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Summary form only given. Commercial expandable graphite was heat at 900 °C to get the worm-like graphene nanosheets. Using sulfuric acid and potassium permanganate to oxidize the expanded graphene nanosheet could further minish the thickness of graphene oxide sheet to less than 1nm, and this way to get the graphene was proved to be mass producible (tens of gram). Free-standing graphene oxide paper was filtered out by membrane filter, and then reduced by annealing at 500 °C The reduced graphene paper was found to be a potent field emitter, characterized by turn on field at 2.4V/μm, and current density of 10mA/cm was received at 4.4 V/μm. Plasma was employed to treat the graphene paper and change the orientation of graphene sheets on its surface. After that the orientation of the graphene sheets changed from lateral to vertically aligned, and induce the formation of cone-like nanotips. The change was revealed by Scanning Electron Microscopy (SEM). And the result can also be proved by the hydrophobicity change of after treating. After plasma treatment, the turn-on field and the threshold field of the graphene paper were reduced from 2.4 V/μm to 1.6 V/μm and 4.4 V/μm to 3.0 V/μm respectively. All the result suggests that the optimized graphene paper can serve as a potential field emitter.

Carbon nanotubes (CNTs)/diamond composite were synthesized by microwave-sintering method and the field emission property was studied. The binding energy of two materials become larger and the carbonization of the diamond less, compare to sintering in the common tube furnace. Scanning electron microscopy (SEM) was used to evaluate the morphological and the structural features. The CNTs were well-proportioned dispersed in composite and formed emission tip. The results of field emission showed that the field emission of CNTs/diamond composite was improved, the current density reached 15mA/cm2, compare to sintering in a horizontal tube furnace (0.88mA/ cm2).