Single-phase high-entropy carbide ceramic powder, preparation method and application thereof

Abstract

The application discloses a single-phase high-entropy carbide ceramic powder and a preparation method and application thereof, and belongs to the technical field of high-entropy ceramic powder materials. The preparation method comprises the following steps: mixing and ball-milling metal oxide powder and carbon powder in an alcohol medium in an air environment to obtain a mixed powder slurry; drying the mixed powder slurry, adding a PVA binder, and pressing into a green body; when the environment is a vacuum environment, placing the green body in a graphite felt heating element inside a vacuum cavity, loading direct current on both ends of the graphite felt heating element through a vacuum electrode, exciting Joule heat under vacuum conditions to perform Joule heating, and obtaining a single-phase high-entropy carbide ceramic powder; or when the environment is an argon environment, placing the green body in the middle of two pieces of graphite felt heating elements arranged in an upper-lower mode, applying direct current from top to bottom, turning on the power supply, exciting argon to form plasma to generate a heating temperature, and obtaining a single-phase high-entropy carbide ceramic powder.

Description

Technical Field

[0001] This invention belongs to the field of high-entropy ceramic powder materials technology, specifically relating to a single-phase high-entropy carbide ceramic powder, its preparation method, and its application. Background Technology

[0002] IVB and Group VB metal carbides are classified as ultra-high temperature ceramics, possessing advantages such as high melting point, high hardness, and excellent temperature resistance, and have been successfully applied in aerospace thermal protection and energy fields. Single-phase high-entropy carbide ceramics are composed of multiple metal elements in approximately equiatomic proportions, exhibiting better hardness, toughness, and strength than single-component carbide ceramics. Furthermore, their oxidation resistance, thermal stability, and radiation resistance are synergistically improved, making them suitable for applications in extreme service environments such as high temperature, oxidation, and radiation. Therefore, the high-purity, efficient, and controllable preparation of single-phase high-entropy carbide ceramic powders is fundamental to ensuring their successful application.

[0003] Currently, the main methods for preparing high-entropy carbide ceramic powders include solid-state reaction, precursor conversion, and molten salt methods. Solid-state reaction involves mechanically alloying (metal powder and carbon powder) or (oxide ceramic powder and carbon powder), followed by high-temperature sintering to form a single-phase solid solution powder through solid-state diffusion. Precursor conversion uses transition metal chlorides and alcohols as metal and carbon sources to obtain a precursor solution, which is then polymerized at high temperatures to obtain high-entropy carbide powders. Molten salt methods involve reacting reactants in a low-melting-point salt medium to obtain high-entropy carbide powders. The mechanical alloying process in solid-state reactions requires special vacuum or atmospheric protection; otherwise, there is a risk of dust explosion and the presence of hard alloy impurities. High-temperature sintering generally uses traditional heating methods with low heating rates (~10℃ / min), high sintering temperatures (~2000℃), and long holding times (~2h). Powders prepared using hot pressing or discharge plasma sintering processes typically require secondary ball milling. Precursor conversion and molten salt methods require specialized raw material processing techniques, have long reaction times (2-8 hours), and the prepared powders require secondary processing, leading to environmental pollution. In summary, current preparation methods generally suffer from problems such as high equipment requirements, high costs, complex processes, low efficiency, high energy consumption, and severe pollution. Furthermore, the prepared high-entropy carbide ceramic powders also exhibit defects such as high impurity content and uneven composition. These problems severely restrict the promotion and application of high-entropy carbide ceramics in practical applications.

[0004] Therefore, developing a rapid synthesis method for single-phase high-entropy carbide ceramics to achieve efficient, high-quality, and controllable preparation of single-phase high-entropy carbide ceramic powder is of great significance for the application of high-entropy carbide ceramics.

[0005] Accelerating the heating rate is an effective way to improve the synthesis efficiency of high-entropy carbide ceramic powders. Current researchers utilize the high-temperature reaction of HfO2, Ta2O5, ZrO2, TiO2, Nb2O5, and carbon powder to generate single-phase (HfO2) ceramic powders. 0.2 Ta 0.2 Zr 0.2 Ti 0.2 Nb 0.2 High-entropy carbide powder was prepared by high-energy ball milling of WC for 2 hours, followed by treatment of the mixed powder at 1600℃ for 1 hour and then further heating to 2000℃ for 2 hours. However, the results showed that this method easily introduces WC impurities, has low heating efficiency, and a long preparation cycle. Another existing technology uses VO2, Nb2O5, MoO3, Ta2O5, TiO2, WO3, and carbon powder to reach 1400℃ within 2 seconds using carbon felt as a heating element to synthesize (VNbMoTaW)C5 and (TiVNbTaW)C5, respectively. The results indicated that improved heating efficiency can promote the synthesis of (VNbMoTaW)C5 and (TiVNbTaW)C5. However, XRD analysis showed that both (VNbMoTaW)C5 and (TiVNbTaW)C5 are multiphase, indicating that the synthesized five-element carbides are multi-element carbide solid solutions rather than single-phase high-entropy carbide ceramic powders, and the powder purity needs to be improved. An existing patent describes a high-entropy carbide ceramic powder, its preparation method, and its application. It utilizes a graphite plate as a heating element, grinding oxides and carbon powder and spreading them evenly on the graphite heating element, then fixing the powder with carbon paper. An AC current of 2.0kW–3.5kW with a current ≤250A is passed through the graphite plate, and the powder is treated at 3000℃ for 5s–30s in a protective atmosphere to obtain single-phase high-entropy carbide ceramic powder. Comparative Example 1 in the patent describes a method using a graphite felt heating element, but it fails to synthesize single-phase high-entropy carbide ceramic powder. The reason cited is that graphite felt, as a heating element, cannot rapidly reach the synthesis temperature of 3000℃. Furthermore, the graphite element used in the above method has low resistivity, requiring a higher current for heating, and the synthesis temperature exceeds 3000℃, necessitating improvements in safety and heating efficiency.

[0006] Therefore, it is necessary to provide a rapid preparation method for single-phase high-entropy carbide ceramics to solve the above problems. Summary of the Invention

[0007] In order to overcome the shortcomings of the prior art, the present invention aims to provide a single-phase high-entropy carbide ceramic powder, its preparation method and application, to solve the technical problems of high-entropy carbide ceramic powder such as high impurity content, uneven composition and slow synthesis rate. It also has the advantages of low equipment requirements, safe and simple process route, low cost, low heating current, low power consumption and no environmental pollution, and is suitable for efficient synthesis and production of single-phase high-entropy carbide ceramic powder in industrial fields.

[0008] To achieve the above objectives, the present invention employs the following technical solution:

[0009] This invention provides a method for preparing single-phase high-entropy carbide ceramic powder, comprising the following steps:

[0010] S1: Mix metal oxide powder and carbon powder in an alcohol medium and ball mill in an air environment to obtain a mixed powder slurry;

[0011] S2: After drying the mixed powder slurry, add PVA binder and press it into a green body;

[0012] S3: When the environment is a vacuum environment, the blank is placed in the graphite felt heating element inside the vacuum chamber. Direct current is applied to both ends of the graphite felt heating element through the vacuum electrode. Joule heating is activated under vacuum conditions to obtain single-phase high-entropy carbide ceramic powder.

[0013] Alternatively, when the environment is argon, the blank is placed between two graphite felt heating elements arranged vertically. The interior of the graphite felt heating elements is composed of carbon fibers. The gap between the two graphite felt heating elements is adjusted until the fibers on the opposite surfaces come into contact with each other. A direct current is applied from top to bottom, the power is turned on, and the tips of the carbon fibers on the opposite surfaces of the two graphite felt heating elements discharge. Argon is excited to form plasma and generate heating temperature to obtain single-phase high-entropy carbide ceramic powder.

[0014] In S1, the metal oxide powder is composed of at least four of the following: MoO3 powder, WO3 powder, HfO2 powder, Ta2O5 powder, ZrO2 powder, TiO2 powder, Nb2O5 powder, VO2 powder, and Cr2O3 powder.

[0015] In the specific implementation process, the molar ratio of each metal atom in the metal oxide powder is equal, and the molar ratio of the metal oxide powder to the carbon powder is 1:1.

[0016] In the specific implementation process, the particle size of the MoO3 powder, WO3 powder, HfO2 powder, Ta2O5 powder, ZrO2 powder, TiO2 powder, Nb2O5 powder, VO2 powder, and Cr2O3 powder is 100nm~1μm, and the purity is 99.9%.

[0017] The toner has a particle size of 20 nm and a purity of 99.9%.

[0018] In the specific implementation process, the mass percentage of the PVA adhesive is 3-5 wt%; the pressing pressure is 20-30 MPa.

[0019] In specific implementation, the graphite felt heating element is one of carbon felt, graphite felt, and carbon paper.

[0020] In the specific implementation process, the process parameters for Joule heating are as follows:

[0021] The DC voltage is 55V, the DC current is 50-60A, and the DC power is 2kW-3kW.

[0022] The Joule heating temperature is 1800℃~2000℃; the Joule heating time is 3~30S; the Joule heating temperature rise curve is linear, trapezoidal or pulsed.

[0023] In practice, the pressure of the vacuum condition is less than 200 Pa.

[0024] In the specific implementation process, the DC current applied from top to bottom is 45A and the voltage is 45V, the time for applying the current from top to bottom is 10S, and the heating temperature is 6000K~8000K.

[0025] The present invention also provides a single-phase high-entropy carbide ceramic powder prepared according to any one of the methods described above.

[0026] This invention also provides the application of single-phase high-entropy carbide ceramic powder prepared according to any one of the methods described above in the fields of nuclear protection (nuclear cladding and first wall materials), aerospace thermal protection component nose cones, wing leading edges, jet engine turbine blades and nozzles, ceramic backing plates for bulletproof vests, tank armor, and ultra-high-speed precision machining tools.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] This invention provides a rapid method for preparing single-phase high-entropy carbide ceramics, including synthesis methods under vacuum and argon atmospheres. Compared to traditional solid-state methods, this synthesis method eliminates the need for mechanical alloying and high-energy ball milling of the mixed powder, avoids the need for special sintering equipment and secondary crushing and ball milling, and simplifies the process and equipment requirements. Furthermore, the vacuum environment eliminates the need for a protective atmosphere and prevents the introduction of hard alloy impurities. Compared to existing graphite felt Joule heating synthesis of high-entropy carbide ceramic powder, this method strictly controls the carbon content and oxide powder ratio, resulting in a single-phase, homogeneous, and high-purity high-entropy carbide ceramic powder. Compared to existing graphite heating element synthesis of high-entropy carbide ceramic powder, the vacuum environment method using a graphite felt heating element requires less current, consumes less power, and reduces the synthesis temperature from 3000℃ to 1800℃.

[0029] Compared to traditional technologies, one of the key features of this invention is the use of PVA binder for pressing. The PVA binder helps shape the ceramic, and at high temperatures, it transforms into carbon, causing the discs to shatter into powder. Another key feature is the direct contact between the green body and the carbon felt, creating a carbon-rich vacuum environment. Both the rich carbon content and the vacuum are crucial for the formation of high-entropy carbide ceramics. A further key feature is the rapid heating mechanism, combining a graphite felt heating element with Joule heating or plasma heating, which can directly reach a specified current to provide a rapid heating environment, further promoting the solid solution and reaction of oxides and carbon. This invention combines three key technical aspects—PVA binder pressing, a carbon-rich vacuum environment, and a rapid heating mechanism combining a graphite felt heating element with Joule heating or plasma heating—to rapidly produce heterogeneous single-phase high-entropy carbide ceramics.

[0030] In summary, the rapid preparation method for single-phase high-entropy carbide ceramics provided by this invention has the advantages of low equipment requirements, safe and simple process route, low cost, low heating current, low power consumption, and no environmental pollution. It is suitable for the efficient synthesis and production of single-phase high-entropy carbide ceramic powder in industrial fields. Attached Figure Description

[0031] Figure 1 This is a flowchart of the rapid preparation method of single-phase high-entropy carbide ceramics according to Example 1 of the present invention;

[0032] Figure 2 The image shows the XRD pattern of the single-phase (HfTaZrTiNb)C5 high-entropy carbide ceramic in Example 1 of the present invention.

[0033] Figure 3 The image shows the XRD pattern of the single-phase (HfTaZrTiNbMoWVCr)C9 high-entropy carbide ceramic in Example 2 of the present invention.

[0034] Figure 4 The image shows the XRD pattern of the single-phase (HfTaZrTiNb)C5 high-entropy carbide ceramic in Example 3 of the present invention.

[0035] Figure 5 The image shows the XRD pattern of the single-phase (HfTaZrTiNb)C5 high-entropy carbide ceramic in Example 5 of the present invention.

[0036] Figure 6 The XRD pattern of the carbide solid solution ceramic in Comparative Example 1 is shown.

[0037] Figure 7 The XRD pattern of the carbide solid solution ceramic in Comparative Example 2 is shown.

[0038] Figure 8 XRD pattern of carbide solid solution ceramic in Comparative Example 3;

[0039] Figure 9 The image shows the XRD pattern of the ceramic mixture of residual oxides and carbide solid solution in Comparative Example 4. Detailed Implementation

[0040] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0041] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0042] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0043] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0044] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0045] This invention provides a single-phase high-entropy carbide ceramic powder, its preparation method, and its application.

[0046] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0047] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0048] The first aspect of this invention provides a method for preparing single-phase high-entropy carbide ceramic powder, comprising the following steps:

[0049] 1) Mix metal oxide powder and carbon powder in an alcohol medium and ball mill in an air environment to obtain a mixed powder slurry;

[0050] The metal oxide powder is composed of at least four of the following: MoO3 powder, WO3 powder, HfO2 powder, Ta2O5 powder, ZrO2 powder, TiO2 powder, Nb2O5 powder, VO2 powder, and Cr2O3 powder. The molar ratio of each metal atom in the above metal oxide powder is 1:1. At the same time, the total amount of metal atoms in the metal oxide powder is in a molar ratio of 1:1 to the carbon powder. The carbon powder cannot be in excess, otherwise the residual carbon will prevent the synthesis of single-phase high-entropy carbide ceramics.

[0051] In the specific implementation process, the particle size of MoO3 powder, WO3 powder, HfO2 powder, Ta2O5 powder, ZrO2 powder, TiO2 powder, Nb2O5 powder, VO2 powder, and Cr2O3 powder is 100nm~1μm, and the purity is 99.9%; the particle size of carbon powder is 20nm, and the purity is 99.9%.

[0052] 2) Dry the mixed powder slurry, add PVA binder, and press it into a green body;

[0053] The PVA binder has a mass percentage of 3-5 wt%. The addition of PVA binder is one of the invention points of this invention. PVA cannot be added in excess, otherwise the residual carbon after cracking will prevent the synthesis of single-phase high-entropy carbide ceramics. Precise control of carbon content and addition of binder for pressing treatment ensure that the powder particles are in close contact. Rapid heating under vacuum conditions is more conducive to the generation of single-phase high-entropy carbide ceramics from the mixed powder. The pressing pressure is 20-30 MPa.

[0054] The preparation of single-phase high-entropy carbide ceramic powder does not require special heating equipment or secondary ball milling. High-entropy solid solution is completed in one step. The process route is safe, simple, and pollution-free.

[0055] 3) When the environment is a vacuum environment, the green body is placed in the graphite felt heating element inside the vacuum chamber. Direct current is applied to both ends of the graphite felt heating element through the vacuum electrode. Joule heating is induced under vacuum conditions to obtain single-phase high-entropy carbide ceramic powder. One of the inventive points of this invention is that the green body and the carbon felt are in direct contact to form a carbon-rich vacuum environment. Both the carbon richness and the vacuum are key factors that are conducive to the formation of high-entropy carbide ceramics.

[0056] Alternatively, when the environment is argon, the blank is placed between two graphite felt heating elements arranged vertically. The interior of the graphite felt heating elements is composed of carbon fibers. The gap between the upper and lower graphite felts is adjusted until the fibers on their opposite surfaces come into contact with each other. A direct current is applied from top to bottom, the power is turned on, and the tips of the carbon fibers on the opposite surfaces of the two graphite felt heating elements discharge. The argon is excited to form plasma and generate heating temperature, thus obtaining single-phase high-entropy carbide ceramic powder.

[0057] One of the inventive points of this invention is that the above-mentioned graphite felt heating element is one of carbon felt, graphite felt and carbon paper. The heating element is made of graphite felt, which has higher heating efficiency, lower power consumption, lower synthesis temperature and shorter heat preservation time. Graphite plates cannot be used, otherwise the heating current and power will be too high, and it will be impossible to obtain single-phase high-entropy carbide ceramic powder.

[0058] Preferably, the Joule heating operation in step 3) is as follows: a DC power of 55V and 50-60A is connected to both ends of the graphite felt heating element, with a power of 2kW-3kW, the heating curve is linear, trapezoidal or pulsed, the reaction time is 3-30s, and the measured temperature is 1800℃-2000℃.

[0059] Preferably, the vacuum environment in step 3) needs to be <200 Pa, otherwise the oxides and carbon powder cannot react completely.

[0060] Preferably, in step 3), the DC current applied from top to bottom is 45A and the voltage is 45V, the time for applying the current from top to bottom is 10S, and the heating temperature is 6000K~8000K.

[0061] The second aspect of the present invention provides a single-phase high-entropy carbide ceramic powder prepared by the above preparation method.

[0062] The third aspect of this invention provides the application of the above-mentioned single-phase high-entropy carbide ceramic powder in the main material or external coating of nuclear protection materials, aerospace thermal protection systems, bulletproof and wear-resistant fields. Specifically, it is applied in nuclear cladding and first wall materials in the field of nuclear protection, nose cones and wing leading edges of aerospace thermal protection components, turbine blades and nozzles of jet engines, ceramic back plates of bulletproof vests, tank armor, and ultra-high-speed precision machining tools.

[0063] Example 1:

[0064] A single-phase high-entropy carbide ceramic powder is prepared by the following steps:

[0065] 1) 1.31g HfO2 powder, 1.38g Ta2O5 powder, 0.77g ZrO2 powder, 0.49g TiO2 powder, 0.83g Nb2O5 powder and 1.20g carbon powder, with a molar ratio of oxide to carbon powder of 1:1, were added to an agate ball mill jar and ball-milled for 4 hours in an alcohol medium. After drying, a mixed powder was obtained.

[0066] 2) Place the mixed powder into an agate mortar and mix with a 5wt.% PVA solution. Press the mixture into a blank using a pressure of 30MPa. Take 0.3g of powder and press it into a blank with a diameter of 10mm and a thickness of 1mm.

[0067] 3) Place the pressed green body into the center of the graphite felt heating element, which is 100mm wide, 20mm thick, and 5mm long. Fix both ends of the graphite felt in the middle of the electrode, which is located inside the vacuum chamber. Connect the vacuum electrode to a DC power supply outside the chamber. Close the vacuum chamber and use a mechanical pump to evacuate the vacuum until the vacuum pressure reaches 200Pa. Set the power input to 55V, 50A DC, with a power of 2.9kW. At this point, the infrared temperature is measured to be 1800℃. Maintain this temperature for 30 seconds, then turn off the power switch and allow it to cool naturally to room temperature. Open the vacuum chamber. After the pressed green body from step 2 is processed, it is converted into powder, resulting in single-phase high-entropy carbide ceramic powder (HfTaZrTiNb)C5. The process flow diagram of this method is shown below. Figure 1 As shown.

[0068] Performance testing:

[0069] The XRD pattern of the high-entropy carbide ceramic powder (HfTaZrTiNb)C5 in this embodiment is as follows: Figure 2 As shown, it is a single-phase high-entropy carbide ceramic with good crystallinity and no impurity phases.

[0070] Example 2:

[0071] A single-phase high-entropy carbide ceramic powder is prepared by the following steps:

[0072] 1) Add 0.76g HfO2 powder, 0.80g Ta2O5 powder, 0.44g ZrO2 powder, 0.28g TiO2 powder, 0.48g Nb2O5 powder, 0.52MoO3 powder, 0.83WO3 powder, 0.30VO2 powder, 0.27Cr2O3 powder and 1.28g carbon powder, with a molar ratio of oxide powder to carbon powder of 1:1, into an agate ball mill jar, and ball mill for 4 hours in an alcohol medium. After drying, a mixed powder is obtained.

[0073] 2) Place the mixed powder into an agate mortar and mix with a 5wt.% PVA solution. Press the mixture into a blank using a pressure of 30MPa. Take 0.3g of powder and press it into a blank with a diameter of 10mm and a thickness of 1mm.

[0074] 3) Place the pressed green body into the center of the graphite felt heating element, which is 100mm wide, 20mm thick, and 5mm long. Fix both ends of the graphite felt in the middle of the electrode, which is located inside the vacuum chamber. Connect the vacuum electrode to a DC power supply outside the chamber. Close the vacuum chamber and use a mechanical pump to evacuate the vacuum until the vacuum pressure reaches 200Pa. Set the power input to 55V, 50A DC, with a power of 2.9kW. At this point, the infrared temperature is measured to be 1800℃. Maintain this temperature for 30 seconds, then turn off the power switch and allow it to cool naturally to room temperature. Open the vacuum chamber. After the pressed green body from step 2 is processed, it is converted into powder, resulting in single-phase high-entropy carbide ceramic powder (HfTaZrTiNbMoWVCr)C9.

[0075] Performance testing:

[0076] The XRD pattern of the high-entropy carbide ceramic powder (HfTaZrTiNbMoWVCr)C9 in this embodiment is as follows: Figure 3 As shown, it is a single-phase high-entropy carbide ceramic with good crystallinity and no impurity phases.

[0077] Example 3:

[0078] A single-phase high-entropy carbide ceramic powder is prepared by the following steps:

[0079] 1) 1.31g HfO2 powder, 1.38g Ta2O5 powder, 0.77g ZrO2 powder, 0.49g TiO2 powder, 0.83g Nb2O5 powder and 1.20g carbon powder, with a molar ratio of oxide to carbon powder of 1:1, were added to an agate ball mill jar and ball-milled for 4 hours in an alcohol medium. After drying, a mixed powder was obtained.

[0080] 2) Place the mixed powder into an agate mortar and mix with a 5wt.% PVA solution. Press the mixture into a blank using a pressure of 30MPa. Take 0.3g of powder and press it into a blank with a diameter of 10mm and a thickness of 1mm.

[0081] 3) Place the pressed green body into the center of the graphite felt heating element, which is 100mm wide, 20mm thick, and 5mm long. Fix both ends of the graphite felt in the middle of the electrode, which is located inside the vacuum chamber. Connect the vacuum electrode to a DC power supply outside the chamber. Close the vacuum chamber and use a mechanical pump to evacuate the vacuum until the vacuum pressure reaches 200Pa. Set the power input to 55V, 50A DC, with a power of 2.9kW. At this point, the infrared temperature is measured to be 1800℃. Hold this temperature for 3 seconds, then turn off the power. Perform 10 pulse cycles, then turn off the switch and allow it to cool naturally to room temperature. Open the vacuum chamber. After the pressed green body from step 2 is processed, it is transformed into powder, resulting in single-phase high-entropy carbide ceramic powder (HfTaZrTiNb)C5.

[0082] Performance testing:

[0083] The XRD pattern of the high-entropy carbide ceramic powder (HfTaZrTiNb)C5 in this embodiment is as follows: Figure 4 As shown, it is a single-phase high-entropy carbide ceramic with good crystallinity and no impurity phases.

[0084] Example 4:

[0085] A single-phase high-entropy carbide ceramic powder is prepared by the following steps:

[0086] 1) 1.31g HfO2 powder, 1.38g Ta2O5 powder, 0.77g ZrO2 powder, 0.49g TiO2 powder, 0.83g Nb2O5 powder and 1.20g carbon powder, with a molar ratio of oxide to carbon powder of 1:1, were added to an agate ball mill jar and ball-milled for 4 hours in an alcohol medium. After drying, a mixed powder was obtained.

[0087] 2) Place the mixed powder into an agate mortar and mix with a 3wt.% PVA solution. Press the mixture into a blank using a pressure of 20MPa. Take 0.3g of powder and press it into a blank with a diameter of 10mm and a thickness of 1mm.

[0088] 3) Place the pressed green body into the center of the graphite felt heating element, which is 100mm wide, 20mm thick, and 5mm long. Fix both ends of the graphite felt in the middle of the electrode, which is located inside the vacuum chamber. Connect the vacuum electrode to a DC power supply outside the chamber. Close the vacuum chamber and use a mechanical pump to evacuate the vacuum until the vacuum pressure reaches 200Pa. Set the power input to 55V, 60A DC, with a power of 2kW. At this point, the infrared temperature is measured to be 2000℃. Hold this temperature for 3 seconds, then turn off the power switch and allow it to cool naturally to room temperature. Open the vacuum chamber. After the pressed green body from step 2 is processed, it is transformed into powder, resulting in single-phase high-entropy carbide ceramic powder (HfTaZrTiNb)C5.

[0089] Example 5:

[0090] 1) 1.31g HfO2 powder, 1.38g Ta2O5 powder, 0.77g ZrO2 powder, 0.49g TiO2 powder, 0.83g Nb2O5 powder and 1.20g carbon powder, with a molar ratio of oxide to carbon powder of 1:1, were added to an agate ball mill jar and ball-milled for 4 hours in an alcohol medium. After drying, a mixed powder was obtained.

[0091] 2) Place the mixed powder into an agate mortar and mix with a 3wt.% PVA solution. Press the mixture into a blank using a pressure of 20MPa. Take 0.3g of powder and press it into a blank with a diameter of 10mm and a thickness of 1mm.

[0092] 3) Place the prepared green body between two graphite felt heating elements, each with a diameter of 25mm and a thickness of 5mm. The gap between the upper and lower graphite felts is 3mm, and the green body is fixed with copper electrode clamps. The electrodes are located inside the vacuum chamber and connected to an external DC power supply via vacuum electrodes. Close the vacuum chamber and use a mechanical pump to evacuate the vacuum until the vacuum pressure reaches 200Pa. Introduce argon gas. Apply a DC current of 45A and a voltage of 45V from top to bottom for 10 seconds. The calculated plasma heating temperature is 8000K. Then turn off the power switch and allow it to cool naturally to room temperature before opening the vacuum chamber. After processing, the green body prepared in step 2 is converted into powder, resulting in single-phase high-entropy carbide ceramic powder (HfTaZrTiNb)C5.

[0093] Performance testing:

[0094] The XRD pattern of the high-entropy carbide ceramic powder (HfTaZrTiNb)C5 in this embodiment is as follows: Figure 5 As shown.

[0095] Comparative Example 1:

[0096] A high-entropy carbide ceramic powder is prepared by setting the heating process to a power input of 55V, 40A DC, with a power of 2.2kW. The infrared temperature measured at this time is 1600℃, which is maintained for 30s. Then the power switch is turned off and it is allowed to cool naturally to room temperature. The rest is exactly the same as in Example 1.

[0097] Performance testing:

[0098] The XRD pattern of the ceramic powder in this comparative example is as follows: Figure 6 As shown. The test results show that the actual product obtained in this comparative example is a multi-component carbide solid solution, not a single-phase high-entropy carbide ceramic powder. The reason is that under the condition of low current, the generated Joule heating temperature is only 1600℃, which is insufficient to synthesize single-phase high-entropy carbide ceramic powder (HfTaZrTiNb)C5.

[0099] Comparative Example 2:

[0100] A high-entropy carbide ceramic powder is prepared by using 1.09g HfO2 powder, 1.15g Ta2O5 powder, 0.64g ZrO2 powder, 0.41g TiO2 powder, 0.69g Nb2O5 powder, and 2.00g carbon powder, with an oxide to carbon powder molar ratio of 1:1.8. The rest is exactly the same as in Example 1.

[0101] Performance testing:

[0102] The XRD pattern of the ceramic powder in this comparative example is as follows: Figure 7 As shown. The test results show that the actual product prepared in this comparative example is a multi-component carbide solid solution, not a single-phase high-entropy carbide ceramic powder (HfTaZrTiNb)C5. The reason is that excessive carbon powder will hinder the high-entropy transformation of the ceramic and can only generate a multi-component carbide solid solution.

[0103] Comparative Example 3:

[0104] A high-entropy carbide ceramic powder is prepared by mixing carbon powder and oxides without adding binder and pressing it into a green body, and the rest is exactly the same as in Example 1.

[0105] Performance testing:

[0106] The XRD pattern of the ceramic powder in this comparative example is as follows: Figure 8 As shown. The test results show that the actual product prepared in this comparative example is a multi-component carbide solid solution, not a single-phase high-entropy carbide ceramic powder (HfTaZrTiNb)C5. The reason is that the powder particles cannot effectively contact each other during the high-temperature synthesis process, and thus cannot form a single-phase high-entropy carbide ceramic.

[0107] Comparative Example 4:

[0108] A high-entropy carbide ceramic powder was synthesized using an inert atmosphere, and otherwise identical to Example 1.

[0109] Performance testing:

[0110] The XRD pattern of the ceramic powder in this comparative example is as follows: Figure 9 As shown. The test results show that the actual product prepared in this comparative example is a mixture of residual oxides and carbide solid solutions, not single-phase high-entropy carbide ceramic powder (HfTaZrTiNb)C5. The reason is that the inert atmosphere protection is not conducive to the reaction between oxides and carbon, and thus cannot form single-phase high-entropy carbide ceramics.

[0111] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a single-phase high-entropy carbide ceramic powder, characterized by, The method comprises the following steps: S1: mixing and ball-milling metal oxide powder and carbon powder in an alcohol medium in an air environment to obtain a mixed powder slurry; S2: drying the mixed powder slurry, adding a PVA binder, and pressing into a green body; S3: when the environment is a vacuum environment, placing the green body in a graphite felt heating element inside a vacuum cavity, applying direct current to both ends of the graphite felt heating element through a vacuum electrode, exciting Joule heat under vacuum conditions to perform Joule heating, and obtaining single-phase high-entropy carbide ceramic powder; or when the environment is an argon environment, placing the green body in the middle of two pieces of graphite felt heating elements arranged above and below, the inside of the graphite felt heating element being composed of carbon fibers, adjusting the gap between the two pieces of graphite felt heating elements arranged above and below until the bristles of the carbon fibers on the opposite surfaces contact each other, and applying direct current from top to bottom, turning on the power supply, discharging the carbon fiber tips on the opposite surfaces of the two pieces of graphite felt heating elements arranged above and below, and exciting argon to form plasma to generate heating temperature, and obtaining single-phase high-entropy carbide ceramic powder; In S1, the metal oxide powder is composed of at least four of MoO3 powder, WO3 powder, HfO2 powder, Ta2O5 powder, ZrO2 powder, TiO2 powder, Nb2O5 powder, VO2 powder, and Cr2O3 powder; the molar ratio of each metal atom in the metal oxide powder is equal, the molar ratio of the metal oxide powder to carbon powder is 1:1, the mass percentage of the PVA binder is 3-5 wt%, the pressure of the pressing is 20-30 MPa, the process parameters of the Joule heating are as follows: the voltage of the direct current is 55 V, the current of the direct current is 50-60 A, the power of the direct current is 2-3 kW, the heating temperature of the Joule heating is 1800-2000 ℃, the time of the Joule heating is 3-30 S, the heating curve of the Joule heating is linear, trapezoidal, or pulsed, the current applied from top to bottom is 45 A, the voltage is 45 V, the time of applying the current from top to bottom is 10 S, and the heating temperature is 6000-8000 K.

2. The method of claim 1, wherein the single-phase high-entropy carbide ceramic powder is prepared by the steps of: preparing a mixed powder of the carbide-forming elements; and sintering the mixed powder at a temperature of 1,500°C to 2,000°C in a vacuum or an inert gas atmosphere. The particle size of the MoO3 powder, WO3 powder, HfO2 powder, Ta2O5 powder, ZrO2 powder, TiO2 powder, Nb2O5 powder, VO2 powder, and Cr2O3 powder is 100 nm-1 μm, and the purity is 99.9%; The particle size of the carbon powder is 20 nm, and the purity is 99.9%.

3. The method of claim 1, wherein the single-phase high-entropy carbide ceramic powder is prepared by the steps of: preparing a mixed powder of the carbide-forming elements; and sintering the mixed powder at a temperature of 1,500°C to 2,000°C in a vacuum or an inert gas atmosphere. The graphite felt heating element is one of carbon felt, graphite felt, and carbon paper.

4. The method of claim 1, wherein the single-phase high-entropy carbide ceramic powder is prepared by the steps of: preparing a mixture of a plurality of carbide powders; and sintering the mixture of the plurality of carbide powders. The pressure of the vacuum condition is less than 200 Pa.

5. Single-phase high-entropy carbide ceramic powder prepared by the method according to any one of claims 1-4.

6. The use of the single-phase high-entropy carbide ceramic powder prepared by the method according to any one of claims 1 to 4 as a nuclear cladding and first wall material in nuclear protection, as a ceramic back plate of a bulletproof vest, as a tank armor, and as an ultra-high-speed finishing tool in the field of nuclear protection.

Images