CN108559392B

CN108559392B - Application of AAO film in morphology characterization of graphene/polymer composite material

Info

Publication number: CN108559392B
Application number: CN201810356306.9A
Authority: CN
Inventors: 高超; 陈琛; 韩燚
Original assignee: Hangzhou Gaoxi Technology Co Ltd
Current assignee: Hangzhou Gaoxi Technology Co Ltd
Priority date: 2018-04-19
Filing date: 2018-04-19
Publication date: 2020-12-08
Anticipated expiration: 2038-04-19
Also published as: CN108559392A

Abstract

The invention discloses an application of an AAO film in the morphology characterization of a graphene/polymer composite material, which comprises the following steps: dissolving the composite material in a good solvent of a polymer, removing most of the polymer through one-step centrifugation, then dripping the polymer on the surface of an Anodic Aluminum Oxide (AAO) membrane, and observing under a Scanning Electron Microscope (SEM), so that the morphology and size information of graphene in the composite material can be obtained. Compared with the traditional method, the method is simple and easy to implement, the unremoved polymer permeates into the pores of the AAO along with the solvent, does not remain on the substrate to influence the observation of the graphene, has high resolution and high contrast, and obtains more accurate size information.

Description

Application of AAO film in morphology characterization of graphene/polymer composite material

Technical Field

The invention belongs to the field of characterization of composite materials, and particularly relates to application of an AAO film in characterization of the morphology of a graphene/polymer composite material.

Background

Graphene is a two-dimensional sheet material composed of honeycomb-shaped carbon atoms and has received worldwide attention since the past. The graphene has attractive mechanical properties (the strength can reach 130GPa, the modulus can reach 1TPa) and electrical properties (the electron mobility can reach 200000 cm)²And (Vs)), thermal performance (4800-5300W/(mk)), so the composite material has a wide application prospect in the field of high-performance composite materials. By introducing the graphene, the mechanical, electrical and thermal properties of the polymer can be effectively improved, and meanwhile, the characteristics of gas barrier, electromagnetic shielding, sterilization, bacteriostasis and the like which are not possessed by the traditional material can be given. Compared with traditional filling reinforcement such as glass fiber, carbon fiber and carbon black, the graphene has lower density and less effective filling amount, thereby showing higher cost performance.

In view of the extremely attractive physical and chemical properties of graphene, how to fully apply the properties becomes a crucial proposition. According to the composite material reinforcement theory, the larger the size of the graphene is, the smaller the defect degree is, the stronger the acting force between the graphene and the matrix is, the stronger the mechanical, electric and heat conducting properties of the obtained composite material are, and otherwise, the composite material is reduced. In the processing process, such as the processes of shearing, ultrasonic treatment, ball milling and the like, the size of the graphene can be reduced by external force, so that the performance of the final composite material is influenced. In addition, due to extremely strong pi-pi interaction and van der waals force among graphene sheets, the graphene is easy to irreversibly stack in the processing process, so that the specific surface area of the final material is greatly reduced, and the application of the graphene in the fields of adsorption, electrochemical energy storage, composite material reinforcement and the like is not facilitated. Therefore, the morphology and size of graphene in the composite material need to be characterized to understand the enhancement effect of graphene.

The most common method for characterizing the morphology of graphene is Scanning Electron Microscope (SEM) observation, in which the morphology of a flat substrate such as a silicon wafer can be observed by depositing a graphene material on the surface, as shown in 104817071a, "a method for sizing graphene materials". However, for graphene/polymer composites, polymers that are difficult to remove completely spontaneously form a film after deposition on a substrate, which interferes with the resolution of graphene when viewed by SEM. Particularly, when covalent grafting is formed between graphene and a polymer, the polymer is coated on the surface of graphene, the edge of graphene is covered on a flat substrate, and the graphene is difficult to observe.

Disclosure of Invention

The invention aims to provide the application of an AAO film in the morphology characterization of a graphene/polymer composite material aiming at the defects of the prior art

The specific operation method comprises the following steps:

dissolving the graphene/polymer composite material in a good solvent of a polymer phase, shaking for dissolving, dripping the solution on the surface of an AAO (anaerobic-anoxic-oxic) membrane, and drying in vacuum; the surface morphology of the AAO film is observed under a Scanning Electron Microscope (SEM).

Further, the dissolving temperature is 20-100 ℃, and the mass ratio of the composite material to the solvent is 1-20: 100.

Further, before the dropping coating, the solution of the graphene/polymer composite material is also subjected to a centrifugal treatment to reduce the polymer content.

Further, the centrifugation speed is not less than 10000 rpm.

Furthermore, the pore diameter of the AAO membrane is 50-500 nm.

According to the invention, the porous property of the AAO membrane is utilized, the graphene dispersion liquid after primary separation from the polymer is deposited on the surface of the AAO, the residual non-separated polymer permeates into a pore channel of the AAO membrane along with the solvent, and the graphene sheet is left on the AAO, so that the appearance of the graphene sheet can be observed. Compared with the traditional method, the method disclosed by the invention has the beneficial effects that on one hand, the influence of the polymer on graphene observation is reduced, the resolution and the accuracy are improved, on the other hand, the repeated centrifugation of the conventional observation method is avoided, the efficiency is greatly improved, and the method has the following beneficial effects:

(1) the operation is simple. In the conventional method, repeated centrifugation operation is required to completely remove the polymer, time and labor are wasted, certain loss of graphene occurs in the process, and the method only needs one-time centrifugation, so that time and labor are saved.

(2) The identification degree is high. Because the polymer can not form a film on the porous substrate, the interference of the polymer on the observation of the graphene is avoided, and the edge of the graphene is suspended above the AAO hole, so that the observation is easier.

(3) Is safe and environment-friendly. Most of solvents of conventional polymers are organic solvents, solvents like PET are phenol-tetrachloroethane mixed solutions, solvents of nylon are formic acid or concentrated sulfuric acid, and a large amount of waste liquid is generated during repeated centrifugation, so that the safety of operators is threatened. The method only needs one-step centrifugation, and is safer and more sanitary.

In conclusion, the morphology of graphene in the polymer can be better observed by adopting an AAO deposition method, and the method has high scientific research value and practicability.

Drawings

FIGS. 1 to 4 are respectively microscopic morphology diagrams of graphene obtained by examples 1 to 4 of the present invention.

Fig. 5 and 6 are the microscopic morphology images of graphene obtained by comparative examples 1 and 2 of the present invention, respectively.

Detailed Description

The method for preparing the graphene-foamed EVA composite material comprises the following steps:

dissolving the graphene/polymer composite material in a good solvent of a polymer phase, shaking for dissolving, dripping the solution on the surface of an AAO (anaerobic-anoxic-oxic) membrane, and drying in vacuum; the surface morphology of the AAO film is observed under a Scanning Electron Microscope (SEM). The dissolving temperature is 20-100 ℃, and the mass ratio of the composite material to the solvent is 1-20: 100. The graphene/polymer composite solution was also centrifuged to reduce the polymer content prior to dispensing. The centrifugal speed is 10000-18000 rpm, and the centrifugal time is 5-30 minutes. The pore diameter of the AAO membrane is 50-500 nm.

A large number of experiments show that the polymer can be fully dissolved at the dissolving temperature of 20-100 ℃, the dissolving speed is too low when the temperature is lower than 20 ℃, even the solvent is solidified, the solvent is obviously volatilized when the temperature is higher than 100 ℃, and the experiment is safe and sanitary. When the mass ratio of the composite material to the solvent is lower than 1:100, the graphene content in the obtained solution is too low because the graphene content in the composite material is generally 0.1-1 wt%, and when the mass ratio is higher than 20:100, the polymer is poorly dissolved, the viscosity of the system is too high, even the polymer is not completely dissolved, and the graphene and the polymer cannot be separated in a centrifugal mode. The centrifugation speed is chosen to be higher than 10000 rpm in order to ensure that the graphene is completely separated from the polymer. The polymer with the AAO aperture being less than 50nm is difficult to permeate into the pore channel and form a film again, so that the graphene observation is influenced, and when the aperture is more than 500nm, the graphene possibly falls into the pore, so that the graphene cannot be observed.

The present invention is described in detail by the following embodiments, which are only used for further illustration of the present invention and should not be construed as limiting the scope of the present invention, and the non-essential changes and modifications made by the person skilled in the art according to the above disclosure are within the scope of the present invention.

Example 1:

taking 1g of graphene/nylon 6 composite slice, dissolving in 30g of 64% formic acid, shaking for dissolving at 60 ℃, centrifuging at 15000 r/min for 10 minutes, pouring out the supernatant, adding 20g of 64% formic acid for redispersion, depositing on the surface of an AAO membrane with the aperture of 200nm, drying in vacuum, and observing under SEM.

The graphene morphology in the graphene/nylon 6 composite slice is obtained through the steps, as shown in fig. 1. It can be seen that the graphene sheets are suspended over the porous AAO substrate, with the edges clearly visible. The surface particulate material may be polymer molecules grafted in situ.

Example 2:

taking 1g of multilayer graphene/nylon 6 composite slice, dissolving in 30g of 64% formic acid, shaking and dissolving at 60 ℃, centrifuging at 15000 r/min for 10 minutes, pouring out supernatant, adding 20g of 64% formic acid for redispersion, depositing on the surface of an AAO membrane with the aperture of 200nm, drying in vacuum, and observing under SEM.

The graphene morphology in the multilayer graphene/nylon 6 composite slice is obtained through the steps, and is shown in fig. 2. It can be seen that the material is thicker overall than in fig. 1, and the layered structure is seen at the edges, being multilayer graphene. The surface has no rough particles, and is smoother.

Example 3:

taking 0.8g of graphene/PET composite slice, dissolving in 25g of phenol/tetrachloroethane (1:1) solution, shaking for dissolving at 40 ℃, centrifuging for 20 minutes at 18000 r/min, pouring out the supernatant, adding 25g of phenol/tetrachloroethane (1:1) solution for redispersion, depositing on the surface of an AAO membrane with the aperture of 200nm, drying in vacuum, and observing under SEM.

The graphene morphology in the graphene/PET composite slice is obtained through the steps, as shown in FIG. 3. It can be seen that the overall morphology is close to that of fig. 1, and is clearly visible.

Example 4:

and (3) dissolving 2g of graphene/PAN composite slice in 20g of dimethylformamide solution, shaking and dissolving at room temperature, centrifuging at 16000 rpm for 20 minutes, pouring out the supernatant, adding 25g of dimethylformamide for redispersion, depositing on the surface of an AAO membrane with the aperture of 200nm, drying in vacuum, and observing under SEM.

The graphene morphology in the graphene/PET composite slice is obtained through the steps, and is shown in FIG. 4. It can be seen that the thickness of graphene is very large and even a layered structure can be seen on the surface, indicating that significant stacking of graphene occurs.

Comparative example 1:

taking 1g of graphene/nylon 6 composite slice, dissolving in 30g of 64% formic acid, shaking for dissolving at 60 ℃, centrifuging at 15000 r/min for 10 minutes, pouring out the supernatant, adding 20g of 64% formic acid for redispersion, depositing on the surface of a silicon wafer, drying in vacuum, and observing under SEM.

The morphology of graphene in the graphene/nylon 6 composite slice is obtained through the steps, as shown in fig. 5. It can be seen that due to the existence of the surface macromolecules, the edge of the graphene cannot be identified at all, and the size information of the graphene cannot be accurately obtained. In addition, the contrast between the background and the sample under SEM observation is low, and the morphological information of graphene cannot be obtained well.

Comparative example 2:

taking 0.8g of graphene/PET composite slice, dissolving in 25g of phenol/tetrachloroethane (1:1) solution, shaking for dissolving at 40 ℃, centrifuging at 18000 r/min for 20 minutes, pouring out the supernatant, adding 25g of phenol/tetrachloroethane (1:1) solution for redispersion, depositing on the surface of a silicon wafer, drying in vacuum, and observing under SEM.

The graphene morphology in the graphene/PET composite slice is obtained through the steps, as shown in FIG. 6. It can be seen that dark areas of the background may be the result of incomplete volatilization of the solvent, while white spots are unremoved polymer particles, and these interference factors all have a serious impact on the observation of the morphology of the graphene.

Claims

1. The application of the AAO film in the morphology characterization of the graphene/polymer composite material is characterized by comprising the following specific steps:

dissolving the graphene/polymer composite material in a good solvent of a polymer phase, oscillating and dissolving, wherein the dissolving temperature is 20-100 ℃, and the mass ratio of the graphene/polymer composite material to the good solvent is 1-20: 100;

centrifuging the solution of the graphene/polymer composite material to reduce the polymer content; wherein the centrifugal speed is not less than 10000 rpm;

dripping the centrifuged solution on the surface of an AAO membrane, and drying in vacuum; observing the surface appearance of the AAO film under a scanning electron microscope; the pore diameter of the AAO membrane is 50-500 nm.