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IrC
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Thank you franklyn. I love this place! Best science on the planet. Mostly I have been using ones such as "NdFeB structure" and variations, without and
with quotes. But I am not very good at searching. I am very good at understanding things once I find them to study. My schooling was 40 to 50 years
ago, we did not have the information overload like today. How I would love to have had the access you people have today to information while all my
brain cells still worked. I have been trying to catch up for over a decade ever since so much good scientific information has become so easily
available. Trust me in the 60's had you been looking for rare earth super magnets and theory 101 you would have had a long search, like 40 years or
so. Back then a simple patent search would have cost thousands, or would have required a 1500 mile trip to the patent office, and a few grand spending
months in a motel carefully going through records by hand, and then God help you if you had to copy very much to take home. Hopefully you will never
even know what a lithograph was. By the 70's Royal copiers with CDS drums were coming into play more and more but cost per copy was high. Se and Te
drums came out later, better but still slow and costly per sheet. Today you can sit in your underwear watching the Simpsons and saving a terrabyte of
patents and other papers such as what you just posted to DVD's. Another thing is it will take a while studying all these information sources thus far
gleaned from this thread just to get better at knowing what to look for in a more focused manner.
However that is the point. To stop learning and discovering is to die or fade away.
"Science is the belief in the ignorance of the experts" Richard Feynman
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chief
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The point is, thats it's not simple enough to just make it possible arguing with f- and d-shells or maybe the diamagnetics of boron ...
==> If it were _that_ simple, then it wouldn't be a problem to make materials with almost _any_ reasonable properties ...
Whoever knows about the reasons of strong magnetism may prove it by finding some new material with according properties ... 
... but I bet: Most here would have trouble making the existing compounds, even though these might be good busines on ebay ... and quite legal ...
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12AX7
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Cobalt platinum:
http://www.platinummetalsreview.com/pdf/pmr-v1-i3-084-086.pd...
This table claims it has 3 times the energy of barium ferrite, which I believe is still used today for cheap ceramic magnets. If the units are
actually MGOe (it says 10^-6, not 10^6?), then NdFeB is about 7 times stronger.
I don't see how you can justify diamagnetism as an active effect. It must be conjugated something silly in order to be more than ppm, in which case
there should also be "ferrodiamagnetic" materials which exhibit macroscopic diamagnetism in the same way that ferromagnetic materials can be
conjugated to produce macroscopic ferromagnets.
Tim
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IrC
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"The point is, thats it's not simple enough to just make it possible arguing with f- and d-shells or maybe the diamagnetics of boron ."
My idea or approach is find the best compositions from all the theory I can find and learn. Study how similar mixtures are processed. Try it with my
stuff. I can kiln 2000 C but it's hell on the coils and I lose some often. Pain in the ass to recoil and paint with ITC-213 and 100 so I prefer not so
hot. I have equipment to pulse fields (quarter squisher tech). But I need to obtain high temp vessels with gas tight abilities, as well as inert
gasses. Problem is any techniques requiring steady multi Tesla fields for long cooling is financially out of my reach at the moment. In any case my
point was you could try infinity but trying the most likely candidates first seems more logical.
So far my ceramic mad sci has been running a quartz tube through my furnace, and running H2 (produced locally on the fly with calcium hydride, water,
and vapor dryers) through it with my latest mix ideas. I sent some to Fleaker and I keep forgetting he asked for more once, or maybe it was just
commenting on them. For health reasons it's been nearly 5 years since I could play mad scientist too much, and over that time I got bored with
superconductors and glow powder. So many selling these (produced in large Chinese plants) on Ebay just not a money maker for the lone small outfit. I
did accumulate stuff to start building a tube furnace but will be a while. Been looking for something fun that I do not have to produce, just invent,
which would help fund even more mad sci. New magnets looks good and looks fun. Without fun whats the point I ask. Just wish I had JohnWW's knowledge
of orbital mechanics that would help, as I mentioned best to start with the most logical and likely prospects first rather than spend eternity trying
everything on the planet.
"I don't see how you can justify diamagnetism as an active effect. It must be conjugated something silly in order to be more than ppm, in which case
there should also be "ferrodiamagnetic" materials which exhibit macroscopic diamagnetism in the same way that ferromagnetic materials can be
conjugated to produce macroscopic ferromagnets."
I think it is involved with increasing the ability to resist demagnetization. I am no expert, but with all the information posted thus far it helps,
only takes time to study.
[Edited on 4-22-2010 by IrC]
"Science is the belief in the ignorance of the experts" Richard Feynman
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chief
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Most commercial Nd2Fe14B-magnets are compressed from the elements, as powder-mixture, in tablet-presses, and then sintered at 1200 Celsius ...
==> Magnetization is done with "magnetizers", mechaniclly stable setups where capacitor-discharges give the magnetic fields ...
So it might be possible for the amateur to make this stuff and sell it, as long as he uses a composition, where the patent-rights have run out, or
maybe some somewhat different composition ...
A tablet-press for maybe 2-cm-magnets would need to have maybe 10 tons of force ...
Thats basically the equipment for manufacturing these: Raw-materials as element-powders, tablet-press, quartz-vessels for the sintering, a bottle of
argon for inert atmosphere ..., and a magnetizer.
==> In case something goes wrong a x-ray-diffraction unit, for analyzing the phases, would b the best bet; some debye-scherrer camera could be made
and would be the most simple thing for the purpose ...
I was once into making these, but had then other priorities ...
The most dangerous part would be the press: The piston and cylinder my break, which means bullet-fast steel flying around ...
[Edited on 23-4-2010 by chief]
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JohnWW
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Further to my speculation above about actinide-based (as distinct from lanthanide) rare-earth magnets, using especially depleted U-238 (of which there
are huge stockpiles, as a byproduct of "enrichment" to obtain U-235, in the U$A and Russia, sitting around awaiting some use) and Pu-244, which are
the longest-lived isotopes of the most suitable metals:
It is to be observed that U is the electronic homolog of Nd, both having one unpaired 5d or 6d electron and three unpaired 4f or 5f electrons;
although in U the 5f electrons are much less strongly held than the 4f electrons in Nd, and unlike the latter can participate readily in electrical
conduction and covalent chemical bonding (with the +6 oxidation state being most common for U, resulting in chemical similarities to Cr, Mo, and W
instead). So, I wonder if anyone has thought of trying an alloy composition of U2Fe14B for permanent magnet properties, or, in view of the larger
atomic radius of U compared to Nd, with the B replaced with Al to produce U2Fe14Al.
Also, Nd and U have four vacant 4f or 5f orbitals, of the seven 4f or 5f that each have, with the result that they have four less than the maximum
possible numbers of unpaired f electrons that Gd and Cm (the latter being however too short-lived and radioactive to be suitable) have. So, I wonder
also if compositions like Gd2Fe14B, which would have the same crystal structure as NdFe14B, have been tried, although Gd is much less abundant than
Nd.
Again, noting that Mn, in the ground metallic state, has the maximum possible number of five unpaired 3d electrons (although pure Mn is
antiferromagnetic, not ferromagnetic), with Fe having one more electron than this, both also having two paired 4s electrons, while Nd has a deficiency
of four 4f electrons that could be unpaired if they were present, I wonder if alloys of Nd (or even Pr or Ce, which are more abundant, or Th-232 which
is the longest-lived of all natural actinide isotopes, with fewer 4f or 5f electrons) with Co, Ni, and Cu (instead of Fe), which have paired surpluses
of 3d electrons beyond the maximum unpaired number that Mn and Fe have, have been tried, in suitable molar proportions although having regard to the
possible viable crystal structures. This would assume that in the alloys the surplus 3d electrons, and the 4s electrons, can enter the vacant
lanthanide or actinide 4f or 5f orbitals, with a larger proportion of the alloying 3d-transition metal being usable with Pr or Ce or Th.
[Edited on 23-4-10 by JohnWW]
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IrC
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Actually chief I was more into coming up with something new, yet trying old to verify the process. No way to compete with the big factories. I
mentioned the quarter squisher tech stuff I have, and figure a 20 ton bottle jack works as a press starting place. Yet still looking for a sleeve (say
a cylinder of quartz several inches thick) which I could wrap stainless tubing around it for the pulse coil, and in effect building a tube furnace
around this. I want to try using the heat, pressure, and pulsed field all at once. With the option to continue the pulses while it was cooling. Two 2
inch tow balls make a good electrode, with a needle at the end of a 10 KV strobe trigger transformer circuit to ionize the gap thereby firing the
pulse I have already perfected. This portion of the idea works very well.
Along John's lines I actually already did acquire the Uranium, and all the other elements he mentioned (as well as many more). Thinking vacuum may be
cheaper to implement rather than inert gas, but have not decided on this idea.
"Science is the belief in the ignorance of the experts" Richard Feynman
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12AX7
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Would you like an induction heater? Sounds like the perfect item for sintering.
Tim
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IrC
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You know Tim that is a very good idea. No idea why I had not even been thinking along those lines other than selective brain fading, i.e. some of my
neurons fire and some do not yet they can never decide which ones will be which type. I remember reading some of your stuff on this subject a few
years ago and was very impressed with your work.
Edit to add however I wonder. Would the fields from induction heating interfere with the magnetic alignment going on. Novel to think about is some way
to use the induction fields tailored to aid the process. Or am I just wishfully imagining things. Got to go find Tim's page and study more.
Fortunately he always has that link on the bottom.
http://webpages.charter.net/dawill/tmoranwms/Elec_IndHeat8.h...
Need to study this page again yet an AC field would seem to act to degauss so I need to wonder about using rapid high power DC pulses orientated
correctly to both heat and not demagnetize at the same time. Or is that even possible I wonder. Seems an AC field would be needed for induction
heating.
[Edited on 4-23-2010 by IrC]
"Science is the belief in the ignorance of the experts" Richard Feynman
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Polverone
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This press release is fairly fluffy, as press releases usually are, but it may give you some names of institutions and people to search for if you
want to keep abreast of academic efforts to find a new generation of permanent magnets.
PGP Key and corresponding e-mail address
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12AX7
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The magnetic field is approximately B = mu_0*N*I/R, or around 25mT for a 2" coil, 5 turns, 200A. Nowhere near the 1T+ needed to magnetize. This
means ferrite pole pieces are an excellent choice if you need to concentrate the heating, and also that very little heating will occur by hysteresis
loss, only eddy currents. (Which has a downside: powdered metals may have very high bulk resistivity, heating slowly unless you use a very high
frequency.)
FYI, I'd be cautious using your quarter shrinker around the same device... it's not designed to handle kA scale induced currents!
Tim
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IrC
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Food for thought. I think I need to look into induction heating at a high enough frequency and low enough field intensity where the heating field
would not interfere with magnetic alignment. I know what you are saying about high pulsed fields, I assume you were talking about inducing Tesla type
voltages back into the heating coil. Much to optimize in such designs. Blocking the lower frequency components of a high pulsed field from creating
back EMF in the heating coils would be hard but higher frequency components could be limited with chokes from the feed into the heating coil. However
this would still leave a Tesla effect back EMF across the turns of the heating coil. Already bored myself to death blowing apart coils (and other
things) on purpose, certainly not something I want to do by accident.
"Science is the belief in the ignorance of the experts" Richard Feynman
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chief
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@IrC: Quartz-tubing as well as glassware can be obtained; prices for raw tubing are around 20 $/Meter (or was it per kg ?)
As for "coming up with something new": Those materials-systems surely have be searched by hundereds of diplomands and doctorants ...; that;s what
always happens when noone has a better idea ...
==> lot's of professors on the world, who just can assign such searching as a task to their students ...
===================
Where the magnetism comes from: As the formula says it's NdFe14B, so it's 14 times more Iron than Neodymium ...
==> Thereby most of the field still comes from the iron ... , the other
elements just permit the existencence and stability of the ordering of the iron-spins ... ; I bet that this would be the most fertile soil for
planting any theories onto ...
===================
Also I wouldn't go for the induction-heating: Any laboratory-furnace that can reach the 1200 Cels will do ...
==> ... also much better controllable, not so easy to overheat anything ...
As long as the material would be pressed as tablets only a Argon-Bottle would be needed; not even any quartz necessary ...
Main busines would be to obtain/get the Elements as powders ... for a rasonable price ...
[Edited on 24-4-2010 by chief]
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chief
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I did some search for similar compounds with "Fe14": All have similar symmetry ..., probably a reflection of what was searched upon ...
+---------+----------------------+
| sgr | sum_form |
+---------+----------------------+
| P42/MNM | B1 Fe14 Pr2 |
| P42/MNM | B1 Fe14 Pr2 |
| P42/MNM | B1 Dy2 Fe14 |
| P42/MNM | B1 Dy2 Fe14 |
| P42/MNM | B1 Fe14 Nd2 |
| P42/MNM | B1 Er2 Fe14 |
| P42/MNM | B1 Er2 Fe14 |
| P42/MNM | B1 Er2 Fe14 |
| P42/MNM | B1 Er2 Fe14 |
| P42/MNM | B1 Fe14 Nd2 |
| P42/MNM | B1 Fe14 Pr1.8 Y0.2 |
| P42/MNM | B1 Fe14 Pr1.7 Y0.3 |
| P42/MNM | B1 Fe14 La0.3 Pr1.7 |
| P42/MNM | B1 Fe14 Nd2 |
| P42/MNM | B1 Fe14 Nd2 |
| P42/MNM | B1 Fe14 Ho2 |
| P42/MNM | B1 Fe14 Ho2 |
| P42/MNM | B1 Fe14 Ho2 |
| P42/MNM | C0.95 B0.05 Ce2 Fe14 |
| P42/MNM | C0.95 B0.05 Ce2 Fe14 |
| P42/MNM | C0.95 B0.05 Ce2 Fe14 |
| P42/MNM | C0.95 B0.05 Ce2 Fe14 |
| P42/MNM | C0.95 B0.05 Fe14 Pr2 |
| P42/MNM | C0.95 B0.05 Fe14 Pr2 |
| P42/MNM | C0.95 B0.05 Fe14 Pr2 |
| P42/MNM | B1 Fe14 N0.317 Y2 |
| P42/MNM | B1 Fe14 La0.2 Pr1.8 |
| P42/MNM | B1 Fe14 Nd2 |
| P42/MNM | B1 Fe14 Tb2 |
| P42/MNM | B1 Fe14 Tb2 |
| P42/MNM | B1 Fe14 N0.3 Y2 |
| P42/MNM | B1 Fe14 Nd2 |
| P42/MNM | H1.04 B1 Fe14 Nd2 |
| P42/MNM | H1.86 B1 Fe14 Nd2 |
| P42/MNM | H3.31 B1 Fe14 Nd2 |
| P42/MNM | H4.73 B1 Fe14 Nd2 |
| P42/MNM | D3.47 B1 Fe14 Y2 |
| P42/MNM | D2.58 B1 Er2 Fe14 |
| P42/MNM | D3.7 B1 Ce2 Fe14 |
| P42/MNM | B1 Ce2 Fe14 |
| P42/MNM | B1 Ce2 Fe14 |
| P42/MNM | B1 Dy1 Fe14 Nd1 |
| P42/MNM | B1 Dy1 Fe14 Nd1 |
| P42/MNM | B1 Er2 Fe14 |
| P42/MNM | B1 Fe14 Lu2 |
| P42/MNM | B1 Fe14 Lu2 |
| P42/MNM | B1 Er2 Fe14 |
| P42/MNM | B1 Fe14 Nd2 |
| P42/MNM | B1 Fe14 Tm2 |
| P42/MNM | B1 Fe14 Tm2 |
| P42/MNM | B1 Fe14 Nd2 |
| P42/MNM | B1 Fe14 Nd2 |
| P42/MNM | B1 Fe14 Gd2 |
| P42/MNM | B1 Fe14 Y2 |
| P42/MNM | B1 Fe14 Y2 |
| P42/MNM | B1 Fe14 Tb2 |
| P42/MNM | B1 Ce2 Fe14 |
| P42/MNM | B1 Fe14 Nd2 |
| P1 | B1 Fe14 Nd2 |
| P1 | B1 Fe14 Nd2 |
| P42/MNM | B1 Fe14 Nd2 |
+---------+----------------------+
===================
The only thing with Uranium, Iron and Boron:
P6/MMM | B2 Fe3 U1
===================
the only similar thing with Thorium:
PBAM | B10 Fe1 Th2
===================
Here something with not exactly Fe14:
FM3-M | B6 Fe13.4 Ir3.84 Pr3.72
===================
Praseodymium-compounds
sgr | sum_form |
+---------+-------------------------+
| FM3-M | B6 Fe13.4 Ir3.84 Pr3.72 |
| P42/MNM | B1 Fe14 Pr2 |
| P42/MNM | B1 Fe14 Pr2 |
| P42/MNM | B1 Fe14 Pr1.8 Y0.2 |
| P42/MNM | B1 Fe14 Pr1.7 Y0.3 |
| P42/MNM | B1 Fe14 La0.3 Pr1.7 |
| P42/MNM | C0.95 B0.05 Fe14 Pr2 |
| P42/MNM | C0.95 B0.05 Fe14 Pr2 |
| P42/MNM | C0.95 B0.05 Fe14 Pr2 |
| P42/MNM | B1 Fe14 La0.2 Pr1.8 |
| P42/MNM | B1 Co2.8 Fe11.2 Pr2 |
| P42/MNM | B1 Fe9.8 Mn4.2 Pr2
=========================
nothing for Promethium
=========================
Samarium
| sgr | sum_form |
+--------+---------------+
| PBAM | B4 Fe1 Sm1 |
| P42/NZ | B60 Fe60 Sm17
=========================
nothing for Europium
=========================
Gadoliniunm:
sgr | sum_form |
+---------+---------------------------------------------------+
| P121/C1 | H1.3 B0.56 Be1.44 Ca0.28 Fe0.22 Gd0.72 O10 Si2 Y1 |
| PCCN | B28 Fe28 Gd8 |
| P42/MNM | B1 Fe14 Gd2 |
| P3121 | B4 Fe3 Gd1 O12 |
| R32H | B4 Fe3 Gd1 O12 |
| IM3-M | B0.12 Fe0.83 Gd0.05
====================
Terbium:
sgr | sum_form |
+---------+----------------+
| P42/MNM | B1 Fe14 Tb2 |
| P42/MNM | B1 Fe14 Tb2 |
| R32H | B4 Fe3 O12 Tb1 |
| P42/MNM | B1 Fe14 Tb2
====================
Dysprosium:
sgr | sum_form |
+---------+------------------------------------------------------+
| P42/MNM | B1 Dy2 Fe14 |
| P42/MNM | B1 Dy2 Fe14 |
| P121/C1 | H0.5 B0.36 Be1.64 Ca0.14 Dy0.38 Fe0.66 O10 Si2 Y1.48 |
| P121/C1 | H0.6 B0.64 Be1.36 Ca0.22 Dy0.4 Fe0.5 O10 Si2 Y1.38 |
| P121/C1 | H0.6 B0.66 Be1.34 Ca0.3 Dy0.28 Fe0.54 O10 Si2 Y1.42 |
| P121/C1 | H0.4 B0.18 Be1.82 Ca0.06 Dy0.36 Fe0.76 O10 Si2 Y1.58 |
| P121/C1 | H0.3 B0.24 Be1.76 Ca0.13 Dy0.13 Fe0.82 O10 Si2 Y1.74 |
| P121/C1 | H0.3 B0.18 Be1.82 Ca0.04 Dy0.46 Fe0.78 O10 Si2 Y1.5 |
| FD3-MS | B0.2 Dy1 Fe1.8 |
| FD3-MS | B0.6 Dy1 Fe1.4 |
| P42/MNM | B1 Dy1 Fe14 Nd1 |
| P42/MNM | B1 Dy1 Fe14 Nd1 |
| IM3-M | B0.059 Dy0.094 Fe0.823 Si0.024 |
=========================
Holmium:
| sgr | sum_form |
+---------+------------------------------+
| P4-C2 | B68 Fe68 Ho20 |
| P42/MNM | B1 Fe14 Ho2 |
| P42/MNM | B1 Fe14 Ho2 |
| P42/MNM | B1 Fe14 Ho2 |
| IM3-M | B0.06 Fe0.825 Ho0.095 Si0.02 |
==========================
Erbium
sgr | sum_form |
+---------+---------------------+
| P42/MNM | B1 Er2 Fe14 |
| P42/MNM | B1 Er2 Fe14 |
| P42/MNM | B1 Er2 Fe14 |
| P42/MNM | B1 Er2 Fe14 |
| P42/MNM | D2.58 B1 Er2 Fe14 |
| P6/MMM | B1 Er1 Fe4 |
| P42/MNM | B1 Er2 Fe14 |
| I4/MMM | B2 Er1 Fe2 |
| P42/MNM | B1 Er2 Fe6 Mn8 |
| P42/MNM | B1 Er2 Fe6 Mn8 |
| P42/MNM | B1 Er2 Fe8 Mn6 |
| P42/MNM | B1 Er2 Fe8 Mn6 |
| P42/MNM | B1 Er2 Fe9 Mn5 |
| P42/MNM | B1 Er2 Fe10 Mn4 |
| P42/MNM | B1 Er2 Fe10 Mn4 |
| P42/MNM | B1 Er2 Fe11 Mn3 |
| P42/MNM | B1 Er2 Fe11 Mn3 |
| P42/MNM | B1 Er2 Fe12 Mn2 |
| P42/MNM | B1 Er2 Fe13 Mn1 |
| P42/MNM | B1 Er2 Fe14 |
| IM3-M | B0.04 Er0.09 Fe0.87 |
=========================
Thulium:
sgr | sum_form |
+---------+-------------+
| P42/MNM | B1 Fe14 Tm2 |
| P42/MNM | B1 Fe14 Tm2 |
=========================
nothing for Ytterbium
==========================
Luthetium:
| sgr | sum_form |
+---------+-------------+
| P42/MNM | B1 Fe14 Lu2 |
| P42/MNM | B1 Fe14 Lu2 |
| PBAM | B6 Fe1 Lu2 |
============================================
============================================
Was too lazy to find tthe references now; following can be seen:
==> mostly P42/MNM space-group, no Actinide-compound with that symmetry
==> noone said (so far) the actinide-compounds were magnetic ... ...
==> mostly Fe14 in the lanthanide-structures ...; of course they are all the same ...
... so either: Only the isostructural compounds were grazed, for circumventing the patents of the competition or maybe finding higher
curie-tempertures
=============================================
Basically it's one known structure-type, all with Fe-14-coordination and P42/MNM -symmetry ; that's what it boils down to so far ...
[Edited on 24-4-2010 by chief]
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watson.fawkes
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Quote: Originally posted by IrC  | | I think I need to look into induction heating at a high enough frequency and low enough field intensity where the heating field would not interfere
with magnetic alignment. |
This sounds like needless worrying. You'll generally be sintering at a temperature
above the Curie point, where the magnetic domains are in a "liquid" phase (as opposed to the "solid" phase below it) and will move around freely,
following your driving field.
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chief
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Just thought it might help:
All the known compounds with the p42/mnm-symmetry:
Attachment: p42_mnm.txt (16kB)
This file has been downloaded 983 times
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IrC
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Actually Watson from experience building electrets I find having the field on before the point of becoming a solid (or in the case here of making
magnets, a crystal structure) and letting the material continue in the field as it cools works best. It would seem to me keeping the field on through
the whole process of cooling past the Curie temperature would help moments prefer a certain orientation aas they settle into a lattice structure. Then
using the quarter squisher pulse of extremely strong field would then cause the structure to be aligned in the optimum orientation.
Of course it seems trying to use induction heating would create engineering problems. My original thought was only having one coil, the pulse coil,
and building a kiln around this structure. My thought about an extremely thick walled quartz tube was aimed at keeping the material under mechanical
pressure through the heating and cooling cycle. Simply making the material the same way it is now being done would seem to me to be creating what we
already have, rather than coming up with new and stronger (in field strength) magnet materials.
[Edited on 4-24-2010 by IrC]
"Science is the belief in the ignorance of the experts" Richard Feynman
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franklyn
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As with a simple iron bar , heating the material to the curie temperature and
allowing it to cool within an externally applied magnetic field will polarize the
remanent field of the magnet itself. This is usually done cold by a powerfully
pulsed electromagnet. Magnet alloys are either cast as the AlNiCO or sintered
powder such as the common Ferrite. There is an optimal minimal magnetic
domain size that may contain anywhere from a few tens of thousands to
several million atoms. Since this is a crystal of ordered unit cells mechanical
powdering of the melt produces the right size. The directions or axis of a
magnetic domain which can become permanently polarized , called anisotropic,
determines the resistance to demagnetization. NdFeB powdered domains have
a single anisotropic orientation making them extremely resistant to nucleation
( when adjacent domains form a closed magnetic loop which does not exhibit
a magnetic field externally ). This property is exploited by first orienting the
loose individual crystal domains directionally with an applied magnetic field
and mild vibrating agitation. The bulk material is isostatically pressed in this
state to retain the crystal bias and sintered to weld the powder grains together
to keep the magnetic anisotropy. The same method is used having the powder
mixed within a plastic binder , easier to process but with reduced properties.
Magnetization is also done cold although the highest performing grades can
actually be heated up to their curie points of 80 ºC. Lower performing grades
have higher curie points over 100 ºC. up to about 150 ºC. for lowest grades.
Grade is just the product of the remanent field called B and the coercive H
field that would be applied externally of opposite polarity needed to reduce
the remanent field to zero. Very commonly availble NdFeB magnets can be
had at anything above 35N (BH) up to 42N. The highest commercially available
is 55N , but this has a disturbingly low curie point of around 55ºC.
So what determines grades you may ask. The single domain crystal will be
mechanically wedged into a space with adjacent crystals. The internal unit
cells of a crystal grain are not necessarily oriented with the external contours
of the grain , so the intrinsic anisotropic direction of the crystal will only
approximately line up with the direction of the bulk magnet. This will
adversely affect the overall properties of the magnet since nucleation will
result more easily. The higher curie points of the lower grades indicates that
most crystal domains retain the desired magnetized direction. As those that
are more marginal are aligned their contribution to the magnet is seen. These
marginally oriented crystals also are the first to nucleate at lower temperature
and adversely affect the magnets overall performance. A high grade ~ 50N if
warmed to its curie temperature will degrade into a lower grade having a
somewhat higher curie temperature.
Grades you see are largely the result of handling and processing rather than
the theoretical properties of the material itself.
Directional casting as is done for aircraft engine parts will produce a single
large crystal of an alloy. Trouble is that the constituent elements of many
magnetic materials are not miscible so do not form a solution. The best that
can be done is to produce a heterogeneous blend of the elements. Rapidly
quenching an agitated melt ( before the composition can separate ) is the
method employed for the production of powders.
More common magnetic alloys that have multiple anisotropic magnetic
directions , when cast as a large crystal , nucleation occurs at a runaway
rate much as dominoes falling. Aggregation of individual domain crystals
mitigates this occurence; which explains the optimal size paradigm.
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12AX7
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IrC, do you typically charge your quarter shrinker to the point where the coil is destroyed? If the coil survives, it may be effective to switch
between power sources, thus disconnecting the induction heater when the pulse is required. You'll have to make your own switch I'm afraid, which
could be a few slabs of copper and a lever with latching action. Pull the big Frankenstein-esque lever *CLUNK*, then fire away.
Tim
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IrC
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I have but only when that is what I wanted to do. If one terminal of the induction heating can be grounded then the switch is simple. Ground, through
coil to tow hitch ball. Open circuit to pulser. So connecting to the coil is simple, low current path needing to carry only the induction heating
current. A side connection to ball - coil junction. I will go look at some of your circuitry to see.
If this earlier work of yours is still similar to your current design the bottom is grounded so this idea would work fine. However in a newer one you
have R601 and "inverter control" outputs between the bottom of the work coil and ground complicating things. However DPDT switching would still work
keeping your "tank coil" on the heater supply side of the circuit. That should work except it would require the pulser to not be ground referenced on
the cap bank side. I doubt circulating currents from a say 1 KW heating source would be greater than a couple hundred amperes as far as considering
the switch ratings. Something surplus or maybe building one does not seem a difficult problem.
I did not see the rest of the circuit to study where you go from "- + inverter current". Hard to figure the ground reference issue unless I can see
the whole circuit. Maybe you have that on there somewhere, your site is way beyond where it was last time I looked, much more to search through.
Oh yeah I forgot. Images copyright 12AX7 and borrowed from his site.
[Edited on 4-25-2010 by IrC]
"Science is the belief in the ignorance of the experts" Richard Feynman
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12AX7
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That circuit comes from page 6 I believe, so you'll find the control circuit and what it does with inverter current (if anything) there.
I don't think I was using current at the time, actually, so you'll probably have a hard time figuring that one out. 
Here's a representative drawing of the current "state of the art":
Power comes in, is rectified and filtered, and the inverter is coupled to the output transformer. The secondary winding is copper tubing like so, so the output network is completely isolated (I should probably add some small capacitors to it, just to keep RFI down).
Just because a quarter shrinker is a big mess of crap when it fires, I'd like to see some filtering between them, since even with the isolated output,
there will be a lot of noise carried on that connection. You could make a common-mode filter choke using a stack of toroids just large enough to pass
the copper tubes through. Should be able to find 3/4-1" i.d. ferrites on eBay or surplus sites for under a buck each, and heck, 10 would be fine (a
stack of about 5", roughly).
It would also be nice to have a provision to short out the induction heater (at the disconnect switch), to prevent induced voltage. Induced noise
would be either from capacitance of the switch, or if it's not wide enough, a spark could jump, something that obviously should be avoided.
I can make a diagram for this. This fits in the realm of EMC (electromagnetic compliance), a rather extreme case you'll admit (I can't imagine how a
quarter shrinker could possibly pass any organization's emissions tests ), a
subject which I myself am gathering knowledge on but am still quite green about. EMC is about dealing with the parasitic squigglies of real
components, so it's voodoo magic getting real devices to pass. The standards of which I am considering here aren't likely to pass any organization's
standards, anyway, but considering the magnitude of voltage and current nearby, I'd like to make sure this thing doesn't get shocked just from the
fields.
Tim
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watson.fawkes
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| Quote: Originally posted by IrC | | Actually Watson from experience building electrets I find having the field on before the point of becoming a solid (or in the case here of making
magnets, a crystal structure) and letting the material continue in the field as it cools works best. It would seem to me keeping the field on through
the whole process of cooling past the Curie temperature would help moments prefer a certain orientation aas they settle into a lattice structure. Then
using the quarter squisher pulse of extremely strong field would then cause the structure to be aligned in the optimum orientation.
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We're talking about several different field configurations here. All I was saying is that in the heating
phase, presumably the first phase, you don't have to worry about overall magnetic field alignment in the ceramic, exactly because (as you point out)
its macroscopic magnetic field alignment locks in as it cools, which is some later phase. All this means that induction heating can work just fine for
you if what you're using it for is to get to sintering temperatures.
I should also point out that you don't need an external magnetic field that's as strong as the field locked into the final material. The purpose of
the external field is to align magnetic domains to some common external reference so that as they lock in they will all be pointing in the same
direction. The magnetic domains are what's called a "spin glass". If you're trying to get maximum alignment in the glass, what you need is not big
pulses but rather an annealing process. You're annealing magnetic alignment rather than the crystal structure, in this case. One form of annealing is
to hold the material just barely below the Curie point. This gives some amount of spin mobility, not enough to destabilize the long-range order, but
enough for the last recalcitrant domains to find their way into the overall alignment.
I should make sure I understand what you're doing, I realize. Perhaps you mean you want to use high-power pulse energy to drive densification of the
ceramic. If so, you'll be sintering above the Curie point, so the magnetic domain alignment won't be relevant. If this is the case, Barsoum's book
Fundamentals of Ceramics was where I really learned about the physics of sintering. I will highly recommend if you're planning some lab work
in this area.
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IrC
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Good advice, right now I am doing a lot of study and thinking of design ideas, including Tim's concerns. Searching for the book online, may have to
just buy a copy. I am looking at the design where I could use a single coil for both heating and magnetic pulsing, would be simpler to build. I can
see how to build a switch to take care of the things Tim mentioned. Does not look to difficult. So much good information has been provided by members
so far I am going to spend a while carefully studying all of it before I say too much more, helps if I ask better questions and this is best done with
a good handle on the subject. Which also eliminates asking too many uninformed questions.
Below is a long list of relevant patents.
Attachment: ndfeb.doc (36kB)
This file has been downloaded 510 times
[Edited on 4-28-2010 by IrC]
"Science is the belief in the ignorance of the experts" Richard Feynman
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quantumcorespacealchemyst
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what about running a direct current of high amps throught the material to melt it and then switch the input of the electrodes to the aligning field
current/pulses from there untill after it solidifies?
the uranium bond in valence 3 state, any good info on this?
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