KR100579319B1 - apparatus of processing carbon nanotubes and method thereof - Google Patents

Abstract

The present invention relates to a surface treatment apparatus and method for a powdery carbon structure such as carbon nanotubes, and performs surface treatment by irradiating ultraviolet rays to the powdered carbon structure to be treated in a gas atmosphere containing oxygen. According to the surface treatment apparatus and method of the powdery carbon structure, carbon nanotubes having high dispersibility and solubility in an organic solvent can be produced without using a chemical solvent such as a strong oxidizing agent, and contaminant by-products caused by acidic chemicals It does not occur, it is eco-friendly, bulk processing is possible, and provides the advantage of increasing the yield.

Description

Apparatus of processing carbon nanotubes and method

1 is a process chart showing a surface treatment process of carbon nanotubes according to a preferred embodiment of the present invention,

2 is a cross-sectional view schematically showing a surface treatment apparatus of a powdery carbon structure according to the present invention,

3a and 3b is a process chart showing a surface treatment process of the carbon nanotubes according to another embodiment of the present invention,

4 to 7 are photographs showing the results of dissolving by applying different solvents to compare the dispersion degree of UVO treated carbon nanotubes and untreated carbon nanotubes,

8 is a photograph showing the result of dissolving in a solvent with a polymer while varying the amount of UVO-treated carbon nanotubes.

<Description of Symbols for Major Parts of Drawings>

210: chamber 220: ultraviolet light generator

The present invention relates to a surface treatment apparatus and method for a powdery carbon structure, and more particularly, to a surface treatment apparatus and method for a powdery carbon structure that can increase the dispersibility of carbon nanotubes in an organic solvent.

Carbon nanotubes are usually carbon materials having a high aspect ratio ranging from 1 to 100 nanometers (nm) in diameter and from several nanometers (nm) to several tens of micrometers (μm) in length. .

Carbon nanotubes exhibit conductive or semiconducting properties depending on their structure, and are used as materials for forming display devices, secondary batteries, and electron emitting devices.

In addition, carbon nanotubes are being used as additives in various composite materials due to their high electrical conductivity, thermal stability, tensile strength and resilience.

Recently, as methods for producing high quality carbon nanotubes at low cost have been developed, various methods for applying carbon nanotubes as additives of composite materials have been attempted. For example, the use of carbon nanotubes as additives to enhance the functions of ultra-high strength structural composites formed by combining polymers and organic materials, functional composite materials using electronic shielding films, and high thermal conductivity is being investigated. .

It is important to effectively disperse the bundles of carbon nanotubes in a solvent in order to make functional composites containing carbon nanotubes. As an example, in order to make an ultrahigh-strength polymer composite material in which carbon nanotubes are dispersed, it is necessary to uniformly disperse carbon nanotubes in a polymer matrix.

However, carbon nanotubes have a problem of having very low dispersion in solvents due to long lengths and strong attraction between carbon nanotubes.

 In order to improve such a problem, a lot of researches have been conducted on techniques for mixing carbon nanotubes with polymer materials by dispersing through chemical and physical pre-treatment processes.

Known methods up to now include a method of oxidizing the surface of the carbon nanotubes with a strong acid solution such as sulfuric acid, hydrochloric acid, nitric acid and the like to increase the dispersibility of the carbon nanotube material itself.

McCarthy has reported a method of treating carbon fiber surfaces with sulfuric acid in Polymer Chem. 30 (1): 420 (1990). This method is a method for forming a carboxyl group (COOH) on the surface of the carbon fiber, it is disclosed in the US Patent No. 5,698,175 proposed by Hiura, which also has the effect of removing impurities, and is useful for adding functional groups to the surface It is known that it can be utilized. In addition, the treatment of the surface of the carbon nanotubes with a solution of sulfonic acid, alkali metal chloride and hydrogen peroxide may cause effective oxidation. 6,099,960 and 6,099,965.

In addition, as reported by Esumi in the process of dispersing carbon nanotubes containing nitric acid or nitric acid mixed with sulfuric acid (Carbon 34: 279-281 (1996)). have.

In addition, Korean Patent Application No. 2000-0030351 and Korean Patent Application No. 2001-0047617 disclose a method of treating carbon nanotubes based on an acid or an acid.

However, the method of chemically treating carbon nanotubes using an acid solution as listed above has the following problems.

First, the yield is low because the separation extraction must be repeated through centrifugation and filter for each treatment step using a large amount of acid solvent.

Second, the process is complicated, the process takes a lot of time, the process is expensive.

Third, it is difficult to treat by-products of chemicals generated in the treatment process, and these by-products may pollute the environment.

Because of these problems, the wet chemical treatment method is difficult to apply industrially to the processing of a large amount of carbon nanotubes.

On the other hand, as another method of increasing the dispersibility of carbon nanotubes, Korean Patent Application No. 2003-0029184 discloses a method of chemically and physically bonding organic molecules to carbon nanotubes so that organic molecules are wrapped around the surface of carbon nanotubes and treated. It is. Therefore, this method can significantly increase the solubility of the carbon nanotubes in the solvent, but the organic functional group is included on the surface of the carbon nanotubes, and the reaction process is complicated and expensive.

In addition, when the carbon nanotubes are mixed with other plastics or polymers, the outer surface of the carbon nanotubes is hidden in the functional group, and thus the properties of the desired carbon nanotubes are not sufficiently expressed.

The present invention was devised to improve the above problems, and provides a surface treatment method of a powdery carbon structure that can induce surface oxidation of the powdery carbon structure by dry to increase dispersibility in various solvents. There is a purpose.

In order to achieve the above object, the surface treatment method of the powdery carbon structure according to the present invention includes a UVO treatment step of irradiating ultraviolet light to the powdered carbon structure to be treated in a gas atmosphere containing oxygen.

Preferably the wavelength of the ultraviolet ray is applied to 100nm to 300nm. More preferably, the wavelength of the ultraviolet ray is 253.7 nm wavelength alone, but can be emitted together with the wavelength of 253.7 nm and 184.9 nm.

In addition, the gas may include ozone.

The powdery carbon structure includes at least one of carbon nanotubes, carbon fibers, and carbon black.

In addition, the wet treatment step of treating the treated powder-type carbon structure to an acidic aqueous solution before or after the UVO treatment step; may further include.

In addition, in order to achieve the above object, the apparatus for treating the surface of the powdery carbon structure according to the present invention is a chamber in which a gas inlet and a gas outlet are formed and the container containing the powdered carbon structure to be treated can be seated. Wow; And an ultraviolet generator installed in the chamber to emit ultraviolet rays to the vessel.

Hereinafter, a method and apparatus for surface treatment of a powdery carbon structure according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a process chart showing a surface treatment method of carbon nanotubes according to the present invention.

Referring to the drawings, in the carbon nanotube surface treatment method, the carbon nanotubes to be treated are treated by irradiating ultraviolet rays in an oxygen atmosphere (hereinafter referred to as UVO treatment) (step 100).

Here, the oxygen atmosphere refers to an atmosphere in which oxygen alone or a gas mixed with oxygen, for example, air is applied. In addition, it is of course possible to supply additional ozone to increase the reactivity.

The irradiation time of the ultraviolet light may be appropriately applied in consideration of the amount of carbon nanotubes to be treated. For example, 20 seconds to 500 minutes may be applied.

In addition, the amount of carbon nanotubes to be used for one irradiation may be appropriately applied to the extent that the ultraviolet rays are evenly irradiated.

An example of a surface treatment apparatus capable of performing the surface treatment method of such carbon nanotubes is shown in FIG. 2.

The surface treatment apparatus 200 includes a chamber 210 and an ultraviolet generator 220.

The chamber 210 is provided with a gas inlet 223 and a gas outlet 225. Of course, a blower fan (not shown) may be further installed at the gas outlet 225 or the gas inlet 223.

An oxygen supplier (not shown) may be further installed to supply oxygen into the chamber 210 through the gas inlet 223 or a separate inlet (not shown).

The stage 227 is installed in the chamber 210 to seat the container 300 containing the carbon nanotube powder to be treated.

The stage 227 may be provided with an apparatus, for example, a vibration applying apparatus, an ultrasonic applying apparatus, or the like, into which the carbon nanotube powder to be treated contained in the vessel 300 may be agitated.

In addition, a heater (not shown) may be further provided to increase the temperature inside the chamber 210.

When the heater is provided, the temperature inside the chamber 210 may be raised to a temperature appropriately determined at 550 degrees or less, which is the melting temperature of the carbon nanotubes.

In contrast, when no heater is provided, the reaction may be performed at room temperature by ultraviolet irradiation.

The ultraviolet generator 220 may be any one capable of emitting ultraviolet rays in the wavelength band of 100 to 300 nanometers, and preferably, the one capable of emitting both 253.7 nm wavelength and 253.7 nm and 184.9 nm wavelengths together is applied.

As an example of the ultraviolet generator 220, a low pressure mercury lamp may be used.

Preferably, the distance between the UV generator 220 and the carbon nanotubes to be treated is determined to be 1 cm (cm) to 30 center meters (cm) apart from the stage 227 and the UV generator 220.

The process of surface treatment of carbon nanotubes using the apparatus 200 will be described in more detail in the air atmosphere.

First, the carbon nanotubes in powder form to be surface treated are placed in the container 300 and placed on the stage 227.

Then, the ultraviolet ray generator 220 is operated. Then, a reaction is performed in which the surface of the carbon nanotubes is treated by the air introduced through the gas inlet 223 and the ultraviolet rays irradiated from the ultraviolet generator 220.

In describing the reaction process, ultraviolet rays having a wavelength of 184.9 nm among ultraviolet rays emitted from the ultraviolet generator 220 decompose oxygen (O ₂ ) to generate active oxygen atoms and ozone (O ₃ ), and have a wavelength of 253.7 nm. Ultraviolet light decomposes the generated ozone into oxygen radicals and is absorbed by the amorphous carbon atoms present in the carbon nanotubes to separate the carbon-carbon bonds. In addition, a chemical reaction occurs to generate a carboxyl group (COO-) on the surface of a carbon nanotube by reaction of an active oxygen atom with carbon.

Carbon nanotubes surface-treated through this reaction process have a high dispersibility for the solvent. In addition, impurities generated during the carbon nanotube manufacturing process may be removed. This UVO treatment process can be used to remove impurities in addition to the surface treatment to increase the solvent dispersion.

On the other hand, the by-product gas generated in the reaction process in the chamber 210 is discharged through the gas outlet 225. Here, the by-product gas can be released into the atmosphere as a non-pollutant such as carbon dioxide, carbon monoxide, nitrogen gas, etc., thereby providing the advantage that no by-product treatment is required.

Carbon nanotubes that can be applied to this surface treatment process can be applied regardless of the previous manufacturing process and structure. That is, as the production method of carbon nanotubes known to date, an electric discharge method, a laser deposition method, a gas phase synthesis method, a plasma chemical vapor deposition method, a thermal chemical vapor deposition method and the like are known, and the carbon nanotubes synthesized and manufactured by these manufacturing methods are It can be applied to all surface treatments.

In addition, the surface treatment described above may be applied to single-walled single-walled carbon nanotubes, multi-walled multi-walled carbon nanotubes, or other structured carbon nanotubes. have.

In addition, powder type carbon structures that can be applied to UVO treatment include carbon fibers, carbon black, and the like in addition to carbon nanotubes.

On the other hand, the surface treatment method by UVO treatment can be combined with the conventional wet treatment method is a matter of course.

That is, after wet treatment with an acid solution as shown in FIG. 3a (step 90), a UVO treatment step (100) is performed, or a UVO treatment step (step 100) as shown in FIG. 3b is then performed. Of course, the process of wet treatment with an acid solution (step 190) can be performed.

Here, the wet treatment step (step 90) (step 190) using an acid solution refers to a process of adding carbon nanotubes to an acid solution generated by diluting nitric acid, hydrochloric acid, or sulfuric acid with water.

Hereinafter, an embodiment of the experiment to confirm whether the carbon nanotubes having undergone the surface treatment by UVO treatment have high dispersibility for various solvents will be described with reference to FIGS. 4 to 7.

Examples described below generally select several solvents from among solvents used to dissolve polymers or organic materials, and inject carbon nanotubes subjected to UVO treatment and carbon nanotubes not subjected to UVO treatment for each selected solvent. Dispersion, ie, solubility, was visually analyzed and analyzed using ultraviolet spectroscopy.

UVO-treated carbon nanotubes in Example were obtained by irradiating ultraviolet rays for 60 minutes at room temperature under an air atmosphere.

In Figures 4 to 7, the container indicated by a represents a solution in which carbon nanotubes treated with UVO are dissolved in a corresponding solvent, and the container denoted b contains a solution in which carbon nanotubes not treated with UVO are dissolved in a corresponding solvent. will be.

First Embodiment

UVO treated carbon nanotubes and untreated carbon nanotubes were dissolved in DMF (N, N-dimethylformamide) solution, respectively, and the results of the comparison are shown in FIG. 4.

As can be seen visually through Figure 4 solution (a) dissolved carbon nanotubes undergoing UVO treatment appears to be opaque black color due to high dispersion, carbon nanotubes not subjected to UVO treatment The dissolved solution (b) appears transparent by low dispersion.

In addition, each of the above solutions was measured by UV-visible spectroscopy (UV-visible spectroscopy), UVO treated carbon nanotubes solubility was 38.1 mg / L, solubility of 320% than the carbon nanotubes without UVO treatment High.

Second Embodiment

UVO-treated carbon nanotubes and untreated carbon nanotubes were dissolved in a pyridine solution, which is a different solvent, under the same conditions as in the first embodiment, and the results are shown in FIG. 5. As can be seen visually through Figure 5 the carbon nanotubes undergoing UVO treatment is more dispersed.

In addition, as measured by ultraviolet spectroscopy, the solubility of the UV nanotubes was improved by about 432% compared to the UV nanotubes.

Third Embodiment

Carbon nanotubes and untreated carbon nanotubes treated under the same conditions as in the first embodiment were dissolved in a solution of THF (tetrahydrofuran), another solvent, and the results are shown in FIG. 6. As can be seen visually through Figure 6 the carbon nanotubes undergoing UVO treatment is more dispersed.

In addition, as measured by ultraviolet spectroscopy, the solubility of the UV nanotubes was improved by about 346% compared to the UV nanotubes.

Fourth Embodiment

Carbon nanotubes and untreated carbon nanotubes treated under the same conditions as in the first embodiment were dissolved in a different solvent of 1, 2-dichlorobenzene, which is a different solvent as described above, and the results are shown in FIG. 7. As can be seen visually through Figure 7, the carbon nanotubes undergoing UVO treatment is more dispersed.

In addition, as measured by ultraviolet spectroscopy, the solubility of the UV nanotubes was 371% higher than that of the UV nanotubes.

On the other hand, the UVO treatment conditions described above are varied, that is, oxygen is forcibly supplied into the chamber 210, and the distance between the UV generator 220 and the carbon nanotubes and the amount of the carbon nanotubes to be treated are appropriately changed. Even when irradiated with ultraviolet rays for 20 minutes, it was confirmed that the solubility of more than 1000% increased than before treatment.

Carbon nanotubes subjected to UVO treatment as can be seen through the above examples have a higher dispersibility before UVO treatment regardless of the type of solvent.

On the other hand, UVO-treated carbon nanotubes can be easily prepared by dissolving the carbon nanotubes in a solvent together with plastics or polymers to uniformly disperse the carbon nanotubes.

As an experimental example for confirming that the composite can be prepared by the above method, UVO-treated carbon nanotubes and polymethylmethacrylate polymer powders were dissolved in DMF (N, N-dimethylformamide) solution. Is shown. The four containers, respectively designated as a, b, c, and d in FIG. 8, represent 0.01 wt%, 0.02 wt%, 0.1 wt%, and 2 wt% of carbon nanotubes, respectively, based on polymethylmethacrylate. This is another solution.

As can be seen visually through Figure 8 it can be seen that even if added to the solvent with the polymer is well dispersed.

For reference, in the case where the amount of carbon nanotubes is small, the change of color is not largely distinguished by the small amount, despite the high solubility, but the color gradually changes to black due to the high dispersing force as the amount is increased. .

These results generally indicate that carbon nanotubes are dispersed in a uniformly dispersed form when considering that the carbon nanotubes are added in an amount of 0.5 to 1% by weight in order to obtain electrical conductivity when the composite is formed by mixing the carbon nanotubes in the polymer matrix. It can be easily formed. That is, the polymer-carbon nanotube solution having a single phase can be easily prepared by directly dissolving the polymer in the carbon nanotube solution dissolved in a solvent.

According to the surface treatment apparatus and method of the powdery carbon structure according to the present invention as described above, it is possible to prepare carbon nanotubes having high dispersibility and solubility in an organic solvent without using a chemical solvent such as a strong oxidizing agent. Because it can be produced by pollutant by-products caused by acidic chemicals, it is environmentally friendly, can be processed in large quantities, and can provide a high yield.

Claims (6)

delete delete delete delete In the method of treating the surface of the powdery carbon structure, It includes; UVO treatment step of irradiating the ultraviolet light to the powder-treated carbon structure in the gas atmosphere containing oxygen; And a wet treatment step of treating the treated powdered carbon structure to an acidic aqueous solution before or after the UVO treatment step. In the apparatus for treating the surface of the powdery carbon structure, A chamber in which a gas inlet and a gas outlet are formed and to seat the container containing the powdered carbon structure to be treated; And an ultraviolet generator installed in the chamber to emit ultraviolet rays to the container.

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