Apparatus and method for producing equi-stoichiometric ratio of tantalum carbide powder

Abstract

The application discloses a device for preparing balanced stoichiometric ratio of carbonized tantalum powder, which comprises a heater, a reaction crucible, a heat preservation layer and a pressing element. The heater is arranged on the inner side of the heat preservation wall in the reaction cavity in a circumferential direction. The reaction crucible is arranged at the center of the bottom of the reaction cavity, and the upper end of the reaction crucible is arranged in an open mode. The reaction crucible is filled with tantalum powder and a carbon source in the tantalum powder. After the tantalum powder is pressed, the carbon source is located at the center of the tantalum powder, and the carbon source is excessive relative to the tantalum powder. The heat preservation layer is filled between the outer side wall of the reaction crucible and the heater and between the bottom wall of the reaction crucible and the heat preservation wall of the bottom. The pressing element is used for pressing the tantalum powder and giving a specific pressure to the tantalum powder during high-temperature synthesis. The pressing element comprises a pressing shaft and a pressing plate. The bottom of the pressing shaft is fixedly connected with the pressing plate, and the upper end of the pressing shaft penetrates through and extends out of the furnace cover. The application further discloses a process for preparing the carbonized tantalum powder. The carbonized tantalum powder prepared by in-situ self-diffusion of the carbon source at high temperature has higher purity and does not have residual free carbon.

Description

Technical Field

[0001] This invention relates to the field of tantalum carbide, and in particular to an apparatus and method for preparing tantalum carbide powder with a balanced stoichiometric ratio. Background Technology

[0002] With the rapid development of the domestic semiconductor market, especially in related industries represented by third-generation semiconductor silicon carbide, TaC coating provides excellent protection for graphite in the demanding processing of semiconductor and compound semiconductor materials. Its role is to extend the lifespan of graphite components, maintain reaction stoichiometry, and inhibit impurity migration into epitaxial and crystal growth applications, thereby providing higher yield and quality advantages. Furthermore, it can prevent the graphite component from participating in the growth process at the crystal edge contact point, further improving crystal yield and quality. It can be said that graphite-based tantalum carbide coating is an indispensable part of the growth process of semiconductor and compound semiconductor crystal materials. As of 2021, the sales volume in the Chinese market reached US$26 million, demonstrating its broad future market prospects.

[0003] For the preparation of tantalum carbide coatings for use in third-generation semiconductor graphite components, high-temperature curing sintering and thermal spraying methods are crucial for achieving high-purity, ultrafine tantalum carbide powder with a balanced stoichiometric Ta / C ratio. Therefore, researching a superior tantalum carbide powder preparation device and process is essential. Traditional methods such as thermal carbon reduction and sol-gel methods require pre-mixing of tantalum and carbon powders, which can introduce impurities and residual carbon. Furthermore, decarbonization gas needs to be introduced after the reaction, making the process complex and discontinuous. Summary of the Invention

[0004] 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 tantalum carbide powder with a balanced stoichiometric ratio, which uses a large-sized block of carbon or carbon powder placed in a carbon source crucible as a carbon source, and gradually diffuses into the tantalum powder surrounding the outer edge to form high-purity tantalum carbide powder with a balanced stoichiometric ratio.

[0005] This invention also proposes a method for preparing stoichiometric tantalum carbide powder by self-diffusion, which eliminates the need to mix tantalum powder and carbon powder in advance, avoids the problem of residual carbon, and eliminates the need for complex processes such as introducing carbon removal gas.

[0006] According to a first aspect of the present invention, an apparatus for preparing tantalum carbide powder with a balanced stoichiometric ratio is provided, the apparatus comprising a furnace body and an insulating wall, the furnace body defining a reaction chamber, a through hole being formed at the center of the upper end of the furnace body, the through hole being sealed by a removable furnace cover, and at least one insulating wall being provided inside the sidewall of the reaction chamber, further comprising:

[0007] A heater, which is circumferentially disposed on the inner side of the insulation wall within the reaction chamber;

[0008] A reaction crucible is disposed at the center of the bottom of the reaction chamber, with the upper end of the reaction crucible being open. The reaction crucible is filled with tantalum powder and a carbon source located within the tantalum powder. After the tantalum powder is compressed, the carbon source is located at the center of the tantalum powder.

[0009] A heat insulation layer is provided between the outer wall of the reaction crucible and the heater, and between the bottom wall of the reaction crucible and the bottom heat insulation wall.

[0010] A pressure-applying component is used to press the tantalum powder and apply specific pressure to the tantalum powder during high-temperature synthesis. The pressure-applying component includes a pressing shaft and a pressing plate. The bottom of the pressing shaft is fixedly connected to the pressing plate, and the upper end of the pressing shaft passes through and extends out of the furnace cover.

[0011] In some embodiments, the carbon source is a block of graphite; or,

[0012] The carbon source is carbon powder, which is placed in a carbon source crucible. The carbon source crucible is sealed by a crucible lid. The carbon source crucible and the crucible lid are made of graphite. Multiple through holes are uniformly formed on the bottom wall, side wall, and crucible lid of the carbon source crucible. The particle size of the carbon powder is larger than the diameter of the through holes.

[0013] In some embodiments, when the carbon source is a graphite block, a graphite rod is vertically fixed at the center of the upper surface of the graphite block; when the carbon source is carbon powder, a graphite rod is vertically fixed at the center of the upper surface of the carbon source crucible.

[0014] The reaction crucible is equipped with an inner crucible, the inner crucible and the reaction crucible are aligned on the central axis. The upper end of the graphite rod extends vertically from the bottom center of the inner crucible from bottom to top. The top of the graphite rod is detachably connected to the central pressing shaft, and the graphite rod and the central pressing shaft are aligned on the central axis.

[0015] In some embodiments, after pressing is completed, a heat-insulating felt is laid horizontally above the pressing plate on the reaction crucible;

[0016] The bottom of the inner crucible is covered with a second heat-insulating felt, the thickness of which is the same as that of the first heat-insulating felt. After pressing, the upper surfaces of the first and second heat-insulating felts are flush with the upper surface of the first heat-insulating felt.

[0017] In some embodiments, there are multiple pressure-applying components, which are evenly arranged circumferentially above the reaction crucible, and the pressing plates of all the pressure-applying components are combined together to form a ring.

[0018] In some embodiments, the pressure-applying component includes a pressure-applying component one and a pressure-applying component two. The pressing plate of the pressure-applying component one is annular, and the inner diameter of the pressing plate of the pressure-applying component one is not less than the diameter of the carbon source, and its outer diameter is not greater than the inner diameter of the reaction crucible. The bottom of the pressing shaft is connected to the pressing plate through a connecting rod, and the connecting rod is inverted U-shaped. The central axis of the pressing plate coincides with the central axis of the pressing shaft. The pressing plate of the pressure-applying component two is circular, and the diameter of the pressing plate of the pressure-applying component two is not greater than the inner diameter of the reaction crucible.

[0019] After pressing is completed, a heat-insulating felt three is laid horizontally above the pressing plate of the second pressing component on the reaction crucible. The heat-insulating felt three is circular and is adapted to the reaction crucible.

[0020] According to a second aspect of the present invention, a method for preparing tantalum carbide powder with equilibrium stoichiometry comprises the following steps:

[0021] (1) Tantalum powder pretreatment: First, clean the tantalum powder, then dry it for later use;

[0022] (2) Loading: First, connect the graphite rod above the carbon source through the inner crucible and the second insulation felt to the central pressing shaft. Press the central pressing shaft to make the carbon source be located in the designated position of the reaction crucible. Load the tantalum powder processed in step (1) into the reaction crucible until it reaches the top of the reaction crucible. Press the pressure component down until the upper surface of the first insulation felt and the second insulation felt are flush with the upper surface of the insulation layer. After loading is completed, turn off the furnace.

[0023] (3) High-temperature synthesis: The reaction chamber is evacuated, high-purity Ar is introduced as filler, and the chamber is evacuated again. This process is repeated 1-2 times until the pressure is maintained at 1.0 × 10⁻⁶. -5 Below Pa, heating begins, and the temperature rises to 1800-1850℃ within 1.5-2 hours, is maintained for 3-5 hours, and then increases to 2250-2264℃ within the following 30-72 minutes, and is maintained for 60-72 hours. After the synthesis stage is completed, the temperature drops to 0 within 5-6 hours, and after cooling for 12 hours, the pressure is reduced to atmospheric pressure, and the furnace is opened to take samples.

[0024] Further, in step (1), the tantalum powder has a particle size greater than 300 mesh and a purity greater than 5N. The specific steps of step (1) are as follows: the tantalum powder is soaked in ultrapure water and ultrasonically cleaned for 0.5-1h, then placed in anhydrous ethanol and ultrasonically cleaned for 0.5-1h, and repeated 3-5 times. After cleaning, the tantalum powder is placed in a quartz desiccator and dried in a vacuum dryer at 50-80℃ for 2-5h. After drying, it is ready for use.

[0025] In step (2), the pressure applied to the tantalum powder by the pressure-applying component is 1.5-2.5 MPa.

[0026] According to a second aspect of the present invention, a method for preparing tantalum carbide powder with balanced stoichiometry is used in the process of applying pressure using pressure applying element one and pressure applying element two, and the preparation method includes the following steps:

[0027] (1) Tantalum powder pretreatment: First, clean the tantalum powder, then dry it for later use;

[0028] (2) Loading: The loading is carried out in three stages. First, a layer of tantalum powder is spread evenly at the bottom of the reaction crucible. After spreading, pressure is applied to the tantalum powder using pressure component two to make the tantalum powder compact. Pressure component two is moved up, and then the carbon source is placed flat in the center of the tantalum powder. Then, tantalum powder is poured into the surrounding sides to completely cover the carbon source. The pressure component is replaced with pressure component one, and pressure component one is used to press and flatten the tantalum powder around the carbon source. Finally, the remaining tantalum powder is loaded into the reaction crucible. The pressure component is replaced with pressure component two, and heat insulation felt three is placed on the pressing plate. Pressure component two is activated to flatten the tantalum powder. Finally, the height of pressure component two is adjusted so that the upper surface of heat insulation felt three is flush with the upper surface of the heat insulation layer, forming a complete thermal field.

[0029] (3) High-temperature synthesis: The reaction chamber is evacuated, high-purity Ar is introduced as filler, and the chamber is evacuated again. This process is repeated 1-2 times until the pressure is maintained at 1.0 × 10⁻⁶. -5 Below Pa, heating begins. In the first stage, the temperature rises to 1800-1850℃ within 30-36 minutes, and the pressure is maintained at 3.5-4.2 MPa for 5-15 minutes. Then, the temperature is increased to 2000-2050℃ within 30-48 minutes, and the pressure is maintained at 3.5-4.2 MPa. In the second stage, the temperature rises to 2210-2240℃ within 5 minutes and is maintained for 50-52 hours. After that, the pressure is released to 0, and the temperature is rapidly reduced to 80℃ or below. The furnace is then opened for sampling.

[0030] Furthermore, in step (2), the mass of the tantalum powder first spread accounts for 35%-40% of the total tantalum powder loading, and the mass of the tantalum powder second poured in accounts for 20%-30% of the total tantalum powder loading.

[0031] 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

[0032] Figure 1 This is a schematic diagram of the apparatus for preparing tantalum carbide powder with balanced stoichiometry according to Embodiment 1 of the present invention before pressing.

[0033] Figure 2 This is a cross-sectional view of the apparatus for preparing tantalum carbide powder with balanced stoichiometry according to Embodiment 1 of the present invention.

[0034] Figure 3This is a schematic diagram of the apparatus for preparing tantalum carbide powder with balanced stoichiometry according to Embodiment 1 of the present invention after pressing is completed;

[0035] Figure 4 This is an enlarged view of the reaction crucible in the apparatus for preparing tantalum carbide powder with balanced stoichiometry according to Embodiment 2 of the present invention.

[0036] Figure 5 yes Figure 4 Schematic diagram of the inner crucible;

[0037] Figure 6 This is a schematic diagram of the apparatus for preparing tantalum carbide powder with balanced stoichiometry according to Embodiment 3 of the present invention when pressing tantalum powder below a carbon source;

[0038] Figure 7 This is a schematic diagram of the apparatus for preparing tantalum carbide powder with balanced stoichiometry according to Embodiment 3 of the present invention when pressing tantalum powder around a carbon source.

[0039] Figure 8 This is a schematic diagram of the apparatus for preparing tantalum carbide powder with balanced stoichiometry according to Embodiment 3 of the present invention when pressing tantalum powder above the carbon source.

[0040] Figure 9 This is a schematic diagram of the apparatus for preparing tantalum carbide powder with balanced stoichiometry according to Embodiment 3 of the present invention after pressing is completed;

[0041] Figure 10 This is a schematic diagram illustrating the principle of preparing tantalum carbide powder according to an embodiment of the present invention;

[0042] Figure 11 This is a schematic diagram of tantalum carbide powder and carbon source graphite block after the reaction in Example 1 is completed.

[0043] Figure 12 The image shows the energy dispersive spectroscopy (EDS) analysis of the tantalum carbide powder sample prepared in Example 1.

[0044] Figure label:

[0045] Device 100,

[0046] Furnace body 10, reaction chamber 11, furnace cover 12;

[0047] Insulated wall 20;

[0048] Heater 30;

[0049] Reaction crucible 40, tantalum powder 41, carbon source 42, graphite rod 43, carbon source crucible 421, crucible lid 422, through hole two 423;

[0050] Insulation layer 50, insulation felt 1 51, insulation felt 2 52, insulation felt 3 53;

[0051] Pressure application component 60, pressing shaft 61, pressing plate 62, central pressing shaft 63, pressure application component one 64, pressure application component two 65, connecting rod 641;

[0052] Inner crucible 70. Detailed Implementation

[0053] 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.

[0054] 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.

[0055] Example 1

[0056] The following is for reference. Figures 1-3 An apparatus 100 for preparing tantalum carbide powder with a balanced stoichiometric ratio according to an embodiment of the present invention is described. The apparatus 100 includes a furnace body 10 and an insulation wall 20. A reaction chamber 11 is defined within the furnace body 10. A through-hole (not shown) is provided at the center of the upper end of the furnace body 10. The through-hole is sealed by a removable furnace cover 12. At least one insulation wall 20 is provided inside the side wall of the reaction chamber 11. The apparatus also includes:

[0057] Heater 30 is arranged circumferentially on the inner side of the insulation wall 20;

[0058] The reaction crucible 40 is located at the bottom center of the reaction chamber 11. The upper end of the reaction crucible 40 is open. The reaction crucible 40 is filled with tantalum powder 41 and carbon source 42 located in the tantalum powder 41. After the tantalum powder 41 is compressed, the carbon source 42 is located at the center of the tantalum powder 41, and the carbon source 42 is in excess relative to the tantalum powder 41.

[0059] The insulation layer 50 is filled between the outer wall of the reaction crucible 40 and the heater 30, and between the bottom wall of the reaction crucible 40 and the bottom insulation wall 20. The insulation layer 50 can be an insulation felt.

[0060] The pressure-applying component 60 is used to press the tantalum powder 41 and apply a specific pressure to the tantalum powder 41 during high-temperature synthesis. The pressure-applying component 60 includes a pressing shaft 61 and a pressing plate 62. The bottom of the pressing shaft 61 is fixedly connected to the pressing plate 62, and the upper end of the pressing shaft 61 extends through and out of the furnace cover 12.

[0061] Figure 10 According to the schematic diagram of the TaC powder preparation principle of this invention, it can be understood that by placing the carbon source 42 into the tantalum powder 41 in advance, and after being pressed by the pressure application device 60, the carbon source 42 is located at the center of the tantalum powder 41. The reaction of the tantalum carbide powder at high temperature is mainly based on the in-situ self-diffusion of the carbon source 42. Tantalum carbide powder is prepared by pressurizing the tantalum powder 41 and combining it with a sintering process. Pressurization is beneficial to the mechanical interlocking between the tantalum powder 41 particles, producing plastic deformation, etc., and also to enhancing the interatomic adsorption force, increasing the contact area, and increasing the surface activity. Because carbon has a large atomic size difference with other metal elements, carbon atoms generally have a strong bonding force with metal atoms. In addition, since the mixing enthalpy of carbon and its metal elements is low at high temperatures, carbon atoms are more likely to combine with metal atoms, promoting the formation of intermetallic carbides. Utilizing this principle, after the reaction conditions are met, the outermost carbon atoms of the carbon source 42 begin to detach from the matrix and become free in the tantalum powder 41. Carbon atoms react with tantalum powder 41, with some carbon atoms entering the tantalum atoms until the solid solubility of carbon in tantalum is reached. Subsequently, the remaining carbon continues to diffuse outward, repeating the carburizing process in tantalum. That is, the diffusion layer of carbon atoms formed by the carbon source continues to diffuse outward until all tantalum atoms in the tantalum powder 41 react to form TaC. The advantage of using the apparatus 100 and process of this invention is that the prepared tantalum carbide powder has higher purity, there is no residual free carbon, and it is a reaction process in which carbon source 42 diffuses in situ to provide carbon atoms.

[0062] The reaction crucible 40 is made of graphite material, which can prevent the crucible from reacting with tantalum powder 41 in the early stage. The inner wall of the reaction crucible 40 is coated, and high-temperature resistant coatings such as tantalum carbide coating or tungsten carbide coating can be selected.

[0063] The carbon source 42 is a graphite block, and a graphite rod 43 is vertically fixed to the center of the upper surface of the graphite block;

[0064] The reaction crucible 40 contains an inner crucible 70, the outer diameter of which is smaller than the inner diameter of the reaction crucible 40. The upper surface of the inner crucible 70 is flush with the upper surface of the reaction crucible 40, ensuring that the upper surface of the inner crucible 70 remains flush with the upper surface of the reaction crucible 40 during the pressing of the tantalum powder 41. Both the inner crucible 70 and the reaction crucible 40 are open-top cylindrical shapes. The central axes of the inner crucible 70 and the reaction crucible 40 coincide. The upper end of the graphite rod 43 extends vertically from the bottom center of the inner crucible 70. The top of the graphite rod 43 is detachably connected to the central pressing shaft 63, and the central axis of the graphite rod 43 coincides with that of the central pressing shaft 63.

[0065] There are multiple pressure-applying components 60, which are evenly arranged circumferentially above the reaction crucible 40. The pressing plates 62 of all the pressure-applying components 60 are combined together to form a ring. For example, there can be 2-6 pressure-applying components 60, specifically 2, 3, 4, 5 or 6. In this embodiment, there are four pressure-applying components 60. Figure 2 As shown.

[0066] The setting of the pressure-applying component 60 has the following technical effects:

[0067] (1) By applying pressure to the tantalum powder 41 particles, the surface activation energy of the tantalum powder 41 particles inside the reaction crucible 40 due to Joule heating increases. This is because, under the external mechanical force and heating conditions, the degree of coordination between the tantalum powder 41 particles increases, and the mutual collision and compression of the tantalum powder 41 particles reduces the surface free energy. During the sintering process, the tantalum powder 41 particles usually have a significant thermal effect and are in a high-energy, metastable, and receptive superplastic state. Taking advantage of this characteristic, when sintering reaches this stage, applying sufficient pressure to induce, trigger, and promote its transformation can smoothly transition from a high-energy metastable state to another low-energy stable state, thus reducing the difficulty of the process.

[0068] (2) Pressure is applied by the pressure-applying component 60 to accelerate the diffusion process. The carbon source 42, located in the middle of the pressurized tantalum powder 41, can itself act as a heat source, effectively increasing the local temperature inside the tantalum powder 41. This is achieved by utilizing the heating effect of the carbon source 42 itself. The technical solution of this invention can be seen as the result of the combined effects of heating of the tantalum powder 41 particles, heating of the carbon source 42 itself, and pressure. In addition to the two factors that promote sintering, heating and pressure, the carbon source 42, located in the center of the tantalum powder 41, not only acts as a provider of its own carbon atoms, but its effective exothermic effect can generate local high temperatures, which can cause the tantalum powder 41 in contact with it to react first. Because carbon atoms are small, tantalum has a high affinity for carbon under high temperature conditions. The locally higher temperature increases the adsorption of carbon by tantalum. As the reaction proceeds, the solid solubility of carbon in tantalum in the middle tantalum powder 41 reaches its limit, and then the reaction gradually diffuses outward.

[0069] refer to Figure 3 As shown, after pressing, a heat insulation felt 51 is laid horizontally above the pressing plates 62 of the four pressing components 60. The four heat insulation felts 51 form a ring. A heat insulation felt 52 is laid flat at the bottom of the inner crucible 70. The thickness of the heat insulation felt 52 is the same as that of the heat insulation felt 51. After pressing, the upper surfaces of the heat insulation felts 51 and 52 are flush with the upper surface of the heat insulation layer 50. The four heat insulation felts 51 and 52 form a complete circle. The four heat insulation felts 51, 52 and 50 and the heat insulation layer 50 form a complete thermal field. The heat insulation layer 50, heat insulation felts 51 and 52 can be graphite soft felt.

[0070] Both the pressing shaft 61 and the central pressing shaft 63 are hydraulic shafts. The central pressing shaft 63 is used to adjust the position of the carbon source 42 in the tantalum powder 41. The pressing shaft 61 is connected to the furnace cover 12, which can move the furnace cover 12 up and down to open and close the furnace cover 12. The hydraulic shafts are powered by compressed air or an air compressor.

[0071] The insulation wall material inside the furnace 20 can be a composite high-temperature material, such as high-purity clay clinker, alumina powder, silica powder, chromium quartz sand, other high-temperature resistant fibers or mixtures thereof, which has the effect of heat preservation and a certain strength.

[0072] The heater 30 is a resistance heater, specifically a set of annular closed heaters surrounding the insulation wall 20. Its material is graphite, and both ends of the heater 30 are connected to the copper grid outside the furnace through graphite electrodes.

[0073] The method for preparing stoichiometric tantalum carbide powder using the above-described apparatus 100 includes the following steps:

[0074] (1) Pretreatment of tantalum powder 41: Tantalum powder 41 with a mesh size of 500 or higher is immersed in ultrapure water and ultrasonically cleaned for 1 hour, then placed in anhydrous ethanol and ultrasonically cleaned for 1 hour. This process is repeated 3 times. After cleaning, the tantalum powder is placed in a quartz desiccator and dried in a vacuum dryer at 75°C for 5 hours. After drying, it is ready for use.

[0075] (2) Loading: First, connect the graphite rod 43 above the graphite block through the inner crucible 70, the second insulation felt 52 and the central pressing shaft 63. Press the central pressing shaft 63 so that the carbon source 42 is located in the designated position of the reaction crucible 40. Load the tantalum powder 41 obtained in step (1) into the reaction crucible 40 until it reaches the top of the reaction crucible 40. Press the four pressing parts 60 down until the upper surfaces of the first insulation felt 51 and the second insulation felt 52 are flush with the upper surface of the insulation layer 50. The pressure provided by the pressing parts 60 to the tantalum powder 41 is 1.5-2.5 MPa. After loading is completed, turn off the furnace.

[0076] (3) High-temperature synthesis: Vacuum the reaction chamber 11, introduce high-purity Ar as filler, vacuum again, repeat twice, and finally maintain the pressure at 1.0 × 10⁻⁶. -5 Below Pa, heating begins, and the temperature rises to 1800-1850℃ within 2 hours, is maintained for 5 hours, and then increases to 2250-2264℃ within the next 0.5 hours, and is maintained for 60 hours. After the synthesis stage is completed, the temperature drops to 0 within 5 hours, and after cooling for 12 hours, the pressure is reduced to atmospheric pressure, and the furnace is opened to take samples.

[0077] Figure 11 The image shows a tantalum carbide powder sample prepared in Example 1. As can be seen from the figure, after the synthesis reaction stage, the graphite block used as carbon source 42 remains after the reaction and can be directly removed from the tantalum carbide powder. In addition, the brownish-yellow tantalum carbide powder formed by the reaction does not contain any residual black carbon particles.

[0078] Figure 12 The image shows the energy dispersive spectroscopy (EDS) spectrum of the tantalum carbide powder sample prepared in Example 1. EDS analysis was performed using a Quanta-250 scanning electron microscope (SEM, SU3500) to conduct selected area composition analysis (EDS) on the powder region, revealing stable stoichiometric TaC. Specifically, two test samples were selected sequentially outward from the carbon source 42, with the sample quantity sufficient for one test, capable of being laid flat at a depth of 1×1×0.5 cm. 2 The sample stage is pre-loaded with conductive adhesive to fix the sample. The EDS values ​​of the sample closer to the carbon source are Ta 44.6 at.% - C 55.4 at.%; while those of the sample farther from the carbon source are Ta 39.8 at.% - C 60.2 at.%. Based on the above analysis, the sample is composed of pure tantalum carbide powder and contains no elemental carbon; therefore, subsequent decarbonization processes are unnecessary.

[0079] Unlike traditional methods that use a specific theoretical ratio of carbon powder and tantalum powder 41 to prepare tantalum carbide powder, this invention concentrates the carbon source 42 required by the tantalum powder 41 in the central region, ensuring that the carbon is supersaturated in the tantalum. Through the process, the carbon source 42 gradually diffuses and reacts from the center outwards, eventually forming tantalum carbide. The residual carbon source 42 remains in a fixed position, eliminating the decarburization and cleaning work required in traditional preparation processes. The carbon source 42 is made of graphite, which generates heat and can form a local high-temperature region, promoting diffusion from the inside out. Thus, the reaction gradually moves from the central region near the carbon source 42 to the edge until all the tantalum powder 41 participates in the reaction, ultimately producing TaC.

[0080] Example 2

[0081] The only difference between this embodiment and Embodiment 1 is that...

[0082] The carbon source 42 is carbon powder, and a graphite rod 43 is vertically fixed at the center of the upper surface of the carbon source crucible 421; the carbon source crucible 421 is made of graphite.

[0083] refer to Figure 4-5 As shown, toner is contained within a carbon source crucible 421, which is a hollow cylindrical vessel with a bottom. The upper end of the crucible 421 is sealed with a crucible lid 422. Both the crucible 421 and lid 422 are made of graphite. Multiple through-holes 423 are evenly distributed on the bottom and side walls of the crucible 421 and on the lid 422. The particle size of the toner is larger than the diameter of the through-holes 423. This larger particle size prevents leakage of toner from the through-holes 423. Furthermore, the particle size of the toner is more than 10 times the diameter of the through-holes 423; for example, the toner particle size is 2-5 micrometers, and the through-hole diameter is 0.2-0.5 micrometers. Additionally, the toner is present in excess compared to the tantalum powder 41.

[0084] Understandably, once the reaction conditions are met, the carbon atoms in the carbon powder closest to through-hole 423 begin to detach from the matrix and migrate through through-hole 423 into the tantalum powder 41. The carbon atoms react with the tantalum powder 41, with some carbon atoms entering the tantalum atoms, until the solubility of carbon in tantalum is reached. Under high-temperature conditions, the carbon atoms react with the tantalum atoms, and subsequently, the remaining carbon continues to diffuse outward until all the tantalum atoms in the tantalum powder 41 have reacted to form TaC. Of course, since the carbon source crucible 421 is made of graphite, a small amount of carbon atoms will also participate in the reaction, but these are much smaller than the carbon powder. After the reaction is completed, the carbon source crucible 421 can be transferred away. Since the carbon powder particle size is much larger than the through hole 423, the particle size of the remaining carbon powder after the reaction is still larger than the through hole 423, which can prevent the carbon powder from leaking out of the through hole 423 and contaminating the tantalum carbide powder. The carbon source crucible 421 is made of graphite and generates heat itself, which can form a local high temperature area, promoting the diffusion of carbon atoms from the inside out. Thus, the reaction gradually moves from the central area near the carbon source crucible 421 to the edge until all the tantalum powder 41 participates in the reaction, and finally TaC is obtained.

[0085] In this embodiment, the carbon source 42 is replaced by carbon powder in a carbon source crucible 421 with a through hole 423 instead of a whole piece of graphite, which can improve the reaction rate and efficiency.

[0086] Example 3

[0087] The difference between this embodiment and Embodiment 1 is that,

[0088] refer to Figure 6-9 As shown, the carbon source 42 can be a graphite block or carbon powder placed in the carbon source crucible 421. There is no need to install a graphite rod 43 on the graphite block or the carbon source crucible 421, and there is no need for an inner crucible 70.

[0089] refer to Figures 6-9As shown, the pressure application component 60 includes a first pressure application component 64 and a second pressure application component 65. Both the first pressure application component 64 and the second pressure application component 65 include a pressing shaft 61 and a pressing plate 62. The pressing plate 62 of the first pressure application component 64 is annular, and its inner diameter is not less than the diameter of the carbon source 42, and its outer diameter is not greater than the inner diameter of the reaction crucible 40. The bottom of the pressing shaft 61 of the first pressure application component 64 is fixedly connected to the pressing plate 62 through a connecting rod 641. The connecting rod 641 is inverted U-shaped, and the central axis of the pressing plate 62 coincides with the central axis of the pressing shaft 61. The pressing plate 62 of the second pressure application component 65 is circular, and its diameter is not greater than the inner diameter of the reaction crucible 40. The second pressure application component 65 is used to press the tantalum powder 41 below the carbon source 42.

[0090] After pressing is completed, the reaction crucible 40 is horizontally laid with the heat insulation felt 53 above the pressing plate 62 of the pressure application component 2 65. The heat insulation felt 53 is circular and is adapted to the reaction crucible 40.

[0091] The method for preparing stoichiometric tantalum carbide powder using the above-described apparatus 100 includes the following steps:

[0092] (1) Pretreatment of tantalum powder 41: Tantalum powder 41 with a mesh size of 500 or higher is immersed in ultrapure water and ultrasonically cleaned for 1 hour, then placed in anhydrous ethanol and ultrasonically cleaned for 1 hour. This process is repeated 3 times. After cleaning, the tantalum powder is placed in a quartz desiccator and dried in a vacuum dryer at 75°C for 5 hours. After drying, it is ready for use.

[0093] (2) Loading: The loading is carried out in three stages. First, a layer of tantalum powder 41 is spread evenly on the bottom of the reaction crucible 40. The mass of the first layer of tantalum powder 41 accounts for 35%-40% of the total tantalum powder 41 loading. After the layering is completed, pressure is applied to the tantalum powder 41 using the second pressure device 65 to make the tantalum powder 41 compacted. The second pressure device 65 is moved upward, and then the carbon source 42 is placed flat in the center of the tantalum powder 41. Then, tantalum powder 41 is poured around its sides. The mass of the second layer of tantalum powder 41 is 20%-30% of the total tantalum powder loading, so that it completely coats the carbon. Source 42, replace pressure component 60 with pressure component 1 64, use pressure component 1 64 to press and flatten the tantalum powder 41 around the side of carbon source 42; finally, put the remaining tantalum powder 41 into reaction crucible 40, replace pressure component 60 with pressure component 2 65, and place heat insulation felt 3 53 on the pressing plate 62 of pressure component 2 65, start pressure component 2 65 to flatten tantalum powder 41, finally, adjust the height of pressure component 2 65 so that the upper surface of heat insulation felt 3 53 is flush with the upper surface of heat insulation layer 50, forming a complete thermal field;

[0094] (3) High-temperature synthesis: Vacuum the reaction chamber 11, introduce high-purity Ar as filler, vacuum again, repeat twice, and finally maintain the pressure at 1.0 × 10⁻⁶. -5Below Pa, heating begins. In the first stage, the temperature rises to 1800-1850℃ within 30-36 minutes, and the pressure is maintained at 3.5-4.2 MPa for 10 minutes. Then, within 30-48 minutes, the temperature is increased to 2000-2050℃, and the pressure is maintained at 3.5-4.2 MPa. In the second stage, the temperature rises to 2210-2240℃ within 5 minutes and is maintained for 50-52 hours. After that, the pressure is released to 0, and the temperature is rapidly reduced to 80℃ or below. The furnace is then opened for sampling.

[0095] In this embodiment, the pressing plate 62 of the first pressing component 64 is designed as a ring. During the loading process, the first pressing component 64 and the second pressing component 65 are replaced to complete the pressing operation of the tantalum powder 41. Compared with embodiment 1, this setting eliminates the inner crucible 70, making the structure simpler. The loading process is carried out in steps. At the same time, the pressure application is visualized, which makes it easy to adjust the position of the carbon source 42 in the tantalum powder 41 in a timely manner.

[0096] In summary, this invention, by pre-placing carbon source 42 into tantalum powder 41 and pressing it with pressure device 60, positions carbon source 42 at the center of tantalum powder 41. During high-temperature synthesis, under pressure and high temperature conditions, the thermal motion of carbon atoms in carbon source 42 spontaneously induces diffusion of matter into tantalum powder 41. This diffusion is primarily caused by concentration or temperature differences. Generally, it diffuses from areas of higher concentration to areas of lower concentration until the concentration within each phase becomes uniform or the concentration between the two phases reaches equilibrium. The concentration difference refers to the fact that tantalum atoms near the central carbon source 42 first reach saturation, forming TaC, and then begin to diffuse outwards. The temperature difference refers to the fact that in this invention, carbon source 42 or carbon source crucible 421 also acts as its own heat source, creating a localized temperature difference from the inside out, which also promotes diffusion, i.e., preparing TaC with a balanced stoichiometric ratio.

[0097] The interaction between tantalum and carbon: When tantalum powder (41-fold carbon) and tantalum are heated together, tantalum is diffusely saturated by carbon and forms tantalum carbide (TaC). The solid solubility of carbon in tantalum has a limit; generally, the limit decreases with decreasing temperature. For example, at 2580℃-1500℃, the solid solubility limit is 6.63 at.%-0.3 at.%. Typically, the solid solubility of carbon in tantalum follows this pattern: <1900℃, lnC = 8.23-16700 / T; >1900℃, lnC = 5.18-9900 / T. Therefore, the synthesis temperature selected in this invention is 2210-2240℃. In existing general technical solutions, carbon powder and tantalum powder 41 are first mixed. Some solutions add other auxiliary materials to the mixed powder. In these solutions, the composition ratio is pre-calculated by calculating the amount of carbon and tantalum. However, in the actual synthesis stage, due to the different saturated vapor pressures of the two at different temperatures, carbon may not have enough time to react and may be lost, or the synthesis may be incomplete. Therefore, some technical solutions select intermediate metal compounds of tantalum to reduce its saturated vapor pressure, but the fundamental problem is not solved. In addition, the introduction of other elements and subsequent decarbonization and cleaning processes can easily reduce the purity of the synthesized tantalum carbide powder. In the present invention, a solid carbon source 42 replaces the mixed powder. After synthesis, there is no need for complex processes such as mixing, crushing, decarbonization, and cleaning. Furthermore, by providing the carbon source 42 and a heat source, the tantalum powder 41 particles that come into contact with it first react first. After tantalum adsorbs carbon atoms, it gradually becomes saturated at the synthesis temperature, reaching the solid solubility limit and forming stable TaC. Then, carbon atoms diffuse outward, allowing the reaction to continue. Eventually, all the tantalum powder 41 participates in the reaction to obtain TaC. Of course, it is necessary to ensure that the carbon source 42 is sufficient or excessive. After the reaction is completed, the carbon source 42 can be directly removed.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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 tantalum carbide powder with a balanced stoichiometric ratio, the apparatus comprising a furnace body and insulating cotton, wherein a reaction chamber is defined within the furnace body, a through hole is provided at the center of the upper end of the furnace body, the through hole is sealed by a removable furnace cover, and at least one insulating wall is provided inside the sidewall of the reaction chamber, characterized in that, Also includes: A heater, which is circumferentially disposed on the inner side of the insulation wall within the reaction chamber; A reaction crucible is disposed at the center of the bottom of the reaction chamber, with the upper end of the reaction crucible being open. The reaction crucible is filled with tantalum powder and a carbon source located within the tantalum powder. After the tantalum powder is compressed, the carbon source is located at the center of the tantalum powder, and the carbon source is in excess relative to the tantalum powder. A heat insulation layer is provided between the outer wall of the reaction crucible and the heater, and between the bottom wall of the reaction crucible and the bottom heat insulation wall. A pressure-applying component is used to press the tantalum powder and apply a specific pressure to the tantalum powder during high-temperature synthesis. The pressure-applying component includes a pressing shaft and a pressing plate. The bottom of the pressing shaft is fixedly connected to the pressing plate, and the upper end of the pressing shaft passes through and extends out of the furnace cover.

2. The apparatus for preparing tantalum carbide powder with equilibrium stoichiometry according to claim 1, characterized in that, The carbon source is a block of graphite; or... The carbon source is carbon powder, which is placed in a carbon source crucible. The carbon source crucible is sealed by a crucible lid. The carbon source crucible and the crucible lid are made of graphite. Multiple through holes are uniformly formed on the bottom wall, side wall, and crucible lid of the carbon source crucible. The particle size of the carbon powder is larger than the diameter of the through holes.

3. The apparatus for preparing tantalum carbide powder with equilibrium stoichiometry according to claim 2, characterized in that, When the carbon source is a graphite block, a graphite rod is vertically fixed at the center of the upper surface of the graphite block; when the carbon source is carbon powder, a graphite rod is vertically fixed at the center of the upper surface of the carbon source crucible. The reaction crucible is equipped with an inner crucible, the inner crucible and the reaction crucible are aligned on the central axis. The upper end of the graphite rod extends vertically from the bottom center of the inner crucible from bottom to top. The top of the graphite rod is detachably connected to the central pressing shaft, and the graphite rod and the central pressing shaft are aligned on the central axis.

4. The apparatus for preparing tantalum carbide powder with equilibrium stoichiometry according to claim 3, characterized in that, After pressing is completed, a heat-insulating felt is laid horizontally above the pressing plate on the reaction crucible; The bottom of the inner crucible is covered with a second heat-insulating felt, the thickness of which is the same as that of the first heat-insulating felt. After pressing, the upper surfaces of the first and second heat-insulating felts are flush with the upper surface of the first heat-insulating felt.

5. The apparatus for preparing tantalum carbide powder with equilibrium stoichiometry according to claim 4, characterized in that, There are multiple pressure-applying components, which are evenly arranged circumferentially above the reaction crucible. The pressing plates of all the pressure-applying components are combined together to form a ring.

6. The apparatus for preparing tantalum carbide powder with equilibrium stoichiometry according to claim 2, characterized in that, The pressure-applying components include pressure-applying component one and pressure-applying component two. The pressing plate of pressure-applying component one is annular, and its inner diameter is not less than the diameter of the carbon source, while its outer diameter is not greater than the inner diameter of the reaction crucible. The bottom of the pressing shaft is connected to the pressing plate via a connecting rod, which is inverted U-shaped. The central axis of the pressing plate coincides with the central axis of the pressing shaft. The pressing plate of pressure-applying component two is circular, and its diameter is not greater than the inner diameter of the reaction crucible. After pressing is completed, a heat-insulating felt three is laid horizontally above the pressing plate of the second pressing component on the reaction crucible. The heat-insulating felt three is circular and is adapted to the reaction crucible.

7. A method for preparing tantalum carbide powder with equilibrium stoichiometry, characterized in that, The apparatus of claim 5 comprises the following steps: (1) Tantalum powder pretreatment: First, clean the tantalum powder, then dry it for later use; (2) Loading: First, connect the graphite rod above the carbon source through the inner crucible and the second insulation felt to the central pressing shaft. Press the central pressing shaft to make the carbon source be located in the designated position of the reaction crucible. Load the tantalum powder processed in step (1) into the reaction crucible until it reaches the top of the reaction crucible. Press the pressure component down until the upper surface of the first insulation felt and the second insulation felt are flush with the upper surface of the insulation layer. After loading is completed, turn off the furnace. (3) High-temperature synthesis: The reaction chamber is evacuated, high-purity Ar is introduced as filler, and the chamber is evacuated again. This process is repeated 1-2 times until the pressure is maintained at 1.0 × 10⁻⁶. -5 Below Pa, heating begins, and the temperature rises to 1800-1850℃ within 1.5-2 hours, is maintained for 3-5 hours, and then increases to 2250-2264℃ within the following 30-72 minutes, and is maintained for 60-72 hours. After the synthesis stage is completed, the temperature drops to 0 within 5-6 hours, and after cooling for 12 hours, the pressure is reduced to atmospheric pressure, and the furnace is opened to take samples.

8. The method for preparing tantalum carbide powder with equilibrium stoichiometry according to claim 7, characterized in that, In step (1), the tantalum powder has a particle size greater than 300 mesh and a purity greater than 5N; In step (2), the pressure applied to the tantalum powder by the pressure-applying component is 1.5-2.5 MPa.

9. A method for preparing tantalum carbide powder with equilibrium stoichiometry, characterized in that, The apparatus of claim 6 comprises the following steps: (1) Tantalum powder pretreatment: First, clean the tantalum powder, then dry it for later use; (2) Loading: The loading is carried out in three stages. First, a layer of tantalum powder is spread evenly at the bottom of the reaction crucible. After spreading, pressure is applied to the tantalum powder using pressure component two to make the tantalum powder compact. Pressure component two is moved up, and then the carbon source is placed flat in the center of the tantalum powder. Then, tantalum powder is poured into the surrounding sides to completely cover the carbon source. The pressure component is replaced with pressure component one, and pressure component one is used to press and flatten the tantalum powder around the carbon source. Finally, the remaining tantalum powder is loaded into the reaction crucible. The pressure component is replaced with pressure component two, and heat insulation felt three is placed on the pressing plate. Pressure component two is activated to flatten the tantalum powder. Finally, the height of pressure component two is adjusted so that the upper surface of heat insulation felt three is flush with the upper surface of the heat insulation layer, forming a complete thermal field. (3) High-temperature synthesis: The reaction chamber is evacuated, high-purity Ar is introduced as filler, and the chamber is evacuated again. This process is repeated 1-2 times until the pressure is maintained at 1.0 × 10⁻⁶. -5 Below Pa, heating begins. In the first stage, the temperature rises to 1800-1850℃ within 30-36 minutes, and the pressure is maintained at 3.5-4.2 MPa for 5-15 minutes. Then, the temperature is increased to 2000-2050℃ within 30-48 minutes, and the pressure is maintained at 3.5-4.2 MPa. In the second stage, the temperature rises to 2210-2240℃ within 5 minutes and is maintained for 50-52 hours. After that, the pressure is released to 0, and the temperature is rapidly reduced to 80℃ or below. The furnace is then opened for sampling.

10. The method for preparing tantalum carbide powder with equilibrium stoichiometry according to claim 9, characterized in that, In step (2), the mass of the first layer of tantalum powder accounts for 35%-40% of the total tantalum powder loading, and the mass of the second layer of tantalum powder accounts for 20%-30% of the total tantalum powder loading.

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