Observation of high thermionic field emission current density from spun carbon fibers fabricated from multiwall carbon nanotubes

The spun carbon fibers were fabricated from multi-walled carbon nanotubes by a drawing and twisting method. The thermionic field emission behavior of the carbon fibers was investigated as a function of applied heating power PH and field emission voltage VF. The thermal field emission turn-on voltage and threshold voltage are found at electric field E = 2.6 V/μm and E = 3.0 V/μm, respectively. It is found that the emission current density, dominated by the field emission mechanism, reached up to J0 = 1.3 A/cm2 (PH = 0 W) and J = 3 A/cm2 (PH = 2.0 W) at an emission field of E = 5.0 V/μm. The lifetime with respect to heating power PH, exhibiting about 45 h continuous luminescence under a constant PH = 0.8 W, was investigated in the spun carbon fibers. Our results indicate that high-strength carbon fibers show good performance as a thermionic field emission source.