Sciencemadness Discussion Board

Calcium disilicide CaSi2

chemx01 - 23-4-2011 at 01:17

I was wondering about making some CaSi2 powder to make Siloxene for luminescent reaction, but i want to ask you is there a way that CaSi2 could be produced at home, has anyone ever tried it?

I read in Brauer that it could be prepared from Ca+Si-->CaSi and then CaSi+Si--> CaSi2 in temperatures around 1000°C.
The first step is quite straightfoward it's done under CO2 atmosphere, i'll do it in a glazed porcelain crucible heated by Bunsen.
However the second takes about 15 hours and it's done under H2 atmosphere, which I think it's not neccesary but I might be wrong, do you think that it could work without any atmosphere at all, just covered with a lid and that's it?

Thanks in advance for any suggestions.

KemiRockarFett - 29-4-2011 at 16:38

Press a tablet from the elements and arcmelt it together gently NOT overheating as the Ca will evaporate. You can also try to mix CaH2 with Si and heat it up to 700-800 degrees under H2 pressure or argon for some days. The zintl phase CaSi2 have an anionic covalent network formed by Si- that is isoelctronic to P.

I dont think that heating up reactive Ca in CO2 is intelligent at all.



blogfast25 - 30-4-2011 at 09:57

I don’t know if this helps but I’m sure I inadvertently made some calcium silicide some time back, in an experiment involving SiO2, Al and CaO:

http://www.sciencemadness.org/talk/viewthread.php?tid=10249&...

(scroll to my post at 9.04)

It makes me think it might be possible to obtain CaSi by the reduction of calcium silicate with aluminium:

CaSiO3 + 2 Al --- > CaSi + Al2O3

… which is basically a thermite reaction.

Similarly, Ca3(PO4)2 and CaSO4 can be reduced with Al powder to resp. Ca3P2 and CaS…


[Edited on 30-4-2011 by blogfast25]

KemiRockarFett - 30-4-2011 at 14:53

Quote: Originally posted by blogfast25  
I don’t know if this helps but I’m sure I inadvertently made some calcium silicide some time back, in an experiment involving SiO2, Al and CaO:

http://www.sciencemadness.org/talk/viewthread.php?tid=10249&...

(scroll to my post at 9.04)

It makes me think it might be possible to obtain CaSi by the reduction of calcium silicate with aluminium:

CaSiO3 + 2 Al --- > CaSi + Al2O3

… which is basically a thermite reaction.

Similarly, Ca3(PO4)2 and CaSO4 can be reduced with Al powder to resp. Ca3P2 and CaS…


[Edited on 30-4-2011 by blogfast25]


The self ignitning gas is probably a silan or a aluminiumsilan?
I will say that its higly probably that the resulting compound may have been a mix of CaAlSi, P6/mmm, and the CaAl2Si2 that is even more stable and forms more easily. The first one is as I remember a super conductor and its also possible to hydrogenate it to CaAlSiH with hydrogen attached to the aluminium, P3m1.

blogfast25 - 1-5-2011 at 05:46

KRF:

A silane(s) most likely, indeed.

What on Earth is 'P6/mmm'???

I presume chemx01's purpose is also to make silane, I don't see much use for Ca silicides otherwise...

The WiZard is In - 1-5-2011 at 13:55

Quote: Originally posted by chemx01  
I was wondering about making some CaSi2 powder to make Siloxene for luminescent reaction, but i want to ask you is there a way that CaSi2 could be produced at home, has anyone ever tried it?

Thanks in advance for any suggestions.

Ye old Mollor VI:176 makes mention of a method used by
La Compagnie Generale d'Electrocimie that employees calcium
carbide.

Google.com/books turns up this :— http://tinyurl.com/3bs7xoh

turd - 1-5-2011 at 14:05

Quote: Originally posted by blogfast25  

What on Earth is 'P6/mmm'???

One of the 230 different symmetry groups that crystals can adopt (http://en.wikipedia.org/wiki/Space_group). Or 219 if you don't count enantiomorphs. And of course if you don't consider incommensurates/quasi-crystalline phases crystals. :P

Edit: wrote something very stupid. :o

[Edited on 1-5-2011 by turd]