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Alienwhoexploreyourplanet
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Alumina crucible
Hi everyone , i'm new here , i have a question , if someone can help me thanks a lot , i know its very hard to melt aluminium oxide , something around
2072 °C , so i'm very curious to know how they can make an alumina crucible ( with 99 % aluminium oxide for example ) , do they use a mold or
something ?
thanks
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hissingnoise
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| Quote: | | Hi everyone , i'm new here . . . |
Hmmm, you've come all this way to put a technological question to a species which has just recently ventured out from the 'safety' of its caves?
Er, thermite . . .  ?
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Alienwhoexploreyourplanet
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The question is about crucible hissingnoise
[Edited on 11-8-2011 by Alienwhoexploreyourplanet]
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Bot0nist
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He mentioned termite, which would burn at sufficient temps to get the job done. I doubt that's what they use to manufacture them though. I am not well
versed on the subject but you may want to look into glassy carbon. A member recently did a thread on its use as an exotic anode and mentioned
that there main use is in high temp crucible making.
p.s. He was just being friendly I imagine. Commenting on your moniker.
Do you come in peace...?
[Edited on 11-8-2011 by Bot0nist]
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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Alienwhoexploreyourplanet
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Thanks for the answer Bot0nist , the reason i'm here is that i want to do an alkaline fusion , so i'm looking for a suitable crucible , i want to
understand more about them first ( thats the reason of my topic ) , alumina is one of them and why not glassy carbon so i'll think about too ..
PS : Yes i'm peacefull , me and the other little green heads
[Edited on 11-8-2011 by Alienwhoexploreyourplanet]
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Magpie
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I have done alkaline fusions in a nickel crucible. They can be done in steel also if you want to use a piece of capped pipe.
I'm just guessing but I think that an alumina crucible would be made by sintering alumina that has first been pressed into the desired shape.
[Edited on 11-8-2011 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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Alienwhoexploreyourplanet
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Thanks Magpie , this link http://encyclopedia2.thefreedictionary.com/Alkali-Resistant+... is the confirmation of what you said about nickel with other metallic materials
and nonmetallic inorganic materials who are all suitable for alkaline fusion , and about alumina crucible thats an idea i'll look if there is an
interressant patent about alumina crucibles around the net .
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hissingnoise
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We mean you no harm, but some(?) of us can't resist taking the piss . . .
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blogfast25
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Alumina is attacked by alkali, inclluding molten alkali, forming aluminates. Contamination of your fusion product and damage to the crucible are
likely.
Steel or nickel are a better choice. Not to mention cheaper.
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Alienwhoexploreyourplanet
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No everyone is nice here , and i prefer when they're nice and helpful in the same time ..
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Alienwhoexploreyourplanet
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Quote: Originally posted by blogfast25  | Alumina is attacked by alkali, inclluding molten alkali, forming aluminates. Contamination of your fusion product and damage to the crucible are
likely.
Steel or nickel are a better choice. Not to mention cheaper. |
Excuse me blogfast25 but Aluminum oxide is the most stable (with zirconium oxide) to the action of molten sodium hydroxide at 540°C see my link http://encyclopedia2.thefreedictionary.com/Alkali-Resistant+...
[Edited on 11-8-2011 by Alienwhoexploreyourplanet]
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Neil
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I've made ~90% alumina crucibles via slip casting with the ~10% being silica from the high alumina low silica clay I used as a binder.
To do so you make a mould of your crucible shape, cast it into a block of plaster and then separate the two.
Once the plaster cast is dry a 'slip' can be poured in, then poured out leaving you with a crucible.
Any silica, iron, chloride, magnesium or calcium in the crucible will ruin it when you go to fire it, if you have sintering the alumina in mind.
I've also made crucibles of alumina/silica with thermite by fusing a tube of material with a thermite reaction and then coating the fused shape with
slip and letting the whole thing dry before firing. Bloody useless really.
Anyway once you have the crucible cast, it needs to be fired hot enough and long enough to sinter it. Expect shrinkage and horrible horrible failure
the first couple times.
I'd personally stick with metals or buy the crucibles.
pottery forums have all the relevant charts.
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Alienwhoexploreyourplanet
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Thanks Neil that's very instructive , as you know silica is not a good thing if you want to do an alkaline fusion so the best is an alumina crucible
with pure alumina
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Morgan
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I bought some fused quartz crucibles from these guys but they also sell some alumina products. It might do for your needs.
http://www.advaluetech.com/alumina-crucibles.html
http://www.advaluetech.com/alumina-crucibles.html
Some tidbits.
http://www.azom.com/article.aspx?ArticleID=1389
Forgive me.
http://us.mt.com/us/en/home/products/Laboratory_Analytics_Br...
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Alienwhoexploreyourplanet
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Thanks a lot Morgan , thats exactly the kind of crucible i'm looking for , and the price is very interressant
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watson.fawkes
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I was doing some reading a couple of years ago on the production of this subject. Unfortunately, I don't believe I have copies of the papers I read
any longer, but I recall the gist of them.
MgO is used as a sintering agent for alumina, but are rather low percentages, not more that 0.5% as I recall. There some might interesting work out
there studying grain growth in this system. It's thought that MgO forms a low-melting eutectic with alumina and that pure alumina re-crystallizes out
of this at grain boundaries, increasing grain size and promoting densification.
The temperatures involved, though, are quite high. I don't recall exactly, but I remember that it's way above cone 10, making direct electrical heat
with nichrome or Kanthal wires infeasible. I seem to recall that MoSi2 elements would reach that temperature, but I wasn't interested in springing for
that expense in fixed costs.
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IrC
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Since you are new to this solar system I will help you with this. Aliens must always listen to magpie and blogfast25 on things of this nature. I can
give you a handful of alumina crucibles destroyed doing what you wish to do. I experimented with various hydroxides making aluminate glow powders and
can say from experience invest in the nickel crucible you will not be sorry. This only because I could not afford a platinum one, nickel crucibles are
expensive enough. Chemicals such as NaOH and alumina crucibles do not get along well at elevated temperatures. I do not agree on the cheaper comment I
have many alumina crucibles, they were not as expensive as nickel.
"Science is the belief in the ignorance of the experts" Richard Feynman
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Magpie
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Here's a source for nickel crucibles:
http://www.crscientific.com/nickelcrucibles.html
The single most important condition for a successful synthesis is good mixing - Nicodem
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Alienwhoexploreyourplanet
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Thanks a lot watson.fawkes for the explanation , i think there is lot of advantage to use an alumina crucible , and yes IrC and Magpie , it's true
that nickel crucible will resist more than any other crucible but the price is here to melt everyone lol .. in my link http://encyclopedia2.thefreedictionary.com/Alkali-Resistant+... they talk about copper too , that look very cool because i have more copper than
any other material in my lab , what do u think about this material ?
[Edited on 12-8-2011 by Alienwhoexploreyourplanet]
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Neil
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With my post I assumed you were talking about making a zirconia based crucible not a pure alumina one. I think you are missing the key, your reference
said:
"Many oxides, including Cr2O3, ZrO2, HfO2, ThO2, CeO2, Al2O3, and CdO, are stable in aqueous alkaline media at room temperature and upon
heating; they react with molten alkalies. Aluminum oxide and zirconium oxide are the most stable to the action of molten sodium hydroxide at
540°C"
at the top of the article it says "The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased."
Out on my limb I would suggest there is a translation error. a google search comes back with references to zirconia crucibles for molten caustics.
Perhaps the original article referred to zirconia bonded with alumina crucibles? I assume the original article was in russian....
Ether-way an alumina crucible is going to turn into mush. I've seen a pinch of wood ash eat a fist full of alumina based furnace refractory, a
crucible is not going to do any better. Listen to irC...
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watson.fawkes
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| Quote: Originally posted by Alienwhoexploreyourplanet | | i think there is lot of advantage to use an alumina crucible , and yes IrC and Magpie , it's true that nickel crucible will resist more than any other
crucible but the price is here to melt everyone |
First, molten alkali and alumina are not compatible. You
could get a (compatible) crucible of molten alkali, drop the alumina crucible in it, and dissolve it.
Suppose even that this wasn't the case. The furnace you need to make alumina crucibles yourself isn't trivial. Even just the refractories need to fire
alumina aren't cheap, much less the heating system and adequate controls. If you're trying to save money, DIY alumina crucibles are just not the way
to go.
If you want to save money, buy some nickel sheet metal. Then pound on it enough to make a crucible. The tools needed are way cheaper. The techniques
are basically the same as for custom auto body work. Remember to anneal while working.
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blogfast25
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Yawn. 540 C? Use a soup can. I mean, I thought you were going to FUSE something, you know?
Beware of free dictionaries that create 'content' to cram it with adverts. Bauxite (mineral alumina) is dissolved in 50 % NaOH at much lower
temperatures than 540 C on an industrial scale. Admitted: the Bauxite is powdered very finely. Al is an amphoteric element, so if you want to
contaminate your fusion with a good dollop of aluminate, go right ahead son. You know best!
No, honestly! 
[Edited on 12-8-2011 by blogfast25]
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Alienwhoexploreyourplanet
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| Quote: Originally posted by blogfast25 | [rquote=218680&tid=17248&
Beware of free dictionaries that create 'content' to cram it with adverts. Bauxite (mineral alumina) is dissolved in 50 % NaOH ate much lower
temperatures than 540 C. Admitted: the Bauxite is powdered very finely. Al is an amphoteric element, so if you want to contaminate your fusion with a
good dollop of aluminate, go right ahead son.
No, honestly!
[Edited on 12-8-2011 by blogfast25] |
The reference is the Great Soviet Encyclopedia, 3rd Edition (1970-1979) i understand now why the soviet union melted so fast
[Edited on 12-8-2011 by Alienwhoexploreyourplanet]
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Fleaker
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NaOH does indeed attack even sintered alumina readily.
Silver or gold are great for oxidizing base fusion. Nickel and zirconium are acceptable if it's just base.
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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Alienwhoexploreyourplanet
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Thanks Fleaker , so i think the conclusion is that nickel is the key , if you want a clean alkaline fusion without any contamination .
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