A carbide powder of 5n or more and a method for producing the same

Abstract

The application discloses a 5N or above carbide powder and a preparation method thereof, and belongs to the field of ultrahigh-temperature carbide ceramics. The method is to sequentially perform acoustic resonance mixing and ball milling on ceramic precursor powder and carbon materials, and to obtain a mixed powder after drying; the mixed powder is sequentially subjected to a decontamination reaction and a carbothermic reduction reaction, and thus a 5N or above carbide powder is obtained; the decontaminating agent is selected from at least one of a halogen element hydride, an elemental substance, an alkali metal salt, an alkaline earth metal salt, an ammonium salt and a halogenated hydrocarbon; wherein the halogen element comprises F and / or Cl. The application introduces a special decontaminating agent in a high-temperature reaction process, and controls the temperature and the gas pressure, so that the decontaminating agent is decomposed and reacts with lattice impurities in raw materials to perform deep decontamination, and thus a 5N or above carbide ceramic powder is prepared.

Description

Technical Field

[0001] This invention belongs to the field of ultra-high temperature carbide ceramics, and relates to a carbide powder of 5N grade or higher and its preparation method. Background Technology

[0002] Ultra-high temperature carbide ceramics (such as TaC, ZrC, HfC, NbC, etc.) possess characteristics such as high melting point, high hardness, excellent wear resistance, and thermal shock resistance, and are widely used in thermal protection components of aerospace vehicles, rocket engine nozzles, and high-temperature corrosion-resistant components in the semiconductor industry. Especially in semiconductor manufacturing, the purity requirements for carbide ceramic materials are extremely stringent, typically requiring a purity of 5N level (99.999%) or higher to ensure device performance and yield.

[0003] Currently, high-purity carbide ceramics or coatings can be obtained through processes such as chemical vapor deposition (CVD) or chemical vapor infiltration (CVI). However, these methods have limitations such as large equipment investment, low raw material utilization, high production costs, and difficulty in achieving uniform deposition on complex shaped components.

[0004] In contrast, slurry sintering or carbothermal reduction methods based on powder metallurgy have become important technical routes for preparing carbide ceramic powders due to their simple processes, high raw material utilization, low cost, and suitability for large-scale production. However, the traditional carbothermal reduction method directly uses oxide or hydroxide powders and carbon black as raw materials to react and generate carbides at high temperatures. Since the purity of commercially available ceramic precursor powders is usually only around 4N, and metal elements such as Fe, Al, Ca, and Na often exist in the form of lattice doping, which are difficult to remove through simple physical mixing or washing, the purity of the final carbide product is difficult to exceed the 5N level, which seriously restricts its application in high-end fields.

[0005] To improve the purity of carbides, existing research has attempted to use high-purity raw materials, add additives, or optimize processes. For example, Chinese patent application CN121202132A discloses a method for preparing tantalum carbide powder by carburizing based on the synergistic effect of molten salt activation and catalytic decomposition. This method uses molten salt to surface-activate tantalum powder, improving its reactivity. However, the purity of the tantalum powder used is 99.9% (3N), and the final purity of the obtained tantalum carbide powder is only 99.95% (approximately 3N grade 5), indicating a limited improvement in purity, which is still far from meeting the requirements for 5N grade applications. The limitation of this method lies in its failure to effectively remove deep impurities in the solid solution or within the crystal lattice of the raw material.

[0006] Therefore, there is an urgent need in this field to develop a method that can directly prepare high-purity carbide powder of grade 5N or higher using low-purity commercial raw materials through a simple and efficient process, so as to break through the existing technical bottlenecks and meet the urgent demand for ultra-high purity carbide materials in high-end application fields such as semiconductors. Summary of the Invention

[0007] To address the shortcomings of existing carbide powder preparation methods, such as difficulty in achieving product purity of 5N or higher, excessively high requirements for raw material purity, and complex processes, the first objective of this invention is to provide a method for preparing carbide powders with a purity of 5N or higher. By introducing a specific impurity remover during the high-temperature reaction process and synergistically controlling the temperature and pressure, the impurity remover decomposes to generate active species, which react with lattice impurities exposed by phase transitions or decomposition of the raw materials, generating volatile, low-boiling-point compounds that are promptly removed, thus achieving deep impurity removal. This method can directly prepare carbide powders with a purity of 5N or higher using commercial precursor powders with a purity of only around 4N, demonstrating significant industrial application value.

[0008] The second objective of this invention is to provide a carbide powder with a purity of 5N or higher. The carbide powder obtained by this invention can be a single type of medium-entropy ceramic or high-entropy ceramic carbide powder, with uniform and fine particle size and a purity of 5N or higher, which can be further applied in fields such as semiconductors where powder purity requirements are stringent.

[0009] To achieve the above-mentioned technical objectives, this invention provides a method for preparing carbide powder of 5N grade or higher. The method involves sequentially mixing ceramic precursor powder with carbon material using acoustic resonance and ball milling, followed by drying to obtain a mixed powder. The mixed powder is then subjected to a purification reaction and a carbothermic reduction reaction to obtain carbide powder of 5N grade or higher. During the purification reaction, when the temperature inside the container is within the decomposition temperature range or crystal transformation temperature range of the ceramic precursor powder, the pressure inside the container is increased to above the saturated vapor pressure of the purification agent at that temperature, exposing lattice impurities inside the powder and promoting the decomposition of the purification agent. The purification agent is selected from at least one of the following: hydrides, elements, alkali metal salts, alkaline earth metal salts, ammonium salts, and halogenated hydrocarbons. The halogen elements include F and / or Cl.

[0010] The technical solution of this invention can prepare carbide powders with a purity of 5N or higher using ceramic precursor powders of relatively low purity (e.g., 4N grade). Its core lies in the introduction of a small amount of impurity-removing agent and the synergistic control of temperature and pressure during the impurity removal reaction stage. The mechanism is as follows: during the heating process, when the temperature reaches the decomposition temperature or crystal transformation temperature range of the ceramic precursor powder, the precursor decomposes or undergoes lattice reconstruction, exposing metallic impurities (such as Fe, Al, Ca, Na, Zr, V, etc.) and non-metallic impurities (such as B, P, S, etc.) that were originally bound inside the lattice to the particle surface or grain boundaries. Simultaneously, the selected impurity-removing agent decomposes or vaporizes under specific temperature and negative pressure conditions, releasing highly reactive chlorine (Cl) or fluorine (F) elements. These reactive species rapidly combine with the exposed impurity elements to generate chlorides or fluorides (such as FeCl3, AlCl3, SiF4, BF3, etc.) with low melting points and / or low boiling points. By controlling the pressure inside the reactor to slightly higher than the saturated vapor pressure of the impurity remover at that temperature, it is possible to ensure that the impurity remover releases active species slowly and continuously in gaseous form, avoiding violent boiling that would lead to insufficient contact with the powder. Simultaneously, the continuous inert gas carrier and negative pressure suction ensure that the generated volatile impurity compounds are promptly removed from the reaction system, preventing them from re-condensing or undergoing secondary reactions with the carbide powder. After deep impurity removal, the residual metal impurity content in the system is reduced to an extremely low level. At this point, direct heating to carry out a carbothermic reduction reaction converts the precursor into the target carbide, yielding carbide powder with a purity of 5N or higher.

[0011] As a preferred embodiment, the carbon material includes carbon black.

[0012] As a preferred embodiment, the ceramic precursor powder comprises oxides, hydroxides, or oxygen-containing salts of one or more elements selected from zirconium (Zr), hafnium (Hf), titanium (Ti), tantalum (Ta), niobium (Nb), and tungsten (W). The ceramic precursor powder selected in this invention undergoes decomposition or crystal transformation during heating, thereby exposing impurities within the crystal and creating conditions for impurity removal. When a single component is used, a single high-purity carbide (such as TaC) can be obtained; when multiple components are used, high-purity medium-entropy or high-entropy carbide ceramic powders (such as (Ta, Zr, Nb)C) can be obtained.

[0013] As a preferred embodiment, the purity of the ceramic precursor powder is ≥4N (e.g., commercially available high-purity products), and the purity of the carbon material is >4N5 grade. A significant advantage of this invention is that even using commercially available raw materials with lower purity (e.g., 4N grade), carbide powders of 5N grade or higher can be directly prepared using the process of this invention, thereby significantly reducing dependence on ultra-high purity raw materials.

[0014] As a preferred embodiment, the ceramic precursor powder has a particle size of 0.5~5μm, and the carbon material has a particle size of 20~50nm. The powder particle size used in the process of this invention is a commercially available, commonly used powder particle size, eliminating the need for secondary screening.

[0015] As a preferred embodiment, the molar ratio of the ceramic precursor powder to the carbon material is 1:(2~8). Within the preferred range of this invention, while satisfying the stoichiometric ratio for the carbothermic reduction reaction, an appropriate excess of carbon material can be added to compensate for carbon loss that may occur due to volatilization or reaction with impurities during subsequent high-temperature processing. Insufficient carbon addition will result in unreacted metal oxides remaining in the carbide product or the formation of a carbon-deficient phase, while excessive carbon addition will make it difficult to completely remove excess free carbon in subsequent processes, affecting powder purity and performance.

[0016] As a preferred embodiment, the vibration frequency of the acoustic resonance mixing is 50~80Hz, the working acceleration is 50~100g, and the vibration time is 5~30min. Through the preferred acoustic resonance mixing conditions of this invention, the macroscopic convection and microscopic shearing effects generated by high-frequency, low-amplitude vibration achieve a macroscopically uniform distribution of two powders with significantly different particle sizes.

[0017] As a preferred embodiment, the ball milling is a wet ball milling process, wherein the ball-to-material ratio is (5~10):1, the time is 2~5 hours, and the rotation speed is 50~200 r / min; the ball milling solvent is water. This invention employs a low-speed wet ball milling process. Through the collision and shearing action of the grinding media, the precursor powder can be further refined. More importantly, it allows nanoscale carbon material particles to uniformly coat the surface of the micron-scale precursor powder, forming a tight core-shell structure contact interface to promote the subsequent carbothermic reduction reaction. This invention achieves macroscopic uniformity through acoustic resonance mixing and microscopic coating through wet ball milling; the two processes synergistically solve the problem of mixing uniformity for powders with large particle size differences.

[0018] As a preferred embodiment, the impurity remover is at least one selected from HCl, Cl2, NH4Cl, KCl, NaCl, CaCl, CHClF2, LiF, KF, and NaF. In this invention, the chlorine-containing impurity remover is mainly used to remove metallic impurities such as Fe, Al, and Si from the raw materials, while the fluorine-containing impurity remover is mainly used to remove non-metallic impurities that may be present in the raw materials, such as B, P, and S. More preferably, the impurity remover simultaneously comprises both chlorine-containing and fluorine-containing impurity removers to efficiently remove both metallic and non-metallic impurities. Particularly preferably, the impurity remover is a mixed salt of KF, KCl, and NaCl.

[0019] As a preferred embodiment, when the impurity removal agent used in the impurity removal reaction is solid, the mixed powder is mixed with the impurity removal agent and placed in a container for vibration compaction before proceeding with the impurity removal reaction and the carbothermic reduction reaction in sequence; when the impurity removal agent used in the impurity removal reaction is gaseous, the mixed powder is placed in a container for vibration compaction before proceeding with the impurity removal agent and the carbothermic reduction reaction in sequence.

[0020] As a preferred embodiment, the pressure of the vibration compaction treatment is 1~3MPa. This step, through vibration-assisted pressurization, can effectively increase the bulk density of the powder, reduce the voids between particles, improve the uniformity of heat conduction during high-temperature reactions, and facilitate the smooth discharge of gaseous products generated in the reaction.

[0021] As a preferred embodiment, when the impurity remover is in solid form, its addition amount is 1-10 wt.% of the mixed powder; when the impurity remover is in gaseous form, its flow rate is 10-100 mL / min. In this invention, the amount of impurity remover directly affects the purity of the final powder. If the amount of impurity remover is too low, there will be insufficient active species, and the impurity removal effect will be insignificant; while if the amount is too high, excessive halide ions will be introduced, which will react with the main element, causing material loss, or leaving trace impurities in the finished product, thus leading to a decrease in purity.

[0022] By controlling the gas pressure inside the container, this invention can match the decomposition or crystal transformation temperature ranges of the two substances, and enable the impurity remover to slowly vaporize rather than violently boil within the temperature range of precursor decomposition, thereby ensuring that it can fully contact and react with the lattice impurities exposed by precursor decomposition.

[0023] Furthermore, the pressure inside the container is controlled at 5-20 kPa above the saturated vapor pressure of the impurity remover at a temperature higher than that.

[0024] As a preferred embodiment, after the impurity removal reaction is completed, the container is kept under vacuum, and the temperature is increased to above 1400°C at a rate of 2-10°C / min, and held at this temperature for 1-5 hours to carry out the carbothermic reduction reaction. During this stage, the continuous high temperature and vacuum environment help to further remove residual trace volatile impurities and ensure the complete carbothermic reduction reaction. If the carbothermic reduction temperature is too low, some high-boiling-point impurities such as chlorides / fluorides will not be able to fully volatilize at this stage, resulting in incomplete impurity removal, and the carbothermic reduction reaction itself will also be kinetically inefficient.

[0025] As a more preferred embodiment, when the target product is TaC or NbC, the temperature of the carbothermic reduction reaction is 1400~1700℃ and the holding time is 0.5~2h; when the target product is ZrC, HfC or WC, the temperature of the carbothermic reduction reaction is 1700~2000℃ and the holding time is 0.5~2h.

[0026] As a preferred option, for gaseous impurity removers, a crucible or furnace inlet structure with a gas distribution channel can be used to ensure that the impurity remover gas diffuses uniformly in the powder bed and avoids local concentration differences from affecting the impurity removal effect.

[0027] As a preferred option, if a higher purity carbide powder is required, the carbothermic reduction reaction can be further purified according to the type of impurities. For example, some impurities may form compounds with high melting and boiling points or have properties similar to tantalum that are difficult to separate, requiring higher temperatures for effective removal. If the required temperature is too high, a gaseous impurity remover needs to be introduced to assist the reaction.

[0028] This invention also provides a carbide powder with a purity of 5N or higher, obtained by the above-described preparation method. The carbide powder obtained by this invention can be a single type of medium-entropy ceramic or high-entropy ceramic carbide powder, with uniform and fine particle size and a purity of 5N or higher.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] (1) The present invention completes the removal of impurities and the preparation of carbide powder simultaneously during the reaction process, avoiding secondary pollution caused by powder transfer in traditional multi-step processes and ensuring the stability of high-purity products. At the same time, by first exposing lattice impurities and generating low-melting-point halides in situ to be removed by negative pressure gas flow, and then directly heating for carbothermic reduction, the process flow can be significantly shortened, energy consumption and time costs can be reduced, and the residue of impurity remover and by-products can be further removed in the subsequent reduction stage.

[0031] (2) By introducing a special impurity remover during the high-temperature reaction process and controlling the temperature and pressure, the decomposition or crystal transformation temperature ranges of the two can be matched, and the impurity remover can be slowly vaporized within the temperature range of precursor decomposition, thereby ensuring that it can fully contact and react with the lattice impurities exposed by precursor decomposition, and perform deep impurity removal. Therefore, carbide ceramic powder of 5N grade or above can be prepared using powder raw materials with low purity.

[0032] (3) The preparation method of the present invention can be applied to the preparation of various carbide ceramic powders. Its process parameters can be flexibly adjusted according to the product purity requirements and powder type, and it has industrial application prospects.

[0033] (4) The present invention can use commercial precursor powder with a purity of only about 4N to directly prepare carbide powder with a purity of 5N or higher, which has significant industrial application value. Attached Figure Description

[0034] Figure 1The image shows the microstructure of the TaC ceramic powder prepared in Example 1.

[0035] Figure 2 The image shows the XRD phase diagram of the TaC ceramic powder prepared in Example 1.

[0036] Figure 3 The image shows the microstructure of the TaZrNbC medium-entropy ceramic powder prepared in Example 2.

[0037] Figure 4 The image shows the XRD phase diagram of the TaZrNbC medium-entropy ceramic powder prepared in Example 2. Detailed Implementation

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0039] Example 1

[0040] This embodiment provides a method for preparing high-purity tantalum carbide (TaC) powder, the specific steps of which are as follows:

[0041] S1: Weigh tantalum hydroxide (Ta(OH)5) powder with a purity of 4N as the ceramic precursor powder, with a particle size of 1~5μm. Weigh carbon black powder with a purity of 4N5 grade (99.995%), with a particle size of 20~50nm. Weigh according to the stoichiometric ratio for complete reaction to produce TaC (molar ratio of Ta(OH)5 to C is 1:5), and add an additional 5mol% excess carbon black to compensate for subsequent carbon loss, i.e., the final molar ratio of Ta(OH)5 to C is 1:5.25. Place the weighed powder into a mixing container and perform acoustic resonance mixing, setting the vibration frequency to 60Hz and the vibration acceleration to 80g (where g = 9.8m / s²). 2 The mixing time was 10 minutes. The acoustically resonant mixed powder was then transferred to a nylon ball mill jar, using zirconia balls as the grinding medium at a ball-to-powder mass ratio of 5:1. Pure water was added as the dispersion medium, with the amount of pure water being 90% of the total powder mass. The mixture was wet-milled for 2 hours at 100 rpm in a planetary ball mill. After milling, the slurry was dried in an 80℃ oven for 10 hours to obtain the mixed powder.

[0042] S2: Using a mixed salt of KF, KCl and NaCl in a molar ratio of 1:2:2 as a solid impurity remover, weigh out 5% of the total mass of the dried mixed powder and add it to the powder. Mix again using acoustic resonance, setting the vibration frequency to 55Hz, the acceleration to 100g, and the time to 2min, so that the impurity remover is evenly dispersed.

[0043] S3: The mixed powder is loaded into a graphite crucible, vibrated to compact it on a vibrating platform, and then molded under a pressure of 2 MPa. The graphite crucible containing the compact is placed in a high-temperature atmosphere furnace. Vacuum is applied until the absolute pressure is <10 Pa. The temperature is increased to 200 °C at 10 °C / min, then to 600 °C at 3 °C / min, and held for 1 hour. Subsequently, the temperature is increased to 900 °C at 1 °C / min and held for 0.5 hours. When the temperature reaches 600 °C, the furnace pressure is controlled to be approximately 5 kPa higher than the saturated vapor pressure of the mixed salt at that temperature by finely adjusting the vacuum pump valve and introducing high-purity argon gas. The absolute pressure is maintained within the range of 5–15 kPa between 600 and 900 °C to ensure that the impurity remover slowly and continuously vaporizes and fully reacts with the exposed impurities. After the holding period, the vacuum is stopped, and flowing high-purity argon gas is introduced at a flow rate of 50 mL / min to maintain the furnace pressure at 20 kPa.

[0044] S4: Increase the temperature to 1200℃ at a rate of 5℃ / min, then increase it to 1700℃ at a rate of 2℃ / min, and hold at 1700℃ for 2 hours to carry out the carbothermic reduction reaction. High-purity argon gas is continuously introduced during this process. After 1 hour of holding, the argon gas is turned off, and the furnace is evacuated again to an absolute pressure <1Pa. The furnace is then held under this vacuum for another hour to promote the removal of residual gaseous impurities.

[0045] S5: After the heat preservation period, stop heating and allow the furnace to cool to room temperature while maintaining a vacuum inside. Remove the product, lightly grind and disperse it to obtain high-purity TaC ceramic powder.

[0046] Example 2

[0047] This embodiment provides a method for preparing high-purity medium-entropy carbide (TaZrNbC) powder, the specific steps of which are as follows:

[0048] S1: Weigh tantalum hydroxide, zirconium hydroxide, and niobium hydroxide (4N purity) as ceramic precursor powders, and prepare them according to the equimolar ratio of each metal element in the target product (Ta, Zr, Nb)C (Ta:Zr:Nb = 1:1:1). The particle size of the three precursor powders is 1~5μm. Weigh carbon black powder (4N5 purity, particle size 20~50nm), according to the stoichiometric ratio required for complete reaction to generate (Ta, Zr,Nb)C (total metal hydroxide to C molar ratio of 1:4), and add an additional 8mol% excess carbon black, so that the final total metal hydroxide to C molar ratio is 1:4.32. The mixing, ball milling, and drying processes are the same as S1 in Example 1.

[0049] S2: The dried mixed powder is loaded into a graphite crucible, compacted by vibration, and then molded under a pressure of 2 MPa and placed in a high-temperature furnace. The furnace is evacuated to <10 Pa, heated to 200 °C at 10 °C / min, then to 500 °C at 3 °C / min, and held for 1 hour. Within this temperature range, HCl gas and Ar carrier gas at a flow rate of 30 L / min are introduced. By controlling the vacuum pump speed and gas flow rate, the absolute pressure inside the furnace is maintained at 1~3 kPa (higher than the saturated vapor pressure of HCl at this temperature). Subsequently, the temperature is increased to 800 °C at 1 °C / min and held for 0.5 hours. During this stage, the HCl flow rate is adjusted to 30 mL / min, the Ar flow rate is maintained at 30 L / min, and the pressure is maintained at 3~5 kPa to ensure a sufficient supply of impurity remover and promote the formation and volatilization of impurity chlorides.

[0050] S3: After the heat preservation is completed, the temperature is increased to 1200℃ at a rate of 5℃ / min. At the same time, the HCl flow rate is reduced to 5mL / min and the Ar flow rate is increased to 60L / min. The gas pressure in the furnace is circulated between 5~20kPa three times. Each cycle includes increasing the pressure from 5kPa to 20kPa and then decreasing it back to 5kPa, with a cycle of about 10min. This is to promote the full contact between the gaseous impurity remover and the impurities inside the powder and deep in the stacked layer, as well as the desorption and desorption of the reaction products.

[0051] S4: The temperature is then increased to 1900℃ at a rate of 2℃ / min and held at 1900℃ for 2 hours. During this stage, the flow rate of HCl gas is maintained at 5 mL / min, the flow rate of Ar gas is maintained at 60 L / min, and the furnace pressure is kept stable at 20 kPa. A small amount of HCl is continuously introduced during the carbothermic reduction process to further remove trace impurities that may be leached from the furnace wall or deep layers of powder at high temperatures, ensuring the final product has a purity of 5N. After holding for 1 hour, all gases are shut off, the furnace is evacuated to an absolute pressure of <1 Pa, and the temperature is maintained under this vacuum for another 1 hour.

[0052] S5: After the heat preservation is completed, stop heating and keep the furnace under vacuum to cool to room temperature. Take out the product, lightly grind and disperse it to obtain high-purity TaZrNbC medium-entropy ceramic powder.

[0053] Example 3

[0054] This embodiment provides a method for preparing high-purity tantalum carbide (TaC) powder using a single fluoride impurity remover. The specific steps are as follows:

[0055] S1: Weigh 4N purity tantalum hydroxide (Ta(OH)5) powder as the ceramic precursor powder, with a particle size of 1~5μm. Weigh 4N5 purity carbon black powder, with a particle size of 20~50nm. Weigh according to the stoichiometric ratio for complete reaction to produce TaC (molar ratio of Ta(OH)5 to C is 1:5), and add an additional 5mol% excess carbon black to compensate for subsequent carbon loss, i.e., the final molar ratio of Ta(OH)5 to C is 1:5.25. Place the weighed powder into a mixing container and perform acoustic resonance mixing, setting the vibration frequency to 60Hz, the vibration acceleration to 80g, and the mixing time to 10min. Then transfer the acoustically resonant mixed powder to a nylon ball mill jar, use zirconia balls as the grinding medium, with a ball-to-powder mass ratio of 5:1, add pure water as the dispersion medium (pure water added is 90% of the total powder mass), and wet ball mill at 100r / min for 2h on a planetary ball mill. After ball milling, the slurry was dried in an 80℃ oven for 10 hours to obtain a mixed powder.

[0056] S2: Using KF as a solid impurity remover, weigh out 8% of the total mass of the dry mixed powder and add it to the powder. Mix again using acoustic resonance, setting the vibration frequency to 55Hz, the acceleration to 100g, and the time to 2min, so that KF is evenly dispersed in the mixed powder.

[0057] S3: The mixed powder is loaded into a graphite crucible, vibrated to compact it on a vibrating platform, and then molded under a pressure of 2 MPa. The graphite crucible containing the compact is placed in a high-temperature atmosphere furnace. Vacuum is applied until the absolute pressure is <10 Pa, and the temperature is increased to 200 °C at 10 °C / min, then to 600 °C at 3 °C / min, and held for 1 hour; subsequently, the temperature is increased to 900 °C at 1 °C / min, and held for 0.5 hours. When the temperature reaches 600 °C, the pressure inside the furnace is controlled to be about 5 kPa higher than the saturated vapor pressure of the mixed salt at this temperature by finely adjusting the vacuum pump valve and introducing high-purity argon gas. The absolute pressure is maintained in the range of 5-15 kPa within the range of 600-900 °C to ensure that KF slowly and continuously vaporizes and releases active fluorine elements, which fully react with the lattice impurities exposed by the decomposition of tantalum hydroxide to generate volatile fluorides. After the heat preservation is completed, stop the vacuuming and introduce flowing high-purity argon gas at a flow rate of 50 mL / min to maintain the pressure inside the furnace at 20 kPa.

[0058] S4: Increase the temperature to 1200℃ at a rate of 5℃ / min, then increase it to 1700℃ at a rate of 2℃ / min, and hold at 1700℃ for 2 hours to carry out the carbothermic reduction reaction. High-purity argon gas is continuously introduced during this process. After 1 hour of holding, the argon gas is turned off, and the furnace is evacuated again to an absolute pressure <1Pa. The furnace is then held under this vacuum for another hour to promote the removal of residual gaseous impurities.

[0059] S5: After the heat preservation period, stop heating and allow the furnace to cool to room temperature while maintaining a vacuum inside. Remove the product, lightly grind and disperse it to obtain high-purity TaC ceramic powder.

[0060] Example 4

[0061] The only difference between this embodiment and Example 1 is that the composition of the mixed salt impurity remover in S2 is changed to a KF:KCl:NaCl molar ratio of 1:1:1, while the total addition amount remains 5 wt.%. The remaining steps and parameters are completely consistent with Example 1.

[0062] Comparative Example 1

[0063] The only difference between this comparative example and Example 1 is that no impurity remover is added in S2; all other steps and conditions are the same as in Example 1.

[0064] Because no impurity remover was added, lattice impurities such as Fe, Al, Ca, and Na in the raw materials could not be effectively removed during the heating process, and most of them remained in the final product, resulting in a product purity of only 99.9820%, which is far below the 5N grade requirement.

[0065] Comparative Example 2

[0066] The difference between this comparative example and Example 1 is that no pressure adjustment is performed during the heat preservation stage of step S3. Instead, the furnace is kept in a continuous vacuum state (absolute pressure <10Pa). The remaining steps and conditions are the same as in Example 1.

[0067] Due to improper pressure control during the impurity removal reaction stage, a large amount of the impurity removal agent was lost within the effective operating temperature range and could not fully participate in the impurity removal reaction, resulting in a product purity of only 99.9870%.

[0068] Comparative Example 3

[0069] The only difference between this comparative example and Example 1 is that the mixing method in step S1 is only wet ball milling, omitting the previous acoustic resonance mixing step. The remaining steps and conditions are the same as in Example 1.

[0070] The purity of the carbide powders prepared in each example and comparative example was analyzed. The content of impurity elements was determined by inductively coupled plasma mass spectrometry (ICP-MS), and the specific test results are summarized in Table 1.

[0071] Table 1 shows the performance data for each case.

[0072] Table 1 Comparison of main impurity content and purity of different powder samples

[0073] Figure 1 The image shows the SEM image of the TaC powder obtained in Example 1. It can be observed that the product particles are nearly spherical with a uniform particle size distribution of about 200~500 nm, and there is no obvious agglomeration or abnormally large grains.

[0074] Figure 2 The image shows the XRD pattern of the TaC powder obtained in Example 1. All diffraction peaks in the image correspond one-to-one with the face-centered cubic TaC phase on the standard PDF card. There are no characteristic peaks of any other impurity phases, indicating that the product is pure phase TaC.

[0075] Figure 3 The image shows a SEM image of the TaZrNbC medium-entropy ceramic powder obtained in Example 2. The image shows that the product particles have regular morphology, uniform particle size, and a particle size of approximately 300~600 nm.

[0076] Figure 4 The XRD pattern of the TaZrNbC medium-entropy ceramic powder obtained in Example 2 shows that its diffraction peaks are located between the standard peaks of TaC, ZrC and NbC, exhibiting a single characteristic peak of face-centered cubic solid solution, without phase separation or impurity phase peaks, confirming the formation of a uniform single-phase medium-entropy carbide solid solution.

Claims

1. A method for preparing carbide powder of grade 5N or higher, characterized in that: The ceramic precursor powder and carbon material are sequentially mixed by acoustic resonance and ball milled, and then dried to obtain a mixed powder. The mixed powder is then subjected to a purification reaction and a carbothermic reduction reaction to obtain a carbide powder of 5N or higher. During the impurity removal reaction, when the temperature inside the container is within the decomposition temperature range or crystal transformation temperature range of the ceramic precursor powder, the pressure inside the container is drawn up to above the saturated vapor pressure of the impurity remover at that temperature, exposing the lattice impurities inside the powder and promoting the decomposition of the impurity remover. The impurity removal agent is selected from at least one of the following: hydrides of halogen elements, elemental substances, alkali metal salts, alkaline earth metal salts, ammonium salts, and halogenated hydrocarbons; wherein the halogen elements include F and / or Cl.

2. The method for preparing a 5N or higher grade carbide powder according to claim 1, characterized in that: The carbon material includes carbon black; The ceramic precursor powder includes oxides, hydroxides, or oxygen-containing salts of one or more elements selected from zirconium, hafnium, titanium, tantalum, niobium, and tungsten. The purity of the ceramic precursor powder is ≥4N, and the purity of the carbon material is >4N5 grade; The ceramic precursor powder has a particle size of 0.5~5μm, and the carbon material has a particle size of 20~50nm; The molar ratio of the ceramic precursor powder to the carbon material is 1:(2~8).

3. A method for preparing a 5N or higher grade carbide powder according to claim 1 or 2, characterized in that: The vibration frequency of the acoustic resonance mixture is 50~80Hz, the working acceleration is 50~100g, and the vibration time is 2~30min; The ball milling is a wet ball milling process, wherein the ball-to-material ratio is (5~10):1, the time is 2~5 hours, and the rotation speed is 50~200 r / min; the ball milling solvent includes water.

4. The method for preparing a 5N or higher grade carbide powder according to claim 1, characterized in that: The impurity removal agent is at least one selected from HCl, Cl2, NH4Cl, KCl, NaCl, CaCl, CHClF2, LiF, KF, and NaF.

5. The method for preparing a 5N or higher grade carbide powder according to claim 4, characterized in that: When the impurity removal agent used in the impurity removal reaction is solid, the mixed powder and the impurity removal agent are mixed and placed in a container for vibration compaction, and then the impurity removal reaction and carbothermic reduction reaction are carried out in sequence. When the impurity removal agent used in the impurity removal reaction is in a gaseous state, the mixed powder is placed in a container and subjected to vibration compaction before the impurity removal agent is introduced to carry out the impurity removal reaction and carbothermic reduction reaction in sequence.

6. The method for preparing a 5N or higher grade carbide powder according to claim 5, characterized in that: When the impurity remover is in solid form, its addition amount is 1~10 wt.% of the mixed powder. When the impurity removal agent is in a gaseous state, its flow rate is 10~100 mL / min; The pressure for the vibration compaction treatment is 1~3MPa.

7. The method for preparing a 5N or higher grade carbide powder according to claim 1, characterized in that: During the impurity removal reaction, when the temperature inside the container is within the decomposition temperature range or crystal transformation temperature range of the ceramic precursor powder, the heating rate is controlled at 5~10℃ / min; when the temperature inside the container is within the decomposition temperature range or crystal transformation temperature range of the ceramic precursor powder, the heating rate is controlled at 1~3℃ / min, and the temperature is maintained for 1~2h.

8. The method for preparing a 5N or higher grade carbide powder according to claim 1, characterized in that: After the impurity removal reaction is completed, the container is kept under vacuum and heated to above 1400°C at a rate of 2~10°C / min, and held at that temperature for 1~5 hours to carry out the carbothermic reduction reaction.

9. A carbide powder of grade 5N or higher, characterized in that: It is obtained by the preparation method according to any one of claims 1 to 8.

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