High-entropy ceramic wave-absorbing powder as well as preparation method and application thereof

Abstract

The invention discloses high-entropy ceramic wave-absorbing powder as well as a preparation method and application thereof. The preparation method of the high-entropy ceramic wave-absorbing powder comprises the following steps: 1) preparing mixed powder; 2) pressing the mixed powder into a green body, placing the green body in a protective atmosphere for electric field sintering, and crushing to obtain high-entropy ceramic powder; and 3) performing heat treatment on the high-entropy ceramic powder in a protective atmosphere to obtain the high-entropy ceramic wave-absorbing powder. The preparation method of the high-entropy ceramic wave-absorbing powder has the advantages of being simple, efficient, high in universality, environmentally friendly, capable of greatly improving the wave-absorbing performance of a high-entropy ceramic material and the like, and the obtained high-entropy ceramic wave-absorbing powder is suitable for being used as a stealth coating of aerospace crafts and has very wide application prospects.

Description

Technical Field

[0001] This invention relates to the field of high-entropy ceramics technology, specifically to a high-entropy ceramic microwave absorbing powder, its preparation method, and its application. Background Technology

[0002] Radar absorbing materials enhance electromagnetic compatibility, suppress electromagnetic interference, and provide radar stealth capabilities, making them indispensable key materials in the defense industry. An ideal radar absorbing material must not only possess excellent electromagnetic wave stealth capabilities but also conform to the design principles of being "thin, light, strong, and wide" (e.g., high temperature resistance, oxidation resistance, and high load-bearing capacity). However, traditional organic and metallic radar absorbing materials generally suffer from poor thermal stability and insufficient oxidation resistance in extreme environments such as high temperatures, making it difficult to fully meet the requirements of practical applications.

[0003] High-entropy ceramic materials possess excellent properties such as high electrical conductivity, ultra-high melting point, low thermal conductivity, good corrosion resistance, high high-temperature strength, and good high-temperature oxidation resistance, making them highly promising for applications in high-temperature microwave absorbing agents and microwave absorbing coatings for aerospace vehicles. However, existing high-entropy ceramic microwave absorbing materials generally suffer from impedance mismatch and weak loss capacity, resulting in poor electromagnetic wave absorption performance. Currently, there are very few methods to improve the microwave absorption performance of high-entropy ceramic materials, and existing methods also have significant shortcomings. For example, Zhao et al. disclosed a method to improve the microwave absorption performance of high-entropy ceramic materials by controlling the morphology, firstly by... 0.25 Cr 0.25 Ti 0.25 V 0.25 Acid etching of 3AlC2 to prepare a suspension, followed by multiple centrifugations and drying, yields a two-dimensional high-entropy monolayer sheet structure. While this method can increase the effective absorption bandwidth of high-entropy ceramic materials from 3.6 GHz to 5.6 GHz (Hierarchical flower-like sulfides with increased entropy for electromagnetic wave absorption, Biao Zhao, Zhikai Yan, and Renchao Che. ACS Applied Materials & Interfaces, 2023, 15, 59618-59629), it also has drawbacks such as complex processes (requiring multiple acid etching and peeling post-processing), long preparation cycle (>24h), poor universality (only applicable to MXene systems), and significant environmental pollution (strong acid solution), severely limiting the practical application of high-entropy ceramic microwave absorbing materials.

[0004] Therefore, it is of great significance to develop a simple, efficient, universal, safe, and environmentally friendly method that can significantly improve the wave absorption performance of high-entropy ceramic materials. Summary of the Invention

[0005] The purpose of this invention is to provide a high-entropy ceramic microwave absorbing powder, its preparation method, and its application.

[0006] The technical solution adopted in this invention is:

[0007] A method for preparing high-entropy ceramic microwave absorbing powder includes the following steps:

[0008] 1) Preparation of mixed powders:

[0009] a) Mixing transition metal oxide powder with B powder or C powder to obtain a mixed powder for preparing high-entropy borides or high-entropy carbides;

[0010] b) Mix metal oxide powder with TiO2 powder, wherein the metal oxide powder includes alkaline earth metal oxide powder and rare earth oxide powder, to obtain a mixed powder for preparing high entropy oxides;

[0011] c) Mixing transition metal powder with Si powder yields a mixed powder for preparing high-entropy silicides;

[0012] d) The transition metal powder is mixed with Se powder to obtain a mixed powder for preparing high-entropy selenides;

[0013] 2) The mixed powder is pressed into a green body, then placed in a protective atmosphere for electric field sintering, and then crushed to obtain high-entropy ceramic powder;

[0014] 3) The high-entropy ceramic powder is placed in a protective atmosphere for heat treatment to obtain high-entropy ceramic microwave absorbing powder.

[0015] Preferably, the transition metal oxide powder in step a) is composed of at least five of the following powders in equimolar ratio: HfO2 powder, ZrO2 powder, Ta2O5 powder, Nb2O5 powder, TiO2 powder, V2O5 powder, WO3 powder, MoO3 powder, and Cr2O3 powder.

[0016] Preferably, the molar ratio of the transition metal oxide powder and B powder in step a) is 1:2.0 to 2.2.

[0017] Preferably, the molar ratio of the transition metal oxide powder and C powder in step a) is 1:1.0 to 1.2.

[0018] Preferably, the transition metal oxide powder, B powder and C powder mentioned in step a) have a particle size of 1μm to 3μm and a purity of ≥99.9%.

[0019] Preferably, the metal oxide powder in step b) is composed of at least five of the following: CaO powder, SrO powder, BaO powder, La2O3 powder, Nd2O3 powder, and Sm2O3 powder, in an equimolar ratio. CaO powder, SrO powder, and BaO powder are alkaline earth metal oxide powders, while La2O3 powder, Nd2O3 powder, and Sm2O3 powder are rare earth oxide powders.

[0020] Preferably, the molar ratio of the metal oxide powder and TiO2 powder in step b) is 1:3.0 to 3.2.

[0021] Preferably, the particle size of the metal oxide powder and TiO2 powder in step b) is 1μm to 3μm, and the purity is ≥99.9%.

[0022] Preferably, the transition metal powder in step c) is composed of at least five of the following in an equimolar ratio: Hf powder, Zr powder, Ta powder, Nb powder, Ti powder, W powder, Mo powder, and V powder.

[0023] Preferably, the molar ratio of the transition metal powder and Si powder in step c) is 1:2.2 to 2.5.

[0024] Preferably, the transition metal powder and Si powder mentioned in step c) have a particle size of 1μm to 3μm and a purity of ≥99.9%.

[0025] Preferably, the transition metal powder in step d) is composed of at least five of the following: Fe powder, Co powder, Ni powder, Cu powder, Mn powder, and Zn powder, in equimolar ratio.

[0026] Preferably, the molar ratio of the transition metal powder and Se powder in step d) is 1:2.0 to 2.2.

[0027] Preferably, the transition metal powder and Se powder mentioned in step d) have a particle size of 1μm to 3μm and a purity of ≥99.9%.

[0028] Preferably, the mixing in step 1) includes the following operations: wet ball milling, drying and grinding.

[0029] Preferably, the process parameters for the wet ball milling include: the ball milling medium is anhydrous ethanol, the ball milling equipment is a planetary ball mill, the weight ratio of powder raw material, ZrO2 balls and anhydrous ethanol is 1:4.0-5.0:1.5-2.5, the ball mill speed is 400 r / min-500 r / min, and the ball milling time is 24 h-30 h.

[0030] Preferably, the drying equipment used is a rotary evaporator, the drying temperature is 70℃~90℃, and the drying time is 0.5h~1h.

[0031] Preferably, the pressing in step 2) is carried out under a pressure of 8MPa to 12MPa.

[0032] Preferably, the thickness of the blank in step 2) is 2mm to 5mm.

[0033] Preferably, the protective atmosphere in step 2) is a nitrogen atmosphere or an argon atmosphere.

[0034] Preferably, the electric field sintering in step 2) includes the following operations: wrapping the blank with carbon paper coated with boron nitride and embedding it with graphite felt, then placing the graphite felt into the electric field sintering equipment, then evacuating the vacuum, then filling it with a protective atmosphere, then connecting the two ends of the graphite felt with alternating current and increasing the current from 0A to 35A to 45A at a rate of 5A / s to 8A / s, holding it for 10s to 40s, then continuing to increase the current at a rate of 5A / s to 8A / s to 70A to 90A, holding it for 60s to 90s, then disconnecting the power supply and allowing it to cool naturally to room temperature.

[0035] Preferably, the graphite felt has a length of 150mm to 220mm, a width of 15mm to 25mm, and a thickness of 4mm to 8mm.

[0036] Preferably, the protective atmosphere in step 3) is a nitrogen atmosphere or an argon atmosphere.

[0037] Preferably, the heat treatment in step 3) includes the following operations: the high-entropy ceramic powder is loaded into a graphite crucible and then placed in a tube furnace, then a vacuum is drawn, then a protective atmosphere is introduced, and then the heating rate is controlled at 2℃ / min~4℃ / min to raise the temperature from room temperature to 1200℃~1600℃, and held for 60min~240min.

[0038] A high-entropy ceramic absorbing powder is prepared by the above-described method.

[0039] An aerospace vehicle comprising a stealth coating comprising the aforementioned high-entropy ceramic absorbing powder.

[0040] The beneficial effects of this invention are: the method for preparing high-entropy ceramic absorbing powder of this invention has the advantages of being simple and efficient, highly universal, environmentally friendly, and able to significantly improve the absorbing performance of high-entropy ceramic materials. The obtained high-entropy ceramic absorbing powder is suitable for use in stealth coatings for aerospace vehicles and has a very broad application prospect.

[0041] Specifically:

[0042] 1) The high-entropy ceramic microwave absorbing powder preparation method of the present invention has the advantages of simple equipment, simple and controllable process, fast and efficient, and can simultaneously heat treat multiple samples to improve their microwave absorption performance.

[0043] 2) The method for preparing high-entropy ceramic microwave absorbing powder of the present invention has strong versatility and is applicable to high-entropy ceramic materials of different systems such as high-entropy carbides, high-entropy borides, high-entropy oxides, high-entropy silicides, and high-entropy selenides;

[0044] 3) The high-entropy ceramic microwave absorbing powder preparation method of the present invention is environmentally friendly, requires no acid etching operation, does not emit waste liquid or waste gas, has low energy consumption, low industrialization cost, and is suitable for large-scale industrial application.

[0045] 4) The high-entropy ceramic absorbing powder preparation method of the present invention can significantly improve the microwave absorption performance of high-entropy ceramic materials. For different high-entropy ceramic material systems, it can increase their effective absorption bandwidth to 5.7GHz to 11.2GHz, which can cover the entire X / Ku band, and the microwave absorption performance is significantly improved. Attached Figure Description

[0046] Figure 1 The image shows the XRD pattern of the high-entropy carbide ceramic absorbing powder in Example 1.

[0047] Figure 2 The graph shows the microwave absorption performance test results of the high-entropy carbide ceramic absorbing powder in Example 1.

[0048] Figure 3 The images show the XRD patterns of the high-entropy boride ceramic absorbing powder in Example 2, the high-entropy oxide ceramic absorbing powder in Example 3, the high-entropy silicide ceramic absorbing powder in Example 4, and the high-entropy selenide ceramic absorbing powder in Example 5.

[0049] Figure 4 The graph shows the microwave absorption performance test results of the high-entropy boride ceramic microwave absorbing powder in Example 2.

[0050] Figure 5 The graph shows the microwave absorption performance test results of the high-entropy oxide ceramic microwave absorbing powder in Example 3.

[0051] Figure 6 The graph shows the microwave absorption performance test results of the high-entropy silicide ceramic absorbing powder in Example 4.

[0052] Figure 7 The graph shows the microwave absorption performance test results of the high-entropy selenide ceramic microwave absorbing powder in Example 5.

[0053] Figure 8 The graph shows the microwave absorption performance test results of the high-entropy boride ceramic absorbing powder in Comparative Example 1.

[0054] Figure 9 The graph shows the microwave absorption performance test results of the high-entropy boride ceramic absorbing powder in Comparative Example 2. Detailed Implementation

[0055] The present invention will be further explained and described below with reference to specific embodiments.

[0056] The HfO2 powder, ZrO2 powder, Ta2O5 powder, Nb2O5 powder, TiO2 powder, V5O2 powder, WO3 powder, MoO3 powder, Cr3O2 powder, BaO powder, CaO powder, SrO powder, La2O3 powder, C powder, B powder, Ti powder, Zr powder, Nb powder, Mo powder, W powder, Si powder, Fe powder, Co powder, Ni powder, Cu powder, and Se powder in Examples 1-5 all have a particle size of 1μm to 3μm and a purity of ≥99.9%.

[0057] Example 1:

[0058] A high-entropy carbide ceramic microwave absorbing powder is prepared by the following method:

[0059] 1) Add 1.149g of HfO2 powder, 0.684g of ZrO2 powder, 1.227g of Ta2O5 powder, 0.738g of Nb2O5 powder, 0.443g of TiO2 powder, 0.505g of V5O2 powder, 1.288g of WO3 powder, 0.799g of MoO3 powder, 0.419g of Cr3O2 powder, and 0.667g of C powder to the ball mill jar, then... The grinding jar was fed into a planetary ball mill for wet ball milling. The process parameters for wet ball milling were as follows: the grinding media was anhydrous ethanol, the weight ratio of powder raw material, ZrO2 balls and anhydrous ethanol was 1:4:1.5, the ball mill speed was 500 r / min, and the ball milling time was 24 h. The resulting mixed slurry was then placed in a rotary evaporator and evaporated at 90°C for 1 h. After cooling to room temperature, it was ground and passed through a 200-mesh sieve (to remove sieve residue) to obtain mixed powder.

[0060] 2) After injecting the mixed powder into the mold, apply a pressure of 12 MPa to press it into a blank with a thickness of 2 mm. Then, wrap the blank with carbon paper coated with boron nitride and embed it with a graphite felt that is 220 mm long, 25 mm wide, and 8 mm thick (after cutting the side of the felt). Then, place the graphite felt into an electric field sintering equipment and evacuate it until the vacuum degree is less than 3.0 × 10⁻⁶. -2 Pa, then fill with argon gas, then connect the two ends of the graphite felt to AC power and increase the current from 0A to 40A at a rate of 5A / s, hold for 20s, then continue to increase the current to 90A at a rate of 8A / s, hold for 60s, disconnect the power supply, let it cool naturally to room temperature, then crush and pass through a 300-mesh sieve (to remove sieve residue) to obtain high-entropy carbide ceramic powder;

[0061] 3) After loading the high-entropy carbide ceramic powder into a graphite crucible, place it in a tube furnace and then evacuate it until the vacuum level is less than 3.0 × 10⁻⁶. -2Pa, then argon gas is introduced, and the temperature is raised from room temperature to 1600℃ at a controlled rate of 2℃ / min, held for 240min, and then naturally cooled to room temperature to obtain high-entropy carbide ceramic microwave absorbing powder (nine-membered high-entropy carbide (Hf)). 1 / 9 Zr 1 / 9 Ta 1 / 9 Nb 1 / 9 Ti 1 / 9V 1 / 9 W 1 / 9 Mo 1 / 9 Cr 1 / 9 C, denoted as HEC).

[0062] Performance testing:

[0063] 1) The X-ray diffraction (XRD) pattern of the high-entropy carbide ceramic absorbing powder (HEC) in this embodiment is shown below. Figure 1 As shown.

[0064] Depend on Figure 1 It can be seen that HEC is a single-phase solid solution, and no other impurity phases were found.

[0065] 2) The high-entropy carbide ceramic powder and high-entropy carbide ceramic absorbing powder (HEC) in this embodiment were mixed with paraffin wax at a weight ratio of 7:3, and then processed into coaxial rings with an inner diameter of 3 mm and an outer diameter of 7 mm. The absorption performance was then tested using a network vector analyzer. The test results of the absorption performance are as follows: Figure 2 (The coaxial ring made of high-entropy carbide ceramic powder is denoted as the initial stage, and the coaxial ring made of high-entropy carbide ceramic microwave absorbing powder is denoted as the heat-treated stage.)

[0066] Depend on Figure 2 It can be seen that after heat treatment, the effective absorption bandwidth of high-entropy carbide ceramic powder increases from the initial 8.0 GHz to 11.2 GHz, and the wave absorption performance is greatly improved. The reason is that heat treatment causes strong chemical fluctuations in high-entropy carbide ceramic powder, which increases its polarization loss.

[0067] Example 2:

[0068] A high-entropy boride ceramic microwave absorbing powder is prepared by the following method:

[0069] 1) Add 1.403g of HfO2 powder, 0.821g of ZrO2 powder, 1.472g of Ta2O5 powder, 0.886g of Nb2O5 powder, 0.532g of TiO2 powder and 0.466g of B powder to a ball mill jar, and then put the ball mill jar into a planetary ball mill for wet ball milling. The process parameters of wet ball milling are as follows: the ball milling medium is anhydrous ethanol, the weight ratio of powder raw materials, ZrO2 balls and anhydrous ethanol is 1:5:2, the ball mill speed is 450r / min, and the ball milling time is 30h. Then place the resulting mixed slurry in a rotary evaporator and evaporate it at 90℃ for 1h. After cooling to room temperature, grind it and pass it through a 200-mesh sieve (to remove the sieve residue) to obtain mixed powder.

[0070] 2) After injecting the mixed powder into the mold, apply a pressure of 8 MPa to press it into a blank with a thickness of 2 mm. Then, wrap the blank with carbon paper coated with boron nitride and embed it with a graphite felt that is 150 mm long, 15 mm wide, and 4 mm thick (after cutting the side of the felt). Then, place the graphite felt into an electric field sintering equipment and evacuate it until the vacuum degree is less than 3.0 × 10⁻⁶. -2 Pa, then fill with argon gas, then connect the two ends of the graphite felt to AC power and increase the current from 0A to 40A at a rate of 8A / s, hold for 20s, then continue to increase the current to 90A at a rate of 8A / s, hold for 60s, disconnect the power supply, let it cool naturally to room temperature, then crush and pass through a 300-mesh sieve (to remove sieve residue) to obtain high-entropy boride ceramic powder;

[0071] 3) After loading the high-entropy boride ceramic powder into a graphite crucible, place it into a tube furnace and then evacuate it until the vacuum degree is less than 3.0 × 10⁻⁶. -2 Pa, then argon gas is introduced, and the temperature is raised from room temperature to 1500℃ at a controlled rate of 4℃ / min, held for 120min, and then naturally cooled to room temperature to obtain high-entropy boride ceramic microwave absorbing powder (pentabyte high-entropy boride (Hf)). 1 / 5 Zr 1 / 5 Ta 1 / 5 Nb 1 / 5Ti 1 / 5 B2, denoted as HEB).

[0072] Performance testing:

[0073] 1) The XRD pattern of the high-entropy boride ceramic absorbing powder (HEB) in this embodiment is as follows: Figure 3 As shown.

[0074] Depend on Figure 3 It can be seen that HEB is a single-phase solid solution, and no other impurity phases were found.

[0075] 2) The microwave absorption performance test results of the high-entropy boride ceramic absorbing powder (HEB) in this embodiment are as follows: Figure 4 (The test method is the same as in Example 1; high-entropy boride ceramic powder is used as a comparison, and the coaxial ring made of high-entropy boride ceramic powder is recorded as the initial stage, and the coaxial ring made of high-entropy boride ceramic microwave absorbing powder is recorded as the heat-treated stage.)

[0076] Depend on Figure 4 It can be seen that after heat treatment, the effective absorption bandwidth of high-entropy boride ceramic powder increases from the initial 4.6GHz to 6.4GHz, and the wave absorption performance is greatly improved. The reason is that heat treatment causes strong chemical fluctuations in the high-entropy boride ceramic powder, which increases its polarization loss.

[0077] Example 3:

[0078] A high-entropy oxide ceramic microwave absorbing powder is prepared by the following method:

[0079] 1) Add 1.022g of BaO powder, 0.374g of CaO powder, 0.691g of SrO powder, 1.086g of La2O3 powder, 2.243g of Nd2O5 powder and 4.575g of TiO2 powder to a ball mill jar, and then put the ball mill jar into a planetary ball mill for wet ball milling. The process parameters of wet ball milling are as follows: the ball milling medium is anhydrous ethanol, the weight ratio of powder raw materials, ZrO2 balls and anhydrous ethanol is 1:5:2.5, the ball mill speed is 500r / min, and the ball milling time is 30h. Then place the resulting mixed slurry in a rotary evaporator and evaporate it at 90℃ for 1h. After cooling to room temperature, grind it and pass it through a 200-mesh sieve (to remove the sieve residue) to obtain mixed powder.

[0080] 2) After injecting the mixed powder into the mold, apply a pressure of 12 MPa to press it into a blank with a thickness of 4 mm. Then, wrap the blank with carbon paper coated with boron nitride and embed it with a graphite felt that is 220 mm long, 25 mm wide, and 8 mm thick (after cutting the side of the felt). Then, place the graphite felt into an electric field sintering device and evacuate it until the vacuum degree is less than 3.0 × 10⁻⁶. -2 Pa, then fill with argon gas, then connect the two ends of the graphite felt to AC power and increase the current from 0A to 40A at a rate of 8A / s, hold for 40s, then continue to increase the current to 70A at a rate of 8A / s, hold for 90s, disconnect the power supply, let it cool naturally to room temperature, then crush and pass through a 300-mesh sieve (to remove sieve residue) to obtain high-entropy oxide ceramic powder;

[0081] 3) After loading the high-entropy oxide ceramic powder into a graphite crucible, place it into a tube furnace and then evacuate the furnace until the vacuum level is less than 3.0 × 10⁻⁶. -2Pa, then argon gas is introduced, and the temperature is raised from room temperature to 1200℃ at a controlled rate of 4℃ / min, held for 120min, and then naturally cooled to room temperature to obtain high-entropy oxide ceramic absorbing powder (pentabyte high-entropy oxide (Ba). 1 / 5 Ca 1 / 5 Sr 1 / 5 La 1 / 5Nd 1 / 5 TiO3, denoted as HEO).

[0082] Performance testing:

[0083] 1) The XRD pattern of the high-entropy oxide ceramic absorbing powder (HEO) in this embodiment is as follows: Figure 3 As shown.

[0084] Depend on Figure 3 It can be seen that HEO is a single-phase solid solution, and no other impurity phases were found.

[0085] 2) The microwave absorption performance test results of the high entropy oxide ceramic absorbing powder (HEO) in this embodiment are as follows: Figure 5 (The test method is the same as in Example 1; high-entropy oxide ceramic powder is used as a comparison, the coaxial ring made of high-entropy oxide ceramic powder is called the initial one, and the coaxial ring made of high-entropy oxide ceramic microwave absorbing powder is called the heat treatment one) as shown.

[0086] Depend on Figure 5 It can be seen that after heat treatment, the effective absorption bandwidth of high-entropy oxide ceramic powder increases from the initial 2.8GHz to 5.7GHz, and the wave absorption performance is greatly improved. The reason is that heat treatment causes strong chemical fluctuations in high-entropy oxide ceramic powder, which increases its polarization loss.

[0087] Example 4:

[0088] A high-entropy silicide ceramic microwave absorbing powder is prepared by the following method:

[0089] 1) Add 0.638g of Ti powder, 1.216g of Zr powder, 1.238g of Nb powder, 1.279g of Mo powder, 2.451g of W powder, and 3.744g of Si powder to a ball mill jar, and then put the ball mill jar into a planetary ball mill for wet ball milling. The process parameters for wet ball milling are as follows: the ball milling medium is anhydrous ethanol, the weight ratio of powder raw materials, ZrO2 balls and anhydrous ethanol is 1:4:2.5, the ball mill speed is 500r / min, and the ball milling time is 30h. Then place the resulting mixed slurry in a rotary evaporator and evaporate it at 90℃ for 1h. After cooling to room temperature, grind it and pass it through a 200-mesh sieve (to remove sieve residue) to obtain mixed powder.

[0090] 2) After injecting the mixed powder into the mold, apply a pressure of 12 MPa to press it into a blank with a thickness of 4 mm. Then, wrap the blank with carbon paper coated with boron nitride and embed a graphite felt with a length of 150 mm, a width of 15 mm, and a thickness of 4 mm (after cutting the side of the felt into the blank). Then, place the graphite felt into an electric field sintering equipment and evacuate it until the vacuum degree is less than 3.0 × 10⁻⁶. -2 Pa, then fill with argon gas, then connect the two ends of the graphite felt to AC power and increase the current from 0A to 40A at a rate of 8A / s, hold for 20s, then continue to increase the current to 70A at a rate of 8A / s, hold for 60s, disconnect the power supply, let it cool naturally to room temperature, then crush and pass through a 300-mesh sieve (to remove sieve residue) to obtain high-entropy silicide ceramic powder;

[0091] 3) After loading the high-entropy silicide ceramic powder into a graphite crucible, place it into a tube furnace and then evacuate it until the vacuum degree is less than 3.0 × 10⁻⁶. -2 Pa, then argon gas is introduced, and the temperature is raised from room temperature to 1200℃ at a controlled rate of 4℃ / min, held for 120min, and then naturally cooled to room temperature to obtain high-entropy silicide ceramic microwave absorbing powder (pentabyte high-entropy silicide (Ti)). 1 / 5 Zr 1 / 5 Nb 1 / 5 Mo 1 / 5 W 1 / 5 Si2, denoted as HESi).

[0092] Performance testing:

[0093] 1) The XRD pattern of the high-entropy silicide ceramic absorbing powder (HESi) in this embodiment is as follows: Figure 3 As shown.

[0094] Depend on Figure 3 It can be seen that HESi is a single-phase solid solution, and no other impurity phases were found.

[0095] 2) The microwave absorption performance test results of the high-entropy silicide ceramic absorbing powder (HESi) in this embodiment are as follows: Figure 6 (The test method is the same as in Example 1; high-entropy silicide ceramic powder is used as a comparison, and the coaxial ring made of high-entropy silicide ceramic powder is denoted as the initial one, and the coaxial ring made of high-entropy silicide ceramic microwave absorbing powder is denoted as the heat-treated one.)

[0096] Depend on Figure 6 It can be seen that after heat treatment, the effective absorption bandwidth of high-entropy silicide ceramic powder increases from the initial 3.9GHz to 5.7GHz, and the wave absorption performance is greatly improved. The reason is that heat treatment causes strong chemical fluctuations in the high-entropy silicide ceramic powder, which increases its polarization loss.

[0097] Example 5:

[0098] A high-entropy selenide ceramic microwave absorbing powder is prepared by the following method:

[0099] 1) Add 0.279g of Fe powder, 0.294g of Co powder, 0.293g of Ni powder, 0.317g of Cu powder, 0.274g of Mn powder and 3.948g of Se powder to a ball mill jar, and then put the ball mill jar into a planetary ball mill for wet ball milling. The process parameters of wet ball milling are as follows: the ball milling medium is anhydrous ethanol, the weight ratio of powder raw materials, ZrO2 balls and anhydrous ethanol is 1:5:2.5, the ball mill speed is 400r / min, and the ball milling time is 30h. Then place the obtained mixed slurry in a rotary evaporator and evaporate it at 90℃ for 1h. After cooling to room temperature, grind it and pass it through a 200-mesh sieve (to remove the sieve residue) to obtain mixed powder.

[0100] 2) After injecting the mixed powder into the mold, apply a pressure of 8 MPa to press it into a blank with a thickness of 4 mm. Then, wrap the blank with carbon paper coated with boron nitride and embed a graphite felt with a length of 150 mm, a width of 15 mm, and a thickness of 4 mm (after cutting the side of the felt into the blank). Then, place the graphite felt into an electric field sintering equipment and evacuate it to a vacuum degree of less than 3.0 × 10⁻⁶. -2 Pa, then fill with argon gas, then connect the two ends of the graphite felt to AC power and increase the current from 0A to 40A at a rate of 8A / s, hold for 20s, then continue to increase the current to 70A at a rate of 8A / s, hold for 60s, disconnect the power supply, let it cool naturally to room temperature, then crush and pass through a 300-mesh sieve (to remove sieve residue) to obtain high-entropy selenide ceramic powder;

[0101] 3) After loading the high-entropy selenide ceramic powder into a graphite crucible, place it into a tube furnace and then evacuate it until the vacuum degree is less than 3.0 × 10⁻⁶. -2 Pa, then argon gas is introduced, and the temperature is raised from room temperature to 1500℃ at a controlled rate of 4℃ / min, held for 120min, and then naturally cooled to room temperature to obtain high-entropy selenide ceramic microwave absorbing powder (pentabyte high-entropy selenide (Fe)). 1 / 5 Co 1 / 5 Ni 1 / 5 Cu 1 / 5Mn 1 / 5 Se2, denoted as HESe).

[0102] Performance testing:

[0103] 1) The XRD pattern of the high-entropy selenide ceramic absorbing powder (HESe) in this embodiment is shown below. Figure 3 As shown.

[0104] Depend on Figure 3 It can be seen that HESe is a single-phase solid solution, and no other impurity phases were found.

[0105] 2) The microwave absorption performance test results of the high-entropy selenide ceramic absorbing powder (HESe) in this embodiment are as follows: Figure 7 (The test method is the same as in Example 1; high-entropy selenide ceramic powder is used as a comparison, the coaxial ring made of high-entropy selenide ceramic powder is called the initial one, and the coaxial ring made of high-entropy selenide ceramic microwave absorbing powder is called the heat-treated one) as shown.

[0106] Depend on Figure 7 It can be seen that after heat treatment, the effective absorption bandwidth of high-entropy selenide ceramic powder increases from the initial 4.1GHz to 5.7GHz, and the wave absorption performance is greatly improved. The reason is that heat treatment causes strong chemical fluctuations in the high-entropy selenide ceramic powder, which increases its polarization loss.

[0107] Comparative Example 1:

[0108] A high-entropy boride ceramic microwave absorbing powder (denoted as Sample-1) is identical to Example 2 except that the heat treatment process parameters in step 3) are adjusted from "controlling the heating rate at 4℃ / min to heat from room temperature to 1500℃ and holding for 120min" to "controlling the heating rate at 4℃ / min to heat from room temperature to 1000℃ and holding for 120min".

[0109] Performance testing:

[0110] The microwave absorption performance test results of the high-entropy boride ceramic absorbing powder (Sample-1) in this comparative example are as follows: Figure 8 (The test method is the same as in Example 1; high-entropy boride ceramic powder is used as a comparison, and the coaxial ring made of high-entropy boride ceramic powder is recorded as the initial stage, and the coaxial ring made of high-entropy boride ceramic microwave absorbing powder is recorded as the heat-treated stage.)

[0111] Depend on Figure 8 It can be seen that after heat treatment, the effective absorption bandwidth of high-entropy boride ceramic powder changes very little (less than 1 GHz), and the improvement effect on wave absorption performance is weak. The reason is that the heat treatment temperature is too low and cannot provide enough energy to drive elemental fluctuations.

[0112] Therefore, heat treatment temperature is an extremely critical factor affecting microwave absorption performance.

[0113] Comparative Example 2:

[0114] A high-entropy boride ceramic microwave absorbing powder (denoted as Sample-2) is identical to Example 2 except that the heat treatment process parameters in step 3) are adjusted from "controlling the heating rate at 4℃ / min to heat from room temperature to 1500℃ and holding for 120min" to "controlling the heating rate at 4℃ / min to heat from room temperature to 1500℃ and holding for 30min".

[0115] Performance testing:

[0116] The microwave absorption performance test results of the high-entropy boride ceramic absorbing powder (Sample-2) in this comparative example are as follows: Figure 9 (The test method is the same as in Example 1; high-entropy boride ceramic powder is used as a comparison, and the coaxial ring made of high-entropy boride ceramic powder is recorded as the initial stage, and the coaxial ring made of high-entropy boride ceramic microwave absorbing powder is recorded as the heat-treated stage.)

[0117] Depend on Figure 9 It can be seen that after heat treatment, the effective absorption bandwidth of high-entropy boride ceramic powder changes very little (less than 1 GHz), and the improvement effect on wave absorption performance is weak. The reason is that the heat treatment time is too short and cannot provide enough energy to drive elemental fluctuations.

[0118] Therefore, heat treatment time is an extremely critical factor affecting microwave absorption performance.

[0119] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing high-entropy ceramic microwave absorbing powder, characterized in that, Includes the following steps: 1) Preparation of mixed powders: a) Mixing transition metal oxide powder with B powder or C powder to obtain a mixed powder for preparing high-entropy borides or high-entropy carbides; b) Mix metal oxide powder with TiO2 powder, wherein the metal oxide powder includes alkaline earth metal oxide powder and rare earth oxide powder, to obtain a mixed powder for preparing high entropy oxides; c) Mixing transition metal powder with Si powder yields a mixed powder for preparing high-entropy silicides; d) The transition metal powder is mixed with Se powder to obtain a mixed powder for preparing high-entropy selenides; 2) The mixed powder is pressed into a green body, then placed in a protective atmosphere for electric field sintering, and then crushed to obtain high-entropy ceramic powder; 3) The high-entropy ceramic powder is placed in a protective atmosphere for heat treatment to obtain high-entropy ceramic microwave absorbing powder.

2. The preparation method according to claim 1, characterized in that: Step a) The transition metal oxide powder is composed of at least five of the following powders in equimolar ratio: HfO2 powder, ZrO2 powder, Ta2O5 powder, Nb2O5 powder, TiO2 powder, V2O5 powder, WO3 powder, MoO3 powder, and Cr2O3 powder; Step b) The metal oxide powder is composed of at least five of the following powders in equimolar ratio: CaO powder, SrO powder, BaO powder, La2O3 powder, Nd2O3 powder, and Sm2O3 powder; Step c) The transition metal powder is composed of at least five of the following powders in equimolar ratio: Hf powder, Zr powder, Ta powder, Nb powder, Ti powder, W powder, Mo powder, and V powder; Step d) The transition metal powder is composed of at least five of the following powders in equimolar ratio: Fe powder, Co powder, Ni powder, Cu powder, Mn powder, and Zn powder.

3. The preparation method according to claim 1 or 2, characterized in that: In step a), the molar ratio of transition metal oxide powder to B powder is 1:2.0 to 2.2; in step a), the molar ratio of transition metal oxide powder to C powder is 1:1.0 to 1.2; in step b), the molar ratio of metal oxide powder to TiO2 powder is 1:3.0 to 3.2; in step c), the molar ratio of transition metal powder to Si powder is 1:2.2 to 2.5; in step d), the molar ratio of transition metal powder to Se powder is 1:2.0 to 2.

2.

4. The preparation method according to claim 1 or 2, characterized in that: In step a), the particle size of the transition metal oxide powder, B powder, and C powder is 1 μm to 3 μm, and the purity is ≥99.9%; in step b), the particle size of the metal oxide powder and TiO2 powder is 1 μm to 3 μm, and the purity is ≥99.9%; in step c), the particle size of the transition metal powder and Si powder is 1 μm to 3 μm, and the purity is ≥99.9%; in step d), the particle size of the transition metal powder and Se powder is 1 μm to 3 μm, and the purity is ≥99.9%.

5. The preparation method according to claim 1 or 2, characterized in that: Step 1) The mixing includes the following operations: wet ball milling, drying and grinding; the process parameters of the wet ball milling include: the ball milling medium is anhydrous ethanol, the ball milling equipment is a planetary ball mill, the weight ratio of powder raw material, ZrO2 balls and anhydrous ethanol is 1:4.0~5.0:1.5~2.5, the ball mill speed is 400r / min~500r / min, and the ball milling time is 24h~30h.

6. The preparation method according to claim 1, characterized in that: Step 2) The pressing is carried out under a pressure of 8MPa to 12MPa.

7. The preparation method according to claim 1 or 6, characterized in that: Step 2) The electric field sintering includes the following operations: the blank is wrapped with carbon paper coated with boron nitride and then embedded with graphite felt. The graphite felt is then placed in the electric field sintering equipment, a vacuum is drawn, a protective atmosphere is introduced, and then the two ends of the graphite felt are connected to AC power. The current is increased from 0A to 35A to 45A at a rate of 5A / s to 8A / s and held for 10s to 40s. Then the current is increased to 70A to 90A at a rate of 5A / s to 8A / s and held for 60s to 90s. The power is then disconnected and the material is allowed to cool naturally to room temperature.

8. The preparation method according to any one of claims 1, 2 and 6, characterized in that: Step 3) The heat treatment includes the following operations: the high-entropy ceramic powder is loaded into a graphite crucible and then placed in a tube furnace, then a vacuum is drawn, then a protective atmosphere is introduced, and then the heating rate is controlled at 2℃ / min~4℃ / min to raise the temperature from room temperature to 1200℃~1600℃, and held for 60min~240min.

9. A high-entropy ceramic absorbing powder, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.

10. An aerospace vehicle, characterized in that, It includes a stealth coating; the stealth coating includes the high-entropy ceramic absorbing powder of claim 9.

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