Can molten metals dissolve metal oxides, or vice versa?

[cmb]

Where a metal melts before its oxide, can that oxide be solvated in the liquid metal? Likewise, if the metal oxide melts at a lower temperature can that solvate the metal?

If not generally, can it happen for some metals, or none?

 

[trurle]

Where a metal melts before its oxide, can that oxide be solvated in the liquid metal? Likewise, if the metal oxide melts at a lower temperature can that solvate the metal?

If not generally, can it happen for some metals, or none?

A.f.a.i.k., metal oxides are not generally solvable in metals. Instead, they form a separate slag phases. Metal sulfides are more prone to dissolution though.

 

[Matcon]

I don't think there are any practical examples of this happening. With noble metals, like silver, gold etc, the oxide decomposes at temperatures below the melting point of the metal.

For a metal oxide to dissolve, the metal-oxygen bond strength would need to be close to the metal-metal bond strength. Taking the free energy of formation as a proxy for bond strength and looking at an Ellingham diagram, it looks as though that's not going to happen below the boiling point of the metal.

It ought to be possible to devise an alloy system in which the oxide is stable in the liquid temperature range. If I had to do it, I'd look at low melting point silver alloys and select the other elements based on the phase diagrams of the oxides.

One could also look at manipulating the environment, the oxygen partial pressure in particular.

There has been work done on the surface tension of In-Ga alloys, in which the surface tension is manipulated by application of an electrical potential. At potentials where the surface oxide is reduced, the metal pulls itself into a sphere. Reversing the potential causes it to flatten out (the alloy being liquid at room temperature). Whether the surface oxide is reduced and the oxygen dissolves or the oxygen desorbs from the surface is not clear.