Performance of nanotube sheets suggests possible applications
photo-deflectors & switchable invisibility cloaks VIDEO
"Mirage effect from thermally modulated transparent carbon nanotube
sheet" Aliev A et al 2011 Nanotechnology 22 435704
The single-beam mirage effect, also known as photothermal
deflection, is studied using a free-standing, highly aligned carbon
nanotube aerogel sheet as the heat source. The extremely low
thermal capacitance and high heat transfer ability of these
transparent forest-drawn carbon nanotube sheets enables high
frequency modulation of sheet temperature over an enormous
temperature range, thereby providing a sharp, rapidly changing
gradient of refractive index in the surrounding liquid or
gas.
The advantages of temperature modulation using carbon nanotube
sheets are multiple: in inert gases the temperature can reach >
2500 K; the obtained frequency range for photothermal modulation is
~ 100 kHz in gases and over 100 Hz in high refractive index
liquids; and the heat source is transparent for optical and
acoustical waves. Unlike for conventional heat sources for
photothermal deflection, the intensity and phase of the thermally
modulated beam component linearly depends upon the beam-to-sheet
separation over a wide range of distances. This aspect enables
convenient measurements of accurate values for thermal diffusivity
and the temperature dependence of refractive index for both liquids
and gases. The remarkable performance of nanotube sheets suggests
possible applications as photo-deflectors and for switchable
invisibility cloaks, and provides useful insights into their use as
thermoacoustic projectors and sonar. Visibility cloaking is
demonstrated in a liquid. FULL
Abstract
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