Fibers of reduced graphene oxide nanoribbons.

Reduced graphene oxide nanoribbon fibers were fabricated by using an electrophoretic self-assembly method without the use of any polymer or surfactant. We report electrical and field emission properties of the fibers as a function of reduction degree. In particular, the thermally annealed fiber showed superior field emission performance with a low potential for field emission (0.7 V µm(-1)) and a giant field emission current density (400 A cm(-2)). Moreover, the fiber maintains a high current level of 300 A cm(-2) corresponding to 1 mA during long-term operation.

Crystal-like growth of a metal oxide/CNT composite fiber with electroplated "seed" from a CNT-dispersed nonaqueous electrolyte.

A fabrication technique is developed for the preparation of metal oxide/CNT composites. An essential feature of the technique lies in the use of nonaqueous electrolyte in place of the usual aqueous electrolyte, which ensures well-dispersed CNTs without surfactants. After a "seed" is formed by electroplating on the anode, the seed is simply pulled up at a certain speed to grow a 1D CNT composite structure. The technique leads to a uniform distribution of metal oxide and a high weight fraction of CNT in the composite structure. Moreover, the conductivity of the composite is much higher than that of the CNT fibers fabricated with polymer.

Enhancement of heating performance of carbon nanotube sheet with granular metal.

A strategy for enhancing the heating performance of freestanding carbon nanotube (CNT) sheet is presented that involves decorating the sheet with granular-type palladium (Pd) particles. When Pd is added to the sheet, the heating efficiency of CNT sheet is increased by a factor of 3.6 (99.9 °C cm(2)/W vs 27.3 °C cm(2)/W with no Pd). Suppression of convective heat transfer loss attributes to the enhanced heat generation efficiency. However, higher heating response of CNT/Pd sheet was observed compared to CNT sheet, hence suggesting that the electron-lattice energy exchange could be additional heating mechanism in the presence of granular-type particles of Pd having a diameter of 10 nm or less. CNT sheet/Pd is quite stable, retaining its initial characteristics even after 300 cycles of on-off voltage pulses and shows fast thermal responses of the heating and cooling rates being 154 and -248 °C/s, respectively.

Better than 10 mA field emission from an isolated structure emitter of a metal oxide/CNT composite.

An isolated structure emitter is presented that can deliver a field emission better than 10 mA, a level that is by far the highest ever reported. A composite of CNT (carbon nanotube) and WO(3) is used to grow the point emitter by a crystal-like growth technique. The head of the grown needle that is the emitter is removed by electric discharge machining (EDM). The EDM treatment not only controls the length of the emitter as desired but also makes the tip of the emitter uniform. The thermal heat due to EDM treatment leads to the formation of a tungsten carbide phase, which results in a 3 orders of magnitude reduction in contact resistance. The point emitter is robust in its stability, as evidenced by its on-time resilience against a severe bias test.