If one wants to utlize the heat from molten metal Si by exchanging heat from the molten metal bed, can this bed be made of Tungsten, Molybdenum or Tantalum. I have looked on the internet and have found Tantalum as a good metal having good thermal conductivity, high melting point and good molten metal resistance. But I am concerned about the sticking of molten Si oin the Tungsten,Molybdenum or Tantalum made bed, will molten Si stick to it or not? How good is an idea of making this bed with above mentioned metals.
Please note that tungsten has much higher melting point (3422 °C) than silicon boiling point (2355 °C)(*). Also tantalum has higher melting point (3017 °C). Even the melting point of molybdenum (2623 °C) is higher.
(*) http://www.chemicalelements.com/elements/si.html
Thanks for your reply Mr. Querioz, I know that Tungsten has a higher melting point even Tungsten has the highest melting point of all the metals. What I want to ask is that If I construct a bed made of tungsten and then place molten Si on it, will it stick to it. The molten Si will be allowed to cool on it for days and then it will be broken by impact to take the Si metal out of the bed. Furthermore, A heat transfer from the bed to the water will be taking place inside the bed as well, will tungsten, Molybdenum or tantalum will be suitable material of construction for this type of bed? I hope you will be able to understand and answer my question.
Raheel,
The silicon will be floating on a bed that is hotter than the boiling point of the silicon: so the silicon will boil.
(!)
Sure, you could use tantalum, but silicon is soluble in tantalum (3%) so the floating silicon will not be pure for very long.
And molybdenum is also miscible in silicon - and quite soluble.
http://extras.springer.com/2006/978-3-540-25024-1/00400019b4/paper/00400019b4/00400019b40015.pdf
Thanks for the answer, Mr. Garry. Now after your answer I am thinking of using some metal piping inside a bed (for holding molten Si) made of graphite for heat transfer to water or air, I think that can be the only solution as purity remains the priority.
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