CN1488462A - A method for tailoring and coating nanoparticle surface physicochemical structure - Google Patents

Abstract

A method for tailoring and covering the surface of nanoparticles with physical and chemical structures. By modulating the radio frequency plasma, controlling the pulse ratio, time, power and other discharge conditions, and then controlling the type and content of functional groups, the thickness of the deposited layer, the roughness of the coating, etc., it can be coated on the surface of nanoparticles such as TiO ₂ Selectively "cut" the coating film with specific monomer molecular functional groups, and control the physical form such as the thickness and surface roughness of the coating layer, obtain a coating film with a specific physical and chemical structure, and change the surface physical and chemical properties of nanoparticles structure. Compared with the traditional coating method, this method has the advantages of dry state, normal temperature, less environmental pollution, uniform film layer, controllable thickness, tight combination of coating layer and nano core, and wide range of monomer selection. It can reduce the agglomeration of nanoparticles through steric physical hindrance and chemical compatibility, so as to reflect the special effect of small size on nanoparticles. It can also be used in the development of nanocomposite particles, etc.

Description

A method for tailoring and coating nanoparticle surface physicochemical structure

technical field

The invention relates to a method for coating a layer of thin film on the surface of nanoparticles by using plasma discharge method. Specifically, it relates to a method of tailoring and coating the physical and chemical structure of the surface of nanoparticles, which is to modulate the discharge parameters of the pulsating radio frequency plasma under vacuum plasma conditions, and selectively tailor and design the coating according to the different coating objects. The chemical and physical structure of the film, so as to achieve the purpose of tailoring the surface physical and chemical structure of nanoparticles.

Background technique

At present, the research and application of various structural and functional nanoparticle materials are attracting more and more attention. When forming nanocomposites, only when the size of any one of the phases reaches 100 nanometers or less, the specific functionality brought by its small size can be realized. But at this time, the proportion of surface atoms to the total number of atoms increases sharply, the surface energy increases rapidly, and the agglomeration of particles becomes more serious, so it is difficult to achieve nanoscale dispersion of nanoparticles in the matrix.

Since the dispersion performance of nanomaterials is largely affected by the surface properties of nanoparticles, surface modification is one of the commonly used methods to improve the dispersion of nanoparticles, which is very important for nanomaterials to exhibit their specific functions. Various liquid methods, such as coupling agents, surfactants, organic oligomers, etc., mainly improve the dispersion of nanoparticles by changing the surface chemical structure. However, in the application, there are disadvantages such as low operating temperature and repeated solid-liquid separation operations during the coating process. Gaseous methods such as laser sputtering, plasma coating, etc., can be coated in a simple one-step process. Plasma coating is to crack various polymeric or non-polymerizable monomers by discharge, and then vapor phase polymerization deposition. Through the physical and chemical combination of reactive species and the surface of nanoparticles, a very thin layer of film is coated on the surface of nanoparticles. At present, research in this area is beginning at home and abroad. For example, D Shi et al. applied radio frequency continuous wave plasma polymerization method to obtain extremely thin uniform films on the surface of _Al2O3 and ZnO nanoparticles with a size of _10nm to 150nm (D Shi et al., Appl.Physics Letter, 2001,78 (9): 1243-1245); Dorothee V.Szabo etc. use microwave plasma to coat polymethyl methacrylate (PMMA) film on the surface of Fe ₃ O ₄ nanoparticles (Dorothee V. Szabo et al., Advanced Materials, 1999, 11(15):1313-1316). The plasma coating of the above-mentioned nanoparticles mostly uses the radio frequency continuous wave plasma method, which greatly damages the original structure of the monomer, and it is difficult to retain the functional groups containing oxygen and nitrogen of the original monomer, such as COOH, OH, NH _2, etc., the film layer obtained by polymer coating has a high degree of crosslinking, so the permeability is very low, and it is insoluble and infusible, and has little flexibility in regulating the chemical structure of the deposited film. The recently developed pulsating radio frequency plasma can be used to modify the surface of materials by pulsating the radio frequency plasma, so that the discharge can be performed intermittently between "on" and "off". In the interval of "off", conventional free radical polymerization can be carried out, so that specific functional groups of monomer molecules can be selectively "tailored". For example, Licheng M.Han et al. used it for the film deposition of perfluoroalkylbenzene on flat glass or silicon wafers, selectively retaining the heat-resistant benzene ring in the monomer and the CF functional group that contributes to the insulation performance, and obtained low dielectric properties. Functional film coatings with electrical constant and high thermal stability (Licheng M. Han, et al., 1997, Langmuir, 13:5941). In the research of pulsating radiofrequency plasma polymerization of vinyl acetic acid by Zhang Jing et al., when the pulsation ratio decreases, the content of carboxyl and hydroxyl groups in the polymeric film structure on the glass slide tends to rise (Zhang Jing et al., Acta Physica Sinica, 2003, 52(7) : 1707-1712)

However, there is still a problem of how to coat single particles instead of particle aggregates in the coating of nanoparticles by plasma polymerization. Due to the high surface energy of the aforementioned nanoparticles, the nanoparticles are prone to agglomeration, and it is extremely difficult to coat the surface of a single nanoparticle rather than an aggregate of particles. Moreover, when the plasma polymerization method is used to coat nanoparticles, it is also a problem to be solved to selectively "cut" and retain specific functional groups of monomer molecules.

Therefore, to address these two problems, it is necessary to find improved methods to improve the uniformity of single particle coating, and to more flexibly tailor and change the surface physical and chemical structure of the coating film for different application purposes.

Contents of the invention

Aiming at overcoming the problem of easy agglomeration when coating nanoparticles, to improve the uniformity of single particle coating, and to more flexibly tailor the surface physical and chemical structure of the coating film according to different application purposes, the present invention proposes a nano Particle surface physicochemical structure tailoring coating method. Its principle of action is: first charge the nanoparticles, the particles generate the same-sex plasma sheath potential, use the repulsion of the same-sex sheath potential of the particles, and apply a tangential force through fluidization or shearing, so that the soft agglomeration is easy to destroy, and the nanoparticles Dynamically and constantly renewed exposure to the plasma polymerization atmosphere, the gaseous monomer active species is easy to penetrate into the particles to produce uniform deposition coating. At the same time, control the plasma polymerization discharge conditions, such as discharge time, power, pulse ratio, etc., control the physical and chemical structure of the coating film, and obtain the surface of nanoparticles with variable physical and chemical structures, so as to be suitable for different application purposes.

The nanoparticle surface physicochemical structure cutting coating method of the present invention comprises the following steps:

(1) The coated nanoparticles are pre-charged by a high-voltage electrostatic generator. A commercially available high-voltage electrostatic generator can be used, with a discharge time of 1-20 minutes and a voltage of 10-100KV, and immediately put it into the porous distribution plate of the plasma reactor (as shown in Figure 1) after taking it out;

(2) The reactor is evacuated to a background vacuum degree of ≤10Pa, and the monomer and the carrier gas are mixed in proportion to form a mixed gas, which flows into the plasma reactor at a certain speed through the porous distribution plate, so that the particles are in a fluidized state, Moreover, through the electrostatic repulsion between particles, the soft agglomeration is easy to be destroyed by fluidization or shearing, and the gaseous monomer atoms or groups are easy to penetrate into the particles for uniform deposition and coating. The mixing volume ratio of the monomer and the carrier is 1-10:1-95, the flow rate of the mixed gas is controlled at 5-150 sccm (standard cubic liter per minute), and the vacuum degree of the reactor reaches 15-300 Pa.

(3) Turn on the pulsating radio frequency plasma generator and the stirrer. A discharge is formed in the reactor through a capacitive coupling coil, so that the introduced monomer discharge is polymerized and coated on the surface of nanoparticles. Pulse radio frequency plasma generator frequency 13.56MHz, maximum power 600W. The reactor can be pulsatingly modulated so that the discharge is performed intermittently between "on" and "off", and the pulse ratio (the time of "on" divided by the sum of the time of "on" and "off") is 1-100%, " The time range of "on" is 1μs-50ms, the plasma reactor electrode is capacitively coupled, the discharge power is 2-500W, and the polymerization coating time depends on the coating thickness, which can be 0.1-15 hours. After the reaction, the coated nanoparticles can be collected in a filter collector or collected in the lower part of the reactor. The stirrer in the plasma reactor is composed of 1-40 pairs of knife-shaped blades with a slope of 0-45°, the blades are 0.5-2.0cm wide, driven by a motor, and the stirring speed is 50-2000 rpm. The installation height is 10-50cm to increase the degree of destruction of soft agglomerates, renew the particle surface, make it dynamically dispersed in the plasma atmosphere, and achieve the effect of uniform coating of a single particle.

The monomer can be a compound that can form a gaseous state under normal temperature and pressure or after reduced pressure (except for inert gases and non-polymerizable deposition gases such as oxygen, nitrogen, and hydrogen), which can be selected from alanine, glycine, and lysine, Acrylamide, vinyl acetic acid, acrylic acid, methyl methacrylate, carbon tetrafluoride, hexafluoropropylene, hexamethyldisiloxane, ethylene, acetylene, methane, ethanol, acetone, tetrahydroxyethyltitanium, tetramethyldisiloxane Oxysilane, diethylzinc, tetramethyltin or copper sulfate, etc., the carrier gas can be a non-polymerizable gas with a certain pressure, such as argon, nitrogen, oxygen, hydrogen, compressed air, etc.

The porous distribution plate in the plasma reactor is shown in Figure 2. The lower diameter d ₁ of the hole on the porous distribution plate: the upper diameter d ₂ of the hole = 1: 1-5, the height of the lower diameter of the hole: the total height of the hole = 1-4: 5, the hole area accounts for 1 of the plate area /10～8/10, _d2 is 1～50mm. The porous distribution plate is covered with a stainless steel filter screen or filter paper with a pore size of 50-600 mesh. This arrangement can make the gas distribution uniform, so the nanoparticles are in a good fluidized state under the appropriate gas impulse.

The present invention has following characteristics and effect:

1. The method of the present invention can use the repulsion between the same-sex plasma sheath potentials produced by the particles because the nanoparticles are charged during coating, and apply a tangential force through the fluidization and shearing of the airflow to make the soft agglomeration easy to destroy , Nanoparticles are dynamically updated and exposed to the plasma polymerization atmosphere, and the gaseous monomer active species is easy to penetrate into the particles to produce uniform deposition coating.

2. The radio frequency plasma is pulsated and used for the polymerization of monomers, which can greatly improve the retention rate of oxygen-containing, nitrogen-containing, sulfur-containing and other functional groups in the polymer coating film, and control the coating particles and the matrix polymer. compatibility. It is also possible to coat the particle surface with functional groups that can be further reacted. Overcome the insoluble, infusible, and highly crosslinked defects of radio frequency continuous wave plasma coatings, and regulate the chemical structure of the coating to form a nanoparticle surface that can be tailored to control the chemical structure.

3. Control and adjust the pulsating radio frequency plasma conditions, such as power, pulsation ratio, flow rate, monomer ratio, time, etc., can adjust and control the thickness of the coating layer, surface topology, and change the physical structure of the particle surface. Thus, the fluidity, specific gravity, tightness of combination with matrix material, adsorption, etc. of the coated particles can be changed. In this way, through the steric physical hindrance of the coating, the nanoparticles can be prevented from agglomerating into larger particles, and the dispersion with the matrix polymer can be improved through the chemical compatibility and the physical roughness of the coating, so as to reduce the agglomeration of nanoparticles. properties, in order to reflect the special effects brought by small size to nanoparticles, etc.

4. The coating reaction is carried out in a dry state at room temperature, which is applicable to the coating of soluble and non-soluble nanoparticles, as well as the coating of temperature-sensitive particles. In addition, it overcomes operations such as repeated separation of solvents, has little environmental pollution, and the coating process is relatively simple.

5. A wide range of coating monomers can be selected, which can be used for coating organic, inorganic, and metal films, and is used for the development of various nanocomposite particles, nano/polymer composite materials, nano/metal composite materials, etc. It can also be used in the development of various nanocomposite particles to form inorganic/organic, inorganic/metal, metal/organic, inorganic/metal/organic and other nanocomposite particles.

Description of drawings

Figure 1 is a schematic diagram of a plasma coating reactor device.

Figure 2 is a schematic diagram of the porous distribution plate in the plasma reactor

where _d1 is the lower diameter of the hole _h1 is the height of the lower diameter of the hole

d ₂ the upper diameter of the hole h ₂ the total height of the hole.

Figure 3 is the HRTEM images of TiO _{nanoparticles} before and after plasma acrylic coating

      a is uncoated b   after plasma coating.

Figure 4 is the EDS spectrum of _TiO2 nanoparticles before and after plasma coating with acrylic acid

      a is uncoated b   after plasma coating.

Figure 5 is _an HRTEM image of plasmonic hexamethyldisiloxane coated _Cr2O3 nanoparticles.

Figure 6 is an AFM image of a plasmonic hexamethyldisiloxane film

Among them, the pulsation ratio of a is 3%, the pulsation "on" time is 15ms, and the discharge power is 3W

b Continuous wave, discharge power 30W.

Figure 7 is a comparison chart of the AFM cross-sectional roughness of the plasma hexamethyldisiloxane film

Among them, the pulsation ratio of a is 3%, the pulsation "on" time is 15ms, and the discharge power is 3W

b Continuous wave, discharge power 30W.

Figure 8 is the infrared spectrum of _TiO2 nanoparticles under different isoplasmic coating conditions

where a is not covered

b Acrylic coating, pulsation ratio 2%

c Acrylic coating, pulsation ratio 40%.

Figure 9 is the effect of different coating conditions on the UV absorbance of TiO ₂ nanoparticles.

Detailed ways

Example 1 Uniform Coating of Nanoparticle _TiO2 by Plasma Polymerization

The coating test was carried out using the plasma coating reactor apparatus shown in Fig. 1 . First, the TiO nanoparticles to be coated, with an average particle diameter of about 30nm, are pre-acted by a 50KV high-voltage electrostatic generator for 5 minutes to make it charged. After taking it out, immediately put it into the porous distribution plate 3 at the bottom of the plasma reactor 6 (for detailed structure, refer to Figure 2) above. The reactor 6 is evacuated by the vacuum system 7 to a background vacuum of 5Pa. The monomeric acrylic acid and the carrier gas argon are respectively measured through the flow meter 1, and the volume ratio is 1:50. After being uniformly mixed in the gas mixer 2, they are introduced into the plasma reactor 6 at a flow rate of 10 sccm through the porous distribution plate 3 , so that the particles are in a fluidized state, and the vacuum degree drops to 150Pa. Turn on the pulsating radio frequency plasma generator 5 and the stirrer 4 . The generator 5 forms a discharge in the reactor 6 through the capacitive coupling coil, so that the introduced monomer is discharged and polymerized, and coated on the surface of the nanoparticles. The pulsating radio frequency plasma generator 5 has a frequency of 13.56MHz and a maximum power of 600W. Reactor 6 performs pulse modulation, the discharge pulse ratio is 100%, the "on" time is 1ms, the discharge time is 4 hours, and the discharge power is 20W. Stirrer 4 is composed of 30 pairs of knife-shaped blades with a slope of 30°. The blades are 1 cm wide, the stirring speed is 1000 rpm, and the height of the stirrer installation is 20 cm, so as to improve the degree of destruction of soft agglomerates and update the surface of particles to make them dynamically dispersed. In the plasma atmosphere, the effect of uniform coating of single particles is achieved. After the reaction, the coated particles are collected in the filter collector 8 or in the lower part of the reactor 6 .

After the coating, the sample was detected by high-resolution transmission electron microscopy (HRTEM) (Figure 3). The uncoated TiO ₂ nanoparticles can be seen in its crystal layered structure (a in Figure 3), but there is no translucent amorphous shape on the outer surface. Organic coating layer or coating layer of other layered crystal structure, and TiO ₂ coated by acrylic acid plasma polymerization can be seen in addition to its crystal layered structure, and a layer of translucent amorphous acrylic plasma polymerization can be seen on the outer ring The organic coating layer is evenly coated on the outer ring of TiO ₂ layered crystals, with a thickness of about 5nm (b in Figure 3). X-ray Energy Scattering Spectroscopy (EDS) showed that the titanium peak intensity was higher before coating (a in Figure 4), and the titanium peak intensity decreased to zero after coating (Figure 4 b), and the oxygen peak and carbon peak intensity increased, indicating that The coated plasma polyacrylic film is quite effective and homogeneous, so that titanium element is no longer detected.

Example 2 Cr ₂ O ₃ nanoparticle plasma coating conditions affect the test of coating thickness

The plasma coating reactor device shown in FIG. 1 is used, and the operation steps refer to Example 1.

Take Cr ₂ O ₃ nanoparticles as the coating object, with an average particle size of 150nm, and charge it through a 20KV high-voltage electrostatic generator for 1 minute, and immediately put it into the plasma reactor 6, and vacuumize it to the background vacuum degree of 4Pa. Inject the mixed gas of hexamethyldisiloxane and nitrogen, the volume ratio of the two gases is 10:50, the flow rate is 60 sccm, and the vacuum degree drops to 200 Pa. Turn on the plasma generator 5 and the stirrer 4, control the discharge power to be 40W, the discharge time to be 8 hours, the discharge pulse ratio to be 50%, the pulse "on" time to be 2ms, and the stirring speed to be 500 rpm.

After coating, the sample was detected by high-resolution transmission electron microscopy (HRTEM) (see Figure 5), and the results showed that the surface of the particles was uniformly coated with a plasma-polymerized hexamethyldisiloxane film with a thickness of about 25 nm.

Example 3 The test of the effect of pulsating radio frequency plasma coating conditions on the surface roughness of the coating film

The plasma coating reactor setup shown in Fig. 1 was used.

In order to observe the relationship between the pulsating radio frequency plasma coating conditions and the surface roughness of the coating film, a flat glass sheet is selected as the coating object. After cleaning, it is placed in the plasma reactor 6 and vacuumed to a background vacuum of 4Pa. , into a mixed gas of hexamethyldisiloxane and argon, the volume ratio of the two gases is 10:90, the flow rate is 10 sccm, and the vacuum is reduced to 30 Pa. Turn on the plasma generator 5 for discharge polymerization. The discharge time was 1 hour, and the polymerization was completed. The sample was taken out for atomic force microscope (AFM) analysis. The AFM picture of the obtained sample is shown in FIG. 6 . In Figure 6, the discharge power of a is 3w, the pulse ratio is 3%, and the pulse "on" time is 15ms. In Figure 6, the discharge power of b is 30w, continuous wave. The greater the brightness, the higher the height of the plane. A and b in Fig. 7 are cross-sectional views of samples a and b in Fig. 6 . High and low curves represent fluctuations in the membrane profile. From the test results of the AFM, it can be seen that under the conditions of low pulse ratio and low power (a in Figure 6 and a in Figure 7), the coating is composed of nano-scale particle films, and the roughness of the coating is several nanometers; continuous wave high power In the case (b in Fig. 6 and b in Fig. 7), the coating is composed of micron-sized large particle membranes, and the roughness of the coating is several microns. Changing the coating conditions can effectively change the roughness of the coating.

Example 4 Coating Conditions Affect TiO _Nanoparticle Surface Chemical Structure Test

The plasma coating reactor device shown in FIG. 1 is used, and the operation steps refer to Example 1.

The plasma coating reactor device shown in FIG. 1 is used, and the operation steps refer to Example 1.

Coating target TiO ₂ nanoparticles, with an average particle size of about 30nm, TiO ₂ nanoparticles are pre-acted by a 35KV high-voltage electrostatic generator for 3 minutes to make them charged, and immediately placed in the plasma reactor 6, and vacuumed to the background vacuum 3Pa, a mixed gas of acrylic acid and argon is introduced, the volume ratio of the two gases is 5:50, the flow rate is 35 sccm, and the vacuum degree is reduced to 85Pa. Turn on the plasma generator 5 and the stirrer 4, control the discharge power to 20w, the discharge time to 2 hours, the stirring speed to 1000 rpm, and the discharge pulse ratio to 2% and 40%.

The coated _TiO2 nanoparticle sample and KBr powder were blended and ground into tablets according to a certain ratio, and the infrared spectrum of the coated _TiO2 nanoparticle was measured by the NEXUS-670 Fourier spectrometer produced by Nicolet Company to test the coating. The chemical structure of the coated _TiO2 nanoparticles is shown in Fig. 8. Among Fig. 8 (a) is the infrared spectrogram of uncoated _{TiO2nanoparticle} , among Fig. 8 (b) and (c) are the _TiO2 nanoparticle of coating process when pulse ratio 2%, 40% respectively Infrared spectra. Due to the thin cladding layer, the structure of the infrared transmission spectrum test does not only reflect the surface, so it can be seen in (a)(b)(c) in Figure 8 that there are strong absorption peaks in the range of 400-700cm-1, which is Ti The characteristic absorption peak of the -O-Ti bond has a broad stretching vibration peak of -OH caused by the adsorption of water at around 3300cm-1. The absorption peak around 1631cm-1 is also due to the stretching vibration peak of -OH produced by surface hydroxylation. After the acrylic acid plasma coating treatment with a pulsation ratio of 2%, a new shoulder peak appeared near 1433cm-1, and when the pulsation ratio was 40%, this shoulder peak developed into a new absorption peak. Since the absorption at this position is related to the deformation vibration of CH in groups such as CH ₃ -O- or CH ₂ -O-, the relative intensity of this peak indicates that under different pulsation ratio conditions, the coating film is similar to CH ₃ -O - or CH ₂ -O has different ester groups. Different coating conditions can change the content and even types of groups in the chemical structure of the coating.

Example 5 Coating Conditions Affect TiO ₂ Experiments on the Ultraviolet Absorption Properties of Nanoparticles

The plasma coating reactor device shown in FIG. 1 is used, and the operation steps refer to Example 1.

The TiO ₂ nanoparticles to be coated have an average particle size of about 30nm. The TiO ₂ nanoparticles are subjected to a 100KV high-voltage electrostatic generator for 1 minute, and then placed into the plasma reactor 6 immediately. Vacuumize to the background vacuum degree of 3Pa, and pass a mixed gas of hexamethyldisiloxane and argon, the volume ratio of the two gases is 5:95, and the flow rate is 50 sccm, so that the vacuum degree drops to 150Pa. Turn on the plasma generator 5 and the stirrer 4, control the discharge power to 60w, the discharge time to 4 hours, the stirring speed to 2000 rpm, and the discharge pulse ratio to 5%, 15%, and 40%.

After treatment, the sample was made into a 0.015% suspension with ethylene glycol, poured into a 0.5 cm quartz cuvette, and measured its absorption value in ultraviolet-visible light with a 752 spectrophotometer. The results obtained are shown in Fig. 9 . Under different pulsation ratios, due to the different physical and chemical structures of the coating layer, the light absorption of the coated TiO ₂ nanoparticles in ethylene glycol solution is different. Because of good dispersion, small aggregate particle size, and good absorption of ultraviolet light. Therefore, the quality of light absorption also represents the quality of dispersion. It can be seen from Figure 9 that although the coated _TiO2 nanoparticles have different absorbances in ethylene glycol solutions under different pulsation ratio conditions, they are all better than uncoated _TiO2 nanoparticles. It shows that the dispersibility of coated TiO ₂ nanoparticles in ethylene glycol solution is better than that of uncoated TiO ₂ nanoparticles.

Claims (6)

1. A nanoparticle surface physical and chemical structure cutting and coating method, characterized in that the method comprises the following steps: (1) The coated nanoparticles are charged, taken out and placed in the plasma reactor; (2) The reactor is evacuated to a background vacuum degree of ≤10Pa, and the mixed gas of the monomer and the carrier is introduced at a flow rate of 5-150 sccm, and the mixing volume ratio of the monomer and the carrier gas is 1-10:1-95. Vacuum up to 15-300Pa. (3) Turn on the pulsating radio frequency plasma generator and the stirrer to form a discharge in the reactor, the introduced monomer discharge is polymerized and coated on the surface of the nanoparticles, and the reactor is pulsatingly modulated so that the pulsation ratio is 1-100%, The open time range is 1μs-50ms, the discharge power is 2-500W, the discharge time is 0.1-15 hours, and the stirring speed of the stirrer is 50-2000 rpm. 2. The coating method according to claim 1, characterized in that the monomer is selected from the group consisting of alanine, glycine, lysine, acrylamide, vinyl acetic acid, acrylic acid, methyl methacrylate, tetrafluorinated Carbon, Hexafluoropropylene, Hexamethyldisiloxane, Ethylene, Acetylene, Methane, Ethanol, Acetone, Tetrahydroxyethyltitanium, Tetramethoxysilane, Diethylzinc, Tetramethyltin, or Copper Sulfate. 3. The coating method according to claim 1, characterized in that said carrier gas is argon, nitrogen, oxygen, hydrogen, or compressed air. 4. The coating method according to claim 1, characterized in that the coated nanoparticles are placed on a porous distribution plate in the plasma reactor, and the mixed gas of the monomer and the carrier gas is introduced through the porous distribution plate. 5. The coating method according to claim 4, characterized in that the bottom diameter of the hole on the porous distribution plate: the upper diameter of the hole=1:1-5, the height of the bottom diameter of the hole: the total height of the hole= 1-4:5, the hole area accounts for 1/10-8/10 of the plate area, and the diameter of the upper part of the hole is 1-50mm. 6. The coating method according to claim 1, characterized in that the agitator is composed of 1-40 pairs of knife-shaped blades with a slope of 0-45°, the width of the blades is 0.5-2.0cm, and the agitator The installation height is 10-50cm.

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