Thursday, April 18, 2019


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.

                                                                                                                

                                                                                    By:-  Prof. Y. A. Darji
                                                                         Rai University, Ahmedabad

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