Anti-ablation (Hf-Zr-Ta) C ternary medium-entropy ceramic material and preparation method thereof

Abstract

The invention belongs to the technical field of ceramic materials, and discloses an anti-ablation (Hf-Zr-Ta) C ternary medium-entropy ceramic material and a preparation method thereof. The preparation method comprises the following steps: firstly, mixing HfC, ZrC and TaC powder, adding an absolute ethyl alcohol solvent, and carrying out ball milling to obtain mixed slurry; the preparation method comprises the following steps: preparing a mixed slurry, then drying and sieving the mixed slurry to obtain mixed powder, finally putting the fully mixed complex-phase powder into a graphite mold, and preparing the high-density (Hf-Zr-Ta) C ternary medium-entropy ceramic through spark plasma sintering equipment by utilizing diffusion and in-situ solid solution principles. The medium-entropy carbide ceramic is prepared by adopting a spark plasma sintering technology, the sintering time is remarkably shortened through rapid densification, abnormal growth of crystal grains is synchronously inhibited, and the microstructure uniformity is optimized; the process does not need complex auxiliary equipment, and the single-time production efficiency is remarkably improved; the prepared ceramic has high density and excellent high-temperature ablation resistance, and a compact oxide layer on the surface of the ceramic can effectively block oxygen erosion.

Description

Technical Field

[0001] This invention belongs to the field of ceramic materials technology and discloses an ablation-resistant ternary medium-entropy ceramic material and its preparation method. Background Technology

[0002] Currently, the global demand for hypersonic vehicles with extended endurance is increasingly urgent, necessitating their operation in harsh environments. Certain critical structural components, such as the nose cone, leading edge, aerodynamic control surfaces, engine combustion chamber, and nozzle, will undergo prolonged ablation tests under extremely high temperatures, pressures, and high-enthalpy chemical non-equilibrium flow. To address these demanding operating environments, it is essential to develop new material systems and explore new thermal protection theories. The performance of thermal protection materials not only determines the speed limit of hypersonic vehicles but also directly affects their service life, serving as a fundamental guarantee for the iterative development of aerospace equipment.

[0003] Ultra-high temperature ceramics, due to their high melting point, high strength, and excellent thermal shock resistance, have become the most commonly used thermal protection materials for aerospace applications. However, single-component thermal protection ceramic materials (ZrB2, HfB2, ZrC, HfC, TaC, HfN, etc.) exhibit rapid oxidation / ablation rates in high-speed, high-temperature, and strong airflow erosion environments, failing to meet current performance requirements for hot-end components of hypersonic vehicles. Therefore, developing new ultra-high temperature materials with superior performance to address the issue of highly stable thermal protection has become paramount for hypersonic vehicle development. Multi-component ultra-high temperature carbide ceramics possess higher hardness and elastic modulus, lower thermal conductivity, and superior oxidation / ablation resistance, promising to solve the problems of insufficient stability and poor oxidation / ablation resistance of traditional ultra-high temperature carbide ceramics during extreme environmental operations, making them an important candidate for thermal protection materials for hot-end components of hypersonic vehicles.

[0004] Reference 1, "LiB, LiH, YaoX, et al. Pressureless sintering of HfC-HfB2-SiC-HfSi2 ceramics and their ultra high-temperature ablation resistance[J]. Ceramics International, 2024, 50: 37525-37532," successfully prepared HfC-HfB2-SiC-HfSi2 nanocomposites using pressureless sintering technology. The addition of HfSi2 induced liquid-phase sintering to generate intergranular silicide phases that filled the pores significantly improved the material's densification and demonstrated excellent ablation resistance during plasma ablation at 2700℃. However, this process relies on high-temperature, long-term sintering, which easily leads to grain coarsening. Furthermore, the densification efficiency is low, the density is uncontrollable, and the single-batch yield is limited, making it difficult to meet the high-efficiency fabrication requirements of complex components and restricting its application in the large-scale production of ultra-high-temperature ceramics.

[0005] Reference 2, "Qi H, Wang Zhi, Wu J, et al. Improved mechanical properties of Al2O3 ceramic by in-suit generated Ti3SiC2 and TiC via hot pressing sintering [J]. Ceramics International, 2017, 43(14): 10691-10697," describes the preparation of Al2O3-SiC-Ti multiphase ceramics using vacuum hot pressing sintering technology. It was found that the addition of SiC can regulate the microstructure and properties of the material by generating transition metal carbide reinforcing phases. Although this process can achieve high material density, its microstructure control precision, equipment maintenance costs, and product form limitations remain the core issues restricting the industrialization of high-performance composite materials. Furthermore, due to limitations in mold design and pressure and heat transfer characteristics, it is difficult to prepare large-size or complex geometric parts, making it only suitable for producing simple structural components, and it consumes a large amount of energy.

[0006] Reference 3, "Ren J, Zhang Y, Zhang J, et al. Effects of HfC nanowire amount on the microstructure and ablation resistance of CVD-HfC coating[J]. Ceramics International, 2018, 44(10): 11340-9," describes the preparation of an HfC ceramic coating on the surface of a C / C composite material using chemical vapor deposition (CVD). The coating was applied at an oxyacetylene heat flux density of 2.4 MW / m³. 2Failure occurred after 120 seconds of continuous ablation. This is because the HfO2 formed by the oxidation of HfC becomes porous and loose after prolonged ablation. During the ablation process, oxygen diffuses through these porous structures into the internal SiC layer and even the C / C matrix, exacerbating the damage to the C / C composite material. Furthermore, the loose framework structure of HfO2 cannot withstand the mechanical erosion during the ablation process, leading to severe cracking and detachment of the oxide layer. Therefore, HfC ceramics exhibit poor ablation resistance.

[0007] Reference 4, "Li B, Li H, Yao X, et al. Preparation and ablation resistance of ZrC nanowires-reinforced CVD-ZrC coating on sharp leading edge C / C composites[J]. Applied Surface Science, 2022, 584," describes the preparation of a ZrC ceramic coating on the surface of C / C composites using chemical vapor deposition at an oxyacetylene heat flux density of 2.4 MW / m³. 2 It fails after continuous ablation for 60 seconds. ZrO2 formed by the oxidation and ablation of ZrC has similar properties to HfO2. After long-term ablation, the ZrO2 oxide layer remains loose and porous, which cannot effectively inhibit oxygen diffusion. Moreover, the loose skeleton structure of ZrO2 cannot resist the mechanical erosion during the ablation process, resulting in severe cracking and detachment of the ZrO2 oxide layer. Therefore, the ablation resistance of ZrC ceramics is also poor.

[0008] In summary, traditional pressureless sintering and hot-pressing methods for preparing ceramic bulk materials are not conducive to rapid densification and energy conservation. Although HfC and ZrC ceramics possess numerous advantages, such as high melting points (3890℃ and 3540℃), high thermal stability, and low vapor pressure, the ablation resistance of single-component ceramics remains quite limited. In high-temperature aerobic environments, a single HfC ceramic will form an HfO2 oxide layer on its surface. Due to the phase transformation of HfO2 at high temperatures, the enormous phase transformation stress causes severe damage to the oxide layer. After ablation, single ZrC materials form loose and porous ZrO2, which is difficult to withstand the erosion of high-speed heat flow. Therefore, when facing more severe ablation environments, single HfC or ZrC ceramics cannot effectively protect the ceramic interior. In conclusion, it is crucial to develop a highly efficient and simple method for preparing a novel high-performance ultra-high-temperature ceramic. Summary of the Invention

[0009] To address the insufficient ablation resistance of single-component ultra-high temperature ceramics in atmospheres with extremely high speeds and ultra-high temperatures and oxygen-containing flow, this invention proposes an ablation-resistant (Hf-Zr-Ta)C ternary medium-entropy ceramic material and its preparation method by simplifying the sintering process, reducing preparation costs, and improving densification efficiency. Using HfC powder, ZrC powder, and TaC powder as raw materials, they are first ball-milled and mixed to prepare HfC-ZrC-TaC multiphase powder. Then, an appropriate amount of this multiphase powder is placed in a graphite mold and placed in a spark plasma sintering furnace, where a uniform and dense medium-entropy carbide ceramic block is obtained according to a set program. The (Hf-Zr-Ta)C ternary medium-entropy ceramic exhibits excellent high-temperature stability and ablation resistance, able to withstand ablation by a 2100℃ oxyacetylene flame for 30 seconds with intact structure. This invention provides technical support for the application of multi-component carbide ceramics in aerospace hot-end components.

[0010] Specifically, the technical solution provided by this invention is: an ablation-resistant (Hf-Zr-Ta)C ternary medium-entropy ceramic material and its preparation method, comprising the following steps:

[0011] Step 1: Weigh HfC powder, ZrC powder and TaC powder, and ball mill them together to obtain a uniform HfC-ZrC-TaC multiphase powder;

[0012] Step 2: Take an appropriate amount of the HfC-ZrC-TaC multiphase powder prepared in Step 1 and place it in a graphite mold. The graphite mold and the powder sample are separated by graphite paper, and a layer of carbon felt is placed on the outside of the graphite mold containing the sample.

[0013] Step 3: Place the graphite mold prepared in Step 2 into a spark plasma sintering equipment and perform high-temperature heat treatment under a vacuum atmosphere to obtain a sintered and dense (Hf-Zr-Ta)C single-phase solid solution ceramic.

[0014] Preferably, the purity of the HfC powder, ZrC powder, and TaC powder is all >99.5%, and the particle size is 1-3 μm.

[0015] Preferably, the molar ratio of HfC powder, ZrC powder and TaC powder in step 1 is 1-3:1-3:1-3.

[0016] Preferably, in step 1, the ball milling is carried out in a polytetrafluoroethylene ball milling jar, the grinding ball material is ZrO2, the ball-to-material ratio is 3:1, and during the ball milling process, anhydrous ethanol solution is poured into the ball milling jar and the mixture is ball milled at a speed of 200-400 r / min for 6-12 hours.

[0017] Preferably, in step 2, the graphite paper has a thickness of 0.2 mm and the graphite mold has a diameter of 20 mm.

[0018] Preferably, in step 3, the high-temperature heat treatment includes heating at a rate of 80-120℃ / min to 1600-2200℃ and holding for 12-18 min.

[0019] Preferably, in step 3, the load pressure is 45-55 MPa and the pressure holding time is 12-18 min.

[0020] Preferably, in step 3, after high-temperature heat treatment, the temperature is first reduced to 1000℃ at a cooling rate of 200-300℃ / min, and then cooled to room temperature with the furnace.

[0021] The present invention also discloses an ablation-resistant (Hf-Zr-Ta)C ternary medium-entropy ceramic material prepared by the above preparation method.

[0022] Traditional pressureless sintering processes suffer from slow densification, long sintering times, and difficulty in effectively controlling density. Hot pressing sintering equipment is extremely expensive, has slow heat transfer, and consumes a huge amount of energy, making it unsuitable for mass production. This solution employs spark plasma sintering, which significantly reduces sintering time, simplifies operation, and achieves high density.

[0023] Traditional HfC and ZrC ceramics have high melting points (3890℃ and 3890℃), and their oxides also have high melting points (2810℃ and 2677℃), meaning they can act as a good framework when facing high-temperature flame streams. However, conversely, under high thermal stress, once cracks occur, oxygen rapidly diffuses inward. If the molten phase is not used to fill the cracks and pores, the oxygen erosion on the ceramic surface will be further intensified. The resulting ceramic oxides cannot withstand the erosive effect of the high-speed oxyacetylene flame stream, leading to spalling and triggering a chain reaction that further promotes the diffusion of oxygen-containing streams, thus creating a vicious cycle. Compared to HfC and ZrC ceramics, TaC ceramics have an oxide melting point of only 1800℃, which is lower than the actual testing temperature for oxyacetylene. Therefore, this method employs diffusion and in-situ solid solution methods to prepare a high-temperature ablation-resistant (Hf-Zr-Ta)C ternary carbide medium-entropy ceramic. A 30-second ablation test was conducted using an oxyacetylene ablation apparatus. XRD analysis of the oxide layer after ablation revealed the formation of high-melting-point oxides (Hf,Zr)O2 (melting point approximately 2715℃) and (Hf,Zr)6Ta2O17 (melting point approximately 2244℃), as well as a low-melting-point oxide Ta2O5 (melting point approximately 1800℃). During ablation, the high-melting-point oxides act as the framework phase, while the low-melting-point oxides fill pores and cracks. The synergistic interaction among these components results in a dense and stable oxide layer during ablation, preventing further oxygen penetration and significantly improving the ablation resistance of this ceramic composition.

[0024] In summary, the present invention has the following advantages:

[0025] (1) This invention provides a method for preparing (Hf-Zr-Ta)C ternary medium-entropy ceramics based on spark plasma sintering technology. The core of this method lies in utilizing the interdiffusion and in-situ solid solution mechanism between the HfC, ZrC, and TaC lattices under high temperature and high pressure. Through the synergistic effect of pulsed current-induced plasma activation and axial mechanical pressure, the three carbides rapidly achieve compositional homogenization under metastable conditions, ultimately forming a fine-grained, dense (Hf-Zr-Ta)C single-phase solid solution ceramic. Oxyacetylene ablation tests demonstrate its superior ablation resistance, solving the problems of non-dense microstructure, cracking, and spalling after ablation in single / multi-component carbide ceramics.

[0026] (2) The (Hf-Zr-Ta)C ternary medium-entropy ceramic prepared in this invention has a dense surface, low ablation temperature, and good synergistic effect between phases after oxyacetylene ablation, exhibiting excellent ablation resistance performance, which lays a theoretical foundation for subsequent research on the ablation resistance performance of medium / high-entropy carbide ceramics. Attached Figure Description

[0027] Figure 1 This refers to the relative density of (Hf-Zr-Ta)C ceramic blocks at different sintering temperatures in Examples 1-4 of this invention;

[0028] Figure 2 This refers to the relative densities of the (Hf-Zr-Ta)C ceramic blocks in Example 4 and Comparative Example 1 of this invention.

[0029] Figure 3 This is the XRD pattern of the (Hf-Zr-Ta)C ceramic block before ablation in Example 4 of this invention;

[0030] Figure 4 This is the XRD pattern of the (Hf-Zr-Ta)C ceramic block before ablation in Comparative Example 1 of this invention;

[0031] Figure 5 These are the microstructure and EDS analysis images of the (Hf-Zr-Ta)C ceramic before ablation in Example 4 of this invention;

[0032] Figure 6 These are the microstructure and EDS analysis images of the (Hf-Zr-Ta)C ceramic before ablation in Comparative Example 1 of this invention;

[0033] Figure 7 This is the XRD pattern of the (Hf-Zr-Ta)C ceramic block in Example 4 of this invention after ablation for 30 seconds;

[0034] Figure 8This is the XRD pattern of the (Hf-Zr-Ta)C ceramic block of Comparative Example 1 after ablation for 30 s in this invention;

[0035] Figure 9 These are the microstructure and EDS analysis images of the (Hf-Zr-Ta)C ceramic after ablation in Example 4 of this invention;

[0036] Wherein: (a) SEM image of the ablated surface; (b) magnified view of (a); (c) elemental distribution map corresponding to (b);

[0037] Figure 10 These are the microstructure and EDS analysis images of the (Hf-Zr-Ta)C ceramic after ablation in Comparative Example 1 of this invention;

[0038] Wherein: (a) SEM image of the ablated surface; (b) magnified view of (a); (c) elemental distribution map corresponding to (b);

[0039] Figure 11 These are comparison images of the macroscopic morphology after ablation in Example 4 and Comparative Example 1 of this invention;

[0040] Figure 12 This is a comparison chart of the highest ablation temperature and ablation rate of the ablation surface in Example 4 and Comparative Example 1 of this invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0042] Example 1

[0043] An ablation-resistant (Hf-Zr-Ta)C ternary medium-entropy ceramic material and its preparation method, comprising the following steps:

[0044] Step 1: Weigh HfC powder, ZrC powder and TaC powder in a molar ratio of 1:1:1. Pour the weighed powder into a polytetrafluoroethylene ball mill jar with a ball-to-powder ratio of 3:1. Add industrial alcohol and wet mill for 8 hours. Then dry in a constant temperature drying oven at 70℃ for 10 hours. This step will yield a uniform HfC-ZrC-TaC multiphase powder.

[0045] Step 2: Take 15g of uniform HfC-ZrC-TaC multiphase powder obtained in Step 1 and place it in a graphite mold with a diameter of 20mm. Separate the graphite mold and the powder sample with graphite paper, and put a layer of carbon felt on the outside of the graphite mold containing the sample to reduce the heat radiation generated during the ablation process and prevent the cooling rate from being too fast.

[0046] Step 3: Place the graphite mold prepared in Step 2 into the electroporation (EPO) ablation equipment. Keep the lower pressure head stationary while lowering the upper pressure head, initially setting the pressure to 30 MPa. Using a pre-set program, sintering is performed under vacuum. The temperature is first increased from room temperature to 800°C at a rate of 160°C / min, then increased to 1600°C at a rate of 100°C / min, with the pressure increasing from 30 MPa to 50 MPa during the heating process. After the heating and pressurization process, the temperature and pressure are held for 15 minutes. Heating is then stopped, and the temperature is cooled from 1600°C to 1000°C at a rate of 250°C / min, ending the program. During this cooling process, the pressure is reduced from 50 MPa to 30 MPa. After the program ends, the sample is naturally cooled to room temperature in the furnace. The graphite paper on the sample surface is then removed using a 400-mesh diamond grinding wheel. This step yields a (Hf-Zr-Ta)C medium-entropy ceramic bulk.

[0047] Figure 1 It is the relative density of (Hf-Zr-Ta)C ceramic bulk at different sintering temperatures, derived from... Figure 1 It can be seen that the ceramic block obtained by spark plasma sintering at a sintering temperature of 1600℃ is not dense, with a relative density of only 59.5%.

[0048] Example 2

[0049] An ablation-resistant (Hf-Zr-Ta)C ternary medium-entropy ceramic material and its preparation method, comprising the following steps:

[0050] Step 1: Weigh HfC powder, ZrC powder and TaC powder in a molar ratio of 1:1:1. Pour the weighed powder into a polytetrafluoroethylene ball mill jar with a ball-to-powder ratio of 3:1. Add industrial alcohol and wet mill for 8 hours. Then dry in a constant temperature drying oven at 70℃ for 10 hours. This step will yield a uniform HfC-ZrC-TaC multiphase powder.

[0051] Step 2: Take 15g of uniform HfC-ZrC-TaC multiphase powder obtained in Step 1 and place it in a graphite mold with a diameter of 20mm. Separate the graphite mold and the powder sample with graphite paper, and put a layer of carbon felt on the outside of the graphite mold containing the sample to reduce the heat radiation generated during the ablation process and prevent the cooling rate from being too fast.

[0052] Step 3: Place the graphite mold prepared in Step 2 into the electroporation ablation equipment. Keep the lower pressure head stationary while the upper pressure head descends. At this point, the initial pressure is 30 MPa. Using a preset program, sintering is performed under a vacuum atmosphere. First, the temperature is increased from room temperature to 800°C at a rate of 160°C / min, and then from 800°C to 1800°C at a rate of 100°C / min. The pressure is set to increase from 30 MPa to 50 MPa during the heating process. After the heating and pressurization process is completed, the temperature and pressure are held for 15 minutes. Heating was then stopped, and the temperature was reduced from 1800℃ to 1000℃ at a rate of 250℃ / min until the program ended. During this cooling process, the pressure was set to decrease from 50MPa to 30MPa. After the program ended, the sample was taken out after the furnace cooled naturally to room temperature. The graphite paper on the sample surface was then ground off using a 400-mesh diamond grinding disc. This step yielded a sintered and dense (Hf-Zr-Ta)C medium-entropy ceramic block.

[0053] Figure 1 It is the relative density of (Hf-Zr-Ta)C ceramic bulk at different sintering temperatures, derived from... Figure 1 It can be seen that the ceramic block obtained by spark plasma sintering at a sintering temperature of 1800℃ is not dense, with a relative density of only 67.2%.

[0054] Example 3

[0055] An ablation-resistant (Hf-Zr-Ta)C ternary medium-entropy ceramic material and its preparation method, comprising the following steps:

[0056] Step 1: Weigh HfC powder, ZrC powder and TaC powder in a molar ratio of 1:1:1. Pour the weighed powder into a polytetrafluoroethylene ball mill jar with a ball-to-powder ratio of 3:1. Add industrial alcohol and wet mill for 8 hours. Then dry in a constant temperature drying oven at 70℃ for 10 hours. This step will yield a uniform HfC-ZrC-TaC multiphase powder.

[0057] Step 2: Take 15g of uniform HfC-ZrC-TaC multiphase powder obtained in Step 1 and place it in a graphite mold with a diameter of 20mm. Separate the graphite mold and the powder sample with graphite paper, and put a layer of carbon felt on the outside of the graphite mold containing the sample to reduce the heat radiation generated during the ablation process and prevent the cooling rate from being too fast.

[0058] Step 3: Place the graphite mold prepared in Step 2 into the electroporation ablation equipment. Keep the lower pressure head stationary while lowering the upper pressure head. At this point, the initial pressure is 30 MPa. Using a preset program, sintering is performed under a vacuum atmosphere. First, the temperature is increased from room temperature to 800℃ at a rate of 160℃ / min, and then from 800℃ to 2000℃ at a rate of 100℃ / min. The pressure is set to increase from 30 MPa to 50 MPa during the heating process. After the heating and pressurization process is completed, the temperature and pressure are held for 15 minutes. Heating was then stopped, and the temperature was reduced from 2000℃ to 1000℃ at a rate of 250℃ / min until the program ended. During this cooling process, the pressure was set to decrease from 50MPa to 30MPa. After the program ended, the sample was taken out after the furnace cooled naturally to room temperature. The graphite paper on the surface of the sample was then ground off using a 400-mesh diamond grinding wheel. This step yielded a sintered and dense (Hf-Zr-Ta)C medium-entropy ceramic block.

[0059] Figure 1 It is the relative density of (Hf-Zr-Ta)C ceramic bulk at different sintering temperatures, derived from... Figure 1 It can be seen that the ceramic block obtained by spark plasma sintering at a sintering temperature of 2000℃ is not dense, with a relative density of only 72.73%.

[0060] Example 4

[0061] An ablation-resistant (Hf-Zr-Ta)C ternary medium-entropy ceramic material and its preparation method, comprising the following steps:

[0062] Step 1: Weigh HfC powder, ZrC powder and TaC powder in a molar ratio of 1:1:1. Pour the weighed powder into a polytetrafluoroethylene ball mill jar with a ball-to-powder ratio of 3:1. Add industrial alcohol and wet mill for 8 hours. Then dry in a constant temperature drying oven at 70℃ for 10 hours. This step will yield a uniform HfC-ZrC-TaC multiphase powder.

[0063] Step 2: Take 15g of uniform HfC-ZrC-TaC multiphase powder obtained in Step 1 and place it in a graphite mold with a diameter of 20mm. Separate the graphite mold and the powder sample with graphite paper, and put a layer of carbon felt on the outside of the graphite mold containing the sample to reduce the heat radiation generated during the ablation process and prevent the cooling rate from being too fast.

[0064] Step 3: Place the graphite mold prepared in Step 2 into the electroporation ablation equipment. Keep the lower pressure head stationary while the upper pressure head descends, initially setting the pressure to 30 MPa. Using a preset program, sintering is performed under vacuum. The temperature is first increased from room temperature to 800°C at a rate of 160°C / min, then increased from 800°C to 2200°C at a rate of 100°C / min. The pressure is set to increase from 30 MPa to 50 MPa during the heating process. After the heating and pressurization process is complete, maintain the temperature and pressure for 15 minutes. Heating was then stopped, and the temperature was reduced from 2200℃ to 1000℃ at a rate of 250℃ / min until the program ended. During this cooling process, the pressure was set to decrease from 50MPa to 30MPa. After the program ended, the sample was taken out after the furnace cooled naturally to room temperature. The graphite paper on the surface of the sample was then ground off using a 400-mesh diamond grinding wheel. This step yielded a sintered and dense (Hf-Zr-Ta)C medium-entropy ceramic block.

[0065] Figure 1 It is the relative density of (Hf-Zr-Ta)C ceramic bulk at different sintering temperatures, derived from... Figure 1 It can be seen that the ceramic block obtained by spark plasma sintering at a sintering temperature of 2200℃ has high density, with a relative density of 97.88%, and can be regarded as a fully dense ceramic. Figure 2 The figure shows the relative densities of (Hf-Zr-Ta)C ceramic blocks prepared under different sintering processes. As can be seen from the figure, the ceramic blocks prepared by spark plasma sintering are more dense. Figure 3 The XRD pattern of the (Hf-Zr-Ta)C ceramic bulk before ablation, obtained by the above process, is shown below. Figure 3 It can be seen that (Hf-Zr-Ta)C medium-entropy ceramics can be prepared by diffusion and in-situ solid solution. Figure 5 The image shows the microstructure and EDS analysis of (Hf-Zr-Ta)C ceramic before ablation. As can be seen from the image, no obvious aggregation or segregation of the elements (Hf, Zr, Ta) was observed, indicating that the elements in (Hf-Zr-Ta)C ceramic are uniformly distributed.

[0066] Oxyacetylene ablation test was performed on the prepared (Hf-Zr-Ta)C medium-entropy ceramic bulk:

[0067] The heat flux density of oxyacetylene is 2.4 MW / m³. 2 The acetylene gas flow rate was 0.18 L / s, the oxygen gas flow rate was 0.24 L / s, the acetylene pressure was 0.095 MPa, the oxygen pressure was 0.4 MPa, and the ablation time was 30 s. The (Hf-Zr-Ta)C ceramic block prepared by spark plasma sintering showed a relatively smooth and dense macroscopic surface after ablation. Figure 7The above-mentioned process yielded an XRD pattern of (Hf-Zr-Ta)C ceramic bulk material after ablation. The pattern shows that the ablated oxide layer is mainly composed of the high-melting-point oxide (Hf,Zr)6Ta2O. 17 It is composed of (Hf,Zr)O2 and the low-melting-point oxide Ta2O5.

[0068] Figure 9 These are the microstructure and EDS analysis images of (Hf-Zr-Ta)C ceramic after ablation. The microstructure images show that the oxide layer of the (Hf-Zr-Ta)C ceramic after ablation is smooth and dense, with the solid oxide particles surrounded by a large amount of continuous liquid phase, indicating good ablation resistance. EDS data analysis shows that these solid oxide particles are composed of the high-melting-point oxide (Hf,Zr)6Ta2O. 17 The liquid oxide phase, composed of (Hf,Zr)O2, is Ta2O5. This suggests that during high-temperature ablation, the low-melting-point oxide Ta2O5 melts into a liquid. Compared to TiO2 and Nb2O5, Ta2O5 has a significantly lower coefficient of thermal expansion (TiO2 ~ 8.5 × 10⁻⁶). -6 Nb2O5~5.8×10 -6 Ta2O5~2.36×10 -6 (Hf-Zr-Ta)C ceramics exhibit lower deformation in the high-temperature range, stronger resistance to ceramic cracking, and superior performance stability. Furthermore, its molten flow can fill the pores of the oxide layer, while the solidified network further strengthens the interfacial bonding. This solid-liquid synergistic mechanism significantly enhances the density of the oxide layer and its resistance to ablation in (Hf-Zr-Ta)C ceramics.

[0069] Comparative Example 1

[0070] This comparative example includes the following steps:

[0071] Step 1: Weigh HfO2 powder, ZrO2 powder, Ta2O5 powder, and C powder in a molar ratio of 2:2:1:19. Pour the weighed powder into a polytetrafluoroethylene ball mill jar with a ball-to-powder ratio of 3:1. Add industrial alcohol and wet mill for 8 hours. Then, dry in a constant temperature drying oven at 70℃ for 10 hours. This step yields a uniform oxide mixture powder. Pour the oxide mixture powder into a graphite crucible with the inner wall lined with graphite paper. Then, place it in a high-temperature heat treatment furnace under Ar gas protection. The heating rate is 5℃ / min. After heating to 2100℃, hold at that temperature for 2 hours, and then allow it to cool naturally in the furnace. (Hf-Zr-Ta)C solid solution bulk material was prepared by carbothermal reduction reaction, placed in a polytetrafluoroethylene ball mill jar with a ball-to-material ratio of 3:1, wet-milled with industrial alcohol for 8 hours, and then dried in a constant temperature drying oven at 70℃ for 10 hours. After this step, (Hf-Zr-Ta)C ceramic powder can be obtained.

[0072] Step 2: Take 5g of the (Hf-Zr-Ta)C ceramic powder obtained in Step 1 and place it in an agate mortar. Add 3 drops of PVA solution using a dropper and grind for 10 minutes. Pour the powder into a mold made of Cr12MoV and place the mold under the pressure head of a dry press. Set the load pressure to 30MPa and hold the pressure for 1.5 minutes before unloading. This step will yield a preliminarily formed (Hf-Zr-Ta)C ceramic body.

[0073] Step 3: Wrap the (Hf-Zr-Ta)C ceramic blank obtained in Step 2 with graphite paper, place it in a graphite crucible with graphite paper lining the inner wall, and then place it in a high-temperature heat treatment furnace protected by Ar gas. The heating rate is 5℃ / min. After heating to 2100℃, hold for 2 hours, and then let it cool naturally in the furnace. This step yields a sintered and dense (Hf-Zr-Ta)C ceramic block.

[0074] Figure 2 The figure shows the relative density of (Hf-Zr-Ta)C ceramic blocks prepared under different sintering processes. As can be seen from the figure, the relative density of the ceramic block prepared by the above pressureless sintering process is 82.7%, which is 15.18% lower than that of the ceramic block prepared in Example 4. Figure 4 The above-mentioned process produces the XRD pattern of (Hf-Zr-Ta)C ceramic bulk material before ablation. Figure 4 It can be seen that (Hf-Zr-Ta)C medium-entropy ceramics are prepared by carbothermic reduction reaction. Figure 6 The image shows the microstructure and EDS analysis of (Hf-Zr-Ta)C ceramic before ablation. As can be seen from the image, no obvious aggregation or segregation of the elements (Hf, Zr, Ta) was observed, indicating that the elements in (Hf-Zr-Ta)C ceramic are uniformly distributed.

[0075] The prepared (Hf-Zr-Ta)C ceramic bulk was subjected to oxyacetylene ablation test:

[0076] The heat flux density of oxyacetylene is 2.4 MW / m³. 2 The acetylene gas flow rate was 0.18 L / s, the oxygen gas flow rate was 0.24 L / s, the acetylene pressure was 0.095 MPa, the oxygen pressure was 0.4 MPa, and the ablation time was 30 s. The (Hf-Zr-Ta)C ceramic blocks prepared by combining carbothermal reduction and pressureless sintering showed some cracks and protrusions on the macroscopic surface after ablation, with partial peeling of the oxide layer at the edges and depressions appearing in the ablation center.

[0077] . Figure 8 This is the XRD pattern of (Hf-Zr-Ta)C ceramic bulk after ablation. The figure shows that the oxide layer after ablation is mainly composed of the high-melting-point oxide Hf6Ta2O. 17 TaZr2.75 It is composed of O8 and (Hf,Zr)O2, as well as the low-melting-point oxide Ta2O5.

[0078] Figure 10 These are the microstructure and EDS analysis images of (Hf-Zr-Ta)C ceramic after ablation. The microstructure images show numerous ablation pits and protrusions on the oxide layer surface after ablation, indicating poor resistance to ablation and erosion. EDS data analysis reveals that these protrusions are composed of high-melting-point oxides. This suggests that during high-temperature ablation, due to the ceramic's low density and numerous pores and defects, the melting of low-melting-point oxides prevented rapid healing and densification of these defects. This resulted in severe oxygen infiltration at high temperatures. Combined with the scouring effect of the heat flow during ablation, the low-melting-point oxides were quickly eroded and volatilized, forming numerous pores and pits. Meanwhile, the high-melting-point oxides, due to their high melting point and stability at high temperatures, were retained, forming the protrusions on the oxide layer surface.

[0079] Figure 11 These are comparison images of the macroscopic morphology after ablation of Example 4 and Comparative Example 1; Figure 12 This is a comparison chart of the highest surface temperature and ablation rate of Example 4 and Comparative Example 1. Based on the data in the two tables in the image, it can be concluded that the spark plasma sintering (SPS) process is significantly superior to the pressureless sintering process in terms of ablation resistance, specifically as follows:

[0080] Surface morphology stability: Under the same ablation conditions, the oxide layer surface of the SPS process remains flat and dense, while the oxide layer of the pressureless sintering process shows a large number of protrusions and edge peeling, indicating that SPS can effectively maintain the integrity of the material structure; Superior thermal stability: The highest temperature of the ablation surface of the SPS sample is 91°C lower than that of the pressureless sintering, proving that it has better thermal insulation performance and can more effectively resist high temperature erosion.

[0081] Improved ablation resistance: Mass ablation rate: SPS is negative (-0.17mg / s), indicating that the material surface may gain weight due to oxidation; while pressureless sintering is positive (0.97mg / s), indicating continuous material loss; Linear ablation rate: The absolute value of SPS (1.9μm / s) is much lower than that of pressureless sintering (7.97μm / s), indicating that the surface erosion rate is significantly reduced and the ablation resistance life is extended.

[0082] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A method for preparing an ablation-resistant (Hf-Zr-Ta)C ternary medium-entropy ceramic material, characterized in that, Includes the following steps: Step 1: Weigh HfC powder, ZrC powder and TaC powder, and ball mill them together to obtain a uniform HfC-ZrC-TaC multiphase powder; Step 2: Take an appropriate amount of the HfC-ZrC-TaC multiphase powder prepared in Step 1 and place it in a graphite mold. The graphite mold and the powder sample are separated by graphite paper, and a layer of carbon felt is placed on the outside of the graphite mold containing the sample. Step 3: Place the graphite mold prepared in Step 2 into a spark plasma sintering equipment and perform high-temperature heat treatment under a vacuum atmosphere to obtain a sintered and dense (Hf-Zr-Ta)C single-phase solid solution ceramic.

2. The method for preparing an ablation-resistant (Hf-Zr-Ta)C ternary medium-entropy ceramic material according to claim 1, characterized in that: The purity of the HfC powder, ZrC powder, and TaC powder is all >99.5%, and the particle size is 1-3 μm.

3. The method for preparing an ablation-resistant (Hf-Zr-Ta)C ternary medium-entropy ceramic material according to claim 1, characterized in that: The molar ratio of HfC powder, ZrC powder and TaC powder in step 1 is 1-3:1-3:1-3.

4. The method for preparing an ablation-resistant (Hf-Zr-Ta)C ternary medium-entropy ceramic material according to claim 1, characterized in that: In step 1, the ball milling is carried out in a polytetrafluoroethylene ball milling jar, the grinding ball material is ZrO2, the ball-to-material ratio is 3:1, and during the ball milling process, anhydrous ethanol solution is poured into the ball milling jar and the mixture is ball milled at a speed of 200-400 r / min for 6-12 hours.

5. The method for preparing an ablation-resistant (Hf-Zr-Ta)C ternary medium-entropy ceramic material according to claim 1, characterized in that: In step 2, the graphite paper is 0.2 mm thick and the graphite mold is 20 mm in diameter.

6. The method for preparing an ablation-resistant (Hf-Zr-Ta)C ternary medium-entropy ceramic material according to claim 1, characterized in that: In step 3, the high-temperature heat treatment includes heating at a rate of 80-120℃ / min to 1600-2200℃ and holding for 12-18min.

7. The method for preparing an ablation-resistant (Hf-Zr-Ta)C ternary medium-entropy ceramic material according to claim 1, characterized in that: In step 3, the load pressure is 45-55 MPa, and the pressure holding time is 12-18 min.

8. The method for preparing an ablation-resistant (Hf-Zr-Ta)C ternary medium-entropy ceramic material according to claim 1, characterized in that: In step 3, after high-temperature heat treatment, the temperature is first reduced to 1000℃ at a cooling rate of 200-300℃ / min, and then cooled to room temperature with the furnace.

9. The ablation-resistant (Hf-Zr-Ta)C ternary medium-entropy ceramic material prepared by any one of the preparation methods of claims 1-8.

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