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Brain&Force
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Yellowish orange, it seems. You're right, as I think I'm confusing it with some iron(II) complex. After seeing this post it's evident that there is
plenty of praseodymium.
Do you see any color change in different lighting?
At the end of the day, simulating atoms doesn't beat working with the real things...
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blogfast25
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Quote: Originally posted by Brain&Force  | After seeing this post it's evident that there is plenty of praseodymium.
Do you see any color change in different lighting? |
I'm still not 100 % convinced but find it really difficult to otherwise explain what I've seen.
Unfortunately we've changed over to saver bulbs completely in our house. But I do have a powerful incandescent torch that needs batteries. Will
definitely have a look...
[Edited on 20-10-2014 by blogfast25]
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MrHomeScientist
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I guess I need to quit wasting time playing Destiny and get to it then! 
Lithium makes me nervous though, to be honest. Dan Vizine in another thread cited that lithium's reactivity can change drastically depending on
temperature. Just melting Li in my crucible as a 'dry run' doesn't necessarily mean I'll get the same results when NdF3 is around. The goal
of producing molten Nd will take me to 1024 C, far above Li's melting point of 180 C (but within my furnace's capability, as I've melted copper
before). I'd like to try it this week if at all possible. I'll post results in the neodymium thread to avoid further derailment but link to it from
here for continuity.
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blogfast25
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| Quote: Originally posted by MrHomeScientist |
Lithium makes me nervous though, to be honest. Dan Vizine in another thread cited that lithium's reactivity can change drastically depending on
temperature. Just melting Li in my crucible as a 'dry run' doesn't necessarily mean I'll get the same results when NdF3 is around. The goal
of producing molten Nd will take me to 1024 C, far above Li's melting point of 180 C (but within my furnace's capability, as I've melted copper
before). |
Let me try and put some of your fears to rest.
The reaction between NdF3 and Li, assuming it proceeds (thermodynamics say nothing about kinetics, remember), is likely to start at 400 to 600 C and
the hope is that the calculated ΔH is enough to take the reaction products to above 1024 C (the MP of LiF is lower). This week I'll try and calculate
the actual exotherm ΔT from NIST Shomate data.
Melting Li without argon blanket will set fire to it, so be prepared for that during your dry run. It burns extremely brightly apparently.
What physical form is your Li metal?
Edit:
Adiabatic exotherm for that reduction, based on - 194 kJ/mol reaction heat comes out as ΔT about 830 C. So even if auto-ignition would start as low
as 200 C, end temperature should still surpass both MPs.
[Edited on 21-10-2014 by blogfast25]
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MrHomeScientist
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Here is my Li metal, stored under argon:
Small slugs, around 3/8" long. The plan will be to add NdF3 powder to the crucible first then a few of these on top. The Li will melt and
cover the fluoride before reaction starts. I think my biggest concern at this point is the hot, molten lithium reacting with whatever crucible
material I use. I currently have fused silica (no good), graphite (questionable), and stainless steel (slightly less questionable). I think it would
also be a good idea to have a cover for whatever material I end up using, to help exclude air.
Edit: Your delta-H calculation is very promising! Even if this did not produce enough heat on its own, I could reach that temperature with my furnace
so I think it's looking good.
[Edited on 10-21-2014 by MrHomeScientist]
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blogfast25
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Nice metal (you couldn't teleport some over here, could you?)
But I was thinking of doing it the other way around: load lithium first, then fluoride, so the latter protects the metal somewhat, at least at first.
Then when it melts reaction will start at some point. Argon blanket would of course be better. I'm thinking of a fairly simple design: crucible within
a crucible for instance. A wide copper tube (shut off at one end), pump argon into it, load crucible into it and then load reagents into inner
crucible. Lower assembly into furnace, maintaining low Ar flux into outer crucible...
For what it's worth on Li<sub>2</sub>C<sub>2</sub> Wiki mentions this:
"To prepare pure samples in the laboratory molten lithium + graphite are reacted at high temperature."
One of the entry's references mentions 800 - 900 C, so graphite may be more problematic than I previously thought.
No oxidic materials are really recommendable so that kind leaves various metals, like SS.
What scale are you attempting this? One slug? Less?
[Edited on 21-10-2014 by blogfast25]
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MrHomeScientist
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I'd be happy to send you a sample, assuming international shipping isn't a big deal. My source is the Chinese eBay seller woelen found not too long
ago - he's still got some available.
What I received isn't nearly as clean as his picture, but apparently woelen got great quality. Chinese (lack of) quality control I guess, but
definitely worth the price in my opinion.
My only source of argon right now is bloxygen canisters (little aerosol cans of Ar), so I can't really set up a continuous blanket. The 'nested
crucible' idea is pretty good; I might have to check out the hardware store. Maybe some black iron fittings and caps, after degreasing with acetone,
would work for both crucible and outer casing. Do you think it would be particularly disastrous with no inert cover?
Going by 3Li + NdF3 == Nd + 3LiF , 0.5g Li would react with 4.79g NdF3 to produce 3.5g Nd metal. That seems a good size to work
but minimize danger. I'll have to weigh the slugs to see how many I'd need. I'd guess 2-3. The issue with small amounts is that my steel crucible is
fairly wide, so I'd need to tilt it a little so the Nd is fully covered post reaction.
This has gone fairly off-topic for this thread, for which I apologize. But, if it works, the lithium reduction should be applicable to lanthanum as
well!
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blogfast25
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Ah yes, I saw that seller too. Good price.
Here argon for welding is pretty cheap, proper canister and expander included.
I don't know how deleterious oxygen will be. The worst case scenario is that your 0.5 g of Li ends up burnt to Li<sub>2</sub>O, I guess.
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Dan Vizine
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| Quote: Originally posted by MrHomeScientist | Here is my Li metal, stored under argon:
Small slugs, around 3/8" long. The plan will be to add NdF3 powder to the crucible first then a few of these on top. The Li will melt and
cover the fluoride before reaction starts. I think my biggest concern at this point is the hot, molten lithium reacting with whatever crucible
material I use. I currently have fused silica (no good), graphite (questionable), and stainless steel (slightly less questionable). I think it would
also be a good idea to have a cover for whatever material I end up using, to help exclude air.
Edit: Your delta-H calculation is very promising! Even if this did not produce enough heat on its own, I could reach that temperature with my furnace
so I think it's looking good
[Edited on 10-21-2014 by MrHomeScientist] |
Even though molten Li is fearsome to many materials, unless you want to pay big money for the "right" materials (a tantalum crucible liner slipped
into a larger crucible), or at minimum, a ferritic SS like something in 400 series, the default material is likely to be SS304 or pure iron. It is a
compromise, to be sure.
Here's why...as the nickel content in an alloy increases, it's resistance to heat usually increases while its resistance to leaching by hot, molten
lithium or calcium decreases. This results in some leaching of Ni and Fe but not to destructive failure. For SS 304, leached material may be several
tenths of a per cent in your final product. You can make the reactor and the material contacting the melt out of just one thing. This greatly
simplifies construction, usually.
Pure iron is available, relatively cheap and resists hot, molten Li and Ca quite well. The problem is that you have to rely on whatever shapes you can
find for sale (depending on your mechanical skills and equipment).
It is best used as a liner in a more oxidation resistant larger container.
[Edited on 23-10-2014 by Dan Vizine]
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blogfast25
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Thanks Dan.
Finally, even stronger proof there is a considerable amount of praseodymium in this lanthanum.
Remember that I had calcined about a quarter of a teaspoon of the lanthanum hydroxide and that it had turned dark grey to black. That oxide was then
subjected to an excess hot HCl 37 %. It turned out that nearly all of it had dissolved minus a black residue which I suspect is the mixed Pr(IV,III)
oxide.
Today I isolated it with some mini decantations and then dried it by boiling off the supernatant in a 40 ml ceramic crucible. Black as the ace of
spades:
About 2 ml of 98 % sulphuric acid was added and strongly heated to nearly 400 C (the maximum of my heater/stirrer). Despite strong fumes of SO3 coming
off I could not see the acid making a dent in the black stuff (no wonder it didn’t dissolve in conc. HCl!) So after about 20 minutes I cooled it
down to reasonable levels and added about 5 g of NaHSO<sub>4</sub>. This was heated to medium high propane Bunsen heat and it did the
trick. Bar a few black bits that had crept up to near the top of the crucible the colour disappeared in about 10 minutes. Here’s what it looked like
after cooling:
The mass was soaked in about 10 ml of hot water until it released from the crucible and then transferred to a glass beaker. With stirring/heating it
dissolved to a thin slurry with white insoluble particles, presumed to be poorly soluble Na/Pr double sulphate.
To it was added 5 g of NaOH dissolved in 10 ml of DIW and that mixture simmered/stirred for about 20 minutes. This was then filtered with vacuum on a
ceramic frit filter and washed with minimal amounts of hot water. The presumed hydroxide was scraped off the filter, amounting to about 0.05 ml of
green material which was dissolved in a few drop of conc. HCl forming a green solution. Compared to a tube of DIW:
The photo doesn’t do it justice at all, making even the white kitchen tissue look yellow! It’s quite an intense, slightly ‘dirty’ green. It
may look darker than it is due to a few particles of black residue that had carried over.
[Edited on 22-10-2014 by blogfast25]
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Dan Vizine
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Oh Oh...I read more.
I also apologize for the off-topic comments, but Mr.Home Scientist, I hate to spoil the party, but when you asked "Do you think it would be
particularly disastrous with no inert cover?", I'm sorry to say that you don't have a prayer. You need to protect Li at 1000 C from oxygen, moisture
and nitrogen completely. If you want good results, you'll need good quality argon, you need to sweep all of the atmospheric gas out and maintain a
quality cover. The last part is the hardest.
The good thing is that burning lithium is kind of quiet, not too violent. But, oh those fumes...intensely irritating.
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blogfast25
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| Quote: Originally posted by Dan Vizine | | I also apologize for the off-topic comments, but Mr.Home Scientist, I hate to spoil the party, but when you asked "Do you think it would be
particularly disastrous with no inert cover?", I'm sorry to say that you don't have a prayer. You need to protect Li at 1000 C from oxygen, moisture
and nitrogen completely. |
If I may interject here. We are hoping that this reaction will start much, much lower than 1000 C.
But argon would certainly be better, no contest.
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MrHomeScientist
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Right, hopefully it will start not too far past the melting point of Li. But the desired end result is at least 1024C, for complete melting of all the
products. Will most of the lithium be gone by then, and not pose a large fire risk / problem to the crucible? Unsure at this point. I hope by starting
with 0.5g of Li risks will be minimized.
I should probably just say damn it all and go for it, and see what happens. If there is severe attack of the crucible I'd like to try lining it with
some tantalum foil I have, if for no other reason than to find a use for it.
Edit:
Great progress on the lantanum, blogfast. About how much black material did you have? i.e. what percent Pr would you estimate this material has? How
would bisulfate dissolve it when concentrated sulfuric would not?
[Edited on 10-22-2014 by MrHomeScientist]
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blogfast25
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| Quote: Originally posted by MrHomeScientist | Great progress on the lantanum, blogfast. About how much black material did you have? i.e. what percent Pr would you estimate this material has? How
would bisulfate dissolve it when concentrated sulfuric would not?
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The amount of black material was small because I'd only calcined about half a teaspoon of the contaminated lanthanum hydroxide. Probably about 50 -
100 mg.
I'm not quite sure why the bisulphate made it work. It certainly increases the BP of the mixture. It also converts to pyrosulphate
(S<sub>2</sub>O<sub>7</sub><sup>2-</sup> on
melting. I've used it a few times on stubborn residues/oxides, with success usually.
I don't know how much Pr is in that pool phosphate remover but going by everything that I've seen, I'd say 20 mol % easily of La + Pr. I'll definitely
have a stab at getting it out.
[Edited on 23-10-2014 by blogfast25]
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j_sum1
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@MrHomeScientist
In case you missed it, I posted in the lithium thread details of a molybdenum vessel at low price that you might find useful.
http://www.sciencemadness.org/talk/viewthread.php?tid=32946&...
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Dan Vizine
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Bisulfate and heat rips into many things that even the strongest, most aggressive acids fail to touch.
Nice detective work blogfast25 !
[Edited on 23-10-2014 by Dan Vizine]
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blogfast25
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Thanks Dan. It really felt like a whodunit. Could have been over in 1/2 hour with VIS spectrometry but not as much fun as with a good old
looking glass, I guess.
What do you think about molten Li + copper crucible?
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j_sum1
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Well if it gets up to temp you might get molten copprr as well.
I wonder what the Cu La phase diagram looks like. I bet that's never been done.
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plante1999
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Very interesting work being done here, after the experimenting is done, it might be nice to make a short summary of the work done.
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blogfast25
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| Quote: Originally posted by j_sum1 | Well if it gets up to temp you might get molten copprr as well.
I wonder what the Cu La phase diagram looks like. I bet that's never been done. |
Yep. Off the top of my head I thought Cu MP was 1400 K but that's K. Bummer.
| Quote: Originally posted by plante1999 | Very interesting work being done here, after the experimenting is done, it might be nice to make a short summary of the work done.
|
Will do that on my blog. This weekend I will attempt pH selective precipitation/fractionation.
Here's a slightly better pic of the green REE chloride. Slightly more dilute, in natural sunlight and with a few grans of the black oxide at the
bottom:
[Edited on 23-10-2014 by blogfast25]
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Dan Vizine
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| Quote: Originally posted by blogfast25 |
Thanks Dan. It really felt like a whodunit. Could have been over in 1/2 hour with VIS spectrometry but not as much fun as with a good old
looking glass, I guess.
What do you think about molten Li + copper crucible? |
Well, I see that the Cu question was addressed. The suggested materials for molten Li are TMZ Molybdenum and pure iron. But the reality is that
manufacturers use tantalum or tungsten liners or crucibles inside SS reaction bombs to reduce LaF3. The most frequent reductants are Li and Ca. The
first successful (I2 boosted) reactions were done in dolomite-lined steel bombs, but the purity wasn't good enough.
I'd say that the choice of the best crucible material for your application depends largely on how you plan to exclude oxygen. If a gas-shielded open
crucible is planned, I'd go with pure iron. Pure iron crucibles are on eBay for very low cost.
[Edited on 23-10-2014 by Dan Vizine]
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Brain&Force
Hazard to Lanthanides
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I've got to ask, have you excluded the possibility of any other lanthanides in the mix? I wouldn't be surprised, though, if all of the neodymium and
samarium were removed to make magnets, and the cerium was oxidized away in the beginning. I doubt any other lanthanides would be present, but yttrium
could potentially be present.
I'd like to feature this thread on my radio show. If you're interested in calling in to talk about this, U2U me so we can iron out the details. Also
check the relevant links in my sig.
At the end of the day, simulating atoms doesn't beat working with the real things...
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blogfast25
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| Quote: Originally posted by Dan Vizine | The suggested materials for molten Li are TMZ Molybdenum and pure iron. But the reality is that manufacturers use tantalum or tungsten liners or
crucibles inside SS reaction bombs to reduce LaF3. The most frequent reductants are Li and Ca. The first successful (I2 boosted) reactions were done
in dolomite-lined steel bombs, but the purity wasn't good enough.
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"TMZ"?
You have references for the reduction of LaF3? We thought we were being trailblazers here because all I can find are methods like the ones in Brauer:
molten chlorides electrolysis, chlorides reduction with Ca boosted with I2 or chlorate, mercury amalgam (electrolysis) and even oxides reduction of
higher REE with lanthanum at high T.
| Quote: Originally posted by Brain&Force | I've got to ask, have you excluded the possibility of any other lanthanides in the mix?
I'd like to feature this thread on my radio show. If you're interested in calling in to talk about this, U2U me so we can iron out the details. Also
check the relevant links in my sig. |
As indicated above: no, not at all. But I can't detect what I can't see with the naked eye. I'm not sure it's useful to a priori assume Ce, Nd and Sm
would have been removed: this is a very low tech application and these elements won't impact on product performance.
Re. your radio show, that sounds really great! But I'm neither telegenic nor audiogenic, so I'll politely decline. Might try and listen in though...
[Edited on 23-10-2014 by blogfast25]
[Edited on 23-10-2014 by blogfast25]
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Dan Vizine
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TMZ Molybdenum is Mo with a little Ti and Zr. It's a molybdenum modified to perform especially well at high temperatures.
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Brain&Force
Hazard to Lanthanides
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AAAAH! TMZ! WORSE THAN KEWLS - oh, thanks for the clarification, never mind. 
The only reason I would think the other elements would have been removed would be because of the value of certain other rare earths in different
applications; in other words, this is probably a repurposed waste product from rare earth extraction.
You really should come onto the show - we're a little independent university station, so there's room for whatever. Unfortunately I'm on the west
coast of the US so that by the time I get on, it'll probably be pretty late, likely midnight where you are.
My invitation extends to anyone who wants to come onto the show, though - just click the relevant link in the sig.
At the end of the day, simulating atoms doesn't beat working with the real things...
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