Variable-air-pressure spark discharge device and method

Abstract

The invention provides a variable-air-pressure spark discharge device and method, and relates to the field of spark discharge. The variable air pressure spark discharge device provided by the invention comprises a spark chamber, wherein a pair of spark electrodes is arranged on the inner wall of the spark chamber; a carrier gas channel and a pressure control channel are arranged on the side wall of the spark chamber; the vacuum pump is connected with the spark chamber through a pressure control channel, the vacuum pump is used for extracting gas in the spark chamber, and a valve body with an adjustable opening degree is arranged in the pressure control channel; the working end of the pressure gauge is located in the inner cavity of the spark chamber, and the pressure gauge is used for detecting the pressure value in the inner cavity of the spark chamber. And the particle utilization device is arranged between the spark chamber and the valve body, and the particle utilization device is used for utilizing particles. According to the invention, the air pressure in the inner cavity of the spark chamber can be adjusted, nanoparticles with smaller sizes can be obtained in a low-air-pressure environment, and corresponding nanoparticles with higher charge rate can be obtained in a high-air-pressure environment.

Description

Technical Field

[0001] This invention relates to the field of spark discharge technology, and in particular to a variable pressure spark discharge device and method. Background Technology

[0002] Spark discharge ionizes the gas between electrodes by applying a potential difference between them, creating a high electric field that bombards the electrodes with pulsed high-energy plasma, resulting in an atomic vapor cloud containing the electrode material. Under rapid cooling and quenching conditions, the atomic vapor sublimates to form nanoparticles. Spark discharge is usually carried out at room temperature and pressure. To ensure that the atomic cloud gas dissolved by the two electrodes is fully mixed, the distance between the electrodes should not be too large. At the same time, under the influence of high-energy plasma, the atomic clusters or nanoparticles formed by spark discharge are partially charged, and their charge rate is affected by the parameters of the spark, the gas environment, and the cavity structure.

[0003] Current spark discharge technology and equipment operate at atmospheric pressure, which limits their ability to control nanoparticle parameters and charge rates. 1. Spark control: The energy of spark discharge is affected by capacitance, charging current (frequency) and breakdown voltage. However, under normal pressure, the gas breakdown field strength in a specific gas with a fixed electrode spacing is fixed and cannot be adjusted.

[0004] 2. Dispersion and size control of nanoparticles: The growth behavior of atomic vapor clouds generated by sparks during gas transport is affected by gas pressure. In order to obtain smaller nanoparticles, a higher carrier gas velocity is required to disperse the nanoparticles, which will increase the cost of gas usage.

[0005] 3. Nanoparticles have a low charge rate. Nanoparticles transported from spark plasma at atmospheric pressure have a low charge rate. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a variable pressure spark discharge device and method, which can adjust the gas pressure in the spark chamber to obtain smaller nanoparticles under low pressure and higher charge rates of the corresponding nanoparticles under high pressure.

[0007] The variable pressure spark discharge device provided by this invention includes: a spark chamber, on the inner wall of which a pair of spark electrodes are provided for spark discharge and to form partially charged atomic clusters or nanoparticles from the gas; a carrier gas channel and a pressure control channel are provided on the side wall of the spark chamber, the carrier gas channel being used to introduce carrier gas into the inner cavity of the spark chamber; a vacuum pump, connected to the spark chamber via the pressure control channel, the vacuum pump being used to extract gas from the spark chamber, the pressure control channel being provided with an adjustable valve body; a pressure gauge, the working end of which is located in the inner cavity of the spark chamber, the pressure gauge being used to detect the pressure value in the inner cavity of the spark chamber; and a particle utilization device, located between the spark chamber and the valve body, the particle utilization device being used to utilize particles.

[0008] The present invention also provides a variable pressure spark discharge method, which uses the above-mentioned variable pressure spark discharge device and includes the following steps: Step 1) Continuously introduce carrier gas into the inner cavity of the spark chamber through the carrier gas channel, while simultaneously turning on the vacuum pump to extract the gas from the inner cavity of the spark chamber; adjust the valve opening according to the pressure gauge reading until the pressure value in the inner cavity of the spark chamber stabilizes at the set standard. Step 2) The spark electrode discharges under the set pressure, and the generated exhaust gas is drawn away by the vacuum pump body.

[0009] In one specific embodiment, step 1) is preceded by adjusting the gap distance between the spark electrodes.

[0010] In one specific embodiment, the gap distance between the spark electrodes is 0.01~100 mm.

[0011] In one specific embodiment, the carrier gas flow rate in step 1) is 0.01~100 L / min.

[0012] In one specific embodiment, the pressure value in the spark chamber of step 1) is 0.001~100 bar.

[0013] In one specific embodiment, the carrier gas in step 1) is an inert gas.

[0014] In one specific embodiment, the breakdown voltage between the spark electrodes in step 2) is 200~6000 V.

[0015] In one specific embodiment, the discharge capacitance of the spark capacitor in step 2) is 0.01~100 nF, and the energy of a single spark is controlled to be 0.01~1000 mJ.

[0016] In one specific embodiment, the pressure value in the spark chamber cavity during step 1) is controlled by the following method: Adjust the pumping speed of vacuum pump (4) and the inflow velocity of carrier gas The pressure value in the inner cavity of the spark chamber (2) is shown in the following formula: in, The pressure value inside the spark chamber (2) This represents the mass flow rate of the gas at atmospheric pressure. The volumetric flow rate of the gas extracted by the vacuum pump (4) from the inner cavity of the spark chamber (2) is given.

[0017] The variable pressure spark discharge device and method provided by this invention have the following beneficial effects: By adjusting the gas pressure in the spark chamber, this invention can change the spark discharge breakdown voltage under a fixed electrode spacing. Under low pressure, the volumetric flow rate of the gas increases, the average molecular free path of the gas decreases, and the growth rate of nanoparticles in the gas phase decreases, resulting in smaller nanoparticles. Under high pressure, there are more gas molecules per unit space, and more gas molecules are ionized under the same spark energy, resulting in a higher charge rate for the corresponding nanoparticles. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0019] Figure 2 This is a TEM image of the charged nanoparticles in the comparative example of this invention.

[0020] Figure 3 This is a particle size statistics chart for the comparative example of this invention.

[0021] Figure 4 This is a TEM image of the charged nanoparticles in Embodiment 1 of the present invention.

[0022] Figure 5 This is a particle size statistics chart from Embodiment 1 of the present invention.

[0023] Figure 6 This is a TEM image of the charged nanoparticles in Embodiment 2 of the present invention.

[0024] Figure Labels

[0025] Carrier gas passage 1 Spark Chamber 2 Valve body 3 Vacuum pump 4 Pressure gauge 5 Particle Utilization Device 6 Pressure control channel 7 Detailed Implementation

[0026] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In the description of the present invention, it should be noted that the terms "left side", "right side", "upper side", "lower side", "above", "below", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0027] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0028] Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0029] The variable pressure spark discharge device provided by this invention, such as Figure 1 As shown, it includes a spark chamber 2, on the inner wall of which a pair of spark electrodes are provided. These spark electrodes are used for spark discharge to form partially charged atomic clusters or nanoparticles. The spark electrodes do not contact each other. During spark discharge, a potential difference is applied between the two spark electrodes, creating a high electric field that ionizes the carrier gas between them. The pulsed high-energy plasma formed by the carrier gas bombards the spark electrodes to obtain an atomic vapor cloud containing electrode material. Under high-speed rapid cooling and quenching, the atomic vapor sublimates to form atomic clusters or nanoparticles, and these clusters or nanoparticles are partially charged. Figure 1As shown, the spark chamber 2 has a carrier gas channel 1 and a pressure control channel 7 on its side wall. The carrier gas channel 1 is used to introduce carrier gas into the inner cavity of the spark chamber 2. A vacuum pump 4 is connected to the spark chamber 2 via the pressure control channel 7. The vacuum pump 4 is used to extract gas from the spark chamber 2, which contains partially charged atomic clusters or nanoparticles. The pressure control channel 7 has an adjustable valve body 3. A pressure gauge 5 has its working end located in the inner cavity of the spark chamber 2. The pressure gauge 5 is used to detect the pressure value in the inner cavity of the spark chamber 2. A particle utilization device 6 is located between the spark chamber 2 and the valve body 3. The particle utilization device 6 is used to utilize particles, for example: filtration and collection, deposition coating, and particle-based printing. Specifically, the particle utilization device 6 can collect nanoparticles by filtration, i.e., by placing filter paper, filter membrane, etc., in the channel to collect nanoparticles; or, the particle utilization device 6 can collect nanoparticles by deposition coating, i.e., by diffusion or electric field deposition; or, the particle utilization device 6 can collect nanoparticles by printing particles, i.e., by using electric field force to pull charged material out from the pressure-controlled channel 7 and printing it under the action of electric field, such as directly using a Faraday 3D printing device, or using an aerosol jet printing device to achieve AJP printing.

[0030] The present invention also provides a discharge method for a variable pressure spark discharge device, comprising the following steps: Step 1) Continuously introduce carrier gas into the inner cavity of spark chamber 2 through carrier gas channel 1, and at the same time turn on vacuum pump 4 to extract the gas in the inner cavity of spark chamber 2; adjust the opening of valve body 3 according to the value of pressure gauge 5 until the pressure value in the inner cavity of spark chamber 2 stabilizes at the set standard. Step 2) The spark electrode discharges under the set pressure, and the generated exhaust gas is pumped away by the vacuum pump 4.

[0031] Specifically, before step 1), the method further includes adjusting the gap distance between the spark electrodes. Specifically, the gap distance between the spark electrodes is 0.01~100 mm. Preferably, the gap distance between the spark electrodes is 0.01~0.1 mm, 0.1~1 mm, 1~10 mm, or 10~100 mm.

[0032] Specifically, the carrier gas flow rate in step 1) is 0.01~100 L / min. Preferably, the carrier gas flow rate is 0.01~0.1 L / min, 0.1~1 L / min, 1~10 L / min, or 10~100 L / min.

[0033] Specifically, the pressure value inside the spark chamber 2 in step 1) is 0.001~100 bar. Preferably, the pressure value inside the spark chamber 2 is 0.001~0.01 bar, 0.01~1 bar, or 1~100 bar. As an explanation, spark discharge depends on the ionization of gas molecules, forming an ion avalanche under a sufficient electric field strength. A gas density of 0.001 bar is sufficient to form a spark discharge. Under high gas pressure, the gas breakdown pressure increases, thus requiring only a sufficiently high-voltage power supply to achieve spark discharge.

[0034] Specifically, the carrier gas in step 1) is an inert gas, preferably nitrogen.

[0035] Specifically, the pressure value inside the spark chamber 2 in step 1) is controlled by adjusting the pumping speed of the vacuum pump 4. and the inflow velocity of carrier gas The pressure value inside spark chamber 2 is shown in the following formula: in, This refers to the pressure value inside spark chamber 2. This represents the mass flow rate of the gas at atmospheric pressure. This is the volumetric flow rate of the gas extracted from the inner cavity of the spark chamber 2 by the vacuum pump 4.

[0036] Specifically, the breakdown voltage between the spark electrodes in step 2) is 200~6000 V. Preferably, the breakdown voltage between the spark electrodes is 200~2000 V, 2000~4000 V, or 4000~6000 V.

[0037] Specifically, in step 2), the discharge capacitance of the spark capacitor is 0.01~100 nF, preferably 0.01~0.1 nF, 0.1~1 nF, 1~10 nF, or 10~100 nF. The energy of a single spark is controlled to be 0.01~1000 mJ, preferably 0.001~0.01 mJ, 0.01~1 mJ, or 1~100 mJ.

[0038] Comparative Example In this embodiment, spark discharge is performed under normal pressure, with a gas pressure of 1 bar, a spark electrode spacing of approximately 3 mm, a spark discharge capacitance of 5 nF, a spark breakdown voltage of 3000 V, a single spark energy control value of 12 mJ, and nitrogen as the carrier gas at a flow rate of 4 L / min. The particle utilization device 6 collects nanoparticles using electric field deposition coating. Specifically, the particle utilization device 6 includes a TEM copper mesh placed within a pressure-controlled channel 7. Charged nanoparticles are deposited on the TEM copper mesh, and an external electric field is applied perpendicularly to the TEM copper mesh. After 5 minutes of deposition, the desired positively charged nanoparticles can be collected. The resulting TEM image of the charged nanoparticles is shown below. Figure 2 As shown in the figure, the particle size distribution chart is as follows: Figure 3 As shown.

[0039] Example 1 This embodiment performs spark discharge under low-pressure conditions. The gas pressure inside the spark chamber 2 is maintained at 0.01 bar, the spark electrode spacing is approximately 3 mm, the spark discharge capacitance is 5 nF, the spark breakdown voltage is 200 V, the single spark energy is controlled at 12 mJ, the carrier gas is nitrogen, and the carrier gas flow rate is 0.01 L / min. The particle utilization device 6 collects nanoparticles using electric field deposition coating. Specifically, the particle utilization device 6 includes a TEM copper mesh, which is placed in the pressure-controlled channel 7. Charged nanoparticles are deposited on the TEM copper mesh, and an external electric field is applied perpendicularly to the TEM copper mesh. After 5 minutes of deposition, the desired positively charged nanoparticles can be collected. The resulting TEM image of the charged nanoparticles is shown below. Figure 4 As shown in the figure, the particle size distribution chart is as follows: Figure 5 As shown, experiments have demonstrated that spark discharge under low pressure reduces the average molecular free path of the gas, decreases the growth rate of nanoparticles in the gas phase, and allows for the production of smaller nanoparticles.

[0040] Example 2 This embodiment performs spark discharge under high pressure conditions, using a pressure of 2 bar, a spark electrode spacing of approximately 3 mm, a spark discharge capacitance of 5 nF, a spark breakdown voltage of 6000 V, a single spark energy of 12 mJ, and nitrogen as the carrier gas at a flow rate of 100 L / min. The particle utilization device 6 collects nanoparticles using electric field deposition coating. Specifically, the particle utilization device 6 includes a TEM copper mesh placed within a pressure-controlled channel 7. Charged nanoparticles are deposited on the TEM copper mesh, and an external electric field is applied perpendicularly to the TEM copper mesh. After 5 minutes of deposition, the desired positively charged nanoparticles are collected. The resulting TEM image of the charged nanoparticles is shown below. Figure 6As shown in the figure, the experiment proves that under high pressure, the number of gas molecules per unit space is greater, the number of gas molecules ionized under the same spark energy is greater, and the corresponding nanoparticles have a higher charge rate.

[0041] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A variable pressure spark discharge device, characterized in that, include: A spark chamber (2) is provided with a pair of spark electrodes on its inner wall. The spark electrodes are used for spark discharge and to make the gas form partially charged atomic clusters or nanoparticles. A carrier gas channel (1) and a pressure control channel (7) are provided on the side wall of the spark chamber (2). The carrier gas channel (1) is used to introduce carrier gas into the inner cavity of the spark chamber (2). Vacuum pump (4), the vacuum pump (4) is connected to spark chamber (2) through pressure control channel (7), the vacuum pump (4) is used to extract gas in spark chamber (2), and the pressure control channel (7) is provided with valve body (3) with adjustable opening. Pressure gauge (5), the working end of the pressure gauge (5) is located in the inner cavity of the spark chamber (2), the pressure gauge (5) is used to detect the pressure value in the inner cavity of the spark chamber (2); Particle utilization device (6) is located between spark chamber (2) and valve body (3) and is used to utilize particles.

2. A variable pressure spark discharge method, employing the variable pressure spark discharge device as described in claim 1, comprising the following steps: Step 1) Continuously introduce carrier gas into the inner cavity of the spark chamber (2) through the carrier gas channel (1), and at the same time turn on the vacuum pump (4) to extract the gas in the inner cavity of the spark chamber (2); adjust the opening of the valve body (3) according to the value of the pressure gauge (5) until the pressure value in the inner cavity of the spark chamber (2) stabilizes at the set standard. Step 2) The spark electrode discharges under the set pressure, and the generated exhaust gas is pumped away by the vacuum pump (4).

3. The discharge method of the variable pressure spark discharge device according to claim 2, characterized in that, Step 1) also includes: adjusting the gap distance between the spark electrodes.

4. The discharge method of the variable pressure spark discharge device according to claim 3, characterized in that, The gap between the spark electrodes is 0.01~100 mm.

5. The discharge method of the variable pressure spark discharge device according to claim 2, characterized in that, The carrier gas flow rate in step 1) is 0.01~100 L / min.

6. The discharge method of the variable pressure spark discharge device according to claim 2, characterized in that, The pressure value in the spark chamber (2) of step 1) is 0.001~100 bar.

7. The discharge method of the variable pressure spark discharge device according to claim 2, characterized in that, The carrier gas in step 1) is an inert gas.

8. The discharge method of the variable pressure spark discharge device according to claim 2, characterized in that, The breakdown voltage between the spark electrodes in step 2) is 200~6000 V.

9. The discharge method of the variable pressure spark discharge device according to claim 2, characterized in that, In step 2), the discharge capacitance of the spark capacitor is 0.01~100 nF, and the energy of a single spark is controlled to be 0.01~1000 mJ.

10. The discharge method of the variable pressure spark discharge device according to claim 2, characterized in that, The pressure value inside the spark chamber (2) in step 1) is controlled by adjusting the pumping speed of the vacuum pump (4) as follows. and the inflow velocity of carrier gas The pressure value in the inner cavity of the spark chamber (2) is shown in the following formula: in, The pressure value inside the spark chamber (2) This represents the mass flow rate of the gas at atmospheric pressure. The volumetric flow rate of the gas extracted by the vacuum pump (4) from the inner cavity of the spark chamber (2) is given.

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