Preparation method of boron carbide nanopowder
The sol-gel method combined with mechanical stirring and heat treatment was used to prepare boron carbide nanopowder, which solved the problems of high energy consumption and impurity introduction of pure nano-scale boron carbide powders on industrial scale production, and achieved low-energy consumption and high-efficiency nano-scale boron carbide powder production.
Patent Information
- Application Number
- CN202510606815.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-12
- Publication Date
- 2025-07-11
AI Technical Summary
The prior art is difficult to produce pure nanoscale boron carbide powder on an industrial scale, and there are problems of high energy consumption and metal impurities introduction.
The sol-gel method is used, but the sol-gel method is not used. Boron carbide nanopowder is prepared by mechanical stirring and low-temperature and high-temperature heat treatment, combined with inert atmosphere treatment, so as to avoid the introduction of metal impurities and reduce energy consumption.
It realizes the production of pure and fine nanoscale boron carbide powders with low energy consumption, which are suitable for industrial-scale production.
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Figure CN120288773A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of boron carbide production, and specifically relates to a method for preparing boron carbide nano-powder. Background Art
[0002] There are various processes for synthesizing B4C powder, and the production characteristics and processing costs of each process are different. In traditional methods, boron and carbon are directly synthesized into B4C powder, the reaction is difficult, requiring a high temperature above 2300 °C, and the process is time-consuming and costly, with insufficient product purity and coarse particles; when using carbothermal reduction of boron oxides such as boron trioxide (B2O3) and boric acid (H3BO3) in an electric arc furnace or a resistance furnace to produce B4C, in this process, Mg or Na is usually introduced as a reducing agent, which is likely to introduce other metal ion impurities; moreover, the products obtained by this method are in block and coarse particle form and require subsequent crushing, grinding, and pickling purification.
[0003] In recent years, people have been exploring new preparation methods for B4C powder. For example, methods such as laser irradiation chemical vapor deposition are difficult to carry out large-scale production due to process limitations. With continuous research and development, the sol-gel method has become a quasi-industrial production method, but this method also has the problem of high energy consumption.
[0004] A method that is suitable for industrial production and can produce relatively pure nano-scale boron carbide powder is a technical problem that needs to be solved in this industry. Summary of the Invention
[0005] To solve the above technical problems, the present invention provides a method for preparing boron carbide nano-powder. The production principle of the sol-gel method is adopted but the sol-gel method is not used for production, and nano-scale boron carbide powder is prepared, avoiding the introduction of metal impurities and being suitable for low-energy consumption industrial production.
[0006] The technical solution adopted by this application for this technical problem is as follows:
[0007] A method for preparing boron carbide nano-powder, comprising the following steps:
[0008] Step S1: Prepare materials, and prepare an aqueous solution of a carbon source and a boron source powder.
[0009] Step S2: Under the state of mechanical stirring and kneading, add a certain amount of the aqueous solution of the carbon source in Step S1 to a certain amount of the boron source powder in Step S1, so that the aqueous solution of the carbon source fully infiltrates the boron source powder and remains between the boron source powders to obtain a mixture; continue to stir and knead for 0.5 - 1 h, stand and age at 60 °C for 3 - 5 h, and dry to obtain a mixed powder.
[0010] Step S3: In a reducing atmosphere, the mixed powder obtained in Step S2 is subjected to low-temperature heat treatment at 270 - 300 °C for 1.5 - 2 h, and then heated to 700 - 850 °C for high-temperature heat treatment for 2 - 3 h to obtain a boron carbide precursor;
[0011] Step S4: In an inert atmosphere, the boron carbide precursor obtained in Step S3 is treated at 1100 - 1200 °C for 1.5 - 2 h, and then cooled to obtain boron carbide nanometer powder.
[0012] This solution utilizes the characteristic that the carbon source has a large solubility in water, avoiding the large amount of water required for the dissolution of the boron source, reducing the high energy consumption in the water removal stage, and being able to reach a state close to molecular-level contact, reducing the reaction temperature and particle fineness. After low-temperature heat treatment and high-temperature heat treatment, a state close to the carbon-boron ratio in boron carbide can be achieved, and the conversion rate can be improved.
[0013] Further, in Step S1, the carbon source is one or more of polyhydroxy compounds such as glucose, fructose, and polyvinyl alcohol; the boron source is one or more of boric acid, metaboric acid, and boron oxide.
[0014] Further, in Step S2, the mechanical stirring and kneading state is achieved by using a ball mill. The grinding balls in the ball mill are boron carbide spheres. In addition to the ball mill, a kneader or a kneading machine can also be used, and a dough mixer can be used in the laboratory.
[0015] Further, the addition method of the carbon source aqueous solution is to spray the atomized carbon source aqueous solution onto the surface of the boron source powder. This method can ensure the uniform contact between the carbon source aqueous solution and the boron source, and surround the boron source with the carbon source on the outside.
[0016] Further, in Step S2, the molar ratio of C atoms to B atoms in the mixed material is 2 - 3:5.
[0017] Normally, in the present invention, because a part of water is used, a part of the boron source will evaporate with the water during the subsequent drying process, so the B in the boron source needs to be in excess. However, because the carbon source undergoes complex chemical reactions during the pyrolysis process, the decomposition products cannot be produced completely according to the calculation. Therefore, the present invention makes the C in the carbon source in excess. This can not only produce enough amorphous carbon to improve the conversion rate, but also form a framework due to the existence of this amorphous carbon, thereby reducing the aggregation of B during the reaction process and ensuring the particle size.
[0018] Further, in Step S2, the drying method is as follows:
[0019] Transfer the mixture into a container with stirring and heating functions, heat the mixture under stirring, with a heating rate of 5 - 10 °C / min. When the temperature exceeds 110 °C, adjust the heating rate to 2 - 5 °C / min. When the temperature reaches 160 °C, stop heating and continue stirring until it cools down.
[0020] The above drying method can fully convert the carbon source and boron source. B in the mixture can be converted into metaboric acid below 110 °C and into pyroboric acid at 160 °C, which can reduce the duration of subsequent low-temperature heat treatment and avoid excessive loss of the carbon source during the drying process.
[0021] Further, in step S3, the reducing atmosphere is an inert gas containing CO, where CO accounts for 20 - 30% of the total gas volume.
[0022] The reducing gas can reduce the loss of the carbon source during the cracking process, ensure the sufficiency of C in the reaction system, and also enable the rapid transfer of O in the reaction system to accelerate the cracking process.
[0023] Further, the inert gas is any one of N2 and Ar.
[0024] Further, it also includes the operation of removing free carbon in step S5. Heat the boron carbide nano-powder to 500 - 650 °C and introduce oxygen or air for heat preservation for 1 h.
[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0026] 1. The present invention uses the sol-gel principle to produce boron carbide, minimizing the introduction of metal impurities, striving to achieve molecular-level contact of the materials, reducing the reaction temperature, reducing the addition of water throughout the process, and reducing energy consumption. Therefore, it can produce relatively pure and fine-grained nano-scale boron carbide powder.
[0027] 2. The present invention uses gradient heating at different temperatures during the drying process, enabling the boron source and carbon source to transform between different compounds, achieving a closer contact state, and improving the conversion rate.
[0028] 3. The present invention uses a reducing atmosphere for low-temperature heat treatment and high-temperature heat treatment, promoting the conversion of the boron source and reducing the loss of the carbon source and boron source. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Figure 1 It is a scanning electron microscope image of the boron carbide nano-powder prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION
[0030] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further describes the present invention in detail with reference to specific embodiments.
[0031] The present invention mainly produces boron carbide by using the sol-gel principle, minimizing the introduction of metal impurities, striving to achieve molecular-level contact of materials, reducing the reaction temperature, reducing the addition of water throughout the process, and reducing energy consumption. Therefore, it can produce relatively pure and fine-grained nano-sized boron carbide powder.
[0032] Example 1
[0033] This example includes the following steps:
[0034] Step S1: Prepare 360 g of glucose and dissolve it in 200 g of water to make a glucose aqueous solution (heat to 60 °C to completely dissolve the glucose); prepare another 1860 g of boric acid powder for later use.
[0035] Step S2: Add the boric acid powder into a dough mixer, start the dough mixer, and spray the glucose aqueous solution onto the boric acid powder in the dough mixer using a sprayer during the mixing process, so that the glucose aqueous solution fully infiltrates the boric acid powder and remains between the boric acid powder to obtain a mixture; continue to stir and knead for 0.5 h, let it stand and age at 60 °C for 5 h, and then dry to obtain a mixed powder;
[0036] Step S3: The drying method is as follows: Transfer the mixture into a tray dryer, heat the mixture under stirring, with a heating rate of 5 - 10 °C / min. When the temperature exceeds 110 °C, adjust the heating rate to 2 - 5 °C / min. When the temperature reaches 160 °C, stop heating and continue stirring until it cools down.
[0037] In an N2 atmosphere doped with 20% CO, rotate the mixed powder obtained in Step S3 in a muffle furnace and keep it at 270 - 280 °C for 2 h for low-temperature heat treatment, and then raise the temperature to 850 °C and keep it for 2 h for high-temperature heat treatment to obtain a boron carbide precursor;
[0038] Step S4: Stop introducing CO, keep N2 flowing continuously, raise the temperature of the muffle furnace to 1100 - 1130 °C, keep it for 2 h, and cool it in the furnace to obtain boron carbide nano powder.
[0039] Step S5: Raise the temperature of the boron carbide nano powder to 550 °C, introduce oxygen or air, keep it for 1 h, cool down and discharge the material.
[0040] The scanning electron microscope image of the boron carbide nano powder obtained in this example is as Figure 1 shown.
[0041] Example 2
[0042] This example includes the following steps:
[0043] Step S1: Prepare 360 g of fructose (heated to 40 °C to completely dissolve the fructose), dissolve it in 200 g of water to prepare a fructose aqueous solution; prepare another 1860 g of boric acid powder for standby.
[0044] Step S2: Add the boric acid powder into a dough mixer, start the dough mixer, and during the mixing process, spray the fructose aqueous solution onto the boric acid powder in the dough mixer using a sprayer, so that the fructose aqueous solution fully infiltrates the boric acid powder and remains between the boric acid powder to obtain a mixture; continue to stir and knead for 1 h, age at 60 °C for 3 h, and dry to obtain a mixed powder.
[0045] Step S3: The drying method is as follows: Transfer the mixture into a tray dryer, heat the mixture under stirring, with a heating rate of 5 - 10 °C / min. When the temperature exceeds 110 °C, adjust the heating rate to 2 - 5 °C / min. When the temperature reaches 160 °C, stop heating and continue stirring until it cools.
[0046] In an N2 atmosphere doped with 30% CO, rotate the mixed powder obtained in Step S3 in a muffle furnace, keep it at 270 °C for 3 h for low-temperature heat treatment, and then raise the temperature to 800 °C and keep it at this temperature for 2 h for high-temperature heat treatment to obtain a boron carbide precursor.
[0047] Step S4: Stop introducing CO, keep N2 flowing continuously, raise the temperature of the muffle furnace to 1180 - 1200 °C, keep it at this temperature for 1.5 h, and cool with the furnace to obtain boron carbide nano-powder.
[0048] Step S5: Raise the temperature of the boron carbide nano-powder to 650 °C, introduce oxygen or air, keep it at this temperature for 1 h, cool down and discharge the material.
[0049] Example 3
[0050] This example includes the following steps:
[0051] Step S1: Prepare 560 g of glycerol, mix it with 200 g of water to prepare a glycerol aqueous solution; prepare another 1860 g of boric acid powder for standby.
[0052] Step S2: Add the boric acid powder into a dough mixer, start the dough mixer, and during the mixing process, spray the glycerol aqueous solution onto the boric acid powder in the dough mixer using a sprayer, so that the glycerol aqueous solution fully infiltrates the boric acid powder and remains between the boric acid powder to obtain a mixture; continue to stir and knead for 1 h, age at 60 °C for 3 h, and dry to obtain a mixed powder.
[0053] Step S3: The drying method is as follows: Transfer the mixture into a tray dryer, heat the mixture under stirring, with a heating rate of 5 - 10 °C / min. When the temperature exceeds 110 °C, adjust the heating rate to 2 - 5 °C / min. When the temperature reaches 160 °C, stop heating and continue stirring until it cools down.
[0054] In an N2 atmosphere doped with 30% CO, rotate the mixed powder obtained in Step S3 in a muffle furnace, keep it at 270 °C for 3 h for low-temperature heat treatment, and then raise the temperature to 800 °C and keep it for 2 h for high-temperature heat treatment to obtain a boron carbide precursor.
[0055] Step S4: Stop introducing CO, keep N2 continuously introduced, raise the temperature of the muffle furnace to 1180 - 1200 °C, keep it for 1.5 h, and cool it with the furnace to obtain boron carbide nano-powder.
[0056] Comparative Example 1
[0057] Step S1: Take 247.2 g of boric acid, add water to make the volume up to 1 L, heat it in a water bath to 90 °C to dissolve the boric acid, and prepare a 4 mol / L boric acid solution for standby.
[0058] Take 720.6 g of glucose, add water to make the volume up to 1 L to prepare a 4 mol / L solution for standby.
[0059] Take 15 g of PVA1799, add water to make the volume up to 1 L, heat it in a water bath to 95 °C to prepare a 15 g / L PVA solution for standby.
[0060] Step S2: Add 455 ml of boric acid solution and 545 ml of glucose solution into a beaker, age for 2 h to form a mixed solution of boric acid, glucose and their complexes. After adding 30 g of PVA solution, quickly transfer it to a graphite boat. There is a graphite cushion in the graphite boat. After about 95 seconds, the mixed solution turns into a gel-like state. As time goes by, this gel-like substance gradually becomes stable.
[0061] Step S3: Place the graphite boat in an oven and dry it at 150 °C for 4 h to obtain a white dried gel block with volume shrinkage. Place the above dried gel block together with the graphite boat in a muffle furnace and carbonize it at 700 °C for 2 h to obtain a black block.
[0062] Step S4: Place the block together with the graphite boat in an atmosphere furnace, react at 1250 - 1300 °C for 3 h to obtain a boron carbide material. There is carbon mixed in this material. Roasting at 700 °C for 2 h in an air atmosphere can significantly remove free carbon.
[0063] Step S5: Raise the temperature of the boron carbide nano-powder to 650 °C, introduce oxygen or air, keep it for 1 h, cool down and discharge the material.
[0064] Compared with the comparative example, Examples 1-3 of the present invention do not require the addition of so much water, reducing the energy consumption for water removal. By using a liquid-solid mixed reaction, the space occupied is reduced compared to the liquid-phase reaction. For the same volume of container, more products can be produced per unit time, improving the production efficiency. Although a low-temperature treatment procedure is added, the reaction temperature and duration are reduced. Therefore, the present invention is applicable to industrial production and reduces production energy consumption.
[0065] It should be understood that the specific embodiments described herein are merely used to explain the present invention and are not used to limit the present invention.
Claims
1. A method for preparing boron carbide nano powder, characterized in that, It includes the following steps: Step S1: Prepare materials, and prepare an aqueous solution of a carbon source and a boron source powder. Step S2: Under the state of mechanical stirring and kneading, add a certain amount of the aqueous solution of the carbon source in Step S1 into a certain amount of the boron source powder in Step S1, so that the aqueous solution of the carbon source fully infiltrates the boron source powder and remains between the boron source powders to obtain a mixture; continue stirring and kneading for 0.5 - 1 h, stand and age at 60 °C for 3 - 5 h, and dry to obtain a mixed powder. Step S3: In a reducing atmosphere, heat-treat the mixed powder obtained in Step S3 at 270 - 300 °C for 1.5 - 2 h, and then raise the temperature to 700 - 850 °C for high-temperature heat treatment for 2 - 3 h to obtain a boron carbide precursor. Step S4: In an inert atmosphere, heat-treat the boron carbide precursor obtained in Step S3 at 1100 - 1200 °C for 1.5 - 2 h, and cool to obtain boron carbide nano-powder.
2. The preparation method of boron carbide nano-powder according to claim 1, wherein, In the said Step S1, the carbon source is one or more of polyhydroxy compounds; the boron source is one or more of boric acid, metaboric acid, and boron oxide.
3. The preparation method of boron carbide nano powder according to claim 1, characterized in that, In the said Step S2, the state of mechanical stirring and kneading is realized by using a ball mill, and the grinding balls in the ball mill are boron carbide spheres.
4. The preparation method of boron carbide nano powder according to claim 1, characterized in that, The adding method of the aqueous solution of the carbon source is to spray the atomized aqueous solution of the carbon source onto the surface of the boron source powder.
5. The preparation method of a boron carbide nano-powder according to claim 1, characterized in that, In Step S2, the molar ratio of C atoms to B atoms in the mixture is 2 - 3:
5.
6. The preparation method of boron carbide nano-powder according to claim 1, characterized in that, In the said Step S2, the drying method is as follows: Transfer the mixture into a container with stirring and heating functions, heat the mixture under stirring, and the heating rate is 5 - 10 °C / min. When the temperature exceeds 110 °C, the heating rate is adjusted to 2 - 5 °C / min. When the temperature reaches 160 °C, stop heating and continue stirring until cooling.
7. The preparation method of a boron carbide nano-powder according to claim 1, characterized in that, In the said Step S3, the reducing atmosphere is an inert gas containing CO, and CO accounts for 20 - 30% of the total gas volume.
8. The preparation method of a boron carbide nano-powder according to claim 7, characterized in that, The inert gas is any one of N2 and Ar.
9. The preparation method of a boron carbide nano-powder according to claim 1, characterized in that, It also includes Step S5 for removing free carbon. Heat the boron carbide nano-powder to 500 - 650 °C and introduce oxygen or air to keep warm for 1 h.