CN104540313B - Plasma jet generating device for atmospheric pressure hollow substrate electrode - Google Patents

Abstract

The invention relates to an atmospheric pressure hollow substrate electrode plasma jet generating device. The device comprises a direct current discharge unit and a power supply for providing discharge voltage of the direct current discharge unit; the direct current discharge unit comprises an air duct and an electrode group; the electrode group comprises a high-voltage electrode and a grounding electrode which are cylindrical; the air duct is a hollow tube, and the upper end and the lower end of the air duct are respectively provided with an air inlet port and an air outlet port; the high-voltage electrode is arranged at the axial center of the gas-guide tube, and a hollow metal substrate unit for forming a narrow gas flow channel is also arranged at the ground electrode; the hollow metal substrate unit is cylindrical and is provided with a through hole along the axial direction. The invention provides the plasma jet generating device of the atmospheric hollow substrate electrode, which has simple operation process and low operation cost.

Description

Atmospheric Pressure Hollow Substrate Electrode Plasma Jet Generator

technical field

The invention belongs to the field of plasma technology, and relates to a plasma generating device, in particular to an atmospheric pressure hollow base electrode plasma jet generating device, which can be used for surface treatment of metal materials.

Background technique

In recent years, application-centered research on plasma technology has been active in a wide range of fields such as physics, chemistry, electronics, materials science, and metallurgy and chemical engineering. Because of its high density, low gas temperature, controllable composition, and the ability to produce various active species, low-temperature plasma can be used to change the surface properties of metal materials. For surface modification of metal materials, traditional low-temperature plasma generators require high-frequency power (radio frequency 13.56MHz or microwave 2.45GHz) to maintain the supply of discharge energy, and work in a low-pressure environment, requiring a vacuum pump to evacuate. Therefore, the investment in processing equipment is large and the cost is high.

Compared with the low-pressure discharge plasma generation device with vacuum equipment, the atmospheric pressure gas discharge plasma surface treatment equipment omits the vacuum device, and can perform surface treatment on samples in an atmospheric environment of normal pressure. This surface treatment technology not only reduces operating costs, but also improves work efficiency. Among them, the potential application value of atmospheric pressure plasma jet (APPJ) is the greatest. It generally adopts AC and pulse discharge methods, and directly (sometimes using a single electrode) discharges to generate plasma between two electrodes separated by an insulating medium, and the plasma is taken out of the discharge chamber by the flow of gas to form a plasma jet. Although APPJ is easy to contact with the surface of the treated object, which is beneficial to improve the utilization of active species, but the active species in the plasma, especially metal or non-metal ions, only bombard the surface of the treated sample under the action of airflow. Therefore, the speed and energy of the bombardment of active species are limited, which reduces the efficiency of plasma surface diffusion and infiltration, which is not conducive to the application of APPJ in metal surface modification and decontamination.

Contents of the invention

In order to solve the technical problems existing in the background technology, the present invention provides an atmospheric pressure hollow base electrode plasma jet generating device to solve the problem of metal or nonmetal ion bombardment velocity and Low energy, surface modification of metal materials and low efficiency of decontamination.

The technical solution of the present invention is: an atmospheric pressure hollow substrate electrode plasma jet generator, including a DC discharge unit and a power supply for providing the discharge voltage of the DC discharge unit; the DC discharge unit includes a gas guide tube and an electrode group; the electrode group includes A cylindrical high-voltage electrode and a grounding electrode; the air duct is a hollow tube, and the upper and lower ends are respectively provided with an air inlet port and an air outlet port; the above-mentioned high-voltage electrode is placed in the axial center of the air duct. The above-mentioned ground electrode is also provided with a hollow metal base unit for forming a narrow air flow channel; the above-mentioned hollow metal base unit is in the form of a cylinder, and a through hole is arranged in the axial direction; the through hole of the hollow metal base unit and the air duct Coaxial; the above-mentioned grounding electrode is L-shaped, and the right-angled side is a cylinder and is coaxial with the high-voltage electrode. The unit ends are connected;

A current-limiting resistor is connected in series between the DC discharge unit and the power supply;

The above-mentioned power supply adopts DC or pulse power supply, and the frequency of the pulse power supply is 50Hz to 13.56MHz;

The material of the above-mentioned air guide tube is mica, glass, pottery or polytetrafluoroethylene;

The end faces of the above-mentioned high-voltage electrode and the ground electrode facing each other are planes; the materials of the high-voltage electrode and the ground electrode are aluminum, iron, copper, tungsten, nickel, tantalum, platinum, aluminum alloy, iron alloy, copper alloy, tungsten alloy, nickel alloy, tantalum alloy;

The material of the above-mentioned hollow metal base unit is aluminum or copper or aluminum alloy or copper alloy, and the hole diameter of the through hole of the hollow metal base unit is 4-100 mm.

The advantages of the present invention are:

1. Compared with the traditional low-pressure discharge plasma generating device, the present invention generates plasma jets in an atmospheric environment for surface treatment of metal materials, eliminating the need for vacuum equipment, simplifying the operation process, and reducing operating costs.

2. Compared with the high-frequency power supply of the traditional low-pressure discharge plasma generator, the power supply of the present invention can be a DC power supply, which reduces the requirements for power supply equipment.

3. Compared with the traditional atmospheric pressure plasma jet (APPJ), the plasma jet produced by the device of the present invention has higher electron density, higher ion bombardment velocity and higher ion energy.

Description of drawings

Fig. 1 is a schematic structural diagram of a hollow metal base unit of the present invention;

Fig. 2 is a top view of the DC discharge unit structure of the present invention;

Fig. 3 is a bottom view of the DC discharge unit structure of the present invention;

Fig. 4 is a top view of the main body of the atmospheric pressure hollow substrate electrode plasma jet generating device of the present invention;

5 is a bottom view of the main body of the atmospheric pressure hollow substrate electrode plasma jet generating device of the present invention;

Fig. 6 is the working schematic diagram of the present invention;

Among them: 11-through hole, 10-hollow metal base unit, 20-DC discharge unit, 21-air duct, 22-high voltage electrode, 23-ground electrode, 31-inlet port, 32-outlet port, 40-generating device Main structure, 41-power supply, 42-limiting resistor, 51-processing sample, 52-plasma jet.

detailed description

Referring to Fig. 1-6, the present invention proposes a kind of atmospheric pressure hollow base electrode plasma jet generation device, comprises DC discharge unit 20 and is used to provide the power supply 41 of discharge voltage of DC discharge unit 20; DC discharge unit 20 comprises air duct and electrode group; the electrode group includes a cylindrical high-voltage electrode 22 and a grounding electrode 23; the air guide tube 21 is a hollow tube, and the upper and lower ends are respectively provided with an air inlet port 31 and an air outlet port 32; the high voltage electrode 22 is placed on the air guide tube 21 At the axial center position, the ground electrode 23 is also provided with a hollow metal base unit 10 for forming a narrow airflow channel; the hollow metal base unit 10 is a cylinder, and a through hole is provided along the axial direction; the hollow metal base unit 10 The through hole is coaxial with the airway tube 21; the grounding electrode 23 is L-shaped, and the right-angled side is a cylinder and coaxial with the high-voltage electrode 22, and its end face is opposite to the end face of the high-voltage electrode 22 at the gas outlet port 32 of the airway tube. The right-angled side is a cuboid, connected to the end face of the hollow metal base unit 10; a current-limiting resistor is connected in series between the DC discharge unit 20 and the power supply 41; the power supply 41 adopts a DC or pulse power supply, and the frequency of the pulse power supply is 50Hz to 13.56MHz; The material of 21 is mica, glass, pottery or polytetrafluoroethylene; The end faces facing each other of high voltage electrode 22 and ground electrode 23 are planes; the material of high voltage electrode 22 and ground electrode 23 is aluminum, iron, copper, tungsten, nickel, Tantalum, platinum, aluminum alloy, iron alloy, copper alloy, tungsten alloy, nickel alloy, tantalum alloy; the material of the hollow metal base unit 10 is aluminum or copper or aluminum alloy or copper alloy, and the hole diameter of the through hole part of the hollow metal base unit 10 is 4~100mm.

An atmospheric-pressure hollow base electrode plasma jet generator includes a hollow metal base unit and a DC discharge unit. The hollow metal base unit includes a through hole; the DC discharge unit includes an air duct and two electrodes, one of which is a cylindrical high voltage electrode and the other is a ground electrode. The air guide tube has an inlet port for receiving working gas and an outlet port for letting the gas out. The high-voltage electrode is placed at the center of the airway tube, the ground electrode is L-shaped, the right-angled side is a cylinder, and is coaxial with the high-voltage electrode, and its end face is opposite to the end face of the high-voltage electrode at the air outlet port of the airway tube; The right angle side is a cuboid, which is connected with the base end face.

The working gas can be selected from inert gas, oxygen, propane, ammonia, nitrogen and hydrogen, or a mixture of the above gases, and the suitable flow rate of the working gas is 0.01-10L/min. The hollow metal base unit is preferably aluminum, copper, and an alloy selected from these metals, the diameter of the hollow through-hole part is 4-100 mm, and the height of the hollow part is 10-50 mm. The air guide tube of the DC discharge unit is made of insulating materials such as mica, glass, ceramics or polytetrafluoroethylene, the inner diameter of the air guide tube is 2-10mm, and the outer diameter is 4-12mm. The discharge electrode of the DC discharge unit is made of aluminum, iron, copper, tungsten, nickel, tantalum, platinum, and alloys of these metals, and the electrode diameter is 1-8mm. The discharge gap of the DC discharge unit is preferably 5-15 mm. For high-voltage electrodes, provide direct current or pulse voltage, the voltage amplitude is 100-10000V, and the pulse frequency is 50Hz-13.56MHz.

At the air outlet port of the airway tube, the distance between the end face of the high-voltage electrode and the end face of the airway tube is not greater than 2mm.

The atmospheric-pressure hollow base electrode plasma jet generator provided by the invention realizes the generation of low-temperature plasma with high electron density, high ion bombardment velocity and high ion energy under atmospheric pressure. When working, the high-voltage electrode is connected to the positive pole of the power supply through the current limiting resistor, the ground electrode is connected to the negative pole of the power supply, and grounded. The working gas flows in from the inlet port of the air duct, passes through the annular area between the air duct and the electrodes, and is ejected from the outlet port of the air duct, and the ejected working gas flows into the discharge space where the two electrodes are facing each other. Because the metal base connected to the ground electrode is a hollow structure, due to the effect of inertia, when the flow rate of the working gas is large enough, the working gas continues to flow in the original direction after flowing through the discharge space, and flows through the through holes of the metal base. This feature promotes the formation of a narrow, high-speed gas flow path around the discharge space. Select the appropriate working gas and control the flow of the gas. When the applied voltage of the two electrodes is high enough, the gas in the discharge gap will be broken down, and low-temperature plasma will be generated in the atmospheric environment. The narrow gas flow channel restricts the space for plasma generation, prevents excessive dispersion of plasma, and is conducive to the generation of high-density plasma. Under the joint action of gas flow field and DC electric field, a plasma jet with high electron density, high ion bombardment velocity and high ion energy is formed. The jet can be used for plasma surface treatment of metallic materials.

The atmospheric pressure hollow base electrode plasma jet generator provided by the present invention is composed of a hollow metal base unit, a DC discharge unit and a power supply device. The hollow metal base unit includes a through hole and is made of aluminum, copper or alloy materials thereof. The DC discharge unit consists of an air duct, a high voltage electrode and a ground electrode. The air duct has two ports, one is the inlet port and the other is the air outlet port. The air duct is made of insulating materials such as mica, glass, ceramics or polytetrafluoroethylene; the high-voltage electrode is cylindrical and placed inside the air duct. At the center, the grounding electrode is L-shaped, and the right-angled side is a cylinder, which is coaxial with the high-voltage electrode. catch. Both electrodes are made of heat-resistant metal materials, aluminum, iron, copper, tungsten, nickel, tantalum, platinum, and alloys of these metals can be used, but not limited to the above materials. The power supply equipment provides DC or pulse voltage, and when the voltage is pulsed, its frequency can be changed from power frequency to 13.56MHz radio frequency; the power supply equipment also includes a current-limiting resistor used to prevent the transition from glow discharge to arc discharge.

When working, the sample to be processed is placed on the ground electrode. The working gas flows in from the air inlet port of the air duct, passes through the annular area between the air duct and the high-voltage electrode, is ejected from the gas outlet port, and flows into the discharge space where the two electrodes are facing each other. When the voltage applied between the two electrodes is high enough, the working gas in the discharge space is broken down, and a stable plasma gas discharge occurs.

Due to the inertia and the hollow structure of the metal base, the working gas continues to flow through the through holes of the metal base along the original flow direction, preventing the occurrence of gas backflow and forming a narrow high-speed air flow channel around the discharge space. The narrow gas flow channel restricts the volume of plasma generation, prevents excessive dispersion of plasma, and is conducive to the generation of high-density plasma. The direction of the working gas flow is consistent with the direction of the DC electric field, and the joint action of the gas flow and the electric field on the ions simultaneously enhances the speed and energy of the ions bombarding the sample surface. Plasma jets with high density, high ion bombardment velocity and high ion energy are very suitable for surface treatment of metal materials, that is, through plasma surface diffusion, changing the mechanical properties or anti-corrosion properties of metal devices, and removing surface oil on metal devices.

The structure and working process of the device of the present invention will be further described in detail below.

In different drawings, similar or identical device structure diagrams are shown. FIG. 1 is a schematic diagram of a hollow metal base unit structure 10 of the present invention. The hollow metal base unit 10 includes a through hole 11 . FIG. 2 is a schematic diagram of a DC discharge unit structure 20 of the present invention. Figure 2 is a top view; Figure 3 is a bottom view. The DC discharge unit 20 includes an air duct 21 , a high voltage electrode 22 , and a ground electrode 23 . The air duct 21 has two ports, an air inlet port 31 and an air outlet port 32 . The high-voltage electrode 22 is placed at the center of the airway tube 21; at the gas outlet port 32 of the airway tube 21, the distance between the end surface of the high-voltage electrode 22 and the end surface of the airway tube 21 is not greater than 2mm. The ground electrode 23 is L-shaped, one right-angled side is a cylinder, and its end face is opposite to the end face of the high-voltage electrode 22 with a distance of 5-30 mm; the other right-angled side is a cuboid. Fig. 4 is a top view of the main body of the atmospheric pressure hollow base electrode plasma jet generator of the present invention; Fig. 5 is a bottom view of the main body of the atmospheric pressure hollow base electrode plasma jet generator of the present invention. The ground electrode 23 is in contact with the end surface of the hollow metal base 10 and fixed on the hollow metal base 10 . The high voltage electrode 22, the ground electrode 23, and the through hole 11 are placed coaxially. Fig. 6 is a working diagram of the present invention. The overall structure 50 of the atmospheric-pressure hollow substrate electrode plasma jet generator includes, in addition to the main structure 40, a power supply 41 and a current-limiting resistor 42 used to prevent the transition from glow discharge to arc discharge. The positive pole of the power supply device 41 is connected to the high voltage electrode 22 through the current limiting resistor 42, and the negative pole is connected to the ground electrode 23 and grounded.

During operation, the processed sample 51 is placed on the ground electrode 23 . The working gas flows in from the inlet port 31 of the air duct 21 , flows through the annular area between the high voltage electrode 22 and the air duct 21 , flows out from the gas outlet port 32 , and enters the discharge space opposite the high voltage electrode 22 and the ground electrode 23 . Due to the effect of inertia, the working gas continues to flow into the through hole 11 of the hollow metal substrate 10 . When the voltage applied between the high-voltage electrode 22 and the ground electrode 23 is high enough, a gas discharge occurs between the two electrodes 22 and 23, and under the joint action of the narrow high-speed gas flow channel and the electric field, high-density, high-ion bombardment occurs Velocity and high ion energy plasma jet 52, which can perform surface treatment on the treated sample 51 placed on the ground electrode 23.

The density of the plasma jet, the bombardment velocity and energy of the ions are mainly affected by the electrode distance, the flow rate of the working gas, and the applied voltage. The electrode spacing should be selected as 5-15mm; the working gas flow rate is generally 0.01-10L/min; the applied voltage is usually 100-10000V, and the discharge current is in the order of several milliamperes to tens of milliamperes to generate a stable plasma jet. The energy is usually between a few watts and tens of watts. It should be noted that the above dimensions or parameters are just an example of the plasma generating device of the present invention, and the dimensions of the device are not limited to the above range.

Under the conditions that the diameter of the two electrodes of the device of the present invention can be 1mm, the distance between the electrodes is 6mm, and the inner diameter of the air guide tube is 1.7mm, when the flow rate of the working gas (argon) is 2L/min, and the applied voltage is 2434V, the plasma jet flows from the anode Spray toward the cathode, in a diffuse shape, limited to the discharge space where the two electrodes are facing each other, and the radial radius gradually increases. At this time, the current limiting resistance of the discharge circuit is 100KΩ, the discharge maintenance voltage is 234V, and the discharge current is 22mA. The electrode material is iron, and the potential of the cathode drop region is 165V, which is determined by the formula n _e = j/(Eμ _e e) (electron density n _e , unit charge e, electric field strength E, current density j, and electron mobility μ _e ) It is calculated that the electron number density in the positive column region of the plasma is as high as 10 ¹⁴ , which is 1-2 orders of magnitude higher than that of ordinary DC glow discharge; the ion bombardment speed reaches 2×10 ³ cm/s, which is a static gas 6 times that of discharge; ions move along the direction of the electric field, especially in the cathode drop zone, where the existence of a large potential difference effectively increases the ion bombardment energy.

Claims (6)

1. a kind of atmospheric pressure hollow substrate electrode plasma jet flow generating apparatus, including direct-current discharge unit and straight for providing Banish the power supply of electric unit discharge voltage；The direct-current discharge unit includes airway and electrode group；The electrode group includes one Individual high-field electrode and a ground electrode for cylinder；The airway is hollow pipe, and upper and lower ends are respectively arranged with air inlet Port and air outlet；The high-field electrode is placed in airway axial centre position, it is characterised in that：At the ground electrode also It is provided with to form the hollow metal base unit of narrow gas channel；The hollow metal base unit is in cylinder, and It is axially disposed to have a through hole；The high-field electrode is placed in airway center；At the air outlet of airway, high pressure Electrode end surface is not more than 2mm with the spacing of inducing QI end surfaces；The ground electrode is L-shaped, a right-angle side be cylinder, its end face Facing each other with high-field electrode end face at airway air outlet, spacing is 5～30mm, and another right-angle side is cuboid, with Hollow metal base unit end face connects.

2. atmospheric pressure hollow substrate electrode plasma jet flow generating apparatus according to claim 1, it is characterised in that：Institute State.

3. atmospheric pressure hollow substrate electrode plasma jet flow generating apparatus according to claim 1 and 2, its feature exist In：The power supply adopts direct current or the pulse power, and the frequency of the pulse power is 50Hz to 13.56MHz.

4. atmospheric pressure hollow substrate electrode plasma jet flow generating apparatus according to claim 3, it is characterised in that：Institute The material for stating airway is Muscovitum, glass, ceramics or politef.

5. atmospheric pressure hollow substrate electrode plasma jet flow generating apparatus according to claim 4, it is characterised in that：Institute High-field electrode and ground electrode end face facing each other is stated for plane；The material of the high-field electrode and ground electrode be aluminum, ferrum, Copper, tungsten, nickel, tantalum, platinum, aluminium alloy, ferroalloy, copper alloy, tungsten alloy, nickel alloy, tantalum alloy.

6. atmospheric pressure hollow substrate electrode plasma jet flow generating apparatus according to claim 5, it is characterised in that：Institute The material for stating hollow metal base unit is aluminum or copper or aluminium alloy or copper alloy；The hole of hollow metal base unit throughhole portions Footpath is 4～100mm.