Medium-entropy MAX materials, medium-entropy MXene materials, their synthesis methods and applications

Abstract

This invention discloses a method for synthesizing medium-entropy MAX materials. The method synthesizes medium-entropy MAX materials with configuration number n' by using an initial raw material ratio of configuration number n' and coordinating thermodynamic parameters during sintering, where n' is not equal to n. The method provided by this invention induces a configurational transformation of medium-entropy MAX crystals containing target transition metal elements by synergistically altering thermodynamic conditions through raw material ratio, time, and / or temperature. This allows for the synthesis of potential configurations or medium-entropy MAX and medium-entropy MXene materials that are theoretically difficult to synthesize. Simultaneously, the prepared medium-entropy MXene materials exhibit stable atomic layers but significant lattice distortion, and the increased conformational entropy leads to highly dispersed metal components. These medium-entropy MXene materials have application potential in supercapacitors, batteries, catalysis, electromagnetic shielding, and microwave absorbing materials; and they also have broad application prospects in flexible energy storage devices, electromagnetic shielding, and water treatment.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology, specifically relating to a medium-entropy MAX material, a medium-entropy MXene material, their synthesis methods and applications. Background Art

[0002] Medium-entropy materials possess highly diverse structures, tailored compositions, and unexpected physical and chemical properties, making them suitable for a wide range of applications in energy storage and conversion. Increasing entropy is a material synthesis strategy: in some cases, the addition of different elements leads to an increase in conformational entropy greater than the increase in enthalpy, resulting in a decrease in Gibbs free energy and stability of the crystal structure. In recent years, some high-entropy transition metal carbides in two-dimensional crystals with significant lattice distortion, highly dispersed metallic compositions, and exposed active sites have exhibited superior electrochemical properties in energy storage and conversion.

[0003] MXenes (M n+1 X n T x MAX(M) materials, as novel two-dimensional transition metal carbides and / or nitrides, constitute a large and young family. Recently, top-down material preparation methods have provided a way to selectively etch precursors MAX(M) n+1 AX n The chance of synthesizing MXenes from the A atom layer (groups 13-16) of ) is discussed. The article Science Bulletin, 2023, 68, 1735 points out many publicly disclosed medium-to-high entropy MAX materials, such as the carbides TiVNbMoAlC3 and TiVCrMoAlC3 reported in ACS Nano, 2021, 15(8), 12815, and the high-entropy carbon compound (TiVNbMoAlC3) disclosed in patent CN115745018A. 0.2 Nb 0.2 Ta 0.2 Zr 0.2 V 0.2 By etching the A component of 2AlC, etc., medium-to-high entropy MXene two-dimensional materials were further synthesized, such as: TiVNbMoC3, TiVCrMoC3, (Ti 0.2 Nb 0.2 Ta 0.2 Zr 0.2 V 0.2 )2CT xAnd so on. Size-compatible transition metal elements stabilize MXenes within atomic layers, resulting in medium-to-high entropy MXenes exhibiting significant lattice distortion, leading to high mechanical strain within atomic layers and potentially unexpected properties worthy of further exploration. This article also identifies some potential but difficult-to-synthesize medium-entropy MAX materials and some unsynthesize medium-entropy MXene materials, including medium-entropy MAX materials containing Ti, V, Cr, and Nb with a configuration number n1 = 4, and their MXene materials. Therefore, it is worthwhile to investigate an effective synthetic method to prepare precursor MAX materials with target configurations under the constraint of target elements, thereby obtaining potential medium-entropy MXene materials and their thin film materials. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, the main objective of this invention is to provide a method for synthesizing medium-entropy MAX materials. This method induces a configurational transformation of medium-entropy MAX crystals containing a target transition metal element by synergistically altering thermodynamic conditions through raw material ratios, time, and temperature, thereby synthesizing medium-entropy MAX materials and medium-entropy MXene materials with potential configurations. This objective is achieved through the following technical solutions:

[0005] In a first aspect, there is a method for synthesizing a medium-entropy MAX material, wherein the method synthesizes a medium-entropy MAX material with configuration number n by using an initial raw material ratio of configuration number n' and coordinating thermodynamic parameters during sintering, wherein n' is not equal to n.

[0006] In some specific implementation schemes, when the initial raw material ratio n1' = 2, the thermodynamic parameters are optimized to synthesize a medium-entropy MAX material with a configuration number n1 = 4; when the initial raw material ratio n2' = 3, the thermodynamic parameters are optimized to synthesize a medium-entropy MAX material with a configuration number n2 = 2; and when the initial raw material ratio n3' = 4, the thermodynamic parameters are optimized to synthesize a medium-entropy MAX material with a configuration number n3 = 3.

[0007] Among them, the medium-entropy MAX material with configuration number n1=4 is a medium-entropy MAX material that is predicted by theoretical calculations to be difficult to synthesize simply;

[0008] In some specific implementations, the thermodynamic parameters include the holding temperature and holding time in an inert gas or vacuum environment, wherein the holding temperature is 1400-1600℃ and the holding time is 2h-10h.

[0009] In some specific implementations, the required amount of each element raw material is determined according to the initial element stoichiometric ratio of configuration number n1' = 2, and the medium entropy MAX material with configuration number n1 = 4 can be optimally synthesized by holding at 1500℃ for 8 hours.

[0010] The required amount of each element raw material was determined according to the initial element stoichiometric ratio of configuration number n2'=3. The medium entropy MAX material with configuration number n2=2 can be optimally synthesized by holding at 1500℃ for 4h.

[0011] The required amount of each element raw material was determined according to the initial element stoichiometric ratio of configuration number n3' = 4. The medium entropy MAX material with configuration number n3 = 3 can be optimally synthesized by holding at 1500℃ for 4 hours and then holding at 1600℃ for 2 hours.

[0012] The method for synthesizing medium-entropy MAX materials provided by this invention is based on the applicant's discovery during experiments that optimizing thermodynamic competition strategies can synthesize medium-entropy MAX materials and medium-entropy MXene materials with various configurations.

[0013] Secondly, the present invention also aims to provide a medium-entropy MAX material, which is composed of elements M, A, and X, and has the general chemical formula M. n+1 AX n M is at least four elements selected from scandium, yttrium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, and the lanthanides; A is aluminum; X is carbon; and n is the configuration number.

[0014] In some specific embodiments, M is titanium, vanadium, chromium, or niobium.

[0015] In some specific embodiments, the chemical formula of the medium-entropy MAX material with configuration number n1 = 4 is TiVCrNbAlC3; the chemical formula of the medium-entropy MAX material with configuration number n2 = 2 is Ti 0.6 V 0.6 Cr 0.2 Nb 0.6 The chemical formula of the medium-entropy MAX material with configuration number n3 = 3 is Ti. 0.8 V 0.8 Cr 0.6 Nb 0.8 AlC2.

[0016] Furthermore, in the medium-entropy MAX material TiVCrNbAlC3, the four transition metal M elements (titanium, vanadium, chromium, and niobium) are in a solid solution state.

[0017] Thirdly, the present invention also aims to provide a medium-entropy MXene material, comprising the following steps:

[0018] 1) Etching step: After etching component A in the aforementioned medium-entropy MAX material, a multilayer medium-entropy MXene material is obtained;

[0019] 2) Layering step: After further expanding the interlayer spacing of the multilayer medium-entropy MXene material, it is peeled off to obtain a few-layer or single-layer medium-entropy MXene material.

[0020] In some specific embodiments, the etchant used in the etching step is a liquid-phase halide hydride; the intercalating agent used in the layering step is either a liquid-phase tetramethylammonium hydroxide or a tetrabutylammonium hydroxide.

[0021] In some specific embodiments, the intermediate-entropy MXene material has a two-dimensional layered structure. It is composed of M element, X element, and T surface functional groups, wherein the transition metal M element is limited to titanium, vanadium, chromium, and niobium; the T... x Includes one or more of -F, -O, or -OH.

[0022] In some specific implementations, when the configuration number n1 = 4, the chemical formula of the intermediate-entropy MXene material is Ti. 1.1 V 1.1 Cr 0.4 Nb 1.4 C3T x When the configuration number n² = 2, the chemical formula of the medium-entropy MXene material is Ti. 0.6 V 0.6 Cr 0.2 Nb 0.6 CT x T x x in the range is 0-2.

[0023] In some specific implementations, medium-entropy MXene materials are referred to as multilayer medium-entropy MXene materials and few-layer medium-entropy MXene materials based on the difference in interlayer spacing before and after intercalation and stripping.

[0024] Fourthly, the present invention also aims to provide the application of medium-entropy MAX materials in the preparation of self-supporting thin films;

[0025] In some specific embodiments, the self-supporting film is a flexible medium-entropy MXene self-supporting film with a thickness between 15 μm and 25 μm. This flexible medium-entropy MXene self-supporting film has good mechanical properties, flexibility and conductivity, and has broad application prospects in flexible energy storage devices, electromagnetic shielding, water treatment and other fields.

[0026] Compared with the prior art, the present invention has at least the following advantages:

[0027] 1) The method for synthesizing medium-entropy MAX materials provided in this application induces a transformation of the crystal structure of medium-entropy MAX containing the target transition metal element by synergistically changing the thermodynamic conditions through the ratio of raw materials, time, and temperature. This method is used to synthesize medium-entropy MAX and medium-entropy MXene materials with potential structures or those that are difficult to synthesize according to theoretical calculations.

[0028] 2) The medium-entropy MAX material provided in this application has a layered structure, wherein the transition metal element M in the unit cell of the medium-entropy MAX material with configuration number n1=4 is in a solid solution state and is randomly arranged, and it has excellent compressive strength, with an average Vickers hardness of 577.38Hv1000 / 10.

[0029] 3) The medium-entropy MXene material provided in this application has stable atomic layers but significant lattice distortion, and the increase in conformational entropy also leads to high dispersion of metal components; these all endow the medium-entropy MXene two-dimensional material with new properties, and has application potential in supercapacitors, batteries, catalysis, electromagnetic shielding and microwave absorbing materials; and the medium-entropy MXene material has broad application prospects in flexible energy storage devices, electromagnetic shielding, water treatment and other fields. Attached Figure Description

[0030] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below.

[0031] Figure 1 This is a schematic diagram illustrating the synthesis of materials with the maximum medium entropy (MME) of configuration number n using an initial stoichiometric ratio to achieve a configuration number n' (≠ n). It shows the MME materials synthesized under the constraint of Ti, V, Cr, and Nb transition metal elements, based on the value of the configuration number n'.

[0032] Figure 2 The XRD results are for the optimized synthesis of medium-entropy MAX materials with configuration number n1 = 4. The optimized thermodynamic conditions include the holding temperature (a) and holding time (b); it shows that with an initial sizing ratio of configuration number n1' = 2, the medium-entropy TiVCrNbAlC3 MAX can be optimally synthesized by holding at 1500℃ for 8 h.

[0033] Figure 3 These are the XRD results for the optimized synthesis of medium-entropy MAX materials with an optimized configuration number n2 = 2; the optimized thermodynamic condition is the relative proportion of Cr in the initial stoichiometry; it shows that with an initial stoichiometry of n2' = 3, the optimal synthesis of medium-entropy Ti can be achieved by holding at 1500℃ for 4 h. 0.6 V 0.6 Cr 0.2 Nb 0.6 AlC MAX;

[0034] Figure 4 The XRD results show the optimized synthesis of medium-entropy MAX materials with an optimized configuration number n3=3. The optimized thermodynamic conditions include the relative proportion of Cr in the initial stoichiometry (a) and the synergy between holding time and temperature (b). This demonstrates that with an initial stoichiometry number n3'=4, optimal synthesis of medium-entropy Ti can be achieved by holding at 1500℃ for 4 h followed by heating to 1600℃ and holding for 2 h. 0.8 V 0.8 Cr 0.6 Nb 0.8 AlC2 MAX;

[0035] Figure 5 These are SEM images of medium-entropy MAX materials: medium-entropy TiVCrNbAlC3 MAX with configuration number n1=4 (a), and medium-entropy MAX material Ti with configuration number n2=2. 0.6 V 0.6 Cr 0.2 Nb 0.6 AlC(b) and Ti, a medium-entropy MAX material with configuration number n3 = 3. 0.8 V 0.8 Cr 0.6 Nb 0.8 AlC2(c) shows the two-dimensional layered stacked structure of the medium-entropy MAX material.

[0036] Figure 6 This is an AC-STEM image of the medium-entropy MAX material TiVCrNbAlC3. Based on the principle that the atomic brightness is proportional to the atomic radius, it was determined that the transition metal element M in the synthesized medium-entropy MAX material is in a solid solution state and is randomly arranged.

[0037] Figure 7 These are photographs taken of the surface Vickers strength of a medium-entropy MAX material TiVCrNbAlC3 with configuration number n1=4; based on the size of the indentation, the average Vickers hardness can be calculated to be 577.38 Hv1000 / 10.

[0038] Figure 8 These are the XRD patterns of multilayer and few-layer medium-entropy MXene materials corresponding to medium-entropy MAX materials, where (a) is the medium-entropy MAX material TiVCrNbAlC3 and its corresponding medium-entropy MXene material; (b) is the medium-entropy MAX material Ti 0.6 V 0.6 Cr 0.2 Nb 0.6 AlC and its corresponding medium-entropy MXene material; mainly demonstrating how etching and delamination processes increase the interlayer spacing of two-dimensional sheets;

[0039] Figure 9This is an SEM image (a), elemental distribution diagram, and elemental distribution table of a multilayer medium-entropy MXene material with configuration number n1 = 4; the chemical formula of the medium-entropy MXene material was determined to be Ti through calculation. 1.1 V 1.1 Cr 0.4 Nb 1.4 C3T x ;

[0040] Figure 10 This is an SEM image (a), elemental distribution diagram, and elemental distribution table of a multilayer medium-entropy MXene material with a configuration number n² = 2; the chemical formula of the medium-entropy MXene material was determined to be Ti through calculation. 0.6 V 0.6 Cr 0.2 Nb 0.6 CT x ;

[0041] Figure 11 These are SEM images of multilayer medium-entropy MXene material phases (a) and few-layer or monolayer medium-entropy MXene material phases; showing the "accordion" morphology of multilayer medium-entropy MXene material; and also showing the aerogel-like few-layer or monolayer medium-entropy MXene material after vacuum freeze-drying.

[0042] Figure 12 This is an SEM image of a flexible, medium-entropy MXene self-supporting thin film, showing a thickness of 21.46 μm. Detailed Implementation

[0043] The technical solutions of the present invention are illustrated below through specific embodiments. It should be understood that one or more steps mentioned in the present invention do not preclude the existence of other methods and steps before or after the combined steps, or other methods and steps may be inserted between these explicitly mentioned steps. It should also be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Unless otherwise stated, the numbering of each method step is only for the purpose of identifying each method step, and not for limiting the order of each method or limiting the scope of the present invention. Changes or adjustments to their relative relationships, without substantial changes to the technical content, can also be considered as within the scope of the present invention.

[0044] When a quantity, concentration, or other value or parameter is described as a range, preferred range, or preferred upper and lower limits, it should be understood that it is equivalent to specifically disclosing any range by combining any pair of upper or preferred values ​​with any lower or preferred values, regardless of whether the range is specifically disclosed. Unless otherwise stated, the numerical range values ​​listed herein include the endpoints of the range and all integers and fractions within that range.

[0045] Unless otherwise stated, all percentages, parts, ratios, etc. in this document are by weight.

[0046] The materials, methods, and embodiments described herein are exemplary and should not be construed as limiting unless otherwise stated.

[0047] The method for synthesizing medium-entropy MAX materials provided by this invention involves driving the synthesis of medium-entropy MAX materials containing target transition metal elements by changing thermodynamic conditions. The required amounts of each raw material are determined according to the molar ratio of M, A, and X elements in the raw materials as (n'+1):(1.0~2.0):n'. At high temperature, excess Al element can drive further reaction with the MX phase to synthesize MAX. This reduces the yield of the MX phase during the reaction process, thereby effectively improving the purity of MAX. Specifically, the method includes the following steps:

[0048] 1) Raw material ratio: Determine the required amount of each element raw material according to the initial stoichiometric ratio of the configuration number n' (≠n);

[0049] Pure reagent powders of Ti:V:Cr:Nb:Al:C were weighed and prepared in a configuration number n1' = 2 molar ratio; the molar ratio of Cr can be between 0.2 and 0.5, and the molar ratio of Ti, V and Nb needs to be adjusted accordingly to meet the molar ratio of 2:1:1; in this way, TiVCrNbAlC3 medium entropy MAX material with configuration number n1 = 4 was synthesized.

[0050] Pure reagent powders of Ti:V:Cr:Nb:Al:C were weighed and prepared in a molar ratio of configuration number n2' = 3. The molar ratio of Cr can be between 0.3 and 0.75, requiring corresponding adjustments to the molar ratio of Ti, V, and Nb to achieve a 3:1:2 molar ratio. This method was used to synthesize Ti with a configuration number n2 = 2. 0.6 V 0.6 Cr 0.2 Nb 0.6 Materials with maximum entropy in AlC;

[0051] Pure reagent powders of Ti:V:Cr:Nb:Al:C were weighed and prepared in a molar ratio of configuration number n3' = 4. The molar ratio of Cr can be between 0.8 and 1.0, and the molar ratios of Ti, V, and Nb need to be adjusted accordingly to achieve a molar ratio of 4:(1.0–2.0):3. Ti with configuration number n3 = 3 was synthesized in this manner. 0.8 V 0.8 Cr 0.6 Nb 0.8 AlC2 entropy-maximum materials.

[0052] 2) Place the above raw materials into a ball mill for ball milling and mixing. The ball milling speed is 300 rpm and the ball milling time is 24 hours.

[0053] 3) Sintering, specifically:

[0054] Holding temperature: The raw materials are sintered at a relatively high temperature under a protective atmosphere or vacuum; the vertical furnace is heated to 1473K (1200℃) at a rate of 10K / min, and then heated at a rate of 2K / min; the holding temperature can be selected in the range of 1300℃~1600℃; the further preferred temperature is: the effective temperature range is 1500℃~1600℃;

[0055] Holding time: Each raw material is sintered under a protective atmosphere or vacuum at the aforementioned holding temperature; the holding time can be selected in the range of 2h to 10h; a further preferred temperature is: the effective holding time is 4h to 8h;

[0056] Alternatively, a combination of holding temperature and holding time can be used: each raw material is first sintered at a higher temperature under a protective atmosphere or vacuum, and then the temperature is increased by 100°C to continue sintering; the segmented holding temperature can be selected in the range of 1400°C to 1600°C; the segmented holding time for the first and second segments can be selected in the range of 2h to 4h.

[0057] The medium-entropy MAX material synthesized in this application contains the target elements (Ti, V, Cr, Nb) and has the general chemical formula M. n+1 AX n These medium-entropy MAX materials have a stacked layered structure, resembling "terraced fields"; among them, M represents titanium, vanadium, chromium, and niobium; A represents aluminum; and X represents carbon.

[0058] This application also provides a series of medium-entropy MXene materials containing target elements (Ti, V, Cr, Nb), which have a two-dimensional layered structure and are composed of M elements, X elements and T surface functional groups, wherein the M elements are titanium, vanadium, chromium and niobium; X is carbon; and T includes one or more of -F, -O or -OH.

[0059] In addition, the surface functional groups of the medium-entropy MXene material of the present invention give it good hydrophilicity; at the same time, due to the high electronegativity of these end groups, the two-dimensional sheets generate electrostatic repulsion and can exist stably in aqueous solution.

[0060] Example 1

[0061] This embodiment provides a thermodynamic competition-driven strategy, such as... Figure 1 The diagram illustrates the technical characteristics of synthesizing medium-entropy MAX materials containing Ti, V, Cr, and Nb. The thermodynamic conditions to be adjusted include the initial raw material ratio, and / or holding temperature, and / or holding time, or a combination of holding temperature and holding time. Specifically:

[0062] A1) The initial raw material ratio of (Ti:V:Cr:Nb):Al:C = (0.5:0.5:0.5:0.5):1.0:1.0 was used. The raw materials were put into a ball mill for ball milling and mixing at a speed of 300 rpm for 24 h. The medium entropy TiVCrNbAlC3 MAX material with a configuration number n1 = 4 was optimally synthesized by holding it at 1500℃ for 4 h.

[0063] A2) Using an initial raw material ratio of (Ti:V:Cr:Nb):Al:C = (0.9:0.9:0.3:0.9):1.0:2.0), the aforementioned raw materials were placed in a ball mill for mixing at a speed of 300 rpm for 24 hours. Holding at 1500℃ for 4 hours resulted in the optimal synthesis of intermediate-entropy Ti with a configuration number n² = 2. 0.6 V 0.6 Cr 0.2 Nb 0.6 AlC MAX material;

[0064] A3) Using an initial raw material ratio of (Ti:V:Cr:Nb):Al:C = (1.1:1.1:0.7:1.1):2.0:3.0), the aforementioned raw materials were placed in a ball mill for ball milling and mixing at a speed of 300 rpm for 24 hours. The optimal synthesis of intermediate-entropy Ti with a configuration number n3 = 3 was achieved by holding the mixture at 1500℃ for 4 hours followed by holding it at 1600℃ for 2 hours. 0.8 V 0.8 Cr 0.6 Nb 0.8 AlC2 MAX material;

[0065] 2) Grind or ball mill the sintered block of medium entropy MAX material obtained after sintering to obtain powder of medium entropy MAX material.

[0066] This application conducts performance tests on the prepared medium-entropy MAX material, specifically as follows:

[0067] The thermodynamic competition process of the medium-entropy MAX material in A1 during sintering in the range of 1300-1600℃ was analyzed, and the phases were analyzed by X-ray diffraction. Figure 2 a) Comparative results show that temperature changes induce phase transitions during the sintering of the medium-entropy MAX material; when the temperature rises to 1500℃, the volume of the bulk material decreases sharply, while the Vickers hardness increases sharply. After analyzing the spectrum to determine its characteristic peaks, the α-lattice parameters of the medium-entropy MAX are calculated using the Bragg equation. c-lattice parameters are This confirms the existence of the medium-entropy MAX material TiVCrNbAlC3MAX; simultaneously, the target M4AX3 phase completely disappears when the temperature rises to 1600℃; even after generating the M4AX3 phase at 1500℃ for 2 hours, raising the temperature to 1600℃ yields the same result. Therefore, medium-entropy TiVCrNbAlC3MAX exhibits poor thermal stability above 1600℃. In summary, we believe that the M2AX structure can recombine to form a stable M4AX3 phase, which is related to thermodynamic conditions such as the initial raw material ratio, holding time, and holding temperature. The thermodynamic competition process of medium-entropy MAX during sintering at 1500℃ for different holding times was investigated. Figure 2 (b) It was found that holding the temperature for 6-8 hours was beneficial for further generating the target medium-entropy TiVCrNbAlC3MAX material. During the thermodynamically driven process, excess Al combines with Cr-dominant transition metals to form the MA phase, while other transition metals (Ti, V, Nb) combine with C to form the MX phase. Driven by the temperature effect, the MA and MX phases generated in the early stage of sintering, as intermediate phases for synthesizing medium-entropy MAX, underwent further reactions, thereby improving the purity of the product medium-entropy TiVCrNbAlC3MAX material. The above process helped the inventors optimize the synthesis of the potential medium-entropy TiVCrNbAlC3MAX material through thermodynamic competition.

[0068] XRD analysis was performed on the medium-entropy MAX material prepared by A2, and the results are as follows: Figure 3 As shown, Figure 3 The XRD patterns show the sintering results of the medium-entropy MAX material under the influence of the initial stoichiometric ratio. Figure 3 As can be seen, the relative reduction of Cr element is beneficial to enhancing the competition for the maximum entropy of the configuration number n2=2, weakening the competition for the maximum entropy of other configurations, and thus synthesizing pure Ti. 0.6 V 0.6 Cr 0.2 Nb 0.6 AlC MAX material. The intermediate entropy Ti was calculated using the Bragg equation. 0.6 V 0.6 Cr 0.2 Nb 0.6 The lattice parameters of AlC MAX are: c-lattice parameters are

[0069] XRD analysis was performed on the medium-entropy MAX material prepared from A3, and the results are as follows: Figure 4 As shown, Figure 4 The XRD patterns show the sintering results of the medium-entropy MAX material under the synergistic effects of initial composition and temperature; from Figure 4As can be seen from Figure a, combining the above conclusions on the synthesis of medium-entropy MAX materials with configuration numbers n1=4 and n2=2, medium-entropy MAX materials with configuration number n3=3 can be synthesized to a greater extent within an appropriate range for Cr elements. Subsequently, by increasing the temperature to 1600℃, the less stable MAX material with configuration number n1=4 is induced to decompose, thus synthesizing the medium-entropy MAX material Ti. 0.8 V 0.8 Cr 0.6 Nb 0.8 AlC2, results as follows Figure 4 As shown in b, the intermediate entropy Ti is calculated using the Bragg equation. 0.8 V 0.8 Cr 0.6 Nb 0.8 The lattice parameters of AlC2 MAX are: c-lattice parameters are

[0070] By analyzing the medium-entropy MAX materials TiVCrNbAlC3 and Ti obtained from A1, A2, and A3, 0.6 V 0.6 Cr 0.2 Nb 0.6 AlC and Ti 0.8 V 0.8 Cr 0.6 Nb 0.8 The morphological characteristics of AlC2 were used for performance testing, and the results are as follows: Figure 5 , Figure 6 As shown. (Through) Figure 5 SEM images of the MAX material revealed that the medium-entropy MAX material prepared in this application has a stacked layered structure; through... Figure 6 Observation of the MAX material TiVCrNbAlC3 using AC-STEM images revealed that the medium-entropy MAX material prepared in this application is in a solid solution state based on the difference in brightness between atoms. In the MAX unit cell structure, M and X atoms are arranged with α characteristic structures. This indicates that this application synthesized medium-entropy MAX materials with corresponding elements but different configurations during the optimization process, namely TiVCrNbAlC3 and Ti... 0.6 V 0.6 Cr 0.2 Nb 0.6 AlC and Ti 0.8 V 0.8 Cr 0.6 Nb 0.8 AlC2. Therefore, our thermodynamic competition-driven strategy provides a framework for the preparation of MAX materials that cannot be experimentally synthesized using the original molar ratio.

[0071] In addition, this application also tested the strength of the medium-entropy MAX material TiVCrNbAlC3 prepared by A1 using a hardness tester equipped with a diamond indenter with a square angle of 136 degrees. The results are as follows. Figure 7 As shown, calculations show that the block has excellent compressive strength, and its Vickers hardness is 577.38 Hv1000 / 10.

[0072] Example 2

[0073] Based on Example 1, this example provides a method for synthesizing multilayer medium-entropy MXene materials, specifically: the obtained medium-entropy MAX material is reacted with an etchant at a predetermined temperature, so that the etchant selectively etches the A element component in the medium-entropy MAX material to obtain a medium-entropy two-dimensional MXene material.

[0074] Hydrofluoric acid solution and medium-entropy TiVCrNbAlC3 MAX powder were prepared at a ratio of 20 mL / g for etching. The mixed suspension was magnetically stirred at a reaction temperature of 50 °C for 120 h to selectively etch away the Al layer in the medium-entropy MAX powder, with a stirring speed of 1000 rpm. After completion, the process was repeated by centrifugation and washing with water three times until the pH of the washing solution was >6. Then, the final multilayer medium-entropy MXene suspension was filtered and finally placed in an electrically heated constant-temperature vacuum drying oven and vacuum dried at 60 °C for 12 h to obtain the corresponding multilayer medium-entropy MXene material. Therefore, the optimized etching conditions for the medium-entropy MAX material TiVCrNbAlC3 are: hydrofluoric acid concentration 49%, reaction temperature 50 °C, reaction time 120 h, and stirring speed 1000 rpm.

[0075] In addition, the medium-entropy MAX material Ti 0.6 V 0.6 Cr 0.2 Nb 0.6 The etching method for AlC powder is the same as that for medium-entropy TiVCrNbAlC3 MAX powder, with the hydrofluoric acid concentration remaining at 49%, the etching temperature at 50℃, and the etching speed at 1000 rpm. However, because the MX atomic layers of the MAX with a configuration number n² = 2 are thinner, the etching time is shortened to 24 hours, resulting in better acquisition of medium-entropy MXene material Ti. 0.6 V 0.6 Cr 0.2 Nb 0.6 CT x powder.

[0076] In this embodiment, the performance of the prepared medium-entropy MXene material was tested, and the results are as follows:

[0077] This application presents XRD and SEM scans of the prepared medium-entropy MXene material, with results as follows: Figure 8-10As shown. Among them Figure 8 a is the XRD pattern of the medium-entropy MAX material TiVCrNbAlC3 and its corresponding multilayer medium-entropy MXene. As can be seen from the figure, the crystallinity of the product after etching of the medium-entropy MAX material TiVCrNbAlC3 is significantly reduced, the (002) peak becomes the strongest peak of this phase, and its c-lattice parameter expands to... SEM images show that the multilayered intermediate-entropy MXene material exhibits an accordion-like morphology, while also revealing its distinct layered structure. Figure 9 a). From Figure 9 The SEM-EDS spectra not only confirmed that Al elements were completely etched, but also determined the atomic fraction of the synthesized multilayer medium-entropy MXene material; the chemical formula of the medium-entropy MXene material with configuration number n1=4 can be represented as Ti. 1.1 V 1.1 Cr 0.4 Nb 1.4 C3T x Furthermore, F and O elements (-F, -OH, and -O surface functional groups, i.e., T) were also detected in the etched medium-entropy MXene material. x The distribution of these elements is generated by the reaction of the high surface energy MXene transition metal atomic layer with fluoride ions, water and dissolved oxygen in the solution during the etching process.

[0078] The intermediate entropy Ti in this application 1.1 V 1.1 Cr 0.4 Nb 1.4 C3T x MXene materials are difficult to synthesize directly using simple methods. However, they exist according to theoretical predictions and are a member of the two-dimensional medium-entropy transition carbide family. Furthermore, the medium-entropy Ti in this application... 1.1 V 1.1 Cr 0.4 Nb 1.4 C3T x After etching, the MXene material retains the same structure as the medium-entropy TiVCrNbAlC3 MAX precursor. That is, the M atoms in the MX atomic layer are also arranged in a face-centered cubic stack, and the M elements are still in a solid solution state and are randomly arranged.

[0079] in Figure 8 b detected the medium-entropy maximum material Ti using XRD. 0.6 V 0.6 Cr 0.2 Nb 0.6 As can be seen from the figure, the crystallinity of the product after etching is significantly reduced, and because the interlayer spacing after etching is expanded more randomly, the (002) peak is a broad peak. Figure 10 SEM images of layered medium-entropy MXene material (a) show an accordion-like morphology and a distinct layered structure. Furthermore, this application also determined the atomic fraction of the synthesized medium-entropy MXene material using SEM-EDS, as shown in the results. Figure 10 As shown, we can represent the chemical formula of a medium-entropy MXene material with a configuration number n² = 2 as Ti. 0.6 V 0.6 Cr 0.2 Nb 0.6 CT x For this MXene material, the Cr content is already low and the MX atomic layers are already thin. If only Al is extracted during the etching process, a medium-entropy MXene material can be synthesized. However, if over-etching causes M to be extracted, it will lead to the fragmentation of the medium-entropy MXene material, forming M... x C y Phase. Furthermore, F and O elements (-F, -OH, and -O surface functional groups, i.e., T) were also detected in the etched mid-entropy MXene material. x The distribution of the end groups indicates that the surface functional groups of the medium-entropy MXene material give it good hydrophilicity; and due to the high electronegativity of these end groups, the two-dimensional sheets generate electrostatic repulsion and can exist stably in aqueous solution.

[0080] Example 3

[0081] Based on Example 2, this invention also provides a method for preparing few-layer or single-layer medium-entropy MXene materials by intercalating multilayer medium-entropy MXene materials. The method is applicable to both types of multilayer medium-entropy MXene materials in Example 2, and specifically includes:

[0082] Take 0.5g of dried, multilayered, intermediate-entropy MXene powder and add it to a centrifuge tube containing 5ml of 10wt% tetramethylammonium hydroxide (TMAOH) solution. Then, shake by hand for 10 minutes to perform intercalation treatment, allowing the TMA... + Fully insert the material into the interlayer space of the medium-entropy MXene material to expand the interlayer spacing. Then, repeat the centrifugation and washing with water operation 5 times until the pH of the supernatant is <8.

[0083] High-power ultrasound further expands the interlayer spacing of medium-entropy MXene, eventually exfoliating it into stable few-layer or monolayer medium-entropy MXene nanosheets: the washed suspension is poured into a 50mL gas washing bottle and sonicated for 60min under the condition of ensuring the water temperature is below 25℃ and argon bubbling protection.

[0084] The multilayered medium-entropy MXene that could not be fully exfoliated was separated from the exfoliated few-layer or single-layer medium-entropy MXene material by centrifugation: centrifugation at 3500 rpm for 50 min was used to obtain a dispersion of few-layer or single-layer medium-entropy MXene material; the dispersion was then freeze-dried under vacuum to obtain aerogel-like few-layer medium-entropy MXene powder.

[0085] After separating two types of multilayered intermediate-entropy MXene materials, we detected the corresponding few-layer or single-layer intermediate-entropy MXene materials using XRD. Figure 8 a, 8b); As can be seen from the figure, the etched medium-entropy MXene material Ti 1.1 V 1.1 Cr 0.4 Nb 1.4 C3T x The crystallinity of the crystal is significantly reduced, the (002) peak becomes the strongest peak, and its c-lattice parameter is extended to Figure 11 SEM images of a show few-layer or monolayer mesoentropy Ti layers processed by vacuum freeze-drying. 1.1 V 1.1 Cr 0.4 Nb 1.4 C3T x The MXene material powder is in the form of an aerogel. Figure 11 The HRTEM image of b shows the few-layer mesogenous MXene material Ti 1.1 V 1.1 Cr 0.4 Nb 1.4 C3T x The lattice spacing and layering characteristics of the (002) plane. The materials obtained by this process all exhibit a large specific surface area.

[0086] The medium-entropy two-dimensional carbide material disclosed in this application has a stable atomic layer but significant lattice distortion. The increase in conformational entropy also leads to a high dispersion of the metal component, exposing more active sites, thereby endowing the two-dimensional material with new properties and showing potential applications in supercapacitors, batteries, catalysis, electromagnetic shielding and microwave absorbing materials.

[0087] Example 4

[0088] This embodiment provides a self-supporting film, which is a flexible medium-entropy MXene self-supporting film material. It is obtained by direct vacuum filtration of a colloidal dispersion of the few-layer medium-entropy MXene material from Example 3, and its morphology is as follows: Figure 12 As shown, the thickness of the prepared self-supporting film was tested, and the thickness of the flexible medium-entropy MXene self-supporting film was found to be between 15 μm and 25 μm.

[0089] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for synthesizing a medium-entropy MAX material, characterized in that, The synthesis method involves synthesizing a medium-entropy MAX material with configuration number n' using an initial raw material ratio of configuration number n', in conjunction with thermodynamic parameters during sintering, where n' is not equal to n; wherein the thermodynamic parameters include the holding temperature and holding time in an inert gas or vacuum environment, the holding temperature being 1400-1600℃, and the holding time being 2h-10h; the medium-entropy MAX material is composed of elements M, A, and X, and its general chemical formula is M n+1 AX n The M element is titanium, vanadium, chromium, and niobium; A is aluminum; X is carbon; n is the configuration number; the raw material ratio of the entropy MAX material in TiVCrNbAlC3 with configuration number n1=4 is as follows: pure reagent powders of Ti:V:Cr:Nb:Al:C are weighed and prepared in a molar ratio of configuration number n1'=2; the molar ratio of Cr is between 0.2 and 0.5, and the molar ratio of Ti, V, and Nb needs to be adjusted accordingly to meet the molar ratio of 2:1:

1. Or Ti with configuration number n2=2 0.6 V 0.6 Cr 0.2 Nb 0.6 The raw material ratio for AlC entropy MAX material is as follows: pure reagent powders of Ti:V:Cr:Nb:Al:C are weighed and prepared in a configuration number n2' = 3 molar ratio; the molar ratio of Cr is between 0.3 and 0.75, and the molar ratio of Ti, V and Nb needs to be adjusted accordingly to meet the molar ratio of 3:1:

2. Or Ti with configuration number n3=3 0.8 V 0.8 Cr 0.6 Nb 0.8 The raw material ratio for entropy MAX material in AlC2 is as follows: pure reagent powders of Ti:V:Cr:Nb:Al:C are weighed and prepared in a molar ratio of configuration number n3'=4; the molar ratio of Cr is between 0.8 and 1.0, and the molar ratio of Ti, V and Nb needs to be changed accordingly to meet the molar ratio of 4:(1.0~2.0):

3.

2. A medium-entropy MXene material, characterized in that, Includes the following steps: 1) Etching step: After etching the A component in the medium-entropy MAX material prepared by the synthesis method described in claim 1, a multilayer medium-entropy MXene material is obtained; 2) Layering step: After further expanding the interlayer spacing of the multilayer medium-entropy MXene material, it is peeled off to obtain a few-layer or single-layer medium-entropy MXene material.

3. The medium-entropy MXene material according to claim 2, characterized in that, The etching agent used in the etching step is a type of liquid-phase halide hydride; the intercalating agent used in the layering step is either tetramethylammonium hydroxide or tetrabutylammonium hydroxide, both of which are liquid phases.

4. The medium-entropy MXene material according to claim 2 or 3, characterized in that, Its general chemical formula is M n+1 X n T x T x Representing surface functional groups, the T x Includes one or more of -F, -O, or -OH.

5. The medium-entropy MXene material according to claim 2, characterized in that, When the configuration number n1=4, the chemical formula of the intermediate entropy MXene material is Ti. 1.1 V 1.1 Cr 0.4 Nb 1.4 C3T x When the configuration number n² = 2, the chemical formula of the medium-entropy MXene material is Ti. 0.6 V 0.6 Cr 0.2 Nb 0.6 CT x T x x in the range is 0-2.

6. The application of the medium-entropy MXene material according to any one of claims 2-5 in the preparation of batteries, electromagnetic shielding, microwave absorbing materials, flexible energy storage devices, and water treatment.

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