阅读说明：本技术 一种低温预处理天然石墨制备石墨烯薄膜的方法 (Method for preparing graphene film by pretreating natural graphite at low temperature ) 是由 张瑞军 刘晓静 于 2020-05-22 设计创作，主要内容包括：本发明涉及石墨烯材料技术领域,提供了一种低温预处理天然石墨制备石墨烯薄膜的方法,本发明首先将天然石墨和浓硫酸混合后进行低温预处理,将所得预处理液和氧化剂混合后进行保温处理,得到膨胀石墨；将膨胀石墨和醇类溶剂混合后进行超声分散,将所得石墨烯溶液抽滤成膜,得到石墨烯薄膜。本发明通过低温预处理使硫酸分子运动至石墨层间边缘,为后续与氧化剂的反应节省了时间、缩短了反应路径长度,且浓硫酸用量较少,能够降低废液排放；本发明提供的方法成本低廉,操作简单,不需要经过高温或在特殊的环境条件下制备,极大的降低了能源消耗,且制备得到的石墨烯层数薄、缺陷少,能够实现大面积石墨烯薄膜的制备。(The invention relates to the technical field of graphene materials, and provides a method for preparing a graphene film by pretreating natural graphite at low temperature, which comprises the steps of firstly, mixing the natural graphite and concentrated sulfuric acid, then carrying out low-temperature pretreatment, mixing the obtained pretreatment solution and an oxidant, and then carrying out heat preservation treatment to obtain expanded graphite; and mixing the expanded graphite and the alcohol solvent, performing ultrasonic dispersion, and performing suction filtration on the obtained graphene solution to form a film, thereby obtaining the graphene film. According to the invention, the sulfuric acid molecules move to the edges between the graphite layers through low-temperature pretreatment, so that the time is saved for the subsequent reaction with the oxidant, the reaction path length is shortened, the consumption of concentrated sulfuric acid is less, and the discharge of waste liquid can be reduced; the method provided by the invention has the advantages of low cost and simple operation, does not need high temperature or preparation under special environmental conditions, greatly reduces the energy consumption, and can realize the preparation of large-area graphene films, and the prepared graphene layers have thin number and few defects.)

1. A method for preparing a graphene film by pretreating natural graphite at low temperature comprises the following steps:

(1) mixing natural graphite and concentrated sulfuric acid for low-temperature pretreatment to obtain pretreatment liquid; the temperature of the low-temperature pretreatment is 0-12 ℃;

(2) mixing the pretreatment solution and an oxidant, and then carrying out heat preservation treatment to obtain expanded graphite;

(3) and mixing the expanded graphite and an alcohol solvent, performing ultrasonic dispersion to obtain a graphene solution, and performing suction filtration on the obtained graphene solution to form a film, thereby obtaining the graphene film.

2. The method according to claim 1, wherein the low-temperature pretreatment time is 30s to 12 h.

3. The method according to claim 1, wherein the natural graphite has a particle size of 16-5000 meshes, and the natural graphite and concentrated sulfuric acid are used in a ratio of 1g to 3-6 m L.

4. The method of claim 1, wherein the oxidizing agent comprises one or more of sodium percarbonate, peroxyacetic acid, and ammonium persulfate.

5. The method according to claim 1 or 4, wherein the pre-treatment solution and the oxidizing agent are used in a ratio of 1m L: 1-2 g.

6. The method according to claim 1, wherein the temperature of the heat-preserving treatment is 30 to 50 ℃ and the time is 1.5 to 2.5 hours.

7. The method of claim 1, wherein the alcoholic solvent comprises one or more of absolute ethanol, isopropanol, and ethylene glycol.

8. The method according to claim 1 or 7, wherein the mass ratio of the expanded graphite to the alcohol solvent is 1:100 to 300.

9. The method according to claim 1, wherein the time for ultrasonic dispersion is 10-60 min.

Technical Field

The invention relates to the technical field of graphene materials, in particular to a method for preparing a graphene film by pretreating natural graphite at low temperature.

Background

Graphene as a stable two-dimensional honeycomb lattice structure material has special electronic arrangement and atomic structure, and plays an irreplaceable role in the aspects of electricity, heat, mechanics, optics and the like. Graphene is a hexagonal honeycomb network material formed by carbon atoms, and is one of the most common two-dimensional materials at present. It has excellent mechanical, thermal and electrical properties: theory of thingsTheoretically, the elastic modulus and the Young modulus can respectively reach 1300GPa and 1100GPa, and the elastic modulus and the Young modulus have the values of 3000-6000 W.m^-1·K^-1The heat conductivity and the electron mobility of the material can reach 200000m²·V^-1·s^-1. Therefore, it is important to maximally maintain the unique structure and characteristic properties of graphene during the preparation process.

In 2004, the two-position physics household mechanical stripping method of Manchester university in England prepares single-layer graphene, which initiates the huge research wave of graphene in nanometer. At present, the common methods for preparing graphene are as follows: mechanical lift-off, SiC epitaxial growth, electrochemical lift-off, chemical vapor deposition, liquid phase lift-off, chemical lift-off. However, in the existing methods for preparing graphene, there are problems of low yield, high energy consumption, environmental pollution, complex method, etc., and it is not easy to obtain large-area graphene thin films, which greatly limits the industrial development of graphene.

Disclosure of Invention

In view of this, the invention provides a method for preparing a graphene film by pretreating natural graphite at a low temperature. The method provided by the invention has the advantages of low energy consumption, simple method, low cost and small environmental pollution, and the prepared graphene film has thin number of layers and few defects, and can realize the preparation of large-area graphene films.

In order to achieve the above object, the present invention provides the following technical solutions:

a method for preparing a graphene film by pretreating natural graphite at low temperature comprises the following steps:

(1) mixing natural graphite and concentrated sulfuric acid for low-temperature pretreatment to obtain pretreatment liquid; the temperature of the low-temperature pretreatment is 0-12 ℃;

(2) mixing the pretreatment solution and an oxidant, and then carrying out heat preservation treatment to obtain expanded graphite;

(3) and mixing the expanded graphite and an alcohol solvent, performing ultrasonic dispersion to obtain a graphene solution, and performing suction filtration on the obtained graphene solution to form a film, thereby obtaining the graphene film.

Preferably, the time of the low-temperature pretreatment is 30 s-12 h.

Preferably, the particle size of the natural graphite is 16-5000 meshes; the mass ratio of the natural graphite to the concentrated sulfuric acid is 1: 3-6.

Preferably, the oxidant comprises one or more of sodium percarbonate, peroxyacetic acid and ammonium persulfate.

Preferably, the dosage ratio of the pretreatment solution to the oxidant is 1m L: 1-2 g.

Preferably, the temperature of the heat preservation treatment is 30-50 ℃, and the time is 1.5-2.5 h.

Preferably, the alcohol solvent comprises one or more of absolute ethyl alcohol, isopropyl alcohol and ethylene glycol.

Preferably, the mass ratio of the expanded graphite to the alcohol solvent is 1: 100-300.

Preferably, the time of ultrasonic dispersion is 10-60 min.

The invention provides a method for preparing a graphene film by pretreating natural graphite at low temperature, which comprises the steps of firstly mixing the natural graphite and concentrated sulfuric acid, then carrying out low-temperature pretreatment, mixing the obtained pretreatment solution and an oxidant, and then carrying out heat preservation treatment to obtain expanded graphite; and mixing the expanded graphite and an alcohol solvent, performing ultrasonic dispersion, and performing suction filtration on the obtained graphene solution to form a film, thereby obtaining the graphene film. At low temperature, the concentrated sulfuric acid molecules move slowly, the sulfuric acid molecules move to the edges between the graphite layers through low-temperature pretreatment, so that the time is saved for subsequent reaction with an oxidant, the reaction path length is shortened, the consumption of the concentrated sulfuric acid is less, the waste liquid discharge can be reduced, and a feasible method is found for green preparation of graphene; the method provided by the invention has low cost, and the high-quality graphene can be prepared by using natural graphite; the method provided by the invention is simple to operate, does not need to be prepared at high temperature or under special environmental conditions, and only needs to pre-soak the natural graphite in a low-temperature environment, so that the energy consumption is greatly reduced. The graphene prepared by the method provided by the invention has the advantages of thin number of layers and few defects, can realize the preparation of a large-area graphene film, and the obtained graphene film has higher conductivity, and the example result shows that the graphene film is 1.4 mu m thickThe conductivity of the graphene film can reach 1.6 × 10⁶S/M。

Drawings

Fig. 1 is a statistical result of the number of layers of graphene obtained in example 6;

FIG. 2 is a scanning electron micrograph of graphene obtained in example 6 at different magnifications;

fig. 3 is a macro-topography of the graphene thin film prepared in example 6.

Detailed Description

The invention provides a method for preparing a graphene film by pretreating natural graphite at low temperature, which comprises the following steps:

(1) mixing natural graphite and concentrated sulfuric acid for low-temperature pretreatment to obtain pretreatment liquid; the temperature of the low-temperature pretreatment is 0-12 ℃;

(2) mixing the pretreatment solution and an oxidant, and then carrying out heat preservation treatment to obtain expanded graphite;

(3) and mixing the expanded graphite and an alcohol solvent, performing ultrasonic dispersion to obtain a graphene solution, and performing suction filtration on the obtained graphene solution to form a film, thereby obtaining the graphene film.

The method comprises the steps of mixing natural graphite and concentrated sulfuric acid, and carrying out low-temperature pretreatment to obtain a pretreatment solution, wherein the particle size of the natural graphite is preferably 16-5000 meshes, more preferably 100-4500 meshes, the natural graphite is preferably natural flake graphite, the using amount ratio of the natural graphite to the concentrated sulfuric acid is preferably 1g: 3-6 m L, more preferably 1g: 4-5 m L, the mass fraction of the concentrated sulfuric acid is preferably 96-98%, the low-temperature pretreatment temperature is 0-12 ℃, preferably 3-10 ℃, more preferably 6 ℃, the low-temperature pretreatment time is preferably 30 s-12 h, more preferably 0.5-10 h, more preferably 1-8 h, and in a specific embodiment of the invention, the mixed solution of the natural graphite and the concentrated sulfuric acid is allowed to stand at a required temperature.

After the pretreatment liquid is obtained, the pretreatment liquid and the oxidant are mixed and then subjected to heat preservation treatment to obtain the expanded graphite. In the invention, the oxidant preferably comprises one or more of sodium percarbonate, peroxyacetic acid and ammonium persulfate, and more preferably ammonium persulfate; in the invention, the ammonium persulfate is a weak oxidant, and the weak oxidation effect of the ammonium persulfate can enable the peeled graphene sheet to have a larger area and a thinner sheet layer.

In the invention, the dosage ratio of the pretreatment solution to the oxidant is preferably 1m L: 1-2 g, and more preferably 1m L: 1.3-1.5 g.

In the invention, the temperature of the heat preservation treatment is preferably 30-50 ℃, more preferably 35-45 ℃, and the time of the heat preservation treatment is preferably 1.5-2.5 h, more preferably 2 h. In the embodiment of the invention, the mixed solution of the pretreatment solution and the oxidant is preferably uniformly coated on the watch glass, then the watch glass is covered with the preservative film, and the watch glass is placed in the incubator for heat preservation treatment.

After the heat preservation treatment is finished, the expanded graphite can be obtained, the expanded graphite is preferably washed to be neutral, and then the subsequent preparation of the graphene film is carried out. The washing method of the present invention is not particularly limited, and a washing method known to those skilled in the art may be used.

After the expanded graphite is obtained, the expanded graphite and an alcohol solvent are mixed and subjected to ultrasonic dispersion to obtain a graphene solution, and the graphene solution is subjected to suction filtration to form a film, so that the graphene film is obtained. In the invention, the alcohol solvent preferably comprises one or more of absolute ethyl alcohol, isopropyl alcohol and ethylene glycol, and more preferably absolute ethyl alcohol; the mass ratio of the expanded graphite to the alcohol solvent is preferably 1: 100-300, and more preferably 1: 150-250; the time for ultrasonic dispersion is preferably 10-60 min, and more preferably 20-50 min.

The method has no special requirements on the specific operation method of the suction filtration film formation, and the graphene film can be prepared by using a vacuum filtration method well known by the technical personnel in the field. The graphene film is obtained by using a suction filtration method, is rapid, efficient, simple, convenient and safe, and can realize mass production.

The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention.