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Author: Subject: CaCl2: please help me.
lamura
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[*] posted on 7-9-2006 at 13:50
CaCl2: please help me.


is there someone that could give me a reference on the decomposition temperature of CaCl2?

the melting temp. is 772 C then I expect something like 850-900 C...is it possible?????

please, help me!!!!;)




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12AX7
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[*] posted on 7-9-2006 at 13:57


If it melts, I doubt it decomposes (I may be mistaken). It could certainly boil though.

Tim




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[*] posted on 7-9-2006 at 15:58


Excerp........But calcium chloride is very stable, and its decomposition in this way is incomplete, and requires enormous expenditure of heat, besides that used in evaporating the solution of calcium chloride to dryness.


.........................source,

http://www.lenntech.com/Chemistry/chlorine-industry.htm




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tumadre
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[*] posted on 7-9-2006 at 23:53


plasma temperatures required to decompose it, I boiled it with a carbon arc, didn't smell any CL2
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lamura
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[*] posted on 8-9-2006 at 04:15
CaCl2


Hi to all,

thank you for your replies, but it is clear that after melting the next important temperature is the boiling one.

For my pourposes it's important to know just the decomposition temperature, because I have to force the Ca to react with Carbonium (decomposed from a methane flux) without forming CaC2 end then it is important that the decomposition temperature of CaCl2 could be less then the temperature at which CaC2 is favourized.

In alternative, do you know another salt that releases Ca when it dicomposes???? The decomposition temperature must be less then 800 C.

This is the problem.

thanks to all
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[*] posted on 8-9-2006 at 04:45


Calcium oxalate or azide(might be too rapid) will decompose to calcium under quite low heat. Much less than 800.
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Nicodem
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[*] posted on 8-9-2006 at 09:16


Calcium oxalate surely can't decompose to calcium. I thought it was generally known that it decomposes to CaCO3 and CO. Then at higher temperature, the CaCO3 decomposes to CaO and CO2.

DTG diagram with the decomposition product analysis:



According to this paper Ca(N3)2 and other metal azides do decompose to the metal and N2, but explosively so. :o

CaH2 does not explode when decomposed to Ca and H2, but mixtures of H2 with air or other oxidants can explode. :P




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12AX7
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[*] posted on 8-9-2006 at 10:46


Ca and air or other oxidants can explode, too, what's your point? :P

Tim




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The_Davster
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[*] posted on 8-9-2006 at 14:37


Thanks Nicodem, I just figured it would decomose the same as several heavy metal oxalates, guess not.

Calcium azide just decomposes without explosion(deflagration?) above 110C and lower than 160C, greater than 160C it explodes.

EDIT: Does not CaH2 explode in contact with water? Much more violently then an alkali metal. Source: an old professor of mine.

[Edited on 9-9-2006 by rogue chemist]
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lamura
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[*] posted on 8-9-2006 at 15:03


o my god!....and there is no way to evoid explosion???

the procedure should be the following (one time that the good Ca-salt has been find for this pourpose)

Silicium substrate (with a thin oxide layer : Si/SiO2) and the salt should dissolved in some solution (ethanol, methanol, ...) to drop it on the substrate. After the solvent is evaporated, the substrate will be put into a quartz furnace.

In a continuous flux of argon (to purge the system) and after methane the heater can be turned on.

The goal is that heating decompose decompose the salt and the methane in order to let the Ca atomes to play the role of catalyst toward Carbon atoms (without forming CaC2!!!).

thank you

gian
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[*] posted on 8-9-2006 at 16:44


So you want to....catalyze SiO2 + 2C = 2CO + Si or Si + C = SiC, with calcium? Is calcium a dopant?

Does methane dissociate appreciably at the temperature you desire? I get the feeling it doesn't. Don't you need a plasma or something to get active methyl bits?

And as I mentioned elsewhere ...why not vapor deposit Ca in a vacuum chamber, if available?

Tim




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[*] posted on 9-9-2006 at 16:30


C'mon guys, he's trying to grow large crystals of sparkly moissanite or semiconductor wafers :)

[Edited on 10-9-2006 by FrankRizzo]
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[*] posted on 16-9-2006 at 23:02


Quote:
Originally posted by rogue chemist

Calcium azide just decomposes without explosion(deflagration?) above 110C and lower than 160C, greater than 160C it explodes.


[Edited on 9-9-2006 by rogue chemist]


what is calcium azide exactly? CaN3? the azide ion is confusing..
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[*] posted on 16-9-2006 at 23:10


Quote:
Originally posted by goob
what is calcium azide exactly? CaN3? the azide ion is confusing..

Read the rest of the thread. The rational formula was mentioned and a paper discussing the salt was linked.
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