Processing method of carbon micro-nano structure cold cathode

Abstract

The invention discloses a processing method of a carbon micro-nano structure cold cathode. The processing method comprises the following steps: firstly, pretreating a substrate; adding the slurry into a container, and then removing bubbles; fixing the container on a vibration platform; the audio frequency resonance processing equipment is started, so that the slurry in the container is uniformly dispersed in the vibration process; carrying out a patterning process on the dispersed slurry on the surface of a metal substrate to obtain a micro-nano structure array; and pyrolyzing the patterned micro-nano structure to obtain the carbon structure. According to the method, the cold cathode slurry is prepared through an audio frequency resonance dispersion technology, the carbon micro-nano structure is obtained by combining patterning and pyrolysis technologies, and the method is a processing method for preparing the carbon micro-nano structure cold cathode in a low-cost and large-area mode.

Description

Technical Field

[0001] The invention belongs to the field of micro-nano manufacturing technology, and specifically relates to a method for processing a carbon micro-nano structure cold cathode. Background Art

[0002] Carbon Nanotubes (CNTs) are tubular nanomaterials composed of carbon atoms that have attracted much attention due to their unique physical and chemical properties. This material has the characteristics of small tube diameter, high aspect ratio, and stable physical and chemical properties, making it an ideal field emission electron source material. As a field emission electron source, carbon nanotubes have shown many remarkable advantages. It can produce high current density at a lower voltage and can operate at room temperature without heating, which not only reduces energy consumption but also reduces heat loss. X-ray sources based on carbon nanotubes have fast startup characteristics and high-resolution electron beam output, making them excellent in a variety of applications. In addition, due to the tiny size of carbon nanotubes, X-ray sources based on them are easier to miniaturize, which is crucial for the development of miniature electronic devices.

[0003] The hot cathode technology used in traditional X-ray sources still has problems such as slow startup, high power consumption and high ineffective radiation dose. In contrast, cold cathode X-ray sources have the advantages of cold startup, high-speed imaging, and controllable cathode area, which can effectively solve the inherent defects of hot cathode technology. This technology has developed rapidly in the past decade and has shown great application potential in fields such as medical imaging and industrial detection. Research on new cold cathode field emission sources, such as carbon nanotube field emission sources, aims to overcome the limitations of traditional hot cathodes such as slow startup speed, high working environment requirements, large overall size and high ineffective radiation dose, which will help promote technological innovation, expand applications in biomedicine, non-destructive testing and other fields, improve emission performance and working stability, meet higher precision detection and imaging needs, and promote the upgrading and development of related industries such as medical devices and semiconductor testing equipment. How to solve a series of problems such as poor cathode consistency, weak bonding with the substrate, short life, and expensive processing cost is a consistent goal of current research in the field of cold cathode field emission. Therefore, it is urgent to study low-cost, repeatable, and high-performance carbon micro-nanostructure cold cathode processing methods. Summary of the invention

[0004] The purpose of the present invention is to provide a carbon micro-nano structure cold cathode processing method, through vibration dispersion of carbon nanotubes, patterning process to obtain a micro-nano structure array, pyrolysis to obtain a carbon micro-nano structure, to obtain a high-performance cold cathode.

[0005] A method for processing a carbon micro-nanostructure cold cathode comprises the following steps:

[0006] (1) Pre-treating the substrate;

[0007] (2) Add slurry into a container and remove bubbles before use;

[0008] (3) Fixing the container on the acoustic resonance dispersion device;

[0009] (4) starting the vibration dispersion equipment to evenly disperse the slurry in the container through acoustic resonance;

[0010] (5) patterning the dispersed slurry on the surface of the substrate to obtain a patterned micro-nano structure array;

[0011] (6) Pyrolysis to obtain carbon micro-nanostructure;

[0012] (7) Surface treatment of carbon micro-nano structures.

[0013] Furthermore, the substrate in step (1) is one of iron-nickel-cobalt alloy, stainless steel, graphite, metal nickel, metal copper, metal molybdenum, copper-nickel alloy, ceramic, and polymer plate.

[0014] Furthermore, the pretreatment in step (1) is to remove oxides and stains on the surface by grinding, polishing and solvent cleaning in sequence.

[0015] Furthermore, the slurry in step (2) is a mixture of a binder, a solvent, carbon nanotubes, and nano-metal particles.

[0016] Furthermore, in step (2), air bubbles are removed by vacuuming or vibrating.

[0017] Furthermore, in step (3), the container is fixed on the vibration platform by clamping or gluing.

[0018] Furthermore, the patterning process in step (5) is one of screen printing, electrofluidic printing, nanoimprinting, and photolithography.

[0019] Furthermore, the reducing atmosphere in step (6) is a nitrogen-hydrogen mixture or an argon-hydrogen mixture, and:

[0020] If it is a nitrogen-hydrogen mixed gas, the volume ratio of nitrogen to hydrogen is 80:20 to 98:2;

[0021] If it is an argon-hydrogen mixed gas, the volume ratio of nitrogen to argon is 80:20 to 98:2.

[0022] Furthermore, the surface treatment in step (7) is tape treatment, rubber roller treatment or plasma etching.

[0023] Furthermore, the carbon micro-nanostructure is adjusted by adjusting the slurry components and their ratios, the amplitude, frequency and dispersion time of the vibration platform, different patterning processes, pyrolysis temperature and time;

[0024] In terms of mass ratio, binder: solvent: carbon nanotube: nano metal particle = 10: 1-100: 1-10: 0.1-10;

[0025] Among them, the binder can be a negative photoresist, the co-solvent can be one or more of acetone and N-methylpyrrolidone, the nano metal particles can be one or more of nickel and silicon carbide, the carbon nanotube diameter is 5-50nm, the nanoparticle diameter is less than 50nm, the amplitude is 4mm~20mm, the frequency is 50~300hz, and the emission time is 0.5~12 hours.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The present invention provides a method for preparing a cold cathode field emission electron source for mass production, and the preparation process is simple, efficient and has good repeatability.

[0028] (2) The present invention adds photoresist to the slurry component to assist in the formation of the micro-nano structure and improve the emission performance of the cathode, and uses acoustic resonance to overcome the van der Waals force between nano-sized raw materials, reducing their own agglomeration effect, so that different components can be mixed with each other. A high-performance carbon micro-nano structure cold cathode is formed that is firmly bonded to the substrate, has a large emission current density, and has a low turn-on voltage.

[0029] (3) The morphology pattern of the carbon micro-nanostructure cold cathode in the present invention can be adjusted by changing the patterning process, which is beneficial to change the array parameters after adjusting the slurry components to improve the edge effect between the carbon micro-nanostructures and meet the needs of different application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 : A process flow chart of a specific embodiment of the present invention;

[0031] Figure 2 : Temperature variation curve of the pyrolysis process of the present invention;

[0032] Figure 3 : Electric field intensity-current density curve diagram of the embodiment and the reference example, wherein the triangle in the figure corresponds to the embodiment and the square corresponds to the reference example;

[0033] Figure 4 : FN diagram of the embodiment and the control example, wherein the triangle in the figure corresponds to the embodiment and the square corresponds to the control example;

[0034] Figure 5 : SEM images of embodiments and control examples, wherein (a) corresponds to the control example, and (b) corresponds to the embodiments. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0036] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] The inventors have found through research that the energy generated by the resonance of the acoustic resonance processing equipment can overcome the van der Waals force between carbon nanotubes, reduce the agglomeration effect between carbon nanotubes, and make them evenly dispersed to the target polymer. At the same time, by adjusting the slurry components and their ratios, the frequency, amplitude, time, size and distribution of carbon micro-nano structures, pyrolysis temperature and other parameters of the acoustic resonance processing equipment, the target carbon micro-nano structure can be adjusted. A nitrogen-hydrogen mixed gas or an argon-hydrogen mixed gas is introduced, and after high-temperature annealing, pyrolysis is performed to form a uniform, stable, and substrate-bound carbon micro-nano structure cold cathode.

[0038] The specific embodiment provides a carbon micro-nano structure cold cathode processing method, referring to the attached Figure 1 As shown:

[0039] (1) Pre-treating the metal substrate;

[0040] (2) Add slurry into the container and remove gas;

[0041] (3) Fixing the container on the acoustic resonance processing equipment;

[0042] (4) starting the acoustic resonance processing equipment to make the slurry in the container disperse evenly during the vibration process;

[0043] (5) obtaining a patterned micro-nano structure on the surface of a metal substrate by a patterning process using the dispersed slurry;

[0044] (6) Pyrolysis to obtain carbon structure;

[0045] (7) Surface treatment of carbon micro-nano structures;

[0046] Specifically, the substrate in step 1 is one of iron-nickel-cobalt alloy, stainless steel, graphite, metal nickel, metal copper, metal molybdenum, copper-nickel alloy, ceramic, and polymer plate.

[0047] Specifically, the pretreatment in step 1 is to remove oxides and stains on the surface by grinding, polishing and solvent cleaning in sequence.

[0048] Specifically, the slurry in step 2 is a mixture of a binder, a solvent, carbon nanotubes, and nano-metal particles.

[0049] Specifically, in step 2, air bubbles are removed by vacuuming or vibrating.

[0050] Specifically, in step 3, the container is fixed on the vibration platform by clamping or gluing.

[0051] Specifically, the patterning process in step 5 is one of screen printing, electrofluidic printing, nanoimprinting, and photolithography.

[0052] Specifically, the reducing atmosphere in step 6 is a nitrogen-hydrogen mixed gas or an argon-hydrogen mixed gas, and:

[0053] If it is a nitrogen-hydrogen mixed gas, the volume ratio of nitrogen to hydrogen is 80:20 to 98:2;

[0054] If it is an argon-hydrogen mixed gas, the volume ratio of nitrogen to argon is 80:20 to 98:2.

[0055] Specifically, the surface treatment in step 6 is tape treatment, rubber roller treatment or plasma etching.

[0056] Specifically, the carbon micro-nano structure is adjusted by adjusting the slurry components and their ratios, the amplitude, frequency and dispersion time of the vibration platform, different patterning processes, pyrolysis temperature and time;

[0057] In terms of mass ratio, the binder: the solvent: the carbon nanotube: the nano metal particle = 10: 1-100: 1-10: 0.1-10.

[0058] Among them, the binder can be a negative photoresist, the co-solvent can be one or more of acetone and N-methylpyrrolidone, the nano metal particles can be one or more of nickel and silicon carbide, the carbon nanotube diameter is 5-50nm, the nanoparticle diameter is less than 50nm, the amplitude is 4mm~20mm, the frequency is 50~300hz, and the emission time is 0.5~12 hours.

[0059] Example

[0060] S1. Prepare a 4J29 alloy sheet with a length, width and height of 5mm×5mm×0.5mm. After cleaning, polish it with sandpaper of mesh sizes of 500, 800, 1500 and 2000 respectively. Then apply a proper amount of polishing paste on its surface, polish it with a handheld electric grinder, use anhydrous ethanol and acetone ultrasonic cleaning for 15 minutes, and put it in an oven to dry.

[0061] S2. In an environment without ultraviolet light, weigh 10 g of negative photoresist, 8 ml of N-methylpyrrolidone, 5 g of carbon nanotube powder, 1 g of silicon carbide nanoparticles, and 0.4 g of nickel nanoparticles. While ensuring that the materials do not deteriorate, transfer them to a container and evacuate the materials to remove bubbles.

[0062] S3. Fix the container on the acoustic resonance processing equipment by pressing and clamping the container from the top to ensure that the container remains stable during the resonance process.

[0063] S4. Turn on the acoustic resonance processing equipment, set the vibration direction to up and down, adjust the vibration frequency to 60 Hz, the amplitude to 8 mm, and the acoustic resonance dispersion for 90 minutes.

[0064] S5. Fix the metal substrate at the designated position at the bottom of the screen printing table, cover the screen, ensure that the mesh part covers the entire metal substrate, pour a proper amount of slurry on one side, and use a scraper to scrape the entire metal substrate from the side with slurry, so that the slurry is transferred to the surface of the metal substrate, and obtain the target pattern on the substrate.

[0065] S6, please refer to Figure 2 The patterned substrate was placed in an alumina square crucible, placed in a tube furnace, evacuated, and then nitrogen-hydrogen mixed gas was introduced and purged. After the furnace tube returned to normal pressure, heating was started according to the preset program, and (95:5) nitrogen-hydrogen mixed gas was continuously introduced at a flow rate of 50 sccm.

[0066] S7. Treat the cathode surface with 3M tape, then place it in a plasma etching device and etch with oxygen plasma for 60 seconds.

[0067] S8. Observe the patterned carbon micro-nanostructure, use tape to observe its peeling, use SEM to observe its surface morphology, and apply voltage to observe its field emission performance.

[0068] Comparative Example

[0069] Compared with the embodiment, this comparative example has the same operation except for the different slurry components and dispersion methods. The different steps in this comparative example are as follows:

[0070] S2. Weigh 500 mg of carbon nanotube powder and 500 ml of anhydrous ethanol, and transfer them to a container while ensuring that the material does not deteriorate.

[0071] S3. Transfer the container to an ultrasonic dispersion device, start the device, perform ultrasonic dispersion for 90 minutes, and place the dispersed carbon nanotube suspension in a 60° constant temperature water tank for 1 hour.

[0072] S6. Place the substrate printed with the pattern in an alumina square crucible, place it in a tube furnace, evacuate the furnace, introduce argon gas, heat to 300° and bake for 2 hours to remove organic matter.

[0073] The field emission performance of the embodiment and the comparative example was tested respectively. In this test, diode emission was used, the distance between the cathode and cathode was fixed (500 microns), the electric field between the cathode and cathode was changed by controlling the input voltage, the emission current density of the cold cathode was tested, and the corresponding IV graph and FN graph were drawn. Figure 3 It can be seen that by mixing SU8 glue with carbon nanotube powder, the current density of the cathode under the same electric field is greatly improved. At an electric field strength of 7V / μm, the current density of the embodiment is about ten times that of the control example, wherein the electric field is turned on (the emission current density reaches 10μA / cm 2 At the same time, due to the presence of high viscosity SU8, on the one hand, it assists the formation of carbon nanotube mixed slurry in the patterning process, improves the patterning quality, and on the other hand, as a dielectric material between carbon nanotubes, it reduces the mutual shielding effect when carbon nanotubes agglomerate. After annealing, the glassy carbonized SU8 can also provide a part of the electrons as a field emission source, which is also beneficial to improve the connection performance between the slurry and the substrate. Figure 4 It can be seen that the FN curves of the embodiment and the control example both have good linear characteristics and meet the characteristics of field emission.

[0074] In summary, the present invention uses photoresist as a binder, acetone or N-methylpyrrolidone as a solvent, adds silicon carbide and nickel nanoparticles to improve the connection between the slurry and the substrate, and utilizes resonance equipment for resonance dispersion to prepare a carbon nanotube-containing slurry as a raw material for a carbon micro-nano structure cold cathode. The cathode is patterned to increase the edge effect between the carbon nanotubes, and the target carbon-carbon micro-nano structure is obtained after pyrolysis. The present invention has the advantages of high resolution, low cost, simple process, high performance, etc. The materials used can be purchased through commercial channels or prepared in the laboratory, and are low-cost, suitable for large-scale production, have strong practical value and broad application prospects, and are worthy of promotion in the industry.

[0075] This specification describes examples of embodiments of the present invention, and does not mean that these embodiments illustrate and describe all possible forms of the present invention. Those of ordinary skill in the art will appreciate that the embodiments described herein are to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such special statements and embodiments. Those of ordinary skill in the art can make various other various specific variations and combinations that do not deviate from the essence of the present invention based on these technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. A method for processing a carbon micro-nanostructure cold cathode, characterized in that: The following steps are involved: (1) Pre-treating the substrate; (2) Add slurry into a container and remove bubbles before use; (3) Fixing the container on the acoustic resonance dispersion device; (4) starting the vibration dispersion equipment to evenly disperse the slurry in the container through acoustic resonance; (5) patterning the dispersed slurry on the surface of the substrate to obtain a patterned micro-nano structure array; (6) Pyrolysis to obtain carbon micro-nanostructure; (7) Surface treatment of carbon micro-nano structures.

2. The carbon micro-nanostructure cold cathode processing method according to claim 1, characterized in that: The substrate in step (1) is one of iron-nickel-cobalt alloy, stainless steel, graphite, metal nickel, metal copper, metal molybdenum, copper-nickel alloy, ceramic, and polymer plate.

3. The carbon micro-nanostructure cold cathode processing method according to claim 1, characterized in that: The pretreatment in step (1) is to remove oxides and stains on the surface by grinding, polishing and solvent cleaning in sequence.

4. The carbon micro-nanostructure cold cathode processing method according to claim 1, characterized in that: The slurry in step (2) is a mixture of a binder, a solvent, carbon nanotubes, and nano-metal particles.

5. The carbon micro-nanostructure cold cathode processing method as claimed in claim 1, characterized in that: In step (2), air bubbles are removed by vacuuming or vibrating.

6. The carbon micro-nanostructure cold cathode processing method as claimed in claim 1, characterized in that: In step (3), the container is fixed on the vibration platform by clamping or gluing.

7. The carbon micro-nanostructure cold cathode processing method as claimed in claim 1, characterized in that: The patterning process in step (5) is one of screen printing, electrofluidic printing, nanoimprinting, and photolithography.

8. The carbon micro-nanostructure cold cathode processing method as claimed in claim 1, characterized in that: The reducing atmosphere in step (6) is a nitrogen-hydrogen mixture or an argon-hydrogen mixture, and: If it is a nitrogen-hydrogen mixed gas, the volume ratio of nitrogen to hydrogen is 80:20 to 98:2; If it is an argon-hydrogen mixed gas, the volume ratio of nitrogen to argon is 80:20 to 98:

2.

9. The carbon micro-nanostructure cold cathode processing method as claimed in claim 1, characterized in that: The surface treatment in step (7) is tape treatment, rubber roller treatment or plasma etching.

10. The carbon micro-nanostructure cold cathode processing method as claimed in claim 4, characterized in that: The carbon micro-nano structure can be adjusted by adjusting the slurry components and their ratios, the amplitude, frequency and dispersion time of the vibration platform, different patterning processes, pyrolysis temperature and time; In terms of mass ratio, binder: solvent: carbon nanotube: nano metal particle = 10: 1-100: 1-10: 0.1-10; Among them, the binder can be a negative photoresist, the co-solvent is one or more of acetone and N-methylpyrrolidone, the nano metal particles are one or more of nickel and silicon carbide, the carbon nanotube diameter is 5-50nm, the nanoparticle diameter is less than 50nm, the amplitude is 4mm~20mm, the frequency is 50~300hz, and the emission time is 0.5~12 hours.

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