Improvement of Lighting Uniformity and Phosphor Life in Field Emission Lamps Using Carbon Nanocoils

Abstract

The lighting performances and phosphor degradation in field emission lamps (FELs) with two different kinds of cathode materials—multiwalled carbon nanotubes (MWCNTs) and carbon nanocoils (CNCs)—were compared. The MWCNTs and CNCs were selectively synthesized on 304 stainless steel wire substrates dip-coated with nanosized Pd catalysts by controlling the growth temperature in thermal chemical vapor deposition, and the film uniformity can be optimized by adjusting the growth time. FELs were successfully fabricated by assembling these cathode filaments with a glass bulb-type anode. The FEL with the CNC cathode showed much higher lighting uniformity and light-spot density and a lower current at the same voltage than that with the MWCNT cathode filament, and its best luminous efficiency was as high as 75 lm/W at 8 kV. We also found that, for P22, the phosphor degradation can be effectively suppressed by replacing MWCNTs with CNCs in the cathode, due to the much larger total bright spot area and hence much lower current density loading on the anode.

Fabrication and Simulation of Self-Focusing Field Emission X-ray Tubes

“…Additionally, CNCs are more robust than CNTs because the former are much thicker and thus can withstand a higher current density. Owing to their much larger diameter and higher FE site density, CNCs exhibit better long-term current emission stability, current density, FE efficiency, and lifetime than CNTs [18,19], and so they have already found application in FE lighting [38][39][40][41]. Consequently, CNCs are used as the emitter material in the X-ray tube in this work.…”