Nanotubes

Discussion in 'Chemistry' started by arauca, Jul 17, 2013.

  1. arauca Banned Banned

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    Do Nano tube have polarity ( polar groups attached to carbon atoms )? What are the application of Nanotube ?
     
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  3. KitemanSA Registered Senior Member

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    Which type of nano-tube? There are dozens if not thousands being investigated.
     
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  5. spidergoat Valued Senior Member

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    Applications include high strength composites, bullet proof clothing, and high frequency EM shielding.
     
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  7. arauca Banned Banned

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    Well let me start , how do you attach a hydroxy functionality to a nano tube . To my understanding an basic carbon nanotube is only carbon sort of a Christine arrangement. I have an idea how this is done but to attach an carboy group I do not know how is done , but I have an idea but I am not sure .
     
  8. KitemanSA Registered Senior Member

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    Ok, we've settled on "Carbon" nanotube; but... "Christine arrangement"? "Carboy group"?
     
  9. arauca Banned Banned

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    I meant crystalline arrangement.
     
  10. arauca Banned Banned

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    How do you attach carboxylic groups to a carbon nonotube
     
  11. spidergoat Valued Senior Member

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    Velcro?
     
  12. arauca Banned Banned

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    There is a variety on how to make the nanotube , one of them is carbon ark discharge , were in presence of moisture you attach hydroxil groups, in presence of ammonia you might attach amine goups and so on. then there are process by chemical vapor deposition and so on . I am not familiar how you attach carboxilic groups.
     
  13. arauca Banned Banned

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    Nonotubes produced by carbon arc . any body familiar on how to separate the nontube from amorphous carbon during the electric discharge ?

    Or any body have a free access to find an article ( no abstract I have it ) ACS nano 2011 pages 3943-3953
     
  14. spidergoat Valued Senior Member

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    Have you done a patent search?
     
  15. arauca Banned Banned

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    Yes based on a patent we are traying to duplicate the method to make the nanotube , but the separation of the final product I don't have much confidence
     
  16. arauca Banned Banned

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    The separation is don in several steps: First is to separate nonotube from amorphous carbon . the next step is to separate multiwalled tube , from single walled nonotybes
     
  17. arauca Banned Banned

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    Instead of being a detriment, the waviness may make the nanotube arrays more compliant and therefore useful as thermal interface material for conducting heat away from future high-powered integrated circuits.

    Measurements of nanotube stiffness, which is influenced by a property known as modulus, had suggested that forests of vertically-aligned nanotubes should have a much higher stiffness than what scientists were actually measuring. The reduced effective modulus had been blamed on uneven growth density, and on buckling of the nanotubes under compression.

    However, based on experiments, scanning electron microscope (SEM) imaging and mathematical modeling, the new study found that kinked sections of nanotubes may be the primary mechanism reducing the modulus.

    "We believe that the mechanism making these nanotubes more compliant is a tiny kinkiness in their structure," said Suresh Sitaraman, a professor in the Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. "Although they appear to be perfectly straight, under high magnification we found waviness in the carbon nanotubes that we believe accounts for the difference in what is measured versus what would be expected."

    The research, which was supported by the Defense Advanced Research Projects Agency (DARPA), was published online August 31, 2013, in the journal Carbon. It will appear later in the journal's print edition.

    Carbon nanotubes provide many attractive properties, including high electrical and thermal conductivity, and high strength. Individual carbon nanotubes have a modulus ranging from 100 gigapascals to 1.5 terapascals. Arrays of vertically-aligned carbon nanotubes with a low density would be expected to a have an effective modulus of at least five to 150 gigapascals, Sitaraman said, but scientists have typically measured values that are four orders or magnitude less – between one and 10 megapascals.

    To understand what might be causing this variation, Sitaraman and Ph.D. students Nicholas Ginga and Wei Chen studied forests of carbon nanotubes grown atop a silicon substrate, then covered the tips of the structures with another layer of silicon. They then used sensitive test apparatus – a nanoindenter – to compress samples of the nanotubes and measure their stiffness. Alternately, they also placed samples of the silicon-nanotube sandwiches under tensile stress – pulling them apart instead of compressing them.


    Read more at: http://phys.org/news/2013-10-waviness-carbon-nanotube-forests-stiffness.html#jCp


    What they found was that the effective modulus remained low – as much as 10,000 times less than expected – regardless of whether the nanotube sandwiches were compressed or pulled apart. That suggests growth issues, or buckling, could not fully account for the differences observed.

    To look for potential explanations, the researchers examined the carbon nanotubes using scanning electron microscopes located in Georgia Tech's Institute for Electronics and Nanotechnology facilities. At magnification of 10,000 times, they saw the waviness in sections of the nanotubes.

    "We found very tiny kinks in the carbon nanotubes," said Sitaraman. "Although they appeared to be perfectly straight, there was waviness in them. The more waviness we saw, the lower their stiffness was."

    They also noted that under compression, the nanotubes contact one another, influencing nanotube behavior. These observations were modeled mathematically to help explain what was being seen across the different conditions studied.

    "We took into account the contact between the carbon nanotubes," said Chen. "This allowed us to investigate the extreme conditions under which the deformation of nanotubes is constrained by the presence of neighboring nanotubes in the forest."

    Though the loss of modulus might seem like a problem, it actually may be helpful in thermal management applications, Sitaraman said. The compliance of the nanotubes allows them to connect to a silicon integrated circuit on one side, and be bonded to a copper heat spreader on the other side. The flexibility of the nanotubes allows them to move as the top and bottom structures expand and contract at different rates due to temperature changes.

    "The beauty of the carbon nanotubes is that they act like springs between the silicon chip and the copper heat spreader," said Sitaraman. "They can conduct lots of heat because of good thermal properties, and at the same time, they are supple and compliant."

    Carbon nanotubes have extraordinarily high thermal conductivity, as much as ten times that of copper, making them ideal for drawing heat away from the chips.

    "The demand for heat removal from chips is continuing to increase," said Ginga. "Industry has been looking for new materials and new techniques to add to their toolbox for heat transfer. Different approaches will be needed for different devices, and this provides the industry with a new way to address the challenge."

    Explore further: Densest array of carbon nanotubes grown to date

    More information: Nicholas J. Ginga, Wei Chen and Suresh K. Sitaraman, "Waviness Reduces Effective Modulus of Carbon Nanotube Forests by Several Orders of


    Read more at: http://phys.org/news/2013-10-waviness-carbon-nanotube-forests-stiffness.html#jCp
     
  18. spidergoat Valued Senior Member

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    A commercial enterprise isn't likely to share their proprietary process with you. They don't even share it with anyone who isn't an American citizen.
     
  19. arauca Banned Banned

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    I agree University of Georgia did not help much. .
    As I get to understand the reason the modify the surface by attaching a functional group is to make easier to separate because electrostatic repusion otherwise it is hard to break up the aggregate . I will continue posting perhaps some one might drop something.
     

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