CN100371060C - Electric Field Assisted Dispersion Method of Carbon Nanotubes in Liquid Medium - Google Patents

Abstract

The present invention relates to a method for assisting the dispersal of carbon nanometer tubes in liquid medium by electric field, which belongs to the technical field for enhancing the dispersivity of carbon nanometer tubes. The present invention is applied to the fields of the purification, the sieving, the manipulation, the composite material modification, etc. of the carbon nanometer tubes. The present invention is characterized in that the electric field is applied to the suspending liquid of charged carbon nanometer tubes; meanwhile, ultrasonic dispersion can be made. If the applied electric field is direct current field, the electric field is applied to the outer side of a vessel of the suspending liquid of the charged carbon nanometer tubes, and the voltage is within 25V to 1000V. If the applied electric field is alternating-current field, the electric field is applied to the inner side of the vessel of the suspending liquid of the charged carbon nanometer tubes, the voltage is within 25V to 1000V, and the frequency is within 45Hz to 500Hz. The present invention can remarkably improve the dispersivity of the carbon nanometer tubes in the suspending liquid.

Description

Electric Field Assisted Dispersion Method of Carbon Nanotubes in Liquid Medium

Technical field:

The electric field assisted dispersion method of carbon nanotubes in a liquid medium belongs to the technical field of improving the dispersibility of carbon nanotubes, and is applied in the fields of carbon nanotube purification, screening, manipulation, composite material modification and the like.

Background technique:

Carbon nanotubes (CNTs) have been widely used in the fields of material science and nanotechnology because of their unique structure and excellent physical and mechanical properties since they were first discovered by Japanese scholar Iijima in 1991. However, the CNTs prepared by common methods (such as chemical vapor deposition) are mostly intertwined and agglomerated. For important applications such as composite material modification, it is necessary to obtain good dispersion of CNTs in the matrix material. Therefore, it is first necessary to disperse the intertwined aggregated CNTs in a relevant medium, which is usually a liquid. Currently, there are two main methods for dispersing CNTs: (1) physical methods, such as ball milling, mechanical stirring, and ultrasonic oscillation; (2) chemical methods, such as surfactant treatment. These methods are either ineffective, or will cause CNTs to break and reduce the aspect ratio, weakening their advantages for composite material modification. On the other hand, in recent years, significant progress has been made in the research on the orientation, arrangement, screening and purification of CNTs by using electric field. These results show that electric field is an effective means to manipulate CNTs. But there is no report about applying electric field to CNTs suspension to improve the dispersion of CNTs.

Invention content:

The object of the present invention is to provide a method for controlling and promoting the dispersion of CNTs in a liquid medium by electric field assistance. The present inventors have used the method of applying a DC electric field to the CNTs suspension to prepare the electrophoretic deposition film of CNTs, and verified that the electric field has a significant effect on the migration of CNTs in the suspension. Of course, using an electric field to migrate CNTs requires charging the suspended CNTs in the liquid medium, which requires the matching of the liquid medium and proper treatment of the CNTs. During the migration process of CNTs under the same applied electric field, due to the unequal number of charges carried by each single CNT and the uneven mass size, their acceleration and movement speed are different, so the entangled CNTs can be separated to achieve dispersion. . The invention uses the electric field, an effective means for manipulating CNTs, to disperse the entangled CNTs in the suspension, and effectively improves the dispersibility of the CNTs in the liquid medium. At the same time, the electric field dispersion method is combined with the traditional ultrasonic dispersion method to make them work together on the CNTs suspension. Since the agglomerated CNTs are also disturbed by the ultrasonic wave when they are subjected to the electric field, they will break away from the agglomeration more quickly, that is, better results are obtained. Dispersion effect.

The present invention is characterized in that an electric field is applied to the charged carbon nanotube suspension, and ultrasonic dispersion is performed while applying the electric field.

In this method, if the applied electric field is a direct current electric field, it is applied to the outside of the carbon nanotube suspension container, and the voltage ranges from 25V to 1000V. If the applied electric field is an alternating current electric field, it is applied to the inside of the carbon nanotube suspension container, the voltage is 25V-1000V, and the frequency is 45Hz-500Hz.

Experiments prove that the dispersibility of CNTs in the CNTs suspension prepared by the invention is significantly improved.

Description of drawings:

Figure 1 is a schematic diagram of a device in which a DC electric field acts on a CNTs suspension.

Fig. 2 is a schematic diagram of a device in which an AC electric field acts on a CNTs suspension.

Figure 3 shows the dispersed morphology of CNTs in liquid media under different conditions.

Detailed ways:

The method for controlling and promoting the dispersion of CNTs in a liquid medium by the electric field assisted action proposed by the present invention is that under the action of an external electric field (including a DC electric field and an AC electric field), most of the CNTs that are entwined and agglomerated in the liquid medium can be separated, and separated by a single Or a small amount of aggregated form exists.

To apply an electric field to the charged CNTs suspension, a DC electric field (25V-1000V) or an AC electric field (25V-1000V, 45Hz-500Hz) can be applied. When applying a DC electric field to the CNTs suspension, in order to avoid unnecessary electrochemical reactions on the electrodes, the electrodes are placed externally, as shown in Figure 1, 1 and 2 refer to the electrodes; when an AC electric field is applied to the CNTs suspension, the electrodes are also taken Externally, as shown in Figure 2, 1 and 2 refer to electrodes. Ultrasonic treatment can be performed while applying an electric field, and the effect is better.

The preparation of CNTs charged suspension is an existing technology, which can be prepared by matching and selecting liquid media. A preparation method is provided below:

1) The CNTs prepared by propylene catalytic cracking method are soaked in hydrofluoric acid and nitric acid to remove catalyst particles and impurities, and the agglomerated carbon nanotubes are properly dispersed by ball milling to obtain original CNTs; continue to grind CNTs powder Put into concentrated H ₂ SO ₄ concentrated HNO ₃ mixed solution, continue to boil, wash, filter until neutral, and dry to obtain acid-treated CNTs.

2) Add the above-mentioned acid-treated CNTs to an appropriate amount of matching liquid medium (such as deionized water), and ultrasonically treat for 0.5h to obtain a charged suspension of CNTs; or add the above-mentioned original CNTs to a liquid medium (such as deionized water) , and adding a surfactant, sonicated for 0.5 h to obtain a charged suspension of CNTs.

Further describe the present invention with embodiment below in conjunction with accompanying drawing, but the scope of application of the present invention is not limited by these embodiments.

Example 1

Add 0.5 g of the acid-treated CNTs powder into 100 ml of deionized water, and perform ultrasonic treatment for 0.5 h to obtain a CNTs suspension. After applying a 25V DC electric field to the suspension for 4 hours, take the suspension and drop it on the filter paper with a dropper, and observe it under a scanning electron microscope (SEM) after drying. Compared with the comparison experiment (the suspension was left standing for 4 hours without an electric field), the agglomeration is obvious Reduced, the dispersion effect is significantly improved. As shown in Figure 3(a) and 3(b).

Example 2

Add 0.5 g of the acid-treated CNTs powder into 100 ml of deionized water, and perform ultrasonic treatment for 0.5 h to obtain a CNTs suspension. Apply a 25V DC electric field to the suspension, and ultrasonically treat it at the same time. After 0.5h, use a dropper to take the suspension and drop it on the filter paper. After drying, observe it under the SEM, the same as the comparative experiment (suspension without electric field, pure ultrasonic treatment for 0.5h) In comparison, the agglomeration was significantly reduced and the dispersion effect was significantly improved. As shown in Figure 3(c), 3(d).

Example 3

Add 0.5 g of original CNTs powder and sodium dodecylbenzene sulfonate to 100 ml of deionized water in an appropriate amount, and perform ultrasonic treatment for 0.5 h to obtain a CNTs suspension. After applying a 25V DC electric field to the suspension for 4 hours, the suspension was dropped on the filter paper with a dropper, and observed under SEM after drying, the agglomeration was significantly reduced and the dispersion effect was significantly improved.

Example 4

Add 0.5 g of the acid-treated CNTs powder into 100 ml of deionized water, and perform ultrasonic treatment for 0.5 h to obtain a CNTs suspension. After applying a 250V DC electric field to the suspension for 2 hours, the suspension was dropped on filter paper with a dropper, and observed under a scanning electron microscope (SEM) after drying, the agglomeration was significantly reduced and the dispersion effect was significantly improved.

Example 5

Add 0.5 g of the acid-treated CNTs powder into 100 ml of deionized water, and perform ultrasonic treatment for 0.5 h to obtain a CNTs suspension. After applying a 500V DC electric field to the suspension for 1 h, the suspension was dropped on filter paper with a dropper, and observed under a scanning electron microscope (SEM) after drying, the agglomeration was significantly reduced and the dispersion effect was significantly improved.

Example 6

Add 0.5 g of the acid-treated CNTs powder into 100 ml of deionized water, and perform ultrasonic treatment for 0.5 h to obtain a CNTs suspension. After applying a 1000V DC electric field to the suspension for 0.5h, the suspension was dropped on filter paper with a dropper, and observed under a scanning electron microscope (SEM) after drying, the agglomeration was significantly reduced and the dispersion effect was significantly improved.

Example 7

Add 0.5 g of the acid-treated CNTs powder into 100 ml of deionized water, and perform ultrasonic treatment for 0.5 h to obtain a CNTs suspension. After applying a 25V, 45Hz AC electric field to the suspension for 4 hours, the suspension was dropped on filter paper with a dropper, and observed under a scanning electron microscope (SEM) after drying, the agglomeration was significantly reduced and the dispersion effect was significantly improved. As shown in Figure 3(e).

Example 8

Add 0.5 g of the acid-treated CNTs powder into 100 ml of deionized water, and perform ultrasonic treatment for 0.5 h to obtain a CNTs suspension. After applying a 25V, 250Hz AC electric field to the suspension for 4 hours, the suspension was dropped on filter paper with a dropper, and observed under a scanning electron microscope (SEM) after drying, the agglomeration was significantly reduced and the dispersion effect was significantly improved. As shown in Figure 3(f).

Example 9

Add 0.5 g of the acid-treated CNTs powder into 100 ml of deionized water, and perform ultrasonic treatment for 0.5 h to obtain a CNTs suspension. After applying a 25V, 500Hz AC electric field to the suspension for 4 hours, the suspension was dropped on filter paper with a dropper, and observed under a scanning electron microscope (SEM) after drying, the agglomeration was significantly reduced and the dispersion effect was significantly improved. As shown in Figure 3(g).

Example 10

Add 0.5 g of the acid-treated CNTs powder into 100 ml of deionized water, and perform ultrasonic treatment for 0.5 h to obtain a CNTs suspension. After applying a 100V, 45Hz AC electric field to the suspension for 4 hours, the suspension was dropped on filter paper with a dropper, and observed under a scanning electron microscope (SEM) after drying, the agglomeration was significantly reduced and the dispersion effect was significantly improved. As shown in Figure 3(h).

Example 11

Add 0.5 g of the acid-treated CNTs powder into 100 ml of deionized water, and perform ultrasonic treatment for 0.5 h to obtain a CNTs suspension. After applying a 100V, 250Hz AC electric field to the suspension for 4 hours, the suspension was dropped on filter paper with a dropper, and observed under a scanning electron microscope (SEM) after drying, the agglomeration was significantly reduced and the dispersion effect was significantly improved. As shown in Figure 3(i).

Example 12

Add 0.5 g of the acid-treated CNTs powder into 100 ml of deionized water, and perform ultrasonic treatment for 0.5 h to obtain a CNTs suspension. After applying a 250V, 500Hz AC electric field to the suspension for 4 hours, the suspension was dropped on filter paper with a dropper, and observed under a scanning electron microscope (SEM) after drying, the agglomeration was significantly reduced and the dispersion effect was significantly improved. As shown in Figure 3(j).

Example 13

Add 0.5 g of the acid-treated CNTs powder into 100 ml of deionized water, and perform ultrasonic treatment for 0.5 h to obtain a CNTs suspension. After applying an AC electric field of 500V and 500Hz to the suspension for 1 h, the suspension was dropped on filter paper with a dropper, and observed under a scanning electron microscope (SEM) after drying, the agglomeration was significantly reduced and the dispersion effect was significantly improved.

Example 14

Add 0.5 g of the acid-treated CNTs powder into 100 ml of deionized water, and perform ultrasonic treatment for 0.5 h to obtain a CNTs suspension. After applying an AC electric field of 1000V and 500Hz to the suspension for 0.5h, the suspension was dropped on filter paper with a dropper, and observed under a scanning electron microscope (SEM) after drying, the agglomeration was significantly reduced and the dispersion effect was significantly improved.

Claims (3)

1. the auxiliary process for dispersing of CNT in liquid medium of electric field is characterized in that, is that charged carbon nano tube suspension is applied electric field, carries out ultrasonic dispersion when applying electric field.

2. electric field as claimed in claim 1 is assisted the process for dispersing of CNT in liquid medium, it is characterized in that described electric field is a DC electric field, and its voltage swing is 25V～1000V.

3. electric field as claimed in claim 1 is assisted the process for dispersing of CNT in liquid medium, it is characterized in that described electric field is an AC field, and its voltage swing is 25V～1000V, and frequency is 45Hz～500Hz.

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