A method for in-situ combustion synthesis of high-purity nanometer silicon carbide powder

Abstract

The application provides a method for in-situ combustion synthesis of high-purity nanometer silicon carbide powder, and belongs to the technical field of inorganic nanometer material preparation, and comprises the following steps: placing water-soluble saccharide substances, gel monomers, water-soluble solutions of a crosslinking agent and an initiator into ion exchange columns respectively for filtration purification, then mixing the water-soluble saccharide substances, the gel material and high-purity silicon powder to form a sol, further carrying out in-situ gel solidification and pre-carbonization treatment to obtain a Si / C composite material block; carrying out combustion synthesis reaction on the obtained Si / C composite material, grinding the obtained block-shaped product to obtain the high-purity nanometer silicon carbide powder. The high-purity carbon source and the silicon source are fixed by the gel network, the silicon powder is uniformly embedded in the carbon skeleton, uniform dispersion and close combination of the two are realized, and the in-situ combustion synthesis reaction is efficiently promoted. The raw material cost in the application is low, the preparation process is simple, the environment is friendly, and the application is suitable for industrialized large-scale production of high-purity nanometer silicon carbide powder.

Description

Technical Field

[0001] This invention belongs to the field of inorganic nanomaterial preparation technology, specifically relating to a method for in-situ combustion synthesis of high-purity nano-silicon carbide powder. Background Technology

[0002] Silicon carbide (SiC) possesses a series of excellent properties, including high temperature resistance, high strength, high hardness, excellent electrical and thermal conductivity, and good chemical stability. It has irreplaceable application value in high-tech fields such as semiconductor devices, aerospace engine components, new energy vehicle power modules, and high-temperature structural materials. In particular, high-purity nanoscale SiC powder, with its advantages of high purity, high specific surface area, and high activity, is a core raw material for the preparation of key semiconductor components, space mirrors, and aerospace devices.

[0003] Currently, the main methods for preparing high-purity SiC powder include chemical vapor deposition, carbothermal reduction, sol-gel method, and combustion synthesis. Among these methods, carbothermal reduction is widely studied due to its relatively simple process and low cost. However, traditional carbothermal reduction methods suffer from problems such as uneven mixing of carbon and silicon sources, high reaction temperatures, high energy consumption, wide product particle size distribution, and difficulty in controlling purity. Chemical vapor deposition (CVD) can prepare high-purity SiC powder, but its high raw material costs, complex processes, and low production capacity make it difficult to achieve large-scale industrial production. The sol-gel method has advantages such as good mixing uniformity and low reaction temperatures, but existing technologies often use high-valent carbon sources such as resins, and suffer from problems such as low carbon yield, easy product agglomeration, and the harmfulness of organic solvents to humans. Combustion synthesis has fast reaction speed, low energy consumption, and simple process, and the rapid heating and cooling thermodynamics are conducive to the synthesis of nanoparticles, making it suitable for large-scale production. However, traditional SiC powder combustion synthesis methods have strict requirements on the purity, particle size, crystallinity, and dispersibility of the carbon source, requiring high purity, nanoparticle size, amorphous structure, and high dispersibility. Therefore, conventional carbon materials simply cannot achieve the combustion synthesis of high-purity, nanoscale SiC powder.

[0004] Water-soluble sugars, such as sucrose, glucose, and fructose, are naturally renewable materials with advantages such as low cost, easy availability, non-toxicity, easily controllable purity, and stable carbon content. They also contain only C, H, and O elements, without introducing additional impurities. Chinese patents CN115974047A and CN104176725A disclose methods for preparing high-purity, nano-, amorphous carbon materials using water-soluble sugars as a carbon source, achieving high carbon yield and purity. However, these patents are limited to the preparation of carbon materials and do not involve research on combining this carbon source with a silicon source to prepare SiC nanopowders.

[0005] Therefore, it is urgent to break through the bottleneck of key powder materials for high-end equipment such as semiconductors by achieving deep synergy between low-cost water-soluble sugar carbon (high purity, nanoscale, amorphous) and combustion synthesis process (low energy consumption, high efficiency), and then developing a low-cost, large-scale synthesis method for preparing ultra-high purity, nanoscale SiC powder. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention provides a method for in-situ combustion synthesis of high-purity nano-SiC powder. This method uses water-soluble sugars as the carbon source and high-purity silicon powder as the silicon source. A precursor is prepared using sol-gel technology to achieve uniform dispersion and fixation of the carbon and silicon sources. Through pre-carbonization and combustion synthesis, high-purity, nano-sized SiC powder is prepared, solving problems such as high raw material costs, uneven mixing, difficulty in controlling particle size, and low product purity in traditional methods.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for synthesizing high-purity nano-silicon carbide powder by in-situ combustion includes the following steps:

[0009] S1. Raw material pretreatment:

[0010] Aqueous solutions of water-soluble sugars, gel monomers, crosslinking agents, and initiators were placed in ion exchange columns, filtered and purified, and then vacuum dried to obtain pretreated water-soluble sugars, gel monomers, crosslinking agents, and initiators. High-purity silica powder was dried to remove surface-adsorbed water and impurities.

[0011] Optionally, the water-soluble sugar is selected from one or more of sucrose, glucose, fructose, and maltose; the gel monomer is acrylic acid or polyacrylamide; the initiator is N,N'-methylenebisacrylamide or polyethylene glycol; and the initiator is an aqueous solution of hydrogen peroxide and ascorbic acid.

[0012] Optionally, the ion exchange column is selected from at least one of chelating resin columns, cation exchange resin columns, anion exchange resin columns, and mixed bed columns. In embodiments of the present invention, water-soluble sugars, gel monomers, crosslinking agents, and initiators are each prepared into aqueous solutions, and then the aqueous solutions of the above substances are sequentially filtered and purified through a chelating resin column, a cation exchange resin column, an anion exchange resin column, and a mixed bed column. The purpose of filtration and purification is to remove metallic and non-metallic impurities; filtration and purification 1-3 times is sufficient to achieve the target purity.

[0013] Optionally, the high-purity silicon powder has a purity of ≥99.9999% and a particle size of 500nm-5μm; the drying conditions are: drying in a vacuum drying oven at 60℃-100℃ for 2-8 hours.

[0014] S2. Preparation of precursors using the sol-gel method:

[0015] The pretreated water-soluble sugars, gel monomers, and crosslinking agents obtained in S1 were mixed with deionized water and stirred to dissolve, resulting in a mixed aqueous solution. High-purity silicon powder was added to the mixed aqueous solution and stirred to disperse, resulting in a suspension. Stirring was continued and an initiator was added to the suspension. After stirring evenly, the mixture was allowed to stand for in-situ gel solidification reaction to obtain a composite gel precursor containing carbon and silicon sources.

[0016] Optionally, the mass ratio of the water-soluble sugar, gel monomer, crosslinking agent, and deionized water is (50-300):(10-50):(0.3-3):100; the mass ratio of the high-purity silicon powder to the water-soluble sugar is 1:(0.8-1.5); the initiator is a 5-10% hydrogen peroxide aqueous solution and a 2-5% ascorbic acid aqueous solution, both added at 0.1-1.5% of the weight of the mixed aqueous solution; the stirring rate is 100-300 r / min, and the standing time is 0.5-8 h.

[0017] Taking the mass ratio of high-purity silicon powder to water-soluble sugars as an example, if too much high-purity silicon powder is added, it will result in residual silicon in the product; if too little high-purity silicon powder is added, it will result in residual carbon in the product. Additionally, if the amount of gel monomer and / or crosslinking agent added is too small, it will result in incomplete gelation; if too much, it will make it difficult to completely dissolve the water-soluble sugars, gel monomers, and crosslinking agents after mixing.

[0018] In one embodiment of the present invention, pretreated water-soluble sugars, gel monomers, crosslinking agents, and deionized water are mixed at a mass ratio of (50-300):(10-50):(0.3-3):100, and stirred at room temperature until completely dissolved and clarified to obtain a mixed aqueous solution. High-purity silicon powder is added to the mixed aqueous solution, with a mass ratio of high-purity silicon powder to water-soluble sugars of 1:(0.8-1.5). The mixture is mechanically stirred at a rate of 100-300 r / min for 0.5-1 h to ensure that the silicon powder is uniformly dispersed in the solution to obtain a suspension. Stirring continues, and an initiator is added to the suspension. The initiator is a 5-10% hydrogen peroxide aqueous solution and a 2-5% ascorbic acid aqueous solution, each added at 0.1-1.5% of the weight of the mixed aqueous solution. After stirring evenly, the mixture is allowed to stand at room temperature for 0.5-8 h to solidify in situ, forming a composite gel precursor containing carbon and silicon sources.

[0019] S3, Pre-carbonization treatment

[0020] The composite gel precursor obtained from S2 was placed in a high-temperature forced-air drying oven for pre-carbonization treatment to obtain Si / C composite material bulk material.

[0021] Optionally, the pre-carbonization treatment employs continuous heating or stepped heating, with a temperature range of 100-250℃ and a total holding time of 40-100 hours. A preferred stepped heating process includes: holding at 100-120℃ for 18-40 hours to evaporate deionized water from the gel; then holding at 150-180℃ for 12-36 hours to remove volatile organic impurities from the dried gel; and finally holding at 200-250℃ for 10-24 hours to achieve pre-carbonization of the soluble sugars. This invention removes moisture and volatile organic impurities from the gel through pre-carbonization, allowing water-soluble sugars to initially carbonize and form a carbon skeleton. Simultaneously, silicon powder is embedded within and tightly bonded to the carbon skeleton, resulting in a Si / C composite material bulk.

[0022] S4, in-situ combustion synthesis

[0023] The Si / C composite material obtained in S3 was placed in a combustion synthesis reaction apparatus. After evacuation, inert gas was introduced, and titanium powder was ignited by electricity to initiate the combustion synthesis reaction. After the reaction was completed, a blocky product was obtained, which was then ground to obtain the high-purity nano-silicon carbide powder.

[0024] Optionally, the Si / C composite material undergoing in-situ combustion is in bulk form or crushed into particles; the inert gas is high-purity argon or nitrogen, and the gas filling pressure is 0.1-6 MPa; the grinding is carried out in a grinding equipment lined with polytetrafluoroethylene.

[0025] Optionally, the amount of titanium powder used is 0.5-1 wt% of the Si / C composite material.

[0026] The present invention also provides high-purity nano-silicon carbide powder synthesized by the method, with a total impurity content ≤1ppm, silicon carbide purity ≥99.9999%, and particle size that can be continuously controlled in the range of 30-200nm.

[0027] This invention also provides applications of the high-purity nano-silicon carbide powder in the fields of semiconductors, aerospace, and new energy.

[0028] Compared with the prior art, the present invention has the following significant advantages:

[0029] 1. Using water-soluble sugars as a carbon source has significant advantages, effectively meeting the requirements for combustion synthesis of high-purity nano-SiC powder: Water-soluble sugars are widely available, inexpensive, renewable, and environmentally friendly, effectively solving the problems of high cost, environmental pollution, and purification difficulties associated with carbon sources commonly used in current SiC powder preparation processes, such as graphite powder, resin, and tar. Furthermore, water-soluble sugars contain only C, H, and O elements, fundamentally avoiding the introduction of S, P, Cl, and metallic impurities that may be introduced when using traditional carbon sources such as carbon black and graphite. After ion exchange purification, its purity can be further improved. More importantly, the carbon material formed from the conversion of water-soluble sugars possesses high purity, nanoscale, amorphous form, and high dispersibility—key requirements for the combustion synthesis method of preparing high-purity nano-SiC powder, demonstrating a high degree of compatibility between the two.

[0030] 2. Achieving uniform embedding of silicon powder in the carbon skeleton for efficient in-situ reaction: Using sol-gel technology, water-soluble sugars, gel materials, and high-purity silicon powder are uniformly dispersed at the molecular level in an aqueous solution. After gel solidification, a uniform composite gel precursor is formed. The high-purity carbon source and silicon source are fixed through the gel network, and the silicon powder is uniformly embedded in the carbon skeleton, ensuring that the carbon source and silicon source are tightly bonded at the microscale. This solves the problem of incomplete reaction and low product purity caused by uneven carbon-silicon mixing in traditional methods.

[0031] 3. Innovative In-situ Combustion Synthesis Strategy: This invention employs combustion synthesis technology, which boasts advantages such as low energy consumption, short cycle time, and simple process equipment. Combustion synthesis is performed on Si / C composite blocks formed by silicon powder uniformly embedded within a carbon framework, or on broken powder, achieving in-situ synthesis and transformation at the molecular scale. The in-situ combustion synthesis process is carried out under ultra-rapid heating / cooling conditions, effectively increasing the SiC nucleation rate and inhibiting crystal growth. Utilizing non-equilibrium reaction thermodynamics, the formation of SiC nanoparticles is significantly promoted. Simultaneously, the high-temperature self-cleaning effect generated during combustion further removes low-melting-point impurities such as S, P, and Cl, achieving deep purification of the product and thus facilitating the acquisition of high-purity nano-SiC powder.

[0032] 4. High purity, nanoscale size, and controllable particle size of SiC products: High-purity raw materials undergo pretreatment processes such as ion exchange to deeply remove impurities. Furthermore, the self-cleaning effect of combustion synthesis further purifies the SiC products, ensuring high purity. Water-soluble sugars can be combusted to generate nanoscale carbon particles, and the SiC particles synthesized in situ using these carbon particles as reaction sites also possess nanoscale characteristics. Simultaneously, the in-situ combustion synthesis process effectively improves the nucleation rate and suppresses the growth rate, further achieving nanoscale SiC particle size and ensuring the nanoscale particle size of the SiC products. Precise control of the SiC powder particle size can be achieved through the regulation of the Si / C precursor preparation process and the combustion synthesis process. The synthesized SiC powder products have a total impurity content of less than 1 ppm, a silicon carbide purity exceeding 99.9999%, and a continuously controllable particle size within the range of 30-200 nm. They exhibit a complete crystal structure and excellent physicochemical properties, meeting the requirements of high-end fields such as semiconductors and aerospace.

[0033] 5. The raw materials used are low-cost, the process is simple, environmentally friendly, and suitable for large-scale industrial production: the carbon and silicon sources are inexpensive and widely available; the gel materials and sugars are both environmentally friendly materials; the in-situ combustion synthesis process has low energy consumption, short cycle, simple equipment, and easy operation, making it suitable for large-scale industrial production. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a partial photograph of the Si / C composite material block obtained after pre-carbonization in Example 1 of the present invention;

[0036] Figure 2 This is a photograph of the pre-carbonized Si / C composite material block (partial) in Example 1 of the present invention after in-situ combustion synthesis;

[0037] Figure 3 The image shows the XRD pattern of SiC nanopowder in Example 1 of this invention.

[0038] Figure 4 This is a SEM image of the SiC nanoparticles in Example 1 of the present invention. Detailed Implementation

[0039] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0040] Example 1

[0041] (1) Analytical grade anhydrous glucose was selected as the carbon source and prepared into an aqueous solution. The solution was then filtered three times through an ion exchange column consisting of a chelating resin column, a cation exchange resin column, an anion exchange resin column, and a mixed bed column. Polyacrylamide was selected as the gel monomer, N,N'-methylenebisacrylamide as the crosslinking agent, and hydrogen peroxide and ascorbic acid aqueous solution as the initiator. The solution was prepared into an aqueous solution and then filtered twice through an ion exchange column consisting of the same type of chelating resin column, a cation exchange resin column, an anion exchange resin column, and a mixed bed column. High-purity silica powder with a purity of 99.99993% and a particle size of 3μm was selected and dried in a vacuum drying oven at 80℃ for 6h.

[0042] (2) Prepare a mixed aqueous solution by mixing 150g of water-soluble sugar, 30g of gel monomer, 1.2g of crosslinking agent and 100g of deionized water. Stir at room temperature until completely dissolved and clear. Add 136g of high-purity silica powder to the mixed aqueous solution and mechanically stir at 300r / min for 0.6h to obtain a suspension. Continue stirring and add 0.5g of 5% hydrogen peroxide aqueous solution and 0.5g of 3% ascorbic acid aqueous solution to the suspension. Stir evenly and let stand at room temperature for 3h to solidify the gel.

[0043] (3) The cured precursor was placed in a high-temperature forced-air drying oven and kept at 110℃ for 20h, 150℃ for 15h, and 220℃ for 10h to obtain Si / C composite material blocks. The overall color was grayish-black (silicon powder / carbon powder color), and its morphology was as follows: Figure 1 As shown.

[0044] (4) The pre-carbonized Si / C composite material block was placed in a combustion synthesis reaction apparatus. After evacuation, high-purity nitrogen gas at 4 MPa was introduced, and 2g of titanium powder was ignited to initiate the combustion synthesis reaction. After the reaction, a light green (silicon carbide color) block product was obtained, with the following morphology. Figure 2 As shown in Table 1, SiC powder was obtained by grinding in a ball mill lined with polytetrafluoroethylene. The powder composition analysis results are shown in Table 1, and the purity of the powder is 99.99994%.

[0045] Table 1 GDMS results of SiC nanopowder

[0046]

[0047] Figure 3 The XRD pattern of the powder shows that it is pure β-phase SiC with good crystallinity. Figure 4 The SEM image of the powder shows that the SiC particles are spherical with good uniformity and a particle size of about 105 nm.

[0048] Example 2

[0049] (1) Analytical pure sucrose was selected as the carbon source and prepared into an aqueous solution. It was then filtered four times through an ion exchange column consisting of a chelating resin column, a cation exchange resin column, an anion exchange resin column, and a mixed bed column. Acrylamide was selected as the gel monomer, N,N'-methylenebisacrylamide as the crosslinking agent, and hydrogen peroxide and ascorbic acid aqueous solution as the initiator. It was prepared into an aqueous solution and filtered three times through the same type of ion exchange column. High-purity silica powder with a purity of 99.99996% and a particle size of 0.8 μm was selected and dried in a vacuum drying oven at 80℃ for 4 hours.

[0050] (2) Prepare a mixed aqueous solution by mixing 120g of water-soluble sugar, 25g of gel monomer, 1.1g of crosslinking agent and 100g of deionized water. Stir at room temperature until completely dissolved and clear. Add 100g of high-purity silica powder to the mixed aqueous solution and mechanically stir at 250r / min for 1h to obtain a suspension. Continue stirring and add 1g of 6% hydrogen peroxide aqueous solution and 1g of 2% ascorbic acid aqueous solution to the suspension. Stir evenly and let stand at room temperature for 5h to solidify the gel.

[0051] (3) The cured precursor was placed in a high-temperature drying oven and kept at 100℃ for 25h, 160℃ for 18h, and 240℃ for 12h to obtain Si / C composite material blocks.

[0052] (4) The pre-carbonized Si / C composite material block was crushed into particles and placed in a combustion synthesis reaction apparatus. After evacuation, 1.2 MPa of high-purity argon gas was introduced, and 3g of titanium powder was ignited to initiate the combustion synthesis reaction. After the reaction was completed, the product was placed in a ball mill lined with polytetrafluoroethylene and ground to obtain SiC powder.

[0053] The powder was tested and found to have a purity of 99.99992%; the phase was pure β-phase SiC; the SiC particles had a spherical morphology, good uniformity, and a particle size of approximately 95 nm.

[0054] Example 3

[0055] (1) Analytical grade glucose monohydrate was selected as the carbon source and prepared into an aqueous solution. It was then filtered three times through an ion exchange column consisting of a chelating resin column, a cation exchange resin column, an anion exchange resin column, and a mixed bed column. Polyacrylamide was selected as the gel monomer, polyethylene glycol as the crosslinking agent, and hydrogen peroxide and ascorbic acid aqueous solution as the initiator. It was then prepared into an aqueous solution and filtered three times through the same type of ion exchange column. High-purity silica powder with a purity of 99.99996% and a particle size of 1.5 μm was selected and dried in a vacuum drying oven at 60℃ for 5 h.

[0056] (2) Prepare a mixed aqueous solution by weight ratio of 80g water-soluble sugar, 20g gel monomer, 0.8g crosslinking agent, and 100g deionized water. Stir at room temperature until completely dissolved and clear. Add 88g high-purity silica powder to the mixed aqueous solution and mechanically stir at 280r / min for 0.8h to obtain a suspension. Continue stirring and add an initiator to the suspension. Continue stirring and add 0.8g of 8% hydrogen peroxide aqueous solution and 0.8g of 5% ascorbic acid aqueous solution to the suspension. Stir evenly and let stand at room temperature for 8h to solidify the gel.

[0057] (3) The cured precursor was placed in a high-temperature forced-air drying oven and kept at 120℃ for 27h, 170℃ for 16h, and 210℃ for 11h to obtain Si / C composite material blocks. The pre-carbonized Si / C composite material blocks were placed in a combustion synthesis reaction apparatus, evacuated, and then filled with 6MPa of high-purity nitrogen. 2g of titanium powder was ignited to initiate the combustion synthesis reaction. After the reaction was completed, the product was placed in a ball mill lined with polytetrafluoroethylene and ground to obtain SiC powder.

[0058] The powder was tested and found to have a purity of 99.99993%; the phase was pure β-phase SiC; the SiC particles had a spherical morphology, good uniformity, and a particle size of approximately 85 nm.

[0059] Comparative Example 1

[0060] (1) Analytical grade anhydrous glucose was selected as the carbon source; polyacrylamide was selected as the gel monomer, N,N'-methylenebisacrylamide as the crosslinking agent, and hydrogen peroxide and ascorbic acid aqueous solution as the initiator; high-purity silica powder with a purity of 99.99993% and a particle size of 3μm was selected and dried in a vacuum drying oven at 80℃ for 6h.

[0061] Steps (2) to (4) are the same as in Example 1.

[0062] The powder was tested and found to have a purity of 99.98%, which is three orders of magnitude lower than that of products prepared by ion exchange column purification. This indicates that it is difficult to synthesize ultra-high purity SiC products for semiconductors using low-purity raw materials that have not been purified by ion exchange column. The phase is pure β-phase SiC. The SiC particles have a near-spherical morphology, good uniformity, and a particle size of about 102 nm.

[0063] Comparative Example 2

[0064] Step (1) is the same as in Example 1.

[0065] (2) Prepare a mixed aqueous solution by mixing 80g of water-soluble sugar, 20g of gel monomer, 0.8g of crosslinking agent and 100g of deionized water. Stir at room temperature until completely dissolved and clear. Add 136g of high-purity silica powder to the mixed aqueous solution and mechanically stir at 300r / min for 0.6h to obtain a suspension. Continue stirring and add 0.5g of 5% hydrogen peroxide aqueous solution and 0.5g of 3% ascorbic acid aqueous solution to the suspension. Stir evenly and let stand at room temperature for 3h to solidify the gel.

[0066] Steps (3) to (4) are the same as in Example 1.

[0067] Testing revealed that the powder had a purity of 99.99992%. In addition to β-phase SiC, the product also contained some unreacted residual Si particles. This indicates that reducing the amount of water-soluble sugar resulted in insufficient carbon source, preventing the silicon powder from fully reacting. The SiC particles had a near-spherical morphology and a particle size of approximately 101 nm.

[0068] Comparative Example 3

[0069] Steps (1) to (2) are the same as in Example 1.

[0070] (3) The cured precursor was placed in a high-temperature drying oven, heated to 220°C, and kept at that temperature for 10 hours to obtain Si / C composite material blocks.

[0071] Step (4) is the same as in Example 1.

[0072] The powder was tested and found to have a purity of 99.99972%, which is one order of magnitude lower than the product prepared by step-heating pre-carbonization. This indicates that the step-heating pre-carbonization process is beneficial for removing trace impurities from the raw materials. The phase is pure β-phase SiC. The SiC particles have a near-spherical morphology, good uniformity, and a particle size of approximately 99 nm.

[0073] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for in-situ combustion synthesis of high-purity nano-silicon carbide powder, characterized in that, Includes the following steps: S1. Raw material pretreatment: The aqueous solutions of water-soluble sugars, gel monomers, crosslinking agents and initiators are placed in ion exchange columns for filtration and purification, followed by vacuum drying; the high-purity silicon powder is dried to remove surface-adsorbed water and impurities. S2. Preparation of precursor by sol-gel method: The pretreated water-soluble sugars, gel monomers, crosslinking agents obtained in S1 are mixed with deionized water and stirred to dissolve to obtain a mixed aqueous solution; high-purity silicon powder is added to the mixed aqueous solution and stirred to disperse to obtain a suspension; stirring is continued and an initiator is added to the suspension, and after stirring evenly, it is allowed to stand for in-situ gel solidification reaction to obtain a composite gel precursor containing carbon source and silicon source; S3. Pre-carbonization treatment: The composite gel precursor obtained in S2 is placed in a high-temperature forced-air drying oven for pre-carbonization treatment to obtain Si / C composite material bulk. S4. In-situ combustion synthesis: The Si / C composite material obtained in S3 is placed in a combustion synthesis reaction apparatus, vacuumed and then filled with inert gas. Titanium powder is ignited by electricity to initiate the combustion synthesis reaction. After the reaction is completed, a blocky product is obtained, which is then ground to obtain the high-purity nano-silicon carbide powder. In step S1, the high-purity silicon powder has a purity ≥99.9999% and a particle size of 500nm-5μm; the drying conditions are: drying in a vacuum drying oven at 60℃-100℃ for 2-8 hours; In step S2, the mass ratio of the water-soluble sugar, gel monomer, crosslinking agent, and deionized water is (50-300):(10-50):(0.3-3):100; the mass ratio of the high-purity silicon powder to the water-soluble sugar is 1:(0.8-1.5); the initiator is a 5-10% hydrogen peroxide aqueous solution and a 2-5% ascorbic acid aqueous solution, both added at 0.1-1.5% of the weight of the mixed aqueous solution.

2. The method for in-situ combustion synthesis of high-purity nano-silicon carbide powder according to claim 1, characterized in that, In step S1, the water-soluble sugar is selected from one or more of sucrose, glucose, fructose, and maltose; the gel monomer is acrylic acid or polyacrylamide; the initiator is N,N'-methylenebisacrylamide or polyethylene glycol; and the initiator is an aqueous solution of hydrogen peroxide and ascorbic acid.

3. The method for in-situ combustion synthesis of high-purity nano-silicon carbide powder according to claim 1, characterized in that, In step S1, the ion exchange column is selected from at least one of chelating resin column, cation resin column, anion resin column and mixed bed column.

4. The method for in-situ combustion synthesis of high-purity nano-silicon carbide powder according to claim 1, characterized in that, In step S2, the stirring rate is 100-300 r / min and the settling time is 0.5-8 h.

5. The method for in-situ combustion synthesis of high-purity nano-silicon carbide powder according to claim 1, characterized in that, In step S3, the pre-carbonization treatment adopts a continuous heating or stepped heating method, with a temperature range of 100-250℃ and a total holding time of 40-100h.

6. The method for in-situ combustion synthesis of high-purity nano-silicon carbide powder according to claim 5, characterized in that, In step S3, the stepped heating process includes: holding at 100-120℃ for 18-40 hours, then holding at 150-180℃ for 12-36 hours, and finally holding at 200-250℃ for 10-24 hours.

7. The method for in-situ combustion synthesis of high-purity nano-silicon carbide powder according to claim 1, characterized in that, In step S3, the Si / C composite material undergoing in-situ combustion is either a block or crushed into particles; the inert gas is high-purity argon or nitrogen, and the gas filling pressure is 0.1-6 MPa; the grinding is carried out in a grinding equipment lined with polytetrafluoroethylene. And / or, the amount of titanium powder used is 0.5-1 wt% of the Si / C composite material.

8. The high-purity nano-silicon carbide powder synthesized by the method according to any one of claims 1 to 7, characterized in that, The total impurity content of the silicon carbide powder is ≤1ppm, the purity of silicon carbide is ≥99.9999%, and the particle size can be continuously adjusted within the range of 30-200nm.

9. The application of the high-purity nano-silicon carbide powder according to claim 8, wherein the application includes applications in the fields of semiconductors, aerospace, or new energy.

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