Dispersion is one of the important prerequisites for the application of advanced carbon materials, which is particularly important for graphene materials. On the other hand, the maneuverability and processability of the preparation process (such as rotation diagram) require graphene to be dispersed in water or organic solvents.
However, due to coupling, van der Waals forces and high specific surface area, the graphene will be irreversible agglomeration and even rearrangement back to the graphite structure, making the stable dispersion of graphene very difficult. At present, there are many basic problems to be solved in the dispersion of graphene.
I. graphene dispersion is the only way to achieve industrialization
1. Graphene products are close to theoretical; 2. High dispersion provides operability; 3. The device realizes high-quality utilization of graphene
Research progress of graphene industrialization application
As shown above, the industrialization of graphene must solve two basic problems:
a.the preparation technology of graphene, that is, graphene products with close to theoretical properties can be obtained at a reasonable price. However, the performance of graphene industrial products is uneven and far from the theoretical level.
b.the dispersion technology of graphene, that is, a highly dispersed method that does not damage the structure and properties of graphene.
The value of graphene can only be realized commercially if these two issues are effectively addressed.
II. graphene dispersion needs to solve six basic problems
.Challenging graphene dispersion first from the inevitable requirement on the depth of the graphene dispersion, scatter graphene to the monolithic or primary particle state;
.Results from by chemical modification of graphene dispersion low tolerance of this means even conflict; Chemical modification is bound to interfere with or to some extent destroy the integrity of, thereby reducing or losing the excellent properties of intrinsic graphene;
.From graphene itself neither water nor oil-wet structure characteristics; However, it is difficult for common dispersant molecules to form strong physical adsorption with graphene, so the physical means of using surfactant to disperse graphene will also be limited.
.Results from graphene π-πstructure and strong van der Waals force, make graphene reunion extremely easily, and aggregate is difficult to separate again;
.Also stems from the graphene high length to diameter ratio and specific surface area;
. Graphene dispersion is also facing the actual production operational problems. For example, 4% water-based graphene pastes are already paste and do not have fluidity, making it difficult to transfer, disperse and chemically react materials during production.
III. Dispersion methods of graphene: physical dispersion and chemical dispersion.
Iv. Application of graphene dispersion in heavy anticorrosive coatings
Dispersion of graphene is the key technology in the preparation of high performance graphene heavy anticorrosive coatings. Haibin yu's team designed and synthesized a - surfactant with electrical activity and buffer capacity. Graphene can be efficiently dispersed in water and organic solvents by - interaction with dispersants.
The characteristic peak displacement of dispersing agent and graphene in infrared, Raman and ultraviolet was used to prove the existence of π-π interaction between dispersing agent and graphene. Transmission electron microscopy and atomic force microscopy analysis showed that graphene mainly existed in the form of 3-5 nanometer sheets in solution.
Characterization of dispersion modified graphene:
Using TEM effect of the dispersant dispersion of graphene in resin, further characterization can be found that graphene disperses well in resins, no reunion phenomenon and graphene uniform random arrangement in the resin matrix, the results show that the dispersant after processing of graphene can be effectively dispersed in the epoxy resin, polyurethane resin coating resin.
The results showed that graphene could significantly improve the protective properties of the resin matrix. It is worth mentioning that the dispersion state and content of graphene have an important relationship with the overall protective performance of the coating. If the dispersion of graphene is not uniform, graphene will not only not play a good role, but also may form water vapor channels, accelerating the corrosion failure of the coating.
Dispersion is one of the important preconditions for the industrialization of graphene materials. However, few studies on dispersed graphene powders have been reported at present. Graphene, on the other hand, is not expected to exist as a pure powder, even if it is produced, because unstabilized graphene may reaggregate into graphite (flakes). Therefore, current research focuses on the physical or weak chemical conditions to peel off graphite and form a stable graphene dispersion system.
Physical dispersion method has limited dispersing ability, while though chemical dispersion method has strong dispersing ability, it might generally leads to conjugate lamella structure defects. In comparison, non covalent modification of functional group is a good way, based on the interaction, van der Waals force and π-π can be grafted better polymer in the surface of graphene, so that we can prevent producing defects and damage on the surface of the lamella conjugate structure.