WO2019095602A1

WO2019095602A1 - Method for preparing three-dimensional graphene fiber by means of thermal chemical vapor deposition, and use thereof

Info

Publication number: WO2019095602A1
Application number: PCT/CN2018/080267
Authority: WO
Inventors: 于杰; 曾杰
Original assignee: 哈尔滨工业大学深圳研究生院
Priority date: 2017-11-14
Filing date: 2018-03-23
Publication date: 2019-05-23
Also published as: CN107988660A; CN107988660B

Abstract

Provided are a method for preparing a three-dimensional graphene fiber by means of thermal chemical vapor deposition, and the use thereof. In this fiber, a graphene sheet is fixed on the fiber, and the thickness, density and growth rate of the sheet can be regulated and controlled by changing the growth atmosphere and temperature, so that the problem of graphene agglomeration is solved. Edge layers of the graphene sheet may be a monolayer, the sheets are in contact with each other to form a good three-dimensional conductive network, and the conductivity reaches up to 1.2×105S/m-1. The three-dimensional graphene fiber material has a super-hydrophobic function, and the contact angle reaches 165°; and at the same time, same has a good adsorbing function with regard to an organic matter, and the contact angle is close to 0°. Moreover, the three-dimensional graphene fiber has an excellent electromagnetic shielding function, and the specific electromagnetic shielding efficiency of a self-supporting three-dimensional graphene fiber material with thickness of 3 μm can be up to 60932 dB/cm2/g. The three-dimensional graphene fiber material, due to the unique structure and property, has application potential in many aspects in the fields of functional composite materials, water treatment, electromagnetic shielding, sensors and energy sources.

Description

Method for preparing three-dimensional graphene fiber by thermal chemical vapor deposition and application thereof

Technical field

The invention belongs to the technical field of new materials and relates to a method for preparing three-dimensional graphene fibers by thermal chemical vapor deposition and an application thereof.

Background technique

Graphene has the advantages of large specific surface area, many active edges, high thermal conductivity, high carrier mobility, optical transparency, high strength, flexibility, high chemical stability, etc., in lithium ion batteries, supercapacitors, fuel cell catalysts, and thermal conductivity. / Conductive / high-strength composite materials, adsorption purification, electromagnetic shielding, electronic devices and many other fields have great application prospects (Nanoscale 2014, 6, 1922-1945; National Science Review 2015, 2, 40-53; Materials Today 2016, 19, 428-436), is expected to lead to technological breakthroughs in multiple fields. In addition to electronic device applications, graphene needs to maintain high dispersion of monomers in most applications. Due to the monoatomic lamellar structure of graphene and the inter-layer van der Waals force and π-π interaction, the graphene in powder form is easily agglomerated during use, and even a thick graphite sheet is re-formed, thereby losing graphene. Structural characteristics and superior properties. Therefore, solving the problem of agglomeration of graphene is a fundamental problem in the art. So far, people have done a lot of work in this direction, and developed a variety of methods to prevent graphene agglomeration, the mainstream method is to prepare three-dimensional graphene (Nanoscale 2014, 6, 1922-1945; National Science Review 2015, 2, 40-53; Materials Today 2016, 19, 428-436).

Three-dimensional graphene is to make graphene arranged in three dimensions in space, and the gap between the sheets and the sheets is maintained, supported by each other, and interconnected to form a three-dimensional porous network structure. At present, the methods for preparing three-dimensional graphene can be divided into three categories, namely liquid phase self-assembly, chemical vapor deposition (CVD) and solid phase reaction blowing. Liquid phase self-assembly can be divided into non-template self-assembly and template self-assembly. Non-template self-assembly uses graphene oxide as precursor, dissolves in appropriate solvent (mainly water) to form colloidal suspension, and then uses water heat. Or chemical reduction, self-assembly to form a hydrogel or organogel during the reduction process, and finally obtain a three-dimensional graphene structure by freeze drying or CO ₂ supercritical drying (ACS Nano 2010, 4, 4324–4330; Advanced Functional Materials 2012, 22, 4421-4425). Self-assembly of liquid template can realize three-dimensional assembly of graphene oxide by the action of template, such as PS (ACS Nano 2012, 6, 4020-4028) and SiO2 (Advanced Materials 2013, 242, 4419-4423) microspheres can be used as templates. Honeycomb porous structure, layered porous structure can be obtained by directional freezing (ice template) (Nature Communications 2012, 3, 1241), the template is removed and freeze-dried to obtain a three-dimensional graphene structure. The CVD method is also divided into a template method and a non-template method. The template method mainly uses foamed nickel as a template to grow a layer of graphene on the nickel foam by dissolution/precipitation, and removes the template by acid etching to obtain three-dimensional graphene (Nature Materials 2011, 10,424-428), other templates include nanoporous nickel prepared by de-alloying (Angewandte Chemie International Edition 2014, 53, 4822-4826) and porous alumina (Advanced Functional Materials 2013, 23, 2263-2269), etc. A smaller pore structure is obtained. Non-template CVD can directly grow vertically oriented graphene sheets on a flat substrate (Scientific Reports 2013, 3, 1696), but currently only in plasma, the growth mechanism is derived from ion bombardment and plasma sheath The induction of an electric field. The solid phase reaction gas blowing method is mainly formed by mixing a suitable carbon source with a substance capable of generating a volatile product, and forming a three-dimensional sheet structure under the action of a gas during carbonization (Nature Communications 2013, 4, 2905; Advanced Materals 2013, 5,2474-2480).

Although the preparation technology of three-dimensional graphene materials has made great progress, its structure and performance control are not ideal, and the preparation process is complicated, and there are still some problems to be solved urgently. These problems can be summarized as follows: 1) The pores between the graphene sheets are too large, resulting in a decrease in space utilization efficiency. The liquid crystal self-assembly method and solid phase reaction gas blowing method have a graphene pore size of 0.7 μm to several hundred micrometers (ACS Nano 2010, 4, 4324–4330; Advanced Functional Materials 2012, 22, 4421-4425; ACS Nano 2012 , 6, 4020-4028; Nature Communications 2012, 3, 1241; Nature Communications 2013, 4, 2905; Advanced Materals 2013, 5, 2474-2480), three-dimensional graphene prepared by foam nickel template CVD method due to the inherited commercial foam nickel The pore structure has a pore size of about 400 μm (Nature Materials 2011, 10, 424-428). Smaller pore structures can be obtained by using other special templates, such as three-dimensional graphene pores obtained by liquid phase self-assembly using SiO ₂ microsphere templates up to 30-120 nm (Advanced Materials 2013, 242, 4419-4423), Alloyed nanoporous nickel template CVD grown 3D graphene pores up to 0.1-2.0 μm (Angewandte Chemie International Edition 2014, 53, 4822-4826), 3D graphene pores grown by porous alumina template CVD 80-120 nm (Advanced Functional Materials 2013, 23, 2263-2269). However, the preparation process of these template methods is complicated, the template cost is high, acid etching is required to remove the template, the process generates defects and residual impurities, and industrial application is difficult. 2) Graphene has many defects, many impurities, and poor conductivity. This is determined by the characteristics of the existing preparation methods. The precursor used in liquid phase assembly for preparing three-dimensional graphene is graphene oxide. The redox and repeated solution treatments lead to high defects and impurities, so that the overall properties of the material are conductive. Sex decreases, the current conductivity is only 0.25-100 S/m (Nanoscale 2014, 6, 1922-1945; National Science Review 2015, 2, 40-53; Journal of the American Chemical Society 2010, 132, 14067–14069) . The three-dimensional graphene prepared by the template CVD method has a greatly reduced defect and impurity content, and the conductivity is greatly improved up to 1000 S/m (Nature Materials 2011, 10, 424-428). However, the conductivity of the three-dimensional graphene prepared by the liquid phase method or the CVD method is much lower than that of the graphene and the conductivity of the common metal material, and the space for improvement is large. Although the quality of the three-dimensional graphene prepared by the CVD method is greatly improved, the use of the template and the removal process thereof still cause impurities and structural damage, resulting in unsatisfactory performance. 3) The graphene active edge is not exposed sufficiently, which is not conducive to the improvement of performance. The three-dimensional graphene prepared by the liquid phase method or the template CVD method forms a three-dimensional structure by overlapping the graphene sheets, and the graphene edges thereof are masked and lose their functions. Although plasma CVD can achieve vertical growth of graphene sheets on a substrate, plasma CVD has a small growth area and is not suitable for preparing powders and bulk materials, and thus has limited application potential. The thermal CVD method has a great difficulty in vertically orienting graphene. Therefore, it is of great significance to prepare a new structure of three-dimensional graphene materials through structural innovation and process innovation, so as to achieve higher structural control and performance improvement.

The invention is based on the problems in the application of graphene, and a three-dimensional graphene fiber material is prepared by thermal chemical vapor deposition. In the three-dimensional graphene fiber, the graphene sheet grows vertically on the surface of the fiber, and the sheet is closely connected with the sheet. A three-dimensional graphene network structure is formed, and a pore size formed between the sheet and the sheet is below 100 nm, and the edge of the graphene is exposed to the surface. Since the graphene sheet is fixed on the surface of the fiber, the problem of agglomeration is solved. Compared with the existing three-dimensional graphene material, the gap between the sheet and the sheet is greatly reduced, and the bareness of the edge of the graphene sheet is greatly improved, and the crystal is crystallized due to high temperature growth. The degree is greatly improved. This excellent structure results in a three-dimensional graphene fiber with outstanding properties, and the electrical conductivity reaches 1.2 × 10 ⁵ S / m, which is much higher than the existing three-dimensional graphene material. At the same time, the performance in electromagnetic shielding and superhydrophobic oleophilic is also much better than the existing three-dimensional graphene materials. What is important is that the present invention utilizes thermal chemical vapor deposition to achieve vertical growth of graphene on the surface of the fiber, breaking through the limitations of the prior art that can only vertically grow graphene by plasma chemical vapor deposition, which can be reduced in scale due to thermal chemical vapor deposition. Production, thus the invention has great application value

technical problem

Type the technical problem description paragraph here.

Technical solution

It is an object of the present invention to prepare a three-dimensional graphene material for the problems in current graphene applications, to provide a method for its preparation, and to demonstrate its properties. The prepared three-dimensional graphene fiber material combines the advantages of nano carbon fiber and graphene, and is greatly improved in structure and performance than existing materials. The preparation method adopted by the invention has the advantages of simple and easy process, low cost of raw materials and equipment used, and large-scale production.

The invention provides a method for preparing three-dimensional graphene fibers by thermal chemical vapor deposition, comprising the following steps:

(1) preparing a precursor fiber of a three-dimensional graphene fiber material: obtained by treating a carbon-containing polymer by a spinning method;

(2) Stabilization treatment of the precursor fiber of the three-dimensional graphene fiber material: the precursor fiber obtained in the step (1) is stabilized at an appropriate temperature and atmosphere;

(3) carbonization heat treatment of the stabilized precursor fiber: the stabilized precursor fiber obtained in the step (2) is subjected to carbonization heat treatment in a suitable reaction atmosphere and temperature to obtain a nano carbon fiber;

(4) Growth of graphene on the surface of the carbon nanofiber: The surface of the nanocarbon fiber obtained in the step (3) is vertically grown by using thermal chemical vapor deposition at a suitable reaction atmosphere and temperature to obtain a three-dimensional graphene fiber material.

The specific preparation method is as follows:

The preparation of the precursor fiber of the three-dimensional graphene fiber material in the step (1) means: dissolving the carbon-containing polymer in a suitable solvent to prepare a spinning solution of a suitable concentration, and then spinning to obtain a three-dimensional graphene fiber material. Fore body fiber. The carbon-containing polymer in the step (1) is one or more of polyacrylonitrile (PAN), polyvinylpyrrolidone (PVP), polybenzimidazole (PBI), and has carbonization characteristics. The solvent is one or more of dimethylformamide (DMF), ethanol, dimethylacetamide (DMAC), and water. The polyacrylonitrile (PAN) has a molecular weight ranging from 20,000 to 200,000, and the spinning solution has a concentration ranging from 3 to 20 (wt/v)%; the polyvinylpyrrolidone (PVP) has a molecular weight ranging from 50,000 to 2,000,000, and the spinning solution concentration range is For 6-20 Wt%; polybenzimidazole (PBI) molecular weight range is 20000-40000, spinning solution concentration range 5-20 Wt%.

The electrospinning process parameters are set according to the conventional requirements, and the uniform and stable fibers are prevailed. If the solution concentration is too high, the viscosity will be too high, which will make the solution ejecting difficult. When the concentration is too low, the viscosity will be too low, resulting in the fiber not forming. Only particles of polymer or fibers of non-uniform diameter are ejected.

The equipment used in this step is a conventional electrospinning equipment, and the process has no special requirements. The process parameters of the spinning process are set according to conventional requirements, and the uniform and stable fibers are taken as the standard.

The stabilizing treatment of the precursor fiber of the three-dimensional graphene fiber material in the step (2) means that the precursor fiber obtained in the step (1) is heated to a proper temperature for a suitable time, and then naturally cooled to room temperature to obtain stability. Precursor fiber. The stabilization temperature is selected to be 200-300 °C, and the holding time is generally 0.5-3. h.

The purpose of the stabilization treatment is to crosslink the polymer molecular chains in the fiber. In the process, some non-carbon elements such as H and N will be detached due to the breaking of the chemical bonds, and at the same time, the polymer molecular chains will occur between each other. Bonding produces a stable structure to avoid decomposition or melt blocking of the polymer in subsequent high temperature carbonization processes. When the stabilization temperature is too low, the crosslinking between the molecular chains is incomplete, and in the subsequent high-temperature carbonization process, melting or decomposition may still occur to obtain carbon fibers, and if the stabilization temperature is too high, the polymer will be decomposed or melted. If the stabilization time is too short, the stabilization is insufficient, and there is still a problem of decomposition or melting in the subsequent treatment. If the stabilization time is too long, no further improvement effect is produced, and it is not necessary.

The carbonization heat treatment of the precursor fiber in the step (3) means that the stabilized precursor fiber obtained in the step (2) is subjected to a carbonization heat treatment in an appropriate reaction atmosphere and temperature to obtain a carbon fiber. The reaction atmosphere is one of NH ₃ , Ar, N ₂ , H ₂ or a mixed atmosphere thereof, the carbonization temperature is 500-3000 ° C, and the carbonization temperature is maintained for 0.5-6 h.

If the carbonization temperature is too low, the fiber purity and strength are low, and if the carbonization temperature is too high, the cost is high, but the purity and strength of the fiber are improved, and different carbonization temperatures are selected according to the application requirements of the material.

The step (4) growth of graphene on the surface of the carbon fiber: heat-treating the carbon fiber obtained in the step (3) under a suitable reaction atmosphere and temperature to obtain a three-dimensional graphene fiber material.

This step is the core of the present invention, and the graphene sheets on the surface of the carbon fibers are formed at this step. The specific process is that the carbon fiber obtained in the step (3) is treated at a temperature of 500 to 3000 ° C for a period of time in a mixed atmosphere of H ₂ and hydrocarbon or NH ₃ and a hydrocarbon or a mixture thereof, and then naturally cooled to obtain a three-dimensional graphene fiber. material. Hydrocarbon refers to hydrocarbons including methane, ethylene, acetylene, pentane, acetonitrile, pyrimidine, pyridine, benzene, toluene, methanol, ethanol, propanol, polystyrene, polymethyl methacrylate and the like. One or more of the mixed gases may also be passed through other gases, including water vapor, argon, nitrogen, etc., to achieve structural and performance adjustments.

The key structure of the graphene sheet is to control the balance between the etching rate of carbon and the rate of decomposition of hydrocarbons by hydrogen or ammonia gas. Therefore, the volume ratio of the mixed atmosphere should be based on hydrogen or ammonia and hydrocarbons. The reactivity is determined.

Another object of the present invention is to provide a three-dimensional graphene fiber material which is prepared by the aforementioned method. The graphene sheets of the material are vertically grown on the surface of the fibers and have excellent electrical conductivity. The material has superhydrophobic, super oil absorption properties. The material has excellent electromagnetic shielding properties.

Beneficial effect

The beneficial effects of the present invention over the prior art are:

(1) In this fiber, the graphene sheet is fixed on the fiber, which solves the problem of graphene agglomeration. The number of edge layers of the graphene sheet can reach a single layer, and the sheet and the sheet contact each other to form a good three-dimensional conductive network, conductance. The rate is as high as 1.2 × 10 ⁵ S m ^-1 .

(2) The three-dimensional graphene fiber material has a superhydrophobic function, the contact angle reaches 165 ^o , and the organic matter is well adsorbed, and the contact angle is close to 0 ^o .

(3) Three-dimensional graphene fiber has excellent electromagnetic shielding function, and the electromagnetic shielding effectiveness of self-supporting three-dimensional graphene fiber material of 3 μm thickness is up to 60932 dB cm ² /g.

Due to the unique structure and properties of three-dimensional graphene fiber materials, it has many potential applications in functional composites, water treatment, electromagnetic shielding, sensors and energy.

DRAWINGS

[Correct according to Rule 91 28.05.2018]
1 is a SEM and TEM photograph of a three-dimensional graphite thin fiber material prepared in Example 1 of the present invention, wherein FIG. 1a is a SEM photograph of a three-dimensional graphene fiber, and FIG. 1 b is a low-power TEM photograph of a graphene sheet; FIG. c is a high power TEM photograph of graphene sheets.

2 is a SEM photograph and a Raman spectrum of a three-dimensional graphite thin fiber material prepared in Example 2 of the present invention;

3 is a SEM photograph and a Raman spectrum of a three-dimensional graphite thin fiber material prepared in Example 3 of the present invention;

4 is a SEM photograph and a Raman spectrum of a three-dimensional graphite thin fiber material prepared in Example 4 of the present invention;

5 is a TEM photograph of a three-dimensional graphite thin fiber material prepared in Example 5 of the present invention;

6 is a SEM photograph and a Raman spectrum of a three-dimensional graphite thin fiber material prepared in Example 6 of the present invention;

7 is a SEM photograph and a Raman spectrum of a three-dimensional graphite thin fiber material prepared in Example 7 of the present invention;

8 is a SEM photograph and a Raman spectrum of a three-dimensional graphite thin fiber material prepared in Example 8 of the present invention;

9 is a SEM photograph and a Raman spectrum of a three-dimensional graphite thin fiber material prepared in Example 9 of the present invention;

10 is a SEM photograph and a Raman spectrum of a three-dimensional graphite thin fiber material prepared in Example 10 of the present invention;

Figure 11 is an optical photograph of the surface of water prepared in Example 10 of the present invention;

Figure 12 is an optical photographic view of the surface of the material prepared in Example 10 of the present invention using alcohol and vegetable oil;

Figure 13 is an electromagnetic shielding performance of materials of different thicknesses prepared in Example 10 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The description of the preferred embodiment of the invention is entered here.

Embodiments of the invention

The implementation of the present invention will be described below by way of specific examples and the accompanying drawings, but the present invention is not limited thereto.

In the preferred embodiment described below, the core invention is the thermal chemical vapor phase growth of vertically oriented graphene sheets on a carbon fiber surface. The main process parameters are the ratio of hydrogen or ammonia to hydrocarbon in the atmosphere, growth time, and temperature. The implementation examples include two parts, and Examples 1-10 are preparation processes of three-dimensional graphene fiber materials, and Examples 11-13 are applications of the three-dimensional graphene fibers prepared in Example 10 in water treatment and electromagnetic shielding.

Example 1: Preparation of three-dimensional graphene fiber material

PAN was dissolved in dimethylformamide (DMF) solvent to prepare an electrospinning solution having a mass concentration (wt/v) of 10%, and electrospinning was carried out by a conventional electrospinning apparatus to prepare a precursor fiber. The molecular weight of the PAN used was M _w = 150,000. In the electrospinning, graphite paper was used as the collection substrate, and the spinneret was 15 cm away from the collecting substrate, and the voltage was set to 20 kV.

The PAN fiber prepared by the above electrospinning is then placed in a conventional tube furnace and stabilized in an air environment. It was heated to 250 ° C at a heating rate of 5 ° C / min, kept for 2 h, and then naturally cooled to room temperature to obtain a stabilized fiber.

Finally, the carbonization heat treatment of the precursor fiber is performed, and the stabilized precursor fiber is placed in a conventional tube furnace, and NH ₃ gas is introduced at a flow rate of 80 mL/min, and the pressure in the tube is maintained at 1 atm; The heating rate of °C/min is heated to 1100 °C, kept for 2h, then the ammonia gas is turned off, 40 mL/min CH ₄ and 80 mL/min H _{2 are introduced} , the temperature is kept for 4 hours, and finally CH ₄ and H _{2 are} closed, and 300 mL is introduced. /min Ar, three-dimensional graphene fiber material obtained by furnace cooling.

Figure 1 a) and Figure 1 b) are scanning electron microscopy (SEM) and transmission electron microscopy (TEM) photographs of the prepared three-dimensional graphene fibers, respectively. It can be seen that the vertical fibers of the graphene sheets on the surface of the carbon fibers are axially grown, and the sheets and the sheets are in contact with each other to form a porous network structure. It can be seen from Fig. 1 c) that the edge of the graphene sheet is a single atomic layer thickness.

Example 2: Preparation of three-dimensional graphene fiber material

In the present embodiment, Ar was introduced in the carbonization stage, and the flow rate of Ar was 200 mL/min, and other conditions were the same as in Example 1.

Fig. 2 a) SEM photograph of the prepared fiber, the fiber morphology is similar to that of the case 1, except that the diameter of the graphene fiber becomes large, which is because the NH ₃ in the first embodiment can significantly etch the carbon at a high temperature. And Ar has no etching effect on the fiber. Figure 2 b) is its Raman spectrum. The intensity ratio of the G peak to the 2D peak is 0.97. Since the original carbon fiber and the graphene sheet near the fiber layer contribute to the G peak, the G peak and the 2D peak are The intensity ratio is increased, so it is known from the Raman spectrum that the edge thickness of the graphene sheet is 1-2 layers of graphene.

Example 3: Preparation of three-dimensional graphene fiber material

In the present embodiment example the carbonization stage into N _2, N ₂ flow rate is 200mL / min, other conditions were the same as in Example 1.

Figure 3 a) is a SEM photograph of the prepared material, and the fiber morphology is similar to that of Example 2. Fig. 3 b) is a Raman diagram of the prepared fiber, and the intensity ratio of the G peak to the 2D peak is 0.89, indicating that the edge thickness of the graphene sheet is 1-2 atomic layers.

Example 4: Preparation of three-dimensional graphene fiber material

In the present embodiment, the carbonization stage was introduced with H ₂ , and the flow rate of H ₂ was 200 mL/min, and other conditions were the same as in Example 1.

Figure 4 a) is a SEM photograph of the prepared material, and the fiber morphology is similar to that of Example 2. Figure 4 b) is a Raman diagram of the prepared fiber. The intensity ratio of the G peak to the 2D peak is 0.86, indicating that the edge thickness of the graphene sheet is 1-2 atomic layers.

Example 5: Preparation of three-dimensional graphene fiber material

In the present embodiment example the carbonization stage into a mixed gas of NH ₃ and Ar, and Ar and the flow rate of NH ₃ were 80 mL / min and 200 mL / min, other conditions were the same as in Example 1.

Figure 5 is a TEM photograph of the prepared material, and the fiber morphology is similar to that of Embodiment 1. It can be seen from Fig. 5 b) that the edge thickness of the graphene sheet is 1-2 atomic layers.

Example 6: Preparation of three-dimensional graphene fiber material

In the present embodiment, in the graphene sheet growth stage, a mixed gas of Ar and H ₂ was used as a carrier gas to pass alcohol, and both Ar and H ₂ flow rates were 100 mL/min, and other conditions were the same as in the first embodiment.

Figure 6 a) is a SEM photograph of the prepared material, and the fiber morphology is similar to that of Example 1. Fig. 6 b) is a Raman diagram of the prepared fiber, and the intensity ratio of the G peak to the 2D peak is 0.98, indicating that the edge thickness of the graphene sheet is 1-2 atomic layers.

Example 7: Preparation of three-dimensional graphene fiber material

In the growth stage of the present embodiment, a mixed gas of C ₂ H ₂ , H ₂ and Ar was introduced at a flow rate of 10 mL/min, 60 mL/min, and 300 mL/min, respectively, and other conditions were the same as in the first embodiment.

Figure 7 a) is a SEM photograph of the prepared material, and the fiber morphology is similar to that of Example 1. Fig. 7 b) is a Raman diagram of the prepared fiber, and the intensity ratio of the G peak to the 2D peak is 1.02, indicating that the edge thickness of the graphene sheet is 1-2 atomic layers.

Example 8: Preparation of three-dimensional graphene fiber material

In the present embodiment, a mixed gas of CH ₄ , NH ₃ and Ar was introduced into the growth stage at flow rates of 10 mL/min, 60 mL/min, and 300 mL/min, respectively, and other conditions were the same as in the first embodiment.

Figure 8 a) is a SEM photograph of the prepared material, and the fiber morphology is similar to that of Embodiment 1. Fig. 8 b) is a Raman diagram of the prepared fiber, and the intensity ratio of the G peak to the 2D peak is 1.06, indicating that the edge thickness of the graphene sheet is 1-2 atomic layers.

Example 9: Preparation of three-dimensional graphene fiber material

In the present embodiment, the growth stages were passed through CH ₄ , H ₂ and Ar at flow rates of 10 mL/min, 100 mL/min, 300 mL/min, growth time of 1 h, growth temperature of 1300 ^o C, and other conditions. Both are the same as in the first embodiment.

Figure 9 a) is a SEM photograph of the prepared material, and the fiber morphology is similar to that of Embodiment 1. Although the 1300 ^o C was only grown for 1 h, the fiber diameter was similar to that obtained by growing at 1100 ^o C for 4 h. This is because the higher the temperature, the greater the methane activity and the faster the growth rate of the sheet at high temperatures. Fig. 9 b) is a Raman diagram of the prepared fiber, and the intensity ratio of the G peak to the 2D peak is 1.08, indicating that the edge thickness of the graphene sheet is 1-2 atomic layers.

Example 10: Preparation of three-dimensional graphene fiber material

In the present example, the growth time was 10 h, and other conditions were the same as in Example 1.

Fig. 10 a) is a SEM photograph of the prepared material. It is known from the SEM photograph that the structure of the original fiber disappears, and a continuous, uniform porous structure composed of graphene sheets is formed on the surface of the material. As the growth time increases, the graphene nanosheets gradually grow up, and the graphene sheets between different fibers are in contact with each other to form the unique porous material. The conductivity of the graphene fiber material is as high as 1.2×10 ⁵ S m ^{- 1} . . Fig. 10 b) is a Raman diagram of the prepared fiber, and the intensity ratio of the G peak to the 2D peak is 1.01, indicating that the edge thickness of the graphene sheet is 1-2 atomic layers.

Example 11: Superhydrophobic application of three-dimensional graphene fiber materials

Taking the three-dimensional graphene fiber material prepared in the case 10 as an example, water droplets are applied to the surface of the material, and FIG. 11 is an optical photograph of water on the surface thereof, and water droplets are formed, and the contact angle is 165°, indicating that the three-dimensional graphite The olefinic fiber material has outstanding superhydrophobic properties.

Example 12: Adsorption properties of three-dimensional graphene fiber materials for organic matter

Taking the three-dimensional graphene fiber material prepared in the case 10 as an example, alcohol and vegetable oil were respectively dropped onto the surface of the material. Fig. 12 a) and b) are optical photographs of the surface of alcohol and vegetable oil, respectively, and the contact angle was 0°. It shows that the three-dimensional graphene fiber material has good adsorption properties for organic matter.

Example 13: Electromagnetic shielding application of three-dimensional graphene fiber materials

Electromagnetic shielding application of the three-dimensional graphene fiber material prepared in the case 10, Fig. 13 a) Electromagnetic shielding effectiveness diagram of the three-dimensional graphene material of different thickness in the X-band, thickness of 3, 6.4, 12.7, 26.3 μm three-dimensional graphite The average electromagnetic shielding effectiveness of the olefinic materials is 17, 26, 37, 56 dB, respectively, and the electromagnetic shielding effectiveness is 60932, 43683, 31327 and 22895 dB.cm2 g-1, respectively. Fig. 13 b) is the electromagnetic shielding mechanism diagram of the three-dimensional graphene fiber material of different thickness in the X-band. From this figure, it can be seen that the shielding of the X-band electromagnetic wave of different thickness materials has been mainly absorbed.

The above is a further detailed description of the present invention in connection with the specific preferred embodiments, and the specific embodiments of the present invention are not limited to the description. It will be apparent to those skilled in the art that the present invention may be made without departing from the spirit and scope of the invention.

Industrial applicability

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Sequence table free content

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Claims

A method for preparing three-dimensional graphene fibers by thermal chemical vapor deposition, comprising the steps of:

(1) preparing a precursor fiber of a three-dimensional graphene fiber material: obtained by treating a carbon-containing polymer by a spinning method;

(2) Stabilization treatment of the precursor fibers of the three-dimensional graphene fiber material: the precursor fibers obtained in the step (1) are stabilized at an appropriate temperature and atmosphere;

(3) carbonization heat treatment of the stabilized precursor fiber: the stabilized precursor fiber obtained in the step (2) is subjected to carbonization heat treatment at a suitable atmosphere and temperature to obtain a carbon fiber;

(4) Growth of three-dimensional graphene on the surface of carbon fiber: The carbon fiber obtained in the step (3) is grown by using a thermochemical vapor deposition of a vertically oriented graphene sheet at a suitable reaction atmosphere and temperature to obtain a three-dimensional graphene fiber.
The method according to claim 1, wherein the spinning method in the step (1) is one of an electrospinning, a wet method, a dry method, and a melting method.
The method according to claim 1, wherein the carbon-containing polymer in the step (1) is one or more of polyacrylonitrile, polyvinylpyrrolidone and polybenzimidazole, wherein the poly The molecular weight of acrylonitrile ranges from 20,000 to 200,000, the molecular weight of polyvinylpyrrolidone ranges from 50,000 to 2,000,000, and the molecular weight of polybenzimidazole ranges from 20,000 to 40,000.
The method according to claim 1, characterized in that the stabilizing treatment in the step (2) is carried out in an air or an oxygen-containing atmosphere, the stabilization treatment temperature is 200-300 ° C, and the stabilization time is 0.5-3 h.
The method according to claim 1, wherein the atmosphere in the step (3) is one of NH 3 , Ar, N 2 , H 2 or a mixed atmosphere thereof, and the carbonization temperature is 500-3000 ° C. The time is 0.5-6 h.
The method according to claim 1, wherein the reaction atmosphere in the step (4) is H 2 and a hydrocarbon or NH 3 and a hydrocarbon or a mixed atmosphere thereof, wherein the hydrocarbon is methane, One or more of hydrocarbons such as ethylene, acetylene, pentane, acetonitrile, pyrimidine, pyridine, benzene, toluene, methanol, ethanol, propanol, polystyrene, polymethyl methacrylate, etc. At a temperature of 500-3000 ° C, other gases, including water vapor, argon, nitrogen, etc., may also be introduced into the mixed gas.
A three-dimensional graphene fiber material, which is obtained by the method according to any one of claims 1 to 6, wherein the graphene sheet is vertically grown on the surface of the fiber and has excellent electrical conductivity.
The three-dimensional graphene fiber material according to claim 7, wherein the material has superhydrophobic and super oil absorbing properties.
The three-dimensional graphene fiber material according to claim 7, wherein the material has excellent electromagnetic shielding properties.