A transition metal nitride high-entropy ceramic material and a method of making the same

Abstract

This invention discloses a high-entropy transition metal nitride ceramic material and its preparation method. The preparation method includes the following steps: mixing n kinds of transition metal nitride powders and m kinds of transition metal powders, vacuum drying to obtain a precursor; placing the precursor in a mold and performing pre-pressing treatment to obtain a pre-pressed sample; sintering the pre-pressed sample in a sealed environment at a temperature of 500–3500℃ and a pressure of 2–28 GPa to obtain the high-entropy transition metal nitride ceramic material; wherein n≥1, m≥0, and the total number of transition metal elements in the precursor is four or more. This invention improves the stability of the precursor and reduces the size and distance of particles within the precursor through two pressure treatments, achieving for the first time the synthesis of high-density, high-purity high-entropy transition metal nitride ceramic materials via solid-state reaction.

Description

Technical Field

[0001] This invention relates to the field of high-entropy ceramic materials technology, and particularly to a transition metal nitride high-entropy ceramic material and its preparation method. Background Technology

[0002] High entropy ceramics are considered to be ultra-strong materials with great development potential due to their thermodynamic high entropy effect, structural lattice distortion effect, kinetic hysteresis diffusion effect, and synergistic effect among different atoms. High entropy nitrides (HENs) are ceramic materials containing four or more transition metal elements, each accounting for more than 15% of the total, with nitrogen as the non-metallic element. Their chemical formula is in the form (ABCD…)N, where A, B, C, D… are metallic elements. Similar to high entropy carbides (HECs), the diversity of metallic elements provides HENs with rich and varied design conditions. However, due to their different electronic structures, HENs possess better electrical properties than HECs.

[0003] However, precursor materials for HENs generally exhibit low thermal stability. For example, VN begins to decompose to produce nitrogen gas at 400°C under normal pressure, and TiN begins to decompose to form non-stoichiometric TiN at approximately 1400°C under normal pressure. x Furthermore, in oxygen-containing environments, these decomposition phenomena can lead to the combination of metal atoms with oxygen, resulting in transition metal oxide impurities within the HENs bulk. Therefore, it is difficult to prepare HENs materials using traditional ceramic material preparation methods. Moreover, existing technologies employing chemical reaction synthesis and pressureless / low-pressure sintering methods cannot synthesize high-density, high-purity HENs materials; they can only synthesize cubic-phase HENs materials.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a transition metal nitride high-entropy ceramic material and its preparation method, aiming to solve the problem that the prior art cannot prepare high-density, high-purity transition metal nitride high-entropy ceramic materials.

[0006] The technical solution of the present invention is as follows:

[0007] A first aspect of the present invention provides a method for preparing a high-entropy transition metal nitride ceramic material, comprising the steps of:

[0008] The precursor is obtained by mixing n kinds of transition metal nitride powder and m kinds of transition metal powder and drying under vacuum.

[0009] The precursor is placed in a mold and pre-compressed to obtain a pre-compressed sample;

[0010] In a closed environment, the pre-compressed sample was sintered at a temperature of 500–3500℃ and a pressure of 2–28 GPa to obtain a transition metal nitride high-entropy ceramic material.

[0011] Where n≥1, m≥0, and the total number of transition metal elements in the precursor is four or more.

[0012] Optionally, the transition metal nitride powder is selected from zirconium nitride, titanium nitride, niobium nitride, hafnium nitride, molybdenum nitride, tantalum nitride, tungsten nitride, chromium nitride, vanadium nitride, or aluminum nitride.

[0013] Optionally, the transition metal powder is selected from zirconium, titanium, niobium, hafnium, molybdenum, tantalum, tungsten, chromium, vanadium, or aluminum.

[0014] Optionally, the size of the transition metal nitride powder is 5–50 μm.

[0015] Optionally, the density of the pre-compressed sample is 70-90%.

[0016] Optionally, the vacuum drying temperature is 50–150°C, and the time is 8–16 hours.

[0017] Optionally, the temperature of the pre-compression treatment is 10–30°C, and the pressure inside the mold is 2–4 GPa.

[0018] Optionally, the sintering process takes 5 to 120 minutes.

[0019] Optionally, the sintering process specifically includes the processes of pressurizing, heating, holding, cooling, and depressurizing.

[0020] Optionally, in the sintering process, the pressure increase rate is 1 to 2 GPa / h.

[0021] Optionally, in the sintering process, the heating rate is 40–80 °C / min.

[0022] Optionally, in the sintering process, the holding time is 20 to 40 minutes.

[0023] Optionally, in the sintering process, the cooling rate is 80–120 °C / min.

[0024] Optionally, in the sintering process, the pressure reduction rate is 0.5 to 1 GPa / h.

[0025] In a second aspect, the present invention provides a high-entropy transition metal nitride ceramic material, which is prepared by the preparation method described in the first aspect.

[0026] Beneficial Effects: This invention provides a method for preparing high-entropy transition metal nitride ceramic materials. Through two pressure treatments, the stability of the precursor is improved, and the size and distance of particles within the precursor are reduced. For the first time, high-density, high-purity high-entropy transition metal nitride ceramic materials are synthesized via solid-state reaction. This preparation method is simple to operate and has a stronger nitrogen-retaining effect. It also allows for a wider range of element ratio adjustments and can synthesize various high-entropy transition metal nitride ceramic materials. By controlling the pressure, temperature, and time during the preparation process, high-entropy transition metal nitride ceramic materials with different crystal structures can also be synthesized, particularly the hexagonal phase, which cannot be synthesized using traditional pressureless / low-pressure sintering techniques. Attached Figure Description

[0027] Figure 1 These are simulation diagrams of HENs with different crystal structures synthesized under different conditions; in the diagram, black represents nitrogen atoms, and colored represents different kinds of transition metal atoms, with lattice distortion ignored in the simulation.

[0028] Figure 2 This is the XRD pattern of (HfNbTaTi)N HENs from Embodiment 1 of the present invention.

[0029] Figure 3 This is the XRD pattern of (VNbTaTi)N HENs in Embodiment 2 of the present invention.

[0030] Figure 4 This is the XRD pattern of (VNbTaTi)N HENs in Embodiment 3 of the present invention.

[0031] Figure 5 It is (VNbTaTi)N in Embodiment 4 of the present invention. 0.75 XRD patterns of HENs.

[0032] Figure 6 It is (VNbTaTi)N in Embodiment 4 of the present invention. 0.75 Scanning electron microscope images and elemental analysis diagrams of HENs. Detailed Implementation

[0033] This invention provides a high-entropy transition metal nitride ceramic material and its preparation method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0034] This invention provides a method for preparing high-entropy transition metal nitride ceramic materials, comprising the following steps:

[0035] The precursor is obtained by mixing n kinds of transition metal nitride powder and m kinds of transition metal powder and drying under vacuum.

[0036] The precursor is placed in a mold and pre-compressed to obtain a pre-compressed sample;

[0037] In a closed environment, the pre-compressed sample was sintered at a temperature of 500–3500℃ and a pressure of 2–28 GPa to obtain a transition metal nitride high-entropy ceramic material.

[0038] Where n≥1, m≥0, and the total number of transition metal elements in the precursor is four or more.

[0039] Specifically, in this invention, the density of the precursor is first improved by pre-compression treatment, reducing oxygen and other impurities in the precursor; then, the granular pre-compressed sample is broken or yielded under high pressure by high pressure treatment, thereby reducing the particle size and interparticle porosity and improving the density; then, with the increase of temperature, the granular pre-compressed sample is sintered into a high-density transition metal nitride high-entropy ceramic material.

[0040] Unlike traditional synthesis methods, the high-pressure environment of the high-temperature, high-pressure synthesis method can significantly improve the stability of precursors and reduce their decomposition or deterioration, thereby synthesizing high-purity, high-density nitride ceramics under high temperature and pressure. Furthermore, compared to traditional micron-crystalline materials, the particles in the pre-pressed samples under high pressure tend to fracture to the nanoscale, exhibiting a Hall-Petch Effect and displaying superior mechanical properties and thermal stability. Utilizing the thermodynamic effect of high pressure suppressing grain growth, and by controlling thermodynamic parameters such as pressure, temperature, and chemical composition, nano / micron-structured transition metal nitride high-entropy ceramic materials can be prepared, showing broad application prospects.

[0041] In one embodiment, the transition metal nitride powder is selected from zirconium nitride (ZrN), titanium nitride (TiN), niobium nitride (NbN), hafnium nitride (HfN), molybdenum nitride (MoN), tantalum nitride (TaN), tungsten nitride (W2N), chromium nitride (CrN), vanadium nitride (VN), or aluminum nitride (AlN).

[0042] In one embodiment, the transition metal powder is selected from zirconium (Zr), titanium (Ti), niobium (Nb), hafnium (Hf), molybdenum (Mo), tantalum (Ta), tungsten (W), chromium (Cr), vanadium (V), or aluminum (Al).

[0043] In one embodiment, the size of the transition metal nitride powder is 5 to 50 μm.

[0044] In one embodiment, the density of the pre-compressed sample is 70-90%.

[0045] In one embodiment, the vacuum drying temperature is 50–150°C and the time is 8–16 hours.

[0046] In one embodiment, the temperature of the pre-compression treatment is 10–30°C, and the pressure inside the mold is 2–4 GPa.

[0047] In one embodiment, the sintering process takes 5 to 120 minutes.

[0048] In one embodiment, the sintering process specifically includes the processes of pressurizing, heating, holding, cooling, and depressurizing.

[0049] In one embodiment, the pressure increase rate during the sintering process is 1 to 2 GPa / h.

[0050] In one embodiment, the heating rate during the sintering process is 40–80 °C / min.

[0051] In one embodiment, the holding time during the sintering process is 20 to 40 minutes.

[0052] In one embodiment, during the sintering process, the cooling rate is 80–120 °C / min.

[0053] In one embodiment, during the sintering process, the rate of pressure reduction is 0.5 to 1 GPa / h.

[0054] In one embodiment, the instrument used for the sintering process is a large-cavity press, such as a KAWAI type large-cavity press, a DIA type large-cavity press, or a hinged six-sided top large-cavity press.

[0055] This invention provides a transition metal nitride high-entropy ceramic material, which is prepared using the preparation method described above.

[0056] In one embodiment, the chemical formula of the transition metal nitride high-entropy ceramic material is selected from (VNbTaTi)N x 、(HfNbTaTiZr)N x (AlNbTaTi)N x 、(AlVNbTaTi)N x 、(VNbTaTiZr)N x and (VNbTaTiHf)N x One of them; where 0.5 < x ≤ 1.

[0057] In one embodiment, the transition metal nitride high-entropy ceramic material is a face-centered cubic phase and / or a hexagonal phase.

[0058] Specifically, by controlling and optimizing thermodynamic and kinetic parameters such as pressure, temperature, composition, and holding time (PTXt), high-entropy transition metal nitride ceramic materials with different crystal structures can be prepared. When the sintering conditions are pressure P = 2–5 GPa, temperature T = 500–2500 °C, and time t = 5–120 min, a face-centered cubic phase (Fm-3m 225) high-entropy transition metal nitride ceramic material is prepared; when the sintering conditions are pressure P = 5–28 GPa, temperature T = 500–3000 °C, and time t = 1–120 min, a hexagonal phase (P-6m2 187 or P63 / mmc 194) high-entropy transition metal nitride ceramic material is prepared.

[0059] In one embodiment, the Vickers hardness of the transition metal nitride high-entropy ceramic material is 14–60 GPa.

[0060] In one embodiment, the fracture toughness of the transition metal nitride high-entropy ceramic material is 4–7 MPa m. 1 / 2 .

[0061] The present invention will be further described below through specific embodiments.

[0062] In the following examples, HfN, NbN, TiN, TaN, VN, Ti and other materials are all commercially available products.

[0063] Example 1

[0064] Transition metal nitride powders (HfN, NbN, TiN, TaN, 5–10 μm) were weighed at a molar ratio of 1:1:1:1 and then uniformly mixed in a three-dimensional mixer for 24 hours. The thoroughly mixed powder was placed in a vacuum drying oven and dried at a vacuum of 0.0001 MPa and 110°C for 12 hours to remove moisture or other impurities, yielding the precursor, which was then sealed.

[0065] According to the sample cavity size of the DIA-type large cavity press and the minimum pre-compression density of 70%, weigh an appropriate amount of precursor and load it into a pre-compression mold with a diameter of 3.5 mm. Use a hydraulic tablet press for pre-compression. The pre-compression oil pressure is 5 MPa, the actual pressure inside the mold is 2.16 GPa, and the actual density of the pre-compressed sample is 72.7%.

[0066] The pre-compressed sample was loaded into a high-temperature, high-pressure assembly using pyrophyllite as the pressure-transmitting medium, ZrO2 as the thermal insulation material, and rhenium metal as the heating electrode. The pressure was increased to 4 GPa at a rate of 2 GPa / h, then heated to 1800 °C at a rate of 60 °C / min and held for 30 min. The temperature was then reduced to room temperature at a rate of 100 °C / min. After cooling, the pressure was reduced to atmospheric pressure at a rate of 1 GPa / h, yielding a transition metal nitride high-entropy ceramic material, denoted as (HfNbTaTi)N HENs.

[0067] The XRD pattern of (HfNbTaTi)N HENs in this embodiment is as follows: Figure 2 As shown. By Figure 2 It can be seen that (HfNbTaTi)NHENs are generally face-centered cubic (FCC) single-phase with a density as high as 96.5%, and the small amount of oxide impurities originate from the metal oxide impurities in the HfN precursor. The Vickers hardness of (HfNbTaTi)NHENs in this embodiment is 14.8 (4) GPa, and the fracture toughness is 6.6 (2) MPa m. 1 / 2 This indicates that solid-state reactions under high temperature and high pressure can achieve the preparation of bulk HENs materials.

[0068] Example 2

[0069] Transition metal nitride powders (VN, NbN, TaN, TiN, 5–10 μm) were weighed at a molar ratio of 1:1:1:1 and then uniformly mixed in a three-dimensional mixer for 24 hours. The thoroughly mixed powder was placed in a vacuum drying oven and dried at a vacuum of 0.0001 MPa and 110°C for 12 hours to remove moisture or other impurities, yielding the precursor, which was then sealed.

[0070] According to the sample cavity size of the DIA-type large cavity press and the minimum pre-compression density of 70%, weigh an appropriate amount of precursor and load it into a pre-compression mold with a diameter of 3.5 mm. Use a hydraulic tablet press for pre-compression. The pre-compression oil pressure is 5 MPa, the actual pressure inside the mold is 2.16 GPa, and the actual density of the pre-compressed sample is 75%.

[0071] The pre-compressed sample was loaded into a high-temperature, high-pressure assembly using pyrophyllite as the pressure-transmitting medium, ZrO2 as the thermal insulation material, and rhenium metal as the heating electrode. The pressure was increased to 4 GPa at a rate of 2 GPa / h, then heated to 1500 °C at a rate of 60 °C / min and held for 30 min. The temperature was then reduced to room temperature at a rate of 100 °C / min. After cooling, the pressure was reduced to atmospheric pressure at a rate of 1 GPa / h, yielding a transition metal nitride high-entropy ceramic material, denoted as (VNbTaTi)N HENs.

[0072] The XRD pattern of (VNbTaTi)N HENs in this embodiment is as follows: Figure 3 As shown. By Figure 3 It can be seen that (VNbTaTi)N HENs are generally FCC single-phase with a density as high as 97.3%. Tests showed that the Vickers hardness of (VNbTaTi)N HENs in this embodiment was 18.8 (3) GPa, and the fracture toughness was 4.6 (6) MPa m. 1 / 2 .

[0073] Example 3

[0074] Transition metal nitride powders (VN, NbN, TaN, TiN, 5–10 μm) were weighed at a molar ratio of 1:1:1:1 and then uniformly mixed in a three-dimensional mixer for 24 hours. The thoroughly mixed powder was placed in a vacuum drying oven and dried at a vacuum of 0.0001 MPa and 110°C for 12 hours to remove moisture or other impurities, yielding the precursor, which was then sealed.

[0075] According to the sample cavity size of the KAWAI large-cavity press and the minimum pre-compression density of 70%, weigh an appropriate amount of precursor and load it into a pre-compression mold with a diameter of 3.0 mm. Use a hydraulic tablet press for pre-compression. The pre-compression oil pressure is 5 MPa, the actual pressure inside the mold is 2.94 GPa, and the actual density of the pre-compressed sample is 74.5%.

[0076] The pre-compressed sample was loaded into a high-temperature, high-pressure assembly using MgO as the pressure-transmitting medium, ZrO2 as the thermal insulation material, and rhenium metal as the heating electrode. The pressure was increased to 15 GPa at a rate of 1.5 GPa / h, then heated to 1500 °C at a rate of 60 °C / min and held for 30 min. The temperature was then reduced to room temperature at a rate of 100 °C / min. After cooling, the pressure was reduced to atmospheric pressure at a rate of 1 GPa / h, yielding a transition metal nitride high-entropy ceramic material, denoted as (VNbTaTi)N HENs.

[0077] The XRD pattern of (VNbTaTi)N HENs in this embodiment is as follows: Figure 4 As shown. By Figure 3 and 4It can be seen that, compared with the (VNbTaTi)N HENs of Example 2, under the same temperature and higher pressure conditions, the (VNbTaTi)N HENs of this example did not exhibit a single FCC phase, but rather appeared together with a hexagonal phase. This indicates that HENs with different spatial structures can be prepared under different pressure conditions. Hexagonal pure phase HENs can be synthesized at pressures above 15 GPa. Due to the different structure, this novel HEN has stronger mechanical properties. Testing showed that the Vickers hardness of the (HfNbTaTi)N HENs of this example reached 58.6 (8) GPa, making it a novel superhard material.

[0078] Example 4

[0079] Transition metal nitride powders (VN, NbN, TaN, 5–10 μm) and metallic Ti powder (~48 μm) were weighed at a molar ratio of 1:1:1:1 and then uniformly mixed in a three-dimensional mixer for 24 hours. The thoroughly mixed powder was placed in a vacuum drying oven and dried at a vacuum of 0.0001 MPa and 50°C for 12 hours to remove moisture or other impurities, yielding the precursor, which was then sealed.

[0080] According to the sample cavity size of the KAWAI large-cavity press and the minimum pre-compression density of 70%, weigh an appropriate amount of precursor and load it into a pre-compression mold with a diameter of 3.0 mm. Use a hydraulic tablet press for pre-compression. The pre-compression oil pressure is 5 MPa, the actual pressure inside the mold is 2.94 GPa, and the actual density of the pre-compressed sample is 75%.

[0081] The pre-compressed sample was loaded into a high-temperature, high-pressure assembly using MgO as the pressure-transmitting medium, ZrO2 as the thermal insulation material, and rhenium metal as the heating electrode. The pressure was increased to 4 GPa at a rate of 1.0 GPa / h, then heated to 1900 °C at a rate of 60 °C / min and held for 30 min. The temperature was then reduced to room temperature at a rate of 100 °C / min. After cooling, the pressure was reduced to atmospheric pressure at a rate of 1 GPa / h, yielding a high-entropy transition metal nitride ceramic material containing 25% nitrogen vacancies, denoted as (VNbTaTi)N. 0.75 HENs.

[0082] In this embodiment, (VNbTaTi)N 0.75 The XRD patterns of HENs are as follows Figure 5 As shown. By Figure 5 It can be seen that (VNbTaTi)N 0.75 HENs are generally FCC single-phase. The (VNbTaTi)N in this embodiment... 0.75 The scanning electron microscopy and elemental analysis results of HENs are as follows: Figure 6 As shown. By Figure 6 It can be seen that (VNbTaTi)N0.75 The nitrogen content of HENs is about 71% (nitrogen is a light element, and the measured content is usually lower than the actual value), which is almost consistent with the theoretical value. This means that this method of synthesizing HENs at high temperature and high pressure has a stronger nitrogen retention capacity than the general low pressure or atmospheric pressure method.

[0083] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a high-entropy transition metal nitride ceramic material, characterized in that, Including the following steps: The n kinds of transition metal nitride powders and m kinds of transition metal powders are mixed and dried under vacuum to obtain the precursor. The precursor is placed in a mold and pre-compressed to obtain a pre-compressed sample; In a sealed environment, the pre-compressed sample was sintered at a temperature of 1500~3500℃ and a pressure of 4GPa~28GPa to obtain a high-entropy transition metal nitride ceramic material. Wherein, n≥1, m≥0, and the total number of transition metal elements in the precursor is four or more; The pre-compression treatment temperature is 10~30℃, and the pressure inside the mold is 2~4GPa.

2. The method for preparing high-entropy transition metal nitride ceramic materials according to claim 1, characterized in that, The transition metal nitride powder is selected from zirconium nitride, titanium nitride, niobium nitride, hafnium nitride, molybdenum nitride, tantalum nitride, tungsten nitride, chromium nitride, vanadium nitride, or aluminum nitride; And / or, the transition metal powder is selected from zirconium, titanium, niobium, hafnium, molybdenum, tantalum, tungsten, chromium, vanadium or aluminum.

3. The method for preparing high-entropy transition metal nitride ceramic materials according to claim 1, characterized in that, The size of the transition metal nitride powder is 5~10 μm.

4. The method for preparing high-entropy transition metal nitride ceramic materials according to claim 1, characterized in that, The density of the pre-compressed sample is 70-90%.

5. The method for preparing high-entropy transition metal nitride ceramic materials according to claim 1, characterized in that, The vacuum drying temperature is 50~150℃, and the time is 8~16h.

6. The method for preparing high-entropy transition metal nitride ceramic materials according to claim 1, characterized in that, The sintering process takes 5 to 120 minutes.

7. The method for preparing high-entropy transition metal nitride ceramic materials according to claim 1, characterized in that, The sintering process specifically includes the processes of increasing pressure, increasing temperature, holding temperature, decreasing temperature, and decreasing pressure.

8. The method for preparing high-entropy transition metal nitride ceramic materials according to claim 7, characterized in that, The rate of pressurization is 1~2 GPa / h; and / or the rate of heating is 40~80℃ / min; and / or the holding time is 20~40min; and / or the rate of cooling is 80~120℃ / min; and / or the rate of depressurization is 0.5~1 GPa / h.

9. A high-entropy transition metal nitride ceramic material, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.

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