CN102600775B - SiC-graphene nanocomposite material and preparation method thereof - Google Patents

Abstract

The invention discloses a SiC-graphene nanocomposite material and a preparation method thereof. The SiC-graphene nanocomposite material is a core-shell structure in which an outer shell covers a core, the inner core is SiC nanoparticles, and the outer shell is nano-graphite composed of graphene. . The preparation method includes steps: (1) Precursor cracking: heating and cracking polymer precursors in a chemical vapor deposition furnace under an inert gas atmosphere to form SiC nanoparticles; (2) Chemical vapor deposition: continuing to heat to make SiC nanoparticles The silicon atoms on the surface sublimate and escape, and the remaining carbon atoms reorganize to form graphene fragments, and the graphene fragments grow through deposition to obtain SiC-graphene nanocomposites. The SiC-graphene nanocomposite material of the invention has excellent physical, chemical and mechanical properties, simple preparation process, low cost and wide application range.

Description

SiC-graphene nanocomposite material and preparation method thereof

technical field

The invention relates to the field of nanocomposite materials, in particular to a SiC-graphene nanocomposite material and a preparation method thereof.

Background technique

Graphene is a revolutionary new carbon material formed by densely stacking a single layer of carbon atoms. Its thickness is only 0.335 nanometers. It is currently the thinnest two-dimensional material in the world. Structural units. Graphene has a lattice structure arranged in a two-dimensional honeycomb form. The basic structural unit is a stable carbon six-membered ring. The atoms are combined with strong carbon-carbon bonds, so the graphene structure is very stable. The stable lattice structure of graphene makes it have excellent electrical conductivity. Electrons in graphene move through their orbits without being scattered by lattice defects or the introduction of foreign atoms. Due to the very strong interatomic force, at room temperature, even if the surrounding carbon atoms are squeezed, the electrons in graphene are disturbed very little. Another characteristic of graphene is that the movement speed of electrons reaches 1/300 of the speed of light, far exceeding the movement speed of electrons in general conductors. On the other hand, graphene is a semiconductor with zero energy gap, and its carriers exhibit a linear dispersion relationship near the Fermi level. Due to these excellent electrical properties, graphene is considered as an ideal semiconductor material for next-generation integrated circuits. At the same time, graphene also has good mechanical, optical and thermal properties, with outstanding thermal conductivity (3000W/(mK)) and mechanical properties (1060GPa) and high-speed electron mobility at room temperature (15000cm ² /(V·S) ). Graphene is a real surface solid. The ideal single-layer graphene has a super large specific surface area. Its theoretical specific surface area is as high as 2066m ² /g, which greatly exceeds the specific surface area of activated carbon currently used in electrochemical double layer capacitors. Graphene and graphene-based nanocomposites are expected to be used in many fields due to the above-mentioned excellent electrical, optical, thermal and mechanical properties, such as integrated circuits, micro-electromechanical systems, electrochemical catalysts, supercapacitors, field emission materials, etc.

At present, graphene preparation methods mainly include mechanical exfoliation, crystal epitaxy, and chemical vapor deposition. These preparation methods generally prepare single-layer or multi-layer graphene on the surface of a semiconductor substrate such as SiC single crystal bulk to study its electrical properties. Development of semiconductor materials for next-generation integrated circuits. The recently developed graphene oxide reduction method to prepare graphene can prepare a variety of graphene-based composite materials for applications in the fields of electrochemical catalysts, supercapacitors and field emission materials, but this method includes pre-preparing graphene oxide and subsequent graphite oxide The process of ene reduction and other processes is relatively complicated. However, simple and reliable methods for preparing graphene and graphene-based nanocomposites still need to be further researched and developed.

Contents of the invention

The technical problem to be solved by the present invention is: aiming at the problems existing in the prior art, the present invention provides a SiC-graphene nanocomposite material with a core/shell structure; A method for preparing graphene-based nanocomposites combined with chemical vapor deposition and chemical vapor deposition.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical scheme of a SiC-graphene nanocomposite material, the SiC-graphene nanocomposite material is a core-shell structure with a shell covering the core, and the core is SiC nanoparticles, The shell is nano-graphite composed of graphene.

In the aforementioned SiC-graphene nanocomposite material, the graphene in the nano-graphite preferably has 8-15 layers, and grows along the radial direction of the SiC nanoparticles.

In the aforementioned SiC-graphene nanocomposite material, the SiC-graphene nanocomposite material is preferably spherical particles with a diameter of 100 nm to 300 nm and a feather-like surface.

As a general technical concept, the present invention also provides a method for preparing the above-mentioned SiC-graphene nanocomposite material, comprising the following steps:

(1) Precursor cracking: In a chemical vapor deposition furnace under an inert gas atmosphere, heat the polymer precursor to 800°C to 1200°C at a rate of 5°C/s to 10°C/s, and keep The flow rate of the inert gas is 30 sccm-50 sccm, keep warm for 10 minutes to 50 minutes after reaching the temperature, and form SiC nanoparticles after heating and cracking;

(2) Chemical vapor deposition: Continue heating to raise the temperature to 1300 ℃ ~ 1500 ℃, reduce the inert gas flow rate to 5 sccm ~ 10 sccm, keep warm for 10 minutes to 60 minutes after reaching the temperature; finally cool to room temperature under an inert gas atmosphere , keep the inert gas flow at 5 sccm to 10 sccm during the cooling process, and obtain SiC-graphene nanocomposites.

The main principle of the above preparation method is to sublimate and escape the silicon atoms on the surface of SiC nanoparticles, and recombine the remaining carbon atoms to form graphene fragments; the graphene fragments grow up through chemical vapor deposition to obtain SiC-graphene nanocomposites.

In the above preparation method, the polymer precursor is preferably polycarbosilane.

In the above preparation method, the molecular formula of the polycarbosilane is: [SiH(CH ₃ )CH ₂ ] _n , the molecular weight is 2000, and the softening point is 180°C-220°C.

In the above preparation method, the inert gas is preferably high-purity nitrogen.

Compared with the prior art, the present invention has the advantages of:

1. The SiC-graphene nanocomposite material of the present invention is a core-shell structure, the inner core is SiC nanoparticles, and the outer shell is nano-graphite composed of graphene. It has stable physical and chemical structures and properties, and has a huge specific surface area. It can be applied to the fields of lithium battery electrodes, supercapacitors, field emission cathode materials, electrochemical catalysts and composite material reinforcements.

2. The preparation method of the SiC-graphene nanocomposite material of the present invention is to prepare SiC nanoparticles by the precursor conversion method, and then combine the chemical vapor deposition method to prepare the SiC/graphene-based nanocomposite material. The process steps are very simple. The production cost is low, no special equipment is needed, and it is suitable for continuous and large-scale production.

Description of drawings

Fig. 1 is a structural schematic diagram of the preparation device of the SiC-graphene nanocomposite material of the present invention.

Fig. 2 is a scanning electron micrograph of the SiC-graphene nanocomposite material prepared in Example 1 of the present invention.

3 is a scanning electron micrograph of the SiC-graphene nanocomposite material prepared in Example 2 of the present invention.

Fig. 4 is a transmission electron micrograph of the SiC-graphene nanocomposite material prepared in Example 2 of the present invention.

Fig. 5 is a high-resolution transmission electron micrograph of surface nano-graphite of the SiC-graphene nanocomposite material prepared in Example 2 of the present invention.

Fig. 6 is a scanning electron micrograph of the SiC-graphene nanocomposite material prepared in the comparative example in the specific embodiment of the present invention.

illustration:

1. Tubular chemical vapor deposition furnace; 11. Air inlet; 12. Gas outlet; 2. Alumina crucible; 3. Graphite boat; 4. Graphite substrate.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Embodiment 1 :

A SiC-graphene nanocomposite material of the present invention is a core-shell structure in which an outer shell covers a core, the inner core is SiC nanoparticles, and the outer shell is nano-graphite composed of graphene. SiC-graphene nanocomposites are generally spherical particles with a diameter of 100 nm to 300 nm and a feather-like surface. Graphene in nano-graphite has 8-15 layers and grows along the radial direction of SiC nanoparticles.

The above-mentioned SiC-graphene nanocomposite material is prepared through the following steps:

(1) Preparation:

a. Prepare the process device: as shown in Figure 1, prepare a tubular chemical vapor deposition furnace 1 with an air inlet 11 and an air outlet 12 at both ends, place a graphite boat 3 in the tubular chemical vapor deposition furnace 1, graphite An alumina crucible 2 for accommodating raw materials and a graphite substrate 4 for collecting products are sequentially placed on the boat 3 along the airflow direction (the setting of the graphite substrate is mainly to facilitate the collection of products). The graphite substrate 4 is a graphite sheet cleaned with acetone. In Fig. 1, the direction of the hollow arrow is the airflow direction.

b. 5 grams of polycarbosilane is put into the alumina crucible 2. In the present embodiment, polycarbosilane is selected from PCS (synthesized by CFC Key Laboratory of Aerospace and Materials Institute, National University of Defense Technology), and the technical parameters are as follows: Molecular formula: [SiH( CH ₃ )CH ₂ ] _n ; Molecular weight: 2000; Softening point: 180℃～220℃.

(2) Precursor cracking:

c. Introduce high-purity nitrogen gas into the tubular chemical vapor deposition furnace 1, and repeat 2 to 3 times to empty the air in the furnace.

d. Heat the tubular chemical vapor deposition furnace 1 to 1100 °C at a temperature increase rate of 10 °C/s. During the heating process, keep the nitrogen flow rate at 30 sccm to 50 sccm, and keep it warm for 30 minutes after reaching the temperature. The PCS cracking product contains silane fragments , hydrocarbons and other gases, under the action of nitrogen flow, reach the graphite substrate, and heat and crack to form SiC nanoparticles.

(3) Chemical vapor deposition:

e. Continue heating to raise the temperature to 1300°C, reduce the nitrogen flow rate to 5 sccm-10 sccm, keep warm for 10 minutes after reaching the temperature; then cool to room temperature under nitrogen atmosphere, and keep the nitrogen flow rate at 5 sccm-10 sccm during the cooling process, Finally, the SiC-graphene nanocomposite was collected on the graphite substrate.

f. Turn off the nitrogen gas, take out the graphite boat 3, and collect the powdered product on the graphite substrate 4.

The product obtained above was scanned by electron microscope, and the obtained photo is shown in FIG. 2 . It can be seen from Fig. 2 that the products are spherical with a diameter of 100 nm to 300 nm, and the energy spectrum analysis shows that these products are SiC particles; wherein the visible part of the SiC particles has a rough surface and is covered with a feathery substance, and X-ray diffraction analysis shows that they are SiC particles of the present invention. The SiC-graphene nanocomposite material can be seen from the scanning electron microscope photos, and the graphene in the nanographite has about 8 to 15 layers, and grows along the radial direction of the SiC nanoparticles.

Embodiment 2 :

A SiC-graphene nanocomposite material of the present invention is a core-shell structure in which an outer shell covers a core, the inner core is SiC nanoparticles, and the outer shell is nano-graphite composed of graphene. SiC-graphene nanocomposites are generally spherical particles with a diameter of 100 nm to 200 nm and a feathery surface. Graphene in nano-graphite has 8-15 layers and grows along the radial direction of SiC nanoparticles.

The SiC-graphene nanocomposite material of the present embodiment is prepared through the following steps:

(1) Preparation: Same as Example 1.

(2) Precursor cracking:

c. Introduce high-purity nitrogen gas into the tubular chemical vapor deposition furnace 1, and repeat 2 to 3 times to empty the air in the furnace.

d. Heat the tubular chemical vapor deposition furnace 1 to 800°C at a temperature increase rate of 8°C/s, keep the nitrogen flow rate at 30 sccm to 50 sccm during the heating process, keep it warm for 50 minutes after reaching the temperature, and polymerize the polymer precursor Carbosilane thermally cracks to form SiC nanoparticles.

(3) Chemical vapor deposition:

e. Continue heating to raise the temperature to 1400°C, reduce the nitrogen flow rate to 5 sccm-10 sccm, keep warm for 60 minutes after reaching the temperature; then cool to room temperature under an inert gas atmosphere, and keep the nitrogen flow rate at 5 sccm-10 sccm during the cooling process Continued heating is to sublimate and escape silicon atoms on the surface of SiC nanoparticles, and the remaining carbon atoms recombine to form graphene fragments; graphene fragments grow up through chemical vapor deposition to obtain SiC-graphene nanocomposites.

f. Turn off the nitrogen gas, take out the graphite boat 3, and collect the powdered product on the graphite substrate 4.

Electron microscope scanning was carried out on the product prepared above, and the obtained photos are shown in Fig. 3 , Fig. 4 and Fig. 5 . It can be seen from Figure 3 that the product is spherical with a diameter of 100 nm to 300 nm, the surface is rough, and covered with feathery substances. X-ray diffraction analysis shows that the product is composed of SiC and graphite. It can be seen from Figure 4 that the product is a SiC-graphene nanocomposite material with a core/shell structure, the core is SiC particles with a diameter of 100 nm to 200 nm, and the outer layer is feather-like nanographite, which appears on the surface of SiC particles radial growth. Figure 5 is a high-resolution transmission electron microscope photo of nano-graphite. It can be seen that nano-graphite is composed of freely distributed multi-layer graphene, and each sheet of nano-graphite is composed of 8-15 layers of graphene.

Comparative example :

The SiC-graphene nanocomposite material of this comparative example is prepared through the following steps:

(1) Preparation: Same as Example 1.

(2) Precursor cracking:

c. Introduce high-purity nitrogen gas into the tubular chemical vapor deposition furnace 1, and repeat 2 to 3 times to empty the air in the furnace.

d. Heat the tubular chemical vapor deposition furnace 1 to 1100°C at a temperature increase rate of less than 10°C/s, keep the nitrogen flow rate at 30 sccm to 50 sccm during the heating process, keep warm for 5 minutes after reaching the temperature, and put the polymer precursor Polycarbosilane thermally cracks to form SiC nanoparticles.

(3) Chemical vapor deposition:

e. Continue heating to raise the temperature to 1400°C, reduce the nitrogen flow rate to 5 sccm-10 sccm, keep warm for 90 minutes after reaching the temperature; cool to room temperature, and keep the nitrogen flow rate at 5 sccm-10 sccm during the cooling process.

f. Turn off the nitrogen gas, take out the graphite boat 3, and collect the powdered product on the graphite substrate 4.

The product obtained above was scanned by electron microscope, and the obtained photo is shown in FIG. 6 . It can be seen from Figure 6 that the products are in the shape of strips and spherical shapes with a diameter of 50 nm to 100 nm, and the surface is relatively smooth. Energy spectrum analysis shows that these products are SiC. It can be seen that the products are composed of SiC nanoparticles and no nano-graphite is formed. The reason may be mainly It is because the heating time or holding time is not effectively controlled, so that the SiC nanoparticles grow into SiC nanofibers. It can be seen that in the preparation process of the present invention, the control of process parameters is quite critical and important.

In summary, the present invention adopts the precursor conversion method to prepare SiC nanoparticles, combined with the chemical vapor deposition method to prepare SiC/graphene-based nanocomposites, the production cost is low, no special equipment is required, and it is suitable for continuous and large-scale production. The prepared SiC-graphene nanocomposite material can be applied to the fields of lithium battery electrodes, supercapacitors, field emission cathode materials, electrochemical catalysts and composite material reinforcements.

The above are only preferred implementations of the present invention, and the scope of protection of the present invention is not limited to the above examples, and various technical solutions that have no substantial difference from the concept of the present invention are within the scope of protection of the present invention.

Claims (5)

1. a SiC-graphene nanocomposite material, it is characterized in that, described SiC-graphene nanocomposite material is the hud typed structure of the coated kernel of shell, described kernel is SiC nano particle, described shell is the nano-graphite of Graphene composition, in described nano-graphite, Graphene is 8 layers～15 layers, and along the radial growth of described SiC nano particle, the preparation method of described SiC-graphene nanocomposite material is: (1) precursor cracking: in chemical vapor deposition stove, under inert gas atmosphere, polymeric preceramic body is heated to 800 ℃～1200 ℃ with the speed that heats of 5 ℃/s～10 ℃/s, in heating process, keeping inert gas flow is 30 sccm～50 sccm, after temperature, be incubated 10 minutes～50 minutes, after heating pyrolyze, form SiC nano particle, (2) chemical vapour deposition (CVD): continue heating temperature is risen to 1300 ℃～1500 ℃, inert gas flow is decreased to 5 sccm～10 sccm, after temperature, be incubated 10 minutes～60 minutes, finally under inert gas atmosphere, be cooled to room temperature, it is 5 sccm～10 sccm that cooling procedure keeps inert gas flow, obtains SiC-graphene nanocomposite material, described polymeric preceramic body is Polycarbosilane.

2. SiC-graphene nanocomposite material according to claim 1, is characterized in that, described SiC-graphene nanocomposite material is that diameter 100 nm～300nm and surface are penniform spherical particle.

3. a preparation method for the SiC-graphene nanocomposite material as described in any one in claim 1～2, comprises the following steps:

(1) precursor cracking: in chemical vapor deposition stove, under inert gas atmosphere, polymeric preceramic body is heated to 800 ℃～1200 ℃ with the speed that heats of 5 ℃/s～10 ℃/s, in heating process, keeping inert gas flow is 30 sccm～50 sccm, after temperature, be incubated 10 minutes～50 minutes, after heating pyrolyze, form SiC nano particle, described polymeric preceramic body is Polycarbosilane;

(2) chemical vapour deposition (CVD): continue heating temperature is risen to 1300 ℃～1500 ℃, inert gas flow is decreased to 5 sccm～10 sccm, to the rear insulation of temperature 10 minutes～60 minutes; Finally under inert gas atmosphere, be cooled to room temperature, it is 5 sccm～10 sccm that cooling procedure keeps inert gas flow, obtains SiC-graphene nanocomposite material.

4. preparation method according to claim 3, is characterized in that, described Polycarbosilane molecular formula is: [SiH (CH ₃) CH ₂] _n, molecular weight is 2000, softening point is 180 ℃～220 ℃.

5. preparation method according to claim 4, is characterized in that, described inert gas is high pure nitrogen.

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