Method for carrying out steam-assisted coplanar stretching orientation on two-dimensional lamella

Abstract

The invention belongs to the field of material preparation, and discloses a method for carrying out steam-assisted coplanar stretching orientation on a two-dimensional lamella, the method can be used for carrying out isotropic stretching and steam treatment on a film material containing the two-dimensional lamella at the same time, and steam adopted in the steam treatment contains plasticizing steam. The plasticizing steam is formed by evaporating a plasticizing solvent which has a plasticizing effect on the two-dimensional sheet layer. According to the preparation method, the interlayer Van der Waals force can be weakened, the deformability of the sheet layers can be improved, meanwhile, wrinkles, wrinkles and other irregular forms of the sheet layers are removed or reduced through isotropic stretching, so that the sheet layers can be assembled more uniformly, the assembly orderliness of the sheet layers is improved, the interlayer binding force is increased, the orientation degree of a sheet layer stacking area is improved, and the sheet layers can be assembled more uniformly. The overall performance of the membrane is enhanced.

Description

Technical Field

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

[0002] In recent years, with the rapid development of nanotechnology and materials science, two-dimensional (2D) sheets have attracted widespread attention from the scientific and industrial communities as a new type of material with atomic-level thickness. 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-bonded nature allows guest substances to be inserted into the interlayer gap (vdW gap). However, when layered materials composed of two-dimensional sheets are applied to forms such as macroscopic assembly films of two-dimensional materials, composite assembly films of two-dimensional materials, and composite polymer films of two-dimensional materials, their performance is often difficult to achieve as expected. This is mainly because the folding, curling, and wrinkling of the sheets during the formation process will lead to problems such as low assembly order, low stacking domain orientation, and high intra-membrane porosity, thereby generating a large number of defects in the film that hinder stress transfer, electron transition, and phonon transmission, resulting in its excellent performance being unable to be expressed in the macroscopic material, thereby affecting the overall performance.

[0003] Unlike one-dimensional (1D) and zero-dimensional (0D) nanomaterials, two-dimensional materials are often affected by thermal vibrations, edge instabilities, thermodynamic instabilities, strains in 2D crystals, thermal shrinkage, dislocations, solvent capture, substrate relaxation, surface anchoring, and high surface tension during transfer, and often form uncontrollable structures such as ripples, bends, and wrinkles. In particular, two-dimensional materials with low Young's modulus and shear modulus, low bending stiffness and film elastic modulus are prone to uncontrollable morphological changes in liquid environments (lower Young's modulus means that the sheet has lower stiffness when stretched axially, so the material is softer and easier to deform. Lower shear modulus means that the sheet has higher deformation capacity under shear stress, which is prone to sliding and wrinkling. Smaller bending stiffness means that the two-dimensional material has weaker resistance to bending stress, making it prone to bending or curling. And lower film elastic modulus refers to the elastic performance of the two-dimensional material when facing bending loads, indicating that the sheet is easy to bend). Therefore, these characteristics may lead to ripples, bends and wrinkles in the prepared membrane, which will aggravate the problems of low order of the layers, large interlayer spacing, poor stacking domain orientation and high porosity, thereby reducing the overall performance of the membrane.

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

[0005] To address the above challenges, existing technologies have explored a variety of induction strategies, including mechanical stretching, interface-induced assembly, and rigid sheet-filling-induced assembly, but each has its own limitations, such as:

[0006] Interface-induced assembly method: Using the chemical or physical properties of the interface to induce the orderly arrangement of two-dimensional material sheets, it can be assembled on liquid-gas, liquid-liquid or liquid-solid interfaces. For example, Langmuir-Blodgett (LB) technology is used to prepare highly oriented two-dimensional material films at the gas-liquid interface. However, its operation is complicated 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 a two-dimensional sheet with low out-of-plane flexibility to the asymmetric out-of-plane flexible sheet, such as in the literature 1 (Advanced Materials Interfaces, 2022, 9(18): 2102418) in Ti 3 C 2 The introduction of amino functional groups on the surface of MXene (Ti 3 C 2 -NH 2 ), using Ti 3 C 2 -NH 2 The chemical affinity between graphene and reduced graphene oxide (rGO) was used to prepare films with enhanced ordered nanostructures by freeze-stretching. However, the compatibility and uniformity issues of heterogeneous materials increase the difficulty of quality control and increase the complexity and cost of preparation.

[0008] Mechanical stretching method: The macroscopic assembly film of the two-dimensional material is immersed in a plasticizing solvent, and the orientation of the sheet is improved by uniaxial or biaxial stretching. For example, the literature (Nature Communications, 2020, 11(1): 2645) provides a continuous plasticizing stretching method, which inserts ethanol molecules into the interlayer plasticized graphene oxide film and then uniaxially stretches the film. The reduced graphene film achieves enhanced tensile strength, stiffness and conductivity. However, uniaxial stretching may cause stress concentration in a certain direction, or shrinkage (positive Poisson's ratio material) or expansion (negative Poisson's ratio material) in the vertical direction, affecting the overall uniform stretching effect.

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

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

[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 orientation of a two-dimensional sheet, wherein a film material containing the two-dimensional sheet is isotropically stretched and steam-treated, wherein the steam used for the steam treatment contains plasticizing steam, which is formed by evaporating a plasticizing solvent that has a plasticizing effect on the two-dimensional sheet.

[0013] When the present invention simultaneously performs isotropic stretching and steam treatment on a membrane material containing two-dimensional sheets, plasticized steam molecules can penetrate between the two-dimensional sheets to weaken the interlayer van der Waals force and improve the deformation capacity of the sheets. Isotropic stretching can remove or reduce the folds, wrinkles and other irregular shapes of the sheets, so that they can be assembled more evenly, improve the assembly order of the sheets (tighter and more orderly interlayer assembly), increase the interlayer bonding force (reduce the interlayer spacing), and improve the orientation degree of the sheet stacking domain (increase the stacking domain density and reduce the internal pores), thereby enhancing the overall performance of the membrane.

[0014] The specific mechanism of action of plasticizing steam is as follows: Figure 1As shown, plasticized steam molecules can penetrate into the two-dimensional lamellae by diffusion, and form hydrogen bonds, van der Waals forces and other interactions with polar groups on the surface of the lamellae, thereby weakening the van der Waals forces between the lamellae, reducing the interlaminar rigidity, and increasing the sliding properties between the lamellae; the adsorption of plasticized steam molecules between the lamellae can increase the interlayer spacing, make the lamellae stretch more evenly, and help eliminate the wrinkles and irregular stacking of the lamellae, thereby forming a flatter structure; plasticized steam can increase the molecular mobility on the surface of the lamellae, and some molecular segments are "softened" by the plasticized steam molecules in the steam. This softening effect increases the translational entropy, rotational entropy and kinetic entropy of the two-dimensional lamellae. After the lamellae are flattened and stretched, they are easier to reach an orderly stacking state; at the same time, due to the wetting effect of the plasticizing steam molecules, the internal stress is partially released, which reduces the wrinkles inside and outside the membrane. This effect of releasing internal stress can further improve the overall performance of the membrane; in addition, after the plasticization is completed, with the evaporation of the plasticizing steam, the lamellae are rearranged and orderly stacked. As the stacking height continues to increase, the interlayer spacing gradually decreases accordingly. This change causes the bonding force between the two-dimensional lamellae to gradually increase. Furthermore, the stacking domain orientation of the lamellae also increases, which gradually reduces the pores in the membrane. This series of changes ultimately prompts the material to form a stable structure.

[0015] Isotropic stretching is more conducive to improving the performance of membrane materials containing two-dimensional sheets than uniaxial and biaxial stretching in the prior art, because the tensile stress on the periphery of the membrane is evenly distributed in all directions during isotropic stretching. Compared with uniaxial and biaxial stretching, the stress distribution in the membrane and the influence of sheet orientation will be significantly different: (1) Isotropic stretching: When isotropic stretching is performed on the membrane, the stress will be evenly distributed from the center to the outside, and the sheets will not be stretched biasedly in a specific direction. Uniform stretching will cause the sheets in the membrane to be subjected to the same tensile force in all directions at the same time, flattening and stretching along all directions of the plane, releasing wrinkles and folds caused by uneven stress. Multi-directional stress helps to flatten the sheets and reduce uneven wrinkles. Isotropic stretching helps to form an orderly stacking without deviation in a specific direction, which can make it easier for the sheets to reach a stable ordered state and reduce complex mutual entanglement. Under isotropic stretching, the lamellae are guided to be arranged more evenly in all directions within the plane, avoiding the anisotropy formed by directional rearrangement, reducing the disorder of the overall stacking domain, and promoting uniform arrangement of the stacking domain. Therefore, the lamellae orientation will be evenly distributed in the plane direction, and there will be no inconsistent distribution of the stacking domain due to obvious single orientation, avoiding stress concentration in any local direction. (2) Uniaxial stretching: Stress is applied in a single direction, so that the stress is concentrated in the stretching direction. The lamellae in the film are flat along the uniaxial direction and rearranged roughly parallel to the stretching direction, while shrinkage occurs in the perpendicular direction of the uniaxial direction (Poisson effect), resulting in an increase in the order and orientation of the lamellae along the stretching direction, but it is obviously insufficient in the direction perpendicular to the stretching direction; (3) Biaxial stretching: Stress is applied in the orthogonal direction, and the stress needs to be controlled to be consistent in the two directions. The lamellae in the film tend to be flat and rearranged along the biaxial directions, which to a certain extent enhances the orderly stacking and orientation of the lamellae, especially in the two main axis directions. However, the wrinkle release and orderly arrangement on the non-main stress axis are not as good as isotropic stretching, which easily leads to the problem of excessive stress concentration load in the local direction.

[0016] As the preferred technical solution:

[0017] As described above, a method for steam-assisted coplanar stretching orientation of two-dimensional sheets, wherein the membrane material containing the two-dimensional sheets is a membrane formed by macroscopic assembly of single two-dimensional sheets (two-dimensional sheet macroscopic assembly membrane), a membrane formed by composite assembly of different two-dimensional sheets (two-dimensional sheet composite assembly membrane) or a membrane composite of two-dimensional sheets and polymer materials (two-dimensional sheet composite polymer membrane).

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

[0019] When the thickness of the membrane material containing the two-dimensional lamellae is ≤10 μm, the device (referred to as the first 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;

[0020] When the thickness of the membrane material containing the two-dimensional sheet is greater than 10 μm, the device (referred to as the second device) used for isotropically stretching and steam-treating the membrane material containing the two-dimensional sheet 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 the solvent pool b; at the same time, the process of isotropically stretching and steam-treating the membrane material containing the two-dimensional lamellae is as follows: first, a plasticizing solvent is added to the solvent pool b, and then the membrane material containing the two-dimensional lamellae is fixed between the upper and lower cylinders b by the membrane fixing screws b and the membrane fixing screws b are adjusted to keep the membrane material containing the two-dimensional lamellae in a taut state, and then heated by the heating device b until the plasticizing solvent is vaporized, and at the same time, the regulator is started and kept 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.

[0021] When the first device is used to simultaneously perform isotropic stretching and steam treatment on the membrane material containing two-dimensional sheets, the plasticizing solvent is continuously vaporized during the heating process, so that the vapor pressure of the cavity between the membrane material containing two-dimensional sheets and the solvent pool a gradually increases, which causes the pressure on the lower side of the membrane material containing two-dimensional sheets (i.e., the side close to the solvent pool a) to be greater than the pressure on the upper side. The pressure difference is converted into in-plane stress through boundary constraints and acts on the membrane material containing two-dimensional sheets. However, since the membrane material containing two-dimensional sheets is firmly fixed between the upper and lower layers of cylinders a by the membrane fixing screws a, this fixing method limits the overall movement of the membrane material. Therefore, although the pressure on the lower side is large, the membrane material cannot move upward completely freely. On the contrary, it can only deform in some areas within the frame where it is fixed. With the further vaporization of the plasticizing solvent, the vapor pressure continues to increase, resulting in in-plane stretching caused by the normal pressure, and the membrane material containing two-dimensional sheets gradually undergoes isotropic stretching under restricted conditions, thereby achieving overall uniform stretching of the membrane material.

[0022] The present invention uses "10μm" as the thickness demarcation value, which is limited by the diffusion depth of steam in the film (dominated by Fick's second law). When the film thickness is ≤10μm, the steam pressure can self-consistently realize the "penetration-plasticization-stretching" coupling. Steam molecules can quickly penetrate into the interior of the film and effectively plasticize it in a short time. The stacking structure of the layers in the film is small, and the steam can diffuse evenly to various areas of the film, thereby achieving plasticization and stretching. Therefore, for a film of this thickness, the plasticization of steam and the coplanar stretching effect caused by steam pressure can be achieved at the same time, and the first device can be used. However, when the film thickness is >10μm, the stress attenuation of the core layer must be compensated by mechanical stretching. The stress inhomogeneity of pure steam loading (the ratio of stress inside the film to the stress on the surface of the film) is large, and the edge crack extension is suppressed. Therefore, it is necessary to help the film material plasticize and stretch by epitaxial mechanical stretching. Therefore, for a film of this thickness, the second device is required. 10μm is an empirical value after a large number of experiments. It is not only based on the compatibility of the two devices with the film thickness, but also the performance transition point of the film material under steam plasticization and mechanical stretching. At this critical value, the film thickness changes from easier to stretch orientation to more difficult to stretch orientation, that is, from the boundary where steam treatment can completely penetrate and plasticize the film material to the boundary where the film material begins to show resistance to external forces.

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

[0024] 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;

[0025] 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.

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

[0027] 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.

[0028] 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.

[0029] When the pressing plate is subjected to downward pressure, it will move downward. This displacement is transmitted to the upper bracket through the displacement bracket, causing the upper bracket to move outward. Then, the displacement of the upper bracket is transmitted to the lower bracket, causing the lower bracket to move outward as well. Finally, the displacement of the lower bracket is transmitted to the deformable tube, causing the deformable tube to extend outward. In the process of the deformable tube extending outward, it applies a coplanar tensile displacement to the edge of the membrane in contact with it, thereby generating tensile stress.

[0030] For membrane materials containing two-dimensional sheets with a thickness greater than 10 μm, due to the large thickness, the steam penetration effect is weakened, and the complete orientation of the inner and upper layers of the membrane materials containing two-dimensional sheets cannot be completed. It is necessary to start the stretching device to apply additional in-plane isotropic stretching to the membrane materials containing two-dimensional sheets to ensure that the membrane materials containing two-dimensional sheets complete the orientation process under a uniformly mixed steam environment and isotropic stretching. The maximum stretching displacement (△L) is determined by the initial diameter L of the membrane materials containing two-dimensional sheets. 0 Determine that the shrinkage rate of the unstretched film on the plane before and after orientation is , maximum tensile displacement △L= (L 0 × ) / 2.

[0031] 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 ), and the calculation formula for the shrinkage rate is as follows:

[0032] (%) = ;

[0033] The stretching displacement is controlled by the pressing plate above the device. Below 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 bracket and the lower bracket. When controlling the downward pressing distance (the height measuring bracket can record the change), the outward movement of the lower bracket 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] △H = H = H ;

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

[0036] Substituting the calculation formulas of the planar shrinkage rate 𝛜 and the initial diameter L of the membrane 0 The final calculation formula is:

[0037] △H = H = H ;

[0038] Therefore, after determining the length S of the displacement bracket and the initial height H of the displacement bracket, the maximum pressing displacement can be adjusted according to the initial diameter L of the membrane 0 , the diameter of the membrane after shrinkage . 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.

[0039] In the design of the present invention, the lower bracket includes 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] In the method for steam-assisted coplanar stretching orientation of a two-dimensional sheet as described above, 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.

[0041] As described above, a method for steam-assisted coplanar stretching orientation of a two-dimensional sheet has a Young's modulus of 10-400 GPa, a shear modulus of 4-300 GPa, a bending stiffness of 0.8-20 eV, and a film elastic modulus of 15-300 N / m.

[0042] A method for steam-assisted coplanar stretching orientation of a two-dimensional sheet as described above, wherein the two-dimensional sheet is graphene (G) and the plasticizing solvent is ethanol or acetone;

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

[0044] Alternatively, the two-dimensional sheets are molybdenum disulfide (MoS 2 ), the plasticizing solvent is ethanol or acetone;

[0045] Alternatively, the two-dimensional sheets are tungsten disulfide (WS 2 ), the plasticizing solvent is ethanol or isopropanol;

[0046] Alternatively, the two-dimensional sheets are tin disulfide (SnS 2 ), the plasticizing solvent is ethanol or acetone;

[0047] Alternatively, the 2D sheet is black phosphorus (BP) and the plasticizing solvent is ethanol;

[0048] Alternatively, the two-dimensional sheets are carbon nitride (gC 3 N 4 ), the plasticizing solvent is water or ethanol;

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

[0050] As described above, a method for steam-assisted coplanar stretching orientation of a two-dimensional sheet is described, wherein the two-dimensional sheet is graphene oxide (GO), and the plasticizing solvent is ethanol or isopropanol. Isopropanol has a higher boiling point than ethanol and a lower saturated vapor pressure at the same temperature. When a thicker film (>100 μm) requires higher temperature and longer 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 that the film remains intact during the reaction, as well as the long plasticizing process.

[0051] In the method for steam-assisted coplanar stretching orientation of a two-dimensional sheet as described above, the steam used for steam treatment also contains reducing steam, and the reducing steam is formed by evaporating a reducing agent that has a reducing effect on the two-dimensional sheet.

[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 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 firstly infiltrates plasticized steam molecules into the two-dimensional lamellae to weaken the interlayer van der Waals force and improve the deformation capacity of the lamellae. At the same time, the folds, wrinkles and other irregular shapes of the lamellae are removed or reduced by isotropic stretching, so that the lamellae can be assembled more evenly, thereby improving the assembly order of the lamellae and increasing the interlayer bonding force (reducing the interlayer spacing), and improving the orientation degree of the lamellae stacking domain, thereby enhancing the overall performance of the membrane.

[0057] (2) The present invention adopts different devices when performing isotropic stretching, so as to target membrane materials of two-dimensional sheets with different thicknesses, and ensure that during the stretching process, the tensile stress on the periphery of the membrane materials of two-dimensional sheets with different thicknesses is evenly distributed in all directions, so that the sheets in the membrane are subjected to the same tensile force in all directions at the same time, so that they can 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 in 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 is a schematic diagram of an isotropic stretching and steam treatment device in Example A1 of the present invention;

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

[0061] Figure 4 Schematic diagram of the isotropic stretching and steam treatment device in Example 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 is a top view of the regulator in Example A2 of the present invention;

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

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

[0065] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended 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 fall within the scope limited by the appended claims of the application equally.

[0066] The testing methods of the relevant performance indicators in the following embodiments and comparative examples are as follows:

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

[0068] Interlayer spacing: The membrane material containing two-dimensional lamellae prepared in each embodiment and the membrane material of two-dimensional lamellae after isotropic stretching and steam treatment are used as samples, and X-ray diffraction (XRD) test is performed to obtain XRD patterns. The interlayer spacing d is calculated according to Bragg's law (nλ=2dsinθ) by substituting the ray wavelength λ, diffraction angle θ and diffraction order n (usually 1).

[0069] Herman's orientation factor: The film material containing two-dimensional sheets prepared in each embodiment and the film material containing two-dimensional sheets after isotropic stretching and steam treatment are first used as samples, and then the samples are passed through the small-angle X-ray scattering instrument (SAXS) of the BL16B1 beamline of the Shanghai Light Source Synchrotron Radiation Station to obtain a scattering image, and the scattering intensity distribution of the diffraction spot is obtained. After processing the scattering intensity distribution, the azimuth angle φ is used as a variable to obtain the scattering intensity I( ), the weighted average of the scattering intensity at different azimuth angles is obtained by integration ⟨cos 2 ( )>, according to the Herman's orientation factor calculation formula, the Herman's orientation factor is obtained, and the calculation formula is: Herman's orientation factor = .

[0070] Tensile strength: The membrane material containing the two-dimensional sheet prepared in each embodiment and the membrane material of the two-dimensional sheet after isotropic stretching and steam treatment were first used as samples. When the thickness of the sample was ≤10 μm, the tensile strength was tested by a tensile compression dynamometer (model: American Mark-10 IntelliMESUR 2.3.1). When the thickness of the sample was >10 μm, the tensile strength was tested by an electronic universal material testing machine (INSTRON 5969).

[0071] Example A1

[0072] The apparatus used for isotropically stretching and steam treating a film material containing a two-dimensional sheet with a thickness of ≤10 μm is as follows: Figure 2 , Figure 3 As shown, it includes a solvent tank a1 and a heating device a;

[0073] The top of the solvent pool a is a vertically arranged cylinder a 2, which is divided into two layers, upper and lower, and is detachably connected by 2m membrane fixing screws a 3, m>2, and the 2m membrane fixing screws a 3 are evenly distributed around the circumference of the central axis of the cylinder a 2;

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

[0075] Example A2

[0076] The apparatus used for isotropically stretching and steam treating a film material containing two-dimensional sheets with a thickness of >10 μm is as follows: Figure 4 , Figure 5 As shown, it includes a solvent tank b 5, a heating device b, a deformable tube 9 and a regulator;

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

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

[0079] The regulator is used to control the outward expansion of the cylinder b along the radial direction of the cylinder b;

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

[0081] The displacement bracket 10 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 11, and the lower ends are evenly distributed around a point o, the point o is located on the central axis of the pressing plate 11, and the pressing plate 11 is coaxial with the cylinder b;

[0082] The upper support 12 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. End a of the 2n horizontal rods is hinged to the lower ends of the 2n oblique rods I in a one-to-one correspondence.

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

[0084] like Figure 5 , Figure 6 As shown, the ends b of two adjacent horizontal rods are connected by an arc bar 4, at least one group of relative arc bars 4 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 4 form a circular ring, which extends vertically downward to form a circular tube.

[0085] The lower support 13 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.

[0086] Example B1

[0087] A method for steam-assisted coplanar stretching orientation of a two-dimensional sheet, comprising the following steps:

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

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

[0090] Plasticizing solvent: acetone;

[0091] The apparatus used for isotropic stretching and steam treatment was the apparatus described in Example A1, m was 3, the height of the solvent pool a was 8 cm, and the volume was 25 mL;

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

[0093] water;

[0094] (2) First prepare the concentration to 1 mg mL -1 The two-dimensional sheet dispersion (composed of two-dimensional sheets and water) was then vacuum filtered using a Celgard 3501 membrane as a filtration membrane, and then dried at 40°C for 24 hours, and the filtration membrane was peeled off to obtain a two-dimensional sheet macroscopic assembly membrane;

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

[0096] (3) When the two-dimensional lamellar macroscopic assembly film obtained in step (2) is isotropically stretched and steam-treated, 15 mL of plasticizing solvent is first added to the solvent pool a, and then the two-dimensional lamellar macroscopic assembly film is fixed between the upper and lower cylinders a by the film fixing screw a and the film fixing screw a is adjusted to keep the two-dimensional lamellar macroscopic assembly film taut, and then heated by the heating device a until the plasticizing solvent is vaporized, and then kept warm at 70°C for 12 hours. After post-treatment (rinsing with ethanol, drying in a vacuum oven at 45°C), the two-dimensional lamellar macroscopic assembly film after isotropic stretching and steam treatment is obtained.

[0097] The interlayer spacing of the two-dimensional sheet macro-assembly film after isotropic stretching and steam treatment 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 orientation of a two-dimensional sheet, comprising the following steps:

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

[0101] Two-dimensional sheets: transition metal carbides (Ti 3 C 2 T X MXene), Young's modulus is 250-350GPa, shear modulus is 100-250GPa, bending stiffness is 1-5eV, and film elastic modulus is 200-300N / m;

[0102] Plasticizing solvent: water;

[0103] The apparatus used for isotropic stretching and steam treatment was the apparatus described in Example A1, m was 4, the height of the solvent pool a was 8 cm, and the volume was 25 mL;

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

[0105] water;

[0106] (2) First prepare the concentration to 1 mg mL -1 The two-dimensional sheet dispersion (composed of two-dimensional sheets and water) was then vacuum filtered using a Celgard 3501 membrane as a filtration membrane, and then dried at 40°C for 24 hours to obtain a two-dimensional sheet macroscopic assembly membrane attached to the filtration membrane;

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

[0108] (3) Retaining the filtration membrane, when isotropically stretching and steam-treating the two-dimensional lamellar macroscopic assembly membrane obtained in step (2), first add 15 mL of plasticizing solvent to the solvent pool a, then fix the two-dimensional lamellar macroscopic assembly membrane between the upper and lower cylinders a by the membrane fixing screw a (the filtration membrane is close to the upper cylinder a) and adjust the membrane fixing screw a to keep the two-dimensional lamellar macroscopic assembly membrane taut, and then heat it by the heating device a until the plasticizing solvent is vaporized, and then keep it at 110°C for 24 hours. After post-treatment (peeling off the filtration membrane, rinsing with ethanol, and drying in a vacuum oven at 60°C), the two-dimensional lamellar macroscopic assembly membrane after isotropic stretching and steam treatment is obtained.

[0109] The interlayer spacing of the two-dimensional sheet macro-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 stretching orientation of a two-dimensional sheet, comprising the following steps:

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

[0113] Two-dimensional sheet: MoS2, Young's modulus is 270±100GPa, shear modulus is 60-68GPa, bending stiffness is 9-20eV, film elastic modulus is 180-210N / m;

[0114] Plasticizing solvent: ethanol;

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

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

[0117] water;

[0118] (2) First prepare the concentration to 1 mg mL -1 The two-dimensional sheet dispersion (composed of two-dimensional sheets and water) was then vacuum filtered using a Celgard 3501 membrane as a filtration membrane, and then dried at 40°C for 24 hours, and the filtration membrane was peeled off to obtain a two-dimensional sheet macroscopic assembly membrane;

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

[0120] (3) When the two-dimensional lamellar macroscopic assembly film obtained in step (2) is isotropically stretched and steam-treated, 80 mL of plasticizing solvent is first added to the solvent pool b, and then the two-dimensional lamellar macroscopic assembly film is fixed between the upper and lower cylinders b by the film fixing screws b and the film fixing screws b are adjusted to keep the two-dimensional lamellar macroscopic assembly film taut, and then heated by the heating device b until the plasticizing solvent is vaporized, and at the same time, the pressing plate is pressed downward and kept warm at 90°C for 12 hours (the maximum tensile displacement of the two-dimensional lamellar macroscopic assembly film after the insulation is completed is 2 mm), and the two-dimensional lamellar macroscopic assembly film after isotropic stretching and steam treatment is obtained after post-treatment (rinsing with ethanol and drying in a vacuum oven at 50°C).

[0121] The interlayer spacing of the two-dimensional sheet macro-assembly film after isotropic stretching and steam treatment 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 orientation of a two-dimensional sheet, comprising the following steps:

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

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

[0126] Plasticizing solvent: isopropyl alcohol;

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

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

[0129] water;

[0130] (2) First prepare the concentration to 1 mg mL -1 The two-dimensional sheet dispersion (composed of two-dimensional sheets and water) was then vacuum filtered using a Celgard 3501 membrane as a filtration membrane, and then dried at 40°C for 24 hours, and the filtration membrane was peeled off to obtain a two-dimensional sheet macroscopic assembly membrane;

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

[0132] (3) When the two-dimensional lamellar macroscopic assembly film obtained in step (2) is isotropically stretched and steam-treated, 150 mL of plasticizing solvent is first added to the solvent pool b, and then the two-dimensional lamellar macroscopic assembly film is fixed between the upper and lower cylinders b by the film fixing screws b and the film fixing screws b are adjusted to keep the two-dimensional lamellar macroscopic assembly film taut, and then heated by the heating device b until the plasticizing solvent is vaporized, and at the same time, the pressing plate is pressed downward and kept warm at 100°C for 18 hours (the maximum tensile displacement of the two-dimensional lamellar macroscopic assembly film after the insulation is completed is 1.5 mm), and the two-dimensional lamellar macroscopic assembly film after isotropic stretching and steam treatment is obtained after post-treatment (ethanol washing, drying in a vacuum oven at 55°C).

[0133] The interlayer spacing of the two-dimensional sheet macro-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 orientation of a two-dimensional sheet, comprising the following steps:

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

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

[0138] Plasticizing solvent: acetone;

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

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

[0141] water;

[0142] (2) First prepare the concentration to 1 mg mL -1 The two-dimensional sheet dispersion (composed of two-dimensional sheets and water) was then vacuum filtered using a Celgard 3501 membrane as a filtration membrane, and then dried at 40°C for 24 hours, and the filtration membrane was peeled off to obtain a two-dimensional sheet macroscopic assembly membrane;

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

[0144] (3) When the two-dimensional lamellar macroscopic assembly film obtained in step (2) is isotropically stretched and steam-treated, 180 mL of plasticizing solvent is first added to the solvent pool b, and then the two-dimensional lamellar macroscopic assembly film is fixed between the upper and lower cylinders b by the film fixing screws b and the film fixing screws b are adjusted to keep the two-dimensional lamellar macroscopic assembly film taut, and then heated by the heating device b until the plasticizing solvent is vaporized, and at the same time, the pressing plate is pressed downward and kept warm at 70°C for 24 hours (the maximum tensile displacement of the two-dimensional lamellar macroscopic assembly film after the insulation is completed is 1 mm), and the two-dimensional lamellar macroscopic assembly film after isotropic stretching and steam treatment is obtained after post-treatment (ethanol washing, drying in a vacuum oven at 45°C).

[0145] The interlayer spacing of the two-dimensional sheet macro-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%.

[0146] Example B6

[0147] A method for steam-assisted coplanar stretching orientation of a two-dimensional sheet, comprising the following steps:

[0148] (1) Preparation of raw materials;

[0149] Graphene oxide aqueous solution: concentration 0.5 mg g -1 ;

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

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

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

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

[0154] The graphene oxide aqueous solution was filtered using a Celgard 3501 membrane as a filter membrane, and then dried at 35°C for 12 hours, and the filter membrane was removed to obtain a graphene oxide membrane with a thickness of 5 μm.

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

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

[0157] The grain size of the two-dimensional sheet macro-assembly film after isotropic stretching and steam treatment is 6 nm, the proportion of ordered stacking domains is 90%, the half-peak width 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 reflectivity is 34%, and the conductivity is 2.5×10 5 S·m -1 , tensile strength is 450MPa;

[0158] After isotropic stretching and steam treatment, the interlayer spacing of the two-dimensional sheet macro-assembly film decreased by 18%, the Herman's orientation factor increased by 50%, and the tensile strength increased by 84%.

[0159] Example C1

[0160] A method for steam-assisted coplanar stretching orientation of a two-dimensional sheet, comprising the following steps:

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

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

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

[0164] Two-dimensional sheet B: graphene;

[0165] The Young's modulus of the 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;

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

[0167] Plasticizing solvent: ethanol;

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

[0169] water;

[0170] (2) Mix two-dimensional sheet A, two-dimensional sheet B and water evenly and prepare a concentration of 0.5 mg mL -1 The two-dimensional sheet dispersion is then vacuum filtered using a Celgard 3501 membrane as a filtration membrane, and then dried at 40°C for 24 hours, and the filtration membrane is peeled off to obtain a two-dimensional sheet composite assembly membrane; wherein, 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 1wt%, and the content of the two-dimensional sheet B is 99wt%;

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

[0172] (3) When the two-dimensional lamellar composite assembly membrane obtained in step (2) is isotropically stretched and steam-treated, 20 mL of plasticizing solvent is first added to the solvent pool a, and then the two-dimensional lamellar composite assembly membrane is fixed between the upper and lower cylinders a by the membrane fixing screw a and the membrane fixing screw a is adjusted to keep the two-dimensional lamellar macroscopic assembly membrane taut. The membrane is then heated by the heating device a until the plasticizing solvent is vaporized and then kept at 90°C for 24 hours. After post-treatment (rinsing with ethanol and drying in a vacuum oven at 60°C), the two-dimensional lamellar composite assembly membrane after isotropic stretching and steam treatment is obtained.

[0173] The interlayer spacing of the two-dimensional layered 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%.

[0174] Example C2

[0175] A method for steam-assisted coplanar stretching orientation of a two-dimensional sheet, comprising the following steps:

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

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

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

[0179] Two-dimensional sheet B: MoS2;

[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 film elastic modulus is 180-210 N / m;

[0181] The apparatus used for isotropic stretching and steam treatment was the apparatus described in Example A1, m was 3, the height of the solvent pool a was 8 cm, and the volume was 25 mL;

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

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

[0184] water;

[0185] (2) Mix two-dimensional sheet A, two-dimensional sheet B and water evenly and prepare a concentration of 0.5 mg mL -1 The two-dimensional sheet dispersion is then vacuum filtered using a Celgard 3501 membrane as a filtration membrane, and then dried at 40°C for 24 hours, and the filtration membrane is peeled off to obtain a two-dimensional sheet composite assembly membrane; wherein, 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 50wt%, and the content of the two-dimensional sheet B is 50wt%;

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

[0187] (3) When the two-dimensional lamellar composite assembly membrane obtained in step (2) is isotropically stretched and steam-treated, 15 mL of plasticizing solvent is first added to the solvent pool a, and then the two-dimensional lamellar composite assembly membrane is fixed between the upper and lower cylinders a by the membrane fixing screw a and the membrane fixing screw a is adjusted to keep the two-dimensional lamellar macroscopic assembly membrane taut. The membrane is then heated by the heating device a until the plasticizing solvent is vaporized and then kept at 105°C for 18 hours. After post-treatment (rinsing with ethanol and drying in a vacuum oven at 45°C), the two-dimensional lamellar composite assembly membrane after isotropic stretching and steam treatment is obtained.

[0188] The interlayer spacing of the two-dimensional layered composite 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%.

[0189] Example C3

[0190] A method for steam-assisted coplanar stretching orientation of a two-dimensional sheet, comprising the following steps:

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

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

[0193] The Young's modulus of the 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 the 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 apparatus used for isotropic stretching and steam treatment was the apparatus described in Example A2, with n being 3, m being 4, the height of the solvent pool b being 12 cm, the volume being 250 mL, and the angle between the inclined rod II and the central axis of the cylinder b being 100°;

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

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

[0199] water;

[0200] (2) Mix two-dimensional sheet A, two-dimensional sheet B and water evenly and prepare a concentration of 0.5 mg mL -1 The two-dimensional sheet dispersion is then vacuum filtered using a Celgard 3501 membrane as a filtration membrane, and then dried at 40°C for 24 hours, and the filtration membrane is peeled off to obtain a two-dimensional sheet composite assembly membrane; wherein, 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 1wt%, and the content of the two-dimensional sheet B is 99wt%;

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

[0202] (3) When the two-dimensional lamellar composite assembly membrane obtained in step (2) is isotropically stretched and steam-treated, 180 mL of plasticizing solvent is first added to the solvent pool b, and then the two-dimensional lamellar composite assembly membrane is fixed between the upper and lower cylinders b by the membrane fixing screws b and the membrane fixing screws b are adjusted to keep the two-dimensional lamellar macroscopic assembly membrane taut. The membrane is then heated by the heating device b until the plasticizing solvent is vaporized, and the pressing plate is pressed downward at the same time and kept warm at 105°C for 16 hours (the maximum tensile displacement of the two-dimensional lamellar macroscopic assembly membrane after the insulation is completed is 1 mm). After post-treatment (rinsing with ethanol and drying in a vacuum oven at 55°C), the two-dimensional lamellar composite assembly membrane after isotropic stretching and steam treatment can be obtained.

[0203] The interlayer spacing of the two-dimensional layered 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 orientation of a two-dimensional sheet, comprising the following steps:

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

[0207] Two-dimensional sheet A: MoS2;

[0208] The Young's modulus of the 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 (Ti 3 C 2 T X MXene);

[0210] The Young's modulus of the 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 apparatus used for isotropic stretching and steam treatment was the apparatus described in Example A2, wherein n was 4, m was 3, the height of the solvent pool b was 10 cm, the volume was 150 mL, and the angle between the inclined rod II and the central axis of the cylinder b was 100°;

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

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

[0214] water;

[0215] (2) Mix two-dimensional sheet A, two-dimensional sheet B and water evenly and prepare a concentration of 0.5 mg mL -1 The two-dimensional sheet dispersion is prepared by vacuum filtration using Celgard 3501 membrane as a filtration membrane, and then dried at 40°C for 24 hours to obtain a two-dimensional sheet composite assembly membrane attached to the filtration membrane; wherein, 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 50wt%, and the content of the two-dimensional sheet B is 50wt%;

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

[0217] (3) Retaining the filtration membrane, when isotropically stretching and steam treating the two-dimensional lamellar composite assembly membrane obtained in step (2), first add 80 mL of plasticizing solvent into the solvent pool b, then fix the two-dimensional lamellar composite assembly membrane between the upper and lower cylinders b by the membrane fixing screws b (the filtration membrane is close to the upper cylinder b) and adjust the membrane fixing screws b to keep the two-dimensional lamellar macroscopic assembly membrane taut, and then heat it by the heating device b until the plasticizing solvent is vaporized, and then press the pressing plate downward and keep it warm at 105°C for 24 hours (the maximum tensile displacement of the two-dimensional lamellar macroscopic assembly membrane after the insulation is 5 mm). After post-treatment (peeling off the filtration membrane, rinsing with ethanol, and drying in a vacuum oven at 50°C), the two-dimensional lamellar composite assembly membrane after isotropic stretching and steam treatment can be obtained.

[0218] The interlayer spacing of the two-dimensional layered composite assembled film 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 a two-dimensional sheet, comprising the following steps:

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

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

[0223] The Young's modulus of the two-dimensional sheet A is 272±18GPa, the shear modulus is 60-68GPa, the bending stiffness is 9-20eV, and the film elastic modulus is 160-200N / 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 bending stiffness is 1-3 eV, and the film elastic modulus is 15-30 N / m;

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

[0227] Plasticizing solvent: composed of isopropanol and ethanol in a mass ratio of 99:1;

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

[0229] water;

[0230] (2) Mix two-dimensional sheet A, two-dimensional sheet B and water evenly and prepare a concentration of 0.5 mg mL -1 The two-dimensional sheet dispersion is then vacuum filtered using a Celgard 3501 membrane as a filtration membrane, and then dried at 40° C. for 24 hours, and the filtration membrane is peeled off to obtain a two-dimensional sheet composite assembly membrane; wherein, 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 99wt%, and the content of the two-dimensional sheet B is 1wt%;

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

[0232] (3) When the two-dimensional lamellar composite assembly membrane obtained in step (2) is isotropically stretched and steam-treated, 80 mL of plasticizing solvent is first added to the solvent pool b, and then the two-dimensional lamellar composite assembly membrane is fixed between the upper and lower cylinders b by the membrane fixing screws b and the membrane fixing screws b are adjusted to keep the two-dimensional lamellar macroscopic assembly membrane taut. Then, the membrane is heated by the heating device b until the plasticizing solvent is vaporized, and the pressing plate is pressed downward at the same time and kept warm at 90°C for 18 hours (the maximum tensile displacement of the two-dimensional lamellar macroscopic assembly membrane after the insulation is completed is 2.5 mm). After post-treatment (rinsing with ethanol and drying in a vacuum oven at 60°C), the two-dimensional lamellar composite assembly membrane after isotropic stretching and steam treatment can be obtained.

[0233] After isotropic stretching and steam treatment, the interlayer spacing of the two-dimensional layer composite assembly film 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 orientation of a two-dimensional sheet, comprising the following steps:

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

[0237] Two-dimensional sheets: 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 No. 9005-38-3, viscosity 250-300 cps;

[0241] Deionized water;

[0242] EDTA (ethylenediaminetetraacetic acid);

[0243] Calcium chloride;

[0244] NaOH aqueous solution;

[0245] glass plate;

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

[0247] (2) Preparation of two-dimensional lamellar composite polymer membranes (i.e., membranes composed of two-dimensional lamellar and polymer materials);

[0248] (2.1) Dispersing the polymer material into deionized water, stirring continuously during the addition process to obtain solution A, wherein the content of the polymer material is 0.5wt%;

[0249] (2.2) EDTA, calcium chloride and deionized water were first mixed to obtain a 0.1 M aqueous Ca-EDTA solution, and then a 0.1 mol / L NaOH aqueous solution was added dropwise until the pH of the solution reached 7. Then, the two-dimensional sheet was added and stirred evenly. Finally, the solution was ultrasonicated at a power of 300 W for 30 min and then stirred for 1 h to obtain a uniform dispersion, thereby obtaining a solution B; wherein the molar ratio of EDTA to calcium chloride was 1:1;

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

[0251] (2.3) Solution B was added to Solution A at a rate of 1 drop per second, and the mixture was stirred at 700 rpm during the dropping process. After the dropping process was completed, the mixture was ultrasonicated at a power of 300 W for 30 min and then stirred for 3 h to obtain a suspension. The suspension was then degassed in a vacuum environment for 15 min to remove bubbles generated during the mixing process, thereby obtaining Solution C; wherein the volume ratio of Solution A to Solution B was 1:1;

[0252] (2.4) Solution C was cast on a glass plate, and after being scraped to form a film, it was dried at a constant temperature of 45°C and a constant humidity of 60% for 24 hours, and then the film was peeled off from the glass plate to obtain a two-dimensional lamellar composite polymer film;

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

[0254] (3) When the two-dimensional lamellar composite polymer film obtained in step (2) is isotropically stretched and steam-treated, 80 mL of plasticizing solvent is first added to the solvent pool b, and then the two-dimensional lamellar composite polymer film is fixed between the upper and lower cylinders b by the film fixing screws b and the film fixing screws b are adjusted to keep the two-dimensional lamellar macro-assembly film in a taut state, and then heated by the heating device b until the plasticizing solvent is vaporized, and at the same time, the pressing plate is pressed downward and kept warm at 70°C for 24 hours (the maximum tensile displacement of the two-dimensional lamellar macro-assembly film after the insulation is completed is 2 mm), and the two-dimensional lamellar composite polymer film after isotropic stretching and steam treatment is obtained after post-treatment (ethanol washing, drying in a 45°C vacuum oven).

[0255] The interlayer spacing of the two-dimensional lamellar composite polymer 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%.

[0256] Example D2

[0257] A method for steam-assisted coplanar stretching orientation of a two-dimensional sheet, comprising the following steps:

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

[0259] Two-dimensional sheets: transition metal carbides Ti 3 C 2 T X MXene;

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

[0261] Plasticizing solvent: water;

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

[0263] Deionized water;

[0264] Acetic acid in water;

[0265] Sodium dodecylbenzenesulfonate powder;

[0266] glass plate;

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

[0268] (2) Preparation of two-dimensional lamellar composite polymer membranes (i.e., membranes composed of two-dimensional lamellar and polymer materials);

[0269] (2.1) Dissolve the polymer material in an aqueous solution of acetic acid with a concentration of 1 vol%, stir continuously and heat to 45°C to ensure that it is completely dissolved, to obtain solution A; wherein the concentration of the polymer material is 1% (wt / vol);

[0270] (2.2) The two-dimensional sheet is evenly dispersed in deionized water, and sodium dodecylbenzene sulfonate powder is added thereto and mixed evenly to obtain a solution B, wherein the content of the sodium dodecylbenzene sulfonate 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) Solution B was added to Solution A at a rate of 1 drop per second. The mixture was stirred at 700 rpm during the addition. After the addition was completed, the mixture was ultrasonicated at a power of 300 W for 30 min and then stirred for 3 h to obtain a uniform suspension. Finally, the suspension was degassed in a vacuum environment for 15 min to remove the bubbles generated during the mixing process to obtain Solution C. The volume ratio of Solution A to Solution B was 1:1.

[0273] (2.4) Solution C was cast on a glass plate, and after being scraped to form a film, it was dried at a constant temperature of 45°C and a constant humidity of 60% for 24 hours, and then the film was peeled off from the glass plate to obtain a two-dimensional lamellar composite polymer film;

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

[0275] (3) When the two-dimensional lamellar composite polymer film obtained in step (2) is isotropically stretched and steam-treated, 100 mL of plasticizing solvent is first added to the solvent pool b, and then the two-dimensional lamellar composite polymer film is fixed between the upper and lower cylinders b by the film fixing screws b and the film fixing screws b are adjusted to keep the two-dimensional lamellar macro-assembly film in a taut state, and then heated by the heating device b until the plasticizing solvent is vaporized, and at the same time, the pressing plate is pressed downward and kept warm at 110°C for 12 hours (the maximum tensile displacement of the two-dimensional lamellar macro-assembly film after the insulation is completed is 3 mm), and the two-dimensional lamellar composite polymer film after isotropic stretching and steam treatment is obtained after post-treatment (ethanol washing, drying in a vacuum oven at 45°C).

[0276] After isotropic stretching and steam treatment, the interlayer spacing of the two-dimensional lamellar 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 a two-dimensional sheet, comprising the following steps:

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

[0280] Two-dimensional sheets: MoS2;

[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 film elastic modulus is 180-210 N / m;

[0282] Plasticizing solvent: ethanol;

[0283] Polymer material: sodium alginate, manufactured by Sigma-Aldrich, CAS No. 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] The apparatus used for isotropic stretching and steam treatment was the apparatus described in Example A2, wherein n was 4, m was 3, the height of the solvent pool b was 10 cm, the volume was 150 mL, and the angle between the inclined rod II and the central axis of the cylinder b was 105°;

[0290] (2) Preparation of two-dimensional lamellar composite polymer membranes (i.e., membranes composed of two-dimensional lamellar and polymer materials);

[0291] (2.1) Dispersing the polymer material into deionized water, stirring continuously during the addition process to obtain solution A, wherein the content of the polymer material is 0.5wt%;

[0292] (2.2) EDTA, calcium chloride and deionized water were first mixed to obtain a 0.1 M aqueous Ca-EDTA solution, and then 0.1 mol / L NaOH solution was added dropwise until the pH of the solution reached 7. Then, the two-dimensional sheet was added and stirred evenly. Finally, the solution was ultrasonicated at a power of 300 W for 30 min and then stirred for 1 h to make it evenly dispersed, thereby obtaining solution B; wherein the molar ratio of EDTA to calcium chloride was 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) Solution B was added to Solution A at a rate of 1 drop per second, and the mixture was stirred at 700 rpm during the dropping process. After the dropping process was completed, the mixture was ultrasonicated at a power of 300 W for 30 min and then stirred for 3 h to obtain a suspension. The suspension was then degassed in a vacuum environment for 15 min to remove bubbles generated during the mixing process, thereby obtaining Solution C; wherein the volume ratio of Solution A to Solution B was 1:1;

[0295] (2.4) Solution C was cast on a glass plate, and after being scraped to form a film, it was dried at a constant temperature of 45°C and a constant humidity of 60% for 24 hours, and then the film was peeled off from the glass plate to obtain a two-dimensional lamellar composite polymer film;

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

[0297] (3) When the two-dimensional lamellar composite polymer film obtained in step (2) is isotropically stretched and steam-treated, 120 mL of plasticizing solvent is first added to the solvent pool b, and then the two-dimensional lamellar composite polymer film is fixed between the upper and lower cylinders b by the film fixing screws b and the film fixing screws b are adjusted to keep the two-dimensional lamellar macro-assembly film in a taut state, and then heated by the heating device b until the plasticizing solvent is vaporized, and at the same time, the pressing plate is pressed downward and kept warm at 90°C for 18 hours (the maximum tensile displacement of the two-dimensional lamellar macro-assembly film after the insulation is completed is 3.5 mm), and the two-dimensional lamellar composite polymer film after isotropic stretching and steam treatment is obtained after post-treatment (ethanol washing, drying in a vacuum oven at 45°C).

[0298] The interlayer spacing of the two-dimensional lamellar composite polymer film after isotropic stretching and steam treatment 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 a two-dimensional sheet, comprising the following steps:

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

[0302] Two-dimensional sheets: tungsten disulfide;

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

[0304] Plasticizing solvent: isopropyl alcohol;

[0305] Polymer material: sodium alginate, manufactured by Sigma-Aldrich, CAS No. 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] The apparatus used for isotropic stretching and steam treatment was the apparatus described in Example A2, with n being 3, m being 4, the height of the solvent pool b being 12 cm, the volume being 250 mL, and the angle between the inclined rod II and the central axis of the cylinder b being 100°;

[0312] (2) Preparation of two-dimensional lamellar composite polymer membranes (i.e., membranes composed of two-dimensional lamellar and polymer materials);

[0313] (2.1) Dispersing the polymer material into deionized water, stirring continuously during the addition process to obtain solution A, wherein the content of the polymer material is 0.5wt%;

[0314] (2.2) EDTA, calcium chloride and deionized water were first mixed to obtain a 0.1 M aqueous Ca-EDTA solution, and then 0.1 mol / L NaOH solution was added dropwise until the pH of the solution reached 7. Then, the two-dimensional sheet was added and stirred evenly. Finally, the solution was ultrasonicated at a power of 300 W for 30 min and then stirred for 1 h to make it evenly dispersed, thereby obtaining solution B; wherein the molar ratio of EDTA to calcium chloride was 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) Solution B was added to Solution A at a rate of 1 drop per second, and the mixture was stirred at 700 rpm during the dropping process. After the dropping process was completed, the mixture was ultrasonicated at a power of 300 W for 30 min and then stirred for 3 h to obtain a suspension. The suspension was then degassed in a vacuum environment for 15 min to remove bubbles generated during the mixing process, thereby obtaining Solution C; wherein the volume ratio of Solution A to Solution B was 1:1;

[0317] (2.4) Solution C was cast on a glass plate, and after being scraped to form a film, it was dried at a constant temperature of 45°C and a constant humidity of 60% for 24 hours, and then the film was peeled off from the glass plate to obtain a two-dimensional lamellar composite polymer film;

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

[0319] (3) When the two-dimensional lamellar composite polymer film obtained in step (2) is isotropically stretched and steam-treated, 140 mL of plasticizing solvent is first added to the solvent pool b, and then the two-dimensional lamellar composite polymer film is fixed between the upper and lower cylinders b by the film fixing screws b and the film fixing screws b are adjusted to keep the two-dimensional lamellar macro-assembly film in a taut state, and then heated by the heating device b until the plasticizing solvent is vaporized, and at the same time, the pressing plate is pressed downward and kept warm at 100°C for 24 hours (the maximum tensile displacement of the two-dimensional lamellar macro-assembly film after the insulation is completed is 4 mm), and the two-dimensional lamellar composite polymer film after isotropic stretching and steam treatment is obtained after post-treatment (ethanol washing, drying in a vacuum oven at 45°C).

[0320] After isotropic stretching and steam treatment, the interlayer spacing of the two-dimensional lamellar composite polymer film 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 orientation of a two-dimensional sheet, comprising the following steps:

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

[0324] Two-dimensional sheets: tin disulfide;

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

[0326] Plasticizing solvent: acetone;

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

[0328] Acetic acid in water;

[0329] Sodium dodecylbenzenesulfonate powder;

[0330] Deionized water;

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

[0332] (2) Preparation of two-dimensional lamellar composite polymer membranes (i.e., membranes composed of two-dimensional lamellar and polymer materials);

[0333] (2.1) dissolving the polymer material in an aqueous solution of acetic acid with a concentration of 2 vol%, stirring continuously and heating to 45°C to ensure that it is completely dissolved, thereby obtaining a solution A, wherein the concentration of chitosan powder is 3% (wt / vol);

[0334] (2.2) The two-dimensional sheet is evenly dispersed in deionized water, and sodium dodecylbenzene sulfonate powder is added thereto and mixed evenly to obtain a solution B, wherein the content of the sodium dodecylbenzene sulfonate 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) Solution B was added to Solution A at a rate of 1 drop per second. The mixture was stirred at 700 rpm during the addition. After the addition was completed, the mixture was ultrasonicated at a power of 300 W for 30 min and then stirred for 3 h to obtain a uniform suspension. Finally, the suspension was degassed in a vacuum environment for 15 min to remove the bubbles generated during the mixing process to obtain Solution C. The volume ratio of Solution A to Solution B was 1:1.

[0337] (2.4) Solution C was cast on a glass plate, and after being scraped to form a film, it was dried at a constant temperature of 45°C and a constant humidity of 60% for 24 hours, and then the film was peeled off from the glass plate to obtain a two-dimensional lamellar composite polymer film;

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

[0339] (3) When the two-dimensional lamellar composite polymer film obtained in step (2) is isotropically stretched and steam-treated, 180 mL of plasticizing solvent is first added to the solvent pool b, and then the two-dimensional lamellar composite polymer film is fixed between the upper and lower cylinders b by the film fixing screws b and the film fixing screws b are adjusted to keep the two-dimensional lamellar macro-assembly film in a taut state, and then heated by the heating device b until the plasticizing solvent is vaporized, and at the same time, the pressing plate is pressed downward and kept warm at 70°C for 12 hours (the maximum tensile displacement of the two-dimensional lamellar macro-assembly film after the insulation is completed is 4.5 mm), and the two-dimensional lamellar composite polymer film after isotropic stretching and steam treatment is obtained after post-treatment (ethanol washing, drying in a vacuum oven at 45°C).

[0340] After isotropic stretching and steam treatment, the interlayer spacing of the two-dimensional lamellar 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 layer is isotropically stretched and steam-treated. The steam used in the steam treatment contains plasticizing steam, which is formed by evaporating a plasticizing solvent that has a plasticizing effect on the two-dimensional sheet layer.

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 2, characterized in that: 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.

4. A method for steam-assisted coplanar stretching orientation of a two-dimensional sheet according to claim 3, 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.

5. A method for steam-assisted coplanar stretching orientation of a two-dimensional sheet according to claim 4, 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.

6. A 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.

7. A method for steam-assisted coplanar stretching orientation of a two-dimensional sheet according to claim 6, 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.

8. A method for steam-assisted coplanar stretching orientation of a two-dimensional sheet according to claim 6, characterized in that: The two-dimensional sheet is graphene oxide, and the plasticizing solvent is ethanol or isopropanol.

9. A method for steam-assisted coplanar stretching orientation of a two-dimensional sheet according to claim 8, 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.

10. The 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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