(Hf, Ta, Zr, Nb) C high-entropy carbide powder and preparation method thereof

Abstract

The invention discloses (Hf, Ta, Zr, Nb) C high-entropy carbide powder and a preparation method thereof. The preparation method comprises the following steps: (1) carrying out ball milling on HfC, TaC, ZrC and NbC powder in different proportions, drying, and sieving to obtain mixed powder; (2) in vacuum or inert gas, sintering the mixed powder at high temperature, and cooling to directly obtain (Hf, Ta, Zr, Nb) C high-entropy carbide powder; and (3) the particle size of the powder can be regulated and controlled by controlling the heat preservation time and a ball milling process after sintering. The particle size of the micron-sized (Hf, Ta, Zr and Nb) C high-entropy carbide powder synthesized by the method is controllable, the regulation range is 0.1 mu m-1 mm, the powder purity is high, the components are uniform and easy to regulate, the preparation method is simple, and batch production is facilitated to promote industrial application of the high-entropy carbide powder.

Description

Technical Field

[0001] The invention belongs to the technical field of high entropy ceramics, and specifically relates to a (Hf, Ta, Zr, Nb)C high entropy carbide powder and a preparation method thereof. Background Art

[0002] High entropy carbide ceramics have high melting point, low thermal conductivity, and good oxidation resistance, mechanical properties, chemical stability and radiation stability, which make them suitable for use in extreme environments such as aerospace, nuclear energy and high temperature industries. However, due to the high brittleness of ceramics, their machining performance is poor. In practical applications, it is necessary to consider their processing difficulty and cost, making them difficult to apply directly. Through the study of high entropy carbide powder, high-purity high entropy carbide powder is prepared, which can play a greater role in the application field of ultra-high temperature ceramics.

[0003] Compared with single-component traditional metal carbides, (Hf, Ta, Zr, Nb)C high entropy carbides have lower oxidation rate, better oxidation resistance, good high-temperature creep resistance, higher strength and hardness, and have demonstrated many excellent properties.

[0004] At present, the preparation methods and raw materials of high entropy ceramic powders include: liquid phase method (transition metal compounds and organic compounds), molten salt method (transition metal oxide powders and carbon powder), carbon thermal reduction method (transition metal oxide powders and carbon powder), carbonization reaction method (transition metal powders and carbon powder), and solid solution reaction method (transition metal carbide powders). Among them, the high entropy carbide powder directly synthesized by the solid solution reaction of transition metal carbide powder has high purity, no impurities, and easy to control the proportion.

[0005] The Chinese invention patent with publication number CN 116986907 A reports a method of mixing transition metal carbide powder and Si powder, pressing them into tablets, heat treating them, and finally crushing them by ball milling to obtain single-phase high entropy carbide ceramic powder. The addition of Si powder can reduce the solid solution temperature and promote the sintering of the powder, but the product contains residual silicon impurities, which affects the purity of the powder, and the material needs to be crushed to form powder after heat treatment.

[0006] In order to prepare high-purity and loosely structured high-entropy carbide powder, the present invention uses carbide as a raw material and provides a method for preparing high-entropy carbide powder by pressureless sintering. Summary of the invention

[0007] In view of the deficiencies in the prior art, the first object of the present invention is to provide a method for preparing a (Hf, Ta, Zr, Nb) C high entropy carbide powder. The method of the present invention uses HfC, TaC, ZrC and NbC powders as raw materials, and prepares (Hf, Ta, Zr, Nb) C high entropy carbide powder by diffusion between single-component carbides at high temperature through pressureless sintering after ball milling. The raw materials in the present invention are transition metal carbides, and the product has low free carbon content, is easy to break, and is easy to process subsequently. Using the pressureless sintering method, the preparation process is easy to control, has wide applicability, and is easy to realize industrial production.

[0008] The second object of the present invention is to provide a (Hf, Ta, Zr, Nb)C high entropy carbide powder prepared by the above-mentioned preparation method. The (Hf, Ta, Zr, Nb)C high entropy carbide powder prepared by the present invention is a single-phase solid solution with high purity, uniform composition and controllable grain size.

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] The invention discloses a method for preparing (Hf, Ta, Zr, Nb)C high entropy carbide powder. The method comprises the following steps: ball-milling HfC powder, TaC powder, ZrC powder and NbC powder to obtain mixed powder, and pressurelessly sintering the mixed powder under a protective atmosphere to obtain the (Hf, Ta, Zr, Nb)C high entropy carbide powder.

[0011] In a preferred embodiment, the particle sizes of the HfC powder, TaC powder, ZrC powder and NbC powder are all 1-3 μm, and the purity is ≥99%.

[0012] In a preferred embodiment, the atomic percent ratio of the HfC powder, TaC powder, ZrC powder and NbC powder in the mixed powder is 5 to 60 at.%. In the present invention, by controlling each powder within the above range, a (Hf, Ta, Zr, Nb)C high entropy carbide powder with a single-phase solid solution structure having high purity, uniform composition and controllable grain size can be obtained.

[0013] In a preferred embodiment, the ball milling is wet ball milling, and the ball milling medium of the wet ball milling is anhydrous ethanol. The wet ball milling can reduce the oxidation and agglomeration of the powder.

[0014] In a preferred embodiment, the ball mill uses a cemented carbide ball mill jar, and the grinding balls use cemented carbide balls.

[0015] In a preferred embodiment, the cemented carbide ball is composed of a cemented carbide ball A with a diameter of 5-6 mm, a cemented carbide ball B with a diameter of 7-8 mm, and a cemented carbide ball C with a diameter of 9-10 mm, wherein the mass ratio of cemented carbide ball A: cemented carbide ball B: cemented carbide ball C is 3-6:1-3:1-3.

[0016] In a preferred embodiment, the filling coefficient of the ball mill is 0.2 to 0.5. In the present invention, the filling coefficient of the ball material refers to the proportion of the cemented carbide balls in the cemented carbide ball mill tank.

[0017] In a preferred embodiment, the rotation speed of the ball mill is 100-350 rpm, the ball milling time is 1-30 h, and the ball-to-material ratio is 10-40:1.

[0018] In a preferred embodiment, the ball milling process is paused after every 6 to 12 hours, and the grinding balls and the slurry are stirred, and the powder close to the tank wall is drawn into the slurry, and the ball milling is continued.

[0019] In the present invention, a large number of ball milling process details are controlled. Through the above process details, the raw material powder can be fully activated. The inventors found that the ball milling process will significantly affect the subsequent sintering effect. Ball milling can promote pressureless sintering to obtain (Hf, Ta, Zr, Nb)C high entropy carbide powder with a single-phase solid solution structure.

[0020] In a preferred embodiment, the slurry after ball milling is placed in a vacuum drying oven and dried at a temperature of 40-100° C. for 24-48 hours, then taken out and passed through a 100-300 mesh sieve to obtain a mixed powder.

[0021] In a preferred embodiment, the mixed powder is loaded into the crucible in a free-falling manner to maintain a loose filling state.

[0022] In the actual operation process, the mixed powder is controlled to be slowly loaded into the crucible in a free fall manner. The inventors found that the way the mixed powder is loaded has a significant effect on the morphology of the sintered powder. The loading method of the present invention can form a uniform single-phase solid solution structure, and can make the sintered powder easy to crush, and the particle size distribution of the product obtained after crushing is very narrow.

[0023] Further preferably, after the mixed powder is loaded into the crucible, the crucible lid is covered. By covering the crucible lid, some contamination can be avoided.

[0024] In a preferred embodiment, the pressureless sintering temperature is 1800-2500°C, preferably 1800-2000°C, the pressureless sintering time is ≤10h, preferably 1-2h, and the heating rate is 2-200°C / min, preferably 5-10°C / min.

[0025] Further preferably, the protective atmosphere is Ar gas. In actual operation, after vacuuming, Ar gas is introduced until the pressure reaches normal pressure for pressureless sintering.

[0026] In a preferred embodiment, the powder obtained after the pressureless sintering is subjected to ball milling to obtain (Hf, Ta, Zr, Nb)C high entropy carbide powder, and the ball milling time is ≤30 h, preferably 10-12 h.

[0027] The present invention also provides (Hf, Ta, Zr, Nb)C high entropy carbide powder prepared by the above preparation method.

[0028] In a preferred embodiment, the particle size of the (Hf, Ta, Zr, Nb)C high entropy carbide powder is 0.1 μm~1 mm, preferably 0.1~10 μm.

[0029] The method of the present invention can achieve a particle size distribution of 0.1 μm to 1 mm, and can control the (Hf, Ta, Zr, Nb)C high entropy carbide powder with uniform particle size and narrow particle size distribution through ball milling.

[0030] Principles and advantages

[0031] By improving the ball milling process, refining the powder particle size and increasing the powder activity, the sintering activation energy can be reduced, the element diffusion can be accelerated, and the solid solution between single-component carbides can be facilitated to form high-entropy carbide powders. At the same time, ball milling can improve the uneven particle size distribution of raw material powders, which helps to achieve pressureless sintering to obtain single-phase carbide solid solution powders.

[0032] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0033] (1) The (Hf, Ta, Zr, Nb)C high entropy carbide powder synthesized by the preparation method of the present invention has high purity, uniform composition, and the raw material ratio is easy to adjust;

[0034] (2) The preparation method of the high-performance (Hf, Ta, Zr, Nb)C high-entropy carbide powder of the present invention is simple in process, has controllable particle size, and is suitable for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is the (Hf synthesized in Example 2 0.25 Ta 0.25 Zr 0.25 Nb 0.25 ) XRD pattern of C high entropy carbide powder;

[0036] Figure 2 is the (Hf synthesized in Example 2 0.25 Ta0.25 Zr 0.25 Nb 0.25 ) SEM image of C high entropy carbide powder;

[0037] Figure 3 is the (Hf synthesized in Example 2 0.25 Ta 0.25 Zr 0.25 Nb 0.25 )Particle size distribution of C high entropy carbide powder. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is further described in detail below in conjunction with specific examples and drawings, but it should not be understood as limiting the protection scope and implementation methods of the present invention.

[0039] Example 1

[0040] The specific implementation steps are as follows:

[0041] Weigh HfC, TaC, ZrC and NbC powders with equal atomic ratios, mix them with anhydrous ethanol, use carbide ball milling jars, carbide balls with diameters of 5 mm, 8 mm and 10 mm, weight ratio of 6:3:1, ball milling for 2 h, ball-to-material ratio of 16:1, ball milling speed of 150 rpm, filling factor of 0.3; pause the ball milling program after running for 6 h, take out the ball milling jar, stir the ball milling balls and slurry, roll the powder close to the jar wall into the slurry, continue ball milling, vacuum dry the slurry obtained by ball milling after completion, dry it at 60 °C for 24 h, pass the dried powder through a 100-mesh sieve to obtain a mixed powder, slowly load the mixed powder into a graphite crucible in a free-falling manner, keep it in a loose filling state, and cover the crucible lid; then increase the furnace temperature from room temperature to 1800 at a heating rate of 10 °C / min. The whole process was sintered under pressureless Ar protection and kept at this temperature for 1 h before cooling to room temperature to obtain high entropy carbide powder.

[0042] This example prepared a single-phase (Hf 0.25 Ta 0.25 Zr 0.25 Nb 0.25 )C high entropy carbide powder, with uniform composition distribution, no impurity phase, loose structure and easy to break, and particle size of about 80 μm.

[0043] Example 2

[0044] The HfC, TaC, ZrC and NbC powders with equal atomic ratios were weighed and mixed with anhydrous ethanol. The ball milling was performed using a cemented carbide ball milling jar, and the grinding balls were cemented carbide balls with ball diameters of 5 mm, 8 mm and 10 mm, with a weight ratio of 5:3:2. The ball milling was performed for 12 h, the ball-to-material ratio was 23:1, the ball milling speed was 200 rpm, and the filling coefficient was 0.3. After the ball milling, the slurry obtained by the ball milling was vacuum dried and dried at 40 °C for 48 h. The dried powder was passed through a 100-mesh sieve to obtain a mixed powder. The mixed powder was slowly loaded into a graphite crucible in a free-falling manner, and its loose filling state was maintained, and the crucible lid was covered. Then, the furnace temperature was increased from room temperature to 2000 °C at a heating rate of 10 °C / min. Ar gas protection was used for pressureless sintering during the whole process. After keeping the temperature for 2 h, it was cooled to room temperature to obtain a high entropy carbide powder. The high entropy carbide powder was ball milled for 6 h to obtain the target product.

[0045] This example prepared a single-phase (Hf 0.25 Ta 0.25 Zr 0.25 Nb 0.25 )C high entropy carbide powder, with uniform composition distribution, extremely low impurity content, loose structure and easy to break, and particle size of about 1 μm. Figure 1 (Hf prepared in Example 2 0.25 Ta 0.25 Zr 0.25 Nb 0.25 )C high entropy carbide powder XRD spectrum, the spectrum shows that the prepared powder has formed a single phase (Hf 0.25 Ta 0.25 Zr 0.25 Nb 0.25 )C, and no second phase was found, which also shows that the high entropy carbide powder prepared by this method has high purity. Figure 2 (Hf prepared in Example 2 0.25 Ta 0.25 Zr 0.25 Nb 0.25 )SEM image of C high entropy carbide powder. Figure 3 (Hf prepared in Example 2 0.25 Ta 0.25 Zr 0.25 Nb 0.25 )C high entropy carbide powder particle size distribution diagram. From the figure, we can see that the particle size distribution range is 0.1-8μm, and the particle size distribution is narrow.

[0046] Embodiment 3:

[0047] This example is the same as Example 2 in other process conditions, only the molar ratio of HfC, TaC, ZrC and NbC powders is changed to 9:1:9:1. This example prepares a single-phase (Hf 0.45 Ta 0.05 Zr 0.45 Nb 0.05 )C high entropy carbide powder, with uniform element distribution, no impurity phase, loose structure and easy to break, and particle size of about 1 μm.

[0048] Embodiment 4:

[0049] This example is the same as Example 2 in other process conditions, only the molar ratio of HfC, TaC, ZrC and NbC powders is changed to 7:3:7:3. 0.35 Ta 0.15 Zr 0.35 Nb 0.15 )C high entropy carbide powder has uniform composition, loose structure and is easy to break, with a particle size of about 1 μm.

[0050] Comparative Example 1

[0051] This example has the same other process conditions as Example 1, only the ball milling filling coefficient is changed to 0.55, and finally a single-phase (Hf, Ta, Zr, Nb)C high entropy carbide powder is not synthesized. This is because the filling coefficient is too high, the interference between the ball layers is large, the normal collision of the balls is destroyed, the grinding efficiency is reduced, the powder crushing and refining effect is not good, the sintering activity is low, and it is not conducive to the diffusion between the single-component carbides to form a single phase.

[0052] Comparative Example 2

[0053] This example has the same other process conditions as Example 1, only the particle size of the ZrC raw material is changed to 45 μm, and the single-phase (Hf, Ta, Zr, Nb)C high entropy carbide powder is not synthesized in the end. This is because the raw material with too large particle size is difficult to crush, and the obtained large-particle mixed powder will affect the element diffusion during the sintering process, thereby affecting the solid solution process of the carbide.

[0054] Comparative Example 3

[0055] This example is the same as Example 1 in other process conditions, only the powder loading method is changed, the mixed powder is first pressed and then pressureless sintered. Although a single phase (Hf 0.25 Ta 0.25 Zr 0.25 Nb 0.25 )C high entropy carbide, but it is difficult to crush and ball mill. After ball milling, (Hf 0.25 Ta 0.25 Zr 0.25 Nb 0.25)C The particle size distribution of high entropy carbide powder is uneven. This is because the contact area of ​​the powder particles increases after tableting, which is not conducive to obtaining a loose structure that is easy to break after sintering. Finally, a relatively dense product with high hardness is obtained. Large particles still remain after ball milling and the particle size distribution is uneven.

Claims

1. A method for preparing (Hf, Ta, Zr, Nb)C high entropy carbide powder, characterized in that: HfC powder, TaC powder, ZrC powder and NbC powder are mixed and ball-milled to obtain a mixed powder, and the mixed powder is pressurelessly sintered under a protective atmosphere to obtain (Hf, Ta, Zr, Nb)C high entropy carbide powder.

2. The method for preparing a (Hf, Ta, Zr, Nb)C high entropy carbide powder according to claim 1, characterized in that: The particle sizes of the HfC powder, TaC powder, ZrC powder and NbC powder are all 1-3 μm, and the purity is ≥99%; The atomic percentage of the HfC powder, TaC powder, ZrC powder and NbC powder in the mixed powder is 5-60 at.%.

3. The method for preparing a (Hf, Ta, Zr, Nb)C high entropy carbide powder according to claim 1 or 2, characterized in that: The ball milling is wet ball milling, and the ball milling medium of the wet ball milling is anhydrous ethanol; The ball mill uses a hard alloy ball mill jar, and the grinding balls use hard alloy balls; The filling coefficient of the ball mill is 0.2-0.5; The rotation speed of the ball mill is 100-350 rpm, the ball milling time is 1-30 h, and the ball-to-material ratio is 10-40:

1.

4. The method for preparing a (Hf, Ta, Zr, Nb)C high entropy carbide powder according to claim 3, characterized in that: The cemented carbide balls are composed of a cemented carbide ball A with a diameter of 5-6 mm, a cemented carbide ball B with a diameter of 7-8 mm, and a cemented carbide ball C with a diameter of 9-10 mm, wherein the mass ratio of cemented carbide ball A: cemented carbide ball B: cemented carbide ball C is 3-6:1-3:1-3; During the ball milling process, the ball milling was paused after every 6 to 12 hours, and the grinding balls and the slurry were stirred, and the powder close to the tank wall was rolled into the slurry, and the ball milling was continued.

5. The method for preparing a (Hf, Ta, Zr, Nb)C high entropy carbide powder according to claim 1 or 3, characterized in that: The ball-milled slurry is placed in a vacuum drying oven and dried at 40-100 °C for 24-48 h, then taken out and sieved through a 100-300 mesh sieve to obtain a mixed powder.

6. The method for preparing a (Hf, Ta, Zr, Nb)C high entropy carbide powder according to claim 1 or 3, characterized in that: The mixed powder is loaded into the crucible in a free-falling manner, maintaining its loose filling state; After putting the mixed powder into the crucible, cover the crucible with the lid.

7. The method for preparing a (Hf, Ta, Zr, Nb)C high entropy carbide powder according to claim 1 or 3, characterized in that: The pressureless sintering temperature is 1800-2500°C, the pressureless sintering time is ≤10 h, the heating rate is 2-200°C / min, and (Hf, Ta, Zr, Nb)C high entropy carbide powder is obtained after pressureless sintering.

8. The method for preparing a (Hf, Ta, Zr, Nb)C high entropy carbide powder according to claim 1 or 3, characterized in that: The powder obtained after the pressureless sintering is ball milled to obtain (Hf, Ta, Zr, Nb)C high entropy carbide powder, and the ball milling time is ≤30 h.

9. A (Hf, Ta, Zr, Nb)C high entropy carbide powder prepared by the preparation method according to any one of claims 1 to 8.

10. The (Hf, Ta, Zr, Nb)C high entropy carbide powder according to claim 9, characterized in that: The particle size of the (Hf, Ta, Zr, Nb)C high entropy carbide powder is 0.1 μm~1 mm.

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