CN112811906A

CN112811906A - Medium-entropy MAX phase material, medium-entropy two-dimensional material and preparation method thereof

Info

Publication number: CN112811906A
Application number: CN202110023870.0A
Authority: CN
Inventors: 杨树斌; 杜志国
Original assignee: Beihang University
Current assignee: Beihang University
Priority date: 2021-01-08
Filing date: 2021-01-08
Publication date: 2021-05-18
Also published as: CN114751750B; CN114751750A

Abstract

The invention discloses a medium-entropy MAX phase material, a medium-entropy two-dimensional material and a preparation method thereof, wherein the chemical general formula of the medium-entropy MAX phase material is M_n+1AX_nThe rare earth element is characterized in that M is selected from three or four transition metal elements and lanthanide elements, wherein M contains at least two transition metal elements or lanthanide elements capable of forming a solid solution; the element A is at least one element selected from VIIB, VIII, IB, IIB, IIIA, IVA, VA and VIA groups; the X element is at least one of carbon, nitrogen, boron or oxygen,nis 1, 2, 3, 4, 5 or 6. The component A in the medium-entropy MAX phase material is etched to obtain a medium-entropy two-dimensional material, and the medium-entropy two-dimensional material can be obtained by introducingThe solid-dissolved multi-element transition metal induces the structure to generate lattice distortion, and optimizes the electronic structure, thereby preparing the medium-entropy MAX phase material and the medium-entropy two-dimensional material which can stably exist in a single phase.

Description

Medium-entropy MAX phase material, medium-entropy two-dimensional material and preparation method thereof

Technical Field

The invention relates to the field of new materials, in particular to a medium-entropy MAX phase material, a medium-entropy two-dimensional material and a preparation method thereof.

Background

The MXene two-dimensional material is obtained by selectively etching the component A from the MAX phase, and the earliest reported method for etching the MAX phase is hydrofluoric acid, and the hydrofluoric acid is adopted to etch Ti₃AlC₂MXene Ti is obtained by etching₃C₂. Because hydrofluoric acid has high toxicity, corrosivity and environmental hazard, researchers develop a hydrochloric acid + fluoride salt system to etch the MAX phase, and successfully prepare a series of MXene. In 2020, yellow professor team of Ningbo Material of Chinese academy of sciences etched MAX phase by molten chloride salt method to obtain a series of MXene such as Cl-Ti containing Cl functional group₃C₂，Cl-Ti₂C and Cl-Ti₃CN, and the like. To date, more than 19 mxenes have included Ti₃C₂，Ti₂C，Nb₂C，Nb₄C₃，Ta₄C₃，Ti₃CN、V₄C₃、(Mo_2/3Y_1/3)₂C and the like are successfully prepared, and a large family of two-dimensional materials is greatly enriched. However, the transition metal element composition in the prepared MXene can only reach binary at most, which greatly limits the development of MXene two-dimensional materials.

The constituent elements of the MXene two-dimensional material are highly dependent on a MAX phase of a precursor thereof, and the molecular formula of the MXene two-dimensional material is M_n+1AX_nN =1, 2 or 3, M refers to a transition metal element including Sc, Y, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, etc.; a mainly means elements of the third, fourth and fifth main groups, such as Al, Ga, In, Tl, Si, Ge, Sn, Pb, etc.; x represents C or N. The MAX phase material, as one of the ceramic materials, has the high mechanical strength and the high thermal conductivity of the ceramic, and also has good electrical conductivity due to the special layered structure, and is widely applied to the electrochemical field. On the other hand, the ceramic material is called cermet because of its properties of corrosion resistance, oxidation resistance and the like. To date, over 155 MAX phases have been reported, most of which are single-component MAX phases (i.e., where M is only one metal element), and the MAX phases of multi-component transition metals in MAX phase materials are still limited to binary partial MAX phases, such as TiNbAlC, Mo₂TiAlC₂，Mo₂Ti₂AlC₂And (W)_2/3Y_1/3)₂And (4) AlC. With the exception that position M, A, X is the MAX phase of the single element, recentlyThe solid solution MAX phase is synthesized by scholars, Hamm et al by Cr₂A small amount of Fe element is introduced into the M position of AlC to synthesize (V)_1–xFe_x)₂The AlC realizes the regulation and control of MAX phase magnetism; zr is synthesized by introducing Bi element into A site by Nechiche₂(Al_0.42Bi_0.58) C; treatment of the X site with Cabioc et al yielded Ti₂AlC_x1-N_x. Furthermore, scholars represented by Liu, Z et al have discovered ordered MAX phases, including out-of-plane ordered MAX phases (o-MAX) and in-plane ordered MAX phases (i-MAX). Although the MAX phase family is numerous, the number of MAX phases has nearly stagnated as the range of possible synthetic MAX phases for monophasic or biphasic is too narrow.

According to the calculation formula of entropy S = RlnN, (S represents entropy, R represents gas mole constant, and N represents metal element number), when N is more than or equal to 3 and less than or equal to 5, namely S is more than or equal to 1.1R and less than or equal to 1.61R, the prepared material is the medium-entropy material. According to theoretical calculation, the Gibbs free energy of the intermediate entropy material is higher, so that the intermediate entropy material is easy to decompose or split phase under a high-temperature condition, and the intermediate entropy material with a single-phase structure cannot be prepared.

Disclosure of Invention

Aiming at the technical problems that the medium-entropy MAX phase material and the medium-entropy two-dimensional material are easy to decompose or split in the preparation process and are difficult to prepare a single phase, the invention provides the medium-entropy MAX phase material with a chemical general formula M_n+1AX_nThe M element is selected from three or four transition metal elements and lanthanide elements, wherein, the M element contains at least two transition metal elements and lanthanide elements which can form solid solution; the element A is at least one element selected from VIIs, VIII, I, II, IIIA, IVA, VA and VIA groups; the X element is at least one of carbon, nitrogen, boron or oxygen, and n is 1, 2, 3, 4, 5 or 6.

In some embodiments, at least two of the M elements, transition metal elements and lanthanides capable of forming solid solutions, include: ti and Nb; and/or, Zr and Ta; and/or, Zr and V; and/or, Pt and Au; and/or, W and Mo.

In some embodiments, a is at least one element of aluminum, gallium, indium, lead, silicon, germanium, tin, and sulfur.

The invention also provides a preparation method of the medium-entropy MAX phase material, which comprises the following steps:

the material preparation step: determining the required amount of raw materials containing the elements according to the stoichiometric ratio of each element in the MAX phase material chemical general formula;

sintering: sintering the raw materials at a preset temperature under a protective atmosphere or a vacuum environment to obtain a medium-entropy MAX phase material; wherein the content of the first and second substances,

the chemical formula of the MAX phase material is M_n+1AX_nThe M element is selected from three or four transition metal elements and lanthanide elements, and the M element contains at least two transition metal elements and lanthanide elements capable of forming solid solution; the element A is at least one element selected from VIIs, VIII, I, II, IIIA, IVA, VA and VIA groups; the X element is at least one of carbon, nitrogen, boron and oxygen elements, and n is 1, 2, 3, 4, 5 or 6.

In some embodiments, in the raw material demand of the blending step, the molar ratio of the M element to the A element to the X element is (n + 1) to (1.05-1.2) to n.

In some embodiments, the sintering temperature in the sintering step is between 800 ℃ and 1500 ℃.

The invention also provides a medium-entropy two-dimensional material with a two-dimensional lamellar structure, and the chemical general formula of the medium-entropy two-dimensional material is M_n+1AX_nThe M element is selected from three or four transition metal elements and lanthanide elements, wherein the M element contains at least two transition metal elements and lanthanide elements capable of forming solid solution, X is at least one of carbon, nitrogen, boron and oxygen, and n is 1, 2, 3, 4, 5 or 6.

In some embodiments, the at least two transition metal elements capable of forming a solid solution include Ti and Nb; and/or, Zr and Ta; and/or, Zr and V; and/or, Pt and Au; and/or, W and Mo.

In some embodiments, the thickness of the two-dimensional lamellar structure is between 1nm and 20 nm.

In some embodiments, the surface of the medium-entropy two-dimensional material containing functional groups comprises: one or more of-F, -Cl, -Br or-I.

The invention also provides a preparation method of the medium-entropy two-dimensional material, which comprises the following steps:

MAX phase preparation: preparing the medium-entropy MAX phase material by adopting the preparation method of the medium-entropy MAX phase material;

etching: and reacting the medium-entropy MAX phase material with an etching agent to enable the etching agent to selectively etch the component A in the MAX, thereby obtaining the medium-entropy two-dimensional material.

In some embodiments, the etchant is a hydrofluoric acid solution, an acid solution + fluoride salt system, or a halogen metal salt.

In some embodiments, the etchant is one or more of a simple halogen, a halogen hydride, and a nitrogen hydride in a gas phase in the etching step.

In some embodiments, the etching reaction temperature in the etching step is between 500 ℃ and 1200 ℃.

The invention also comprises the application of the medium-entropy two-dimensional material in catalysis, sensors, electronic devices, super capacitors, batteries, electromagnetic shielding, wave-absorbing materials or superconducting materials.

The method introduces multi-component transition metal (with different atomic radii and d-orbit electron numbers) capable of being dissolved in the MAX phase material to induce the structure to generate lattice distortion and optimize the electronic structure, so as to prepare the medium-entropy MAX phase material capable of stably existing in a single phase and prepare the medium-entropy two-dimensional material by taking the medium-entropy MAX phase material as a precursor, further expand the types of the MAX phase material and the two-dimensional material, deepen the theoretical research of the medium-entropy material and promote the medium-entropy MAX phase material and the medium-entropy two-dimensional material to be practically applied.

Drawings

FIG. 1 illustrates an example of a medium entropy MAX phase (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂AlC and medium entropy two-dimensional material (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xSEM photograph of (a).

FIG. 2 illustrates an example of a medium entropy MAX phase (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂AlC and medium entropy two-dimensional material (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xXRD spectrum of (1).

FIG. 3 illustrates an example of a medium entropy MAX phase (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂XRD patterns of AlC and TiNbAlC.

FIG. 4 Medium entropy two dimensional Material (Ti) in an embodiment of the invention_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xSTEM photograph (a) and atomic distribution maps (b to h) of (A).

FIG. 5 Medium entropy two dimensional Material (Ti) in an embodiment of the invention_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xThe ATM photograph and the thickness analysis chart (b) of (a).

FIG. 6 illustrates a medium entropy MAX phase (Ti) in another embodiment of the present invention_0.25Nb_0.25Ta_0.25Zr_0.25)₂AlC and medium entropy two-dimensional material (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xSEM photograph of (a).

FIG. 7 Medium entropy MAX phase (Ti) in another embodiment of the present invention_0.25Nb_0.25Ta_0.25Zr_0.25)₂AlC and medium entropy two-dimensional material (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xXRD spectrum of (1).

FIG. 8 Medium entropy two dimensional Material (Ti) in another embodiment of the invention_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xThe HRTEM photograph of (A).

FIG. 9 Medium entropy two dimensional Material (Ti) in another embodiment of the invention_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xSTEM photograph (a) and atom distributionFIGS. b to g.

FIG. 10 Medium entropy two dimensional Material (Ti) in another embodiment of the invention_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xThe ATM photograph and the thickness analysis chart (b) of (a).

FIG. 11 illustrates a medium entropy two-dimensional material (TiNbFe)₂And C is a schematic atomic structure diagram.

Detailed Description

The technical solution of the present invention will be described below by way of specific examples. It is to be understood that one or more of the steps mentioned in the present invention does not exclude the presence of other methods or steps before or after the combined steps, or that other methods or steps may be inserted between the explicitly mentioned steps. It should also be understood that these examples are intended only to illustrate the invention and are not intended to limit the scope of the invention. Unless otherwise indicated, the numbering of the method steps is only for the purpose of identifying the method steps, and is not intended to limit the arrangement order of each method or the scope of the implementation of the present invention, and changes or modifications of the relative relationship thereof may be regarded as the scope of the implementation of the present invention without substantial technical change.

The raw materials and apparatuses used in the examples are not particularly limited in their sources, and may be purchased from the market or prepared according to a conventional method well known to those skilled in the art.

Example 1

This example provides a medium entropy MAX phase material with a chemical formula of M_n+1AX_nThe M element is selected from three or four transition metal elements and lanthanide elements, wherein, the M element contains at least two transition metal elements or lanthanide elements capable of forming solid solution; a is at least one element selected from VIIB, VIII, IB, IIB, IIIA, IVA, VA and VIA groups; x is at least one of carbon, nitrogen, boron or oxygen,n1, 2, 3, 4, 5 or 6, corresponding to the "211" configuration, "312" configuration, "413" configuration, "514" configuration, "615" configuration and "716" configuration MAX, respectively.

Wherein the M transition metal element is selected from the group consisting of group IIIB, IVB, VB, VIB, VIIB, VIII, IB, IIB elements, typically the M elements include but are not limited to: scandium, three or four of yttrium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, and lanthanoids (lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, or lutetium); the a elements include, but are not limited to: one or more of aluminum, silicon, phosphorus, sulfur, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, arsenic, selenium, ruthenium, rhodium, palladium, cadmium, indium, tin, antimony, osmium, iridium, platinum, gold, mercury, thallium, lead, bismuth, polonium, or astatine; wherein, MAX phase material of A being at least one element of aluminum, gallium, indium, lead, silicon, germanium, tin or sulfur is easy to prepare.

In the present invention, at least two transition metal elements or lanthanoid elements of M elements capable of forming a solid solution include, but are not limited to: ti, Nb; and/or, Zr, Ta; and/or, Zr, V; and/or, Pt, Au; and/or, W, Mo.

The invention also comprises a medium-entropy two-dimensional material (medium-entropy MXene), wherein the medium-entropy MAX phase material is reacted with an etching agent, so that the etching agent selectively etches the component A in MAX to obtain the medium-entropy two-dimensional material with a two-dimensional lamellar structure, and the chemical general formula of the medium-entropy two-dimensional material is M_n+1X_nThe M element and the X element in the medium-entropy two-dimensional material keep the characteristics of a precursor medium-entropy MAX phase material, wherein the M element contains at least two transition metal elements or lanthanide elements capable of forming a solid solution; x is at least one of carbon, nitrogen, boron or oxygen, n

is

1, 2, 3, 4, 5 or 6.

The two-dimensional lamellar structure is a material with a two-dimensional lamellar structure, the size of which reaches nanometer (1 nm-100 nm) in one-dimensional direction in the three-dimensional structure, is called a two-dimensional material, and the carrier migration and the heat diffusion of the material are limited in a two-dimensional plane, so that the material can show many peculiar properties, such as high specific surface area, large amount of atom exposure and doping of functional atoms on the two-dimensional lamellar structure, and the functional atoms can also generate large amount of atom exposure on the two-dimensional lamellar structure, thereby endowing the two-dimensional material with new performance, for example, M element in the medium-entropy two-dimensional material contains metal atoms (Pt, Pd, Au, Ag, Fe, Co, Ni, Cu or Bi) with catalytic performance, and the atoms have large amount of atom exposure on the surface of the two-dimensional lamellar structure of the medium-entropy two-dimensional material, the large number of exposed atoms can endow the medium-entropy two-dimensional material with excellent catalytic performance; for another example, in the medium-entropy two-dimensional material, the M element contains metal atoms (Pt, Au, V, Hf, W, Mo or Ag) with corrosion resistance, so that the medium-entropy two-dimensional material can be endowed with excellent corrosion resistance.

In some embodiments, the two-dimensional lamellar structure of the medium-entropy two-dimensional material of the present invention is 1-20 atomic layer thick, or the thickness is between 1nm and 20 nm. The medium-entropy two-dimensional material of the invention has the characteristic of ultra-thin thickness and larger specific surface area on the same material quantity, so that metal atoms on the two-dimensional material can generate a large amount of atom exposure.

In some embodiments, the surface of the mesoentropic two-dimensional material of the present invention contains functional groups, including: one or more of-F, -Cl, -Br or-I. The medium-entropy two-dimensional material is obtained by selectively etching the A component in the medium-entropy MAX phase material through an etching agent, wherein the preferable etching agent is acid, metal salt or gas containing halogen, the surface of the obtained medium-entropy two-dimensional material contains corresponding halogen functional groups, and the halogen functional groups have high activity and are easy to perform substitution reaction of the functional groups, so that the modification of the medium-entropy two-dimensional material is realized.

Example 2

The embodiment provides a preparation method of a medium-entropy MAX phase material, which comprises the following steps:

the material preparation step: determining the required amount of raw materials containing the elements according to the stoichiometric ratio of each element in the chemical general formula of the MAX phase material;

sintering: sintering the weighed raw materials at a preset temperature under a protective atmosphere or a vacuum environment to obtain a medium entropy MAX phase material; the MAX phase material contains M elements which are three or four transition metal elements and lanthanide elements, wherein the M elements contain at least two transition metal elements or lanthanide elements capable of forming a solid solution; the element A is at least one element selected from VIIB, VIII, IB, IIB, IIIA, IVA, VA and VIA groups; the X element is at least one of carbon, nitrogen, boron or oxygen, n

is

1, 2, 3, 4, 5 or 6.

Under the high-temperature condition in the sintering step, at least 2 metal powder raw materials added can be preferentially co-melted to form a homogeneous phase generation environment, which is beneficial to the free moving and arrangement of atoms with different radii; the eutectic atoms are directly combined with non-metal elements in the subsequent reaction process to form a single-phase transition metal compound with a layered structure. According to the electron balance theory, d electron orbital electrons of metal elements in M elements are matched with each other, and the electron balance of the single-phase transition metal compound is satisfied.

In a preferred embodiment, in the step of compounding, the molar ratio of the M element, the A element and the X element in the raw materials is (n+1）∶（1.05～1.2）∶nThe required amount of each raw material is determined. Since carbides of MX phase are easily formed during the high temperature reaction in the sintering step, the proper excess of component A can reduce the yield of MX in the reaction process, thereby effectively improving the purity of MAX phase.

In a preferred embodiment, between the batching step and the sintering step, a raw material grinding step is further included: the required amount of raw materials are mixed and ground, preferably, the particle size range of the ground raw materials is between 1nm and 20 μm, more preferably, the particle size range is between 10nm and 500nm, the raw materials are refined and uniformly mixed through grinding, and the formation of the homogeneous MAX phase material in the sintering step is facilitated. In the specific implementation, the grinding step is preferably a ball milling device, and the ball milling is carried out in a ball milling mode, preferably, the ball milling implementation conditions are that the mass ratio of ball materials is 1: 1-30: 1, the ball milling speed is 50 r/min-600 r/min, and the ball milling time is 1-120 h.

In specific implementation, the sintering step is preferably carried out under the conditions that the sintering temperature is between 800 and 1500 ℃, and the sintering time is between 10 and 120 min.

In some embodiments, after the sintering step, a product grinding step is further included: and further grinding the sintered medium-entropy MAX phase material to obtain powder of the medium-entropy MAX phase material.

Example 3

The embodiment provides a preparation method of a medium-entropy two-dimensional material, which comprises the following steps:

MAX phase preparation: in embodiment 2, the preparation method of the medium-entropy MAX phase material is adopted to prepare the medium-entropy MAX phase material, which is not described herein again;

etching: and reacting the medium-entropy MAX phase material with an etching agent, and selectively etching the component A in the MAX by the etching agent to obtain the medium-entropy two-dimensional material.

Optionally, the etchant is hydrofluoric acid solution, the mass concentration of the hydrofluoric acid can be between 1% and 50%, the reaction temperature is between 0 ℃ and 100 ℃, and the reaction time is between 5min and 100 h; optionally, the etchant is an acid solution + fluoride salt system, wherein the acid solution can be one or more of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid, the adopted fluoride salt can be one or more of lithium fluoride, sodium fluoride, potassium fluoride and ammonium fluoride, the reaction temperature is 0-100 ℃, and the reaction time is 5 min-100 h; optionally, the etchant is a halogen metal salt, wherein the halogen metal salt can be FeCl₃，CoCl₂，NiCl₃，CuCl₂，ZnCl₂，CdCl₂，FeBr₃，CoBr₂，NiBr₃，CuBr₂，ZnBr₂，CdBr₂，FeI₃，CoI₂，NiI₃，CuI₂，ZnI₂，CdI₂One or more of the metal halide salt and the medium entropy MAX phase material enter at the temperature of 100-1500 ℃ in protective atmosphere or vacuumAnd etching reaction is carried out.

Optionally, the etchant is one or more of a gaseous halogen simple substance, a halogen hydride and a nitrogen hydride, the simple substance or the hydride gas can react with the component A in the MAX phase material under a certain reaction condition to generate a gaseous product and is removed from a reaction system, so that partial or whole etching of the component A is realized, and the MX-containing two-dimensional material is obtained, does not contain solid impurities and has the excellent characteristic of high purity. Preferably, the halogen element, includes Br₂Or I₂(ii) a Halogen hydrides including HF, HCl, HBr or HI; hydrides of nitrogen family, including NH₃Or H₃And P. Preferably, the etch reaction temperature is between 500 ℃ and 1200 ℃. The high-purity medium-entropy two-dimensional material can be directly obtained by reacting the gas-phase etchant with the MAX-phase material, so that the steps of repeated cleaning, ultrasonic treatment, centrifugal separation, drying and the like in a liquid-phase method (acid liquor etching) are avoided, and the preparation process is greatly simplified.

Example 4

This example was carried out to prepare a medium entropy MAX phase material (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂AlC and medium entropy two-dimensional material (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂For example, the technical features of the present invention are further illustrated, wherein, according to the two-phase diagram, Ti and Nb can be solid-melted in M element, and Ta and Zr can be solid-melted.

Preparation of Medium entropy MAX phase Material (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂AlC, comprising the steps of:

1) the material preparation step: uniformly mixing transition metal powder, aluminum powder and crystalline flake graphite according to a stoichiometric ratio (molar ratio) of 2:1.2:1, wherein the transition metal powder comprises Ti, Nb, Ta and Zr, and the molar ratio of Ti to Nb to Ta to Zr =1:1:1: 1;

2) grinding: mixing and uniformly mixing the powder, and then placing the powder in an agate ball milling tank for ball milling treatment, wherein the ball milling rotation speed is 600rpm, and the ball milling time is 20 hours;

3) sintering: after ball milling, the mixture is groundThe mixture powder is placed in a tube furnace, heated to 1500 ℃ under the protection of argon gas for sintering for 10min, and naturally cooled to room temperature to obtain a medium entropy MAX phase (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂AlC。

In this example, a concentrated hydrochloric acid + lithium fluoride (LiF) system was used as an etchant to prepare a medium entropy two-dimensional material (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂The method comprises the following steps:

40ml of concentrated hydrochloric acid and 2g of LiF are uniformly mixed to be used as an etching agent, and 1g of the prepared medium-entropy MAX phase (Ti) is taken_0.25Nb_0.25Ta_0.25Zr_0.25)₂Placing AlC in an etching agent, reacting for 24h at 50 ℃, and after the reaction is finished, performing centrifugal separation, water washing and drying treatment to obtain the medium-entropy two-dimensional material (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xWherein T is_xRepresents a surface functional group.

Mid-entropy MAX phase (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂AlC and medium entropy two-dimensional material (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xScanning Electron Microscope (SEM) tests were conducted, respectively, and the results are shown in FIGS. 1 (a) and 1 (b), as can be seen by comparison, (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂The shape of AlC is a three-dimensional block structure, and the medium-entropy two-dimensional material (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xThe morphology is a two-dimensional nano sheet, and the nano sheet has the characteristics of ultrathin and soft structure, which shows that the entropy MAX (Ti) is medium_0.25Nb_0.25Ta_0.25Zr_0.25)₂AlC reacts in a hydrochloric acid + LiF etching agent to etch the component A in the medium-entropy MAX phase, so that a corresponding medium-entropy two-dimensional material is obtained. Mid-entropy MAX (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂AlC and medium entropy two-dimensional material (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xThe results of X-ray diffraction (XRD) analysis of each sample are shown in FIG. 2, and the raw material (Ti) is obtained by comparison_0.25Nb_0.25Ta_0.25Zr_0.25)₂The (002) peak in AlC appeared at 12.2 degrees, while the (002) peak in the target product after reaction with the hydrochloric acid + LiF etchant shifted to 7.4 degrees towards a low angle, indicating that the hydrochloric acid + LiF etchant etched during the reaction process (Ti + LiF etchant)_0.25Nb_0.25Ta_0.25Zr_0.25)₂Al element in AlC generates MXene (Ti) with lamellar structure_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xResulting in an enlargement of the interlayer spacing, which is in accordance with (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xThe results of the scanning electron microscope photographs are consistent, and it can be seen from the XRD spectrogram of fig. 3 that the diffraction peaks of the synthesized mid-entropy MAX phase are respectively consistent with the reported tinbolb alc of the single phase, and no impurity peaks of other carbides appear, indicating that the obtained mid-entropy MAX phase is the single phase, and correspondingly, the mid-entropy two-dimensional material prepared by using the mid-entropy MAX phase as a precursor is also the single phase. Target product (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xFig. 4 (a) shows a transparent two-dimensional nanosheet structure, indicating two-dimensional (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xThe two-dimensional nanosheet has the characteristics of ultrathin and soft structure, the two-dimensional nanosheets in the atomic distribution diagram (shown in figures 4 b-h) have uniform Ti, Nb, Ta, Zr, C, O and F element distribution, and the obtained target product is a medium-entropy two-dimensional material (Ti) containing-O-F functional groups_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xAnd there is a significant amount of atomic exposure at the surface of the two-dimensional sheet. The resulting intermediate entropy two-dimensional material (Ti) was prepared by atomic force microscopy AFM testing (as shown in FIGS. 5a and b)_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xThe thickness of (a) is 7.2 nm-16.7 nm, and the film has ultrathin two-dimensional nanometerA sheet structure.

Example 5

In this example, the medium entropy MAX phase (Ti) prepared in example 4 was used_0.25Nb_0.25Ta_0.25Zr_0.25)₂AlC is used as a raw material, commercial liquefied HI gas is used as an etchant, and the method comprises the following steps:

1) placing powdered (Ti) in the tube furnace_0.25Nb_0.25Ta_0.25Zr_0.25)₂AlC；

2) Introducing HI gas into the tubular furnace for a period of time, and sealing the reaction cavity after the reaction cavity in the reaction device is filled with the HI gas;

3) heating the interior of the reaction device to 700 ℃, preserving heat for 30min, and carrying out etching reaction to obtain the target product entropy two-dimensional material (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_x(Medium entropy MXene).

And after the reaction device is naturally cooled to the room temperature, taking out the target product. To (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂Medium entropy MXene (Ti) after reaction of AlC and HCl_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xSEM tests are carried out on the two target products, and the results are shown in FIG. 6, the target product after reaction has an obvious accordion layered structure (FIG. 6 b), the accordion structure has an obvious layer-by-layer stacked expansion structure, and a large number of two-dimensional nano-sheets exist in the target product, which is obviously different from the raw material (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂Lamellar bulk morphology of AlC (fig. 6 a). To (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂AlC and MXene (Ti) with medium entropy_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xXRD analysis was performed, and the results are shown in FIG. 7, which shows that the starting material (Ti) was obtained by comparison_0.25Nb_0.25Ta_0.25Zr_0.25)₂(002) peak in AlC appeared at 12.2 ℃ and in the target product after reaction with hydrogen chloride(002) The peak was shifted to 10 ° at a low angle, indicating that the HI gas was etched in the gas phase reaction (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂Al element in AlC generates medium entropy MXene (Ti) with lamellar structure_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xLeading to the expansion of interlayer spacing, which is consistent with the result of scanning electron micrographs, and the intermediate entropy MXene has a good crystal structure and an ultrathin two-dimensional lamellar structure. As can be seen from the XRD spectrogram of fig. 7, the diffraction peaks of the synthesized mid-entropy MAX phase are respectively consistent with the reported tinbol of the single phase, and no impurity peaks of other carbides appear, which indicates that the obtained mid-entropy MAX phase is the single phase, and correspondingly, the mid-entropy two-dimensional material prepared by using the mid-entropy MAX phase as a precursor is also the single phase. By high resolution electron microscopy HRTEM (FIG. 8), medium entropy two dimensional material (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xIt exhibits regular atomic arrangement and almost transparent characteristics. Entropy MXene (Ti) in target product_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xThe STEM of (A) (FIG. 9) shows a large number of two-dimensional ultrathin nanosheets, indicating that the cells are accordion-like (Ti)_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xA large number of two-dimensional nanosheets can be obtained through simple stripping, the two-dimensional nanosheets have uniform Ti, Nb, Ta, Zr, C and I element distribution (figures 9 b-g), and the obtained target product is a medium-entropy two-dimensional material (Ti) containing I functional groups_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xAnd there is a significant amount of atomic exposure at the surface of the two-dimensional sheet. The resulting intermediate entropy two-dimensional material (Ti) prepared in this example was tested by atomic force microscopy AFM (as shown in FIGS. 10a and b)_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xThe thickness of (A) is about 1 nm. The medium-entropy two-dimensional material (Ti) is prepared by a gas phase method_0.25Nb_0.25Ta_0.25Zr_0.25)₂CT_xAnd because the gas phase is easier to enter the gaps of the layered MAX phase material, compared with the liquid phase etching, the method is easier to prepare and obtain a large amount of single-layer ultrathin medium-entropy two-dimensional materials.

Example 6

This example was carried out to prepare a medium entropy MAX phase material (TiNbFe)₂AlC and mid-entropy two-dimensional material (TiNbFe)₂C is an example to further illustrate the technical features of the present invention, wherein Ti and Nb in the M element can realize solid solution according to a two-phase diagram.

Preparation of Medium entropy MAX phase Material (TiNbFe)₂AlC, comprising the steps of:

1) the material preparation step: uniformly mixing transition metal powder, aluminum powder and crystalline flake graphite according to a stoichiometric ratio (molar ratio) of 2:1.2:1, wherein the transition metal powder comprises Ti, Nb and Fe, and the molar ratio of Ti to Nb to Fe =1:1: 1;

3) sintering: placing the ball-milled mixture powder in a tube furnace, heating to 1000 ℃ under the protection of argon gas, sintering for 120min, and naturally cooling to room temperature to obtain a medium entropy MAX phase (TiNbFe)₂AlC。

The medium entropy MAX phase (TiNbFe) was etched in the same manner as in example 4, using concentrated hydrochloric acid + LiF as the etchant₂AlC to obtain a medium entropy two dimensional material (TiNbFe)₂C, the atomic structure of the two-dimensional sheet is schematically shown in FIG. 11, wherein the medium-entropy two-dimensional material (TiNbFe)₂A large amount of Fe atoms arranged by monoatomic atoms are distributed on the two-dimensional lamellar structure of the C, the Fe atoms have catalytic action, and the prepared medium-entropy two-dimensional material (TiNbFe)₂C may be used as a catalytic material.

The above embodiments are provided only to illustrate some embodiments of the technical features of the present invention, and the present invention includes embodiments not limited thereto, and it will be apparent to those skilled in the art that several modifications and improvements can be made without departing from the inventive concept of the present invention, and the scope of the present invention should be determined by what is defined in the claims.

Claims

1. A medium entropy MAX phase material with chemical formula M_n+1AX_nThe rare earth element is characterized in that M is selected from three or four transition metal elements and lanthanide elements, wherein the M contains at least two transition metal elements and lanthanide elements capable of forming a solid solution; the element A is at least one element selected from VIIB, VIII, IB, IIB, IIIA, IVA, VA and VIA groups; the X element is at least one of carbon, nitrogen, boron or oxygen,nis 1, 2, 3, 4, 5 or 6.

2. A medium entropy MAX phase material as claimed in claim 1, wherein at least two of said M elements, transition metal elements and lanthanides capable of forming solid solutions, comprise: ti and Nb; and/or, Zr and Ta; and/or, Zr and V; and/or, Pt and Au; and/or, W and Mo.

3. A medium entropy MAX phase material as claimed in claim 1, wherein a is at least one element of aluminium, gallium, indium, lead, silicon, germanium, tin and sulphur.

4. A method for preparing a medium-entropy MAX phase material is characterized by comprising the following steps:

sintering: sintering the raw materials at a preset temperature under a protective atmosphere or a vacuum environment to obtain a medium entropy MAX phase material; wherein the content of the first and second substances,

the MAX phase material has a chemical general formula of M_n+1AX_nThe M element is selected from three or four transition metal elements or lanthanide elements, and the M element contains at least two transition metal elements and lanthanide elements capable of forming a solid solution; the element A is at least one element selected from VIIB, VIII, IB, IIB, IIIA, IVA, VA and VIA groups; the X element is carbon,At least one of nitrogen, boron and oxygen, andnis 1, 2, 3, 4, 5 or 6.

5. A process for the preparation of a medium entropy MAX phase material as claimed in claim 4 wherein, in the raw material requirements of said compounding step, the molar ratio of said M element, said A element and said X element is: (n+1）∶（1.05～1.2）∶n。

6. A method of preparation of a medium entropy MAX phase material as claimed in claim 4 wherein, in said sintering step, the sintering temperature is between 800 ℃ and 1500 ℃.

7. The medium-entropy two-dimensional material is characterized by having a two-dimensional lamellar structure with a chemical general formula of M_n+1X_nM is selected from three or four transition metal elements and lanthanoid elements, wherein the M contains at least two transition metal elements and lanthanoid elements capable of forming solid solution, X is at least one of carbon, nitrogen, boron and oxygen, andnis 1, 2, 3, 4, 5 or 6.

8. The medium entropy two-dimensional material of claim 7, wherein the at least two transition metal elements capable of forming a solid solution include Ti and Nb; and/or, Zr and Ta; and/or, Zr and V; and/or, Pt and Au; and/or, W and Mo.

9. The medium entropy two-dimensional material of claim 7, wherein A is at least one element of aluminum, gallium, indium, lead, silicon, germanium, tin, and sulfur.

10. The mid-entropy two-dimensional material of claim 7, wherein the two-dimensional sheet structure has a thickness of between 1nm and 20 nm.

11. The mid-entropy two-dimensional material of any one of claims 7 to 10, wherein the surface of the mid-entropy two-dimensional material containing functional groups comprises: -one or more of-F, -Cl, -Br or-I.

12. A preparation method of a medium-entropy two-dimensional material is characterized by comprising the following steps:

MAX phase preparation: preparing a medium entropy MAX phase material by using the method for preparing a medium entropy MAX phase material as claimed in any one of claims 4 to 6;

13. The method for producing a medium-entropy two-dimensional material according to claim 12, wherein in the etching step, the etchant is a hydrofluoric acid solution, an acid solution + fluoride salt system, or a halogen metal salt.

14. The method for producing a medium-entropy two-dimensional material of claim 12, wherein in the etching step, the etchant is one or more of a simple halogen, a halogen hydride, and a nitrogen hydride in a vapor phase.

15. The method for preparing a medium-entropy two-dimensional material as claimed in claim 14, wherein in the etching step, the etching reaction temperature is between 500 ℃ and 1200 ℃.

16. Use of the medium-entropy two-dimensional material of any one of claims 7 to 10 in catalysis, sensors, electronics, supercapacitors, batteries, electromagnetic shielding, wave-absorbing materials, or superconducting materials.

17. The application of the obtained medium-entropy two-dimensional material prepared by the preparation method of the medium-entropy two-dimensional material as claimed in any one of claims 12 to 15 in catalysis, sensors, electronic devices, supercapacitors, batteries, electromagnetic shielding, wave-absorbing materials or superconducting materials.