Naked Science Forum

Non Life Sciences => Technology => Topic started by: Expectant_Philosopher on 30/09/2014 19:06:14

Title: Can we use magnetic channeling to form continuous graphene tubing?
Post by: Expectant_Philosopher on 30/09/2014 19:06:14

Lasers produce a magnetic channel, could we use chemical vapor deposition of graphene within the magnetic channel created by a laser to form a continuous tubular ribbon?

Title: Re: Can we use magnetic channeling to form continuous graphene tubing?
Post by: evan_au on 01/10/2014 03:47:08

I'd never say "never", but:

• Chemical Vapour Deposition (CVD) usually has a solid substrate (with matching crystal lattice) onto which to deposit a layer of the substance in the vapour phase.
  
• The channel formed by passing a laser through the air does not provide a stable, crystal lattice onto which to grow a perfectly crystalline graphene tube (or carbon nanotube, which is effectively the same thing)
  
• Graphene tends to fold up into a compact shape as soon as it forms, so some sort of substrate or spool with tension is needed to keep it in a useablel shape.
  
• Carbon is not ferromagnetic, so it would have trouble aligning with a magnetic field

Technology in this area is advancing rapidly. CVD on nickel and copper substrates is one current technique. See: http://en.wikipedia.org/wiki/Graphene#Exfoliation

Title: Re: Can we use magnetic channeling to form continuous graphene tubing?
Post by: Expectant_Philosopher on 01/10/2014 22:09:35

i was thinking to use lasers to manipulate graphene atoms shaping them to form the seed pattern for the structure of the tubing.  While carbon may not be ferromagnetic, graphene sheets one atom thick do have reactivity with magnetic fields, acting as a semi-conductor or metal depending on the formulated structure.  I agree with the premise that graphene sheets tend to fold up into tubes, because the graphene wants to find its lowest energy state.  But I was thinking that if we form it in a rolled up state from the start, then it would remain stable in the structure we make.  I think the pattern we initially set for the graphene, we engineer the pattern to be reactive, and would allow it to be guided and supported by the magnetic field produced by the laser.  The manufacturing process would have an initialization state to set the pattern, then a reactive state to form the tubing, with a mechanical reel to uptake the tubing as it formed. 

Title: Re: Can we use magnetic channeling to form continuous graphene tubing?
Post by: chiralSPO on 01/10/2014 22:58:03

We can already grow carbon nanotubes of many varieties. Many of which are essentially rolled up graphene.

http://en.wikipedia.org/wiki/Carbon_nanotube

Title: Re: Can we use magnetic channeling to form continuous graphene tubing?
Post by: evan_au on 02/10/2014 12:03:08

Quote

I agree with the premise that graphene sheets tend to fold up into tubes

My understanding is that in the absence of tension, graphene tends to fold into very complex and compact random shapes, like a piece of crumpled paper.

This is probably due to the Van Der Waals (http://en.wikipedia.org/wiki/Van_der_Waals_force) forces, that attracts the carbon atoms in the sheet to try and line up as close as possible to another sheet of graphene (graphite is essentially many sheets of graphene lined up with each other).

I assume that a single-walled tube more than a few micrometers across would collapse in a similar way.