A high-purity porous tantalum carbide ceramic and its preparation method and application

Abstract

The present invention belongs to the technical field of ultra-high temperature ceramic materials and discloses a high-purity porous tantalum carbide ceramic, a preparation method thereof, and an application thereof. The present invention comprises the following steps: placing a porous graphite substrate horizontally in a vertical vapor deposition chamber, evacuating the chamber, introducing argon gas, increasing the reaction gas pressure to 10-100 mbar, and heating the graphite substrate to a deposition temperature of the tantalum element; delivering an inorganic tantalum salt and hydrogen into the chamber to deposit the tantalum element in a first region; introducing argon gas into the reaction chamber to increase the reaction gas pressure, increasing the carrier gas flow of the inorganic tantalum salt, and increasing the deposition temperature of the tantalum element to deposit the tantalum element in a second region, and repeating the process to deposit the tantalum element on the porous graphite substrate from the inside out; and after the tantalum element is deposited, heating the high-purity porous graphite substrate to react and obtain tantalum carbide. By adjusting the reaction conditions, the reaction gas flow gradually penetrates the porous material at different depths, and the tantalum is uniformly deposited at different positions.

Description

Technical Field

[0001] The present invention belongs to the technical field of ultra-high temperature ceramic materials, and specifically relates to a high-purity porous tantalum carbide ceramic and a preparation method and application thereof. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Porous graphite, a graphite material with a three-dimensional pore structure, boasts excellent thermal and electrical conductivity, mechanical strength, and a high specific surface area, making it widely used in a variety of fields. Due to its excellent specific surface area and electrical conductivity, porous graphite can be used as an electrode material for energy storage devices in the energy sector, providing a larger reaction interface and higher electron transport capacity. Its unique three-dimensional pore structure also allows for applications in water treatment, gas adsorption, and separation, showing promising applications in environmental protection and gas purification.

[0004] However, graphite is susceptible to oxidation and corrosion in high-temperature environments, limiting its application prospects. Ultra-high-temperature ceramics, such as tantalum carbide (TaC) and hafnium carbide (HfC), which have high electrical and thermal conductivity, have become the preferred alternatives to porous graphite.

[0005] Preparation methods for porous tantalum carbide ceramics typically include: pore-forming agent addition, direct foaming, freeze-drying, reactive sintering, template processing, and 3D printing. While each method has its own advantages, it also has limitations. For example, the melting method requires the addition of external additives such as flux, which introduces varying degrees of impurities during the preparation process, reducing the purity of the tantalum carbide and adversely affecting its performance.

[0006] Chemical vapor deposition (CVD) typically deposits a coating on the sample surface, which can clog the pores of the porous material and cause it to lose its porous properties. Therefore, traditional CVD methods are difficult to use for the preparation of tantalum carbide porous ceramics. Summary of the Invention

[0007] In response to the shortcomings of the existing technology, the purpose of the present invention is to provide a high-purity porous tantalum carbide ceramic and its preparation method and application. The present invention adopts a multi-stage chemical vapor infiltration (CVI) method to prepare tantalum carbide in the pores inside porous graphite. Since the raw materials only contain Ta, Cl and H elements, it can effectively solve the problem of introducing foreign impurities during the preparation process.

[0008] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0009] In a first aspect, the present invention provides a method for preparing a high-purity porous tantalum carbide ceramic, comprising the following steps:

[0010] cleaning and drying the high-purity porous graphite substrate;

[0011] A clean, high-purity porous graphite substrate is placed horizontally in a vertical vapor deposition chamber. After the chamber is evacuated, argon gas is introduced to increase the reaction pressure to 10-100 mbar, and the high-purity porous graphite substrate is heated to the deposition temperature of tantalum.

[0012] Using argon as a carrier gas, inorganic tantalum salt and hydrogen are delivered into the chamber and maintained for 0.5-5 hours to achieve tantalum element deposition in the first area;

[0013] Argon gas is introduced into the reaction chamber to pressurize the reaction gas to 10-50 mbar, the carrier gas flow rate of the inorganic tantalum salt is increased by 10-100 sccm, and the deposition temperature of the tantalum element is increased by 10-50°C. The other steps are the same as the tantalum element deposition process in the first area to achieve tantalum element deposition in the second area, and the process is repeated to achieve tantalum element deposition from the inside to the outside on the porous graphite substrate.

[0014] After the tantalum element is deposited, the high-purity porous graphite substrate is heated to 1000-1800°C to react and produce tantalum carbide.

[0015] In the chamber, the reaction gas pressure (the actual pressure inside the reaction chamber) is low, there are fewer gas molecules per unit volume, the collisions between gas molecules are smaller, the resistance is smaller, the inorganic tantalum salt and hydrogen have a good penetration effect, and they will penetrate deep into the porous graphite substrate to deposit tantalum;

[0016] Heating is only performed at the porous graphite substrate, and the reaction gas is at a low, unactivated temperature before reaching the graphite substrate. The reaction gas is activated and reacted during the process of passing through the porous graphite, resulting in a low deposition rate at the front end of the porous graphite, with Ta deposited more concentratedly at the deep end.

[0017] Raising the temperature accelerates the activation of the reactant gases, moving the deposition process closer to the front. Increasing the gas pressure slows the flow of the reactant gases through the porous graphite, allowing them to react and deposit at the front end. Increasing the flow rate of the inorganic tantalum salt carrier gas increases the Ta partial pressure, which in turn increases the deposition rate and amount, compensating for the Ta deposition lost at the front end during the initial cycle and achieving overall uniformity.

[0018] A purified porous graphite substrate is placed in a CVI reactor. Under an inert atmosphere, a mixture of an inorganic tantalum salt carrier gas and hydrogen is delivered to the porous graphite substrate in stages, where it reacts and deposits within the pores of the porous graphite to form tantalum carbide porous ceramics. By controlling the temperature and pressure to adjust the deposition state of the Ta atmosphere at different depths, and thus the uniformity of its penetration within the porous carbon material, a uniformly distributed porous TaC ceramic is obtained.

[0019] The inorganic tantalum salt gas is obtained by heating and sublimating the inorganic tantalum salt, and then mixed and transported with argon as a carrier gas before chemical vapor infiltration. Specifically, the heating and sublimation temperature of the inorganic tantalum salt is 200-800°C.

[0020] In some embodiments, the porous graphite substrate has a thickness of 1-15 mm.

[0021] In some embodiments, the inorganic tantalum salt is tantalum chloride.

[0022] In some embodiments, the high-purity porous graphite substrate is placed in an organic solvent for ultrasonic cleaning for 10-20 minutes. The drying is vacuum drying at a drying temperature of 80-200° C. for 2-4 hours.

[0023] Preferably, the organic solvent is ethanol or acetone.

[0024] In some embodiments, the high-purity porous graphite substrate has a thickness of 1-10 mm and a porosity of 5-50%.

[0025] In some embodiments, the density of the high-purity porous graphite substrate is 0.8-1.5 g / cm 3 , the thermal expansion coefficient is 5.0-7.0×10 -6 ·K -1 .

[0026] In some embodiments, the tantalum element is deposited at a temperature of 700-1300°C.

[0027] Preferably, the heating rate of the porous graphite substrate is 5-15°C / min.

[0028] In some embodiments, the initial flow ratio of the inorganic tantalum salt carrier gas, the reaction gas carrier gas, and the hydrogen gas is 1.8-2.2:3.8-4.2:1.

[0029] In a second aspect, the present invention provides a high-purity porous tantalum carbide ceramic prepared by the preparation method.

[0030] In a third aspect, the present invention provides applications of the high-purity porous tantalum carbide ceramic in water treatment, gas adsorption and separation, semiconductor material growth, or aerospace fields.

[0031] The beneficial effects achieved by one or more embodiments of the present invention are as follows:

[0032] In this invention, a mixture of an inorganic tantalum salt and hydrogen is transported into porous graphite using gravity and air pressure, using an inert gas as a carrier gas. Localizing the heater around the porous graphite substrate effectively prevents the reactants from being activated and reacting before reaching the desired reaction location.

[0033] During the CVI reaction, the mixed reactant gases penetrate the pores and deposit on the pore walls. Heating causes the deposited Ta to react with the carbon element in the porous graphite. To ensure uniform deposition at different depths and reduce blockage of gas pores by reactive particles, reaction conditions are adjusted to allow the reactive gas flow to gradually penetrate the porous material at different depths, depositing Ta uniformly at different locations. Further increasing the temperature causes the Ta to react with the carbon element in the porous graphite to form TaC ceramics. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0035] Figure 1 This is a cross-sectional view of the porous tantalum carbide ceramic prepared in Example 1 of the present invention;

[0036] Figure 2 This is a cross-sectional view of the porous graphite with a surface-enriched tantalum carbide coating prepared in Comparative Example 1 of the present invention;

[0037] Figure 3 This is a cross-sectional view of a porous tantalum carbide ceramic prepared in Example 2 of the present invention;

[0038] Figure 4 This is a cross-sectional view of a porous tantalum carbide ceramic prepared in Example 3 of the present invention;

[0039] Figure 5 This is a schematic diagram of the CVI tantalum carbide ceramic reaction device of the present invention;

[0040] Figure 6 Schematic diagram of the porous tantalum carbide ceramic structure.

[0041] Among them, 31 is a side heater, 32 is a graphite crucible, 33 is a porous graphite support, 34 is a porous graphite base material, 35 is an air inlet, 36 is an exhaust port, 41 is a deep layer, 42 is a middle layer, and 43 is a surface layer. DETAILED DESCRIPTION

[0042] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0043] The present invention will be further described below with reference to the embodiments.

[0044] like Figure 5 The schematic diagram of the CVI tantalum carbide ceramic reaction device shown in the figure shows a porous graphite support 33 fixed in the middle of a graphite crucible 32, with a side heater 31 positioned outside the porous graphite support 33. A porous graphite substrate 34 is placed on top of the porous graphite support 33 and heated by the side heater 31. The reaction gas flows in through the gas inlet 35, reacts in the porous graphite substrate 34 to form porous tantalum carbide ceramic, and the remaining gas is discharged through the exhaust port 36 to the exhaust gas treatment device.

[0045] Taking three cycles of deposition as an example, the deposition process of tantalum is explained. Figure 6 As shown, in the first cycle, the tantalum element is concentrated and deposited at the deep layer 41; in the second cycle, the reaction temperature, reaction gas pressure and carrier gas flow are increased, the reaction rate of the reaction gas in the surface layer is increased, and the tantalum element is concentratedly generated at the middle position 42. Until the third cycle, the tantalum element is concentrated at the surface position 43. After the deposition of the tantalum element is completed, the graphite substrate is heated and reacted to generate tantalum carbide, thereby obtaining a high-purity tantalum carbide ceramic with relatively uniform depth at each depth.

[0046] The inorganic tantalum salt used in the following examples is tantalum chloride.

[0047] Example 1

[0048] 1. Select porous graphite with a thickness of 5 mm and a porosity of 10% as the base material, place it in anhydrous ethanol and ultrasonicate for 15 minutes, then place it in deionized water and ultrasonicate for 5 minutes, and finally place it in an oven and dry it at 150°C in a vacuum environment for 4 hours.

[0049] 2. Place the cleaned porous graphite substrate in the CVI reaction chamber, turn on the mechanical pump, pump the pressure in the chamber to below 10 Pa, turn on the molecular pump, and the pressure reaches 10 -2 At 100 Pa, argon was introduced as the inorganic tantalum salt carrier gas, pressurized to 50 mbar, and the porous graphite substrate was heated to 900°C (the deposition temperature of the Ta element). At the same time, the inorganic tantalum salt evaporation chamber was heated to 400°C to evaporate the inorganic tantalum salt (original mass: 100 g).

[0050] The argon flow rate of the inorganic tantalum salt carrier gas is 500 sccm, which carries the evaporated inorganic tantalum salt to the reaction chamber, and hydrogen is introduced simultaneously with argon as a carrier gas. The gas flow rate of hydrogen is 250 sccm, and the flow rate of argon as a hydrogen carrier gas is 1000 sccm. After maintaining for 2 hours, the introduction of the inorganic tantalum salt carrier gas is stopped.

[0051] 3. Argon was introduced into the reaction chamber, the reaction pressure was increased by 10 mbar, the reaction temperature was raised to 920°C, the argon flow rate of the inorganic tantalum salt carrier gas was 550 sccm, the evaporated inorganic tantalum salt was transported to the reaction chamber, and hydrogen was introduced simultaneously with argon as the carrier gas. The hydrogen gas flow rate was 250 sccm, and the argon flow rate of the hydrogen carrier gas was 1000 sccm. After maintaining for 2 hours, the inorganic tantalum salt carrier gas was stopped;

[0052] 4. Argon was introduced into the reaction chamber, the reaction pressure was increased by 10 mbar, the reaction temperature was raised to 940°C, the argon flow rate of the inorganic tantalum salt carrier gas was 600 sccm, the evaporated inorganic tantalum salt was transported to the reaction chamber, and hydrogen was introduced simultaneously with argon as the carrier gas. The hydrogen gas flow rate was 250 sccm, and the argon flow rate of the hydrogen carrier gas was 1000 sccm. After maintaining this for 2 hours, the inorganic tantalum salt carrier gas was stopped;

[0053] 5. Argon was introduced into the reaction chamber, the reaction pressure was increased by 10 mbar, the reaction temperature was raised to 960°C, the argon flow rate of the inorganic tantalum salt carrier gas was 650 sccm, the evaporated inorganic tantalum salt was transported to the reaction chamber, and hydrogen was introduced simultaneously with argon as the carrier gas. The hydrogen gas flow rate was 250 sccm, and the argon flow rate of the hydrogen carrier gas was 1000 sccm. After maintaining for 2 hours, the inorganic tantalum salt carrier gas was stopped;

[0054] 6. Argon was introduced into the reaction chamber, the reaction pressure was increased by 10 mbar, the reaction temperature was raised to 980°C, the argon flow rate of the inorganic tantalum salt carrier gas was 700 sccm, the evaporated inorganic tantalum salt was transported to the reaction chamber, and hydrogen was introduced simultaneously with argon as the carrier gas, the hydrogen gas flow rate was 250 sccm, and the argon flow rate of the hydrogen carrier gas was 1000 sccm. After maintaining this for 2 hours, the inorganic tantalum salt carrier gas was stopped;

[0055] 7. Argon was introduced into the reaction chamber, the reaction pressure was increased by 10 mbar, the reaction temperature was raised to 1000°C, the argon flow rate of the inorganic tantalum salt carrier gas was 750 sccm, the evaporated inorganic tantalum salt was transported to the reaction chamber, and hydrogen was introduced simultaneously with argon as the carrier gas. The hydrogen gas flow rate was 250 sccm, and the argon flow rate of the hydrogen carrier gas was 1000 sccm. After maintaining for 2 hours, the inorganic tantalum salt carrier gas was stopped;

[0056] 8. Argon was introduced into the reaction chamber, the reaction pressure was increased by 10 mbar, the reaction temperature was raised to 1020°C, the argon flow rate of the inorganic tantalum salt carrier gas was 800 sccm, the evaporated inorganic tantalum salt was transported to the reaction chamber, and hydrogen was introduced simultaneously with argon as the carrier gas, the hydrogen gas flow rate was 250 sccm, and the argon flow rate of the hydrogen carrier gas was 1000 sccm. After maintaining this state for 2 hours, the inorganic tantalum salt carrier gas was stopped;

[0057] 9. Argon was introduced into the reaction chamber, the reaction pressure was increased by 10 mbar, the reaction temperature was raised to 1040°C, the argon flow rate of the inorganic tantalum salt carrier gas was 850 sccm, the evaporated inorganic tantalum salt was transported to the reaction chamber, and hydrogen was introduced simultaneously with argon as the carrier gas, the hydrogen gas flow rate was 250 sccm, and the argon flow rate of the hydrogen carrier gas was 1000 sccm. After maintaining for 2 hours, the introduction of the inorganic tantalum salt carrier gas and hydrogen was stopped;

[0058] 10. Fill the reaction chamber with argon gas to increase the reaction gas pressure to 800 mbar, raise the temperature of the porous graphite substrate to 1300°C and maintain it for 30 minutes to allow the deposited tantalum to react with carbon to form tantalum carbide porous ceramics.

[0059] After the reaction chamber cools to below 50°C, the vacuum pump is turned on to exhaust the gas inside the reaction chamber into the tail gas treatment device until the vacuum level drops below 100 Pa. The vacuum pump is then turned off and argon gas is introduced. After the pressure in the reaction chamber returns to atmospheric pressure, the reaction chamber is opened and the prepared high-purity porous tantalum carbide ceramic is removed.

[0060] The prepared high-purity porous tantalum carbide ceramics were characterized using a scanning electron microscope. The test results showed that the pore walls were evenly covered with tantalum carbide ceramics. Figure 1 shown.

[0061] Comparative Example 1

[0062] Porous graphite with a thickness of 10 mm was selected as the base material, which was placed in anhydrous ethanol and ultrasonicated for 15 min, then placed in deionized water and ultrasonicated for 5 min, and finally placed in an oven and dried at 150 °C in a vacuum environment for 4 h.

[0063] The cleaned porous graphite substrate was placed in a CVD reaction chamber. The mechanical pump was turned on to reduce the pressure in the chamber to below 10 Pa, and the molecular pump was turned on. When the pressure reached a certain level, argon was introduced as a carrier gas to 50 mbar. The reaction chamber was then heated to 1300°C, while the inorganic tantalum salt evaporation chamber was simultaneously heated to 400°C.

[0064] After heating to the specified temperature, an inorganic tantalum salt carrier gas, argon, was introduced at a flow rate of 500 sccm and transported to the reaction chamber. Methane and hydrogen were simultaneously introduced using argon as carrier gas. The reaction carrier gas argon was 1000 sccm, and the gas flow rates of methane and hydrogen were 500 sccm. After maintaining the temperature for 10 hours, a tantalum carbide coating prepared by the traditional CVD method was obtained on the porous graphite surface.

[0065] Figure 2 This is a cross-sectional morphology of the tantalum carbide coating prepared on porous graphite by the traditional CVD method in Comparative Example 1. It can be seen that tantalum carbide is mainly deposited on the surface of the porous graphite base material, and the excessively fast deposition rate causes the pores on the surface of the base material to be quickly blocked, making it difficult for the reaction gas to penetrate into the interior of the porous graphite, and tantalum carbide ceramics cannot be generated inside the porous graphite.

[0066] In comparison, Figure 1 The tantalum carbide obtained in Example 1 can be evenly generated inside the porous graphite, providing comprehensive protection for the entire base material.

[0067] Example 2

[0068] 1. Select porous graphite with a thickness of 3 mm and a porosity of 5% as the base material, place it in anhydrous ethanol and ultrasonicate for 15 minutes, then place it in deionized water and ultrasonicate for 5 minutes, and finally place it in an oven and dry it at 200°C in a vacuum environment for 3 hours.

[0069] 2. Place the cleaned porous graphite substrate in the CVI reaction chamber, turn on the mechanical pump, pump the pressure in the chamber to below 10 Pa, turn on the molecular pump, and the pressure reaches 10 -2 At 100 mbar, argon was introduced as the inorganic tantalum salt carrier gas, and the pressure was increased to 100 mbar. The porous graphite substrate was then heated to 1000°C (the deposition temperature of the Ta element). At the same time, the inorganic tantalum salt evaporation chamber was heated to 300°C to evaporate the inorganic tantalum salt (original mass was 100 g).

[0070] The argon flow rate of the inorganic tantalum salt carrier gas is 250 sccm, which carries the evaporated inorganic tantalum salt to the reaction chamber, and hydrogen is introduced simultaneously with argon as a carrier gas. The gas flow rate of hydrogen is 120 sccm, and the flow rate of argon as a hydrogen carrier gas is 500 sccm. After maintaining for 3 hours, the introduction of the inorganic tantalum salt carrier gas is stopped.

[0071] 3. Argon was introduced into the reaction chamber, the reaction pressure was increased by 20 mbar, the reaction temperature was raised to 1010°C, the argon flow rate of the inorganic tantalum salt carrier gas was 280 sccm, the evaporated inorganic tantalum salt was transported to the reaction chamber, and hydrogen was introduced simultaneously with argon as the carrier gas. The hydrogen gas flow rate was 120 sccm, and the argon flow rate of the hydrogen carrier gas was 500 sccm. After maintaining for 3 hours, the inorganic tantalum salt carrier gas was stopped;

[0072] 4. Argon was introduced into the reaction chamber, the reaction pressure was increased by 20 mbar, the reaction temperature was raised to 1020°C, the argon flow rate of the inorganic tantalum salt carrier gas was 310 sccm, the evaporated inorganic tantalum salt was transported to the reaction chamber, and hydrogen was introduced simultaneously with argon as the carrier gas. The hydrogen gas flow rate was 120 sccm, and the argon flow rate of the hydrogen carrier gas was 500 sccm. After maintaining for 3 hours, the inorganic tantalum salt carrier gas was stopped;

[0073] 5. Argon was introduced into the reaction chamber, the reaction pressure was increased by 20 mbar, the reaction temperature was raised to 1030°C, the argon flow rate of the inorganic tantalum salt carrier gas was 340 sccm, the evaporated inorganic tantalum salt was transported to the reaction chamber, and hydrogen was introduced simultaneously with argon as the carrier gas. The hydrogen gas flow rate was 120 sccm, and the argon flow rate of the hydrogen carrier gas was 500 sccm. After maintaining for 3 hours, the inorganic tantalum salt carrier gas was stopped;

[0074] 6. Argon was introduced into the reaction chamber, the reaction pressure was increased by 20 mbar, the reaction temperature was raised to 1040°C, the argon flow rate of the inorganic tantalum salt carrier gas was 370 sccm, the evaporated inorganic tantalum salt was transported to the reaction chamber, and hydrogen was introduced simultaneously with argon as the carrier gas. The hydrogen gas flow rate was 120 sccm, and the argon flow rate of the hydrogen carrier gas was 500 sccm. After maintaining for 2 hours, the inorganic tantalum salt carrier gas was stopped;

[0075] 7. Argon was introduced into the reaction chamber, the reaction pressure was increased by 20 mbar, the reaction temperature was raised to 1050°C, the argon flow rate of the inorganic tantalum salt carrier gas was 400 sccm, the evaporated inorganic tantalum salt was transported to the reaction chamber, and hydrogen was introduced simultaneously with argon as the carrier gas. The hydrogen gas flow rate was 120 sccm, and the argon flow rate of the hydrogen carrier gas was 500 sccm. After maintaining this state for 2 hours, the inorganic tantalum salt carrier gas was stopped;

[0076] 8. Argon was introduced into the reaction chamber, the reaction pressure was increased by 20 mbar, the reaction temperature was raised to 1060°C, the argon flow rate of the inorganic tantalum salt carrier gas was 430 sccm, the evaporated inorganic tantalum salt was transported to the reaction chamber, and hydrogen was introduced simultaneously with argon as the carrier gas. The hydrogen gas flow rate was 120 sccm, and the argon flow rate of the hydrogen carrier gas was 500 sccm. After maintaining for 3 hours, the inorganic tantalum salt carrier gas was stopped;

[0077] 9. Argon was introduced into the reaction chamber, the reaction pressure was increased by 20 mbar, the reaction temperature was raised to 1080°C, the argon flow rate of the inorganic tantalum salt carrier gas was 460 sccm, the evaporated inorganic tantalum salt was transported to the reaction chamber, and hydrogen was introduced simultaneously with argon as a carrier gas, the hydrogen gas flow rate was 120 sccm, and the argon flow rate of the hydrogen carrier gas was 500 sccm. After maintaining for 3 hours, the introduction of the inorganic tantalum salt carrier gas and hydrogen was stopped;

[0078] 10. Argon was introduced into the reaction chamber, the reaction pressure was increased by 20 mbar, the reaction temperature was raised to 1090°C, the argon flow rate of the inorganic tantalum salt carrier gas was 490 sccm, the evaporated inorganic tantalum salt was transported to the reaction chamber, and hydrogen was introduced simultaneously with argon as a carrier gas, the hydrogen gas flow rate was 120 sccm, and the argon flow rate of the hydrogen carrier gas was 500 sccm. After maintaining for 3 hours, the introduction of the inorganic tantalum salt carrier gas and hydrogen was stopped;

[0079] 10. Fill the reaction chamber with argon gas to increase the reaction gas pressure by 20 mbar, raise the temperature of the porous graphite substrate to 1400°C, and maintain it for 30 minutes to allow the deposited tantalum to react with carbon to form tantalum carbide porous ceramics.

[0080] Stop introducing the reaction gas, wait until the reaction chamber is cooled to below 50°C, turn on the vacuum pump to exhaust the gas in the reaction chamber into the tail gas treatment device until the vacuum degree is below 100 Pa, then turn off the vacuum pump and introduce argon. After the pressure in the reaction chamber rises to normal pressure, open the reaction chamber and take out the prepared high-purity porous tantalum carbide ceramic. Figure 3 As shown, the obtained porous tantalum carbide ceramics have good crystallinity and porosity.

[0081] Example 3

[0082] 1. Select porous graphite with a thickness of 8 mm and a porosity of 20% as the base material, place it in anhydrous ethanol and ultrasonicate for 20 minutes, then place it in deionized water and ultrasonicate for 5 minutes, and finally place it in an oven and dry it at 100°C in a vacuum environment for 4 hours.

[0083] 2. Place the cleaned porous graphite substrate in the CVI reaction chamber, turn on the mechanical pump, pump the pressure in the chamber to below 10 Pa, turn on the molecular pump, and the pressure reaches 10 -2 At 1000 Pa, argon was introduced as the inorganic tantalum salt carrier gas, pressurized to 300 mbar, and the porous graphite substrate was heated to 1000°C (the deposition temperature of the Ta element). At the same time, the inorganic tantalum salt evaporation chamber was heated to 500°C to evaporate the inorganic tantalum salt (original mass was 100g).

[0084] The argon flow rate of the inorganic tantalum salt carrier gas is 400 sccm, which carries the evaporated inorganic tantalum salt to the reaction chamber, and hydrogen is introduced simultaneously with argon as a carrier gas. The gas flow rate of hydrogen is 200 sccm, and the flow rate of argon as a hydrogen carrier gas is 800 sccm. After maintaining this for 3 hours, the introduction of the inorganic tantalum salt carrier gas is stopped.

[0085] 3. Argon was introduced into the reaction chamber to increase the reaction pressure by 30 mbar and the reaction temperature to 1015°C. The argon flow rate of the inorganic tantalum salt carrier gas was 460 sccm, carrying the evaporated inorganic tantalum salt into the reaction chamber. Hydrogen was introduced simultaneously using argon as a carrier gas. The hydrogen flow rate was 200 sccm and the argon flow rate of the hydrogen carrier gas was 800 sccm. After maintaining this for 1.5 hours, the introduction of the inorganic tantalum salt carrier gas was stopped.

[0086] 4. Argon was introduced into the reaction chamber to increase the reaction pressure by 30 mbar and the reaction temperature to 1030°C. The argon flow rate of the inorganic tantalum salt carrier gas was 520 sccm, carrying the evaporated inorganic tantalum salt into the reaction chamber. Hydrogen was introduced simultaneously using argon as a carrier gas. The hydrogen flow rate was 200 sccm and the argon flow rate of the hydrogen carrier gas was 800 sccm. After maintaining this state for 1.5 hours, the introduction of the inorganic tantalum salt carrier gas was stopped.

[0087] 5. Argon was introduced into the reaction chamber to increase the reaction pressure by 30 mbar and the reaction temperature to 1045°C. The argon flow rate of the inorganic tantalum salt carrier gas was 580 sccm, carrying the evaporated inorganic tantalum salt into the reaction chamber. Hydrogen was introduced simultaneously using argon as a carrier gas. The hydrogen flow rate was 200 sccm and the argon flow rate of the hydrogen carrier gas was 800 sccm. After maintaining this for 1.5 hours, the introduction of the inorganic tantalum salt carrier gas was stopped.

[0088] 6. Argon was introduced into the reaction chamber, the reaction pressure was increased by 30 mbar, the reaction temperature was raised to 1060°C, the argon flow rate of the inorganic tantalum salt carrier gas was 640 sccm, the evaporated inorganic tantalum salt was transported to the reaction chamber, and hydrogen was introduced simultaneously with argon as the carrier gas. The hydrogen gas flow rate was 200 sccm, and the argon flow rate of the hydrogen carrier gas was 800 sccm. After maintaining this for 1.5 hours, the introduction of the inorganic tantalum salt carrier gas was stopped;

[0089] 7. Argon was introduced into the reaction chamber to increase the reaction pressure by 30 mbar and the reaction temperature to 1075°C. The argon flow rate of the inorganic tantalum salt carrier gas was 720 sccm, carrying the evaporated inorganic tantalum salt into the reaction chamber. Hydrogen was introduced simultaneously using argon as a carrier gas. The hydrogen flow rate was 200 sccm and the argon flow rate of the hydrogen carrier gas was 800 sccm. After maintaining this for 1.5 hours, the introduction of the inorganic tantalum salt carrier gas was stopped.

[0090] Stop introducing the reaction gas, wait until the reaction chamber is cooled to below 50°C, turn on the vacuum pump to exhaust the gas in the reaction chamber into the tail gas treatment device until the vacuum degree is below 100 Pa, then turn off the vacuum pump and introduce argon. After the pressure in the reaction chamber rises to normal pressure, open the reaction chamber and take out the prepared high-purity porous tantalum carbide ceramic. Figure 4 As shown, the obtained porous tantalum carbide ceramics have good crystallinity and porosity.

[0091] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing high-purity porous tantalum carbide ceramics, characterized by: The steps include: Cleaning and drying a high-purity porous graphite substrate; wherein the high-purity porous graphite substrate has a thickness of 1-10 mm and a porosity of 5-50%; A clean, high-purity porous graphite substrate is placed horizontally in a vertical vapor deposition chamber. After the chamber is evacuated, argon gas is introduced to increase the reaction pressure to 10-100 mbar. The high-purity porous graphite substrate is heated to the deposition temperature of the tantalum element, which is 700-1300°C. Argon is used as a carrier gas to deliver inorganic tantalum salt and hydrogen into the chamber for 0.5-5 hours to achieve tantalum element deposition in the first area; the initial flow ratio of inorganic tantalum salt carrier gas, reaction gas carrier gas and hydrogen is 1.8-2.2:3.8-4.2:1; Argon gas is introduced into the reaction chamber to pressurize the reaction gas to 10-50 mbar, the carrier gas flow rate of the inorganic tantalum salt is increased by 10-100 sccm, and the deposition temperature of the tantalum element is increased by 10-50°C. The other steps are the same as the tantalum element deposition process in the first area to achieve tantalum element deposition in the second area, and the process is repeated to achieve tantalum element deposition from the inside to the outside on the porous graphite substrate. After the tantalum element is deposited, the high-purity porous graphite substrate is heated to 1000-1800°C to react and obtain tantalum carbide porous ceramics.

2. The method for preparing high-purity porous tantalum carbide ceramics according to claim 1, wherein: The high-purity porous graphite substrate is placed in an organic solvent for ultrasonic cleaning, the ultrasonic cleaning time is 10-20 minutes, and the drying is vacuum drying, the drying temperature is 80-200° C., and the drying time is 2-4 hours.

3. The method for preparing high-purity porous tantalum carbide ceramics according to claim 2, wherein: The organic solvent is ethanol or acetone.

4. The method for preparing high-purity porous tantalum carbide ceramics according to claim 1, wherein: The density of high-purity porous graphite substrate is 0.8-1.5g / cm 3 , the thermal expansion coefficient is 5.0-7.0×10 -6 ·K -1 .

5. The method for preparing the high-purity porous tantalum carbide ceramic according to claim 1, wherein: The heating rate of the porous graphite substrate was 5-15 °C / min.

6. A high-purity porous tantalum carbide ceramic, characterized by: Prepared by the preparation method according to any one of claims 1 to 5.

7. Application of the high-purity porous tantalum carbide ceramic according to claim 6 in water treatment, gas adsorption and separation, semiconductor material growth or aerospace fields.

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