CN114507029B

CN114507029B - Method for preparing stable carbon nano tube dispersion

Info

Publication number: CN114507029B
Application number: CN202210267436.1A
Authority: CN
Inventors: 芦泽宇; 董晓斌
Original assignee: Southeast University
Current assignee: Southeast University
Priority date: 2022-03-18
Filing date: 2022-03-18
Publication date: 2022-10-14
Anticipated expiration: 2042-03-18
Also published as: CN114507029A

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

Method for preparing stable carbon nano tube dispersion

Technical Field

The invention relates to preparation of a carbon nano tube dispersion, in particular to a preparation method of a stable carbon nano tube dispersion.

Background

Carbon Nanotubes (CNTs) have a special internal structure, have special properties such as light weight, high strength, high heat resistance, high specific surface area and the like, are far superior to other fibers, and are considered as "super fibers" in the future. The carbon nano tube can improve the strength and the toughness of the cement-based composite material, obviously improve the durability of the cement-based composite material, and combine the CNTs with good dispersion with a cement matrix, so that the cement-based composite material can not only be endowed with a plurality of novel functional performances such as electric conduction, heat conduction, electromagnetic shielding, piezoelectricity and the like, but also provide a new development space for a new generation of structural composite materials and functional composite materials. However, the problem that the aqueous dispersion of the carbon nano-tube is poor in dispersion and easy to agglomerate in the basic matrix of the cement is the fundamental reason for restricting the performance of the nano-material for efficiently strengthening the cement-based material.

At present, many scholars at home and abroad carry out related research on the problems of dispersion and secondary agglomeration of the carbon nanotubes, wherein the most common dispersion method adopts a technology of combining a surfactant and ultrasonic dispersion, the method is relatively simple to operate, and the dispersion effect and the stability of the method are insufficient.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a stable carbon nanotube dispersion, which solves the problems of poor dispersion effect and insufficient stability of the existing carbon nanotube dispersion.

The technical scheme is as follows: the preparation method of the stable carbon nanotube dispersion comprises the following steps:

(1) Mixing and stirring the surfactant and the deionized water uniformly;

(2) Adding the carbon nano tube into the mixed solution obtained in the step (1), uniformly stirring and performing ultrasonic dispersion;

(3) 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.

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

And (2) stirring in the step (1) by adopting a magnetic stirrer, wherein the stirring time is 150-180S.

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

And (3) performing water bath dispersion by using an ultrasonic disperser at the temperature of 20-30 ℃ for 30min, wherein the ultrasonic power is 100%.

The temperature of the low-temperature freezing treatment in the step (3) is-15 ℃ to-10 ℃.

And (3) ensuring the dispersibility, wherein the crushed particles obtained in the step (3) are ice-coated particles, and the particle size is less than 0.8mm.

The coating comprises, by weight, 1 part of carbon nanotubes, 1 part of a surfactant and 98 parts of deionized water.

The technical principle is as follows:

the invention combines surfactant, ultrasonic dispersion and freezing and crushing to obtain the slow-release nano particles, the slow-release nano particles are ice-coated nano particles, and are slowly and gradually released along with the gradual melting of ice, so that the problem of agglomeration of instantaneous nano materials in a cement matrix caused by overlarge concentration of the nano materials can be avoided. The solid carrier has a size of a millimeter level, has better dispersibility than nano-sized materials, can ensure that the loaded nano-materials are uniformly dispersed in the cement matrix along with the stirring process, and solves the problem of non-uniform dispersion of the nano-materials in the cement-based materials. In addition, the slow release process of the nano material is in a low-temperature environment, so that the thermal motion of the nano material is reduced, and the secondary agglomeration of the nano material is avoided.

Has the advantages that: the slow-release nano particles can avoid the problem that instantaneous nano materials are agglomerated in a cement matrix due to overlarge concentration, have good dispersion effect and high stability, do not use corrosive concentrated acid to pretreat the carbon nano tubes, do not damage the structures of the carbon nano tubes to a certain degree, and do not generate secondary pollutants such as waste acid, waste water and the like, and have simple process and simple and convenient operation; compared with the aqueous dispersion, the dispersion has good dispersibility and high stability, can effectively avoid the damage to the carbon nano tube and the generation of pollutants such as waste water, waste acid and the like, and has low requirement on the environment.

Drawings

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

Detailed Description

Example 1

The preparation of the stable carbon nanotube dispersoid comprises the following steps of selecting 1 part of carbon nanotube, 1 part of surfactant and 98 parts of deionized water according to the parts by weight.

Adding a surfactant into deionized water, and magnetically stirring for 150-180S, and then adding carbon nanotubes into a solution in which the surfactant is completely dissolved, and magnetically stirring for 150-180S; and carrying out water bath ultrasonic dispersion on the completely stirred carbon nano tube aqueous solution for 30min at the temperature of 20-30 ℃, freezing the ultrasonically dispersed carbon nano tube aqueous dispersion, crushing the completely frozen aqueous dispersion to obtain the carbon nano tube dispersion, wherein the diameter of the carbon nano tube is 20-40 nm, the length of the carbon nano tube is 0.5-15 um, stirring the carbon nano tube dispersion by a magnetic stirrer for 150-180S, the temperature of the low-temperature freezing treatment is-15-10 ℃, the size of the crushed particles is less than 0.8mm, and the crushed particles are ice-coated particles.

Comparative example 1

The preparation of the stable carbon nano tube dispersoid comprises the following components in parts by weight:

1 part of carbon nano tube, 1 part of surfactant and 98 parts of deionized water.

Adding a surfactant into deionized water, and magnetically stirring for 150-180S, and then adding carbon nanotubes into a solution in which the surfactant is completely dissolved, and magnetically stirring for 150-180S; carrying out ultrasonic dispersion on the completely stirred carbon nano tube aqueous solution for 30min; freezing the carbon nano tube aqueous dispersion liquid after ultrasonic dispersion, and crushing the aqueous dispersion liquid into tiny particles with the size less than 1mm after the aqueous dispersion liquid is completely frozen, namely the carbon nano tube solid dispersion.

Example 1 and comparative example 1 the dispersion particle size test was performed on the suspensions after standing for 10 minutes, 30 minutes and 60 minutes in a simulated cement pore solution alkaline environment (PH = 13) at a normal temperature of 20 ℃, and the test results are respectively shown in table 1.

Example 1 and comparative example 1 were left to stand in a simulated alkaline environment (PH = 13) at a room temperature of 20 ℃ for 1 minute, 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, and 60 minutes, and then the suspensions were subjected to uv-vis spectrophotometer tests, and the test results are shown in table 2, respectively.

Table 1 simulates the average particle size and specific surface area of a standing suspension of a cement pore solution in an alkaline environment

Table 2 simulates the UV absorption rate of a standing suspension in an alkaline environment of a cement pore solution

The particle size and specific surface area in the suspensions of example 1 and comparative example 1 were compared for different standing times in table 1. Compared to comparative example 1, the ice particles in example 1 released carbon nanotubes with an average size and specific surface area that was almost half of the carbon nanotubes directly dispersed in water in comparative example 1. This illustrates that the ice particles in example 1 release aggregated sizes of carbon nanotubes that are smaller than the aggregated sizes of carbon nanotubes directly dispersed in water in comparative example 1. The particle size of the agglomerated CNTs should be larger than that of well dispersed CNTs, and thus, the above test results confirm that the ice particles in example 1 release carbon nanotubes with much better dispersion and stability than the carbon nanotubes directly dispersed in water in the comparative example 1 in an alkaline environment simulating a cement pore solution.

The UV absorption in the suspensions of example 1 and comparative example 1 at different standing times are compared in Table 2. Compared with the comparative example 1, the ultraviolet light absorption rate of the carbon nanotubes released by the ice particles in the example 1 is higher than that of the carbon nanotubes directly dispersed in water in the comparative example 1 by 30 to 40 percent. According to lambert-beer's law, the higher uv absorbance indicates a larger surface area of the carbon nanotubes exposed in the suspension, representing a better dispersion of the carbon nanotubes. Thus, the above test results confirm that the carbon nanotubes released from the ice particles in example 1 are much more dispersed and stable in the alkaline environment of the simulated cement pore solution than the carbon nanotubes directly dispersed in water in comparative example 1.

According to the analysis of all the above test results, there are three main reasons for the improvement of the dispersion degree of the carbon nanotubes. First, the micro-scale ice particles are more easily uniformly distributed in the mixture during mechanical stirring than the aqueous dispersion of carbon nanotubes, and thus 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 the 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 alleviating the secondary agglomeration of the carbon nanotubes. Third, the temperature of the suspension of example 1 is much lower than that of the suspension of comparative example 1, and thus the CNTs released from ice move at a slower rate than those directly dispersed in water, thereby reducing the possibility of contact between adjacent CNTs and reducing the rate of agglomeration of CNTs. By these three ways, the dispersibility and stability of example 1 are much better than the carbon nanotubes directly dispersed in water in comparative example 1.

Claims

1. A method for preparing a stable carbon nanotube dispersion, comprising the steps of:

(1) Mixing and stirring the surfactant and the deionized water uniformly;

(3) Freezing the carbon nanotube aqueous dispersion liquid subjected to ultrasonic dispersion, and crushing the carbon nanotube aqueous dispersion liquid after the aqueous dispersion liquid is completely frozen to obtain a carbon nanotube dispersion;

the surfactant in the step (1) is polyvinylpyrrolidone with the N content of 12-13%;

the crushed particles obtained in the step (3) are ice-coated particles, and the particle size is less than 0.8mm;

the temperature of the freezing treatment in the step (3) is-15 ℃ to-10 ℃.

2. The method for preparing the stable carbon nanotube dispersion of claim 1, wherein the stirring in step (1) is performed by a magnetic stirrer for 150-180 s.

3. The method of claim 1, wherein the carbon nanotubes in step (2) have a diameter of 20nm to 40nm and a length of 0.5um to 15um, and the stirring is performed by a magnetic stirrer for 150s to 180s.

4. The method for preparing a stable carbon nanotube dispersion according to claim 1, wherein the step (2) comprises dispersing in a water bath using an ultrasonic disperser at 20-30 ℃ for 30min and with 100% ultrasonic power.

5. The method of claim 1, wherein the carbon nanotubes are added in an amount of 1 part by weight, the surfactant is added in an amount of 1 part by weight, and the deionized water is added in an amount of 98 parts by weight.