A non-metallic ultrafine powder preparation system and method based on a plasma transferred arc

Abstract

The present application relates to the technical field of non-metallic ultrafine powder preparation, and particularly relates to a non-metallic ultrafine powder preparation system and method based on plasma transferred arc, which comprises a reaction furnace body provided with a heat insulation layer and a double-layer shell with water cooling, a plasma generator with a secondary arc transfer function is arranged in a first cavity of the furnace body, a water-cooled graphite crucible and a water-cooled powder feeding pipe are installed in the first cavity, a powder feeding port of the water-cooled powder feeding pipe is connected to a powder feeder, the first cavity is further provided with a viewing window with a water-cooled protection mechanism and a thermocouple for monitoring the temperature of an arc column of the plasma generator; a second cavity of the furnace body is configured to communicate with a side of the first cavity away from the plasma generator, and the second cavity is provided with an ultrafine powder outlet. The present application utilizes the transferred arc to prepare non-metallic powder, can fully exert the advantages of the transferred arc, and realizes long-term stable non-metallic ultrafine powder preparation work of the plasma transferred arc.

Description

Technical Field

[0001] This invention relates to the field of non-metallic ultrafine powder preparation technology, and more specifically, to a non-metallic ultrafine powder preparation system and method based on plasma transfer arc. Background Technology

[0002] Currently, in the field of materials preparation, electric arc plasma is often used to prepare ultra-high purity ultrafine powders. Electric arc plasma has high electrothermal conversion efficiency, which can achieve mass production at a lower cost.

[0003] In existing technologies, plasma devices used for preparing ultrafine powders employ two types of plasma equipment: transferred arc plasma generators and non-transferred arc plasma generators. Non-transferred arc plasma generators, due to their low temperature, are not suitable for the vaporization of non-conductive materials, while transferred arc plasma generators require conductive materials to heat effectively and cannot heat inorganic materials in a non-molten state. Transferred arc plasma generators, on the other hand, have higher temperatures and are suitable for various working atmospheres (nitrogen, argon, hydrogen, etc.). They offer advantages in preparing nanomaterials, including good sphericity, small particle size (down to 10-50 nm), and high preparation efficiency. If transferred arc plasma generators can be used to prepare non-metallic powders, fully utilizing their advantages, it would have significant practical implications for the promotion and expansion of non-metallic powder preparation technology.

[0004] To address the aforementioned issues, we propose a non-metallic ultrafine powder preparation system and method based on plasma transfer arc. Summary of the Invention

[0005] The purpose of this invention is to provide a non-metallic ultrafine powder preparation system and method based on plasma transfer arc, so as to solve the problem that existing transfer arcs cannot prepare non-metallic powders.

[0006] The embodiments of the present invention are achieved through the following technical solution: a non-metallic ultrafine powder preparation system based on plasma transfer arc, comprising a reactor body, wherein the outer wall of the reactor body is provided with a heat insulation layer and a double-layer shell from the inside out, the gap between the layers of the double-layer shell is connected to the furnace body water inlet and furnace body water outlet, the reactor body includes a first cavity, a second cavity, and a plasma power supply, the plasma power supply is used to power a plasma generator with a two-stage arc transfer function, the plasma generator is disposed on the side wall of the first cavity, the second cavity is configured to communicate with the side of the first cavity away from the plasma generator, the second cavity is provided with an ultrafine powder outlet, and an observation window is also provided on one side of the first cavity, the observation window being provided with a water-cooling protection mechanism.

[0007] The first cavity is equipped with a conductive graphite-based ink-cooled crucible for preparing the molten material. A water-cooled powder feeding pipe is provided on the side wall of the first cavity. The powder outlet of the water-cooled powder feeding pipe extends above the conductive graphite-based ink-cooled crucible, and the powder inlet of the water-cooled powder feeding pipe is connected to a powder feeder.

[0008] The side wall of the first cavity is equipped with a thermocouple for monitoring the temperature of the arc column of the plasma generator.

[0009] According to a preferred embodiment, a first metal sleeve is provided around the outside of the water-cooled powder delivery pipe, and the first metal sleeve has a first water-cooled interlayer.

[0010] According to a preferred embodiment, the side wall of the first cavity is provided with a flange, the water-cooled powder delivery pipe is provided through the central hole of the flange, and a transition sleeve is provided between the first metal sleeve and the flange.

[0011] According to a preferred embodiment, the first metal sleeve includes an inner sleeve, an outer sleeve, an inlet spout, and an outlet spout;

[0012] The inner sleeve and outer sleeve are sequentially arranged around the outside of the water-cooled powder delivery pipe. A first interlayer is formed between the inner sleeve and the water-cooled powder delivery pipe, and a second interlayer is formed between the outer sleeve and the inner sleeve. The first interlayer and the second interlayer are connected. The water inlet is connected to the second interlayer, and the water outlet is connected to the first interlayer, so that a double-layer cooling water channel is formed on the outside of the water-cooled powder delivery pipe.

[0013] According to a preferred embodiment, the first interlayer and the second interlayer are connected at their first ends near the powder outlet of the water-cooled powder delivery pipe, forming a return water bend structure.

[0014] According to a preferred embodiment, the water inlet and water outlet are respectively connected to the second interlayer and the second end of the first interlayer near the powder inlet of the powder feeding pipe.

[0015] According to a preferred embodiment, the conductive graphite graphite-cooled crucible includes a graphite crucible body and a second metal sleeve surrounding the outside of the graphite crucible body. The second metal sleeve has a second water-cooling jacket, and a heat-insulating material is cast between the second metal sleeve and the graphite crucible body.

[0016] According to a preferred embodiment, the second metal sleeve includes a metal outer sleeve and a metal base plate;

[0017] The metal jacket is arranged around the outside of the graphite crucible body, and the metal base plate is located at the bottom of the graphite crucible body and connected to the metal jacket.

[0018] According to a preferred embodiment, the bottom of the metal jacket is connected to the metal base plate, and the top extends along the height direction of the second metal jacket. The top of the metal jacket and the outer side of the graphite crucible body form an anti-jump arc structure.

[0019] This invention also provides a method for preparing non-metallic ultrafine powders based on a plasma transfer arc, applied to the aforementioned non-metallic ultrafine powder preparation system based on a plasma transfer arc, comprising:

[0020] Cooling water is supplied to the double-layer shell, the observation window, the conductive graphite ink-cooled crucible, and the water-cooled powder delivery pipe at their respective water-cooling inlets.

[0021] The plasma generator's arc ignition directly acts on the conductive graphite-based cold crucible. When the temperature obtained by the thermocouple meets the set value, the powder feeder is activated.

[0022] The powder feeding amount is gradually increased. During the powder feeding process, the melting of the material at the bottom of the conductive graphite ink cold crucible is observed through the observation window until a uniform melt is formed inside the conductive graphite ink cold crucible, covering the bottom of the crucible directly opposite the electric arc column and forming a semi-solid, semi-fluid anti-splash layer on the outer edge of the crucible bottom.

[0023] Once the melt thickness reaches the set value, increase the output power of the plasma power supply and adjust the powder feeding rate until the incoming powder material and the vaporized material reach equilibrium.

[0024] The vaporized material produced by vaporization is condensed into ultrafine powder in the second chamber and then discharged through the ultrafine powder outlet.

[0025] The present invention provides a non-metallic ultrafine powder preparation system and method based on a plasma transfer arc, which has at least the following advantages and beneficial effects: The present invention initiates the arc in the presence of no material in the conductive graphite-based cold crucible, allowing the plasma arc column to act stably on the crucible. Powder is fed when the set temperature is reached, until a uniform melt forms inside the crucible, covering the bottom of the crucible directly opposite the arc column and forming a semi-solid, semi-fluid anti-splash layer along the outer edge of the crucible bottom. Non-metallic and inorganic materials become conductive at high temperatures or in a molten state. The entire process is cooled by water-cooling mechanisms in each component to prevent rapid ablation. Once the melt thickness reaches the set value, the plasma power output is increased, and the powder feeding rate is adjusted until the incoming powder material and the vaporized material reach equilibrium, thus achieving long-term stable non-metallic ultrafine powder preparation via a plasma transfer arc. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the non-metallic ultrafine powder preparation system based on plasma transfer arc provided in Embodiment 1 of the present invention;

[0027] Figure 2 This is a schematic flowchart of the method for preparing non-metallic ultrafine powder based on plasma transfer arc provided in Embodiment 1 of the present invention;

[0028] Icons: 1-Plasma power supply, 2-Forward power cable, 3-Negative power cable, 4-Plasma generator, 5-Water-cooled powder delivery pipe outlet, 6-Powder inlet, 7-Water-cooled powder delivery pipe inlet, 8-Transition sleeve, 9-Water-cooled powder delivery pipe, 10-Furnace body outlet, 11-Powder outlet, 12-Insulation layer, 13-Powder, 14-Conductive graphite ink-cooled crucible, 15-Furnace outer shell, 16-Furnace inner shell, 17- 18-Ultrafine powder outlet, 19-Furnace body water inlet, 20-Generator external support, 21-Generator insulating sleeve, 22-Furnace body upper flange, 23-Vaporized material, 24-Observation window flange, 25-Observation window, 26-Plasma arc column, 27-Furnace bottom positive electrode, 28-Reaction furnace body, 29-Generator gas source, 30-Powder feeder, 31-Thermocouple, 32-Cooling collection device. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0030] Example 1

[0031] This embodiment provides a non-metallic ultrafine powder preparation system based on a plasma transfer arc. (See also...) Figure 1 As shown, Figure 1 The diagram shows the overall structure of the system, which includes a reactor body 28. The outer wall of the reactor body 28 is provided with a heat insulation layer 12 and a double-layer shell from the inside out. The heat insulation layer 12 and the double-layer shell are connected and fixed by the upper flange 22 of the reactor body 28. The double-layer shell is composed of an outer shell 15 and an inner shell 16. The gap between the outer shell 15 and the inner shell 16 is connected to the furnace body water inlet 19 and the furnace body water outlet 10, so that the gap between the outer shell 15 and the inner shell 16 forms a furnace body cooling water channel, which dissipates heat from the furnace body.

[0032] The reactor body 28 includes a first chamber, a second chamber, and a plasma power supply 1. The plasma power supply 1 supplies power to a plasma generator 4 with a two-stage arc transfer function, i.e., dual function of non-transfer arc and transfer arc, via a reverse power supply cable. In one embodiment, the plasma power supply 1 is selected as a plasma power supply 1 with a two-stage arc transfer function, a full inverter design, and IGBT module output. The plasma generator 4 is located on the side wall of the first chamber, and its input end is connected to the generator gas source 29. In another embodiment, the plasma generator 4 is located at the top of the reactor body 28. An external generator support 20 is provided on the upper part of the upper flange 22 of the reactor body 28. The plasma generator 4 is installed through the external generator support 20, and an insulating sleeve 21 is directly provided between the plasma generator 4 and the external generator support 20.

[0033] The second cavity is configured to communicate with the side of the first cavity away from the plasma generator 4. The second cavity is provided with an ultrafine powder outlet 18. The first cavity is also provided with an observation window 25 with a strong light lens on one side. The observation window 25 is connected to the side wall of the reactor body 28 through an observation window flange 24. The observation window 25 is provided with a water-cooling protection mechanism.

[0034] Furthermore, a conductive graphite-cooled crucible 14 for preparing the melt is installed in the first cavity via a crucible conductive support frame 17. The positive power supply cable 2 of the plasma power supply 1 is connected to the conductive graphite-cooled crucible 14 via the positive electrode 27 at the furnace bottom. A water-cooled powder feeding pipe 9 is provided on the side wall of the first cavity. The powder outlet 11 of the water-cooled powder feeding pipe 9 extends above the conductive graphite-cooled crucible 14, and the powder inlet 6 of the water-cooled powder feeding pipe 9 is connected to the powder feeder 30. The gas-powder mixture is fed by... The powder enters through the inlet 6 of the water-cooled powder feeding pipe 9 and is ejected through the outlet 11. The ejected gas-powder mixture directly enters the conductive graphite-cooled crucible 14. The powder 13 in contact with the arc column will form a melt and vapor 23 at high temperature (such as the silicon vaporization temperature of 2300℃). The vapor 23 will rapidly condense in the furnace to form nano-sized particles, while the material in contact with the graphite crucible will become a solid. A thermocouple 31 for monitoring the temperature of the arc column of the plasma generator 4 is provided on the side wall of the first cavity.

[0035] Specifically, the side wall of the first cavity is provided with a flange, the water-cooled powder delivery pipe 9 is provided through the central hole of the flange, and a transition sleeve 8 is provided between the first metal sleeve and the flange, so as to achieve a sealed connection with the central hole of the flange through the transition sleeve 8.

[0036] The water-cooled powder delivery pipe 9 is surrounded by a first metal sleeve. The first metal sleeve has a first water-cooled jacket. The first water-cooled jacket is arranged around the powder delivery direction of the water-cooled powder delivery pipe 9 and has a water-cooled powder delivery pipe inlet 5 and a water-cooled powder delivery pipe outlet 7. By supplying cooling water into the first water-cooled jacket, a cooling water channel is formed on the outside of the water-cooled powder delivery pipe 9.

[0037] By installing a first metal sleeve with a first water-cooled jacket on the outside of the water-cooled powder feeding pipe 9, the first water-cooled jacket can protect the entire water-cooled powder feeding pipe 9 from high-temperature erosion under the high temperature of the furnace, and can also protect the powder 13 at the powder outlet 11 from sintering and agglomeration caused by high temperature, thereby realizing continuous feeding of powder 13.

[0038] In this embodiment, the inner diameter of the water-cooled powder delivery pipe 9 is not less than 6mm. The first metal sleeve is made of stainless steel, and its components are connected by argon arc welding, including an inner sleeve, an outer sleeve, a water inlet, and a water outlet. The inner and outer sleeves are sequentially arranged around the outside of the water-cooled powder delivery pipe 9. A first interlayer is formed between the inner sleeve and the water-cooled powder delivery pipe 9, and a second interlayer is formed between the outer sleeve and the inner sleeve. The first and second interlayers are connected, the water inlet is connected to the second interlayer, and the water outlet is connected to the first interlayer, thus forming a double-layer cooling water path on the outside of the water-cooled powder delivery pipe 9. Preferably, the cooling water is pure water or deionized water supplied through the water inlet at a pressure of not less than 0.3Mpa at room temperature (25℃-30℃).

[0039] Considering that the end of the water-cooled powder delivery pipe 9 is closest to the high-temperature area, in this embodiment, the first and second interlayers are connected at the first ends near the powder outlet 11 of the water-cooled powder delivery pipe 9 to form a return water bend structure. This return water bend structure design ensures that the cooling water can evenly surround and cool the entire water-cooled powder delivery pipe 9, while ensuring the cooling effect at the end of the water-cooled powder delivery pipe 9 and reducing the impact of high temperature on the end of the water-cooled powder delivery pipe 9. The double-layer cooling water circuit design can protect the entire water-cooled powder delivery pipe 9 from high-temperature erosion under the high temperature of the furnace, and also protect the powder 13 at the powder outlet 11 of the water-cooled powder delivery pipe 9 from the impact of high temperature.

[0040] Furthermore, the water inlet is connected to the second end of the second interlayer near the powder inlet 6 of the water-cooled powder delivery pipe 9, and the water outlet is connected to the second end of the first interlayer near the powder inlet 6 of the water-cooled powder delivery pipe 9. Preferably, the water inlet and water outlet are arranged on opposite sides to increase the contact surface between the cooling water flow and the water-cooled powder delivery pipe 9 and improve the heat transfer effect.

[0041] The conductive graphite-cooled crucible 14 includes a graphite crucible body and a second metal sleeve surrounding the outside of the graphite crucible body. The second metal sleeve has a second water-cooled jacket, and a heat-insulating material is cast between the second metal sleeve and the graphite crucible body.

[0042] In one embodiment of this invention, the second metal sleeve is made of stainless steel and includes a metal outer sleeve and a metal base plate, with the components connected by argon arc welding. The metal outer sleeve surrounds the outside of the graphite crucible body, and the metal base plate is located at the bottom of the graphite crucible body and connected to the metal outer sleeve. Because the bottom of the graphite crucible body is in direct contact with the metal base plate for conducting current, and due to the presence of heat-insulating material, the graphite crucible body remains at a low temperature.

[0043] Furthermore, the bottom of the metal jacket is connected to the metal base plate, and the top extends along the height direction of the second metal jacket. The top of the metal jacket and the outer side of the graphite crucible body form an anti-jump arc structure.

[0044] Further, see Figure 2 As shown, this embodiment also provides a method for preparing non-metallic ultrafine powder 13 based on a plasma transfer arc, applied to the aforementioned non-metallic ultrafine powder preparation system based on a plasma transfer arc, comprising the following steps:

[0045] Step 1: With the reactor body 28 under a slight negative pressure, power on the plasma power supply 1.

[0046] Step 2: Turn on the plasma generator 4 and supply cooling water to the water inlets corresponding to the double-layer shell, observation window 25, conductive graphite ink-cooled crucible 14 and water-cooled powder delivery pipe 9 respectively, and check to ensure that the cooling water of the above components flows normally.

[0047] Step 3: Perform arc ignition when there is no material inside the conductive graphite cold crucible 14. Let the plasma arc column 26 act directly on the conductive graphite cold crucible 14. The operating power should not exceed 40kw. As the temperature gradually rises, when the thermocouple 31 shows a temperature greater than 1300℃, the next step can be performed.

[0048] Step 4: Start the powder feeder 30 and adjust the powder feeding rate, gradually increasing it from small to large. For the first 5 minutes, the rate should be approximately 5-10 g / min. During the powder feeding process, observe the melting of the material at the bottom of the conductive graphite ink cold crucible 14 through the observation window 25. If the newly fed material is found to melt quickly into a liquid state, the powder feeding rate can be gradually increased to 20-50 g / min until a uniform melt is formed inside the conductive graphite ink cold crucible 14, covering the bottom of the crucible directly opposite the arc column and forming a semi-solid, semi-fluid anti-splash layer on the outer edge of the crucible bottom. Adjust the powder feeding rate so that the thickness of the uniform melt formed inside the conductive graphite ink cold crucible 14 is approximately 20-30 mm. This prevents the plasma arc column 26 from directly acting on the bottom of the conductive graphite ink cold crucible 14 for a long time, and prevents the conductive graphite ink cold crucible 14 from being rapidly ablated under the long-term action of the high-temperature plasma arc column 26, which would cause carbon powder generated during ablation to enter the material and cause contamination.

[0049] Step 5: Increase the output power of plasma power supply 1 so that the operating power of plasma generator 4 reaches 50-80kw. At the same time, gradually increase or decrease the powder feeding rate so that the powder feeding rate reaches 5-10g / min. Observe through the strong light filter at the observation window 25 that the incoming powder 13 material and the vaporized material reach equilibrium. That is, the incoming powder 13 material can fill the vaporized material so that the amount in the conductive graphite ink cold crucible 14 remains basically unchanged. In this way, the powder vaporization work can be carried out for a long time.

[0050] When the vaporized material leaves the plasma arc column 26 on the surface of the conductive graphite-based cold crucible 14, the temperature drops rapidly and it condenses into nano-sized particles. The longer the condensation time, the larger the particle size. Because the furnace body 28 is under negative pressure, a large airflow is formed, which quickly carries the formed nano-sized particles to the side of the conductive graphite-based cold crucible 14 and downward into the second cavity. The particles are then discharged through the ultrafine powder outlet 18 and enter the subsequent cooling and collection equipment 32.

[0051] The method provided in this embodiment can prepare non-metallic powder 13 with a particle size in the range of 10-200 nanometers, with a yield of approximately 100 g / h-1500 g / h. It is applicable to inorganic substances, oxides of inorganic substances, nitrides, etc., such as silicon and boron.

[0052] In summary, this invention enables arc ignition in the conductive graphite-based cold crucible 14 without any material inside, allowing the plasma arc column 26 to stably act on the conductive graphite-based cold crucible 14. Powder is fed when the set temperature is reached, until a uniform melt forms inside the conductive graphite-based cold crucible 14, covering the bottom of the crucible directly opposite the arc column and forming a semi-solid, semi-fluid anti-splash layer along the outer edge of the crucible bottom. Non-metallic and inorganic materials become conductive at high temperatures or in a molten state. The entire process is cooled by water-cooling mechanisms in each component to prevent rapid ablation. Once the melt thickness reaches the set value, the output power of the plasma power supply 1 is increased, and the powder feeding rate is adjusted until the incoming powder 13 and the vaporized material reach equilibrium. This enables long-term, stable plasma transfer arc preparation of non-metallic ultrafine powder 13.

[0053] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A non-metallic ultrafine powder preparation system based on plasma transfer arc, comprising a reactor body (28), wherein the outer wall of the reactor body (28) is provided with a heat insulation layer (12) and a double shell from the inside to the outside, the gap between the layers of the double shell is connected to the furnace body water inlet (19) and the furnace body water outlet (10), the reactor body (28) includes a first cavity, a second cavity and a plasma power supply (1), the plasma power supply (1) is used to supply power to a plasma generator (4) with a two-stage arc transfer function, the plasma generator (4) is disposed on the side wall of the first cavity, the second cavity is configured to communicate with the side of the first cavity away from the plasma generator (4), the second cavity is provided with an ultrafine powder outlet (18), and an observation window (25) is also provided on one side of the first cavity, the observation window (25) is provided with a water-cooling protection mechanism, characterized in that, The first cavity is equipped with a conductive graphite-cooled crucible (14) for preparing the melt. The conductive graphite-cooled crucible (14) includes a graphite crucible body and a second metal sleeve surrounding the outside of the graphite crucible body. The second metal sleeve has a second water-cooled jacket. A heat-insulating material is cast between the second metal sleeve and the graphite crucible body. The second metal sleeve includes a metal base plate. The metal base plate is located at the bottom of the graphite crucible body and is in direct contact with the bottom of the graphite crucible body. A water-cooled powder feeding pipe (9) is provided on the side wall of the first cavity. The powder outlet (11) of the water-cooled powder feeding pipe (9) extends to the top of the conductive graphite ink-cooled crucible (14). The powder inlet (6) of the water-cooled powder feeding pipe (9) is connected to the powder feeder (30). The side wall of the first cavity is provided with a thermocouple (31) for monitoring the temperature of the arc column of the plasma generator (4).

2. The non-metallic ultrafine powder preparation system based on plasma transfer arc as described in claim 1, characterized in that, The water-cooled powder delivery pipe (9) is surrounded by a first metal sleeve, which has a first water-cooled jacket.

3. The non-metallic ultrafine powder preparation system based on plasma transfer arc as described in claim 2, characterized in that, The first cavity has a flange on its side wall, and the water-cooled powder delivery pipe (9) is installed through the center hole of the flange. A transition sleeve (8) is provided between the first metal sleeve and the flange.

4. The non-metallic ultrafine powder preparation system based on plasma transfer arc as described in claim 3, characterized in that, The first metal sleeve includes an inner sleeve, an outer sleeve, an inlet nozzle, and an outlet nozzle; The inner sleeve and outer sleeve are arranged around the outside of the water-cooled powder delivery pipe (9) in sequence. The inner sleeve and the water-cooled powder delivery pipe (9) form a first interlayer, and the outer sleeve and the inner sleeve form a second interlayer. The first interlayer and the second interlayer are connected. The water inlet is connected to the second interlayer, and the water outlet is connected to the first interlayer, so that a double-layer cooling water channel is formed on the outside of the water-cooled powder delivery pipe (9).

5. The non-metallic ultrafine powder preparation system based on plasma transfer arc as described in claim 4, characterized in that, The first and second interlayers are connected at the first end of the powder outlet (11) of the water-cooled powder delivery pipe (9) to form a return water bend structure.

6. The non-metallic ultrafine powder preparation system based on plasma transfer arc as described in claim 5, characterized in that, The water inlet and water outlet are respectively connected to the second layer and the second end of the first layer near the powder inlet (6) of the powder delivery pipe.

7. The non-metallic ultrafine powder preparation system based on plasma transfer arc as described in any one of claims 1 to 6, characterized in that, The second metal sleeve also includes a metal outer sleeve; The metal jacket is arranged around the outside of the graphite crucible body, and the metal base plate is connected to the metal jacket.

8. The non-metallic ultrafine powder preparation system based on plasma transfer arc as described in claim 7, characterized in that, The bottom of the metal jacket is connected to the metal base plate, and the top extends along the height direction of the second metal jacket. The top of the metal jacket and the outer side of the graphite crucible body form an anti-jump arc structure.

9. A method for preparing non-metallic ultrafine powder (13) based on a plasma transfer arc, applied to the non-metallic ultrafine powder preparation system based on a plasma transfer arc as described in any one of claims 1 to 8, characterized in that, include: Cooling water is supplied to the water inlets corresponding to the double-layer shell, the observation window (25), the conductive graphite ink-cooled crucible (14), and the water-cooled powder delivery pipe (9), respectively. The plasma generator (4) ignites an arc and acts directly on the conductive graphite ink cold crucible (14). When the temperature obtained by the thermocouple (31) meets the set value, the powder feeder (30) is turned on. The amount of powder fed is gradually increased. During the powder feeding process, the melting of the material at the bottom of the conductive graphite ink cold crucible (14) is observed through the observation window (25) until a uniform melt is formed inside the conductive graphite ink cold crucible (14) covering the bottom of the crucible directly opposite the electric arc column and forming a semi-solid and semi-fluid anti-splash layer on the outer edge of the bottom of the crucible. After the thickness of the melt reaches the set value, increase the output power of the plasma power supply (1) and adjust the powder feeding amount until the incoming powder (13) material and the vaporized material reach equilibrium. The vaporized material generated by vaporization is condensed into ultrafine powder (13) in the second chamber and then discharged through the ultrafine powder outlet (18).

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