Highly Versatile Carbon-Nanotube(CNTs) for Different
Spaceflight Applications
Introduction and Specification of CNT
Nanotechnology is
the emerging field of science, which deals with Nanoparticles and their
production. CNTs are Nanoparticles with a size range of 1-100 nm (ISO/TS 27687,
2008), with unique electrical, thermal, mechanical and vibrational properties,
having a wide range of applications in the fields of electronics, computers,
aerospace and other industries. Humans get exposed to high concentrations of
these particles during the manufacturing process and usage of nano based
products. CNTs are a form of carbon with a cylindrical shape and were first
observed by Morinobu
Endo at the beginning of the 1970s, Shinshu University, Japan and later Sumio
Iijima, Japanese physicist found Carbon Nanotube in 1991 at Nagoya University, Japan. The soot was produced by the arc-discharge
synthesis of fullerenes. These tubes are made up of thick sheets of carbon
called graphene, which were rolled up to form a seam less cylinder. On the
basis of number of tubes present, the CNTs are classified as Single walled
(SWCNTs), Double walled (DWCNTs) and Multiwalled (MWCNTs) carbon nanotubes.
CNTs made up of
pure carbon are proving to be highly versatile for all types of spaceflight
applications. In the most recent application of the carbon-nanotube coating,
optical engineer John Hagopian, a contractor at NASA’s Goddard Space Flight
Center in Greenbelt, Maryland, and Goddard scientist Lucy Lim have grown an
array of miniscule, button-shaped bumps of multi-walled nanotubes on a silicon
wafer.
The dots, which
measure only 100 microns in diameter roughly the size of a human hair would
serve as the “ammunition” source for a mini electron probe. This type of
instrument analyzes the chemical properties of rocks and soil on airless
bodies, like the Moon or an asteroid.
The Nanotech-Sized Electron Gun
Key instrument, of
course, are the carbon nanotubes, which are excellent electron emitters.
Discovered in 1991, these structures also exhibit an array of useful
electronic, magnetic and mechanical properties.
To create these
highly versatile structures, technicians place a silicon wafer or some other
substrate inside a furnace. As the oven heats, they bathe the substrate with a
carbon feedstock gas to produce the thin coating of nearly invisible hair-like
structures.
For the electron
emitter, Hagopian and Lim using this technique grew tiny, circular dots of
carbon nanotubes in a grid pattern that Goddard’s detector branch fashioned
using photolithography. Positioned above and below the lattice of dots are
silicon wires or traces and a grid that produce two different voltages, these
voltages create an electrical field that activates the release of electrons
contained within the carbon-nanotube bumps or forests.
Summary
In the experiment investigation, it is proven that, carbon-nanotube coatings prove to be highly
effective at absorbing 99.8 percent of the light that strikes them and is the
reason why they appear black. When light penetrates the nanotube forest, tiny
gaps between the tubes prevent the light from bouncing. However, these gaps
don’t absorb the light. The light’s electric field excites electrons in the
carbon nanotubes, turning light to heat and effectively absorbing it.
Hagopian, Scientist at NASA and he is working on growing
intricately patterned nanotubes onto a component that changes the pattern of
light that has diffracted off the edges of telescope structures using coronagraphic masks, which blocks starlight. For Researchers, the NASA’s
Small Business Innovative Research Program has funded the effort.
Rai University, Ahmedabad
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