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Method for removing amorphous carbon in carbon nanotubes

A technology for removing carbon nanotubes and carbon nanotubes, which is applied in the field of purification of carbon nanotubes or carbon nanofibers, can solve problems such as environmental pollution, loss of carbon nanotubes, and oxidation loss of carbon nanotubes, and achieve the effect of simple operation

Inactive Publication Date: 2013-03-13
CHENGDU ORGANIC CHEM CO LTD CHINESE ACAD OF SCI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

On the one hand, operating at high temperature consumes a lot of energy, on the other hand, carbon nanotubes are also prone to reaction loss at this temperature
Although air oxidation can be carried out at a lower temperature, the oxidation of amorphous carbon is an exothermic process. The oxidation reaction will cause the nearby temperature to rise rapidly, and carbon nanotubes will also be oxidized and lost due to the increase in temperature.
In addition, the hot gas flow generated during the oxidation process will also bring out the dust of carbon nanotubes, which not only causes the loss of carbon nanotubes, but also pollutes the environment
In summary, so far there is no ideal process for removing amorphous carbon from carbon nanotubes

Method used

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  • Method for removing amorphous carbon in carbon nanotubes
  • Method for removing amorphous carbon in carbon nanotubes
  • Method for removing amorphous carbon in carbon nanotubes

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0022] Example 1 Weigh 5g of single-walled carbon nanotube crude product (amorphous carbon content greater than 90%), 110g of analytically pure anhydrous lithium chloride and 90g of potassium chloride, pulverize and mix in a soybean milk machine for 5 minutes, and mix the mixed material Transfer to a stainless steel reaction tube with an inner diameter of 35 mm, a height of 500 mm, and one end closed, and vibrate. The open end of the reaction tube is sealed with a rubber stopper with an air inlet pipe and an air outlet pipe, and nitrogen gas is introduced to remove the air in the reaction pipe. The stainless steel reaction tube was placed in a well-type resistance furnace, and the temperature was raised to 450°C to be constant. After 30 minutes, a molten salt solution was formed. Change the nitrogen gas to pure oxygen, control the flow rate between 10-16L / hr, and ensure that the temperature of the reaction system rises to 480°C at the maximum. After 2 hours of reaction, the re...

Embodiment 2

[0023] Example 2 Weigh 100g of crude multi-walled carbon nanotubes with an outer diameter of less than 8nm, 120g of analytically pure anhydrous lithium chloride, and 80g of potassium chloride, and grind and mix them intermittently in a soybean milk machine for 10 minutes, and operate according to the steps in Example 1. The reaction temperature is kept constant at 480° C., the maximum temperature does not exceed 510° C., and the reaction time is 4 hours. Finally, 89 g of the product was obtained with a yield of 89%. Thermal analysis data showed that the light-off temperature of the obtained small-diameter multi-walled carbon nanotubes was 587°C in air. The results of transmission electron microscopy analysis of the obtained samples were as follows: figure 2 shown.

Embodiment 3

[0024] Example 3 Weigh 50g of single-walled carbon nanotube crude product (amorphous carbon content greater than 90%), 100g of analytically pure anhydrous lithium chloride and 100g of potassium chloride and grind and mix them intermittently in a soybean milk machine for 5 minutes, according to Example 1 Step operation, the reaction temperature is constant at 550°C, the maximum temperature does not exceed 580°C, and the reaction time is 4 hours. Finally, 1.6 g of the product was obtained with a yield of 3.2%. Thermal analysis data showed that the light-off temperature of the obtained single-walled carbon nanotubes in air was 609°C. The transmission electron micrographs of the obtained single-walled carbon nanotubes are as follows: image 3 shown.

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Abstract

The invention discloses a method for removing amorphous carbon in carbon nanotubes, which comprises the following steps: suspending the carbon nanotubes into molten salt solution, and introducing oxygen or air into the molten salt solution. The oxidation reaction of the amorphous carbon and oxygen in the oxygen or the air is performed to generate carbon dioxide at a temperature of between 400 and 600 DEG C, while the oxidation reaction of the carbon nanotubes of crystal structures is almost not performed at the temperature. Because a molten salt solution system has uniform temperature without the phenomenon of local overheating, the carbon nanotubes are prevented from being oxidized because of local high temperature. Simultaneously, because the nanotubes are in the molten salt solution all the time, the carbon nanotubes are not easy to bring out from access environment by air flow so as to reduce the loss of the carbon nanotubes and avoid environmental pollution. After a period of time, the amorphous carbon is oxidized and removed; the molten salt solution blocks after being cooled; molten salt blocks are taken out and put into pure water to dissolve molten salt completely to obtain the carbon nanotubes of which the amorphous carbon is removed through filtration or centrifugal sedimentation.

Description

technical field [0001] The invention belongs to the field of carbon nanomaterial preparation, and is particularly suitable for the purification of carbon nanotubes or nanocarbon fibers. Background technique [0002] No matter the carbon nanotubes prepared by arc method, laser ablation method or catalytic chemical vapor deposition method contain amorphous carbon to varying degrees, especially single-walled carbon nanotubes and double-walled carbon nanotube products, the weight of amorphous carbon The content sometimes reaches more than 98%, generally more than 90%. To obtain carbon nanotubes with higher purity, it is necessary to go through the process of removing amorphous carbon. At present, there are many processes for removing amorphous carbon, such as potassium dichromate-sulfuric acid system, concentrated nitric acid-sulfuric acid system, hydrogen peroxide-sodium hydroxide system and other liquid phase systems, as well as air oxidation, carbon dioxide oxidation, water ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01B31/02
Inventor 瞿美臻林浩强周固民孙静
Owner CHENGDU ORGANIC CHEM CO LTD CHINESE ACAD OF SCI
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