No abstract

Utilizing highly oriented multiwalled carbon nanotube aerogel sheets, we fabricated micrometer-thick freestanding carbon nanotube (CNT) polarizers. Simple winding of nanotube sheets on a U-shaped polyethylene reel enabled rapid and reliable polarizer fabrication, bypassing lithography or chemical etching processes. With the remarkable extinction ratio reaching ∼37 dB in the broad spectral range from 0.1 to 2.0 THz, combined with the extraordinary gravimetric mechanical strength of CNTs, and the dispersionless character of freestanding sheets, the commercialization prospects for our CNT terahertz polarizers appear attractive.

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.

Highly uniform and large-area single-walled carbon-nanotube (SWNT) networks are realized by the dip-coating method, which is based on fundamental fluid-dynamic phenomena such as capillary condensation and surface tension. The changes in the polarity and hydration properties of the substrate affect the morphology of the SWNT networks and result in nonlinear growth of the networks in the repetitive dip-coating process. The density and the thickness of the SWNT networks are controlled by processing variables including number of dip coatings, concentration of SWNT colloidal solution, and withdrawal velocity. The networks have uniform sheet resistances and high optical transmittance in the visible wavelength range.

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.