CN102869182A - Large-volume microwave plasma generating device based on coupling window radiation - Google Patents

Abstract

The invention relates to a large-volume microwave plasma generating device based on coupling window radiation, belonging to the technical field of microwave applications. The generating device includes a rectangular waveguide, an inductive coupling window, a resonant cavity shell, a rectangular quartz glass frame, a short-circuit piston, an absorbing substance and a handle. The rectangular waveguide communicates with one end of the resonant cavity through an inductive coupling window, and the shell of the resonant cavity is provided with a pressure measurement port, a working gas inlet and a working gas outlet. The rectangular quartz glass frame is placed in the resonant cavity, and its two ends are inlaid on the side walls of the resonant cavity, forming a closed space with the side walls of the resonant cavity on both sides. The short-circuit piston is placed at the other end of the resonant cavity, and the short-circuit piston is in sliding fit with the shell of the resonant cavity. The absorbing substance is fixed on the front end of the short-circuit piston, and the handle is fixed on the rear end of the short-circuit piston. The device can generate large-volume microwave plasma under normal temperature and pressure, and can efficiently prepare nanometer materials and treat waste gas and tail gas.

Description

A Large Volume Microwave Plasma Generating Device Based on Coupling Window Radiation

technical field

The invention relates to a large-volume microwave plasma generating device based on coupling window radiation, belonging to the technical field of microwave applications.

Background technique

As one of the three key technologies of mankind in the 21st century, materials science and technology play a vital role in the national economy and national defense. The emergence of nanotechnology has created a new era of materials science research. Different from macroscopic materials, the electronic structure and crystal structure of the surface of nanomaterials (0.1~100nm) change, resulting in surface effects, small size effects, quantum effects, macroscopic quantum tunneling effects and interface effects, etc.; and exhibit excellent Optical, electrical, magnetic and chemical properties, so it has broad application prospects in many fields.

At present, there are many methods for preparing nanomaterials, but each method has its own objective shortcomings. Such as the traditional wet method, the process is complicated, the chemical state of the particle surface is difficult to control, the anaerobic condition is difficult to create, and continuous and automated mass production cannot be realized; the gas phase-liquid phase method: low chemical activity, slow reaction speed, poor broad spectrum, Only a few kinds of nanoparticles can be prepared; DC plasma and dielectric barrier discharge plasma method: there are electrodes and the electric field has polarity and inhomogeneity, and it is easy to chain and agglomerate the generated nano-magnetic particles and finally make positive The connection of the negative electrodes leads to breakdown between the electrodes; chemical vapor deposition (CVD) and radio frequency plasma methods: the temperature is too high, vacuum conditions are required, and the energy consumption is large.

Due to its many advantages, microwave plasma is expected to synthesize nanomaterials with higher purity, controllable particle size, narrower particle size distribution, and no hard agglomeration. Its advantages are: high electron temperature, lower working pressure, high ionization degree (about 10 times higher); high reaction equilibrium constant, large temperature gradient, high homogeneous nucleation rate, and finer powder; the fluctuation effect of high-frequency electromagnetic field The convection effect caused by the large temperature gradient makes the particle size more uniform; there is no internal electrode, the plasma is pure; the excited state particles have a long life, and there are many chemically active species; the microwave energy heats the reactant molecules uniformly and rapidly, through the microwave The characteristics of "instantaneous heating" and "instantaneous stop of heating" can artificially control the crystallization speed; microwave plasma can be controlled in a specific space, which is convenient for application.

In the process of urbanization and industrialization, the world economy has developed by leaps and bounds, but it has also brought many environmental pollution problems, such as industrial waste gas and automobile exhaust emissions, which have brought serious harm to the environment and human physical and mental health. Scientific analysis shows that automobile exhaust contains hundreds of different compounds, among which pollutants include solid suspended particles, carbon monoxide, carbon dioxide, hydrocarbons, nitrogen oxides, lead, and sulfur oxides. The harmful exhaust gas emitted by a car in a year is three times larger than its own weight. The British Association for Clean Air and Environmental Protection once published a research report saying that compared with the victims of traffic accidents, the number of people who die from air pollution in the UK is 10 times more than that of the victims of traffic accidents every year. Therefore, the treatment of these exhaust gases has become an urgent problem to be solved. Due to its high electron temperature, high degree of ionization, long lifetime of excited particles, many chemically active species, and mature microwave technology, microwave plasma has also become the first choice for waste gas treatment.

Contents of the invention

The purpose of the present invention is to propose a large-volume microwave plasma generating device based on coupling window radiation, which is used for the preparation of nanomaterials and the treatment of industrial waste gas and automobile exhaust gas, and enables it to work for a long time under normal pressure, which is convenient for large-scale large-scale industrial applications.

The large-volume microwave plasma generating device based on coupling window radiation proposed by the present invention includes a rectangular waveguide, an inductive coupling window, a resonant cavity shell, a rectangular quartz glass frame, a short-circuit piston, an absorbing material and a handle; The type coupling window is connected with one end of the resonant cavity, and the shell of the resonant cavity is provided with an air pressure measurement port, a working gas inlet and a working gas outlet; the rectangular quartz glass frame is placed in the resonant cavity, and the two sides of the rectangular quartz glass frame The end is inlaid on the side wall of the resonant cavity, and the rectangular quartz glass frame forms a closed space with the side walls of the resonant cavity on both sides; the short-circuit piston is placed at the other end of the resonant cavity, and the short-circuit piston is in sliding fit with the shell of the resonant cavity; The absorbing substance is fixed on the front end of the short-circuit piston and located inside the resonant cavity, and the handle is fixed on the rear end of the short-circuit piston and located outside the resonant cavity.

The large-volume microwave plasma generating device based on coupling window radiation proposed by the present invention has the advantages of being able to generate large-volume microwave plasma at normal temperature and pressure, and efficiently prepare nanomaterials and treat exhaust gas. Compared with other existing microwave coupling methods, such as hole coupling and slit coupling, the plasma device of the present invention has an extremely high coupling efficiency of the inductive coupling window, which basically eliminates the loss of microwave transmission and coupling. It can form a large volume of microwave plasma in a sealed environment. On the one hand, it can ensure high material purity in the preparation of nanomaterials, and on the other hand, it can prevent the exhaust gas from diffusing to other areas during the exhaust gas treatment process. In the plasma generating device of the present invention, the adjustable sliding short-circuit piston installed at the tail of the rectangular resonant cavity can freely adjust the length of the resonant cavity so that the microwave can reach the best resonance state; the rectangular resonant cavity is spliced by multiple metal plates, which can Ensure that the microwave does not leak and cause personal harm, and at the same time facilitate the disassembly and installation of the device.

Description of drawings

Fig. 1 is a schematic structural diagram of a large-volume microwave plasma generating device based on coupling window radiation proposed by the present invention.

Fig. 2 is a cross-sectional view along line A-A of Fig. 1 .

Fig. 3 is a B-B sectional view of Fig. 2 .

FIG. 4 is an electric field distribution diagram of a section corresponding to FIG. 1 .

FIG. 5 is an electric field distribution diagram of a section corresponding to FIG. 2 .

In Figures 1 to 3, 1 is the connecting flange, 2 is the rectangular waveguide, 3 is the inductive coupling window, 4 is the resonant cavity shell, 5 is the rectangular quartz glass frame, 6 is the air pressure measurement port, and 7 is the working gas inlet , 8 is a short-circuit piston, 9 is an absorbing substance, 10 is a handle, and 11 is a working gas outlet.

Detailed ways

The large-volume microwave plasma generator based on coupling window radiation proposed by the present invention has a structure as shown in Figure 1, including a rectangular waveguide 2, an inductive coupling window 3, a resonant cavity shell 4, a rectangular quartz glass frame 5, and a short-circuit piston 8 , absorbent material 9 and handle 10. The rectangular waveguide 2 communicates with one end of the resonant cavity through an inductive coupling window 3 , and the resonant cavity housing 4 is provided with a pressure measurement port 6 , a working gas inlet 7 and a working gas outlet 11 . The rectangular quartz glass frame 5 is placed in the resonant cavity, the two ends of the rectangular quartz glass frame 5 are inlaid on the side walls of the resonant cavity, and the rectangular quartz glass frame 5 forms a closed space with the side walls of the resonant cavity on both sides. The short-circuit piston 8 is placed at the other end of the resonant cavity, and the short-circuit piston 8 is in sliding fit with the shell 4 of the resonant cavity. The absorbing substance 9 is fixed on the front end of the short-circuit piston 8 and is located in the resonant cavity. The handle 10 is fixed on the rear end of the short circuit piston 8 and is located outside the resonance cavity.

In the plasma generating device proposed by the present invention, the model of the rectangular waveguide is BJ22. Among them, the microwave coupling device is welded and connected with the flange and the inductive coupling window in sequence, and is connected with the external standard microwave device through the flange. This microwave coupling device is based on the inductive coupling window, and the inductive coupling window can be The microwave is enclosed in the rectangular resonant cavity to the greatest extent, so that the microwave can be fed into the rectangular resonant cavity freely and unobstructed. When the microwave resonates inside the rectangular resonant cavity, only a very small amount of microwave can be reflected to the microwave source through the coupling window , where the coupling window can also be designed as a capacitive or resonant coupling window. The rectangular resonant cavity is composed of three parts, which are the rectangular resonant cavity shell, the rounded rectangular quartz glass frame, the air inlet and outlet ports and the air pressure measurement interface welded on the front and rear copper plates of the rectangular resonant cavity. The rectangular resonator is essentially a cuboid with different lengths, widths and heights. It is spliced by six copper plates. This design is for easy disassembly and installation. Multiple air holes are opened on the front and rear copper plates of the rectangular resonator. They are working gas inlet, outlet and air pressure measurement port respectively. The rounded rectangular quartz glass frame is inlaid inside the rectangular resonant cavity. The rounded rectangular quartz glass frame has only four sides, and the other two sides are the front and rear copper plates of the rectangular resonant cavity. This design can not only ensure the formation of a sealed working gas space , this sealed working space is extremely important for generating microwave plasma with different pressures or different working gases, and it can also facilitate the entry and exit of working gases and measure the pressure of working gases in the rounded rectangular quartz glass frame. The rounded rectangular quartz glass frame provides A sealed space is crucial in the preparation of nanomaterials and exhaust gas treatment. The rectangular resonant cavity is connected with the microwave coupling device in the form of welding or screw fixing, and the microwave is fed into the rectangular resonant cavity through the inductive coupling window and further radiated into the rounded rectangular quartz glass frame. The resonator can also be designed as a cylindrical resonator. The adjustable sliding short-circuit piston is directly inserted into the copper plate at the rear end of the rectangular resonant cavity in a sliding fit. It can slide freely within a certain distance to adjust the length of the rectangular resonant cavity, so that the microwave can generate good resonance inside the rectangular resonant cavity. , generate a large-volume strong electric field area, and then generate a large-volume microwave plasma in the rounded rectangular quartz glass frame, improving the efficiency of nanomaterial preparation and exhaust gas treatment.

Below in conjunction with accompanying drawing, introduce the working principle of the device of the present invention in detail:

The invention relates to a microwave plasma generating device for preparing nanometer materials and treating industrial waste gas and automobile exhaust gas, comprising a microwave coupling device, a rectangular resonant cavity and an adjustable sliding short-circuit piston. Flange 1, BJ22 rectangular waveguide 2 and inductive coupling window 3 are welded together sequentially, and then the inductive coupling window is welded together with the left copper plate of the rectangular resonant cavity 4, and the six copper plates are fastened with screws to form the rectangular resonant cavity 4, which can be The adjusted sliding short-circuit piston is directly inserted into the middle of the right copper plate of the rectangular resonant cavity 4, and the rounded rectangular quartz glass frame is embedded in the front and rear copper plates of the rectangular resonant cavity 4 to form a closed space. The air pressure measurement interface 6 and the air inlet of the working gas 7. The gas outlet 11 of the working gas is respectively welded on the front and rear copper plates of the rectangular resonant cavity 4 . The entire microwave plasma generating device is connected with external standard microwave devices by screws through the flange 1 .

Microwaves are transmitted through the BJ22 rectangular waveguide 2 and coupled to the interior of the rectangular resonant cavity 4 through the inductive coupling window 3. Since the rounded rectangular quartz glass frame 5 basically has no effect on the transmission of microwaves, the microwave can be fed into the rounded rectangular quartz glass frame 5 Inside, the length of the rectangular resonant cavity 4 can be changed by adjusting the position of the adjustable sliding short-circuit piston, so that the microwave resonates inside the rectangular resonant cavity 4, and a large volume of strong microwave electric field is formed inside the rounded rectangular quartz glass frame 5, and the plasma The cross-sectional electric field distribution of the generating device is shown in Figures 4 and 5. The strong microwave electric field ionizes the working gas inside the rounded rectangular quartz glass frame 5 to generate large-volume microwave plasma.

For the preparation of nanomaterials, the gas inlet 7 is connected to the reaction mixture gas, the gas outlet 11 is connected to a user-defined material collector, and the air pressure measurement interface 6 is connected to a barometer to measure the working gas pressure inside the rounded rectangular quartz glass frame. The nanomaterials formed after the reaction mixture gas passes through the microwave plasma can enter the collector through the gas outlet 11 through the gas flow. By adjusting the gas pressure and microwave power of the working gas, it can be used to prepare nanomaterials with different characteristics. For the treatment of industrial waste gas and automobile exhaust, the air inlet 7 leads to waste gas or tail gas, and the air outlet 11 is connected to the device of the next processing procedure or directly connected to the atmosphere. Step-by-step treatment procedures or direct access to the atmosphere, different waste gas or tail gas pressure and microwave power correspond to different waste gas or tail gas treatment efficiency.

Claims (1)

1. A large-volume microwave plasma generating device based on coupling window radiation, characterized in that the plasma generating device comprises a rectangular waveguide, an inductive coupling window, a resonant cavity shell, a rectangular quartz glass frame, a short-circuit piston, an absorbing substance and a handle ; The rectangular waveguide communicates with one end of the resonant cavity through an inductive coupling window, and the resonant cavity housing is provided with an air pressure measurement port, a working gas inlet and a working gas outlet; the rectangular quartz glass frame is placed in the resonant cavity Inside, the two ends of the rectangular quartz glass frame are inlaid on the side walls of the resonant cavity, and the rectangular quartz glass frame forms a closed space with the side walls of the resonant cavity on both sides; the short-circuit piston is placed at the other end of the resonant cavity, and the short-circuit piston It is in sliding fit with the shell of the resonant cavity; the absorbing substance is fixed on the front end of the short-circuit piston and located inside the resonant cavity, and the handle is fixed on the rear end of the short-circuit piston and located outside the resonant cavity.

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