Carol King, via Facebook asked:
Can Graphene be converted to Diamond-phene?
Dave - Iíll start off with diamond and graphite, the large scale structures Ė three dimensional structures. Graphite and diamond have got incredibly different structures even though they're both just made out of carbon atoms. In graphite, you've got a whole series of planes made up of hexagonally arranged carbon atoms, all tesselating together with an atom where all the hexagons meet. Whereas diamond is this tetrahedral structure with each carbon atom being bonded very strongly to four others at the corners of a tetrahedral pyramid or triangular based pyramid. This is the reason why diamond is incredibly strong. It bonds in every possible direction whereas graphite is very strongly bonded inside the plains, but very weakly between them, so they slide across each other, and itís quite a good lubricant.
Ben - So, if you wanted to convert between the two, you actually have to break and then remake quite a lot of bonds, so it must be quite an intensive process?
Dave - Yes, that's right and diamond is only actually stable under very, very high pressures. The stable form of carbon at room temperature and pressure is graphite. So, in order to convert graphene or graphite into diamond, for a start, you'd have to use incredibly high pressures. And also, diamond is an intrinsically three dimensional structure so a single plain of it, equivalent of graphene, wouldnít really make sense. It will be incredibly unstable and it would immediately convert back into something like graphene or just fall apart.
Ben - So, graphene itself is not a better source for making something like a flat sheet of diamond. You may as well just use any old carbon kicking about.
Dave - Yeah, that's right and itís probably a lot easier to get it from some kind of gas like methane or something in a CVD process like they've talked about earlier.