High-entropy MAX phase material and preparation method and application thereof

Abstract

The invention belongs to the field of inorganic nonmetal conductive ceramics, and particularly relates to a high-entropy MAX phase material and a preparation method and application thereof, the molecular formula of the high-entropy MAX phase material is M2AlC, and M is selected from at least three of Ti, Zr, Hf, Nb, Ta and V. The prepared high-entropy MAX phase material not only has excellent high temperature resistance and corrosion resistance, but also has potential electromagnetic shielding performance.

Description

[0001] This application claims priority to a prior application filed on April 24, 2023, with application number 2023104491143, entitled “A high entropy MAX phase material, preparation method and application thereof”. The entire text of the prior application is incorporated into this application by reference. Technical Field

[0002] The invention belongs to the field of inorganic non-metallic conductive ceramics, and in particular relates to a high-entropy MAX phase material and a preparation method and application thereof. Background Art

[0003] MAX phase is a type of ternary carbide and / or nitride with a hexagonal layered structure, composed of three elements: M, A and X. Its general chemical formula is M n+1 AX n (n=1, 2, 3), where M is a transition metal element, A is mainly a IIIA to VA element, and X is carbon and / or nitrogen. MAX phase materials can also be called metal ceramics or conductive ceramics, which are composed of layered transition metal carbonitrides and A atomic layers stacked on each other. This unique structure makes MAX phase materials not only have the excellent properties of traditional ceramics, but also have the characteristics of metal materials, such as low density, high modulus, good thermal conductivity, good processing performance, good high-temperature mechanical properties, excellent conductivity, corrosion resistance and oxidation resistance. It has broad application prospects in the fields of high-power electrical contact, friction and wear, and accident-tolerant nuclear fuel cladding materials.

[0004] High-entropy MAX phase materials refer to MAX phase materials that contain at least four (for example, five) transition metal elements. The composition of high-entropy MAX phase materials is complex, and the atoms of the constituent elements are randomly and disorderly distributed in the lattice positions. Therefore, high-entropy MAX phase materials have a high-entropy effect in thermodynamics, a slow diffusion effect in kinetics, a lattice distortion effect in structure, and a cocktail effect in performance. The mixing of multiple main elements in high-entropy MAX phase materials leads to the maximum mixing entropy of the material. The high mixing entropy inhibits the formation of intermetallic compounds and promotes the formation of saturated solid solutions with simple crystal structures. Under the coupling of multiple mechanisms, high-entropy MAX phase materials have many excellent properties that traditional materials cannot match, such as outstanding performance in mechanics, electromagnetism, high temperature resistance, and corrosion resistance. At present, research on high-entropy materials is still mainly focused on changing the types of constituent elements and crystal structures. Summary of the invention

[0005] In order to improve the deficiencies of the prior art, the present invention proposes a high entropy MAX phase material, which has excellent high temperature resistance and corrosion resistance.

[0006] In a first aspect, the present invention provides a high entropy MAX phase material having a molecular formula of M2AlC, wherein M is selected from at least three of Ti, Zr, Hf, Nb, Ta and V, preferably selected from Ti, Zr, Hf, Nb and V.

[0007] According to an embodiment of the present invention, the molecular formula of the high entropy MAX phase material is (Ti 0.2 Zr 0.2 Hf 0.2 V 0.2 Nb 0.2 )2AlC.

[0008] According to an embodiment of the present invention, the high entropy MAX phase material is a hexagonal layered structure.

[0009] In a second aspect, the present invention provides a method for preparing the above-mentioned high entropy MAX phase material, comprising the following steps:

[0010] S1. Mixing the powder containing M, Al powder and C powder uniformly to obtain composite powder;

[0011] The powder containing M is selected from at least three of Ti powder, ZrC powder, HfC powder, V powder, Nb powder and Ta powder, for example, selected from Ti powder, ZrC powder, HfC powder, V powder and Nb powder;

[0012] S2. The composite powder is first vacuum hot-pressed, and then sintered at a temperature of 1400° C. to 1700° C. for 4 to 8 hours. After cooling, a high-entropy MAX phase ceramic material is obtained.

[0013] According to an embodiment of the present invention, the molar ratio of the Ti powder, ZrC powder, HfC powder, V powder, Nb powder, Al powder and C powder is (0.35-0.45):(0.35-0.45):(0.35-0.45):(0.35-0.45):(0.35-0.45):1.1:(0.15-0.25), for example, the molar ratio of the Ti powder, ZrC powder, HfC powder, V powder, Nb powder, Al powder and C powder is 0.4:0.4:0.4:0.4:0.4:1.1:0.2.

[0014] According to an embodiment of the present invention, in step S1, the mixing includes adopting technical means known in the art including ball milling, grinding, mixing using a mixer, etc. For example, the powder containing M (such as Ti powder, ZrC powder, HfC powder, V powder, Nb powder), Al powder and C powder are evenly mixed by ball milling.

[0015] According to an embodiment of the present invention, the ball milling includes adding powder containing M (such as Ti powder, ZrC powder, HfC powder, V powder, Nb powder), Al powder and C powder into a ball milling container, dispersing them in a dispersion liquid, and ball milling with silicon nitride as a grinding medium.

[0016] According to an embodiment of the present invention, the dispersion liquid is selected from organic solvents, such as acetone.

[0017] According to an embodiment of the present invention, the diameter of the silicon nitride is 5-15 nm, for example, 10 nm.

[0018] According to an embodiment of the present invention, the ball-to-material ratio of the ball mill is (10-20): 1. The rotation speed is 200-600 r / min, and the ball milling time is 10-30 h.

[0019] As an example, the ball-to-material ratio of the ball mill is 15:1, the rotation speed is 400 r / min, and the ball milling time is 24 h.

[0020] According to an embodiment of the present invention, the following steps are further included before step S2: drying the ball-milled composite powder and then sieving it.

[0021] According to an embodiment of the present invention, the drying comprises the following steps: drying the composite powder at a temperature of 50 to 70° C. for 1 to 5 hours, for example, drying the composite powder at a temperature of 60° C. in a rotary evaporator for 3 hours.

[0022] According to an embodiment of the present invention, the sieve mesh size of the sieving is 150-250 mesh, for example, 200 mesh, so that the powder size is 15 μm.

[0023] According to an embodiment of the present invention, during the screening, for the powder particles that cannot pass through the sieve, the powder is ground into powder using a mortar and then passed through the sieve.

[0024] According to an embodiment of the present invention, screening is performed using a standard 92A type vibrating screen machine.

[0025] According to the implementation scheme of the present invention, step S2 specifically includes the following steps: first, pressurizing and pressing the composite powder under vacuum, then heating to 1400°C to 1700°C under an inert gas flow and sintering for 4 to 8 hours, and naturally reducing the pressure and temperature to obtain a high-entropy MAX phase ceramic material.

[0026] According to an embodiment of the present invention, in step S2, during the pressing process, the applied pressure is 20-40 MPa, and the holding time is 1-15 min, for example, the pressure is 30 MPa, and the holding time is 5 min.

[0027] According to an embodiment of the present invention, the heating during sintering includes first heating at 5 to 15°C / min-1 From room temperature to 1200℃, then at 1~5℃·min -1 The heating rate is from 1200℃ to 1600℃.

[0028] According to an embodiment of the present invention, the pressure in the sintering is the same as the pressing process pressure.

[0029] As an example, during sintering, the pressure is 30 MPa, and the temperature is 10 ° C. min. -1 From room temperature to 1200℃, then at 2℃·min -1 The heating rate was from 1200°C to 1600°C and kept at this temperature for 5h.

[0030] According to an embodiment of the present invention, the inert gas flow includes at least one of helium, argon and neon, for example, argon.

[0031] In a third aspect, the present invention also provides an application of the above-mentioned high entropy MAX phase material in high-power electrical contact, friction and wear, and accident-tolerant nuclear fuel cladding materials, for example, as electromagnetic shielding material, anti-corrosion material or high-temperature resistant material.

[0032] Beneficial Effects

[0033] (1) The present invention adopts a vacuum hot pressing sintering method to prepare high entropy MAX phase ceramics, and adopts a relatively high temperature and pressure for sintering. On the one hand, the method of the present invention can transfer temperature and pressure more evenly and fully under vacuum hot pressing, and the structure of the MAX phase is more dense and uniform, and the obtained performance will be more excellent; on the other hand, it can effectively reduce the contamination of impurities to the sample.

[0034] (2) The preparation method of the present invention solid-dissolves three or more transition metal elements at the M position of the MAX phase for sintering, and utilizes the "high entropy effect" of multiple principal elements to make the MAX phase ceramics "high entropy" at the M position, thereby obtaining more excellent mechanical properties, high temperature resistance and corrosion resistance.

[0035] (3) The inventors unexpectedly discovered that when preparing high-entropy MAX phase materials, due to a certain degree of mismatch between the atomic radius and valence electrons of the solvent metal atoms, the formation of the high-entropy MAX phase is always accompanied by a large lattice strain or defect, but this may bring excellent electromagnetic shielding performance to the high-entropy MAX phase material; the present invention refers to the preparation method of traditional ternary MAX phase materials and multinary MAX phase materials, and then comprehensively considers the characteristics of high-entropy materials such as high-entropy ceramics and high-entropy alloys to prepare the multinary MAX phase material, which not only has relatively excellent high temperature resistance and corrosion resistance, but also has potential electromagnetic shielding performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1This is a scanning electron microscope image of the high entropy MAX phase material prepared in Example 1;

[0037] Figure 2 This is a scanning electron microscope image of the high entropy MAX phase material prepared in Comparative Example 1;

[0038] Figure 3 This is an electrochemical impedance test diagram of the high entropy MAX phase material prepared in Example 1;

[0039] Figure 4 This is the electrochemical impedance test diagram of the high entropy MAX phase material prepared in Comparative Example 1. DETAILED DESCRIPTION

[0040] The high entropy MAX phase material of the present invention, its preparation method and application will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary illustrations and explanations of the present invention, and should not be construed as limiting the scope of protection of the present invention. The one or more steps mentioned in the present invention do not exclude the existence of other methods and steps before and after the combination step, or other methods and steps may be inserted between these explicitly mentioned steps. It should also be understood that all technologies implemented based on the above contents of the present invention are covered within the scope of protection that the present invention is intended to protect.

[0041] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0042] The sources of the raw materials and instruments used in the following examples are not particularly limited and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0043] Test Method

[0044] The relative density of the sample was tested by Archimedes drainage method;

[0045] The three-point bending strength method was used to test the room temperature and high temperature bending strength of the specimens;

[0046] The hardness of the sample was measured by Vickers hardness method;

[0047] The fracture toughness of the samples was tested by the three-point bending fracture method of single-edge notched beam.

[0048] Example 1

[0049] A method for preparing a high entropy MAX phase material comprises the steps of:

[0050] S101, ball milling step: ball mill Ti powder, ZrC powder, HfC powder, V powder, Nb powder, Al powder and C powder in a ratio of 0.4:0.4:0.4:0.4:0.4:1.1:0.2, the ball milling process is: ball-to-material ratio is 15:1, the rotation speed is 400r / min, the time is 24h, the ball milling medium is 10mm silicon nitride ball, and the mixed powder is obtained after ball milling.

[0051] S102, drying step: drying the mixed powder of step S101 under vacuum at 60° C. using a rotary evaporator for 3 hours to obtain a dry powder.

[0052] S103, sieving step: using a standard 92A type vibrating sieving machine and a 200 mesh screen to sieve the dry powder obtained in step S102, the mixed powder after sieving has a powder particle size of 15 μm.

[0053] S104, sintering step: placing the sieved mixed powder in a graphite mold and sintering it in a vacuum hot-pressing sintering furnace. The sintering method is as follows: evacuating the sintering furnace to below 20 Pa at room temperature, pressurizing it to 30 MPa, heating it from room temperature to 1200°C at a rate of 10°C / min, and then heating it at a rate of 2°C·min -1 The heating rate was increased from 1200℃ to 1600℃ and kept at this temperature for 5h. After the end of the heat preservation, the pressure and temperature were immediately reduced, and the sample was cooled with the furnace. Finally, (Ti 0.2 Zr 0.2 Hf 0.2 V 0.2 Nb 0.2 )2AlC ceramic material, that is, high entropy MAX phase material.

[0054] The high entropy MAX phase material prepared in this example was subjected to structural characterization and electrochemical performance testing. Figure 1 This is a scanning electron microscope image of the high-entropy MAX phase prepared in this embodiment. From the microscopic area, it can be seen that the layered structure and fault structure are arranged relatively neatly. The residual granular material may be the precipitated elemental aluminum. The phenomenon that some layered structures in the figure have faults may be caused by the precipitation of aluminum elements.

[0055] Figure 3 This is an electrochemical impedance test diagram of the high-entropy MAX phase material prepared in this embodiment, in which the high-frequency region is approximately a semicircle and gradually transitions to a straight line in the low-frequency region. The transfer of charge is manifested as a semicircle in the high-frequency region, and its arc is equivalent to the resistance of charge transfer. It can be seen from the figure that the high-entropy MAX phase material in this embodiment has good charge transfer performance and conductivity.

[0056] Comparative Example 1

[0057] The present invention provides a method for preparing a high entropy MAX phase material, comprising the steps of:

[0058] S201. Ball milling step: mix Ti powder, ZrC powder, HfC powder, V powder, Nb powder, Al powder and C powder in a ratio of 0.4:0.4:0.4:0.4:0.4:1.1:0.2. The ball milling process is: ball-to-material ratio of 15:1, rotation speed of 400 r / min, time of 24 h, and 10 mm silicon nitride balls are used as ball milling media to obtain mixed powder.

[0059] S202, drying step: drying the mixed powder of step S201 under vacuum at 60° C. using a rotary evaporator for 3 hours to obtain a dry powder.

[0060] S203, sieving step: using a standard 92A type vibrating sieving machine and a 200 mesh screen to sieve the dry powder in step S202, the mixed powder after sieving has a powder particle size of 15 μm.

[0061] S204, sintering step: placing the screened mixed powder in a graphite mold and sintering in a vacuum hot-pressing sintering furnace. The sintering method is as follows: evacuating the sintering furnace to below 20 Pa at room temperature, pressurizing it to 30 MPa, heating it from room temperature to 1200°C at a rate of 10°C / min, and then heating it at a rate of 2°C·min -1 The heating rate was increased from 1200℃ to 1400℃, and the temperature was kept for 5h. After the temperature was kept, the pressure and temperature were immediately reduced. The sample was cooled with the furnace, and finally (Ti 0.2 Zr 0.2 Hf 0.2 V 0.2 Nb 0.2 )2AlC ceramic material, that is, high entropy MAX phase material.

[0062] The high entropy MAX phase material prepared in this comparative example was subjected to structural characterization and electrochemical performance testing. Figure 2 This is a scanning electron microscope image of the high entropy MAX phase prepared in this comparative example, which has an obvious layered structure but no fault structure.

[0063] Figure 4 This is the electrochemical impedance test diagram of the high-entropy MAX phase material prepared in this comparative example. It can be seen from the figure that the arc radius of the sample is relatively large, which may be due to the presence of impurity phases in the sample. The image in the low-frequency area is approximately a straight line, indicating that the charge transfer performance and conductivity of the sample are relatively general.

[0064] Comparative Example 2

[0065] The present invention provides a method for preparing a high entropy MAX phase material, comprising the steps of:

[0066] S301, ball milling step: ball mill Ti powder, ZrC powder, HfC powder, V powder, Nb powder, Al powder and C powder in a ratio of 0.4:0.4:0.4:0.4:0.4:1:0.2, the ball milling process is: ball-to-material ratio is 15:1, the rotation speed is 400r / min, the time is 24h, the ball milling medium is 10mm silicon nitride ball, and a mixed powder is obtained.

[0067] S302, drying step: drying the mixed powder of step S301 under vacuum at 60°C using a rotary evaporator for 3 hours to obtain a dry powder.

[0068] S303, sieving step: using a standard 92A type vibrating sieving machine and a 200 mesh screen to sieve the dry powder of step S302, the mixed powder after sieving has a powder particle size of 15 μm.

[0069] S304, sintering step: placing the sieved mixed powder in a graphite mold and sintering in a vacuum hot-pressing sintering furnace. The sintering method is as follows: evacuating the sintering furnace to below 20 Pa at room temperature, pressurizing it to 30 MPa, heating it from room temperature to 1200°C at a rate of 10°C / min, and then heating it at a rate of 2°C·min -1 The heating rate was increased from 1200℃ to 1600℃, and the temperature was kept for 5h. After the temperature was kept, the pressure and temperature were immediately reduced. The sample was cooled with the furnace, and finally (Ti 0.2 Zr 0.2 Hf 0.2 V 0.2 Nb 0.2 )2AlC ceramic material.

[0070] The above examples are used to illustrate the specific implementation of the present invention. However, the protection scope of the present invention is not limited to the above exemplary implementation. Any modification, equivalent substitution, improvement, etc. made by those skilled in the art within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A high entropy MAX phase material, characterized in that: The molecular formula of the high entropy MAX phase material is M2AlC, wherein M is selected from at least three of Ti, Zr, Hf, Nb, Ta and V; preferably selected from Ti, Zr, Hf, Nb and V. Preferably, the molecular formula of the high entropy MAX phase material is (Ti 0.2 Zr 0.2 Hf 0.2 V 0.2 Nb 0.2 )2AlC.

2. A method for preparing the high entropy MAX phase material according to claim 1, characterized in that: The steps include: S1. Mixing the powder containing M, Al powder and C powder uniformly to obtain composite powder; The powder containing M is selected from at least three of Ti powder, ZrC powder, HfC powder, V powder, Nb powder and Ta powder, for example, selected from Ti powder, ZrC powder, HfC powder, V powder and Nb powder; S2. The composite powder is first vacuum hot-pressed, and then sintered at a temperature of 1400° C. to 1700° C. for 4 to 8 hours. After cooling, a high-entropy MAX phase ceramic material is obtained.

3. The method for preparing a high entropy MAX phase material according to claim 2, characterized in that: The molar ratio of the Ti powder, ZrC powder, HfC powder, V powder, Nb powder, Al powder and C powder is 0.35-0.45):(0.35-0.45):(0.35-0.45):(0.35-0.45):(0.35-0.45):1.1:(0.15-0.25).

4. The method for preparing a high entropy MAX phase material according to claim 2, characterized in that: In step S1, the mixing includes uniformly mixing the powder containing M, Al powder and C powder by ball milling.

5. The method for preparing the high entropy MAX phase material according to any one of claims 2 to 4, characterized in that: Before step S2, the following steps are also included: drying the ball-milled composite powder and then screening it.

6. The method for preparing a high entropy MAX phase material according to claim 5, characterized in that: The drying comprises the following steps: placing the composite powder at a temperature of 50 to 70° C. and drying it for 1 to 5 hours.

7. The method for preparing a high entropy MAX phase material according to claim 5, characterized in that: The size of the sieve for sieving is 150-250 meshes.

8. The method for preparing a high entropy MAX phase material according to any one of claims 2 to 4, characterized in that: Step S2 specifically includes the following steps: firstly, compressing the composite powder under vacuum, then heating to 1400°C to 1700°C under an inert gas flow and sintering for 4 to 8 hours, and then naturally reducing the pressure and temperature to obtain a high entropy MAX phase ceramic material. Preferably, in step S2, during the pressing process, the applied pressure is 20-40 MPa, and the holding time is 1-15 min.

9. The method for preparing a high entropy MAX phase material according to claim 8, characterized in that: The heating process of sintering includes heating at 5-15°C·min -1 From room temperature to 1200℃, then at 1~5℃·min -1 The heating rate is from 1200℃ to 1600℃.

10. Use of the high entropy MAX phase material according to claim 1 or the high entropy MAX phase material prepared by the method according to any one of claims 2 to 9 in high-power electrical contact, friction and wear, and accident-tolerant nuclear fuel cladding materials, for example, as electromagnetic shielding materials, anti-corrosion materials or high-temperature resistant materials.

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