CN101439934B - Slurry for printing composite nano diamond thin film on glass substrate and preparation thereof - Google Patents

Abstract

The present invention relates to the technology in the field of information display, especially the slurry used for printing composite nano-diamond films on glass substrates and its preparation method, which is characterized in that it comprises the following steps: a. Grinding the raw materials, mixing nano-graphite and nano-diamond , and ethyl cellulose are ground to a particle size of 10-100 nanometers as raw materials for subsequent use; b, preparing nano-diamond slurry, raw material nano-graphite, nano-diamond, and ethyl cellulose in a weight ratio of 3-6: 8-16: Mix 6-12 ratio as solute, add solute into solvent according to weight ratio 2-4:5-10, ultrasonically disperse for 7-9 hours, then heat and stir at 300-373K, pass through 350-450 mesh sieve, and cool naturally to room temperature. The slurry used for printing the composite nano-diamond film on the glass substrate in the present invention has lower cost and is suitable for large-area and uniform preparation of the composite nano-diamond film on the glass substrate.

Description

Slurry used for printing composite nano-diamond film on glass substrate and preparation method thereof

technical field

The invention relates to the technology in the field of information display, especially the paste used for printing composite nano-diamond film on glass substrate and its preparation method. The paste used for printing composite nano-diamond film on the glass substrate can be used to prepare composite nano-diamond film , used to make display cathodes for polar expeditions, aerospace, etc.

Background technique

Diamond crystals have the highest hardness among substances existing in nature, and its Mohs hardness is 10. The melting point of diamond is 4000°C; it also has high thermal conductivity. The thermal conductivity of natural type II diamond at room temperature is 26W/(CM·K), which is 5 times that of copper. The thermal conductivity of natural I-type diamond at room temperature is 9W/(CM·K), and the thermal conductivity of artificial high-quality single crystal diamond is 18-20W/(CM·K) at room temperature. The thermal conductivity is 4.5-6.5W/(CM·K), while the thermal conductivity of general artificial polycrystalline diamond is 4-10W/(CM·K) at room temperature. Excellent thermal conductivity makes it the material of choice for microwave electron sources requiring fast thermal diffusion.

The value of the bandgap width of diamond is 5.3-5.5eV, the dielectric constant εr is 5.58±0.03, the resistivity of natural diamond is 1010Ω·CM, and the resistivity of natural II diamond at room temperature is 1-108Ω·CM. The main energy level is located about 0.37eV above the valence band with a high saturation carrier velocity. The breakdown field strength of diamond is as high as 100×105V/cm. Diamond has good chemical stability, acid and corrosion resistance. Even though various acids have little effect on diamond at high temperature, larger diamond crystals in the air are stable below 600-700°C and diamond micropowder crystals are below 450-500°C. Although the work function of diamond is as high as 5.8eV, diamond has a negative electron affinity. In particular, there are SP ³ bonds inside the nano-diamond crystal, which makes it have high mechanical strength and chemical stability, which determines its good insulation, stability and high hardness; the smaller the nano-diamond crystal grain, the more SP ² bonds on the surface , the better its field emission performance. Therefore, the use of nano-diamond film as an electron source has become a hot spot in the field of electron emission research in the world.

At present, the methods for preparing nano-diamond films at home and abroad are cleaner and more reliable than the early high-temperature and high-pressure explosion method, and can deposit high-quality films. At present, the mainstream methods for preparing diamond films include chemical vapor deposition (MOCVD) and hot wire MPCVD. method, radio frequency discharge method, plasma torch method, etc. Researchers at home and abroad have also conducted extensive exploration and _research on what kind of gas source atmosphere _is used to deposit high- _quality nano-diamond films. N ₂ etc.

Although there are many methods for preparing diamond films, none of these growth methods can produce large-area uniform diamond films with good field emission performance, and the slurry used for printing composite nano-diamond films on glass substrates is the key technology for film preparation. .

Contents of the invention

One of the purposes of the present invention is to provide a slurry for printing a composite nano-diamond film on a glass substrate, which has lower cost and is suitable for preparing a large-area uniform diamond film on a glass substrate;

Another object of the present invention is to provide a method for preparing the slurry used for printing the composite nano-diamond film on the above-mentioned glass substrate.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A slurry used for printing a composite nano-diamond film on a glass substrate is characterized in that it consists of:

Solute 2-4 parts

Solvent 5-10 parts

Wherein the solute is composed in parts by weight

Nano graphite 3-6 parts

Nano diamond 8-16 parts

Ethyl cellulose 6-12 parts.

Wherein the solvent is terpineol.

A method for preparing the slurry used for printing a composite nano-diamond film on a glass substrate, which is particularly characterized in that it comprises the following steps:

a. Grinding raw materials

Grinding nano-graphite, nano-diamond, and ethyl cellulose to a particle size of 10-100 nanometers as raw materials for subsequent use;

b, preparation of nano-diamond slurry

Mix the raw materials nano-graphite, nano-diamond, and ethyl cellulose in a weight ratio of 3-6:8-16:6-12 as a solute, and add the solute into a solvent at a weight ratio of 2-4:5-10, and ultrasonically disperse 7-9 hours or until the solute is fully dispersed in the solvent, then heat and stir at 300-373K, pass through a 350-450 mesh sieve to evenly distribute nano-diamonds and nano-graphite, and cool naturally to room temperature.

Wherein the solvent is terpineol in the step b.

The slurry used for printing the composite nano-diamond film on the glass substrate in the present invention has lower cost and is suitable for large-area and uniform preparation of the composite nano-diamond film on the glass substrate. Utilizing the present invention, the composite nano-diamond thin film prepared by introducing nano-graphite as the conductive grain boundary improves the characteristic of electron emission and high electron emission efficiency. Diamond has good chemical stability, acid and corrosion resistance. The display cathode prepared by screen-printing composite nano-diamond film can be used to make displays for polar expeditions, aerospace and the like. The present invention uses nano-diamond as the emitter, nano-graphite as the conductive medium, and prepares a large-area and uniform composite nano-diamond film on a glass substrate with a low-cost screen printing method, which can prepare a field emission performance that is very good and can be used. Display cathodes in harsh environments.

Detailed ways

The method for preparing composite nano-diamond film by screen printing is as follows:

1. Preparation of slurry for printing composite nano-diamond film on glass substrate

Slurry preparation process for printing composite nano-diamond film on glass substrate: Weighing of nano-diamond, nano-graphite, and ethyl cellulose → grinding → adding to solvent for long-term ultrasonic dispersion → sieving → heating and stirring → sieving → Cool to room temperature.

Since nano-diamond particles are easy to agglomerate together to form larger aggregates with several weakly connected interfaces, this brings great difficulties to the uniform distribution of nanoparticles on the surface of the metal substrate, thus affecting the electron emission. Uniformity, so the nano-diamond and nano-graphite are ground separately before the preparation of the slurry to make the agglomerates disperse and the particle size becomes smaller. Ethylcellulose is also preferably ground.

The time for ultrasonic dispersion during the heating process is generally 6-9 hours, until the nano-diamond, nano-graphite, and ethyl cellulose are fully dispersed in the solvent terpineol. Nanoparticles are easy to agglomerate, and the composite diamond slurry is prepared, and its dispersion is carried out in three steps. The first step is to weigh nano-diamond, nano-graphite, and ethyl cellulose according to 3:8:6, mix and grind and stir evenly; the second step is to add solvent, heat to 373K and ultrasonically disperse for 7-9 hours to make them agglomerate together The composite nanodiamonds were disassembled. The third step is to further filter the paste with a high-mesh sieve (more than 400 mesh), by means of mechanical external force to remove large particles therein, and to ensure that the size of the composite nano-diamond aggregates that have not been well dispersed is mechanically adjusted. Under the action of external force, it is on a suitable scale, so that the composite nano-diamond is evenly distributed. The dispersed thin pasty slurry became viscous on cooling to room temperature.

2. Preparation of composite nanodiamond films by screen printing

The nets used for four-screen printing of composite nano-diamond films on glass substrates include metal screens and polyester screens, and the texture and mesh number of the screens can be determined according to the needs of actual printing. The suitable screen mesh number is 300-400 mesh, the finer the printing lines, the higher the mesh number required. The printing equipment is an automatic or manual screen printing machine.

When it is necessary to print specific graphics, the screen plate for printing must be prepared first. The plate-making process is: drawing the original → making positive pictures → selecting the screen frame → stretching the screen → sticking the screen → screen pre-treatment (cleaning) → applying photosensitive glue → drying → printing → developing → revision → secondary exposure → drying → Printing.

When printing, the manual printing machine and the automatic printing machine operate in slightly different ways, but the principle is the same. They are all used to print composite nano-diamond films on the glass substrate with a scraper (called a printer in an automatic printing machine). The paste is passed through the screen plate and printed onto the surface of the substrate (conductive glass substrate) under the screen. Using the screen printing method above on the conductive glass substrate, the slurry used for printing the composite nano-diamond film on the above glass substrate is printed on the conductive glass substrate as the electron emission cathode of the display.

3. Thermal sintering treatment after printing

Since the slurry material surrounds the nanodiamond emitter in the printed composite nanodiamond film without heat sintering, it must be heat sintered.

Thermal sintering has two purposes: on the one hand, the film is dried and firmly bonded to the conductive glass substrate, and on the other hand, the pulping material contained in the film is decomposed and evaporated. If the pulping material (ethyl cellulose) cannot be fully decomposed and evaporated, these materials will be tightly wrapped on the nano-diamond emitter after the printing layer is dried, making it unable to emit electrons, so it must be processed in the subsequent heat treatment process. be removed from. Only when the nano-diamond emitter is exposed on the surface of the film is it conducive to electron field emission.

The thermal sintering curve includes 3 heating stages, 3 constant temperature stages and 1 cooling stage. The constant temperature in the first stage is mainly to dry the nano-diamond film, and the constant temperature in the second stage is mainly to make the surface of the nano-diamond printing layer more uniform and smooth through the effect of the surface tension of the slurry itself, which is a self-modification process. And make the printing layer fully dry. The constant temperature process in the third stage is to decompose and volatilize the dried pulping material at high temperature. The last is the natural cooling process.

4. Hydrogen plasma treatment after thermal sintering

After the screen-printed composite nano-diamond film cathode sample is thermally sintered for hydrogen plasma treatment, the plasma generator generates high-voltage and high-frequency energy, which is activated and controlled in the nozzle steel pipe to generate low-temperature hydrogen plasma. Compressed air sprays hydrogen plasma onto the surface of the nano-diamond film. When the hydrogen plasma meets the surface, chemical effects and physical changes occur, the molecular chain structure of the surface is changed, and the number of SP ² bonds increases, allowing the tunneling of electrons. And the emission becomes easy; and the diamond tips on the surface of the composite nano-diamond film are evenly distributed, and the stability of the electron field emission is improved.

Example 1

A method for preparing a composite nano-diamond film by screen printing, comprising the following steps:

a. Grinding of nano-diamond and nano-graphite: before slurry preparation, 30 grams of nano-graphite, 80 grams of nano-diamond and 60 grams of ethyl cellulose are ground to a particle size of 100 nanometers, fully mixed as a solute;

b. Preparation of nano-diamond slurry: add the mixed solute to terpineol in a mass ratio of 1:5, ultrasonically disperse for 8 hours until the solute is fully dispersed in the solvent, then heat and stir at 373K, pass through 400 mesh After sieving, the nano-diamond and nano-graphite are evenly distributed, and naturally cooled to room temperature for use;

C, screen printing prepares composite nano-diamond film: select mesh number to be 350 object wire mesh or polyester screen, carry out screen printing on glass plate by screen printing machine with the nano-diamond slurry that last step obtains;

d. Thermal sintering after printing: raise the temperature to T ₁ K and keep it for 20 minutes, then raise the temperature to T ₂ K and keep it for 130 minutes, then raise the temperature to T ₃ K and keep it for 80 minutes, then cool it down to room temperature for use.

e. Hydrogen plasma treatment: Generating low-temperature hydrogen plasma through a plasma generator, spraying hydrogen plasma on the surface of the nano-diamond film obtained in the previous step with the help of compressed air at 0.70W/ ^cm2 , and keeping the time for 1.5 minutes to make the nano-diamond emit The tips are evenly distributed on the surface of the film.

Example 2

A method for preparing a composite nano-diamond film by screen printing, comprising the following steps:

a. Grinding of nano-diamond and nano-graphite: Before slurry preparation, 60 grams of nano-graphite, 160 grams of nano-diamond, and 120 grams of ethyl cellulose are ground to a particle size of 100 nanometers, and fully mixed as a solute;

b. Preparation of nano-diamond slurry: add the mixed solute to terpineol in a mass ratio of 2:10, ultrasonically disperse for 8 hours until the solute is fully dispersed in the solvent, then heat and stir at 343K, pass through 400 mesh After sieving, the nano-diamond and nano-graphite are evenly distributed, and naturally cooled to room temperature for use.

All the other parts are identical with embodiment 1.

Example 3

A method for preparing a composite nano-diamond film by screen printing, comprising the following steps:

a. Grinding of nano-diamond and nano-graphite: before slurry preparation, 15 grams of nano-graphite, 40 grams of nano-diamond, and 30 grams of ethyl cellulose are ground to a particle size of 100 nanometers, fully mixed as a solute;

b. Preparation of nano-diamond slurry: add the mixed solute to terpineol in a mass ratio of 1:5, ultrasonically disperse for 9 hours until the solute is fully dispersed in the solvent, then heat and stir at 333K, pass through 350 mesh After sieving, the nano-diamond and nano-graphite are evenly distributed, and naturally cooled to room temperature for use.

All the other parts are identical with embodiment 1.

Example 4

A method for preparing a composite nano-diamond film by screen printing, comprising the following steps:

a. Grinding of nano-diamond and nano-graphite: before slurry preparation, 15 grams of nano-graphite, 60 grams of nano-diamond, and 30 grams of ethyl cellulose are ground to a particle size of 60 nanometers, fully mixed as a solute;

b. Preparation of nano-diamond slurry: add the mixed solute to terpineol in a mass ratio of 1:2.5, ultrasonically disperse for 7 hours until the solute is fully dispersed in the solvent, then heat and stir at 300K, pass through 450 mesh After sieving, the nano-diamond and nano-graphite are evenly distributed, and naturally cooled to room temperature for use.

All the other parts are identical with embodiment 1.

Claims (1)

1. the preparation method of the slurry of a printing composite nano diamond thin film on glass substrate use is characterized in that, comprises the following steps:

A, raw material is ground

It is that the 10-100 nanometer is as raw material for standby that nano-graphite, Nano diamond and ethyl cellulose are ground to granularity;

B, preparation Nano diamond slurry

With raw material nano graphite, Nano diamond and ethyl cellulose by weight 3-6: 8-16: the 6-12 mixed is as solute, by weight 2-4: 5-10 solute is added in the solvent, ultra-sonic dispersion 7-9 hour or in solvent, fully disperse to solute, heated and stirred under 300-373K then, after crossing the 350-450 mesh sieve, make Nano diamond and nano-graphite uniform distribution, naturally cool to room temperature and get final product; Wherein solvent is a Terpineol 350.