Flexible electrode-coated coaxial dielectric barrier discharge device for material synthesis

Abstract

The utility model provides a kind of flexible electrode coating type coaxial dielectric barrier discharge device for material synthesis, including outer tube, inner tube, inner electrode, flexible outer electrode, gas inlet hole, hole limit plug, plug;Through the collaborative design of three-section flexible outer electrode and guard ring electrode, the high uniformity of discharge zone electric field is realized while end electric field can be weakened;By tangential oblique gas inlet to form spiral flow field, the problems of powder deposition and airflow turbulence are solved, at the same time, the direct contact between material and reactor is isolated, and the probability of material contamination is reduced;Through the full-coated dielectric protection layer of inner and outer electrodes, the loss of electrodes in air is reduced, and the service life of electrodes is prolonged;And through the combination structure of end plug and limit plug, material escape and end blockage are effectively inhibited. The whole device has significant advantages over traditional DBD equipment in terms of treatment uniformity, running stability, material purity guarantee and engineering practicability, and has good popularization and application prospect.

Description

Technical Field

[0001] This utility model belongs to the field of plasma material processing technology, and more specifically, it relates to a flexible electrode-coated coaxial dielectric barrier discharge device for material synthesis. Background Technology

[0002] Dielectric barrier discharge (DBD), a typical non-equilibrium low-temperature plasma technology, has been widely used in polymer film modification, fiber surface activation, and powder material processing due to its ability to efficiently generate highly active particles at ambient pressure. By introducing reactive gases such as O2, N2, NH3, and Ar, DBD can introduce functional groups such as hydroxyl, carboxyl, and amino groups onto the material surface, significantly improving its wettability, dispersibility, and interfacial bonding properties. It is particularly suitable for the surface modification of nanomaterials such as humic acid, graphene, and metal-organic frameworks (MOFs).

[0003] Currently, DBD devices used for powder or nanomaterial processing mainly include flat plate type, coaxial tube type, and sliding arc / jet type structures. Among them, the flat plate type device has a simple structure and is suitable for thin film or sheet processing, but it is difficult to achieve uniform exposure and sufficient dispersion of loose powders. The coaxial tube type DBD has an axisymmetric electric field distribution and a long reaction path, and is often used for gas processing or pipeline inner wall modification. Although some studies have attempted to use it for powder modification, the problem of powder deposition on the inner wall of the electrode or dielectric tube is common, leading to uneven discharge, reduced processing efficiency, or even local blockage. The sliding arc or jet type devices are mostly used for local surface treatment or gas phase activation, and have limited ability to deeply and comprehensively modify bulk nanomaterials.

[0004] Furthermore, existing coaxial DBD devices still face numerous technical bottlenecks in practical applications. First, traditional internal electrodes are typically directly exposed to the plasma environment, making them susceptible to sputtering or corrosion over long-term operation. This not only shortens electrode lifespan but can also introduce metallic impurities, affecting the purity and functional properties of nanomaterials. Second, external electrodes often employ rigid metal rings or wound wires, making it difficult to tightly conform to the outer walls of dielectric tubes with varying diameters or curvatures, resulting in uneven electric field distribution and poor discharge stability. Third, the conventional straight-through inlet method creates an uneven airflow field, causing powder agglomeration or deposition within the tube, and the outlet gas often carries unreacted particles, leading to material loss and environmental pollution. Simultaneously, the device lacks an effective particle interception mechanism, resulting in dust and scale buildup after a period of operation, making maintenance difficult and hindering continuous operation. Utility Model Content

[0005] The purpose of this invention is to overcome the problems of electrode contamination, uneven discharge, powder deposition and escape, and poor structural adaptability in existing coaxial dielectric barrier discharge devices when processing powders and nanomaterials, and to provide a flexible electrode-coated coaxial dielectric barrier discharge device for material synthesis. This device achieves a stable, uniform, efficient, and low-pollution plasma processing process by optimizing the electrode structure, enhancing dielectric protection, and improving airflow organization and particle control.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A flexible electrode-coated coaxial dielectric barrier discharge device for material synthesis includes:

[0008] The outer tube is a hollow tubular structure closed at one end;

[0009] An inner tube is coaxially inserted through the closed end of the outer tube at its center; both the inner and outer tubes are made of quartz or ceramic material, and a ring-shaped plasma discharge cavity is formed between them.

[0010] The inner electrode is axially inserted inside the inner tube and its outer surface is covered with a dielectric protective layer to prevent the inner electrode from being directly exposed to the plasma, thus preventing sputtering and corrosion, improving electrode life and reducing metal contamination.

[0011] The flexible external electrode is segmented and covers the outer wall of the outer tube. It can adaptively fit the outer tube according to the curvature or diameter of the outer tube to ensure uniform electric field distribution.

[0012] The inlet port is located at the inlet end of the outer tube and is arranged tangentially to introduce the reactive gas and form a spiral propulsion flow field in the discharge cavity, thereby enhancing the mixing efficiency of the gas and powder materials, reducing material deposition, and avoiding contamination of the material by the reactor under plasma excitation.

[0013] A perforated limiting plug is installed inside the outer tube near the tail end to balance the airflow and prevent material from overflowing with the airflow.

[0014] A plug is provided at the outlet end of the outer tube, and it has a through hole to prevent air from diffusing into the reactor and to discharge waste gas.

[0015] Both the inner wall of the outer tube and the outer wall of the inner tube are provided with a dielectric protective layer, which further enhances the insulation and anti-pollution ability of the dielectric surface, prevents powder from adhering and depositing in the discharge area, and improves discharge stability.

[0016] Preferably, the dielectric protective layer is made of any one of silicon dioxide, aluminum oxide, or silicon nitride, and has good dielectric properties and chemical stability.

[0017] Preferably, the flexible outer electrode is made of conductive rubber, flexible metal foil or carbon-based conductive composite material, which has good flexibility and conductivity, can fit the outer wall of the outer tube with different diameters or curvatures, and can adapt to a variety of working scenarios.

[0018] Preferably, the flexible external electrode includes three main electrode regions, with guard ring electrodes at both ends to improve the edge electric field distribution, suppress the edge discharge effect, and enhance the discharge uniformity.

[0019] Preferably, the flexible external electrode is also wrapped with a dielectric protective layer to protect the electrode from environmental corrosion and mechanical damage, thereby extending its service life.

[0020] Preferably, the perforated limiting plug is made of ceramic or quartz material, and its internal through hole diameter is 5~20 µm, which can ensure gas flow and effectively prevent larger particles from entering the inner tube area.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) By completely covering the outer surface of the inner electrode with a highly insulating and corrosion-resistant dielectric protective layer, the metal inner electrode is effectively prevented from being directly exposed to the high-energy plasma environment, which fundamentally suppresses the problems of electrode sputtering and metal ion contamination, and ensures the functional integrity and subsequent application performance of the modified material.

[0023] (2) The external electrode is designed with a segmented coating of flexible conductive material, which can closely fit the outer wall of quartz or ceramic tubes of different diameters or curvatures. This significantly improves the contact quality between the electrode and the dielectric tube, eliminates local electric field distortion or discharge dead zones caused by poor contact, and thus achieves a more uniform and stable annular plasma distribution. At the same time, this flexible structure not only enhances the versatility and scalability of the device, but also facilitates installation and disassembly. It is particularly suitable for the needs of multi-scale laboratory experiments or rapid replacement and maintenance in industrial sites, greatly improving the flexibility and engineering applicability of the equipment.

[0024] (3) By setting up guard ring electrodes, the electric field concentration phenomenon in the edge area of ​​the main electrode can be effectively improved, the edge discharge effect can be suppressed, and the electric field distribution in the entire discharge area can be smoother and more uniform. The dielectric layer outside the outer electrode not only prevents external gas, moisture and dust from eroding the conductive layer, but also avoids the risk of electric shock that may occur during operation, thus improving the safety and long-term operational stability of the device.

[0025] (4) By tangentially tilting the inlet holes, the reactant gas enters the discharge cavity in a spiral manner, forming a stable swirling flow field. This spiral propulsion flow field uses centrifugal force to cause the powder particles to diffuse towards the outer tube wall and move in a suspended state, which significantly reduces the agglomeration of particles in the central region and the deposition on the tube wall, prolongs the effective residence time of the material in the plasma region, and improves the collision frequency and reaction efficiency between active particles and the material surface, thereby achieving a more thorough and uniform surface modification effect. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall structure of the device;

[0027] Figure 2 This is a schematic diagram of the exploded structure of the device;

[0028] Figure 3 This is a schematic diagram of the end structure of the device;

[0029] Figure 4 This is a sectional view of plane AA;

[0030] Figure 5 This is a sectional view of the BB plane;

[0031] In the diagram, the correspondence between component names and drawing numbers is as follows:

[0032] 1-Outer tube, 2-Inner electrode, 3-Inner tube, 4-Flexible outer electrode, 5-Plug, 51-Through hole, 6-Perforated limiting plug, 7-Guarding ring electrode, 8-Dielectric protection layer, 9-Gas inlet, 100-Plasma discharge cavity. Detailed Implementation

[0033] The embodiments of this utility model will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of this utility model.

[0034] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" 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. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0035] Example:

[0036] like Figures 1-5As shown, the flexible electrode-coated coaxial dielectric barrier discharge device used for material synthesis comprises an outer tube 1 and an inner tube 3 made of high-purity fused silica. The outer tube 1 is a hollow cylinder closed at one end, and the inner tube 3 is coaxially inserted into and fixedly installed at the closed end of the outer tube 1, forming an annular space between the two, constituting a plasma discharge cavity 100. By using silica material for both the outer tube 1 and the inner tube 3, the main structure possesses excellent dielectric strength, thermal stability, and chemical inertness, effectively withstanding the effects of high-frequency and high-voltage electric fields and resisting long-term corrosion by reactive oxygen species and nitrogen species, ensuring the reliability of the device during long-term operation.

[0037] To address the problem of uneven electric field distribution caused by traditional rigid external electrodes, this invention employs a three-segment flexible external electrode 4, with each main electrode segment evenly arranged on the outer wall of the outer tube 1. The electrode material is conductive rubber composite silver nanowires, possessing excellent flexibility and conductivity, allowing for close contact with quartz tubes of different diameters or slight bends, ensuring continuous and reliable electrical contact and significantly improving discharge uniformity. Guard ring electrodes 7 are also provided on the outer sides of the main electrodes at both ends. These guard ring electrodes 7 do not contact the flexible external electrode 4 and are spaced 2-3 mm apart. Located at the potential edge region, they are used to adjust the electric field gradient at the ends, suppress edge discharge concentration, avoid local overheating or breakdown, and ensure that the plasma throughout the discharge region exhibits a uniform and stable filamentary or glow discharge pattern.

[0038] To prevent sputtering corrosion of the inner electrode 2 in the plasma environment, which could lead to contamination of the nanomaterials by metal particles, this embodiment inserts an inner electrode inside the inner tube 3 and coats its outer surface with a silicon dioxide dielectric protective layer 8. This protective layer completely covers the metal electrode, achieving electrical conduction while isolating it from direct plasma bombardment. This fundamentally eliminates the damage to the electrode caused by gases, moisture, and dust in the air, extending its service life and ensuring that functional materials such as graphene and MOFs maintain high purity and structural integrity during the modification process.

[0039] In terms of gas dynamics design, the traditional axial straight-through air intake method is abandoned. Instead, the air inlet 9 is located at the inlet end of the outer tube 1 and is tangentially connected at a 30° angle to the tube wall. After the reactive gas enters through this inlet, it forms a spiral propulsion flow field under the action of centrifugal force, moving forward in a vortex shape along the discharge cavity 100. This structure not only enhances the airflow disturbance and powder particle dispersion effect, and prolongs their residence time in the plasma zone, but more importantly, it forms a stable "air curtain" isolation effect, reducing direct contact between the powder and the medium tube wall. This effectively reduces wall deposition and blockage problems caused by electrostatic adsorption or high-temperature sintering, while also avoiding contamination of the material by the medium tube wall in the plasma state. At the same time, the closed inlet structure also prevents the material from being ejected in reverse with the airflow, improving the feeding stability.

[0040] At the outlet end, two key functional components are installed: a perforated limiting plug 6 and a plug with through holes 5. The perforated limiting plug 6 is located inside the outer tube 1 near the tail end, and its end face is evenly distributed with holes, the diameter of which is controlled at about 5~20 µm. It is used to stabilize the airflow and prevent material from overflowing from the reaction zone and reactor.

[0041] The plug 5 is installed at the outlet end of the outer pipe, through which gas is discharged evenly, preventing air from seeping in; at the same time, powder particles cannot pass smoothly through the micropores due to inertia and are trapped in the cavity, which greatly reduces the loss caused by material leakage with the airflow and improves the material recovery rate and processing efficiency.

[0042] Furthermore, this solution offers good maintainability and long-term operational adaptability. The flexible external electrode 4 is also covered with a dielectric protective layer 8 to resist environmental moisture, dust contamination, and mechanical scratches, extending electrode life. All key components, including the plug 5, the flexible external electrode 4, and the perforated limiting plug 6, adopt a detachable modular design. When dust accumulation, scaling, or performance degradation occurs after a period of operation, quick replacement is possible without disassembling the main chamber, significantly reducing maintenance difficulty and downtime, and meeting the needs of batch and continuous industrial applications.

[0043] In summary, this embodiment achieves highly uniform electric field in the discharge zone through the synergistic design of a three-segment flexible external electrode and a guard ring electrode; it solves the problems of powder deposition and airflow turbulence by forming a spiral flow field through tangentially inclined air intake; it completely avoids the risk of metal contamination by fully encapsulating the inner and outer electrodes with a dielectric protective layer; and it effectively suppresses material escape and end blockage through the combination of an end plug and a limiting plug. The entire device has significant advantages over traditional DBD equipment in terms of processing uniformity, operational stability, material purity assurance, and engineering practicality. It is particularly suitable for large-scale surface functionalization modification of high-end nanomaterials and has promising prospects for widespread application.

[0044] The embodiments of this utility model are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the utility model to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical applications of this utility model, and to enable those skilled in the art to understand this utility model and design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A flexible electrode-coated coaxial dielectric barrier discharge device for material synthesis, characterized in that, include: The outer tube (1) is hollow with one end closed. The inner tube (3) is coaxially inserted through the center of the outer tube (1) along the closed section of the outer tube (1); the inner tube (3) and the outer tube (1) are made of quartz or ceramic material, and a plasma discharge cavity (100) is formed between the inner tube (3) and the outer tube (1). The inner electrode (2) is axially inserted in the inner tube (3), and the outer surface of the inner electrode (2) is covered with a dielectric protective layer (8). The flexible external electrode (4) is segmented and covers the outer wall of the outer tube (1); The air inlet (9) is tangentially inclined at the inlet end of the outer tube (1) to introduce the reactive gas and form a spiral propulsion flow field; A perforated limiting plug (6) is installed inside the outer tube (1) and located at the tail of the outer tube (1); A plug (5) with a through hole (51) is provided at the outlet end of the outer tube (1) for uniform exhaust and to suppress the powder from escaping with the airflow. The inner wall of the outer tube (1) and the outer wall of the inner tube (3) are provided with a medium protection layer (8).

2. The flexible electrode-coated coaxial dielectric barrier discharge device for material synthesis according to claim 1, characterized in that, The dielectric protective layer (8) is any one of silicon dioxide, aluminum oxide or silicon nitride.

3. The flexible electrode-coated coaxial dielectric barrier discharge device for material synthesis according to claim 1, characterized in that, The flexible outer electrode (4) is made of conductive rubber, flexible metal foil or carbon-based conductive composite material, and can be attached to the outer wall of the outer tube (1) with different diameters or curvatures.

4. The flexible electrode-coated coaxial dielectric barrier discharge device for material synthesis according to claim 1, characterized in that, The flexible external electrode (4) includes three main electrode regions, and guard ring electrodes (7) are provided at both ends.

5. The flexible electrode-coated coaxial dielectric barrier discharge device for material synthesis according to claim 1, characterized in that, The flexible external electrode (4) is covered with a dielectric protective layer (8).

6. The flexible electrode-coated coaxial dielectric barrier discharge device for material synthesis according to claim 1, characterized in that, The perforated limiting plug (6) is made of ceramic or quartz material, and the through hole in the perforated limiting plug (6) has a diameter of 5~20µm.

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