CN113061862A

CN113061862A - Preparation method of two-dimensional metal nano material

Info

Publication number: CN113061862A
Application number: CN202010002544.7A
Authority: CN
Inventors: 王子鉴; 汪卫华; 柳延辉
Original assignee: Institute of Physics of CAS
Current assignee: Institute of Physics of CAS
Priority date: 2020-01-02
Filing date: 2020-01-02
Publication date: 2021-07-02

Abstract

The invention relates to a preparation method of a two-dimensional metal nano material, which is a self-supporting film ultrasonic method and comprises the following steps: preparing a metal target, preparing a metal film, separating the self-supporting metal film by a chemical stripping method, ultrasonically dispersing the self-supporting metal film and performing post-treatment. The two-dimensional metal nano preparation method can be simultaneously suitable for common metals, amorphous alloys and high-entropy alloys.

Description

Preparation method of two-dimensional metal nano material

Technical Field

The invention relates to a preparation method of a two-dimensional metal nano material.

Background

In 2004, Andre gemm and Konstantin Novoselov, two scientists at manchester university, uk, mechanically peeled the graphite sheet for the first time by means of a "tape-stripping" method to graphene consisting of only one layer of carbon atoms. These two scientists also acquired the 2010 nobel prize in physics with work on graphene research. Graphene has been highly concerned, widely researched and praised in the world, and even known as "black gold" because of its superior properties such as ultra-high electron mobility, highest electrical and thermal conductivities among known materials, extremely high mechanical strength, chemical inertness, good light transmittance and flexibility. To date, graphene has penetrated more than 40 leading edge application areas such as computer hardware, lithium and solar cells, flexible display screens, composites, 3D printing, sensors, etc. More importantly, the successful preparation of graphene leads to the hot tide of the research of two-dimensional nano materials. Today, scientists have synthesized two-dimensional nanomaterials such as transition metal chalcogenides, transition metal oxides and hydroxides, transition metal carbides and carbonitrides, hexagonal boron nitride, silylene, and phospholene in succession. The two-dimensional nano materials represented by the graphene not only have huge technical application potential, but also provide an important research model for basic scientific exploration.

The successful preparation of these two-dimensional nanomaterials is mainly attributed to the intrinsic layered atomic structural characteristics of their precursor materials. For example, a precursor material of graphene, graphite, is considered to be formed by stacking multiple layers of graphene, covalent bonds with strong bonding force exist in graphene layers of a monoatomic layer, and van der waals force with weak bonding force exists between layers of the multiple layers of graphene. The structural requirement, namely the intrinsic layered atomic structure, greatly limits the types of two-dimensional nano materials and reduces the opportunity of obtaining novel performance. Therefore, the development of a new and more universal preparation method of the two-dimensional nano material has important significance.

The metal material is a key material with both scientific value and practical application value, and plays a very important role in promoting the development and progress of the human society. The properties of metallic materials are closely related to the size, morphology, chemical composition, atomic structure, etc. of the material. Thus, a "two-dimensional metallic nanomaterial" in the broader sense refers to a metallic material when the thickness of the metallic material is reduced to a single or a few atomic layers, such a two-dimensional metallic nanomaterial is likely to acquire unique properties different from bulk metal. For example, due to the reduction of dimensionality, two-dimensional metal nanomaterials can exhibit novel physical, chemical and mechanical properties such as higher electron mobility, higher density of unsaturated coordinated surface atoms, higher aspect ratio, larger specific surface area and higher surface energy. The properties possibly enable the two-dimensional metal nano material to have potential application values in the fields of catalysis, fuel cells, sensing, surface enhanced Raman spectroscopy, biological imaging, near-infrared photothermal therapy, magnetic recording and the like. In addition, two-dimensional metal nanomaterials can also have a significant impact on basic scientific research. However, due to the non-orientation of the metal bond, the metal atoms tend to form a close-packed structure in three-dimensional space, and thus do not have the aforementioned intrinsic layered atomic structure characteristics, and thus it is difficult to obtain a desired two-dimensional metal nanomaterial by a method similar to that of preparing graphene. Therefore, how to effectively prepare two-dimensional metal nanomaterials becomes an important challenge, and this is a prerequisite for exploring the peculiar properties of such materials.

After many years of exploration and accumulation, various chemical, physical and mechanical methods for preparing two-dimensional metal nanomaterials have been developed. The chemical method mainly comprises a carbon monoxide limited growth method, a template synthesis method, a seed crystal growth method, a hydrothermal or solvothermal method, a wet chemical synthesis method, a nano particle self-assembly method, a local chemical reduction method and the like. Carbon monoxide can be tightly adsorbed on the metal surface, thereby inhibiting the growth of metal atoms in this orientation. Two-dimensional metal nanomaterials such as Pd, PdAg, PdNi and PtPdAg can be synthesized using a carbon monoxide limited growth method, but this method has not been widely put into practical use due to the difficulty in precisely controlling the crystal nucleation and growth kinetics during synthesis. The template synthesis rule is that the growth of the metal nano material in the third dimension is inhibited through a two-dimensional template. By selecting a proper template, the method can be used for synthesizing two-dimensional metal nano materials with core-shell structures, such as Au @ Ag, Au @ Pt, Ag @ Pd and the like. The seed crystal growth method can also synthesize two-dimensional metal nano materials with core-shell structures such as Au @ Ag, Pd @ Pt and Pd @ Au through two steps of preparing seed crystals and growing the seed crystals. Hydrothermal and solvothermal methods are widely used for synthesizing various nanomaterials, such as two-dimensional metal nanomaterials, e.g., Rh, Ru, PtCu, PtAg, PtAgCo, PtCuBi, and PtCuBiMn, due to their simple operation. However, since the hydrothermal method is very sensitive to the experimental conditions, it is difficult to ensure that samples with the same quality can be obtained from different batches of experiments. Furthermore, since all reactions are performed in a sealed autoclave, it is difficult to explore the growth mechanism of the two-dimensional metal nanomaterial in the method. The wet chemical synthesis method is regarded as a convenient and fast bottom-up synthesis strategy with strong repeatability and controllability, can obtain the two-dimensional metal nano material dispersed in the solvent at a high yield and is convenient to apply. The method can be used for synthesizing two-dimensional metal nano materials such as PdCu, PtBi, PdPb and the like, and is also used for preparing Au and PdMo with sub-nanometer thickness recently, and the ultrathin two-dimensional metal nano material is also vividly called as metal alkene. The two-dimensional metal nano material with highly controllable thickness and larger size can be obtained through the self-organization of the nano crystals or the nano particles. Although this method is simple, efficient, and low-cost, the product is very sensitive to experimental conditions (especially the use of a surfactant), and the resulting two-dimensional metal nanomaterial exhibits poor crystallinity due to random distribution of individual grains and weak bonding force between grains. The partial chemical reduction method can produce two-dimensional metal nanomaterials containing no noble metal elements, such as Ni, NiCo, NiMo, etc., by reducing metal salts, and thus is considered to have stronger universality. Although these bottom-up chemical synthesis methods can better control the thickness and morphology of the resulting two-dimensional metal nanomaterials, they still have some inherent limitations. For example, these methods usually use toxic metal salts and organic surfactants, which remain on the surface of the two-dimensional metal nanomaterial obtained and thus the intrinsic properties of the material cannot be sufficiently exhibited. In addition, the application range of the chemical synthesis methods is very limited at present, and the chemical synthesis methods are mainly used for synthesizing two-dimensional metal nano materials containing noble metal elements. In addition, these chemical synthesis methods also have difficulty in preparing two-dimensional materials of advanced metal materials such as high-entropy alloys and amorphous alloys. The high-entropy alloy generally refers to a single-phase alloy obtained by mixing five or more components in a nearly equal proportion, and has the characteristics of fracture resistance, tensile strength, corrosion resistance, oxidation resistance and the like superior to those of the traditional alloy. Recently, carbon thermal impact and nano-droplet electrodeposition and other methods are adopted to simultaneously reduce a plurality of metal salts to prepare single-phase high-entropy alloy nanoparticles which can contain up to eight components. The methods need complicated experimental steps and strict control processes, are difficult to scale and apply to other metal material systems, and cannot obtain the two-dimensional metal nano material.

Physical vapor deposition processes can grow metal films down to a few nanometers in thickness on a substrate with high controllability. However, it is often difficult to separate the metal film from the substrate, and a suitable substrate needs to be selected if a free-standing metal film (i.e., a two-dimensional metal nanomaterial as broadly referred to herein) is to be obtained. For example, the NaCl crystal can be used as a substrate, and can be dissolved and removed by immersing the substrate in warm water, so that only the metal thin film layer thereon remains, and the required two-dimensional metal nanomaterial can be obtained, but the current commercial NaCl substrate has a small size and is expensive, and is difficult to be used for large-scale preparation of the two-dimensional metal nanomaterial. Similarly, 3D printed hydrogels, photoresists, etc. can also be used as removable substrates, but the use of these substrates complicates the manufacturing process, increases cost, and still only allows for very limited quantities or quality of two-dimensional metallic nanomaterials.

In view of good plasticity of metal materials, it has been proposed to prepare two-dimensional metal nanomaterials by a repeated folding-rolling method. Specifically, a foil strip of a metal such as Ag is laminated with Al foil, and then folded and rolled with a rolling mill, and this process is repeated about 20 times to obtain a composite structure like "multi-layer pancake". And then dissolving the Al layer in the solution by using an alkaline solution to obtain the two-dimensional metal nano material with the thickness as low as 1 nm. However, this method cannot be applied to a metal material having high brittleness such as an amorphous alloy.

Amorphous alloy, or metallic glass, is usually made by rapidly cooling a high-temperature melt, has the characteristics of high strength, hardness, excellent soft magnetism, corrosion resistance and the like, and has wide application prospect in the fields of structural materials, precise instruments, catalysis, micro-electro-mechanical systems, medical implants and the like. Therefore, the two-dimensional amorphous alloy nano-material is attracting more and more the interest of researchers, and how to prepare the two-dimensional amorphous alloy nano-material also becomes the focus of attention. Gas atomization and mechanical milling processes are the two main methods for preparing amorphous alloy powders, but the resulting powder particle size is typically in the order of microns. Attempts have also been made to prepare two-dimensional amorphous alloy nanomaterials by other methods. When the amorphous alloy is in a supercooled liquid phase region, namely when the temperature is between the glass transition temperature and the crystallization temperature, the viscosity of the material is obviously reduced, and a certain time window can be set before crystallization for carrying out thermoplastic forming processing on the amorphous alloy. By utilizing the characteristic, people prepare the amorphous alloy micro-nano rod array by a template method, prepare amorphous alloy micro-nano wires by a hot drawing method, and prepare amorphous alloy nano strips and the like by a polymer-coated multistage co-drawing method. However, the amorphous alloy systems applicable to these methods are very limited, and usually are amorphous components (such as Pd/Pt-Ni-Cu-P and Au-Ag-Pd-Cu-Si) which are based on noble metals, have strong glass forming ability and good oxidation resistance, and it is difficult to obtain two-dimensional amorphous alloy nano-materials with a characteristic size of several nanometers. In addition, these methods are not applicable to common crystalline metals and alloy materials.

In summary, a two-dimensional metal nano-material preparation method suitable for common metals, amorphous alloys and high-entropy alloys at the same time is still lacking at present.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a preparation method of a two-dimensional metal nano material which is simultaneously suitable for common metals, amorphous alloys and high-entropy alloys.

According to an embodiment of the present invention, the present invention provides a method for preparing a two-dimensional metal nanomaterial, the method being a self-supporting thin film ultrasound method.

The preparation method of the two-dimensional metal nano material comprises the following steps:

(1) preparing a metal target material: carrying out batching, smelting and casting according to the required components to obtain a metal target material;

(2) preparing a metal film: using an Al target and the metal target obtained in the step (1), and utilizing a physical vapor deposition method to sequentially deposit an Al film and a required metal film on a substrate;

(3) chemical lift-off to separate the free-standing metal film: soaking the sample obtained in the step (2) in an alkaline solution at room temperature, removing the Al film (sacrificial layer) between the substrate and the metal film to obtain a self-supporting metal film, and then cleaning;

(4) ultrasonically dispersed self-supporting metal films: placing the cleaned self-supporting metal film in the step (3) into a centrifuge tube, adding an organic solvent, and placing the centrifuge tube into an ultrasonic cleaning machine for ultrasonic treatment to obtain a two-dimensional nano metal material dispersed in the organic solvent;

(5) and (3) post-treatment: and (4) placing the centrifugal tube subjected to the ultrasonic treatment in the step (4) in a centrifugal machine for centrifugation, separating the two-dimensional metal nano material from the organic solvent, and placing the separated two-dimensional metal nano material in an oven for drying to obtain the required two-dimensional metal nano material in a powder form.

The method according to the present invention, wherein, in the step (1), the melting method is an arc melting method or an induction melting method, depending on whether the metallic material to be melted contains a low melting point, volatile, highly reactive element; preferably, most metal materials, particularly transition metal materials with great industrial application value, are smelted for multiple times (>5 times) by adopting the arc smelting method, the smelting current is 300-350A each time, and the smelting time is 30-60 s, so that all components are uniformly mixed; the casting method can be a common casting method or a suction casting method, and a copper mold suction casting method is preferred.

The method according to the invention, wherein in the step (2), the physical vapor deposition method is ion beam sputtering deposition, magnetron sputtering or the like; preferably, the metal film is prepared by an ion beam sputtering deposition method, and the pressure of the coating argon is 2.0 multiplied by 10^-2～3.0×10^-2Pa, preferably 2.4X 10^-2～2.7×10^-2Pa, most preferably 2.5X 10^-2Pa, ion energy of 700-800 eV, preferably 750-800 eV, most preferably 750eV, ion beam current of 10-90 mA, preferably 30-70 mA, most preferably 50mA, and the converted deposition rate is about 5 nm/min.

Method and apparatus according to the inventionThe ion beam sputtering deposition method is preferred in the step (2), wherein in the step (1), the size of the metal target is 10 × 10 × 0.2cm³Of square target material or

Preferably 10X 0.2cm³The square target ensures that the ion beam emitted by the ion source completely bombards the metal target, thereby ensuring that the deposited film only contains a small amount of or no impurities except the required components.

According to the method of the present invention, in the step (2), the thickness of the Al film is 5 to 100nm, preferably 5 to 20nm, and most preferably 5nm, that is, the Al film uniformly covering the substrate can be obtained with a small amount of Al.

According to the method of the invention, in the step (2), the thickness of the metal thin film is 5-100 nm, preferably 5-20 nm, so as to highlight the two-dimensional characteristics of the obtained metal nano material. In fact, the thickness of the metal film can reach the micron order, so the method of the invention can be used for preparing micron-sized metal sheets.

According to the method of the present invention, in the step (2), the thin film deposition process may be repeated a plurality of times, i.e., repeatedly depositing the Al film and the desired metal thin film in succession, to thereby prepare a multi-layered composite thin film, so as to improve the yield of the two-dimensional metal nanomaterial obtained from a single preparation process.

The method of the present invention, wherein, in the step (2), the temperature of the substrate is around room temperature; the material of the substrate may be selected from inexpensive commercial materials such as SiO₂Metal foils or sheets, and some polymeric materials, etc., for example, the dimensions may be such that

Preferably, it is

To increase the number or quality of the samples obtained as much as possible; preferably, Polycarbonate (PC) plates are usedThe substrate has enough rigidity and flexibility, and is convenient to cut and clamp.

The method of the invention, wherein, in the step (3), the alkaline solution is KOH or NaOH solution; preferably, a KOH solution with the concentration of 1mol/L is adopted; the soaking time is 0.5-12 h, preferably 2h, so that all or most of the Al film (sacrificial layer) can be removed to obtain the self-supporting metal film with required components; the cleaning method comprises the step of washing deionized water and absolute ethyl alcohol for multiple times (more than or equal to 3 times) in sequence.

The method according to the present invention, wherein, in the step (4), the organic solvent is ethanol, isopropanol or the like, preferably ethanol; the amount of the organic solvent added depends on the type of the centrifuge and the volume of the corresponding centrifuge tube, and is generally about 2/3 of the volume of the centrifuge tube, and a 7mL centrifuge tube is preferred; the frequency of the ultrasonic cleaning machine is 40kHz, the ultrasonic power is 60 or 120W, and 60W is preferred; the temperature of the ultrasonic wave is 20-80 ℃, the optimal temperature is 25-35 ℃, the optimal temperature is 25 ℃, and the time of the ultrasonic wave is 10-120 min, the optimal time is 30 min.

According to the method of the present invention, for example, when a 7mL centrifuge tube is used in the step (4), the maximum rotation speed of the centrifuge tube in the step (5) is 12000rpm (corresponding to 10464 Xg centrifugal force), preferably 8000-12000 rpm, and most preferably 10000 rpm; the centrifugation time is 5-15 min, preferably 10 min; the temperature of the oven is 60 ℃, and the drying time is 2-12 h, preferably 3 h.

The preparation method of the two-dimensional metal nano material utilizes the Al film sacrificial layer and ultrasonic dispersion to prepare the two-dimensional metal nano material, and compared with the prior art, the preparation method has the advantages that:

1. the preparation method of the present invention is a general technique in the art for each step, such as preparation of metal target, preparation of metal thin film, separation of self-supporting metal thin film by chemical lift-off, ultrasonic dispersion of self-supporting metal thin film, and post-treatment (centrifugation and drying), so that it can effectively prepare two-dimensional metal nanomaterial without additional custom-made equipment or equipment, but through orderly integration.

2. Because the two-dimensional metal nano material is derived from the metal film prepared by the physical vapor deposition method in the preparation method, the method is not only suitable for the traditional crystalline metal and alloy, but also can be used for preparing advanced metal materials such as two-dimensional amorphous alloy, high-entropy alloy nano material and the like, and is not limited to noble metal elements, so that the method has a very wide applicable component range; in addition, the physical vapor deposition method has effectiveness and universality in metal film preparation, so that the preparation method is a two-dimensional metal nano-material preparation method with strong applicability.

3. The method has strong regulation and control performance and repeatability. The method has a series of adjustable parameters, including the components of the metal target, argon pressure, ion energy, ion beam current, deposition time, the number of film layers during ion beam sputtering deposition, frequency, power, temperature, time and the like during ultrasonic. By controlling the parameters, the composition, thickness, size, structure, energy state and the like of the obtained two-dimensional metal nano material can be regulated and controlled. Moreover, since these parameters can be precisely controlled, and complicated reduction reactions are not involved, the preparation method of the present invention is highly controllable and has good reproducibility.

4. The preparation method is economical and effective and has large-scale potential. The substrate used in the preparation of the metal film is selected from cheap commercial materials such as polycarbonate, the sacrificial layer material is cheap Al, the cost is far lower than that of sacrificial layer materials such as NaCl crystals, hydrogel, photoresist and the like used in other similar methods, and the multilayer composite metal film is convenient to prepare in a single experiment, so that the yield of the obtained two-dimensional metal nano material can be improved. In addition, multiple steps in the method, such as the preparation process of the multilayer film, can be programmed without manual operation, so that the method is convenient for large-scale production and saves cost.

Drawings

Embodiments of the invention are described in detail below with reference to the attached drawing figures, wherein:

fig. 1 illustrates a flow chart of a method for preparing a two-dimensional metallic nanomaterial according to an embodiment of the present invention;

FIG. 2 shows an optical photograph of the CuZr amorphous/Al multilayer metal thin film obtained in example 1;

FIG. 3 shows an optical photograph of the two-dimensional CuZr amorphous alloy nanomaterial dispersed in ethanol in example 1;

FIG. 4 shows an XRD pattern of the two-dimensional CuZr amorphous alloy nano-material powder prepared in example 1;

FIG. 5 shows an SEM image of a two-dimensional CuZr amorphous alloy nanomaterial prepared in example 1;

FIG. 6 shows the XRD pattern of the two-dimensional FeCoNiCrCu high-entropy alloy nano-material powder prepared in example 2;

fig. 7 shows an XRD pattern of the two-dimensional elemental Ag metal nanomaterial prepared in example 3.

Detailed Description

This section generally describes the materials and equipment used in the examples of the invention. Although many materials and instruments are known in the art for carrying out the purpose of the present invention, the invention is described herein in as much detail as possible. It will be clear to those skilled in the art that, in this context, the materials and apparatus used in the present invention are well known in the art, unless otherwise specified. The materials and instruments used in the following examples are as follows:

materials: the raw materials of Cu, Zr, Fe, Co, Ni, Cr and the like are purchased from non-ferrous metals Co Ltd of Beijing Jiaming platinum industry; analytically pure KOH and absolute ethyl alcohol are purchased from chemical reagents of national drug group, Inc.; PC and Al plates were purchased from elutriation nets.

The instrument comprises the following steps: the electric arc furnace is purchased from Beijing Tekkonidae photoelectricity Co., Ltd, model electromagnetic suspension smelting furnace; the ion beam sputtering deposition coating machine is purchased from the Kyoto Edwatson ion beam technology research institute, Inc. of Beijing, model LDJ 100-F100; the ultrasonic cleaning machine is purchased from Jie union cleaning equipment Limited company in Shenzhen, model JP-020S; the high speed centrifuge was purchased from Shanghai Nursery science instruments, Inc. model TGL-16C.

The preparation method of the two-dimensional amorphous alloy nano material is mainly divided into five steps, as shown in the flow chart of figure 1. Firstly, preparing a metal target material by a smelting and casting method according to needs; then, an Al film and a desired metal thin film are successively deposited on an inexpensive commercial substrate by a physical vapor deposition method; dissolving the film in an alkaline solution to remove the Al film serving as a sacrificial layer, obtaining a self-supporting metal film, and cleaning; then, putting the self-supporting metal film into a centrifuge tube, adding a proper amount of organic solvent, and carrying out ultrasonic treatment for a proper time to obtain a two-dimensional metal nano material dispersed in the organic solvent; and finally, centrifuging by using a high-speed centrifuge to separate the two-dimensional metal nano material, and drying in an oven to obtain the required powder sample.

Example 1 preparation of two-dimensional CuZr amorphous alloy nanomaterial

Step one, preparing a metal target: cu and Zr with the raw material purity higher than 99.9 wt% (weight percentage) are mixed according to the atomic percentage of 1: 1, preparing the materials. Repeatedly melting for 6 times (about 60s for each melting) in an electric arc furnace with titanium-adsorbed argon atmosphere under 350A current until Cu and Zr are uniformly mixed, and cooling to obtain Cu₅₀Zr₅₀And (5) alloy ingot casting. Melting Cu₅₀Zr₅₀Alloy ingot casting, suction casting the alloy ingot into a copper mold to obtain Cu with uniform components₅₀Zr₅₀Alloy target (10X 0.2 cm)³)。

Step two, preparing a metal film: the Cu obtained in the step one₅₀Zr₅₀The alloy target and the commercially available Al target were mounted on a target table of an ion beam sputter deposition coater, and a commercially available PC substrate (about

) Mounted to a substrate table of a coater. The coating condition is argon pressure of 2.5 multiplied by 10^-2Pa, ion energy of 750eV, ion beam current of 50mA, and corresponding deposition rate of about 5 nm/min. The deposition rate can ensure the Cu obtained by deposition₅₀Zr₅₀The alloy film is amorphous. Depositing Al film of 5nm thickness and 5nm thickness successivelyCu of (2)₅₀

Zr

₅₀20 layers of amorphous alloy film. An optical photograph of the obtained CuZr amorphous/Al multilayer metal thin film is shown in FIG. 2.

Step three, separating the self-supporting metal film by a chemical stripping method: depositing Al film and Cu on the PC substrate₅₀Zr₅₀Immersing the CuZr amorphous/Al multilayer metal film consisting of the amorphous alloy film in 1mol/L KOH solution, standing for 2h at room temperature, removing the Al film serving as a sacrificial layer, and obtaining self-supporting Cu₅₀Zr₅₀The amorphous alloy film was washed 3 times with deionized water and ethanol, respectively.

Step four, ultrasonically dispersing the self-supporting metal film: collecting the self-supporting Cu obtained in step three₅₀Zr₅₀The amorphous alloy film is placed in a 7mL centrifuge tube, and 5mL ethanol is added. Placing the centrifuge tube in an ultrasonic cleaning machine, performing ultrasonic treatment at 25 deg.C for 30min at 40kHz and 60W to obtain two-dimensional Cu dispersed in ethanol₅₀Zr₅₀Amorphous alloy nano material. FIG. 3 is an optical photograph of the dispersion (two-dimensional CuZr amorphous alloy nano-materials dispersed in ethanol).

Step five, post-treatment: placing 7mL centrifuge tube in a centrifuge, centrifuging for 10min at 10000rpm, and separating two-dimensional Cu₅₀Zr₅₀Amorphous alloy nano-material and ethanol. Pouring ethanol into an organic waste liquid bottle, and then adding the obtained two-dimensional Cu₅₀Zr₅₀Putting the amorphous alloy nano material into a drying oven, and drying for 3h at 60 ℃ to obtain the final two-dimensional Cu in a powder form₅₀Zr₅₀Amorphous alloy nano material.

FIG. 4 shows the XRD pattern of the two-dimensional CuZr amorphous alloy nano-material powder prepared in example 1, and the XRD result shows that the Cu is obtained₅₀Zr₅₀The material is indeed amorphous.

FIG. 5 shows two-dimensional Cu obtained in example 1₅₀Zr₅₀SEM image of amorphous alloy nano material.

Example 2 preparation of two-dimensional FeCoNiCrCu high-entropy alloy nanomaterial

Step one, preparing a metal target: purity of raw materialMore than 99.9 wt% (weight percent) of Fe, Co, Ni, Cr and Cu components are calculated according to the atomic percent of 1: 1: 1: 1: 1, preparing the materials. Repeatedly melting 6 times (about 60s for each time) in an electric arc furnace with titanium-adsorbed argon atmosphere under 350A current until Fe, Co, Ni, Cr and Cu are uniformly mixed, and cooling to obtain Fe₂₀Co₂₀Ni₂₀Cr₂₀Cu₂₀High entropy alloy ingot (hereinafter referred to as FeCoNiCrCu directly). Melting FeCoNiCrCu high-entropy alloy cast ingot, suction-casting the alloy cast ingot into a copper mold to obtain a FeCoNiCrCu high-entropy alloy target material (10 multiplied by 0.2 cm) with uniform components³)。

Step two, preparing a metal film: mounting the FeCoNiCrCu high-entropy alloy target obtained in the step one and a commercially-purchased Al target on a target table of an ion beam sputtering deposition coating machine, and mounting a commercially-purchased PC substrate (about

) Mounted to a substrate table of a coater. The coating condition is argon pressure of 2.5 multiplied by 10^-2Pa, ion energy of 750eV, ion beam current of 50mA, and corresponding deposition rate of about 5 nm/min. 20 layers of 5nm thick Al film and 10nm thick FeCoNiCrCu high entropy alloy film were deposited successively.

Step three, separating the self-supporting metal film by a chemical stripping method: and D, immersing the multilayer metal film which is deposited on the PC substrate and consists of the Al film and the FeCoNiCrCu high-entropy alloy film into a 1mol/L KOH solution, standing for 2h at room temperature, removing the Al film serving as a sacrificial layer to obtain a self-supporting FeCoNiCrCu high-entropy alloy film, and washing 3 times by deionized water and ethanol respectively.

Step four, ultrasonically dispersing the self-supporting metal film: and (4) collecting the self-supporting FeCoNiCrCu high-entropy alloy film obtained in the step three into a 7mL centrifuge tube, and adding 5mL ethanol. And placing the centrifugal tube in an ultrasonic cleaning machine, and performing ultrasonic treatment at the temperature of 25 ℃ for 30min at the frequency of 40kHz and the power of 60W to obtain the two-dimensional FeCoNiCrCu high-entropy alloy nano material dispersed in ethanol.

Step five, post-treatment: and placing the 7mL centrifuge tube into a centrifuge according to the use instruction, centrifuging for 10min at the rotating speed of 10000rpm, and separating the two-dimensional FeCoNiCrCu high-entropy alloy nano material from ethanol. And pouring ethanol into an organic waste liquid bottle, putting the obtained two-dimensional FeCoNiCrCu high-entropy alloy nano material into a drying oven, and drying at 60 ℃ for 3 hours to obtain the final powder-form two-dimensional FeCoNiCrCu high-entropy alloy nano material. Fig. 6 is an XRD pattern of the two-dimensional FeCoNiCrCu high-entropy alloy nanomaterial obtained in this embodiment.

Examples 3 to 18 preparation of two-dimensional nanomaterials

In examples 3 to 18, a series of two-dimensional metal nanomaterials of common metals, amorphous alloys and high-entropy alloys were prepared using the preparation method of the present invention. For different metal materials (as shown in table 1 below), the thickness of the metal film in step two is different, and the other steps are substantially the same.

TABLE 1

Examples	Metal material	Two-dimensional material thickness/nm
			3	Simple substance Ag	5
4	Elemental Co	8
			5	Elemental Fe	8
6	Elemental Pt	5
			7	Amorphous Cu-Zr	10
8	Amorphous Cu-Zr	100
			9	Amorphous Ni-Ta	15
10	Amorphous Pd-Si	20
			11	Amorphous Fe-Si-B	20
12	Amorphous Ir-Ni-Ta	5
			13	Amorphous Ir-Ni-Ta	10
14	High entropy Fe-Co-Ni-Cr-Cu	5
			15	High entropy Fe-Co-Ni-Cr-Cu	20
16	High entropy Fe-Co-Ni-Cr-Mn	15
			17	High entropy Hf-Zr-Ti-Ni-Cu	50
18	High entropy Hf-Zr-Ti-Ni-Cu	10

As can be seen from the above, the two-dimensional metal nano-preparation method of the invention can be simultaneously applied to common metals, amorphous alloys and high-entropy alloys.

Claims

1. A preparation method of a two-dimensional metal nano material is a self-supporting film ultrasonic method, and comprises the following steps:

(3) chemical lift-off to separate the free-standing metal film: soaking the sample obtained in the step (2) in an alkaline solution at room temperature, removing the Al film between the substrate and the metal film to obtain a self-supporting metal film, and then cleaning;

2. The method for preparing a two-dimensional metallic nanomaterial according to claim 1, wherein in the step (1), the melting method is an arc melting method or an induction melting method.

3. The method for preparing two-dimensional metallic nanomaterial according to claim 1, wherein in the step (2), the physical vapor deposition method is ion beam sputtering deposition or magnetron sputtering.

4. The method of claim 3, wherein the ion beam sputter deposition method is used to form a metal thin film, and the argon pressure for coating is 2.0 x 10^-2～3.0×10^-2Pa, ion energy of 700-800 eV, and ion beam current of 10-90 mA.

5. The method for preparing a two-dimensional metal nanomaterial according to claim 1, wherein in the step (2), the thickness of the Al film is 5-100 nm.

6. The method for preparing a two-dimensional metal nanomaterial according to claim 1, wherein in the step (2), the thickness of the metal thin film is 5-100 nm.

7. The method for preparing a two-dimensional metallic nanomaterial according to claim 1, wherein in the step (2), an Al film and a desired metal thin film are repeatedly deposited successively, thereby preparing a multilayer composite thin film.

8. The method for preparing a two-dimensional metallic nanomaterial according to claim 1, wherein in the step (3), the alkaline solution is a KOH or NaOH solution; the soaking time is 0.5-12 h; the cleaning method comprises the step of sequentially washing the deionized water and the absolute ethyl alcohol for multiple times.

9. The method for preparing a two-dimensional metallic nanomaterial according to claim 1, wherein in the step (4), the organic solvent is ethanol or isopropanol; the frequency of the ultrasonic cleaning machine is 40kHz, and the ultrasonic power is 60 or 120W; the temperature of the ultrasonic wave is 20-80 ℃, and the time of the ultrasonic wave is 10-120 min.

10. The method for preparing two-dimensional metal nano-material according to claim 1, wherein in the step (5), the maximum rotation speed of the centrifugal tube is 12000 rpm; the centrifugation time is 5-15 min; the temperature of the oven is 60 ℃, and the drying time is 2-12 h.