High-entropy aluminum silicide ceramic as well as preparation method and application thereof

Abstract

The invention discloses high-entropy aluminum silicide ceramic as well as a preparation method and application thereof. The preparation method of the high-entropy aluminum silicide ceramic comprises the following steps: 1) fully and uniformly mixing transition metal powder, aluminum powder and silicon powder to prepare mixed powder; 2) pressing the mixed powder into a green body, and then performing electric field sintering, crushing and screening to obtain high-entropy aluminum silicide powder; and 3) pressing the high-entropy aluminum silicide powder into a green body, and carrying out spark plasma sintering to obtain the high-entropy aluminum silicide ceramic. The high-entropy aluminum silicide ceramic disclosed by the invention has excellent oxidation resistance and ablation resistance under an ultra-high-temperature condition, is suitable for being used as a hot end part protection material of a hypersonic aircraft, and is simple and convenient in preparation process, simple to operate, short in reaction time and suitable for large-scale industrial production and application.

Description

Technical Field

[0001] The present invention relates to the technical field of high-entropy ceramics, and particularly relates to a high-entropy aluminum silicide ceramic, a preparation method thereof, and an application thereof. Background Art

[0002] With the continuous increase in the flight Mach number of new hypersonic aircraft, the performance requirements for their hot-end protection systems are also getting higher and higher (for example: higher oxidation and ablation resistance temperatures, longer service life, etc.). High-entropy silicide ceramics have characteristics such as high hardness, high melting point, low thermal conductivity, and excellent corrosion resistance, and are suitable as protective materials for hot-end components of hypersonic aircraft, with very broad application prospects.

[0003] However, the existing high-entropy silicide ceramics generally have low oxidation and ablation resistance performance under ultra-high temperature conditions (≥2000 °C), and simply cannot fully meet the performance requirements of the protective materials for hot-end components of hypersonic aircraft. For example, Juan Kuang, Qianqian Wang, etc. developed a method to improve the oxidation and ablation resistance performance of high-entropy silicide ceramics. By adding Y2O3 to modify (NbMoTaW)Si2, a high-viscosity Y-Si-O and high-melting-point Y(Nb 0.5 Ta 0.5 )O4 framework is formed during oxidation, thereby hindering the further infiltration of oxygen. However, the finally obtained high-entropy silicide ceramic has a high linear ablation rate (-0.067 μm / s) at 2100 °C, and the oxidation and ablation resistance time is short (180 s), and cannot meet the long-term service requirements of the hot-end components of hypersonic aircraft in extremely high-temperature environments, greatly limiting its practical application in the field of hypersonic aircraft (Ablation-resistant yttrium-modified high entropy refractory metal silicide (NbMoTaW)Si2 coating for oxidizing environments up to 2100 °C, Mater. Today 2024, 80: 156-166.).

[0004] Therefore, it is of great significance to develop a high-entropy silicide ceramic with excellent oxidation and ablation resistance performance under ultra-high temperature conditions. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-entropy aluminum silicide ceramic, a preparation method thereof, and an application thereof.

[0006] The technical solution adopted by the present invention is:

[0007] A method for preparing a high-entropy aluminum silicide ceramic comprises the following steps:

[0008] 1) Mix transition metal powders, aluminum powder and silicon powder and perform wet ball milling. The transition metal powders are at least four of Hf powder, Zr powder, Ta powder, Nb powder, Ti powder, V powder, Mo powder, Cr powder and W powder, and then dry to obtain a mixed powder;

[0009] 2) Press the mixed powder into a green body, wrap the green body with graphite paper coated with boron nitride and then embed it in a graphite felt, and then place it in a protective atmosphere, energize the graphite felt to perform electric field sintering on the green body, and then perform crushing and screening to obtain high-entropy aluminum silicide powder;

[0010] 3) Embed the graphite paper coated with boron nitride into a graphite mold, then load the high-entropy aluminum silicide powder and press it into a green body, and then place it in a protective atmosphere, connect a pulsed current to the graphite mold to perform spark plasma sintering on the green body, and thus obtain the high-entropy aluminum silicide ceramic.

[0011] Preferably, in step 1), the ratio of the total molar amount of metal atoms in the transition metal powders to the total molar amount of aluminum powder and silicon powder is 1:2.

[0012] Preferably, in step 1), the molar ratio of the aluminum powder to the silicon powder is 1:1.5 to 4.

[0013] Preferably, in step 1), the particle size of the aluminum powder is ≤10 μm and the purity is ≥99%.

[0014] Preferably, in step 1), the particle size of the silicon powder is ≤2 μm and the purity is ≥99.9%.

[0015] Preferably, in step 1), the particle sizes of the Hf powder, Zr powder, Ta powder, Nb powder, Ti powder, V powder, Mo powder, Cr powder and W powder are all 1 μm to 3 μm and the purities are all ≥99.5%.

[0016] Preferably, the process parameters of the wet ball milling in step 1) include: the ball milling medium is anhydrous ethanol, the ball milling equipment is a planetary ball mill, the weight ratio of the powder raw materials, ZrO2 balls and anhydrous ethanol is 1:2 to 3:1.5 to 2, and the ball milling time is 10 h to 20 h.

[0017] Preferably, the pressing in step 2) is carried out under the condition of a pressure of 9 MPa to 12 MPa and the pressure holding time is 2 min to 4 min.

[0018] Preferably, the green body in step 2) is cylindrical, with a diameter ≤16 mm and a thickness ≤3.2 mm.

[0019] Preferably, the length of the graphite felt in step 2) is 105 mm to 120 mm, the width is 16 mm to 20 mm, and the thickness is 5 mm to 8 mm.

[0020] Preferably, the protective atmosphere in step 2) is an argon atmosphere.

[0021] Preferably, the electric field sintering in step 2) includes the following operations: Connect both ends of the graphite felt to an alternating current, increase the current from 0 A to 10 A to 15 A at a rate of 3 A / s to 5 A / s, maintain for 10 s to 20 s, then increase the current to 20 A to 30 A at a rate of 3 A / s to 5 A / s, maintain for 50 s to 70 s, cut off the power supply, and cool naturally. The ultra-fast and ultra-high temperature synthesis environment formed by electric field sintering can promote the complete reaction of raw materials to form a high-entropy main phase, inhibit element segregation, reduce the loss of raw materials, and ensure the obtainment of high-purity and uniform particle size high-entropy aluminum silicide powder.

[0022] Preferably, the pulverization method in step 2) is grinding.

[0023] Preferably, the mesh number of the sieve used for screening in step 2) is 200 mesh to 300 mesh.

[0024] Preferably, the pressing in step 3) is carried out under the condition of a pressure of 30 MPa to 50 MPa.

[0025] Preferably, the green body in step 3) is cylindrical with a diameter ≤ 20 mm.

[0026] Preferably, the protective atmosphere in step 3) is an argon atmosphere.

[0027] Preferably, the spark plasma sintering in step 3) includes the following operations: Connect the graphite mold to a pulsed current, heat from room temperature (25 °C ± 5 °C) to 1300 °C to 1400 °C at a heating rate of 100 °C / min to 120 °C / min, hold for 10 min to 15 min, cut off the power supply, and cool naturally. During the spark plasma sintering process, the pulsed current and the generated plasma promote the rapid sintering and densification of the green body, while reducing the temperature required for dense sintering. Eventually, a high-density high-entropy aluminum silicide ceramic can be prepared.

[0028] Preferably, the spark plasma sintering in step 3) is carried out under a pressure-holding state, and the applied pressure is 30 MPa to 50 MPa.

[0029] A high-entropy aluminum silicide ceramic is made by the above preparation method.

[0030] A hypersonic vehicle hot-end component contains the above high-entropy aluminum silicide ceramic.

[0031] A hypersonic vehicle, which includes the above-mentioned high-entropy aluminosilicide ceramic.

[0032] The beneficial effects of the present invention are as follows: The high-entropy aluminosilicide ceramic of the present invention has excellent oxidation resistance and ablation resistance under ultra-high temperature conditions (2100 °C), is suitable for use as a protective material for the hot-end components of hypersonic vehicles, and its preparation process is simple, the operation is easy, and the reaction time is short, making it suitable for large-scale industrial production and application.

[0033] Specifically:

[0034] 1) The high-entropy aluminosilicide ceramic of the present invention contains a structure of silica glass phase + alumina double oxide layer, which greatly improves the oxidation resistance and ablation resistance of the high-entropy aluminosilicide ceramic under ultra-high temperature conditions;

[0035] 2) The elements of the high-entropy aluminosilicide ceramic of the present invention are evenly distributed, with a high density (the density is 97.1% - 98.6%), and the ceramic grain boundaries are clean without impurities;

[0036] 3) The linear ablation rate of the high-entropy aluminosilicide ceramic of the present invention after oxidation at 2100 °C for 80 min is only 0.022 μm / s at the lowest. Compared with the high-entropy silicide ceramic reported in the literature (ablated at 2100 °C for 180 s, the linear ablation rate reaches -0.067 μm / s), the oxidation resistance and ablation resistance time are extended by about 26 times, and the absolute value of the linear ablation rate is only 32.8% of the reported value, which can well meet the long-term service requirements of the hot-end components of hypersonic vehicles in extremely high-temperature environments and has a very broad application prospect;

[0037] 4) The preparation process of the high-entropy aluminosilicide ceramic of the present invention is simple, the operation is easy, the reaction time is short (the total time of two sinterings ≤ 30 min), and the process has good repeatability and high synthesis efficiency, making it suitable for large-scale industrial production and application. Description of the Drawings

[0038] Figure 1 XRD diagrams of the high-entropy aluminosilicide ceramics in Examples 1 - 3.

[0039] Figure 2 SEM diagram and EDS element surface distribution diagram of the high-entropy aluminosilicide ceramic in Example 2.

[0040] Figure 3 XRD diagrams of the high-entropy silicide ceramic in Comparative Example 1 and the high-entropy aluminosilicide ceramics in Comparative Examples 2 - 3. Detailed Embodiments

[0041] The present invention will be further explained and illustrated below in conjunction with specific embodiments.

[0042] In Examples 1 to 3 and Comparative Examples 1 to 3, the particle sizes of Ta powder, Mo powder, Cr powder, W powder and Zr powder are all 1 μm to 3 μm, and the purities are all ≥ 99.5%.

[0043] In Examples 1 to 3 and Comparative Examples 2 to 3, the particle size of the aluminum powder is ≤ 10 μm, and the purity is ≥ 99%.

[0044] In Examples 1 to 3 and Comparative Examples 1 to 3, the particle size of the silicon powder is ≤ 2 μm, and the purity is ≥ 99.9%.

[0045] Example 1:

[0046] A high-entropy aluminum silicide ceramic, and its preparation method is as follows:

[0047] 1) Add 5.7 g of Ta powder, 5.8 g of W powder, 3.0 g of Mo powder, 0.3 g of Cr powder, 2.5 g of aluminum powder and 3.9 g of silicon powder (the ratio of the total molar amount of metal atoms in Ta powder, W powder, Mo powder and Cr powder to the total molar amount of aluminum powder and silicon powder is 1:2; the molar ratio of aluminum powder to silicon powder is 1:1.5) into a nylon ball milling tank, then add anhydrous ethanol and zirconia ball milling beads. The weight ratio of the powder raw materials, zirconia ball milling beads and anhydrous ethanol is 1:2:1.5. Then install the nylon ball milling tank into a planetary ball mill, ball mill for 10 h, then take out the material and evaporate the anhydrous ethanol to dryness to obtain a mixed powder;

[0048] 2) Load 2.5 g of the mixed powder into a mold (the inner cavity of the mold is cylindrical with a diameter of 16 mm), slowly apply pressure to 9 MPa, and hold the pressure for 2 min to form a green body (with a thickness of about 2.5 mm). Then, make 3 through holes with a length of about 20 mm and spaced about 5 mm apart in the middle position on the side of a graphite felt with a length of 105 mm, a width of 16 mm and a thickness of 5 mm. Then wrap the green body with graphite paper coated with boron nitride and embed it in the graphite felt. Then clamp both ends of the graphite felt along the length direction with electrodes and place it in a reaction kettle. Close the reaction kettle chamber door, turn on the mechanical pump and the bypass valve to evacuate the reaction kettle cavity until the value of the vacuum pressure gauge reaches 10 Pa. Then turn on the molecular pump and the gate valve to continue the evacuation process until the value of the vacuum pressure gauge is less than 1.0×10 -2 Pa, then slowly introduce argon gas until the cavity is in a semi-vacuum state. Then turn on the power switch to connect both ends of the graphite felt to alternating current, increase the current from 0 A to 10 A at a rate of 3 A / s, hold for 10 s, then increase the current to 20 A at a rate of 3 A / s, hold for 50 s, turn off the power, and cool with the furnace. Then take out the material for grinding, and pass through a 200-mesh sieve to obtain a high-entropy aluminum silicide powder;

[0049] 3) Embed the graphite paper with a boron nitride coating on its surface into a graphite mold. The graphite mold is cylindrical with an inner diameter of 10.4 mm. After embedding the graphite paper with a boron nitride coating, the actual inner diameter of the graphite mold is 10 mm. Then, load 2.2 g of high-entropy aluminosilicate powder, and use upper and lower pressure columns to clamp the powder in the middle of the graphite mold. Next, place the graphite mold in a spark plasma sintering reaction chamber, adjust the pressure of the pressure head to 2.4 kN (30 MPa) to press the high-entropy aluminosilicate powder into a green body, and maintain this pressure. Then, introduce argon gas, turn on the power supply, connect the upper and lower pressure columns of the graphite mold to a pulsed current, and heat from room temperature to 1300 °C at a heating rate of 100 °C / min, hold for 10 min, turn off the power switch, and cool with the furnace to obtain high-entropy aluminosilicate ceramic (denoted as HEAS-1).

[0050] Performance test:

[0051] 1) The X-ray diffraction spectrum (XRD) pattern of the high-entropy aluminosilicate ceramic (HEAS-1) in this example is as Figure 1 shown.

[0052] It can be seen from Figure 1 that the high-entropy aluminosilicate ceramic (HEAS-1) is a pure phase without other impurity phases, indicating its high purity.

[0053] 2) The density of the high-entropy aluminosilicate ceramic (HEAS-1) in this example measured by the Archimedes method is 97.1%, indicating its high density.

[0054] 3) The oxidation depth of the high-entropy aluminosilicate ceramic (HEAS-1) in this example after laser high-temperature oxidation at 2100 °C for 80 min is 0.59 mm, and the linear ablation rate is 0.049 μm / s, indicating its excellent oxidation resistance and ablation resistance under ultra-high temperature conditions.

[0055] Note:

[0056] The calculation formula for the oxidation depth (ΔD) is as follows: ΔD = D0 - D1, where D0 is the initial thickness of the high-entropy aluminosilicate ceramic test sample (block) (unit: mm), and D1 is the central thickness of the residual matrix measured after removing the ablation pit oxide layer after oxidation (unit: mm).

[0057] The calculation formula for the linear ablation rate is as follows: linear ablation rate = (D0 - D2) / t, where D0 is the initial thickness of the high-entropy aluminosilicate ceramic test sample (block) (unit: μm), D2 is the central thickness of the test sample including the oxide layer after oxidation (unit: μm), and t is the oxidation duration (unit: s).

[0058] Example 2:

[0059] A high-entropy aluminum silicide ceramic, and its preparation method is as follows:

[0060] 1) Add 5.1 g of Ta powder, 5.2 g of W powder, 2.7 g of Mo powder, 0.8 g of Cr powder, 2.4 g of aluminum powder, and 4.6 g of silicon powder (the ratio of the total molar amount of metal atoms in Ta powder, W powder, Mo powder, and Cr powder to the total molar amount of aluminum powder and silicon powder is 1:2; the molar ratio of aluminum powder to silicon powder is 1:2) into a nylon ball milling tank, then add anhydrous ethanol and zirconia ball milling beads. The weight ratio of the powder raw materials, zirconia ball milling beads, and anhydrous ethanol is 1:2.5:1.8. Then place the nylon ball milling tank into a planetary ball mill, ball mill for 15 h, then take out the material and evaporate the anhydrous ethanol to dryness to obtain a mixed powder;

[0061] 2) Load 2.4 g of the mixed powder into a mold (the inner cavity of the mold is cylindrical with a diameter of 16 mm), slowly apply pressure to 10 MPa, and hold the pressure for 3 min to form a green body (with a thickness of about 2.5 mm). Then draw 3 through holes with a length of about 20 mm and spaced about 5 mm apart in the middle position on the side of a graphite felt with a length of 110 mm, a width of 18 mm, and a thickness of 6 mm. Then wrap the green body with graphite paper coated with boron nitride and embed it in the graphite felt. Then clamp both ends of the graphite felt along the length direction with electrodes and place it in a reaction kettle. Close the reaction kettle chamber door, turn on the mechanical pump and the side extraction valve to evacuate the reaction kettle cavity until the value of the vacuum pressure gauge reaches 10 Pa. Then turn on the molecular pump and the gate valve to continue the evacuation process until the value of the vacuum pressure gauge is less than 1.0×10 -2 Pa. Then slowly introduce argon gas until the cavity is in a semi-vacuum state. Then turn on the power switch to connect both ends of the graphite felt to alternating current, increase the current from 0 A to 12 A at a rate of 4 A / s, hold for 15 s, then increase the current to 25 A at a rate of 4 A / s, hold for 60 s, turn off the power, and cool with the furnace. Then take out the material and grind it, and then pass it through a 250-mesh sieve to obtain high-entropy aluminum silicide powder;

[0062] 3) Inlay the graphite paper coated with boron nitride into a graphite mold. The graphite mold is cylindrical with an inner diameter of 10.4 mm. After inlaying the graphite paper coated with boron nitride, the actual inner diameter of the graphite mold is 10 mm. Then load 2.1 g of high-entropy aluminum silicide powder, and use upper and lower pressure columns to clamp the powder in the middle of the graphite mold. Then place the graphite mold in the discharge plasma sintering reaction cavity, adjust the pressure of the pressure head to 3.2 kN (40 MPa) to press the high-entropy aluminum silicide powder into a green body, and keep this pressure all the time. Then introduce argon gas, turn on the power, connect the upper and lower pressure columns of the graphite mold to pulsed current, and then heat from room temperature to 1350 °C at a heating rate of 110 °C / min, hold for 12 min, turn off the power switch, and cool with the furnace to obtain the high-entropy aluminum silicide ceramic (denoted as HEAS-2).

[0063] Performance Test:

[0064] 1) The XRD pattern of the high-entropy aluminosilicide ceramic (HEAS-2) in this example is as shown in Figure 1 the figure.

[0065] It can be seen from Figure 1 that the high-entropy aluminosilicide ceramic (HEAS-2) is a pure phase without other impurity phases, indicating its high purity.

[0066] 2) The scanning electron microscope (SEM) image and EDS elemental surface distribution map of the high-entropy aluminosilicide ceramic (HEAS-2) in this example are as shown in Figure 2 the figure.

[0067] It can be seen from Figure 2 that the high-entropy aluminosilicide ceramic (HEAS-2) has a high density. The density measured by the Archimedes method is 97.4%. The EDS results show that the distribution of each metal element is uniform and there is no obvious element segregation.

[0068] 3) The oxidation depth of the high-entropy aluminosilicide ceramic (HEAS-2) in this example after laser high-temperature oxidation at 2100°C for 80 min is 0.34 mm, and the linear ablation rate is 0.022 μm / s, indicating that it has excellent antioxidant and anti-ablative properties under ultra-high temperature conditions.

[0069] Example 3:

[0070] A high-entropy aluminosilicide ceramic is prepared as follows:

[0071] 1) Add 1.8 g of Ta powder, 5.5 g of W powder, 2.9 g of Mo powder, 1.6 g of Cr powder, 1.3 g of aluminum powder and 5.3 g of silicon powder (the total molar amount of metal atoms in Ta powder, W powder, Mo powder and Cr powder is in a ratio of 1:2 to the total molar amount of aluminum powder and silicon powder; the molar ratio of aluminum powder to silicon powder is 1:4) into a nylon ball milling tank, then add anhydrous ethanol and zirconia milling beads. The weight ratio of the powder raw material, zirconia milling beads and anhydrous ethanol is 1:3:2. Then place the nylon ball milling tank into a planetary ball mill and mill for 20 h. Then take out the material and evaporate the anhydrous ethanol to obtain a mixed powder.

[0072] 2) Load 2.4 g of the mixed powder into a mold (the inner cavity of the mold is cylindrical with a diameter of 16 mm), slowly apply pressure up to 12 MPa, hold the pressure for 4 min to form a green body (with a thickness of about 2.4 mm). Then, draw 3 through holes with a length of about 20 mm and spaced about 5 mm apart in the middle of the side of a graphite felt with a length of 120 mm, a width of 20 mm, and a thickness of 8 mm. Then, wrap the green body with graphite paper coated with boron nitride and embed it in the graphite felt. Then, clamp both ends of the graphite felt along the length direction with electrodes and place it in a reaction kettle. Close the door of the reaction kettle cavity, open the mechanical pump and the bypass valve to evacuate the reaction kettle cavity until the value of the vacuum pressure gauge reaches 10 Pa. Then, turn on the molecular pump and the gate valve to continue the evacuation process until the value of the vacuum pressure gauge is less than 1.0×10 -2 Pa. Then, slowly introduce argon gas until the cavity is in a semi-vacuum state. Then, turn on the power switch to connect both ends of the graphite felt to alternating current. Increase the current from 0 A to 15 A at a rate of 5 A / s and hold for 20 s. Then, increase the current to 30 A at a rate of 5 A / s and hold for 70 s. Turn off the power and cool it in the furnace. Then, take out the material for grinding and pass it through a 300-mesh sieve to obtain the high-entropy aluminosilicide powder;

[0073] 3) Embed the graphite paper coated with boron nitride into a graphite mold. The graphite mold is cylindrical with an inner diameter of 10.4 mm. After embedding the graphite paper coated with boron nitride, the actual inner diameter of the graphite mold is 10 mm. Then, load 2.2 g of the high-entropy aluminosilicide powder, and use upper and lower pressing columns to clamp the powder in the middle of the graphite mold. Then, place the graphite mold in the discharge plasma sintering reaction cavity, adjust the pressure of the pressure head to 4 kN (50 MPa) to press the high-entropy aluminosilicide powder into a green body, and keep this pressure all the time. Then, introduce argon gas, turn on the power, connect the upper and lower pressing columns of the graphite mold to pulsed current, and heat from room temperature to 1400 °C at a heating rate of 120 °C / min, hold for 15 min, turn off the power switch, and cool it in the furnace to obtain the high-entropy aluminosilicide ceramic (denoted as HEAS-3).

[0074] Performance test:

[0075] 1) The XRD pattern of the high-entropy aluminosilicide ceramic (HEAS-3) in this example is as Figure 1 shown.

[0076] It can be seen from Figure 1 that the high-entropy aluminosilicide ceramic (HEAS-3) is a pure phase without other impurity phases, indicating its high purity.

[0077] 2) The measured density of the high-entropy aluminosilicide ceramic (HEAS-3) in this example by the Archimedes method is 98.6%, indicating its high density.

[0078] 3) The oxidation depth of the high-entropy aluminosilicide ceramic (HEAS-3) in this example after 80 minutes of laser high-temperature oxidation at 2100 °C is 0.51 mm, and the linear ablation rate is 0.047 μm / s, indicating that it has excellent oxidation resistance and ablation resistance under ultra-high temperature conditions.

[0079] Comparative Example 1:

[0080] A high-entropy silicide ceramic (denoted as HES-1), except that when preparing, the powder raw material composition in step 1) is adjusted from "5.7 g of Ta powder, 5.8 g of W powder, 3.0 g of Mo powder, 0.3 g of Cr powder, 2.5 g of aluminum powder and 3.9 g of silicon powder (the total molar amount of metal atoms in Ta powder, W powder, Mo powder and Cr powder is in a ratio of 1:2 to the total molar amount of aluminum powder and silicon powder; the molar ratio of aluminum powder to silicon powder is 1:1.5)" to "4.5 g of Ta powder, 4.6 g of W powder, 2.4 g of Mo powder, 1.3 g of Cr powder and 5.6 g of silicon powder (the total molar amount of metal atoms in Ta powder, W powder, Mo powder and Cr powder is in a ratio of 1:2 to the molar amount of silicon powder)", the rest is exactly the same as Example 1.

[0081] Performance test:

[0082] 1) The XRD pattern of the high-entropy silicide ceramic (HES-1) in this comparative example is as Figure 3 shown.

[0083] It can be Figure 3 seen that the high-entropy silicide ceramic (HES-1) is a pure phase without other impurity phases.

[0084] 2) The density of the high-entropy silicide ceramic (HES-1) in this comparative example measured by the Archimedes method is 97.8%.

[0085] 3) The high-entropy silicide ceramic (HES-1) in this comparative example was broken down after 60 minutes of laser high-temperature oxidation at 2100 °C. The oxidation depth was as high as 3.05 mm, and the linear ablation rate was as high as 0.847 μm / s, indicating that its oxidation resistance and ablation resistance under ultra-high temperature conditions are poor and cannot meet the long-term service requirements of the hot-end components of hypersonic aircraft in extremely high-temperature environments.

[0086] Comparative Example 2:

[0087] A high-entropy aluminosilicide ceramic, and its preparation method is as follows:

[0088] 1) Add 4.5 g of Ta powder, 4.6 g of W powder, 2.4 g of Mo powder, 2.3 g of Zr powder, 2.1 g of aluminum powder, and 4.4 g of silicon powder (the ratio of the total molar amount of metal atoms in Ta powder, W powder, Mo powder, and Zr powder to the total molar amount of aluminum powder and silicon powder is 1:2; the molar ratio of aluminum powder to silicon powder is 1:2) into a nylon ball milling tank, then add anhydrous ethanol and zirconia ball milling beads. The weight ratio of the powder raw materials, zirconia ball milling beads, and anhydrous ethanol is 1:2:1.5. Then place the nylon ball milling tank into a planetary ball mill and mill for 6 h. Then take out the material and evaporate the anhydrous ethanol to obtain a mixed powder;

[0089] 2) Load 2.2 g of the mixed powder into a mold (the inner cavity of the mold is cylindrical with a diameter of 16 mm), slowly apply pressure to 10 MPa, and hold the pressure for 3 min to form a green body (with a thickness of about 2.5 mm). Then draw 3 through holes with a length of about 20 mm and spaced about 5 mm apart in the middle position on the side of a graphite felt with a length of 110 mm, a width of 20 mm, and a thickness of 5 mm. Then wrap the green body with graphite paper coated with boron nitride and embed it in the graphite felt. Then clamp both ends of the graphite felt along the length direction with electrodes and place it in a reaction kettle. Close the door of the reaction kettle cavity, turn on the mechanical pump and the bypass valve to evacuate the reaction kettle cavity until the value of the vacuum pressure gauge reaches 10 Pa. Then turn on the molecular pump and the gate valve to continue the evacuation process until the value of the vacuum pressure gauge is less than 1.0×10 -2 Pa. Then slowly introduce argon gas until the cavity is in a semi-vacuum state. Then turn on the power switch to connect both ends of the graphite felt to alternating current. Increase the current from 0 A to 8 A at a rate of 2 A / s and hold for 30 s. Then increase the current to 18 A at a rate of 3 A / s and hold for 5 s. Turn off the power and cool with the furnace. Then take out the material and grind it, and then pass it through a 100-mesh sieve to obtain high-entropy aluminum silicide powder;

[0090] 3) Embed the graphite paper coated with boron nitride into a graphite mold. The graphite mold is cylindrical with an inner diameter of 10.4 mm. After embedding the graphite paper coated with boron nitride, the actual inner diameter of the graphite mold is 10 mm. Then load 2.2 g of high-entropy aluminum silicide powder, and use upper and lower pressure columns to clamp the powder in the middle of the graphite mold. Then place the graphite mold in the discharge plasma sintering reaction cavity, adjust the pressure of the pressure head to 2 kN (25 MPa) to press the high-entropy aluminum silicide powder into a green body, and keep this pressure all the time. Then introduce argon gas, turn on the power, connect the upper and lower pressure columns of the graphite mold to pulsed current, and then heat from room temperature to 1200 °C at a heating rate of 80 °C / min, hold for 10 min, turn off the power switch, and cool with the furnace to obtain high-entropy aluminum silicide ceramic (denoted as HEAS-4).

[0091] Performance test:

[0092] 1) The XRD pattern of the high-entropy aluminosilicide ceramic (HEAS-4) in this comparative example is as follows Figure 3 shown.

[0093] It can be seen from Figure 3 that the high-entropy aluminosilicide ceramic (HEAS-4) contains impurity phases ZrSi, Zr 10 (AlSi)3 and Zr5Si3, indicating that its purity is relatively low.

[0094] 2) The density of the high-entropy aluminosilicide ceramic (HEAS-4) in this comparative example measured by the Archimedes method is 96.2%.

[0095] 3) After the high-entropy aluminosilicide ceramic (HEAS-4) in this comparative example is laser-oxidized at 2100 °C for 80 min, the oxidation depth is 1.68 mm and the linear ablation rate is 0.343 μm / s. Both the oxidation depth and the linear ablation rate are much higher than those of the high-entropy aluminosilicide ceramic in Example 1, indicating that its antioxidant and anti-ablation properties under ultra-high temperature conditions are poor and cannot meet the long-term service requirements of the hot-end components of hypersonic vehicles in extremely high temperature environments.

[0096] Comparative Example 3:

[0097] A high-entropy aluminosilicide ceramic (denoted as HEAS-5), except that when preparing, the powder raw material composition in step 1) is adjusted from "5.1 g of Ta powder, 5.2 g of W powder, 2.7 g of Mo powder, 0.8 g of Cr powder, 2.4 g of aluminum powder and 4.6 g of silicon powder (the total molar amount of metal atoms in Ta powder, W powder, Mo powder and Cr powder is in a ratio of 1:2 to the total molar amount of aluminum powder and silicon powder; the molar ratio of aluminum powder to silicon powder is 1:2)" to "5.1 g of Ta powder, 5.2 g of W powder, 2.7 g of Mo powder, 0.8 g of Cr powder, 1.0 g of aluminum powder and 6.1 g of silicon powder (the total molar amount of metal atoms in Ta powder, W powder, Mo powder and Cr powder is in a ratio of 1:2 to the total molar amount of aluminum powder and silicon powder; the molar ratio of aluminum powder to silicon powder is 1:6)", and the rest is exactly the same as in Example 2.

[0098] Performance test:

[0099] 1) The XRD pattern of the high-entropy aluminosilicide ceramic (HEAS-5) in this comparative example is as follows Figure 3 shown.

[0100] It can be seen from Figure 3 that the high-entropy aluminosilicide ceramic (HEAS-5) is a pure phase and does not contain other impurity phases.

[0101] 2) The density of the high-entropy aluminosilicide ceramic (HEAS-5) in this comparative example measured by the Archimedes method is 98.4%.

[0102] 3) The oxidation depth of the high-entropy aluminosilicide ceramic (HEAS-5) in this comparative example after 80 minutes of laser high-temperature oxidation at 2100 °C is 0.638 mm, and the linear ablation rate is 0.101 μm / s. Both the oxidation depth and the linear ablation rate are much higher than those of the high-entropy aluminosilicide ceramic in Example 2, indicating that its oxidation resistance and ablation resistance under ultra-high temperature conditions are poor and it cannot meet the long-term service requirements of the hot-end components of hypersonic aircraft in extremely high-temperature environments.

[0103] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A preparation method of a high-entropy aluminum silicide ceramic, characterized in that, It includes the following steps: 1) Mix the transition metal powder, aluminum powder and silicon powder and carry out wet ball milling. The transition metal powder is at least four of Hf powder, Zr powder, Ta powder, Nb powder, Ti powder, V powder, Mo powder, Cr powder and W powder, and then dry to obtain a mixed powder; 2) Press the mixed powder into a green body, wrap the green body with graphite paper coated with boron nitride on the surface and then embed it in a graphite felt, and then place it in a protective atmosphere, energize the graphite felt to carry out electric field sintering on the green body, and then carry out crushing and screening to obtain a high-entropy aluminum silicide powder; 3) Embed the graphite paper coated with boron nitride on the surface into a graphite mold, then load the high-entropy aluminum silicide powder and press it into a green body, and then place it in a protective atmosphere, connect the graphite mold with a pulsed current to carry out spark plasma sintering on the green body, and then a high-entropy aluminum silicide ceramic is obtained.

2. The preparation method according to claim 1, wherein: In step 1), the ratio of the total molar amount of metal atoms in the transition metal powder to the total molar amount of aluminum powder and silicon powder is 1:2; in step 1), the molar ratio of the aluminum powder to the silicon powder is 1:1.5 to 4.

3. The preparation method according to claim 1 or 2, characterized in that: In step 1), the particle size of the aluminum powder is ≤10 μm and the purity is ≥99%; in step 1), the particle size of the silicon powder is ≤2 μm and the purity is ≥99.9%; in step 1), the particle sizes of the Hf powder, Zr powder, Ta powder, Nb powder, Ti powder, V powder, Mo powder, Cr powder and W powder are all 1 μm to 3 μm and the purities are all ≥99.5%.

4. The preparation method according to claim 1 or 2, characterized in that: The process parameters of the wet ball milling in step 1) include: the ball milling medium is anhydrous ethanol, the ball milling equipment is a planetary ball mill, the weight ratio of the powder raw material, ZrO2 balls and anhydrous ethanol is 1:2 to 3:1.5 to 2, and the ball milling time is 10 h to 20 h.

5. The preparation method according to claim 1, characterized in that: The pressing in step 2) is carried out under the condition of a pressure of 9 MPa to 12 MPa, and the pressure holding time is 2 min to 4 min; in step 2), the green body is cylindrical, the diameter is ≤16 mm and the thickness is ≤3.2 mm; in step 2), the length of the graphite felt is 105 mm to 120 mm, the width is 16 mm to 20 mm, and the thickness is 5 mm to 8 mm.

6. The preparation method according to claim 1 or 5, characterized in that: The electric field sintering in step 2) includes the following operations: Connect the two ends of the graphite felt with alternating current and increase the current from 0 A to 10 A to 15 A at a rate of 3 A / s to 5 A / s, hold for 10 s to 20 s, and then increase the current to 20 A to 30 A at a rate of 3 A / s to 5 A / s, hold for 50 s to 70 s, cut off the power supply, and cool naturally.

7. The preparation method according to claim 1, characterized in that: The pressing in step 3) is carried out under the condition of a pressure of 30 MPa to 50 MPa; in step 3), the green body is cylindrical and the diameter is ≤20 mm.

8. The preparation method according to claim 1 or 7, characterized in that: The spark plasma sintering in step 3) includes the following operations: Connect the graphite mold with a pulsed current, heat up from room temperature to 1300 °C to 1400 °C at a heating rate of 100 °C / min to 120 °C / min, keep warm for 10 min to 15 min, cut off the power supply, and cool naturally.

9. A high-entropy aluminosilicide ceramic, characterized in that, Made by the preparation method described in any one of claims 1 to 8.

10. A hypersonic vehicle hot-end component, characterized in that, Containing the high-entropy aluminum silicide ceramic described in claim 9.

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