A method for steam-assisted coplanar stretching and orientation of two-dimensional sheets

Abstract

The present invention belongs to the field of material preparation, and discloses a method for steam-assisted coplanar tensile orientation of two-dimensional sheets. This method simultaneously performs isotropic stretching and steam treatment on a film material containing two-dimensional sheets. The steam used in the steam treatment contains plasticizing steam, and the plasticizing steam is formed by the evaporation of a plasticizing solvent that has a plasticizing effect on the two-dimensional sheets. The present invention can weaken the intermolecular van der Waals forces to improve the deformation ability of the sheets. At the same time, through isotropic stretching, wrinkles, folds, and other irregularities of the sheets are removed or reduced, enabling them to be assembled more uniformly, improving the assembly orderliness of the sheets while increasing the interfacial bonding force, and improving the orientation degree of the sheet stacking domains, thereby enhancing the overall performance of the film.

Description

Technical Field

[0001] The present invention belongs to the field of material preparation, and relates to a method for steam-assisted coplanar stretching and orientation of two-dimensional sheets. Background Art

[0002] In recent years, with the rapid development of nanotechnology and materials science, two-dimensional (2D) sheets, as a new type of material with atomic-level thickness, have attracted extensive attention in the scientific and industrial communities. The layered materials composed of 2D sheets are characterized by strong in-plane covalent chemical bonds within each atomic layer and weak out-of-plane van der Waals (vdW) interactions between adjacent layers. This non-bonding property enables guest substances to insert into the interlayer gaps (vdW gaps). However, when the layered materials composed of 2D sheets are applied to forms such as two-dimensional material macroscopic assembly films, two-dimensional material composite assembly films, and two-dimensional material composite polymer films, their performance often fails to meet expectations. The main reason is that the folding, curling, and wrinkling of the sheets during the formation process may lead to problems such as low assembly orderliness, low stacking domain orientation, and high porosity within the film, resulting in a large number of defects that hinder stress transfer, electron transition, and phonon transmission within the film, preventing the excellent performance from being manifested in macroscopic materials and thus affecting the overall performance.

[0003] Different from one-dimensional (1D) and zero-dimensional (0D) nanomaterials, two-dimensional materials are often affected by factors such as thermal vibration, edge instability, thermodynamic instability, strain in 2D crystals, thermal contraction, dislocations, solvent trapping, substrate relaxation, surface anchoring, and high surface tension during transfer, and often form uncontrollable structures such as ripples, bends, and wrinkles. Especially for two-dimensional materials with lower Young's modulus and shear modulus, smaller bending stiffness and thin film elastic modulus, uncontrollable morphological changes are likely to occur in the liquid phase environment (a lower Young's modulus means lower stiffness of the sheet during axial stretching, so the material is softer and easier to deform. A lower shear modulus means higher deformation ability of the sheet under shear stress, and it is prone to sliding and wrinkling. A smaller bending stiffness indicates weaker resistance of the two-dimensional material to bending stress, making it prone to bending or curling. And a lower thin film elastic modulus refers to the elastic performance of the two-dimensional material under bending load, indicating that the sheet is easy to bend). Therefore, these characteristics may lead to an exacerbation of problems such as low sheet orderliness, large interlayer spacing, poor stacking domain orientation, and high porosity in the formed film, thereby reducing the comprehensive performance of the film.

[0004] These above-mentioned problems not only limit the applications of two-dimensional materials in fields such as high electrical conductivity, high thermal conductivity, high electromagnetic shielding, and high separation efficiency, but also hinder their wide promotion in multiple fields such as precision electronic devices, flexible sensor devices, advanced optical devices, aerospace equipment, and environmental governance. Therefore, improving the layer stacking order and stacking domain orientation of two-dimensional material assembly films is a key issue faced in current research, and solving these problems is crucial for enhancing the anisotropic properties and comprehensive performance of materials.

[0005] To address the above challenges, the prior art has explored various induction strategies, including methods such as mechanical stretching, interface-induced assembly, and rigid sheet filling-induced assembly, but they each have limitations. For example:

[0006] Interface-induced assembly method: Utilize the chemical or physical properties of the interface to induce the ordered arrangement of two-dimensional material sheets, which can be assembled at liquid-gas, liquid-liquid, or liquid-solid interfaces. For example, using the Langmuir-Blodgett (LB) technique to prepare highly oriented two-dimensional material films at the gas-liquid interface. However, its operation is complex, and it is difficult to prepare large-area films with uniform and controllable thickness.

[0007] Rigid sheet filling-induced assembly method: It is to add two-dimensional sheets with lower out-of-plane flexibility to the asymmetric out-of-plane flexible sheets. For example, in reference 1 (Advanced Materials Interfaces, 2022, 9(18): 2102418), amino functional groups (Ti3C2-NH2) were introduced on the surface of Ti3C2MXene, and a film with enhanced ordered nanostructure was prepared by the freeze-drawing method using the chemical affinity between Ti3C2-NH2 and reduced graphene oxide (rGO). However, the compatibility and uniformity issues of heterogeneous materials increase the difficulty of quality control and improve the preparation complexity and cost.

[0008] Mechanical stretching method: Immerse the macroscopic assembly film of two-dimensional materials in a plasticizing solvent, and improve the sheet orientation through uniaxial or biaxial stretching. For example, reference (Nature Communications, 2020, 11(1): 2645) provides a continuous plasticizing stretching method, which inserts ethanol molecules into the interlayer of the graphene oxide film for plasticization and then uniaxially stretches the film. The reduced graphene oxide film realizes the enhancement of tensile strength, stiffness, and electrical conductivity. However, uniaxial stretching may cause stress concentration in a certain direction, or shrinkage (for materials with positive Poisson's ratio) or expansion (for materials with negative Poisson's ratio) in the perpendicular direction, affecting the overall uniform stretching effect.

[0009] Therefore, a method for vapor-assisted coplanar stretching and orientation of two-dimensional sheets is needed to solve the above problems, which is of great significance. Summary of the Invention

[0010] The object of the present invention is to solve the problems existing in the prior art and provide a method for steam-assisted coplanar stretching and orientation of two-dimensional sheets.

[0011] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0012] A method for steam-assisted coplanar stretching and orientation of two-dimensional sheets, which simultaneously performs isotropic stretching and steam treatment on a film material containing two-dimensional sheets. The steam used in the steam treatment contains plasticizing steam, and the plasticizing steam is formed by the evaporation of a plasticizing solvent having a plasticizing effect on the two-dimensional sheets.

[0013] When the present invention simultaneously performs isotropic stretching and steam treatment on a film material containing two-dimensional sheets, the plasticizing steam molecules can penetrate between the two-dimensional sheets to weaken the intermolecular van der Waals forces and improve the deformation ability of the sheets. Isotropic stretching can remove or reduce the wrinkles, creases and other irregularities of the sheets, enabling them to be assembled more uniformly, improving the assembly orderliness of the sheets (more compact and orderly interlayer assembly) while increasing the interlayer bonding force (reducing the interlayer spacing), and improving the orientation degree of the sheet stacking domain (increasing the stacking domain density and reducing the internal pores), enhancing the overall performance of the film.

[0014] The specific action mechanism of the plasticizing steam is as follows: as Figure 1 shown, the plasticizing steam molecules can penetrate between the two-dimensional sheets through diffusion, form hydrogen bonds, van der Waals forces and other interactions with the polar groups on the sheet surface, weaken the van der Waals forces between the sheets, reduce the intermolecular rigidity, and increase the slipperiness between the sheets; the adsorption of the plasticizing steam molecules between the sheets can increase the interlayer spacing, make the sheets stretch more evenly, and help to eliminate the wrinkles and irregular stacking of the sheets, thus forming a flatter structure; the plasticizing steam can promote the increase of the molecular mobility on the sheet surface, and some molecular segments are "softened" due to the plasticizing steam molecules in the steam. This softening effect promotes the increase of the translational entropy, rotational entropy and motion entropy of the two-dimensional sheets. After the sheets are flattened and stretched, they are more likely to reach an ordered stacking state; at the same time, due to the wetting effect of the plasticizing steam molecules, part of the internal stress is released, reducing the wrinkles inside and outside the film. This effect of releasing the internal stress can further improve the overall performance of the film; in addition, after the plasticization is completed, as the plasticizing steam volatilizes, rearrangement and ordered stacking occur between the sheets. As the stacking height continuously increases, the interlayer spacing gradually decreases accordingly. This change leads to a gradual increase in the bonding force between the two-dimensional sheets. Further, the orientation of the sheet stacking domain also increases, resulting in a gradual decrease in the pores in the film. This series of changes ultimately prompts the material to form a stable structure.

[0015] Isotropic stretching is more beneficial for improving the performance of film materials containing two-dimensional sheets compared to uniaxial and biaxial stretching in the prior art. Because during isotropic stretching, the tensile stress on the periphery of the film is evenly distributed in all directions. Compared with uniaxial and biaxial stretching, there are obvious differences in the influence of the stress distribution in the film and the orientation of the sheets: (1) Isotropic stretching: When isotropic stretching is performed on the film, the stress will be evenly distributed from the center to the outside, and will not preferentially stretch the sheets in a specific direction. The uniform stretching will cause the sheets in the film to be simultaneously subjected to the same tensile force in all directions, flatten and stretch along all directions of the plane, releasing wrinkles and folds caused by uneven stress. The multi-directional stress helps to flatten the sheets comprehensively and reduce uneven folds. Isotropic stretching helps to form an ordered packing without deviation in a specific direction, which can prompt the sheets to more easily reach a stable ordered state and reduce complex entanglements. Under isotropic stretching, the sheets are guided to be more evenly arranged in all directions within the plane, avoiding the anisotropy formed by directional rearrangement, reducing the disorder of the overall packing domain, and promoting the uniform arrangement of the packing domain. Therefore, the sheet orientation will be evenly distributed in the plane direction, without causing inconsistent packing domain distribution due to obvious single orientation, and avoiding stress concentration in any local direction. (2) Uniaxial stretching: The stress is applied in a single direction, causing the stress to concentrate in the stretching direction. The sheets in the film flatten along the uniaxial direction and are roughly rearranged parallel to the stretching direction, while shrinkage (Poisson effect) occurs in the direction perpendicular to the uniaxial direction, resulting in an increase in the order and orientation of the sheets along the stretching direction, but being significantly insufficient in the direction perpendicular to the stretching direction; (3) Biaxial stretching: Stress is applied in orthogonal directions, and it is necessary to control the stress to be consistent in two directions. The sheets in the film tend to flatten and rearrange along the biaxial directions, enhancing the ordered packing and orientation of the sheets to a certain extent, especially in the two principal axis directions. However, the release of wrinkles and the ordered arrangement in the non-principal stress axes are not as good as isotropic stretching, which easily leads to the problem of excessive local direction stress concentration load.

[0016] As a preferred technical solution:

[0017] A method for steam-assisted coplanar stretching and orientation of two-dimensional sheets as described above, where the film material containing two-dimensional sheets is a film macroscopically assembled from a single two-dimensional sheet (two-dimensional sheet macroscopic assembly film), a film assembled by composite of different two-dimensional sheets (two-dimensional sheet composite assembly film), or a film composed of a composite of two-dimensional sheets and a polymer material (two-dimensional sheet composite polymer film).

[0018] A method for steam-assisted coplanar stretching and orientation of two-dimensional sheets as described above, where the thickness of the film material containing two-dimensional sheets is 100 nm - 1 mm, and the content of two-dimensional sheets is 50 - 100 wt%;

[0019] When the thickness of the film material containing two-dimensional sheets ≤ 10 μm, the device for simultaneously performing isotropic stretching and steam treatment on the film material containing two-dimensional sheets (denoted as the first device) includes a solvent pool a and a heating device a; the top of the solvent pool a is a vertically arranged cylinder a, which is divided into upper and lower layers and is detachably connected by 2m film fixing screws a, where m > 2, and the 2m film fixing screws a are circumferentially and evenly distributed around the central axis of the cylinder a; the heating device a is used to heat the solvent pool a; the process of simultaneously performing isotropic stretching and steam treatment on the film material containing two-dimensional sheets is as follows: first, add a plasticizing solvent into the solvent pool a, then fix the film material containing two-dimensional sheets between the upper and lower layers of the cylinder a through the film fixing screws a and adjust the film fixing screws a to keep the film material containing two-dimensional sheets in a taut state, then heat it through the heating device a until the plasticizing solvent vaporizes, and then keep it warm. After post-treatment, the film material containing two-dimensional sheets after isotropic stretching and steam treatment is obtained;

[0020] When the thickness of the film material containing two-dimensional sheets > 10 μm, the device for simultaneously performing isotropic stretching and steam treatment on the film material containing two-dimensional sheets (denoted as the second device) includes a solvent pool b, a heating device b, a deformable tube, and a regulator; the bottom of the deformable tube is hermetically connected to the top of the solvent pool b, the top of the deformable tube is a vertically arranged cylinder b, which is divided into upper and lower layers and is detachably connected by 2m film fixing screws b, where m > 2, and the 2m film fixing screws b are circumferentially and evenly distributed around the central axis of the cylinder b; the regulator is used to control the radial outward expansion of the cylinder b; the heating device b is used to heat the solvent pool b; the process of simultaneously performing isotropic stretching and steam treatment on the film material containing two-dimensional sheets is as follows: first, add a plasticizing solvent into the solvent pool b, then fix the film material containing two-dimensional sheets between the upper and lower layers of the cylinder b through the film fixing screws b and adjust the film fixing screws b to keep the film material containing two-dimensional sheets in a taut state, then heat it through the heating device b until the plasticizing solvent vaporizes, simultaneously start the regulator and keep it warm. After the insulation ends, the maximum tensile displacement of the film material containing two-dimensional sheets is 1 - 5 mm. After post-treatment, the film material containing two-dimensional sheets after isotropic stretching and steam treatment is obtained.

[0021] When using the first device to perform isotropic stretching and steam treatment on a film material containing two-dimensional sheets simultaneously, during the heating process, the plasticizing solvent continuously vaporizes, causing the vapor pressure in the cavity between the film material containing two-dimensional sheets and the solvent pool a to gradually increase. This results in a greater pressure on the lower side (i.e., the side closer to the solvent pool a) of the film material containing two-dimensional sheets than on its upper side. The pressure difference is converted into in-plane stress through boundary constraints and acts on the film material containing two-dimensional sheets. However, since the film material containing two-dimensional sheets is firmly fixed between the upper and lower cylinders a by the film fixing screw a, this fixing method limits the overall movement of the film material. Therefore, although the pressure on the lower side is greater, the film material cannot move upward completely freely. Instead, it can only deform in some areas within the frame in which it is fixed. As the plasticizing solvent further vaporizes and the vapor pressure continues to increase, generating in-plane stretching caused by normal pressure, the film material containing two-dimensional sheets gradually undergoes isotropic stretching under restricted conditions, thus achieving overall uniform stretching of the film material.

[0022] The present invention takes "10 μm" as the thickness demarcation value. Limited by the diffusion depth of steam in the film (dominated by Fick's second law), when the film thickness ≤ 10 μm, the vapor pressure can self-consistently achieve the coupling of "penetration - plasticization - stretching". Steam molecules can quickly penetrate into the interior of the film and effectively plasticize it in a short time. The lamellar stacking structure in the thin film is small, and steam can uniformly diffuse into all regions of the film, thereby achieving plasticization and stretching. Therefore, for a film of this thickness, the plasticization effect of steam and the co-planar stretching effect caused by the vapor pressure can be achieved simultaneously, and the first device can be used. However, when the film thickness > 10 μm, mechanical stretching must be used to compensate for the stress attenuation of the core layer. The stress non-uniformity (the ratio of the stress received inside the film to the stress on the film surface) caused by pure steam loading is large, and at the same time, the propagation of edge cracks is suppressed. Therefore, external mechanical stretching must be used to assist the plasticization and stretching of the film material. Therefore, for a film of this thickness, the second device needs to be used. 10 μm is an empirical value after a large number of experiments, which is not only based on the compatibility between the two devices and the film thickness, but also the performance transition point of the film material under steam plasticization and mechanical stretching. At this critical value, the thickness of the film undergoes a transition from being relatively easy to stretch and orient to being relatively difficult to stretch and orient, that is, the boundary from when steam treatment can completely penetrate and plasticize the film material to when the film material begins to show resistance to external forces.

[0023] A method for steam-assisted co-planar stretching and orientation of two-dimensional sheets as described above, the regulator includes a displacement bracket, a pressing plate, an upper bracket, a limiting structure, and a lower bracket;

[0024] The displacement support is a conical cap-shaped structure with the tip facing upward, including 2n inclined rods I, where n > 2. The upper ends of the 2n inclined rods I are simultaneously connected to the center of the lower surface of the pressing disk, and the lower ends are circumferentially and uniformly distributed around a point o, which is located on the central axis of the pressing disk. The pressing disk is coaxial with the cylinder b;

[0025] The upper-layer support includes 2n horizontal rods, which are radially distributed around the point o. The two ends of the horizontal rods are respectively denoted as the a-end and the b-end, and the a-end is closer to the point o than the b-end. The a-ends of the 2n horizontal rods are respectively hinged to the lower ends of the 2n inclined rods I in one-to-one correspondence;

[0026] The limiting structure restricts the 2n horizontal rods to move only along their own length directions;

[0027] The b-ends of adjacent 2 horizontal rods are each connected by 1 arc bar. At least one set of opposite arc bars consists of three segments: left, middle, and right. The middle segment consists of a separated inner layer and outer layer. The outer layer of the middle segment is fixedly connected to the left segment, and the inner layer of the middle segment is fixedly connected to the right segment; all the arc bars enclose a ring, and the ring extends vertically downward to form a circular tube;

[0028] The lower-layer support includes 2n inclined rods II, which are distributed in an umbrella shape around the central axis of the cylinder b. The included angle between the inclined rods II and the central axis of the cylinder b is 100 - 105°. The lower layer of the cylinder b extends radially outward and then is connected to the upper ends of the 2n inclined rods II, and the lower ends of the 2n inclined rods II are connected to the circular tube.

[0029] When the pressing disk receives a downward pressure, it will undergo a downward displacement. This displacement is transmitted to the upper-layer support through the displacement support, causing the upper-layer support to also move outward. Then, the displacement of the upper-layer support is transmitted to the lower-layer support, causing the lower-layer support to also move outward. Finally, the displacement of the lower-layer support is transmitted to the deformable tube, causing the deformable tube to extend outward. During the outward extension of the deformable tube, it applies a coplanar tensile displacement to the edge of the membrane in contact with it, thereby generating tensile stress.

[0030] For a membrane material containing two-dimensional sheets with a thickness greater than 10 μm, due to the relatively large thickness, the penetration effect of steam is weakened, and it is impossible to complete the complete orientation inside and on the upper layer of the membrane material containing two-dimensional sheets. It is necessary to start the stretching device to apply an additional in-plane isotropic stretch to the membrane material containing two-dimensional sheets to ensure that the membrane material containing two-dimensional sheets completes the orientation process under a uniform mixed steam environment and isotropic stretch. Among them, the maximum tensile displacement (△L) is determined by the initial diameter L0 of the membrane material containing two-dimensional sheets, and the shrinkage rate of the unstretched membrane in the plane before and after orientation is ∈, and the maximum tensile displacement △L = (L0 × ∈) / 2.

[0031] The shrinkage rate ∈(%) of the membrane material containing two-dimensional sheets on the plane can be calculated through experiments (that is, placing the membrane material containing two-dimensional sheets in a vacuum environment at 100 °C for 12 h, continuously evacuating during this period, and measuring its average diameter L after taking it out and cooling it to room temperature). T ) The calculation formula for the shrinkage rate is as follows:

[0032]

[0033] The stretching displacement is controlled by the pressing plate above the device. Under the pressing plate is the length S of the inclined rod I that can control the edge to move outward (the initial included angle between the inclined rod I and the pressing plate is 45°), which is used to control the outward movement of the upper support and the lower support. When controlling the downward pressing distance (the height measuring support can record the change), the outward movement of the lower support causes the deformable tube to extend outward, and then generates an outward coplanar stretching displacement on the membrane fixed on the deformable tube. Since the maximum stretching displacement is related to the maximum pressing displacement, the calculation formula for the maximum pressing displacement △H is as follows:

[0034]

[0035] In the formula, S is the length of the inclined rod I of the displacement support, and H is the initial height of the displacement support (that is, the vertical distance between the pressing plate and the upper support);

[0036] Substituting into the calculation formulas for the plane shrinkage rate ∈ and the initial diameter L0 of the membrane, the final calculation formula is:

[0037]

[0038] Therefore, after determining the length S of the displacement support and the initial height H of the displacement support, the maximum pressing displacement can be adjusted according to the initial diameter L0 of the membrane and the diameter L after the membrane shrinks. The actual pressing displacement does not exceed the maximum pressing displacement and is adjusted according to the required stretching ratio. The stretching ratio is y (0 < y < 1), and the actual pressing displacement is y × △H. Adjust the actual pressing displacement according to the application requirements. T To adjust the maximum pressing displacement according to the initial diameter L0 of the membrane and the diameter L after the membrane shrinks, and the actual pressing displacement does not exceed the maximum pressing displacement. Adjust according to the required stretching ratio y (0 < y < 1), and the actual pressing displacement is y × △H. Adjust the actual pressing displacement according to the application requirements.

[0039] In the present invention, the lower support is designed to include 2n inclined rods II. On the one hand, it is to disperse the extended external force to the entire plane, reduce the stress concentration in a single direction, and avoid stress overload in a local direction; on the other hand, it is to provide a small displacement to cause a small deformation of the deformable tube.

[0040] For a method of steam-assisted coplanar stretching and orientation of two-dimensional sheets as described above, the regulator further includes a height measuring support, which is vertically arranged on one side of the pressing plate and fixedly connected to the upper support.

[0041] A method for steam-assisted coplanar tensile orientation of two-dimensional sheets as described above, where the Young's modulus of the two-dimensional sheets is 10 - 400 GPa, the shear modulus is 4 - 300 GPa, the bending stiffness is 0.8 - 20 eV, and the thin film elastic modulus is 15 - 300 N / m.

[0042] A method for steam-assisted coplanar tensile orientation of two-dimensional sheets as described above, where the two-dimensional sheets are graphene (G), and the plasticizing solvent is ethanol or acetone;

[0043] Or, the two-dimensional sheets are transition metal carbides (MXene), and the plasticizing solvent is water or ethanol;

[0044] Or, the two-dimensional sheets are molybdenum disulfide (MoS2), and the plasticizing solvent is ethanol or acetone;

[0045] Or, the two-dimensional sheets are tungsten disulfide (WS2), and the plasticizing solvent is ethanol or isopropanol;

[0046] Or, the two-dimensional sheets are tin disulfide (SnS2), and the plasticizing solvent is ethanol or acetone;

[0047] Or, the two-dimensional sheets are black phosphorus (BP), and the plasticizing solvent is ethanol;

[0048] Or, the two-dimensional sheets are graphitic carbon nitride (g-C3N4), and the plasticizing solvent is water or ethanol;

[0049] Or, the two-dimensional sheets are layered double hydroxides (LDH), and the plasticizing solvent is water or ethanol.

[0050] A method for steam-assisted coplanar tensile orientation of two-dimensional sheets as described above, where the two-dimensional sheets are graphene oxide (GO), and the plasticizing solvent is ethanol or isopropanol. The boiling point of isopropanol is higher than that of ethanol, and its saturated vapor pressure at the same temperature is lower. When a thicker film (>100 μm) requires higher temperature and longer time for plasticizing conditions, isopropanol can be used to plasticize the thick film. At high temperature (>120 °C), the lower saturated vapor pressure of isopropanol can ensure the integrity of the film during the reaction process and a long plasticizing process.

[0051] A method for steam-assisted coplanar tensile orientation of two-dimensional sheets as described above, where the steam used in the steam treatment also contains reducing steam, and the reducing steam is formed by the evaporation of a reducing agent that has a reducing effect on the two-dimensional sheets.

[0052] For two-dimensional graphene oxide sheets, after film formation, chemical reduction treatment is required to remove oxygen-containing functional groups attached to the sheets, so as to achieve its electrical and thermal conductivity. However, during the reduction process, due to a series of problems such as the gas produced by the deoxygenation reaction, the violent thermal fluctuations caused by the heating of the sheets, and the increase in the stacking distance between the sheets, the performance of the reduced film is difficult to reach the ideal state, which is specifically manifested in deficiencies in mechanical strength, electrical conductivity, and thermal conductivity.

[0053] The present invention reduces and coplanar stretches the film simultaneously under the reducing steam and plasticizing steam environment, which can suppress the uncontrollable deformation of the sheet layers during the reduction process, improve the assembly orderliness, increase the interlayer bonding force and stacking domain orientation, and enhance the overall performance of the film after the reduction treatment.

[0054] According to the above method for steam-assisted coplanar stretching orientation of two-dimensional sheets, after isotropic stretching and steam treatment, the interlayer spacing of the two-dimensional sheets is reduced by 5-20%, the Herman's orientation factor is increased by 10-50%, and the tensile strength is increased by 10-80%.

[0055] Beneficial effects:

[0056] (1) The present invention first improves the deformation capacity of the sheet by infiltrating plasticized steam molecules into the two-dimensional sheet layers to weaken the interlayer van der Waals force, and at the same time removes or reduces the wrinkles, wrinkles and other irregular shapes of the sheet layers through isotropic stretching, so that the sheet layers can be assembled more evenly, thereby improving the assembly order of the sheet layers while increasing the interlayer bonding force (reducing the interlayer spacing), and improving the orientation degree of the sheet stacking domain, thereby enhancing the overall performance of the membrane.

[0057] (2) The present invention uses different devices when performing isotropic stretching to target membrane materials with two-dimensional sheets of different thicknesses, and ensures that during the stretching process, the tensile stress on the periphery of the membrane materials with two-dimensional sheets of different thicknesses is evenly distributed in all directions, so that the sheets in the membrane are simultaneously subjected to the same tensile force in all directions, thereby being able to be flattened and stretched along all directions of the plane to release wrinkles and folds caused by uneven stress; in addition, the sheets are guided to be arranged more evenly in all directions within the plane, and the anisotropy formed by directional rearrangement is avoided, the disorder of the overall stacking domain is reduced, and the uniform arrangement of the stacking domain is promoted. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is a schematic diagram of steam plasticization assisted coplanar stretching of the present invention;

[0059] Figure 2 Schematic diagram of an isotropic stretching and steam treatment device in Example A1 of the present invention;

[0060] Figure 3It is the top view of the isotropic stretching and steam treatment device in Embodiment A1 of the present invention;

[0061] Figure 4 It is the schematic diagram of the isotropic stretching and steam treatment device in Embodiment A2 of the present invention; in the figure, 45° is the initial angle; S is the length of the inclined rod I of the displacement bracket; H is the initial height of the displacement bracket, that is, the vertical distance between the pressing plate and the upper bracket; △H is the maximum pressing displacement; △L is the maximum stretching displacement;

[0062] Figure 5 It is the top view of the regulator in Embodiment A2 of the present invention;

[0063] Figure 6 It is the side view of the middle section of the arc strip in the upper bracket of the present invention;

[0064] Among them, 1 - solvent pool a, 2 - cylinder a, 3 - film fixing screw a, 4 - arc strip, 5 - solvent pool b, 6 - height measuring bracket, 7 - limiting structure, 8 - film fixing screw b, 9 - deformable tube, 10 - displacement bracket, 11 - pressing plate, 12 - upper bracket, 13 - lower bracket, 14 - cylinder b. Detailed implementation manners

[0065] The present invention will be further described below in conjunction with the detailed implementation manners. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0066] The test methods for the relevant performance indicators in the following examples and comparative examples are as follows:

[0067] Mass per unit area D: Mass per unit area D = concentration of the two-dimensional sheet dispersion (mg·g -1 ) × mass (g) of the two-dimensional sheet dispersion / area (cm 2 ) of the film material containing two-dimensional sheets, and the unit is mg·cm -2 .

[0068] Layer spacing: The film materials containing two-dimensional sheets prepared in each example and the film materials of two-dimensional sheets after isotropic stretching and steam treatment are used as samples, and the XRD patterns are obtained by X-ray diffraction (XRD) test. According to Bragg's law (nλ = 2dsinθ), the layer spacing d is calculated by substituting the ray wavelength λ, diffraction angle θ, and diffraction order n (usually 1).

[0069] Herman's orientation factor: First, take the film materials containing two-dimensional lamellae prepared in each example and the film materials of two-dimensional lamellae after isotropic stretching and steam treatment as samples. Then, obtain the scattering images of the samples through a small-angle X-ray scattering instrument (SAXS) at the BL16B1 beamline of the Shanghai Synchrotron Radiation Facility, acquire the scattering intensity distribution of the diffraction spots, process the scattering intensity distribution with the azimuth angle φ as the variable to obtain the scattering intensity I(φ), and obtain the weighted average <cos 2 (φ)> of the scattering intensity at different azimuth angles through integration. According to the calculation formula of Herman's orientation factor, the Herman's orientation factor is obtained. The calculation formula is: Herman's orientation factor = (3<cos 2 φ> - 1) / 2.

[0070] Tensile strength: First, take the film materials containing two-dimensional lamellae prepared in each example and the film materials of two-dimensional lamellae after isotropic stretching and steam treatment as samples. When the thickness of the sample ≤ 10 μm, its tensile strength is tested by a tensile-compression force tester (model: Mark-10 IntelliMESUR 2.3.1, USA). When the thickness of the sample > 10 μm, its tensile strength is tested by an electronic universal material testing machine (INSTRON 5969).

[0071] Example A1

[0072] The device for simultaneously performing isotropic stretching and steam treatment on the film material containing two-dimensional lamellae with a thickness ≤ 10 μm, as shown in Figure 2 、 Figure 3 , includes a solvent pool a1 and a heating device a;

[0073] The top of the solvent pool a is a vertically arranged cylinder a2. The cylinder a2 is divided into upper and lower layers and is detachably connected by 2m membrane fixing screws a3, where m > 2, and the 2m membrane fixing screws a3 are circumferentially evenly distributed around the central axis of the cylinder a2;

[0074] The heating device a is used to heat the solvent pool a1.

[0075] Example A2

[0076] The device for simultaneously performing isotropic stretching and steam treatment on the film material containing two-dimensional lamellae with a thickness > 10 μm, as shown in Figure 4 、 Figure 5 , includes a solvent pool b5, a heating device b, a deformable tube 9, and a regulator;

[0077] The bottom of the deformable tube 9 is hermetically connected to the top of the solvent pool b 5. The top of the deformable tube 9 is a vertically arranged cylinder b 14, which is divided into upper and lower layers and is detachably connected by 2m membrane fixing screws b 8, where m > 2, and the 2m membrane fixing screws b 8 are circumferentially and evenly distributed around the central axis of the cylinder b 14;

[0078] The heating device b is used to heat the solvent pool b 5;

[0079] The regulator is used to control the cylinder b 14 to expand radially outward along the cylinder b 14;

[0080] The regulator includes a displacement bracket 10, a pressing disc 11, an upper layer bracket 12, a limiting structure 7, a lower layer bracket 13 and a height measuring bracket 6;

[0081] The displacement bracket 10 is a conical cap-shaped structure with the tip upwards, including 2n inclined rods I, where n > 2. The upper ends of the 2n inclined rods I are simultaneously connected to the center of the lower surface of the pressing disc 11, and the lower ends are circumferentially and evenly distributed around a point o, and the point o is located on the central axis of the pressing disc 11, and the pressing disc 11 is coaxial with the cylinder b 14;

[0082] The upper layer bracket 12 includes 2n horizontal rods, and the 2n horizontal rods are radially distributed around the point o. The two ends of the horizontal rods are respectively denoted as the a end and the b end, and the a end is closer to the point o than the b end. The a ends of the 2n horizontal rods are respectively hinged to the lower ends of the 2n inclined rods I one by one;

[0083] The limiting structure 7 restricts the 2n horizontal rods to move only along their own length directions;

[0084] As Figure 5 、 Figure 6 shown, the b ends of adjacent 2 horizontal rods are each connected by 1 arc bar 4. At least one group of opposite arc bars 4 consists of left, middle and right sections. The middle section consists of a separated inner layer and an outer layer. The outer layer of the middle section is fixedly connected to the left section, and the inner layer of the middle section is fixedly connected to the right section; all the arc bars 4 enclose a ring, and the ring extends vertically downward to form a circular tube;

[0085] The lower layer bracket 13 includes 2n inclined rods II, and the 2n inclined rods II are distributed in an umbrella shape around the central axis of the cylinder b 14. The included angle between the inclined rods II and the central axis of the cylinder b 14 is 100 - 105°. The lower layer of the cylinder b 14 extends radially outward and is connected to the upper ends of the 2n inclined rods II, and the lower ends of the 2n inclined rods II are connected to the circular tube.

[0086] Example B1

[0087] A method for steam-assisted coplanar tensile orientation of two-dimensional sheets, the steps are as follows:

[0088] (1) Preparation of raw materials and the apparatus used;

[0089] Two-dimensional sheet: Graphene, with Young's modulus of 100 - 400 GPa, shear modulus of 250 - 300 GPa, bending stiffness of 0.8 - 1.5 eV, and film elastic modulus of 220 N / m;

[0090] Plasticizing solvent: Acetone;

[0091] Apparatus for isotropic stretching and vapor treatment: The apparatus described in Example A1, where m = 3, the height of solvent pool a is 8 cm, and the volume is 25 mL;

[0092] Celgard 3501 membrane: Average pore size is 0.22 μm, effective filtration diameter is 4 cm, and the area is 12.57 cm 2 ;

[0093] Water;

[0094] (2) First, prepare a two-dimensional sheet dispersion (composed of two-dimensional sheets and water) with a concentration of 1 mg·mL -1 , then use the Celgard 3501 membrane as the filtration membrane for vacuum filtration, and after drying at 40 °C for 24 h, peel off the filtration membrane to obtain a two-dimensional sheet macroscopic assembly membrane;

[0095] The obtained two-dimensional sheet macroscopic assembly membrane (i.e., the membrane macroscopically assembled from a single two-dimensional sheet) has a thickness of 100 nm, a mass area density D of 0.3 mg·cm -2 , a layer spacing of 0.4 nm, a Herman's orientation factor of 0.75, and a tensile strength of 500 MPa;

[0096] (3) When performing isotropic stretching and vapor treatment on the two-dimensional sheet macroscopic assembly membrane prepared in step (2), first add 15 mL of the plasticizing solvent to solvent pool a, then fix the two-dimensional sheet macroscopic assembly membrane between the upper and lower cylindrical bodies a through membrane fixing screw a and adjust membrane fixing screw a to keep the two-dimensional sheet macroscopic assembly membrane in a taut state. Then heat it with heating device a until the plasticizing solvent vaporizes, and then keep it at 70 °C for 12 h. After post-treatment (ethanol rinsing, drying in a vacuum oven at 45 °C), obtain the two-dimensional sheet macroscopic assembly membrane after isotropic stretching and vapor treatment.

[0097] After isotropic stretching and vapor treatment, the layer spacing of the two-dimensional sheet macroscopic assembly membrane is reduced by 10%, the Herman's orientation factor is increased by 30%, and the tensile strength is increased by 60%.

[0098] Example B2

[0099] A method for steam-assisted coplanar stretching and orientation of two-dimensional sheets, the steps are as follows:

[0100] (1) Preparation of raw materials and the devices used;

[0101] Two-dimensional sheet: Transition metal carbide (Ti3C2T X MXene), with a Young's modulus of 250 - 350 GPa, a shear modulus of 100 - 250 GPa, a bending stiffness of 1 - 5 eV, and a film elastic modulus of 200 - 300 N / m;

[0102] Plasticizing solvent: Water;

[0103] Devices for isotropic stretching and steam treatment: The devices described in Example A1, where m = 4, the height of solvent pool a is 8 cm, and the volume is 25 mL;

[0104] Celgard 3501 membrane: The average pore diameter is 0.22 μm, the effective filtration diameter is 4 cm, and the area is 12.57 cm 2 ;

[0105] Water;

[0106] (2) First, prepare a two-dimensional sheet dispersion with a concentration of 1 mg·mL -1 (composed of two-dimensional sheets and water), then use the Celgard 3501 membrane as the filtration membrane for vacuum filtration, and dry it at 40 °C for 24 h to obtain a two-dimensional sheet macroscopic assembly film attached to the filtration membrane;

[0107] The thickness of the obtained two-dimensional sheet macroscopic assembly film (i.e., the film assembled by a single two-dimensional sheet macroscopically) is 10 μm, the mass area density D is 2 mg·cm -2 , the layer spacing is 1.5 nm, the Herman's orientation factor is 0.6, and the tensile strength is 300 MPa;

[0108] (3) Retain the filtration membrane. When performing isotropic stretching and steam treatment on the two-dimensional sheet macroscopic assembly film prepared in step (2), first add 15 mL of the plasticizing solvent to solvent pool a, then fix the two-dimensional sheet macroscopic assembly film between the upper and lower cylinders a through membrane fixing screw a (the filtration membrane is closely attached to the upper cylinder a) and adjust membrane fixing screw a to keep the two-dimensional sheet macroscopic assembly film in a taut state. Then heat it to vaporize the plasticizing solvent through heating device a, and keep it at 110 °C for 24 h. After post-treatment (peeling off the filtration membrane, rinsing with ethanol, and drying in a 60 °C vacuum oven), a two-dimensional sheet macroscopic assembly film after isotropic stretching and steam treatment is obtained.

[0109] The layer spacing of the two-dimensional sheet macroscopic assembly film after isotropic stretching and steam treatment is reduced by 8%, the Herman's orientation factor is increased by 25%, and the tensile strength is increased by 50%.

[0110] Example B3

[0111] A method for steam-assisted coplanar tensile orientation of two-dimensional sheets, the steps are as follows:

[0112] (1) Preparation of raw materials and the devices used;

[0113] Two-dimensional sheet: molybdenum disulfide, with a Young's modulus of 270 ± 100 GPa, a shear modulus of 60 - 68 GPa, a bending stiffness of 9 - 20 eV, and a thin film elastic modulus of 180 - 210 N / m;

[0114] Plasticizing solvent: ethanol;

[0115] Devices for isotropic stretching and steam treatment: the devices described in Example A2, n is 4, m is 3, the height of solvent pool b is 10 cm, the volume is 150 mL, and the angle between the inclined rod II and the central axis of cylinder b is 102°;

[0116] Celgard 3501 membrane: the average pore size is 0.22 μm, the effective filtration diameter is 4 cm, and the area is 12.57 cm 2 ;

[0117] Water;

[0118] (2) First, prepare a two-dimensional sheet dispersion (composed of two-dimensional sheets and water) with a concentration of 1 mg·mL -1 , then use the Celgard 3501 membrane as the filtration membrane for vacuum filtration, and dry it at 40 °C for 24 h, then peel off the filtration membrane to obtain the two-dimensional sheet macroscopic assembly membrane;

[0119] The thickness of the obtained two-dimensional sheet macroscopic assembly membrane (i.e., the membrane macroscopically assembled by a single two-dimensional sheet) is 50 μm, the mass area density D is 10 mg·cm -2 , the layer spacing is 0.65 nm, the Herman's orientation factor is 0.65, and the tensile strength is 600 MPa;

[0120] (3) When performing isotropic stretching and steam treatment on the two-dimensional sheet macroscopic assembly membrane prepared in step (2), first add 80 mL of the plasticizing solvent to the solvent pool b, then fix the two-dimensional sheet macroscopic assembly membrane between the upper and lower cylinders b through the membrane fixing screw b and adjust the membrane fixing screw b to keep the two-dimensional sheet macroscopic assembly membrane in a taut state, then heat it through the heating device b until the plasticizing solvent vaporizes, and at the same time press down the pressing plate and keep it at 90 °C for 12 h (the maximum tensile displacement of the two-dimensional sheet macroscopic assembly membrane after the heat preservation is 2 mm), and obtain the two-dimensional sheet macroscopic assembly membrane after isotropic stretching and steam treatment through post-treatment (ethanol rinsing, drying in a vacuum oven at 50 °C).

[0121] After isotropic stretching and steam treatment, the layer spacing of the two-dimensional sheet macroscopic assembly film is reduced by 20%, the Herman's orientation factor is increased by 50%, and the tensile strength is increased by 80%.

[0122] Example B4

[0123] A method for steam-assisted coplanar stretching and orientation of two-dimensional sheets, the steps are as follows:

[0124] (1) Preparation of raw materials and the devices used;

[0125] Two-dimensional sheets: tungsten disulfide, with a Young's modulus of 272 ± 18 GPa, a shear modulus of 60 - 68 GPa, a bending stiffness of 9 - 20 eV, and a thin film elastic modulus of 160 - 200 N / m;

[0126] Plasticizing solvent: isopropyl alcohol;

[0127] Devices for isotropic stretching and steam treatment: the devices described in Example A2, where n is 3, m is 4, the height of the solvent pool b is 12 cm, the volume is 250 mL, and the angle between the inclined rod II and the central axis of the cylinder b is 103°;

[0128] Celgard 3501 membrane: average pore size is 0.22 μm, effective filtration diameter is 4 cm, and the area is 12.57 cm 2 ;

[0129] Water;

[0130] (2) First, prepare a two-dimensional sheet dispersion solution with a concentration of 1 mg·mL -1 (composed of two-dimensional sheets and water), then perform vacuum filtration using the Celgard 3501 membrane as the filtration membrane, dry at 40 °C for 24 h, and peel off the filtration membrane to obtain the two-dimensional sheet macroscopic assembly film;

[0131] The obtained two-dimensional sheet macroscopic assembly film (i.e., the film assembled by a single two-dimensional sheet macroscopically) has a thickness of 500 μm, a mass area density D of 15 mg·cm -2 , a layer spacing of 0.65 nm, a Herman's orientation factor of 0.7, and a tensile strength of 600 MPa;

[0132] (3) When performing isotropic stretching and steam treatment on the two-dimensional sheet macroscopic assembly film prepared in step (2), first add 150 mL of plasticizing solvent to the solvent pool b, and then fix the two-dimensional sheet macroscopic assembly film between the upper and lower cylinders b through the film fixing screw b and adjust the film fixing screw b to keep the two-dimensional sheet macroscopic assembly film in a taut state. Then heat it to vaporize the plasticizing solvent through the heating device b, and at the same time press down the pressing plate and keep it at 100 °C for 18 h (the maximum tensile displacement of the two-dimensional sheet macroscopic assembly film after the heat preservation is 1.5 mm). After post-treatment (ethanol rinsing, drying in a vacuum oven at 55 °C), the two-dimensional sheet macroscopic assembly film after isotropic stretching and steam treatment is obtained.

[0133] The layer spacing of the two-dimensional sheet macroscopic assembly film after isotropic stretching and steam treatment is reduced by 15%, the Herman's orientation factor is increased by 40%, and the tensile strength is increased by 60%.

[0134] Example B5

[0135] A method for steam-assisted coplanar stretching and orientation of two-dimensional sheets, the steps are as follows:

[0136] (1) Preparation of raw materials and devices used;

[0137] Two-dimensional sheet: Tin disulfide, with a Young's modulus of 20 - 60 GPa, a shear modulus of 10 - 20 GPa, a bending stiffness of 1 - 5 eV, and a thin film elastic modulus of 40 - 80 N / m;

[0138] Plasticizing solvent: Acetone;

[0139] Devices used for isotropic stretching and steam treatment: The devices described in Example A2, n is 4, m is 3, the height of the solvent pool b is 12, the volume is 250 mL, and the angle between the inclined rod II and the central axis of the cylinder b is 105°;

[0140] Celgard 3501 membrane: The average pore size is 0.22 μm, the effective filtration diameter is 4 cm, and the area is 12.57 cm 2 ;

[0141] Water;

[0142] (2) First, prepare a two-dimensional sheet dispersion (composed of two-dimensional sheets and water) with a concentration of 1 mg·mL -1 , then perform vacuum filtration using the Celgard 3501 membrane as the filtration membrane, and dry it at 40 °C for 24 h, and then peel off the filtration membrane to obtain the two-dimensional sheet macroscopic assembly film;

[0143] The thickness of the obtained two-dimensional sheet macroscopic assembly film (i.e., the film assembled by a single two-dimensional sheet macroscopically) is 1 mm, and the mass area density D is 20 mg·cm-2 The layer spacing is 0.62 nm, the Herman's orientation factor is 0.6, and the tensile strength is 200 MPa;

[0144] (3) When performing isotropic stretching and steam treatment on the two-dimensional sheet macroscopic assembly film prepared in step (2), first add 180 mL of plasticizing solvent to the solvent pool b, then fix the two-dimensional sheet macroscopic assembly film between the upper and lower cylinders b through the film fixing screw b and adjust the film fixing screw b to keep the two-dimensional sheet macroscopic assembly film in a taut state. Then heat it to vaporize the plasticizing solvent through the heating device b, and at the same time press down the pressing plate and keep it at 70 °C for 24 h (the maximum tensile displacement of the two-dimensional sheet macroscopic assembly film after the heat preservation is 1 mm). After post-treatment (ethanol rinsing, drying in a vacuum oven at 45 °C), the two-dimensional sheet macroscopic assembly film after isotropic stretching and steam treatment is obtained.

[0145] After isotropic stretching and steam treatment, the layer spacing of the two-dimensional sheet macroscopic assembly film is reduced by 5%, the Herman's orientation factor is increased by 10%, and the tensile strength is increased by 10%.

[0146] Example B6

[0147] A method for steam-assisted coplanar stretching and orientation of two-dimensional sheets, the steps are as follows:

[0148] (1) Preparation of raw materials;

[0149] Aqueous solution of graphene oxide: the concentration is 0.5 mg·g -1 ;

[0150] A mixed solution of aqueous hydrogen iodide solution and ethanol: the concentration of the aqueous hydrogen iodide solution is 45 wt%, and the volume ratio of the aqueous hydrogen iodide solution to ethanol is 1:2;

[0151] Celgard 3501 membrane: the average pore diameter is 0.22 μm, the effective filtration diameter is 4 cm, and the area is 12.57 cm 2 ;

[0152] The device used for isotropic stretching and steam treatment: the device described in Example A1, m = 3, the height of the solvent pool b is 8 cm, and the volume is 25 mL;

[0153] (2) Preparation of graphene oxide membrane;

[0154] After filtering the aqueous solution of graphene oxide with the Celgard 3501 membrane, dry it at 35 °C for 12 h, remove the filter membrane, and obtain a graphene oxide membrane with a thickness of 5 μm;

[0155] The thickness of the graphene oxide membrane is 100 nm, and the mass area density D is 1 mg·cm-2 , the layer spacing is 0.44 nm, the Herman's orientation factor is 0.53, and the tensile strength is 245 MPa;

[0156] (3) Add a 15 mL mixture of aqueous hydrogen iodide solution and ethanol to the solvent pool a. Then, fix the graphene oxide film between the upper and lower cylinders a through the film fixing screw a and adjust the film fixing screw a to keep the two-dimensional sheet macroscopic assembly film in a taut state. Then, heat it with the heating device a until the plasticizing solvent vaporizes, and keep it at 90 °C for 6 h. After post-treatment (taking out the film, rinsing with ethanol, and drying in a vacuum oven at 40 °C), a two-dimensional sheet macroscopic assembly film after isotropic stretching and steam treatment is obtained.

[0157] The grain size height of the two-dimensional sheet macroscopic assembly film after isotropic stretching and steam treatment is 6 nm, the proportion of the ordered packing domain is 90%, the full width at half maximum of the XRD diffraction peak is 1.2°, the Herman's orientation factor is 0.8, the surface roughness is 12.5 nm, the surface reflectance is 34%, and the conductivity is 2.5×10 5 S·m -1 , and the tensile strength is 450 MPa;

[0158] The layer spacing of the two-dimensional sheet macroscopic assembly film after isotropic stretching and steam treatment is reduced by 18%, the Herman's orientation factor is increased by 50%, and the tensile strength is increased by 84%.

[0159] Example C1

[0160] A method for steam-assisted coplanar stretching and orientation of two-dimensional sheets, the steps are as follows:

[0161] (1) Preparation of raw materials and devices used;

[0162] Two-dimensional sheet A: black phosphorus;

[0163] The Young's modulus of two-dimensional sheet A is 27±4 GPa, the shear modulus is 4 - 10 GPa, the bending stiffness is 1 - 2 eV, and the thin film elastic modulus is 20 - 100 N / m;

[0164] Two-dimensional sheet B: graphene;

[0165] The Young's modulus of two-dimensional sheet B is 100 - 400 GPa, the shear modulus is 250 - 300 GPa, the bending stiffness is 0.8 - 1.5 eV, and the thin film elastic modulus is 220 N / m;

[0166] Devices used for isotropic stretching and steam treatment: the devices described in Example A1, m is 3, the height of the solvent pool a is 10 cm, and the volume is 35 mL;

[0167] Plasticizing solvent: ethanol;

[0168] Celgard 3501 membrane: The average pore size is 0.22 μm, the effective filtration diameter is 4 cm, and the area is 12.57 cm 2 ;

[0169] Water;

[0170] (2) After uniformly mixing two-dimensional sheet A, two-dimensional sheet B and water, a two-dimensional sheet dispersion with a concentration of 0.5 mg·mL -1 is prepared. Then, using the Celgard 3501 membrane as the filtration membrane, vacuum filtration is carried out, and after drying at 40 °C for 24 h, the filtration membrane is peeled off to obtain the two-dimensional sheet composite assembly membrane; among them, based on the total amount of two-dimensional sheet A and two-dimensional sheet B, the content of two-dimensional sheet A is 1 wt%, and the content of two-dimensional sheet B is 99 wt%;

[0171] The obtained two-dimensional sheet composite assembly membrane (i.e., the membrane composed of different two-dimensional sheet composites) has a thickness of 10 μm, a mass area density D of 3 mg·cm -2 , a layer spacing of 0.42 nm, a Herman's orientation factor of 0.72, and a tensile strength of 420 MPa;

[0172] (3) When performing isotropic stretching and steam treatment on the two-dimensional sheet composite assembly membrane prepared in step (2), first add 20 mL of plasticizing solvent to the solvent pool a, and then fix the two-dimensional sheet composite assembly membrane between the upper and lower cylinders a through the membrane fixing screw a and adjust the membrane fixing screw a to keep the two-dimensional sheet macroscopic assembly membrane in a taut state. Then, heat it through the heating device a until the plasticizing solvent vaporizes and keep it at 90 °C for 24 h. After post-treatment (ethanol rinsing, drying in a 60 °C vacuum oven), the two-dimensional sheet composite assembly membrane after isotropic stretching and steam treatment is obtained.

[0173] After isotropic stretching and steam treatment, the layer spacing of the two-dimensional sheet composite assembly membrane is reduced by 5%, the Herman's orientation factor is increased by 10%, and the tensile strength is increased by 10%.

[0174] Example C2

[0175] A method for steam-assisted coplanar stretching and orientation of two-dimensional sheets, the steps are as follows:

[0176] (1) Preparation of raw materials and the devices used;

[0177] Two-dimensional sheet A: Carbon nitride;

[0178] The Young's modulus of two-dimensional sheet A is 100 - 250 GPa, the shear modulus is 60 - 200 GPa, the bending stiffness is 1 - 3 eV, and the thin film elastic modulus is 15 - 30 N / m;

[0179] Two-dimensional sheet B: molybdenum disulfide;

[0180] The Young's modulus of the two-dimensional sheet B is 270 ± 100 GPa, the shear modulus is 60 - 68 GPa, the bending stiffness is 9 - 20 eV, and the thin film elastic modulus is 180 - 210 N / m;

[0181] Device for isotropic stretching and steam treatment: the device described in Example A1, m is 3, the height of the solvent pool a is 8 cm, and the volume is 25 mL;

[0182] Plasticizing solvent: composed of water and acetone with a mass ratio of 1:1;

[0183] Celgard 3501 membrane: the average pore diameter is 0.22 μm, the effective filtration diameter is 4 cm, and the area is 12.57 cm 2 ;

[0184] Water;

[0185] (2) After mixing the two-dimensional sheet A, the two-dimensional sheet B and water evenly, a two-dimensional sheet dispersion with a concentration of 0.5 mg·mL -1 is prepared. Then, using the Celgard 3501 membrane as the filtration membrane, vacuum filtration is carried out, and then it is dried at 40 °C for 24 h. After peeling off the filtration membrane, a two-dimensional sheet composite assembly membrane is obtained; among them, based on the total amount of the two-dimensional sheet A and the two-dimensional sheet B, the content of the two-dimensional sheet A is 50 wt%, and the content of the two-dimensional sheet B is 50 wt%;

[0186] The thickness of the obtained two-dimensional sheet composite assembly membrane (i.e., the membrane composed of different two-dimensional sheet composites) is 200 nm, the mass area density D is 0.3 mg·cm -2 , the layer spacing is 0.6 nm, the Herman's orientation factor is 0.65, and the tensile strength is 400 MPa;

[0187] (3) When performing isotropic stretching and steam treatment on the two-dimensional sheet composite assembly membrane prepared in step (2), first add 15 mL of the plasticizing solvent to the solvent pool a, and then fix the two-dimensional sheet composite assembly membrane between the upper and lower cylinders a through the membrane fixing screw a and adjust the membrane fixing screw a to keep the two-dimensional sheet macroscopic assembly membrane in a taut state. Then, heat it to 105 °C and keep it warm for 18 h after the plasticizing solvent vaporizes through the heating device a. After post-treatment (ethanol rinsing, drying in a vacuum oven at 45 °C), a two-dimensional sheet composite assembly membrane after isotropic stretching and steam treatment is obtained.

[0188] After isotropic stretching and steam treatment, the layer spacing of the two-dimensional sheet composite assembly membrane is reduced by 15%, the Herman's orientation factor is increased by 40%, and the tensile strength is increased by 60%.

[0189] Example C3

[0190] A method for steam-assisted coplanar stretching and orientation of two-dimensional sheets, the steps are as follows:

[0191] (1) Preparation of raw materials and the devices used;

[0192] Two-dimensional sheet A: Layered double hydroxide;

[0193] The Young's modulus of two-dimensional sheet A is 10 - 30 GPa, the shear modulus is 10 - 20 GPa, and the film elastic modulus is 100 - 300 N / m;

[0194] Two-dimensional sheet B: Graphene;

[0195] The Young's modulus of two-dimensional sheet B is 100 - 400 GPa, the shear modulus is 250 - 300 GPa, the bending stiffness is 0.8 - 1.5 eV, and the film elastic modulus is 220 N / m;

[0196] The devices used for isotropic stretching and steam treatment: the device described in Example A2, n is 3, m is 4, the height of the solvent pool b is 12 cm, the volume is 250 mL, and the angle between the inclined rod II and the central axis of the cylinder b is 100°;

[0197] Plasticizing solvent: composed of water and ethanol with a mass ratio of 1:99;

[0198] Celgard 3501 membrane: The average pore diameter is 0.22 μm, the effective filtration diameter is 4 cm, and the area is 12.57 cm 2 ;

[0199] Water;

[0200] (2) Mix two-dimensional sheet A, two-dimensional sheet B and water evenly and prepare a two-dimensional sheet dispersion with a concentration of 0.5 mg·mL -1 . Then, using the Celgard 3501 membrane as the filtration membrane, perform vacuum filtration, and dry at 40 °C for 24 h. Peel off the filtration membrane to obtain a two-dimensional sheet composite assembly membrane; among them, based on the total amount of two-dimensional sheet A and two-dimensional sheet B, the content of two-dimensional sheet A is 1 wt%, and the content of two-dimensional sheet B is 99 wt%;

[0201] The obtained two-dimensional sheet composite assembly membrane (i.e., the membrane composed of different two-dimensional sheets composite-assembled) has a thickness of 450 μm, a mass area density D of 15 mg·cm -2 , a layer spacing of 0.44 nm, a Herman's orientation factor of 0.7, and a tensile strength of 480 MPa;

[0202] (3) When performing isotropic stretching and steam treatment on the two-dimensional sheet composite assembly film prepared in step (2), first add 180 mL of plasticizing solvent to the solvent pool b. Then fix the two-dimensional sheet composite assembly film between the upper and lower cylinders b through the film fixing screw b and adjust the film fixing screw b to keep the two-dimensional sheet macroscopic assembly film in a taut state. After heating it to vaporize the plasticizing solvent through the heating device b, simultaneously press down the pressing plate and keep it at 105 °C for 16 h (the maximum tensile displacement of the two-dimensional sheet macroscopic assembly film after the heat preservation is 1 mm). After post-treatment (ethanol rinsing, drying in a vacuum oven at 55 °C), the two-dimensional sheet composite assembly film after isotropic stretching and steam treatment can be obtained.

[0203] The layer spacing of the two-dimensional sheet composite assembly film after isotropic stretching and steam treatment is reduced by 5%, the Herman's orientation factor is increased by 10%, and the tensile strength is increased by 10%.

[0204] Example C4

[0205] A method for steam-assisted coplanar stretching and orientation of two-dimensional sheets, the steps are as follows:

[0206] (1) Preparation of raw materials and the devices used;

[0207] Two-dimensional sheet A: molybdenum disulfide;

[0208] The Young's modulus of two-dimensional sheet A is 270 ± 100 GPa, the shear modulus is 60 - 68 GPa, the bending stiffness is 9 - 20 eV, and the film elastic modulus is 180 - 210 N / m;

[0209] Two-dimensional sheet B: transition metal carbide (Ti3C2T X MXene);

[0210] The Young's modulus of two-dimensional sheet B is 250 - 350 GPa, the shear modulus is 100 - 250 GPa, the bending stiffness is 1 - 5 eV, and the film elastic modulus is 200 - 300 N / m;

[0211] The devices used for isotropic stretching and steam treatment: the devices described in Example A2, n is 4, m is 3, the height of the solvent pool b is 10 cm, the volume is 150 mL, and the included angle between the inclined rod II and the central axis of the cylinder b is 100°;

[0212] Plasticizing solvent: composed of acetone and water with a mass ratio of 1:1;

[0213] Celgard 3501 membrane: the average pore diameter is 0.22 μm, the effective filtration diameter is 4 cm, and the area is 12.57 cm 2 ;

[0214] Water;

[0215] (2) After uniformly mixing two-dimensional sheet A, two-dimensional sheet B and water, a two-dimensional sheet dispersion with a concentration of 0.5 mg·mL -1 is prepared. Then, using a Celgard 3501 membrane as the suction filtration membrane, vacuum suction filtration is carried out, and then it is dried at 40 °C for 24 h to obtain a two-dimensional sheet composite assembly membrane attached to the suction filtration membrane; among them, based on the total amount of two-dimensional sheet A and two-dimensional sheet B, the content of two-dimensional sheet A is 50 wt%, and the content of two-dimensional sheet B is 50 wt%;

[0216] The obtained two-dimensional sheet composite assembly membrane (i.e., the membrane composed of different two-dimensional sheet composites) has a thickness of 1 mm, a mass area density D of 20 mg·cm -2 , a layer spacing of 1.2 nm, a Herman's orientation factor of 0.6, and a tensile strength of 300 MPa;

[0217] (3) Retaining the suction filtration membrane, when performing isotropic stretching and steam treatment on the two-dimensional sheet composite assembly membrane prepared in step (2), first add 80 mL of plasticizing solvent to the solvent pool b, and then fix the two-dimensional sheet composite assembly membrane between the upper and lower cylinders b through the membrane fixing screw b (the suction filtration membrane is closely attached to the upper cylinder b) and adjust the membrane fixing screw b to keep the two-dimensional sheet macroscopic assembly membrane in a taut state. Then, after heating to vaporize the plasticizing solvent through the heating device b, simultaneously press down the pressing plate and keep it at 105 °C for 24 h (the maximum tensile displacement of the two-dimensional sheet macroscopic assembly membrane after the insulation is 5 mm). After post-treatment (peeling off the suction filtration membrane, rinsing with ethanol, and drying in a 50 °C vacuum oven), the two-dimensional sheet composite assembly membrane after isotropic stretching and steam treatment can be obtained.

[0218] The layer spacing of the two-dimensional sheet composite assembly membrane after isotropic stretching and steam treatment is reduced by 20%, the Herman's orientation factor is increased by 30%, and the tensile strength is increased by 80%.

[0219] Example C5

[0220] A method for steam-assisted coplanar stretching orientation of two-dimensional sheets, the steps are as follows:

[0221] (1) Preparation of raw materials and devices used;

[0222] Two-dimensional sheet A: Tungsten disulfide;

[0223] The Young's modulus of two-dimensional sheet A is 272 ± 18 GPa, the shear modulus is 60 - 68 GPa, the bending stiffness is 9 - 20 eV, and the thin film elastic modulus is 160 - 200 N / m;

[0224] Two-dimensional sheet B: Carbon nitride;

[0225] The Young's modulus of the two-dimensional sheet B is 100 - 250 GPa, the shear modulus is 60 - 200 GPa, the flexural rigidity is 1 - 3 eV, and the film elastic modulus is 15 - 30 N / m;

[0226] The device for isotropic stretching and steam treatment: the device described in Example A2, where n = 3, m = 4, the height of the solvent pool b is 10 cm, the volume is 150 mL, and the angle between the inclined rod II and the central axis of the cylinder b is 105°;

[0227] The plasticizing solvent: composed of isopropyl alcohol and ethanol with a mass ratio of 99:1;

[0228] Celgard 3501 membrane: the average pore diameter is 0.22 μm, the effective filtration diameter is 4 cm, and the area is 12.57 cm 2 ;

[0229] Water;

[0230] (2) After uniformly mixing the two-dimensional sheet A, the two-dimensional sheet B and water, a two-dimensional sheet dispersion with a concentration of 0.5 mg·mL -1 is prepared. Then, using the Celgard 3501 membrane as the filtration membrane, vacuum filtration is carried out, and then it is dried at 40 °C for 24 h. After peeling off the filtration membrane, a two-dimensional sheet composite assembly membrane is obtained; among them, based on the total amount of the two-dimensional sheet A and the two-dimensional sheet B, the content of the two-dimensional sheet A is 99 wt%, and the content of the two-dimensional sheet B is 1 wt%;

[0231] The thickness of the obtained two-dimensional sheet composite assembly membrane (i.e., the membrane composed of different two-dimensional sheet composites) is 100 μm, the mass area density D is 10 mg·cm -2 , the layer spacing is 0.67 nm, the Herman's orientation factor is 0.63, and the tensile strength is 350 MPa;

[0232] (3) When performing isotropic stretching and steam treatment on the two-dimensional sheet composite assembly membrane prepared in step (2), first add 80 mL of the plasticizing solvent to the solvent pool b. Then, fix the two-dimensional sheet composite assembly membrane between the upper and lower cylinders b through the membrane fixing screw b and adjust the membrane fixing screw b to keep the two-dimensional sheet macroscopic assembly membrane in a taut state. Then, heat it through the heating device b until the plasticizing solvent vaporizes. At the same time, press down the pressing plate and keep it at 90 °C for 18 h (after the insulation ends, the maximum tensile displacement of the two-dimensional sheet macroscopic assembly membrane is 2.5 mm). After post-treatment (ethanol rinsing, drying in a 60 °C vacuum oven), the two-dimensional sheet composite assembly membrane after isotropic stretching and steam treatment can be obtained.

[0233] The layer spacing of the two-dimensional sheet composite assembly film after isotropic stretching and steam treatment is reduced by 10%, the Herman's orientation factor is increased by 50%, and the tensile strength is increased by 50%.

[0234] Example D1

[0235] A method for steam-assisted coplanar stretching and orientation of two-dimensional sheets, the steps are as follows:

[0236] (1) Preparation of raw materials and the devices used;

[0237] Two-dimensional sheet: Graphene;

[0238] The Young's modulus of the two-dimensional sheet is 100 - 400 GPa, the shear modulus is 250 - 300 GPa, the bending stiffness is 0.8 - 1.5 eV, and the film elastic modulus is 220 N / m;

[0239] Plasticizing solvent: Acetone;

[0240] Polymer material: Sodium alginate, manufactured by Sigma-Aldrich, CAS number is 9005 - 38 - 3, viscosity is 250 - 300 cps;

[0241] Deionized water;

[0242] EDTA (Ethylenediaminetetraacetic acid);

[0243] Calcium chloride;

[0244] NaOH aqueous solution;

[0245] Glass plate;

[0246] The device for isotropic stretching and steam treatment: The device described in Example A2, n is 3, m is 3, the height of the solvent pool b is 8 cm, the volume is 50 mL, and the angle between the inclined rod II and the central axis of the cylinder b is 100°;

[0247] (2) Prepare a two-dimensional sheet composite polymer film (i.e., a film composed of a two-dimensional sheet and a polymer material);

[0248] (2.1) Disperse the polymer material into deionized water, and continuously stir evenly during the addition process to obtain solution A; among them, the content of the polymer material is 0.5 wt%;

[0249] (2.2) First, mix EDTA, calcium chloride, and deionized water evenly to obtain an aqueous Ca-EDTA solution with a concentration of 0.1 M. Then, add 0.1 mol / L NaOH aqueous solution dropwise until the pH of the solution reaches 7. Subsequently, add two-dimensional sheets and stir evenly. Finally, ultrasonicate at a power of 300 W for 30 min and then continue stirring for 1 h to make it evenly dispersed, obtaining solution B; wherein, the molar ratio of EDTA to calcium chloride is 1:1;

[0250] In steps (2.1)-(2.2), the mass ratio of the two-dimensional sheets to the polymer material is 99:1;

[0251] (2.3) Add solution B to solution A at a rate of 1 drop per second. During the dropping process, stir at a speed of 700 rpm. After the dropping is completed, ultrasonicate at a power of 300 W for 30 min and then continue stirring for 3 h to obtain a suspension. Subsequently, degas it in a vacuum environment for 15 min to remove the bubbles generated during the mixing process, obtaining solution C; wherein, the volume ratio of solution A to solution B is 1:1;

[0252] (2.4) Pour solution C onto a glass plate, scrape to form a film, and then dry it at a constant temperature of 45 °C and a constant humidity of 60% for 24 h. After that, peel the film from the glass plate to obtain a two-dimensional sheet composite polymer film;

[0253] The thickness of the prepared two-dimensional sheet composite polymer film is 50 μm, the mass area density D is 0.3 mg·cm -2 , the layer spacing is 0.65 nm, the Herman’s orientation factor is 0.45, and the tensile strength is 200 MPa;

[0254] (3) When performing isotropic stretching and steam treatment on the two-dimensional sheet composite polymer film prepared in step (2), first add 80 mL of plasticizing solvent to solvent pool b. Then, fix the two-dimensional sheet composite polymer film between the upper and lower cylinders b through membrane fixing screw b and adjust membrane fixing screw b to keep the two-dimensional sheet macroscopic assembly film in a taut state. Then, heat it through heating device b until the plasticizing solvent vaporizes. At the same time, press down the pressing plate and keep it at 70 °C for 24 h (after the insulation is completed, the maximum tensile displacement of the two-dimensional sheet macroscopic assembly film is 2 mm). After post-treatment (ethanol rinsing, drying in a 45 °C vacuum oven), obtain the two-dimensional sheet composite polymer film after isotropic stretching and steam treatment.

[0255] After isotropic stretching and steam treatment, the layer spacing of the two-dimensional sheet composite polymer film decreases by 5%, the Herman’s orientation factor increases by 10%, and the tensile strength increases by 10%.

[0256] Example D2

[0257] A method for steam-assisted coplanar stretching and orientation of two-dimensional sheets, the steps are as follows:

[0258] (1) Preparation of raw materials and devices used;

[0259] Two-dimensional sheet: Transition metal carbide Ti3C2T X MXene;

[0260] The Young's modulus of the two-dimensional sheet is 250 - 350 GPa, the shear modulus is 100 - 250 GPa, the bending stiffness is 1 - 5 eV, and the film elastic modulus is 200 - 300 N / m;

[0261] Plasticizing solvent: Water;

[0262] Polymer material: Chitosan, manufactured by Shanghai Aladdin Biochemical Technology Co., Ltd., product number C105799, CAS number 9012 - 76 - 4;

[0263] Deionized water;

[0264] Acetic acid aqueous solution;

[0265] Sodium dodecylbenzenesulfonate powder;

[0266] Glass plate;

[0267] Device for isotropic stretching and steam treatment: The device described in Example A2, n is 3, m is 4, the height of solvent pool b is 8 cm, the volume is 100 mL, and the angle between the inclined rod II and the central axis of the cylinder b is 105°;

[0268] (2) Preparation of a two-dimensional sheet composite polymer membrane (i.e., a membrane composed of a composite of two-dimensional sheets and a polymer material);

[0269] (2.1) Dissolve the polymer material in an acetic acid aqueous solution with a concentration of 1 vol%, stir continuously and heat to 45 °C. After ensuring its complete dissolution, obtain solution A; among them, the concentration of the polymer material is 1% (wt / vol);

[0270] (2.2) Uniformly disperse the two-dimensional sheet in deionized water, and then add sodium dodecylbenzenesulfonate powder and mix evenly to obtain solution B; among them, the content of sodium dodecylbenzenesulfonate powder is 0.5 wt%;

[0271] In steps (2.1) - (2.2), the mass ratio of the two-dimensional sheet to the polymer material is 85:15;

[0272] (2.3) Add solution B to solution A at a rate of 1 drop per second. Stir at a speed of 700 rpm during the dropping process. After the dropping is completed, ultrasonicate at a power of 300 W for 30 min and then continue stirring for 3 h to obtain a homogeneous suspension. Finally, degas the suspension in a vacuum environment for 15 min to remove the bubbles generated during the mixing process, obtaining solution C; wherein, the volume ratio of solution A to solution B is 1:1;

[0273] (2.4) Pour solution C onto a glass plate, scrape and coat to form a film, and then dry it at a constant temperature of 45 °C and a constant humidity of 60% for 24 h. Then peel the film from the glass plate to obtain a two-dimensional sheet composite polymer film;

[0274] The thickness of the prepared two-dimensional sheet composite polymer film is 100 μm, and the mass area density D is 2 mg·cm -2 , the layer spacing is 0.62 nm, the Herman’s orientation factor is 0.4, and the tensile strength is 180 MPa;

[0275] (3) When performing isotropic stretching and steam treatment on the two-dimensional sheet composite polymer film prepared in step (2), first add 100 mL of plasticizing solvent to the solvent pool b. Then fix the two-dimensional sheet composite polymer film between the upper and lower cylinders b through the membrane fixing screw b and adjust the membrane fixing screw b to keep the two-dimensional sheet macroscopic assembly film in a taut state. Then heat it through the heating device b until the plasticizing solvent vaporizes. At the same time, press down the pressing plate and keep it at 110 °C for 12 h (the maximum tensile displacement of the two-dimensional sheet macroscopic assembly film is 3 mm after the heat preservation ends). After post-treatment (ethanol rinsing, drying in a vacuum oven at 45 °C), obtain the two-dimensional sheet composite polymer film after isotropic stretching and steam treatment.

[0276] After isotropic stretching and steam treatment, the layer spacing of the two-dimensional sheet composite polymer film is reduced by 8%, the Herman’s orientation factor is increased by 20%, and the tensile strength is increased by 25%.

[0277] Example D3

[0278] A method for steam-assisted coplanar stretching orientation of two-dimensional sheets, the steps are as follows:

[0279] (1) Preparation of raw materials and the devices used;

[0280] Two-dimensional sheet: molybdenum disulfide;

[0281] The Young's modulus of the two-dimensional sheet is 270 ± 100 GPa, the shear modulus is 60 - 68 GPa, the bending stiffness is 9 - 20 eV, and the thin film elastic modulus is 180 - 210 N / m;

[0282] Plasticizing solvent: ethanol;

[0283] Polymer material: Sodium alginate, manufactured by Sigma-Aldrich, CAS number 9005-38-3, viscosity 250 - 300 cps;

[0284] Deionized water;

[0285] EDTA (Ethylenediaminetetraacetic acid);

[0286] Calcium chloride;

[0287] NaOH aqueous solution;

[0288] Glass plate;

[0289] Device for isotropic stretching and steam treatment: The device described in Example A2, n = 4, m = 3, the height of solvent pool b is 10 cm, the volume is 150 mL, and the angle between the inclined rod II and the central axis of the cylinder b is 105°;

[0290] (2) Prepare a two-dimensional sheet composite polymer membrane (i.e., a membrane composed of a two-dimensional sheet and a polymer material);

[0291] (2.1) Disperse the polymer material into deionized water, and keep stirring evenly during the addition process to obtain Solution A; among them, the content of the polymer material is 0.5 wt%;

[0292] (2.2) First, mix EDTA, calcium chloride, and deionized water evenly to obtain an aqueous Ca-EDTA solution with a concentration of 0.1 M. Then, dropwise add 0.1 mol / L NaOH solution until the pH of the solution is 7. Subsequently, add two-dimensional sheets to it and stir evenly. Finally, ultrasonicate at a power of 300 W for 30 min and then continue to stir for 1 h to make it evenly dispersed to obtain Solution B; among them, the molar ratio of EDTA to calcium chloride is 1:1;

[0293] In steps (2.1)-(2.2), the mass ratio of the two-dimensional sheet to the polymer material is 75:25;

[0294] (2.3) Add Solution B to Solution A at a rate of 1 drop per second, stir at a speed of 700 rpm during the addition process. After the addition is completed, ultrasonicate at a power of 300 W for 30 min and then continue to stir for 3 h to obtain a suspension. Subsequently, defoam it in a vacuum environment for 15 min to remove the bubbles generated during the mixing process to obtain Solution C; among them, the volume ratio of Solution A to Solution B is 1:1;

[0295] (2.4) Pour Solution C onto a glass plate, scrape it into a film, and dry it at a constant temperature of 45 °C and a constant humidity of 60% for 24 h. Then, peel the film from the glass plate to obtain a two-dimensional sheet composite polymer membrane;

[0296] The thickness of the prepared two-dimensional sheet composite polymer membrane is 500 μm, and the mass area density D is 10 mg·cm -2 , the layer spacing is 0.58 nm, the Herman's orientation factor is 0.35, and the tensile strength is 150 MPa;

[0297] (3) When performing isotropic stretching and steam treatment on the two-dimensional sheet composite polymer membrane prepared in step (2), first add 120 mL of plasticizing solvent to the solvent pool b, and then fix the two-dimensional sheet composite polymer membrane between the upper and lower cylinders b through the membrane fixing screw b and adjust the membrane fixing screw b to keep the two-dimensional sheet macroscopic assembly membrane in a taut state. Then heat it to vaporize the plasticizing solvent through the heating device b. At the same time, press down the pressing plate and keep it at 90 °C for 18 h (the maximum tensile displacement of the two-dimensional sheet macroscopic assembly membrane after the heat preservation is 3.5 mm). After post-treatment (ethanol rinsing, drying in a vacuum oven at 45 °C), the two-dimensional sheet composite polymer membrane after isotropic stretching and steam treatment is obtained.

[0298] After isotropic stretching and steam treatment, the layer spacing of the two-dimensional sheet composite polymer membrane is reduced by 12%, the Herman's orientation factor is increased by 35%, and the tensile strength is increased by 45%.

[0299] Example D4

[0300] A method for steam-assisted coplanar stretching orientation of two-dimensional sheets, the steps are as follows:

[0301] (1) Preparation of raw materials and devices used;

[0302] Two-dimensional sheet: tungsten disulfide;

[0303] The Young's modulus of the two-dimensional sheet is 272 ± 18 GPa, the shear modulus is 60 - 68 GPa, the bending stiffness is 9 - 20 eV, and the thin film elastic modulus is 160 - 200 N / m;

[0304] Plasticizing solvent: isopropyl alcohol;

[0305] Polymer material: sodium alginate, manufactured by Sigma-Aldrich, CAS number 9005-38-3, viscosity 250 - 300 cps;

[0306] Deionized water;

[0307] EDTA (ethylenediaminetetraacetic acid);

[0308] Calcium chloride;

[0309] NaOH aqueous solution;

[0310] Glass plate;

[0311] Apparatus for isotropic stretching and steam treatment: the apparatus described in Example A2, where n is 3, m is 4, the height of the solvent pool b is 12 cm, the volume is 250 mL, and the angle between the inclined rod II and the central axis of the cylinder b is 100°;

[0312] (2) Prepare a two-dimensional sheet composite polymer membrane (i.e., a membrane composed of a two-dimensional sheet and a polymer material);

[0313] (2.1) Disperse the polymer material into deionized water and continuously stir evenly during the addition process to obtain Solution A; among them, the content of the polymer material is 0.5 wt%;

[0314] (2.2) First, mix EDTA, calcium chloride, and deionized water evenly to obtain an aqueous Ca-EDTA solution with a concentration of 0.1 M. Then, dropwise add 0.1 mol / L NaOH solution until the pH of the solution is 7. Subsequently, add two-dimensional sheets to it and stir evenly. Finally, ultrasonicate at a power of 300 W for 30 min and then continue to stir for 1 h to make it evenly dispersed to obtain Solution B; among them, the molar ratio of EDTA to calcium chloride is 1:1;

[0315] In steps (2.1)-(2.2), the mass ratio of the two-dimensional sheet to the polymer material is 65:35;

[0316] (2.3) Add Solution B to Solution A at a rate of 1 drop per second, stir at a speed of 700 rpm during the dropping process. After the dropping is completed, ultrasonicate at a power of 300 W for 30 min and then continue to stir for 3 h to obtain a suspension. Subsequently, defoam it in a vacuum environment for 15 min to remove the bubbles generated during the mixing process to obtain Solution C; among them, the volume ratio of Solution A to Solution B is 1:1;

[0317] (2.4) Pour Solution C onto a glass plate, scrape it into a film, and dry it at a constant temperature of 45 °C and a constant humidity of 60% for 24 h. Then, peel the film from the glass plate to obtain a two-dimensional sheet composite polymer membrane;

[0318] The thickness of the prepared two-dimensional sheet composite polymer membrane is 800 μm, the mass area density D is 15 mg·cm -2 , the layer spacing is 0.55 nm, the Herman's orientation factor is 0.3, and the tensile strength is 120 MPa;

[0319] (3) When performing isotropic stretching and steam treatment on the two-dimensional sheet composite polymer membrane obtained in step (2), first add 140 mL of plasticizing solvent to the solvent pool b, then fix the two-dimensional sheet composite polymer membrane between the upper and lower cylinders b through the membrane fixing screw b and adjust the membrane fixing screw b to keep the two-dimensional sheet macroscopic assembly membrane in a taut state. Then heat it through the heating device b until the plasticizing solvent vaporizes. At the same time, press down the pressing plate and keep it at 100 °C for 24 h (the maximum stretching displacement of the two-dimensional sheet macroscopic assembly membrane after the heat preservation is 4 mm). After post-treatment (ethanol rinsing, drying in a vacuum oven at 45 °C), the two-dimensional sheet composite polymer membrane after isotropic stretching and steam treatment is obtained.

[0320] The layer spacing of the two-dimensional sheet composite polymer membrane after isotropic stretching and steam treatment is reduced by 15%, the Herman's orientation factor is increased by 42%, and the tensile strength is increased by 70%.

[0321] Example D5

[0322] A method for steam-assisted coplanar stretching and orientation of two-dimensional sheets, the steps are as follows:

[0323] (1) Preparation of raw materials and the devices used;

[0324] Two-dimensional sheet: Tin disulfide;

[0325] The Young's modulus of the two-dimensional sheet is 20 - 60 GPa, the shear modulus is 10 - 20 GPa, the bending stiffness is 1 - 5 eV, and the thin film elastic modulus is 40 - 80 N / m;

[0326] Plasticizing solvent: Acetone;

[0327] Polymer material: Chitosan, manufactured by Shanghai Aladdin Biochemical Technology Co., Ltd., product number C105799, CAS number 9012 - 76 - 4;

[0328] Acetic acid aqueous solution;

[0329] Sodium dodecylbenzenesulfonate powder;

[0330] Deionized water;

[0331] The devices used for isotropic stretching and steam treatment: The devices described in Example A2, n is 4, m is 3, the height of the solvent pool b is 12 cm, the volume is 250 mL, and the included angle between the inclined rod II and the central axis of the cylinder b is 100°;

[0332] (2) Preparation of a two-dimensional sheet composite polymer membrane (i.e., a membrane composed of a two-dimensional sheet and a polymer material);

[0333] (2.1) Dissolve the polymer material in an aqueous acetic acid solution with a concentration of 2 vol%, continuously stir and heat to 45 °C until it is completely dissolved to obtain Solution A; among them, the concentration of chitosan powder is 3% (wt / vol);

[0334] (2.2) Uniformly disperse the two-dimensional sheet in deionized water, and then add sodium dodecylbenzenesulfonate powder and mix evenly to obtain Solution B; among them, the content of sodium dodecylbenzenesulfonate powder is 0.5 wt%;

[0335] In steps (2.1)-(2.2), the mass ratio of the two-dimensional sheet to the polymer material is 1:1;

[0336] (2.3) Add Solution B to Solution A at a rate of 1 drop per second. During the dropping process, stir at a speed of 700 rpm. After the dropping is completed, ultrasonicate at a power of 300 W for 30 min and then continue to stir for 3 h to obtain a uniform suspension. Finally, de-bubble the suspension in a vacuum environment for 15 min to remove the bubbles generated during the mixing process to obtain Solution C; among them, the volume ratio of Solution A to Solution B is 1:1;

[0337] (2.4) Pour Solution C onto a glass plate, scrape and coat to form a film, and then dry it at a constant temperature of 45 °C and a constant humidity of 60% for 24 h. Then peel the film from the glass plate to obtain a two-dimensional sheet composite polymer film;

[0338] The thickness of the prepared two-dimensional sheet composite polymer film is 1 mm, the mass area density D is 20 mg·cm -2 , the layer spacing is 0.50 nm, the Herman's orientation factor is 0.25, and the tensile strength is 100 MPa;

[0339] (3) When performing isotropic stretching and steam treatment on the two-dimensional sheet composite polymer film prepared in step (2), first add 180 mL of plasticizing solvent to the solvent pool b, and then fix the two-dimensional sheet composite polymer film between the upper and lower cylinders b through the membrane fixing screw b and adjust the membrane fixing screw b to keep the two-dimensional sheet macroscopic assembly film in a taut state. Then heat it through the heating device b until the plasticizing solvent vaporizes. At the same time, press down the pressing plate and keep it at 70 °C for 12 h (after the heat preservation, the maximum tensile displacement of the two-dimensional sheet macroscopic assembly film is 4.5 mm). After post-treatment (ethanol rinsing, drying in a vacuum oven at 45 °C), obtain the two-dimensional sheet composite polymer film after isotropic stretching and steam treatment.

[0340] After isotropic stretching and steam treatment, the layer spacing of the two-dimensional sheet composite polymer film is reduced by 20%, the Herman's orientation factor is increased by 50%, and the tensile strength is increased by 80%.

Claims

1. A method for steam-assisted coplanar stretching orientation of a two-dimensional sheet, characterized in that: At the same time, the membrane material containing the two-dimensional sheet is isotropically stretched and steam-treated, wherein the steam used in the steam treatment contains plasticizing steam, and the plasticizing steam is formed by evaporating a plasticizing solvent that has a plasticizing effect on the two-dimensional sheet; The thickness of the membrane material containing the two-dimensional sheet is 100nm-1mm, and the content of the two-dimensional sheet is 50-100wt%; When the thickness of the membrane material containing the two-dimensional lamellae is ≤10 μm, the device used for isotropically stretching and steam-treating the membrane material containing the two-dimensional lamellae at the same time includes a solvent pool a and a heating device a; the top of the solvent pool a is a vertically arranged cylinder a, the cylinder a is divided into an upper and lower layer and is detachably connected by 2m membrane fixing screws a, m>2, and the 2m membrane fixing screws a are evenly distributed around the circumference of the central axis of the cylinder a; the heating device a is used to heat the solvent pool a; the process of isotropically stretching and steam-treating the membrane material containing the two-dimensional lamellae at the same time is: first, a plasticizing solvent is added to the solvent pool a, and then the membrane material containing the two-dimensional lamellae is fixed between the upper and lower layers of the cylinder a by the membrane fixing screws a and the membrane fixing screws a are adjusted to keep the membrane material containing the two-dimensional lamellae in a taut state, and then heated by the heating device a until the plasticizing solvent is vaporized, and then kept warm, and after post-treatment, the membrane material containing the two-dimensional lamellae after isotropic stretching and steam treatment is obtained; When the thickness of the membrane material containing the two-dimensional lamellae is greater than 10 μm, the device used for isotropically stretching and steam treating the membrane material containing the two-dimensional lamellae at the same time includes a solvent pool b, a heating device b, a deformable tube and a regulator; the bottom of the deformable tube is sealed and connected to the top of the solvent pool b, the top of the deformable tube is a vertically arranged cylinder b, the cylinder b is divided into an upper and lower layer and is detachably connected by 2m membrane fixing screws b, m>2, and the 2m membrane fixing screws b are evenly distributed around the circumference of the central axis of the cylinder b; the regulator is used to control the radial outward expansion of the cylinder b along the cylinder b; the heating device b is used to heat Hot solvent pool b; the process of isotropically stretching and steam-treating the membrane material containing the two-dimensional lamellae at the same time is as follows: first, add the plasticizing solvent into the solvent pool b, then fix the membrane material containing the two-dimensional lamellae between the upper and lower cylinders b by the membrane fixing screws b and adjust the membrane fixing screws b to keep the membrane material containing the two-dimensional lamellae in a taut state, and then heat it by the heating device b until the plasticizing solvent is vaporized, and at the same time start the regulator and keep it warm. After the insulation is completed, the maximum tensile displacement of the membrane material containing the two-dimensional lamellae is 1-5mm. After post-treatment, the membrane material containing the two-dimensional lamellae after isotropic stretching and steam treatment is obtained.

2. A method for steam-assisted coplanar stretching orientation of a two-dimensional sheet according to claim 1, characterized in that: The membrane material containing two-dimensional sheets is a membrane macroscopically assembled from a single two-dimensional sheet, a membrane compositely assembled from different two-dimensional sheets, or a membrane composited from two-dimensional sheets and polymer materials.

3. A method for steam-assisted coplanar stretching orientation of a two-dimensional sheet according to claim 1, characterized in that: The regulator includes a displacement bracket, a pressing plate, an upper bracket, a limiting structure and a lower bracket; The displacement bracket is a conical cap-shaped structure with the tip at the top, comprising 2n inclined rods I, n>2, the upper ends of the 2n inclined rods I are simultaneously connected to the center of the lower surface of the pressing plate, and the lower ends are evenly distributed around a point o, the point o is located on the central axis of the pressing plate, and the pressing plate is coaxial with the cylinder b; The upper support includes 2n horizontal rods, which are radially distributed around point o. The two ends of the horizontal rods are respectively marked as end a and end b. End a is closer to point o than end b. The ends a of the 2n horizontal rods are respectively hinged to the lower ends of the 2n oblique rods I in a one-to-one correspondence. The limiting structure restricts the 2n horizontal rods to move only along their own length direction; The b ends of two adjacent horizontal rods are each connected by an arc bar, and at least one set of opposite arc bars is composed of three sections: left, middle and right. The middle section is composed of a separated inner layer and outer layer. The outer layer of the middle section is fixedly connected to the left section, and the inner layer of the middle section is fixedly connected to the right section. All the arc bars form a circular ring, and the circular ring extends vertically downward to form a circular tube. The lower support includes 2n oblique rods II, which are distributed in an umbrella shape around the central axis of the cylinder b. The angle between the oblique rods II and the central axis of the cylinder b is 100-105°. The lower layer of the cylinder b extends radially outward and is connected to the upper ends of the 2n oblique rods II, and the lower ends of the 2n oblique rods II are connected to the circular tube.

4. A method for steam-assisted coplanar stretching orientation of a two-dimensional sheet according to claim 3, characterized in that: The regulator also includes a height measuring bracket, which is vertically arranged on one side of the pressing plate and fixedly connected to the upper bracket.

5. The method for steam-assisted coplanar stretching orientation of a two-dimensional sheet according to claim 1, characterized in that: The Young's modulus of the two-dimensional layer is 10-400 GPa, the shear modulus is 4-300 GPa, the bending stiffness is 0.8-20 eV, and the film elastic modulus is 15-300 N / m.

6. A method for steam-assisted coplanar stretching orientation of a two-dimensional sheet according to claim 5, characterized in that: The two-dimensional sheet is graphene, and the plasticizing solvent is ethanol or acetone; Alternatively, the two-dimensional sheets are transition metal carbides and the plasticizing solvent is water or ethanol; Alternatively, the two-dimensional sheet is molybdenum disulfide and the plasticizing solvent is ethanol or acetone; Alternatively, the two-dimensional sheet is tungsten disulfide and the plasticizing solvent is ethanol or isopropanol; Alternatively, the two-dimensional sheet is tin disulfide and the plasticizing solvent is ethanol or acetone; Alternatively, the two-dimensional sheet is black phosphorus and the plasticizing solvent is ethanol; Alternatively, the two-dimensional sheet is carbon nitride and the plasticizing solvent is water or ethanol; Alternatively, the two-dimensional sheets are layered double hydroxides and the plasticizing solvent is water or ethanol.

7. A method for steam-assisted coplanar stretching orientation of a two-dimensional sheet according to claim 5, characterized in that: The two-dimensional sheet is graphene oxide, and the plasticizing solvent is ethanol or isopropanol.

8. A method for steam-assisted coplanar stretching orientation of a two-dimensional sheet according to claim 7, characterized in that: The steam used in the steam treatment also contains reducing steam, which is formed by evaporating a reducing agent having a reducing effect on the two-dimensional sheet.

9. A method for steam-assisted coplanar stretching orientation of a two-dimensional sheet according to claim 1, characterized in that: After isotropic stretching and steam treatment, the interlayer spacing of the two-dimensional sheets is reduced by 5-20%, the Herman's orientation factor is increased by 10-50%, and the tensile strength is increased by 10-80%.

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