CN114507029B - Method for preparing stable carbon nano tube dispersion - Google Patents

Abstract

The invention discloses a preparation method of a stable carbon nano tube dispersion, which comprises the steps of mixing and stirring a surfactant and deionized water uniformly; adding the carbon nano tube into the mixed solution, uniformly stirring and performing ultrasonic dispersion; freezing the carbon nano tube aqueous dispersion liquid after ultrasonic dispersion, and crushing the carbon nano tube aqueous dispersion liquid after the aqueous dispersion liquid is completely frozen, namely obtaining the carbon nano tube dispersion. The invention effectively avoids the problem of agglomeration of the instantaneous nano-material in the matrix of the cementing material due to overlarge concentration by preparing the slow-release nano-particles, and has good dispersion effect and high stability.

Description

Preparation method of stable carbon nanotube dispersion

technical field

The invention relates to the preparation of carbon nanotube dispersions, in particular to a preparation method of stable carbon nanotube dispersions.

Background technique

Carbon nanotubes (CNTs) possess a special internal structure and have special properties such as light weight, high strength, high heat resistance, and high specific surface area, which are far superior to other fibers and are considered to be the "super fibers" in the future. Carbon nanotubes can improve the strength and toughness of cement-based composites, and significantly improve their durability. Combining well-dispersed CNTs with the cement matrix can not only endow the cement-based composites with many new functional properties such as electrical and thermal conductivity, electromagnetic shielding, and piezoelectricity. , and can also provide a new development space for a new generation of structural composite materials and functional composite materials. However, the problem of poor dispersion and easy agglomeration of carbon nanotube aqueous dispersions in the alkaline cement matrix is the fundamental reason that restricts the efficient enhancement of the performance of cement-based materials by nanomaterials.

At present, many scholars at home and abroad have carried out related research on the dispersion and secondary agglomeration of carbon nanotubes. The most commonly used dispersion method is the combination of surfactant and ultrasonic dispersion. This method is relatively simple to operate, but its dispersion The effect and its stability are insufficient.

SUMMARY OF THE INVENTION

Purpose of the invention: The purpose of the present invention is to provide a stable carbon nanotube dispersion to solve the problems of poor dispersion effect and insufficient stability of the existing carbon nanotube dispersion.

Technical scheme: the preparation method of the stable carbon nanotube dispersion of the present invention comprises the following steps:

(1) Mix and stir the surfactant and deionized water evenly;

(2) adding carbon nanotubes into the mixed solution of step (1), stirring evenly and performing ultrasonic dispersion;

(3) The carbon nanotube aqueous dispersion after ultrasonic dispersion is subjected to freezing treatment, and the aqueous dispersion is completely frozen and then crushed, that is, the carbon nanotube dispersion.

Preferably, in the step (1), the surfactant is polyvinylpyrrolidone with an N content of 12-13%.

In the step (1), a magnetic stirrer is used for stirring, and the stirring time is 150S～180S.

The diameter of the carbon nanotubes in the step (2) is 20nm-40nm, the length is 0.5um-15um, and the magnetic stirrer is stirred for 150S-180S.

The step (3) uses an ultrasonic disperser for water bath dispersion, the temperature is 20°C to 30°C, the time is 30 minutes, and the ultrasonic power is 100%.

The temperature at which the low-temperature freezing treatment is performed in the step (3) is -15°C to -10°C.

To ensure dispersibility, the ice-coated particles obtained by crushing in the step (3) are smaller than 0.8 mm in size.

In parts by weight, 1 part of carbon nanotubes, 1 part of surfactant, and 98 parts of deionized water were added.

Technical principle:

The invention adopts the combination of surfactant, ultrasonic dispersion and freezing and crushing to obtain slow-release nanoparticles. The slow-release nanoparticles are ice-wrapped nanoparticles, which are slowly and gradually released as the ice gradually melts, so as to avoid the instantaneous excessive concentration of nanomaterials. The problem is that it causes agglomeration in the cement matrix. The size of the solid carrier is nearly millimeters, which is more excellent in dispersibility than nano-scale materials. It can ensure that the loaded nano-materials are evenly dispersed in the cement matrix with the stirring process, and solve the problem of uneven dispersion of nano-materials in cement-based materials. In addition, the slow release process of nanomaterials is in a low temperature environment, which reduces the thermal motion of nanomaterials, thereby avoiding secondary agglomeration of nanomaterials.

Beneficial effects: the slow-release nanoparticles of the present invention can avoid the problem of agglomeration in the cement matrix caused by the excessive instantaneous concentration of nanomaterials, have good dispersion effect and high stability, and the present invention does not use corrosive concentrated acid to affect carbon nanotubes. Pretreatment will neither damage the structure of carbon nanotubes to a certain extent nor generate secondary pollutants such as waste acid wastewater, the process is simple, and the operation is simple; It has good dispersibility and high stability, which can effectively avoid damage to carbon nanotubes, generation of waste water, waste acid and other pollutants, and has low environmental requirements.

Description of drawings

Fig. 1 is a process flow diagram of the present invention.

Detailed ways

Example 1

For the preparation of the stable carbon nanotube dispersion, firstly, 1 part of carbon nanotubes, 1 part of surfactant, and 98 parts of deionized water were selected according to the parts by weight.

Take the surfactant and add it into deionized water and stir magnetically for 150S～180S, then take carbon nanotubes and add them into the solution in which the surfactant has been completely dissolved and stir magnetically for 150S～180S; the fully stirred carbon nanotube aqueous solution is ultrasonically dispersed in a water bath for 30min, and the temperature is 20 ° C ~ 30 ° C, the carbon nanotube aqueous dispersion after ultrasonic dispersion is subjected to freezing treatment, and the aqueous dispersion is completely frozen and then broken, that is, carbon nanotube dispersion, the diameter of carbon nanotubes is 20nm ~ 40nm, and the length is 0.5 nm. um～15um, stir with magnetic stirrer for 150S～180S, the temperature of low temperature freezing treatment is -15℃～-10℃, the size of the particles obtained by crushing is less than 0.8mm, and the particles obtained by crushing are ice-coated particles.

Comparative Example 1

The preparation of the stable carbon nanotube dispersion, firstly in parts by weight, includes the following components:

1 part of carbon nanotubes, 1 part of surfactant, 98 parts of deionized water.

Take the surfactant and add it to deionized water and stir magnetically for 150S～180S, then take the carbon nanotubes and add them into the solution in which the surfactant has been completely dissolved and stir magnetically for 150S～180S; ultrasonically disperse the fully stirred carbon nanotube aqueous solution for 30min; The dispersed aqueous carbon nanotube dispersion liquid is subjected to freezing treatment, and after the aqueous dispersion is completely frozen, it is broken into tiny particles with a size of less than 1 mm, that is, a solid dispersion of carbon nanotubes.

Example 1 and Comparative Example 1 were left standing for 10 minutes, 30 minutes and 60 minutes under the simulated cement pore solution alkaline environment (PH=13) at normal temperature 20° C. The suspension was taken to carry out the dispersion particle size test test, and the test results were as follows: Table 1.

Example 1 and Comparative Example 1 were left standing for 1 minute, 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes and 60 minutes under a simulated alkaline environment (PH=13) at room temperature 20°C Visible spectrophotometer test, the test results are shown in Table 2.

Table 1 Average particle size and specific surface area of the static suspension under the alkaline environment of simulated cement pore solution

Table 2 The UV absorbance of the static suspension under the alkaline environment of the simulated cement pore solution

Table 1 compares the particle size and specific surface area in the suspensions of Example 1 and Comparative Example 1 for different standing times. Compared with Comparative Example 1, the average size and specific surface area of the carbon nanotubes released by the ice particles in Example 1 were almost half of those of the carbon nanotubes directly dispersed in water in Comparative Example 1. This indicates that the aggregate size of the carbon nanotubes released by the ice particles in Example 1 is smaller than that of the carbon nanotubes directly dispersed in water in Comparative Example 1. The particle size of the agglomerated CNTs should be larger than that of the well-dispersed CNTs. Therefore, the above test results confirmed the dispersibility and stability of the carbon nanotubes released by the ice particles in Example 1 in the alkaline environment of the simulated cement pore solution. Much better than the carbon nanotubes directly dispersed in water in Comparative Example 1.

Table 2 compares the ultraviolet light absorption rates in the suspensions of Example 1 and Comparative Example 1 for different standing times. Compared with Comparative Example 1, the ultraviolet light absorption rate of the carbon nanotubes released by the ice particles in Example 1 is 30%-40% higher than that of the carbon nanotubes directly dispersed in water in Comparative Example 1. According to the Lambert-Beer law, a higher UV absorption rate indicates a larger surface area of the carbon nanotubes exposed to the suspension, representing better dispersion of the carbon nanotubes. Therefore, the above test results confirm that the carbon nanotubes released by the ice particles in Example 1 have much better dispersibility and stability than the carbon nanotubes directly dispersed in water in Comparative Example 1 in the alkaline environment of the simulated cement pore solution.

According to the analysis of all the test results above, there are three main reasons that lead to the improvement of the dispersion degree of carbon nanotubes. First, compared with the carbon nanotube aqueous dispersion, during the mechanical stirring process, the micro-scale ice particles are more likely to be uniformly distributed in the mixture, so the initial distance between the carbon nanotubes in Example 1 can be increased, which helps To avoid immediate volume agglomeration due to excessive concentration of carbon nanotubes. Secondly, the carbon nanotubes in Example 1 are slowly released during the ice melting process of the ice particles, which is beneficial to alleviate the secondary agglomeration of carbon nanotubes. Third, the temperature of the suspension of Example 1 is much lower than that of the suspension of Comparative Example 1, so the ice-released CNTs move slower than the CNTs directly dispersed in water, thus reducing the possibility of contact between adjacent CNTs , which reduces the agglomeration rate of CNTs. Through these three methods, the dispersibility and stability of Example 1 are much better than those of carbon nanotubes directly dispersed in water in Comparative Example 1.

Claims (5)

1. a preparation method of stable carbon nanotube dispersion, is characterized in that, comprises the steps: (1) Mix and stir the surfactant and deionized water evenly; (2) adding carbon nanotubes into the mixed solution of step (1), stirring evenly and performing ultrasonic dispersion; (3) freezing treatment of the carbon nanotube aqueous dispersion after ultrasonic dispersion, and breaking after the aqueous dispersion is completely frozen, that is, carbon nanotube dispersion; In the step (1), the surfactant is polyvinylpyrrolidone with an N content of 12-13%; What the step (3) crushes is ice-coated particles, and the particle size is less than 0.8 mm; The temperature of the freezing treatment in the step (3) is -15°C to -10°C. 2 . The preparation method of the stable carbon nanotube dispersion according to claim 1 , wherein, in the step (1), a magnetic stirrer is used for stirring, and the stirring time is 150s˜180s. 3 . 3. the preparation method of stable carbon nanotube dispersion according to claim 1, is characterized in that, the diameter of carbon nanotube in described step (2) is 20nm～40nm, and length is 0.5um～15um, and stirring adopts magnetic force Stir with a stirrer, and the stirring time is 150s to 180s. 4. The preparation method of stable carbon nanotube dispersion according to claim 1, wherein the step (2) uses an ultrasonic disperser to carry out water bath dispersion, the temperature is 20 ℃～30 ℃, the time is 30min, the ultrasonic power 100%. 5 . The method for preparing a stable carbon nanotube dispersion according to claim 1 , wherein, in parts by weight, 1 part of carbon nanotubes, 1 part of surfactant, and 98 parts of deionized water are added. 6 .

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