Is it possible to take many small diamond fragments, melt them and then recrystallize them into a larger diamond?
I assume it is possible to reach that temperature as the melting point of diamond is known.
It would have to take place in a vaccum as well as carbon will easily oxidize at this temperature.
Can you melt carbon… ever? I thought it just sublimed.
Now, if you want to build a big diamond from smaller, I imagine something like Jon Kuhn’s glass sculptures.
1.) If you take small pieces of diamond and try to asemble them into a larger diamond, it’s 99.999% certain that the crystal planes won’t line up, and so you won’t have a big single crystal. This won’t have as much strength along the lines where the pieces join, and will come apart easily. I used to grow crystals, and it’s appallingly easy to grow a polycrystalline mass instead of a single crystal. Polycrystalline masses don’t look anywhere near as pretty as single crystals, and they do come apart easily.
2.) are you suggesting melting the edges of the pieces to stick things together? I don’t think you can melt diamond. You might be able to squeeze them together under high temperature and pressure and get them to stick. To say that this is not an easy thing to do, in any case, is an understatement.
According to this phase diagram for carbon, you’ll need to melt your diamonds at 1000°C and 5,000,000 psi to favor diamond formation over graphite formation.
Is this possible?
Why not feed it cheap graphite instead of expensive diamonds then?
Of course it’s possible, we can make synthetic diamonds in the lab today. But there’s no sense in using geologically created diamonds as the feedstock for synthetic diamonds because it doesn’t matter what source the carbon comes from, and there are lots of cheaper pure carbon sources than diamond.
Oops, I read the graph wrong. Diamond becomes the more stable form above a few tens of atmospheres.
Gemesis grows diamond crystals at 850psi and 1600°C, but they start with carbon. Starting with diamond might speed things up a bit, but that’s about it.
-Gemesis website with pictures of diamonds and slinky music.
Alas, that only works if the crystal structure is a stable one under the growing conditions, and it it’s thermodynamically possible to “plate out” atoms from solution onto your seed crystal. Since no one’s grown diamonds this way, you can bet that it’s not. Besides, you need something your “diamond salts” – that’s pure carbon – is going to dissolve in.
The chemical vapor deposition method described in the wiki article is essentially a way to do this, but with vapor instead of a liquid solution. Still not easy, or it would not have needed such a long period of development.
Besides, from my experience with crystal growth, I can say that you’d better have a REALLY clean seed crystal, or else you’ll end up with those parasitic non-aligned crystals sticking to your big one. So make sure all the little bits of crystal are COMPLETELY cleaned away (with growing from melt, you typically do this by melting off any tiny bits in the melt. They’re smaller than the seed, so they melt off first).