Aetius - 9-6-2006 at 18:03
Sorry if i ve posted in the wrong section , molten magnesium being a pretty reactive material i thought it was the most appropriate section .
I am looking for a non toxic non hygroscopic oxide that is resistant to molten magnesium at around 800 C° which is different of MgO LiO and Al2O3.
i think scandia might do the trick but i do not have the entropy values for molten magnesium .
Anyway heres my calculations (theses values are for 298 k and could lead to false results when extrapolated to 1073 k, in this case i would gladly
accept corrections):
Scandium: S°solid=34.6 J/mol , S°gas= 174.8 J/mol,
Scandium oxide :
Delta Hf = -1908.8 kj/mol , delta Gf = -1819.4 kj/mol , S°solid 77.0 j/mol.
Magnesium metal : S°solid =32.7j/mol , S°gas=148.7j/mol,,S°liquid (extrapolated)= (32.7+148.7)/2=107.1j/mol.
Magnesium Oxide Delta Hf = -601.6kj/mol , delta Gf=-569.3 kj/mol ,S°solid=27 j/mol.
3 Mg + Sc2O3 --> 3MgO + 2Sc
Txdelta S (solid scandium):
1073 x (3x27+2x 34.6 - 3*107-77) =1073x -247 = -265 kj
Delta H= 3*-601 +1908.8 = + 105 kj
Delta G=105 +265= + 370 kj
So in theory the reduction of Scandia by molten magnesium should not be possible , anyone could confirm/infirm this?
[Edited on 10-6-2006 by Aetius]
12AX7 - 9-6-2006 at 20:40
Scandium oxide, holy hell, ROTFLMAO!
Oh, if only economics didn't overlap with physical practice.
Why doesn't MgO work? CaO? ZrO2?
Fe metal will stand liquid Mg, if oxidation isn't a problem (I can't imagine it is, with liquid Mg around!).
Tim
Fulmen - 10-6-2006 at 01:27
May I ask what you are trying to do here? I used to work at a magnesium plant, and we used steel (mild and stainless) to handle molten metal.
kazaa81 - 10-6-2006 at 01:29
Why not praseodimium oxide? 
Seriously, steel or just mild iron is able to withstand molten Mg, since iron melts at a higher temp. than Mg. The thing I would be best worried about
is oxidation of Mg...what atmosphere are you using to do this experiment? He, Ar?