Preparation Of Few Layer Graphene And Its Composites By Plasma Assisted Ball Milling

Graphene is widely used in microelectronics components, energy storage material, multifunctional composites and biomedical materials due to its unique two-dimensional structure and excellent physical chemical properties. Nowadays the preparation methods of graphene contain mechanical exfoliation, SiC epitaxial growth, chemical vapor deposition and chemical oxidation reduction, however graphene sheets prepared by the above methods exist serious drawbacks such as poor electrical conductivity, difficult to be transferred from substrate and mass production. Based on this, this paper aimed at “Preparation of few layer graphene and its composites by plasma assisted ball milling”, synthetically considered carbon source, ball milling time and ball milling medium. In this paper, the performance of the few layer graphene(FLG) composites were also conducted, including GeO2/FLG as anode materials for lithium ion battery, Mg/FLG composites for hydrogen storage and hydrolysis and Fe2O3/FLG as a catalyst for oxygen reduction reaction.Expanded graphite is easier to be exfoliated into FLG nanosheets and chosen as carbon precursor, which is due to that the expanded graphite prepared by annealing at 1000 ℃ possesses porous structure with relatively low content of oxygen and sulfur and relatively large specific surface compared with the purchased expandable graphite. When adding relatively hard WC particle as ball milling medium, Raman 2D peaks of WC/FLG composites shift towards low wave number, which confirms that FLG nanosheets are successfully prepared. TEM results demonstrate that the FLG nanosheets prepared by ball milling for 8 h only contains 6 layers. Different ball milling mediums, including BN, Zn O, Fe2O3, GeO2, WC and Mg2 Si, have insignificantly effects on the morphology of FLG, but have significant influence on the layer number of FLG. Higher Moh’s hardness of ball milling medium has benefit to prepare thin layer graphene. On the other side, when the dielectric constant of ball mill medium is around 8.0, the prepared FLG nanosheets are less than 7 layers.GeO2/FLG composites as lithium ion battery cathode material show high discharge storage capacity being about 1322 mAh/g for the first cycle, 850 mAh/g for the second discharge and remains 400 mAh/g after 70 cycles. Mg/FLG composites possess about 5.5 wt.% reversible hydrogen storage capacity, which is close to the theory hydrogen storage. In addition, the Mg/FLG composites also show great hydrolysis performance, namely hydrolyze completely within 20 min and release 702 m L/g hydrogen gas, and the hydrolysis activation energy is determined to be 50.6 KJ/mol. Mg/FLG samples have excellent hydrolysis properties mainly due to the prepared few layer graphene nanosheets possess numerous defects and active sites. The Fe2O3/FLG composites functioned as a catalyst for oxygen reduction reaction(ORR) with the initial potential of oxygen reduction peak being around at-0.25 V vs. SCE.