CN112811415B - Plastic processing material taking two-dimensional sheet material as main body and preparation method and application thereof - Google Patents

Abstract

The invention discloses a plastic processing material whose main body is a two-dimensional sheet material, belonging to the field of plastic processing materials. The material at least includes a main body layer and an activation layer located between the main body layers; the activation layer is composed of a fluid activation medium, and the contact angle between the activation medium and the two-dimensional sheet material is less than 80° by interpenetrating With a layered structure, the composite film has excellent plastic processing properties. Furthermore, the orientation degree of the two-dimensional sheets in the material is high after processing, and the vertical or parallel orientation of the sheets can be flexibly adjusted according to specific practical requirements. The method has a simple process and is a universal method for preparing two-dimensional macroscopic assembly materials with a special three-dimensional structure, which is simple and controllable, and has strong practicability.

Description

A plastic processing material with two-dimensional sheet material as the main body and its preparation method and application

Technical Field

The invention belongs to the field of plastic processing materials, and specifically relates to a plastic processing material with a two-dimensional sheet material as a main body, and a preparation method and application thereof.

Background Art

Plastic processing is an efficient processing method with strong economic power. It has become a standard industrial technology, covering the fields of metal forging and polymer processing and forming. Typical plastic forming (such as forging, rolling, stamping, etc.) basically requires a certain plastic deformation ability to shape the material into a fixed shape part. In metals and polymers, the plastic deformation ability can be guaranteed by grain boundary sliding or dislocation sliding in metals and thermally activated movement of chains in polymers.

Two-dimensional sheet materials are composed of a single layer or a few layers of atoms or molecules, which are connected by strong covalent bonds or ionic bonds within the layer, and weaker van der Waals forces between the layers. They have excellent mechanical, electrical and thermal properties due to their unique planar two-dimensional structure. At present, two-dimensional sheet materials mainly include graphene (GN), topological insulators (TI), transition metal dichalcogenides (TMDCs), black phosphorus (BP), etc. Two-dimensional materials have always been the focus of attention in many fields due to their unique micro-nano physical and chemical properties, which provides a basis for the preparation of macroscopic materials with superior performance. However, the interaction between two-dimensional sheets limits their processability.

For two-dimensional materials, they show inherent brittleness and cannot meet the basic requirements of plastic deformation. Some researchers mixed polymers with two-dimensional materials to prepare a "plasticine"-like solid, which has extremely high plasticity and can be processed into any shape. However, the content of two-dimensional nanosheets in such composite materials is extremely low, usually less than 10%, and the two-dimensional nanosheets are randomly oriented. The resulting macroscopic composite materials lack the typical micro-nano physical and chemical characteristics of two-dimensional materials, such as electrical and thermal conductivity. So far, it is still a huge challenge to efficiently and accurately manufacture two-dimensional macroscopic assembly materials with three-dimensional fine structures.

Summary of the invention

As one aspect of the present invention, the present invention provides a plastic processing material with a two-dimensional sheet material as the main body, which solves the application defects of existing plastic processing materials including metals and plastics in the fields of photothermal conversion, electrothermal conversion, energy storage, catalysis, semiconductor devices, etc.

As another aspect of the present invention, the present invention provides a plastic processing material with a two-dimensional sheet material as the main body, the mass of the two-dimensional sheet material accounts for more than 50% of the total mass, the two-dimensional nanosheets are oriented along the plane, and the obtained macro-composite material has the excellent physical and chemical characteristics of the two-dimensional sheet material (electrical conductivity, thermal conductivity, etc.).

As another aspect of the present invention, the present invention provides a plastic processing material with a two-dimensional sheet material as the main body, with a minimum processing accuracy of 60nm, a maximum stretching ratio of 100%, and a maximum punching depth ratio (punching depth/composite film thickness) of 1000%. The material has a main layer-activation layer cross-interpenetrating layer structure, wherein the main layer at least includes a two-dimensional sheet material laid along a plane, the activation layer is composed of an activation medium, the activation medium can flow in a specific temperature range, and the contact angle between the activation medium and the two-dimensional sheet material is less than 80°. Among them, the introduction of the activation layer can expand the interlayer spacing of the main layer (for example, for the main layer of graphene oxide, the interlayer spacing can be expanded from 0.8nm to 3nm at most), according to the calculation formula of the inter-plane van der Waals force:

The expansion of the interlayer spacing will lead to the power-law attenuation of the interlayer van der Waals force, thereby promoting the relative movement of the entire main layer, making the material with two-dimensional sheet materials as the main body possible to be plastically processed.

In some embodiments, the main layer comprises 1 to 50 layers of the two-dimensional sheet material in the thickness direction. The increase in the thickness of the main layer will lead to a decrease in the plasticization effect of the activation layer, so that the macroscopic material lacks sufficient plasticity to ensure processing accuracy and fidelity. Therefore, the preferred number of layers of the main layer in the thickness direction is less than 30 layers.

In some embodiments, the thickness of the activation layer is less than 5 nm, preferably less than 3.3 nm. The increase in the thickness of the activation layer brings about an increase in the overall plasticity of the macroscopic material, but at the same time leads to a decrease in the mass proportion of the two-dimensional sheet material, and the two-dimensional nanosheets become less oriented along the plane, gradually losing the original excellent physical and chemical characteristics (electrical conductivity, thermal conductivity, etc.) of the two-dimensional sheet material.

The activation medium can flow in a specific temperature range, which means that it has fluidity at room temperature or under heating conditions. As long as the activation medium has fluidity under any temperature conditions, it can be used in the present invention and only needs to be plasticized at a specific temperature.

Another aspect of the present application provides application of the above-mentioned plastic processing material in plastic processing, including but not limited to forging, rolling, and stamping.

On the other hand, the present application provides a method for preparing the above-mentioned plastic processing material, which comprises: mixing a dispersion of a two-dimensional sheet material with activated molecules, coating the mixture into a film under the action of a shear field, and after drying, the activated molecules form an activated medium with fluidity, thereby obtaining a main layer-activated layer interpenetrating layer composite material.

In the present application, the concentration of the two-dimensional sheet material, the ratio to the activated molecules, and the size of the shear field all have an impact on the various parameters of the plastic processing material of the present application. Generally, the lower the content of the two-dimensional sheet material, the smaller the ratio to the activated molecules, and the fewer the number of sheets contained in a single main layer, the stronger the plastic processing ability; the higher the content of the two-dimensional sheet material, the greater the ratio to the activated molecules, and the more sheets contained in a single main layer, the more physical and chemical characteristics of the original two-dimensional sheet material are retained in the macroscopic material after processing. Those skilled in the art can adjust the parameters according to the aforementioned trend adaptability to obtain plastic processing materials with corresponding performance.

In the present application, the activated molecules blended with the two-dimensional sheet material form an activated medium, and the activated medium must meet the following requirements: the contact angle with the two-dimensional sheet material is less than 80°. Therefore, for different main materials, it is necessary to select a corresponding activated medium. The main layer two-dimensional sheet material and its supporting activated medium applicable to the present application at least include those indicated in the following table:

In the present application, the shear field has an effect on the orientation and distribution of the main layer and the activation layer. Generally, under the same material ratio, the larger the shear field, the more regular the orientation of the main layer and the activation layer, the more uniform the thickness, and the formation of a layered structure of two-dimensional nanosheets/activated molecules alternately stacked. Generally, the methods include spin coating, scraping coating, centrifugation, etc.

A plastic processing method for a high-content two-dimensional material composite film, the method comprising:

The plastic processing material provided by the present invention is mainly composed of a two-dimensional sheet material, with an activation layer inserted between the layers, and has both the characteristics of plastic processing and the characteristics of a two-dimensional material, and has the following beneficial effects:

(1) Under the action of a high-speed shear field, a composite film of two-dimensional nanosheets and plasticizer molecules assembled layer by layer is formed (Figure 1), in which the content of two-dimensional nanosheets exceeds 50% and the thickness of the main layer is less than 50 layers. This layered structure of alternating stacking of two-dimensional nanosheets/activated molecules improves the free movement of the two-dimensional sheets within the layer, which is beneficial to the macroscopic and microscopic plastic deformation of the composite film.

(2) We have achieved direct plastic forming of near-solid-state two-dimensional materials for the first time. This technology enables us to process two-dimensional materials in the same way as metals and polymers. By using different templates, we can easily manufacture macroscopic assemblies of two-dimensional materials with rich fine structures, including origami, relief, and periodic arrays, showing high resolution at multiple scales from 200μm to 390nm. Compared with the current mainstream solution processing, the plastic forming technology of two-dimensional materials has better processing accuracy, excellent controllability of structural features, and higher efficiency.

(3) Plastic processing of composite films assembled from two-dimensional nanosheets/plasticizer molecules is a material-based manufacturing technology with high processing accuracy (up to 60 nm), fast processing speed, and mild environment. It is feasible in a wide range of two-dimensional material systems (such as molybdenum disulfide and MXene).

(4) The macroscopic assembly material obtained after plastic processing inherits the electrical, optical, mechanical and other properties of the original two-dimensional material, and the internal nanosheets are oriented regularly and are easy to control. The design of the surface microstructure can effectively control the photothermal conversion, humidity response, hydrophilicity and hydrophobicity of the macroscopic assembly material.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1. The layered structure of two-dimensional nanosheet main layer and active layer molecules stacked alternately.

Figure 2. XRD of graphene oxide-glycerol interpenetrating layered composite film (α represents the mass ratio of glycerol to graphene oxide).

Figure 3. Relationship between the plastic processing ability of the graphene oxide-glycerol interpenetrating layer composite film and the thickness of the activation layer in Example 1.

FIG. 4 is a scanning electron microscope image of the nanorod structure obtained in Example 1.

Figure 5. Change in contact angle of graphene oxide film before and after imprinting.

Figure 6. Mechanical properties of graphene oxide/PVA composite films with activation layers of different thicknesses obtained in Example 2 at different temperatures.

Figure 7. Graphene oxide/PVA composite film with surface periodic structure obtained in Example 2. (a) SEM image of the metal template used. (b) SEM image of the three-dimensional periodic structure on the surface of the graphene oxide/PVA composite film after imprinting. (c) White light diffraction image of the three-dimensional periodic structure on the surface of the graphene oxide/PVA composite film after imprinting.

Figure 8. Pure molybdenum disulfide film with surface periodic structure obtained in Example 3.

DETAILED DESCRIPTION

The present invention is further described below in conjunction with the embodiments, but the protection scope of the present invention is not limited thereto.

Example 1

8mg/ml graphene oxide suspension (purchased from Hangzhou Gaoxin Technology Co., Ltd., size 2-30um, carbon-oxygen ratio 1.5-2.2) was blended with glycerol solutions of different concentrations to remove bubbles, and seven slurries with glycerol content and graphene oxide content ratio (α) of 0, 0.1, 0.2, 0.4, 0.6, 0.8 and 1 were prepared. Film was formed by scraping at a fixed speed of 200cm/min to prepare a graphene oxide/glycerol composite film with a thickness of about 30um. According to XRD measurement, the obtained composite film has peaks, indicating that it has a uniformly distributed alternating layered structure, the interlayer spacing of the composite film is linearly related to the mass ratio of glycerol to graphene oxide, and the thickness of the active layer varies from 0.8 to 3.3nm (Figure 2). It can be seen from the XRD pattern of Figure 2 that with the increase of the glycerol mass ratio, the position of the (002) peak gradually decreases, which indicates that the thickness of the active layer (interlayer spacing of the main layer) gradually increases, and the plasticity of the overall film is gradually enhanced. At the same time, with the increase of glycerol mass ratio, the half-width of the (002) peak gradually expands, which indicates that the regularity of the layered structure of alternating stacking of two-dimensional graphene oxide sheets/glycerol molecules gradually decreases, that is, the overall orientation of the material deteriorates.

From the relationship diagram of the plastic processing ability of the graphene oxide-glycerol interpenetrating layer composite film and the thickness of the activation layer in Figure 3, it can be seen that with the increase of the thickness of the activation layer (α gradually increases), the plastic processing of the overall composite film is improved, which is specifically reflected in the increase of plastic tensile deformation strain.

The graphene oxide/glycerol composite film was placed on an AAO (diameter 13mm, pore size 390nm) template and imprinted on a press with a pressure of 50MPa and a temperature of room temperature. The AAO/graphene oxide/glycerol composite film sample was immersed in a 10% phosphoric acid solution and heated at 60°C for 10h, and the AAO template was removed to finally obtain a graphene oxide/glycerol composite film with a nano-columnar surface structure. (Figure 4) Under a scanning electron microscope, it can be observed that the composite film has a layered structure with solid nano-columns of about 400nm on the surface. The height of the nano-columns can be freely adjusted between 400nm-3μm by adjusting the imprinting time and pressure.

The obtained film with surface nanocolumn structure was attached to a glass slide and tested for water contact angle. The contact angle was <65°, indicating good hydrophilicity. However, the contact angle of the unprinted graphene oxide/glycerol composite film was >90°, indicating no hydrophilicity. (Figure 5)

The graphene oxide/glycerol composite film with a nano-columnar surface structure obtained above was subjected to a thermal reduction treatment at 1600°C to remove the glycerol activation layer, and finally a reduced graphene oxide nano-column array was obtained. The conductivity of a single column in the array was about 10,000 S/m, which fully retained the high conductivity characteristics of the graphene derivatives.

Example 2

A 10 mg/ml graphene oxide suspension (GO, purchased from Hangzhou Gaoxin Technology Co., Ltd., size 2-30 um, carbon-oxygen ratio 2.14) was blended with a 1% PVA solution to remove bubbles, and three slurries with a PVA content to graphene oxide content ratio (α) of 0, 0.5 and 1 were prepared. The film was formed by scraping at a fixed speed of 500 cm/min to prepare a graphene oxide/PVA composite film material with a thickness of about 15 um. When the α range is between 0-1, the interlayer spacing changes from 0.8 nm to 3.3 nm. It can be seen from the mechanical properties diagram of the graphene oxide/PVA composite film with different thicknesses of activation layers at different temperatures in Figure 6 that at room temperature, with the increase in the thickness of the polymer PVA activation layer (α gradually increases), the plastic processing of the overall composite film is improved, which is specifically reflected in the increase in plastic tensile deformation strain and the decrease in Young's modulus. When the temperature rises to 95°C, which is higher than the PVA transition temperature, the plastic processing of the overall composite film is further improved. When the thickness of the PVA activation layer is 3.3nm, the elongation of the composite film at 95°C increases from 1.5% to 6%, while the Young's modulus decreases from 8GPa to 3GPa. It is worth noting that the composite film with an interlayer spacing of 0.8nm is a pure graphene oxide film, which fails to show obvious temperature-induced plasticization characteristics. This is because the pure graphene oxide film lacks the characteristic layered structure of alternating main layer/activation layer stacking, further confirming a plastic processing material with a two-dimensional sheet material as the main body, characterized in that it includes at least a main layer and an activation layer located between the main layers.

The graphene oxide/PVA composite film is placed on a metal (pore size 43μm) template and embossed on a press at a pressure of 100MPa and a temperature of 95°C. The metal template and the graphene oxide/PVA composite film are demoulded to finally obtain a graphene oxide/PVA composite film with a surface periodic structure. (Figure 7) Under a scanning electron microscope, it can be observed that the surface of the composite film has a periodic three-dimensional structure with a height of about 50μm. The graphene oxide/PVP composite film with a periodic three-dimensional structure obtained above is subjected to a 1600°C thermal reduction treatment to remove the PVP activation layer, and finally a reduced graphene oxide film with a surface three-dimensional pattern is obtained. The reduced graphene oxide film has an electrical conductivity of about 300,000S/m and a thermal conductivity of about 100W/m K, which fully retains the high electrical conductivity and high thermal conductivity characteristics of graphene derivatives.

Example 3

A 1 mg/ml molybdenum disulfide suspension was used to prepare a molybdenum disulfide film of about 5 μm thickness by vacuum filtration. The obtained molybdenum disulfide film was placed in an ethanol solution and soaked for 5 min. The composite film was placed on a metal template and embossed on a hot press at a pressure of 50 MPa, a temperature of 60°C, and a time of 4 hours. After demolding, a molybdenum disulfide film with a surface three-dimensional structure was finally obtained. (Figure 8) Under a scanning electron microscope, it can be observed that the composite film has a layered structure, with rounded rectangular protrusions with a width of 50 μm and a length of 100 μm on the surface, and the protrusion height can reach up to 20 μm. The film is used as an electrode material, and the energy density of the capacitor can reach 1000 W kg ^-1 at a current density of 50A g ^-1 .

Claims (6)

1. A plastic processing material with a two-dimensional sheet material as the main body, characterized in that it comprises at least a main layer and an activation layer located between the main layers; the main layer comprises at least a two-dimensional sheet material laid along a plane, the activation layer is composed of an activation medium with fluidity, and the contact angle between the activation medium and the two-dimensional sheet material is less than 80°; the mass of the two-dimensional sheet material accounts for more than 50% of the total mass; the main layer comprises 1 to 50 layers of the two-dimensional sheet material in the thickness direction; the thickness of the activation layer is less than 5 nm. 2. The plastic processing material according to claim 1 is characterized in that the fluid activating medium is fluid at room temperature or fluid under heating conditions. 3. Application of the plastic processing material as claimed in claim 1 in plastic processing includes forging, rolling, extrusion, drawing, deep drawing, bending, shearing and stamping. 4. The method for preparing a plastic processing material according to claim 1, characterized in that the method comprises: blending a two-dimensional sheet material dispersion with activated molecules, coating the mixture under the action of a shear field to form a film, and after drying, the activated molecules form an activated medium with fluidity, thereby obtaining a main layer-activated layer interpenetrating layer composite material; Or an assembly of dry two-dimensional sheet materials is immersed in an activated molecule melt or solution, and the activated molecules enter the assembly to form an activated layer, thereby obtaining a main layer-activated layer interpenetrating layer composite material. 5. The preparation method according to claim 4 is characterized in that the activated molecules blended with the two-dimensional sheet material include one or more of ethanol, glycerol, acetic acid, propylene glycol, polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidone, polylactic acid, polyacrylonitrile, and polyethylene oxide. 6 . The preparation method according to claim 4 , characterized in that the shear field is obtained by one or more methods of spin coating, scraping, and centrifugation.

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