I would like to know if anyone can enlighten me on the significance of this research for possible use of graphene as material in aviation. Or is it still to earlier to tell anything about the possible usefulness of this material graphene. From what I heard on the radio tonight it could make aircraft allot lighter, but is there also a catch to this?
KELPkid From United States of America, joined Nov 2005, 6474 posts, RR: 3
Reply 1, posted (4 years 4 months 3 weeks 5 days 17 hours ago) and read 9121 times:
Since the arcticle you linked mentioned that it is transparent, maybe Airbus could use it to make the invisible plane that their engineering think tank proposed? Although, the conents of the plane would be most assuredly visible It would make debugging fuel system and hydraulic problems easy for the pilots...
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
DocLightning From United States of America, joined Nov 2005, 20798 posts, RR: 60
Reply 2, posted (4 years 4 months 3 weeks 5 days 15 hours ago) and read 9081 times:
Quoting KELPkid (Reply 1): Since the arcticle you linked mentioned that it is transparent,
Not so much, actually.
Yes, a single sheet of graphene is transparent but graphene is really the same thing as graphite. The difference is that the sheets of graphene in graphite are very small and irregular in outline. Because there is no overriding covalent bonding between the sheets, graphite loses a lot of strength, especially when handling shear forces Graphene is simply a single layer of graphite made arbitrarily large and entirely covalently linked.
Now, in atomic structure, the electrons in a given atom are usually at "ground state," which means that they will fill the lowest-energy unoccupied orbital. In low atomic number elements, including carbon (#6), that means that generally only orbital shells 1 and 2 are filled with electrons. Now, those low-level orbitals are extremely low-energy. It takes a lot of energy to kick the electrons in a carbon atom up to the next orbital shell (for example from a 2p orbital to a 3s orbital). So if I fire a sufficiently strong photon at a carbon atom, it will absorb it as the electron it's hit jumps up...and then re-emit it (usually as a different wavelength) an instant later when the electron falls back down. When carbon forms its diamond allotrope, all the orbitals are hybridized in the tetrahedral 2sp3 orbital configuration and it takes a very high-energy (short-wavelength) photon to kick a photon to a different orbital.
Graphite has an interesting property. It is made up of a bunch of sp2-hybridized carbons that are all double-bonded to adjacent carbon atoms. Because the double bond that connects the carbon atoms involves the remaining p orbital that is perpendicular to the plane of the carbon nuclei, electrons can actually freely move around from one bond to another, which means that they become "delocalized." The electron orbitals from one carbon to the next start to overlap in a way that they can't in the sp3-hybridized diamond allotrope and so the overall number of energy levels available to a given electron is very large. Thus, graphene will absorb photons of a very wide range of wavelengths (and remember, wavelength of a photon is inversely proportional to its energy). This is precisely why graphite is black; it absorbs all visible photons. Oh, and it re-emits those photons as infra-red (heat).
A single sheet of graphene is thin enough that it can't catch every photon that passes through. But to build an airplane from graphene, you will need many more layers than that. And that will make a black, essentially opaque material that will be absolutely BRUTAL during a ground stop at, say, GRU.
HaveBlue From United States of America, joined Jan 2004, 2141 posts, RR: 1
Reply 4, posted (4 years 4 months 3 weeks 5 days 12 hours ago) and read 9029 times:
DocLightning that was an amazing, if hard to read fast, description... thank you! I had to re read it and I won't pretend to understand everything you said but I got the overall idea of it and thanks for the detailed explanation. Very interesting.
DocLightning From United States of America, joined Nov 2005, 20798 posts, RR: 60
Reply 5, posted (4 years 4 months 3 weeks 5 days 8 hours ago) and read 8987 times:
Consider this diagram:
This is a benzene molecule, which is basically the smallest unit of graphite that you can have. It is what is called an aromatic ring. As you can see, there are six carbons in a coplanar hexagonal arrangement. The left figure shows the Lewis structure of the ring. Notice how half of the carbons are double-bonded to each-other and half are single-bonded.
The right figure shows the actual arrangement of the orbitals in the double bonds. The orbitals that form the second bond are called pi orbitals and each contains one electron. In reality, the electrons can travel freely around the ring. The double bonds shown in the left figure don't actually exist. What actually happens is that there is one-and-a-half bonds between each carbon and its neighbor, and the electrons are delocalized, traveling freely from one pi orbital to the next.
What this means is that in the following figure the two structures are one and the same; they are not rotations of each-other. If you were to replace two adjacent hydrogen atoms on the ring with tritium, there would be simultaneously a single and double bond between those two carbons. When this happens, the two different figures are called "resonance forms" and they are both theoretical concepts. The reality is that there are 1.5 bonds between each carbon.
And so this is the result:
OK, but I'm talking about benzene. What does this have to do with graphite?
Well, graphite is a bunch of benzene rings that are all linked together, like this:
Never mind the vertical bonds. They represent weak interactions between adjacent sheets of graphite. But this illustrates how a single electron could quickly travel from end of the sheet to the other. But only in the plane of the sheet. Current cannot cross through the sheet because it would then have to pass through a region of zero electron density and that is not allowed.
parapente From United Kingdom, joined Mar 2006, 1729 posts, RR: 10
Reply 6, posted (4 years 4 months 3 weeks 5 days 6 hours ago) and read 8950 times:
May I add my thanks Doc,
As a general point the whole "Graphene" and indeed "Nanotubes" development gives us a glimpse of the future - perhaps 20-30 years on in commercial terms.The possibilities are wide.Electronics/super conductivity and structures as stated.But also (I understand) as high density energy Capacitors. As such these types of "nano" developments will open up phenominal horizons one day.
As was once stated."the stone age did not end 'cos they ran out of stones".Nor will the the fossil energy age end 'cos they ran out of it (note Global Warming etc). It looks like it will be replaced by a new age of efficiency in around 20 years time. I also note there is an ongoing revolution in the efficiency of solar panels as well.
The industrial revolution as we have known it for the past 150 years is coming to and end.It has served us well - but the end, I believe, is (as they say!) neigh!
AKiss20 From United States of America, joined Sep 2007, 658 posts, RR: 5
Reply 9, posted (4 years 4 months 3 weeks 4 days 15 hours ago) and read 8760 times:
As I mentioned before with carbon nanotubes, I can see graphene as being a possible use in lightning strike compatibility. Current composites are strong insulators and as such provide no path for lightning to travel through the fuse and exit. Boeing had to add quite a bit of weight in metal to the 787 fuse to provide a conductive path iirc. Both carbon nanotubes (which can be impregnated in the composite) or graphene (which could be added as a layer to the composite "sandwhich") could be use as ultra-light weight conductive paths for the entire fuse.
Change will not come if we wait for some other person or some other time. We are the ones we've been waiting for. We are