AU2020100844A4

AU2020100844A4 - A Preparation Method and Application Of Graphene Nanotubes

Info

Publication number: AU2020100844A4
Application number: AU2020100844A
Authority: AU
Inventors: Peng Chen; Zeyu GUO; Jie Wu; Xiaofang Yu
Original assignee: Inner Mongolia Agricultural University
Current assignee: Inner Mongolia Agricultural University
Priority date: 2020-05-26
Filing date: 2020-05-26
Publication date: 2020-07-02
Anticipated expiration: 2028-05-26

Abstract

The invention discloses a method for preparing graphene nanotubes. Graphene oxide is placed in a solvent to be ultrasonically dispersed to obtain a graphene oxide dispersion liquid, and then a solute is added to obtain a mixed solution. After electrospinning, pre-oxidation, carbonization under specific conditions, graphene nanotubes are finally obtained by ammonia gas treatment. The graphene nanotubes prepared by the present invention have excellent field emission effect performance, the opening electric field is 0 21V/ m, and the threshold electric field is 0 .42V/ m, which has great application value in the preparation of intelligent switching devices. Drawings a) 30 20 0' 1 0. CA oi 2 - - ----------- 1 4 000 0.1 020 0.3 0.4 E (VIpm) Figure 3 30 20(C) 106pA J=21.6mAcm 2 240 0 -10 -20 0 3 6 9 12 15 18 Time hrs.) Figure 4 2/3

Description

Drawings

a) 30

20

0' 1 0. CA oi

2 - - ----------- 1 4

000 0.1 020 0.3 0.4

E (VIpm)

Figure 3

2 20(C) 106pA J=21.6mAcm

240

-10

-20 0 3 6 9 12 15 18 Time hrs.)

Figure 4

2/3

Descriptions A Preparation Method and Application of Graphene Nanotubes

Technical Field

[0001] The invention relates to the technical field of graphene, in particular to a preparation method and application of graphene nanotubes.

Background Technology

[0002] Graphene has a series of unique physical and chemical properties, such as ultrahigh mechanical strength, high young's modulus, excellent electron mobility at room temperature, very high thermal conductivity, excellent optical absorption properties, and complete impermeability to any gas. Since 2004, Andre Geim and Konstantin Novoselov of the University of Manchester in the United Kingdom have been using transparent tape to prepare and received extensive attention. As a two-dimensional sheet material, graphene has a single structure, but its macroscopic structure can change in many ways, such as two-dimensional thin film and three-dimensional macroscopic structure, which broadens the application field of graphene.

[0003] Graphene-based nanomaterials are graphene topological structures, which greatly retain the inherent properties of graphene, meanwhile, new physical appearances and structures are prepared by physical or chemical methods, giving them special properties.

[0004] Electrospinning is a new type of spinning technology, which is developed based on the principle of high-speed injection of charged liquid electrolyte in a high-voltage electrostatic field. Its core is that the charged liquid flows and deforms in the high-voltage electrostatic field, and then passes through the melt Cooling or solvent volatilization and solidification so as to obtain fibrous materials at the submicron or even nanometer level. It has the characteristics of low cost and large-scale preparation of nanofibers, and it has been widely used in the preparation of polymer nanofibers. It has been a research hotspot in recent years. However, there is no report on the continuous preparation of continuous graphene nanotubes by electrospinning technology.

Invention Summary

[0005] The invention aims to provide a preparation method and application of graphene nanotubes. The method disclosed in the present invention can make dispersed, irregular-shaped graphene nanosheets interconnected by nitrogen atoms at high temperature, meanwhile, carbon nanofibers are used as templates to make them continuous graphene nanotubes. The prepared graphene nanotubes have excellent field emission effects, and can be used to prepare intelligent switching devices to solve the problems in the prior art.

[0006] In order to achieve the above object, the present invention discloses a method for preparing graphene nanotubes, the preparation method includes the following steps:

[0007] 1) The graphene oxide is placed in a solvent to be ultrasonically dispersed 2~3h to obtain a graphene oxide dispersion liquid, and then a solute is added to the graphene oxide dispersion and stirred in 65°C water bath for 24 hours. Where the mass ratio of graphene oxide

Descriptions to solute is 1/11~1/5, and the total mass concentration range of graphene oxide and solute is 10 %~15%;

[0008] 2)In the electrospinning device, the solution prepared in step 1) is used to prepare nanocomposite fiber strands. The conditions for preparing electrospinning are: voltage is 25kv, the distance between the needle and the substrate is 25 cm, and the feed rate of the solution is 1 ml / h;

[0009] 3)The nanocomposite fiber raw wire prepared in step 2) is pre-oxidized at a temperature of 220~240°C for 100~120 min, then, the temperature is raised to 950~1050°C under the protection of inert gas, and then, ammonia gas is introduced to react for 30~60 min. After the reaction is finished, the graphene nanotubes can be prepared by stopping the ammonia gas, introducing the inert gas and cooling with the furnace.

[0010] Further, the graphene oxide is prepared from microcrystalline graphite.

[0011] Microcrystalline graphite is purified at high temperature, and its fixed carbon content can reach 99.99% or higher, its particles are aggregated by many tiny crystals. Therefore, the graphene oxide sheet prepared by the conventional method using the raw material of microcrystalline graphite is very small, and the gas generated by the reaction can be pushed to the edge to form nanotubes in the restricted template of carbon nanofibers.

[0012] Further, in step 1), the solute is polyacrylonitrile when the solvent is N ,N dimethylformamide or N ,N- dimethylacetamide or a mixture of the two in any ratio.

[0013] Further, in step 1), when the solvent is water, the solute is any one of polyvinyl alcohol, polyvinylpyrrolidone, hydroxypropyl cellulose.

[0014] Further, the inert gas is any one of nitrogen, argon, and helium.

[0015] In order to achieve another purpose mentioned above, the graphene nanotubes prepared by the method disclosed by the invention are used in the preparation of intelligent switching devices.

[0016] The present invention has the following advantages:

[0017] The present invention has the characteristics of simple preparation process and easy operation, and the prepared graphene nanotubes have excellent field emission effect. Its opening electric field is 0 21V mand its threshold electric field is 0 42VAn, which has great application value in the preparation of intelligent switching devices.

Description with Drawings

[0018] Figure 1 is a scanning electron microscope (SEM) morphology diagram of the graphene nanotubes prepared in Embodiment 1.

Descriptions

[0019] Figure 2 shows the results of X-ray photoelectron spectroscopy (XPS), where the ammonia atmosphere refers to the X-ray photoelectron spectrogram of the graphene nanotubes prepared in Embodiment 1. The argon atmosphere refers to the X-ray photoelectron spectrum of the composite nanofibers prepared without ammonia gas treatment (the other steps are the same as in Example 1). It can be drawn from the figure that the N element of graphene nanotubes prepared by ammonia treatment is significantly higher than that of composite nanofibers prepared without ammonia treatment. This shows that N atoms enter the inside of the graphene structure, and N atoms form a closed tubular structure by linking with carbon atoms at the edges.

[0020] Figure 3 is a graph of the field emission effect performance of graphene nanotubes prepared in Embodiment 1 (relationship between applied electric field and current).

[0021] Figure 4 is a graph showing the emission current of graphene nanotubes prepared in Embodiment 1 with time. It can be seen from the figure that the graphene nanotubes have a stable field emission current at a fixed current.

[0022]Figue 5 is a schematic diagram ofthe graphene nanotube forming process ofthe posent invention. Graphene nanotubes can be obtained by pparing carbon /graphene nanocomposite fibers through electospinning technology, and then undergoing pe-oxidation, carbonization and ammonia activationtmatment In the process oftube formation, the cylindrical structum of carbon nanofibers plays the role of skeleton and confinement During the carbonization process, the ammonia gas introduced will etch the amorphous carbon, and the nitrogen atoms (N) connect the carbon atoms at the edges ofgraphenenanosheets to formgraphene nanotubes.

Detailed Description of the Presently Preferred Embodiments

[0023] The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0024] The preparation method of graphene oxide in the following embodiments is as follows:

[0025]360 mL of concentrated sulfuric acid (H2SO4) and 40 mL of concentrated phosphoric acid (H3PO4) are measured and added to mixed powders containing 3.0 g of microcrystalline graphite and 18 g of potassium permanganate, respectively. The obtained mixed solution is gradually heated to 50°C in a water bath and stirred for 12 hours, then, it is cooled to room temperature and slowly poured into 3mL of 30% hydrogen peroxide (H202). After filtration and centrifugation, the supernatant is removed, the remaining solid material in the lower part is continuously washed with 200 mL of distilled water, 200 mL of hydrochloric acid (30% HCl) and 200 mL of ethanol until it is neutral, and finally dried in a vacuum drying cabinet at 60 0 C. for 48 hours.

[0026] Embodiment 1

[0027] The preparation method of the graphene nanofibers of this embodiment includes the following steps:

[0028] 1) 0.12g of graphene oxide is dissolved in 8gN, N-dimethylformamide, and subjected to ultrasonic

Descriptions

treatment in N- dimethylformamide for 2 hours to obtain the graphene oxide dispersion. 1.08 g of polyacrylonitrile is added to the above graphene oxide dispersion and stirred for 24 hours in a water bath at °C. Where the mass ratio of graphene oxide to polyacrylonitrile is 1/9, and the total mass concentration range of graphene oxide and polyacrylonitrile is 12%;

[0029] 2) In the electrospinning device, the solution prepared in step 1) is used to prepare nanocomposite fiber strands. The conditions for preparing electrospinning are: voltage is 25kv, the distance between the needle and the substrate is 25 cm, and the feed rate of the solution is 1ml/h;

[0030] The nanocomposite fiber raw wire prepared in step 2) is pre-oxidized at a temperature of 220°C for 120 min, then, the temperature is raised to 1000°C under the protection of inert gas, and then, ammonia gas is introduced to react for 40 min. After the reaction is finished, the graphene nanotubes can be prepared by stopping the ammonia gas, introducing the inert gas and cooling with the furnace.

[0031] Embodiment2

[0032] The preparation method of the graphene nanofibers of this embodiment includes the following steps:

[0033] 1) 0.08g of graphene oxide is dissolved in 3.9 g of water and subjected to ultrasonic treatment for 2 hours to obtain a graphene oxide dispersion. 0.4g of polyvinyl alcohol is added to the above graphene oxide dispersion and stirred for 24 hours in a water bath at 65°C, where the mass ratio of graphene oxide to polyvinyl alcohol is 1/5, and the total mass concentration range of graphene oxide and polyvinyl alcohol is 11%;

[0034] 2) In the electrospinning device, the solution prepared in step 1) is used to prepare nanocomposite fiber strands. The conditions for preparing electrospinning are: voltage is 25kv, the distance between the needle and the substrate is 25 cm, and the feed rate of the solution is 1ml/h;

[0035] 3)The nanocomposite fiber raw wire prepared in step 2) is pre-oxidized at a temperature of 240°C for 100 min, then, the temperature is raised to 950°C under the protection of inert gas, and then, ammonia gas is introduced to react for 60 min. After the reaction is finished, the graphene nanotubes can be prepared by stopping the ammonia gas, introducing the inert gas and cooling with the furnace.

[0036] Embodiment 3

[0037] The preparation method of the graphene nanofibers of this example includes the following steps:

Descriptions

[0038] 1) 0 .1Ig of graphene oxide is dissolved in 9gN, N-dimethylformamide, and subjected to ultrasonic treatment in N- dimethylformamide for 2 hours to obtain the graphene oxide dispersion. 0.89 g of polyacrylonitrile is added to the above graphene oxide dispersion and stirred for 24 hours in a water bath at 65°C. Where the mass ratio of graphene oxide to polyacrylonitrile is 1/8, and the total mass concentration range of graphene oxide and polyacrylonitrile is 10%;

[0039] 2) In the electrospinning device, the solution prepared in step 1) is used to prepare nanocomposite fiber strands. The conditions for preparing electrospinning are: voltage is 25kv, the distance between the needle and the substrate is 25 cm, and the feed rate of the solution is 1ml/h;

[0040] 3) The nanocomposite fiber raw wire prepared in step 2) is pre-oxidized at a temperature of 230°C for 110 min, then, the temperature is raised to 1050°C under the protection of inert gas, and then, ammonia gas is introduced to react for 30 min. After the reaction is finished, the graphene nanotubes can be prepared by stopping the ammonia gas, introducing the inert gas and cooling with the furnace.

[0041] Embodiment4

[0042] The preparation method of the graphene nanofibers of this embodiment includes the following steps:

[0043] 1) 0.083g of graphene oxide is dissolved in 5.8g of water and subjected to ultrasonic treatment for 2 hours to obtain a graphene oxide dispersion. 0.917g of polyvinylpyrrolidone is added to the above graphene oxide dispersion and stirred for 24 hours in a water bath at 65°C. Where the mass ratio of graphene oxide to polyacrylonitrile is 1/11, and the total mass concentration range of graphene oxide and polyacrylonitrile is 15%;

[0044] 2) In the electrospinning device, the solution prepared in step 1) is used to prepare nanocomposite fiber strands. The conditions for preparing electrospinning are: voltage is 25kv, the distance between the needle and the substrate is 25 cm, and the feed rate of the solution is 1ml/h;

[0045] 3)The nanocomposite fiber raw wire prepared in step 2) is pre-oxidized at a temperature of 225°C for 120 min, then, the temperature is raised to 1050°C under the protection of inert gas, and then, ammonia gas is introduced to react for 35 min. After the reaction is finished, the graphene nanotubes can be prepared by stopping the ammonia gas, introducing the inert gas and cooling with the furnace.

[0046] Test Example

[0047] This test example is used to illustrate that the graphene nanotubes produced by the present invention have excellent field emission effects.

Descriptions

[0048] The test conditions for the field emission effect are: the graphene nanotubes prepared in Embodiment 1 are placed in a spherical closed space, and the spherical closed container is evacuated until the degree of vacuum is maintained at 10-5 Pa. The positive electrode is a cylindrical iron probe with a diameter of 1mm. The graphene nanotubes are fixed on the copper step as the negative electrode with conductive adhesive, and the distance between the electrodes is mm. The current-voltage (I-V) characteristics for testing are characterized by a customized diode

I-V test system.

[0049] The test results show that: the opening electric field is 0.21V / m (J= 10tA / cm2 ), and the threshold electric field is 0.42V / m (J= OmA / cm2).

[0050] Although the present invention has been described in detail above with a general description and specific embodiments, on the basis of the present invention, some modifications or improvements can be made, which is obvious to the technical personnel in the field. Therefore, these modifications or improvements made on the basis of not deviating from the spirit of the present invention belong to the scope claimed by the present invention.

Claims

1. A method for preparing graphene nanotubes is characterized in that the method includes the following steps:

1) The graphene oxide is placed in a solvent to be ultrasonically dispersed 2~3h to obtain a graphene oxide dispersion liquid, and then a solute is added to the graphene oxide dispersion and stirred in 65°C water bath for 24 hours. Where the mass ratio of graphene oxide to solute is 1/11~ 1/5, and the total mass concentration range of graphene oxide and solute is 10 %~15%;

2) In the electrospinning device, the solution prepared in step 1) is used to prepare nanocomposite fiber strands. The conditions for preparing electrospinning are: voltage is 25kv, the distance between the needle and the substrate is 25 cm, and the feed rate of the solution is 1ml/h;

3) The nanocomposite fiber raw wire prepared in step 2) is pre-oxidized at a temperature of 220~-240°C for 100~-120 min, then, the temperature is raised to 950~-1050°C under the protection of inert gas, and then, ammonia gas is introduced to react for 30~60 min. After the reaction is finished, the graphene nanotubes can be prepared by stopping the ammonia gas, introducing the inert gas and cooling with the furnace.

2. The method for preparing graphene nanotubes according to claim 1 is characterized in that the graphene oxide is prepared from microcrystalline graphite.

3. The method for preparing graphene nanotubes according to claim 1 is characterized in that in step 1), the solute is polyacrylonitrile when the solvent is N,N- dimethylformamide or N ,N- dimethylacetamide or a mixture of the two in any ratio.

4. The method for preparing graphene nanotubes according to claim 1 is characterized in that in step 1), when the solvent is water, the solute is any one of polyvinyl alcohol, polyvinylpyrrolidone,hydroxypropyl cellulose.

5. The method for preparing graphene nanotubes according to claim 1 is characterized in that the inert gas is any one of nitrogen, argon, and helium.

6. According to any one of claims 1 to 5, the graphene nanotubes obtained by the preparation method described in any one of claims are used in the preparation of intelligent switching devices.