not quite a fluff post, but not quite informative either
November 28th, 2007 by Ψ*ΨAn apology, first–There’s really nothing carbon-based in the photo except for the styrofoam cup. What you see is a little neodymium magnet levitating over a pellet of a yttrium barium cuprate superconductor. This wasn’t even research-related in the least–it was part of one of my two remaining classes (and by “remaining” I mean I only have three weeks of undergradding left).
So, even though the stuff in the photo is super-cool in an electronic sense, I’m definitely not going to write anything resembling a post on superconductors. Too bad, because the subject is interesting enough to maybe deserve a post here. Unfortunately for all involved, though, I already wrote (read: “lost sleep over”) a lab report on the subject, and it was long and painful.[1] So I won’t bore you with details about the crystal structure of the material or why a superconductor can levitate a magnet.[2] I’m hella burned out on this stuff and pretty much everything else.[3]
And don’t forget to vote for your favorite lolnano!
[1] Anyone up for a bonfire this December? I’m looking at you, mevans…don’t think there are any other locals lurking about. You KNOW you want to burn that biochem text, don’t you?
[2] It is, however, likely that Uncle Al will resume ranting about these things in the comment section, since he is crazy enough to rant about them on unrelated posts.
[3] “Senioritis.”
so, are you graduating in December? Enjoy the senior slide and Biochem texts don’t burn very well at all.
Yup! December 14thish is the last day I have to actually do anything.
Biochem texts…I take it you know this from experience?
Uncle Al burned his German textbook. After ACS-mandated 15 credit-hrs of excruciating Bierstube bullshit, turnabout. A high temp and processible (wires) Type II supercon will get you tenure. Meissner effect for quick diagnosis, William A. Little for the boojum,
Phys. Rev. 134 A1416-A1424 (1964)
Uncle Al for the chemistry (hydrogens and pi-bonds removed from polymer stereograms for simpler viewing),
http://www.mazepath.com/uncleal/pyrene1.png
not bad
http://www.mazepath.com/uncleal/pave1.png
not bad at all
and presumptive synthesis,
ArH -> ArCHO -> ArCH(OH)-(C=O)Ar -> O=C(Ar)-(Ar)C=O
O=C(Ar)-(Ar)C=O -> H2C=C(Ar)-(Ar)C=CH2
Curr. Org, Syn. 2(2) 231 2005; Tebbe is nice
H2C=C(Ar)-(Ar)C=CH2 -> [=C(Ar)-(Ar)C=]n + H2C=CH2
ADMET; Schrock, possibly Grubbs
Dope the polymer. For solubility have long alkyl, polyethoxy (aqueous), or polyisopropoxy (non-aqueous) chains to get self-ordering liquid crystals. At worst the products don’t work. At not quite worst… you work it out. Feel free to substitute Little’s red-to-IR dyes for Uncle Al’s UV fluorophores.
Acc. Chem. Res. 38(9) 745-754 (2005)
His post-doc said it wasn’t worth trying. Process not product!
We live in a Golden Age. Stop complaining about all the yellow. (There is only one reported chiral supercon, AuBe, and that crystal structure is contested. Anything with a net unpaired electron in its crystallographic unit cell is conductive.) It’s 2007 – have you bootlegged anything interesting this year?
I had no idea what you were talking about until I checked for comments in moderation…lots of links apparently gets it flagged by Akismet. (And, yeah, you did miss one–the “/” is your friend.)
Two png’s released the hounds? Sometimes a cigar is only a banana.
Doesn’t anybody want a Tc = 300 C supercon polymer that lyotropic liquid crystal spins like Kevlar? If its valence electrons support Little’s exciton mechanism, can the stuff have any chemistry at all (like breaking fibers in in body armor) unless the whole of it quenches? Silly DARPA, the future is chemistry not engineering.
There was a very recent report that somebody figured out how to make these high-T cuprate ceramic semiconductors shine like laser but in the long sub-IR range ( shorter than microwave). Apparently they took advantage of the natural layered structure of these cuprates that has a tiny non-conductive junctions with a relatively large gap – and by applying a voltage across these junctions they made the supeconductor shine. The radiation was not coherent as such but when they put it in a resonance cavity and fine-tuned the voltage just the vawelengt to fit the cavity the out-of sych amplitudes canceled out and what came out was coherent.
To me this sounds a to shiny diode lasers but the mechanism of emission is different (not that I would understand it)
So it would be great if you could make the superconducting piece in your teaching lab to levitate above a permanent magnet while melting some unsuspecting evil bystanders though a concrete wall.
Fun fact about that demo: If you take a straw and blow air at the side of the floating magnet it spins really fast.
OR…it falls off the pellet.
Hey, that part of it is left as an exercise to the reader
We use a cubical magnet, which I’d imagine works better when spinning.
The best levitation we have at work is our giant pie plate levitator, which has some huge coils on top.
Sweet, I didn’t realize you guys got a picture of this! Now all we have to do is go back in time and discover the Meissner effect before Meissner…
About the bonfire, hell yeah, and I’d LOVE to toast the inorganic book too!
You graduate in the winter? Are you doing anything cool until grad school starts(I assume it starts in the fall, as not many places I’ve looked at accept spring admissions for Chem programs)?
It starts in the fall…of 2009. If you’re curious about what I’m doing until then, it’s on my Facebook profile (which means I’m sick of explaining it to people).
psi*psi is going to set up a garage lab after graduation, to quickly repay the student loans. (One day there will be a movie about the Kentucky connection – with aged Leonard DiCaprio cast as the not-so-brillinat agent frantically chasing after villanous redhead in wealthy suburbs)
A garage lab might be tempting if I had any student loans to take care of.
I like DiCaprio, though, with the notably awful exception of Titanic…he was super awesome in The Departed, among others.
and…hey? why am i villanous?
No student loan?!?
scholarships + 4 years lab teching to feed myself
not easy to work through school, but it’s harder for people who don’t have flexible schedules, so…not that bad. while it might have been nice if my parents had paid my tuition, it would have meant a lot less time at the bench
depends what you will be making in the garage… I suppose its gonna be a solar-panel crime syndicate? Or a bootleg gasoline adulterated with kittens?
i would never do that to kittens!
if i had a garage (which i don’t, but my father does) i’d probably use it for other things. wouldn’t mind being a little more dexterous with a soldering iron, or maybe making one of these.
unfortunately, working in two non-garage labs is probably going to eat all my free time.
High Tc superconductors are groovy, but they are some brittle SOBs. The science involved is top notch, but I still doubt I’m getting a levicar out of them.
I haven’t kept up with it, but I remember when magnesium diboride was found to be superconducting. Tc is “high”, but not liquid nitrogen high. High enough that electrical refrigeration will work, though (40K, I think). It has a really high critical field, so it might be useful for wires or the like before one of the perovskites.
It has a graphite-esque structure which is also interesting. When I was at NHMFL, I had a cube down the hall from Schrieffer, (the S in BCS theory of superconductivity) and he made a big deal about the symmetry involved in the MgB2 superconducting state, and that there were multiple energy levels (i.e. different electron states) contributing to the superconductivity.
Apparently BCS theory had long predicted this, but it hadn’t been unequivocally observed. We were at some shindig at the lab for another famous science guy, so I just nodded and kept wolfing down the hors d’oeurves they wheeled out when fancy company came by.
Levicars sound fun! although…i imagine that driving one might be a little like hydroplaning in a normal car, which is not so fun. I’d probably just t-bone someone else. My insurance is pretty unhappy with my driving a regular car…
B2Mg -based NMR magnets would be great: I am helping with re-filling liquid He in our magnets, about 4 times a year – and it is pretty stressfull operation every time (since we absolutely cannot afford an accidental quench). Anything that can get liquid He out of the magnets would be a great improvement. No more worrying about the He levels – a hurricane eye passion over the compus the last time caused a boil-off of about 10% of He in the magnets, because of the sudden pressure drop…(besides it is getting increasingly difficult to buy liquid He down here in FL becasue there are now some disruptions in supply. )
I heard that Bruker build a high-Tc supeconducting magnet for NMR that was based on the cuprate -rare-earth oxides – but it was way too expensive/difficult to make so it never became comecialised.
The Meissner effect!