Five-element high-entropy carbide ceramic and preparation method thereof

Abstract

The invention relates to the technical field of high-entropy ceramics, and discloses a quinary high-entropy carbide ceramic and a preparation method thereof.The quinary high-entropy carbide ceramic (TiZrHfTaV) C is prepared by mixing transition metal carbides TiC, ZrC, HfC, TaC and VC, drying, grinding, sieving and sintering. In the quinary high-entropy carbide ceramic (TiZrHfTaV) C, the molar ratio of Ti to Zr to Hf to Ta to V is 0.25: 0.25: 0.2: 0.2: 0.1. The preparation method is easy and convenient to operate, short in reaction time and simple in technological process, and the prepared product is excellent in performance and has wide application prospects.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-entropy ceramics, in particular to a five-element high-entropy carbide ceramic and a preparation method thereof. BACKGROUND

[0002] High-entropy materials were proposed in 2004 as innovative materials with broad application prospects. High-entropy materials are mixtures close to equimolar, which maximize configurational entropy to achieve a more stable system. By adding elements and adjusting concentrations, high-entropy materials exhibit excellent performance stability and multifunctionality, breaking through the performance limits of traditional materials and having great development potential. In 2015, (MgNiCoCuZn)O ceramics with a rock salt structure were first reported by Rost et al. (Nature Comunications 2015, 6:8485), successfully expanding the concept of high-entropy alloys to the ceramic field. In the decade since then, the types of high-entropy ceramics have been increasing, from the initial oxide ceramics to carbide, nitride, boride, silicide, and sulfide systems. High-entropy ceramics have shown revolutionary application prospects in ultra-high temperature protection and extreme environment service, and their application range has also been expanding.

[0003] Compared to single-component carbides, high-entropy carbide ceramics exhibit higher hardness and Young's modulus, can withstand greater pressure and impact, have lower thermal conductivity and can be used for high-temperature insulation to effectively prevent heat transfer, and have excellent oxidation resistance and ablation resistance, enabling stable service in ultra-high temperature oxygen environments. At the same time, various properties can be adjusted by changing the composition to meet different application scenarios.

[0004] Currently, traditional high-entropy carbide systems, such as those composed of Ti, Zr, Hf, Ta, and Nb, have been widely studied. These systems exhibit high hardness, high melting point, and good high-temperature stability due to the high-entropy effect. However, carbides have a rock salt structure, strong covalent bonds, and high melting points, so the sintering temperature required for traditional powder sintering is often higher than 2000℃. In the high-temperature sintering process, atomic diffusion rates are slow, requiring high sintering temperatures and long holding times, which presents technical challenges such as high preparation temperatures and high costs. The existing mainstream systems also have deficiencies such as insufficient performance during high-temperature long-time service and single functionality, making it difficult to balance mechanical properties and high-temperature oxidation resistance. For example, the (TiZrHfTaNb)C system, although having high hardness and melting point, its high-temperature oxidation resistance cannot meet the needs of the aerospace field. In an oxygen environment above 1500℃, the material surface easily undergoes oxidation, forming a loose oxide layer, which leads to a decrease in the structural integrity and mechanical properties of the material.

[0005] Therefore, there is an urgent need for a quinary high-entropy carbide ceramic and a preparation method thereof to solve the above technical problems. SUMMARY

[0006] The present application aims to solve the above technical problems of high cost and high preparation temperature, and provide a quinary high-entropy carbide ceramic and a preparation method thereof to expand the exploration field of high-entropy carbide ceramic system.

[0007] To achieve the above object, the present application is implemented according to the following technical solutions:

[0008] A preparation method of a quinary high-entropy carbide ceramic, comprising the following steps:

[0009] The transition metal carbides TiC, ZrC, HfC, TaC and VC are mixed, dried, ground and sieved, and sintered to obtain a quinary high-entropy carbide ceramic (TiZrHfTaV)C.

[0010] The quinary high-entropy carbide ceramic (TiZrHfTaV)C prepared in the present application, "(TiZrHfTaV)C" represents the abbreviation of the quinary high-entropy carbide ceramic, and is not the chemical formula of the ceramic.

[0011] Preferably, in the quinary high-entropy carbide ceramic (TiZrHfTaV)C, the molar ratio of Ti, Zr, Hf, Ta and V is 0.25:0.25:0.2:0.2:0.1.

[0012] Preferably, the mixing process is: the transition metal carbides are ball-milled and wet-mixed to obtain a slurry; the ball-milling speed is 300 rpm, and the ball-milling time is 16 h.

[0013] Specifically, the ball-to-material ratio during ball-milling is 8:1. Ethanol is added to the transition metal carbides, and a planetary ball mill is used for ball-milling. In order to avoid contamination of the sample during ball-milling, tungsten carbide balls with good chemical stability and high hardness are used.

[0014] Preferably, the drying process is: the slurry is dried with a rotary evaporator to obtain a mixed powder.

[0015] Preferably, the temperature of rotary evaporation is 50℃, and the rotary evaporation time is 60-90 min.

[0016] Preferably, the grinding and sieving process is: the mixed powder is ground to refine the particle size with a mortar, and then sieved through a 200-mesh sieve to obtain a sieved powder.

[0017] Preferably, the sintering process is: the sieved powder is loaded into a mold, and a spark plasma sintering furnace is used to sinter the powder at a pressure of 50 MPa and a temperature of 2000℃ for 5 min, and then naturally cooled to room temperature.

[0018] In order to ensure that the sample is not in contact with the mold (graphite mold) pollution, carbon paper is used inside the mold to avoid sample pollution.

[0019] Preferably, the heating program of the sintering process is: increasing to 1800 DEG C at a heating rate of 100 DEG C / min, and then increasing to 2000 DEG C at a heating rate of 100 DEG C / min.

[0020] Specifically, the heating rate of the sintering process is 100 DEG C / min, in order to reduce the vacuum degree and avoid excessive contact with air, first heat preservation at 1800 DEG C for 10 min, and then heat to 2000 DEG C for 5 min.

[0021] In order to avoid the composition segregation caused by multi-stage sintering, the process uses metal carbide powder as raw material, and adopts one-step sintering method to carry out SPS sintering (discharge plasma sintering).

[0022] The application also includes a five-element high-entropy carbide ceramic (TiZrHfTaV)C prepared by the above preparation method.

[0023] Principle of action:

[0024] The application provides a five-element high-entropy carbide ceramic material and a preparation method thereof, and the five transition metal elements include Ti, Zr, Hf, Ta and V. The single solid solution phase with face-centered cubic structure is successfully prepared under the condition of 2000 DEG C. The five transition metal carbides are uniformly mixed by ball milling, dried by rotary evaporation, and then subjected to simple grinding and sieving to control the powder particle size. Then, the discharge plasma sintering furnace (SPS) is used for sintering, so that the high-entropy carbide ceramic material with single-phase structure and uniform element distribution is prepared. The preparation method is simple in operation, short in reaction time and simple in process, and the prepared product has excellent performance and wide application prospect.

[0025] The discharge plasma sintering is used under certain temperature and pressure to prepare the single solid solution phase (TiZrHfTaV)C high-entropy carbide ceramic by comparing and controlling the content of V element.

[0026] The application innovatively introduces the high-cost-performance V element in the traditional system, optimizes the element ratio, adopts one-step sintering process, reduces the sintering temperature and holding time, and refines the grain, so that the high-entropy carbide ceramic has better mechanical properties. The discharge plasma sintering technology is used under the condition of 2000 DEG C and 50 MPa constant temperature and pressure, and the molar ratio of the five transition metal elements Ti, Zr, Hf, Ta and V is explored, so that the single solid solution phase high-entropy carbide ceramic is prepared.

[0027] In the process, the discharge plasma sintering technology realizes the reduction of diffusion activation energy, and the 50MPa axial pressure promotes the particle rearrangement, so that the sintering temperature is reduced by 200-300 DEG C compared with the traditional method. And the constant temperature and constant pressure one-step process avoids the composition segregation caused by multi-stage sintering, and inhibits the preferential evaporation of low melting point components by controlling the heating rate.

[0028] In terms of composition, the element V is introduced, and the synergistic effect of V with other elements in the crystal structure is utilized to form a dense and complex oxide layer during the high temperature process, which improves the high temperature oxidation resistance performance and reduces the preparation cost. The process aims to prepare a high-entropy carbide ceramic system that is difficult to synthesize single phase at a temperature of 2000 DEG C, refine the grain to improve the mechanical properties, explore the element distribution, and promote the exploration of high-entropy carbide ceramic material system.

[0029] The ratio of the five elements in the single solid solution high-entropy ceramic system is determined to exclude the interference of impurity phase, further improve the mechanical properties of the sample, and lay a foundation for further development of this kind of material.

[0030] Advantages:

[0031] 1. The present application provides a preparation method of five-element high-entropy carbide ceramic, which has specific elements and proportions, and prepares five-element carbide with single solid solution phase. Through the synergistic effect between elements, the oxidation resistance and low thermal conductivity of the material at high temperature are optimized, which meets the performance requirements of aviation thermal insulation and further expands the development of high-entropy carbide ceramic field;

[0032] 2. The present application introduces high cost-effective V element, which not only reduces the raw material cost, but also endows the material with excellent high temperature service performance and mechanical properties;

[0033] 3. The present application adopts one-step sintering, realizes the reduction of sintering temperature of high-entropy carbide ceramic compared with traditional method, and has simple preparation process, low synthesis temperature, and controlled grain growth to improve the mechanical properties. DETAILED DESCRIPTION

[0034] Figure 1 is the XRD pattern of the sample prepared in the present application comparative example 1 at 2000 DEG C, 50MPa;

[0035] Figure 2 is the SEM graph of the sample prepared in the present application comparative example 1 at 2000 DEG C, 50MPa;

[0036] Figure 3 is the XRD pattern of the sample prepared in the present application comparative example 2 at 2000 DEG C, 50MPa;

[0037] Figure 4is the XRD pattern of the sample prepared in the present application comparative example 3 under the condition of 2000℃, 50MPa;

[0038] Figure 5 is the XRD pattern of the sample prepared in the present application comparative example 4 under the condition of 2000℃, 50MPa;

[0039] Figure 6 is the XRD pattern of the sample prepared in the present application example 1 under the condition of 2000℃, 50MPa;

[0040] Figure 7 is the SEM pattern of the sample prepared in the present application example 1 under the condition of 2000℃, 50MPa;

[0041] Figure 8 is the mechanical property of the sample prepared in the present application example 1 under the condition of 2000℃, 50MPa under different load;

[0042] Figure 9 is the thermal conductivity of the sample prepared in the present application example 1 under the condition of 2000℃, 50MPa under different temperature. DETAILED DESCRIPTION

[0043] The present application will be further described in the following specific examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0044] The purity of all raw materials in the present application is not particularly limited, and the conventional purity used in the art is used in the present application.

[0045] The device used in the present application is not particularly limited, and the device commonly used in the art is used.

[0046] The sintering process of each of the following examples and comparative examples is completed using a discharge plasma hot pressing sintering furnace. The heating rate of the sintering process is 100℃ / min, first at 1800℃ for 10min, then heated to 2000℃ for 5min.

[0047] Comparative example 1

[0048] Five kinds of metal carbide powders TiC, ZrC, HfC, TaC, VC were weighed and mixed in a molar ratio of Ti:Zr:Hf:Ta:V = 0.2:0.2:0.2:0.2:0.2, and ethanol was added. Tungsten carbide was used as the ball milling medium. The ball milling speed was 300 rpm, the ball-to-material ratio was 8:1, and the ball milling time was 16 h. After ball milling, the slurry was poured out and dried on a rotary evaporator at 50°C for 75 min. The dried powder was simply ground using an agate mortar, and then sieved through a 200-mesh screen. The sieved powder was loaded into an SPS mold, and a (TiZrHfTaV)C high-entropy carbide ceramic was prepared under the conditions of 2000°C and 50 MPa for 5 min. After stopping heating, the sample was naturally cooled to room temperature and then decompressed.

[0049] Comparative Example 2

[0050] Five kinds of metal carbide powders TiC, ZrC, HfC, TaC, VC were weighed and mixed in a molar ratio of Ti:Zr:Hf:Ta:V = 0.2:0.2:0.2:0.2:0.2, and ethanol was added. Tungsten carbide was used as the ball milling medium. The ball milling speed was 300 rpm, the ball-to-material ratio was 8:1, and the ball milling time was 16 h. After ball milling, the slurry was poured out and dried on a rotary evaporator at 50°C for 75 min. The dried powder was simply ground using an agate mortar, and then sieved through a 200-mesh screen. The sieved powder was loaded into an SPS mold, and a (TiZrHfTaV)C high-entropy carbide ceramic was prepared under the conditions of 2000°C and 50 MPa for 5 min. After stopping heating, the sample was naturally cooled to room temperature and then decompressed.

[0051] Comparative Example 3

[0052] Five kinds of metal carbide powders TiC, ZrC, HfC, TaC, VC were weighed and mixed in a molar ratio of Ti:Zr:Hf:Ta:V = 0.143:0.285:0.285:0.143:0.143, and ethanol was added. Tungsten carbide was used as the ball milling medium. The ball milling speed was 300 rpm, the ball-to-material ratio was 8:1, and the ball milling time was 16 h. After ball milling, the slurry was poured out and dried on a rotary evaporator at 50°C for 75 min. The dried powder was simply ground using an agate mortar, and then sieved through a 200-mesh screen. The sieved powder was loaded into an SPS mold, and a (TiZrHfTaV)C high-entropy carbide ceramic was prepared under the conditions of 2000°C and 50 MPa for 5 min. After stopping heating, the sample was naturally cooled to room temperature and then decompressed.

[0053] Comparative Example 4

[0054] Five kinds of metal carbide powders TiC, ZrC, HfC, TaC, VC are proportioned and weighed with a molar ratio of Ti:Zr:Hf:Ta:V = 0.125:0.25:0.25:0.25:0.125, the powders are ground using an agate mortar, and the grinding time is at least 1 h or more. Then the sieved powders are loaded into an SPS mold, and (TiZrHfTaV)C high-entropy carbide ceramics are prepared under the conditions of 2000℃ and 50MPa for 5min, and then naturally cooled to room temperature after stopping heating, and then pressure relief.

[0055] Example 1

[0056] A preparation method of a five-element high-entropy carbide ceramic, comprising the following steps:

[0057] Five kinds of metal carbide powders TiC, ZrC, HfC, TaC, VC are proportioned and weighed with a molar ratio of Ti:Zr:Hf:Ta:V = 0.25:0.25:0.2:0.2:0.1, ethanol is added, and ball milling is performed using tungsten carbide as the ball milling medium, the ball milling speed is 300rpm, the ball-to-material ratio is 8:1, the ball milling is performed for 16h, then the slurry is poured out, and the dried powder is simply ground using an agate mortar, then the sieved powders are loaded into an SPS mold, and (TiZrHfTaV)C five-element high-entropy carbide ceramics are prepared under the conditions of 2000℃ and 50MPa for 5min, and then naturally cooled to room temperature after stopping heating, and then pressure relief.

[0058] As shown in FIG. 1, it is an XRD pattern of a sample prepared in Example 1 under the conditions of 2000℃ and 50MPa; Figure 1

[0059] As shown in FIG. 2, it is an SEM image of a sample prepared in Example 1 under the conditions of 2000℃ and 50MPa; Figure 2 As shown in FIG. 3, it is an XRD pattern of a sample prepared in Comparative Example 1 under the conditions of 2000℃ and 50MPa;

[0060] Figure 3 As shown in FIG. 4, it is an SEM image of a sample prepared in Comparative Example 1 under the conditions of 2000℃ and 50MPa;

[0061] As shown in FIG. 5, it is an XRD pattern of a sample prepared in Comparative Example 2 under the conditions of 2000℃ and 50MPa; Figure 4 As shown in FIG. 6, it is an SEM image of a sample prepared in Comparative Example 2 under the conditions of 2000℃ and 50MPa;

[0062] Figure 5 As shown in FIG. 7, it is an XRD pattern of a sample prepared in Comparative Example 3 under the conditions of 2000℃ and 50MPa;

[0063] As shown in FIG. 8, it is an SEM image of a sample prepared in Comparative Example 3 under the conditions of 2000℃ and 50MPa; Figure 6 ​​​Figure 2 shows the XRD pattern of the sample prepared in Example 1 under the condition of 2000℃ and 50MPa.

[0064] Figure 3 shows the SEM image of the sample prepared in Example 1 under the condition of 2000℃ and 50MPa. Figure 7

[0065] Figure 4 shows the mechanical properties of the sample prepared in Example 1 under the condition of 2000℃ and 50MPa under different loads. Figure 8

[0066] Figure 5 shows the thermal conductivity of the sample prepared in Example 1 under the condition of 2000℃ and 50MPa under different temperatures. Figure 9

[0067] Comparing the above examples and the comparative examples, the difference lies in that the proportions of the five metal carbide powders are different, the molar ratio of V element in Example 1 is reduced, and the proportions of Ti and Zr are increased.

[0068] Comparing Comparative Example 1 and Comparative Example 2, the difference lies in the grinding method, and from the XRD patterns of Figure 1 and Figure 3 , it can be seen that the grinding method has some effect on the experimental results, but the effect is not large, and the main effect is whether the carbide powders are mixed uniformly and without pollution.

[0069] Comparing the above Comparative Examples 1 to 5, the difference lies in that the molar ratio of V element is continuously reduced, and from the XRD patterns of Figure 1 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , it can be seen that reducing the molar ratio of V element is beneficial to the formation of single-phase solid solution, and finally when the molar ratio of V element is reduced to 0.1, the sample forms a single solid solution phase.

[0070] Comparing the SEM images of Figure 2 and Figure 7 corresponding to Comparative Example 1 and Example 1, it can be seen that Figure 2 V element in Figure 7 exists aggregation, and when the molar ratio of V element is reduced to 0.1, the transition metal elements are uniformly distributed and there is no segregation phenomenon.

[0071] Figures 1 to 7 In combination with , the above phenomenon shows that when the molar ratio of V element is reduced to 0.1, a single-phase (TiZrHfTaV)C five-element high-entropy carbide ceramic can be successfully prepared.

[0072] Figure 8 ​​​It can be understood that, with the continuous increase of the indentation load, the Vickers hardness of the prepared five-element high-entropy carbide ceramic (TiZrHfTaV)C of the embodiment 1 of the present application also gradually decreases from 33.55±1.56 GPa to 23.14±1.02 GPa.

[0073] The (TiZrHfNbTa)C high-entropy carbide ceramic in the prior art has a Vickers hardness of 20.4 GPa under the condition of an indentation load of 9.8 N, which is lower than the high-entropy carbide ceramic prepared in the embodiment 1 of the present application. And compared with the Vickers hardness of each single-element metal carbide, the Vickers hardness of the high-entropy carbide ceramic in the embodiment 1 of the present application is higher than the Vickers hardness of the single-element metal carbide. For example, in the prior art, the Vickers hardness of HfC is 22 GPa under the condition of an indentation load of 4.9 N, while the Vickers hardness of the high-entropy carbide ceramic in the embodiment 1 of the present application is higher than the Vickers hardness of HfC.

[0074] From the above data, it can be understood that, with the continuous increase of the indentation load, the Vickers hardness of the prepared five-element high-entropy carbide ceramic (TiZrHfTaV)C of the embodiment 1 of the present application gradually decreases from 33.55±1.56 GPa to 23.14±1.02 GPa. Figure 9 It can be understood that, with the increase of the temperature, the thermal conductivity of the prepared five-element high-entropy carbide ceramic (TiZrHfTaV)C of the embodiment 1 of the present application gradually increases, although the thermal conductivity at the temperature of 1000℃ is slightly lower than the thermal conductivity at the temperature of 800℃, but the decrease is very small; with the increase of the temperature, the thermal diffusivity of the prepared five-element high-entropy carbide ceramic (TiZrHfTaV)C of the embodiment 1 of the present application gradually increases. Figure 9 Figure 9 The (TaHfNbZr)C sample in the prior art has a thermal conductivity of 10.7 W / m*K at room temperature, and its thermal conductivity at 1000℃ is close to 25 W / m*K. The thermal conductivity of the high-entropy carbide ceramic prepared in the embodiment 1 of the present application increases from 11.24 W / m*K at room temperature to 21.08 W / m*K at 1000℃, which has a smaller increase and a lower thermal conductivity at high temperature, and can better meet the demand of aviation heat insulation.

[0075] Meanwhile, the oxidation process of the multi-element high-entropy carbide ceramic can be divided into three stages, i.e., initial oxidation, formation of dense oxidation layer, and oxidation stable period, and the core mechanism is that the multi-elements cooperatively form a dense and low-diffusion-coefficient composite oxidation layer. Therefore, the high-entropy carbide ceramic in the embodiment 1 of the present application has the advantages of low oxidation rate and high oxidation layer stability, and has better oxidation resistance and higher thermal stability than the original element metal carbides such as TiC and HfC.

[0076]

[0077] ​​The technical solutions of the present application are not limited to the above specific embodiments, and any technical variations made according to the technical solutions of the present application fall within the protection scope of the present application.

Claims

1. A method for preparing pentagonal high-entropy carbide ceramics, characterized in that: Includes the following steps: The transition metal carbides TiC, ZrC, HfC, TaC, and VC were mixed, dried, ground, sieved, and sintered to prepare the pentagonal high-entropy carbide ceramic (TiZrHfTaV)C.

2. The method for preparing a pentagonal high-entropy carbide ceramic according to claim 1, characterized in that: In the pentagonal high-entropy carbide ceramic (TiZrHfTaV)C, the molar ratio of Ti, Zr, Hf, Ta, and V is 0.25:0.25:0.2:0.2:0.

1.

3. The method for preparing a pentagonal high-entropy carbide ceramic according to claim 1, characterized in that: The mixing process is as follows: the transition metal carbides are ball-milled and wet-mixed to obtain a slurry; the ball milling speed is 300 rpm and the ball milling time is 16 h.

4. The method for preparing a pentagonal high-entropy carbide ceramic according to claim 3, characterized in that: The drying process involves drying the slurry using a rotary evaporator to obtain a mixed powder.

5. The method for preparing a pentagonal high-entropy carbide ceramic according to claim 4, characterized in that: The temperature for rotary evaporation is 50℃, and the time for rotary evaporation is 60-90 minutes.

6. The method for preparing a pentagonal high-entropy carbide ceramic according to claim 4, characterized in that: The grinding and sieving process is as follows: the mixed powder is ground into fine particles using a mortar and pestle and then passed through a 200-mesh sieve to obtain the sieved powder.

7. The method for preparing a pentagonal high-entropy carbide ceramic according to claim 6, characterized in that: The sintering process is as follows: the sieved powder is loaded into a mold and held in a discharge plasma sintering furnace at a pressure of 50 MPa and a temperature of 2000 °C for 5 minutes, and then naturally cooled to room temperature.

8. The method for preparing a pentagonal high-entropy carbide ceramic according to claim 7, characterized in that: The heating program for the sintering process is as follows: heat to 1800℃ at a heating rate of 100℃ / min and hold for 10min, then heat to 2000℃ at a heating rate of 100℃ / min.

9. The pentagonal high-entropy carbide ceramic (TiZrHfTaV)C prepared by the preparation method according to any one of claims 1 to 8.

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