CN1303260C - Process for preparing carbon nano tube film through electrophoresis deposition - Google Patents

Abstract

A method for preparing a carbon nanotube film by electrophoretic deposition, belonging to the technical field of nanomaterials, the method includes carbon nanotube purification and surface modification, formation of a stable carbon nanotube suspension, electrophoretic deposition of a carbon nanotube film, and film drying and secondary electrophoretic deposition in several steps. The invention has the advantages of simple production equipment, fast film formation, controllable film thickness, unrestricted substrate shape, simple process and is suitable for mass production.

Description

A kind of electrophoretic deposition preparation method of carbon nanotube thin film

technical field

The invention relates to a preparation method of a carbon nanotube film, in particular to an electrophoretic deposition preparation method, and belongs to the technical field of nanometer materials.

Background technique

Carbon nanotubes are currently an ideal one-dimensional nanomaterial prepared artificially. Due to their unique composition and structure, carbon nanotubes exhibit many unique physical properties, and are widely used in sensors, flat panel displays, supercapacitors, composite materials, etc. a wide range of applications. Among them, the prospect of the application of the macroscopic film structure composed of carbon nanotubes according to certain rules is more exciting.

At present, the preparation methods of carbon nanotube films mainly include direct growth method and post-processing method.

The direct growth method is to use arc discharge, laser ablation, chemical vapor deposition and other preparation methods to directly grow carbon nanotube films on a certain material substrate. The advantage is that the structure and size of carbon nanotubes can be adjusted through process conditions, and the patterning of carbon nanotubes can be realized through the graphics of the substrate or catalyst; the disadvantage is that various processing methods are required to improve the performance of carbon nanotube films , The selectivity to the substrate is relatively strong, and due to the limitation of the current process conditions, most of these processes require high temperature conditions, so it is impossible to use low melting point materials as the substrate, such as plexiglass, which greatly limits the use of carbon nanotube films in sensors, Field emission display devices and other applications. At the same time, because the high temperature condition will destroy the microelectronic circuit, it leads to the incompatibility between the preparation process of the carbon nanotube film and the microelectronic process.

The post-treatment method is to modify and improve the performance of carbon nanotubes on the basis of the preparation of carbon nanotubes by the above-mentioned methods, and then obtain a uniform and uniform carbon nanotube film through a certain post-treatment process. The biggest feature of the post-processing method is that it does not require high substrates, avoids high temperatures in the process, and may achieve compatibility with microelectronics processes. At present, common post-processing methods for preparing carbon nanotube films include spraying, evaporation, etc. Although these methods are simple in process, the film forming speed is relatively slow, and the film thickness is difficult to control, which is not suitable for mass production, automatic production, industrial Promotion is difficult.

Electrophoretic deposition refers to the phenomenon that the charged solid particles in the suspension move in a directional manner and deposit on electrodes with opposite charges and a certain shape under the action of an electric field. It includes two steps of electrophoresis and deposition: electrophoresis, also known as electromigration, refers to the physical and chemical phenomenon of directional movement of charged particles in a certain medium due to the action of an electric field; deposition refers to the aggregation of particles into a film or block. At present, the research on the application of electrophoretic deposition in coating technology is very in-depth. With its characteristics of uniform film thickness, good appearance, no environmental hazards, safe operation, automatic process, and suitable for streamlined production, it is widely used in automobiles, home appliances, light industry, Metal and other industries have been widely used.

At present, the main problems in the preparation of carbon nanotube films by electrophoretic deposition are poor controllability of film thickness and poor film uniformity.

Contents of the invention

The purpose of the present invention is to provide a preparation method for obtaining a carbon nanotube film with uniform film thickness. The method relates to a method for preparing a carbon nanotube film by electrophoretic deposition, comprising the following five steps:

1. Purification and surface modification of carbon nanotubes

Mix the prepared carbon nanotubes with 30% hydrogen peroxide solution, filter out the carbon nanotubes after ultrasonic oscillation for 10-120 minutes; use carbon disulfide to wash the carbon nanotubes 3-5 times; use anhydrous methanol to wash the carbon nanotubes Nanotubes 3 to 5 times; drying; the above-mentioned carbon nanotubes are mixed with concentrated acid and heated at 70 to 150° C. for 10 to 120 minutes under reflux. Said concentrated acid refers to 98% concentrated sulfuric acid, 69% concentrated nitric acid and Any one of the three mixed acids of the two; filter out the carbon nanotubes; wash the carbon nanotubes with deionized water for 3 to 10 times and dry them;

2. Formation of stable suspension of carbon nanotubes

Dispersing the above-mentioned carbon nanotubes in water or an organic solvent, said organic solvent can be any one in ethanol, acetone or their mixture; adding inorganic salt, said inorganic salt can be magnesium chloride, magnesium nitrate, Any one of aluminum chloride and aluminum nitrate; ultrasonic oscillation for 10 to 120 minutes, and standing for 10 to 120 minutes to form a stable suspension electrophoretic solution of various concentrations;

3. Electrophoretic deposition of carbon nanotube films

The substrate required to grow the film is used as the cathode of the electric pool. The cathode can be any conductive material that is not corroded during the electrophoresis process, or an insulator that is not corroded during the electrophoresis process or a conductive material with a certain pattern on the semiconductor surface. Materials; metal electrodes are used as anodes, and the anodes can be any one of platinum electrodes, gold electrodes, and copper electrodes; carbon nanotube suspensions are used as electrophoretic fluid; under DC 10-100 volts, according to the required Film thickness electrophoresis for 30 seconds to 20 minutes;

4. Film drying

Dry the product obtained from the cathode together with the cathode at 25°C to 200°C for 1 to 120 minutes;

5. Secondary electrophoresis

The cathode is then put into the above electric pool for secondary electrophoresis; after 30 seconds to 20 minutes, the product obtained from the cathode is taken out and dried to obtain a carbon nanotube film.

The preferred implementation conditions of the present invention are:

Carbon nanotubes are less than 80 nanometers in diameter.

Carbon nanotubes are less than 30 microns in length.

Concentrated acid is formed by mixing 98% concentrated sulfuric acid and 69% concentrated nitric acid in a volume ratio of 3:1.

Heating to reflux time is less than 30 minutes.

The dispersing solvent is absolute ethanol.

The inorganic salt is magnesium chloride or magnesium nitrate.

The anode is a platinum electrode.

The electrophoresis voltage is 50-80 volts direct current.

The electrophoresis time is 1 to 20 minutes.

Drying or drying temperature is 10 ~ 50 ℃.

Drying or drying time is 1 to 30 minutes.

The second electrophoresis time is 1-20 minutes.

Features of the present invention:

1. Compared with other existing methods, the carbon nanotube film obtained by the method provided by the present invention has the characteristics of short production cycle, uniform and compact carbon nanotube film, and the carbon nanotube can be modified in advance;

2. The present invention can control the thickness of the carbon nanotube film by changing the deposition voltage and deposition time;

3. The present invention can control the patterning of the carbon nanotube film by changing the electrode pattern;

4. The electrophoretic deposition method adopted in the present invention is convenient and simple to implement, does not require high equipment, and the deposition process is easy to external control;

5. The present invention has short electrophoresis time, and the electrophoresis process can be carried out in various solvents, especially in water phase and common organic solvents, has little environmental pollution and is cheap, and is suitable for industrial production.

The invention has many advantages such as simple production equipment, fast film formation, controllable film thickness, unrestricted substrate shape for depositing films, etc., simple processing technology, suitable for large-scale and automatic production, and easy for industrial popularization and application.

Detailed ways

Example 1

1. The black powder of multi-walled carbon nanotubes prepared by nano-agglomeration technology has a purity greater than 80%, an inner diameter of 2-30 nanometers, an outer diameter of 5-60 nanometers, and an aggregate size of tens of microns. The carbon nanotubes are mixed with 30% hydrogen peroxide solution, ultrasonically oscillated for 10 minutes and then filtered; the carbon nanotubes are repeatedly washed three times with carbon disulfide; the carbon nanotubes are repeatedly washed three times with anhydrous methanol; and dried. The above carbon nanotubes were mixed with 75 ml of 98% concentrated sulfuric acid and 25 ml of 69% concentrated nitric acid, heated under reflux at 75° C. for 10 minutes, and the carbon nanotubes were filtered out; the carbon nanotubes were washed with deionized water and dried.

2. Weigh 50 mg of the above-mentioned carbon nanotubes, add 100 ml of absolute ethanol and 512 mg of magnesium chloride, ultrasonically oscillate for 20 minutes, and stand for 30 minutes to form a black, stable suspension of carbon nanotubes.

3. Use the above-mentioned carbon nanotube suspension as the electrophoretic fluid, and use the patterned gold silicon wafer as the cathode of the electric swimming pool, and use the gold sheet as the anode of the electric swimming pool; the relative distance between the cathode and the anode is 4 cm; in the electric swimming pool A DC voltage of 50 volts was applied between the cathode and the anode, and the cathode was taken out after 4 minutes.

4. Stand the above cathode at room temperature for 2 minutes and 30 seconds;

5. Put the cathode into the battery pool again, apply a DC voltage of 50 volts for 1 minute; take out the cathode and dry it at room temperature.

As a result, a black, uniform and patterned carbon nanotube film grown on a silicon wafer can be obtained. The measurement results showed that the average thickness of the edge of the film was about 87 microns.

Example 2

1. The black powder of multi-walled carbon nanotubes prepared by nano-agglomeration technology has a purity greater than 80%, an inner diameter of 2-30 nanometers, an outer diameter of 5-60 nanometers, and an aggregate size of tens of microns. The carbon nanotubes are mixed with 30% hydrogen peroxide solution, ultrasonically oscillated for 10 minutes and then filtered; the carbon nanotubes are repeatedly washed three times with carbon disulfide; the carbon nanotubes are repeatedly washed three times with anhydrous methanol; and dried. The above carbon nanotubes were mixed with 75 ml of 98% concentrated sulfuric acid and 25 ml of 69% concentrated nitric acid, heated under reflux at 75° C. for 10 minutes, and the carbon nanotubes were filtered out; the carbon nanotubes were washed with deionized water and dried.

2. Weigh 50 mg of the above-mentioned carbon nanotubes, add 100 ml of absolute ethanol and 512 mg of magnesium chloride, ultrasonically oscillate for 20 minutes, and stand for 30 minutes to form a black, stable suspension of carbon nanotubes.

3. Use the above-mentioned carbon nanotube suspension as the electrophoretic fluid, and use the patterned gold silicon wafer as the cathode of the electric swimming pool, and use the gold sheet as the anode of the electric swimming pool; the relative distance between the cathode and the anode is 1 cm; in the electric swimming pool A DC voltage of 90 volts was applied between the cathode and the anode, and the cathode was taken out after 4 minutes.

4. Stand the above-mentioned cathode at room temperature for 2 minutes;

5. Put the cathode into the battery pool again, apply a DC voltage of 50 volts for 1 minute; take out the cathode and dry it at room temperature.

As a result, a black, uniform and patterned carbon nanotube film grown on a silicon wafer can be obtained. Measurements showed that the average thickness of the film edge was about 245 microns.

Claims (1)

1. A preparation method for electrophoretic deposition of a carbon nanotube film, comprising three steps of purification treatment and surface modification of carbon nanotubes, formation of a stable suspension of carbon nanotubes, and electrophoretic deposition of a carbon nanotube film. Said purification treatment and The surface modification is as follows: mix the prepared carbon nanotubes with a hydrogen peroxide solution with a concentration of 30%, filter out the carbon nanotubes after ultrasonic oscillation for 10-120 minutes; wash the carbon nanotubes with carbon disulfide for 3-5 times; Wash the carbon nanotubes with water and methanol for 3-5 times; dry; mix the above-mentioned carbon nanotubes with concentrated acid and heat them under reflux at 70-150°C for 10-120 minutes. The concentrated acid refers to 98% concentrated sulfuric acid, 69 % concentrated nitric acid and the mixed acid of the two; filter out the carbon nanotubes; use deionized water to wash the carbon nanotubes for 3 to 10 times and dry them; the stable suspension of the carbon nanotubes The formation is: dispersing the purified carbon nanotubes in water or an organic solvent, the organic solvent can be ethanol, acetone or any of their mixtures; adding an inorganic salt, the inorganic salt can be It is any one of magnesium chloride, magnesium nitrate, aluminum chloride, and aluminum nitrate; ultrasonic vibration for 10 to 120 minutes, and standing for 10 to 120 minutes to form a stable suspension electrophoretic solution of various concentrations; the so-called electrophoretic deposition carbon The nanotube film is: the substrate required for growing the film is used as the cathode of the electric pool. The cathode can be any conductive material that is not corroded during the electrophoresis process, or an insulator or a semiconductor surface that is not corroded during the electrophoresis process. A conductive material with a certain pattern; a metal electrode is used as an anode, and the said anode can be any one of a platinum electrode, a gold electrode, or a copper electrode; Next, electrophoresis for 30 seconds to 20 minutes according to the required film thickness; it is characterized in that it is dried after the carbon nanotube film is formed, and the second electrophoretic deposition is performed.