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I intend to bring solid Alumina Oxide into a liquid state, for the purpose of pouring the substance into a mold. Subsequently, I will allow it to cool with an ambient air temperature of 70f, slowly allowing it to return it to a solid state. Melting will be performed with a gas mixture.

My question is, will the Alumina Oxide return to the original molecular structure as is was prior to melting it from a solid state?

Thank you for your time and consideration.

Rob

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    $\begingroup$ Good luck melting it in the first place without special equipment. $\endgroup$ – Jon Custer Jan 9 '16 at 23:15
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    $\begingroup$ You realize that the melting point of alumina is 2,072 °C?!? What are you going to contain the melt in and what mold material are you going to use? // Frankly this is the sort of question that if you have to ask then you don't have a clue what you are doing and you shouldn't attempt the experiment. $\endgroup$ – MaxW Jan 9 '16 at 23:16
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    $\begingroup$ There is no alumina oxide. Alumina is aluminium oxide. $\endgroup$ – matt_black Jan 10 '16 at 0:02
  • $\begingroup$ related chemistry.stackexchange.com/questions/16640/… $\endgroup$ – Mithoron Jan 10 '16 at 15:47
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First of all, there is no such thing as "alumina oxide". Alumina is aluminium oxide. Melting alumina is pretty hard, its melting point is above 2000 degrees Celsius. It's so high that people use it as a container (crucible) for melting other stuff. Such high temperatures are not easily achieved without melting a bunch of stuff around it.

Let's assume that you did manage to melt it, maybe using one of those fancy levitation laser techniques. Your mold has to be heat resistant and inert so it will not melt or react with the molten alumina. Graphite is usually a good one.

Now, you were asking about the structure. Assuming that you started with regular crystalline alumina (aka corundum), then yes: the resulting material after cooling in air will be the same corundum. Amorphous alumina (glass) will only form by extremely rapid cooling, for example dropping a very small amount to ice cold water. In all normal circumstances it will be crystalline.

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