Variable diameter assembly for a plasma evaporation chamber and method of implementation

Abstract

A variable-diameter assembly device and implementation method for a plasma evaporation chamber includes a chamber wall, a variable-diameter inner liner, a variable-diameter guide rail, and thermocouples. The reaction chamber is an integral DC arc plasma evaporation chamber. The anode copper seat within the reaction chamber is located at the center of the bottom surface of the variable-diameter inner liner. The cathode is moved up and down by a lifting rod. A crucible is placed on the anode copper seat, and plasma is formed between the cathode and the anode material. The variable-diameter inner liner has an arc-shaped vertical cylindrical structure. Each inner liner plate can move along the variable-diameter guide rail, thereby adjusting the radius of the inner liner and controlling the particle size and distribution. Thermocouples are used to detect the temperature distribution within the space formed by the variable-diameter inner liner. This invention, through the design and implementation of a variable-diameter inner liner inside the evaporation chamber, can effectively change the particle growth space and control the particle size and distribution by adjusting the temperature gradient field. Without changing the overall size of the chamber, the size of key areas inside the chamber can be significantly adjusted, achieving control over the quality of the particulate product, improving energy utilization, and reducing preparation costs.

Description

Technical Field

[0001] This invention belongs to the technical field of nano / micro metal and alloy powder production equipment. Specifically, it relates to a variable diameter combination device for the generation chamber in the powder preparation process, and particularly to the control technology and application of particle size and distribution in the large-scale preparation of metal powder using high-temperature plasma. Background Technology

[0002] Physical vapor deposition (PVD) is a common method for industrial powder material preparation. High-temperature plasma, a highly efficient evaporation heat source, can be used to prepare high-purity nano / micron-sized metal and composite powder materials. In the reaction chamber, bulk raw materials evaporate and decompose into corresponding gaseous states. Supersaturated gaseous atoms undergo nucleation in the high-temperature region of the plasma and continue to grow within the temperature gradient space of the chamber, ultimately forming powder particles. A growth space with a certain temperature gradient becomes one of the important factors for controlling the particle size and distribution of the powder. Plasma fixed-arc or transferred-arc methods have advantages in powder preparation, such as simple operation, low cost, fast synthesis speed, high product purity, and environmental friendliness, and are widely used in industrial powder production. However, PVD powder material preparation also has limitations, such as being limited to certain types of metal alloys and having a relatively wide particle size distribution. Related technological research is developing from large-scale powder preparation technology towards obtaining higher-quality powder products, achieving powder product diversification, exploring their formation mechanisms, and forming complete and controllable synthesis processes to achieve nano / micron-sized powder materials with controllable average particle size and uniform distribution.

[0003] Common methods involve adjusting reaction power and reaction gas pressure for control. For example, patent CN201210389646.4 describes obtaining alloy particles with a diameter range of 100-3000 nm by changing the inlet gas pressure. Lu Chengjie et al. from Nanjing University of Technology, in synthesizing nano-nickel powder, found that increasing the current from 250 A to 600 A increased the nickel powder particle size by 3.4 times. Increasing energy power or gas phase pressure to improve the supply rate and concentration of growth materials can, to some extent, control the powder particle size, but it has limitations in controlling particle size distribution. Therefore, more effective methods and corresponding technologies are needed to improve the control of powder particle size and distribution, and further achieve uniform particle size distribution based on powder yield scale. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a variable-diameter combination device and implementation method for a plasma evaporation chamber. It designs a novel vacuum evaporation chamber for DC arc plasma equipment. Unlike the traditional single evaporation chamber, the chamber incorporates a variable-diameter high-melting-point metal inner liner that moves via a sliding track. The purpose is to regulate the temperature space and temperature field during the powder formation process, thereby controlling the average size and distribution of powder particles to meet the quality requirements of submicron / nanoscale powder materials.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A variable diameter assembly for a plasma evaporation chamber, including an attached... Figure 1 and attached Figure 2 The chamber wall 6, variable diameter inner liner 8, variable diameter guide rail 9, and thermocouple shown are placed in the reaction chamber 1, which is an integral DC arc plasma evaporation chamber.

[0007] The reaction chamber 1 is equipped with a cathode 2, plasma 3, anode copper seat 4, crucible 5, and anode material 7. The anode copper seat 4 is located in the middle of the bottom surface of the variable diameter inner liner 8 and is placed coaxially with the cylindrical structure formed by the variable diameter inner liner 8. The cathode 2 can be moved up and down by a lifting rod, which can adjust the distance between the cathode 2 and the anode material 7. The crucible 5 serves as the reaction container for the anode material 7 and is placed on the anode copper seat 4. Plasma 3 is formed between the cathode 2 and the anode material 7, which is the main region for particle nucleation.

[0008] The chamber wall 6 serves as the insulation wall for the evaporation chamber, aiming to protect the internal temperature of the entire reaction chamber. An exhaust pipe 12 is located below the chamber wall 6.

[0009] The variable-diameter inner liner 8 consists of multiple pieces, each arc-shaped, forming a vertical cylindrical structure. The internal space of the inner liner is the main field for particle growth, and they are connected to each other by loosely fixed screws 10. The bottom of each inner liner piece is fixed to a slider and contacts a variable-diameter guide rail 9. The variable-diameter guide rail 9 is radially positioned between the chamber wall 6 and the cylindrical structure formed by the variable-diameter inner liner 8. The inner liner pieces can move synchronously radially along the variable-diameter guide rail 9, and the bottom of the inner liner pieces can move towards the arc zone along the variable-diameter guide rail 9, thereby adjusting the radius of the inner liner and providing variable space for particle growth, thus controlling the particle size and distribution. The direction of movement of the circulating gas and particulate products inside the reaction chamber is as shown in the airflow direction: the circulating gas enters from top to bottom into the space between the variable-diameter inner liner and the inner wall of the chamber, flows to the outlet pipe at the bottom of the reaction chamber, and the circulating gas and powder products are carried away from the reaction chamber and flow to the next circulation unit.

[0010] The thermocouple is used to detect the temperature distribution in the space formed by the variable-diameter inner liner.

[0011] Furthermore, the thermocouple includes thermocouple II14 and thermocouple I13; thermocouple II14 is located in the inner liner and is used to monitor the temperature of the inner liner wall; thermocouple I13 is located inside the chamber wall 6 and is used to monitor the temperature change of the chamber wall 6.

[0012] Furthermore, the maximum adjustable radius of the variable-diameter inner liner 8 is 1200mm, the minimum adjustable radius is 500mm (the minimum inner liner position 15 is 500mm away from the center of the electric arc), and the maximum variable diameter range is 700mm. By adjusting this space size, combined with the concentration of growth material and the space temperature gradient, the particle size and distribution state can be adjusted, and the obtained powder particle size can be adjusted within the range of 150-300nm.

[0013] Furthermore, the upper end of the cathode 2 is connected to the lifting rod, which is insulated, and the linear distance of the cathode 2's lifting is within the range of 3-5 cm. The cathode 2 is made of a high-temperature resistant conductive material and uses a graphite electrode. The crucible 5 serves as the reaction vessel for the anode material 7 and is made of a material that is inert to the anode material 7 at high temperatures. The anode material 7 is characterized by being a conductive raw material, including a metal block, a graphite block, or a conductive composite block. An electric arc is formed between the cathode and the anode material, and the arc is powered by an arc power source.

[0014] Furthermore, the variable-diameter inner liner 8 is composed of 16 or more arc-shaped insulating material sheets, and the material of the inner liner is a high-melting-point metal, including molybdenum, tungsten, niobium, tantalum, and zirconium.

[0015] Furthermore, the variable-diameter inner liner moves synchronously on the variable-diameter guide rail 9, thereby changing the diameter of the cylinder formed by the inner liner.

[0016] Furthermore, the reaction chamber wall 6 is an insulation structure, consisting of an outer vacuum layer and an inner insulation cotton layer, which provides good insulation for the interior of the reaction chamber, making full use of plasma heat and avoiding energy loss.

[0017] A method for implementing a variable-diameter assembly for a plasma evaporation chamber includes the following steps:

[0018] (1) Assemble the variable diameter device of the plasma evaporation chamber, place the crucible 5 on the anode copper seat 4, add the anode material 7 into the crucible 5, and the anode material 7 is continuously supplied by the automatic feeding system.

[0019] (2) Evacuate the entire reaction chamber and equipment to 1 Pa, and fill it with working gas N2 to 100 kPa. Turn on the arc power supply and set the arc current to 600 A. Initiate an arc between the tip of cathode 2 and anode material 7 to form high-temperature nitrogen ions 3. Anode material 7 begins to melt, forming a molten liquid surface in crucible 5, which then evaporates and vaporizes. Adjust the position of cathode 2 up and down using the lifting rod, with a linear distance of 3-5 cm, until a stable, non-drifting arc is formed between cathode 2 and the molten liquid surface, achieving optimal evaporation efficiency. As the distance between the cathode and the molten liquid surface changes, the amplitude of the arc working voltage signal changes; the larger the distance, the larger the voltage, and vice versa. This voltage signal will be fed back to the feeding system to automatically control the material supply.

[0020] (3) Within the stable plasma arc region, three temperature zones are formed: the inner flame, the middle flame, and the outer flame. Evaporation and vaporization mainly occur in the highest temperature zone of the inner flame, typically reaching 10,000-15,000 K, depending on the type and activity of the working gas. Particle nucleation mainly occurs in the high-temperature inner flame region of plasma 3; the nucleation rate depends on the concentration of the growth material and is constrained by the rate at which the growth material is provided and the gas pressure. Particle growth mainly occurs in the space outside the plasma arc, i.e., the growth region between the arc region and the variable-diameter inner liner 8; the growth process is constrained by the concentration of the growth material and the temperature gradient space.

[0021] (4) Inside the cylinder formed by the variable diameter inner liner 8, the nucleation and growth process of the particles is completed. These powder particles are driven by the circulating gas, and enter the next circulation unit through the airflow direction 11 and the outlet pipe 12, and finally obtain the powder product.

[0022] The working principle and innovation of this invention: The basic process of preparing submicron / nano-scale powders using the physical vapor phase method is as follows: A high-temperature heat source (thermal plasma, high-energy laser, resistance heating, electromagnetic induction heating, etc.) is used to evaporate the bulk raw material and form a gaseous state. When the gaseous concentration of a certain component element reaches a supersaturated state and approaches its melting point temperature, nucleation centers begin to appear, forming solid-phase crystal nuclei that gradually grow into particles. The innovation of this invention lies in altering the particle growth space and temperature conditions during the preparation of powder materials using DC arc plasma, adding new control methods to effectively control the particle size and its distribution.

[0023] The beneficial effects of this invention are as follows:

[0024] Traditional DC arc plasma evaporation chambers have a fixed inner diameter, resulting in a fixed particle growth space and temperature field. This invention, through the design and implementation of a variable-diameter inner liner within the evaporation chamber, effectively alters the particle growth space and regulates particle size and distribution by adjusting the temperature gradient field. Beyond factors such as plasma power, gas pressure, and gas circulation rate, this invention provides a novel and effective method for adjusting the characteristics of particulate products. Without altering the overall chamber dimensions, the size of key areas within the chamber can be significantly adjusted, enabling control over particulate product quality while simultaneously improving energy efficiency and reducing preparation costs. Attached Figure Description

[0025] Figure 1 This is a front view of the device of the present invention;

[0026] Figure 2 This is a top view of the device of the present invention.

[0027] In the diagram: 1. Reaction chamber, 2. Cathode, 3. Plasma, 4. Anode copper seat, 5. Crucible, 6. Chamber wall, 7. Anode material, 8. Variable diameter inner liner, 9. Variable diameter guide rail, 10. Inner liner fixing screw, 11. Airflow direction, 12. Outlet pipe, 13. Thermocouple I, 14. Thermocouple II, 15. Position of the smallest diameter inner liner, 16. Inner liner variable diameter range. Detailed Implementation

[0028] To make the objectives, technical solutions, and features of the present invention clearer, a detailed description will be given below in conjunction with the embodiments of the present invention. However, the scope of the present invention is not limited to the following examples.

[0029] Specific procedures for powder preparation:

[0030] (1) As attached Figure 1 As shown, the variable diameter device of the plasma evaporation chamber of the present invention includes a cathode 2, a plasma 3, a crucible 5, etc. The cathode 2 is a graphite electrode. The crucible 5 is placed on the anode copper seat 4. Material 7 is added to the crucible 5. Material 7 is a nickel block weighing 10 kg (a nickel ball with a diameter of about 1 cm). Material 7 is continuously supplied by an automatic feeding system.

[0031] (2) Evacuate the entire equipment to 1 Pa and fill it with working gas N2 to 100 kPa. Turn on the arc power supply and set the arc current to 600 A. Initiate an arc between the tip of cathode 2 and material 7 to form high-temperature nitrogen ions 3. Material 7 begins to melt, forming a molten liquid surface in the crucible, which then evaporates and vaporizes. Adjust the position of cathode 2 up and down using the operating lever, with a linear distance of 3-5 cm, until the arc formed between cathode 2 and the molten liquid surface is stable and the evaporation efficiency is optimal. As the distance between the cathode and the molten liquid surface changes, the amplitude of the arc working voltage signal changes; the larger the distance, the larger the voltage, and vice versa. This voltage signal will be fed back to the feeding system to automatically control the material supply.

[0032] (3) Within the stable plasma arc region, three temperature zones are formed: the inner flame, the middle flame, and the outer flame. Evaporation and vaporization mainly occur in the highest temperature zone of the inner flame, typically reaching 10,000-15,000 K, depending on the type and activity of the working gas. Particle nucleation mainly occurs in the high-temperature inner flame region of the plasma; the nucleation rate depends on the concentration of the growth material and is constrained by the rate at which the growth material is provided and the gas pressure. Particle growth mainly occurs in the space outside the plasma arc, i.e., the growth region between the arc region and the variable-diameter inner liner 8; the growth process is constrained by the concentration of the growth material and the temperature gradient space.

[0033] (4) The variable-diameter inner liner 8 consists of multiple sets of radially movable blades that move synchronously along the variable-diameter guide rail 9, adjusting the radius of the resulting cylinder, i.e., the size of the particle growth space, while simultaneously controlling the temperature gradient value for particle growth. The temperature gradient is determined by thermocouples 14 at the variable-diameter inner liner 8. In a small-radius inner liner with a small temperature gradient space, small and uniformly distributed particles are easily formed; in a large-radius inner liner with a large temperature gradient space, larger particles with a wider size distribution are easily formed.

[0034] (5) Inside the cylinder formed by the variable-diameter inner liner 8, the nucleation and growth process of the particles is completed. These powder particles are driven by the circulating gas, and enter the next circulation unit through the airflow direction 11 and the exhaust pipe, finally obtaining the powder product. The maximum adjustable radius of the variable-diameter inner liner 8 is 1200 mm, the minimum adjustable radius is 500 mm, and the maximum diameter range is 700 mm. By adjusting the size of this space, combined with the concentration of the growth material and the temperature gradient of the space, the particle size and distribution state can be adjusted, and the obtained powder particle size can be adjusted within the range of 150-300 nm.

[0035] The above specific embodiments are merely one implementation of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make several changes without departing from the concept of the present invention, including but not limited to changing the type of raw materials, gas pressure, power supply, auxiliary heat source, carrier gas circulation rate, feeding method, etc., all of which fall within the protection scope of the present invention.

Claims

1. A variable diameter assembly device for a plasma evaporation chamber, characterized in that, The variable diameter assembly includes a reaction chamber (1), a chamber wall (6), a variable diameter inner liner (8), a variable diameter guide rail (9), and a thermocouple. The reaction chamber (1) is an integral DC arc plasma evaporation chamber. The cathode (2), plasma (3), anode copper seat (4), crucible (5), and anode material (7) in the reaction chamber (1) are located in the cylindrical structure formed by the variable diameter inner liner (8); the anode copper seat (4) is located in the middle of the bottom surface of the variable diameter inner liner (8) and is placed coaxially with the cylindrical structure formed by the variable diameter inner liner (8); the cathode (2) is moved up and down by the lifting rod to adjust the distance between the cathode (2) and the anode material (7); the crucible (5) serves as the reaction container for the anode material (7) and is placed on the anode copper seat (4); plasma (3) is formed between the cathode (2) and the anode material (7); The chamber wall (6) is the heat insulation wall of the evaporation chamber, and an exhaust pipe (12) is provided below it; The variable-diameter inner liner (8) consists of multiple inner liner plates, each of which is arc-shaped, forming a vertical cylindrical structure. The internal space of the inner liner is the main field area for particle growth, and they are connected to each other by loosely fixed screws (10). The bottom of each inner liner plate is connected to the variable-diameter guide rail (9) by a slider. The variable-diameter guide rail (9) is radially located between the chamber wall (6) and the cylindrical structure formed by the variable-diameter inner liner (8). All inner liner plates move synchronously along the variable-diameter guide rail (9) to adjust the radius of the inner liner, providing variable space for particle growth, thereby controlling the particle size and distribution. The circulating gas inside the reaction chamber enters the space between the outer wall of the variable-diameter inner liner (8) and the inner wall of the reaction chamber (1) from top to bottom. At the gas outlet pipe, the circulating gas and powder products are carried away from the reaction chamber and flow to the next circulation unit. The thermocouple is used to detect the temperature distribution in the space formed by the variable-diameter inner liner; The variable-diameter inner liner (8) has a maximum radius of 1200 mm and a minimum radius of 500 mm. By adjusting the size of this space, combined with the concentration of growth material and the temperature gradient of the space, the particle size and distribution can be adjusted, and the obtained powder particle size can be adjusted within the range of 150~300 nm.

2. The variable diameter assembly device for a plasma evaporation chamber according to claim 1, characterized in that, The thermocouples include thermocouple II (14) and thermocouple I (13); thermocouple II (14) is located in the inner liner and is used to monitor the temperature of the inner liner wall; thermocouple I (13) is located inside the chamber wall (6) and is used to monitor the temperature change of the chamber wall (6).

3. The variable diameter assembly device for a plasma evaporation chamber according to claim 1, characterized in that, The upper end of the cathode (2) is connected to the lifting rod, and the lifting rod is insulated. The linear distance of the cathode (2) is 3-5cm.

4. The variable diameter assembly device for a plasma evaporation chamber according to claim 1, characterized in that, The cathode (2) is made of a high-temperature conductive material; the crucible (5) is made of a material that is inert to the anode material (7) at high temperatures; the anode material (7) is a conductive raw material, and an electric arc is formed between the cathode (2) and the anode material (7), and the electric arc is powered by an electric arc power source; the variable diameter inner liner (8) is made of a heat-insulating and high-melting-point metal.

5. The variable diameter assembly device for a plasma evaporation chamber according to claim 4, characterized in that, The cathode (2) is a graphite electrode; the anode material (7) includes a metal block, a graphite block, or a conductive composite block; the variable diameter inner liner (8) is made of molybdenum, tungsten, niobium, tantalum, or zirconium.

6. The variable diameter assembly device for a plasma evaporation chamber according to claim 1, characterized in that, The reaction chamber wall (6) is a heat-insulating structure, consisting of an outer vacuum layer and an inner heat-insulating cotton layer.

7. A method for implementing a variable diameter assembly device for a plasma evaporation chamber as described in any one of claims 1-6, characterized in that, Includes the following steps: (1) Assemble the variable diameter device of the plasma evaporation chamber, place the crucible (5) on the anode copper seat (4), add anode material (7) into the crucible (5), and the anode material (7) is continuously supplied by the automatic feeding system; (2) Evacuate the entire equipment and fill it with working gas N2 to 100kPa; turn on the arc power supply and set the arc current to 600A. An arc is formed between the tip of the cathode (2) and the anode material (7) to form a high-temperature plasma 3; the anode material (7) begins to melt and forms a molten liquid surface in the crucible (5). The liquid surface evaporates and vaporizes; the position of the cathode (2) is adjusted up and down by the lifting rod. The straight distance of the lifting rod is in the range of 3-5cm until a stable arc that does not drift is formed between the cathode (2) and the molten liquid surface, and the evaporation efficiency is optimal; as the distance between the cathode and the molten liquid surface changes, the amplitude of the arc working voltage signal changes. The larger the distance, the larger the voltage value, and vice versa; this voltage signal will be fed back to the feeding system to automatically control the supply of materials; (3) Within the stable plasma arc region, three temperature regions are formed: inner flame, middle flame, and outer flame. The vaporization process mainly occurs in the highest temperature region of the inner flame, which can reach 10,000-15,000 K. The nucleation process of particles mainly occurs in the high-temperature inner flame region of the plasma (3). The nucleation rate depends on the concentration of the growth material and is subject to the rate of supply of the growth material and the gas pressure. The particle growth process mainly occurs in the space outside the plasma arc, that is, the growth region between the arc region and the variable diameter inner liner (8). The growth process is subject to the concentration of the growth material and the temperature gradient space. (4) Inside the cylinder formed by the variable diameter inner liner (8), the nucleation and growth process of the particles is completed. These powder particles are driven by the circulating gas and enter the next circulation unit through the airflow direction 11 and the outlet pipe (12) to finally obtain the powder product.

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