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Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
Hi all. I think I may have stumbled across something truly weird.
Was mixing up another batch of low melting point metal for removing IC's. For various reasons (impure lead and/or crystalline bismuth) this batch had a LOT of impurities which showed up as annoying black/silvery crystals in the melt.
Did the usual trick of removing all the crud by scraping the nearly crystallised alloy with a spoon end, and saved this alloy. Then re-melted to salvage what I could (indium=$$$)
So I ended up with about a quarter gram of black and silver flakes which were basically useless. Just to see what happened I got a strong neodymium magnet and checked to see if any of the flakes stuck.
Was very surprised to see that some did- not only that but upon further cooling (the flakes were pretty hot still) more stuck.
So far I have about 10 flakes varying in size from 0.2mm to 2mm, all of which stick to a magnet even though none of the components should be magnetic.
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
well, if they stick to the magnet they are not diamagnetic (by definition...), I would guess that you had some Fe, or a little bit of a Nd magnet, or something similar in the mix.
Registered Member #261
Joined: Mon Feb 27 2006, 12:34AM
Location:
Posts: 22
Bismuth is the most diamagnetic of all elements, meaning it opposes magnetic fields. This is due to the unfilled 6p orbitals I would assume, there are 3 unpaired electrons in those orbitals.
However, some bismuth alloys are magnetic. MnBi is an alloy known as 'Bismanol', the navy uses it for its high coercive force.
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
There's a nickel iron alloy with pretty much the same thermal expansion as glass. (called kovar IIRC) the IC industry uses it to make the pins on ICs ( I don't know why- perhaps they just haven't changed the mix since they were making valves). Bits of that in the mix are a lot more likely than ferromagnetic mixtures of non magnetic materials. Having said that, some heusler alloys are magnetic even though their components aren't.
Registered Member #99
Joined: Thu Feb 09 2006, 06:10PM
Location: florida, usa
Posts: 637
Swany wrote ...
Bismuth is the most diamagnetic of all elements, meaning it opposes magnetic fields. This is due to the unfilled 6p orbitals I would assume, there are 3 unpaired electrons in those orbitals.
However, some bismuth alloys are magnetic. MnBi is an alloy known as 'Bismanol', the navy uses it for its high coercive force.
I beleive pyrolytic graphite is 15 times more diamagnetic than bismuth. I have some, and it will levitate above strong magnets. Matt
Registered Member #964
Joined: Wed Aug 22 2007, 12:39AM
Location: Stockton, CA
Posts: 134
mattrg2 wrote ...
Swany wrote ...
Bismuth is the most diamagnetic of all elements, meaning it opposes magnetic fields. This is due to the unfilled 6p orbitals I would assume, there are 3 unpaired electrons in those orbitals.
However, some bismuth alloys are magnetic. MnBi is an alloy known as 'Bismanol', the navy uses it for its high coercive force.
I beleive pyrolytic graphite is 15 times more diamagnetic than bismuth. I have some, and it will levitate above strong magnets. Matt
Pyrolytic graphite is just a certain crystal formation of carbon, not an element. Bismuth is the most diamagnetic Element yet to be discovered.
On topic:
Thats pretty cool. I haven;t done anything with liquid metal, but I've read lots about it.
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
Try putting some in an ultrasonic field. It forms "ripples" :)
Setting up a standing wave and then slowly cooling the metal would probably result in some very interesting formations, a bit like ferrorfluid on a speaker.
(btw the 59c alloy works well for this, Email me for a free sample.)
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Possible giant diamagnetism in BiPbSnIn ?
