IrC
International Hazard
Posts: 2710
Registered: 7-3-2005
Location: Eureka
Member Is Offline
Mood: Discovering
|
|
Pyrolytic Carbon
I have been trying to understand why only certain forms of carbon exhibit diamagnetism strong enough to float above my N52 magnets. Notably my
Pyrolytic Carbon, while graphene and other forms (allotropes) do not appear to float above the magnets (or at least the effect is too weak for me to
see).
https://en.wikipedia.org/wiki/Graphene
https://en.wikipedia.org/wiki/Pyrolytic_carbon
Taking a couple quoted portions of this page:
"Pyrolytic carbon is a material similar to graphite, but with some covalent bonding between its graphene sheets as a result of imperfections in its
production."
"Pyrolytic carbon samples usually have a single cleavage plane, similar to mica, because the graphene sheets crystallize in a planar order, as opposed
to graphite, which forms microscopic randomly oriented zones. Because of this, pyrolytic carbon exhibits several unusual anisotropic properties. It is
more thermally conductive along the cleavage plane than graphite, making it one of the best planar thermal conductors available."
What I am looking for is insight into the reason why Pyrolytic Carbon so strongly levitates as opposed to other forms of carbon and so far (to me at
least) it appears the focus needs to be on the subject of covalent bonding. Yet considering the subject of Network Covalent Solids only diamond and
graphite are mentioned, neither of which appear to want to float above a magnet (as far as I can tell).
http://chemwiki.ucdavis.edu/Physical_Chemistry/Physical_Prop...
Looking at "Pyrolytic carbon is a material similar to graphite, but with some covalent bonding between its graphene sheets as a result of
imperfections in its production", I assume they mean Pyrolytic Carbon consists of sheets of graphene. Yet graphene is not so diamagnetic leading me to
conclude it is the covalent bonding that should be considered in understanding the very strong diamagnetism.
Does anyone having a greater understanding in this area wish to provide more insight?
"Science is the belief in the ignorance of the experts" Richard Feynman
|
|
|
aga
Forum Drunkard
Posts: 7030
Registered: 25-3-2014
Member Is Offline
|
|
How did you make your Pyrolytic carbon ?
Perhaps it's a quantum effect ?
Seems perfectly feasible in the agaspace model of matter.
[Edited on 1-8-2015 by aga]
|
|
|
IrC
International Hazard
Posts: 2710
Registered: 7-3-2005
Location: Eureka
Member Is Offline
Mood: Discovering
|
|
I bought it although I am thinking of doing some experiments making it. I have a graphite crucible that sits new unused in a big box. Over 70 pounds
weight and far too large for anything I can ever think to use it for. Been sitting for years must be time to do something with it. If I cut the top
foot of it off I would still have a larger crucible than I would ever need anyway and that would give me 20 or 30 pounds to experiment with. I was
thinking I could shape two pieces for electrodes to make a carbon arc setup to generate high temperatures since the walls are 5 or 6 inches thick at
the top (the thinnest part of the crucible). I just don't have a lot of room or time to do things like making my own. Also I would need to study the
subject of manufacturing Pyrolytic Carbon. Think I'll go searching for patents to study.
So far the only references I can find involve starting with hydrocarbons not graphite, but hopefully a method exists to start with pure graphite since
I have plenty of that on hand.
"Science is the belief in the ignorance of the experts" Richard Feynman
|
|
|
battoussai114
Hazard to Others
Posts: 235
Registered: 18-2-2015
Member Is Offline
Mood: Not bad.... Not bad.
|
|
How familiar are you with molecular orbital theory? I remember having the magnetic behavior of different materials explained to me with the said
theory in mind during some inorganic chemistry lectures last year. I don't have my notebook with me now and I won't risk making a fool of myself by
getting it wrong, but tomorrow I'll see if I manage to post my notes here.
|
|
|
Chiral Case
Harmless
Posts: 3
Registered: 18-6-2015
Location: Netherlands
Member Is Offline
Mood: No Mood
|
|
Pyrolytic graphite has a roughly equal diamagnetic susceptibility compared to natural graphite:
http://www.rrfisica.cat/rrfisica/m_madruenyo_001/DBFischbach...
The main difference between natural and pyrolytic graphite is crystal size; natural graphite single crystals are usually smaller than a square mm,
whereas pyolytic graphite can be several square centimeters.
Why does that matter? I guess that's because graphite is highly anisotropic; it's only strongly diamagnetic perpendicular to the crystal plane.
|
|
|
IrC
International Hazard
Posts: 2710
Registered: 7-3-2005
Location: Eureka
Member Is Offline
Mood: Discovering
|
|
I can take a 25mm square 1mm thick sheet of Pyrolytic Carbon and float it a few mm above N48 to N52 magnets, whereas if the same size sheet of
graphite floats I sure cannot see it.
http://www.scitoyscatalog.com/category/M.html
You can buy the kit of 4 magnets and Pyrolytic Carbon square for about $35 here if you wish to see the effect.
Yet another fact I had not read before was on the wiki page:
"A recent discovery in Japan shows that pyrolytic carbon can respond to laser light or sufficiently powerful natural sunlight by spinning or moving in
the direction of the field gradient.[2] The carbon's magnetic susceptibility changes upon illumination, leading to an unbalanced magnetization of the
material and thus a sideways force."
This point "carbon's magnetic susceptibility changes upon illumination" I find very interesting. Many odd properties stem from this material and being
so out of the normal experience we have in life I tend to agree with Aga that some type of quantum effect being exhibited on a macroscopic level is at
play here.
I can take a 25mm square 1mm thick sheet of Pyrolytic Carbon and float it a few mm above N48 to N52 magnets, whereas if the same size sheet of
graphite floats I sure cannot see it.
http://www.scitoyscatalog.com/category/M.html
You can buy the kit of 4 magnets and Pyrolytic Carbon square for about $35 here if you wish to see the effect.
Yet another fact I had not read before was on the wiki page:
"A recent discovery in Japan shows that pyrolytic carbon can respond to laser light or sufficiently powerful natural sunlight by spinning or moving in
the direction of the field gradient.[2] The carbon's magnetic susceptibility changes upon illumination, leading to an unbalanced magnetization of the
material and thus a sideways force."
This point "carbon's magnetic susceptibility changes upon illumination" I find very interesting. Many odd properties stem from this material and being
so out of the normal experience we have in life I tend to agree with Aga that some type of quantum effect being exhibited on a macroscopic level is at
play here.
* However this does not mean I believe in 'the agaspace model of matter', I'm not even sure what that is.
Perhaps he can clarify.
"Science is the belief in the ignorance of the experts" Richard Feynman
|
|
|
battoussai114
Hazard to Others
Posts: 235
Registered: 18-2-2015
Member Is Offline
Mood: Not bad.... Not bad.
|
|
The laser one I'd guess relates to phosphorescence as predicted by the Batou Model of Photon Induced Spin Change.... Meaning that just like
phosphorescent materials the carbon is probably absorbing photons and getting electrons locked in an excited state with its spin inverted, maybe the
effect is big enough in the pyrolitic carbon as to induce noticeable changes in magnetic domains due to changes in several valence electrons.
|
|
|
Sulaiman
International Hazard
Posts: 3558
Registered: 8-2-2015
Location: 3rd rock from the sun
Member Is Offline
|
|
Graphite foil is much cheaper than pyrolytic graphite
and it levitates almost as well.
e.g. I use this http://www.ebay.co.uk/itm/Graphite-Foil-Gland-Packing-for-la...
|
|
|
IrC
International Hazard
Posts: 2710
Registered: 7-3-2005
Location: Eureka
Member Is Offline
Mood: Discovering
|
|
Never considered that before, I found the following link (better for me since mail is so expensive from England).
http://www.ebay.com/itm/99-5-Pure-Graphite-Flexible-Foil-She...
Still while you say both forms have the same diamagnetism I have to wonder why my 25x25x1mm squares of graphite do not float like the same weight
square of Pyrolytic Carbon. Going to get some of this graphite foil since it is so light maybe it will even do better.
"Science is the belief in the ignorance of the experts" Richard Feynman
|
|
|
Sulaiman
International Hazard
Posts: 3558
Registered: 8-2-2015
Location: 3rd rock from the sun
Member Is Offline
|
|
the nice thing with graphite foil, apart from the obvious cost saving,
is that with a sharp knife you can cut various shapes,
which work better or worse.
From memory, an X shape aligns over the joins in the magnets and was the highest floating shape that I made.
If is not quite as high floating as pyrolytic graphite, but almost the same,
small thin pieces levitate best,
so the answer to your question is; 1mm is too thick.
(no, I do not kow the math !)
P.S.
putting a steel plate on the bottom of the magnets improves lift,
putting more than one layer of magnets improves lift ....
and of course, bigger N numbers work better.
I think that my best are 10mm N50 cubes.
P.P.S. anyone managed to keep large NdFeB magnets chip-free ? 
[Edited on 2-8-2015 by Sulaiman]
|
|
|
j_sum1
Administrator
Posts: 6229
Registered: 4-10-2014
Location: Unmoved
Member Is Online
Mood: Organised
|
|
Quote: Originally posted by battoussai114  | | How familiar are you with molecular orbital theory? I remember having the magnetic behavior of different materials explained to me with the said
theory in mind during some inorganic chemistry lectures last year. I don't have my notebook with me now and I won't risk making a fool of myself by
getting it wrong, but tomorrow I'll see if I manage to post my notes here. |
If anyone is interested, here is a series of youtube tutorials on molecular orbital theory. Part VI deals with paramagnetism and diamagnetism. I
haven't watched them all but they seem to be of above average quality as far as explanation goes.
Part I
Part II
Part III
Part IV
Part V
Part VI
|
|
|
unionised
International Hazard
Posts: 5104
Registered: 1-11-2003
Location: UK
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by IrC |
Still while you say both forms have the same diamagnetism I have to wonder why my 25x25x1mm squares of graphite do not float like the same weight
square of Pyrolytic Carbon.
|
Chiral case pointed out that graphite is only strongly diamagnetic in one direction (with respect to the crystal axis).
If you got lots of squares of pyrolytic graphite and stuck them together to make a cube, then cut a slice off that like a layer cake perpendicular to
all the PG sheets the resulting sheet wouldn't levitate.
The arrangement of crystals in the graphite sheet is pretty much random so roughly 1 in 3 is contributing the large diamagnetism but 2 in 3 are only
contributing weight.
|
|
|
Sulaiman
International Hazard
Posts: 3558
Registered: 8-2-2015
Location: 3rd rock from the sun
Member Is Offline
|
|
I believe that the graphite sheet is rolled flat/thin in several stages,
could the graphite sheet have more than random alignment ?
|
|
|
Oscilllator
National Hazard
Posts: 659
Registered: 8-10-2012
Location: The aqueous layer
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by unionised |
The arrangement of crystals in the graphite sheet is pretty much random so roughly 1 in 3 is contributing the large diamagnetism but 2 in 3 are only
contributing weight. |
I'm not well versed in the ways of magnetism, but if 1 in 3 crystals produce an upwards force, wouldn't about 1 in 3 produce a force downwards in
addition to their weight, completely negating any upwards force?
To me this sounds like when iron is apparently unmagnetised the reality is that lots of tiny grains in the iron have random orientations and so the
net result is the material is only paramagnetic, not ferromagnetic.
|
|
|
battoussai114
Hazard to Others
Posts: 235
Registered: 18-2-2015
Member Is Offline
Mood: Not bad.... Not bad.
|
|
Since magnetism is the topic, here's 10 minutes worth of a decent explanation on these guys:
https://www.youtube.com/watch?v=hFAOXdXZ5TM
https://www.youtube.com/watch?v=1TKSfAkWWN0
These are from infotainment channels and as such don't go much into fancy equations and stuff, but it gets anyone interested at least some info on the
subject.
| Quote: Originally posted by Oscilllator | | Quote: Originally posted by unionised |
To me this sounds like when iron is apparently unmagnetised the reality is that lots of tiny grains in the iron have random orientations and so the
net result is the material is only paramagnetic, not ferromagnetic. |
That's about it. What makes iron ferromagnetic is that its magnetic domains are easily changed to match the external magnetic field and once they're
aligned there will be a non-negligible magnetic moment and unless the domains are forced back into a random state by heat they basically stay like
that acting like a magnet.
I remember taking a small course on nanomaterials and one of the points they made on how these materials cold allow innovation on several fields was
how easy it was to get nanoparticles to magnetize due to that fact that bellow a certain cluster size they tend to have a single domain and as such
are really easy to be changed in order to get it pointing to the external field.
|
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
