide coating according to claim 1, characterized in that, The clamping component includes at least three sets of graphite clamps, which are evenly distributed on the outer edge of the accommodating space and fixedly installed on the graphite disk. Graphite bolts for clamping the graphite substrate penetrate the sidewalls of the three sets of graphite clamps.

4. The apparatus for preparing a graphite-based tantalum carbide coating according to claim 2, characterized in that, The rotation system is provided in two sets, and they are arranged symmetrically.

5. The apparatus for preparing a graphite-based tantalum carbide coating according to claim 4, characterized in that, The vacuum sintering furnace also includes The furnace body, the internal space of which constitutes a reaction chamber; A pressure gauge is installed on the top wall of the furnace body to monitor the pressure in the reaction chamber. The pressure gauge is connected to the control system of the vacuum sintering furnace. A resistance heater is symmetrically installed at the top and bottom of the reaction chamber, and the resistance heater is electrically connected to the control system of the vacuum sintering furnace; A temperature measuring gun is mounted on the outer wall of the vacuum sintering furnace via a bracket. A temperature measuring tube passes through the side wall of the vacuum sintering furnace opposite to the temperature measuring gun. The temperature measuring gun monitors the temperature inside the reaction chamber through the temperature measuring tube. A gas supply pipe, wherein the outlet end of the gas supply pipe is connected to the reaction chamber, and the inlet end is connected to the process gas pipeline; A vacuum system is provided, wherein the vacuum system’s pumping end is connected to the reaction chamber, its outlet end is connected to the tail gas treatment system, and the vacuum system is electrically connected to the control system of the vacuum sintering furnace. A furnace frame, on which the furnace body is mounted; The furnace wall of the vacuum sintering furnace is hollow and filled with cooling water.

6. A method for controlling the apparatus for preparing a graphite-based tantalum carbide coating according to any one of claims 1-5, characterized in that, Specifically as follows: In the first stage, the tantalum carbide mixture is loaded into the graphite matrix. After installing the graphite cap, the graphite matrix is ​​placed into the receiving space and clamped and fixed in the receiving space by the clamping components. The vacuum sintering furnace control system controls the vacuum pumping system to evacuate the reaction chamber to 1.22-1.32 Pa, and high-purity argon gas is introduced into the reaction chamber through the gas supply pipe to fill it. The vacuum is then reduced to below 5 Pa, and this process is repeated M times. When the set amount of argon gas is introduced, the gas supply pipe is closed. Finally, high-purity argon gas is introduced into the reaction chamber through the gas supply pipe to maintain the pressure in the reaction chamber at 45-65 Pa. Subsequently, the control system of the vacuum sintering furnace controls the motor of the rotating system to work and controls the motor speed to 400-600 r / min; at the same time, the control system of the vacuum sintering furnace controls the resistance heater to work, and the temperature measuring gun monitors the temperature in the reaction chamber in real time through the temperature measuring tube. This stage lasts for 168-200 hours, with the temperature of the reaction chamber maintained at 50-60℃. In the last 50 hours of this stage, the control system controls the resistance heater to slowly raise the temperature of the reaction chamber to 1650-1950℃, with a heating rate of 50℃ / min or less. In the second stage, high-purity hydrogen gas is introduced into the reaction chamber through a gas pipeline at a flow rate of 5-7 sccm. The pressure in the reaction chamber is controlled at 150-200 Pa, and the temperature of the reaction chamber is heated to 2250-2280℃ within 5 hours. At the same time, the control system controls the motor speed to drop to 0 and then maintains the temperature for 50 hours. At this temperature, sintering treatment is carried out on the graphite substrate to coat its inner wall with tantalum carbide coating. In the third stage, the cooling rate is controlled at 50℃ / min or below to cool the temperature to 1600-1800℃. At the same time, the pressure in the reaction chamber is increased to 300Pa. This process condition is maintained for 6-8 hours, while the hydrogen flow rate is still controlled at 5-7 sccm. After that, the cooling rate is controlled at 50℃ / min or below to reduce the temperature to 1200-1600℃, and the high-purity hydrogen is shut off. At this time, the hydrogen flow rate is 0 sccm. Finally, the cooling rate is controlled at 50℃ / min or below to cool the temperature in the reaction chamber to below 800℃, and the pressure is increased to 1.5 kPa. At the same time, the argon flow rate is increased to 7000 sccm. After cooling with the furnace for 48 hours, the furnace is opened and samples are taken. At this time, the inner wall of the graphite matrix is ​​coated with tantalum carbide, completing the preparation of the graphite-based tantalum carbide coating.

7. The control method for the apparatus for preparing a graphite-based tantalum carbide coating according to claim 6, characterized in that, The tantalum carbide mixture includes a number of tantalum spheres and tantalum carbide raw material powder, wherein the total mass of the tantalum spheres and the mass ratio of the tantalum carbide raw material powder is (1.5-2.5):1; wherein the tantalum carbide raw material powder is composed of tantalum powder, tantalum carbide powder and carbon powder in a mass ratio of 5:3:

2.

8. The control method for the apparatus for preparing a graphite-based tantalum carbide coating according to claim 7, characterized in that, The tantalum sphere has a diameter of 3-5 mm.

9. The control method for the apparatus for preparing a graphite-based tantalum carbide coating according to claim 8, characterized in that, The particle size of the tantalum powder, tantalum carbide powder, and carbon powder is 300-500 mesh.

10. A method for controlling an apparatus for preparing a graphite-based tantalum carbide coating according to claim 8 or 9, characterized in that, The preparation method of the tantalum carbide raw material powder includes the following steps: S1 mixes tantalum powder, tantalum carbide powder, and carbon powder evenly in a mixer according to a set mass ratio, then adds a binder. The mass of the binder is 1 / 10 of the total mass of the tantalum powder, tantalum carbide powder, and carbon powder. The mixture is then cured at 80°C to form a solidified product. The solidified product is then pulverized in a powder mill to obtain raw material powder one. S2 dissolves the adhesive in a water bath at a temperature above 100°C. Then, the raw material powder and the adhesive at a temperature above 100°C are mixed at a mass ratio of 1:(0.4-0.75) to obtain tantalum carbide raw material powder, which is in a fluid state.

11. The control method for the apparatus for preparing a graphite-based tantalum carbide coating according to claim 10, characterized in that, The adhesive is a polyester organic material.

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