A method for preparing nano silicon spheres using gas phase self-propagating high temperature synthesis technology

Abstract

The invention discloses a method for preparing nano silicon spheres by using gas phase self-propagation high temperature synthesis technology, and relates to the field of silicon nano materials. The method introduces energetic gas into a reactor, uses a detonation wave to propagate at a speed of not less than 2800m / s, impacts, heats, splits and liquefies silicon powder, and forms nano silicon spheres. The diameter of the nano silicon spheres is between 40 and 120nm. The technology has the advantages of fast reaction, simple process, low energy consumption, etc. The prepared nano silicon material has excellent mechanical properties and broad application prospects, and is particularly suitable for electronic devices and lithium ion battery negative electrode materials.

Description

Technical Field

[0001] The invention relates to the field of silicon nanomaterials, and in particular to a method for preparing nano silicon balls by utilizing gas phase self-propagation high temperature synthesis technology. Background Art

[0002] Silicon nanomaterials have broad application prospects in optoelectronics, energy, biomedicine and other fields due to their unique physical and chemical properties, and have attracted extensive attention from researchers. Among them, nanosilicon spheres have shown excellent performance in lithium-ion battery negative electrode materials, field effect transistors, photodetectors and other aspects due to their high specific surface area and quantum confinement effect.

[0003] Traditional methods for preparing nano-silicon spheres mainly include vapor deposition, solution chemistry, and template methods. Vapor deposition methods such as chemical vapor deposition (CVD) and physical vapor deposition (PVD) obtain silicon nanostructures by depositing and growing silicon sources in the gas phase on a substrate. They have good controllability but complex equipment and high costs. The solution chemistry method reduces silicon precursors such as silicon tetrachloride and trichlorosilane in a solution. The synthesis process is simple, but the morphology and size of the product are difficult to control. The template method first prepares templates such as porous alumina and mesoporous silica, and then grows silicon nanowires under the confinement of the template. A highly ordered silicon nanowire array can be obtained, but the process of preparing the template is relatively cumbersome.

[0004] In recent years, gas phase self-propagating high temperature synthesis technology (SHS) has attracted attention as an emerging material synthesis method. SHS utilizes the heat released by the chemical reaction between reactants to synthesize materials in a short time by self-propagation. It has the advantages of fast reaction rate, low energy consumption and high product purity. At present, SHS has been successfully applied to the preparation of various inorganic functional materials such as ceramics, intermetallic compounds and composite materials.

[0005] Introducing SHS into the preparation of silicon nanomaterials is expected to achieve rapid, low-cost, and large-scale production. Zhang et al. used single-element silicon powder as raw material and prepared silicon nanowires with a diameter of 50-200nm and a length of up to tens of microns by SHS in an argon atmosphere. The reaction can occur above 1200°C and lasts for less than 1 minute. Huo et al. used a similar method to add a small amount of iron oxide as a catalyst to silicon powder to prepare silicon nanospheres with good dispersion, and the particle size was concentrated around 100nm. These studies show that SHS is an effective way to prepare silicon nanomaterials.

[0006] However, the current research on the preparation of silicon nanomaterials by SHS mainly focuses on a single morphology (spherical or linear), and the understanding of the reaction mechanism and influencing factors is not deep enough, and the structure and performance of the product need to be further optimized. Therefore, developing a new method for preparing nanosilicon spheres by SHS and deeply understanding its formation mechanism are of great significance for expanding the application of silicon nanomaterials. Summary of the invention

[0007] In view of this, the purpose of the present invention is to propose a method for preparing nano-silicon spheres using gas phase self-propagating high temperature synthesis technology, which not only makes significant progress in improving the performance of nano-silicon materials, but also provides a solid foundation for its promotion in industrial applications. By further optimizing process parameters and exploring new application scenarios, the present invention is expected to play a greater role in the future.

[0008] The technical solutions adopted are:

[0009] A method for preparing nano silicon spheres using gas phase self-propagating high temperature synthesis technology,

[0010] The following steps are involved:

[0011] (1) Raw material preparation: high-purity silicon powder with an average particle size of 5-25 μm is selected as the precursor;

[0012] (2) Loading the reactor: The silicon powder obtained in step (1) is evenly spread on the substrate in the reactor with a thickness of 1-5 mm;

[0013] (3) Sealing the reactor: placing the substrate containing silicon powder into the reactor and sealing the reactor;

[0014] (4) Vacuum treatment: Use a vacuum pump to evacuate the reactor to -0.08 to -0.1 MPa;

[0015] (5) Filling the reactor with energetic gas: a mixture of hydrogen and oxygen is charged into the reactor in a mixing ratio of 2:1;

[0016] The inflation pressure is controlled at 0.2-0.4MPa;

[0017] (6) Ignition and detonation: Use 30-50J of energy to ignite and trigger energetic gas detonation;

[0018] (7) Reaction: The detonation wave propagates in the reactor at a speed of 2800±100 m / s, impacting, heating, splitting and liquefying the silicon powder;

[0019] (8) Isentropic cooling: After the reaction is completed, the reaction vessel is naturally cooled to room temperature in a closed reactor;

[0020] (9) Product collection: open the reactor and collect the reaction product;

[0021] (10) Post-treatment: The collected product is subjected to ultrasonic dispersion and centrifugal separation to remove the existing agglomerates to obtain the final nano-silicon sphere product.

[0022] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0023] The purity of the high-purity silicon powder in step (1) is not less than 99.9%, the particle size distribution D90 ≤ 30 μm, D50 is 5-10 μm, and D10 ≥ 1 μm;

[0024] The preparation method of the high-purity silicon powder is as follows: Si3N4 balls are used as ball milling media, the mass ratio of silicon powder to ball milling media is 1:(5-10), the ball milling time is 12-16 hours, and then the silicon powder is heat treated in argon gas at a temperature of 500-800°C for 1-3 hours.

[0025] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0026] The operation of evenly tiling in step (2) is as follows:

[0027] Place the substrate on a horizontal and stable work surface; slowly pour the silicon powder obtained in step (1) on the substrate to form an initial powder layer; use a scraper tool to gently push along the surface of the substrate to evenly spread the initial powder layer until it covers the entire surface of the substrate; use a tool with precise measurement function to detect the thickness of the powder layer to ensure that the thickness of the silicon powder is within the range of 1-5mm; perform multi-point detection of the powder layer thickness to ensure that the silicon powder is evenly laid and the thickness error does not exceed 0.5mm; if the local powder layer thickness is uneven or exceeds the range of 1-5mm, use a scraper tool to make local adjustments until the requirements are met.

[0028] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0029] The operation of sealing the reactor in step (3) includes:

[0030] Check the inner wall of the reactor to ensure that there are no impurities or residues; place the substrate containing silicon powder into the reactor to avoid shaking that may cause uneven distribution of silicon powder; fix the substrate in the center of the reactor and use a fixing device to ensure that the substrate does not move during the reaction. The fixing device is a high-temperature resistant ceramic bracket, and its height is adapted to the thickness of the substrate; check the sealing ring of the reactor to ensure that it is intact; evenly apply high-temperature vacuum sealing grease on the surface of the sealing ring, where the temperature resistance range of high-temperature vacuum sealing grease is -40℃ to 300℃; align the reactor cover with the reactor body, slowly cover it and align it with the bolt hole; tighten the bolts in sequence according to the cross-diagonal order, and use a torque wrench to ensure that the tightening torque of each bolt is consistent. The torque range of the torque wrench used is 10-50N·m, and the accuracy is not less than ±2%; after completing the initial tightening, perform the second round of tightening in the same order again, where the tightening torque of the bolts is 30-40N·m; finally, use an air tightness tester to test the sealing performance of the reactor to ensure that the leakage rate is less than 1×10 -9 Pa·m 3 / s.

[0031] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0032] The vacuum treatment in step (4) includes:

[0033] Check the working status of the vacuum pump to ensure that the oil level is normal and there is no abnormal noise. The vacuum pump is a rotary vane vacuum pump with a maximum vacuum degree of no less than 1×10 -2 Pa, the exhaust rate is not less than 20L / s; connect the vacuum pump to the vacuum interface of the reactor to ensure that the connection is well sealed; open the vacuum valve of the reactor; start the vacuum pump and start the vacuum pumping process; use a vacuum gauge to monitor the vacuum degree in the reactor in real time, where the vacuum gauge is a digital vacuum gauge with an accuracy of not less than ±1%; when the vacuum degree reaches -0.08MPa, continue to vacuum for 5-10min to ensure that the gas in the reactor is fully exhausted; when the vacuum degree is stable in the range of -0.08 to -0.1MPa, close the vacuum valve of the reactor; turn off the vacuum pump and remove the connection with the reactor.

[0034] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0035] The operation of charging the energetic gas in step (5) includes: checking the pressure of the steel cylinder and the purity of the gas; connecting the steel cylinder to the air inlet of the reactor and ensuring that the connection is well sealed; slowly opening the valve of the steel cylinder and adjusting the pressure reducing valve to allow the gas to be charged into the reactor at a rate of 0.05-0.1 MPa / min; using a pressure sensor to monitor the pressure change in the reactor in real time; when the pressure in the reactor reaches 0.2 MPa, closing the valve of the steel cylinder and stopping the charging; maintaining the pressure of 0.2 MPa for 5-10 minutes and observing whether the pressure is stable; closing the air inlet valve of the reactor and removing the connection with the steel cylinder.

[0036] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0037] The ignition and detonation operation in step (6) includes: inserting an ignition device into an ignition port reserved in the reactor and ensuring that it is located in the central area of ​​the energetic gas, wherein the ignition device is a heating wire or a spark plug, the wire diameter of the heating wire is 0.1-0.5 mm, the resistance is 1-10 Ω, the temperature resistance is not less than 2000° C., the electrode spacing of the spark plug is 0.5-1.5 mm, and the voltage resistance is not less than 10 kV; connecting the ignition device to an external power supply or an ignition control system; setting the parameters of the ignition control system, including ignition energy, ignition temperature, and ignition pressure; Ignition time, the setting range of ignition energy is 30-50J, the setting range of ignition time is 1-10ms, and the ignition time is 100ms-2s; check the pressure and temperature in the reactor to ensure that they are within the safe range; start the ignition control system to provide 30-50J of energy within the preset time to trigger the explosion of energetic gas; within 1-2s after ignition, turn off the power of the ignition device to prevent continuous discharge from affecting the reaction process; monitor the pressure and temperature changes in the reactor to ensure that they are within the safe range.

[0038] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0039] The process of detonation wave propagation and reaction in step (7) includes: the energetic gas rapidly decomposes under the action of ignition energy, releasing a large amount of heat to form a high-temperature and high-pressure detonation wave; the detonation wave propagates in the reactor at a speed of 2800±100m / s, violently impacting and compressing the silicon powder particles; under the impact of the detonation wave, the surface of the silicon powder particles rapidly heats up to 1800-2000K, and surface melting occurs; under the high pressure of the detonation wave, the molten silicon powder particles undergo plastic deformation and breakage to form nano-scale silicon particles; as the detonation wave continues to propagate, high-speed collision and fusion occur between the nano-silicon particles to form nano-silicon balls with more uniform sizes; after the detonation wave propagates to the end of the reactor, it is reflected and transmitted back to perform secondary impact and reorganization on the formed nano-silicon balls; after multiple impacts and reorganizations, the size distribution of the nano-silicon balls becomes more uniform and the agglomeration phenomenon is reduced; as the temperature and pressure in the reactor gradually decrease, the reaction automatically terminates to obtain the final product.

[0040] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0041] Before collecting the product in step (9), ensure that the temperature in the reactor drops to room temperature, and check the pressure in the reactor to ensure that it has dropped to normal pressure.

[0042] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0043] The post-processing operations in step (10) include:

[0044] Ultrasonic dispersion treatment:

[0045] The nano-silicon sphere product collected in step (9) is transferred to ethanol at a volume ratio of 10:1-50:1 to form a suspension; the suspension is ultrasonically treated using an ultrasonic cleaner with a frequency of 20 kHz and a power of 300 W; the ultrasonic treatment time is 10-30 min, and the temperature is controlled at 20-40° C.;

[0046] Centrifugal separation:

[0047] The suspension after ultrasonic treatment was transferred to a 50 mL centrifuge tube; the suspension was centrifuged using a centrifuge with a maximum speed of 15000 rpm and a refrigeration function; the centrifugation time was 15 min and the speed was 5000-10000 rpm;

[0048] Product collection and drying:

[0049] The drying temperature is 40-60℃, the pressure is not higher than 100Pa, and the drying time is 12-24h;

[0050] Product Characterization and Storage:

[0051] The dried product is characterized and analyzed; the product is sealed and stored in an inert atmosphere; the product should be protected from light, moisture and stored at room temperature.

[0052] In summary, the beneficial effects of the present invention are:

[0053] Improve material properties: Nano-silicon spheres prepared by gas phase self-propagating high temperature synthesis technology show excellent mechanical properties. The hardness and Young's modulus of nano-silicon spheres are significantly improved. These properties make them have significant advantages in applications requiring high strength and high stiffness.

[0054] Strong controllability: The present invention can precisely adjust the morphology and size of nano-silicon materials within a certain range by adjusting synthesis process parameters, such as reaction temperature, pressure and gas composition, so as to achieve effective control of its mechanical properties. This controllability provides greater flexibility for material design.

[0055] Simple process: Compared with other preparation methods, gas phase self-propagation high temperature synthesis technology has the advantages of simple operation, short reaction time and low energy consumption. This method does not require complex equipment or harsh reaction conditions, is suitable for large-scale production, and reduces production costs.

[0056] Wide application: Due to its excellent mechanical properties and controllable structural characteristics, the prepared nano-silicon materials have wide application potential in electronic devices, composite materials, sensors and other fields. Especially in micro-electromechanical systems (MEMS), lithium-ion battery negative electrode materials, etc., nano-silicon materials can significantly improve device performance.

[0057] Environmentally friendly: The gas-phase self-propagating high-temperature synthesis technology adopted in the present invention reduces the dependence on organic solvents and other chemical reagents, reduces the risk of environmental pollution, and is in line with the development direction of green chemistry.

[0058] In summary, the present invention has not only made significant progress in improving the performance of nano-silicon materials, but also provided a solid foundation for its promotion in industrial applications. By further optimizing process parameters and exploring new application scenarios, the present invention is expected to play a greater role in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 This is a scanning electron microscope image in Example 1 of the present invention;

[0060] Figure 2 for Figure 1 Enlarged view of part A. DETAILED DESCRIPTION

[0061] The present invention is described in detail below through specific examples, but the use and purpose of these exemplary implementation modes are only used to illustrate the present invention, and do not constitute any form of limitation on the actual protection scope of the present invention, nor limit the protection scope of the present invention to them.

[0062] Example 1

[0063] A method for preparing nano silicon spheres using gas phase self-propagating high temperature synthesis technology,

[0064] The following steps are involved:

[0065] (1) Raw material preparation: High-purity silicon powder with an average particle size of 5 μm was selected as the precursor;

[0066] (2) Loading the reactor: The silicon powder obtained in step (1) is evenly spread on the substrate in the reactor with a thickness of 1 mm;

[0067] (3) Sealing the reactor: placing the substrate containing silicon powder into the reactor and sealing the reactor;

[0068] (4) Vacuum treatment: Use a vacuum pump to evacuate the reactor to -0.08 MPa;

[0069] (5) Filling the reactor with energetic gas: a mixture of hydrogen and oxygen is charged into the reactor in a mixing ratio of 2:1;

[0070] The inflation pressure is controlled at 0.2MPa;

[0071] (6) Ignition and detonation: Use 30J of energy to ignite and trigger energetic gas detonation;

[0072] (7) Reaction: The detonation wave propagates in the reactor at a speed of 2800±100 m / s, impacting, heating, splitting and liquefying the silicon powder;

[0073] (8) Isentropic cooling: After the reaction is completed, the reaction vessel is naturally cooled to room temperature in a closed reactor;

[0074] (9) Product collection: open the reactor and collect the reaction product;

[0075] (10) Post-treatment: The collected product is subjected to ultrasonic dispersion and centrifugal separation to remove the existing agglomerates to obtain the final nano-silicon sphere product.

[0076] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0077] The purity of the high-purity silicon powder in step (1) is not less than 99.9%, the particle size distribution D90 ≤ 30 μm, D50 is 5-10 μm, and D10 ≥ 1 μm;

[0078] The preparation method of the high-purity silicon powder is as follows: Si3N4 balls are used as ball milling media, the mass ratio of silicon powder to ball milling media is 1:5, the ball milling time is 16 hours, and then the silicon powder is heat treated in argon gas at a temperature of 500°C for 3 hours.

[0079] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0080] The operation of evenly tiling in step (2) is as follows:

[0081] Place the substrate on a horizontal and stable work surface; slowly pour the silicon powder obtained in step (1) on the substrate to form an initial powder layer; use a scraper tool to gently push along the surface of the substrate to evenly spread the initial powder layer until it covers the entire surface of the substrate; use a tool with precise measurement function to detect the thickness of the powder layer to ensure that the silicon powder is laid at a thickness of 1 mm; perform multi-point detection of the powder layer thickness to ensure that the silicon powder is laid evenly and the thickness error does not exceed 0.5 mm; if the local powder layer thickness is uneven or exceeds the range of 1 mm, use a scraper tool to make local adjustments until the requirements are met.

[0082] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0083] The operation of sealing the reactor in step (3) includes:

[0084] Check the inner wall of the reactor to ensure that there are no impurities or residues; place the substrate containing silicon powder into the reactor to avoid shaking that may cause uneven distribution of silicon powder; fix the substrate in the center of the reactor and use a fixing device to ensure that the substrate does not move during the reaction. The fixing device is a high-temperature resistant ceramic bracket, and its height is adapted to the thickness of the substrate; check the sealing ring of the reactor to ensure that it is intact; evenly apply high-temperature vacuum sealing grease on the surface of the sealing ring, where the temperature resistance range of high-temperature vacuum sealing grease is -40℃ to 300℃; align the reactor cover with the reactor body, slowly cover it and align it with the bolt holes; tighten the bolts in sequence according to the cross-diagonal order, and use a torque wrench to ensure that the tightening torque of each bolt is consistent. The torque range of the torque wrench used is 10N·m, and the accuracy is not less than ±2%; after completing the initial tightening, perform the second round of tightening in the same order again, where the tightening torque of the bolts is 40N·m; finally, use an air tightness tester to test the sealing performance of the reactor to ensure that the leakage rate is less than 1×10 -9 Pa·m 3 / s.

[0085] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0086] The vacuum treatment in step (4) includes:

[0087] Check the working status of the vacuum pump to ensure that the oil level is normal and there is no abnormal noise. The vacuum pump is a rotary vane vacuum pump with a maximum vacuum degree of no less than 1×10 -2 Pa, the exhaust rate is not less than 20L / s; connect the vacuum pump to the vacuum interface of the reactor to ensure that the connection is well sealed; open the vacuum valve of the reactor; start the vacuum pump and start the vacuum pumping process; use a vacuum gauge to monitor the vacuum degree in the reactor in real time, where the vacuum gauge is a digital vacuum gauge with an accuracy of not less than ±1%; when the vacuum degree reaches -0.08MPa, continue to vacuum for 5 minutes to ensure that the gas in the reactor is fully exhausted; when the vacuum degree is stable within -0.08MPa, close the vacuum valve of the reactor; turn off the vacuum pump and remove the connection with the reactor.

[0088] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0089] The operation of charging the energetic gas in step (5) includes: checking the pressure of the steel cylinder and the purity of the gas; connecting the steel cylinder to the air inlet of the reactor and ensuring that the connection is well sealed; slowly opening the valve of the steel cylinder and adjusting the pressure reducing valve to allow the gas to be charged into the reactor at a rate of 0.05 MPa / min; using a pressure sensor to monitor the pressure change in the reactor in real time; when the pressure in the reactor reaches 0.2 MPa, closing the valve of the steel cylinder and stopping the charging; maintaining the pressure of 0.2 MPa for 10 minutes and observing whether the pressure is stable; closing the air inlet valve of the reactor and removing the connection with the steel cylinder.

[0090] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0091] The ignition and detonation operation in step (6) includes: inserting the ignition device into the ignition port reserved in the reactor and ensuring that it is located in the central area of ​​the energetic gas, wherein the ignition device is a heating wire or a spark plug, the wire diameter of the heating wire is 0.1 mm, the resistance is 10Ω, the temperature resistance is not less than 2000°C, the electrode spacing of the spark plug is 0.5 mm, and the voltage resistance is not less than 10kV; connecting the ignition device to an external power supply or an ignition control system; setting the parameters of the ignition control system, including ignition energy and ignition time, the setting range of the ignition energy is 30J, the setting range of the ignition time is 10ms, and the ignition time is 100ms; checking the pressure and temperature in the reactor to ensure that they are within a safe range; starting the ignition control system to provide 50J of energy within a preset time to trigger the detonation of the energetic gas; within 1s after ignition, turning off the power supply of the ignition device to prevent continuous discharge from affecting the reaction process; monitoring the pressure and temperature changes in the reactor to ensure that they are within a safe range.

[0092] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0093] The process of detonation wave propagation and reaction in step (7) includes: the energetic gas rapidly decomposes under the action of ignition energy, releasing a large amount of heat to form a high-temperature and high-pressure detonation wave; the detonation wave propagates in the reactor at a speed of 2800±100 m / s, violently impacting and compressing the silicon powder particles; under the impact of the detonation wave, the surface of the silicon powder particles rapidly heats up to 1800K, and surface melting occurs; under the high pressure of the detonation wave, the molten silicon powder particles undergo plastic deformation and breakage to form nano-scale silicon particles; as the detonation wave continues to propagate, high-speed collision and fusion occur between the nano-silicon particles to form nano-silicon balls with more uniform sizes; after the detonation wave propagates to the end of the reactor, it is reflected and transmitted back to perform secondary impact and reorganization on the formed nano-silicon balls; after multiple impacts and reorganizations, the size distribution of the nano-silicon balls becomes more uniform and the agglomeration phenomenon is reduced; as the temperature and pressure in the reactor gradually decrease, the reaction automatically terminates to obtain the final product.

[0094] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0095] Before collecting the product in step (9), ensure that the temperature in the reactor drops to room temperature, and check the pressure in the reactor to ensure that it has dropped to normal pressure.

[0096] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0097] The post-processing operations in step (10) include:

[0098] Ultrasonic dispersion treatment:

[0099] The nano-silicon sphere product collected in step (9) was transferred into ethanol at a volume ratio of 10:1 to form a suspension; the suspension was ultrasonically treated using an ultrasonic cleaner with a frequency of 20 kHz and a power of 300 W; the ultrasonic treatment time was 30 min and the temperature was controlled at 20° C.;

[0100] Centrifugal separation:

[0101] The suspension after ultrasonic treatment was transferred to a 50 mL centrifuge tube; the suspension was centrifuged using a centrifuge with a maximum speed of 15000 rpm and refrigeration function; the centrifugation time was 15 min and the speed was 5000 rpm;

[0102] Product collection and drying:

[0103] The drying temperature is 40°C, the pressure is not higher than 100Pa, and the time is 24h;

[0104] Product Characterization and Storage:

[0105] The dried product is characterized and analyzed; the product is sealed and stored in an inert atmosphere; the product should be protected from light, moisture and stored at room temperature.

[0106] The microstructure of the product Figure 1 and Figure 2 shown.

[0107] Example 2

[0108] A method for preparing nano silicon spheres using gas phase self-propagating high temperature synthesis technology,

[0109] The following steps are involved:

[0110] (1) Raw material preparation: High-purity silicon powder with an average particle size of 25 μm was selected as the precursor;

[0111] (2) Reactor loading: The silicon powder obtained in step (1) is evenly spread on the substrate in the reactor with a thickness of 5 mm;

[0112] (3) Sealing the reactor: placing the substrate containing silicon powder into the reactor and sealing the reactor;

[0113] (4) Vacuum treatment: Use a vacuum pump to evacuate the reactor to -0.1 MPa;

[0114] (5) Filling the reactor with energetic gas: a mixture of hydrogen and oxygen is charged into the reactor in a mixing ratio of 2:1;

[0115] The inflation pressure is controlled at 0.4MPa;

[0116] (6) Ignition and detonation: Use 50J of energy to ignite and trigger energetic gas detonation;

[0117] (7) Reaction: The detonation wave propagates in the reactor at a speed of 2800±100 m / s, impacting, heating, splitting and liquefying the silicon powder;

[0118] (8) Isentropic cooling: After the reaction is completed, the reaction vessel is naturally cooled to room temperature in a closed reactor;

[0119] (9) Product collection: open the reactor and collect the reaction product;

[0120] (10) Post-treatment: The collected product is subjected to ultrasonic dispersion and centrifugal separation to remove the existing agglomerates to obtain the final nano-silicon sphere product.

[0121] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0122] The purity of the high-purity silicon powder in step (1) is not less than 99.9%, the particle size distribution D90 ≤ 30 μm, D50 is 5-10 μm, and D10 ≥ 1 μm;

[0123] The preparation method of the high-purity silicon powder is as follows: Si3N4 balls are used as ball milling media, the mass ratio of silicon powder to ball milling media is 1:10, the ball milling time is 16 hours, and then the silicon powder is heat treated in argon gas at a heat treatment temperature of 800°C for 3 hours.

[0124] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0125] The operation of evenly tiling in step (2) is as follows:

[0126] Place the substrate on a horizontal and stable work surface; slowly pour the silicon powder obtained in step (1) on the substrate to form an initial powder layer; use a scraper tool to gently push along the surface of the substrate to evenly spread the initial powder layer until it covers the entire surface of the substrate; use a tool with precise measurement function to detect the thickness of the powder layer to ensure that the silicon powder laying thickness is within 5mm; perform multi-point detection of the powder layer thickness to ensure that the silicon powder is evenly laid and the thickness error does not exceed 0.5mm; if the local powder layer thickness is uneven or exceeds the range of 5mm, use a scraper tool to make local adjustments until the requirements are met.

[0127] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0128] The operation of sealing the reactor in step (3) includes:

[0129] Check the inner wall of the reactor to ensure that there are no impurities or residues; place the substrate containing silicon powder into the reactor to avoid uneven distribution of silicon powder due to shaking; fix the substrate in the center of the reactor and use a fixing device to ensure that the substrate does not move during the reaction process. The fixing device is a high-temperature resistant ceramic bracket, and its height is adapted to the thickness of the substrate; check the sealing ring of the reactor to ensure that it is intact; evenly apply high-temperature vacuum sealing grease on the surface of the sealing ring, where the temperature resistance range of high-temperature vacuum sealing grease is -40℃ to 300℃; align the reactor cover with the reactor body, slowly cover it and align it with the bolt hole; tighten the bolts in sequence according to the cross-diagonal order, and use a torque wrench to ensure that the tightening torque of each bolt is consistent. The torque range of the torque wrench used is 50N·m, and the accuracy is not less than ±2%; after completing the initial tightening, perform the second round of tightening in the same order again, where the tightening torque of the bolt is 40N·m; finally, use an airtightness tester to test the sealing performance of the reactor to ensure that the leakage rate is less than 1×10 -9 Pa·m 3 / s.

[0130] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0131] The vacuum treatment in step (4) includes:

[0132] Check the working status of the vacuum pump to ensure that the oil level is normal and there is no abnormal noise. The vacuum pump is a rotary vane vacuum pump with a maximum vacuum degree of no less than 1×10 -2 Pa, the exhaust rate is not less than 20L / s; connect the vacuum pump to the vacuum interface of the reactor to ensure that the connection is well sealed; open the vacuum valve of the reactor; start the vacuum pump and start the vacuum pumping process; use a vacuum gauge to monitor the vacuum degree in the reactor in real time, where the vacuum gauge is a digital vacuum gauge with an accuracy of not less than ±1%; when the vacuum degree reaches -0.08MPa, continue to vacuum for 10 minutes to ensure that the gas in the reactor is fully exhausted; when the vacuum degree stabilizes at -0.1MPa, close the vacuum valve of the reactor; turn off the vacuum pump and remove the connection with the reactor.

[0133] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0134] The operation of charging the energetic gas in step (5) includes: checking the pressure of the steel cylinder and the purity of the gas; connecting the steel cylinder to the air inlet of the reactor and ensuring that the connection is well sealed; slowly opening the valve of the steel cylinder and adjusting the pressure reducing valve to allow the gas to be charged into the reactor at a rate of 0.1 MPa / min; using a pressure sensor to monitor the pressure change in the reactor in real time; when the pressure in the reactor reaches 0.2 MPa, closing the valve of the steel cylinder and stopping the charging; maintaining the pressure of 0.2 MPa for 10 minutes and observing whether the pressure is stable; closing the air inlet valve of the reactor and removing the connection with the steel cylinder.

[0135] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0136] The ignition and detonation operation in step (6) includes: inserting the ignition device into the ignition port reserved in the reactor and ensuring that it is located in the central area of ​​the energetic gas, wherein the ignition device is a heating wire or a spark plug, the wire diameter of the heating wire is 0.5 mm, the resistance is 10Ω, the temperature resistance is not less than 2000°C, the electrode spacing of the spark plug is 1.5 mm, and the voltage resistance is not less than 10kV; connecting the ignition device to an external power supply or an ignition control system; setting the parameters of the ignition control system, including ignition energy and ignition time, the setting range of the ignition energy is 50J, the setting range of the ignition time is 10ms, and the ignition time is 2s; checking the pressure and temperature in the reactor to ensure that they are within a safe range; starting the ignition control system to provide 50J of energy within a preset time to trigger the detonation of the energetic gas; within 2s after ignition, turning off the power supply of the ignition device to prevent continuous discharge from affecting the reaction process; monitoring the pressure and temperature changes in the reactor to ensure that they are within a safe range.

[0137] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0138] The process of detonation wave propagation and reaction in step (7) includes: the energetic gas rapidly decomposes under the action of ignition energy, releasing a large amount of heat to form a high-temperature and high-pressure detonation wave; the detonation wave propagates in the reactor at a speed of 2800±100 m / s, violently impacting and compressing the silicon powder particles; under the impact of the detonation wave, the surface of the silicon powder particles rapidly heats up to 2000K, and surface melting occurs; under the high pressure of the detonation wave, the molten silicon powder particles undergo plastic deformation and breakage to form nano-scale silicon particles; as the detonation wave continues to propagate, high-speed collision and fusion occur between the nano-silicon particles to form nano-silicon balls with more uniform sizes; after the detonation wave propagates to the end of the reactor, it is reflected and transmitted back to perform secondary impact and reorganization on the formed nano-silicon balls; after multiple impacts and reorganizations, the size distribution of the nano-silicon balls becomes more uniform and the agglomeration phenomenon is reduced; as the temperature and pressure in the reactor gradually decrease, the reaction automatically terminates to obtain the final product.

[0139] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0140] Before collecting the product in step (9), ensure that the temperature in the reactor drops to room temperature, and check the pressure in the reactor to ensure that it has dropped to normal pressure.

[0141] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0142] The post-processing operations in step (10) include:

[0143] Ultrasonic dispersion treatment:

[0144] The nano-silicon sphere product collected in step (9) was transferred to ethanol at a volume ratio of 50:1 to form a suspension; the suspension was ultrasonically treated using an ultrasonic cleaner with a frequency of 20 kHz and a power of 300 W; the ultrasonic treatment time was 30 min and the temperature was controlled at 40° C.;

[0145] Centrifugal separation:

[0146] The suspension after ultrasonic treatment was transferred to a 50 mL centrifuge tube; the suspension was centrifuged using a centrifuge with a maximum speed of 15000 rpm and refrigeration function; the centrifugation time was 15 min and the speed was 10000 rpm;

[0147] Product collection and drying:

[0148] The drying temperature is 60°C, the pressure is not higher than 100Pa, and the time is -24h;

[0149] Product Characterization and Storage:

[0150] The dried product is characterized and analyzed; the product is sealed and stored in an inert atmosphere; the product should be protected from light, moisture and stored at room temperature.

[0151] Example 3

[0152] A method for preparing nano silicon spheres using gas phase self-propagating high temperature synthesis technology,

[0153] The following steps are involved:

[0154] (1) Raw material preparation: High-purity silicon powder with an average particle size of 125 μm was selected as the precursor;

[0155] (2) Loading the reactor: The silicon powder obtained in step (1) is evenly spread on the substrate in the reactor with a thickness of 3 mm;

[0156] (3) Sealing the reactor: placing the substrate containing silicon powder into the reactor and sealing the reactor;

[0157] (4) Vacuum treatment: Use a vacuum pump to evacuate the reactor to -0.1 MPa;

[0158] (5) Filling the reactor with energetic gas: a mixture of hydrogen and oxygen is charged into the reactor in a mixing ratio of 2:1;

[0159] The inflation pressure is controlled at 0.3MPa;

[0160] (6) Ignition and detonation: Use 40J of energy to ignite and trigger energetic gas detonation;

[0161] (7) Reaction: The detonation wave propagates in the reactor at a speed of 2800±100 m / s, impacting, heating, splitting and liquefying the silicon powder;

[0162] (8) Isentropic cooling: After the reaction is completed, the reaction vessel is naturally cooled to room temperature in a closed reactor;

[0163] (9) Product collection: open the reactor and collect the reaction product;

[0164] (10) Post-treatment: The collected product is subjected to ultrasonic dispersion and centrifugal separation to remove the existing agglomerates to obtain the final nano-silicon sphere product.

[0165] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0166] The purity of the high-purity silicon powder in step (1) is not less than 99.9%, the particle size distribution D90 ≤ 30 μm, D50 is 5-10 μm, and D10 ≥ 1 μm;

[0167] The preparation method of the high-purity silicon powder is as follows: Si3N4 balls are used as ball milling media, the mass ratio of silicon powder to ball milling media is 1:8, the ball milling time is 14 hours, and then the silicon powder is heat treated in argon at a temperature of 700°C for 2 hours.

[0168] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0169] The operation of evenly tiling in step (2) is as follows:

[0170] Place the substrate on a horizontal and stable work surface; slowly pour the silicon powder obtained in step (1) on the substrate to form an initial powder layer; use a scraper tool to gently push along the surface of the substrate to evenly spread the initial powder layer until it covers the entire surface of the substrate; use a tool with precise measurement function to detect the thickness of the powder layer to ensure that the thickness of the silicon powder is within the range of 1-5mm; perform multi-point detection of the powder layer thickness to ensure that the silicon powder is evenly laid and the thickness error does not exceed 0.5mm; if the local powder layer thickness is uneven or exceeds the range of 1-5mm, use a scraper tool to make local adjustments until the requirements are met.

[0171] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0172] The operation of sealing the reactor in step (3) includes:

[0173] Check the inner wall of the reactor to ensure that there are no impurities or residues; place the substrate containing silicon powder into the reactor to avoid uneven distribution of silicon powder due to shaking; fix the substrate in the center of the reactor and use a fixing device to ensure that the substrate does not move during the reaction process. The fixing device is a high-temperature resistant ceramic bracket, and its height is adapted to the thickness of the substrate; check the sealing ring of the reactor to ensure that it is intact; evenly apply high-temperature vacuum sealing grease on the surface of the sealing ring, where the temperature resistance range of high-temperature vacuum sealing grease is -40℃ to 300℃; align the reactor cover with the reactor body, slowly cover it and align it with the bolt hole; tighten the bolts in sequence according to the cross-diagonal order, and use a torque wrench to ensure that the tightening torque of each bolt is consistent. The torque range of the torque wrench used is 30N·m, and the accuracy is not less than ±2%; after completing the initial tightening, perform the second round of tightening in the same order again, where the tightening torque of the bolts is 35N·m; finally, use an air tightness tester to test the sealing performance of the reactor to ensure that the leakage rate is less than 1×10 -9 Pa·m 3 / s.

[0174] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0175] The vacuum treatment in step (4) includes:

[0176] Check the working status of the vacuum pump to ensure that the oil level is normal and there is no abnormal noise. The vacuum pump is a rotary vane vacuum pump with a maximum vacuum degree of no less than 1×10 -2 Pa, the exhaust rate is not less than 20L / s; connect the vacuum pump to the vacuum interface of the reactor to ensure that the connection is well sealed; open the vacuum valve of the reactor; start the vacuum pump and start the vacuum pumping process; use a vacuum gauge to monitor the vacuum degree in the reactor in real time, where the vacuum gauge is a digital vacuum gauge with an accuracy of not less than ±1%; when the vacuum degree reaches -0.08MPa, continue to vacuum for 8min to ensure that the gas in the reactor is fully exhausted; when the vacuum degree is stable in the range of -0.08 to -0.1MPa, close the vacuum valve of the reactor; turn off the vacuum pump and remove the connection with the reactor.

[0177] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0178] The operation of charging the energetic gas in step (5) includes: checking the pressure of the steel cylinder and the purity of the gas; connecting the steel cylinder to the air inlet of the reactor and ensuring that the connection is well sealed; slowly opening the valve of the steel cylinder and adjusting the pressure reducing valve to allow the gas to be charged into the reactor at a rate of 0.08 MPa / min; using a pressure sensor to monitor the pressure change in the reactor in real time; when the pressure in the reactor reaches 0.2 MPa, closing the valve of the steel cylinder and stopping the charging; maintaining the pressure of 0.2 MPa for 8 minutes and observing whether the pressure is stable; closing the air inlet valve of the reactor and removing the connection with the steel cylinder.

[0179] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0180] The ignition and detonation operation in step (6) includes: inserting the ignition device into the ignition port reserved in the reactor and ensuring that it is located in the central area of ​​the energetic gas, wherein the ignition device is a heating wire or a spark plug, the wire diameter of the heating wire is 0.3 mm, the resistance is 6 Ω, the temperature resistance is not less than 2000°C, the electrode spacing of the spark plug is 1.0 mm, and the voltage resistance is not less than 10 kV; connecting the ignition device to an external power supply or an ignition control system; setting the parameters of the ignition control system, including ignition energy and ignition time, the setting range of the ignition energy is 40 J, the setting range of the ignition time is 6 ms, and the ignition time is 1 s; checking the pressure and temperature in the reactor to ensure that they are within a safe range; starting the ignition control system to provide 40 J of energy within a preset time to trigger the detonation of the energetic gas; within 1.5 s after ignition, turning off the power supply of the ignition device to prevent continuous discharge from affecting the reaction process; monitoring the pressure and temperature changes in the reactor to ensure that they are within a safe range.

[0181] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0182] The process of detonation wave propagation and reaction in step (7) includes: the energetic gas rapidly decomposes under the action of ignition energy, releasing a large amount of heat to form a high-temperature and high-pressure detonation wave; the detonation wave propagates in the reactor at a speed of 2800±100 m / s, violently impacting and compressing the silicon powder particles; under the impact of the detonation wave, the surface of the silicon powder particles rapidly heats up to 2000K, and surface melting occurs; under the high pressure of the detonation wave, the molten silicon powder particles undergo plastic deformation and breakage to form nano-scale silicon particles; as the detonation wave continues to propagate, high-speed collision and fusion occur between the nano-silicon particles to form nano-silicon balls with more uniform sizes; after the detonation wave propagates to the end of the reactor, it is reflected and transmitted back to perform secondary impact and reorganization on the formed nano-silicon balls; after multiple impacts and reorganizations, the size distribution of the nano-silicon balls becomes more uniform and the agglomeration phenomenon is reduced; as the temperature and pressure in the reactor gradually decrease, the reaction automatically terminates to obtain the final product.

[0183] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0184] Before collecting the product in step (9), ensure that the temperature in the reactor drops to room temperature, and check the pressure in the reactor to ensure that it has dropped to normal pressure.

[0185] The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology,

[0186] The post-processing operations in step (10) include:

[0187] Ultrasonic dispersion treatment:

[0188] The nano-silicon sphere product collected in step (9) was transferred to ethanol at a volume ratio of 40:1 to form a suspension; the suspension was ultrasonically treated using an ultrasonic cleaner with a frequency of 20 kHz and a power of 300 W; the ultrasonic treatment time was 20 min and the temperature was controlled at 30° C.;

[0189] Centrifugal separation:

[0190] The suspension after ultrasonic treatment was transferred to a 50 mL centrifuge tube; the suspension was centrifuged using a centrifuge with a maximum speed of 15000 rpm and refrigeration function; the centrifugation time was 15 min and the speed was 8000 rpm;

[0191] Product collection and drying:

[0192] The drying temperature is 50°C, the pressure is not higher than 100Pa, and the time is 18h;

[0193] Product Characterization and Storage:

[0194] The dried product is characterized and analyzed; the product is sealed and stored in an inert atmosphere; the product should be protected from light, moisture and stored at room temperature.

[0195] test

[0196] The performance test of the nano silicon spheres prepared in Examples 1-3 is as follows:

[0197] Mechanical properties test: Nanoindentation test was carried out on the nano-silicon spheres to measure their hardness and Young's modulus.

[0198] Table 1 Test results

[0199]

[0200] Hardness of nano silicon balls:

[0201] The nano silicon sphere of Example 1 has the highest hardness, which is 16.5±1.5GPa, followed by Example 3, which is 16.3±1.4GPa, and Example 2 has the lowest hardness, which is 15.7±1.2GPa. This shows that the hardness of the nano silicon spheres obtained under different preparation conditions is different, but the difference is not obvious. Hardness reflects the ability of a material to resist local plastic deformation, which is related to the microstructure and surface state of the material. Example 1 forms a nano silicon sphere structure with a denser surface and fewer defects, thereby having a higher hardness.

[0202] Young's modulus of nano-silicon spheres:

[0203] The Young's modulus of the nano-silicon spheres in Example 2 is the highest, which is 37±5GPa, followed by Example 3, which is 36±5GPa, and Example 1 is the lowest, which is 35±5GPa. This shows that the Young's modulus of the nano-silicon spheres obtained under different preparation conditions is slightly different, but there is still a certain trend of change. The Young's modulus of the nano-silicon spheres is related to their size distribution, surface state and internal structure. Example 2 forms a nano-silicon sphere structure with a more uniform size and a smoother surface, thereby having a higher Young's modulus.

[0204] In general, nano-silicon spheres are three-dimensional solid structures with relatively balanced properties in all directions.

[0205] Comparison with bulk silicon material performance:

[0206] By comparing with the literature data, we found that the mechanical properties of the nano silicon spheres prepared in Examples 1-3 are significantly better than those of bulk silicon materials. For example, the Young's modulus of bulk silicon is about 130-185 GPa, while the hardness of the nano silicon spheres can reach 15.7-16.5 GPa. This shows that the nanoscale effect and special microstructure can significantly improve the mechanical properties of silicon materials.

[0207] In summary, the nano-silicon spheres prepared by gas-phase self-propagating high-temperature synthesis technology have excellent mechanical properties, which are significantly better than bulk silicon materials. By adjusting the preparation process parameters, the tensile strength, hardness and Young's modulus of nano-silicon materials can be adjusted within a certain range. This provides important experimental data support for expanding the application of nano-silicon materials in mechanically sensitive fields. In future research, we can further optimize the preparation process, conduct in-depth research on the structure-activity relationship between microstructure and mechanical properties, and lay the foundation for the development of high-performance nano-silicon-based mechanical devices and composite materials.

[0208] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. All equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing nano silicon spheres using gas phase self-propagating high temperature synthesis technology, characterized in that: The following steps are involved: (1) Raw material preparation: high-purity silicon powder with an average particle size of 5-25 μm is selected as the precursor; (2) Loading the reactor: The silicon powder obtained in step (1) is evenly spread on the substrate in the reactor with a thickness of 1-5 mm; (3) Sealing the reactor: placing the substrate containing silicon powder into the reactor and sealing the reactor; (4) Vacuum treatment: Use a vacuum pump to evacuate the reactor to -0.08 to -0.1 MPa; (5) Filling the reactor with energetic gas: a mixture of hydrogen and oxygen is charged into the reactor in a mixing ratio of 2:1; The inflation pressure is controlled at 0.2-0.4MPa; (6) Ignition and detonation: Use 30-50J of energy to ignite and trigger energetic gas detonation; (7) Reaction: The detonation wave propagates in the reactor at a speed of 2800±100 m / s, impacting, heating, splitting and liquefying the silicon powder; (8) Isentropic cooling: After the reaction is completed, it is cooled naturally to room temperature; (9) Product collection: open the reactor and collect the reaction product; (10) Post-treatment: The collected product is subjected to ultrasonic dispersion and centrifugal separation to remove the existing agglomerates to obtain the final nano-silicon spheres.

2. The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology according to claim 1, characterized in that: The purity of the high-purity silicon powder in step (1) is not less than 99.9%, the particle size distribution D90 ≤ 30 μm, D50 is 5-10 μm, and D10 ≥ 1 μm; The preparation method of the high-purity silicon powder is as follows: Si3N4 balls are used as ball milling media, the mass ratio of silicon powder to ball milling media is 1:(5-10), the ball milling time is 12-16h, and then the silicon powder is heat treated in argon gas at a temperature of 500-800°C for 1-3h.

3. The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology according to claim 1, characterized in that: The operation of evenly tiling in step (2) is as follows: Place the substrate on a horizontal and stable work surface; slowly pour the silicon powder obtained in step (1) on the substrate to form an initial powder layer; use a scraper tool to gently push along the surface of the substrate to evenly spread the initial powder layer until it covers the entire surface of the substrate; use a tool with precise measurement function to detect the thickness of the powder layer to ensure that the thickness of the silicon powder is within the range of 1-5mm; perform multi-point detection of the powder layer thickness to ensure that the silicon powder is evenly laid and the thickness error does not exceed 0.5mm; if the local powder layer thickness is uneven or exceeds the range of 1-5mm, use a scraper tool to make local adjustments until the requirements are met.

4. The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology according to claim 1, characterized in that: The operation of sealing the reactor in step (3) includes: Check the inner wall of the reactor to ensure that there are no impurities or residues; place the substrate containing silicon powder into the reactor to avoid shaking that may cause uneven distribution of silicon powder; fix the substrate in the center of the reactor and use a fixing device to ensure that the substrate does not move during the reaction. The fixing device is a high-temperature resistant ceramic bracket, and its height is adapted to the thickness of the substrate; check the sealing ring of the reactor to ensure that it is intact; evenly apply high-temperature vacuum sealing grease on the surface of the sealing ring, where the temperature resistance range of high-temperature vacuum sealing grease is -40℃ to 300℃; align the reactor cover with the reactor body, slowly cover it and align it with the bolt hole; tighten the bolts in sequence according to the cross-diagonal order, and use a torque wrench to ensure that the tightening torque of each bolt is consistent. The torque range of the torque wrench used is 10-50N·m, and the accuracy is not less than ±2%; after completing the initial tightening, perform the second round of tightening in the same order again, where the tightening torque of the bolts is 30-40N·m; finally, use an air tightness tester to test the sealing performance of the reactor to ensure that the leakage rate is less than 1×10 -9 Pa·m 3 / s.

5. The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology according to claim 1, characterized in that: The vacuum treatment in step (4) includes: Check the working status of the vacuum pump to ensure that the oil level is normal and there is no abnormal noise. The vacuum pump is a rotary vane vacuum pump with a maximum vacuum degree of no less than 1×10 -2 Pa, the exhaust rate is not less than 20L / s; connect the vacuum pump to the vacuum interface of the reactor to ensure that the connection is well sealed; open the vacuum valve of the reactor; start the vacuum pump and start the vacuum pumping process; use a vacuum gauge to monitor the vacuum degree in the reactor in real time, where the vacuum gauge is a digital vacuum gauge with an accuracy of not less than ±1%; when the vacuum degree reaches -0.08MPa, continue to vacuum for 5-10min to ensure that the gas in the reactor is fully exhausted; when the vacuum degree is stable in the range of -0.08 to -0.1MPa, close the vacuum valve of the reactor; turn off the vacuum pump and remove the connection with the reactor.

6. The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology according to claim 1, characterized in that: The operation of charging the energetic gas in step (5) includes: checking the pressure of the steel cylinder and the purity of the gas; connecting the steel cylinder to the air inlet of the reactor and ensuring that the connection is well sealed; slowly opening the valve of the steel cylinder and adjusting the pressure reducing valve to allow the gas to be charged into the reactor at a rate of 0.05-0.1 MPa / min; using a pressure sensor to monitor the pressure change in the reactor in real time; when the pressure in the reactor reaches 0.2 MPa, closing the valve of the steel cylinder and stopping the charging; maintaining the pressure of 0.2 MPa for 5-10 minutes and observing whether the pressure is stable; closing the air inlet valve of the reactor and removing the connection with the steel cylinder.

7. The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology according to claim 1, characterized in that: The ignition and detonation operation in step (6) includes: inserting an ignition device into an ignition port reserved in the reactor and ensuring that it is located in the central area of ​​the energetic gas, wherein the ignition device is a heating wire or a spark plug, the wire diameter of the heating wire is 0.1-0.5 mm, the resistance is 1-10 Ω, the temperature resistance is not less than 2000° C., the electrode spacing of the spark plug is 0.5-1.5 mm, and the voltage resistance is not less than 10 kV; connecting the ignition device to an external power supply or an ignition control system; setting the parameters of the ignition control system, including ignition energy, ignition temperature, and ignition pressure; Ignition time, the setting range of ignition energy is 30-50J, the setting range of ignition time is 1-10ms, and the ignition time is 100ms-2s; check the pressure and temperature in the reactor to ensure that they are within the safe range; start the ignition control system to provide 30-50J of energy within the preset time to trigger the explosion of energetic gas; within 1-2s after ignition, turn off the power of the ignition device to prevent continuous discharge from affecting the reaction process; monitor the pressure and temperature changes in the reactor to ensure that they are within the safe range.

8. The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology according to claim 1, characterized in that: The process of detonation wave propagation and reaction in step (7) includes: the energetic gas rapidly decomposes under the action of ignition energy, releases a large amount of heat, and forms a high-temperature and high-pressure detonation wave; the detonation wave propagates in the reactor at a speed of 2800±100m / s, violently impacting and compressing the silicon powder particles; under the impact of the detonation wave, the surface of the silicon powder particles rapidly heats up to 1800-2000K, and surface melting occurs; under the high pressure of the detonation wave, the molten silicon powder particles undergo plastic deformation and breakage to form nano-scale silicon particles; as the detonation wave continues to propagate, high-speed collision and fusion occur between the nano-silicon particles to form nano-silicon balls with more uniform sizes; after the detonation wave propagates to the end of the reactor, it is reflected and transmitted back to perform secondary impact and reorganization on the formed nano-silicon balls; after multiple impacts and reorganizations, the size distribution of the nano-silicon balls becomes more uniform and the agglomeration phenomenon is reduced; as the temperature and pressure in the reactor gradually decrease, the reaction automatically terminates to obtain the final product.

9. The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology according to claim 1, characterized in that: Before collecting the product in step (9), ensure that the temperature in the reactor drops to room temperature, and check the pressure in the reactor to ensure that it has dropped to normal pressure.

10. The method for preparing nano silicon spheres by using gas phase self-propagating high temperature synthesis technology according to claim 1, characterized in that: The post-processing operations in step (10) include: Ultrasonic dispersion treatment: The nano-silicon sphere product collected in step (9) is transferred to ethanol at a volume ratio of 10:1-50:1 to form a suspension; the suspension is ultrasonically treated using an ultrasonic cleaner with a frequency of 20 kHz and a power of 300 W; the ultrasonic treatment time is 10-30 min, and the temperature is controlled at 20-40° C.; Centrifugal separation: The suspension after ultrasonic treatment was transferred to a 50 mL centrifuge tube; the suspension was centrifuged using a centrifuge with a maximum speed of 15000 rpm and a refrigeration function; the centrifugation time was 15 min and the speed was 5000-10000 rpm; Product collection and drying: The drying temperature is 40-60℃, the pressure is not higher than 100Pa, and the drying time is 12-24h; Product Characterization and Storage: The dried product is characterized and analyzed; the product is sealed and stored in an inert atmosphere; the product should be protected from light, moisture and stored at room temperature.

Images