JP2004352608A - Method for dispersing carbon nano-structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an improved method for dispersing a carbon nano-structure. <P>SOLUTION: The surface of the carbon nano-structure is fluorinated with a fluorine-containing gas and the fluorinated carbon nano-structure is dispersed in a solvent. The resultant carbon nano-structure dispersion is useful in various industrial fields. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for improving the dispersibility of a carbon nano-structure in a solvent by fluorinating the surface of the carbon nano-structure.

  Carbon nanostructures, such as carbon nanofibers, fullerenes, carbon nanotubes and carbon nanohorns, can be used in various fields such as electromagnetic wave shielding, electronic devices or inorganic-organic composites due to their excellent physical, chemical and electrical properties. Used in the field.

  However, such carbon nanostructures tend to aggregate when mixed into a substrate, deteriorating their unique properties. Therefore, there have been many attempts to develop carbon nanostructures with good dispersibility that do not aggregate in the substrate.

  For example, a method of dispersing carbon nanotubes in a solvent using a surfactant has been disclosed (see Patent Document 1), but this method does not provide a completely dispersed carbon nanotube dispersion.

Therefore, the present inventors have completed the present invention by developing a method for improving the dispersibility of the carbon nanostructure by performing a surface treatment on the carbon nanostructure.
Korean Patent Publication No. 2002-77506

  Therefore, an object of the present invention is to provide an effective method for individually separating carbon nanostructures in a solvent.

  According to one embodiment of the present invention, the present invention provides a method for producing a carbon nanostructure, comprising: fluorinating the surface of a carbon nanostructure with a fluorine-containing gas, and then dispersing the fluorinated carbon nanostructure in a solvent. A method for dispersing a structure is provided.

  According to the present invention, a carbon nanostructure that has been fluorinated before dispersion can be dispersed in a solvent with a uniform particle size.

Hereinafter, the present invention will be described in more detail.
The method according to the present invention is characterized in that the carbon nanostructure is preliminarily fluorinated before being dispersed.

  As schematically shown in FIG. 1, according to one embodiment of the present invention, the carbon nanostructure is purified if necessary, fluorinated (S10), and then fluorinated. Is dispersed in a solvent (S20). Optionally, the fluorinated carbon nanostructure dispersion is subjected to ultrasonic treatment (S30), and the pH of the dispersion is adjusted to a target range using an acid or alkali solution (S40). Then, the degree of dispersion of the carbon nanostructure dispersion obtained by the dispersion method of the present invention is analyzed (S50).

  Specifically, in the method of the present invention, the carbon nanostructure to be dispersed may be synthesized by a known synthesis method, for example, a chemical vapor deposition method (CVD), an arc method, an laser ablation method, or the like. Any type of carbon nanostructure that has been used can be used.

  Such a carbon nanostructure may be heat-treated in a known manner, for example, in an oxidizing gas atmosphere such as air at 400 to 800 ° C., or may be an inorganic strong acid such as hydrochloric acid, nitric acid, hydrofluoric acid or sulfuric acid. , The amorphous carbon or the catalytic metal may be removed for purification.

  According to the present invention, the purified or unpurified carbon nanostructure is treated with fluorine gas at -20 to 500C. The fluorine gas is used at an atomic ratio of fluorine to carbon of 0.001 to 50: 100, preferably 0.001 to 30: 100, and more preferably 0.001 to 5: 100. By such a fluorination treatment, the fluorine group covers a part of the surface of the carbon nanostructure, thereby reducing the interaction between the carbon nanostructure particles in the solvent and reducing the aggregation of the carbon nanostructure. Suppress. The fluorinated carbon nanostructure is dispersed in a solvent as individual particles (in the case of a single-walled carbon nanotube, the particle size is 1 to 3 nm), and the unique characteristics of the carbon nanostructure itself can be exhibited.

  In the present invention, examples of solvents that can be used as a matrix include distilled water, isopropanol, dimethylformamide, chloroform, dichloroethane, methylpyrrolidone, tetrahydrofuran, decane or a mixture thereof.

  The solvent may optionally contain a surfactant, a water-soluble polymer or a mixture thereof as a dispersant in an amount of 0.001 to 5.0% by weight based on the solvent. The surfactant and the water-soluble polymer may be mixed preferably in a weight ratio of 1: 0.8.

  Examples of the surfactant include sodium dodecyl sulfate, sodium dodecyl benzene sulfate, sodium butyl benzene sulfate, dodecyl trimethyl ammonium bromide, Triton X-100, benzalkonium chloride or a mixture thereof.

  Examples of the water-soluble polymer include acacia, cyclodextrin, polyvinylpyrrolidone, carboxymethylcellulose or a mixture thereof.

  In the method of the present invention, the dispersion of the carbon nanostructure can be promoted by treating the carbon nanostructure dispersion liquid with ultrasonic waves of 100 to 750 W for 10 minutes to 2 hours as appropriate.

  Further, if necessary, an acid or alkali solution is added to the carbon nanostructure dispersion to adjust the pH of the dispersion to a range of 8 to 14, so that the dispersion effect can be enhanced.

(Example)
Hereinafter, the present invention will be described in more detail with reference to the following examples. However, these are only for illustrating the present invention, and do not limit the scope of the present invention.

[Example 1]
Single-walled carbon nanotubes synthesized by a conventional CVD method were purified by oxidation treatment with air at a temperature of 400 ° C. using a tubular reactor. The purified carbon nanotubes were further fluorinated at 40 ° C. for 30 minutes under an atmosphere of 0.1 bar of fluorine gas (F ₂ ). The fluorinated carbon nanotubes were dispersed in chloroform to obtain a carbon nanotube dispersion.

[Comparative Example 1]
The single-walled carbon nanotubes synthesized by the conventional arc method were purified by oxidation treatment with air at 400 ° C. using a tubular reactor. The purified carbon nanotubes were dispersed in distilled water by omitting the fluorination treatment step of Example 1 to obtain a carbon nanotube dispersion.

[Comparative Example 2]
A carbon nanotube dispersion was obtained in the same manner as in Comparative Example 1, except that 500 W of ultrasonic waves was applied to distilled water for 30 minutes.

[Example 2]
The fluorinated carbon nanotubes according to Example 1 were dispersed in a 0.01% by weight aqueous solution of sodium dodecylbenzene sulfate, and 500 W ultrasonic waves were applied thereto for 30 minutes to obtain a carbon nanotube dispersion.

[Example 3]
A carbon nanotube dispersion was obtained in the same manner as in Example 2, except that 0.1% by weight of an aqueous solution of carboxymethyl cellulose was used instead of the aqueous solution of sodium dodecylbenzene sulfate.

[Comparative Example 3]
A carbon nanotube dispersion was obtained in the same manner as in Example 2, except that a non-fluorinated carbon nanotube was used instead of the fluorinated carbon nanotube.

[Example 4]
A carbon nanotube dispersion was obtained in the same manner as in Example 1, except that the single-walled carbon nanotube and isopropyl alcohol were used instead of the single-walled carbon nanotube and distilled water, respectively.

Experimental Example 1 Particle Size Distribution of Carbon Nanotube Dispersion The particle size distribution of the carbon nanotube dispersions obtained in Comparative Examples 1 to 3 and Examples 1 to 3 was measured using a particle size analyzer (ELS-8000; Otsuka Electronics Co., Ltd.). The results are shown in FIGS. 2 to 7, respectively. 2 to 7, the horizontal axis indicates the measured diameter of the carbon nanotube or the carbon nanotube bundle, and the vertical axis indicates the relative distribution.

  FIG. 2 is a diagram showing a particle size distribution of a carbon nanotube dispersion obtained by performing only a purification step without a fluorination treatment according to Comparative Example 1, wherein the carbon nanotubes have a wide range of 100 to 4,500 nm. It can be seen that they are dispersed in a wide range of sizes.

  FIG. 3 is a diagram showing a particle size distribution of a carbon nanotube dispersion obtained by performing purification and ultrasonic treatment without fluorination treatment according to Comparative Example 2, wherein the carbon nanotubes have a particle size of 100 to 1,000 nm. It can be seen that they are still distributed over a wide size range.

  FIG. 4 is a diagram showing the particle size distribution of a carbon nanotube dispersion obtained by performing purification, surfactant and ultrasonic treatment without fluorination treatment according to Comparative Example 3, wherein the carbon nanotubes are single It can be seen that the particles are dispersed in a size range of 10 to 15 nm, which is larger than that of the single-walled carbon nanotube.

  FIG. 5 is a diagram showing a particle size distribution of a carbon nanotube dispersion obtained by performing purification and fluorination treatment according to Example 1, wherein carbon nanotubes are dispersed in a size range of 1 to 2.5 nm. You can see that it is done.

  FIG. 6 is a diagram showing a particle size distribution of a carbon nanotube dispersion obtained by performing purification, fluorination treatment, surfactant, and ultrasonic treatment in accordance with Example 2, wherein the carbon nanotubes are 1 to 3. It can be seen that the particles are dispersed in a size range of 3 nm.

  FIG. 7 is a diagram showing a particle size distribution of a carbon nanotube dispersion obtained by performing purification, fluorination treatment, water-soluble polymer, and ultrasonic treatment according to Example 3, wherein It can be seen that the particles are dispersed in a size range of 0.7 to 3 nm.

  Thus, the fluorinated carbon nanotubes can be dispersed in a uniform particle size range of 3 nm or less corresponding to the diameter of the single-walled carbon nanotube.

3 is a flowchart schematically illustrating a method of dispersing carbon nanostructures into individual particles according to an embodiment of the present invention. FIG. 3 is a view showing a particle size distribution of the carbon nanotube dispersion obtained in Comparative Example 1. FIG. 9 is a view showing a particle size distribution of the carbon nanotube dispersion obtained in Comparative Example 2. FIG. 9 is a view showing a particle size distribution of the carbon nanotube dispersion obtained in Comparative Example 3. FIG. 2 is a view showing a particle size distribution of a fluorinated carbon nanotube dispersion liquid according to Example 1 of the present invention. It is a figure which shows the particle size distribution of the carbon nanotube dispersion liquid which carried out the fluorination process which concerns on Example 2 of this invention. FIG. 4 is a view showing a particle size distribution of a fluorinated carbon nanotube dispersion liquid according to Example 3 of the present invention.

Claims (12)

  A method for dispersing a carbon nanostructure, comprising: fluorinating a surface of a carbon nanostructure with a fluorine-containing gas; and dispersing the fluorinated carbon nanostructure in a solvent.   The method according to claim 1, wherein the fluorination treatment is performed at a temperature of -20 to 500C.   The method according to claim 1, wherein the atomic ratio of fluorine to carbon in the fluorinated carbon nanostructure is 0.001 to 50: 100.   The method of claim 1, further comprising purifying the carbon nanostructure before the fluorination treatment.   The method according to claim 4, wherein the purification step is performed by heat-treating the carbon nanostructure in an oxidizing gas atmosphere or by treating with a strong inorganic acid.   The method according to claim 1, wherein the solvent is selected from the group consisting of distilled water, isopropanol, dimethylformamide, chloroform, dichloroethane, methylpyrrolidone, tetrahydrofuran, decane and mixtures thereof.   The method according to claim 6, wherein the solvent comprises a dispersant selected from the group consisting of a surfactant, a water-soluble polymer, and a mixture thereof.   The surfactant is selected from the group consisting of sodium dodecyl sulfate, sodium dodecylbenzene sulfate, sodium butylbenzene sulfate, dodecyltrimethylammonium bromide, Triton X-100, benzalkonium chloride and mixtures thereof. The method according to claim 7, wherein   The method according to claim 7, wherein the water-soluble polymer is selected from the group consisting of acacia, cyclodextrin, polyvinylpyrrolidone, carboxymethylcellulose, and a mixture thereof.   The method according to claim 1, further comprising subjecting the fluorinated carbon nanostructure dispersion to ultrasonic treatment.   The method according to claim 1, further comprising adjusting the pH of the fluorinated carbon nanostructure dispersion to a range of 8 to 14.   A carbon nanostructure dispersion obtained by the method according to claim 1.

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