A method for producing nanometal

Abstract

The application relates to the technical field of nano metal production, and specifically discloses a nano metal production method and a high-efficiency nano metal production device. The nano metal production method is performed in the high-efficiency nano metal production device, and the high-efficiency nano metal production device comprises an evaporation chamber, a heat preservation layer and a molten pool are arranged in the evaporation chamber, the interval between the molten pool and the heat preservation layer is 50-100 mm, the evaporation chamber is provided with a molten pool ventilation opening and a protective wind ventilation opening, the protective wind ventilation opening is located above the molten pool ventilation opening, the top of the evaporation chamber is provided with a first ventilation pipe and an air outlet pipeline, the air outlet pipeline is located on the two sides of the first ventilation pipe, a second ventilation pipe is arranged in the first ventilation pipe, a main process air opening is formed between the first ventilation pipe and the second ventilation pipe, the bottom of the first ventilation pipe is provided with an air outlet opening, the air outlet opening is communicated with the main process air opening, one side of the air outlet opening close to the axis of the first ventilation pipe is vertically arranged, and the other side of the air outlet opening is inclined to the outer wall direction of the molten pool, an electric arc generator is arranged in the second ventilation pipe, and an electric arc surrounding air opening is formed between the electric arc generator and the second ventilation pipe.

Description

Technical Field

[0001] This application relates to the field of nanometal production technology, and in particular to a method for producing nanometals. Background Technology

[0002] Nanoscale metal powders are widely used in coatings, deposition processes, and other fields to improve workpiece surface properties and achieve high-precision manufacturing due to their excellent physical and chemical properties. The electric arc method is an ideal method for preparing nanoscale metal powders, utilizing the high-energy plasma generated by an electric arc to heat the metal raw material, causing it to evaporate.

[0003] The yield of nanoparticles produced by the electric arc method is directly proportional to the effective evaporation rate and effective evaporation area of ​​the metal raw material. The effective evaporation rate is positively correlated with the saturated evaporation pressure and convective diffusion rate of the metal raw material. Increasing the raw material temperature can increase the saturated evaporation pressure, thereby increasing the evaporation rate. However, if the convective diffusion capacity is insufficient, the evaporated metal vapor cannot leave the evaporation surface in time, and some vapor will recondense, leading to a decrease in the actual evaporation rate.

[0004] Therefore, the key to achieving high yield lies in synergistically increasing the evaporation temperature, enhancing the steam diffusion rate, and expanding the effective evaporation area. However, excessively high evaporation temperatures can easily lead to overheating and failure of the molten pool walls and insulation materials, resulting in an operational upper limit. Furthermore, the metal vapor generated during evaporation cools and nucleates into nanoparticles during its outward migration. Without sufficient gas drag, these particles easily deposit on the furnace inner walls, failing to be effectively transported to the collection system, causing product loss and equipment contamination.

[0005] Common nanomaterial production technologies have significant shortcomings. For example, while patent CN100457339C uses multiple electric arcs to provide sufficient heat for metal evaporation, it does not explain how to form and maintain an effective evaporation surface, nor does it address the issues of efficient vapor diffusion and effective particle transport. Patent CN116765410A, although involving process gases, does not detail the specific impact of air distribution structure, location, and airflow on particle growth and transport. Furthermore, excessive gas flow into the arc sheath gas channel can easily lead to arc instability, energy loss due to excess gas, and low thermal efficiency.

[0006] Therefore, there is an urgent need to develop an electric arc nanomaterial production technology and device that can precisely and synergistically control evaporation temperature, steam concentration distribution, diffusion rate and particle transport efficiency in order to break through existing bottlenecks and achieve stable preparation of high-yield, high-quality nanopowders. Summary of the Invention

[0007] In order to coordinate the control of evaporation temperature, steam concentration distribution, diffusion rate and particle transport efficiency, and achieve stable preparation of high-yield, high-quality nanopowders, this application provides a method for producing nano-metals.

[0008] This application provides a method for producing nano-metals, employing the following technical solution:

[0009] A method for producing nanometals is carried out in a high-efficiency nanometal production apparatus. The apparatus includes an evaporation chamber, an insulation layer, and a molten pool nested within the insulation layer. A molten pool process air channel is formed between the molten pool and the insulation layer, with a width of 50-100 mm. The evaporation chamber has molten pool ventilation openings located on both sides of the molten pool. Protective air ventilation openings are located on both sides of the evaporation chamber, above the molten pool ventilation openings. A first ventilation channel is provided at the top of the evaporation chamber. The system includes a duct and an exhaust duct. The first ventilation duct is coaxially arranged with the evaporation chamber. The exhaust duct is inclined on both sides of the first ventilation duct. A second ventilation duct is installed inside the first ventilation duct. A main process air outlet is formed between the first ventilation duct and the second ventilation duct. An air outlet is provided at the bottom of the first ventilation duct. The air outlet is connected to the main process air outlet. The side of the air outlet closest to the axis of the first ventilation duct is vertically arranged. The other side of the air outlet is inclined towards the outer wall of the molten pool. An arc generator is installed inside the second ventilation duct. An arc surrounds the air outlet between the arc generator and the second ventilation duct.

[0010] The method for producing nano-metals includes the following steps:

[0011] Q1. Load metal raw materials into the molten pool and replace the gas in the evaporation chamber with an inert atmosphere;

[0012] Q2. Molten pool process air is introduced into the evaporation chamber through the molten pool vent, protective air is introduced into the evaporation chamber through the protective air vent, and electric arc circulating air is introduced into the evaporation chamber through the electric arc circulating air vent.

[0013] Q3. Introduce the main process air into the evaporation chamber through the main process air outlet. Adjust the main process air volume according to the temperature of the outlet air duct to maintain the outlet air duct temperature at 800-1200K.

[0014] Q4. Start the arc generator and gradually increase the single-channel arc current to 200A.

[0015] By adopting the above technical solutions, the entire molten pool is controlled in a molten state by increasing the process air in the molten pool, ensuring the maximum evaporation area. The main process air and the surrounding air of the electric arc generator are set separately to avoid interference from the electric arc area by the large air volume. At the same time, the jet structure of the main process air and the air outlet ensures the convection diffusion rate of metal vapor and the transport capacity of nanoparticles, thereby improving the yield of nanoparticles. By setting the air outlet pipe at an angle, the problem of air outlet obstruction due to turbulence is avoided. The evaporation temperature, vapor concentration distribution, diffusion rate and particle transport efficiency are precisely and synergistically controlled, realizing the stable preparation of high-yield and high-quality nanoparticles.

[0016] Optionally, thermocouples are provided on both sides of the evaporation chamber, with the measuring ends of the thermocouples penetrating the evaporation chamber and extending into the process air channel of the molten pool.

[0017] By adopting the above technical solution and setting thermocouples, the input current can be controlled during operation to adjust the temperature of the molten pool process air, thereby achieving optimal power input, saving energy, and protecting the sidewalls and insulation layer of the molten pool from overheating.

[0018] Optionally, the axis of the air outlet duct forms an angle of 20°-30° with the axis of the first ventilation duct.

[0019] Optionally, the air outlet duct is a Laval duct.

[0020] By adopting the above technical solutions, and by optimizing the position and tilt angle of the air outlet duct and adding a scaling nozzle structure, the problem of obstructed airflow due to turbulence can be avoided.

[0021] Optionally, in step Q1, the pressure in the evaporation chamber is reduced to 10 by displacing the gas in the evaporation chamber using a vacuum pump unit. -4 The pressure was initially set to 0.06 MPa, then nitrogen was introduced to restore the pressure to 0.06 MPa. This process was repeated multiple times.

[0022] Optionally, the velocity of the main process air is 10 m / s, and the velocity of the molten pool process air is 0.2 m / s.

[0023] Optionally, the air volume of both the protective wind and the arc circulating wind is 50 SLPM.

[0024] Optionally, thermocouples are provided on both sides of the evaporation chamber. The measuring end of the thermocouple passes through the evaporation chamber and extends into the molten pool process air channel. In step Q4, the temperature of the molten pool process air is adjusted to 1500-2000K by adjusting the current of the electrodes.

[0025] In summary, this application includes at least one of the following beneficial technical effects:

[0026] 1. By increasing the process air in the molten pool, the entire molten pool is controlled in a molten state, ensuring the maximum evaporation area; the main process air and the surrounding air of the arc generator are set separately to avoid interference from the arc area by large air volume. At the same time, the jet structure of the main process air and the air outlet ensures the convection diffusion rate of metal vapor and the transport capacity of nanoparticles, thereby improving the yield of nanoparticles; by setting the air outlet pipe at an angle, the problem of air outlet obstruction due to turbulence is avoided. The evaporation temperature, vapor concentration distribution, diffusion rate and particle transport efficiency are precisely and synergistically controlled, realizing the stable preparation of high-yield and high-quality nanoparticles.

[0027] 2. By setting up thermocouples, the input current can be controlled during operation, thereby adjusting the temperature of the molten pool process air, achieving optimal power input, saving energy, and protecting the sidewalls and insulation layer of the molten pool from overheating;

[0028] 3. By optimizing the position and tilt angle of the air outlet duct and adding a scaling nozzle structure, the problem of obstructed airflow due to turbulence can be avoided. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of a high-efficiency nano-metal production device in an embodiment of this application.

[0030] Figure 2 yes Figure 1 Enlarged view of point A in the middle.

[0031] Figure 3 yes Figure 1 Enlarged view of point B in the middle.

[0032] Explanation of reference numerals in the attached drawings: 1. Evaporation chamber; 2. Insulation layer; 3. Receiving section; 4. Flow section; 5. Molten pool; 6. Molten pool process air passage; 7. Molten pool vent; 8. Thermocouple; 9. Protective air vent; 10. First ventilation duct; 11. Second ventilation duct; 12. Arc generator; 13. Arc surround air vent; 14. Main process air vent; 15. Air outlet; 16. Air outlet duct. Detailed Implementation

[0033] The following is in conjunction with the appendix Figure 1-3 This application will be described in further detail.

[0034] Example

[0035] This application discloses a high-efficiency nano-metal production apparatus.

[0036] Reference Figure 1A high-efficiency nano-metal production device includes an evaporation chamber 1. The inner wall and bottom of the evaporation chamber 1 are provided with a heat insulation layer 2. In this embodiment, the heat insulation layer 2 is made of zirconium oxide. The evaporation chamber 1 includes a receiving portion 3 and a flow portion 4. The receiving portion 3 is cylindrical, and the flow portion 4 is located above the receiving portion 3. The flow portion 4 is integrally formed with the receiving portion 3, and the interior of the flow portion 4 communicates with the interior of the receiving portion 3. The cross-sectional radius of the flow portion 4 is larger than the cross-sectional radius of the receiving portion 3. The inner wall of the flow portion 4 is provided with the heat insulation layer 2, and the inner wall and bottom of the receiving portion 3 are also provided with the heat insulation layer 2.

[0037] Reference Figure 1 and Figure 2 The receiving section 3 contains a molten pool 5, which is located at the bottom of the evaporation chamber 1 and embedded in the insulation layer 2. The molten pool 5 is a cylindrical crucible with an arc-shaped top, the center of which is lower than the sides. A gap exists between the sidewall of the molten pool 5 and the insulation layer 2 of the receiving section 3, forming a molten pool process air channel 6. In this embodiment, the width of the molten pool process air channel 6 is 50 mm. Two molten pool ventilation openings 7 are provided on the sidewall of the receiving section 3, extending horizontally through the receiving section 3 and the insulation layer 2. These openings are symmetrically arranged around the axis of the receiving section 3. Thermocouples 8 are installed on both sides of the receiving section 3, one end of which penetrates the sidewall of the receiving section 3 and extends into the molten pool process air channel 6. Thermocouples 8 are fixedly connected to the receiving section 3 and are located above the molten pool ventilation openings 7. The input current is controlled by thermocouple 8 to maintain the temperature at a level 200-300°C higher than the melting point of the raw material, thereby ensuring the maximum evaporation area while preventing the temperature of the molten pool 5 wall and the insulation layer 2 from becoming too high.

[0038] Reference Figure 1 A protective air vent 9 is provided on the side wall of the circulation section 4, and the protective air vent 9 penetrates the circulation section 4 and the insulation layer 2 in the horizontal direction. There are two protective air vents 9, and the two protective air vents 9 are symmetrically arranged around the axis of the circulation section.

[0039] Reference Figure 1 The top of the circulation section 4 is provided with a first ventilation pipe 10 and a second ventilation pipe 11. The first ventilation pipe 10 is a cylinder with its opening facing upwards. One end of the first ventilation pipe 10 passes through the circulation section 4 and extends into the circulation section 4. The first ventilation pipe 10 is fixedly connected to the circulation section 4, and its axis coincides with the axis of the evaporation chamber 1. The second ventilation pipe 11 is a cylinder with openings at both ends. The second ventilation pipe 11 is located inside the first ventilation pipe 10. One end of the second ventilation pipe 11 passes through the bottom of the first ventilation pipe 10 and extends into the circulation section 4. The second ventilation pipe 11 is fixedly connected to the first ventilation pipe 10, and its axis coincides with the axis of the first ventilation pipe 10.

[0040] Reference Figure 1 and Figure 3 An arc generator 12 is slidably connected inside the second ventilation duct 11, forming an arc-encircling vent 13 between the second ventilation duct 11 and the arc generator 12. A main process vent 14 is formed between the first ventilation duct 10 and the second ventilation duct 11. An air outlet 15 is opened at the bottom of the first ventilation duct 10, and the air outlet 15 is connected to the main process vent 14. The air outlets 15 are symmetrically arranged on both sides of the second ventilation duct 11. The side of the air outlet 15 closest to the axis of the first ventilation duct 10 is vertically arranged, and the bottom of the other side of the air outlet 15 is inclined towards the outer wall of the molten pool 5.

[0041] Reference Figure 1 The top of the circulation section 4 is provided with two air outlet ducts 16, which are symmetrically arranged on both sides of the first ventilation duct 10. The axis of the air outlet duct 16 forms a 30° angle with the axis of the first ventilation duct 10. One end of the air outlet duct 16 passes through the circulation section 4, and the air outlet duct 16 is fixedly connected to the circulation section 4. A reducing nozzle is provided inside the air outlet duct 16, that is, the air outlet duct 16 is a Laval duct. The total area of ​​the openings of the air outlet duct 16 is greater than the sum of the areas of all process air inlets.

[0042] The implementation principle of a high-efficiency nano-metal production device in this application is as follows:

[0043] By increasing the process air channel 6 and the process air flow in the molten pool, the entire molten pool 5 is kept in a molten state, ensuring the maximum evaporation area. By adding thermocouples 8 and adjusting the input current during operation to regulate the temperature of the process air, optimal power input can be achieved, saving energy while protecting the sidewalls of the molten pool 5 and the insulation layer 2 from overheating. The main process air and the surrounding air of the arc generator are set up separately to avoid interference from large air volumes in the arc area. Simultaneously, the jet structure of the main process air and the outlet 15 ensures the convection and diffusion rate of metal vapor and the transport capacity of nanoparticles, improving the yield of nanoparticles. By optimizing the position and tilt angle of the outlet duct 16 and adding a scaling nozzle structure, problems caused by turbulence in the airflow are avoided. Precise and coordinated control of evaporation temperature, steam concentration distribution, diffusion rate, and particle transport efficiency enables the stable preparation of high-yield, high-quality nanoparticles.

[0044] Application examples

[0045] This application discloses a method for producing nano-metals, which is carried out in a high-efficiency nano-metal production apparatus disclosed in the embodiments, and includes the following steps:

[0046] S1. Load metal raw materials into the molten pool 5 and adjust the height of the electric arc generator;

[0047] S2. Start the vacuum pump unit to reduce the pressure in evaporation chamber 1 to 10.-4 The pressure was initially set to 0.06 MPa, then nitrogen was introduced to restore the pressure to 0.06 MPa. This process was repeated three times.

[0048] S3. Introduce main process air into evaporation chamber 1 through main process air outlet 14, and adjust the main process air volume to achieve a velocity of 10 m / s. Introduce molten pool process air into evaporation chamber 1 through molten pool vent 7, and adjust the molten pool process air volume to achieve a velocity of 0.2 m / s. Introduce protective air into evaporation chamber 1 through protective air vent 9, and introduce arc circulating air into evaporation chamber 1 through arc circulating air outlet 13. Set the air volume of both protective air and arc circulating air to 50 SLPM.

[0049] S4. Start the power supply of arc generator 12 to establish an arc between arc generator 12 and the metal material in molten pool 5. Gradually increase the single-channel arc current to 200 A;

[0050] S5. Adjust the current of thermocouple 8 to make the temperature of the molten pool process air 2000K. Adjust the main process air volume according to the temperature of the outlet duct 16 to maintain the temperature of the outlet duct 16 between 800-1200K.

[0051] In this application example, the distance between the axis of the main process vent 14 and the axis of the evaporation chamber 1 is 100 mm, and the width of the molten pool process air channel is 50 mm. The metal raw material is copper powder, and the average particle size of the obtained nano-metal powder is 150 nm. When the input power (excluding furnace heat dissipation) is 10 kW, the output is 1 kg / h; when the input power is 20 kW, the output is 3 kg / h.

[0052] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for producing nano-metals, characterized in that, The process is carried out in a high-efficiency nano-metal production device, which includes an evaporation chamber (1), an insulation layer (2) and a molten pool (5) nested in the insulation layer (2) in the evaporation chamber (1), a molten pool process air channel (6) is formed between the molten pool (5) and the insulation layer (2), the width of the molten pool process air channel (6) is 50-100mm, a molten pool ventilation port (7) is opened on the evaporation chamber (1), the molten pool ventilation port (7) is located on both sides of the molten pool (5), a protective air ventilation port (9) is opened on both sides of the evaporation chamber (1), the protective air ventilation port (9) is located above the molten pool ventilation port (7), a first ventilation pipe (10) and an air outlet pipe (16) are provided on the top of the evaporation chamber (1), the first ventilation pipe (10) is provided on the top of the evaporation chamber (1), and the first ventilation pipe (10) is provided on the top of the evaporation chamber (1). 0) The air outlet pipe (16) is coaxially arranged with the evaporation chamber (1). The air outlet pipe (16) is inclinedly arranged on both sides of the first ventilation pipe (10). The first ventilation pipe (10) is provided with a second ventilation pipe (11). The first ventilation pipe (10) and the second ventilation pipe (11) form a main process air outlet (14). The bottom of the first ventilation pipe (10) is provided with an air outlet (15). The air outlet (15) is connected to the main process air outlet (14). The air outlet (15) is vertically arranged on the side close to the axis of the first ventilation pipe (10). The other side of the air outlet (15) is inclined towards the outer wall of the molten pool (5). The second ventilation pipe (11) is provided with an electric arc generator (12). The electric arc generator (12) and the second ventilation pipe (11) form an electric arc surrounding air outlet (13). The method for producing nano-metals includes the following steps: Q1. Load metal raw materials into the molten pool (5) and replace the gas in the evaporation chamber (1) with an inert atmosphere; Q2. Molten pool process air is introduced into the evaporation chamber (1) through the molten pool vent (7), protective air is introduced into the evaporation chamber (1) through the protective air vent (9), and electric arc circulating air is introduced into the evaporation chamber (1) through the electric arc circulating air vent (13). Q3. Introduce the main process air into the evaporation chamber (1) through the main process air outlet (14), and adjust the main process air volume according to the temperature of the air outlet duct (16) to maintain the temperature of the air outlet duct (16) at 800-1200K. Q4. Start the arc generator (12) and gradually increase the single-channel arc current to 200A.

2. The method for producing nano-metals according to claim 1, characterized in that: Thermocouples (8) are provided on both sides of the evaporation chamber (1). One end of the thermocouple (8) passes through the evaporation chamber (1) and extends into the molten pool process air channel (6).

3. The method for producing nano-metals according to claim 1, characterized in that: The axis of the air outlet duct (16) forms an angle of 20°-30° with the axis of the first ventilation duct (10).

4. The method for producing nano-metals according to claim 3, characterized in that: The air outlet duct (16) is a Laval duct.

5. The method for producing nano-metals according to claim 1, characterized in that: In step Q1, the gas inside the evaporation chamber (1) is replaced by a vacuum pump unit, reducing the pressure in the evaporation chamber (1) to 10. -4 The pressure was initially set to 0.06 MPa, then nitrogen was introduced to restore the pressure to 0.06 MPa. This process was repeated multiple times.

6. The method for producing nano-metals according to claim 1, characterized in that: The velocity of the main process air is 10 m / s, and the velocity of the molten pool process air is 0.2 m / s.

7. The method for producing nano-metals according to claim 1, characterized in that: The air volume of both the protective wind and the arc circulatory wind is 50 SLPM.

8. A method for producing nano-metals according to claim 1, characterized in that: Thermocouples (8) are provided on both sides of the evaporation chamber (1). One end of the thermocouple (8) passes through the evaporation chamber (1) and extends into the molten pool process air channel (6). In step Q4, the temperature of the molten pool process air is adjusted to 1500-2000K by adjusting the current of the electrodes.

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