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D4RR3N
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La metal with Bi
I have some La metal and also a quantity of the element Bi, I dont have much use for it at the moment and so was thinking of heating a quantity of La
and Bi together to make LaBi, I was just wondering firstly if it would need to be done in a vacuum and secondly what would be the correct weight
ratios?
Anyone know of any interesting experiments to do with these elements. I was also thinking of growing a Bi crystal, they look amazing.
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not_important
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Lanthanum is pretty reactive, in vac or under argon.
Weight ration - see your periodic table.
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chemrox
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Are you sharing La?
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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D4RR3N
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Hi chemrox, I dont have much La in comparison to Bi, The annoying thing about the La metal is that when it was posted to me Import must have slit
open the package to look inside. When they did this they made a small slit in the vacuum sealed bag which I did not notice to later. The result is
that the surface of the material is covered in oxide which I will probably have to remove with a wire brush.
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D4RR3N
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In order to make LaBi what temperature would I need to heat the La and Bi to, La melts at 920C whilst Bi melts at 271.5C
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12AX7
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If they are in perfect contact, you can calculate the diffusion constant at room temperature. Who needs heat?
Tim
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D4RR3N
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"If they are in perfect contact, you can calculate the diffusion constant at room temperature"
I wish I could
I will need to heat it I think because the La is in lump and the Bi is in needle form, If I heat the mixture to the melting point of Bi will it
dissolve the La lump?
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12AX7
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Do you have a phase diagram for the system? Any idea of the heat of formation of LaBi?
The canonical alloying method heats both to the highest melting point, optionally gives a little stir, then the material is cast (in a mold, or cooled
in situ if necessary).
Neither will do anything with oxides around, and worse yet, will do a whole lot more than nothing if oxygen is available. I would recommend a vacuum
arc furnace or vacuum or inert gas induction furnace. Probably a fused quartz crucible would suffice. A flux would be good too; do you know if La is
reactive enough to reduce a silica flux? If not, regular window glass would be a good flux; if so, it would still be a good flux BUT would leave you
with an unknown silicon (and probably sodium) impurity.
Tim
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not_important
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| Quote: | Originally posted by D4RR3N
In order to make LaBi what temperature would I need to heat the La and Bi to, La melts at 920C whilst Bi melts at 271.5C |
Several papers seem to indicate heating the metals in a silica/quartz tube or capsule to roughly 850 C
The rare earth pnictides formation all seem to be exothermic, even for bismuth. I'd be cautious on heating much at once until I'd tried a few small
samples.
As a comparison, lithium melts at 180 C, bismuth at 271 C. To make Li3Bi you heat the two metals together in a tantalum crucible in an inert
atmosphere; when the react commences the crucible is heated to incandescence as Li3Bi is formed - mp around 1200 C.
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D4RR3N
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| Quote: | Originally posted by 12AX7
Do you have a phase diagram for the system? Any idea of the heat of formation of LaBi?
The canonical alloying method heats both to the highest melting point, optionally gives a little stir, then the material is cast (in a mold, or cooled
in situ if necessary).
Neither will do anything with oxides around, and worse yet, will do a whole lot more than nothing if oxygen is available. I would recommend a vacuum
arc furnace or vacuum or inert gas induction furnace. Probably a fused quartz crucible would suffice. A flux would be good too; do you know if La is
reactive enough to reduce a silica flux? If not, regular window glass would be a good flux; if so, it would still be a good flux BUT would leave you
with an unknown silicon (and probably sodium) impurity.
Tim |
I could not find much info on LaBi at all, I dont know what temperature LaBi is formed but I do know that La is fairly reactive and reacts with many
elements directly. I would rather not use a flux.
I was thinking that if I heated the Bi to melting point it would react with the La directly and dissolve it, Im thinking of how gold dissolves in
mercury......I have no idea really
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D4RR3N
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| Quote: | Originally posted by not_important
| Quote: | Originally posted by D4RR3N
In order to make LaBi what temperature would I need to heat the La and Bi to, La melts at 920C whilst Bi melts at 271.5C |
Several papers seem to indicate heating the metals in a silica/quartz tube or capsule to roughly 850 C
The rare earth pnictides formation all seem to be exothermic, even for bismuth. I'd be cautious on heating much at once until I'd tried a few small
samples.
As a comparison, lithium melts at 180 C, bismuth at 271 C. To make Li3Bi you heat the two metals together in a tantalum crucible in an inert
atmosphere; when the react commences the crucible is heated to incandescence as Li3Bi is formed - mp around 1200 C. |
Im so glad you told me the reaction may be exothermic as I was going to mix it all in one go
I think La reacts with silicon so I'm wondering what I can heat this mixture in now, this is quickly becoming more complicated then I first
thought
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not_important
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Do a search for LaBi lanthanum, even without access to full papers you'll find several references that heat the mixed elements together in a
(fused) silica container.
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D4RR3N
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I think I read the same extract, LaBi formed in a sealed tube by heating to 850C.
Im guessing that they put the LaBi mixture in the tube, vacuum sealed it and then put the whole tube into a tube furnace at 850C.
850C is not far-off the melting point of La, I did not think it would need such a high temperature. Bismuth would be a vapour at that temperature,
the tube would become highly pressurised and may burst.
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JohnWW
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In makimng such an intermetallic compound, it should be sufficient for only one of the two metals to be melted; the other should then dissolve in it,
if any intermetallic compound is going to form..
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unionised
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850C is only about half the boiling point of Bi, though I'm surprised it needs heating that much. The tube would still be under a partial vacuum at
that temperature. What's the melting point of the product? Perhaps thay want to be sure that the product all melts to ensure the reaction is complete
and the product homogeneous.
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D4RR3N
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I dont know the melting point of LaBi, I am also surprised that a temperature of 850C is needed because I thought LaBi would be formed close to the
melting point of Bi which is 272C
Is it possible to calculate what temperature is required?
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12AX7
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Melt the damn stuff and you'll have no question as to its formation.
Tim
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not_important
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| Quote: | Originally posted by D4RR3N
I dont know the melting point of LaBi, I am also surprised that a temperature of 850C is needed because I thought LaBi would be formed close to the
melting point of Bi which is 272C
Is it possible to calculate what temperature is required? |
I suspect such calculations may be difficult. Repeating:
lithium melts at 180 C, bismuth at 271 C, Li3Bi at around 1200 C. The exothermic nature of the reaction insure complete melting for all but small
amounts of starting materials. If that didn't happen, you could see a shell of the pnictide forming around the higher melting element, leading
to incomplete reaction.
I suggest that you try to find a phase diagram and other information on this before proceeding. If full papers are behind registration firewalls, but
look as if they may have the needed data, perhaps someone could fetch it for you.
This PDF preview looks as it may be helpful.
[Edited on 14-10-2008 by not_important]
Attachment: La-Bi-phase.pdf (73kB)
This file has been downloaded 895 times
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D4RR3N
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| Quote: | Originally posted by 12AX7
Melt the damn stuff and you'll have no question as to its formation.
Tim |
I would do if I had a vacuum furnace but I dont so I have to adapt the furnace I have which is a muffle furnace with a max temp of 1100C.
I am going to see if I can find a long quartz tube which has a flat bottom, put the mixture in, plug the open end with a rubber stopper and vacuum
pump the air out. If the tube is long enough I wont need to worry about pressure causing the tube to burst or thermal reaching the rubber stopper as
only one end will be inserted into the furnace.
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D4RR3N
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| Quote: | Originally posted by not_important
| Quote: | Originally posted by D4RR3N
I dont know the melting point of LaBi, I am also surprised that a temperature of 850C is needed because I thought LaBi would be formed close to the
melting point of Bi which is 272C
Is it possible to calculate what temperature is required? |
I suspect such calculations may be difficult. Repeating:
lithium melts at 180 C, bismuth at 271 C, Li3Bi at around 1200 C. The exothermic nature of the reaction insure complete melting for all but small
amounts of starting materials. If that didn't happen, you could see a shell of the pnictide forming around the higher melting element, leading
to incomplete reaction.
I suggest that you try to find a phase diagram and other information on this before proceeding. If full papers are behind registration firewalls, but
look as if they may have the needed data, perhaps someone could fetch it for you.
This PDF preview looks as it may be helpful.
[Edited on 14-10-2008 by not_important] |
Thanks for the diagram, it mentioned that heating was preformed over several days, also LaBi at 1615C
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not_important
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That extended time could be to allow diffusion to even out the composition. In effect liquid Bi and Bi-rich alloy dissolve La until the alloy freezes,
but diffusion allows the remaining La to diffuse into the alloy body. Just guessing on this.
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12AX7
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Wow, the La end looks exactly like iron!
Sure illustrates the "bismuthide" character of this compound. Should be pretty easy to make then! Combine La and Bi filings (under inert or vacuum),
ignite, check that mixture reaches white heat; if not, toss on some arc or induction heat to finish the job. Even if it doesn't melt, the exotherm is
a sure sign that something is going on.
Tim
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D4RR3N
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Now that I seen that chart with LaBi formed at 1615C suddenly the other extract which mentioned heating to 850C is more attractive
I have been trying to find a suitable fused quartz tube to heat the mixture but have not been able to find what is essentially a huge test tube. The
only thing I can find which looks remotely like what I'm looking for is a 2000ml borosilicate measuring cylinder with removable foot, take the plastic
foot off and its basically a large test tube.
I'm thinking of putting the lower end of this tube into my furnace (upright) and plugging the other with a rubber stopper with vacuum tube in centre.
Any better ideas considering I dont have a arc or vacuum furnace, basically got to use what I have.
With Borosilicate glass I will probably only be able to heat to 750C max.
[Edited on 14-10-2008 by D4RR3N]
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unionised
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I don't think borosilcate glass will stand the temperature- particulalry not under the strees of being evacuated.
http://www.glassonweb.com/articles/article/376/
Even fused quartz might be pushing it slightly.
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watson.fawkes
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@not_important: Great phase diagram! One of the more interesting I've seen, with both positive and negative azeotropic aspects. (Not the best word,
since properly "zeotrope" refers to liquid-gas transitions, but I digress.)
@D4RR3N: The horizontal line at 932° C is the melting point of LaBi<sub>2</sub>; above this line this compound is liquid. Now look
at the rectangular region from 50%-75% Bi and 932° - 1615° C. Below the curved line is a mixture of liquid
LaBi<sub>2</sub> and solid LaBi. This is the crystal-pulling range of this mixture.
Part of this region is within the stated 1100° range of your furnace. You might be able to pull solid crystals out of the melt. It will take a
bit of equipment construction, to be sure, not the least because you'll likely need an argon shield. Sorry, am I making a big project for you?
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