Coaxial metal electrode plasma discharge device

Abstract

The invention provides a coaxial metal electrode plasma discharge device, which comprises a positive electrode and a negative electrode which are coaxially arranged in a reaction cavity, a plasma generation area is arranged between the positive electrode and the negative electrode, and the coaxial double-electrode structure can obtain a real downstream plasma in a low-pressure vacuum state. A plurality of through holes are formed in the surface of the positive electrode, most electrons and ions of the downstream plasma are restrained between the electrodes to oscillate back and forth, and more active groups such as metastable state atoms, excited molecules and free radicals are gathered outside the positive electrode through the through holes and are in contact reaction with materials. The device is designed according to the plasma down-current discharge principle, due to the fact that no shielding or blind area exists in the reaction process, discharge is stable, uniformity is good, the device is sensitive to the material surface temperature, the device has the advantages of cleaning, activation, polymerization and the like of high polymer material sheets and films, and the device has wide industrial application prospects.

Description

Technical Field

[0001] The invention relates to a plasma discharge device, in particular to a coaxial metal electrode plasma discharge device. Background Art

[0002] Low-temperature plasma, also known as non-equilibrium plasma, is a form of matter that is different from solid, liquid, and gas. This aggregated state is composed of atoms, molecules, excited atoms and molecules, ions, electrons, photons, and free radicals. During the plasma discharge process, although the electron temperature is very high, the temperature of heavy particles (such as ions, atoms, etc.) is very low, and the entire system is in a low-temperature state. This characteristic enables low-temperature plasma to be highly active in chemical reactions without causing significant damage to the material itself. Therefore, it is widely used in multiple material processing fields such as surface cleaning, activation, deposition, and polymerization.

[0003] Compared with traditional chemical reaction methods, the low-temperature plasma generated by the plasma discharge device not only has a richer variety of active particles and stronger activity, but also is easier to react with the surface of the contacted material and various gases. As a gas discharge method, the low-pressure vacuum plasma discharge technology is based on the principle of maintaining a vacuum reaction chamber at a certain vacuum degree and applying a high-frequency voltage to the electrode to excite the gas ionization and produce a glow plasma. This technology has a high degree of flexibility and can meet the needs of surface treatment of various materials by adopting different discharge structures, introducing a variety of process gases, and adjusting parameters such as power, time and gas pressure. However, there are also some difficult to solve problems in the prior art. For example, most traditional low-pressure vacuum plasma discharge devices use flat electrodes, and the anode and cathode plates are placed vertically or horizontally. When processing large-area plates or thin film materials, the plasma discharge is uneven due to electrode shielding, which in turn affects the surface treatment effect of the material. The existing technology also uses multiple columnar electrodes for material processing and controls the electrode temperature through water cooling, but a relatively high gas temperature is still generated between the two electrodes, which will have an adverse effect on temperature-sensitive materials, especially polymer sheets and films, and cannot achieve the ideal cleaning, activation and polymerization effects. There is also a risk of plasma metal sputtering. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a coaxial metal electrode plasma discharge device, comprising a box body, wherein a reaction cavity is provided inside the box body; A gas input assembly, used for introducing process gas into the reaction chamber; A plasma generating component is used to provide excitation energy to the reaction cavity to ionize the process gas to generate plasma; A vacuum generating assembly, used for providing and maintaining a vacuum reaction environment for the reaction chamber; And at least one group of electrode feeding components arranged in the reaction cavity, used to connect the reaction cavity and the plasma generating component, each group of electrode feeding components consists of a columnar cathode electrode and an anode electrode coaxially sleeved on the outside of the cathode electrode, so as to generate plasma between the cathode electrode and the anode electrode, and a plurality of through holes are arranged along the circumference of the anode electrode.

[0005] Furthermore, the through hole is obtained by punching a side wall of the metal pipe.

[0006] Furthermore, the anode electrode is prepared by welding a metal mesh.

[0007] Furthermore, the inner diameter of the cathode electrode is 12-24 mm, and the wall thickness is 4-7 mm; the inner diameter of the anode electrode is 18-56 mm, and the wall thickness is 4-6 mm; and the size difference between the inner diameter of the anode electrode and the outer diameter of the cathode electrode is 5-30 mm.

[0008] Furthermore, the box body is provided with mounting plates on both sides of the reaction cavity, the two ends of the anode electrode are connected to the inner side of the mounting plates, and the two ends of the cathode electrode extend out of the outer side of the box body.

[0009] Furthermore, the gas input component includes a gas source, which is connected to the reaction cavity through an air intake pipeline; the air intake pipeline is connected with a flow meter for monitoring the gas flow and a solenoid valve for controlling the on-off of the air intake pipeline, and the flow meter and the solenoid valve are electrically connected to a control center to control the input of process gas according to the instructions of the control center.

[0010] Furthermore, the plasma generating assembly includes a matcher connected to the side of the box, the matcher is connected to the plasma generator through a signal line, the pulse frequency of the plasma generator is 25-100kHz, and the industrial frequency range is 2MHz, 15.56MHz, 27.12MHz, 40.68MHz, and 60MHz.

[0011] Furthermore, the vacuum generating assembly includes a vacuum pump disposed outside the box, and the vacuum pump is connected to the reaction cavity through a vacuum pipeline. A vacuum gauge for monitoring and feeding back the vacuum degree is installed on the side wall of the box, which is used to monitor and feed back the vacuum degree in the reaction cavity in real time.

[0012] Furthermore, a temperature control component is provided, which includes a temperature control source arranged outside the box, and the temperature control source is loaded with a liquid medium. The temperature control source transmits the liquid medium to each cathode electrode through a circulation pipeline.

[0013] Furthermore, conduits for connecting circulation pipelines are provided at both ends of the cathode electrode.

[0014] The present invention provides a coaxial metal electrode plasma discharge device, comprising a box, a gas input component, a vacuum generating component, a plasma generating component, and an anode electrode and a cathode electrode coaxially arranged in a reaction chamber, wherein the area between the anode electrode and the cathode electrode is a plasma generating area, and such a coaxially arranged double electrode structure can obtain a true downstream plasma under a low-pressure vacuum state. A plurality of through holes are provided on the surface of the anode electrode, and most of the electrons and ions of the downstream plasma are constrained to oscillate back and forth between the electrodes, and some photons are radiated out, and more active groups such as metastable atoms, excited molecules, and free radicals gather outside the anode electrode through the through holes and react with the material in contact, which belongs to a non-destructive plasma chemical treatment.

[0015] The present invention is designed based on the principle of plasma downstream discharge. Since there is no shielding or blind spot during the reaction, and the discharge is stable and uniform, and it is relatively sensitive to the surface temperature of the material, it is particularly advantageous in the cleaning, activation, and polymerization of polymer sheets and films, and has broad industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the structure of a coaxial metal electrode plasma discharge device; Figure 2 It is a schematic diagram of the position of the electrode feed assembly in the box; Figure 3 It is a schematic diagram of the connection between the electrode feed assembly and the mounting plate; Figure 4 is a schematic diagram of the structure of the electrode feed assembly; Figure 5 is the position of each particle within the electrode feed assembly; Figure 6 This is a comparison diagram of the water drop angle test of a sample material; Figure 7 This is a schematic diagram of the comparison of water drop angle tests at another position of the sample material.

[0017] Reference numerals: box body 1, reaction chamber 11, door panel 12, observation window 13, mounting plate 14, fastening sleeve 15, lining 16; Gas input assembly 2, gas source 21, air intake pipeline 22, solenoid valve 23, flow meter 24; Vacuum generating assembly 3, vacuum pump 31, vacuum pipeline 32, vacuum gauge 33; Plasma generating assembly 4, plasma generator 41, matching device 42, signal line 43; Electrode feeding assembly 5, cathode electrode 51, anode electrode 52, through hole 53; Temperature control component 6, temperature control source 61, circulation pipeline 62, conduit 63; Positive ion a, electron b, photon c, excited atom d, excited molecule e, free radical f. DETAILED DESCRIPTION

[0018] like Figure 1 The coaxial metal electrode plasma discharge device shown comprises a housing 1, wherein a reaction chamber 11 for plasma treatment is provided inside the housing 1, and a gas input assembly 2, a vacuum generating assembly 3 and a plasma generating assembly 4 are connected to the side of the housing 1. The gas input assembly 2 is used to introduce process gas into the reaction chamber 11; the plasma generating assembly 4 provides excitation energy to the reaction chamber 11 to ionize the process gas to generate plasma; and the vacuum generating assembly 3 provides and maintains a vacuum reaction environment for the reaction chamber 11.

[0019] like Figure 2 and Figure 4 As shown, the box body 1 is generally a box-type structure with a hollow interior, and the reaction cavity 11 is provided with a plurality of electrode feed assemblies 5 consisting of a cathode electrode 51 and an anode electrode 52, and the electrode feed assemblies 5 are used to connect the plasma generating assembly 4 and the reaction cavity 11. The cathode electrode 51 and the anode electrode 52 are both tubular electrodes, and the axial sides of the cathode electrode 51 penetrate the two sides of the reaction cavity 11 and are electrically connected to the high-voltage electrode, and the anode electrode 52 is sleeved on the outside of the cathode electrode 51 and grounded, and the anode electrode 52 is coaxially arranged with the cathode electrode 51, and the process gas between the anode electrode 52 and the cathode electrode 51 will be ionized under vacuum conditions to generate plasma.

[0020] A plurality of through holes 53 are arranged on the circumference of the anode electrode 52. The anode electrode 52 with through holes 53 can be obtained by punching holes in the side wall of a metal tube, or by welding a metal material of a mesh structure into a tubular structure. The through holes 53 can be circular, square, polygonal or other special shapes, and the aperture of each through hole 53 is preferably 3-10 mm. Figure 5 The working principle of the present invention is as follows: the gas molecules and atoms between the anode electrode 52 and the cathode electrode 51 are excited to the energy level due to the energy obtained. Due to the electric field formed by the electrode feed assembly 5, most of the electrons b and positive ions a generated by the gas ionization are confined in the gap between the anode electrode 52 and the cathode electrode 51 to oscillate back and forth, while the excited atoms d, excited molecules e, free radicals f and other active groups and a small amount of free electrons b will be collected from the through hole 53 to the outside of the anode electrode 52. The excited atoms d and excited molecules e will also radiate part of the photons c of a specific wavelength and color to the outside of the anode electrode 52 when they transition to the ground state. The part of the active groups has certain energy and chemical characteristics with the photons c, and can interact with the atoms or molecules on the surface of the material, implementing a non-destructive plasma chemical treatment process for the material body. The through holes 53 are evenly arranged along the length direction and circumference of the anode electrode 52 to ensure that the active groups outside the anode electrode 52 can be evenly distributed as much as possible.

[0021] The electrode feed components 5 of this embodiment are arranged in two rows along the upper and lower sides of the box body 1. The material is placed on the surface of the anode electrode 52 according to the processing position of the material, and the surface of the electrode feed component 5 is the processing area. For example, if both sides of the material need to be processed, the material can be placed between two rows of electrode feed components 5. Since the anode electrode 52 is a columnar structure, it has only a very small contact area with the surface of the material. There is almost no shielding and blind area when the active ions react with the surface of the material, and the surface of the material can fully react. The electrode feed components 5 of each row are arranged in multiple columns side by side to fully support the material and maintain the uniformity of the reaction of the material everywhere.

[0022] The radius and length of each group of positive electrodes 52 and negative electrodes 51 do not need to be set to be exactly the same, and can be set according to the specific requirements of the product shape and the shape of the reaction cavity 11. For example, each electrode feed assembly 5 is subjected to a diameter reduction treatment for special materials. In this embodiment, the inner diameter of the negative electrode 51 is 12-24 mm, and the wall thickness is 4-7 mm; the inner diameter of the positive electrode 52 is 18-56 mm, and the wall thickness is 4-6 mm; the size difference between the inner diameter of the positive electrode 52 and the outer diameter of the negative electrode 51 is preferably 5-30 mm, and under the above conditions, a better plasma dispersion effect is achieved.

[0023] like Figure 3 As shown, the box body 1 is made of metal materials such as aluminum alloy and stainless steel. One side of the box body 1 is open and a door panel 12 is hinged on the end face of the opening. The material can be loaded into the reaction cavity 11 at the end face of the opening. An observation window 13 is provided on the door panel 12, which can observe the processing status of the material during the reaction process. The box body 1 is provided with mounting plates 14 on both sides of the reaction cavity 11. The mounting plates 14 are provided with mounting holes at both ends of each group of electrode feed components 5. The two ends of the positive electrode 52 can be abutted or clamped on the inner side of the mounting plate 14, and then the negative electrode 51 is installed into the mounting hole from the outside of the box body 1. The installation position of the negative electrode 51 is quickly located, and the installation is convenient. At the same time, the coaxial fixation of the positive electrode 52 and the negative electrode 51 is realized. A fastening component is provided at the position corresponding to the installation hole on the outside of the box body 1, which is used to fix the two end positions of the negative electrode 51. The fastening component can adopt common threads or other common fastening methods. In this embodiment, a liner 16 is installed in the installation through hole 53, one end of the liner 16 extends out of the installation through hole 53 and is fixedly connected to the outside of the box body 1, which can prevent the cathode electrode 51 from being worn due to direct contact with the pipe wall of the installation through hole; a fastening sleeve 15 is sleeved on the outside of the cathode electrode 51, and the fastening sleeve 15 is radially clamped between the cathode electrode 51 and the liner 16. When the cathode electrode 51 is installed in the installation through hole 53, the fastening sleeve 15 can be firstly sleeved on one side of the cathode electrode 51, and after the cathode electrode 51 is in place, the fastening sleeve 15 is clamped in the liner 16; then the liner 16 and the fastening sleeve 15 are installed on the other side of the cathode electrode 51 to complete the fixation of the cathode electrode 51.

[0024] The gas input assembly 2 includes a gas source 21, and the gas source 21 is connected to the reaction cavity 11 through an air intake pipeline 22. The air intake pipeline 22 is connected with a flow meter 24 for monitoring the gas flow and a solenoid valve 23 for controlling the on-off of the air intake pipeline 22. The flow meter 24 and the solenoid valve 23 are electrically connected to a control center to control the input of process gas according to the instructions of the control center.

[0025] The plasma generating assembly 4 includes a matcher 42 connected to the side of the housing 1, and the matcher 42 is connected to the plasma generator 41 through a signal line 43. The signal released by the plasma generator 41 drives the high-frequency boost module via the matcher 42, thereby generating high-voltage electric energy. The matcher 42 adjusts the impedance of the matching network so that the output impedance of the high-frequency generator matches the load impedance. This high voltage is applied to the electrode feed assembly 5. When it reaches a preset critical value, it will cause the surrounding process gas to ionize and trigger a discharge phenomenon, and finally generate a low-temperature plasma.

[0026] The plasma generator 41 in this embodiment uses a sine wave or pulse wave power supply, the pulse frequency is between 25-100 kHz, and the industrial frequency band selects high frequency scenarios such as 2 MHz, 15.56 MHz, 27.12 MHz, 40.68 MHz, and 60 MHz.

[0027] The vacuum generating assembly 3 includes a vacuum pump 31 disposed outside the housing 1, and the vacuum pump 31 is connected to the reaction chamber 11 through a vacuum pipe 32 to maintain a vacuum environment in the reaction chamber 11. A vacuum gauge 33 is installed on the side wall of the housing 1 for real-time monitoring and feedback of the vacuum degree in the reaction chamber 11.

[0028] The electrode feed assembly 5 provided by the present invention reacts uniformly at various locations on the surface of the material, and the temperature difference caused by the local reaction difference is small, so the material can be processed at a more appropriate temperature. On this basis, the present embodiment is also provided with a temperature control assembly 6, and the temperature control assembly 6 includes a temperature control source 61 arranged on the outside of the housing 1, and the temperature control source 61 is loaded with a liquid medium, and the liquid medium is transmitted to each cathode electrode 51 through a circulation pipeline 62. The present embodiment uses cooling water as the liquid medium, and when the temperature needs to be increased, it can be replaced with heating kerosene, etc. Specifically, the two end portions of the cathode electrode 51 are provided with a conduit 63 for connecting the circulation pipeline 62, and the circulating water enters or flows out of the cathode electrode 51 through the opening of the conduit 63, and the heat exchange of the reaction area is realized by the circulating water, so as to achieve plasma treatment in a low temperature environment.

[0029] The material was treated by plasma discharge device. The sample material treated was FEP sheet. Figure 6 and Figure 7Schematic diagrams of water drop angle tests at two positions of the material are shown, wherein Figure a represents the water drop angle test diagram of the two positions before treatment, both of which are 106°; Figure b shows the treatment at the same positions using the discharge device provided by this embodiment, and the water drop angles obtained by the test are 41.5° and 40.5° respectively; Figure c uses a conventional square plate discharge device and performs corresponding tests, and the water drop angles obtained are 62° and 50.5°. It can be seen that the discharge device provided by the present invention can better react with the material for plasma, and the uniformity of the material at various locations is significantly improved.

[0030] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A coaxial metal electrode plasma discharge device, characterized in that: It comprises a box body (1), wherein a reaction cavity (11) is provided inside the box body (1); A gas input component (2) for introducing process gas into the reaction chamber (11); A plasma generating component (4) is used to provide excitation energy to the reaction cavity (11) to ionize the process gas to generate plasma; A vacuum generating assembly (3) for providing and maintaining a vacuum reaction environment for the reaction chamber (11); and at least one set of electrode feed components (5) disposed in the reaction cavity (11) and used to connect the reaction cavity (11) and the plasma generating component (4); each set of electrode feed components (5) is composed of a columnar cathode electrode (51) and an anode electrode (52) coaxially sleeved on the outside of the cathode electrode (51) so as to generate plasma between the cathode electrode (51) and the anode electrode (52); and a plurality of through holes (53) are arranged along the circumference of the anode electrode (52).

2. The coaxial metal electrode plasma discharge device according to claim 1, characterized in that: The through hole (53) is obtained by punching a hole in the side wall of the metal pipe.

3. The coaxial metal electrode plasma discharge device according to claim 1, characterized in that: The positive electrode (52) is prepared by welding a metal mesh.

4. The coaxial metal electrode plasma discharge device according to claim 1, characterized in that: The inner diameter of the cathode electrode (51) is 12-24 mm, and the wall thickness is 4-7 mm; the inner diameter of the anode electrode (52) is 18-56 mm, and the wall thickness is 4-6 mm; the size difference between the inner diameter of the anode electrode (52) and the outer diameter of the cathode electrode (51) is 5-30 mm.

5. The coaxial metal electrode plasma discharge device according to claim 1, characterized in that: The box body (1) is provided with mounting plates (14) on both sides of the reaction cavity (11); two ends of the anode electrode (52) are connected to the inner side of the mounting plates (14); and two ends of the cathode electrode (51) extend out of the outer side of the box body (1).

6. The coaxial metal electrode plasma discharge device according to claim 1, characterized in that: The gas input assembly (2) comprises a gas source (21), the gas source (21) being connected to the reaction chamber (11) via an air intake pipeline (22); a flow meter (24) for monitoring the gas flow rate and a solenoid valve (23) for controlling the on-off of the air intake pipeline (22) are connected to the air intake pipeline (22); the flow meter (24) and the solenoid valve (23) are electrically connected to a control center, and the input of the process gas is controlled according to instructions from the control center.

7. The coaxial metal electrode plasma discharge device according to claim 1, characterized in that: The plasma generating assembly (4) comprises a matching device (42) connected to the side of the housing (1); the matching device (42) is connected to the plasma generator (41) via a signal line (43); the pulse frequency of the plasma generator (41) is 25-100 kHz, and the industrial frequency range is 2 MHz, 15.56 MHz, 27.12 MHz, 40.68 MHz, and 60 MHz.

8. The coaxial metal electrode plasma discharge device according to claim 1, characterized in that: The vacuum generating assembly (3) comprises a vacuum pump (31) arranged outside the box (1), and the vacuum pump (31) is connected to the reaction chamber (11) via a vacuum pipeline (32); a vacuum gauge (33) for monitoring and providing feedback of the vacuum degree is installed on the side wall of the box (1), and is used for real-time monitoring and providing feedback of the vacuum degree in the reaction chamber (11).

9. The coaxial metal electrode plasma discharge device according to claim 1, characterized in that: A temperature control component (6) is also provided, the temperature control component (6) comprising a temperature control source (61) provided outside the box (1), the temperature control source (61) being loaded with a liquid medium, the temperature control source (61) transmitting the liquid medium to each cathode electrode (51) via a circulation pipeline (62).

10. The coaxial metal electrode plasma discharge device according to claim 9, characterized in that: Both end portions of the cathode electrode (51) are provided with conduits (63) for connecting to a circulation pipeline (62).

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