A flexible carbon nanomesh film material and a method of making the same

Abstract

The application discloses a flexible carbon nanometer net film material and a preparation method thereof, and belongs to the technical field of nanometer fiber electrode materials. The preparation of the flexible carbon nanometer net film material comprises the following steps: dissolving a polymer in a solvent A to obtain a solution B; ultrasonically dispersing the solution B in a solvent C to obtain a spraying net emulsion; wherein the solution B and the solvent C are immiscible; performing electrostatic spraying on the spraying net emulsion to obtain a polymer nanometer net film; performing pre-oxidation on the polymer nanometer net film; applying longitudinal and transverse tension to the polymer nanometer net film under a protective atmosphere; calcining the polymer nanometer net film; and cooling the polymer nanometer net film to obtain the flexible carbon nanometer net film material. The flexible carbon nanometer net film material has an efficient conductive network, exhibits excellent conductive performance and flexibility, and has a wide application in the fields of wearable devices, flexible sensors, energy storage devices and biomedical devices.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of nanofiber electrode materials, and particularly relates to a flexible carbon nanonet film material and a preparation method thereof. BACKGROUND

[0002] Flexible electronic devices have attracted extensive attention in recent years in the fields of wearable devices, flexible sensors, energy storage devices (such as flexible supercapacitors and lithium ion batteries), biomedical devices, etc. Carbon nanomaterials have the characteristics of light weight, electrical conductivity, and adjustable structure, and have important research and application value for the development of flexible electronic devices with light weight and high capacity. However, when nanocarbon materials (including quantum dots, carbon nanotubes, graphene, etc.) are assembled into macro-sized materials, the electrical conductivity is greatly reduced due to the lack of effective connection between nanomaterials.

[0003] In recent years, electrospun carbon nanofiber films have become an important research direction in the field of flexible electronics due to their high specific surface area, good electrical conductivity, porous structure, mechanical stability, and processability. However, the diameters of existing electrospun carbon nanofibers are all in the sub-micron scale (>200 nm), which limits the further improvement of the specific surface area. In addition, these carbon fiber film materials are randomly deposited and assembled by one-dimensional carbon fibers, and there is a lack of good connectivity between the fibers, which limits the improvement of their electrical conductivity (electrical conductivity <130 S / cm). Therefore, it is urgent to develop two-dimensional carbon nanofiber film materials with good interconnection structure between nanofibers and macro size.

[0004] Chinese patent CN106992288A discloses a kind of antimony / carbon nanofiber flexible material and its preparation method and application, specifically soluble antimony salt and imidazole organic matter are dissolved in organic solvent respectively, then polyacrylonitrile N-N-dimethylformamide solution is added to obtain a uniform electrospinning solution containing antimony nanoparticles, and antimony / carbon nanofiber flexible material is obtained by electrospinning, pre-oxidation and carbonization. However, the carbon material inevitably introduces antimony nanoparticles, which limits the application range of the carbon fiber material. In addition, the carbon material still lacks connectivity between fibers, which limits the improvement of its electrical conductivity.

[0005] Chinese patent CN111180727A discloses a preparation method and application of a flexible dense carbon nanofiber film, specifically a polymer and a carbon source are dissolved in a solvent to obtain a uniform and stable precursor solution, and the precursor solution is subjected to electrospinning, pre-oxidation and carbonization to obtain a flexible dense carbon nanofiber film. Although there are certain bonding points between the carbon fibers in the film, the mechanical stability of the point-like connection structure is poor. In addition, the fibers are all in the sub-micron scale (~200 nm), which limits the further improvement of the specific surface area.

[0006] Therefore, it is urgent to develop a flexible two-dimensional carbon nanonet film with good continuity between fibers without introducing oxide nanoparticles. SUMMARY

[0007] [Technical Problem]

[0008] The existing carbon nanofiber film material has thick fiber diameter, poor fiber interconnectivity and poor conductivity, which seriously limits its application.

[0009] [Technical Solution]

[0010] In order to solve the above technical problems, the purpose of the present application is to provide a flexible carbon nanonet film material and a preparation method thereof, which has good conductivity and flexibility, and effectively solves the problems of thick fiber diameter, poor fiber interconnectivity and poor conductivity of the existing carbon nanofiber film material.

[0011] In order to achieve the above purpose, the technical solution provided is as follows:

[0012] The present application provides a preparation method of a flexible carbon nanonet film material, which comprises the following steps:

[0013] (1) dissolving a polymer in a solvent A to obtain a solution B;

[0014] (2) ultrasonically dispersing the solution B obtained in step (1) in a solvent C to obtain a spraying net emulsion; wherein the solution B and the solvent C are immiscible;

[0015] (3) electrostatically spraying the spraying net emulsion obtained in step (2) to obtain a polymer nanonet film;

[0016] (4) pre-oxidizing the polymer nanonet film obtained in step (3) under a protective atmosphere and applying longitudinal and transverse tension, calcining, and cooling to obtain a flexible carbon nanonet film material.

[0017] In an embodiment, the polymer in step (1) is at least one of polyacrylonitrile, polyethylene terephthalate, polyimide, polyaramid, phenolic resin, polyethylene, polystyrene, polyurethane, or a mixture of any two or three of the above polymers.

[0018] In one embodiment, the polyacrylonitrile has a molecular weight of 10,000-1,000,000; the polyethylene terephthalate has a molecular weight of 20,000-50,000; the polyimide has a molecular weight of 50,000-100,000; the polyaramid has a molecular weight of 50,000-150,000; the phenol-formaldehyde resin has a molecular weight of 500-5,000; the polyethylene has a molecular weight of 100,000-400,000; the polystyrene has a molecular weight of 250,000-700,000; and the polyurethane has a molecular weight of 50,000-150,000.

[0019] In one embodiment, the solvent A in step (1) is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, ethanol, chloroform, dichloromethane, and methylpyrrolidone, or a mixture of several thereof.

[0020] In one embodiment, the mass fraction of the polymer in the solution B in step (1) is 5-20%.

[0021] In one embodiment, the ultrasonic power in step (2) is 500-2,500 w.

[0022] In one embodiment, the particle size of the spray emulsion in step (2) is 10-100 nm.

[0023] In one embodiment, the solvent C in step (2) is at least one of carbon tetrachloride, carbon tetrafluoride, n-hexane, cyclohexane, isobutane, n-butane, heptane, n-dodecane, n-tetradecane, hexadecane, and petroleum ether.

[0024] In one embodiment, the mass ratio of the solution B to the solvent C in step (2) is 1:99-20:80.

[0025] In one embodiment, the electrostatic spraying in step (3) has the following parameters: temperature 10-30°C, relative humidity 20%-70%, perfusion speed 0.1-30 mL / h, voltage 5-60 kV, distance between the receiving device and the spinneret 10-30 cm, slide distance 1-10 cm, and the receiving device is a metal roller.

[0026] In one embodiment, the pre-oxidation process in step (4) is performed in a muffle furnace under an air atmosphere, at a temperature increasing rate of 1-5°C / min to 150-300°C, and for 0.5-2 h.

[0027] In one embodiment, the protective atmosphere in step (4) is at least one of argon and nitrogen.

[0028] In an embodiment, the step (4) of applying the longitudinal and transverse tension is to place the nanomesh film into a tube furnace with a function of bidirectional drawing in the longitudinal and transverse directions, the longitudinal drawing tension is 1-20 MPa, and the transverse drawing tension is 1-20 MPa.

[0029] In an embodiment, the calcination temperature of the step (4) is to heat to 450-600 DEG C at a heating rate of 2-10 DEG C / min, heat preservation for 3-6 h, then heat to 900-1200 DEG C at a heating rate of 2-5 DEG C / min, heat preservation for 1-4 h, and finally slow cooling with the furnace.

[0030] The application further provides the flexible carbon nanomesh film material obtained by the preparation method.

[0031] The application further provides application of the flexible carbon nanomesh film material in the fields of wearable devices, flexible sensors, energy storage devices and biomedical devices.

[0032] Beneficial effects:

[0033] Compared with the prior art, the application has the following beneficial effects:

[0034] 1. The application utilizes the deformation and phase separation of emulsion droplets of a polymer solution in an electric field to form a highly stable porous mesh structure, and the method has good universality and can be applied on a large scale.

[0035] 2. The application utilizes bidirectional stretching carbonization technology to optimize the molecular rearrangement and structural evolution of carbon fibers in the heat treatment process, avoid cracks and defects of the carbon fibers when rapidly heated, reduce the formation of micropores, help the structural consistency of the fibers in the nanomesh, form a more efficient conductive network, and thus make the material have good conductive performance and flexibility.

[0036] 3. The application utilizes emulsion electrospinning technology to form a fiber network with a significant hierarchical channel structure and good connectivity between the fibers. This structure reduces the problem of lack of good connectivity between the fibers caused by random deposition and assembly of the fibers in the traditional nanofiber membrane, and helps efficient transmission of electrons in the nanomesh film. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 Fig. 1 is a SEM image of the nanomesh film of the application Example 1-4; (a) is Example 1; (b) is Example 2; (c) is Example 3; (d) is Example 4.

[0038] Figure 2 Fig. 2 is a SEM image of the product prepared in Comparative Example 1 and Comparative Examples 3-4; (a) is Comparative Example 1; (b) is Comparative Example 3; (c) is Comparative Example 4. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application. The following specific embodiments further describe the present application.

[0040] Embodiment 1

[0041] A preparation method of a flexible carbon nanometer net film material, comprising the following steps:

[0042] (1) polyacrylonitrile with a molecular weight of 90000 is added into N, N-dimethylformamide solvent, the mass percentage of the polyacrylonitrile is 12wt%, and the polyacrylonitrile is fully dissolved to prepare a uniform solution A;

[0043] (2) the solution A is added into n-hexane solvent, the mass ratio of the solution A to the n-hexane is 1:4, and an ultrasonic machine with a power of 800W is used for ultrasonic treatment until the solution A is completely emulsified, the particle size is 10-100nm, and a spraying net emulsion is obtained;

[0044] (3) under the conditions that the humidity is 45% and the ambient temperature is 27℃, the spraying net emulsion is added into an electrostatic spinning device, electrostatic spinning is carried out under the conditions that the electrostatic voltage is 20kV, the flow rate of the injection pump is 0.5mL / h, and the fiber receiving distance is 20cm, and a polyacrylonitrile nanometer net film is obtained;

[0045] (4) the polyacrylonitrile nanometer net film is pre-oxidized in a muffle furnace, the temperature is raised to 240℃ at a temperature raising rate of 5℃ / min in an air atmosphere, and the pre-oxidized fiber film is placed in a tube furnace, the nanometer net film is stretched in the longitudinal direction with a tension of 2MPa and in the transverse direction with a tension of 2MPa in a nitrogen atmosphere, the calcination temperature is raised to 450℃ at a temperature raising rate of 10℃ / min, and then raised to 1200℃ at a temperature raising rate of 5℃ / min, and the temperature is kept for 1h, and finally the furnace is slowly cooled, and a flexible carbon nanometer net film material is obtained.

[0046] Embodiment 2

[0047] A preparation method of a flexible carbon nanometer net film material, comprising the following steps:

[0048] (1) polystyrene with a molecular weight of 520000 is added into N, N-dimethylformamide and dissolved, the mass percentage of the polystyrene is 10wt%, and the polystyrene is fully dissolved to prepare a uniform solution A;

[0049] (2) Solution A is added to the hexadecane solvent, the mass ratio of solution A to hexadecane is 1:9, and the solution A is completely emulsified by using a 900W ultrasonic machine, the particle size is 10-100nm, and a spraying network emulsion is obtained;

[0050] (3) The spraying network emulsion is added to the electrospinning device under the conditions of 45% humidity and 25℃ ambient temperature, electrospinning is carried out under the conditions of an electrostatic voltage of 30kV, an injection pump flow rate of 1mL / h, and a fiber receiving distance of 15cm, and a polystyrene nanometer network film is obtained;

[0051] (4) The polystyrene nanometer network film is pre-oxidized in a muffle furnace, the temperature is raised to 300℃ at a rate of 3℃ / min in an air atmosphere, and the temperature is kept for 2h; then the pre-oxidized fiber film is placed in a tube furnace, the nanometer network film is stretched longitudinally at a tension of 4MPa and transversely at a tension of 4MPa in a nitrogen atmosphere, the calcination temperature is raised to 550℃ at a rate of 5℃ / min in a nitrogen atmosphere, the temperature is kept for 3h, then the temperature is raised to 1100℃ at a rate of 5℃ / min, the temperature is kept for 1h, and finally the furnace is slowly cooled, thereby obtaining a flexible carbon nanometer network film material.

[0052] Example 3

[0053] A preparation method of a flexible carbon nanometer network film material, comprising the following steps:

[0054] (1) Polyimide with a molecular weight of 80000 is added to dimethyl sulfoxide for dissolution, the mass percentage of the polyimide is 10wt%, and the polyimide is fully dissolved to prepare a uniform solution A;

[0055] (2) Solution A is added to petroleum ether solvent, the mass ratio of solution A to petroleum ether is 1:4, and the solution A is completely emulsified by using an 800W ultrasonic machine, the particle size is 10-100nm, and a spraying network emulsion is obtained;

[0056] (3) The spraying network emulsion is added to the electrospinning device under the conditions of 50% humidity and 23℃ ambient temperature, electrospinning is carried out under the conditions of an electrostatic voltage of 25kV, an injection pump flow rate of 1.5m / h, and a fiber receiving distance of 20cm, and a polyimide nanometer network film is obtained;

[0057] (4) The polyimide nanomesh film is pre-oxidized in a muffle furnace, heated to 200°C at a heating rate of 2°C / min under air atmosphere, and kept for 1.5 h. Then the pre-oxidized fiber film is placed in a tube furnace, and the nanomesh film is stretched longitudinally at a tension of 4 MPa and transversely at a tension of 4 MPa under nitrogen atmosphere, calcined at a heating rate of 8°C / min to 550°C for 4 h, then at a heating rate of 5°C / min to 1200°C for 1 h, and finally slowly cooled with the furnace to obtain the flexible carbon nanomesh film material.

[0058] Example 4

[0059] A method for preparing a flexible carbon nanomesh film material, comprising the following steps:

[0060] (1) Polyurethane with a molecular weight of 80000 is dissolved in N,N-dimethylacetamide, the mass percentage of the polyurethane is 10wt%, and the polyurethane is fully dissolved to prepare a uniform solution A;

[0061] (2) Solution A is added to a carbon tetrachloride solvent, the mass ratio of solution A to carbon tetrachloride is 1:3, and an ultrasonic machine with a power of 1000W is used for ultrasonic treatment until the solution A is completely emulsified, the particle size is 10-100 nm, and a spraying emulsion is obtained;

[0062] (3) The spraying emulsion is added to an electrospinning device under the conditions of a humidity of 40%, an ambient temperature of 25°C, an electrostatic voltage of 20kV, a flow rate of an injection pump of 1m / h, and a fiber receiving distance of 25cm to perform electrospinning, and a polyurethane nanomesh film is obtained;

[0063] (4) The polyurethane nanomesh film is pre-oxidized in a muffle furnace, heated to 250°C at a heating rate of 3°C / min, and kept for 2 h. Then the pre-oxidized nanofiber mesh film is placed in a tube furnace, and the nanofiber mesh film is stretched longitudinally at a tension of 6 MPa and transversely at a tension of 6 MPa under nitrogen atmosphere, calcined at a heating rate of 5°C / min to 500°C for 5 h, then at a heating rate of 2°C / min to 1100°C for 1 h, and finally slowly cooled with the furnace to obtain the flexible carbon nanomesh film material.

[0064] Comparative Example 1

[0065] The difference from Example 1 is that in step (2), solution A is added to n-hexane solvent, and is not subjected to ultrasonic dispersion, but is only subjected to physical stirring, and the particle size obtained is 7-12mm, and other parameters and conditions are the same as those of Example 1.

[0066] The SEM image of the product obtained in this comparative example is shown in Figure 2 a.

[0067] From Figure 2 It can be seen from

[0068] Comparative Example 2

[0069] The difference between Example 1 and Comparative Example 2 is that in step (2), solution A is added into N,N-dimethylformamide, and other parameters and conditions are the same as those in Example 1.

[0070] The product prepared in this comparative example has poor mechanical properties, is easy to break and brittle, and the bending stiffness is difficult to measure.

[0071] Comparative Example 3

[0072] The difference between Example 1 and Comparative Example 3 is that in step (2), solution A is added into N,N-dimethylacetamide, and other parameters and conditions are the same as those in Example 1.

[0073] The SEM image of the product prepared in this comparative example is shown in Figure 2 b. Figure 2 It can be seen from

[0074] The product prepared in this comparative example is difficult to be self-supporting, easy to break and brittle, and the bending stiffness is difficult to measure.

[0075] Comparative Example 4

[0076] The difference between Example 1 and Comparative Example 4 is that step (2) is directly omitted, and a uniform solution A is used for preparation, and other parameters and conditions are the same as those in Example 1.

[0077] The SEM image of the product prepared in this comparative example is shown in Figure 2 c.

[0078] It can be seen from Figure 2 c. Compared with Example 1, the product obtained in Comparative Example 4 has only continuous nanofibers, and no nanomesh is formed, which is mainly because solution A is a uniform polymer solution, and the viscosity of the solution is moderate, and the molecular chain entanglement has a certain entanglement.

[0079] Performance Test

[0080] 1. Carbon nanomesh film conductivity test

[0081] The conductivity of the prepared flexible carbon nanomesh film material is tested by using ST-2258C four-probe tester. First, the thickness and shape of the flexible carbon nanomesh film material sample are corrected, then the sample is placed flat on the test table, and the forward and reverse conductivities are measured, three points of each sample are randomly selected for testing, and the average value is taken as the conductivity, unit S / cm.

[0082] 2. Flexible test of carbon nanomesh film

[0083] The softness of the nanomesh film is tested according to international standard ASTM D2923-01, the nanomesh film with an area of 10 cm*10 cm is placed flat on the upper end of the slit, and the axis of the film is aligned with the test slit on the instrument table. During the test, the stress sensing probe vertically presses the fiber film into the slit to a certain depth, and then releases the pressure. At this time, the softness tester automatically displays the bending stiffness of the nanomesh film, unit mN.

[0084] The results are shown in Table 1:

[0085] Table 1. Properties of materials prepared in examples and comparative examples

[0086]

[0087] The above examples are not intended to limit the scope of the present application, and the described steps are not intended to limit the execution order. Those skilled in the art can make obvious improvements to the present application in combination with existing common knowledge, which also falls within the protection scope defined by the claims of the present application.

Claims

1. A method for preparing a flexible carbon nanofiber membrane material, characterized in that, The preparation method includes the following steps: (1) Dissolve the polymer in solvent A to obtain solution B; the polymer is either polyacrylonitrile or polyimide; The solvent A is at least one or a mixture of several of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, chloroform, dichloromethane, and methylpyrrolidone; (2) The solution B obtained in step (1) is ultrasonically dispersed in solvent C to obtain a sprayed emulsion; wherein, solution B and solvent C are immiscible; the particle size of the sprayed emulsion is 10-100 nm. (3) Electrostatically spray the emulsion obtained in step (2) to obtain a polymer nanomembrane; (4) The polymer nanomembrane obtained in step (3) is pre-oxidized, calcined under a protective atmosphere with longitudinal and transverse tension, and cooled to obtain a flexible carbon nanomembrane material.

2. The preparation method according to claim 1, characterized in that, The ultrasonic power in step (2) is 500-2500W.

3. The preparation method according to claim 1, characterized in that, The solvent C in step (2) is one or more of carbon tetrachloride, carbon tetrafluoride, n-hexane, cyclohexane, isobutane, n-butane, heptane, n-dodecane, n-tetradecane, hexadecane, and petroleum ether.

4. The preparation method according to claim 1, characterized in that, The parameters of the electrostatic spraying net in step (3) are: temperature 10-30℃, relative humidity 20%-70%, injection speed 0.1-30mL / h, voltage 5-60kV, distance between the receiving device and the spinneret 10-30cm, distance between the slide table 1-10cm, and the receiving device is a metal roller.

5. The preparation method according to claim 1, characterized in that, Step (4) involves applying longitudinal and transverse tension by placing the nanomembrane into a tubular furnace with bidirectional longitudinal and transverse stretching functions. The longitudinal stretching tension is 1-20 MPa, and the transverse stretching tension is 1-20 MPa.

6. A flexible carbon nanomembrane material obtained by the preparation method according to any one of claims 1 to 5.

7. The application of the flexible carbon nanomembrane material according to claim 6 in the fields of wearable devices, flexible sensors, energy storage devices, and biomedical devices.

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