CN106082227A - A kind of fluidized-bed chemical vapor deposition preparation method of nanometer silicon carbide granule - Google Patents

Abstract

The invention relates to a fluidized bed chemical vapor deposition preparation method of silicon carbide nanoparticles, which comprises adopting the fluidized bed chemical vapor deposition method, heating the precursor material hexamethyldisilane to generate steam, and entering the flow through the gas carrying method. Fluidized bed reactor; the precursor steam undergoes pyrolysis reaction in the high temperature zone to form silicon carbide nanoparticles; the nanoparticles are transported to the upper part of the reactor under the action of fluidization gas, sucked out by a negative pressure device, and collected to obtain silicon carbide nanopowder Body; heat treatment at high temperature under an inert atmosphere to obtain well-crystallized silicon carbide nanoparticles. The obtained silicon carbide nanoparticles are cubic phase silicon carbide, the particle shape is spherical, the particle size distribution is narrow, and the particle size is adjustable from 5 to 300 nanometers. By adjusting the reaction atmosphere, pure silicon carbide, silicon-rich or carbon-rich silicon carbide nanoparticles can be obtained. The invention has simple technological process, convenient technological operation and low cost, and is beneficial to realize industrialized production.

Description

A fluidized bed chemical vapor deposition preparation method of silicon carbide nanoparticles

technical field

The invention relates to the technical field of silicon carbide material preparation, in particular to a method for preparing silicon carbide nanoparticles by fluidized bed chemical vapor deposition.

Background technique

Silicon carbide materials are widely used as high-temperature structural components and new sub-components due to their wide electronic band gap, excellent high-temperature mechanical properties, low thermal expansion coefficient, high thermal conductivity, and resistance to radiation, corrosion, and oxidation. In aerospace, chemical industry, energy, electronics and other fields. By reducing the particle size of silicon carbide nanomaterials to the nanometer level, due to the size effect, silicon carbide materials will exhibit many novel properties different from bulk materials, further broadening its application fields. Nano-sized silicon carbide particles also exhibit excellent high-temperature sintering performance, overcome the current difficulty of sintering silicon carbide, and significantly reduce the sintering temperature. It is expected to be used in silicon carbide link technology and new silicon carbide-based nuclear fuel elements. Applications.

At present, the methods for preparing silicon carbide nanoparticles mainly include: (1) high-temperature reaction method of carbon and silicon mixture; (2) chemical vapor deposition method; (3) sol-gel method; (4) microwave or plasma high-temperature synthesis method, etc. . Using these methods to synthesize silicon carbide nanoparticles, on the one hand, it is relatively difficult to control the morphology and size of the reaction product, and it is even more challenging to prepare monodisperse silicon carbide nanoparticles with good sphericity, narrow particle size distribution, and adjustable size; On the one hand, the obtained SiC nanoparticles often contain other elemental impurities, and the stoichiometric ratio of SiC cannot be designed and effectively regulated. In addition, some methods require high energy input, which puts forward high requirements on equipment, and cannot realize mass continuous production of products.

Contents of the invention

In order to solve the problems in the prior art, the purpose of the present invention is to provide a method for preparing spherical silicon carbide nanoparticles with adjustable size and controllable composition, which can realize industrial production.

In order to achieve the purpose of the present invention, the present invention provides a fluidized bed chemical vapor deposition preparation method of silicon carbide nanoparticles, the preparation method specifically includes the following steps:

1) Heating the fluidized bed reactor to a certain temperature, feeding a certain amount of fluidizing gas and adding a certain amount of inert fluidized particles;

2) heating the precursor material hexamethyldisilane to generate steam, and the steam enters the fluidized bed reactor through the gas carrier;

3) The vapor of the precursor material undergoes a pyrolysis reaction in the high temperature zone of the fluidized bed reactor to form silicon carbide nanoparticles;

4) The silicon carbide nanoparticles are transported to the upper part of the fluidized bed reactor under the action of fluidizing gas, sucked out by a negative pressure device, and collected to obtain silicon carbide nanopowders;

5) heat-treating the obtained silicon carbide nanopowder in an argon atmosphere to obtain silicon carbide nanoparticles with good crystallization.

Further, the inert fluidized particles are particles that do not react with the precursor at the preparation temperature, preferably metal or ceramic particles; more preferably zirconia particles, alumina particles, metal cobalt particles or metal iron particles particles.

Further, the heating method of the precursor is water bath or electric heating, and the heating temperature is 30-110°C.

Further, the fluidizing gas is hydrogen or argon or a mixture thereof.

Further, the carrier gas is hydrogen or argon.

Further, the volume ratio of the carrier gas to the fluidizing gas is 0.1%-50%.

Further, the temperature in the high temperature zone of the fluidized bed reactor in step 3) is 750-1450°C.

Further, the ratio of hydrogen to argon in the reaction system in step 3) is controlled to be 30% to 70%, and the temperature in the high temperature zone of the fluidized bed reactor is 750 to 1300°C to obtain pure phase silicon carbide nanoparticles.

Further, the ratio of hydrogen to argon in the reaction system in step 3) is controlled from 70% to infinity, and the temperature in the high temperature zone of the fluidized bed reactor is 750-1200°C to obtain silicon-rich silicon carbide nanoparticles, silicon The mass fraction is 0-8%.

Further, the ratio of hydrogen to argon in the reaction system in step 3) is controlled to be 0 to 30%, and the reaction temperature in the high temperature zone is 750 to 1450° C. to obtain carbon-rich silicon carbide nanoparticles, and the mass fraction of carbon is 0 to 30%. 10%.

Further, the heat treatment temperature in step 5) is 1300-1500° C., and the heat treatment time is 1-4 hours.

The present invention also provides silicon carbide nanoparticles prepared by the above method. The silicon carbide nanoparticles are cubic phase silicon carbide, the particle shape is spherical, and the particle size is adjustable from 5 to 300 nanometers.

The present invention also provides a fluidized reaction device for preparing the above-mentioned silicon carbide nanoparticles, which is a hollow cylindrical tube body, the bottom of the tube body is a precursor steam inlet, and the upper part of the tube body is provided with a product outlet, and A device that creates a negative pressure is connected. This equipment is especially suitable for the preparation of monodisperse silicon carbide nanoparticles.

The beneficial effects of the present invention are:

The silicon carbide nanoparticles prepared in the invention are cubic phase silicon carbide, the shape of the particles is monodisperse spherical, and the particle size distribution is very narrow, and the particle size is adjustable from 5 to 300 nanometers. By controlling the gas ratio of the reaction system, pure silicon carbide, silicon-rich or carbon-rich silicon carbide nanoparticles can be obtained. Pure silicon carbide nanoparticles can enrich the application range of existing silicon carbide nanomaterials and can be used as raw materials to reduce the sintering temperature of dense silicon carbide ceramic materials. Carbon-containing or silicon-containing silicon carbide nanoparticles can be used as composite materials to obtain new coupling properties, and use them as templates to prepare carbon-silicon system materials with mesoporous structures. In the present invention, by designing the reactor structure, the silicon carbide nano particle product can be sucked out from the product discharge port on the upper part of the fluidized tube by using negative pressure, so as to realize continuous preparation. The invention has simple technological process, convenient technological operation and low cost, and can realize large-scale production.

Description of drawings

Fig. 1 is the transmission electron micrograph of silicon carbide nanoparticles obtained in Example 1 of the present invention;

Fig. 2 is the XRD spectrogram of silicon carbide nanoparticles obtained in Example 1 of the present invention;

Fig. 3 is the transmission electron micrograph of silicon carbide nanoparticles obtained in Example 2 of the present invention;

Fig. 4 is the scanning electron micrograph of silicon carbide nanoparticles obtained in Example 5 of the present invention;

Fig. 5 is the XRD spectrogram of silicon carbide nanoparticles obtained in Example 5 of the present invention;

Fig. 6 is an XRD spectrum of silicon carbide nanoparticles obtained in Example 7 of the present invention.

detailed description

The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

Example 1

The precursor hexamethyldisilane was heated to 80°C by heating in a water bath, argon was used as the carrier gas, the flow rate of the carrier gas was 0.3L/min, and a mixed gas of hydrogen and argon was used as the fluidizing gas, H The flow rate of ₂ is 1.2L/min, and the flow rate of Ar is 1.5L/min. Heat the fluidized bed reactor to 900°C, add zirconia fluidized particles and feed the carrier gas, and collect the powder through the powder collection system at the top of the reactor. The obtained powder was heat-treated in an argon atmosphere at 1300° C. for 1 hour.

The transmission electron microscope photograph of gained product is as shown in Figure 1, and visible gained product is monodisperse spherical particle, and particle size distribution is very narrow, and the average particle size of product is 120 nanometers, and the XRD spectrogram of product is as shown in Figure 2, by comparing For the standard card, it can be seen that the product is silicon carbide in the cubic phase, and there are no other impurity phases.

Example 2

The precursor hexamethyldisilane was heated to 80°C by heating in a water bath, argon was used as the carrier gas, the flow rate of the carrier gas was 0.1L/min, a mixed gas of hydrogen and argon was used as the fluidizing gas, H The flow rate of ₂ is 1.5L/min, and the flow rate of Ar is 0.9L/min. Heat the fluidized bed reactor to 900°C, add zirconia fluidized particles and feed the carrier gas, and collect the powder through the powder collection system at the top of the reactor. The obtained powder was heat-treated in an argon atmosphere at 1300° C. for 1 hour.

The transmission electron micrograph of the product obtained is shown in Figure 3. It can be seen that the product obtained is a monodisperse spherical particle, and the average particle size of the product is 15 nanometers. The XRD test is carried out on the product. By comparing the standard card product, it is the silicon carbide of the cubic phase, and No other miscellaneous phase.

Example 3

The precursor hexamethyldisilane was heated to 100°C by electric heating, hydrogen was used as the carrier gas, the flow rate of the carrier gas was 2.0L/min, the mixed gas of hydrogen and argon was used as the fluidizing gas, H ₂ The flow rate of Ar is 1.0L/min, and the flow rate of Ar is 1.5L/min. Heat the fluidized bed reactor to 800°C, add metal cobalt fluidized particles and pass through the carrier gas, and collect the powder through the powder collection system at the top of the reactor. The obtained powder was heat-treated in an argon atmosphere at 1400° C. for 2 hours.

The obtained product is monodisperse spherical particles, the particle size distribution is very narrow, and the average particle size of the product is 280 nanometers. The XRD test is carried out on the product, and the standard card product is cubic silicon carbide without other impurities.

Example 4

The precursor hexamethyldisilane was heated to 75°C by electric heating, hydrogen was used as the carrier gas, the flow rate of the carrier gas was 1.0L/min, the mixed gas of hydrogen and argon was used as the fluidizing gas, H ₂ The flow rate of Ar is 1.0L/min, and the flow rate of Ar is 4.0L/min. Heat the fluidized bed reactor to 1100°C, add alumina fluidized particles and pass through the carrier gas, and collect the powder through the powder collection system at the top of the reactor. The obtained powder was heat-treated at 1450° C. for 3 hours in an argon atmosphere.

The obtained product is monodisperse spherical particles, the particle size distribution is very narrow, and the average particle size of the product is 50 nanometers. The product is tested by XRD. By comparing the standard card product, the product is cubic silicon carbide, and there is no other impurity.

Example 5

Heat the precursor hexamethyldisilane to 80°C by heating in a water bath, use argon as the carrier gas, the flow rate of the carrier gas is 0.3L/min, use argon as the fluidizing gas, and the flow rate of Ar is 3.7L /min. Heat the fluidized bed reactor to 1000°C, add zirconia fluidized particles and feed the carrier gas, and collect the powder through the powder collection system at the top of the reactor. The obtained powder was heat-treated in an argon atmosphere at 1300° C. for 1 hour.

The scanning electron microscope photograph of gained product is as shown in Figure 4, and visible gained product is monodisperse spherical particle, and particle size distribution is very narrow, and the average particle size of product is 50 nanometers, and the XRD spectrogram of product is as shown in Figure 5, by comparing For the standard card, it can be seen that the product is cubic silicon carbide and a small amount of carbon, and the mass fraction of carbon is 4.0%.

Example 6

The precursor hexamethyldisilane was heated to 90°C by heating in a water bath, argon was used as the carrier gas, the flow rate of the carrier gas was 0.6L/min, and a mixed gas of hydrogen and argon was used as the fluidizing gas, H The flow rate of ₂ is 1.0L/min, and the flow rate of Ar is 3.4L/min. Heat the fluidized bed reactor to 1250°C, add alumina fluidized particles and pass through the carrier gas, and collect the powder through the powder collection system at the top of the reactor. The obtained powder was heat-treated in an argon atmosphere at 1400° C. for 4 hours.

The obtained product is monodisperse spherical particles, the particle size distribution is very narrow, the average particle size of the product is 30 nanometers, the product is subjected to XRD test, and it can be seen that the product is cubic silicon carbide and a small amount of carbon by comparing the standard card. The mass fraction of carbon is 5.6%.

Example 7

The precursor hexamethyldisilane was heated to 80°C by heating in a water bath, hydrogen was used as the carrier gas, the flow rate of the carrier gas was 2.0L/min, the mixed gas of hydrogen and argon was used as the fluidizing gas, H ₂ The flow rate of Ar is 4.0L/min, and the flow rate of Ar is 0.6L/min. Heat the fluidized bed reactor to 850°C, add metal iron fluidized particles and pass through the carrier gas, and collect the powder through the powder collection system at the top of the reactor. The obtained powder was heat-treated in an argon atmosphere at 1350° C. for 1 hour.

The obtained product is monodisperse spherical particles, the particle size distribution is very narrow, and the average particle size of the product is 150 nanometers. The XRD spectrum of the product is shown in Figure 6. It can be seen that the product is cubic phase silicon carbide by comparing the standard card And a small amount of silicon, the mass fraction of silicon is 3.5%.

Example 8

Heat the precursor hexamethyldisilane to 70°C by heating in a water bath, use argon as the carrier gas, the flow rate of the carrier gas is 0.4L/min, use hydrogen as the fluidization gas, and the flow rate of _H2 is 6.0L /min,. Heat the fluidized bed reactor to 1100°C, add zirconia fluidized particles and feed the carrier gas, and collect the powder through the powder collection system at the top of the reactor. The obtained powder was heat-treated in an argon atmosphere at 1400° C. for 2 hours.

The obtained product is a monodisperse spherical particle with a narrow particle size distribution. The average particle size of the product is 40 nanometers. The XRD test is carried out on the product. By comparing the standard card, it can be seen that the product is cubic silicon carbide and a small amount of silicon. The mass fraction of silicon is 4.8%.

Example 9

The precursor hexamethyldisilane was heated to 90°C by heating in a water bath, argon was used as the carrier gas, the flow rate of the carrier gas was 5.4L/min, and a mixed gas of hydrogen and argon was used as the fluidizing gas, H The flow rate of ₂ is 120.0L/min, and the flow rate of Ar is 50.0L/min. Heat the fluidized bed reactor to 1150°C, add alumina fluidized particles and pass through the carrier gas, and collect the powder through the powder collection system at the top of the reactor. The obtained powder was heat-treated in an argon atmosphere at 1400° C. for 4 hours.

The obtained product is monodisperse spherical particles, the particle size distribution is very narrow, and the average particle size of the product is 35 nanometers. XRD test is carried out on the product, and it can be seen that the product is cubic phase silicon carbide by comparison with the standard card.

Although the present invention has been described in detail with general descriptions and specific embodiments above, it is obvious to those skilled in the art that some modifications or improvements can be made on the basis of the present invention. Therefore, the modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the protection scope of the present invention.

Claims (10)

1. the fluidized-bed chemical vapor deposition preparation method of a nanometer silicon carbide granule, it is characterised in that described preparation method Specifically include following steps:

1) fluidized-bed reactor is heated to uniform temperature, is passed through a certain amount of fluidizing gas simultaneously, and adds a certain amount of lazy Property fluidized particles；

2) heating of precursor material hexamethyldisilane being produced steam, steam enters fluidized-bed reactor by gas carrier band；

3) there is pyrolytic reaction in precursor material steam in fluidized-bed reactor high-temperature region, forms nanometer silicon carbide granule；

4) described nanometer silicon carbide granule is transported to reactor top under the effect of fluidizing gas, by negative pressure device sucking-off, Collection obtains nano-sized SiC powder；

5) gained nano-sized SiC powder is carried out under an argon atmosphere heat treatment, obtain the nanometer silicon carbide of well-crystallized Grain.

Preparation method the most according to claim 1 and 2, it is characterised in that described non-reactive fluidizing granule is in described preparation At a temperature of the granule that do not reacts with described presoma, preferably metal or ceramic particle；More preferably zirconia particles, oxygen Change alumina particles, metallic cobalt granule or iron granule.

Preparation method the most according to claim 1 and 2, it is characterised in that the mode of heating of described precursor be water-bath or Electrical heating, heating-up temperature is 30～110 DEG C.

Preparation method the most according to claim 1 and 2, it is characterised in that described fluidizing gas is hydrogen or argon or two The mixed gas of person；Described carrier band gas is hydrogen or argon；Preferably, described carrier band gas and the volume ratio of fluidizing gas It is 0.1%～50%.

Preparation method the most according to claim 1 and 2, it is characterised in that step 3) described fluidized-bed reactor high-temperature region Temperature is 750～1450 DEG C.

Preparation method the most according to claim 1 and 2, it is characterised in that step 5) described heat treatment temperature be 1300～ 1500 DEG C, heat treatment time is 1～4 hour.

7. according to the preparation method described in any one of claim 1-6, it is characterised in that rate-determining steps 3) in described reaction system Hydrogen is 30%～70% with the ratio of argon, and described fluidized-bed reactor high-temperature region temperature is 750～1300 DEG C, and reaction obtains Pure phase silicon carbide nano-particle；Or

Rate-determining steps 3) ratio of hydrogen and argon is 70% to infinity in described reaction system, described fluidized-bed reactor is high Warm area temperature is 750～1200 DEG C, obtains the nanometer silicon carbide granule of Silicon-rich, and the mass fraction of silicon is 0～8%；Or

Rate-determining steps 3) hydrogen is 0 to 30% with the ratio of argon in described reaction system, high-temperature region reaction temperature be 750～ 1450 DEG C, obtaining the nanometer silicon carbide granule of rich carbon, the mass fraction of carbon is 0～10%.

8. the nanometer silicon carbide granule that prepared by method described in any one of claim 1-7.

Nanometer silicon carbide granule the most according to claim 8, it is characterised in that described nanometer silicon carbide granule is Emission in Cubic Carborundum, grain shape is spherical, and particle size is adjustable in 5～300 nanometers.

10. the fluid bed reaction apparatus being used for preparing nanometer silicon carbide granule, it is characterised in that it is hollow cylindrical tube Body, described its bottom is precursor steam inlet, and body top is provided with product discharge mouth, and connection has the dress that can form negative pressure Put.