ABSTRACT
When a carbon nanotube paste is formulated based on highly functional hyperbranched polymers such as dipentaerythritol hexaacrylate, the volume shrinkage during thermal curing builds up internal stress that generates microcrack patterns on the printed surface. The nanotubes exposed in the cracks emit electrons successfully at such an extremely low electric field as 0.5 V µm( - 1), and reach 25.5 mA cm( - 2) of current density at 2 Vµm( - 1) from an optimized paste concerning mainly the size and spatial uniformity of the crack. In addition to the superior field emission properties with low manufacturing cost, this activation-free technology can provide a minimized nanohazard in the device fabrication process, compared to those conventional activation technologies developing serious nanoflakes by using destructive methods.
ABSTRACT
The multi-stage effect has been revisited through growing carbon nanotube field emitters on single strand carbon fiber with a thickness of 11 µm. A prepared linear electron source exhibits a turn-on field as low as 0.4 V µm(-1) and an extremely high field enhancement factor of 19,300, when compared with those results from reference nanotube emitters grown on flat silicone wafer; 3.0 V µm(-1) and 2500, respectively. In addition, we introduce a novel method to grow nanotubes uniformly around the circumference of carbon fibers by using direct resistive heating on the continuously feeding carbon threads. These results open up not only a new path for synthesizing nanocomposites, but also offer an excellent linear electron source for special applications such as backlight units for liquid crystal displays and multi-array x-ray sources.
Subject(s)
Crystallization/methods , Lighting/instrumentation , Nanotechnology/instrumentation , Nanotubes, Carbon/chemistry , Nanotubes, Carbon/radiation effects , Electromagnetic Fields , Electrons , Equipment Design , Equipment Failure Analysis , Linear Models , Materials Testing , Nanotubes, Carbon/ultrastructure , Particle SizeABSTRACT
This paper describes the fabrication of a backlight unit for liquid crystal display based on printed carbon nanotube field emitters with lateral gate and additional mesh structures. The device architecture has been optimized through field emission characterization and supporting numerical simulation. The emission current depends strongly on the cathode-gate gap, mesh position, and mesh bias. Direct observation of luminous images on a phosphor screen reveals that the electron beams undergo a noticeable shrinkage along the lateral direction with increasing anode bias, which is in good agreement with the simulation results. We suggest and demonstrate a modified structure equipped with double emitter edges leading to approximately 20% improved phosphor efficiency (34.4 lm W(-1)) and luminance (9600 cd m(-2)), compared to those from a single edge structure.
