A method for preparing porous tantalum carbide ceramics by combining template method and carbothermal reduction method

Abstract

The present invention discloses a method for preparing porous tantalum carbide ceramics by combining a template method with a carbothermal reduction method, which relates to the field of carbide porous ceramic materials. The method for preparing porous tantalum carbide ceramics by combining the template method with the carbothermal reduction method disclosed in the present invention immerses a polyurethane foam template with a rough pore rib surface in a reaction slurry containing tantalum, rolls and extrudes the excess slurry, and repeats the impregnation-pressing process multiple times. The polyurethane foam template with a rough pore rib surface after the impregnation treatment is dried to obtain a tantalum carbide preform. The tantalum carbide preform is placed in a high-temperature furnace, evacuated, heated and kept warm with a gradient heating program for sintering, and then cooled to prepare porous tantalum carbide ceramics. The operation of the present invention is simple. It can not only regulate the porosity of the porous ceramics, but also remove the carbon impurities remaining from the template, thereby controlling the filtration performance of the tantalum carbide porous ceramics and improving the purity of the porous ceramics, and further realizing industrial-scale production.

Description

Technical Field

[0001] The present invention belongs to the field of carbide porous ceramic materials, and particularly relates to a method for preparing porous tantalum carbide ceramics by combining a template method and a carbothermal reduction method. Background Art

[0002] Porous ceramic materials, with their excellent physical and chemical properties such as extremely high melting points, hardness, extraordinary chemical corrosion resistance and high-temperature stability, show great application potential in many fields. Compared with traditional ceramics, their significantly increased specific surface area, optimized porosity and controllable pore structure not only extend the service life but also endow the materials with excellent regeneration performance, making them ideal choices in fields such as thermal insulation, electrode construction and high-efficiency filtration. In the industrial field, porous ceramic materials such as zirconia, silicon carbide and alumina have developed to the stage of mature application, and they can maintain a stable form in extremely high-temperature (1000 - 1700 °C) environments, showing extraordinary heat resistance. Facing the challenge of higher temperatures (above 2000 °C), the existing material systems are inadequate and there is an urgent need for a breakthrough in new materials.

[0003] Tantalum carbide ceramics are ultra-high-temperature ceramics with a melting point of up to 3880 °C, and can still maintain good mechanical properties and chemical stability in ultra-high-temperature environments above 3000 °C, and are widely used in the high-temperature field and the semiconductor field. However, despite the broad prospects, the current research on porous tantalum carbide ceramics is still in its infancy. For example, the literature "Adsorption properties and preparation of porous TaC ceramics with regular steps", Ning-Ning Yan et al., 《Journal of Alloys and Compounds》, Volume 731, Pages 971 - 977, discloses a method for preparing porous TaC ceramics, using carbon powder and tantalum pentoxide as raw materials, and preparing porous tantalum carbide ceramics by using die pressing and high-temperature sintering methods. However, the pore structure of the porous ceramics prepared by this method cannot be regulated, and the porosity is relatively low, about 65%. Chinese invention patent CN117902916A discloses a porous TaC ceramic material, which combines a molten salt method and a reaction sintering method to prepare porous TaC ceramics at a lower temperature, and its porosity can reach more than 90%. However, the porosity of the porous ceramics prepared by this method cannot be regulated either, and the strength is relatively low, and it is currently impossible to achieve industrial application.

[0004] At present, the commonly used methods for preparing porous materials include adding pore-forming agents, direct foaming, organic foam impregnation, reaction sintering process, sol-gel method, biological template method and 3D printing. Among them, most porous ceramics use organic foam impregnation method, which uses prepared ceramic slurry to impregnate organic foam (usually sponge-like polyurethane), and then burns off the organic matter and sinters the ceramic body to obtain porous ceramic products. This method is not only simple in process and easy to operate, but also does not require complex equipment and has low preparation cost. It is an effective and economical method for preparing high porosity (70-95%) porous ceramics. However, in the process of removing the template, residual carbon impurities may be caused in the sample. If porous ceramics such as zirconium oxide and alumina are sintered in an air atmosphere, these residual carbons are easily oxidized and decomposed. However, when preparing non-oxide porous ceramics, the sintering atmosphere is mostly inert, which makes it difficult to effectively remove the residual carbon impurities, thereby affecting the purity and mechanical properties of the material, which has become a technical problem that needs to be solved urgently. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing porous tantalum carbide ceramics by combining a template method with a carbon thermal reduction method. The method is simple to operate and can not only regulate the porosity of the porous ceramics, but also remove carbon impurities remaining in the template, thereby controlling the filtration performance of the tantalum carbide porous ceramics and improving the purity of the porous ceramics, thereby realizing industrial-scale production.

[0006] In order to achieve the purpose of the present invention, the present invention provides a method for preparing porous tantalum carbide ceramics by combining a template method with a carbothermal reduction method, which specifically comprises the following steps:

[0007] S1. Dipping the polyurethane foam template with a rough surface of the pore reinforcement into the reaction slurry containing tantalum, rolling and squeezing out the excess slurry, and repeating the dipping-pressing multiple times;

[0008] The tantalum-containing reaction slurry is composed of the following raw materials in parts by mass: 30-60% tantalum source, 3-15% carbon source, 1-10% binder, 0.1-1.0% dispersant and 20-50% solvent; the tantalum source is composed of tantalum carbide ceramic powder, tantalum pentoxide and tantalum-containing compound, and the powder particle size is 1-5 μm; the amount of tantalum pentoxide used is 10-30% of the total mass of the tantalum source; the amount of tantalum-containing compound used is 1-10% of the total mass of the tantalum source; the tantalum-containing compound is any one or more of potassium fluorotantalate, tantalum oxyfluoride, tantalum fluoride and tantalum chloride; a tantalum compound mixed with potassium fluorotantalate and tantalum oxyfluoride, wherein the mass ratio of potassium fluorocarbonate is 10-50%;

[0009] S2. Dry the surface-roughened polyurethane foam template of the pore ribs after impregnation treatment to obtain a tantalum carbide preform. The drying process is as follows: Keep the surface-roughened polyurethane foam template of the pore ribs after impregnation treatment at 30 - 60 °C, 80 - 120 °C, and 150 - 220 °C for 1 h respectively, and the heating rate in all three temperature ranges is 5 °C / min;

[0010] S3. Place the tantalum carbide preform in a high-temperature furnace, evacuate it, and then heat and hold it for sintering with a gradient heating program, and then cool it to obtain porous tantalum carbide ceramics. The sintering process is as follows: Heat it to 500 - 800 °C at a heating rate of 1 - 5 °C / min and hold for 1 h; then heat it to 1000 - 1500 °C at a heating rate of 3 - 10 °C / min and hold for 1 h; then heat it to 1500 - 1800 °C at a heating rate of 1 - 5 °C / min and hold for 1 h; finally, heat it to 1800 - 2500 °C at a heating rate of 1 - 5 °C / min and hold for 2 h; then cool it to 600 °C at a cooling rate of 5 °C / min, and then cool it to room temperature with the furnace, and that's it.

[0011] The present invention uses the method of carbothermal reduction and sintering of tantalum source and carbon source to generate tantalum carbide ceramics, avoiding the disadvantages of difficult sintering and densification caused by the strong covalent bonds existing in tantalum carbide itself during the direct sintering process of tantalum carbide powder. Intermediate products generated during the carbothermal reduction process, such as Ta, Ta2C, etc., have high reaction activity and are prone to react and sinter with the residual carbon source.

[0012] Since binders, dispersants, solvents, and polyurethane foam templates will decompose and release gases during the sintering process, and the final product after decomposition is carbon, when sintering in an air atmosphere, these residual carbons are easily removed by reaction with oxygen in the air, while under the protection of an inert atmosphere, these residual carbons will be retained and remain dispersed between ceramic particles, ultimately resulting in difficult sintering of ceramic particles in the polyurethane foam template skeleton and a sharp decline in the compressive strength of the prepared porous ceramics. The present invention uses tantalum carbide ceramic powder as the seed crystal in the reaction sintering process, and the remaining tantalum source can undergo carbothermal reduction reactions with the carbon source and residual carbon, and ultimately generate tantalum carbide ceramics. The generated tantalum carbide will gradually grow and sinter with the added tantalum carbide particles as the seed crystal.

[0013] In the present invention, special attention should be paid during the drying process of the reaction slurry. Excessive temperature or too fast heating rate will cause the slurry attached to the skeleton to crack during the drying process, ultimately leading to a decline in the mechanical properties of the ceramics. Therefore, the present invention performs heat preservation treatments at three appropriate temperature intervals respectively to ensure the adhesion effect of the slurry during the drying process, thereby improving the mechanical properties of the tantalum carbide ceramics of the present invention.

[0014] The specific heating rate curve of the present invention is formulated according to the thermogravimetric analysis curve of the sample. The high-temperature furnace is used to heat and keep warm according to a certain heating curve, ensuring that different materials proceed slowly during the decomposition process, avoiding an increase in ceramic framework cracks and a decrease in mechanical properties, and thus ensuring the high porosity of the porous tantalum carbide ceramic of the present invention while also ensuring relatively excellent mechanical strength.

[0015] The main object of the present invention is to optimize the process of preparing porous tantalum carbide ceramic by using the template method. Specifically, aiming at the problem of residual carbon on the porous tantalum carbide ceramic framework caused by the decomposition of the template after ceramic sintering, an effective solution is proposed. To solve this problem, porous tantalum carbide ceramic is prepared by using the template method combined with carbothermal reduction method. The key raw material required for carbothermal reduction is tantalum pentoxide, and controlling its content can simply and effectively solve the problem of residual carbon.

[0016] Further, the preparation method of the tantalum-containing reaction slurry is as follows: weigh tantalum source, carbon source, binder, dispersant and solvent according to a certain ratio, mix them evenly and then place them in a ball mill tank for ball milling. During ball milling, control the ball-to-material ratio to be 3-5:1, the ball milling speed to be 200-450 r / min, and the ball milling time to be 2-8 h.

[0017] The melting points and reaction activities of different tantalum-containing compounds are different. Multiple tantalum-containing compounds will react at different temperatures and different stages, and are coupled with the polymer materials volatilized at different stages to promote the sintering of ceramic particles. At the same time, some tantalum-containing compounds such as tantalum chloride can dissolve in the solvent, making the tantalum source in the slurry more evenly distributed, ensuring that the residual carbon can react completely.

[0018] Further, the carbon source is composed of resin and carbon powder. Among them, the resin is selected from phenolic resin or / and furan resin; the usage amount of the resin is 3-10% of the total mass of the carbon source.

[0019] The product decomposed from the preferred resin component of the present invention is resin carbon, and the residual carbon rate can reach 30-70%. The decomposed resin carbon has relatively high activity, and the resin can dissolve in the solvent and evenly wrap around the tantalum source particles, enabling the carbothermal reduction reaction to proceed completely and evenly. Moreover, the resin can also be used as a binder; the carbon powder can react with the tantalum source as a carbon source and can also be used as a filler to reduce the large shrinkage caused by the decomposition of the resin.

[0020] Further, the preparation method of the polyurethane foam template with rough pore ribs is as follows: add an alkali solution with a mass concentration of 5-30% to the polyurethane foam template for hydrolysis treatment. The hydrolysis temperature is 30-80 °C, and the hydrolysis time is 0.5-6 h. After washing and drying, the polyurethane foam template with rough pore ribs is obtained.

[0021] Further, the pore density of the polyurethane foam template with rough pore ribs is any one of 40 ppi, 50 ppi, 60 ppi, 80 ppi or 100 ppi; the pore density of the polyurethane foam template with rough pore ribs in the present invention is not limited to the listed ones, and templates with different pore densities can be selected according to requirements.

[0022] Further, the alkali solution is any one or a mixed solution of more than one of potassium hydroxide, sodium hydroxide, barium hydroxide, and magnesium hydroxide.

[0023] In the present invention, the hydrolysis temperature and time are regulated according to the pore density, composition, and mass of the polyurethane foam template with rough pore ribs; due to the influence of the polyurethane preparation process, there will be residual films between the skeleton meshes of the polyurethane foam template, and these films will block the impregnated reaction slurry, resulting in uneven impregnation of the reaction slurry. The reaction of polyurethane with alkali can remove these pore-blocking films. Polyurethanes with different pore densities and different compositions often contain different fillers and have different reaction activities with the alkali solution. Therefore, it is necessary to control the mass of the alkali solution, hydrolysis temperature, and hydrolysis time; after hydrolysis, it is necessary to ensure that the films between the foam body meshes are completely removed and the skeleton of the polyurethane foam template becomes rough, and at the same time, it is necessary to ensure that the polyurethane foam template with rough pore ribs has good compression resilience.

[0024] Further, the binder is composed of a high-temperature binder and a low-temperature binder. Among them, the high-temperature binder is 5-10% of the total mass of the tantalum-containing reaction slurry, and the low-temperature binder is 0.5-2% of the total mass of the tantalum-containing reaction slurry;

[0025] The high-temperature binder is a transition metal or / and an oxide;

[0026] The low-temperature binder is polyacrylamide or / and polyvinyl butyral.

[0027] Further, the transition metal is any one or more of iron, cobalt, and nickel;

[0028] The oxide is any one or more of alumina, yttrium oxide, and silicon oxide.

[0029] The preferred high-temperature binder in the present invention is mainly used to promote the sintering between tantalum carbide ceramic particles at high temperatures; the low-temperature binder is mainly used to fix the reaction slurry on the skeleton of the polyurethane foam template at low temperatures.

[0030] Further, the dispersant is any one or more of fish oil, trioctyl phosphate, and fatty acids; the dispersant component is soluble in the organic solvent selected in the present invention.

[0031] Further, the solvent is an organic solvent;

[0032] The organic solvent is selected from any one or more of absolute ethanol, ethyl acetate, n-propanol, benzyl alcohol, toluene, phenol, and dimethyl phthalate.

[0033] In the present invention, by combining solvents with different boiling points, staged volatilization of the slurry can be achieved, enabling the fillers in the slurry to be evenly and densely distributed on the polyurethane foam template skeleton, without cracking of the slurry attached to the polyurethane foam template skeleton due to too fast drying rate, which ultimately leads to excessive cracks in the porous ceramic skeleton after sintering and a decrease in the mechanical properties of the ceramic.

[0034] Further, the above-mentioned rolling and extrusion method is as follows: Immerse the polyurethane foam template with rough pore ribs on the surface after treatment into the mixed slurry and press repeatedly until all the pores are filled with the slurry. Then, put the template filled with the slurry into a rolling press for rolling. The roll gap of the rolling press is 20 - 50% of the thickness of the polyurethane foam template with rough pore ribs on the surface, and the roll gap needs to be adjusted to a suitable size according to the viscosity of the slurry. Roll repeatedly until the slurry in the polyurethane foam template with rough pore ribs on the surface no longer flows out, so as to avoid blocking the pores of the template with excess slurry.

[0035] In the present invention, a suitable roll gap is set to use a rolling press to extrude the excess slurry in the polyurethane foam template with rough pore ribs on the surface. The size of the roll gap needs to be adjusted appropriately. It is necessary to extrude the excess slurry to reduce slurry hole blockage, and at the same time, it is necessary to pay attention not to extrude the slurry attached to the polyurethane foam template skeleton. Then, through multiple impregnation and extrusion, finally, a certain thickness of slurry is attached to the polyurethane foam template skeleton.

[0036] The present invention has achieved the following beneficial effects:

[0037] 1. The preparation process of the present invention is simple, without the need for special equipment, and the cost is relatively low.

[0038] 2. The porous tantalum carbide ceramic prepared by the present invention has a high porosity, and the pore structure and porosity can be regulated. Porous tantalum carbide ceramics with different shapes, different sizes, and different porosities can be designed according to different requirements.

[0039] 3. The porous tantalum carbide ceramic prepared by the present invention has a high purity, without residual carbon after the decomposition of polymer materials. The prepared ceramic has a high compressive strength and can meet industrial applications. Description of the Drawings

[0040] Figure 1 It is the backscattered electron image of the tantalum carbide porous ceramic material obtained by the preparation method of Example 1 of the present invention;

[0041] Figure 2 It is the physical image of the tantalum carbide porous ceramic material obtained by the preparation method of Example 1 of the present invention;

[0042] Figure 3Backscattered electron image of the tantalum carbide porous ceramic material obtained by the preparation method of Comparative Example 1 of the present invention;

[0043] Figure 4 Physical image of the tantalum carbide porous ceramic material obtained by the preparation method of Comparative Example 2 of the present invention. Specific embodiments

[0044] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0045] The porous tantalum carbide ceramic of the present invention and its preparation method will be described below with reference to specific embodiments.

[0046] Example 1. The preparation method of the porous tantalum carbide ceramic in this Example 1 is as follows:

[0047] 1. Immerse the cut polyurethane foam template with 50 ppi into 10% NaOH aqueous solution, hydrolyze it in a water bath at 50 °C for 4 h. After hydrolysis, repeatedly wash it with clean water and dry it to obtain a polyurethane foam template with rough pore ribs on the surface.

[0048] 2. Weigh tantalum carbide (i.e., tantalum carbide ceramic powder), tantalum pentoxide, potassium hexafluorotantalate, oxotantalum fluoride, phenolic resin, carbon powder, nickel, trioctyl phosphate, polyvinyl butyral, ethanol, and xylene respectively according to the mass ratio of 30:20:2.5:2.5:2:2.5:0.5:0.1:0.2:30:9.7. Then put the weighed samples into a zirconia ball milling tank and carry out ball milling according to the ball-to-material ratio of 3:1. After ball milling, a mixed slurry is obtained.

[0049] 3. Immerse the obtained polyurethane foam template with rough pore ribs into the mixed slurry and press it repeatedly until all the holes are filled with the slurry. Then put the template filled with the slurry into a rolling press and roll it. The roll gap of the rolling press is 40% of the thickness of the polyurethane foam template with rough pore ribs on the surface. Roll it repeatedly until the slurry in the polyurethane foam template with rough pore ribs on the surface no longer flows out to avoid blocking the template holes with excess slurry.

[0050] 4. Then put the template impregnated with the slurry into an oven for drying. The drying process is: keep it at 50 °C, 80 °C, and 160 °C for 1 h each, and the heating rate is 5 °C / min.

[0051] 5. After drying is completed, place the sample into a high-temperature carbon tube furnace, conduct vacuum pumping, then heat it up to 800 °C at a heating rate of 3 °C / min and hold for 1 h; after the holding is completed, introduce argon until slightly positive pressure, then heat it up to 1500 °C at a heating rate of 5 °C / min and hold for 1 h; then heat it up to 1800 °C at a heating rate of 5 °C / min and hold for 1 h; finally, heat it up to 2200 °C at a heating rate of 3 °C / min and hold for 2 h; subsequently, cool it down to 600 °C at a cooling rate of 5 °C / min, and then cool it in the furnace to room temperature, and take out the porous tantalum carbide ceramic sample.

[0052] Figure 1 As shown in the backscattered electron image of the scanning electron microscope of the porous tantalum carbide ceramic material prepared in Example 1, it can be seen in the figure that the framework is very clean and there are no impurities such as residual carbon attached to the surface. As Figure 2 shown, it is a physical image of the tantalum carbide porous ceramic sample prepared in Example 1.

[0053] Example 2, the preparation method of the porous tantalum carbide ceramic in this Example 2 is as follows:

[0054] 1. Immerse the cut polyurethane foam template with 60 ppi into 10% NaOH aqueous solution, hydrolyze it in a water bath at 50 °C for 4 h. After the hydrolysis is completed, repeatedly wash it clean with clear water and dry it to obtain a polyurethane foam template with rough surface of the pore ribs.

[0055] 2. Weigh tantalum carbide, tantalum pentoxide, carbon powder, phenolic resin, nickel, trioctyl phosphate, polyvinyl butyral, ethanol, and xylene respectively according to the mass ratio of 40 : 20 : 1.5 : 3 : 0.5 : 0.1 : 0.2 : 25 : 9.7. Subsequently, put the weighed samples into a zirconia ball milling tank and conduct ball milling according to the ball-to-material ratio of 3:1. After the ball milling is completed, a mixed slurry is obtained.

[0056] 3. Immerse the obtained polyurethane foam template with rough surface of the pore ribs into the mixed slurry and press it repeatedly until all the holes are filled with the slurry. Subsequently, put the template filled with the slurry into a roll press and roll it. The roll gap of the roll press is 40% of the thickness of the polyurethane foam template with rough surface of the pore ribs, and roll it repeatedly until the slurry in the polyurethane foam template with rough surface of the pore ribs no longer flows out to avoid blocking the holes of the template with excess slurry.

[0057] 4. Subsequently, put the polyurethane foam template with rough surface of the pore ribs immersed with the slurry into an oven for drying. The drying process is to hold at 50 °C, 80 °C, and 160 °C for 1 h each, and the heating rate is 5 °C / min.

[0058] 5. After drying is completed, place the sample in a high-temperature carbon tube furnace, perform vacuum pumping, then heat it to 800 °C at a heating rate of 3 °C / min and hold for 1 h; after the holding is completed, introduce argon until slightly positive pressure, then heat it to 1500 °C at a heating rate of 5 °C / min and hold for 1 h; then heat it to 1800 °C at a heating rate of 5 °C / min and hold for 1 h; finally, heat it to 2200 °C at a heating rate of 3 °C / min and hold for 2 h; subsequently, cool it to 600 °C at a cooling rate of 5 °C / min, and then cool it in the furnace to room temperature, and take out the porous tantalum carbide ceramic sample.

[0059] Example 3. The preparation method of the porous tantalum carbide ceramic in this Example 3 is as follows:

[0060] 1. Immerse the cut polyurethane foam template with 80 ppi in a 10% aqueous NaOH solution, hydrolyze it in a water bath at 50 °C for 4 h. After hydrolysis, repeatedly wash it with clean water and dry it to obtain a polyurethane foam template with rough pore ribs on the surface.

[0061] 2. Weigh tantalum carbide, tantalum pentoxide, potassium hexafluorotantalate, carbon powder, furan resin, nickel, trioctyl phosphate, polyvinyl butyral, ethanol, and xylene respectively according to the mass ratio of 35 : 20 : 5 : 1.5 : 3 : 0.5 : 0.1 : 0.2 : 25 : 9.7. Subsequently, put the weighed samples into a zirconia ball milling tank and perform ball milling according to a ball-to-material ratio of 3:1. After ball milling, a mixed slurry is obtained.

[0062] 3. Immerse the treated polyurethane foam template with rough pore ribs in the mixed slurry and press it repeatedly until all the holes are filled with the slurry. Subsequently, put the template filled with the slurry into a rolling press and roll it. The roll gap of the rolling press is 40% of the thickness of the polyurethane foam template with rough pore ribs on the surface. Roll it repeatedly until the slurry in the polyurethane foam template with rough pore ribs on the surface no longer flows out to avoid blocking the template holes with excess slurry.

[0063] 4. Subsequently, put the template immersed with the slurry into an oven for drying. The drying process is to hold at 50 °C, 80 °C, and 160 °C for 1 h each, and the heating rate is 5 °C / min.

[0064] 5. After drying is completed, place the sample into a high-temperature carbon tube furnace, conduct vacuum pumping, then heat it at a heating rate of 3 °C / min to 800 °C, and hold for 1 h; after the holding ends, introduce argon until slightly positive pressure, then heat it at a heating rate of 5 °C / min to 1500 °C, and hold for 1 h; then heat it at a heating rate of 5 °C / min to 1800 °C, and hold for 1 h; finally, heat it at a heating rate of 3 °C / min to 2200 °C, and hold for 2 h; subsequently, cool it at a cooling rate of 5 °C / min to 600 °C, then cool it in the furnace to room temperature, and take out the porous tantalum carbide ceramic sample.

[0065] Detect the porosity and compressive strength of the porous tantalum carbide ceramic samples prepared in the above Examples 1 to 3, and the test results are shown in Table 1.

[0066] Table 1 Performance test results of porous tantalum carbide ceramic materials

[0067]

[0068] Comparative Example 1, the preparation process of the porous tantalum carbide ceramic sample in this Comparative Example 1 is the same as that in Example 1, specifically referring to Example 1. The difference is that the tantalum-containing reaction slurry in this Comparative Example 1 is composed of tantalum carbide, nickel, trioctyl phosphate, polyvinyl butyral, ethanol, and xylene with a mass ratio of 60:3:0.1:0.2:27:9.7.

[0069] As Figure 3 shown, it is the backscattered electron image of the scanning electron microscope of the porous tantalum carbide ceramic sample prepared in Comparative Example 1. It can be seen from the figure that there are many impurities enriched on the skeleton, and its main component is carbon.

[0070] Comparative Example 2, the preparation process of the porous tantalum carbide ceramic sample in this Comparative Example 2 is the same as that in Example 1, specifically referring to Example 1. The difference is that the tantalum-containing reaction slurry in this comparative example is composed of tantalum pentoxide, carbon powder, phenolic resin, nickel, trioctyl phosphate, polyvinyl butyral, ethanol, and xylene with a mass ratio of 56.5:3:3:0.5:0.1:0.2:27:9.7.

[0071] As Figure 4 shown, it is the physical image of the porous tantalum carbide ceramic sample prepared in Comparative Example 2. The figure shows that the sintered porous tantalum carbide ceramic sample is cracked and broken.

[0072] Comparative Example 3, the preparation process of the porous tantalum carbide ceramic sample in this Comparative Example 3 is the same as that in Example 1, specifically referring to Example 1. The difference is that the drying process of the sample in this comparative example is to place the sample in an oven, then heat it to 120 °C and hold for 5 h, then take out the sample, and sinter it according to the sintering process of Example 1.

[0073] After sintering, there are no obvious cracks in the sample macroscopically, but the compressive strength is very low, only 0.56 MPa.

[0074] Comparative Example 4: The preparation process of the porous tantalum carbide ceramic sample in this Comparative Example 4 is the same as that in Example 1, specifically referring to Example 1. The difference is that the sintering process in this comparative example is to raise the temperature to 800 °C at a heating rate of 3 °C / min and hold for 1 h. During the holding process, argon is flushed into the furnace until slightly positive pressure, and then the temperature is raised to 2300 °C at a heating rate of 5 °C / min and held for 3 h, and then cooled to room temperature with the furnace.

[0075] After sintering, the sample shrinks unevenly, and cracking occurs in local areas.

[0076] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0077] The above-described embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A method for preparing porous tantalum carbide ceramics by combining a template method with a carbothermal reduction method, characterized in that: The specific steps include: S1. Dipping the polyurethane foam template with a rough surface of the pore reinforcement into the reaction slurry containing tantalum, rolling and squeezing out the excess slurry, and repeating the dipping-pressing multiple times; The tantalum-containing reaction slurry is composed of the following raw materials in parts by weight: 30-60% tantalum source, 3-15% carbon source, 1-10% binder, 0.1-1.0% dispersant and 20-50% solvent; The tantalum source is composed of tantalum carbide ceramic powder, tantalum pentoxide and tantalum-containing compounds, and the amount of tantalum pentoxide used is 10-30% of the total mass of the tantalum source; The usage amount of the tantalum-containing compound is 1-10% of the total mass of the tantalum source; the tantalum-containing compound is any one or more of potassium fluorotantalate, tantalum oxyfluoride, tantalum fluoride, and tantalum chloride; S2. Drying the rough surface of the polyurethane foam template after the impregnation treatment to obtain a tantalum carbide preform, wherein the drying process is as follows: the polyurethane foam template with rough surface of the pores after the impregnation treatment is kept warm for 1 hour at three temperature intervals of 30 to 60°C, 80 to 120°C, and 150 to 220°C, and the heating rate of the three temperature intervals is 5°C / min; S3. Place the tantalum carbide preform in a high-temperature furnace, evacuate it, then heat it with a gradient heating program and keep it warm for sintering, and cool it to obtain a porous tantalum carbide ceramic. The sintering process is as follows: heat it to 500-800°C at a heating rate of 1-5°C / min, and keep it warm for 1 hour; after the insulation is completed, introduce argon gas to a slightly positive pressure, and then heat it to 1000-1500°C at a heating rate of 3-10°C / min, and keep it warm for 1 hour; then heat it to 1500-1800°C at a heating rate of 1-5°C / min, and keep it warm for 1 hour; finally, heat it to 1800-2500°C at a heating rate of 1-5°C / min, and keep it warm for 2 hours; then cool it to 600°C at a cooling rate of 5°C / min, and then cool it to room temperature with the furnace.

2. The method for preparing porous tantalum carbide ceramics by combining a template method with a carbon thermal reduction method according to claim 1, characterized in that: The preparation method of the polyurethane foam template with rough pore rib surface is as follows: adding an alkali solution with a mass concentration of 5 to 30% to the polyurethane foam template for hydrolysis treatment, the hydrolysis temperature is 30 to 80° C., the hydrolysis time is 0.5 to 6 hours, and washing and drying to obtain the polyurethane foam template with rough pore rib surface; The pore density of the polyurethane foam template with a rough pore rib surface is any one of 40ppi, 50ppi, 60ppi, 80ppi or 100ppi; The alkaline solution is any one or more mixed solutions of potassium hydroxide, sodium hydroxide, barium hydroxide and magnesium hydroxide.

3. The method for preparing porous tantalum carbide ceramics by combining template method with carbothermal reduction method according to claim 1, characterized in that: The preparation method of the tantalum-containing reaction slurry is as follows: tantalum source, carbon source, binder, dispersant and solvent are weighed in a certain proportion, mixed evenly and placed in a ball mill for ball milling. During ball milling, the ball-to-material ratio is controlled to be 3 to 5:1, the ball milling speed is 200 to 450 r / min, and the ball milling time is 2 to 8 hours.

4. The method for preparing porous tantalum carbide ceramics by combining template method with carbothermal reduction method according to claim 1, characterized in that: The tantalum-containing compound is a mixture of potassium tantalate fluoroate and tantalum oxyfluoride, wherein the mass of the potassium tantalate fluoroate is 10-50% of the mass of the tantalum-containing compound.

5. The method for preparing porous tantalum carbide ceramics by combining template method with carbothermal reduction method according to claim 3, characterized in that: The carbon source is composed of resin and carbon powder, wherein the resin is selected from phenolic resin and / or furan resin; the usage amount of the resin is 3-10% of the total mass of the carbon source.

6. The method for preparing porous tantalum carbide ceramics by combining template method with carbothermal reduction method according to claim 3, characterized in that: The binder is composed of a high-temperature binder and a low-temperature binder; the high-temperature binder accounts for 5-10% of the total mass of the reaction slurry containing tantalum; the low-temperature binder accounts for 0.5-2% of the total mass of the reaction slurry containing tantalum.

7. The method for preparing porous tantalum carbide ceramics by combining template method with carbothermal reduction method according to claim 3, characterized in that: The dispersant is any one or more of fish oil, trioctyl phosphate, and fatty acid; the solvent is an organic solvent; the organic solvent is selected from any one or more of anhydrous ethanol, ethyl acetate, n-propanol, benzyl alcohol, toluene, phenol, and dimethyl phthalate.

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