CN116281975A - A Method for Preparation of Nanomaterials by AC Combination Plasma - Google Patents

Abstract

The invention relates to a method for preparing nano materials by alternating current combined plasmas, which comprises the steps of preliminarily ionizing buffer gas through a high-frequency alternating current rotary sliding arc under a negative pressure condition, further exciting single-phase or three-phase power frequency discharge, generating stable high-power arc, introducing raw material gas, then generating cracking reaction, and nucleating and growing in a downlink fluidized bed to obtain the nano materials. The invention has reasonable design, prepares carbon black particles, graphene sheets, nitrogen-doped graphene sheets and silicon nitride particles by alternating current combined plasmas under the negative pressure condition, has convenient and fast product separation and recovery, simple process flow, no need of a catalyst and a substrate, low cost, environmental protection and suitability for continuous large-scale preparation of nano materials.

Description

A Method for Preparation of Nanomaterials by AC Combination Plasma

Technical field:

The invention belongs to the technical field of preparation of nanometer materials, and in particular relates to a method for preparing nanometer materials by alternating current combined plasma.

Background technique:

In recent years, the research on nanomaterials has been quite active. Two-dimensional nanomaterials such as graphene are particularly prominent due to their special structure, high electron mobility, good thermal conductivity, large specific surface area and strong mechanical strength. With the continuous development of plasma technology, it has shown unique advantages in the field of nanomaterial science and technology, especially in the preparation, modification and application of nanomaterials.

The Chinese Patent Publication No. CN111453719A discloses a high-quality graphene and its preparation method. In this invention, an oxidant solution is added to graphite powder for micro-expansion, followed by microwave plasma treatment to obtain graphene. This invention introduces microwave plasma technology into the process of preparing graphene, and uses graphite powder as raw materials to prepare graphene through a specific process, thereby improving the problems of long reaction time, many graphene defects, and environmental pollution from waste liquid. In the preparation process, operations such as washing, purification, and drying are required, the steps are complicated, the operation is cumbersome, and the equipment price is high.

Chinese Patent Publication No. CN109534328A discloses a two-dimensional nitrogen-doped graphene and its preparation method. The invention anneals the copper sheet at high temperature, and under the action of the plasma generator, ammonia and methane are cracked, and the Under the catalysis of copper, it is deposited on the surface of the copper substrate, and the nitrogen-doped graphene material is assembled. The preparation temperature of nitrogen-doped graphene is reduced to 400°C, the reaction time is also greatly shortened, the operation is simple, and the repeatability is good. However, substrates are required in the preparation process, and the yield is low, which is not suitable for large-scale production.

Chinese Patent Publication No. CN113200528A discloses a preparation method and equipment for high-purity α-phase silicon nitride powder. The invention uses high-purity nitrogen plasma under the action of a catalyst, and high-purity silicon powder is rapidly reacted by plasma arc to obtain The amorphous silicon nitride powder is finally calcined in a tube furnace to obtain α-phase silicon nitride. The product obtained by the method has uniform particle size distribution and high purity. However, the preparation method is still the reaction of gas and solid, and high-purity silicon powder will be deposited in the plasma area more often, hindering the continuous progress of the reaction.

Compared with other forms of plasma, high-frequency AC rotating sliding arc plasma has simple equipment structure, low cost, convenient operation, and will not be limited by pressure changes. Therefore, sliding arc discharge has been widely used and researched in methane gas reforming, pollutant degradation, nanomaterial preparation, modification and other fields. Compared with high-frequency AC power, generators and transformers of single-phase or three-phase power frequency AC power supply are simpler in structure and have excellent performance. When outputting the same power under the same conditions, the power loss is less, which can effectively save energy. The combined use of these two AC arc plasmas can expand the discharge area and maintain long-term stable discharge, which is suitable for large-scale preparation of nanomaterials. This case was born from this.

Invention content:

The present invention makes improvements to the problems existing in the above-mentioned prior art, that is, the technical problem to be solved by the present invention is to provide a method for preparing nanomaterials with alternating current combined plasma, the process is simple and reasonable, no catalyst and substrate are required, and the cost is low. Green and environmentally friendly, it is suitable for continuous large-scale preparation of nanomaterials.

In order to achieve the above purpose, the technical solution adopted by the present invention is: a method for preparing nanomaterials with AC combined plasma, including sequentially connected gas flow control devices, high-frequency AC rotating sliding arc plasma generators, single-phase or three-phase An AC arc plasma generator, a fluidized bed, and a dedusting device, the outlet end of the dedusting device is connected to the tail gas treatment device through an induced draft system, and the outlet end of the dedusting device is connected to the collecting device, including the following steps:

(1) Turn on the air induction system to adjust the pressure of the plasma reaction area of the high-frequency AC rotary sliding arc plasma generator, single-phase or three-phase AC arc plasma generator, and form a negative pressure condition;

(2) Pass the buffer gas into the plasma reaction area of the high-frequency AC rotating sliding arc plasma generator, turn on the high-frequency AC power supply, and crack the buffer gas to form rotating sliding arc plasma; the buffer gas after initial ionization then enters In the plasma reaction area of the single-phase or three-phase AC arc plasma generator, turn on the single-phase or three-phase AC power supply, and the initially ionized buffer gas forms a stable single-phase or three-phase AC power supply under the action of the single-phase or three-phase AC power supply. Phase AC arc plasma;

(3) Feed in the raw material gas, the raw material gas passes through the plasma reaction area of the high-frequency AC rotary sliding arc plasma generator and the single-phase or three-phase AC arc plasma generator in turn, and the raw material gas enters the fluidized bed after cracking , free radicals continue to grow into nanopowder materials through nucleation and growth;

(4) The nano-material product processed in step (3) enters the separation and dust removal device, and the separated nano-material product enters the collection device, and the nano-material is obtained after cooling; the exhaust gas from the separation is sent to the exhaust gas treatment through the induced draft system device.

Further, the gas flow control device is a connected rotameter and a mass flow meter; the induced air system is an induced fan or a vacuum pump; the separation and dust removal device is a connected cyclone separator and bag filter.

Further, the high-frequency AC rotary sliding arc plasma generator is connected with an electrode air cooling device; the single-phase or three-phase AC arc plasma generator is provided with a leakage protection device.

Further, the nanomaterial is carbon black particles, graphene sheets, nitrogen-doped graphene sheets or silicon nitride particles.

Further, the fluidized bed adopts the structure of a descending fluidized bed, and the gas pressure is maintained at a negative pressure condition of 20-90 kPa.

Further, in step (2), the power of the high-frequency AC rotating sliding arc plasma generator is 1-200kW, and the frequency is 30 kHz-300kHz; the power of the single-phase or three-phase AC arc plasma generator 5kW ~ 2000 kW, the frequency is 50Hz.

Further, in step (2), the buffer gas is one or more of argon, helium, and neon, and the total gas flow is 4-100L/min; in step (3), the raw gas is methane , ethane, propane, nitrogen, ammonia, nitrogen, silane, hydrogen, one or more, respectively as carbon source, nitrogen source, silicon source, additive, the total gas flow is 0.5-20 L/min.

Further, the flow ratio of the buffer gas to the raw material gas is between 1:1 and 20:1; the residence time of the buffer gas, raw gas and solid product in the fluidized bed is 0.5-10s.

Further, in step (2), the electrodes of the single-phase or three-phase AC arc plasma generator are composed of two or three graphite rods. When a single-phase AC arc plasma generator is used, the single-phase AC arc plasma When the electrode of the bulk generator is composed of two graphite rods, the electrode and the feed gas are in the same horizontal plane, and the angle between the two graphite rods is 0° to 180°; when a three-phase AC arc plasma generator is used, the three-phase When the electrodes of the AC arc plasma generator are composed of three graphite rods, the three graphite rods are arranged in the same horizontal plane according to the phase difference or parallel arrangement, and the angle between the phase difference arrangement is 120°.

Further, the electrode distance of the single-phase or three-phase AC arc plasma generator can be automatically adjusted after the graphite electrode is stripped, and the electrode distance of the normal discharge of the single-phase or three-phase AC arc after the AC sliding arc is started is 1-10mm Expand to 1-40mm; the temperature in the plasma area is 500K-10000K.

Compared with the prior art, the present invention has the following effects: the design of the present invention is reasonable, under the condition of negative pressure, the buffer gas is preliminarily ionized through the high-frequency AC rotating sliding arc, and then the single-phase or three-phase power frequency discharge is excited to generate a stable large Power arc, the cracking reaction occurs after the raw material gas is introduced, nucleation and growth in the downward fluidized bed to obtain nanomaterials, the whole method uses gas phase raw materials, the product separation and recovery is convenient, the process is simple, no catalyst and substrate are required, and the cost is low. Green and environmentally friendly, it is suitable for continuous large-scale preparation of nanomaterials.

Description of drawings:

Fig. 1 is a flow chart of an embodiment of the present invention;

Fig. 2 is the SEM figure of the carbon black particle that embodiment 1 makes among the present invention;

Fig. 3 is the SEM figure of the graphene that embodiment 2 makes among the present invention;

Fig. 4 is the SEM figure of the nitrogen-doped graphene that embodiment 3 makes among the present invention;

5 is an SEM image of nitrogen-doped graphene prepared in Comparative Example 2 of the present invention.

Detailed ways:

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

In describing the present invention, it should be understood that the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", The orientations or positional relationships indicated by "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention, rather than indicating or It should not be construed as limiting the invention by implying that a referenced device or element must have a particular orientation, be constructed, and operate in a particular orientation.

As shown in Figure 1, the present invention is a method for preparing nanomaterials with AC combined plasma. A plasma generator, a fluidized bed, and a separation and dust removal device. The gas outlet of the separation and dust removal device is connected to the tail gas treatment device through an air induction system, and the discharge end of the separation and dust removal device is connected to the collection device. Under the condition of negative pressure, the buffer gas is preliminarily ionized through the high-frequency AC rotating sliding arc, and then the single-phase or three-phase power frequency discharge is excited to generate a stable high-power arc. Nucleation, growth to obtain nanomaterials. The specific method for preparing nanomaterials comprises the following steps:

(1) Turn on the air induction system to adjust the pressure of the plasma reaction area of the high-frequency AC rotary sliding arc plasma generator, single-phase or three-phase AC arc plasma generator, and form a negative pressure condition in the plasma reaction area;

(2) Pass the buffer gas into the plasma reaction area of the high-frequency AC rotating sliding arc plasma generator, turn on the high-frequency AC power supply, and crack the buffer gas to form rotating sliding arc plasma; the buffer gas after initial ionization then enters In the plasma reaction area of the single-phase or three-phase AC arc plasma generator, turn on the single-phase or three-phase AC power supply, and the initially ionized buffer gas forms a stable single-phase or three-phase AC power supply under the action of the single-phase or three-phase AC power supply. Phase AC arc plasma;

(3) Feed in the raw material gas, the raw material gas passes through the plasma reaction area of the high-frequency AC rotary sliding arc plasma generator and the single-phase or three-phase AC arc plasma generator in turn, and the raw material gas enters the fluidized bed after cracking , free radicals continue to grow into nanopowder materials through nucleation and growth;

(4) The nano-material product processed in step (3) enters the separation and dust removal device, and the separated nano-material product enters the collection device, and the nano-material is obtained after cooling; the exhaust gas from the separation is sent to the exhaust gas treatment through the induced draft system device.

In this embodiment, the gas flow control device is a connected rotameter and a mass flowmeter, and the gas flow is adjusted by the rotameter and the mass flowmeter. Preferably, the flow range of the mass flow meter is 0-200 L/min, preferably 50-150 L/min.

In this embodiment, the induced draft system is an induced draft fan or a vacuum pump.

In this embodiment, the separation and dedusting device is a connected cyclone separator and bag filter, and the nanomaterial obtained in step (4) is separated from the gas product by the cyclone separator and bag filter, and the gas is evacuated or recycled. Wherein, the height of the cyclone separator is 200-600cm, and the diameter is 40-60cm.

In this embodiment, the collection device is divided into a ceramic or corundum tube with a height of 20-40 cm and a diameter of 10-20 cm, and a stainless steel settling tube with a height of 50-100 cm and a diameter of 20-40 cm, which can be replaced according to the replacement of the fluidized bed reactor.

In this embodiment, the high-frequency AC rotating sliding arc plasma generator is connected with an electrode air cooling device for air cooling the electrodes. The power of the high-frequency AC rotating sliding arc plasma generator is 1-200kW, and the frequency is 30kHz-300kHz. The electrodes of the high-frequency AC rotating sliding arc plasma generator are composed of conical stainless steel electrodes and cylindrical high-purity graphite. This part of the structure is the prior art, for example, refer to a sliding arc plasma device disclosed in CN216217684U, and the motor structure of the high-frequency AC rotating sliding arc plasma generator will not be repeated here.

In this embodiment, the single-phase or three-phase AC arc plasma generator is provided with a leakage protection device for leakage protection. The power of the single-phase or three-phase AC arc plasma generator is 5kW-2000kW, and the frequency is 50Hz. The single-phase or three-phase AC arc plasma generator is above the AC rotating sliding arc, and the electrodes of the single-phase or three-phase AC arc plasma generator are composed of two or three graphite rods. For the plasma generator, when the electrode of the single-phase AC arc plasma generator is composed of two graphite rods, the electrode and the feed gas are in the same horizontal plane, and the angle between the two graphite rods is 0° to 180°, that is, basically parallel or opposites. When a three-phase AC arc plasma generator is used, when the electrodes of the three-phase AC arc plasma generator are composed of three graphite rods, the three graphite rods are in the same horizontal plane, arranged evenly or basically in parallel according to the phase difference, that is: each electrode Arrange evenly according to the phase difference arrangement angle of 120°, or the electrodes are basically parallel at an angle of 0°.

In this embodiment, the nanomaterials are solid powder nanomaterials such as carbon black particles, graphene sheets, nitrogen-doped graphene sheets, or silicon nitride. The invention utilizes the advantages of easy arc starting of high-frequency alternating current rotating arc, and combines with the characteristics of high efficiency of single-phase or three-phase alternating current plasma to effectively expand the plasma reaction area. Carbon black particles, graphene materials, nitrogen-doped graphene, and silicon nitride are obtained by directly cracking gas reactants. The particle size of the obtained carbon black particles is 50-100nm; the size of graphene sheets is 100-300nm, and the 2-6 layers; the size of nitrogen-doped graphene sheets is 100-200nm, and the number of layers is 3-10 layers; the particle size of silicon nitride particles is 10-50 nm; the type and particle size of nanomaterials can be determined by general The type of buffer gas, the type of raw material gas, and the control of process conditions.

In this embodiment, the fluidized bed adopts the structure of a descending fluidized bed reactor, and the gas pressure is maintained at a negative pressure condition of 20-90 kPa, which is regulated by a vacuum pump. Further, the fluidized bed is connected to the single-phase or three-phase AC arc plasma reactor through a flare, the diameter of the fluidized bed is 3-8 times the diameter of the single-phase or three-phase AC arc plasma reactor, and the height is 3-8 times that of the single-phase AC arc plasma reactor. Or 3-10 times the height of the three-phase AC arc plasma reactor. The residence time of the buffer gas, raw material gas and solid product in the fluidized bed is 0.5-10 s.

In this embodiment, in step (2), the buffer gas is one or more of argon, helium, and neon that are prone to cracking, and the total gas flow rate is 4-100L/min. L/min is the best, and the gas flow is adjusted by rotameter and mass flowmeter.

In this embodiment, in step (3), the raw material gas is one or more of methane, ethane, propane, nitrogen, ammonia, nitrogen, silane, and hydrogen, which are used as carbon source, nitrogen source, silicon source, Additives, the total gas flow rate is 0.5-20 L/min, preferably 2-15 L/min, the gas flow rate is adjusted by a rotameter and a mass flow meter; the flow ratio of the buffer gas to the raw material gas is between 1:1 and Between 20:1, preferably 5:1 to 10:1.

In this embodiment, the electrode distance of the single-phase or three-phase AC arc plasma generator can be automatically adjusted after the graphite electrodes are peeled off. -10mm is expanded to 1-40mm; the temperature in the plasma region is 500K-10000K.

In this embodiment, the high-frequency alternating current arc can continuously break down the buffer gas between the electrodes, making it less prone to ionization. Compared with high-frequency AC power, generators and transformers of single-phase or three-phase power frequency AC power supply are simpler in structure and have excellent performance. When the single-phase or three-phase alternating current outputs the same power under the same conditions, the power loss is less, which can effectively save energy. Combining these two AC arc plasmas, the AC rotating sliding arc plasma can run from the bottom to the top to form a plasma group, making it easier to form an arc with a single-phase or three-phase AC arc, and the electrode distance can be elongated and reduced Electrode wear increases the plasma reaction area. At the same time, the negative pressure condition can increase the gas flow rate, reduce the gas density, and make the gas that is difficult to ionize easier to ionize. The combination with the down-flowing fluidized bed can make the free radical nucleation and growth of nanomaterials more fully, and increase the output. The method can maintain stable discharge for a long time, and is suitable for long-term large-scale preparation of nanometer materials. The combination of these two plasmas not only improves the synthesis efficiency of carbon materials, but also can form and expand a stable plasma region to achieve the effect of long-term large-scale synthesis. The present invention is based on it, utilizes alternating current combined plasma, and uses gas as a raw material to prepare carbon black particles, graphene, nitrogen-doped graphene, and silicon nitride particles. The invention has the advantages of convenient separation and recovery of process products, simple process flow, no need for catalysts and substrates, low cost, environmental protection, and is suitable for continuous large-scale preparation of nanometer materials.

The specific implementation process:

(1) Turn on the induced draft fan or vacuum pump to adjust the pressure in the plasma reaction area, and turn on the plasma electrode air cooling device, leakage protection device, and mass flow meter;

(2) Pass the buffer gas into the plasma reaction area, turn on the high-frequency AC power supply, and crack to form a rotating sliding arc plasma. The initially ionized buffer gas forms a stable single-phase or three-phase AC power supply under the action of a single-phase or three-phase AC power supply. Three-phase AC arc plasma;

(3) Pass the raw material gas into the plasma generator and the downward fluidized bed, and pass through the combined plasma area. After the raw material gas is cracked, it enters the downward fluidized bed, and the free radicals continue to grow into nanopowder through nucleation and growth. body material;

(4) The nano-material products processed in step (3) are separated through a collection system such as a cyclone separator and a bag collector, and then enter the collection device, and the nano-materials are obtained after cooling; the tail gas is properly treated and purified through the induced draft system Reuse as raw material.

Example 1

Utilize the method for preparing carbon black particle by alternating current combination plasma, concrete steps are as follows:

(1) Turn on the vacuum pump, adjust the pressure in the plasma area to 80 kPa, turn on the plasma electrode air cooling device, set it to 60 L/min, turn on the mass flow meter, and turn on the leakage protection device;

(2) Pass the argon gas into the plasma reaction area, adjust the flow rate to 50 L/min through the rotameter and the mass flow meter respectively, turn on the high-frequency AC power supply and crack to form a rotating sliding arc plasma, and the initially ionized argon gas Under the action of three-phase AC power supply, a stable three-phase AC arc plasma is formed;

(3) Pass ethane into the plasma generator and the downward fluidized bed, adjust the flow rate to 10 L/min through the rotameter and the mass flow meter respectively, pass through the combined plasma area, and after the ethane is cracked, enter the downward flow In a fluidized bed, free radicals continue to nucleate and grow;

(4) The carbon black particles obtained after the reaction are separated with the argon gas through the collection system such as the cyclone separator and the bag collector, and enter the collection device, and the product is obtained after cooling. The tail gas passes through the induced draft system, and is used as a raw material after proper treatment and purification reuse;

(5) The collected carbon black particles are black nano-powder in the form of spherical agglomerates with a diameter of 50-100 nm. The morphology is shown in Figure 2.

Example 2

Utilize the method for preparing graphene by alternating current combination plasma, concrete steps are as follows:

(1) Turn on the vacuum pump, adjust the pressure in the plasma area to 60 kPa, turn on the plasma electrode air cooling device, set it to 60 L/min, turn on the mass flow meter, and turn on the leakage protection device;

(2) Pass argon and helium into the plasma reaction area, adjust the flow rate to 100 L/min and 10 L/min through the rotameter and mass flow meter respectively, turn on the high-frequency AC power supply and crack to form a rotating sliding arc Plasma, the initially ionized argon gas forms a stable three-phase AC arc plasma under the action of a three-phase AC power supply;

(3) Feed methane and hydrogen into the plasma generator and the downward fluidized bed, adjust the flow rates to 10 L/min and 2 L/min respectively through the rotameter and mass flow meter, pass through the combined plasma area, methane and After the hydrogen is cracked, it enters the downward fluidized bed, and the free radicals continue to nucleate and grow;

(4) After the reaction, the graphene sheet is obtained, along with the argon and helium through the collection system such as the cyclone separator and the bag collector, and is separated and enters the collection device, and the product is obtained after cooling, and the tail gas is properly treated through the induced draft system Purified and reused as raw materials;

(5) The collected graphene is black nano-powder in flake shape with a diameter of 100-300 nm. The morphology is shown in Figure 3.

Example 3

The method for preparing nitrogen-doped graphene by alternating current combined plasma, the specific steps are as follows:

(1) Turn on the vacuum pump, adjust the pressure in the plasma area to 50 kPa, turn on the plasma electrode air cooling device, set it to 60 L/min, turn on the mass flow meter, and turn on the leakage protection device;

(2) Pass argon gas and neon gas into the plasma reaction area, adjust the flow rate to 80 L/min and 20 L/min respectively through the rotameter and mass flow meter, turn on the high-frequency AC power supply and crack to form a rotating sliding arc Plasma, the initially ionized argon and neon gas form a stable three-phase AC arc plasma under the action of a three-phase AC power supply;

(3) Feed methane and nitrogen into the plasma generator and the downward fluidized bed, adjust the flow rates to 5 L/min and 15 L/min respectively through the rotameter and mass flow meter, pass through the combined plasma area, methane and After the nitrogen is cracked, it enters the descending fluidized bed, and the free radicals continue to nucleate and grow;

(4) After the reaction, the nitrogen-doped graphene sheet is obtained. As the argon and neon gas pass through the collection system such as the multi-stage cyclone separator and the bag collector, they are separated and enter the collection device. After cooling, the product is obtained. Wind system, after proper treatment and purification, it can be reused as raw material;

(5) The collected nitrogen-doped graphene is a black nano-powder in the form of flakes with a diameter of 100-200 nm. The morphology is shown in Figure 4.

Comparative example 1

The method for preparing nitrogen-doped graphene by alternating current combined plasma, the specific steps are as follows:

(1) Turn on the induced draft fan, the pressure in the plasma area is normal pressure, turn on the plasma electrode air cooling device, set it to 60 L/min, turn on the mass flow meter, and turn on the leakage protection device;

(2) Pass argon gas and neon gas into the plasma reaction area, adjust the flow rate to 80 L/min and 20 L/min respectively through the rotameter and mass flow meter, turn on the high-frequency AC power supply and crack to form a rotating sliding arc Plasma, the primary ionized argon and neon gas forms a three-phase AC arc plasma under the action of a three-phase AC power supply;

(3) Feed methane and nitrogen into the plasma generator and the descending fluidized bed, adjust the flow rates to 5 L/min and 15 L/min respectively through the rotameter and mass flow meter, pass through the combined plasma area, and the arc is extinguished , ignition failure.

Comparative example 2

The method for preparing nitrogen-doped graphene by alternating current combined plasma, the specific steps are as follows:

(1) Turn on the vacuum pump, adjust the pressure in the plasma area to 50 kPa, turn on the plasma electrode air cooling device, set it to 60 L/min, turn on the mass flow meter, and turn on the leakage protection device;

(2) Pass argon gas and neon gas into the plasma reaction area, adjust the flow rate to 80 L/min and 20 L/min respectively through the rotameter and mass flow meter, turn on the high-frequency AC power supply and crack to form a rotating sliding arc Plasma, the primary ionized argon and neon gas forms a three-phase AC arc plasma under the action of a three-phase AC power supply;

(3) Feed methane and nitrogen into the plasma generator and the downward fluidized bed, adjust the flow rates to 5 L/min and 15 L/min respectively through the rotameter and mass flow meter, pass through the combined plasma area, methane and After the nitrogen is cracked, it directly enters the collection device, and the product is obtained after cooling, and finally the gas is separated from the nitrogen-doped graphene sheet;

(4) The output of the product directly entering the collection device is 50%-70% lower than that of the product entering the collection device after passing through the downward fluidized bed.

The advantages of the present invention are:

(1) The present invention can prepare nanomaterials with high value in practical research fields and industrial applications, and can regulate their morphology and structure; under negative pressure conditions, carbon black particles, graphene Sheets, nitrogen-doped graphene sheets, silicon nitride particles, convenient separation and recovery of products, simple process, no need for catalysts and substrates, low cost, green and environmentally friendly, suitable for continuous large-scale preparation of nanomaterials; negative pressure can be carried out Operation, increase the gas flow rate to increase the processing capacity per unit time and increase the production rate;

(2) The present invention can prepare conductive carbon black and small-diameter graphene, which are piled up into a grape-like structure with a layer number of 2-6 layers; the conductive carbon black and graphene in the product form a one-dimensional and two-dimensional structure combination to enhance conductivity, Nitrogen-doped graphene and silicon nitride can be directly synthesized in one step by using nitrogen, ammonia, and silane gas reactants without solid-state catalysts;

(3) Compared with other plasma methods, the present invention has higher efficiency, larger processing capacity, and reduced power consumption; the combined AC plasma method not only improves the synthesis efficiency of nanomaterials, but also increases the discharge gap and reduces the electrode The carbon deposition between them can form and expand a stable plasma area to achieve the effect of long-term large-scale synthesis;

(4) The present invention combines the AC combined plasma with the down-flowing fluidized bed to increase the reaction time, fully nucleate and grow free radicals, and increase the yield of nanomaterials.

If the present invention discloses or relates to parts or structural parts that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (for example, using bolts or screws), or it can also be understood as: Non-detachable fixed connection (such as riveting, welding), of course, the mutual fixed connection can also be replaced by an integrated structure (such as manufactured by integral forming by casting process) (except that the integral forming process cannot be used obviously).

In addition, unless otherwise stated, the terms used in any of the technical solutions disclosed in the present invention to indicate positional relationships or shapes include states or shapes that are similar, similar or close to them.

Any component provided by the present invention can be assembled from multiple individual components, or can be a single component manufactured by integral forming process.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that: the present invention can still be Modifications to the specific implementation of the invention or equivalent replacement of some technical features; without departing from the spirit of the technical solution of the present invention, should be included in the scope of the technical solution claimed in the present invention.

Claims (10)

1. A method for preparing nanomaterials by alternating current combined plasma, characterized in that: comprising a gas flow control device connected in sequence, a high-frequency alternating current rotating sliding arc plasma generator, a single-phase or three-phase alternating arc plasma generator, The fluidized bed and the separation dust removal device, the outlet end of the separation dust removal device is connected to the tail gas treatment device through the induced air system, and the discharge end of the separation dust removal device is connected to the collection device, including the following steps: (1) Turn on the air induction system to adjust the pressure of the plasma reaction area of the high-frequency AC rotary sliding arc plasma generator, single-phase or three-phase AC arc plasma generator, and form a negative pressure condition; (2) Pass the buffer gas into the plasma reaction area of the high-frequency AC rotating sliding arc plasma generator, turn on the high-frequency AC power supply, and crack the buffer gas to form rotating sliding arc plasma; the buffer gas after initial ionization then enters In the plasma reaction area of the single-phase or three-phase AC arc plasma generator, turn on the single-phase or three-phase AC power supply, and the initially ionized buffer gas forms a stable single-phase or three-phase AC power supply under the action of the single-phase or three-phase AC power supply. Phase AC arc plasma; (3) Feed in the raw material gas, the raw material gas passes through the plasma reaction area of the high-frequency AC rotary sliding arc plasma generator and the single-phase or three-phase AC arc plasma generator in turn, and the raw material gas enters the fluidized bed after cracking , free radicals continue to grow into nanopowder materials through nucleation and growth; (4) The nano-material product processed in step (3) enters the separation and dust removal device, and the separated nano-material product enters the collection device, and the nano-material is obtained after cooling; the exhaust gas from the separation is sent to the exhaust gas treatment through the induced draft system device. 2. the method for preparing nanomaterials by a kind of AC combined plasma according to claim 1, characterized in that: the gas flow control device is a connected rotameter and a mass flowmeter; fan or vacuum pump; the separation and dust removal device is a connected cyclone separator and bag filter. 3. The method for preparing nanomaterials with AC combined plasma according to claim 1, characterized in that: the high-frequency AC rotating sliding arc plasma generator is connected with an electrode air cooling device; the single-phase or three-phase The alternating current arc plasma generator is equipped with a leakage protection device. 4. A method for preparing nanomaterials with alternating current combined plasma according to claim 1, wherein the nanomaterials are carbon black particles, graphene sheets, nitrogen-doped graphene sheets or silicon nitride particles. 5. The method for preparing nanomaterials with alternating current combined plasma according to claim 1, characterized in that: the fluidized bed adopts the structure of a downward fluidized bed, and the gas pressure is maintained at a negative pressure condition of 20-90 kPa . 6. A method for preparing nanomaterials with AC combined plasma according to claim 1, characterized in that in step (2), the power of the high-frequency AC rotating sliding arc plasma generator is 1-200kW, The frequency is 30 kHz-300 kHz; the power of the single-phase or three-phase AC arc plasma generator is 5kW-2000 kW, and the frequency is 50Hz. 7. A method for preparing nanomaterials with AC combined plasma according to claim 1, characterized in that: in step (2), the buffer gas is one or more of argon, helium, and neon species, the total gas flow rate is 4-100L/min; in step (3), the raw material gas is one or more of methane, ethane, propane, nitrogen, ammonia, nitrogen, silane, hydrogen, respectively as carbon source , nitrogen source, silicon source, additives, the total gas flow is 0.5-20 L/min. 8. The method for preparing nanomaterials with AC combined plasma according to claim 1, characterized in that: the flow ratio of the buffer gas to the raw material gas is between 1:1 and 20:1; the buffer gas, raw material The residence time of gas and solid products in the fluidized bed is 0.5-10s. 9. A method for preparing nanomaterials with AC combined plasma according to claim 1, characterized in that: in step (2), the electrodes of the single-phase or three-phase AC arc plasma generator consist of two or Composed of three graphite rods, when a single-phase AC arc plasma generator is used, when the electrode of the single-phase AC arc plasma generator is composed of two graphite rods, the electrode and the feed gas are in the same horizontal plane, and the two graphite rods are clamped The angle is 0° to 180°; when a three-phase AC arc plasma generator is used, when the electrodes of the three-phase AC arc plasma generator are composed of three graphite rods, the three graphite rods are arranged in the same horizontal plane according to the phase difference or parallel Arranged, and the difference between the arrangement angle is 120°. 10. The method for preparing nanomaterials with AC combined plasma according to claim 9, characterized in that: the electrode distance of the single-phase or three-phase AC arc plasma generator can be automatically adjusted after the graphite electrodes are stripped, and the AC The electrode distance of normal discharge of single-phase or three-phase AC arc after sliding arc ignition is expanded from 1-10mm to 1-40mm; the temperature in the plasma area is 500K-10000K.

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