A method for preparing carbon nanoribbons

Abstract

The present application relates to a kind of preparation methods of carbon nanometer strip, belong to carbon material technical field.The preparation method of the present application includes the following steps, S1, preparation has the dense carbon nanometer film of defect-rich structure;S2, on the dense carbon nanometer film of defect-rich structure of S1, build polymer film, obtain carbon nanometer composite polymer film;S3, carbon nanometer composite polymer film of S2 is uniaxially stretched, dense carbon nanometer film forms channel crack after stress training, remove polymer film, obtain the carbon nanometer strip of described.The preparation method of the present application has the advantages of convenient operation, preparation condition is mild controllable, suitable for large-scale preparation, especially with the advantage of strong universality, can be combined with various nanometer dense carbon nanometer film preparation technology.In addition, by the matching adjustment of the geometric size and ordered structure of dense carbon nanometer film, defect-rich structure, the thickness of polymer film, the geometric size, edge structure etc. of nanometer carbon strip can be flexibly adjusted.

Description

Technical Field

[0001] This invention belongs to the field of carbon materials technology, and particularly relates to a method for preparing carbon nanoribbons. Background Technology

[0002] Nanoscale carbon films with confined width dimensions form carbon nanoribbons. These quasi-one-dimensional materials exhibit physical properties distinct from the bulk film, with the boundary atoms playing a crucial role in their physical properties. Since the carbon atom content is higher at the edges, adsorption, doping, and trimming at the edges can further alter the physicochemical properties of the nanoribbons. Therefore, developing convenient methods for preparing carbon nanoribbons is of great significance.

[0003] In recent years, various methods for preparing carbon nanoribbons have been developed. These methods can be divided into two categories: bottom-up and top-down methods. Bottom-up methods include organic synthesis, SiC epitaxial growth, and CVD growth. Organic synthesis involves synthesizing various organic monomers (such as biphenyl compounds), requiring precise selection of precursor molecules and accurate control of the reaction route. SiC epitaxial growth utilizes the sublimation and escape of silicon atoms on the surface of SiC when heated in a vacuum or inert atmosphere, with the remaining carbon atoms rearranging on the step surface of the SiC wafer. When using CVD growth for carbon nanoribbon synthesis, it is necessary to combine template-assisted growth, confined growth, and other techniques to prepare carbon nanoribbons with an aspect ratio ≠ 1. Top-down methods first prepare carbon nanofilms and then further prepare carbon nanoribbons. This method for fabricating carbon nanotube films into carbon nanoribbons includes several approaches: etching using the tip of a high-bias scanning tunneling microscope, cutting using plasma and ion beams with template assistance, or replication and transfer using lithography. Additionally, carbon nanoribbons can be obtained by tearing the sidewalls of carbon nanotubes and then flattening them. Graphene oxide and other ribbons can also be produced through wet spinning, followed by reduction to obtain multilayer graphite nanoribbons. However, existing technologies still suffer from problems such as expensive equipment, pollutant emissions, cumbersome processes, and difficulties in large-scale production. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing carbon nanoribbons. A polymer film matrix composed of soluble polymers is constructed on a dense carbon nanofilm with a defect-rich structure, supporting the carbon nanofilm to form a carbon nanocomposite polymer film structure. By subjecting the polymer film structure to uniaxial stretching, stress is conducted through the polymer film to the dense carbon nanofilm, causing the dense carbon nanofilm to form equally spaced channel cracks parallel to the stretching direction under stress. These channel cracks penetrate the film thickness direction, dividing the dense carbon nanofilm into carbon ribbons perpendicular to the stretching direction. Individual carbon nanoribbons are obtained by removing the polymer film matrix.

[0005] The purpose of this invention is to provide a method for preparing carbon nanoribbons, comprising the following steps:

[0006] S1. Prepare dense carbon nanofilms with defect-rich structures;

[0007] S2. Construct a polymer film on the dense carbon nanofilm with a defect-rich structure described in S1 to obtain a carbon nanocomposite polymer film.

[0008] S3. The carbon nanocomposite polymer film described in S2 is subjected to uniaxial stretching. After stress training, channel cracks are formed in the dense carbon nanofilm. The polymer film is then removed to obtain the carbon nanoribbons.

[0009] In one embodiment of the present invention, in S1, the dense carbon nanofilm refers to a carbon film that does not contain pores at the nanoscale or above.

[0010] In one embodiment of the present invention, defect structures are inevitably introduced into materials under normal circumstances due to external factors such as processing or use, and these defects are randomly distributed within the material. When the thin film is subjected to tensile strain, it is affected by the randomly distributed defects, resulting in larger crack spacing. Introducing abundant defect structures into the material through defect engineering to form a defect-rich material is an important means of controlling the electrical, catalytic, and mechanical properties of materials. Stretching a defect-rich thin film and stress training can introduce channel crack structures with small crack spacing into the film.

[0011] In one embodiment of the present invention, in S1, the dense carbon nanofilm with a defect-rich structure refers to a carbon film with a rich defect structure and without nanoscale or larger pore structures.

[0012] In one embodiment of the present invention, in S1, the method for preparing the dense carbon nanofilm is selected from one or more of CVD growth, chemical synthesis, thermal carbonization and laser carbonization.

[0013] In one embodiment of the present invention, in S1, the dense carbon nanofilm can be amorphous or a carbon material with a highly ordered structure.

[0014] In one embodiment of the present invention, in S1, the defect-rich structure in the dense carbon nanofilm is selected from one or more of point defects, line defects, and surface defects.

[0015] Furthermore, the point defect is selected from one or more of atomic vacancies, interstitial atoms, and impurity atoms.

[0016] Furthermore, the line defects are steps and dislocations in ordered carbon materials.

[0017] Furthermore, the surface defect is a stacking fault structure in a multilayer graphene structure.

[0018] In one embodiment of the present invention, in S1, the defect-rich structure in the dense carbon nanofilm is achieved by doping a heterogeneous material in the carbonization precursor.

[0019] In one embodiment of the present invention, the heterogeneous material is selected from one or more of the following: inorganic clusters, nanoparticles, non-carbon-forming small molecule compounds, non-carbon-forming polymer compounds, and components in which the ordered arrangement of carbon atoms obtained during the carbonization process is inconsistent with the bulk structure of the dense carbon nanofilm.

[0020] Furthermore, the inorganic clusters or nanoparticles are SiO₂. x .

[0021] Furthermore, the non-carbon-forming small molecule compound or the non-carbon-forming polymer compound is a compound with a carbon residue rate of <20% when carbonized at 700°C under an inert atmosphere.

[0022] Furthermore, the component obtained during the carbonization process that has an ordered arrangement of carbon atoms that is inconsistent with the bulk structure of the dense carbon nanofilm is a product of the carbonization precursor being replaced by B, S, P and halogens.

[0023] In one embodiment of the present invention, the doping is performed as follows:

[0024] Heterogeneous materials are pre-distributed on the substrate, and then carbonized precursors are further distributed;

[0025] And / or, doping heterogeneous materials into the carbonized precursor.

[0026] In one embodiment of the present invention, in S1, the thickness of the dense carbon nanofilm is 0.35nm-50nm.

[0027] In one embodiment of the present invention, in S2, the polymer film is selected from a soluble polymer film or a composite film composed of a soluble polymer film and an insoluble polymer film, and the junction of the dense carbon nanofilm and the polymer film is a soluble polymer film.

[0028] In one embodiment of the present invention, in S2, the soluble polymer is selected from water-soluble polyvinyl alcohol and / or alcohol-soluble polyvinyl butyral ester.

[0029] In one embodiment of the present invention, in S2, the thickness of the polymer film is 10μm-100μm.

[0030] In one embodiment of the present invention, in S2, the area of ​​the dense carbon nanofilm is smaller than that of the polymer film.

[0031] In one embodiment of the present invention, in S2, the elastic modulus of the dense carbon nanofilm is greater than that of the polymer film.

[0032] In one embodiment of the present invention, before S3, the process further includes transferring the carbon nanocomposite polymer film off the substrate.

[0033] Furthermore, the transfer is performed in the following manner:

[0034] Simple peeling;

[0035] And / or, the carbon nanocomposite polymer film together with the substrate is immersed in water, and water permeates into the interface between the carbon film and the substrate from the seam, using the water wetting effect to peel off the carbon nanocomposite polymer film.

[0036] In one embodiment of the invention, in S3, a tensile load generated by uniaxial stretching is applied to the edge region of the substrate without film coverage, the strain of which is 0.5%-15%, generating channel cracks in the dense carbon nanofilm.

[0037] In one embodiment of the present invention, in S3, the uniaxial stretching method is manual stretching or automatic mechanical stretching.

[0038] In one embodiment of the present invention, in S3, the removal is performed by soaking in a solvent to remove the polymer film and obtain individual carbon nanoribbons.

[0039] Furthermore, the solvent is a good solvent for soluble polymers, so that the polymer film can be removed from the carbon nanoribbons to obtain independent carbon nanoribbons.

[0040] In one embodiment of the present invention, in S3, the width of the carbon nanoribbons is 1nm-50nm.

[0041] The technical solution of the present invention has the following advantages compared with the prior art:

[0042] (1) In the preparation method described in this invention, when the carbon nanocomposite polymer film is subjected to uniaxial stretching and tensile load, shear stress is generated at the interface between the polymer film and the dense carbon nanofilm due to the modulus mismatch between the polymer film and the dense carbon nanofilm. To balance this shear stress field, the carbon nanofilm is subjected to tensile stress along the stretching direction. When this stress value is greater than the initial fracture strain of the carbon nanofilm, cracks are generated in the film perpendicular to the stretching direction, converting the strain potential energy into the surface energy of the newly formed cracks to reduce the energy of the entire system. Since the tensile fracture strain of the selected polymer is much higher than that of the dense carbon nanofilm, the dense carbon nanofilm fractures before the polymer. As the stress increases, the crack density increases accordingly, and the crack spacing decreases accordingly. Further increasing the tensile strain, new cracks appear at the symmetrical position between two adjacent cracks. With continuous increase in tensile strain, equally spaced cracks appear in the dense carbon nanofilm, dividing the originally complete film into uniform carbon strips.

[0043] The fracture strength and fracture location of dense carbon nanofilms are affected by the defect structure. When no defect-rich structure is introduced, the spacing of channel cracks formed by dense carbon nanofilms under uniaxial tension is at the micrometer level or above. It is impossible to obtain channel cracks with spacing at the nanoscale, and therefore it cannot be used to prepare carbon nanoribbons with width at the nanoscale.

[0044] (2) The preparation method of the present invention prepares a dense carbon nanofilm with a defect-rich structure by using a carbonization precursor with heterogeneous materials, and then combines it with a polymer film. The heterogeneous component can be an inorganic cluster or nanoparticle that is incompatible with the precursor, or it can be a non-carbon-forming small molecule or polymer compound, or it can be a component whose ordered arrangement of carbon atoms obtained during the carbonization process is inconsistent with the bulk structure of the dense carbon nanofilm.

[0045] (3) In the preparation method described in this invention, when the tensile stress on the dense carbon nanofilm with a defect-rich structure is greater than the fracture strength at the defect during uniaxial stretching, the dense carbon nanofilm will generate cracks at the pre-introduced defect locations. Compared to a dense carbon nanofilm without pre-introduced defects, the pre-introduced defect-rich structure allows the dense carbon nanofilm to obtain a series of channel cracks arranged parallel to the stretching direction and spaced at the nanometer level under stress training. Carbon nanoribbons can then be conveniently obtained by removing the polymer substrate.

[0046] (4) Compared to other existing top-down carbon nanoribbon preparation techniques, the preparation method of this invention constructs a dense carbon nanofilm with a defect-rich structure. Utilizing the stress training effect achieved through a convenient uniaxial stretching technique, nanometer-sized channel cracks are introduced into the dense carbon nanofilm, thereby obtaining carbon nanoribbons with widths in the nanometer range. This preparation method is convenient to operate, has mild and controllable preparation conditions, is suitable for large-scale preparation, and is particularly versatile, allowing it to be combined with various nano-dense carbon nanofilm preparation techniques. Furthermore, by matching and adjusting the geometric dimensions and ordered structure, defect-rich structure, and polymer film thickness of the dense carbon nanofilm, the geometric dimensions and edge structure of the carbon nanoribbons can be flexibly adjusted. Attached Figure Description

[0047] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein:

[0048] Figure 1 This is an atomic force microscope image of the cracked, dense nanocarbon thin film of Example 1 of the present invention;

[0049] Figure 2 A micrograph of the carbon nanoribbons of Example 1 of the present invention;

[0050] Figure 3 This is an atomic force microscope image of the cracked, dense nanocarbon thin film of Example 2 of the present invention;

[0051] Figure 4 The image shows a micrograph of the carbon nanoribbons in Example 2 of this invention.

[0052] Figure 5 This is a micrograph of the cracked, dense nano-carbon film of Comparative Example 1 of the present invention. Detailed Implementation

[0053] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0054] In this invention, unless otherwise stated, the area of ​​dense carbon nanofilms is smaller than that of polymer films.

[0055] In this invention, unless otherwise stated, the elastic modulus of dense carbon nanofilms is greater than that of polymer films.

[0056] In this invention, unless otherwise stated, the tensile fracture strain of dense carbon nanofilms is less than that of polymer films.

[0057] Example 1

[0058] The method for preparing carbon nanoribbons of the present invention specifically includes the following steps:

[0059] S1. Dense carbon nanofilms with defect-rich structures are prepared by laser direct writing of polyimide:

[0060] First, ultrasound is used to separate 1nm silicon-based oxide nanoparticles (SiO2). x ) was blended with polyamic acid, a polyimide precursor, to obtain a mixture with a doping ratio of 0.01 wt%;

[0061] The mixture was then spin-coated onto a quartz substrate and heated to prepare a PI film with a thickness of 100 nm.

[0062] Finally, a CO2 laser cutting machine was used for direct laser writing carbonization. The writing power was 1.8W and the writing speed was 15mm / s. The processing was carried out by line scanning with a line spacing of 50μm. The carbonized writing area was 3mm×3mm, resulting in a dense nano-carbon film with a defect-rich structure and a thickness of 50nm.

[0063] S2. Preparation of carbon nanocomposite polymer films

[0064] A carbon nanocomposite polymer film is formed by spin-coating a 30 μm thick polyvinyl butyral polymer film onto a dense carbon nanofilm with a defect-rich structure.

[0065] Mechanical peeling is used to separate the composite film from the quartz substrate.

[0066] S3. Preparation of carbon nanoribbons

[0067] A carbon nanocomposite polymer film is clamped on a uniaxial tensile jig. By changing the distance between the jigs, a strain of 7% is applied to the film, introducing through cracks into the dense carbon nanofilm and forming a cracked dense carbon nanofilm.

[0068] The composite membrane was slowly immersed in anhydrous ethanol with the polyvinyl butyral film facing down, and the ethanol dissolved the polyvinyl butyral film. Carbon nanoribbons were suspended in anhydrous ethanol and then retrieved using a glass slide, spreading them on the surface of the slide.

[0069] Figure 1 The image shown is an atomic force microscope image of a cracked, dense carbon nanotube film. The bright areas represent carbon nanoribbon regions, and the dark areas represent cracked regions. The average crack spacing is 20 nm.

[0070] Figure 2 The image shown is a microscope image of carbon nanoribbons, which are 20 nm wide.

[0071] This embodiment uses SiO doping. x As a heterogeneous component of the carbonization precursor, due to SiO x It exhibits high thermal stability and does not undergo pyrolysis or decomposition during thermal carbonization, thus resulting in a dense nano-carbon film of SiO2. x Doped carbon nanofilms, under stress, SiO x Fracture first occurs at the interface with the surrounding carbon material, therefore SiO... x The doped carbon nanofilm is a dense carbon nanofilm with a defect-rich structure. When this defect-rich dense carbon nanofilm is subjected to uniaxial tensile testing, the initial fracture strain is significantly lower than that of the dense carbon nanofilm without the defect-rich structure in the comparative example. For the same reason, at a smaller strain (~7%), the defect-rich structure allows the dense carbon nanofilm to acquire a series of channel cracks arranged parallel to the tensile direction and spaced 20 nm apart under stress training. Furthermore, carbon nanoribbons with a width of 20 nm can be easily obtained by removing the polymer substrate.

[0072] Example 2

[0073] The method for preparing carbon nanoribbons of the present invention specifically includes the following steps:

[0074] S1. Dense carbon nanofilms with defect-rich structures are prepared by laser direct writing of polyimide:

[0075] First, the spheroidal graphite method is used to prepare nano-silicon-based oxides (SiO2) with a particle size of 1 nm. x ) was blended with polyamic acid, a polyimide precursor, to obtain a mixture with a doping ratio of 0.01 wt%;

[0076] The mixture was then spin-coated onto a quartz substrate and heated to prepare a PI film with a thickness of 30 nm.

[0077] Finally, a CO2 laser cutting machine was used for laser direct writing carbonization. The writing power was 1.7W and the writing speed was 10mm / s. The processing was carried out by line scanning with a line spacing of 50μm. The carbonized writing area was 3mm×3mm, resulting in a dense nano-carbon film with a defect-rich structure and a thickness of 15nm.

[0078] S2. Preparation of carbon nanocomposite polymer films

[0079] A carbon nanocomposite polymer film is formed by spin-coating a 20 μm thick polyvinyl butyral polymer film onto a dense carbon nanofilm with a defect-rich structure.

[0080] Using a blade, cut along the four sides of the polymer film, then immerse the lifted corner of the composite film along with the quartz sheet in water. Water seeps into the interface between the carbon nanocomposite polymer film and the quartz from the seam, causing the carbon nanocomposite polymer film to separate from the quartz substrate.

[0081] S3. Preparation of carbon nanoribbons

[0082] A carbon nanocomposite polymer film is clamped on a uniaxial tensile jig. By changing the distance between the jigs, a strain of 5% is applied to the film, introducing through cracks into the dense carbon nanofilm and forming a cracked dense carbon nanofilm.

[0083] The composite membrane was slowly immersed in anhydrous ethanol with the polyvinyl butyral film facing down, and the ethanol dissolved the polyvinyl butyral film. Carbon nanoribbons were suspended in anhydrous ethanol and then retrieved using a glass slide, spreading them on the surface of the slide.

[0084] Figure 3 The image shown is an atomic force microscope image of a cracked, dense carbon nanotube film. The bright areas are carbon nanotube strip regions, and the dark areas are cracked regions. The average crack spacing is 7 nm.

[0085] Figure 4 The image shown is a microscope image of carbon nanoribbons, which are 7 nm wide.

[0086] This embodiment uses SiO doping. x As a heterogeneous component of the carbonization precursor, the initial fracture strain of this defect-rich dense carbon nanofilm during uniaxial tensile testing is significantly lower than that of the dense carbon nanofilm without the defect-rich structure introduced in the comparative embodiment. For a given material, the fracture toughness of the film is affected by its thickness. At the same elastic modulus and fracture strain / fracture strength, the fracture toughness of the dense carbon nanofilm decreases with decreasing thickness. Therefore, in this embodiment, reducing the thickness of the carbon nanofilm allows for the acquisition of a dense carbon film with lower fracture toughness. Thus, a lower tensile stress is required to construct a series of channel cracks with a crack spacing of 7 nm in the film. Furthermore, carbon nanoribbons with a width of 7 nm can be easily obtained by removing the polymer substrate.

[0087] Comparative Example 1

[0088] S1. Dense carbon nanofilms are prepared by laser direct writing of polyimide:

[0089] Then, the polyimide precursor polyamic acid was spin-coated onto a quartz substrate and heated to prepare a PI film with a thickness of 30 nm.

[0090] Finally, a CO2 laser cutting machine was used for laser direct writing carbonization. The writing power was 1.7W and the writing speed was 10mm / s. The processing was carried out by line scanning with a line spacing of 50μm. The carbonized writing area was 3mm×3mm, resulting in a dense nano-carbon film with a thickness of 15nm.

[0091] S2. Preparation of carbon nanocomposite polymer films

[0092] A carbon nanocomposite polymer film with a thickness of 20 μm was spin-coated onto a dense carbon nanofilm.

[0093] Using a blade, cut along the four sides of the polymer film, then immerse the lifted corner of the composite film along with the quartz sheet in water. Water seeps into the interface between the carbon nanocomposite polymer film and the quartz from the seam, causing the carbon nanocomposite polymer film to separate from the quartz substrate.

[0094] S3. Preparation of carbon nanoribbons

[0095] A carbon nanocomposite polymer film is clamped on a uniaxial tensile jig. By changing the distance between the jigs, a strain of 15% is applied to the film, introducing through cracks into the dense carbon nanofilm and forming a cracked dense carbon nanofilm.

[0096] Figure 5 The image shown is an atomic force microscope image of a cracked, dense carbon nanofilm with an average crack spacing of 1.5 μm.

[0097] Dense carbon nanofilms and their carbon nanocomposite polymer films obtained via laser direct writing carbonization technology, when subjected to 15% uniaxial tension, generate shear stress at the interface between the polymer film and the carbon nanofilm, thereby transferring the tensile stress on the polymer film to the carbon nanofilm. Once the stress on the carbon nanofilm exceeds its initial fracture strain, cracks form in the film perpendicular to the stretching direction. In the aforementioned dense carbon nanofilms without the introduction of defect-rich structures, due to the low intrinsic defect density and large initial fracture strain, the spacing of the channel cracks formed under uniaxial tension is on the micrometer scale, making it impossible to obtain carbon nanoribbons with widths on the nanoscale.

[0098] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing carbon nanoribbons, characterized in that, Includes the following steps: S1. Prepare a dense carbon nanofilm with a defect-rich structure; the defect-rich structure in the dense carbon nanofilm is achieved by doping a heteromaterial into a carbonization precursor; S2. Construct a polymer film on the dense carbon nanofilm with a defect-rich structure described in S1 to obtain a carbon nanocomposite polymer film. S3. The carbon nanocomposite polymer film described in S2 is subjected to uniaxial stretching. After stress training, channel cracks are formed in the dense carbon nanofilm. The polymer film is then removed to obtain the carbon nanoribbons.

2. The method for preparing carbon nanoribbons according to claim 1, characterized in that, In S1, the method for preparing the dense carbon nanofilm is selected from one or more of CVD growth, chemical synthesis, thermal carbonization, and laser carbonization.

3. The method for preparing carbon nanoribbons according to claim 1, characterized in that, In S1, the defect-rich structure in the dense carbon nanofilm is selected from one or more of point defects, line defects, and surface defects.

4. The method for preparing carbon nanoribbons according to claim 1, characterized in that, In S1, the heterogeneous material is selected from one or more of the following: inorganic clusters, nanoparticles, non-carbon-forming small molecule compounds, non-carbon-forming polymer compounds, and components whose ordered arrangement of carbon atoms during the carbonization process is inconsistent with the bulk structure of the dense carbon nanofilm.

5. The method for preparing carbon nanoribbons according to claim 1, characterized in that, In S1, the doping method is as follows: Heterogeneous materials are pre-distributed on the substrate, and then carbonized precursors are further distributed; And, heterogeneous materials are doped into the carbonized precursor.

6. The method for preparing carbon nanoribbons according to claim 1, characterized in that, In S1, the thickness of the dense carbon nanofilm is 0.35nm-50nm.

7. The method for preparing carbon nanoribbons according to claim 1, characterized in that, In S2, the polymer film is selected from soluble polymer films or composite films composed of soluble and insoluble polymer films, and the interface between the dense carbon nanofilm and the polymer film is a soluble polymer film.

8. The method for preparing carbon nanoribbons according to claim 1, characterized in that, In S3, the strain of the uniaxial tension is 0.5%-15%.

9. The method for preparing carbon nanoribbons according to claim 1, characterized in that, In S3, the width of the carbon nanoribbons is 1nm-50nm.

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