CN115636414A - Silicon carbide composite particles with high specific surface area, and preparation method and application thereof - Google Patents

Abstract

The invention discloses a silicon carbide composite particle with high specific surface area, a preparation method and application thereof, wherein the preparation method comprises the following steps: dissolving a metal salt in silica sol, and controlling the molar ratio of metal to silicon element to be 0.1-10; adding starch into the silica sol mixture containing the metal salt, controlling the mass ratio of the starch to the silica sol mixture containing the metal salt to be 20-80, uniformly stirring, heating to boil, and keeping the boiling state for 5-30 minutes to obtain a first mixture; adding starch into the first mixture to enable the total mass of the starch added last time and the starch added this time to reach 0.5-1.5 times of the mass of the silica sol so as to obtain a first mixture; performing vacuum pugging on the first mixture for 3-5 times to obtain precursor pug; drying for 1-5 hours at 50-80 ℃ to obtain a precursor mud blank; and heating the precursor mud blank to 1000-1800 ℃ in an oxygen-free environment and keeping the temperature for 5-20 hours. The invention can directly prepare millimeter-sized particles.

Description

A kind of high specific surface area silicon carbide composite particle and its preparation method and application

technical field

The invention relates to a silicon carbide composite particle with a high specific surface area and a preparation method and application thereof, belonging to the technical field.

Background technique

Silicon carbide is an inorganic ceramic material. At present, silicon carbide in my country is mainly produced by the Acheson method, that is, coke powder and quartz sand are mixed in a certain proportion and heated in an electric arc furnace to above 2000°C to form silicon carbide. The product produced by this method is α-SiC, which is mainly used in the fields of cutting, grinding, metallurgy, high-temperature ceramics, and semiconductors.

Catalyst support is an important class of functional materials and an important part of supported catalysts, which plays a role in supporting and dispersing active components, so it is required to have a relatively high specific surface area. Silicon carbide has the characteristics of stable chemical properties, good electrical and thermal conductivity, etc., and is very suitable as a catalyst carrier. However, the specific surface area of current commercial silicon carbide is very low, generally less than 1 square meter per gram (m ² /g). Therefore, many scholars at home and abroad have proposed many methods for preparing silicon carbide with high specific surface area. For example, French scholars proposed a "shape memory synthesis" method, that is, first reacting silicon powder and silicon oxide at high temperature to produce SiO, and then reacting gas phase SiO with porous carbon to prepare silicon carbide with a specific surface area of about 30m ² /g. Another example, Chinese patent (02130060.7) discloses a method for preparing silicon carbide mesoporous materials with high specific surface area. In this method, phenolic resin, ethyl silicate, etc. are co-hydrolyzed under the action of a catalyst to form a gel, and then in an inert atmosphere Preparation of silicon carbide with high specific surface area under heating gel. For another example, Chinese patent (200710008663.8) discloses a method for synthesizing silicon carbide at low temperature. In this method, sucrose, tetraethyl orthosilicate, etc. are hydrolyzed to form a gel, which is then dried and heated in an inert atmosphere to prepare silicon carbide. For another example, Chinese patent (201110307547.2) discloses a method for preparing β-nano silicon carbide. In this method, starch, water glass and metal nitrate are mixed in a certain proportion, dried and then heated in an inert atmosphere to prepare silicon carbide. Due to the strong alkalinity of water glass in the precursor, the atmosphere furnace is seriously corroded at high temperature. Another example, the Chinese patent (202111037246.2) first hydrothermally treats sucrose, silica sol, etc. at about 200°C, then filters to obtain a carbon-silicon precursor, and then reacts at high temperature to prepare silicon carbide after drying.

However, among the above methods, the shape memory synthesis method requires complex equipment, and the elemental silicon impurities contained in the product are difficult to remove; the sol-gel method consumes a long time when forming a gel and drying the gel; the hydrothermal method has high-pressure equipment, Precursor separation is difficult and other problems. In addition, these methods generally obtain nano- or micron-sized silicon carbide powders, which require high-temperature sintering and molding when used as catalysts or adsorbents.

Therefore, it is necessary to design a silicon carbide composite particle with a high specific surface area that is cheap to make, relatively simple to make, and directly in millimeter order after being made.

Contents of the invention

In order to solve the deficiencies of the prior art, the purpose of the present invention is to provide a silicon carbide composite particle with a high specific surface area and its preparation method and application, which solves the problem in the prior art that the raw material is cheap, the production is relatively simple, and the production is relatively simple. After being formed, it becomes millimeter-scale silicon carbide composite particles with high specific surface area.

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

A method for preparing silicon carbide composite particles with high specific surface area, comprising the steps of:

1) dissolving the metal salt in the silica sol, and controlling the molar ratio of the metal to the silicon element to be 0.1-10:100 to obtain a silica sol mixture containing the metal salt;

2) adding starch to the metal salt-containing silica sol mixture, and controlling the mass ratio of the starch and the metal salt-containing silica sol mixture to 20-80:100, stirring evenly, heating to boiling, and maintaining the boiling state for 5-30 minutes, to obtain the first mixture;

3) adding starch to the first mixture, so that the total mass of the starch added in step 2) and the starch added in step 3) reaches 0.5-1.5 times the mass of the silica sol, to obtain a second mixture;

4) Vacuum refining the second mixture for 3-5 times to obtain the precursor mud;

5) Make the precursor mud into a preset shape with a mold, and dry it at 50-80°C for 1-5 hours to obtain the precursor mud;

6) Precursor mud is placed in an oxygen-free environment and heated to 1000-1800° C. and kept for 5-20 hours to obtain silicon carbide composite particles.

As a preferred solution of the present invention, the metal salt is a soluble salt compound of one of iron, cobalt and nickel.

As a preferred version of the present invention, in step 6), the realization method of anaerobic environment comprises:

Use nitrogen or inert gas to replace the air in the high-temperature furnace cavity; or embed the green body with carbon powder; or put the green body in a sealed container and then put it in a high-temperature furnace for calcination.

As a preferred solution of the present invention, the starch is a starch product obtained from various crops.

In order to solve the above technical problems, the present invention further provides the following technical solutions:

A high specific surface area silicon carbide composite particle.

As a preferred solution of the present invention, the radial size of a single particle is in the range of 1-50 mm;

The specific surface area is in the range of 30-300 m ² /g.

As a preferred version of the present invention, in parts by mass, the particles include:

Silicon carbide 35-100 parts, silicon oxide 0-35 parts, carbon 0-25 parts, metal 0-5 parts.

The present invention also provides an application of high specific surface area silicon carbide composite particles in the preparation of silicon carbide/silicon dioxide composite particles, wherein the high specific surface area silicon carbide composite particles are heated to 500-800 ℃ and kept for 1-3 hours, after cooling, soak in dilute hydrochloric acid for 0.5-2 hours, filter and dry to obtain silicon carbide/silicon oxide composite particles.

The present invention also provides an application of high specific surface area silicon carbide composite particles in the preparation of silicon carbide/carbon composite particles, removing silicon dioxide in the particles according to requirements: obtaining the high specific surface area silicon carbide composite particles The particles are placed in hydrofluoric acid or sodium hydroxide solution, soaked for 0.5-3 hours, filtered and then soaked in dilute hydrochloric acid for 0.5-2 hours, filtered and dried to obtain silicon carbide/carbon composite particles.

The present invention also provides an application of silicon carbide composite particles with high specific surface area in the preparation of silicon carbide particles. The silicon carbide composite particles with high specific surface area are heated to 500-800° C. in an air atmosphere and kept for 1-3 Hours, after cooling, soak in dilute hydrochloric acid for 0.5-2 hours, filter and dry to obtain silicon carbide/silicon oxide composite particles;

Then put the particles obtained from silicon carbide/silicon oxide composite particles in hydrofluoric acid or sodium hydroxide solution, soak for 0.5-3 hours, filter and then soak in dilute hydrochloric acid for 0.5-2 hours, filter and dry to obtain silicon carbide particles.

The beneficial effect that the present invention reaches:

The present invention proposes to use starch and silica sol as carbon source and silicon source respectively, after azeotroping to form a paste, then add starch to form a dough-like object, and then form a ball, strip, and net shape through mechanical extrusion and processing Wait for particles of different shapes, and then react at high temperature to form silicon carbide composite particles with high specific surface area. The diameter of the obtained particles is 1-50 mm, and they are directly millimeter-scale high specific surface area silicon carbide composite particles without secondary treatment. It can be used as a catalyst carrier;

The invention uses starch and silica sol with low price and wide sources as main raw materials, which can significantly reduce the production cost of silicon carbide with high specific surface area;

In the present invention, starch and silica sol are azeotroped under normal pressure, and the starch molecules are crosslinked by boiling, and at the same time, they are uniformly mixed with silica sol, the process is safe, and no complicated equipment is required. The preparation process of the precursor is simple and the product Various shapes, easy industrialization and other advantages;

The invention can be fired into silicon carbide or silicon carbide composite particles in various shapes, which is convenient to be directly used as catalyst carrier, adsorbent and the like.

Detailed ways

The present invention will be further described below. The following examples are only used to illustrate the technical solution of the present invention more clearly, but not to limit the protection scope of the present invention.

Aiming at the problems of complex equipment and long time-consuming preparation of precursors in the current preparation method of silicon carbide with high specific surface area, the present invention provides a method for preparing silicon carbide composite particles with high specific surface area, which includes the following steps:

1) dissolving the metal salt in the silica sol, and controlling the molar ratio of the metal to the silicon element to be 0.1-10:100 to obtain a silica sol mixture containing the metal salt;

2) adding starch to the metal salt-containing silica sol mixture, and controlling the mass ratio of the starch and the metal salt-containing silica sol mixture to 20-80:100, stirring evenly, heating to boiling, and maintaining the boiling state for 5-30 minutes, to obtain the first mixture;

3) adding starch to the first mixture, so that the total mass of the starch added in step 2) and the starch added in step 3) reaches 0.5-1.5 times the mass of the silica sol, to obtain a second mixture;

4) Vacuum refining the second mixture for 3-5 times to obtain the precursor mud;

5) Make the precursor mud into a preset shape with a mold, and dry it at 50-80°C for 1-5 hours to obtain the precursor mud;

6) Precursor mud is placed in an oxygen-free environment and heated to 1000-1800° C. and kept for 5-20 hours to obtain silicon carbide composite particles.

The present invention proposes to use starch and silica sol as carbon source and silicon source respectively, after azeotroping to form a paste, then add starch to form a dough-like object, and then form a ball, strip, and net shape through mechanical extrusion and processing Particles with different shapes, and then reacted at high temperature to form silicon carbide composite particles with high specific surface area. The present invention uses starch and silica sol with low price and wide sources as the main raw materials, which can significantly reduce the production cost of silicon carbide with high specific surface area; in the present invention, starch and silica sol are azeotroped under normal pressure, and the starch is boiled Molecules are cross-linked, and at the same time, they are evenly mixed with silica sol, the process is safe, and no complicated equipment is required. It has the advantages of simple precursor preparation process, various product shapes, and easy industrialization; the invention can be fired into silicon carbide of various shapes. Or silicon carbide composite particles, which are convenient to be directly used as catalyst carrier, adsorbent, etc.

As a preferred solution of the present invention, the metal salt is a soluble salt compound of one of iron, cobalt and nickel.

As a preferred version of the present invention, in step 6), the realization method of anaerobic environment comprises:

Use nitrogen or inert gas to replace the air in the high-temperature furnace cavity; or embed the green body with carbon powder; or put the green body in a sealed container and then put it in a high-temperature furnace for calcination.

As a preferred solution of the present invention, the starch is a starch product obtained from various crops.

In order to solve the above technical problems, the present invention further provides the following technical solutions:

A high specific surface area silicon carbide composite particle.

As a preferred solution of the present invention, the radial size of a single particle is in the range of 1-50 mm;

The specific surface area is in the range of 30-300 m ² /g.

As a preferred version of the present invention, in parts by mass, the particles include:

Silicon carbide 35-100 parts, silicon oxide 0-35 parts, carbon 0-25 parts, metal 0-5 parts.

The present invention also provides an application of high specific surface area silicon carbide composite particles in the preparation of silicon carbide/silicon dioxide composite particles, wherein the high specific surface area silicon carbide composite particles are heated to 500-800 ℃ and kept for 1-3 hours, after cooling, soak in dilute hydrochloric acid for 0.5-2 hours, filter and dry to obtain silicon carbide/silicon oxide composite particles.

The present invention also provides an application of high specific surface area silicon carbide composite particles in the preparation of silicon carbide/carbon composite particles, removing silicon dioxide in the particles according to requirements: obtaining the high specific surface area silicon carbide composite particles The particles are placed in hydrofluoric acid or sodium hydroxide solution, soaked for 0.5-3 hours, filtered and then soaked in dilute hydrochloric acid for 0.5-2 hours, filtered and dried to obtain silicon carbide/carbon composite particles.

The present invention also provides an application of silicon carbide composite particles with high specific surface area in the preparation of silicon carbide particles. The silicon carbide composite particles with high specific surface area are heated to 500-800° C. in an air atmosphere and kept for 1-3 Hours, after cooling, soak in dilute hydrochloric acid for 0.5-2 hours, filter and dry to obtain silicon carbide/silicon oxide composite particles;

Then put the particles obtained from silicon carbide/silicon oxide composite particles in hydrofluoric acid or sodium hydroxide solution, soak for 0.5-3 hours, filter and then soak in dilute hydrochloric acid for 0.5-2 hours, filter and dry to obtain silicon carbide particles.

The commercial silica sol used in the following examples has a silicon dioxide content of 30% and a density of 1.2 g/cm3; the metal salts used are all chemically pure.

Example 1

Weigh 1000 g of silica sol, add 2.42 g of Fe(NO ₃ ) ₃ into it, stir to dissolve completely, then add 200 g of cornstarch, stir evenly, heat to boiling and keep for 15 minutes. After cooling, add 300 grams of cornstarch to it, mix briefly, and use a mud trainer to practice 3 times to obtain the precursor mud. The precursor mud is made into spherical particles with a diameter of 1 mm. After being treated in an oven at 50°C for 4 hours, it is placed in an argon atmosphere furnace and heated to 1000°C for 20 hours. After that, it is naturally lowered to room temperature to obtain silicon carbide. Compound pellets.

Example 2

Weigh 1000 g of silica sol, add 20.20 g of Fe(NO ₃ ) ₃ ·9H ₂ O to it, stir to dissolve completely, then add 400 g of sweet potato starch, stir evenly, heat to boiling and keep for 5 minutes. After cooling, 600 grams of cornstarch was added thereto, mixed briefly and then practiced 5 times with a mud trainer to obtain the precursor mud. The precursor mud is made into a cylinder with a diameter of 4 mm and a height of 5 mm. After being treated in an oven at 60°C for 3 hours, it is placed in a nitrogen atmosphere furnace and heated to 1400°C for 15 hours. After that, it is naturally lowered to room temperature. Cylindrical silicon carbide composite particles were obtained.

For further processing, the above-mentioned cylindrical silicon carbide composite particles were heated to 500°C in an air atmosphere and kept for 3 hours, cooled naturally to room temperature, taken out, soaked in 0.1M hydrochloric acid for 2 hours, filtered out and washed with tap water for 3 hours. After drying or drying for a few times, cylindrical silicon carbide/silicon oxide composite particles are obtained.

Example 3

Weigh 1000 g of silica sol, add 38.03 g of FeCl ₂ into it, stir to dissolve it completely, then add 500 g of tapioca starch, stir evenly, heat to boiling and keep for 5 minutes. After cooling, add 700 grams of ordinary flour to it, mix briefly, and use a mud trainer to practice 4 times to obtain the precursor mud. The precursor mud is made into a ring with an outer diameter of 10 mm, an inner diameter of 4 mm, and a height of 5 mm. After being treated in an oven at 50 ° C for 3 hours, it is placed in an argon atmosphere furnace and heated to 1600 ° C for 10 hours. Naturally lowered to room temperature, the ring-shaped silicon carbide composite particles are obtained.

For further processing, the above-mentioned annular silicon carbide composite particles were placed in 3M NaOH solution, soaked at room temperature for 5 hours, filtered out and then soaked in 0.3M hydrochloric acid for 1 hour, washed with tap water for 3 times after filtering out, and then aired Dried or oven-dried to obtain circular silicon carbide/carbon composite particles.

Example 4

Weigh 1000 grams of silica sol, add 1.86 grams of ferrocene (Fe(C ₅ H ₅ ) ₂ ) to it, stir to dissolve it completely, then add 400 grams of cornstarch, stir well, heat to boiling and keep for 15 minutes . After cooling, add 500 grams of cornstarch to it, mix briefly, and use a mud trainer to practice 3 times to obtain the precursor mud. The precursor mud is made into spherical particles with a diameter of 6 mm. After being treated in an oven at 70°C for 2 hours, it is placed in an argon atmosphere furnace and heated to 1300°C for 10 hours. After that, it is naturally lowered to room temperature to obtain silicon carbide. Compound pellets.

Example 5

Weigh 1000 g of silica sol, add 9.15 g of Co(NO ₃ ) ₂ into it, stir to dissolve it completely, then add 500 g of potato starch, stir evenly, heat to boiling and keep for 10 minutes. After cooling, add 800 grams of ordinary flour to it, mix briefly, and practice 5 times with a mud mill to obtain the precursor mud. The precursor mud is made into a round cake-shaped mesh screen with a diameter of 50 mm, a thickness of 5 mm, and a mesh diameter of 2 mm. After being treated in an oven at 50 ° C for 5 hours, it is heated to 1600 ° C in an argon atmosphere furnace and kept for 15 Hours later, it was naturally lowered to room temperature, and mesh-like silicon carbide composite particles were obtained.

Example 6

Weigh 1000 g of silica sol, add 25.96 g of CoCl ₂ into it, stir to dissolve it completely, then add 200 g of potato starch, stir evenly, heat to boiling and keep for 30 minutes. After cooling, add 800 grams of ordinary flour to it, mix briefly, and practice 5 times with a mud mill to obtain the precursor mud. The precursor mud is made into spherical particles with a diameter of 3 mm, and after being treated in an oven at 80°C for 1 hour, it is placed in a nitrogen atmosphere furnace and heated to 1500°C for 12 hours, and then naturally cooled to room temperature to obtain small spherical particles. Silicon carbide composite particles.

Example 7

Weigh 1000 g of silica sol, add 119.00 g of CoCl ₂ ·6H ₂ O to it, stir to dissolve completely, then add 300 g of tapioca starch, stir evenly, heat to boiling and keep for 25 minutes. After cooling, add 1000 grams of ordinary flour to it, mix briefly, and practice 5 times with a mud mill to obtain the precursor mud. The precursor mud was molded into cylindrical particles with a diameter of 10 mm and a height of 5 mm, and treated in an oven at 80°C for 1 hour. Afterwards, put the cylindrical green body in a container made of corundum and cover it with excess carbon powder, then place it in a high-temperature furnace with the air inlet closed and heat it to 1500°C for 8 hours, then cool it down to room temperature naturally, and sieve out the carbon powder to obtain cylindrical silicon carbide composite particles.

For further processing, the above-mentioned cylindrical silicon carbide composite particles were heated to 600°C in an air atmosphere and kept for 2 hours, cooled to room temperature naturally, taken out, soaked in 0.1M hydrochloric acid for 2 hours, filtered out and washed with tap water for 3 After drying or drying for a few times, cylindrical silicon carbide/silicon oxide composite particles are obtained.

For further processing, the above-mentioned cylindrical silicon carbide/silicon oxide composite particles were placed in 2M NaOH solution, soaked at room temperature for 4 hours, filtered out and then soaked in 1.0M hydrochloric acid for 1 hour, and washed with tap water for 3 hours after filtering out. After drying or drying for a few times, cylindrical silicon carbide particles are obtained.

Example 8

Weigh 1000 g of silica sol, add 5.49 g of Ni(NO ₃ ) ₂ into it, stir to dissolve completely, then add 800 g of cornstarch, stir evenly, heat to boiling and keep for 5 minutes. After cooling, 700 grams of cornstarch was added thereto, and after simple mixing, it was practiced 4 times with a mud trainer to obtain the precursor mud. The precursor mud is made into spherical particles with a diameter of 5 mm by a mold. After being treated in an oven at 70°C for 4 hours, it is placed in an argon atmosphere furnace and heated to 1700°C for 6 hours. After that, it is naturally lowered to room temperature to obtain silicon carbide. Compound pellets.

Example 9

Weigh 1000 g of silica sol, add 29.08 g of Ni(NO ₃ ) ₂ ·6H ₂ O into it, stir to dissolve completely, then add 600 g of cornstarch, stir evenly, heat to boiling and keep for 5 minutes. After cooling, add 600 grams of ordinary flour to it, mix briefly, and practice 5 times with a mud mill to obtain the precursor mud. The precursor mud was made into ring-shaped particles with an outer diameter of 20 mm, an inner diameter of 6 mm, and a height of 7 mm. After being treated in an oven at 70 ° C for 4 hours, it was heated to 1800 ° C in an argon atmosphere furnace and kept for 5 Hours later, it was cooled down to room temperature naturally, and the annular silicon carbide composite particles were obtained.

Example 10

Weigh 1000 g of silica sol, add 25.92 g of NiCl ₂ into it, stir to dissolve it completely, then add 200 g of cornstarch, stir evenly, heat to boiling and keep for 30 minutes. After cooling, add 1000 grams of ordinary flour to it, mix briefly, and practice 5 times with a mud mill to obtain the precursor mud. The precursor mud is made into a circular cake-shaped mesh screen with a diameter of 40 mm, a thickness of 8 mm, and a mesh diameter of 3 mm. After being treated in an oven at 60 ° C for 4 hours, it is heated to 1300 ° C in an argon atmosphere furnace and kept for 20 Hours later, it was naturally lowered to room temperature, and mesh-like silicon carbide composite particles were obtained.

For further processing, the above-mentioned mesh-shaped silicon carbide composite particles were placed in 10% HF solution, soaked at room temperature for 5 hours, filtered out and then soaked in 0.1M hydrochloric acid for 1 hour, washed with tap water for 3 times after filtering out Drying or oven drying can obtain mesh-like silicon carbide/carbon composite particles.

Example 11

Weigh 1000 grams of silica sol, add 2.57 grams of nickel acetylacetonate therein, stir to make it dissolve completely, then add 400 grams of cornstarch, stir evenly, heat to boiling and keep for 5 minutes. After cooling, add 600 grams of ordinary flour to it, mix briefly, and use a mud trainer to practice 4 times to obtain the precursor mud. The precursor mud is made into cylindrical particles with a diameter of 10 mm and a height of 10 mm. After being treated in an oven at 70 ° C for 4 hours, it is placed in an argon atmosphere furnace and heated to 1700 ° C for 6 hours. After that, it is naturally cooled to room temperature , that is, cylindrical silicon carbide composite particles are obtained.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, some improvements and modifications can also be made. It should also be regarded as the protection scope of the present invention.

Claims (10)

1. A preparation method of silicon carbide composite particles with high specific surface area is characterized by comprising the following steps:

1) Dissolving a metal salt in silica sol, and controlling the molar ratio of metal to silicon element to be 0.1-10;

2) Adding starch into the silica sol mixture containing the metal salt, controlling the mass ratio of the starch to the silica sol mixture containing the metal salt to be 20-80, uniformly stirring, heating to boil, and keeping the boiling state for 5-30 minutes to obtain a first mixture;

3) Adding starch into the first mixture, so that the total mass of the starch added in the step 2) and the starch added in the step 3) is 0.5-1.5 times of the mass of the silica sol, and obtaining a second mixture;

4) Performing vacuum pugging on the second mixture for 3-5 times to obtain precursor pug;

5) Making the precursor pug into a preset shape by using a mould, and drying for 1-5 hours at 50-80 ℃ to obtain a precursor pug blank;

6) And heating the precursor mud blank to 1000-1800 ℃ in an oxygen-free environment and keeping the temperature for 5-20 hours to obtain the silicon carbide composite particles.

2. The method of claim 1, wherein the metal salt is a soluble salt compound of one of iron, cobalt and nickel.

3. The method for preparing high surface area silicon carbide composite particles according to claim 1, wherein in step 6), the oxygen-free environment is achieved by a method comprising:

replacing air in the high-temperature furnace cavity with nitrogen or inert gas; or embedding the blank with carbon powder; or placing the blank body in a sealed container and then placing the sealed container in a high-temperature furnace for calcining.

4. The method of preparing high surface area silicon carbide composite particles according to claim 1, wherein the starch is a starch-based product obtained from various agricultural crops.

5. A high specific surface area silicon carbide composite particle produced by the production method according to any one of claims 1 to 4.

6. The high surface area silicon carbide composite particles according to claim 5, wherein the single particles have a radial dimension in the range of 1 to 50 mm;

the specific surface area is between 30 and 300m ² In the range of/g.

7. The high surface area silicon carbide composite particles according to claim 5, wherein the particles comprise, in parts by mass:

35-100 parts of silicon carbide, 0-35 parts of silicon oxide, 0-25 parts of carbon and 0-5 parts of metal.

8. The use of the high surface area silicon carbide composite particles according to claim 5 in the preparation of silicon carbide/silica composite particles, wherein the high surface area silicon carbide composite particles are heated to 500-800 ℃ in an air atmosphere and maintained for 1-3 hours, cooled, then soaked with dilute hydrochloric acid for 0.5-2 hours, filtered and dried to obtain silicon carbide/silica composite particles.

9. Use of high surface area silicon carbide composite particles according to claim 5 in the preparation of silicon carbide/carbon composite particles, wherein the ratio of silica: and placing the particles obtained from the silicon carbide composite particles with high specific surface area in a hydrofluoric acid or sodium hydroxide solution, soaking for 0.5-3 hours, filtering, soaking for 0.5-2 hours by using dilute hydrochloric acid, filtering, and drying to obtain the silicon carbide/carbon composite particles.

10. The use of the high surface area silicon carbide composite particles of claim 5 in the preparation of silicon carbide particles, wherein the high surface area silicon carbide composite particles are heated to 500-800 ℃ in an air atmosphere and maintained for 1-3 hours, cooled, then soaked with dilute hydrochloric acid for 0.5-2 hours, filtered and dried to obtain silicon carbide/silicon oxide composite particles;

then placing the particles obtained from the silicon carbide/silicon oxide compound particles into hydrofluoric acid or sodium hydroxide solution, soaking for 0.5-3 hours, filtering, then soaking for 0.5-2 hours by using dilute hydrochloric acid, filtering and drying to obtain silicon carbide particles.