Field Emission Performance of Holey Expanded Graphite

Abstract

Expanded graphite (EG) has promising applications in field emission due to its high conductivity, thermal stability and low cost. In this paper, the field emission performance of EG is modulated by introducing hole defects through partial air oxidation. First, EG was prepared by electrochemical intercalation and microwave-assisted expansion methods. Subsequently, EG was heat treated in air at different temperatures to obtain holey expanded graphite (HEG). Finally, bulk HEG cathodes were prepared by the cold pressing method and the effect of holes on the field emission performance was investigated. The results showed that the conductivity and tensile properties of EG were significantly improved after heat treatment. Optimal heat treatment parameters were obtained at 400°C in an air atmosphere. The turn-on field (at 1 mA/cm2) and threshold field (at 10 mA/cm2) were 3.01 V/μm and 3.42 V/μm, respectively, with a maximum current density of 1359.17 mA/cm2 (at 5.83 V/μm) and a maximum field enhancement factor of 2407. The voltage fluctuation is only 1.1% over 24 h at 3 mA @ 440.33 mA/cm2, indicating good emission stability and lifespan.

Keywords: Expanded graphite, Heat treatment, Hole, Field emission