Method for synthesizing carbon-silicon and carbon-boron powder by using carbon source

Abstract

The invention belongs to the technical field of powder material preparation, and particularly relates to a method for synthesizing carbon-silicon and carbon-boron powder by using a carbon source. The heavy component mixture generated in the boron isotope separation process through a chemical exchange method is used as a novel carbon source, the problems that a traditional carbon source is high in cost and complex in technology are solved by optimizing the raw material ratio, the calcination technology and post-treatment parameters, industrial waste resource utilization is achieved, and meanwhile powder with the excellent structure and performance is prepared. The boron isotope separation heavy component mixture is used as a carbon source for the first time, waste is turned into wealth, the cost is reduced, industrial waste discharge is reduced, and the method conforms to the green chemistry concept. The invention provides an efficient, environment-friendly and controllable carbon silicon / carbon boron powder synthesis method through raw material innovation and process optimization, and has remarkable economic value and technical advantages.

Description

Technical Field

[0001] This invention belongs to the field of powder material preparation technology, specifically relating to a method for synthesizing carbon silicon and carbon boron powders using a mixture of heavy components generated by boron isotope separation via chemical exchange as a carbon source. Background Technology

[0002] Silicon carbide and boron carbide powders possess excellent properties such as high hardness, high strength, high temperature resistance, and chemical stability, making them valuable for applications in high-end fields such as aerospace (e.g., high-temperature coatings), electronic devices (e.g., semiconductor substrates), and the nuclear industry (e.g., neutron shielding materials). Especially when isotopically enriched boron or silicon is incorporated into the materials (e.g., boron-10 enriched boron carbide used in nuclear reactor control rods, and silicon-28 enriched silicon carbide used in quantum devices), their physicochemical properties (e.g., neutron absorption cross-section, thermal conductivity, and electrical properties) can be further optimized to meet the functional requirements of specific applications.

[0003] Traditional preparation of silicon-carbon and boron-carbon powders faces two major technical bottlenecks: 1) Carbon source cost and environmental issues: Traditional carbon sources (such as high-purity graphite and resin) are expensive, and some preparation processes (such as chemical vapor deposition) require the use of toxic precursors (such as chlorosilanes), posing a risk of environmental pollution. At the same time, the heavy component mixture (containing organic matter such as anisole and phenol) generated during the chemical exchange method for boron isotope separation is classified as hazardous waste due to its toxicity and flammability. Direct incineration or landfilling would not only waste carbon resources but also potentially cause soil and water pollution.

[0004] 2) Limitations of isotope-enriched material preparation: In existing technologies, isotope-enriched carbon-silicon and carbon-boron powders typically rely on the reaction of high-purity isotope elements (such as boron-11 / 10 enriched powder and silicon-29 enriched silicon powder) with traditional carbon sources, resulting in extremely high raw material costs. Furthermore, the uniformity of isotope distribution during the reaction process is difficult to control, easily leading to fluctuations in material performance. In addition, research on the resource utilization of isotope separation byproducts (such as the mixture of heavy components after boron isotope separation) is lacking, and an effective technical pathway for converting hazardous waste into isotope powder carbon sources has not yet been established.

[0005] In recent years, with the increasing demand for isotope-enriched powders in fields such as nuclear technology and quantum electronics, how to prepare high-performance powders using isotope separation byproducts in a low-cost and environmentally friendly manner has become a research hotspot in the materials field. Currently, there is no scheme to use a mixture of boron isotope-separated heavy components as a carbon source to prepare powders in combination with isotope-enriched boron / silicon raw materials. Therefore, there is an urgent need to develop novel processes that balance hazardous waste resource utilization with low-cost isotope material preparation. Summary of the Invention

[0006] The purpose of this invention is to propose a method for the efficient synthesis of carbon silicon and carbon boron powders. The method utilizes a mixture of heavy components generated during the separation of boron isotopes by chemical exchange as a novel carbon source. By optimizing the raw material ratio, calcination process and post-processing parameters, the method solves the problems of high cost and complex process of traditional carbon sources, realizes the resource utilization of industrial waste, and prepares powders with excellent structure and performance.

[0007] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution: A method for synthesizing silicon-carbon and boron-carbon powders using a carbon source includes the following steps: 1) Raw material preparation: The heavy component mixture produced by the chemical exchange method for boron isotope separation is used as a carbon source and filtered; Prepare a silicon source or a boron source; prepare a deoxidizing agent, wherein the deoxidizing agent is a metal elemental powder or gas; 2) Mixing: Mix the carbon source and silicon source or boron source from step 1) in a certain proportion to obtain a mixed product; 3) Low-temperature calcination: The mixed product from step 2) is subjected to low-temperature calcination reaction in air or oxygen / nitrogen mixed atmosphere to obtain low-temperature calcination intermediate product; 4) High-temperature reduction calcination: The metal element powder deoxidizing reducing agent in step 1) is mixed with the low-temperature calcination intermediate product in step 3) in a certain proportion and then subjected to gradient high-temperature calcination; or the low-temperature calcination intermediate product in step 3) is subjected to gradient high-temperature calcination under the condition of gaseous deoxidizing reducing agent. 5) Post-processing: After cooling the calcined product from step 4) to room temperature, it is subjected to grinding, acid washing, water washing and drying in sequence to obtain silicon carbon and boron carbon powder.

[0008] Specifically, in step 1), the heavy component mixture includes one or more of anisole, phenol, methyl anisole, and methyl phenol.

[0009] Preferably, in order to control the content of carbon and oxygen atoms in the mixture, the heavy component mixture is composed of anisole, phenol, methyl anisole and methyl phenol, wherein the mass fraction of each component is: anisole 10%~50%, phenol 10%~50%, methyl anisole 1%~20%, and methyl phenol 1%~20%.

[0010] Specifically, in step 1), the silicon source is nano-silicon powder or silicon-28 enriched nano-silicon powder.

[0011] Specifically, in step 1), the boron source is boric acid or boron-10 enriched boric acid.

[0012] Specifically, in step 1), the silicon source material or boron source material is in a natural abundance or isotope enriched form.

[0013] Specifically, in step 1), the deoxidizing reducing agent is at least one elemental metal powder selected from magnesium, lithium, sodium, calcium, aluminum, and zinc, or at least one gas selected from hydrogen, carbon monoxide, and ammonia.

[0014] Preferably, in order to increase the contact area between the raw materials, the particle size of the metal element powder is less than 100 mesh, the particle size of the nano-silicon powder is 50~200 nm, the purity of the boric acid is ≥99%, and the filtration accuracy of the heavy component mixture is 5~10 μm.

[0015] Specifically, in step 2), in order to ensure that silicon and carbon react fully to form the SiC main phase and retain an appropriate amount of carbon to regulate the microstructure, the C:Si molar ratio of the carbon source to the silicon source is 1.2~2.5:1, preferably 1.8~2.2:1.

[0016] Specifically, in step 2), in order to generate B4C and B by controlling the boron-carbon ratio... 12 The C:B molar ratio of the carbon source to the boron source is 2~5:1, preferably 3~4:1, and is a boron-doped carbon-based structure such as C3.

[0017] Preferably, in step 2), in order to better mix the raw materials, the mixing step adopts ball milling or stirring mixing. The ball milling speed is 200~300 r / min and the mixing time is 2~3h; the stirring mixing speed is 500~600 r / min and the mixing time is 1~2h. During the mixing process, the ambient temperature is controlled at 20~30℃.

[0018] Specifically, in step 3), a gradient heating method is used during low-temperature calcination.

[0019] Specifically, in step 3), the reaction temperature during low-temperature calcination is 100~500℃.

[0020] Preferably, in step 3), in order to promote the complete carbonization of each component in the mixture and form an ordered porous structure with boron or silicon, so that free carbon is oxidized and removed, the gradient heating of the low-temperature calcination is as follows: the first stage is heated to 100~150℃ and held for 1.5~2 h at a heating rate of 3-6℃ / min; the second stage is heated to 150~200℃ and held for 2.5-3 h at a heating rate of 3-6℃ / min; the third stage is heated to 200~500℃ and held for 3.5-4 h at a heating rate of 3-6℃ / min.

[0021] Preferably, in step 3), the low-temperature calcination is carried out in an oxygen / nitrogen mixed atmosphere or in an air atmosphere, wherein the oxygen concentration (volume fraction) of the oxygen / nitrogen mixed atmosphere is 5%~20%, and the process in an air atmosphere is an open reaction.

[0022] Specifically, in step 4), when the deoxidizing agent is a metallic elemental powder, under argon protection, the deoxidizing agent is added to the low-temperature calcination intermediate product of step 3), ball-milled or stirred, and then transferred to a tube furnace for gradient high-temperature calcination under an argon atmosphere. When the deoxidizing reducing agent is gaseous, the low-temperature calcination intermediate product is ground and then transferred to a tube furnace for gradient high-temperature calcination in an atmosphere of gaseous deoxidizing reducing agent and / or argon.

[0023] Specifically, in step 4), the gradient high-temperature calcination is performed by first holding the temperature at 600~900℃ for 1-6 hours, and then raising the temperature to 1000~2000℃ and holding it for 1-6 hours.

[0024] Preferably, in step 4), in order to reduce the boron or silicon oxides generated during the low-temperature calcination process to boron or silicon elemental and promote their better reaction with carbon; during the high-temperature reduction calcination process, the mass ratio of the metal elemental powder deoxidizing reducing agent to the low-temperature calcination intermediate product is 1:5~1:20; the volume ratio of the gaseous deoxidizing reducing agent to argon is 1:10~1:50, and the total gas flow rate is controlled at 10~100 mL / min; the heating rate of the gradient high-temperature calcination is 5~20℃ / min.

[0025] Preferably, in step 5), in order to remove impurities from the product, the post-treatment step involves acid washing with a hydrochloric acid or sulfuric acid solution with a mass fraction of 5% to 20%, an acid washing temperature of 50 to 80°C, and an acid washing time of 1 to 3 hours; after washing with water until neutral, the drying temperature is 80 to 120°C, and the drying time is 6 to 12 hours.

[0026] Furthermore, based on a general inventive concept, the present invention also provides silicon carbide powder or boron carbide powder prepared by the above method.

[0027] The silicon carbide powder prepared by this invention can be used as an abrasive raw material; after sintering, it can be made into silicon carbide ceramics for structural parts in high temperature, high pressure and strong corrosion environments; it can also be used as a reinforcing phase of composite materials and refractory and heat-insulating materials.

[0028] The carbon boron powder prepared by this invention can be molded and sintered to make shielding plates and shielding containers for use in the nuclear industry and medical fields, and is a good neutron shielding material; after sintering, it can be made into high-temperature furnace components (such as thermocouple protection tubes), rocket engine nozzles (resistant to high-temperature gas erosion), and high-temperature crucibles in the metallurgical industry (for melting precious metals); it can be made into wear-resistant parts or bulletproof products; it can also be used as abrasive and polishing materials as well as reinforcement for composite materials.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Raw material innovation: This invention is the first to use a mixture of boron isotope-separated and recombined components as a carbon source, turning waste into treasure, reducing costs and industrial waste emissions, which is in line with the concept of green chemistry. 2. Process optimization: In this invention, low-temperature segmented calcination precisely controls the carbon source decomposition process, avoiding component loss caused by local overheating; In the high-temperature reduction stage, the carbon-silicon / boron bonding structure in the powder is directionally controlled by adjusting the ratio of reducing agent, gas flow rate and heating rate, thereby improving the density and stability of the material. Post-processing parameter optimization effectively removes impurities, ensuring material purity and uniformity. 3. Wide range of applications: The raw materials can be selected in the form of isotope enrichment, and the prepared powders are suitable for high-end fields with special requirements for isotope composition, such as nuclear industry, electronic devices, and special ceramics, thus broadening the application scenarios of materials. This invention provides an efficient, environmentally friendly, and controllable method for synthesizing silicon-carbon / boron-carbon powders through raw material innovation and process optimization, which has significant economic value and technological advantages. Detailed Implementation

[0030] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] In the following examples, room temperature refers to 25±5℃.

[0032] Example 1 A method for synthesizing silicon carbide powder using a carbon source, the specific steps of which are as follows: 1) Raw material preparation: The heavy component mixture separated by boron isotope separation by chemical exchange method (including the following components by mass fraction: 30% anisole, 30% phenol, 21% methyl anisole, and 19% methyl phenol) was filtered through diatomaceous earth (filtration accuracy 5 μm); the heavy component mixture was obtained by referring to the method in reference CN118681406A; Prepare nano-silicon powder (particle size 100 nm, natural abundance); prepare deoxidizing reducing agent, specifically magnesium powder (particle size <100 mesh). 2) Mixing: The heavy component mixture from step 1) was mixed with nano-silicon powder at a C:Si molar ratio of 1.8:1 using ball milling. The ball milling speed was 300 r / min, the time was 2 h, and the ambient temperature was 25℃. 3) Low-temperature calcination: The mixed product from step 2) is placed in a tube furnace and subjected to gradient heating in an oxygen / nitrogen mixed atmosphere (oxygen concentration (volume fraction) 10%): First stage: heating to 120℃, holding for 2 h, heating rate 5℃ / min; Second stage: heating to 180℃, holding for 3 h, heating rate 5℃ / min; Third stage: heating to 300℃, holding for 4 h, heating rate 5℃ / min, thereby achieving low-temperature calcination; 4) High-temperature reduction calcination: Under argon protection, the magnesium powder from step 1) and the low-temperature calcination product from step 3) are mixed at a mass ratio of 1:10 and ground in a planetary ball mill for 30 min; then transferred to a tube furnace for high-temperature calcination under an argon atmosphere, specifically with gradient heating: first stage: 600℃ for 3 h, heating rate 10℃ / min; second stage: 1500℃ for 2 h, heating rate 10℃ / min. 5) Post-processing: After cooling the calcined product from step 4) to room temperature, grind it, then acid wash it with a 10% hydrochloric acid solution at 60°C for 2 h, then wash it with water until neutral, and dry it at 100°C for 10 h to obtain silicon carbide powder with a yield of 83% (based on silicon).

[0033] The product obtained in Example 1 (mass fraction) contains SiC: 99.55%, C: 0.05%, Si: 0.05%, SiO2: 0.13%, Fe2O3: 0.04%, other metallic impurities: 0.18%, and powder particle size: D50 < 0.4 μm.

[0034] Example 2 A method for synthesizing silicon carbide powder using a carbon source, the specific steps of which are as follows: 1) Raw material preparation: The heavy component mixture separated by boron isotope separation by chemical exchange method (including the following components by mass fraction: 50% anisole, 10% phenol, 10% methyl anisole, and 30% methyl phenol) is filtered through diatomaceous earth (filtration accuracy 8μm); the heavy component mixture is obtained by referring to the method in reference CN118681406A; Prepare nano-silicon powder (particle size 150 nm, natural abundance); prepare a deoxygenating reducing agent, specifically carbon monoxide gas; 2) Mixing step: The heavy component mixture from step 1) is mixed with nano-silicon powder at a C:Si molar ratio of 2.5:1 by stirring. The stirring speed is 500 r / min, the time is 1.5 h, and the ambient temperature is 22℃. 3) Low-temperature calcination: The mixed product from step 2) is placed in a tube furnace and subjected to gradient heating in an oxygen / nitrogen mixed atmosphere (oxygen concentration (volume fraction) 15%): First stage: heating to 130℃, holding for 1.5 h, heating rate 4℃ / min; Second stage: heating to 170℃, holding for 2.5 h, heating rate 4℃ / min; Third stage: heating to 350℃, holding for 4 h, heating rate 4℃ / min, thereby achieving low-temperature calcination; 4) High-temperature reduction calcination: The low-temperature calcination product from step 3) was ball-milled (250 r / min, 30 min) and then transferred to a tube furnace. A carbon monoxide / argon mixed gas (volume ratio 1:30, total flow rate 80 mL / min) was introduced for high-temperature calcination. Specifically, the temperature was increased in a gradient: first stage: 600℃ for 2 h, heating rate 15℃ / min; second stage: 1800℃ for 2 h, heating rate 15℃ / min. 5) Post-processing: After cooling the calcined product from step 4) to room temperature, grind it, then acid wash it with 12% sulfuric acid solution at 70°C for 2 h, then wash it with water until neutral, and dry it at 110°C for 8 h to obtain silicon carbide powder with a yield of 78% (based on silicon).

[0035] The product obtained in Example 2 (mass fraction) contains SiC: 99.02%, C: 0.45%, Si: 0.03%, SiO2: 0.09%, Fe2O3: 0.26%, other metallic impurities: 0.15%, and powder particle size: D50 < 0.5 μm.

[0036] Example 3 A method for synthesizing silicon carbide powder using a carbon source, the specific steps of which are as follows: 1) Raw material preparation: The heavy component mixture separated by boron isotope separation by chemical exchange method (including the following components by mass fraction: 10% anisole, 50% phenol, 20% methyl anisole, and 20% methyl phenol) is filtered through diatomaceous earth (filtration accuracy 5μm); the heavy component mixture is obtained by the method in reference CN118681406A; Prepare nano-silicon powder (particle size 80 nm, natural abundance); prepare deoxidizing and reducing agent: specifically zinc powder (particle size <100 mesh). 2) Mixing: The heavy component mixture from step 1) was mixed with nano-silicon powder at a C:Si molar ratio of 2.0:1 using ball milling. The ball milling speed was 300 r / min, the time was 2 h, and the ambient temperature was 28℃. 3) Low-temperature calcination: The mixed product from step 2) is placed in an air atmosphere (open reaction) and subjected to gradient heating: First stage: heating to 140℃, holding for 2 h, heating rate 5℃ / min; Second stage: heating to 190℃, holding for 3 h, heating rate 5℃ / min; Third stage: heating to 400℃, holding for 3.5 h, heating rate 5℃ / min, thereby achieving low-temperature calcination; 4) High-temperature reduction calcination: Under argon protection, the zinc powder from step 1) and the low-temperature calcination product from step 3) are mixed at a mass ratio of 1:8 and ground in a planetary ball mill for 30 min; then transferred to a tube furnace for high-temperature calcination under an argon atmosphere, specifically with gradient heating: first stage: 800℃ for 3 h, heating rate 15℃ / min; second stage: 1600℃ for 3 h, heating rate 10℃ / min. 5) Post-processing: After cooling the calcined product from step 4) to room temperature, grind it, then acid wash it with a 10% hydrochloric acid solution at 60°C for 2.5 h, then wash it with water until neutral, and dry it at 90°C for 10 h to obtain silicon carbide powder with a yield of 88% (based on silicon).

[0037] The product obtained in Example 3 (mass fraction) contains SiC: 98.80%, C: 0.27%, Si: 0.13%, SiO2: 0.15%, Fe2O3: 0.14%, other metallic impurities: 0.51%, and powder particle size: D50 < 0.3 μm.

[0038] Example 4 A method for synthesizing silicon carbide powder using a carbon source, the specific steps of which are as follows: 1) Raw material preparation: The heavy component mixture separated by boron isotope separation by chemical exchange method (including the following components by mass fraction: 10% anisole, 40% phenol, 20% methyl anisole, and 30% methyl phenol) is filtered through diatomaceous earth (filtration accuracy 10 μm); the heavy component mixture is obtained by the method in reference CN118681406A; Prepare the silicon source: silicon-28 enriched nano-silicon powder (abundance 99%, particle size 200 nm); prepare the deoxidizing reducing agent, specifically, a mixture of aluminum powder and magnesium powder (mass ratio 1:1, particle size <100 mesh). 2) Mixing: The heavy component mixture from step 1) was mixed with the silicon source at a C:Si molar ratio of 1.2:1 using ball milling. The ball milling speed was 300 r / min, the time was 2 h, and the ambient temperature was 25℃. 3) Low-temperature calcination: The mixed product from step 2) is placed in a tube furnace and subjected to gradient heating in an oxygen / nitrogen mixed atmosphere (oxygen concentration (volume fraction) 10%): First stage: heating to 110℃, holding for 2 h, heating rate 3℃ / min; Second stage: heating to 160℃, holding for 3 h, heating rate 3℃ / min; Third stage: heating to 250℃, holding for 4 h, heating rate 3℃ / min, thereby achieving low-temperature calcination; 4) High-temperature reduction calcination: Under argon protection, the deoxidizing reducing agent from step 1) and the low-temperature calcination product from step 3) are mixed at a mass ratio of 1:20 and ground in a planetary ball mill for 30 min; then transferred to a tube furnace for high-temperature calcination under an argon atmosphere, specifically with gradient heating: first stage: 700℃ for 4 h, heating rate 10℃ / min; second stage: 1500℃ for 4 h, heating rate 8℃ / min. 5) Post-processing: After cooling the calcined product from step 4) to room temperature, grind it, then acid wash it with 20% sulfuric acid solution at 80℃ for 1 h, then wash it with water until neutral, and dry it at 120℃ for 6 h to obtain silicon-28 enriched carbon silicon powder with a yield of 90% (based on silicon).

[0039] The product obtained in Example 4 (mass fraction) contains SiC: 99.90%, C: 0.03%, Si: 0.03%, SiO2: 0.02%, Fe2O3: 0.01%, other metal impurities: 0.01%, and powder particle size: D50 < 0.4 μm.

[0040] Example 5 A method for synthesizing boron carbon powder using a carbon source, the specific steps of which are as follows: 1) Raw material preparation: The heavy component mixture separated by boron isotope separation by chemical exchange method (including the following components by mass fraction: 50% anisole, 25% phenol, 15% methyl anisole, and 10% methyl phenol) is filtered through diatomaceous earth (filtration accuracy 8μm); the heavy component mixture is obtained by the method in reference CN118681406A; Prepare boric acid (solid) (99.5% purity, natural abundance); prepare a deoxygenating reducing agent, specifically hydrogen gas (5N gas); 2) Mixing: The heavy component mixture from step 1) was mixed with boric acid at a C:B molar ratio of 3:1 by stirring at a speed of 500 r / min for 1.5 h at an ambient temperature of 20℃. 3) Low-temperature calcination: The mixed product from step 2) is subjected to a gradient heating process in an air atmosphere (open reaction): First stage: heating to 150℃ and holding for 1.5 h at a rate of 3℃ / min; Second stage: heating to 200℃ and holding for 2.5 h at a rate of 3℃ / min; Third stage: heating to 400℃ and holding for 3.5 h at a rate of 3℃ / min, thereby achieving low-temperature calcination. 4) High-temperature reduction calcination: Under argon protection, the low-temperature calcination product was mixed with magnesium powder at a mass ratio of 100:1 and ball-milled (250 r / min, 30 min). Then, it was transferred to a tube furnace and calcined at high temperature in a hydrogen / argon mixed atmosphere (volume ratio 1:20, gas flow rate 50 mL / min). Specifically, the temperature was increased in a gradient: first stage: 800℃ for 2 h at a rate of 15℃ / min; second stage: 1800℃ for 3 h at a rate of 15℃ / min. 5) Post-processing: After cooling the calcined product from step 4) to room temperature, grind it, then acid wash it with 15% sulfuric acid solution at 70℃ for 1.5 h, then wash it with water until neutral, and dry it at 120℃ for 8 h to obtain carbon boron powder with a yield of 85% (calculated as boron).

[0041] The product obtained in Example 5 (mass fraction) contained: total B content: 80%, total B content + total C content: 99%, B soluble in nitric acid: 0.12%, B soluble in water: 0.06%, F: 20 ppm, Cl: 63 ppm, Ca: 0.12%, Fe: 0.23%.

[0042] Example 6 A method for synthesizing boron carbon powder using a carbon source, the specific steps of which are as follows: 1) Raw material preparation: The heavy component mixture separated by boron isotope separation by chemical exchange method (including the following components by mass fraction: 20% anisole, 50% phenol, 20% methyl anisole, and 10% methyl phenol) is filtered through diatomaceous earth (filtration accuracy 10 μm); the heavy component mixture is obtained by referring to the method in reference CN118681406A; Prepare boron-10 enriched boric acid (isotopic abundance 95%); prepare a deoxidizing reducing agent, specifically aluminum powder (particle size <100 mesh). 2) Mixing: The heavy component mixture from step 1) was mixed with boric acid at a C:B molar ratio of 4:1 using ball milling. The ball milling speed was 300 r / min, the time was 2 h, and the ambient temperature was 30℃. 3) Low-temperature calcination: The mixed product from step 2) is placed in a tube furnace and subjected to gradient heating in an oxygen / nitrogen mixed atmosphere (oxygen concentration (volume fraction) 5%): First stage: heating to 100 ℃, holding for 2 h, rate 6 ℃ / min; Second stage: heating to 150 ℃, holding for 3 h, rate 6 ℃ / min; Third stage: heating to 500 ℃, holding for 3.5 h, rate 6 ℃ / min, thereby achieving low-temperature calcination; 4) High-temperature reduction calcination: Under argon protection, the aluminum powder from step 1) and the low-temperature calcination product from step 3) are mixed at a mass ratio of 1:15 and ground in a planetary ball mill for 30 min; then transferred to a tube furnace for high-temperature calcination under an argon atmosphere, specifically with gradient heating: first stage: 900℃ for 6 h at a rate of 5℃ / min; second stage: 2000℃ for 1 h at a rate of 5℃ / min. 5) Post-processing: After cooling the calcined product from step 4) to room temperature, grind it, then acid wash it with 5% hydrochloric acid solution at 50°C for 3 h, then wash it with water until neutral, and dry it at 80°C for 12 h to obtain boron-10 enriched carbon boron powder with a yield of 81% (based on boron).

[0043] The product obtained in Example 6 (mass fraction) had a boron-10 abundance of 95%, total B content of 79%, total B content + total C content of 98.5%, B soluble in nitric acid of 0.24%, B soluble in water of 0.11%, F of 10 ppm, Cl of 51 ppm, Ca of 0.26%, and Fe of 0.15%.

[0044] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above. Those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for synthesizing carbon silicon and carbon boron powders using a carbon source, characterized in that, Includes the following steps: 1) Raw material preparation: The heavy component mixture produced by the chemical exchange method for boron isotope separation is used as a carbon source and filtered; Prepare a silicon source or a boron source; prepare a deoxidizing agent, wherein the deoxidizing agent is a metal elemental powder or gas; 2) Mixing: Mix the carbon source and silicon source or boron source from step 1) in a certain proportion to obtain a mixed product; 3) Low-temperature calcination: The mixed product from step 2) is subjected to low-temperature calcination reaction in air or oxygen / nitrogen mixed atmosphere to obtain low-temperature calcination intermediate product; 4) High-temperature reduction calcination: The metal element powder deoxidizing reducing agent in step 1) is mixed with the low-temperature calcination intermediate product in step 3) in a certain proportion and then subjected to gradient high-temperature calcination; or the low-temperature calcination intermediate product in step 3) is subjected to gradient high-temperature calcination under the condition of gaseous deoxidizing reducing agent. 5) Post-processing: After cooling the calcined product from step 4) to room temperature, it is subjected to grinding, acid washing, water washing and drying in sequence to obtain silicon carbide powder or boron carbide powder.

2. The method according to claim 1, characterized in that, The heavy component mixture includes one or more of anisole, phenol, methyl anisole, and methyl phenol; In step 1), the silicon source is nano-silicon powder or silicon-28 enriched nano-silicon powder; In step 1), the boron source is boric acid or boron-10 enriched boric acid; In step 1), the deoxidizing reducing agent is at least one elemental metal powder selected from magnesium, lithium, sodium, calcium, aluminum, and zinc, or at least one gas selected from hydrogen, carbon monoxide, and ammonia.

3. The method according to claim 1, characterized in that, In step 2), the C:Si molar ratio of the carbon source to the silicon source is 1.2~2.5:1; In step 2), the C:B molar ratio of the carbon source to the boron source is 2~5:

1.

4. The method according to claim 1, characterized in that, In step 2), the mixing step adopts ball milling or stirring mixing. The ball milling speed is 200~300 r / min and the mixing time is 2~3h; the stirring mixing speed is 500~600 r / min and the mixing time is 1~2h. The ambient temperature is controlled at 20~30℃ during the mixing process.

5. The method according to claim 1, characterized in that, In step 3), a gradient heating method is used during low-temperature calcination; The gradient heating process for the low-temperature calcination is as follows: the first stage involves heating to 100~150℃ and holding for 1.5~2 h at a rate of 3-6℃ / min; the second stage involves heating to 150~200℃ and holding for 2.5-3 h at a rate of 3-6℃ / min; and the third stage involves heating to 200~500℃ and holding for 3.5-4 h at a rate of 3-6℃ / min. In step 3), the low-temperature calcination is carried out in an oxygen / nitrogen mixed atmosphere or in an air atmosphere.

6. The method according to claim 1, characterized in that, In step 4), when the deoxidizing agent is a metallic elemental powder, the deoxidizing agent is added to the low-temperature calcination intermediate product of step 3) under argon protection, ball-milled or stirred, and then subjected to gradient high-temperature calcination under an argon atmosphere. When the deoxidizing reducing agent is a gas, the low-temperature calcination intermediate product is ground and then subjected to gradient high-temperature calcination in an atmosphere of gaseous deoxidizing reducing agent and / or argon.

7. The method according to claim 1, characterized in that, In step 4), the gradient high-temperature calcination is performed by first holding the temperature at 600~900℃ for 1-6 hours, and then raising the temperature to 1000~2000℃ and holding it for 1-6 hours.

8. The method according to claim 1, characterized in that, During the high-temperature reduction calcination process, the mass ratio of the metal element powder deoxidizing reducing agent to the low-temperature calcination intermediate product is 1:5 to 1:20; the volume ratio of the gaseous deoxidizing reducing agent to argon is 1:10 to 1:50, and the total gas flow rate is controlled at 10 to 100 mL / min; the heating rate of the gradient high-temperature calcination is 5 to 20 °C / min.

9. The method according to claim 1, characterized in that, In step 5), the post-treatment step involves pickling with a hydrochloric acid or sulfuric acid solution with a mass fraction of 5% to 20%, at a temperature of 50 to 80°C, for a time of 1 to 3 hours; after washing with water until neutral, the drying temperature is 80 to 120°C, and the drying time is 6 to 12 hours.

10. Silicon carbide powder or boron carbide powder prepared by any of the methods described in claims 1 to 9.