High-toughness (Ta, Nb, Zr, V) C high-entropy ceramic material and preparation method thereof

Abstract

The invention discloses a high-toughness (Ta, Nb, Zr, V) C high-entropy ceramic material and a preparation method thereof.The preparation method comprises the following steps that 1, TaC powder, NbC powder, ZrC powder and VC powder are added into absolute ethyl alcohol, and ultrasonic treatment and stirring are conducted at the same time; (2) adding polyethylene glycol 2000 into the mixed slurry obtained in the step (1), carrying out ball milling, then carrying out vacuum drying, cooling and sieving to obtain mixed powder; and (3) filling the mixed powder into a graphite mold, carrying out pressure forming, and carrying out plasma sintering by keeping the pressure for pressure forming. The high-entropy ceramic material has a special core ring structure, is high in density and small in average grain size of crystal grains, and has relatively high hardness, fracture toughness and bending strength.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic materials, and in particular relates to a high-strength and high-toughness (Ta, Nb, Zr, V)C high-entropy ceramic material and a preparation method thereof. Background Art

[0002] Ceramic materials possess the characteristics of high hardness, high wear resistance, and high chemical stability, but their poor fracture toughness greatly limits their application scenarios. High-entropy ceramics are an emerging type of ceramic material. Their multi-principal component composition mechanism gives them a huge space for performance regulation, making them one of the most promising materials. However, common high-entropy carbide ceramics have the problem of high hardness but poor fracture toughness and flexural strength. This mismatch in properties limits the application of high-entropy ceramics. Therefore, the development of high-entropy ceramic materials that combine high hardness and high toughness has become a research hotspot in the field of brittle and hard materials.

[0003] In traditional materials, the balance between hardness and toughness is often a trade-off. Designing ceramic materials with both high hardness and high toughness remains a significant scientific and technological challenge. Furthermore, the material's microstructure, including interface structure, morphology, defect distribution, and phase composition, also profoundly influences mechanical properties. Refining the microstructure and morphology of high-entropy ceramics to create self-toughening microstructures will provide a key approach to preparing high-hardness, high-toughness, and high-entropy ceramics. Summary of the Invention

[0004] In response to the defects of the prior art, the present invention provides a high-strength and tough (Ta, Nb, Zr, V)C high-entropy ceramic material and a preparation method thereof. The obtained high-entropy ceramic material has a special core ring structure, good mechanical properties, and both high hardness and fracture toughness.

[0005] A method for preparing a high-strength and high-toughness (Ta, Nb, Zr, V)C high-entropy ceramic material comprises the following steps: (1) TaC powder, NbC powder, ZrC powder, and VC powder were added to anhydrous ethanol and ultrasonically treated while stirring; (2) adding polyethylene glycol 2000 to the mixed slurry obtained in step (1), ball milling, vacuum drying, cooling, and sieving to obtain a mixed powder; (3) The mixed powder is placed in a graphite mold, press-formed, and then plasma sintered while maintaining the press-forming pressure.

[0006] Preferably, the mass ratio of the TaC powder, NbC powder, ZrC powder, VC powder and polyethylene glycol 2000 is (30-35): (32-38): (15-20): (12-14.3): 0.1.

[0007] Preferably, the sintering conditions are: heating to 700°C at 350°C / min, then heating to 1000°C at 50°C / min, then heating to 1580-1720°C at 100°C / min, and sintering at this temperature for 7-15 minutes; then water cooling to 700°C at 120-150°C / min, and finally cooling to room temperature with the furnace. The vacuum is maintained throughout the sintering process.

[0008] More preferably, the sintering conditions are: heating to 700°C at 350°C / min, then heating to 1000°C at 50°C / min, then heating to 1600°C at 100°C / min, and sintering at this temperature for 11 minutes; then water cooling to 700°C at 120-150°C / min, and finally cooling to room temperature with the furnace. The vacuum is maintained throughout the sintering process.

[0009] Preferably, the particle size of the TaC powder, NbC powder, ZrC powder, and VC powder (vanadium carbide) is 1-3 μm.

[0010] Preferably, the ultrasonic treatment and simultaneous stirring time is 20-40 min.

[0011] Preferably, the ball milling conditions are as follows: the ball mill body is made of stainless steel, the ball mill medium is made of tungsten carbide, the ball-to-material ratio is 10:1, the ball milling time is 12-24 hours, and the ball mill speed is 150-200 r / min.

[0012] Preferably, the vacuum drying conditions are: vacuum degree <40 Pa, temperature 120-140° C., and drying time 3-4 h.

[0013] Preferably, the pressure molding is performed by using a hydraulic press at 30 MPa.

[0014] A high-strength and high-toughness (Ta, Nb, Zr, V)C high-entropy ceramic material is prepared by the preparation method of the present invention.

[0015] Advantages of the present invention: (1) The prepared (Ta, Nb, Zr, V)C high-entropy ceramic material has high density, small average grain size, high hardness, fracture toughness and flexural strength; (2) The high-entropy ceramic material prepared by the present invention has a special core-ring structure. When subjected to external loads, a large number of dislocations accumulate at the interface between the "ring" phase and the "core" phase. The "ring" phase generates back stress, and the "core" phase generates positive stress. Under the interaction, a large amount of energy is absorbed, showing high hardness characteristics. When the absorbed energy exceeds the threshold, cracks will nucleate in the "ring" phase with lower strength. Since the "core" phase requires more energy to produce plastic deformation, the crack path is extended, and the toughness is improved at this time. This makes the high-entropy carbonized ceramic prepared by the present invention have both high hardness and high toughness characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The XRD patterns of the ceramic materials of Example 1, Example 2 and Comparative Example 1 are shown; Figure 2 The SEM images of the ceramic material surfaces of Example 1 and Comparative Example 1 are shown; Figure 3 The SEM images of the surface indentation and fracture surface of the ceramic material of Example 1 are shown. DETAILED DESCRIPTION

[0017] Example 1 A method for preparing a high-strength and high-toughness (Ta, Nb, Zr, V)C high-entropy ceramic material comprises the following steps: (1) Add 6.56 g of TaC powder, 7.08 g of NbC powder, 3.5 g of ZrC powder, and 2.86 g of VC powder to 500 mL of anhydrous ethanol, ultrasonically treat, and stir for 30 min; wherein the particle size of TaC powder, NbC powder, ZrC powder, and VC powder is 1-3 μm; (2) Add 0.02 g of polyethylene glycol 2000 to the mixed slurry obtained in step (1), place the slurry in a stainless steel ball mill, add tungsten carbide (WC) ball milling medium at a ball-to-material mass ratio of 10:1, set the speed to 200 r / min, and ball mill for 20 hours. In order to prevent the powder from overheating, stop the machine every 30 minutes, cool it naturally for 30 minutes, and then restart it; place the ball-milled slurry in a ZK-40 vacuum hot drying oven, vacuum dry it at a vacuum degree of 35 Pa and 140°C for 4 hours, and pass it through a 100-mesh sieve after cooling to obtain a mixed powder; (3) The mixed powder is loaded into a graphite mold with a diameter of 20 mm and lined with graphite paper, and is pressurized at 30 MPa using a hydraulic press. The pressurized pressure is maintained, and the pressed blank and the graphite mold are sent into a plasma vacuum sintering furnace together with the graphite mold. The vacuum is maintained, and the pressure of 30 MPa is maintained during the sintering process. The first step is to heat to 700°C at 350°C / min, the second step is to heat to 1000°C at 50°C / min, the third step is to heat to 1600°C at 100°C / min, and sinter at this temperature for 11 minutes. The fourth step is to water cool to 700°C at 130°C / min, and then cool to room temperature with the furnace. The vacuum is maintained throughout the sintering process.

[0018] Example 2 In the third step, the temperature was raised to 1700° C. at a rate of 100° C. / min and sintered for 11 minutes. Other steps were the same as those in Example 1.

[0019] Example 3 A method for preparing a high-strength and high-toughness (Ta, Nb, Zr, V)C high-entropy ceramic material comprises the following steps: (1) Add 6 g of TaC powder, 6.4 g of NbC powder, 3 g of ZrC powder, and 2.4 g of VC powder to 500 mL of anhydrous ethanol, ultrasonically treat, and stir for 20 min; wherein the particle size of TaC powder, NbC powder, ZrC powder, and VC powder is 1-3 μm; (2) Add 0.02 g of polyethylene glycol 2000 to the mixed slurry obtained in step (1), place the slurry in a stainless steel ball mill, add tungsten carbide (WC) ball milling medium at a ball-to-material mass ratio of 10:1, set the speed to 150 r / min, and ball mill for 12 hours. In order to prevent the powder from overheating, stop the machine every 30 minutes, cool it naturally for 30 minutes, and then restart it; place the ball-milled slurry in a ZK-40 vacuum hot drying oven, vacuum dry it at a vacuum degree of 35 Pa and 120°C for 4 hours, and pass it through a 100-mesh sieve after cooling to obtain a mixed powder; (3) The mixed powder is loaded into a graphite mold with a diameter of 20 mm and lined with graphite paper, and is pressurized at 30 MPa using a hydraulic press. The pressurized pressure is maintained, and the pressed blank and the graphite mold are sent into a plasma vacuum sintering furnace together with the graphite mold. The vacuum is maintained, and the pressure of 30 MPa is maintained during the sintering process. The first step is to heat to 700°C at 350°C / min, the second step is to heat to 1000°C at 50°C / min, the third step is to heat to 1580°C at 100°C / min, and sinter at this temperature for 15 minutes. The fourth step is to water cool to 700°C at 130°C / min, and then cool to room temperature with the furnace. The vacuum is maintained throughout the sintering process.

[0020] Example 4 A method for preparing a high-strength and high-toughness (Ta, Nb, Zr, V)C high-entropy ceramic material comprises the following steps: (1) 7 g of TaC powder, 7.6 g of NbC powder, 4 g of ZrC powder, and 2.86 g of VC powder were added to 500 mL of anhydrous ethanol, and ultrasonically treated while stirring for 40 min; wherein the particle size of TaC powder, NbC powder, ZrC powder, and VC powder was 1-3 μm; (2) Add 0.02 g of polyethylene glycol 2000 to the mixed slurry obtained in step (1), place the slurry in a stainless steel ball mill, add tungsten carbide (WC) ball milling medium at a ball-to-material mass ratio of 10:1, set the speed to 200 r / min, and ball mill for 24 hours. In order to prevent the powder from overheating, stop the machine every 30 minutes, cool it naturally for 30 minutes, and then restart it; place the ball-milled slurry in a ZK-40 vacuum hot drying oven, vacuum dry it at a vacuum degree of 35 Pa and 140°C for 4 hours, and pass it through a 100-mesh sieve after cooling to obtain a mixed powder; (3) The mixed powder is loaded into a graphite mold with a diameter of 20 mm and lined with graphite paper, and is pressurized at 30 MPa using a hydraulic press. The pressurized pressure is maintained, and the pressed blank and the graphite mold are sent into a plasma vacuum sintering furnace together with the graphite mold. The vacuum is maintained, and the pressure of 30 MPa is maintained during the sintering process. The first step is to heat the blank to 700°C at 350°C / min, the second step is to heat the blank to 1000°C at 50°C / min, the third step is to heat the blank to 1720°C at 100°C / min, and sinter at this temperature for 7 minutes. The fourth step is to water cool the blank to 700°C at 130°C / min, and then cool the blank to room temperature with the furnace. The vacuum is maintained throughout the sintering process.

[0021] Comparative Example 1 In the third step, the temperature was raised to 1800° C. at 100° C. / min and sintered for 11 minutes. Other steps were the same as those in Example 1.

[0022] Performance testing 1. Mechanical properties testing The hardness, fracture toughness and flexural strength of the ceramic materials were tested. The results are shown in Table 1.

[0023] Table 1 Mechanical properties of ceramic materials As shown in Table 1, the comprehensive mechanical properties of the material are the best when the sintering temperature is 1600 ℃ and the holding time is 11 min. At this time, the hardness, fracture toughness and flexural strength are 22.64 GPa, 8.85 MPa•m 1 / 2 , 441 MPa. However, when the sintering temperature is 1800℃, its fracture toughness decreases significantly.

[0024] 2. XRD phase analysis The ceramic materials prepared in Example 1, Example 2 and Comparative Example 1 were subjected to XRD testing. Figure 1 .Depend on Figure 1 It can be seen that all three ceramic materials form a single high-entropy phase high-entropy ceramic with FCC structure.

[0025] 3. Scanning Electron Microscopy In order to remove surface impurities and smooth the surface, the ceramic materials obtained in Example 1 and Comparative Example 1 were polished and then subjected to scanning electron microscopy. The results are shown in FIG. Figure 2 , wherein (a) is a scanning electron microscope image of the ceramic material of Example 1, (b) is a partially enlarged scanning electron microscope image of Example 1, and (c) is a scanning electron microscope image of the ceramic material of Comparative Example 1; Figure 2 As can be seen, the ceramic materials in Example 1 and Comparative Example 1 are uniform in texture and both have an FCC structure. However, a core ring structure is observed in the ceramic material of Example 1, while in Comparative Example 1, the core ring structure disappears when the sintering temperature reaches 1800°C. This shows that sintering temperature has a crucial influence on the microscopic morphology of ceramic materials.

[0026] At the same time, the surface indentation and fracture surface of the ceramic material of Example 1 were subjected to scanning electron microscopy. Figure 3 ,in, Figure 3 (a) and (b) are SEM images of the surface, and (c) is a SEM image of the fracture surface. It can be seen that in (a) and (b), there is a core-ring structure composed of alternating "soft" and "hard" structural units. The hard core phase prevents crack propagation while the soft ring phase guides crack deflection. As a result, there are multiple propagation forms such as bridging and deflection during the fracture process. The tortuous path consumes a lot of fracture energy, thereby inhibiting the expansion of the crack and achieving a toughening effect. Figure 3 As shown in (c), there is both transgranular fracture and intergranular fracture in the crack propagation under fracture failure, which is a mixed transgranular and intergranular fracture mode.

[0027] Based on this Figure 3 From the mechanical properties in Table 1, we can see that under the same physical phase, different microstructures have huge differences in mechanical properties. Figure 2 Comparison of samples with core-ring structure in (a) and (b) Figure 2 The sample without the core ring structure in (c) shows a significant improvement in fracture toughness while maintaining high hardness performance. This demonstrates that the special core ring structure synthesized by the present invention has a good toughening effect.

[0028] In summary, the ceramic material prepared by the present invention has a core-ring structure. The "core" phase with higher hardness can withstand a larger load, while the softer "ring" phase helps to absorb energy, slow down the expansion of cracks, and improve the toughness of the material.

Claims

1. A method for preparing a high-strength and high-toughness (Ta, Nb, Zr, V)C high-entropy ceramic material, characterized by: The following steps are involved: (1) TaC powder, NbC powder, ZrC powder, and VC powder were added to anhydrous ethanol and ultrasonically treated while stirring; (2) adding polyethylene glycol 2000 to the mixed slurry obtained in step (1), ball milling, vacuum drying, cooling, and sieving to obtain a mixed powder; (3) The mixed powder is placed in a graphite mold, press-formed, and then plasma sintered while maintaining the press-forming pressure.

2. The method for preparing the high-strength and high-toughness (Ta, Nb, Zr, V)C high-entropy ceramic material according to claim 1, characterized in that: The mass ratio of the TaC powder, NbC powder, ZrC powder, VC powder and polyethylene glycol 2000 is (30-35): (32-38): (15-20): (12-14.3): 0.

1.

3. The method for preparing the high-strength and high-toughness (Ta, Nb, Zr, V)C high-entropy ceramic material according to claim 1, characterized in that: The sintering conditions are as follows: heating to 700°C at 350°C / min, then heating to 1000°C at 50°C / min, then heating to 1580-1720°C at 100°C / min, sintering at this temperature for 7-15 minutes; then water cooling to 700°C at 120-150°C / min, and finally cooling to room temperature with the furnace. Vacuum is maintained throughout the sintering process.

4. The method for preparing the high-strength and high-toughness (Ta, Nb, Zr, V)C high-entropy ceramic material according to claim 3, characterized in that: The sintering conditions are as follows: heating to 700°C at 350°C / min, then heating to 1000°C at 50°C / min, then heating to 1600°C at 100°C / min, sintering at this temperature for 11 minutes; then water cooling to 700°C at 120-150°C / min, and finally cooling to room temperature with the furnace. Vacuum is maintained throughout the sintering process.

5. The method for preparing the high-strength and high-toughness (Ta, Nb, Zr, V)C high-entropy ceramic material according to claim 1, characterized in that: The particle sizes of the TaC powder, NbC powder, ZrC powder and VC powder are all 1-3 μm.

6. The method for preparing the high-strength and high-toughness (Ta, Nb, Zr, V)C high-entropy ceramic material according to claim 1, characterized in that: The ultrasonic treatment and stirring time is 20-40 minutes.

7. The method for preparing the high-strength and high-toughness (Ta, Nb, Zr, V)C high-entropy ceramic material according to claim 1, characterized in that: The ball milling conditions are as follows: the ball mill body is made of stainless steel, the ball mill medium is made of tungsten carbide, the ball-to-material ratio is 10:1, the ball milling time is 12-24 hours, and the ball mill speed is 150-200 r / min.

8. The method for preparing the high-strength and high-toughness (Ta, Nb, Zr, V)C high-entropy ceramic material according to claim 1, characterized in that: The vacuum drying conditions are: vacuum degree <40 Pa, temperature 120-140° C., and drying time 3-4 h.

9. The method for preparing the high-strength and high-toughness (Ta, Nb, Zr, V)C high-entropy ceramic material according to claim 1, characterized in that: The press molding was performed using a hydraulic press at 30 MPa.

10. A high-strength and high-toughness (Ta, Nb, Zr, V)C high-entropy ceramic material, characterized by: It is prepared by the preparation method according to any one of claims 1 to 9.

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