Perparation Graphene By Liquid Direction Exfoliation In A Rotating Packed Bed

The graphene is a unique cellular network with a single atomic layer, which exhibits excellent performance in many areas and become the main research object. In view of the unique properties of graphene, it has been widely used as curved screen, graphene battery and supercapacitor.In this study, different factors effect on the yield and structure of graphenein an internal circulation rotating packed bed (RPB). Futhermore, a new method for controllable large-scale preparation of the high-quality graphene was initially established.The main results of this study as follow:(1) Exfoliated time, loaded liquid, the initial concentration of graphite powder and rotational speed are main influence factors of concentration and number of layers of graphene preparation byliquid direct exfoliation in an internal circulation rotating packed bed. The concentration of graphene increased and then decreased as exfoliated time increased.The rotational speed is a critical factorsin the exfoliated process. The lowest shear rate (104s-1) cannot be reached under a lower rotational speed, while graphene can be broken into small pieces easily, which results in a serious agglomeration and a lower concentration of graphene under a higher rotational speed. The initial concentration of graphite has a positive effect on the number of layers of graphene in a certain concentrarion. The abnormal operation of the system in an internal circulation RPB can be resulted from a more initial concentration of graphite.(2) A lower layers of graphene can be attributed to add the auxiliary exfoliated reagents into N-Methylpyrrolidone (NMP) under Organic solvent system. However, in an aqueous surfactant system, both the exfoliation process and graphene dispersion in water can be enhanced by the existence of sodium dodecyl benzene sulfonate (SDBS).(3) Two methods was used in this study to pretreat graphite:1, thermal expansion method, the advantage of this method is that the layer distance can be increased. And thus the graphite can be exfoliated easier. 2, microwave, the advantage of this method is that the energe consumption is lower.(4) In this study, the mechanism of graphene preparation was interupted. In the exfoliation process, the graphite is mainly affected by the shear force which generated by the rotating packed. The shear force play a role in exfoliating graphite into graphene while the shear force is parallel to thegraphite layers.The shear force play a role in cutting a graphite into two pieces of graphite or bending the graphite while the shearing direction is perpendicular to the graphite layers. Whereas, the shear force play a role in breaking the graphite into small pieces while the shear force meets the graphite in the other direction. Besides the shear force, the graphite is also affected by the viscous force from the suspension. And there are three ways:lifting separation, sliding separation and scroll effect.The scroll effect predominated over the other two ways result from a lower resistence force. In addition, the graphite particle can also be deformed and interlamellar separated by collided between different graphite particles or between graphite and the inner wall.(5) The method of perparation graphene by liquid direct exfoliation in a rotating packed bed was first introduced in this study. The results show that not only the preparation rate of the graphene can be improved, but also the defects of graphene can be avoided in a RPB. Futhermore, this method gives a new aspect for graphene industrialization.